Diabetes Care, Vol 18, Issue 6 825-833, Copyright © 1995 by American Diabetes Association
Insulin sensitivity is not impaired in Mexican-American women without a family history of diabetes
E Bonora, G Gulli, R Bonadonna, S Del Prato, A Solini and RA DeFronzo
Department of Internal Medicine, University of Texas Health Science Center, San Antonio 78231, USA.
OBJECTIVE--The purpose of this research was to compare insulin sensitivity
in Mexican-Americans and non-Hispanic whites without a family history of
diabetes to establish whether insulin resistance is a defect intrinsically
related to subjects of Mexican origin. RESEARCH DESIGN AND METHODS--In
study A, we compared insulin sensitivity in 12 Mexican-American and 12
non-Hispanic white women with normal glucose tolerance and no family
history of diabetes. In study B, we compared insulin sensitivity in two
groups of normal glucose-tolerant Mexican-Americans, nine with a positive
(FHD+) and nine with a negative (FHD-) family history of diabetes. In both
studies, the groups were closely matched for age, total body fat content,
and fat topography. Insulin sensitivity was assessed with the euglycemic
insulin clamp (20 microU.min-1.m2 surface area) which was performed in
combination with tritiated glucose infusion and indirect calorimetry. Total
fat mass and fat-free mass (FFM) were assessed by a tritiated water
dilution technique, and regional fat distribution was evaluated by
anthropometry and magnetic resonance imaging. RESULTS--During a 4-h
euglycemic insulin clamp (study A), rates (mg.min-1.kg FFM-1) of total
(6.32 +/- 0.64 vs. 6.62 +/- 0.81), oxidative (3.54 +/- 0.24 vs. 3.51 +/-
0.19), and nonoxidative (2.78 +/- 0.48 vs. 3.11 +/- 0.75) glucose
utilization were similar in Mexican-Americans and non-Hispanic whites;
hepatic glucose production (0.33 +/- 0.13 vs. 0.35 +/- 0.13) was suppressed
similarly in both groups. During a 2-h euglycemic insulin clamp (study B),
Mexican-Americans with FHD+ had lower rates of insulin-mediated total (3.55
+/- 0.39 vs. 5.93 +/- 0.59, P < 0.001), oxidative (3.31 +/- 0.25 vs.
4.32 +/- 0.17, P < 0.01), and nonoxidative (0.24 +/- 0.28 vs. 1.61 +/-
0.49, P < 0.01) glucose disposal than subjects with FHD-; suppression of
hepatic glucose production (0.24 +/- 0.14 vs. 0.18 +/- 0.12) was similar in
both groups. CONCLUSIONS--These results indicate that in the absence of a
family history of non-insulin-dependent diabetes mellitus, Mexican-American
women are not less sensitive to insulin than non-Hispanic white women.