beta(3)-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 Trp64Ar g variant of the beta (3)-adrenergic receptor (AR) gene in obesity and insu lin resistance in nondiabetic, subjects. In 476 nondiabetic Japanese-Americ ans (M/F = 204/272), the Trp64Arg variant of the beta (3)-AR gene was exami ned. The presence or absence of the Trp64Arg mutation was examined in DNA s eparated 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 an d 0.17 for females, almost the same as the reported values in Japanese, The re was no difference in the frequency of the beta (3)-AR gene variant betwe en 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, to tal insulin, and HOMA, an index of insulin resistance, were all significant ly higher than obese males without the mutation. In females, the index of o besity, insulin resistance, or lipid metabolism did not differ significantl y 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 vari ant is not important as an obesity-inducing factor in Japanese. However, in males, when obesity becomes obvious, the beta (3)-AR gene variant is consi dered to influence the enhancement of insulin resistance. in association wi th visceral obesity. (C) 2001 Elsevier Science Ireland Ltd. All rights rese rved.