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Risi R, Vidal-Puig A, Bidault G. An adipocentric perspective of pancreatic lipotoxicity in diabetes pathogenesis. J Endocrinol 2024; 262:e230313. [PMID: 38642584 PMCID: PMC11227041 DOI: 10.1530/joe-23-0313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Accepted: 04/16/2024] [Indexed: 04/22/2024]
Abstract
Obesity and diabetes represent two increasing and invalidating public health issues that often coexist. It is acknowledged that fat mass excess predisposes to insulin resistance and type 2 diabetes mellitus (T2D), with the increasing incidence of the two diseases significantly associated. Moreover, emerging evidence suggests that obesity might also accelerate the appearance of type 1 diabetes (T1D), which is now a relatively frequent comorbidity in patients with obesity. It is a common clinical finding that not all patients with obesity will develop diabetes at the same level of adiposity, with gender, genetic, and ethnic factors playing an important role in defining the timing of diabetes appearance. The adipose tissue (AT) expandability hypothesis explains this paradigm, indicating that the individual capacity to appropriately store energy surplus in the form of fat within the AT determines and prevents the toxic deposition of lipids in other organs, such as the pancreas. Thus, we posit that when the maximal storing capacity of AT is exceeded, individuals will develop T2D. In this review, we provide insight into mechanisms by which the AT controls pancreas lipid content and homeostasis in case of obesity to offer an adipocentric perspective of pancreatic lipotoxicity in the pathogenesis of diabetes. Moreover, we suggest that improving AT function is a valid therapeutic approach to fighting obesity-associated complications including diabetes.
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Affiliation(s)
- Renata Risi
- Department of Experimental Medicine, Sapienza University of Rome, Sapienza University of Rome, Rome, Italy
- University of Cambridge Metabolic Research Laboratories, Wellcome Trust-MRC Institute of Metabolic Science, Cambridge, UK
| | - Antonio Vidal-Puig
- University of Cambridge Metabolic Research Laboratories, Wellcome Trust-MRC Institute of Metabolic Science, Cambridge, UK
- Cambridge University Nanjing Centre of Technology and Innovation, Nanjing, P. R. China
- Centro de Investigacion Principe Felipe, Valencia, Spain
| | - Guillaume Bidault
- University of Cambridge Metabolic Research Laboratories, Wellcome Trust-MRC Institute of Metabolic Science, Cambridge, UK
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2
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Gjela M, Askeland A, Mellergaard M, Drewes AM, Handberg A, Frøkjær JB. Intra-pancreatic fat deposition and its relation to obesity: a magnetic resonance imaging study. Scand J Gastroenterol 2024; 59:742-748. [PMID: 38557425 DOI: 10.1080/00365521.2024.2333365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Accepted: 03/17/2024] [Indexed: 04/04/2024]
Abstract
OBJECTIVES Intra-pancreatic fat deposition (IPFD) is suspected to be associated with various medical conditions. This study aimed to assess pancreatic fat content in lean and obese individuals, characterize obese individuals with and without IPFD, and explore the underlying mechanisms. MATERIALS AND METHODS Sixty-two obese individuals without diabetes and 35 lean controls underwent magnetic resonance imaging (MRI) using proton density fat fraction (PDFF) maps to evaluate pancreatic and hepatic fat content, and visceral adipose tissue (VAT) content. Pancreatic fibrosis was explored by T1 relaxation time and MR elastography (MRE) measurements. Associations between pancreatic fat, measures of obesity and metabolic syndrome were examined using uni- and multivariate regression analyses. RESULTS Pancreatic PDFF was higher in obese than in lean controls (median 8.0%, interquartile range (6.1;13.3) % vs 2.6(1.7;3.9)%, p < 0.001). Obese individuals with IPFD (PDFF ≥6.2%) had higher waist circumference (114.0 ± 12.5 cm vs 105.2 ± 8.7 cm, p = 0.007) and VAT (224.9(142.1; 316.1) cm2 vs 168.2(103.4; 195.3) cm2, p < 0.001) than those without. In univariate analysis, pancreatic PDFF in obese individuals correlated with BMI (r = 0.27, p = 0.03), waist circumference (r = 0.44, p < 0.001), VAT (r = 0.37, p = 0.004), hepatic PDFF (r = 0.25, p = 0.046) and diastolic blood pressure (r = 0.32, p = 0.01). However, in multivariate analysis, only VAT was associated to pancreatic fat content. MRI measures of pancreatic fibrosis indicated no evident fibrosis in relation to increased pancreatic fat content. CONCLUSIONS Pancreatic fat content was increased in obese individuals compared with lean controls and predominantly correlated with the amount of visceral adipose tissue. Pancreatic fat content was not clearly linked to measures of pancreatic fibrosis.
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Affiliation(s)
- Mimoza Gjela
- Department of Radiology, Aalborg University Hospital, Aalborg, Denmark
- Department of Clinical Biochemistry, Aalborg University Hospital, Aalborg, Denmark
| | - Anders Askeland
- Department of Clinical Biochemistry, Aalborg University Hospital, Aalborg, Denmark
- Department of Clinical Medicine, Aalborg University, Aalborg, Denmark
| | - Maiken Mellergaard
- Department of Clinical Biochemistry, Aalborg University Hospital, Aalborg, Denmark
- Department of Clinical Medicine, Aalborg University, Aalborg, Denmark
| | - Asbjørn Mohr Drewes
- Department of Clinical Medicine, Aalborg University, Aalborg, Denmark
- Department of Gastroenterology, Aalborg University Hospital, Aalborg, Denmark
| | - Aase Handberg
- Department of Clinical Biochemistry, Aalborg University Hospital, Aalborg, Denmark
- Department of Clinical Medicine, Aalborg University, Aalborg, Denmark
| | - Jens Brøndum Frøkjær
- Department of Radiology, Aalborg University Hospital, Aalborg, Denmark
- Department of Clinical Medicine, Aalborg University, Aalborg, Denmark
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3
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Nag S, Mandal S, Mukherjee O, Majumdar T, Mukhopadhyay S, Kundu R. Vildagliptin inhibits high fat and fetuin-A mediated DPP-4 expression, intracellular lipid accumulation and improves insulin secretory defects in pancreatic beta cells. Biochim Biophys Acta Mol Basis Dis 2024; 1870:167047. [PMID: 38296116 DOI: 10.1016/j.bbadis.2024.167047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 01/16/2024] [Accepted: 01/26/2024] [Indexed: 02/05/2024]
Abstract
Dipeptidyl peptidase-4 (DPP-4), a ubiquitous proteolytic enzyme, inhibits insulin secretion from pancreatic beta cells by inactivating circulating incretin hormones GLP-1 and GIP. High circulating levels of DPP-4 is presumed to compromise insulin secretion in people with type 2 diabetes (T2D). Our group recently reported lipid induced DPP-4 expression in pancreatic beta cells, mediated by the TLR4-NFkB pathway. In the present study, we looked at the role of Vildagliptin on pancreatic DPP-4 inhibition, preservation of islet mass and restoration of insulin secretion. MIN6 mouse insulinoma cells incubated with palmitate and fetuin-A, a proinflammatory organokine associated with insulin resistance, showed activation of TLR4-NFkB pathway, which was rescued on Vildagliptin treatment. In addition, Vildagliptin, by suppressing palmitate-fetuin-A mediated DPP-4 expression in MIN6, prevented the secretion of IL-1beta and fetuin-A in the culture media. DPP-4 siRNA abrogated TLR4-NFkB pathway mediated islet cell inflammation. Vildagliptin also reduced palmitate-fetuin-A mediated intracellular lipid accumulation in MIN6 and isolated islets from high fat fed (HFD) mice as observed by Oil O Red staining with downregulation of CD36 and PPARgamma. Vildagliptin also preserved islet mass and rescued insulin secretory defect in HFD mice. Our results suggest that inhibition of DPP-4 by Vildagliptin protects pancreatic beta cells from the deleterious effects of lipid and fetuin-A, preserves insulin secretory functions and improves hyperglycemia.
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Affiliation(s)
- Snehasish Nag
- Cell Signaling Laboratory, Department of Zoology, Siksha Bhavana (Institute of Science), Visva-Bharati University, Santiniketan 731235, India
| | - Samanwita Mandal
- Cell Signaling Laboratory, Department of Zoology, Siksha Bhavana (Institute of Science), Visva-Bharati University, Santiniketan 731235, India
| | - Oindrila Mukherjee
- Cell Signaling Laboratory, Department of Zoology, Siksha Bhavana (Institute of Science), Visva-Bharati University, Santiniketan 731235, India
| | - Tanmay Majumdar
- National Institute of Immunology (NII), Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Satinath Mukhopadhyay
- Department of Endocrinology & Metabolism, Institute of Post-Graduate Medical Education & Research-Seth Sukhlal Karnani Memorial Hospital (IPGME&R-SSKM), Kolkata 700020, India
| | - Rakesh Kundu
- Cell Signaling Laboratory, Department of Zoology, Siksha Bhavana (Institute of Science), Visva-Bharati University, Santiniketan 731235, India.
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4
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Zeng W, Cai N, Liu J, Liu K, Lin S, Zeng L. Caveolin-1 deficiency alleviates palmitate-induced intracellular lipid accumulation and inflammation in pancreatic β cells. J Physiol Biochem 2024; 80:175-188. [PMID: 38032518 DOI: 10.1007/s13105-023-00995-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 10/31/2023] [Indexed: 12/01/2023]
Abstract
Lipotoxicity-induced pancreatic β cell damage is a strong predictor of type 2 diabetes mellitus (T2DM). Our previous work showed that Caveolin-1 (Cav-1) depletion decreased β-cell apoptosis and improved β-cell viability. Further microarray analysis indicated significant changes in the expression of genes related to fatty acid metabolism and inflammation. The objective of this study was to explore the role of Cav-1 in intracellular lipid accumulation and inflammation in β cells under lipotoxic conditions. Here, we established a β-cell-specific Cav-1 knockout (β-Cav-1 KO) mouse model and a CAV-1 depleted β cell line (NIT-1). We found that Cav-1 silencing significantly reduced palmitate (PA)-induced intracellular triglyceride (TG) accumulation and decreased proinflammatory factor expression in both the mouse and cell models. Further mechanistic investigation revealed that amelioration of lipid metabolism was achieved through the downregulation of lipogenic markers (SREBP-1c, FAS and ACC) and upregulation of a fatty acid oxidation marker (CPT-1). Meanwhile, decrease of inflammatory cytokines (IL-6, TNF-α, and IL-1β) secretion was found with the involvement of the IKKβ/NF-κB signaling pathways. Our findings suggest that Cav-1 is of considerable importance in regulating lipotoxicity-induced β-cell intracellular lipid accumulation and inflammation.
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Affiliation(s)
- Wen Zeng
- Department of Endocrinology and Metabolism, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China
- Guangdong Provincial Key Laboratory of Diabetology, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China
- Guangzhou Municipal Key Laboratory of Mechanistic and Translational Obesity Research, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China
- Medical Center for Comprehensive Weight Control, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China
| | - Nan Cai
- Department of Endocrinology and Metabolism, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China
- Guangdong Provincial Key Laboratory of Diabetology, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China
- Guangzhou Municipal Key Laboratory of Mechanistic and Translational Obesity Research, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China
- Medical Center for Comprehensive Weight Control, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China
| | - Jia Liu
- Department of Endocrinology and Metabolism, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China
- Guangzhou Municipal Key Laboratory of Mechanistic and Translational Obesity Research, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China
- Medical Center for Comprehensive Weight Control, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China
| | - Kunying Liu
- Department of Endocrinology and Metabolism, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China
- Guangdong Provincial Key Laboratory of Diabetology, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China
| | - Shuo Lin
- Department of Endocrinology and Metabolism, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China.
- Guangdong Provincial Key Laboratory of Diabetology, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China.
- Guangzhou Municipal Key Laboratory of Mechanistic and Translational Obesity Research, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China.
- Medical Center for Comprehensive Weight Control, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China.
| | - Longyi Zeng
- Department of Endocrinology and Metabolism, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China.
- Guangdong Provincial Key Laboratory of Diabetology, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China.
- Guangzhou Municipal Key Laboratory of Mechanistic and Translational Obesity Research, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China.
- Medical Center for Comprehensive Weight Control, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, Guangdong, China.
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5
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Munika E, Gunawan S, Wuyung PE, Soetikno V. Beneficial Effects of 6-Gingerol on Fatty Pancreas Disease in High-Fat High-Fructose Diet-Induced Metabolic Syndrome Rat Model. Pancreas 2024; 53:e193-e198. [PMID: 38127814 DOI: 10.1097/mpa.0000000000002287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
OBJECTIVE To examine the effects of 6-gingerol (6-G) in overcoming fatty pancreas disease of high-fat high-fructose (HFHF) diet-induced metabolic syndrome in rats. MATERIALS AND METHODS Male Sprague-Dawley rats were randomly divided into 5 groups. The healthy-control group (normal diet, n = 5) received a standard diet. The HFHF group (HFHF; n = 20) received an HFHF diet and a single-dose intraperitoneal injection of streptozotocin (22 mg/kgBW) at week 8. Metabolic syndrome-confirmed rats received 6-G at doses of 50 (6-G 50, n = 5), 100 (6-G 100, n = 5), and 200 (6-G 200, n = 5) mg/kgBW, respectively, for 8 weeks. All rats were killed at week 16. Pancreatic tissue and blood samples were obtained for histological and amylase analysis. RESULTS The serum amylase, MDA, mRNA of TNF-α, and IL-6 significantly increased, whereas GPx decreased in the HFHF group as compared with the normal diet group, respectively. Rats in the HFHF group showed pancreatic lipid accumulation and a decreased mean number of α- and β-cells in the pancreas. Meanwhile, all rats in 6-G at all dose groups showed improvement in all parameters and histopathological scores for lipid accumulation. CONCLUSIONS 6-Gingerol could attenuate pancreatic lipid accumulation and improve the cell number of α- and β-cells in the pancreas, leading to improvements in fatty pancreas disease.
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Affiliation(s)
- Eka Munika
- From the Faculty of Medicine, Universitas Indonesia
| | - Shirly Gunawan
- Department of Pharmacology, Faculty of Medicine, Universitas Tarumanegara
| | | | - Vivian Soetikno
- Pharmacology and Therapeutics, Faculty of Medicine, Universitas Indonesia, Jakarta, Indonesia
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6
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Janikiewicz J, Dobosz AM, Majzner K, Bernas T, Dobrzyn A. Stearoyl-CoA desaturase 1 deficiency exacerbates palmitate-induced lipotoxicity by the formation of small lipid droplets in pancreatic β-cells. Biochim Biophys Acta Mol Basis Dis 2023; 1869:166711. [PMID: 37054998 DOI: 10.1016/j.bbadis.2023.166711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 03/28/2023] [Accepted: 03/30/2023] [Indexed: 04/15/2023]
Abstract
The accelerating accumulation of surplus lipids in the pancreas triggers structural and functional changes in type 2 diabetes-affected islets. Pancreatic β-cells exhibit a restricted capacity to store fat reservoirs in lipid droplets (LDs), which act as transient buffers to prevent lipotoxic stress. With the increasing incidence of obesity, growing interest has been seen in the intracellular regulation of LD metabolism for β-cell function. Stearoyl-CoA desaturase 1 (SCD1) is critical for producing unsaturated fatty acyl moieties for fluent storage into and out of LDs, likely affecting the overall rate of β-cell survival. We explored LD-associated composition and remodeling in SCD1-deprived INS-1E cells and in pancreatic islets in wildtype and SCD1-/- mice in the lipotoxic milieu. Deficiency in the enzymatic activity of SCD1 led to decrease in the size and number of LDs and the lower accumulation of neutral lipids. This occurred in parallel with a higher compactness and lipid order inside LDs, followed by changes in the saturation status and composition of fatty acids within core lipids and the phospholipid coat. The lipidome of LDs was enriched in 18:2n-6 and 20:4n-6 in β-cells and pancreatic islets. These rearrangements markedly contributed to differences in protein association with the LD surface. Our findings highlight an unexpected molecular mechanism by which SCD1 activity affects the morphology, composition and metabolism of LDs. We demonstrate that SCD1-dependent disturbances in LD enrichment can impact proper pancreatic β-cells and islet functioning, which may have considerable therapeutic value for the management of type 2 diabetes.
