Etiology of inflammatory bowel disease: A unified hypothesis

Figure 6 Ulcerative colitis and Crohn’s disease are likely just two symptoms of the same morbidity rather than two different diseases. A: The structure of mucin; B: Mechanistic sketch of the temporal changes of ulcerative colitis (UC) and Crohn’s disease (CD) and their relationship. A reduction in gut bacteria along with the improved hygiene and increased intake of dietary chemicals like saccharin and sucralose will result in impairment in digestive proteases inactivation. The poorly inactivated proteases will work together with glycosidases from the gut bacteria to cause accelerated degradation of the mucus layer that is proposed here paralleling the risk of developing inflammatory bowel disease (IBD = UC + CD). UC and CD differ in that UC is caused by the increased infiltration of bacteria and the resultant recruitment of neutrophils and formation of crypt abscess, while CD is caused by increased infiltration of luminal antigens and particles and the resultant recruitment of macrophages and formation of granulomas. Thus the reduction in gut bacteria along with the modernization or other factors will result in a shift of predominance from the bacteria-meditated UC to antigen/particle-mediated CD. Max: maximum.