THE FEMALE INSULIN ADVANTAGE IN A BIRACIAL COHORT - RESULTS FROM THE MIAMI COMMUNITY-HEALTH STUDY

OBJECTIVE: To determine the extent to which gender differences in the rate of insulin-mediated glucose disposal are influenced by difference s in body fatness. DESIGN: A cross-sectional study of a biracial sampl e of men and women drawn from a population-based study. SUBJECTS: Twen ty-five 25-44 year old residents of Dade County, FL. Twenty-five Afric an-Americans (14 men and 11 women) and 28 white, nonHispanics (15 men and 13 women). All participants were free of diabetes mellitus (WHO Cr iteria). MEASUREMENTS: All persons volunteered to undergo a hyperinsul inemic euglycemic clamp procedure to determine the rate of insulin-med iated glucose disposal (insulin sensitivity, M). Several measures of b ody fatness were quantified and the percentage body fat determined acc ording to published equations. RESULTS: Men and women had similar unad justed M values. Within each gender and ethnic group M was inversely r elated to percentage body fat (r = -0.55 to -0.84; p < 0.05). After ad justment for percentage body fat, women were more insulin sensitive th an men (10.1 vs 5.1 mg/kg/min among African-Americans and 10.1 vs 6.9 mg/kg/min among white, nonHispanics; p < 0.05 for each). When M was ex pressed per unit of fat free mass, women were still significantly more insulin sensitive than men (p < 0.05 for each ethnic group). In multi variate analyses, gender and percentage body fat were independently re lated to M in both ethnic groups accounting for 70% of the variance am ong African-American participants and 34% of the variance among white non Hispanic participants. CONCLUSION: The similar M values between me n and women despite the higher percent body fat among women indicate t hat women are more insulin sensitive in muscle tissue than men. This w as substantiated when M was normalized for fat free mass. This 'insuli n advantage' may be related to the lower risk of coronary disease expe rienced by women and the loss of this advantage may in part underlie t he stronger deleterious effects of diabetes that women suffer.