United Kingdom

Background: Periodic paralysis (PP) is a rare genetic muscle disease caused by mutations in skeletal muscle ion channels and characterised by episodic flaccid paralysis in association with high (HyperPP) or low serum potassium. Around age 40 the severity of attacks reduces or attacks may even stop but permanent progressive weakness develops. The reason for this is not known. This phenotype transition coincides with the age at which muscle mass and optimal motor function start to decline in healthy individuals. We sought to determine if the phenotype transition in PP is linked to the normal ageing phenotype transition and to explore the mechanisms involved. Methods: A mouse model of Hyper PP, known as Draggen (I582V in SCN4A), was compared to wild-type littermates across a range of ages (13-104 weeks). These mice have already been shown to have episodic attacks and develop permanent progressive weakness from middle age. Only male mice were used as penetrance is incomplete in females. We adapted the Muscle Velocity Recovery Cycle technique from humans to examine murine muscle excitability in vivo. We then examined changes in potassium-induced weakness or caffeine contracture force with age using ex vivo muscle tension testing. Muscles were further characterised by either western blot, histology, or energy charge measurement. For normally distributed data a student’s t-test (±Welch correction) or One or Two-way ANOVA was performed to determine significance. For data that was not normally distributed, Welch Rank test, Mann Whitney U test or Kruskal Wallis ANOVA was performed. When an ANOVA was significant (P&lt;0.05) post hoc Tukey testing was used. Conclusions: 1. The phenotype transition with age is replicated in a mouse model of PP. 2. Intrinsic muscle ageing protects against potassium-induced weakness in Draggen mice. However, it also appears to accelerate impairment of sarcoplasmic reticulum calcium release, mitochondrial impairment and the development of core-like regions, suggesting acquired RyR1 dysfunction as the potential aetiology. 3. This work provides a first description of mechanisms involved in phenotype transition with age in PP. It also a demonstrates how studying phenotype transition with age in monogenic disease can yield novel insights into both disease physiology and the ageing process itself.

ISTRC 2021 - International Sarcopenia Translational Research Conference

Ageing Contributes to Phenotype Transition in the Draggen Mouse Model of Periodic Paralysis

channelopathy

aging

sarcopenia

Welcome to the inaugural International Sarcopenia Translational Research Conference.  “Where Worlds Meet” – the event brings together a broad range of researchers and practitioners in a truly interdisciplinary forum, covering discovery science through to clinical practice.

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Background: Periodic paralysis (PP) is a rare genetic muscle disease caused by mutations in skeletal muscle ion channels and characterised by episodic flaccid paralysis in association with high (HyperPP) or low serum potassium. Around age 40 the severity of attacks reduces or attacks may even stop but permanent progressive weakness develops. The reason for this is not known. This phenotype transition coincides with the age at which muscle mass and optimal motor function start to decline in healthy individuals. We sought to determine if the phenotype transition in PP is linked to the normal ageing phenotype transition and to explore the mechanisms involved. Methods: A mouse model of Hyper PP, known as Draggen (I582V in SCN4A), was compared to wild-type littermates across a range of ages (13-104 weeks). These mice have already been shown to have episodic attacks and develop permanent progressive weakness from middle age. Only male mice were used as penetrance is incomplete in females. We adapted the Muscle Velocity Recovery Cycle technique from humans to examine murine muscle excitability in vivo. We then examined changes in potassium-induced weakness or caffeine contracture force with age using ex vivo muscle tension testing. Muscles were further characterised by either western blot, histology, or energy charge measurement. For normally distributed data a student’s t-test (±Welch correction) or One or Two-way ANOVA was performed to determine significance. For data that was not normally distributed, Welch Rank test, Mann Whitney U test or Kruskal Wallis ANOVA was performed. When an ANOVA was significant (P<0.05) post hoc Tukey testing was used. Conclusions: 1. The phenotype transition with age is replicated in a mouse model of PP. 2. Intrinsic muscle ageing protects against potassium-induced weakness in Draggen mice. However, it also appears to accelerate impairment of sarcoplasmic reticulum calcium release, mitochondrial impairment and the development of core-like regions, suggesting acquired RyR1 dysfunction as the potential aetiology. 3. This work provides a first description of mechanisms involved in phenotype transition with age in PP. It also a demonstrates how studying phenotype transition with age in monogenic disease can yield novel insights into both disease physiology and the ageing process itself.

