β3-adrenergic receptor gene variant is associated with upper body obesity only in obese Japanese-American men but not in women

We investigated gender differences in the relationships between the Trp64Arg variant of the beta (3)-adrenergic receptor (AR) gene in obesity and insulin resistance in nondiabetic, subjects. In 476 nondiabetic Japanese-Americans (M/F = 204/272), the Trp64Arg variant of the beta (3)-AR gene was examined. The presence or absence of the Trp64Arg mutation was examined in DNA separated from leukocytes in peripheral blood using the PCR-RFLP method. The frequency of abnormal allele of the beta (3)-AR gene was 0.18 for males and 0.17 for females, almost the same as the reported values in Japanese, There was no difference in the frequency of the beta (3)-AR gene variant between obese and non obese subjects for each gender. However, among obese males (body mass index greater than or equal to 24.2 kg/m(2)), with the beta (3)-AR gene mutation, the waist-to-hip ratio, fasting insulin, 2-h insulin, total insulin, and HOMA, an index of insulin resistance, were all significantly higher than obese males without the mutation. In females, the index of obesity, insulin resistance, or lipid metabolism did not differ significantly between the subjects with or without the beta (3)-AR gene variant either in the obese and non-obese group, We suggest that the beta (3)-AR gene variant is not important as an obesity-inducing factor in Japanese. However, in males, when obesity becomes obvious, the beta (3)-AR gene variant is considered to influence the enhancement of insulin resistance. in association with visceral obesity. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.