PCLO rs2522833 impacts HPA system activity in healthy young adults

Dietary emulsifier consumption alters gene expression in the amygdala and paraventricular nucleus of the hypothalamus in mice

Dietary emulsifier consumption promotes systemic low-grade inflammation, metabolic deregulation, and possibly an anxiety-like phenotype. The latter finding suggests that dietary emulsifiers impact brain areas that modulate stress responses. The goal of the current study was to test whether emulsifier consumption is associated with changes in gene expression in the amygdala and the paraventricular nucleus of the hypothalamus (PVN), two brain areas that are involved in behavioral and neuroendocrine responses to stress. Using RNA-Seq, we compared groups consuming either carboxymethylcellulose or polysorbate 80 for 12-weeks. A total of 243 genes were differentially expressed in the amygdala and PVN of emulsifier-treated mice compared to controls. There was minimal overlap of differentially expressed genes in CMC- and P80-treated animals, suggesting that each emulsifier acts via distinct molecular mechanisms to produce an anxiety-like phenotype. Furthermore, gene ontology and pathway analysis revealed that various stress, metabolic, and immune terms and pathways were altered by emulsifiers. These findings are the first to demonstrate that emulsifier consumption changes gene expression in brain regions that are critical for stress responding, providing possible molecular mechanisms that may underly the previously observed anxiety-like phenotype.

Systemic neuro-dysregulation in depression: Evidence from genome-wide association

Depression is the world's leading cause of disability. Greater understanding of the neurobiological basis of depression is necessary for developing novel treatments with improved efficacy and acceptance. Recently, major advances have been made in the search for genetic variants associated with depression which may help to elucidate etiological mechanisms. The present review has two major objectives. First, we offer a brief review of two major biological systems with strong evidence for involvement in depression pathology: neurotransmitter systems and the stress response. Secondly, we provide a synthesis of the functions of the 269 genes implicated by the most recent genome-wide meta-analysis, supporting the importance of these systems in depression and providing insights into other possible mechanisms involving neurodevelopment, neurogenesis, and neurodegeneration. Our goal is to undertake a broad, preliminary stock-taking of the most recent hypothesis-free findings and examine the weight of the evidence supporting these existing theories and highlighting novel directions. This qualitative review and accompanying gene function table provides a valuable resource and guide for basic and translational researchers, with suggestions for future mechanistic research, leveraging genetics to prioritize studies on the neurobiological processes involved in depression etiology and treatment.

Stress, mood, and cortisol during daily life in women with Premenstrual Dysphoric Disorder (PMDD)

Premenstrual Dysphoric Disorder (PMDD) is characterized by significant emotional, physical and behavioral distress during the late luteal phase that remits after menses onset. Outlined as a new diagnostic category in DSM-5, the mechanisms underlying PMDD are still insufficiently known. Previous research suggests that PMDD exacerbates with stressful events, indicating a dysregulation of the hypothalamic-pituitary-adrenal axis. However, studies measuring stress-related processes in affected women in real-time and real-life are lacking. We conducted an Ambulatory Assessment (AA) study to compare subjective stress reactivity together with basal and stress-reactive cortisol activity across the menstrual cycle in women with and without PMDD. Women with current PMDD (n = 61) and age- and education matched controls (n = 61) reported momentary mood, rumination, and daily events via smartphones at semi-random time points 8 times a day over two consecutive days per cycle phase (menstrual, follicular, ovulatory, and late luteal). Twenty minutes after assessments participants collected saliva cortisol samples. Three additional morning samples determined the cortisol awakening response (CAR). Women with PMDD reported particular high daily life stress and high arousal negative affect (NA_high) towards stressors during the late luteal phase. High momentary stress levels were linked to lower levels of high arousal positive affect (PA_high) and to higher levels of rumination in PMDD women compared to controls irrespective of cycle phase. Across groups, more stress was linked to higher levels of low arousal NA (NA_low) and to lower levels of low arousal PA (PA_low). Moreover, PMDD was associated with a delayed CAR peak and a flattened diurnal cortisol slope. While neither group showed cortisol reactivity towards daily life stress directly, high momentary NA_high and low momentary PA predicted high levels of cortisol across groups, whereas high momentary rumination predicted high cortisol output only in healthy women. In this AA-study we identified important stress-related psychological and endocrinological within-person variability in women with PMDD during daily life. Further research is warranted targeting identified AA-based mechanisms to study their predictive role for the clinical course of PMDD and to provide evidence-based therapeutic options for affected women.

Psychosocial functioning and the cortisol awakening response: Meta-analysis, P-curve analysis, and evaluation of the evidential value in existing studies

Cortisol levels rise immediately after awakening and peak approximately 30-45min thereafter. Psychosocial functioning influences this cortisol awakening response (CAR), but there is considerable heterogeneity in the literature. The current study used p-curve and meta-analysis on 709 findings from 212 studies to test the evidential value and estimate effect sizes of four sets of findings: those associating worse psychosocial functioning with higher or lower cortisol increase relative to the waking period (CARi) and to the output of the waking period (AUCw). All four sets of findings demonstrated evidential value. Psychosocial predictors explained 1%-3.6% of variance in CARi and AUCw responses. Based on these effect sizes, cross-sectional studies assessing CAR would need a minimum sample size of 617-783 to detect true effects with 80% power. Depression was linked to higher AUCw and posttraumatic stress to lower AUCw, whereas inconclusive results were obtained for predictor-specific effects on CARi. Suggestions for future CAR research are discussed.

