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Posey EA, Davis TA. Review: Nutritional regulation of muscle growth in neonatal swine. Animal 2023; 17 Suppl 3:100831. [PMID: 37263816 PMCID: PMC10621894 DOI: 10.1016/j.animal.2023.100831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 12/31/2022] [Accepted: 01/06/2023] [Indexed: 06/03/2023] Open
Abstract
Despite advances in the nutritional support of low birth weight and early-weaned piglets, most experience reduced extrauterine growth performance. To further optimize nutritional support and develop targeted intervention strategies, the mechanisms that regulate the anabolic response to nutrition must be fully understood. Knowledge gained in these studies represents a valuable intersection of agriculture and biomedical research, as low birth weight and early-weaned piglets face many of the same morbidities as preterm and low birth weight infants, including extrauterine growth faltering and reduced lean growth. While the reasons for poor growth performance are multifaceted, recent studies have increased our understanding of the role of nutrition in the regulation of skeletal muscle growth in the piglet. The purpose of this review is to summarize the published literature surrounding advances in the current understanding of the anabolic signaling that occurs after a meal and how this response is developmentally regulated in the neonatal pig. It will focus on the regulation of protein synthesis, and especially the upstream and downstream effectors surrounding the master protein kinase, mechanistic target of rapamycin complex 1 (mTORC1) that controls translation initiation. It also will examine the regulatory pathways associated with the postprandial anabolic agents, insulin and specific amino acids, that are upstream of mTORC1 and lead to its activation. Lastly, the integration of upstream signaling cascades by mTORC1 leading to the activation of translation initiation factors that regulate protein synthesis will be discussed. This review concludes that anabolic signaling cascades are stimulated by both insulin and amino acids, especially leucine, through separate pathways upstream of mTORC1, and that these stimulatory pathways result in mTORC1 activation and subsequent activation of downstream effectors that regulate translation initiation Additionally, it is concluded that this anabolic response is unique to the skeletal muscle of the neonate, resulting from increased sensitivity to the rise in both insulin and amino acid after a meal. However, this response is dampened in skeletal muscle of the low birth weight pig, indicative of anabolic resistance. Elucidation of the pathways and regulatory mechanisms surrounding protein synthesis and lean growth allow for the development of potential targeted therapeutics and intervention strategies both in livestock production and neonatal care.
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Affiliation(s)
- E A Posey
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
| | - T A Davis
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA.
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Rudar M, Naberhuis JK, Suryawan A, Nguyen HV, Fiorotto ML, Davis TA. Prematurity blunts protein synthesis in skeletal muscle independently of body weight in neonatal pigs. Pediatr Res 2023:10.1038/s41390-022-02456-3. [PMID: 36627358 DOI: 10.1038/s41390-022-02456-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 11/30/2022] [Accepted: 12/21/2022] [Indexed: 01/11/2023]
Abstract
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 < 0.05). Protein synthesis in gastrocnemius (P < 0.01), but not in longissimus dorsi muscle, was blunted by preterm birth. 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.
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Affiliation(s)
- Marko Rudar
- Department of Animal Sciences, Auburn University, Auburn, AL, USA
| | - Jane K Naberhuis
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA
| | - Agus Suryawan
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA
| | - Hanh V Nguyen
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA
| | - Marta L Fiorotto
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA
| | - Teresa A Davis
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA.
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Rudar M, Naberhuis JK, Suryawan A, Nguyen HV, Stoll B, Style CC, Verla MA, Olutoye OO, Burrin DG, Fiorotto ML, Davis TA. Intermittent bolus feeding does not enhance protein synthesis, myonuclear accretion, or lean growth more than continuous feeding in a premature piglet model. Am J Physiol Endocrinol Metab 2021; 321:E737-E752. [PMID: 34719946 PMCID: PMC8714968 DOI: 10.1152/ajpendo.00236.2021] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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; n = 30) or continuously (CONT; n = 14) for 21 days. Body composition was measured by dual-energy X-ray absorptiometry (DXA) and muscle growth was assessed by morphometry, myonuclear accretion, and satellite cell abundance. Tissue anabolic signaling and fractional protein synthesis rates were determined in INT pigs in postabsorptive (INT-PA) and postprandial (INT-PP) states and in CONT pigs. Body weight gain and composition did not differ between INT and CONT pigs. Longissimus dorsi (LD) protein synthesis was 34% greater in INT-PP than INT-PA pigs (P < 0.05) but was not different between INT-PP and CONT pigs. Phosphorylation of 4EBP1 and S6K1 and eIF4E·eIF4G abundance in LD paralleled changes in LD protein synthesis. Satellite cell abundance, myonuclear accretion, and fiber cross-sectional area in LD did not differ between groups. These results suggest that, unlike pigs born at term, intermittent bolus feeding does not enhance lean growth more than continuous feeding in pigs born preterm. Premature birth attenuates the capacity of skeletal muscle to respond to cyclical surges in insulin and amino acids with intermittent feeding in early postnatal life.NEW & NOTEWORTHY Extrauterine growth restriction often occurs in premature infants but may be mitigated by optimizing enteral feeding strategies. We show that intermittent bolus feeding does not increase skeletal muscle protein synthesis, myonuclear accretion, or lean growth more than continuous feeding in preterm pigs. This attenuated anabolic response of muscle to intermittent bolus feeding, compared with previous observations in pigs born at term, may contribute to deficits in lean mass that many premature infants exhibit into adulthood.
