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Guo M, Huang X, Zhang J, Huang Y, Tang Y, Wen H, Xu Y, Zhang S, Wei X, Sun S, Zhu Q. Palmitic acid induces β-cell ferroptosis by activating ceramide signaling pathway. Exp Cell Res 2024; 440:114134. [PMID: 38901790 DOI: 10.1016/j.yexcr.2024.114134] [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: 01/03/2024] [Revised: 06/02/2024] [Accepted: 06/15/2024] [Indexed: 06/22/2024]
Abstract
Individuals with type 2 diabetes mellitus frequently display heightened levels of palmitic acid (PA) in their serum, which may lead to β-cell damage. The involvement of ferroptosis, a form of oxidative cell death in lipotoxic β-cell injury remains uncertain. Here, we have shown that PA induces intracellular lipid peroxidation, increases intracellular Fe2+ content and decreases intracellular glutathione peroxidase 4 (GPX4) expression. Furthermore, PA causes distinct changes in pancreatic islets and INS-1 cells, such as mitochondrial atrophy and increased membrane density. Furthermore, the presence of the ferroptosis inhibitor has a significant mitigating effect on PA-induced β-cell damage. Mechanistically, PA increased ceramide content and c-Jun N-terminal kinase (JNK) phosphorylation. The ceramide synthase inhibitor effectively attenuated PA-induced β-cell damage and GPX4/Fe2+ abnormalities, while inhibiting JNK phosphorylation. Additionally, the JNK inhibitor SP600125 improved PA-induced cell damage. In conclusion, by promoting ceramide synthesis, PA inhibited GPX4 expression and increased intracellular Fe2+ to induce β-cell ferroptosis. Moreover, JNK may be a downstream mechanism of ceramide-triggered lipotoxic ferroptosis in β-cells.
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Affiliation(s)
- Maojun Guo
- Department of Endocrinology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, 210011, China
| | - Xiaolong Huang
- Department of Endocrinology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, 210011, China
| | - Junhan Zhang
- Department of Endocrinology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, 210011, China
| | - Ying Huang
- Department of Endocrinology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, 210011, China
| | - Ying Tang
- Department of Endocrinology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, 210011, China
| | - Honghua Wen
- Department of Endocrinology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, 210011, China
| | - Yanan Xu
- Department of Endocrinology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, 210011, China; Department of Endocrinology, The First People's Hospital of Lianyungang, Lianyungang, Jiangsu, 222002, China
| | - Shaokun Zhang
- Department of Endocrinology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, 210011, China; Department of Infectious Diseases, Taizhou Second People's Hospital, Taizhou, Jiangsu, 225500, China
| | - Xiao Wei
- Department of Endocrinology, Affiliated Hospital of Integrated Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, 210028, China
| | - Shuoshuo Sun
- The Second Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, 325000, China
| | - Qun Zhu
- Department of Endocrinology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, 210011, China.
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Anastasiou IA, Eleftheriadou I, Tentolouris A, Koliaki C, Kosta OA, Tentolouris N. CDATA[The Effect of Oxidative Stress and Antioxidant Therapies on Pancreatic β-cell Dysfunction: Results from in Vitro and in Vivo Studies. Curr Med Chem 2021; 28:1328-1346. [PMID: 32452321 DOI: 10.2174/0929867327666200526135642] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 04/07/2020] [Accepted: 04/25/2020] [Indexed: 11/22/2022]
Abstract
BACKGROUND Oxidative stress is a hallmark of many diseases. A growing body of evidence suggests that hyperglycemia-induced oxidative stress plays an important role in pancreatic β-cells dysfunction and apoptosis, as well as in the development and progression of diabetic complications. Considering the vulnerability of pancreatic β-cells to oxidative damage, the induction of endogenous antioxidant enzymes or exogenous antioxidant administration has been proposed to protect pancreatic β-cells from damage. OBJECTIVES The present review aims to provide evidence of the effect of oxidative stress and antioxidant therapies on pancreatic β-cell function, based on in vitro and in vivo studies. METHODS The MEDLINE and EMBASE databases were searched to retrieve available data. RESULTS Due to poor endogenous antioxidant mechanisms, pancreatic β-cells are extremely sensitive to Reactive Oxygen Species (ROS). Many natural extracts have been tested in vitro in pancreatic β-cell lines in terms of their antioxidant and diabetes mellitus ameliorating effects, and the majority of them have shown a dose-dependent protective role. On the other hand, there is relatively limited evidence regarding the in vitro antioxidant effects of antidiabetic drugs on pancreatic β -cells. Concerning in vivo studies, several natural extracts have shown beneficial effects in the setting of diabetes by decreasing blood glucose and lipid levels, increasing insulin sensitivity, and by up-regulating intrinsic antioxidant enzyme activity. However, there is limited evidence obtained from in vivo studies regarding antidiabetic drugs. CONCLUSION Antioxidants hold promise for developing strategies aimed at the prevention or treatment of diabetes mellitus associated with pancreatic β-cells dysfunction, as supported by in vitro and in vivo studies. However, more in vitro studies are required for drugs.
