Age-Dependent Developmental Changes of Selenium Content and Selenoprotein Expression and Content in Longissimus Dorsi Muscle and Liver of Duroc Pigs.

The trace element selenium (Se) plays a key role in development and various physiological processes, mainly through its transformation into selenoproteins. To investigate the developmental patterns of Se content and expression of selenoproteins, the liver and longissimus dorsi (LD) muscle of Duroc pigs were collected at 1, 21, 80, and 185 days of age (7 pigs each age) for the determination of Se content, mRNA expression of selenoproteins, and concentrations of glutathione peroxidase (GPX), thioredoxin reductase (TrxR or TXNRD), and selenoprotein P (SELP). The results showed that age significantly affected the expression of GPX1, GPX2, GPX3, TXNRD1, TXNRD2, TXNRD3, iodothyronine deiodinases 2 (DIO2), DIO3, SELF, SELH, SELM, SELP, SELS, SELW, and selenophosphate synthetase2 (SPS2) in the liver, as well as GPX3, GPX4, TXNRD1, TXNRD2, DIO2, DIO3, SELF, SELN, SELP, SELR, SELS, and SELW in the LD muscle of Duroc pigs. The concentrations of GPX, TrxR, and SELP showed an increasing trend with age, and they were positively correlated with Se content at 1, 21, and 185 days of age and negatively correlated at 80 days of age, both in the liver and LD muscle. The Se content decreased at the age of 80 days, especially in the LD muscle. In summary, our study revealed developmental changes in Se content and expression of selenoproteins in the liver and LD muscle of Duroc pigs at different growth stages, which provided a theoretical basis for further study of Se nutrition and functions of selenoproteins.

Combined supplementation with Lactobacillus sp. and Bifidobacterium thermacidophilum isolated from Tibetan pigs improves growth performance, immunity, and microbiota composition in weaned piglets.

Probiotics, such as Lactobacillus and Bifidobacterium, promote growth in piglets by modulating gut microbiota composition and improving the host immune system. A strain of Lactobacillus sp. and Bifidobacterium thermacidophilum were previously isolated from fresh feces of Tibetan pigs. The effects of these isolated strains on growth performance, intestinal morphology, immunity, microbiota composition, and their metabolites were evaluated in weaned piglets. Thirty crossbred piglets were selected and fed either a basal diet (CON), a basal diet supplemented with aureomycin (ANT), or a basal diet supplemented with Lactobacillus sp. and B. thermacidophilum (LB) for 28 d. The piglets in the ANT and LB groups had significantly higher body weight gain than those in the CON group (P < 0.05). Piglets in the ANT and LB groups had regularly arranged villi and microvilli in the small intestine. Furthermore, they had improved immune function, as indicated by decreased serum concentrations of inflammatory cytokines (P < 0.05), improved components of immune cells in the blood, mesenteric lymph nodes, and spleen. Additionally, metagenomic sequencing indicated a significant shift in cecal bacterial composition and alterations in microbiota functional profiles following Lactobacillus sp. and B. thermacidophilum supplementation. Metabolomic results revealed that the metabolites were also altered, and Kyoto Encyclopedia of Genes and Genomes analysis revealed that several significantly altered metabolites were enriched in glycerophospholipid and cholesterol metabolism (P < 0.05). Furthermore, correlation analysis showed that several bacterial members were closely related to the alterations in metabolites, including Bacteroides sp., which were negatively correlated with triglyceride (16:0/18:0/20:4[5Z,8Z,11Z,14Z]), the metabolite that owned the highest variable importance of projection scores. Collectively, our findings suggest that combined supplementation with Lactobacillus sp. and B. thermacidophilum significantly improved the growth performance, immunity, and microbiota composition in weaned piglets, making them prospective alternatives to antibiotics in swine production.

