The acute effects of a single dose of ethanol on biochemical indices of skeletal muscle composition: time course changes and comparison with the effects of endotoxin.
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Animals↗
Biomedical subjects
V R Preedy
Publications and source records attributed to V R Preedy.
Ethanol induced cardiovascular disease.
Although the beneficial effects of mild or moderate ethanol consumption have been implied with respect to coronary artery disease, excessive ethanol consumption can result in alcoholic heart muscle disease (AHMD). The latter is characterized by features consistent with dilated cardiomyopathy with concomitant ventricular dysfunction and histopathological abnormalities. By definition, no other cause for the abnormalities in AHMD is demonstrated, other than excessive alcohol consumption. The metabolic basis of AHMD is probably multi-factorial, and the alterations of myocardial biochemistry are contributing factors for the precipitation and progression of the disease. The latter may reverse with abstention. Evidence is provided to support the contention that the abnormalities include central defects in protein metabolism, which perhaps are engendered by free radicals and/or the formation of acetaldehyde adducts. The latter may initiate the formation of auto-antibodies, therefore providing an auto-immune basis for AHMD in chronic alcohol misuse. Evidence is also provided to show that acetaldehyde is a potent perturbant of protein synthesis, and reduces the formation of new contractile proteins.
Acetaldehyde↗
Chronic alcoholic myopathy: transcription and translational alterations.
Alcoholic myopathy is characterized by selective atrophy of type II fibers and affected subjects lose up to 20% of the entire musculature. Between one- and two-thirds of all alcohol abusers are affected. In acute studies, defective rates of translation occur and type II fiber-predominant muscles are more adversely affected than type I fiber-predominant muscles. Furthermore, acetaldehyde is also a potent modulator of translation, and contractile and noncontractile proteins are affected equally. In chronic ethanol feeding there is rapid and sustained loss of ribosomal RNA. Recent attention has focused on the observation that total messenger RNA (mRNA) falls after ethanol consumption, but mRNA for specific myofibrillary contractile proteins are unaffected, implicating a role for translational modifications in the initial stages of the myopathy. Clinical studies have also shown that chronic alcohol abusers have defective rates of muscle protein synthesis and whole-body protein metabolism. The modulations in transcription and translation are not mediated by availability of amino acids, the effects of endocrine dysfunction (cortisol and growth hormone), liver impairment, or malnutrition. Free radicals, however, may be contributory mediators. Receptor-mediated events and the putative roles of growth factors are generally unexplored, though a distinguishing feature of acute ethanol administration is a reduction in circulating IGF-I. Thus, ethanol may act directly on muscle, although other concordant processes may coexist.
Alcoholism↗
The deleterious effects of alcohol on the heart: involvement of protein turnover.
Ethanol ingestion can induce a variety of metabolic changes in the heart, and recent studies have even suggested that moderate ethanol intake confers cardio-protective effects in reducing mortality due to coronary artery disease. However, in this review we explore the consequences of excessive ethanol intake or alcohol misuse. We investigate the epidemiology of alcohol misuse, and thereafter present evidence supporting the existence of a specific alcoholic heart muscle disease (AHMD). The prevalence of AHMD is described and the contributing mechanisms are discussed. These include the involvement of free radicals, defects in intermediary metabolism and the formation of acetaldehyde adducts. Special attention has been paid to ethanol-induced changes in protein turnover. Our studies show that ethanol impairs the protein synthetic pathways, affecting the contractile proteins per se, as well as the subcellular organelles as exemplified by the mitochondria. Acetaldehyde appears to be a particularly potent toxin. The experiments described in this review emphasize the need for investigative studies in intact models. The mechanisms inherent in the pathogenesis of AHMD may be applicable to other heart muscle disorders.
Alcohol Drinking↗
Alcohol and muscle disease.
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Acute Disease↗
The extraction of smooth muscle contractile and noncontractile proteins from the rat small intestine: measurement of protein synthesis and effects of ethanol toxicity.
