Associations of Free Fatty Acids With Insulin Secretion and Action Among African‐American and European‐American Girls and Women

Ethnic differences in insulin secretion and action between African Americans (AAs) and European Americans (EAs) may influence mobilization of free fatty acids (FFAs). We tested the hypotheses that FFA concentrations would be associated with measures of insulin secretion and action before and during a glucose challenge test. Subjects were 48 prepubertal girls, 60 premenopausal women, and 46 postmenopausal women. Fasting insulin (insulin₀), the acute insulin response to glucose (AIR_g), the insulin sensitivity index (S_I), basal and nadir FFA (FFA₀, FFA_nadir), and nadir time (TIME_nadir) were determined during an intravenous glucose tolerance test (IVGTT). Stepwise multiple linear regression (MLR) analysis was conducted to identify associations of FFA₀, FFA_nadir, and TIME_nadir with ethnicity, age group, insulin measures, indexes of body composition from dual‐energy X‐ray absorptiometry, and measures of fat distribution from computed tomography scan. In this population, insulin₀ and AIR_g were higher among AAs vs. EAs, whereas S_I was lower, independent of age group. MLR analyses indicated that FFA₀ was best predicted by lean tissue mass (LTM), leg fat mass, ethnicity (lower in AAs), S_I, and insulin₀. FFA_nadir was best predicted by FFA₀, age group, and intra‐abdominal adipose tissue (IAAT). TIME_nadir was best predicted by leg fat mass, AIR_g, and S_I. In conclusion, indexes of insulin secretion and action were associated with FFA dynamics in healthy girls and women. Lower FFA₀ among AAs was independent of insulin₀ and S_I. Whether lower FFA₀ is associated with substrate oxidation or risk for obesity remains to be determined.