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Affiliation(s)
- Ioanna A Anastasiou
- Diabetes Center, First Department of Propaedeutic Internal Medicine, Medical School, National and Kapodistrian University of Athens, Laiko General Hospital, 17 AgiouThoma St., 11527 Athens, Greece
| | - Ioanna Eleftheriadou
- Diabetes Center, First Department of Propaedeutic Internal Medicine, Medical School, National and Kapodistrian University of Athens, Laiko General Hospital, 17 AgiouThoma St., 11527 Athens, Greece
| | - Anastasios Tentolouris
- Diabetes Center, First Department of Propaedeutic Internal Medicine, Medical School, National and Kapodistrian University of Athens, Laiko General Hospital, 17 AgiouThoma St., 11527 Athens, Greece
| | - Chrysi Koliaki
- Diabetes Center, First Department of Propaedeutic Internal Medicine, Medical School, National and Kapodistrian University of Athens, Laiko General Hospital, 17 AgiouThoma St., 11527 Athens, Greece
| | - Ourania A Kosta
- Diabetes Center, First Department of Propaedeutic Internal Medicine, Medical School, National and Kapodistrian University of Athens, Laiko General Hospital, 17 AgiouThoma St., 11527 Athens, Greece
| | - Nikolaos Tentolouris
- Diabetes Center, First Department of Propaedeutic Internal Medicine, Medical School, National and Kapodistrian University of Athens, Laiko General Hospital, 17 AgiouThoma St., 11527 Athens, Greece
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Sun Y, Wang J, Guo X, Zhu N, Niu L, Ding X, Xie Z, Chen X, Yang F. Oleic Acid and Eicosapentaenoic Acid Reverse Palmitic Acid-induced Insulin Resistance in Human HepG2 Cells via the Reactive Oxygen Species / JUN Pathway. GENOMICS PROTEOMICS & BIOINFORMATICS 2021; 19:754-771. [PMID: 33631425 PMCID: PMC9170756 DOI: 10.1016/j.gpb.2019.06.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Revised: 06/18/2019] [Accepted: 06/27/2019] [Indexed: 12/17/2022]
Abstract
Oleic acid (OA), a monounsaturated fatty acid (MUFA), has previously been shown to reverse saturated fatty acid palmitic acid (PA)-induced hepatic insulin resistance (IR). However, its underlying molecular mechanism is unclear. In addition, previous studies have shown that eicosapentaenoic acid (EPA), a ω-3 polyunsaturated fatty acid (PUFA), reverses PA-induced muscle IR, but whether EPA plays the same role in hepatic IR and its possible mechanism involved need to be further clarified. Here, we confirmed that EPA reversed PA-induced IR in HepG2 cells and compared the proteomic changes in HepG2 cells after treatment with different free fatty acids (FFAs). A total of 234 proteins were determined to be differentially expressed after PA+OA treatment. Their functions were mainly related to responses to stress and endogenous stimuli, lipid metabolic process, and protein binding. For PA+EPA treatment, the PA-induced expression changes of 1326 proteins could be reversed by EPA, 415 of which were mitochondrial proteins, with most of the functional proteins involved in oxidative phosphorylation (OXPHOS) and tricarboxylic acid (TCA) cycle. Mechanistic studies revealed that the protein encoded by JUN and reactive oxygen species (ROS) play a role in OA- and EPA-reversed PA-induced IR, respectively. EPA and OA alleviated PA-induced abnormal adenosine triphosphate (ATP) production, ROS generation, and calcium (Ca2+) content. Importantly, H2O2-activated production of ROS increased the protein expression of JUN, further resulting in IR in HepG2 cells. Taken together, we demonstrate that ROS/JUN is a common response pathway employed by HepG2 cells toward FFA-regulated IR.
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Affiliation(s)
- Yaping Sun
- Key Laboratory of Protein and Peptide Pharmaceuticals & Laboratory of Proteomics, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jifeng Wang
- Key Laboratory of Protein and Peptide Pharmaceuticals & Laboratory of Proteomics, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Xiaojing Guo
- Key Laboratory of Protein and Peptide Pharmaceuticals & Laboratory of Proteomics, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Nali Zhu
- Key Laboratory of Protein and Peptide Pharmaceuticals & Laboratory of Proteomics, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Lili Niu
- Key Laboratory of Protein and Peptide Pharmaceuticals & Laboratory of Proteomics, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Xiang Ding
- Key Laboratory of Protein and Peptide Pharmaceuticals & Laboratory of Proteomics, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Zhensheng Xie
- Key Laboratory of Protein and Peptide Pharmaceuticals & Laboratory of Proteomics, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Xiulan Chen
- Key Laboratory of Protein and Peptide Pharmaceuticals & Laboratory of Proteomics, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Fuquan Yang
- Key Laboratory of Protein and Peptide Pharmaceuticals & Laboratory of Proteomics, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China.
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Beta Cell Physiological Dynamics and Dysfunctional Transitions in Response to Islet Inflammation in Obesity and Diabetes. Metabolites 2020; 10:metabo10110452. [PMID: 33182622 PMCID: PMC7697558 DOI: 10.3390/metabo10110452] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 10/02/2020] [Accepted: 10/10/2020] [Indexed: 02/07/2023] Open
Abstract
Beta cells adapt their function to respond to fluctuating glucose concentrations and variable insulin demand. The highly specialized beta cells have well-established endoplasmic reticulum to handle their high metabolic load for insulin biosynthesis and secretion. Beta cell endoplasmic reticulum therefore recognize and remove misfolded proteins thereby limiting their accumulation. Beta cells function optimally when they sense glucose and, in response, biosynthesize and secrete sufficient insulin. Overnutrition drives the pathogenesis of obesity and diabetes, with adverse effects on beta cells. The interleukin signaling system maintains beta cell physiology and plays a role in beta cell inflammation. In pre-diabetes and compromised metabolic states such as obesity, insulin resistance, and glucose intolerance, beta cells biosynthesize and secrete more insulin, i.e., hyperfunction. Obesity is entwined with inflammation, characterized by compensatory hyperinsulinemia, for a defined period, to normalize glycemia. However, with chronic hyperglycemia and diabetes, there is a perpetual high demand for insulin, and beta cells become exhausted resulting in insufficient insulin biosynthesis and secretion, i.e., they hypofunction in response to elevated glycemia. Therefore, beta cell hyperfunction progresses to hypofunction, and may progressively worsen towards failure. Preserving beta cell physiology, through healthy nutrition and lifestyles, and therapies that are aligned with beta cell functional transitions, is key for diabetes prevention and management.