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Affiliation(s)
- Marko Rudar
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
- Department of Animal Sciences, Auburn University, Auburn, Alabama
| | - Jane K Naberhuis
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Agus Suryawan
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Hanh V Nguyen
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Barbara Stoll
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Candace C Style
- The Department of Pediatric Surgery, Nationwide Children's Hospital, Columbus, Ohio
| | - Mariatu A Verla
- Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, Texas
| | - Oluyinka O Olutoye
- The Department of Pediatric Surgery, Nationwide Children's Hospital, Columbus, Ohio
| | - Douglas G Burrin
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Marta L Fiorotto
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Teresa A Davis
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
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Rudar M, Naberhuis JK, Suryawan A, Nguyen HV, Stoll B, Style CC, Verla MA, Olutoye OO, Burrin DG, Fiorotto ML, Davis TA. Prematurity blunts the insulin- and amino acid-induced stimulation of translation initiation and protein synthesis in skeletal muscle of neonatal pigs. Am J Physiol Endocrinol Metab 2021; 320:E551-E565. [PMID: 33427053 PMCID: PMC7988778 DOI: 10.1152/ajpendo.00203.2020] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
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.
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Affiliation(s)
- Marko Rudar
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
- Department of Animal Sciences, Auburn University, Auburn, Alabama
| | - Jane K Naberhuis
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Agus Suryawan
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Hanh V Nguyen
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Barbara Stoll
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Candace C Style
- Division of Pediatric Surgery, Michael E. DeBakey Department of Surgery, Texas Children's Hospital, Baylor College of Medicine, Houston, Texas
| | - Mariatu A Verla
- Division of Pediatric Surgery, Michael E. DeBakey Department of Surgery, Texas Children's Hospital, Baylor College of Medicine, Houston, Texas
| | - Oluyinka O Olutoye
- Division of Pediatric Surgery, Michael E. DeBakey Department of Surgery, Texas Children's Hospital, Baylor College of Medicine, Houston, Texas
| | - Douglas G Burrin
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Marta L Fiorotto
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Teresa A Davis
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
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Suryawan A, Rudar M, Fiorotto ML, Davis TA. Differential regulation of mTORC1 activation by leucine and β-hydroxy-β-methylbutyrate in skeletal muscle of neonatal pigs. J Appl Physiol (1985) 2020; 128:286-295. [PMID: 31944890 DOI: 10.1152/japplphysiol.00332.2019] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
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.
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Affiliation(s)
- Agus Suryawan
- US Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Marko Rudar
- US Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Marta L Fiorotto
- US Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Teresa A Davis
- US Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
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Son DH, Hwang NH, Chung WH, Seong HS, Lim H, Cho ES, Choi JW, Kang KS, Kim YM. Whole-genome resequencing analysis of 20 Micro-pigs. Genes Genomics 2019; 42:263-272. [PMID: 31833050 DOI: 10.1007/s13258-019-00891-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 11/14/2019] [Indexed: 12/22/2022]
Abstract
BACKGROUND Miniature pigs have been increasingly used as mammalian model animals for biomedical research because of their similarity to human beings in terms of their metabolic features and proportional organ sizes. However, despite their importance, there is a severe lack of genome-wide studies on miniature pigs. OBJECTIVE In this study, we performed whole-genome sequencing analysis of 20 Micro-pigs obtained from Medi Kinetics to elucidate their genomic characteristics. RESULTS Approximately 595 gigabase pairs (Gb) of sequence reads were generated to be mapped to the swine reference genome assembly (Sus scrofa 10.2); on average, the sequence reads covered 99.15% of the reference genome at an average of 9.6-fold coverage. We detected a total of 19,518,548 SNPs, of which 8.7% were found to be novel. With further annotation of all of the SNPs, we retrieved 144,507 nonsynonymous SNPs (nsSNPs); of these, 5968 were found in all 20 individuals used in this study. SIFT prediction for these SNPs identified that 812 nsSNPs in 402 genes were deleterious. Among these 402 genes, we identified some genes that could potentially affect traits of interest in Micro-pigs, such as RHEB and FRAS1. Furthermore, we performed runs of homozygosity analysis to locate potential selection signatures in the genome, detecting several loci that might be involved in phenotypic characteristics in Micro-pigs, such as MSTN, GDF5, and GDF11. CONCLUSION In this study, we identified numerous nsSNPs that could be used as candidate genetic markers with involvement in traits of interest. Furthermore, we detected putative selection footprints that might be associated with recent selection applied to miniature pigs.
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Affiliation(s)
- Da-Hye Son
- College of Animal Life Science, Kangwon National University, Chuncheon, 24341, Republic of Korea
| | - Nam-Hyun Hwang
- College of Animal Life Science, Kangwon National University, Chuncheon, 24341, Republic of Korea
| | - Won-Hyong Chung
- Research Division of Food Functionality, Research Group of Healthcare, 245, Nongsaengmyeong-ro, Iseo-myeon, Wanju-gun, Jeollabuk-do, 55365, Republic of Korea
| | - Ha-Seung Seong
- College of Animal Life Science, Kangwon National University, Chuncheon, 24341, Republic of Korea
| | - Hyungbum Lim
- Medikinetics Co., Ltd, 4 Hansan-gil, Cheongbuk-eup, Pyeongtaek-si, Gyeonggi-do, 17792, Republic of Korea
| | - Eun-Seok Cho
- Division of Swine Science, National Institute of Animal Science, RDA, Cheonan, 31000, Republic of Korea
| | - Jung-Woo Choi
- College of Animal Life Science, Kangwon National University, Chuncheon, 24341, Republic of Korea.
| | - Kyung-Soo Kang
- Medikinetics Co., Ltd, 4 Hansan-gil, Cheongbuk-eup, Pyeongtaek-si, Gyeonggi-do, 17792, Republic of Korea.
| | - Yong-Min Kim
- Division of Swine Science, National Institute of Animal Science, RDA, Cheonan, 31000, Republic of Korea.
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Naberhuis JK, Suryawan A, Nguyen HV, Hernandez-Garcia A, Cruz SM, Lau PE, Olutoye OO, Stoll B, Burrin DG, Fiorotto ML, Davis TA. Prematurity blunts the feeding-induced stimulation of translation initiation signaling and protein synthesis in muscle of neonatal piglets. Am J Physiol Endocrinol Metab 2019; 317:E839-E851. [PMID: 31503514 PMCID: PMC6879862 DOI: 10.1152/ajpendo.00151.2019] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
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 Ks in 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 Ks regardless of GAB. Liver Ks was 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.