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Affiliation(s)
- Justyna Janikiewicz
- Laboratory of Cell Signaling and Metabolic Disorders, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland.
| | - Aneta M Dobosz
- Laboratory of Cell Signaling and Metabolic Disorders, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Katarzyna Majzner
- Faculty of Chemistry, Jagiellonian University, Cracow, Poland; Jagiellonian University, Jagiellonian Centre for Experimental Therapeutics (JCET), Cracow, Poland
| | - Tytus Bernas
- Department of Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine, Richmond, USA
| | - Agnieszka Dobrzyn
- Laboratory of Cell Signaling and Metabolic Disorders, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland.
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7
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Dobosz AM, Janikiewicz J, Krogulec E, Dziewulska A, Ajduk A, Szpila M, Nieznańska H, Szczepankiewicz AA, Wypych D, Dobrzyn A. Inhibition of stearoyl-CoA desaturase 1 in the mouse impairs pancreatic islet morphogenesis and promotes loss of β-cell identity and α-cell expansion in the mature pancreas. Mol Metab 2022; 67:101659. [PMID: 36529318 PMCID: PMC9801219 DOI: 10.1016/j.molmet.2022.101659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 12/02/2022] [Accepted: 12/10/2022] [Indexed: 12/23/2022] Open
Abstract
Abnormalities that characterize the pathophysiology of type 2 diabetes (T2D) include deficiencies of β-cells and the expansion of α-cells in pancreatic islets, manifested by lower insulin release and glucagon oversecretion. The molecular mechanisms that determine intra-islet interactions between pancreatic α- and β-cells are still not fully understood. The present study showed that stearoyl-coenzyme A (CoA) desaturase 1 (SCD1), an enzyme that is implicated in fatty acid metabolism, serves as a checkpoint in the control of endocrine cell equilibrium in pancreatic islets. Our data showed that SCD1 activity is essential for proper α-cell and β-cell lineage determination during morphogenesis of the pancreas and the maintenance of mature β-cell identity. The inhibition of SCD1 expression/activity led to both a decrease in the expression of β-cell signature genes (e.g., Pdx1, Nkx6.1, MafA, and Neurod1, among others) and induction of the expression of the dedifferentiation marker Sox9 in mature pancreatic islets. The transcriptional repression of Pdx1 and MafA in SCD1-deficient β-cells was related to the excessive methylation of promoter regions of these transcription factors. In contrast, SCD1 ablation favored the formation of α-cells over β-cells throughout pancreas organogenesis and did not compromise α-cell identity in adult pancreatic islets. Such molecular changes that were caused by SCD1 downregulation resulted in the mislocalization of α-cells within the core of islets and increased the ratio of pancreatic α- to β-cell mass. This was followed by islet dysfunction, including impairments in glucose-stimulated insulin release, simultaneously with elevations of basal glucagon secretion. Altogether, these findings provide additional mechanistic insights into the role of SCD1 in the pathogenesis of T2D.
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Affiliation(s)
- Aneta M. Dobosz
- Laboratory of Cell Signaling and Metabolic Disorders, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland,Corresponding author.
| | - Justyna Janikiewicz
- Laboratory of Cell Signaling and Metabolic Disorders, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland.
| | - Ewelina Krogulec
- Laboratory of Cell Signaling and Metabolic Disorders, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland.
| | - Anna Dziewulska
- Laboratory of Cell Signaling and Metabolic Disorders, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland.
| | - Anna Ajduk
- Department of Embryology, Institute of Developmental Biology and Biomedical Sciences, Faculty of Biology, University of Warsaw, Warsaw, Poland.
| | - Marcin Szpila
- Department of Embryology, Institute of Developmental Biology and Biomedical Sciences, Faculty of Biology, University of Warsaw, Warsaw, Poland.
| | - Hanna Nieznańska
- Laboratory of Electron Microscopy, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland.
| | - Andrzej A. Szczepankiewicz
- Laboratory of Electron Microscopy, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Dorota Wypych
- Laboratory of Cell Signaling and Metabolic Disorders, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland.
| | - Agnieszka Dobrzyn
- Laboratory of Cell Signaling and Metabolic Disorders, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland.
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8
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Lee S, Xu H, Van Vleck A, Mawla AM, Li AM, Ye J, Huising MO, Annes JP. β-Cell Succinate Dehydrogenase Deficiency Triggers Metabolic Dysfunction and Insulinopenic Diabetes. Diabetes 2022; 71:1439-1453. [PMID: 35472723 PMCID: PMC9233299 DOI: 10.2337/db21-0834] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 03/26/2022] [Indexed: 11/20/2022]
Abstract
Mitochondrial dysfunction plays a central role in type 2 diabetes (T2D); however, the pathogenic mechanisms in pancreatic β-cells are incompletely elucidated. Succinate dehydrogenase (SDH) is a key mitochondrial enzyme with dual functions in the tricarboxylic acid cycle and electron transport chain. Using samples from human with diabetes and a mouse model of β-cell-specific SDH ablation (SDHBβKO), we define SDH deficiency as a driver of mitochondrial dysfunction in β-cell failure and insulinopenic diabetes. β-Cell SDH deficiency impairs glucose-induced respiratory oxidative phosphorylation and mitochondrial membrane potential collapse, thereby compromising glucose-stimulated ATP production, insulin secretion, and β-cell growth. Mechanistically, metabolomic and transcriptomic studies reveal that the loss of SDH causes excess succinate accumulation, which inappropriately activates mammalian target of rapamycin (mTOR) complex 1-regulated metabolic anabolism, including increased SREBP-regulated lipid synthesis. These alterations, which mirror diabetes-associated human β-cell dysfunction, are partially reversed by acute mTOR inhibition with rapamycin. We propose SDH deficiency as a contributing mechanism to the progressive β-cell failure of diabetes and identify mTOR complex 1 inhibition as a potential mitigation strategy.
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Affiliation(s)
- Sooyeon Lee
- Division of Endocrinology, Department of Medicine, Stanford University, Stanford, CA
| | - Haixia Xu
- Division of Endocrinology, Department of Medicine, Stanford University, Stanford, CA
| | - Aidan Van Vleck
- Division of Endocrinology, Department of Medicine, Stanford University, Stanford, CA
| | - Alex M. Mawla
- Department of Neurobiology, Physiology and Behavior, College of Biological Sciences, University of California, Davis, Davis, CA
| | - Albert Mao Li
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA
- Cancer Biology Program, Stanford University School of Medicine, Stanford, CA
| | - Jiangbin Ye
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA
- Cancer Biology Program, Stanford University School of Medicine, Stanford, CA
| | - Mark O. Huising
- Department of Neurobiology, Physiology and Behavior, College of Biological Sciences, University of California, Davis, Davis, CA
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, Davis, CA
| | - Justin P. Annes
- Division of Endocrinology, Department of Medicine, Stanford University, Stanford, CA
- Stanford ChEM-H and Diabetes Research Center, Stanford University School of Medicine, Stanford, CA
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9
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Castell AL, Vivoli A, Tippetts TS, Frayne IR, Angeles ZE, Moullé VS, Campbell SA, Ruiz M, Ghislain J, Des Rosiers C, Holland WL, Summers SA, Poitout V. Very-Long-Chain Unsaturated Sphingolipids Mediate Oleate-Induced Rat β-Cell Proliferation. Diabetes 2022; 71:1218-1232. [PMID: 35287172 PMCID: PMC9163557 DOI: 10.2337/db21-0640] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 03/09/2022] [Indexed: 11/13/2022]
Abstract
Fatty acid (FA) signaling contributes to β-cell mass expansion in response to nutrient excess, but the underlying mechanisms are poorly understood. In the presence of elevated glucose, FA metabolism is shifted toward synthesis of complex lipids, including sphingolipids. Here, we tested the hypothesis that sphingolipids are involved in the β-cell proliferative response to FA. Isolated rat islets were exposed to FA and 16.7 mmol/L glucose for 48-72 h, and the contribution of the de novo sphingolipid synthesis pathway was tested using the serine palmitoyltransferase inhibitor myriocin, the sphingosine kinase (SphK) inhibitor SKI II, or knockdown of SphK, fatty acid elongase 1 (ELOVL1) and acyl-CoA-binding protein (ACBP). Rats were infused with glucose and the lipid emulsion ClinOleic and received SKI II by gavage. β-Cell proliferation was assessed by immunochemistry or flow cytometry. Sphingolipids were analyzed by liquid chromatography-tandem mass spectrometry. Among the FAs tested, only oleate increased β-cell proliferation. Myriocin, SKI II, and SphK knockdown all decreased oleate-induced β-cell proliferation. Oleate exposure did not increase the total amount of sphingolipids but led to a specific rise in 24:1 species. Knockdown of ACBP or ELOVL1 inhibited oleate-induced β-cell proliferation. We conclude that unsaturated very-long-chain sphingolipids produced from the available C24:1 acyl-CoA pool mediate oleate-induced β-cell proliferation in rats.
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Affiliation(s)
- Anne-Laure Castell
- Montreal Diabetes Research Center, CRCHUM, Montreal, Quebec, Canada
- Department of Medicine, Université de Montréal, Montreal, Quebec, Canada
| | - Alexis Vivoli
- Montreal Diabetes Research Center, CRCHUM, Montreal, Quebec, Canada
- Department of Medicine, Université de Montréal, Montreal, Quebec, Canada
| | - Trevor S. Tippetts
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT
| | | | - Zuraya Elisa Angeles
- Montreal Diabetes Research Center, CRCHUM, Montreal, Quebec, Canada
- Department of Medicine, Université de Montréal, Montreal, Quebec, Canada
| | - Valentine S. Moullé
- Montreal Diabetes Research Center, CRCHUM, Montreal, Quebec, Canada
- Department of Medicine, Université de Montréal, Montreal, Quebec, Canada
| | - Scott A. Campbell
- Montreal Diabetes Research Center, CRCHUM, Montreal, Quebec, Canada
- Department of Medicine, Université de Montréal, Montreal, Quebec, Canada
| | - Matthieu Ruiz
- Metabolomic Platform, Montreal Heart Institute Research Center, Montreal, Quebec, Canada
| | - Julien Ghislain
- Montreal Diabetes Research Center, CRCHUM, Montreal, Quebec, Canada
| | - Christine Des Rosiers
- Metabolomic Platform, Montreal Heart Institute Research Center, Montreal, Quebec, Canada
- Department of Nutrition, Université de Montréal, Montreal, Quebec, Canada
| | - William L. Holland
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT
| | - Scott A. Summers
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT
| | - Vincent Poitout
- Montreal Diabetes Research Center, CRCHUM, Montreal, Quebec, Canada
- Department of Medicine, Université de Montréal, Montreal, Quebec, Canada
- Corresponding author: Vincent Poitout,
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10
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Biondi G, Marrano N, Borrelli A, Rella M, Palma G, Calderoni I, Siciliano E, Lops P, Giorgino F, Natalicchio A. Adipose Tissue Secretion Pattern Influences β-Cell Wellness in the Transition from Obesity to Type 2 Diabetes. Int J Mol Sci 2022; 23:ijms23105522. [PMID: 35628332 PMCID: PMC9143684 DOI: 10.3390/ijms23105522] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 05/11/2022] [Accepted: 05/13/2022] [Indexed: 12/10/2022] Open
Abstract
The dysregulation of the β-cell functional mass, which is a reduction in the number of β-cells and their ability to secure adequate insulin secretion, represents a key mechanistic factor leading to the onset of type 2 diabetes (T2D). Obesity is recognised as a leading cause of β-cell loss and dysfunction and a risk factor for T2D. The natural history of β-cell failure in obesity-induced T2D can be divided into three steps: (1) β-cell compensatory hyperplasia and insulin hypersecretion, (2) insulin secretory dysfunction, and (3) loss of β-cell mass. Adipose tissue (AT) secretes many hormones/cytokines (adipokines) and fatty acids that can directly influence β-cell function and viability. As this secretory pattern is altered in obese and diabetic patients, it is expected that the cross-talk between AT and pancreatic β-cells could drive the maintenance of the β-cell integrity under physiological conditions and contribute to the reduction in the β-cell functional mass in a dysmetabolic state. In the current review, we summarise the evidence of the ability of the AT secretome to influence each step of β-cell failure, and attempt to draw a timeline of the alterations in the adipokine secretion pattern in the transition from obesity to T2D that reflects the progressive deterioration of the β-cell functional mass.
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11
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Differential routing and disposition of the long-chain saturated fatty acid palmitate in rodent vs human beta-cells. Nutr Diabetes 2022; 12:22. [PMID: 35443738 PMCID: PMC9021209 DOI: 10.1038/s41387-022-00199-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 03/15/2022] [Accepted: 03/28/2022] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND Rodent and human β-cells are differentially susceptible to the "lipotoxic" effects of long-chain saturated fatty acids (LC-SFA) but the factors accounting for this are unclear. Here, we have studied the intracellular disposition of the LC-SFA palmitate in human vs rodent β-cells and present data that reveal new insights into the factors regulating β-cell lipotoxicity. METHODS The subcellular distribution of the LC-SFA palmitate was studied in rodent (INS-1E and INS-1 823/13 cells) and human (EndoC-βH1) β-cells using confocal fluorescence and electron microscopy (EM). Protein expression was assessed by Western blotting and cell viability, by vital dye staining. RESULTS Exposure of INS-1 cells to palmitate for 24 h led to loss of viability, whereas EndoC-βH1 cells remained viable even after 72 h of treatment with a high concentration (1 mM) of palmitate. Use of the fluorescent palmitate analogue BODIPY FL C16 revealed an early localisation of the LC-SFA to the Golgi apparatus in INS-1 cells and this correlated with distention of intracellular membranes, visualised under the EM. Despite this, the PERK-dependent ER stress pathway was not activated under these conditions. By contrast, BODIPY FL C16 did not accumulate in the Golgi apparatus in EndoC-βH1 cells but, rather, co-localised with the lipid droplet-associated protein, PLIN2, suggesting preferential routing into lipid droplets. When INS-1 cells were treated with a combination of palmitate plus oleate, the toxic effects of palmitate were attenuated and BODIPY FL C16 localised primarily with PLIN2 but not with a Golgi marker. CONCLUSION In rodent β-cells, palmitate accumulates in the Golgi apparatus at early time points whereas, in EndoC- βH1 cells, it is routed preferentially into lipid droplets. This may account for the differential sensitivity of rodent vs human β-cells to "lipotoxicity" since manoeuvres leading to the incorporation of palmitate into lipid droplets is associated with the maintenance of cell viability in both cell types.