PCLO rs2522833-mediated gray matter volume reduction in patients with drug-naive, first-episode major depressive disorder

Major depressive disorder (MDD) has been linked to differences in the volume of certain areas of the brain and to variants in the piccolo presynaptic cytomatrix protein (PCLO), but the relationship between PCLO and brain morphology has not been studied. A single-nucleotide polymorphism (SNP) in PCLO, rs2522833, is thought to affect protein stability and the activity of the hypothalamic-pituitary-adrenal axis. We investigated the relationship between cortical volume and this SNP in first-episode, drug-naive patients with MDD or healthy control subjects. Seventy-eight participants, including 30 patients with MDD and 48 healthy control subjects, were recruited via interview. PCLO rs2522833 genotyping and plasma cortisol assays were performed, and gray matter volume was estimated using structural magnetic resonance images. Among the individuals carrying the C-allele of PCLO rs2522833, the volume of the left temporal pole was significantly smaller in those with MDD than in healthy controls (family-wise error-corrected, P=0.003). No differences were detected in other brain regions. In addition, the C-carriers showed a larger volume reduction in the left temporal pole than those in the individuals with A/A genotype (P=0.0099). Plasma cortisol levels were significantly higher in MDD-affected C-carriers than in the healthy control C-carriers (12.76±6.10 vs 9.31±3.60 nm, P=0.045). We conclude that PCLO SNP rs2522833 is associated with a gray matter volume reduction in the left temporal pole in drug-naive, first-episode patients with MDD carrying the C-allele.

The Genetics of Stress-Related Disorders: PTSD, Depression, and Anxiety Disorders

Research into the causes of psychopathology has largely focused on two broad etiologic factors: genetic vulnerability and environmental stressors. An important role for familial/heritable factors in the etiology of a broad range of psychiatric disorders was established well before the modern era of genomic research. This review focuses on the genetic basis of three disorder categories-posttraumatic stress disorder (PTSD), major depressive disorder (MDD), and the anxiety disorders-for which environmental stressors and stress responses are understood to be central to pathogenesis. Each of these disorders aggregates in families and is moderately heritable. More recently, molecular genetic approaches, including genome-wide studies of genetic variation, have been applied to identify specific risk variants. In this review, I summarize evidence for genetic contributions to PTSD, MDD, and the anxiety disorders including genetic epidemiology, the role of common genetic variation, the role of rare and structural variation, and the role of gene-environment interaction. Available data suggest that stress-related disorders are highly complex and polygenic and, despite substantial progress in other areas of psychiatric genetics, few risk loci have been identified for these disorders. Progress in this area will likely require analysis of much larger sample sizes than have been reported to date. The phenotypic complexity and genetic overlap among these disorders present further challenges. The review concludes with a discussion of prospects for clinical translation of genetic findings and future directions for research.

FRAS1-related extracellular matrix 3 (FREM3) single-nucleotide polymorphism effects on gene expression, amygdala reactivity and perceptual processing speed: An accelerated aging pathway of depression risk

The A allele of the FRAS1-related extracellular matrix protein 3 (FREM3) rs7676614 single nucleotide polymorphism (SNP) was linked to major depressive disorder (MDD) in an early genome-wide association study (GWAS), and to symptoms of psychomotor retardation in a follow-up investigation. In line with significant overlap between age- and depression-related molecular pathways, parallel work has shown that FREM3 expression in postmortem human brain decreases with age. Here, we probe the effect of rs7676614 on amygdala reactivity and perceptual processing speed, both of which are altered in depression and aging. Amygdala reactivity was assessed using a face-matching BOLD fMRI paradigm in 365 Caucasian participants in the Duke Neurogenetics Study (DNS) (192 women, mean age 19.7 ± 1.2). Perceptual processing speed was indexed by reaction times in the same task and the Trail Making Test (TMT). The effect of rs7676614 on FREM3 mRNA brain expression levels was probed in a postmortem cohort of 169 Caucasian individuals (44 women, mean age 50.8 ± 14.9). The A allele of rs7676614 was associated with blunted amygdala reactivity to faces, slower reaction times in the face-matching condition (p < 0.04), as well as marginally slower performance on TMT Part B (p = 0.056). In the postmortem cohort, the T allele of rs6537170 (proxy for the rs7676614 A allele), was associated with trend-level reductions in gene expression in Brodmann areas 11 and 47 (p = 0.066), reminiscent of patterns characteristic of older age. The low-expressing allele of another FREM3 SNP (rs1391187) was similarly associated with reduced amygdala reactivity and slower TMT Part B speed, in addition to reduced BA47 activity and extraversion (p < 0.05). Together, these results suggest common genetic variation associated with reduced FREM3 expression may confer risk for a subtype of depression characterized by reduced reactivity to environmental stimuli and slower perceptual processing speed, possibly suggestive of accelerated aging.

