Effect Of Capsaicin On Prevention Of Cholesterol Gallstones In C57BL/6 Mice With Lithogenic Diet Feeding

Background:Gallstone is a disease caused by metabolic abnormalities of gallbladder bile,of which cholesterol gallstone is a main symptom.Currently,surgery is the most effective treatment for cholesterolgallstone.However,being a destructive method,surgery may cause partial organ deficiency,digestive function depression,anatomical structure change,and higher possibility of bile reflux.Therefore,exploring the etiology and pathogenesis of cholesterol gallstone is crucial for its treatment and prevention.Capsaicin,the main active ingredient in pepper,has variety of physiological functions according to recent studies.The function of capsaicin includes reducing fat accumulation,decreasing blood pressure to protect cardiovascular system,increasing energy expenditure,promoting metabolism and down-regulating cholesterol levels.Capsaicin is an agonist of TRPV1,which can decrease the expression of cholesterol metabolism critical rate-limiting enzyme HMG-CoA reductase,increase the expression of CYP7A1 in liver effectively,and promote the conversion of cholesterol to bile acids.Capsaicin also has anti-inflammatory effects.However,no study shows capsaicin prevents cholesterol gallstone,and the effect and mechanism of capsaicin in preventing the formation of cholesterol gallstone is also need to be investigated.Objective:The aims of the study are to establish the C57BL/6 mouse models of cholesterol gallstones induced by high-fat diet,to investigate the mechanism of capsaicin in preventing and treating of cholesterol gallstones in both molecular and animal levels,to understand the pathogenesis of cholesterol gallstones,and providing experimental basis for capsaicin as a novel and potential therapy medicine for cholesterol gallstones.Materials and Methods:30 female C57BL/6 mice were randomly divided into 3 groups and fed with different diets: the control group was fed with normal diet,the model group was fed with normal diet and lithogenic diet,the treatment group was fed with normal diet,lithogenic diet and capsaicin.After treatment for 8 weeks,the level of serum triglyceride(TG),totalcholesterol(TC),highdensitylipoproteincholesterol(HDL-C)and low densitylipoproteincholesterol(LDL-C)were detected,the formation of gallbladder bile cholesterol crystals were observed by polarizationmicroscope.The expression of COX-2,MUC5 AC and TRPV1 in gall bladder wall were examined by immunohistochemical staining,the expression of CYP7A1,HMG-Co A and TRPV1 in liver tissues were detected by immunohistochemical staining and Western Blotting.The inflammatory changes of gallbladder mucosa were observed by histopathology methods.Results:1.The gallbladder stone formation rate in control group was 0%(0/10),and model group was 100%(10/10),and treatment group was 20%(2/10).Polarization microscope observation of the gallbladder showed that the model group had more cholesterol crystals with obvious characteristics,which did not appear in the control group.The treatment group only showed sporadic cholesterol crystals.2.Compared to control group mice,the levels of TC,TG,LDL-C in the model group mice were significantly elevated with HDL-C dropped.Compared to model group mice,the most decreased index in treatment group mice were LDL-C,TC and TG,with HDL-C level significantly elevated.Also,the symptoms of gallbladder pathological inflammation in the treatment group mice were significantly reduced compared to model group mice.3.Compared to control group,the model group had higher expression of COX-2 and MUC5 AC,and lower expression of TRPV1.The treatment group had lower expression of COX-2 and MUC5 AC,and higher expression of TRPV1.The expressions of CYP7A1 and TRPV1 in liver were significantly down-regulated in the model group,while HMG-Co A reductase expression was significantly up-regulated.The expressions of CYP7A1 and TRPV1 in treatment group were up-regulated and HMG-CoA reductase expression was down-regulated.Conclusions:1.The C57BL/6 mouse models of cholesterol gallstones induced by high-fat lithogenic diet was established with high stability and efficiency..2.Capsaicin upregulate CYP7A1 activity and downregulate HMG-Co A reductase activity in liver by activating TRPV1,which interfere the process of formation of gallbladder cholesterol gallstones in mice.3.Capsaicin reduce the expression of COX-2 and MUC5 AC in gallbladder via activating TRPV1,which suppresses inflammatory reaction in gallbladder,to interfere the formation gallbladder cholesterol gallstones in mice.