Ileal antimicrobial peptide expression is dysregulated in old age.

In an effort to understand the mechanisms underlying the high prevalence of gastrointestinal tract disorders in old age, we investigated the expression of intestinal antimicrobial peptides in the terminal small intestine of aged mice. Our results show that old mice have reduced transcript levels of ileal α-defensins and lysozyme, two important types of intestinal antimicrobial peptides produced by Paneth cells. In contrast, expression of the C-type lectins Reg3b and Reg3g, as well as β-defensin 1, angiogenin 4 and Relmb, which are made by several epithelial cell types, was significantly upregulated in aged animals suggesting an ongoing response to epithelial distress. Those changes in antimicrobial peptide gene expression associated with histological damage of the ileal epithelium and subtle modifications in the composition of the commensal microbiota. Our findings suggest that dysregulation of antimicrobial peptides expression is a feature of homeostasis disruption in the aged intestine and may contribute to geriatric gastrointestinal dysfunction.