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Agoncillo ML, Gao Z, De Kraker HC, McHardy SF, Messing RO, Small L, Schmitz-Peiffer C. Effects of a protein kinase C epsilon inhibitor on insulin signalling in lipid-treated HepG2 hepatocytes and glucose tolerance in fat-fed mice. Eur J Pharmacol 2025; 997:177465. [PMID: 40054721 DOI: 10.1016/j.ejphar.2025.177465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2025] [Revised: 02/23/2025] [Accepted: 03/04/2025] [Indexed: 05/02/2025]
Abstract
AIMS Protein kinase C epsilon (PKCε) plays a causative role in the development of glucose intolerance, and is a potential target for the treatment of type 2 diabetes. Here, we examined the effects of the PKCε inhibitor CIDD-0150612 (CP612) on insulin action in palmitate-treated HepG2 hepatocytes in vitro and on glucose homeostasis in fat-fed mice in vivo. METHODS HepG2 cells were treated with palmitate and CP612 and stimulated with insulin. Insulin signalling was examined by immunoblotting and glucose incorporation into glycogen was measured using glucose tracer. Mice were fed a high-fat diet and treated with CP612 prior to glucose tolerance tests and tissue harvest. Proteomic analysis of liver was carried out by mass spectrometry. RESULTS CP612 promoted Akt phosphorylation in a highly insulin-dependent manner and reversed the inhibition of insulin-stimulated Akt phosphorylation and glucose incorporation into glycogen by palmitate. Fat-fed mice treated with CP612 had reduced fat mass, but not lean mass, compared with vehicle-treated littermates. Mice treated acutely with CP612 exhibited elevated fasting blood glucose. However, mice studied 24h after the last dose had lower fasting glucose and improved glucose tolerance with a lower insulin excursion. Proteomic analysis of liver from CP612-treated fat-fed mice indicated a reduction in gluconeogenic gene expression and decreased phosphorylation of the transcription factor Foxk1. CONCLUSIONS The PKCε inhibitor CP612 had beneficial effects on insulin action in hepatocytes and on fat mass and glucose homeostasis in mice. Because certain effects were not previously observed in genetically PKCε-deficient mice, off-target effects may be partly responsible.
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Affiliation(s)
- Miguel L Agoncillo
- Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, NSW, 2010, Australia.
| | - Zhongmin Gao
- Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, NSW, 2010, Australia.
| | - Harmannus C De Kraker
- Department of Chemistry, Center for Innovative Drug Discovery, University of Texas San Antonio, One UTSA Circle, San Antonio, TX, 78249, USA.
| | - Stanton F McHardy
- Department of Chemistry, Center for Innovative Drug Discovery, University of Texas San Antonio, One UTSA Circle, San Antonio, TX, 78249, USA.
| | - Robert O Messing
- Department of Neuroscience, University of Texas at Austin, E 24th Street, Austin, TX, 78712, USA.
| | - Lewin Small
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, NSW, 2006, Australia.
| | - Carsten Schmitz-Peiffer
- Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, NSW, 2010, Australia; Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, NSW, 2006, Australia; St Vincent's Clinical School, University of New South Wales, 390 Victoria St, Darlinghurst, NSW, NSW 2010, Australia.
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2
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Sue N, Thai LM, Boslem E, Chu KY, Yan C, Mackin L, Hughes WE, Fontaine-Titley A, Barkauskas D, Cottle L, Thomas HE, Schmitz-Peiffer C, Shi YC, Timpson P, Herrmann D, Whitham M, Biden TJ. ER stress disrupts insulin release in murine models of type 2 diabetes by impairing retromer action and constitutive secretion. Cell Rep 2025; 44:115691. [PMID: 40366805 DOI: 10.1016/j.celrep.2025.115691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2024] [Revised: 03/12/2025] [Accepted: 04/22/2025] [Indexed: 05/16/2025] Open
Abstract
Using in vitro models of lipotoxicity and islets from the db/db mouse model of type 2 diabetes (T2D), we show that endoplasmic reticulum (ER) stress impairs β cell function. This is unrelated to apoptosis or alterations in insulin content or proinsulin processing, despite expansion of the Golgi compartment. Instead, the constitutive secretory pathway and endocytic recycling are disrupted, as revealed by depletion of glycosylated proteins and syntaxins from the plasma membrane (PM) and accumulation of E-cadherin in the retromer. This involves the PERK arm of the unfolded protein response. Proteomics identified multiple PM proteins mislocalized by ER stress, notably axon-guidance and cell-adhesion proteins, and many with glycosylphosphatidylinositol linkages. A retromer chaperone attenuated defective insulin secretion from islets of both db/db and high-fat-fed mice. By identifying different endpoints and mechanisms, our results redefine the relevance of ER stress to β cell failure. They also implicate retromer chaperones as potential T2D therapeutics.
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Affiliation(s)
- Nancy Sue
- Garvan Institute of Medical Research, Sydney, NSW, Australia
| | - Le May Thai
- Garvan Institute of Medical Research, Sydney, NSW, Australia
| | - Ebru Boslem
- Garvan Institute of Medical Research, Sydney, NSW, Australia
| | - Kwan Yi Chu
- Garvan Institute of Medical Research, Sydney, NSW, Australia
| | - Chenxu Yan
- Garvan Institute of Medical Research, Sydney, NSW, Australia
| | - Leanne Mackin
- St. Vincent's Medical Research Institute, Melbourne, VIC, Australia
| | | | | | | | - Louise Cottle
- Garvan Institute of Medical Research, Sydney, NSW, Australia; Charles Perkins Centre, University of Sydney, Camperdown, NSW, Australia
| | - Helen E Thomas
- St. Vincent's Medical Research Institute, Melbourne, VIC, Australia
| | - Carsten Schmitz-Peiffer
- Garvan Institute of Medical Research, Sydney, NSW, Australia; Charles Perkins Centre, University of Sydney, Camperdown, NSW, Australia
| | - Yan-Chuan Shi
- Garvan Institute of Medical Research, Sydney, NSW, Australia; St Vincent's Clinical School, Faculty of Medicine, UNSW Sydney, Sydney, NSW, Australia
| | - Paul Timpson
- Garvan Institute of Medical Research, Sydney, NSW, Australia; St Vincent's Clinical School, Faculty of Medicine, UNSW Sydney, Sydney, NSW, Australia
| | - David Herrmann
- Garvan Institute of Medical Research, Sydney, NSW, Australia; St Vincent's Clinical School, Faculty of Medicine, UNSW Sydney, Sydney, NSW, Australia
| | - Martin Whitham
- Garvan Institute of Medical Research, Sydney, NSW, Australia; School of Sport, Exercise & Rehabilitation Sciences, University of Birmingham, Edgbaston, Birmingham, UK
| | - Trevor J Biden
- Garvan Institute of Medical Research, Sydney, NSW, Australia; St Vincent's Clinical School, Faculty of Medicine, UNSW Sydney, Sydney, NSW, Australia.
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Holendová B, Stokičová L, Plecitá-Hlavatá L. Lipid Dynamics in Pancreatic β-Cells: Linking Physiology to Diabetes Onset. Antioxid Redox Signal 2024; 41:865-889. [PMID: 39495600 DOI: 10.1089/ars.2024.0724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2024]
Abstract
Significance: Glucose-induced lipid metabolism is essential for preserving functional β-cells, and its disruption is linked to type 2 diabetes (T2D) development. Lipids are an integral part of the cells playing an indispensable role as structural components, energy storage molecules, and signals. Recent Advances: Glucose presence significantly impacts lipid metabolism in β-cells, where fatty acids are primarily synthesized de novo and/or are transported from the bloodstream. This process is regulated by the glycerolipid/free fatty acid cycle, which includes lipogenic and lipolytic reactions producing metabolic coupling factors crucial for insulin secretion. Disrupted lipid metabolism involving oxidative stress and inflammation is a hallmark of T2D. Critical Issues: Lipid metabolism in β-cells is complex involving multiple simultaneous processes. Exact compartmentalization and quantification of lipid metabolism and its intermediates, especially in response to glucose or chronic hyperglycemia, are essential. Current research often uses non-physiological conditions, which may not accurately reflect in vivo situations. Future Directions: Identifying and quantifying individual steps and their signaling, including redox, within the complex fatty acid and lipid metabolic pathways as well as the metabolites formed during acute versus chronic glucose stimulation, will uncover the detailed mechanisms of glucose-stimulated insulin secretion. This knowledge is crucial for understanding T2D pathogenesis and identifying pharmacological targets to prevent this disease. Antioxid. Redox Signal. 41, 865-889.
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Affiliation(s)
- Blanka Holendová
- Laboratory of Pancreatic Islet Research, Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
| | - Linda Stokičová
- Laboratory of Pancreatic Islet Research, Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
- Charles University, Prague, Czech Republic
| | - Lydie Plecitá-Hlavatá
- Laboratory of Pancreatic Islet Research, Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
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4
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Moroni-González D, Sarmiento-Ortega VE, Diaz A, Brambila E, Treviño S. Pancreas-Liver-Adipose Axis: Target of Environmental Cadmium Exposure Linked to Metabolic Diseases. TOXICS 2023; 11:223. [PMID: 36976988 PMCID: PMC10059892 DOI: 10.3390/toxics11030223] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Revised: 02/17/2023] [Accepted: 02/19/2023] [Indexed: 06/18/2023]
Abstract
Cadmium has been well recognized as a critical toxic agent in acute and chronic poisoning cases in occupational and nonoccupational settings and environmental exposure situations. Cadmium is released into the environment after natural and anthropogenic activities, particularly in contaminated and industrial areas, causing food pollution. In the body, cadmium has no biological activity, but it accumulates primarily in the liver and kidney, which are considered the main targets of its toxicity, through oxidative stress and inflammation. However, in the last few years, this metal has been linked to metabolic diseases. The pancreas-liver-adipose axis is largely affected by cadmium accumulation. Therefore, this review aims to collect bibliographic information that establishes the basis for understanding the molecular and cellular mechanisms linked to cadmium with carbohydrate, lipids, and endocrine impairments that contribute to developing insulin resistance, metabolic syndrome, prediabetes, and diabetes.
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Affiliation(s)
- Diana Moroni-González
- Laboratory of Chemical-Clinical Investigations, Department of Clinical Chemistry, Faculty of Chemistry Science, Meritorious Autonomous University of Puebla, Ciudad Universitaria, Puebla 72560, Mexico
| | - Victor Enrique Sarmiento-Ortega
- Laboratory of Chemical-Clinical Investigations, Department of Clinical Chemistry, Faculty of Chemistry Science, Meritorious Autonomous University of Puebla, Ciudad Universitaria, Puebla 72560, Mexico
| | - Alfonso Diaz
- Department of Pharmacy, Faculty of Chemistry Science, Meritorious Autonomous University of Puebla, 22 South. FCQ9, Ciudad Universitaria, Puebla 72560, Mexico
| | - Eduardo Brambila
- Laboratory of Chemical-Clinical Investigations, Department of Clinical Chemistry, Faculty of Chemistry Science, Meritorious Autonomous University of Puebla, Ciudad Universitaria, Puebla 72560, Mexico
| | - Samuel Treviño
- Laboratory of Chemical-Clinical Investigations, Department of Clinical Chemistry, Faculty of Chemistry Science, Meritorious Autonomous University of Puebla, Ciudad Universitaria, Puebla 72560, Mexico
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5
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Sarmiento-Ortega VE, Moroni-González D, Díaz A, Eduardo B, Samuel T. Oral Subacute Exposure to Cadmium LOAEL Dose Induces Insulin Resistance and Impairment of the Hormonal and Metabolic Liver-Adipose Axis in Wistar Rats. Biol Trace Elem Res 2022; 200:4370-4384. [PMID: 34846673 DOI: 10.1007/s12011-021-03027-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Accepted: 11/10/2021] [Indexed: 02/07/2023]
Abstract
Cadmium is a nonessential transition metal considered one of the more hazardous environmental contaminants. The population is chronically exposed to this metal at low concentrations, designated as the LOAEL (lowest observable adverse effect level) dose. We aimed to investigate whether oral subacute exposure to cadmium LOAEL disrupts hormonal and metabolic effects of the liver-adipose axis in Wistar rats. Fifty male Wistar rats were separated into two groups: control (standard normocalorie diet + water free of cadmium) and cadmium (standard normocalorie diet + drinking water with 32.5 ppm CdCl2). After 1 month, zoometry, a serum lipid panel, adipokines, and proinflammatory cytokines were evaluated. Tests of glucose and insulin tolerance (ITT) and insulin resistance were performed. Histological studies on structure, triglyceride distribution, and protein expression of the insulin pathway were performed in the liver and retroperitoneal adipose tissue. In both tissues, the cadmium, triglyceride, glycogen, and proinflammatory cytokine contents were also quantified. The cadmium group developed dyslipidemia, glucose intolerance, hyperinsulinemia, hyperleptinemia, inflammation, and selective insulin resistance in the liver and adipose tissue. In the liver, glycogen synthesis was diminished, while de novo lipogenesis increased, which was associated with low GSK3β-pS9 and strong expression of SREBP-1c. Dysfunctional adipose tissue was observed with hypertrophy and lipolysis, without changes in SREBP-1c expression and low glycogen synthesis. Both tissues accumulated cadmium and developed inflammation. In conclusion, oral subacute cadmium LOAEL dose exposure induces inflammation, insulin signaling modifications, an early insulin resistance stage (insensibility), and impairment of the hormonal and metabolic liver-adipose axis in Wistar rats.
