Time-course Of Transcriptomic Responses In Skeletal Muscle During Recovery From Endurance Exercise Indicates Prolonged Muscular Inflammation

Introduction Re-programming of gene expression is fundamental for skeletal muscle adaptations in response to endurance exercise. Although inflammatory responses in muscle following muscle-damaging exercise can persist for days, there is a paucity of global gene expression data beyond 48 hours following exercise. This study aimed to investigate the changes in the transcriptome of skeletal muscle until 96 hours after an endurance exercise trial (EXTRI; one hour of cycling followed by one hour of running). Data on the transcriptome of circulating neutrophils from participants in the current study indicated that the neutrophil transcriptional activity was related to the muscle-damaging component of the EXTRI (Neubauer et al. 2013, J Appl Physiol.). We hypothesised that the muscular transcriptome would particularly reflect interactions between muscle and infiltrating leukocytes. Methods Eight healthy, endurance-trained, male individuals participated. Skeletal muscle samples were taken one week before the EXTRI, 3, 48, and 96 hours post-EXTRI. RNA was extracted from muscle tissue. Differential gene expression was evaluated using Illumina microarrays, and validated with q-PCR. Gene set enrichment analysis identified functionally related gene sets chosen from the Molecular Signatures Database. Results Significantly (FWER p-value Conclusions The current data indicate that many of the coordinated gene expression responses in skeletal muscle, particularly at 96 hours post-EXTRI, were related with exercise-induced muscle damage, and the subsequent accumulation of muscle leukocytes. The substantial transcriptional activity 96 h post-EXTRI was strongly associated with inflammatory and immune responses, and suggests that muscular recovery, from a transcriptional perspective, is incomplete 96 hours after exercise

Adenosine and its receptors in the heart: Regulation, retaliation and adaptation

The purine nucleoside adenosine is an important regulator within the cardiovascular system, and throughout the body. Released in response to perturbations in energy state, among other stimuli, local adenosine interacts with 4 adenosine receptor sub-types on constituent cardiac and vascular cells: A 1 , A 2A , A 2B , and A 3 ARs. These G-protein coupled receptors mediate varied responses, from modulation of coronary flow, heart rate and contraction, to cardioprotection, inflammatory regulation, and control of cell growth and tissue remodeling. Research also unveils an increasingly complex interplay between members of the adenosine receptor family, and with other receptor groups. Given generally favorable effects of adenosine receptor activity (e.g. improving the balance between myocardial energy utilization and supply, limiting injury and adverse remodeling, suppressing inflammation), the adenosine receptor system is an attractive target for therapeutic manipulation. Cardiovascular adenosine receptor-based therapies are already in place, and trials of new treatments underway. Although the complex interplay between adenosine receptors and other receptors, and their wide distribution and functions, pose challenges to implementation of site/target specific cardiovascular therapy, the potential of adenosinergic pharmacotherapy can be more fully realized with greater understanding of the roles of adenosine receptors under physiological and pathological conditions. This review addresses some of the major known and proposed actions of adenosine and adenosine receptors in the heart and vessels, focusing on the ability of the adenosine receptor system to regulate cell function, retaliate against injurious stressors, and mediate longer-term adaptive responses. © 2010 Elsevier B.V

Coupling of myocardial stress resistance and signalling to voluntary activity and inactivity

© 2016 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd Aims: We examined coupling of myocardial ischaemic tolerance to physical activity and inactivity, and whether this involves modulation of survival (AKT, AMPK, ERK1/2, HSP27, EGFR) and injury (GSK3ß) proteins implicated in ischaemic preconditioning and calorie restriction. Methods: Proteomic modifications were assessed in ventricular myocardium, and tolerance to 25-min ischaemia in ex vivo perfused hearts from C57Bl/6 mice subjected to 14-day voluntary activity in running-naïve animals (Active); 7 days of subsequent inactivity (Inactive); brief (day 3) restoration of running (Re-Active); or time-matched inactivity. Results: Active mice increased running speed and distance by 75–150% over 14 days (to ~40 m min -1 and 10 km day -1 ), with Active hearts resistant to post-ischaemic dysfunction (40–50% improvements in ventricular pressure development, diastolic pressure and dP/dt). Cardioprotection was accompanied by ~twofold elevations in AKT, AMPK, HSP27 and GSK3ß phosphorylation and EGFR expression. Ischaemic tolerance was reversed in Inactive hearts, paralleling reduced EGFR expression and GSK3ß and ERK1/2 phosphorylation (AKT, AMPK, HSP27 phosphorylation unaltered). Running characteristics, ischaemic tolerance, EGFR expression and GSK3ß phosphorylation returned to Active levels within 1–3 days of restored activity (without changes in AKT, AMPK or HSP27 phosphorylation). Transcriptional responses included activity-dependent Anp induction vs. Hmox1 and Sirt3 suppression, and inactivity-dependent Adora2b induction. Conclusions: Data confirm the sensitive coupling of ischaemic tolerance to activity: voluntary running induces cardioprotection that dissipates within 1 week of inactivity yet recovers rapidly upon subsequent activity. While exercise in naïve animals induces a molecular profile characteristic of preconditioning/calorie restriction, only GSK3ß and EGFR modulation consistently parallel activity- and inactivity-dependent ischaemic tolerance

