An Age-Related Morphometric Profile of Skeletal Muscle in Healthy Untrained Women.

There is a paucity of data on muscle biopsies in females of mixed ages in terms of age-related changes. Cross sections of autopsy material including the quadriceps femoris and biceps brachii muscles were obtained from 23 healthy women, aged 24-82 years, who had suffered sudden death. We calculated the percentage of the number, and the mean diameter, of type I and type II muscle fibers within the fascicles as well as in their peripheral parts. The number of type II fibers were shown to reduce significantly with age (p < 0.005), especially in the fascicle periphery, but the percentage of type 1 fibers did not alter significantly. It was noted that type II fibers diminished in size with age, indicating a relationship between fiber size and age. This result became more apparent in the fascicle periphery (p < 0.05). In women, type II muscle fibers were seen to reduce in size and number with advancing age. We postulate that regular physical activity can increase the size of type II muscle fibers, thus helping to both prevent and treat age-related muscle loss.

Caveolinopathies in Greece.

INTRODUCTION: Mutations in the CAV3 gene are usually inherited in an autosomal dominant manner and lead to distinct disorders including limb-girdle muscular dystrophy 1C, rippling muscle disease, and isolated creatine kinase elevation. PATIENTS AND METHODS: The features of the first patients with caveolin-3 deficiency from Greece are presented. Patients' phenotypes ranged from asymptomatic creatine kinase elevation to severe weakness of lower extremities. Clinical evaluation disclosed muscle hypertrophy in 2 patients, whereas percussion-induced muscle mounding was a consistent finding in all of them. Muscle histopathology was variable and unrelated with disease severity. The diagnosis was based on the immunohistochemical study of caveolin-3 expression and molecular analysis of the caveolin-3 gene. CONCLUSIONS: Clinical manifestations and histochemical findings in caveolinopathy patients may be mild or nonspecific or overlapping with features of other muscular dystrophies. Immunohistochemical study of caveolin-3 expression on muscle biopsy should be routinely performed when investigating isolated hyperCKemia or undetermined myopathy especially in the presence of percussion-induced muscle mounding.

Phenotypic variability and molecular genetics in proximal myotonic myopathy.

INTRODUCTION: Myotonic dystrophy type 2 (DM2) is an autosomal dominant inherited disorder with (CCTG)n repeat expansion in intron 1 of the CNBP gene. METHODS: We studied the first 16 Greek DM2 patients who had undergone thorough evaluation. RESULTS: The age at diagnosis ranged from 38 to 69 years. The initial symptoms were proximal weakness, myalgias, and myotonia. Clinical myotonia was elicited in 10 patients, whereas electromyographic myotonic discharges were observed in almost all patients. Subcapsular cataract was frequently present, but cardiac arrhythmias were rare. CONCLUSIONS: In this study of Greek DM2 patients, proximal weakness was the most common initial symptom. Myalgias were also reported in a few patients, yet myotonia was not a major complaint. Although DM2 is considered relatively benign, there are patients who may be affected severely. Thus, a high index of suspicion must be maintained to make a timely diagnosis, especially in those of reproductive age.

Increased dysferlin expression in Duchenne muscular dystrophy.

OBJECTIVE: To investigate dysferlin expression in muscle biopsies from patients with Duchenne muscular dystrophy (DMD). Dysferlin is known to have a role in the process of membrane fusion and muscle membrane repair in skeletal muscle fibers. STUDY DESIGN: We analyzed 20 muscle biopsy samples of DMD patients with immunohistochemical techniques to determine the expression of dysferlin. Immunoblotting was performed to assess dysferlin abundance in dystrophic muscle. RESULTS: Dysferlin showed various immunostaining patterns in dystrophic muscle, including reduced, normal, or enhanced sarcolemmal expression and intracellular immunostaining of the protein. Immunoblotting revealed that dysferlin was upregulated in 15 out of the 20 samples (75%). The abundance of the protein was analogous to the number of fibers with enhanced sarcolemmal expression of the protein. CONCLUSION: These data suggest that although dysferlin is not an integral part of the dystrophin-glycoprotein complex, its expression is altered in Duchenne muscular dystrophy.

Muscle lim protein isoform negatively regulates striated muscle actin dynamics and differentiation.

