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Extrauterine growth restriction is a common complication of preterm birth. Leucine (Leu) is an agonist for the mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) signaling pathway that regulates translation initiation and protein synthesis in skeletal muscle. Previously, we showed that intermittent intravenous pulses of Leu to neonatal pigs born at term receiving continuous enteral nutrition increases muscle protein synthesis and lean mass accretion. Our objective was to determine the impact of intermittent intravenous pulses of Leu on muscle protein anabolism in preterm neonatal pigs administered continuous parenteral nutrition.Following preterm delivery (on day 105 of 115 gestation), pigs were fitted with umbilical artery and jugular vein catheters and provided continuous parenteral nutrition. Four days after birth, pigs were assigned to receive intermittent Leu (1600 µmol kgLeu concentration in the longissimus dorsi and gastrocnemius muscles increased in the leucine (LEU) group compared with the alanine (ALA) group (P 0.0001). Despite the Leu-induced disruption of the Sestrin2·GATOR2 complex, which inhibits mTORC1 activation, in these muscles (P 0.01), the abundance of mTOR·RagA and mTOR·RagC was not different. Accordingly, mTORC1-dependent activation of 4EBP1, S6K1, eIF4E·eIF4G, and protein synthesis were not different in any muscle between the LEU and ALA groups.Intermittent pulses of Leu do not enhance muscle protein anabolism in preterm pigs supplied continuous parenteral nutrition.

Optimizing enteral nutrition for premature infants may help mitigate extrauterine growth restriction and adverse chronic health outcomes. Previously, we showed in neonatal pigs born at term that lean growth is enhanced by intermittent bolus compared with continuous feeding. The objective was to determine if prematurity impacts how body composition, muscle protein synthesis, and myonuclear accretion respond to feeding modality. Following preterm delivery, pigs were fed equivalent amounts of formula delivered either as intermittent boluses (INT

Background Postnatal growth failure in premature infants is associated with reduced lean mass accretion. Prematurity impairs the feeding-induced stimulation of translation initiation and protein synthesis in the skeletal muscle of neonatal pigs. The objective was to determine whether body weight independently contributes to the blunted postprandial protein synthesis. Methods Preterm and term pigs that were either fasted or fed were stratified into quartiles according to birth weight to yield preterm and term groups of similar body weight; first and second quartiles of preterm pigs and third and fourth quartiles of term pigs were compared (preterm-fasted, n = 23; preterm-fed, n = 25; term-fasted, n = 21; term-fed, n = 21). Protein synthesis rates and mechanistic target of rapamycin complex 1 (mTORC1) activation in skeletal muscle were determined. Results Relative body weight gain was lower in preterm compared to term pigs. Prematurity attenuated the feeding-induced increase in mTORC1 activation in longissimus dorsi and gastrocnemius muscles (P P Conclusion A lower capacity of skeletal muscle to respond adequately to feeding may contribute to reduced body weight gain and lean mass accretion in preterm infants. Impact This study has shown that the feeding-induced increase in protein synthesis of skeletal and cardiac muscle is blunted in neonatal pigs born preterm compared to pigs born at term independently of birth weight. These findings support the notion that preterm birth, and not low birth weight, impairs the capacity of skeletal and cardiac muscle to upregulate mechanistic target of rapamycin-dependent anabolic signaling pathways and protein synthesis in response to the postprandial increase in insulin and amino acids. These observations suggest that a blunted anabolic response to feeding contributes to reduced lean mass accretion and altered body composition in preterm infants.

When neonatal pigs continuously fed formula are supplemented with leucine pulses, muscle protein synthesis and body weight gain are enhanced. To identify the responsible mechanisms, we combined plasma metabolomic analysis with transcriptome expression of the transcriptome and protein catabolic pathways in skeletal muscle. Piglets (n = 23, 7-day-old) were fed continuously a milk replacement formula via orogastric tube for 21 days with an additional parenteral infusion (800 μmol kg(−1) h(−1)) of either leucine (LEU) or alanine (CON) for 1 h every 4 h. Plasma metabolites were measured by liquid chromatography-mass spectrometry. Gene and protein expression analyses of longissimus dorsi muscle were performed by RNA-seq and Western blot, respectively. Compared with CON, LEU pigs had increased plasma levels of leucine-derived metabolites, including 4-methyl-2-oxopentanoate, beta-hydroxyisovalerate, β-hydroxyisovalerylcarnitine, and 3-methylglutaconate (P ≤ 0.05). Leucine pulses downregulated transcripts enriched in the Kyoto Encyclopedia of Genes and Genomes terms “spliceosome,” “GAP junction,” “endocytosis,” “ECM-receptor interaction,” and “DNA replication”. Significant correlations were identified between metabolites derived from leucine catabolism and muscle genes involved in protein degradation, transcription and translation, and muscle maintenance and development (P ≤ 0.05). Further, leucine pulses decreased protein expression of autophagic markers and serine/threonine kinase 4, involved in muscle atrophy (P ≤ 0.01). In conclusion, results from our studies support the notion that leucine pulses during continuous enteral feeding enhance muscle mass gain in neonatal pigs by increasing protein synthetic activity and downregulating protein catabolic pathways through concerted responses in the transcriptome and metabolome.

Extrauterine growth restriction is a common complication of preterm birth and is associated with reduced lean growth and long-term morbidities. We previously showed that intermittent pulses of leucine during continuous orogastric feeding increases mTORC1 signaling to protein synthesis in skeletal muscle of neonatal pigs born at term. The objective of this study was to determine the extent to which leucine pulses during continuous feeding would promote lean growth by enhancing mTORC1 signaling in a preterm piglet model. Pigs delivered by cesarean section at 105 d gestation were continuously fed a protein and energy balanced milk-replacer diet [195 kcal ME and 13.5 g protein (kg body weight; BW)-1·d-1)]. Pigs (n=11-12) were randomly assigned to Leucine (LEU) or Alanine (ALA, isonitrogenous control) groups and treatments were administered as a pulse (1.6 mmol·kg BW-1·h-1) for 1 h every 4 h for 21 d. Body composition was determined by DXA and indices of amino acid signaling and mTORC1 activation were determined postprandially, 60 min after initiation of the last pulse. LEU pigs had a 10% greater average daily gain (ADG) (P < 0.05) than ALA pigs. Total lean mass tended to be greater (+13%; P < 0.06) in LEU compared with ALA, and longissimus dorsi muscle weight was 17% heavier in LEU than ALA pigs (P=0.01). Indices of mTORC1 activation, i.e., phosphorylation of S6K1 and 4EBP1 and abundance of the eIF4E-eIF4G complex, were increased in longissimus dorsi and gastrocnemius muscle of LEU compared with ALA pigs (P < 0.05). These results show that leucine supplementation during continuous feeding enhances mTORC1-activated translation initiation in skeletal muscle leading to an increase in muscle mass and lean growth in a preterm piglet model. Research was supported by NIH and USDA.

