Obesity, Type II diabetes and the β2 adrenoceptor gene Gln27Glu polymorphism in the Tongan population

Abstract

As there is a high prevalence of obesity in Tonga, we aimed to determine the distribution of the β2 adrenoceptor gene Gln27Glu polymorphism and to assess its relevance to obesity and to Type II diabetes, known to be prevalent in that population. A random sample of 1022 individuals from Tonga were genotyped for the Gln27Glu polymorphism in the β2 adrenoceptor gene. To assess the prevalence of obesity we measured body-mass index (BMI), fat-free mass, percentage fat and waist-to-hip ratio (WHR). To assess glucose metabolism we measured HbA1c, fasting blood glucose, fasting serum insulin, and 1- and 2-h glucose; we also measured serum lipid and creatinine levels. We found that 84% of the Tongan men and 93% of the women were overweight or obese (BMI⩾25kg/m2) and 15.1% had Type II diabetes. Genotype frequencies among the 1022 Tongans were: Gln/Gln 90.3% and Gln/Glu 9.6%; we found one Glu/Glu homozygote. The mean BMI (±S.D.) for men was not significantly different for those who were homozygous (30.2±5.4kg/m2) or heterozygous (30.1±5.5kg/m2) for the Gln allele; this was also true for women (33.7±6.2kg/m2 for homozygous and 34.0±5.6kg/m2 for heterozygous). The Glu allele was not associated with other measures of obesity or abnormal glucose metabolism in this generally overweight population. There is a unique frequency of the Gln/Glu β2 adrenoceptor polymorphism among Tongans. We found no association of the polymorphism with obesity measures or Type II diabetes-related variables in the Tongan population among whom we documented a high prevalence of obesity and Type II diabetes and a low frequency of the Glu allele.