Toxicity assessment of hydrogen peroxide on Toll-like receptor system, apoptosis, and mitochondrial respiration in piglets and IPEC-J2 cells

Effects of Hericium erinaceus polysaccharide in porcine IPEC-J2 intestinal epithelial cells against apoptosis induced by oxidative stress

This study was intended to investigate whether Hericium erinaceus polysaccharides (HEP) prevent oxidative stress and apoptosis of intestinal porcine epithelial cells from jejunum (IPEC-J2 cells) induced by hydrogen peroxide (H2O2). Crude HEP were extracted and purified by chromatography. The ultraviolet and infrared spectra and monosaccharide composition of HEP were analyzed. Reactive oxygen species (ROS) generation was quantified by flow cytometry method, and lactate dehydrogenase (LDH) and malondialdehyde (MDA) production were determined by TBARS. Also, apoptosis was analyzed by flow cytometry method and the apoptosis-related regulatory molecules were determined by microplate or western blotting method. Our results showed that pretreatment of IPEC-J2 cells with HEP significantly scavenged ROS and reduced LDH and MDA production. HEP also reduced apoptosis and kept polarity of the mitochondrial membrane potential. Moreover, HEP increased the content of caspase-3 and PARP, and protein expression of Bcl-2, while inhibited Bax and Bad and reduced the content of caspase-9 and release of CytC. Meanwhile, HEP inhibited the protein expression of TNFR1, FAS, and FASL, and decreased the content of caspase-8. The results indicated that HEP had a protective effect against oxidative stress in IPEC-J2 cells and the underlying mechanism was reducing apoptosis via mitochondrial and death receptor pathways.

Accurate models and nutritional strategies for specific oxidative stress factors: Does the dose matter in swine production?

Oxidative stress has been associated with a number of physiological problems in swine, including reduced production efficiency. Recently, although there has been increased research into regulatory mechanisms and antioxidant strategies in relation to oxidative stress-induced pig production, it remains so far largely unsuccessful to develop accurate models and nutritional strategies for specific oxidative stress factors. Here, we discuss the dose and dose intensity of the causes of oxidative stress involving physiological, environmental and dietary factors, recent research models and the antioxidant strategies to provide theoretical guidance for future oxidative stress research in swine.

Role of Mitophagy in Regulating Intestinal Oxidative Damage

The mitochondrion is also a major site for maintaining redox homeostasis between reactive oxygen species (ROS) generation and scavenging. The quantity, quality, and functional integrity of mitochondria are crucial for regulating intracellular homeostasis and maintaining the normal physiological function of cells. The role of oxidative stress in human disease is well established, particularly in inflammatory bowel disease and gastrointestinal mucosal diseases. Oxidative stress could result from an imbalance between ROS and the antioxidative system. Mitochondria are both the main sites of production and the main target of ROS. It is a vicious cycle in which initial ROS-induced mitochondrial damage enhanced ROS production that, in turn, leads to further mitochondrial damage and eventually massive intestinal cell death. Oxidative damage can be significantly mitigated by mitophagy, which clears damaged mitochondria. In this review, we aimed to review the molecular mechanisms involved in the regulation of mitophagy and oxidative stress and their relationship in some intestinal diseases. We believe the reviews can provide new ideas and a scientific basis for researching antioxidants and preventing diseases related to oxidative damage.

Glycine Alleviated Intestinal Injury by Inhibiting Ferroptosis in Piglets Challenged with Diquat

The purpose of this research was to examine the impact of glycine on intestinal injury caused by oxidative stress in piglets. A 2 × 2 factorial experiment with diets (basic diet vs. 1% glycine diet) and oxidative stress (saline vs. diquat) was conducted on 32 weanling piglets. On day 21, all piglets received an injection of either saline or diquat. After 7 days, all pigs were slaughtered and intestinal samples were collected. Dietary glycine supplementation improved intestinal mucosal morphology, increased the activities of disaccharidases and enhanced intestinal mucosal antioxidant capacity, while regulating the expression of ferroptosis mediators in the piglets under oxidative stress. These findings suggested that dietary glycine supplementation improved the morphology and function of the intestinal mucosa, which was involved in regulating antioxidant capacity and ferroptosis.

