Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0016382 (flushing)
 6,387 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Research into the causes of alcoholism is a relatively recent scientific endeavor. One area of study which could lead to better understanding of the disease is the possibility of a genetic predisposition to alcoholism. Recent work has demonstrated that people have varying complements of enzymes to metabolize alcohol. Current knowledge is examined about the influence of various ethanol metabolizing enzymes on alcohol consumption by Asians and members of other ethnic groups. The two principal enzymes involved in ethanol oxidative metabolism are alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). ADH is responsible for the metabolism of ethanol to acetaldehyde. ALDH catalyzes the conversion of acetaldehyde to acetate. The different isozymes account for the diversity of alcohol metabolism among individuals. An isozyme of ADH (beta 2 beta 2) is found more frequently in Asians than in whites, and an ALDH isozyme (ALDH2), although present in Asians, often is in an inactive form. The presence of an inactive form of ALDH2 is thought to be responsible for an increase in acetaldehyde levels in the body. Acetaldehyde is considered responsible for the facial flushing reaction often observed among Asians who have consumed alcohol. A dysphoric reaction to alcohol, producing uncomfortable sensations, is believed to be a response to deter further consumption. Although the presence of an inactive ALDH2 isozyme may serve as a deterrent to alcohol consumption, its presence does not fully explain the levels of alcohol consumption by those with the inactive isozyme. Other conditions, such as social pressure, and yet undetermined biological factors, may play a significant role in alcohol consumption.
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PMID:Research on alcohol metabolism among Asians and its implications for understanding causes of alcoholism. 251 95

A much higher incidence of alcohol flushing among Orientals in comparison to Caucasians, i.e., greater than 50% vs 5%-10%, has been attributed to racial differences in alcohol-metabolizing enzymes. A large majority of Orientals are "atypical" in alcohol dehydrogenase-2 locus (ADH2), and their livers exhibit significantly higher ADH activity than the livers of most Caucasians. Approximately 50% of Orientals lack the mitochondrial aldehyde dehydrogenase (ALDH2) activity, and elimination of acetaldehyde might be disturbed. We determined by means of hybridization of genomic DNA samples with allele specific oligonucleotide probes, genotypes of the ADH2 and ALDH2 loci in Japanese alcohol flushers and nonflushers. We found that all individuals with homozygous atypical ALDH2(2)/ALDH2(2) and most of those with heterozygous atypical ALDH1(2)/ALDH2(2) were alcohol flushers, while all subjects with homozygous usual ALDH1(2)/ALDH1(2) were nonflushers. Frequency of the atypical ADH2(2) was found to be higher in alcohol flushers than in nonflushers, but the statistical significance was not established in the sample size examined.
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PMID:Genotype of alcohol dehydrogenase and aldehyde dehydrogenase loci in Japanese alcohol flushers and nonflushers. 271 75

Although mitochondrial aldehyde dehydrogenase (ALDH2) has been thought to play a major role in acetaldehyde detoxification, and the high incidence of 'alcohol flushing' among Orientals is attributed to the inherited deficiency of ALDH2, the role of cytosolic aldehyde dehydrogenase (ALDH1) cannot be ignored. On the premise that alcohol flushing in Caucasians could be related to ALDH1 abnormalities, we examined the enzyme properties and electrophoretic mobilities of ALDH1 partially purified from red blood cells of nine unrelated alcohol flushers. One exhibited very low activity (10-20% of control level), and another exhibited moderately low activity (60%) and altered kinetic properties. The electrophoretic mobilities of these two samples were also distinguishable from the control samples. Immunological quantitation indicated that the amounts of ALDH1 protein in these two samples were not reduced in parallel with their enzyme deficiency. In the first case, the two characteristics, i.e. very low enzyme activity and alcohol flushing, were inherited by her daughter.
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PMID:Cytosolic aldehyde dehydrogenase (ALDH1) variants found in alcohol flushers. 272 94

An ethnic predisposition to ethanol-provoked flushing among diverse Mongoloid populations may be the consequence of a delayed oxidation and accumulation of acetaldehyde. Orientals who flush after oral alcohol are more likely to have cutaneous erythema after topical ethanol or propanol, and the cutaneous vascular reaction to primary alcohols is actually provoked by the corresponding aldehyde. The cutaneous reaction to primary alcohols can be totally blocked by pretreatment with 4-methylpyrazole, a potent inhibitor of alcohol dehydrogenase.
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PMID:Cutaneous vascular sensitivity to lower aliphatic alcohols and aldehydes in Orientals. 293 66

