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muscle protein breakdown

Grant M Tinsley, Amy H Givan, Austin J Graybeal, Michael I Villarreal, Austin G Cross
This study was a randomised, double-blind, placebo-controlled cross-over trial examining the effects of β-hydroxy β-methylbutyrate free acid (HMB-FA) supplementation on muscle protein breakdown, cortisol, testosterone and resting energy expenditure (REE) during acute fasting. Conditions consisted of supplementation with 3 g/d HMB-FA or placebo during a 3-d meat-free diet followed by a 24-h fast. Urine was collected before and during the 24-h fast for analysis of 3-methylhistidine:creatinine ratio (3MH:CR)...
March 2018: British Journal of Nutrition
Joey S J Smeets, Astrid M H Horstman, Olaf E M G Schijns, Jim T A Dings, Govert Hoogland, Annemie P Gijsen, Joy P B Goessens, Freek G Bouwman, Will K W H Wodzig, Edwin C Mariman, Luc J C van Loon
All tissues undergo continuous reconditioning via the complex orchestration of changes in tissue protein synthesis and breakdown rates. Skeletal muscle tissue has been well studied in this regard, and has been shown to turnover at a rate of 1-2% per day in vivo in humans. Few data are available on protein synthesis rates of other tissues. Because of obvious limitations with regard to brain tissue sampling no study has ever measured brain protein synthesis rates in vivo in humans. Here, we applied stable isotope methodology to directly assess protein synthesis rates in neocortex and hippocampus tissue of six patients undergoing temporal lobectomy for drug-resistant temporal lobe epilepsy (Clinical trial registration: NTR5147)...
February 8, 2018: Brain: a Journal of Neurology
Yukiko Kitase, Julian A Vallejo, William Gutheil, Harika Vemula, Katharina Jähn, Jianxun Yi, Jingsong Zhou, Marco Brotto, Lynda F Bonewald
Exercise has beneficial effects on metabolism and on tissues. The exercise-induced muscle factor β-aminoisobutyric acid (BAIBA) plays a critical role in the browning of white fat and in insulin resistance. Here we show another function for BAIBA, that of a bone-protective factor that prevents osteocyte cell death induced by reactive oxygen species (ROS). l-BAIBA was as or more protective than estrogen or N-acetyl cysteine, signaling through the Mas-Related G Protein-Coupled Receptor Type D (MRGPRD) to prevent the breakdown of mitochondria due to ROS...
February 6, 2018: Cell Reports
Tanner Stokes, Amy J Hector, Robert W Morton, Chris McGlory, Stuart M Phillips
Skeletal muscle supports locomotion and serves as the largest site of postprandial glucose disposal; thus it is a critical organ for physical and metabolic health. Skeletal muscle mass is regulated by the processes of muscle protein synthesis (MPS) and muscle protein breakdown (MPB), both of which are sensitive to external loading and aminoacidemia. Hyperaminoacidemia results in a robust but transient increase in rates of MPS and a mild suppression of MPB. Resistance exercise potentiates the aminoacidemia-induced rise in MPS that, when repeated over time, results in gradual radial growth of skeletal muscle (i...
February 7, 2018: Nutrients
S Keisin Wang, Linden A Green, Ashley R Gutwein, Alok K Gupta, Clifford M Babbey, Raghu L Motaganahalli, Andres Fajardo, Michael P Murphy
OBJECTIVE: Previous in vitro and animal studies have suggested that osteopontin (OPN), an inflammatory extracellular matrix protein, is involved in the formation and growth of abdominal aortic aneurysms (AAAs). However, the mechanism by which this occurs continues to be nebulous. The relationship between OPN and inflammation-suppressing lymphocytes present in the human AAA condition was investigated and presented herein. METHODS: Serum OPN concentrations were measured in healthy, risk factor-matched non-AAA and AAA patients by enzyme-linked immunosorbent assay (ELISA)...
February 3, 2018: Journal of Vascular Surgery
Barbara Strasser, Konstantinos Volaklis, Dietmar Fuchs, Martin Burtscher
Muscle atrophy is an unfortunate effect of aging and many diseases and can compromise physical function and impair vital metabolic processes. Low levels of muscular fitness together with insufficient dietary intake are major risk factors for illness and mortality from all causes. Ultimately, muscle wasting contributes significantly to weakness, disability, increased hospitalization, immobility, and loss of independence. However, the extent of muscle wasting differs greatly between individuals due to differences in the aging process per se as well as physical activity levels...