The impact of an experimentally induced increase in arterial blood pressure on left ventricular twist mechanics

© 2015 The Authors. Experimental Physiology © 2015 The Physiological Society New Findings: What is the central question of this study? Increases in blood pressure elicited by isometric hand-grip exercise (IHG) have been shown to impair ventricular twist mechanics. However, the utility of the IHG model is confounded by a concurrent increase in heart rate, which independently influences ventricular mechanics. What is the main finding and its importance? We show that a period of post-IHG circulatory occlusion isolates the effect of an arterial blood pressure increase from heart rate and magnifies the impairment of left ventricular twist when compared with IHG alone. A protocol using IHG followed by brief circulatory occlusion may serve as a useful tool in examining and understanding the relationships between afterload and cardiac function in various disease states. The effects of isometric hand-grip exercise (IHG) coupled with a period of postexercise circulatory occlusion (OCC; known to sustain exercise-induced increases in blood pressure while facilitating a decrease in heart rate) on left ventricular (LV) twist mechanics was examined. Two-dimensional speckle-tracking echocardiography was used to assess LV apical and basal rotation and LV twist in 19 healthy participants (23 ± 2 years old) at rest, during 3 min of IHG (performed at 40% maximal voluntary contraction) and 3 min of OCC immediately following IHG. The IHG elicited significant (P  <  0.001) increases in mean arterial pressure (rest, 91 ± 1 mmHg; IHG, 122 ± 2 mmHg) and heart rate (rest, 65 ± 2 beats min -1 ; IHG, 91 ± 4 beats min -1 ). Mean arterial pressure remained elevated during OCC (116 ± 2 mmHg; P  <  0.001 versus rest), whereas heart rate returned to resting levels (68 ± 3 beats min -1 ; P = 0.159 versus rest). Apical rotation decreased significantly (P  <  0.01) by 10 ± 5% during IHG and 21 ± 4% during OCC, whereas basal rotation remained unchanged from rest. Left ventricular twist decreased from rest to IHG (12 ± 5%; P = 0.015) and OCC (21 ± 4%; P = 0.001), whereas a decrease in LV untwist rate was observed only during OCC. An increase in blood pressure generated by IHG, and maintained by a period of OCC, impairs aspects of LV twist mechanics. Postexercise circulatory occlusion isolated the effect of the arterial blood pressure rise (from heart rate), magnifying the impairment of LV twist mechanics when compared with IHG, whilst also negatively impacting LV relaxation. We propose that a protocol using isometric exercise followed by circulatory occlusion provides a method for studying the effects of blood pressure changes on LV twist mechanics

Impact of high-intensity endurance exercise on regional left and right ventricular myocardial mechanics

