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Lubaczeuski C, Bozadjieva-Kramer N, Louzada RA, Gittes GK, Leibowitz G, Bernal-Mizrachi E. Time-dependent effects of endogenous hyperglucagonemia on glucose homeostasis and hepatic glucagon action. JCI Insight 2023; 8:e162255. [PMID: 37140984 PMCID: PMC10393226 DOI: 10.1172/jci.insight.162255] [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: 06/02/2022] [Accepted: 05/03/2023] [Indexed: 05/05/2023] Open
Abstract
Elevation of glucagon levels and increase in α cell proliferation is associated with states of hyperglycemia in diabetes. A better understanding of the molecular mechanisms governing glucagon secretion could have major implications for understanding abnormal responses to hypoglycemia in patients with diabetes and provide novel avenues for diabetes management. Using mice with inducible induction of Rheb1 in α cells (αRhebTg mice), we showed that short-term activation of mTORC1 signaling is sufficient to induce hyperglucagonemia through increased glucagon secretion. Hyperglucagonemia in αRhebTg mice was also associated with an increase in α cell size and mass expansion. This model allowed us to identify the effects of chronic and short-term hyperglucagonemia on glucose homeostasis by regulating glucagon signaling in the liver. Short-term hyperglucagonemia impaired glucose tolerance, which was reversible over time. Liver glucagon resistance in αRhebTg mice was associated with reduced expression of the glucagon receptor and genes involved in gluconeogenesis, amino acid metabolism, and urea production. However, only genes regulating gluconeogenesis returned to baseline upon improvement of glycemia. Overall, these studies demonstrate that hyperglucagonemia exerts a biphasic response on glucose metabolism: Short-term hyperglucagonemia lead to glucose intolerance, whereas chronic exposure to glucagon reduced hepatic glucagon action and improved glucose tolerance.
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Affiliation(s)
- Camila Lubaczeuski
- Department of Medicine, Division Endocrinology, Metabolism and Diabetes, Miller School of Medicine, University of Miami, Miami, Florida, USA
| | - Nadejda Bozadjieva-Kramer
- Veterans Affairs Ann Arbor Healthcare System, Research Service, Ann Arbor, Michigan, USA
- Department of Surgery, University of Michigan, Ann Arbor, Michigan, USA
| | - Ruy A. Louzada
- Department of Medicine, Division Endocrinology, Metabolism and Diabetes, Miller School of Medicine, University of Miami, Miami, Florida, USA
| | - George K. Gittes
- Childrens Hospital, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Gil Leibowitz
- Diabetes Unit and Endocrine Service, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Ernesto Bernal-Mizrachi
- Department of Medicine, Division Endocrinology, Metabolism and Diabetes, Miller School of Medicine, University of Miami, Miami, Florida, USA
- Diabetes Unit and Endocrine Service, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
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2
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Jain C, Bilekova S, Lickert H. Targeting pancreatic β cells for diabetes treatment. Nat Metab 2022; 4:1097-1108. [PMID: 36131204 DOI: 10.1038/s42255-022-00618-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Accepted: 07/13/2022] [Indexed: 11/09/2022]
Abstract
Insulin is a life-saving drug for patients with type 1 diabetes; however, even today, no pharmacotherapy can prevent the loss or dysfunction of pancreatic insulin-producing β cells to stop or reverse disease progression. Thus, pancreatic β cells have been a main focus for cell-replacement and regenerative therapies as a curative treatment for diabetes. In this Review, we highlight recent advances toward the development of diabetes therapies that target β cells to enhance proliferation, redifferentiation and protection from cell death and/or enable selective killing of senescent β cells. We describe currently available therapies and their mode of action, as well as insufficiencies of glucagon-like peptide 1 (GLP-1) and insulin therapies. We discuss and summarize data collected over the last decades that support the notion that pharmacological targeting of β cell insulin signalling might protect and/or regenerate β cells as an improved treatment of patients with diabetes.
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Affiliation(s)
- Chirag Jain
- Institute of Diabetes and Regeneration Research, Helmholtz Zentrum München, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
- Immunology Discovery, Genentech Inc., South San Francisco, CA, USA
| | - Sara Bilekova
- Institute of Diabetes and Regeneration Research, Helmholtz Zentrum München, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Heiko Lickert
- Institute of Diabetes and Regeneration Research, Helmholtz Zentrum München, Neuherberg, Germany.
- German Center for Diabetes Research (DZD), Neuherberg, Germany.
- Chair of β-Cell Biology, Technische Universität München, School of Medicine, Klinikum Rechts der Isar, München, Germany.
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3
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Skovsø S, Panzhinskiy E, Kolic J, Cen HH, Dionne DA, Dai XQ, Sharma RB, Elghazi L, Ellis CE, Faulkner K, Marcil SAM, Overby P, Noursadeghi N, Hutchinson D, Hu X, Li H, Modi H, Wildi JS, Botezelli JD, Noh HL, Suk S, Gablaski B, Bautista A, Kim R, Cras-Méneur C, Flibotte S, Sinha S, Luciani DS, Nislow C, Rideout EJ, Cytrynbaum EN, Kim JK, Bernal-Mizrachi E, Alonso LC, MacDonald PE, Johnson JD. Beta-cell specific Insr deletion promotes insulin hypersecretion and improves glucose tolerance prior to global insulin resistance. Nat Commun 2022; 13:735. [PMID: 35136059 PMCID: PMC8826929 DOI: 10.1038/s41467-022-28039-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Accepted: 01/05/2022] [Indexed: 01/23/2023] Open
Abstract
Insulin receptor (Insr) protein is present at higher levels in pancreatic β-cells than in most other tissues, but the consequences of β-cell insulin resistance remain enigmatic. Here, we use an Ins1cre knock-in allele to delete Insr specifically in β-cells of both female and male mice. We compare experimental mice to Ins1cre-containing littermate controls at multiple ages and on multiple diets. RNA-seq of purified recombined β-cells reveals transcriptomic consequences of Insr loss, which differ between female and male mice. Action potential and calcium oscillation frequencies are increased in Insr knockout β-cells from female, but not male mice, whereas only male βInsrKO islets have reduced ATP-coupled oxygen consumption rate and reduced expression of genes involved in ATP synthesis. Female βInsrKO and βInsrHET mice exhibit elevated insulin release in ex vivo perifusion experiments, during hyperglycemic clamps, and following i.p. glucose challenge. Deletion of Insr does not alter β-cell area up to 9 months of age, nor does it impair hyperglycemia-induced proliferation. Based on our data, we adapt a mathematical model to include β-cell insulin resistance, which predicts that β-cell Insr knockout improves glucose tolerance depending on the degree of whole-body insulin resistance. Indeed, glucose tolerance is significantly improved in female βInsrKO and βInsrHET mice compared to controls at 9, 21 and 39 weeks, and also in insulin-sensitive 4-week old males. We observe no improved glucose tolerance in older male mice or in high fat diet-fed mice, corroborating the prediction that global insulin resistance obscures the effects of β-cell specific insulin resistance. The propensity for hyperinsulinemia is associated with mildly reduced fasting glucose and increased body weight. We further validate our main in vivo findings using an Ins1-CreERT transgenic line and find that male mice have improved glucose tolerance 4 weeks after tamoxifen-mediated Insr deletion. Collectively, our data show that β-cell insulin resistance in the form of reduced β-cell Insr contributes to hyperinsulinemia in the context of glucose stimulation, thereby improving glucose homeostasis in otherwise insulin sensitive sex, dietary and age contexts.
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Affiliation(s)
- Søs Skovsø
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Evgeniy Panzhinskiy
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Jelena Kolic
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Haoning Howard Cen
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Derek A Dionne
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Xiao-Qing Dai
- Alberta Diabetes Institute and Department of Pharmacology, University of Alberta, Edmonton, Canada
| | - Rohit B Sharma
- Division of Endocrinology, Diabetes and Metabolism and the Weill Center for Metabolic Health, Weill Cornell Medicine, New York, NY, USA
| | - Lynda Elghazi
- Department of Ophthalmology and Visual Sciences, University of Michigan Kellogg Eye Center, Ann Arbor, MI, USA
| | - Cara E Ellis
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Katharine Faulkner
- Department of Mathematics, University of British Columbia, Vancouver, BC, Canada
| | - Stephanie A M Marcil
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Peter Overby
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Nilou Noursadeghi
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Daria Hutchinson
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Xiaoke Hu
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Hong Li
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Honey Modi
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Jennifer S Wildi
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - J Diego Botezelli
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Hye Lim Noh
- Program in Molecular Medicine University of Massachusetts Medical School, Worcester, MA, USA
- Charles River Laboratories, Shrewsbury, MA, USA
| | - Sujin Suk
- Program in Molecular Medicine University of Massachusetts Medical School, Worcester, MA, USA
| | - Brian Gablaski
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Massachusetts Medical School, Worcester, MA, USA
- Charles River Laboratories, Shrewsbury, MA, USA
| | - Austin Bautista
- Alberta Diabetes Institute and Department of Pharmacology, University of Alberta, Edmonton, Canada
| | - Ryekjang Kim
- Alberta Diabetes Institute and Department of Pharmacology, University of Alberta, Edmonton, Canada
| | - Corentin Cras-Méneur
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, MI, USA
| | - Stephane Flibotte
- UBC Life Sciences Institute Bioinformatics Facility, University of British Columbia, Vancouver, BC, Canada
| | - Sunita Sinha
- UBC Sequencing and Bioinformatics Consortium, Pharmaceutical Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Dan S Luciani
- BC Children's Hospital Research Institute, Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Corey Nislow
- UBC Sequencing and Bioinformatics Consortium, Pharmaceutical Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Elizabeth J Rideout
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Eric N Cytrynbaum
- Department of Mathematics, University of British Columbia, Vancouver, BC, Canada
| | - Jason K Kim
- Program in Molecular Medicine University of Massachusetts Medical School, Worcester, MA, USA
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Massachusetts Medical School, Worcester, MA, USA
| | - Ernesto Bernal-Mizrachi
- Division of Endocrinology, Diabetes and Metabolism, University of Miami Miller School of Medicine and Miami VA Health Care System, Miami, FL, USA
| | - Laura C Alonso
- Division of Endocrinology, Diabetes and Metabolism and the Weill Center for Metabolic Health, Weill Cornell Medicine, New York, NY, USA
| | - Patrick E MacDonald
- Alberta Diabetes Institute and Department of Pharmacology, University of Alberta, Edmonton, Canada
| | - James D Johnson
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada.
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4
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Pancreatic β-Cell O-GlcNAc Transferase Overexpression Increases Susceptibility to Metabolic Stressors in Female Mice. Cells 2021; 10:cells10102801. [PMID: 34685781 PMCID: PMC8534823 DOI: 10.3390/cells10102801] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2021] [Revised: 10/14/2021] [Accepted: 10/14/2021] [Indexed: 01/21/2023] Open
Abstract
The nutrient-sensor O-GlcNAc transferase (Ogt), the sole enzyme that adds an O-GlcNAc-modification onto proteins, plays a critical role for pancreatic β-cell survival and insulin secretion. We hypothesized that β-cell Ogt overexpression would confer protection from β-cell failure in response to metabolic stressors, such as high-fat diet (HFD) and streptozocin (STZ). Here, we generated a β-cell-specific Ogt in overexpressing (βOgtOE) mice, where a significant increase in Ogt protein level and O-GlcNAc-modification of proteins were observed in islets under a normal chow diet. We uncovered that βOgtOE mice show normal peripheral insulin sensitivity and glucose tolerance with a regular chow diet. However, when challenged with an HFD, only female βOgtOE (homozygous) Hz mice developed a mild glucose intolerance, despite increased insulin secretion and normal β-cell mass. While female mice are normally resistant to low-dose STZ treatments, the βOgtOE Hz mice developed hyperglycemia and glucose intolerance post-STZ treatment. Transcriptome analysis between islets with loss or gain of Ogt by RNA sequencing shows common altered pathways involving pro-survival Erk and Akt and inflammatory regulators IL1β and NFkβ. Together, these data show a possible gene dosage effect of Ogt and the importance O-GlcNAc cycling in β-cell survival and function to regulate glucose homeostasis.
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5
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Long-Chain Acylcarnitines Decrease the Phosphorylation of the Insulin Receptor at Tyr1151 Through a PTP1B-Dependent Mechanism. Int J Mol Sci 2021; 22:ijms22126470. [PMID: 34208786 PMCID: PMC8235348 DOI: 10.3390/ijms22126470] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 06/11/2021] [Accepted: 06/14/2021] [Indexed: 01/26/2023] Open
Abstract
The accumulation of lipid intermediates may interfere with energy metabolism pathways and regulate cellular energy supplies. As increased levels of long-chain acylcarnitines have been linked to insulin resistance, we investigated the effects of long-chain acylcarnitines on key components of the insulin signalling pathway. We discovered that palmitoylcarnitine induces dephosphorylation of the insulin receptor (InsR) through increased activity of protein tyrosine phosphatase 1B (PTP1B). Palmitoylcarnitine suppresses protein kinase B (Akt) phosphorylation at Ser473, and this effect is not alleviated by the inhibition of PTP1B by the insulin sensitizer bis-(maltolato)-oxovanadium (IV). This result indicates that palmitoylcarnitine affects Akt activity independently of the InsR phosphorylation level. Inhibition of protein kinase C and protein phosphatase 2A does not affect the palmitoylcarnitine-mediated inhibition of Akt Ser473 phosphorylation. Additionally, palmitoylcarnitine markedly stimulates insulin release by suppressing Akt Ser473 phosphorylation in insulin-secreting RIN5F cells. In conclusion, long-chain acylcarnitines activate PTP1B and decrease InsR Tyr1151 phosphorylation and Akt Ser473 phosphorylation, thus limiting the cellular response to insulin stimulation.
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6
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Zhang AM, Wellberg EA, Kopp JL, Johnson JD. Hyperinsulinemia in Obesity, Inflammation, and Cancer. Diabetes Metab J 2021; 45:285-311. [PMID: 33775061 PMCID: PMC8164941 DOI: 10.4093/dmj.2020.0250] [Citation(s) in RCA: 79] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Accepted: 12/23/2020] [Indexed: 12/13/2022] Open
Abstract
The relative insufficiency of insulin secretion and/or insulin action causes diabetes. However, obesity and type 2 diabetes mellitus can be associated with an absolute increase in circulating insulin, a state known as hyperinsulinemia. Studies are beginning to elucidate the cause-effect relationships between hyperinsulinemia and numerous consequences of metabolic dysfunctions. Here, we review recent evidence demonstrating that hyperinsulinemia may play a role in inflammation, aging and development of cancers. In this review, we will focus on the consequences and mechanisms of excess insulin production and action, placing recent findings that have challenged dogma in the context of the existing body of literature. Where relevant, we elaborate on the role of specific signal transduction components in the actions of insulin and consequences of chronic hyperinsulinemia. By discussing the involvement of hyperinsulinemia in various metabolic and other chronic diseases, we may identify more effective therapeutics or lifestyle interventions for preventing or treating obesity, diabetes and cancer. We also seek to identify pertinent questions that are ripe for future investigation.
