Role Of Leptin Receptor In Cholesterol Gallstone Formation In Mice

Objective:In this study,we used the method of high-fat and high cholesterol induced gallstone to establish gallstone model by feeding C57BL/6J mice with normal expression of leptin receptor（OB-R,LEPR,also known as db）and LEPR deficient leprdb/db mice with high-fat induced gallstone diet.Leptin was given during the model making period to observe the stone formation of gallbladder stones,the levels of leptin,TC,TG,and the expression of LEPR and scavenger receptor class-B type I（SR-BI）in the liver of mice.Objective to explore the potential relationship between leptin,LEPR and gallstone formation in mice.Methods:C57BL/6J mice and lepr^db/dbmice were randomly divided into 4 groups（n=6）by random number table method after one week of adaptive feeding with common maintenance diet.（1）LEPR normal saline control group（C57-NS）;（2）LEPR normal leptin experimental group（C57-Leptin）;（3）LEPR deficient saline control group(Lepr^db/db-NS);（4）LEPR deficient leptin experimental group(Lepr^db/db-Leptin).All mice were fed with high-fat diet for6 weeks,and then given intraperitoneal injection.The mice in Leptin experimental group were divided into C57-Leptin group and Lepr^db/db-Leptin group.The mice in both groups were intraperitoneally injected with 3 ug/g Leptin dry powder solution.The mice in the saline control group were divided into C57-NS and Lepr^db/db-NS groups,which were injected intraperitoneally with the same volume of normal saline.Intraperitoneal injection was carried out every other day for 2 weeks.The content of leptin in serum was detected by ELISA,TC and TG in serum were measured by single Reagent Colorimetry,and the expression of LEPR and SR-BI in liver tissue was detected by immunohistochemistry.Result:1.Comparison of stone formation rate:the stone formation rates of C57-NS group,C57-Leptin group,Lepr^db/db-NS group and Lepr^db/db-Leptin group were 66.7%,83.3%,0%and0%,respectively.2.Comparison of serum Leptin content:the results of intra group comparison of serum Leptin content in normal LEPR expression group showed that the serum Leptin content in C57-Leptin group was higher than that in C57-NS group（P<0.05）;the serum Leptin content in Lepr^db/db-NS group was higher than that in C57-NS group（P<0.01）;the serum Leptin content in Lepr^db/db-Leptin group was higher than that in C57-Leptin group（P<0.01）.3.Comparison of serum TC and TG content:the results of intra group comparison of serum TC content in normal LEPR expression group showed that the level in C57-Leptin group was lower than that in C57-NS group（P<0.05）;the level in Lepr^db/db-NS group was higher than that in C57-NS group（P<0.01）;the level of serum TC in Lepr^db/db-Leptin group was higher than that in C57-Leptin group（P<0.01）.The results of intra group comparison of serum TG content in normal LEPR expression group showed that C57-Leptin group was lower than C57-NS group（P<0.05）;among groups,Lepr^db/db-NS group was higher than C57-NS group（P<0.01）;Lepr^db/db-Leptin group was higher than C57-Leptin group（P<0.01）.4.Comparison of liver LEPR and SR-BI immunohistochemical expression:compared with different experimental groups,the expression of liver LEPR in normal LEPR group was higher than that in C57-NS group（P<0.01）.The expression of SR-BI in C57-Leptin group was higher than that in C57-NS group（P<0.01）;the expression of SR-BI in C57-NS group was higher than that in Lepr^db/db-NS group（P<0.05）;the expression of SR-BI in C57-Leptin group was higher than that in Lepr^db/db-Leptin group（P<0.01）.Conclusion:1.Under the condition of high-fat and high cholesterol diet,LEPR deficient mice could not form cholesterol gallstones,suggesting that LEPR may be an important protein involved in the formation of cholesterol gallstones.2.The expression of SR-BI and LEPR in mice with normal LEPR expression could be increased by injecting high level of Leptin.There was no significant change in the expression of SR-BI and LEPR in mice with LEPR expression deficiency after injecting high level of Leptin.3.The role of LEPR in cholesterol gallstone is related to serum leptin.Leptin combined with LEPR can up regulate the expression of SR-BI protein to reduce the content of serum TC and TG,increase the level of bile cholesterol in mice,promote the precipitation of cholesterol crystals,and then lead to the formation of cholesterol gallstone.