Document Type : review article
Authors
1
Department of Sports Biological Sciences, Faculty of Sports and Health Sciences, Shahid Beheshti University, Tehran, Iran
2
Department of Sports Biological Sciences. Faculty of Sports and Health Sciences. Shahid Beheshti University. Tehran. Iran
Abstract
Resistance exercise leads to the stimulation of muscle protein synthesis, known as exercise-induced muscle hypertrophy. Several hormonal and nutritional factors, directly or indirectly impacting cellular pathways activated by exercise, influence muscle protein synthesis. Among these, acute and chronic alcohol consumption disrupts the balance between anabolic and catabolic mechanisms and affects muscles and heart activity in a different process. However, there is uncertainty regarding the precise mechanisms involved. This systematic review discusses the effects of alcohol consumption on muscle protein synthesis and degradation with emphasis on the hypertrophy pathway of mTOR and hormones involved in exercise-induced muscle protein synthesis. For this purpose, comprehensive searches were performed in Pubmed, Google Scholar, and Web of Science regarding the impact of alcohol consumption on protein synthesis processes, with an emphasis on the mTOR pathway in skeletal muscle following resistance exercise, in the time frame of 2010 to 2024. The following keywords were used to search in the title and keywords: protein synthesis, alcohol, ethanol, skeletal muscle, mTOR signaling, resistance exercise, and hypertrophy. After reviewing the articles, a total of 71 articles were selected for the current review. Previous studies indicate a decrease in growth hormone, testosterone, and insulin-like growth factor along with a negative effect on mTOR due to acute alcohol consumption, which ultimately leading to reduced hypertrophy. 15-20% decrease in basal protein synthesis in skeletal muscle is observed twenty-four hours after alcohol consumption, mostly in type II fibers, and particularly in type IIx fibers, which provide the greatest response to muscular hypertrophy after regular exercise. Chronic alcohol consumption also increases cortisol levels and activates the ubiquitin-proteasome pathway, leading to the activation of atrophic pathways and subsequent muscle mass reduction. Over consumption of alcohol is associated with a 50% prevalence of alcoholic myopathy, which also causes abnormal hypertrophy and diastolic dysfunction in the left ventricle of the heart. Chronic alcohol consumption leads to cardiomyopathy or structural and functional abnormalities of the cardiac muscle. Therefore, considering that alcohol can have negative effects on muscle protein synthesis even up to one day after consumption and disrupt hypertrophic signaling pathways, can have an effect on cardiovascular health, and athletes need to be aware of the detrimental effects and consequences. Understanding the negative effects of alcohol on these physiological processes is crucial for promoting a healthy lifestyle and optimizing exercise outcomes in health and sports.
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