Abstract Body: Atherosclerosis is a chronic inflammatory disease characterized by the buildup of lipid-rich plaques in the arteries. The interleukin 22 (IL22) cytokine is known to regulate tissue repair, antimicrobial peptide production, and the intestinal epithelial barrier. Our earlier work showed that IL22 protects from atherosclerosis by restricting pro-atherogenic microbiota and inflammatory metabolite production that in turn promote macrophage activation. To test the role of hepatocyte-specific and intestinal epithelial cell-specific IL22R signaling in atherosclerosis, we generated two novel mouse lines: Ldlr^-/-Il22ra1^f/fAlbumin^Cre (Ldlr^-/-Il22ra1^ΔHEP) and Ldlr^-/-Il22ra1^f/fVillin^Cre (Ldlr^-/-Il22ra1^ΔIEC) to ablate the IL22RA1 receptor subunit in hepatocytes and intestinal epithelial cells, respectively; and analyzed disease development after 16 weeks of Western Diet (WD) feeding. We found that WD-fed Ldlr^-/-Il22ra1^ΔHEP and Ldlr^-/-Il22ra1^ΔIEC mice exhibited larger atherosclerotic lesions compared to Il22ra1-sufficient controls when mice were separately housed. However, co-housing reduced atherosclerosis in Ldlr^-/-Il22ra1^ΔHEP mice and limited the difference in phenotype. Ldlr^-/-Il22ra1^ΔHEP mice showed downregulation of genes involved in peroxisome proliferator-activated receptor (PPAR) signaling in aortas and altered bile acid metabolism genes in livers as compared to controls. Aortas of Ldlr^-/-Il22ra1^ΔIEC mice also displayed heightened inflammatory marker expression, and colons of separately housed Ldlr^-/-Il22ra1^ΔIEC mice showed downregulation of antimicrobial peptides as determined by RNA sequencing. Shotgun intestinal microbiota sequencing revealed expansion of multiple pro-inflammatory bacteria species in cecal contents of WD-fed Ldlr^-/-Il22ra1^ΔIEC mice. In both models, we also observed alterations in bile acids, serum lipids, and metabolites in serum and cecal contents in separately housed mice while differences were diminished upon co-housing. We conclude that liver and intestinal IL22RA1 signaling is atheroprotective, acting through the regulation of microbiota and lipid metabolism.