Effects of dietary supplementation with glutamate and aspartate on diquat-induced oxidative stress in piglets

Effects of Lysine deficiency and Lys-Lys dipeptide on cellular apoptosis and amino acids metabolism

SCOPE

Lysine (Lys) is a common limiting amino acids (AA) for humans and animals and plays an important role in cell proliferation and metabolism, while metabolism of Lys deficiency and its dipeptide is still obscure. Thus, this study mainly investigated the effects of Lys deficiency and Lys-Lys dipeptide on apoptosis and AA metabolism in vitro and in vivo models.

METHODS AND RESULTS

Lys deficiency induced cell-cycle arrest and apoptosis and upregulated Lys transporters in vitro and in vivo. SLC7A11, a cystine-glutamate antiporter, was markedly upregulated by Lys deficiency and then further mediated cystine uptake and glutamate release, which was negatively regulated by cystine and glutamate transporters. Meanwhile, Lys deprivation upregulated pept1 expression, which might improve Lys-Lys dipeptide absorption to compensate for the reduced Lys availability. Lys-Lys dipeptide alleviated Lys deficiency induced cell-cycle arrest and apoptosis and influenced AA metabolism. Furthermore, the mammalian target of rapamycin signal might be involved in sensing cellular Lys starvation and Lys-Lys dipeptide.

CONCLUSIONS

Altogether, these studies suggest that Lys deficiency impairs AA metabolism and causes apoptosis. Lys-Lys dipeptide serves as a Lys source and alleviates Lys deficiency induced cellular imbalance.

Arginine metabolism and its protective effects on intestinal health and functions in weaned piglets under oxidative stress induced by diquat

The intestine plays key roles in maintaining body arginine (Arg) homoeostasis. Meanwhile, the intestine is very susceptible to reactive oxygen species. In light of this, the study aimed to explore the effects of Arg supplementation on intestinal morphology, Arg transporters and metabolism, and the potential protective mechanism of Arg supplementation in piglets under oxidative stress. A total of thirty-six weaned piglets were randomly allocated to six groups with six replicates and fed a base diet (0·95 % Arg,) or base diet supplemented with 0·8 % and 1·6 % l-Arg for 1 week, respectively. Subsequently, a challenge test was conducted by intraperitoneal injection of diquat, an initiator of radical production, or sterile saline. The whole trial lasted 11 d. The diquat challenge significantly decreased plasma Arg concentration at 6 h after injection (P<0·05), lowered villus height in the jejunum and ileum (P<0·05) as well as villus width and crypt depth in the duodenum, jejunum and ileum (P<0·05). Oxidative stress significantly increased cationic amino acid transporter (CAT)-1, CAT-2 and CAT-3, mRNA levels (P<0·05), decreased arginase II (ARGII) and inducible nitric oxide synthase mRNA levels, and increased TNF- α mRNA level in the jejunum (P<0·05). Supplementation with Arg significantly decreased crypt depth (P<0·05), suppressed CAT-1 mRNA expression induced by diquat (P<0·05), increased ARGII and endothelial nitric oxide synthase mRNA levels (P<0·05), and effectively relieved the TNF- α mRNA expression induced by diquat in the jejunum (P<0·05). It is concluded that oxidative stress decreased Arg bioavailability and increased expression of inflammatory cytokines in the jejunum, and that Arg supplementation has beneficial effects in the jejunum through regulation of the metabolism of Arg and suppression of inflammatory cytokine expression in piglets.

Magnolol pretreatment attenuates heat stress-induced IEC-6 cell injury

OBJECTIVE

Heat stress (HS) is an important environmental stressor that adversely influences livestock during the summer. The aim of this study was to investigate whether magnolol protects against HS-induced intestinal epithelial cell injury.

MATERIALS AND METHODS

An intestinal epithelial cell line (IEC-6) was subjected to HS at 42 °C, with and without magnolol pretreatment. Cell injury was detected by monitoring lactate dehydrogenase (LDH) release. MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay was used to assess cell proliferation and viability, including identifying effective concentrations of magnolol. Flow cytometry confirmed G1-phase cell-cycle arrest and its alleviation by magnolol. Active DNA synthesis was measured by incorporation of nucleic acid 5-ethynyl-2'-deoxyuridine (EdU). G1-phase cell-cycle-related gene expression was assessed by real-time reverse transcription polymerase chain reaction (RT-PCR) and levels of G1-phase-related proteins by Western blotting.

