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The influence of insulin on lipolysis in African American and Caucasian prepubertal, premenopausal, and postmenopausal females

by Goree, Laura Lee

Abstract (Summary)
African Americans, compared to Caucasians, may have chronically suppressed free fatty acid (FFA) mobilization due to basal and postprandial hyperinsulinemia. The purpose of this study was to determine if lower FFA among African Americans are due to higher insulin concentration and if this ethnic difference in FFA, beta cell function, and insulin suppression of FFA declines with age. Subjects who qualified underwent a frequently-sampled intravenous glucose tolerance test (FSIGT) for determination of insulin sensitivity (Si) and the acute insulin response to glucose (AIRg). Body composition and fat distribution were assessed with dual-energy x-ray absorptiometry (DXA) and computed tomography (CT), respectively. Analysis was completed using data from 154 females. Correlation coefficients between basal FFA and body fat showed that within postmenopausal African American women, basal FFA was associated with both leg fat (p=0.044) and subcutaneous abdominal adipose tissue (SAAT) (p=0.048), and tended to be associated with total body fat (p=0.051). Ethnicity, age group, and Si were significantly associated with AIRg (p<0.0001). After adjusting for Si, AIRg was higher among African Americans versus Caucasians and declined with age. The (age x ethnicity) interaction term was not significant. Basal FFA was significantly associated only with Si (p=0.035), such that higher Si was associated with lower basal FFA. Higher basal insulin only with Si (p=0.035), such that higher Si was associated with lower basal FFA. Higher ii basal insulin levels were also significantly associated with lower basal FFA after adjusting for age, race, Si, and total body fat (p=0.036). However, we could not statistically attribute lower nadir FFA among African Americans to higher insulin. Multiple linear regression modeling results showed that nadir FFA were significantly lower among African Americans versus Caucasians (p < 0.05). Nadir FFA was significantly associated with age group (p=0.023), such that nadir FFA declined with age, and with Si, such that higher Si was associated with lower nadir FFA. Although the physiological reason for lower FFA in African Americans is not clear, it might be due to ethnic differences in fat distribution or catecholamines. iii
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Advisor:

School:University of Alabama at Birmingham

School Location:USA - Alabama

Source Type:Master's Thesis

Keywords:african americans european continental ancestry group fatty acids nonesterified female insulin lipolysis

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