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Congenital heart defects (CHDs) are the leading cause of death in live-born infants. Currently, patches used in the repair of CHDs are exclusively inert and non-degradable, which increases the risk of arrhythmia, follow-up surgeries, and sudden cardiac death. In this preliminary study, we sought to fabricate biodegradable scaffolds that can support cardiac regeneration in the repair of CHDs. We electrospun biodegradable scaffolds using various blends of polyurethane (PU) and polycaprolactone (PCL) with and without sacrificial poly(ethylene oxide) (PEO) particles and assessed the mechanical properties, cell infiltration levels, and inflammatory response in vitro (surface cell seeding) and in vivo (subcutaneous mouse implant). We hypothesized that a blend of the two polymers would preserve the low stiffness of PU as well as the high cell infiltration observed in PCL scaffolds. The inclusion of PU in the blends, even as low as 10%, decreased cell infiltration both in vitro and in vivo. The inclusion of sacrificial PEO increased pore sizes, reduced Young’s moduli, and reduced the inflammatory response in all scaffold types. Collectively, we have concluded that a PCL patch electrospun with sacrificial PEO particles is the most promising scaffold for further assessment as in our heart defect model.

Fibroblasts produce the majority of collagen in the heart and are thought to regulate extracellular matrix (ECM) turnover. Although fibrosis accompanies many cardiac pathologies and is generally deleterious, the role of fibroblasts in maintaining the basal ECM network and in fibrosis in vivo is poorly understood. We genetically ablated fibroblasts in mice to evaluate the impact on homeostasis of adult ECM and cardiac function after injury. Fibroblast-ablated mice demonstrated a substantive reduction in cardiac fibroblasts, but fibrillar collagen and the ECM proteome were not overtly altered when evaluated by quantitative mass spectrometry and N-terminomics. However, the distribution and quantity of collagen VI, microfibrillar collagen that forms an open network with the basement membrane, was reduced. In fibroblast-ablated mice, cardiac function was better preserved following angiotensin II/phenylephrine (AngII/PE)-induced fibrosis and myocardial infarction (MI). Analysis of cardiomyocyte function demonstrated altered sarcomere shortening and slowed calcium decline in both uninjured and AngII/PE-infused fibroblast-ablated mice. After MI, the residual resident fibroblasts responded to injury, albeit with reduced proliferation and numbers immediately after injury. These results indicate that the adult mouse heart tolerates a significant degree of fibroblast loss with a potentially beneficial impact on cardiac function after injury. The cardioprotective effect of controlled fibroblast reduction may have therapeutic value in heart disease.

Fibroblasts produce the majority of collagen in the heart and are thought to regulate extracellular matrix (ECM) turnover. Although fibrosis accompanies many cardiac pathologies and is generally deleterious, the role of fibroblasts in maintaining the basal ECM network and in fibrosis in vivo is poorly understood. We genetically ablated fibroblasts in mice to evaluate the impact on homeostasis of adult ECM and cardiac function after injury. Fibroblast-ablated mice demonstrated a substantive reduction in cardiac fibroblasts, but fibrillar collagen and the ECM proteome were not overtly altered when evaluated by quantitative mass spectrometry and N-terminomics. However, the distribution and quantity of collagen VI, microfibrillar collagen that forms an open network with the basement membrane, was reduced. In fibroblast-ablated mice, cardiac function was better preserved following angiotensin II/phenylephrine (AngII/PE)-induced fibrosis and myocardial infarction (MI). Analysis of cardiomyocyte function demonstrated altered sarcomere shortening and slowed calcium decline in both uninjured and AngII/PE-infused fibroblast-ablated mice. After MI, the residual resident fibroblasts responded to injury, albeit with reduced proliferation and numbers immediately after injury. These results indicate that the adult mouse heart tolerates a significant degree of fibroblast loss with a potentially beneficial impact on cardiac function after injury. The cardioprotective effect of controlled fibroblast reduction may have therapeutic value in heart disease.

Heart disease is the leading cause of death in the United States among both adults and infants. In adults, 5-year survival after a heart attack is

Based on a patent-analysis method, this paper compares the firm-level technology pathways of wind turbine firms from China and Europe, and examines the firms’ unique innovation strategies that may lead to these pathways being modified to capitalize on any opportunities that arise. This paper finds that Chinese firms have different firm-level pathways compared to their European counterparts, whereby they are influenced by different innovation strategies that involve technological foci, learning, and R&D collaboration, as well as globalization strategies. We find that European firms are stronger in most of these strategic dimensions, while Chinese firms demonstrate a strong learning capacity and customized innovations. We propose that there might be a limited divergence of the sector-level technological trajectories between China and Europe. In addition, we suggest that there is limited opportunity for Chinese firms to leapfrog with regard to the existing technology trajectories and surpass their European counterparts in the near future.

Background The aging process is often associated with the presence of sarcopenia. Although changes in the plasma concentration of several amino acids have been observed in older adults, it remains unclear whether these changes are related to disturbances in whole body production and/or interconversions. Methods We studied 10 healthy young (~ 22.7 y) and 17 older adults (~ 64.8 y) by administering a mixture of stable amino acid tracers in a pulse and in a primed constant infusion. We calculated whole body production (WBP) and metabolite to metabolite interconversions. In addition, we measured body composition, muscle function, and provided questionnaires to assess daily dietary intake, physical activity, mood (anxiety, depression) and markers of cognitive function. Plasma enrichments and metabolite concentrations were measured by GC- and LC-MS/MS and statistics were performed by student t-test. Results Older adults had a 11% higher body mass index (p = 0.04) and 27% reduced peak leg extension force (p = 0.02) than the younger group, but comparable values for muscle mass, mood and cognitive function. Although small differences in several plasma amino acid concentrations were observed, we found older adults had about 40% higher values of WBP for glutamine (221 ± 27 vs. 305 ± 21 μmol/kg ffm/h, p = 0.03) and tau-methylhistidine (0.15 ± 0.01 vs. 0.21 ± 0.02 μmol/kg ffm/h, p = 0.04), 26% lower WBP value for arginine (59 ± 4 vs. 44 ± 4 μmol/kg ffm/h, p = 0.02) and a reduction in WBP (50%; 1.23 ± 0.15 vs. 0.69 ± 0.06 μmol/kg ffm/h, p = 0.001) and concentration (25%; 3.5 ± 0.3 μmol/l vs. 2.6 ± 0.2 μmol/l, p = 0.01) for β-Hydroxy β-Methylbutyrate. No differences were observed in protein catabolism. Clearance of arginine was decreased (27%, p = 0.03) and clearance of glutamine (58%, p = 0.01), leucine (67%, p = 0.001) and KIC (76%, p = 0.004) were increased in older adults. Conclusions Specific differences exist between young and older adults in amino acid metabolism.

