Platelet Monoamine Oxidase B Activity Research Articles

Platelet Serotonin (5-HT) Concentration, Platelet Monoamine Oxidase B (MAO-B) Activity and HTR2A, HTR2C, and MAOB Gene Polymorphisms in Asthma.

The complex role of the serotonin system in respiratory function and inflammatory diseases such as asthma is unclear. Our study investigated platelet serotonin (5-HT) levels and platelet monoamine oxidase B (MAO-B) activity, as well as associations with HTR2A (rs6314; rs6313), HTR2C (rs3813929; rs518147), and MAOB (rs1799836; rs6651806) gene polymorphisms in 120 healthy individuals and 120 asthma patients of different severity and phenotypes. Platelet 5-HT concentration was significantly lower, while platelet MAO-B activity was considerably higher in asthma patients; however, they did not differ between patients with different asthma severity or phenotypes. Only the healthy subjects, but not the asthma patients, carrying the MAOB rs1799836 TT genotype had significantly lower platelet MAO-B activity than the C allele carriers. No significant differences in the frequency of the genotypes, alleles, or haplotypes for any of the investigated HTR2A, HTR2C and MAOB gene polymorphisms have been observed between asthma patients and healthy subjects or between patients with various asthma phenotypes. However, the carriers of the HTR2C rs518147 CC genotype or C allele were significantly less frequent in severe asthma patients than in the G allele carriers. Further studies are necessary to elucidate the involvement of the serotonergic system in asthma pathophysiology.

Detention in Juvenile Correctional Facilities Is Associated with Higher Platelet Monoamine Oxidase B Activity in Males.

Juvenile delinquency is related to several biological factors, yet very few vulnerability biomarkers have been identified. Previous data suggest that the enzyme monoamine oxidase B (MAO-B) influences several personality traits linked to the propensity to engage in delinquent behavior. Building on this evidence, we assessed whether conduct disorder (CD), juvenile delinquency adjudications, or detention in a correctional facility were associated with either platelet MAO-B activity or the MAOB rs1799836 polymorphism. The study enrolled 289 medication-free male youths, including 182 individuals detained in a correctional facility (with or without a diagnosis of CD). Of the remaining 107 participants, 26 subjects had a diagnosis of CD, and 81 were mentally healthy controls. Platelet MAO-B activity was determined by spectrophotofluorometry, while MAOB rs1799836 was genotyped using qPCR. Platelet MAO-B activity, corrected for age and smoking, was significantly higher in juvenile detainees (p < 0.001), irrespective of CD diagnosis. MAOB rs1799836 was not associated with platelet MAO-B activity or with detention in a correctional facility, CD diagnosis, or delinquent behavior. These data suggest that detention in a juvenile correctional facility increases platelet MAO-B activity in male adolescents. Future studies are needed to determine the mechanisms and functional significance of MAO-B peripheral elevation in juvenile male detainees.

Timed consumption of a New Zealand blackcurrant juice support positive affective responses during a self-motivated moderate walking exercise in healthy sedentary adults