The existence of racial differences in alcohol sensitivity between Oriental and Caucasian populations has been well documented. The primary manifestation is a highly visible facial flushing (47-85% in Orientals vs 3-29% in Caucasians) accompanied by other objective and subjective symptoms of discomfort. Even among different Oriental groups, subtle differences in the flushing response and alcohol consumption can exist. North and South American Indian populations differ in phenotypes for alcohol dehydrogenase and aldehyde dehydrogenase, but systematic studies comparing degree of flushing, alcohol elimination rates and blood acetaldehyde levels in these populations are lacking. Although flushing does not automatically 'immunize' an individual against alcohol use, those susceptible tend to consume less alcohol, at least in Orientals. However, the flushing phenomenon cannot be the sole explanation for differences in incidences of alcoholism among different racial groups. Socio-cultural, environmental and genetic factors also have to be considered. An increased incidence of flushing has been found to associate with a familial risk of development of future alcoholism in a Caucasian population. It remains to be determined whether the same is true in Orientals. Most biochemical investigations of the flushing phenomenon have focused on aspects of alcohol metabolism. Based on recent findings, a convincing mechanism is the higher accumulation of acetaldehyde in flushing subjects because they have an unusual, less-active liver aldehyde dehydrogenase isozyme (ALDHI). The possibility that an 'atypical' alcohol dehydrogenase, which is present in 85-90% of Oriental subjects, can contribute to increased blood acetaldehyde levels in flushing subjects cannot be ruled out. Based on results of a small number of pedigree studies which demonstrated familial resemblances in flushing, a pharmacogenetic defect in ALDHI has been proposed to be responsible for flushing. Other possible biochemical mechanisms (e.g. prostaglandins) and genetic defects need to be investigated.
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PMID:Racial differences in alcohol sensitivity. 293 17

Chlorpropamide (CP), a sulfonylurea-type oral hypoglycemic agent, is known to provoke a flushing reaction reminiscent of the disulfiram-ethanol reaction in certain individuals. This is manifested in rodents by an increase in blood acetaldehyde levels after ethanol administration. When the sulfonamide N1-nitrogen of CP was substituted with an ethyl group, the product, N1-ethylchlorpropamide, was found to be three times as active as CP in raising ethanol-derived blood acetaldehyde. However, whereas CP lowered fasting blood glucose in rats measured over 6 h, N1-ethylchlorpropamide was devoid of hypoglycemic activity, suggesting that the latter might be potentially useful as an alcohol deterrent agent.
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PMID:A nonhypoglycemic chlorpropamide analog that inhibits aldehyde dehydrogenase. 305 78

Differences in the pharmacokinetics of alcohol absorption and elimination are, in part, genetically determined. There are polymorphic variants of the two main enzymes responsible for ethanol oxidation in liver, alcohol dehydrogenase and aldehyde dehydrogenase. The frequency of occurrence of these variants, which have been shown to display strikingly different catalytic properties, differs among different racial populations. Since the activity of alcohol dehydrogenase in liver is a rate-limiting factor for ethanol metabolism in experimental animals, it is likely that the type and content of the polymorphic isoenzyme subunit encoded at ADH2, beta-subunit, and at ADH3, the gamma-subunit, are contributing factors to the genetic variability in ethanol elimination rate. The recent development of methods for genotyping individuals at these loci using white cell DNA will allow us to test this hypothesis as well as any relationship between ADH genotype and the susceptibility to alcoholism or alcohol-related pathology. A polymorphic variant of human liver mitochondrial aldehyde dehydrogenase, ADLH2, which has little or no acetaldehyde oxidizing activity has been identified. Individuals with the deficient ALDH2 phenotype do not have altered ethanol elimination rates but they do exhibit high blood acetaldehyde levels and dysphoric symptoms such as facial flushing, nausea and tachycardia, after drinking alcohol. Because acetaldehyde is so reactive, it binds to free amino groups of proteins including a 37 kilodalton hepatic protein-acetaldehyde adduct and may elicit an antibody response. We would predict that individuals who have low ALDH2 activity because of liver disease or because they have the inactive ALDH2 variant isoenzyme might form more protein-acetaldehyde adducts and elicit a greater immune response. These adducts may represent good biological markers of alcohol abuse and may also play a role in liver injury due to chronic alcohol consumption.
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PMID:Genetic polymorphism of enzymes of alcohol metabolism and susceptibility to alcoholic liver disease. 306 25