Probiotics such as Lactobacillus and Bifidobacterium have growth- and immunity-promoting effects in piglets. Thirty weaned piglets were selected and fed either a basal diet, a basal diet supplemented with aureomycin, or a basal diet supplemented with Lactobacillus sp. and Bifidobacterium thermacidophilum isolated from Tibetan pigs for 28 d. The results showed that combined supplementation with B. thermacidophilum and Lactobacillus sp. significantly improved growth performance, intestinal morphology, and immunity in weaned piglets, which is similar to piglets treated with antibiotics. They also improved cecal bacterial composition as indicated by the metagenomic sequencing results. Metabolomic results revealed that the altered metabolites were primarily enriched in glycerophospholipid and cholesterol metabolism. Correlation analysis showed that many bacterial members were closely related to the alterations of metabolites, suggesting B. thermacidophilum and Lactobacillus sp. exert effects via bacterial metabolism. Thus, Lactobacillus sp. and B. thermacidophilum could potentially be used as a prospective alternative of antibiotic growth promoters in piglets.

Serine Administration Improves Selenium Status, Oxidative Stress, and Mitochondrial Function in Longissimus Dorsi Muscle of Piglets with Intrauterine Growth Retardation.

Intrauterine growth retardation (IUGR) causes oxidative stress in the skeletal muscle. Serine and selenoproteins are involved in anti-oxidative processes; however, whether IUGR affects selenium status and whether serine has beneficial effects remain elusive. Here, we investigated the effects of serine administration on selenium nutritional status and oxidative stress in the longissimus dorsi muscle of piglets with IUGR. Six newborn Min piglets having normal birth weight were administered saline, and 12 IUGR piglets were either administered saline or 0.8% serine. The results showed a lower selenium content in skeletal muscle in IUGR piglets, which was restored after serine administration. IUGR piglets showed a disturbed expression of genes encoding selenoproteins, with decreased expression of GPX2, GPX4, TXNRD1, and TXNRD3 and increased expression of DIO1, DIO2, SELF, SELM, SELP, and SELW. Notably, serine administration restored the expression levels of these genes. In accordance with the changes in gene expression, the activity of GPX, TXNRD, and DIO and the content of GSH and SELP were also altered, whereas serine administration restored their contents and activities. Moreover, we observed severe oxidative stress in the skeletal muscle of IUGR piglets, as indicated by decreased GSH content and increased MDA and PC content, whereas serine administration alleviated these changes. In conclusion, our results indicate that IUGR piglets showed a disturbed expression of genes encoding selenoproteins, accompanied by severe oxidative stress. Serine administration can improve selenium status, oxidative stress, and mitochondrial function in the longissimus dorsi muscle of piglets with IUGR. These results suggest that serine could potentially be used in the treatment of IUGR in piglets.

Effects of Different Levels of Organic Trace Minerals on Oxidative Status and Intestinal Function in Weanling Piglets.

An experiment was conducted to compare the effects of replacing inorganic trace minerals (ITM) with different levels of complex organic trace minerals (OTM) on the growth performance, oxidative status, and intestinal function of piglets. Weanling piglets were assigned to five groups: a control group fed a basal diet supplemented with inorganic trace minerals and the other four groups fed basal diets supplemented with different levels of OTMs. The results showed that diets supplemented with 50 ppm Fe, 30 ppm Zn, 15 ppm Mn, and 0.2 ppm Se from OTM (L-OTM), or with 75 ppm Fe, 45 ppm Zn, 22.5 ppm Mn, and 0.3 ppm Se from OTM (M-OTM) significantly decreased the diarrhea ratio in the piglets compared with those supplemented with 100 ppm Fe, 90 ppm Zn, 40 ppm Mn, and 0.4 ppm Se from ITM. Compared with those in the ITM group, the piglets in the M-OTM group had significantly higher serum CuZnSOD, MnSOD, and GSH-Px levels. Moreover, piglets in the L-OTM and M-OTM groups had higher Sod and Gpx gene expression than those in the ITM group. Additionally, piglets in the L-OTM and M-OTM groups had significantly higher villus height than those in the ITM group, and the M-OTM group piglets had lower serum diamine oxidase content and higher ileal ZO-1 and occludin protein expression levels than those in the ITM group. These results indicate that replacing dietary ITMs with OTMs could decrease diarrhea occurrence and improve the oxidative status and intestinal barrier function in weanling piglets.

Effects of two concentrations of dietary tribasic zinc sulfate on growth performance, gut morphology, and zinc transporter expression levels in pigs.

