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Aging is related to an inevitable loss of muscle mass and strength. The mechanisms behind age-related loss of muscle tissue are not fully understood but may, among other things, be induced by age-related differences in myogenic regulatory factors. Resistance exercise training and deconditioning offers a model to investigate differences in myogenic regulatory factors that may be important for age-related loss of muscle mass and strength. Nine elderly (82 &plusmn, 7 years old) and nine young, healthy persons (22 &plusmn, 2 years old) participated in the study. Exercise consisted of six weeks of resistance training of the quadriceps muscle followed by eight weeks of deconditioning. Muscle biopsy samples before and after training and during the deconditioning period were analyzed for MyoD, myogenin, insulin-like growth-factor I receptor, activin receptor IIB, smad2, porin, and citrate synthase. Muscle strength improved with resistance training by 78% (95.0 &plusmn, 22.0 kg) in the elderly to a similar extent as in the young participants (83.5%, 178.2 &plusmn, 44.2 kg) and returned to baseline in both groups after eight weeks of deconditioning. No difference was seen in expression of muscle regulatory factors between elderly and young in response to exercise training and deconditioning. In conclusion, the capacity to gain muscle strength with resistance exercise training in elderly was not impaired, highlighting this as a potent tool to combat age-related loss of muscle function, possibly due to preserved regulation of myogenic factors in elderly compared with young muscle.

Aim To assess the degree and progression of cardiac involvement in patients with limb-girdle type 2 (LGMD2) and Becker muscular dystrophies (BMD). Methods A follow-up study of 100 LGMD2 (types A–L) and 30 BMD patients assessed by electrocardiogram (ECG) and echocardiography, supplemented by Holter-monitoring at follow-up. Results After a median of 8.9years (range 0.4–13.7), twelve patients had died: LGMD2 (n=10, mean age 61±11years), BMD (n=2, age 43 and 45years). Of the remaining 118 patients, 89 completed follow-up: LGMD2 (n=64, age 48±13years) and BMD (n=25, age 40±13years). In BMD, LVEF decreased from 60% (10–62) to 50% (10–64), p=0.02 corresponding to a one percentage drop annually. Among patients with LGMD2, LVEF decreased significantly in patients with LGMD type 2I (n=28) from 59% (15–72) to 55% (20–61), p=0.03, i.e. a 0.4 percentage drop annually, and LVEF≤50% was associated with increased mortality in this subgroup. In LGMD2E, 3/5 patients (60%) at baseline and 4/5 (80%) at follow-up had LVEF≤50%. ECG abnormalities were non-progressive in BMD and in all subgroups of LGMD2. SVT and NSVT were present in both groups: BMD (3/14 (21%) and (2/14 (14%)), LGMD2 (16/51 (31%) and 8/51 (16%)), respectively, all asymptomatic. Conclusion LVEF decreased significantly in patients with BMD and LGMD2I, and the majority of patients with LGMD2E had left ventricular systolic dysfunction. This study emphasizes the need for tailored regular cardiac assessments according to molecular diagnosis with special focus on BMD and LGMD types 2I and 2E.

Introduction We investigated the effect of high-intensity exercise on plasma creatine kinase (CK) in patients with muscular dystrophies. Methods Fourteen patients with Becker (BMD), facioscapulohumeral (FSHD), or limb-girdle type 2 (LGMD2) muscular dystrophy, and 8 healthy subjects performed 5 cycling tests: an incremental max test, and tests at 65%, 75%, 85%, and 95% of maximal oxygen uptake (VO2max). Heart rate and oxygen consumption were measured during the tests, and plasma CK was measured before, immediately after, and 24 hours after exercise. Results All subjects were able to perform high-intensity exercise at the different levels. In patients with LGMD2 and FSHD, CK normalized 24 hours after exercise compared with the pre-exercise value, whereas those with BMD and healthy controls had elevated CK values 24 hours after exercise. Conclusions The findings suggest that high-intensity exercise is generally well tolerated in patients with LGMD2 and FSHD, whereas those with BMD may be more prone to exercise-induced damage. Muscle Nerve 48: 897–901, 2013