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Affiliation(s)
- Jane K Naberhuis
- United States Department of Agriculture, Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Agus Suryawan
- United States Department of Agriculture, Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Hanh V Nguyen
- United States Department of Agriculture, Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Adriana Hernandez-Garcia
- United States Department of Agriculture, Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Stephanie M Cruz
- Division of Pediatric Surgery, Michael E. DeBakey Department of Surgery, Texas Children's Hospital, Baylor College of Medicine, Houston, Texas
| | - Patricio E Lau
- Division of Pediatric Surgery, Michael E. DeBakey Department of Surgery, Texas Children's Hospital, Baylor College of Medicine, Houston, Texas
| | - Oluyinka O Olutoye
- Division of Pediatric Surgery, Michael E. DeBakey Department of Surgery, Texas Children's Hospital, Baylor College of Medicine, Houston, Texas
| | - Barbara Stoll
- United States Department of Agriculture, Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Douglas G Burrin
- United States Department of Agriculture, Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Marta L Fiorotto
- United States Department of Agriculture, Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
| | - Teresa A Davis
- United States Department of Agriculture, Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas
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Suryawan A, Davis TA. Amino Acid- and Insulin-Induced Activation of mTORC1 in Neonatal Piglet Skeletal Muscle Involves Sestin2-GATOR2, Rag A/C-mTOR, and RHEB-mTOR Complex Formation. J Nutr 2018; 148:825-833. [PMID: 29796625 PMCID: PMC6669959 DOI: 10.1093/jn/nxy044] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 02/14/2018] [Indexed: 12/18/2022] Open
Abstract
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 < 0.05) and late endosomal/lysosomal adaptor, MAPK and mTOR activator 1/2 (LAMTOR1/2), vacuolar H+-ATPase (V-ATPase), and Sestrin2 were higher (94%, 141%, 145%, and 127%, respectively; P < 0.05) in 6- than in 26-d-old pigs. Both AA and INS groups increased phosphorylation of GRB10 (P < 0.05) compared with control in 26- but not in 6-d-old pigs. Formation of Ras-related GTP-binding protein A (RagA)-mTOR, RagC-mTOR, and Ras homolog enriched in brain (RHEB)-mTOR complexes was increased (P < 0.05) and Sestrin2-GTPase activating protein activity towards Rags 2 (GATOR2) complex was decreased (P < 0.05) by both AA and INS groups and these responses were greater (P < 0.05) in 6- than in 26-d-old pigs. Conclusion The results suggest that formation of RagA-mTOR, RagC-mTOR, RHEB-mTOR, and Sestrin2-GATOR2 complexes may be involved in the AA- and INS-induced activation of mTORC1 in skeletal muscle of neonates after a meal and that enhanced activation of the mTORC1 signaling pathway in neonatal muscle is in part due to regulation by DEPTOR, GRB10, REDD2, LAMTOR1/2, V-ATPase, and Sestrin2.
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Affiliation(s)
- Agus Suryawan
- US Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX
| | - Teresa A Davis
- US Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX,Address correspondence to TAD (e-mail: )
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Do KT, Jung SW, Park KD, Na CS. Effect of single nucleotide polymorphism on the total number of piglets born per parity of three different pig breeds. ASIAN-AUSTRALASIAN JOURNAL OF ANIMAL SCIENCES 2017; 31:628-635. [PMID: 28823139 PMCID: PMC5930272 DOI: 10.5713/ajas.17.0028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 03/29/2017] [Accepted: 07/28/2017] [Indexed: 02/04/2023]
Abstract
Objective To determine the effects of genomic breeding values (GBV) and single nucleotide polymorphisms (SNP) on the total number of piglets born (TNB) in 3 pig breeds (Berkshire, Landrace, and Yorkshire). Methods After collecting genomic information (Porcine SNP BeadChip) and phenotypic TNB records for each breed, the effects of GBV and SNP were estimated by using single step best linear unbiased prediction (ssBLUP) method. Results The heritability estimates for TNB in Berkshire, Landrace, and Yorkshire breeds were 0.078, 0.107, and 0.121, respectively. The breeding value estimates for TNB in Berkshire, Landrace, and Yorkshire breeds were in the range of −1.34 to 1.47 heads, −1.79 to 1.87 heads, and −2.60 to 2.94 heads, respectively. Of sows having records for TNB, the reliability of breeding value for individuals with SNP information was higher than that for individuals without SNP information. Distributions of the SNP effects on TNB did not follow gamma distribution. Most SNP effects were near zero. Only a few SNPs had large effects. The numbers of SNPs with absolute value of more than 4 standard deviations in Berkshire, Landrace, and Yorkshire breeds were 11, 8, and 19, respectively. There was no SNP with absolute value of more than 5 standard deviations in Berkshire or Landrace. However, in Yorkshire, four SNPs (ASGA 0089457, ASGA0103374, ALGA0111816, and ALGA0098882) had absolute values of more than 5 standard deviations. Conclusion There was no common SNP with large effect among breeds. This might be due to the large genetic composition differences and the small size of reference population. For the precise evaluation of genetic performance of individuals using a genomic selection method, it may be necessary to establish the appropriate size of reference population.