CD133 increases oxidative glucose metabolism of HT29 cancer cells by mitochondrial uncoupling and its inhibition enhances reactive oxygen species-inducing therapy

OBJECTIVE

A better understanding of the metabolic phenotype of stem-like cancer cells could provide targets to help overcome chemoresistance. In this study, we hypothesized that colon cancer cells with the stem cell feature of CD133 expression have increased proton leakage that influences glucose metabolism and offers protection against reactive oxygen species (ROS)-inducing treatment.

METHODS AND RESULTS

In HT29 colon cancer cells, 18 F-fluorodeoxyglucose (FDG) uptake was increased by CD133 selection and decreased by CD133 silencing. In CD133(+) cells, greater 18 F-FDG uptake was accompanied by increased oxygen consumption rate (OCR) and reduced mitochondrial membrane potential and mitochondrial ROS, indicating increased proton leakage. The uncoupling protein inhibitor genipin reversed the increased 18 F-FDG uptake and greater OCR of CD133(+) cells. The ROS-inducing drug, piperlongumine, suppressed CD133(-) cell survival by stimulating mitochondrial ROS generation but was unable to influence CD133(+) cells when used alone. However, cotreatment of CD133(+) cells with genipin and piperlongumine efficiently stimulated mitochondrial ROS for an enhanced antitumor effect with substantially reduced CD133 expression.

CONCLUSION

These results demonstrate that mitochondrial uncoupling is a metabolic feature of CD133(+) colon cancer cells that provides protection against piperlongumine therapy by suppressing mitochondrial ROS generation. Hence, combining genipin with ROS-inducing treatment may be an effective strategy to reverse the metabolic feature and eliminate stem-like colon cancer cells.

Polyphenols Sourced from Ilex latifolia Thunb. Relieve Intestinal Injury via Modulating Ferroptosis in Weanling Piglets under Oxidative Stress

Polyphenols sourced from Ilex latifolia Thunb. (PIT) contain high levels of phenolic acids, tannic acids, triterpenoids and so on, which play important roles in antioxidant function. This study was conducted to investigate the effects of PIT against intestinal injury in piglets under oxidative stress. Thirty-two weanling piglets were arranged by a 2 × 2 factorial experiment with diets (basal diet vs. PIT diet) and oxidative stress (saline vs. diquat). All piglets were injected with saline or diquat on d 21, respectively. After 7 days, all pigs were slaughtered and intestinal samples were collected. PIT enhanced jejunal villus heights and crypt depth in the piglets under oxidative stress. PIT increased the activities of intestinal mucosal lactase, sucrase and maltase in the challenged piglets. PIT also increased the jejunal ratio of protein to DNA and ileal protein content. PIT increased the jejunal activities of GSH-PX and GSH content and reduced the ileal MDA amounts. Furthermore, PIT regulated the expression of ferroptosis mediators, such as TFR1, HSPB1, SLC7A11 and GPX4. These results indicate that dietary PIT supplementation enhances the histological structure and function of the intestinal mucosa, which is involved in modulating antioxidant capacity and ferroptosis.

Cadmium exposure triggers oxidative stress, necroptosis, Th1/Th2 imbalance and promotes inflammation through the TNF-α/NF-κB pathway in swine small intestine

Cadmium (Cd) is a toxic environmental pollutant and induces toxic effects to organism. Nevertheless, the mechanism of Cd-induced toxicity in swine remains obscure. To explore this, 10 healthy 6-week-old weaned swine were placed into two groups stochastically, the Cd group was treated with a commercial diet containing 20 mg/kg Cd for 40 days. The results of histopathological and ultrastructural observations showed typical necrosis features and inflammatory cell infiltration in Cd group. Excessive Cd suppressed T-AOC and SOD activities, increased MDA content and ROS levels. Cd diet elevated the expression of RIPK1, RIPK3, and MLKL to activate the RIPK3-dependent necroptosis pathway. Results of Th1 and Th2 cytokines indicated that the levels of IL-4, IL-6 and IL10 was increased, while the level of IFN-γ was decreased, illustrating Th1/Th2 immune imbalance leads to aggravate inflammatory responses. Cd activated the TNF-α/NF-κB pathway and induced inflammatory responses via increasing the expression of HO-1, IL-1β, iNOS, COX2. Heat shock proteins were notably elevated in response to inflammatory reactions. And these effects were inhibited by necrostatin-1 (Nec-1) and N-acetyl-cysteine (NAC). Altogether, these data demonstrated that Cd induced necroptosis and inflammation to aggravate small intestine injury in swine by increasing the excessive accumulation of ROS and imbalanced Th1/Th2, respectively.