Tribasic zinc sulfate (TBZ) is insoluble in water and chemically less active than zinc sulfate, making it more suitable to be used in pig diet. To investigate the effects of TBZ on the growth performance, gut morphology, and zinc transporter expression levels, we performed a single-factor experiment and 168 pigs were allocated to three groups with seven pens per treatment. Pigs were either fed a basal diet without zinc supplementation (control group), or a basal diet supplemented with TBZ at 100 mg/kg diet (LTBZ group) or 1000 mg/kg diet (HTBZ group). We found that daily weight gain and feed intake were higher in the LTBZ group than in the HTBZ and control groups. The pigs in the LTBZ group had a higher villus height and villus height/crypt depth ratio when compared with other pigs. Moreover, the pigs in the LTBZ group exhibited higher mRNA expression levels of solute carrier family 39 and lower expression levels of solute carrier family 30 than those fed the HTBZ-supplemented diet. Together, these results indicate that TBZ may potentially be used as a dietary zinc source for young growing pigs and that dietary supplementation with LTBZ benefits growth performance and gut morphology.

Serine Supplementation in the Diets of Late Gestating and Lactating Sows Improves Selenium Nutritional Status in Sows and Their Offspring.

Serine can regulate selenoprotein expression, and dietary serine is correlated with the contents of plasma selenoprotein P (Sepp1) and milk selenium (Se) in lactating mothers. Based on this, we investigated the effects of serine supplementation in the diets of late gestating and lactating sows on Sepp1 and Se contents in sows and their offspring. A total of 72 sows were assigned to four groups. During the experiment, sows were fed either a basal diet or basal diets supplemented with three different levels of serine. The results showed that maternal dietary serine had no effect on the Se content in the serum of sows and their offspring, whereas it significantly increased the Se content in the liver of piglets at the age of 21 days. Maternal dietary serine significantly increased Sepp1 content, either in the serum of sows or that in their offspring at the ages of 3 days, 7 days, and 21 days. Additionally, maternal dietary serine significantly increased litter weight and the average body weight of piglets at the age of 11 days. Notably, a positive correlation was found between the average body weight of piglets at the age of 11 days and serum Sepp1 content in piglets, at the age of either 3 days or 7 days. In conclusion, maternal dietary serine supplementation could improve Se nutritional status in sows and their offspring. These beneficial changes may contribute to the higher body weight of the offspring.

Dietary Serine Supplementation Regulates Selenoprotein Transcription and Selenoenzyme Activity in Pigs.

The synthesis of selenocysteine and its incorporation into selenoproteins require serine during the action of seryl-tRNA synthetase. In view of this, we conducted this study to explore the effects of dietary serine supplementation on selenoprotein transcription and selenoenzyme activity in pigs. A total of 35 crossbred barrows (28 days old) were randomly assigned to five treatment groups. During the 42-day growth experiment, pigs were fed either a basal diet with no supplemented serine or diets supplemented with 0.25%, 0.5%, 0.75%, or 1% serine. The results showed that serine supplementation had no effect on the selenium content in the serum, skeletal muscle, and kidney of pigs. However, dietary supplementation with 0.5% serine significantly increased the selenium content in the liver. Diets supplemented with different levels of serine significantly increased the gene expression of glutathione peroxidase 1 (Gpx1), Gpx2, thioredoxin reductase 1 (Txnrd1), Txnrd2, and selenoprotein P (Sepp1) in the skeletal muscle and liver of pigs. Moreover, pigs supplemented with 0.5% serine had the highest selenoprotein P concentration and glutathione peroxidase (GPx) and thioredoxin reductase (TrxR) activities in the skeletal muscle, which were significantly higher than those in the control pigs. Additionally, pigs supplemented with 0.25% serine had the highest GPx and TrxR activities in the liver, which were significantly higher than those in the control pigs. In conclusion, dietary serine supplementation could improve selenoprotein transcription and selenoenzyme activity in pigs, with the appropriate concentrations of serine to be included in the diet being 0.25% or 0.5%.

Effects of Iron Deficiency on Serum Metabolome, Hepatic Histology, and Function in Neonatal Piglets.

