MAO-B Activity in Platelets and the MAO-B Gene Polymorphism are Differently Related to Personality Traits in Alcohol Dependent Patients

Aims: Since monamine oxidase B (MAO-B) platelet activity has been found to be associated with impulsivity, aggression, sensation seeking, and alcoholism, the main goal of the current study to be investigated is the question, if similar associations can be found with the polymorphism rs1799836 of the MAO B gene coding for activity of the enzyme MAO B.

Study Design: The study was an experimental group comparison.

Place and Duration of Study: It was carried out at the Psychiatric Giessen University Clinic, the Psychiatric Vitos Clinic and two outpatient psychotherapy treatment centers at the city of Giessen, Germany, between September 2010 and July 2011. Laboratory analyses were only completed in 2012 /2013

Methodology: 60 male alcohol dependent patients aged 27 to 68 years were tested individually after detoxification in hospital and subsequent withdrawal. Tests were questionnaires on alcohol history and personality scales (aggression, impulsivity and sensation seeking) followed by a computer test measuring impulsive premature responding and reaction time. In addition, blood samples for determination of platelet MAO B activity and genotyping of the MAO B gene were drawn.

Results: Analyses of covariance using genotypes and classes of enzyme activity as independent factors and controlling for age and smoking revealed that the genetic disposition and MAO B activity were not related.(means of MAO B levels, genotype A vs G: P = .228). However, genotype G participants exhibited shorter reaction times (P =.045) and higher aggression scores (P = .043) than A, while genotype A scored higher on experience seeking P= .016) than G. High MAO-B platelet levels were associated with high motor impulsivity (P = .017), but only in genotype A with attentional impulsivity. (interaction: P = .031)

Conclusion: The MAO B gene is newly detected to be relevant to personality but is probably not related to MAO B activity .Results are discussed as possibly resulting from different dopamine levels mediated by differences in genotype effects on MAO-B brain activity.