Muscle wasting in chronic alcoholics: comparative histochemical and biochemical studies

Interaction Between Alcohol and Exercise

Alcohol use, particularly excessive alcohol consumption is one of the most serious health risks in the world. A relationship between sport, exercise and alcohol consumption is clear and long-standing. Alcohol continues to be the most frequently consumed drug among athletes and habitual exercisers and alcohol-related problems appear to be more common in these individuals. Alcohol use is directly linked to the rate of injury sustained in sport events and appears to evoke detrimental effects on exercise performance capacity. The model of alcohol consumption in human experimental studies has either been acute (single dose) or chronic (repeated doses over a period). These studies suggested that alcohol consumption decreases the use of glucose and amino acids by skeletal muscles, adversely affects energy supply and impairs the metabolic process during exercise. In addition, chronic alcohol use is associated with increased citrate synthase activity and decreased cross-sectional area of type I, IIa and IIb fibres. There is evidence to suggest that exercise may attenuate the ethanol-induced decline in hepatic mitochondria and accelerates ethanol metabolism by the liver. Exercise training seems to reduce the extent of the oxidative damage caused by ethanol. Evidence generated from in vitro experiments and animal studies have also suggested that ethanol administration decreased skeletal muscle capillarity and increased pyruvate kinase and lactate dehydrogenase activities. Substantial epidemiological evidence has been accrued showing that moderate ingestion of alcohol may reduce the incidence of cardiovascular diseases. Although the existing evidence is often confusing and disparate, one of the mechanisms by which alcohol may reduce the incidence of mortality of cardiovascular diseases is through raising levels of high-density lipoprotein cholesterol. Available evidence suggests that exercise and moderate alcohol consumption may have favourable effects on blood coagulation and fibrinolysis; however, compelling experimental evidence is lacking to endorse this notion. Occasional and chronic alcohol consumption is usually linked with unfavourable alterations in platelet aggregation and function and may be associated with platelet-related thrombus formation. Although the effects of alcohol consumption on the rheological properties of the blood are not known, recent experimental evidence suggests that alcohol use following exercise is associated with unfavourable changes in the main determinants of blood viscosity. It is well documented that alcohol use modulates the immune system and impairs host defence. Compelling evidence is also mounting to suggest that chronic alcohol use is linked with adverse effects on the body systems and organs including the brain, the cardiovascular system and the liver.

Metabolic effects of alcohol on skeletal muscle

The purpose of this review is to summarize our current understanding of the acute and chronic interactions between alcohol and nutrient metabolism in skeletal muscle. Insulin is well known to play an important regulatory role in nutrient, especially glucose, uptake and utilization in skeletal muscle. Several studies have shown that alcohol can acutely reduce the normal metabolic responses of skeletal muscle to the action of insulin. The most obvious of these is an acute impairment in glucose metabolism associated with alcohol consumption. While the exact mechanism(s) underlying this acute insulin resistance is presently unclear, several possible factors are discussed in this review. In contrast to these short-term effects, the effects of alcohol on skeletal muscle insulin sensitivity in chronic alcohol abusers are not as well established. Chronic alcohol abuse is known to be associated with skeletal myopathies, believed to result from alcohol induced abnormalities in muscle protein synthesis. Finally, the alcohol-mediated impairments of many aspects of skeletal muscle metabolism are discussed in relation to the insulin resistance associated broad spectrum of common lifestyle-related disorders, including non-insulin dependent diabetes mellitus and obesity, the consequences of which may be important to the pathogenesis of alcohol-related diseases.