Objectives: Postnatal growth faltering is common after preterm birth. Recently we showed that premature birth in piglets impairs normal postnatal weight gain and skeletal muscle protein synthesis compared to piglets born at term. This response is associated with a reduction in the feeding-induced activation of Akt and subsequent downstream signaling, despite no change in insulin receptor activation. The aim of this study was to identify key regulators of Akt responsible for the blunted anabolic response in preterm muscle. Methods: Piglets delivered by cesarean section 11 d (preterm/PT) or 2 d (term/T) before term birth were fed by total parenteral nutrition. On day 3, after 4 h fasting, piglets were fasted one additional h or fed orally a sow milk replacer (per kg body weight: 31.5 kcal, 1.3 g carbohydrate, 2.7 g amino acids BW, 1.6 g lipid). Positive and negative regulators of Akt activity in longissimus dorsi muscle were determined by Western blot. Results: Phosphorylation of Akt1 and Akt2, but not Akt3, was lower in PT than in T pigs (P < 0.05). Phosphorylation of Akt activators, PDK1 and mTORC2, and the abundance of Ubl4A, a positive regulator of Akt, were lower in PT than in T (P < 0.05). Abundance of Akt inhibitors, PHLPP and SHIP2, but not PTEN, was higher in PT than in T (P < 0.05). Activation of the Akt phosphatase, PP2A, was unaffected by feeding in PT but inhibited by feeding in T pigs (P < 0.05). Conclusions: These results show that the feeding-induced activation of positive regulators of Akt is reduced by preterm birth, whereas the activation of negative regulators is enhanced. Our findings suggest that premature birth impairs the activation of Akt that is essential for channeling dietary nutrients for anabolism and likely contributes to the postnatal growth faltering of prematurity. Research Support: NIH and USDA.

Extrauterine growth restriction in premature infants is largely attributed to reduced lean mass accretion and is associated with long-term morbidities. Previously, we demonstrated that prematurity blunts the feeding-induced stimulation of translation initiation signaling and protein synthesis in skeletal muscle of neonatal pigs. The objective of the current study was to determine whether the blunted feeding response is mediated by reduced responsiveness to insulin, amino acids, or both. Pigs delivered by cesarean section preterm (PT; 103 days, n = 25) or at term (T; 112 days, n = 26) were subject to euinsulinemic-euaminoacidemic-euglycemic (FAST), hyperinsulinemic-euaminoacidemic-euglycemic (INS), or euinsulinemic-hyperaminoacidemic-euglycemic (AA) clamps four days after delivery. Indices of mechanistic target of rapamycin complex 1 (mTORC1) signaling and fractional protein synthesis rates were measured after 2 h. Although longissimus dorsi (LD) muscle protein synthesis increased in response to both INS and AA, the increase was 28% lower in PT than in T. Upstream of mTORC1, Akt phosphorylation, an index of insulin signaling, was increased with INS but was 40% less in PT than in T. The abundances of mTOR·RagA and mTOR·RagC, indices of amino acid signaling, increased with AA but were 25% less in PT than in T. Downstream of mTORC1, eIF4E·eIF4G abundance was increased by both INS and AA but attenuated by prematurity. These results suggest that preterm birth blunts both insulin- and amino acid-induced activation of mTORC1 and protein synthesis in skeletal muscle, thereby limiting the anabolic response to feeding. This anabolic resistance likely contributes to the high prevalence of extrauterine growth restriction in prematurity. NEW & NOTEWORTHY Extrauterine growth faltering is a major complication of premature birth, but the underlying cause is poorly understood. Our results demonstrate that preterm birth blunts both the insulin-and amino acid-induced activation of mTORC1-dependent translation initiation and protein synthesis in skeletal muscle, thereby limiting the anabolic response to feeding. This anabolic resistance likely contributes to the reduced accretion of lean mass and extrauterine growth restriction of premature infants.

Background: Orogastric tube feeding is frequently prescribed for neonates who cannot ingest food normally. In a piglet model of the neonate, greater skeletal muscle growth is sustained by upregulation of translation initiation signaling when nutrition is delivered by intermittent bolus meals, rather than continuously. Objectives: The objective of this study was to determine the long-term effects of feeding frequency on organ growth and the mechanism by which feeding frequency modulates protein anabolism in these organs. Methods: Eighteen neonatal pigs were fed by gastrostomy tube the same amount of a sow milk replacer either by continuous infusion (CON) or on an intermittent bolus schedule (INT). After 21 d of feeding, the pigs were killed without interruption of feeding (CON; n = 6) or immediately before (INT-0; n = 6) or 60 min after (INT-60; n = 6) a meal, and fractional protein synthesis rates and activation indexes of signaling pathways that regulate translation initiation were measured in the heart, jejunum, ileum, kidneys, and liver. Results: Compared with continuous feeding, intermittent feeding stimulated the growth of the liver (+64%), jejunum (+48%), ileum (+40%), heart (+64%), and kidney (+56%). The increases in heart, kidney, jejunum, and ileum masses were proportional to whole body lean weight gain, but liver weight gain was greater in the INT-60 than the CON, and intermediate for the INT-0 group. For the liver and ileum, but not the heart, kidney, and jejunum, INT-60 compared with CON pigs had greater fractional protein synthesis rates (22% and 48%, respectively) and was accompanied by an increase in ribosomal protein S6 kinase 1 and eukaryotic initiation factor 4E binding protein 1 phosphorylation. Conclusions: These results suggest that intermittent bolus compared with continuous orogastric feeding enhances organ growth and that in the ileum and liver, intermittent feeding enhances protein synthesis by stimulating translation initiation. National Institute of Arthritis and Musculoskeletal and Skin DiseasesUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute of Arthritis & Musculoskeletal & Skin Diseases (NIAMS) [AR044474, AR46308]; National Institute of Child Health and Human DevelopmentUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD) [HD072891, HD085573, HD099080]; National Institute of Diabetes and Digestive and Kidney DiseasesUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute of Diabetes & Digestive & Kidney Diseases (NIDDK) [DK15658]; United States Department of Agriculture National Institute of Agriculture [2013-67015-20438]; USDA/ARSUnited States Department of Agriculture (USDA)USDA Agricultural Research Service [3092-51000-060] Supported by National Institute of Arthritis and Musculoskeletal and Skin Diseases Grants AR044474 (TAD) and AR46308 (MLF), National Institute of Child Health and Human Development HD072891 (TAD), HD085573 (TAD), and HD099080 (TAD and MLF), National Institute of Diabetes and Digestive and Kidney Diseases DK15658 (SRK), United States Department of Agriculture National Institute of Agriculture grant 2013-67015-20438 (TAD), and by the USDA/ARS under Cooperative Agreement no. 3092-51000-060 (TAD). Public domain – authored by a U.S. government employee

