Glycine has the greatest rate of deposition in whole-body proteins among all amino acids in neonates, but its provision from sow’s milk meets only 20% of the requirement of suckling piglets. The results of our recent studies indicate that piglets with intrauterine growth restriction (IUGR) have a reduced ability to synthesize glycine. The present study determined the role of glycine in the growth of sow-reared IUGR piglets. In Experiment 1, 56 newborn piglets (postnatal day 0) with a low birth weight (<1.10 kg) were selected from 14 litters, providing 4 IUGR piglets/litter that were allotted randomly into one of four treatment groups (14 piglets/group). Piglets received oral administration of either 0, 0.1, 0.2 or 0.4 g glycine/kg body weight (BW) twice daily (i.e., 0, 0.2, 0.4 or 0.8 g glycine/kg BW/day) between 0 and 14 days of age. L-Alanine was used as the isonitrogenous control. The BWs of all piglets were recorded each week during the experiment. Two weeks after the initiation of glycine supplementation, blood and tissue samples were collected for biochemical analyses. In Experiment 2, rates of muscle protein synthesis in tissues were determined on day 14 using the 3H-phenylalanine flooding dose technique. Compared with piglets in the control group, oral administration of 0.2, 0.4 and 0.8 g glycine/kg BW/day did not affect their milk intake (p > 0.05) but increased (p < 0.05) concentrations of glycine in plasma by 1.52-, 1.94-, and 2.34-fold, respectively, and body weight by 20%, 37%, and 34%, respectively. The dose of 0.4 g glycine/kg BW/day was the most cost-effective. Consistent with its growth-promoting effect, glycine supplementation stimulated (p < 0.05) the phosphorylation of mechanistic target of rapamycin (MTOR), eukaryotic initiation factor 4E binding protein 1 (4E-BP1), and ribosomal protein S6 kinase beta-1 (p70S6K) as well as protein synthesis in skeletal muscle, compared with the control group. Collectively, oral administration of glycine activated the MTOR signaling pathway in skeletal muscle and enhanced the growth performance of IUGR piglets. These results indicate that endogenous synthesis of glycine is inadequate to meet the needs of IUGR piglets during the suckling period and that oral supplementation with glycine to these compromized neonates can improve their growth performance.

Glycine has the greatest rate of deposition in whole-body proteins among all amino acids in neonates, but is remarkably deficient in the milk of mammals including pigs, humans, and cows. Results of our recent studies indicate that piglets with intrauterine growth restriction (IUGR) have a reduced ability to synthesize glycine. The present study determined the role of dietary glycine in the growth of sow-reared IUGR piglets. In Experiment 1, 56 newborn piglets (postnatal day 0) with low birth weights (< 1.10 kg) were from 14 litters, providing 4 IUGR piglets/litter that were allotted randomly into one of four treatment groups (14 piglets/group). Piglets received oral administration of either 0, 0.1, 0.2 or 0.4 g glycine/kg body weight twice daily (i.e., 0, 0.2, 0.4 or 0.8 g glycine/kg body weight/d) between 0 and 14 d of age. L-Alanine was used as the isonitrogenous control. The body weights of all piglets were recorded each week during the experiment. Two weeks after the initiation of glycine supplementation, blood and tissue samples were collected for biochemical analyses. In Experiment 2, rates of protein synthesis in tissues were determined using the 3H-phenylalanine flooding dose technique. Results were analyzed statistically using one-way or two-way ANOVA. The consumption of milk by IUGR piglets measured at 13 d of age was 236 ± 15, 228 ± 12, 244 ± 18, and 240 ± 16 mL/kg BW/d, respectively, in the 0, 0.2, 0.4, and 0.8 g glycine/kg BW/day groups (P > 0.05). Concentrations of serine in plasma were 18% and 25% greater (P < 0.05) in piglets receiving oral administration of 0.4 and 0.8 g glycine/kg BW/day, respectively, than those in the control group. Compared with piglets in the control group, oral administration of 0.2, 0.4 and 0.8 g glycine/kg body weight/d increased (P < 0.05) concentrations of glycine in plasma by 1.52-, 1.94-, and 2.34-fold, respectively, as well as body weight by 20%, 37%, and 34%, respectively. Consistent with its growth-promoting effect, glycine supplementation increased (P < 0.05) the phosphorylation of mechanistic target of rapamycin (MTOR), eukaryotic initiation factor 4E binding protein 1 (4E-BP1), and ribosomal protein S6 kinase beta-1 (S6K1) by 330%, 170%, and 180%, respectively, and the fractional rate of protein synthesis by 16%, in longissimus lumborum muscle, compared with the control group. Collectively, oral administration of glycine activated the MTOR signaling pathway in skeletal muscle and promoted the growth performance of IUGR piglets. These results indicate that the endogenous synthesis of glycine is inadequate to meet the metabolic needs of IUGR piglets during the suckling period. (Supported by Agriculture and Food Research Initiative Competitive Grant 2014-67015-21770 from the USDA National Institute of Food and Agriculture)

