Muscle regeneration in mitochondrial myopathies.

Mitochondrial myopathies cover a diverse group of disorders in which ragged red and COX-negative fibers are common findings on muscle morphology. In contrast, muscle degeneration and regeneration, typically found in muscular dystrophies, are not considered characteristic features of mitochondrial myopathies. We investigated regeneration in muscle biopsies from 61 genetically well-defined patients affected by mitochondrial myopathy. Our results show that the perturbed energy metabolism in mitochondrial myopathies causes ongoing muscle regeneration in a majority of patients, and some were even affected by a dystrophic morphology. The results add to the complexity of the pathogenesis underlying mitochondrial myopathies, and expand the knowledge about the impact of energy deficiency on another aspect of muscle structure and function.

Short- and long-term effects of endurance training in patients with mitochondrial myopathy.

BACKGROUND AND PURPOSE: It is unknown whether prolonged training is a safe treatment to alleviate exercise intolerance in patients with mitochondrial DNA (mtDNA) mutations. METHODS: The effect of 3 and 12 months training and 3-12 months deconditioning was studied in four patients carrying different mtDNA mutations. RESULTS: Three-month moderate-intensity training increased oxidative capacity by 23%, which was sustained after 6-12 months of low-intensity training. Training and deconditioning did not induce adverse effects on clinical symptoms, muscle morphology and mtDNA mutation load in muscle. CONCLUSION: Long-term training effectively improves exercise capacity in patients with mitochondrial myopathy, and appears to be safe.

Fat metabolism during exercise in patients with McArdle disease.

OBJECTIVE: It is known that muscle phosphorylase deficiency restricts carbohydrate utilization, but the implications for muscle fat metabolism have not been studied. We questioned whether patients with McArdle disease can compensate for the blocked muscle glycogen breakdown by enhancing fat oxidation during exercise. METHODS: We studied total fat oxidation by indirect calorimetry and palmitate turnover by stable isotope methodology in 11 patients with McArdle disease and 11 healthy controls. Cycle exercise at a constant workload of 50% to 60% of maximal oxygen uptake capacity was used to evaluate fatty acid oxidation (FAO) in the patients. Healthy controls were exercised at the same absolute workload. RESULTS: We found that palmitate oxidation and disposal, total fat oxidation, and plasma levels of palmitate and total free fatty acids (FFAs) were significantly higher, whereas total carbohydrate oxidation was lower, during exercise in patients with McArdle disease vs healthy controls. We found augmented fat oxidation with the onset of a second wind, but further increases in FFA availability, as exercise continued, did not result in further increases in FAO. CONCLUSION: These results indicate that patients with McArdle disease have exaggerated fat oxidation during prolonged, low-intensity exercise and that increased fat oxidation may be an important mechanism of the spontaneous second wind. The fact that increasing availability of free fatty acids with more prolonged exercise did not increase fatty acid oxidation suggests that blocked glycogenolysis may limit the capacity of fat oxidation to compensate for the energy deficit in McArdle disease.

Effect of aerobic training in patients with spinal and bulbar muscular atrophy (Kennedy disease).

OBJECTIVE: We examined the effect of aerobic exercise in patients with spinal and bulbar muscular atrophy (SBMA). SBMA is caused by a defect androgen receptor. This defect causes motor neuron death, but considering the important function of androgens in muscle, it is possible that muscle damage in SBMA also occurs independently of motor neuron damage. METHODS: Eight patients with SBMA engaged in regular cycling exercise for 12 weeks. Maximum oxygen uptake (Vo(2max)), maximal work capacity (W(max)), muscle morphology, citrate synthase (CS) activity, body composition, EMG, static strength measurements, lung function, plasma proteins, and hormones were evaluated before and after training. Evaluation of improvements in activities of daily living (ADL) was conducted after training. RESULTS: W(max) increased by 18%, and CS activity increased by 35%. There was no significant change in Vo(2max) or any of the other variables examined before and after training, and the patients with SBMA did not feel improvements in ADL. CONCLUSIONS: Frequent, moderate-intensity aerobic conditioning is of little beneficial effect in patients with spinal and bulbar muscular atrophy (SBMA). High levels of plasma creatine kinase and muscle regeneration indicate a primary myopathic affection, which, in parallel with the motor neuron deficiency, may attenuate the response to exercise training in patients with SBMA.

Is muscle glycogenolysis impaired in X-linked phosphorylase b kinase deficiency?

