logo
    Abstract The excretion of endogenous creatinine and 3‐methylhistidine by subjects with muscle diseases has been measured in order to assess muscle mass and fractional rates of myofibrillar protein degradation. Increases in the rates of myofibrillar protein breakdown were observed in all subjects with Duchenne, Becker, autosomal recessive Duchenne‐like, and limb‐girdle muscular dystrophy; dystrophia myotonica; myotonia congenita; peroneal muscular atrophy; myasthenia gravis; and central core disease; in some cases of spinal muscular atrophy; but in no cases of facioscapulohumeral muscular dystrophy or dystonia musculorum deformans. All increases in myofibrillar protein breakdown were associated with reductions in muscle proportion below the normal. Muscle‐wasting diseases may respond to therapy directed towards an inhibition of muscle protease activity; the efficacy of such therapy can be monitored by the 3‐methylhistidine–to–creatinine excretion ratio.
    Myofibril
    Citations (45)
    Phosphorus 31 nuclear magnetic resonance (31P NMR) signals were recorded from intact human erythrocytes for 16 hours. Total phosphate concentration, which was estimated as the sum of the individual 31P signals, was 25% lower in erythrocytes from men with myotonic dystrophy than in control erythrocytes. The inorganic-phosphate fraction contained the highest average phosphate concentration over the 16-hour period, and made the major contribution to the difference in total phosphate between the two groups. This result was not observed in erythrocytes from either women with myotonic dystrophy or patients with Duchenne's dystrophy and may be due to a change in cell membrane permeability to inorganic phosphate, which leads to lower steady-state concentrations of the intracellular phosphates.
    Dystrophy
    Myotonic dystrophy is frequently associated with testicular atrophy. Since androgens may play a role in the maintenance of muscle mass, we have studied the levels of plasma testosterone and gonadotropins and of urinary 17-ketosteroids in 22 men with myotonic dystrophy, 36 normal men, and 16 men (control group) with muscle wasting. Results were correlated with muscle mass as estimated by creatinine excretion and total body potassium. Patients with myotonic dystrophy had significantly lower testosterone and higher gonadotropin levels than normal, and these changes were progressive in longitudinal studies. Testosterone levels were also lower than normal in disease control subjects. There was no correlation between low testosterone levels and diminished muscle mass in either myotonic dystrophy or disease control patients. The low plasma concentration of testosterone in men with myotonic dystrophy and other neuromuscular diseases does not appear to be directly related to their muscle wasting. This study does not exclude the possibility that an alteration in testosterone receptor or tissue effects may contribute to a loss of muscle tissue.
    Muscle Atrophy
    Abstract: The thenar muscles and gastrocnemius of a patient with myotonic dystrophy were investigated, at rest, by phosphorus nuclear magnetic resonance spectroscopy. A decrease in phosphocreatine level and an increase in inorganic phosphate and phosphodiester levels were found in the gastrocnemius, which was clinically spared, whilst the thenar muscles, which were wasted and affected by myotonia, exhibited only an increased inorganic phosphate level and an elevated pH. These findings were comparable with those found in other muscular disorders, such as Duchenne's and Becker's dystrophies, as well as in limb girdle dystrophy. They suggested that the abnormalities observed were unrelated to myotonia or wasting, and the possibility of a secondary mitochondrial disorder in myotonic dystrophy, is to be considered.
    Abnormality
    Bioenergetics
    Dystrophy
    Citations (0)
    To evaluate possible progressive metabolic changes in Duchenne muscular dystrophy, we used 31P nuclear magnetic resonance spectroscopy to measure high-energy phosphate compounds and phosphorylated diesters (PDE) in resting gastrocnemius muscle of 14 Duchenne patients and 10 normal boys. The patients had higher inorganic phosphate (Pi), intracellular pH, and PDE; and lower phosphocreatine (PCr) and PCr/Pi ratio; ATP was not significantly different. The patients showed significant age-related decreases in PCr and PCr/Pi, and increases in Pi and PDE, but ATP did not change. In normal boys, ATP increased with age, but PCr and Pi did not. These studies imply progressive metabolic deterioration in Duchenne dystrophy.
    Intracellular pH
    Gastrocnemius muscle
    Citations (135)