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12
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Tong X, Liu S, Stein R, Imai Y. Lipid Droplets' Role in the Regulation of β-Cell Function and β-Cell Demise in Type 2 Diabetes. Endocrinology 2022; 163:6516108. [PMID: 35086144 PMCID: PMC8826878 DOI: 10.1210/endocr/bqac007] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Indexed: 01/29/2023]
Abstract
During development of type 2 diabetes (T2D), excessive nutritional load is thought to expose pancreatic islets to toxic effects of lipids and reduce β-cell function and mass. However, lipids also play a positive role in cellular metabolism and function. Thus, proper trafficking of lipids is critical for β cells to maximize the beneficial effects of these molecules while preventing their toxic effects. Lipid droplets (LDs) are organelles that play an important role in the storage and trafficking of lipids. In this review, we summarize the discovery of LDs in pancreatic β cells, LD lifecycle, and the effect of LD catabolism on β-cell insulin secretion. We discuss factors affecting LD formation such as age, cell type, species, and nutrient availability. We then outline published studies targeting critical LD regulators, primarily in rat and human β-cell models, to understand the molecular effect of LD formation and degradation on β-cell function and health. Furthermore, based on the abnormal LD accumulation observed in human T2D islets, we discuss the possible role of LDs during the development of β-cell failure in T2D. Current knowledge indicates that proper formation and clearance of LDs are critical to normal insulin secretion, endoplasmic reticulum homeostasis, and mitochondrial integrity in β cells. However, it remains unclear whether LDs positively or negatively affect human β-cell demise in T2D. Thus, we discuss possible research directions to address the knowledge gap regarding the role of LDs in β-cell failure.
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Affiliation(s)
- Xin Tong
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee 37232, USA
| | - Siming Liu
- Department of Internal Medicine Carver College of Medicine, Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa 52242, USA
| | - Roland Stein
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee 37232, USA
| | - Yumi Imai
- Department of Internal Medicine Carver College of Medicine, Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa 52242, USA
- Iowa City Veterans Affairs Medical Center, Iowa City, Iowa 52246, USA
- Correspondence: Yumi Imai, MD, Department of Internal Medicine Carver College of Medicine, Fraternal Order of Eagles Diabetes Research Center, University of Iowa, 200 Hawkins Dr, PBDB Rm 3318, Iowa City, IA 52242, USA.
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13
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Aggarwal R, Peng Z, Zeng N, Silva J, He L, Chen J, Debebe A, Tu T, Alba M, Chen CY, Stiles EX, Hong H, Stiles BL. Chronic Exposure to Palmitic Acid Down-Regulates AKT in Beta-Cells through Activation of mTOR. THE AMERICAN JOURNAL OF PATHOLOGY 2022; 192:130-145. [PMID: 34619135 PMCID: PMC8759041 DOI: 10.1016/j.ajpath.2021.09.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 09/09/2021] [Accepted: 09/22/2021] [Indexed: 01/03/2023]
Abstract
High circulating lipids occurring in obese individuals and insulin-resistant patients are considered a contributing factor to type 2 diabetes. Exposure to high lipid concentration is proposed to both protect and damage beta-cells under different circumstances. Here, by feeding mice a high-fat diet (HFD) for 2 weeks to up to 14 months, the study showed that HFD initially causes the beta-cells to expand in population, whereas long-term exposure to HFD is associated with failure of beta-cells and the inability of animals to respond to glucose challenge. To prevent the failure of beta-cells and the development of type 2 diabetes, the molecular mechanisms that underlie this biphasic response of beta-cells to lipid exposure were explored. Using palmitic acid (PA) in cultured beta-cells and islets, the study demonstrated that chronic exposure to lipids leads to reduced viability and inhibition of cell cycle progression concurrent with down-regulation of a pro-growth/survival kinase AKT, independent of glucose. This AKT down-regulation by PA is correlated with the induction of mTOR/S6K activity. Inhibiting mTOR activity with rapamycin induced Raptor and restored AKT activity, allowing beta-cells to gain proliferation capacity that was lost after HFD exposure. In summary, a novel mechanism in which lipid exposure may cause the dipole effects on beta-cell growth was elucidated, where mTOR acts as a lipid sensor. These mechanisms can be novel targets for future therapeutic developments.
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Affiliation(s)
- Richa Aggarwal
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California
| | - Zhechu Peng
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California
| | - Ni Zeng
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California
| | - Joshua Silva
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California
| | - Lina He
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California
| | - Jingyu Chen
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California
| | - Anketse Debebe
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California
| | - Taojian Tu
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California
| | - Mario Alba
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California
| | - Chien-Yu Chen
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California
| | - Eileen X. Stiles
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California
| | - Handan Hong
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California
| | - Bangyan L. Stiles
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California,Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, California,Address correspondence to Bangyan L. Stiles, Ph.D., Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, CA 90033.
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14
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Horii T, Kozawa J, Fujita Y, Kawata S, Ozawa H, Ishibashi C, Yoneda S, Nammo T, Miyagawa JI, Eguchi H, Shimomura I. Lipid droplet accumulation in β cells in patients with type 2 diabetes is associated with insulin resistance, hyperglycemia and β cell dysfunction involving decreased insulin granules. Front Endocrinol (Lausanne) 2022; 13:996716. [PMID: 36204103 PMCID: PMC9530467 DOI: 10.3389/fendo.2022.996716] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 09/05/2022] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND OBJECTIVE Pancreatic fat is a form of ectopic fat. Lipid droplets (LDs) are also observed in β cells; however, the pathophysiological significance, especially for β cell function, has not been elucidated. Our aim was to assess LD accumulation in β cells in various stages of glucose intolerance and to clarify its relationship with clinical and histological parameters. METHODS We examined 42 Japanese patients who underwent pancreatectomy. The BODIPY493/503-positive (BODIPY-positive) area in β cells was measured in pancreatic sections from 32 patients. The insulin granule numbers were counted in an additional 10 patients using electron microscopy. RESULTS The BODIPY-positive area in β cells in preexisting type 2 diabetes patients was higher than that in normal glucose tolerance patients (p = 0.031). The BODIPY-positive area in β cells was positively correlated with age (r = 0.45, p = 0.0097), HbA1c (r = 0.38, p = 0.0302), fasting plasma glucose (r = 0.37, p = 0.045), and homeostasis model assessment insulin resistance (r = 0.41, p = 0.049) and negatively correlated with an increase in the C-peptide immunoreactivity level by the glucagon test (r = -0.59, p = 0.018). The ratio of mature insulin granule number to total insulin granule number was reduced in the patients with rich LD accumulation in β cells (p = 0.039). CONCLUSIONS Type 2 diabetes patients had high LD accumulation in β cells, which was associated with insulin resistance, hyperglycemia, aging and β cell dysfunction involving decreased mature insulin granules.
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Affiliation(s)
- Tomomi Horii
- Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Junji Kozawa
- Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
- Department of Diabetes Care Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
- *Correspondence: Junji Kozawa,
| | - Yukari Fujita
- Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
- Department of Community Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Satoshi Kawata
- Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Harutoshi Ozawa
- Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
- Department of Lifestyle Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Chisaki Ishibashi
- Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Sho Yoneda
- Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
- Yoneda Clinic, Osaka, Japan
| | - Takao Nammo
- Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
- Department of Diabetes Care Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
| | | | - Hidetoshi Eguchi
- Department of Gastroenterological Surgery, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Iichiro Shimomura
- Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Japan
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15
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Chan JY, Bensellam M, Lin RCY, Liang C, Lee K, Jonas JC, Laybutt DR. Transcriptome analysis of islets from diabetes-resistant and diabetes-prone obese mice reveals novel gene regulatory networks involved in beta-cell compensation and failure. FASEB J 2021; 35:e21608. [PMID: 33977593 DOI: 10.1096/fj.202100009r] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2021] [Revised: 03/23/2021] [Accepted: 04/05/2021] [Indexed: 01/02/2023]
Abstract
The mechanisms underpinning beta-cell compensation for obesity-associated insulin resistance and beta-cell failure in type 2 diabetes remain poorly understood. We used a large-scale strategy to determine the time-dependent transcriptomic changes in islets of diabetes-prone db/db and diabetes-resistant ob/ob mice at 6 and 16 weeks of age. Differentially expressed genes were subjected to cluster, gene ontology, pathway and gene set enrichment analyses. A distinctive gene expression pattern was observed in 16 week db/db islets in comparison to the other groups with alterations in transcriptional regulators of islet cell identity, upregulation of glucose/lipid metabolism, and various stress response genes, and downregulation of specific amino acid transport and metabolism genes. In contrast, ob/ob islets displayed a coordinated downregulation of metabolic and stress response genes at 6 weeks of age, suggestive of a preemptive reconfiguration in these islets to lower the threshold of metabolic activation in response to increased insulin demand thereby preserving beta-cell function and preventing cellular stress. In addition, amino acid transport and metabolism genes were upregulated in ob/ob islets, suggesting an important role of glutamate metabolism in beta-cell compensation. Gene set enrichment analysis of differentially expressed genes identified the enrichment of binding motifs for transcription factors, FOXO4, NFATC1, and MAZ. siRNA-mediated knockdown of these genes in MIN6 cells altered cell death, insulin secretion, and stress gene expression. In conclusion, these data revealed novel gene regulatory networks involved in beta-cell compensation and failure. Preemptive metabolic reconfiguration in diabetes-resistant islets may dampen metabolic activation and cellular stress during obesity.
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Affiliation(s)
- Jeng Yie Chan
- Garvan Institute of Medical Research, Sydney, NSW, Australia.,School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Mohammed Bensellam
- Garvan Institute of Medical Research, Sydney, NSW, Australia.,Pôle D'endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
| | - Ruby C Y Lin
- School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia.,Centre for Infectious Diseases and Microbiology, Westmead Institute for Medical Research, Sydney, NSW, Australia.,Sydney Medical School, The University of Sydney, Sydney, NSW, Australia
| | - Cassandra Liang
- Garvan Institute of Medical Research, Sydney, NSW, Australia
| | - Kailun Lee
- Garvan Institute of Medical Research, Sydney, NSW, Australia
| | - Jean-Christophe Jonas
- Pôle D'endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
| | - D Ross Laybutt
- Garvan Institute of Medical Research, Sydney, NSW, Australia.,School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
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16
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Kirilmaz OB, Salegaonkar AR, Shiau J, Uzun G, Ko HS, Lee HF, Park S, Kwon G. Study of blood glucose and insulin infusion rate in real-time in diabetic rats using an artificial pancreas system. PLoS One 2021; 16:e0254718. [PMID: 34270619 PMCID: PMC8284668 DOI: 10.1371/journal.pone.0254718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 07/01/2021] [Indexed: 11/19/2022] Open
Abstract
Artificial pancreas system (APS) is an emerging new treatment for type 1 diabetes mellitus. The aim of this study was to develop a rat APS as a research tool and demonstrate its application. We established a rat APS using Medtronic Minimed Pump 722, Medtronic Enlite sensor, and the open artificial pancreas system as a controller. We tested different dilutions of Humalog (100 units/ml) in saline ranged from 1:3 to 1:20 and determined that 1:7 dilution works well for rats with ~500g bodyweight. Blood glucose levels (BGL) of diabetic rats fed with chow diet (58% carbohydrate) whose BGL was managed by the closed-loop APS for the total duration of 207h were in euglycemic range (70-180 mg/dl) for 94.5% of the time with 2.1% and 3.4% for hyperglycemia (>180mg/dl) and hypoglycemia (<70 mg/dl), respectively. Diabetic rats fed with Sucrose pellets (94.8% carbohydrate) for the experimental duration of 175h were in euglycemic range for 61% of the time with 35% and 4% for hyperglycemia and hypoglycemia, respectively. Heathy rats fed with chow diet showed almost a straight line of BGL ~ 95 mg/dl (average 94.8 mg/dl) during the entire experimental period (281h), which was minimally altered by food intake. In the healthy rats, feeding sucrose pellets caused greater range of BGL in high and low levels but still within euglycemic range (99.9%). Next, to study how healthy and diabetic rats handle supra-physiological concentrations of glucose, we intraperitoneally injected various amounts of 50% dextrose (2, 3, 4g/kg) and monitored BGL. Duration of hyperglycemia after injection of 50% dextrose at all three different concentrations was significantly greater for healthy rats than diabetic rats, suggesting that insulin infusion by APS was superior in reducing BGL as compared to natural insulin released from pancreatic β-cells. Ex vivo studies showed that islets isolated from diabetic rats were almost completely devoid of pancreatic β-cells but with intact α-cells as expected. Lipid droplet deposition in the liver of diabetic rats was significantly lower with higher levels of triacylglyceride in the blood as compared to those of healthy rats, suggesting lipid metabolism was altered in diabetic rats. However, glycogen storage in the liver determined by Periodic acid-Schiff staining was not altered in diabetic rats as compared to healthy rats. A rat APS may be used as a powerful tool not only to study alterations of glucose and insulin homeostasis in real-time caused by diet, exercise, hormones, or antidiabetic agents, but also to test mathematical and engineering models of blood glucose prediction or new algorithms for closed-loop APS.
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MESH Headings
- Animals
- Blood Glucose/analysis
- Blood Glucose/drug effects
- Diabetes Mellitus, Experimental/blood
- Diabetes Mellitus, Experimental/chemically induced
- Diabetes Mellitus, Experimental/diagnosis
- Diabetes Mellitus, Experimental/therapy
- Diabetes Mellitus, Type 1/blood
- Diabetes Mellitus, Type 1/chemically induced
- Diabetes Mellitus, Type 1/diagnosis
- Diabetes Mellitus, Type 1/therapy
- Glycated Hemoglobin/analysis
- Humans
- Infusions, Intravenous/instrumentation
- Infusions, Intravenous/methods
- Insulin/administration & dosage
- Male
- Pancreas, Artificial
- Rats
- Streptozocin/administration & dosage
- Streptozocin/toxicity
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Affiliation(s)
- Omer Batuhan Kirilmaz
- School of Engineering, Southern Illinois University Edwardsville, Edwardsville, Illinois, United States of America
| | | | - Justin Shiau
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, Illinois, United States of America
| | - Guney Uzun
- School of Engineering, Southern Illinois University Edwardsville, Edwardsville, Illinois, United States of America
| | - Hoo Sang Ko
- School of Engineering, Southern Illinois University Edwardsville, Edwardsville, Illinois, United States of America
| | - H. Felix Lee
- School of Engineering, Southern Illinois University Edwardsville, Edwardsville, Illinois, United States of America
| | - Sarah Park
- Research and Instructional Services, Duke University, Durham, North Carolina, United States of America
| | - Guim Kwon
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, Illinois, United States of America
- * E-mail:
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17
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Mishra A, Liu S, Promes J, Harata M, Sivitz W, Fink B, Bhardwaj G, O'Neill BT, Kang C, Sah R, Strack S, Stephens S, King T, Jackson L, Greenberg AS, Anokye-Danso F, Ahima RS, Ankrum J, Imai Y. Perilipin 2 downregulation in β cells impairs insulin secretion under nutritional stress and damages mitochondria. JCI Insight 2021; 6:144341. [PMID: 33784258 PMCID: PMC8262280 DOI: 10.1172/jci.insight.144341] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 03/24/2021] [Indexed: 12/15/2022] Open
Abstract
Perilipin 2 (PLIN2) is a lipid droplet (LD) protein in β cells that increases under nutritional stress. Downregulation of PLIN2 is often sufficient to reduce LD accumulation. To determine whether PLIN2 positively or negatively affects β cell function under nutritional stress, PLIN2 was downregulated in mouse β cells, INS1 cells, and human islet cells. β Cell–specific deletion of PLIN2 in mice on a high-fat diet reduced glucose-stimulated insulin secretion (GSIS) in vivo and in vitro. Downregulation of PLIN2 in INS1 cells blunted GSIS after 24-hour incubation with 0.2 mM palmitic acid. Downregulation of PLIN2 in human pseudoislets cultured at 5.6 mM glucose impaired both phases of GSIS, indicating that PLIN2 is critical for GSIS. Downregulation of PLIN2 decreased specific OXPHOS proteins in all 3 models and reduced oxygen consumption rates in INS1 cells and mouse islets. Moreover, we found that PLIN2-deficient INS1 cells increased the distribution of a fluorescent oleic acid analog to mitochondria and showed signs of mitochondrial stress, as indicated by susceptibility to fragmentation and alterations of acyl-carnitines and glucose metabolites. Collectively, PLIN2 in β cells has an important role in preserving insulin secretion, β cell metabolism, and mitochondrial function under nutritional stress.
