Key result
Higher adiposity is linked to reduced insulin sensitivity and impaired beta-cell function across ethnic groups.
Why the study?
Type 2 diabetes prevalence is higher among African Americans than European Americans, peaks at middle age, and relates to obesity. Whether the association of adiposity with insulin sensitivity and beta-cell function differs by ethnicity and age was unknown.
Does the association of adiposity (% body fat) with insulin sensitivity and beta-cell function differ by ethnicity (African American vs. European American) and age group in healthy normoglycemic females?
Cross-Sectional (n=168)
No
Does the association of adiposity (% body fat) with insulin sensitivity and beta-cell function differ by ethnicity (African American vs. European American) and age group in healthy normoglycemic females?
Answers are grounded in this paper and cite their sources.
The metabolic impact of adiposity differs by ethnicity and age, predominantly reducing insulin sensitivity in European American females while directly impairing beta-cell insulin secretion in postmenopausal African American women.
The prevalence of type 2 diabetes is higher among African Americans (AA) vs. European Americans (EA), is highest at middle age, and is related to obesity. This study was conducted to test the hypothesis that the association of adiposity (percent body fat (%fat)) with indexes of insulin sensitivity (S(I)) and β-cell function would differ with ethnicity and age. Subjects were 168 healthy, normoglycemic AA and EA girls and women aged 7-12 years, 18-32 years, and 40-70 years. An intravenous glucose tolerance test (IVGTT) was used to assess indexes of insulin secretion and action: S(I), acute C-peptide secretion (X0); basal, first-phase, second-phase, and total β-cell responsivity to glucose (PhiB, Phi1, Phi2, and Phi(TOT), respectively); and the disposition index (DI = S(I) × Phi(TOT)). %Fat was assessed with dual energy X-ray absorptiometrys. Adiposity was significantly associated with S(I) among EA (-0.57, P < 0.001) but not AA (-0.20, P = 0.09). Adiposity appeared stimulatory to β-cell function in the two groups of younger subjects and in EA, but inhibitory in postmenopausal women, particularly AA postmenopausal women. Among AA postmenopausal women, %fat was inversely associated with Phi1 (r = -0.57, P < 0.05) and Phi(TOT) (r = -0.68, P < 0.01). These results suggest that the impact of adiposity on insulin secretion and action differs with age and ethnicity.
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Chandler-Laney et al. (2010) conducted a cross-sectional in Normoglycemic healthy females (evaluation of adiposity, insulin sensitivity, and beta-cell function) (n=168). Adiposity (percent body fat [%fat] assessed by dual-energy X-ray absorptiometry, and intra-abdominal/subcutaneous adipose tissue assessed by CT) vs. Differences across ethnicity (African American vs. European American) and age groups (7-12, 18-32, and 40-70 years) was evaluated on Association of percent body fat (%fat) with insulin sensitivity (SI) and indices of beta-cell responsivity to glucose (Phi1 and PhiTOT) derived from intravenous glucose tolerance test (IVGTT) (r = -0.57 (SI in EA); r = -0.20 (SI in AA); r = -0.57 (Phi1 in postmenopausal AA); r = -0.68 (PhiTOT in postmenopausal AA), p=<0.001 (SI in EA); 0.09 (SI in AA); <0.05 (Phi1 in postmenopausal AA); <0.01 (PhiTOT in postmenopausal AA)). Adiposity (%fat) was inversely associated with insulin sensitivity in European Americans (r=-0.57, P<0.001) and with total beta-cell responsivity in postmenopausal African Americans (r=-0.68, P<0.01).
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