Metabolites as signalling molecules.

Traditional views of cellular metabolism imply that it is passively adapted to meet the demands of the cell. It is becoming increasingly clear, however, that metabolites do more than simply supply the substrates for biological processes; they also provide critical signals, either through effects on metabolic pathways or via modulation of other regulatory proteins. Recent investigation has also uncovered novel roles for several metabolites that expand their signalling influence to processes outside metabolism, including nutrient sensing and storage, embryonic development, cell survival and differentiation, and immune activation and cytokine secretion. Together, these studies suggest that, in contrast to the prevailing notion, the biochemistry of a cell is frequently governed by its underlying metabolism rather than vice versa. This important shift in perspective places common metabolites as key regulators of cell phenotype and behaviour. Yet the signalling metabolites, and the cognate targets and transducers through which they signal, are only beginning to be uncovered. In this Review, we discuss the emerging links between metabolism and cellular behaviour. We hope this will inspire further dissection of the mechanisms through which metabolic pathways and intermediates modulate cell function and will suggest possible drug targets for diseases linked to metabolic deregulation.

An AT-hook domain in MeCP2 determines the clinical course of Rett syndrome and related disorders.

Mutations in the X-linked MECP2 cause Rett syndrome, a devastating neurological disorder typified by a period of apparently normal development followed by loss of cognitive and psychomotor skills. Data from rare male patients suggest symptom onset and severity can be influenced by the location of the mutation, with amino acids 270 and 273 marking the difference between neonatal encephalopathy and death, on the one hand, and survival with deficits on the other. We therefore generated two mouse models expressing either MeCP2-R270X or MeCP2-G273X. The mice developed phenotypes at strikingly different rates and showed differential ATRX nuclear localization within the nervous system, over time, coinciding with phenotypic progression. We discovered that MeCP2 contains three AT-hook-like domains over a stretch of 250 amino acids, like HMGA DNA-bending proteins; one conserved AT-hook is disrupted in MeCP2-R270X, lending further support to the notion that one of MeCP2's key functions is to alter chromatin structure.

All differential on the splicing front: Host alternative splicing alters the landscape of virus-host conflict.

Alternative RNA splicing is a co-transcriptional process that richly increases proteome diversity, and is dynamically regulated based on cell species, lineage, and activation state. Virus infection in vertebrate hosts results in rapid host transcriptome-wide changes, and regulation of alternative splicing can direct a combinatorial effect on the host transcriptome. There has been a recent increase in genome-wide studies evaluating host alternative splicing during viral infection, which integrates well with prior knowledge on viral interactions with host splicing proteins. A critical challenge remains in linking how these individual events direct global changes, and whether alternative splicing is an overall favorable pathway for fending off or supporting viral infection. Here, we introduce the process of alternative splicing, discuss how to analyze splice regulation, and detail studies on genome-wide and splice factor changes during viral infection. We seek to highlight where the field can focus on moving forward, and how incorporation of a virus-host co-evolutionary perspective can benefit this burgeoning subject.

Alternative splicing liberates a cryptic cytoplasmic isoform of mitochondrial MECR that antagonizes influenza virus.

Viruses must balance their reliance on host cell machinery for replication while avoiding host defense. Influenza A viruses are zoonotic agents that frequently switch hosts, causing localized outbreaks with the potential for larger pandemics. The host range of influenza virus is limited by the need for successful interactions between the virus and cellular partners. Here we used immunocompetitive capture-mass spectrometry to identify cellular proteins that interact with human- and avian-style viral polymerases. We focused on the proviral activity of heterogenous nuclear ribonuclear protein U-like 1 (hnRNP UL1) and the antiviral activity of mitochondrial enoyl CoA-reductase (MECR). MECR is localized to mitochondria where it functions in mitochondrial fatty acid synthesis (mtFAS). While a small fraction of the polymerase subunit PB2 localizes to the mitochondria, PB2 did not interact with full-length MECR. By contrast, a minor splice variant produces cytoplasmic MECR (cMECR). Ectopic expression of cMECR shows that it binds the viral polymerase and suppresses viral replication by blocking assembly of viral ribonucleoprotein complexes (RNPs). MECR ablation through genome editing or drug treatment is detrimental for cell health, creating a generic block to virus replication. Using the yeast homolog Etr1 to supply the metabolic functions of MECR in MECR-null cells, we showed that specific antiviral activity is independent of mtFAS and is reconstituted by expressing cMECR. Thus, we propose a strategy where alternative splicing produces a cryptic antiviral protein that is embedded within a key metabolic enzyme.

