Brain Gene Expression Profiling of Individuals With Dual Diagnosis Who Died by Suicide

The Perinatal Microbiota-Gut-Brain Axis: Implications for Postpartum Depression

BACKGROUND

Pregnancy and childbirth are accompanied by widespread maternal physiological adaptations and hormonal shifts that have been suggested to result in a period of vulnerability for the development of mood disorders such as postpartum depression (PPD). There is also evidence of peripartum changes in the composition of the gut microbiota, but the potential contribution of intestinal microbes to the adaptations, or subsequent vulnerabilities, during this period are unknown.

SUMMARY

Here, we outline key pathways involved in peripartum adaptations including GABAergic signaling, oxytocin, and immunomodulation that are also associated with susceptibility to mood disorders and present evidence that these pathways are modulated by gut microbes. We also discuss the therapeutic potential of the microbiota-gut-brain axis in PPD and identify future directions for research to help realize this potential.

KEY MESSAGES

Peripartum adaptations are associated with shifts in gut microbial composition. Disruption of GABAergic, oxytocin, and immunomodulatory pathways may contribute to vulnerability of mood disorders including PPD. These key adaptive pathways are modulated by intestinal microbes suggesting a role for the gut microbiota in determining susceptibility to PPD. More research is needed to confirm relationship between gut microbes and PPD and to gain the mechanistic understanding required to realize the therapeutic potential of microbiota-gut-brain axis in this mood disorder.

Gene Expression Analysis in Postmortem Brains from Individuals Who Died by Suicide: A Systematic Review

Around the world, more the 700,000 individuals die by suicide every year. It is necessary to understand the mechanisms associated with suicidal behavior. Recently, an increase in gene expression studies has been in development. Through a systematic review, we aimed to find a candidate gene in gene expression studies on postmortem brains of suicide completers. Databases were systematically searched for published studies. We performed an online search using PubMed, Scopus and Web of Science databases to search studies up until May 2023. The terms included were "gene expression", "expressed genes", "microarray", "qRT-PCR", "brain samples" and "suicide". Our systematic review included 59 studies covering the analysis of 1450 brain tissues from individuals who died by suicide. The majority of gene expression profiles were obtained of the prefrontal cortex, anterior cingulate cortex, dorsolateral prefrontal cortex, ventral prefrontal cortex and orbital frontal cortex area. The most studied mRNAs came of genes in glutamate, γ-amino-butyric acid and polyamine systems. mRNAs of genes in the brain-derived neurotrophic factor, tropomyosin-related kinase B (TrkB), HPA axis and chemokine family were also studied. On the other hand, psychiatric comorbidities indicate that suicide by violent death can alter the profile of mRNA expression.

Genetics and epigenetics of self-injurious thoughts and behaviors: Systematic review of the suicide literature and methodological considerations

Suicide is a multifaceted and poorly understood clinical outcome, and there is an urgent need to advance research on its phenomenology and etiology. Epidemiological studies have demonstrated that suicidal behavior is heritable, suggesting that genetic and epigenetic information may serve as biomarkers for suicide risk. Here we systematically review the literature on genetic and epigenetic alterations observed in phenotypes across the full range of self-injurious thoughts and behaviors (SITB). We included 577 studies focused on genome-wide and epigenome-wide associations, candidate genes (SNP and methylation), noncoding RNAs, and histones. Convergence of specific genes is limited across units of analysis, although pathway-based analyses do indicate nervous system development and function and immunity/inflammation as potential underlying mechanisms of SITB. We provide suggestions for future work on the genetic and epigenetic correlates of SITB with a specific focus on measurement issues.