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Dreher SI, Grubba P, von Toerne C, Moruzzi A, Maurer J, Goj T, Birkenfeld AL, Peter A, Loskill P, Hauck SM, Weigert C. IGF1 promotes human myotube differentiation toward a mature metabolic and contractile phenotype. Am J Physiol Cell Physiol 2024; 326:C1462-C1481. [PMID: 38690930 DOI: 10.1152/ajpcell.00654.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 02/26/2024] [Accepted: 02/26/2024] [Indexed: 05/03/2024]
Abstract
Skeletal muscle mediates the beneficial effects of exercise, thereby improving insulin sensitivity and reducing the risk for type 2 diabetes. Current human skeletal muscle models in vitro are incapable of fully recapitulating its physiological functions especially muscle contractility. By supplementation of insulin-like growth factor 1 (IGF1), a growth factor secreted by myofibers in vivo, we aimed to overcome these limitations. We monitored the differentiation process starting from primary human CD56-positive myoblasts in the presence/absence of IGF1 in serum-free medium in daily collected samples for 10 days. IGF1-supported differentiation formed thicker multinucleated myotubes showing physiological contraction upon electrical pulse stimulation (EPS) following day 6. Myotubes without IGF1 were almost incapable of contraction. IGF1 treatment shifted the proteome toward skeletal muscle-specific proteins that contribute to myofibril and sarcomere assembly, striated muscle contraction, and ATP production. Elevated PPARGC1A, MYH7, and reduced MYH1/2 suggest a more oxidative phenotype further demonstrated by higher abundance of proteins of the respiratory chain and elevated mitochondrial respiration. IGF1-treatment also upregulated glucose transporter (GLUT)4 and increased insulin-dependent glucose uptake compared with myotubes differentiated without IGF1. To conclude, addition of IGF1 to serum-free medium significantly improves the differentiation of human myotubes that showed enhanced myofibril formation, response to electrical pulse stimulation, oxidative respiratory capacity, and glucose metabolism overcoming limitations of previous standards. This novel protocol enables investigation of muscular exercise on a molecular level.NEW & NOTEWORTHY Human skeletal muscle models are highly valuable to study how exercise prevents type 2 diabetes without invasive biopsies. Current models did not fully recapitulate the function of skeletal muscle especially during exercise. By supplementing insulin-like growth factor 1 (IGF1), the authors developed a functional human skeletal muscle model characterized by inducible contractility and increased oxidative and insulin-sensitive metabolism. The novel protocol overcomes the limitations of previous standards and enables investigation of exercise on a molecular level.
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Affiliation(s)
- Simon I Dreher
- Department for Diagnostic Laboratory Medicine, Institute for Clinical Chemistry and Pathobiochemistry, University Hospital Tübingen, Tübingen, Germany
| | - Paul Grubba
- Department for Diagnostic Laboratory Medicine, Institute for Clinical Chemistry and Pathobiochemistry, University Hospital Tübingen, Tübingen, Germany
| | - Christine von Toerne
- Metabolomics and Proteomics Core Helmholtz Center Munich, German Research Center for Environmental Health, Neuherberg, Germany
| | - Alessia Moruzzi
- NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, Germany
- Department for Microphysiological Systems, Institute of Biomedical Engineering, Faculty of Medicine, Eberhard Karls University Tübingen, Tübingen, Germany
| | - Jennifer Maurer
- Department for Diagnostic Laboratory Medicine, Institute for Clinical Chemistry and Pathobiochemistry, University Hospital Tübingen, Tübingen, Germany
| | - Thomas Goj
- Department for Diagnostic Laboratory Medicine, Institute for Clinical Chemistry and Pathobiochemistry, University Hospital Tübingen, Tübingen, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Andreas L Birkenfeld
- German Center for Diabetes Research (DZD), Neuherberg, Germany
- Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Zentrum München, University of Tübingen, Tübingen, Germany
- Department of Internal Medicine IV, University Hospital Tübingen, Tübingen, Germany
| | - Andreas Peter
- Department for Diagnostic Laboratory Medicine, Institute for Clinical Chemistry and Pathobiochemistry, University Hospital Tübingen, Tübingen, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
- Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Zentrum München, University of Tübingen, Tübingen, Germany
| | - Peter Loskill
- NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, Germany
- Department for Microphysiological Systems, Institute of Biomedical Engineering, Faculty of Medicine, Eberhard Karls University Tübingen, Tübingen, Germany
| | - Stefanie M Hauck
- Metabolomics and Proteomics Core Helmholtz Center Munich, German Research Center for Environmental Health, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Cora Weigert
- Department for Diagnostic Laboratory Medicine, Institute for Clinical Chemistry and Pathobiochemistry, University Hospital Tübingen, Tübingen, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
- Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Zentrum München, University of Tübingen, Tübingen, Germany
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Park S, Jevtovic F, Krassovskaia PM, Chaves AB, Zheng D, Treebak JT, Houmard JA. Effect of resveratrol on insulin action in primary myotubes from lean individuals and individuals with severe obesity. Am J Physiol Endocrinol Metab 2024; 326:E398-E406. [PMID: 38324260 DOI: 10.1152/ajpendo.00299.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 01/29/2024] [Accepted: 01/31/2024] [Indexed: 02/08/2024]
Abstract
Resveratrol, a natural polyphenol compound contained in numerous plants, has been proposed as a treatment for obesity-related disease processes such as insulin resistance. However, in humans there are conflicting results concerning the efficacy of resveratrol in improving insulin action; the purpose of the present study was to determine whether obesity status (lean, severely obese) affects the response to resveratrol in human skeletal muscle. Primary skeletal muscle cells were derived from biopsies obtained from age-matched lean and insulin-resistant women with severe obesity and incubated with resveratrol (1 µM) for 24 h. Insulin-stimulated glucose oxidation and incorporation into glycogen, insulin signal transduction, and energy-sensitive protein targets [AMP-activated protein kinase (AMPK), Sirt1, and PGC1α] were analyzed. Insulin-stimulated glycogen synthesis, glucose oxidation, and AMPK phosphorylation increased with resveratrol incubation compared with the nonresveratrol conditions (main treatment effect for resveratrol). Resveratrol further increased IRS1, Akt, and TBC1D4 insulin-stimulated phosphorylation and SIRT1 content in myotubes from lean women, but not in women with severe obesity. Resveratrol improves insulin action in primary human skeletal myotubes derived from lean women and women with severe obesity. In women with obesity, these improvements may be associated with enhanced AMPK phosphorylation with resveratrol treatment.NEW & NOTEWORTHY A physiologically relevant dose of resveratrol increases insulin-stimulated glucose oxidation and glycogen synthesis in myotubes from individuals with severe obesity. Furthermore, resveratrol improved insulin signal transduction in myotubes from lean individuals but not from individuals with obesity. Activation of AMPK plays a role in resveratrol-induced improvements in glucose metabolism in individuals with severe obesity.
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Affiliation(s)
- Sanghee Park
- Human Performance Laboratory, East Carolina University, Greenville, North Carolina, United States
- Department of Kinesiology, East Carolina University, Greenville, North Carolina, United States
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, North Carolina, United States
- Department of Exercise Rehabilitation, Gachon University, Incheon, Republic of Korea
| | - Filip Jevtovic
- Human Performance Laboratory, East Carolina University, Greenville, North Carolina, United States
- Department of Kinesiology, East Carolina University, Greenville, North Carolina, United States
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, North Carolina, United States
| | - Polina M Krassovskaia
- Human Performance Laboratory, East Carolina University, Greenville, North Carolina, United States
- Department of Kinesiology, East Carolina University, Greenville, North Carolina, United States
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, North Carolina, United States
| | - Alec B Chaves
- Human Performance Laboratory, East Carolina University, Greenville, North Carolina, United States
- Department of Kinesiology, East Carolina University, Greenville, North Carolina, United States
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, North Carolina, United States
| | - Donghai Zheng
- Human Performance Laboratory, East Carolina University, Greenville, North Carolina, United States
- Department of Kinesiology, East Carolina University, Greenville, North Carolina, United States
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, North Carolina, United States
| | - Jonas T Treebak
- Section of Integrative Physiology, Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Joseph A Houmard
- Human Performance Laboratory, East Carolina University, Greenville, North Carolina, United States
- Department of Kinesiology, East Carolina University, Greenville, North Carolina, United States
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, North Carolina, United States
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Mäkinen S, Datta N, Rangarajan S, Nguyen YH, Olkkonen VM, Latva-Rasku A, Nuutila P, Laakso M, Koistinen HA. Finnish-specific AKT2 gene variant leads to impaired insulin signalling in myotubes. J Mol Endocrinol 2023; 70:JME-21-0285. [PMID: 36409629 PMCID: PMC9874976 DOI: 10.1530/jme-21-0285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Accepted: 11/21/2022] [Indexed: 11/22/2022]
Abstract
Finnish-specific gene variant p.P50T/AKT2 (minor allele frequency (MAF) = 1.1%) is associated with insulin resistance and increased predisposition to type 2 diabetes. Here, we have investigated in vitro the impact of the gene variant on glucose metabolism and intracellular signalling in human primary skeletal muscle cells, which were established from 14 male p.P50T/AKT2 variant carriers and 14 controls. Insulin-stimulated glucose uptake and glucose incorporation into glycogen were detected with 2-[1,2-3H]-deoxy-D-glucose and D-[14C]-glucose, respectively, and the rate of glycolysis was measured with a Seahorse XFe96 analyzer. Insulin signalling was investigated with Western blotting. The binding of variant and control AKT2-PH domains to phosphatidylinositol (3,4,5)-trisphosphate (PI(3,4,5)P3) was assayed using PIP StripsTM Membranes. Protein tyrosine kinase and serine-threonine kinase assays were performed using the PamGene® kinome profiling system. Insulin-stimulated glucose uptake and glycogen synthesis in myotubes in vitro were not significantly affected by the genotype. However, the insulin-stimulated glycolytic rate was impaired in variant myotubes. Western blot analysis showed that insulin-stimulated phosphorylation of AKT-Thr308, AS160-Thr642 and GSK3β-Ser9 was reduced in variant myotubes compared to controls. The binding of variant AKT2-PH domain to PI(3,4,5)P3 was reduced as compared to the control protein. PamGene® kinome profiling revealed multiple differentially phosphorylated kinase substrates, e.g. calmodulin, between the genotypes. Further in silico upstream kinase analysis predicted a large-scale impairment in activities of kinases participating, for example, in intracellular signal transduction, protein translation and cell cycle events. In conclusion, myotubes from p.P50T/AKT2 variant carriers show multiple signalling alterations which may contribute to predisposition to insulin resistance and T2D in the carriers of this signalling variant.
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Affiliation(s)
- Selina Mäkinen
- Minerva Foundation Institute for Medical Research, Tukholmankatu, Helsinki, Finland
- Department of Medicine, University of Helsinki and Helsinki University Hospital, Haartmaninkatu, Helsinki, Finland
| | - Neeta Datta
- Minerva Foundation Institute for Medical Research, Tukholmankatu, Helsinki, Finland
- Department of Medicine, University of Helsinki and Helsinki University Hospital, Haartmaninkatu, Helsinki, Finland
| | - Savithri Rangarajan
- Pam Gene International B.V., Wolvenhoek, BJ ´s-Hertogenbosch, The Netherlands
| | - Yen H Nguyen
- Minerva Foundation Institute for Medical Research, Tukholmankatu, Helsinki, Finland
- Department of Medicine, University of Helsinki and Helsinki University Hospital, Haartmaninkatu, Helsinki, Finland
| | - Vesa M Olkkonen
- Minerva Foundation Institute for Medical Research, Tukholmankatu, Helsinki, Finland
- Department of Anatomy, Faculty of Medicine, Haartmaninkatu, University of Helsinki, Helsinki, Finland
| | - Aino Latva-Rasku
- Turku PET Centre, University of Turku, Kiinamyllynkatu, Turku, Finland
- Turku PET Centre, Turku University Hospital, Kiinamyllynkatu, Turku, Finland
| | - Pirjo Nuutila
- Turku PET Centre, University of Turku, Kiinamyllynkatu, Turku, Finland
- Turku PET Centre, Turku University Hospital, Kiinamyllynkatu, Turku, Finland
| | - Markku Laakso
- Institute of Clinical Medicine, Internal Medicine, University of Eastern Finland and Kuopio University Hospital, Puijonlaaksontie, Kuopio, Finland
| | - Heikki A Koistinen
- Minerva Foundation Institute for Medical Research, Tukholmankatu, Helsinki, Finland
- Department of Medicine, University of Helsinki and Helsinki University Hospital, Haartmaninkatu, Helsinki, Finland
- Correspondence should be addressed to H A Koistinen:
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McIlvenna LC, Patten RK, McAinch AJ, Rodgers RJ, Stepto NK, Moreno-Asso A. Transforming Growth Factor Beta 1 Alters Glucose Uptake but Not Insulin Signalling in Human Primary Myotubes From Women With and Without Polycystic Ovary Syndrome. Front Endocrinol (Lausanne) 2021; 12:732338. [PMID: 34707569 PMCID: PMC8544291 DOI: 10.3389/fendo.2021.732338] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 09/22/2021] [Indexed: 12/24/2022] Open
Abstract
Women with polycystic ovary syndrome (PCOS), commonly have profound skeletal muscle insulin resistance which can worsen other clinical features. The heterogeneity of the condition has made it challenging to identify the precise mechanisms that cause this insulin resistance. A possible explanation for the underlying insulin resistance may be the dysregulation of Transforming Growth Factor-beta (TGFβ) signalling. TGFβ signalling contributes to the remodelling of reproductive and hepatic tissues in women with PCOS. Given the systemic nature of TGFβ signalling and its role in skeletal muscle homeostasis, it may be possible that these adverse effects extend to other peripheral tissues. We aimed to determine if TGFβ1 could negatively regulate glucose uptake and insulin signalling in skeletal muscle of women with PCOS. We show that both myotubes from women with PCOS and healthy women displayed an increase in glucose uptake, independent of changes in insulin signalling, following short term (16 hr) TGFβ1 treatment. This increase occurred despite pro-fibrotic signalling increasing via SMAD3 and connective tissue growth factor in both groups following treatment with TGFβ1. Collectively, our findings show that short-term treatment with TGFβ1 does not appear to influence insulin signalling or promote insulin resistance in myotubes. These findings suggest that aberrant TGFβ signalling is unlikely to directly contribute to skeletal muscle insulin resistance in women with PCOS in the short term but does not rule out indirect or longer-term effects.
