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Truchan NA, Brar HK, Gallagher SJ, Neuman JC, Kimple ME. A single-islet microplate assay to measure mouse and human islet insulin secretion. Islets 2015; 7:e1076607. [PMID: 26452321 PMCID: PMC4708880 DOI: 10.1080/19382014.2015.1076607] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
One complication to comparing β-cell function among islet preparations, whether from genetically identical or diverse animals or human organ donors, is the number of islets required per assay. Islet numbers can be limiting, meaning that fewer conditions can be tested; other islet measurements must be excluded; or islets must be pooled from multiple animals/donors for each experiment. Furthermore, pooling islets negates the possibility of performing single-islet comparisons. Our aim was to validate a 96-well plate-based single islet insulin secretion assay that would be as robust as previously published methods to quantify glucose-stimulated insulin secretion from mouse and human islets. First, we tested our new assay using mouse islets, showing robust stimulation of insulin secretion 24 or 48 h after islet isolation. Next, we utilized the assay to quantify mouse islet function on an individual islet basis, measurements that would not be possible with the standard pooled islet assay methods. Next, we validated our new assay using human islets obtained from the Integrated Islet Distribution Program (IIDP). Human islets are known to have widely varying insulin secretion capacity, and using our new assay we reveal biologically relevant factors that are significantly correlated with human islet function, whether displayed as maximal insulin secretion response or fold-stimulation of insulin secretion. Overall, our results suggest this new microplate assay will be a useful tool for many laboratories, expert or not in islet techniques, to be able to precisely quantify islet insulin secretion from their models of interest.
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Affiliation(s)
- Nathan A Truchan
- Department of Medicine; Division of Endocrinology, Diabetes & Metabolism; University of Wisconsin-Madison; Madison, WI USA
- William S Middleton Memorial Veterans Hospital; Madison, WI USA
| | - Harpreet K Brar
- Department of Medicine; Division of Endocrinology, Diabetes & Metabolism; University of Wisconsin-Madison; Madison, WI USA
- William S Middleton Memorial Veterans Hospital; Madison, WI USA
| | - Shannon J Gallagher
- Department of Medicine; Division of Endocrinology, Diabetes & Metabolism; University of Wisconsin-Madison; Madison, WI USA
- William S Middleton Memorial Veterans Hospital; Madison, WI USA
| | - Joshua C Neuman
- Interdisciplinary Graduate Program in Nutritional Sciences; University of Wisconsin-Madison; Madison, WI USA
- William S Middleton Memorial Veterans Hospital; Madison, WI USA
| | - Michelle E Kimple
- Department of Medicine; Division of Endocrinology, Diabetes & Metabolism; University of Wisconsin-Madison; Madison, WI USA
- Interdisciplinary Graduate Program in Nutritional Sciences; University of Wisconsin-Madison; Madison, WI USA
- William S Middleton Memorial Veterans Hospital; Madison, WI USA
- Correspondence to: Michelle E Kimple;
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102
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Pepin E, Higa A, Schuster-Klein C, Bernard C, Sulpice T, Guardiola B, Chevet E, Alquier T. Deletion of apoptosis signal-regulating kinase 1 (ASK1) protects pancreatic beta-cells from stress-induced death but not from glucose homeostasis alterations under pro-inflammatory conditions. PLoS One 2014; 9:e112714. [PMID: 25383781 PMCID: PMC4226582 DOI: 10.1371/journal.pone.0112714] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Accepted: 10/14/2014] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Type 2 diabetes is characterized by pancreatic beta-cell dysfunction and is associated with low-grade inflammation. Recent observations suggest that apoptosis signal-regulating kinase 1 (ASK1) is involved in beta-cell death in response to different stressors. In this study, we tested whether ASK1 deficiency protects beta-cells from glucolipotoxic conditions and cytokines treatment or from glucose homeostasis alteration induced by endotoxemia. METHODOLOGY/PRINCIPAL FINDINGS Insulin secretion was neither affected upon shRNA-mediated downregulation of ASK1 in MIN6 cells nor in islets from ASK1-deficient mice. ASK1 silencing in MIN6 cells and deletion in islets did not prevent the deleterious effect of glucolipotoxic conditions or cytokines on insulin secretion. However, it protected MIN6 cells from death induced by ER stress or palmitate and islets from short term caspase activation in response to cytokines. Moreover, endotoxemia induced by LPS infusion increased insulin secretion during hyperglycemic clamps but the response was similar in wild-type and ASK1-deficient mice. Finally, insulin sensitivity in the presence of LPS was not affected by ASK1-deficiency. CONCLUSIONS/SIGNIFICANCE Our study demonstrates that ASK1 is not involved in beta-cell function and dysfunction but controls stress-induced beta-cell death.
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Affiliation(s)
| | - Arisa Higa
- Inserm U1053, Team Endoplasmic Reticulum Stress and Cancer, Université de Bordeaux, Bordeaux, France, 33076
| | | | | | - Thierry Sulpice
- Betagenex Inc, Laval, QC, Canada, H7V5B7
- Physiogenex SAS, Labège, France, 31670
| | | | - Eric Chevet
- Inserm U1053, Team Endoplasmic Reticulum Stress and Cancer, Université de Bordeaux, Bordeaux, France, 33076
| | - Thierry Alquier
- Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l’Université de Montréal (CRCHUM), and Departments of Medicine, Biochemistry and Cell Biology and Pathology, Université de Montréal, Montréal, QC, Canada, H3T 1J4
- * E-mail:
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103
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Hatanaka M, Maier B, Sims EK, Templin AT, Kulkarni RN, Evans-Molina C, Mirmira RG. Palmitate induces mRNA translation and increases ER protein load in islet β-cells via activation of the mammalian target of rapamycin pathway. Diabetes 2014; 63:3404-15. [PMID: 24834975 PMCID: PMC4171659 DOI: 10.2337/db14-0105] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Saturated free fatty acids (FFAs) have complex effects on the islet β-cell, acutely promoting adaptive hyperplasia but chronically impairing insulin release. The acute effects of FFAs remain incompletely defined. To elucidate these early molecular events, we incubated mouse β-cells and islets with palmitate and then studied mRNA translation by polyribosomal profiling and analyzed signaling pathways by immunoblot analysis. We found that palmitate acutely increases polyribosome occupancy of total RNA, consistent with an increase in mRNA translation. This effect on translation was attributable to activation of mammalian target of rapamycin (mTOR) pathways via L-type Ca(2+) channels but was independent of insulin signaling. Longer incubations led to depletion of polyribosome-associated RNA, consistent with activation of the unfolded protein response (UPR). Pharmacologic inhibition of mTOR suppressed both the acute effects of palmitate on mRNA translation and the chronic effects on the UPR. Islets from mice fed a high-fat diet for 7 days showed increases in polyribosome-associated RNA and phosphorylation of S6K, both consistent with activation of mTOR. Our results suggest that palmitate acutely activates mRNA translation and that this increase in protein load contributes to the later UPR.
