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Skeletal muscle hypertrophy

Alex S Ribeiro, Brad J Schoenfeld, Steven J Fleck, Fábio L C Pina, Matheus A Nascimento, Edilson S Cyrino
The purpose of the present study was to investigate the effect of resistance training (RT) performed in a pyramid (PR) versus a traditional (TD) system on muscular strength, muscle mass, and hormonal responses in older women. Twenty-five older women (67.6 ± 5.1 years, 65.9 ± 11.1 kg, 154.7 ± 5.8 cm, and 27.5 ± 4.5 kg m) performed both a TD and PR system RT program in a balanced crossover design. The TD program consisted of 3 sets of 8-12 RM with a constant load for the 3 sets, whereas the PR system consisted of 3 sets of 12/10/8 RM with incrementally higher loads for each set...
September 23, 2016: Journal of Strength and Conditioning Research
John G Conboy
The Rbfox genes encode an ancient family of sequence-specific RNA binding proteins (RBPs) that are critical developmental regulators in multiple tissues including skeletal muscle, cardiac muscle, and brain. The hallmark of Rbfox proteins is a single high-affinity RRM domain, highly conserved from insects to humans, that binds preferentially to UGCAUG motifs at diverse regulatory sites in pre-mRNA introns, mRNA 3'UTRs, and pre-miRNAs hairpin structures. Versatile regulatory circuits operate on Rbfox pre-mRNA and mRNA to ensure proper expression of Rbfox1 protein isoforms, which then act on the broader transcriptome to regulate alternative splicing networks, mRNA stability and translation, and microRNA processing...
October 17, 2016: Wiley Interdisciplinary Reviews. RNA
Chris McGlory, Michaela C Devries, Stuart M Phillips
Exercise results in the rapid remodelling of skeletal muscle imparting a positive impact on human health. This process is underpinned by acute and chronic changes in both gene and protein synthesis. In this short review we provide a brief summary of our current understanding regarding how exercise influences these processes as well as the subsequent impact on muscle protein turnover and resultant shift in muscle phenotype. We explore concepts of ribosomal biogenesis and the potential role of increased translational capacity versus translational efficiency in contributing to muscular hypertrophy...
October 14, 2016: Journal of Applied Physiology
Malek Kammoun, Philippe Pouletaut, Francis Canon, Malayannan Subramaniam, John R Hawse, Muriel Vayssade, Sabine F Bensamoun
As transforming growth factor (TGF)-β inducible early gene-1 is highly expressed in skeletal muscle, the effect of TIEG1 gene deletion on the passive mechanical properties of slow and fast twitch muscle fibers was analyzed. Twenty five muscle fibers were harvested from soleus (Sol) and extensor digitorum longus (EDL) muscles from TIEG1-/- (N = 5) and control (N = 5) mice. Mechanical tests were performed on fibers and the dynamic and static stresses were measured. A viscoelastic Hill model of 3rd order was used to fit the experimental relaxation test data...
2016: PloS One
Belinda Spoto, Anna Pisano, Carmine Zoccali
Insulin resistance (IR) is an early metabolic alteration in CKD patients, being apparent when the glomerular filtration rate is still within the normal range and becoming almost universal in those who reach the ESKF. The skeletal muscle represents the primary site of IR in CKD and post-receptor alterations are recognized as the main defect underlying IR in this condition. Estimates of IR based on fasting insulin concentration are easier but may not be adequate in CKD patients because renal insufficiency reduces insulin catabolism...
October 5, 2016: American Journal of Physiology. Renal Physiology
Manuela Marabita, Martina Baraldo, Francesca Solagna, Judith Johanna Maria Ceelen, Roberta Sartori, Hendrik Nolte, Ivan Nemazanyy, Stéphane Pyronnet, Marcus Kruger, Mario Pende, Bert Blaauw
Loss of skeletal muscle mass and force aggravates age-related sarcopenia and numerous pathologies, such as cancer and diabetes. The AKT-mTORC1 pathway plays a major role in stimulating adult muscle growth; however, the functional role of its downstream mediators in vivo is unknown. Here, we show that simultaneous inhibition of mTOR signaling to both S6K1 and 4E-BP1 is sufficient to reduce AKT-induced muscle growth and render it insensitive to the mTORC1-inhibitor rapamycin. Surprisingly, lack of mTOR signaling to 4E-BP1 only, or deletion of S6K1 alone, is not sufficient to reduce muscle hypertrophy or alter its sensitivity to rapamycin...
October 4, 2016: Cell Reports
Alexander Kalinkovich, Gregory Livshits
Sarcopenia, an age-associated decline in skeletal muscle mass coupled with functional deterioration, may be exacerbated by obesity leading to higher disability, frailty, morbidity and mortality rates. In the combination of sarcopenia and obesity, the state called sarcopenic obesity (SOB), some key age- and obesity-mediated factors and pathways may aggravate sarcopenia. This review will analyze the mechanisms underlying the pathogenesis of SOB. In obese adipose tissue (AT), adipocytes undergo hypertrophy, hyperplasia and activation resulted in accumulation of pro-inflammatory macrophages and other immune cells as well as dysregulated production of various adipokines that together with senescent cells and the immune cell-released cytokines and chemokines create a local pro-inflammatory status...