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Affiliation(s)
- Luke C. McIlvenna
- Institute for Health and Sport, Victoria University, Melbourne, VIC, Australia
| | - Rhiannon K. Patten
- Institute for Health and Sport, Victoria University, Melbourne, VIC, Australia
| | - Andrew J. McAinch
- Institute for Health and Sport, Victoria University, Melbourne, VIC, Australia
- Australian Institute for Musculoskeletal Science (AIMSS), Victoria University, Melbourne, VIC, Australia
| | - Raymond J. Rodgers
- Discipline of Obstetrics and Gynaecology, School of Medicine, Robinson Research Institute, The University of Adelaide, Adelaide, SA, Australia
| | - Nigel K. Stepto
- Institute for Health and Sport, Victoria University, Melbourne, VIC, Australia
- Australian Institute for Musculoskeletal Science (AIMSS), Victoria University, Melbourne, VIC, Australia
| | - Alba Moreno-Asso
- Institute for Health and Sport, Victoria University, Melbourne, VIC, Australia
- Australian Institute for Musculoskeletal Science (AIMSS), Victoria University, Melbourne, VIC, Australia
- *Correspondence: Alba Moreno-Asso,
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Nakashima K, Ishida A, Shimamoto S, Ijiri D, Ohtsuka A. Insulin Stimulation of Protein Synthesis and mTOR Signaling in Chick Myotube Cultures. J Poult Sci 2020; 57:205-9. [PMID: 32733154 DOI: 10.2141/jpsa.0190082] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Insulin stimulates protein synthesis in skeletal muscles. Protein synthesis is controlled by the mechanistic target of rapamycin (mTOR) signaling in skeletal muscles. This study was conducted to investigate the effect of insulin on protein synthesis and mTOR signaling in chick myotube cultures. Chick myotubes were incubated with insulin (1 µg/ml) for 1 h. Protein synthesis, measured using the surface sensing of translation method, was significantly increased by insulin. The phosphorylation of AKT (Thr308 and Ser473), p70 ribosomal S6 kinase 1 (S6K1, Thr389), S6 ribosomal protein (Ser235/236), and eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1, Thr37/46) was also significantly increased by insulin. These results suggest that insulin stimulates protein synthesis via mTOR signaling (phosphorylation of AKT, S6K1, S6 ribosomal protein, and 4E-BP1) in chick myotube cultures.
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Luca E, Turcekova K, Hartung A, Mathes S, Rehrauer H, Krützfeldt J. Genetic deletion of microRNA biogenesis in muscle cells reveals a hierarchical non-clustered network that controls focal adhesion signaling during muscle regeneration. Mol Metab 2020; 36:100967. [PMID: 32240622 PMCID: PMC7139120 DOI: 10.1016/j.molmet.2020.02.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 02/19/2020] [Accepted: 02/20/2020] [Indexed: 12/20/2022] Open
Abstract
OBJECTIVE Decreased muscle mass is a major contributor to age-related morbidity, and strategies to improve muscle regeneration during ageing are urgently needed. Our aim was to identify the subset of relevant microRNAs (miRNAs) that partake in critical aspects of muscle cell differentiation, irrespective of computational predictions, genomic clustering or differential expression of the miRNAs. METHODS miRNA biogenesis was deleted in primary myoblasts using a tamoxifen-inducible CreLox system and combined with an add-back miRNA library screen. RNA-seq experiments, cellular signalling events, and glycogen synthesis, along with miRNA inhibitors, were performed in human primary myoblasts. Muscle regeneration in young and aged mice was assessed using the cardiotoxin (CTX) model. RESULTS We identified a hierarchical non-clustered miRNA network consisting of highly (miR-29a), moderately (let-7) and mildly active (miR-125b, miR-199a, miR-221) miRNAs that cooperate by directly targeting members of the focal adhesion complex. Through RNA-seq experiments comparing single versus combinatorial inhibition of the miRNAs, we uncovered a fundamental feature of this network, that miRNA activity inversely correlates to miRNA cooperativity. During myoblast differentiation, combinatorial inhibition of the five miRNAs increased activation of focal adhesion kinase (FAK), AKT, and p38 mitogen-activated protein kinase (MAPK), and improved myotube formation and insulin-dependent glycogen synthesis. Moreover, antagonizing the miRNA network in vivo following CTX-induced muscle regeneration enhanced muscle mass and myofiber formation in young and aged mice. CONCLUSION Our results provide novel insights into the dynamics of miRNA cooperativity and identify a miRNA network as therapeutic target for impaired focal adhesion signalling and muscle regeneration during ageing.
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Affiliation(s)
- Edlira Luca
- Division of Endocrinology, Diabetes, and Clinical Nutrition, University Hospital Zurich, 8091, Switzerland
| | - Katarina Turcekova
- Division of Endocrinology, Diabetes, and Clinical Nutrition, University Hospital Zurich, 8091, Switzerland; Competence Center Personalized Medicine UZH/ETH, ETH Zurich and University of Zurich, 8091, Switzerland
| | - Angelika Hartung
- Division of Endocrinology, Diabetes, and Clinical Nutrition, University Hospital Zurich, 8091, Switzerland
| | - Sebastian Mathes
- Division of Endocrinology, Diabetes, and Clinical Nutrition, University Hospital Zurich, 8091, Switzerland; Zurich Center for Integrative Human Physiology, University of Zurich, 8091, Switzerland
| | - Hubert Rehrauer
- Functional Genomics Center Zurich UZH/ETH, ETH Zurich and University of Zurich, 8091, Switzerland
| | - Jan Krützfeldt
- Division of Endocrinology, Diabetes, and Clinical Nutrition, University Hospital Zurich, 8091, Switzerland; Competence Center Personalized Medicine UZH/ETH, ETH Zurich and University of Zurich, 8091, Switzerland; Zurich Center for Integrative Human Physiology, University of Zurich, 8091, Switzerland.
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Bergman RN, Piccinini F, Kabir M, Kolka CM, Ader M. Hypothesis: Role of Reduced Hepatic Insulin Clearance in the Pathogenesis of Type 2 Diabetes. Diabetes 2019; 68:1709-1716. [PMID: 31431441 PMCID: PMC6702636 DOI: 10.2337/db19-0098] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 06/02/2019] [Indexed: 12/19/2022]
Abstract
There is wide variance among individuals in the fraction of insulin cleared by the liver (20% to 80%). Hepatic insulin clearance is 67% lower in African Americans than European Americans. Clearance is also lower in African American children 7-13 years of age. Lower hepatic insulin clearance will result in peripheral hyperinsulinemia: this exacerbates insulin resistance, which stresses the β-cells, possibly resulting in their ultimate failure and onset of type 2 diabetes. We hypothesize that lower insulin clearance can be a primary cause of type 2 diabetes in at-risk individuals.
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Affiliation(s)
- Richard N Bergman
- Diabetes and Obesity Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA
| | - Francesca Piccinini
- Diabetes and Obesity Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA
| | - Morvarid Kabir
- Diabetes and Obesity Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA
| | - Cathryn M Kolka
- Diabetes and Obesity Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA
| | - Marilyn Ader
- Diabetes and Obesity Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA
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8
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Gaster M. The diabetic phenotype is preserved in myotubes established from type 2 diabetic subjects: a critical appraisal. APMIS 2018; 127:3-26. [DOI: 10.1111/apm.12908] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2018] [Accepted: 11/05/2018] [Indexed: 01/08/2023]
Affiliation(s)
- Michael Gaster
- Laboratory for Molecular Physiology Department of Pathology and Department of Endocrinology Odense University Hospital Odense Denmark
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Mizgier ML, Cataldo LR, Gutierrez J, Santos JL, Casas M, Llanos P, Contreras-Ferrat AE, Moro C, Bouzakri K, Galgani JE. Effect of Human Myotubes-Derived Media on Glucose-Stimulated Insulin Secretion. J Diabetes Res 2017; 2017:1328573. [PMID: 28286777 PMCID: PMC5329672 DOI: 10.1155/2017/1328573] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2016] [Revised: 01/01/2017] [Accepted: 01/17/2017] [Indexed: 12/11/2022] Open
Abstract
Fasting to postprandial transition requires a tight adjustment of insulin secretion to its demand, so tissue (e.g., skeletal muscle) glucose supply is assured while hypo-/hyperglycemia are prevented. High muscle glucose disposal after meals is pivotal for adapting to increased glycemia and might drive insulin secretion through muscle-released factors (e.g., myokines). We hypothesized that insulin influences myokine secretion and then increases glucose-stimulated insulin secretion (GSIS). In conditioned media from human myotubes incubated with/without insulin (100 nmol/L) for 24 h, myokines were qualitatively and quantitatively characterized using an antibody-based array and ELISA-based technology, respectively. C57BL6/J mice islets and Wistar rat beta cells were incubated for 24 h with control and conditioned media from noninsulin- and insulin-treated myotubes prior to GSIS determination. Conditioned media from insulin-treated versus nontreated myotubes had higher RANTES but lower IL6, IL8, and MCP1 concentration. Qualitative analyses revealed that conditioned media from noninsulin- and insulin-treated myotubes expressed 32 and 23 out of 80 myokines, respectively. Islets incubated with conditioned media from noninsulin-treated myotubes had higher GSIS versus control islets (p < 0.05). Meanwhile, conditioned media from insulin-treated myotubes did not influence GSIS. In beta cells, GSIS was similar across conditions. In conclusion, factors being present in noninsulin-stimulated muscle cell-derived media appear to influence GSIS in mice islets.
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Affiliation(s)
- Maria L. Mizgier
- Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Luis R. Cataldo
- Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Juan Gutierrez
- Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - José L. Santos
- Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Mariana Casas
- Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Paola Llanos
- Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Institute for Research in Dental Sciences, Facultad de Odontología, Universidad de Chile, Santiago, Chile
| | - Ariel E. Contreras-Ferrat
- Exercise Science Laboratory, School of Kinesiology, Faculty of Medicine, Universidad Finis Terrae, Santiago, Chile
| | - Cedric Moro
- INSERM UMR1048, Institut des Maladies Métaboliques et Cardiovasculaires, Université Paul Sabatier, Toulouse, France
| | - Karim Bouzakri
- Departement de Génétique et Développement, CMU, Université de Genève, Genève, Switzerland
- UMR DIATHEC, EA 7294, Centre Européen d'Etude du Diabète, Université de Strasbourg, Strasbourg, France
| | - Jose E. Galgani
- Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
- UDA-Ciencias de la Salud, Carrera de Nutrición y Dietética, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
- *Jose E. Galgani:
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Ordelheide AM, Gommer N, Böhm A, Hermann C, Thielker I, Machicao F, Fritsche A, Stefan N, Häring HU, Staiger H. Granulocyte colony-stimulating factor (G-CSF): A saturated fatty acid-induced myokine with insulin-desensitizing properties in humans. Mol Metab 2016; 5:305-16. [PMID: 27069870 DOI: 10.1016/j.molmet.2016.02.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 02/02/2016] [Accepted: 02/08/2016] [Indexed: 01/01/2023] Open
Abstract
Objective Circulating long-chain free fatty acids (FFAs) are important metabolic signals that acutely enhance fatty acid oxidation, thermogenesis, energy expenditure, and insulin secretion. However, if chronically elevated, they provoke inflammation, insulin resistance, and β-cell failure. Moreover, FFAs act via multiple signaling pathways as very potent regulators of gene expression. In human skeletal muscle cells differentiated in vitro (myotubes), we have shown in previous studies that the expression of CSF3, the gene encoding granulocyte colony-stimulating factor (G-CSF), is markedly induced upon FFA treatment and exercise. Methods and results We now report that CSF3 is induced in human myotubes by saturated, but not unsaturated, FFAs via Toll-like receptor 4-dependent and -independent pathways including activation of Rel-A, AP-1, C/EBPα, Src, and stress kinases. Furthermore, we show that human adipocytes and myotubes treated with G-CSF become insulin-resistant. In line with this, a functional polymorphism in the CSF3 gene affects adipose tissue- and whole-body insulin sensitivity and glucose tolerance in human subjects with elevated plasma FFA concentrations. Conclusion G-CSF emerges as a new player in FFA-induced insulin resistance and thus may be of interest as a target for prevention and treatment of type 2 diabetes. CSF3, the gene encoding G-CSF, is induced in human myotubes by saturated, but not unsaturated, FFAs. CSF3 expression is induced via Toll-like receptor 4-dependent and -independent pathways. Human adipocytes and myotubes treated with G-CSF become insulin-resistant. A CSF3 SNP affects insulin sensitivity and glucose tolerance in human subjects with elevated plasma FFA concentrations. G-CSF emerges as a new player in FFA-induced insulin resistance.
