Tiejun Li

Metabolomic analysis of the response of growing pigs to dietary L-arginine supplementation.

Arginine plays an important role regulating nutrient metabolism, but the underlying mechanisms are largely unknown. This study was conducted to determine the effect of dietary arginine supplementation on the metabolome in serum of growing pigs using 1H nuclear magnetic resonance spectroscopy. Sixteen 120-day-old pigs (48xa0±xa01xa0kg) were randomly assigned to one of two groups, representing supplementation with 0 or 1.0% l-arginine to corn- and soybean meal-based diets. Serum was collected after a 46-day period of treatment. Dietary arginine supplementation decreased fat deposition and increased protein accretion in the body. Principal component analysis showed that serum concentrations of low density lipoprotein, very low density lipoprotein, and urea were lower, but concentrations of creatinine, tricarboxylic acid cycle metabolites, ornithine, lysine and tyrosine were greater in arginine-supplemented than in control pigs. Additionally, the arginine treatment affected serum concentrations of nitrogenous and lipid signaling molecules (glycerophosphorylcholine and myo-inositol) and intestinal bacterial metabolites (formate, ethanol, methylamine, dimethylamine, acetate, and propionate). These novel findings suggest that dietary arginine supplementation alters the catabolism of fat and amino acids in the whole body, enhances protein synthesis in skeletal muscle, and modulates intestinal microbial metabolism in growing pigs.

Impaired translation initiation activation and reduced protein synthesis in weaned piglets fed a low-protein diet.

Weanling mammals (including infants) often experience intestinal dysfunction when fed a high-protein diet. Recent work with the piglet (an animal model for studying human infant nutrition) shows that reducing protein intake can improve gut function during weaning but compromises the provision of essential amino acids (EAA) for muscle growth. The present study was conducted with weaned pigs to test the hypothesis that supplementing deficient EAA (Lys, Met, Thr, Trp, Leu, Ile and Val) to a low-protein diet may maintain the activation of translation initiation factors and adequate protein synthesis in tissues. Pigs were weaned at 21 days of age and fed diets containing 20.7, 16.7 or 12.7% crude protein (CP), with the low-CP diets supplemented with EAA to achieve the levels in the high-CP diet. On Day 14 of the trial, tissue protein synthesis was determined using the phenylalanine flooding dose method. Reducing dietary CP levels decreased protein synthesis in pancreas, liver, kidney and longissimus muscle. A low-CP diet reduced the phosphorylation of eukaryotic initiation factor (eIF) 4E-binding protein-1 (4E-BP1) in skeletal muscle and liver while increasing the formation of an inactive eIF4E.4E-BP1 complex in muscle. Dietary protein deficiency also decreased the phosphorylation of mammalian target of rapamycin (mTOR) and the formation of an active eIF4E.eIF4G complex in liver. These results demonstrate for the first time that chronic feeding of a low-CP diet suppresses protein synthesis in animals partly by inhibiting mTOR signaling. Additionally, our findings indicate that supplementing deficient EAA to low-protein diets is not highly effective in restoring protein synthesis or whole-body growth in piglets. We suggest that conditionally essential amino acids (e.g., glutamine and arginine) may be required to maintain the activation of translation initiation factors and optimal protein synthesis in neonates.

Effects of dietary supplementation with an expressed fusion peptide bovine lactoferricin-lactoferrampin on performance, immune function and intestinal mucosal morphology in piglets weaned at age 21 d

Lactoferrin has antimicrobial activity associated with peptide fragments lactoferricin (LFC) and lactoferrampin (LFA) released on digestion. These two fragments have been expressed in Photorhabdus luminescens as a fusion peptide linked to protein cipB. The construct cipB-LFC-LFA was tested as an alternative to antimicrobial growth promoters in pig production. Sixty piglets with an average live body weight of 5.42 (sem 0.59) kg were challenged with enterotoxigenic Escherichia coli and randomly assigned to four treatment groups fed a maize-soyabean meal diet containing either no addition (C), cipB at 100 mg/kg (C+B), cipB-LFC-LFA at 100 mg/kg (C+L) or colistin sulfate at 100 mg/kg (C+CS) for 3 weeks. Compared with C, dietary supplementation with C+L for 3 weeks increased daily weight gain by 21 %, increased recovery from diarrhoea, enhanced serum glutathione peroxidase (GPx), peroxidase (POD) and total antioxidant content (T-AOC), liver GPx, POD, superoxide dismutase and T-AOC, Fe, total Fe-binding capacity, IgA, IgG and IgM levels (P < 0.05), decreased the concentration of E. coli in the ileum, caecum and colon (P < 0.05), increased the concentration of lactobacilli and bifidobacteria in the ileum, caecum and colon (P < 0.05), and promoted development of the villus-crypt architecture of the small intestine. Growth performance was similar between C+L- and C+CS-supplemented pigs. The present results indicate that LFC-LFA is an effective alternative to the feed antibiotic CS for enhancing growth performance in piglets weaned at age 21 d.