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Affiliation(s)
- Victor Enrique Sarmiento-Ortega
- Laboratory of Chemical-Clinical Investigations, Department of Clinical Chemistry, Faculty of Chemistry Science, Autonomous University of Puebla, 14 South, FCQ1, University City, C.P.72560, Puebla, Mexico
| | - Diana Moroni-González
- Laboratory of Chemical-Clinical Investigations, Department of Clinical Chemistry, Faculty of Chemistry Science, Autonomous University of Puebla, 14 South, FCQ1, University City, C.P.72560, Puebla, Mexico
| | - Alfonso Díaz
- Department of Pharmacy, Faculty of Chemistry Science, Autonomous University of Puebla, 22 South, FC91, University City, C.P. 72560, Puebla, Mexico
| | - Brambila Eduardo
- Laboratory of Chemical-Clinical Investigations, Department of Clinical Chemistry, Faculty of Chemistry Science, Autonomous University of Puebla, 14 South, FCQ1, University City, C.P.72560, Puebla, Mexico
| | - Treviño Samuel
- Laboratory of Chemical-Clinical Investigations, Department of Clinical Chemistry, Faculty of Chemistry Science, Autonomous University of Puebla, 14 South, FCQ1, University City, C.P.72560, Puebla, Mexico.
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6
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Alshehade S, Alshawsh MA, Murugaiyah V, Asif M, Alshehade O, Almoustafa H, Al Zarzour RH. The role of protein kinases as key drivers of metabolic dysfunction-associated fatty liver disease progression: New insights and future directions. Life Sci 2022; 305:120732. [PMID: 35760093 DOI: 10.1016/j.lfs.2022.120732] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Revised: 06/08/2022] [Accepted: 06/21/2022] [Indexed: 02/07/2023]
Abstract
Metabolic dysfunction-associated fatty liver disease (MAFLD), proposed in 2020 is a novel term for non-alcoholic fatty liver disease (NAFLD) which was coined for the first time in 1980. It is a leading cause of the most chronic liver disease and hepatic failure all over the world, and unfortunately, with no licensed drugs for treatment yet. The progress of the disease is driven by the triggered inflammatory process, oxidative stress, and insulin resistance in many pathways, starting with simple hepatic steatosis to non-alcoholic steatohepatitis, fibrosis, cirrhosis, and liver cancer. Protein kinases (PKs), such as MAPK, ErbB, PKC, PI3K/Akt, and mTOR, govern most of the pathological pathways by acting on various downstream key points in MAFLD and regulating both hepatic gluco- lipo-neogenesis and inflammation. Therefore, modulating the function of those potential protein kinases that are effectively involved in MAFLD might be a promising therapeutic approach for tackling this disease. In the current review, we have discussed the key role of protein kinases in the pathogenesis of MAFLD and performed a protein-protein interaction (PPI) network among the main proteins of each kinase pathway with MAFLD-related proteins to predict the most likely targets of the PKs in MAFLD. Moreover, we have reported the experimental, pre-clinical, and clinical data for the most recent investigated molecules that are activating p38-MAPK and AMPK proteins and inhibiting the other PKs to improve MAFLD condition by regulating oxidation and inflammation signalling.
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Affiliation(s)
- Salah Alshehade
- Department of Pharmacology, School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia; Department of Pharmacology, Faculty of Medicine, Universiti Malaya, 50603 Kuala Lumpur, Malaysia
| | | | - Vikneswaran Murugaiyah
- Department of Pharmacology, School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia
| | - Muhammad Asif
- Department of Pharmacology, Faculty of Pharmacy, The Islamia University of Bahawalpur, 63100, Punjab, Pakistan
| | - Omayma Alshehade
- Department of Paediatrics, Faculty of Medicine, Damascus University, Damascus, Syria
| | - Hassan Almoustafa
- Department of Pharmacology, Faculty of Medicine, Universiti Malaya, 50603 Kuala Lumpur, Malaysia
| | - Raghdaa Hamdan Al Zarzour
- Department of Pharmacology, School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia; Department of Pharmacology, Faculty of Pharmacy, Arab International University, Damascus, Syria.
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7
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Apostolopoulou M, Mastrototaro L, Hartwig S, Pesta D, Straßburger K, de Filippo E, Jelenik T, Karusheva Y, Gancheva S, Markgraf D, Herder C, Nair KS, Reichert AS, Lehr S, Müssig K, Al-Hasani H, Szendroedi J, Roden M. Metabolic responsiveness to training depends on insulin sensitivity and protein content of exosomes in insulin-resistant males. SCIENCE ADVANCES 2021; 7:eabi9551. [PMID: 34623918 PMCID: PMC8500512 DOI: 10.1126/sciadv.abi9551] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
High-intensity interval training (HIIT) improves cardiorespiratory fitness (VO2max), but its impact on metabolism remains unclear. We hypothesized that 12-week HIIT increases insulin sensitivity in males with or without type 2 diabetes [T2D and NDM (nondiabetic humans)]. However, despite identically higher VO2max, mainly insulin-resistant (IR) persons (T2D and IR NDM) showed distinct alterations of circulating small extracellular vesicles (SEVs) along with lower inhibitory metabolic (protein kinase Cε activity) or inflammatory (nuclear factor κB) signaling in muscle of T2D or IR NDM, respectively. This is related to the specific alterations in SEV proteome reflecting down-regulation of the phospholipase C pathway (T2D) and up-regulated antioxidant capacity (IR NDM). Thus, SEV cargo may contribute to modulating the individual metabolic responsiveness to exercise training in humans.
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Affiliation(s)
- Maria Apostolopoulou
- Department of Endocrinology and Diabetology, Medical Faculty and University Hospital, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- German Center for Diabetes Research, Partner Düsseldorf, München-Neuherberg, Germany
| | - Lucia Mastrototaro
- Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- German Center for Diabetes Research, Partner Düsseldorf, München-Neuherberg, Germany
| | - Sonja Hartwig
- German Center for Diabetes Research, Partner Düsseldorf, München-Neuherberg, Germany
- Institute for Clinical Biochemistry and Pathobiochemistry German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Dominik Pesta
- Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- German Center for Diabetes Research, Partner Düsseldorf, München-Neuherberg, Germany
| | - Klaus Straßburger
- German Center for Diabetes Research, Partner Düsseldorf, München-Neuherberg, Germany
- Institute for Biometrics and Epidemiology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Elisabetta de Filippo
- Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- German Center for Diabetes Research, Partner Düsseldorf, München-Neuherberg, Germany
| | - Tomas Jelenik
- Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- German Center for Diabetes Research, Partner Düsseldorf, München-Neuherberg, Germany
| | - Yanislava Karusheva
- Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- German Center for Diabetes Research, Partner Düsseldorf, München-Neuherberg, Germany
| | - Sofiya Gancheva
- Department of Endocrinology and Diabetology, Medical Faculty and University Hospital, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- German Center for Diabetes Research, Partner Düsseldorf, München-Neuherberg, Germany
| | - Daniel Markgraf
- Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- German Center for Diabetes Research, Partner Düsseldorf, München-Neuherberg, Germany
| | - Christian Herder
- Department of Endocrinology and Diabetology, Medical Faculty and University Hospital, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- German Center for Diabetes Research, Partner Düsseldorf, München-Neuherberg, Germany
| | - K. Sreekumaran Nair
- Division of Endocrinology, Diabetes and Nutrition, Mayo Clinic, Rochester, MN, USA
| | - Andreas S. Reichert
- Institute of Biochemistry and Molecular Biology I, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Stefan Lehr
- German Center for Diabetes Research, Partner Düsseldorf, München-Neuherberg, Germany
- Institute for Clinical Biochemistry and Pathobiochemistry German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Karsten Müssig
- Department of Endocrinology and Diabetology, Medical Faculty and University Hospital, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- German Center for Diabetes Research, Partner Düsseldorf, München-Neuherberg, Germany
| | - Hadi Al-Hasani
- German Center for Diabetes Research, Partner Düsseldorf, München-Neuherberg, Germany
- Institute for Clinical Biochemistry and Pathobiochemistry German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Julia Szendroedi
- Department of Endocrinology and Diabetology, Medical Faculty and University Hospital, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- German Center for Diabetes Research, Partner Düsseldorf, München-Neuherberg, Germany
- Department of Internal Medicine, Heidelberg University, Heidelberg, Germany
| | - Michael Roden
- Department of Endocrinology and Diabetology, Medical Faculty and University Hospital, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- German Center for Diabetes Research, Partner Düsseldorf, München-Neuherberg, Germany
- Corresponding author.
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8
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Ben-Haroush Schyr R, Al-Kurd A, Moalem B, Permyakova A, Israeli H, Bardugo A, Arad Y, Hefetz L, Bergel M, Haran A, Azar S, Magenheim I, Tam J, Grinbaum R, Ben-Zvi D. Sleeve Gastrectomy Suppresses Hepatic Glucose Production and Increases Hepatic Insulin Clearance Independent of Weight Loss. Diabetes 2021; 70:2289-2298. [PMID: 34341005 PMCID: PMC8576500 DOI: 10.2337/db21-0251] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 07/28/2021] [Indexed: 11/13/2022]
Abstract
Bariatric operations induce weight loss, which is associated with an improvement in hepatic steatosis and a reduction in hepatic glucose production. It is not clear whether these outcomes are entirely due to weight loss, or whether the new anatomy imposed by the surgery contributes to the improvement in the metabolic function of the liver. We performed vertical sleeve gastrectomy (VSG) on obese mice provided with a high-fat high-sucrose diet and compared them to diet and weight-matched sham-operated mice (WMS). At 40 days after surgery, VSG-operated mice displayed less hepatic steatosis compared with WMS. By measuring the fasting glucose and insulin levels in the blood vessels feeding and draining the liver, we showed directly that hepatic glucose production was suppressed after VSG. Insulin levels were elevated in the portal vein, and hepatic insulin clearance was elevated in VSG-operated mice. The hepatic expression of genes associated with insulin clearance was upregulated. We repeated the experiment in lean mice and observed that portal insulin and glucagon are elevated, but only insulin clearance is increased in VSG-operated mice. In conclusion, direct measurement of glucose and insulin in the blood entering and leaving the liver shows that VSG affects glucose and insulin metabolism through mechanisms independent of weight loss and diet.
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Affiliation(s)
- Rachel Ben-Haroush Schyr
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Hadassah Medical School-The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Abbas Al-Kurd
- Department of Surgery, Hadassah Medical Center-Mt. Scopus, Jerusalem, Israel
| | - Botros Moalem
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Hadassah Medical School-The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Anna Permyakova
- Obesity and Metabolism Laboratory, Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Hadar Israeli
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Hadassah Medical School-The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Aya Bardugo
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Hadassah Medical School-The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Yhara Arad
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Hadassah Medical School-The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Liron Hefetz
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Hadassah Medical School-The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Michael Bergel
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Hadassah Medical School-The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Arnon Haran
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Hadassah Medical School-The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Shahar Azar
- Obesity and Metabolism Laboratory, Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Itia Magenheim
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Hadassah Medical School-The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Joseph Tam
- Obesity and Metabolism Laboratory, Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Ronit Grinbaum
- Department of Surgery, Hadassah Medical Center-Mt. Scopus, Jerusalem, Israel
| | - Danny Ben-Zvi
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Hadassah Medical School-The Hebrew University of Jerusalem, Jerusalem, Israel
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9
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Nagao M, Esguerra JLS, Asai A, Ofori JK, Edlund A, Wendt A, Sugihara H, Wollheim CB, Oikawa S, Eliasson L. Potential Protection Against Type 2 Diabetes in Obesity Through Lower CD36 Expression and Improved Exocytosis in β-Cells. Diabetes 2020; 69:1193-1205. [PMID: 32198214 PMCID: PMC7243297 DOI: 10.2337/db19-0944] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Accepted: 03/09/2020] [Indexed: 12/18/2022]
Abstract
Obesity is a risk factor for type 2 diabetes (T2D); however, not all obese individuals develop the disease. In this study, we aimed to investigate the cause of differential insulin secretion capacity of pancreatic islets from donors with T2D and non-T2D (ND), especially obese donors (BMI ≥30 kg/m2). Islets from obese donors with T2D had reduced insulin secretion, decreased β-cell exocytosis, and higher expression of fatty acid translocase CD36. We tested the hypothesis that CD36 is a key molecule in the reduced insulin secretion capacity. Indeed, CD36 overexpression led to decreased insulin secretion, impaired exocytosis, and reduced granule docking. This was accompanied by reduced expression of the exocytotic proteins SNAP25, STXBP1, and VAMP2, likely because CD36 induced downregulation of the insulin receptor substrate (IRS) proteins, suppressed the insulin-signaling phosphatidylinositol 3-kinase/AKT pathway, and increased nuclear localization of the transcription factor FoxO1. CD36 antibody treatment of the human β-cell line EndoC-βH1 increased IRS1 and exocytotic protein levels, improved granule docking, and enhanced insulin secretion. Our results demonstrate that β-cells from obese donors with T2D have dysfunctional exocytosis likely due to an abnormal lipid handling represented by differential CD36 expression. Hence, CD36 could be a key molecule to limit β-cell function in T2D associated with obesity.