Muscle lim protein (MLP) has emerged as a critical regulator of striated muscle physiology and pathophysiology. Mutations in cysteine and glycine-rich protein 3 (CSRP3), the gene encoding MLP, have been directly associated with human cardiomyopathies, whereas aberrant expression patterns are reported in human cardiac and skeletal muscle diseases. Increasing evidence suggests that MLP has an important role in both myogenic differentiation and myocyte cytoarchitecture, although the full spectrum of its intracellular roles has not been delineated. We report the discovery of an alternative splice variant of MLP, designated as MLP-b, showing distinct expression in neuromuscular disease and direct roles in actin dynamics and muscle differentiation. This novel isoform originates by alternative splicing of exons 3 and 4. At the protein level, it contains the N-terminus first half LIM domain of MLP and a unique sequence of 22 amino acids. Physiologically, it is expressed during early differentiation, whereas its overexpression reduces C2C12 differentiation and myotube formation. This may be mediated through its inhibition of MLP/cofilin-2-mediated F-actin dynamics. In differentiated striated muscles, MLP-b localizes to the sarcomeres and binds directly to Z-disc components, including α-actinin, T-cap and MLP. The findings of the present study unveil a novel player in muscle physiology and pathophysiology that is implicated in myogenesis as a negative regulator of myotube formation, as well as in differentiated striated muscles as a contributor to sarcomeric integrity.

Effects of Strength vs. Ballistic-Power Training on Throwing Performance.

The purpose of the present study was to investigate the effects of 6 weeks strength vs. ballistic-power (Power) training on shot put throwing performance in novice throwers. Seventeen novice male shot-put throwers were divided into Strength (N = 9) and Power (n = 8) groups. The following measurements were performed before and after the training period: shot put throws, jumping performance (CMJ), Wingate anaerobic performance, 1RM strength, ballistic throws and evaluation of architectural and morphological characteristics of vastus lateralis. Throwing performance increased significantly but similarly after Strength and Power training (7.0-13.5% vs. 6.0-11.5%, respectively). Muscular strength in leg press increased more after Strength than after Power training (43% vs. 21%, respectively), while Power training induced an 8.5% increase in CMJ performance and 9.0 - 25.8% in ballistic throws. Peak power during the Wingate test increased similarly after Strength and Power training. Muscle thickness increased only after Strength training (10%, p < 0.05). Muscle fibre Cross Sectional Area (fCSA) increased in all fibre types after Strength training by 19-26% (p < 0.05), while only type IIx fibres hypertrophied significantly after Power training. Type IIx fibres (%) decreased after Strength but not after Power training. These results suggest that shot put throwing performance can be increased similarly after six weeks of either strength or ballistic power training in novice throwers, but with dissimilar muscular adaptations. Key pointsBallistic-power training with 30% of 1RM is equally effective in increasing shot put performance as strength training, in novice throwers, during a short training cycle of six weeks.In novice shot putters with relatively low initial muscle strength/mass, short-term strength training might be more important since it can increase both muscle strength and shot put performance.The ballistic type of power training resulted in a significant increase of the mass of type IIx muscle fibres and no change in their proportion. Thus, this type of training might be used effectively during the last weeks before competition, when the strength training load is usually reduced, in order to increase muscle power and shot put performance in novice shot putters.

OX40-OX40L expression in idiopathic inflammatory myopathies.

OBJECTIVE: To examine whether both OX40 and its ligand OX40L are expressed in idiopathic inflammatory myopathies and to investigate the types of inflammatory cells expressing OX40L. STUDY DESIGN: Immunohistochemistry was performed in limb muscle specimens from dermatomyositis, polymyositis and inclusion body myositis patients to analyze the expression of OX40 and its ligand OX40L. Double immunofluorescence labeling was performed to clarify the phenotype of inflammatory cells expressing OX40L. RESULTS: OX40 and OX40L expressing cells were observed in all subsets of inflammatory myopathies following a similar pattern of distribution mainly in the perimysium. In polymyositis and inclusion body myositis inflammatory cells expressing the receptors invaded non-necrotic muscle fibers. OX40L expression was also found in endothelial blood cells in all dermatomyositis and some polymyositis specimens. In all subsets of inflammatory myopathies OX40L was expressed by T cells (CD4+ and CD8+), macrophages (CD68+), B cells (CD20+) and myeloid dendritic cells (BDCA1+). Plasmacytoid dendritic cells (BDCA2+) expressing OX40L were found only in dermatomyositis and polymyositis. CONCLUSION: The simultaneous expression of both OX40 and its ligand OX40L in idiopathic inflammatory myopathies suggests that they might participate in disease pathogenesis. Expression of OX40L by different types of cells within the inflamed muscle implies that OX40-OX40L interaction may contribute in disease mechanisms through different pathways.