OBJECTIVES: Lean growth in preterm neonates is poor and may increase the lifelong risk for adverse health outcomes. Strategies are needed to promote skeletal muscle growth in the postnatal period. Skeletal muscle growth, which accounts for the largest fraction of lean mass accretion, requires the coordinated activation of protein synthesis, satellite cell (SC; muscle stem cell) proliferation, differentiation, and fusion into muscle fibers. The objective of this study was to determine the effect of feeding modality on SC abundance, myonuclear accretion, and lean growth in preterm neonatal pigs. METHODS: Pigs delivered 10 d preterm by C-section (952 ± 205 g) were fitted with an umbilical artery catheter (later replaced with jugular vein catheter) and an orogastric tube for parenteral and enteral nutrition, respectively. Pigs were assigned to continuous (CONT; n = 14; 7.5 mL/[kg·h]) or intermittent bolus (INT; n = 30; 30 mL/kg every 4 h) feeding for 21 d (210 kcal/kg and 16 g protein/kg per d); pigs were advanced from parenteral to enteral feeding over 6 d. Bromodeoxyuridine (BrdU; 25 mg·kg(−1)) was administered to pigs every 12 h from days 19 to 20, inclusive, to label proliferating cells. Body composition was measured by DXA on day 21. Satellite cell (Pax7+) abundance, myonuclear accretion, and muscle fiber cross-sectional area (CSA) were quantified in the longissimus dorsi muscle by immunofluorescence. RESULTS: Sublaminal Pax7+ SC abundance was similar between CONT and INT groups (60.9 vs. 58.3 ± 6.0 per 1000 fibers). The proportion of sublaminal relative to total Pax7+ SCs was similar between CONT and INT groups (78.8 vs. 78.8 ± 2.2%). The abundance of BrdU + myonuclei, an index of myonuclear accretion, did not differ between CONT and INT groups (26.7 vs. 26.7 ± 3.4 per 1000 fibers). Total myonuclei did not differ between CONT and INT groups (420 vs. 403 ± 16 per 1000 fibers). Muscle fiber CSA did not differ between CONT and INT groups (210 vs. 237 ± 15 µm(2)). Lean and fat masses were similar between groups. CONCLUSIONS: Unlike term pigs, CONT feeding does not blunt lean growth in preterm pigs compared to INT feeding. The absence of increased lean growth with INT feeding is consistent with the similar SC abundance, myonuclear accretion, and muscle fiber CSA between feeding modalities. FUNDING SOURCES: Research was supported by NIH and USDA.

Background: Orogastric tube feeding is indicated in neonates with an impaired ability to ingest food normally and can be administered with an intermittent bolus or continuous feeding schedule. Objectives: The objectives were to 1) compare the long-term effect of continuous with intermittent feeding on growth using the newborn pig as a model, 2) determine whether feeding frequency alters lean tissue and fat mass gain, and 3) identify the signaling mechanisms by which protein deposition is controlled in skeletal muscle in response to feeding frequency. Design: Neonatal pigs were fed the same amount of a balanced formula by orogastric tube either as an intermittent bolus meal every 4 h (INT) or as a continuous infusion (CON). Body composition was assessed at the start and end of the study by dual-energy X-ray absorptiometry, and hormone and substrate profiles, muscle mass, protein synthesis, and indexes of nutrient and insulin signaling were measured after 21 d. Results: Body weight, lean mass, spine length, and skeletal muscle mass were greater in the INT group than in the CON group. Skeletal muscle fractional protein synthesis rates were greater in the INT group after a meal than in the CON group and were associated with higher circulating branched-chain amino acid and insulin concentrations. Skeletal muscle protein kinase B (PKB) and ribosomal protein S6 kinase phosphorylation and eukaryotic initiation factor (eIF) 4E-eIF4G complex formation were higher, whereas eIF2 alpha phosphorylation was lower in the INT group than in the CON group, indicating enhanced activation of insulin and amino acid signaling to translation initiation. Conclusions: These results suggest that when neonates are fed the same amounts of nutrients as intermittent meals rather than continuously there is greater lean growth. This response can be ascribed, in part, to the pulsatile pattern of amino acids, insulin, or both induced by INT, which enables the responsiveness of anabolic pathways to feeding to be sustained chronically in skeletal muscle. National Institute of Arthritis and Musculoskeletal and Skin Diseases grants [AR044474, AR46308]; National Institute of Child Health and Human Development grants [HD072891, HD085573]; USDA National Institute of Agriculture grant [2013-67015-20438]; USDA-Agricultural Research ServiceUnited States Department of Agriculture (USDA) [6250-510000-055] Supported by National Institute of Arthritis and Musculoskeletal and Skin Diseases grants AR044474 (TAD) and AR46308 (MLF), National Institute of Child Health and Human Development grants HD072891 (TAD) and HD085573 (TAD), USDA National Institute of Agriculture grant 2013-67015-20438 (TAD), and by the USDA-Agricultural Research Service under cooperative agreement 6250-510000-055 (TAD). Public domain – authored by a U.S. government employee

Background Feeding stimulates protein synthesis in skeletal muscle of neonates and this response is regulated through activation of mechanistic target of rapamycin complex 1 (mTORC1). The identity of signaling components that regulate mTORC1 activation in neonatal muscle has not been fully elucidated. Objective We investigated the independent effects of the rise in amino acids (AAs) and insulin after a meal on the abundance and activation of potential regulators of mTORC1 in muscle and whether the responses are modified by development. Methods Overnight-fasted 6- and 26-d-old pigs were infused for 2 h with saline (control group) or with a balanced AA mixture (AA group) or insulin (INS group) to achieve fed levels while insulin or AAs, respectively, and glucose were maintained at fasting levels. Muscles were analyzed for potential mTORC1 regulatory mechanisms and results were analyzed by 2-factor ANOVA followed by Tukey's post hoc test. Results The abundances of DEP domain-containing mTOR-interacting protein (DEPTOR), growth factor receptor bound protein 10 (GRB10), and regulated in development and DNA damage response 2 (REDD2) were lower (65%, 73%, and 53%, respectively; P

Corrosion is a destructive symptom that affects the properties of a metal, which means that the physical properties and quality of the metal decrease due to the electrochemical reaction between the metal and its environment so that the strength of the metal decreases. Corrosion control can be used to avoid the negative impact of corrosion, through the pack carburizing treatment method. The material used in this research is AISI 1045 steel. To determine the effect of pack carburizing on the corrosion rate of steel, the research was carried out by varying the suhue of the carburizing pack and corrosive media. In this study, the pack carburizing process with suhue variations used was 750°C, 850°C, 950°C and the corroding media used were air, fresh water and sea water. This was observed in accordance with the application of AISI 1045 material. The corrosive process through corrosive media was carried out for 720 hours. The results showed that pack carburized steel at a temperature of 950°C had a lower corrosion rate than pack carburized steel at 750°C. Also, air corrosive media provides a lower corrosion rate compared to seawater corrosion rate.