RESULTS

HS induced IEC-6 cell injury and decreased cell viability, as demonstrated by data from LDH and MTS assays, respectively. Based on a number of criteria, IEC-6 cells subjected to HS were arrested in the G1 phase of the cell cycle. Magnolol pretreatment decreased HS-induced cell injury through relief of this cell-cycle arrest.

CONCLUSIONS

Magnolol pretreatment attenuates HS-induced injury in IEC-6 cells. Magnolol is potentially promising as a protective strategy for HS in livestock.

Dietary soy isoflavones alleviate dextran sulfate sodium-induced inflammation and oxidative stress in mice

It has been hypothesized that soy isoflavones exhibit anti-oxidative and anti-inflammatory functions, however, the effects of soy isoflavones on inflammatory bowel diseases remain unknown. Therefore, the present study aimed to investigate the effect and underlying mechanism of dietary soy isoflavones on dextran sulfate sodium (DSS)-induced colitis. Mice were administered DSS and soy isoflavones, and histomorphometry, oxidative stress, inflammation and intestinal tight junctions were determined. The current study demonstrated that dietary soy isoflavones alleviated DSS-induced growth suppression, colonic inflammatory response, oxidative stress and colonic barrier dysfunction. DSS treatment was indicated to activate Toll-like receptor 4 (TRL4) and myeloid differentiation protein 88 (MyD88) in mice, whereas dietary soy isoflavones inhibited Myd88 expression in DSS-challenged mice. In conclusion, dietary soy isoflavones alleviate DSS-induced inflammation in mice, which may be associated with enhancing antioxidant function and inhibiting the TLR4/MyD88 signal.

Biogenic Nanoselenium Particles Effectively Attenuate Oxidative Stress-Induced Intestinal Epithelial Barrier Injury by Activating the Nrf2 Antioxidant Pathway

In the present study, a new form of selenium nanoparticle (biogenic nanoselenium (BNS) particles) was synthesized using bacteria. The protection of BNS particles against oxidative stress-induced intestinal barrier dysfunction and the inherent mechanisms of this process were investigated, and selenomethionine (SeMet) and chemically synthesized nanoselenium (Nano-Se) particles were used for comparison. Characterization of BNS particles revealed that they were monodispersed and homogeneous spheres, with an average size of 139.43 ± 7.44 nm. In the mouse model of intestinal oxidative stress, BNS particles were found to protect the mouse intestinal barrier function and preserve intestinal redox homeostasis more efficiently than SeMet and Nano-Se. In vitro experiments with porcine jejunum epithelial (IPEC-J2) cells verified the stronger epithelial barrier-protecting effect of BNS particles against oxidative stress, with reduced cell apoptosis and an improved cell redox state. BNS activated the nuclear factor (erythroid-derived-2)-like 2 (Nrf2) and increased the expression of its downstream genes, including thioredoxin reductase (TXNRD)-1, NADPH dehydrogenase (NQO)-1, heme oxygenase (HO)-1, and thioredoxin (Trx), in dose- and time-dependent manners. In contrast, SeMet and Nano-Se merely enhanced the activity of the selenoenzymes TXNRD-1 and glutathione peroxidase (GPx)-1, indicating the role of selenium donors. Moreover, the knock down of Nrf2 significantly blocked the antioxidative effect of BNS, confirming that BNS protects the intestinal barrier from oxidative stress-induced damage by activating Nrf2 and its downstream genes. Our results suggest that BNS is a promising selenium species with potential application in treating oxidative stress-related intestinal diseases.

Adaptive downregulation of pheomelanin-related Slc7a11 gene expression by environmentally induced oxidative stress

Pheomelanin is a sulphur-containing yellow-to-reddish pigment whose synthesis consumes the main intracellular antioxidant (glutathione; GSH) and its precursor cysteine. Cysteine used for pheomelanogenesis cannot be used for antioxidant protection. We tested whether the expression of Slc7a11, the gene regulating the transport of cysteine to melanocytes for pheomelanogenesis, is environmentally influenced when cysteine/GSH are most required for antioxidant protection. We found that zebra finches Taeniopygia guttata developing pheomelanin-pigmented feathers during a 12-day exposure to the pro-oxidant diquat dibromide downregulated the expression of Slc7a11 in feather melanocytes, but not the expression of other genes that affect pheomelanogenesis by mechanisms different from cysteine transport such as MC1R and Slc45a2. Accordingly, diquat-treated birds did not suffer increased oxidative stress. This indicates that some animals have evolved an adaptive epigenetic lability that avoids damage derived from pheomelanogenesis. This mechanism should be explored in human Slc7a11 to help combat some cancer types related to cysteine consumption.

