The complexity of multidisciplinary respiratory care in amyotrophic lateral sclerosis.

Motor neurone disease/amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder with no known cure, where death is usually secondary to progressive respiratory failure. Assisting people with ALS through their disease journey is complex and supported by clinics that provide comprehensive multidisciplinary care (MDC). This review aims to apply both a respiratory and a complexity lens to the key roles and areas of practice within the MDC model in ALS. Models of noninvasive ventilation care, and considerations in the provision of palliative therapy, respiratory support, and speech and language therapy are discussed. The impact on people living with ALS of both inequitable funding models and the complexity of clinical care decisions are illustrated using case vignettes. Considerations of the impact of emerging antisense and gene modifying therapies on MDC challenges are also highlighted. The review seeks to illustrate how MDC members contribute to collective decision-making in ALS, how the sum of the parts is greater than any individual care component or health professional, and that the MDC per se adds value to the person living with ALS. Through this approach we hope to support clinicians to navigate the space between what are minimum, guideline-driven, standards of care and what excellent, person-centred ALS care that fully embraces complexity could be. Educational aims: To highlight the complexities surrounding respiratory care in ALS.To alert clinicians to the risk that complexity of ALS care may modify the effectiveness of any specific, evidence-based therapy for ALS.To describe the importance of person-centred care and shared decision-making in optimising care in ALS.

Oral digoxin effects on exercise performance, K+ regulation and skeletal muscle Na+ ,K+ -ATPase in healthy humans.

We investigated whether digoxin lowered muscle Na+ ,K+ -ATPase (NKA), impaired muscle performance and exacerbated exercise K+ disturbances. Ten healthy adults ingested digoxin (0.25 mg; DIG) or placebo (CON) for 14 days and performed quadriceps strength and fatiguability, finger flexion (FF, 105%peak-workrate , 3 × 1 min, fourth bout to fatigue) and leg cycling (LC, 10 min at 33% V O 2 peak ${\rm{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{peak}}}$ and 67% V O 2 peak ${\rm{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{peak}}}$ , 90% V O 2 peak ${\rm{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{peak}}}$ to fatigue) trials using a double-blind, crossover, randomised, counter-balanced design. Arterial (a) and antecubital venous (v) blood was sampled (FF, LC) and muscle biopsied (LC, rest, 67% V O 2 peak ${\rm{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{peak}}}$ , fatigue, 3 h after exercise). In DIG, in resting muscle, [3 H]-ouabain binding site content (OB-Fab ) was unchanged; however, bound-digoxin removal with Digibind revealed total ouabain binding (OB+Fab ) increased (8.2%, P = 0.047), indicating 7.6% NKA-digoxin occupancy. Quadriceps muscle strength declined in DIG (-4.3%, P = 0.010) but fatiguability was unchanged. During LC, in DIG (main effects), time to fatigue and [K+ ]a were unchanged, whilst [K+ ]v was lower (P = 0.042) and [K+ ]a-v greater (P = 0.004) than in CON; with exercise (main effects), muscle OB-Fab was increased at 67% V O 2 peak ${\rm{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{peak}}}$ (per wet-weight, P = 0.005; per protein P = 0.001) and at fatigue (per protein, P = 0.003), whilst [K+ ]a , [K+ ]v and [K+ ]a-v were each increased at fatigue (P = 0.001). During FF, in DIG (main effects), time to fatigue, [K+ ]a , [K+ ]v and [K+ ]a-v were unchanged; with exercise (main effects), plasma [K+ ]a , [K+ ]v , [K+ ]a-v and muscle K+ efflux were all increased at fatigue (P = 0.001). Thus, muscle strength declined, but functional muscle NKA content was preserved during DIG, despite elevated plasma digoxin and muscle NKA-digoxin occupancy, with K+ disturbances and fatiguability unchanged. KEY POINTS: The Na+ ,K+ -ATPase (NKA) is vital in regulating skeletal muscle extracellular potassium concentration ([K+ ]), excitability and plasma [K+ ] and thereby also in modulating fatigue during intense contractions. NKA is inhibited by digoxin, which in cardiac patients lowers muscle functional NKA content ([3 H]-ouabain binding) and exacerbates K+ disturbances during exercise. In healthy adults, we found that digoxin at clinical levels surprisingly did not reduce functional muscle NKA content, whilst digoxin removal by Digibind antibody revealed an ∼8% increased muscle total NKA content. Accordingly, digoxin did not exacerbate arterial plasma [K+ ] disturbances or worsen fatigue during intense exercise, although quadriceps muscle strength was reduced. Thus, digoxin treatment in healthy participants elevated serum digoxin, but muscle functional NKA content was preserved, whilst K+ disturbances and fatigue with intense exercise were unchanged. This resilience to digoxin NKA inhibition is consistent with the importance of NKA in preserving K+ regulation and muscle function.