An investigation was made into the optimum conditions for the extraction and measurement of intestinal smooth muscle contractile proteins of laboratory rats. Isolation of the seromuscular layer was achieved by "mucosal stripping" (using a glass slide); isolation of contractile proteins were achieved by differential solubility (using high and low ionic buffers and ultracentrifugation). Histological evidence revealed that after mucosal striping all cells of the longitudinal and circular muscle layers of the seromuscular region remained intact. Assay of brush-border marker enzyme activities confirmed that mucosal striping did indeed remove the mucosa and there was very little villus contamination of the smooth muscle tissue preparations. Optimum physical conditions for the isolation of seromuscular and mucosal myofibrillary proteins were identified. We ascertained that considerable amounts of myofibrillarly proteins reside in the mucosa, but could be adequately separated by mucosal striping. Improved recoveries of purified contractile proteins necessitated the inclusion of protease inhibitors during all processing steps. Using the optimum method, polyacrylamide gel electrophoresis of contractile proteins showed that the predominant smooth muscle contractile proteins, i.e., myosin heavy chain, actin, tropomyosin, and myosin light chains, were indeed preferentially isolated by our methodology. Using these techniques we demonstrated that the synthesis rates of intestinal contractile proteins were reduced by acute ethanol dosage. These results may be responsible for, or reflect, alcohol-induced defects in intestinal motility.
Animals↗
Ethanol-induced inhibition of ventricular protein synthesis in vivo and the possible role of acetaldehyde.
We have determined the extent to which acute ethanol administration perturbs the synthesis of ventricular contractile and non-contractile proteins in vivo. Male Wistar rats were treated with a standard dose of ethanol (75 mmol kg-1 body weight; i.p.). Controls were treated with isovolumetric amounts of saline (0.15 mol l-1 NaCl). Two metabolic inhibitors of ethanol metabolism were also used namely 4-methylpyrazole (alcohol dehydrogenase inhibitor) and cyanamide (acetaldehyde dehydrogenase inhibitor) which in ethanol-dosed rats have been shown to either decrease or increase acetaldehyde formation, respectively. After 2.5 h, fractional rates of protein synthesis (i.e. the percentage of tissue protein renewed each day) were measured with a large (i.e. 'flooding') dose of L-[4-3H]phenylalanine (150 mumol (100 g)-1 body weight into a lateral vein). This dose of phenylalanine effectively floods all endogenous free amino acid pools so that the specific radioactivity of the free amino acid at the site of protein synthesis (i.e. the amino acyl tRNA) is reflected by the specific radioactivity of the free amino acid in acid-soluble portions of cardiac homogenates. The results showed that ethanol alone and ethanol plus 4-methylpyrazole decreased the fractional rates of mixed, myofibrillar (contractile) and sarcoplasmic (non-contractile) protein synthesis to the same extent (by approx. 25 per cent). Profound inhibition (i.e. 80 per cent) in the fractional rates of mixed, myofibrillar and sarcoplasmic protein synthesis occurred when cyanamide was used to increase acetaldehyde formation. There was also a significant decrease in cardiac DNA content. The results suggest that acute ethanol-induced cardiac injury in the rat may be mediated by both acetaldehyde and ethanol.
Acetaldehyde↗
Optimum conditions for the assay of cardiac RNA: comparative content and effect of hypertension.
An investigation was made into techniques for the routine measurement of cardiac ribonucleic acid (RNA). Conditions were defined for the determination of rat ventricular RNA, based on uv absorption spectrophotometry. Optimum RNA hydrolysis occurred at 0.3 mol/liter alkali at 37 degrees C for 1 h. Suitable correction factors for non-RNA material were also described and these gave similar results to RNA assayed by colorimetric methods. It was concluded that many of the methods previously reported may cause artifactual observations (in some cases apparent negative amounts of RNA). The technique was applied to the assay of RNA in various regions of the heart (i.e., left and right atrial and the left and right ventricular regions) and compared with noncardiac tissues (i.e., skeletal muscle, liver, bone, intestine, and kidney). The left ventricular RNA concentrations were comparable to the right ventricle and the interventricular septum, but approximately half that of atria. There were very little differences between left and right atrial regions. Differences between atrial and ventricular regions were reduced when data were expressed relative to DNA. The cardiac RNA content was shown to be comparable to skeletal muscle and bone. However, cardiac RNA concentrations were lower than those of kidney, liver, lung, and small intestine. Data were also expressed relative to DNA and showed that cardiac RNA/DNA ratios were higher than those of skeletal muscle and lower than those of bone, kidney, liver, lung, and small intestine. The assay procedure for cardiac RNA was applied to investigations in the hypertrophied left ventricle induced by aortic constriction. After 10 days the RNA concentration (mg/g wet wt) and RNA content (mg/region) increased by 7 and 43%, respectively.
