The goal of the present study was to determine whether loss of the insulin receptor alters the molecular landscape of the intestinal mucosa, using intestinal-epithelial insulin receptor knockout (IE-irKO) mice and both genetic (IRfl/fl and Villin-cre) controls. Quantitative proteomic analysis by liquid chromatography mass spectrometry was applied to jejunal and colonic mucosa from mice fed a normal chow diet and mice fed a Western diet (WD). Jejunal mucosa from IE-irKO mice demonstrated alterations in all intestinal cell lineages: Paneth, goblet, absorptive, and enteroendocrine cells. Only goblet and absorptive cells were affected in the colon. Also, a marked effect of WD consumption was found on the gut proteome. A substantial reduction was detected in Paneth cell proteins with antimicrobial activity, including lysozyme C-1, angiogenin-4, cryptdin-related sequence 1C-3 and -2, α-defensin 17, and intelectin-1a. The key protein expressed by goblet cells, mucin-2, was also reduced in the IE-irKO mice. Proteins involved in lipid metabolism, including aldose reductase-related protein 1, 15-hydroxyprostaglandin dehydrogenase, apolipoprotein A-II, and pyruvate dehydrogenase kinase isozyme 4, were increased in the mucosa of WD-fed IE-irKO mice compared with controls. In contrast, expression of the nutrient-responsive gut hormones, glucose-dependent insulinotropic polypeptide and neurotensin, was reduced in the jejunal mucosa of IE-irKO mice, and the expression of proteins of the P-type adenosine triphosphatases and the solute carrier-transporter family was reduced in the colon of WD-fed IE-irKO mice. In conclusion, IE-irKO mice display a distinct molecular phenotype, suggesting a biological role of insulin and its receptor in determining differentiated cell specificity in the intestinal epithelium.
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