Few studies focused on the effects of iron on characterizing alterations of metabolic processes in neonatal piglets. In the present study, 16 neonatal piglets were randomly assigned to two groups. In the first group piglets were given an intramuscularly injection of iron dextran at 150 mg as a positive control (CON) and the second group were not supplemented with iron as a negative control for iron deficiency (ID). At day 8, iron status, serum biochemical parameters, serum metabolome, hepatic histology, and hepatic expression of genes for the metabolism were analyzed. Results indicated that piglets without iron supplementation had significantly reduced iron values and increased blood urea nitrogen concentrations at day 8 (p < 0.05). Analysis of serum metabolome revealed that concentrations of serum lysine, leucine, tyrosine, methionine, and cholesterol were significantly decreased while concentrations of 3-Methyldioxyindole, chenodeoxycholate acid, indoleacetic acid, icosadienoic acid, phenylpyruvic acid, pantothenic acid, ursocholic acid, and cholic acid were significantly increased in iron deficient piglets (p < 0.05). Furthermore, expressions of cyp7a1 and the urea cycle enzyme (ornithinetranscarbamoylase and argininosuccinate synthetase) were significantly increased in iron deficient pigs (p < 0.05). The present experimental results indicated that neonatal piglets without iron supplementation drop to borderline anemia within 8 days after birth. Iron deficiency led to a series of metabolic changes involved in tyrosine metabolism, phenylalanine metabolism, bile secretion, primary bile acid biosynthesis, steroid biosynthesis, and upregulated activities of the urea cycle enzymes in the liver of neonatal piglets, suggesting early effects on metabolic health of neonatal piglets.

Maternal serine supply from late pregnancy to lactation improves offspring performance through modulation of metabolic pathways.

Maternal dietary serine affects free amino acid content in milk and the antioxidant ability of progeny. However, whether maternal dietary serine has any effects on offspring performance in pigs and related metabolic consequences remains unknown. This study was conducted to investigate the effects of different levels of maternal dietary serine from late pregnancy to lactation on sow reproductive performance and offspring performance, and on the metabolome of milk and the serum of sows and their offspring. The results showed that sows fed a diet supplemented with 25% serine of the basal diet (l-Ser) had a higher litter weight, and higher average piglet weight at birth and aged 21 days when compared with sows fed the basal diet (CON). We found a large number of metabolites in both colostrum and milk that differed significantly between sows in the CON and l-Ser groups. Additionally, twenty metabolites differed in the serum of piglets aged 21 days between the CON and l-Ser groups. Most of these metabolites are involved in purine and pyrimidine metabolism, glutathione and taurine metabolism, as well as phospholipid and sphingolipid metabolism, which may contribute to the growth-promoting effects of serine on offspring. Our results imply that maternal serine has the potential to improve offspring outcomes.

Maternal dietary uridine supplementation reduces diarrhea incidence in piglets by regulating the intestinal mucosal barrier and cytokine profiles.

BACKGROUND: Nucleotides play an important role in the regulation of cellular energy and protein homeostasis, which facilitate the repair, recovery and repletion of tissue function. This study tested the effects of maternal uridine (UR) supplementation during late pregnancy and lactation of sows on the immune function of the small intestine in neonatal and suckling piglets. RESULTS: Results showed that compared to the control group, maternal dietary UR supplementation significantly decreased incidence of diarrhea in suckling piglets (P < 0.01); and increased both duodenal and ileal average villus height (P < 0.01) as well as villus height/crypt depth in ileum (P = 0.017) in neonatal piglets. RT-qPCR results showed that maternal UR supplementation decreased mRNA expression of claudin-1 in jejunum and ileum of neonatal piglets (P < 0.05), while significantly increased mRNA expression of claudin-1 in duodenum and jejunum of suckling piglets. Furthermore, in suckling piglets, maternal dietary UR supplementation increased mRNA expression of IL-6, IL-8 and IL-1ß in duodenum, jejunum and ileum (P < 0.05), increased IL-10 expression in both jejunal and ileal mucosa (P < 0.05) and increased mRNA expression of IKB and TLR4 in ileal mucosa (P < 0.05). CONCLUSIONS: These results suggest that maternal dietary supplementation with UR contributed to reducing incidence of diarrhea by regulating cytokine secretion and intestinal mucosal barrier function in suckling piglets. © 2020 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.

