MicroRNA-148a Deficiency Promotes Hepatic Lipid Metabolism And Hepatocarcinogenesis In Mice

Hepatic Cellularcarcinoma(HCC)presented serious threaten to health of Chinese local residents,and its patients increased with population growth and social aging.MicroRNAs(miRNAs,miRs)were involved in many physiologic and disease processes including HCC by virtue of degrading specific target mRNAs or inhibiting their translation.Previous study of our group proved that microRNA-148a(miR-148a),a target of c-Myc which is a vital transcription factor in the progression of HCC,could inhibit the growth of HCC cell lines.To better understand the mechanism of miR-148 a inhibiting HCC,here we constructed miR-148 a knock out(KO)mice,used in vitro or in vivo gene expressionand silencing-based approaches,studied the role of miR-148 a in liver physiology such as liver injury and repairment and HCC,also studied the role of miR-148 a in cholesterol and triglyceride homeostasis,further explored the regulatory mechanisms and networks of miR-148 a using transcriptome sequencing technology.Our study presented that miR-148 a was an evolutionarily conserved miRNA with high expression in liver of mice.Downregulation of miR-148 a was found in HCC samples compared with paired normal hepatic tissues,and correlated with poor clinical outcomes in HCC patients.At the cellular level,miR-148 a inhibited tumor growth of orthotopic liver cancer and lung colonization of HCC cells.Our study successfully constructed miR-148 a KO mice using traditional homologous recombination technology,and found that miR-148 a deletion significantly accelerated N-Nitrosodiethylamine-(DEN-)induced hepatocarcinogenesis in mice under regular chow diet(RCD)or high fat diet(HFD),and restoration of miR-148 a reversed these effects.Mechanistically,we found that miR-148 a deficiency upregulated expression of most genes involved in lipogenesis and fatty acid uptake,and then significantly promoted lipid accumulation and hepatic steatosis in mice.miR-148 a deletion upregulated expression of most cholesterol biosynthetic related genes,and increased cholesterol synthesis in mice liver and total cholesterol(TC)levels in serum and liver.We also found that miR-148 a deficiency increased damage of liver by external toxins and reduced repairment ability.Through combination with transcriptome sequencing and bioinfomatic prediction and followed experiments,miR-148 a was found to directly target and inhibit expression of genes involved in lipid metabolism such as PGC1?,SIRT7,HMGCR and genes involved in liver injury regulation such as YBX1,and thus inhibited hepatocarcinogenesis of mice.Taken together,here we revealed crucial roles of miR-148 a in the hepatic lipid metabolism and hepatocarcinogenesis.These findings contributed to uncover the exhaustive molecular mechanisms of miR-148a's function as a tumor suppressor of HCC.They further identified miR-148 a as a potential therapeutic target for HCC.