Family, healthcare professional, and societal preferences for the treatment of infantile spinal muscular atrophy: A discrete choice experiment.

AIM: To understand the factors that most influence decision-making in the treatment of infantile spinal muscular atrophy (SMA). METHOD: A discrete choice experiment was conducted among parents of people with SMA (parents), healthcare professionals (HCPs), and members of the Australian general population (GenPop). Respondents were asked to accept/reject treatment for an infant newly diagnosed with SMA in eight hypothetical scenarios, characterized by different combinations of the attributes of the treatment offered. The results were analyzed using probability analysis. RESULTS: Completed responses were provided from 1113 individuals (1024 GenPop, 21 parents, 68 HCPs). Respondents were more likely to accept treatments that improved functioning and mobility. Treatments with higher costs, invasive delivery, and risks of adverse events were accepted less often. Cost most affected treatment choices by HCPs and GenPop, while change in mobility and mode of administration were most influential for parents. INTERPRETATION: These results highlight the importance of understanding value for money and clinical impact in affecting treatment choice, which are crucial for effective planning of healthcare and the successful implementation of treatment programmes for SMA. What this paper adds Spinal muscular atrophy (SMA) treatments with a higher chance of improving functioning and mobility are preferred by the general population, parents, and healthcare professionals. Treatments with higher costs, invasive delivery, and risk of adverse events are less preferred. Willingness to pay for SMA treatments increases with impact on functioning.

Peripheral nerve maturation and excitability properties from early childhood: Comparison of motor and sensory nerves.

OBJECTIVE: Understanding of maturational properties of sensory and motor axons is of central importance for determining the impact of nerve changes in health and in disease in children and young adults. METHODS: This study investigated maturation of sensory axons using axonal excitability parameters of the median nerve in 47 children, adolescents and young adults (25 males, 22 females; age range 1-25 years) and compared them to concurrent motor studies. RESULTS: The overall pattern of sensory maturation was similar to motor maturation demonstrating prolongation of the strength duration time constant (P < 0.001), reduction of hyperpolarising threshold electrotonus (P = 0.002), prolongation of accommodation half-time (P = 0.005), reduction in hyperpolarising current-threshold slope (P = 0.03), and a shift to the right of the refractory cycle curve (P < 0.001), reflecting changes in passive membrane properties and fast potassium channel conductances. Sensory axons, however, had a greater increase in strength duration time constant and more attenuated changes in depolarising threshold electrotonus and current-threshold parameters, attributable to a more depolarised resting membrane potential evident from early childhood and maintained in adults. Peak amplitude was established early in sensory axons whereas motor amplitude increased with age (P < 0.001), reflecting non-axonal motor unit changes. CONCLUSIONS: Maturational trajectories of sensory and motor axons were broadly parallel in children and young adults, but sensory-motor differences were initiated early in maturation. SIGNIFICANCE: Identifying the evolution of biophysical changes within and between sensory and motor axons through childhood and adolescence is fundamental to understanding developmental physiology and interpreting disease-related changes in immature nerves.

