The Role And Mechanism Of Chlorogenic Acid In Nonalcoholic Fatty Liver Disease

The first part:Chlorogenic acid protects against hepatocellular lipid accumulation in HepG2 cellsAims:Non-alcoholic fatty liver disease(NAFLD)has become one of the most prevalent,chronic liver diseases worldwide.Previous studies have revealed various biological properties of chlorogenic acid(CGA),an important polyphenol component of coffee,including hypoglycemic and hypolipidemic effects.This study aimed to investigate the possible mechanisms underlying the effects of CGA on the development of NAFLD in HepG2 cells.Methods and Materials:To establish a cellular model of hepatic steatosis,HepG2 cells were exposed to free fatty acids(FFA)for 48 hours.For evaluating the effect of CGA on development of hepatic steatosis,HepG2 cells were exposed to multi-doses and multi-times of CGA.Western blot and quantitative Real-time RT-PCR(qRT-PCR)were used to evaluate the protein expression and mRNA levels.Furthermore,small interfering RNA(siRNA)or inhibitors were used to inhibit the expression of Sirtuin 1(SIRT1),AMP-activated protein kinase(AMPK),Liver kinase B1(LKB1)and Calcium/calmodulin-dependent protein kinase kinase 2 beta(CaMKKP).In addition,we used triglyceride detection and Oil Red O to evaluate the role of CGA in hepatic fat accumulation.Results:The present study shows that CGA(50?M 24h)protected against hepatocellular lipid accumulation in HepG2 cells.The lipogenesis-lowering effect of CGA was abolished by pharmacological inhibitions or genetic knockdowns of SIRT1,AMPK or LKB1.However,the activation of SIRT1-AMPK pathway by CGA is not affected by pharmacological inhibition of CaMKK?.Furthermore,the administration of CGA increased fatty acid oxidation and decreased fatty acid synthesis.Conclusions:In conclusion,the present study establishes a protective role of CGA in hepatocyte lipid metabolism,via a molecular cross-talk between SIRT1 and LKB1/AMPK signaling.The second part:Chlorogenic acid protects against hepatocellular lipid accumulation in miceAims:Given the findings of the first part(in vitro),this study aimed to investigate the possible mechanisms underlying the effects of CGA on the development of NAFLD in mice.Methods and Materials:For evaluating the effect of CGA on development of hepatic steatosis,five-six week-old mice were randomly divided into four groups,feeding standard chow,standard chow + CGA,high fat diet(HFD),or HFD + CGA for 8 weeks,respectively.Western blot and qRT-PCR were used to evaluate the protein expression and mRNA levels.In addition,we used triglyceride detection and Oil Red O to analyze the role of CGA in hepatic fat accumulation.Results:The present study shows that CGA protected against HFD-induced hepatocellular lipid accumulation in mice.It increased the protein level of SIRT1,which consequently leads to the activation of AMPK pathway.In mouse liver in vivo,CGA enhanced fatty acid oxidation and countered accumulated lipids caused by HFD.Conclusions:Our findings have potential implications in CGA protecting against hepatocellular lipid accumulation associated with NAFLD and metabolic disorders.