BackgroundAffective responses experienced during exercise are a significant determinant on exercise adherence. We have previously demonstrated that consumption of New Zealand (NZ) blackcurrants preserves cognition by attenuating the feeling of fatigue. This positive affective response correlated with the ability of blackcurrant polyphenols to support monoamine neurotransmission via inhibition of monoamine oxidase-B (MAO-B) activity. Here we explore how the consumption of a NZ blackcurrant juice (BJ) influenced affective responses and potential ergogenic action on the motivation to adhere to a low impact walking exercise.MethodsIn a parallel randomized controlled study (Trial registration #: ACTRN12617000319370p, registered 28th February 2017, http://www.anzctr.org.au/), 40 healthy sedentary male and female participants drank a BJ or matched placebo (PLA) (n = 20 per group), 1 h prior to a self-motivated treadmill walk, where heart rate and affective responses (exertion [ES] or feeling / mood [FS]) scores) were recorded at 3 or 5 min intervals. Blood glucose, lactate, malondialdehyde (MDA) and platelet MAO-B activity were measured pre- and post-exercise and comparisons were conducted using with Student’s t-tests. Subjective data were analysed using 2-way ANOVA with appropriate post hoc tests.ResultsConsuming a BJ 1 h prior to exercise caused a 90% decline in platelet MAO-B activity. The exercise had no significant (p > 0.05) effect on blood lactate, glucose or plasma MDA levels. Assessment of affective responses over the first 60 mins (adjusting for participant drop-out) revealed a time-dependent ES increase in both groups, with ES reported by participants in the BJ group consistently lower than those in the PLA group (p < 0.05). FS declined in PLA and BJ groups over 60 mins, but an inverse relationship with ES was only observed within the PLA group (r2 = 0.99, p = 0.001). Whilst the average time walked by participants in the BJ group was 11 mins longer than the PLA group (p = 0.3), and 30% of the BJ group achieving > 10 km compared to only 10% for the PLA group (p = 0.28), statistical significance was not achieved.ConclusionOur findings demonstrate that drinking a polyphenolic-rich NZ blackcurrant juice 1 h prior to exercise supports positive affective responses during a self-motivated exercise.

Platelet monoamine oxidase activity and interpersonal violence in male suicide attempters

Low platelet monoamine oxidase B (MAO-B) activity, proxy of low central serotonergic functions, has been shown to correlate with criminal behavior in adolescents that come from an unfavorable psychosocial environment but not in adolescents from good conditions, indicating a link between environment, MAO-B activity and aggressive behavior. The purpose of this study was to examine the association between MAO-B activity and lifetime interpersonal violence in suicide attempters. The study included a total of 28 suicide attempters (18 men and 10 women). Assessments of childhood exposure to and expressed interpersonal violence during childhood and as an adult were carried out with the Karolinska Interpersonal Violence Scale (KIVS). Platelet MAO-B activity was measured with 2-phenylethylamine (b-PEA) as substrate. Broken down by gender, the correlations between platelet MAO-B activity and both exposure scores to interpersonal violence as a child and expressed lifetime interpersonal violence were significant in male suicide attempters (r = −0.61, p = 0.035; r = −0.84, p = 0.0005), but not in women. Our finding of significant associations between interpersonal violence and low MAO-B activity need to be replicated in other cohorts of suicide attempters.

Associations of MAOA-VNTR or 5HTT-LPR alleles with attention-deficit hyperactivity disorder symptoms are moderated by platelet monoamine oxidase B activity

The monoamine systems have been suggested to play a role in the biological basis of attention-deficit hyperactivity disorder (ADHD) symptoms. Thus, polymorphisms, for example, in the monoamine oxidase A (MAOA) and the serotonin transporter (5HTT) genes have been associated with ADHD-like phenotypes. Furthermore, platelet monoamine oxidase B (MAOB) activity has frequently been linked to impulsiveness-related traits. In this study, we have studied ADHD symptoms with regard to the combination of platelet MAOB activity and MAOA-variable number of tandem repeats (VNTR) or 5HTT-LPR genotype. The study group consisted of 156 adolescent twin pairs, that is, 312 individuals, who participated in a previous study. ADHD symptoms were scored with a structured clinical interview of both the twins and a parent using Kiddie Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version. The presence of a short 5HTT-LPR or short MAOA-VNTR allele, in combination with high levels of platelet MAOB enzyme activity was associated with higher scores of ADHD-like problems (P<0.001 and 0.01, respectively). This re-examination of ADHD scores in a nonclinical sample suggests that effects of MAOA-VNTR and 5HTT-LPR are moderated by platelet MAOB activity.