October 1, 2016: Ageing Research Reviews
Mathew J Wong, Crystal Kantores, Julijana Ivanovska, Amish Jain, Robert P Jankov
Chronic neonatal pulmonary hypertension (PHT) frequently results in early death. Systemically administered Rho-kinase (ROCK) inhibitors prevent and reverse chronic PHT in neonatal rats, but at the cost of severe adverse effects, including systemic hypotension and growth restriction. Simvastatin has pleiotropic inhibitory effects on isoprenoid intermediates that may limit activity of RhoA, which signals upstream of ROCK. We therefore hypothesized that statin treatment would safely limit pulmonary vascular RhoA activity and prevent and reverse experimental chronic neonatal PHT via downstream inhibitory effects on pathological ROCK activity...
September 30, 2016: American Journal of Physiology. Lung Cellular and Molecular Physiology
Zhu Li, Julie L Frey, G William Wong, Marie-Claude Faugere, Michael J Wolfgang, Jason K Kim, Ryan C Riddle, Thomas L Clemens
Recent studies have identified the osteoblast as an insulin responsive cell that participates in global energy homeostasis. Here we show that Glut4 is required for insulin-dependent uptake and oxidation of glucose in mature osteoblasts. In primary cultures of mouse osteoblasts, insulin increased uptake and oxidation of (14)C-glucose in a dose-dependent fashion, but did not significantly affect uptake or oxidation of (14)C-oleate. In vitro, undifferentiated osteoblasts expressed three high affinity glucose transporters: Glut1, Glut4, and Glut3...
September 30, 2016: Endocrinology
Satoru Ato, Yuhei Makanae, Kohei Kido, Satoshi Fujita
Resistance training with eccentric contraction has been shown to augment muscle hypertrophy more than other contraction modes do (i.e., concentric and isometric contraction). However, the molecular mechanisms involved remain unclear. The purpose of this study was to investigate the effect of muscle contraction mode on mammalian target of rapamycin complex 1 (mTORC1) signaling using a standardized force-time integral (load (weight) × contraction time). Male Sprague-Dawley rats were randomly assigned to three groups: eccentric contraction, concentric contraction, and isometric contraction...
October 2016: Physiological Reports
Takeshi Shimoide, Naoyuki Kawao, Yukinori Tamura, Hironobu Morita, Hiroshi Kaji
Skeletal muscle hypertrophy and wasting are induced by hypergravity and microgravity, respectively. However, the mechanisms by which gravity change regulates muscle mass still remain unclear. We previously reported that hypergravity increases muscle mass via the vestibular system in mice. In this study, we performed comparative DNA microarray analysis of the soleus muscle from mice kept in 1 or 3 g environments with or without vestibular lesions. Mice were kept in 1 g or 3 g environment for 4 weeks by using a centrifuge 14 days after surgical bilateral vestibular lesions...
October 21, 2016: Biochemical and Biophysical Research Communications
Fausto Antonio Panizzolo, Andrew J Maiorana, Louise H Naylor, Lawrence G Dembo, David G Lloyd, Daniel J Green, Jonas Rubenson
BACKGROUND: Alterations in skeletal muscle function and architecture have been linked to the compromised exercise capacity characterizing chronic heart failure (CHF). However, how passive skeletal muscle force is affected in CHF is not clear. Understanding passive force characteristics in CHF can help further elucidate the extent to which altered contractile properties and/or architecture might affect muscle and locomotor function. Therefore, the aim of this study was to investigate passive force in a single muscle for which non-invasive measures of muscle size and estimates of fiber force are possible, the soleus (SOL), both in CHF patients and age- and physical activity-matched control participants...
2016: PeerJ
Haoliang Hu, Lu He, Lanfang Li, Linxi Chen
The G-protein-coupled receptor APJ and its endogenous ligand apelin are widely expressed in many peripheral tissues and central nervous system, including adipose tissue, skeletal muscles and hypothalamus. Apelin/APJ system, involved in numerous physiological functions like angiogenesis, fluid homeostasis and energy metabolism regulation, is notably implicated in the development of different pathologies such as diabetes and its complications. Increasing evidence suggests that apelin regulates insulin sensitivity, stimulates glucose utilization and enhances brown adipogenesis in different tissues associated with diabetes...
September 2016: Molecular Genetics and Metabolism
Sied Kebir, Zacharias Orfanos, Julia Schuld, Markus Linhart, Christian Lamberz, Peter F M van der Ven, Jan Schrickel, Gregor Kirfel, Dieter O Fürst, Rainer Meyer
Pressure overload induces cardiac remodeling involving both the contractile machinery and intercalated disks (IDs). Filamin C (FlnC) and Xin actin-binding repeat-containing proteins (XIRPs) are multi-adapters localizing in IDs of higher vertebrates. Knockout of the gene encoding Xin (Xirp1) in mice leads to a mild cardiac phenotype with ID mislocalization. In order to amplify this phenotype, we performed transverse aortic constriction (TAC) on control and Xirp1-deficient mice. TAC induced similar left ventricular hypertrophy in both genotypes, suggesting that the lack of Xin does not lead to higher susceptibility to cardiac overload...
