Calcitriol supports gut barriers and regulates defensin and cathelicidin (antimicrobial proteins that could modify the gut microorganisms into healthier compositions). It could protect lungs from infection, upregulate the expressions of tight junction proteins connexion 43 and E-cadherin in the gut, maintain the normal function of renal epithelial barriers, and improve the functions of corneal epithelial barriers function. Here, CDH1 is linked to infection.