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Affiliation(s)
- Anni M.Y. Zhang
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada
| | - Elizabeth A. Wellberg
- Department of Pathology, University of Oklahoma Health Sciences Center, Stephenson Cancer Center, Harold Hamm Diabetes Center, Oklahoma City, OK, USA
| | - Janel L. Kopp
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada
| | - James D. Johnson
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada
- Corresponding author: James D. Johnson https://orcid.org/0000-0002-7523-9433 Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, 2329 W Mall Vancouver, BC V6T 1Z4, Vancouver, BC, Canada E-mail:
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7
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Abstract
We present the third case of alpelisib-induced diabetic ketoacidosis. Alpelisib is an antineoplastic agent that inhibits phosphatidylinositol 3-kinase (PI3K), which plays a key role in multiple biological processes such as cell differentiation, proliferation, and survival. Thereby, the inhibition of this pathway should cause antitumor activity. Alpelisib was recently approved by the Food and Drug Administration (FDA) for use in PIK3CA-mutated breast cancer. This mutation is a common indicator of poor prognosis and is also the most commonly mutated gene in hormone receptor (HR)-positive and human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer. During its trial, ketoacidosis was reported in only 0.7% of patients, with the more common side effects (>20%) being diarrhea (58%), rash (52%), nausea (45%), fatigue (42%), decreased appetite (36%), stomatitis (30%), vomiting (27%), weight loss (27%), and alopecia (20%). As breast cancer is the second most common cancer in women and approximately 40% of HR+/HER2- advanced breast cancer patients have a PIK3CA mutation, alpelisib will be prescribed more by oncologists and, therefore, appropriate screening with fasting plasma glucose, hemoglobin A1c (HbA1C), and monitoring during drug administration is of utmost importance.
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Affiliation(s)
- Paul Nguyen
- Internal Medicine, Wayne State University School of Medicine, Detroit, USA
| | - Aya Musa
- Endocrinology, Diabetes and Metabolism, Wayne State University School of Medicine, Detroit, USA
| | - Julie Samantray
- Endocrine Oncology, Karmanos Cancer Center, Detroit, USA.,Endocrinology, Diabetes and Metabolism, Wayne State University School of Medicine, Detroit, USA
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8
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Šrámek J, Němcová-Fürstová V, Kovář J. Molecular Mechanisms of Apoptosis Induction and Its Regulation by Fatty Acids in Pancreatic β-Cells. Int J Mol Sci 2021; 22:4285. [PMID: 33924206 PMCID: PMC8074590 DOI: 10.3390/ijms22084285] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 04/09/2021] [Accepted: 04/16/2021] [Indexed: 02/06/2023] Open
Abstract
Pancreatic β-cell failure and death contribute significantly to the pathogenesis of type 2 diabetes. One of the main factors responsible for β-cell dysfunction and subsequent cell death is chronic exposure to increased concentrations of FAs (fatty acids). The effect of FAs seems to depend particularly on the degree of their saturation. Saturated FAs induce apoptosis in pancreatic β-cells, whereas unsaturated FAs are well tolerated and are even capable of inhibiting the pro-apoptotic effect of saturated FAs. Molecular mechanisms of apoptosis induction by saturated FAs in β-cells are not completely elucidated. Saturated FAs induce ER stress, which in turn leads to activation of all ER stress pathways. When ER stress is severe or prolonged, apoptosis is induced. The main mediator seems to be the CHOP transcription factor. Via regulation of expression/activity of pro- and anti-apoptotic Bcl-2 family members, and potentially also through the increase in ROS production, CHOP switches on the mitochondrial pathway of apoptosis induction. ER stress signalling also possibly leads to autophagy signalling, which may activate caspase-8. Saturated FAs activate or inhibit various signalling pathways, i.e., p38 MAPK signalling, ERK signalling, ceramide signalling, Akt signalling and PKCδ signalling. This may lead to the activation of the mitochondrial pathway of apoptosis, as well. Particularly, the inhibition of the pro-survival Akt signalling seems to play an important role. This inhibition may be mediated by multiple pathways (e.g., ER stress signalling, PKCδ and ceramide) and could also consequence in autophagy signalling. Experimental evidence indicates the involvement of certain miRNAs in mechanisms of FA-induced β-cell apoptosis, as well. In the rather rare situations when unsaturated FAs are also shown to be pro-apoptotic, the mechanisms mediating this effect in β-cells seem to be the same as for saturated FAs. To conclude, FA-induced apoptosis rather appears to be preceded by complex cross talks of multiple signalling pathways. Some of these pathways may be regulated by decreased membrane fluidity due to saturated FA incorporation. Few data are available concerning molecular mechanisms mediating the protective effect of unsaturated FAs on the effect of saturated FAs. It seems that the main possible mechanism represents a rather inhibitory intervention into saturated FA-induced pro-apoptotic signalling than activation of some pro-survival signalling pathway(s) or metabolic interference in β-cells. This inhibitory intervention may be due to an increase of membrane fluidity.
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Affiliation(s)
- Jan Šrámek
- Department of Biochemistry, Cell and Molecular Biology & Center for Research of Diabetes, Metabolism and Nutrition, Third Faculty of Medicine, Charles University, Ruská 87, 100 00 Prague, Czech Republic;
| | - Vlasta Němcová-Fürstová
- Department of Biochemistry, Cell and Molecular Biology & Center for Research of Diabetes, Metabolism and Nutrition, Third Faculty of Medicine, Charles University, Ruská 87, 100 00 Prague, Czech Republic;
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9
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Arous C, Mizgier ML, Rickenbach K, Pinget M, Bouzakri K, Wehrle-Haller B. Integrin and autocrine IGF2 pathways control fasting insulin secretion in β-cells. J Biol Chem 2020; 295:16510-16528. [PMID: 32934005 PMCID: PMC7864053 DOI: 10.1074/jbc.ra120.012957] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 08/09/2020] [Indexed: 12/20/2022] Open
Abstract
Elevated levels of fasting insulin release and insufficient glucose-stimulated insulin secretion (GSIS) are hallmarks of diabetes. Studies have established cross-talk between integrin signaling and insulin activity, but more details of how integrin-dependent signaling impacts the pathophysiology of diabetes are needed. Here, we dissected integrin-dependent signaling pathways involved in the regulation of insulin secretion in β-cells and studied their link to the still debated autocrine regulation of insulin secretion by insulin/insulin-like growth factor (IGF) 2-AKT signaling. We observed for the first time a cooperation between different AKT isoforms and focal adhesion kinase (FAK)-dependent adhesion signaling, which either controlled GSIS or prevented insulin secretion under fasting conditions. Indeed, β-cells form integrin-containing adhesions, which provide anchorage to the pancreatic extracellular matrix and are the origin of intracellular signaling via FAK and paxillin. Under low-glucose conditions, β-cells adopt a starved adhesion phenotype consisting of actin stress fibers and large peripheral focal adhesion. In contrast, glucose stimulation induces cell spreading, actin remodeling, and point-like adhesions that contain phospho-FAK and phosphopaxillin, located in small protrusions. Rat primary β-cells and mouse insulinomas showed an adhesion remodeling during GSIS resulting from autocrine insulin/IGF2 and AKT1 signaling. However, under starving conditions, the maintenance of stress fibers and the large adhesion phenotype required autocrine IGF2-IGF1 receptor signaling mediated by AKT2 and elevated FAK-kinase activity and ROCK-RhoA levels but low levels of paxillin phosphorylation. This starved adhesion phenotype prevented excessive insulin granule release to maintain low insulin secretion during fasting. Thus, deregulation of the IGF2 and adhesion-mediated signaling may explain dysfunctions observed in diabetes.
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Affiliation(s)
- Caroline Arous
- Department of Cell Physiology and Metabolism, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland.
| | - Maria Luisa Mizgier
- UMR DIATHEC, Centre Européen d'Etude du Diabète, UMR DIATHEC, Strasbourg, France
| | - Katharina Rickenbach
- Department of Cell Physiology and Metabolism, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland
| | - Michel Pinget
- UMR DIATHEC, Centre Européen d'Etude du Diabète, UMR DIATHEC, Strasbourg, France
| | - Karim Bouzakri
- UMR DIATHEC, Centre Européen d'Etude du Diabète, UMR DIATHEC, Strasbourg, France
| | - Bernhard Wehrle-Haller
- Department of Cell Physiology and Metabolism, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland
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10
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Kolic J, Beet L, Overby P, Cen HH, Panzhinskiy E, Ure DR, Cross JL, Huizinga RB, Johnson JD. Differential Effects of Voclosporin and Tacrolimus on Insulin Secretion From Human Islets. Endocrinology 2020; 161:5902465. [PMID: 32894758 PMCID: PMC7567406 DOI: 10.1210/endocr/bqaa162] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 09/02/2020] [Indexed: 12/16/2022]
Abstract
The incidence of new onset diabetes after transplant (NODAT) has increased over the past decade, likely due to calcineurin inhibitor-based immunosuppressants, including tacrolimus (TAC) and cyclosporin. Voclosporin (VCS), a next-generation calcineurin inhibitor, is reported to cause fewer incidences of NODAT but the reason is unclear. While calcineurin signaling plays important roles in pancreatic β-cell survival, proliferation, and function, its effects on human β-cells remain understudied. In particular, we do not understand why some calcineurin inhibitors have more profound effects on the incidence of NODAT. We compared the effects of TAC and VCS on the dynamics of insulin secretory function, programmed cell death rate, and the transcriptomic profile of human islets. We studied 2 clinically relevant doses of TAC (10 ng/mL, 30 ng/mL) and VCS (20 ng/mL, 60 ng/mL), meant to approximate the clinical trough and peak concentrations. TAC, but not VCS, caused a significant impairment of 15 mM glucose-stimulated and 30 mM KCl-stimulated insulin secretion. This points to molecular defects in the distal stages of exocytosis after voltage-gated Ca2+ entry. No significant effects on islet cell survival or total insulin content were identified. RNA sequencing showed that TAC significantly decreased the expression of 17 genes, including direct and indirect regulators of exocytosis (SYT16, TBC1D30, PCK1, SMOC1, SYT5, PDK4, and CREM), whereas VCS has less broad, and milder, effects on gene expression. Clinically relevant doses of TAC, but not VCS, directly inhibit insulin secretion from human islets, likely via transcriptional control of exocytosis machinery.
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Affiliation(s)
- Jelena Kolic
- Diabetes Research Group, Life Sciences Institute, Department of Cellular and Physiological Sciences & Department of Surgery, University of British Columbia, Vancouver, Canada
| | - Leanne Beet
- Diabetes Research Group, Life Sciences Institute, Department of Cellular and Physiological Sciences & Department of Surgery, University of British Columbia, Vancouver, Canada
| | - Peter Overby
- Diabetes Research Group, Life Sciences Institute, Department of Cellular and Physiological Sciences & Department of Surgery, University of British Columbia, Vancouver, Canada
| | - Haoning Howard Cen
- Diabetes Research Group, Life Sciences Institute, Department of Cellular and Physiological Sciences & Department of Surgery, University of British Columbia, Vancouver, Canada
| | - Evgeniy Panzhinskiy
- Diabetes Research Group, Life Sciences Institute, Department of Cellular and Physiological Sciences & Department of Surgery, University of British Columbia, Vancouver, Canada
| | - Daren R Ure
- Hepion Pharmaceuticals, Edmonton, Alberta, Canada
| | | | | | - James D Johnson
- Correspondence: Professor James D. Johnson, PhD, Faculty of Medicine, Department of Cellular and Physiological Sciences & Department of Surgery, The University of British Columbia, Life Sciences Institute, 5358 – 2350 Health Sciences Mall, Vancouver, British Columbia, Canada, V6T 1Z3. E-mail: ; Twitter: @JimJohnsonSci
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11
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Metabolic Effects of Selective Deletion of Group VIA Phospholipase A 2 from Macrophages or Pancreatic Islet Beta-Cells. Biomolecules 2020; 10:biom10101455. [PMID: 33080873 PMCID: PMC7602969 DOI: 10.3390/biom10101455] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 10/08/2020] [Accepted: 10/13/2020] [Indexed: 12/11/2022] Open
Abstract
To examine the role of group VIA phospholipase A2 (iPLA2β) in specific cell lineages in insulin secretion and insulin action, we prepared mice with a selective iPLA2β deficiency in cells of myelomonocytic lineage, including macrophages (MØ-iPLA2β-KO), or in insulin-secreting β-cells (β-Cell-iPLA2β-KO), respectively. MØ-iPLA2β-KO mice exhibited normal glucose tolerance when fed standard chow and better glucose tolerance than floxed-iPLA2β control mice after consuming a high-fat diet (HFD). MØ-iPLA2β-KO mice exhibited normal glucose-stimulated insulin secretion (GSIS) in vivo and from isolated islets ex vivo compared to controls. Male MØ-iPLA2β-KO mice exhibited enhanced insulin responsivity vs. controls after a prolonged HFD. In contrast, β-cell-iPLA2β-KO mice exhibited impaired glucose tolerance when fed standard chow, and glucose tolerance deteriorated further when introduced to a HFD. β-Cell-iPLA2β-KO mice exhibited impaired GSIS in vivo and from isolated islets ex vivo vs. controls. β-Cell-iPLA2β-KO mice also exhibited an enhanced insulin responsivity compared to controls. These findings suggest that MØ iPLA2β participates in HFD-induced deterioration in glucose tolerance and that this mainly reflects an effect on insulin responsivity rather than on insulin secretion. In contrast, β-cell iPLA2β plays a role in GSIS and also appears to confer some protection against deterioration in β-cell functions induced by a HFD.
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12
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Hu L, He F, Huang M, Zhao Q, Cheng L, Said N, Zhou Z, Liu F, Dai YS. SPARC promotes insulin secretion through down-regulation of RGS4 protein in pancreatic β cells. Sci Rep 2020; 10:17581. [PMID: 33067534 PMCID: PMC7567887 DOI: 10.1038/s41598-020-74593-w] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Accepted: 10/05/2020] [Indexed: 02/06/2023] Open
Abstract
SPARC-deficient mice have been shown to exhibit impaired glucose tolerance and insulin secretion, but the underlying mechanism remains unknown. Here, we showed that SPARC enhanced the promoting effect of Muscarinic receptor agonist oxotremorine-M on insulin secretion in cultured mouse islets. Overexpression of SPARC down-regulated RGS4, a negative regulator of β-cell M3 muscarinic receptors. Conversely, knockdown of SPARC up-regulated RGS4 in Min6 cells. RGS4 was up-regulated in islets from sparc -/- mice, which correlated with decreased glucose-stimulated insulin secretion (GSIS). Furthermore, inhibition of RGS4 restored GSIS in the islets from sparc -/- mice, and knockdown of RGS4 partially decreased the promoting effect of SPARC on oxotremorine-M-stimulated insulin secretion. Phosphoinositide 3-kinase (PI3K) inhibitor LY-294002 abolished SPARC-induced down-regulation of RGS4. Taken together, our data revealed that SPARC promoted GSIS by inhibiting RGS4 in pancreatic β cells.
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Affiliation(s)
- Li Hu
- Department of Metabolism and Endocrinology, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.,National Clinical Research Center for Metabolic Disease, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.,Metabolic Syndrome Research Center, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Fengli He
- Department of Metabolism and Endocrinology, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.,National Clinical Research Center for Metabolic Disease, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.,Metabolic Syndrome Research Center, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Meifeng Huang
- Department of Metabolism and Endocrinology, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.,National Clinical Research Center for Metabolic Disease, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.,Metabolic Syndrome Research Center, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Qian Zhao
- Institute of Reproductive and Stem Cell Engineering, Central South University, Changsha, Hunan, China
| | - Lamei Cheng
- Institute of Reproductive and Stem Cell Engineering, Central South University, Changsha, Hunan, China
| | - Neveen Said
- Department of Cancer Biology, Wake Forest University School of Medicine, Winston-Salem, NC, USA
| | - Zhiguang Zhou
- Department of Metabolism and Endocrinology, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.,National Clinical Research Center for Metabolic Disease, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.,Metabolic Syndrome Research Center, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Feng Liu
- Department of Metabolism and Endocrinology, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.,National Clinical Research Center for Metabolic Disease, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.,Metabolic Syndrome Research Center, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.,Department of Pharmacology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Yan-Shan Dai
- Department of Metabolism and Endocrinology, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China. .,National Clinical Research Center for Metabolic Disease, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China. .,Metabolic Syndrome Research Center, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China. .,Bristol-Myers Squibb Company, Princeton, NJ, USA.
