Brain and liver monoamine oxidase type A and type B activity in alcoholics and controls

Greater monoamine oxidase a binding in alcohol dependence

BACKGROUND

Alcohol dependence (AD) is a multiorgan disease in which excessive oxidative stress and apoptosis are implicated. Monoamine oxidase A (MAO-A) is an important enzyme on the outer mitochondrial membrane that participates in the cellular response to oxidative stress and mitochondrial toxicity. It is unknown whether MAO-A levels are abnormal in AD. We hypothesized that MAO-A VT, an index of MAO-A level, is elevated in the prefrontal cortex (PFC) during AD, because markers of greater oxidative stress and apoptosis are reported in the brain in AD and a microarray analysis reported greater MAO-A messenger RNA in the PFC of rodents exposed to alcohol vapor.

METHODS

Sixteen participants with alcohol dependence and 16 healthy control subjects underwent [(11)C]-harmine positron emission tomography. All were nonsmoking, medication- and drug-free, and had no other past or present psychiatric or medical illnesses.

RESULTS

MAO-A VT was significantly greater in the PFC (37%, independent samples t test, t₃₀ = 3.93, p < .001), and all brain regions analyzed (mean 32%, multivariate analysis of variance, F₇,₂₄ = 3.67, p = .008). Greater duration of heavy drinking correlated positively with greater MAO-A VT in the PFC (r = .67, p = .005) and all brain regions analyzed (r = .73 to .57, p = .001-.02).

CONCLUSIONS

This finding represents a new pathological marker present in AD that is therapeutically targetable through direct inhibition or by novel treatments toward oxidative/pro-apoptotic processes implicated by MAO-A overexpression.

The urinary excretion of tryptophan and tryptophan metabolites in the chronic ethanol-fed rat

An investigation was made into the hypothesis that chronic ethanol ingestion disturbs the metabolism of tryptophan which is reflected by alterations in the urinary excretion of the metabolites 5-hydroxyindoleacetic acid (5-HIAA), anthranilic acid (AA) and indoleacetic acid (IAA). In particular, we investigated whether experimental chronic alcoholism is associated with a decrease in the tryptophan metabolite ratios as suggested in the literature. Male Wistar rats were chronically fed a nutritionally-complete liquid diet in which ethanol comprised 35% of total calories: controls were pair-fed identical amounts of the same diet in which ethanol was replaced by isocaloric glucose. At 6 weeks, 24 h urine samples were collected for the analysis of tryptophan, 5-HIAA, AA and IAA by HPLC. During ethanol-feeding there were reductions in the daily urinary excretion (i.e. mumol/24 h) of tryptophan (-57%, P = 0.026) and concomitant increases in 5-HIAA excretion (62%, P = 0.057). Expression of data in terms of lean tissue mass (i.e. urinary creatinine) revealed identical conclusions. An analysis was performed on the molar ratios of these urinary analytes. The tryptophan: total metabolite ratio was significantly decreased (by -53%), but the AA: total metabolite ratio was not significantly altered (P = 0.102). The ratios 5-HIAA/AA and 5-HIAA/IAA were slightly increased, but they did not attain statistical significance (P > 0.351). It was concluded that chronic ethanol feeding is associated with significant changes in the urinary excretion of tryptophan and its related metabolites.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain gamma-aminobutyrate transaminase and monoamine oxidase activities in suicide victims

The activity of gamma-aminobutyrate amino-transferase (GABA-T) and monoamine oxidase (MAO-A and -B) was measured in 42 postmortem human brains. Three brain regions (frontal cortex, cingulate cortex and hypothalamus) from 23 controls without known neurological or psychiatric disorder and from 19 suicide victims were analysed. The suicide victims were classified according to the use of violent and non-violent methods and to the presence or absence of a known history of depressive disorder. No difference was found between the series of suicide victims and the control subjects with regard to GABA-T activity. Carbon monoxide poisoning and death by drug overdose, however, were found to reduce the activity. The MAO-B activity did not differ between the groups. With MAO-A, however, a significant elevation (t = 2.01; P less than 0.05) was found in the hypothalamic region of the suicide victims. The difference seemed to be confined to the subgroup of suicides with a record of depressive disorder.

Platelet monoamine oxidase and plasma dopamine-beta-hydroxylase activities in non-abstinent chronic alcoholics. Relation to clinical parameters

Platelet monoamine oxidase (MAO) and plasma dopamine-beta-hydroxylase (DBH) activities were determined in 27 male non-abstinent chronic alcoholics. Compared to 24 normals, no significant difference in both enzyme activities was found. Alcoholics with at least one alcoholic first degree relative had a trend toward lower platelet MAO activity compared to those without such a history. Matched pair analysis showed that alcoholics of the former subgroup had significantly lower MAO activity than controls. Demented alcoholics had significantly reduced plasma DBH activity compared with the non-demented subgroup and with age, and sex, matched controls.