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Affiliation(s)
- Masayuki Hatanaka
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN
| | - Bernhard Maier
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN
| | - Emily K Sims
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN
| | - Andrew T Templin
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN
| | - Rohit N Kulkarni
- Section on Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Harvard Medical School, Boston, MA
| | - Carmella Evans-Molina
- Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN Department of Medicine, Indiana University School of Medicine, Indianapolis, IN Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN
| | - Raghavendra G Mirmira
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN Department of Medicine, Indiana University School of Medicine, Indianapolis, IN Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN
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104
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Role of free fatty acid receptors in the regulation of energy metabolism. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1841:1292-300. [DOI: 10.1016/j.bbalip.2014.06.002] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Revised: 05/26/2014] [Accepted: 06/02/2014] [Indexed: 12/25/2022]
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105
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Dranse HJ, Kelly MEM, Hudson BD. Drugs or diet?--Developing novel therapeutic strategies targeting the free fatty acid family of GPCRs. Br J Pharmacol 2014; 170:696-711. [PMID: 23937426 DOI: 10.1111/bph.12327] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2013] [Revised: 07/17/2013] [Accepted: 07/29/2013] [Indexed: 02/07/2023] Open
Abstract
Free fatty acids (FFAs) are metabolic intermediates that may be obtained through the diet, synthesized endogenously, or produced via fermentation of carbohydrates by gut microbiota. In addition to serving as an important source of energy, FFAs are known to produce a variety of both beneficial and detrimental effects on metabolic and inflammatory processes. While historically, FFAs were believed to produce these effects only through intracellular targets such as peroxisome proliferator-activated receptors, it has now become clear that FFAs are also agonists for several GPCRs, including a family of four receptors now termed FFA1-4. Increasing evidence suggests that FFA1-4 mediate many of the beneficial properties of FFAs and not surprisingly, this has generated significant interest in the potential of these receptors as therapeutic targets for the treatment of a variety of metabolic and inflammatory disorders. In addition to the traditional strategy of developing small-molecule therapeutics targeting these receptors, there has also been some consideration given to alternate therapeutic approaches, specifically by manipulating endogenous FFA concentrations through alteration of either dietary intake, or production by gut microbiota. In this review, the current state of knowledge for FFA1-4 will be discussed, together with their potential as therapeutic targets in the treatment of metabolic and inflammatory disorders. In particular, the evidence in support of small molecule versus dietary and microbiota-based therapeutic approaches will be considered to provide insight into the development of novel multifaceted strategies targeting the FFA receptors for the treatment of metabolic and inflammatory disorders.
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Affiliation(s)
- H J Dranse
- Department of Pharmacology, Dalhousie University, Halifax, NS, Canada
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106
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Abstract
Free fatty acids (FFAs) exert both positive and negative effects on beta cell survival and insulin secretory function, depending on concentration, duration, and glucose abundance. Lipid signals are mediated not only through metabolic pathways, but also through cell surface and nuclear receptors. Toxicity is modulated by positive signals arising from circulating factors such as hormones, growth factors and incretins, as well as negative signals such as inflammatory mediators and cytokines. Intracellular mechanisms of lipotoxicity include metabolic interference and cellular stress responses such as oxidative stress, endoplasmic reticulum (ER) stress, and possibly autophagy. New findings strengthen an old hypothesis that lipids may also impair compensatory beta cell proliferation. Clinical observations continue to support a role for lipid biology in the risk and progression of both type 1 (T1D) and type 2 diabetes (T2D). This review summarizes recent work in this important, rapidly evolving field.
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Affiliation(s)
- Rohit B Sharma
- Diabetes Center of Excellence, University of Massachusetts Medical School, 368 Plantation Street, Worcester, MA, 01605, USA
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107
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Defossa E, Wagner M. Recent developments in the discovery of FFA1 receptor agonists as novel oral treatment for type 2 diabetes mellitus. Bioorg Med Chem Lett 2014; 24:2991-3000. [PMID: 24881568 DOI: 10.1016/j.bmcl.2014.05.019] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Revised: 04/30/2014] [Accepted: 05/05/2014] [Indexed: 12/12/2022]
Abstract
Despite the availability of established medication for treatment of type 2 diabetes mellitus (T2DM) there still remains a significant unmet need for new effective, oral antidiabetic agents that improve glycemic control while maintaining an excellent safety profile. In this regard the FFA1 receptor has emerged as an attractive target in recent years. Activation of the FFA1 receptor has been shown to not only amplify glucose induced insulin secretion from pancreatic beta cells but also to stimulate incretin secretion from intestinal endocrine cells. The current review highlights on the latest developments and clinical data from evolving research on the potential of FFA1 agonists as effective treatment for T2DM.
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Affiliation(s)
- Elisabeth Defossa
- Lead Generation to Candidate Realization, Sanofi Deutschland GmbH, Industriepark Hoechst, 65926 Frankfurt, Germany.
| | - Michael Wagner
- Diabetes Division, Sanofi Deutschland GmbH, Industriepark Hoechst, 65926 Frankfurt, Germany.