poster

Background: Resistance exercise (RE) is increasingly acknowledged as a primary countermeasure to age related chronic disease and represents an effective strategy for counteracting age-associated declines in muscle strength and physical performance. However, as training induced adaptation is primarily driven by the physiological stress imposed (i.e. the internal training response), eliciting a consistent and standardised training dose is necessary to maximise the potential of RE. Method: Thirty community-dwelling - older adults (71.7 ± 3.6 years; 12 female) naïve to RE, performed 6 weeks of twice weekly, machine-based progressive RE involving a combination of upper- and lower-body exercises (leg press, leg curl, chest press, upright row). RE programming - Participants performed 2-3 sets of 8-10 repetitions for each exercise per session with intensity set at 70% of estimated 1RM in session 1. Load was increased when participants completed the prescribed number of repetitions in the final set while maintaining proper form in two consecutive workouts. Quantification of training response - Internal training response was quantified using ratings of perceived exertion (RPE). Following each RE session, participants provided an overall rating of perceived exertion (sRPE) and differential ratings of perceived exertion for upper-body muscle exertion (sRPE-U) and lower-body muscle exertion (sRPE-L) using the CR100 scale3 . External load was quantified as relative volume load (no. of sets x no. of reps x %1RM). Data were analysed using mixed linear models. Results: Twenty-nine participants completed the intervention with an overall attendance of 97%. Conclusions: RE induced a substantial internal training response. There was no systematic change, but large interindividual variability in response, across the duration of the intervention. These metrics should be validated against objective measures of RE response such as improved muscle function.

Quantifying the internal training response to resistance exercise in older adults: findings from the Milk Intervention Muscle AgeiNg (MIlkMAN) pilot study

Background: Patients with single, large-scale mitochondrial DNA (mtDNA) deletions often present with mitochondrial myopathy for which no treatment is available. Exercise intervention induces beneficial effects in mitochondrial myopathy; however, we do not yet understand the mechanism for this. Aim of the project: This study investigates biochemical, genetic and molecular changes triggered by resistant exercise training to identify exercise modulators on a molecular level in mitochondrial myopathy patients. Material and methods: Pre- and post-exercise vastus lateralis biopsies were taken from a cohort of single, large-scale mtDNA deletion patients (n = 5) after 16 weeks of supervised high-intensity resistant exercise training. Biopsies were assessed for changes in oxidative phosphorylation, mtDNA deletion level, fibre type and size, and differentially expressed (DE) genes (Figure 1). Conclusions: Resistance exercise training was safe and effective for our cohort of single, large-scale mtDNA patients. After exercise: • mitochondrial mass increase correlates with aerobic capability, • complex IV OXPHOS defect ameliorates in all patients, • fibre type I undergo hypertrophy mechanism in 4 patients, • there is differential gene expression. Future investigations of DE genes on SKM tissue with IMC will allow us to characterize their function on a protein level and to highlight potential exercise modulator(s) in mitochondrial myopathy patients.

The effects of resistant exercise training in mitochondrial myopathy patients

Background: Sarcopenia • low muscle quality and quantity • can potentially be represented with psoas muscle area (PMA) Lower PMA associated with adverse outcomes in multiple surgical populations Lower PMA in EVAR population – more conflicting results. Study question: • What are the associations between PMA and mortality in patient’s older than 65 year old with asymptomatic infrarenal AAA undergoing EVAR? • What are the associations between PMA and length of stay, complications, discharge destination and readmissions within 30 days? Methods: Retrospective observational study in single centre tertiary metropolitan hospital Inclusion criteria: Asymptomatic infrarenal AAA from 1/1/13-31/12/17, >65yo Exclusion criteria: Connective tissue disease, mycotic or inflammatory AAA, emergency / non elective cases Primary outcome: Survival from day of operation (in days) Secondary outcomes: 30-day readmissions related to EVAR, Discharge destination (home, residential care, rehabilitation), Complications post surgery (including delirium, infection, post operative bleeding, DVT/PE), Length of stay (days). Results: 122 patients had an EVAR for infrarenal AAA 5 patients excluded as symptomatic 18 patients did not have PMA data (could not find imaging) – no significant differences found between the 2 groups 97 patients in total assessed Characteristics of patients in final analysis as per Table 1. Association found between 5-year mortality and the lowest tertile of PMA, strengthened by adjusting for age, sex and BMI (Figure 1, Table 2) Length of stay appears to be associated with PMA – unlikely clinically significant No significant associations between PMA and complications, discharge destination and readmissions within 30 days – minimal data in other studies to compare to.

