AJP - Regulatory, Integrative and Comparative Physiology, Vol 262, Issue 4 684-R688, Copyright © 1992 by American Physiological Society

ARTICLES

Skeletal muscle composition in dietary obesity-susceptible and dietary obesity-resistant rats

J. Abou Mrad, F. Yakubu, D. Lin, J. C. Peters, J. B. Atkinson and J. O. Hill
Department of Pediatrics, Vanderbilt University, Nashville, Tennessee 37232.

The intent of this study was to determine whether a relationship exists between susceptibility to high-fat diet (HFD)-induced obesity and skeletal muscle fiber type. Forty-four adult male Wistar rats were given ad libitum access to a HFD (60% of calories from fat) for 4 wk. Rats were then grouped into quartiles for total weight gain, and the top-quartile [obesity prone (OP)] rats were compared with the bottom-quartile [obesity resistant (OR)] rats. OP rats gained 1.5 times as much weight as OR rats. OR rats had a significantly higher proportion of type I muscle fibers in the medial head of the gastrocnemius muscle than OP rats both before (determined from a muscle biopsy) and after the HFD feeding period. A greater proportion of type I fibers may be associated with a greater capacity for fat oxidation, which would favor resistance to body fat accumulation. Preexisting differences in muscle fiber composition may play a role in determining susceptibility to dietary obesity.

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