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Agrawal M, Kharkar P, Moghe S, Mahajan T, Deka V, Thakkar C, Nair A, Mehta C, Bose J, Kulkarni-Almeida A, Bhedi D, Vishwakarma RA. Discovery of thiazolyl-phthalazinone acetamides as potent glucose uptake activators via high-throughput screening. Bioorg Med Chem Lett 2013; 23:5740-3. [PMID: 23992862 DOI: 10.1016/j.bmcl.2013.07.067] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Revised: 07/24/2013] [Accepted: 07/30/2013] [Indexed: 02/08/2023]
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Hartung A, Ordelheide AM, Staiger H, Melzer M, Häring HU, Lammers R. The Akt substrate Girdin is a regulator of insulin signaling in myoblast cells. Biochim Biophys Acta 2013; 1833:2803-11. [PMID: 23886629 DOI: 10.1016/j.bbamcr.2013.07.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Revised: 07/10/2013] [Accepted: 07/16/2013] [Indexed: 11/21/2022]
Abstract
Akt kinases are important mediators of the insulin signal, and some Akt substrates are directly involved in glucose homeostasis. Recently, Girdin has been described as an Akt substrate that is expressed ubiquitously in mammals. Cells overexpressing Girdin show an enhanced Akt activity. However, not much is known about Girdin's role in insulin signaling. We therefore analyzed the role of Girdin in primary human myotubes and found a correlation between Girdin expression and insulin sensitivity of the muscle biopsy donors, as measured by a hyperinsulinemic-euglycemic clamp. To understand this finding on a cellular level, we then investigated the function of Girdin in C2C12 mouse myoblasts. Girdin knock-down reduced Akt and insulin receptor substrate-1 phosphorylation. In contrast, stable overexpression of Girdin in C2C12 cells strikingly increased insulin sensitivity through a massive upregulation of the insulin receptor and enhanced tyrosine phosphorylation of insulin receptor substrate-1. Furthermore, Akt and c-Abl kinases were constitutively activated. To investigate medium-term insulin responses we measured glucose incorporation into glycogen. The Girdin overexpressing cells showed a high basal glycogen synthesis that peaked already at 1nM insulin. Taken together, we characterized Girdin as a new and major regulator of the insulin signal in myoblasts and skeletal muscle.
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Staiger H, Böhm A, Scheler M, Berti L, Machann J, Schick F, Machicao F, Fritsche A, Stefan N, Weigert C, Krook A, Häring HU, de Angelis MH. Common genetic variation in the human FNDC5 locus, encoding the novel muscle-derived 'browning' factor irisin, determines insulin sensitivity. PLoS One 2013; 8:e61903. [PMID: 23637927 DOI: 10.1371/journal.pone.0061903] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Accepted: 03/14/2013] [Indexed: 12/22/2022] Open
Abstract
Aims/hypothesis Recently, the novel myokine irisin was described to drive adipose tissue ‘browning’, to increase energy expenditure, and to improve obesity and insulin resistance in high fat-fed mice. Here, we assessed whether common single nucleotide polymorphisms (SNPs) in the FNDC5 locus, encoding the irisin precursor, contribute to human prediabetic phenotypes (overweight, glucose intolerance, insulin resistance, impaired insulin release). Methods A population of 1,976 individuals was characterized by oral glucose tolerance tests and genotyped for FNDC5 tagging SNPs. Subgroups underwent hyperinsulinaemic-euglycaemic clamps, magnetic resonance imaging/spectroscopy, and intravenous glucose tolerance tests. From 37 young and 14 elderly participants recruited in two different centres, muscle biopsies were obtained for the preparation of human myotube cultures. Results After appropriate adjustment and Bonferroni correction for the number of tested variants, SNPs rs16835198 and rs726344 were associated with in vivo measures of insulin sensitivity. Via interrogation of publicly available data from the Meta-Analyses of Glucose and Insulin-related traits Consortium, rs726344’s effect on insulin sensitivity was replicated. Moreover, novel data from human myotubes revealed a negative association between FNDC5 expression and appropriately adjusted in vivo measures of insulin sensitivity in young donors. This finding was replicated in myotubes from elderly men. Conclusions/interpretation This study provides evidence that the FNDC5 gene, encoding the novel myokine irisin, determines insulin sensitivity in humans. Our gene expression data point to an unexpected insulin-desensitizing effect of irisin.
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Abstract
Hormones are involved in a plethora of processes including development and growth, metabolism, mood, and immune responses. These essential functions are dependent on the ability of the hormone to access its target tissue. In the case of endocrine hormones that are transported through the blood, this often means that the endothelium must be crossed. Many studies have shown that the concentrations of hormones and nutrients in blood can be very different from those surrounding the cells on the tissue side of the blood vessel endothelium, suggesting that transport across this barrier can be rate limiting for hormone action. This transport can be regulated by altering the surface area of the blood vessel available for diffusion through to the underlying tissue or by the permeability of the endothelium. Many hormones are known to directly or indirectly affect the endothelial barrier, thus affecting their own distribution to their target tissues. Dysfunction of the endothelial barrier is found in many diseases, particularly those associated with the metabolic syndrome. The interrelatedness of hormones may help to explain why the cluster of diseases in the metabolic syndrome occur together so frequently and suggests that treating the endothelium may ameliorate defects in more than one disease. Here, we review the structure and function of the endothelium, its contribution to the function of hormones, and its involvement in disease.
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Affiliation(s)
- Cathryn M Kolka
- Diabetes and Obesity Research Institute, Department of Biomedical Science, Cedars-Sinai Medical Center, Los Angeles, California, USA.
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Ordelheide AM, Heni M, Thamer C, Machicao F, Fritsche A, Stefan N, Häring HU, Staiger H. In vitro responsiveness of human muscle cell peroxisome proliferator-activated receptor δ reflects donors' insulin sensitivity in vivo. Eur J Clin Invest 2011; 41:1323-9. [PMID: 21615395 DOI: 10.1111/j.1365-2362.2011.02547.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND Peroxisome proliferator-activated receptor δ (PPARδ) activation enhances muscular fatty acid oxidation and oxidative phosphorylation, and muscle's oxidative capacity positively associates with whole-body insulin sensitivity. Therefore, we asked here whether human muscle cell PPARD expression is a determinant of donors' insulin sensitivity. MATERIALS AND METHODS Skeletal muscle cells derived from 38 nondiabetic donors were differentiated in vitro to myotubes, and gene (mRNA) expression was quantified by real-time RT-PCR. Donors' insulin sensitivity was calculated from plasma insulin and glucose levels during oral glucose tolerance test (OGTT) and hyperinsulinemic-euglycemic clamp. RESULTS Basal myotube PPARD expression was closely related to the expression of its target genes PDK4 and ANGPTL4 (P = 0·0312 and P = 0·0003, respectively). Basal PPARD, PDK4 and ANGPTL4 expression levels were not associated with donors' insulin sensitivity (P > 0·2, all). Treatment of myotubes with a selective high-affinity PPARδ agonist (GW501516) did not change mean PPARD, but enhanced mean PDK4 and ANGPTL4 expression 13- and 16-fold, respectively (P < 0·0001, both). The individual PDK4 and ANGPTL4 expression levels reached upon GW501516 treatment were associated with donors' insulin sensitivity neither (P > 0·2, both). However, GW501516-mediated fold increments in PDK4 and ANGPTL4 expression, reflecting PPARδ responsiveness, were positively associated with donors' insulin sensitivity derived from OGTT (P = 0·0182 and P = 0·0231, respectively) and hyperinsulinemic-euglycemic clamp (P = 0·0046 and P = 0·0258, respectively). CONCLUSIONS Using a highly selective pharmacological tool, we show here that the individual responsiveness of human muscle cell PPARδ, rather than the absolute PPARD expression level, represents a major determinant of insulin sensitivity.
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Affiliation(s)
- Anna-Maria Ordelheide
- Division of Endocrinology, Diabetology, Angiology, Nephrology, and Clinical Chemistry, Department of Internal Medicine, Member of the German Center for Diabetes Research (DZD e.V.), Eberhard Karls University Tübingen, Tübingen, Germany
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Ordelheide AM, Heni M, Gommer N, Gasse L, Haas C, Guirguis A, Machicao F, Häring HU, Staiger H. The myocyte expression of adiponectin receptors and PPARδ is highly coordinated and reflects lipid metabolism of the human donors. Exp Diabetes Res 2011; 2011:692536. [PMID: 21331343 DOI: 10.1155/2011/692536] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/03/2010] [Revised: 12/21/2010] [Accepted: 01/05/2011] [Indexed: 11/24/2022]
Abstract
Muscle lipid oxidation is stimulated by peroxisome proliferator-activated receptor (PPAR) δ or adiponectin receptor signalling. We studied human myocyte expression of the PPARδ and adiponectin receptor genes and their relationship to lipid parameters of the donors. The mRNA levels of the three adiponectin receptors, AdipoR1, AdipoR2, and T-cadherin, were highly interrelated (r ≥ 0.91). However, they were not associated with GPBAR1, an unrelated membrane receptor. In addition, the adiponectin receptors were positively associated with PPARδ expression (r ≥ 0.75). However, they were not associated with PPARα. Using stepwise multiple linear regression analysis, PPARδ was a significant determinant of T-cadherin (P = .0002). However, pharmacological PPARδ activation did not increase T-cadherin expression. The myocyte expression levels of AdipoR1 and T-cadherin were inversely associated with the donors' fasting plasma triglycerides (P < .03). In conclusion, myocyte expression of PPARδ and the adiponectin receptors are highly coordinated, and this might be of relevance for human lipid metabolism in vivo.
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Zhou SS, Li D, Sun WP, Guo M, Lun YZ, Zhou YM, Xiao FC, Jing LX, Sun SX, Zhang LB, Luo N, Bian FN, Zou W, Dong LB, Zhao ZG, Li SF, Gong XJ, Yu ZG, Sun CB, Zheng CL, Jiang DJ, Li ZN. Nicotinamide overload may play a role in the development of type 2 diabetes. World J Gastroenterol 2009; 15:5674-84. [PMID: 19960564 PMCID: PMC2789220 DOI: 10.3748/wjg.15.5674] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate whether nicotinamide overload plays a role in type 2 diabetes.
METHODS: Nicotinamide metabolic patterns of 14 diabetic and 14 non-diabetic subjects were compared using HPLC. Cumulative effects of nicotinamide and N1-methylnicotinamide on glucose metabolism, plasma H2O2 levels and tissue nicotinamide adenine dinucleotide (NAD) contents of adult Sprague-Dawley rats were observed. The role of human sweat glands and rat skin in nicotinamide metabolism was investigated using sauna and burn injury, respectively.
RESULTS: Diabetic subjects had significantly higher plasma N1-methylnicotinamide levels 5 h after a 100-mg nicotinamide load than the non-diabetic subjects (0.89 ± 0.13 μmol/L vs 0.6 ± 0.13 μmol/L, P < 0.001). Cumulative doses of nicotinamide (2 g/kg) significantly increased rat plasma N1-methylnicotinamide concentrations associated with severe insulin resistance, which was mimicked by N1-methylnicotinamide. Moreover, cumulative exposure to N1-methylnicotinamide (2 g/kg) markedly reduced rat muscle and liver NAD contents and erythrocyte NAD/NADH ratio, and increased plasma H2O2 levels. Decrease in NAD/NADH ratio and increase in H2O2 generation were also observed in human erythrocytes after exposure to N1-methylnicotinamide in vitro. Sweating eliminated excessive nicotinamide (5.3-fold increase in sweat nicotinamide concentration 1 h after a 100-mg nicotinamide load). Skin damage or aldehyde oxidase inhibition with tamoxifen or olanzapine, both being notorious for impairing glucose tolerance, delayed N1-methylnicotinamide clearance.
CONCLUSION: These findings suggest that nicotinamide overload, which induced an increase in plasma N1-methylnicotinamide, associated with oxidative stress and insulin resistance, plays a role in type 2 diabetes.
