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Obes Res. 2004 May;12(5):761-9.

Effects of weight loss and physical activity on muscle lipid content and droplet size.

Author information

1
Division of Endocrinology and Metabolism, Department of Medicine, University of Pittsburgh School of Medicine, Pennsyvania, USA.

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 approximately 10% WL and approximately 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.

PMID:
15166296
DOI:
10.1038/oby.2004.92
[Indexed for MEDLINE]
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