中链三酰甘油对高脂饮食大鼠血脂及心肌瘦素表达的影响

The effect of medium chain triglyceride on blood lipid and expression of leptin in myocardium of rats fed with high fat diet

目的 探讨高脂膳食中富含中链三酰甘油（MCT）对大鼠血脂及心肌组织瘦素水平的影响.方法 选择4周龄SD雄性大鼠32只,按随机数字表法分为为对照组〔n=8,给予按美国营养学会（AIN93）标准配制的普通饲料〕、普通高脂饲料组〔HFD组（n=16）,给予23%猪油＋5%玉米油〕、MCT组（n=8,给予23%MCT＋5%玉米油）,饲养8周后,将HFD组再按随机数字表法分为两组,每组8只,一组继续给予普通高脂饲料喂养,另一组（HFD＋MCT组）换为MCT高脂饲料,继续喂养8周.每周观察大鼠进食量和体质量的变化,16周后采集大鼠尾静脉血测定血清三酰甘油（TG）、总胆固醇（TC）、低密度脂蛋白胆固醇（LDL-C）、高密度脂蛋白胆固醇（HDL-C）水平;用半定量反转录-聚合酶链反应（RT-PCR）测定大鼠心肌组织瘦素mRNA表达;用酶联免疫吸附试验（ELISA）测定心肌组织和血清瘦素含量.结果 与对照组比较,各高脂饲料组每日进食量比较差异均无统计学意义（均P〉0.05）,HFD组、MCT组、HFD＋MCT组最终体质量、血脂水平、心肌组织瘦素mRNA表达水平、心肌瘦素和血清瘦素含量均明显增加,以HFD组增加最明显〔体质量（g）：395±13比326±10,TG（mmol/L）：2.01±0.06比1.46±0.07,TC（mmol/L）：2.67±0.12比1.62±0.06,LDL-C（mmol/L）：1.72±0.12比1.10±0.07,HDL-C（mmol/L）：2.07±0.03比1.56±0.05,mRNA表达（灰度值）：0.357±0.023比0.202±0.004,心肌瘦素（pg/mg）：19.30±2.81比11.50±1.40,血清瘦素（μg/L）：14.63±4.50比8.21±2.98,均P〈0.05〕,MCT组增加最少〔分别为（363±9）g、（1.65±0.07）mmol/L、（2.30±0.06）mmol/L、（1.38±0.05）mmol/L、（1.85±0.04）mmol/L、0.255±0.005、（14.44±1.87）pg/mg、（10.56±2.20）μg/L〕.结论 高脂膳食能显著升高大鼠体质量、血脂水平和心肌、血清瘦素的含量,而MCT能一定程度上缓解高脂饮食造成的上述影响,具有潜在的心血管保护作用.

Objective To investigate the effects of medium-chain triglyceride （MCT） on levels of blood lipids and leptin in myocardium tissue.Methods Thirty-two male Sprague-Dawley （SD） rats aged 4 weeks were divided into control group [n = 8, given normal diet prepared by American Nutrition Society （AIN93）], common high fat diet group [HFD group （n = 16）, given 23% lard＋ 5% corn oil], MCT group （n = 8, given 23% MCT＋ 5% corn oil） by random number table, after 8 weeks of feeding, the HFD group was further randomly subdivided into HFD group fed with diet as before and （HFD＋ MCT） group whose diet was replaced bythe diet in MCT group, each subgroup 8 rats, and all the rats continued to be fed for further 8 weeks. The rats＇ diet intake and the changes of their body weight were observed weekly. After total 16 weeks, the rat tail venous blood was collected, the levels of triglycerides （TG）, total cholesterol （TC）, low density lipoprotein cholesterol （LDL-C） and high density lipoprotein cholesterol （HDL-C） in serum were measured; The expression of leptin mRNA in rat myocardium was measured by semi-quantitative reverse transcription-polymerase chain reaction （RT-PCR）, and the contents of leptin in myocardium tissue and serum were measured by enzyme-linked immunosorbent assay （ELISA）.Results Compared with the control group, the difference in daily food intake quantity of any one of the high fat diet groups was not statistically significant （allP 〉 0.05）; the final body weight, blood lipid level , the level of leptin mRNA expression in myocardium, contents of leptin in myocardium and serum in the HFD, MCT, and HFD＋ MCT groups were all significantly higher, the increase was the most pronounced in the HFD group [body weight （g）： 395±13 vs. 326±10, TG （mmol/L）： 2.01±0.06 vs. 1.46±0.07, TC （mmol/L）： 2.67±0.12 vs. 1.62±0.06, LDL-C （mmol/L）： 1.72±0.12 vs. 1.10±0.07, HDL-C （mmol/L）： 2.07±0.03 vs. 1.56±0.05, mRNA espression （gray value）： 0.357±0.023 vs. 0.202±0.004, leptin in myocardium （pg/mg）： 19.30±2.81 vs. 11.50±1.40, leptin in serum （μg/L）： 14.63±4.50 vs. 8.21±2.98, allP 〈 0.05], and the least increase was in the MCT group [respectively was （363±9） g, （1.65±0.07） mmol/L, （2.30±0.06） mmol/L, （1.38±0.05） mmol/L, （1.85±0.04） mmol/L, 0.255±0.005 （gray value）, （14.44±1.87） pg/mg, （10.56±2.20）μg/L].Conclusion The high fat diet can significantly increase the body weight, blood lipid level and the contents of leptin in rat myocardium and serum, and MCT can alleviate the above effects of high fat diet to a certain degree, thus it has the potential of cardiovascular protection.