Non-steroidal anti-inflammatory drugs (NSAIDs) are widely overused in sports. The temporal effects of combined NSAID consumption and resistance exercise training (RET) on muscle cross-sectional area (CSA), volume and targeted mRNA transcripts (n = 93) were quantified. Seventeen trained males (24.5 ± 1.1 years, body mass index (BMI) 24.2 ± 0.7 kg/m2) consumed either placebo (PLA; n = 8) or diclofenac (75 mg, NSAID; n = 9) daily for 12 weeks and performed 3×30 maximal, isokinetic knee extensions in the non-dominant leg (90°/s) thrice each week. Quadriceps muscle CSA and volume were measured at baseline, 28 days and 84 days (3T MRI). Vastus lateralis biopsies were obtained at baseline, 24 h, 7 days, 28 days and 84 days for mRNA abundance measurements (RT-PCR microfluidic cards). Work output throughout RET was no different between groups. Muscle CSA was increased from baseline in both groups at 28 days (PLA 4.3 ± 2.5%, P = 0.039; NSAID 4.6 ± 3.7%, P = 0.011), but only in the NSAID group at 84 days (PLA 3.9 ± 0.8%, NSAID 8.6 ± 5.3%; P < 0.001; NSAID vs. PLA, P = 0.038), and was paralleled by muscle volume changes. RET increased isometric strength (∼40%-50%), but gains were no different between groups. Based on mRNA expression changes several cellular functions associated with muscle mass and metabolic regulation were altered in both groups throughout RET and were greater in NSAID at 28 and 84 days. NSAID intervention produced greater muscle hypertrophy than PLA, which occurred between 28 and 84 days of RET and was paralleled by more pronounced muscle mRNA changes. These collective events were not accompanied by greater strength gains, suggesting that using NSAIDs alongside RET may not be optimal for enhancing sports performance. KEY POINTS: Non-steroidal anti-inflammatory drug (NSAID) ingestion over 84 days of resistance exercise training increased muscle cross-sectional area and volume gains compared to placebo ingestion in young, trained male volunteers, and this occurred predominantly from day 28 to day 84 of training. In parallel with this, alterations in gene networks associated with a number of cellular functions linked to regulation of muscle mass and muscle metabolism were detected in the NSAID group relative to placebo. This greater resistance training-induced hypertrophy associated with NSAID ingestion was not accompanied by greater gains in isometric knee extensor strength or isokinetic work output during training compared to resistance training alone.

Abstract Background Bed‐rest (BR) of only a few days duration reduces muscle protein synthesis and induces skeletal muscle atrophy and insulin resistance, but the scale and juxtaposition of these events have not been investigated concurrently in the same individuals. Moreover, the impact of short‐term exercise‐supplemented remobilization (ESR) on muscle volume, protein turnover and leg glucose uptake (LGU) in humans is unknown. Methods Ten healthy males (24 ± 1 years, body mass index 22.7 ± 0.6 kg/m2) underwent 3 days of BR, followed immediately by 3 days of ESR consisting of 5 × 30 maximal voluntary single‐leg isokinetic knee extensions at 90°/s each day. An isoenergetic diet was maintained throughout the study (30% fat, 15% protein and 55% carbohydrate). Resting LGU was calculated from arterialized‐venous versus venous difference across the leg and leg blood flow during the steady‐state of a 3‐h hyperinsulinaemic–euglycaemic clamp (60 mU/m2/min) measured before BR, after BR and after remobilization. Glycogen content was measured in vastus lateralis muscle biopsy samples obtained before and after each clamp. Leg muscle volume (LMV) was measured using magnetic resonance imaging before BR, after BR and after remobilization. Cumulative myofibrillar protein fractional synthetic rate (FSR) and whole‐body muscle protein breakdown (MPB) were measured over the course of BR and remobilization using deuterium oxide and 3‐methylhistidine stable isotope tracers that were administered orally. Results Compared with before BR, there was a 45% decline in insulin‐stimulated LGU (P < 0.05) after BR, which was paralleled by a reduction in insulin‐stimulated leg blood flow (P < 0.01) and removal of insulin‐stimulated muscle glycogen storage. These events were accompanied by a 43% reduction in myofibrillar protein FSR (P < 0.05) and a 2.5% decrease in LMV (P < 0.01) during BR, along with a 30% decline in whole‐body MPB after 2 days of BR (P < 0.05). Myofibrillar protein FSR and LMV were restored by 3 days of ESR (P < 0.01 and P < 0.01, respectively) but not by ambulation alone. However, insulin‐stimulated LGU and muscle glycogen storage were not restored by ESR. Conclusions Three days of BR caused concurrent reductions in LMV, myofibrillar protein FSR, myofibrillar protein breakdown and insulin‐stimulated LGU, leg blood flow and muscle glycogen storage in healthy, young volunteers. Resistance ESR restored LMV and myofibrillar protein FSR, but LGU and muscle glycogen storage remained depressed, highlighting divergences in muscle fuel and protein metabolism. Furthermore, ambulation alone did not restore LMV and myofibrillar protein FSR in the non‐exercised contralateral limb, emphasizing the importance of exercise rehabilitation following even short‐term BR.