Effects of exercise training during infusion on late-onset Pompe disease patients receiving enzyme replacement therapy.

Pompe disease is an autosomal recessive disorder caused by the deficiency of acid α-glucosidase resulting in lysosomal accumulation of glycogen and abnormal autophagic function. The late-onset form of the disease is characterized by progressive skeletal and respiratory muscle dysfunction. Enzyme replacement therapy (ERT, Genzyme Corporation, Cambridge, MA, USA) was recently introduced and resulted in significant prolongation of the life expectancy of the patients with the infantile form while the results were less significant for the late-onset form. It has been postulated that the weak influence of ERT in late-onset patients might be due to a non-effective delivery of the recombinant enzyme to the skeletal muscles perhaps due to the relatively low blood flow to the resting skeletal muscles during infusion. Exercise training acutely increases the blood flow to the exercising muscles. Thus, it was hypothesized that exercise training during enzyme infusion might increase the effectiveness of the ERT therapy. Five late-onset Pompe disease patients receiving ERT and following regular exercise training for approximately 10 months, followed a 6-month period of exercise training during infusion of the recombinant enzyme. Before and after this period, body composition, isometric strength and 6 minute walking distance were determined. Analysis of the results revealed that none of these parameters changed significantly after the 6-month intervention period (e.g. 6 minute walking distance before: 532±31 m, vs. after: 527±29 m, P=0.246). These results suggest that exercise training during infusion may not add significant functional changes in late-onset Pompe patients receiving ERT and undergoing regular exercise training.

Delayed contrast enhancement on cardiac MRI unmasks subclinical cardiomyopathy in a case of myotonic dystrophy type 2.

Current evidence suggests cardiac involvement and electrocardiographic changes of increasing frequency with age in patients with myotonic dystrophy type 2 (DM2). Myocyte hypertrophy with concurrent fibrosis seems to be the anatomical correlate. Moreover, morphological and functional changes indicative of subclinical cardiomyopathy have been demonstrated by means of cardiac magnetic resonance imaging (CMRI) and spectroscopy in patients with no overt cardiac disease. We present a 68-year-old woman with genetically established DM2 and no clinical, electrocardiographic or echocardiographic signs indicative of cardiac involvement. CMRI revealed delayed contrast enhancement of the anterior portion of the interventricular septum, indicating myocardial involvement. Contrast-enhanced CMRI might be a useful diagnostic tool in assessing cardiac involvement in cases of DM2. The role of delayed contrast enhancement should be further investigated in order to elucidate the cardiac features of this fascinating multisystem disease.

Bone density in patients with late onset Pompe disease.

BACKGROUND: Pompe disease is an inherited metabolic disorder characterized by α-glycosidase deficiency, which leads to lysosomal glycogen accumulation in many different tissues. The infantile form is the most severe with a rapidly fatal outcome, while the late onset form has a greater phenotypic variability, characterized by skeletal muscle dysfunction and early respiratory involvement. Bone mineral density (BMD) has been recently reported to be reduced in many patients with both forms of the disease. Enzyme replacement therapy (ERT) is now available with an undefined, impact on BMD in patients with late onset disease. OBJECTIVES: The present study aimed to investigate BMD in patients with late onset form of Pompe disease before and after ERT initiation. PATIENTS AND METHODS: Dual x-ray absorptiometry (DEXA) was examined in four newly diagnosed patients with late onset Pompe disease and in four adults under ERT before and after ERT initiation with a treatment duration of 18 to 36 months. RESULTS: The initial DEXA showed normal total body BMD z-score in all the patients, while L2-L4 and femoral neck BMD was reduced in three and two patients, respectively. After ERT administration, two patients had an improvement in L2-L4 lumbar spine and one patient in femoral neck BMD z-score with values within normal range. CONCLUSIONS: The results suggested that regional BMD may moderately reduce in some patients with the late onset form of Pompe disease, although profound osteopenia was not observed. The improvement of measurements in L2-L4 and femoral neck BMD z-score in some patients with low pre-treatment values after ERT administration needs to be confirmed in larger scale studies.

