Insulin response in relation to insulin sensitivity: an appropriate beta-cell response in black South African women.
OBJECTIVE
The purpose of this study was to characterize differences in the acute insulin response to glucose (AIR(g)) relative to insulin sensitivity (S(I)) in black and white premenopausal normoglycemic South African women matched for body fatness.


METHODS
Cross-sectional analysis including 57 black and white South African women matched for BMI, S(I), AIR(g), and the disposition index (AIR(g) x S(I)) were performed using a frequently sampled intravenous glucose tolerance test with minimal model analysis, and similar measures were analyzed using an oral glucose tolerance test (OGTT). Body composition was assessed by dual-energy X-ray absorptiometry and computed tomography.


RESULTS
S(I) was significantly lower (4.4 +/- 0.8 vs. 9.4 +/- 0.8 and 2.9 +/- 0.8 vs. 6.0 +/- 0. 8 x 10(-5) min(-1)/[pmol/l], P < 0.001) and AIR(g) was significantly higher (1,028 +/- 255 vs. 352 +/- 246 and 1,968 +/- 229 vs. 469 +/- 246 pmol/l, P < 0.001), despite similar body fatness (30.9 +/- 1.4 vs. 29.7 +/- 1.3 and 46.8 +/- 1.2 vs. 44.4 +/- 1.3%) in the normal-weight and obese black women compared with their white counterparts, respectively. Disposition index, a marker of beta-cell function, was not different between ethnic groups (3,811 +/- 538 vs. 2,966 +/- 518 and 3,646 +/- 485 vs. 2,353 +/- 518 x 10(-5) min, P = 0.10). Similar results were obtained for the OGTT-derived measures.


CONCLUSIONS
Black South African women are more insulin resistant than their white counterparts but compensate by increasing their insulin response to maintain normal glucose levels, suggesting an appropriate beta-cell response for the level of insulin sensitivity.
Goedecke
Julia H
JH
Department of Human Biology, UCT/MRC Research Unit for Exercise Science and Sports Medicine, University of Cape Town, Cape Town, South Africa. julia.goedecke@uct.ac.za
Dave
Joel A
JA
Faulenbach
Mirjam V
MV
Utzschneider
Kristina M
KM
Lambert
Estelle V
EV
West
Sacha
S
Collins
Malcolm
M
Olsson
Tommy
T
Walker
Brian R
BR
Seckl
Jonathan R
JR
Kahn
Steven E
SE
Levitt
Naomi S
NS
D000273:Adipose Tissue / Q000033:anatomy & histology; D044383:Black People; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism*; D001823:Body Composition; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology / Q000401:mortality; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology*; D000078790:Insulin Secretion; D009765:Obesity / Q000097:blood / Q000453:epidemiology; D017697:Premenopause; D012016:Reference Values; D013019:South Africa / Q000453:epidemiology; D044465:White People
D001786:Blood Glucose; D007328:Insulin