The objective of this study was to evaluate the nutritional values of three new corn varieties (high-iron corn, cadmium-resistant corn, low-phytate phosphorus corn) cultivated with molecular marker-assisted selection breeding technique fed to growing pigs and broilers. Exp. 1 was conducted to compare the nutritional values of high-iron corn, high-chromium corn, low-phytate phosphorus corn and conventional corn fed to growing pigs based on a 15 × 2 Youden square design. Exp.2 was conducted to compare the nutritional values of high-iron corn, low-phytate phosphorus corn and conventional corn fed to broilers based on a completely randomized design. Parameters including nutrient digestibility, available energy and amino acids, and mineral deposition were measured. The results shows that the iron content in the high-iron corn and the cadmium content in the cadmium-resistant corn were 29.608 mg/kg and 0.0057 mg/kg, respectively, both were greater than those in the other three kinds of corns. When fed to growing pigs, the neutral detergent fiber digestibility of the high-iron corn group was lower than that of the conventional corn group (p < 0.05), and the acid detergent fiber digestibility of the high-iron group and the low-phytate phosphorus corn group was lower than that of the conventional corn group (p < 0.01). In addition, the digestible energy value of the high-iron corn in growing pigs was lower than that of the conventional corn (p < 0.05). When fed to broilers, it was observed that the tibia length of the low-phytate phosphorus corn group and the high-iron corn group was lower than that of the conventional corn group (p < 0.05). Moreover, the iron emission in feces of broilers fed the low-phytate phosphorus corn was lower than those fed the conventional corn and the high-iron corn (p < 0.05). In conclusion, modern breeding techniques could provide new plant ingredients which have potential benefits to pig and broiler production, but the comprehensive effects may be better when applied to growing pigs considering growth performance and environment effects. The breeding techniques related to the current study rarely changed the available energy values of the corn in growing pigs and broilers.

This study tested the hypothesis that the synthesis of glycine from 4-hydroxyproline (an abundant amino acid in milk and neonatal blood) was impaired in tissues of piglets with intrauterine growth restriction (IUGR), thereby contributing to a severe glycine deficiency in these compromised neonates. At 0, 7, 14, and 21 days of age, IUGR piglets were euthanized, and tissues (liver, small intestine, kidney, pancreas, stomach, skeletal muscle, and heart) were obtained for metabolic studies, as well as the determination of enzymatic activities, cell-specific localization, and expression of mRNAs for glycine-synthetic enzymes. The results indicated relatively low enzymatic activities for 4-hydroxyproline oxidase (OH-POX), proline oxidase, serine hydroxymethyltransferase, threonine dehydrogenase (TDH), alanine: glyoxylate transaminase, and 4-hydroxy-2-oxoglutarate aldolase in the kidneys and liver from 0- to 21-day-old IUGR pigs, in the pancreas of 7- to 21-day-old IUGR pigs, and in the small intestine and skeletal muscle (except TDH) of 21-day-old IUGR pigs. Accordingly, the rates of conversion of 4-hydroxyproline into glycine were relatively low in tissues of IUGR piglets. The expression of mRNAs for glycine-synthetic enzymes followed the patterns of enzymatic activities and was also low. Immunohistochemical analyses revealed the relatively low abundance of OH-POX protein in the liver, kidney, and small intestine of IUGR piglets, and the lack of OH-POX zonation in their livers. These novel results provide a metabolic basis to explain why the endogenous synthesis of glycine is insufficient for optimum growth of IUGR piglets and have important implications for improving the nutrition and health of other mammalian neonates including humans with IUGR.