Platelet monoamine oxidase activity predicts alcohol sensitivity and voluntary alcohol intake in rhesus monkeys

Platelet monoamine oxidase B (MAO-B) has been proposed to be a biological marker for the properties of monoamine systems, with low activity being associated with vulnerability for high scores on personality traits such as sensation seeking, monotony avoidance, and impulsiveness, as well as for vulnerability for alcoholism. In the present study, platelet MAO-B activity was analysed in 78 rhesus macaques, and its relation to voluntary alcohol intake and behaviours after intravenous alcohol administration was observed.Monkeys with low platelet MAO-B activity had low levels of 5-hydroxyindole acetic acid in cerebrospinal fluid and showed excessive aggression after alcohol administration. A novel finding was that animals with low platelet MAO-B activity showed less intoxication following alcohol administration. As we have shown previously, they also voluntarily consumed more alcohol. We here replicate results from studies on both humans and non-human primates, showing the utility of platelet MAO as a marker for risk behaviours and alcohol abuse. Furthermore, we link platelet MAO activity to alcohol sensitivity.

Platelet Monoamine Oxidase B Activity Did Not Predict Destructive Personality Traits or Violent Recidivism: A Prospective Study in Male Forensic Psychiatric Examinees

Aims: This prospective study was designed to replicate previous findings of an association between the platelet monoamine oxidase B (MAO-B) activity and factors of relevance for criminal behaviour in a well-documented clinical study population. Methods: Subjects (n = 77, aged 17–76 years, median 30 years) were recruited among consecutive perpetrators of severe interpersonal violent and/or sexual crimes referred to forensic psychiatric investigation. Participants were extensively investigated by structured psychiatric, psychological and social workups, including state-of-the-art rating instruments and official records, and with laboratory tests including venous blood sampling for determination of MAO-B activity. A subset of 36 individuals had lumbar punctures to measure cerebrospinal fluid concentrations of monoamine neurotransmitter metabolites. Results: Platelet MAO-B activity did not show any significant correlation with assessments of childhood behavioural disorders, substance abuse, or psychosocial adversity, nor with any crime-related factors, such as scores on the Life History of Aggression Scale, the Psychopathy Checklist or recidivistic violent crime. No significant correlation was found between MAO-B and any of the monoamine metabolites. Analyses in subgroups of smokers/non-smokers did not change this overall result. Conclusions: The findings of the present study did not support the use of MAO-B as a biological marker for aggression-related personality traits or as a predictor for violent recidivism among violent offenders.

Altered Platelet Monoamine Oxidase-B Activity in Idiopathic Parkinson’s Disease

A case-control study was undertaken to investigate the status of platelet monoamine oxidase-B (MAO-B) activity in Indian cases of idiopathic Parkinson's disease. A significant increase in the activity of platelet MAO-B was observed in Parkinson's cases (n = 26) as compared to controls (n = 26). No significant change in the activity of the enzyme was observed while the data was analysed with respect to age, sex and duration of disease. A trend of decrease in platelet MAO-B activity was observed in Parkinson's cases with respect to stage although the change was not significant. No correlation in platelet MAO-B activity was observed with respect to age and sex in the control subjects. Parkinson's cases treated with L-DOPA and MAO-B inhibitor exhibited decreased platelet MAO-B activity as compared to drug naive cases and those treated with L-DOPA alone. Interestingly, Parkinson's cases treated with L-DOPA and amantadine also had lower platelet MAO-B activity as compared to drug naive cases and those treated with L-DOPA alone. Activity of platelet MAO-B in Parkinson's patients was increased in naive cases and those treated with L-DOPA alone or in combination with other drugs compared to controls. The results of the present study indicate that phenotypic activity of platelet MAO-B is high in Indian Parkinson's cases. Further, action mechanism of drugs used in the treatment of Parkinson's disease could be understood by assay of platelet MAO-B activity. It is an interesting observation and may be looked further in large number of cases.

