Controlled trial of whole body protein synthesis and plasma amino acid concentrations in yearling horses fed graded amounts of lysine

Mastellar, S.L.; Coleman, Robert J.; Urschel, Kristine L.

doi:10.1016/j.tvjl.2016.07.007

Cited by 12 publications

(12 citation statements)

References 44 publications

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“…An increase in protein synthesis was observed at 204 μM as well as at 408 μM leucine but not at 102 μM leucine (P < 0.02; Figure 2). Average plasma leucine concentrations in the horse range between 80 and 160 μM (Westermann et al, 2011;Peters et al, 2013;Mastellar et al, 2016) just below the concentration at which statistical differences were observed in this study. No effect was observed between 25 and 102 μM leucine, suggesting that in these experiments those concentrations did not reach the threshold needed to detect an increase in 3 H-Phe incorporation into equine satellite cell proteins.…”

Section: Protein Synthesis Assaycontrasting

confidence: 59%

Cultured equine satellite cells as a model system to assess leucine stimulated protein synthesis in horse muscle

DeBoer

Martinson

Pampusch

et al. 2018

Journal of Animal Science

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Leucine has been shown to stimulate the mammalian/mechanistic target of rapamycin (mTOR) signaling pathway which plays numerous key regulatory roles in cell growth, survival, and metabolism including protein synthesis in a number of species. However, previous work with equine satellite cells has suggested distinct species differences in regards to physiological effects and the magnitude of responses to growth factors and regulators. Because there is limited research available regarding the role of leucine in regulating equine skeletal muscle protein synthesis, the objective of this study was to evaluate the effect of leucine on the mTOR signaling pathway in cultured equine satellite. Protein synthesis was evaluated by measuring the incorporation of [3H] Phenylalanine (3HPhe) in equine satellite cell myotube cultures treated with a leucine titration ranging from 0 to 408 µM. Our results show a 1.8-fold increase (P < 0.02) in protein synthesis at levels slightly greater than those found in the general circulation, 204 and 408 µM when compared to a no leucine control (0 µM). Puromycin incorporation, a nonradioactive surface sensing of translation (SUnSET) methodology, was also measured in cells treated with leucine (LEU; 408 µM), a no-leucine control (CON), and a puromycin-negative vehicle (PURO-). These results demonstrated a 180% increase (P = 0.0056) in puromycin incorporation in LEU compared to CON cultures. To evaluate the mTOR signaling pathway, equine satellite cell myotube cultures were treated with leucine (LEU; 408 µM) or a no-leucine control (CON) in the presence or absence of rapamycin (LR and CR, respectively), an inhibitor of mTOR. The mTOR inhibitor, rapamycin, suppressed phosphorylation of mTOR (P < 0.01) and rS6 (P < 0.01) with an increase in phosphorylation of rS6 in leucine-treated cultures observed when compared to control cultures (P < 0.05). Similarly, there was a 27% increase (P < 0.005) in the hyperphosphorylated γ-form of 4E-BP1 compared to total 4E-BP1 in LEU compared to CON cultures with leucine-induced phosphorylation of 4E-BP1 completely blocked by rapamycin with a smaller decrease observed in CR compared to CON cultures. The major finding of this study was that leucine activated the mTOR translation initiation pathway and increased transcription of global proteins in cultured equine satellite cells. Use of the cell culture system with primary equine muscle cell lines provides the opportunity to distinguish the impact of leucine on muscle and protein synthesis, independent of systemic interactions.

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Section: Protein Synthesis Assaycontrasting

confidence: 59%

Cultured equine satellite cells as a model system to assess leucine stimulated protein synthesis in horse muscle

DeBoer

Martinson

Pampusch

et al. 2018

Journal of Animal Science

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“…In previous studies, skeletal muscle mass accumulation was attributed to the relative efficiency between muscle protein synthesis and degradation [3,4,33]. Nevertheless, our GO enrichment analysis results obtained from the iTRAQ analysis showed that there were great changes in skeletal muscle structure and muscle cell function.…”

Section: Discussionmentioning

confidence: 62%

“…Lysine (Lys) is the first limiting essential amino acid for mammals consuming a predominantly cereal-based diet [1,2]. The important role of Lys in promoting skeletal muscle growth has already been demonstrated in animal husbandry, and this effect was attributed to increased protein synthesis [3,4]. Moreover, the functions of Lys in preventing human illnesses, such as osteoporosis and maldevelopment, have been intensively studied to protect human health [5,6].…”