Eight weeks AET reduced respiratory exchange ratio (RER) during steady-state submaximal exercise in healthy older (HO), healthy young (HY) and COPD volunteers, signifying a shift towards lipid oxidation and prompted mRNA expression changes in muscle of similar magnitude in all groups (Latimer et al, ERJ, 2022). We assessed whether muscle mRNA changes were paralleled by changes in protein abundance, and if responses differed between groups. We retrospectively analysed abundance of quadriceps protein products for 9 highly responsive mRNAs (Western blot) after 1,4 & 8 weeks of AET (30min cycling at 65%WPEAK, 3/wk) in HY (n=10, 28+5yr), HO (n=10, 71+5yr) and COPD (n=20, 70+6yr, FEV1 56%). Change in muscle mRNA and protein product abundance did not correlate in HY, HO or COPD (p>0.05 at all time points), nor did early changes in mRNA abundance predict subsequent protein abundance changes with large inter-subject variability apparent in protein responses to training (Fig 1). Robust and consistent muscle mRNA responses to AET in HO, HY & COPD were not reflected by muscle protein abundance changes. This may be attributable to variable protein translation efficiency between individuals and the semi-quantitative nature of Western blotting. Collectively the data suggest the decline in RER during steady-state exercise probably reflects changes in substrate availability and mobilisation with AET rather than muscle level protein adaptation.

AbstractBackgroundBed rest (BR) reduces whole‐body insulin‐stimulated glucose disposal (GD) and alters muscle fuel metabolism, but little is known about metabolic adaptation from acute to chronic BR nor the mechanisms involved, particularly when volunteers are maintained in energy balance.MethodsHealthy males (n = 10, 24.0 ± 1.3 years), maintained in energy balance, underwent 3‐day BR (acute BR). A second cohort matched for sex and body mass index (n = 20, 34.2 ± 1.8 years) underwent 56‐day BR (chronic BR). A hyperinsulinaemic euglycaemic clamp (60 mU/m2/min) was performed to determine rates of whole‐body insulin‐stimulated GD before and after BR (normalized to lean body mass). Indirect calorimetry was performed before and during steady state of each clamp to calculate rates of whole‐body fuel oxidation. Muscle biopsies were taken to determine muscle glycogen, metabolite and intramyocellular lipid (IMCL) contents, and the expression of 191 mRNA targets before and after BR. Two‐way repeated measures analysis of variance was used to detect differences in endpoint measures.ResultsAcute BR reduced insulin‐mediated GD (Pre 11.5 ± 0.7 vs. Post 9.3 ± 0.6 mg/kg/min, P < 0.001), which was unchanged in magnitude following chronic BR (Pre 10.2 ± 0.4 vs. Post 7.9 ± 0.3 mg/kg/min, P < 0.05). This reduction in GD was paralleled by the elimination of the 35% increase in insulin‐stimulated muscle glycogen storage following both acute and chronic BR. Acute BR had no impact on insulin‐stimulated carbohydrate (CHO; Pre 3.69 ± 0.39 vs. Post 4.34 ± 0.22 mg/kg/min) and lipid (Pre 1.13 ± 0.14 vs. Post 0.59 ± 0.11 mg/kg/min) oxidation, but chronic BR reduced CHO oxidation (Pre 3.34 ± 0.18 vs. Post 2.72 ± 0.13 mg/kg/min, P < 0.05) and blunted the magnitude of insulin‐mediated inhibition of lipid oxidation (Pre 0.60 ± 0.07 vs. Post 0.85 ± 0.06 mg/kg/min, P < 0.05). Neither acute nor chronic BR increased muscle IMCL content. Plentiful mRNA abundance changes were detected following acute BR, which waned following chronic BR and reflected changes in fuel oxidation and muscle glycogen storage at this time point.ConclusionsAcute BR suppressed insulin‐stimulated GD and storage, but the extent of this suppression increased no further in chronic BR. However, insulin‐mediated inhibition of fat oxidation after chronic BR was less than acute BR and was accompanied by blunted CHO oxidation. The juxtaposition of these responses shows that the regulation of GD and storage can be dissociated from substrate oxidation. Additionally, the shift in substrate oxidation after chronic BR was not explained by IMCL accumulation but reflected by muscle mRNA and pyruvate dehydrogenase kinase 4 protein abundance changes, pointing to lack of muscle contraction per se as the primary signal for muscle adaptation.