Congenital heart defects (CHDs) affect 1 in 120 newborns in the United States. Surgical repair of structural heart defects often leads to arrhythmia and increased risk of heart failure. Our laboratory previously developed an acellular fibrin patch reinforced with a biodegradable poly(ether ester urethane) urea mesh that resulted in improved heart function when tested in a rat right ventricle wall replacement model compared to fixed pericardium. However, this patch did not drive significant neotissue formation. In this study, we modified the patch materials and prevascularized this patch with human umbilical vein endothelial cells and c-Kit(+) human amniotic fluid stem cells. Rudimentary capillary-like networks formed in the fibrin after culture of cell-encapsulated patches for 3 days in vitro. Prevascularized patches and non-cell loaded patch controls were implanted onto full-thickness heart wall defects created in the right ventricle of athymic nude rats. Two months after surgery, defect repair with prevascularized patches resulted in improved heart function and the patched heart area exhibited greater vascularization and muscularization, less fibrosis, and increased M2 macrophage infiltration compared to acellular patches.

Eco-Industrial Parks are a proven approach that balances environmental protection practices and regional industrial development. However, it is a challenge to relocate small and medium-sized enterprises into industrial parks. Recently in China, there is a new phenomenon where interfirm alliances have started to facilitate local government in promoting the relocation of small enterprises to industrial parks. In this paper, we attempt to identify the role that these interfirm alliances can play. This study uses a survey method to investigate this question in Jieyang City, and 598 valid questionnaires were collected. The validity and reliability of the relevant factors were tested using factor analysis, and ordered logit-regression was adopted to quantitatively assess the effect of the extracted factors on the dependent variable. The results highlight five key influencing factors in alliances: policy, market, managerial, financial, and technical. All factors significantly affect the relocation decisions of small enterprises according to various firm characteristics. Among these factors, the financial factor has the strongest influence on alliances among manufacturing firms. Policy and managerial aspects of alliances are critical to encouraging small enterprises to move into industrial parks while larger enterprises consider financial and technical effects to be more important. The market factor of alliances affects family-owned SMEs much more than it does for other enterprises. In summary, interfirm alliances are an essential policy implementation tool that has the potential to help local government in promoting the relocation of enterprises into eco-industrial parks and to improve industrial environmental performance.

The Chinese government attempts to use market-oriented measures, such as energy performance contracts (EPCs) rather than mere policy mandates, to encourage manufacturers to voluntarily adopt green technologies. However, the low use rate of EPCs in existing diffusion projects calls for an in-depth examination. This article, therefore, aims to investigate the adoption risks that thwart key stakeholders, as well as the stakeholders' trust that may mitigate the aforementioned risks, through a case study of the national-level diffusion project. Using network analysis, this study identifies four critical risks that are associated to key stakeholders, that is, information asymmetry, funding support, payback period savings potential, and technical competences. Furthermore, it discloses the linkages between stakeholders' trust perceptions and the aforementioned risks. This outcome gives us new insights about what can be improved to better promote EPCs in diffusion projects on a national scale.

Small-and-medium-sized enterprises (SMEs) are significant to China's emission reduction programme. This research aims to improve our understanding of the challenge of diffusing green-manufacturing technologies among SMEs in China. Specifically, this study examines the Chinese Government's effort to facilitate reduction of energy consumption among SMEs through Energy Performance Contracts (EPCs) to incentivize domestic manufacturers to adopt energy efficient measures (EEMs) in order to reduce demand for energy and corresponding drop in emissions. The data is gathered from relevant EPC stakeholders in the National Motor Upgrading Demonstration Project and its implementation in Dongguan city, which is based on 30 in-depth interviews and 6 focus group discussions. Using stakeholder analysis, this study finds that guaranteed energy savings model is the favorite model in implementation, given the gained benefits outweigh committed resources, and the control capability overrides possible risks among the two core stakeholders. The outcomes of this study may allow the government to have a clear understanding of stakeholder perception of the different EPC models used in China so the design and deployment of these mechanisms can be improved.

Background/Aims: Endoplasmic reticulum (ER) stress has emerged as a potential mechanism contributing to diabetes and its comorbidities. However, the importance of ER stress in diabetic vascular dysfunction is unclear. The purpose of this study was to examine the effects of the ER stress inhibitor, tauroursodeoxycholic acid (TUDCA), on arterial stiffness and endothelial dysfunction in type 2 diabetic mice. Methods: Carotid and mesenteric artery endothelial function were assessed via ex vivo pressure myography, and arterial stiffness was measured by aortic pulse wave velocity. The effects of TUDCA were examined both acutely (ex vivo) and chronically (250 mg/kg/day; i.p., 4 weeks). Results: Compared to control C57BL/6J mice, db/db (DB) mice did not display carotid artery endothelial dysfunction; however, mesenteric artery endothelial function was markedly impaired. Acute incubation and chronic administration of TUDCA improved endothelium-dependent dilation in DB mesenteric arteries, without affecting endothelium-independent dilation. Chronic TUDCA administration also reduced arterial stiffness and was associated with reductions in ER stress markers in aortic and perivascular adipose tissue. Conclusions: These results suggest that ER stress may represent a novel cause of, and therapeutic target for, diabetic vascular dysfunction.

Our objective was to develop a quick and simplified method for the determination of β-Hydroxy-β-methylbutyrate (HMB) and ɑ-ketoisocaproic acid (KIC) concentrations and enrichments by GC/MS/MS to determine the turnover rate of HMB in humans. In experiment 1, we provided a pulse of L-[5,5,5- 2 H 3 ]leucine to younger adults in the postabsorptive state then collected blood samples over a 4 h time period. In experiment 2, we provided a pulse of [3,4,methyl- 13 C 3 ]HMB to older adults in the postabsorptive state then collected blood samples over a 3 h time period. Plasma concentrations of KIC and HMB and MPE of KIC and HMB were determined by GC/MS/MS. Plasma enrichment of leucine was determined by LC/MS/MS. To determine plasma enrichment of [5,5,5- 2 H 3 ]HMB and [3,4,methyl- 13 C 3 ]HMB, samples were derivatized using pentafluorobenzyl bromide and analyzed using chemical ionization mode. The final methods used included multiple reaction monitoring of transitions 117.3 > 59.3 for M + 0 and 120.3 > 59.3 for M + 3. In experiment 1, peak MPE of Leu peaked at 9.76% generating a peak MPE of KIC at 2.67% and a peak HMB MPE of 0.3%. In experiment 2, the rate of appearance for HMB was 0.66 μmol/kg ffm/h. We calculated that production of HMB in humans accounts for 0.66% of total leucine turnover.