Section: Introductionmentioning

confidence: 99%

mTORC1 Mediates Lysine-Induced Satellite Cell Activation to Promote Skeletal Muscle Growth

Jin

Yang

et al. 2019

Cells

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As the first limiting amino acid, lysine (Lys) has been thought to promote muscle fiber hypertrophy by increasing protein synthesis. However, the functions of Lys seem far more complex than that. Despite the fact that satellite cells (SCs) play an important role in skeletal muscle growth, the communication between Lys and SCs remains unclear. In this study, we investigated whether SCs participate directly in Lys-induced skeletal muscle growth and whether the mammalian target of rapamycin complex 1 (mTORC1) pathway was activated both in vivo and in vitro to mediate SC functions in response to Lys supplementation. Subsequently, the skeletal muscle growth of piglets was controlled by dietary Lys supplementation. Isobaric tag for relative and absolute quantitation (iTRAQ) analysis showed activated SCs were required for longissimus dorsi muscle growth, and this effect was accompanied by mTORC1 pathway upregulation. Furthermore, SC proliferation was governed by medium Lys concentrations, and the mTORC1 pathway was significantly enhanced in vitro. After verifying that rapamycin inhibits the mTORC1 pathway and suppresses SC proliferation, we conclude that Lys is not only a molecular building block for protein synthesis but also a signal that activates SCs to manipulate muscle growth via the mTORC1 pathway.

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“…Lysine has been suggested as the first limiting amino acid in growing horses (Graham et al, 1994;Ott, Asquith, & Feaster, 1981;Potter & Huchton, 1975). Moreover, a previous study reported that histidine might be a candidate for a limiting amino acid in equine diet, which mainly consisted of soy hull and corn (Mastellar, Coleman, & Urschel, 2016;Tanner et al, 2014), and the experimental diets used in the present study were also composed of large amounts of soy hull (38%, as-fed basis) and corn (16%, as-fed basis; Table 1). These previous findings support a possibility that one or more of the other amino acids may have been more limiting than threonine, resulting in a lack of responsiveness of phenylalanine oxidation to increasing levels of dietary threonine.…”

Section: Discussionmentioning

confidence: 92%

Using the indicator amino acid oxidation technique to study threonine requirements in horses receiving a predominantly forage diet

Mok

Levesque

Urschel

2018

Animal Physiology Nutrition

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Threonine has been reported to be the second limiting amino acid in typical equine diets, but its actual requirement has not been determined in horses. To evaluate amino acid metabolism and requirements, the indicator amino acid oxidation (IAAO) method has been successfully used in other species. The objective of this research was to estimate threonine requirements in mature horses fed timothy hay and concentrate in 4:1 ratio using the IAAO method. Six Thoroughbred mares (579.9 ± 46.7 kg) received each of 6 levels of threonine intake, 41, 51, 61, 70, 80 and 89 mg/kg BW/day, in a randomly determined order. Each study period was 7-day long, and on day 6, blood samples were collected before and 90 min after feeding to measure amino acid concentrations using HPLC. On day 7, horses underwent IAAO procedures, which included a 2-hr primed, constant intravenous infusion of [ C]sodium bicarbonate to measure total CO production and a 4-hr primed, constant oral administration of [1- C]phenylalanine to estimate phenylalanine oxidation to CO . Blood and breath samples were collected to measure blood [ C]phenylalanine, using GC-MS analysis and breath CO enrichment, using an infrared isotope analyser. Increasing threonine intake levels did not affect plasma phenylalanine oxidation by the ANOVA test (p > 0.05) but resulted in a linear decrease in phenylalanine oxidation (p = 0.04) without a breakpoint by the orthogonal linear contrast. This study is the first attempt to evaluate threonine requirements in horses by the IAAO method; however, threonine requirements are still unknown in mature horses at this time.

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Controlled trial of whole body protein synthesis and plasma amino acid concentrations in yearling horses fed graded amounts of lysine

Cited by 12 publications

References 44 publications

Cultured equine satellite cells as a model system to assess leucine stimulated protein synthesis in horse muscle

Cultured equine satellite cells as a model system to assess leucine stimulated protein synthesis in horse muscle

mTORC1 Mediates Lysine-Induced Satellite Cell Activation to Promote Skeletal Muscle Growth

Using the indicator amino acid oxidation technique to study threonine requirements in horses receiving a predominantly forage diet

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