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Affiliation(s)
- Mototsugu Nagao
- Department of Clinical Sciences, Malmö, Islet Cell Exocytosis, Lund University Diabetes Centre, Lund University, Clinical Research Centre, Malmö, Sweden
- Department of Endocrinology, Diabetes and Metabolism, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
| | - Jonathan L S Esguerra
- Department of Clinical Sciences, Malmö, Islet Cell Exocytosis, Lund University Diabetes Centre, Lund University, Clinical Research Centre, Malmö, Sweden
| | - Akira Asai
- Department of Clinical Sciences, Malmö, Islet Cell Exocytosis, Lund University Diabetes Centre, Lund University, Clinical Research Centre, Malmö, Sweden
- Department of Endocrinology, Diabetes and Metabolism, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
- Food and Health Science Research Unit, Graduate School of Agricultural Science, Tohoku University, Sendai, Japan
| | - Jones K Ofori
- Department of Clinical Sciences, Malmö, Islet Cell Exocytosis, Lund University Diabetes Centre, Lund University, Clinical Research Centre, Malmö, Sweden
| | - Anna Edlund
- Department of Clinical Sciences, Malmö, Islet Cell Exocytosis, Lund University Diabetes Centre, Lund University, Clinical Research Centre, Malmö, Sweden
| | - Anna Wendt
- Department of Clinical Sciences, Malmö, Islet Cell Exocytosis, Lund University Diabetes Centre, Lund University, Clinical Research Centre, Malmö, Sweden
| | - Hitoshi Sugihara
- Department of Endocrinology, Diabetes and Metabolism, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
| | - Claes B Wollheim
- Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Shinichi Oikawa
- Department of Endocrinology, Diabetes and Metabolism, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
| | - Lena Eliasson
- Department of Clinical Sciences, Malmö, Islet Cell Exocytosis, Lund University Diabetes Centre, Lund University, Clinical Research Centre, Malmö, Sweden
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10
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Kolczynska K, Loza-Valdes A, Hawro I, Sumara G. Diacylglycerol-evoked activation of PKC and PKD isoforms in regulation of glucose and lipid metabolism: a review. Lipids Health Dis 2020; 19:113. [PMID: 32466765 PMCID: PMC7257441 DOI: 10.1186/s12944-020-01286-8] [Citation(s) in RCA: 98] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 05/14/2020] [Indexed: 12/15/2022] Open
Abstract
Protein kinase C (PKC) and Protein kinase D (PKD) isoforms can sense diacylglycerol (DAG) generated in the different cellular compartments in various physiological processes. DAG accumulates in multiple organs of the obese subjects, which leads to the disruption of metabolic homeostasis and the development of diabetes as well as associated diseases. Multiple studies proved that aberrant activation of PKCs and PKDs contributes to the development of metabolic diseases. DAG-sensing PKC and PKD isoforms play a crucial role in the regulation of metabolic homeostasis and therefore might serve as targets for the treatment of metabolic disorders such as obesity and diabetes.
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Affiliation(s)
- Katarzyna Kolczynska
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur Street, 02-093, Warszawa, Poland
| | - Angel Loza-Valdes
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur Street, 02-093, Warszawa, Poland
| | - Izabela Hawro
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur Street, 02-093, Warszawa, Poland
| | - Grzegorz Sumara
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur Street, 02-093, Warszawa, Poland.
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11
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Schmitz-Peiffer C. Deconstructing the Role of PKC Epsilon in Glucose Homeostasis. Trends Endocrinol Metab 2020; 31:344-356. [PMID: 32305097 DOI: 10.1016/j.tem.2020.01.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 01/22/2020] [Accepted: 01/24/2020] [Indexed: 02/06/2023]
Abstract
The failure of insulin to suppress glucose production by the liver is a key aspect of the insulin resistance seen in type 2 diabetes. Lipid-activated protein kinase C epsilon has long been identified as an important mediator of diet-induced glucose intolerance and hepatic insulin resistance and the current view emphasizes a mechanism involving phosphorylation of the insulin receptor by the kinase to inhibit downstream insulin action. However, the significance of this direct effect in the liver has now been challenged by tissue-specific deletion of PKCε, which demonstrated a more prominent role for the kinase in adipose tissue to promote glucose intolerance. New insights regarding the role of PKCε therefore contribute to the understanding of indirect effects on hepatic glucose metabolism.
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Affiliation(s)
- Carsten Schmitz-Peiffer
- Garvan Institute of Medical Research, Darlinghurst Sydney, NSW 2010, Australia; St Vincent's Clinical School, University of New South Wales, Sydney, NSW 2010, Australia.
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12
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Role of c-Jun N-terminal Kinase (JNK) in Obesity and Type 2 Diabetes. Cells 2020; 9:cells9030706. [PMID: 32183037 PMCID: PMC7140703 DOI: 10.3390/cells9030706] [Citation(s) in RCA: 151] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 02/16/2020] [Accepted: 03/11/2020] [Indexed: 12/13/2022] Open
Abstract
Obesity has been described as a global epidemic and is a low-grade chronic inflammatory disease that arises as a consequence of energy imbalance. Obesity increases the risk of type 2 diabetes (T2D), by mechanisms that are not entirely clarified. Elevated circulating pro-inflammatory cytokines and free fatty acids (FFA) during obesity cause insulin resistance and ß-cell dysfunction, the two main features of T2D, which are both aggravated with the progressive development of hyperglycemia. The inflammatory kinase c-jun N-terminal kinase (JNK) responds to various cellular stress signals activated by cytokines, free fatty acids and hyperglycemia, and is a key mediator in the transition between obesity and T2D. Specifically, JNK mediates both insulin resistance and ß-cell dysfunction, and is therefore a potential target for T2D therapy.
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13
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Lytrivi M, Castell AL, Poitout V, Cnop M. Recent Insights Into Mechanisms of β-Cell Lipo- and Glucolipotoxicity in Type 2 Diabetes. J Mol Biol 2019; 432:1514-1534. [PMID: 31628942 DOI: 10.1016/j.jmb.2019.09.016] [Citation(s) in RCA: 267] [Impact Index Per Article: 44.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2019] [Revised: 09/15/2019] [Accepted: 09/16/2019] [Indexed: 12/24/2022]
Abstract
The deleterious effects of chronically elevated free fatty acid (FFA) levels on glucose homeostasis are referred to as lipotoxicity, and the concurrent exposure to high glucose may cause synergistic glucolipotoxicity. Lipo- and glucolipotoxicity have been studied for over 25 years. Here, we review the current evidence supporting the role of pancreatic β-cell lipo- and glucolipotoxicity in type 2 diabetes (T2D), including lipid-based interventions in humans, prospective epidemiological studies, and human genetic findings. In addition to total FFA quantity, the quality of FFAs (saturation and chain length) is a key determinant of lipotoxicity. We discuss in vitro and in vivo experimental models to investigate lipo- and glucolipotoxicity in β-cells and describe experimental pitfalls. Lipo- and glucolipotoxicity adversely affect many steps of the insulin production and secretion process. The molecular mechanisms underpinning lipo- and glucolipotoxic β-cell dysfunction and death comprise endoplasmic reticulum stress, oxidative stress and mitochondrial dysfunction, impaired autophagy, and inflammation. Crosstalk between these stress pathways exists at multiple levels and may aggravate β-cell lipo- and glucolipotoxicity. Lipo- and glucolipotoxicity are therapeutic targets as several drugs impact the underlying stress responses in β-cells, potentially contributing to their glucose-lowering effects in T2D.
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Affiliation(s)
- Maria Lytrivi
- ULB Center for Diabetes Research, Medical Faculty, Université Libre de Bruxelles, Brussels, Belgium; Division of Endocrinology, Erasmus Hospital, Université Libre de Bruxelles, Brussels, Belgium
| | - Anne-Laure Castell
- CRCHUM, Montréal, QC, Canada; Department of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Vincent Poitout
- CRCHUM, Montréal, QC, Canada; Department of Medicine, Université de Montréal, Montréal, QC, Canada.
| | - Miriam Cnop
- ULB Center for Diabetes Research, Medical Faculty, Université Libre de Bruxelles, Brussels, Belgium; Division of Endocrinology, Erasmus Hospital, Université Libre de Bruxelles, Brussels, Belgium.
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14
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Santo-Domingo J, Galindo AN, Cominetti O, De Marchi U, Cutillas P, Dayon L, Wiederkehr A. Glucose-dependent phosphorylation signaling pathways and crosstalk to mitochondrial respiration in insulin secreting cells. Cell Commun Signal 2019; 17:14. [PMID: 30786936 PMCID: PMC6381748 DOI: 10.1186/s12964-019-0326-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 02/08/2019] [Indexed: 01/13/2023] Open
Abstract
Background Glucose is the main secretagogue of pancreatic beta-cells. Uptake and metabolism of the nutrient stimulates the beta-cell to release the blood glucose lowering hormone insulin. This metabolic activation is associated with a pronounced increase in mitochondrial respiration. Glucose stimulation also initiates a number of signal transduction pathways for the coordinated regulation of multiple biological processes required for insulin secretion. Methods Shotgun proteomics including TiO2 enrichment of phosphorylated peptides followed by liquid chromatography tandem mass spectrometry on lysates from glucose-stimulated INS-1E cells was used to identify glucose regulated phosphorylated proteins and signal transduction pathways. Kinase substrate enrichment analysis (KSEA) was applied to identify key regulated kinases and phosphatases. Glucose-induced oxygen consumption was measured using a XF96 Seahorse instrument to reveal cross talk between glucose-regulated kinases and mitochondrial activation. Results Our kinetic analysis of substrate phosphorylation reveal the molecular mechanism leading to rapid activation of insulin biogenesis, vesicle trafficking, insulin granule exocytosis and cytoskeleton remodeling. Kinase-substrate enrichment identified upstream kinases and phosphatases and time-dependent activity changes during glucose stimulation. Activity trajectories of well-known glucose-regulated kinases and phosphatases are described. In addition, we predict activity changes in a number of kinases including NUAK1, not or only poorly studied in the context of the pancreatic beta-cell. Furthermore, we pharmacologically tested whether signaling pathways predicted by kinase-substrate enrichment analysis affected glucose-dependent acceleration of mitochondrial respiration. We find that phosphoinositide 3-kinase, Ca2+/calmodulin dependent protein kinase and protein kinase C contribute to short-term regulation of energy metabolism. Conclusions Our results provide a global view into the regulation of kinases and phosphatases in insulin secreting cells and suggest cross talk between glucose-induced signal transduction and mitochondrial activation. Electronic supplementary material The online version of this article (10.1186/s12964-019-0326-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jaime Santo-Domingo
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park Bâtiment G, 1015, Lausanne, Switzerland.
| | - Antonio Núñez Galindo
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park Bâtiment G, 1015, Lausanne, Switzerland
| | - Ornella Cominetti
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park Bâtiment G, 1015, Lausanne, Switzerland
| | - Umberto De Marchi
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park Bâtiment G, 1015, Lausanne, Switzerland
| | - Pedro Cutillas
- Analytical Signalling Group, Centre for Cell Signalling, Queen Mary University of London, London, UK
| | - Loïc Dayon
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park Bâtiment G, 1015, Lausanne, Switzerland
| | - Andreas Wiederkehr
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park Bâtiment G, 1015, Lausanne, Switzerland
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15
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Brandon AE, Liao BM, Diakanastasis B, Parker BL, Raddatz K, McManus SA, O'Reilly L, Kimber E, van der Kraan AG, Hancock D, Henstridge DC, Meikle PJ, Cooney GJ, James DE, Reibe S, Febbraio MA, Biden TJ, Schmitz-Peiffer C. Protein Kinase C Epsilon Deletion in Adipose Tissue, but Not in Liver, Improves Glucose Tolerance. Cell Metab 2019; 29:183-191.e7. [PMID: 30318338 DOI: 10.1016/j.cmet.2018.09.013] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Revised: 07/16/2018] [Accepted: 09/12/2018] [Indexed: 02/02/2023]
Abstract
Protein kinase C epsilon (PKCɛ) activation in the liver is proposed to inhibit insulin action through phosphorylation of the insulin receptor. Here, however, we demonstrated that global, but not liver-specific, deletion of PKCɛ in mice protected against diet-induced glucose intolerance and insulin resistance. Furthermore, PKCɛ-dependent alterations in insulin receptor phosphorylation were not detected. Adipose-tissue-specific knockout mice did exhibit improved glucose tolerance, but phosphoproteomics revealed no PKCɛ-dependent effect on the activation of insulin signaling pathways. Altered phosphorylation of adipocyte proteins associated with cell junctions and endosomes was associated with changes in hepatic expression of several genes linked to glucose homeostasis and lipid metabolism. The primary effect of PKCɛ on glucose homeostasis is, therefore, not exerted directly in the liver as currently posited, and PKCɛ activation in this tissue should be interpreted with caution. However, PKCɛ activity in adipose tissue modulates glucose tolerance and is involved in crosstalk with the liver.
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Affiliation(s)
- Amanda E Brandon
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia; School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia
| | - Bing M Liao
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia
| | - Barbara Diakanastasis
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia
| | - Benjamin L Parker
- School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia
| | - Katy Raddatz
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia
| | - Sophie A McManus
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia
| | - Liam O'Reilly
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia
| | - Erica Kimber
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia
| | | | - Dale Hancock
- School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia
| | | | - Peter J Meikle
- Baker Heart and Diabetes Institute, Melbourne, VIC 3004, Australia
| | - Gregory J Cooney
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia; School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia
| | - David E James
- School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia
| | - Saskia Reibe
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia
| | - Mark A Febbraio
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia; St Vincent's Clinical School, University of New South Wales, Sydney, NSW 2010, Australia
| | - Trevor J Biden
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia; St Vincent's Clinical School, University of New South Wales, Sydney, NSW 2010, Australia
| | - Carsten Schmitz-Peiffer
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia; St Vincent's Clinical School, University of New South Wales, Sydney, NSW 2010, Australia.
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16
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Cantley J, Davenport A, Vetterli L, Nemes NJ, Whitworth PT, Boslem E, Thai LM, Mellett N, Meikle PJ, Hoehn KL, James DE, Biden TJ. Disruption of beta cell acetyl-CoA carboxylase-1 in mice impairs insulin secretion and beta cell mass. Diabetologia 2019; 62:99-111. [PMID: 30334081 PMCID: PMC6290731 DOI: 10.1007/s00125-018-4743-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 08/22/2018] [Indexed: 11/29/2022]
Abstract
AIMS/HYPOTHESIS Pancreatic beta cells secrete insulin to maintain glucose homeostasis, and beta cell failure is a hallmark of type 2 diabetes. Glucose triggers insulin secretion in beta cells via oxidative mitochondrial pathways. However, it also feeds mitochondrial anaplerotic pathways, driving citrate export and cytosolic malonyl-CoA production by the acetyl-CoA carboxylase 1 (ACC1) enzyme. This pathway has been proposed as an alternative glucose-sensing mechanism, supported mainly by in vitro data. Here, we sought to address the role of the beta cell ACC1-coupled pathway in insulin secretion and glucose homeostasis in vivo. METHODS Acaca, encoding ACC1 (the principal ACC isoform in islets), was deleted in beta cells of mice using the Cre/loxP system. Acaca floxed mice were crossed with Ins2cre mice (βACC1KO; life-long beta cell gene deletion) or Pdx1creER mice (tmx-βACC1KO; inducible gene deletion in adult beta cells). Beta cell function was assessed using in vivo metabolic physiology and ex vivo islet experiments. Beta cell mass was analysed using histological techniques. RESULTS βACC1KO and tmx-βACC1KO mice were glucose intolerant and had defective insulin secretion in vivo. Isolated islet studies identified impaired insulin secretion from beta cells, independent of changes in the abundance of neutral lipids previously implicated as amplification signals. Pancreatic morphometry unexpectedly revealed reduced beta cell size in βACC1KO mice but not in tmx-βACC1KO mice, with decreased levels of proteins involved in the mechanistic target of rapamycin kinase (mTOR)-dependent protein translation pathway underpinning this effect. CONCLUSIONS/INTERPRETATION Our study demonstrates that the beta cell ACC1-coupled pathway is critical for insulin secretion in vivo and ex vivo and that it is indispensable for glucose homeostasis. We further reveal a role for ACC1 in controlling beta cell growth prior to adulthood.