AMPK-PINK1/Parkin Mediated Mitophagy Is Necessary for Alleviating Oxidative Stress-Induced Intestinal Epithelial Barrier Damage and Mitochondrial Energy Metabolism Dysfunction in IPEC-J2

The imbalance of redox biology and oxidative stress leads to intestinal barrier injury and mitophagy. However, much uncertainty still exists about the role of mitophagy in oxidative stress and intestinal function. Here, we showed the effects of hydrogen peroxide (H₂O₂)-induced oxidative stress on intestinal epithelial cell oxidation balance, intestinal barrier function and mitochondrial energy metabolism and its underlying mechanism. In this study, we found that H₂O₂-induced oxidative stress activated adenosine monophosphate-activated protein kinase (AMPK) and enhanced mitophagy in intestinal porcine epithelial cells (IPEC-J2). While compound C (AMPK inhibitor) and mdivi-1 (mitophagy inhibitor) significantly reduced the activity of superoxide dismutase (SOD) and increased mitochondrial reactive oxygen species (ROS) levels in H₂O₂ treated cells. Moreover, compound C and mdivi-1 significantly reduced the trans-epithelium electrical resistant (TER) and increased the fluorescein isothiocyanate-dextran (FD4) flux in H₂O₂ treated IPEC-J2. Furthermore, compound C and mdivi-1 significantly reduced the activity of mitochondrial complex II. Seahorse XF96 data showed that compound C + mdivi-1+ H₂O₂ treatment significantly reduced maximum respiratory oxygen consumption and spare respiratory capacity. Additionally, compound C or mdivi-1 treatment reduced the formation of mitochondrial autophagosomes. These results unveiled that AMPK and PINK1/Parkin mediated mitophagy is necessary for alleviating oxidative stress induced intestinal epithelial barrier damage and mitochondrial energy metabolism dysfunction in IPEC-J2.

Research Progress on Oxidative Stress and Its Nutritional Regulation Strategies in Pigs

Oxidative stress refers to the dramatic increase in the production of free radicals in human and animal bodies or the decrease in the ability to scavenging free radicals, thus breaking the antioxidation-oxidation balance. Various factors can induce oxidative stress in pig production. Oxidative stress has an important effect on pig performance and healthy growth, and has become one of the important factors restricting pig production. Based on the overview of the generation of oxidative stress, its effects on pigs, and signal transduction pathways, this paper discussed the nutritional measures to alleviate oxidative stress in pigs, in order to provide ideas for the nutritional research of anti-oxidative stress in pigs.

Immune, inflammatory, autophagic and DNA damage responses to long-term H2O2 exposure in different tissues of common carp (Cyprinus carpio)

Hydrogen peroxide (H₂O₂) is a stable reactive oxygen species (ROS) in aquatic environment, and high concentration of ambient H₂O₂ may directly or indirectly affect aquatic animal health. However, the response mechanism of fish to ambient H₂O₂ has not been well studied yet. Therefore, the aim of the study was to investigate the immune, inflammatory, autophagic and DNA damage responses to long-term H₂O₂ exposure in different tissues of common carp. The results showed that H₂O₂ exposure induced a significant immune response, with alterations in the levels of immune parameters including AKP, ACP, LZM, C3, HSP90 and HSP70 in different tissues. The inflammatory response evoked by H₂O₂ exposure was associated with the activations of TLRs and NF-κB (P65) in the majority of tested tissues. The autophagy process was significantly affected by H₂O₂ exposure, evidenced by the upregulations of the autophagy-related genes in liver, gills, muscle, intestines, heart and spleen and the downregulations in kidney. Meanwhile, the mRNA level of atm, a primary transducer of DNA damage response, was upregulated in liver, gills, intestines and spleen, and the DNA damage was evidenced by increased 8-OHdG level in intestines after H₂O₂ exposure. Moreover, cell cycle regulation-related genes, including cyclin A1, B and/or E1, highly expressed in all tested tissues except heart after H₂O₂ exposure. Interestingly, IBR analysis exhibited that immune, inflammatory, autophagic and DNA damage responses to H₂O₂ exposure were in a dose-dependent and tissue-specific manner. These data may contribute to understanding H₂O₂ toxicity for fish and assessing potential risk of H₂O₂ in aquatic environment.

