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Szendroedi J, Roden M. Mitochondrial fitness and insulin sensitivity in humans. Diabetologia 2008; 51:2155-67. [PMID: 18802678 DOI: 10.1007/s00125-008-1153-2] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2008] [Accepted: 04/15/2008] [Indexed: 02/06/2023]
Abstract
Human mitochondria can be studied either in biopsies or by measuring flux through ATP synthase and phosphocreatine recovery using magnetic resonance spectroscopy. Myocellular ATP production (flux through ATP synthase [fATP]) increases by up to 90% during 8 h of insulin stimulation. Fasting mitochondrial function is 14-40% lower than in controls in the presence of insulin resistance, as seen in those with type 2 diabetes, their insulin-resistant relatives or the obese. Insulin-stimulated fATP is abolished in insulin-resistant relatives and patients with type 2 diabetes, and patients frequently show decreased mitochondrial size/density. Age, fat mass, physical activity, plasma NEFA and glucose all correlate negatively with mitochondrial function, but it is for methodological reasons difficult to determine whether reduced mitochondrial content or function account for reduced ATP production in insulin resistance. Experimental plasma NEFA elevation appears to inhibit mitochondrial function by interfering with the metabolic actions of insulin, which might explain impaired mitochondrial function in obesity. Alternatively, primary mitochondrial abnormalities, as seen in those with inherited risk of type 2 diabetes, could decrease lipid oxidation, thereby raising circulating and intracellular NEFA levels. In type 2 diabetes, chronic hyperglycaemia and dyslipidaemia could first diminish the function, and subsequently reduce the size or density of mitochondria via oxidative stress and apoptosis. Many questions remain unsolved, including (1) which mechanisms regulate mitochondrial adaptation to nutrient overload; (2) what factors control the expression of genes encoding mitochondrial proteins and other signals involved in mitochondrial biogenesis; (3) which geno/phenotypes are associated with both insulin resistance and mitochondrial abnormalities; and (4) which are the most promising targets for improving mitochondrial fitness in insulin resistance?
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Affiliation(s)
- J Szendroedi
- First Medical Department, Hanusch Hospital (Teaching Hospital of the Medical University of Vienna), Vienna, Austria
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202
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Earnest CP. Exercise interval training: An improved stimulus for improving the physiology of pre-diabetes. Med Hypotheses 2008; 71:752-61. [DOI: 10.1016/j.mehy.2008.06.024] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2008] [Revised: 04/22/2008] [Accepted: 06/23/2008] [Indexed: 10/21/2022]
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203
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Blouin CM, Le Lay S, Lasnier F, Dugail I, Hajduch E. Regulated association of caveolins to lipid droplets during differentiation of 3T3-L1 adipocytes. Biochem Biophys Res Commun 2008; 376:331-5. [DOI: 10.1016/j.bbrc.2008.08.154] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2008] [Accepted: 08/28/2008] [Indexed: 10/25/2022]
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204
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Turner N, Heilbronn LK. Is mitochondrial dysfunction a cause of insulin resistance? Trends Endocrinol Metab 2008; 19:324-30. [PMID: 18804383 DOI: 10.1016/j.tem.2008.08.001] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2008] [Revised: 08/12/2008] [Accepted: 08/12/2008] [Indexed: 01/03/2023]
Abstract
Insulin resistance is a key defect associated with obesity and type-2 diabetes. The precise factors that lead to insulin resistance have not been elucidated fully, but there is a strong association between insulin resistance and inappropriate lipid accumulation in insulin-target tissues. Over the past decade, several studies have reported changes in markers of mitochondrial metabolism in insulin-resistant individuals. These observations have led to the theory that compromised mitochondrial oxidative function, particularly in skeletal muscle, causes excess lipid deposition and the development of insulin resistance. Here, we review the latest findings regarding the link between mitochondrial metabolism and insulin action and, in particular, highlight several recent studies that call into question the cause-and-effect relationship between mitochondrial dysfunction and insulin resistance.
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Affiliation(s)
- Nigel Turner
- Diabetes and Obesity Research Program, Garvan Institute of Medical Research, 384 Victoria St, Darlinghurst, NSW 2010, Australia.
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205
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Larade K, Jiang Z, Zhang Y, Wang W, Bonner-Weir S, Zhu H, Bunn HF. Loss of Ncb5or results in impaired fatty acid desaturation, lipoatrophy, and diabetes. J Biol Chem 2008; 283:29285-91. [PMID: 18682384 DOI: 10.1074/jbc.m804645200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Targeted ablation of the novel flavoheme reductase Ncb5or knock-out (KO) results in progressive loss of pancreatic beta-cells and white adipose tissue over time. Lipoatrophy persisted in KO animals in which the confounding metabolic effects of diabetes were eliminated by islet transplantation (transplanted knockout (TKO)). Lipid profiles in livers prepared from TKO animals were markedly deficient in triglycerides and diacylglycerides. Despite enhanced expression of stearoyl-Co-A desaturase-1, levels of palmitoleic and oleic acids (Delta9 fatty acid desaturation) were decreased in TKO relative to wild type controls. Treatment of KO hepatocytes with palmitic acid reduced cell viability and increased apoptosis, a response blunted by co-incubation with oleic acid. The results presented here support the hypothesis that Ncb5or supplies electrons for fatty acid desaturation, offer new insight into the regulation of a crucial step in fatty acid biosynthesis, and provide a plausible explanation for both the diabetic and the lipoatrophic phenotype in Ncb5or(-/-) mice.
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Affiliation(s)
- Kevin Larade
- Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA
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206
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Bell M, Wang H, Chen H, McLenithan JC, Gong DW, Yang RZ, Yu D, Fried SK, Quon MJ, Londos C, Sztalryd C. Consequences of lipid droplet coat protein downregulation in liver cells: abnormal lipid droplet metabolism and induction of insulin resistance. Diabetes 2008; 57:2037-45. [PMID: 18487449 PMCID: PMC2494696 DOI: 10.2337/db07-1383] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
OBJECTIVE Accumulation of intracellular lipid droplets (LDs) in non-adipose tissues is recognized as a strong prognostic factor for the development of insulin resistance in obesity. LDs are coated with perilipin, adipose differentiation-related protein, tail interacting protein of 47 kd (PAT) proteins that are thought to regulate LD turnover by modulating lipolysis. Our hypothesis is that PAT proteins modulate LD metabolism and therefore insulin resistance. RESEARCH DESIGN AND METHODS We used a cell culture model (murine AML12 loaded with oleic acid) and small interfering RNA to directly assess the impact of PAT proteins on LD accumulation, lipid metabolism, and insulin action. PAT proteins associated with excess fat deposited in livers of diet-induced obese (DIO) mice were also measured. RESULTS Cells lacking PAT proteins exhibited a dramatic increase in LD size and a decrease in LD number. Further, the lipolytic rate increased by approximately 2- to 2.5-fold in association with increased adipose triglyceride lipase (ATGL) at the LD surface. Downregulation of PAT proteins also produced insulin resistance, as indicated by decreased insulin stimulation of Akt phosphorylation (P < 0.001). Phosphoinositide-dependent kinase-1 and phosphoinositide 3-kinase decreased, and insulin receptor substrate-1 307 phosphorylation increased. Increased lipids in DIO mice livers were accompanied by changes in PAT composition but also increased ATGL, suggesting a relative PAT deficiency. CONCLUSIONS These data establish an important role for PAT proteins as surfactant at the LD surface, packaging lipids in smaller units and restricting access of lipases and thus preventing insulin resistance. We suggest that a deficiency of PAT proteins relative to the quantity of ectopic fat could contribute to cellular dysfunction in obesity and type 2 diabetes.
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Affiliation(s)
- Ming Bell
- Geriatric Research, Education and Clinical Center, Baltimore Veterans Affairs Health Care Center, Division of Gerontology, Department of Medicine, School of Medicine, University of Maryland, Baltimore, Maryland, USA
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207
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Cardona F, Tunez I, Tasset I, Murri M, Tinahones F. Similar increase in oxidative stress after fat overload in persons with baseline hypertriglyceridemia with or without the metabolic syndrome. Clin Biochem 2008; 41:701-5. [DOI: 10.1016/j.clinbiochem.2008.03.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2007] [Revised: 02/21/2008] [Accepted: 03/01/2008] [Indexed: 01/28/2023]
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208
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Essop MF, Camp HS, Choi CS, Sharma S, Fryer RM, Reinhart GA, Guthrie PH, Bentebibel A, Gu Z, Shulman GI, Taegtmeyer H, Wakil SJ, Abu-Elheiga L. Reduced heart size and increased myocardial fuel substrate oxidation in ACC2 mutant mice. Am J Physiol Heart Circ Physiol 2008; 295:H256-65. [PMID: 18487439 DOI: 10.1152/ajpheart.91489.2007] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The cardiac-enriched isoform of acetyl-CoA carboxylase (ACC2) is a key regulator of mitochondrial fatty acid (FA) uptake via carnitine palmitoyltransferase 1 (CPT1). To test the hypothesis that oxidative metabolism is upregulated in hearts from animals lacking ACC2 (employing a transgenic Acc2-mutant mouse), we assessed cardiac function in vivo and determined rates of myocardial substrate oxidation ex vivo. When examined by echocardiography, there was no difference in systolic function, but left ventricular mass of the Acc2-mutant (MUT) mouse was significantly reduced ( approximately 25%) compared with wild-types (WT). Reduced activation of the mammalian target of rapamycin (mTOR) and its downstream target p70S6K was found in MUT hearts. Exogenous oxidation rates of oleate were increased approximately 22%, and, unexpectedly, exogenous glucose oxidation rates were also increased in MUT hearts. Using a hyperinsulinemic-euglycemic clamp, we found that glucose uptake in MUT hearts was increased by approximately 83%. Myocardial triglyceride levels were significantly reduced in MUT vs. WT while glycogen content was the same. In parallel, transcript levels of PPARalpha and its target genes, pyruvate dehydrogenase kinase-4 (PDK-4), malonyl-CoA decarboxylase (MCD), and mCPT1, were downregulated in MUT mice. In summary, we report that 1) Acc2-mutant hearts exhibit a marked preference for the oxidation of both glucose and FAs coupled with greater utilization of endogenous fuel substrates (triglycerides), 2) attenuated mTOR signaling may result in reduced heart sizes observed in Acc2-mutant mice, and 3) Acc2-mutant hearts displayed normal functional parameters despite a significant decrease in size.