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108
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Oie S, Matsuzaki K, Yokoyama W, Tokunaga S, Waku T, Han SI, Iwasaki N, Mikogai A, Yasuzawa-Tanaka K, Kishimoto H, Hiyoshi H, Nakajima Y, Araki T, Kimura K, Yanagisawa J, Murayama A. Hepatic rRNA transcription regulates high-fat-diet-induced obesity. Cell Rep 2014; 7:807-20. [PMID: 24746822 DOI: 10.1016/j.celrep.2014.03.038] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 01/14/2014] [Accepted: 03/12/2014] [Indexed: 10/25/2022] Open
Abstract
Ribosome biosynthesis is a major intracellular energy-consuming process. We previously identified a nucleolar factor, nucleomethylin (NML), which regulates intracellular energy consumption by limiting rRNA transcription. Here, we show that, in livers of obese mice, the recruitment of NML to rRNA gene loci is increased to repress rRNA transcription. To clarify the relationship between obesity and rRNA transcription, we generated NML-null (NML-KO) mice. NML-KO mice show elevated rRNA level, reduced ATP concentration, and reduced lipid accumulation in the liver. Furthermore, in high-fat-diet (HFD)-fed NML-KO mice, hepatic rRNA levels are not decreased. Both weight gain and fat accumulation in HFD-fed NML-KO mice are significantly lower than those in HFD-fed wild-type mice. These findings indicate that rRNA transcriptional activation promotes hepatic energy consumption, which alters hepatic lipid metabolism. Namely, hepatic rRNA transcriptional repression by HFD feeding is essential for energy storage.
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Affiliation(s)
- Shohei Oie
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan; Center for Tsukuba Advanced Research Alliance, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan
| | - Kazuya Matsuzaki
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan; Center for Tsukuba Advanced Research Alliance, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan
| | - Wataru Yokoyama
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan; Center for Tsukuba Advanced Research Alliance, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan
| | - Shinji Tokunaga
- Department of Peripheral Nervous System Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawa-higashi, Kodaira, Tokyo 187-8502, Japan
| | - Tsuyoshi Waku
- Graduate School of Pharmaceutical Sciences, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Song-Iee Han
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan; Center for Tsukuba Advanced Research Alliance, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan
| | - Naoya Iwasaki
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan; Center for Tsukuba Advanced Research Alliance, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan
| | - Aya Mikogai
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan; Center for Tsukuba Advanced Research Alliance, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan
| | - Kayoko Yasuzawa-Tanaka
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan; Center for Tsukuba Advanced Research Alliance, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan
| | - Hiroyuki Kishimoto
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan; Center for Tsukuba Advanced Research Alliance, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan
| | - Hiromi Hiyoshi
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan; Center for Tsukuba Advanced Research Alliance, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan
| | - Yuka Nakajima
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan; Center for Tsukuba Advanced Research Alliance, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan
| | - Toshiyuki Araki
- Department of Peripheral Nervous System Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawa-higashi, Kodaira, Tokyo 187-8502, Japan; Department of Electrical Engineering and Bioscience, Graduate School of Advanced Science and Engineering, Waseda University, 1-104 Totsukamachi, Shinjuku-ku, Tokyo 169-8050, Japan
| | - Keiji Kimura
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan
| | - Junn Yanagisawa
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan; Center for Tsukuba Advanced Research Alliance, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan
| | - Akiko Murayama
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan; Center for Tsukuba Advanced Research Alliance, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8577, Japan.
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109
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El-Azzouny M, Evans CR, Treutelaar MK, Kennedy RT, Burant CF. Increased glucose metabolism and glycerolipid formation by fatty acids and GPR40 receptor signaling underlies the fatty acid potentiation of insulin secretion. J Biol Chem 2014; 289:13575-88. [PMID: 24675078 DOI: 10.1074/jbc.m113.531970] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Acute fatty acid (FA) exposure potentiates glucose-stimulated insulin secretion in β cells through metabolic and receptor-mediated effects. We assessed the effect of fatty acids on the dynamics of the metabolome in INS-1 cells following exposure to [U-(13)C]glucose to assess flux through metabolic pathways. Metabolite profiling showed a fatty acid-induced increase in long chain acyl-CoAs that were rapidly esterified with glucose-derived glycerol-3-phosphate to form lysophosphatidic acid, mono- and diacylglycerols, and other glycerolipids, some implicated in augmenting insulin secretion. Glucose utilization and glycolytic flux increased, along with a reduction in the NADH/NAD(+) ratio, presumably by an increase in conversion of dihydroxyacetone phosphate to glycerol-3-phosphate. The fatty acid-induced increase in glycolysis also resulted in increases in tricarboxylic cycle flux and oxygen consumption. Inhibition of fatty acid activation of FFAR1/GPR40 by an antagonist decreased glycerolipid formation, attenuated fatty acid increases in glucose oxidation, and increased mitochondrial FA flux, as evidenced by increased acylcarnitine levels. Conversely, FFAR1/GPR40 activation in the presence of low FA increased flux into glycerolipids and enhanced glucose oxidation. These results suggest that, by remodeling glucose and lipid metabolism, fatty acid significantly increases the formation of both lipid- and TCA cycle-derived intermediates that augment insulin secretion, increasing our understanding of mechanisms underlying β cell insulin secretion.
