Alcohol tolerance gene
Alcohols create a group of organic compounds derived from hydrocarbons and containing one or more hydroxyl (-OH) groups. In alcoholic beverage ethanol (C2H5OH, ethyl alcohol) is found, the substance is known to be psychoactive.
Psychoactive substances are those that cause certain psychological effects and when consumed regularly lead to both psychological and physical addiction.
The capacity of the body to tolerate certain amounts of alcohol is known as alcohol tolerance.
The conception of alcohol tolerance includes direct tolerance, the continuation of ebriety and resistance to the development of alcohol dependence.
The average adult metabolizes 0.6 Oz of ethanol for 90 minutes. The liver breaks down alcohol by producing enzymes called alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). Alcohol dehydrogenase acts by catalyzing the oxidation of alcohols to aldehydes.
It is considered that when a person consumes alcohol in large amounts regularly the liver produces more enzymes and the activity of alcohol dehydrogenase is elevated, therefore the metabolism of ethanol happens faster. As the alcohol is eliminated quickly the person experiences the need to drink more in order to reach the same effect as before.
On the other hand the brain is also involved in alcohol tolerance. Some effects of alcohol occur due to the suppression of neurotransmitters. The inhibition of GABA system results in decreased alertness, the feeling of sleepiness and relaxation.
As the alcohol consumption increases the brain gets used to to ethanol and as follows an individual requires higher quantities of alcohol to experience the desirable condition.
The scientists have identified an alcohol tolerance gene. Individuals who carry this gene may be more susceptible to alcohol abuse.
According to the results of the research, those who can tolerate higher doses of alcohol are more likely to suffer from alcohol dependence in the future. Such persons consume large doses of alcohol before they feel the symptoms of intoxication and are susceptible to alcohol dependence.
A sequence CHRNA5 () on chromosome 15 was found to be associated with alcohol tolerance.
The above-mentioned research was conducted in the Ernest Gallo Clinic and Research Center, California.
313 students from 18 to 29 years old participated in this research. The investigated individuals had to drink 20% ethanol solution in 8 minutes. Later the students had to complete a form regarding their feelings in different periods of time after the drink to estimate the intoxication. The scientists also evaluated the body sway.
Their DNA sequences were analyzed and the sequence CHRNA5 was identified to be connected with the alcohol tolerance.
Alcohol dependence and ADH and ALDH genes
The alleles that encode the synthesis of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) affect the alcohol metabolism and susceptibility to alcoholism. For example, the functional variants of allele ADH1B*2 and ADH1B*3 are associated with higher enzyme activity and rapid transformation of ethanol to acetaldehyde. This substance causes facial flushing (alcohol flush reaction) and an aversion to alcohol. These effects appear to be protective against alcoholism. ADH1B and ADLH2 are strongly associated with risk of developing alcohol abuse. Other alleles variants are associated with different metabolism rates and mechanisms of action. Some of them are protective whereas the other increase the risk of dependence.