February 2018: Aging and Disease
Robert W Morton, Daniel A Traylor, Peter J M Weijs, Stuart M Phillips
PURPOSE OF REVIEW: Skeletal muscle mass with aging, during critical care, and following critical care is a determinant of quality of life and survival. In this review, we discuss the mechanisms that underpin skeletal muscle atrophy and recommendations to offset skeletal muscle atrophy with aging and during, as well as following, critical care. RECENT FINDINGS: Anabolic resistance is responsible, in part, for skeletal muscle atrophy with aging, muscle disuse, and during disease states...
April 2018: Current Opinion in Critical Care
Michael L Rossetti, Jennifer L Steiner, Bradley S Gordon
Androgen-deficiency promotes muscle atrophy in part by increasing autophagy-mediated muscle protein breakdown during the fasted state, but factors contributing to this remain undefined. To identify novel factors, mice were subjected to sham or castration surgery. Seven-weeks post-surgery, mice were fasted overnight, refed for 30 min, and fasted another 4.5 h before sacrifice. BNIP3-mediated turnover of mitochondria was increased within the atrophied tibialis anterior (TA) of castrated mice and related to the magnitude of muscle atrophy and autophagy activation (i...
January 29, 2018: Molecular and Cellular Endocrinology
Kevin D Tipton, D Lee Hamilton, Iain J Gallagher
Muscle protein breakdown (MPB) is an important metabolic component of muscle remodeling, adaptation to training, and increasing muscle mass. Degradation of muscle proteins occurs via the integration of three main systems-autophagy and the calpain and ubiquitin-proteasome systems. These systems do not operate independently, and the regulation is complex. Complete degradation of a protein requires some combination of the systems. Determination of MPB in humans is technically challenging, leading to a relative dearth of information...
January 24, 2018: Sports Medicine
Marcus Waskiw-Ford, Hugo J W Fung, Erica Gavel, Olivera Ivanisevic, Julia M Malowany, Michael Rosenblat
Skeletal muscle is a vital tissue for health and functionality and is constantly 'turning over' through the reciprocal processes of protein synthesis and protein breakdown. This article is protected by copyright. All rights reserved.
January 23, 2018: Journal of Physiology
Lena Gamrin-Gripenberg, Martin Sundström-Rehal, Daniel Olsson, Jonathan Grip, Jan Wernerman, Olav Rooyackers
BACKGROUND: There is extensive documentation on skeletal muscle protein depletion during the initial phase of critical illness. However, for intensive care unit (ICU) long-stayers, objective data are very limited. In this study, we examined skeletal muscle protein and amino acid turnover in patients with a prolonged ICU stay. METHODS: Patients (n = 20) were studied serially every 8-12 days between days 10 and 40 of their ICU stay as long as patients stayed in the ICU...
January 23, 2018: Critical Care: the Official Journal of the Critical Care Forum
Jean-Baptiste Michel, Guillaume Jondeau, Dianna M Milewicz
Vascular Smooth Muscle Cells (vSMCs) play a crucial role in both the pathogenesis of Aneurysms and Dissections of the ascending thoracic aorta (TAAD) in humans and in the associated adaptive compensatory responses, since thrombosis and inflammatory processes are absent in the majority of cases. Aneurysms and dissections share numerous characteristics, including aetiologies and histopathological alterations: vSMC disappearance, medial areas of mucoid degeneration, and ExtraCellular Matrix (ECM) breakdown. Three aetiologies predominate in TAAD in humans: i) genetic causes in heritable familial forms, ii) an association with bicuspid aortic valves and iii) a sporadic degenerative form linked to the aortic aging process...
January 17, 2018: Cardiovascular Research
Carlos Alberto Arcaro, Renata Pires Assis, Neusa Maria Zanon, Sílvia Paula-Gomes, Luiz C C Navegantes, Isis Carmo Kettelhut, Iguatemy Lourenço Brunetti, Amanda Martins Baviera
Advances in the knowledge of the mechanisms controlling protein breakdown in skeletal muscles have allowed the exploration of new options for treating muscle wasting conditions. Pentoxifylline (PTX), a nonselective phosphodiesterase (PDE) inhibitor, attenuates the loss of muscle mass during catabolic conditions, mainly via inhibiting protein breakdown. The aim of this study was to explore the mechanisms by which PTX inhibits proteolysis in the soleus and extensor digitorum longus (EDL) muscles of streptozotocin-induced diabetic rats...
December 14, 2017: Journal of Applied Physiology
Gordon L Klein
PURPOSE OF REVIEW: Burn injury results in resorptive bone loss, failure to make new bone, and muscle protein breakdown resulting in cachexia. The purpose of this review is to examine the relationship between bone loss and muscle atrophy in burn injury with a view to understanding the process at work and how it may apply to other conditions that have similar features. RECENT FINDINGS: We present data suggesting that the use of bisphosphonates in the first 10 days following the burn prevents not only the resorptive bone loss but also the muscle wasting...