Hydrogen sulfide from a NaHS source attenuates dextran sulfate sodium (DSS)-induced inflammation via inhibiting nuclear factor-κB

This study investigated the alleviating effects of hydrogen sulfide (H2S), derived from sodium hydrosulfide (NaHS), on inflammation induced by dextran sulfate sodium (DSS) in both in vivo and in vitro models. We found that NaHS injection markedly decreased rectal bleeding, diarrhea, and histological injury in DSS-challenged mice. NaHS (20 μmol/L) reversed DSS-induced inhibition in cell viability in Caco-2 cells and alleviated pro-inflammation cytokine expression in vivo and in vitro, indicating an anti-inflammatory function for H2S. It was also found that H2S may regulate cytokine expression by inhibiting the nuclear factor-κB (NF-κB) signaling pathway. In conclusion, our results demonstrated that H2S alleviated DSS-induced inflammation in vivo and in vitro and that the signal mechanism might be associated with the NF-κB signaling pathway.

N-Acetyl-L-cysteine Protects the Enterocyte against Oxidative Damage by Modulation of Mitochondrial Function

The neonatal small intestine is susceptible to damage caused by oxidative stress. This study aimed to evaluate the protective role of antioxidant N-acetylcysteine (NAC) in intestinal epithelial cells against oxidative damage induced by H₂O₂. IPEC-J2 cells were cultured in DMEM-H with NAC and H₂O₂. After 2-day incubation, IPEC-J2 cells were collected for analysis of DNA synthesis, antioxidation capacity, mitochondrial respiration, and cell apoptosis. The results showed that H₂O₂ significantly decreased (P < 0.05) proliferation rate, mitochondrial respiration, and antioxidation capacity and increased cell apoptosis and the abundance of associated proteins, including cytochrome C, Bcl-XL, cleaved caspase-3, and total caspase-3. NAC supplementation remarkably increased (P < 0.05) proliferation rate, antioxidation capacity, and mitochondrial bioenergetics but decreased cell apoptosis. These findings indicate that NAC might rescue the intestinal injury induced by H₂O₂.

Effects of Glutamate and Aspartate on Serum Antioxidative Enzyme, Sex Hormones, and Genital Inflammation in Boars Challenged with Hydrogen Peroxide

Background. Oxidative stress is associated with infertility. This study was conducted to determine the effects of glutamate and aspartate on serum antioxidative enzymes, sex hormones, and genital inflammation in boars suffering from oxidative stress. Methods. Boars were randomly divided into 4 groups: the nonchallenged control (CON) and H₂O₂-challenged control (BD) groups were fed a basal diet supplemented with 2% alanine; the other two groups were fed the basal diet supplemented with 2% glutamate (GLU) or 2% aspartate (ASP). The BD, GLU, and ASP groups were injected with hydrogen peroxide (H₂O₂) on day 15. The CON group was injected with 0.9% sodium chloride solution on the same day. Results. Dietary aspartate decreased the malondialdehyde (MDA) level in serum (P < 0.05) compared with the BD group. Additionally, aspartate maintained serum luteinizing hormone (LH) at a relatively stable level. Moreover, glutamate and aspartate increased transforming growth factor-β1 (TGF-β1) and interleukin-10 (IL-10) levels in the epididymis and testis (P < 0.05) compared with the BD group. Conclusion. Both glutamate and aspartate promoted genital mRNA expressions of anti-inflammatory factors after oxidative stress. Aspartate more effectively decreased serum MDA and prevented fluctuations in serum sex hormones after H₂O₂ challenge than did glutamate.