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Affiliation(s)
- James Cantley
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK.
| | - Aimee Davenport
- Diabetes and Obesity Research Program, Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
| | - Laurène Vetterli
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK
| | - Nandor J Nemes
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK
| | - P Tess Whitworth
- Diabetes and Obesity Research Program, Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
| | - Ebru Boslem
- Diabetes and Obesity Research Program, Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
| | - Le May Thai
- Diabetes and Obesity Research Program, Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
| | - Natalie Mellett
- Baker IDI Heart and Diabetes Institute, Melbourne, VIC, Australia
| | - Peter J Meikle
- Baker IDI Heart and Diabetes Institute, Melbourne, VIC, Australia
| | - Kyle L Hoehn
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
| | - David E James
- The Charles Perkins Centre, School of Molecular Biosciences, School of Medicine, University of Sydney, Sydney, NSW, Australia
| | - Trevor J Biden
- Diabetes and Obesity Research Program, Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
- St Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Darlinghurst, NSW, Australia
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17
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Petersen MC, Shulman GI. Mechanisms of Insulin Action and Insulin Resistance. Physiol Rev 2018; 98:2133-2223. [PMID: 30067154 PMCID: PMC6170977 DOI: 10.1152/physrev.00063.2017] [Citation(s) in RCA: 1700] [Impact Index Per Article: 242.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 03/22/2018] [Accepted: 03/24/2018] [Indexed: 12/15/2022] Open
Abstract
The 1921 discovery of insulin was a Big Bang from which a vast and expanding universe of research into insulin action and resistance has issued. In the intervening century, some discoveries have matured, coalescing into solid and fertile ground for clinical application; others remain incompletely investigated and scientifically controversial. Here, we attempt to synthesize this work to guide further mechanistic investigation and to inform the development of novel therapies for type 2 diabetes (T2D). The rational development of such therapies necessitates detailed knowledge of one of the key pathophysiological processes involved in T2D: insulin resistance. Understanding insulin resistance, in turn, requires knowledge of normal insulin action. In this review, both the physiology of insulin action and the pathophysiology of insulin resistance are described, focusing on three key insulin target tissues: skeletal muscle, liver, and white adipose tissue. We aim to develop an integrated physiological perspective, placing the intricate signaling effectors that carry out the cell-autonomous response to insulin in the context of the tissue-specific functions that generate the coordinated organismal response. First, in section II, the effectors and effects of direct, cell-autonomous insulin action in muscle, liver, and white adipose tissue are reviewed, beginning at the insulin receptor and working downstream. Section III considers the critical and underappreciated role of tissue crosstalk in whole body insulin action, especially the essential interaction between adipose lipolysis and hepatic gluconeogenesis. The pathophysiology of insulin resistance is then described in section IV. Special attention is given to which signaling pathways and functions become insulin resistant in the setting of chronic overnutrition, and an alternative explanation for the phenomenon of ‟selective hepatic insulin resistanceˮ is presented. Sections V, VI, and VII critically examine the evidence for and against several putative mediators of insulin resistance. Section V reviews work linking the bioactive lipids diacylglycerol, ceramide, and acylcarnitine to insulin resistance; section VI considers the impact of nutrient stresses in the endoplasmic reticulum and mitochondria on insulin resistance; and section VII discusses non-cell autonomous factors proposed to induce insulin resistance, including inflammatory mediators, branched-chain amino acids, adipokines, and hepatokines. Finally, in section VIII, we propose an integrated model of insulin resistance that links these mediators to final common pathways of metabolite-driven gluconeogenesis and ectopic lipid accumulation.
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Affiliation(s)
- Max C Petersen
- Departments of Internal Medicine and Cellular & Molecular Physiology, Howard Hughes Medical Institute, Yale University School of Medicine , New Haven, Connecticut
| | - Gerald I Shulman
- Departments of Internal Medicine and Cellular & Molecular Physiology, Howard Hughes Medical Institute, Yale University School of Medicine , New Haven, Connecticut
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18
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Metcalfe LK, Smith GC, Turner N. Defining lipid mediators of insulin resistance - controversies and challenges. J Mol Endocrinol 2018; 62:JME-18-0023. [PMID: 30068522 DOI: 10.1530/jme-18-0023] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 07/04/2018] [Accepted: 07/31/2018] [Indexed: 12/31/2022]
Abstract
Essential elements of all cells, lipids play important roles in energy production, signalling and as structural components. Despite these critical functions, excessive availability and intracellular accumulation of lipid is now recognised as a major factor contributing to many human diseases, including obesity and diabetes. In the context of these metabolic disorders, ectopic deposition of lipid has been proposed to have deleterious effects of insulin action. While this relationship has been recognised for some time now, there is currently no unifying mechanism to explain how lipids precipitate the development of insulin resistance. This review summarises the evidence linking specific lipid molecules to the induction of insulin resistance, describing some of the current controversies and challenges for future studies in this field.
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Affiliation(s)
- Louise K Metcalfe
- L Metcalfe, Department of Pharmacology, School of Medical Sciences, UNSW Australia, Kensington, Australia
| | - Greg C Smith
- G Smith, Department of Pharmacology, School of Medical Sciences, UNSW Australia, Kensington, Australia
| | - Nigel Turner
- N Turner, Department of Pharmacology, School of Medical Sciences, University of New South Wales, Sydney, Australia
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19
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mTORC2 Signaling: A Path for Pancreatic β Cell's Growth and Function. J Mol Biol 2018; 430:904-918. [PMID: 29481838 DOI: 10.1016/j.jmb.2018.02.013] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 02/14/2018] [Accepted: 02/14/2018] [Indexed: 12/16/2022]
Abstract
The mechanistic target of rapamycin (mTOR) signaling pathway is an evolutionary conserved pathway that senses signals from nutrients and growth factors to regulate cell growth, metabolism and survival. mTOR acts in two biochemically and functionally distinct complexes, mTOR complex 1 (mTORC1) and 2 (mTORC2), which differ in terms of regulatory mechanisms, substrate specificity and functional outputs. While mTORC1 signaling has been extensively studied in islet/β-cell biology, recent findings demonstrate a distinct role for mTORC2 in the regulation of pancreatic β-cell function and mass. mTORC2, a key component of the growth factor receptor signaling, is declined in β cells under diabetogenic conditions and in pancreatic islets from patients with type 2 diabetes. β cell-selective mTORC2 inactivation leads to glucose intolerance and acceleration of diabetes as a result of reduced β-cell mass, proliferation and impaired glucose-stimulated insulin secretion. Thereby, many mTORC2 targets, such as AKT, PKC, FOXO1, MST1 and cell cycle regulators, play an important role in β-cell survival and function. This indicates mTORC2 as important pathway for the maintenance of β-cell homeostasis, particularly to sustain proper β-cell compensatory response in the presence of nutrient overload and metabolic demand. This review summarizes recent emerging advances on the contribution of mTORC2 and its associated signaling on the regulation of glucose metabolism and functional β-cell mass under physiological and pathophysiological conditions in type 2 diabetes.
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20
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Chandrashekaran IR, Norton RS, Schmitz-Peiffer C. Characterisation of peptide interactions that regulate PKCε activation. FEBS Lett 2018; 592:179-189. [PMID: 29266266 DOI: 10.1002/1873-3468.12953] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 11/13/2017] [Accepted: 12/10/2017] [Indexed: 11/09/2022]
Abstract
Targeting the interaction between PKC isoforms and their anchoring proteins can specifically regulate kinase activity. εV1-2 and pseudoεRACK peptides, derived from the PKCε C2 domain, modulate its association with receptor for activated C-kinase 2 (RACK2) and thus its function. Details of these interactions remain obscure, and we therefore investigated binding of these peptides using biophysical techniques. Surface plasmon resonance (SPR) indicated that the inhibitory εV1-2 peptide bound to RACK2, and inhibited PKCε binding as expected. In contrast, SPR and NMR demonstrated that the activating pseudoεRACK peptide and related sequences did not bind to PKCε, indicating that their mechanisms of action do not involve binding to the kinase as previously proposed. Our results clarify which interactions could be targeted in developing new therapeutics that inhibit PKCε-RACK2 interaction.
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Affiliation(s)
- Indu R Chandrashekaran
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia
| | - Raymond S Norton
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia
| | - Carsten Schmitz-Peiffer
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, Darlinghurst, Australia.,St Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Sydney, Australia
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21
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Fleming AK, Storz P. Protein kinase C isoforms in the normal pancreas and in pancreatic disease. Cell Signal 2017; 40:1-9. [PMID: 28826907 DOI: 10.1016/j.cellsig.2017.08.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 08/17/2017] [Indexed: 12/16/2022]
Abstract
Protein Kinase C isoforms have been implicated in regulating multiple processes within the healthy pancreas. Moreover, their dysregulation contributes to all aspects of pancreatic disease. In this review, with a focus on acinar, ductal, and islet cells, we highlight the roles and contributions of the different PKC isoforms to normal pancreas function. We also discuss the contribution of PKC enzymes to pancreatic diseases, including insulin resistance and diabetes mellitus, as well as pancreatitis and the development and progression of pancreatic cancer.
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Affiliation(s)
- Alicia K Fleming
- Department of Cancer Biology, Mayo Clinic, Jacksonville, FL, USA
| | - Peter Storz
- Department of Cancer Biology, Mayo Clinic, Jacksonville, FL, USA.
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22
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Xie Y, Cui C, Nie A, Wang Y, Ni Q, Liu Y, Yin Q, Zhang H, Li Y, Wang Q, Gu Y, Ning G. The mTORC2/PKC pathway sustains compensatory insulin secretion of pancreatic β cells in response to metabolic stress. Biochim Biophys Acta Gen Subj 2017; 1861:2039-2047. [PMID: 28435021 DOI: 10.1016/j.bbagen.2017.04.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2016] [Revised: 03/31/2017] [Accepted: 04/18/2017] [Indexed: 12/24/2022]
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23
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Trexler AJ, Taraska JW. Regulation of insulin exocytosis by calcium-dependent protein kinase C in beta cells. Cell Calcium 2017; 67:1-10. [PMID: 29029784 DOI: 10.1016/j.ceca.2017.07.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Revised: 07/25/2017] [Accepted: 07/27/2017] [Indexed: 12/27/2022]
Abstract
The control of insulin release from pancreatic beta cells helps ensure proper blood glucose level, which is critical for human health. Protein kinase C has been shown to be one key control mechanism for this process. After glucose stimulation, calcium influx into beta cells triggers exocytosis of insulin-containing dense-core granules and activates protein kinase C via calcium-dependent phospholipase C-mediated generation of diacylglycerol. Activated protein kinase C potentiates insulin release by enhancing the calcium sensitivity of exocytosis, likely by affecting two main pathways that could be linked: (1) the reorganization of the cortical actin network, and (2) the direct phosphorylation of critical exocytotic proteins such as munc18, SNAP25, and synaptotagmin. Here, we review what is currently known about the molecular mechanisms of protein kinase C action on each of these pathways and how these effects relate to the control of insulin release by exocytosis. We identify remaining challenges in the field and suggest how these challenges might be addressed to advance our understanding of the regulation of insulin release in health and disease.
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Affiliation(s)
- Adam J Trexler
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States
| | - Justin W Taraska
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States.
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24
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Corydalis edulis Maxim. Promotes Insulin Secretion via the Activation of Protein Kinase Cs (PKCs) in Mice and Pancreatic β Cells. Sci Rep 2017; 7:40454. [PMID: 28091547 PMCID: PMC5238372 DOI: 10.1038/srep40454] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Accepted: 11/30/2016] [Indexed: 12/29/2022] Open
Abstract
Corydalis edulis Maxim., a widely grown plant in China, had been proposed for the treatment for type 2 diabetes mellitus. In this study, we found that C. edulis extract (CE) is protective against diabetes in mice. The treatment of hyperglycemic and hyperlipidemic apolipoprotein E (ApoE)−/− mice with a high dose of CE reduced serum glucose by 28.84% and serum total cholesterol by 17.34% and increased insulin release. We also found that CE significantly enhanced insulin secretion in a glucose-independent manner in hamster pancreatic β cell (HIT-T15). Further investigation revealed that CE stimulated insulin exocytosis by a protein kinase C (PKC)-dependent signaling pathway and that CE selectively activated novel protein kinase Cs (nPKCs) and atypical PKCs (aPKCs) but not conventional PKCs (cPKCs) in HIT-T15 cells. To the best of our knowledge, our study is the first to identify the PKC pathway as a direct target and one of the major mechanisms underlying the antidiabetic effect of CE. Given the good insulinotropic effect of this herbal medicine, CE is a promising agent for the development of new drugs for treating diabetes.