The Landscape of Interactions between Hypoxia-Inducible Factors and Reactive Oxygen Species in the Gastrointestinal Tract

The gastrointestinal tract (GT) is the major organ involved in digestion, absorption, and immunity, which is prone to oxidative destruction by high levels of reactive oxygen species (ROS) from luminal oxidants, such as food, drugs, and pathogens. Excessive ROS will lead to oxidative stresses and disrupt essential biomolecules, which also act as cellular signaling molecules in response to growth factors, hormones, and oxygen tension changes. Hypoxia-inducible factors (HIFs) are critical regulators mediating responses to cellular oxygen tension changes, which are also involved in energy metabolism, immunity, renewal, and microbial homeostasis in the GT. This review discusses interactions between HIF (mainly HIF-1α) and ROS and relevant diseases in the GT combined with our lab's work. It might help to develop new therapies for gastrointestinal diseases associated with ROS and HIF-1α.

The Associated Regulatory Mechanisms of Zinc Lactate in Redox Balance and Mitochondrial Function of Intestinal Porcine Epithelial Cells

Zinc lactate (ZnLA) is a new organic zinc salt which has antioxidant properties in mammals and can improve intestinal function. This study explored the effects of ZnLA and ZnSO₄ on cell proliferation, Zn transport, antioxidant capacity, mitochondrial function, and their underlying molecular mechanisms in intestinal porcine epithelial cells (IPEC-J2). The results showed that addition of ZnLA promoted cell proliferation, inhibited cell apoptosis and IL-6 secretion, and upregulated the mRNA expression and concentration of MT-2B, ZNT-1, and CRIP, as well as affected the gene expression and activity of oxidation or antioxidant enzymes (e.g., CuZnSOD, CAT, and Gpx1, GSH-PX, LDH, and MDA), compared to ZnSO₄ or control. Compared with the control, ZnLA treatment had no significant effect on mitochondrial membrane potential, whereas it markedly increased the mitochondrial basal OCR, nonmitochondrial respiratory capacity, and mitochondrial proton leakage and reduced spare respiratory capacity and mitochondrial reactive oxygen (ROS) production in IPEC-J2 cells. Furthermore, ZnLA treatment increased the protein expression of Nrf2 and phosphorylated AMPK, but reduced Keap1 and p62 protein expression and autophagy-related genes LC3B-1 and Beclin mRNA abundance. Under H₂O₂-induced oxidative stress conditions, ZnLA supplementation markedly reduced cell apoptosis and mitochondrial ROS levels in IPEC-J2 cells. Moreover, ZnLA administration increased the protein expression of Nrf2 and decreased the protein expression of caspase-3, Keap1, and p62 in H₂O₂-induced IPEC-J2 cells. In addition, when the activity of AMPK was inhibited by Compound C, ZnLA supplementation did not increase the protein expression of nuclear Nrf2, but when Compound C was removed, the activities of AMPK and Nfr2 were both increased by ZnLA treatment. Our results indicated that ZnLA could improve the antioxidant capacity and mitochondrial function in IPEC-J2 cells by activating the AMPK-Nrf2-p62 pathway under normal or oxidative stress conditions. Our novel finding also suggested that ZnLA, as a new feed additive for piglets, has the potential to be an alternative for ZnSO₄.

Ulva prolifera Extract Alleviates Intestinal Oxidative Stress via Nrf2 Signaling in Weaned Piglets Challenged With Hydrogen Peroxide

Background

Ulva prolifera extract contains a variety of functional active substances. Whether these substances had any beneficial effects on the small intestine of weaned piglets under oxidative stress remained unknown.

Method

We explored the effects of U. prolifera extract on oxidative stress and related mechanisms in weaned piglets and intestinal porcine epithelial cells (IPEC-J2) challenged with hydrogen peroxide.

