Alcohol metabolism

The metabolic processes which take place in our body are turning digestible substances into other compounds. During their metabolism, some of the metabolized compounds become more or less toxic than the original substance. One of the metabolic processes is called oxidation. It helps, for instance, to clean the ingested alcohol from our body. It is necessary to clean the alcohol from the blood to avoid its toxicity on cells and organs in human organism. A portion of the alcohol is excreted unchanged in breath and urine, while the remaining portion gets metabolized in liver. Percentage of alcohol is always higher when measured in the blood, than in the breath. After the ingestion, alcohol gets absorbed from the stomach and intestines into the bloodstream, which transports it to various parts of our body, including liver. It is in the liver that the most of alcohol’s degradation occurs. Alcohol-dehydrogenase (ALD) is the liver enzyme that helps to metabolize alcohol into acetaldehyde, which is subsequently catabolized to acetate, and eventually, to carbon-dioxide and water. Other enzymes, like cytochrome P450IIE1 (CYP2E1) also help to run alcohol metabolic processes. Levels of CYP2E1 can be increased in chronic alcohol abuse. Speed of alcohol metabolism is individual and it depends on the quantity of liver enzymes. It depends on other factors as well. For example, the main alcohol catabolic enzymes are alcohol-dehydrogenase and aldehyde-dehydrogenase, which come in different molecular forms. Also, their quantity and functionality depend on racial and genetic differences and so does the speed of alcohol metabolism. After one alcoholic drink, alcohol can be detected after 3 hours. Following two alcoholic drinks, it can be detected after 4,5 hours and after three drinks, it takes 6 hours for detection in blood. After four alcoholic drinks, alcohol can be detected after 7 hours. The same amount of alcohol consumed over a longer period of time results in lower blood levels of alcohol.

It is considered that after consuming one drink of alcohol, it takes 30-45 minutes to reach its peak concentration. The process of alcohol degradation takes longer than the alcohol absorption process. Therefore, we have to be careful in order to avoid the intoxication due to a fast intake of alcoholic beverages. Absorption and the rest of alcohol metabolism are being influenced by the other factors, such as food intake and gender. The quality and quantity of food in stomach influence alcohol absorption. On an empty stomach, alcohol is absorbed three times faster than when a stomach is full. After consuming the same quantity of alcohol, women will have higher concentration of alcohol in blood than men. This makes female gender more susceptible to alcohol induced diseases. Women also have less of the ALD enzyme in gastrointestinal wall, thus allowing more alcohol to pass into blood.

Although alcohol has high energetic potential, its use does not lead to an increase in body mass, especially in women. Alcohol intake can also affect the balance of sex hormones. Misuse of alcohol can destroy testicles and sperm production, and reduce testosterone synthesis, all leading to feminization of men (for instance, increased breasts). In women, increased alcohol consumption leads to an increase in estradiol production, therefore causing a disbalance of sex hormones. Alcohol consumption also affects metabolism and efficacy of medications. For example, CYP2E1 enzymes are very much engaged in alcohol metabolism, but also in metabolism of various drugs. For example, simultaneous use of alcohol and acetaminophen (analgetic, antipyretic) causes degradation of acetaminophen to compounds that may be toxic to liver (hepatotoxic).

Increased alcohol metabolism and deterioration of hepatic function can be detected by monitoring the level of certain markers, usually connected to alcohol metabolism. Glycoprotein transferrin (CDT), for instance, helps in transporting iron but is also related to alcohol metabolism. CDT is considered as one of the most reliable markers for detecting (ab)normal alcohol metabolism and subsequently chronic misuse of alcohol. Other markers include gamma-glutamyl transferase (GGT) which facilitates transport of amino acids through cellular membrane, aspartate transaminase (AST) which facilitates transition of aspartate and alpha-ketoglutarate to oxaloacetate and glutamate, alanine transaminase (ALT) which facilitates transition of alanine and alpha-ketoglutarate to pyruvate and glutamate. It takes 2-5 weeks of alcohol abstinence for increased levels of GGT to return to normal values. On the other hand, CDT levels take 1-2 months of abstinence to normalize. Therefore, CDT levels are considered as the most reliable markers of chronic alcohol misuse, but using the combination of all available markers (CDT, GGT, ALT, AST, HDL cholesterol, MCV – Mean Corpuscular Volume of erythrocytes, is still recommended in order to get the best insight into the potential liver dysfunction.

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