Pro12Ala of the Peroxisome Proliferator–Activated Receptor-γ2 Gene Is Associated With Lower Serum Insulin Levels in Nonobese African Americans
The Atherosclerosis Risk in Communities Study
- W.H. Linda Kao1,
- Josef Coresh12,
- Alan R. Shuldiner3,
- Eric Boerwinkle4,
- Molly S. Bray4 and
- Frederick L. Brancati12
- 1Department of Epidemiology, the Johns Hopkins University School of Hygiene and Public Health, Baltimore, Maryland
- 2Department of Medicine, the Johns Hopkins University School of Medicine, Baltimore, Maryland
- 3Division of Endocrinology, Diabetes and Nutrition, University of Maryland School of Medicine, and Baltimore Veterans Hospital Geriatrics Research and Education Clinical Center, Baltimore, Maryland
- 4Human Genetics Center, Institute of Molecular Medicine, University of Texas Houston Health Science Center, Houston, Texas
Abstract
Recent research suggests that the Pro12Ala variant in peroxisome proliferator–activated receptor-γ2 (PPAR-γ2) is associated with diabetes- and obesity-related traits, and that its effects may be modified by obesity status. We characterized this variant in a population-based sample of 1,441 middle-aged African-American individuals with respect to diabetes-, obesity-, and other cardiovascular-related traits, both cross-sectionally and prospectively. The overall frequency of Ala12 was 1.9% (95% CI 1.5–2.5%), significantly lower than in Caucasian populations. Consistent with previous findings in Caucasians, African Americans with type 2 diabetes tended to be less likely to have the Pro/Ala genotype than those without (odds ratio [OR] 0.64, 95% CI 0.34–1.20); however, this OR was not statistically significant. Among nonobese individuals, the Pro/Ala genotype was associated with significantly lower ln(insulin) (P = 0.001), lower ln(HOMA-IR) (homeostasis model assessment of insulin resistance) (P = 0.002), higher fasting glucose-to-insulin ratio (P = 0.005), and lower diastolic blood pressure (P = 0.02). Among overweight individuals (BMI 25–29.9 kg/m2), the Pro/Ala genotype was associated with greater BMI (P = 0.02), waist-to-hip ratio (P = 0.01), and waist circumference (P = 0.04). Among obese individuals, there was no association between any of the diabetes- or obesity-related traits and the Pro12Ala PPAR-γ2 variant. We conclude that among nonobese African Americans, the Pro/Ala genotype is associated with markers of greater insulin sensitivity.
Footnotes
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Address correspondence and reprint requests to Dr. W.H. Linda Kao, Department of Epidemiology, the Johns Hopkins University, 615 N. Wolfe St., Room W6513, Baltimore, MD 21205. E-mail: wkao{at}jhsph.edu.
Received for publication 29 August 2002 and accepted in revised form 18 February 2003.
ARIC, Atherosclerosis Risk in Communities; HOMA-IR, homeostasis model assessment of insulin resistance; PPAR-γ2, peroxisome proliferator–activated receptor-γ2.
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