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13
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Alejandro EU, Jo S, Akhaphong B, Llacer PR, Gianchandani M, Gregg B, Parlee SD, MacDougald OA, Bernal-Mizrachi E. Maternal low-protein diet on the last week of pregnancy contributes to insulin resistance and β-cell dysfunction in the mouse offspring. Am J Physiol Regul Integr Comp Physiol 2020; 319:R485-R496. [PMID: 32877242 PMCID: PMC7717124 DOI: 10.1152/ajpregu.00284.2019] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 08/17/2020] [Accepted: 08/17/2020] [Indexed: 12/17/2022]
Abstract
Maternal low-protein diet (LP) throughout gestation affects pancreatic β-cell fraction of the offspring at birth, thus increasing their susceptibility to metabolic dysfunction and type 2 diabetes in adulthood. The present study sought to strictly examine the effects of LP during the last week of gestation (LP12.5) alone as a developmental window for β-cell programming and metabolic dysfunction in adulthood. Islet morphology analysis revealed normal β-cell fraction in LP12.5 newborns. Normal glucose tolerance was observed in 6- to 8-wk-old male and female LP12.5 offspring. However, male LP12.5 offspring displayed glucose intolerance and reduced insulin sensitivity associated with β-cell dysfunction with aging. High-fat diet exposure of metabolically normal 12-wk-old male LP12.5 induced glucose intolerance due to increased body weight, insulin resistance, and insufficient β-cell mass adaptation despite higher insulin secretion. Assessment of epigenetic mechanisms through microRNAs (miRs) by a real-time PCR-based microarray in islets revealed elevation in miRs that regulate insulin secretion (miRs 342, 143), insulin resistance (miR143), and obesity (miR219). In the islets, overexpression of miR143 reduced insulin secretion in response to glucose. In contrast to the model of LP exposure throughout pregnancy, islet protein levels of mTOR and pancreatic and duodenal homeobox 1 were normal in LP12.5 islets. Collectively, these data suggest that LP diet during the last week of pregnancy is critical and sufficient to induce specific and distinct developmental programming effects of tissues that control glucose homeostasis, thus causing permanent changes in specific set of microRNAs that may contribute to the overall vulnerability of the offspring to obesity, insulin resistance, and type 2 diabetes.
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Affiliation(s)
- Emilyn U Alejandro
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, Minnesota
- Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine, Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, Michigan
| | - Seokwon Jo
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, Minnesota
| | - Brian Akhaphong
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, Minnesota
| | - Pau Romaguera Llacer
- Division of Endocrinology, Metabolism and Diabetes, University of Miami, Miami, Florida
| | - Maya Gianchandani
- Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine, Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, Michigan
| | - Brigid Gregg
- Department of Pediatrics, University of Michigan Medical School, Ann Arbor, Michigan
| | - Sebastian D Parlee
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan
| | - Ormond A MacDougald
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan
| | - Ernesto Bernal-Mizrachi
- Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine, Brehm Center for Diabetes Research, University of Michigan Medical School, Ann Arbor, Michigan
- Veterans Affairs Ann Arbor Healthcare System, Ann Arbor, Michigan
- Miami Veterans Affairs Healthcare System University of Miami, Miami, Florida
- Division of Endocrinology, Metabolism and Diabetes, University of Miami, Miami, Florida
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14
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Nguyen LD, Fischer TT, Abreu D, Arroyo A, Urano F, Ehrlich BE. Calpain inhibitor and ibudilast rescue β cell functions in a cellular model of Wolfram syndrome. Proc Natl Acad Sci U S A 2020; 117:17389-17398. [PMID: 32632005 PMCID: PMC7382278 DOI: 10.1073/pnas.2007136117] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Wolfram syndrome is a rare multisystem disease characterized by childhood-onset diabetes mellitus and progressive neurodegeneration. Most cases are attributed to pathogenic variants in a single gene, Wolfram syndrome 1 (WFS1). There currently is no disease-modifying treatment for Wolfram syndrome, as the molecular consequences of the loss of WFS1 remain elusive. Because diabetes mellitus is the first diagnosed symptom of Wolfram syndrome, we aimed to further examine the functions of WFS1 in pancreatic β cells in the context of hyperglycemia. Knockout (KO) of WFS1 in rat insulinoma (INS1) cells impaired calcium homeostasis and protein kinase B/Akt signaling and, subsequently, decreased cell viability and glucose-stimulated insulin secretion. Targeting calcium homeostasis with reexpression of WFS1, overexpression of WFS1's interacting partner neuronal calcium sensor-1 (NCS1), or treatment with calpain inhibitor and ibudilast reversed deficits observed in WFS1-KO cells. Collectively, our findings provide insight into the disease mechanism of Wolfram syndrome and highlight new targets and drug candidates to facilitate the development of a treatment for this disorder and similar diseases.
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Affiliation(s)
- Lien D Nguyen
- Department of Pharmacology, Yale University, New Haven, CT 06520
- Interdepartmental Neuroscience Program, Yale University, New Haven, CT 06520
| | - Tom T Fischer
- Department of Pharmacology, Yale University, New Haven, CT 06520
- Institute of Pharmacology, University of Heidelberg, 69117 Heidelberg, Germany
| | - Damien Abreu
- Department of Medicine, Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, MO 63110
- Medical Scientist Training Program, Washington University School of Medicine, St. Louis, MO 63110
| | - Alfredo Arroyo
- Department of Pharmacology, Yale University, New Haven, CT 06520
| | - Fumihiko Urano
- Department of Medicine, Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, MO 63110
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110
| | - Barbara E Ehrlich
- Department of Pharmacology, Yale University, New Haven, CT 06520;
- Interdepartmental Neuroscience Program, Yale University, New Haven, CT 06520
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15
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AKT1 Regulates Endoplasmic Reticulum Stress and Mediates the Adaptive Response of Pancreatic β Cells. Mol Cell Biol 2020; 40:MCB.00031-20. [PMID: 32179553 DOI: 10.1128/mcb.00031-20] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 03/12/2020] [Indexed: 12/31/2022] Open
Abstract
Isoforms of protein kinase B (also known as AKT) play important roles in mediating insulin and growth factor signals. Previous studies have suggested that the AKT2 isoform is critical for insulin-regulated glucose metabolism, while the role of the AKT1 isoform remains less clear. This study focuses on the effects of AKT1 on the adaptive response of pancreatic β cells. Using a mouse model with inducible β-cell-specific deletion of the Akt1 gene (βA1KO mice), we showed that AKT1 is involved in high-fat-diet (HFD)-induced growth and survival of β cells but is unnecessary for them to maintain a population in the absence of metabolic stress. When unchallenged, βA1KO mice presented the same metabolic profile and β-cell phenotype as the control mice with an intact Akt1 gene. When metabolic stress was induced by HFD, β cells in control mice with intact Akt1 proliferated as a compensatory mechanism for metabolic overload. Similar effects were not observed in βA1KO mice. We further demonstrated that AKT1 protein deficiency caused endoplasmic reticulum (ER) stress and potentiated β cells to undergo apoptosis. Our results revealed that AKT1 protein loss led to the induction of eukaryotic initiation factor 2 α subunit (eIF2α) signaling and ER stress markers under normal-chow-fed conditions, indicating chronic low-level ER stress. Together, these data established a role for AKT1 as a growth and survival factor for adaptive β-cell response and suggest that ER stress induction is responsible for this effect of AKT1.
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16
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Rachdaoui N. Insulin: The Friend and the Foe in the Development of Type 2 Diabetes Mellitus. Int J Mol Sci 2020; 21:ijms21051770. [PMID: 32150819 PMCID: PMC7084909 DOI: 10.3390/ijms21051770] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2020] [Revised: 02/29/2020] [Accepted: 03/02/2020] [Indexed: 12/14/2022] Open
Abstract
Insulin, a hormone produced by pancreatic β-cells, has a primary function of maintaining glucose homeostasis. Deficiencies in β-cell insulin secretion result in the development of type 1 and type 2 diabetes, metabolic disorders characterized by high levels of blood glucose. Type 2 diabetes mellitus (T2DM) is characterized by the presence of peripheral insulin resistance in tissues such as skeletal muscle, adipose tissue and liver and develops when β-cells fail to compensate for the peripheral insulin resistance. Insulin resistance triggers a rise in insulin demand and leads to β-cell compensation by increasing both β-cell mass and insulin secretion and leads to the development of hyperinsulinemia. In a vicious cycle, hyperinsulinemia exacerbates the metabolic dysregulations that lead to β-cell failure and the development of T2DM. Insulin and IGF-1 signaling pathways play critical roles in maintaining the differentiated phenotype of β-cells. The autocrine actions of secreted insulin on β-cells is still controversial; work by us and others has shown positive and negative actions by insulin on β-cells. We discuss findings that support the concept of an autocrine action of secreted insulin on β-cells. The hypothesis of whether, during the development of T2DM, secreted insulin initially acts as a friend and contributes to β-cell compensation and then, at a later stage, becomes a foe and contributes to β-cell decompensation will be discussed.
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Affiliation(s)
- Nadia Rachdaoui
- Department of Animal Sciences, Room 108, Foran Hall, Rutgers, the State University of New Jersey, 59 Dudley Rd, New Brunswick, NJ 08901, USA
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17
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Jara MA, Werneck-De-Castro JP, Lubaczeuski C, Johnson JD, Bernal-Mizrachi E. Pancreatic and duodenal homeobox-1 (PDX1) contributes to β-cell mass expansion and proliferation induced by Akt/PKB pathway. Islets 2020; 12:32-40. [PMID: 32876522 PMCID: PMC7527019 DOI: 10.1080/19382014.2020.1762471] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Maintenance of pancreatic β-cell mass and function is fundamental to glucose homeostasis and to prevent diabetes. The PI3 K-Akt-mTORC1 pathway is critical for β-cells mass and function, while PDX1 has been implicated in β-cell development, maturation, and function. Here we tested whether Akt signaling requires PDX1 expression to regulate β-cell mass, proliferation, and glucose homeostasis. In order to address that, we crossed a mouse model overexpressing constitutively active Akt mutant in β-cells (β-caAkt) with mice lacking one allele of PDX1gene (β-caAkt/pdx1+/-). While the β-caAkt mice exhibit higher plasma insulin levels, greater β-cell mass and improved glucose tolerance compared to control mice, the β-caAkt/pdx1+/- mice are hyperglycemic and intolerant to glucose. The changes in glucose homeostasis in β-caAkt/pdx1+/- were associated with a 60% reduction in β-cell mass compared to β-caAkt mice. The impaired β-cell mass in the β-caAkt/pdx1+/- mice can be explained by a lesser β-cell proliferation measured by the number of Ki67 positive β-cells. We did not observe any differences in apoptosis between β-caAkt/pdx1+/- and β-caAkt mice. In conclusion, PDX1 contributes to β-cell mass expansion and glucose metabolism induced by activation of Akt signaling.
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Affiliation(s)
- Mark Anthony Jara
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - Joao Pedro Werneck-De-Castro
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, Miller School of Medicine, University of Miami, Miami, FL, USA
- Miami VA Health Care System, Miami, FL, USA
| | - Camila Lubaczeuski
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - James D. Johnson
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, Canada
| | - Ernesto Bernal-Mizrachi
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, Miller School of Medicine, University of Miami, Miami, FL, USA
- Miami VA Health Care System, Miami, FL, USA
- CONTACT Ernesto Bernal-Mizrachi Department Of Internal Medicine, Division Of Endocrinology, Diabetes and Metabolism, University of Miami Miller School of Medicine, Miami, FL33136, USA
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18
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Ostrovskaya RU, Ivanov SV, Gudasheva TA, Seredenin SB. A Novel Dipeptide NGF Mimetic GK-2 Selectively Activating the PI3K/AKT Signaling Pathway Promotes the Survival of Pancreatic β-Cells in a Rat Model of Diabetes. Acta Naturae 2019; 11:48-57. [PMID: 31024748 PMCID: PMC6475863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Indexed: 11/16/2022] Open
Abstract
We investigated the cytoprotective effect of a novel low-molecular-weight NGF mimetic, GK-2 (hexamethylenediamide bis-N-monosuccinyl-L-glutamyl-L-lysine), on pancreatic β-cells. The neuroprotective effect of GK-2 had been previously shown to be associated with selective activation of the PI3K/Akt signaling pathway. In this study, rats with streptozotocin (STZ)-induced type 2 diabetes mellitus were used. Metformin was used as a reference drug. STZ was immunohistochemically demonstrated to reduce the number of β-cells and affect their morphological structure. Treatment of diabetic animals with GK-2 (at a dose of 0.5 mg/kg intraperitoneally or 5 mg/kg orally) or metformin (300 mg/kg orally) for 28 days reduced the damaging effect of STZ. The effect of GK-2 on manifestations of STZ-induced diabetes, such as hyperglycemia, weight loss, polyphagia, and polydipsia, was comparable to that of metformin, while the cytoprotective activity of GK-2 was slightly stronger than that of metformin. A strong positive correlation between morphometric parameters and the blood glucose level was revealed. The GK-2 cytoprotective effect on β-cells is supposed to manifest through the PI3K/Akt signaling pathway.
