We investigated the relationship between the Trp64Arg mutation in the β₃-adrenergic receptor gene and insulin sensitivity, which was evaluated by the euglycemic-hyperinsulinemic-clamp technique, in 54 patients with impaired glucose tolerance (IGT) or non-insulin dependent diabetes mellitus (NIDDM) who were not receiving insulin therapy. The frequencies of Trp/Trp, Trp/Arg, and Arg/Arg genotypes in the patients were 63.0, 33.3, and 3.7%, respectively, which did not differ significantly from those of the 227 controls (67.0, 31.3, and 1.8 %, respectively). The mean glucose infusion rate of the 34 patients with Trp/Trp did not differ from that of the 18 patients with Trp/Arg (4.3 ± 2.2 and 5.3 ± 2.4 mg/kg/min, respectively); while that of the 2 patients with Arg/Arg was 11.5 mg/kg/min. There were no differences in the BMI or fat distribution in the abdomen between each genotype of patients, although the frequency of the Arg64 allele tended to increase with body mass index (BMI) in the control subjects under 60 years of age, which suggests that the mutation is involved in weight gain.
(Internal Medicine 36: 603-606, 1997)