Abstract Introduction Inflammation induces changes in muscle protein turnover and mass and dampens insulin stimulated glucose disposal and oxidation. Limited information is available regarding the molecular regulation of these events. We determined the acute effects of lipopolysaccharide (LPS) infusion on targeted muscle mRNA expression. Methods Seven healthy, males (age 21.9±0.6 yrs, BMI 23.4±1.2 kg.m-2) participated in this ethically approved randomised crossover design study. On 2 occasions separated by >2 weeks, subjects underwent a 4h hyperinsulinaemic euglycaemic clamp combined with a primed mixed amino-acid (6 g.h-1; to create a ‘fed-state’) infusion, immediately following bolus saline (control) or LPS (4 ng.kg-1) infusion. Vastus lateralis muscle biopsies were obtained at baseline, 120 and 240 min. Muscle mRNA expression was measured (191 targets deemed to be representative of insulin sensitivity, carbohydrate and fat metabolism, inflammation, and protein turnover) using microfluidics TaqMan array cards. Results Plasma [TNF alpha] was markedly elevated above control following 60 min of LPS infusion (P<0.05) and remained elevated. Following gene filtering (>1.5 fold change in muscle mRNA expression from baseline, P<0.05), Ingenuity Pathway Analysis identified several metabolic functions significantly altered from baseline after 120 and 240 min in control. The magnitude of change in each metabolic function (-log p value) and the size of each gene network was substantially greater after LPS. Conclusion Muscle mRNAs respond rapidly to insulin and amino acid infusion in humans, but the magnitude of response was greater in the presence of LPS and may underpin changes in muscle protein and fuel metabolism seen under these conditions. Take-home message Endotoxaemia acts rapidly (within 2 to 4 hours) to alter the expression levels of muscle mRNAs known to be intimately involved in the molecular regulation of muscle mass, insulin resistance and fuel oxidation in human volunteers under controlled conditions of insulin and nutrient availability. This may play a role in the changes in muscle metabolism seen under such conditions.

Background Chronic obstructive pulmonary disease (COPD) patients exhibit lower peak oxygen uptake ( V ′ O 2 peak ), altered muscle metabolism and impaired exercise tolerance compared with age-matched controls. Whether these traits reflect muscle-level deconditioning (impacted by ventilatory constraints) and/or dysfunction in mitochondrial ATP production capacity is debated. By studying aerobic exercise training (AET) at a matched relative intensity and subsequent exercise withdrawal period we aimed to elucidate the whole-body and muscle mitochondrial responsiveness of healthy young (HY), healthy older (HO) and COPD volunteers to whole-body exercise. Methods HY (n=10), HO (n=10) and COPD (n=20) volunteers were studied before and after 8 weeks of AET (65% V ′ O 2 peak ) and after 4 weeks of exercise withdrawal. V ′ O 2 peak , muscle maximal mitochondrial ATP production rate (MAPR), mitochondrial content, mitochondrial DNA (mtDNA) copy number and abundance of 59 targeted fuel metabolism mRNAs were determined at all time-points. Results Muscle MAPR (normalised for mitochondrial content) was not different for any substrate combination in HO, HY and COPD at baseline, but mtDNA copy number relative to a nuclear-encoded housekeeping gene (mean± sd ) was greater in HY (804±67) than in HO (631±69; p=0.041). AET increased V ′ O 2 peak in HO (17%; p=0.002) and HY (21%; p<0.001), but not COPD (p=0.603). Muscle MAPR for palmitate increased with training in HO (57%; p=0.041) and HY (56%; p=0.003), and decreased with exercise withdrawal in HO (−45%; p=0.036) and HY (−30%; p=0.016), but was unchanged in COPD (p=0.594). mtDNA copy number increased with AET in HY (66%; p=0.001), but not HO (p=0.081) or COPD (p=0.132). The observed changes in muscle mRNA abundance were similar in all groups after AET and exercise withdrawal. Conclusions Intrinsic mitochondrial function was not impaired by ageing or COPD in the untrained state. Whole-body and muscle mitochondrial responses to AET were robust in HY, evident in HO, but deficient in COPD. All groups showed robust muscle mRNA responses. Higher relative exercise intensities during whole-body training may be needed to maximise whole-body and muscle mitochondrial adaptation in COPD.

