Yingying Liu

Effect of dietary arginine and N-carbamoylglutamate supplementation on reproduction and gene expression of eNOS, VEGFA and PlGF1 in placenta in late pregnancy of sows

The objectives of this study were to investigate the potential mechanisms of dietary arginine (Arg) and N-carbamoylglutamate (NCG) supplementation on reproductive performance of sows. Twenty-seven crossbred (Landrace×Large White) sows with similar body weight and parity at day (90±1) of gestation were assigned randomly into 3 groups (n=9) control group, Arg group, NCG group, and fed with the following diets: a control diet, and the control diet supplemented with 1.0% Arg or 0.1% NCG. Litter size was recorded. Blood samples were obtained for biochemical analyses. Placenta chorioallantoic membrane tissue collected immediately after birth to preserve in RNA stabilizer for mRNA analysis of endothelial nitric oxide synthase (eNOS), endothelial growth factor a (VEGFA) and placenta growth factor 1 (PlGF1) by real time-PCR. The results showed that compared with the control group, the average birth weight of all piglets born alive were 16.2% and 14.3% higher in the Arg and NCG groups (P<0.05), respectively; plasma VEGFA was higher in the Arg group (P<0.05). The expression of VEGFA in the allantochorion tissue of the NCG-supplemented group was higher (P<0.01), and tended to be higher in the Arg-supplemented group (0.05<P<0.1). NCG significantly increased protein concentration of PlGF1 in plasma (P<0.05), and enhanced PlGF1mRNA expression in allantochorion tissue of placenta (P<0.01). The results suggested that dietary Arg and NCG supplementation play important roles in meliorating placental vascular function and promoting the nutrients supply to fetus.

Key mediators of intracellular amino acids signaling to mTORC1 activation.

Mammalian target of rapamycin complex 1 (mTORC1) is activated by amino acids to promote cell growth via protein synthesis. Specifically, Ras-related guanosine triphosphatases (Rag GTPases) are activated by amino acids, and then translocate mTORC1 to the surface of late endosomes and lysosomes. Ras homolog enriched in brain (Rheb) resides on this surface and directly activates mTORC1. Apart from the presence of intracellular amino acids, Rag GTPases and Rheb, other mediators involved in intracellular amino acid signaling to mTORC1 activation include human vacuolar sorting protein-34 (hVps34) and mitogen-activating protein kinase kinase kinase kinase-3 (MAP4K3). Those molecular links between mTORC1 and its mediators form a complicate signaling network that controls cellular growth, proliferation, and metabolism. Moreover, it is speculated that amino acid signaling to mTORC1 may start from the lysosomal lumen. In this review, we discussed the function of these mediators in mTORC1 pathway and how these mediators are regulated by amino acids in details.

Dietary protein intake affects expression of genes for lipid metabolism in porcine skeletal muscle in a genotype-dependent manner

Skeletal muscle is a major site for the oxidation of fatty acids (FA) in mammals, including humans. Using a swine model, we tested the hypothesis that dietary protein intake regulates the expression of key genes for lipid metabolism in skeletal muscle. A total of ninety-six barrows (forty-eight pure-bred Bama mini-pigs (fatty genotype) and forty-eight Landrace pigs (lean genotype)) were fed from 5 weeks of age to market weight. Pigs of fatty or lean genotype were randomly assigned to one of two dietary treatments (low- or adequate-protein diet), with twenty-four individually fed pigs per treatment. Our data showed that dietary protein levels affected the expression of genes involved in the anabolism and catabolism of lipids in the longissimus dorsi and biceps femoris muscles in a genotype-dependent manner. Specifically, Bama mini-pigs had more intramuscular fat, SFA and MUFA, as well as elevated mRNA expression levels of lipogenic genes, compared with Landrace pigs. In contrast, Bama mini-pigs had lower mRNA expression levels of lipolytic genes than Landrace pigs fed an adequate-protein diet in the growing phase. These data are consistent with higher white-fat deposition in Bama mini-pigs than in Landrace pigs. In conclusion, adequate provision of dietary protein (amino acids) plays an important role in regulating the expression of key lipogenic genes, and the growth of white adipose tissue, in a genotype- and tissue-specific manner. These findings have important implications for developing novel dietary strategies in pig production.