Lower Psoas Muscle Area (PMA) is associated with increased mortality after endovascular aneurysm repair in older adults

Background: There is a paucity of cross-sectional research on muscle morphology, function, and functional capability in all age-bands of healthy adults. Therefore, age-related differences in indices of skeletal muscle health across the adult lifespan is unknown. Aim: To evaluate indices of muscle morphology, function and functional capability in a sample of healthy adults aged 18-70yrs. Methods: Study design: Cross sectional study included 274 healthy adults completed the study (mean ± SD: age = 41.9yrs ± 16.1; height = 169.3cm ± 10.2; weight = 72.4kg ± 15.2). Measurements: B mode Ultrasonography and Tensiomyography were used to measure muscle thickness, pennation angle, fascicle length, tissue composition and contractile properties in the vastus lateralis. Measurements of grip strength (handheld dynamometry) and functional capability (1-minute chair rise test) were also undertaken for each participant. Physical activity levels of each participant were recorded (self reported) via the International Physical Activity Questionnaire (short form) to categorise participants physical activity levels as high, moderate or low. Data analysis: Descriptive statistics, correlations, one-way ANOVAs, and multiple regressions were performed (SPSS v25). Results: Descriptive statistics: Age-related characteristics (mean ± standard deviation) per age band are displayed in table 1. Generally indices of skeletal muscle health were lower in the 60-70yr age band compared to the younger age bands. ANOVA and post hoc analysis: Differences in muscle morphology, function and functional capability between the 18-29 age band and the 50-59 and 60- 70 age bands. Physical activity: The mean total MET-min/week (across 7 days) was smaller for the 50-59yr adults (2660.7) compared to the younger groups (18- 29 = 4420.5; 30-39 = 2884.1 and 40-49 = 3232.5). Summary and conclusion: Younger adults (18-29 years) had larger measurements of muscle morphology, strength and functional capability compared to the older adults (60-70 years). Assuming linearity, after 50 years, the difference between decades is equivalent to -0.9% per decade for muscle thickness and strength and -0.5% per decade for muscle architecture. This led to a subsequent difference in functional capability of -1.0% per decade after 50 years of age. Physical activity likely acts to abate detrimental differences in indices of muscle health and maintain functional capacity for activities of daily living. A longitudinal study is required in a sample of healthy female and male adults aged 18-70 years of age to understand the true decline in indices of muscle health due to age.

Age-related characteristics of skeletal muscle health across 18-70 years

Background: Sarcopenia refers to the progressive loss of skeletal muscle mass and function, generally associated with ageing (1). There is growing evidence that sarcopenia is more common in people with cognitive impairment (2). Dementia is the term applied to the clinical syndrome of progressive cognitive decline, negatively impacting on daily function (3). A diagnosis of dementia relies on history taking, examination, and limited investigations, including neuroimaging. A challenging aspect of dementia assessment is that disease severity (assessed on neuropathological features) is not always well correlated with clinical severity (4). Physical frailty may also influence the clinical severity, whereby frailer people are more likely to have a clinical diagnosis of dementia with the same burden of neuropathology as more robust individuals (5). Sarcopenia, representing the physical component of frailty, may provide a clinical tool with which to risk stratify. In terms of sarcopenia evaluation and assessment of skeletal muscle mass and quality, Magnetic Resonance Imaging (MRI) and Computer Tomography (CT) are considered to be gold standards, and Dual-energy X-ray and Bioelectrical impedance analysis are commonly used instruments. However, the clinical evaluation of sarcopenia remains challenging, and a variety of novel tools are being investigated for validity, convenience, and cost-efficiency. Included amongst these are the evaluation of a number of different muscles on CT or MRI, including, recently, the temporalis muscle, as visualised on routine imaging of the brain, as a surrogate marker of sarcopenia evaluation (2). For example, Leitner et al. demonstrated that TMT was associated with Skeletal Muscle Index, suggesting that TMT was reflective of generalised sarcopenia in patients with newly diagnosed brain metastases (6). However, there are currently no studies focussing on patients with memory complaints. Methods: The study cohort comprised of 111 patients attending the memory clinic in 2014. The inclusion criteria were as follows: (a) available coronal MRI of the brain of adequate quality for morphometric assessment, and (b) Frailty Index (FI) data available. FI measures frailty as a ratio between health deficits present in the individual, and the total number of health deficits measured, which is constructed following the guidelines by Rockwood et al (7). Frailty was defined as FI ≥ 0.25, as previously published (7). TMT was analysed on coronal, T1-weighted MR images. The orbital roof and Sylvian fissure were utilised as anatomical landmarks. Measurements were taken perpendicular to the long axis of the muscle. TMT was measured bilaterally, and the average was calculated, resulting in one mean TMT per patient. Shapiro-Wilk test was utilised to assess for normality of distribution of muscle thickness across the cohort. Spearmen correlation test was used to investigate the relationship between TMT and FI. Mann-Whitney U test was utilized to compare distribution of TMT between frail and non-frail patients. Results: Assessment by Shapiro-Wilk test (p = 0.002) suggested a low probability of normal distribution of TMT measures. Spearman correlation test was thus used, and a significant negative correlation of modest magnitude was demonstrated between average TMT and frailty as assessed using FI (rho = -0.24, p = 0.01). Mann-Whitney U test revealed significant difference (Z = -3.341, p = 0.001) in the distribution pattern of average TMT between non-frail (median = 5.7mm, interquartile range = 4.8-6.8) and frail (4.5mm, IQR =4.0-5.6). Together, this supports the hypothesis that increased TMT is associated with decreased frailty in this cohort, and may act as a radiological biomarker of sarcopenia. This is in agreement with previously published studies in other patient groups. This is the first study to examine the use of TMT measurement on coronal MRI in patients with memory complaints; since this is a routine investigation in this cohort, the measurement of TMT may, in future, represent a convenient and fast method by which sarcopenia and frailty can be assessed objectively. Future studies might explore the relationship between TMT and long-term clinical outcomes. Conclusions: The findings of this study support the published literature, and suggest that temporalis muscle thickness, as measured on MRI, may act as a radiological biomarker of sarcopenia in a memory clinic cohort.

