Hepatic miR-149-5p upregulation fosters steatosis, inflammation and fibrosis development in mice and in human liver organoids.

Background & Aims: The incidence of metabolic dysfunction-associated steatotic liver disease (MASLD) is increasing worldwide. Alterations of hepatic microRNA (miRNA) expression/activity significantly contribute to the development and progression of MASLD. Genetic polymorphisms of miR-149 are associated with an increased susceptibility to MASLD development in humans. Aberrant expression of miR-149 was also associated with metabolic alterations in several organs, but the impact of hepatic miR-149-5p deregulation in MASLD remains poorly characterized.

Methods: MiR-149-5p was downregulated in the livers of mice by transduction with hepatotropic adeno-associated virus 8 harboring short-hairpin RNAs (shRNAs) specific for miR-149-5p (shmiR149) or scrambled shRNAs (shCTL). MASLD was then induced with a methionine/choline-deficient (MCD, n = 7 per group) diet or a fructose/palmitate/cholesterol-enriched (FPC, n = 8-12 per group, per protocol) diet. The impact of miR-149-5p modulation on MASLD development was assessed and using multi-lineage 3D human liver organoids (HLOs) and Huh7 cells.

Results: MiR-149-5p expression was strongly upregulated in mouse livers from different models of MASLD (2-4-fold increase in , mice, high-fat and FPC-fed mice). downregulation of miR-149-5p led to an amelioration of diet-induced hepatic steatosis, inflammation/fibrosis, and to increased whole-body fatty acid consumption. In HLOs, miR-149-5p overexpression promoted lipid accumulation, inflammation and fibrosis. analyses of human Huh7 cells overexpressing miR-149-5p indicated that glycolysis and intracellular lipid accumulation was promoted, while mitochondrial respiration was impaired. Translatomic analyses highlighted deregulation of multiple potential miR-149-5p targets in hepatocytes involved in MASLD development.

Conclusions: MiR-149-5p upregulation contributes to MASLD development by affecting multiple metabolic/inflammatory/fibrotic pathways in hepatocytes. Our results further demonstrate that HLOs are a relevant 3D model to investigate hepatic steatosis and inflammation/fibrosis development.

Impact And Implications: Our research shows compelling evidence that miR-149-5p plays a pivotal role in the development and progression of MASLD. By employing and innovative models using multi-lineage human liver organoids, we demonstrate that miR-149-5p upregulation significantly impacts hepatocyte energy metabolism, exacerbating hepatic steatosis and inflammation/fibrosis by modulating a wide network of target genes. These findings not only shed light on the intricate miR-149-5p-dependent molecular mechanisms underlying MASLD, but also underscore the importance of human liver organoids as valuable 3D models for studying the disease's pathogenesis.