Skeletal muscle metabolism and body fat content in men and women

The purpose of the present study was to verify the relationships between indicators of body fat content and specific characteristics of skeletal muscle in a large sample of men and women. Six skinfold thicknesses (sigma 6S) and maximal oxygen uptake (VO2 max) were measured in 348 Caucasian subjects (149 women and 199 men). Fiber type proportions (type I, type IIA, and type IIB) and activity levels of marker enzymes for the Krebs cycle (malate dehydrogenase, MDH) and for the fatty acid oxidation (3-hydroxyacyl CoA dehydrogenase, HADH) pathways were determined in vastus lateralis muscle samples. No significant correlation was found between fiber type proportions and sigma 6S. Significant and negative correlations were, however, obtained in both genders between the sigma 6S and MDH enzyme activity (r = -0.23; p < 0.01), but not between the sigma 6S and HADH enzyme activity. When individuals with low and high amount of subcutaneous fat but paired for VO2max were compared, vastus lateralis of fat men exhibited the same proportion of type I fiber (38.6 +/- 10.3 vs 38.5 +/- 13.4%) and HADH activity level (3.43 +/- 1.05 vs. 3.34 +/- 0.81 U/g), but had about 20% less MDH enzyme activity than vastus lateralis of leaner men (158 +/- 35 vs. 198 +/- 43 U/g;p < 0.05). No difference was found in any of these muscle phenotypes when comparisons were made between women with low and high amount of subcutaneous fat but also paired for VO2max. Moreover, no relations were observed between skeletal muscle fiber type proportion or metabolic markers with relative subcutaneous fat distribution.(ABSTRACT TRUNCATED AT 250 WORDS)