Introduction: In this study we investigated the effect of strength training in patients with limb-girdle muscular dystrophy (LGMD) and Becker muscular dystrophy (BMD). Methods: In 2 studies we compared the effect of low-intensity training (LOIT; n = 8) and high-intensity training (HIT; n = 4) in muscles of the upper and lower extremities. Patients were tested for maximal strength and endurance before and after the training program. Results: LOIT training over 6 months resulted in increased biceps strength and endurance. HIT training increased endurance and strength in wrist flexion and extension and in elbow flexion. One patient discontinued HIT training due to muscle soreness and mildly increased plasma CK levels without strength deterioration. Conclusions: Both LOIT and HIT increased muscle strength and endurance in some of the muscles tested and were well tolerated in most patients. Our findings suggest that supervised resistance training may be considered in the management of patients with LGMD2 and BMD. Muscle Nerve, 2013

Studies in a dystrophinopathy model (the mdx mouse) suggest that exercise training may be deleterious for muscle integrity, but exercise has never been studied in detail in humans with defects of dystrophin. We studied the effect of endurance training on conditioning in patients with the dystrophinopathy, Becker muscular dystrophy (BMD). Eleven patients with BMD and seven matched, healthy subjects cycled 50, 30 min sessions at 65% of their maximal oxygen uptake (VO(2max)) over 12 weeks, and six patients continued cycling for 1 year. VO(2max), muscle biopsies, echocardiography, plasma creatine kinase (CK), lower extremity muscle strength and self-reported questionnaires were evaluated before, after 12 weeks and 1 year of training. Endurance training for 12 weeks, improved VO(2max) by 47 +/- 11% and maximal workload by 80 +/- 19% in patients (P < 0.005). This was significantly higher than in healthy subjects (16 +/- 2% and 17 +/- 2%). CK levels did not increase with training, and number of central nuclei, necrotic fibres and fibres expressing neonatal myosin heavy chain did not change in muscle biopsies. Strength in muscles involved in cycle exercise (knee extension, and dorsi- and plantar-flexion) increased significantly by 13-40%. Cardiac pump function, measured by echocardiography, did not change with training. All improvements and safety markers were maintained after 1 year of training. Endurance training is a safe method to increase exercise performance and daily function in patients with BMD. The findings support an active approach to rehabilitation of patients with BMD.

Objectives The prevalence of limb girdle muscular dystrophy type 2I (LGMD2I) in northern Europe is unknown. We investigated this and the genotype–phenotype relation in LGMD2I. Methods Prospective clinical and molecular screening of 118 Danish patients registered with LGMD was performed to divide patients into LGMD subtypes. Results One hundred three patients fulfilled the clinical criteria for LGMD2. Thirty-eight had LGMD2I (27 homozygous, 11 compound heterozygous for 826C>A), 23 had sarcoglycanopathy, 2 dysferlinopathy, 12 calpainopathy, and 4 Becker muscular dystrophy. The 24 patients with no molecular diagnosis did not harbor fukutin-related protein gene (FKRP) mutations. A clear clinical delineation was found between patients homozygous and compound heterozygous for the 826C>A mutation. Homozygous patients had later debut, milder clinical progression, and less muscle weakness compared with compound heterozygous patients, who were all wheelchair bound by their mid-20s. Impaired cardiac pump function was found in both groups. Interpretation This study reports a different distribution of LGMD subtypes in Denmark than seen in other geographic regions, with a threefold to fourfold higher prevalence of LGMD2I than elsewhere. The findings support a clear clinical delineation between patients homozygous and compound heterozygous for the 826C>A mutation in FKRP. The findings suggest that, in the studied region, screening for the 826C>A mutation will identify all persons with LGMD2I. Ann Neurol 2006;59:808–815

MDMA (3,4 Methylenedioxy-methamphetamine) binds and blocks the presynaptic serotonin reuptake transporters and postsynaptic serotonin 5-HT2A receptors, with highest affinity for the first. Whether 5-HT2A receptor density decreases due to MDMA's direct effect on postsynaptic serotonin receptors is at present not known. This study analyzes whether direct stimulation of the postsynaptic 5-HT2A receptor by MDMA in organotypic hippocampal cultures results in cell death and downregulation of this receptor. Fifty or 100 microM MDMA was added to 1 week old cultures, made of 11 day old rat pups. Fluorojade and immunostaining for MAP2 and 5-HT2A to determine neurodegeneration, and changes in receptor density, respectively, resulted in no significant differences. MDMA's neurotoxicity and regulation of post-synaptic 5-HT2A receptors thus seems to require the presence of intact serotonergic terminals.