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110
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Riz M, Pedersen MG, Toffolo GM, Haschke G, Schneider HC, Klabunde T, Margerie D, Cobelli C. Minimal modeling of insulin secretion in the perfused rat pancreas: a drug effect case study. Am J Physiol Endocrinol Metab 2014; 306:E627-34. [PMID: 24425760 DOI: 10.1152/ajpendo.00603.2013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The experimental protocol of the perfused rat pancreas is commonly used to evaluate β-cell function. In this context, mathematical models become useful tools through the determination of indexes that allow the assessment of β-cell function in different experimental groups and the quantification of the effects of antidiabetic drugs, secretagogues, or treatments. However, a minimal model applicable to the isolated perfused rat pancreas has so far been unavailable. In this work, we adapt the C-peptide minimal model applied previously to the intravenous glucose tolerance test to obtain a specific model for the experimental settings of the perfused pancreas. Using the model, it is possible to estimate indexes describing β-cell responsivity for first (ΦD) and second phase (ΦS, T) of insulin secretion. The model was initially applied to untreated pancreata and afterward used for the assessment of pharmacologically relevant agents (the gut hormone GLP-1, the potent GLP-1 receptor agonist lixisenatide, and a GPR40/FFAR1 agonist, SAR1) to quantify and differentiate their effect on insulin secretion. Model fit was satisfactory, and parameters were estimated with good precision for both untreated and treated pancreata. Model application showed that lixisenatide reaches improvement of β-cell function similarly to GLP-1 (11.7- vs. 13.1-fold increase in ΦD and 2.3- vs. 2.8-fold increase in ΦS) and demonstrated that SAR1 leads to an additional improvement of β-cell function in the presence of postprandial GLP-1 levels.
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Affiliation(s)
- Michela Riz
- Department of Information Engineering, University of Padua, Paduaa, Italy; and
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111
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Wagner R, Staiger H, Ullrich S, Stefan N, Fritsche A, Häring HU. Untangling the interplay of genetic and metabolic influences on beta-cell function: Examples of potential therapeutic implications involving TCF7L2 and FFAR1. Mol Metab 2014; 3:261-7. [PMID: 24749055 PMCID: PMC3986492 DOI: 10.1016/j.molmet.2014.01.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 01/07/2014] [Accepted: 01/07/2014] [Indexed: 12/24/2022] Open
Abstract
Deteriorating beta-cell function is a common feature of type 2 diabetes. In this review, we briefly address the regulation of beta-cell function, and discuss some of the main determinants of beta-cell failure. We will focus on the role of interactions between the genetic background and metabolic environment (insulin resistance, fuel supply and flux as well as metabolic signaling). We present data on the function of the strongest common diabetes risk variant, the single nucleotide polymorphism (SNP) rs7903146 in TCF7L2. As also mirrored by its interaction with glycemia on insulin secretion, this SNP in large part confers resistance against the incretin effect. Genetic influence on insulin secretion also interacts with free fatty acids, as evidenced by data on rs1573611 in FFAR1. Several medications marketed by now or currently under development for diabetes treatment engage these pathways, and therapeutic implications from these findings are soon to be expected.
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Affiliation(s)
- Robert Wagner
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Nephrology, Vascular Disease and Clinical Chemistry, University Hospital of the Eberhard Karls University, Tübingen, Germany ; German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Harald Staiger
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Nephrology, Vascular Disease and Clinical Chemistry, University Hospital of the Eberhard Karls University, Tübingen, Germany ; Institute for Diabetes Research and Metabolic Diseases of the Helmholz Centre Munich at the University of Tübingen (IDM), Tübingen, Germany ; German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Susanne Ullrich
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Nephrology, Vascular Disease and Clinical Chemistry, University Hospital of the Eberhard Karls University, Tübingen, Germany ; Institute for Diabetes Research and Metabolic Diseases of the Helmholz Centre Munich at the University of Tübingen (IDM), Tübingen, Germany ; German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Norbert Stefan
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Nephrology, Vascular Disease and Clinical Chemistry, University Hospital of the Eberhard Karls University, Tübingen, Germany ; Institute for Diabetes Research and Metabolic Diseases of the Helmholz Centre Munich at the University of Tübingen (IDM), Tübingen, Germany ; German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Andreas Fritsche
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Nephrology, Vascular Disease and Clinical Chemistry, University Hospital of the Eberhard Karls University, Tübingen, Germany ; Institute for Diabetes Research and Metabolic Diseases of the Helmholz Centre Munich at the University of Tübingen (IDM), Tübingen, Germany ; German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Hans-Ulrich Häring
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Nephrology, Vascular Disease and Clinical Chemistry, University Hospital of the Eberhard Karls University, Tübingen, Germany ; Institute for Diabetes Research and Metabolic Diseases of the Helmholz Centre Munich at the University of Tübingen (IDM), Tübingen, Germany ; German Center for Diabetes Research (DZD), Neuherberg, Germany
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112
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Hara T, Ichimura A, Hirasawa A. Therapeutic role and ligands of medium- to long-chain Fatty Acid receptors. Front Endocrinol (Lausanne) 2014; 5:83. [PMID: 24917851 PMCID: PMC4040920 DOI: 10.3389/fendo.2014.00083] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Accepted: 05/18/2014] [Indexed: 01/22/2023] Open
Abstract
Medium- and long-chain free fatty acids (FFAs) are energy source for whole body and biological metabolites and components. In these decades, some research groups have reported that the biological functions of medium- to long-chain FFAs are exerted through G-protein coupled receptor designated free fatty acid receptor (FFAR). As the medium- to long-chain FFAs-activated FFARs, FFA1 and FFA4 are reported to be expressed widely in whole body and regulate various physiological processes. FFA1 expressed in pancreatic β-cells has been shown to be involved in insulin secretion. FFA4 expressed in intestine, adipocytes, and macrophages has been shown to be involved in incretin secretion, differentiation, and anti-inflammatory effect, respectively. These physiological functions have been focused on the treatment of metabolic disorders. In addition, these receptors have been also reported to be expressed in several other tissues such as intestine for FFA1, and tongue and stomach for FFA4. The recent functional studies indicated that they also contributed to energy homeostasis. Further, the number of synthetic compounds of FFA1 and FFA4 strongly promoted the physiological characterization of the receptors and their own therapeutic utility. In this article, we will discuss the recent progress regarding the therapeutic potential of these receptors and its ligands.
