Effects Of Dietary Myo-inositol On Growth Performance,Intestinal Health,Body Health,Gill Health And Flesh Quality,as Well As The Mechanisms In Young Grass Carp(Ctenopharyngodon Idella)

The aim of this study was to investigate the effects of myo-inositol on the growth performance,intestinal health,body health,gill health and flesh quality,as well as the mechanisms in young grass carp(Ctenopharyngodon idella).A total of 540 healthy young grass carp(initial weight 221.83±0.84 g)were randomly divided into 6 treatment groups with 3 replicates for each group.Grass carp were fed six diets containing graded myo-inositol levels of(27.0,137.9,286.8,438.6,587.7 and 737.3 mg/kg)for 10 weeks,to investigate the effects of myo-inositol on growth performance and flesh quality of grass carp.At the end of the growth trail,fish were challenged with Aeromonas hydrophila for 14 days to investigate the effects of myo-inositol on intestinal health and body health,as well as the potential mechanisms of fish.Meanwhile,fish were selected for the infection of Flavobacterium columnare for 3 days to investigate the effects of myo-inositol on gill health as well as the potential mechanisms in fish.Under this experimental condition,we found that:optimal dietary myo-inositol(286.8 mg/kg)increased the percentage weight gain(PWG),specific growth rate(SGR),feed intake(FI)and feed efficiency(FE)of young grass carp(P<0.05).Meanwhile,optimal myo-inositol increased the protein,lipid,flavor amino acids and PUFA)contents(P<0.05),decreased lactate content,and cathepsin B and L activities(P<0.05),suggesting that optimal myo-inositol could increase fish flesh quality.However,we found that myo-inositol had no effect on pH value,shear force and cooking lose(P>0.05).Meanwhile,the optimal myo-inositol significantly increased the ability of defensing against enteritis,skin lesion and gill rot disease in young grass carp,which might be associated with the imporment of intestinal health,body health and gill health.Further research found that:(1)the optimal myo-inositol significantly decreased reactive oxygen species(ROS),malondialdehyde(MDA)and protein carbonyl(PC)contents(P<0.05);increased the activities of anti-hydroxyl radical(AHR),anti-superoxide anion(ASA),copper-zinc superoxide dismutase(CuZnSOD),manganese superoxide dismutase(MnSOD),glutathione peroxidase(GPx),catalase(CAT),glutathione transferase(GST)and glutathione reductase(GR),and the content of glutathione(GSH)(P<0.05);up-regulated the mRNA levels of CuZnSOD,MnSOD,CAT,GPxla,GPxlb,GPx4a,GPx4b,GSTP1(not intestine),GSTP2(not intestine),GSTO1,GST02,GR as well as signaling molecule Nrf2,and down-regulated Keap1 and Keaplb mRNA levels(P<0.05),suggesting that myo-inositol could enhance the capacity of against oxidative damage and reduce the oxidative damage in intestines,head kidneys,spleen,skin and gills in young grass carp.(2)Meanwhile,the optimal myo-inositol significantly up-regulated the mRNA levels of B-cell lymphoma protein-2(Bcl-2),inhibitor of apoptosis proteins(IAP)and myeloid cell leukemia-1(Mcl-1)(P<0.05),whereas down-regulated the mRNA levels of cysteinyl aspartic acid-protease(caspase-2/-/3/-7/-8-9),apoptotic protease activating factor-1(Apaf-1)and Bcl-2 associated X protein(Bax)(P<0.05),fatty acid synthetase ligand(FasL),c-Jun N-terminal kinase(JNK)and p38 mitogen activated protein kinase(p38MAPK),suggesting that myo-inositol could reduce the extent of apoptosis in intestines,head kidneys,spleen,skin and gills in young grass carp.(3)Besides,the optimal myo-inositol up-regulated the mRNA levels of cyclins(cyclin B,cyclin D and cyclin E)as well as E2F4(P<0.05),suggesting that myo-inositol could promote proliferation in the intestine and gill of grass carp.(4)Furthermore,the optimal myo-inositol up-regulated the mRNA levels of zo-1,zo-2,occludin,claudin-b,claudin-c,claudin-f,claudin-3c,claudin-7a,claudin-7b and claudin-11,whereas down-regulated claudin-12,claudin-15a,claudin-15b(not intestine)and myosin light chain kinase(MLCK)(P<0.05),suggesting that myo-inositol could improve the structural integrity and enhance the physical barrier function in the intestines,head kidney,spleen,skin and gills of grass carp.(5)Finally,the optimal myo-inositol enhance immune function in intestines,head kidney,spleen,skin and gills of grass carp:? increased lysozyme(LZ)and acid phosphatase(ACP)activities,and complement 3(C3),C4 and immunoglobulin M(IgM)contents(P<0.05)and up-regulated the mRNA levels of liver-expressed antimicrobial peptide 2(LEAP-2A),LEAP-2B,hepcidin,p-defensin-1 and mucin2(P<0.05),suggesting that myo-inositol could increase antibacterial capacity in intestines,head kidney,spleen,skin and gills of grass carp.? down-regulated the mRNA levels of pro-inflammatory cytokines IL-1p(not distal intestine),tumor necrosis factor ?(TNF-?),IL-6(not intestine),IL-8,IL-12p40(not intestine)and IL-17D(not intestine)(P<0.05),but had no effect on the mRNA levels of IFN-y2(P>0.05);up-regulated the mRNA levels of anti-inflammatory IL-10(not in DI),IL-11,IL-4/13A(not in intestine),IL-4/13B(not in the spleen),transforming growth factor?1(TGF-?1)and TGF-(32(not in gill)(P<0.05);down-regulated the mRNA levels of pro-inflammatory signaling molecules nuclear factor-KB p65(NF-?B p65),I?B kinase a(IKK?),IKK? and 1KK?(P<0.05);up-regulated the mRNA levels of anti-inflammatory signaling molecules inhibitor of ?B?(I?B?),target of rapamycin(TOR)and ribosomal S6 protein kinasel(S6K1)(P<0.05),suggesting that myo-inositol could reduce inflammation in grass carp.In summary,myo-inositol could improve the growth performance and disease resistance of grass carp.The ability of disease resistance is related to the health statu of intestine,body and gill health in grass carp.Myo-inositol could increase antioxidant capacity by up-regulating the gene expression of antioxidant enzyme and improving the activity of antioxidant enzymes in the intestine,head head kidney,spleen,skin and gill of grass carp;myo-inositol could suppress excessive apoptosis by inhibiting the JNK mitochondrial apoptotic pathway and the p38MAPK death receptor pathway in the intestine,head head kidney,spleen,skin and gill of grass carp;myo-inositol could up-regulate the gene expression of cyclin B,cyclin D,cyclin E,and E2F4 in gill and intestine,and promote cell proliferation of grass carp;myo-inositol could improve intercellular structure integrity by regulating the gene expression of tight junction in the intestine,head head kidney,spleen,skin and gill of grass carp.Under this experimental condition,based on the the growth performance(PWG),disease resistance(enteritis,skin lesion and gill rot),the myo-inositol requirements for grass carp(221.8-792.9g)were estimated to be 276.7,408.8,353.8 and 285.8 mg/kg diet,respectively.