Animals↗
Protein synthesis in the major salivary glands of the rat and the effects of re-feeding and acute ethanol injection.
Rates of protein synthesis in the major salivary glands of the rat were accurately determined in vivo using the 'flooding dose' technique and the effects of reflex stimulation through feeding or acute ethanol treatment were assessed. Rats were divided into three groups. The control group was fasted overnight, the re-fed group was also fasted then re-fed the following morning and the third group received an intraperitoneal injection of ethanol after an overnight fast. In control rats the sublingual gland had a higher rate of protein synthesis than the other glands. After a feed the rate of protein synthesis in parotid glands was approximately double that of controls whilst that of the submandibular glands had increased by 24% and the sublingual glands remained unchanged. Acute ethanol injection led to a reduced rate of protein synthesis in all glands. The higher rate of protein synthesis in sublingual glands under fasting conditions may be related to the spontaneous secretion of fluid and protein from this gland, which would require a constant replenishment of secretory protein by synthesis. Protein synthesis in the parotid gland, like secretion, appears to be closely linked with the reflex stimulation caused by mastication. The smaller increase in rate of protein synthesis seen in the submandibular gland after a re-feed does not appear to have been recorded before. It could be mediated by the increased reflex stimuli caused by mastication or by some circulating factor. The mechanism by which ethanol reduces protein synthesis in all glands is uncertain.
Analysis of Variance↗
Gastrointestinal protein turnover and alcohol misuse.
Acute and chronic ethanol ingestion causes a variety of pathological changes in the gastrointestinal tract, including gross morphological lesions and functional changes. We review whether these alterations also include changes in protein turnover, to explain the frequently observed villus atrophy and smooth muscle myopathy. The possibility that different regions of the gastrointestinal tract express diverse sensitivities is explored. Acute ethanol dosage profoundly reduced the synthesis of proteins in proximal regions of the rat gastrointestinal tract, but distal regions were less affected. In response to chronic ethanol exposure, similar regional sensitivities of the intestine were observed. In chronic studies the small intestine effects were characterised by selective losses of RNA, principally from the stomach and jejunum. We speculate whether the effects on protein synthesis were primarily due to ethanol or the consequence of acetaldehyde formation. We also determined whether changes in protein synthesis occurred secondary to alterations in nucleotide composition. The possible mediation by free-radical formation or impaired antioxidant status are also discussed. The overall results indicate that both acetaldehyde and ethanol are potent protein synthetic inhibitors and may contribute to the genesis of intestinal myopathy, possibly contributing towards motility disturbances and secondary malnutrition via malabsorption.
Alcoholic Intoxication↗
Effect of thyroidectomy and adrenalectomy on changes in liver glutathione and malonaldehyde levels after acute ethanol injection.
At low concentrations ethanol is metabolized largely by alcohol dehydrogenase to acetaldehyde, while at higher concentrations a microsomal ethanol oxidising system (MEOS) is involved, namely cytochrome P450 IIE1, which also probably generates free radical species. In hyperthyroidism hepatic glutathione stores are depleted and net superoxide anion production occurs. In contrast, in hypothyroidism hepatic glutathione may be increased and thus renders the liver less sensitive to alcohol generated free radical production. Steroid hormones inhibit lipid peroxidation. Sixty male Wistar rats either underwent thyroidectomy, adrenalectomy, or sham procedures. Twenty control animals were pair fed with thyroidectomized animals, whilst another twenty fed ad libitum. An intraperitoneal injection of alcohol (75 mmol/kg) was given 2.5 h prior to sacrifice to half the animals in each group, the remainder receiving saline. The total hepatic glutathione contents of the pair fed and the ad libitum groups were not different, but were significantly increased by thyroidectomy (p = < 0.001). This effect was significantly reduced by alcohol (p < 0.01). The sham procedures and dietary restrictions had no effect. The ethanol alone reduced total hepatic glutathione, but this only reached statistical significance in the thyroidectomized and sham-adrenalectomized groups. Hepatic malonaldehyde (MDA) levels were significantly reduced in the thyroidectomy group but alcohol had no effect on them. We conclude that hypothyroidism increased hepatic glutathione status, presumably by reducing radical production by enzyme systems, which would otherwise consume this important scavenger. Long term exposure to ethanol with induction of MEOS is probably required for it to generate toxic levels of free radical species.