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Affiliation(s)
- Takafumi Hara
- Department of Pharmacogenomics, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
- *Correspondence: Takafumi Hara, Department of Pharmacogenomics, Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida-Shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan e-mail:
| | - Atsuhiko Ichimura
- Department of Molecular Medicine and Therapy, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Akira Hirasawa
- Department of Pharmacogenomics, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
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Watterson KR, Hudson BD, Ulven T, Milligan G. Treatment of type 2 diabetes by free Fatty Acid receptor agonists. Front Endocrinol (Lausanne) 2014; 5:137. [PMID: 25221541 PMCID: PMC4147718 DOI: 10.3389/fendo.2014.00137] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 08/07/2014] [Indexed: 12/11/2022] Open
Abstract
Dietary free fatty acids (FFAs), such as ω-3 fatty acids, regulate metabolic and anti-inflammatory processes, with many of these effects attributed to FFAs interacting with a family of G protein-coupled receptors. Selective synthetic ligands for free fatty acid receptors (FFA1-4) have consequently been developed as potential treatments for type 2 diabetes (T2D). In particular, clinical studies show that Fasiglifam, an agonist of the long-chain FFA receptor, FFA1, improved glycemic control and reduced HbA1c levels in T2D patients, with a reduced risk of hypoglycemia. However, this ligand was removed from clinical trials due to potential liver toxicity and determining if this is a target or a ligand-specific feature is now of major importance. Pre-clinical studies also show that FFA4 agonism increases insulin sensitivity, induces weight loss, and reduces inflammation and the metabolic and anti-inflammatory effects of short chain fatty acids (SCFAs) are linked with FFA2 and FFA3 activation. In this review, we therefore show that FFA receptor agonism is a potential clinical target for T2D treatment and discuss ongoing drug development programs within industry and academia aimed at improving the safety and effectiveness of these potential treatments.
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Affiliation(s)
- Kenneth R. Watterson
- Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Brian D. Hudson
- Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Trond Ulven
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense, Denmark
| | - Graeme Milligan
- Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
- *Correspondence: Graeme Milligan, Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, UK e-mail:
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114
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Huang H, Dai MH, Tao YX. Physiology and Therapeutics of the Free Fatty Acid Receptor GPR40. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 121:67-94. [DOI: 10.1016/b978-0-12-800101-1.00003-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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115
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Zhao Y, Zha D, Wang L, Qiao L, Lu L, Mei L, Chen C, Qiu J. Phenotypic characterization of GPR120-expressing cells in the interstitial tissue of pancreas. Tissue Cell 2013; 45:421-7. [DOI: 10.1016/j.tice.2013.07.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Revised: 07/18/2013] [Accepted: 07/18/2013] [Indexed: 01/27/2023]
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116
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Kaku K. Fasiglifam as a new potential treatment option for patients with type 2 diabetes. Expert Opin Pharmacother 2013; 14:2591-600. [DOI: 10.1517/14656566.2013.851668] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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117
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Kristinsson H, Smith DM, Bergsten P, Sargsyan E. FFAR1 is involved in both the acute and chronic effects of palmitate on insulin secretion. Endocrinology 2013; 154:4078-88. [PMID: 24035997 DOI: 10.1210/en.2013-1352] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Free fatty acids (FFAs) have pleiotropic effects on the pancreatic β-cell. Although acute exposure to FFAs stimulates glucose-stimulated insulin secretion (GSIS), prolonged exposure impairs GSIS and causes apoptosis. FFAs exert their effects both via intracellular metabolism and interaction with the FFA receptor 1 (FFAR1/GPR40). Here we studied the role of FFAR1 in acute and long-term effects of palmitate on GSIS and insulin content in isolated human islets by using the FFAR1 agonist TAK-875 and the antagonist ANT203. Acute palmitate exposure potentiated GSIS approximately 3-fold, whereas addition of the antagonist decreased this potentiation to approximately 2-fold. In the absence of palmitate, the agonist caused a 40% increase in GSIS. Treatment with palmitate for 7 days decreased GSIS to 70% and insulin content to 25% of control level. These negative effects of long-term exposure to palmitate were ameliorated by FFAR1 inhibition and further aggravated by additional stimulation of the receptor. In the absence of extracellularly applied palmitate, long-term treatment with the agonist caused a modest increase in GSIS. The protective effect of FFAR1 inhibition was verified by using FFAR1-deficient MIN6 cells. Improved β-cell function by the antagonist was paralleled by the decreased apoptosis and lowered oxidation of palmitate, which may represent the potential mechanisms of protection. We conclude that FFAR1 in the pancreatic β-cell plays a substantial role not only in acute potentiation of GSIS by palmitate but also in the negative long-term effects of palmitate on GSIS and insulin content.
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Affiliation(s)
- Hjalti Kristinsson
- PhD, Department of Medical Cell Biology, Uppsala University, Box 571, SE-751 23 Uppsala, Sweden.
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118
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Modulating GPR40: therapeutic promise and potential in diabetes. Drug Discov Today 2013; 18:1301-8. [PMID: 24051395 DOI: 10.1016/j.drudis.2013.09.003] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 08/22/2013] [Accepted: 09/09/2013] [Indexed: 12/16/2022]
Abstract
The class A G-protein-coupled receptor GPR40 is predominantly expressed in pancreatic beta cells and plays a major part in fatty acid amplification of glucose-induced insulin secretion. GPR40 agonists are being developed for the treatment of type 2 diabetes. Preclinical studies have shown that GPR40 activation improves glucose control, and recent Phase II trials provided proof-of-concept for this approach. The pharmacology of GPR40 is only partially understood but recent findings suggest that full agonism of the receptor could, in addition to stimulating insulin release, engage the enteroinsular axis. Much remains to be discovered regarding the biology of the receptor to inform the development of GPR40-based drugs.