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Affiliation(s)
- R. U. Ostrovskaya
- V. V. Zakusov Research Institute of Pharmacology, Baltiyskaya Str. 8, 125315, Moscow, Russia
| | - S. V. Ivanov
- V. V. Zakusov Research Institute of Pharmacology, Baltiyskaya Str. 8, 125315, Moscow, Russia
| | - T. A. Gudasheva
- V. V. Zakusov Research Institute of Pharmacology, Baltiyskaya Str. 8, 125315, Moscow, Russia
| | - S. B. Seredenin
- V. V. Zakusov Research Institute of Pharmacology, Baltiyskaya Str. 8, 125315, Moscow, Russia
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19
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Li J, Wang Z, Ren L, Fan L, Liu W, Jiang Y, Lau HK, Liu R, Wang Q. Antagonistic interaction between Nodal and insulin modulates pancreatic β-cell proliferation and survival. Cell Commun Signal 2018; 16:79. [PMID: 30409165 PMCID: PMC6225724 DOI: 10.1186/s12964-018-0288-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 10/25/2018] [Indexed: 12/21/2022] Open
Abstract
Background Insulin signaling pathway in β-cell is essential to promote β-cells proliferation and survival, while Nodal–ALK7–Smad3 signaling involves β-cells apoptosis. We attempted to address inter-relationship between Nodal and insulin in modulating β-cell proliferation and apoptosis. Methods Using INS-1 β-cells and isolated rat islets, we examined the effects of Nodal, insulin, or the two combined on β-cell proliferation and/or apoptosis. Results The β-cells under high-glucose or palmitate conditions showed significant up-regulation of Nodal expression and activation of its downstream signaling pathway resulted in increased cleaved caspase-3. Insulin treatment led to significantly attenuated Nodal-induced cell apoptotic pathway. Similar results were found in directly Nodal-treated β-cell that insulin could partially block Nodal-induced up-regulation of ALK7–Smad3–caspase-3 signaling pathways with significantly attenuated β-cell apoptosis. Interestingly, we found that insulin-induced Akt activation and downstream molecules including GSK-3β, β-catenin and ERK1/2 was significantly attenuated by the co-treatment with Nodal, resulted in decreased cell proliferation. Furthermore, Nodal decreased glucose-evoked calcium influx and played a negative role during glucose-stimulated insulin secretion in the β-cells. Immunocytochemistry studies showed that Nodal treatment translocated Smad3 from cytosol mostly to the nucleus; however, co-treatment with insulin significantly decreased Smad3 nuclear localization. Co-immunoprecipitation experiments showed a directly interaction between Smad3 and Akt, and this interaction was enhanced by co-treatment with insulin. Conclusions Our data suggest that the antagonistic interaction between Nodal and insulin has a role in the regulation of β-cell mass and secretion. Electronic supplementary material The online version of this article (10.1186/s12964-018-0288-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Junfeng Li
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University, Shanghai, China.,Department of Endocrinology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Zhihong Wang
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University, Shanghai, China
| | - Liwei Ren
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University, Shanghai, China
| | - Linling Fan
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University, Shanghai, China
| | - Wenjuan Liu
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University, Shanghai, China
| | - Yaojing Jiang
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University, Shanghai, China
| | - Harry K Lau
- Division of Endocrinology and Metabolism, Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, Ontario, Canada.,Department of Physiology and Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Rui Liu
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University, Shanghai, China
| | - Qinghua Wang
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University, Shanghai, China. .,Division of Endocrinology and Metabolism, Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, Ontario, Canada. .,Department of Physiology and Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
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20
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Rachdaoui N, Polo-Parada L, Ismail-Beigi F. Prolonged Exposure to Insulin Inactivates Akt and Erk 1/2 and Increases Pancreatic Islet and INS1E β-Cell Apoptosis. J Endocr Soc 2018; 3:69-90. [PMID: 30697602 PMCID: PMC6344346 DOI: 10.1210/js.2018-00140] [Citation(s) in RCA: 12] [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: 05/09/2018] [Accepted: 10/29/2018] [Indexed: 12/18/2022] Open
Abstract
Chronic hyperinsulinemia, in vivo, increases the resistance of peripheral tissues to insulin by desensitizing insulin signaling. Insulin, in a heterologous manner, can also cause IGF-1 resistance. The aim of the current study was to investigate whether insulin-mediated insulin and IGF-1 resistance develops in pancreatic β-cells and whether this resistance results in β-cell decompensation. Chronic exposure of rat islets or INS1E β-cells to increasing concentrations of insulin decreased AktS473 phosphorylation in response to subsequent acute stimulation with 10 nM insulin or IGF-1. Prolonged exposure to high insulin levels not only inhibited AktS473 phosphorylation, but it also resulted in a significant inhibition of the phosphorylation of P70S6 kinase and Erk1/2 phosphorylation in response to the acute stimulation by glucose, insulin, or IGF-1. Decreased activation of Akt, P70S6K, and Erk1/2 was associated with decreased insulin receptor substrate 2 tyrosine phosphorylation and insulin receptor β-subunit abundance; neither IGF receptor β-subunit content nor its phosphorylation were affected. These signaling impairments were associated with decreased SERCA2 expression, perturbed plasma membrane calcium current and intracellular calcium handling, increased endoplasmic reticulum stress markers such as eIF2αS51 phosphorylation and Bip (GRP78) expression, and increased islet and β-cell apoptosis. We demonstrate that prolonged exposure to high insulin levels induces not only insulin resistance, but in a heterologous manner causes resistance to IGF-1 in rat islets and insulinoma cells resulting in decreased cell survival. These findings suggest the possibility that chronic exposure to hyperinsulinemia may negatively affect β-cell mass by increasing β-cell apoptosis.
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Affiliation(s)
- Nadia Rachdaoui
- Division of Clinical and Molecular Endocrinology, Department of Medicine, Case Western Reserve University, Cleveland, Ohio
| | - Luis Polo-Parada
- Department of Medical Pharmacology and Physiology, Dalton Cardiovascular Research Center, University of Missouri-Columbia, Columbia, Missouri
| | - Faramarz Ismail-Beigi
- Division of Clinical and Molecular Endocrinology, Department of Medicine, Case Western Reserve University, Cleveland, Ohio
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21
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Huang X, Liu G, Guo J, Su Z. The PI3K/AKT pathway in obesity and type 2 diabetes. Int J Biol Sci 2018; 14:1483-1496. [PMID: 30263000 PMCID: PMC6158718 DOI: 10.7150/ijbs.27173] [Citation(s) in RCA: 814] [Impact Index Per Article: 135.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Accepted: 07/10/2018] [Indexed: 02/06/2023] Open
Abstract
Obesity and type 2 diabetes mellitus are complicated metabolic diseases that affect multiple organs and are characterized by hyperglycaemia. Currently, stable and effective treatments for obesity and type 2 diabetes mellitus are not available. Therefore, the mechanisms leading to obesity and diabetes and more effective ways to treat obesity and diabetes should be identified. Based on accumulated evidences, the PI3K/AKT signalling pathway is required for normal metabolism due to its characteristics, and its imbalance leads to the development of obesity and type 2 diabetes mellitus. This review focuses on the role of PI3K/AKT signalling in the skeletal muscle, adipose tissue, liver, brain and pancreas, and discusses how this signalling pathway affects the development of the aforementioned diseases. We also summarize evidences for recently identified therapeutic targets of the PI3K/AKT pathway as treatments for obesity and type 2 diabetes mellitus. PI3K/AKT pathway damaged in various tissues of the body leads to obesity and type 2 diabetes as the result of insulin resistance, and in turn, insulin resistance exacerbates the PI3K/AKT pathway, forming a vicious circle.
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Affiliation(s)
- Xingjun Huang
- Guangdong Engineering Research Center of Natural Products and New Drugs, Guangdong Provincial University Engineering Technology Research Center of Natural Products and Drugs, Guangdong Pharmaceutical University, Guangzhou (510006), China.,Guangdong Metabolic Diseases Research Center of Integrated Chinese and Western Medicine, Guangdong Pharmaceutical University, Guangzhou (510006), China
| | - Guihua Liu
- Shenzhen Center for Disease Control and Prevention, 8 Longyuan Road, Nanshan District, Shenzhen (518055), China
| | - Jiao Guo
- Guangdong Metabolic Diseases Research Center of Integrated Chinese and Western Medicine, Guangdong Pharmaceutical University, Guangzhou (510006), China
| | - Zhengquan Su
- Guangdong Engineering Research Center of Natural Products and New Drugs, Guangdong Provincial University Engineering Technology Research Center of Natural Products and Drugs, Guangdong Pharmaceutical University, Guangzhou (510006), China.,Guangdong Metabolic Diseases Research Center of Integrated Chinese and Western Medicine, Guangdong Pharmaceutical University, Guangzhou (510006), China
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22
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Paschen M, Moede T, Valladolid-Acebes I, Leibiger B, Moruzzi N, Jacob S, García-Prieto CF, Brismar K, Leibiger IB, Berggren PO. Diet-induced β-cell insulin resistance results in reversible loss of functional β-cell mass. FASEB J 2018; 33:204-218. [PMID: 29957055 PMCID: PMC6355083 DOI: 10.1096/fj.201800826r] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Although convincing in genetic models, the relevance of β-cell insulin resistance in diet-induced type 2 diabetes (T2DM) remains unclear. Exemplified by diabetes-prone, male, C57B1/6J mice being fed different combinations of Western-style diet, we show that β-cell insulin resistance occurs early during T2DM progression and is due to a combination of lipotoxicity and increased β-cell workload. Within 8 wk of being fed a high-fat, high-sucrose diet, mice became obese, developed impaired insulin and glucose tolerances, and displayed noncompensatory insulin release, due, at least in part, to reduced expression of syntaxin-1A. Through reporter islets transplanted to the anterior chamber of the eye, we demonstrated a concomitant loss of functional β-cell mass. When mice were changed from diabetogenic diet to normal chow diet, the diabetes phenotype was reversed, suggesting a remarkable plasticity of functional β-cell mass in the early phase of T2DM development. Our data reinforce the relevance of diet composition as an environmental factor determining different routes of diabetes progression in a given genetic background. Employing the in vivo reporter islet–monitoring approach will allow researchers to define key times in the dynamics of reversible loss of functional β-cell mass and, thus, to investigate the underlying, molecular mechanisms involved in the progression toward T2DM manifestation.—Paschen, M., Moede, T., Valladolid-Acebes, I., Leibiger, B., Moruzzi, N., Jacob, S., García-Prieto, C. F., Brismar, K., Leibiger, I. B., Berggren, P.-O. Diet-induced β-cell insulin resistance results in reversible loss of functional β-cell mass.
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Affiliation(s)
- Meike Paschen
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | - Tilo Moede
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | - Ismael Valladolid-Acebes
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | - Barbara Leibiger
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | - Noah Moruzzi
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | - Stefan Jacob
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | - Concha F García-Prieto
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | - Kerstin Brismar
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | - Ingo B Leibiger
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
| | - Per-Olof Berggren
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Stockholm, Sweden
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23
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Zhang Y, Warnock GL, Ao Z, Park YJ, Safikhan N, Ghahary A, Marzban L. Amyloid formation reduces protein kinase B phosphorylation in primary islet β-cells which is improved by blocking IL-1β signaling. PLoS One 2018; 13:e0193184. [PMID: 29474443 PMCID: PMC5825069 DOI: 10.1371/journal.pone.0193184] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Accepted: 02/02/2018] [Indexed: 12/31/2022] Open
Abstract
Amyloid formation in the pancreatic islets due to aggregation of human islet amyloid polypeptide (hIAPP) contributes to reduced β-cell mass and function in type 2 diabetes (T2D) and islet transplantation. Protein kinase B (PKB) signaling plays a key role in the regulation of β-cell survival, function and proliferation. In this study, we used human and hIAPP-expressing transgenic mouse islets in culture as two ex vivo models of human islet amyloid formation to: 1. Investigate the effects of amyloid formation on PKB phosphorylation in primary islet β-cells; 2. Test if inhibition of amyloid formation and/or interleukin-1β (IL-1β) signaling in islets can restore the changes in β-cell phospho-PKB levels mediated by amyloid formation. Human and hIAPP-expressing mouse islets were cultured in elevated glucose with an amyloid inhibitor (Congo red) or embedded within collagen matrix to prevent amyloid formation. To block the IL-1β signaling, human islets were treated with an IL-1 receptor antagonist (anakinra) or a glucagon-like peptide-1 agonist (exenatide). β-cell phospho-PKB levels, proliferation, apoptosis, islet IL-1β levels and amyloid formation were assessed. Amyloid formation in both cultured human and hIAPP-expressing mouse islets reduced β-cell phospho-PKB levels and increased islet IL-1β levels, both of which were restored by prevention of amyloid formation either by the amyloid inhibitor or embedding islets in collagen matrix, resulting in improved β-cell survival. Furthermore, inhibition of IL-1β signaling by treatment with anakinra or exenatide increased β-cell phospho-PKB levels, enhanced proliferation and reduced apoptosis in amyloid forming human islets during 7-day culture. These data suggest that amyloid formation leads to reduced PKB phosphorylation in β-cells which is associated with elevated islet IL-1β levels. Inhibitors of amyloid or amyloid-induced IL-1β production may provide a new approach to restore phospho-PKB levels thereby enhance β-cell survival and proliferation in conditions associated with islet amyloid formation such as T2D and clinical islet transplantation.
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Affiliation(s)
- Yun Zhang
- Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Garth L. Warnock
- Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Ziliang Ao
- Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Yoo Jin Park
- Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Nooshin Safikhan
- Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Aziz Ghahary
- Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Lucy Marzban
- Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
- * E-mail:
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24
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Bozadjieva N, Blandino-Rosano M, Chase J, Dai XQ, Cummings K, Gimeno J, Dean D, Powers AC, Gittes GK, Rüegg MA, Hall MN, MacDonald PE, Bernal-Mizrachi E. Loss of mTORC1 signaling alters pancreatic α cell mass and impairs glucagon secretion. J Clin Invest 2017; 127:4379-4393. [PMID: 29106387 DOI: 10.1172/jci90004] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Accepted: 09/26/2017] [Indexed: 01/19/2023] Open
Abstract
Glucagon plays a major role in the regulation of glucose homeostasis during fed and fasting states. However, the mechanisms responsible for the regulation of pancreatic α cell mass and function are not completely understood. In the current study, we identified mTOR complex 1 (mTORC1) as a major regulator of α cell mass and glucagon secretion. Using mice with tissue-specific deletion of the mTORC1 regulator Raptor in α cells (αRaptorKO), we showed that mTORC1 signaling is dispensable for α cell development, but essential for α cell maturation during the transition from a milk-based diet to a chow-based diet after weaning. Moreover, inhibition of mTORC1 signaling in αRaptorKO mice and in WT animals exposed to chronic rapamycin administration decreased glucagon content and glucagon secretion. In αRaptorKO mice, impaired glucagon secretion occurred in response to different secretagogues and was mediated by alterations in KATP channel subunit expression and activity. Additionally, our data identify the mTORC1/FoxA2 axis as a link between mTORC1 and transcriptional regulation of key genes responsible for α cell function. Thus, our results reveal a potential function of mTORC1 in nutrient-dependent regulation of glucagon secretion and identify a role for mTORC1 in controlling α cell-mass maintenance.
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Affiliation(s)
- Nadejda Bozadjieva
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, and.,Graduate Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Manuel Blandino-Rosano
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, and.,Department of Internal Medicine, Division Endocrinology, Metabolism and Diabetes, Miller School of Medicine, University of Miami, Miami, Florida, USA
| | - Jennifer Chase
- Graduate Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Xiao-Qing Dai
- Alberta Diabetes Institute and Department of Pharmacology, Edmonton, Alberta, Canada
| | - Kelsey Cummings
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, and
| | - Jennifer Gimeno
- Department of Internal Medicine, Division Endocrinology, Metabolism and Diabetes, Miller School of Medicine, University of Miami, Miami, Florida, USA
| | - Danielle Dean
- Department of Medicine, Division of Diabetes, Endocrinology, and Metabolism, and
| | - Alvin C Powers
- Department of Medicine, Division of Diabetes, Endocrinology, and Metabolism, and.,Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee, USA.,VA Tennessee Valley Healthcare, Nashville, Tennessee, USA
| | - George K Gittes
- Children's Hospital, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | | | | | - Patrick E MacDonald
- Alberta Diabetes Institute and Department of Pharmacology, Edmonton, Alberta, Canada
| | - Ernesto Bernal-Mizrachi
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, and.,Graduate Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, Michigan, USA.,Department of Internal Medicine, Division Endocrinology, Metabolism and Diabetes, Miller School of Medicine, University of Miami, Miami, Florida, USA.,Veterans Affairs Medical Center, Miami, Florida, USA
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25
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Nygren PJ, Mehta S, Schweppe DK, Langeberg LK, Whiting JL, Weisbrod CR, Bruce JE, Zhang J, Veesler D, Scott JD. Intrinsic disorder within AKAP79 fine-tunes anchored phosphatase activity toward substrates and drug sensitivity. eLife 2017; 6:e30872. [PMID: 28967377 PMCID: PMC5653234 DOI: 10.7554/elife.30872] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2017] [Accepted: 09/28/2017] [Indexed: 12/23/2022] Open
Abstract
Scaffolding the calcium/calmodulin-dependent phosphatase 2B (PP2B, calcineurin) focuses and insulates termination of local second messenger responses. Conformational flexibility in regions of intrinsic disorder within A-kinase anchoring protein 79 (AKAP79) delineates PP2B access to phosphoproteins. Structural analysis by negative-stain electron microscopy (EM) reveals an ensemble of dormant AKAP79-PP2B configurations varying in particle length from 160 to 240 Å. A short-linear interaction motif between residues 337-343 of AKAP79 is the sole PP2B-anchoring determinant sustaining these diverse topologies. Activation with Ca2+/calmodulin engages additional interactive surfaces and condenses these conformational variants into a uniform population with mean length 178 ± 17 Å. This includes a Leu-Lys-Ile-Pro sequence (residues 125-128 of AKAP79) that occupies a binding pocket on PP2B utilized by the immunosuppressive drug cyclosporin. Live-cell imaging with fluorescent activity-sensors infers that this region fine-tunes calcium responsiveness and drug sensitivity of the anchored phosphatase.