Continuous feeding does not elicit an optimal anabolic response but is required for some premature infants. We reported previously that intermittent intravenous pulses of Leu (800 μmol Leu·kg-1·h-1 every 4 h) to continuously fed pigs born at term enhanced skeletal muscle mTOR signaling and protein synthesis (PS). The objective of this study was to determine if the anabolic response of skeletal muscle to intermittent Leu pulses is altered following premature birth. Pigs delivered 10 d preterm by cesarean section were advanced to full oral feeding over four days (195 kcal·kg-1·d-1; 13.5 g protein·kg-1·d-1). Pigs were assigned to 1 of 4 treatments: 1) ALA (continuous feeding; 800 μmol Ala·kg-1·h-1 every 4 h; n = 7); 2) L1× (continuous feeding; 800 μmol Leu·kg-1·h-1 every 4 h; n = 6); 3) L2× (continuous feeding; 1600 μmol Leu·kg-1·h-1 every 4 h; n = 6); and 4) INT (intermittent feeding every 4 h; n = 5). Pigs received a Phe tracer 30 min following the amino acid pulse or intermittent feeding to measure PS in longissimus dorsi muscle. Anabolic signaling downstream of mTOR was determined by immunoblot.ResultsPS was higher in L2× and INT compared to ALA (P < 0.05) but was not different between L2× and INT; PS in L1× was intermediate and not different from other groups. Phosphorylation of 4EBP1 and S6K1 was higher in INT compared to L1× and ALA groups (P < 0.05) but was not different compared to L2×. Phosphorylation of 4EBP1, but not S6K1, was higher in L2× compared to ALA (P < 0.05); phosphorylation of 4EBP1 and S6K1 was not different between L1× and L2×.ConclusionsThese results demonstrate that intravenous Leu enhances mTOR activation and PS in LD muscle of continuously fed preterm pigs. However, the amount required may be higher than in pigs born at term.Source of Research SupportNIH and USDA.

Livestock animals are important dual-purpose models that benefit both agricultural and biomedical research. The neonatal pig is an appropriate model for the human infant to assess long-term effects of early life nutrition on growth and metabolic outcomes. Previously we have demonstrated that prematurity blunts the feeding-induced stimulation of translation initiation and protein synthesis in skeletal muscle of neonatal pigs. The objective of this study was to determine whether reduced sensitivity to insulin and/or amino acids drives this blunted response. Pigs were delivered by caesarean section at preterm (PT, 103 d gestation) or at term (T, 112 d gestation) and fed parenterally for 4 d. On day 4, pigs were subject to euinsulinemic-euaminoacidemic-euglycemic (FAST), hyperinsulinemic-euaminoacidemic-euglycemic (INS), or euinsulinemic-hyperaminoacidemic-euglycemic (AA) clamps for 120 min, yielding six treatments: PT-FAST (n = 7), PT-INS (n = 9), PT-AA (n = 9), T-FAST (n = 8), T-INS (n = 9), and T-AA (n = 9). A flooding dose of L-[4-3H]Phe was injected into pigs 30 min before euthanasia. Birth weight and relative body weight gain were lower in PT than T pigs (P < 0.001). Plasma insulin concentration was increased from ~3 to ~100 µU/mL in INS compared to FAST and AA pigs (P < 0.001); plasma BCAA concentration was increased from ~250 to ~1,000 µmol/L in AA compared to FAST and INS pigs (P < 0.001). Despite achieving similar insulin and amino acid levels, longissimus dorsi AKT phosphorylation, mechanistic target of rapamycin (mTOR)·Rheb abundance, mTOR activation, and protein synthesis were lower in PT-INS than T-INS pigs (Table 1). Although amino-acid induced dissociation of Sestrin2 from GATOR2 was not affected by prematurity, mTOR·RagA abundance, mTOR·RagC abundance, mTOR activation, and protein synthesis were lower in PT-AA than T-AA pigs. The impaired capacity of premature skeletal muscle to respond to insulin or amino acids and promote protein synthesis likely contributes to reduced lean mass accretion. Research was supported by NIH and USDA.

Leucine (Leu) and its metabolite β-hydroxy-β-methylbutyrate (HMB) stimulate mechanistic target of rapamycin (mTOR) complex 1 (mTORC1)-dependent protein synthesis in the skeletal muscle of neonatal pigs. This study aimed to determine whether HMB and Leu utilize common nutrient-sensing mechanisms to activate mTORC1. In study 1, neonatal pigs were fed one of five diets for 24 h: low protein (LP), high protein (HP), or LP supplemented with 4 (LP+HMB4), 40 (LP+HMB40), or 80 (LP+HMB80) μmol HMB·kg body wt−1·day−1. In study 2, neonatal pigs were fed for 24 h: LP, LP supplemented with Leu (LP+Leu), or HP diets delivering 9, 18, and 18 mmol Leu·kg body wt−1·day−1, respectively. The upstream signaling molecules that regulate mTORC1 activity were analyzed. mTOR phosphorylation on Ser2448 and Ser2481 was greater in LP+HMB40, LP+HMB80, and LP+Leu than in LP and greater in HP than in HMB-supplemented groups ( P < 0.05), whereas HP and LP+Leu were similar. Rheb-mTOR complex formation was lower in LP than in HP ( P < 0.05), with no enhancement by HMB or Leu supplementation. The Sestrin2-GATOR2 complex was more abundant in LP than in HP and was reduced by Leu ( P < 0.05) but not HMB supplementation. RagA-mTOR and RagC-mTOR complexes were higher in LP+Leu and HP than in LP and HMB groups ( P < 0.05). There were no treatment differences in RagB-SH3BP4, Vps34-LRS, and RagD-LRS complex abundances. Phosphorylation of Erk1/2 and TSC2, but not AMPK, was lower in LP than HP ( P < 0.05) and unaffected by HMB or Leu supplementation. Our results demonstrate that HMB stimulates mTORC1 activation in neonatal muscle independent of the leucine-sensing pathway mediated by Sestrin2 and the Rag proteins. NEW & NOTEWORTHY Dietary supplementation with either leucine or its metabolite β-hydroxy-β-methylbutyrate (HMB) stimulates protein synthesis in skeletal muscle of the neonatal pig. Our results demonstrate that both leucine and HMB stimulate mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) phosphorylation in neonatal muscle. This leucine-stimulated process involves dissociation of the Sestrin2-GATOR2 complex and increased binding of Rag A/C to mTOR. However, HMB’s activation of mTORC1 is independent of this leucine-sensing pathway.

