小鼠肝脏胆酸合成及转运基因表达的昼夜节律

Circadian-and sex-variations of bile acid synthesis and transport gene expression in livers of mice

目的观察昆明种小鼠肝脏胆酸合成基因及转运体表达的昼夜节律变化。方法成年昆明种小鼠48只,适应性饲养1周后,随机分为6组(每组8只,雌雄各半),分别于06∶00、10∶00、14∶00、18∶00、22∶00、02∶00不同时间点收集动物肝脏,提取肝脏总RNA,采用实时荧光定量RT-PCR法检测肝脏胆酸代谢途径相关基因的mRNA表达。结果小鼠胆酸合成限速酶Cyp7a1,Cyp27a1mRNA最高表达在18∶00,且雌性表达高于雄性;而Cyp8b1和Cyp7b1表达最高则在10∶00,其中Cyp7b1表现为雄性高于雌性;肝脏核受体FXR在18∶00表达最高;且雌性表达高于雄性,SHP雌性表达最高在18∶00,而雄性最高表达则出现在10∶00;转运体Ntcp的最高表达在18∶00,Bsep最高表达则在14∶00,且雌性表达高于雄性。结论小鼠肝脏胆酸代谢基因表达存在昼夜节律性,且存在性别差异。

Objective This study is to examine diurnal - and sex -variations in expression of bile acid synthesis and transport genes in mice. Methods Adult Kunming mice were housed in SPF - grade facilities, with controlled light/dark cycles （ light on 8 ： 00 - 20： 00 ） and free access the standard rodent chow. Livers were collected at 6： 00, 10： 00, 14： 00, 18： 00, 22： 00, and 2：00 during a 24 - h period. Hepatic total RNA was isolated, purified and subjected to real - time RT - PCR analysis. Results The bile acid synthesis rate - limitgene Cyp7al showed diurnal rhythm, peaked at 18：00 with a peak/tough ratio of 10 - fold, while Cyp27al had a peak/tough ratio of 3 -fold. The nuclear receptor farnesoid X receptor （FXR） and small heterodimer partner （SHP） also showed similar circadian variation, and peaked during the dark - phase. Hepatic bile acid transporter Na ＋/taurocholate co -transporting ploypeptide （Ntcp） and bile salt export pump （Bsep） also showed circadian rhythm, with a peak around 14： 00. The expression of clock genes Clock and Nrldl showed typical circadian patterns. Furthermore, expression of Cyp7bl is male dominant, while females have higher expression of Cyp7al, Cyp27al, FXR and Bsep. Conclusion The bile acid synthesis genes have diurnal rhythms and sex -differences.