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Staiger H, Haas C, Machann J, Werner R, Weisser M, Schick F, Machicao F, Stefan N, Fritsche A, Häring HU. Muscle-derived angiopoietin-like protein 4 is induced by fatty acids via peroxisome proliferator-activated receptor (PPAR)-delta and is of metabolic relevance in humans. Diabetes 2009; 58:579-89. [PMID: 19074989 PMCID: PMC2646056 DOI: 10.2337/db07-1438] [Citation(s) in RCA: 146] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
OBJECTIVE Long-chain fatty acids (LCFAs) contribute to metabolic homeostasis in part via gene regulation. This study's objective was to identify novel LCFA target genes in human skeletal muscle cells (myotubes). RESEARCH DESIGN AND METHODS In vitro methods included culture and treatment of human myotubes and C2C12 cells, gene array analysis, real-time RT-PCR, Western blotting, ELISA, chromatin immunoprecipitation, and RNA interference. Human subjects (two cohorts) were characterized by oral glucose tolerance test, hyperinsulinemic-euglycemic clamp, magnetic resonance imaging and spectroscopy, and standard blood analyses (glucose, insulin, C-peptide, and plasma lipids). RESULTS We show here that ANGPTL4 (encoding angiopoietin-like protein 4) represents a prominent LCFA-responsive gene in human myotubes. LCFA activated peroxisome proliferator-activated receptor (PPAR)-delta, but not PPAR-alpha or -gamma, and pharmacological activation of PPAR-delta markedly induced ANGPTL4 production and secretion. In C2C12 myocytes, knockdown of PPARD, but not of PPARG, blocked LCFA-mediated ANGPTL4 induction, and LCFA treatment resulted in PPAR-delta recruitment to the ANGPTL4 gene. In addition, pharmacological PPAR-delta activation induced LIPE (encoding hormone-sensitive lipase), and this response crucially depended on ANGPTL4, as revealed by ANGPTL4 knockdown. In a human cohort of 108 thoroughly phenotyped subjects, plasma ANGPTL4 positively correlated with fasting nonesterified fatty acids (P = 0.0036) and adipose tissue lipolysis (P = 0.0012). Moreover, in 38 myotube donors, plasma ANGPTL4 levels and adipose tissue lipolysis in vivo were reflected by basal myotube ANGPTL4 expression in vitro (P = 0.02, both). CONCLUSIONS ANGPTL4 is produced by human myotubes in response to LCFA via PPAR-delta, and muscle-derived ANGPTL4 seems to be of systemic relevance in humans.
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Affiliation(s)
- Harald Staiger
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Angiology, Nephrology, and Clinical Chemistry, Eberhard-Karls-University Tübingen, Tübingen, Germany.
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Chiu JD, Richey JM, Harrison LN, Zuniga E, Kolka CM, Kirkman E, Ellmerer M, Bergman RN. Direct administration of insulin into skeletal muscle reveals that the transport of insulin across the capillary endothelium limits the time course of insulin to activate glucose disposal. Diabetes 2008; 57:828-35. [PMID: 18223011 DOI: 10.2337/db07-1444] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Intravenous insulin infusion rapidly increases plasma insulin, yet glucose disposal occurs at a much slower rate. This delay in insulin's action may be related to the protracted time for insulin to traverse the capillary endothelium. An increased delay may be associated with the development of insulin resistance. The purpose of the present study was to investigate whether bypassing the transendothelial insulin transport step and injecting insulin directly into the interstitial space would moderate the delay in glucose uptake observed with intravenous administration of the hormone. RESEARCH DESIGN AND METHODS Intramuscular injections of saline (n = 3) or insulin (n = 10) were administered directly into the vastus medialis of anesthetized dogs. Injections of 0.3, 0.5, 0.7, 1.0, and 3.0 units insulin were administered hourly during a basal insulin euglycemic glucose clamp (0.2mU x min(-1) x kg(-1)). RESULTS Unlike the saline group, each incremental insulin injection caused interstitial (lymph) insulin to rise within 10 min, indicating rapid diffusion of the hormone within the interstitial matrix. Delay in insulin action was virtually eliminated, indicated by immediate dose-dependent increments in hindlimb glucose uptake. Additionally, bypassing insulin transport by direct injection into muscle revealed a fourfold greater sensitivity to insulin of in vivo muscle tissue than previously reported from intravenous insulin administration. CONCLUSIONS Our results indicate that the transport of insulin to skeletal muscle is a rate-limiting step for insulin to activate glucose disposal. Based on these results, we speculate that defects in insulin transport across the endothelial layer of skeletal muscle will contribute to insulin resistance.
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Affiliation(s)
- Jenny D Chiu
- Department of Physiology and Biophysics, University of Southern California, Keck School of Medicine, 1333 San Pablo St., MMR 626, Los Angeles, CA 90033, USA
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Ciaraldi TP, Nikoulina SE, Bandukwala RA, Carter L, Henry RR. Role of glycogen synthase kinase-3 alpha in insulin action in cultured human skeletal muscle cells. Endocrinology 2007; 148:4393-9. [PMID: 17569761 DOI: 10.1210/en.2006-0932] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
An association between glycogen synthase kinase-3 (GSK3) in skeletal muscle and insulin resistance has been demonstrated in type 2 diabetic patients. In addition, inhibition of GSK3 improves insulin action. The aim of the present study was to elucidate the role of the alpha-isoform of GSK3 in insulin resistance in human skeletal muscle cells from nondiabetic subjects maintained in culture. Transfection of muscle cells with specific antisense oligonucleotides resulted in a 30-50% decrease of GSK3alpha protein expression (P < 0.05). Whereas neither the basal fractional velocity of glycogen synthase (GS FV) (an indicator of the activation state of the enzyme) nor glucose uptake (GU) were altered, reducing GSK3alpha expression resulted in increases in insulin stimulation of both GS FV and GU. GSK3alpha overexpression (60-100% increase over control) did not alter basal GS FV or GU but impaired insulin stimulation of both responses. Knockdown of GSK alpha also led to an increase in insulin receptor substrate-1 protein expression but did not alter insulin stimulation of pS473-Akt phosphorylation. However, GSK3alpha overexpression impaired insulin action on pS473-Akt. In summary, we concluded the following: 1) modulation of GSK3alpha expression has no effect on basal GU and glycogen synthase activities; 2) reduction of GSK3alpha expression results in improvements in insulin action; and 3) elevation of GSK3alpha in human skeletal muscle cells can induce insulin resistance for several responses. We conclude that GSK3alpha is an important regulator of muscle insulin action.
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Affiliation(s)
- Theodore P Ciaraldi
- Veterans Affairs San Diego Healthcare System, 3350 La Jolla Village Drive, San Diego, California 92161, USA
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Weigert C, Düfer M, Simon P, Debre E, Runge H, Brodbeck K, Häring HU, Schleicher ED. Upregulation of IL-6 mRNA by IL-6 in skeletal muscle cells: role of IL-6 mRNA stabilization and Ca2+-dependent mechanisms. Am J Physiol Cell Physiol 2007; 293:C1139-47. [PMID: 17615159 DOI: 10.1152/ajpcell.00142.2007] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Skeletal muscle cells have been established as significant producers of IL-6 during exercise. This IL-6 production is discussed as one possible mediator of the beneficial effects of physical activity on glucose and fatty acid metabolism. IL-6 itself could be the exercise-related factor that upregulates and maintains its own production. We investigated this hypothesis and the underlying molecular mechanism in cultured C(2)C(12) cells. IL-6 led to a rapid and prolonged increase in IL-6 mRNA, which was also found in human myotubes. Because IL-6 has been shown to activate AMP-activated kinase (AMPK), we studied whether, in turn, activated AMPK induces IL-6 expression. Pharmacological activation of AMPK with 5-aminoimidazole-4-carboxamide-1-beta-4-ribofuranoside upregulated IL-6 mRNA expression, which was blocked by knockdown of AMPK alpha(1) and alpha(2) using small, interfering RNA (siRNA) oligonucleotides. However, the effect of IL-6 was shown to be independent of AMPK, since the siRNA approach silencing the AMPK alpha-subunits did not reduce the upregulation of IL-6 induced by IL-6 stimulation. The self-stimulatory effect of IL-6 partly involves a Ca(2+)-dependent pathway: IL-6 increased intracellular Ca(2+), and intracellular blockade of Ca(2+) with a Ca(2+) chelator reduced the IL-6-mediated increase in IL-6 mRNA levels. Moreover, inhibition of Ca(2+)/calmodulin-dependent kinase kinase with STO-609 or the siRNA approach decreased IL-6 mRNA levels of control and IL-6-stimulated cells. A major, STO-609-independent mechanism is the IL-6-mediated stabilization of its mRNA. The data suggest that IL-6 could act as autocrine factor upregulating its mRNA levels, thereby supporting its function as an exercise-activated factor in skeletal muscle cells.
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Affiliation(s)
- Cora Weigert
- Dept. of Internal Medicine, Division of Endocrinology, Metabolism, Pathobiochemistry and Clinical Chemistry, Univ. of Tuebingen, Otfried-Mueller-Straaae 10, D-72076 Tuebingen, Germany.
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Stefan N, Thamer C, Staiger H, Machicao F, Machann J, Schick F, Venter C, Niess A, Laakso M, Fritsche A, Häring HU. Genetic variations in PPARD and PPARGC1A determine mitochondrial function and change in aerobic physical fitness and insulin sensitivity during lifestyle intervention. J Clin Endocrinol Metab 2007; 92:1827-33. [PMID: 17327385 DOI: 10.1210/jc.2006-1785] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
CONTEXT Mitochondrial function is associated with aerobic physical fitness and insulin sensitivity and may play an important role in the pathophysiology of type 2 diabetes. Peroxisome proliferator-activated receptor (PPAR)-delta (gene PPARD) and PPARgamma coactivator 1alpha (gene PPARGC1A) are determinants of mitochondrial function in animals and in vitro. OBJECTIVE The objective of this study was to establish whether single-nucleotide polymorphisms (SNPs) in PPARD and PPARGC1A modulate the effect of exercise training on change in aerobic physical fitness and insulin sensitivity and whether they affect mitochondrial function in human myotubes in vitro. SETTING The study setting was the Tuebingen Lifestyle Intervention Program in a university teaching hospital. RESULTS After 9 months of intervention, the minor G allele of SNP rs2267668 in PPARD and the minor serine-encoding allele of the common Gly482Ser SNP in PPARGC1A were independently associated with less increase in individual anaerobic threshold (n = 136, P = 0.002 and P = 0.005), a precise measurement of aerobic physical fitness. Moreover, individual anaerobic threshold (+11%) and insulin sensitivity (+4%) increased less in subjects carrying the minor alleles at both SNPs (X/G-X/Ser), compared with homozygous carriers of the major alleles (A/A-Gly/Gly, +120% and +40%; P < 0.0001 and P = 0.015), suggesting an additive effect of the SNPs. In addition, low skeletal muscle mitochondrial function in vitro was detected in young carriers of the G allele of the SNP rs2267668 in PPARD (n = 19, P = 0.02). CONCLUSIONS These data provide evidence that the rs2267668 A/G SNP in PPARD and the Gly482Ser SNP in PPARGC1A have both independent and additive effects on the effectiveness of aerobic exercise training to increase aerobic physical fitness and insulin sensitivity.
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Affiliation(s)
- Norbert Stefan
- Department of Internal Medicine, Otfried-Müller-Strasse 10, D-72076 Tübingen, Germany.
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Abstract
Selective resistance to the effects of insulin on glucose metabolism in skeletal muscle and adipose tissue is a key feature of polycystic ovary syndrome (PCOS). The pathogenesis of insulin resistance in skeletal muscle in PCOS involves interaction of in vivo environmental factors with intrinsic defects in insulin signaling. We aimed to determine whether (1) intrinsic defects in insulin action/signaling and cytokine secretion were present in adipose cells in PCOS and (2) insulin resistance can be induced in control adipose cells by culture in medium conditioned by insulin-resistant PCOS fibroblasts. Subcutaneous abdominal preadipocytes from obese women with PCOS (n = 7) and age- and body mass index-matched controls (n = 5) were cultured for several generations in vitro. Basal and insulin-stimulated glycogen synthesis and basal glucose transport did not differ in the preadipocytes from women with PCOS and controls. Abundance of insulin receptor (IR) beta subunit, insulin receptor substrate (IRS) 1 and 2, p85 subunit of phosphatidylinositol 3-kinase, and extracellular signal-regulated kinase (ERK)1/2 activation did not differ. Secretion of tumor necrosis factor alpha and interleukin 6 did not differ. Insulin action on glycogen synthesis in control preadipocytes was not altered by coculture with or growth in media conditioned by PCOS skin fibroblasts with constitutive serine phosphorylation of IRbeta subunit (IR ser+), indicating that IR ser+ cells do not secrete an insulin resistance-inducing factor. We conclude that in contrast to skeletal muscle and skin fibroblasts, there is no evidence for intrinsic defects in insulin signaling in the PCOS adipose cell lineage, indicating that insulin resistance in these cells is likely due to factors in the in vivo environment.