Identifying Incidental Biomarkers of Sarcopenia from Routine Imaging in a Memory Clinic Cohort

Background: • Strength and balance training can improve mobility and decrease fall risk in older adults. • But less 5% of older adults, 65 years and older, get enough strength and balance training. • Initiating strength training when protein intake in insufficient can limit gains in muscle strength and cause weight loss. • The biggest challenge is in developing real-world, sustainable models on balance and strength training for older adults with chronic conditions. Methods: • The study is an 8-week, assessor blinded, multisite, stepped wedged, pilot randomized controlled trial. • Participants enrolled in the study received: i. A single one-on-one session with the exercise physiologist; ii. 16 exercise physiologist-led, 1-hour group sessions on balance and functional strength training; iii.2 dietitian-led, 1-hour group sessions on protein intake. • There were 3 urban sites and 1 rural site (Kinnect to Wellness). • We analyzed secondary outcomes using exploratory analyses. Main findings: • The MoveStrong program was feasible in terms of recruitment and adherence. 

Encouraging pre-frail older adults to "MoveStrong": A pilot randomized controlled trial

Background: Visual impairment is common in older adults. The most common causes of age-related visual impairment are presbyopia, cataracts, macular degeneration, and glaucoma, which affect visual acuity. Only two studies have shown that visual impairment can be a predictor of low muscle mass and low muscle strength, indicating a potential correlation between visual impairment and sarcopenia. Methods: Older adults were recruited from the community, and their sarcopenia status was identified using the SARCF questionnaire. Visual acuity was assessed through smartphone-based visual acuity measurement (Smart Optometry) (Figure 1), and values were presented in decimal form. The visual acuity level was categorised into normal visual function (≥0.8), mild visual loss (0.3–0.8), and moderate to severe visual loss (<0.3). Pearson correlation test was performed to measure the association between the SARC-F score and visual acuity. An analysis of variance with a post hoc Bonferroni test was conducted to compare SARC-F scores among different visual acuity levels. This study was approved by the Taipei Medical University Joint Institutional Review Board (N202002009) and registered on clinical.trials.gov (NCT04702828). Results: In total, 100 community-dwelling older adults were recruited. A significant association was noted between SARC-F score and visual acuity (p < 0.001, r = −0.348). Old people with moderate to severe visual loss had significantly higher SARC-F scores relative to those with normal visual function (p = 0.049, 95% confidence interval [CI] = −4.695 to −0.011) and mild vision loss (p = 0.025, 95% CI = −2.379 to −0.117). Conclusions: Sarcopenia is associated with vision loss in older adults. Only when visual acuity reaches a moderate level does it exert a large effect on sarcopenia. This may be due to the reduction of muscle function in visually impaired older adults who restrict themselves from engaging in physical activities. The improvement of visual impairment, such as through prescription glasses or surgical intervention, are required to prevent sarcopenia. Older adults with visual impairment should be advised to undergo sarcopenia assessment.