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Affiliation(s)
- Akansha Mishra
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA
| | - Siming Liu
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA
| | - Joseph Promes
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA
| | - Mikako Harata
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA
| | - William Sivitz
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA.,Iowa City Veterans Affairs Medical Center, Iowa City, Iowa, USA
| | - Brian Fink
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA.,Iowa City Veterans Affairs Medical Center, Iowa City, Iowa, USA
| | - Gourav Bhardwaj
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA
| | - Brian T O'Neill
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA.,Iowa City Veterans Affairs Medical Center, Iowa City, Iowa, USA
| | - Chen Kang
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Rajan Sah
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Stefan Strack
- Department of Neuroscience and Pharmacology, Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa, USA
| | - Samuel Stephens
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA
| | - Timothy King
- Department of Internal Medicine, Eastern Virginia Medical School, Norfolk, Virginia, USA
| | - Laura Jackson
- Department of Internal Medicine, Eastern Virginia Medical School, Norfolk, Virginia, USA
| | - Andrew S Greenberg
- Obesity and Metabolism Laboratory, Jean Mayer United States Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston, Massachusetts, USA
| | | | - Rexford S Ahima
- Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - James Ankrum
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA.,Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, Iowa, USA
| | - Yumi Imai
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, USA
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18
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Corezola do Amaral ME, Kravets V, Dwulet JM, Farnsworth NL, Piscopio R, Schleicher WE, Miranda JG, Benninger RKP. Caloric restriction recovers impaired β-cell-β-cell gap junction coupling, calcium oscillation coordination, and insulin secretion in prediabetic mice. Am J Physiol Endocrinol Metab 2020; 319:E709-E720. [PMID: 32830549 PMCID: PMC7750515 DOI: 10.1152/ajpendo.00132.2020] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 08/14/2020] [Accepted: 08/14/2020] [Indexed: 12/16/2022]
Abstract
Caloric restriction can decrease the incidence of metabolic diseases, such as obesity and Type 2 diabetes mellitus. The mechanisms underlying the benefits of caloric restriction involved in insulin secretion and glucose homeostasis are not fully understood. Intercellular communication within the islets of Langerhans, mediated by Connexin36 (Cx36) gap junctions, regulates insulin secretion dynamics and glucose homeostasis. The goal of this study was to determine whether caloric restriction can protect against decreases in Cx36 gap junction coupling and altered islet function induced in models of obesity and prediabetes. C57BL6 mice were fed with a high-fat diet (HFD), showing indications of prediabetes after 2 mo, including weight gain, insulin resistance, and elevated fasting glucose and insulin levels. Subsequently, mice were submitted to 1 mo of 40% caloric restriction (2 g/day of HFD). Mice under 40% caloric restriction showed reversal in weight gain and recovered insulin sensitivity, fasting glucose, and insulin levels. In islets of mice fed the HFD, caloric restriction protected against obesity-induced decreases in gap junction coupling and preserved glucose-stimulated calcium signaling, including Ca2+ oscillation coordination and oscillation amplitude. Caloric restriction also promoted a slight increase in glucose metabolism, as measured by increased NAD(P)H autofluorescence, as well as recovering glucose-stimulated insulin secretion. We conclude that declines in Cx36 gap junction coupling that occur in obesity can be completely recovered by caloric restriction and obesity reversal, improving Ca2+ dynamics and insulin secretion regulation. This suggests a critical role for caloric restriction in the context of obesity to prevent islet dysfunction.
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Affiliation(s)
| | - Vira Kravets
- Barbara Davis Center for Childhood Diabetes, University of Colorado Anschutz Medical Campus, Aurora, Denver, Colorado
- Department of Bioengineering, University of Colorado Anschutz Medical Campus, Aurora, Denver, Colorado
| | - JaeAnn M. Dwulet
- Department of Bioengineering, University of Colorado Anschutz Medical Campus, Aurora, Denver, Colorado
| | - Nikki L. Farnsworth
- Barbara Davis Center for Childhood Diabetes, University of Colorado Anschutz Medical Campus, Aurora, Denver, Colorado
| | - Robert Piscopio
- Department of Bioengineering, University of Colorado Anschutz Medical Campus, Aurora, Denver, Colorado
| | - Wolfgang E. Schleicher
- Department of Bioengineering, University of Colorado Anschutz Medical Campus, Aurora, Denver, Colorado
| | - Jose Guadalupe Miranda
- Department of Bioengineering, University of Colorado Anschutz Medical Campus, Aurora, Denver, Colorado
| | - Richard K. P. Benninger
- Barbara Davis Center for Childhood Diabetes, University of Colorado Anschutz Medical Campus, Aurora, Denver, Colorado
- Department of Bioengineering, University of Colorado Anschutz Medical Campus, Aurora, Denver, Colorado
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19
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Liu S, Promes JA, Harata M, Mishra A, Stephens SB, Taylor EB, Burand AJ, Sivitz WI, Fink BD, Ankrum JA, Imai Y. Adipose Triglyceride Lipase Is a Key Lipase for the Mobilization of Lipid Droplets in Human β-Cells and Critical for the Maintenance of Syntaxin 1a Levels in β-Cells. Diabetes 2020; 69:1178-1192. [PMID: 32312867 PMCID: PMC7243295 DOI: 10.2337/db19-0951] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Accepted: 02/28/2020] [Indexed: 12/11/2022]
Abstract
Lipid droplets (LDs) are frequently increased when excessive lipid accumulation leads to cellular dysfunction. Distinct from mouse β-cells, LDs are prominent in human β-cells. However, the regulation of LD mobilization (lipolysis) in human β-cells remains unclear. We found that glucose increases lipolysis in nondiabetic human islets but not in islets in patients with type 2 diabetes (T2D), indicating dysregulation of lipolysis in T2D islets. Silencing adipose triglyceride lipase (ATGL) in human pseudoislets with shRNA targeting ATGL (shATGL) increased triglycerides (TGs) and the number and size of LDs, indicating that ATGL is the principal lipase in human β-cells. In shATGL pseudoislets, biphasic glucose-stimulated insulin secretion (GSIS), and insulin secretion to 3-isobutyl-1-methylxanthine and KCl were all reduced without altering oxygen consumption rate compared with scramble control. Like human islets, INS1 cells showed visible LDs, glucose-responsive lipolysis, and impairment of GSIS after ATGL silencing. ATGL-deficient INS1 cells and human pseudoislets showed reduced SNARE protein syntaxin 1a (STX1A), a key SNARE component. Proteasomal degradation of Stx1a was accelerated likely through reduced palmitoylation in ATGL-deficient INS1 cells. Therefore, ATGL is responsible for LD mobilization in human β-cells and supports insulin secretion by stabilizing STX1A. The dysregulated lipolysis may contribute to LD accumulation and β-cell dysfunction in T2D islets.
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Affiliation(s)
- Siming Liu
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
| | - Joseph A Promes
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
| | - Mikako Harata
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
| | - Akansha Mishra
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
| | - Samuel B Stephens
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
| | - Eric B Taylor
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
| | - Anthony J Burand
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA
| | - William I Sivitz
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
| | - Brian D Fink
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
| | - James A Ankrum
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
- Roy J. Carver Department of Biomedical Engineering, University of Iowa, Iowa City, IA
| | - Yumi Imai
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA
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20
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Tremmel DM, Feeney AK, Mitchell SA, Chlebeck PJ, Raglin S, Fernandez LA, Odorico JS, Sackett SD. Hypertension, but not body mass index, is predictive of increased pancreatic lipid content and islet dysfunction. Am J Transplant 2020; 20:1105-1115. [PMID: 31715064 PMCID: PMC7103563 DOI: 10.1111/ajt.15698] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 10/15/2019] [Accepted: 11/04/2019] [Indexed: 01/25/2023]
Abstract
Pancreatic steatosis is thought to be a negative risk factor for pancreas transplant outcomes. Despite considering donor body mass index (BMI) and the visualization of intercalated fat as indicators of donor pancreas lipid content, transplant surgeons do not use a quantitative method to directly measure steatosis when deciding to transplant a pancreas. In this study, we used nondiabetic human pancreata donated for research to measure the pancreatic and islet-specific lipid content to determine which clinical markers correlate best with lipid content. Interestingly, we found that BMI and age correlate with increased pancreatic lipid content (Panc-LC) in men, but not women. Our findings further suggest that total Panc-LC correlates with an increase in islet lipid content for both men and women. We noted that pancreata donated from individuals with a history of hypertension have increased Panc-LC independent of donor BMI or sex. Moreover, we identify hypertension as a risk factor for reduced islet function after islet isolation. Together, our findings emphasize differences in pancreas graft quality related to pancreatic and islet lipid content, which may not be predicted by assessing BMI alone but may be influenced by a donor history of hypertension.
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Affiliation(s)
- Daniel M. Tremmel
- Division of Transplantation, Department of Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, 53705, USA.,Co-first authors
| | - Austin K. Feeney
- Division of Transplantation, Department of Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, 53705, USA.,Co-first authors
| | - Samantha A. Mitchell
- Division of Transplantation, Department of Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, 53705, USA
| | - Peter J. Chlebeck
- Division of Transplantation, Department of Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, 53705, USA
| | - Sierra Raglin
- Division of Transplantation, Department of Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, 53705, USA
| | - Luis A. Fernandez
- Division of Transplantation, Department of Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, 53705, USA
| | - Jon S. Odorico
- Division of Transplantation, Department of Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, 53705, USA
| | - Sara D. Sackett
- Division of Transplantation, Department of Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, 53705, USA
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21
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Tong X, Dai C, Walker JT, Nair GG, Kennedy A, Carr RM, Hebrok M, Powers AC, Stein R. Lipid Droplet Accumulation in Human Pancreatic Islets Is Dependent On Both Donor Age and Health. Diabetes 2020; 69:342-354. [PMID: 31836690 PMCID: PMC7034188 DOI: 10.2337/db19-0281] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 12/08/2019] [Indexed: 12/13/2022]
Abstract
Human but not mouse islets transplanted into immunodeficient NSG mice effectively accumulate lipid droplets (LDs). Because chronic lipid exposure is associated with islet β-cell dysfunction, we investigated LD accumulation in the intact human and mouse pancreas over a range of ages and states of diabetes. Very few LDs were found in normal human juvenile pancreatic acinar and islet cells, with numbers subsequently increasing throughout adulthood. While accumulation appeared evenly distributed in postjuvenile acinar and islet cells in donors without diabetes, LDs were enriched in islet α- and β-cells from donors with type 2 diabetes (T2D). LDs were also found in the islet β-like cells produced from human embryonic cell-derived β-cell clusters. In contrast, LD accumulation was nearly undetectable in the adult rodent pancreas, even in hyperglycemic and hyperlipidemic models or 1.5-year-old mice. Taken together, there appear to be significant differences in pancreas islet cell lipid handling between species, and the human juvenile and adult cell populations. Moreover, our results suggest that LD enrichment could be impactful to T2D islet cell function.
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Affiliation(s)
- Xin Tong
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN
| | - Chunhua Dai
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt, University Medical Center, Nashville, TN
| | - John T Walker
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN
| | - Gopika G Nair
- Diabetes Center, Department of Medicine, University of California, San Francisco, San Francisco, CA
| | - Arion Kennedy
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC
| | - Rotonya M Carr
- Division of Gastroenterology, Department of Medicine, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA
| | - Matthias Hebrok
- Diabetes Center, Department of Medicine, University of California, San Francisco, San Francisco, CA
| | - Alvin C Powers
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt, University Medical Center, Nashville, TN
- Department of Veterans Affairs, Tennessee Valley Healthcare System, Nashville, TN
| | - Roland Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN
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22
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Esmaeili Mohsen Abadi S, Balouchzadeh R, Uzun G, Ko HS, Lee HF, Park S, Kwon G. Tracking changes of the parameters of glucose-insulin homeostasis during the course of obesity in B6D2F1 mice. Heliyon 2020; 6:e03251. [PMID: 32042976 PMCID: PMC7002827 DOI: 10.1016/j.heliyon.2020.e03251] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 10/25/2019] [Accepted: 01/14/2020] [Indexed: 12/12/2022] Open
Abstract
Obesity is one of the primary causes of type 2 diabetes mellitus (T2DM). To better understand how obesity impairs glucose-insulin homeostasis, we tracked fasting blood glucose and insulin levels and the key components of glucose-insulin homeostasis for 7 months in high fat diet (HFD; 45% fat) fed mice (n = 8). Every 2 weeks we measured body weight, fasting blood glucose and insulin levels, and estimated 5 key rate constants of glucose-insulin homeostasis using the methods established previously (Heliyon 3: e00310, 2017). Mice gained weight steadily, more than doubling their weights after 7 months (23.6 ± 0.5 to 52.3 ± 1.4 g). Fasting (basal) insulin levels were elevated (221.3 ± 16.7 to 1043.1 ± 90.5 pmol l-1) but fasting blood glucose levels unexpectedly returned to the baseline levels (152.8 ± 7.0 to 152.0 ± 7.2 mg/dl) despite significantly elevated levels (216.8 ± 44.9 mg/dl, average of 3 highest values for 8 mice) during the experimental period. After 7 months of HFD feeding, the rate constants for insulin secretion (k1), insulin-independent glucose uptake (k3), and insulin concentration where liver switches from glucose uptake to release (Ipi) were significantly elevated. Insulin-dependent glucose uptake (k2) and rate constant of liver glucose transfer (k4) were lowered but no statistical significance was reached. The novel and key finding of this study is the wide range of fluctuations of the rate constants during the course of obesity, reflecting the body's compensatory responses against metabolic alterations caused by obesity.