ADHD and Disruptive behavior scores – associations with MAO-A and 5-HTT genes and with platelet MAO-B activity in adolescents

BackgroundPharmacological and genetic studies suggest the importance of the dopaminergic, serotonergic, and noradrenergic systems in the pathogenesis of Attention Deficit Hyperactivity Disorder (ADHD) and Disruptive Behavior Disorder (DBD). We have, in a population-based sample, studied associations between dimensions of the ADHD/DBD phenotype and Monoamine Oxidase B (MAO-B) activity in platelets and polymorphisms in two serotonergic genes: the Monoamine Oxidase A Variable Number of Tandem Repeats (MAO-A VNTR) and the 5-Hydroxytryptamine Transporter gene-Linked Polymorphic Region (5-HTT LPR).MethodsA population-based sample of twins, with an average age of 16 years, was assessed for ADHD/DBD with a clinical interview; Kiddie Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version (K-SADS-PL). Blood was drawn from 247 subjects and analyzed for platelet MAO-B activity and polymorphisms in the MAO-A and 5-HTT genes.ResultsWe found an association in girls between low platelet MAO-B activity and symptoms of Oppositional Defiant Disorder (ODD). In girls, there was also an association between the heterozygote long/short 5-HTT LPR genotype and symptoms of conduct disorder. Furthermore the heterozygote 5-HTT LPR genotype in boys was found to be associated with symptoms of Conduct Disorder (CD). In boys, hemizygosity for the short MAO-A VNTR allele was associated with disruptive behavior.ConclusionOur study suggests that the serotonin system, in addition to the dopamine system, should be further investigated when studying genetic influences on the development of Disruptive Behavior Disorders.

Platelet Monoamine Oxidase Kinetics, Alcoholism Subtypes and Cigarette Smoking

In trying to dissociate the effect of alcohol and tobacco use on platelet monoamine oxidase-B (MAO-B) activity, we compared the enzyme kinetics in controls (n = 66) and alcohol-dependent patients (n = 81), subdivided according to the severity of both, alcohol and tobacco use. Platelet MAO-B kinetics was measured spectrophotofluorimetrically in chronic alcohol intoxication and after 3 weeks abstinence. In alcoholic patients, an increased Michaelis-Menten constant (16%, p < 0.01) was shown, notwithstanding smoking status. Maximal velocity did not differ between patients and controls when adjusted for smoking. In cigarette smokers, a highly significant dose-dependent reduction of platelet MAO velocity (40%, p < 0.001) was demonstrated, with a similar degree of reduction in patients and controls. Tobacco use itself had no influence on MAO affinity. No differences were shown between subtype 1 and 2 alcoholics, or between the day of admission and the 21st day of abstinence. In conclusion, it seems that both, alcohol and tobacco consumption, may contribute to the lowering of overall platelet MAO-B activity. The effect of alcohol is small, due to interference with substrate binding, and not alteration of catalytic activity. In contrast, the effect of cigarette smoking is pronounced and relates to the dose-dependent reduction of platelet MAO velocity, with no influence on its affinity.

Associations between platelet monoamine oxidase-B activity and acquired colour vision loss in a fish-eating population

Platelet monoamine oxidase-B (MAO-B) has been considered a surrogate biochemical marker of neurotoxicity, as it may reflect changes in the monoaminergic system in the brain. Colour vision discrimination, in part a dopamine dependent process, has been used to identify early neurological effects of some environmental and industrial neurotoxicants. The objective of this cross-sectional study was to explore the relationship between platelet MAO-B activity and acquired colour discrimination capacity in fish-consumers from the St. Lawrence River region of Canada. Assessment of acquired dyschromatopsia was determined using the Lanthony D-15 desaturated panel test. Participants classified with dyschromatopsia ( n = 81) had significantly lower MAO-B activity when compared to those with normal colour vision ( n = 32) (26.5 ± 9.6 versus 31.0 ± 9.9 nmol/min/20 μg, P = 0.030)). Similarly, Bowman's Colour Confusion Index (CCI) was inversely correlated with MAO-B activity when the vision test was performed with the worst eye only ( r = − 0.245, P = 0.009), the best eye only ( r = − 0.188, P = 0.048) and with both eyes together ( r = − 0.309, P = 0.001). Associations remained significant after adjustment for age and gender when both eyes ( P = 0.003) and the worst eye ( P = 0.045) were tested. Adjustment for heavy smoking weakened the association between MAO-B and CCI in the worst eye ( P = 0.140), but did not alter this association for both eyes ( P = 0.006). Adjustment for blood-mercury concentrations did not change the association. This study suggests a relationship between reduced MAO-B activity and acquired colour vision loss and both are associated with tobacco smoking. Therefore, results show that platelet MAO-B may be used as a surrogate biochemical marker of acquired colour vision loss.