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Affiliation(s)
- Anne Corbould
- Division of Women's Health, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
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Weigert C, Hennige AM, Lehmann R, Brodbeck K, Baumgartner F, Schaüble M, Häring HU, Schleicher ED. Direct cross-talk of interleukin-6 and insulin signal transduction via insulin receptor substrate-1 in skeletal muscle cells. J Biol Chem 2006; 281:7060-7. [PMID: 16418171 DOI: 10.1074/jbc.m509782200] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The exercise-induced interleukin (IL)-6 production and secretion within skeletal muscle fibers has raised the question of a putative tissue-specific function of IL-6 in the energy metabolism of the muscle during and after the exercise. In the present study, we followed the hypothesis that IL-6 signaling may directly interact with insulin receptor substrate (IRS)-1, a keystone in the insulin signaling cascade. We showed that IL-6 induces a rapid recruitment of IRS-1 to the IL-6 receptor complex in cultured skeletal muscle cells. Moreover, IL-6 induced a rapid and transient phosphorylation of Ser-318 of IRS-1 in muscle cells and in muscle tissue, but not in the liver of IL-6-treated mice, probably via the IL-6-induced co-recruitment of protein kinase C-delta. This Ser-318 phosphorylation improved insulin-stimulated Akt phosphorylation and glucose uptake in myotubes since transfection with an IRS-1/Glu-318 mutant simulating a permanent phospho-Ser-318 modification increased Akt phosphorylation and glucose uptake. Noteworthily, two inhibitory mechanisms of IL-6 on insulin action, phosphorylation of the inhibitory Ser-307 residue of IRS-1 and induction of SOCS-3 expression, were only found in liver but not in muscle of IL-6-treated mice. Thus, the data provided evidence for a possible molecular mechanism of the physiological metabolic effects of IL-6 in skeletal muscle, thereby exerting short term beneficial effects on insulin action.
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Affiliation(s)
- Cora Weigert
- Department of Internal Medicine, Division of Endocrinology, Metabolism, Pathobiochemistry and Clinical Chemistry, University of Tübingen, Otfried-Müller-Strasse 10, D-72076 Germany.
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Haugaard SB, Andersen O, Madsbad S, Frøsig C, Iversen J, Nielsen JO, Wojtaszewski JFP. Skeletal muscle insulin signaling defects downstream of phosphatidylinositol 3-kinase at the level of Akt are associated with impaired nonoxidative glucose disposal in HIV lipodystrophy. Diabetes 2005; 54:3474-83. [PMID: 16306364 DOI: 10.2337/diabetes.54.12.3474] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
More than 40% of HIV-infected patients on highly active antiretroviral therapy (HAART) experience fat redistribution (lipodystrophy), a syndrome associated with insulin resistance primarily affecting insulin-stimulated nonoxidative glucose metabolism (NOGM(ins)). Skeletal muscle biopsies, obtained from 18 lipodystrophic nondiabetic patients (LIPO) and 18 nondiabetic patients without lipodystrophy (NONLIPO) before and during hyperinsulinemic (40 mU.m(-2).min(-1))-euglycemic clamps, were analyzed for insulin signaling effectors. All patients were on HAART. Both LIPO and NONLIPO patients were normoglycemic (4.9 +/- 0.1 and 4.8 +/- 0.1 mmol/l, respectively); however, NOGM(ins) was reduced by 49% in LIPO patients (P < 0.001). NOGM(ins) correlated positively with insulin-stimulated glycogen synthase activity (I-form, P < 0.001, n = 36). Glycogen synthase activity (I-form) correlated inversely with phosphorylation of glycogen synthase sites 2+2a (P < 0.001, n = 36) and sites 3a+b (P < 0.001, n = 36) during clamp. Incremental glycogen synthase-kinase-3alpha and -3beta phosphorylation was attenuated in LIPO patients (Ps < 0.05). Insulin-stimulated Akt Ser473 and Akt Thr308 phosphorylation was decreased in LIPO patients (P < 0.05), whereas insulin receptor substrate-1-associated phosphatidylinositol (PI) 3-kinase activity increased significantly (P < 0.001) and similarly (NS) in both groups during clamp. Thus, low glycogen synthase activity explained impaired NOGM(ins) in HIV lipodystrophy, and insulin signaling defects were downstream of PI 3-kinase at the level of Akt. These results suggest mechanisms for the insulin resistance greatly enhancing the risk of type 2 diabetes in HIV lipodystrophy.
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Affiliation(s)
- Steen B Haugaard
- Department of Infectious Diseases, Clinical Research Unit 136, Hvidovre University Hospital, DK 2650 Hvidovre, Copenhagen, Denmark.
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26
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Kaltenbach S, Staiger H, Weisser M, Haas C, Stumvoll M, Machicao F, Häring HU. Adiponectin receptor gene expression in human skeletal muscle cells is not regulated by fibrates and thiazolidinediones. Int J Obes (Lond) 2005; 29:760-5. [PMID: 15824748 DOI: 10.1038/sj.ijo.0802957] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND Thiazolidinediones as PPARgamma agonists and fibrates as PPARalpha agonists improve insulin sensitivity in insulin-responsive tissues. Recent data show an induction of adiponectin receptor 2 (AdipoR2) by PPARalpha and PPARgamma agonists in human macrophages. OBJECTIVE In this study, we examined the effects of thiazolidinediones and fibrates on the expression of adiponectin receptors in human skeletal muscle cells, an important cell type in the context of insulin resistance. RESULTS AND METHODS In vitro differentiated human myotubes treated with troglitazone or rosiglitazone (20 h) showed no significant changes in AdipoR1 and AdipoR2 mRNA expression. PPARgamma activation was controlled by determination of PPARgamma mRNA induction. Likewise, differentiated myotubes treated with Wy-14,643 or fenofibrate (20 h) revealed no significant regulation of AdipoR1 and AdipoR2 mRNA. PPARalpha activation was assessed by measuring PDHK4 mRNA expression. CONCLUSION Induction of AdipoR gene expression in human skeletal muscle cells is not involved in the insulin-sensitizing effects of thiazolidinediones or fibrates.
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Affiliation(s)
- S Kaltenbach
- Department of Endocrinology, Metabolism and Pathobiochemistry, Medical Clinic Tübingen, Eberhard-Karls-University Tübingen, Germany
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27
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Staiger H, Staiger K, Haas C, Weisser M, Machicao F, Häring HU. Fatty acid-induced differential regulation of the genes encoding peroxisome proliferator-activated receptor-gamma coactivator-1alpha and -1beta in human skeletal muscle cells that have been differentiated in vitro. Diabetologia 2005; 48:2115-8. [PMID: 16132959 DOI: 10.1007/s00125-005-1895-z] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2005] [Accepted: 05/26/2005] [Indexed: 11/27/2022]
Abstract
AIMS/HYPOTHESIS The transcriptional coactivator peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha) enhances metabolically relevant pathways, such as gluconeogenesis, fatty acid oxidation, thermogenesis, oxidative phosphorylation and mitochondrial biogenesis. Since regulation of the expression of the gene encoding PGC-1alpha (PPARGC1A) by nutrients/metabolites has not been assessed in detail, the aim of this study was to determine whether PPARGC1A (and PPARGC1B) expression is modulated by common plasma fatty acids in human skeletal muscle cells. METHODS Human myotubes that had been differentiated in vitro were treated with 0.5 mmol/l myristate (C14:0), palmitate (C16:0), stearate (C18:0), palmitoleate (C16:1omega7), oleate (C18:1omega9) or linoleate (C18:2omega6). PPARGC1A/B mRNA was quantified by RT-PCR. Mitochondrial activity was determined by formazan formation. RESULTS Untreated cells expressed 28-fold more PPARGC1B mRNA than PPARGC1A mRNA (13.33+/-2.86 vs 0.47+/-0.08 fg/mug total RNA, n=5). PPARGC1A expression was increased two- to three-fold by all unsaturated fatty acids (UFAs) tested (p<0.05 each, n=5). In contrast, saturated fatty acids (SFAs) did not modulate PPARGC1A expression. Furthermore, the effect of linoleate was not blunted by palmitate. PPARGC1B mRNA expression was not increased by either the UFAs or the SFAs. SFAs reduced PPARGC1B expression (p<0.05 for palmitate and stearate, n=5). Notably, linoleate reversed palmitate's repressive effect on PPARGC1B. Myotube mitochondrial activity was increased by all UFAs (p<0.01 each, n=5), but was impaired by the SFA stearate (p<0.001, n=5). CONCLUSIONS/INTERPRETATION We report here that fatty acids differentially regulated expression of the genes encoding the PGC-1 isoforms. Since these effects were accompanied by significant changes in mitochondrial activity, we suggest that the fatty acid-induced regulation of expression of these genes plays an important role in muscle oxidative metabolism.
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Affiliation(s)
- H Staiger
- Department of Internal Medicine, Division of Endocrinology, Metabolism and Pathobiochemistry, Eberhard-Karls-University Tübingen, Tübingen, Germany
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Guerrero-Romero F, Rodríguez-Morán M, González-Ortiz M, Martínez-Abundis E. Early decrease of the percent of HOMA ɛ-cell function is independently related to family history of diabetes in healthy young nonobese individuals. Diabetes & Metabolism 2005; 31:382-6. [PMID: 16369201 DOI: 10.1016/s1262-3636(07)70208-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
OBJECTIVE To determine the relationship between family history of diabetes (FHD) and decrease in percent of HOMA beta-cell function (HOMA-beta%) index in healthy betanon-obese Mexican subjects. MATERIALS AND METHODS Forty-eight individuals (30 women and 18 men) with FHD were compared vs 48 control subjects (30 women and 18 men) in a cross-sectional study matched by age, sex, and Waist-to-Hip ratio. Pregnancy, obesity, being overweight, alcohol consumption, high blood pressure, and heavy physical activity were exclusion criteria. All the participants were required to have a Body Mass Index < 25 kg/m2 and serum fasting and 2-hours postload glucose levels lower than 6.1 mmol/l and 7.8 mmol/l, respectively. The reciprocal of serum fasting insulin concentrations (1/Ins0) (microU/ml) and HOMA-B% index were used as indicators of insulin sensitivity and beta-cell function. RESULTS Average age was of 19.4 +/- 3.6 vs 19.8 +/- 2.6, P = 0.66 for the subjects with and without FHD. HOMA-beta% index was significantly lower in the subjects with FHD (186.1 +/- 74.1 vs 252.7 +/- 149.5, P = 0.01). For similar levels of insulin sensitivity, subjects with FHD showed lower HOMA-beta% index than control subjects (P < 0.001). Multivariate regression analysis showed a strong and independent relationship between FHD and decrease of HOMA-beta% index (OR 2.6, CI95% 1.2-4.3, P = 0.01). CONCLUSIONS This study shows that normal-weight offspring of type 2 diabetes subjects exhibited a significant decrease of HOMA-beta% index suggesting that FHD exerts an independent early negative effect on beta-cell function.
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Affiliation(s)
- F Guerrero-Romero
- Medical Research Unit in Clinical Epidemiology, General Hospital of the Mexican Institute of Social Security (MISS), Durango, Mexico.
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29
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Weigert C, Hennige AM, Brischmann T, Beck A, Moeschel K, Schaüble M, Brodbeck K, Häring HU, Schleicher ED, Lehmann R. The phosphorylation of Ser318 of insulin receptor substrate 1 is not per se inhibitory in skeletal muscle cells but is necessary to trigger the attenuation of the insulin-stimulated signal. J Biol Chem 2005; 280:37393-9. [PMID: 16129678 DOI: 10.1074/jbc.m506134200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Ser/Thr phosphorylation of insulin receptor substrate 1 (IRS) is one key mechanism to stimulate and/or attenuate insulin signal transduction. Using a phospho-specific polyclonal antibody directed against phosphorylated Ser(318) of IRS-1, we found a rapid and transient insulin-stimulated phosphorylation of Ser(318) in human and rodent skeletal muscle cell models and in muscle tissue of insulin-treated mice. None of the investigated insulin resistance-associated factors (e.g. high glucose, tumor necrosis factor-alpha, adrenaline) stimulated the phosphorylation of Ser(318). Studying the function of this phosphorylation, we found that replacing Ser(318) by alanine completely prevented both the attenuation of insulin-stimulated Akt/protein kinase B Ser(473) phosphorylation and glucose uptake after 60 min of insulin stimulation. Unexpectedly, after acute insulin stimulation, we observed that phosphorylation of Ser(318) is not inhibitory but rather enhances insulin signal transduction because introduction of Ala(318) led to a reduction of the insulin-stimulated Akt/protein kinase B phosphorylation. Furthermore, replacing Ser(318) by glutamate, i.e. mimicking phosphorylation, improved glucose uptake after acute insulin stimulation. These data suggest that phosphorylation of Ser(318) is not per se inhibitory but is necessary to trigger the attenuation of the insulin-stimulated signal in skeletal muscle cells. Investigating the molecular mechanism of insulin-stimulated Ser(318) phosphorylation, we found that phosphatidylinositol 3-kinase-mediated activation of atypical protein kinase C-zeta and recruitment of protein kinase C-zeta to IRS-1 was responsible for this phosphorylation. We conclude that Ser(318) phosphorylation of IRS-1 is an early physiological event in insulin-stimulated signal transduction, which attenuates the continuing action of insulin.