Evaluation of electronic measurement of capillary refill for Sepsis screening at ED triage.

OBJECTIVE: To evaluate the association between capillary refill time (CRT) measured by a medical device and sepsis among patients presenting to the Emergency Department (ED). METHODS: This prospective observational study enrolled adult and pediatric patients during ED triage when sepsis was considered a potential diagnosis by the triage nurse. Patients were enrolled at an academic medical center between December 2020 and June 2022. CRT was measured by a research assistant using an investigational medical device. The outcomes included sepsis and septic shock defined using sep-3 criteria, septic shock defined as IV antibiotics and a vasopressor requirement, ICU admission, and hospital mortality. Other measures included patient demographics and vital signs at ED triage. We evaluated univariate associations between CRT and sepsis outcomes. RESULTS: We enrolled 563 patients in the study, 48 met Sep-3 criteria, 5 met Sep-3 shock criteria, and 11 met prior septic shock criteria (IV antibiotics and vasopressors to maintain mean arterial pressure of 65). Sixteen patients were admitted to the ICU. The mean age was 49.1 years, and 51% of the cohort was female. The device measured CRT was significantly associated with the diagnosis of sepsis by sep-3 criteria (OR 1.23, 95% CI 1.06-1-43), septic shock by sep-3 criteria (OR 1.57, 95% CI 1.02-2.40), and septic shock defined as receipt of IV antibiotics and a vasopressor requirement (OR 1.37, 95% CI 1.03-1.82). Patients with CRT >3.5 s measured by the DCR device had an odds ratio of 4.67 (95%CI 1.31-16.1) of septic shock (prior definition), and an odds ratio of 3.97 (95% CI 1.99-7.92) of ICU admission, supporting the potential for the 3.5-s cutoff of the DCR measurement. CONCLUSIONS: CRT measured by a medical device at ED triage was associated with the diagnosis of sepsis. Objective CRT measurement using a medical device may be a relatively simple way to improve sepsis diagnosis during ED triage.

Clinical practice guideline for the management of paediatric Charcot-Marie-Tooth disease.

BACKGROUND AND OBJECTIVES: Charcot-Marie-Tooth disease (CMT) is the most common inherited neuropathy and often presents during childhood. Guidelines for the optimal management of common problems experienced by individuals with CMT do not exist, for either children or adults. We formed the Paediatric CMT Best Practice Guidelines Consortium to develop evidence and consensus-based recommendations for the clinical management of children and adolescents with CMT, with the primary objective of promoting optimal, standardised care globally. METHODS: Development of this clinical practice guideline involved a series of systematic reviews covering 10 clinical questions, modified Delphi methodology involving an international panel of clinicians to generate consensus where evidence did not exist, and application of the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach to evaluate the body of literature and formulate recommendations. RESULTS: The final guideline includes three evidence-based and 31 consensus-based recommendations. They encompass the management of muscle weakness, balance and mobility impairment, sensory symptoms, muscle cramps, impaired upper limb function, respiratory impairment, maintenance of joint range of motion and non-surgical management of joint deformity. Consensus was not achieved in some management areas, reflecting differences in practice between clinicians and healthcare settings, and highlighting the need for further research. CONCLUSIONS: This clinical practice guideline provides practical and implementable guidance on the management of common clinical problems experienced by children with CMT and advocates for improved access to multidisciplinary care. Successful dissemination and implementation of these recommendations will be critical in ensuring their application across multiple healthcare settings.

Validated transport conditions maintain the quality of washed red blood cells.