BACKGROUND: Eccentric cycling (ECC) may be an attractive exercise method in COPD because of both low cardiorespiratory demand and perception of effort compared with conventional concentric cycling (CON) at matched mechanical loads. However, it is unknown whether ECC can be performed by individuals with COPD at an intensity able to cause sufficient metabolic stress to improve aerobic capacity. RESEARCH QUESTION: What are the cardiopulmonary and metabolic responses to ECC in people with COPD and healthy volunteers when compared with CON at matched mechanical loads? STUDY DESIGN AND METHODS: Thirteen people with COPD (mean +/- SD age, 64 +/- 9 years; FEV1, 45 +/- 19% predicted; BMI, 24 +/- 4 kg/m(2); oxygen uptake at peak exercise [(V)over dotO(2peak)], 15 +/- 3 mL/kg/min) and 9 age-matched control participants (FEV1, 102 +/- 13% predicted; BMI, 28+/- 5 kg/m(2); (V)over dotO(2peak), 23 +/- 5 mL/kg/min), performed up to six 4-min bouts of ECC and CON at matched mechanical loads of increasing intensity. In addition, 12 individuals with COPD underwent quadriceps muscle biopsies before and after 20 min of ECC and CON at 65% peak power. RESULTS: At matched mechanical loads, oxygen uptake, minute ventilation, heart rate, systolic BP, respiratory exchange ratio (all P <.001), capillary lactate, perceived breathlessness, and leg fatigue (P <.05) were lower in both groups during ECC than CON. Muscle lactate content increased (P = .008) and muscle phosphocreatine decreased (P = .012) during CON in COPD, which was not evident during ECC. INTERPRETATION: Cardiopulmonary and blood lactate responses during submaximal ECC were less compared with during CON at equivalent mechanical workloads in healthy participants and COPD patients, and this was confirmed at a muscle level in COPD patients. Submaximal ECC was well tolerated and allowed greater mechanical work at lower ventilatory cost. However, in people with COPD, a training intervention based on ECC is unlikely to stimulate cardiovascular and metabolic adaptation to the same extent as CON.

Muscle fatigue (MF) declines the capacity of muscles to complete a task over time at a constant load. MF is usually short-lasting, reversible, and is experienced as a feeling of tiredness or lack of energy. The leading causes of short-lasting fatigue are related to overtraining, undertraining/deconditioning, or physical injury. Conversely, MF can be persistent and more serious when associated with pathological states or following chronic exposure to certain medication or toxic composites. In conjunction with chronic fatigue, the muscle feels floppy, and the force generated by muscles is always low, causing the individual to feel frail constantly. The leading cause underpinning the development of chronic fatigue is related to muscle wasting mediated by aging, immobilization, insulin resistance (through high-fat dietary intake or pharmacologically mediated Peroxisome Proliferator-Activated Receptor (PPAR) agonism), diseases associated with systemic inflammation (arthritis, sepsis, infections, trauma, cardiovascular and respiratory disorders (heart failure, chronic obstructive pulmonary disease (COPD))), chronic kidney failure, muscle dystrophies, muscle myopathies, multiple sclerosis, and, more recently, coronavirus disease 2019 (COVID-19). The primary outcome of displaying chronic muscle fatigue is a poor quality of life. This type of fatigue represents a significant daily challenge for those affected and for the national health authorities through the financial burden attached to patient support. Although the origin of chronic fatigue is multifactorial, the MF in illness conditions is intrinsically linked to the occurrence of muscle loss. The sequence of events leading to chronic fatigue can be schematically denoted as: trigger (genetic or pathological) -> molecular outcome within the muscle cell -> muscle wasting -> loss of muscle function -> occurrence of chronic muscle fatigue. The present review will only highlight and discuss current knowledge on the molecular mechanisms that contribute to the upregulation of muscle wasting, thereby helping us understand how we could prevent or treat this debilitating condition.