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Affiliation(s)
- Patrick J Nygren
- Department of PharmacologyHoward Hughes Medical Institute, University of WashingtonSeattleUnited States
| | - Sohum Mehta
- Department of PharmacologyUniversity of California, San DiegoSan DiegoUnited States
| | - Devin K Schweppe
- Department of Genome SciencesUniversity of WashingtonSeattleUnited States
| | - Lorene K Langeberg
- Department of PharmacologyHoward Hughes Medical Institute, University of WashingtonSeattleUnited States
| | - Jennifer L Whiting
- Department of PharmacologyHoward Hughes Medical Institute, University of WashingtonSeattleUnited States
| | - Chad R Weisbrod
- National High Magnetic Field LaboratoryFlorida State UniversityTallahasseeUnited States
| | - James E Bruce
- Department of Genome SciencesUniversity of WashingtonSeattleUnited States
| | - Jin Zhang
- Department of PharmacologyUniversity of California, San DiegoSan DiegoUnited States
| | - David Veesler
- Department of BiochemistryUniversity of WashingtonSeattleUnited States
| | - John D Scott
- Department of PharmacologyHoward Hughes Medical Institute, University of WashingtonSeattleUnited States
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26
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Zhang F, Tzanakakis ES. Optogenetic regulation of insulin secretion in pancreatic β-cells. Sci Rep 2017; 7:9357. [PMID: 28839233 PMCID: PMC5571193 DOI: 10.1038/s41598-017-09937-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 08/01/2017] [Indexed: 02/06/2023] Open
Abstract
Pancreatic β-cell insulin production is orchestrated by a complex circuitry involving intracellular elements including cyclic AMP (cAMP). Tackling aberrations in glucose-stimulated insulin release such as in diabetes with pharmacological agents, which boost the secretory capacity of β-cells, is linked to adverse side effects. We hypothesized that a photoactivatable adenylyl cyclase (PAC) can be employed to modulate cAMP in β-cells with light thereby enhancing insulin secretion. To that end, the PAC gene from Beggiatoa (bPAC) was delivered to β-cells. A cAMP increase was noted within 5 minutes of photostimulation and a significant drop at 12 minutes post-illumination. The concomitant augmented insulin secretion was comparable to that from β-cells treated with secretagogues. Greater insulin release was also observed over repeated cycles of photoinduction without adverse effects on viability and proliferation. Furthermore, the expression and activation of bPAC increased cAMP and insulin secretion in murine islets and in β-cell pseudoislets, which displayed a more pronounced light-triggered hormone secretion compared to that of β-cell monolayers. Calcium channel blocking curtailed the enhanced insulin response due to bPAC activity. This optogenetic system with modulation of cAMP and insulin release can be employed for the study of β-cell function and for enabling new therapeutic modalities for diabetes.
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Affiliation(s)
- Fan Zhang
- Department of Chemical and Biological Engineering, Tufts University, Medford, MA, 02155, USA.
| | - Emmanuel S Tzanakakis
- Department of Chemical and Biological Engineering, Tufts University, Medford, MA, 02155, USA. .,Clinical and Translational Science Institute, Tufts Medical Center, Boston, MA, 02111, USA.
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27
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Alejandro EU, Bozadjieva N, Blandino-Rosano M, Wasan MA, Elghazi L, Vadrevu S, Satin L, Bernal-Mizrachi E. Overexpression of Kinase-Dead mTOR Impairs Glucose Homeostasis by Regulating Insulin Secretion and Not β-Cell Mass. Diabetes 2017; 66:2150-2162. [PMID: 28546423 PMCID: PMC5521866 DOI: 10.2337/db16-1349] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 05/01/2017] [Indexed: 12/20/2022]
Abstract
Regulation of glucose homeostasis by insulin depends on β-cell growth and function. Nutrients and growth factor stimuli converge on the conserved protein kinase mechanistic target of rapamycin (mTOR), existing in two complexes, mTORC1 and mTORC2. To understand the functional relevance of mTOR enzymatic activity in β-cell development and glucose homeostasis, we generated mice overexpressing either one or two copies of a kinase-dead mTOR mutant (KD-mTOR) transgene exclusively in β-cells. We examined glucose homeostasis and β-cell function of these mice fed a control chow or high-fat diet. Mice with two copies of the transgene [RIPCre;KD-mTOR (Homozygous)] develop glucose intolerance due to a defect in β-cell function without alterations in β-cell mass with control chow. Islets from RIPCre;KD-mTOR (Homozygous) mice showed reduced mTORC1 and mTORC2 signaling along with transcripts and protein levels of Pdx-1. Islets with reduced mTORC2 signaling in their β-cells (RIPCre;Rictorfl/fl) also showed reduced Pdx-1. When challenged with a high-fat diet, mice carrying one copy of KD-mTOR mutant transgene developed glucose intolerance and β-cell insulin secretion defect but showed no changes in β-cell mass. These findings suggest that the mTOR-mediated signaling pathway is not essential to β-cell growth but is involved in regulating β-cell function in normal and diabetogenic conditions.
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Affiliation(s)
- Emilyn U Alejandro
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, MI
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, MN
| | - Nadejda Bozadjieva
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, MI
| | - Manuel Blandino-Rosano
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, MI
- Division of Endocrinology, Metabolism and Diabetes, University of Miami, Miami, FL
| | - Michelle Ann Wasan
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, MN
| | - Lynda Elghazi
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, MI
| | | | - Leslie Satin
- Department of Pharmacology, University of Michigan, Ann Arbor, MI
| | - Ernesto Bernal-Mizrachi
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, MI
- Division of Endocrinology, Metabolism and Diabetes, University of Miami, Miami, FL
- VA Ann Arbor Healthcare System, Ann Arbor, MI
- Miami VA Healthcare System, Miami, FL
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28
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Freyberg Z, Aslanoglou D, Shah R, Ballon JS. Intrinsic and Antipsychotic Drug-Induced Metabolic Dysfunction in Schizophrenia. Front Neurosci 2017; 11:432. [PMID: 28804444 PMCID: PMC5532378 DOI: 10.3389/fnins.2017.00432] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 07/13/2017] [Indexed: 12/12/2022] Open
Abstract
For decades, there have been observations demonstrating significant metabolic disturbances in people with schizophrenia including clinically relevant weight gain, hypertension, and disturbances in glucose and lipid homeostasis. Many of these findings pre-date the use of antipsychotic drugs (APDs) which on their own are also strongly associated with metabolic side effects. The combination of APD-induced metabolic changes and common adverse environmental factors associated with schizophrenia have made it difficult to determine the specific contributions of each to the overall metabolic picture. Data from drug-naïve patients, both from the pre-APD era and more recently, suggest that there may be an intrinsic metabolic risk associated with schizophrenia. Nevertheless, these findings remain controversial due to significant clinical variability in both psychiatric and metabolic symptoms throughout patients' disease courses. Here, we provide an extensive review of classic and more recent literature describing the metabolic phenotype associated with schizophrenia. We also suggest potential mechanistic links between signaling pathways associated with schizophrenia and metabolic dysfunction. We propose that, beyond its symptomatology in the central nervous system, schizophrenia is also characterized by pathophysiology in other organ systems directly related to metabolic control.
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Affiliation(s)
- Zachary Freyberg
- Department of Psychiatry, University of PittsburghPittsburgh, PA, United States
- Department of Cell Biology, University of PittsburghPittsburgh, PA, United States
| | - Despoina Aslanoglou
- Department of Psychiatry, University of PittsburghPittsburgh, PA, United States
| | - Ripal Shah
- Department of Psychiatry and Behavioral Sciences, Stanford UniversityStanford, CA, United States
| | - Jacob S. Ballon
- Department of Psychiatry and Behavioral Sciences, Stanford UniversityStanford, CA, United States
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29
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Loss of mTORC1 signalling impairs β-cell homeostasis and insulin processing. Nat Commun 2017; 8:16014. [PMID: 28699639 PMCID: PMC5510183 DOI: 10.1038/ncomms16014] [Citation(s) in RCA: 110] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 05/22/2017] [Indexed: 12/15/2022] Open
Abstract
Deregulation of mTOR complex 1 (mTORC1) signalling increases the risk for metabolic diseases, including type 2 diabetes. Here we show that β-cell-specific loss of mTORC1 causes diabetes and β-cell failure due to defects in proliferation, autophagy, apoptosis and insulin secretion by using mice with conditional (βraKO) and inducible (MIP-βraKOf/f) raptor deletion. Through genetic reconstitution of mTORC1 downstream targets, we identify mTORC1/S6K pathway as the mechanism by which mTORC1 regulates β-cell apoptosis, size and autophagy, whereas mTORC1/4E-BP2-eIF4E pathway regulates β-cell proliferation. Restoration of both pathways partially recovers β-cell mass and hyperglycaemia. This study also demonstrates a central role of mTORC1 in controlling insulin processing by regulating cap-dependent translation of carboxypeptidase E in a 4EBP2/eIF4E-dependent manner. Rapamycin treatment decreases CPE expression and insulin secretion in mice and human islets. We suggest an important role of mTORC1 in β-cells and identify downstream pathways driving β-cell mass, function and insulin processing. Deregulation of mTORC1 pathway has been associated with several human diseases including diabetes, neurodegeneration and cancer. Here Blandino-Rosano et al. show that mTORC1 signalling controls insulin secretion and β-cell maintenance by regulation of β-cell proliferation, apoptosis and autophagy and insulin processing.
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30
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Nagy L, Márton J, Vida A, Kis G, Bokor É, Kun S, Gönczi M, Docsa T, Tóth A, Antal M, Gergely P, Csóka B, Pacher P, Somsák L, Bai P. Glycogen phosphorylase inhibition improves beta cell function. Br J Pharmacol 2017; 175:301-319. [PMID: 28409826 DOI: 10.1111/bph.13819] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2016] [Revised: 04/03/2017] [Accepted: 04/05/2017] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND AND PURPOSE Glycogen phosphorylase (GP) is the key enzyme for glycogen degradation. GP inhibitors (GPi-s) are glucose lowering agents that cause the accumulation of glucose in the liver as glycogen. Glycogen metabolism has implications in beta cell function. Glycogen degradation can maintain cellular glucose levels, which feeds into catabolism to maintain insulin secretion, and elevated glycogen degradation levels contribute to glucotoxicity. The purpose of this study was to assess whether influencing glycogen metabolism in beta cells by GPi-s affects the function of these cells. EXPERIMENTAL APPROACH The effects of structurally different GPi-s were investigated on MIN6 insulinoma cells and in a mouse model of diabetes. KEY RESULTS GPi treatment increased glycogen content and, consequently, the surface area of glycogen in MIN6 cells. Furthermore, GPi treatment induced insulin receptor β (InsRβ), Akt and p70S6K phosphorylation, as well as pancreatic and duodenal homeobox 1(PDX1) and insulin expression. In line with these findings, GPi-s enhanced non-stimulated and glucose-stimulated insulin secretion in MIN6 cells. The InsRβ was shown to co-localize with glycogen particles as confirmed by in silico screening, where components of InsR signalling were identified as glycogen-bound proteins. GPi-s also activated the pathway of insulin secretion, indicated by enhanced glycolysis, mitochondrial oxidation and calcium signalling. Finally, GPi-s increased the size of islets of Langerhans and improved glucose-induced insulin release in mice. CONCLUSION AND IMPLICATIONS These data suggest that GPi-s also target beta cells and can be repurposed as agents to preserve beta cell function or even ameliorate beta cell dysfunction in different forms of diabetes. LINKED ARTICLES This article is part of a themed section on Inventing New Therapies Without Reinventing the Wheel: The Power of Drug Repurposing. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.2/issuetoc.
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Affiliation(s)
- Lilla Nagy
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.,MTA-DE Cell Biology and Signaling Research Group, Debrecen, Hungary
| | - Judit Márton
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - András Vida
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.,MTA-DE Lendület Laboratory of Cellular Metabolism, Debrecen, Hungary
| | - Gréta Kis
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Éva Bokor
- Department of Organic Chemistry, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary
| | - Sándor Kun
- Department of Organic Chemistry, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary
| | - Mónika Gönczi
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Tibor Docsa
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Attila Tóth
- Department of Cardiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Miklós Antal
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.,MTA-DE Neuroscience Research Group, Debrecen, Hungary
| | - Pál Gergely
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Balázs Csóka
- Department of Surgery, Rutgers - New Jersey Medical School, Newark, NJ, USA.,Center for Immunity and Inflammation, Rutgers - New Jersey Medical School, Newark, NJ, USA
| | - Pal Pacher
- NIAAA, National Institutes of Health, Laboratory of Physiologic Studies, Rockville, MD, USA
| | - László Somsák
- Department of Organic Chemistry, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary
| | - Péter Bai
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.,MTA-DE Lendület Laboratory of Cellular Metabolism, Debrecen, Hungary.,Research Center for Molecular Medicine, University of Debrecen, Debrecen, Hungary
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31
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Chau GC, Im DU, Kang TM, Bae JM, Kim W, Pyo S, Moon EY, Um SH. mTOR controls ChREBP transcriptional activity and pancreatic β cell survival under diabetic stress. J Cell Biol 2017; 216:2091-2105. [PMID: 28606928 PMCID: PMC5496625 DOI: 10.1083/jcb.201701085] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 04/05/2017] [Accepted: 05/01/2017] [Indexed: 02/06/2023] Open
Abstract
Through in vivo analyses of mTOR deficiency and in vitro studies of human and mouse pancreatic islets, Chau et al. show that mTOR plays a critical role in β cell survival in diabetes. mTOR associates with and inhibits the transcriptional ChREBP–Mlx complex, suppressing TXNIP expression and β cell death. Impaired nutrient sensing and dysregulated glucose homeostasis are common in diabetes. However, how nutrient-sensitive signaling components control glucose homeostasis and β cell survival under diabetic stress is not well understood. Here, we show that mice lacking the core nutrient-sensitive signaling component mammalian target of rapamycin (mTOR) in β cells exhibit reduced β cell mass and smaller islets. mTOR deficiency leads to a severe reduction in β cell survival and increased mitochondrial oxidative stress in chemical-induced diabetes. Mechanistically, we find that mTOR associates with the carbohydrate-response element–binding protein (ChREBP)–Max-like protein complex and inhibits its transcriptional activity, leading to decreased expression of thioredoxin-interacting protein (TXNIP), a potent inducer of β cell death and oxidative stress. Consistent with this, the levels of TXNIP and ChREBP were highly elevated in human diabetic islets and mTOR-deficient mouse islets. Thus, our results suggest that a nutrient-sensitive mTOR-regulated transcriptional network could be a novel target to improve β cell survival and glucose homeostasis in diabetes.
