Association of cannabinoid type 1 receptor and fatty acid amide hydrolase genetic polymorphisms in C hinese patients with irritable bowel syndrome

Background and Aim The endocannabinoid system is involved in the pathophysiology of irritable bowel syndrome ( IBS ). Here, we investigated whether genetic variants of the cannabinoid type 1 receptor ( CNR1 ) and fatty acid amide hydrolase ( FAAH ) are associated with the pathogenesis of IBS . Methods In total, 292 patients with IBS and 298 healthy controls were enrolled. Polymerase chain reaction ( PCR ) and DNA sequencing were applied to determine the genotyping of polymorphic triplet AAT repeats located at the 3′‐end of the CNR1 gene. The single nucleotide polymorphism ( SNP ) C385A at the FAAH gene (rs324420) was determined by PCR using T aq M an SNP G enotyping A ssay S ets. Results A total of eight alleles with AAT triplet repeats in the CNR1 gene were detected. The alleles were divided into two groups (≤ 10 and > 10) and three genotypes (≤ 10/≤ 10, ≤ 10/> 10, and > 10/> 10). The frequency of > 10 alleles was significantly higher in the IBS group (90.6%) when compared with the control group {81.7%, P  < 0.001, odds ratio ( OR ) (95% confidence interval [ CI ]) = −0.128}. In addition, the genotypes > 10/> 10 were significantly associated with IBS ( P  < 0.001, OR [95% CI ] = −0.163). The frequency of the A allele and the distribution of the AA genotype in the FAAH gene in the IBS group were not significantly different from those in the control group ( P  > 0.05), even though the frequency of the AA genotype was lower in the IBS group (1.0%) than that in the control group (3.4%, P  = 0.089, OR [95% CI ] = 3.345). Conclusions The variation in the ( AAT ) n repeat of the CNR1 gene conferred an increased risk for developing IBS , while rs324420 ( C 385) in the FAAH gene was not associated with IBS pathogenesis.