LINK TO RESEARCH
International journal of obesity and related metabolic disorders
P A Velasquez-Mieyer 1 ,
P A Cowan,
G E Umpierrez,
R H Lustig,
A K Cashion,
G A Burghen
Obese African-American (AA) subjects have higher resting and stimulated
insulin concentrations than obese Caucasians (C), which could not be
explained by the severity of obesity or the degree of insulin sensitivity.
We investigated whether differences in glucagon-like peptide-1 (GLP-1), the
most potent incretin that regulates insulin secretion, might explain racial
differences in insulin response. Accordingly, we measured fasting and
stimulated glucose, insulin, and GLP-1 levels during a 3-h oral glucose
tolerance test (OGTT) in 26 obese C (age 38+/-2 y, body mass index 44+/-1
kg/m(2)) and 16 obese AA (age 36+/-2 y, BMI 46+/-2 kg/m(2)) subjects.
Corrected insulin response (CIR(30)), a measure of beta-cell activity,
whole body insulin sensitivity index (WBISI), and area under the curve
(AUC) for insulin, GLP-1, and C-peptide/insulin ratio were computed from
the OGTT. Glucose levels, fasting and during the OGTT, were similar between
racial groups; 32% of the C and 31% of the AA subjects had impaired glucose
tolerance. With a similar WBISI, AAs had significantly higher CIR(30)
(2.3+/-0.4 vs 1.01+/-0.1), insulin response (IAUC: 23 974+/-4828 vs 14
478+/-1463), and lower insulin clearance (0.07+/-0.01 vs 0.11+/-0.01) than
C (all, P<0.01). Obese AAs also had higher fasting GLP-1 (6.7+/-2.5 vs 4.5+/-1.1) and GLP-1AUC (1174.7+/-412 vs 822.4+/-191) than C (both, P<0.02). Our results indicate that obese AAs had higher concentrations of GLP-1 both at fasting and during the OGTT than obese C. The increased GLP-1 concentration could explain the greater insulin concentration and the increased prevalence of hyperinsulinemia-associated disorders including obesity and type 2 diabetes in AAs.
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