A meta-analysis on relationship of MAOB intron 13 polymorphisms, interactions with smoking/COMT H158L polymorphisms with the risk of PD

Individual and Combined Effect of MAO-A/MAO-B Gene Variants and Adverse Childhood Experiences on the Severity of Major Depressive Disorder

BACKGROUND

Major depressive disorder (MDD) is a mood disorder with a high prevalence worldwide that causes disability and, in some cases, suicide. Although environmental factors play a crucial role in this disease, other biological factors may predispose individuals to MDD. Genetic and environmental factors influence mental disorders; therefore, a potential combined effect of MAO-A/MAO-B gene variants may be a target for the study of susceptibility to MDD. This study aimed to evaluate the effects of MAO-A and -B gene variants when combined with adverse childhood experiences (ACEs) on the susceptibility and severity of symptoms in MDD.

METHODS

A case-control study was performed, including 345 individuals, 175 MDD cases and 170 controls. Genotyping was performed using real-time PCR with hydrolysis probes. The analysis of the rs1465107 and rs1799836 gene variants of MAO-A and -B, respectively, was performed either alone or in combination with ACEs on the severity of depression, as determined through specific questionnaires, including DSM-IV diagnostic criteria for MDD.

RESULTS

According to individual effects, the presence of ACEs, as well as the allele G of the rs1465107 of MAO-A, is associated with a higher severity of depression, more significantly in females. Furthermore, the allele rs1799836 G of MAO-B was associated with the severity of depression, even after being adjusted by gene variants and ACEs (IRR = 1.67, p = 0.01). In males, the allele rs1799836 G of MAO-B was shown to interact with SNP with ACEs (IRR = 1.70, p < 0.001). According to combined effect analyses, the severity of depression was associated with ACEs when combined with either allele rs1465107 of MAO-A or allele rs17993836 of MAO-B, whereas SNP risk association was influenced by gender.

CONCLUSIONS

The severity of depression is related to either individual or combined effects of temperamental traits and genetic susceptibility of specific genes such as MAO-A and MAO-B.

The role of monoamine oxidase enzymes in the pathophysiology of neurological disorders

Monoamine oxidase enzymes are responsible for the degredation of serotonin, dopamine, and norepinephrine in the central neurvous system. Although it has been nearly 100 years since they were first described, we are still learning about their role in the healthy brain and how they are altered in various disease states. The present review provides a survey of our current understanding of monoamine oxidases, with a focus on their contributions to neuropsychiatric, neurodevelopmental, and neurodegenerative disease. Important species differences in monoamine oxidase function and development in the brain are highlighted. Sex-specific monoamine oxidase regulatory mechanisms and their implications for various neurological disorders are also discussed. While our understanding of these critical enzymes has expanded over the last century, gaps exist in our understanding of sex and species differences and the roles monoamine oxidases may play in conditions often comorbid with neurological disorders.

Advances in understanding genomic markers and pharmacogenetics of Parkinson's disease

INTRODUCTION

The inheritance pattern of Parkinson's disease (PD) is likely multifactorial (owing to the interplay of genetic predisposition and environmental factors). Many pharmacogenetic studies have tried to establish a possible role of candidate genes in PD risk. Several studies have focused on the influence of genes in the response to antiparkinsonian drugs and in the risk of developing side-effects of these drugs.

AREAS COVERED

This review presents an overview of current knowledge, with particular emphasis on the most recent advances, both in case-control association studies on the role of candidate genes in the risk for PD as well as pharmacogenetic studies on the role of genes in the development of side effects of antiparkinsonian drugs. The most reliable results should be derived from meta-analyses of case-control association studies on candidate genes involving large series of PD patients and controls, and from genome-wide association studies (GWAS).

EXPERT OPINION

Prospective studies of large samples involving several genes with a detailed history of exposure to environmental factors in the same cohort of subjects, should be useful to clarify the role of genes in the risk for PD. The results of studies on the role of genes in the development of side-effects of antiparkinsonian drugs should, at this stage, only be considered preliminary.