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25
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Kaneko YK, Ishikawa T. [Regulation of Lipid Metabolism by Diacylglycerol Kinases in Pancreatic β-cells]. YAKUGAKU ZASSHI 2017; 136:461-5. [PMID: 26935087 DOI: 10.1248/yakushi.15-00246-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The appropriate secretion of insulin from pancreatic β-cells is essential for regulating blood glucose levels. Glucose-stimulated insulin secretion (GSIS) involves the following steps: Glucose uptake by pancreatic β-cells is metabolized to produce ATP. Increased ATP levels result in the closure of ATP-sensitive K(+) (KATP) channels, resulting in membrane depolarization that activates voltage-dependent Ca(2+) channels to subsequently trigger insulin secretion. In addition to this primary mechanism through KATP channels, insulin secretion is regulated by cyclic AMP and diacylglycerol (DAG), which mediate the effects of receptor agonists such as GLP-1 and acetylcholine. Glucose by itself can also increase the levels of these second messengers. Recently, we have shown an obligatory role of diacylglycerol kinase (DGK), an enzyme catalyzing the conversion of DAG to phosphatidic acid, in GSIS. Of the 10 known DGK isoforms, we focused on type-I DGK isoforms (i.e., DGKα, DGKβ, and DGKγ), which are activated by Ca(2+). The protein expression of DGKα and DGKγ was detected in mouse pancreatic islets and the pancreatic β-cell line MIN6. Depletion of these DGKs by a specific inhibitor or siRNA decreased both [Ca(2+)]i and insulin secretion in MIN6 cells. Similar [Ca(2+)]i responses were induced by DiC8, a membrane-permeable DAG analog. These results suggest that DGKα and DGKγ play crucial roles in insulin secretion, and that their depletion impairs insulin secretion through DAG accumulation. In this article, we review the current understanding of the roles of DAG- and DGK-signaling in pancreatic β-cells, and discuss their pathophysiological roles in the progression of type-2 diabetes.
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Affiliation(s)
- Yukiko K Kaneko
- Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka
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26
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Santo-Domingo J, Chareyron I, Dayon L, Núñez Galindo A, Cominetti O, Pilar Giner Giménez M, De Marchi U, Canto C, Kussmann M, Wiederkehr A. Coordinated activation of mitochondrial respiration and exocytosis mediated by PKC signaling in pancreatic β cells. FASEB J 2016; 31:1028-1045. [PMID: 27927723 DOI: 10.1096/fj.201600837r] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Accepted: 11/22/2016] [Indexed: 12/17/2022]
Abstract
Mitochondria play a central role in pancreatic β-cell nutrient sensing by coupling their metabolism to plasma membrane excitability and insulin granule exocytosis. Whether non-nutrient secretagogues stimulate mitochondria as part of the molecular mechanism to promote insulin secretion is not known. Here, we show that PKC signaling, which is employed by many non-nutrient secretagogues, augments mitochondrial respiration in INS-1E (rat insulinoma cell line clone 1E) and human pancreatic β cells. The phorbol ester, phorbol 12-myristate 13-acetate, accelerates mitochondrial respiration at both resting and stimulatory glucose concentrations. A range of inhibitors of novel PKC isoforms prevent phorbol ester-induced respiration. Respiratory response was blocked by oligomycin that demonstrated PKC-dependent acceleration of mitochondrial ATP synthesis. Enhanced respiration was observed even when glycolysis was bypassed or fatty acid transport was blocked, which suggested that PKC regulates mitochondrial processes rather than upstream catabolic fluxes. A phosphoproteome study of phorbol ester-stimulated INS-1E cells maintained under resting (2.5 mM) glucose revealed a large number of phosphorylation sites that were altered during short-term activation of PKC signaling. The data set was enriched for proteins that are involved in gene expression, cytoskeleton remodeling, secretory vesicle transport, and exocytosis. Interactome analysis identified PKC, C-Raf, and ERK1/2 as the central phosphointeraction cluster. Prevention of ERK1/2 signaling by using a MEK1 inhibitor caused a marked decreased in phorbol 12-myristate 13-acetate-induced mitochondrial respiration. ERK1/2 signaling module therefore links PKC activation to downstream mitochondrial activation. We conclude that non-nutrient secretagogues act, in part, via PKC and downstream ERK1/2 signaling to stimulate mitochondrial energy production to compensate for energy expenditure that is linked to β-cell activation.-Santo-Domingo, J., Chareyron, I., Dayon, L., Galindo, A. N., Cominetti, O., Giménez, M. P. G., De Marchi, U., Canto, C., Kussmann, M., Wiederkehr, A. Coordinated activation of mitochondrial respiration and exocytosis mediated by PKC signaling in pancreatic β cells.
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Affiliation(s)
- Jaime Santo-Domingo
- Mitochondrial Function, Nestlé Institute of Health Sciences, Lausanne, Switzerland
| | - Isabelle Chareyron
- Mitochondrial Function, Nestlé Institute of Health Sciences, Lausanne, Switzerland
| | - Loïc Dayon
- Systems Nutrition, Metabonomics and Proteomics, Nestlé Institute of Health Sciences, Lausanne, Switzerland
| | - Antonio Núñez Galindo
- Systems Nutrition, Metabonomics and Proteomics, Nestlé Institute of Health Sciences, Lausanne, Switzerland
| | - Ornella Cominetti
- Systems Nutrition, Metabonomics and Proteomics, Nestlé Institute of Health Sciences, Lausanne, Switzerland
| | - María Pilar Giner Giménez
- Systems Nutrition, Metabonomics and Proteomics, Nestlé Institute of Health Sciences, Lausanne, Switzerland
| | - Umberto De Marchi
- Mitochondrial Function, Nestlé Institute of Health Sciences, Lausanne, Switzerland
| | - Carles Canto
- Diabetes and Metabolic Health, Nestlé Institute of Health Sciences, Lausanne, Switzerland
| | - Martin Kussmann
- Systems Nutrition, Metabonomics and Proteomics, Nestlé Institute of Health Sciences, Lausanne, Switzerland
| | - Andreas Wiederkehr
- Mitochondrial Function, Nestlé Institute of Health Sciences, Lausanne, Switzerland;
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27
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Wuttke A, Yu Q, Tengholm A. Autocrine Signaling Underlies Fast Repetitive Plasma Membrane Translocation of Conventional and Novel Protein Kinase C Isoforms in β Cells. J Biol Chem 2016; 291:14986-95. [PMID: 27226533 PMCID: PMC4946917 DOI: 10.1074/jbc.m115.698456] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Indexed: 01/08/2023] Open
Abstract
PKC signaling has been implicated in the regulation of many cell functions, including metabolism, cell death, proliferation, and secretion. Activation of conventional and novel PKC isoforms is associated with their Ca2+- and/or diacylglycerol (DAG)-dependent translocation to the plasma membrane. In β cells, exocytosis of insulin granules evokes brief (<10 s) local DAG elevations (“spiking”) at the plasma membrane because of autocrine activation of P2Y1 purinoceptors by ATP co-released with insulin. Using total internal reflection microscopy, fluorescent protein-tagged PKCs, and signaling biosensors, we investigated whether DAG spiking causes membrane recruitment of PKCs and whether different classes of PKCs show characteristic responses. Glucose stimulation of MIN6 cells triggered DAG spiking with concomitant repetitive translocation of the novel isoforms PKCδ, PKCϵ, and PKCη. The conventional PKCα, PKCβI, and PKCβII isoforms showed a more complex pattern with both rapid and slow translocation. K+ depolarization-induced PKCϵ translocation entirely mirrored DAG spiking, whereas PKCβI translocation showed a sustained component, reflecting the subplasma membrane Ca2+ concentration ([Ca2+]pm), with additional effect during DAG spikes. Interference with DAG spiking by purinoceptor inhibition prevented intermittent translocation of PKCs and reduced insulin secretion but did not affect [Ca2+]pm elevation or sustained PKCβI translocation. The muscarinic agonist carbachol induced pronounced transient PKCβI translocation and sustained recruitment of PKCϵ. When rise of [Ca2+]pm was prevented, the carbachol-induced DAG and PKCϵ responses were somewhat reduced, but PKCβI translocation was completely abolished. We conclude that exocytosis-induced DAG spikes efficiently recruit both conventional and novel PKCs to the β cell plasma membrane. PKC signaling is thus implicated in autocrine regulation of β cell function.
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Affiliation(s)
- Anne Wuttke
- From the Department of Medical Cell Biology, Uppsala University, Biomedical Centre, Box 571, 75123 Uppsala, Sweden
| | - Qian Yu
- From the Department of Medical Cell Biology, Uppsala University, Biomedical Centre, Box 571, 75123 Uppsala, Sweden
| | - Anders Tengholm
- From the Department of Medical Cell Biology, Uppsala University, Biomedical Centre, Box 571, 75123 Uppsala, Sweden
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28
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Seed Ahmed M, Ahmed MS, Pelletier J, Leumann H, Gu HF, Östenson CG. Expression of Protein Kinase C Isoforms in Pancreatic Islets and Liver of Male Goto-Kakizaki Rats, a Model of Type 2 Diabetes. PLoS One 2015; 10:e0135781. [PMID: 26398746 PMCID: PMC4580567 DOI: 10.1371/journal.pone.0135781] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Accepted: 07/27/2015] [Indexed: 02/03/2023] Open
Abstract
Protein kinase C (PKC) is a family of protein kinases controlling protein phosphorylation and playing important roles in the regulation of metabolism. We have investigated expression levels of PKC isoforms in pancreatic islets and liver of diabetic Goto-Kakizaki (GK) rats with and without insulin treatment to evaluate their association with glucose homeostasis. mRNA and protein expression levels of PKC isoforms were assessed in pancreatic islets and liver of Wistar rats and GK rats with or without insulin treatment. PKCα and PKCζ mRNA expressions were down-regulated in islets of GK compared with Wistar rats. PKCα and phosphorylated PKCα (p-PKCα) protein expressions were decreased in islets of GK compared with insulin-treated GK and Wistar rats. PKCζ protein expression in islets was reduced in GK and insulin-treated GK compared with Wistar rats, but p-PKCζ was decreased only in GK rats. Islet PKCε mRNA and protein expressions were lower in GK compared with insulin-treated GK and Wistar rats. In liver, PKCδ and PKCζ mRNA expressions were decreased in both GK and insulin-treated GK compared with Wistar rats. Hepatic PKCζ protein expression was diminished in both GK rats with and without insulin treatment compared with Wistar rats. Hepatic PKCε mRNA expression was down-regulated in insulin-treated GK compared with GK and Wistar rats. PKCα, PKCε, and p-PKCζ expressions were secondary to hyperglycaemia in GK rat islets. Hepatic PKCδ and PKCζ mRNA expressions were primarily linked to hyperglycaemia. Additionally, hepatic PKCε mRNA expression could be under control of insulin.
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Affiliation(s)
- Mohammed Seed Ahmed
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, Solna, Stockholm, Sweden; Department of Physiology, Faculty of Medicine, University of Khartoum, Khartoum, Sudan
| | | | - Julien Pelletier
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, Solna, Stockholm, Sweden
| | - Hannes Leumann
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, Solna, Stockholm, Sweden
| | - Harvest F Gu
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, Solna, Stockholm, Sweden
| | - Claes-Göran Östenson
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, Solna, Stockholm, Sweden
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29
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Cai Y, Lydic TA, Turkette T, Reid GE, Olson LK. Impact of alogliptin and pioglitazone on lipid metabolism in islets of prediabetic and diabetic Zucker Diabetic Fatty rats. Biochem Pharmacol 2015; 95:46-57. [PMID: 25801003 DOI: 10.1016/j.bcp.2015.03.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 03/13/2015] [Indexed: 12/30/2022]
Abstract
Prolonged exposure of pancreatic beta (β) cells to elevated glucose and free fatty acids (FFA) as occurs in type 2 diabetes results in loss of β cell function and survival. In Zucker Diabetic Fatty (ZDF) rats, β cell failure is associated with increased triacylglyceride (TAG) synthesis and disruption of the glycerolipid/FFA (GL/FFA) cycle, a critical arm of glucose-stimulated insulin secretion (GSIS). The aim of this study was to determine the impact of activation of PPARγ and increased incretin action via dipeptidyl-peptidase inhibition using pioglitazone and/or alogliptin, respectively, on islet lipid metabolism in prediabetic and diabetic ZDF rats. Transition of control prediabetic ZDF rats to diabetes was associated with reduced plasma insulin levels, reduced islet insulin content and GSIS, reduced stearoyl-CoA desaturase 2 (SCD 2) expression, and increased islet TAG, diacylglyceride (DAG) and ceramides species containing saturated FA. Treatment of prediabetic ZDF rats with a combination of pioglitazone and alogliptin, but not individually, prevented the transition to diabetes and was associated with marked lowering of islet TAG and DAG levels. Pioglitazone and alogliptin, however, did not restore SCD2 expression, the degree of FA saturation in TAG, DAG or ceramides, islet insulin content, or lower ceramide levels. These findings are consistent with activation of PPARγ and increased incretin action working in concert to restore GL/FFA cycle in β cells of ZDF rats. Restoration of the GL/FFA cycle without correcting islet FA desaturation, production of islet ceramides, and/or insulin sensitivity, however, may place these islets at risk for β cell failure.
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Affiliation(s)
- Ying Cai
- Department of Physiology, Michigan State University, East Lansing, MI 48824, USA.
| | - Todd A Lydic
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA.
| | - Thomas Turkette
- Department of Physiology, Michigan State University, East Lansing, MI 48824, USA.
| | - Gavin E Reid
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA; Department of Chemistry, Michigan State University, East Lansing, MI 48824 USA.
| | - L Karl Olson
- Department of Physiology, Michigan State University, East Lansing, MI 48824, USA.