Results

U. prolifera extract was found to mainly consist of polyphenols and unsaturated fatty acids. U. prolifera extract increased total antioxidant capacity and superoxide dismutase (SOD) activity, while it decreased malondialdehyde content, in the serum of weaned piglets challenged with hydrogen peroxide. Moreover, U. prolifera extract increased mRNA expression of SOD and catalase, as well as the intestinal expression of nuclear NF-E2-related factor 2 (Nrf2), both in vitro and in vivo. Furthermore, U. prolifera extract decreased reactive oxygen species and improved mitochondrial respiration in IPEC-J2 cells treated with hydrogen peroxide. However, AMPK inhibition did not affect nuclear Nrf2 expression and only partially affected the effects of U. prolifera extract on oxidative stress.

Conclusion

We suggest that U. prolifera extract alleviates oxidative stress via Nrf2 signaling, but independent of AMPK pathway in weaned piglets challenged with hydrogen peroxide. These results shed new insight into the potential applications of U. prolifera extract as a therapeutic agent for the prevention and treatment of oxidative stress-induced intestinal diseases.

High-content fluorescence imaging with the metabolic flux assay reveals insights into mitochondrial properties and functions

Metabolic flux technology with the Seahorse bioanalyzer has emerged as a standard technique in cellular metabolism studies, allowing for simultaneous kinetic measurements of respiration and glycolysis. Methods to extend the utility and versatility of the metabolic flux assay would undoubtedly have immediate and wide-reaching impacts. Herein, we describe a platform that couples the metabolic flux assay with high-content fluorescence imaging to simultaneously provide means for normalization of respiration data with cell number; analyze cell cycle distribution; and quantify mitochondrial content, fragmentation state, membrane potential, and mitochondrial reactive oxygen species. Integration of fluorescent dyes directly into the metabolic flux assay generates a more complete data set of mitochondrial features in a single assay. Moreover, application of this integrated strategy revealed insights into mitochondrial function following PGC1a and PRC1 inhibition in pancreatic cancer and demonstrated how the Rho-GTPases impact mitochondrial dynamics in breast cancer.

Serine is required for the maintenance of redox balance and proliferation in the intestine under oxidative stress

Serine has critical roles in maintaining cell growth and redox balance in cancer cells. However, the role of exogenous serine played in oxidative response and proliferation in normal mammalian intestine need to be further elucidated. We used a mouse model and intestinal porcine epithelial cells (IPEC-J2) to reveal that exogenous serine deficiency did not lead to redox imbalance and inhibition of proliferation in the intestine. However, serine deficiency exacerbated oxidative stress, mitochondrial dysfunction, apoptosis, and inhibition of proliferation in IPEC-J2 cells challenged by hydrogen peroxide, while serine supplementation rescued redox imbalance and those proliferation defects. Importantly, serine supplementation restored the glutathione content and decreased the accumulation of reactive oxygen species, while no such effects were observed when glutathione synthesis was inhibited. Additionally, serine supplementation increased nuclear nrf2 expression in IPEC-J2 cells. These results suggested that serine alleviates oxidative stress through supporting glutathione synthesis and activating nrf2 signaling. We further found that serine supplementation activated the mTOR pathway, while inhibition of mTOR diminished the effects of serine on promoting proliferation, suggesting critical roles of the mTOR pathway in this context. Taken together, our study underlines the importance of serine in the maintenance of redox status and proliferation in the intestine and reveals a novel potential mechanism that mediates these effects.

Curcumin ameliorates oxidative stress-induced intestinal barrier injury and mitochondrial damage by promoting Parkin dependent mitophagy through AMPK-TFEB signal pathway

