Exercise Intolerance in Facioscapulohumeral Muscular Dystrophy

Analysis of Body Fluid Distribution, Phase Angle and Its Association With Maximal Oxygen Consumption in Facioscapulohumeral Dystrophy: An Observational Study

Background and Aims

Body composition parameters associated with aerobic fitness, mirrored by maximal oxygen consumption (V̇O2max), have recently gained interest as indicators of physical efficiency in facioscapulohumeral dystrophy (FSHD). Bioimpedance analysis (BIA) allows a noninvasive and repeatable estimate of body composition but is based on the use of predictive equations which, if used in cohorts with different characteristics from those for which the equation was originally formulated, could give biased results. Instead, the phase angle (PhA), a BIA raw bioelectrical parameter reflecting body fluids distribution, could provide reliable data for such analysis.

Methods

33 clinically and genetically characterized FSHD patients (mean age 35.7; 10 females) and 27 sex and age-matched healthy controls (HC) were included in the analysis. BIA was used to evaluate body fluids distribution (intracellular water [ICW], extracellular water [ECW], and total body water [TBW]), and PhA, while cardiopulmonary exercise test was used to estimate V̇O2max.

Results

The groups were comparable for ECW and TBW. Instead, patients showed lower values of ICW (p = 0.020), ICW/ECW ratio (p < 0.001), and PhA (p < 0.001). Moreover, patients reported lower V̇O2max (p = 0.001 for absolute values; p = 0.002 for values expressed in relation to body weight) which, unlike HC, was not associated to PhA.

Conclusion

Based on our results, PhA of FSHD patients is lower than HC. Since PhA mirrors the ICW/ECW ratio, the lower share of ICW seems to be the basis of such difference. Given the lack of association with V̇O2max, PhA cannot be considered a reliable indicator of aerobic fitness in FSHD.

Bioimpedance analysis of fat free mass and its subcomponents and relative associations with maximal oxygen consumption in facioscapulohumeral dystrophy

PURPOSE

Fat free mass (FFM) is considered the metabolically active component of human body and is positively associated with maximal oxygen uptake (VO 2 max ). However, FFM is composed of metabolically active and inactive subcomponents whose proportion can vary depending on body composition and clinical condition, possibly affecting such association. Although it is known that in facioscapulohumeral dystrophy (FSHD) peculiar changes in body composition occur, it is unclear whether there are alterations in FFM composition and, if so, whether such alterations affect the association towardsVO 2 max compared to healthy subjects (HS).

METHODS

To address this issue, 27 FSHD patients (mean age 37.3; 9 female) and 27 sex and age matched HS, underwent an assessment ofVO 2 max by cardiopulmonary exercise tests (CPET) and body composition, with reference to FFM and its subcomponents, by bioimpedance analysis.

RESULTS

In between-groups comparison, patients showed lower amounts of body cell mass (BCM) and intracellular water (ICW) which reflect in lower BCM/FFM ratio and higher extracellular to intracellular water ratio (ECW/ICW). Patients'VO 2 max was lower than HS and, even if with lower associative values than HS, correlated with FFM and BCM, while BCM/FFM and ECW/ICW ratios associations were observed only in HS.

CONCLUSION

FSHD patients showed lower amount of BCM and ICW. BCM resulted as the parameter with the highest associative value with VO2max in both groups. SinceVO 2 max is associated with functional ability in dystrophic patients, BCM, rather than FFM, could be an additional body composition-based clinical stratification factor.

Maximal Oxygen Consumption Is Negatively Associated with Fat Mass in Facioscapulohumeral Dystrophy

Facioscapulohumeral dystrophy (FSHD) leads to progressive changes in body composition such as loss of muscle mass and increase in adiposity. In healthy subjects, anthropometric parameters are associated with the maximum volume of oxygen consumed per minute (VO2max), which is a health and function indicator in several populations of subjects, both healthy and pathological. Since VO2max can be difficult to test in patients with FSHD due to exercise intolerance, the identification of associated anthropometric parameters could provide new easily obtainable elements for the patients' clinical stratification. The aim of this study was to evaluate whether anthropometric and body composition parameters are associated with VO2max in patients with FSHD. A total of 22 subjects with a molecular genetics-based diagnosis of FSHD (6 females, 16 males, mean age of 35.18 years) were recruited for the study. VO2max was measured by cardiopulmonary exercise tests (CPETs) on a cycle ergometer, utilizing a step incremental technique (15 Watts (W) every 30 s). Weight (Kg) and height (m) were obtained and utilized to calculate body mass index (BMI). Body composition parameters (fat mass (FM), fat free mass (FFM), and body cell mass (BCM)) were obtained by bioelectrical impedance analysis (BIA). Significant negative associations were found between VO2max and FM (Spearman correlation coefficient (SCC) -0.712), BMI (SCC -0.673), age (SCC -0.480), and weight (SCC -0.634), unlike FFM and BCM. Our results indicate that FM, BMI, age, and body weight are negatively associated with VO2max in patients with FSHD. This evidence may help practitioners to better stratify patients with FSHD.