Background: To our knowledge the efficacy of soy-dairy protein blend (PB) supplementation with resistance exercise training (RET) has not been evaluated in a longitudinal study. Objective: Our aim was to determine the effect of PB supplementation during RET on muscle adaptation. Methods: In this double-blind randomized clinical trial, healthy young men [18–30 y; BMI (in kg/m2): 25 ± 0.5] participated in supervised whole-body RET at 60–80% 1-repetition maximum (1-RM) for 3 d/wk for 12 wk with random assignment to daily receive 22 g PB (n = 23), whey protein (WP) isolate (n = 22), or an isocaloric maltodextrin (carbohydrate) placebo [(MDP) n = 23]. Serum testosterone, muscle strength, thigh muscle thickness (MT), myofiber cross-sectional area (mCSA), and lean body mass (LBM) were assessed before and after 6 and 12 wk of RET. Results: All treatments increased LBM (P 0.10) between treatments. Testosterone was not altered. Conclusions: PB supplementation during 3 mo of RET tended to slightly enhance gains in whole-body and arm LBM, but not leg muscle mass, compared with RET without protein supplementation. Although protein supplementation minimally enhanced gains in LBM of healthy young men, there was no enhancement of gains in strength. This trial was registered at clinicaltrials.gov as {"type":"clinical-trial","attrs":{"text":"NCT01749189","term_id":"NCT01749189"}}NCT01749189.

The development of targeted therapeutics for cancer continues to receive intense research attention as laboratories and pharmaceutical companies seek to develop drugs and technologies that improve treatment efficacy and mitigate harmful side effects. In the aftermath of World War I, it was discovered that mustard gas destroys rapidly dividing cells and could be used to treat cancer. Since then, chemotherapy has remained a predominant treatment for cancer; however, the destruction of dividing cells throughout the body yields devastating side effects including off-target damage of the digestive tract, bone marrow, skin, and reproductive tract. Furthermore, the high mutation rate of cancerous cells often renders chemotherapy ineffective long-term. Therapies with improved specificity, localization, and efficacy are redefining cancer treatment. Herein, we define and summarize the principal advancements in targeted cancer treatment and briefly comment on the march towards personalized medicine in the treatment of human cancer.

Incorporation of deuterium from deuterium oxide (2H2O) into biological components is a commonly used approach in metabolic studies. Determining the dilution of deuterium in the body water pool (BW) can be used to estimate body composition. We describe three sensitive GC-MS/MS methods to measure water enrichment in BW . Samples were reacted with NaOH and U-13C3-acetone in an autosampler vial to promote deuterium exchange with U-13C3-acetone hydrogens. Headspace injections were made of U-13C3-acetone-saturated air onto a 30m DB-1MS column in EI-mode. Subjects ingested 30ml 2H2O and plasma samples were collected. BW was determined by standard equation. DXA scans were performed to calculate body mass, body volume and bone mineral content. A 4 compartmental model was used to estimate body composition (fat and fat free mass). Full scan experiments generated a m/z 45 peak and to a lesser extent a m/z 61 peak. Product fragment ions further monitored included 45 and 46 using selected ion monitoring (SIM;Method1), the 61>45 and 62>46 transition using multiple reaction monitoring (MRM;Method2) and the Neutral Loss, 62>45, transition (Method3). MRM methods were optimized for collision energy (CE) and collision-induced dissociation (CID) argon gas pressure with 6eV CE and 1.5 mTorr CID gas being optimal. Method2 was used for finally determination of 2H2O enrichment of subjects due to lower natural background. We have developed a sensitive method to determine 2H2O enrichment in body water to enable measurement of FM and FFM.

Background Type 2 diabetes (T2D) is associated with generalized vascular dysfunction characterized by increases in large artery stiffness, endothelial dysfunction, and vascular smooth muscle dysfunction. Sodium glucose cotransporter 2 inhibitors (SGLT2i) represent the most recently approved class of oral medications for the treatment of T2D, and have been shown to reduce cardiovascular and overall mortality. Although it is currently unclear how SGLT2i decrease cardiovascular risk, an improvement in vascular function is one potential mechanism. The aim of the current study was to examine if dapagliflozin, a widely prescribed STLT2i, improves generalized vascular dysfunction in type 2 diabetic mice. In light of several studies demonstrating a bi-directional relation between orally ingested medications and the gut microbiota, a secondary aim was to determine the effects of dapagliflozin on the gut microbiota. Methods Male diabetic mice (Db, n = 24) and control littermates (Con; n = 23) were randomized to receive either a standard diet or a standard diet containing dapagliflozin (60 mg dapagliflozin/kg diet; 0.006%) for 8 weeks. Arterial stiffness was assessed by aortic pulse wave velocity; endothelial function and vascular smooth muscle dysfunction were assessed by dilatory responses to acetylcholine and sodium nitroprusside, respectively. Results Compared to untreated diabetic mice, diabetic mice treated with dapagliflozin displayed significantly lower arterial stiffness (Db = 469 cm/s vs. Db + dapa = 435 cm/s, p

Cardiovascular disease is the leading cause of death in the United States with type 2 diabetes (T2D) representing a major risk factor in its development. Vascular dysfunction, characterized by arterial stiffness and endothelial dysfunction occur prior to overt cardiovascular disease and predict future cardiovascular events and mortality in diabetic individuals. Dysfunction of the endoplasmic reticulum (ER), or ER stress, is associated with the development and progression of chronic metabolic diseases such as obesity and T2D. However, the role of ER stress in the development of vascular dysfunction observed in T2D is unclear. We hypothesized that inhibiting ER stress would improve both measures of vascular dysfunction observed in diabetic mice. Male C57BL/6J Leprdb (DB) male mice lacking the leptin receptor were used as a model of T2D. Starting at 4 months of age DB mice were given intraperitoneal injections of ER stress inhibitor, tauroursodeoxycholic acid (TUDCA) at 250mg/kg/day for 4 weeks. C57BL/6J mice were used as controls (n=8 for all groups). Pulse wave velocity (PWV) was measured at baseline (prior to treatment) and after TUDCA treatment. Secondary order mesenteric resistance arteries (MRA) were used to determine endothelial dependent dilation (EDD). DB mice not treated with TUDCA were used for acute studies of EDD by incubating the MRA for 1hr with 0.5mM TUDCA. At baseline, DB mice displayed increased arterial stiffness compared to C57BL/6J controls as measured by PWV (457±25 vs 348±26 cm/s, p These data support the hypothesis that ER stress contributes to the vascular dysfunction observed in T2D and suggest that ER stress may be a potential target in the treatment of T2D related vascular stiffening and dysfunction.

