Insulin Response in Relation to Insulin Sensitivity
An appropriate β-cell response in black South African women
- Julia H. Goedecke, PHD1,2,
- Joel A. Dave, MB, CHB, PHD3,
- Mirjam V. Faulenbach, MD4,
- Kristina M. Utzschneider, MD4,
- Estelle V. Lambert, PHD1,
- Sacha West, PHD1,
- Malcolm Collins, PHD1,2,
- Tommy Olsson, MD5,
- Brian R. Walker, MD6,
- Jonathan R. Seckl, MB, PHD6,
- Steven E. Kahn, MB, CHB4 and
- Naomi S. Levitt, MB, CHB2
- 1Department of Human Biology, UCT/MRC Research Unit for Exercise Science and Sports Medicine, University of Cape Town, Cape Town, South Africa;
- 2South African Medical Research Council, Cape Town, South Africa;
- 3Endocrine Unit, Department of Medicine, University of Cape Town, Cape Town, South Africa;
- 4Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, VA Puget Sound Health Care System and University of Washington, Seattle, Washington;
- 5Department of Medicine, Umeå University, Umeå, Sweden;
- 6Endocrinology Unit, Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, Scotland.
- Corresponding author: Julia H. Goedecke, julia.goedecke{at}uct.ac.za
Abstract
OBJECTIVE The purpose of this study was to characterize differences in the acute insulin response to glucose (AIRg) relative to insulin sensitivity (SI) in black and white premenopausal normoglycemic South African women matched for body fatness.
RESEARCH DESIGN AND METHODS Cross-sectional analysis including 57 black and white South African women matched for BMI, SI, AIRg, and the disposition index (AIRg × SI) 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 SI was significantly lower (4.4 ± 0.8 vs. 9.4 ± 0.8 and 2.9 ± 0.8 vs. 6.0 ± 0. 8 × 10−5 min−1/[pmol/l], P < 0.001) and AIRg 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 β-cell function, was not different between ethnic groups (3,811 ± 538 vs. 2,966 ± 518 and 3,646 ± 485 vs. 2,353 ± 518 × 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 β-cell response for the level of insulin sensitivity.
Footnotes
-
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
- Received November 13, 2008.
- Accepted January 30, 2009.
-
Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. See http://creativecommons.org/licenses/by-nc-nd/3.0/ for details.
- © 2009 by the American Diabetes Association.
