The Effect of Chronic Alcohol Ingestion on Whole Body and Muscle Protein Synthesis — A Stable Isotope Study

Abstract

The cause of the proximal myopathy associated with chronic alcohol ingestion has yet to be established. The clinical feature of muscle wasting implies either inhibited skeletal muscle protein synthesis, stimulated breakdown or a combination of both. Previous data suggest that breakdown is reduced, rather than promoted. This provides evidence, albeit indirect, that the myopathy is the result of inhibited muscle protein synthesis, which has been demonstrated recently in the rat model. We have examined the influence of chronic alcohol intake on post-absorptive fractional skeletal muscle protein synthesis in man using a primed continuous (1 mg/kg/hr) infusion of L-[1-13C]leucine for 8 hr. Percutaneous quadriceps muscle biopsies (200 mg) were taken after 2 and 8 hr of the infusion for measurement of the incorporation of 13C leucine into muscle protein. Plasma 13C enrichment of alpha-ketoisocaproic acid, the deaminated product of leucine, was used to represent that of the precursor pool. We studied 6 fully ambulant alcoholics, who exhibited no overt evidence of skeletal muscle disease and who had consumed at least 100 g alcohol daily for a minimum of 10 years. Mean (+/- S.D.) fractional muscle protein synthesis was 0.0274 +/- 0.0087 (95% confidence intervals 0.0204-0.0344%/hr). This value is significantly lower than recently published control values obtained using identical protocols which range from 0.046 to 0.055%/hr. In addition, whole body leucine oxidation was lower (P less than 0.05) in the chronic alcoholics than in healthy controls, whereas neither whole body protein synthesis nor breakdown was significantly reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of alcohol consumption on whole-body protein turnover in healthy adults

“…Our calculated S was found to be similar to the data described for healthy adults in the range of 3.0-4.0 g kg −1 day −1 [22,26]. However, only few results are available so far in the scientific literature on the effect of alcohol drinking on the protein turnover in humans [34][35][36][37]. Understandably, our findings are difficult to compare with the data of other studies since different groups of subjects, stable isotope-labelled tracer substances, methodologies, dosages, and units, respectively, were used.…”

“…Understandably, our findings are difficult to compare with the data of other studies since different groups of subjects, stable isotope-labelled tracer substances, methodologies, dosages, and units, respectively, were used. Pacy et al [34] examined the influence of alcohol intake on the fractional skeletal muscle protein synthesis in chronic alcoholics with a daily alcohol intake of at least 100 g for more than 10 years using the primed continuous infusion technique with l-[1-13 C]leucine. Assuming a leucine content of 8% of the whole-body protein, the converted S amounted to 3.23 g kg −1 day −1 and Downloaded by [134.117.…”

Oxidants antioxidants and alcohol implications for skeletal and cardiac muscle

“…Clinical studies with stable isotopes have shown that rates of skeletal muscle protein synthesis in alcohol misusers are lower than the rates seen in non-alcoholic control subjects (26). Animal studies also show that ethanol reduces skeletal muscle protein synthesis in acutely and chronically ethanol-dosed rats, though most studies have focused on the acute model.…”

Acute alcohol administration inhibits the refeeding response after starvation in rat skeletal muscle

“…Although the precise mechanism of the pathogenicity is unknown, a number of pathways have been proposed, including an increased generation of reactive oxygen species and disrupted membrane function (1,14). In skeletal muscle, as in other tissues, alcohol has been shown to promote a reduction in the fractional rate of protein synthesis (k s ) (17,23). There appears to be very little effect of alcohol on the rate of protein degradation, at least with acute alcohol treatment (10).…”