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Affiliation(s)
- Gia Cac Chau
- Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, Gyeonggi-do, Korea
| | - Dong Uk Im
- Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences and Technology, Samsung Medical Center, Sungkyunkwan University, Seoul, Korea
| | - Tong Mook Kang
- Department of Physiology, Single Cell Network Research Center, Sungkyunkwan University School of Medicine, Suwon, Gyeonggi-do, Korea
| | - Jeong Mo Bae
- Department of Pathology, Seoul National University College of Medicine, Seoul National University Hospital, Seoul Metropolitan Government Boramae Medical Center, Seoul, Korea
| | - Won Kim
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Seoul National University College of Medicine, Seoul Metropolitan Government Boramae Medical Center, Seoul, Korea
| | - Suhkneung Pyo
- School of Pharmacy, Sungkyunkwan University, Suwon, Gyeonggi-do, Korea
| | - Eun-Yi Moon
- Department of Bioscience and Biotechnology, Sejong University, Seoul, Korea
| | - Sung Hee Um
- Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, Gyeonggi-do, Korea .,Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences and Technology, Samsung Medical Center, Sungkyunkwan University, Seoul, Korea
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Shirakawa J, Fernandez M, Takatani T, El Ouaamari A, Jungtrakoon P, Okawa ER, Zhang W, Yi P, Doria A, Kulkarni RN. Insulin Signaling Regulates the FoxM1/PLK1/CENP-A Pathway to Promote Adaptive Pancreatic β Cell Proliferation. Cell Metab 2017; 25:868-882.e5. [PMID: 28286049 PMCID: PMC5382039 DOI: 10.1016/j.cmet.2017.02.004] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Revised: 01/09/2017] [Accepted: 02/08/2017] [Indexed: 12/01/2022]
Abstract
Investigation of cell-cycle kinetics in mammalian pancreatic β cells has mostly focused on transition from the quiescent (G0) to G1 phase. Here, we report that centromere protein A (CENP-A), which is required for chromosome segregation during the M-phase, is necessary for adaptive β cell proliferation. Receptor-mediated insulin signaling promotes DNA-binding activity of FoxM1 to regulate expression of CENP-A and polo-like kinase-1 (PLK1) by modulating cyclin-dependent kinase-1/2. CENP-A deposition at the centromere is augmented by PLK1 to promote mitosis, while knocking down CENP-A limits β cell proliferation and survival. CENP-A deficiency in β cells leads to impaired adaptive proliferation in response to pregnancy, acute and chronic insulin resistance, and aging in mice. Insulin-stimulated CENP-A/PLK1 protein expression is blunted in islets from patients with type 2 diabetes. These data implicate the insulin-FoxM1/PLK1/CENP-A pathway-regulated mitotic cell-cycle progression as an essential component in the β cell adaptation to delay and/or prevent progression to diabetes.
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Affiliation(s)
- Jun Shirakawa
- Section on Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Harvard Stem Cell Institute, Boston, MA 02215, USA
| | - Megan Fernandez
- Section on Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Harvard Stem Cell Institute, Boston, MA 02215, USA
| | - Tomozumi Takatani
- Section on Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Harvard Stem Cell Institute, Boston, MA 02215, USA
| | - Abdelfattah El Ouaamari
- Section on Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Harvard Stem Cell Institute, Boston, MA 02215, USA
| | - Prapaporn Jungtrakoon
- Section on Genetics and Epidemiology, Joslin Diabetes Center and Harvard Medical School, Boston, MA 02215, USA
| | - Erin R Okawa
- Section on Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Harvard Stem Cell Institute, Boston, MA 02215, USA
| | - Wei Zhang
- Section on Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Harvard Stem Cell Institute, Boston, MA 02215, USA
| | - Peng Yi
- Section on Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Harvard Stem Cell Institute, Boston, MA 02215, USA
| | - Alessandro Doria
- Section on Genetics and Epidemiology, Joslin Diabetes Center and Harvard Medical School, Boston, MA 02215, USA
| | - Rohit N Kulkarni
- Section on Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Harvard Stem Cell Institute, Boston, MA 02215, USA.
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Safi SZ, Qvist R, Ong G, Karimian H, Imran M, Shah I. Stimulation of β-adrenergic receptors plays a protective role via increased expression of RAF-1 and PDX-1 in hyperglycemic rat pancreatic islet (RIN-m5F) cells. Arch Med Sci 2017; 13:470-480. [PMID: 28261303 PMCID: PMC5332455 DOI: 10.5114/aoms.2016.64131] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 07/14/2015] [Indexed: 12/31/2022] Open
Abstract
INTRODUCTION It is a widely held view that a progressive reduction of beta-cell mass occurs in the progression of diabetes. RAF-1 kinase and pancreas duodenal homeobox 1 (PDX-1) are major factors that promote survival of cells and maintain normal insulin functions. In this study we investigated the effect of a β-adrenergic receptor agonist and antagonist on RAF-1 and PDX-1, and their respective effects on apoptosis and insulin release in RIN-m5F cells. MATERIAL AND METHODS RIN-m5F cells were cultured in normal (5 mM) and high (25 mM) glucose to mimic diabetic conditions, followed by treatment with 5 µM, 10 µM and 20 µM of isoproterenol and isoproterenol + propranolol for 6, 12 and 24 h. Western blotting and reverse transcription analysis were performed to examine the expression of RAF-1 and PDX-1. Annexin-V-FITC and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assays were used to investigate apoptosis. ELISA was used to measure insulin levels. Reverse transcription polymerase chain reaction was conducted to investigate the expression of genes. RESULTS Stimulation of β-adrenergic receptors with isoproterenol significantly induced RAF-1 and PDX-1 genes in a concentration-dependent and time-independent manner. Changes were significant both at protein and mRNA levels. Up-regulation of RAF-1 and PDX-1 was accompanied by improved insulin levels and reduced apoptosis. Concentrations of 10 µM and 20 µM for 12 and 24 h were more effective in achieving significant differences in the experimental and control groups. Propranolol reversed the effect of isoproterenol mostly at maximum concentrations and time periods. CONCLUSIONS A positive effect of a β-adrenergic agonist on RAF-1 and PDX-1, reduction in β-cell apoptosis and improved insulin contents can help to understand the pathogenesis of diabetes and to develop novel approaches for the β-cell dysfunction in diabetes.
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Affiliation(s)
- Sher Zaman Safi
- Department of Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
- Interdisciplinary Research Center in Biomedical Materials (IRCBM), COMSATS Institute of Information Technology, Lahore, Pakistan
| | - Rajes Qvist
- Department of Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Gracie Ong
- Department of Anesthesiology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Hamed Karimian
- Department of Pharmacy, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Muhammad Imran
- Biochemistry Section, Institute of Chemical Sciences, University of Peshawar, Peshawar, Pakistan
| | - Ikram Shah
- Department of Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
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Tumour-specific PI3K inhibition via nanoparticle-targeted delivery in head and neck squamous cell carcinoma. Nat Commun 2017; 8:14292. [PMID: 28194032 PMCID: PMC5316830 DOI: 10.1038/ncomms14292] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 12/14/2016] [Indexed: 02/08/2023] Open
Abstract
Alterations in PIK3CA, the gene encoding the p110α subunit of phosphatidylinositol 3-kinase (PI3Kα), are frequent in head and neck squamous cell carcinomas. Inhibitors of PI3Kα show promising activity in various cancer types, but their use is curtailed by dose-limiting side effects such as hyperglycaemia. In the present study, we explore the efficacy, specificity and safety of the targeted delivery of BYL719, a PI3Kα inhibitor currently in clinical development in solid tumours. By encapsulating BYL719 into P-selectin-targeted nanoparticles, we achieve specific accumulation of BYL719 in the tumour milieu. This results in tumour growth inhibition and radiosensitization despite the use of a sevenfold lower dose of BYL719 compared with oral administration. Furthermore, the nanoparticles abrogate acute and chronic metabolic side effects normally observed after BYL719 treatment. These findings offer a novel strategy that could potentially enhance the efficacy of PI3Kα inhibitors while mitigating dose-limiting toxicity in patients with head and neck squamous cell carcinomas. Head and neck squamous cell carcinomas (HNSCC) often harbour PIK3CA mutations but PI3Kα inhibitors can cause some side effects. Here, the authors develop P-selectin targeted nanoparticles to enhance tumour-specific delivery of a PI3Kα inhibitor to HNSCC PDX and orthotopic xenograft models.
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35
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Yuan T, Rafizadeh S, Azizi Z, Lupse B, Gorrepati KDD, Awal S, Oberholzer J, Maedler K, Ardestani A. Proproliferative and antiapoptotic action of exogenously introduced YAP in pancreatic β cells. JCI Insight 2016; 1:e86326. [PMID: 27812538 DOI: 10.1172/jci.insight.86326] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Loss of functional pancreatic β cells is a hallmark of both type 1 and 2 diabetes. Identifying the pathways that promote β cell proliferation and/or block β cell apoptosis is a potential strategy for diabetes therapy. The transcriptional coactivator Yes-associated protein (YAP), a major downstream effector of the Hippo signaling pathway, is a key regulator of organ size and tissue homeostasis by modulating cell proliferation and apoptosis. YAP is not expressed in mature primary human and mouse β cells. We aimed to identify whether reexpression of a constitutively active form of YAP promotes β cell proliferation/survival. Overexpression of YAP remarkably induced β cell proliferation in isolated human islets, while β cell function and functional identity genes were fully preserved. The transcription factor forkhead box M1 (FOXM1) was upregulated upon YAP overexpression and necessary for YAP-dependent β cell proliferation. YAP overexpression protected β cells from apoptosis triggered by multiple diabetic conditions. The small redox proteins thioredoxin-1 and thioredoxin-2 (Trx1/2) were upregulated by YAP; disruption of the Trx system revealed that Trx1/2 was required for the antiapoptotic action of YAP in insulin-producing β cells. Our data show the robust proproliferative and antiapoptotic function of YAP in pancreatic β cells. YAP reconstitution may represent a disease-modifying approach to restore a functional β cell mass in diabetes.
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Affiliation(s)
- Ting Yuan
- Centre for Biomolecular Interactions Bremen, University of Bremen, Bremen, Germany
| | - Sahar Rafizadeh
- Centre for Biomolecular Interactions Bremen, University of Bremen, Bremen, Germany
| | - Zahra Azizi
- Centre for Biomolecular Interactions Bremen, University of Bremen, Bremen, Germany
| | - Blaz Lupse
- Centre for Biomolecular Interactions Bremen, University of Bremen, Bremen, Germany
| | | | - Sushil Awal
- Centre for Biomolecular Interactions Bremen, University of Bremen, Bremen, Germany
| | - Jose Oberholzer
- Division of Transplantation, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Kathrin Maedler
- Centre for Biomolecular Interactions Bremen, University of Bremen, Bremen, Germany.,German Center for Diabetes Research (DZD) project partner, University of Bremen, Bremen, Germany
| | - Amin Ardestani
- Centre for Biomolecular Interactions Bremen, University of Bremen, Bremen, Germany
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Bhattacharya S, McElhanon KE, Gushchina LV, Weisleder N. Role of phosphatidylinositol-4,5-bisphosphate 3-kinase signaling in vesicular trafficking. Life Sci 2016; 167:39-45. [PMID: 27760304 DOI: 10.1016/j.lfs.2016.10.018] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 10/13/2016] [Accepted: 10/14/2016] [Indexed: 02/07/2023]
Abstract
Phosphatidylinositol-4,5-bisphosphate 3-kinases (PI3Ks) are regulatory enzymes involved in the generation of lipid species that modulate cellular signaling pathways through downstream effectors to influence a variety of cellular functions. Years of intensive study of PI3Ks have produced a significant body of literature in many areas, including that PI3K can mediate intracellular vesicular trafficking and through these actions contribute to a number of important physiological functions. This review focuses on the crucial roles that PI3K and AKT, a major downstream partner of PI3K, play in the regulation of vesicle trafficking during various forms of vesicular endocytosis and exocytosis.
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Affiliation(s)
- Sayak Bhattacharya
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, 473 W. 12th Ave., Columbus, OH 43210-1252, United States
| | - Kevin E McElhanon
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, 473 W. 12th Ave., Columbus, OH 43210-1252, United States
| | - Liubov V Gushchina
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, 473 W. 12th Ave., Columbus, OH 43210-1252, United States
| | - Noah Weisleder
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, 473 W. 12th Ave., Columbus, OH 43210-1252, United States.
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37
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Blandino-Rosano M, Scheys JO, Jimenez-Palomares M, Barbaresso R, Bender AS, Yanagiya A, Liu M, Rui L, Sonenberg N, Bernal-Mizrachi E. 4E-BP2/SH2B1/IRS2 Are Part of a Novel Feedback Loop That Controls β-Cell Mass. Diabetes 2016; 65:2235-48. [PMID: 27217487 PMCID: PMC4955981 DOI: 10.2337/db15-1443] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 05/09/2016] [Indexed: 01/08/2023]
Abstract
The mammalian target of rapamycin complex 1 (mTORC1) regulates several biological processes, although the key downstream mechanisms responsible for these effects are poorly defined. Using mice with deletion of eukaryotic translation initiation factor 4E-binding protein 2 (4E-BP2), we determine that this downstream target is a major regulator of glucose homeostasis and β-cell mass, proliferation, and survival by increasing insulin receptor substrate 2 (IRS2) levels and identify a novel feedback mechanism by which mTORC1 signaling increases IRS2 levels. In this feedback loop, we show that 4E-BP2 deletion induces translation of the adaptor protein SH2B1 and promotes the formation of a complex with IRS2 and Janus kinase 2, preventing IRS2 ubiquitination. The changes in IRS2 levels result in increases in cell cycle progression, cell survival, and β-cell mass by increasing Akt signaling and reducing p27 levels. Importantly, 4E-BP2 deletion confers resistance to cytokine treatment in vitro. Our data identify SH2B1 as a major regulator of IRS2 stability, demonstrate a novel feedback mechanism linking mTORC1 signaling with IRS2, and identify 4E-BP2 as a major regulator of proliferation and survival of β-cells.