BACKGROUND: Washing red blood cell (RBC) units prior to transfusion is indicated for certain patients. In the United States, units stored at 1°C-6°C or transported at 1°C-10°C are available for issue up to 24 h, if not used immediately. The washing procedure commonly utilizes room temperature saline resulting in units starting out above the allowed temperature range. This leads to wastage if units are issued and returned too quickly before having a chance to equilibrate in a transport cooler. STUDY DESIGN AND METHODS: Here we performed an experimental study of washed RBC quality comparing "ideal" storage conditions in a blood bank refrigerator to a "real-world" simulation of unit transport, including holding in a transport cooler. Twelve RBC units were washed and allocated evenly into either condition. RESULTS: Measurements at 0, 1, 3, 6, 12, and 24 h post-washing revealed that placement in a transport cooler was associated with higher unit temperature prior to 12 h (p = .013) with a maximum difference of 9.3°C. Despite this difference, several measures of unit quality including extracellular potassium, pH, lactate, and free hemoglobin were indistinguishable between conditions (p = .382, .224, .286, .691, respectively). We selected half of the tested units from our irradiated inventory and confirmed increased potassium leak (p < .001) and accumulation of free hemoglobin (p = .012) in irradiated units. DISCUSSION: Washed units stored under approved transport conditions are acceptable to return to inventory up to 24 h after washing and we provide a prediction interval-based temperature threshold for rejecting these units, permitting reduced waste.

Capillary Refill Technology to Enhance the Accuracy of Peripheral Perfusion Evaluation in Sepsis.

Background: Monitoring of capillary refill time (CRT) is a common bedside assessment used to ascertain peripheral perfusion in a patient for a vast array of conditions. The literature has shown that a change in CRT can be used to recognize life-threatening conditions that cause decreased perfusion, such as sepsis, and aid in resuscitation. The current practice for calculating CRT invites subjectivity and produces a highly variable result. Innovative technology may be able to standardize this process and provide a reliable and accurate value for use in diagnostics and treatment. This study aimed to assess a new technology (DCR by ProMedix Inc.) for rapid, bedside, and noninvasive detection of CRT. Methods: This was a secondary analysis of a prospective observational study evaluating the accuracy of new technology towards CRT-guided diagnosis of sepsis. It was carried out in the adult emergency departments (ED) of an academic tertiary care medical center. Patients seeking care in the ED were determined eligible if they were > 18 years in age and exhibited chief complaints suggestive of possible sepsis. The CRT produced by the technology was compared to the gold standard manual waveform assessment. Results: 218 consecutive subject enrollments were included and multiple measurements were made on each patient. Data with irregular waveforms were excluded. A total of 692 waveforms were evaluated for CRT values by a pair of trained PhD biomedical engineers. The average age of the cohort was 50.62 and 51.4% female. Results showed a Pearson correlation coefficient of 0.91 for the device CRT compared to the CRT gold standard. The Pearson correlation coefficient for the two independent engineering review of the waveform data was 0.98. This device produces accurate, consistent results and eliminates the subjectivity of CRT measurements that is in practice currently.

Canadian Guidelines for Hereditary Transthyretin Amyloidosis Polyneuropathy Management.

Hereditary transthyretin-mediated (hATTR) amyloidosis is a progressive disease caused by mutations in the TTR gene leading to multisystem organ dysfunction. Pathogenic TTR aggregation, misfolding, and fibrillization lead to deposition of amyloid in multiple body organs and frequently involve the peripheral nerve system and the heart. Common neurologic manifestations include: sensorimotor polyneuropathy (PN), autonomic neuropathy, small-fiber PN, and carpal tunnel syndrome. Many patients have significant progression due to diagnostic delays as hATTR PN is not considered within the differential diagnosis. Recently, two effective novel disease-modifying therapies, inotersen and patisiran, were approved by Health Canada for the treatment of hATTR PN. Early diagnosis is crucial for the timely introduction of these disease-modifying treatments that reduce impairments, improve quality of life, and extend survival. In this guideline, we aim to improve awareness and outcomes of hATTR PN by making recommendations directed to the diagnosis, monitoring, and treatment in Canada.

