Cichoric Acid Prevents Free Fatty Acids Induced Lipid Metabolism Disorders Via Regulating Bmal1 In Hepg2 Cells

With the variation of the modern life style,non-alcoholic fatty liver disease(NAFLD)has become the most common chronic liver disease,and its pathogenesis,prevention and treatment have become a major public health problem in the whole world.Recent research found that there was a intimate relationship between rhythm disorder and metabolic imbalance,and circadian clock was involved in regulating behavior and many physiological functions.Cichoric acid(CA),a polyphenol component from Echinacea purpurea,exhibits preventive effects on liver lipid metabolism disorders in obesity.The research was aimed to explore the effects and possible mechanisms of circadian rhythm signaling during the process of CA attenuated lipid accumulation in hepatic HepG2 cells induced by free fatty acids(FFA),and to provide the theoretical base of prevention and treatment of NAFLD.The main contents and results are as follows:(1)In order to mimic liver steatosis in vitro,and to explore the effects of CA on lipid metabolism disorder.HepG2 cells,an immortalized cell line,were treated with100 μM FFA(2:1,oleate: palmitate)and CA(50 μM,100 μM and 200 μM)for 24 h.It was found that CA treatments improved cell morphology changes,lipid droplets formation,mitochondrial function and oxidized status,which were triggered by FFA in a dose dependent way.In addition,200 μM CA co-treatments dramatically reduced the lipogenesis protein expression of FAS,ACC and SREBP-1,and a significant increase in the phosphorylation of Akt and the p-GSK3β/GSK3β.(2)Besides,100 μM FFA and 200 μM CA co-treatment adjusted the circadian misalignment and the relatively shallow daily oscillations of the clock genes induced by FFA,including Bmal1,Clock,Per1,Per2,Cry1,Cry2 and Reverbα.CA also increased the core protein expression level of BMAL1 and CLOCK in a dose dependent way.(3)Moreover,both silencing Clock and Bmal1 suppressed the improvement of PGC-1α and SIRT1 by CA.Silencing Bmal1 significantly blocked Akt/GSK3β pathway and the expressions of FAS and ACC in both protein and gene levels.Oil red O staining results showed that si-Bmal1 markedly up-regulated lipid droplet accumulation compared to FFA+CA group,while si-Clock did not change lipid level significantly.In conclusion,our results demonstrated that CA possesses a Bmal1-dependent efficacy against lipid accumulation by strengthening the Akt/GSK3β signaling pathways and modulating the downstream expressions related to lipid metabolism,which indicated that CA might be served as a promising natural nutraceutical for the regulation of NAFLD.