Relationship between platelet monoamine oxidase-B (MAO-B) activity and mercury exposure in fish consumers from the Lake St. Pierre region of Que., Canada

Mercury (Hg) is a widespread neurotoxic compound that bio-accumulates in fish and marine mammals. Monoamine oxidase (MAO; EC 1.4.3.4) regulates biogenic amine concentration in the brain and peripheral tissue and has been shown to be a molecular target of Hg compounds in animal models. Blood platelet monoamine oxidase-B (MAO-B) activity may reflect MAO function in the central nervous tissue. Therefore, the objective of this study was to evaluate the relationship between platelet MAO-B and Hg exposure in fish-eating adults ( n = 127) living along the St. Lawrence River (Lake St. Pierre, Que., Canada). Hg concentrations were determined in blood and hair samples. A significant negative association was observed between platelet MAO-B activity and blood-Hg ( r = −0.193, p = 0.029) but not with hair-Hg levels ( r = −0.125, p = 0.169). Multiple linear regression analysis demonstrated that blood-Hg ( β = −4.6, p = 0.011) and heavy smoking ( β = −8.5, p = 0.001) were associated with reduced platelet MAO activity in the total population. In addition, this reduction in MAO-B activity appeared to be associated with blood-Hg concentrations above 3.4 μg/L (75th percentile). Possible gender related differences were also observed and are discussed. Our results suggest that MAO-B activity in blood platelets may be a useful tool to assess biochemical effects of Hg exposure in human populations. These changes in platelet MAO-B may reflect enzymatic changes in nervous tissue and should be further investigated as a surrogate marker of neurotoxicity.

Platelet MAO-B, personality, and psychopathology.

The article investigates the relationships between platelet monoamine oxidase-B (MAO-B) activity, personality, and psychopathology (Diagnostic and Statistical Manual of Mental Disorders [4th ed.; American Psychiatric Association, 1994] diagnoses. These relationships were assessed in 178 incarcerated male juvenile delinquents. Even after controlling for smoking, the authors found that both Internalizing and Externalizing Psychopathology were negatively related to MAO-B activity. In the final reduced model, novelty seeking fully mediated the relationships between MAO-B and Externalizing Psychopathology but not between MAO-B and Internalizing Psychopathology. It was hypothesized that low platelet MAO-B activity does not directly predispose individuals to psychopathology but is related to specific personality traits, which in turn represent a vulnerability factor for psychopathology. Future studies should help clarify the nature of the relationships between personality, biological markers, and psychopathology.

Platelet monoamine oxidase B (MAO-B) activity and its relationship to DL-fenfluramine-induced prolactin response in healthy men

Several techniques are used to assess central serotonergic neurotransmission in man, e.g. challenge tests (hormonal and physiological responses to serotonin active drugs), platelet MAO-B activity as well as brain imaging techniques. Little is known about how these tests relate to each other. The aim of the present study was therefore to investigate if platelet MAO-B activity could be related to hormonal and temperature responses to the serotonin active drug DL-fenfluramine in healthy men. Twelve male subjects without any history of psychiatric disorders or drug abuse/dependencies were recruited. Prior to the challenge with 60 mg DL-fenfluramine, which was given orally, blood for determination of platelet MAO-B activity was drawn. Blood samples for determination of serum prolactin and serum cortisol were drawn at baseline and thereafter every hour for the following six hours. In addition, body temperature was measured at the same time-points. Delta-values were calculated as the difference between the baseline values and the highest (prolactin and cortisol) or lowest value (temperature) thereafter. There was a strong positive correlation (r = 0.75, p < 0.02) between platelet MAO-B activity and Delta-prolactin. No correlations were found to Delta-cortisol, Delta-temperature or any of the baseline values. The results support the notion that the peripheral marker platelet MAO-B activity is related to the function of the central serotonergic neurotransmitter system as assessed by the prolactin response to 60 mg DL-fenfluramin.