Lignes directrices sur la prise en charge de l'amylose héréditaire à transthyrétine, accompagnée de polyneuropathie, au Canada.L'amylose héréditaire à transthyrétine (ATTRh) est une maladie évolutive, causée par des mutations du gène de la transthyrétine (TTR), qui entraînent un dysfonctionnement plurisystémique. L'agrégation, le mauvais repliement et la fibrillisation pathogènes de la TTR aboutissent au dépôt de protéines amyloïdes dans plusieurs organes, et affectent souvent le système nerveux périphérique et le cœur. Les troubles neurologiques fréquents comprennent une polyneuropathie sensorimotrice (PN), une neuropathie autonome, une polyneuropathie des petites fibres et le syndrome du canal carpien. Chez bon nombre de patients, la maladie a connu une évolution importante en raison de la pose tardive du diagnostic, la PN-ATTRh ne faisant pas l'objet d'un diagnostic différentiel. Santé Canada a approuvé, depuis peu, deux nouveaux médicaments modificateurs de la PN-ATTRh et efficaces contre l'affection, soit l'inotersen et le patisiran. La pose précoce du diagnostic revêt une importance cruciale dans l'instauration, en temps opportun, de ces tout nouveaux traitements qui atténuent les troubles, améliorent la qualité de vie et prolongent la survie. Les auteurs, par l'élaboration de la nouvelle ligne directrice, espèrent sensibiliser la communauté médicale à la PN-ATTRh, et améliorer les résultats cliniques qui y sont associés, en formulant des recommandations sur le diagnostic et le traitement de la maladie au Canada ainsi que sur la surveillance de son évolution.

MeCP2 Levels Regulate the 3D Structure of Heterochromatic Foci in Mouse Neurons.

Methyl-CpG binding protein 2 (MeCP2) is a nuclear protein critical for normal brain function, and both depletion and overexpression of MeCP2 lead to severe neurodevelopmental disease, Rett syndrome (RTT) and MECP2 multiplication disorder, respectively. However, the molecular mechanism by which abnormal MeCP2 dosage causes neuronal dysfunction remains unclear. As MeCP2 expression is nearly equivalent to that of core histones and because it binds DNA throughout the genome, one possible function of MeCP2 is to regulate the 3D structure of chromatin. Here, to examine whether and how MeCP2 levels impact chromatin structure, we used high-resolution confocal and electron microscopy and examined heterochromatic foci of neurons in mice. Using models of RTT and MECP2 triplication syndrome, we found that the heterochromatin structure was significantly affected by the alteration in MeCP2 levels. Analysis of mice expressing either MeCP2-R270X or MeCP2-G273X, which have nonsense mutations in the upstream and downstream regions of the AT-hook 2 domain, respectively, showed that the magnitude of heterochromatin changes was tightly correlated with the phenotypic severity. Postnatal alteration in MeCP2 levels also induced significant changes in the heterochromatin structure, which underscored importance of correct MeCP2 dosage in mature neurons. Finally, functional analysis of MeCP2-overexpressing mice showed that the behavioral and transcriptomic alterations in these mice correlated significantly with the MeCP2 levels and occurred in parallel with the heterochromatin changes. Taken together, our findings demonstrate the essential role of MeCP2 in regulating the 3D structure of neuronal chromatin, which may serve as a potential mechanism that drives pathogenesis of MeCP2-related disorders.SIGNIFICANCE STATEMENT Neuronal function is critically dependent on methyl-CpG binding protein 2 (MeCP2), a nuclear protein abundantly expressed in neurons. The importance of MeCP2 is underscored by the severe childhood neurologic disorders, Rett syndrome (RTT) and MECP2 multiplication disorders, which are caused by depletion and overabundance of MeCP2, respectively. To clarify the molecular function of MeCP2 and to understand the pathogenesis of MECP2-related disorders, we performed detailed structural analyses of neuronal nuclei by using mouse models and high-resolution microscopy. We show that the level of MeCP2 critically regulates 3D structure of heterochromatic foci, and this is mediated in part by the AT-hook 2 domain of MeCP2. Our results demonstrate that one primary function of MeCP2 is to regulate chromatin structure.

