Parathyroid hormone-related protein aggravates nonalcoholic fatty liver disease induced by methionine choline-deficient diet in mice

Abstract

To study the effect of parathyroid hormone-related protein (PTHrP) on nonalcoholic fatty liver disease (NAFLD) induced by methionine choline-deficient diet (MCD) in mice. Twelve male C57BL/6J mice were randomized into blank control group, vehicle group and PTHrP group (n=4). The mice in vehicle group and PTHrP group received injections of a control adeno-associated virus (AAV) vector and an AVV vector carrying PTHrP (AAV-PTHrP) gene, respectively, followed one week later by MCD feeding for 3 weeks; the mice in the blank control were fed a normal diet for 4 weeks. Body weight changes of the mice were monitored during the experiment. At the end of the experiment, liver tissues were harvested from the mice for histological analysis using HE staining, oil red O staining, and Sirius red staining. The levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), triglyceride, and free fatty acids (FFAs) in the liver and serum were detected to assess hepatic impairment and lipid metabolism of the mice. Cell models of NAFLD were established in mouse and human normal liver cells by treatment with 250 μmol/L FFAs for 24 h, and the effect of AAV-PTHrP on lipid deposition and viability of the cells were tested using Oil Red O and Nile red staining and CCK8 assay. Treatment with AAV-PTHrP, as compared with the control AVV vector, caused more rapid reduction of body weight in mice with MCD feeding and significantly increased the levels of AST (P < 0.05), ALT (P < 0.05), triglyceride (P < 0.01) and FFA (P < 0.05) in the liver and the scores of NAS (P < 0.01) and SAF (P < 0.05). HE and Oil red O staining of the liver tissue revealed obvious lipid deposition after MCD feeding, which was more serious in PTHrP group. In the cell experiment, FFAs induced steatosis in both mouse and human hepatocytes, and treatment with PTHrP increased the accumulation of lipid droplets and lowered the viability of the cell model of NAFLD (P < 0.01 or 0.05). PTHrP may aggravate MCD-induced NAFLD in mice by promoting the deposition of lipid droplets in the hepatocytes.