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30
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Morampudi V, Conlin VS, Dalwadi U, Wu X, Marshall KC, Nguyen C, Vallance BA, Jacobson K. Vasoactive intestinal peptide prevents PKCε-induced intestinal epithelial barrier disruption during EPEC infection. Am J Physiol Gastrointest Liver Physiol 2015; 308:G389-402. [PMID: 25501546 DOI: 10.1152/ajpgi.00195.2014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We previously showed that vasoactive intestinal peptide (VIP) protects against bacterial pathogen-induced epithelial barrier disruption and colitis, although the mechanisms remain poorly defined. The aim of the current study was to identify cellular pathways of VIP-mediated protection with use of pharmacological inhibitors during enteropathogenic Escherichia coli (EPEC) infection of Caco-2 cell monolayers and during Citrobacter rodentium-induced colitis. EPEC-induced epithelial barrier disruption involved the PKC pathway but was independent of functional cAMP, Rho, and NF-κB pathways. VIP mediated its protective effects by inhibiting EPEC-induced PKC activity and increasing expression of the junctional protein claudin-4. Short-term treatment with TPA, which is known to activate PKC, was inhibited by VIP pretreatment, while PKC degradation via long-term treatment with TPA mimicked the protective actions of VIP. Immunostaining for specific PKC isotypes showed upregulated expression of PKCθ and PKCε during EPEC infection. Treatment with specific inhibitors revealed a critical role for PKCε in EPEC-induced barrier disruption. Furthermore, activation of PKCε and loss of barrier integrity correlated with claudin-4 degradation. In contrast, inhibition of PKCε by VIP pretreatment or the PKCε inhibitor maintained membrane-bound claudin-4 levels, along with barrier function. Finally, in vivo treatment with the PKCε inhibitor protected mice from C. rodentium-induced colitis. In conclusion, EPEC infection increases intracellular PKCε levels, leading to decreased claudin-4 levels and compromising epithelial barrier integrity. VIP inhibits PKCε activation, thereby attenuating EPEC-induced barrier disruption.
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Affiliation(s)
- V Morampudi
- Child and Family Research Institute, British Columbia Children's Hospital, Vancouver, British Columbia, Canada; Division of Gastroenterology, British Columbia Children's Hospital, Vancouver, British Columbia, Canada; and
| | - V S Conlin
- Child and Family Research Institute, British Columbia Children's Hospital, Vancouver, British Columbia, Canada; Division of Gastroenterology, British Columbia Children's Hospital, Vancouver, British Columbia, Canada; and
| | - U Dalwadi
- Child and Family Research Institute, British Columbia Children's Hospital, Vancouver, British Columbia, Canada; Division of Gastroenterology, British Columbia Children's Hospital, Vancouver, British Columbia, Canada; and
| | - X Wu
- Child and Family Research Institute, British Columbia Children's Hospital, Vancouver, British Columbia, Canada; Division of Gastroenterology, British Columbia Children's Hospital, Vancouver, British Columbia, Canada; and
| | - K C Marshall
- Child and Family Research Institute, British Columbia Children's Hospital, Vancouver, British Columbia, Canada; Division of Gastroenterology, British Columbia Children's Hospital, Vancouver, British Columbia, Canada; and
| | - C Nguyen
- Child and Family Research Institute, British Columbia Children's Hospital, Vancouver, British Columbia, Canada; Division of Gastroenterology, British Columbia Children's Hospital, Vancouver, British Columbia, Canada; and
| | - B A Vallance
- Child and Family Research Institute, British Columbia Children's Hospital, Vancouver, British Columbia, Canada; Division of Gastroenterology, British Columbia Children's Hospital, Vancouver, British Columbia, Canada; and
| | - K Jacobson
- Child and Family Research Institute, British Columbia Children's Hospital, Vancouver, British Columbia, Canada; Division of Gastroenterology, British Columbia Children's Hospital, Vancouver, British Columbia, Canada; and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
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31
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Kaneko YK, Ishikawa T. Diacylglycerol Signaling Pathway in Pancreatic β-Cells: An Essential Role of Diacylglycerol Kinase in the Regulation of Insulin Secretion. Biol Pharm Bull 2015; 38:669-73. [DOI: 10.1248/bpb.b15-00060] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Yukiko K. Kaneko
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, University of Shizuoka
| | - Tomohisa Ishikawa
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, University of Shizuoka
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32
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Soni MS, Rabaglia ME, Bhatnagar S, Shang J, Ilkayeva O, Mynatt R, Zhou YP, Schadt EE, Thornberry NA, Muoio DM, Keller MP, Attie AD. Downregulation of carnitine acyl-carnitine translocase by miRNAs 132 and 212 amplifies glucose-stimulated insulin secretion. Diabetes 2014; 63:3805-14. [PMID: 24969106 PMCID: PMC4207388 DOI: 10.2337/db13-1677] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We previously demonstrated that micro-RNAs (miRNAs) 132 and 212 are differentially upregulated in response to obesity in two mouse strains that differ in their susceptibility to obesity-induced diabetes. Here we show the overexpression of miRNAs 132 and 212 enhances insulin secretion (IS) in response to glucose and other secretagogues including nonfuel stimuli. We determined that carnitine acyl-carnitine translocase (CACT; Slc25a20) is a direct target of these miRNAs. CACT is responsible for transporting long-chain acyl-carnitines into the mitochondria for β-oxidation. Small interfering RNA-mediated knockdown of CACT in β-cells led to the accumulation of fatty acyl-carnitines and enhanced IS. The addition of long-chain fatty acyl-carnitines promoted IS from rat insulinoma β-cells (INS-1) as well as primary mouse islets. The effect on INS-1 cells was augmented in response to suppression of CACT. A nonhydrolyzable ether analog of palmitoyl-carnitine stimulated IS, showing that β-oxidation of palmitoyl-carnitine is not required for its stimulation of IS. These studies establish a link between miRNA-dependent regulation of CACT and fatty acyl-carnitine-mediated regulation of IS.
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Affiliation(s)
- Mufaddal S Soni
- Department of Biochemistry, University of Wisconsin, Madison, WI
| | - Mary E Rabaglia
- Department of Biochemistry, University of Wisconsin, Madison, WI
| | | | - Jin Shang
- Department of Metabolic Disorders-Diabetes, Merck Research Laboratories, Rahway, NJ
| | - Olga Ilkayeva
- Sarah W. Stedman Nutrition and Metabolism Center, Department of Medicine, Duke University, Durham, NC
| | - Randall Mynatt
- Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, LA
| | - Yun-Ping Zhou
- Department of Metabolic Disorders-Diabetes, Merck Research Laboratories, Rahway, NJ
| | - Eric E Schadt
- Institute for Genomics and Multiscale Biology, Mount Sinai School of Medicine, New York, NY
| | - Nancy A Thornberry
- Department of Metabolic Disorders-Diabetes, Merck Research Laboratories, Rahway, NJ
| | - Deborah M Muoio
- Sarah W. Stedman Nutrition and Metabolism Center, Department of Medicine, Duke University, Durham, NC Departments of Medicine and Pharmacology and Cancer Biology, Duke University, Durham, NC
| | - Mark P Keller
- Department of Biochemistry, University of Wisconsin, Madison, WI
| | - Alan D Attie
- Department of Biochemistry, University of Wisconsin, Madison, WI
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33
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Liao BM, Raddatz K, Zhong L, Parker BL, Raftery MJ, Schmitz-Peiffer C. Proteomic analysis of livers from fat-fed mice deficient in either PKCδ or PKCε identifies Htatip2 as a regulator of lipid metabolism. Proteomics 2014; 14:2578-87. [PMID: 25175814 DOI: 10.1002/pmic.201400202] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Revised: 08/13/2014] [Accepted: 08/27/2014] [Indexed: 11/08/2022]
Abstract
Insulin resistance contributes to the development of Type 2 diabetes, and is associated with lipid oversupply. Deletion of isoforms of the lipid-activated protein kinase C (PKC) family, PKCδ or PKCε, improves insulin action in fat-fed mice, but differentially affects hepatic lipid metabolism. To investigate the mechanisms involved, we employed an in vivo adaptation of SILAC to examine the effects of a fat diet together with deletion of PKCδ or PKCε on the expression of liver proteins. We identified a total of 3359 and 3488 proteins from the PKCδ and PKCε knockout study groups, respectively, and showed that several enzymes of lipid metabolism were affected by the fat diet. In fat-fed mice, 23 proteins showed changes upon PKCδ deletion while 19 proteins were affected by PKCε deletion. Enzymes of retinol metabolism were affected by the absence of either PKC. Pathway analysis indicated that monosaccharide metabolism was affected only upon PKCδ deletion, while isoprenoid biosynthesis was affected in a PKCε-specific manner. Certain proteins were regulated inversely, including HIV-1 tat interactive protein 2 (Htatip2). Overexpression or knockdown of Htatip2 in hepatocytes affected fatty acid storage and oxidation, consistent with a novel role in mediating the differential effects of PKC isoforms on lipid metabolism. All MS data have been deposited in the ProteomeXchange with identifier PXD000971 (http://proteomecentral.proteomexchange.org/dataset/PXD000971).
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Affiliation(s)
- Bing M Liao
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
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Greene MW, Burrington CM, Luo Y, Ruhoff MS, Lynch DT, Chaithongdi N. PKCδ is activated in the liver of obese Zucker rats and mediates diet-induced whole body insulin resistance and hepatocyte cellular insulin resistance. J Nutr Biochem 2013; 25:281-8. [PMID: 24524901 DOI: 10.1016/j.jnutbio.2013.10.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Revised: 09/06/2013] [Accepted: 10/08/2013] [Indexed: 02/06/2023]
Abstract
Insulin resistance can arise when pathological levels of free fatty acids (FFAs) and proinflammatory cytokines disrupt insulin signaling. Protein kinase C delta (PKCδ) is a FFA- and a proinflammatory cytokine-regulated protein kinase that is associated with inhibition of insulin signaling and action. To gain insight into the role of PKCδ in insulin resistance, PKCδ activation was studied in a genetic model of obesity-linked insulin resistance. PKCδ was found to be activated in the liver of obese insulin-resistant Zucker rats and in isolated cultured hepatocytes. PKCδ was further studied in PKCδ-null mice and their wild-type littermates fed a high-fat or control diet for 10 weeks. PKCδ-null mice on a high-fat diet had improved insulin sensitivity and hepatic insulin signaling compared to wild-type littermates. Additionally, the deleterious effect of a high-fat diet on glucose tolerance in wild-type mice was completely blocked in PKCδ-null mice. To directly test the role of PKCδ in cellular insulin resistance, primary hepatocytes from the high-fat diet mice were isolated and stimulated with insulin. Primary hepatocytes from PKCδ-null mice had improved insulin-stimulated Akt and FOXO phosphorylation compared to hepatocytes from wild-type littermates. Consistent with this result, tumor necrosis factor alpha-mediated inhibition of insulin signaling was blocked in PKCδ knockdown primary hepatocytes. These results indicate that PKCδ plays a role in insulin resistance and is consistent with the hypothesis that PKCδ is a negative regulator of insulin signaling and thus may be a therapeutic target for the treatment of type 2 diabetes.
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Affiliation(s)
- Michael W Greene
- Boshell Metabolic Diseases and Diabetes Program, Auburn University, Auburn, AL 36849, USA; College of Human Sciences, Auburn University, Auburn, AL 36849, USA; Bassett Research Institute, Bassett Healthcare Network, Cooperstown, NY, USA.
| | | | - Yuwen Luo
- College of Human Sciences, Auburn University, Auburn, AL 36849, USA
| | - Mary S Ruhoff
- Bassett Research Institute, Bassett Healthcare Network, Cooperstown, NY, USA
| | - Darin T Lynch
- Bassett Research Institute, Bassett Healthcare Network, Cooperstown, NY, USA
| | - Niyutchai Chaithongdi
- Department of Internal Medicine, Bassett Medical Center, Bassett Healthcare Network, Cooperstown, NY, USA
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Guebre-Egziabher F, Alix PM, Koppe L, Pelletier CC, Kalbacher E, Fouque D, Soulage CO. Ectopic lipid accumulation: A potential cause for metabolic disturbances and a contributor to the alteration of kidney function. Biochimie 2013; 95:1971-9. [PMID: 23896376 DOI: 10.1016/j.biochi.2013.07.017] [Citation(s) in RCA: 121] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 07/18/2013] [Indexed: 01/06/2023]
Abstract
Ectopic lipid accumulation is now known to be a mechanism that contributes to organ injury in the context of metabolic diseases. In muscle and liver, accumulation of lipids impairs insulin signaling. This hypothesis accounts for the mechanism of insulin resistance in obesity, type 2 diabetes, aging and lipodystrophy. Increasing data suggest that lipid accumulation in the kidneys could also contribute to the alteration of kidney function in the context of metabolic syndrome and obesity. Furthermore and more unexpectedly, animal models of kidney disease exhibit a decreased adiposity and ectopic lipid redistribution suggesting that kidney disease may be a state of lipodystrophy. However, whether this abnormal lipid partitioning during chronic kidney disease (CKD) may have any functional impact in these tissues needs to be investigated. Here, we provide a perspective by defining the problem and analyzing the possible causes and consequences. Further human studies are required to strengthen these observations, and provide novel therapeutic approaches.
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Affiliation(s)
- Fitsum Guebre-Egziabher
- Université de Lyon, INSERM U1060, CarMeN, INSA de Lyon, Univ Lyon-1, F-69621 Villeurbanne, France; Hospices Civils de Lyon, Department of Nephrology, Hôpital E Herriot, Lyon F-69003, France.
