Alterations in Lipid Metabolism Mediate Inflammation, Fibrosis, and Proliferation in a Mouse Model of Chronic Cholestatic Liver Injury

Background & Aims

The liver controls central processes of lipid and bile acid homeostasis. We aimed to investigate whether alterations in lipid metabolism contribute to the pathogenesis of chronic cholestatic liver disease in mice.

Methods

We used microarray and metabolic profiling analyses to identify alterations in systemic and hepatic lipid metabolism in mice with disruption of the gene ATP-binding cassette sub-family B member 4 (Abcb4^−/− mice), a model of inflammation-induced cholestatic liver injury, fibrosis, and cancer.

Results

Alterations in Abcb4^−/− mice, compared with wild-type mice, included deregulation of genes that control lipid synthesis, storage, and oxidation; decreased serum levels of cholesterol and phospholipids; and reduced hepatic long-chain fatty acyl-CoAs (LCA-CoA). Feeding Abcb4^−/− mice the side chain–modified bile acid 24-norursodeoxycholic acid (norUDCA) reversed their liver injury and fibrosis, increased serum levels of lipids, lowered phospholipase and triglyceride hydrolase activities, and restored hepatic LCA-CoA and triglyceride levels. Additional genetic and nutritional studies indicated that lipid metabolism contributed to chronic cholestatic liver injury; crossing peroxisome proliferator-activated receptor (PPAR)-α–deficient mice with Abcb4^−/− mice (to create double knockouts) or placing Abcb4^−/− mice on a high-fat diet protected against liver injury, with features similar to those involved in the response to norUDCA. Placing pregnant Abcb4^−/− mice on high-fat diets prevented liver injury in their offspring. However, fenofibrate, an activator of PPARα, aggravated liver injury in Abcb4^−/− mice.

Conclusions

Alterations in lipid metabolism contribute to the pathogenesis and progression of cholestatic liver disease in mice.

Keywords:  Cholestasis , Canalicular Phospholipid Flippase , Hepatocellular Cancer , PSC

Abbreviations used in this paper:  AP, alkaline phosphatase, BA, bile acid, C/EBPα, CCAAT/enhancer binding protein α, CH, cholesterol, DAG, diacylglycerol, DKO, double knockout, FA, fatty acid, FFA, free fatty acid, HDL, high-density lipoprotein, HFD, high-fat diet, LCA-CoA, long-chain acyl-CoA ester, norUDCA, 24-norursodeoxycholic acid, PL, phospholipid, PPAR, peroxisome proliferator-activated receptor, TG, triglyceride, WT, wild-type