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Fatty Acid-Stimulated Insulin Secretion vs. Lipotoxicity. Molecules 2018; 23:molecules23061483. [PMID: 29921789 PMCID: PMC6100479 DOI: 10.3390/molecules23061483] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 06/13/2018] [Accepted: 06/15/2018] [Indexed: 12/29/2022] Open
Abstract
Fatty acid (FA)-stimulated insulin secretion (FASIS) is reviewed here in contrast to type 2 diabetes etiology, resulting from FA overload, oxidative stress, intermediate hyperinsulinemia, and inflammation, all converging into insulin resistance. Focusing on pancreatic islet β-cells, we compare the physiological FA roles with the pathological ones. Considering FAs not as mere amplifiers of glucose-stimulated insulin secretion (GSIS), but as parallel insulin granule exocytosis inductors, partly independent of the KATP channel closure, we describe the FA initiating roles in the prediabetic state that is induced by retardations in the glycerol-3-phosphate (glucose)-promoted glycerol/FA cycle and by the impaired GPR40/FFA1 (free FA1) receptor pathway, specifically in its amplification by the redox-activated mitochondrial phospholipase, iPLA2γ. Also, excessive dietary FAs stimulate intestine enterocyte incretin secretion, further elevating GSIS, even at low glucose levels, thus contributing to diabetic hyperinsulinemia. With overnutrition and obesity, the FA overload causes impaired GSIS by metabolic dysbalance, paralleled by oxidative and metabolic stress, endoplasmic reticulum stress and numerous pro-apoptotic signaling, all leading to decreased β-cell survival. Lipotoxicity is exerted by saturated FAs, whereas ω-3 polyunsaturated FAs frequently exert antilipotoxic effects. FA-facilitated inflammation upon the recruitment of excess M1 macrophages into islets (over resolving M2 type), amplified by cytokine and chemokine secretion by β-cells, leads to an inevitable failure of pancreatic β-cells.
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Toll-Like Receptors: Regulators of the Immune Response in the Human Gut. Nutrients 2018; 10:nu10020203. [PMID: 29438282 PMCID: PMC5852779 DOI: 10.3390/nu10020203] [Citation(s) in RCA: 134] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 02/08/2018] [Accepted: 02/09/2018] [Indexed: 12/28/2022] Open
Abstract
Toll-like receptors (TLRs) are powerful molecular regulators by which the immune system may "sense" the environment and protect the host from pathogens or endogenous threats. In mammalian cells, several TLRs were identified with a tissue and cell type-specific distribution. Understanding the functions of specific TLRs is crucial for the development and discovery of compounds useful to maintaining or re-establishing homeostasis in the gastrointestinal tract (GIT). Due to their relevance in regulating the inflammatory response in the GIT, we will focus here on TLR2, TLR4, and TLR5. In particular, we describe (a) the molecular pathways activated by the stimulation of these receptors with their known bacterial ligands; (b) the non-bacterial ligands known to interact directly with TLR2 and TLR4 and their soluble forms. The scope of this minireview is to highlight the importance of bacterial and non-bacterial compounds in affecting the gut immune functions via the activation of the TLRs.
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Identification of islet-enriched long non-coding RNAs contributing to β-cell failure in type 2 diabetes. Mol Metab 2017; 6:1407-1418. [PMID: 29107288 PMCID: PMC5681241 DOI: 10.1016/j.molmet.2017.08.005] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Revised: 08/10/2017] [Accepted: 08/14/2017] [Indexed: 11/21/2022] Open
Abstract
Objective Non-coding RNAs constitute a major fraction of the β-cell transcriptome. While the involvement of microRNAs is well established, the contribution of long non-coding RNAs (lncRNAs) in the regulation of β-cell functions and in diabetes development remains poorly understood. The aim of this study was to identify novel islet lncRNAs differently expressed in type 2 diabetes models and to investigate their role in β-cell failure and in the development of the disease. Methods Novel transcripts dysregulated in the islets of diet-induced obese mice were identified by high throughput RNA-sequencing coupled with de novo annotation. Changes in the level of the lncRNAs were assessed by real-time PCR. The functional role of the selected lncRNAs was determined by modifying their expression in MIN6 cells and primary islet cells. Results We identified about 1500 novel lncRNAs, a number of which were differentially expressed in obese mice. The expression of two lncRNAs highly enriched in β-cells, βlinc2, and βlinc3, correlated to body weight gain and glycemia levels in obese mice and was also modified in diabetic db/db mice. The expression of both lncRNAs was also modulated in vitro in isolated islet cells by glucolipotoxic conditions. Moreover, the expression of the human orthologue of βlinc3 was altered in the islets of type 2 diabetic patients and was associated to the BMI of the donors. Modulation of the level of βlinc2 and βlinc3 by overexpression or downregulation in MIN6 and mouse islet cells did not affect insulin secretion but increased β-cell apoptosis. Conclusions Taken together, the data show that lncRNAs are modulated in a model of obesity-associated type 2 diabetes and that variations in the expression of some of them may contribute to β-cell failure during the development of the disease. Mouse pancreatic islets express a large number of novel long non-coding RNAs. Many long non-coding RNAs are differentially expressed in the islets of obese mice. The level of two islet long non-coding RNAs correlates to body weight and glycemia. The expression of these islet long non-coding RNAs is altered in Type 2 diabetes. Altered expression of these long non-coding RNAs sensitise β-cells to apoptosis.