Objectives: Meal feeding enhances skeletal muscle protein synthesis and lean growth more than continuous feeding in piglets. This enhanced muscle protein synthesis with meal feeding is associated with increased activation of mTORC1-dependent translation initiation. The mechanism underlying this response is unknown. We aimed to identify insulin and amino acid signaling components involved in the enhanced lean growth that results from meal feeding vs. continuous feeding in term-born pigs. Methods: Newborn piglets were fed for 21 d an equal amount of sow milk replacer (12.8 g protein and 155 kcal/(kg BW.d)) by gastrostomy tube either as intermittent bolus meals every 4 h (MEAL) or by continuous infusion (CON). After 21 d, gastrocnemius muscle was collected from CON, and before (MEAL-0) or 60 min after a meal (MEAL-60). Components of the insulin and amino acid signaling pathways up- and downstream of mTORC1 that regulate protein translation were measured. Results: Phosphorylation of AKT and TCS2 was greater in MEAL-60 than in MEAL-0 and CON (P < 0.05). The association of Sestrin2 with GATOR2 was similar in CON and MEAL-0 but was lower in MEAL-60 (P < 0.05). The abundances of RagA-mTOR, RagC-mTOR, and Rheb-mTOR, but not CASTOR1-GATOR2, complexes were higher in MEAL-60 than in CON and MEAL-0 (P < 0.05). The phosphorylation of S6K1 and 4EBP1 was higher in MEAL-60 than CON and MEAL-0 (P < 0.05). The abundances of Sestrin2, GATOR2, CASTOR1, RagA, RagC, and Rheb and the phosphorylation of eIF2alpha, eEF2, ERK1/2 and AMPK were unaffected by treatments. Conclusions: Our results demonstrate that the enhanced rate of skeletal muscle protein synthesis and lean growth with meal feeding compared with continuous feeding are due to the enhanced activation of both insulin and amino acid signaling pathways that result in the greater stimulation of translation initiation. Support: NIH HD085573, USDA CRIS 6250-51000-055, NIH HD072891, USDA NIFA 2013-67015-20438.

OBJECTIVES: Our recent study in a piglet model of the human neonate born at full term showed that intermittent bolus feeding promotes greater rates of protein synthesis in skeletal muscle than continuous feeding, leading to an increase in lean growth. This enhanced rate of muscle protein synthesis with intermittent bolus feeding is associated with an increased activation of mTORC1-dependent translation initiation. However, the mechanism underlying this response is unknown. In this study, we aimed to identify the insulin and/or amino acid signaling components involved in the enhanced stimulation of lean growth by intermittent bolus compared to continuous feeding in term-born pigs. METHODS: Term piglets (2–3 d old) were fed for 21 d an equal amount (240 ml/kg body weight [BW]/d) of sow milk replacer containing 12.8 g protein and 175 kcal/kg BW/d. Feedings were administered by gastrostomy tube either as intermittent bolus meals every 4 h (INT) or by continuous infusion (CON). After 21 d, gastrocnemius muscle was collected from CON, INT-0 (before a meal) and INT-60 (60 min after a meal) groups. Upstream and downstream insulin and amino acid signaling components of relevance to mTORC1 activation and protein translation were measured. RESULTS: Phosphorylation of AKT and TCS2 was greater in INT-60 than in INT-0 and CON groups (P

Postnatal growth of lean mass is commonly blunted in preterm infants and may contribute to short- and long-term morbidities. To determine whether preterm birth alters the protein anabolic response to feeding, piglets were delivered at term or preterm, and fractional protein synthesis rates (Ks) were measured at 3 days of age while fasted or after an enteral meal. Activation of signaling pathways that regulate protein synthesis and degradation were determined. Relative body weight gain was lower in preterm than in term. Gestational age at birth (GAB) did not alter fasting plasma glucose or insulin, but when fed, plasma insulin and glucose rose more slowly, and reached peak value later, in preterm than in term. Feeding increased Ksin longissimus dorsi (LD) and gastrocnemius muscles, heart, pancreas, and kidney in both GAB groups, but the response was blunted in preterm. In diaphragm, lung, jejunum, and brain, feeding increased Ksregardless of GAB. Liver Kswas greater in preterm than term and increased with feeding regardless of GAB. In all tissues, changes in 4EBP1, S6K1, and PKB phosphorylation paralleled changes in Ks. In LD, eIF4E·eIF4G complex formation, phosphorylation of TSC2, mTOR, and rpS6, and association of mammalian target of rapamycin (mTOR1) complex with RagA, RagC, and Rheb were increased by feeding and blunted by prematurity. There were no differences among groups in LD protein degradation markers. Our results demonstrate that preterm birth reduces weight gain and the protein synthetic response to feeding in muscle, pancreas, and kidney, and this is associated with blunted insulin- and/or amino acid-induced translation initiation signaling.

BACKGROUND: Rapid growth of skeletal muscle in the neonate requires the coordination of protein deposition and myonuclear accretion. During this developmental stage, muscle protein synthesis is highly sensitive to amino acid supply, especially Leu, but we do not know if this is true for satellite cells, the source of muscle fiber myonuclei. OBJECTIVE: We examined whether dietary protein restriction reduces myonuclear accretion in the neonatal pig, and if any reduction in myonuclear accretion is mitigated by restoring Leu intake. METHODS: Neonatal pigs (1.53 ± 0.2 kg) were fitted with jugular vein and gastric catheters and fed 1 of 3 isoenergetic milk replacers every 4 h for 21 d: high protein [HP; 22.5 g protein/(kg/d); n= 8]; restricted protein [RP; 11.2 g protein/(kg/d); n= 10]; or restricted protein with Leu [RPL; 12.0 g protein/(kg/d); n= 10]. Pigs were administered 5-bromo-2’-deoxyuridine (BrdU; 15 mg/kg) intravenously every 12 h from days 6 to 8. Blood was sampled on days 6 and 21 to measure plasma Leu concentrations. On day 21, pigs were killed and the longissimus dorsi (LD) muscle was collected to measure cell morphometry, satellite cell abundance, myonuclear accretion, and insulin-like growth factor (IGF) system expression. RESULTS: Compared with HP pigs, postprandial plasma Leu concentration in RP pigs was 37% and 47% lower on days 6 and 21, respectively (P

OBJECTIVES: Extrauterine growth restriction in premature infants is associated with reduced lean mass and long-term morbidities. We have reported previously that intermittent parenteral pulses of Leu promote skeletal muscle mTOR signaling and protein synthesis of continuously fed neonatal pigs born at term. The objective of this study was to determine the effect of prematurity on the response of skeletal muscle anabolic pathways to intermittent parenteral Leu pulses in continuously fed pigs. METHODS: Pigs delivered 10 d preterm by C-section were fitted with jugular vein and carotid artery catheters and an orogastric feeding tube. Pigs were advanced from parenteral to enteral feeding over 4 d (195 kcal · kg(−1) · d(−1); 13.5 g protein · kg(−1) · d(−1)). On day 4, pigs were assigned to 1 of 4 treatments: 1) ALA (continuous feeding, 7.5 mL · kg(−1) · h(−1); 800 μmol Ala · kg(−1) · h(−1) every 4 h; n = 7); 2) L1 × (continuous feeding; 800 μmol Leu · kg(−1) · h(−1) every 4 h; n = 6); 3) L2 × (continuous feeding; 1600 μmol Leu · kg(−1) · h(−1) every 4 h; n = 6); and 4) INT (intermittent feeding; 30 mL · kg(−1) fed over 15 min every 4 h; n = 5). On day 5, pigs received L-[ring-(2)H(5)]-Phe 30 min after starting the pulse (groups 1, 2, and 3) or meal feeding (group 4). Pigs were euthanized 30 min after isotope injection and longissimus dorsi muscle was collected. Protein synthesis was determined by LC/MS-MS. Indices of amino acid signaling and mTOR activation were determined by immunoprecipitation and immunoblot assays. RESULTS: Skeletal muscle protein synthesis was higher in L2 × (+37%) and INT (+31%) compared to ALA (P

