Effects Of Honeysckle Extract On The Lipid Metabolism And Gut Microbiota Of Grass Carp(Ctenopharyngodon Idella)

Grass carp(Ctenopharyngodon idella)has the hightest yield in freshwater aquaculture in China,with fast growing speed,wide feed source,delicious quality and many other excellent characteristics.However,highly susceptible to metabolic related diseases in intensive farming model due to low fat utilization and poor premunition have inhabited the development.Therefore,it is very important to regulate the glycolipid metabolic function and improve the health level of animals through nutrition measures.As a Chinese herbal feed additive,Lonicera japonica Thunb(Honeysuckle,HE)has already been proved having many biofunctions on mammal,such as improving animal metabolism and enhancing immunity.However,the effects on growth,lipid metabolism and gut microbiota on fish are not clear until now.In this experiment,450 tails grass carp(initial weight 54.95±3.80 g)were selected,and divided into 5 processing groups(3 replicates in each group and 30 fish in each replicate).Five different experimental feeds were formulated by adding 0%(NC,normal control),0.25%(LHE),0.5%(MHE),1%(HHE)honeysuckle extract and 1% of ginseng(Panax ginseng C.A.Mey)extract(GSE,positive control)into the basic diet.8 weeks feeding experiment later,the growth performance,liver fat content,serum biochemical indexes,organization form,lipid metabolism related genes mRNA expression,SCFAs content,midintestinal digestive enzyme activity and structure and diversity of gut microbiota were detected.Then Sperman correlation analysis of these data was carried out.1.Effects of honeysuckle extract on growth performance,lipid content and serum biochemical indexes of grass carp(Ctenopharyngodon idella).Compared with NC group,the survival rate(SR)in LHE,MHE and HHE group was significantly improved(P < 0.05)and a significant decrease of hepatosomatic index(HSI),TC content and hepatopancreas fat content(HFC)in MHE and HHE group(P < 0.05)was detected.However,the weight gain rate(WGR),feed coefficient(FCR),specific growth rate(SGR),Viscerosomatic index(VSI),condition factor(CF)showed no significant difference(P > 0.05).Also,no significant differences were observed on serum CHE,HDL-C,TP and ALB(P > 0.05).But HDL-C was significantly increased and TG was significantly reduced in LHE,MHE and HHE group(P < 0.05).2.Effects of honeysuckle extract on organizational form of hepatopancreas and midintestine,digestive enzyme activity and SCFAs content of grass carp(Ctenopharyngodon idella).Compared with the NC group,the cells size in the liver of MHE and HHE group were normal.Less vacuolar degeneration and number of lipid droplets were observed in these groups as well.With the increasing of adding concentration,the villous height and muscular thickness had a gradually upward tendency,and the intestinal integrity was improved.Moreover,the midintestinal trypsin and lipase activity were all significantly increased by adding honeysuckle extract(P < 0.05),although the amylase activity was not observed(P > 0.05).Furthermore,total SCFAs(T-SCFAs)content in LHE,MHE and HHE group was significantly increased(P < 0.05).3.Effects of honeysuckle extract on the mRNA relative expression of lipid metabolism related gene of grass carp(Ctenopharyngodon idella).The mRNA expression level of genes(fas,srebp1,acc1 and pparγ)related to lipogenesis metabolism in MHE and HHE group were mostly found significantly down-regulated(P < 0.05).Genes related to lipolysis in MHE and HHE group,such as cpt1,lpl,atgl and pparα were also found up-regulated.(P < 0.05).Besides,the relative expression of claudin-3 and occludin mRNA relative expression in MHE and HHE group was significantly up-regulated compared with NC group(P < 0.05),but keeping the same tendency with GSE group.However,zo-1 mRNA relative expression had no significant change(P > 0.05).4.Effects of honeysuckle extract on gut microbiota structure and diversity of grass carp(Ctenopharyngodon idella).The intestinal microbiota in grass carp were found significantly changed after adding 0.5% and 1% honeysuckle extract.The proportion of Firmicutes were detected significantly enhanced in MHE and HHE group,but the proportion of Proteobacteria and Fusobacteria were detected decreased.Also,a number of probiotic bacteria,such as Lactobacillus and Fructobacillus,increased sharply in MHE,HHE group(P < 0.05),while Aeromonas,Vibrio and other opportunistic pathogenic bacteria were found significantly reduced(P < 0.05).According to the spearman correlation analysis,an obviously negative correlation between Lactobacillus or other probiotic bacteria abundance with hepatopancreas fat content,blood lipid level and relative expression of lipogenesis related genes were detected(P < 0.05).Moreover,Aeromonas,Vibrio and some other opportunistic pathogenic bacteria were found positively correlated with these lipogenesis indexes(P < 0.05).In conclusion,honeysuckle extract displayed a good effect on hepatopancreas and intestinal barrier function protecting,lipid-lowering,and SCFAs producing.Also,the diversity and richness of gut microbiota were changed following adding honeysuckle extract,including increasing the number of probiotic bacteria and restraining potential harmful bacteria proliferation.In addition,the molecular mechanism of honeysuckle might act by regulating the structure of the intestinal microbiota.