Correlation of the Taq1 dopamine D2 receptor gene and percent body fat in obese and screened control subjects: a preliminary report

While there is a considerable body of literature correlating the role of dopaminergic genes and obesity, body mass index, body type, overeating, carbohydrate binging, energy expenditure and low dopamine D2 receptor (D2R) receptor density, there is a paucity of research concerning the dopamine D2 receptor gene (DRD2) variants and percent body fat. We report here the potential association of DRD2 genotypes and the percent fat phenotype. In this study we genotyped 122 obese/overweight (O/OW) Caucasian subjects and 30 non-obese Caucasian controls, screened to exclude substance abuse. The subjects were assessed for weight, body mass index (BMI; kg m(-2)) and percent body fat using dual energy X-ray absorptiometry (DEXA). The sample was separated into two independent groups; those with the Taq1 A1 allele (A1/A1 or A1/A2) and those without the A1 allele (A2/A2). The controls had a normal range of body fat (25-31% for females and 18-25% for males). The O/OW subjects had a percent body fat value of over 32% for females and over 25% for males. For the O/OW subjects, the mean BMI was 29.3 ± 6.25 kg m(-2), mean body fat was 42.1 ± 7.5% and mean weight was 82.7 ± 21.7 kg. The DRD2 Taq1 A1 allele was present in 67% of the O/OW subjects compared to 3.3% of super controls (A group), 33.3% of screened (for drug abuse and obesity) controls (B group) and unscreened literature controls 29.4% (P≤ 0.001). Comparing all cases with more than 34% body fat, utilizing logistic regression analysis, the DRD2 A1 allele accounts for 45.9% of the variance, which is statistically significant (χ(2) = 43.47, degrees of freedom (df) = 1, P < 0.0001). These results are consistent with a role for the DRD2 gene in obesity, as measured by percent body fat as well as by weight and BMI.