Ethanol-induced flushing (EIF) occurs in up to 80% of Asians and is characterized by facial flushing, tachycardia, and increased cardiac output. Since endogenous opiates and prostaglandins may be mediators of flushing syndromes, we attempted to block EIF in four Asian flushers with single doses of either the opiate antagonist nalmefene, or the prostaglandin synthesis inhibitor indomethacin. Nonflushers (2 Caucasian, 2 Asian) and four Asian flushers were given on separate days water, ethanol (0.4 g/kg p.o.), ethanol plus nalmefene (2 mg i.v.), or ethanol plus indomethacin (50 mg p.o.). Ethanol concentrations of flushers and nonflushers were similar. Mean (+/- SEM) plasma acetaldehyde concentrations of flushers (28.2 +/- 11.8 microM) were significantly greater than nonflushers (1.4 +/- 0.5 microM) following ethanol ingestion (p less than 0.001). Ethanol alone always induced a significant rise in facial skin temperature [mean area under the curve (AUC) = 5142 +/- 648 % delta T x min, p less than 0.01] and of pulse (mean AUC = 1622 +/- 120 bpm x min, p less than 0.001) in flushers compared to water ingestion. A single dose of nalmefene (2 mg i.v.) but not indomethacin (50 mg p.o.), reduced the mean (+/- SEM) ethanol-induced rise in facial skin temperature of flushers by 58 +/- 14% (p less than 0.05) without changing plasma acetaldehyde concentrations. These data are preliminary evidence that the opiate antagonist, nalmefene, blocks some of the vascular manifestations of EIF without altering the elevated plasma concentrations of acetaldehyde.
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PMID:Opiate antagonist nalmefene inhibits ethanol-induced flushing in Asians: a preliminary study. 306 20

The cutaneous vasodilation produced by ethanol is exaggerated when acetaldehyde levels are increased after aldehyde dehydrogenase inhibition, producing a flushing reaction, the mechanism of which is unknown. The authors investigated whether ethanol and its metabolites affect the vascular release of prostacyclin, a potent vasodilator, and whether such an effect might be modified by chronic alcohol consumption. Aortic rings from rats fed Chow ad libitum or pair-fed liquid diets containing either ethanol (36% of energy) or isocaloric carbohydrate for 4 to 5 weeks were incubated in Krebs-Ringer bicarbonate supplemented with saturating amounts of arachidonate (10-20 microM) in the presence of ethanol (10-100 mM), acetaldehyde (10-100 microM) or acetate (1.25-5 mM). Prostacyclin was measured by the radioimmunoassay of 6-keto-prostaglandin F1 alpha. Acetaldehyde produced a concentration-dependent stimulation of prostacyclin production both in alcohol-fed and control rats, whereas acetate did not. This effect was associated with increased conversion of arachidonate (either exogenous or released with A23187) and of prostaglandin endoperoxide H2 to prostacyclin. Ethanol did not affect prostacyclin release in control rats, but, in aortas from alcohol-fed animals, 50 mM ethanol did stimulate prostacyclin formation. These effects may contribute to the cardiovascular responses associated with high blood acetaldehyde levels in flushers and with high ethanol levels in alcoholics. In conclusion, acetaldehyde is a potent stimulant of vascular prostacyclin production. This effect is due, at least in part, to enhanced activity of prostacyclin synthase. Ethanol acquires such a stimulatory effect on prostacyclin formation after chronic alcohol consumption.
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PMID:Acute and chronic effects of ethanol and its metabolites on vascular production of prostacyclin in rats. 310 Jul 72

The metabolism of acetaldehyde has received considerable attention in the past years owing to its acute and chronic toxic effects in humans. Aldehyde dehydrogenase (ALDH) catalyzes the oxidation of acetaldehyde in liver and other organs. Two major isozymes of hepatic ALDH (ALDH I or E2 and ALDH II or E1), which differ in their structural and functional properties, have been characterized in humans. The ALDH I with a low Km for acetaldehyde is predominantly of mitochondrial origin and ALDH II which has a relatively higher Km is of cytosolic origin. An inherited deficiency of ALDH I isozyme has been found among Japanese and Chinese which is primarily responsible for producing acute alcohol sensitivity symptoms (flushing response) after drinking mild doses of alcohol. Biochemical, immunochemical and molecular genetics data indicate a structural mutation in the ALDH I isozyme gene responsible for the loss in catalytic activity. Population genetic studies indicate a wide prevalence of this ALDH polymorphism among individuals of Mongoloid race. Flushing response to alcohol shows familial resemblances and preliminary family data from Japan, China and Korea hint to an autosomal codominant inheritance for ALDH I isozyme deficiency. The ALDH polymorphism is apparently responsible for the low incidence of alcoholism in Japanese, Chinese and Koreans. Alcohol-induced sensitivity due to ALDH isozyme deficiency may act as an inhibitory factor against excessive alcohol drinking thereby imparting a protection against alcoholism.
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PMID:Polymorphism of aldehyde dehydrogenase and alcohol sensitivity. 310 30


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