Long-term effects of oral tea polyphenols and Lactobacillus brevis M8 on biochemical parameters, digestive enzymes, and cytokines expression in broilers

This study investigates the long-term effects of oral tea polyphenols (TPs) and Lactobacillus brevis M8 (LB) on biochemical parameters, digestive enzymes, and cytokines expression in broilers. In experiment 1, 240 broiler chickens were selected to investigate the effects of 0.06 g/kg body weight (BW) TP and 1.0 ml/kg BW LB on broilers; in experiment 2, 180 broiler chickens were assigned randomly to three groups to investigate the effects of different dosages of TP (0.03, 0.06, and 0.09 g/kg BW) combined with 1.0 ml/kg BW LB on broilers; in experiment 3, 180 broiler chickens were assigned randomly to three groups to investigate the effects of different dosages of LB (0.5, 1.0, and 1.5 ml/kg BW) combined with 0.06 g/kg BW TP on broilers. The results showed that TP and LB affected serum biochemical parameters, and TP reduced serum cholesterol (CHO) and low-density lipoprotein cholesterol (LDL-C) abundances in a dosage-dependent manner (P<0.05) on Day 84. Meanwhile, broilers fed a diet supplemented with TP or LB had a lower intestinal lipase activity on Day 84 compared with the control group (P<0.05). Middle and high dosages of TP increased pancreatic lipase and proventriculus pepsin activities (P<0.05). Also middle and high dosages of LB significantly enhanced pancreatic lipase activity (P<0.05), while high LB supplementation inhibited intestinal trypsase (P<0.05) on Day 84. Furthermore, both TP and LB reduced intestinal cytokine expression and nuclear factor-κ B (NF-κB) mRNA level on Days 56 and 84. In conclusion, long-term treatment of TP and LB improved lipid metabolism and digestive enzymes activities, and affected intestinal inflammatory status, which may be associated with the NF-κB signal.

UII/GPR14 is involved in NF-κB-mediated colonic inflammation in vivo and in vitro

The present study was conducted to investigate the molecular mechanism of urotensin II (UII) and its receptor, G protein‑coupled receptor 14 (GPR14), in colonic inflammation. Urantide, a special antagonist of GPR14, and GPR14-siRNA were used to inhibit GPR14 signaling in dextran sulfate sodium (DSS)‑induced inflammation in mice and Caco-2 cells. The results showed that urantide alleviated rectal bleeding, histological injury and production of interleukin (IL)-17 and tumor necrosis factor‑α (TNF‑α) caused by DSS in mice. GPR14-siRNA transfection subsequent with GPR14 inhibition reduced DSS-induced interferon-γ (IFN)-γ production in Caco-2 cells. Meanwhile, both in vivo and in vitro data demonstrated that inhibition of UII/GPR14 alleviated nuclear factor-κB (NF-κB) activation caused by DSS. In conclusion, UII/GPR14 signaling was involved in the DSS-induced colonic inflammation and its inhibition may serve as a potential therapeutic target, which may be associated with the NF-κB signaling pathway.

N-carbamylglutamate and L-arginine improved maternal and placental development in underfed ewes

The objectives of this study were to determine how dietary supplementation ofN-carbamylglutamate (NCG) and rumen-protected L-arginine (RP-Arg) in nutrient-restricted pregnant Hu sheep would affect (1) maternal endocrine status; (2) maternal, fetal, and placental antioxidation capability; and (3) placental development. From day 35 to day 110 of gestation, 32 Hu ewes carrying twin fetuses were allocated randomly into four groups: 100% of NRC-recommended nutrient requirements, 50% of NRC recommendations, 50% of NRC recommendations supplemented with 20g/day RP-Arg, and 50% of NRC recommendations supplemented with 5g/day NCG product. The results showed that in maternal and fetal plasma and placentomes, the activities of total antioxidant capacity and superoxide dismutase were increased (P<0.05); however, the activity of glutathione peroxidase and the concentration of maleic dialdehyde were decreased (P<0.05) in both NCG- and RP-Arg-treated underfed ewes. The mRNA expression of vascular endothelial growth factor and Fms-like tyrosine kinase 1 was increased (P<0.05) in 50% NRC ewes than in 100% NRC ewes, and had no effect (P>0.05) in both NCG- and RP-Arg-treated underfed ewes. A supplement of RP-Arg and NCG reduced (P<0.05) the concentrations of progesterone, cortisol, and estradiol-17β; had no effect on T4/T3; and improved (P<0.05) the concentrations of leptin, insulin-like growth factor 1, tri-iodothyronine (T3), and thyroxine (T4) in serum from underfed ewes. These results indicate that dietary supplementation of NCG and RP-Arg in underfed ewes could influence maternal endocrine status, improve the maternal–fetal–placental antioxidation capability, and promote fetal and placental development during early-to-late gestation.

