The Combined Effect of β2- and β3-Adrenergic Receptor Genotypes on Hyperglycemic Risk in the Korean Population

Adrenergic receptors play a major role in thermogenesis and lipolysis in brown and visceral adipose tissues, and have been implicated in the pathogenesis of obesity and metabolic disorders. The purpose of this study was to estimate the effects of $\beta$2-adrenergic receptor ($\beta$2AR) and $\beta$3-adrenergic receptor ($\beta$3AR) genotypes on hyperglycemia and obesity in the Korean population. A representative sample consisting of 530 Korean men and women were measured for height, weight, BMI, WHR, obesity index and body composition. The genotypes of $\beta$2AR polymorphism in codon 27 and $\beta$3AR polymorphism in codon 64 were analyzed by the PCR RFLP method. Serum concentrations of fasting glucose, total cholesterol, HDL cholesterol and triglyceride were determined. The frequencies of $\beta$2AR and $\beta$3AR genotype were: both wild type, 62.5% ; only $\beta$2AR variant type, 12.8% ; only $\beta$3AR variant type, 18.8% ; and both variant type, 5.8% ; the frequency of E and R alleles were 0.098 and 0.137, respectively. Among the physiological parameters, fasting glucose level was significantly higher in subjects with both variant type compared with the three other types (p <0.05), Subjects with both variant type had 12%, 12% and 9.3% increases in serum glucose levels compared with wild type, only $\beta$2AR variant type, and only $\beta$3AR variant type, respectively. When logistic regression analysis was conducted to estimate the risk for hyperglycemia, the subjects were selected for fasting blood glucose concentrations of more than 6.105 m㏖/L (110 mg/dL), and the odds ratios were 1.215 (p=0.636) for only $\beta$2AR variant type,1.659 (p=0.089) for only $\beta$3AR variant type, and 3.078 (p=0.011) for both variant type. These results suggest that the interaction of $\beta$2AR and $\beta$3AR variant genotypes has a strong association with increased glucose levels, and might be a significant risk factor for hyperglycemia among Korean subjects.