上海交通大学学报（医学版）

上海交通大学学报（医学版）

• 论著（基础研究） • 上一篇    下一篇

甲硫氨酸负荷致同型半胱氨酸轻度升高对大鼠肝脏脂质代谢的影响及机制研究

孙珍珍1，彭川2，郑金英1，李继斌1   

  1. 1.重庆医科大学 公共卫生与管理学院医学与社会研究中心  健康领域社会风险预测治理协同创新中心， 重庆 400016；2.重庆医科大学附属第一医院糖脂代谢中心， 重庆 400016
  • 出版日期:2015-07-28 发布日期:2015-08-27
  • 通讯作者: 李继斌, 电子信箱: ljb21st@126.com。
  • 作者简介:孙珍珍（1987—）， 女， 硕士生; 电子信箱: zzysxf@163.com。

Effects of moderate increase of homocysteine caused by methionine load on lipids metabolism of rat liver and possible mechanisms

SUN Zhen-zhen1, PENG Chuan2, ZHENG Jin-ying1, LI Ji-bin1   

  1. 1.Medical and Social Research Center and Innovation Center for Social Risk Governance in Health, School of Public Health and Management, Chongqing Medical University, Chongqing 400016, China； 2.Glucose and Lipid Metabolism Center, the First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China
  • Online:2015-07-28 Published:2015-08-27

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摘要：

目的  了解高甲硫氨酸摄入对肝脏脂质代谢的影响及可能机制。方法  选取6周龄健康SD雄性大鼠20只，随机分为对照组和甲硫氨酸负荷组。适应性喂养2周后，对照组饲以正常饮食并采用PBS灌胃，甲硫氨酸负荷组在正常饮食基础上采用甲硫氨酸灌胃，持续喂养8周，每周称取体质量，处死后收集血液和肝脏组织。肝脏称重并计算脏器系数；肝组织切片H-E染色进行组织学观察；血生化分析仪测定血清生化指标；采用ELISA法测定血清同型半胱氨酸水平；real-time PCR检测大鼠肝组织脂代谢相关酶基因的表达水平。在体外培养的HepG2细胞，油红O染色光学显微镜观察甲硫氨酸负荷或同型半胱氨酸处理对细胞中脂质沉积的影响，Western blotting检测同型半胱氨酸处理后细胞中成熟型肝组织甾醇调节元件结合蛋白1c （n-SREBP1c）表达的变化。结果  甲硫氨酸负荷组与对照组大鼠体质量的增长无明显差异，但甲硫氨酸负荷组的脏器系数显著高于对照组（P<0.05）；甲硫氨酸负荷组大鼠肝脏出现轻微小泡性脂肪变性，但未出现炎症和明显肝功能损害；甲硫氨酸负荷组大鼠血清同型半胱氨酸、血清总胆固醇及高密度脂蛋白水平显著高于对照组（P<0.05）；甲硫氨酸负荷组肝组织Fas、Acc、Scd1、Cpt1α mRNA表达与对照组比较差异无统计学意义（P>0.05）。在甲硫氨酸或同型半胱氨酸作用下，HepG2细胞发生明显的脂质蓄积；同型半胱氨酸处理HepG2细胞n-SREBP1c表达显著增高。结论  甲硫氨酸摄入过量将导致肝脏轻微脂肪变性，且与血液中同型半胱氨酸水平升高有关。甲硫氨酸负荷导致的同型半胱氨酸水平轻度升高可通过调节肝细胞脂质代谢关键转录因子的活化，对肝脏脂质代谢造成影响。

关键词: 甲硫氨酸, 同型半胱氨酸, 肝脏, 脂质代谢

Abstract:

Objective   To explore the effects of the high methionine intake on lipids metabolism of liver and the possible mechanisms. Methods  Twenty healthy 6-week old SD rats were selected and randomly divided into the control group and methionine group. After 2 weeks of acclimation, rats of the control group were fed with standard chow and received PBS gavages, while rats of the methionine group were fed with standard chow and received methionine gavages for 8 weeks. The body weight of rats was measured every week. The samples of blood and liver tissue were collected, the weight of livers was measured, and the organ coefficient was calculated after rats were sacrificed. The liver tissue was sliced and H-E stained and the morphologic observation was performed. Biochemical indexes of serum were detected by automatic biochemical analyzing system. The level of serum homocysteine was detected by ELISA. The gene expression levels of enzymes relevant to lipid metabolism were detected by quantitative real-time PCR. HepG2 cells were cultured in vitro and stained by oil red O. The effects of methionine load or homocysteine treatment on the lipids deposition in HepG2 cell were observed under optical microscope. The change of expression level of n-SREBP1c was detected by Western blotting after being treated by homocysteine. Results The difference of increase of body weight between the control group and methionine group was insignificant, while the organ coefficient of methionine group was significantly higher than that of the control group (P<0.05). Rats of the methionine group developed mild microvesicular steatosis, but no inflammation or obvious hepatic dysfunction was found. Levels of plasma homocysteine, TC, and HDL of the methionine group were significantly higher than those of the control group (P<0.05). The differences of mRNA expressions of Fas, Acc, Scd1, and Cpt1α in the liver tissue between two groups were not statistically significant (P>0.05). Treatment with methionine or homocysteine led to obvious lipids deposition in HepG2 cells. The expression of n-SREBP1c in HepG2 cells significantly increased after being treated by homocysteine. Conclusion   Excessive methionine intake may result in mild hepatic steatosis, which is associated with the increase of homocysteine in blood. Moderate increase of homocysteine level caused by methionine load can effect the lipids metabolism of liver by regulating the activity of a key transcription factor of lipids metabolism of hepatic cells.

Key words: methionine, homocysteine, liver, lipids metabolism