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Affiliation(s)
- Kyoung-Tag Do
- Department of Animal Biotechnology, Jeju National University, Jeju 63243, Korea
| | | | - Kyung-Do Park
- Department of Animal Biotechnology, Chonbuk National University, Jeonju 54896, Korea
| | - Chong-Sam Na
- Department of Animal Biotechnology, Chonbuk National University, Jeonju 54896, Korea
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10
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Xu W, Bai K, He J, Su W, Dong L, Zhang L, Wang T. Leucine improves growth performance of intrauterine growth retardation piglets by modifying gene and protein expression related to protein synthesis. Nutrition 2016; 32:114-21. [DOI: 10.1016/j.nut.2015.07.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2014] [Revised: 05/31/2015] [Accepted: 07/07/2015] [Indexed: 01/10/2023]
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Co-dependence of genotype and dietary protein intake to affect expression on amino acid/peptide transporters in porcine skeletal muscle. Amino Acids 2015; 48:75-90. [PMID: 26255284 DOI: 10.1007/s00726-015-2066-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Accepted: 07/29/2015] [Indexed: 10/23/2022]
Abstract
A total of 96 barrows (48 pure-bred Bama mini-pigs representing fatty genotype, and 48 Landrace pigs representing lean genotype) were randomly assigned to either a low- or adequate-protein treatment diet. The experimental period commenced at 5 weeks of age and extended to the finishing period. After euthanasia, blood and skeletal muscle samples were collected from pigs at the nursery, growing, and finishing phases. Our results indicate that the concentrations of free AAs in the plasma and muscle decreased as the age of the pigs increased. In addition, a strain × growth phase interaction (P < 0.05) was observed for the free AA pool in the plasma and muscle. The low-protein diet upregulated (P < 0.05) the mRNA levels for T1R1/T1R3 involved in glutamate binding, but downregulated (P < 0.05) the mRNA levels for PAT1, PAT2, and ASCT2, which transport neutral AAs into muscles. Bama mini-pigs had higher (P < 0.05) mRNA levels for LAT1, SNAT2, and EAAC1, but a lower (P < 0.05) mRNA level for PepT1, compared with Landrace pigs. Collectively, our findings indicate that adequate provision of dietary protein plays an important role in regulating profiles of free AA pools and expression of key AA/peptide transporters/transceptors in a genotype- and tissue-specific manner.
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12
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Gordon BS, Williamson DL, Lang CH, Jefferson LS, Kimball SR. Nutrient-induced stimulation of protein synthesis in mouse skeletal muscle is limited by the mTORC1 repressor REDD1. J Nutr 2015; 145:708-13. [PMID: 25716553 PMCID: PMC4381770 DOI: 10.3945/jn.114.207621] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 01/29/2015] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND In skeletal muscle, the nutrient-induced stimulation of protein synthesis requires signaling through the mechanistic target of rapamycin complex 1 (mTORC1). Expression of the repressor of mTORC1 signaling, regulated in development and DNA damage 1 (REDD1), is elevated in muscle during various atrophic conditions and diminished under hypertrophic conditions. The question arises as to what extent REDD1 limits the nutrient-induced stimulation of protein synthesis. OBJECTIVE The objective was to examine the role of REDD1 in limiting the response of muscle protein synthesis and mTORC1 signaling to a nutrient stimulus. METHODS Wild type REDD1 gene (REDD1(+/+)) and disruption in the REDD1 gene (REDD1(-/-)) mice were feed deprived for 16 h and randomized to remain feed deprived or refed for 15 or 60 min. The tibialis anterior was then removed for analysis of protein synthesis and mTORC1 signaling. RESULTS In feed-deprived mice, protein synthesis and mTORC1 signaling were significantly lower in REDD1(+/+) than in REDD1(-/-) mice. Thirty minutes after the start of refeeding, protein synthesis in REDD1(+/+) mice was stimulated by 28%, reaching a value similar to that observed in feed-deprived REDD1(-/-) mice, and was accompanied by increased phosphorylation of mTOR (Ser2448), p70S6K1 (Thr389), and 4E-BP1 (Ser65) by 81%, 167%, and 207%, respectively. In refed REDD1(-/-) mice, phosphorylation of mTOR (Ser2448), p70S6K1 (Thr389), and 4E-BP1 (Ser65) were significantly augmented above the values observed in refed REDD1(+/+) mice by 258%, 405%, and 401%, respectively, although protein synthesis was not coordinately increased. Seventy-five minutes after refeeding, REDD1 expression in REDD1(+/+) mice was reduced (∼15% of feed-deprived REDD1(+/+) values), and protein synthesis and mTORC1 signaling were not different between refed REDD1(+/+) mice and REDD1(-/-) mice. CONCLUSIONS The results show that REDD1 expression limits protein synthesis in mouse skeletal muscle by inhibiting mTORC1 signaling during periods of feed deprivation and that a reduction in its expression is necessary for maximal stimulation of protein synthesis in response to refeeding.
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Affiliation(s)
- Bradley S Gordon
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, PA; and
| | - David L Williamson
- Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY
| | - Charles H Lang
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, PA; and
| | - Leonard S Jefferson
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, PA; and
| | - Scot R Kimball
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, PA; and
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Effects of dietary n-6:n-3 PUFA ratio on fatty acid composition, free amino acid profile and gene expression of transporters in finishing pigs. Br J Nutr 2015; 113:739-48. [PMID: 25704496 DOI: 10.1017/s0007114514004346] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Revealing the expression patterns of fatty acid and amino acid transporters as affected by dietary n-6:n-3 PUFA ratio would be useful for further clarifying the importance of the balance between n-6 and n-3 PUFA. A total of ninety-six finishing pigs were fed one of four diets with the ratio of 1:1, 2·5:1, 5:1 and 10:1. Pigs fed the dietary n-6:n-3 PUFA ratio of 5:1 had the highest (P< 0·05) daily weight gain, and those fed the dietary n-6:n-3 PUFA ratio of 1:1 had the largest loin muscle area (P< 0·01). The concentration of n-3 PUFA was raised as the ratio declined (P< 0·05) in the longissimus dorsi and subcutaneous adipose tissue. The contents of tryptophan, tasty amino acids and branched-chain amino acids in the longissimus dorsi were enhanced in pigs fed the dietary n-6:n-3 PUFA ratios of 1:1-5:1. The mRNA expression level of the fatty acid transporter fatty acid transport protein-1 (FATP-1) was declined (P< 0·05) in the longissimus dorsi of pigs fed the dietary n-6:n-3 PUFA ratios of 1:1-5:1, and increased (P< 0·05) in the subcutaneous adipose tissue of pigs fed the dietary n-6:n-3 PUFA ratios of 5:1 and 10:1. The expression profile of FATP-4 was similar to those of FATP-1 in the adipose tissue. The mRNA expression level of the amino acid transceptors LAT1 and SNAT2 was up-regulated (P< 0·05) in the longissimus dorsi of pigs fed the dietary n-6:n-3 PUFA ratios of 1:1 and 2·5:1. In conclusion, maintaining the dietary n-6:n-3 PUFA ratios of 1:1-5:1 would facilitate the absorption and utilisation of fatty acids and free amino acids, and result in improved muscle and adipose composition.