Arginine, N-carbamylglutamate, and glutamine exert protective effects against oxidative stress in rat intestine

The objective of the current study is to evaluate the effects of dietary supplementation with arginine (ARG), N-carbamylglutamate (NCG), and glutamine (GLN) on rat intestinal morphology and antioxidant status under oxidative stress. Rats were fed for 30 d with one of the following iso-nitrogenous diets: basal diet (BD), BD plus 1% ARG, BD plus 0.1% NCG, and BD plus 1% GLN. On day 28, half of the rats fed BD were intraperitoneally injected with 12 mg/kg body weight of diquat (DT; i.e., the DT group) and the other half was intraperitoneally injected with sterile solution (i.e., the control group). The other diet groups were intraperitoneally injected with 12 mg/kg body weight of DT (i.e., DT + 1% GLN [DT + GLN], DT + 1% ARG [DT + ARG], and DT + 0.1% NCG [DT + NCG]). Rat jejunum samples obtained at 48 h after DT injection were analyzed. Results showed that DT significantly decreased catalase (CAT) activity and glutathione (GSH) content by 58.25% and 56.57%, respectively, and elevated malondialdehyde (MDA) content and crypt depth (CD) by 19.39% and 22.13%, respectively, in the jejunum (P < 0.05, relative to the control group). Compared with the DT group, the DT + GLN group exhibited significantly improved villus height (VH), villus width (VW), villus surface area (VSA), CD and total antioxidant capacity (T-AOC) activity (P < 0.05); the DT + ARG group exhibited significantly increased the ratio of VH to CD (H:D) and T-AOC activity (P < 0.05); the DT + GLN, DT + ARG and DT + NCG groups exhibited significantly enhanced CAT activity and GSH content as well as decreased MDA content (P < 0.05). Moreover, VH, VW, VSA, CD and GSH content in the DT + GLN group were higher whereas MDA content was lower compared with the corresponding values observed in both the DT + ARG and the DT + NCG groups (P < 0.05). The H:D ratio in the DT + ARG group significantly increased compared with that in the DT + NCG and DT + GLN groups (P < 0.05). Collectively, this study suggested that dietary supplementation with 1% GLN, 0.1% NCG, and 1% ARG was effective in enhancing the antioxidant status and maintaining the morphological structure of rat jejunum under oxidative stress; of these supplements, 1% GLN exerted the greatest effects on mitigating oxidative stress.

Endoplasmic Reticulum Stress in Heat- and Shake-Induced Injury in the Rat Small Intestine

We investigated the mechanisms underlying damage to rat small intestine in heat- and shake-induced stress. Eighteen Sprague-Dawley rats were randomly divided into a control group and a 3-day stressed group treated 2 h daily for 3 days on a rotary platform at 35°C and 60 r/min. Hematoxylin and eosin-stained paraffin sections of the jejunum following stress revealed shedding of the villus tip epithelial cells and lamina propria exposure. Apoptosis increased at the villus tip and extended to the basement membrane. Photomicrographs revealed that the microvilli were shorter and sparser; the nuclear envelope invaginated and gaps in the karyolemma increased; and the endoplasmic reticulum (ER) swelled significantly. Gene microarray analysis assessed 93 differentially expressed genes associated with apoptosis, ER stress, and autophagy. Relevant genes were compiled from the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. Forty-one genes were involved in the regulation of apoptosis, fifteen were related to autophagy, and eleven responded to ER stress. According to KEGG, the apoptosis pathways, mitogen-activated protein kinase(MAPK) signaling pathway, the mammalian target of rapamycin (mTOR) signaling pathway, and regulation of autophagy were involved. Caspase3 (Casp3), caspase12 (Casp12), and microtubule-associate proteins 1 light chain 3(LC3) increased significantly at the villus tip while mTOR decreased; phosphorylated-AKT (P-AKT) decreased. ER stress was involved and induced autophagy and apoptosis in rat intestinal damage following heat and shake stress. Bioinformatic analysis will help determine the underlying mechanisms in stress-induced damage in the small intestine.