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Kulkarni H, Mamtani M, Wong G, Weir JM, Barlow CK, Dyer TD, Almasy L, Mahaney MC, Comuzzie AG, Duggirala R, Meikle PJ, Blangero J, Curran JE. Genetic correlation of the plasma lipidome with type 2 diabetes, prediabetes and insulin resistance in Mexican American families. BMC Genet 2017; 18:48. [PMID: 28525987 PMCID: PMC5438505 DOI: 10.1186/s12863-017-0515-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2016] [Accepted: 05/11/2017] [Indexed: 01/15/2023] Open
Abstract
Background Differential plasma concentrations of circulating lipid species are associated with pathogenesis of type 2 diabetes (T2D). Whether the wide inter-individual variability in the plasma lipidome contributes to the genetic basis of T2D is unknown. Here, we investigated the potential overlap in the genetic basis of the plasma lipidome and T2D-related traits. Results We used plasma lipidomic data (1202 pedigreed individuals, 319 lipid species representing 23 lipid classes) from San Antonio Family Heart Study in Mexican Americans. Bivariate trait analyses were used to estimate the genetic and environmental correlation of all lipid species with three T2D-related traits: risk of T2D, presence of prediabetes and homeostatic model of assessment – insulin resistance. We found that 44 lipid species were significantly genetically correlated with one or more of the three T2D-related traits. Majority of these lipid species belonged to the diacylglycerol (DAG, 17 species) and triacylglycerol (TAG, 17 species) classes. Six lipid species (all belonging to the triacylglycerol class and containing palmitate at the first position) were significantly genetically correlated with all the T2D-related traits. Conclusions Our results imply that: a) not all plasma lipid species are genetically informative for T2D pathogenesis; b) the DAG and TAG lipid classes partially share genetic basis of T2D; and c) 1-palmitate containing TAGs may provide additional insights into the genetic basis of T2D. Electronic supplementary material The online version of this article (doi:10.1186/s12863-017-0515-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Hemant Kulkarni
- South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, Brownsville, TX, 78520, USA.
| | - Manju Mamtani
- South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, Brownsville, TX, 78520, USA
| | - Gerard Wong
- Baker IDI Heart and Diabetes Institute, Melbourne, VIC, Australia
| | - Jacquelyn M Weir
- Baker IDI Heart and Diabetes Institute, Melbourne, VIC, Australia
| | | | - Thomas D Dyer
- South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, Brownsville, TX, 78520, USA
| | - Laura Almasy
- South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, Brownsville, TX, 78520, USA
| | - Michael C Mahaney
- South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, Brownsville, TX, 78520, USA
| | - Anthony G Comuzzie
- Department of Genetics, Texas Biomedical Research Institute, San Antonio, TX, USA
| | - Ravindranath Duggirala
- South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, Brownsville, TX, 78520, USA
| | - Peter J Meikle
- Baker IDI Heart and Diabetes Institute, Melbourne, VIC, Australia
| | - John Blangero
- South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, Brownsville, TX, 78520, USA
| | - Joanne E Curran
- South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, Brownsville, TX, 78520, USA
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Chen Y, Carlessi R, Walz N, Cruzat VF, Keane K, John AN, Jiang FX, Carnagarin R, Dass CR, Newsholme P. Pigment epithelium-derived factor (PEDF) regulates metabolism and insulin secretion from a clonal rat pancreatic beta cell line BRIN-BD11 and mouse islets. Mol Cell Endocrinol 2016; 426:50-60. [PMID: 26868448 DOI: 10.1016/j.mce.2016.02.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Revised: 01/23/2016] [Accepted: 02/05/2016] [Indexed: 02/05/2023]
Abstract
Pigment epithelium-derived factor (PEDF) is a multifunctional glycoprotein, associated with lipid catabolism and insulin resistance. In the present study, PEDF increased chronic and acute insulin secretion in a clonal rat β-cell line BRIN-BD11, without alteration of glucose consumption. PEDF also stimulated insulin secretion from primary mouse islets. Seahorse flux analysis demonstrated that PEDF did not change mitochondrial respiration and glycolytic function. The cytosolic presence of the putative PEDF receptor - adipose triglyceride lipase (ATGL) - was identified, and ATGL associated stimulation of glycerol release was robustly enhanced by PEDF, while intracellular ATP levels increased. Addition of palmitate or ex vivo stimulation with inflammatory mediators induced β-cell dysfunction, effects not altered by the addition of PEDF. In conclusion, PEDF increased insulin secretion in BRIN-BD11 and islet cells, but had no impact on glucose metabolism. Thus elevated lipolysis and enhanced fatty acid availability may impact insulin secretion following PEDF receptor (ATGL) stimulation.
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Affiliation(s)
- Younan Chen
- School of Biomedical Sciences, CHIRI Biosciences, Curtin University, GPO Box U1987, Perth, Western Australia, Australia; Key Laboratory of Transplant Engineering and Immunology, NHFPC; Regenerative Medicine Research Center, West China Hospital, Sichuan University, Chengdu, PR China.
| | - Rodrigo Carlessi
- School of Biomedical Sciences, CHIRI Biosciences, Curtin University, GPO Box U1987, Perth, Western Australia, Australia
| | - Nikita Walz
- School of Biomedical Sciences, CHIRI Biosciences, Curtin University, GPO Box U1987, Perth, Western Australia, Australia
| | - Vinicius Fernandes Cruzat
- School of Biomedical Sciences, CHIRI Biosciences, Curtin University, GPO Box U1987, Perth, Western Australia, Australia
| | - Kevin Keane
- School of Biomedical Sciences, CHIRI Biosciences, Curtin University, GPO Box U1987, Perth, Western Australia, Australia
| | - Abraham N John
- Harry Perkins Institute of Medical Research, Centre for Medical Research, University of Western Australia, Nedlands, Western Australia 6009, Australia
| | - Fang-Xu Jiang
- Harry Perkins Institute of Medical Research, Centre for Medical Research, University of Western Australia, Nedlands, Western Australia 6009, Australia
| | - Revathy Carnagarin
- School of Pharmacy, CHIRI Biosciences, Curtin University, GPO Box U1987, Perth, Western Australia, Australia
| | - Crispin R Dass
- School of Pharmacy, CHIRI Biosciences, Curtin University, GPO Box U1987, Perth, Western Australia, Australia
| | - Philip Newsholme
- School of Biomedical Sciences, CHIRI Biosciences, Curtin University, GPO Box U1987, Perth, Western Australia, Australia.
