Association analyses of adrenergic receptor polymorphisms with obesity and metabolic alterations

Genes involved in the regulation of catecholamine function may be important in obesity because of the role catecholamines play in energy expenditure and lipolysis. To determine if common single nucleotide polymorphisms (SNPs) in beta(1)-adrenergic receptor (ADRB1), beta(2)-adrenergic receptor (ADRB2), beta(3)-adrenergic receptor (ADRB3), and alpha(2)-adrenergic receptor (ADRA2A) genes associate with obesity and metabolic alterations, we recruited 74 healthy African American and 161 white men and women (age, 18-49 years) to participate in this case-control genetic association study. Genotypes were determined by polymerase chain reaction and restriction fragment length polymorphism. Associations between genotype and body mass index (BMI), percentage of body fat (by measuring skinfold thickness in 7 different sites), fasting (12-hour) plasma glucose, insulin, potassium concentrations, glycated hemoglobin, and insulin resistance (homeostasis model assessment [HOMA(IR)] score) were performed. Among whites, the ADRB1 Arg389-->Gly variant associated with insulin concentrations and HOMA(IR): mean +/- SD values for insulin and HOMA(IR) in Arg389 homozygotes and carriers of the Gly were 10 +/- 7.0 and 12 +/- 9.4 micro IU/mL (P = .02) and 2.1 +/- 1.7 and 2.6 +/- 2.2 (P = .057), respectively. Systolic blood pressure was higher in whites for carriers of the ADBR1 Ser49 compared to Gly49 homozygotes (124 +/- 12.6 vs 119 +/- 11.3 mm Hg, respectively; P = .02). Subsequent analysis revealed that these associations were attributable to a higher BMI among obese participants. The ADRA2A G1780A SNP associated with BMI and percentage of body fat in African Americans (P = .05). Interactions were detected between ADRA2A C-1291G and ADRB2 Gln27-->Glu variants for obesity in African Americans and between ADRA2A C-1291G SNP and ADBR1 haplotype for obesity in whites. We conclude that common SNPs in adrenergic receptor genes may be important susceptibility loci for obesity and related alterations. Because of the limited size of our populations, our results should be interpreted with caution and should be replicated in larger populations.