Nutritive value of feedstuffs and diets for pigs: I. Chemical composition, apparent ileal and faecal digestibilities

The chemical composition, including amino acid content, and ileal and faecal digestibility was determined for 39 batches of 38 different feedstuffs and 18 mixed diets. Considerable variation was found in both chemical composition and digestibility among cereals and cereal by-products, legumes, animal protein feedstuffs, oil seed meals, protein and mineral concentrates and mixed diets. Within the different classes of feedstuffs and diets, variation was small for mixed diets and protein and mineral concentrates. A large variation was found for animal protein feedstuffs and oil seed meals, especially for apparent ileal digestibilities of amino acids. However, there was good agreement between the results and those reported in the literature. The digestibilities of nutrients were affected by many factors, including cell wall constituents, the balance of mineral and trace elements and anti-nutritional factors. Faecal digestibility was higher than ileal digestibility. In general, the differences between apparent faecal digestibilities were smaller than for apparent ileal digestibilities. This indicates that the modifying action of microflora in the large intestine is irregular, therefore the digestibility measured at the end of the ileum is more reliable. However, the high ileal digestibility of cell wall constituents indicates that the influence of the microflora begins before the end of the ileum, and other methods such as isotope dilution techniques should be used to more accurately determine digestion and absorption.

Birth oxidative stress and the development of an antioxidant system in newborn piglets

Abstract Birth oxidative stress is an oxidative response to a sudden transition process from maternal mediated respiration in uterus to autonomous pulmonary respiration outside the uterus. Meanwhile, oxidative stress has been demonstrated to be associated with various pathologies recorded in newborns. So, this research aimed to study the oxidative stress and the development of antioxidant system in newborn piglets. The measured variables include plasma lipid, protein and DNA oxidant injury, the activities of plasma antioxidant enzymes and the jejunal and ileal antioxidant gene expressions at 1, 7, 14, and 21 days after birth. Meanwhile, the nuclear factor erythroid 2-related factor 2 (Nrf2), transcription factor p65, and tumor protein 53 (p53) were determined by western blot. The results showed that newborn piglets suffered seriously from birth oxidative stress because of the naive antioxidant system. In addition, oxidant injury activated Nrf2 signaling pathway, resulting in the expression of antioxidant genes and release of antioxidant enzymes. With the development of antioxidant system, the oxidative balance gradually recovered on Day 7 after birth. In conclusion, birth caused oxidative stress and the oxidative balance gradually recovered with the development of antioxidant system.

Dietary arginine supplementation enhances intestinal expression of SLC7A7 and SLC7A1 and ameliorates growth depression in mycotoxin-challenged pigs

This study tested the hypothesis that dietary l-arginine supplementation confers beneficial effects on growing pigs fed a mold-contaminated diet. The measured variables included: (1) the average daily weight gain and feed:gain ratio; (2) activities of total superoxide dismutase, glutathione peroxidase, diamine oxidase, as well as amino acid and d-lactate concentrations in serum; (3) intestinal morphology; (4) expression of the genes for SLC7A7 (amino acid transporter light chain, y+L system, family 7, member 7), SLC7A1 (cationic amino acid transporter, y+ system, family 7, member 1), SLC1A1 (neuronal/epithelial high affinity glutamate transporter, system XAG, member 1), SLC5A1 (sodium/glucose cotransporter, family 5, member 1) in the ileum and jejunum. Mycotoxins in feedstuffs resulted in an enlarged small intestine mass, oxidative injury in tissues, and reduced growth performance in pigs. Dietary arginine supplementation enhanced (Pxa0<xa00.05) expression of jejunal SLC7A7 and ileal SLC7A1, in comparison with the control and mycotoxin groups. In addition, supplementing 1xa0% l-arginine to the mycotoxin-contaminated feed had the following beneficial effects (Pxa0<xa00.05): (1) alleviating the imbalance of the antioxidant system in the body; (2) ameliorating intestinal abnormalities; and (3) attenuating whole-body growth depression, compared with the mycotoxin group without arginine treatment. Collectively, these results indicate that dietary supplementation with l-arginine exerts a protective role in pigs fed mold-contaminated foods. The findings may have important nutritional implications for humans and other mammals.