Signaling Pathways Related to Protein Synthesis and Amino Acid Concentration in Pig Skeletal Muscles Depend on the Dietary Protein Level, Genotype and Developmental Stages

Muscle growth is regulated by the homeostatic balance of the biosynthesis and degradation of muscle proteins. To elucidate the molecular interactions among diet, pig genotype, and physiological stage, we examined the effect of dietary protein concentration, pig genotype, and physiological stages on amino acid (AA) pools, protein deposition, and related signaling pathways in different types of skeletal muscles. The study used 48 Landrace pigs and 48 pure-bred Bama mini-pigs assigned to each of 2 dietary treatments: lower/GB (Chinese conventional diet)- or higher/NRC (National Research Council)-protein diet. Diets were fed from 5 weeks of age to respective market weights of each genotype. Samples of biceps femoris muscle (BFM, type I) and longissimus dorsi muscle (LDM, type II) were collected at nursery, growing, and finishing phases according to the physiological stage of each genotype, to determine the AA concentrations, mRNA levels for growth-related genes in muscles, and protein abundances of mechanistic target of rapamycin (mTOR) signaling pathway. Our data showed that the concentrations of most AAs in LDM and BFM of pigs increased (P<0.05) gradually with increasing age. Bama mini-pigs had generally higher (P<0.05) muscle concentrations of flavor-related AA, including Met, Phe, Tyr, Pro, and Ser, compared with Landrace pigs. The mRNA levels for myogenic determining factor, myogenin, myocyte-specific enhancer binding factor 2 A, and myostatin of Bama mini-pigs were higher (P<0.05) than those of Landrace pigs, while total and phosphorylated protein levels for protein kinase B, mTOR, and p70 ribosomal protein S6 kinases (p70S6K), and ratios of p-mTOR/mTOR, p-AKT/AKT, and p-p70S6K/p70S6K were lower (P<0.05). There was a significant pig genotype-dependent effect of dietary protein on the levels for mTOR and p70S6K. When compared with the higher protein-NRC diet, the lower protein-GB diet increased (P<0.05) the levels for mTOR and p70S6K in Bama mini-pigs, but repressed (P<0.05) the level for p70S6K in Landrace pigs. The higher protein-NRC diet increased ratio of p-mTOR/mTOR in Landrace pigs. These findings indicated that the dynamic consequences of AA profile and protein deposition in muscle tissues are the concerted effort of distinctive genotype, nutrient status, age, and muscle type. Our results provide valuable information for animal feeding strategy.

Effects of dietary protein/energy ratio on growth performance, carcass trait, meat quality, and plasma metabolites in pigs of different genotypes.

BackgroundThe protein/energy ratio is important for the production performance and utilization of available feed resources by animals. Increased protein consumption by mammals leads to elevated feed costs and increased nitrogen release into the environment. This study aimed to evaluate the effects of dietary protein/energy ratio on the growth performance, carcass traits, meat quality, and plasma metabolites of pigs of different genotypes.MethodsBama mini-pigs and Landrace pigs were randomly assigned to two dietary treatment groups (Chinese conventional diet with low protein/energy ratio or National Research Council diet with high protein/energy ratio; n = 24 per treatment) in a 2 × 2 factorial arrangement. Blood and muscle samples were collected at the end of the nursery, growing, and finishing phases.ResultsWe observed significant interactions (P < 0.05) between breed and diet for total fat percentage, intramuscular fat (IMF) content, protein content in biceps femoris (BF) muscle, and plasma urea nitrogen (UN) concentration in the nursery phase; for average daily gain (ADG), average daily feed intake (ADFI), dry matter, IMF content in psoas major (PM) muscle, and plasma total protein and albumin concentrations in the growing phase; and for drip loss and plasma UN concentration in the finishing phase. Breed influenced (P < 0.05) growth performance, carcass traits, and meat quality, but not plasma metabolites. Throughout the trial, Landrace pigs showed significantly higher (P < 0.05) ADG, ADFI, dressing percentage, lean mass rate, and loin-eye area than did Bama mini-pigs, but significantly lower (P < 0.05) feed/gain ratio, fat percentage, backfat thickness, and IMF content. Dietary protein/energy ratio influenced the pH value, chemical composition of BF and PM muscles, and plasma activities of glutamic-pyruvic transaminase and gamma-glutamyl transpeptidase, and plasma concentration of UN.ConclusionsCompared with Landrace pigs, Bama mini-pigs showed slower growth and lower carcass performance, but had better meat quality. Moreover, unlike Landrace pigs, the dietary protein/energy ratio did not affect the growth performance of Bama mini-pigs. These results suggest that, in swine production, low dietary protein/energy ratio may be useful for reducing feed costs and minimizing the adverse effects of ammonia release into the environment.