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Affiliation(s)
- M Faadiel Essop
- Department of Physiological Sciences, Stellenbosch University, Stellenbosch, South Africa
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209
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Chanseaume E, Bielicki G, Tardy AL, Renou JP, Freyssenet D, Boirie Y, Morio B. Impaired resting muscle energetics studied by (31)P-NMR in diet-induced obese rats. Obesity (Silver Spring) 2008; 16:572-7. [PMID: 18239558 DOI: 10.1038/oby.2007.91] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
OBJECTIVE Mitochondrial activity is altered in skeletal muscle of obese, insulin-resistant or type 2 diabetic patients. We hypothesized that this situation was associated with profound adaptations in resting muscle energetics. For that purpose, we used in vivo (31)P-nuclear magnetic resonance ((31)P-NMR) in male sedentary Wistar rats fed with obesogenic diets known to induce alterations in muscle mitochondrial activity. METHODS AND PROCEDURES Two experimental diets (high sucrose and high fat) were provided for 6 weeks at two levels of energy (standard, N and high, H) and compared to control diet. The rates of the adenosine triphosphate (ATP) exchange between phosphocreatine (PCr) and gamma-ATP (k(a)) and beta-adenosine diphosphate (beta-ADP) to beta-ATP (k(b)) were evaluated using (31)P-NMR in resting gastrocnemius muscle. Muscle contents in phosphorylated compounds as well as creatine, were assessed using (31)P-NMR and biochemical assays, respectively. RESULTS ATP content increased by 6.7-8.5% in standard-energy high-sucrose (NSU), high-energy high-fat (HF) and high-energy high-sucrose (HSU) groups compared to control (P < 0.05), whereas PCr content decreased by 4.2-6.4% (P < 0.01). Consequently, PCr to ATP ratio decreased in NSU, HF, and HSU groups, compared to control (P < 0.01). Furthermore in high-energy groups (HF and HSU) compared to control, creatine contents were decreased by 14-19% (P < 0.001), whereas k(a) and k(b) fluxes were increased by 89-133% (P < 0.001) and 243-277% (P < 0.01), respectively. DISCUSSION Our in vivo data showed adaptations of resting skeletal muscle energetics in response to high-energy diets. Increased activity of enzymes catalyzing ATP production may reflect a compensatory mechanism to face impaired mitochondrial ATP synthesis in order to preserve intracellular energy homeostasis.
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210
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Amengual J, Ribot J, Bonet ML, Palou A. Retinoic acid treatment increases lipid oxidation capacity in skeletal muscle of mice. Obesity (Silver Spring) 2008; 16:585-91. [PMID: 18239600 DOI: 10.1038/oby.2007.104] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
OBJECTIVE All-trans retinoic acid (ATRA), a carboxylic form of vitamin A, favors in mice a mobilization of body fat reserves that correlates with an increment of oxidative and thermogenic capacity in adipose tissues. The objective of this study has been to investigate the effect of ATRA treatment on skeletal muscle capacity for fatty-acid catabolism. METHODS AND PROCEDURES Tissue composition and gene expression related to lipid and oxidative metabolism were analyzed in skeletal muscle of mice acutely treated with ATRA or vehicle (olive oil). RESULTS ATRA treatment triggered a dose-dependent increase in the muscle mRNA expression levels of selected enzymes, transporters and transcription factors involved in fatty-acid oxidation, respiration, and thermogenesis namely: muscle-type carnitine palmitoyltransferase 1, acyl CoA oxidase 1, subunit II of cytochrome oxidase, uncoupling protein 3, peroxisome proliferator-activated receptor-gamma co-activator -1alpha and peroxisome proliferator-activated receptor-delta (PPARdelta). The treatment also resulted in the upregulation of the mRNA levels of acetyl-CoA carboxylase 2 (ACC2), a key regulatory enzyme for mitochondrial fatty-acid oxidation in muscle. Skeletal muscle protein levels of PPARdelta and retinoid X receptor gamma, a partner for many nuclear receptors involved in lipid metabolism, were increased after ATRA treatment. Muscle lipid content was decreased. DISCUSSION These results indicate that ATRA treatment increases the capacity of skeletal muscle for fatty-acid oxidation. Knowledge of nutrients or nutrient-derivatives capable of enhancing oxidative metabolism in muscle and other tissues can contribute to new avenues of prevention and treatment of obesity and related disorders.
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Affiliation(s)
- Jaume Amengual
- Laboratory of Molecular Biology, Nutrition and Biotechnology, Universitat de les Illes Balears, Palma de Mallorca, Spain
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211
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Graier WF, Trenker M, Malli R. Mitochondrial Ca2+, the secret behind the function of uncoupling proteins 2 and 3? Cell Calcium 2008; 44:36-50. [PMID: 18282596 DOI: 10.1016/j.ceca.2008.01.001] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2007] [Revised: 01/07/2008] [Accepted: 01/07/2008] [Indexed: 12/20/2022]
Abstract
The underlying molecular action of the novel uncoupling proteins 2 and 3 (UCP2 and UCP3) is still under debate. The proteins have been implicated in many cell functions, including the regulation of insulin secretion and regulation of reactive oxygen species (ROS) generation. These effects have mainly been explained by suggesting that the proteins establish a proton leak through the inner mitochondrial membrane (IMM). However, accumulating data question this mechanism and suggest that UCP2 and UCP3 may play other roles, including carrying free fatty acids from the matrix towards the intermembrane space, or contributing to the mitochondrial Ca(2+) uniport. Accordingly, in this review we reflect on these actions of UCP2/UCP3 and discuss alternative explanations for the molecular mechanisms by which UCP2/UCP3 might contribute to aspects of cell function. Based on the potential role of UCP2/UCP3 in regulating mitochondrial Ca(2+) uptake, we propose a scheme whereby these proteins integrate Ca(2+)-dependent signal transduction and energy metabolism in order to meet the energy demand of the cell for its continuous response, adaptation, and stimulation to environmental input.
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Affiliation(s)
- Wolfgang F Graier
- Institute of Molecular Biology and Biochemistry, Molecular and Cellular Physiology Research Unit, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, Graz, Austria.
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212
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Feuvray D, Darmellah A. Diabetes-related metabolic perturbations in cardiac myocyte. DIABETES & METABOLISM 2008; 34 Suppl 1:S3-9. [DOI: 10.1016/s1262-3636(08)70096-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2007] [Accepted: 10/30/2007] [Indexed: 12/21/2022]
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213
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Thomas C, Auwerx J, Schoonjans K. Bile acids and the membrane bile acid receptor TGR5--connecting nutrition and metabolism. Thyroid 2008; 18:167-74. [PMID: 18279017 DOI: 10.1089/thy.2007.0255] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A multitude of endocrine, neural, and metabolic signaling pathways are activated upon food intake to coordinate the effective use of the available energy. Bile acids (BAs) are released from the gallbladder after each meal and subsequently facilitate the digestion of nutrients. Since concentrations of BAs increase postprandially in the serum, they are also signals of food availability that bridge nutrition with metabolism. Both nuclear and membrane receptors mediate BA signaling. Whereas the nuclear receptor farnesoid X receptor mainly affects enterohepatic lipid homeostasis, the G protein-coupled receptor TGR5 stimulates glucagon-like protein 1 production in enteroendocrine cells and activates thyroid hormone in brown adipose tissue and muscle, through the stimulation of type 2 iodothyronine deiodinase (D2). Through its insulinotropic effects, TGR5 may improve glucose homeostasis; through the activation of D2, it will stimulate energy expenditure and protect against the onset of obesity. These properties position TGR5 as an attractive and "drugable" target in our fight against the metabolic syndrome.
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Affiliation(s)
- Charles Thomas
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), CNRS/INSERM/ULP, Illkirch, France
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214
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Wright D, Sutherland L. Antioxidant supplemention in the treatment of skeletal muscle insulin resistance: potential mechanisms and clinical relevance. Appl Physiol Nutr Metab 2008; 33:21-31. [DOI: 10.1139/h07-155] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The incidence of type 2 diabetes has increased dramatically over the past several decades and this trend is projected to continue into the foreseeable future. Skeletal muscle insulin resistance is thought to be a key development in the pathogenesis of type 2 diabetes. Given this fact, interventions that prevent or reverse impairments in skeletal muscle action can have profound effects on whole-body glucose homeostasis. Traditional approaches used in this regard include exercise, weight loss, and insulin-sensitizing drugs such as thiazolidinediones (TZDs). Although these interventions have proven effective in improving glucose homeostasis, there are adherence issues seen with lifestyle interventions and undesirable side effects have been reported with TZDs. With these points in mind, the development of alternative strategies to maintain or improve skeletal muscle insulin sensitivity is warranted. In this context, the purpose of the present review is to highlight the role of antioxidant compounds in the prevention and treatment of skeletal muscle insulin resistance. Specifically, we will briefly describe the mechanisms of insulin-stimulated skeletal muscle glucose uptake and the potential mediators of oxidative stress induced insulin resistance, highlight data suggesting that antioxidant compounds can have beneficial effects on skeletal muscle insulin action, and discuss potential mechanisms mediating this effect.
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Affiliation(s)
- David Wright
- Alberta Institute of Human Nutrition, 3-18b Ag/For Centre, University of Alberta, Edmonton, AB T6G 2P5
| | - Lindsey Sutherland
- Alberta Institute of Human Nutrition, 3-18b Ag/For Centre, University of Alberta, Edmonton, AB T6G 2P5
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215
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Phielix E, Mensink M. Type 2 diabetes mellitus and skeletal muscle metabolic function. Physiol Behav 2008; 94:252-8. [PMID: 18342897 DOI: 10.1016/j.physbeh.2008.01.020] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2007] [Revised: 01/23/2008] [Accepted: 01/25/2008] [Indexed: 12/22/2022]
Abstract
Type 2 diabetic patients are characterized by a decreased fat oxidative capacity and high levels of circulating free fatty acids (FFAs). The latter is known to cause insulin resistance, in particularly in skeletal muscle, by reducing insulin stimulated glucose uptake, most likely via accumulation of lipid inside the muscle cell. A reduced skeletal muscle oxidative capacity can exaggerate this. Furthermore, type 2 diabetes is associated with impaired metabolic flexibility, i.e. an impaired switching from fatty acid to glucose oxidation in response to insulin. Thus, a reduced fat oxidative capacity and metabolic inflexibility are important components of skeletal muscle insulin resistance. The cause of these derangements in skeletal muscle of type 2 diabetic patients remains to be elucidated. An impaired mitochondrial function is a likely candidate. Evidence from both in vivo and ex vivo studies supports the idea that an impaired skeletal muscle mitochondrial function is related to the development of insulin resistance and type 2 diabetes mellitus. A decreased mitochondrial oxidative capacity in skeletal muscle was revealed in diabetic patients, using in vivo 31-Phosphorus Magnetic Resonance Spectroscopy (31P-MRS). However, quantification of mitochondrial function using ex vivo high-resolution respirometry revealed opposite results. Future (human) studies should challenge this concept of impaired mitochondrial function underlying metabolic defects and prove if mitochondria are truly functional impaired in insulin resistance, or low in number, and whether it represents the primary starting point of pathogenesis of insulin resistance, or is just an other feature of the insulin resistant state.
