On alcoholic myopathy

Effects of alcohol on skeletal and cardiac muscle

The acute and chronic toxic effects of alcohol on skeletal and cardiac muscle are clinically important. Muscle weakness and atrophy are the main manifestations of skeletal myopathy, and arrhythmias and progressive left-ventricular dysfunction are those of cardiomyopathy. Most patients remain asymptomatic from these effects for a long time. Myocyte atrophy and death are the main pathological findings. A clear dose-related effect has been established with ethanol consumption, with gender and some specific gene polymorphisms being factors of increased susceptibility to alcohol-induced muscle damage. Pathogenic mechanisms are pleiotropic, the most relevant being disturbances in carbohydrate, protein, and energy cell turnover, signal transduction, and induction of apoptosis and gene dysregulation. Ethanol abstinence is the only effective treatment, although controlled drinking is useful in patients who do not achieve abstinence. Persistent high-dose consumption results in deterioration of muscle and heart function, with a high mortality due to arrhythmias and progression of heart failure.

Effect of chronic alcoholism on human muscle glycogen and glucose metabolism

To determine the effect of alcohol on carbohydrate metabolism, 48 human muscle biopsies from chronic alcoholics were studied. The level of glycogen and the activities of the enzymes catalyzing glycogen and glucose metabolism were analyzed. Chronic alcohol intake produced an increase in glycogen concentration and a decrease in pyruvate kinase activity before the first signs of myopathy appeared. When myopathy was present, glycogen decreased. These changes may contribute to the decline in skeletal muscle performance in these patients.

Effects of postnatal administration of ethanol on the M. gastrocnemius of the albino mouse

A combined morphometric-histochemical (mATPase) study of the effects of ethanol during postnatal development on the m. gastrocnemius has been performed in the albino mouse. The experimental group received ethanol in the drinking water until sacrifice at the age of 40 days. Based on the fiber composition, three different areas are distinguished in the m. gastrocnemius of the mouse. The typical location of these areas does not change after ethanol administration. However, postnatal administration of ethanol produces a selective atrophy and a decrease of the number of type IIb (fast glycolytic) fibers. Concurrently, the number of type IIa (fast oxidative-glycolytic) fibers increases.

The effects of alcoholism on skeletal and cardiac muscle

To determine the prevalence of alcoholic myopathy and cardiomyopathy, we studied a group of 50 asymptomatic alcoholic men (mean age, 38.5 years) entering an outpatient treatment program. Studies performed included an assessment of muscle strength by electronic myometer, muscle biopsy, echocardiography, and radionuclide cardiac scanning, with comparison to healthy control subjects of similar age. The patients' mean (+/- SEM) daily alcohol consumption was 243 +/- 13 g over an average of 16 years. These patients had no clinical or laboratory signs of malnutrition or electrolyte imbalance. Forty-two percent of the patients, as compared with none of the controls, had strength of less than 20 kg as measured in the deltoid muscle. Muscle-biopsy specimens from 23 patients (46 percent) had histologic evidence of myopathy. In the cardiac studies, when the alcoholic patients were compared with 20 healthy controls, the patients had a significantly lower mean ejection fraction (59 vs. 67 percent), a lower mean shortening fraction (33 vs. 38 percent), a greater mean end-diastolic diameter (51 vs. 49 mm), and a greater mean left ventricular mass (123 vs. 106 g per square meter of body-surface area). One third of the alcoholics had an ejection fraction of 55 percent or less, as compared with none of the controls. Endomyocardial biopsy specimens from six patients with ejection fractions below 50 percent showed histologic changes of cardiomyopathy. The estimated total lifetime dose of ethanol correlated inversely with muscular strength (r = -0.65; P less than 0.001). In an analysis that also included six patients with symptomatic alcoholic cardiomyopathy, the estimated total lifetime dose of ethanol correlated inversely with the ejection fraction (r = -0.58; P less than 0.001) and directly with the left ventricular mass (r = 0.59; P less than 0.001). We conclude that myopathy of skeletal muscle and cardiomyopathy are common among persons with chronic alcoholism and that alcohol is toxic to striated muscle in a dose-dependent manner.

Muscle fiber composition and length-tension relationships in rats chronically exposed to alcohol

Adult Fischer 344 rats were fed an alcohol diet (7-9 g/kg/day) for 12 weeks and were compared to pair-fed controls with regard to the contraction and fiber characteristics of the gastrocnemius and plantaris muscles of the leg. Muscles were isolated in situ with blood and nerve supplies intact. The muscles were stretched by 1 mm increments and were stimulated at each muscle length with a voltage (1 msec pulse) that had been observed to produce maximal twitch force at the initial muscle length. Maximal twitch tension was found to be only 10% less in alcohol than pair-fed rats and the increase in force resulting from stretching was approximately 15% less in alcohol than pair-fed rats. No significant changes in sciatic nerve conduction velocities were produced by alcohol exposure. Moreover, no significant differences in muscle weight or the number and size of Type I, Type IIa or Type IIb muscle fibers were observed. Although the 12 weeks of alcohol exposure affected muscle physiology and histology in the direction of increased impairment, the differences were not large enough to be statistically significant.