Enantiomers of 4-aminopentanoic acid act as false GABAergic neurotransmitters and impact mouse behavior.

Imbalance in the metabolic pathway linking excitatory and inhibitory neurotransmission has been implicated in multiple psychiatric and neurologic disorders. Recently, we described enantiomer-specific effects of 2-methylglutamate, which is not decarboxylated to the corresponding methyl analogue of gamma-aminobutyric acid (GABA): 4-aminopentanoic acid (4APA). Here, we tested the hypothesis that 4APA also has enantiomer-specific actions in brain. Mouse cerebral synaptosome uptake (nmol/mg protein over 30 min) of (R)-4APA or (S)-4APA was time and temperature dependent; however, the R enantiomer had greater uptake, reduction of endogenous GABA concentration, and release following membrane depolarization than did the S enantiomer. (S)-4APA exhibited some weak agonist (GABAA α4ß3δ, GABAA α5ß2γ2, and GABAB B1/B2) and antagonist (GABAA α6ß2γ2) activity while (R)-4APA showed weak agonist activity only with GABAA α5ß2γ2. Both 4APA enantiomers (100 mg/kg IP) were detected in mouse brain 10 min after injection, and by 1 hr had reached concentrations that were stable over 6 hr; both enantiomers were cleared rapidly from mouse serum over 6 hr. Two-month-old mice had no mortality following 100-900 mg/kg IP of each 4APA enantiomer but did have similar dose-dependent reduction in distance moved in a novel cage. Neither enantiomer at 30 or 100 mg/kg impacted outcomes in 23 measures of well-being, activity chamber, or withdrawal from hot plate. Our results suggest that enantiomers of 4APA are active in mouse brain, and that (R)-4APA may act as a novel false neurotransmitter of GABA. Future work will focus on disease models and on possible applications as neuroimaging agents.

Creatine transport and pathological changes in creatine transporter deficient mice.

The severe impact on brain function and lack of effective therapy for patients with creatine (Cr) transporter deficiency motivated the generation of three ubiquitous Slc6a8 deficient mice (-/y). While each mouse knock-out line has similar behavioral effects at 2 to 3 months of age, other features critical to the efficient use of these mice in drug discovery are unclear or lacking: the concentration of Cr in brain and heart differ widely between mouse lines, there are limited data on histopathologic changes, and no data on Cr uptake. Here, we determined survival, measured endogenous Cr and uptake of its deuterium-labeled analogue Cr-d3 using a liquid chromatography coupled with tandem mass spectrometry assay, and performed comprehensive histopathologic examination on the Slc6a8-/y mouse developed by Skelton et al. Our results show that Slc6a8-/y mice have widely varying organ-specific uptake of Cr-d3, significantly diminished growth with the exception of brain, progressive vacuolar myopathy, and markedly shortened lifespan.

Practice Guidelines for Canadian Neurophysiology Laboratories During the COVID-19 Pandemic.

The COVID-19 pandemic has had a major impact on clinical practice. Safe standards of practice are essential to protect health care workers while still allowing them to provide good care. The Canadian Society of Clinical Neurophysiologists, the Canadian Association of Electroneurophysiology Technologists, the Association of Electromyography Technologists of Canada, the Board of Registration of Electromyography Technologists of Canada, and the Canadian Board of Registration of Electroencephalograph Technologists have combined to review current published literature about safe practices for neurophysiology laboratories. Herein, we present the results of our review and provide our expert opinion regarding the safe practice of neurophysiology during the COVID-19 pandemic in Canada.

Omega-3 fatty acid supplementation attenuates skeletal muscle disuse atrophy during two weeks of unilateral leg immobilization in healthy young women.

