Prenatal programming of stress responsiveness and behaviours: Progress and perspectives

Parental exposure to stress or glucocorticoids either before or during pregnancy can have profound influences on neurodevelopment, neuroendocrine function and behaviours in offspring. Specific outcomes are dependent on the nature, intensity and timing of the exposure, as well as species, sex and age of the subject. Most recently, it has become evident that outcomes are not confined to first-generation offspring and that there may be intergenerational and transgenerational transmission of effects. There has been intense focus on the mechanisms by which such early exposure leads to long-term and potential transgenerational outcomes, and there is strong emerging evidence that epigenetic processes (histone modifications, DNA methylation, and small non-coding RNAs) are involved. New knowledge in this area may allow the development of interventions that can prevent, ameliorate or reverse the long-term negative outcomes associated with exposure to early adversity. This review will focus on the latest research, bridging human and pre-clinical studies, and will highlight some of the limitations, challenges and gaps that exist in the field.

A randomised placebo controlled clinical trial on the efficacy of Caralluma fimbriata supplement for reducing anxiety and stress in healthy adults over eight weeks

BACKGROUND

This study investigated the efficacy of a succulent, Caralluma fimbriata extract (CFE) in reducing anxiety and stress in healthy adults.

METHODS

An 8 week double-blind randomised clinical trial, in which 97 adults self-reporting mild to moderate anxiety were given 500 mg b.d. CFE (n = 49), or 500 mg b.d. placebo (n = 48). Anxiety and stress were measured at baseline, week 4, and week 8 to investigate the timing of treatment effect using the GAD-7, Perceived Stress Scale (PSS), Positive and Negative Affect Schedule (PANAS), and salivary cortisol. Data were analysed using mixed ANOVAs on SPSS v.24.

RESULTS

Results indicated a significant reduction in anxiety and stress in both groups at week 4 and week 8. The reduction in the CFE group was significantly greater (p < .05) than in the placebo group on the GAD-7 and PSS at week 4 and week 8, and in Negative affect at week 4. Improvement in Positive affect was greater in the CFE group than in the placebo group at week 8. Cortisol analysis indicated that CFE may act through the Hypothalamic-Pituitary-Adrenal (HPA) axis, showing statistically significant changes in males, but not in females.

LIMITATIONS

Self-reported instruments involve subjective interpretation thus salivary cortisol was employed as a more objective measure. The study would benefit from a larger sample and longer trial, and the inclusion of a wait-list group to allow comparison between treatment and no treatment.

CONCLUSIONS

The findings indicate that CFE is superior to placebo in reducing subclinical anxiety and stress over 8 weeks.

Chronic exposure to inorganic mercury alters stress responses in male prairie voles (Microtus ochrogaster)

Male, but not female, prairie voles that experience chronic exposure to inorganic mercury display aberrant social behavior - avoiding unfamiliar conspecifics rather than approaching them. The mechanisms that underlie such behavioral changes are unknown, but likely involve the hypothalamus-pituitary-adrenal (HPA) axis. We tested this hypothesis by providing voles of both sexes with mercury chloride in their drinking water for ten weeks and then staging same-sex dyadic encounters after which plasma was assayed for corticosterone as an index of HPA activity. Consistent with sex-specific behavioral responses previously reported, mercury-treated males had lower plasma corticosterone after social encounters than did similarly-treated females or males that consumed normal drinking water. The results suggest that mercury-treated males may be less inclined toward social engagement with conspecifics due to reduced HPA activity.

Cortisol awakening response is decreased in patients with first-episode psychosis and increased in healthy controls with a history of severe childhood abuse

BACKGROUND

Childhood abuse is highly prevalent in psychosis patients, but whether/how it affects hypothalamic-pituitary-adrenal (HPA) axis at the onset of psychosis remains unclear. We aimed to investigate the effects of severity of childhood abuse on HPA axis activity, in first-episode psychosis (FEP) and healthy controls.