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Iismaa SE, Aplin M, Holman S, Yiu TW, Jackson K, Burchfield JG, Mitchell CJ, O’Reilly L, Davenport A, Cantley J, Schmitz-Peiffer C, Biden TJ, Cooney GJ, Graham RM. Glucose homeostasis in mice is transglutaminase 2 independent. PLoS One 2013; 8:e63346. [PMID: 23717413 PMCID: PMC3661676 DOI: 10.1371/journal.pone.0063346] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Accepted: 03/29/2013] [Indexed: 11/18/2022] Open
Abstract
Transglutaminase type 2 (TG2) has been reported to be a candidate gene for maturity onset diabetes of the young (MODY) because three different mutations that impair TG2 transamidase activity have been found in 3 families with MODY. TG2 null (TG2−/−) mice have been reported to be glucose intolerant and have impaired glucose-stimulated insulin secretion (GSIS). Here we rigorously evaluated the role of TG2 in glucose metabolism using independently generated murine models of genetic TG2 disruption, which show no compensatory enhanced expression of other TGs in pancreatic islets or other tissues. First, we subjected chow- or fat-fed congenic SV129 or C57BL/6 wild type (WT) and TG2−/− littermates, to oral glucose gavage. Blood glucose and serum insulin levels were similar for both genotypes. Pancreatic islets isolated from these animals and analysed in vitro for GSIS and cholinergic potentiation of GSIS, showed no significant difference between genotypes. Results from intraperitoneal glucose tolerance tests (GTTs) and insulin tolerance tests (ITTs) were similar for both genotypes. Second, we directly investigated the role of TG2 transamidase activity in insulin secretion using a coisogenic model that expresses a mutant form of TG2 (TG2R579A), which is constitutively active for transamidase activity. Intraperitoneal GTTs and ITTs revealed no significant differences between WT and TG2R579A/R579A mice. Given that neither deletion nor constitutive activation of TG2 transamidase activity altered basal responses, or responses to a glucose or insulin challenge, our data indicate that glucose homeostasis in mice is TG2 independent, and question a link between TG2 and diabetes.
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Affiliation(s)
- Siiri E. Iismaa
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia
- University of New South Wales, Sydney, New South Wales, Australia
- * E-mail: (SEI); (RMG)
| | - Mark Aplin
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia
| | - Sara Holman
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia
| | - Ting W. Yiu
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia
- University of New South Wales, Sydney, New South Wales, Australia
| | - Kristy Jackson
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia
| | - James G. Burchfield
- Diabetes and Obesity Division, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Christopher J. Mitchell
- Diabetes and Obesity Division, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Liam O’Reilly
- Diabetes and Obesity Division, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Aimee Davenport
- Diabetes and Obesity Division, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - James Cantley
- Diabetes and Obesity Division, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Carsten Schmitz-Peiffer
- Diabetes and Obesity Division, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Trevor J. Biden
- Diabetes and Obesity Division, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Gregory J. Cooney
- Diabetes and Obesity Division, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Robert M. Graham
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia
- University of New South Wales, Sydney, New South Wales, Australia
- * E-mail: (SEI); (RMG)
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Schmitz-Peiffer C. The tail wagging the dog--regulation of lipid metabolism by protein kinase C. FEBS J 2013; 280:5371-83. [PMID: 23587021 DOI: 10.1111/febs.12285] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2013] [Revised: 03/19/2013] [Accepted: 04/11/2013] [Indexed: 12/12/2022]
Abstract
Upon their discovery almost 40 years ago, isoforms of the lipid-activated protein kinase C (PKC) family were initially regarded only as downstream effectors of the second messengers calcium and diacylglycerol, undergoing activation upon phospholipid hydrolysis in response to acute stimuli. Subsequently, several isoforms were found to be associated with the inhibitory effects of lipid over-supply on glucose homeostasis, especially the negative cross-talk with insulin signal transduction, observed upon accumulation of diacylglycerol in insulin target tissues. The PKC family has therefore attracted much attention in diabetes and obesity research, because intracellular lipid accumulation is strongly correlated with defective insulin action and the development of type 2 diabetes. Causal roles for various isoforms in the generation of insulin resistance have more recently been confirmed using PKC-deficient mice. However, during characterization of these animals, it became increasingly evident that the enzymes play key roles in the modulation of lipid metabolism itself, and may control the supply of lipids between tissues such as adipose and liver. Molecular studies have also demonstrated roles for PKC isoforms in several aspects of lipid metabolism, such as adipocyte differentiation and hepatic lipogenesis. While the precise mechanisms involved, especially the identities of protein substrates, are still unclear, the emerging picture suggests that the currently held view of the contribution of PKC isoforms to metabolism is an over-simplification. Although PKCs may inhibit insulin signal transduction, these enzymes are not merely downstream effectors of lipid accumulation, but in fact control the fate of fatty acids, thus the tail wags the dog.
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Affiliation(s)
- Carsten Schmitz-Peiffer
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, NSW, Australia; St Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
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Carracedo S, Braun U, Leitges M. Expression pattern of protein kinase C ϵ during mouse embryogenesis. BMC DEVELOPMENTAL BIOLOGY 2013; 13:16. [PMID: 23639204 PMCID: PMC3668281 DOI: 10.1186/1471-213x-13-16] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Accepted: 04/24/2013] [Indexed: 12/29/2022]
Abstract
BACKGROUND Protein kinase C epsilon (PKCϵ) belongs to the novel PKC subfamily, which consists of diacylglycerol dependent- and calcium independent-PKCs. Previous studies have shown that PKCϵ is important in different contexts, such as wound healing or cancer. In this study, we contribute to expand the knowledge on PKCϵ by reporting its expression pattern during murine midgestation using the LacZ reporter gene and immunostaining procedures. RESULTS Sites showing highest PKCϵ expression were heart at ealier stages, and ganglia in older embryos. Other stained domains included somites, bone, stomach, kidney, and blood vessels. CONCLUSIONS The seemingly strong expression of PKCϵ in heart and ganglia shown in this study suggests a important role of this isoform in the vascular and nervous systems during mouse development. However, functional redundancy with other PKCs during midgestation within these domains and others reported here possibly exists since PKCϵ deficient mice do not display obvious embryonic developmental defects.
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Affiliation(s)
- Sergio Carracedo
- Biotechnology Centre of Oslo, University of Oslo, Gaustadalleen 21, Oslo, N-0349, Norway.
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Pedersen DJ, Diakanastasis B, Stöckli J, Schmitz-Peiffer C. Protein kinase Cε modulates insulin receptor localization and trafficking in mouse embryonic fibroblasts. PLoS One 2013; 8:e58046. [PMID: 23469261 PMCID: PMC3585804 DOI: 10.1371/journal.pone.0058046] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 01/30/2013] [Indexed: 12/03/2022] Open
Abstract
We have previously shown that deletion of protein kinase C epsilon (PKCε) in mice results in protection against glucose intolerance caused by a high fat diet. This was in part due to reduced insulin uptake by hepatocytes and insulin clearance, which enhanced insulin availability. Here we employed mouse embryonic fibroblasts (MEFs) derived from wildtype (WT) and PKCε-deficient (PKCε−/−) mice to examine this mechanistically. PKCε−/− MEFs exhibited reduced insulin uptake which was associated with decreased insulin receptor phosphorylation, while downstream signalling through IRS-1 and Akt was unaffected. Cellular fractionation demonstrated that PKCε deletion changed the localization of the insulin receptor, a greater proportion of which co-fractionated with flotillin-1, a marker of membrane microdomains. Insulin stimulation resulted in redistribution of the receptor in WT cells, while this was markedly reduced in PKCε−/− cells. These alterations in insulin receptor trafficking were associated with reduced expression of CEACAM1, a receptor substrate previously shown to modulate insulin clearance. Virally-mediated reconstitution of PKCε in MEFs increased CEACAM1 expression and partly restored the sensitivity of the receptor to insulin-stimulated redistribution. These data indicate that PKCε can affect insulin uptake in MEFs through promotion of receptor-mediated endocytosis, and that this may be mediated by regulation of CEACAM1 expression.
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Affiliation(s)
- David J. Pedersen
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Barbara Diakanastasis
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Jacqueline Stöckli
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
- St Vincent’s Clinical School, Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia
| | - Carsten Schmitz-Peiffer
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
- St Vincent’s Clinical School, Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia
- * E-mail:
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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: 43] [Impact Index Per Article: 3.6] [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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41
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Peterson TA, Stamnes M. ARF1-regulated coatomer directs the steady-state localization of protein kinase C epsilon at the Golgi apparatus. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012. [PMID: 23195223 DOI: 10.1016/j.bbamcr.2012.11.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Protein kinase C epsilon (PKCε) contributes to multiple signaling pathways affecting human disease. The function of PKCε requires it to undergo changes in subcellular distribution in response to signaling events. While the mechanisms underlying this translocation are incompletely understood, it involves the receptor for activated C kinase protein (RACK2/β'-COP). This receptor also functions as a vesicle coat protein in the secretory pathway where it is regulated by the small GTP-binding protein ADP-ribosylation factor, ARF1. We inhibited ARF1 activation to test the requirement for RACK2/β'-COP in PKCε localization in NIH3T3 fibroblasts. We found that steady-state localization of PKCε at the Golgi complex requires ARF1-regulated RACK2/β'-COP function. By contrast, we did not observe any defects in phorbol ester-induced translocation when ARF1 was inhibited. We also found that PKCε bound to isolated membranes through two distinct mechanisms. One mechanism was dependent upon RACK2/β'-COP while a second was RACK2/β'-COP-independent and stimulated by phorbol esters. Finally, we show that RACK2/β'-COP affects the subcellular distribution of a constitutively active form of PKCε, in a manner similar to what we observed for wild-type PKCε. Together, our data support a role for RACK2/β'-COP in the steady-state localization of PKCε at the Golgi apparatus, which may be independent of its role during PKCε translocation to the cell surface.
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Affiliation(s)
- Tabitha A Peterson
- Department of Molecular Physiology & Biophysics, Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, IA 52242, USA
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Bensellam M, Laybutt DR, Jonas JC. The molecular mechanisms of pancreatic β-cell glucotoxicity: recent findings and future research directions. Mol Cell Endocrinol 2012; 364:1-27. [PMID: 22885162 DOI: 10.1016/j.mce.2012.08.003] [Citation(s) in RCA: 219] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 07/11/2012] [Accepted: 08/01/2012] [Indexed: 02/06/2023]
Abstract
It is well established that regular physiological stimulation by glucose plays a crucial role in the maintenance of the β-cell differentiated phenotype. In contrast, prolonged or repeated exposure to elevated glucose concentrations both in vitro and in vivo exerts deleterious or toxic effects on the β-cell phenotype, a concept termed as glucotoxicity. Evidence indicates that the latter may greatly contribute to the pathogenesis of type 2 diabetes. Through the activation of several mechanisms and signaling pathways, high glucose levels exert deleterious effects on β-cell function and survival and thereby, lead to the worsening of the disease over time. While the role of high glucose-induced β-cell overstimulation, oxidative stress, excessive Unfolded Protein Response (UPR) activation, and loss of differentiation in the alteration of the β-cell phenotype is well ascertained, at least in vitro and in animal models of type 2 diabetes, the role of other mechanisms such as inflammation, O-GlcNacylation, PKC activation, and amyloidogenesis requires further confirmation. On the other hand, protein glycation is an emerging mechanism that may play an important role in the glucotoxic deterioration of the β-cell phenotype. Finally, our recent evidence suggests that hypoxia may also be a new mechanism of β-cell glucotoxicity. Deciphering these molecular mechanisms of β-cell glucotoxicity is a mandatory first step toward the development of therapeutic strategies to protect β-cells and improve the functional β-cell mass in type 2 diabetes.
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Affiliation(s)
- Mohammed Bensellam
- Université catholique de Louvain, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Brussels, Belgium
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Raddatz K, Frangioudakis G, Diakanastasis B, Liao BM, Leitges M, Schmitz-Peiffer C. Deletion of protein kinase Cε in mice has limited effects on liver metabolite levels but alters fasting ketogenesis and gluconeogenesis. Diabetologia 2012; 55:2789-2793. [PMID: 22814763 DOI: 10.1007/s00125-012-2647-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Accepted: 06/18/2012] [Indexed: 11/26/2022]
Abstract
AIMS/HYPOTHESIS Protein kinase Cε (PKCε) is emerging as a key mediator of lipid-induced insulin resistance in liver and hepatic lipid metabolism itself. We investigated whether PKCε plays a role in other metabolic processes, to further examine its suitability as a therapeutic target. METHODS We measured amino acid, organic acid and sugar levels by liquid and gas chromatography-mass spectrometry of liver extracts from chow and fat-fed wild-type (WT) and PKCε-deficient (Prkce(-/-)) mice. Fed and fasting glucose, ketone and fatty acid levels were measured in blood. Triacylglycerol levels and gluconeogenic and ketogenic enzyme expression were measured in liver. The effect of fasting on epididymal fat pad mass was also determined. RESULTS Metabolomic analysis indicated that the short-term high-fat diet affected over 20 compounds, including a 50% reduction in the glucogenic amino acid alanine. Prkce deletion resulted only in a reduction of 4-hydroxyproline and aspartate and an increase in glutamate. However, upon fasting, Prkce(-/-) mice were better able to maintain blood glucose levels and also exhibited lower levels of the ketone β-hydroxybutyrate compared with WT mice. Upon fasting, Prkce deletion also resulted in lower liver and plasma lipids and a smaller reduction in fat pad mass. CONCLUSIONS/INTERPRETATION Metabolomic analysis provided new insights into the effects of a high-fat diet on liver metabolite levels. Glucose homeostasis under fasting conditions is improved in Prkce(-/-) mice, which, in turn, may reduce the mobilisation of lipid from adipose tissue, reducing the availability of ketogenic substrate in the liver. Together with the protection against fat-diet-induced glucose intolerance previously observed in the fed state, these findings indicate PKCε as a unique therapeutic target for the improvement of glucose homeostasis.
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Affiliation(s)
- K Raddatz
- Diabetes and Obesity Program, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, NSW, 2010, Australia
- Competence Centre Functional Genomics-Pathoproteomics, University of Greifswald, Greifswald, Germany
| | - G Frangioudakis
- Diabetes and Obesity Program, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, NSW, 2010, Australia
- School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - B Diakanastasis
- Diabetes and Obesity Program, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, NSW, 2010, Australia
| | - B M Liao
- Diabetes and Obesity Program, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, NSW, 2010, Australia
| | - M Leitges
- Biotechnology Centre of Oslo, University of Oslo, Oslo, Norway
| | - C Schmitz-Peiffer
- Diabetes and Obesity Program, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, NSW, 2010, Australia.
- St Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia.