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119
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Mancini AD, Poitout V. Les récepteurs membranaires des acides gras de la cellule β. Med Sci (Paris) 2013; 29:715-21. [DOI: 10.1051/medsci/2013298009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
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120
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Signaling mechanisms of glucose-induced F-actin remodeling in pancreatic islet β cells. Exp Mol Med 2013; 45:e37. [PMID: 23969997 PMCID: PMC3789261 DOI: 10.1038/emm.2013.73] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Accepted: 06/24/2013] [Indexed: 12/12/2022] Open
Abstract
The maintenance of whole-body glucose homeostasis is critical for survival, and is controlled by the coordination of multiple organs and endocrine systems. Pancreatic islet β cells secrete insulin in response to nutrient stimuli, and insulin then travels through the circulation promoting glucose uptake into insulin-responsive tissues such as liver, skeletal muscle and adipose. Many of the genes identified in human genome-wide association studies of diabetic individuals are directly associated with β cell survival and function, giving credence to the idea that β-cell dysfunction is central to the development of type 2 diabetes. As such, investigations into the mechanisms by which β cells sense glucose and secrete insulin in a regulated manner are a major focus of current diabetes research. In particular, recent discoveries of the detailed role and requirements for reorganization/remodeling of filamentous actin (F-actin) in the regulation of insulin release from the β cell have appeared at the forefront of islet function research, having lapsed in prior years due to technical limitations. Recent advances in live-cell imaging and specialized reagents have revealed localized F-actin remodeling to be a requisite for the normal biphasic pattern of nutrient-stimulated insulin secretion. This review will provide an historical look at the emergent focus on the role of the actin cytoskeleton and its regulation of insulin secretion, leading up to the cutting-edge research in progress in the field today.
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121
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Abstract
The pancreatic islet β cell senses circulating levels of calorigenic nutrients to secrete insulin according to the needs of the organism. Altered insulin secretion is linked to various disorders such as diabetes, hypoglycemic states, and cardiometabolic diseases. Fuel stimuli, including glucose, free fatty acids, and amino acids, promote insulin granule exocytosis primarily via their metabolism in β cells and the production of key signaling metabolites. This paper reviews our current knowledge of the pathways involved in both positive and negative metabolic signaling for insulin secretion and assesses the role of established and candidate metabolic coupling factors, keeping recent developments in focus.
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Affiliation(s)
- Marc Prentki
- Molecular Nutrition Unit, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, QC, Canada.
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122
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Abstract
The stimulation of insulin secretion by glucose can be modulated by multiple nutritive, hormonal, and pharmacological inputs. Fatty acids potentiate insulin secretion through the generation of intracellular signaling molecules and through the activation of cell surface receptors. The G-protein-coupled receptor 40 (GPR40), also known as free fatty acid receptor 1 (we will use GPR40 in this review), has emerged as an important component in the fatty acid augmentation of insulin secretion. By signaling predominantly through Gαq/11, GPR40 increases intracellular calcium and activates phospholipases to generate diacylglycerols resulting in increased insulin secretion. Synthetic small-molecule agonists of GPR40 enhance insulin secretion in a glucose-dependent manner in vitro and in vivo with a mechanism similar to that found with fatty acids. GPR40 agonists have shown efficacy in increasing insulin secretion and lowering blood glucose in rodent models of type 2 diabetes. Recent phase I and phase II clinical trials in humans have shown that the GPR40 agonist TAK-875 reduces fasting and postprandial blood glucose and lowers HbA1c with efficacy equal to that of the sulfonylurea glimepiride without inducing hypoglycemia or evidence of tachyphylaxis. These data suggest that targeting the GPR40 receptor can be a viable therapeutic option for the treatment of type 2 diabetes.
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Affiliation(s)
- Charles F Burant
- Department of Internal Medicine and Michigan Metabolomics and Obesity Center, University of Michigan, Ann Arbor, Michigan, USA.
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123
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Song WJ, Mondal P, Li Y, Lee SE, Hussain MA. Pancreatic β-cell response to increased metabolic demand and to pharmacologic secretagogues requires EPAC2A. Diabetes 2013; 62:2796-807. [PMID: 23578994 PMCID: PMC3717830 DOI: 10.2337/db12-1394] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Incretin hormone action on β-cells stimulates in parallel two different intracellular cyclic AMP-dependent signaling branches mediated by protein kinase A and exchange protein activated by cAMP islet/brain isoform 2A (EPAC2A). Both pathways contribute toward potentiation of glucose-stimulated insulin secretion (GSIS). However, the overall functional role of EPAC2A in β-cells as it relates to in vivo glucose homeostasis remains incompletely understood. Therefore, we have examined in vivo GSIS in global EPAC2A knockout mice. Additionally, we have conducted in vitro studies of GSIS and calcium dynamics in isolated EPAC2A-deficient islets. EPAC2A deficiency does not impact GSIS in mice under basal conditions. However, when mice are exposed to diet-induced insulin resistance, pharmacologic secretagogue stimulation of β-cells with an incretin hormone glucagon-like peptide-1 analog or with a fatty acid receptor 1/G protein-coupled receptor 40 selective activator, EPAC2A is required for the increased β-cell response to secretory demand. Under these circumstances, EPAC2A is required for potentiating the early dynamic increase in islet calcium levels after glucose stimulation, which is reflected in potentiated first-phase insulin secretion. These studies broaden our understanding of EPAC2A function and highlight its significance during increased secretory demand or drive on β-cells. Our findings advance the rationale for developing EPAC2A-selective pharmacologic activators for β-cell-targeted pharmacotherapy in type 2 diabetes.
