Mechanism Of Activation Of TRPV1 In Regulation Of Intestinal Cholesterol Absorption

Background and Objectives:Abnormal metabolism of cholesterol in the body can lead to atherosclerosis,which can advance the development of cardiovascular and cerebrovascular disease.It is a threat to human health.Since the reform and opening up,the national dietary structure has changed deeply.So much lipid intake had led to abnormal lipid metabolism.The prevalence of cardiovascular and cerebrovascular disease increased year by year.Recently,the pathogenesis of atherosclerosis became the focus.The synthesis and absorption of cholesterol had effects on TC and LDL-C levels in the body.As we all know,statins were used to block the process of cholesterol synthesis,on the other hand ezetimibe was used to inhibit cholesterol absorption.These drugs were produced for dyslipidemia,which were expensive and had some side effects,so they could not be used for the prevention of early dyslipidemia.How to prevent early dyslipidemia? Generally,lipid levels had a great relationship with daily diet.Therefore,dietary factors were the convenient and feasible effective measures to start the early intervention of dyslipidemia.Our previous studies had confirmed that dietary capsaicin could activate TRPV1 channel on VSMCs by affectting the intracellular cholesterol metabolism,and prevent the accumulation of cholesterol in VSMCs.It has been confirmed that TRPV1 was also expressed in the intestine,and in recent years the reports gradually increased,the proteins involved in the process of intestinal cholesterol absorption,such as Niemann-Pick C1-Like 1,ATP-binding cassette subfamily G 5 / 8 and Acy1 coenzyme A cholesterol Acyltransferases1/2 molecules were gradually known.However,the activation of intestinal TRPV1 for intestinal cholesterol absorption and the mechanism was not yet clear.Our study have focused on capsaicin activation of intestinal TRPV1 about intestinal cholesterol absorption and molecular mechanisms,which provides evidence for dietary capsaicin about regulation of dyslipidemia.Materials and Methods:This study was divided into clinical data analysis and basic experiments.Clinical data were analyzed with normal subjects.In basic experiments,C57 BL / 6J wild type and TRPV1-/-type mice were randomly divided into three groups separately: normal group(Cont group),high fat group(HFD group)and high fat plus capsaicin group(Hcaps group).1.Study the normal subjects general information blood lipid levels and do statistical analysis.2.C57 BL / 6J wild type and TRPV1-/-mice were used as the research objects.Record the basic information such as weight.3.Serum biochemical markers such as TG,TC,HDL-C and LDL-C were measured by biochemical methods.4.Determination of cholesterol absorption markers in mouse serum by gas chromatography-mass spectrometry,namely,campesterol,stigmasterol and β-sitosterol.5.Caco-2 cells were treated with by cholesterol micelles as the stimulating factor,and the cholesterol transporters of Caco-2 cells were determined after intervened by TRPV1 agonist capsaicin and capsazepin.6.The expression of PKA,LXR,NPC1L1,ABCG5/8 and ACAT1/2 in small intestine of mice were investigated by western blotting.Results:1.There was no significant difference in sex,age,systolic blood pressure(SBP),diastolic blood pressure(DBP),salt intake,waist circumference,triglycerides(TG)and high-density lipoprotein-cholesterol(HDL-C)between the normal diet group and the spicy group(P> 0.05).Compared with the normal diet group,the TC and LDL-C in the spicy group were significantly lower(P <0.05).The difference was also statistically significant(P <0.05)after regulation with sex,age,systolic blood pressure,diastolic blood pressure,salt intake,waist circumference and Body Mass Index(BMI)(P <0.05).2.There was no significant difference in body weight in wild type mice.The serum TC of HFD group was higher than that of Cont group(P <0.01),while that in Hcaps group was lower than that in HFD group(P <0.05).In TRPV1-/-type mice,the body weight of HFD group was higher than Cont group(P <0.05).The serum TC of HFD group increased compared with Cont group.(P <0.01).There was no significant difference between HFD group and Hcaps group.3.In wild type mice,compared with the HFD group,the levels of campesterol / TC,stigmasterol / TC and β-sitosterol / TC decreased all after capsaicin intervention(P <0.05).In TRPV1-/-type mice,the levels of campesterol / TC and β-sitosterol / TC in Hcaps group were lower than those in HFD group(P <0.05),but after capsaicin intervention,the levels of stigmasterol / TC had trend to increase.4.Results of cholesterol transport rates in Caco-2 cellsCompared with Cont group,the outward transport rate of cholesterol in the micelle group decreased significantly(P <0.05).After capsaicin intervention,the outward transport rate increased significantly(P <0.01).5.The molecules of protein expression in intestine related to cholesterol metabolism5.1 In wild type mice,the expression of PKA and LXR protein in the HFD group was higher than that in Cont group(P <0.01 and P <0.05).After capsaicin intervention,the changes could be reversed.TRPV1-/-type mice did not have the above changes.5.2 In wild type mice,the expression of ABCG5 protein in HFD group was higher than that in Cont group(P <0.05).It was further increased after capsaicin intervention(P <0.05).The expression of ABCG8 protein in HFD group was decreased compared with the Cont group(P <0.05),and it was increased after capsaicin intervention(P <0.05).In TRPV1-/-type mice,the expression of ABCG5 protein was significantly lower in the HFD group than that in the Cont group(P <0.01).The expression of ABCG8 protein was no obvious difference in each groups.There was no significant difference in the expression of NPC1L1 protein in each groups.5.3 In wild type mice,the expression of ACAT1 and ACAT2 protein in the HFD group was higher than that in the Cont group(P <0.05 and P <0.01).After capsaicin intervention,the expression of ACAT2 protein was decreased(P <0.05).In TRPV1-/-type mice,there was no significant difference in ACAT2 protein expression in each groups.There was no significant difference in ACAT2 protein expression between TRPV1-/-mice groups.Conclusions:1.Clinical data analyses and experimental animal studies have shown that dietary capsaicin can reduce serum LDL-C and TC levels.2.Activation of TRPV1 by capsaicin reduces the level of cholesterol absorption markers in mouse serum.3.Activation of TRPV1 by capsaicin was able to up-regulate the expression of ABCG5/8,down-regulate the expression of ACAT2 in the small intestine of mice,which promote the outward transport of cholesterol,inhibit cholesterol esterification in the small intestine,and decrease the serum TC levels.