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Affiliation(s)
| | - Ramin Balouchzadeh
- School of Engineering, Southern Illinois University Edwardsville, Edwardsville, IL, 62026, United States
| | - Guney Uzun
- School of Engineering, Southern Illinois University Edwardsville, Edwardsville, IL, 62026, United States
| | - Hoo Sang Ko
- School of Engineering, Southern Illinois University Edwardsville, Edwardsville, IL, 62026, United States
| | - H Felix Lee
- School of Engineering, Southern Illinois University Edwardsville, Edwardsville, IL, 62026, United States
| | - Sarah Park
- Library and Information Services, Southern Illinois University Edwardsville, Edwardsville, IL, 62026, United States
| | - Guim Kwon
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL, 62026, United States
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23
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Esch N, Jo S, Moore M, Alejandro EU. Nutrient Sensor mTOR and OGT: Orchestrators of Organelle Homeostasis in Pancreatic β-Cells. J Diabetes Res 2020; 2020:8872639. [PMID: 33457426 PMCID: PMC7787834 DOI: 10.1155/2020/8872639] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 11/06/2020] [Accepted: 11/24/2020] [Indexed: 02/08/2023] Open
Abstract
The purpose of this review is to integrate the role of nutrient-sensing pathways into β-cell organelle dysfunction prompted by nutrient excess during type 2 diabetes (T2D). T2D encompasses chronic hyperglycemia, hyperlipidemia, and inflammation, which each contribute to β-cell failure. These factors can disrupt the function of critical β-cell organelles, namely, the ER, mitochondria, lysosomes, and autophagosomes. Dysfunctional organelles cause defects in insulin synthesis and secretion and activate apoptotic pathways if homeostasis is not restored. In this review, we will focus on mTORC1 and OGT, two major anabolic nutrient sensors with important roles in β-cell physiology. Though acute stimulation of these sensors frequently improves β-cell function and promotes adaptation to cell stress, chronic and sustained activity disturbs organelle homeostasis. mTORC1 and OGT regulate organelle function by influencing the expression and activities of key proteins, enzymes, and transcription factors, as well as by modulating autophagy to influence clearance of defective organelles. In addition, mTORC1 and OGT activity influence islet inflammation during T2D, which can further disrupt organelle and β-cell function. Therapies for T2D that fine-tune the activity of these nutrient sensors have yet to be developed, but the important role of mTORC1 and OGT in organelle homeostasis makes them promising targets to improve β-cell function and survival.
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Affiliation(s)
- Nicholas Esch
- Department of Integrative Biology & Physiology, University of Minnesota Medical School, University of Minnesota, Minneapolis, Minnesota, USA
| | - Seokwon Jo
- Department of Integrative Biology & Physiology, University of Minnesota Medical School, University of Minnesota, Minneapolis, Minnesota, USA
| | - Mackenzie Moore
- Department of Integrative Biology & Physiology, University of Minnesota Medical School, University of Minnesota, Minneapolis, Minnesota, USA
- Department of Surgery, University of Minnesota Medical School, University of Minnesota, Minneapolis, Minnesota, USA
| | - Emilyn U. Alejandro
- Department of Integrative Biology & Physiology, University of Minnesota Medical School, University of Minnesota, Minneapolis, Minnesota, USA
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24
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Protective effects of Clec11a in islets against lipotoxicity via modulation of proliferation and lipid metabolism in mice. Exp Cell Res 2019; 384:111613. [PMID: 31494095 DOI: 10.1016/j.yexcr.2019.111613] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Revised: 08/29/2019] [Accepted: 09/04/2019] [Indexed: 01/12/2023]
Abstract
The lipotoxicity is considered as one of the risk for diabetes. Here we report C-type lectin domain family 11, member A (Clec11a) as a new regulator in islet playing a protective role in lipotoxicity induced dysfunction. Islet transcriptome sequencing was performed using the high-fat diet induced obesity (DIO) mice model. We found a significant decrease of Clec11a expression in islets of DIO mice compared to normal control mice, which was further confirmed by real-time PCR. Immunostaining demonstrated the localization of the Clec11a protein in mouse islets. Administration of recombinant human Clec11a (rClec11a) protein promoted the proliferation of islet cells and rescued the inhibition of fatty acid on cell proliferation, which involved the activation of Erk signaling pathway. We also found that the rClec11a altered the expression of genes involved in lipid metabolism.
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25
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Wang C, Liu Z, Zhang P, Ma X, Che K, Wang Y. The differences in homeostasis model assessment values in type 2 diabetic patients with different lengths of history of diabetes. ARCHIVES OF ENDOCRINOLOGY AND METABOLISM 2019; 63:222-227. [PMID: 31066759 PMCID: PMC10522207 DOI: 10.20945/2359-3997000000134] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 03/17/2019] [Indexed: 11/23/2022]
Abstract
OBJECTIVE Type 2 diabetes (T2DM) is characterized by the progressive deterioration of pancreatic islet β-cell function over time and insulin resistance. Knowing more about the differences in pancreatic islet function in T2DM patients who have had diabetes for different lengths of time can help improve therapy for T2DM. SUBJECTS AND METHODS We conducted a cross-sectional study to compare islet β-cell function and insulin resistance in T2DM patients (n = 3,254) who had had diabetes for different lengths of time and those in normal controls (n = 794) using ANOVA and LSD analysis. RESULTS We found that compared with that in normal controls, HOMA-β in T2DM patients with a history of diabetes of less than 1 year was lower (approximately 52% of that of normal controls, p = 0.003), while HOMA-IR in these patients was higher (approximately 50% of that of normal controls, p = 0.007). Compared with that in other diabetic patients, HOMA-β in patients with a history of diabetes of more than 30 years was the lowest. HOMA-IR in patients with a history of diabetes of between 20 and 30 years was lower than that in other diabetic patients (p < 0.05). CONCLUSIONS There were obvious decreases in HOMA-β and increases in HOMA-IR in T2DM patients with a history of diabetes of less than 1 year compared with those in normal controls. Therefore, early screening and intervention for T2DM might help improve islet function and delay the progression of diabetes.
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Affiliation(s)
- Chen Wang
- Endocrinology DepartmentThe Affiliated Hospital of Qingdao UniversityQingdaoShandongChinaEndocrinology Department, The Affiliated Hospital of Qingdao University, Qingdao, Shandong, China
| | - Zaibo Liu
- Department of General SurgeryPeople’s Hospital of HaiyangYantaiShandongChinaDepartment of General Surgery, People’s Hospital of Haiyang, Yantai, Shandong, China
| | - Peng Zhang
- Department of Gastroenterology,The Affiliated Hospital of Qingdao UniversityQingdaoShandongChinaDepartment of Gastroenterology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong, China
| | - Xiaolong Ma
- Endocrinology DepartmentThe Affiliated Hospital of Qingdao UniversityQingdaoShandongChinaEndocrinology Department, The Affiliated Hospital of Qingdao University, Qingdao, Shandong, China
| | - Kui Che
- Laboratory of Thyroid DiseaseThe Affiliated Hospital of Qingdao UniversityQingdaoShandongChinaLaboratory of Thyroid Disease, The Affiliated Hospital of Qingdao University, Qingdao, Shandong, China
| | - Yangang Wang
- Endocrinology DepartmentThe Affiliated Hospital of Qingdao UniversityQingdaoShandongChinaEndocrinology Department, The Affiliated Hospital of Qingdao University, Qingdao, Shandong, China
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26
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Imai Y, Cousins RS, Liu S, Phelps BM, Promes JA. Connecting pancreatic islet lipid metabolism with insulin secretion and the development of type 2 diabetes. Ann N Y Acad Sci 2019; 1461:53-72. [PMID: 30937918 DOI: 10.1111/nyas.14037] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 01/24/2019] [Accepted: 01/30/2019] [Indexed: 02/06/2023]
Abstract
Obesity is the major contributing factor for the increased prevalence of type 2 diabetes (T2D) in recent years. Sustained positive influx of lipids is considered to be a precipitating factor for beta cell dysfunction and serves as a connection between obesity and T2D. Importantly, fatty acids (FA), a key building block of lipids, are a double-edged sword for beta cells. FA acutely increase glucose-stimulated insulin secretion through cell-surface receptor and intracellular pathways. However, chronic exposure to FA, combined with elevated glucose, impair the viability and function of beta cells in vitro and in animal models of obesity (glucolipotoxicity), providing an experimental basis for the propensity of beta cell demise under obesity in humans. To better understand the two-sided relationship between lipids and beta cells, we present a current view of acute and chronic handling of lipids by beta cells and implications for beta cell function and health. We also discuss an emerging role for lipid droplets (LD) in the dynamic regulation of lipid metabolism in beta cells and insulin secretion, along with a potential role for LD under nutritional stress in beta cells, and incorporate recent advancement in the field of lipid droplet biology.
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Affiliation(s)
- Yumi Imai
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa
| | - Ryan S Cousins
- Department of Internal Medicine, Eastern Virginia Medical School, Norfolk, Virginia
| | - Siming Liu
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa
| | - Brian M Phelps
- Department of Internal Medicine, Eastern Virginia Medical School, Norfolk, Virginia
| | - Joseph A Promes
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa
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27
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Ji J, Petropavlovskaia M, Khatchadourian A, Patapas J, Makhlin J, Rosenberg L, Maysinger D. Type 2 diabetes is associated with suppression of autophagy and lipid accumulation in β-cells. J Cell Mol Med 2019; 23:2890-2900. [PMID: 30710421 PMCID: PMC6433726 DOI: 10.1111/jcmm.14172] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 12/14/2018] [Accepted: 12/29/2018] [Indexed: 01/05/2023] Open
Abstract
Both type 2 diabetes (T2D) and obesity are characterized by excessive hyperlipidaemia and subsequent lipid droplet (LD) accumulation in adipose tissue. To investigate whether LDs also accumulate in β-cells of T2D patients, we assessed the expression of PLIN2, a LD-associated protein, in non-diabetic (ND) and T2D pancreata. We observed an up-regulation of PLIN2 mRNA and protein in β-cells of T2D patients, along with significant changes in the expression of lipid metabolism, apoptosis and oxidative stress genes. The increased LD buildup in T2D β-cells was accompanied by inhibition of nuclear translocation of TFEB, a master regulator of autophagy and by down-regulation of lysosomal biomarker LAMP2. To investigate whether LD accumulation and autophagy were influenced by diabetic conditions, we used rat INS-1 cells to model the effects of hyperglycaemia and hyperlipidaemia on autophagy and metabolic gene expression. Consistent with human tissue, both LD formation and PLIN2 expression were enhanced in INS-1 cells under hyperglycaemia, whereas TFEB activation and autophagy gene expression were significantly reduced. Collectively, these results suggest that lipid clearance and overall homeostasis is markedly disrupted in β-cells under hyperglycaemic conditions and interventions ameliorating lipid clearance could be beneficial in reducing functional impairments in islets caused by glucolipotoxicity.
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Affiliation(s)
- Jeff Ji
- Department of Pharmacology and Therapeutics, McGill University, Montreal, QC, Canada
| | | | - Armen Khatchadourian
- Department of Pharmacology and Therapeutics, McGill University, Montreal, QC, Canada
| | - Jason Patapas
- Department of Surgery, McGill University, Montreal, QC, Canada
| | - Julia Makhlin
- Department of Surgery, McGill University, Montreal, QC, Canada
| | | | - Dusica Maysinger
- Department of Pharmacology and Therapeutics, McGill University, Montreal, QC, Canada
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28
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Liang H, Nie J, Van Skike CE, Valentine JM, Orr ME. Mammalian Target of Rapamycin at the Crossroad Between Alzheimer's Disease and Diabetes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1128:185-225. [PMID: 31062331 DOI: 10.1007/978-981-13-3540-2_10] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Accumulating evidence suggests that Alzheimer's disease may manifest as a metabolic disorder with pathology and/or dysfunction in numerous tissues. Adults with Alzheimer's disease suffer with significantly more comorbidities than demographically matched Medicare beneficiaries (Zhao et al, BMC Health Serv Res 8:108, 2008b). Reciprocally, comorbid health conditions increase the risk of developing Alzheimer's disease (Haaksma et al, PLoS One 12(5):e0177044, 2017). Type 2 diabetes mellitus is especially notable as the disease shares many overlapping pathologies observed in patients with Alzheimer's disease, including hyperglycemia, hyperinsulinemia, insulin resistance, glucose intolerance, dyslipidemia, inflammation, and cognitive dysfunction, as described in Chap. 8 of this book (Yoshitake et al, Neurology 45(6):1161-1168, 1995; Leibson et al, Am J Epidemiol 145(4):301-308, 1997; Ott et al, Neurology 53(9):1937-1942, 1999; Voisin et al, Rev Med Interne 24(Suppl 3):288s-291s, 2003; Janson et al. Diabetes 53(2):474-481, 2004; Ristow M, J Mol Med (Berl) 82(8):510-529, 2004; Whitmer et al, BMJ 330(7504):1360, 2005, Curr Alzheimer Res 4(2):103-109, 2007; Ohara et al, Neurology 77(12):1126-1134, 2011). Although nondiabetic older adults also experience age-related cognitive decline, diabetes is uniquely associated with a twofold increased risk of Alzheimer's disease, as described in Chap. 2 of this book (Yoshitake et al, Neurology 45(6):1161-1168, 1995; Leibson et al, Am J Epidemiol 145(4):301-308, 1997; Ott et al. Neurology 53(9):1937-1942, 1999; Ohara et al, Neurology 77(12):1126-1134, 2011). Good glycemic control has been shown to improve cognitive status (Cukierman-et al, Diabetes Care 32(2):221-226, 2009), and the use of insulin sensitizers is correlated with a lower rate of cognitive decline in older adults (Morris JK, Burns JM, Curr Neurol Neurosci Rep 12(5):520-527, 2012). At the molecular level, the mechanistic/mammalian target of rapamycin (mTOR) plays a key role in maintaining energy homeostasis. Nutrient availability and cellular stress information, both extracellular and intracellular, are integrated and transduced through mTOR signaling pathways. Aberrant regulation of mTOR occurs in the brains of patients with Alzheimer's disease and in numerous tissues of individuals with type 2 diabetes (Mannaa et al, J Mol Med (Berl) 91(10):1167-1175, 2013). Moreover, modulating mTOR activity with a pharmacological inhibitor, rapamycin, provides wide-ranging health benefits, including healthy life span extension in numerous model organisms (Vellai et al, Nature 426(6967):620, 2003; Jia et al, Development 131(16):3897-3906, 2004; Kapahi et al, Curr Biol 14(10):885-890, 2004; Kaeberlein et al, Science 310(5751):1193-1196, 2005; Powers et al, Genes Dev 20(2):174-184, 2006; Harrison et al, Nature 460(7253):392-395, 2009; Selman et al, Science 326(5949):140-144, 2009; Sharp ZD, Strong R, J Gerontol A Biol Sci Med Sci 65(6):580-589, 2010), which underscores its importance to overall organismal health and longevity. In this chapter, we discuss the physiological role of mTOR signaling and the consequences of mTOR dysregulation in the brain and peripheral tissues, with emphasis on its relevance to the development of Alzheimer's disease and link to type 2 diabetes.
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Affiliation(s)
- Hanyu Liang
- Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Jia Nie
- Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Candice E Van Skike
- Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Joseph M Valentine
- Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Miranda E Orr
- Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
- San Antonio Geriatric Research, Education and Clinical Center, South Texas Veterans Health Care System, San Antonio, TX, USA.
- Glenn Biggs Institute for Alzheimer's & Neurodegenerative Diseases, San Antonio, TX, USA.
