Free Fatty Acid Flux in African American and Caucasian Adults – Effect of Sex and Race

OBJECTIVE: Obesity, insulin resistance and diabetes disproportionately affect African American (AA) women. Abnormal adipose tissue free fatty acid (FFA) release is associated with these conditions. Resting energy expenditure (REE) and sex predict FFA release in Caucasians, but whether this is true in AA is unknown. We sought to understand the sex-specific relationships between FFA release, REE and race. DESIGN AND METHODS: 100 adults (47% AA, 50% male, age 32±8y (mean ± SD)) from 3 different centers underwent duplicate measures of FFA release ([U-(13)C] palmitate) and REE (indirect calorimetry). Body composition was determined by DXA and abdominal imaging. RESULTS: AA participants had lower REE, but similar FFA concentrations and flux compared with Caucasian participants. The significant predictors of palmitate release were REE, sex, and race. REE and FFA flux were correlated in both sexes and both races. In a multiple-linear regression analysis with palmitate flux as the dependent variable and REE, sex, race, total fat mass, fat free mass, and insulin as independent variables, REE was the only independent predictor of FFA release in men. Both REE and race predicted palmitate flux in women. CONCLUSIONS: FFA flux is related to REE, but the relationship differs in AA and Caucasian women.