Gene expression correlates of advanced epigenetic age and psychopathology in postmortem cortical tissue

Abstract

Psychiatric stress has been associated with accelerated epigenetic aging (i.e., when estimates of cellular age based on DNA methylation exceed chronological age) in both blood and brain tissue. Little is known about the downstream biological effects of accelerated epigenetic age on gene expression. In this study we examined associations between DNA methylation-derived estimates of cellular age that range from decelerated to accelerated relative to chronological age ("DNAm age residuals") and transcriptome-wide gene expression. This was examined using tissue from three post-mortem cortical regions (ventromedial and dorsolateral prefrontal cortex and motor cortex, n = 97) from the VA National PTSD Brain Bank. In addition, we examined how posttraumatic stress disorder (PTSD) and alcohol-use disorders (AUD) moderated the association between DNAm age residuals and gene expression. Transcriptome-wide results across brain regions, psychiatric diagnoses, and cohorts (full sample and male and female subsets) revealed experiment-wide differential expression of 11 genes in association with PTSD or AUD in interaction with DNAm age residuals. This included the inflammation-related genes IL1B, RCOR2, and GCNT1. Candidate gene class analyses and gene network enrichment analyses further supported differential expression of inflammation/immune gene networks as well as glucocorticoid, circadian, and oxidative stress-related genes. Gene co-expression network modules suggested enrichment of myelination related processes and oligodendrocyte enrichment in association with DNAm age residuals in the presence of psychopathology. Collectively, results suggest that psychiatric stress accentuates the association between advanced epigenetic age and expression of inflammation genes in the brain. This highlights the role of inflammatory processes in the pathophysiology of accelerated cellular aging and suggests that inflammatory pathways may link accelerated cellular aging to premature disease onset and neurodegeneration, particularly in stressed populations. This suggests that anti-inflammatory interventions may be an important direction to pursue in evaluating ways to prevent or delay cellular aging and increase resilience to diseases of aging.

Keywords: Accelerated aging; Alcohol; DNA methylation; Epigenetic age; PTSD; RNA.

Fig. 1

The figure shows the association between DNAm age residuals (X-axis) and gene expression (Y-axis, as regularized log-transformed expression values) as a function of PTSD or AUD diagnosis (the moderator) for five of the eleven genes that achieved experiment-wide significance across all transcriptome-wide analyses (across brain regions, diagnoses, and cohorts). Interaction plots for the remaining differentially expressed genes are shown in Fig. S3. PTSD = posttraumatic stress disorder; AUD = alcohol-use disorder.

Fig. 2

The figure shows the results for the same five experiment-wide significant genes of interest across all analyses, not limited to the experiment-wide region, cohort, or diagnosis. This shows the pattern of results across models for these genes. The cohort is listed along the X-axis and corresponding log2 fold change in expression along the Y axis. PTSD = posttraumatic stress disorder; AUD = alcohol-use disorder. *nominal significance (p < .05). **experiment-wide significance (p_{cor-experiment} < .05).