Mitochondrial phosphoenolpyruvate carboxykinase (PEPCK-M) and serine biosynthetic pathway genes are co-ordinately increased during anabolic agent-induced skeletal muscle growth

Abstract

We aimed to identify novel molecular mechanisms for muscle growth during administration of anabolic agents. Growing pigs (Duroc/(Landrace/Large-White)) were administered Ractopamine (a beta-adrenergic agonist; BA; 20 ppm in feed) or Reporcin (recombinant growth hormone; GH; 10 mg/48 hours injected) and compared to a control cohort (feed only; no injections) over a 27-day time course (1, 3, 7, 13 or 27-days). Longissimus Dorsi muscle gene expression was analyzed using Agilent porcine transcriptome microarrays and clusters of genes displaying similar expression profiles were identified using a modified maSigPro clustering algorithm. Anabolic agents increased carcass (p = 0.002) and muscle weights (Vastus Lateralis: p < 0.001; Semitendinosus: p = 0.075). Skeletal muscle mRNA expression of serine/one-carbon/glycine biosynthesis pathway genes (Phgdh, Psat1 and Psph) and the gluconeogenic enzyme, phosphoenolpyruvate carboxykinase-M (Pck2/PEPCK-M), increased during treatment with BA, and to a lesser extent GH (p < 0.001, treatment x time interaction). Treatment with BA, but not GH, caused a 2-fold increase in phosphoglycerate dehydrogenase (PHGDH) protein expression at days 3 (p < 0.05) and 7 (p < 0.01), and a 2-fold increase in PEPCK-M protein expression at day 7 (p < 0.01). BA treated pigs exhibit a profound increase in expression of PHGDH and PEPCK-M in skeletal muscle, implicating a role for biosynthetic metabolic pathways in muscle growth.

Specific targeting of TGF-β family ligands demonstrates distinct roles in the regulation of muscle mass in health and disease

“…Phosphorylation of effector molecules in the insulin-like growth factor (IGF)-stimulated protein synthesis pathway, mTOR and S6RP, was significantly enhanced after combined activin B and myostatin prodomain treatment. In addition, RNA-Seq showed that complete inhibition of Smad2/3 signaling in muscle resulted in markedly increased expression of growth factor (Igf2, increased 2.4-fold), amino acid transport (Slc7a5, fourfold; Lat2, 3.8-fold), and amino acid biosynthesis (Psat1, 3.7-fold) genes critical for protein synthesis (33)(34)(35). In terms of protein degradation, the expression of the E3 ubiquitin ligases Fbxo32 (MAFbx/atrogin1), Trim63 (MuRF1), and Fbxo30 (Musa1) (7,22), which classically drive this pathway in muscle, was not substantially reduced after 8 wk of myostatin/activin blockade.…”

The Beta-adrenergic agonist, Ractopamine, increases skeletal muscle expression of Asparagine Synthetase as part of an integrated stress response gene program

“…For a full description of the study design, see 14 from which the samples used herein were generated. The project was approved by The University of Nottingham Ethical Review Committee and conducted in accordance with the UK Animals (Scientific Procedures) Act of 1986 (Project License PPL 40/3010).…”

“…These studies revealed impressive alterations in gene expression by BA, but the strength of the data set was limited by the use of only 2 time points. We recently 14 expanded on these studies, employing a pig microarray to analyse temporal changes to the pig skeletal muscle transcriptome in response to BA and growth hormone (GH) administration spanning ~4 weeks, using time points at 1, 3, 7, 13 and 27 days, which, to date, is the most comprehensive data set of its kind. In that study 14 , we identified coordinate increases in expression of mitochondrial phosphoenolpyruvate carboxykinase 2 (PEPCK-M) and 3-phosphoglycerate dehydrogenase (PHGDH) in response to BA.…”

“…We attributed the identification of these enzymes to the use of such an extensive time course; however, the microarray employed did not provide full coverage of the pig transcriptome. Therefore, in line with NC3R guidelines to reduce the number of animals used in research 15 , we performed RNA-sequencing on the same samples 14 to obtain better coverage of the skeletal muscle transcriptome in response to GH or BA treatment. The aim being to investigate global alterations in skeletal muscle gene expression during administration of GH or the synthetic BA, Ractopamine, and thereby identify novel molecular events underpinning the “muscle modifying” effects of this anabolic compound.…”

Modulatory effect of Kolin PlusTM, a polyherbal formulation on muscle growth development in choline deficient diet model of broilers: a microarray approach

“…35 Brown et al suggested that increased expression of PHGDH genes enhanced the skeletal muscle growth in ractopamine treated pigs. 36 Furthermore, upregulation of PHGDH gene was correlated with higher muscle content in broilers. 37 Ankyrin Repeat Domain 2 (ANKRD2) prominently expressed in skeletal than cardiac muscle, which played an intriguing role in skeletal muscle plasticity.…”