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Abstract
PURPOSE OF REVIEW Neonates with feeding difficulties can be fed by orogastric tube, using either continuous or bolus delivery. This review reports on recent findings that bolus is advantageous compared to continuous feeding in supporting optimal protein anabolism. RECENT FINDINGS Whether bolus or continuous feeding is more beneficial has been controversial, largely due to limitations inherent in clinical studies, such as the presence of confounding variables and the inability to use invasive approaches. Recent studies using the piglet as a model of the human neonate showed that, compared to continuous feeding, bolus feeding enhances protein synthesis and promotes greater protein deposition. The increase in protein synthesis occurs in muscles of varying fiber type and in visceral tissues whereas muscle protein degradation is largely insensitive to feeding pattern. This higher protein synthesis rate is enabled by the rapid and profound increases in circulating amino acids and insulin that occur following a bolus feed, which activate the intracellular signaling pathways leading to mRNA translation. SUMMARY Recent findings indicate that bolus feeding enhances protein synthesis more than continuous feeding and promotes greater protein anabolism. The difference in response is attributable to the pulsatile pattern of amino acid-induced and insulin-induced translation initiation induced only by bolus feeding.
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Affiliation(s)
- Teresa A. Davis
- USDA/ARS Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA, 77030
| | - Marta L. Fiorotto
- USDA/ARS Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA, 77030
| | - Agus Suryawan
- USDA/ARS Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA, 77030
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Carlin MB, Tanner RE, Agergaard J, Jalili T, McClain DA, Drummond MJ. Skeletal muscle Ras-related GTP binding B mRNA and protein expression is increased after essential amino acid ingestion in healthy humans. J Nutr 2014; 144:1409-14. [PMID: 25056691 PMCID: PMC4130827 DOI: 10.3945/jn.114.196691] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Essential amino acids (EAAs) are potent stimulators of mechanistic target of rapamycin complex 1 (mTORC1) signaling and muscle protein synthesis. However, regulators upstream of mTORC1 that are responsive to EAA availability are not well described, especially in human skeletal muscle. The purpose of this study was to determine changes in leucyl-tRNA synthetase (LARS/LARS) and Ras-related GTP binding B (RAGB/RAGB) mRNA and protein expression in healthy human skeletal muscle after acute EAA ingestion. Muscle biopsies sampled from the vastus lateralis were obtained from 13 young adults (7 males, 6 females; aged 22.9 ± 0.9 y; body mass index 21.7 ± 0.9 kg/m(2)) in the fasting state (baseline) and 1 and 3 h after EAA (13 g; 2.4 g of Leu) ingestion. Real-time quantitative polymerase chain reaction and Western blotting were used to determine changes in LARS/LARS and RAGB/RAGB mRNA and protein expression, respectively. Stable isotope tracers and gas chromatography mass spectrometry were used to determine Leu intracellular concentrations and muscle protein synthesis. EAA ingestion increased RAGB/RAGB mRNA (∼60%) and protein (∼100%) abundance in adult skeletal muscle (P ≤ 0.05). EAAs also increased muscle Leu concentrations (∼130%), mTOR phosphorylation (∼30%), and muscle protein synthesis (∼50%; P ≤ 0.05) but did not alter muscle LARS/LARS abundance (P > 0.05). We conclude that acute EAA ingestion is capable of increasing RAGB expression in human skeletal muscle. Future work is needed to determine whether this adaptive response is important to promote muscle protein anabolism in humans. This trial was registered at clinicaltrials.gov as NCT01669590.