Glycine from sow's milk only meets 20% of the requirement of suckling piglets. However, how glycine is synthesized endogenously in neonates is not known. This study determined glycine synthesis from 4-hydroxyproline (an abundant amino acid in milk and neonatal blood) in tissues of sow-reared piglets with normal birth weights. Piglets were euthanized at 0, 7, 14 and 21 days of age, and their tissues were used to determine glycine synthesis from 0 to 5 mM 4-hydroxyproline, activities and mRNA expression of key glycine-synthetic enzymes, and their cell-specific localization. Activities of 4-hydroxyproline oxidase (OH-POX), proline oxidase (POX), serine hydroxymethyltransferase (SHMT), threonine dehydrogenase (TDH), alanine:glyoxylate transaminase (AGT), and 4-hydroxy-2-oxoglutarate aldolase (HOA) occurred in the kidneys and liver from all age groups of piglets, and in the pancreas of 7- to 21-day-old piglets. Activities of OH-POX and HOA were absent from the small intestine of newborn pigs but present in the small intestine of 7- to 21-day-old piglets and in the skeletal muscle of 14- to 21-day-old piglets. Between days 0 and 21 of age, the enzymatic activities of OH-POX, AGT, and HOA decreased in the liver and kidneys but increased in the pancreas and small intestine with age. The mRNA levels of these three enzymes changed in a manner similar to their enzymatic activities. In contrast to OH-POX, AGT, and HOA, the enzymatic activities of POX, SHMT, and TDH were present in the kidneys, liver, and intestine of all age groups of piglets. Glycine was synthesized from 0.1 to 5 mM 4-hydroxyproline in the liver and kidney from 0- to 21-day-old piglets, as well as the pancreas, small intestine, and skeletal muscle from 14- to 21-day-old piglets in a concentration-dependent manner. Collectively, our findings indicate that 4-hydroxyproline is used for the synthesis of glycine in tissues of piglets to compensate for the deficiency of glycine in milk.

BACKGROUNDDietary supplementation with L-arginine (Arg) has been shown to increase the volume of fetal fluids in gestating swine. Aquaporins (AQPs), known as water channel proteins, are essential for embryonic growth and development. It was not known if Arg mediates water transport through AQPs in porcine conceptus trophectoderm (pTr2) cells.METHODSpTr2 cells derived from pregnant gilts on day 12 of gestation were cultured in customized Arg-free Dulbecco's modified Eagle's Ham medium (DMEM) supplemented with either 0.00, 0.25, or 0.50 mM Arg.RESULTSArg treatment increased water transport and the expression of AQP3, which was abundantly expressed in pTr2 cells at both the mRNA and protein levels. Arg also increased the expression of iNOS and the synthesis of nitric oxide (NO) in pTr2 cells. The presence of Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME; an inhibitor of NO synthase) significantly attenuated the Arg-induced expression of AQP3. Furthermore, 0.50 mM Arg increased the concentrations of cAMP and the abundances of phosphorylated cAMP-dependent protein kinase A (PKA), phosphorylated PKA α/β/γ, and phosphorylated CREB. These effects of Arg were mimicked by Forskolin (a cell-permeable activator of adenylyl cyclase), but inhibited by H-89 (an inhibitor of cAMP-dependent protein kinase).CONCLUSIONSThe results of this study demonstrate that Arg regulates AQP3 expression and promotes water transport in pTr2 cells through NO- and cAMP-dependent signaling pathways.