Prenusinersen economic and health-related quality of life burden of spinal muscular atrophy.

OBJECTIVE: To quantify the economic and health-related quality of life (HRQoL) burden incurred by households with a child affected by spinal muscular atrophy (SMA). METHODS: Hospital records, insurance claims, and detailed resource use questionnaires completed by caregivers were used to capture the direct and indirect costs to households of 40 children affected by SMA I, II, and III in Australia between 2016 and 2017. Prevalence costing methods were used and reported in 2017 US dollar (USD) purchasing power parity (PPP). The HRQoL for patients and primary caregivers was quantified with the youth version of the EQ-5D and CareQoL multiattribute utility instruments and Australian utility weights. RESULTS: The average total annual cost of SMA per household was $143,705 USD PPP for all SMA types (SMA I $229,346, SMA II $150,909, SMA III $94,948). Direct costs accounted for 56% of total costs. The average total indirect health care costs for all SMA types were $63,145 per annum and were highest in families affected by SMA II. Loss of income and unpaid informal care made up 24.2% and 19.8% respectively, of annual SMA costs. Three of 4 (78%) caregivers stated that they experienced financial problems because of care tasks. The loss in HRQoL of children affected by SMA and caregivers was substantial, with average caregiver and patient scores of 0.708 and 0.115, respectively (reference range 0 = death and 1 = full health). CONCLUSION: Our results demonstrate the substantial and far-ranging economic and quality of life burden on households and society of SMA and are essential to fully understanding the health benefits and cost-effectiveness associated with emerging disease-modifying therapies for SMA.

"The Whole Game is Changing and You've Got Hope": Australian Perspectives on Treatment Decision Making in Spinal Muscular Atrophy.

INTRODUCTION: The natural history and treatment of spinal muscular atrophy (SMA) is currently being transformed by the development and availability of novel therapies, with significant related changes in practice. This not only has important implications for the health and wellbeing of patients with SMA and their families, as well as improves the quality of care. OBJECTIVE: The present study aimed to investigate the processes and factors that influence treatment and healthcare decisions for children and adults with SMA and their families and healthcare providers. METHODS: Four focus groups comprising adults, or parents of children and adolescents, with SMA and an expert panel of healthcare providers (N = 25) explored experiences of SMA, its treatment and related decision making and expectations for future care. Group discussions were recorded and transcribed verbatim for thematic analysis using NVivo12.0. RESULTS: People with SMA, their families and healthcare providers described confronting complex healthcare decisions in the context of a rapidly changing SMA treatment environment. Across all groups, five key themes were identified: hope, yearning and searching, patient-centred care and support, community and a sense of connectedness and weighing up potential treatment benefits and costs. Essential to these themes was the notion of what it means to live with SMA and complexities relating to 'quality of life'. CONCLUSION: Identifying and more deeply understanding the factors that influence patient, family and healthcare providers' decision making regarding SMA treatment is an important first step in improving the quality of patient- and family-centred care and in informing clinical practice and future health policy incorporating personalized medicine and optimal supportive and mental health care.

Health, wellbeing and lived experiences of adults with SMA: a scoping systematic review.