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Affiliation(s)
| | | | - Jakob Agergaard
- Institute of Sports Medicine Copenhagen, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark
| | | | | | - Micah J. Drummond
- Department of Physical Therapy, University of Utah, Salt Lake City, UT; and,To whom correspondence should be addressed. E-mail:
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Suryawan A, Davis TA. Regulation of protein degradation pathways by amino acids and insulin in skeletal muscle of neonatal pigs. J Anim Sci Biotechnol 2014; 5:8. [PMID: 24438646 PMCID: PMC3901752 DOI: 10.1186/2049-1891-5-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2013] [Accepted: 01/14/2014] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND The rapid gain in lean mass in neonates requires greater rates of protein synthesis than degradation. We previously delineated the molecular mechanisms by which insulin and amino acids, especially leucine, modulate skeletal muscle protein synthesis and how this changes with development. In the current study, we identified mechanisms involved in protein degradation regulation. In experiment 1, 6- and 26-d-old pigs were studied during 1) euinsulinemic-euglycemic-euaminoacidemic, 2) euinsulinemic-euglycemic-hyperaminoacidemic, and 3) hyperinsulinemic-euglycemic-euaminoacidemic clamps for 2 h. In experiment 2, 5-d-old pigs were studied during 1) euinsulinemic-euglycemic-euaminoacidemic-euleucinemic, 2) euinsulinemic-euglycemic-hypoaminoacidemic-hyperleucinemic, and 3) euinsulinemic-euglycemic-euaminoacidemic-hyperleucinemic clamps for 24 h. We determined in muscle indices of ubiquitin-proteasome, i.e., atrogin-1 (MAFbx) and muscle RING-finger protein-1 (MuRF1) and autophagy-lysosome systems, i.e., unc51-like kinase 1 (UKL1), microtubule-associated protein light chain 3 (LC3), and lysosomal-associated membrane protein 2 (Lamp-2). For comparison, we measured ribosomal protein S6 (rpS6) and eukaryotic initiation factor 4E (eIF4E) activation, components of translation initiation. RESULTS Abundance of atrogin-1, but not MuRF1, was greater in 26- than 6-d-old pigs and was not affected by insulin, amino acids, or leucine. Abundance of ULK1 and LC3 was higher in younger pigs and not affected by treatment. The LC3-II/LC3-I ratio was reduced and ULK1 phosphorylation increased by insulin, amino acids, and leucine. These responses were more profound in younger pigs. Abundance of Lamp-2 was not affected by treatment or development. Abundance of eIF4E, but not rpS6, was higher in 6- than 26-d-old-pigs but unaffected by treatment. Phosphorylation of eIF4E was not affected by treatment, however, insulin, amino acids, and leucine stimulated rpS6 phosphorylation, and the responses decreased with development. CONCLUSIONS The rapid growth of neonatal muscle is in part due to the positive balance between the activation of protein synthesis and degradation signaling. Insulin, amino acids, and, particularly, leucine, act as signals to modulate muscle protein synthesis and degradation in neonates.
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Affiliation(s)
| | - Teresa A Davis
- United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA.
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Wang P, Drackley J, Stamey-Lanier J, Keisler D, Loor J. Effects of level of nutrient intake and age on mammalian target of rapamycin, insulin, and insulin-like growth factor-1 gene network expression in skeletal muscle of young Holstein calves. J Dairy Sci 2014; 97:383-91. [DOI: 10.3168/jds.2013-7042] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 09/15/2013] [Indexed: 11/19/2022]
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Rundqvist HC, Lilja MR, Rooyackers O, Odrzywol K, Murray JT, Esbjörnsson M, Jansson E. Nutrient ingestion increased mTOR signaling, but not hVps34 activity in human skeletal muscle after sprint exercise. Physiol Rep 2013; 1:e00076. [PMID: 24303161 PMCID: PMC3841023 DOI: 10.1002/phy2.76] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 08/03/2013] [Accepted: 08/05/2013] [Indexed: 12/11/2022] Open
Abstract
Nutrient provision after sprint exercise enhances mammalian target of rapamycin (mTOR) signaling. One suggested that nutrient sensor is the class III phosphatidylinositol 3-kinase, vacuolar protein sorting 34 (Vps34), not previously studied in human skeletal muscle. It is hypothesized that oral ingestion of essential amino acids (EAA) and carbohydrates (Carb) increases Vps34 activity and mTOR signaling in human skeletal (hVps34) muscle after sprint exercise. Nine subjects were performed 3 × 30-sec all-out sprints with or without ingestion of EAA + Carb or placebo drinks in a randomized order with a month interval. Muscle biopsies were performed at rest and 140 min after last sprint and analyzed for p-mTOR, p-p70S6k, p-eEF2 and for hVps34 activity and hVps34 protein content. Venous blood samples were collected and analyzed for amino acids, glucose, lactate, and insulin. During the sprint exercise session, EAA, glucose, and insulin in blood increased significantly more in EAA + Carb than in placebo. P-mTOR and p-p70S6k were significantly increased above rest in EAA + Carb (P = 0.03, P = 0.007) 140 min after last sprint, but not in placebo. Activity and protein expression of hVps34 were not significantly changed from rest in EAA + Carb 140 min after the last sprint. However, hVps34 activity and protein expression tended to increase in placebo (both P = 0.08). In conclusion, on the contrary to the hypothesis, no increase in activation of hVps34 was found following sprint exercise in EAA + Carb condition. In spite of this, the results support an activation of mTOR during this condition. However, this does not exclude the permissive role of hVps34 in mediating the amino acid-induced activation of mTOR and muscle protein synthesis.
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Affiliation(s)
- Håkan C Rundqvist
- Division of Clinical Physiology, Department of Laboratory Medicine, Karolinska Institutet Stockholm, Sweden ; Department of Clinical Physiology, Karolinska University Hospital Stockholm, Sweden
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Viscera and muscle protein synthesis in neonatal pigs is increased more by intermittent bolus than by continuous feeding. Pediatr Res 2013; 74:154-62. [PMID: 23736770 PMCID: PMC4183190 DOI: 10.1038/pr.2013.89] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Accepted: 01/05/2013] [Indexed: 11/09/2022]
Abstract
BACKGROUND Continuous and intermittent bolus orogastric feedings are strategies used in infants unable to tolerate normal feeds. METHODS To determine the effects of feeding modality on protein synthesis in different tissues, neonatal pigs received a balanced formula by orogastric tube as an intermittent bolus feed every 4 h or as a continuous infusion, or were fasted overnight. RESULTS As compared with fasting, protein synthesis in gastrocnemius, masseter, and soleus muscles; left ventricle; liver; pancreas; jejunum; and kidney increased in bolus- and continuously fed pigs, but the greatest increase occurred after a bolus meal. Tuberous sclerosis complex (TSC2), the proline-rich AKT substrate of 40 kDa (PRAS40), eukaryotic initiation factor (eIF) 4E binding protein (4EBP1), and ribosomal protein S6 kinase 1 (S6K1) phosphorylation in all tissues, and the proportion of ribosomal protein S4 in liver polysomes were enhanced 90 min following the bolus meal but not immediately before the meal or during continuous feeding. Eukaryotic elongation factor 2 (eEF2) and eIF2α phosphorylation were unaffected by feeding. CONCLUSION These results suggest that intermittent bolus feeding increases protein synthesis in muscles of different fiber types and visceral tissues to a greater extent than continuous feeding by stimulating translation initiation.
