Breaking the synergism of iron overload and miR-122 to rescue lipid accumulation and peroxidation in MASLD

MASLD is a multifactorial disease with specific subtypes being featured by hepatic iron overload and loss of miR-122, a liver-specific microRNA regulating hepatic lipid homeostasis. Previously we reported the mechanism of iron overload decreasing miR-122. Interestingly, we found that mice lacking miR-122 were highly sensitive to iron overload-induced steatosis and fibrosis. The present study aimed to disclose the downstream mechanisms and the preventive measures targeting miR-122. We first validated the decreases in iron-related genes and miR-122 in MASLD. By using LC-MS/MS and gas-chromatography, we found that the combination of miR-122 knockout and iron overload significantly increased the production and peroxidation of polyunsaturated fatty acids (PUFAs). However, miR-122 knockout itself only incurred lipid accumulation, suggesting a synergistic effect of miR-122 knockout and iron overload in lipid peroxidation. We then located the key enzymes involved in PUFA production and peroxidation by the transcriptome and proteome analysis. Mechanistically, miR-122 and iron regulated fatty acid synthesis through Aacs, fatty acid desaturation through Fads2, and PUFAs oxidation through CYPs. Re-supplementation of miR-122 by recombinant adeno-associated virus or agomir effectively broke the synergism of miR-122 knockout and iron overload in vivo. We further designed a miR-122 expression reporter cell model for high-throughput screening on 2543 natural compounds, and eventually found and validated that the dihydroberberine could upregulate miR-122 expression and correct iron overload-induced lipid disorders. These results identified the synergistic role of miR-122 and iron in PUFAs production and peroxidation, and also proposed the potential application of dihydroberberine as a preventive and therapeutic candidate for MASLD.