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Ardestani A, Lupse B, Kido Y, Leibowitz G, Maedler K. mTORC1 Signaling: A Double-Edged Sword in Diabetic β Cells. Cell Metab 2018; 27:314-331. [PMID: 29275961 DOI: 10.1016/j.cmet.2017.11.004] [Citation(s) in RCA: 122] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 10/11/2017] [Accepted: 11/15/2017] [Indexed: 12/21/2022]
Abstract
The mechanistic target of rapamycin complex 1 (mTORC1) is a central regulator of metabolic and nutrient cues that integrates environmental inputs into downstream signaling pathways to control cellular metabolism, growth, and survival. While numerous in vitro and in vivo studies reported the positive functions of mTORC1 in the regulation of β cell survival and proliferation under physiological conditions, more recent work demonstrates the opposite in the long term; this is exemplified by the constitutive inappropriate hyper-activation of mTORC1 in diabetic islets or β cells under conditions of increased β cell stress and metabolic demands. These recent findings uncover mTORC1's importance as an emerging significant player in the development and progression of β cell failure in type 2 diabetes and suggest that mTORC1 may act as a "double edge sword" in the regulation of β cell mass and function in response to metabolic stress such as nutrient overload and insulin resistance.
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Affiliation(s)
- Amin Ardestani
- University of Bremen, Centre for Biomolecular Interactions Bremen, Bremen 28359, Germany.
| | - Blaz Lupse
- University of Bremen, Centre for Biomolecular Interactions Bremen, Bremen 28359, Germany
| | - Yoshiaki Kido
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan; Division of Metabolism and Disease, Department of Biophysics, Kobe University Graduate School of Health Sciences, Kobe 654-0142, Japan
| | - Gil Leibowitz
- Endocrinology and Metabolism Service and the Hadassah Diabetes Unit, Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem 91120, Israel
| | - Kathrin Maedler
- University of Bremen, Centre for Biomolecular Interactions Bremen, Bremen 28359, Germany.
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Khan S, Kowluru A. CD36 mediates lipid accumulation in pancreatic beta cells under the duress of glucolipotoxic conditions: Novel roles of lysine deacetylases. Biochem Biophys Res Commun 2017; 495:2221-2226. [PMID: 29274335 DOI: 10.1016/j.bbrc.2017.12.111] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 12/19/2017] [Indexed: 12/13/2022]
Abstract
The cluster of differentiation 36 (CD36) is implicated in the intake of long-chain fatty acids and fat storage in various cell types including the pancreatic beta cell, thus contributing to the pathogenesis of metabolic stress and diabetes. Recent evidence indicates that CD36 undergoes post-translational modifications such as acetylation-deacetylation. However, putative roles of such modifications in its functional activation and onset of beta cell dysregulation under the duress of glucolipotoxicity (GLT) remain largely unknown. Using pharmacological approaches, we validated, herein, the hypothesis that acetylation-deacetylation signaling steps are involved in CD36-mediated lipid accumulation and downstream apoptotic signaling in pancreatic beta (INS-1832/13) cells under GLT. Exposure of these cells to GLT resulted in significant lipid accumulation without affecting the CD36 expression. Sulfo-n-succinimidyl oleate (SSO), an irreversible inhibitor of CD36, significantly attenuated lipid accumulation under GLT conditions, thus implicating CD36 in this metabolic step. Furthermore, trichostatin A (TSA) or valproic acid (VPA), known inhibitors of lysine deacetylases, markedly suppressed GLT-associated lipid accumulation with no discernible effects on CD36 expression. Lastly, SSO or TSA prevented caspase 3 activation in INS-1832/13 cells exposed to GLT conditions. Based on these findings, we conclude that an acetylation-deacetylation signaling step might regulate CD36 functional activity and subsequent lipid accumulation and caspase 3 activation in pancreatic beta cells exposed to GLT conditions. Identification of specific lysine deacetylases that control CD36 function should provide novel clues for the prevention of beta-cell dysfunction under GLT.
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Affiliation(s)
- Sabbir Khan
- β-Cell Biochemistry Laboratory, John D. Dingell VA Medical Center, and Department of Pharmaceutical Sciences, Wayne State University, Detroit, MI, 48201, USA
| | - Anjaneyulu Kowluru
- β-Cell Biochemistry Laboratory, John D. Dingell VA Medical Center, and Department of Pharmaceutical Sciences, Wayne State University, Detroit, MI, 48201, USA.
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31
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Dave T, Tilles AW, Vemula M. A Cell-Based Assay to Investigate Hypolipidemic Effects of Nonalcoholic Fatty Liver Disease Therapeutics. SLAS DISCOVERY 2017; 23:274-282. [PMID: 29132235 DOI: 10.1177/2472555217741077] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
In the recent past, there has been a growing interest in developing nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) therapeutics. As a result, a need for in vitro cell models of human hepatic steatosis and high-throughput assays to measure intracellular lipid levels has arisen. To address this growing need, we optimized the conditions based on the current literature to fatten HepG2 hepatocytes by adding a mixture of saturated and unsaturated fatty acids (oleate/palmitate, 2:1 molar ratio) without inducing any overt cytotoxicity. Our results indicate that hepatocytes fatten in a concentration- (0.75-1.5 mM of fatty acids) and time-dependent manner, with a substantial increase in intracellular lipid levels seen within 6 h. Additionally, a method to quantify lipid levels in cells using a fluorescent reagent that is more sensitive than that in conventional assays and adaptable for high-throughput screening is presented. Lastly, the utility of the in vitro cell model and an assay based on AdipoRed to measure hypolipidemic effects of therapeutic drugs is demonstrated using fenofibrate, a molecule that was previously shown to lower lipid levels in the liver.
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Knobeloch T, Abadi SEM, Bruns J, Zustiak SP, Kwon G. Injectable Polyethylene Glycol Hydrogel for Islet Encapsulation: an in vitro and in vivo Characterization. Biomed Phys Eng Express 2017. [PMID: 29527325 DOI: 10.1088/2057-1976/aa742b] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
An injection of hydrogel-encapsulated islets that controls blood glucose levels over long term would provide a much needed alternative treatment for type 1 diabetes mellitus (T1DM). To this end, we tested the feasibility of using an injectable polyethylene glycol (PEG) hydrogel as a scaffold for islet encapsulation. Encapsulated islets cultured in vitro for 6 days showed excellent cell viability and released insulin with higher basal and stimulated insulin secretion than control islets. Host responses to PEG hydrogels were studied by injecting PEG hydrogels (no treatment and vehicle controls used) into the peritoneal cavities of B6D2F1 mice and monitoring alterations in body weight, food and water intake, and blood glucose levels. After 2 weeks, peritoneal cavity cells were harvested, followed by hydrogel retrieval, and extraction of spleens. Body weights, food and water intake, and blood glucose levels were unaltered in mice injected with hydrogels compared to no treatment and vehicle-injected control mice. Frozen sections of a hydrogel showed the presence of tissues and small number of immune cells surrounding the hydrogel but no cell infiltration into the hydrogel bulk. Spleen sizes were not significantly different under the experimental conditions. Peritoneal cavity cells were slightly higher in mice injected with hydrogels compared to control mice but no statistical difference between vehicle- and hydrogel-injected mice was noted. As an in vivo feasibility study, streptozotocin-induced diabetic mice were injected with vehicle or hydrogels containing 50 islets each into two sites, the peritoneal cavity and a subcutaneous site on the back. Transient control of blood glucose levels were observed in mice injected with hydrogels containing islets. In summary, we developed an injectable PEG hydrogel that supported islet function and survival in vitro and in vivo and elicited only a mild host response. Our work illustrates the feasibility of using injectable PEG hydrogels for islet encapsulation.
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Affiliation(s)
- Tracy Knobeloch
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL 62026
| | | | - Joseph Bruns
- Biomedical Engineering, St. Louis University, St. Louis, MO 63103
| | | | - Guim Kwon
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL 62026
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Moullé VS, Vivot K, Tremblay C, Zarrouki B, Ghislain J, Poitout V. Glucose and fatty acids synergistically and reversibly promote beta cell proliferation in rats. Diabetologia 2017; 60:879-888. [PMID: 28078385 PMCID: PMC5376373 DOI: 10.1007/s00125-016-4197-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 12/08/2016] [Indexed: 12/31/2022]
Abstract
AIMS/HYPOTHESIS The mechanisms underlying pancreatic islet mass expansion have attracted considerable interest as potential therapeutic targets to prevent or delay the onset of type 2 diabetes. While several factors promoting beta cell proliferation have been identified, in the context of nutrient excess the roles of glucose or NEFA in relation to insulin resistance remain unclear. Here we tested the hypothesis that glucose and NEFA synergistically and reversibly promote beta cell proliferation in the context of nutrient-induced insulin resistance. METHODS Using 72 h infusions of glucose (GLU) or the oleate-enriched lipid emulsion ClinOleic (CLI), singly or in combination, we assessed beta cell proliferation, islet mass and insulin sensitivity in male Lewis rats. The effects of nutrients and endogenous circulating factors were examined in isolated and transplanted islets. Reversibility was studied 3 and 6 days after the end of the infusion. RESULTS GLU infusions modestly stimulated beta cell proliferation, CLI alone had no effect and GLU+CLI infusions markedly stimulated beta cell proliferation. Insulin sensitivity was equally decreased in GLU and GLU+CLI infusions. GLU+CLI infusions also stimulated beta cell proliferation in islets transplanted under the kidney capsule, albeit to a lesser extent compared with endogenous islets. Ex vivo, the combination of glucose and NEFA enhanced beta cell proliferation in rat and human islets independently from secreted insulin, and serum from GLU+CLI-infused rats potentiated the effect of glucose. Glucose tolerance, beta cell proliferation and islet mass were all restored to normal levels 6 days after termination of the infusion. CONCLUSIONS/INTERPRETATION Glucose and NEFA synergistically and reversibly promote beta cell proliferation in part via direct action on the beta cell and independently from secreted insulin.
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Affiliation(s)
- Valentine S Moullé
- Montreal Diabetes Research Center, University of Montreal, Montreal, QC, Canada
- The University of Montreal Hospital Research Centre (CRCHUM), 900 Saint-Denis, Montreal, QC, H2X 0A9, Canada
| | - Kevin Vivot
- Montreal Diabetes Research Center, University of Montreal, Montreal, QC, Canada
- The University of Montreal Hospital Research Centre (CRCHUM), 900 Saint-Denis, Montreal, QC, H2X 0A9, Canada
| | - Caroline Tremblay
- Montreal Diabetes Research Center, University of Montreal, Montreal, QC, Canada
- The University of Montreal Hospital Research Centre (CRCHUM), 900 Saint-Denis, Montreal, QC, H2X 0A9, Canada
| | - Bader Zarrouki
- Montreal Diabetes Research Center, University of Montreal, Montreal, QC, Canada
- The University of Montreal Hospital Research Centre (CRCHUM), 900 Saint-Denis, Montreal, QC, H2X 0A9, Canada
| | - Julien Ghislain
- Montreal Diabetes Research Center, University of Montreal, Montreal, QC, Canada
- The University of Montreal Hospital Research Centre (CRCHUM), 900 Saint-Denis, Montreal, QC, H2X 0A9, Canada
| | - Vincent Poitout
- Montreal Diabetes Research Center, University of Montreal, Montreal, QC, Canada.
- The University of Montreal Hospital Research Centre (CRCHUM), 900 Saint-Denis, Montreal, QC, H2X 0A9, Canada.
- Department of Medicine, University of Montreal, Montreal, QC, Canada.
- Department of Biochemistry and Molecular Medicine, University of Montreal, Montreal, QC, Canada.
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34
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Perrotta I. Interaction between lipid droplets and endoplasmic reticulum in human atherosclerotic plaques. Ultrastruct Pathol 2017; 41:1-9. [DOI: 10.1080/01913123.2016.1269861] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Ida Perrotta
- Department of Biology, Ecology and Earth Sciences (Di.B.E.S.T.), Centre for Microscopy and Microanalysis (CM2), Transmission Electron Microscopy Laboratory, University of Calabria, Cosenza, Italy
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35
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Initial hyperinsulinemia and subsequent β-cell dysfunction is associated with elevated palmitate levels. Pediatr Res 2016; 80:267-74. [PMID: 27064244 DOI: 10.1038/pr.2016.80] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 03/03/2016] [Indexed: 12/16/2022]
Abstract
BACKGROUND The prevalence of obesity-related diabetes in childhood is increasing and circulating levels of nonesterified fatty acids may constitute a link. Here, the association between palmitate and insulin secretion was investigated in vivo and in vitro. METHODS Obese and lean children and adolescents (n = 80) were included. Palmitate was measured at fasting; insulin and glucose during an oral glucose tolerance test (OGTT). Human islets were cultured for 0 to 7 d in presence of 0.5 mmol/l palmitate. Glucose-stimulated insulin secretion (GSIS), insulin content and apoptosis were measured. RESULTS Obese subjects had fasting palmitate levels between 0.10 and 0.33 mmol/l, with higher average levels compared to lean subjects. While obese children with elevated palmitate (>0.20 mmol/l) had accentuated insulin levels during OGTT, obese adolescents with high palmitate had delayed first-phase insulin response. In human islets exposed to palmitate for 2 d GSIS was twofold enhanced, but after 7 d attenuated. Intracellular insulin content decreased time-dependently in islets cultured in the presence of palmitate and cleaved caspase 3 increased. CONCLUSION The rapid accentuated and delayed insulin secretory responses observed in obese children and adolescents, respectively, with high palmitate levels may reflect changes in islet secretory activity and integrity induced by extended exposure to the fatty acid.
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36
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Kanikarla-Marie P, Jain SK. Hyperketonemia and ketosis increase the risk of complications in type 1 diabetes. Free Radic Biol Med 2016; 95:268-77. [PMID: 27036365 PMCID: PMC4867238 DOI: 10.1016/j.freeradbiomed.2016.03.020] [Citation(s) in RCA: 106] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 03/16/2016] [Accepted: 03/21/2016] [Indexed: 12/19/2022]
Abstract
Diets that boost ketone production are increasingly used for treating several neurological disorders. Elevation in ketones in most cases is considered favorable, as they provide energy and are efficient in fueling the body's energy needs. Despite all the benefits from ketones, the above normal elevation in the concentration of ketones in the circulation tend to illicit various pathological complications by activating injurious pathways leading to cellular damage. Recent literature demonstrates a plausible link between elevated levels of circulating ketones and oxidative stress, linking hyperketonemia to innumerable morbid conditions. Ketone bodies are produced by the oxidation of fatty acids in the liver as a source of alternative energy that generally occurs in glucose limiting conditions. Regulation of ketogenesis and ketolysis plays an important role in dictating ketone concentrations in the blood. Hyperketonemia is a condition with elevated blood levels of acetoacetate, 3-β-hydroxybutyrate, and acetone. Several physiological and pathological triggers, such as fasting, ketogenic diet, and diabetes cause an accumulation and elevation of circulating ketones. Complications of the brain, kidney, liver, and microvasculature were found to be elevated in diabetic patients who had elevated ketones compared to those diabetics with normal ketone levels. This review summarizes the mechanisms by which hyperketonemia and ketoacidosis cause an increase in redox imbalance and thereby increase the risk of morbidity and mortality in patients.
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Affiliation(s)
- Preeti Kanikarla-Marie
- Department of Pediatrics, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130, USA
| | - Sushil K Jain
- Department of Pediatrics, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130, USA.