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Adegoke OA, Abdullahi A, Tavajohi-Fini P. mTORC1 and the regulation of skeletal muscle anabolism and mass. Appl Physiol Nutr Metab 2012; 37:395-406. [DOI: 10.1139/h2012-009] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The mass and integrity of skeletal muscle is vital to whole-body substrate metabolism and health. Indeed, defects in muscle metabolism and functions underlie or exacerbate diseases like diabetes, rheumatoid arthritis, and cancer. Physical activity and nutrition are the 2 most important environmental factors that can affect muscle health. At the molecular level, the mammalian target of rapamycin complex 1 (mTORC1) is a critical signalling complex that regulates muscle mass. In response to nutrition and resistance exercise, increased muscle mass and activation of mTORC1 occur in parallel. In this review, we summarize recent findings on mTORC1 and its regulation in skeletal muscle in response to resistance exercise, alone or in combination with intake of protein or amino acids. Because increased activity of the complex is implicated in the development of muscle insulin resistance, obesity, and some cancers (e.g., ovarian, breast), drugs that target mTORC1 are being developed or are in clinical trials. However, various cancers are associated with extensive muscle wasting, due in part to tumour burden and malnutrition. This muscle wasting may also be a side effect of anticancer drugs. Because loss of muscle mass is associated not only with metabolic abnormalities but also dose limiting toxicity, we review the possible implications for skeletal muscle of long-term inhibition of mTORC1, especially in muscle wasting conditions.
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Affiliation(s)
- Olasunkanmi A.J. Adegoke
- School of Kinesiology and Health Science, Muscle Health Research Centre, York University, 4700 Keele Street, Toronto ON M3J 5P3, Canada
| | - Abdikarim Abdullahi
- School of Kinesiology and Health Science, Muscle Health Research Centre, York University, 4700 Keele Street, Toronto ON M3J 5P3, Canada
| | - Pegah Tavajohi-Fini
- School of Kinesiology and Health Science, Muscle Health Research Centre, York University, 4700 Keele Street, Toronto ON M3J 5P3, Canada
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Abundance of amino acid transporters involved in mTORC1 activation in skeletal muscle of neonatal pigs is developmentally regulated. Amino Acids 2012; 45:523-30. [PMID: 22643846 DOI: 10.1007/s00726-012-1326-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Accepted: 05/15/2012] [Indexed: 01/22/2023]
Abstract
Previously we demonstrated that the insulin- and amino acid-induced activation of the mammalian target of rapamycin complex 1 (mTORC1) is developmentally regulated in neonatal pigs. Recent studies have indicated that members of the System A transporter (SNAT2), the System N transporter (SNAT3), the System L transporters (LAT1 and LAT2), and the proton-assisted amino acid transporters (PAT1 and PAT2) have crucial roles in the activation of mTORC1 and that the abundance of amino acid transporters is positively correlated with their activation. This study aimed to determine the effect of the post-prandial rise in insulin and amino acids on the abundance or activation of SNAT2, SNAT3, LAT1, LAT2, PAT1, and PAT2 and whether the response is modified by development. Overnight fasted 6- and 26-day-old pigs were infused for 2 h with saline (Control) or with insulin or amino acids to achieve fed levels while amino acids or insulin, respectively, as well as glucose were maintained at fasting levels. The abundance of SNAT2, SNAT3, LAT1, LAT2, PAT1, and PAT2 was higher in muscle of 6- compared with 26-day-old pigs. The abundance of the PAT2-mTOR complex was greater in 6- than in 26-day-old pigs, consistent with the higher activation of mTORC1. Neither insulin nor amino acids altered amino acid transporter or PAT2-mTOR complex abundance. In conclusion, the amino acid transporters, SNAT 2/3, LAT 1/2, and PAT1/2, likely have important roles in the enhanced amino acid-induced activation of mTORC1 in skeletal muscle of the neonate.
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Song Y, Pillow JJ. Ontogeny of proteolytic signaling and antioxidant capacity in fetal and neonatal diaphragm. Anat Rec (Hoboken) 2012; 295:864-71. [PMID: 22396157 DOI: 10.1002/ar.22436] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Accepted: 01/24/2012] [Indexed: 01/23/2023]
Abstract
Although upregulation of protein degradation pathways contributes to the development of muscle weakness in response to muscle injury and inflammation in the adult diaphragm, less is known about the preterm diaphragm. Muscle development during the antenatal and early postnatal periods normally results in net growth. However, the structural and functional immaturity of the preterm diaphragm may predispose it to injury and inflammation induced by adverse antenatal and postnatal exposures. Characterization of the ontogeny of diaphragm protein degradation pathways in early life is essential to recognize altered signaling pathways under pathologic conditions in preterm babies. We assessed the relative role of the major proteolytic pathways and antioxidant capacity during muscle maturation in ovine fetuses and lambs from 75 days to 200 days postconceptual age. Gene expression and protein content of calpain and caspase 3 exhibited a similar profile with advancing gestation, increasing from 75 days to 100 days/128 days and subsequently decreasing gradually toward the end of gestation. In contrast, ubiquitin conjugating and ligase genes did not change during gestation. All proteolytic genes examined (except Ubiquitin) were upregulated rapidly after delivery, with a similar developmental trend observed in calpain II protein content as well as calpain protease activity. In contrast, antioxidant gene expression demonstrated a steady increase from 75 days gestation to 24 hr after birth, followed by a significant reduction at 7 weeks of postnatal age (P ≤ 0.002). The proteolytic signaling and antioxidant capacity patterns reflect the adaptive process to metabolic change and muscle maturity with development.