Background: Postexercise protein or amino acid ingestion restores muscle protein synthesis in older adults and represents an important therapeutic strategy for aging muscle. However, the precise nutritional factors involved are unknown. Objective: The purpose of this study was to determine the role of increased postexercise Leu ingestion on skeletal muscle myofibrillar protein synthesis (MyoPS), mammalian/mechanistic target of rapamycin complex 1 signaling, and amino acid transporter (AAT) mRNA expression in older men over a 24-h post–resistance exercise (RE) time course. Methods: During a stable isotope infusion trial (l-[ring-13C6]Phe; l-[1-13C]Leu), older men performed RE and, at 1 h after exercise, ingested 10 g of essential amino acids (EAAs) containing either a Leu content similar to quality protein (control, 1.85 g of Leu, n = 7) or enriched Leu (LEU; 3.5 g of Leu, n = 8). Muscle biopsies (vastus lateralis) were obtained at rest and 2, 5, and 24 h after exercise. Results: p70 S6 kinase 1 phosphorylation was increased in each group at 2 h (P < 0.05), whereas 4E binding protein 1 phosphorylation increased only in the LEU group (P < 0.05). MyoPS was similarly increased (∼90%) above basal in each group at 5 h (P < 0.05) and remained elevated (∼90%) at 24 h only in the LEU group (P < 0.05). The mRNA expression of select AATs was increased at 2 and 5 h in each group (P < 0.05), but AAT expression was increased at 24 h only in the LEU group (P < 0.05). Conclusions: Leu-enriched EAA ingestion after RE may prolong the anabolic response and sensitivity of skeletal muscle to amino acids in older adults. These data emphasize the potential importance of adequate postexercise Leu ingestion to enhance the response of aging muscle to preventive or therapeutic exercise-based rehabilitation programs. This trial was registered at clinicaltrials.gov as {"type":"clinical-trial","attrs":{"text":"NCT00891696","term_id":"NCT00891696"}}NCT00891696.

High-quality proteins such as soy, whey, and casein are all capable of promoting muscle protein synthesis postexercise by activating the mammalian target of rapamycin (mTORC1) signaling pathway. We hypothesized that a protein blend of soy and dairy proteins would capitalize on the unique properties of each individual protein and allow for optimal delivery of amino acids to prolong the fractional synthetic rate (FSR) following resistance exercise (RE). In this double-blind, randomized, clinical trial, 19 young adults were studied before and after ingestion of ∼19 g of protein blend (PB) or ∼18 g whey protein (WP) consumed 1 h after high-intensity leg RE. We examined mixed-muscle protein FSR by stable isotopic methods and mTORC1 signaling with western blotting. Muscle biopsies from the vastus lateralis were collected at rest (before RE) and at 3 postexercise time points during an early (0–2 h) and late (2–4 h) postingestion period. WP ingestion resulted in higher and earlier amplitude of blood branched-chain amino acid (BCAA) concentrations. PB ingestion created a lower initial rise in blood BCAA but sustained elevated levels of blood amino acids later into recovery (P < 0.05). Postexercise FSR increased equivalently in both groups during the early period (WP, 0.078 ± 0.009%; PB, 0.088 ± 0.007%); however, FSR remained elevated only in the PB group during the late period (WP, 0.074 ± 0.010%; PB, 0.087 ± 0.003%) (P < 0.05). mTORC1 signaling similarly increased between groups, except for no increase in S6K1 phosphorylation in the WP group at 5 h postexercise (P < 0.05). We conclude that a soy-dairy PB ingested following exercise is capable of prolonging blood aminoacidemia, mTORC1 signaling, and protein synthesis in human skeletal muscle and is an effective postexercise nutritional supplement.

Administration of the mTORC1 inhibitor, rapamycin, to humans blocks the increase in skeletal muscle protein synthesis in response to resistance exercise or amino acid ingestion. Objective To determine whether rapamycin administration influences basal post-absorptive protein synthesis or breakdown in human skeletal muscle. Materials/Methods Six young (26 ± 2 years) subjects were studied during two separate trials, in which each trial was divided into two consecutive 2 h basal periods. The trials were identical except during one trial a single oral dose (16 mg) of rapamycin was administered immediately prior to the second basal period. Muscle biopsies were obtained from the vastus lateralis at 0, 2, and 4 h to examine protein synthesis, mTORC1 signaling, and markers of autophagy (LC3B-I and LC3B-II protein) associated with each 2 h basal period. Results During the Control trial, muscle protein synthesis, whole body protein breakdown (phenylalanine Ra), mTORC1 signaling, and markers of autophagy were similar between both basal periods (p > 0.05). During the Rapamycin trial, these variables were similar to the Control trial (p > 0.05) and were unaltered by rapamycin administration (p > 0.05). Thus, post-absorptive muscle protein metabolism and mTORC1 signaling were not affected by rapamycin administration. Conclusions Short-term rapamycin administration may only impair protein synthesis in human skeletal muscle when combined with a stimulus such as resistance exercise or increased amino acid availability.

Essential amino acid (EAA) ingestion enhances postexercise muscle protein synthesis, and, in particular, the anabolic response of older adults appears sensitive to the quantity of ingested leucine. The effect of leucine ingestion on muscle breakdown following resistance exercise (RE) is less understood. The purpose of this study was to identify the impact of postexercise leucine ingestion on the ubiquitin proteasome and autophagosomal-lysosomal systems following acute RE in older men. Subjects (72 ± 2 yr) performed RE and 1 h postexercise ingested 10 g of EAA containing a leucine quantity similar to quality protein (control, 1.8 g leucine, n = 7) or enriched in leucine (leucine, 3.5 g leucine, n = 8). Stable isotope infusion and muscle biopsies (vastus lateralis) obtained at rest and 2, 5, and 24 h postexercise were used to examine protein content (Western blot), mRNA expression (RT-quantitative PCR), and muscle protein fractional breakdown rate (FBR). Muscle-specific RING finger 1 mRNA increased in both groups at 2 and 5 h ( P < 0.05). LC3 mRNA increased, and the LC3BII-to-LC3BI ratio decreased at all postexercise time points in control ( P < 0.05). Conversely, LC3 mRNA only increased at 2 h, and the LC3BII-to-LC3BI ratio only decreased at 2 and 5 h in leucine ( P < 0.05). Tumor necrosis factor receptor-associated factor-6 mRNA increased ( P < 0.05) in control at 5 h. FBR was not statistically different between groups or from basal 24 h postexercise ( P > 0.05). These data indicate that ingesting a larger quantity of leucine following RE may further reduce postexercise skeletal muscle autophagy in older men; however, it does not appear to influence the acute postexercise elevation in markers of the ubiquitin proteasome system or the breakdown of intact proteins. NEW & NOTEWORTHY The impact of postexercise leucine ingestion on processes of skeletal muscle breakdown in older adults is not well understood. Additional postexercise leucine ingestion appears to further reduce autophagy, but it does not interfere with the increase in ubiquitin proteasome system markers or the breakdown of intact proteins in skeletal muscle of older men. Postexercise leucine ingestion may promote a healthier protein pool and favorable muscle adaptations in older adults through greater accretion of myofibrillar proteins.

