皇竹草对草鱼脂肪蓄积及肠道菌群组成的影响

Effects of Pennisetum sinese Roxb meal on fat accumulation and intestinal microbiota composition of juvenile grass carp (Ctenopharyngodon idella)

为探讨皇竹草(Pennisetum sinese Roxb)对草鱼(Ctenopharyngodon idella)脂肪蓄积和肠道菌群组成的影响,配制3组分别含0(对照组)、10%和20%皇竹草粉的等氮等能纯化饲料(蛋白质水平33%,脂肪水平8%),饲喂草鱼稚鱼[(28.51±0.04)g] 8周,每组饲料饲喂3个重复。结果显示,饲料中添加10%和20%皇竹草粉能显著降低腹腔脂肪指数。相比对照组,皇竹草粉组的草鱼肝脏脂滴数量均明显减少,脂肪细胞大小明显变小。血清中的甘油三酯(TG)、总胆固醇(TC)和游离脂肪酸(NEFA)的含量随着皇竹草粉水平的升高呈下降趋势,其中20%添加水平相比对照组草鱼显著降低。皇竹草粉组肝脏中的TG、TC和NEFA的含量均显著下降。肝脏和腹腔脂肪组织中过氧化物酶体增殖物激活受体γ(pparγ)等脂肪生成相关5个基因在摄食皇竹草粉后显著下调,pparα等4个脂肪分解相关基因在摄食皇竹草粉后显著上调,肝脏组织中法尼酯X受体(fxr)基因在摄食皇竹草粉后显著上调。微生物宏基因组学结果显示,10%和20%皇竹草粉组草鱼肠道内容物中肠道微生物的Ace、chao1、Shannon和Simpson指数均与对照组差异显著,表明皇竹草粉提高了草鱼肠道内菌群种类的丰度和多样性。从门分类来看,与脂肪蓄积相关菌群厚壁菌门(Firmicutes)的比例在皇竹草组中显著降低,拟杆菌门(Bacteroidetes)比例呈上升趋势。饲料中添加一定量的皇竹草粉可降低草鱼体脂蓄积,推测肠道菌群的改善是这一过程中的重要环节。

In order to evaluate the effects of dietary Pennisetum sinese Roxb meal on the fat accumulation and intestinal microbiota composition of juvenile grass carp(Ctenopharyngodon idella),three isonitrogenous and isoenergetic purified diets containing 0%(control group),10% and 20% Pennisetum sinese Roxb meal were designed(protein level 33%,fat level 8%),and fed juveniles grass carp [(28.51± 0.04) g] for 8 weeks.Each diet was randomly assigned into triplicate tanks.The results showed that fish fed 10% and 20% pennisetum sinese Roxb meal significantly reduced their abdominal fat index.The microstructure of the tissue section showed the hepatic lipid droplets number and the adipocyte size in the Pennisetum sinese Roxb meal group were reduced compared with the control group.Serum levels of triglycerides(TG),total cholesterol(TC) and non-esterified fatty acids(NEFA) showed a downward trend with the Pennisetum sinese Roxb meal content increasing,and the 20% group had significantly lower values than the control group.The hepatic content of TG,TC,and NEFA were significantly decreased in the Pennisetum sinese Roxb meal supplemented groups.Five lipogenic genes including peroxisome proliferator-activated receptor γ(pparγ) in the liver and abdominal adipose tissue were significantly down-regulated after the fish consuming Pennisetum sinese Roxb meal.Peroxisome proliferator-activated receptor-α(pparα) and other three lipid catabolic genes were significantly up-regulated after the fish fed on the Pennisetum sinese Roxb meal-supplemented diets.The expression of farnesoid X receptor(fxr) gene in the liver was significantly up-regulated in fish feeding Pennisetum sinese Roxb meal.The metagenomics results of the intestinal flora showed the Ace,chao1,Shannon,and Simpson indexes of the intestinal microbiota of grass carp in the 10% and 20% Pennisetum sinese Roxb meal groups were significantly different from those in the control group,indicating dietary Pennisetum sinese Roxb meal increased the abundance and diversity of the intestinal flora of grass carp.From the perspective of phylum classification,the proportion of Firmicutes was significantly lowered in the Pennisetum sinese Roxb meal groups,whereas the proportion of Bacteroides showed an upward trend,and these two bacteria are reported to be associated with fat accumulation in mammals.The results demonstrate that Pennisetum sinese Roxb meal could reduce body fat accumulation,possibly via the improvement of intestinal flora composition in juvenile grass carp.