Effect of chronic ethanol ingestion and exercise training on skeletal muscle in rat

The aim of this study was to investigate the interactive effects of exercise training and chronic ethanol consumption on metabolism, capillarity, and myofibrillar composition in rat limb muscles. Male Wistar rats were treated in separate groups as follows: non exercised-control; ethanol (15%) in animals' drinking water for 12 weeks; exercise training in treadmill and ethanol administration plus exercise for 12 weeks. Ethanol administration decreased capillarity and increased piruvate kinase and lactate dehydrogenase activities in white gastrocnemius; in plantaris muscle, ethanol increased citrate synthase activity and decreased cross-sectional area of type I, IIa, and IIb fibres. Exercise increased capillarity in all four limb muscles and decreased type I fibre area in plantaris. The decreased capillarity effect induced by ethanol in some muscles, was ameliorated when alcohol was combined with exercise. While alcoholic myopathy affects predominantly type IIb fibres, ethanol administration and aerobic exercise in some cases can affect type I and type IIa fibre areas. The exercise can decrease some harmful effects produced by ethanol in the muscle, including the decrease in the fibre area and capillary density.

[Study of ultrastructural alterations in gastrocnemius muscle of C57 BL10 mice after prolonged ethanol ingestion]

The effects of chronic alcoholism on gastrocnemius muscle of well-nourished mice were morphologically studied to test the direct toxic role of ethanol on skeletal muscle. Thirty male young adult C57BL10 mice were divided in two groups: Group A (control) consisting of ten mice that drank water and Group B (alcoholic) consisting of twenty mice that drank 25% ethanol. All mice were allowed a balanced laboratory chow. The animals were kept on this ad libitum regimen under the same conditions of environment for 48 weeks and were weighed once a week. The daily dietary consumption and caloric intake were estimated, the animals having had a substantial weight gain, showing no signs of malnutrition. At the end of the experiment the animals were killed for morphological studies. No abnormalities were observed by conventional microscopy. Striking deviations from normal were verified by electron microscopy in all specimens. Dilatation of sarcoplasmic reticulum was a common feature, sometimes resulting in the formation of large vesicles and involving the terminal cisternae with the displacement of the triads. Areas of narrowing, splitting and loss of myofibrils were seen. Zones of complete disorganization of miofibrils could be occasionally observed. Mitochondria were generally normal. Peculiar tubular aggregates seen commonly in periodic paralysis and other human pathological conditions, were encountered in both control and alcoholic mice. Intramuscular nerves and neuromuscular junctions were normal. Important abnormalities in muscle capillaries were observed, consisting of swelling of endothelial cells and thickening of the basal lamina. A diffuse microvesicular lipid infiltration was seen in the cytoplasm of the hepatocytes which seems to be a further evidence of the toxic role played by ethanol. We concluded that prolonged ingestion of ethanol, representing 14.4% of total calories, produces in the gastrocnemius muscle of well-nourished C57BL10 mice a distinct spectrum of ultrastructural changes which reflects a direct toxic effect on the skeletal muscle. These alterations are similar to those described in human chronic alcoholic myopathy.

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.

Chronic alcoholic myopathy and nutritional status

To investigate the prevalence of alcoholic myopathy and its relationship to the nutritional status, we performed a muscle biopsy on the vastum lateralis of 60 consecutive hospitalized alcoholic patients using a Tru-Cut needle, processing it for light microscope and ultrastructural analysis. The nutritional status was assessed by anthropometric measurements such as midarm circumference, triceps skinfold and midarm muscle area, and serum albumin. The hallmark of chronic alcoholic myopathy, fiber muscle atrophy, was present in 33% of the patients, necrosis scarcely being observed (1.5%). Ultrastructural alterations as lipid and glycogen accumulation or mitochondrial and myofibrillar alterations were nonspecific and observed in nearly all the cases where atrophy was present. Malnutrition was frequent in our patients: 39% and 34% showed a triceps skinfold and a midarm muscle area, respectively, under the fifth populational percentile. Patients with muscle fiber atrophy or ultrastructural changes showed a worse nutritional status, not only regarding muscle protein (assessed by midarm muscle area or creatininuria and explained by fiber atrophy), but also regarding fat stores assessed by triceps skinfold. Toxic effect of ethanol and malnutrition may act synergistically leading to chronic alcoholic myopathy.