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Affiliation(s)
- Cora Weigert
- Department of Internal Medicine IV, University Hospital Tuebingen, Germany
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30
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Weigert C, Hennige AM, Brodbeck K, Häring HU, Schleicher ED. Interleukin-6 acts as insulin sensitizer on glycogen synthesis in human skeletal muscle cells by phosphorylation of Ser473 of Akt. Am J Physiol Endocrinol Metab 2005; 289:E251-7. [PMID: 15755769 DOI: 10.1152/ajpendo.00448.2004] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Previous studies showed an insulin-"desensitizing" action of IL-6 on glycogen synthesis in hepatocytes. We recently found no inhibition of the proximal steps of the insulin signal cascade in human skeletal muscle cells. Because these data indicate a possible tissue-specific effect of IL-6, we investigated the influence of IL-6 on insulin-stimulated glycogen synthesis in these cells. At first, we found that incubation of the cells with 20 ng/ml IL-6 alone induced phosphorylation of Ser473 of Akt, but not of Thr308 time dependently and we observed that IL-6 augments insulin-induced Ser473 and Thr308 phosphorylation in the low nanomolar range of insulin. Moreover, IL-6 increased insulin-stimulated phosphorylation of glycogen synthase kinase-3. Accordingly, IL-6 enhanced glycogen synthesis in the presence of 3 and 10 nM insulin, whereas IL-6 alone had only a marginal effect. IL-6 treatment of C57Bl/6 mice readily stimulated phosphorylation of Ser473 in skeletal muscle. Our result that IL-6 did not induce Ser473 phosphorylation in the liver of these mice suggests a tissue-specific effect. Together, our data demonstrate a novel insulin-sensitizing function of IL-6 on glycogen synthesis in skeletal muscle cells and indicate that IL-6 exerts cell/tissue-specific effects on insulin action.
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Affiliation(s)
- Cora Weigert
- Dept. of Internal Medicine, Div. of Endocrinology, Metabolism, Pathobiochemistry and Clinical Chemistry, Univ. of Tübingen, Otfried-Müller-Strasse 10, D-72076 Tübingen, Germany
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31
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Cha BS, Ciaraldi TP, Park KS, Carter L, Mudaliar SR, Henry RR. Impaired fatty acid metabolism in type 2 diabetic skeletal muscle cells is reversed by PPARgamma agonists. Am J Physiol Endocrinol Metab 2005; 289:E151-9. [PMID: 15727952 DOI: 10.1152/ajpendo.00141.2004] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The impact of type 2 diabetes on the ability of muscle to accumulate and dispose of fatty acids and triglycerides was evaluated in cultured muscle cells from nondiabetic (ND) and type 2 diabetic (T2D) subjects. In the presence of 5 microM palmitate, T2D muscle cells accumulated less lipid than ND cells (11.5 +/- 1.2 vs. 15.1 +/- 1.4 nmol/mg protein, P < 0.05). Chronic treatment (4 days) with the peroxisome proliferator-activated receptor-gamma (PPARgamma) agonist troglitazone increased palmitate accumulation, normalizing uptake in T2D cells. There were no significant differences between groups with regard to the relative incorporation of palmitate into neutral lipid species. This distribution was also unaffected by troglitazone treatment. beta-Oxidation of both long-chain (palmitate) and medium-chain (octanoate) fatty acids in T2D muscle cells was reduced by approximately 40% compared with ND cells. Palmitate oxidation occurred primarily in mitochondrial ( approximately 40-50% of total) and peroxisomal (20-30%) compartments. The diabetes-related defect in palmitate oxidation was localized to the mitochondrial component. Both palmitate and octanoate oxidation were stimulated by a series of thiazolidinediones. Oxidation in T2D muscle cells was normalized after treatment. Troglitazone increased the mitochondrial component of palmitate oxidation. Skeletal muscle cells from T2D subjects express defects in free fatty acid metabolism that are retained in vitro, most importantly defects in beta-oxidation. These defects can be corrected by treatment with PPARgamma agonists. Augmentation of fatty acid disposal in skeletal muscle, potentially reducing intramyocellular triglyceride content, may represent one mechanism for the lipid-lowering and insulin-sensitizing effects of thiazolidinediones.
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Affiliation(s)
- Bong-Soo Cha
- Veterans Affairs San Diego Healthcare System, 3350 La Jolla Village Drive, San Diego, CA 92161, USA
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Pender C, Goldfine ID, Kulp JL, Tanner CJ, Maddux BA, MacDonald KG, Houmard JA, Youngren JF. Analysis of insulin-stimulated insulin receptor activation and glucose transport in cultured skeletal muscle cells from obese subjects. Metabolism 2005; 54:598-603. [PMID: 15877289 DOI: 10.1016/j.metabol.2004.11.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Obesity is associated with impaired insulin-stimulated glucose disposal in the skeletal muscle, but whether this is an intrinsic or acquired factor is unknown. In many patients with type 2 diabetes mellitus (T2D) and their nondiabetic relatives, who have a genetic predisposition for diabetes, insulin resistance is maintained in cultured muscle cells. To study the association of obesity with defects in insulin action, we investigated insulin stimulation of both insulin receptor (IR) autophosphorylation and subsequent glucose transport in primary skeletal muscle cell cultures obtained from both nonobese and obese nondiabetic subjects. In these 2 groups, there was no difference in the ability of insulin to induce autophosphorylation of the IR, phosphorylation of the downstream serine kinase Akt/PKB, or stimulation of glucose transport. Moreover, there were no major differences in cultured muscle cell content of either the IR, the IR antagonist PC-1, or GLUT 1 and GLUT 4. These data therefore indicate that the insulin resistance associated with obesity is not maintained in cultured muscle cells and suggest that this insulin resistance is an acquired feature of obesity.
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Affiliation(s)
- Celia Pender
- Division of Diabetes and Endocrine Research, Department of Medicine, Mount Zion Medical Center, University of California-San Francisco, Box 1616, San Francisco, CA 94143, USA
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Corbould A, Kim YB, Youngren JF, Pender C, Kahn BB, Lee A, Dunaif A. Insulin resistance in the skeletal muscle of women with PCOS involves intrinsic and acquired defects in insulin signaling. Am J Physiol Endocrinol Metab 2005; 288:E1047-54. [PMID: 15613682 DOI: 10.1152/ajpendo.00361.2004] [Citation(s) in RCA: 172] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Insulin resistance in polycystic ovary syndrome (PCOS) is due to a postbinding defect in signaling that persists in cultured skin fibroblasts and is associated with constitutive serine phosphorylation of the insulin receptor (IR). Cultured skeletal muscle from obese women with PCOS and age- and body mass index-matched control women (n = 10/group) was studied to determine whether signaling defects observed in this tissue in vivo were intrinsic or acquired. Basal and insulin-stimulated glucose transport and GLUT1 abundance were significantly increased in cultured myotubes from women with PCOS. Neither IR beta-subunit abundance and tyrosine autophosphorylation nor insulin receptor substrate (IRS)-1-associated phosphatidylinositol (PI) 3-kinase activity differed in the two groups. However, IRS-1 protein abundance was significantly increased in PCOS, resulting in significantly decreased PI 3-kinase activity when normalized for IRS-1. Phosphorylation of IRS-1 on Ser312, a key regulatory site, was significantly increased in PCOS, which may have contributed to this signaling defect. Insulin signaling via IRS-2 was also decreased in myotubes from women with PCOS. In summary, decreased insulin-stimulated glucose uptake in PCOS skeletal muscle in vivo is an acquired defect. Nevertheless, there are intrinsic abnormalities in glucose transport and insulin signaling in myotubes from affected women, including increased phosphorylation of IRS-1 Ser312, that may confer increased susceptibility to insulin resistance-inducing factors in the in vivo environment. These abnormalities differ from those reported in other insulin resistant states consistent with the hypothesis that PCOS is a genetically unique disorder conferring an increased risk for type 2 diabetes.
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Affiliation(s)
- Anne Corbould
- Division of Women's Health, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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Abstract
PURPOSE To examine noninsulin- (basal) and insulin-mediated glucose uptake in human skeletal muscle cells from endurance-trained and sedentary individuals. METHODS Muscle biopsies (vastus lateralis) were obtained from competitive, endurance-trained athletes (N=12; VO2peak 64.9+/-2.3 mL.kg-1.min-1) and their sedentary counterparts (N=8; VO2peak 51.8+/-2.2 mL.kg-1.min-1), and isolated satellite cells allowed to proceed to myotubes. RESULTS The myotubes exhibited a dose response for glucose uptake with increasing insulin concentrations; maximal glucose uptake was approximately 1.5-fold over basal. In relation to exercise training status, basal glucose uptake was significantly (P<0.05) elevated by approximately 75% in the endurance-trained versus sedentary men (20.1+/-2.1 vs 11.9+/-1.9 pmol.mg protein-1.min-1, respectively). This difference persisted at insulin concentrations of 10 and 1000 etaM, although the relative increase in insulin-mediated glucose uptake (fold increase over basal) did not differ between the sedentary and endurance-trained cells. CONCLUSIONS These data suggest that cultured skeletal muscle cells from endurance-trained athletes may differ in respect to basal glucose uptake.
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Affiliation(s)
- Jason R Berggren
- Human Performance Laboratory, Department of Exercise & Sport Science, and Diabetes/Obesity Center, East Carolina University, Greenville, NC 27858, USA.
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Gaster M, Beck-Nielsen H. The reduced insulin-mediated glucose oxidation in skeletal muscle from type 2 diabetic subjects may be of genetic origin—evidence from cultured myotubes. Biochim Biophys Acta Mol Basis Dis 2004; 1690:85-91. [PMID: 15337174 DOI: 10.1016/j.bbadis.2004.05.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2004] [Revised: 05/25/2004] [Accepted: 05/25/2004] [Indexed: 11/24/2022]
Abstract
Several defects in response to insulin have been described in vivo and in vitro in type 2 diabetes: a decreased glucose transport, defective glucose oxidation and altered glycogen synthesis. At present, it is unknown whether glucose oxidation is primarily affected or secondarily affected by, e.g. increased free fatty acids (FFA). The aim of this study was to evaluate whether myotubes established from type 2 diabetic subjects express a primarily or a FFA-induced reduced insulin-mediated glucose oxidation. We have therefore investigated glucose oxidation under basal, physiological conditions and during acute insulin stimulation with/without FFA. We found that myotubes established from type 2 diabetic subjects express a reduced insulin-stimulated increase in glucose oxidation. Moreover, an acute exposure to FFA reduces insulin-mediated glucose oxidation without alterations in glucose uptake and glycogen synthesis. Thus, we conclude that the diminished increase in insulin-stimulated glucose oxidation seen in type 2 diabetic subjects in vivo may be of genetic origin. Moreover, the glucose-fatty acid cycle seems not to be crucial for the pathophysiology of insulin resistance.
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Affiliation(s)
- Michael Gaster
- Department of Endocrinology, Odense University Hospital, DK-5000, Odense, Denmark.
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36
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Staiger H, Kaltenbach S, Staiger K, Stefan N, Fritsche A, Guirguis A, Péterfi C, Weisser M, Machicao F, Stumvoll M, Häring HU. Expression of adiponectin receptor mRNA in human skeletal muscle cells is related to in vivo parameters of glucose and lipid metabolism. Diabetes 2004; 53:2195-201. [PMID: 15331527 DOI: 10.2337/diabetes.53.9.2195] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The adiponectin receptors, AdipoR1 and AdipoR2, are thought to transmit the insulin-sensitizing, anti-inflammatory, and atheroprotective effects of adiponectin. In this study, we examined whether AdipoR mRNA expression in human myotubes correlates with in vivo measures of insulin sensitivity. Myotubes from 40 metabolically characterized donors expressed 1.8-fold more AdipoR1 than AdipoR2 mRNA (588 +/- 35 vs. 321 +/- 39 fg/microg total RNA). Moreover, the expression levels of both receptors correlated with each other (r = 0.45, P < 0.01). AdipoR1 mRNA expression was positively correlated with in vivo insulin and C-peptide concentrations, first-phase insulin secretion, and plasma triglyceride and cholesterol concentrations before and after adjustment for sex, age, waist-to-hip ratio, and body fat. Expression of AdipoR2 mRNA clearly associated only with plasma triglyceride concentrations. In multivariate linear regression models, mRNA expression of AdipoR1, but not AdipoR2, was a determinant of first-phase insulin secretion independent of insulin sensitivity and body fat. Finally, insulin did not directly modify myotube AdipoR1 mRNA expression in vitro. In conclusion, we provide evidence that myotube mRNA levels of both receptors are associated with distinct metabolic functions but not with insulin sensitivity. AdipoR1, but not AdipoR2, expression correlated with insulin secretion. The molecular nature of this link between muscle and beta-cells needs to be further clarified.
