MUC5AC and colitis: Mucin Muc2 is the major glycoprotein in the colonic mucus, and MUC2 deficiency can lead to impaired epithelial barrier function, intestinal flora imbalance, and spontaneous colitis, and studies have demonstrated that the probiotic mixture VSL#3 reduces colonic inflammation and improves intestinal barrier function in Muc2 mucin deficient mice [49].