© The Author 2017. Aims Strenuous endurance exercise acutely increases myocardial wall stress and evokes transient functional cardiac perturbations. However, it is unclear whether exercise-induced functional cardiac disturbances are ubiquitous throughout the myocardium or are segment specific. The aim of this study was to examine the influence of high-intensity endurance exercise on global and segmental left (LV) and right (RV) ventricular tissue deformation (strain). Methods and results Echocardiography was used to measure strain in 23 active men (age: 28±2 years; VO 2 peak : 4.5±0.7 L min -1 ) at rest and during a standardized low-intensity exercise challenge, before and after a 90-min high-intensity endurance cycling intervention. Following the cycling intervention, LV and RV global strain decreased at rest (LV: -18.4±0.4% vs.-17.7±0.4%, P < 0.05; RV:-27.6±0.7% vs.-26.4±0.6%, P < 0.05) and by a greater extent during the lowintensity exercise challenge (LV: -21.3±0.4% vs. -19.2±0.5%, P < 0.01; RV: -28.4±0.8% vs.-23.5±0.9%, P < 0.01). Reductions in LV strain were unique to regions of RV attachment (e.g. LV septum: -24.4±0.5% vs.-21.4±0.6%, P < 0.01) with lateral (218.9±0.4% vs. 218.4±0.5%) and posterior segments (-19.5±0.4% vs.-18.8±0.7%) unaffected. Similarly, augmentation of strain from rest to exercise was abolished in the RV free wall (-1.1±1.0% vs. 2.9±1.2%, P < 0.01), reduced in the septum (-4.6±0.4% vs. -2.4±0.5%, P < 0.01), and unchanged in the lateral (-1.2±0.6% vs. -0.9±0.6%) and posterior walls (-1.7±0.6% vs. -1.3±0.7%). Conclusion Changes in ventricular strain following high-intensity exercise are more profound in the right ventricle than in the left ventricle. Reductions in LV strain were unique to the septal myocardium and may reflect ventricular interactions secondary to exercise-induced RV dysfunction

Voluntary running in mice beneficially modulates myocardial ischemic tolerance, signaling kinases, and gene expression patterns

Exercise triggers hormesis, conditioning hearts against damaging consequences of subsequent ischemia-reperfusion (I/R). We test whether "low-stress" voluntary activity modifies I/R tolerance and molecular determinants of cardiac survival. Male C57BL/6 mice were provided 7-day access to locked (7SED) or rotating (7EX) running-wheels before analysis of cardiac prosurvival (Akt, ERK 1/2) and prodeath (GSK3ß) kinases, transcriptomic adaptations, and functional tolerance of isolated hearts to 25-min ischemia/45-min reperfusion. Over 7 days, 7EX mice increased running from 2.1 ± 0.2 to 5.3 ± 0.3 km/day (mean speed 38 ± 2 m/min), with activity improving myocardial I/R tolerance: 7SED hearts recovered 43 ± 3% of ventricular force with diastolic contracture of 33 ± 3 mmHg, whereas 7EX hearts recovered 63 ± 5% of force with diastolic dysfunction reduced to 23 ± 2 mmHg (P < 0.05). Cytosolic expression (total protein) of Akt and GSK3ß was unaltered, while ERK 1/2 increased 30% in 7EX vs. 7SED hearts. Phosphorylation of Akt and ERK 1/2 was unaltered, whereas GSK3ß phosphorylation increased ~90%. Microarray interrogation identified significant changes (=1.3-fold expression change, =5% FDR) in 142 known genes, the majority (92%) repressed. Significantly modified paths/networks related to inflammatory/immune function (particularly interferon-dependent), together with cell movement, growth, and death. Of only 14 induced transcripts, 3 encoded interrelated sarcomeric proteins titin, a-actinin, and myomesin-2, while transcripts for protective actin-stabilizing ND1-L and activator of mitochondrial biogenesis ALAS1 were also induced. There was no transcriptional evidence of oxidative heat-shock or other canonical "stress" responses. These data demonstrate that relatively brief voluntary activity substantially improves cardiac ischemic tolerance, an effect independent of shifts in Akt, but associated with increased total ERK 1/2 and phospho-inhibition of GSK3ß. Transcriptomic data implicate inflammatory/immune and sarcomeric modulation in activity-dependent protection. © 2012 the American Physiological Society

Evidence that a higher ATP cost of muscular contraction contributes to the lower mechanical efficiency associated with COPD: preliminary findings

Impaired metabolism in peripheral skeletal muscles potentially contributes to exercise intolerance in chronic obstructive pulmonary disease (COPD). We used 31P-magnetic resonance spectroscopy (31P-MRS) to examine the energy cost and skeletal muscle energetics in six patients with COPD during dynamic plantar flexion exercise compared with six well-matched healthy control subjects. Patients with COPD displayed a higher energy cost of muscle contraction compared with the controls (control: 6.1 ± 3.1% of rest·min−1·W−1, COPD: 13.6 ± 8.3% of rest·min−1·W−1, P = 0.01). Although, the initial phosphocreatine resynthesis rate was also significantly attenuated in patients with COPD compared with controls (control: 74 ± 17% of rest/min, COPD: 52 ± 13% of rest/min, P = 0.04), when scaled to power output, oxidative ATP synthesis was similar between groups (6.5 ± 2.3% of rest·min−1·W−1 in control and 7.8 ± 3.9% of rest·min−1·W−1 in COPD, P = 0.52). Therefore, our results reveal, for the first time that in a small subset of patients with COPD a higher ATP cost of muscle contraction may substantially contribute to the lower mechanical efficiency previously reported in this population. In addition, it appears that some patients with COPD have preserved mitochondrial function and normal energy supply in lower limb skeletal muscle