Effects of dynamic feeding low and high methionine diets on egg quality traits in laying hens

&NA; This study was conducted to investigate effects of dynamic feeding low and high methionine (MET) diets on performance, egg quality traits, and serum metabolites in laying hens. A total of 180 laying hens (Brown Hy‐line, 41 wk old) were allocated into 3 equal groups with 6 replicates each. The average egg production (EP) of each group was around 87% during one‐week statistics before the formal experiment (P = 0.989). The control group (CON) received the control diet (contained 0.30% MET) at both 07:30 h and 15:30 hours. The low‐high group (LH) received a low MET diet (containing 0.27% MET) at 07:30 h and high MET diet (containing 0.33% MET) at 15:30 hours. The high‐low group (HL) received a high MET diet at 07:30 h and low MET diet at 15:30 hours. After 10 wk, blood samples were collected at 4‐hour intervals in a daily cycle initially starting at 07:30 h before feeding. Results showed that the MET intake of a d was not influenced by the treatments (P > 0.05), respectively. The EP of the LH and HL group increased by 2.28 and 2.45% when compared with the CON group (P > 0.05). The hens in the LH group had a lower albumen ratio and thicker eggshell thickness than both CON and HL groups. Egg yolk ratio of the LH group was higher than the HL group (P < 0.05). The serum total cholesterol (TC), total triglyceride (TG), total protein (TP), and calcium (Ca) of the LH group was significantly lower at 07:30 h than the CON and HL groups, and the serum TG of the HL group was lower at 07:30 h than the CON group (P < 0.05). Meanwhile, the LH group also had the lowest value of serum TP at 23:30 h and 03:30 h (P < 0.05). These results demonstrated that dynamic feeding low and high MET diets might alter the circadian variation of serum TC, TG, TP, and Ca, which is consistent with the change of component ratio of egg albumen and yolk and eggshell thickness.

Alteration of inflammatory cytokines, energy metabolic regulators, and muscle fiber type in the skeletal muscle of postweaning piglets

This study was conducted to determine the alterations of inflammatory cytokines, energy metabolic regulators, and muscle fiber type in the LM of the piglets postweaning. Crossbred piglets (Landrace × Large White) weaned at 14 d age were randomly selected from 8 litters and slaughtered at 0 (W0), 1 (W1), 3 (W3), 5 (W5), or 7 (W7) days postweaning. The glycogen content, free glucose concentration, and enzyme activities, including ATPase (Na/K, Ca/Mg), creatine kinase, and lactic dehydrogenase (LDH), were detected in the skeletal muscle tissue. Concentrations of proinflammatory cytokines, including IL-1β, IL-6, and tumor necrosis factor-α (TNF-α), and anti-inflammatory cytokines, including IL-10 and transforming growth factor-β1 (TGF-β1), were measured in serum. The mRNA abundance of the above cytokines, energy metabolic regulators, and muscle fiber type related genes were determined via real-time quantitative PCR analysis. The adenosine monophosphate-activated protein kinase α (AMPKα) signaling was measured by Western blot analysis. Our results showed ATPase activities were lower on W7 d but LDH activity was higher on W3 d after weaning ( < 0.05). Serum TNF-α concentration was markedly increased on W1 d, then returned to the value of preweaning ( < 0.05), and almost all the values of inflammatory cytokines were reduced to a low point on W5 d after weaning. Additionally, the IL-6 mRNA abundance was upregulated during W3 to W7 d, but cytokine TNF-α was upregulated just on W7 d ( < 0.05). The mRNA abundance of AMPKα and uncoupling protein (UCP) 3 were both higher on W1 and W3 d, and UCP2 was higher on W7 d postweaning ( < 0.05). Myosin heavy chain (MyHC) I and MyHC IIx-type fibers were enhanced on W1 d, then returned to the value of preweaning, and the MyHC IIb-type fiber was significantly increased on W5 and W7 d ( < 0.05). Meanwhile, the value of P-AMPKα/T-AMPKα increased on W3 d postweaning ( < 0.05) compared with that on W0 d. These results indicate that weaning stress induced inflammation in skeletal muscle tissue during at least 7 d postweaning. It upregulated the expression of proinflammatory cytokines, which then stimulated the AMPKα and UCP involved in energy metabolism events, accompanied by significant alterations in muscle fiber type.