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Affiliation(s)
- Yong Song
- Centre for Neonatal Research and Education, The University of Western Australia, Crawley 6009, Western Australia, Australia
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Gazzaneo MC, Suryawan A, Orellana RA, Torrazza RM, El-Kadi SW, Wilson FA, Kimball SR, Srivastava N, Nguyen HV, Fiorotto ML, Davis TA. Intermittent bolus feeding has a greater stimulatory effect on protein synthesis in skeletal muscle than continuous feeding in neonatal pigs. J Nutr 2011; 141:2152-8. [PMID: 22013195 PMCID: PMC3223872 DOI: 10.3945/jn.111.147520] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Orogastric tube feeding, using either continuous or intermittent bolus delivery, is common in infants for whom normal feeding is contraindicated. To compare the impact of different feeding strategies on muscle protein synthesis, after withholding food overnight, neonatal pigs received a complete formula orally as a bolus feed every 4 h or were continuously fed. Protein synthesis rate and translational mechanisms in skeletal muscle were examined after 0, 24, and 25.5 h. Plasma amino acid and insulin concentrations increased minimally and remained constant in continuously fed compared to feed-deprived pigs; however, the pulsatile meal feeding pattern was mimicked in bolus-fed pigs. Muscle protein synthesis was stimulated by feeding and the greatest response occurred after a bolus meal. Bolus but not continuous feeds increased polysome aggregation, the phosphorylation of protein kinase B, tuberous sclerosis complex 2, proline-rich Akt substrate of 40 kDa, eukaryotic initiation factor (eIF) 4E binding protein (4EBP1), and rp S6 kinase and enhanced dissociation of the 4EBP1 ·eIF4E complex and formation of the eIF4E ·eIF4G complex compared to feed deprivation (P < 0.05). Activation of insulin receptor substrate-1, regulatory associated protein of mammalian target of rapamycin, AMP-activated protein kinase, eukaryotic elongation factor 2, and eIF2α phosphorylation were unaffected by either feeding modality. These results suggest that in neonates, intermittent bolus feeding enhances muscle protein synthesis to a greater extent than continuous feeding by eliciting a pulsatile pattern of amino acid- and insulin-induced translation initiation.
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Affiliation(s)
- María C. Gazzaneo
- USDA/Agriculture Research Service Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX; and
| | - Agus Suryawan
- USDA/Agriculture Research Service Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX; and
| | - Renán A. Orellana
- USDA/Agriculture Research Service Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX; and
| | - Roberto Murgas Torrazza
- USDA/Agriculture Research Service Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX; and
| | - Samer W. El-Kadi
- USDA/Agriculture Research Service Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX; and
| | - Fiona A. Wilson
- USDA/Agriculture Research Service Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX; and
| | - Scot R. Kimball
- USDA/Agriculture Research Service Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX; and
| | - Neeraj Srivastava
- USDA/Agriculture Research Service Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX; and
| | - Hanh V. Nguyen
- USDA/Agriculture Research Service Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX; and
| | - Marta L. Fiorotto
- USDA/Agriculture Research Service Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX; and
| | - Teresa A. Davis
- USDA/Agriculture Research Service Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX; and,To whom correspondence should be addressed. E-mail:
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Gazzaneo MC, Orellana RA, Suryawan A, Tuckow AP, Kimball SR, Wilson FA, Nguyen HV, Torrazza RM, Fiorotto ML, Davis TA. Differential regulation of protein synthesis and mTOR signaling in skeletal muscle and visceral tissues of neonatal pigs after a meal. Pediatr Res 2011; 70:253-60. [PMID: 21654549 PMCID: PMC3152601 DOI: 10.1203/pdr.0b013e3182276cfa] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Protein synthesis (PS) increases after a meal in neonates, but the time course of the changes in PS in different tissues after a meal is unknown. We aimed to evaluate the changes in tissue PS, mammalian target of rapamycin complex 1 (mTORC1) activation, and proportion of ribosomal protein (rp) mRNAs in polysomes over 4 h after a bolus meal in neonatal pigs (n = 6/group; 5- to 7-d-old). The results show a more sustained increase in PS in glycolytic compared with mixed fiber type muscles and no changes in oxidative muscles. PS increased in liver, jejunum, and pancreas but not in kidney and heart. Feeding did not affect AMP-activated protein kinase or RAS-related GTP binding B activation. Phosphorylation of tuberous sclerosis complex 2, proline-rich Akt substrate of 40 kD, mTOR, eukaryotic initiation factor 4E binding protein, and rp S6 kinase 1 increased in all tissues after feeding. The proportion of mRNAs encoding rp S4 and S8 in liver polysomes increased within 30 min postfeeding. These results suggest that feeding stimulates mTORC1 signaling in muscle and viscera, but mTORC1 activation alone is not sufficient to stimulate PS in all tissues.
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Affiliation(s)
- María C Gazzaneo
- Department of Pediatrics, United States Department of Agriculture/Agriculture Research Service, Children's Nutrition Research Center, Baylor College of Medicine, Houston, Texas 77030, USA
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25
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Frost RA, Lang CH. mTor signaling in skeletal muscle during sepsis and inflammation: where does it all go wrong? Physiology (Bethesda) 2011; 26:83-96. [PMID: 21487027 DOI: 10.1152/physiol.00044.2010] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The mammalian target of rapamycin (mTOR) is an evolutionarily conserved protein kinase that exquisitely regulates protein metabolism in skeletal muscle. mTOR integrates input from amino acids, growth factors, and intracellular cues to make or break muscle protein. mTOR accomplishes this task by stimulating the phosphorylation of substrates that control protein translation while simultaneously inhibiting proteasomal and autophagic protein degradation. In a metabolic twist of fate, sepsis induces muscle atrophy in part by the aberrant regulation of mTOR. In this review, we track the steps of normal mTOR signaling in muscle and examine where they go astray in sepsis and inflammation.
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Affiliation(s)
- Robert A Frost
- Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA
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