Background Most embryonic loss in pigs occurs before d 30 of gestation. Dietary supplementation with L -arginine (Arg) during early gestation can enhance the survival and development of conceptuses (embryo/fetus and its extra-embryonic membranes) in gilts. However, the underlying mechanisms remain largely unknown. Methods Between d 14 and 30 of gestation, each gilt was fed daily 2 kg of a corn- and soybean-meal based diet (12% crude protein) supplemented with either 0.4% Arg (as Arg-HCl) or an isonitrogenous amount of L -alanine (Control). There were 10 gilts per treatment group. On d 30 of gestation, gilts were fed either Arg-HCl or L -alanine 30 min before they were hysterectomized, followed by the collection of placentae, embryos, fetal membranes, and fetal fluids. Amniotic and allantoic fluids were analyzed for nitrite and nitrate [NOx; stable oxidation products of nitric oxide (NO)], polyamines, and amino acids. Placentae were analyzed for syntheses of NO and polyamines, water and amino acid transport, concentrations of amino acid-related metabolites, and the expression of angiogenic factors and aquaporins (AQPs). Results Compared to the control group, Arg supplementation increased ( P < 0.05) the number of viable fetuses by 1.9 per litter, the number and diameter of placental blood vessels (+ 25.9% and + 17.0% respectively), embryonic survival (+ 18.5%), total placental weight (+ 36.5%), the total weight of viable fetuses (+ 33.5%), fetal crown-to-rump length (+ 4.7%), and total allantoic and amniotic fluid volumes (+ 44.6% and + 75.5% respectively). Compared to control gilts, Arg supplementation increased ( P < 0.05) placental activities of GTP cyclohydrolase-1 (+ 33.1%) and ornithine decarboxylase (+ 29.3%); placental syntheses of NO (+ 26.2%) and polyamines (+ 28.9%); placental concentrations of NOx (+ 22.5%), tetrahydrobiopterin (+ 21.1%), polyamines (+ 20.4%), cAMP (+ 27.7%), and cGMP (+ 24.7%); total amounts of NOx (+ 61.7% to + 96.8%), polyamines (+ 60.7% to + 88.7%), amino acids (+ 39% to + 118%), glucose (+ 60.5% to + 62.6%), and fructose (+ 41.4% to + 57.0%) in fetal fluids; and the placental transport of water (+ 33.9%), Arg (+ 78.4%), glutamine (+ 89.9%), and glycine (+ 89.6%). Furthermore, Arg supplementation increased ( P < 0.05) placental mRNA levels for angiogenic factors [ VEGFA120 (+ 117%), VEGFR1 (+ 445%), VEGFR2 (+ 373%), PGF (+ 197%), and GCH1 (+ 126%)] and AQPs [ AQP1 (+ 280%), AQP3 (+ 137%), AQP5 (+ 172%), AQP8 (+ 165%), and AQP9 (+ 127%)]. Conclusion Supplementing 0.4% Arg to a conventional diet for gilts between d 14 and d 30 of gestation enhanced placental NO and polyamine syntheses, angiogenesis, and water and amino acid transport to improve conceptus development and survival.

Most embryonic loss in pigs occurs before d 30 of gestation. Dietary supplementation with L-arginine (Arg) during early gestation can enhance the survival and development of conceptuses (embryo/fetus and its extra-embryonic membranes) in gilts. However, the underlying mechanisms remain largely unknown. Between d 14 and 30 of gestation, each gilt was fed daily 2 kg of a corn- and soybean-meal based diet (12

本试验旨在研究饲粮添加L-肉碱对生长育肥母猪生长性能、胴体品质和肉品质的影响.选取体重[(30.42±3.24)kg]相近的PIC商品母猪420头,随机分为2组,每组7个重复,每个重复30头.对照组饲喂基础饲粮,试验组在基础饲粮的基础上添加100 mg/kg L-肉碱.试验期共计105 d.结果表明:1)与对照组相比,试验组生长育肥母猪各阶段平均日增重、平均日采食量、料重比和存活率均无显著差异(P＞0.05).2)与对照组相比,饲粮添加L-肉碱显著提高生长育肥母猪背膘厚度、背最长肌长度和重量(P＜0.05),显著降低下颌脂肪指数(P＜0.05),显著降低背最长肌剪切力、滴水损失、肌纤维直径和面积(P＜0.05),显著提高背最长肌肌纤维密度(P＜0.05).3)与对照组相比,饲粮添加L-肉碱提高生长育肥母猪背最长肌肌内脂肪含量(P＜0.05),但显著降低背最长肌亚油酸、花生酸和花生三烯酸含量(P＜0.05).4)与对照组相比,饲粮添加L-肉碱显著提高生长育肥母猪背最长肌脂肪酸合成酶(FAS)mRNA相对表达量(P＜0.05),显著降低背最长肌肌球蛋白重链Ⅱb(MyHC Ⅱb)mRNA相对表达量(P＜0.05).综上所述,饲粮添加100 mg/kg L-肉碱对生长育肥母猪生长性能无显著影响,但可以影响背最长肌肌内脂肪沉积和肌纤维性状,并改善胴体品质和肉品质.

