Alpha-2-adrenergic receptor gene polymorphism in Turkish population with irritable bowel syndrome

Irritable bowel syndrome is a multifactorial functional gastrointestinal disorder affecting more than 10% of world population. Genetic component in pathophysiology of irritable bowel syndrome is still unknown. The aim of this study was to examine the potential impact of C-1291G polymorphism in α2-adrenergic receptor gene promoter region in the etiology of the disease.

This prospective case-control study included 100 irritable bowel syndrome patients and 100 healthy controls adjusted for sex and age. The subjects were genotyped by using polymerase chain reaction amplification of the promoterregion of α2-adrenergic receptor gene. Allele and genotype frequencies were compared in patient and control groups. The study was approved by the University ethics committee.

The frequency of C allele was 72% and 75%, G allele was 28% and 25% in patient and control groups, respectively (p>0.05). We found that the frequencies of C1291C, C1291G, and G1291G genotypes were 50, 44, and 6%, respectively, in the patient group and 51, 48, and 1%, respectively, in the control group (p>0.05). The subgroup analysis of patients revealed that 70 patients were constipation-predominant, 27 patients were alternating diarrhea and constipation, and 3 patients were diarrhea-predominant irritable bowel syndrome.

No significant association was observed between α2-adrenergic receptor gene C-1291G polymorphism and irritable bowel syndrome in Turkish population. The high number of constipation predominant irritable bowel syndrome and very low number of diarrhea predominant irritable bowel syndrome patients might be the reason for statistical non-significance since α2-adrenergic receptor gene is found to be responsible for mediating intestinal antisecretory action and probably is involved in the pathogenesis of diarrhea predominant irritable bowel syndrome. Further investigations are needed.