不同膳食脂肪酸对大鼠肝脏SREBP-1c基因表达和非酒精性脂肪肝发生的影响

Effects of dietary fatty acids on expression of gene sterol-regulatory elementary binding protein-1c and occurrence of non-alcoholic fatty liver disease in rats

目的探讨不同膳食脂肪酸构成对非酒精性脂肪肝(nonalcoholic fatty liver disease,NAFLD)发生、发展的影响及其与固醇调节元件结合蛋白-1c(SREBP-1c)的关系。方法 100只成年SD大鼠,按随机数字表法分为5组:对照组、NAFLD模型组、单不饱和脂肪酸组(monounsaturated fatty acid,MUFA)、n-6多不饱和脂肪酸组(n-6 polyunsaturated fatty acids,n-6 PUFA)和4∶1 n-6/n-3 PUFA组,每组20只。对照组用基础饲料喂养,其余各组饲料中加1%胆固醇和10%不同油脂(分别是10%猪油、10%橄榄油、10%玉米油、8%玉米油+2%鱼油)。分别于第8、16周时,采用HE染色观察肝脏脂肪变性情况,测定血清和肝脏中脂质含量,采用实时定量PCR分析SREBP-1c、FAS mRNA表达,Western blot检测SREBP-1c、FAS的蛋白表达。结果 NAFLD模型组大鼠体质量显著高于对照组和其他膳食脂肪酸组(P<0.05),模型组、MUFA组大鼠肝脏中TG含量显著高于对照组(P<0.05),而n-6 PUFA组和4∶1n-6/n-3 PUFA组大鼠血清中TG及肝脏中TC、TG浓度显著低于模型组(P<0.05);HE染色后,NAS量化评分显示模型组大鼠肝脏脂肪变性程度较对照组、MUFA组、n-6 PUFA组、4∶1 n-6/n-3 PUFA组严重;与对照组比较,NAFLD模型组大鼠肝脏SREBP-1c与FAS mRNA表达升高,MUFA组、n-6 PUFA组和4∶1 n-6/n-3 PUFA组SREBP-1c蛋白表达降低(P<0.05)。结论降低膳食中饱和脂肪酸,增加不饱和脂肪酸(尤其是适当比例的n-6/n-3 PUFA)可下调高脂喂养大鼠肝内SREBP-1c的表达,延缓高脂膳食引起的NAFLD发生、发展。

Objective To investigate the effects of dietary fatty acids on the development and progression of non-alcoholic fatty liver disease （ NAFLD ） and the correlation with the expression of sterol regulatory element binding protein-1 c （SREBP-1 c）. Methods A total of 100 SD rats were randomly divided into 5 groups with different diets ： control group （ standard-chow diet）, NAFLD model group （ standard-chow diet with 10% lard and 1% cholesterol）, mono-unsaturated fatty acid （MUFA） group （standard-chow diet with 10% olive oil and 1% cholesterol）, n-6 poly-unsaturated fatty acid （n-6 PUFA） group （standard-chow diet with 10% corn oil and 1% cholesterol） , and 4：1 n-6/n-3 poly-unsaturated fatty acid （4：1 n-6/n-3 PUFA） group （standard-chow diet with 8% corn oil, 2% fish oil and 1% cholesterol）. Each group had 20 rats. The hepatic steatosis was observed by hematoxylin and eosin （HE） staining after feeding for 8 and 16 weeks. The concentrations of total cholesterol （TC） and triglyceride （TG） in serum and liver were measured. The mRNA levels of SREBP-lc and FAS were measured by quantitative real-time PCR, and their protein levels by Western blotting. Results In NAFLD model group, the body mass of rats were significantly higher than that in control group and other groups （ P 〈 0.05 ）. The TG level in the liver was significantly higher in NAFLD model group and MUFA group than that in control group （P 〈 0.05 ）, but TG levels in the serum, and TC and TG levels in the liver in both n-6 PUFA group and 4：1 n-6/n-3PUFA group were significantly lower than those in NAFLD model group （ P 〈 0.05 ）. HE staining showed that the fatty degeneration in NAFLD model group was more severe than in control group, MUFA group, n-6 PUFA group and 4：1 n-6/n-3 PUFA group. Compared to the control group, the expression levels of SREBP-1c and FAS were significantly higher in NAFLD model group, and the protein expression of SREBP-1 c was significantly lower in MUFA group, n-6 PUFA group and 4：1 n-6/n-3 PUFA group. Conclusion Increasing the amount of n-3 PUFA, particularly in a 4 ： 1 ratio of n-6 PUFA to n-3 PUFA, and decreasing saturated fatty acid may prevent the occurrence and development of NAFLD in high-fat fed rats, which is partly modulated by down-regulation of SREBP-1 c.