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Dai C, Kayton NS, Shostak A, Poffenberger G, Cyphert HA, Aramandla R, Thompson C, Papagiannis IG, Emfinger C, Shiota M, Stafford JM, Greiner DL, Herrera PL, Shultz LD, Stein R, Powers AC. Stress-impaired transcription factor expression and insulin secretion in transplanted human islets. J Clin Invest 2016; 126:1857-70. [PMID: 27064285 DOI: 10.1172/jci83657] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 02/24/2016] [Indexed: 12/11/2022] Open
Abstract
Type 2 diabetes is characterized by insulin resistance, hyperglycemia, and progressive β cell dysfunction. Excess glucose and lipid impair β cell function in islet cell lines, cultured rodent and human islets, and in vivo rodent models. Here, we examined the mechanistic consequences of glucotoxic and lipotoxic conditions on human islets in vivo and developed and/or used 3 complementary models that allowed comparison of the effects of hyperglycemic and/or insulin-resistant metabolic stress conditions on human and mouse islets, which responded quite differently to these challenges. Hyperglycemia and/or insulin resistance impaired insulin secretion only from human islets in vivo. In human grafts, chronic insulin resistance decreased antioxidant enzyme expression and increased superoxide and amyloid formation. In human islet grafts, expression of transcription factors NKX6.1 and MAFB was decreased by chronic insulin resistance, but only MAFB decreased under chronic hyperglycemia. Knockdown of NKX6.1 or MAFB expression in a human β cell line recapitulated the insulin secretion defect seen in vivo. Contrary to rodent islet studies, neither insulin resistance nor hyperglycemia led to human β cell proliferation or apoptosis. These results demonstrate profound differences in how excess glucose or lipid influence mouse and human insulin secretion and β cell activity and show that reduced expression of key islet-enriched transcription factors is an important mediator of glucotoxicity and lipotoxicity.
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38
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Life and death of β cells in Type 1 diabetes: A comprehensive review. J Autoimmun 2016; 71:51-8. [PMID: 27017348 DOI: 10.1016/j.jaut.2016.02.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Revised: 01/31/2016] [Accepted: 02/01/2016] [Indexed: 01/03/2023]
Abstract
Type 1 diabetes (T1D) is an autoimmune disorder characterized by the destruction of insulin-producing pancreatic β cells. Immune modulators have achieved some success in modifying the course of disease progression in T1D. However, there are parallel declines in C-peptide levels in treated and control groups after initial responses. In this review, we discuss mechanisms of β cell death in T1D that involve necrosis and apoptosis. New technologies are being developed to enable visualization of insulitis and β cell mass involving positron emission transmission that identifies β cell ligands and magnetic resonance imaging that can identify vascular leakage. Molecular signatures that identify β cell derived insulin DNA that is released from dying cells have been described and applied to clinical settings. We also consider changes in β cells that occur during disease progression including the induction of DNA methyltransferases that may affect the function and differentiation of β cells. Our findings from newer data suggest that the model of chronic long standing β cell killing should be reconsidered. These studies indicate that the pathophysiology is accelerated in the peridiagnosis period and manifest by increased rates of β cell killing and insulin secretory impairments over a shorter period than previously thought. Finally, we consider cellular explanations to account for the ongoing loss of insulin production despite continued immune therapy that may identify potential targets for treatment. The progressive decline in β cell function raises the question as to whether β cell failure that is independent of immune attack may be involved.
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Johns M, Esmaeili Mohsen Abadi S, Malik N, Lee J, Neumann WL, Rausaria S, Imani-Nejad M, McPherson T, Schober J, Kwon G. Oral administration of SR-110, a peroxynitrite decomposing catalyst, enhances glucose homeostasis, insulin signaling, and islet architecture in B6D2F1 mice fed a high fat diet. Arch Biochem Biophys 2016; 596:126-37. [PMID: 26970045 DOI: 10.1016/j.abb.2016.03.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Revised: 02/23/2016] [Accepted: 03/02/2016] [Indexed: 01/03/2023]
Abstract
Peroxynitrite has been implicated in type 2 diabetes and diabetic complications. As a follow-up study to our previous work on SR-135 (Arch Biochem Biophys 577-578: 49-59, 2015), we provide evidence that this series of compounds are effective when administered orally, and their mechanisms of actions extend to the peripheral tissues. A more soluble analogue of SR-135, SR-110 (from a new class of Mn(III) bis(hydroxyphenyl)-dipyrromethene complexes) was orally administered for 2 weeks to B6D2F1 mice fed a high fat-diet (HFD). Mice fed a HFD for 4 months gained significantly higher body weights compared to lean diet-fed mice (52 ± 1.5 g vs 34 ± 1.3 g). SR-110 (10 mg/kg daily) treatment significantly reduced fasting blood glucose and insulin levels, and enhanced glucose tolerance as compared to HFD control or vehicle (peanut butter) group. SR-110 treatment enhanced insulin signaling in the peripheral organs, liver, heart, and skeletal muscle, and reduced lipid accumulation in the liver. Furthermore, SR-110 increased insulin content, restored islet architecture, decreased islet size, and reduced tyrosine nitration. These results suggest that a peroxynitrite decomposing catalyst is effective in improving glucose homeostasis and restoring islet morphology and β-cell insulin content under nutrient overload.
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Affiliation(s)
- Michael Johns
- Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, IL, 62026, USA
| | | | - Nehal Malik
- Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, IL, 62026, USA
| | - Joshua Lee
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL, 62026, USA
| | - William L Neumann
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL, 62026, USA
| | - Smita Rausaria
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL, 62026, USA
| | - Maryam Imani-Nejad
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL, 62026, USA
| | - Timothy McPherson
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL, 62026, USA
| | - Joseph Schober
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL, 62026, USA
| | - Guim Kwon
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL, 62026, USA.
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Brissova M, Shostak A, Fligner CL, Revetta FL, Washington MK, Powers AC, Hull RL. Human Islets Have Fewer Blood Vessels than Mouse Islets and the Density of Islet Vascular Structures Is Increased in Type 2 Diabetes. J Histochem Cytochem 2015. [PMID: 26216139 DOI: 10.1369/0022155415573324] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Human and rodent islets differ substantially in several features, including architecture, cell composition, gene expression and some aspects of insulin secretion. Mouse pancreatic islets are highly vascularized with interactions between islet endothelial and endocrine cells being important for islet cell differentiation and function. To determine whether human islets have a similar high degree of vascularization and whether this is altered with diabetes, we examined the vascularization of islets from normal human subjects, subjects with type 2 diabetes (T2D), and normal mice. Using an integrated morphometry approach to quantify intra-islet capillary density in human and mouse pancreatic sections, we found that human islets have five-fold fewer vessels per islet area than mouse islets. Islets in pancreatic sections from T2D subjects showed capillary thickening, some capillary fragmentation and had increased vessel density as compared with non-diabetic controls. These changes in islet vasculature in T2D islets appeared to be associated with amyloid deposition, which was noted in islets from 8/9 T2D subjects (and occupied 14% ± 4% of islet area), especially around the intra-islet capillaries. The physiological implications of the differences in the angioarchitecture of mouse and human islets are not known. Islet vascular changes in T2D may exacerbate β cell/islet dysfunction and β cell loss.
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Affiliation(s)
- Marcela Brissova
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University, Nashville Medical Center, Tennessee (MB, AS, ACP)
| | - Alena Shostak
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University, Nashville Medical Center, Tennessee (MB, AS, ACP)
| | - Corinne L Fligner
- Department of Pathology, University of Washington, Seattle, Washington (CLF)
| | - Frank L Revetta
- Department of Pathology, Vanderbilt University Medical Center, Nashville, Tennessee (FLR, MKW)
| | - Mary K Washington
- Department of Pathology, Vanderbilt University Medical Center, Nashville, Tennessee (FLR, MKW)
| | - Alvin C Powers
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University, Nashville Medical Center, Tennessee (MB, AS, ACP),Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee (ACP),VA Tennessee Valley Healthcare System, Nashville, Tennessee (ACP)
| | - Rebecca L Hull
- Department of Pathology, Vanderbilt University Medical Center, Nashville, Tennessee (FLR, MKW),Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, VA Puget Sound Health Care System and University of Washington, Seattle, Washington (RLH)
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Ferdaoussi M, Dai X, Jensen MV, Wang R, Peterson BS, Huang C, Ilkayeva O, Smith N, Miller N, Hajmrle C, Spigelman AF, Wright RC, Plummer G, Suzuki K, Mackay JP, van de Bunt M, Gloyn AL, Ryan TE, Norquay LD, Brosnan MJ, Trimmer JK, Rolph TP, Kibbey RG, Manning Fox JE, Colmers WF, Shirihai OS, Neufer PD, Yeh ETH, Newgard CB, MacDonald PE. Isocitrate-to-SENP1 signaling amplifies insulin secretion and rescues dysfunctional β cells. J Clin Invest 2015; 125:3847-60. [PMID: 26389676 DOI: 10.1172/jci82498] [Citation(s) in RCA: 138] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 07/24/2015] [Indexed: 01/02/2023] Open
Abstract
Insulin secretion from β cells of the pancreatic islets of Langerhans controls metabolic homeostasis and is impaired in individuals with type 2 diabetes (T2D). Increases in blood glucose trigger insulin release by closing ATP-sensitive K+ channels, depolarizing β cells, and opening voltage-dependent Ca2+ channels to elicit insulin exocytosis. However, one or more additional pathway(s) amplify the secretory response, likely at the distal exocytotic site. The mitochondrial export of isocitrate and engagement with cytosolic isocitrate dehydrogenase (ICDc) may be one key pathway, but the mechanism linking this to insulin secretion and its role in T2D have not been defined. Here, we show that the ICDc-dependent generation of NADPH and subsequent glutathione (GSH) reduction contribute to the amplification of insulin exocytosis via sentrin/SUMO-specific protease-1 (SENP1). In human T2D and an in vitro model of human islet dysfunction, the glucose-dependent amplification of exocytosis was impaired and could be rescued by introduction of signaling intermediates from this pathway. Moreover, islet-specific Senp1 deletion in mice caused impaired glucose tolerance by reducing the amplification of insulin exocytosis. Together, our results identify a pathway that links glucose metabolism to the amplification of insulin secretion and demonstrate that restoration of this axis rescues β cell function in T2D.
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42
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León Fradejas M, Kandil D, Papadimitriou JC, del Pino Flórez Rial M, Prieto Sánchez E, Drachenberg CB. Islet Amyloid in Whole Pancreas Transplants for Type 1 Diabetes Mellitus (DM): Possible Role of Type 2 DM for Graft Failure. Am J Transplant 2015; 15:2495-500. [PMID: 25926270 DOI: 10.1111/ajt.13269] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 02/03/2015] [Accepted: 02/08/2015] [Indexed: 01/25/2023]
Abstract
Long-term results with whole pancreas (WPTx) and islet transplantation (IT) continue to be suboptimal. Graft failure with undetectable C-peptide level is attributed to graft sclerosis (chronic rejection), recurrence of Type 1 diabetes mellitus (DM), or insufficient islet mass. In contrast, graft failure with measurable C-peptide has overlapping clinical features with Type 2 DM (suggesting persistent but insufficient β cell function), but is poorly understood. In general, the morphological substrate for islet failure is unclear because grafted islets are not routinely evaluated. We present two patients with graft failure at 5 and 8 years after successful WPTx for Type 1 DM, presenting with preserved C-peptide levels. On histopathology, the islets had preserved both α and β cell populations but also prominent accumulation of islet amyloid (IA), the morphological hallmark of Type 2 DM. IA previously reported in IT, represents fibrillary aggregates of islet amyloid polypeptide, a hormone normally cosecreted with insulin. Accumulation of IA correlates quantitatively with the development of hyperglycemia and is known to cause β cell dysfunction and loss. Accumulation of IA and development of Type 2 DM should be considered and studied as a potential cause of long-term islet failure in IT and WPTx.
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Affiliation(s)
- M León Fradejas
- Department of Pathology, Hospital Universitario Regional Carlos Haya, Malaga, Andalucia, Spain
| | - D Kandil
- Department of Pathology, University of Massachusetts Medical School, Worcester, MA
| | - J C Papadimitriou
- Department of Pathology, University of Maryland School of Medicine, Baltimore, MD
| | - M del Pino Flórez Rial
- Department of Pathology, Hospital Universitario Regional Carlos Haya, Malaga, Andalucia, Spain
| | - E Prieto Sánchez
- Department of Pathology, Hospital Universitario Regional Carlos Haya, Malaga, Andalucia, Spain
| | - C B Drachenberg
- Department of Pathology, University of Maryland School of Medicine, Baltimore, MD
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Hurwitz BE, Schneiderman N, Marks JB, Mendez AJ, Gonzalez A, Llabre MM, Smith SR, Bizzotto R, Santini E, Manca ML, Skyler JS, Mari A, Ferrannini E. Adaptation of β-Cell and Endothelial Function to Carbohydrate Loading: Influence of Insulin Resistance. Diabetes 2015; 64:2550-9. [PMID: 25754957 PMCID: PMC4477346 DOI: 10.2337/db15-0106] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 03/02/2015] [Indexed: 12/23/2022]
Abstract
High-carbohydrate diets have been associated with β-cell strain, dyslipidemia, and endothelial dysfunction. We examined how β-cell and endothelial function adapt to carbohydrate overloading and the influence of insulin resistance. On sequential days in randomized order, nondiabetic subjects (classified as insulin-sensitive [IS] [n = 64] or insulin-resistant [IR] [n = 79] by euglycemic clamp) received four mixed meals over 14 h with either standard (300 kcal) or double carbohydrate content. β-Cell function was reconstructed by mathematical modeling; brachial artery flow-mediated dilation (FMD) was measured before and after each meal. Compared with IS, IR subjects showed higher glycemia and insulin hypersecretion due to greater β-cell glucose and rate sensitivity; potentiation of insulin secretion, however, was impaired. Circulating free fatty acids (FFAs) were less suppressed in IR than IS subjects. Baseline FMD was reduced in IR, and postprandial FMD attenuation occurred after each meal, particularly with high carbohydrate, similarly in IR and IS. Throughout the two study days, higher FFA levels were significantly associated with lower (incretin-induced) potentiation and impaired FMD. In nondiabetic individuals, enhanced glucose sensitivity and potentiation upregulate the insulin secretory response to carbohydrate overloading. With insulin resistance, this adaptation is impaired. Defective suppression of endogenous FFA is one common link between impaired potentiation and vascular endothelial dysfunction.
