棕榈酸下调促甲状腺素受体减少大鼠甲状腺滤泡上皮细胞甲状腺球蛋白合成和分泌

Palmitic acid inhibits the synthesis and secretion of thyroglobulin of rat thyroid follicular epithelial cell by downregulating thyrotropin receptor

目的探讨促甲状腺素受体(TSHR)在脂毒性诱导甲状腺功能损伤中的作用。方法用不同剂量棕榈酸(PA)刺激大鼠甲状腺滤泡上皮细胞(RTC),油红O染色观察细胞脂质含量,RT-PCR和Western blot检测各组TSHR、Ttf1和SSBP1 mRNA及蛋白表达水平,ELISA检测细胞上清液TSHR蛋白水平,免疫荧光法检测膜TSHR,并和正常对照组进行比较。用PA刺激TSHR过表达(TSHR OE)的RTC(PA+TSHR OE组)和正常的RTC(PA组),检测各组细胞内Tg mRNA、cAMP水平,细胞内及上清液Tg蛋白,并与对照组进行比较。结果PA各组细胞光镜下染成橘红色。与对照组比较,PA各组Ttf1、SSBP1、TSHR mRNA和蛋白表达下降(均P<0.05),上清液及膜TSHR蛋白降低(P<0.05),部分呈剂量依赖性变化。与对照组比较,PA组细胞Tg mRNA表达下降(P<0.05),细胞和上清液中Tg蛋白水平降低(P<0.05),细胞内cAMP水平下降(P<0.05);TSHR过表达组Tg mRNA表达上调(P<0.05),细胞和上清液Tg蛋白水平增加(P<0.05),细胞内cAMP水平相似(P>0.05)。与PA组比较,PA+TSHR OE组的细胞Tg mRNA、细胞和上清液Tg蛋白水平均上调(P<0.05),伴cAMP水平升高(P<0.05)。结论PA可致RTC内脂质沉积,Tg合成和分泌减少。该作用可能是通过下调TSHR/cAMP信号通路实现的。

Objective Exploring the role of thyrotropin receptor(TSHR)in lipotoxicity-induced thyroid function damage.Methods Rat thyroid follicular epithelial cells(RTC)were stimulated with different doses of palmitic acid(PA),and the lipid content of the cells was observed through Oil Red O staining.The expression levels of TSH receptor(TSHR),Ttf1,and SSBP1 mRNA and protein in each group were detected using RT-PCR and Western blot.The TSHR protein level in the cell culture supernatant was measured using ELISA.Membrane TSHR was assessed through immunofluorescence and compared with the control group.We used PA to stimulate the TSHR over-expression(TSHR OE)and normal RTC,as PA+TSHR OE group and PA group respectively,then testing Tg mRNA and protein,cAMP and Tg in cell supernatants levels,then comparing with the control.Results RTC were stained into peau d′orange in PA groups.Compared with the control group,we found TTf1,SSBP1 and TSHR mRNA as well as protein levels in PA groups were decreased(all P<0.05),TSHR of the cell membrane and supernatants were reduced(all P<0.05),characterizing dose-dependent changes partly.Moreover,we found in PA group Tg mRNA level was downregulated(P<0.05),Tg protein levels were reduced in the supernatants and cells(P<0.05),cAMP level was decreased in cells(P<0.05);in TSHR OE group,Tg mRNA level was upregulated(P<0.05),Tg protein levels in cells and supernatants were increased(all P<0.05),cAMP level was similar.Compared with the PA group,we found in PA+TSHR OE group Tg mRNA level was upregulated(P<0.05),Tg protein levels were increased in the supernatants and cells(all P<0.05),cAMP level was elevated in cells(P<0.05).Conclusion PA induces lipid deposition in RTC,decreased synthesis and secretion of Tg.This effect is likely achieved through the downregulation of the TSHR/cAMP signaling pathway.