谷物膳食纤维对高胆固醇饮食小鼠脂质代谢及肠道菌群的影响

本研究旨在探讨谷物膳食纤维(DF)对高胆固醇饮食小鼠的脂质代谢和肠道菌群的影响。选取C57BL/6J小鼠30只,并根据体重随机分为4组,分别饲喂基础饲粮(对照,CO组,n=8)、基础饲粮+5 g/kg DF(CO+DF组,n=8)、高脂高胆固醇饲粮(HF组,n=7)及高脂高胆固醇饲粮+5 g/kg DF(HF+DF组,n=7)。试验期8周,测定各组小鼠生长性能、血清和肝脏生化指标、粪便总胆固醇(TC)、短链脂肪酸(SCFA)、相关肝脏胆固醇和胆汁酸(BA)蛋白表达及肠道菌群。结果表明:1)CO+DF组的最终体重显著低于CO组(P<0.05),与HF组相比,CO组和HF+DF组的4周和最终体重均显著降低(P<0.05),肝脏和脂肪的重量显著减少(P<0.05)。且与HF组相比,DF+HF组摄食效率显著降低(P<0.05)。2)CO+DF组血清TC、甘油三酯(TG)含量及天冬氨酸转氨酶(AST)和丙氨酸转氨酶(ALT)活性以及肝脏TC和TG含量显著低于CO组(P<0.05),CO组和HF+DF组显著低于HF组(P<0.05),粪便TC含量仅在HF+DF组显著低于HF组(P<0.05)。3)DF对肝脏胆固醇调节元件结合蛋白-2(SREBP-2)、3-羟基-3-甲基戊二酰辅酶A还原酶(HMGR)、肝脏X受体α(LXRα)、微管相关蛋白1轻链3-Ⅰ(LC3-Ⅰ)和微管相关蛋白1轻链3-Ⅱ(LC3-Ⅱ)蛋白表达没有显著影响(P>0.05)。CO+DF组肝脏胆固醇7-羟化酶(Cyp7a1)的蛋白表达水平显着低于CO组(P<0.05),但HF组和HF+DF组之间没有显著差异(P>0.05)。4)HF+DF组的粪便总SCFA和丙酸盐含量显著高于HF组(P<0.05)。与相应的对照组相比,CO+DF组和HF+DF组的粪便丁酸盐含量显著增加(P<0.05)。5)在门水平上,DF组厚壁菌门(Firmicutes)相对丰度减少,HF+DF组的拟杆菌门(Bacteroidetes)相对丰度高于HF组。梭状芽孢杆菌属ⅪⅤa(ClostridiumⅪⅤ)相对丰度在CO+DF组和HF+DF组显著增加(P<0.05)。此外,与其他组相比,仅HF+DF组中阿克曼菌属(Akkermansia)相对丰度显著增加(P<0.05)。由此可见,每千克饲粮添加5 g DF可降低饲喂含脂45%饲粮小鼠的体重和肝脏脂肪含量,降低血清TC、TG含量及AST和ALT活性以及肝脏TC和TG含量,降低胆固醇合成相关蛋白Cyp7a1的表达水平,提高总SCFA含量及肠道有益菌群和优势菌群相对丰度。

Effects of Grain Dietary Fiber on Lipid Metabolism and Intestinal Microflora in Mice with High Cholesterol Diet

The purpose of this study was to investigate the effects of grain dietary fiber(DF)on lipid metabolism and intestinal flora in mice with high cholesterol diet.Thirty C57BL/6J mice were selected and randomly divided into four groups according to body weight.They were fed a basal diet(CO group,n=8)and the basal diet+5 g/kg DF(CO+DF group,n=8),high fat and high cholesterol diet(HF group,n=7)and the high fat and high cholesterol diet+5 g/kg DF diet(HF+DF group,n=7).The experiment period was 8 weeks,and the growth performance,serum and liver biochemical indicators,the contents of fecal total cholesterol(TC),short-chain fatty acid(SCFA),related liver cholesterol and bile acid(BA)protein expression and intestinal flora of each group were measured.The results showed as follows:1)the final body weight in the CO+DF group was significantly lower than that in the CO group(P<0.05).Compared with the HF group,the CO group and the HF+DF group had significant reductions in body weight at 4 weeks and final(P<0.05),and the weights of liver and fat were significantly reduced(P<0.05).Compared with the HF group,the feeding efficiency in DF+HF group significantly reduced(P<0.05).2)The contents of TC,triglyceride(TG),the activities of aspartate aminotransferase(AST)and alanine aminotransferase(ALT)in serum and the contents of TC and TG in liver in CO+DF group were significantly lower than those in CO group(P<0.05),CO group and HF+DF group were significantly lower than HF group(P<0.05),fecal TC content in HF+DF group was significantly lower than that in the HF group(P<0.05).3)DF did not affect the protein expression of sterol regulatory element binding protein-2(SREBP-2),3-hydroxy-3-methylglutaryl coenzyme A reductase(HMGR),liver X receptorα(LXRα),microtubule-associated protein 1 light chain 3(LC3-Ⅰ)and-Ⅱ(P>0.05).The expression level of cholesterol 7α-hydroxylase(Cyp7a1)in the CO+DF group was significantly lower than that in the CO group(P<0.05),but there was no significant difference between the HF and HF+DF groups(P>0.05).4)The fecal total SCFA and propionate contents in the HF+DF group were significantly higher than those in the HF group(P<0.05).Compared with the corresponding control group,the fecal butyrate content in the CO+DF and HF+DF groups increased significantly(P<0.05).5)At the phylum level,DF reduced Firmicutes relative abundance,and the relative abundance of Bacteroidetes in the HF+DF group was significantly higher than that in the HF group.The relative abundance of ClostridiumⅪⅤa was significantly increased in the CO+DF and HF+DF groups(P<0.05).In addition,compared to other groups,only the relative abundance of Akkermansia in the HF+DF group increased significantly(P<0.05).In conclusion,it’s shown that adding 5 g DF per kilogram of diet can reduce body weight and fat content of mice fed 45%fat diet,reduce the contents of TC and TG and the activities of AST and ALT in serum,the contents of TC and TG in liver,reduce the expression level of cholesterol synthesis-related protein Cyp7a1,and increase total SCFA content,intestinal beneficial flora and the relative abundance of dominant flora.