Combination of polymorphisms in OB-R and the OB gene associated with insulin resistance in Nauruan males

Abstract

OBJECTIVE: To investigate the relationship between polymorphisms in the OB-R and OB genes and metabolic markers for obesity and glucose intolerance in a population of Nauruan men. In addition, we examined the effect of the simultaneous presence of the three polymorphisms on the phenotype of individuals in this population.

DESIGN AND SUBJECTS: This study was conducted in a population from the Pacific Island of Nauru. Populations in this region have some of the highest recorded rates of obesity and type 2 diabetes and are therefore of great interest in the genetic analysis of these diseases. Two hundred and thirty-two male subjects were examined in this cross-sectional study. All subjects were non-diabetic and the group had a mean age of 31 y and a mean body weight of 104 kg.

MEASUREMENTS: Several phenotypic measures of body fatness and fat distribution (anthropometry), fasting plasma insulin, glucose and leptin concentrations, blood pressure and 2 h plasma glucose concentration, genotypes of subjects for the Gln223Arg, PRO1019pro (OB-R gene) and OB gene polymorphisms.

RESULTS: Individually, the OB gene and Gln223Arg OB-R polymorphisms were not associated with the obese or glucose-intolerant phenotype in this population. Individuals with the PRO1019pro polymorphism were found to have elevated insulin concentrations and diastolic blood pressure (P_c=0.04). In addition, individuals found to simultaneously exhibit homozygosity of the common allele of all three polymorphisms (genotypes: Arg/Arg, pro/pro and II/II) exhibited significantly elevated fasting insulin levels (P_c=0.03).

CONCLUSIONS: Pacific Island populations exhibit a remarkably high prevalence rate of obesity and type 2 diabetes and represent a unique population for genetic studies of obesity. In the present study we have revealed that a specific combination of alleles in OB and OB-R, two candidate genes for obesity, may confer an increased risk for the development of insulin resistance in Nauruan males.