Secondary bile acids in portal blood contribute to liver regeneration in a rat model of partial hepatectomy

Gut metabolites via the portal vein affect several liver functions, including regeneration. Here, we investigated gut microbiota-derived metabolites in portal and peripheral serum during liver regeneration. We developed rat models of 70% partial hepatectomy (PHx) with and without prior gut microbiota modulation by three-week antibiotic (Abx) treatment. Sham without Abx were used as controls and compared to sham with Abx. Liver regeneration at day 2 following PHx was assessed by expression of proliferating cell nuclear antigen (PCNA) protein in liver tissues and cyclin genes in primary hepatocytes. High pressure liquid chromatography-mass spectrometry (HPLC-MS) based portal and peripheral venous serum metabolomics was performed to identify differentially altered metabolites (DAMs). Compared to controls, rat livers at day 2 post-PHx showed significant upregulation in the average number of PCNA-positive cells, which positively correlated with the expression of cell cycle genes in hepatocytes. In Abx-treated PHx, we observed reduced PCNA-positivity and downregulation in gene expression of various cyclins in hepatocytes compared to PHx. We identified 224 DAMs between controls vs PHx and 189 DAMs between Abx-treated PHx vs PHx in portal serum. Many common DAMs showed opposite expression trends in PHx vs controls and then Abx+PHx vs PHx in portal serum, such as sphingosine-1-phosphate and deoxycholic acid. In vitro studies with deoxycholic acid demonstrated that it enhanced the viability and proliferation of primary hepatocytes and hepatocyte organoids. The study underscores the critical role of deoxycholic acid in portal blood in enhancing hepatocyte proliferation and subsequently, liver regeneration.