Effect of aerobic and resistance exercise training on late-onset Pompe disease patients receiving enzyme replacement therapy.

Pompe disease is a rare autosomal recessive disorder characterized by the deficiency of acid α-glycosidase resulting in lysosomal accumulation of glycogen. The late-onset disease form is characterized by progressive skeletal and respiratory muscle dysfunction. In addition to the recently introduced enzyme replacement therapy (ERT), treatments such as protein-enriched diet and exercise training have been proposed, although little is known about their effectiveness on the physical condition of such patients. Aim of the present study was to investigate the effect of exercise training on muscular strength and body composition in five patients with late-onset Pompe disease receiving ERT. All subjects followed a 20 week lasting program of supervised aerobic and progressive resistance exercise training. Before and after the training period, body composition was determined with dual X-ray absorptiometry and isometric muscular strength was measured with a specialized load transducer. Functional capacity was assessed using the 6-min shuttle walk test. A significant increase in muscular strength (15-50% at various body parts, p<0.05) and 6-minute walking distance (203.8 ± 177 m before vs. 248.2 ± 184 m after, p<0.01) was observed after training, whereas total and lower extremities lean body mass did not change significantly. These results suggest that exercise training has a positive effect on muscular strength and functional capacity in patients on ERT with late-onset Pompe disease.

Effect of pulmonary rehabilitation on peripheral muscle fiber remodeling in patients with COPD in GOLD stages II to IV.

BACKGROUND: In most patients with COPD, rehabilitative exercise training partially reverses the morphologic and structural abnormalities of peripheral muscle fibers. However, whether the degree of improvement in muscle fiber morphology and typology with exercise training varies depending on disease severity remains unknown. METHODS: Forty-six clinically stable patients with COPD classified by GOLD (Global Initiative for Obstructive Lung Disease) as stage II (n = 14), III (n = 18), and IV (n = 14) completed a 10-week comprehensive pulmonary rehabilitation program consisting of high-intensity exercise three times weekly. RESULTS: At baseline, muscle fiber mean cross-sectional area and capillary density did not significantly differ between patients with COPD and healthy control subjects, whereas muscle fiber type I and II proportion was respectively lower (P < .001) and higher (P < .002) in patients with GOLD stage IV compared with healthy subjects and patients with GOLD stages II and III. Exercise training improved, to a comparable degree, functional capacity and the St. George Respiratory Questionnaire health-related quality of life score across all three GOLD stages. Vastus lateralis muscle fiber mean cross-sectional area was increased (P < .001) in all patient groups (stage II: from 4,507 ± 280 µm² to 5,091 ± 271 µm² [14% ± 3%]; stage III: from 3,753 ± 258 µm² to 4,212 ± 268 µm² [14% ± 3%]; stage IV: from 3,961 ± 266 µm² to 4,551 ± 262 µm² [17% ± 5%]), whereas all groups exhibited a comparable reduction (P < .001) in type IIb fiber proportion (stage II: by 6% ± 2%; stage III: by 6% ± 1%; stage IV: by 7% ± 1%) and an increase (P < .001) in capillary to fiber ratio (stage II: from 1.48 ± 0.10 to 1.81 ± 0.10 [23% ± 5%]; stage III: from 1.29 ± 0.06 to 1.56 ± 0.09 [21% ± 5%]; stage IV: from 1.43 ± 0.10 to 1.71 ± 0.13 [18 ± 3%]). The magnitude of changes in the aforementioned variables did not differ across GOLD stages. CONCLUSIONS: Functional capacity and morphologic and typologic adaptations to rehabilitation in peripheral muscle fibers were similar across GOLD stages II to IV. Pulmonary rehabilitation should be implemented in patients at all COPD stages.

The degree of p70 S6k and S6 phosphorylation in human skeletal muscle in response to resistance exercise depends on the training volume.

