MARC1 downregulation reduces hepatocyte lipid content by increasing beta-oxidation.

Abstract

Background: Metabolic dysfunction-associated steatotic liver disease (MASLD) is a global epidemic. MASLD has a strong genetic component, and a common missense variant (rs2642438) in the mitochondrial amidoxime-reducing component 1 (MARC1) gene confers protection against its onset and severity. However, there are contrasting results regarding the mechanisms entangling this protection.

Methods: We downregulated MARC1 in primary human hepatocytes (PHH) using short interfering RNA (siRNA). Neutral lipid content was measured by Oil-Red O staining and fatty acid oxidation measured using radiolabeled tracers. RNA-seq and proteomic analysis using LC-MS were also performed. Additionally, we analyzed data from 239,075 participants from the UK Biobank.

Results: Downregulation of MARC1 reduced neutral lipid content in PHH homozygous for the wild type (p.A165, risk) but not for the mutant (p.T165, protective) protein. Experimental results demonstrated that this reduction was mediated by an increased fatty acid utilization by beta-oxidation. Consistently, 3-hydroxybutyrate levels, a by-product of β-oxidation, were higher in carriers of the rs2642438 minor allele from the UK Biobank indicating higher β-oxidation in these individuals. Moreover, downregulation of MARC1 p.A165 variant resulted in a more favorable phenotype by reducing ferroptosis and reactive oxygen species levels.

Conclusions: MARC1 downregulation in carriers of the risk allele results in lower hepatocyte neutral lipids content due to higher β-oxidation, and upregulates beneficial pathways for cell survival.