Therapeutic opportunities for alcoholic steatohepatitis and nonalcoholic steatohepatitis: exploiting similarities and differences in pathogenesis

Alcoholic steatohepatitis (ASH) and nonalcoholic steatohepatitis (NASH) are among the most frequent causes of chronic liver disease in the United States. Although the two entities are triggered by different etiologies - chronic alcohol consumption (ASH) and obesity-associated lipotoxicity (NASH) - they share overlapping histological and clinical features owing to common pathogenic mechanisms. These pathogenic processes include altered hepatocyte lipid metabolism, organelle dysfunction (i.e., ER stress), hepatocyte apoptosis, innate immune system activation, and hepatic stellate cell activation. Nonetheless, there are several disease-specific molecular signaling pathways, such as differential pathway activation downstream of TLR4 (MyD88-dependence in NASH versus MyD88-independence in ASH), inflammasome activation and IL-1 beta signaling in ASH, insulin resistance and lipotoxicity in NASH, and dysregulation of different microRNAs, which clearly highlight that ASH and NASH are two distinct biological entities. Both pathogenic similarities and differences have therapeutic implications. In this Review, we discuss these pathogenic mechanisms and their therapeutic implications for each disease, focusing on both shared and distinct targets.