OBJECTIVE: It is unclear to what extent muscle phosphorylase b kinase (PHK) deficiency is associated with exercise-related symptoms and impaired muscle metabolism, because 1) only four patients have been characterized at the molecular level, 2) reported symptoms have been nonspecific, and 3) lactate responses to ischemic handgrip exercise have been normal. METHODS: We studied a 50-year-old man with X-linked PHK deficiency using ischemic forearm and cycle ergometry exercise tests to define the derangement of muscle metabolism. We compared our findings with those in patients with McArdle disease and in healthy subjects. RESULTS: Sequencing of PHKA1 showed a novel pathogenic mutation (c.831G>A) in exon 7. There was a normal increase of plasma lactate during forearm ischemic exercise, but lactate did not change during dynamic, submaximal exercise in contrast to the fourfold increase in healthy subjects. Constant workload elicited a second wind in all patients with McArdle disease, but not in the patient with PHK deficiency. IV glucose administration appeared to improve exercise tolerance in the patient with PHK deficiency, but not to the same extent as in the patients with McArdle disease. Lipolysis was higher in the patient with PHK deficiency than in controls. CONCLUSION: These findings demonstrate that X-linked PHK deficiency causes a mild metabolic myopathy with blunted muscle glycogen breakdown and impaired lactate production during dynamic exercise, which impairs oxidative capacity only marginally. The different response of lactate to submaximal and maximal exercise is likely related to differential activation mechanisms for myophosphorylase.

Endurance training: an effective and safe treatment for patients with LGMD2I.

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.

Tissue specific distribution of the 3243A->G mtDNA mutation.

BACKGROUND: The 3243A-->G is a common pathogenic mitochondrial DNA (mtDNA) point mutation causing a variety of different phenotypes. Segregation of this mutation to different tissues during embryonic life and postnatally is still enigmatic. OBJECTIVE: To investigate the tissue distribution of this mutation. METHODS: In 65 individuals from nine families segregating the 3243A-->G mutation, the mutation load (% mutated mtDNA) was determined in various tissues. Mutation load was measured in two to four cell types--blood leucocytes, buccal cells, skeletal muscle cells, and urine epithelial cells (UEC)--derived from all three embryogenic germ layers. RESULTS: There was a significant correlation among mutation loads in the four tissues (r = 0.80-0.89, p<0.0001). With blood serving as reference, the mutation load was increased by 16% in buccal mucosa, by 31% in UEC, and by 37% in muscle. There were significant differences between the mitotic tissues blood, buccal mucosa, and UEC (p<0.0001), but no difference between UEC and muscle. Using the present data as a cross sectional investigation, a negative correlation of age with the mutation load was found in blood, while the mutation load in muscle did not change with time; 75% of the children presented with higher mutation loads than their mothers in mitotic tissues but not in the post-mitotic muscle. CONCLUSIONS: There appears to be a uniform distribution of mutant mtDNA throughout the three germ layers in embryogenesis. The significant differences between mutation loads of the individual tissue types indicate tissue specific segregation of the 3243A-->G mtDNA later in embryogenesis.

The ultrastructure of follicle cells in fetal guinea-pig ovaries.

The development of the follicle cells in fetal guinea-pig ovaries has been examined in the electron microscope. The findings were as follows: at days 34 and 38 there were broad intercellular clefts within the germinal cords. However, a continuous layer of thin cytoplasmic processes from the follicle cells separated the germinal cords from the stromal compartment. The germinal cords were everywhere limited by a basal lamina. During all the period examined coated vesicles, possibly emptying their contents into the region of the basal lamina, were observed in the follicle cells. At days 42, 46 and 50 the cellular membranes were closely apposed with an intercellular distance of about 200 A. Complexes of deeply interdigitating folds of the membrane of neighboring follicle cells were observed. The follicle cells forming part of the primordial follicles at days 54 and 58 were characterized by a disappearance of these folds and by the appearance of bundles of microfilaments in the cytoplasm. These were especially numerous at day 66. At days 34 and 38 gap junctions were observed between the follicle cells, but not between the follicle cells and the germinal cells. During the entire period examined junctions resembling desmosomes without filaments were observed between the follicle cells as well as between the follicle cells and the germinal cells. The ultrastructure of the follicle cells is considered in detail and the functional significance of the findings discussed.

Secondary amenorrhoea and oral contraceptives.