Early intervention following trauma may mitigate genetic risk for PTSD in civilians: a pilot prospective emergency department study

BACKGROUND

Civilian posttraumatic stress disorder (PTSD) and combat PTSD are major public health concerns. Although a number of psychosocial risk factors have been identified related to PTSD risk, there are no accepted, robust biological predictors that identify who will develop PTSD or who will respond to early intervention following trauma. We wished to examine whether genetic risk for PTSD can be mitigated with an early intervention.

METHOD

65 emergency department patients recruited in 2009-2010 at Grady Memorial Hospital in Atlanta, Georgia, who met criterion A of DSM-IV PTSD received either 3 sessions of an exposure intervention, beginning in the emergency department shortly after trauma exposure or assessment only. PTSD symptoms were assessed 4 and 12 weeks after trauma exposure. A composite additive risk score was derived from polymorphisms in 10 previously identified genes associated with stress-response (ADCYAP1R1, COMT, CRHR1, DBH, DRD2, FAAH, FKBP5, NPY, NTRK2, and PCLO), and gene x treatment effects were examined. The intervention included 3 sessions of imaginal exposure to the trauma memory and additional exposure homework. The primary outcome measure was the PTSD Symptom Scale-Interview Version or DSM-IV-based PTSD diagnosis in patients related to genotype and treatment group.

RESULTS

A gene x intervention x time effect was detected for individual polymorphisms, in particular the PACAP receptor, ADCYAP1R1, as well as with a combined genotype risk score created from independent SNP markers. Subjects who did not receive treatment had higher symptoms than those who received intervention. Furthermore, subjects with the "risk" genotypes who did not receive intervention had higher PTSD symptoms compared to those with the "low-risk" or "resilience" genotypes or those who received intervention. Additionally, PTSD symptoms correlated with level of genetic risk at week 12 (P < .005) in the assessment-only group, but with no relationship in the intervention group, even after controlling for age, sex, race, education, income, and childhood trauma. Using logistic regression, the number of risk alleles was significantly associated with likelihood of PTSD diagnosis at week 12 (P < .05).

CONCLUSIONS

This pilot prospective study suggests that combined genetic variants may serve to predict those most at risk for developing PTSD following trauma. A psychotherapeutic intervention initiated in the emergency department within hours of the trauma may mitigate this risk. The role of genetic predictors of risk and resilience should be further evaluated in larger, prospective intervention and prevention trials.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00895518.

No evidence for the association between a polymorphism in the PCLO depression candidate gene with memory bias in remitted depressed patients and healthy individuals

The PCLO rs2522833 candidate polymorphism for depression has been associated to monoaminergic neurotransmission. In healthy and currently depressed individuals, the polymorphism has been found to affect activation of brain areas during memory processing, but no direct association of PCLO with memory bias was found. We hypothesized that the absence of this association might have been obscured by current depressive symptoms or genetically driven individual differences in reactivity to stressful events. Experiencing stressful childhood events fosters dysfunctional assumptions that are related to cognitive biases, and may modulate the predisposition for depression via epigenetic effects. The association between PCLO and memory bias, as well as interaction between PCLO and childhood events was studied in patients remitted from depression (N = 299), as well as a sample of healthy individuals (N = 157). The participants performed an emotional verbal memory task after a sad mood induction. Childhood trauma and adversity were measured with a questionnaire. The Genotype main effect, and Genotype by Childhood Events interaction were analyzed for memory bias in both samples. PCLO risk allele carrying remitted depressed patients did not show more negatively biased memory than non-risk allele carriers, not even patients with stressful childhood events. A similar pattern of results was found in healthy individuals. Memory bias may not be strongly associated with the PCLO rs2522833 polymorphism. We did not find any support for the PCLO-childhood events interaction, but the power of our study was insufficient to exclude this possibility.

Neurogenetics of depression: a focus on reward processing and stress sensitivity

Major depressive disorder (MDD) is etiologically complex and has a heterogeneous presentation. This heterogeneity hinders the ability of molecular genetic research to reliably detect the small effects conferred by common genetic variation. As a result, significant research efforts have been directed at investigating more homogenous intermediate phenotypes believed to be more proximal to gene function and lie between genes and/or environmental effects and disease processes. In the current review we survey and integrate research on two promising intermediate phenotypes linked to depression: reward processing and stress sensitivity. A synthesis of this burgeoning literature indicates that a molecular genetic approach focused on intermediate phenotypes holds significant promise to fundamentally improve our understanding of the pathophysiology and etiology of depression, which will be required for improved diagnostic definitions and the development of novel and more efficacious treatment and prevention strategies. We conclude by highlighting challenges facing intermediate phenotype research and future development that will be required to propel this pivotal research into new directions.