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Carreras A, Kayali F, Zhang J, Hirotsu C, Wang Y, Gozal D. Metabolic effects of intermittent hypoxia in mice: steady versus high-frequency applied hypoxia daily during the rest period. Am J Physiol Regul Integr Comp Physiol 2012; 303:R700-9. [PMID: 22895743 DOI: 10.1152/ajpregu.00258.2012] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Intermittent hypoxia (IH) is a frequent occurrence in sleep and respiratory disorders. Both human and murine studies show that IH may be implicated in metabolic dysfunction. Although the effects of nocturnal low-frequency intermittent hypoxia (IH(L)) have not been extensively examined, it would appear that IH(L) and high-frequency intermittent hypoxia (IH(H)) may elicit distinct metabolic adaptations. To this effect, C57BL/6J mice were randomly assigned to IH(H) (cycles of 90 s 6.4% O(2) and 90 s 21% O(2) during daylight), IH(L) (8% O(2) during daylight hours), or control (CTL) for 5 wk. At the end of exposures, some of the mice were subjected to a glucose tolerance test (GTT; after intraperitoneal injection of 2 mg glucose/g body wt), and others were subjected to an insulin tolerance test (ITT; 0.25 units Humulin/kg body wt), with plasma leptin and insulin levels being measured in fasting conditions. Skeletal muscles were harvested for GLUT4 and proliferator-activated receptor gamma coactivator 1-α (PGC1-α) expression. Both IH(H) and IH(L) displayed reduced body weight increases compared with CTL. CTL mice had higher basal glycemic levels, but GTT kinetics revealed marked differences between IH(L) and IH(H), with IH(L) manifesting the lowest insulin sensitivity compared with either IH(H) or CTL, and such findings were further confirmed by ITT. No differences emerged in PGC1-α expression across the three experimental groups. However, while cytosolic GLUT4 protein expression remained similar in IH(L), IH(H), and CTL, significant decreases in GLUT4 membrane fraction occurred in hypoxia and were most pronounced in IH(L)-exposed mice. Thus IH(H) and IH(L) elicit differential glucose homeostatic responses despite similar cumulative hypoxic profiles.
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Affiliation(s)
- Alba Carreras
- Dept. of Pediatrics, Univ. of Chicago, Chicago, IL 60637, USA
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45
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The role of fatty acid metabolism and lipotoxicity in pancreatic β-cell injury: Identification of potential therapeutic targets. Acta Pharm Sin B 2012. [DOI: 10.1016/j.apsb.2012.05.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Prentki M, Madiraju SRM. Glycerolipid/free fatty acid cycle and islet β-cell function in health, obesity and diabetes. Mol Cell Endocrinol 2012; 353:88-100. [PMID: 22108437 DOI: 10.1016/j.mce.2011.11.004] [Citation(s) in RCA: 124] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 11/07/2011] [Accepted: 11/07/2011] [Indexed: 12/16/2022]
Abstract
Pancreatic β-cells secrete insulin in response to fluctuations in blood fuel concentrations, in particular glucose and fatty acids. However, chronic fuel surfeit can overwhelm the metabolic, signaling and secretory capacity of the β-cell leading to its dysfunction and death - often referred to as glucolipotoxicity. In β-cells and many other cells, glucose and lipid metabolic pathways converge into a glycerolipid/free fatty acid (GL/FFA) cycle, which is driven by the substrates, glycerol-3-phosphate and fatty acyl-CoA, derived from glucose and fatty acids, respectively. Although the overall operation of GL/FFA cycle, consisting of lipolysis and lipogenesis, is "futile" in terms of energy expenditure, this metabolic cycle likely plays an indispensable role for various β-cell functions, in particular insulin secretion and excess fuel detoxification. In this review, we discuss the significance of GL/FFA cycle in the β-cell, its regulation and role in generating essential metabolic signals that participate in the lipid amplification arm of glucose stimulated insulin secretion and in β-cell growth. We propose the novel concept that the lipolytic segment of GL/FFA cycle is instrumental in producing signals for insulin secretion, whereas, the lipogenic segment generates signals relevant for β-cell survival/death and growth/proliferation.
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Affiliation(s)
- Marc Prentki
- Departments of Nutrition and Biochemistry, University of Montreal, Montreal Diabetes Research Center, CR-CHUM, Technopôle Angus, 2901, Montreal, Canada QC H1W 4A4.
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Summanen M, Granqvist N, Tuominen RK, Yliperttula M, Verrips CT, Boonstra J, Blanchetot C, Ekokoski E. Kinetics of PKCε activating and inhibiting llama single chain antibodies and their effect on PKCε translocation in HeLa cells. PLoS One 2012; 7:e35630. [PMID: 22536418 PMCID: PMC3334965 DOI: 10.1371/journal.pone.0035630] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Accepted: 03/19/2012] [Indexed: 12/11/2022] Open
Abstract
Dysregulation of PKCε is involved in several serious diseases such as cancer, type II diabetes and Alzheimer's disease. Therefore, specific activators and inhibitors of PKCε hold promise as future therapeutics, in addition to being useful in research into PKCε regulated pathways. We have previously described llama single chain antibodies (VHHs) that specifically activate (A10, C1 and D1) or inhibit (E6 and G8) human recombinant PKCε. Here we report a thorough kinetic analysis of these VHHs. The inhibiting VHHs act as non-competitive inhibitors of PKCε activity, whereas the activating VHHs have several different modes of action, either increasing Vmax and/or decreasing Km values. We also show that the binding of the VHHs to PKCε is conformation-dependent, rendering the determination of affinities difficult. Apparent affinities are in the micromolar range based on surface plasmon resonance studies. Furthermore, the VHHs have no effect on the activity of rat PKCε nor can they bind the rat form of the protein in immunoprecipitation studies despite the 98% identity between the human and rat PKCε proteins. Finally, we show for the first time that the VHHs can influence PKCε function also in cells, since an activating VHH increases the rate of PKCε translocation in response to PMA in HeLa cells, whereas an inhibiting VHH slows down the translocation. These results give insight into the mechanisms of PKCε activity modulation and highlight the importance of protein conformation on VHH binding.
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Affiliation(s)
- Milla Summanen
- Cell Biology, Department of Biology, University of Utrecht, Utrecht, The Netherlands
- Division of Pharmacology and Toxicology, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Niko Granqvist
- Division of Biopharmaceutics and Pharmacokinetics, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Raimo K. Tuominen
- Division of Pharmacology and Toxicology, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Marjo Yliperttula
- Division of Biopharmaceutics and Pharmacokinetics, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - C. Theo Verrips
- Cell Biology, Department of Biology, University of Utrecht, Utrecht, The Netherlands
| | - Johannes Boonstra
- Cell Biology, Department of Biology, University of Utrecht, Utrecht, The Netherlands
- * E-mail:
| | - Christophe Blanchetot
- Cell Biology, Department of Biology, University of Utrecht, Utrecht, The Netherlands
| | - Elina Ekokoski
- Division of Pharmacology and Toxicology, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
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Bergman BC, Hunerdosse DM, Kerege A, Playdon MC, Perreault L. Localisation and composition of skeletal muscle diacylglycerol predicts insulin resistance in humans. Diabetologia 2012; 55:1140-50. [PMID: 22252470 PMCID: PMC3296871 DOI: 10.1007/s00125-011-2419-7] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Accepted: 11/21/2011] [Indexed: 01/10/2023]
Abstract
AIMS/HYPOTHESIS We sought to evaluate if the cellular localisation and molecular species of diacylglycerol (DAG) were related to insulin sensitivity in human skeletal muscle. METHODS Healthy sedentary obese controls (Ob; n = 6; mean±SEM age 39.5 ± 2.3 years; mean ± SEM BMI 33.3 ± 1.4 kg/m(2)), individuals with type 2 diabetes (T2D; n = 6; age 44 ± 1.8 years; BMI 30.1 ± 2.3 kg/m(2)), and lean endurance-trained athletes (Ath; n = 10; age 35.4 ± 3.1 years; BMI 23.3 ± 0.8 kg/m(2)) were studied. Insulin sensitivity was determined using an IVGTT. Muscle biopsy specimens were taken after an overnight fast, fractionated using ultracentrifugation, and DAG species measured using liquid chromatography/MS/MS. RESULTS Total muscle DAG concentration was higher in the Ob (mean ± SEM 13.3 ± 1.0 pmol/μg protein) and T2D (15.2 ± 1.0 pmol/μg protein) groups than the Ath group (10.0 ± 0.78 pmol/μg protein, p = 0.002). The majority (76-86%) DAG was localised in the membrane fraction for all groups, but was lowest in the Ath group (Ob, 86.2 ± 0.98%; T2D, 84.2 ± 1.2%; Ath, 75.9 ± 2.7%; p = 0.008). There were no differences in cytoplasmic DAG species (p > 0.12). Membrane DAG species C18:0/C20:4, Di-C16:0 and Di-C18:0 were significantly more abundant in the T2D group. Cytosolic DAG species were negatively related to activation of protein kinase C (PKC)ε but not PKCθ, whereas membrane DAG species were positively related to activation of PKCε, but not PKCθ. Only total membrane DAG (r = -0.624, p = 0.003) and Di-C18:0 (r = -0.595, p = 0.004) correlated with insulin sensitivity. Disaturated DAG species were significantly lower in the Ath group (p = 0.001), and significantly related to insulin sensitivity (r = -0.642, p = 0.002). CONCLUSIONS/INTERPRETATION These data indicate that both cellular localisation and composition of DAG influence the relationship to insulin sensitivity. Our results suggest that only saturated DAG in skeletal muscle membranes are related to insulin resistance in humans.
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Affiliation(s)
- B C Bergman
- University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA.
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Åkerfeldt MC, Laybutt DR. Inhibition of Id1 augments insulin secretion and protects against high-fat diet-induced glucose intolerance. Diabetes 2011; 60:2506-14. [PMID: 21940780 PMCID: PMC3178288 DOI: 10.2337/db11-0083] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
OBJECTIVE The molecular mechanisms responsible for pancreatic β-cell dysfunction in type 2 diabetes remain unresolved. Increased expression of the helix-loop-helix protein Id1 has been found in islets of diabetic mice and in vitro models of β-cell dysfunction. Here, we investigated the role of Id1 in insulin secretion and glucose homeostasis. RESEARCH DESIGN AND METHODS Id1 knockout (Id1(-/-)) and wild-type mice were fed a chow or high-fat diet. Glucose tolerance, insulin tolerance, β-cell mass, insulin secretion, and islet gene expression were assessed. Small interfering RNA (siRNA) was used to silence Id1 in MIN6 cells, and responses to chronic palmitate treatment were assessed. RESULTS Id1(-/-) mice exhibited an improved response to glucose challenge and were almost completely protected against glucose intolerance induced by high-fat diet. This was associated with increased insulin levels and enhanced insulin release from isolated islets, whereas energy intake, body weight, fat pad weight, β-cell mass, and insulin action were unchanged. Islets from Id1(-/-) mice displayed reduced stress gene expression and were protected against high-fat diet-induced downregulation of β-cell gene expression (pancreatic duodenal homeobox-1, Beta2, Glut2, pyruvate carboxylase, and Gpr40). In MIN6 cells, siRNA-mediated inhibition of Id1 enhanced insulin secretion after chronic palmitate treatment and protected against palmitate-mediated loss of β-cell gene expression. CONCLUSIONS These findings implicate Id1 as a negative regulator of insulin secretion. Id1 expression plays an essential role in the etiology of glucose intolerance, insulin secretory dysfunction, and β-cell dedifferentiation under conditions of increased lipid supply.
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50
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Taguchi K, Kobayashi T, Matsumoto T, Kamata K. Dysfunction of endothelium-dependent relaxation to insulin via PKC-mediated GRK2/Akt activation in aortas of ob/ob mice. Am J Physiol Heart Circ Physiol 2011; 301:H571-83. [DOI: 10.1152/ajpheart.01189.2010] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In diabetic states, hyperinsulinemia may negatively regulate Akt/endothelial nitric oxide synthase (eNOS) activation. Our main aim was to investigate whether and how insulin might negatively regulate Akt/eNOS activities via G protein-coupled receptor kinase 2 (GRK2) in aortas from ob/ob mice. Endothelium-dependent relaxation was measured in aortic rings from ob/ob mice (a type 2 diabetes model). GRK2, β-arrestin2, and Akt/eNOS signaling-pathway protein levels and activities were mainly assayed by Western blotting. Plasma insulin was significantly elevated in ob/ob mice. Insulin-induced relaxation was significantly decreased in the ob/ob aortas [vs. age-matched control (lean) ones]. The response in ob/ob aortas was enhanced by PKC inhibitor or GRK2 inhibitor. Akt (at Thr308) phosphorylation and eNOS (at Ser1177) phosphorylation, and also the β-arrestin2 protein level, were markedly decreased in the membrane fraction of insulin-stimulated ob/ob aortas (vs. insulin-stimulated lean ones). These membrane-fraction expressions were enhanced by GRK2 inhibitor and by PKC inhibitor in the ob/ob group but not in the lean group. PKC activity was much greater in ob/ob than in lean aortas. GRK2 protein and activity levels were increased in ob/ob and were greatly reduced by GRK2 inhibitor or PKC inhibitor pretreatment. These results suggest that in the aorta in diabetic mice with hyperinsulinemia an upregulation of GRK2 and a decrease in β-arrestin2 inhibit insulin-induced stimulation of the Akt/eNOS pathway and that GRK2 overactivation may result from an increase in PKC activity.
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Affiliation(s)
- Kumiko Taguchi
- Department of Physiology and Morphology, Institute of Medicinal Chemistry, Hoshi University, Shinagawa-ku, Tokyo, Japan
| | - Tsuneo Kobayashi
- Department of Physiology and Morphology, Institute of Medicinal Chemistry, Hoshi University, Shinagawa-ku, Tokyo, Japan
| | - Takayuki Matsumoto
- Department of Physiology and Morphology, Institute of Medicinal Chemistry, Hoshi University, Shinagawa-ku, Tokyo, Japan
| | - Katsuo Kamata
- Department of Physiology and Morphology, Institute of Medicinal Chemistry, Hoshi University, Shinagawa-ku, Tokyo, Japan
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