Effects of Dietary Serine Supplementation on Intestinal Integrity, Inflammation and Oxidative Status in Early-Weaned Piglets.

BACKGROUND/AIMS: Early weaning often causes gut dysfunction. Since serine alleviates oxidative stress and inflammatory response which are accompany with early weaning, we conducted the study to explore whether serine improves intestinal function in early-weaned piglets. METHODS: Twenty-eight weaned piglets (aged 21 d) were fed either a basal diet or a basal diet plus 0.2% serine. We determined the effects of dietary serine supplementation on intestinal morphology by hematoxylin and eosin staining, expression of tight junction proteins (TJPs) by immunoblotting and immunofluorescence, expression of inflammatory cytokines and apoptosis markers by RT-qPCR and the level of antioxidant enzymes with ELISA kits in early-weaned piglets. RESULTS: Serine supplementation increased daily body weight gain while decreasing diarrhea incidence. Both the jejunum and ileum of serine-supplemented piglets showed regularly arranged villi and microvilli. Moreover, dietary serine increased TJP expression, and alleviated apoptosis, inflammation, and oxidative stress in the intestine of early-weaned piglets. CONCLUSION: Our findings suggest that serine has the potential for use as a feed additive to prevent gut dysfunction caused by weaning.

Serine prevented high-fat diet-induced oxidative stress by activating AMPK and epigenetically modulating the expression of glutathione synthesis-related genes.

Serine deficiency has been observed in patients with nonalcoholic fatty liver disease (NAFLD). Whether serine supplementation has any beneficial effects on the prevention of NAFLD remains unknown. The present study was conducted to investigate the effects of serine supplementation on hepatic oxidative stress and steatosis and its related mechanisms. Forty male C57BL/6J mice (9week-old) were randomly assigned into four groups (n=10) and fed: i) a low-fat diet; ii) a low-fat diet supplemented with 1% (wt:vol) serine; iii) a high-fat (HF) diet; and iv) a HF diet supplemented with 1% serine, respectively. Palmitic acid (PA)-treated primary hepatocytes separated from adult mice were also used to study the effects of serine on oxidative stress. The results showed that serine supplementation increased glucose tolerance and insulin sensitivity, and protected mice from hepatic lipid accumulation, but did not significantly decreased HF diet-induced weight gain. In addition, serine supplementation protected glutathione (GSH) antioxidant system and prevented hypermethylation in the promoters of glutathione synthesis-related genes, while decreasing reactive oxygen species (ROS) in mice fed a HF diet. Moreover, we found that serine supplementation increased phosphorylation and S-glutathionylation of AMP-activated protein kinase α subunit (AMPKα), and decreased ROS, malondialdehyde and triglyceride contents in PA-treated primary hepatocytes. However, while AMPK activity or GSH synthesis was inhibited, the abovementioned effects of serine on PA-treated primary hepatocytes were not observed. Our results suggest that serine supplementation could prevent HF diet-induced oxidative stress and steatosis by epigenetically modulating the expression of glutathione synthesis-related genes and through AMPK activation.

Hyperhomocysteinemia and cardiovascular disease in animal model.

Hyperhomocysteinemia is an independent risk factor for cardiovascular disease and is associated with primary causes of mortality and morbidity throughout the world. Several studies have been carried out to evaluate the effects of a diet inducing cystathionine-ß-synthase, methyltetrafolate, folic acid, and vitamin B supplemented with methionine on the homocysteine metabolism and in lowering the plasma total homocysteine levels. A large number of molecular and biomedical studies in numerous animals, such as mice, rabbits, and pigs, have sought to elevate the plasma total homocysteine levels and to identify a disease model for human hyperhomocysteinemia. However, a specific animal model is not suitable for hyperhomocysteinemia in terms of all aspects of cardiovascular disease. In this review article, the experimental progress of animal models with plasma total homocysteine levels is examined to identify a feasible animal model of hyperhomocysteinemia for different aspects.

Serine alleviates oxidative stress via supporting glutathione synthesis and methionine cycle in mice.