METHODS

We recruited 169 FEP patients and 133 controls with different degrees of childhood physical and sexual abuse (i.e. no abuse exposure, non-severe abuse exposure, and severe abuse exposure). Saliva samples were collected to measure cortisol awakening response with respect to ground (CARg), increase (CARi) and diurnal (CDD) cortisol levels. Two-way ANOVA analyses were conducted to test the relationships between severity of childhood abuse and psychosis on cortisol levels in individuals with psychosis and healthy controls with and without childhood abuse history.

RESULTS

A statistically significant interaction between childhood abuse and psychosis on CARg was found (F_(2,262) = 4.60, p = 0.011, ω² = 0.42). Overall, controls showed a U-shaped relationship between abuse exposure and CARg, while patients showed an inverted U-shaped relationship. CARg values were markedly different between patients and controls with either no abuse history or exposure to severe childhood abuse. No significant differences were found when looking at CARi and CDD.

CONCLUSIONS

Our results show a divergent effect of severe childhood abuse on HPA axis activity in patients with first-episode psychosis and in controls. In the presence of exposure to severe childhood abuse, a blunted CARg and a less reactive HPA axis may represent one of the biological mechanisms involved in the development of psychosis.

Maternal witness to intimate partner violence during childhood and prenatal family functioning alter newborn cortisol reactivity

Witnessing intimate partner violence (IPV) during childhood is a risk factor for mental health problems across the lifespan. Less is known about the intergenerational consequences of witnessing IPV, and if the current family climate buffers intergenerational effects of witnessing violence. The mother's experience of witnessing IPV against her own mother during childhood, prenatal family dysfunction, and prenatal perceived stress were examined as predictors of offspring cortisol in the first month of life (N = 218 mother-infant dyads). Mothers reported on witnessing IPV in their childhoods, prenatal family dysfunction, and prenatal perceived stress in pregnancy. At 2 days and again at 1 month postpartum, infants engaged in a neurobehavioral exam to assess infant cortisol reactivity. Infants whose mothers witnessed IPV in childhood exhibited alterations in their baseline cortisol and their cortisol reactivity at 1 month of age, whereas family dysfunction during pregnancy was associated with baseline cortisol and cortisol reactivity at 2 days of age. Prenatal perceived stress was not associated with infant cortisol at 2 days or 1 month. Prenatal family dysfunction and perceived stress did not moderate effects of the mother's experience of witnessing IPV. Results support the view that maternal experiences in childhood and during pregnancy exert intergenerational effects on the HPA stress response system.

Digging deeper in the differential effects of inflammatory and psychosocial stressors in remitted depression: Effects on cognitive functioning

BACKGROUND

Major Depressive Disorder (MDD) covers a wide spectrum of symptoms, including cognitive dysfunction, which can persist during remission. Both inflammatory states and psychosocial stress play a role in MDD pathogenesis.

METHODS

The effects of inflammatory (i.e., Salmonella typhi vaccine) and psychosocial stressor (i.e., Trier Social Stress Test), as well as their combination were investigated on cognition in women (aged 25-45 years, n = 21) with (partially) remitted MDD and healthy controls (n = 18) in a single-blind placebo-controlled study. In a crossover design, patients received on the first day one of the aforementioned interventions and on the other day a placebo, or vice versa, with a washout period of 7-14 days. Short-term and verbal memory, working memory, attention, verbal fluency, information processing speed, psychomotor function, and measures of attentional bias to emotions were measured. Exploratory analyses were performed to assess the correlation between biomarkers of inflammation and the Hypothalamic-Pituitary-Adrenal axis and cognitive functioning.

RESULTS

In patients, inflammatory stress decreased information processing speed and verbal memory, and increased working memory; after psychosocial stress, there was an increase in attention. There was also an increased negative attentional bias in patients after inflammatory stress. Neither stressor had any effect in controls.

LIMITIATIONS

Limitations are the relatively small sample size and antidepressant use by a part of the participants. The effects of the stressors were also measured a relatively short period after administration.

CONCULSION

Patients were sensitive to the cognitive effects of inflammation and psychosocial stress on cognition, while controls were not.

