Parenteral nutrition results in peripheral ileal to hepatic circadian discordance in mice

Abstract

Background: We have developed a mouse model of Parenteral Nutrition Associated Liver Disease in which PN infusion results in cholestatic liver injury. In the liver, the master circadian genes Arntl/Bmal drive rhythmic gene expression and regulate circadian expression of hepatic functions including bile acid synthesis. The aim of this study was to examine the effect of continuous PN on ileal and hepatic expression of circadian regulatory (CR) genes, FXR signaling and bile acid synthesis in mice. Methods: WT mice were exposed to continuous soy oil lipid emulsion-based PN infusion through a central venous catheter for 4 days (PN). Water was provided ad libitum, but no nutrients were provided enterally. On d4, mice were sacrificed every 6 hours (7AM, 1PM, 7PM and 1AM), and ileal, hepatic tissue and serum harvested. From tissue samples, the relative expression of circadian transcription factors and FXR signaling was assessed. Results: Administration of 4d PN increased hepatic injury, inflammatory cytokine expression and gut permeability. In the ileum, PN activated FXR and induced expression of Fgf15 and Nr0b2. In the liver, expression of FXR-downstream targets was dysregulated. PN administrations impacted hepatic and ileal circadian transcription factor mRNA expression which was discordant between the two organs. Conclusions: Dysregulation of circadian regulatory machinery is in part due to discordance of the gut-liver axis during PN. Pharmacologic targeting of CR as a therapeutic strategy for PNALD thus deserves further investigation.