MCJ (also called DnaJC1), located in the mitochondrial inner membrane, was identified as a co-chaperone to inhibit the functions of electron transfer chain (ETC) complex I.364As the ETC serves as the outlet for products of FA β-oxidation, an excessive amount of MCJ may contribute to NAFLD development via abnormally increased FA accumulation.52 Here, DNAJC15 is linked to metabolic dysfunction-associated steatotic liver disease.