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Affiliation(s)
- Esther Phielix
- Department of Human Biology, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), Maastricht University, Maastricht, the Netherlands.
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216
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UCP-2 and UCP-3 proteins are differentially regulated in pancreatic beta-cells. PLoS One 2008; 3:e1397. [PMID: 18167556 PMCID: PMC2164968 DOI: 10.1371/journal.pone.0001397] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2007] [Accepted: 12/10/2007] [Indexed: 11/19/2022] Open
Abstract
Background Increased uncoupling protein-2 (UCP-2) expression has been associated with impaired insulin secretion, whereas UCP-3 protein levels are decreased in the skeleton muscle of type-2 diabetic subjects. In the present studies we hypothesize an opposing effect of glucose on the regulation of UCP-2 and UCP-3 in pancreatic islets. Methodology Dominant negative UCP-2 and wild type UCP-3 adenoviruses were generated, and insulin release by transduced human islets was measured. UCP-2 and UCP-3 mRNA levels were determined using quantitative PCR. UCP-2 and UCP-3 protein expression was investigated in human islets cultured in the presence of different glucose concentrations. Human pancreatic sections were analyzed for subcellular localization of UCP-3 using immunohistochemistry. Principal Findings Dominant negative UCP-2 expression in human islets increased insulin secretion compared to control islets (p<0.05). UCP-3 mRNA is expressed in human islets, but the relative abundance of UCP-2 mRNA was 8.1-fold higher (p<0.05). Immunohistochemical analysis confirmed co-localization of UCP-3 protein with mitochondria in human beta-cells. UCP-2 protein expression in human islets was increased ∼2-fold after high glucose exposure, whereas UCP-3 protein expression was decreased by ∼40% (p<0.05). UCP-3 overexpression improved glucose-stimulated insulin secretion. Conclusions UCP-2 and UCP-3 may have distinct roles in regulating beta-cell function. Increased expression of UCP-2 and decreased expression of UCP-3 in humans with chronic hyperglycemia may contribute to impaired glucose-stimulated insulin secretion. These data imply that mechanisms that suppress UCP-2 or mechanisms that increase UCP-3 expression and/or function are potential therapeutic targets to offset defects of insulin secretion in humans with type-2 diabetes.
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217
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Kaput J, Perlina A, Hatipoglu B, Bartholomew A, Nikolsky Y. Nutrigenomics: concepts and applications to pharmacogenomics and clinical medicine. Pharmacogenomics 2007; 8:369-90. [PMID: 17391074 DOI: 10.2217/14622416.8.4.369] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The maintenance of health and the prevention and treatment of chronic diseases are influenced by naturally occurring chemicals in foods. In addition to supplying the substrates for producing energy, a large number of dietary chemicals are bioactive--that is, they alter the regulation of biological processes and, either directly or indirectly, the expression of genetic information. Nutrients and bioactives may produce different physiological phenotypes among individuals because of genetic variability and not only alter health, but also disease initiation, progression and severity. The study and application of gene-nutrient interactions is called nutritional genomics or nutrigenomics. Nutrigenomic concepts, research strategies and clinical implementation are similar to and overlap those of pharmacogenomics, and both are fundamental to the treatment of disease and maintenance of optimal health.
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Affiliation(s)
- Jim Kaput
- Department of Surgery, University of Illinois Chicago, 909 South Wolcott Street MC 958, Chicago, IL 60612, USA.
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218
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Schrauwen-Hinderling VB, Roden M, Kooi ME, Hesselink MK, Schrauwen P. Muscular mitochondrial dysfunction and type 2 diabetes mellitus. Curr Opin Clin Nutr Metab Care 2007; 10:698-703. [PMID: 18089950 DOI: 10.1097/mco.0b013e3282f0eca9] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
PURPOSE OF REVIEW Muscular mitochondrial dysfunction, leading to the accumulation of fat in skeletal muscle, has been proposed to be involved in the development of type 2 diabetes mellitus. Here, we review human studies that investigated various aspects of mitochondrial function in relation to muscular insulin sensitivity and/or diabetes. RECENT FINDINGS In-vivo magnetic resonance spectroscopy allows assessment of mitochondrial functionality from adenosine triphosphate flux in the nonexercising state and from phosphocreatine recovery from (sub)maximal exercising. Application of both approaches revealed reduced mitochondrial oxidative capacity in insulin-resistant (pre)diabetic humans. Reductions in mitochondrial density may contribute to, or even underlie, these findings as well as intrinsic defects in mitochondrial respiration. So far, only two studies reported measurements of mitochondrial respiratory capacity in intact mitochondria in diabetic patients, with inconsistent findings. SUMMARY Muscular mitochondrial aberrations in type 2 diabetes mellitus can be detected, but it is so far unclear if these aberrations are causally related to the development of the disease. Alternatively, mitochondrial dysfunction may simply be the consequence of elevated plasma fatty acids or glucose levels.
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219
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Kamijo Y, Hora K, Kono K, Takahashi K, Higuchi M, Ehara T, Kiyosawa K, Shigematsu H, Gonzalez FJ, Aoyama T. PPARalpha protects proximal tubular cells from acute fatty acid toxicity. J Am Soc Nephrol 2007; 18:3089-100. [PMID: 17978304 DOI: 10.1681/asn.2007020238] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Affiliation(s)
- Yuji Kamijo
- Department of Metabolic Regulation, Institute on Aging and Adaptation, Shinshu University School of Medicine, Matsumoto, Japan.
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220
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Li H, Black PN, Chokshi A, Sandoval-Alvarez A, Vatsyayan R, Sealls W, DiRusso CC. High-throughput screening for fatty acid uptake inhibitors in humanized yeast identifies atypical antipsychotic drugs that cause dyslipidemias. J Lipid Res 2007; 49:230-44. [PMID: 17928635 DOI: 10.1194/jlr.d700015-jlr200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Fatty acids are implicated in the development of dyslipidemias, leading to type 2 diabetes and cardiovascular disease. We used a standardized small compound library to screen humanized yeast to identify compounds that inhibit fatty acid transport protein (FATP)-mediated fatty acid uptake into cells. This screening procedure used live yeast cells expressing human FATP2 to identify small compounds that reduced the import of a fluorescent fatty acid analog, 4,4-difluoro-5-methyl-4-bora-3a,4a-diaza-s-indacene-3-dodecanoic acid (C(1)-BODIPY-C(12)). The library used consisted of 2,080 compounds with known biological activities. Of these, approximately 1.8% reduced cell-associated C(1)-BODIPY-C(12) fluorescence and were selected as potential inhibitors of human FATP2-mediated fatty acid uptake. Based on secondary screens, 28 compounds were selected as potential fatty acid uptake inhibitors. Some compounds fell into four groups with similar structural features. The largest group was structurally related to a family of tricyclic, phenothiazine-derived drugs used to treat schizophrenia and related psychiatric disorders, which are also known to cause metabolic side effects, including hypertriglyceridemia. Potential hit compounds were studied for specificity of interaction with human FATP and efficacy in human Caco-2 cells. This study validates this screening system as useful to assess the impact of drugs in preclinical screening for fatty acid uptake.
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Affiliation(s)
- Hong Li
- Center for Metabolic Disease, Ordway Research Institute, Inc., Albany Medical College, Albany, NY 12208, USA
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221
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Wadley GD, Choate J, McConell GK. NOS isoform-specific regulation of basal but not exercise-induced mitochondrial biogenesis in mouse skeletal muscle. J Physiol 2007; 585:253-62. [PMID: 17916611 DOI: 10.1113/jphysiol.2007.141309] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Nitric oxide is a potential regulator of mitochondrial biogenesis. Therefore, we investigated if mice deficient in endothelial nitric oxide synthase (eNOS-/-) or neuronal NOS (nNOS-/-) have attenuated activation of skeletal muscle mitochondrial biogenesis in response to exercise. eNOS-/-, nNOS-/- and C57Bl/6 (CON) mice (16.3 +/- 0.2 weeks old) either remained in their cages (basal) or ran on a treadmill (16 m min(-1), 5% grade) for 60 min (n = 8 per group) and were killed 6 h after exercise. Other eNOS-/-, nNOS-/- and CON mice exercise trained for 9 days (60 min per day) and were killed 24 h after the last bout of exercise training. eNOS-/- mice had significantly higher nNOS protein and nNOS-/- mice had significantly higher eNOS protein in the EDL, but not the soleus. The basal mitochondrial biogenesis markers NRF1, NRF2alpha and mtTFA mRNA were significantly (P< 0.05) higher in the soleus and EDL of nNOS-/- mice whilst basal citrate synthase activity was higher in the soleus and basal PGC-1alpha mRNA higher in the EDL. Also, eNOS-/- mice had significantly higher basal citrate synthase activity in the soleus but not the EDL. Acute exercise increased (P< 0.05) PGC-1alpha mRNA in soleus and EDL and NRF2alpha mRNA in the EDL to a similar extent in all genotypes. In addition, short-term exercise training significantly increased cytochrome c protein in all genotypes (P< 0.05) in the EDL. In conclusion, eNOS and nNOS are differentially involved in the basal regulation of mitochondrial biogenesis in skeletal muscle but are not critical for exercise-induced increases in mitochondrial biogenesis in skeletal muscle.
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Affiliation(s)
- G D Wadley
- Department of Physiology, University of Melbourne, Parkville, Victoria, 3010, Australia.
