Interleukin 10 genotypes in irritable bowel syndrome: evidence for an inflammatory component?

BACKGROUND AND AIMS Inflammation may play a role in the pathogenesis of irritable bowel syndrome in some individuals, such as in those who develop symptoms following a dysenteric illness. Persisting inflammation, resulting from an imbalance of cytokines regulating the inflammatory response, is one possible mechanism. As the elaboration of cytokines is under genetic control, this study was designed to establish whether there might be a genetic predisposition to an altered pattern of anti-inflammatory cytokine production in patients with irritable bowel syndrome. SUBJECTS A total of 230 unselected patients with irritable bowel syndrome and 450 healthy, ethnically matched controls were studied. METHODS DNA was extracted from peripheral blood leucocytes of subjects. Allele and genotype frequencies were determined for the anti-inflammatory cytokine interleukin 10 at the site (-1082) concerned with production in lymphocytes. Transforming growth factor beta(1) (codons 10 and 25) genotypes were also examined in a smaller group of subjects. RESULTS Patients with irritable bowel syndrome had significantly reduced frequencies of the high producer genotype for interleukin 10 than controls (21% v 32%; p=0.003). There was no apparent relationship with any particular bowel habit subtype. Genotypes for transforming growth factor beta(1) were not altered. CONCLUSIONS These preliminary results suggest that at least some patients with irritable bowel syndrome may be genetically predisposed to produce lower amounts of the anti-inflammatory cytokine interleukin 10. This lends some support to the hypothesis that there may be an inflammatory or genetic component in some cases of this condition and that further studies in specific irritable bowel syndrome subgroups are justified.