SCOPE: Serine lies at the central node linking biosynthetic flux from glycolysis to glutathione synthesis and one-carbon metabolic cycle which are closely related to antioxidant capacity. The present study was conducted to determine the effects of serine supplementation on oxidative stress and its relative mechanisms. METHODS AND RESULTS: Diquat treatment was performed to induce oxidative stress in mice and primary hepatocytes. The results showed that hepatic glutathione anti-oxidant systems were impaired and reactive oxygen species and homocysteine were increased in diquat-induced mice and hepatocytes, while such disadvantageous changes were diminished by serine supplementation both in vivo and in vitro. However, when cystathionine ß-synthase expression was inhibited by interference RNA in hepatocytes, the effects of serine supplementation on the improvement of glutathione synthesis and the alleviation of oxidative stress were diminished. Moreover, when hepatocytes were treated with cycloleucine, an inhibitor of methionine adenosyltransferase, the effects of serine supplementation on the improvement of methionine cycle and the alleviation of DNA hypomethylation and oxidative stress were also diminished. CONCLUSION: Our results indicated that serine supplementation alleviated oxidative stress via supporting glutathione synthesis and methionine cycle, mostly by condensing with homocysteine to synthesize cysteine and providing one-carbon units for homocysteine remethylation.

Effects of dietary supplementation with tribasic zinc sulfate or zinc sulfate on growth performance, zinc content and expression of zinc transporters in young pigs.

An experiment was conducted to compare the effects of zinc sulfate (ZS) and tribasic zinc sulfate (TBZ) as sources of supplemental zinc on growth performance, serum zinc (Zn) content and messenger RNA (mRNA) expression of Zn transporters (ZnT1/ZnT2/ZnT5/ZIP4/DMT1) of young growing pigs. A total of 96 Duroc × Landrace × Yorkshire pigs were randomly allotted to two treatments and were fed a basal diet supplemented with 100 mg/kg Zn from either ZS or TBZ for 28 days. Feed : gain ratio in pigs fed TBZ were lower (P < 0.05) than pigs fed ZS, and average daily weight gain tended to increase (0.05 ≤ P ≤ 0.10) in pigs fed TBZ. Compared with pigs fed ZS, pigs fed TBZ had a higher CuZn-superoxide dismutase and Zn content in serum (P < 0.05) while they had a lower Zn content in feces (P < 0.05). In addition, ZIP4 mRNA expression of zinc transporter in either duodenum or jejunum of pigs fed TBZ were higher (P < 0.05) than pigs fed ZS. These results indicate that TBZ is more effective in serum Zn accumulation and intestinal Zn absorption, and might be a potential substitute for ZS in young growing pigs.

AMPK/α-Ketoglutarate Axis Regulates Intestinal Water and Ion Homeostasis in Young Pigs.

Water and ion absorption via sensitive aquaporins (AQPs) and ion channels is of critical importance in intestinal health. However, whether α-ketoglutarate (AKG) could improve intestinal water and ion homeostasis in lipopolysaccharide (LPS)-challenged piglets and whether the AMP-activated protein kinase (AMPK) pathway is involved remains largely unknown. This study was conducted to investigate the effect of dietary AKG supplementation on the small intestinal water and ion homeostasis through modulating the AMPK pathway in a piglet diarrhea model. A total of 32 weaned piglets were used in a 2 × 2 factorial design; the major factors were diet (basal diet or 1% AKG diet) and challenge (Escherichia coli LPS or saline). The results showed that LPS challenge increased the diarrhea index and affected the concentrations of serum Na+, K+, Cl-, glucose, and AKG and its metabolites in piglets fed the basal or AKG diet. However, the addition of AKG attenuated diarrhea incidence and reversed these serum parameter concentrations. Most AQPs (e.g., AQP1, AQP3, AQP4, AQP5, AQP8, AQP10, and AQP11) and ion transporters (NHE3, ENaC, and DRA/PAT1) were widely distributed in the duodenum and jejunum of piglets. We also found that AKG up-regulated the expression of intestinal epithelial AQPs while inhibiting the expression of ion transporters. LPS challenge decreased (P < 0.05) the gene and protein expression of the AMPK pathway (AMPKα1, AMPKα2, SIRT1, PGC-1α, ACC, and TORC2) in the jejunum and ileum. Notably, AKG supplementation enhanced the abundance of these proteins in the LPS-challenged piglets. Collectively, AKG plays an important role in increasing water and ion homeostasis through modulating the AMPK pathway. Our novel finding has important implications for the prevention and treatment of gut dysfunction in neonates.