Background: Outcome measures for clinical trials in neuromuscular diseases are typically based on physical assessments which are dependent on patient effort, combine the effort of different muscle groups, and may not be sensitive to progression over short trial periods in slow-progressing diseases. We hypothesised that quantitative fat imaging by MRI (Dixon technique) could provide more discriminating quantitative, patient-independent measurements of the progress of muscle fat replacement within individual muscle groups. Objective: To determine whether quantitative fat imaging could measure disease progression in a cohort of limb-girdle muscular dystrophy 2I (LGMD2I) patients over a 12 month period. Methods: 32 adult patients (17 male;15 female) from 4 European tertiary referral centres with the homozygous c.826C.A mutation in the fukutin-related protein gene (FKRP) completed baseline and follow up measurements 12 months later. Quantitative fat imaging was performed and muscle fat fraction change was compared with (i) muscle strength and function assessed using standardized physical tests and (ii) standard T1-weighted MRI graded on a 6 point scale. Results: There was a significant increase in muscle fat fraction in 9 of the 14 muscles analyzed using the quantitative MRI technique from baseline to 12 months follow up. Changes were not seen in the conventional longitudinal physical assessments or in qualitative scoring of the T1w images. Conclusions: Quantitative muscle MRI, using the Dixon technique, could be used as an important longitudinal outcome measure to assess muscle pathology and monitor therapeutic efficacy in patients with LGMD2I.

We investigated the effect of high-intensity exercise on plasma creatine kinase (CK) in patients with muscular dystrophies.Fourteen patients with Becker (BMD), facioscapulohumeral (FSHD), or limb-girdle type 2 (LGMD2) muscular dystrophy, and 8 healthy subjects performed 5 cycling tests: an incremental max test, and tests at 65%, 75%, 85%, and 95% of maximal oxygen uptake (VO2max ). Heart rate and oxygen consumption were measured during the tests, and plasma CK was measured before, immediately after, and 24 hours after exercise.All subjects were able to perform high-intensity exercise at the different levels. In patients with LGMD2 and FSHD, CK normalized 24 hours after exercise compared with the pre-exercise value, whereas those with BMD and healthy controls had elevated CK values 24 hours after exercise.The findings suggest that high-intensity exercise is generally well tolerated in patients with LGMD2 and FSHD, whereas those with BMD may be more prone to exercise-induced damage.

Background Limb girdle muscular dystrophy (LGMD) type 2A is caused by mutations in the CAPN3 gene and complete lack of functional calpain 3 leads to the most severe muscle wasting. Calpain 3 is suggested to be involved in maturation of contractile elements after muscle degeneration. The aim of this study was to investigate how mutations in the four functional domains of calpain 3 affect muscle regeneration. Methods We studied muscle regeneration in 22 patients with LGMD2A with calpain 3 deficiency, in five patients with LGMD2I, with a secondary reduction in calpain 3, and in five patients with Becker muscular dystrophy (BMD) with normal calpain 3 levels. Regeneration was assessed by using the developmental markers neonatal myosin heavy chain (nMHC), vimentin, MyoD and myogenin and counting internally nucleated fibers. Results We found that the recent regeneration as determined by the number of nMHC/vimentin-positive fibers was greatly diminished in severely affected LGMD2A patients compared to similarly affected patients with LGMD2I and BMD. Whorled fibers, a sign of aberrant regeneration, was highly elevated in patients with a complete lack of calpain 3 compared to patients with residual calpain 3. Regeneration is not affected by location of the mutation in the CAPN3 gene. Conclusions Our findings suggest that calpain 3 is needed for the regenerative process probably during sarcomere remodeling as the complete lack of functional calpain 3 leads to the most severe phenotypes.

