Effect of weight loss on muscle lipid content in morbidly obese subjects

Abstract

The purpose of this study was to test the hypothesis that weight loss results in a reduction in intramuscular lipid (IMCL) content that is concomitant with enhanced insulin action. Muscle biopsies were obtained from morbidly obese individuals [body mass index (BMI) 52.2 Ϯ 2.5 kg/m 2 ; n ϭ 6] before and after gastric bypass surgery, an intervention that improves insulin action. With intervention, there was a 47% reduction (P Ͻ 0.01) in BMI and a 93% decrease in homeostasis model assessment, or HOMA (7.0 Ϯ 1.9 vs. 0.5 Ϯ 0.1). Histochemically determined IMCL content decreased (P Ͻ 0.05) by ϳ30%. In relation to fiber type, IMCL was significantly higher in type I vs. type II fibers. In both fiber types, there were reductions in IMCL and trends for muscle atrophy. Despite these two negating factors, the IMCL-to-fiber area ratio still decreased by ϳ44% with weight loss. In conclusion, despite differing initial levels and possible atrophy, weight loss appears to decrease IMCL deposition to a similar relative extent in type I and II muscle fibers. This reduction in intramuscular triglyceride may contribute to enhanced insulin action seen with weight loss. insulin resistance; obesity; skeletal muscle; triglyceride RECENT EVIDENCE INDICATES that the accumulation of triglyceride within skeletal muscle is related to insulin resistance. In humans, a negative association between whole-body insulin action and intramuscular lipid (IMCL) content has been observed (5,7,11,17,23,25,31,33). An elevated IMCL deposition has also been reported in obese individuals (6,7,18), obese individuals with type 2 diabetes (6), and the insulin resistantrelatives of type 2 diabetics (11,24). It is hypothesized that intermediates derived from IMCL sources such as triglyceride, i.e., long-chain acyl-CoAs and/or ceramide, directly induce insulin resistance by impeding insulin signal transduction (30). This type of mechanism would explain the negative relationship between IMCL accumulation and insulin action.Although an elevated IMCL content has been documented in a variety of insulin-resistant populations, information on the ability to reduce IMCL and concomitantly enhance insulin action with intervention, such as weight loss, is sparse and controversial. Either a reduction (6, 7) or no change (7, 19) in muscle triglyceride deposition with weight loss has been reported. However, in some of these studies, insulin action was either not measured (6) or did not improve (7, 19), making it difficult to elucidate the interaction between IMCL and insulin action. The purpose of the present study was to test the hypothesis that weight loss results in a reduction in IMCL content that is concomitant with enhanced insulin action. This was accomplished by examining IMCL deposition before and after a weight loss intervention (gastric bypass surgery) known to normalize insulin action in insulin-resistant, morbidly obese individuals (26).Although IMCL content is related to insulin action, a measurement of overall muscle triglyceride content may not be indicative of w...

Increased Secretion and Expression of Myostatin in Skeletal Muscle From Extremely Obese Women

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“…The homeostasis model assessment (HOMA) for insulin resistance and ␤-cell function was calculated from fasting plasma glucose and insulin concentrations (15). Estimates of insulin resistance using the HOMA have been well documented as a reliable estimate of basal insulin resistance and correlate well with the euglycemic-hyperinsulinemic clamp for evaluating insulin sensitivity (15). Stable isotope labeling and collection of secreted proteins.…”

Effect of diet-induced obesity and metabolic syndrome on skeletal muscles of Ossabaw miniature swine

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“…The size of lipid aggregates was not affected by obesity, but the number of lipid droplets within muscle fibers was two times as abundant and had a more central distribution in obese compared with lean individuals (24). Weight loss results in the decreased IMCL content (11,12).…”

Effects of duodenal-jejunal bypass on structure of diaphragm in western diet obese rats

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