Effects of Alpha-Ketoglutarate on Glutamine Metabolism in Piglet Enterocytes in Vivo and in Vitro.

Alpha-ketoglutarate (AKG) plays a vital part in the tricarboxylic acid cycle and is a key intermediate in the oxidation of L-glutamine (Gln). The study was to evaluate effects of AKG on Gln metabolism in vivo and in vitro. A total of twenty-one piglets were weaned at 28 days with a mean body weight (BW) of 6.0 ± 0.2 kg, and randomly divided into 3 groups: corn soybean meal based diet (CON group); the basal diet with 1% alpha-ketoglutarate (AKG treatment group); and the basal diet with 1% L-glutamine (GLN treatment group). Intestinal porcine epithelial cells-1 (IPEC-1) were incubated to investigate effects of 0.5, 2, and 3 mM AKG addition on Gln metabolism. Our results showed that there were no differences (P > 0.05) among the 3 treatments in initial BW, final BW, and average daily feed intake. However, average daily gain (P = 0.013) and gain:feed (P = 0.041) of the AKG group were greater than those of the other two groups. In comparison with the CON group, the AKG and GLN groups exhibited an improvement in villus length, mucosal thickness, and crypt depth in the jejunum of piglets. Serum concentrations of Asp, Glu, Val, Ile, Tyr, Phe, Lys, and Arg in the piglets fed the 1% AKG or Gln diet were lower than those in the CON group. Compared with the CON group, the mRNA expression of jejunal and ileal amino acid (AA) transporters in the AKG and GLN groups were significantly increased (P < 0.05). Additionally, the in vitro study showed that the addition of 0.5, 2, and 3 mM AKG dose-dependently decreased (P < 0.05) the net utilization of Gln and formulation of ammonia, Glu, Ala, and Asp by IPEC-1. In conclusion, dietary AKG supplementation, as a replacement for Gln, could improve Gln metabolism in piglet enterocytes and enhance the utilization of AA.

miR-27b overexpression improves mitochondrial function in a Sirt1-dependent manner

Resveratrol improves mitochondrial function, and recent evidences demonstrate that miRNAs play important roles in certain effects of resveratrol. In the current study, we found that a microRNA, miR-27b, was significantly induced in a dose-dependent way in skeletal muscle and C2C12 myoblast treated with resveratrol. Our results showed that overexpression of miR-27b could mimic the effects of resveratrol on improving mitochondrial function and glucose uptake in skeletal muscle cells. Subsequently, we found that FOXO1 was a potential target of miR-27b, and the effects of resveratrol on mitochondrial function were significantly affected after inhibition of miR-27b. Moreover, the effects of miR-27b on mitochondrial function were lost after inhibition of Sirt1, although miR-27b and FOXO1 expression were not influenced. Taken together, these data suggested that overexpression of miR-27b could benefit mitochondrial function, while the effects of overexpressed miR-27b were Sirt1-dependent

miR-27b overexpression improves mitochondrial function in a Sirt1-dependent manner.

Resveratrol improves mitochondrial function, and recent evidences demonstrate that miRNAs play important roles in certain effects of resveratrol. In the current study, we found that a microRNA, miR-27b, was significantly induced in a dose-dependent way in skeletal muscle and C2C12 myoblast treated with resveratrol. Our results showed that overexpression of miR-27b could mimic the effects of resveratrol on improving mitochondrial function and glucose uptake in skeletal muscle cells. Subsequently, we found that FOXO1 was a potential target of miR-27b, and the effects of resveratrol on mitochondrial function were significantly affected after inhibition of miR-27b. Moreover, the effects of miR-27b on mitochondrial function were lost after inhibition of Sirt1, although miR-27b and FOXO1 expression were not influenced. Taken together, these data suggested that overexpression of miR-27b could benefit mitochondrial function, while the effects of overexpressed miR-27b were Sirt1-dependent.