Omega-3 (n-3) fatty acid supplementation enhances muscle protein synthesis and muscle size. Whether n-3 fatty acid supplementation attenuates human muscle disuse atrophy is unknown. We determined the influence of n-3 fatty acid supplementation on muscle size, mass, and integrated rates of myofibrillar protein synthesis (MyoPS) following 2 wk of muscle disuse and recovery in women. Twenty women (BMI = 23.0 ± 2.3 kg/m2, age = 22 ± 3 yr) underwent 2 wk of unilateral limb immobilization followed by 2 wk of return to normal activity. Starting 4 wk prior to immobilization, participants consumed either 5 g/d of n-3 fatty acid or an isoenergetic quantity of sunflower oil (control). Muscle size and mass were measured pre- and postimmobilization, and after recovery. Serial muscle biopsies were obtained to measure integrated (daily) MyoPS. Following immobilization, the decline in muscle volume was greater in the control group compared to the n-3 fatty acid group (14 vs. 8%, P < 0.05) and was not different from preimmobilization at recovery in the n-3 fatty acid group; however, it was still lower in the control group ( P < 0.05). Muscle mass was reduced in the control group only ( P < 0.05). MyoPS was higher in the n-3 group compared with the control group at all times ( P < 0.05). We conclude that n-3 fatty acid supplementation attenuates skeletal muscle disuse atrophy in young women, which may be mediated by higher rates of MyoPS.-McGlory, C., Gorissen, S. H. M., Kamal, M., Bahniwal, R., Hector, A. J., Baker, S. K., Chabowski, A., Phillips, S. M. Omega-3 fatty acid supplementation attenuates skeletal muscle disuse atrophy during two weeks of unilateral leg immobilization in healthy young women.

Chronic Inflammatory Demyelinating Polyneuropathy: Time to Maximal Recovery in Patients Receiving Intravenous Immunoglobulin Therapy.

BACKGROUND: The response of chronic inflammatory demyelinating polyneuropathy (CIDP) to intravenous immunoglobulins (IVIgs) treatment is well established. However, it remains unclear whether patients not responding to two IVIg treatments or those whose condition stabilizes (ICE trial) may benefit from additional doses. We aim to identify the time period required to reach maximal strength gains from IVIg treatment. METHODS: Retrospective chart review of 14 patients with CIDP was performed. Change in handgrip (HG), Knee extension (KE), elbow flexion, and dorsiflexion was analyzed with a dynamometer during IVIg therapy. Strength improvements in Nm or kg, cumulative grams (g) of IVIg, and time in days required for maximal strength recovery were determined per function (± standard error of the mean). Ancillary therapy was recorded for all patients. RESULTS: Improvements in strength of each function were significant (p < 0.05). Earliest improvement was in HG (137.07 ± 21.23) and latest in KE (238.15 ± 38.9). Majority of patients improved by 200 days of therapy. HG required the lowest cumulative grams of IgG (561.71 ± 97.21) and KE the most (798 ± 120.7). CONCLUSION: Our study has demonstrated the effectiveness of multiple treatments with IVIg to reach significant improvement in strength. Different muscle groups manifested different time dependency, reflecting the requirement of variable amounts of IVIg. Improvement was identified on an ongoing basis, with therapy lasting between 20.2 and 37.3 weeks, requiring between 562 and 798 g of IVIg.

Pronounced energy restriction with elevated protein intake results in no change in proteolysis and reductions in skeletal muscle protein synthesis that are mitigated by resistance exercise.