OBJECTIVES: Preterm birth is a risk factor for growth faltering. We recently showed in a neonatal piglet model of prematurity that premature birth decreases weight gain and skeletal muscle protein synthesis. This is associated with reduced insulin-induced activation of signaling components downstream of Akt but with no change in the activation of the IR/IRS-1/PI3K axis upstream of Akt. The aim of this study was to identify key regulatory molecules involved in Akt activation that are responsible for the differential response of skeletal muscle to insulin in preterm compared to term pigs. METHODS: Piglets were delivered by cesarean section 11 d (preterm/PT) or 2 d (term/T) before term birth and a jugular vein catheter was placed for delivery of total parenteral nutrition. On day 3, after 4 h fasting, piglets were fasted one additional h or fed an elemental diet (31.5 kcal/kg, 1.3 g/kg carbohydrate, 2.7 g/kg amino acids, and 1.6 g/kg lipid), similar in composition to sow milk, via oral gavage. Longissimus dorsi muscle was collected following euthanasia (fasted state or 60 min after feeding). Positive and negative regulators of Akt activity were determined by immunoprecipitation and immunoblotting assays. RESULTS: Akt1 and Akt2 phosphorylation were lower in PT than in T pigs (P

Sepsis disrupts skeletal muscle proteostasis and mitigates the anabolic response to leucine (Leu) in muscle of mature animals. We have shown that Leu stimulates muscle protein synthesis (PS) in healthy neonatal piglets. To determine if supplemental Leu can stimulate PS and reduce protein degradation (PD) signaling in neonatal muscle during endotoxemia, overnight-fasted neonatal pigs were infused for 8 h with LPS or saline while plasma amino acids, glucose, and insulin were maintained at fasting levels during pancreatic-substrate clamps. Leu or saline was infused during the last hour. Markers of PS and PD were determined in skeletal muscle. Compared with controls, Leu increased PS in longissimus dorsi (LD), gastrocnemius, and soleus muscles. LPS decreased PS in these three muscles by 36%, 28%, and 38%, but Leu antagonized that reduction by increasing PS by 84%, 81%, and 83%, respectively, when supplemented to LPS. Leu increased eukaryotic translation initiation factor (eIF)3b-raptor interactions, eIF4E-binding protein-1, and S6 kinase 1 phosphorylation as well as eIF4E·eIF4G complex formation in LD, gastrocnemius, and soleus muscles of control and LPS-treated pigs. In LD muscle, LPS increased the light chain (LC)3-II-to-LC3 ratio and muscle-specific RING finger (MuRF-1) abundance but not atrogin-1 abundance or AMP-activated protein kinase-α phosphorylation. Leu supplementation to LPS-treated pigs reduced the LC3-II-to-LC3 ratio, MuRF-1 abundance, and AMP-activated protein kinase-α phosphorylation compared with LPS alone. In conclusion, parenteral Leu supplementation attenuates the LPS-induced reduction in PS by stimulating mammalian target of rapamycin complex 1-dependent translation and may reduce PD by attenuating autophagy-lysosome and MuRF-1 signaling in neonatal skeletal muscle.

Acute infection promotes skeletal muscle wasting and insulin resistance, but the effect of insulin on energy and substrate sensing in skeletal muscle of chronically infected neonates has not been studied. Eighteen 2-d-old pigs underwent cecal ligation and puncture (CLP) or sham surgery (CON) to induce a chronic infection for 5 d. On d 5, pancreatic-substrate clamps were performed to attain fasting or fed insulin levels but to maintain glucose and amino acids in the fasting range. Total fractional protein synthesis rates (Ks), translational control mechanisms, and energy sensing and degradation signal activation were measured in longissimus dorsi muscle. In fasting conditions, CLP reduced Ks and sirtuin 1 (SIRT1) and increased AMP-activated protein kinase α (AMPKα) activation and muscle RING-finger protein-1 (MuRF1). Insulin treatment increased Ks and mitochondrial protein synthesis, enhanced translation activation, and reduced SIRT1 in CON. In contrast, in CLP, insulin treatment increased Ks, protein kinase B (PKB) and Forkhead box O1 phosphorylation, antagonized AMPK activation, and decreased peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α), MuRF1, and SIRT1. Energy and substrate sensing in skeletal muscle by the PKB–AMPK–SIRT1–PGC-1α axis is impacted by chronic infection in neonatal pigs and can be modulated by insulin.

Neonatal pigs are used as a model to study and optimize the clinical treatment of infants who are unable to maintain oral feeding. Using this model, we have shown previously that pulsatile administration of leucine during continuous feeding over 24 h via orogastric tube enhanced protein synthesis in skeletal muscle compared with continuous feeding alone. To determine the long-term effects of leucine pulses, neonatal piglets ( n = 11–12/group) were continuously fed formula via orogastric tube for 21 days, with an additional parenteral infusion of either leucine (CON + LEU; 800 μmol·kg−1·h−1) or alanine (CON + ALA) for 1 h every 4 h. The results show that body and muscle weights and lean gain were ∼25% greater, and fat gain was 48% lower in CON + LEU than CON + ALA; weights of other tissues were unaffected by treatment. Fractional protein synthesis rates in longissimus dorsi, gastrocnemius, and soleus muscles were ∼30% higher in CON + LEU compared with CON + ALA and were associated with decreased Deptor abundance and increased mTORC1, mTORC2, 4E-BP1, and S6K1 phosphorylation, SNAT2 abundance, and association of eIF4E with eIF4G and RagC with mTOR. There were no treatment effects on PKB, eIF2α, eEF2, or PRAS40 phosphorylation, Rheb, SLC38A9, v-ATPase, LAMTOR1, LAMTOR2, RagA, RagC, and LAT1 abundance, the proportion of polysomes to nonpolysomes, or the proportion of mRNAs encoding rpS4 or rpS8 associated with polysomes. Our results demonstrate that pulsatile delivery of a leucine supplement during 21 days of continuous enteral feeding enhances lean growth by stimulating the mTORC1-dependent translation initiation pathway, leading to protein synthesis in skeletal muscle of neonates.

