RACIAL-DIFFERENCES IN PLASMA LEPTIN CONCENTRATIONS IN OBESE POSTMENOPAUSAL WOMEN

Leptin may play an important role in the regulation of body weight by influencing energy intake and expenditure. Differences in body composi tion, resting energy expenditure (REE), and physical activity between African-American and Caucasian women could be reflective of racial dif ferences in plasma leptin concentrations. Thus, we examined racial dif ferences in leptin levels and the relationships of leptin to body comp osition and resting metabolism in obese postmenopausal African-America n (n = 28) and Caucasian (n = 29) women matched for level of body fat. African-American and Caucasian women were similar in age (64.1 +/- 1. 3 vs. 63.2 +/- 1.0 yr), body weight (84.7 +/- 3.3 vs. 80.4 +/- 1.3 kg) , adipose tissue mass (39.7 +/- 2.8 vs. 38.0 +/- 1.0 kg), waist to hip ratio (0.81 +/- 0.02 vs. 0.81 +/- 0.01), and maximal aerobic capacity (1.5 +/- 0.05 vs. 1.6 +/- 0.05 L/min). African-American women had gre ater lean tissue mass than Caucasian women (41.8 +/- 1.1 vs. 39.3 +/- 0.6 kg; P = 0.05). The leptin concentration was 20% lower in African-A merican than Caucasian women (36.0 +/- 4.8 vs. 45.8 +/- 3.5; P < 0.05) , whereas REE values were similar. Leptin correlated strongly with per cent body fat in African-American (r = 0.71; P < 0.0001) and Caucasian women (r = 0.61; P < 0.001) and with REE in African-American (r = 0.5 8; P < 0.001), but not Caucasian, women (r = 0.08). These findings sug gest racial differences in plasma leptin levels and in leptin's role i n the regulation of REE, which may play a role in the greater incidenc e of obesity in the African-American compared to the Caucasian populat ion.