Recent reviews have highlighted the existence of an association between microRNAs (miRNAs) and non-alcoholic fatty liver disease (NAFLD). miRNAs have been linked to cholesterol metabolism, which is significantly dysregulated in NAFLD and leads to hepatic free cholesterol accumulation. Despite this, the link between miRNAs and cholesterol metabolism as well as their contribution to NAFLD pathophysiology in humans remains unclear.
The aim of this systematic review was to investigate the associations between 13 miRNAs, NAFLD, and cholesterol metabolism. It additionally assessed these miRNAs’ potential as biomarkers for the diagnosis of NAFLD.
Four miRNAs (miR122, 34a, 132 and 21) were highly expressed in patients with non-alcoholic steatohepatitis (NASH), the progressive form of NAFLD. All 4 miRNAs were found to increase with disease severity and their expression significantly correlated with other markers of NAFLD onset and progression (e.g., ALT, AST, and NAFLD score). However, serum miR122 in particular was found to be increased even before liver function tests detected altered ALT and AST levels, which are characteristic of liver disease. As such, these miRNAs, and specifically miR122, were found to play a role in the development and progression of NAFLD via effects on cholesterol metabolism.
Future research into miRNAs in NAFLD should confirm the validity of adding serum miRNAs (miR122, miR34a and miR379) to biomarker panels used to both diagnose and monitor NAFLD.