Understanding trauma-induced hippocampal subfield volume changes in the context of age and health

Subfield-specific longitudinal changes of hippocampal volumes in patients with early-stage bipolar disorder

BACKGROUND

The hippocampus is a heterogeneous structure composed of biologically and functionally distinct subfields. Hippocampal aberrations are proposed to play a fundamental role in the etiology of psychotic symptoms. Bipolar disorder (BPD) has substantial overlap in symptomatology and genetic liability with schizophrenia (SZ), and reduced hippocampal volumes, particularly at the chronic illness stages, are documented in both disorders. Studies of hippocampal subfields in the early stage of BPD are limited and cross-sectional findings to date report no reduction in hippocampal volumes. To our knowledge, there have been no longitudinal studies of BPD evaluating hippocampal volumes in the early phase of illness. We investigated the longitudinal changes in hippocampal regions and subfields in BPD mainly and in early stage of psychosis (ESP) patients more broadly and compared them to those in controls (HC).

METHODS

Baseline clinical and structural MRI data were acquired from 88 BPD, from a total of 143 ESP patients, and 74 HCs. Of those, 66 participants (23 HC, 43 patients) completed a 12-month follow-up visit. The hippocampus regions and subfields were segmented using Freesurfer automated pipeline.

RESULTS

We found general baseline deficits in hippocampal volumes among BPD and ESP cohorts. Both cohorts displayed significant increases in the anterior hippocampal region and dentate gyrus compared with controls. Additionally, antipsychotic medications were positively correlated with the posterior region at baseline.

CONCLUSION

These findings highlight brain plasticity in BPD and in ESP patients providing evidence that deviations in hippocampal volumes are adaptive responses to atypical signaling rather than progressive degeneration.

Significant age by childhood trauma interactions on grey matter volumes: A whole brain VBM analysis

BACKGROUND

Childhood trauma is deleterious to long term brain development. The changes are variable, and depend on gender, age and the nature of the trauma. In this exploratory analysis, we investigated the effects of exposure to emotional trauma on grey matter (GM) volumes in adolescent females.

METHODS

We explored GM volumes in non-clinical females aged 12-17 years who had been exposed to either higher (HET; N = 75) or minimal (MET; N = 127) emotional trauma. High-resolution T1-weighted structural images were analysed with an optimised FSL-VBM protocol. The General Linear Model was run on HET versus MET with continuous age as an interaction. Mean GM volumes were extracted from significant corrected age interaction statistical maps and scrutinised with SPSS®.

RESULTS

We observed greater HET*age than MET*age interactions (corrected p-value = 0.0002), in 4 separate bilateral cortical regions associated with mood disorders. Scrutiny of these regions showed significant GM volume enlargements in the early adolescent HET group (p = 0.017) and reductions in the late adolescent HET group (p < 0.0001). Notably, there were no differences in middle adolescence (p > 0.05).

LIMITATIONS

Causality cannot be inferred from this cross-sectional study and the onset of trauma cannot be determined using retrospective measures.

CONCLUSIONS

Whilst GM volumes diminish from early adolescence onwards, our results show that HET impacts this brain development, perhaps first via unstable adaptative mechanisms, followed by maladaptive processes in late adolescence. This suggests that compromises of emotional and cognitive self-regulation in mood disorders may underpin the structural abnormalities observed across multiple brain regions in these teenage girls.

Accelerated hippocampal biological aging in bipolar disorder

OBJECTIVES

Evidence suggests accelerated aging mechanisms in bipolar disorder (BD), including DNA methylation (DNAm) aging in blood. However, it is unknown whether such mechanisms are also evident in the brain, in particular in association with other biological clocks. To investigate this, we interrogated genome-wide DNAm in postmortem hippocampus from 32 BD-I patients and 32 non-psychiatric controls group-matched for age and sex from the NIMH Human Brain Collection Core.

METHODS

DNAm age and epigenetic aging acceleration were estimated using the Horvath method. Telomere length (TL) and mitochondrial DNA (mtDNA) copy number were quantified by real-time PCR. Between-group differences were assessed by linear regression and univariate general linear models with age, sex, race, postmortem interval, tissue pH, smoking, and body mass index included as co-variates.

RESULTS

Groups did not differ for epigenetic aging acceleration when considering the entire sample. However, after splitting the sample by the median age, an epigenetic aging acceleration was detected in patients compared to controls among older subjects (P = .042). While TL did not differ between groups, a reduction in mtDNA copy number was observed in patients compared to controls (P = .047). In addition, significant correlations were observed between epigenetic aging acceleration and TL (r = -.337, P = .006), as well as between TL and mtDNA copy number (r = .274, P = .028).

CONCLUSIONS

Hippocampal aging may underlie neurocognitive dysfunctions observed in BD patients. Moreover, our results suggest a complex cross-talk between biological clocks in hippocampus that may underlie clinical manifestations of premature aging in BD.

Understanding trauma-induced hippocampal subfield volume changes in the context of age and health. Response to Malhi et al

It is important to integrate findings converging from different perspectives to better contextualize hippocampal subfield changes induced by childhood trauma (CT). Here we integrate Malhi's et al. model on this issue. Understanding the complex neurobiological mechanisms underpinning CT could address the multifaceted nature of resilience to traumatic life experiences that may cause different effects in health and disease.