October 15, 2016: Experimental Cell Research
Bilal Al Jaam, Katy Heu, Florian Pennarubia, Alexandre Segelle, Laetitia Magnol, Agnès Germot, Sébastien Legardinier, Véronique Blanquet, Abderrahman Maftah
Postnatal skeletal muscle growth results from the activation of satellite cells and/or an increase in protein synthesis. The Notch signalling pathway maintains satellite cells in a quiescent state, and once activated, sustains their proliferation and commitment towards differentiation. In mammals, POFUT1-mediated O-fucosylation regulates the interactions between NOTCH receptors and ligands of the DELTA/JAGGED family, thus initiating the activation of canonical Notch signalling. Here, we analysed the consequences of downregulated expression of the Pofut1 gene on postnatal muscle growth in mutant Pofut1(cax/cax) (cax, compact axial skeleton) mice and differentiation of their satellite cell-derived myoblasts (SCDMs)...
September 2016: Open Biology
Terezie Pelikánová
UNLABELLED: Diabetic retinopathy (DR) develops in patients with both type 1 and type 2 diabetes and is the major cause of vision loss and blindness in the working population. The main risk factor of DR is hyperglycemia accompanied by enhanced mitochondrial production of reactive oxygen species and oxidative stress, formation of advanced glycation end products (AGE) and hexosamines, increase in polyol metabolism of glucose. The severity of vascular injury depends on the individual genetic background and is modified by other epigenetic, metabolic and haemodynamic factors, including hypertension, dyslipidemia and oxidative stress...
2016: Vnitr̆ní Lékar̆ství
Amy E Vincent, John P Grady, Mariana C Rocha, Charlotte L Alston, Karolina A Rygiel, Rita Barresi, Robert W Taylor, Doug M Turnbull
Myofibrillar myopathies (MFM) are characterised by focal myofibrillar destruction and accumulation of myofibrillar elements as protein aggregates. They are caused by mutations in the DES, MYOT, CRYAB, FLNC, BAG3, DNAJB6 and ZASP genes as well as other as yet unidentified genes. Previous studies have reported changes in mitochondrial morphology and cellular positioning, as well as clonally-expanded, large-scale mitochondrial DNA (mtDNA) deletions and focal respiratory chain deficiency in muscle of MFM patients...
October 2016: Neuromuscular Disorders: NMD
Shouyu Xu, Xueyun Liu, Zhenhuang Chen, Gaoquan Li, Qin Chen, Guoqing Zhou, Ruijie Ma, Xinmiao Yao, Xiao Huang
Blood flow restriction (BFR) under low-intensity resistance training (LIRT) can produce similar effects upon muscles to that of high-intensity resistance training (HIRT) while overcoming many of the restrictions to HIRT that occurs in a clinical setting. However, the potential molecular mechanisms of BFR induced muscle hypertrophy remain largely unknown. Here, using a BFR rat model, we aim to better elucidate the mechanisms regulating muscle hypertrophy as induced by BFR and reveal possible clinical therapeutic targets for atrophy cases...
December 15, 2016: Gene
Tu A Vo, Trina F Galloway, Tora Bardal, Christine K Halseth, Gunvor Øie, Elin Kjørsvik
Dynamics between hypertrophy (increase in cell size) and hyperplasia (increase in cell numbers) of white and red muscle in relation to body size (standard length - SL), and the influence of the first-feeding diets on muscle growth were investigated in Atlantic cod larvae (Gadus morhua). Cod larvae were fed copepod nauplii or rotifers of different nutritional qualities from 4 to 29 days post hatching (dph), Artemia nauplii from 20 to 40 dph and a formulated diet from 36 to 60 dph. The short period of feeding with cultivated copepod nauplii had a positive effect on both muscle hyperplasia and hypertrophy after the copepod/rotifer phase (19 dph), and a positive long term effect on muscle hypertrophy (60 dph)...
September 9, 2016: Biology Open
F Baruffaldi, D Montarras, V Basile, L De Feo, S Badodi, M Ganassi, R Battini, C Nicoletti, C Imbriano, A Musarò, S Molinari
The transcription factor MEF2C (Myocyte Enhancer Factor 2C) plays an established role in the early steps of myogenic differentiation. However, the involvement of MEF2C in adult myogenesis and in muscle regeneration has not yet been systematically investigated. Alternative splicing of mammalian MEF2C transcripts gives rise to two mutually exclusive protein variants: MEF2Cα2 which exerts a positive control of myogenic differentiation, and MEF2Cα1, in which the α1 domain acts as trans-repressor of the MEF2C pro-differentiation activity itself...
September 10, 2016: Stem Cells
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