Background The major fuel for exercising muscle at low exercise intensities is fat. Objective To investigate the role of fat metabolism in McArdle disease (also known as glycogen storage disease type V), an inborn error of muscle glycogenolysis, by manipulating free fatty acid availability for oxidation during exercise. Design Randomized, placebo-controlled, crossover trial. Setting Hospitalized care. Patients Ten patients (8 men and 2 women) with McArdle disease. Interventions Patients cycled at a constant workload corresponding to 70% of their maximum oxygen consumption. In random order and on separate days, patients received nicotinic acid (a known blocker of lipolysis) to decrease the availability of free fatty acids or 20% Intralipid infusion to increase free fatty acid availability during exercise. Results were compared with placebo (isotonic sodium chloride solution infusion) and glucose infusion trials. Main Outcome Measures Exercise tolerance was assessed by heart rate response to exercise during different infusions. Results Free fatty acid levels more than tripled by Intralipid infusion and were halved by nicotinic acid administration. Heart rate was significantly higher during exercise in the Intralipid infusion and nicotinic acid trials compared with the placebo and glucose infusion trials, an effect that was observed before and after the patients had experienced the second wind phenomenon. Conclusions Lipids are an important source of fuel for exercising muscle in McArdle disease, but maximal rates of fat oxidation seem limited and cannot be increased above physiologically normal rates during exercise. This limitation is probably caused by a metabolic bottleneck in the tricarboxylic acid cycle due to impaired glycolytic flux in McArdle disease. Therapies aimed at enhancing fat use in McArdle disease should be combined with interventions targeting expansion of the tricarboxylic acid cycle.

Objective To investigate the extent of cardiac involvement in patients with 1 of the 12 groups of recessively inherited limb-girdle muscular dystrophy type 2 (LGMD2A-L) and Becker muscular dystrophy (BMD). Design Prospective screening. Setting Neuromuscular Clinic and Department of Cardiology at Rigshospitalet. Patients One hundred one patients with LGMD2A-I and BMD and 29 patients with LGMD2 and no molecular diagnosis. Main Outcome Measures Clinical investigation, echocardiography, and electrocardiographic findings. Results Cardiac involvement was present in 24 of 100 patients (24%) with LGMD2A-I and in 14 of 30 patients (47%) with BMD. Only a few patients with LGMD2A and unclassified LGMD2 had mild cardiac involvement, whereas 29% and 67% of patients with LGMD2I and LGMD2E, respectively, had cardiac involvement. Cardiac involvement was not correlated with age, muscle strength, or the level of dystrophic changes on muscle biopsy. Conclusions This study demonstrates a high prevalence of cardiac involvement in patients with LGMD2I, LGMD2E, and BMD. Patients with LGMD2A, LGMD2D, and unclassified LGMD2 have a much lower and milder prevalence of cardiac involvement.

Calpainopathy or limb-girdle muscular dystrophy type 2A (LGMD2A) is generally recognized as the most prevalent form of recessive LGMD and is caused by mutations in the CAPN3 gene. Out of a cohort of 119 patients fulfilling clinical criteria for LGMD2, referred to our neuromuscular clinic, 46 were suspected to have LGMD2A, based on western blot results. Four of these patients were shown to have LGMD2I upon molecular analysis, whereas 16 of the remaining 42 patients harbored mutations in CAPN3 by both direct genomic sequencing and cDNA analyses. In 10 patients, we identified both mutant alleles. In three other, only one heterozygous mutation could be identified on the genomic level; however, CAPN3 cDNA analyses demonstrated homozygosity for the mutant allele, indicating the presence of an unidentified allele that somehow compromise correct CAPN3 RNA processing. In the three remaining patients, only a single heterozygous mutation could be identified both at the genomic level and on full-length CAPN3 cDNA. All three patients exhibited a highly abnormal western blot for calpain-3 and clinical characteristics of LGMD2A. Only three of the genetically confirmed LGMD2A patients were of Danish origin, indicating a five- to sixfold lower prevalence in Denmark compared to other European countries. A total of 16 different CAPN3 mutations were identified, of which 5 were novel. The present study demonstrates the value of cDNA analysis for CAPN3 in LGMD2A patients and indicates that calpainopathy is an uncommon cause of LGMD in the Denmark.

We studied the effect of aerobic training on conditioning in patients with limb-girdle muscular dystrophy type 2I (LGMD2I). Nine patients with LGMD2I cycled fifty 30-minute sessions at 65% of their maximal oxygen uptake over 12 weeks. Training significantly improved work capacity, paralleled by self-reported improvements. Creatine kinase levels did not increase significantly, and muscle morphology was unaffected. Moderate-intensity endurance training is a safe method to increase exercise performance and daily function in patients with LGMD2I.