Adrenal Glands↗
Synthesis of ventricular mitochondrial proteins in vivo: effect of acute ethanol toxicity.
Most studies on the pathological responses of the heart to ethanol have been conducted in isolated systems. The objectives of this study were to determine (1) the synthesis rate of ventricular mitochondrial proteins in vivo and (2) whether the synthesis rates of these proteins are perturbed by acute ethanol exposure in vivo. Fractional rates of protein synthesis [defined as the percentage of tissue protein renewed each day; i.e., ks (%/day)] were determined in male Wistar rats by in vivo injection of a flooding dose of L-[4-3H] phenylalanine. Subsarcolemmal mitochondria were released by polytron treatment, and the isolation of interfibrillar mitochondria involved treatment of the cardiac homogenate with the proteolytic enzyme Nagarse. In the control rats mean ks values of 22.4%/day were observed for mixed cardiac proteins. The synthesis rates of subsarcolemmal and interfibrillar mitochondrial proteins were lower, i.e., 16.9%/day and 10.9%/day, respectively. Acute ethanol administration (75 mmol/kg body weight ip, 2.5 hr) depressed the fractional rate of protein synthesis in all cardiac fractions, including those pertaining to the mitochondria, as follows: mixed fraction--21%, p < 0.01; subsarcolemmal mitochondria--23%, p < 0.01; interfibrillar mitochondria--26%, p < 0.05; and nuclear fraction--20%, p < 0.05. In conclusion, the reduced synthesis rate of the mitochondrial proteins in response to acute ethanol exposure may in some way be partly connected with the depression in myocardial contractility and associated functional damage of mitochondrial metabolism.
Alcoholic Intoxication↗
The urinary excretion of tryptophan and tryptophan metabolites in the chronic ethanol-fed rat.
An investigation was made into the hypothesis that chronic ethanol ingestion disturbs the metabolism of tryptophan which is reflected by alterations in the urinary excretion of the metabolites 5-hydroxyindoleacetic acid (5-HIAA), anthranilic acid (AA) and indoleacetic acid (IAA). In particular, we investigated whether experimental chronic alcoholism is associated with a decrease in the tryptophan metabolite ratios as suggested in the literature. Male Wistar rats were chronically fed a nutritionally-complete liquid diet in which ethanol comprised 35% of total calories: controls were pair-fed identical amounts of the same diet in which ethanol was replaced by isocaloric glucose. At 6 weeks, 24 h urine samples were collected for the analysis of tryptophan, 5-HIAA, AA and IAA by HPLC. During ethanol-feeding there were reductions in the daily urinary excretion (i.e. mumol/24 h) of tryptophan (-57%, P = 0.026) and concomitant increases in 5-HIAA excretion (62%, P = 0.057). Expression of data in terms of lean tissue mass (i.e. urinary creatinine) revealed identical conclusions. An analysis was performed on the molar ratios of these urinary analytes. The tryptophan: total metabolite ratio was significantly decreased (by -53%), but the AA: total metabolite ratio was not significantly altered (P = 0.102). The ratios 5-HIAA/AA and 5-HIAA/IAA were slightly increased, but they did not attain statistical significance (P > 0.351). It was concluded that chronic ethanol feeding is associated with significant changes in the urinary excretion of tryptophan and its related metabolites.(ABSTRACT TRUNCATED AT 250 WORDS)
Alcoholism↗
Mechanisms of ethanol-induced cardiac damage.
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Alcohol Drinking↗
Biochemical and muscle studies in patients with acute onset post-viral fatigue syndrome.