trans-4-Hydroxy-l-proline is highly abundant in collagen (accounting for about one-third of body proteins in humans and other animals). This imino acid (loosely called amino acid) and its minor analogue trans-3-hydroxy-l-proline in their ratio of approximately 100:1 are formed from the post-translational hydroxylation of proteins (primarily collagen and, to a much lesser extent, non-collagen proteins). Besides their structural and physiological significance in the connective tissue, both trans-4-hydroxy-l-proline and trans-3-hydroxy-l-proline can scavenge reactive oxygen species and have both structural and physiological significance in animals. The formation of trans-4-hydroxy-l-proline residues in protein kinases B and DYRK1A, eukaryotic elongation factor 2 activity, and hypoxia-inducible transcription factor plays an important role in regulating their phosphorylation and catalytic activation as well as cell signaling in animal cells. These biochemical events contribute to the modulation of cell metabolism, growth, development, responses to nutritional and physiological changes (e.g., dietary protein intake and hypoxia), and survival. Milk, meat, skin hydrolysates, and blood, as well as whole-body collagen degradation provide a large amount of trans-4-hydroxy-l-proline. In animals, most (nearly 90%) of the collagen-derived trans-4-hydroxy-l-proline is catabolized to glycine via the trans-4-hydroxy-l-proline oxidase pathway, and trans-3-hydroxy-l-proline is degraded via the trans-3-hydroxy-l-proline dehydratase pathway to ornithine and glutamate, thereby conserving dietary and endogenously synthesized proline and arginine. Supplementing trans-4-hydroxy-l-proline or its small peptides to plant-based diets can alleviate oxidative stress, while increasing collagen synthesis and accretion in the body. New knowledge of hydroxyproline biochemistry and nutrition aids in improving the growth, health and well-being of humans and other animals.

为研究湿基发酵豆粕对蛋鸡产蛋性能、养分表观代谢率和蛋品质指标的影响,试验选取23周龄罗曼粉壳蛋鸡6000羽,随机分为2个组,每组6个重复,每个重复500羽.对照组全程饲喂基础饲粮,试验组在基础饲粮中添加5％湿基发酵豆粕替代等量豆粕进行饲喂,试验为期6周.结果表明:添加5％湿基发酵豆粕,蛋鸡的脏蛋率、畸形蛋率显著降低(P<0.01),合格蛋率(P<0.01)、粗蛋白表观代谢率和磷表观代谢率均显著提高(P=0.01),但产蛋率、破蛋率、软壳蛋率、平均日采食量、平均蛋重、蛋重、蛋白高度、蛋黄重、蛋壳重和蛋白重无显著变化(P>0.05);试验第6周,哈夫单位(Haugh Unit)显著提高(P=0.05),蛋黄比色显著降低(P<0.01).试验结果表明,在蛋鸡饲粮中添加5％湿基发酵豆粕可以提高合格蛋率并改善鸡蛋品质.

The objective of current study was to investigate the effects of dietary N-Carbamylglutamate (NCG) supplementation on growth performance, carcass characteristics, meat quality and muscle fiber trait of finishing pigs; Methods: A total of 350 female PIC pigs (30.41 +/- 3.24kg) were divided into 2 treatments with 7 replicates of 25 each for a 105-day trial. Two treatment diets included a basal diet (control) and an experimental diet with 0.1% NCG supplementation in the basal diet. Growth performance was evaluated for each phase. Carcass characteristics and meat quality were determined in the last phase.; (3) Results: The results indicated that growth performance was not affected by treatments in all phases(P>0.05). NCG tended to improve dressing percentage (P=0.06). NCG not only increased the longissimus dorsi muscle length and weight, marbling score, intramuscular fat (IMF) level and tenderness, but also decreased drip loss of LM muscle (P<0.05). Mandibular fat index was decreased by NCG (P<0.05). NCG supplementation increased the myosin heavy chain (MyHC) I, MyHC-IIa and fatty acid synthase (FAS) mRNA expression, but decreased myofiber cross-sectional area and muscle fiber diameter (P<0.05); Conclusions: Dietary 0.1% NCG supplementation could improve the carcass trait and meat quality through modulating the genes expression associating with myofiber development and intramuscular fat deposition in finishing pigs.