Introduction: Resistance exercise (RE) stimulates a muscle protein anabolic response partially through enhanced satellite cell (SC) activity, however, age- and gender-related changes in SC content over a 24-h time course are not known. Methods: Ten young (27 ± 2 years) men and women and 11 older (70 ± 2 years) men and women performed an acute bout of RE. Myofiber and SC characteristics were determined from muscle biopsies of the vastus lateralis using immunohistochemistry. Immunoblotting was used to determine phosphorylation of cyclin-dependent kinase-2 and protein expression of p27Kip1 and cyclin D1. Results: Pax7+ SC were significantly increased in young men 24 h following RE. Percent SC were significantly increased in older women at 6 and 24 h following RE. Aging decreased myonuclear domain and increased protein expression of p27Kip1. Conclusions: An acute bout of RE increases SC content in young men at 24 h and older women at 6 and 24 h. Muscle Nerve 46: 51–59, 2012

Skeletal muscle atrophy during bed rest is attributed, at least in part, to slower basal muscle protein synthesis (MPS). Essential amino acids (EAA) stimulate mammalian target of rapamycin (mTORC1) signaling, amino acid transporter expression, and MPS and are necessary for muscle mass maintenance, but there are no data on the effect of inactivity on this anabolic mechanism. We hypothesized that bed rest decreases muscle mass in older adults by blunting the EAA stimulation of MPS through reduced mTORC1 signaling and amino acid transporter expression in older adults. Six healthy older adults (67 ± 2 yr) participated in a 7-day bed rest study. We used stable isotope tracers, Western blotting, and real-time qPCR to determine the effect of bed rest on MPS, muscle mTORC1 signaling, and amino acid transporter expression and content in the postabsorptive state and after acute EAA ingestion. Bed rest decreased leg lean mass by ∼4% ( P < 0.05) and increased postabsorptive mTOR protein ( P < 0.05) levels while postabsorptive MPS was unchanged ( P > 0.05). Before bed rest acute EAA ingestion increased MPS, mTOR (Ser2448), S6 kinase 1 (Thr389, Thr421/Ser424), and ribosomal protein S6 (Ser240/244) phosphorylation, activating transcription factor 4, L-type amino acid transporter 1 and sodium-coupled amino acid transporter 2 protein content ( P < 0.05). However, bed rest blunted the EAA-induced increase in MPS, mTORC1 signaling, and amino acid transporter protein content. We conclude that bed rest in older adults significantly attenuated the EAA-induced increase in MPS with a mechanism involving reduced mTORC1 signaling and amino acid transporter protein content. Together, our data suggest that a blunted EAA stimulation of MPS may contribute to muscle loss with inactivity in older persons.

Satellite cells are a heterogeneous population of myogenic precursors responsible for muscle growth and repair in mammals. The objectives of the experiment were to examine the growth rates and degree of heterogeneity within bovine satellite cells (BSC) isolated from young and adult animals. The BSC were harvested from the semimembranosus of young (4.3 ± 0.5 d) and adult (estimated 24 to 27 mo) cattle and cultured en masse. Young animal BSC re-enter the cell cycle sooner and reach maximal 5-ethynyl-2'-deoxyuridine (EdU) incorporation earlier (P < 0.05) than adult contemporaries. Adult BSC contain fewer (P < 0.05) MyoD and myogenin immunopositive nuclei than BSC isolated from young animals after 3, 4, and 5 d in culture. These results indicate that BSC from young animals activate, proliferate, and differentiate sooner than isolates from adult animals. Lineage heterogeneity within BSC was examined using antibodies specific for Pax7 and Myf5, lineage markers of satellite cells, and myoblasts. Immunocytochemistry revealed the majority of Pax7-expressing BSC also express Myf5; a minor population (~5%) fails to exhibit Myf5 immunoreactivity. The percentage of Pax7:Myf5 BSC from young animals decreases sooner (P < 0.05) in culture than adult BSC, indicating a more rapid rate of muscle fiber formation. A subpopulation immunopositive for Myf5 only was identified in both ages of BSC isolates. The growth kinetics and heterogeneity of young BSC was further evaluated by clonal analysis. Single cell clones were established and analyzed after 10 d. Colonies segregated into 2 groups based upon population doubling time. Immunostaining of the slow-growing colonies (population doubling time ≥ 3 d) revealed that a portion exhibited asymmetric distribution of the lineage markers Pax7 and Myf5, similar to self-renewable mouse muscle stem cells. In summary, these results offer insight into the heterogeneity of BSC and provide evidence for subtle differences between rodent and bovine myogenic precursors.

The relationship between mammalian target of rapamycin complex 1 (mTORC1) signaling and muscle protein synthesis during instances of amino acid surplus in humans is based solely on correlational data. Therefore, the goal of this study was to use a mechanistic approach specifically designed to determine whether increased mTORC1 activation is requisite for the stimulation of muscle protein synthesis following L-essential amino acid (EAA) ingestion in humans. Examination of muscle protein synthesis and signaling were performed on vastus lateralis muscle biopsies obtained from 8 young (25 ± 2 y) individuals who were studied prior to and following ingestion of 10 g of EAA during 2 separate trials in a randomized, counterbalanced design. The trials were identical except during 1 trial, participants were administered a single oral dose of a potent mTORC1 inhibitor (rapamycin) prior to EAA ingestion. In response to EAA ingestion, an ~60% increase in muscle protein synthesis was observed during the control trial, concomitant with increased phosphorylation of mTOR (Ser(2448)), ribosomal S6 kinase 1 (Thr(389)), and eukaryotic initiation factor 4E binding protein 1 (Thr(37/46)). In contrast, prior administration of rapamycin completely blocked the increase in muscle protein synthesis and blocked or attenuated activation of mTORC1-signaling proteins. The inhibition of muscle protein synthesis and signaling was not due to differences in either extracellular or intracellular amino acid availability, because these variables were similar between trials. These data support a fundamental role for mTORC1 activation as a key regulator of human muscle protein synthesis in response to increased EAA availability. This information will be useful in the development of evidence-based nutritional therapies targeting mTORC1 to counteract muscle wasting associated with numerous clinical conditions.