BACKGROUND: Spinal muscular atrophy (SMA) is a neurodegenerative disease that has a substantial and multifaceted burden on affected adults. While advances in supportive care and therapies are rapidly reshaping the therapeutic environment, these efforts have largely centered on pediatric populations. Understanding the natural history, care pathways, and patient-reported outcomes associated with SMA in adulthood is critical to advancing health policy, practice and research across the disease spectrum. The aim of this study was to systematically review research investigating the healthcare, well-being and lived experiences of adults with SMA. METHODS: In accordance with the Preferred Reported Items for Systematic Reviews and Meta-Analysis guidelines, seven electronic databases were systematically searched until January 2020 for studies examining clinical (physical health, natural history, treatment) and patient-reported (symptoms, physical function, mental health, quality of life, lived experiences) outcomes in adults with SMA. Study risk of bias and the level of evidence were assessed using validated tools. RESULTS: Ninety-five articles met eligibility criteria with clinical and methodological diversity observed across studies. A heterogeneous clinical spectrum with variability in natural history was evident in adults, yet slow declines in motor function were reported when observational periods extended beyond 2 years. There remains no high quality evidence of an efficacious drug treatment for adults. Limitations in mobility and daily activities associated with deteriorating physical health were commonly reported, alongside emotional difficulties, fatigue and a perceived lack of societal support, however there was no evidence regarding effective interventions. CONCLUSIONS: This systematic review identifies the many uncertainties regarding best clinical practice, treatment response, and long-term outcomes for adults with SMA. This comprehensive identification of the current gaps in knowledge is essential to guide future clinical research, best practice care, and advance health policy with the ultimate aim of reducing the burden associated with adult SMA.

"Getting ready for the adult world": how adults with spinal muscular atrophy perceive and experience healthcare, transition and well-being.

BACKGROUND: Spinal muscular atrophy (SMA) has profound implications across a lifetime for people with the condition and their families. Those affected need long-term multidisciplinary medical and supportive care to maintain functional mobility, independence and quality of life. Little is known about how adults with SMA experience healthcare, or the components of care perceived as important in promoting well-being. The purpose of this study was to use qualitative research methodology to explore the lived experiences of healthcare and wellbeing of adults with SMA. Purposive sampling was used to recruit adolescents and adults with SMA, their parents and partners. Face-to-face or telephone-based semi-structured interviews were recorded and analysed using inductive thematic analysis. RESULTS: Across a total of 25 interviews (19 people with SMA, 5 parents, 1 partner) many participants described disengagement from health services and major gaps in care throughout adulthood. Disengagement was attributed to the perceived low value of care, as well as pragmatic, financial and social barriers to navigating the complex healthcare system and accessing disability services. Adults with SMA valued healthcare services that set collaborative goals, and resources with a positive impact on their quality of life. Mental health care was highlighted as a major unmet need, particularly during times of fear and frustration in response to loss of function, social isolation, stigma, and questions of self-worth. Alongside this, participants reported resilience and pride in their coping approaches, particularly when supported by informal networks of family, friends and peers with SMA. CONCLUSIONS: These findings provide insight into the lived experiences, values and perspectives of adults with SMA and their carers, revealing major, ongoing unmet healthcare needs, despite many realising meaningful and productive lives. Findings indicate the necessity of accessible, patient- and family-centered multidisciplinary care clinics that address currently unmet physical and mental health needs. Understanding the lived experiences of people with SMA, particularly during times of transition, is critical to advancing health policy, practice and research. Future studies are needed to quantify the prevalence, burden and impact of mental health needs whilst also exploring potential supportive and therapeutic strategies.

Myotonic dystrophy type 1: clinical manifestations in children and adolescents.

OBJECTIVE: Myotonic dystrophy type 1 (DM1) is an autosomal-dominant neuromuscular disease with variable severity affecting all ages; however, current care guidelines are adult-focused. The objective of the present study was to profile DM1 in childhood and propose a framework to guide paediatric-focused management. DESIGN, SETTING AND PATIENTS: 40 children with DM1 (mean age 12.8 years; range 2-19) were studied retrospectively for a total of 513 follow-up years at Sydney Children's Hospital. 143 clinical parameters were recorded. RESULTS: The clinical spectrum of disease in childhood differs from adults, with congenital myotonic dystrophy (CDM1) having more severe health issues than childhood-onset/juvenile patients (JDM1). Substantial difficulties with intellectual (CDM1 25/26 96.2%; JDM1 9/10, 90.0%), fine motor (CDM1 23/30, 76.6%; JDM1 6/10, 60.0%), gastrointestinal (CDM1 17/30, 70.0%; JDM1 3/10, 30.0%) and neuromuscular function (CDM1 30/30, 100.0%; JDM1 25/30, 83.3%) were evident. CONCLUSION: The health consequences of DM1 in childhood are diverse, highlighting the need for paediatric multidisciplinary management approaches that encompass key areas of cognition, musculoskeletal, gastrointestinal, respiratory, cardiac and sleep issues.

