Resisstance Exercise On Ovariectomized Mouse Liver Endocannabinoid/CB1 Receptor Pathway And The Effect Of Lipid Metabolism

PurposeTo investigate the effects of resistant exercises on the expression of endocannabinoid-2-arachidenyl glycerin(2-AG)and its receptor CB1 protein in liver of ovariectomized mice,and the expression of PPARα/γ and SREBP1 in liver.To analyze the mechanism of resistance exercise on liver lipid metabolism through endocannabinoid system /CB1 receptor pathway,so as to provide theoretical basis for anti-resistance exercise to improve lipid metabolism in menopausal obese women.MethodThirty-six 11-week-old female mice were randomly divided into three groups:sham operation group(S),ovariectomy group(O)and postovariectomy exercise group(AO).Sham operation was performed on mice in group S,bilateral ovaries were removed in group X,and after removal of bilateral ovaries,mice in group AX recovered for 4 weeks,and then underwent weight-bearing climbing and resistance exercise for another 6 weeks.Group AX mice weight-bearing ladder resistance exercise program,exercise intervention was performed every Monday,Wednesday and Friday,and 8 times of weight-bearing ladder anti-resistance exercise were performed on each exercise intervention day,twice/group,a total of 4 groups,with interval of 1min within the group and 2 min between the groups.In the first week,exercise weight was 0%,30%,50% of body weight;At week 2-3,weight bearing was the same,50%weight for 4 times + 75% weight for 4 times;In week 4-6,the weight was the same,50% body weight for 3 exercises + 75% body weight for 3 exercises + 90% body weight for 2 exercises.Weekly weight changes were recorded and weight weights were adjusted during the intervention period,The relevant indexes of lipid metabolism in mice were detected,the blood and liver of mice was collected.The content of 2-AG in liver was detected by mass spectrometry after 6 weeks of intervention,The protein expressions of CB1,PPARα/γ and SREBP1 in liver were detected by Western-blot.Graph Pad Prism8.0.2 was used to make charts and analyze the data.Descriptive statistical analysis was used for data,and Mean and standard error(Mean±SEM)were used to represent the data.Conventional one-way analysis of variance was used to compare the two groups,P < 0.05 and P < 0.01 indicated significant differences.Results:(1)Compared with the mice in group S,the body weight of group O mice increased significantly(P < 0.05),and the perirenal fat weight increased significantly(P < 0.01);compared with group O,the perirenal fat of AO group was decreased,and the difference was significant(P < 0.05),but the body weight and Lee’s index were not significantly changed(P > 0.05).(2)Compared with mice in group S,FFA and TG concentrations in liver of group O were increased with significant differences(P < 0.01),LDL-C concentration was increased with significant differences(P < 0.05),and TC and HDL-C concentrations in liver of group AO were decreased with significant differences(P <0.01).There were no significant differences in TG,FFA and LDL-C(P > 0.05);Compared with mice in group O,the concentration of TG and FFA in liver of mice in group AO was decreased with significant difference(P < 0.01),and the concentration of LDL-C was decreased with significant difference(P < 0.05);compared with the mice in group S,the concentrations of TC,TG,FFA and LDL-C in serum of group O were increased,and there were significant differences(P < 0.01);the concentration of HDL-C was decreased significantly(P < 0.05);the concentrations of FFA and LDL-C in serum of group AO were increased,and there were significant differences(P <0.01);compared with group O,the concentrations of TC and TG in serum of AO group were decreased,with significant differences(P < 0.05),and the concentrations of FFA and LDL-C were decreased,with significant differences(P < 0.01).(3)Compared with mice in group S,the concentration of 2-AG in liver of mice in group O and group AO was significantly increased(P < 0.01),but there was no significant difference in liver of mice in group AO compared with mice in group O(P > 0.05).(4)Compared with mice in group S,the expression of liver CB1 receptor protein in group O was increased with significant differences(P < 0.05),and the expression of PPARγ and SREBP1 were increased with significant differences(P <0.01);Compared with group O,the expression levels of liver CB1 receptor,PPARγand SREBP1 in AO group were decreased,and there were significant differences(P <0.01),but there were no significant differences in PPARα protein expression among the three groups(P > 0.05).Conclusions:(1)After ovariectomized mice,the weight of perirenal fat increased,and the liver cells showed obvious fatty degeneration and lipid metabolism disorder.(2)The concentration of endocannabinoid 2-Ag and the expression of CB1 receptor protein in the liver of mice were significantly increased after ovariectation,as were the expressions of PPARγ and SREBP1 proteins that promote lipid synthesis,suggesting that the endocannabinoid /CB1 receptor pathway was activated,which may promote fat synthesis and lead to lipid metabolism disorder after ovariectomized mice.(3)Although 6 weeks of resistance exercise could not effectively reduce the body weight of ovariectomized mice,it could reduce hepatocyte steatosis,significantly reduce perirenal fat weight and improve abnormal liver fat metabolism.(4)6-week resistance exercise could not significantly improve the increase of2-AG concentration in the liver of mice caused by ovaries removal,but could inhibit the overactivation of the endocannabinoid system by down-regulating the protein expression of CB1 receptor,which may improve liver lipid metabolism by down-regulating the CB1 receptor /SREBP1 pathway.