The molecular mechanisms by which free fatty acids (FFA) inhibit muscle glucose oxidation is still elusive. We recently showed that C2C12 myotubes treated with palmitate (PAL) presented with greater protein expression levels of PDK4 and transcription factors PPARα and PPARδ and lower p-FOXO/t-FOXO protein ratios when compared to control. This was complemented with the hallmarks of metabolic inflexibility (MI), i.e., reduced rates of glucose uptake, PDC activity and maximal pyruvate-derived ATP production rates (MAPR). However, the relative contribution of these transcription factors to the increase in PDK4 and reduced glucose oxidation could not be established. Therefore, by using a similar myotube model, a series of individual siRNA gene silencing experiments, validated at transcriptional and translation levels, were performed in conjunction with measurements of glucose uptake, PDC activity, MAPR and concentrations of metabolites reflecting PDC flux (lactate and acetylcarnitine). Gene silencing of PPARα, δ and FOXO1 individually reduced PAL-mediated inhibition of PDC activity and increased glucose uptake, albeit by different mechanisms as only PPARδ and FOXO1 silencing markedly reduced PDK4 protein content. Additionally, PPARα and FOXO1 silencing, but not PPARδ, increased MAPR with PAL. PPARδ silencing also decreased FOXO1 protein. Since FOXO1 silencing did not alter PPARδ protein, this suggests that FOXO1 might be a PPARδ downstream target. In summary, this study suggests that the molecular mechanisms by which PAL reduces PDC-mediated glucose-derived pyruvate oxidation in muscle occur primarily through increased PPARδ and FOXO1 mediated increases in PDK4 protein expression and secondarily through PPARα mediated allosteric inhibition of PDC flux. Furthermore, since PPARδ seems to control FOXO1 expression, this may reflect an important role for PPARδ in preventing glucose oxidation under conditions of increased lipid availability.

BACKGROUND & AIMS:This post hoc study aimed to determine whether major elective abdominal surgery had any acute impact on mitochondrial pyruvate dehydrogenase complex (PDC) activity and maximal mitochondrial ATP production rates (MAPR) in a large muscle group (vastus lateralis -VL) distant to the site of surgical trauma.METHODS:Fifteen patients undergoing major elective open abdominal surgery were studied. Muscle biopsies were obtained after the induction of anesthesia from the VL immediately before and after surgery for the determination of PDC and maximal MAPR (utilizing a variety of energy substrates).RESULTS:Muscle PDC activity was reduced by >50% at the end of surgery compared with pre-surgery (p < 0.05). Muscle MAPR were comprehensively suppressed by surgery for the substrate combinations: glutamate + succinate; glutamate + malate; palmitoylcarnitine + malate; and pyruvate + malate (all p < 0.05), and could not be explained by a lower mitochondrial yield.CONCLUSIONS:PDC activity and mitochondrial ATP production capacity were acutely impaired in muscle distant to the site of surgical trauma. In keeping with the limited data available, we surmise these events resulted from the general anesthesia procedures employed and the surgery related trauma. These findings further the understanding of the acute dysregulation of mitochondrial function in muscle distant to the site of major surgical trauma in patients, and point to the combination of general anesthesia and trauma related inflammation as being drivers of muscle metabolic insult that warrants further investigation.CLINICAL TRIAL REGISTRATION:Registered at (NCT01134809).

High‐load eccentric training reputedly produces greater muscle hypertrophy than concentric training, possibly due to greater loading and/or inflammation. We quantified the temporal impact of combined maximal concentric‐eccentric training vs maximal concentric training on muscle cross‐sectional area (CSA), volume, and targeted mRNA expression (93 transcripts). Eight recreationally active males (24 ± 5 years, BMI 23.5 ± 2.5 kg/m2) performed 3 x 30 maximal eccentric isokinetic knee extensions and 2 x 30 maximal concentric knee extensions in dominant limb (ECC + CON) and 5 x 30 maximal concentric contractions (CON) in the non‐dominant limb for 12 weeks (all 90°/s, 3x/wk). Quadriceps muscle CSA and volume were measured at baseline, 28 days (d), and 84 d in both limbs (3T MRI). Resting vastus lateralis biopsies were obtained from both limbs at baseline, 24 hours (h), 7, 28, and 84 d for mRNA abundance measurements (RT‐PCR microfluidic cards). Work output was greater throughout training in ECC + CON vs CON (20.8 ± 9.7%, P < .001). Muscle CSA increased from baseline in both limbs at 28 d (CON 4.3 ± 2.6%, ECC + CON 4.0 ± 1.9%, both P < .001) and 84d (CON 3.9 ± 2.3%, ECC + CON 4.0 ± 3.1%, both P < .001), and muscle volume and isometric strength at 84 d (CON 44.8 ± 40.0%, P < .001; ECC + CON 36.9 ± 40.0%, P < .01), but no between‐limb differences existed in any parameter. Ingenuity Pathway Analysis identified several cellular functions associated with regulation of muscle mass and metabolism as altered by both modalities at 24 h and 7 d, but particularly with ECC + CON. However, mRNA responses waned thereafter, regardless of modality. Initial muscle mRNA responses to training did not reflect chronic training‐induced hypertrophy. Moreover, ECC + CON did not produce greater hypertrophy than CON, despite greater loading throughout and a differential mRNA response during the initial training week.