The facioscapulohumeral muscular dystrophy - health index: Italian validation of a disease-specific measure of symptomatic burden

PURPOSE

The aim of this study was to adapt the Facioscapulohumeral Muscular Dystrophy - Health Index (FSHD-HI) to an Italian population affected by FSHD by translating, validating, and testing this instrument in an Italian cohort.

MATERIALS AND METHODS

Italian FSHD patients were interviewed regarding the form and content of the translated instrument. Subsequently, forty FSHD patients were recruited to test the reliability (Intraclass Correlation Coefficient, ICC for test-retest; and Cronbach's Alpha for Internal consistency), known groups (Mann-Whitney U test and Area Under the Curve, AUC) and concurrent validity (Pearson's and Spearman's Rank Correlation Coefficient) of the instrument by serially completing the FSHD-HI and an extensive set of tests measuring the neuromotor, psychological and cognitive functions, and perceived quality of life (QoL) aspects.

RESULTS

The Italian translation of the FSHD-HI and its subscales were highly relevant to patients, had a high internal consistency (Cronbach's Alpha = 0.90), optimal test-retest reliability (ICC= 0.95), and was significantly associated with motor function, respiratory function, and QoL assessments.

CONCLUSIONS

Overall, the Italian FSHD-HI is a valid and well-suited measurement of the multi-dimensional aspects of disease burden in FSHD patients.

Fitness and walking outcomes following aerobic and lower extremity strength training in facioscapulohumeral dystrophy: a case series

Facioscapulohumeral muscular dystrophy (FSHD) is a common form of adult muscular dystrophy often resulting also in cardiorespiratory deconditioning and weakness of the lower limbs. Although previous studies examined outcomes of interventions aimed at improving either cardiorespiratory fitness or muscle strength, the potential benefits of a rehabilitation program targeting both remain unexplored. Thus, the aim of this study was to evaluate changes following participation in a rehabilitation program combining aerobic and strength exercises. We conducted a retrospective analysis of 10 subjects with FSHD who participated in our rehabilitation program during 2018 and 2019. Each of the 20 sessions consisted of aerobic training on a cycloergometer and a moderate lower limb strength exercises on an isokinetic machine in combination with conventional therapy. The primary outcomes were walking speed, aerobic performance and isokinetic strength of the knee extensors and flexors. The secondary outcomes were fatigue, insomnia. VO2max and walking speed increased significantly by 2.125 ml·kg-1·min-1 [95% confidence interval (CI): 0.75-3.62, P = 0.022] and 0.28 m/s (95% CI: 0.16-0.4, P = 0.002), respectively. The effect size was small for V02max (Hedge's g, 0.44; 95% CI: -0.5 to 1.37) and large for walking speed (Hedge's g, 0.99; 95% CI: 0.06-1.92). The knee flexor strength significantly increased at rehabilitation discharge (repeated measures analysis of variance P = 0.004). Positive changes in fatigue and insomnia were also observed. Our preliminary results provide evidence that a relatively short course of a comprehensive rehabilitation program targeting both cardiorespiratory fitness and knee muscle strength can be beneficial for people with FSHD, which warrants further prospective studies.