January 17, 2018: Current Osteoporosis Reports
Haixiang Yu, Adam Fellows, Kirsty Foote, Zhaoqing Yang, Nichola Figg, Trevor Littlewood, Martin Bennett
OBJECTIVE: Vascular smooth muscle cell (VSMC) apoptosis accelerates atherosclerosis and promotes breakdown of the extracellular matrix, but the mechanistic links between these 2 processes are unknown. The forkhead protein FOXO3a (forkhead transcription factor O subfamily member 3a) is activated in human atherosclerosis and induces a range of proapoptotic and other transcriptional targets. We, therefore, determined the mechanisms and consequences of FOXO3a activation in atherosclerosis and arterial remodeling after injury...
January 11, 2018: Arteriosclerosis, Thrombosis, and Vascular Biology
Carmen Fiuza-Luces, Alejandro Santos-Lozano, Francisco Llavero, Rocío Campo, Gisela Nogales-Gadea, Jorge Díez Bermejo, Carlos Balandrón, África González-Murillo, Joaquín Arenas, Miguel A Martín, Antoni L Andreu, Tomàs Pinós, Beatriz G Gálvez, Juan A López, Jesús Vázquez, José L Zugaza, Alejandro Lucia
McArdle disease is an inborn disorder of skeletal muscle glycogen metabolism that results in blockade of glycogen breakdown due to mutations in the myophosphorylase gene. We recently developed a mouse model carrying the homozygous p.R50X common human mutation (McArdle mouse), facilitating the study of how glycogen availability affects muscle molecular adaptations to endurance exercise training. Using quantitative differential analysis by liquid chromatography with tandem-mass spectrometry, we analysed the quadriceps muscle proteome of 16-week-old McArdle (n = 5) and wild-type (WT) (n = 4) mice previously subjected to 8-week moderate-intensity treadmill training or to an equivalent control (no training) period...
January 7, 2018: Journal of Physiology
Kenneth H K Wong, Yin Cai, Fan Ying, Xinyi Chen, Paul M Vanhoutte, Eva H C Tang
AIMS: Repressor activator protein 1 (Rap1) is conventionally known as a static structural component of the telomere, but recent evidence indicates that it exerts functions within and outside the nucleus taking part in metabolic regulation and promoting inflammatory responses. The present study investigated whether or not Rap1 deletion affects oxidative stress and nitric oxide (NO) bioavailability in the vascular wall, thus modulating endothelial function. METHODS AND RESULTS: Vascular responsiveness was studied in wire myographs in aortae from Rap1 wildtype and knockout mice...
December 22, 2017: Journal of Molecular and Cellular Cardiology
Bingquan Yang, Jie Sun, Yang Yuan, Zilin Sun
AIMS/INTRODUCTION: Atorvastatin is usually used to decrease the amount of fatty substances in individuals with type 2 diabetes mellitus. However, it can cause side effects, such as breakdown of skeletal muscle tissue. This study focuses on the effects of atorvastatin on autophagy of the skeletal muscles in diabetic rats. MATERIALS AND METHODS: Diabetes in rats in the diabetic (D) and atorvastatin (T) groups was induced using streptozotocin (65 mg/kg, intraperitoneal injection)...
December 15, 2017: Journal of Diabetes Investigation
Savant S Thakur, Kristy Swiderski, James G Ryall, Gordon S Lynch
Duchenne muscular dystrophy is the most common and severe of the muscular dystrophies, a group of inherited myopathies caused by different genetic mutations leading to aberrant expression or complete absence of cytoskeletal proteins. Dystrophic muscles are prone to injury, and regenerate poorly after damage. Remorseless cycles of muscle fibre breakdown and incomplete repair lead to progressive and severe muscle wasting, weakness and premature death. Many other conditions are similarly characterized by muscle wasting, including sarcopenia, cancer cachexia, sepsis, denervation, burns, and chronic obstructive pulmonary disease...
January 19, 2018: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
Renate Jonker, Nicolaas E P Deutz, Rajesh Harrykissoon, Anthony J Zachria, Eugene A Veley, Mariëlle P K J Engelen
After bolus and continuous enteral feeding of the same protein, different digestion and absorption kinetics and anabolic responses are observed. Establishing which mode of feeding has the highest anabolic potential in patients with chronic obstructive pulmonary disease (COPD) may aid in the prevention of muscle wasting, but an important confounding factor is the duration of assessments after bolus feeding. We hypothesized that the anabolic response to bolus and continuous feeding in COPD patients is comparable when methodological issues are addressed...
January 16, 2018: Clinical Science (1979-)
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