Rationale: Immobilisation reduces insulin-mediated whole body glucose disposal (GD) (1). The rate of decline of insulin stimulated GD and changes in carbohydrate (CHO) oxidation over the acute to chronic bed rest (BR) setting remain to be fully elucidated, as do to the physiological drivers of these events under conditions where energy balance is maintained. We, therefore, determined whole body GD, CHO oxidation and intramyocellular lipid (IMCL) content during acute and chronic BR whilst maintaining energy balance.

Background Eccentric cycling (ECC) may be an attractive exercise modality in COPD due to lower cardiorespiratory demand and perception of effort compared to conventional concentric cycling (CON) at equivalent mechanical workloads. However, it is unknown whether ECC can be performed by individuals with COPD at an intensity able to induce metabolic adaptation. Methods 13 individuals with COPD (mean ± SD age 64 ± 9 years, FEV1%pred 45 ± 19%, BMI 24 ± 4 kg.m-2, &Vdot;O2peak15 ± 3 ml.kg-1.min-1) and 9 age matched controls (FEV1%pred 102 ± 13%, BMI 28 ± 5 kg.m-2, &Vdot;O2peak23 ± 5 ml.kg-1.min-1), performed up to six 4-minute bouts of ECC and CON at matched mechanical loads of increasing intensity. In addition, 12 individuals with COPD underwent quadriceps muscle biopsies (vastus lateralis) before and immediately after 20 minutes of ECC and CON at 65% peak power. Modalities were compared using linear mixed models. Results The gradient of the slope of &Vdot;O2 (ml.min-1)/Power (Watts) during ECC was 2.8-fold and 3.3-fold lower than CON for COPD and control participants, respectively. At matched mechanical loads, minute ventilation, heart rate, systolic blood pressure, RER (all p<0.001), capillary [lactate], perceived breathlessness and leg fatigue (p<0.05) were lower during ECC than CON in both groups. Muscle lactate content increased (p=0.01), and muscle phosphocreatine decreased (p=0.03) during CON in COPD, which was not evident during ECC (see table 1). ECC was well received by individuals with COPD with 76% preferring it to CON. Conclusion Cardiopulmonary and blood lactate responses during submaximal ECC were less compared to CON at equivalent mechanical workloads in health and COPD, and this was confirmed at a muscle level in COPD. Submaximal ECC was well tolerated and allowed greater mechanical work at lower ventilatory cost. However, in people with COPD, the lower metabolic cost of ECC is unlikely to stimulate cardiovascular and metabolic adaptation to a training intervention to the same extent as CON.

Background: Voluntary resistance exercise (RE) training increases muscle mass and strength in patients with chronic obstructive pulmonary disease (COPD). Nonvolitional transcutaneous neuromuscular electrical stimulation (NMES) may be an alternative strategy for reducing ambulatory muscle weakness in patients unable to perform RE training, but little comparative data are available. This study, therefore, investigated changes in muscle mRNA abundance of a number of gene targets in response to a single bout of NMES compared with RE. Methods: Twenty-six patients with stable COPD (15 male; FEV1, 43±18% predicted; age, 64±8 years; fat free mass index, 16.6±1.8 kg/m2) undertook 30 minutes of quadriceps NMES (50 Hz, current at the limit of tolerance) or 5×30 maximal voluntary isokinetic knee extensions. Vastus lateralis muscle biopsies were obtained at rest immediately before and 24 hours after intervention. Expression of 384 targeted mRNA transcripts was assessed by real time TaqMan PCR. Significant change in expression from baseline was determined using the ΔΔCT method with a false discovery rate (FDR) of <5%. Results: NMES and RE altered mRNA abundance of 18 and 68 genes, respectively (FDR <5%), of which 14 genes were common to both interventions and of the same magnitude of fold change. Biological functions of upregulated genes included inflammation, hypertrophy, muscle protein turnover, and muscle growth, whilst downregulated genes included mitochondrial and cell signaling functions. Conclusions: Compared with NMES, RE had a broader impact on mRNA abundance and, therefore, appears to be the superior intervention for maximizing transcriptional responses in the quadriceps of patients with COPD. However, if voluntary RE is not feasible in a clinical setting, NMES by modifying expression of genes known to impact upon muscle mass and strength may have a positive influence on muscle function.

