The Function And Mechanisms Of Milk Fat Globule-EGF Factor 8(MFGE8) In Nonalcoholic Fatty Liver Disease

Background and Aims: With the change of life style,nonalcoholic fatty liver disease(NAFLD)has gradually developed into the largest chronic liver disease in the world.NAFLD has been recognized as a major couse of advanced liver diseases,metabolic disorder and cardiovascular diseases due to its extensive pathogenesis involving systemic dyslipidemia,inflammation,oxidative stress and other complex regulatory mechanisms.However,there is no effectively pharmacological intervention for NAFLD therapy in clinic.Milk Fat Globule-EGF Factor 8 Protein(MFGE8)is a membrane related glycoprotein,which has been found to play an important role in immune and inflammatory response,organ homeostasis,tissue repair and remodeling.The purpose of this study is to explore whether MFGE8 plays a regulatory role in the NAFLD process and the underlying regulatory mechanism.Methods: We constructed Mfge8 hepatocyte-specific knockout mice and established NAFLD model by high fat diet,high fat/ high cholesterol diet and ob/ob.By measuring body weight and liver weight,detecting blood glucose and insulin level,and performing pathological staining and q PCR assay,we analyzed the function of MFGE8 in mice.Smilarly,through Oil Red O staining and q PCR assay,we analyzed the function of MFGE8 in Mfge8 knockout of primary hepatocytes,which stimulated by PA to induce lipid accumulation.In addition,western blot,immunofluorescence,immunocoprecipitation and other molecular biological techniques were used to explore the specific regulatory targets and involved signal transduction pathways of MFGE8 in hepatocytes.Results: The protein expression of hepatocyte MFGE8 was significantly downregulted in fatty livers of mice.Compared with the control group,PA induced Mfge8 knockout hepatocytes significantly increased lipid accumulation and inflammation.Hepatocyte-specific Mfge8 knockout mice significantly increased diet-induced liver lipid accumulation and inflammation compared to the Flox controls.By transcriptome analysis,it was found that MFGE8 mainly regulated the inflammatory signaling pathway.Mechanistically,MFGE8 negatively regulated the ASK1-JNK/P38 signaling pathway.In hepatocytes,MFGE8 directly interacted with ASK1 to inhibit ASK1 dimerization and phosphorylation,leading to suppressed JNK/p38 MAPK signaling pathway.Conclusion: MFGE8 functions as a negative regulator of NAFLD process by inhibiting ASK1 dimerization and the downstream JNK/p38 inflammatory signaling pathway,providing theoretical basis for further understanding of disease occurrence process and subsequent clinical drug development at the cellular and molecular level.