Policosanol Is The Inhibition Of 3 - Hydroxy-3 - Methyl-glutaryl Coenzyme A Reductase Activity

Policosanol is a natural mixture of higher primary aliphatic alcohols isolated and purified from sugar cane(Saccharum officinarum,L.)wax,whose main component is octacosanol.The mixture has been shown to decrease cholesterol in animal models,healthy volunteers,and patients with typeⅡhypercholesterolemia.Policosanol,a new cholesterol lowering drug,is believed to decrease total cholesterol(TC),low-density lipoprotein(LDL),and increase high-density lipoprotein(HDL)by inhibiting cholesterol synthesis and increasing LDL processing.Large animal studies and clinical tests have revealed that policosanol has shown cholesterol-lowering potency comparable to that of statins,and yet appears to be devoid of toxic risk.The hypocholesterolemic effect appears to result from a decrease in cholesterol synthesis by suppression of HMG-CoA reductase activity,but the exact mechanism by which policosanol inhibits the activity of HMG-CoA reductase still remains unclear.The previous inhibition of enzyme up-regulation by policosanol suggests to date a depression of de novo synthesis of HMG-CoA reductase and/or stimulation of its degradation.The other study suggest that policosanol or a metabolite decreases HMG-CoA reductase activity by activating AMP-kinase.The aim of this study was to approach the HMG-CoA reductase activity-decreasing action and the possible mechanism of action from the vitro experiment.Objective Through detecting the activity of the HMG-CoA reductase in the HepG2 cells,judging the effect of HMG-CoA reductase activity-decreasing of policosanol,and then discussing the possible mechanism of cholesteroldecreasing. Methods Human HepG2 were selected to make an experiment in completely randomized design in vitro.For determining the dose of policosanol and insulin about this study and assuring the accuration of the experimental result,MTT assay was done to identify the direct influence to the HepG2 cell growth with policosanol,insuline and alcohol.To reflex the effect of prohibition of policosanol on the HepG2 cells growth,the cell survival rate and LDH leakage from the cell were done.According the pertinent literatures and MTT assay,we can determine the dose of the test.The cells were cultivated routinely and test were subjected when cells were in the period of logarithmical growth and in good condition.The cells were divided into seventeen groups including control group,positive control group,policosanol group,insulin group and the cross dose group of policosanol and insulin.The activity of HMT-CoA reductase was detected via monitoring the absorption point decreasing of NADPH in the wave length of 340nm in the body cells and the microsome of the HepG2 cells by ultraviolet spectro-velocity method.Results(1)The concentration of the policosanol and insulin in this study are 5μg/ml,10μg/ml and 20μg/ml.(2)NADPH have absorption peak in the wave length of 340nm.The qulity control is very good about the sensitivity,recovery rate and reproducibility.The natural oxidation rate is 0.0009·min^-1.(3)The activity of HMG-CoA reductase in the dose groups of policosanol within 5μg/ml-2Oμg/ml has significant difference compared with the control groups and the cross groups of policosanol and insulin either in the body HepG2 cells or the microsome of the HepG2,and the activity of HMG-CoA reductase exists the dose-effect relationship.Conclusion Our study demonstrated that policosanol can significantly decrease the activity of HMG-CoA reductase which is the key enzyme of the cholesterol synthesis.In the process of policosanol decreasing the cholesterol, the activity depressing of HMG-CoA reductase might be the primary pathway.