Supplementation of branched-chain amino acids in protein-restricted diets modulates the expression levels of amino acid transporters and energy metabolism associated regulators in the adipose tissue of growing pigs

This experiment was conducted to investigate the effects of branched-chain amino acids (BCAA) supplemented in protein-restricted diets on the growth performance and the expression profile of amino acid transporters and energy metabolism related regulators in the white adipose tissue (WAT) of different regional depots including dorsal subcutaneous adipose (DSA) and abdominal subcutaneous adipose (ASA). A total of 24 crossbred barrows (7.40 ± 0.70 kg) were randomly divided into 4 groups and were fed the following isocaloric diets for 33 days: 1) a recommended adequate protein diet (AP, 20% CP, as a positive control); 2) a low protein diet (LP, 17% CP); 3) the LP diet supplemented with BCAA (LP + B, 17% CP) to reach the same level of the AP diet group; 4) the LP diet supplemented with 2 times the amount of BCAA (LP + 2B, 17% CP). The daily gain and daily feed intake of the LP diet group were the lowest among all the treatments (P < 0.01). The feed conversion was improved markedly in the group of LP + B compared with the LP diet group (P < 0.05). No significant difference was noted for the serum biochemical parameter concentrations of glucose, triglyceride, nonesterified fatty acid and insulin among the groups (P > 0.05). Moreover, BCAA supplementation down-regulated the expression levels of amino acid transporters including L-type amino acid transporter 1 and sodium-coupled neutral amino acid transporter 2 in DSA, but up-regulated the expression level of L-type amino acid transporter 4 in ASA (P < 0.05). Meanwhile, the energy sensor AMP-activated protein kinase α was activated in the DSA of pigs fed LP diet and in the ASA of the pigs fed AP or LP + 2B diets (P < 0.05). The mRNA expression profile of the selected mitochondrial component and mitochondrial biogenesis associated regulators in DSA and ASA also responded differently to dietary BCAA supplementation. These results suggested that the growth performance of growing pigs fed protein restricted diets supplemented with BCAA could catch up to that of the pigs fed AP diets. The results also partly demonstrated that the regulation mechanisms of BCAA are different in the adipose tissues of different depots.

Effects of dietary ramie powder at various levels on carcass traits and meat quality in finishing pigs

This study investigated the effects of ramie (0, 3, 6, 9, or 12%) included in finishing diets on carcass traits and meat quality of Xiangcun black pigs. Results showed that ramie decreased (linear, P < .05) backfat depth while it increased (linear, P < .05) loin-eye area. A quadratic effect of shear force in longissimus thoracis (LT) was observed, and the lowest value was noted in the 6% ramie group. Protein content in LT was linearly increased by ramie (linear, P < .01). Meanwhile, dietary ramie linearly decreased lipogenic genes mRNA levels and fiber cross-sectional area, but it linearly increased total fiber number of LT. These results suggest that ramie included in the diet <9% is an effective feed crop to partly improve carcass trait and muscle chemical composition without negatively affecting growth performance, and the underlying mechanism may be due to the changed lipogenic potential and myofiber characteristics induced by ramie.