Gender differences in basal protein kinetics in young adults

Gender affects energy expenditure and influences the relative utilization o f carbohydrate and fat as fuels. However, little is known about the possibl e effects of gender on protein metabolism. Thus, Ne compared whole body and plasma (albumin and fibrinogen) protein kinetics in the basal postabsorpti ve state in young, untrained volunteers divided into two groups according t o gender (women: n = 17; age, 24 +/- 4 yr; men: n = 17; age, 25 +/- 2 yr). The two groups were matched for body mass index. Protein kinetics were meas ured by means of L- [1-C-14] leucine infusion. The leucine whole body rate of appearance, an index of proteolysis, and nonoxidative rate of disappeara nce, an index of protein synthesis, were similar in the two groups. However , the leucine oxidation rate was significantly lower in women compared to m en (0.25 +/- 0.07 vs. 0.31 +/- 0.08 mu mol/kg min; P = 0.0062). Similar res ults were obtained when data were adjusted for estimated body composition. Albumin and frbrinogen fractional secretion rates were not different in the two groups. In conclusion, in the basal state leucine oxidation is lower i n women than in men regardless of body composition. This could be one of th e factors contributing to the lower metabolic rate in women.