We evaluated growth-related responses to ractopamine in steers and heifers. Sixteen Angus steers (512 kg) and 16 Angus heifers (473 kg) housed in individual pens were used in a complete block design. At 90 to 97 d before the experiment, steers were implanted with 120 mg of trenbolone acetate and 24 mg of estradiol-17beta (Component TE-S) and heifers were implanted with 140 mg of trenbolone acetate and 14 mg of estradiol-17beta (Component TE-H). Treatments were arranged as a 2 x 2 factorial and included sex (steer vs. heifer) and ractopamine-HCl (0 or 200 mg/d). Cattle were fed a diet based on steam-flaked corn once daily. Blood and LM and biceps femoris (BF) biopsy samples were collected on d 0 (before ractopamine feeding) and after 14 and 28 d of ractopamine feeding. Serum insulin concentrations were not affected by ractopamine or sex. Serum IGF-I concentrations were greater in steers than heifers (P0.001), and steers demonstrated greater IGF-I mRNA expression in BF than heifers (P = 0.05). Ractopamine decreased serum IGF-I concentrations in heifers on d 14, but increased serum IGF-I concentrations in steers on d 28 (sex x ractopamine x day interaction; P = 0.03). Ractopamine did not affect (Por= 0.19) mRNA expression of IGF-I, IGFBP-3, or calpastatin in BF or LM. However, ractopamine led to increases in LM expression of IGFBP-5 in heifers, but to decreases in expression in steers (ractopamine x sex interaction; P = 0.04). Ractopamine decreased myosin heavy chain IIA mRNA expression in BF (P = 0.04) but not in LM (P = 0.99). Ractopamine decreased beta(2)-receptor mRNA expression in LM of steers on d 14, but not on d 28; in contrast, expression of beta(2)-receptor mRNA in LM of heifers was not affected by ractopamine (sex x ractopamine x day interaction; P = 0.03). Although there were a few criteria for which ractopamine led to differences in response between steers and heifers, there were no striking disparities to suggest that the effectiveness of ractopamine would markedly differ between sexes.

Two experiments evaluated the effects of conventional and natural feedlot management systems (MS) on ractopamine-HCl (RAC) response in yearling steers. Feedlot performance, carcass characteristics, skeletal muscle gene expression, and circulating IGF-I concentrations were measured. The conventional system included a combined trenbolone acetate and estradiol implant, Revalor-S (IMP), as well as monensin-tylosin feed additives (IA). Treatments were arranged in a 2 x 2 factorial and included: 1) natural (NAT): no IMP-no IA, no RAC; 2) natural plus (NAT+): no IMP-no IA, RAC; 3) conventional (CON): IMP-IA, no RAC; and 4) conventional plus (CON+): IMP-IA, RAC. In Exp. 1, one hundred twenty crossbred steers (initial BW = 400 +/- 26 kg) were allotted randomly to treatment in a randomized complete block design (BW was blocking criteria); pen was the experimental unit. In Exp. 2, twenty-four individually fed crossbred steers (initial BW = 452 +/- 25 kg) were used in a randomized complete block design (BW was blocking criteria) and assigned to the same treatments as Exp. 1, with 6 steers/treatment. In Exp. 2, serum was harvested on d 0 and 31 and within the 28-d RAC feeding period, at d 0, 14, and 28. Longissimus biopsy samples were taken on d 0, 14, and 28 of the RAC feeding period for mRNA analysis of beta-adrenergic receptors and steady-state IGF-I mRNA. In Exp. 1, ADG, G:F, final BW, and HCW were greatest for CON+ (P 0.10). Circulating IGF-I concentration was increased on d 31 by the conventional MS, and concentration was greater throughout the study than NAT steers (P 0.40). Management system did not affect beta(1)-AR, beta(2)-AR, beta(3)-AR, or IGF-I mRNA (P > 0.18), yet a trend (P = 0.06) for MS x RAC for beta(2)-AR mRNA was detected. These results indicate that response to RAC is affected by feedlot management practices.

The aim of this study was to examine the effects of a Western diet (WD) and supplementation with Fuzhuan tea on large artery stiffness, as determined by aortic pulse wave velocity (aPWV).Mice were subjected to a standard diet (SD; n = 12) or WD (n = 10) for 7 mo, and were then separated to receive nonsupplemented drinking water (SD-W and WD-W) or water supplemented with Fuzhuan tea (SD-T and WD-T) (200 mg/kg daily); mice were then maintained on their respective diets for an additional 2 mo.After the initial 7-mo feeding period, WD elicited a modest and significantly greater increase in body weight than did SD (39.6 ± 0.71 versus 34.5 ± 1.16 g; P 0.01). PWV was significantly elevated in WD but not in SD (459.3 ± 4.8 versus 422.4 ± 6.4 cm/s; P 0.001). Following an additional 2 mo, PWV continued to increase in WD-W, but returned to control levels in WD-T (WD-W: 519.8 ± 12.8; WD-T: 426.5 ± 18.6; SD-W: 429.7 ± 8.6; SD-T: 429.1 ± 6.1 cm/s; P 0.001, WD-W versus all groups). The increase in PWV in WD-W was accompanied by an increase in aortic collagen (WD-W: 38.8 ± 4.6 versus SD-W: 17.5 ± 5.1 percent cross-sectional area; P 0.05).The results of the present study suggest that the increase in arterial stiffness after modest, diet-induced weight gain can be reversed by supplementation with Fuzhuan tea.

The purpose of this study was to examine whether ingesting a pre-workout dietary supplement (PWS) with and without synephrine (S) during training affects training responses in resistance-trained males. Resistance-trained males (N = 80) were randomly assigned to supplement their diet in a double-blind manner with either a flavored placebo (PLA); a PWS containing beta-alanine (3 g), creatine nitrate as a salt (2 g), arginine alpha-ketoglutarate (2 g), N-Acetyl-L-Tyrosine (300 mg), caffeine (284 mg), Mucuna pruiriens extract standardized for 15% L-Dopa (15 mg), Vitamin C as Ascorbic Acid (500 mg), niacin (60 mg), folate as folic acid (50 mg), and Vitamin B12 as Methylcobalamin (70 mg); or, the PWS supplement with Citrus aurantium extract containing 20 mg of synephrine (PWS + S) once per day for 8-weeks during training. Participants donated a fasting blood sample and had body composition (DXA), resting heart rate and blood pressure, cognitive function (Stroop Test), readiness to perform, bench and leg press 1 RM, and Wingate anaerobic capacity assessments determined a 0, 4, and 8-weeks of standardized training. Data were analyzed by MANOVA with repeated measures. Performance and cognitive function data were analyzed using baseline values as covariates as well as mean changes from baseline with 95% confidence intervals (CI). Blood chemistry data were also analyzed using Chi-square analysis. Although significant time effects were seen, no statistically significant overall MANOVA Wilks’ Lambda interactions were observed among groups for body composition, resting heart and blood pressure, readiness to perform questions, 1RM strength, anaerobic sprint capacity, or blood chemistry panels. MANOVA univariate analysis and analysis of changes from baseline with 95% CI revealed some evidence that cognitive function and 1RM strength were increased to a greater degree in the PWS and/or PWS + S groups after 4- and/or 8-weeks compared to PLA responses. However, there was no evidence that PWS + S promoted greater overall training adaptations compared to the PWS group. Dietary supplementation of PWS and PWS + S did not increase the incidence of reported side effects or significantly affect the number of blood values above clinical norms compared to PLA. Results provide some evidence that 4-weeks of PWS and/or PWS + S supplementation can improve some indices of cognitive function and exercise performance during resistance-training without significant side effects in apparently health males. However, these effects were similar to PLA responses after 8-weeks of supplementation and inclusion of synephrine did not promote additive benefits. This trial ( NCT02999581 ) was retrospectively registered on December 16th 2016.

