Nitro-fatty acids protect against steatosis and fibrosis during development of nonalcoholic fatty liver disease in mice.

Abstract

Nonalcoholic fatty liver disease (NAFLD) and resulting nonalcoholic steatohepatitis (NASH) are reaching global epidemic proportions. Lack of non-invasive diagnostic tools and effective therapies constitute two of the major hurdles for a bona fide treatment and a reversal of NASH progression and/or regression of the disease. Nitro-oleic acid (OA-NO₂) has been proven effective in multiple experimental models of inflammation and fibrosis. Thus, the potential benefit of in vivo administration of OA-NO₂ to treat advanced NAFLD was tested herein in a model of long-term NASH diet-induced liver damage. Non-invasive imaging (e.g. photoacustic-ultrasound (PA-US)) was pursued to establish advanced experimental model of NASH in mice in which both steatosis and fibrosis were diagnosed prior experimental therapy with OA-NO₂. Experimental controls included equimolar amounts of the non-nitrated oleic acid (OA). CLAMS and NMR-based analysis was used for energy metabolism. CLAMS and NMR-based analysis demonstrates that OA-NO₂ improves body composition and energy metabolism and inhibits hepatic triglyceride (TG) accumulation. Photoacoustic-ultrasound imaging revealed a robust inhibition of liver steatosis and fibrosis by OA-NO₂. RNA-sequencing analysis uncovered inflammation and fibrosis as major pathways suppressed by OA-NO₂ administration, as well as regulation of lipogenesis and lipolysis pathways, with a robust inhibition of SREBP1 proteolytic activation and subsequent lipogenesis gene expression by OA-NO₂. These results were further supported by histological analysis and quantification of lipid accumulation, lobular inflammation (F4/80 staining) and fibrosis (collagen deposition, αSMA staining) as well as established parameters of liver damage (ALT). In vitro studies indicate that OA-NO₂ inhibits TG biosynthesis and accumulation in hepatocytes and inhibits fibrogenesis in human stellate cells. OA-NO₂ improve steatohepatitis and fibrosis and may constitute an effective therapeutic approach against advanced NAFLD that warrants further clinical evaluation.