Eight-seven cases of secondary amenorrhoea of more than 6 months' duration developing after treatment with oral contraceptives (group I) were compared with 227 cases of secondary amenorrhoea not preceded by treatment with combined tablets (group II). The two groups were collected during the same period. The average age of the patients was 4 years higher in group I than in group II. Oligomenorrhoea and previously occurred in 30% of group I and in 46% of group II. Pronounced predisposing factors., such as psychogenic trauma and stress with or without considerable change in body weight, were encountered in 26% in group I and 56% in group II. The incidence of increased urinary output of 17-keto steroids, 17-ketogenic steroids and of hirsutism was slightly higher in group II. The percentage of eosinophilic cells in vaginal scrapings was low in 20% in group I as compared with 46% in group II. Spontaneous return of pituitary-ovarian function occurred in 40% in both groups. Patients recovering spontaneously in group I presented a maximum during the first few months, followed by a steady and fairly uniform decline. Spontaneous recovery in group II was more or less independent of time. It seems reasonable to believe that oral contraceptives did promote or contribute to the development of secondary amenorrhoea in about 50%, representing cases with various predisposing factors. A causal relation between oral contraceptives and secondary amenorrhoea was indicated in the remaining 50% because of perfectly normal ovarian function before treatment and absence of predisposing factors.

PIP: 87 cases (Group 1) of secondary amenorrhea starting immediately after treatment with estrogen-gestagen tablets and 227 cases (Group 2) with secondary amenorrhea not preceded by hormonal therapy were studied. In all cases the amenorrhea had been of more than 6 months' duration. Endocrine studies included urinary output of 17-keto steroids, 17-ketogenic steroids, and total gonadotropins. Basal metabolic rate, protein bound iodine (PBI), and triiodothyronine were measured and the percentage of eosinophilic cells in vaginal scrapings was assessed. Radiological examination of the sella turcica and visual field testing were carried out. Group 1 patients averaged 4 years older than those in Group 2. In 28% of cases, treatment with oral contraceptives had been given for menstrual irregularities only. Oligomenorrhea had been present previously in 30% of Group 1 and in 46% of Group 2 patients (p equals .05). Increased urinary output of 17-keto steroids and 17-ketogenic steroids, and of hirsutism were slightly higher in Group 2. Eosinophilic cells in vaginal scrapings were low in 20% of Group 1 patients and in 46% of Group 2 patients. Psychogenic factors or severe stress had been noted in 26% of Group 1 and in 56% of Group 2 patients (p equals .0125). Galctorrhea had occurred in 1 patient in Group 1 and in 4 in Group 2. Spontaneous recovery of pituitary-ovarian function occurred in 40% of both groups. Type of menstrual pattern before therapy in Group 1 did not alter spontaneous re covery rates. But when the interval between menarche and start of hormonal therapy had been shorter than 5 years the spontaneous recovery was greater, 32 vs. 42%, when it had been longer than 5 years. Other predisposing factors may explain the development of secondary amenorrhea in about 50% of cases occurring after treatment with oral contraceptives . In the other 50%, a causal relationship of the therapy is suggested.

Surface epithelium of the fetal guinea-pig ovary: a light and electron microscopic study.

The surface epithelium in fetal guinea-pig ovaries was examined from the time of early sexual differentiation, about 34-days, until approximately ten days before birth. At day 34 the epithelium varied greatly in appearance as seen in the light microscope and possessed a superficial layer of flattened or culoidal cells. By day 58 the epithelium had changed into one layer of regularly arranged columnar cells. During the same period the number of germinal cells decreased. Connections between the germinal cords and the surface epithelium were observed from day 34, being especially numerous and broad at days 34 and 42 and decreasing in number and size from day 46 onwards. The basement membrane beneath the epithelium gradually increased in thickness. In the electron microscope two types of somatic cells could be distinguished. One type formed a superifical single layer connected by junctional complexes and exhibited intracellular bundles 60 A microfilaments running straight through the apical part of the cell, attached to junctional complexes on either side. These bundles were found frequently between days 34 and 42, but were rarely seen after the forth-sixth day. Microvillous projections into the coelomic cavity were especially numerous from day 34 to day 46. The other type of somatic cells lay in close proximity to the germinal cells: microfilaments or junctional complexes were not observed. The subepithelial basement lamina was continuous with that surrounding the connections and the germinal cords.