NAT2 polymorphism associated with plasma glucose concentration in Canadian Oji-Cree

The prevalence of type 2 diabetes in the Oji-Cree of Northern Ontario is among the highest of any population in the world. We previously demonstrated that markers D8S264 and D22S683 were both linked and associated with type 2 diabetes in the Oji-Cree. Among the possible candidate genes for type 2 diabetes and related traits on chromosomes 8p and 22q were NAT2 and CYP2D6, respectively. We thus explored the possible association of NAT2 and CYP2D6 alleles and diabetes-related traits in a sample of 112 Oji-Cree subjects with type 2 diabetes and 481 Oji-Cree subjects without type 2 diabetes. We found no difference in the allele and genotype frequencies of the NAT2 G191A, C282T, C481T, G590A, A803G and G857A, and the CYP2D6 G1934A polymorphisms between Oji-Cree subjects with and without type 2 diabetes. However, we found a significant association between the NAT2 C282T polymorphism and plasma fasting glucose concentration. Specifically, NAT2 282T/T homozygotes had significantly higher plasma fasting glucose than 282C/C homozygotes, and heterozygotes had intermediate levels of this trait. Thus, variation in NAT2 or CYP2D6 was not associated with the presence of type 2 diabetes, and would not be causative for this phenotype in Oji-Cree. However, NAT2 might be a 'modifier gene' affecting the level of glycaemia in non-diabetic subjects.