The gut epithelial is known as the most critical barrier for protection against harmful antigens and pathogens. Oxidative stress has been implicated in the dysfunction of the intestine barrier. Hence, effective and safe therapeutic approaches for maintaining intestinal redox balance are urgently needed. Curcumin has gained attention for its vast beneficial biological function via antioxidative stress. However, whether the curcumin can relief intestine damage and mitochondrial injury induced by oxidative stress is still unclear. In this study, we found that curcumin can effectively ameliorate hydrogen peroxide (H₂O₂)-induced oxidative stress, intestinal epithelial barrier injury and mitochondrial damage in porcine intestinal epithelial cells (IPEC-J2 cells) in a PTEN-induced putative kinase (PINK1)-Parkin mitophagy dependent way. Mechanistically, depletion of Parkin (a mitophagy related protein) abolished curcumin's protective action on anti-oxidative stress, improving intestinal barrier and mitochondrial function in porcine intestinal epithelial cells (IPEC-J2) induced by H₂O₂. Consistently, the protective effect of curcumin was not found in cells transfected with GFP-ParkinΔUBL, which encodes a mutant Parkin protein without the ubiquitin E3 ligase activity, indicating that the ubiquitin E3 ligase of Parkin is required for curcumin's protective effects. On the other hand, we also found that the protective function of curcumin was diminished when PRKAA1 was depleted in IPEC-J2 cells treated with H₂O₂. Immunofluorescence and luciferase assay showed that curcumin dramatically enhanced nuclear translocation and transcriptional activity of transcription factor EB (TFEB) in IPEC-J2 cells treated with H₂O₂, and it was ameliorated by co-treated with compound C, an Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) inhibitor, which means curcumin promotes TFEB transcript via AMPK signal pathway. Consistent with in vitro data, dietary curcumin protected intestinal barrier function, improved redox status, alleviated mitochondrial damage, triggered mitophagy and influenced AMPK-TFEB signal pathway in a well-established pig oxidative stress model by challenging with diquat. Taken together, these results unveil that curcumin ameliorates oxidative stress, enhances intestinal barrier function and mitochondrial function via the induction of Parkin dependent mitophagy through AMPK activation and subsequent TFEB nuclear translocation.

Uridine/UMP metabolism and their function on the gut in segregated early weaned piglets

Uridine monophosphate (UMP) is a major nucleotide analogue in mammalian milk and uridine (UR) is its gastro-intestinal metabolite in vivo. This study aims to investigate the functional effects of UMP and UR on the gut in vitro and in vivo. Twenty-one piglets were randomly allotted into three groups, the control group, UMP group and UR group, and orally administered UMP or UR for 10 days. Results showed that UMP and UR supplements improved the ADG of piglets, and decreased the diarrhea rate. UR increased the jejunum villus length/crypt depth ratio, Claudin-3 and E-cadherin expression, and the pyrimidine nucleotide metabolic enzymes including CMPK1, RRM2, UPRT, CTPS1 and CTPS2 in the duodenal mucosa. Both the UMP and UR decreased the expression of CAD and RRM2 at the jejunal mucosa. Moreover, UMP and UR increased the apoptosis ratio of intestinal epithelial cells in in vivo and in vitro experiments. Taken together, oral administration of UR and UMP could improve the small intestinal morphology, promote epithelial cell apoptosis and renewal of intestinal villus tips, and benefit intestinal development and health thus improving the growth performance and reducing the risk of diarrhea in early-weaned piglets.

Effects of Dietary L-arginine Supplementation from Conception to Post- Weaning in Piglets

Weaned piglets experience sudden changes in their dietary patterns such as withdrawal from the easily digestible watery milk to a coarse cereal diet with both systemic and intestinal disruptions coupling with the expression of pro-inflammatory proteins which affects the immune system and the concentrations of haptoglobin including both positive and negative acute-phase proteins in the plasma. L-arginine is an important protein amino acid for piglets, but its inadequate synthesis is a nutritional problem for both sows and piglets. Recent studies indicated that dietary supplementation of L-arginine increased feed intake, uterine growth, placental growth and nutrient transport, maternal growth and health, embryonic survival, piglets birth weight, piglet's growth, and productivity, and decreased stillbirths. L-arginine is essential in several important pathways involved in the growth and development of piglets such as nitric oxide synthesis, energy metabolism, polyamine synthesis, cellular protein production and muscle accretion, and the synthesis of other functional amino acids. However, the underlying molecular mechanism in these key pathways remains largely unresolved. This review was conducted on the general hypothesis that L-arginine increased the growth and survival of post-weaning piglets. We discussed the effects of dietary L-arginine supplementation during gestation, parturition, lactation, weaning, and post-weaning in pigs as each of these stages influences the health and survival of sows and their progenies. Therefore, the aim of this review was to discuss through a logical approach the effects of L-arginine supplementation on piglet's growth and survival from conception to postweaning.