Financial, opportunity and psychosocial costs of spinal muscular atrophy: an exploratory qualitative analysis of Australian carer perspectives.

OBJECTIVES: Spinal muscular atrophy (SMA) has profound implications for patients and families. The aim of the present study was to gain insights into the effects caring for a child with SMA has on the costs incurred by families caring for a child with SMA from carer perspectives to identify gaps in provision of care, inform public policy and cost-effectiveness analyses. DESIGN: Interpretive phenomenological analysis guided the delivery and analysis of semi-structured interviews undertaken to explore the financial, opportunity and psychosocial costs associated with caring for children with SMA. PARTICIPANTS AND SETTING: Parents of children with SMA types II and III from a single Australian paediatric neuromuscular clinic participated in this study. RESULTS: A range of experiences were reported and information saturation (n=7) was reached endorsing themes, including: significant financial and caregiving burdens, adjusted career choices and limitations on career progression and a complex landscape of access to funding, equipment, support and resources. Opportunity costs of foregone employment, purchases and leisure activities were substantial, as were emotional and social impacts. Participants voiced determination and resilience, and called for continued efforts to improve supportive care services and resources. CONCLUSIONS: The range and nature of costs met by families caring for a child with SMA were found to be expansive and not typically recognised. These include high direct costs associated with goods and services, indirect costs associated with voluntary care, substantial and long-term opportunities foregone in paid employment and career progression and unmeasured or hidden costs associated with mental health burden.

New and developing therapies in spinal muscular atrophy.

Great progress has been made in the clinical translation of several therapeutic strategies for spinal muscular atrophy (SMA), including measures to selectively address Survival Motor Neuron (SMN) protein deficiency with SMN1 gene replacement or modulation of SMN2 encoded protein levels, as well as neuroprotective approaches and supporting muscle strength and function. This review highlights these novel therapies. This is particularly vital with the advent of the first disease modifying therapy, which has brought to the fore an array of questions surrounding who, how and when to treat, and stimulated challenges in resource limited healthcare systems to streamline access for those eligible for drug therapy. The overhaul of the landscape for all those involved in SMA extends to the design of further drug trials and the necessity of multidisciplinary supportive care to potentiate the effects of disease modifying medications. The impact of respiratory complications in SMA is central to management in the current era of emerging novel therapies. These fundamental changes in our knowledge and management approach to those with SMA are explored further in this review.

Nusinersen for SMA: expanded access programme.

BACKGROUND: Spinal muscular atrophy (SMA) is a devastating motor neuron disorder causing progressive muscle weakness and respiratory insufficiency. We present the initial Australian experiences implementing the expanded access programme (EAP) to enable preapproval access to nusinersen, the first disease-modifying therapy, for SMA type 1. METHODS: An Australian multicentre, open-label EAP for nusinersen enrolled patients with infantile-onset SMA type 1 from November 2016 to September 2017. Standard-of-care medical therapy and treatment with intrathecal nusinersen were provided to all patients. Clinical and diagnostic characteristics, molecular genetics, treatment administered, and functional motor outcomes were assessed. RESULTS: A total of 20 patients with SMA type 1 met the inclusion criteria, of whom 16 consented and received nusinersen treatment. Median time to diagnosis from symptom onset was 5.0 months and was correlated with age of onset (r=0.54, P<0.05). Management shifts included proactive nutritional and pulmonary support in all newly diagnosed patients with increased complexity of decision making. Supplemental nutrition with or without nocturnal non-invasive ventilation was implemented during follow-up in new diagnoses with age of onset <3 months and 2 SMN2 copies. CONCLUSIONS: The nusinersen EAP highlights difficulties in achieving early diagnosis and/or prevention, the evolution of optimal clinical care in a time of uncertain prognostication, resource implications and ethical issues in clinical practice for SMA type 1. These challenges are broadly relevant to the realisation of all novel therapeutics in neurological disorders.

