Replication of interleukin 23 receptor and autophagy-related 16-like 1 association in adult-and pediatric-onset inflammatory bowel disease in Italy

AIM: To investigate gene variants in a large Italian inflammatory bowel disease (IBD) cohort, and to analyze the correlation of sub-phenotypes (including age at diagnosis) and epistatic interaction with other IBD genes. METHODS: Total of 763 patients with Crohn's disease (CD, 189 diagnosed at age < 19 years), 843 with ulcerative colitis (UC, 179 diagnosed <19 years), 749 healthy controls, and 546 healthy parents (273 trios) were included in the study. The rs2241880 [autophagy-related 16-like 1 (ATG16L1)], rs11209026 and rs7517847 [interleukin 23 receptor (IL23R)], rs2066844, rs2066845, rs2066847 (CARD15), rs1050152 (OCTN1), and rs2631367 (OCTN2) gene variants were genotyped. RESULTS: The frequency of G allele of ATG16L1 SNP (Ala197Thr) was increased in patients with CD compared with controls (59% vs 54% respectively) (OR = 1.25, CI = 1.08-1.45, P = 0.003), but not in UC (55%). The frequency of A and G (minor) alleles of Arg381Gln, rs11209026 and rs7517847 variants of IL23R were reduced significantly in CD (4%, OR = 0.62, CI = 0.45-0.87, P = 0.005; 28%, OR = 0.64, CI = 0.55-0.75, P < 0.01), compared with controls (6% and 38%, respectively). The A allele (but not G) was also reduced signifi cantly in UC (4%, OR = 0.69, CI = 0.5-0.94, P = 0.019). No association was demonstrated with sub-phenotypes and interaction with CARD15 , and OCTN1/2 genes, although both gene variants were associated with pediatric-onset disease. CONCLUSION: The present study confirms the association of IL23R polymorphisms with IBD, and ATG16L1 with CD, in both adult- and pediatric-onset subsets in our study population.

Etiology of inflammatory bowel disease:A unified hypothesis

Inflammatory bowel disease(IBD),including both ulcerative colitis(UC) and Crohn's disease(CD),emerged and dramatically increased for about a century.Despite extensive research,its cause remains regarded as unknown.About a decade ago,a series of findings made me suspect that saccharin may be a key causative factor for IBD,through its inhibition on gut bacteria and the resultant impaired inactivation of digestive proteases and over digestion of the mucus layer and gut barrier(the Bacteria-Protease-Mucus-Barrier hypothesis).It explained many puzzles in IBD such as its emergence and temporal changes in last century.Recently I further found evidence suggesting sucralose may be also linked to IBD through a similar mechanism as saccharin and have contributed to the recent worldwide increase of IBD.This new hypothesis suggests that UC and CD are just two symptoms of the same morbidity,rather than two different diseases.They are both caused by a weakening in gut barrier and only differ in that UC is mainly due to increased infiltration of gut bacteria and the resultant recruitment of neutrophils and formation of crypt abscess,while CD is mainly due to increased infiltration of antigens and particles from gut lumen and the resultant recruitment of macrophages and formation of granulomas.It explained the delayed appearance but accelerated increase of CD over UC and many other phenomena.This paper aims to provide a detailed description of a unified hypothesis regardingthe etiology of IBD,including the cause and mechanism of IBD,as well as the relationship between UC and CD.