w cytowanych badaniach raczej bierze sie pod uwage wieksze ilosci alkoholy, wiec nie sadze, aby jedno piwo na tydzien zaszkodzilo w sposob widoczny
Protein Synthesis
Both ethanol and its metabolic byproduct, aldehyde, have been shown to reduce protein synthesis in skeletal muscle (85, 86, 87, 88). To make matters worse, it is predominately Type II, fast-twitch fibers that are affected, with type IIB being hit the hardest (85, 86, 87). This is not a good thing for bodybuilders, and it is a very bad thing for athletes.
With acute administration of real-world doses (.8 - 2.0g/kg) of ethanol, reductions in protein synthesis of 20-30% have been seen within about one to two hours of administration, this is before the previously reviewed hormonal changes occur, indicating that alcohol is exerting a direct effect (85, 86, 88). Within 24 hours, decreases of as high as 63% have been shown to occur (86), which likely reflects the added contribution of negative hormonal changes.
The mechanism behind this is not fully characterized. Reduction in both mRNA (86) and translational efficiency (87) have been observed. The generation of free-radicals, which are known to be increased by ethanol (89, 90), could be involved (91). Low levels of selenium and alpha-tocopherol (vitamin E) are found in alcoholics with myopathy (muscle wasting) (92). However, there is also evidence that does not support this theory (93). Another possibility is direct ischemic damage (94).
85. Preedy VR, Keating JW, Peters TJ. The acute effects of ethanol and acetaldehyde on rates of protein synthesis in type I and type II fibre-rich skeletal muscles of the rat. Alcohol Alcohol 1992 May;27(3):241-51
86. Reilly ME, Mantle D, Richardson PJ, Salisbury J, Jones J, Peters TJ, Preedy VR. Studies on the time-course of ethanol's acute effects on skeletal muscle protein synthesis: comparison with acute changes in proteolytic activity. Alcohol Clin Exp Res 1997 Aug;21(5):792-8
87. Reilly ME, McKoy G, Mantle D, Peters TJ, Goldspink G, Preedy VR. Protein and mRNA levels of the myosin heavy chain isoforms Ibeta, IIa, IIx and IIb in type I and type II fibre-predominant rat skeletal muscles in response to chronic alcohol feeding. J Muscle Res Cell Motil 2000;21(8):763-73
88. Preedy VR, Peters TJ. Acute effects of ethanol on protein synthesis in different muscles and muscle protein fractions of the rat. Clin Sci (Colch) 1988 May;74(5):461-6
89. Nordmann R. Oxidative stress from alcohol in the brain. Alcohol Alcohol 1987;Suppl 1:75-82
90. Mantle D, Preedy VR. Free radicals as mediators of alcohol toxicity. Adverse Drug React Toxicol Rev 1999 Nov;18(4):235-52
91. Manso CF. Alcohol and free radicals. Various consequences: protein synthesis, endocrine disorders, immunity. Role of stress.Acta Med Port 1997 Nov;10(11):809-17
92. Preedy VR, Peters TJ. Alcohol and skeletal muscle disease. Alcohol Alcohol 1990;25(2-3):177-87
93. Koo-Ng R, Falkous G, Reilly M, Peters TJ, Mantle D, Preedy VR. Carbonyl levels in type I and II fiber-rich muscles and their response to chronic ethanol feeding in vivo and hydroxyl and superoxide radicals in vitro. Alcohol Clin Exp Res 2000 Dec;24(12):1862-8
94. Preedy VR, Patel VB, Reilly ME, Richardson PJ, Falkous G, Mantle D. Oxidants, antioxidants and alcohol: implications for skeletal and cardiac muscle. Front Biosci 1999 Aug 1;4:e58-66
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