Voluntary wheel running improves molecular and functional deficits in a murine model of facioscapulohumeral muscular dystrophy

Endurance exercise training is beneficial for skeletal muscle health, but it is unclear if this type of exercise can target or correct the molecular mechanisms of facioscapulohumeral muscular dystrophy (FSHD). Using the FLExDUX4 murine model of FSHD characterized by chronic, low levels of pathological double homeobox protein 4 (DUX4) gene expression, we show that 6 weeks of voluntary, free wheel running improves running performance, strength, mitochondrial function, and sarcolemmal repair capacity, while slowing/reversing skeletal muscle fibrosis. These improvements are associated with restored transcriptional activity of gene networks/pathways regulating actin cytoskeletal signaling, vascular remodeling, inflammation, fibrosis, and muscle mass toward wild-type (WT) levels. However, FLExDUX4 mice exhibit blunted increases in mitochondrial content with training and persistent transcriptional overactivation of hypoxia, inflammatory, angiogenic, and cytoskeletal pathways. These results identify exercise-responsive and non-responsive molecular pathways in FSHD, while providing support for the use of endurance-type exercise as a non-invasive treatment option.

The Facioscapulohumeral Muscular Dystrophy-Health Index: Development and evaluation of a disease-specific outcome measure

INTRODUCTION/AIMS

As promising therapeutic interventions are tested among patients with facioscapulohumeral muscular dystrophy (FSHD), there is a clear need for valid and reliable outcome tools to track disease progression and therapeutic gain in clinical trials and for clinical monitoring. Our aim was to develop and validate the Facioscapulohumeral Muscular Dystrophy-Health Index (FSHD-HI) as a multifaceted patient-reported outcome measure (PRO) designed to measure disease burden in adults with FSHD.

METHODS

Through initial interviews with 20 individuals and a national cross-sectional study with 328 individuals with FSHD, we identified the most prevalent and impactful symptoms in FSHD. The most relevant symptoms were included in the FSHD-HI. We used patient interviews, test-retest reliability evaluation, known groups validity testing, and factor analysis to evaluate and optimize the FSHD-HI.

RESULTS

The FSHD-HI contains 14 subscales that measure FSHD disease burden from the patient's perspective. Fourteen adults with FSHD participated in semistructured beta interviews and found the FSHD-HI to be clear, usable, and relevant to them. Thirty-two adults with FSHD participated in test-retest reliability assessments, which demonstrated the high reliability of the FSHD-HI total score (intraclass correlation coefficient = 0.924). The final FSHD-HI and its subscales also demonstrated a high internal consistency (Cronbach α = 0.988).

DISCUSSION

The FSHD-HI provides researchers and clinicians with a reliable and valid mechanism to measure multifaceted disease burden in patients with FSHD. The FSHD-HI may facilitate quantification of therapeutic effectiveness, as demonstrated by its use as a secondary and exploratory measure in several clinical trials.

Baroreflex sensitivity in facioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy (FSHD), a common form of muscular dystrophy, is caused by a genetic mutation that alters DUX4 gene expression. This mutation contributes to significant skeletal muscle loss. Although it is suggested that cardiac muscle may be spared, people with FSHD have demonstrated autonomic dysregulation. It is unknown if baroreflex function, an important regulator of blood pressure (BP), is impaired in people with FSHD. We examined if baroreflex sensitivity (BRS) is blunted in patients with FSHD. Thirty minutes of resting BP, heart rate, and cardiovagal BRS were measured in 13 patients with FSHD (age: 50 ± 13 years, avg ± SD) and 17 sex- and age-matched controls (age: 47 ± 14 years, p > 0.05). People with FSHD were less active (Activity Metabolic Index, AMI) (FSHD: 24 ± 30; controls: 222 ± 175 kcal/day; p < 0.001) but had a similar body mass index compared with controls (FSHD: 27 ± 4; controls: 27 ± 4 kg/m2 ; p > 0.05). BRSup (hypertensive response), BRSdown (hypotensive response), and total BRS were similar between groups (BRSup: FSHD: 12 ± 8; controls: 12 ± 5 ms/mmHg; BRSdown: FSHD: 10 ± 4; controls: 13 ± 6 ms/mmHg; BRS: FSHD: 14 ± 9; controls: 13 ± 6 ms/mmHg; p > 0.05). Mean arterial pressure was similar between groups (FSHD: 96 ± 7; controls: 91 ± 6mmHg). Individuals with FSHD had an elevated heart rate compared with controls (FSHD: 65 ± 8; controls: 59 ± 8 BPM; p = 0.03), but when co-varied for AMI, this relationship disappeared (p = 0.39). These findings suggest that BRS is not attenuated in people with FSHD, but an elevated heart rate may be due to low physical activity levels, a potential consequence of limited mobility.