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222
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Noland RC, Woodlief TL, Whitfield BR, Manning SM, Evans JR, Dudek RW, Lust RM, Cortright RN. Peroxisomal-mitochondrial oxidation in a rodent model of obesity-associated insulin resistance. Am J Physiol Endocrinol Metab 2007; 293:E986-E1001. [PMID: 17638705 DOI: 10.1152/ajpendo.00399.2006] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Peroxisomal oxidation yields metabolites that are more efficiently utilized by mitochondria. This is of potential clinical importance because reduced fatty acid oxidation is suspected to promote excess lipid accumulation in obesity-associated insulin resistance. Our purpose was to assess peroxisomal contributions to mitochondrial oxidation in mixed gastrocnemius (MG), liver, and left ventricle (LV) homogenates from lean and fatty (fa/fa) Zucker rats. Results indicate that complete mitochondrial oxidation (CO(2) production) using various lipid substrates was increased approximately twofold in MG, unaltered in LV, and diminished approximately 50% in liver of fa/fa rats. In isolated mitochondria, malonyl-CoA inhibited CO(2) production from palmitate 78%, whereas adding isolated peroxisomes reduced inhibition to 21%. These data demonstrate that peroxisomal products may enter mitochondria independently of CPT I, thus providing a route to maintain lipid disposal under conditions where malonyl-CoA levels are elevated, such as in insulin-resistant tissues. Peroxisomal metabolism of lignoceric acid in fa/fa rats was elevated in both liver and MG (LV unaltered), but peroxisomal product distribution varied. A threefold elevation in incomplete oxidation was solely responsible for increased hepatic peroxisomal oxidation (CO(2) unaltered). Alternatively, only CO(2) was detected in MG, indicating that peroxisomal products were exclusively partitioned to mitochondria for complete lipid disposal. These data suggest tissue-specific destinations for peroxisome-derived products and emphasize a potential role for peroxisomes in skeletal muscle lipid metabolism in the obese, insulin-resistant state.
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Affiliation(s)
- Robert C Noland
- Department of Physiology, East Carolina University, Greenville, NC 27858, USA
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223
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Davis SN, Umpierrez GE. Diabetic ketoacidosis in type 2 diabetes mellitus—pathophysiology and clinical presentation. ACTA ACUST UNITED AC 2007; 3:730-1. [PMID: 17848925 DOI: 10.1038/ncpendmet0641] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2007] [Accepted: 07/16/2007] [Indexed: 11/09/2022]
Affiliation(s)
- Stephen N Davis
- Division of Diabetes, Endocrinology, and Metabolism, Vanderbilt University School of Medicine, Nashville, TN 37232-6303, USA.
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224
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Wang T, Shankar K, Ronis MJ, Mehendale HM. Mechanisms and outcomes of drug- and toxicant-induced liver toxicity in diabetes. Crit Rev Toxicol 2007; 37:413-59. [PMID: 17612954 DOI: 10.1080/10408440701215100] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Increase dincidences of hepatotoxicity have been observed in diabetic patients receiving drug therapies. Neither the mechanisms nor the predisposing factors underlying hepatotoxicity in diabetics are clearly understood. Animal studies designed to examine the mechanisms of diabetes-modulated hepatotoxicity have traditionally focused only on bioactivation/detoxification of drugs and toxicants. It is becoming clear that once injury is initiated, additional events determine the final outcome of liver injury. Foremost among them are two leading mechanisms: first, biochemical mechanisms that lead to progression or regression of injury; and second, whether or not timely and adequate liver tissue repair occurs to mitigate injury and restore liver function. The liver has a remarkable ability to repair and restore its structure and function after physical or chemical-induced damage. The dynamic interaction between biotransformation-based liver injury and compensatory tissue repair plays a pivotal role in determining the ultimate outcome of hepatotoxicity initiated by drugs or toxicants. In this review, mechanisms underlying altered hepatotoxicity in diabetes with emphasis on both altered bioactivation and liver tissue repair are discussed. Animal models of both marked sensitivity (diabetic rats) and equally marked protection (diabetic mice) from drug-induced hepatotoxicity are described. These examples represent a remarkable species difference. Availability of the rodent diabetic models offers a unique opportunity to uncover mechanisms of clinical interest in averting human diabetic sensitivity to drug-induced hepatotoxicities. While the rat diabetic models appear to be suitable, the diabetic mouse models might not be suitable in preclinical testing for potential hepatotoxic effects of drugs or toxicants, because regardless of type 1 or type2 diabetes, mice are resistant to acute drug-or toxicant-induced toxicities.
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Affiliation(s)
- T Wang
- Department of Toxicology, College of Pharmacy, University of Louisiana at Monroe, Monroe, Louisiana 71209, USA
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225
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Nicolson GL. Metabolic syndrome and mitochondrial function: molecular replacement and antioxidant supplements to prevent membrane peroxidation and restore mitochondrial function. J Cell Biochem 2007; 100:1352-69. [PMID: 17243117 DOI: 10.1002/jcb.21247] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Metabolic syndrome consists of a cluster of metabolic conditions, such as hypertriglyceridemia, hyper-low-density lipoproteins, hypo-high-density lipoproteins, insulin resistance, abnormal glucose tolerance and hypertension, that-in combination with genetic susceptibility and abdominal obesity-are risk factors for type 2 diabetes, vascular inflammation, atherosclerosis, and renal, liver and heart disease. One of the defects in metabolic syndrome and its associated diseases is excess cellular oxidative stress (mediated by reactive oxygen and nitrogen species, ROS/RNS) and oxidative damage to mitochondrial components, resulting in reduced efficiency of the electron transport chain. Recent evidence indicates that reduced mitochondrial function caused by ROS/RNS membrane oxidation is related to fatigue, a common complaint of MS patients. Lipid replacement therapy (LRT) administered as a nutritional supplement with antioxidants can prevent excess oxidative membrane damage, restore mitochondrial and other cellular membrane functions and reduce fatigue. Recent clinical trials have shown the benefit of LRT plus antioxidants in restoring mitochondrial electron transport function and reducing moderate to severe chronic fatigue. Thus LRT plus antioxidant supplements should be considered for metabolic syndrome patients who suffer to various degrees from fatigue.
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Affiliation(s)
- Garth L Nicolson
- Department of Molecular Pathology, The Institute for Molecular Medicine, Huntington Beach, California 92647, USA.
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226
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Noland RC, Thyfault JP, Henes ST, Whitfield BR, Woodlief TL, Evans JR, Lust JA, Britton SL, Koch LG, Dudek RW, Dohm GL, Cortright RN, Lust RM. Artificial selection for high-capacity endurance running is protective against high-fat diet-induced insulin resistance. Am J Physiol Endocrinol Metab 2007; 293:E31-41. [PMID: 17341547 DOI: 10.1152/ajpendo.00500.2006] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Elevated oxidative capacity, such as occurs via endurance exercise training, is believed to protect against the development of obesity and diabetes. Rats bred both for low (LCR)- and high (HCR)-capacity endurance running provide a genetic model with inherent differences in aerobic capacity that allows for the testing of this supposition without the confounding effects of a training stimulus. The purpose of this investigation was to determine the effects of a high-fat diet (HFD) on weight gain patterns, insulin sensitivity, and fatty acid oxidative capacity in LCR and HCR male rats in the untrained state. Results indicate chow-fed LCR rats were heavier, hypertriglyceridemic, less insulin sensitive, and had lower skeletal muscle oxidative capacity compared with HCR rats. Upon exposure to an HFD, LCR rats gained more weight and fat mass, and their insulin resistant condition was exacerbated, despite consuming similar amounts of metabolizable energy as chow-fed controls. These metabolic variables remained unaltered in HCR rats. The HFD increased skeletal muscle oxidative capacity similarly in both strains, whereas hepatic oxidative capacity was diminished only in LCR rats. These results suggest that LCR rats are predisposed to obesity and that expansion of skeletal muscle oxidative capacity does not prevent excess weight gain or the exacerbation of insulin resistance on an HFD. Elevated basal skeletal muscle oxidative capacity and the ability to preserve liver oxidative capacity may protect HCR rats from HFD-induced obesity and insulin resistance.
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Affiliation(s)
- Robert C Noland
- Department of Physiology, East Carolina University, Greenville, North Carolina 27834, USA
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227
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Lê KA, Tappy L, D'Alessio DA. Mitochondrial dysfunction and insulin resistance: a matter of lifestyle? Curr Opin Clin Nutr Metab Care 2007; 10:494-7. [PMID: 17563469 DOI: 10.1097/mco.0b013e3281e72abf] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Kim-Anne Lê
- Department of Physiology, Lausanne University School of Biology and Medicine, Lausanne Switzerland
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228
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Chu KY, Leung PS. Angiotensin II Type 1 receptor antagonism mediates uncoupling protein 2-driven oxidative stress and ameliorates pancreatic islet beta-cell function in young Type 2 diabetic mice. Antioxid Redox Signal 2007; 9:869-78. [PMID: 17508912 DOI: 10.1089/ars.2007.1590] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
We recently identified a local pancreatic islet renin-angiotensin system (RAS), and demonstrated that it is upregulated in an animal model of obesity-induced type 2 diabetes mellitus (T2DM). Moreover, angiotensin II type 1 receptor (AT1R) antagonism improves beta-cell function and glucose tolerance in young T2DM mice and delays the onset of diabetes. Meanwhile, obesity-induced T2DM results in oxidative stress-mediated activation of uncoupling protein 2 (UCP2), a negative regulator of islet function. In the present study, we postulated that some of the protective effects of AT1R antagonism might be mediated through interference with this pathway and tested this hypothesis in a T2DM animal model. Losartan, an AT1R antagonist, was given to 4-week-old obese db/db mice for a period of 8 weeks. UCP2-driven oxidative damage and apoptosis were then analyzed in isolated islets. Losartan selectively inhibited oxidative stress via downregulation of NADPH oxidase; this in turn suppressed UCP2 expression, thus improving beta-cell insulin secretion and decreasing apoptosis-induced beta-cell mass loss in db/db mouse islets. These data indicate that islet AT1R activation in young diabetic mice can generate progressive islet beta-cell failure through UCP-driven oxidative damage.
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Affiliation(s)
- Kwan Yi Chu
- Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong, China
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229
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Putman CT, Martins KJB, Gallo ME, Lopaschuk GD, Pearcey JA, MacLean IM, Saranchuk RJ, Pette D. Alpha-catalytic subunits of 5'AMP-activated protein kinase display fiber-specific expression and are upregulated by chronic low-frequency stimulation in rat muscle. Am J Physiol Regul Integr Comp Physiol 2007; 293:R1325-34. [PMID: 17553841 DOI: 10.1152/ajpregu.00609.2006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
5'-AMP-activated protein kinase (AMPK) signaling initiates adaptive changes in skeletal muscle fibers that restore homeostatic energy balance. The purpose of this investigation was to examine, in rats, the fiber-type protein expression patterns of the alpha-catalytic subunit isoforms in various skeletal muscles, and changes in their respective contents within the tibialis anterior (TA) after chronic low-frequency electrical stimulation (CLFS; 10 Hz, 10 h daily), applied for 4 +/- 1.2 or 25 +/- 4.8 days. Immunocytochemical staining of soleus (SOL) and medial gastrocnemius (MG) showed that 86 +/- 4.1 to 97 +/- 1.4% of type IIA fibers stained for both the alpha1- and alpha2-isoforms progressively decreased to 63 +/- 12.2% of type IID/X and 9 +/- 2.4% of IIB fibers. 39 +/- 11.4% of IID/X and 83 +/- 7.9% of IIB fibers expressed only the alpha2 isoform in the MG, much of which was localized within nuclei. alpha1 and alpha2 contents, assessed by immunoblot, were lowest in the white gastrocnemius [WG; 80% myosin heavy chain (MHC) IIb; 20% MHCIId/x]. Compared with the WG, alpha1 content was 1.6 +/- 0.08 (P < 0.001) and 1.8 +/- 0.04 (P < 0.0001)-fold greater in the red gastrocnemius (RG: 13%, MHCIIa) and SOL (21%, MHCIIa), respectively, and increased in proportion to MHCIIa content. Similarly, alpha2 content was 1.4 +/- 0.10 (P < 0.02) and 1.5 +/- 0.07 (P < 0.001)-fold greater in RG and SOL compared with WG. CLFS induced 1.43 +/- 0.13 (P < 0.007) and 1.33 +/- 0.08 (P < 0.009)-fold increases in the alpha1 and alpha2 contents of the TA and coincided with the transition of faster type IIB and IID/X fibers toward IIA fibers. These findings indicate that fiber types differ with regard to their capacity for AMPK signaling and that this potential is increased by CLFS.