Lymphocyte muscarinic receptors and platelet monoamine oxidase-B as biomarkers of CNS function: effects of age and gender in healthy humans

Lymphocyte cholinergic muscarinic receptors (MRs) and platelet monoamine oxidase-B (MAO-B) activity are considered surrogate markers of the same parameters in the central nervous system. Lymphocyte MR binding and platelet MAO-B activity were measured in a consistent number of healthy human adults and analysed according to gender and age. The mean value ± S.D. of MR binding neither differed between males (12.2 ± 10.0 fmol/10 6 cells, range: 0.5–37.9, n = 86) and females (10.7 ± 9.7 fmol/10 6 cells, range: 0.5–39.7, n = 69) nor among age groups. MAO-B activity was significantly higher in women (geometric mean: 11.3 nmol/mg protein/h, with 65% of values from 7.3 to 17.6; n = 43), than in men (7.7 nmol/mg protein/h, with 65% of values from 4.5 to 13; n = 95). Males aged 56–66 years displayed a higher, though not statistically significant, basal enzyme activity than younger subjects. Altogether these data indicate gender-related differences in MAO activity, but not in MR binding, and inter-individual differences in the basal values of both peripheral blood markers in healthy subjects.

495 A new in vitro model for testing developmental neurotoxicity

Platelet monoamine oxidase-B (MAO-B) has been considered a surrogate biochemical marker of neurotoxicity, as it may reflect changes in the monoaminergic system in the brain. Colour vision discrimination, in part a dopamine dependent process, has been used to identify early neurological effects of some environmental and industrial neurotoxicants. The objective of this cross-sectional study was to explore the relationship between platelet MAO-B activity and acquired colour discrimination capacity in fish-consumers from the St. Lawrence River region of Canada. Assessment of acquired dyschromatopsia was determined using the Lanthony D-15 desaturated panel test. Participants classified with dyschromatopsia (n = 81) had significantly lower MAO-B activity when compared to those with normal colour vision (n = 32) (26.5 ± 9.6 versus 31.0 ± 9.9 nmol/min/20 μg, P = 0.030)). Similarly, Bowman's Colour Confusion Index (CCI) was inversely correlated with MAO-B activity when the vision test was performed with the worst eye only (r = − 0.245, P = 0.009), the best eye only (r = − 0.188, P = 0.048) and with both eyes together (r = − 0.309, P = 0.001). Associations remained significant after adjustment for age and gender when both eyes (P = 0.003) and the worst eye (P = 0.045) were tested. Adjustment for heavy smoking weakened the association between MAO-B and CCI in the worst eye (P = 0.140), but did not alter this association for both eyes (P = 0.006). Adjustment for blood-mercury concentrations did not change the association. This study suggests a relationship between reduced MAO-B activity and acquired colour vision loss and both are associated with tobacco smoking. Therefore, results show that platelet MAO-B may be used as a surrogate biochemical marker of acquired colour vision loss.

Tobacco Leaf, Smoke and Smoking, MAO Inhibitors, Parkinson’s Disease and Neuroprotection; Are There Links?

