Science? Here's an explanation. For you lazy phucks... It says alcohol impairs protein synthesis.
ONE OF THE METABOLIC hallmarks of chronic alcohol abuse is the negative nitrogen balance resulting from a net catabolism of skeletal muscle proteins (34). An imbalance in protein metabolism, when prolonged, leads to the erosion of lean body mass (LBM) and the proximal myopathy commonly observed in alcoholics (29, 42). It has been estimated that 40-60% of all alcoholics exhibit skeletal muscle disease (42). The maintenance of muscle protein stores is essential because decreases in LBM are causally linked to increases in morbidity and mortality (22). Although alcohol affects all muscle groups to some extent, the fast-twitch type II fibers appear to be particularly vulnerable (29, 42). Available evidence suggests that malnutrition per se does not cause the myopathy, but deficiencies in the nutritional status may exacerbate the disease (4).
Chronic ethanol consumption increases whole body rates of leucine turnover and oxidation in fed rats (3), suggesting the presence of a reduced rate of protein synthesis and/or an increased rate of protein degradation. However, whole body measurements represent the sum of many vastly different organ systems (e.g., muscle and nonmuscle protein synthesis and hepatic secretory protein synthesis) and provide little information concerning individual processes or tissues. However, when the in vivo rate of protein synthesis was measured with the flooding-dose technique (8), acute alcohol intoxication, produced by the intraperitoneal injection of ethanol, markedly decreased the rate of protein synthesis in skeletal muscle, heart, intestine, bone, and skin (34). Moreover, chronic alcohol feeding of rats has also been demonstrated to reduce protein synthesis in skeletal muscle (33).
Although the alcohol-induced decrease in muscle protein synthesis has been recognized for a number of years, the mechanism for the impairment has been largely unexplored. In this regard, Preedy and Peters (33) demonstrated that chronic alcohol consumption produces relatively rapid and large decreases in the amount of total RNA in skeletal muscle. Because the large majority (>80%) of total muscle RNA is ribosomal, these data suggest that at least part of the alcohol-induced impairment in protein synthesis occurs secondary to a reduced number of ribosomes. However, the decrement in protein synthesis in this early study was greater than the decrease in RNA, indicating an impairment in translational efficiency as well. Translational efficiency reflects how well the existing protein synthetic machinery is functioning. Translation of mRNA involves a complex series of reactions, which can be categorized into three phases: initiation, elongation, and termination (5). There are no data pertaining to alcohol-induced alterations on various steps in the pathway of translation. Translational efficiency can be regulated by alterations in either peptide-chain initiation, elongation, or both. Because other catabolic conditions have previously been determined to impair translation initiation, the purpose of the present study was to determine whether chronic alcohol consumption in rats alters specific steps in the initiation process.
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