微量元素锶改善大鼠非酒精性脂肪肝的机制研究

Mechanism of the trace element strontium on alleviating non-alcoholic fatty liver disease in rats

目的探讨微量元素锶改善大鼠非酒精性脂肪肝的机制。方法 50只SD大鼠随机分为对照组、模型组、18 mg/L锶组、36 mg/L锶组和辛伐他汀组。对照组进食普通饲料,其余4组进食高脂饲料,第6周起给予18 mg/L和36 mg/L锶组浓度分别为18 mg/L和36 mg/L含锶饮用水,第11周起进行灌胃,18 mg/L和36 mg/L锶组分别灌浓度为18 mg/L和36 mg/L含锶水3 m L/kg体重,辛伐他汀组灌辛伐他汀10 mg/kg体重,对照组与模型组灌生理盐水3 m L/kg体重。第14周末处死大鼠,检测血清TG、TC、LDL-C和肝组织TG、TC含量,并行肝组织油红O染色观察脂肪变性情况,免疫组化检测肝组织GRP78、SREBP2、HMGCR和LDLr蛋白表达水平。结果与对照组比较,模型组的血清TC、LDL-C和肝TC、TG均升高(P<0.05),与模型组比较,36 mg/L锶组血清TC、LDL-C和肝TC、TG均降低(P<0.05)。油红O染色显示模型组肝组织含大量的红染脂质颗粒,18 mg/L锶组、36 mg/L锶组及辛伐他汀组红染颗粒均较模型组不同程度减少(P<0.05)。免疫组化结果显示:模型组大鼠肝组织GRP78、SREBP2、HMGCR和LDLr蛋白表达水平,18mg/L锶组大鼠肝组织GRP78、SREBP2和LDLr蛋白表达水平,36 mg/L锶组大鼠肝组织LDLr蛋白表达水平及辛伐他汀组大鼠肝组织SREBP2和LDLr蛋白表达水平均明显高于对照组(P<0.05)。36 mg/L锶组大鼠肝组织GRP78、SREBP2和HMGCR蛋白表达水平明显低于模型组,而LDLr蛋白表达水平明显高于模型组;辛伐他汀组大鼠肝组织GRP78和HMGCR蛋白表达水平明显低于模型组(P<0.05);而18 mg/L锶组大鼠肝组织GRP78、SREBP2、HMGCR和LDLr蛋白表达水平较模型组无显著差异(P>0.05)。结论长期较高浓度锶摄入可改善脂代谢紊乱,减轻NAFLD,其作用机制可能与调节内质网应激、HMGCR活性和LDLr的功能等有关。

Objective To investigate the mechanism of trace element strontium on alleviating non-alcoholic fatty liver disease （NAFLD） in rats. Methods Fifty SD rats were randomly divided into five groups. The control group was fed with ordinary diet and the other four groups were fed with a high fat diet. From the 6th week, rats in the strontium 18mg/L and 36 mg/L groups were fed with water with strontium in concentration of 18 mg/L and 36 mg/L respectively. These two groups were separately given strontium water （3 mL/kg b. w. ） by garage from the 1 lth week, while the Simvastatin group was given simvastatin （10 mg/kg b. w. ） by gavage from the llth week. Rats in other groups were given matching normal saline by gavage at the same period. The rats were killed and the TG, TC, LDL-C levels in their serum and the TG, TC levels in the liver were detected at the end of the 14th week. The lipid accumulation in the liver tissue was observed using oil red O staining. The protein expression levels of GRP78, SREBP2, HMGCR and LDLr in the liver tissue were assessed with immunohistochemical staining. Results The levels of serum TC, LDL-C and liver TC, TG in the NAFLD group were significantly higher than that of the control group （P 〈 0. 05 ）. The levels of serum TC, LDL-C and liver TC, TG in the strontium 36 mg/L group were significantly lower than that of the NAFLD group （ P 〈 0. 05 ）. ORO staining showed that lipid accumulation in liver increased abnormally in the NAFLD group compared with the control group, while the lipids accumulation in the liver decreased obviously in the strontium 18 mg/L group, 36 mg/L group and simvastatin group compared with the NAFLD group to a different degree. Immunohistochemical staining showed that the protein expression levels of GRP78, SREBP2, HMGCR and LDLr in the NAFLD group, those of GRP78, SREBP2 and LDLr in the strontium 18 mg/L group, those of LDLr in the strontium 36 mg/L group and those of SREBP2 and LDLr in the Simvastation group significantly increased compared with those of the control group （ P 〈 0. 05 ）. The protein expression levels of GRP78, SREBP2 and HMGCR in the strontium 36 mg/L group decreased obviously compared with those of the NAFLD group, while those of LDLr in the strontium 36 mg/L group increased compared with those of the NAFLD group （ P 〈0.05）. The protein expression levels of GRP78 and HMGCR in the simvastatin group decreased compared with the NAFLD group（P 〈 0.05）. The protein expression levels of GRP78, SREBP2, HMGCR and LDLr in the strontium 18 mg/ L group had no significant difference compared with the NAFLD group （P 〉 0.05 ）. Conclusions Intake of trace element strontium at high concentration for long time can alleviate the disorder of lipid metabolism and non-alcoholic fatty acid liver disease （NAFLD） in rats. Its mechanism is probably related to its adjusting of endoplasmic reticulum stress, the activity of HMGCR and the function of LDLr.