Non-Alcoholic Steatohepatitis: From Pathophysiology to Novel Therapies

Non-alcoholic fatty liver (NAFL) disease is defined by an accumulation of liver fat exceeding 5% of its weight in the absence of significant alcoholic intake. In 5-20%, there is a progression from NAFL to non-alcoholic steatohepatitis (NASH). Until now, it is not well understood why only some patients develop NASH, and currently, no drugs are licensed for this indication. Different T-cell populations such as T-regulatory, Th1 and Th17 cells play a central role in the immunopathogenesis of fatty liver disease and open the option of future interleukin (IL)-17-based therapeutics. The inflammatory process underlying NASH is furthermore characterized by elevated expression of pro-inflammatory cytokines such as TNFα and IL-1β. Anakinra, a recombinant version of IL-1Ra shows promising metabolic effects with improved hyperglycemia and beta-cell secretory function in a double-blind placebo controlled randomized trial in type 2 diabetic patients but such studies are still in their preliminary stages for NASH. Several studies point out that bile acid farnesoid X receptor (FXR)-mediated signals (such as the enterohepatic hormone fibroblast growth factor 15/19) are involved in the regulation of triglyceride and glucose metabolism. Recent clinical trials have revealed a beneficial impact of the FXR agonist obeticholic acid on body weight, insulin sensitivity and liver histology in patients with NASH. Further potential novel therapeutic targets in NASH are currently in phase II clinical development.