Udgivelsesdato: 2005-May-10 LGMD type 2I, caused by mutations in the fukutin-related protein, is a common form of LGMD. The phenotype resembles Duchenne/Becker muscular dystrophy. A point mutation, L276I has been found in all patients with LGMD2I studied so far. The authors screened for this mutation in 102 sporadic cases of Duchenne/Becker mutation-negative patients and found 13 patients with LGMD2I.

Patients with Limb girdle muscular dystrophy type 2I (LGMD2I) are characterized by progressive muscle weakness and wasting primarily in the proximal muscles, while distal muscles often are spared. Our aim was to investigate if wasting could be caused by impaired regeneration in the proximal compared to distal muscles. Biopsies were simultaneously obtained from proximal and distal muscles of the same patients with LGMD2I (n = 4) and healthy subjects (n = 4). The level of past muscle regeneration was evaluated by counting internally nucleated fibers and determining actively regenerating fibers by using the developmental markers embryonic myosin heavy chain (eMHC) and neural cell adhesion molecule (NCAM) and also assessing satellite cell activation status by myogenin positivity. Severe muscle histopathology was occasionally observed in the proximal muscles of patients with LGMD2I whereas distal muscles were always relatively spared. No difference was found in the regeneration markers internally nucleated fibers, actively regenerating fibers or activation status of satellite cells between proximal and distal muscles. Protein turnover, both synthesis and breakdown, as well as cellular stress were highly increased in severely affected muscles compared to mildly affected muscles. Our results indicate that alterations in the protein turnover and myostatin levels could progressively impair the muscle mass maintenance and/or regeneration resulting in gradual muscular atrophy.

Patients with limb girdle muscular dystrophy (LGMD2I) are characterized by progressive muscle weakness and wasting primarily in the proximal muscles, while distal muscles often are spared. We are interested in finding out if this is caused by impaired or uneven regeneration in the proximal compared to distal muscles. Biopsies were simultaneously obtained from proximal and distal muscles of the same moderately affected LGMD2I patients (N = 5) and healthy subjects (N = 4). The level of past muscle regeneration was evaluated by counting internally nucleated fibers and determining recent regeneration by using the developmental marker NCAM and embryonic myosin heavy chain (eMHC) as well as myogenin for satellite cell activation status. Markers for protein synthesis Akt/mTOR/p70S6K, for protein breakdown MAFbx and MURF, the negative regulator of muscle mass myostatin, and for cellular stress p90RSK, p38 and JNK were analysed by Western blotting. We found a significant increase in activity of key molecular signaling pathways, specifically myogenesis, protein synthesis and degradation in more severely affected muscles associated with marked atrophy increased degree of muscle histopathology. Level of muscle regeneration was surprisingly comparable in the proximal and distal muscles. Our results indicate that muscle mass maintenance and/or cellular stress negatively affects proximal muscles leading to progressively more muscle wasting in these muscles compared to distal muscles in patients with LGMD2I.

Background The balance between muscle regeneration and ongoing degeneration is a relationship that greatly influences the progression of muscular dystrophy. Numerous factors may influence the muscle regeneration, but more information about the relationship between genotype, clinical severity and the ability to regenerate is needed. Methods Muscle biopsies were obtained from the tibialis anterior muscle, and frozen sections were stained for general histopathological and immunohistological evaluation. Differences between groups were considered statistical significant at P < 0.05 using Student's unpaired t-test. Results We found that all patients with limb-girdle muscular dystrophy type 2I (LGMD2I) had a large number of internally nucleated fibers, a sign of previous regeneration. The level of expression of muscle-specific developmental proteins, such as neonatal myosin heavy chain (nMHC) and myogenin, was related to the clinical severity. Additionally, we found that the majority of nMHC-positive fibers did not stain positively for utrophin in patients who were compound heterozygous for the L276I mutation, suggesting that the predominant form of regeneration in these patients is fiber repair rather than formation of new fibers. Double staining showed that many smaller nMHC-positive fibers were positive for antibodies against the glycosylation on α-dystroglycan, suggesting that such glycosylation may be a result of muscle regeneration. Conclusion Severely affected patients with LGMD2I have a high level of muscle degeneration, which leads to a high rate of regeneration, but this is insufficient to change the imbalance between degeneration and regeneration, ultimately leading to progressive muscle wasting. Detailed information regarding the level and rate of muscle regeneration and potential obstructions of the regenerative pathway should be of use for future therapies involving satellite-cell activation.