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Tschapalda K, Zhang YQ, Liu L, Golovnina K, Schlemper T, Eichmann TO, Lal-Nag M, Sreenivasan U, McLenithan J, Ziegler S, Sztalryd C, Lass A, Auld D, Oliver B, Waldmann H, Li Z, Shen M, Boxer MB, Beller M. A Class of Diacylglycerol Acyltransferase 1 Inhibitors Identified by a Combination of Phenotypic High-throughput Screening, Genomics, and Genetics. EBioMedicine 2016; 8:49-59. [PMID: 27428418 PMCID: PMC4919474 DOI: 10.1016/j.ebiom.2016.04.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Revised: 04/02/2016] [Accepted: 04/12/2016] [Indexed: 12/13/2022] Open
Abstract
Excess lipid storage is an epidemic problem in human populations. Thus, the identification of small molecules to treat or prevent lipid storage-related metabolic complications is of great interest. Here we screened > 320.000 compounds for their ability to prevent a cellular lipid accumulation phenotype. We used fly cells because the multifarious tools available for this organism should facilitate unraveling the mechanism-of-action of active small molecules. Of the several hundred lipid storage inhibitors identified in the primary screen we concentrated on three structurally diverse and potent compound classes active in cells of multiple species (including human) and negligible cytotoxicity. Together with Drosophila in vivo epistasis experiments, RNA-Seq expression profiles suggested that the target of one of the small molecules was diacylglycerol acyltransferase 1 (DGAT1), a key enzyme in the production of triacylglycerols and prominent human drug target. We confirmed this prediction by biochemical and enzymatic activity tests. We identified > 600 potent small molecule inhibitors of cellular lipid storage deposition. RNA-Seq expression profiling discriminated the activity of three lead scaffolds and guided subsequent functional studies. We discovered a class of DGAT1 inhibitors, which is active in fly and mammalian cell lines as well as whole flies.
Obesity and other lipid storage associated diseases are a growing health threat of human populations. In an undirected phenotypic screen, we identified pharmacologically active small molecules that reduce or enhance lipid storage. Our work focuses on three lead structures that prevent lipid storage in diverse cellular systems including cells from a diabetes patient. In order to elucidate the compound mechanisms-of-action and cellular targets, we used a combination of RNA-Seq transcriptional profiling and diverse functional assays. Our results strongly suggest that one of our lead structures represents a class of inhibitors targeting the key lipogenic enzyme diacylglycerol acyltransferase 1.
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Affiliation(s)
- Kirsten Tschapalda
- Systems Biology of Lipid Metabolism, Heinrich Heine University Düsseldorf, Germany; Institute for Mathematical Modeling of Biological Systems, Heinrich Heine University Düsseldorf, Germany; Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany; Department of Molecular Developmental Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Ya-Qin Zhang
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, USA
| | - Li Liu
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, USA
| | - Kseniya Golovnina
- National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, USA
| | - Thomas Schlemper
- Systems Biology of Lipid Metabolism, Heinrich Heine University Düsseldorf, Germany; Institute for Mathematical Modeling of Biological Systems, Heinrich Heine University Düsseldorf, Germany
| | | | - Madhu Lal-Nag
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, USA
| | - Urmila Sreenivasan
- Department of Medicine, Division of Endocrinology University of Maryland School of Medicine, USA
| | - John McLenithan
- Department of Medicine, Division of Endocrinology University of Maryland School of Medicine, USA
| | - Slava Ziegler
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Carole Sztalryd
- Department of Medicine, Division of Endocrinology University of Maryland School of Medicine, USA; Baltimore VA Medical Center, VA Research Service, Geriatric Research, Education and Clinical Center (GRECC) and VA Maryland Health Care System, Department of Medicine, Division of Endocrinology University of Maryland School of Medicine, USA
| | - Achim Lass
- Institute of Molecular Biosciences, University of Graz, Austria
| | - Douglas Auld
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, USA
| | - Brian Oliver
- National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, USA
| | - Herbert Waldmann
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Zhuyin Li
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, USA
| | - Min Shen
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, USA
| | - Matthew B Boxer
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, USA
| | - Mathias Beller
- Systems Biology of Lipid Metabolism, Heinrich Heine University Düsseldorf, Germany; Institute for Mathematical Modeling of Biological Systems, Heinrich Heine University Düsseldorf, Germany.