Preservation of lean body mass (LBM) may be important during dietary energy restriction (ER) and requires equal rates of muscle protein synthesis (MPS) and muscle protein breakdown (MPB). Currently, the relative contribution of MPS and MPB to the loss of LBM during ER in humans is unknown. We aimed to determine the impact of dietary protein intake and resistance exercise on MPS and MPB during a controlled short-term energy deficit. Adult men (body mass index, 28.6 ± 0.6 kg/m2; age 22 ± 1 yr) underwent 10 d of 40%-reduced energy intake while performing unilateral resistance exercise and consuming lower protein (1.2 g/kg/d, n = 12) or higher protein (2.4 g/kg/d, n = 12). Pre- and postintervention testing included dual-energy X-ray absorptiometry, primed constant infusion of ring-[13C6]phenylalanine, and 15[N]phenylalanine to measure acute postabsorptive MPS and MPB; D2O to measure integrated MPS; and gene and protein expression. There was a decrease in acute MPS after ER (higher protein, 0.059 ± 0.006 to 0.051 ± 0.009%/h; lower protein, 0.061 ± 0.005 to 0.045 ± 0.006%/h; P < 0.05) that was attenuated with resistance exercise (higher protein, 0.067 ± 0.01%/h; lower protein, 0.061 ± 0.006%/h), and integrated MPS followed a similar pattern. There was no change in MPB (energy balance, 0.080 ± 0.01%/hr; ER rested legs, 0.078 ± 0.008%/hr; ER exercised legs, 0.079 ± 0.006%/hr). We conclude that a reduction in MPS is the main mechanism that underpins LBM loss early in ER in adult men.-Hector, A. J., McGlory, C., Damas, F., Mazara, N., Baker, S. K., Phillips, S. M. Pronounced energy restriction with elevated protein intake results in no change in proteolysis and reductions in skeletal muscle protein synthesis that are mitigated by resistance exercise.

Effects of music, video, and 360-degree video on cycle ergometer exercise at the ventilatory threshold.

Despite the seemingly ubiquitous presence of audiovisual stimuli in modern exercise facilities, there is a dearth of research examining the effects of audiovisual stimuli in combination during exercise. Accordingly, we examined the influence of a range of audiovisual stimuli on the improvement of affective, perceptual, and enjoyment responses to cycle ergometer exercise at the ventilatory threshold (VT), an intensity that is associated with the most affect-related interindividual variability. A within-subject design was employed, and participants (N = 18) completed a 25-minute protocol that consisted of 2 minutes of seated rest, 5 minutes of warm-up, 10 minutes of exercise at VT, 5 minutes of cooldown, and 3 minutes of seated rest. Participants exercised at VT under music, video, music-video, 360-degree video, 360-degree video with music, and control conditions. The results revealed a condition × time interaction for perceived activation and a main effect of condition for state attention and perceived enjoyment. The 360-degree video with music condition elicited the most positive affective valence, greatest perceived activation, most dissociative thoughts, and highest ratings of perceived enjoyment. The present findings indicate that audiovisual stimuli can influence affective, perceptual, and enjoyment responses to cycle ergometer exercise at the VT. Given the emerging support pertaining to a positive relationship between affective responses and exercise adherence, audiovisual stimuli, such as 360-degree video with music, should be considered as a means by which to promote an enjoyable exercise experience.

Effects of lorazepam and baclofen on short- and long-latency afferent inhibition.

KEY POINTS: Short-latency afferent inhibition (SAI) is modulated by GABAA receptor activity, whereas the pharmacological origin of long-latency afferent inhibition remains unknown. This is the first study to report that long-latency afferent inhibition (LAI) is reduced by the GABAA positive allosteric modulator lorazepam, and that both SAI and LAI are not modulated by the GABAB agonist baclofen. These findings advance our understanding of the neural mechanisms underlying afferent inhibition. ABSTRACT: The afferent volley evoked by peripheral nerve stimulation has an inhibitory influence on transcranial magnetic stimulation induced motor evoked potentials. This phenomenon, known as afferent inhibition, occurs in two phases: short-latency afferent inhibition (SAI) and long-latency afferent inhibition (LAI). SAI exerts its inhibitory influence via cholinergic and GABAergic activity. The neurotransmitter receptors that mediate LAI remain unclear. The present study aimed to determine whether LAI is contributed by GABAA and/or GABAB receptor activity. In a double-blinded, placebo-controlled study, 2.5 mg of lorazepam (GABAA agonist), 20 mg of baclofen (GABAB agonist) and placebo were administered to 14 males (mean age 22.7 ± 1.9 years) in three separate sessions. SAI and LAI, evoked by stimulation of the median nerve and recorded from the first dorsal interosseous muscle, were quantified before and at the peak plasma concentration following drug ingestion. Results indicate that lorazepam reduced LAI by ∼40% and, in support of previous work, reduced SAI by ∼19%. However, neither SAI, nor LAI were altered by baclofen. In a follow-up double-blinded, placebo-controlled study, 10 returning participants received placebo or 40 mg of baclofen (double the dosage used in Experiment 1). The results obtained indicate that SAI and LAI were unchanged by baclofen. This is the first study to show that LAI is modulated by GABAA receptor activity, similar to SAI, and that afferent inhibition does not appear to be a GABAB mediated process.