Six Holstein steers (231 +/- 17 kg) housed in metabolism crates were used in a randomized complete block design with three blocks of two steers based on previous serum insulin-like growth factor (IGF)-I concentrations. One of the two steers in each block was implanted with 120 mg trenbolone acetate and 24 mg oestradiol-17beta on day 0. None of the steers was fed ractopamine-HCl in the initial 28 days, and then all steers were fed 200 mg of ractopamine-HCl per steer daily from day 28 until the end of the trial. Steers were fed a corn-based diet (62% rolled corn, 20% expeller soya bean meal and 15% alfalfa hay) twice daily with an average dry matter intake of 4.8 kg/day. Blood and M. longissimus biopsy samples were collected prior to implantation and on days 14, 28, 42 and 56. There was an implant x ractopamine interaction for retained nitrogen (p < 0.05); ractopamine feeding led to only small improvements in nitrogen retention for implanted steers (45.9 g/day vs. 44.5 g/day), whereas ractopamine led to larger increases in nitrogen retention for non-implanted steers (39.0 g/day vs. 30.4 g/day). Implantation increased (p < 0.05) and ractopamine tended to decrease (p = 0.06) serum IGF-I concentrations. Implantation tended to increase (p = 0.16) and ractopamine decreased (p < 0.05) mRNA expression of IGF-I in the M. longissimus. Ractopamine decreased mRNA expression of beta(1)- and beta(2)-receptors in M. longissimus (p

Pre-workout supplements can increase energy availability and/or exercise capacity. We examined the effects of ingesting a pre-workout supplement with and without synephrine for 8w in 78 healthy, resistance-trained men (22 ± 3 y). Subjects were randomly assigned to treatments of: (1) a dextrose flavored placebo (PLA); (2) a supplement containing 3.0 g beta alanine, 2 g creatine nitrate, 2 g arginine AKG, 300 mg of N-acetyl tyrosine, 270 mg caffeine, 15 mg of Mucuna pruriens (PWS) or (3) PWS + 20 mg of synephrine (PWS+S). Primary outcomes: Cognitive function (CF) via a Stroop test. Secondary outcome: Rate of readiness via a visual analogue scale (RTP-VAS). Measures were assessed at 0, 4 & 8 w. We used GLM statistical analyses covaried for age and respective baseline measures to determine mean (95% CI) change from baseline. We observed a significant increase in CF for the word test at 4 wks for PWS+S (5.64 count; 2.09, 9.19) and PLA (3.9 count; 0.39, 7.45), and 8 wks for PWS (7.55 count; 4.14, 10.97), PWS+S ...

Our aim was to examine the acute (5 h) hemodynamic (HR & BP) and hematologic profiles for a (1) Placebo (PL), (2) Creatine (CR, 5 g), (3) Creatine Nitrate (CrN; 1 g CR; 0.5 N) and (4) CrN2X (2 g CR; 1.0 g N) formula administered in a randomized, double-blind manner with 7d of washout between treatments. Participants (N=13; 22 ± 2 y) presented for testing after abstaining from exercise and fasting for 8 h. Initial unsupplemented measures (Time 0) were assessed, followed by supplement ingestion and serial sampling (0.5, 1, 2, 3, 4, 5h). Variables included heart rate, blood pressure, liver (ALP, AST, ALT), kidney (creatinine, BUN), and muscle (CK, LDH) enzymes, glucose and blood lipids. Analyses included GLM and LSD post-hoc procedures. Significant within group perturbations were noted for LDL-C (CR, PL), HDL-C (CrN, CrN2X), triglycerides (CrN2X, PL), glucose (CrN2X), creatinine (all), CK (CrN2X, PL), BUN (all), ALT (PL) over the 5h study period (all, P < 0.03). Corresponding between group differences (all, ...

Pre-workout supplements can increase energy availability and/or exercise capacity. We examined the effects of ingesting a pre-workout supplement with and without synephrine for 8w in 78 healthy, re...

We examined 28d of randomly assigned of (1) Placebo (PL), (2) Creatine (CR, 3 g), (3) Creatine Nitrate (CrN; 1 g CR; 0.5 N) and (4) CrN2X (2 g CR; 1.0 g N) on exercise performance and body composition. Participants (N=48; 21 ±3 y) presented for fasting (12h) testing after abstaining from exercise and alcohol for 48h. Performance (reps at 70% of bench press 1 RM [BP] and repeated sprints on cycle ergometer) was measured at 0 & 4 wks. Body composition (DXA) was measured at 0, 1, & 4 wks. We used GLM to examine mean change (95% CI) from baseline. While all three treatment groups significantly increased BP repetition at 4 wks, total BP lifting volume was greater at 4 wks for CrN2X (294.6 lbs; 95% CI, 196, 393) vs CrN (164.2 lbs; 95% CI, 25, 304) and PL (187.1 lbs;95% CI, 37, 336, both p=0.02). No treatment effects were observed for cycle ergometry testing (peak or mean power, fatigue slope, and total work). While no difference in fat mass were observed for any treatment group, CrN2X did augment lean mass (1.2...