This study was designed to evaluate the effects of guanidinoacetic acid (GAA) on growth performance, carcass characteristics, meat and muscle fibre traits of growing-finishing gilts. 300 female PIC pigs were randomly divided (30.10 ± 2.94 kg) into 2 treatments with 6 replicates of 25 each for a 100-day trial. Two dietary treatments were comprised of a control diet and a control diet fortified with 450 mg/kg GAA. Growth performance was evaluated for each phase. Carcass characteristics and meat quality were determined at last phase. Gilts had free access to feed and water during the experiment. The result indicated that GAA did not affect growth performance (p > 0.05). GAA not only increased longissimus dorsi (LM) muscle weight but also decreased its shear force, b*value and drip loss (p < 0.05). Mandibular fat index was decreased by GAA (p < 0.05). GAA upregulated myosin heavy chain (MyHC) I mRNA expression with lower myofibre cross-sectional area and fibre diameter in LM muscle (p < .05). In conclusion, GAA can improve carcass characteristics and meat quality by changing muscle fibre characteristics and reducing mandibular fat index in finishing gilts.

Dietary polyamines and amino acids (AAs) are crucial for human growth, development, reproduction, and health. However, the scientific literature shows large variations in polyamine and AA concentrations among major staple foods of plant origin, and there is a scarcity of information regarding their complete composition of AAs. To provide a much-needed database, we quantified polyamines, agmatine, and AAs in select plant-source foods. On the dry matter basis, total polyamines were most abundant in corn grains, followed by soybeans, sweet potatoes, pistachio nuts, potatoes, peanuts, wheat flour and white rice in descending order. Glutamine was the most abundant AA in pistachio nuts, wheat flour and white rice, arginine in peanuts, leucine in corn grains, glutamate in soybeans, and asparagine in potatoes and sweet potatoes. Glutamine was the second most abundant AA in corn grains, peanuts, potatoes, and soybeans, arginine in pistachio nuts, proline in wheat flour, and glutamate in sweet potatoes and white rice. Free AAs represented ≤ 3.1% of total AAs in corn grains, peanuts, pistachio nuts, soybeans, wheat flour and white rice, but 34.4% and 28.5% in potatoes and sweet potatoes, respectively. Asparagine accounted for 32.3%, 17.5%, and 19.4% of total free AAs in potatoes, sweet potatoes, and white rice, respectively. The content of histidine, glycine, lysine, tryptophan, methionine, cysteine, and threonine was relatively low in corn grains, potatoes, sweet potatoes, and white rice. All of the analyzed plant-source foods lacked taurine, creatine, carnosine and anserine (antioxidants that are abundant in meats and also present in milk), and contained little 4-hydroxyproline. Proper proportions of plant- and animal-source products are likely most desirable for optimizing human nutrition and health.

This experiment was conducted to evaluate the effects of different sources and levels of trace elements on growth performance, carcass composition and mineral excretion levels of broilers. In a completely randomised experimental design, 900 one-day-old male Ross-308 broilers were assigned to 5 treatments, with 6 replicates of 30 birds each. The control group (CITE) was fed with a basal diet containing regular inclusion levels of inorganic trace elements. Treatment groups were supplied with reduced levels (30% and 50% of the regular level) of inorganic (ITE) or organic trace elements (OTE), respectively. Groups 50% ITE, 30% OTE and 50% OTE diets had equivalent average daily gain (ADG), average daily feed intake (ADFI), feed to gain ratio (F/G ratio) and mortality rate compared with group CITE in any phase. However, compared with group CITE chicks in group 30% ITE have lower ADG and ADFI and higher F/G ratio. The carcass yields were not affected by dietary treatments. Compared with group CITE, in groups 30% ITE, 50% ITE, 30% OTE and 50% OTE the shear force values of the breast muscle were only 71.8%, 83.4%, 63.5% and 59.4% (p < 0.05), respectively. Birds received diets containing reduced levels of trace elements had diminished excretions of Mn and Zn throughout the entire period (p < 0.01). In conclusion, the reduced supplementation of trace elements had no or slightly negative impact on growth performance, carcass yield and meat quality, but decreased faecal mineral excretion. Moreover, the trace element supply as OTE played a limited role on performance and excretion and was only partly beneficial for animal performance in case the trace element supply was reduced to 30%.

