Monoamine Oxidase as a Potential Biomarker of the Efficacy of Treatment of Mental Disorders

The review summarizes the results of our own studies and published data on the biological markers of psychiatric disorders, with special emphasis on the activity of platelet monoamine oxidase. Pharmacotherapy studies in patients with the mixed anxiety-depressive disorder and first episode of schizophrenia have shown that the activity of platelet monoamine oxidase could serve as a potential biomarker of the efficacy of therapeutic interventions in these diseases.

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.

A Biomarker of Risk-Prone Behavioral Phenotype Correlates With Winning in a Game of Skill

The predisposition to take risk is a personality trait associated with dangerous or maladaptive behavior. Related to this, biomarkers associated with risk proneness such as low platelet monoamine oxidase (MAO) activity level are typically considered as prognostic for higher likelihood of undesirable behavior in real-life settings. In this study we explored whether this biomarker is also indicative of risk proneness in a game situation where serious real-life adaptations and motivations are absent or minimized and risk is more or less symbolic. We adapted a game of skill where in order to get a high score “risky” actions had to be taken by the players. Scores obtained in the game correlated with the (relatively low) platelet MAO activity. Our results show that (1) the same markers that are informative for real-life behavior and adaptations involving risk and/or sensorimotor skills based performance may be informative also in a game setting, (2) in specific circumstances biomarkers associated with predisposition to risk may be associated with success, and (3) the novel game of skill tested in this context has a potential to be developed to a model of risk-involving behavior allowing quantifiable dependent measures of performance and purposeful manipulation of variables without real adverse effects on health or social relations.

Potential neurobiological ADHD biomarkers

ObjectivesPathogenetic mechanisms of hyperkinetic syndrome (HKS) or attention deficit hyperactivity disorder (ADHD) are not clear.AimTo elucidate some aspects of monoamine involvement in pathogenesis of disorder and response of monoaminergic systems to psychostimulant medication.MethodsLevels of different monoamines, their metabolites and N-methylnicotinamide (end product of kynurenine pathway) were measured in daily samples of urine from children (7–11 years old) with mild and severe HKS using fluorimetric and chromatographic methods as well as platelet monoamine oxidase (MAO) activity. Thirty children with mild HKS received psychostimulant Sydnocarb 5–15 mg daily for 1–1.5 months (for ethical reasons children with severe HKS were not included in study).ResultsHKS was accompanied by activation of dopaminergic and inhibition of noradrenergic systems. There were found metabolic differences between two forms of HKS. Compared with mild HKS, severe HKS was characterized by significant 2-fold increase of MAO activity and L-dopa, dopamine and adrenaline excretion. After sydnocarb treatment children's clinical status improved along with decrease of excretion of homovanillic, vanillylmandelic and 5-hydroxyindoleacetic acids and increase of N-methylnicotinamide.ConclusionsResults indicate that dopaminergic and noradrenergic systems play important role in pathogenesis of HKS. Clinical improvement of HKS children was accompanied by significant increase of N-methylnicotinamide excretion. It is proposed that increased urine excretion of kynurenine metabolite–N-methylnicotinamide and N-methylnicotinamide/5-hydroxyindoleacetic acid ratio can serve as potential biomarkers for evaluation of efficacy of psychostimulant medication. We hypothesize that kynurenine system plays significant role in pathogenesis of HKS/ADHD.Disclosure of interestThe authors have not supplied their declaration of competing interest.