Mechanisms Of DEAD-Box Helicase 17 (DDX17) In The Development Of Nonalcoholic Fatty Liver Disease

Objective: Nonalcoholic fatty liver disease(NAFLD)is the most common chronic liver disease;however,at present,there is still a short of effective treatments.This study aims to explore the underlying mechanism of DEAD-Box Helicase 17(DDX17)in the occurrence and development of NAFLD,in order to explore new potential therapeutic targets.Methods: In this study,liver samples from clinical NAFLD patients were collected and NASH models were constructed using high fat diet(HFD)and methionine and choline deficiency diet(MCD),respectively.m RNA and protein levels of DDX17 were detected in the above liver samples.Subsequently,L02 knockdown and overexpressing DDX17 cell lines were established to verify the role of DDX17 in the induction of palmitic acid and oleic acid(PAOA)in liver lipid deposition.We established hepatocyte-specific DDX17 deficient mice in order to explore the effects of DDX17 on NASH induced by a HFD as well as MCD in adult male mice.In terms of molecular mechanism exploration,RNA-seq and lipidomic analyses were performed to explore the effects of DDX17 on hepatic lipid accumulation,inflammatory activation and fibrosis in the development of NASH.Meanwhile,the key genes and specific mechanisms of DDX17 in NASH progression were explored in combination with CUT-tag sequencing,chromatin immunoprecipitation(Ch IP)and dual luciferase reporter assays.Finally,14,15-Epoxyeicosatrienoic acids(14,15-EETs),a metabolite of cyp2c29,and its antagonists were applied to confirm that cyp2c29 is a key target of DDX17 in the regulation of lipid metabolism and M1-type macrophage activation.Finally,the correlation of DDX17 and cyp2c29 with hepatic steatosis and M1-type macrophages activation was verified in NAFLD samples.Results: In this study,we found that DDX17 was markedly increased in the livers of NASH patients and mice after HFD or MCD administration.After introducing lentiviruses into hepatocyte L02 for DDX17 knockdown or overexpression,we found that lipid accumulation induced by palmitic acid/oleic acid(PAOA)in L02 cells,were noticeably weakened by DDX17 knockdown but augmented by DDX17 overexpression.Furthermore,hepatocytespecific DDX17 knockout significantly alleviated hepatic steatosis,inflammatory response,and fibrosis in mice after the administration of MCD and HFD.Mechanistically,our analysis of RNA-seq indicated that DDX17 regulated these pathways,which are related to lipid metabolism,inflammatory activation,and fibrosis formation in NASH progression,and further focused on the CYP450 family genes involved in lipid metabolism.Meanwhile,cyp2c29 was identified as a key downstream gene of DDX17 in the CUT-tag sequencing analysis.Furthermore,Ch IP and dual luciferase reporter assays indicated that DDX17 transcriptionally represses cyp2c29 gene expression by cooperating with CCCTC binding factor(CTCF)and DEAD-Box Helicase 5(DDX5).Using absolute quantitative lipidomics analysis,we identified a hepatocyte-specific DDX17 deficiency that decreased lipid accumulation and altered lipid composition in the livers of mice after MCD administration.Finally,14,15-EETs,a metabolite of cyp2c29,and its antagonists were used to confirm that cyp2c29 can mediate DDX17 regulation of hepatocyte lipid metabolism and activation of M1-type macrophages.Finally,in the NAFLD samples,DDX17 was positively correlated with hepatic steatosis and M1-type macrophage activation,while cyp2c29 was negatively correlated with hepatic steatosis and M1-type macrophage activation.Conclusion: These results suggest that DDX17 plays a role in NASH development by promoting lipid accumulation in hepatocytes and inducing the activation of M1 macrophages and subsequent inflammatory responses and fibrosis trough the transcriptional repression of cyp2c29 in mice.Therefore,DDX17/cyp2c29/14,15-EETs axis could be a promising therapeutic target for NASH management.This study further explored the pathogenesis of DDX17 in the regulation of NAFLD,and provided theoretical support for drug development in the treatment of NAFLD and related chronic liver diseases.