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Affiliation(s)
- Harald Staiger
- Department of Internal Medicine IV, Medical Clinic Tübingen, Otfried-Müller-Str. 10, D-72076 Tübingen, Germany
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Hill RA, Strat AL, Hughes NJ, Kokta TJ, Dodson MV, Gertler A. Early insulin signaling cascade in a model of oxidative skeletal muscle: mouse Sol8 cell line. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research 2004; 1693:205-11. [PMID: 15363634 DOI: 10.1016/j.bbamcr.2004.08.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2004] [Revised: 07/12/2004] [Accepted: 08/12/2004] [Indexed: 10/26/2022]
Abstract
Cell models provide important tools to investigate the mechanisms modulating the insulin-signaling cascade. Insulin interaction and subsequent signaling of cells is complex and regulated at multiple levels: receptor abundance, binding dynamics, phosphorylation/dephosphorylation of tyrosine and serine/threonine residues, and subsequent interactions of key intracellular messengers. We report early insulin signaling events in the mouse Sol8 myogenic cell line. Sol8 cells responded to insulin by increasing total IRS-1, p85 PI3-kinase and tyrosine phosphorylated IRS-1 (pY-IRS-1) at 10 min (P<0.05), but not at 1 min of insulin stimulation. The dose-response relationships at 10-min insulin (10 to 300 nM) stimulation showed that IRS-1 and pY-IRS-1 responded to 100 and 300 nM insulin, and the p85 PI3-kinase response peaked at 30 nM insulin. PI3-kinase appeared to be present in high abundance and, in response to insulin, recruitment to the insulin receptor tyrosine kinase (IR) of IRS-1 and PI3-kinase was observed. The increase in IRS-1 detected in IR immunoprecipitates was twofold, while the corresponding increase in PI3-kinase was threefold, suggesting direct recruitment of PI3-kinase to the IR. PI3-kinase detected in IRS-1 immunoprecipitates in response to insulin increased 1.7-fold. An ultimate target of this pathway, GLUT4 recruitment to the PM, was delayed (30 min), the increase in GLUT4 being of similar magnitude (1.6-fold) to the early signaling events. Saturation binding analysis indicated that IR in the plasma membrane was not down-regulated in response to insulin. The present study suggests that early signaling events in the insulin cascade are invoked in Sol8 myogenic cells and that this cell line provides a useful model to study insulin signaling.
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Affiliation(s)
- Rodney A Hill
- Department of Animal and Veterinary Science, University of Idaho, Moscow, Idaho 83844, USA.
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Weigert C, Brodbeck K, Staiger H, Kausch C, Machicao F, Häring HU, Schleicher ED. Palmitate, but not unsaturated fatty acids, induces the expression of interleukin-6 in human myotubes through proteasome-dependent activation of nuclear factor-kappaB. J Biol Chem 2004; 279:23942-52. [PMID: 15028733 DOI: 10.1074/jbc.m312692200] [Citation(s) in RCA: 219] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Circulating interleukin-6 (IL-6), insulin, and free fatty acid (FFA) concentrations are associated with impaired insulin action in obese and type 2 diabetic individuals. However, a causal relationship between elevated plasma FFAs and IL-6 has not been shown. Because skeletal muscle represents a major target of impaired insulin action, we studied whether FFAs may affect IL-6 expression in human myotubes. We demonstrate that specifically saturated FFAs, e.g. palmitate (0.25 mm), induce IL-6 mRNA expression and protein secretion by a proteasome-dependent mechanism that leads to a rapid and chronic activation of nuclear factor-kappaB. Insulin, high glucose concentrations, or unsaturated FFAs did not activate IL-6 expression. In fact, the unsaturated FFA linoleate inhibited palmitate-induced IL-6 production. Because inhibition of palmitate metabolism by the acyl-CoA synthetase inhibitor triacsin C did not abolish IL-6 expression, it appears that the palmitate molecule per se exerts the observed effects. Furthermore, we show that in human myotubes, IL-6 activates the phosphorylation of signal transducer and activator of transcription 3 in concentrations similar to hepatocytes. However, no inhibitory effect of IL-6 on insulin action, determined as phosphatidylinositol 3-kinase association with insulin receptor substrate-1, Akt phosphorylation, and glycogen synthesis, was detected. We conclude that IL-6 expression may be modulated by the composition of circulating FFA, e.g. by diet, and that skeletal muscle cells could be target cells for IL-6.
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Affiliation(s)
- Cora Weigert
- Department of Internal Medicine, Division of Endocrinology, Metabolism and Pathobiochemistry, University of Tübingen, Tübingen 72076, Germany
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Abstract
Skeletal muscle is an important tissue for the proper maintenance of glucose homeostasis as it accounts for the major portion of glucose disposal following infusion or ingestion of glucose. Thus, cellular mechanisms regulating glucose uptake in skeletal muscle have a major impact on whole-body glucose homeostasis. Glucose transport into skeletal muscle is a rate-limiting step for glucose utilization under physiological conditions and a site of insulin resistance in patients with non-insulin-dependent diabetes mellitus (NIDDM). Defects in insulin signalling have been coupled to impaired glucose uptake in skeletal muscle from NIDDM patients. Although the exact aetiology is unclear, genetic and environmental (high-energy diets combined with a sedentary lifestyle) factors contribute to the onset of NIDDM. Furthermore, hyperglycaemia is linked with insulin resistance. This chapter will consider mechanisms for glucose disposal in skeletal muscle, potential sites of insulin resistance in skeletal muscle in NIDDM patients and the impact of hyperglycaemia on insulin action.
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Affiliation(s)
- Juleen R Zierath
- Department of Surgical Sciences, Section for Integrative Physiology, Karolinska Institutet, von Eulers väg 4, II, SE-171 77 Stockholm, Sweden.
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Beck-Nielsen H, Vaag A, Poulsen P, Gaster M. Metabolic and genetic influence on glucose metabolism in type 2 diabetic subjects--experiences from relatives and twin studies. Best Pract Res Clin Endocrinol Metab 2003; 17:445-67. [PMID: 12962696 DOI: 10.1016/s1521-690x(03)00041-1] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Based on our investigations in first-degree relatives, in twins in general, and in monozygotic twins discordant for type 2 diabetes, we have studied the inheritance of glucose intolerance, insulin resistance and insulin secretion in order to evaluate the role of genes versus environment in the development of type 2 diabetes. Insulin resistance in type 2 diabetes is mainly linked to glucose disposal in skeletal muscle, i.e. reduced glycogen synthesis. In order to investigate the genetic component responsible for the reduced glycogen synthase activity and reduced glucose transport, we also investigated cultured myotubes based on in vivo skeletal muscle biopsies. The results obtained in our own studies are discussed in comparison with the international literature. We conclude that both genetic and environmental factors play a role in the development of type 2 diabetes (hyperglycaemia), and that only subjects who are genetically disposed to insulin resistance and who possess beta-cells which are unable to compensate for the degree of insulin resistance seem to develop type 2 diabetes. Variables of two gene alleles disposing to insulin resistance have been identified, and their role is discussed. The most important environmental factor seems to be obesity, but intrauterine malnutrition also plays a role. The cellular mechanism responsible for obesity/lipid-induced diabetes mellitus is discussed with specific emphasis on the role of accumulation of long-chain AcylCoA and triglycerides in liver, muscle and beta-cells.
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Weigert C, Klopfer K, Kausch C, Brodbeck K, Stumvoll M, Häring HU, Schleicher ED. Palmitate-induced activation of the hexosamine pathway in human myotubes: increased expression of glutamine:fructose-6-phosphate aminotransferase. Diabetes 2003; 52:650-6. [PMID: 12606504 DOI: 10.2337/diabetes.52.3.650] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The nutrient sensing capacity of the hexosamine biosynthetic pathway (HBP) has been implicated in the development of insulin resistance of skeletal muscle. To study the molecular mechanism of the free fatty acid (FFA)-induced activation of the HBP myotubes obtained from muscle biopsies of metabolically characterized, subjects were stimulated with different fatty acids for 20 h. Incubation with the saturated fatty acids palmitate and stearate (0.5 mmol/l) resulted in a three- to fourfold increase in mRNA expression of glutamine:fructose-6-phosphate aminotransferase (GFAT), the key and rate-limiting enzyme of the hexosamine pathway. Unsaturated fatty acids or 30 mmol/l glucose had little or no effect. Palmitate increased the amount of GFAT protein nearly two-fold, and subsequently, the concentration of UDP-N-acetylglucosamine, the end product of the HBP, was 1.3-fold enhanced in the palmitate-stimulated myotubes. The nonmetabolized fatty acid bromopalmitate had no effect. The DNA binding activity of the transcription factor Sp1, a target downstream of the HBP, was increased by palmitate and completely lost after enzymatic removal of O-GlcNAc. No correlation was found between the palmitate-induced increase in GFAT protein and the insulin resistance in the respective subjects. The findings reveal a new mechanism for how FFAs induce the activation of the HBP.
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Affiliation(s)
- Cora Weigert
- Department of Internal Medicine, Division of Endocrinology, Metabolism and Pathobiochemistry, University of Tübingen, Otfried-Müller-Strasse 10, D-72076 Tübingen, Germany
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42
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Abstract
The incidence of type 2 diabetes mellitus (T2D) and obesity is increasing rapidly worldwide, reaching epidemic proportions. Insulin resistance is a key feature in both conditions and plays an important pathophysiological role. Over the last two decades a central role in the origin of insulin resistance has emerged for defects in the intracellular insulin signaling cascade leading to glucose uptake. Herein, we will 1) review insulin signaling pathways leading to glucose uptake, 2) review mouse models of insulin resistance that demonstrate the pathophysiologic importance of specific defects of these pathways and 3) discuss the molecular basis for insulin resistance in some human disease states known to be associated with insulin resistance. Finally, we will briefly mention some novel treatment targets for T2D stemming from this knowledge.
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Affiliation(s)
- Peter Vollenweider
- Department of Internal Medicine, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
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Haupt A, Kausch C, Dahl D, Bachmann O, Stumvoll M, Häring HU, Matthaei S. Effect of glimepiride on insulin-stimulated glycogen synthesis in cultured human skeletal muscle cells: a comparison to glibenclamide. Diabetes Care 2002; 25:2129-32. [PMID: 12453949 DOI: 10.2337/diacare.25.12.2129] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE To examine the effect of glimepiride on insulin-stimulated glycogen synthesis in cultured human skeletal muscle cells in comparison with glibenclamide. RESEARCH DESIGN AND METHODS Myotubes derived from glucose-tolerant subjects were incubated with glimepiride or glibenclamide (0-100 micro mol/l) for 4 h and with or without insulin (100 nmol/l) for 2 h, and subsequently glycogen synthesis was determined. RESULTS Glimepiride had no significant effect on basal glycogen synthesis; in contrast, glimepiride caused a dose-dependent increase of insulin-stimulated glycogen synthesis, with a maximal effect of 39.97 +/- 8.4% (mean +/- SEM, n = 4, P < 0,02). The time course of this glimepiride effect on insulin-stimulated glycogen synthesis showed a peak after 12 h incubation with a half maximal effect after 4 h. Preincubation of the myotubes with wortmannin (100 nmol/l), an inhibitor of phosphatidylinositol (PI)- 3 kinase, caused an inhibition of this glimepiride effect on insulin-stimulated glycogen synthesis. In contrast to glimepiride, incubation of myotubes with glibenclamide (0-100nmol/l), a second generation sulfonylurea, had no significant effect on basal or insulin-stimulated glycogen synthesis. CONCLUSIONS Incubation of cultured human skeletal muscle cells derived from glucose-tolerant subjects with glimepiride caused a dose-dependent increase of insulin-stimulated glycogen synthesis using therapeutic glimepiride concentrations. This glimepiride effect seems to be mediated via the PI3 kinase pathway. In contrast to glimepiride, glibenclamide had no significant effect on basal or insulin-stimulated glycogen synthesis. These results suggest that glimepiride, beside its well-known effect to stimulate insulin secretion, possess an insulin-sensitizing action in cultured human skeletal muscle cells in support of the concept of an extrapancreatic action of glimepiride.
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Affiliation(s)
- Axel Haupt
- University of Tübingen, Department of Endocrinology and Metabolism, Germany
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Smith U. Impaired ('diabetic') insulin signaling and action occur in fat cells long before glucose intolerance--is insulin resistance initiated in the adipose tissue? Int J Obes (Lond) 2002; 26:897-904. [PMID: 12080441 DOI: 10.1038/sj.ijo.0802028] [Citation(s) in RCA: 146] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2001] [Revised: 02/12/2002] [Accepted: 02/19/2002] [Indexed: 12/12/2022]
Abstract
This review postulates and presents recent evidence that insulin resistance is initiated in the adipose tissue and also suggests that the adipose tissue may play a pivotal role in the induction of insulin resistance in the muscles and the liver. Marked impairments in insulin's intracellular signaling cascade are present in fat cells from type 2 diabetic patients, including reduced IRS-1 gene and protein expression, impaired insulin-stimulated PI3-kinase and PKB/Akt activities. In contrast, upstream insulin signaling in skeletal muscle from diabetic subjects only shows modest impairments and PKB/Akt activation in vivo by insulin appears normal. However, insulin-stimulated glucose transport and glycogen synthesis are markedly reduced. Similar marked impairments in insulin signaling, including reduced IRS-1 expression, impaired insulin-stimulated PI3-kinase and PKB/Akt activities are also seen in some (approximately 30%) normoglycemic individuals with genetic predisposition for type 2 diabetes. In addition, GLUT4 expression is markedly reduced in these cells, similar to what is seen in diabetic cells. The individuals with reduced cellular expression of IRS-1 and GLUT4 are also markedly insulin resistant and exhibit several characteristics of the Insulin Resistance Syndrome.Thus, a 'diabetic' pattern is seen in the fat cells also in normoglycemic subjects and this is associated with a marked insulin resistance in vivo. It is proposed that insulin resistance and/or its effectors is initiated in fat cells and that this may secondarily encompass other target tissues for insulin, including the impaired glucose transport in the muscles.
