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Effects of Weight Loss and Physical Activity on Muscle Lipid Content and Droplet Size

2004; Wiley; Volume: 12; Issue: 5 Linguagem: Inglês

10.1038/oby.2004.92

1550-8528

Jing He, Bret H. Goodpaster, David E. Kelley,

Diet and metabolism studies

Abstract Objectives : To address the potential effects of weight loss and physical activity (WL + Ex) on intramyocellular lipid (IMCL) and lipid droplet size in overweight and obese previously sedentary individuals. Research Methods and Procedures : IMCL and lipid droplet size was determined in vastus lateralis, obtained by percutaneous biopsy, from 21 obese volunteers (9 men/12 women), using Oil Red O staining, along with succinate dehydrogenase histochemistry and mitochondrial immunohistochemistry as measures of skeletal muscle oxidative capacity. Insulin sensitivity (IS) was determined by glucose clamp. Results : A 4‐month WL + Ex intervention resulted in ∼10% WL and ∼15% increase in maximal oxygen uptake, leading to a 46% increase in IS (all p < 0.01). IMCL did not significantly change ( p = 0.36). However, the size of lipid droplets decreased after WL + Ex ( p < 0.01), and this decrease in lipid droplet size correlated with increased IS ( p < 0.01) and the amount of physical activity ( p < 0.05). Succinate dehydrogenase activity and mitochondrial labeling increased significantly ( p < 0.01), without a significant shift in fiber type distribution. Discussion : In summary, IMCL does not decrease in response to WL + Ex in obese, previously sedentary individuals, yet the lipid within muscle is dispersed into smaller droplets. This change in the size of lipid droplets, likely coupled with a concomitant increase in oxidative enzyme capacity, is correlated to improved IS.