Regular performance of resistance exercise induces an increase in skeletal muscle mass, however, the molecular mechanisms underlying this effect are not yet fully understood. The purpose of the present investigation was to examine acute changes in molecular signalling in response to resistance exercise involving different training volumes. Eight untrained male subjects carried out one, three and five sets of 6 repetition maximum (RM) in leg press exercise in a random order. Muscle biopsies were taken from the vastus lateralis both prior to and 30 min after each training session and the effect on protein signalling was studied. Phosphorylation of Akt was not altered significantly after any of the training protocols, whereas that of the mammalian target of rapamycin was enhanced to a similar extent by training at all three volumes. The phosphorylation of p70S6 kinase (p70(S6k)) was elevated threefold after 3 × 6 RM and sixfold after 5 × 6 RM, while the phosphorylation of S6 was increased 30- and 55-fold following the 3 × 6 RM and 5 × 6 RM exercises, respectively. Moreover, the level of the phosphorylated form of the gamma isoform of p38 MAPK was enhanced three to fourfold following each of the three protocols, whereas phosphorylation of ERK1/2 was unchanged 30 min following exercise. These findings indicate that when exercise is performed in a fasted state, the increase in phosphorylation of signalling molecules such as p70(S6k) and the S6 ribosomal protein in human muscle depends on the exercise volume.

Toward understanding cognitive impairment in patients with myotonic dystrophy type 1.

Cognitive dysfunction and sleep disruption are two frequent but underestimated features of adult onset myotonic dystrophy type 1 (MD1). In order to investigate the MD1 cognitive profile and its relationship with sleep disruption, 23 patients with genetically proved MD1 (mild-moderate in severity) underwent neuropsychological (nps) and polysomnography assessment. Patients scored lower than controls on almost all nps tests but cognitive impairments were mostly observed in executive functions (z-score = -2.14), with complex attention (z-score = -1.04), memory (z-score = -0.65), constructions (z-score = -1.29), and reasoning (z-score = -0.75) being slightly affected. Moderate-severe sleep apnea (apnea-hypopnea index [AHI] > or =15) was very frequent with most of the apneas being of the obstructive type. However, we found hardly any evidence of association between subjective, objective sleep parameters, and nps performance (p > .001). Thus, in our cohort of 23 adult MD1 patients, mild cognitive dysfunction, which is mostly related to the dysfunction of frontal association cortex and its underlying neural networks, does not seem to be significantly influenced by sleep disruption, which is mainly caused by obstructive apnea events.

Muscle fibre type composition and body composition in hammer throwers.

Aim of the present study was to describe the muscle fibre type composition and body composition of well-trained hammer throwers. Six experienced hammer throwers underwent the following measurements: one repetition maximum in squat, snatch, and clean, standing broad jump, backward overhead shot throw and the hammer throw. Dual x-ray absorptiometry was used for body composition analysis. Fibre type composition and cross sectional area was determined in muscle biopsy samples of the right vastus lateralis. Eight physical education students served as a control group. One repetition maximum in squat, snatch and clean for the hammer throwers was 245 ± 21, 132 ± 13 and 165 ± 12kg, respectively. Lean body mass was higher in hammer throwers (85.9 ± 3. 9kg vs. 62.7 ± 5.1kg (p < 0.01). The percentage area of type II muscle fibres was 66.1 ± 4% in hammer throwers and 51 ± 8% in the control group (p < 0.05). Hammer throwers had significantly larger type IIA fibres (7703 ± 1171 vs. 5676 ± 1270µm(2), p < 0.01). Hammer throwing performance correlated significantly with lean body mass (r = 0.81, p < 0.05). These data indicate that hammer throwers have larger lean body mass and larger muscular areas occupied by type II fibres, compared with relatively untrained subjects. Moreover, it seems that the enlarged muscle mass of the hammer throwers contributes significantly to the hammer throwing performance. Key pointsWell-trained hammer throwers had increased lean body mass, higher type IIA muscle fibres cross sectional areas, as well as higher bone mineral density, compared to controls.Increased lean body mass was closely related with hammer throwing performance.The relative high percentage of type IIX muscle fibres in vastus lateralis in hammer throwers warrants further investigation.

Coinheritance of Noonan syndrome and Becker muscular dystrophy.

We describe for the first time a case of a 9-year old boy with co-existence of dystrophinopathy and Noonan syndrome (NS). Although the patient has a severe muscular clinical phenotype, consistent with Duchenne muscular dystrophy (DMD), the diagnosis of Becker muscular dystrophy (BMD) was proposed based on family history (brother with BMD) and confirmed by muscle immunohistochemistry, and molecular study shown an in-frame DMD gene mutation. The patient also fulfilled the clinical criteria of NS and he harbors a hotspot mutation on PTPN11 gene. This genetic combination may be an explanation for the variability of clinical expression in the family.