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Affiliation(s)
- U Smith
- The Lundberg Laboratory for Diabetes Research, Department of Internal Medicine, Sahlgrenska Academy at Göteborg University, Göteborg, Sweden.
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45
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Abstract
Insulin resistance is a characteristic feature of type II diabetes mellitus and obesity. Although defects in glucose homeostasis have been recognized for decades, the molecular mechanisms accounting for impaired whole body glucose uptake are still not fully understood. Skeletal muscle constitutes the largest insulin-sensitive organ in humans; thus, insulin resistance in this tissue will have a major impact on whole body glucose homeostasis. Intense efforts are under way to define the molecular mechanisms that regulate glucose metabolism and gene expression in insulin-sensitive tissues. Knowledge of the human genome sequence, used in concert with gene and/or protein array technology, will provide a powerful means to facilitate efforts in revealing molecular targets that regulate glucose homeostasis in type II diabetes mellitus. This will offer quicker ways forward to identifying gene expression profiles in insulin-sensitive and insulin-resistant human tissue. This review will present our current understanding of potential defects in insulin signal transduction pathways, with an emphasis on mechanisms regulating glucose transport in skeletal muscle from people with type II diabetes mellitus. Elucidation of the pathways involved in the regulation of glucose homeostasis will offer insight into the causation of insulin resistance and type II diabetes mellitus. Furthermore, this will identify biochemical entry points for drug intervention to improve glucose homeostasis.
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Affiliation(s)
- Juleen R Zierath
- Department of Clinical Physiology, Karolinska Hospital, Karolinska Institutet, Stockholm, Sweden.
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Korsheninnikova E, Seppälä-Lindroos A, Vehkavaara S, Goto T, Virkamäki A. Elevated fasting insulin concentrations associate with impaired insulin signaling in skeletal muscle of healthy subjects independent of obesity. Diabetes Metab Res Rev 2002; 18:209-16. [PMID: 12112939 DOI: 10.1002/dmrr.272] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
BACKGROUND Insulin signaling is impaired in the skeletal muscle of obese subjects but whether defects in skeletal muscle insulin signaling also characterize insulin resistance of non-obese individuals is unknown. The detection of insulin signaling defects in muscle biopsies is hampered by the variation of the contaminating non-muscle elements such as blood, connective tissue, fat, and blood vessel structures. Freeze-drying and macroscopic purification of the muscle fibers prior to the analysis might offer a possibility to minimize the analytical variation due to these contaminants. METHODS In the present study we first determined whether insulin signaling could be reliably assessed in freeze-dried muscle specimens, which are free of non-muscle contaminants, and then applied this method to the study of insulin signaling in weight-matched insulin-sensitive and insulin-resistant non-diabetic men. RESULTS In rat muscle, increases in tyrosine phosphorylation of insulin receptor (IR) and activity of the insulin receptor substrate-1 (IRS-1)-associated phosphatidylinositol (PI) 3-kinase activity by insulin were similar or higher in freeze-dried and purified muscle than wet muscle. Prior to freeze-drying and purification, biopsies of human vastus lateralis muscle contained between 1% and 40% non-muscle contaminants (11+/-3%, mean+/-SEM, n=19). In freeze-dried biopsies of human vastus lateralis muscle taken before and after 30 min of hyperinsulinemia (serum free insulin 61+/-1 mU/l) in 13 non-diabetic men, insulin increased IR tyrosine phosphorylation 1.4-fold (p<0.05) and IRS-1-associated PI 3-kinase activity 1.7-fold (p<0.005). Insulin-stimulated PI 3-kinase activity was significantly inversely correlated with the fasting serum insulin concentration (r=-0.57, p<0.05). When divided according to the median fasting serum insulin concentration, the men with high fasting insulin [HI, n=7, age 44+/-3 years, body mass index (BMI) 25+/-1 kg/m(2)] as compared to the men with low fasting insulin [LI, n=6, age 45+/-3 years (NS), BMI 24+/-1 kg/m(2) (NS)] had lower rates of whole-body glucose uptake (3.4+/-0.4 vs 5.5+/-0.3 mg/kg min, p<0.005), higher fasting plasma glucose concentrations (5.9+/-0.2 vs 5.2+/-0.1 mmol/l, p<0.05), higher fasting serum triglycerides (1.4+/-0.2 vs 0.9+/-0.1 mmol/l, p<0.05) and lower high-density lipoprotein (HDL) cholesterol concentrations (1.3+/-0.1 vs 1.7+/-0.1 mmol/l, p<0.05). Insulin-stimulated IR tyrosine phosphorylation (p<0.05) and IRS-1-associated PI 3-kinase activity (p<0.05) were significantly lower in the HI than the LI group. CONCLUSIONS Taken together these data demonstrate that early insulin signaling events can be reliably assessed in freeze-dried human skeletal muscle, and that in vivo insulin resistance and its accompanying features are associated with defects in early insulin signaling events in human skeletal muscle independent of body weight.
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Vollenweider P, Ménard B, Nicod P. Insulin resistance, defective insulin receptor substrate 2-associated phosphatidylinositol-3' kinase activation, and impaired atypical protein kinase C (zeta/lambda) activation in myotubes from obese patients with impaired glucose tolerance. Diabetes 2002; 51:1052-9. [PMID: 11916925 DOI: 10.2337/diabetes.51.4.1052] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Impaired glucose tolerance (IGT) is characterized by insulin resistance. Recently, defects in the insulin-signaling cascade have been implicated in the pathogenesis of insulin resistance. To study insulin signaling in IGT, we used human skeletal muscle cells in primary culture from patients with IGT and control subjects. In these cultured myotubes, we assessed insulin-induced 2-deoxyglucose uptake and early steps of the metabolic insulin-signaling cascade. Myotubes in culture from patients with IGT had insulin-induced glucose uptake that was roughly 30-50% less than that from control subjects. This insulin resistance was associated with impaired insulin receptor substrate (IRS)-2-associated phosphatidylinositol 3' (PI3) kinase activation and IRS-2 tyrosine phosphorylation as well as significantly decreased protein kinase C (PKC)-zeta/lambda activation in response to insulin. IRS-1- associated PI3 kinase activation and insulin receptor autophosphorylation were comparable in the two groups. Protein expression levels for the insulin receptor, IRS-1, IRS-2, the p85 regulatory subunit of PI3 kinase, Akt, PKC-zeta/lambda, GLUT1, and GLUT4 were also similar in the two groups. In conclusion, myotubes from patients with IGT have impaired insulin-induced glucose uptake. This is associated with impaired IRS-2-associated PI3 kinase activation and PKC-zeta/lambda activation. Our results suggest that these defects may contribute to insulin resistance in IGT patients.
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Affiliation(s)
- Peter Vollenweider
- Department of Internal Medicine, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
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Gaster M, Petersen I, Højlund K, Poulsen P, Beck-Nielsen H. The diabetic phenotype is conserved in myotubes established from diabetic subjects: evidence for primary defects in glucose transport and glycogen synthase activity. Diabetes 2002; 51:921-7. [PMID: 11916908 DOI: 10.2337/diabetes.51.4.921] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The most well-described defect in the pathophysiology of type 2 diabetes is reduced insulin-mediated glycogen synthesis in skeletal muscles. It is unclear whether this defect is primary or acquired secondary to dyslipidemia, hyperinsulinemia, or hyperglycemia. We determined the glycogen synthase (GS) activity; the content of glucose-6-phosphate, glucose, and glycogen; and the glucose transport in satellite cell cultures established from diabetic and control subjects. Myotubes were precultured in increasing insulin concentrations for 4 days and subsequently stimulated acutely by insulin. The present study shows that the basal glucose uptake as well as insulin-stimulated GS activity is reduced in satellite cell cultures established from patients with type 2 diabetes. Moreover, increasing insulin concentrations could compensate for the reduced GS activity to a certain extent, whereas chronic supraphysiological insulin concentrations induced insulin resistance in GS and glucose transport activity. Our data suggest that insulin resistance in patients with type 2 diabetes comprises at least two important defects under physiological insulin concentrations: a reduced glucose transport under basal conditions and a reduced GS activity under acute insulin stimulation, implicating a reduced glucose uptake in the fasting state and a diminished insulin-mediated storage of glucose as glycogen after a meal.
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Affiliation(s)
- Michael Gaster
- Department of Endocrinology, Odense University Hospital, Odense, Denmark.
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Abstract
Delta-6 Desaturase, one of the rate-limiting enzymes, catalyzes the conversion of linoleic acid (C18:2 omega6) into gamma-linolenic acid (C18:3 omega6), arachidonic acid (C20:4 omega6), and further metabolites. Recently, it has been shown that human Delta-6 desaturase is expressed not only in liver but in a variety of human tissues, including muscle. Skeletal muscle is a major site of insulin action, and insulin sensitivity may be related to the fatty acid composition of muscle lipids. We examined the effects of troglitazone on the regulation of Delta-6 desaturase gene expression in human muscle cell cultures obtained from muscle biopsies (n = 15). Delta-6 Desaturase mRNA and peroxisome proliferator-activated receptor gamma2 (PPARgamma2) mRNA were quantified by two-step RT-PCR, and the activity of the Delta-6 desaturase enzyme was estimated by gas chromatographic analysis of the omega 6-C18:3/C18:2 fatty acids ratio. In cells treated with 11.5 micromol troglitazone for 4 days, PPARgamma2 mRNA levels were significantly increased (301.0 +/- 51.5%, P < 0.05) and Delta-6 desaturase mRNA levels were significantly decreased (41.7 +/- 5.9%, P < 0.0005) compared with the untreated controls. In accordance with the decrease of Delta-6 desaturase mRNA, there was a significant decrease in the omega6-C18:3/C18:2 ratio down to 47.4 +/- 7.5% in cholesterol esters, 54.2 +/- 7.4% in phospholipids, 56.7 +/- 6.5% in nonesterified fatty acids, and 67.7 +/- 5.9% in triglycerides. The troglitazone-induced decrease in Delta-6 desaturase mRNA is associated with a change in the unsaturated fatty acid composition of the muscle cells. These results add new aspects to the known thiazolidinedione effects on lipid metabolism.
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Affiliation(s)
- Hans Günther Wahl
- Department of Endocrinology and Metabolism, University of Tübingen, Tübingen, Germany.
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Storgaard H, Song XM, Jensen CB, Madsbad S, Björnholm M, Vaag A, Zierath JR. Insulin signal transduction in skeletal muscle from glucose-intolerant relatives of type 2 diabetic patients [corrected]. Diabetes 2001; 50:2770-8. [PMID: 11723060 DOI: 10.2337/diabetes.50.12.2770] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
To determine whether defects in the insulin signal transduction cascade are present in skeletal muscle from prediabetic individuals, we excised biopsies from eight glucose-intolerant male first-degree relatives of patients with type 2 diabetes (IGT relatives) and nine matched control subjects before and during a euglycemic-hyperinsulinemic clamp. IGT relatives were insulin-resistant in oxidative and nonoxidative pathways for glucose metabolism. In vivo insulin infusion increased skeletal muscle insulin receptor substrate-1 (IRS-1) tyrosine phosphorylation (P = 0.01) and phosphatidylinositide 3-kinase (PI 3-kinase) activity (phosphotyrosine and IRS-1 associated) in control subjects (P < 0.02) but not in IGT relatives (NS). The incremental increase in insulin action on IRS-1 tyrosine phosphorylation was lower in IGT relatives versus control subjects (P < 0.05). The incremental defects in signal transduction noted for IRS-1 and PI 3-kinase may be attributed to elevated basal phosphorylation/activity of these parameters, because absolute phosphorylation/activity under insulin-stimulated conditions was similar between IGT relatives and control subjects. Insulin increased Akt serine phosphorylation in control subjects and IGT relatives, with a tendency for reduced phosphorylation in IGT relatives (P = 0.12). In conclusion, aberrant phosphorylation/activity of IRS-1, PI 3-kinase, and Akt is observed in skeletal muscle from relatives of patients with type 2 diabetes with IGT. However, the elevated basal activity of these signaling intermediates and the lack of a strong correlation between these parameters to glucose metabolism suggests that other defects of insulin signal transduction and/or downstream components of glucose metabolism may play a greater role in the development of insulin resistance in skeletal muscle from relatives of patients with type 2 diabetes.
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Affiliation(s)
- H Storgaard
- Department of Endocrinology, Hvidovre Hospital and Clinical Trial Unit, University of Copenhagen, Copenhagen, Denmark
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