A survey of muscle function in detoxified alcoholics

Selected characteristics of arm and leg muscle contraction were examined in a racially mixed group of male detoxified alcoholics (N = 45, ages 20-49) and age-matched controls (N = 75). Lifetime drinking histories estimated the mean lifetime consumption of ethanol to be 8.96, 12.1 and 20.4 kg ethanol/kg body weight for alcoholic subjects aged 20-29, 30-39 and 40-49, respectively. The severity of the alcohol dependence syndrome (ADS scale) was marked in alcoholics, but was not age-dependent. Alcoholics did not differ significantly from controls on health status or physical activity scales. The performance of alcoholic subjects was impaired on all muscle function measures, with relatively more impairment found in older alcoholics. Maximal knee extension force generated at 3 muscle lengths (hip, angle, 45 degrees, 90 degrees, 180 degrees) was impaired only in alcoholics 30-49 years of age. Forearm (handgrip) muscle strength was impaired in all age groups of alcoholics. Maximal muscle (biceps) contraction speed at 3 levels of resistance was impaired only in alcoholics in their fifth decade of life. The greatest deficit in alcoholics (all age groups) was observed in the anaerobic power (bicycle ergometer) test. Thus, the magnitude of dysfunction and the extent of age-relatedness was found to be a function of the muscle test employed.

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.

Chronic alcoholic proximal wasting: physiological, morphological and biochemical studies in skeletal muscle

Electromyography, muscle histochemistry and assay of all glycolytic enzymes, phosphorylase, glycogen, carnitine and several mitochondrial marker enzymes in skeletal muscle (vastus lateralis) were carried out in two groups. One group comprised chronic alcoholic patients with prominent proximal wasting, the other was an alcoholic group with normal neuromuscular examination. Biochemical results were compared with data from control groups with normal muscle histology and with non-alcohol related type 2b fibre atrophy. Either 2b atrophy factor or 2b variability coefficient were increased in all wasted alcoholic patients, with normal values in alcoholics without wasting. Electromyography studies were usually normal in proximal muscles, although several patients had mild distal neuropathies. A significant fall in activity of phosphorylase and all glycolytic enzymes was found in wasted alcoholics with reference to normal controls. In the non-ethanolic 2b atrophy group the activity of several glycolytic enzymes was also significantly lower, but for each enzyme the mean activity was not depressed to the same extent as in the wasted alcoholic group. Muscle glycogen, carnitine, and mitochondrial marker enzyme activities (isocitrate dehydrogenase, monoamine oxidase, cytochrome oxidase) were normal in alcoholics with proximal wasting. It is concluded that there is no deficiency of mitochondrial marker enzymes in wasted alcoholics and that a significant depression in glycogenolytic and glycolytic enzyme activity is seen which is explained in part, but probably not fully, by 2b fibre atrophy.

Chronic alcoholic skeletal myopathy--common and reversible

Although musculoskeletal symptoms are common in alcoholics, little is known of the prevalence of muscle pathology in this group. Quadriceps muscle biopsies were performed in 151 alcoholics (105 men). Ninety patients showed type 2 fibre atrophy predominantly affecting the type 2b anaerobic glycolytic fibres. In contrast, 7 biopsies revealed some muscle necrosis and only 1 patient had acute rhabdomyolysis. Amongst those alcoholics with muscle atrophy the quantity of alcohol consumed in the year prior to biopsy correlated significantly with the severity of the atrophy. Atrophy was not associated with vitamin B12, folate, pyridoxine, riboflavin or thiamine deficiencies. Although patients with severe liver disease, peripheral neuropathy or malnutrition were more likely to have muscle atrophy, nerve conduction studies showed that atrophy and neuropathy each occurred independently. Sequential studies in abstaining alcoholics showed a significant improvement within 3 months and often complete recovery within a year. Continued consumption of alcohol was associated with persistence or progression of the atrophy. This study shows that reversible type 2b muscle fibre atrophy is a frequent finding in alcoholics and suggests that it is directly related to alcohol consumption and is not a consequence of malnutrition, vitamin deficiency or peripheral neuropathy.