L-Glutamate Enhances Barrier and Antioxidative Functions in Intestinal Porcine Epithelial Cells

BACKGROUND

L-Glutamate (Glu) is a major amino acid in milk and postweaning diets for mammals (including pigs and human infants). However, effects of Glu on intestinal mucosal barrier and antioxidative functions are unknown.

OBJECTIVE

This study tested the hypothesis that Glu may enhance the barrier function of intestinal porcine epithelial cell line 1 (IPEC-1) cells by upregulating the expression of tight junction proteins.

METHODS

IPEC-1 cells were cultured with or without Glu in the presence or absence of 1 mmol/L diquat (an oxidant) for indicated time points. Cell numbers, transepithelial electrical resistance (TEER), mRNA, and protein abundance of glutamate transporter, the release of lactate dehydrogenase (LDH), and the abundance of tight junction proteins were determined.

RESULTS

Compared with 0 mmol/L Glu, 0.5-, 1-, and 2 mmol/L Glu stimulated (P < 0.05) cell growth by 13-37% at 24 h and 12-34% at 48 h, respectively. In addition, 0.5 mmol/L Glu increased (P < 0.05) TEER (by 58% at 24 h and by 98% at 48 h, respectively). These effects of Glu were associated with increased mRNA abundance of Glu transporter solute carrier family 1 member 1 (SLC1A1) by 30-130% and protein abundance of excitatory amino acid transporter 3 (encoded by SLC1A1) by 19-34%, respectively. In a cell model of oxidative stress induced by 1 mmol/L diquat, 0.5 mmol/L Glu enhanced cell viability, TEER, and membrane integrity (as indicated by the reduced release of LDH) in IPEC-1 cells by increasing the abundance of the tight junction proteins occludin, claudin-3, zonula occludens (ZO)-2, and ZO-3.

CONCLUSION

These findings indicate that Glu plays an important role in mucosal barrier function by enhancing cell growth and maintaining membrane integrity in response to oxidative stress.

Pyrrolidine Dithiocarbamate Inhibits NF-KappaB Activation and Upregulates the Expression of Gpx1, Gpx4, Occludin, and ZO-1 in DSS-Induced Colitis

Inflammatory bowel disease (IBD) correlates with oxidative stress, inflammation, and alteration in several signal pathways, including nuclear transcription factor-kappaB (NF-κB). Pyrrolidine dithiocarbamate (PDTC), an inhibitor of NF-κB, has been widely demonstrated to exhibit an antioxidant and anti-inflammatory function. This study aimed to test the hypothesis that NF-κB inhibitor PDTC confers a beneficial role in a colitis model induced by dextran sodium sulfate (DSS) in mouse. The results showed that DSS decreased daily weight gain, induced colonic inflammation, suppressed the expression of antioxidant enzymes and tight junctions, and activated NF-κB and nuclear factor erythroid 2-related factor 2/Kelch-like ECH-associated protein 1 (Nrf2/Keap1) signaling pathways. PDTC significantly upregulated (P < 0.05) Gpx1, Gpx4, occludin, and ZO-1 expressions in the DSS-induced colitis model. Meanwhile, PDTC reversed (P < 0.05) the activation of NF-κB signal pathway caused by DSS treatment. In conclusion, PDTC could serve as an adjuvant therapy for the patient with IBD.

Dietary supplementation with L-glutamate and L-aspartate alleviates oxidative stress in weaned piglets challenged with hydrogen peroxide

This study was to evaluate the protective roles of L-glutamate (Glu) and L-aspartate (Asp) in weaned piglets challenged with H2O2. Forty weaned piglets were assigned randomly into one of five groups (8 piglets/group): (1) control group (NC) in which pigs were fed a corn- and soybean meal-based diet and received intraperitoneal administration of saline; (2) H2O2 group (PC) in which pigs were fed the basal diet and received intraperitoneal administration of 10 % H2O2 (1 ml/kg body weight once on days 8 and repeated on day 11); (3) PC + Glu group (PG) in which pigs were fed the basal diet supplemented with 2.0 % Glu before intraperitoneal administration of 10 % H2O2; (4) PC + Asp group (PA) in which pigs were fed the basal diet supplemented with 1.0 % Asp before intraperitoneal administration of 10 % H2O2; (5) PC + Glu + Asp group (PGA) in which pigs were fed the basal diet supplemented with 2.0 % Glu plus 1.0 % Asp before intraperitoneal administration of 10 % H2O2. Measured parameters included daily feed intake (DFI), average daily gain (ADG), feed conversion rate (FCR), and serum anti-oxidative enzyme activities (catalase, superoxide dismutase, glutathione peroxidase-1), serum malondialdehyde and H2O2 concentrations, serum amino acid (AA) profiles, and intestinal expression of AA transporters. Dietary supplementation with Glu, Asp or their combination attenuated the decreases in DFI, ADG and feed efficiency, the increase in oxidative stress, the alterations of serum AA concentrations, and the changed expression of intestinal AA transporters in H2O2-challenged piglets. Thus, dietary supplementation with Glu or Asp alleviates growth suppression and oxidative stress, while restoring serum the amino acid pool in H2O2-challenged piglets.

