Fat distribution and insulin response in prepubertal African American and white children

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Abstract
Ethnic differences in obesity-related disease prevalence may relate to differences in fat distribution or metabolism. We conducted a study in 73 African American and white children to examine the relation between fat distribution and insulin and to determine whether ethnic differences in fat distribution or in adiposity-insulin relations contribute to differences in insulin concentrations. Fasting and postchallenge insulin concentrations were determined by oral-glucose-tolerance test, total body fat by dual-energy X-ray absorptiometry, and subcutaneous abdominal (SAAT) and intraabdominal (IAAT) adipose tissue by computerized tomography. African Americans had greater fasting insulin (x +/- SD: 79 +/- 37 compared with 55 +/- 23 pmol/L, P < 0.01), incremental 30-min insulin (567 +/- 438 compared with 300 +/- 304 pmol/L, P < 0.001), and incremental area under the insulin curve (AUC; 262 +/- 209 compared with 164 +/- 156 pmol/L, P < 0.01). In multiple linear regression, fasting insulin was independently related to total fat within both ethnic groups (model R2 = 0.42 and 0.52 for African Americans and whites, respectively), incremental 30-min insulin to total fat and IAAT in whites only (model R2 = 0.71), and AUC to SAAT in African Americans only (model R2 = 0.49). Adjusting insulin indexes for adiposity did not eliminate the significant effect of ethnicity. In general, relations between adiposity and insulin were stronger in whites than in African Americans. African American children had higher insulin concentrations than white children after total body fat, IAAT, and SAAT were controlled for. However, strong relations between adiposity (total and abdominal) and insulin in both groups suggest that obesity may contribute to disease risk regardless of ethnicity.