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MESH Headings
- AMP-Activated Protein Kinases
- Animals
- Blotting, Western
- Catalysis
- Cell Nucleus/metabolism
- Electric Stimulation
- Electrophoresis, Polyacrylamide Gel
- Gene Expression Regulation, Enzymologic/physiology
- Immunohistochemistry
- Isoenzymes/biosynthesis
- Isoenzymes/genetics
- Male
- Multienzyme Complexes/biosynthesis
- Multienzyme Complexes/genetics
- Multienzyme Complexes/metabolism
- Muscle Fibers, Fast-Twitch/enzymology
- Muscle Fibers, Fast-Twitch/physiology
- Muscle Fibers, Skeletal/enzymology
- Muscle Fibers, Skeletal/physiology
- Muscle Fibers, Slow-Twitch/enzymology
- Muscle Fibers, Slow-Twitch/physiology
- Muscle, Skeletal/enzymology
- Muscle, Skeletal/physiology
- Myosin Heavy Chains/metabolism
- Protein Serine-Threonine Kinases/biosynthesis
- Protein Serine-Threonine Kinases/genetics
- Protein Serine-Threonine Kinases/metabolism
- Rats
- Rats, Sprague-Dawley
- Up-Regulation/physiology
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Affiliation(s)
- Charles T Putman
- Faculty of Physical Education and Recreation and The Centre for Neuroscience, Faculty of Medicine & Dentistry, University of Alberta, E-417 Van Vliet Centre, Edmonton, Alberta, Canada.
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230
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Holloway GP, Thrush AB, Heigenhauser GJF, Tandon NN, Dyck DJ, Bonen A, Spriet LL. Skeletal muscle mitochondrial FAT/CD36 content and palmitate oxidation are not decreased in obese women. Am J Physiol Endocrinol Metab 2007; 292:E1782-9. [PMID: 17311893 DOI: 10.1152/ajpendo.00639.2006] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A reduction in fatty acid oxidation has been associated with lipid accumulation and insulin resistance in the skeletal muscle of obese individuals. We examined whether this decrease in fatty acid oxidation was attributable to a reduction in muscle mitochondrial content and/or a dysfunction in fatty acid oxidation within mitochondria obtained from skeletal muscle of age-matched, lean [body mass index (BMI) = 23.3 +/- 0.7 kg/m2] and obese women (BMI = 37.6 +/- 2.2 kg/m2). The mitochondrial marker enzymes citrate synthase (-34%), beta-hydroxyacyl-CoA dehydrogenase (-17%), and cytochrome c oxidase (-32%) were reduced (P < 0.05) in obese participants, indicating that mitochondrial content was diminished. Obesity did not alter the ability of isolated mitochondria to oxidize palmitate; however, fatty acid oxidation was reduced at the whole muscle level by 28% (P < 0.05) in the obese. Mitochondrial fatty acid translocase (FAT/CD36) did not differ in lean and obese individuals, but mitochondrial FAT/CD36 was correlated with mitochondrial fatty acid oxidation (r = 0.67, P < 0.05). We conclude that the reduction in fatty acid oxidation in obese individuals is attributable to a decrease in mitochondrial content, not to an intrinsic defect in the mitochondria obtained from skeletal muscle of obese individuals. In addition, it appears that mitochondrial FAT/CD36 may be involved in regulating fatty acid oxidation in human skeletal muscle.
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Affiliation(s)
- Graham P Holloway
- Department of Human Health & Nutritional Sciences, University of Guelph, 50 Stone Rd., Guelph, Ontario, Canada N1G2W1.
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231
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Mogensen M, Sahlin K, Fernström M, Glintborg D, Vind BF, Beck-Nielsen H, Højlund K. Mitochondrial respiration is decreased in skeletal muscle of patients with type 2 diabetes. Diabetes 2007; 56:1592-9. [PMID: 17351150 DOI: 10.2337/db06-0981] [Citation(s) in RCA: 423] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
We tested the hypothesis of a lower respiratory capacity per mitochondrion in skeletal muscle of type 2 diabetic patients compared with obese subjects. Muscle biopsies obtained from 10 obese type 2 diabetic and 8 obese nondiabetic male subjects were used for assessment of 3-hydroxy-Acyl-CoA-dehydrogenase (HAD) and citrate synthase activity, uncoupling protein (UCP)3 content, oxidative stress measured as 4-hydroxy-2-nonenal (HNE), fiber type distribution, and respiration in isolated mitochondria. Respiration was normalized to citrate synthase activity (mitochondrial content) in isolated mitochondria. Maximal ADP-stimulated respiration (state 3) with pyruvate plus malate and respiration through the electron transport chain (ETC) were reduced in type 2 diabetic patients, and the proportion of type 2X fibers were higher in type 2 diabetic patients compared with obese subjects (all P < 0.05). There were no differences in respiration with palmitoyl-l-carnitine plus malate, citrate synthase activity, HAD activity, UCP3 content, or oxidative stress measured as HNE between the groups. In the whole group, state 3 respiration with pyruvate plus malate and respiration through ETC were negatively associated with A1C, and the proportion of type 2X fibers correlated with markers of insulin resistance (P < 0.05). In conclusion, we provide evidence for a functional impairment in mitochondrial respiration and increased amount of type 2X fibers in muscle of type 2 diabetic patients. These alterations may contribute to the development of type 2 diabetes in humans with obesity.
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Affiliation(s)
- Martin Mogensen
- Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark
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232
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Abstract
Mitochondria are fundamental for oxidative energy production and impairment of their functionality can lead to reduced ATP synthesis and contribute to initiation of apoptosis. Endocrine tissues critically rely on oxidative phosphorylation so that mitochondrial abnormalities may either be causes or consequences of diminished hormone production or action. Abnormalities typical for diseases caused by mitochondrial DNA mutations such as Kearns-Sayre syndrome or mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes syndrome are also seen in certain endocrine diseases. Lack or excess of thyroid hormones, major ubiquitous regulators of mitochondrial content and activity, cause muscular abnormalities and multisystem disorders. Mitochondria are a further prerequisite for steroidogenesis as well as insulin secretion and action. Recent studies showed that reduced mitochondrial ATP synthesis in skeletal muscle is a feature of certain hereditary and acquired forms of insulin resistance and diabetes mellitus. Finally, ageing is not only accompanied by various degrees of hormonal deficiency and insulin resistance but is also associated with a progressive decline of mitochondrial number and function. Future research is needed to examine whether mitochondrial abnormalities are the cause or consequence of ageing and frequent metabolic diseases such as obesity and type 2 diabetes mellitus, and to address mitochondria as a target for novel therapeutic regimes.
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Affiliation(s)
- R Stark
- Hanusch Hospital, Karl-Landsteiner Institute for Endocrinology and Metabolism, Heinrich Collin Strasse 30, A-1140 Vienna, Austria
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233
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Buettner R, Schölmerich J, Bollheimer LC. High-fat diets: modeling the metabolic disorders of human obesity in rodents. Obesity (Silver Spring) 2007; 15:798-808. [PMID: 17426312 DOI: 10.1038/oby.2007.608] [Citation(s) in RCA: 750] [Impact Index Per Article: 44.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
RESEARCH METHODS AND PROCEDURES High-fat (HF) diet feeding can induce obesity and metabolic disorders in rodents that resemble the human metabolic syndrome. However, this dietary intervention is not standardized, and the HF-induced phenotype varies distinctly among different studies. The question which HF diet type is best to model the metabolic deterioration seen in human obesity remains unclear. Therefore, in this review, metabolic data obtained with different HF diet approaches are compiled. Both whole-body and organ-specific diet effects are analyzed. RESULTS On the basis of these results, we conclude that animal fats and omega-6/omega-9-containing plant oils can be used to generate an obese and insulin-resistant phenotype in rodents, whereas fish oil-fed animals do not develop these disorders. DISCUSSION Looking at the present data, it does not seem possible to define an ideal HF diet, and an exact definition of diet composition and a thorough metabolic characterization of the HF diet effects in a researcher's specific laboratory setting remains essential for metabolic studies with this model.
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Affiliation(s)
- Roland Buettner
- Department of Internal Medicine I, University of Regensburg, 93042 Regensburg, Germany.
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234
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Ukropcova B, Sereda O, de Jonge L, Bogacka I, Nguyen T, Xie H, Bray GA, Smith SR. Family history of diabetes links impaired substrate switching and reduced mitochondrial content in skeletal muscle. Diabetes 2007; 56:720-7. [PMID: 17327442 DOI: 10.2337/db06-0521] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Insulin resistance is associated with metabolic inflexibility, impaired switching of substrate oxidation from fatty acids to glucose in response to insulin. Impaired switching to fat oxidation in response to a high-fat diet (HFD) is hypothesized to contribute to insulin resistance. The objective of this study was to test the hypothesis that defects in substrate switching in response to insulin and a HFD are linked to reduced mitochondrial biogenesis and occur before the development of diabetes. Metabolic flexibility was measured in young sedentary men with (n = 16) or without (n = 34) a family history of diabetes by euglycemic-hyperinsulinemic clamp. Flexibility correlated with fat oxidation measured in a respiratory chamber after a 3-day HFD. Muscle mitochondrial content was higher in flexible subjects with high fat oxidation after a HFD and contributed 49% of the variance. Subjects with a family history of diabetes were inflexible and had reduced HFD-induced fat oxidation and muscle mitochondrial content but did not differ in the amount of body or visceral fat. Metabolic inflexibility, lower adaptation to a HFD, and reduced muscle mitochondrial mass cluster together in subjects with a family history of diabetes, supporting the role of an intrinsic metabolic defect of skeletal muscle in the pathogenesis of insulin resistance.