The potential neuroprotective properties of monoamine oxidase B (MAO-B) inhibitors have been of interest in part because of the role that this enzyme plays in the bioactivation of the parkinsonian inducing neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Interestingly, tobacco smokers have lowered levels of brain and blood platelet MAO-B activity and a well documented lowered incidence of Parkinson’s disease (PD) compared to non-smokers. This correlation has led to the intriguing question of whether there are possible relationships between smoking, MAO-B activity and PD. Recent studies have evaluated specific components of tobacco smoke for their MAO inhibiting and neuroprotective properties. This chapter summarizes the relevant literature relating to the basic questions in these areas. We have undertaken studies to identify possible inhibitors of MAO-B in the tobacco leaf and tobacco smoke and have evaluated one such compound in the MPTP PD mouse model. In this chapter we report on the results of these studies and present a discussion of potential avenues of research and their implication with respect to PD, smoking and monoamine oxidase.

Platelet monoamine oxidase B in family history positive and family history negative type 1 alcohol-dependent subjects.

In the present study platelet monoamine oxidase B (MAO-B) activity was investigated in 76 male type 1 alcohol-dependent subjects with and without a family history of alcoholism. Platelet MAO-B activity did not differ between family history positive (FHP) and family history negative alcohol-dependent subjects. The smoking status of the subjects was registered and there was still no difference between the groups when possible effects of smoking were taken into account. It should, however, be noted that platelet MAO-B activity was lower in alcohol-dependent subjects with three or four alcohol-dependent first-degree relatives. Although this latter finding should be interpreted with caution due to the small number of subjects, it cannot be excluded that FHP alcohol-dependent subjects with a large number of alcohol-dependent first-degree relatives may have lower platelet MAO-B activity.

PLATELET MONOAMINE OXIDASE B ACTIVITY AS A STATE MARKER FOR ALCOHOLISM: TREND OVER TIME DURING WITHDRAWAL AND INFLUENCE OF SMOKING AND GENDER

The present study evaluated time-related changes in platelet monoamine oxidase B (MAO-B) activity in an Italian cohort of alcohol-dependent subjects (n = 98) during early abstinence, and the effect of potential confounding factors, such as gender and smoking status, on the temporal trend of the enzyme activity. While still under the influence of ethanol (time point T1), the mean value of platelet MAO-B activity in alcoholics was 6.4 +/- 3.1 nmol/mg of protein/h. This increased by >40% (to 9.3 +/- 4.4 nmol/mg of protein/h) after 8 days of withdrawal (T2), and remained stable thereafter (T3 and T4: 15 and 22 days of abstinence, respectively). In a cohort of 138 healthy subjects, MAO activity levels averaged 9.9 +/- 0.9 nmol/mg of protein/h. In the group of alcoholic patients, alcohol intake cessation was confirmed by the progressive decrease of serum % carbohydrate-deficient transferrin (CDT), which was pathologically above the reference limits (6%) at T1 (7.8 +/- 3.3%), declined to 6.6 +/- 2.1% at T2 and reached physiological values at T3 and T4. In a subgroup of cirrhotic alcoholics, %CDT did not decrease over time, while MAO activity rose after the first week of abstinence, without further change at T3 and T4. During early withdrawal, neither gender nor tobacco smoking affected the temporal pattern of MAO activity. MAO-B can be regarded as a state marker of alcohol consumption. The temporal pattern of platelet MAO-B activity may be used for the diagnostic assessment of alcoholism and early abstinence, regardless of gender and smoking status.

Platelet monoamine oxidase-B activity in type 1 alcohol-dependent subjects in sustained full remission.

The present study investigated platelet monoamine oxidase-B (MAO-B) activity in male alcohol-dependent subjects in sustained full remission (minimum 1 year), to exclude possible transient changes in platelet MAO-B activity, which occur up to several months after the end of alcohol intake. MAO-B activity was examined in 16 alcohol-dependent subjects, characterized as type 1 alcoholics, with an abstinence period of 6 +/- 7 years (mean +/- SD) and in 12 healthy controls. The long-term abstinent alcohol-dependent subjects did not differ from controls in platelet MAO-B activity. Type 1 male alcohol-dependent subjects appear to have normal platelet MAO-B activity. The possibility, however, cannot be excluded that type 2 long-term abstinent alcoholics may have lower platelet MAO-B activity.