Microvascular adaptations to resistance training are independent of load in resistance-trained young men.

Resistance training promotes microvasculature expansion; however, it remains unknown how different resistance training programs contribute to angiogenesis. Thus, we recruited experienced resistance-trained participants and determined the effect of 12 wk of either high-repetition/low-load or low-repetition/high-load resistance training performed to volitional fatigue on muscle microvasculature. Twenty men performed either a high-repetition [20-25 repetitions, 30-50% of 1-repetition maximum (1RM); n = 10] or a low-repetition (8-12 repetitions, 75-90% of 1RM; n = 10) resistance training program. Muscle biopsies were taken before and after resistance training, and immunohistochemistry was used to assess fiber type (I and II)-specific microvascular variables. High-repetition/low-load and low-repetition/high-load groups were not different in any variable before resistance training. Both protocols resulted in an increase in capillarization. Specifically, after resistance training, the capillary-to-fiber ratio, capillary contacts, and capillary-to-fiber perimeter exchange index were elevated, and sharing factor was reduced. These data demonstrate that resistance training performed to volitional failure, using either high repetition/low load or low repetition/high load, induced similar microvascular adaptations in recreationally resistance-trained young men.

Leucine, Not Total Protein, Content of a Supplement Is the Primary Determinant of Muscle Protein Anabolic Responses in Healthy Older Women.

Background: Older adults show a blunted muscle protein synthesis (MPS) response to postprandial hyperaminoacidemia relative to younger adults. Evidence suggests that this anabolic resistance can be overcome by consuming greater quantities of leucine. Objective: The purpose of this trial was to determine whether the addition of leucine to a smaller dose (10 g) of milk proteins would, when compared with a larger dose (25 g) of whey protein isolate (WPI), result in similar increases in acute (hourly) and integrated (daily) myofibrillar protein synthesis (myoPS). Methods: Healthy older (mean ± SD age: 69 ± 1 y) women (n = 11/group) were randomly assigned with the use of a single-blind, parallel-group design to twice-daily consumption of either WPI [25 g WPI (3 g l-leucine)] or leucine (LEU; 10 g milk protein with 3 g total l-leucine) for 6 d. Participants performed unilateral resistance exercise to allow assessment of the impact of the supplement alone and with resistance exercise. We determined acute (13C6-phenylanine) and integrated [using deuterated water (D2O)] rates of myoPS in the fasting (acute), basal (integrated), nonexercised, and exercised states. Results: Acute myoPS increased in both legs in response to LEU (fed: 45%; fed+exercise: 71%; P < 0.001) and WPI (fed: 29%; fed+exercise: 47%; P < 0.001) compared with fasting; the increase was greater with LEU than with WPI in the exercised leg (46%; P = 0.04) but not in the rested leg (P = 0.07). The acute myoPS response was greater in the exercised leg than in the rested leg for both WPI (63%) and LEU (58%) (P < 0.001). Integrated myoPS increased with WPI and LEU in the exercised leg (both 9%; P < 0.001) during supplementation, and with WPI (3%; P = 0.02) but not LEU (2%, P = 0.1) in the rested leg compared with the basal state. Conclusions: A lower-protein (10 compared with 25 g/dose), leucine-matched beverage induced similar increases in acute and integrated myoPS in healthy older women. Lower-protein supplements with added leucine may represent an advantageous approach in older adults to maintain skeletal muscle anabolic sensitivity and attenuate muscle loss; however, further work is needed using longer-term interventions to substantiate these findings. This trial was registered at www.clinicaltrials.gov as NCT02282566.