Impaired muscle function contributes to exercise intolerance in COPD, but it is unclear if the muscle level adaptive response to exercise training in COPD is blunted. We therefore aimed to determine temporal muscle mRNA responses to aerobic exercise training (AET) and subsequent training cessation in COPD and healthy controls (HC) & examined associations with ΔVO2PEAK during training. 19 patients with COPD (6 male; mean ±SD 70±6yrs; FEV1%pred 57±16; VO2PEAK 24.4±7.4ml/min/kg lean mass) & 10 HC (5 male; 71±5yrs; FEV1%pred 113±21; VO2PEAK 29.7±4) had vastus lateralis biopsies (fasted resting) at baseline; after 1,4 & 8wk of cycle AET (30min, 3/wk, 65% peak power); and 4wk after training cessation. 94 exercise-responsive mRNAs were quantified in muscle by RT-PCR and analysed using Ingenuity Pathway Analysis (IPA, Qiagen) to detect biological functions significantly changed from baseline. IPA identified altered biological functions after 1,4 & 8wk of training and after 4wk training cessation in HC and COPD (Fig). The magnitude and pattern of mRNA responses were similar in COPD and HC, & persisted 4wk after training cessation. VO2PEAK increased 18% in HC (p<.01) but was unaltered in COPD after AET. Changes in mRNA expression were dissociated from whole-body ΔVO2PEAK in COPD. These data support the contention that the responsiveness of skeletal muscle to AET in COPD is not blunted, at least at the level of mRNA expression.

Background/objectives Increased risk of type 2 diabetes mellitus (T2DM) is linked to impaired muscle mitochondrial function and reduced mitochondrial DNA copy number (mtDNA num ). However, studies have failed to control for habitual physical activity levels, which directly influences both mtDNA copy number and insulin sensitivity. We, therefore, examined whether physical conditioning status (maximal oxygen uptake, V̇O 2max ) was associated with skeletal muscle mitochondrial volume and mtDNA num , and was predictive of T2DM in overweight, middle-aged men. Methods Whole-body physiological (ISI—insulin sensitivity index, HOMA-IR, V̇O 2max ) and muscle biochemical/molecular (vastus lateralis; mtDNA num , mitochondrial and glycolytic enzymes activity, lipid content and markers of lipid peroxidation) measurements were performed in three groups of overweight, middle-aged male volunteers ( n = 10 per group): sedentary T2DM (ST2DM); sedentary control (SC) and non-sedentary control (NSC), who differed in aerobic capacity (ST2DM < SC < NSC). Results mtDNA num was greater in NSC versus SC and ST2DM ( P < 0.001; P < 0.001), and less in ST2DM versus SC ( P < 0.01). Across all groups, mtDNA num positively correlated with ISI ( P < 0.001; r = 0.688) and V̇O 2max (normalised to free fat mass; r = 0.684, P < 0.001), and negatively correlated to HOMA-IR ( r = −0.544, P < 0.01). The activity of mitochondrial enzymes (GluDH, CS and β-HAD) was greater in NSC than ST2DM ( P < 0.01, P < 0.001 and P < 0.05) and SC ( P < 0.05, P < 0.01 and P < 0.05), but similar between ST2DM and SC. Intramuscular-free fatty acids, triglycerides and malondialdehyde contents were similar between ST2DM and SC. Conclusions Body composition and indices of muscle mitochondrial volume/function were similar between SC and ST2DM. However, mtDNA num differed and was positively associated with ISI, HOMA-IR and V̇O 2max across all groups. Collectively, the findings support the contention that habitual physical activity is a key component of T2DM development, possibly by influencing mtDNA num .