AIMS: To investigate in detail various biochemical and pathophysiological indices of muscle pathology in acute onset post-viral fatigue syndrome (PVFS). METHODS: Twenty three patients with PVFS (of mean duration 4.6 years) were subjected to needle biopsy for histomorphometry and total RNA contents. Plasma analysis included serology and creatine kinase activities. Indices of whole body mass were also measured--namely, whole body potassium content and plasma carnosinase activities. RESULTS: About 80% of the patients had serology indicative of persistent enteroviral infection as determined by VP1 antigen assay. Only about 10% of that same group of patients had serological indications of current enterovirus infection by IgM assay; a separate subset of 10% showed antibody changes suggestive of reactivation of Epstein-Barr virus. Quantitative morphometric analysis of skeletal muscle fibres indicated that the quadriceps muscle was normal or displayed only minor abnormalities in 22 patients. The Quetelet's Index (body mass index) and whole-body potassium values (index of lean body mass) were not affected in PVFS. The mean plasma carnosinase and creatinine kinase activities were also generally normal in these patients. The mean muscle RNA composition--mg RNA/mg DNA: was significantly reduced in acute onset PVFS by about 15%. The protein:DNA ratio was not significantly affected. CONCLUSIONS: Patients with acute onset PVFS, therefore, lose muscle protein synthetic potential, but not muscle bulk. Histopathology is consistent with these observations. These perturbations may contribute to the apparent feature of perceived muscle weakness associated with the persistent viral infection in the muscle themselves.
Adolescent↗
The relationship between muscle fibre atrophy factor, plasma carnosinase activities and muscle RNA and protein composition in chronic alcoholic myopathy.
The relationship between chronic ethanol consumption and muscle biopsy morphometry (i.e. atrophy factor), plasma analytes, including carnosinase activities and tissue composition was investigated. In approximately half of chronic alcohol misusers there was Type II-fibre atrophy, which was correlated with reductions in muscle protein and serum carnosinase activities. The protein composition was also correlated with RNA composition. These results directly implicate defects in protein and RNA turnover as characteristics of chronic alcoholic myopathy and re-affirms the routine diagnostic use of fibre-type morphometry to identify these patients.
Adult↗
Effect of acute ethanol dosage on nucleotide levels in the rat jejunum: relationship to protein synthesis.
The effects of an acute dose of ethanol (75 mmol/kg body weight; i.p.) on nucleotide levels in the rat jejunum were investigated. After 2.5 hr, ethanol exposure significantly reduced ATP and GTP contents and increased ADP and GDP contents. There were no statistically significant effects on pyrimidine nucleotides or IMP. Fractional rates of jejunal protein synthesis were also significantly reduced by ethanol. It was concluded that purine nucleotides are sensitive to acute ethanol administration in the rat jejunum. This may explain why rates of protein synthesis are decreased in the jejunum, as these nucleotides play a key role in polypeptide formation.
Alcoholic Intoxication↗
Rates of protein synthesis in different regions of the normotensive and hypertrophied heart in response to acute alcohol toxicity.
The objective of study was (a) to investigate whether protein synthesis in different regions of the heart (i.e. left and right atria, left and right ventricles) expressed equal sensitivity to acute ethanol dosage, and (b) to ascertain whether concomitant cardiac abnormalities (i.e. experimental hypertrophic heart disease) exacerbated these responses. Acute ethanol dosage (75 mmol/kg body weight, i.p.) to mature male Wistar rats reduced the fractional rate of protein synthesis (ks, %/day) in all regions (atria and ventricles) of the normal and overloaded (30 days aortic constricted) hearts. The responses in ks were variable. In normal heart, the atrial tissues showed a slightly greater decrease in ks (approx. -30%) when compared to the ventricular regions (approx -20%). The most pronounced effects occurred in the hypertrophied left ventricular tissues where the depressive effects of ethanol on the rate of protein synthesis were potentiated in the presence of hypertrophy (ks reduced by approx 40%). Other regions of the overloaded heart did not show additional sensitivity to the effects of ethanol on protein synthesis in the presence of chronic hypertension. In conclusion, the deleterious effects of ethanol on the left ventricle are additive in the presence of chronic hypertrophy. These results may have important implications for other cardiac abnormalities where there is also concomitant ethanol exposure.
Alcohol Drinking↗