An experiment was conducted to determine the relationship between feeding ractopamine and different amounts of MP on growth and carcass characteristics of feedlot heifers. Seventy-two crossbred heifers (475 kg of initial BW) were fed individually a diet based on steam-flaked corn for ad libitum intake for 29 d. Heifers were implanted with 140 mg of trenbolone acetate and 14 mg of estradiol- 17β 60 d before the experiment. Treatments were arranged as a 2 x 3 factorial and included 0 or 200 mg ofractopamine-HCl (23 ppm)/ d, and urea, solvent soybean meal, or expeller soybean meal (ESBM) as the predominant protein supplement. The amounts of MP supplied by the urea, solvent soybean meal, and ESBM diets were 688, 761, and 808 g/ d, respectively, calculated according to level 1 of the NRC model. Body weights were obtained 1 d before ractopamine feeding and at slaughter. Blood samples were obtained 1 d before starting the experiment and 13 d later. Ractopamine improved ADG, efficiency of gain, carcass-adjusted ADG, and carcass-adjusted efficiency of gain (P < 0.01). ForADG, heifers demonstrated a ractopamine x protein source interaction (P < 0.05); heifers not fed ractopamine had greater ADG when fed ESBM than when fed urea, whereas for heifers fed ractopamine there were no differences (P ≥ 0.10) among protein supplements. This interaction was not observed for carcass-adjusted ADG (P = 0.60). Final live weights (P = 0.02) and carcass weights (P = 0.01) were greater with ractopamine feeding. Carcass marbling scores and yield grades were not affected by ractopamine or protein source (P ≥ 0.39). Plasma total α-amino N and glucose concentrations decreased more from pretreatment concentrations when heifers were fed ractopamine (P < 0.05). Feeding ractopamine to heifers for 28 d before slaughter improved ADG and efficiency of gain without any large effects on carcass characteristics. The MP supply does not need to be increased from that provided by finishing diets based on steam-flaked corn with urea as the primary N supplement to allow the maximal response to ractopamine by finishing heifers.

An experiment was conducted to evaluate the interaction between steroidal implantation and feeding ractopamine on nitrogen retention, blood metabolites, and messenger RNA (mRNA) expression. Six Holstein steers (initially weighing 509 lb) were implanted or not with Revalor-S (120 mg trenbolone acetate plus 24 mg estradiol-17β), and all were fed no ractopamine for the initial 28 days and then 2 grams per steer daily of Optaflexx (200 mg/day ractopamine-HCl) on days 29 through 56. Implantation increased nitrogen retention. Optaflexx increased nitrogen retention in nonimplanted steers, but did not significantly increase retained nitrogen in implanted steers. Implantation increased serum insulin-like growth factor (IGF)-I concentration. Optaflexx, however, numerically decreased serum IGF-I concentrations. Implantation numerically increased IGF-I mRNA in the longissimus muscle, but expression of IGF-I mRNA was significantly decreased when Optaflexx was fed. Both growth promotants increased nitrogen retention in steers, but, despite perceived differences in their mode of action, the combination yielded a less than additive response for nitrogen retention.

An experiment was conducted to determine the relationship between metabolizable protein supply and feeding OptaflexxTM (ractopamine-HCl) on growth and carcass characteristics of feedlot heifers. Seventy-two crossbred heifers (initially weighing 1048 lb) were fed diets based on steam-flaked corn. Treatments were arranged as a 2 × 3 factorial and included: 0 or 2 grams per heifer daily of OptaflexxTM (0 or 200 mg/day ractopamine-HCl), and diets containing one of three different protein sources (urea, solvent soybean meal, and expeller soybean meal). OptaflexxTM was fed for the final 28 days before slaughter. OptaflexxTM improved daily gain, feed efficiency, carcass-adjusted daily gain, and carcass-adjusted feed efficiency. Responses in gain and efficiency based on final live weights were dependent on protein source; for heifers fed no OptaflexxTM, performance was best with expeller soybean meal, whereas performance was best with urea-based diets when OptaflexxTM was added to diets. Gains and efficiencies based on carcass weights were not affected by dietary protein source. Final live weights were 20 lb greater and carcass weights were 15 lb greater when heifers were fed OptaflexxTM. Carcass characteristics were impacted little by either OptaflexxTM or dietary protein source. It does not seem that dietary metabolizable protein supply needs to be increased from that of typical finishing diets to achieve maximum response to OptaflexxTM. Introduction

Restriction of blood flow to a contracting muscle during low-intensity resistance exercise (BFR exercise) stimulates mTORC1 signaling and protein synthesis in human muscle within 3 h postexercise. However, there is a lack of mechanistic data to provide a direct link between mTORC1 activation and protein synthesis in human skeletal muscle following BFR exercise. Therefore, the primary purpose of this study was to determine whether mTORC1 signaling is necessary for stimulating muscle protein synthesis after BFR exercise. A secondary aim was to describe the 24-h time course response in muscle protein synthesis and breakdown following BFR exercise. Sixteen healthy young men were randomized to one of two groups. Both the control (CON) and rapamycin (RAP) groups completed BFR exercise; however, RAP was administered 16 mg of the mTOR inhibitor rapamycin 1 h prior to BFR exercise. BFR exercise consisted of four sets of leg extension exercise at 20% of 1 RM. Muscle biopsies were collected from the vastus lateralis before exercise and at 3, 6, and 24 h after BFR exercise. Mixed-muscle protein fractional synthetic rate increased by 42% at 3 h postexercise and 69% at 24 h postexercise in CON, whereas this increase was inhibited in the RAP group. Phosphorylation of mTOR (Ser2448) and S6K1 (Thr389) was also increased in CON but inhibited in RAP. Mixed-muscle protein breakdown was not significantly different across time or groups. We conclude that activation of mTORC1 signaling and protein synthesis in human muscle following BFR exercise is inhibited in the presence of rapamycin.

Bed rest induces significant loss of leg lean mass in older adults. Systemic and tissue inflammation also accelerates skeletal muscle loss, but it is unknown whether inflammation is associated to inactivity-induced muscle atrophy in healthy older adults. We determined if short-term bed rest increases toll-like receptor 4 (TLR4) signaling and pro-inflammatory markers in older adult skeletal muscle biopsy samples. Six healthy, older adults underwent seven consecutive days of bed rest. Muscle biopsies (vastus lateralis) were taken after an overnight fast before and at the end of bed rest. Serum cytokine expression was measured before and during bed rest. TLR4 signaling and cytokine mRNAs associated with pro- and anti-inflammation and anabolism were measured in muscle biopsy samples using Western blot analysis and qPCR. Participants lost ∼4% leg lean mass with bed rest. We found that after bed rest, muscle levels of TLR4 protein expression and interleukin-6 (IL-6), nuclear factor-κB1, interleukin-10, and 15 mRNA expression were increased after bed rest ( P < 0.05). Additionally, the cytokines interferon-γ, and macrophage inflammatory protein-1β, were elevated in serum samples following bed rest ( P < 0.05). We conclude that short-term bed rest in older adults modestly increased some pro- and anti-inflammatory cytokines in muscle samples while systemic changes in pro-inflammatory cytokines were mostly absent. Upregulation of TLR4 protein content suggests that bed rest in older adults increases the capacity to mount an exaggerated, and perhaps unnecessary, inflammatory response in the presence of specific TLR4 ligands, e.g., during acute illness.