Emerging therapies and challenges in spinal muscular atrophy.

Spinal muscular atrophy (SMA) is a hereditary neurodegenerative disease with severity ranging from progressive infantile paralysis and premature death (type I) to limited motor neuron loss and normal life expectancy (type IV). Without disease-modifying therapies, the impact is profound for patients and their families. Improved understanding of the molecular basis of SMA, disease pathogenesis, natural history, and recognition of the impact of standardized care on outcomes has yielded progress toward the development of novel therapeutic strategies and are summarized. Therapeutic strategies in the pipeline are appraised, ranging from SMN1 gene replacement to modulation of SMN2 encoded transcripts, to neuroprotection, to an expanding repertoire of peripheral targets, including muscle. With the advent of preliminary trial data, it can be reasonably anticipated that the SMA treatment landscape will transform significantly. Advancement in presymptomatic diagnosis and screening programs will be critical, with pilot newborn screening studies underway to facilitate preclinical diagnosis. The development of disease-modifying therapies will necessitate monitoring programs to determine the long-term impact, careful evaluation of combined treatments, and further acceleration of improvements in supportive care. In advance of upcoming clinical trial results, we consider the challenges and controversies related to the implementation of novel therapies for all patients and set the scene as the field prepares to enter an era of novel therapies. Ann Neurol 2017;81:355-368.

Activation of mTOR signalling in young and old human skeletal muscle in response to combined resistance exercise and whey protein ingestion.

PURPOSE: To investigate the impact of whey protein ingestion and resistance exercise training on the phosphorylation of mRNA translational signalling proteins in the skeletal muscle of young and old men. METHODS: Sixteen healthy young (aged 18-25 years) and 15 healthy older men (aged 60-75 years) completed 12 weeks of resistance exercise and were randomly assigned to consume a whey protein (WPI) or placebo drink after each session. Muscle biopsies were collected before and 2 h after an acute exercise bout at the beginning and the end of training. RESULTS: All subjects significantly increased strength after following strength training. Phosphorylation of mTOR was significantly greater in the WPI groups compared with placebo for both younger and older subjects. Phosphorylation of p70(S6K), eIF4G, and 4EBP1 was greater for older subjects consuming WPI. Phosphorylation of rpS6, eIF4G, and 4EBP1 tended to increase in the younger subjects that had consumed WPI. Post-training, younger subjects demonstrated a similar pattern of mTOR phosphorylation as seen pre-training. In contrast, the initial heightened phosphorylation of mTOR, p70(S6K), rpS6, and eIF4G in older muscle to combined resistance exercise and WPI ingestion became less pronounced after repeated training sessions. CONCLUSIONS: In the untrained state, resistance exercise coupled with WPI increases the phosphorylation of proteins involved in mRNA translation compared with exercise alone. Post-training, WPI- and exercise-induced protein phosphorylation was reduced in older men, but not in younger men. Thus, strategies to induce hypertrophy should utilize protein and resistance training concurrently. Further investigations should delineate interventions that will maintain sensitivity to anabolic stimuli in older populations.

Plasma amino acid response after ingestion of different whey protein fractions.