Influence of exercise intensity and duration on functional and biochemical perturbations in the human heart

© 2016 The Physiological Society. Strenuous endurance exercise induces transient cardiac perturbations with ambiguous health outcomes. The present study investigated the magnitude and time-course of exercise-induced functional and biochemical cardiac perturbations by manipulating the exercise intensity-duration matrix. Echocardiograph-derived left (LV) and right (RV) ventr icular global longitudinal strain (GLS), and serum high-sensitivity cardiac troponin (hs-cTnI) concentration, were examined in 10 males (age: 27 ± 4 years; V?O2, peak : 4.0 ± 0.8 l min -1 ) before, throughout (50%, 75% and 100%), and during recovery (1, 3, 6 and 24 h) from two exercise trials. The two exercise trials consisted of 90 and 120 min of heavy- and moderate-intensity cycling, respectively, with total mechanical work matched. LVGLS decreased (P < 0.01) during the 90 min trial only, with reductions peaking at 1 h post (pre: -19.9 ± 0.6%; 1 h post: -18.5 ± 0.7%) and persisting for > 24 h into recovery. RVGLS decreased (P < 0.05) during both exercise trials with reductions in the 90 min trial peaking at 1 h post (pre: -27.5 ± 0.7%; 1 h post: -25.1 ± 0.8%) and persisting for > 24 h into recovery. Serum hs-cTnI increased (P < 0.01) during both exercise trials, with concentrations peaking at 3 h post but only exceeding cardio-healthy reference limits (14 ng l -1 ) in the 90 min trial (pre: 4.2 ± 2.4 ng l -1 ; 3 h post: 25.1 ± 7.9 ng l -1 ). Exercise-induced reductions in ventricular strain and increases in cardiac injury markers persist for 24 h following exercise that is typical of day-to-day endurance exercise training; however, the magnitude and time-course of this response can be altered by manipulating the intensity-duration matrix. Key points: Strenuous endurance exercise induces transient functional and biochemical cardiac perturbations that persist for 24-48 h. The magnitude and time-course of exercise-induced reductions in ventricular function and increases in cardiac injury markers are influenced by the intensity and duration of exercise. In a human experimental model, exercise-induced reductions in ventricular strain and increases in cardiac troponin are greater, and persist for longer, when exercise is performed within the heavy- compared to moderate-intensity exercise domain, despite matching for total mechanical work. The results of the present study help us better understand the dose-response relationship between endurance exercise and acute cardiac stress/injury, a finding that has implications for the prescription of day-to-day endurance exercise regimes

Gene networks in skeletal muscle following endurance exercise are coexpressed in blood neutrophils and linked with blood inflammation markers

Copyright © 2017 the American Physiological Society. It remains incompletely understood whether there is an association between the transcriptome profiles of skeletal muscle and blood leukocytes in response to exercise or other physiological stressors. We have previously analyzed the changes in the muscle and blood neutrophil transcriptome in eight trained men before and 3, 48, and 96 h after 2 h cycling and running. Because we collected muscle and blood in the same individuals and under the same conditions, we were able to directly compare gene expression between the muscle and blood neutrophils. Applying weighted gene coexpression network analysis (WGCNA) as an advanced network-driven method to these original data sets enabled us to compare the muscle and neutrophil transcriptomes in a rigorous and systematic manner. Two gene networks were identified th at were preserved between skeletal muscle and blood neutrophils, functionally related to mitochondria and posttranslational processes. Strong preservation measures (Z summary > 10) for both muscle-neutrophil gene networks were evident within the postexercise recovery period. Muscle and neutrophil gene coexpression was strongly correlated in the mitochondria-related network (r = 0.97; P = 3.17E-2). We also identified multiple correlations between muscular gene subnetworks and exercise-induced changes in blood leukocyte counts, inflammation, and muscle damage markers. These data reveal previously unidentified gene coexpression between skeletal muscle and blood neutrophils following exercise, showing the value of WGCNA to understand exercise physiology. Furthermore, these findings provide preliminary evidence in support of the notion that blood neutrophil gene networks may potentially help us to track physiological and pathophysiological changes in the muscle