Background & aims: Postoperative hyperglycaemia is common in patients having major surgery and is associated with adverse outcomes. This study aimed to determine whether bacteraemia contributed to postoperative systemic inflammation, and whether increases in the expression of muscle mRNAs and proteins reflecting increased muscle inflammation, atrophy and impaired carbohydrate oxidation were evident at the time of surgery, and both local and distant to the site of trauma, and could be associated with impaired glucoregulation. Methods: Fifteen adult patients without diabetes undergoing major abdominal surgery participated in this observational study set in a university teaching hospital. Arterialised-venous blood samples and muscle biopsies were obtained before and after major elective abdominal surgery, from sites local (rectus abdominis - RA) and remote to the site of surgery (vastus lateralis - VL). The main outcome measures included blood glucose concentrations, gut permeability and changes in expression of muscle mRNAs and proteins linked to inflammation and glucose regulation. Results: Immediately postoperatively, RA demonstrated markedly increased mRNA expression levels of cathepsin-L (7.5-fold, P < 0.05), FOXO1 (10.5-fold, P < 0.05), MAFbx (11.5-fold, P < 0.01), PDK4 (7.8-fold, P < 0.05), TNF-alpha (16.5-fold, P < 0.05) and IL-6 (1058-fold, P < 0.001). A similar, albeit blunted, response was observed in VL. Surgery also increased expression of proteins linked to inflammation (IL-6; 6-fold, P < 0.01), protein degradation (MAFbx; 4.5-fold, P < 0.5), and blunted carbohydrate oxidation (PDK4; 4-fold, P < 0.05) in RA but not VL. Increased systemic inflammation (TNF-alpha, P < 0.05; IL-6, P < 0.001), and impaired postoperative glucose tolerance (P < 0.001), but not bacteraemia (although gut permeability was increased significantly, P < 0.05) or increased plasma cortisol, were noted 48 h postoperatively. Conclusions: A systemic postoperative proinflammatory response was accompanied by muscle inflammation and metabolic dysregulation both local and remote to the site of surgery, and was not accompanied by bacteraemia. (C) 2017 The Authors. Published by Elsevier Ltd.

Objectives To characterise the sketetal muscle metabolic phenotype during early critical illness. Methods Vastus lateralis muscle biopsies and serum samples (days 1 and 7) were obtained from 63 intensive care patients (59% male, 54.7±18.0 years, Acute Physiology and Chronic Health Evaluation II score 23.5±6.5). Measurements and main results From day 1 to 7, there was a reduction in mitochondrial beta-oxidation enzyme concentrations, mitochondrial biogenesis markers (PGC1α messenger mRNA expression (−27.4CN (95% CI −123.9 to 14.3); n=23; p=0.025) and mitochondrial DNA copy number (−1859CN (IQR −5557–1325); n=35; p=0.032). Intramuscular ATP content was reduced compared tocompared with controls on day 1 (17.7mmol/kg /dry weight (dw) (95% CI 15.3 to 20.0) vs. 21.7 mmol/kg /dw (95% CI 20.4 to 22.9); p<0.001) and decreased over 7 days (−4.8 mmol/kg dw (IQR −8.0–1.2); n=33; p=0.001). In addition, the ratio of phosphorylated:total AMP-K (the bioenergetic sensor) increased (0.52 (IQR −0.09–2.6); n=31; p<0.001). There was an increase in intramuscular phosphocholine (847.2AU (IQR 232.5–1672); n=15; p=0.022), intramuscular tumour necrosis factor receptor 1 (0.66 µg (IQR −0.44–3.33); n=29; p=0.041) and IL-10 (13.6 ng (IQR 3.4–39.0); n=29; p=0.004). Serum adiponectin (10.3 µg (95% CI 6.8 to 13.7); p<0.001) and ghrelin (16.0 ng/mL (IQR −7–100); p=0.028) increased. Network analysis revealed a close and direct relationship between bioenergetic impairment and reduction in muscle mass and between intramuscular inflammation and impaired anabolic signaling. ATP content and muscle mass were unrelated to lipids delivered. Conclusions Decreased mitochondrial biogenesis and dysregulated lipid oxidation contribute to compromised skeletal muscle bioenergetic status. In addition, intramuscular inflammation was associated with impaired anabolic recovery with lipid delivery observed as bioenergetically inert. Future clinical work will focus on these key areas to ameliorate acute skeletal muscle wasting. Trial registration number NCT01106300.