Dietary l -arginine supplementation enhances intestinal development and expression of vascular endothelial growth factor in weanling piglets

Oral administration of L-arginine has been reported to prevent gut disease in human infants. However, little is known about the effects of dietary arginine supplementation on intestinal development of weaned piglets. In the present study, twenty 21-d-old castrated piglets with 5·3 (SEM 0·13) kg body weight (BW) were weaned from sows, individually housed and randomly assigned to one of the two maize- and soyabean meal-based diets supplemented with 0 or 1% L-arginine. After consuming the diets for 7 d, six pigs were randomly selected from each group to obtain various tissues. Compared with control pigs, dietary supplementation with 1% L-arginine did not affect feed intake but enhanced (P<0·05) the relative weight of the small intestine (+33 %), daily BW gain (+38 %) and feed efficiency (+28 %). The villus height of the duodenum, jejunum and ileum in arginine-supplemented piglets was 21, 28 and 25% greater (P<0·05) than in the nonsupplemented control group. Arginine supplementation increased (P<0·05) protein levels for vascular endothelial growth factor(VEGF) in duodenal, jejunal and ileal mucosae by 14, 39 and 35 %, respectively. Compared with the control group, dietary supplementation with 1% L-arginine increased (P<0·05) plasma concentrations of arginine and insulin (+36 %), and decreased (P<0·05) plasma concentrations of cortisol (233 %), NH3 (221 %) and urea (219 %). These results indicate that arginine supplementation enhances intestinal growth, development and expression of VEGF in early-weaned pigs fed a maize- and soyabean meal-based diet. The findings may have important implications for neonatal pigs under stressful or diseased conditions.

Reduced expression of intestinal N-acetylglutamate synthase in suckling piglets: a novel molecular mechanism for arginine as a nutritionally essential amino acid for neonates

The objective of this study was to determine developmental changes in mRNA and protein levels for N-acetylglutamate synthase (NAGS; a key enzyme in synthesis of citrulline and arginine from glutamine/glutamate and proline) in the small intestine of suckling piglets. The porcine NAGS gene was cloned using the real-time polymerase-chain reaction (RT-PCR) method. The porcine NAGS gene encoded 368 amino acid residues and had a high degree of sequence similarity to the “conserved domain” of human and mouse NAGS genes. The porcine NAGS gene was expressed in E. coli BL21 and a polyclonal antibody against the porcine NAGS protein was developed. Real-time RT-PCR and western-blot analyses were performed to quantify NAGS mRNA and protein, respectively, in the jejunum and ileum of 1- to 28-day-old pigs. Results indicated that intestinal NAGS mRNA levels were lower in 7- to 28-day-old than in 1-day-old pigs. Immunochemical analysis revealed that NAGS protein was localized in enterocytes of the gut. Notably, intestinal NAGS protein abundance declined progressively during the 28-day suckling period. The postnatal decrease in NAGS protein levels was consistent with the previous report of reduced NAGS enzymatic activity as well as reduced synthesis of citrulline and arginine in the small intestine of 7- to 28-day-old pigs. Collectively, these results suggest that intestinal NAGS expression is regulated primarily at the post-transcriptional level. The findings also provide a new molecular basis to explain that endogenous synthesis of arginine is impaired in sow-reared piglets and arginine is a nutritionally essential amino acid for the neonates.

Amino acid metabolism in the portal-drained viscera of young pigs: effects of dietary supplementation with chitosan and pea hull

Recent studies indicate extensive catabolism of amino acids (AA) by the portal-drained viscera (PDV) of pigs and humans. Because of ethical concerns over invasive surgical procedures on infants or adults, in vivo investigations are often performed with the pig which is both an agriculturally important livestock species and a widely used animal model for nutritional and physiological studies in humans. Here, we described a new technique for implanting chronic catheters into the portal vein, ileal mesenteric vein, and carotid artery to study AA metabolism in the PDV of young pigs. This method allowed for the reduction of surgery time by 1xa0h and measurements of the entry of dietary AA into the portal circulation. Using such an approach, we found that dietary supplementation with 100xa0mg/kg chitosan (a prebiotic and a polysaccharide not digested by animal cells) reduced oxygen consumption, as well as the net absorption of dietary AA into the portal vein, thereby enhancing their bioavailability for extraintestinal tissues. In contrast, opposite results were obtained with dietary supplementation of 12% pea-hull (containing 95% of fermentable nonstarch polysaccharide). Thus, this improved technique is useful to quantify in vivo absorption and metabolism of dietary AA in young pigs.

Effects of Dietary Supplementation with Glutamate and Aspartate on Diquat-Induced Oxidative Stress in Piglets

This study aimed to investigate the protective effects of dietary glutamate and aspartate supplementations on diquat-induced oxidative stress in piglets. Diquat injection significantly reduced growth performance, including body weight, average daily weight gain, and feed intake (P<0.05). Meanwhile, diquat administration induced oxidative stress evidenced by the decreased serum nitric oxide (NO) and elevated malondialdeyhde (MDA) concentration (P<0.05). Furthermore, diquat-induced oxidative stress disrupted intestinal absorption system and decreased serum threonine, serine, and glycine levels. Dietary supplementation with glutamate improved final body weight, antioxidant system, and expressions of amino acids transporters and enhanced serum glutamate concentration compared with diquat group (P<0.05). While aspartate failed to alleviate diquat-induced oxidative stress, growth depression, and dysfunction of nutrients absorption except for liver relative weight. In conclusion, dietary supplementation with glutamate confers beneficial effects on diquat-induced oxidative stress in piglets, while aspartate exhibits little effects.