Tag Archives: Accumulation

Mitochondrial-Targeted Catalase Protects Against High-Fat Diet-Induced Muscle Insulin Resistance by Decreasing Intramuscular Lipid Accumulation

We explored the role of reactive oxygen species (ROS) in the pathogenesis of muscle insulin resistance. We assessed insulin action in vivo with a hyperinsulinemic-euglycemic clamp in mice expressing a mitochondrial-targeted catalase (MCAT) that were fed regular chow (RC) or a high-fat diet (HFD) or underwent an acute infusion of a lipid emulsion. RC-fed MCAT mice were similar to littermate wild-type (WT) mice. However, HFD-fed MCAT mice were protected from diet-induced insulin resistance. In contrast, an acute lipid infusion caused muscle insulin resistance in both MCAT and WT mice. ROS production was decreased in both HFD-fed and lipid-infused MCAT mice and cannot explain the divergent response in insulin action. MCAT mice had subtly increased energy expenditure and muscle fat oxidation with decreased intramuscular diacylglycerol (DAG) accumulation, protein kinase C- (PKC) activation, and impaired insulin signaling with HFD. In contrast, the insulin resistance with the acute lipid infusion was associated with increased muscle DAG content in both WT and MCAT mice. These studies suggest that altering muscle mitochondrial ROS production does not directly alter the development of lipid-induced insulin resistance. However, the altered energy balance in HFD-fed MCAT mice protected them from DAG accumulation, PKC activation, and impaired muscle insulin signaling.

Diabetes Journal current issue





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A New Simple Method for the Measurement of Visceral Fat Accumulation by Bioelectrical Impedance

Miwa Ryo, Kazuhisa Maeda, Tomohiro Onda, Mitsuhiro Katashima, Akiko Okumiya, Makoto Nishida, Tohru Yamaguchi, Tohru Funahashi, Yuji Matsuzawa, Tadashi Nakamura, Iichiro Shimomura
Feb 1, 2005; 28:451-453
BR Metabolic Syndrome/Insulin Resistance Syndrome/Pre-Diabetes
Diabetes Care: Most-Read Full-Text Articles





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Relative Contribution of Intramyocellular Lipid to Whole-Body Fat Oxidation Is Reduced With Age but Subsarcolemmal Lipid Accumulation and Insulin Resistance Are Only Associated With Overweight Individuals

Insulin resistance is closely related to intramyocellular lipid (IMCL) accumulation, and both are associated with increasing age. It remains to be determined to what extent perturbations in IMCL metabolism are related to the aging process per se. On two separate occasions, whole-body and muscle insulin sensitivity (euglycemic-hyperinsulinemic clamp with 2-deoxyglucose) and fat utilization during 1 h of exercise at 50% VO2max ([U-13C]palmitate infusion combined with electron microscopy of IMCL) were determined in young lean (YL), old lean (OL), and old overweight (OO) males. OL displayed IMCL content and insulin sensitivity comparable with those in YL, whereas OO were markedly insulin resistant and had more than twofold greater IMCL in the subsarcolemmal (SSL) region. Indeed, whereas the plasma free fatty acid Ra and Rd were twice those of YL in both OL and OO, SSL area only increased during exercise in OO. Thus, skeletal muscle insulin resistance and lipid accumulation often observed in older individuals are likely due to lifestyle factors rather than inherent aging of skeletal muscle as usually reported. However, age per se appears to cause exacerbated adipose tissue lipolysis, suggesting that strategies to reduce muscle lipid delivery and improve adipose tissue function may be warranted in older overweight individuals.

Diabetes Journal current issue





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