Racial and sex differences in the polymorphisms of the endocannabinoid receptor genes in obesity

Obesity is a global epidemic and prevalence of obesity is higher in African Americans (AAs) compared to Caucasians. The endocannabinoid system (EC) and polymorphism in the endocannabinoid receptor type 1 (CNR1) gene 3813A/G and 4895A/G and in the fatty acid amide hydrolase (FAAH) are associated with obesity. The objective was to explore racial and sex differences in these polymorphisms and the biochemical abnormalities seen in obesity.

A cross-sectional study of 667 subjects (53.67% female; 49.18% AA; 69.72% were obese (body mass index [BMI] ≥30)) were screened for CNR1 3813, 4895 and FAAH 385 polymorphisms using a real-time polymerase chain reaction (PCR) system.

Subjects with FAAH 385 polymorphisms were more likely to be obese (75.14% vs. 67.81, P = 0.046). There were no significant sex differences for CNR1 3813 and CNR1 4895; or between obese and control group. AAs had higher prevalence of CNR1 3813 (OR, 2.80, 95% CI, 1.95-4.04) and FAAH 385 (OR, 2.48, 95% CI, 1.82-3.38). Association between African American race and the three genotypes persisted after adjustment of all the variables (P < 0.001).

FAAH 385 polymorphism is more likely seen in obese and in older subjects. AAs had higher prevalence of CNR1 3813 and FAAH 385 polymorphisms; and lower prevalence of CNR1 4895 polymorphism. These findings may explain some of the racial differences, but not the sex differences in the clinical expression of obesity.