BACKGROUND Sepsis induces loss of skeletal muscle mass by activating the ubiquitin proteasome (UPS) and autophagy systems. Although muscle protein synthesis in healthy neonatal piglets is responsive to amino acid (AA) stimulation, it is not known if amino acids (AA) can prevent the activation of muscle protein degradation induced by sepsis. We hypothesize that AA attenuate the sepsis-induced activation of UPS and autophagy in neonates. METHODS Newborn pigs were infused for 8 h with liposaccharide (LPS) (0 and 10 µg·kg−1·h−1), while circulating glucose and insulin were maintained at fasting levels; circulating AA were clamped at fasting or fed levels. Markers of protein degradation and AA transporters in longissimus dorsi (LD) were examined. RESULTS Fasting AA increased muscle microtubule-associated protein light 1 chain 3 II (LC3-II) abundance in LPS compared to control, while fed AA levels decreased LC3-II abundance in both LPS and controls. There was no effect of AA supplementation on AMP-activated protein kinase, forkhead box O1 and O4 phosphorylation, nor on sodium-coupled neutral AA transporter 2 and light chain AA transporter 1, muscle RING-finger protein-1 and muscle Atrophy F-Box/Atrogin-1 abundance. CONCLUSIONS These findings suggest that supplementation of AA antagonize autophagy signal activation in skeletal muscle of neonates during endotoxemia.

Postnatal growth failure reduces lean mass accretion and increases adiposity. Previously we showed that preterm birth impairs the feeding-induced stimulation of mechanistic target of rapamycin (mTOR), translation initiation, and protein synthesis in skeletal muscle of neonatal pigs. Considering that pig body weight can vary widely at birth, we wished to differentiate the effect of prematurity versus BW on these responses. Pigs delivered by caesarean section at preterm (103 d) or term (112 d) gestation were fed parenterally for 4 d. On day 4, all pigs were fasted for 4 h and were either fasted one additional hour or fed an elemental meal by oral gavage, yielding four treatment groups: preterm fasted, preterm fed, term fasted, and term fed. A flooding dose of L-[4-3H]Phe was injected into pigs 30 min after feeding (30 min before euthanasia). Preterm and term pigs were stratified according to birth weight such that preterm pigs with the highest birth weight were compared to term pigs with the lowest birth weight (n = 10–13 per group). Despite similar birth weight of pigs in these two subgroups, relative body weight gain of preterm pigs was 33% lower than term pigs (22.0 vs. 32.9 ± 1.6 g·kg-1·d-1, P < 0.001). Gastrocnemius protein synthesis increased after feeding in both preterm and term pigs, but the increase was 18% lower in preterm than in term pigs pigs (Table 1). Feeding-induced AKT phosphorylation and mTOR-dependent 4EBP1 and S6K1 phosphorylation mirrored the pattern in protein synthesis. These results suggest that prematurity (rather than low birth weight, which is frequently associated with preterm birth) perturbs mTOR activation and protein synthesis after feeding. However, it is unclear whether an inadequate response to feeding also underpins poor growth in intrauterine growth restricted piglets. Research was supported by NIH and USDA.

The purpose of this study is to compare the hardness of glass fiber reinforced composite materials with the hardness of netted fiber-reinforced composite materials. Glass fiber is a commercial fiber that has been used in various industries while nettle fiber is a natural fiber that is more environmentally friendly. Composite material has several advantages, namely the form that can be adjusted, high strength, lightweight and resistant to corrosion. Nettle plants are plants that have strong fibers in the bark. In this study, nettle composites were made with variations in the weight fractions of 10%, 15%, and 20%. Hardness testing used the Shore D Durometer. The results of the hardness value of glass fiber composites with weight fractions of 10%, 15%, and 20% are 82.4 Shore D, 84.5 Shore D, and 86.5 Shore D, show an increase in stable hardness because the glass fiber factor is already commercial, the fiber strength is evenly distributed. The hardness values of nettle fiber composites with fractions of 10%, 15%, and 20% are 81.6 Shore D, 85 Shore D, and 86.6 Shore D, the hardness value of each nettle composite increases with the addition of fiber weight fraction but is unstable due to the strength factor of each nettle single fiber uneven. Furthermore, with the right treatment, nettle fiber can replace glass fiber.

OBJECTIVES: Postnatal growth faltering is a common complication of premature birth. Our recent study in a neonatal pig model of prematurity showed that preterm birth reduces weight gain and protein synthesis in skeletal muscle and this is associated with blunted insulin-induced activation of signaling components downstream of AKT. However, prematurity does not affect the activation of the IR/IRS-1/PI3K axis. In this study, we aimed to identify components in the AKT signaling pathway in skeletal muscle that underlie the differential response to insulin between preterm and term pigs. METHODS: Cesarean-derived piglets delivered 11 d (preterm) or 2 d (term) before term were fitted with a jugular vein catheter for delivery of total parenteral nutrition. On day 3, all piglets were fasted for 4 h and then assigned randomly to fast one additional h or to receive an elemental meal by oral gavage. Macronutrient content of the elemental meal mimicked sow milk composition at day 3 of lactation. Piglets were euthanized for tissue collection in the fasted state or 60 min after feeding. The longissimus dorsi muscle was collected and subjected to Western blot and immunoprecipitation assays for analyzing upstream regulators of AKT activity. RESULTS: Phosphorylation of PDK1 and mTORC2 was lower in preterm than term pigs (P

Background: Early weaning of pigs frequently results in growth faltering. Supplementation with leucine or its metabolite, beta-hydroxy-beta-methylbutyrate (HMB), enhances protein synthesis in skeletal muscle of neonatal pigs by stimulating mTORC1-dependent translation initiation. Recent studies have identified signaling components that may be involved in leucine-induced mTORC1 activation, however, the mechanism by which HMB activates mTORC1 is unclear. Objective: We investigated potential mechanisms of HMB-induced mTORC1 activation through amino acid-sensing components in neonatal muscle. In study 1, overnight-fasted neonatal pigs were fed one of five diets for 24 h: low protein (LP), high protein (HP), or LP supplemented with 4 (LP+HMB4), 40 (LP+HMB40), or 80 (LP+HMB80) μmol HMB/(kg body wt·day). In study 2, fasted neonatal pigs were fed for 24 h: LP, LP supplemented with leucine (LP+Leu), or HP diets. Upstream signaling components relevant to mTORC1 activation were analyzed. Results: Phosphorylation of mTOR (Ser2448 and Ser2481) was greater in LP+HMB40, LP+HMB80, and LP+Leu than LP, and was greater in HP than all HMB. Rheb-mTOR formation was higher in HP, but not HMB and LP+Leu, than LP. RagA-mTOR and RagC-mTOR complexes were higher in LP+Leu and HP than LP and HMB. Sestrin2-GATOR2 formation was lower in LP+Leu and HP than LP, but was unaffected by HMB. Phosphorylation of Erk1/2 and TSC2, but not AMPK, was greater in HP than LP and unaffected by HMB or leucine. There were no treatment effects on RagB-SH3BP4, Vps34-LRS, and RagD-LRS complex formation. Conclusions: Our results demonstrate that supplementation with either leucine or HMB stimulates mTORC1 activation in muscle of neonatal pigs. This leucine-stimulated process involves dissociation of the Sestrin2-GATOR2 complex and increased Rag A/C binding to mTOR. HMB’s action on mTORC1 is independent of these leucine-sensing components. Support: USDA NIFA 2013-67015-20438, NIH HD085573, NIH HD072891, Abbott Nutrition, USDA CRIS 6250-51000-055.