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Affiliation(s)
- Manuel Blandino-Rosano
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI
| | - Joshua O Scheys
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI
| | - Margarita Jimenez-Palomares
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI
| | - Rebecca Barbaresso
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI
| | - Aaron S Bender
- Diabetes, Obesity and Metabolism Institute, The Icahn School of Medicine at Mount Sinai, New York, NY
| | - Akiko Yanagiya
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
| | - Ming Liu
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI
| | - Liangyou Rui
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI
| | - Nahum Sonenberg
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
| | - Ernesto Bernal-Mizrachi
- Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI VA Ann Arbor Healthcare System, Ann Arbor, MI
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Cras-Méneur C, Conlon M, Zhang Y, Pasca Di Magliano M, Bernal-Mizrachi E. Early pancreatic islet fate and maturation is controlled through RBP-Jκ. Sci Rep 2016; 6:26874. [PMID: 27240887 PMCID: PMC4886527 DOI: 10.1038/srep26874] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 05/10/2016] [Indexed: 01/29/2023] Open
Abstract
Notch signaling is known to control early pancreatic differentiation through Ngn3 repression. In later stages, downstream of Notch, the Presenilins are still required to maintain the endocrine fate allocation. Amongst their multiple targets, it remains unclear which one actually controls the maintenance of the fate of the early islets. Conditional deletions of the Notch effector RBP-Jκ with lineage tracing in Presenilin-deficient endocrine progenitors, demonstrated that this factor is central to the control of the fate through a non-canonical Notch mechanism. RBP-Jκ mice exhibit normal islet morphogenesis and function, however, a fraction of the progenitors fails to differentiate and develop into disorganized masses resembling acinar to ductal metaplasia and chronic pancreatitis. A subsequent deletion of RBP-Jκ in forming β-cells led to the transdifferentiation into the other endocrine cells types, indicating that this factor still mediates the maintenance of the fate within the endocrine lineage itself. These results highlight the dual importance of Notch signaling for the endocrine lineage. Even after Ngn3 expression, Notch activity is required to maintain both fate and maturation of the Ngn3 progenitors. In a subset of the cells, these alterations of Notch signaling halt their differentiation and leads to acinar to ductal metaplasia.
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Affiliation(s)
- Corentin Cras-Méneur
- University of Michigan in Ann Arbor, Internal Medicine Department, MEND Division Brehm Tower, 1000 Wall St, Ann Arbor, MI 48105-1912, USA
| | - Megan Conlon
- University of Michigan in Ann Arbor, Internal Medicine Department, MEND Division Brehm Tower, 1000 Wall St, Ann Arbor, MI 48105-1912, USA
| | - Yaqing Zhang
- University of Michigan in Ann Arbor, Department of Surgery, General Surgery Division 4304 Cancer Center, 1500 E. Medical Center Drive, Ann Arbor MI 48109-5936, USA
| | - Marina Pasca Di Magliano
- University of Michigan in Ann Arbor, Department of Surgery, General Surgery Division 4304 Cancer Center, 1500 E. Medical Center Drive, Ann Arbor MI 48109-5936, USA
| | - Ernesto Bernal-Mizrachi
- University of Miami Miller School of Medicine, Department of General Internal Medicine, Division of Endocrinology, Diabetes and Metabolism 1400 NW 10th Ave, Miami, FL 33136-1031, USA
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Lakshmipathi J, Alvarez-Perez JC, Rosselot C, Casinelli GP, Stamateris RE, Rausell-Palamos F, O'Donnell CP, Vasavada RC, Scott DK, Alonso LC, Garcia-Ocaña A. PKCζ Is Essential for Pancreatic β-Cell Replication During Insulin Resistance by Regulating mTOR and Cyclin-D2. Diabetes 2016; 65:1283-96. [PMID: 26868297 PMCID: PMC4839210 DOI: 10.2337/db15-1398] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 02/06/2016] [Indexed: 12/23/2022]
Abstract
Adaptive β-cell replication occurs in response to increased metabolic demand during insulin resistance. The intracellular mediators of this compensatory response are poorly defined and their identification could provide significant targets for β-cell regeneration therapies. Here we show that glucose and insulin in vitro and insulin resistance in vivo activate protein kinase C ζ (PKCζ) in pancreatic islets and β-cells. PKCζ is required for glucose- and glucokinase activator-induced proliferation of rodent and human β-cells in vitro. Furthermore, either kinase-dead PKCζ expression (KD-PKCζ) or disruption of PKCζ in mouse β-cells blocks compensatory β-cell replication when acute hyperglycemia/hyperinsulinemia is induced. Importantly, KD-PKCζ inhibits insulin resistance-mediated mammalian target of rapamycin (mTOR) activation and cyclin-D2 upregulation independent of Akt activation. In summary, PKCζ activation is key for early compensatory β-cell replication in insulin resistance by regulating the downstream signals mTOR and cyclin-D2. This suggests that alterations in PKCζ expression or activity might contribute to inadequate β-cell mass expansion and β-cell failure leading to type 2 diabetes.
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Affiliation(s)
- Jayalakshmi Lakshmipathi
- Diabetes, Obesity and Metabolism Institute, Division of Endocrinology, Diabetes and Bone Diseases, The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Juan Carlos Alvarez-Perez
- Diabetes, Obesity and Metabolism Institute, Division of Endocrinology, Diabetes and Bone Diseases, The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Carolina Rosselot
- Diabetes, Obesity and Metabolism Institute, Division of Endocrinology, Diabetes and Bone Diseases, The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Gabriella P Casinelli
- Division of Pediatric Hematology/Oncology and Blood and Marrow Transplantation, Department of Pediatrics, Children's Hospital of Pittsburgh, Pittsburgh, PA
| | - Rachel E Stamateris
- Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Francisco Rausell-Palamos
- Diabetes, Obesity and Metabolism Institute, Division of Endocrinology, Diabetes and Bone Diseases, The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Christopher P O'Donnell
- Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, University of Pittsburgh, Pittsburgh, PA
| | - Rupangi C Vasavada
- Diabetes, Obesity and Metabolism Institute, Division of Endocrinology, Diabetes and Bone Diseases, The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Donald K Scott
- Diabetes, Obesity and Metabolism Institute, Division of Endocrinology, Diabetes and Bone Diseases, The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Laura C Alonso
- Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Adolfo Garcia-Ocaña
- Diabetes, Obesity and Metabolism Institute, Division of Endocrinology, Diabetes and Bone Diseases, The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY
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40
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Stamateris RE, Sharma RB, Kong Y, Ebrahimpour P, Panday D, Ranganath P, Zou B, Levitt H, Parambil NA, O'Donnell CP, García-Ocaña A, Alonso LC. Glucose Induces Mouse β-Cell Proliferation via IRS2, MTOR, and Cyclin D2 but Not the Insulin Receptor. Diabetes 2016; 65:981-95. [PMID: 26740601 PMCID: PMC5314707 DOI: 10.2337/db15-0529] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2015] [Accepted: 12/29/2015] [Indexed: 12/21/2022]
Abstract
An important goal in diabetes research is to understand the processes that trigger endogenous β-cell proliferation. Hyperglycemia induces β-cell replication, but the mechanism remains debated. A prime candidate is insulin, which acts locally through the insulin receptor. Having previously developed an in vivo mouse hyperglycemia model, we tested whether glucose induces β-cell proliferation through insulin signaling. By using mice lacking insulin signaling intermediate insulin receptor substrate 2 (IRS2), we confirmed that hyperglycemia-induced β-cell proliferation requires IRS2 both in vivo and ex vivo. Of note, insulin receptor activation was not required for glucose-induced proliferation, and insulin itself was not sufficient to drive replication. Glucose and insulin caused similar acute signaling in mouse islets, but chronic signaling differed markedly, with mammalian target of rapamycin (MTOR) and extracellular signal-related kinase (ERK) activation by glucose and AKT activation by insulin. MTOR but not ERK activation was required for glucose-induced proliferation. Cyclin D2 was necessary for glucose-induced β-cell proliferation. Cyclin D2 expression was reduced when either IRS2 or MTOR signaling was lost, and restoring cyclin D2 expression rescued the proliferation defect. Human islets shared many of these regulatory pathways. Taken together, these results support a model in which IRS2, MTOR, and cyclin D2, but not the insulin receptor, mediate glucose-induced proliferation.
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Affiliation(s)
- Rachel E Stamateris
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Rohit B Sharma
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Yahui Kong
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Pantea Ebrahimpour
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Deepika Panday
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Pavana Ranganath
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Baobo Zou
- Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Helena Levitt
- Division of Endocrinology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | | | - Christopher P O'Donnell
- Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Adolfo García-Ocaña
- Diabetes, Obesity and Metabolism Institute, Division of Endocrinology, Diabetes and Bone Disease, The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Laura C Alonso
- Diabetes Center of Excellence, Department of Medicine, University of Massachusetts Medical School, Worcester, MA
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Gelam Honey Attenuates the Oxidative Stress-Induced Inflammatory Pathways in Pancreatic Hamster Cells. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2016; 2016:5843615. [PMID: 27034691 PMCID: PMC4808561 DOI: 10.1155/2016/5843615] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Revised: 08/23/2015] [Accepted: 10/01/2015] [Indexed: 01/22/2023]
Abstract
Purpose. Type 2 diabetes consists of progressive hyperglycemia and insulin resistance, which could result from glucose toxicity, inflammatory cytokines, and oxidative stress. In the present study we investigated the effect of Gelam honey and quercetin on the oxidative stress-induced inflammatory pathways and the proinflammatory cytokines. Methods. HIT-T15 cells were cultured and preincubated with the extract of Gelam honey (20, 40, 60, and 80 μg/mL), as well as quercetin (20, 40, 60, and 80 μM), prior to stimulation by 20 and 50 mM glucose. Results. HIT-T15 cells cultured under hyperglycemic condition showed a significant increase in the inflammatory pathways by phosphorylating JNK, IKK-β, and IRS-1 at Ser307 (p < 0.05). There was a significant decrease in the phosphorylation of Akt at Ser473 (p < 0.05). Pretreatment with Gelam honey and quercetin reduced the expression of phosphorylated JNK, IKK-β, and IRS-1, thereby significantly reducing the expression of proinflammatory cytokines like TNF-α, IL-6, and IL-1β (p < 0.05). At the same time there was a significant increase in the phosphorylated Akt showing the protective effects against inflammation and insulin resistance (p < 0.05). In conclusion, our data suggest the potential use of the extract from Gelam honey and quercetin in modulating the inflammation induced insulin signaling pathways.
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The Potential Protective Action of Vitamin D in Hepatic Insulin Resistance and Pancreatic Islet Dysfunction in Type 2 Diabetes Mellitus. Nutrients 2016; 8:147. [PMID: 26959059 PMCID: PMC4808876 DOI: 10.3390/nu8030147] [Citation(s) in RCA: 81] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 02/26/2016] [Accepted: 02/29/2016] [Indexed: 02/06/2023] Open
Abstract
Vitamin D deficiency (i.e., hypovitaminosis D) is associated with increased insulin resistance, impaired insulin secretion, and poorly controlled glucose homeostasis, and thus is correlated with the risk of metabolic diseases, including type 2 diabetes mellitus (T2DM). The liver plays key roles in glucose and lipid metabolism, and its dysregulation leads to abnormalities in hepatic glucose output and triglyceride accumulation. Meanwhile, the pancreatic islets are constituted in large part by insulin-secreting β cells. Consequently, islet dysfunction, such as occurs in T2DM, produces hyperglycemia. In this review, we provide a critical appraisal of the modulatory actions of vitamin D in hepatic insulin sensitivity and islet insulin secretion, and we discuss the potential roles of a local vitamin D signaling in regulating hepatic and pancreatic islet functions. This information provides a scientific basis for establishing the benefits of the maintenance, or dietary manipulation, of adequate vitamin D status in the prevention and management of obesity-induced T2DM and non-alcoholic fatty liver disease.
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Liu H, Zheng J, Li RH. Clinical efficacy of 'Spleen-kidney-care' Yiqi Huayu and Jiangzhuo traditional Chinese medicine for the treatment of patients with diabetic nephropathy. Exp Ther Med 2015; 10:1096-1102. [PMID: 26622446 DOI: 10.3892/etm.2015.2627] [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: 02/28/2014] [Accepted: 08/19/2014] [Indexed: 12/28/2022] Open
Abstract
The aim of the present study was to investigate the effect of the traditional Chinese medicine (TCM), 'Spleen-kidney-care' Yiqi Huayu and Jiangzhuo decoction (SKC-YJ), as an adjuvant therapy in diabetic nephropathy (DN) treatment. In total, 72 patients with DN were randomly divided into control (n=54) and experimental (n=18) groups, with the latter administered SKC-YJ treatment. Indicators for determining the condition of the patients included the levels of proteinuria, blood glucose, glycosylated hemoglobin, blood lipids, blood viscosity and C-reactive protein, which were used to analyze the treatment protocols for DN. Following SKC-YJ treatment, the urinary albumin excretion rate, fasting blood glucose, 2 h-postprandial blood glucose, glycosylated hemoglobin, triglyceride, total cholesterol, blood viscosity, fibrinogen and C-reactive protein levels were detected in the two groups, and were all demonstrated to decrease significantly following treatment with SKC-YJ. Furthermore, the results revealed that SKC-YJ treatment exhibited no significant side-effects on the blood, liver and renal functions or gastrointestinal reactions. By contrast, SKC-YJ improved the symptoms of nausea, vomiting and diarrhea in the patients with DN, while showing no allergic reaction during the observation period. Therefore, SKC-YJ treatment was shown to significantly improve the clinical efficacy of DN treatment, illustrating novel roles for TCM in DN treatment.
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Affiliation(s)
- Hong Liu
- Department of Nephrology, Chongqing Hospital of Traditional Chinese Medicine, Chongqing 400021, P.R. China
| | - Jin Zheng
- Department of Nephrology, Chongqing Hospital of Traditional Chinese Medicine, Chongqing 400021, P.R. China
| | - Rong-Heng Li
- Cooperation Department of Chinese and Western Medicine, First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China
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Lee HJ, Choi YJ, Park SY, Kim JY, Won KC, Son JK, Kim YW. Hexane Extract of Orthosiphon stamineus Induces Insulin Expression and Prevents Glucotoxicity in INS-1 Cells. Diabetes Metab J 2015; 39:51-8. [PMID: 25729713 PMCID: PMC4342537 DOI: 10.4093/dmj.2015.39.1.51] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Accepted: 06/02/2014] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Hyperglycemia, a characteristic feature of diabetes, induces glucotoxicity in pancreatic β-cells, resulting in further impairment of insulin secretion and worsening glycemic control. Thus, preservation of insulin secretory capacity is essential for the management of type 2 diabetes. In this study, we evaluated the ability of an Orthosiphon stamineus (OS) extract to prevent glucotoxicity in insulin-producing cells. METHODS We measured insulin mRNA expression and glucose-stimulated insulin secretion (GSIS) in OS-treated INS-1 cells after exposure to a high glucose (HG; 30 mM) concentration. RESULTS The hexane extract of OS elevated mRNA expression of insulin as well as pancreatic and duodenal homeobox-1 of INS-1 cells in a dose-dependent manner. The hexane OS extract also increased the levels of phosphorylated phosphatidylinositol 3-kinase (PI3K) in a concentration-dependent manner. Additionally, Akt phosphorylation was elevated by treatment with 100 and 200 µmol of the hexane OS extract. Three days of HG exposure suppressed insulin mRNA expression and GSIS; these expressions were restored by treatment with the hexane OS extract. HG elevated peroxide levels in the INS-1 cells. These levels were unaffected by OS treatment under both normal and hyperglycemic conditions. CONCLUSION Our results suggested that the hexane extract of OS elevates insulin mRNA expression and prevents glucotoxicity induced by a 3-day treatment with HG. This was associated with the activation of PI-3K and Akt.