Sarcopenia and Vision Loss in Community-Dwelling Older Adults

Introduction: 1) Dietary intake and nutritional status is a key factor in the outcomes of older individuals. Changes in dietary habits, and nutritional intake contribute considerably to the progression of frailty and sarcopenia. 2) Robust and highly acceptable home urine collection can provide objective dietary information, with minimal burden and can be used to detect shifts in dietary intake in individuals who may be transitioning into a pre-frail or frail state. Methods: 1) 38 individuals aged over 60, collected three rst morning void spot urine samples over the course of a week, immediately after attending physical capability screening. Dietary intake biomarkers were measured using Liquid Chromatography (LC) Mass Spectrometry (MS). 2) Participants completed urine sampling and physical screening again, after 12-weeks to validate observations made at baseline. Results: Higher concentrations of protein exposure biomarkers were associated with positive outcomes in the various physical capability tests. 1-Methylhistidine (1-MH) and 3- Methylhistidine (3-MH) are both biomakers of poultry and high quality red meat intake, and were signicantly associated with the 5-Chair Stand Test; 1-MH (r = -0.55, P < 0.001), 3-MH (r = -0.38, P = 0.012). Categorisation of grip strength (Low; < 22 Kg in Females and < 32 Kg in Males), showed elevated excretion of the dietary protein biomarker taurine (P = 0.03) and para-Cresol Glucuronide (P = 0.04), which is produced following intestinal catabolism of dietary tyrosine. Conclusions: This pilot study has demonstrated the feasibility of home urine collection in a group of older individuals. On-going studies are using this urine sampling protocol for undernutrition screening in the community and investigating the link between nutritional status and surgical outcomes. 

Biomarkers of dietary intake and their association with physical capability assessments

Introduction: Sarcopenia is defined as the presence of both decreased muscle mass and reduced muscle function. It is highly prevalent amongst the elderly. Current treatment approaches involve exercise and dietary programmes. The RANK-RANKL pathway, a major regulator of bone mass, is inhibited by endogenous osteoprotegerin (OPG) and therapeutic Denosumab. Hypothesis: RANK-RANKL inhibition exerts beneficial effects on muscle mass or function. Study objectives: To determine the effect of OPG on myogenesis and muscle atrophy/hypertrophy in primary myoblasts in vitro. Results: Cytotoxicity of hOPG on primary mouse myoblasts/tubes - MTT was used to measure the cytotoxicity of hOPG on primary mouse myoblasts/tubes - No significant changes in viability were observed in treated proliferating and differentiating myoblasts (data not included here). - OPG treated to myotubes significantly increased their viability. The effect of hOPG on myotube phenotype - MF20 immuno-histochemical staining was used to investigate myotube phenotype when subject to hOPG treatment. - hOPG significantly increased fusion index when treated to differentiating myoblasts for 5 days, and significantly increased, in a dose dependent manner, all phenotype parameters when treated to myotubes. Conclusions: Summary of findings • hOPG (5-20 ng/ml) is not cytotoxic to myoblasts, differentiating myoblasts and myotubes. • hOPG significantly improves the viability of myotubes • Myotube diameter and fusion index is significantly improved when hOPG 5 ng/ml is treated to differentiating myoblasts • hOPG significantly improves myotube phenotype (dose dependent) when treated at late stages of myogenesis • Inhibition of RANKL may influence muscle.

Can RANKL inhibition ameliorate sarcopenia? An in vitro study.

Introduction:
This research explores dietitians’ determinants of
practice in delivering advice on physical activity in older
adults to prevent sarcopenia. Evidence suggests
additional benefits from combined nutrition and exercise
for the prevention of sarcopenia 3,4, however dietitians
are not often considered as providers of advice on
physical activity. Dietitians are in an ideal position to
maximise every opportunity to provide comprehensive,
holistic advice and ultimately reduce the amount of
professionals patients have to engage with 2,5,6,7,8.
Methodology:
Qualitative methodology was chosen to explore indepth attitudes, opinions and perspectives of
participants.
The epistemological approach isinterpretivism, which
believes we understand and interpret the world
through our experiences, including through our social,
cultural, moral, ideological and political understanding.
The ontological position is relativism which believes
that there are multiple socially constructed realities. 
Conclusion:
Physical activity interventions should be included for all
older adults at risk of sarcopenia as an early intervention
for prevention, therefore, dietitians should offer advice on
physical activity as part of the Making Every Contact Count
initiative as a minimum. Role merging and upskilling of
dietitians can improve patient care and optimise services in
line with the NHS Long Term Plan (2019).

Ageing Contributes to Phenotype Transition in the Draggen Mouse Model of Periodic Paralysis

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