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11
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Jung IR, Choi SE, Jung JG, Lee SA, Han SJ, Kim HJ, Kim DJ, Lee KW, Kang Y. Involvement of iron depletion in palmitate-induced lipotoxicity of beta cells. Mol Cell Endocrinol 2015; 407:74-84. [PMID: 25779532 DOI: 10.1016/j.mce.2015.03.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 01/28/2015] [Accepted: 03/10/2015] [Indexed: 12/28/2022]
Abstract
High levels of plasma free fatty acid are thought to contribute to the loss of pancreatic beta-cells in type 2 diabetes. In particular, saturated fatty acid such as palmitate or stearate can induce apoptosis in cultured beta cells (lipotoxicity). Endoplasmic reticulum stress is a critical mediator of free fatty acid-induced lipotoxicity. Recently, disorders in mitochondrial respiratory metabolism have been linked to lipotoxicity. Since iron is a critical component of respiratory metabolism, this study is initiated to determine whether abnormal iron metabolism is involved in palmitate-induced beta cell death. Immunoblotting analysis showed that treatment of INS-1 beta cells with palmitate reduced the level of transferrin receptor 1 (TfR1), but increased the level of heavy chain ferritin (FTH). In addition, palmitate reduced intracellular labile iron pool. Whereas iron depletion through treatment with iron-chelators deferoxamine or deferasirox augmented palmitate-induced cell death, iron supplementation with ferric chloride, ferrous sulfate, or holo-transferrin significantly protected cells against palmitate-induced death. Furthermore, overexpression of TfR1 reduced palmitate-induced cell death, whereas knockdown of TfR1 augmented cell death. In particular, treatment with deferoxamine increased the level of endoplasmic reticulum (ER) stress markers phospho-PERK, phospho-eIF2α, CHOP and phospho-c-Jun N-terminal kinase. Treatment with chemical chaperone significantly protected cells against deferoxamine-induced apoptosis. Iron supplementation also protected cells against palmitate-induced primary islet death. These data suggest that iron depletion plays an important role in palmitate-induced beta cell death through inducing ER stress. Therefore, attempts to block iron depletion might be able to prevent beta cell loss in type 2 diabetes.
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Affiliation(s)
- Ik-Rak Jung
- Department of Physiology, Ajou University School of Medicine, Suwon, Kyunggi-do 442-749, Republic of Korea; Department of Biomedical Science, The Graduate School, Ajou University School of Medicine, Suwon, Kyunggi-do 442-749, Republic of Korea
| | - Sung-E Choi
- Department of Physiology, Ajou University School of Medicine, Suwon, Kyunggi-do 442-749, Republic of Korea
| | - Jong-Gab Jung
- Department of Biomedical Science, The Graduate School, Ajou University School of Medicine, Suwon, Kyunggi-do 442-749, Republic of Korea; Department of Endocrinology and Metabolism, Ajou University School of Medicine, Suwon, Kyunggi-do 442-749, Republic of Korea
| | - Sang-A Lee
- Department of Endocrinology and Metabolism, Ajou University School of Medicine, Suwon, Kyunggi-do 442-749, Republic of Korea
| | - Seung Jin Han
- Department of Endocrinology and Metabolism, Ajou University School of Medicine, Suwon, Kyunggi-do 442-749, Republic of Korea
| | - Hae Jin Kim
- Department of Endocrinology and Metabolism, Ajou University School of Medicine, Suwon, Kyunggi-do 442-749, Republic of Korea
| | - Dae Jung Kim
- Department of Endocrinology and Metabolism, Ajou University School of Medicine, Suwon, Kyunggi-do 442-749, Republic of Korea
| | - Kwan-Woo Lee
- Department of Endocrinology and Metabolism, Ajou University School of Medicine, Suwon, Kyunggi-do 442-749, Republic of Korea
| | - Yup Kang
- Department of Physiology, Ajou University School of Medicine, Suwon, Kyunggi-do 442-749, Republic of Korea; Department of Biomedical Science, The Graduate School, Ajou University School of Medicine, Suwon, Kyunggi-do 442-749, Republic of Korea.
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12
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Berná G, Oliveras-López MJ, Jurado-Ruíz E, Tejedo J, Bedoya F, Soria B, Martín F. Nutrigenetics and nutrigenomics insights into diabetes etiopathogenesis. Nutrients 2014; 6:5338-69. [PMID: 25421534 PMCID: PMC4245593 DOI: 10.3390/nu6115338] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Revised: 10/17/2014] [Accepted: 11/04/2014] [Indexed: 01/17/2023] Open
Abstract
Diabetes mellitus (DM) is considered a global pandemic, and the incidence of DM continues to grow worldwide. Nutrients and dietary patterns are central issues in the prevention, development and treatment of this disease. The pathogenesis of DM is not completely understood, but nutrient-gene interactions at different levels, genetic predisposition and dietary factors appear to be involved. Nutritional genomics studies generally focus on dietary patterns according to genetic variations, the role of gene-nutrient interactions, gene-diet-phenotype interactions and epigenetic modifications caused by nutrients; these studies will facilitate an understanding of the early molecular events that occur in DM and will contribute to the identification of better biomarkers and diagnostics tools. In particular, this approach will help to develop tailored diets that maximize the use of nutrients and other functional ingredients present in food, which will aid in the prevention and delay of DM and its complications. This review discusses the current state of nutrigenetics, nutrigenomics and epigenomics research on DM. Here, we provide an overview of the role of gene variants and nutrient interactions, the importance of nutrients and dietary patterns on gene expression, how epigenetic changes and micro RNAs (miRNAs) can alter cellular signaling in response to nutrients and the dietary interventions that may help to prevent the onset of DM.
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Affiliation(s)
- Genoveva Berná
- Department of Stem Cells, Andalusian Center of Molecular Biology and Regenerative Medicine, University Pablo Olavide (CABIMER-UPO), Seville 41091, Spain.
| | - María Jesús Oliveras-López
- Department of Stem Cells, Andalusian Center of Molecular Biology and Regenerative Medicine, University Pablo Olavide (CABIMER-UPO), Seville 41091, Spain.
| | - Enrique Jurado-Ruíz
- Department of Stem Cells, Andalusian Center of Molecular Biology and Regenerative Medicine, University Pablo Olavide (CABIMER-UPO), Seville 41091, Spain.
| | - Juan Tejedo
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), CIBER of Diabetes and Associated Metabolic Diseases, Instituto de Salud Carlos III, Madrid 28029, Spain.
| | - Francisco Bedoya
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), CIBER of Diabetes and Associated Metabolic Diseases, Instituto de Salud Carlos III, Madrid 28029, Spain.
| | - Bernat Soria
- Department of Stem Cells, Andalusian Center of Molecular Biology and Regenerative Medicine, University Pablo Olavide (CABIMER-UPO), Seville 41091, Spain.
| | - Franz Martín
- Department of Stem Cells, Andalusian Center of Molecular Biology and Regenerative Medicine, University Pablo Olavide (CABIMER-UPO), Seville 41091, Spain.
