Monoamine oxidase type B polymorphism in combat related posttraumatic stress disorder

Introduction: Neurobiological basis of posttraumatic stress disorder (PTSD) involves the alternations in different neurotransmitter systems such as noradrenalin, dopamine and serotonin. Monoamine oxydase (MAO) is an enzyme responsible for the degradation of different endogenous and exogenous amines. Endogenous amines involve neurotransmitters (noradrenaline, dopamine and serotonin) and therefore MAO plays a central role in the metabolism of monoamine neurotransmitters. There are two isoforms of MAO, MAO-A and MAO-B. These subtypes are encoded by two different genes, placed near each other on X chromosome (region Xp11.23-11.4). In platelets MAO exists in MAO-B isoform, and it has been proposed to be a biomarker for different personality characteristics and psychiatric disorders. Platelet MAO or MAO-B activity is under influence of various factors, such as smoking, gender, age, ethnicity, some neurodegenerative diseases and lithium or haloperidol treatment. One of the factors assumed to influence platelet MAO activity might be a polymorphism of MAO-B gene on the polymorphic region of the intron 13. The molecular basis of this polymorphism is A/G substitution 36 bp upstream from the intron 13-exon 14 boundary. Aim of the study was to determine the distribution of the MAO-B genotypes in Croatian war veterans with PTSD, in war veterans who were exposed to the similar combat experience but did not develop PTSD, and in healthy control subjects. Methods: The study included medication-free male Caucasian subjects who did not have neurodegenerative diseases: 91 war veterans with PTSD, 36 war veterans without PTSD and 100 healthy control subjects. DNA was isolated from their blood samples, and the method used for genotyping was a real-time PCR using Taqman – based allele – specific polymerase chain reaction assay. Results: The results showed no differences in the distribution of A allele or G allele of the MAO-B gene between healthy control subjects, war veterans without PTSD, war veterans with PTSD with psychotic symptoms and war veterans with PTSD with non-psychotic symptoms. Discussion: Therefore, no association was found in the allele frequencies of the MAO-B genotype in PTSD. In agreement with our data, no significant association between the allele frequency and A/G polymorphism in intron 13 of the MAO-B gene was found in schizophrenia, schizophrenia with or without tardive dyskinesia, schizophrenia with aggressive behavior, migraine, Parkinson’ s disease, or depressed state. Since our data did not confirm the hypothesis that the appearance of A allele or G allele is associated with the etiology or development of PTSD, further studies should evaluate other polymorphisms, presumably related to MAO-A gene, to determine functional significance and associations with different traits or disease.