The objective of this study was to determine if enteral leucine or branched-chain amino acid (BCAA) supplementation increases muscle protein synthesis in neonates who consume less than their protein and energy requirements, and whether this increase is mediated via the upregulation of the mechanistic target of rapamycin complex 1 (mTORC1) pathway or the decrease in muscle protein degradation signaling. Neonatal pigs were fed milk replacement diets containing reduced energy and protein (R), R supplemented with BCAA (RBCAA), R supplemented with leucine (RL), or complete protein and energy (CON) at 4-h intervals for 9 (n = 24) or 21 days (n = 22). On days 9 and 21, post-prandial plasma amino acids and insulin were measured at intervals for 4 h; muscle protein synthesis rate and activation of mTOR-related proteins were determined at 120 min post-feeding in muscle. For all parameters measured, the effects of diet were not different between day 9 or day 21. Compared to CON and R, plasma leucine and BCAA were higher (P ≤ 0.01) in RL- and RBCAA-fed pigs, respectively. Body weight gain, protein synthesis, and activation of S6 kinase (S6K1), 4E-binding protein (4EBP1), and eukaryotic initiation factor 4 complex (eIF4E·eIF4G) were decreased in RBCAA, RL, and R relative to CON (P

Most low-birth weight infants experience extrauterine growth failure due to reduced nutrient intake as a result of feeding intolerance. The objective of this study was to determine whether prolonged enteral leucine supplementation improves lean growth in neonatal pigs fed a restricted protein diet. Neonatal pigs ( n = 14–16/diet, 5 days old, 1.8 ± 0.3 kg) were fed by gastric catheter a whey-based milk replacement diet with either a high protein (HP) or restricted protein (RP) content or RP supplemented with leucine to the same level as in the HP diet (RPL). Pigs were fed 40 ml·kg body wt−1·meal−1 every 4 h for 21 days. Feeding the HP diet resulted in greater total body weight and lean body mass compared with RP-fed pigs ( P < 0.05). Masses of the longissimus dorsi muscle, heart, and kidneys were greater in the HP- than RP-fed pigs ( P < 0.05). Body weight, lean body mass, and masses of the longissimus dorsi, heart, and kidneys in pigs fed the RPL diet were intermediate to RP- and HP-fed pigs. Protein synthesis and mTOR signaling were increased in all muscles with feeding ( P < 0.05); leucine supplementation increased mTOR signaling and protein synthesis rate in the longissimus dorsi ( P < 0.05). There was no effect of diet on indices of protein degradation signaling in any tissue ( P > 0.05). Thus, when protein intake is chronically restricted, the capacity for leucine supplementation to enhance muscle protein accretion in neonatal pigs that are meal-fed milk protein-based diets is limited.

Teknologi gasifikasi tipe downdraft adalah salah satu teknologi untuk mengkonversikan bahan bakar padat atau biomassa padat secara thermokimia dengan temperatur 6000-7000 C menjadi bahan bakar gas mampu bakar dengan kebutuhan udara 20 – 40% Stoikiometri dimana suplai udara masuk dari atas menuju dasar reaktor dan proses gasifikasi terjadi di dasar reaktor. Sampah kota atau ( Municipal Solid Westes) adalah bahan buangan yang terdiri dari bahan organik dan anorganik yang mempunyai nilai kalor sehingga dapat digunakan sebagai bahan bakar. Penelitian ini bertujuan untuk mengetahui performansi dari gasifier tipe dwondraft dengan variasi perlakuan awal bahan bakar kering, pellet, dan briket. Perbedaan perlakuan bahan bakar akan menghasilkan nilai kalor dan karakteristik bahan bakar yang berbeda sehingga nantinya akan didapatkan bahan bakar yang paling efektif. Hasil penelitian menunjukan bahwa efisiensi tertinggi didapatkan pada variasi perlakuan awal bahan bakar sampah kota yang di briketkan yaitu sebesar 61,32% dan FCR tertinggi terjadi pada bahan bakar pellet yaitu 4,61 kg/jam. Gasification type Downdraft technology is one technology to convert thermochemical solid or biomass fuels with temperatures of 6000-7000 C into combustible gas fuels with air requirements of 20 - 40% Stoichiometry where the supply of air enters from above to the reactor base and gasification process occurs at the bottom of the reactor. Municipal solid waste is a waste material consisting of organic and inorganic materials that has a heating value, so that it can be used as fuel of gasification. This study aims to determine the performance of the dwondraft gasifier with variations in the pretreatment of dry MSW, pellets and briquettes. Differences in fuel treatment will produce different heating values ??and fuel characteristics so that the most effective fuel will be found later. The results showed that the highest efficiency was found in the variation of initial treatment municipal solid waste briquettes which was 61,32%, and the highest FCR occurs in pellet fuel which is 4.61 kg / hour.

Suboptimal nutrient intake represents a limiting factor for growth and long-term survival of low-birth weight infants. Both nutrient intolerance and the risk of developing feeding-related pathologies have led to the implementation of feeding protocols below nutrient requirements, that often result in periods of malnourishment with potential long-term adverse consequences for the neonate. A parallel situation when early growth is compromised is encountered during early weaning of pigs, caused by a reduction in food intake due to stress, environmental changes, and a shift from liquid to solid diet, in conjunction with an increase in nutrient requirements. The resulting growth retardation and mortality represents a major production loss for the swine industry. In the neonate, the primary driving force for the elevated rate of protein accretion is the capacity to attain high rates of protein synthesis after feeding. Studies in neonatal pigs have shown that the sharp increase in muscle protein synthesis after eating is mediated by the rise in amino acids and insulin, which activate independent signaling pathways that converge at mammalian target of rapamycin complex 1 (mTORC1), leading to the activation of key regulators of translation. Leucine is the most effective single amino acid in triggering translation initiation factor activation. Pulsatile administration of leucine during continuous orogastric feeding of a milk replacer during 21 days enhances muscle protein synthesis by stimulating phosphorylation of mTORC1 and its downstream effectors, including ribosomal protein S6 kinase 1 (S6K1) and eukaryotic initiation factor 4 binding protein 1 (4EBP1), while downregulates both cellular autophagy systems and insulin-independent pathways involved in protein catabolism. Prolonged leucine supplementation under protein and energy restriction increases the activation of S6K1 and 4EBP1 but does not improved protein synthesis and body growth in neonates. Whether the anabolic effects of leucine can be sustained chronically to promote lean growth requires further study.