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Affiliation(s)
- Barbara Ukropcova
- Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA 70808, USA
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235
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Abstract
An epidemic surge in the incidence of obesity has occurred worldwide over the past two decades. This alarming trend has been triggered by lifestyle habits that encourage overconsumption of energy-rich foods while also discouraging regular physical activity. These environmental influences create a chronic energy imbalance that leads to persistent weight gain in the form of body fat and a host of other abnormalities in metabolic homeostasis. As adiposity increases, so does the risk of developing comorbidities such as diabetes, hypertension, and cardiovascular disease. The intimate association between obesity and systemic metabolic dysregulation has inspired a new area of biochemistry research in which scientists are seeking to understand the molecular mechanisms that link chronic lipid oversupply to tissue dysfunction and disease development. The purpose of this chapter is to review recent findings in this area, placing emphasis on lipid-induced functional impairments in the major peripheral organs that control energy flux: adipose tissue, the liver, skeletal muscle, and the pancreas.
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Affiliation(s)
- Deborah M Muoio
- Sarah W. Stedman Nutrition and Metabolism Center and Departments of Pharmacology and Cancer Biology, Medicine, Duke University Medical Center, Durham, North Carolina 27704, USA.
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236
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Chanséaume E, Tardy AL, Salles J, Giraudet C, Rousset P, Tissandier A, Boirie Y, Morio B. Chronological approach of diet-induced alterations in muscle mitochondrial functions in rats. Obesity (Silver Spring) 2007; 15:50-9. [PMID: 17228031 DOI: 10.1038/oby.2007.511] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVE Mitochondrial dysfunction might predispose individuals to develop insulin resistance. Our objective was to determine whether mitochondrial dysfunction or insulin resistance was the primary event during high-fat (HF) diet. RESEARCH METHODS AND PROCEDURES Rats were fed an HF diet for 0, 3, 6, 9, 14, 20, or 40 days and compared with control. Soleus and tibialis muscle mitochondrial activity were assessed using permeabilized fiber technique. Insulin [area under the curve for insulin (AUC(I))] and glucose [area under the curve for glucose (AUC(G))] responses to intraperitoneal glucose tolerance test as well as fasting plasma non-esterified fatty acids (NEFAs), triglyceride, and glycerol concentrations were determined. RESULTS AUC(I) and AUC(G) were altered from Day 6 (p < 0.01 vs. Day 0). In soleus, oxidative phosphorylation (OXPHOS) activity was transiently enhanced by 26% after 14 days of HF diet (p < 0.05 vs. Day 0) conjointly with 62% increase in NEFA concentration (p < 0.05 vs. Day 0). This was associated with normalized AUC(G) at Day 14 and with a decline of plasma NEFA concentration together with stabilization of intra-abdominal adiposity at Day 20. Prolongation of HF diet again caused an increase in plasma NEFA concentration, intra-abdominal adiposity, AUC(I), and AUC(G). At Day 40, significant decrease in OXPHOS activity was observed in soleus. DISCUSSION Mitochondria first adapt to overfeeding in oxidative muscle limiting excess fat deposition. This potentially contributes to maintain glucose homeostasis. Persistent overfeeding causes insulin resistance and results in a slow decline in oxidative muscle OXPHOS activity. This shows that the involvement of mitochondria in the predisposition to insulin resistance is mainly due to an inability to face prolonged excess fat delivery.
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Affiliation(s)
- Emilie Chanséaume
- Lipid and Energy Metabolism Research Unit, Human Nutrition Laboratory, Institut National de la Recherche Agronomique, Unité Mixte de Recherche 1019, Clermont-Ferrand, France
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237
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Boon H, Blaak EE, Saris WHM, Keizer HA, Wagenmakers AJM, van Loon LJC. Substrate source utilisation in long-term diagnosed type 2 diabetes patients at rest, and during exercise and subsequent recovery. Diabetologia 2007; 50:103-12. [PMID: 17131144 DOI: 10.1007/s00125-006-0482-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2006] [Accepted: 09/01/2006] [Indexed: 11/21/2022]
Abstract
AIMS/HYPOTHESIS Disturbances in substrate source metabolism and, more particularly, in fatty acid metabolism, play an important role in the aetiology and progression of type 2 diabetes. However, data on substrate source utilisation in type 2 diabetes are inconclusive. METHODS [U-(13)C]palmitate and [6,6-(2)H(2)]glucose tracers were used to assess plasma NEFA and glucose oxidation rates and to estimate the use of muscle- and/or lipoprotein-derived triacylglycerol and muscle glycogen. Subjects were ten male patients who had a long-term (7 +/- 1 years) diagnosis of type 2 diabetes and were overweight, and ten matched healthy, male control subjects. Muscle biopsy samples were collected before and after exercise to assess muscle fibre type-specific intramyocellular lipid and glycogen content. RESULTS At rest and during exercise, the diabetes patients had greater values than the controls for palmitate rate of appearance (Ra) (rest, 2.46 +/- 0.18 and 1.85 +/- 0.20 respectively; exercise, 3.71 +/- 0.36 and 2.84 +/- 0.20 micromol kg(-1) min(-1)) and rate of disappearance (Rd) (rest, 2.45 +/- 0.18 and 1.83 +/- 0.20; exercise, 3.64 +/- 0.35 and 2.80 +/- 0.20 micromol kg(-1) min(-1) respectively). This was accompanied by significantly higher fat oxidation rates at rest and during recovery in the diabetes patients (rest, 0.11 +/- 0.01 in diabetes patients and 0.09 +/- 0.01 in controls; recovery, 0.13 +/- 0.01 and 0.11 +/- 0.01 g/min respectively), despite significantly greater plasma glucose Ra, Rd and circulating plasma glucose concentrations. Furthermore, exercise significantly lowered plasma glucose concentrations in the diabetes patients, as a result of increased blood glucose disposal. CONCLUSION This study demonstrates that substrate source utilisation in long-term-diagnosed type 2 diabetes patients, in whom compensatory hyperinsulinaemia is no longer present, shifts towards an increase in whole-body fat oxidation rate and is accompanied by disturbances in fat and carbohydrate handling.
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Affiliation(s)
- H Boon
- Department of Human Biology, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), Maastricht University, Maastricht, The Netherlands.
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238
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Lee HJ, Park MK, Lee KI, An YJ, Kim JM, Park JY, Han Y, Hong SH, Choi SS, Yoo YH, Suh JD, Kim DK. Prevention of Diabetes by Fenofibrate in OLETF Rats: Hepatic Mechanism for Reducing Visceral Adiposity. ACTA ACUST UNITED AC 2007. [DOI: 10.4093/jkda.2007.31.1.63] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Hye-Jeong Lee
- Pharmacology Department, Medical College of Dong-A University, Korea
| | - Mi-Kyoung Park
- Internal Medicine Department, Medical College of Dong-A University, Korea
| | - Kyung Il Lee
- Internal Medicine Department, Baptist Hospital, Korea
| | - Young-Jun An
- Internal Medicine Department, Bando Hospital, JinJu, Korea
| | - Ji Min Kim
- Internal Medicine Department, Hanseo Hospital, Korea
| | - Ja Young Park
- Internal Medicine Department, Dong-A University Medical Center, Korea
| | - Young Han
- Graduate School, Dong-A University, Korea
| | - Sook-Hee Hong
- Pathology Department, Medical College of Dong-A University, Korea
| | - Sun-Seob Choi
- Diagnostic Radiology Department, Medical College of Dong-A University, Korea
| | - Young Hyun Yoo
- Anatomy Department, Medical College of Dong-A University, Korea
| | - Joon Duk Suh
- Physiology Department, Medical College of Dong-A University, Korea
| | - Duk Kyu Kim
- Internal Medicine Department, Medical College of Dong-A University, Korea
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239
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van den Hoek AM, Heijboer AC, Voshol PJ, Havekes LM, Romijn JA, Corssmit EPM, Pijl H. Chronic PYY3-36 treatment promotes fat oxidation and ameliorates insulin resistance in C57BL6 mice. Am J Physiol Endocrinol Metab 2007; 292:E238-45. [PMID: 16940471 DOI: 10.1152/ajpendo.00239.2006] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
PYY(3-36) is a gut-derived hormone acting on hypothalamic nuclei to inhibit food intake. We recently showed that PYY(3-36) acutely reinforces insulin action on glucose disposal in mice. We aimed to evaluate effects of PYY(3-36) on energy metabolism and the impact of chronic PYY(3-36) treatment on insulin sensitivity. Mice received a single injection of PYY(3-36) or were injected once daily for 7 days, and energy metabolism was subsequently measured in a metabolic cage. Furthermore, the effects of chronic PYY(3-36) administration (continuous and intermittent) on glucose turnover were determined during a hyperinsulinemic-euglycemic clamp. PYY(3-36) inhibited cumulative food intake for 30 min of refeeding after an overnight fast (0.29 +/- 0.04 vs. 0.56 +/- 0.12 g, P = 0.036) in an acute setting, but not after 7 days of daily dosing. Body weight, total energy expenditure, and physical activity were not affected by PYY(3-36). However, it significantly decreased the respiratory quotient. Both continuous and intermittent PYY(3-36) treatment significantly enhanced insulin-mediated whole body glucose disposal compared with vehicle treatment (81.2 +/- 6.2 vs. 77.1 +/- 5.2 vs. 63.4 +/- 5.5 micromol.min(-1).kg(-1), respectively). In particular, PYY(3-36) treatment increased glucose uptake in adipose tissue, whereas its impact on glucose disposal in muscle did not attain statistical significance. PYY(3-36) treatment shifts the balance of fuel use in favor of fatty acids and enhances insulin sensitivity in mice, where it particularly promotes insulin-mediated glucose disposal. Notably, these metabolic effects of PYY(3-36) remain unabated after chronic administration, in contrast to its anorexic effects.