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Affiliation(s)
- Woo-Jin Song
- Department of Pediatrics, Johns Hopkins University, Baltimore, Maryland
| | - Prosenjit Mondal
- Department of Pediatrics, Johns Hopkins University, Baltimore, Maryland
| | - Yuanyuan Li
- Department of Pediatrics, Johns Hopkins University, Baltimore, Maryland
| | - Suh Eun Lee
- Department of Pediatrics, Johns Hopkins University, Baltimore, Maryland
| | - Mehboob A. Hussain
- Department of Pediatrics, Johns Hopkins University, Baltimore, Maryland
- Department of Medicine, Johns Hopkins University, Baltimore, Maryland
- Department of Biological Chemistry, Johns Hopkins University, Baltimore, Maryland
- Corresponding author: Mehboob A. Hussain,
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124
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Mancini AD, Poitout V. The fatty acid receptor FFA1/GPR40 a decade later: how much do we know? Trends Endocrinol Metab 2013; 24:398-407. [PMID: 23631851 DOI: 10.1016/j.tem.2013.03.003] [Citation(s) in RCA: 122] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Revised: 03/18/2013] [Accepted: 03/21/2013] [Indexed: 11/18/2022]
Abstract
Glucose homeostasis requires the highly coordinated regulation of insulin secretion by pancreatic β cells. This is primarily mediated by glucose itself, but other nutrients, including free fatty acids (FFAs), potentiate the insulinotropic capacity of glucose. A decade ago, the seven-transmembrane domain receptor (7TMR) GPR40 was demonstrated to be predominantly expressed in β cells and activated by long-chain FFAs. This discovery added a new dimension to our understanding of FFA-mediated control of glucose homeostasis. Furthermore, GPR40 has drawn considerable interest as a novel therapeutic target to enhance insulin secretion in type 2 diabetes. However, our understanding of the biology of GPR40 remains incomplete and its physiological role controversial. Here we summarize the current state of knowledge and emerging concepts regarding the role of GPR40 in regulating glucose homeostasis.
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Affiliation(s)
- Arturo D Mancini
- Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Department of Medicine, Université de Montréal, Montréal, QC, Canada
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125
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Graciano MF, Valle MM, Curi R, Carpinelli AR. Evidence for the involvement of GPR40 and NADPH oxidase in palmitic acid-induced superoxide production and insulin secretion. Islets 2013; 5:139-48. [PMID: 23817296 DOI: 10.4161/isl.25459] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
G protein coupled receptor 40 (GPR40) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex have been shown to be involved in the fatty acid amplification of glucose-stimulated insulin secretion (GSIS). The effect of palmitic acid on superoxide production and insulin secretion by INS-1E cells and the possible involvement of GPR40 and NADPH oxidase in these processes were examined in this study. Cells were incubated during 1 h with palmitic acid in low and high glucose concentrations, a GPR40 agonist (GW9508) and inhibitors of NADPH oxidase (diphenyleneiodonium, DPI) and PKC (calphostin C). GW9508 induced superoxide production at 2.8 and 5.6 mM glucose concentrations and stimulated insulin secretion at 16.7 mM glucose concentration involving both PKC and NADPH oxidase activation. Palmitic acid induced superoxide production through NADPH oxidase and GPR40-dependent pathways and the stimulation of insulin secretion in the presence of a high glucose concentration was reduced by knockdown of GPR40 using siRNA. Our results suggest that palmitic acid induces superoxide production and potentiates GSIS through NADPH oxidase and GPR40 pathways in pancreatic ? cells.
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Affiliation(s)
- Maria Fernanda Graciano
- Department of Physiology and Biophysics; Institute of Biomedical Sciences; University of São Paulo (USP); São Paulo, SP Brazil
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126
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Abstract
Secretory granule biogenesis is a pivotal process for regulated release of hormones and neurotransmitters. A prominent example is the pancreatic β cell that secretes insulin, a major anabolic hormone controlling cellular metabolism upon nutrient availability. We recently described a checkpoint mechanism that halts scission of nascent secretory granules at the trans-Golgi network (TGN) until complete loading of insulin is achieved. We demonstrated that the Bin/Amphiphysin/Rvs (BAR) domain-containing protein Arfaptin-1 prevents granule scission until it is phosphorylated by Protein Kinase D (PKD). Arfaptin-1 phosphorylation releases its binding to ADP-rybosylation factor (ARF) allowing scission to occur. Lack of this control mechanism in β cells resulted in premature scission, generation of dysfunctional insulin granules and impaired regulated insulin secretion without affecting constitutive release of other transport carriers. Here we discuss two important questions related to this work: How might completion of granule loading be sensed by PKD, and how does Arfaptin-1 specifically regulate insulin granule formation in beta cells?
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Affiliation(s)
- Helmuth Gehart
- IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire); INSERM; CNRS; Université de Strasbourg; Illkirch, France ; Institute of Cell Biology; ETH Zurich; Zurich, Switzerland
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127
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Komatsu M, Takei M, Ishii H, Sato Y. Glucose-stimulated insulin secretion: A newer perspective. J Diabetes Investig 2013; 4:511-6. [PMID: 24843702 PMCID: PMC4020243 DOI: 10.1111/jdi.12094] [Citation(s) in RCA: 154] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Accepted: 03/12/2013] [Indexed: 01/23/2023] Open
Abstract
Existing concepts and models for glucose-stimulated insulin secretion (GSIS) are overviewed and a newer perspective has been formulated toward the physiological understanding of GSIS. A conventional model has been created on the basis of in vitro data on application of a square wave high glucose in the absence of any other stimulatory inputs. Glucose elicits rapid insulin release through an adenosine triphosphate-sensitive K(+) channel (KATP channel)-dependent mechanism, which is gradually augmented in a KATP channel-independent manner. Biphasic GSIS thus occurs. In the body, the β-cells are constantly exposed to stimulatory signals, such as glucagon-like peptide 1 (GLP-1), parasympathetic inputs, free fatty acid (FFA), amino acids and slightly suprathreshold levels of glucose, even at fasting. GLP-1 increases cellular cyclic adenosine monophosphate, parasympathetic stimulation activates protein kinase C, and FFA, amino acids and glucose generate metabolic amplification factors. Plasma glucose concentration gradually rises postprandially under such tonic stimulation. We hypothesize that these stimulatory inputs together make the β-cells responsive to glucose independently from its action on KATP channels. Robust GSIS in patients with a loss of function mutation of the sulfonylurea receptor, a subunit of KATP channels, is compatible with this hypothesis. Furthermore, pre-exposure of the islets to an activator of protein kinase A and/or C makes β-cells responsive to glucose in a KATP channel- and Ca(2+)-independent manner. We hypothesize that GSIS occurs in islet β-cells without glucose regulation of KATP channels in vivo, for which priming with cyclic adenosine monophosphate, protein kinase C and non-glucose nutrients are required. To understand the physiology of GSIS, comprehensive integration of accumulated knowledge is required.