Milk is an important food for mammalian neonates, but its insufficient production is a nutritional problem for humans and other animals. Recent studies indicate that dietary supplementation with l-arginine (Arg) increases milk production in mammals, including sows, rabbits, and cows. However, the underlying molecular mechanisms remain largely unknown. The present study was conducted with porcine mammary epithelial cells (PMECs) to test the hypothesis that Arg enhances milk protein synthesis via activation of the mechanistic target of rapamycin (mTOR) cell signaling. PMECs were cultured for 4 days in Arg-free basal medium supplemented with 10, 50, 200, or 500 μmol/L Arg. Rates of protein synthesis and degradation in cells were determined with the use of l-[ring-2,4-3H]phenylalanine. Cell medium was analyzed for β-casein and α-lactalbumin, whereas cells were used for quantifying total and phosphorylated levels of mTOR, ribosomal protein S6 kinase (p70S6K), 4E-binding protein 1 (4EBP1), ubiquitin, and proteasome. Addition of 50–500 μmol/L Arg to culture medium increased (P < 0.05) the proliferation of PMECs and the synthesis of proteins (including β-casein and α-lactalbumin), while reducing the rates of proteolysis, in a dose-dependent manner. The phosphorylated levels of mTOR, p70S6K and 4EBP1 were elevated (P < 0.05), but the abundances of ubiquitin and proteasome were lower (P < 0.05), in PMECs supplemented with 200–500 μmol/L Arg, compared with 10–50 μmol/L Arg. These results provide a biochemical basis for the use of Arg to enhance milk production by sows and have important implications for improving lactation in other mammals (including humans and cows).

Glycine has crucial roles in nutrition and metabolism and is the most abundant AA in the plasma of newborn pigs (approximately 1 mM; 2- to 3-fold greater concentrations than in plasma of other species). Quantitative analysis has shown that the classic pathways for glycine synthesis (from serine, threonine, and choline) are insufficient to meet the metabolic requirements of neonatal pigs. Therefore, we hypothesized that there is an additional pathway for endogenous synthesis of glycine. On d 1, 7, 14, and 21 of lactation, milk samples were obtained from 6 sows. Six piglets were euthanized on each of those days to obtain plasma and tissue samples for analyses of AA, enzyme activities, and expression of proteins and mRNA. Data were analyzed by 1-way ANOVA. Our results indicated high concentrations of hydroxyproline as a tripeptide in sow's milk and plasma from piglets. The specific activities of hydroxyproline oxidase (OH-POX), alanine:glyoxylate aminotransferase, and 4-hydroxy-2-oxoglutarate aldolase, which are key enzymes for synthesis of glycine from hydroxyproline, decreased (P < 0.05) in the liver and kidneys between d 1 and 21 but increased (P < 0.05) in the pancreas and small intestine. Similar results were obtained for the expression of mRNA for those enzymes and for proline oxidase (POX). For the serine- and threonine-dependent glycine pathways, specific activities and expression of mRNA for serine hydroxymethyltransferase and threonine dehydrogenase increased (P < 0.05) between d 1 and 21. Immunohistochemistry (IHC) revealed that the localization of OH-POX and POX proteins in the liver switched from periportal to perivenous hepatocytes with age, which indicated a change in hepatic catabolism of hydroxyproline and proline. In the kidneys, the abundance of OH-POX and POX proteins appeared to decrease with age. Results of IHC also revealed the presence of OH-POX and POX in the pancreas, small intestine, stomach, skeletal muscle, and gallbladder. These findings indicate the presence of the hydroxyproline–glycine pathway for the synthesis of glycine from milk- and endogenous collagen–derived hydroxyproline via interorgan metabolism in neonatal pigs, which may compensate for a severe deficiency of glycine in sow's milk. Supported by funds from the USDA National Institute of Food and Agriculture.