Preinduction of heat shock protein 70 protects mice against post-infection irritable bowel syndrome via NF-κB and NOS/NO signaling pathways

This study aimed to investigate the protective effects of preinduction of heat shock protein 70 (HSP70) on Trichinella spiralis infection-induced post-infectious irritable bowel syndrome (PI-IBS) in mice. Trichinella spiralis infection significantly reduced HSP70 abundance, ileal villus height and crypt depth, expression of tight junctions, serum lysine and arginine concentrations, and ileal SCL7A6 and SCL7A7 mRNA levels, induced inflammatory response, and activated NF-κB signaling pathway. Meanwhile, the heat treatment upregulated HSP70 expression, and then reversed intestinal dysfunction and inflammatory response. Preinduction of HSP70 enhanced serum arginine and intestinal SCL7A7 expression and inhibited NF-κB activation compared with PI-IBS model. Treatment with pyrrolidine dithiocarbamate (PDTC, an NF-κB inhibitor) and N-nitro-L-arginine methyl ester hydrochloride (L-NAME, a nitric oxide synthase inhibitor, NOS) further demonstrated that preinduction of HSP70 might inhibit NF-κB and activated NOS/nitric oxide (NO) signaling pathways. In conclusion, preinduction of HSP70 by heat treatment may confer beneficial effects on Trichinella spiralis infection-induced PI-IBS in mice, and the protective effect of HSP70 may be associated with inhibition of NF-κB and stimulation of NOS/NO signaling pathways.

Arginyl-glutamine dipeptide attenuates experimental colitis by enhancing antioxidant function and inhibiting nuclear factor-kappaB

This study aimed to investigate the effect and underlying mechanism of Arginyl-glutamine (AG) dipeptide on dextran sulfate sodium (DSS)-induced colitis byin vivoandin vitromodels.

Glucocorticoids retard skeletal muscle development and myoblast protein synthesis through a mechanistic target of rapamycin (mTOR)-signaling pathway in broilers (Gallus gallus domesticus)

Glucocorticoids exert a well-known catabolic protein action on skeletal muscle. The mechanistic target of rapamycin (mTOR) signaling pathway acts as a central regulator of protein metabolism. Whether glucocorticoids regulate protein synthesis through the mTOR pathway in skeletal muscle of chickens remains unknown. This study was performed to characterize the effect of glucocorticoids on the mTOR pathway in skeletal muscle development in chickens, and on protein synthesis in cultured embryonic myoblasts. Male 29-d-old chickens were given a dexamethasone injection (2 mg/kg) twice per day for 4 d (n = 16). Chicken embryonic myoblasts were exposed to dexamethasone for 24 h (100 µmol/L, n = 4 cultures). The interaction between dexamethasone and leucine was also investigated. ANOVA and Duncan's multiple test were used to analyze the effects of the dexamethasone and leucine treatments. The results showed that dexamethasone decreased body weight gain, body weight, and feed efficiency. Protein synthesis was inhibited by in vitro dexamethasone exposure. Phosphorylation of mTOR and ribosomal protein S6 protein kinase (p70S6K) were inhibited by dexamethasone, suggesting the mTOR pathway may be involved in dexamethasone-regulated muscle protein synthesis. Phosphorylation of AMP-activated protein kinase (AMPK) was not altered in vitro but was reduced in vivo by dexamethasone. These results imply that the mTOR and AMPK pathways are both involved in retarding muscle development and protein synthesis by glucocorticoids, but the mTOR pathway is a critical point linking glucocorticoid and protein synthesis. Leucine, at least partially, inhibited the effects of dexamethasone on protein synthesis via the mTOR pathway.