Association of dopamine D2 receptor polymorphisms Ser311Cys and TaqIA with obesity or type 2 diabetes mellitus in Pima Indians

OBJECTIVES: To investigate whether (a) variants within the dopamine D2 receptor gene (DRD2) are associated with obesity and type 2 diabetes in Pima Indians, and (b) whether variation in this gene could be responsible for previously observed linkage to these phenotypes, at chromosome location 11q23-24, in this population. DESIGN: Two single nucleotide polymorphisms (SNPs), Ser311Cys and TaqIA, within the DRD2 gene were genotyped by allelic discrimination PCR in subjects who had provided evidence of linkage to diabetes and obesity in an autosome-wide scan. SUBJECTS: A total of 1187 subjects were genotyped, including 947 full heritage Pima Indians (80%). Descriptive statistics for all subjects analyzed, for whom clinical data were available, were (mean +/- s.d.): age at time of last exam = 41 +/- 15 y; birth year = 1950 +/- 14; age-sex-adjusted body mass index (BMI; adjusted to a mean age of 35 y) = 36 +/- 8 kg/m2; male = 44%; diabetic = 57%. For full heritage Pimas only: age = 43 +/- 15 y; birth year = 1948 +/- 14; sex-age-adjusted BMI = 36 +/- 8 kg/m2; male = 43%; diabetic = 59%. RESULTS: Neither polymorphism was significantly associated with diabetes in full heritage Pimas. Individuals with a 'CG' genotype at the Ser311Cys SNP had a higher BMI than those with a 'CC' genotype (36.7 vs 35.5 kg/m2, P = 0.04). Linkage analysis of BMI, adjusted for either polymorphism, resulted in LOD scores that were similar to those obtained without adjustment. CONCLUSION: Heterozygotes at the Ser311Cys DRD2 polymorphism had a slightly higher BMI than homozygotes, however neither the Ser311Cys nor the TaqIA polymorphism accounted for the linkage with BMI on chromosome 11 in Pima Indians