| Spermine is a ubiquitous cellular component with numerous biological functions.Scientific evidences have indicated that spermine could maintain the health of young animals by accelerating gut development and maturation.Nevertheless,no information is available concerning the effects of spermine supplementation and its prolonged administration on the health status of the thymus and spleen in piglets.Considering these observations,this work was aimed to investigate the changes of metabolite,antioxidant status,immune function and related signalling molecules in the thymus and spleen of piglet fed diets with or without spermine.2(spermine;0 or 0.4 mmol/kg BW)X 4(supplemented time;7 h or 3,6 or 7 days)factorial experimental design was employed in the current study.Eighty 12-day-old piglets(Duroc X Landrace X Yorkshire)with initial body weights(BWs)of 3.27-3.33 kg obtained from 10 healthy multiparous sows with the same litter size(eight piglets/litter).All piglets were randomly distributed into eight experimental groups and every group is one treatment.Match-restricted intake was used in this experiment.In brief,the spermine-treated suckling piglets were supplied with sufficient nutrient intake,and other corresponding control groups of the piglets were supplied the same amount of nutrient ingestion.Thus,the spermine-supplemented piglets were given free access to milk-based spermine(0.4 mmol kg-1 BW)for 7 h or 3,6 or 9 days,and matched-control piglets were supplied the same quantity of formula milk given to the spermine-treated piglets with physiological saline once a day for 7 h or 3,6 or 9 days.Results are as follows:1)Antioxidant status:Irrespective of supplementation period,spermine ingestion improved glutathione(GSH)content(+10.79%and+18.20%),total antioxidant capacity(T-AOC)(+12.22%and +26.97%),anti-superoxide anion(ASA)capacity(+16.14%and +25.35%),anti-hydroxyl radical(AHR)activity(+15.91%and +23.77%),catalase(CAT)activity(+15.47%and+60.06%),total superoxide dismutase(T-SOD)activity(+8.88%and +21.03%),glutathion peroxidase(GPx)activity(+15.13%and +24.05%)and glutathion-S-transferase(GST)activity(+26.98%and +57.04%),but decreased malonaldehyde(MDA)content(-12.90%and-7.53%)and protein carbonyl(PC)level(-13.39%and-14.92%)in the thymus and spleen(P<0.05),respectively.Further RT-PCR analysis showed that spermine intake could up-regulated SOD1,GPxl,CAT,glutathione reductase(GR)and NF-E2-related factor 2(Nrf2)mRNA levels(P<0.05)and down-regulated Kelch-like ECH-associated protein 1(Keapl)gene expression in the thymus and spleen(P<0.05),and improved GST gene expression of the thymus(P<0.05),but did not influence GST mRNA level of the spleen(P>0.05).Extended spermine supplementation also markedly increased GSH content and the activities of ASA,GST,T-AOC,CAT,T-SOD and GPx(P<0.05),in contrast,reduced MDA content and PC level in the thymus and spleen of piglets(P<0.05).AHR activity of the spleen was significantly improved(P<0.05),however,no significant differences were observed in the thymus between spermine-supplemented time periods(P>0.05).Additionally,extended spermine administration enhanced GPxl,CAT,SOD1,GR and Nrf2 gene transcripts and reduced Keap1 mRNA expression of the thymus and spleen(P<0.05),and increased the gene expression of GST in the thymus(P<0.05),but had no significant effect on GST mRNA level of the spleen(P>0.05).Notably,the spermine-supplemented time for the optimal effects of antioxidant status in immune organs of piglet was determined to be 6 days.2)Immune status:Regardless of treatment time,in the thymus and spleen,mRNA expressions of tumor necrosis factor a(TNF-a),interleukin 1β(IL-1β),interleukin 2(IL-2),interleukin 6(IL-6),interleukin 12(IL-12),interferon y(IFNy),inducible nitric oxide synthase(iNOS),cluster of differentiation 8(CD8)and integrin beta-2(CD18)were lower(P<0.05),by contrast,immune globulin M(IgM),transforming growth factor β1(TGF-β1)and interleukin 10(IL-10)gene transcripts(P<0.05)were higher in spermine supplementation than those in the control groups.We also observed that dietary spermine supplementation significantly reduced interleukin 8(IL-8)mRNA expression in the spleen and lymphocyte function-associated antigen 1(LFA-1)gene expression in the thymus(P<0.05),but did not affect LFA-1 mRNA level of the spleen and IL-8 gene expression of the thymus in piglets(P>0.05).Furthermore,dietary supplementation with spermine could change gene expression of signaling molecules associated with immune pathways.Dietary spermine administration significantly down-regulated signal transducer and activator of transcription 3(STAT3),Janus kinase 2(JAK2),nuclear factor-kappa B P65(NF-κB P65)and eukaryotic IF4E-binding protein 1(4EBP1)mRNA expressions(P<0.05),in contrast,markedly up-regulated mammalian target of rapamycin(mTOR)and ribosomal protein S6 kinase 1(S6K1)gene expressions of the thymus and spleen in piglets(P<0.05).Extended spermine supplementation also markedly down-regulated TNF-a,IL-1β,IL-2,IL-6,IL-12,IFNy,CD8 and CD18 mRNA levels(P<0.05),in contrast,up-regulated IgM,IL-10 and TGF-β1 gene expressions of the thymus and spleen(P<0.05).Gene expression of LFA-1 in the thymus and IL-8 mRNA level in the spleen were significantly decreased(P<0.05),but no significant differences were observed in IL-8 gene expression of the thymus and LFA-1 mRNA level of the spleen between spermine-supplemented time periods(P>0.05).Moreover,extended spermine intake significantly improved the gene expressions of mTOR and S6K1(P<0.05),but decreased JAK2,4EBP1,STAT3 and NF-κB P65 mRNA expressions(P<0.05)in the thymus and spleen.Remarkably,the spermine-supplemented time for the optimal effects of immune function in immune organs of piglet was determined to be 6 days.3)Nutrition metabolism:Spermine supplementation significantly reduced the levels of aspartic acid and isocytosine in the thymus(P<0.05),and decreased the levels of formate scvllo-inositol and glycerophosphocholine in the spleen(P<0.05).Taken together,dietary supplementation with spermine can improve the antioxidant status of thymus and spleen by mitigating lipid and protein oxidative damage,increasing free radical scavenging ability,promoting non-enzymatic and enzymatic antioxidant defense system,and regulating the mRNA levels of signaling molecules associated with antioxidant pathways.Additionally,spermine administration can enhance immune status of thymus and spleen,as evidenced by the enhanced humoral immunity and cellular immunity,and decreased inflammatory response by regulating the gene expressions of signaling molecules related to immune pathways.Spermine supplementation also can regulate nutrition metabolism process of the body by affecting some common systemic metabolic processes.Importantly,based on the results of antioxidant status and immune function,the spermine-supplemented time for the optimal roles of immune organs in piglet was determined to be 6 days. |
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