Multi-strain yeast fraction product supplementation can alleviate weaning stress and improve performance and health of piglets raised under low sanitary conditions

BACKGROUND

This study was conducted to evaluate the health benefits to weaning pigs, raised under low sanitary conditions, of dietary supplementation with a multi-strain yeast fraction product (Cyberlindnera jadinii and Saccharomyces cerevisiae). In total, 160 weaning pigs (7.21 ± 1.05 kg) were randomly allotted to two dietary treatments in a 6-week feeding trial. The dietary treatments included a corn-soybean meal-based basal diet (CON) and CON + 2 g kg^-1 multi-strain yeast fraction product (MsYF) during weeks 1-2 and 0.4 g kg^-1 MsYF during weeks 3-6.

RESULTS

The MsYF supplementation increased (P < 0.05) body weight (BW) at day 42 and average daily gain (ADG) during days 1-14 and days 1-42 (P < 0.05) compared to CON. The total tract digestibility of dry matter (DM), fecal Lactobacillus counts, and serum immunoglobulin G (IgG) concentration at day 42 were higher (P < 0.05) in pigs fed a MsYF supplemented diet. The concentration of serum haptoglobin in pigs receiving a MsYF-supplemented diet was higher (P < 0.05) at days 7, 14, and 42 than those receiving CON. The mRNA expression for INF-γ and TNF-α genes were lower (P < 0.05) at days 14 and 7 respectively and the expression of IL-6 and TLR-2 genes was lower (P < 0.01) at days 7 and 14 in pigs fed an MsFY supplemented diet than those fed CON.

CONCLUSION

Supplementation with a multi-strain yeast fraction product had a positive effect on ADG during the early post-weaning period and led to better health in weaning pigs. © 2019 Society of Chemical Industry.

Prevention of Oxidative Stress by α-Ketoglutarate via Activation of CAR Signaling and Modulation of the Expression of Key Antioxidant-Associated Targets in Vivo and in Vitro

α-Ketoglutarate (AKG) can act as an antioxidant both in vitro and in vivo. However, the mechanisms of the protective effects of AKG are still not well understood. We evaluated the effects of AKG supplementation on the regulation of the constitutive-androstane-receptor (CAR) pathway in porcine intestinal cells and piglets exposed to H₂O₂. Our data showed that AKG treatment significantly increased not only the intra- and extracellular levels of AKG (26.9 ± 1.31 μmol/g protein, 1064.4 ± 39.80 μmol/L medium) but also those of Asp (29.3 ± 0.21 μmol/g, 4.20 ± 0.11 μmol/L), Gln (24.82 ± 1.50 μmol/g, 1087.80 ± 16.10 μmol/L), and Glu (91.90 ± 3.6 μmol/g, 19.76 ± 1.00 μmol/L). There was approximately a 4-fold increase in α-ketoglutarate dehydrogenase mRNA levels in enterocytes and a simultaneous reduction in ROS levels ( P < 0.05). Moreover, AKG treatment increased the activities of the antioxidant enzymes and the efficiency of cellular respiration ( P < 0.05). AKG also regulated the mRNA levels of the target genes involved in antioxidant responses and xenobiotic detoxification in enterocytes. Increases in the protein levels of SOD1, SOD2, CAR, RXRα, and UCP2 and marked reductions in the expression levels of Nrf2 and Keap1 proteins ( P < 0.05) were observed after AKG administration in the H₂O₂-induced piglets. Our results indicated that AKG may protect against oxidative stress by activating CAR signaling and modulating the expression of key antioxidant-related targets, which improves cellular respiration and antioxidant capacity. The in vivo and in vitro effects of AKG suggest that it may prove to be useful in the reduction of oxidative stress in animal and human trials and subsequent prevention of gastrointestinal pathologies.

The Antioxidative Function of Alpha-Ketoglutarate and Its Applications

Alpha-ketoglutarate (AKG) is a crucial intermediate of the Krebs cycle and plays a critical role in multiple metabolic processes in animals and humans. Of note, AKG contributes to the oxidation of nutrients (i.e., amino acids, glucose, fatty acids) and then provides energy for cell processes. As a precursor of glutamate and glutamine, AKG acts as an antioxidant agent as it directly reacts with hydrogen peroxide with formation of succinate, water, and carbon dioxide; meanwhile, it discharges plenty of ATP by oxidative decarboxylation. Recent studies also show that AKG has alleviative effect on oxidative stress as a source of energy and an antioxidant in mammalian cells. In this review, we highlight recent advances in the antioxidative function of AKG and its applications in animals and humans.

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.