Type 2 diabetes has become a global public health problem affecting approximately 380 million people throughout the world. It can cause many complications and lead to greater mortality. At present, there is no available medicine for effectively preventing diabetes. L-arginine, a functional amino acid, the precursor of nitric oxide, plays a crucial role in maintenance, reproduction, growth, anti-aging and immunity for animals. Growing clinical evidence indicates that dietary L-arginine supplementation can reduce obesity, decrease arterial blood pressure, resist oxidation and normalize endothelial dysfunction to bring about remission of type 2 diabetes. The potential molecular mechanism may play a role in modulating glucose homeostasis, promoting lipolysis, maintaining hormone levels, ameliorating insulin resistance, and fetal programing in early stages. The possible signaling pathway of the beneficial effects of L-arginine likely involves L-arginine-nitric oxide pathway through which cell signal protein can be activated. Accumulating studies have indicated that L-arginine may have potential to prevent and/or relieve type 2 diabetes via restoring insulin sensitivity in vivo.

l-Arginine has been reported to enhance brown adipose tissue developments in fetal lambs of obese ewes, but the underlying mechanism is unknown. The present study tested the hypothesis that l-arginine stimulates growth and development of brown adipocyte precursor cells (BAPCs) through activation of mammalian target of rapamycin cell signaling. BAPCs isolated from fetal lambs at day 90 of gestation were incubated   for 6 h in arginine-free DMEM, and then cultured in DMEM with concentrations of 50, 100, 200, 500 or 1000 μmol l-arginine/L for 24–96 h. Cell proliferation, protein turnover, the mammalian target of rapamycin (mTOR) signaling pathway and pre-adipocyte differentiation markers were determined. l-arginine treatment enhanced (P < 0.05) BAPC growth and protein synthesis, while inhibiting proteolysis in a dose-dependent manner. Compared with 50 and 100 μmol/L (the concentrations of arginine in the maternal plasma of obese ewes), 200 μmol l-arginine/L (the concentrations of arginine in the maternal plasma of obese ewes receiving arginine supplementation) increased (P < 0.05) the abundances of phosphorylated mTOR, P70S6K and 4EBP1, as well as the abundances of PGC1α, UCP1, BMP7 and PRDM16. These novel findings indicate that increasing extra-cellular arginine concentration from 50 to 200 µmol/L activates mTOR cell signaling in BAPCs and enhances their growth and development in a dose-dependent manner. Our results provide a mechanism for arginine supplementation to enhance the development of brown adipose tissue in fetal lambs.

Pigs exhibit severe naturally occurring intrauterine growth restriction (IUGR). Under current feeding programs, approximately 20 to 25% of piglets are born with a birth weight of <1.1 kg. Intrauterine growth restriction accounts for 76% of preweaning deaths. To date, IUGR piglets are culled on farms and there are no effective nutritional means to prevent their death or enhance their growth. In the present study, we conducted an experiment to determine the effects of l-arginine supplementation on the growth and survival of IUGR piglets. In this experiment, 88 IUGR piglets (with a mean birth weight of 0.85 kg) from 22 sows (4 IUGR piglets/sow) were randomly assigned into 4 groups. They were nursed by sows and orally administered 0, 0.1, 0.2, or 0.4 g l-arginine (in the form of l-arginine HCl) per kilogram BW twice daily. The total doses of l-arginine were 0, 0.2, 0.4, or 0.8 g/d per kilogram BW. Appropriate amounts of l-alanine were added to the oral l-arginine solutions so that all groups of piglets received the same amount of nitrogen. Piglets were weighed on d 1, 7, and 14 of age. On d 14, blood samples (1 mL) were obtained from the jugular vein of piglets at 1 h after suckling, and their milk consumption was measured over a 9-h period using the weigh–suckle–weigh technique. Milk intake did not differ (P > 0.05) among the 4 groups of piglets. Oral administration of Arg increased (P < 0.05) Arg concentrations in the plasma in a dose-dependent manner. When compared with the control group (ADG = 152 g/d between d 1 and 14), IUGR piglets administered 0.2 and 0.4 g l-arginine/d per kilogram BW increased (P < 0.05) by 19 and 31%, respectively. The ADG did not differ (P > 0.05) between the controls and the IUGR piglets receiving 0.8 g l-arginine/d per kilogram BW. The survival rates of the IUGR piglets were 50, 75, 90, and 90%, respectively, for the 0, 0.2, 0.4, and 0.8 g l-arginine/d per kilogram BW groups. Growth and survival of IUGR piglets can be improved through supplementation of l-arginine HCl. Supported by USDA National Institute of Food and Agriculture grants and Texas A&M University.