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Affiliation(s)
- Anita M van den Hoek
- Leiden University Medical Center, Dept. of Endocrinology and Metabolic diseases, P. O. Box 9600, 2300 RC Leiden, The Netherlands
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240
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Rachek LI, Musiyenko SI, LeDoux SP, Wilson GL. Palmitate induced mitochondrial deoxyribonucleic acid damage and apoptosis in l6 rat skeletal muscle cells. Endocrinology 2007; 148:293-9. [PMID: 17023529 DOI: 10.1210/en.2006-0998] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
A major characteristic of type 2 diabetes mellitus (T2DM) is insulin resistance in skeletal muscle. A growing body of evidence indicates that oxidative stress that results from increased production of reactive oxygen species and/or reactive nitrogen species leads to insulin resistance, tissue damage, and other complications observed in T2DM. It has been suggested that muscular free fatty acid accumulation might be responsible for the mitochondrial dysfunction and insulin resistance seen in T2DM, although the mechanisms by which increased levels of free fatty acid lead to insulin resistance are not well understood. To help resolve this situation, we report that saturated fatty acid palmitate stimulated the expression of inducible nitric oxide (NO) synthase and the production of reactive oxygen species and NO in L6 myotubes. Additionally, palmitate caused a significant dose-dependent increase in mitochondrial DNA (mtDNA) damage and a subsequent decrease in L6 myotube viability and ATP levels at concentrations as low as 0.5 mM. Furthermore, palmitate induced apoptosis, which was detected by DNA fragmentation, caspase-3 cleavage, and cytochrome c release. N-acetyl cysteine, a precursor compound for glutathione formation, aminoguanidine, an inducible NO synthase inhibitor, and 5,10,15,20-tetrakis(4-sulphonatophenyl) porphyrinato iron (III), a peroxynitrite inhibitor, all prevented palmitate-induced mtDNA damage and diminished palmitate-induced cytotoxicity. We conclude that exposure of L6 myotubes to palmitate induced mtDNA damage and triggered mitochondrial dysfunction, which caused apoptosis. Additionally, our findings indicate that palmitate-induced mtDNA damage and cytotoxicity in skeletal muscle cells were caused by overproduction of peroxynitrite.
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Affiliation(s)
- L I Rachek
- Department of Cell Biology and Neuroscience, University of South Alabama, Mobile, Alabama 36688, USA.
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Cole AR, Astell A, Green C, Sutherland C. Molecular connexions between dementia and diabetes. Neurosci Biobehav Rev 2007; 31:1046-63. [PMID: 17544131 DOI: 10.1016/j.neubiorev.2007.04.004] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2006] [Revised: 03/27/2007] [Accepted: 04/11/2007] [Indexed: 12/29/2022]
Abstract
Recent evidence suggests that the molecular defects associated with the development of diabetes also contribute to an increased risk of all types of dementia, including Alzheimer's disease, vascular dementia and Pick's disease. Indeed, the presence of type II diabetes mellitus results in a two to three fold higher risk of developing dementia [Fontbonne et al., 2001. Changes in cognitive abilities over a 4-year period are unfavourably affected in elderly diabetic subjects: results of the Epidemiology of Vascular Aging Study. Diabetes Care 24, 366-370; Gregg et al., 2000. Is diabetes associated with cognitive impairment and cognitive decline among older women? Study of Osteoporotic Fractures Research Group. Archives of Internal Medicine 160, 174-180; Peila et al., 2002. Type 2 diabetes, APOE gene, and the risk for dementia and related pathologies: The Honolulu-Asia Aging Study. Diabetes 51, 1256-1262]. There are currently 250 million people worldwide (>2 million in the UK) diagnosed with diabetes, and this number is predicted to double within the next 20 years, therefore the associated risk translates into a potential explosion in the appearance of dementia in the population. This review primarily focuses on the proposed molecular links between insulin action, Diabetes and Alzheimer's disease, while discussing the potential for therapeutic intervention to alleviate these disorders. In particular, we will review the regulation of glycogen synthase kinase-3 (GSK-3) and its neuronal substrates.
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Affiliation(s)
- Adam R Cole
- Division of Pathology and Neurosciences, University of Dundee, Ninewells Hospital, Dundee, Scotland, UK
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242
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Hammond LE, Albright CD, He L, Rusyn I, Watkins SM, Doughman SD, Lemasters JJ, Coleman RA. Increased oxidative stress is associated with balanced increases in hepatocyte apoptosis and proliferation in glycerol-3-phosphate acyltransferase-1 deficient mice. Exp Mol Pathol 2006; 82:210-9. [PMID: 17258706 PMCID: PMC1865130 DOI: 10.1016/j.yexmp.2006.12.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2006] [Revised: 12/06/2006] [Accepted: 12/13/2006] [Indexed: 01/07/2023]
Abstract
The absence of mouse mitochondrial glycerol-3-phosphate acyltransferase-1 (Gpat1-/-) increases the amount of arachidonate in liver phospholipids and increases beta-hydroxybutyrate and acyl-carnitines, suggesting an elevated rate of liver fatty acid oxidation. We asked whether these alterations might increase reactive oxygen species (ROS), apoptosis, or hepatocyte proliferation. Compared to wildtype controls, liver mitochondria from Gpat1-/- mice showed a 20% increase in the rate of ROS production and a markedly increased sensitivity to the induction of the mitochondrial permeability transition. Mitochondrial phosphatidylethanolamine and phosphatidylcholine from Gpat1-/- liver contained 21% and 67% more arachidonate, respectively, than wildtype controls, and higher amounts of 4-hydroxynonenal, a product of arachidonate peroxidation. Oxidative stress was associated with an increase in apoptosis, and with 3-fold and 15-fold higher TUNEL positive cells in liver from young and old Gpat1-/- mice, respectively, compared to age-matched controls. Compared to controls, bromodeoxyuridine labeling was 50% and 7-fold higher in livers from young and old Gpat1-/- mice, respectively, but fewer glutathione-S-transferase positive cells were present. Thus, Gpat1-/- liver exhibits increased oxidative stress and sensitivity of the mitochondrial permeability transition pore, and a balanced increase in apoptosis and proliferation.
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Affiliation(s)
- Linda E Hammond
- Department of Nutrition, CB#7461, 2301 Michael Hooker Research Building, Columbia Street, University of North Carolina, Chapel Hill, NC 27599, USA
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243
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Conley KE, Amara CE, Jubrias SA, Marcinek DJ. Mitochondrial function, fibre types and ageing: new insights from human muscle in vivo. Exp Physiol 2006; 92:333-9. [PMID: 17170059 DOI: 10.1113/expphysiol.2006.034330] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Mitochondrial changes are at the centre of a wide range of maladies, including diabetes, neurodegeneration and ageing-related dysfunctions. Here we describe innovative optical and magnetic resonance spectroscopic methods that non-invasively measure key mitochondrial fluxes, ATP synthesis and O(2) uptake, to permit the determination of mitochondrial coupling efficiency in vivo (P/O: half the ratio of ATP flux to O(2) uptake). Three new insights result. First, mitochondrial coupling can be measured in vivo with the rigor of a biochemical determination and provides a gold standard to define well-coupled mitochondria (P/O approximately 2.5). Second, mitochondrial coupling differs substantially among muscles in healthy adults, from values reflective of well-coupled oxidative phosphorylation in a hand muscle (P/O = 2.7) to mild uncoupling in a leg muscle (P/O = 2.0). Third, these coupling differences have an important impact on cell ageing. We found substantial uncoupling and loss of cellular [ATP] in a hand muscle indicative of mitochondrial dysfunction with age. In contrast, stable mitochondrial function was found in a leg muscle, which supports the notion that mild uncoupling is protective against mitochondrial damage with age. Thus, greater mitochondrial dysfunction is evident in muscles with higher type II muscle fibre content, which may be at the root of the preferential loss of type II fibres found in the elderly. Our results demonstrate that mitochondrial function and the tempo of ageing varies among human muscles in the same individual. These technical advances, in combination with the range of mitochondrial properties available in human muscles, provide an ideal system for studying mitochondrial function in normal tissue and the link between mitochondrial defects and cell pathology in disease.
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Affiliation(s)
- Kevin E Conley
- Department of Radiology, Box 357115, University of Washington Medical Center, Seattle, WA 98195-7115, USA.
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244
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Sell H, Dietze-Schroeder D, Eckel J. The adipocyte-myocyte axis in insulin resistance. Trends Endocrinol Metab 2006; 17:416-22. [PMID: 17084639 DOI: 10.1016/j.tem.2006.10.010] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2006] [Revised: 10/13/2006] [Accepted: 10/24/2006] [Indexed: 12/16/2022]
Abstract
Insulin resistance in skeletal muscle is linked to an elevated adipose tissue mass, as is found in obesity, but can also be observed in lipodystrophy, in which adipose tissue is greatly reduced. Adipose tissue releases endocrine and metabolic mediators and is actively involved in crosstalk with skeletal muscle, a process that precedes and underlies the development of insulin resistance in muscles. Adipokines including tumor necrosis factor alpha, interleukin-6, leptin and adiponectin influence insulin signaling in skeletal muscle. Free fatty acids, their metabolites and ectopic fat in muscle also contribute to insulin resistance. Recent research indicates inflammation, endoplasmic reticulum stress and oxidative stress could be underlying mechanisms at the center of the development of insulin resistance. Insights into the role of macrophages in adipose tissue add to the complicated interplay between adipose tissue and skeletal muscle.
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Affiliation(s)
- Henrike Sell
- Institute of Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, Düsseldorf, Germany
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245
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Lim SC, Tan HH, Goh SK, Subramaniam T, Sum CF, Tan IK, Lee BL, Ong CN. Oxidative burden in prediabetic and diabetic individuals: evidence from plasma coenzyme Q(10). Diabet Med 2006; 23:1344-9. [PMID: 17116186 DOI: 10.1111/j.1464-5491.2006.01996.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM Individuals with diabetes and prediabetes are at risk of vascular injury. However, the exact mechanisms are unclear. The mitochondria mobile electron carrier coenzyme Q(10) (CoQ(10)) is a potent lipophilic antioxidant. We hypothesize that oxidative stress, detectable as changes in plasma CoQ(10) concentrations and composition, plays an important role in vascular disease in diabetes. METHODS We measured plasma CoQ(10) concentrations (including reduced ubiquinol and oxidized ubiquinone subfractions) in 60 subjects with normal glucose tolerance [NGT; fasting plasma glucose (FPG) < 5.5 mmol/l], 63 with impaired fasting glucose (IFG; FPG 5.6-6.9 mmol/l) and 69 with Type 2 diabetes (DM; FPG > 6.9 mmol/l). RESULTS In men and women, the total CoQ(10)/total cholesterol ratio was reduced in DM (mean +/-sd) [male (M) 0.09 +/- 0.04; female (F) 0.07 +/- 0.04] compared with NGT (0.29 +/- 0.08; 0.21 +/- 0.07) and IFG (0.27 +/- 0.07; 0.23 +/- 0.07) (DM vs. NGT and IFG P = 0.001). A stepwise reduction in the plasma ubiquinol fraction (ubiquinol/total CoQ10) was observed from NGT (M 0.93 +/- 0.06; F 0.95 +/- 0.06) compared with IFG (0.43 +/- 0.25; 0.41 +/- 0.15) and DM (0.24 +/- 0.11; F 0.29 +/- 0.16) (DM vs. IFG vs. NGT P = 0.001). In contrast, the plasma ubiquinone/ubiquinol ratio increased from NGT (M 0.08 +/- 0.07, F 0.06 +/- 0.08) to IFG (2.14 +/- 1.84, 1.75 +/- 1.04) to DM (4.77 +/- 4.88, 3.81 +/- 3.71) (DM vs. IFG vs. NGT P = 0.001). These differences remained after adjusting for age, body mass index and FPG. CONCLUSIONS The change in CoQ(10) with increasing FPG concentration suggests an increase in oxidative burden, already evident in the prediabetic IFG individuals. This increase in oxidative stress might contribute to the increased risk of vascular disease.