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Affiliation(s)
- Mitsuhisa Komatsu
- Department of Internal Medicine Division of Diabetes, Endocrinology and Metabolism Shinshu University School of Medicine Matsumoto Nagano Japan
| | - Masahiro Takei
- Department of Internal Medicine Division of Diabetes, Endocrinology and Metabolism Shinshu University School of Medicine Matsumoto Nagano Japan
| | - Hiroaki Ishii
- Department of Internal Medicine Division of Diabetes, Endocrinology and Metabolism Shinshu University School of Medicine Matsumoto Nagano Japan
| | - Yoshihiko Sato
- Department of Internal Medicine Division of Diabetes, Endocrinology and Metabolism Shinshu University School of Medicine Matsumoto Nagano Japan
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128
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Mineo H, Ogita A, Kanayama N, Kawagishi M, Sato E, Yamamoto N, Arai K, Izawa MA. Effect of the chemical specificity of benzoic acid and its analogs on osmotic fragility in erythrocytes of Sprague-Dawley rats in vitro. Eur J Pharmacol 2013; 702:142-8. [PMID: 23376564 DOI: 10.1016/j.ejphar.2013.01.029] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 01/10/2013] [Accepted: 01/16/2013] [Indexed: 01/14/2023]
Abstract
We examined the chemical specificity of benzoic (benzene-carboxylic) acid and its derivatives in increasing osmotic fragility (OF) in rat red blood cells (RBCs) in vitro. Benzoic acid increased the OF in the rat RBCs in a dose-dependent manner. Replacement of the carboxylic group with a phosphoric group also increased the OF in RBCs, whereas substitution of the carboxylic group by a sulfonic, amide or hydroxy group did not affect the OF. Replacement of the benzene nucleus with a cyclohexane ring or a straight hydrocarbon chain with six carbons resulted in a greater increase in OF than that induced by benzoic acid. Introduction of a methyl group, chloride or bromide at the m- and p-positions of the benzene ring considerably enhanced the increase in OF induced by benzoic acid. Substitution of the amino and hydroxy group at the m- and p- positions abolished the increase in OF induced by benzoic acid. The introduction of these elements at the o-position showed an almost equal increase in OF as that observed for benzoic acid. A molecule of benzoic acid is composed of both hydrophilic (carboxylic group) and hydrophobic (benzene ring) components. Replacement of the hydrophilic component changed the balance formed between hydrophobic and hydrophilic components in the moiety, resulting alterations to its interaction with the RBC membrane. The size, form and elements introduced into the benzene ring also affected its affinity to the cell membrane, and changed the osmotic resistance in rat RBCs.
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Affiliation(s)
- Hitoshi Mineo
- Faculty of Human Science, Hokkaido Bunkyo University, Eniwa, Hokkaido 061-1449, Japan.
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129
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Wuttke A, Idevall-Hagren O, Tengholm A. P2Y₁ receptor-dependent diacylglycerol signaling microdomains in β cells promote insulin secretion. FASEB J 2013; 27:1610-20. [PMID: 23299857 DOI: 10.1096/fj.12-221499] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Diacylglycerol (DAG) controls numerous cell functions by regulating the localization of C1-domain-containing proteins, including protein kinase C (PKC), but little is known about the spatiotemporal dynamics of the lipid. Here, we explored plasma membrane DAG dynamics in pancreatic β cells and determined whether DAG signaling is involved in secretagogue-induced pulsatile release of insulin. Single MIN6 cells, primary mouse β cells, and human β cells within intact islets were transfected with translocation biosensors for DAG, PKC activity, or insulin secretion and imaged with total internal reflection fluorescence microscopy. Muscarinic receptor stimulation triggered stable, homogenous DAG elevations, whereas glucose induced short-lived (7.1 ± 0.4 s) but high-amplitude elevations (up to 109 ± 10% fluorescence increase) in spatially confined membrane regions. The spiking was mimicked by membrane depolarization and suppressed after inhibition of exocytosis or of purinergic P2Y₁, but not P2X receptors, reflecting involvement of autocrine purinoceptor activation after exocytotic release of ATP. Each DAG spike caused local PKC activation with resulting dissociation of its substrate protein MARCKS from the plasma membrane. Inhibition of spiking reduced glucose-induced pulsatile insulin secretion. Thus, stimulus-specific DAG signaling patterns appear in the plasma membrane, including distinct microdomains, which have implications for the kinetic control of exocytosis and other membrane-associated processes.
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Affiliation(s)
- Anne Wuttke
- Department of Medical Cell Biology, Uppsala University, Biomedical Centre, Uppsala, Sweden
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130
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Ellwanger K, Hausser A. Physiological functions of protein kinase D in vivo. IUBMB Life 2013; 65:98-107. [PMID: 23288632 DOI: 10.1002/iub.1116] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2012] [Accepted: 10/25/2012] [Indexed: 11/10/2022]
Abstract
The cellular functions of the serine/threonine protein kinase D (PKD) have been extensively studied within the last decade and distinct roles such as fission of vesicles at the Golgi compartment, coordination of cell migration and invasion, and regulation of gene transcription have been correlated with this kinase family. Here, we highlight the current state of in vivo studies on PKD function with a focus on animal models and discuss the molecular basis of the observed phenotypic characteristics associated with this kinase family.
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Affiliation(s)
- Kornelia Ellwanger
- Institute of Cell Biology and Immunology, University of Stuttgart, Allmandring 31, Stuttgart, Germany
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131
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Hara T, Kimura I, Inoue D, Ichimura A, Hirasawa A. Free Fatty Acid Receptors and Their Role in Regulation of Energy Metabolism. Rev Physiol Biochem Pharmacol 2013; 164:77-116. [DOI: 10.1007/112_2013_13] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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132
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Ferdaoussi M, Bergeron V, Kebede M, Mancini A, Alquier T, Poitout V. Free Fatty Acid Receptor 1: A New Drug Target for Type 2 Diabetes? Can J Diabetes 2012. [DOI: 10.1016/j.jcjd.2012.08.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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