BACKGROUND AND OBJECTIVES: The digestion rate of proteins and subsequent absorption of amino acids can independently modulate protein metabolism. The objective of the present study was to examine the blood amino acid response to whey protein isolate (WPI), ß-lactoglobulin-enriched WPI, hydrolysed WPI and a flavour-identical control. METHODS: Eight healthy adults (four female, four male) were recruited (mean±standard error of the mean: age, 27.0±0.76 years; body mass index, 23.2±0.8 kg/cm(2)) and after an overnight fast consumed 500 ml of each drink, each containing 25g protein, in a cross-over design. Blood was taken at rest and then every 15 min for 2 h post ingestion. RESULTS: Ingesting the ß-lactoglobulin-enriched WPI drink resulted in significantly greater plasma leucine concentrations at 45-120 min and significantly greater branched-chain amino acid concentrations at 60-105 min post ingestion compared with hydrolysed WPI. No differences were observed between WPI and ß-lactoglobulin-enriched WPI, and all protein drinks resulted in elevated blood amino acids compared with flavour-identical control. CONCLUSIONS: In conclusion, whole proteins resulted in a more rapid absorption of leucine and branched-chain amino acid into the blood compared with the hydrolysed molecular form of whey protein.

Whey protein ingestion activates mTOR-dependent signalling after resistance exercise in young men: a double-blinded randomized controlled trial.

The effect of resistance exercise with the ingestion of supplementary protein on the activation of the mTOR cascade, in human skeletal muscle has not been fully elucidated. In this study, the impact of a single bout of resistance exercise, immediately followed by a single dose of whey protein isolate (WPI) or placebo supplement, on the activation of mTOR signalling was analyzed. Young untrained men completed a maximal single-legged knee extension exercise bout and were randomized to ingest either WPI supplement (n = 7) or the placebo (n = 7). Muscle biopsies were taken from the vastus lateralis before, and 2, 4 and 24 h post-exercise. WPI or placebo ingestion consumed immediately post-exercise had no impact on the phosphorylation of Akt (Ser473). However, WPI significantly enhanced phosphorylation of mTOR (Ser2448), 4E-BP1 (Thr(37/46)) and p70(S6K) (Thr389) at 2 h post-exercise. This study demonstrates that a single dose of WPI, when consumed in modest quantities, taken immediately after resistance exercise elicits an acute and transient activation of translation initiation within the exercised skeletal muscle.

Exercise-induced activation of STAT3 signaling is increased with age.

Activation of the transcription factor signal transducers and activators of transcription (STAT) 3 is common to many inflammatory cytokines and growth factors, with recent evidence of involvement in skeletal muscle regeneration. The purpose of this study was to determine whether STAT3 signaling activation is regulated differentially, at rest and following intense resistance exercise, in aged human skeletal muscle. Skeletal muscle biopsies were harvested from healthy younger (n = 11, 20.4 +/- 0.8 years) and older men (n = 10, 67.4 +/- 1.3 years) under resting conditions and 2 h after the completion of resistance exercise. No differences were evident at rest, whereas the phosphorylation of STAT3 was significantly increased in old (23-fold) compared to young (5-fold) subjects after exercise. This correlated with significantly higher induction of the STAT3 target genes including; interleukin-6 (IL-6), JUNB, c-MYC, and suppressor of cytokine signaling (SOCS) 3 mRNA in older subjects following exercise. Despite increased SOCS3 mRNA, cellular protein abundance was suppressed. SOCS3 protein is an important negative regulator of STAT3 activation and cytokine signaling. Thus, in aged human muscle, elevated responsiveness of the STAT3 signaling pathway and suppressed SOCS3 protein are evident following resistance exercise. These data suggest that enhanced STAT3 signaling responsiveness to proinflammatory factors may impact on mechanisms of muscle repair and regeneration.

Impaired expression of Notch signaling genes in aged human skeletal muscle.