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13
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Wang X, Welsh N. Bcl-2 maintains the mitochondrial membrane potential, but fails to affect production of reactive oxygen species and endoplasmic reticulum stress, in sodium palmitate-induced β-cell death. Ups J Med Sci 2014; 119:306-15. [PMID: 25266628 PMCID: PMC4248070 DOI: 10.3109/03009734.2014.962714] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Sodium palmitate causes apoptosis of β-cells, and the anti-apoptotic protein Bcl-2 has been shown to counteract this event. However, the exact mechanisms that underlie palmitate-induced pancreatic β-cell apoptosis and through which pathway Bcl-2 executes the protective effect are still unclear. METHODS A stable Bcl-2-overexpressing RINm5F cell clone (BMG) and its negative control (B45) were exposed to palmitate for up to 8 h, and cell viability, mitochondrial membrane potential (Δψm), reactive oxygen species (ROS) generation, endoplasmic reticulum (ER) stress, and NF-κB activation were studied in time course experiments. RESULTS Palmitate exposure for 8 h resulted in increased cell death rates, and this event was partially counteracted by Bcl-2. Bcl-2 overexpression promoted in parallel also a delayed induction of GADD153/CHOP and a weaker phosphorylation of BimEL in palmitate-exposed cells. At earlier time points (2-4 h) palmitate exposure resulted in increased generation of ROS, a decrease in mitochondrial membrane potential (Δψm), and a modest increase in the phosphorylation of eIF2α and IRE1α. BMG cells produced similar amounts of ROS and displayed the same eIF2α and IRE1α phosphorylation rates as B45 cells. However, the palmitate-induced dissipation of Δψm was partially counteracted by Bcl-2. In addition, basal NF-κB activity was increased in BMG cells. CONCLUSIONS Our results indicate that Bcl-2 counteracts palmitate-induced β-cell death by maintaining mitochondrial membrane integrity and augmenting NF-κB activity, but not by affecting ROS production and ER stress.
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Affiliation(s)
- Xuan Wang
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Nils Welsh
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
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14
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Abstract
Palmitic acid, or hexadecanoic acid, a 16-carbon saturated fatty acid (FA), accounts for approximately 38% of the total circulating FA in lean or obese humans. In an article published in BMC Medicine, Hall et al. report that cultured islets from healthy donors, when exposed to palmitate, undergo changes in CpG methylation that are associated with modifications of expression in 290 genes. Their results provide a first look at the mechanisms used by the endocrine pancreas of humans to keep a durable genomic imprint from their exposure to FA that can influence gene expression and possibly cell phenotype in the long term. It is likely that such studies will help understand the epigenetic response of β cells to a disturbed metabolic environment, especially one created by obesity.
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Affiliation(s)
| | - Pierre Bougnères
- Inserm U986, Pincus Building, Bicêtre Hospital, Paris Sud University, 94275 Le Kremlin Bicêtre, France.
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15
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Abdulreda MH, Berggren PO. Islet inflammation in plain sight. Diabetes Obes Metab 2013; 15 Suppl 3:105-16. [PMID: 24003927 PMCID: PMC3777660 DOI: 10.1111/dom.12160] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Accepted: 04/10/2013] [Indexed: 01/09/2023]
Abstract
Although, diabetes is reaching pandemic proportions, the exact aetiology of either type 1 (T1D) or type 2 diabetes (T2D) remains to be determined. Mounting evidence, however, suggests that islet inflammation is a likely common denominator during early development of either type of the disease. In this review, we highlight some of the inflammatory mechanisms that appear to be shared between T1D and T2D, and we explore the utility of intravital imaging in the study of islet inflammation. Intravital imaging has emerged as an indispensable tool in biomedical research and a variety of in vivo imaging approaches have been developed to study pancreatic islet physiology and pathophysiology in the native environment in health and disease. However, given the scattered distribution of the islets of Langerhans within the 'sea' of the exocrine pancreas located deep within the body and the fact that the islets only constitute 1-2% of the total volume of pancreatic tissue, studying the pancreatic islet in situ has been challenging. Here, we focus on a new experimental approach that enables studying local islet inflammation with single-cell resolution in the relevant context of the in vivo environment non-invasively and longitudinally and, thereby improving our understanding of diabetes pathogenesis.
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Affiliation(s)
- Midhat H. Abdulreda
- Diabetes Research Institute, University of Miami Miller School of Medicine, Stockholm, Sweden
- Department of Surgery, University of Miami Miller School of Medicine, Stockholm, Sweden
| | - Per-Olof Berggren
- Diabetes Research Institute, University of Miami Miller School of Medicine, Stockholm, Sweden
- Department of Surgery, University of Miami Miller School of Medicine, Stockholm, Sweden
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
- Correspondence details: The Rolf Luft Research Center for Diabetes and Endocrinology Karolinska Institutet, Karolinska University Hospital L1 SE-171 76 Stockholm, Sweden Phone +46 8 517 757 31, +46 70 729 5731 Fax +46 8 517 717 81
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16
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Abstract
PURPOSE OF REVIEW The purpose of this review is to discuss recent studies reporting on the influence of fatty acids on gene expression in relation to inflammation and immune responses. RECENT FINDINGS Saturated fatty acids promote, whereas several n-3 fatty acids, in particular eicosapentaenoic and docosahexaenoic acids, some isomers of conjugated linoleic acid, and punicic acid suppress, expression of inflammatory genes. The most common targets of fatty acids are genes encoding cytokines, chemokines, cyclooxygenase, nitric oxide synthase, and matrix metalloproteinases. The anti-inflammatory actions of fatty acids often involve inhibition of activation of nuclear factor-κB and activation of peroxisome proliferator-activated receptors α and γ. Common upstream events include actions on Toll-like receptors and via G-protein coupled receptors. Fatty acids can influence expression of genes involved in immune and inflammatory cell development and differentiation. Recent studies using genome-wide analyses demonstrate that dietary fatty acids can alter expression of a large number (many hundreds) of genes in human peripheral blood mononuclear cells. SUMMARY A wide range of fatty acids alter expression of genes involved in development, differentiation, and function of cells involved in inflammation and immunity.