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Affiliation(s)
- S C Lim
- Department of Medicine, Alexandra Hospital, Singapore 159964, Republic of Singapore.
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Park J, Choe SS, Choi AH, Kim KH, Yoon MJ, Suganami T, Ogawa Y, Kim JB. Increase in glucose-6-phosphate dehydrogenase in adipocytes stimulates oxidative stress and inflammatory signals. Diabetes 2006; 55:2939-49. [PMID: 17065329 DOI: 10.2337/db05-1570] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
In adipocytes, oxidative stress and chronic inflammation are closely associated with metabolic disorders, including insulin resistance, obesity, cardiovascular disease, and type 2 diabetes. However, the molecular mechanisms underlying these metabolic disorders have not been thoroughly elucidated. In this report, we demonstrate that overexpression of glucose-6-phosphate dehydrogenase (G6PD) in adipocytes stimulates oxidative stress and inflammatory responses, thus affecting the neighboring macrophages. Adipogenic G6PD overexpression promotes the expression of pro-oxidative enzymes, including inducible nitric oxide synthase and NADPH oxidase, and the activation of nuclear factor-kappaB (NF-kappaB) signaling, which eventually leads to the dysregulation of adipocytokines and inflammatory signals. Furthermore, secretory factors from G6PD-overexpressing adipocytes stimulate macrophages to express more proinflammatory cytokines and to be recruited to the adipocytes; this would cause chronic inflammatory conditions in the adipose tissue of obesity. These effects of G6PD overexpression in adipocytes were abolished by pretreatment with NF-kappaB inhibitors or antioxidant drugs. Thus, we propose that a high level of G6PD in adipocytes may mediate the onset of metabolic disorders in obesity by increasing the oxidative stress and inflammatory signals.
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Affiliation(s)
- Jiyoung Park
- Department of Biological Sciences, Seoul National University, San 56-1, Sillim-Dong, Kwanak-Gu, Seoul, Korea
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Thyfault JP, Cree MG, Zheng D, Zwetsloot JJ, Tapscott EB, Koves TR, Ilkayeva O, Wolfe RR, Muoio DM, Dohm GL. Contraction of insulin-resistant muscle normalizes insulin action in association with increased mitochondrial activity and fatty acid catabolism. Am J Physiol Cell Physiol 2006; 292:C729-39. [PMID: 17050616 DOI: 10.1152/ajpcell.00311.2006] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Acute exercise can reverse muscle insulin resistance, but the mechanism(s) of action are unknown. With the use of a hindlimb perfusion model, we have found that acute contraction restores insulin-stimulated glucose uptake in muscle of obese Zucker rats to levels witnessed in lean controls. Previous reports have suggested that obesity-related insulin resistance stems from lipid oversupply and tissue accumulation of toxic lipid intermediates that impair insulin signaling. We reasoned that contraction might activate hydrolysis and oxidation of intramuscular lipids, thus alleviating "lipotoxicity" and priming the muscle for enhanced insulin action. Indeed, analysis of mitochondrial-derived acyl-carnitine esters suggested that contraction caused robust increases in beta-oxidative flux and mitochondrial oxidation. As predicted, contraction decreased intramuscular triacylglycerol content; however, diacylglycerol and long chain acyl-CoAs, lipid intermediates presumed to trigger insulin resistance, were either unchanged or increased. In muscles from obese animals, insulin-stimulated tyrosine phosphorylation of the insulin receptor and insulin receptor substrate-1 remained impaired after contraction, whereas phosphorylation of the downstream signaling protein, AS160, was partially restored. These results suggest that acute exercise enables diabetic muscle to circumvent upstream defects in insulin signal transduction via mechanisms that are more tightly coupled to increased mitochondrial energy metabolism than the lowering of diacylglycerol and long chain acyl-CoA.
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Affiliation(s)
- John P Thyfault
- Dept. of Nutritional Sciences and Internal Medicine, Univ. of Missouri, Harry S. Truman VA Hospital-Research, Columbia, MO 65211, USA.
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Hoeks J, Hesselink MKC, Russell AP, Mensink M, Saris WHM, Mensink RP, Schrauwen P. Peroxisome proliferator-activated receptor-gamma coactivator-1 and insulin resistance: acute effect of fatty acids. Diabetologia 2006; 49:2419-26. [PMID: 16896940 DOI: 10.1007/s00125-006-0369-2] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2006] [Accepted: 05/25/2006] [Indexed: 01/07/2023]
Abstract
AIMS/HYPOTHESIS Peroxisome proliferator-activated receptor (PPAR)-gamma coactivator-1 (PPARGC1), a coactivator regulating the transcription of genes involved in oxidative metabolism, is downregulated in patients with type 2 diabetes and in their first-degree relatives. Whether this downregulation is a cause or effect of early aberrations in the development of insulin resistance, such as disturbances in fat metabolism, is unknown. We examined whether lipid-induced insulin resistance was associated with downregulation of expression of skeletal muscle genes involved in oxidative metabolism and mitochondrial biogenesis in humans. MATERIALS AND METHODS Nine healthy lean male subjects underwent a 6-h hyperinsulinaemic-euglycaemic clamp with simultaneous infusion of either a lipid emulsion or glycerol as a control. Blood was sampled at regular time points and muscle biopsies were taken before and after every test. Intramuscular triacylglycerol (IMTG) content was determined by Oil Red O staining and gene expression was measured by quantitative PCR. RESULTS Lipid infusion resulted in a approximately 2.7-fold increase in plasma NEFA levels and a 31+/-6% decrease in insulin sensitivity (p=0.001). The infusion of lipids resulted in a approximately 1.6-fold increase in IMTG (p=0.02), whereas during the clamp with glycerol infusion IMTG tended to decrease to approximately 53% of preinfusion levels (p=0.065). Lipid infusion decreased PPARGC1A, PPARGC1B and PPARA expression to approximately 61, 77 and approximately 52% of basal values respectively, whereas expression of uncoupling protein 3 was upregulated 1.8-fold (all p<0.05). CONCLUSIONS/INTERPRETATION Acute elevation of plasma NEFA levels, leading to muscular fat accumulation and insulin resistance, downregulates PPARGC1A, PPARGC1B and PPARA expression, suggesting that the decrease in PPARGC1 expression observed in the (pre)diabetic state may be the result, rather than the cause of lipid-induced insulin resistance.
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Affiliation(s)
- J Hoeks
- Department of Human Biology, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), Maastricht University, P.O. Box 616, 6200 MD, Maastricht, The Netherlands.
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Minnaard R, Schrauwen P, Schaart G, Hesselink MKC. UCP3 in muscle wasting, a role in modulating lipotoxicity? FEBS Lett 2006; 580:5172-6. [PMID: 16962595 DOI: 10.1016/j.febslet.2006.08.066] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2006] [Revised: 07/17/2006] [Accepted: 08/18/2006] [Indexed: 11/30/2022]
Abstract
UCP3 has been postulated to function in the defense against lipid-induced oxidative muscle damage (lipotoxicity). We explored this hypothesis during cachexia in rats (zymosan-induced sepsis), a condition characterized by increased oxidative stress and supply of fatty acids to the muscle. Muscle UCP3 protein content was increased 2, 6 and 11 days after zymosan injection. Plasma FFA levels were increased at day 2, but dropped below control levels on days 6 and 11. Muscular levels of the lipid peroxidation byproduct 4-hydroxy-2-nonenal (4-HNE) were increased at days 6 and 11 in zymosan-treated rats, supporting a role for UCP3 in modulating lipotoxicity during cachexia.
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Affiliation(s)
- Ronnie Minnaard
- Department of Movement Sciences, Nutrition and Toxicology Research Institute Maastricht, NUTRIM, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
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Chanseaume E, Malpuech-Brugère C, Patrac V, Bielicki G, Rousset P, Couturier K, Salles J, Renou JP, Boirie Y, Morio B. Diets high in sugar, fat, and energy induce muscle type-specific adaptations in mitochondrial functions in rats. J Nutr 2006; 136:2194-200. [PMID: 16857840 DOI: 10.1093/jn/136.8.2194] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Obesity is often associated with insulin resistance and mitochondrial dysfunction within skeletal muscles, but the causative factors are not clearly identified. The present study examined the role of nutrition, both qualitatively and quantitatively, in the induction of muscle mitochondrial defects. Two experimental diets [high sucrose (SU) and high fat (F)] were provided for 6 wk to male Wistar rats at 2 levels of energy [standard (N) and high (H)] and compared with a standard energy cornstarch-based diet (C). Insulin sensitivity (intraperitoneal glucose tolerance test, IPGTT) and intramyocellular triglyceride (IMTG) content (1H MRS) were determined at wk 5. Mitochondrial oxidative phosphorylation and superoxide anion radical (MSR) production were assessed on soleus (oxidative) and tibialis (glycolytic) muscles. Experimental diets induced hyperinsulinemia during IPGTT (P < 0.01 vs. C). Rats in the HSU and HF groups were hyperglycemic relative to the C group, P < 0.05 vs. C. The severity of insulin resistance paralleled IMTG accumulation (P < 0.05). In soleus, mitochondrial respiration and ATP production rates were lower in HSU and HF than in C (P < 0.05). By contrast, respiration was unaffected by the diets in tibialis, whereas ATP production tended to be lower in rats fed the experimental diets compared with C (P = 0.09). Mitochondrial adaptations were associated with more than a 50% reduction in MSR production in HSU and HF compared with C in both soleus (P < 0.05) and tibialis (P < 0.01). Changes in mitochondrial functions in the NSU and NF groups were intermediate and not significantly different from C. Therefore, excess fat or sucrose and more importantly, excess energy intake by rats is associated with muscle type-specific mitochondrial adaptations, which contribute to decrease mitochondrial production of ATP and reactive oxygen species.
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