Notch signaling is essential for myogenesis and the regenerative potential of skeletal muscle; however, its regulation in human muscle is yet to be fully characterized. Increased expression of Notch3, Jagged1, Hes1, and Hes6 gene transcripts were observed during differentiation of cultured human skeletal muscle cells. Furthermore, significantly lower expressions of Notch1, Jagged1, Numb, and Delta-like 1 were evident in muscle biopsies from older men (60-75 years old) compared to muscle from younger men (18-25 years old). Importantly, with supervised resistance exercise training, expression of Notch1 and Hes6 genes were increased and Delta-like 1 and Numb expression were decreased. The differences in Notch expression between the age groups were no longer evident following training. These results provide further evidence to support the role of Notch in the impaired regulation of muscle mass with age and suggest that some of the benefits provided by resistance training may be mediated through the Notch signaling pathway.

STAT3 signaling is activated in human skeletal muscle following acute resistance exercise.

The transcription factor signal transducer and activator of transcription 3 (STAT3) has been identified as a mediator of cytokine signaling and implicated in hypertrophy; however, the importance of this pathway following resistance exercise in human skeletal muscle has not been investigated. In the present study, the phosphorylation and nuclear localization of STAT3, together with STAT3-regulated genes, were measured in the early recovery period following intense resistance exercise. Muscle biopsy samples from healthy subjects (7 males, 23.0 + 0.9 yr) were harvested before and again at 2, 4, and 24 h into recovery following a single bout of maximal leg extension exercise (3 sets, 12 repetitions). Rapid and transient activation of phosphorylated (tyrosine 705) STAT3 was observed at 2 h postexercise. STAT3 phosphorylation paralleled the transient localization of STAT3 to the nucleus, which also peaked at 2 h postexercise. Downstream transcriptional events regulated by STAT3 activation peaked at 2 h postexercise, including early responsive genes c-FOS (800-fold), JUNB (38-fold), and c-MYC (140-fold) at 2 h postexercise. A delayed peak in VEGF (4-fold) was measured 4 h postexercise. Finally, genes associated with modulating STAT3 signaling were also increased following exercise, including the negative regulator SOCS3 (60-fold). Thus, following a single bout of intense resistance exercise, a rapid phosphorylation and nuclear translocation of STAT3 are evident in human skeletal muscle. These data suggest that STAT3 signaling is an important common element and may contribute to the remodeling and adaptation of skeletal muscle following resistance exercise.

Influence of preexercise muscle glycogen content on transcriptional activity of metabolic and myogenic genes in well-trained humans.

To determine whether preexercise muscle glycogen content influences the transcription of several early-response genes involved in the regulation of muscle growth, seven male strength-trained subjects performed one-legged cycling exercise to exhaustion to lower muscle glycogen levels (Low) in one leg compared with the leg with normal muscle glycogen (Norm) and then the following day completed a unilateral bout of resistance training (RT). Muscle biopsies from both legs were taken at rest, immediately after RT, and after 3 h of recovery. Resting glycogen content was higher in the control leg (Norm leg) than in the Low leg (435 +/- 87 vs. 193 +/- 29 mmol/kg dry wt; P < 0.01). RT decreased glycogen content in both legs (P < 0.05), but postexercise values remained significantly higher in the Norm than the Low leg (312 +/- 129 vs. 102 +/- 34 mmol/kg dry wt; P < 0.01). GLUT4 (3-fold; P < 0.01) and glycogenin mRNA abundance (2.5-fold; not significant) were elevated at rest in the Norm leg, but such differences were abolished after exercise. Preexercise mRNA abundance of atrogenes was also higher in the Norm compared with the Low leg [atrogin: approximately 14-fold, P < 0.01; RING (really interesting novel gene) finger: approximately 3-fold, P < 0.05] but decreased for atrogin in Norm following RT (P < 0.05). There were no differences in the mRNA abundance of myogenic regulatory factors and IGF-I in the Norm compared with the Low leg. Our results demonstrate that 1) low muscle glycogen content has variable effects on the basal transcription of select metabolic and myogenic genes at rest, and 2) any differences in basal transcription are completely abolished after a single bout of heavy resistance training. We conclude that commencing resistance exercise with low muscle glycogen does not enhance the activity of genes implicated in promoting hypertrophy.