The relationship between heat shock protein 72 expression in skeletal muscle and insulin sensitivity is dependent on adiposity

Decreased gene expression of heat shock protein 72 (HSP72) in skeletal muscle is associated with insulin resistance in humans. We aimed to determine whether HSP72 protein expression in insulin-sensitive tissues is related to criterion standard measures of adiposity and insulin resistance in a young healthy human population free of hyperglycemia. Healthy participants (N = 17; age, 30 ± 3 years) underwent measurement of body composition (dual-energy x-ray absorptiometry), a maximum aerobic capacity test (Vo_2max), an oral glucose tolerance test, and a hyperinsulinemic-euglycemic clamp (M) to access insulin sensitivity. Skeletal muscle and subcutaneous adipose tissue biopsies were obtained by percutaneous needle biopsy. HSP72 protein expression in skeletal muscle was inversely related to percentage body fat (r = -0.54, P < .05) and remained significant after adjustment for age and sex (P < .05). Insulin sensitivity was also related to HSP72 protein expression in skeletal muscle (r = 0.52, P < .05); however, this relationship disappeared after adjustment for percentage body fat (P = .2). In adipose tissue, HSP72 protein expression was not related to adiposity or insulin sensitivity. Physical activity and aerobic fitness did not show any association with HSP72 protein expression in either tissue studied. A lower expression of HSP72 protein in human skeletal muscle was associated with increased adiposity and decreased insulin sensitivity in healthy individuals. These findings are consistent with rodent data suggesting that HSP72 stimulates fat oxidation with consequent reduction in fat storage and adiposity.