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Affiliation(s)
- Hae-Jung Lee
- Department of Pediatrics, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, Korea
| | - Yoon-Jung Choi
- Department of Physiology, Yeungnam University College of Medicine, Daegu, Korea
| | - So-Young Park
- Department of Physiology, Yeungnam University College of Medicine, Daegu, Korea
| | - Jong-Yeon Kim
- Department of Physiology, Yeungnam University College of Medicine, Daegu, Korea
| | - Kyu-Chang Won
- Department of Internal Medicine, Yeungnam University College of Medicine, Daegu, Korea
| | - Jong-Keun Son
- Yeungnam University College of Pharmacy, Gyeongsan, Korea
| | - Yong-Woon Kim
- Department of Physiology, Yeungnam University College of Medicine, Daegu, Korea
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Gregg B, Elghazi L, Alejandro EU, Smith MR, Blandino-Rosano M, El-Gabri D, Cras-Méneur C, Bernal-Mizrachi E. Exposure of mouse embryonic pancreas to metformin enhances the number of pancreatic progenitors. Diabetologia 2014; 57:2566-75. [PMID: 25249235 PMCID: PMC4417192 DOI: 10.1007/s00125-014-3379-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 08/28/2014] [Indexed: 01/23/2023]
Abstract
AIMS/HYPOTHESIS Developing beta cells are vulnerable to nutrient environmental signals. Early developmental processes that alter the number of pancreatic progenitors can determine the number of beta cells present at birth. Metformin, the most widely used oral agent for treating diabetes, alters intracellular energy status in part by increasing AMP-activated protein kinase (AMPK) signalling. This study examined the effect of metformin on developing pancreas and beta cells. METHODS Pancreatic rudiments from CD-1 mice at embryonic day 13.0 (E13.0) were cultured with metformin, 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR, an AMPK activator) or vehicle control in vitro. In another set of studies, pregnant C57BL/6 mice were treated with metformin throughout gestation. Embryonic (E14.0) and neonatal pancreases were then analysed for their morphometry. RESULTS In vitro metformin treatment led to an increase in the proliferation and number of pancreatic duodenal homeobox 1-positive (PDX1(+)) progenitors. These results were reproduced by in vitro culture of embryonic pancreas rudiments with AICAR, suggesting that AMPK activation was involved. Similarly, metformin administration to pregnant dams induced an increase in both PDX1(+) and neurogenin 3-positive progenitors in the embryonic pancreas at E14.0 and these changes resulted in an increased beta cell fraction in neonates. CONCLUSIONS/INTERPRETATION These results indicate that exposure to metformin during gestation modulates the early steps of beta cell development (prior to E14.0) towards an increase in the number of pancreatic and endocrine progenitors. These changes ultimately result in a higher beta cell fraction at birth. These findings are of clinical importance given that metformin is currently used for the treatment of gestational diabetes.
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Affiliation(s)
- Brigid Gregg
- Department of Pediatrics, Division of Endocrinology, Diabetes and Metabolism, University of Michigan, Ann Arbor, Michigan, USA
| | - Lynda Elghazi
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, Brehm Center for Diabetes Research, University of Michigan, Ann Arbor, Michigan, USA
| | - Emilyn U. Alejandro
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, Brehm Center for Diabetes Research, University of Michigan, Ann Arbor, Michigan, USA
| | - Michelle R. Smith
- Department of Pediatrics, Division of Endocrinology, Diabetes and Metabolism, University of Michigan, Ann Arbor, Michigan, USA
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, Brehm Center for Diabetes Research, University of Michigan, Ann Arbor, Michigan, USA
| | - Manuel Blandino-Rosano
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, Brehm Center for Diabetes Research, University of Michigan, Ann Arbor, Michigan, USA
| | - Deena El-Gabri
- Department of Pediatrics, Division of Endocrinology, Diabetes and Metabolism, University of Michigan, Ann Arbor, Michigan, USA
| | - Corentin Cras-Méneur
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, Brehm Center for Diabetes Research, University of Michigan, Ann Arbor, Michigan, USA
| | - Ernesto Bernal-Mizrachi
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, Brehm Center for Diabetes Research, University of Michigan, Ann Arbor, Michigan, USA
- VA Ann Arbor Healthcare System, Ann Arbor, Michigan
- Corresponding author: Dr. Ernesto Bernal-Mizrachi VA Ann Arbor Healthcare System, Ann Arbor, Michigan., Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, Michigan 48109-0678, USA., Phone: +1 (734) 615-0262, Fax: +1 (734) 936-6684,
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Bridges D, Saltiel AR. Phosphoinositides: Key modulators of energy metabolism. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1851:857-66. [PMID: 25463477 DOI: 10.1016/j.bbalip.2014.11.008] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 10/31/2014] [Accepted: 11/10/2014] [Indexed: 12/19/2022]
Abstract
Phosphoinositides are key players in many trafficking and signaling pathways. Recent advances regarding the synthesis, location and functions of these lipids have dramatically improved our understanding of how and when these lipids are generated and what their roles are in animal physiology. In particular, phosphoinositides play a central role in insulin signaling, and manipulation of PtdIns(3,4,5)P₃levels in particular, may be an important potential therapeutic target for the alleviation of insulin resistance associated with obesity and the metabolic syndrome. In this article we review the metabolism, regulation and functional roles of phosphoinositides in insulin signaling and the regulation of energy metabolism. This article is part of a Special Issue entitled Phosphoinositides.
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Affiliation(s)
- Dave Bridges
- Departments of Physiology and Pediatrics, University of Tennessee Health Science Center, Memphis, TN, USA; Children's Foundation Research Institute, Le Bonheur Children's Hospital, Memphis, TN, USA.
| | - Alan R Saltiel
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
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Alejandro EU, Gregg B, Wallen T, Kumusoglu D, Meister D, Chen A, Merrins MJ, Satin LS, Liu M, Arvan P, Bernal-Mizrachi E. Maternal diet-induced microRNAs and mTOR underlie β cell dysfunction in offspring. J Clin Invest 2014; 124:4395-410. [PMID: 25180600 DOI: 10.1172/jci74237] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Accepted: 07/24/2014] [Indexed: 01/07/2023] Open
Abstract
A maternal diet that is low in protein increases the susceptibility of offspring to type 2 diabetes by inducing long-term alterations in β cell mass and function. Nutrients and growth factor signaling converge through mTOR, suggesting that this pathway participates in β cell programming during fetal development. Here, we revealed that newborns of dams exposed to low-protein diet (LP0.5) throughout pregnancy exhibited decreased insulin levels, a lower β cell fraction, and reduced mTOR signaling. Adult offspring of LP0.5-exposed mothers exhibited glucose intolerance as a result of an insulin secretory defect and not β cell mass reduction. The β cell insulin secretory defect was distal to glucose-dependent Ca2+ influx and resulted from reduced proinsulin biosynthesis and insulin content. Islets from offspring of LP0.5-fed dams exhibited reduced mTOR and increased expression of a subset of microRNAs, and blockade of microRNA-199a-3p and -342 in these islets restored mTOR and insulin secretion to normal. Finally, transient β cell activation of mTORC1 signaling in offspring during the last week of pregnancy of mothers fed a LP0.5 rescued the defect in the neonatal β cell fraction and metabolic abnormalities in the adult. Together, these findings indicate that a maternal low-protein diet alters microRNA and mTOR expression in the offspring, influencing insulin secretion and glucose homeostasis.
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Jiang Q, Ding S, Wu J, Liu X, Wu Z. Norepinephrine stimulates mobilization of endothelial progenitor cells after limb ischemia. PLoS One 2014; 9:e101774. [PMID: 25007164 PMCID: PMC4090158 DOI: 10.1371/journal.pone.0101774] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Accepted: 06/11/2014] [Indexed: 11/19/2022] Open
Abstract
Objective During several pathological processes such as cancer progression, thermal injury, wound healing and hindlimb ischemia, the mobilization of endothelial progenitor cells (EPCs) mobilization was enhanced with an increase of sympathetic nerve activity and norepinephrine (NE) secretion, yet the cellular and molecular mechanisms involved in the effects of NE on EPCs has less been investigated. Methods and Results EPCs from BMs, peripheral circulation and spleens, the VEGF concentration in BM, skeletal muscle, peripheral circulation and spleen and angiogenesis in ischemic gastrocnemius were quantified in mice with hindlimbs ischemia. Systemic treatment of NE significantly increased EPCs number in BM, peripheral circulation and spleen, VEGF concentration in BM and skeletal muscle and angiogenesis in ischemic gastrocnemius in mice with hind limb ischemia, but did not affair VEGF concentration in peripheral circulation and spleen. EPCs isolated from healthy adults were cultured with NE in vitro to evaluate proliferation potential, migration capacity and phosphorylations of Akt and eNOS signal moleculars. Treatment of NE induced a significant increase in number of EPCs in the S-phase in a dose-dependent manner, as well as migrative activity of EPCs in vitro (p<0.05). The co-treatment of Phentolamine, I127, LY294002 and L-NAME with NE blocked the effects of NE on EPCs proliferation and migration. Treatment with NE significantly increased phosphorylation of Akt and eNOS of EPCs. Addition of phentolamine and I127 attenuated the activation of Akt/eNOS pathway, but metoprolol could not. Pretreatment of mice with either Phentolamine or I127 significantly attenuated the effects of NE on EPCs in vivo, VEGF concentration in BM, skeletal muscle and angiogenesis in ischemic gastrocnemius, but Metoprolol did not. Conclusion These results unravel that sympathetic nervous system regulate EPCs mobilization and their pro-angiogenic capacity via α adrenoceptor, β 2 adrenoceptor and meanwhile Akt/eNOS signaling pathway.
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Affiliation(s)
- Qijun Jiang
- Department of Cardiology, Wuhan General Hospital of Guangzhou Military, Wuhan, Hubei, China
- Department of Cardiology, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Shifang Ding
- Department of Cardiology, Wuhan General Hospital of Guangzhou Military, Wuhan, Hubei, China
- * E-mail:
| | - Jianxiang Wu
- Department of Cardiology, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Xing Liu
- Department of Cardiology, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Zonggui Wu
- Department of Cardiology, Changzheng Hospital, Second Military Medical University, Shanghai, China
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Bhatnagar S, Soni MS, Wrighton LS, Hebert AS, Zhou AS, Paul PK, Gregg T, Rabaglia ME, Keller MP, Coon JJ, Attie AD. Phosphorylation and degradation of tomosyn-2 de-represses insulin secretion. J Biol Chem 2014; 289:25276-86. [PMID: 25002582 DOI: 10.1074/jbc.m114.575985] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The abundance and functional activity of proteins involved in the formation of the SNARE complex are tightly regulated for efficient exocytosis. Tomosyn proteins are negative regulators of exocytosis. Tomosyn causes an attenuation of insulin secretion by limiting the formation of the SNARE complex. We hypothesized that glucose-dependent stimulation of insulin secretion from β-cells must involve reversing the inhibitory action of tomosyn. Here, we show that glucose increases tomosyn protein turnover. Within 1 h of exposure to 15 mM glucose, ~50% of tomosyn was degraded. The degradation of tomosyn in response to high glucose was blocked by inhibitors of the proteasomal pathway. Using (32)P labeling and mass spectrometry, we showed that tomosyn-2 is phosphorylated in response to high glucose, phorbol esters, and analogs of cAMP, all key insulin secretagogues. We identified 11 phosphorylation sites in tomosyn-2. Site-directed mutagenesis was used to generate phosphomimetic (Ser → Asp) and loss-of-function (Ser → Ala) mutants. The Ser → Asp mutant had enhanced protein turnover compared with the Ser → Ala mutant and wild type tomosyn-2. Additionally, the Ser → Asp tomosyn-2 mutant was ineffective at inhibiting insulin secretion. Using a proteomic screen for tomosyn-2-binding proteins, we identified Hrd-1, an E3-ubiquitin ligase. We showed that tomosyn-2 ubiquitination is increased by Hrd-1, and knockdown of Hrd-1 by short hairpin RNA resulted in increased abundance in tomosyn-2 protein levels. Taken together, our results reveal a mechanism by which enhanced phosphorylation of a negative regulator of secretion, tomosyn-2, in response to insulin secretagogues targets it to degradation by the Hrd-1 E3-ubiquitin ligase.
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Affiliation(s)
| | | | | | - Alexander S Hebert
- Chemistry and Biomolecular Chemistry, University of Wisconsin, Madison, Wisconsin 53706
| | | | | | | | | | | | - Joshua J Coon
- Chemistry and Biomolecular Chemistry, University of Wisconsin, Madison, Wisconsin 53706
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Rachdi L, Kariyawasam D, Aïello V, Herault Y, Janel N, Delabar JM, Polak M, Scharfmann R. Dyrk1A induces pancreatic β cell mass expansion and improves glucose tolerance. Cell Cycle 2014; 13:2221-9. [PMID: 24870561 PMCID: PMC4111677 DOI: 10.4161/cc.29250] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 05/15/2014] [Accepted: 05/15/2014] [Indexed: 01/27/2023] Open
Abstract
Type 2 diabetes is caused by a limited capacity of insulin-producing pancreatic β cells to increase their mass and function in response to insulin resistance. The signaling pathways that positively regulate functional β cell mass have not been fully elucidated. DYRK1A (also called minibrain/MNB) is a member of the dual-specificity tyrosine phosphorylation-regulated kinase (DYRK) family. A significant amount of data implicates DYRK1A in brain growth and Down syndrome, and recent data indicate that Dyrk1A haploinsufficient mice have a low functional β cell mass. Here we ask whether Dyrk1A upregulation could be a way to increase functional β cell mass. We used mice overexpressing Dyrk1A under the control of its own regulatory sequences (mBACTgDyrk1A). These mice exhibit decreased glucose levels and hyperinsulinemia in the fasting state. Improved glucose tolerance is observed in these mice as early as 4 weeks of age. Upregulation of Dyrk1A in β cells induces expansion of β cell mass through increased proliferation and cell size. Importantly, mBACTgDyrk1A mice are protected against high-fat-diet-induced β cell failure through increase in β cell mass and insulin sensitivity. These studies show the crucial role of the DYRK1A pathway in the regulation of β cell mass and carbohydrate metabolism in vivo. Activating the DYRK1A pathway could thus represent an innovative way to increase functional β cell mass.
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Affiliation(s)
- Latif Rachdi
- INSERM U1016; Institut Cochin; Faculté de Médecine Cochin; Université Paris Descartes; Paris, France
| | - Dulanjalee Kariyawasam
- INSERM U1016; Institut Cochin; Faculté de Médecine Cochin; Université Paris Descartes; Paris, France
- Hôpital Universitaire Necker Enfants Malades; Endocrinologie Gynécologie Diabétologie Pédiatriques; IMAGINE Institute; Paris, France
| | - Virginie Aïello
- INSERM U1016; Institut Cochin; Faculté de Médecine Cochin; Université Paris Descartes; Paris, France
| | - Yann Herault
- Institut de Génétique et de Biologie Moléculaire et Cellulaire; Translational Medicine and Neuroscience Program; IGBMC; CNRS; INSERM; Université de Strasbourg; UMR7104, UMR964, and Institut Clinique de la Souris; ICS; GIE CERBM; Illkirch, France
| | - Nathalie Janel
- Sorbonne Paris Cité; Unité de Biologie Fonctionnelle et Adaptative (BFA); CNRS UMR 8251; Paris Diderot University; Paris, France
| | - Jean-Maurice Delabar
- Sorbonne Paris Cité; Unité de Biologie Fonctionnelle et Adaptative (BFA); CNRS UMR 8251; Paris Diderot University; Paris, France
| | - Michel Polak
- INSERM U1016; Institut Cochin; Faculté de Médecine Cochin; Université Paris Descartes; Paris, France
- Hôpital Universitaire Necker Enfants Malades; Endocrinologie Gynécologie Diabétologie Pédiatriques; IMAGINE Institute; Paris, France
| | - Raphaël Scharfmann
- INSERM U1016; Institut Cochin; Faculté de Médecine Cochin; Université Paris Descartes; Paris, France
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