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Affiliation(s)
- Barry E Hurwitz
- Behavioral Medicine Research Center, University of Miami, Miami, FL Division of Endocrinology, Diabetes, and Metabolism, Miller School of Medicine, University of Miami, Miami, FL Department of Psychology, University of Miami, Coral Gables, FL
| | - Neil Schneiderman
- Behavioral Medicine Research Center, University of Miami, Miami, FL Department of Psychology, University of Miami, Coral Gables, FL
| | - Jennifer B Marks
- Division of Endocrinology, Diabetes, and Metabolism, Miller School of Medicine, University of Miami, Miami, FL
| | - Armando J Mendez
- Behavioral Medicine Research Center, University of Miami, Miami, FL Division of Endocrinology, Diabetes, and Metabolism, Miller School of Medicine, University of Miami, Miami, FL
| | - Alex Gonzalez
- Behavioral Medicine Research Center, University of Miami, Miami, FL
| | - Maria M Llabre
- Behavioral Medicine Research Center, University of Miami, Miami, FL Department of Psychology, University of Miami, Coral Gables, FL
| | - Steven R Smith
- Translational Research Institute for Metabolism and Diabetes, Florida Hospital, Orlando, FL
| | - Roberto Bizzotto
- National Research Council Institute of Biomedical Engineering, Padua, Italy
| | - Eleonora Santini
- Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Maria Laura Manca
- Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Jay S Skyler
- Division of Endocrinology, Diabetes, and Metabolism, Miller School of Medicine, University of Miami, Miami, FL
| | - Andrea Mari
- National Research Council Institute of Biomedical Engineering, Padua, Italy
| | - Ele Ferrannini
- Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy National Research Council Institute of Clinical Physiology, Pisa, Italy
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Johns M, Fyalka R, Shea JA, Neumann WL, Rausaria S, Msengi EN, Imani-Nejad M, Zollars H, McPherson T, Schober J, Wooten J, Kwon G. SR-135, a peroxynitrite decomposing catalyst, enhances β-cell function and survival in B6D2F1 mice fed a high fat diet. Arch Biochem Biophys 2015; 577-578:49-59. [PMID: 25935364 DOI: 10.1016/j.abb.2015.04.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 04/14/2015] [Accepted: 04/17/2015] [Indexed: 02/07/2023]
Abstract
Peroxynitrite has been implicated in β-cell dysfunction and insulin resistance in obesity. Chemical catalysts that destroy peroxynitrite, therefore, may have therapeutic value for treating type 2 diabetes. To this end, we have recently demonstrated that Mn(III) bis(hydroxyphenyl)-dipyrromethene complexes, SR-135 and its analogs, can effectively catalyze the decomposition of peroxynitrite in vitro and in vivo through a 2-electron mechanism (Rausaria et al., 2011). To study the effects of SR-135 on glucose homeostasis in obesity, B6D2F1 mice were fed with a high fat-diet (HFD) for 12 weeks and treated with vehicle, SR-135 (5mg/kg), or a control drug SRB for 2 weeks. SR-135 significantly reduced fasting blood glucose and insulin levels, and enhanced glucose tolerance as compared to HFD control, vehicle or SRB. SR-135 also enhanced glucose-stimulated insulin secretion based on ex vivo studies. Moreover, SR-135 increased insulin content, restored islet architecture, decreased islet size, and reduced tyrosine nitration and apoptosis. These results suggest that a peroxynitrite decomposing catalyst enhances β-cell function and survival under nutrient overload.
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Affiliation(s)
- Michael Johns
- Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States
| | - Robert Fyalka
- Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States
| | - Jennifer A Shea
- Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States
| | - William L Neumann
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States
| | - Smita Rausaria
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States
| | - Eliwaza Naomi Msengi
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States
| | - Maryam Imani-Nejad
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States
| | - Harry Zollars
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States
| | - Timothy McPherson
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States
| | - Joseph Schober
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States
| | - Joshua Wooten
- Department of Kinesiology and Health Education, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States
| | - Guim Kwon
- School of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States.
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Kayton NS, Poffenberger G, Henske J, Dai C, Thompson C, Aramandla R, Shostak A, Nicholson W, Brissova M, Bush WS, Powers AC. Human islet preparations distributed for research exhibit a variety of insulin-secretory profiles. Am J Physiol Endocrinol Metab 2015; 308:E592-602. [PMID: 25648831 PMCID: PMC4385877 DOI: 10.1152/ajpendo.00437.2014] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Accepted: 01/30/2015] [Indexed: 12/21/2022]
Abstract
Human islet research is providing new insights into human islet biology and diabetes, using islets isolated at multiple US centers from donors with varying characteristics. This creates challenges for understanding, interpreting, and integrating research findings from the many laboratories that use these islets. In what is, to our knowledge, the first standardized assessment of human islet preparations from multiple isolation centers, we measured insulin secretion from 202 preparations isolated at 15 centers over 11 years and noted five distinct patterns of insulin secretion. Approximately three quarters were appropriately responsive to stimuli, but one quarter were dysfunctional, with unstable basal insulin secretion and/or an impairment in stimulated insulin secretion. Importantly, the patterns of insulin secretion by responsive human islet preparations (stable Baseline and Fold stimulation of insulin secretion) isolated at different centers were similar and improved slightly over the years studied. When all preparations studied were considered, basal and stimulated insulin secretion did not correlate with isolation center, biological differences of the islet donor, or differences in isolation, such as Cold Ischemia Time. Dysfunctional islet preparations could not be predicted from the information provided by the isolation center and had altered expression of genes encoding components of the glucose-sensing pathway, but not of insulin production or cell death. These results indicate that insulin secretion by most preparations from multiple centers is similar but that in vitro responsiveness of human islets cannot be predicted, necessitating preexperimental human islet assessment. These results should be considered when one is designing, interpreting, and integrating experiments using human islets.
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Affiliation(s)
- Nora S Kayton
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Gregory Poffenberger
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Joseph Henske
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Chunhua Dai
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Courtney Thompson
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Radhika Aramandla
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Alena Shostak
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Wendell Nicholson
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Marcela Brissova
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - William S Bush
- Center for Human Genetics Research, Department of Biomedical Informatics, Vanderbilt University Medical Center, Nashville, Tennessee; and
| | - Alvin C Powers
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee; Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee; Veterans Affairs Tennessee Valley Healthcare System, Nashville, Tennessee
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Trevino MB, Machida Y, Hallinger DR, Garcia E, Christensen A, Dutta S, Peake DA, Ikeda Y, Imai Y. Perilipin 5 regulates islet lipid metabolism and insulin secretion in a cAMP-dependent manner: implication of its role in the postprandial insulin secretion. Diabetes 2015; 64:1299-310. [PMID: 25392244 PMCID: PMC4375085 DOI: 10.2337/db14-0559] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Elevation of circulating fatty acids (FA) during fasting supports postprandial (PP) insulin secretion that is critical for glucose homeostasis and is impaired in diabetes. We tested our hypothesis that lipid droplet (LD) protein perilipin 5 (PLIN5) in β-cells aids PP insulin secretion by regulating intracellular lipid metabolism. We demonstrated that PLIN5 serves as an LD protein in human islets. In vivo, Plin5 and triglycerides were increased by fasting in mouse islets. MIN6 cells expressing PLIN5 (adenovirus [Ad]-PLIN5) and those expressing perilipin 2 (PLIN2) (Ad-PLIN2) had higher [(3)H]FA incorporation into triglycerides than Ad-GFP control, which support their roles as LD proteins. However, Ad-PLIN5 cells had higher lipolysis than Ad-PLIN2 cells, which increased further by 8-Br-cAMP, indicating that PLIN5 facilitates FA mobilization upon cAMP stimulation as seen postprandially. Ad-PLIN5 in islets enhanced the augmentation of glucose-stimulated insulin secretion by FA and 8-Br-cAMP in G-protein-coupled receptor 40 (GPR40)- and cAMP-activated protein kinase-dependent manners, respectively. When PLIN5 was increased in mouse β-cells in vivo, glucose tolerance after an acute exenatide challenge was improved. Therefore, the elevation of islet PLIN5 during fasting allows partitioning of FA into LD that is released upon refeeding to support PP insulin secretion in cAMP- and GPR40-dependent manners.
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Affiliation(s)
- Michelle B Trevino
- Department of Internal Medicine, Strelitz Diabetes Center, Eastern Virginia Medical School, Norfolk, VA
| | - Yui Machida
- Department of Internal Medicine, Strelitz Diabetes Center, Eastern Virginia Medical School, Norfolk, VA
| | - Daniel R Hallinger
- Department of Internal Medicine, Strelitz Diabetes Center, Eastern Virginia Medical School, Norfolk, VA
| | - Eden Garcia
- Department of Internal Medicine, Strelitz Diabetes Center, Eastern Virginia Medical School, Norfolk, VA
| | - Aaron Christensen
- Department of Internal Medicine, Strelitz Diabetes Center, Eastern Virginia Medical School, Norfolk, VA
| | - Sucharita Dutta
- Leroy T. Canoles Cancer Research Center, Eastern Virginia Medical School, Norfolk, VA
| | | | - Yasuhiro Ikeda
- Department of Molecular Medicine, Mayo Clinic, Rochester, MN
| | - Yumi Imai
- Department of Internal Medicine, Strelitz Diabetes Center, Eastern Virginia Medical School, Norfolk, VA
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47
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Oh YS. Mechanistic insights into pancreatic beta-cell mass regulation by glucose and free fatty acids. Anat Cell Biol 2015; 48:16-24. [PMID: 25806118 PMCID: PMC4371177 DOI: 10.5115/acb.2015.48.1.16] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2014] [Accepted: 02/04/2015] [Indexed: 01/14/2023] Open
Abstract
Pancreatic islets are responsible for blood glucose homeostasis. Reduced numbers of functional (insulin-secreting) beta-cells in pancreatic islets underlies diabetes. Restoration of the secretion of the proper amount of insulin is a goal. Beta-cell mass is increased by neogenesis, proliferation and cell hypertrophy, and is decreased by beta-cell death primarily through apoptosis. Many hormones and nutrients affect beta-cell mass, and glucose and free fatty acid are thought to be the most important determinants of beta-cell equilibrium. A number of molecular pathways have been implicated in beta-cell mass regulation and have been studied. This review will focus on the role of the principle metabolites, glucose and free fatty acid, and the downstream signaling pathways regulating beta-cell mass by these metabolites.
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Affiliation(s)
- Yoon Sin Oh
- Lee Gil Ya Cancer and Diabetes Institute, Gachon University, Incheon, Korea. ; Gachon Medical Research Institute, Gil Hospital, Incheon, Korea
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48
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Wang D, Tian M, Qi Y, Chen G, Xu L, Zou X, Wang K, Dong H, Lu F. Jinlida granule inhibits palmitic acid induced-intracellular lipid accumulation and enhances autophagy in NIT-1 pancreatic β cells through AMPK activation. JOURNAL OF ETHNOPHARMACOLOGY 2015; 161:99-107. [PMID: 25510732 DOI: 10.1016/j.jep.2014.12.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Revised: 11/06/2014] [Accepted: 12/01/2014] [Indexed: 06/04/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Jinlida granule (JLDG), composed of seventeen Chinese medical herbs, is a widely used Chinese herbal prescription for treating diabetes mellitus. However, the mechanism underlying this effect remains unclear. To determine the main components in JLDG and to explore the effect of JLDG on autophagy and lipid accumulation in NIT-1 pancreatic β cells exposed to politic acid (PA) through AMP activated protein kinase (AMPK) signaling pathway. MATERIALS AND METHODS JLDG was prepared and the main components contained in the granules were identified by ultra performance liquid chromatography (UPLC) fingerprint. Intracellular lipid accumulation in NIT-1 cells was induced by culturing with medium containing PA. Intracellular lipid droplets were observed by Oil Red O staining and triglyceride (TG) content was measured by colorimetric assay. The formation of autophagosomes was observed under transmission electron microscope. The expression of AMPK and phospho-AMPK (pAMPK) proteins as well as its downstream fatty acid metabolism-related proteins (fatty acid synthase, FAS; acetyl-coA carboxylase, ACC; carnitine acyltransferase 1, CPT-1) and autophagy-related genes (mammal target of rapamycin, mTOR; tuberous sclerosis complex 1, TSC1; microtubule-associated protein 1 light chain 3, LC3-II) were determined by Western blot. The expression of sterol regulating element binding protein 1c (SREBP-1c) mRNA was examined by real time PCR (RT-PCR). RESULTS Our data showed that JLDG could significantly reduce PA-induced intracellular lipid accumulation in NIT-1 pancreatic β cells. This effect was associated with increased protein expression of pAMPK and AMPK in NIT-1 cells. Treatment with JLDG also decreased the expression of AMPK downstream lipogenic genes (SREBP-1c mRNA, FAS and ACC proteins) whereas increased the expression of fatty acid oxidation gene (CPT-1 protein). Additionally, JLDG-treated cells displayed a markedly increase in the number of autophagosomes which was accompanied by the down-regulation of mTOR and the up-regulation of TSC1 and LC3-II proteins expression. However, when AMPK phosphorylation was inhibited by Compound C, JLDG supplementation did not exhibit any effect on the expression of these AMPK downstream molecules in NIT-1 cells. CONCLUSIONS The results suggest that JLDG could reduce intracellular lipid accumulation and enhance the autophagy in NIT-1 pancreatic β cells cultured with PA. The mechanism is possibly mediated by AMPK activation.
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Affiliation(s)
- Dingkun Wang
- Institute of Integrated Traditional Chinese and Western Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Min Tian
- Institute of Integrated Traditional Chinese and Western Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Yuan Qi
- Shijiazhuang YiLing Pharmaceutical Co., Ltd., Shijiazhuang, Hebei 050035, China
| | - Guang Chen
- Department of Integrated Traditional Chinese and Western Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Lijun Xu
- Institute of Integrated Traditional Chinese and Western Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Xin Zou
- Institute of Integrated Traditional Chinese and Western Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Kaifu Wang
- Institute of Integrated Traditional Chinese and Western Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China
| | - Hui Dong
- Institute of Integrated Traditional Chinese and Western Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China.
| | - Fuer Lu
- Institute of Integrated Traditional Chinese and Western Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China.
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Abstract
Free fatty acids (FFAs) exert both positive and negative effects on beta cell survival and insulin secretory function, depending on concentration, duration, and glucose abundance. Lipid signals are mediated not only through metabolic pathways, but also through cell surface and nuclear receptors. Toxicity is modulated by positive signals arising from circulating factors such as hormones, growth factors and incretins, as well as negative signals such as inflammatory mediators and cytokines. Intracellular mechanisms of lipotoxicity include metabolic interference and cellular stress responses such as oxidative stress, endoplasmic reticulum (ER) stress, and possibly autophagy. New findings strengthen an old hypothesis that lipids may also impair compensatory beta cell proliferation. Clinical observations continue to support a role for lipid biology in the risk and progression of both type 1 (T1D) and type 2 diabetes (T2D). This review summarizes recent work in this important, rapidly evolving field.
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Affiliation(s)
- Rohit B Sharma
- Diabetes Center of Excellence, University of Massachusetts Medical School, 368 Plantation Street, Worcester, MA, 01605, USA
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50
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Abstract
Because obesity rates have increased dramatically over the past 3 decades, type 2 diabetes has become increasingly prevalent as well. Type 2 diabetes is associated with decreased pancreatic β-cell mass and function, resulting in inadequate insulin production. Conversely, in nondiabetic obesity, an expansion in β-cell mass occurs to provide sufficient insulin and to prevent hyperglycemia. This expansion is at least in part due to β-cell proliferation. This review focuses on the mechanisms regulating obesity-induced β-cell proliferation in humans and mice. Many factors have potential roles in the regulation of obesity-driven β-cell proliferation, including nutrients, insulin, incretins, hepatocyte growth factor, and recently identified liver-derived secreted factors. Much is still unknown about the regulation of β-cell replication, especially in humans. The extracellular signals that activate proliferative pathways in obesity, the relative importance of each of these pathways, and the extent of cross-talk between these pathways are important areas of future study.
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Affiliation(s)
| | - Mieke Baan
- Division of Endocrinology, Department of Medicine, and,School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI; and
| | - Dawn Belt Davis
- Division of Endocrinology, Department of Medicine, and William S. Middleton Memorial Veterans Hospital, Madison, Wisconsin
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