EGCG Ameliorates High Fat Diet Induced Metabolic Disorders Depending On Bmal1

Circadian clock is an intrinsic biological timing mechanism that organisms evolved to temporally organize behavioral and physiological processes.There are emerging evidences that desynchronization of circadian rhythm may contribute to metabolic disorders,and some phytochemicals may be able to mitigate metabolic disorders,although the underlying mechanisms remain unclear.Chronic desynchronization of circadian rhythm is the risk for many metabolic diseases.Our modern society is characterized by shift work and jet lag,which lead to disturbed wake/sleep cycle.Sleep problems are also more prevalent in the obese population.（-）-Epigallocatechin-3-gallate（EGCG）is the major ingredient of polyphenols in tea,which exerted multiple beneficial effects including anti-obesity.Previous researches reported that high fat diet induced metabolic disorders and the desynchronization of circadian rhythm.However,the underlying mechanism remains unclear.Some phytochemical flavones were reported to alleviate metabolic disorders induced by high fat diets associated with altering the circadian rhythm in mice.The manipulation of the circadian system seems to be a potential target to ameliorate metabolic syndromes.To our knowledge,there is still no direct evidence of whether phytochemicals ameliorate metabolic homeostasis depending on the circadian system.Whether EGCG ameliorated high fat diet induced metabolic disorders through the circadian rhythm is still unclear.Here we investigated the protective effect of EGCG against metabolism induced by a high fat diet in Bmal1^-/-mice and their WT littermates.Our study found that EGCG reversed the lipids metabolic disorder and circadian misalignment triggered by HFD in the WT mice rather than Bmal1^-/-mice.The diminished protective effects of EGCG in Bmal1deficient mice refined the relationship between the circadian system and lipids metabolic disorder,implying the vital role of circadian system in phytochemical’s anti-obesity function.This study examined the protective effects of EGCG on high fat diet induced lipids metabolic disorders and circadian rhythm desynchronization in WT mice and the metabolic changes in Bmal1 deficient mice.In this study,wild type mice and Bmal1^-/-mice consume diets with control,high-fat diet（HFD）,or HFD with EGCG intragastric administration for10 weeks.EGCG effectively protects HFD triggered adipose tissues accumulation and hyperlipidemia in wild type mice,which vanished in the Bmal1-/-mice.EGCG also restores HFD triggered serum lipidomic and hepatic transcriptomic profiles changes depending on Bmal1.Except for the metabolic disorders induced by HFD,EGCG also ameliorates the impaired metabolic rhythm in the wild type mice.Data from comprehensive lab animal monitoring system（CLAMS）revealed that high fat diet decreased the oxygen consumption and carbon dioxide production,which was ameliorated by EGCG in WT mice.These metabolic parameters were not changed in different dietary conditions of Bmal1 deficient mice.We found that EGCG exerts anti-hyperglycemia and anti-obesity induced by high fat diet in WT mice,which are absent in Bmal1 deficient mice.Transcriptomics of liver tissues revealed perturbed energy metabolism triggered by high fat diet,which was reversed by EGCG administration.The paucity of DEGs in the livers between KHD and KHE suggests that there is no significant difference between their metabolic status.Plasma lipidomics revealed perturbed lipid metabolism induced by high fat diet in both genotype mice and identified potential lipid biomarkers which were ameliorated by EGCG in a Bmal1 dependent manner.To explore the underlying mechanism of vanished protective effects of EGCG in Bmal1 deficient mice triggered by high fat diet,we explored the inhibitory effects of EGCG in the differentiation of 3T3-L1 cell with or without Bmal1-si RNA.Bmal1 and Klf9 m RNA expression increased during the differentiation of 3T3-L1 cell,which were inhibited by EGCG administration.EGCG showed incapable inhibition of the promoted adipogenesis by pioglitazone in Bmal1 knock-down 3T3-L1 cells.Western Blot analysis of PPARγalso showed that there was no substantial difference in pioglitazone restored adipogenesis in Bmal1 knock-down 3T3-L1 cells with or without EGCG treatment.Two binding sites in the promoter of Klf9 was identified for its interaction with Bmal1.The diminished protective of EGCG in HFD induced lipid metabolic disorders enlarge the linkage between circadian rhythm and energy metabolism,also provided more information on the protective effective of EGCG on HFD induced metabolic disorder through Bmal1 related pathway.Furthermore,our study provides evidence that EGCG inhibits adipogenic differentiation of pre-adipocytes through the Bmal1-Klf9-PPARγpathway.