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Affiliation(s)
- Philip C Calder
- Human Development and Health Academic Unit, Faculty of Medicine, University of Southampton, Southampton, UK.
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17
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Selvik LKM, Fjeldbo CS, Flatberg A, Steigedal TS, Misund K, Anderssen E, Doseth B, Langaas M, Tripathi S, Beisvag V, Lægreid A, Thommesen L, Bruland T. The duration of gastrin treatment affects global gene expression and molecular responses involved in ER stress and anti-apoptosis. BMC Genomics 2013; 14:429. [PMID: 23805861 PMCID: PMC3698217 DOI: 10.1186/1471-2164-14-429] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 06/19/2013] [Indexed: 01/13/2023] Open
Abstract
Background How cells decipher the duration of an external signal into different transcriptional outcomes is poorly understood. The hormone gastrin can promote a variety of cellular responses including proliferation, differentiation, migration and anti-apoptosis. While gastrin in normal concentrations has important physiological functions in the gastrointestine, prolonged high levels of gastrin (hypergastrinemia) is related to pathophysiological processes. Results We have used genome-wide microarray time series analysis and molecular studies to identify genes that are affected by the duration of gastrin treatment in adenocarcinoma cells. Among 403 genes differentially regulated in transiently (gastrin removed after 1 h) versus sustained (gastrin present for 14 h) treated cells, 259 genes upregulated by sustained gastrin treatment compared to untreated controls were expressed at lower levels in the transient mode. The difference was subtle for early genes like Junb and c-Fos, but substantial for delayed and late genes. Inhibition of protein synthesis by cycloheximide was used to distinguish between primary and secondary gastrin regulated genes. The majority of gastrin upregulated genes lower expressed in transiently treated cells were primary genes induced independently of de novo protein synthesis. This indicates that the duration effect of gastrin treatment is mainly mediated via post-translational signalling events, while a smaller fraction of the differentially expressed genes are regulated downstream of primary transcriptional events. Indeed, sustained gastrin treatment specifically induced prolonged ERK1/2 activation and elevated levels of the AP-1 subunit protein JUNB. Enrichment analyses of the differentially expressed genes suggested that endoplasmic reticulum (ER) stress and survival is affected by the duration of gastrin treatment. Sustained treatment exerted an anti-apoptotic effect on serum starvation-induced apoptosis via a PKC-dependent mechanism. In accordance with this, only sustained treatment induced anti-apoptotic genes like Clu, Selm and Mcl1, while the pro-apoptotic gene Casp2 was more highly expressed in transiently treated cells. Knockdown studies showed that JUNB is involved in sustained gastrin induced expression of the UPR/ER stress related genes Atf4, Herpud1 and Chac1. Conclusion The duration of gastrin treatment affects both intracellular signalling mechanisms and gene expression, and ERK1/2 and AP-1 seem to play a role in converting different durations of gastrin treatment into distinct cellular responses.
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Affiliation(s)
- Linn-Karina M Selvik
- Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology-NTNU, Trondheim N-7489, Norway
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18
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Abstract
Beta cell dysfunction and insulin resistance are inherently complex with their interrelation for triggering the pathogenesis of diabetes also somewhat undefined. Both pathogenic states induce hyperglycemia and therefore increase insulin demand. Beta cell dysfunction results from inadequate glucose sensing to stimulate insulin secretion therefore elevated glucose concentrations prevail. Persistently elevated glucose concentrations above the physiological range result in the manifestation of hyperglycemia. With systemic insulin resistance, insulin signaling within glucose recipient tissues is defective therefore hyperglycemia perseveres. Beta cell dysfunction supersedes insulin resistance in inducing diabetes. Both pathological states influence each other and presumably synergistically exacerbate diabetes. Preserving beta cell function and insulin signaling in beta cells and insulin signaling in the glucose recipient tissues will maintain glucose homeostasis.
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Affiliation(s)
- Marlon E. Cerf
- Diabetes Discovery Platform, South African Medical Research CouncilCape Town, South Africa
- *Correspondence: Marlon E. Cerf, Diabetes Discovery Platform, South African Medical Research Council, PO Box 19070, Tygerberg, Cape Town 7505, South Africa. e-mail:
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19
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Abstract
β-Cell dysfunction is a critical component in the development of type 2 diabetes. Whilst both genetic and environmental factors contribute to the development of the disease, relatively little is known about the molecular network that is responsible for diet-induced functional changes in pancreatic β-cells. Recent genome-wide association studies for diabetes-related traits have generated a large number of candidate genes that constitute possible links between dietary factors and the genetic susceptibility for β-cell failure. Here, we summarize recent approaches for identifying nutritionally regulated transcripts in islets on a genome-wide scale. Polygenic mouse models for type 2 diabetes have been instrumental for investigating the mechanism of diet-induced β-cell dysfunction. Enhanced oxidative metabolism, triggered by a combination of dietary carbohydrates and fat, appears to play a critical role in the pathophysiology of diet-induced impairment of islets. More systematic studies of gene-diet interactions in β-cells of rodent models in combination with genetic profiling might reveal the regulatory circuits fundamental for the understanding of diet-induced impairments of β-cell function in humans.
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Affiliation(s)
- A Chadt
- German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
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