Tauroursodeoxycholic Acid Attenuates Progression of Steatohepatitis in Mice Fed a Methionine-Choline-Deficient Diet

Endoplasmic reticulum (ER) stress has been implicated in the development of nonalcoholic steatohepatitis. A methionine-choline-deficient (MCD) diet induces robust ER stress response and steatohepatitis, but the effects of ER stress modulation on the course of steatohepatitis remain uncertain. The present study evaluated whether reducing ER stress using the chemical chaperone tauroursodeoxycholic acid (TUDCA) could limit hepatocyte lipoapoptosis and progression of MCD diet-induced steatohepatitis. HuH7 cells stably transfected with sodium taurocholate cotransporting polypeptide (HuH-Ntcp cells) and palmitate (PA) were used. Experimental steatohepatitis was induced in male C57BL/6 mice using an MCD diet, and three different doses of TUDCA (500, or 1,000 mg/kg, once daily; or 500 mg/kg twice daily) were administered by gavage from the start of the MCD diet regimen or after 4 weeks. TUDCA reduced PA-induced ER stress as manifested by decreased eIF2 alpha phosphorylation, XBP1 splicing and expression of BiP, ATF4, and CHOP in HuH-Ntcp cells. TUDCA also decreased PA-induced JNK phosphorylation, Puma up-regulation and Bax activation, which in turn suppressed caspase-dependent hepatocyte lipoapoptosis. Mice given TUDCA did not show a significant decrease in the intrahepatic triglyceride contents and steatosis. However, TUDCA treatment significantly reduced hepatic damage compared to controls for both early and late treatment groups. TUDCA treatment reduced the expression of ER stress markers and pro-apoptotic proteins, leading to decreased apoptosis and oxidative stress. Finally, TUDCA reduced histological fibrosis along with the down-regulation of pro-fibrotic gene expression in both early and late treatment groups. These results show that TUDCA attenuates the progression of MCD diet-induced steatohepatitis by reducing ER stress.