Hyperactivation of the hypothalamo-pituitary-adrenocortical axis in streptozotocin-diabetic gerbils (Gerbillus gerbillus)

This study was designed to investigate the HPA-axis impairment in the streptozotocin (STZ)-diabetic gerbils (Gerbillus gerbillus). Twenty-six male gerbils (body weight ~27 g) were divided into 3 groups: vehicle control (n = 10), 2 days of diabetes (n = 09) and 30 days of diabetes (n = 07). The latter 2 groups received an intraperitoneal injection of STZ (150 mg/kg of body weight). At 2 and 30 days of diabetes, streptozotocin-diabetic gerbils underwent a retro-orbital puncture for assessment of biochemical and hormonal parameters. Subsequently the animals were decapitated and the adrenal glands were removed, weighed and processed for light microscopy and stereology. Nondiabetic control gerbils that had been injected with citrate buffer were examined as a comparison. At 2 days of diabetes, STZ gerbils exhibited symptoms that are characteristic of human diabetes type 1. The adrenal gland showed significant increase in weight, associated with a larger cortex layer, hypertrophy of the fasciculate cells and a significant decrease in the nucleocytoplasmic index. These changes were associated with higher plasma ACTH and cortisol concentrations compared to nondiabetic controls. At 30 days postdiabetes, ACTH levels remained elevated, whereas cortisol levels decreased compared to the early stage of diabetes. Histological analysis revealed the existence of a band of connective tissue (collagen) that separates the cortical and medullary zones and is not present in humans or laboratory rodents, which represents a striking change seen throughout the disease. STZ-induced diabetes mellitus in Gerbillus gerbillus resulted in hyperactivation of the HPA axis in the early stages of diabetes mellitus which did not persist into the final stages of the disease, suggesting a possible reduction in adrenocortical sensitivity over time.

PINK1 deficiency is associated with increased deficits of adult hippocampal neurogenesis and lowers the threshold for stress-induced depression in mice

Parkinson's disease (PD) is characterized by motor impairments and several non-motor features, including frequent depression and anxiety. Stress-induced deficits of adult hippocampal neurogenesis (AHN) have been linked with abnormal affective behavior in animals. It has been speculated that AHN defects may contribute to affective symptoms in PD, but this hypothesis remains insufficiently tested in animal models. Mice that lack the PD-linked kinase PINK1 show impaired differentiation of adult-born neurons in the hippocampus. Here, we examined the relationship between AHN deficits and affective behavior in PINK1^-/- mice under basal (no stress) conditions and after exposure to chronic stress. PINK1 loss and corticosterone negatively and jointly affected AHN, leading to lower numbers of neural stem cells and newborn neurons in the dentate gyrus of corticosterone-treated PINK1^-/- mice. Despite increased basal AHN deficits, PINK1-deficient mice showed normal affective behavior. However, lack of PINK1 sensitized mice to corticosterone-induced behavioral despair in the tail suspension test at a dose where wildtype mice were unaffected. Moreover, after two weeks of chronic restraint stress male PINK1^-/- mice displayed increased immobility in the forced swim test, and protein expression of the glucocorticoid receptor in the hippocampus was reduced. Thus, while impaired AHN as such is insufficient to cause affective dysfunction in this PD model, PINK1 deficiency may lower the threshold for chronic stress-induced depression in PD. Finally, PINK1-deficient mice displayed reduced basal voluntary wheel running but normal rotarod performance, a finding whose mechanisms remain to be determined.

Subclinical Lipopolysaccharide from Salmonella Enteritidis Induces Dysregulation of Bioactive Substances from Selected Brain Sections and Glands of Neuroendocrine Axes

Bacterial lipopolysaccharide (LPS) can contribute to the pathogenesis and the clinical symptoms of many diseases such as cancer, mental disorders, neurodegenerative as well as metabolic diseases. The asymptomatic carrier state of Salmonella spp. is a very important public health problem. A subclinical single dose of LPS obtained from S. Enteritidis (5 μg/kg, i.v.) was administered to discern the consequences of changes of various brain peptides such as corticotropin-releasing hormone (CRH), gonadotropin-releasing hormone (GnRH), thyrotropin-releasing hormone (TRH), galanin (GAL), neuropeptide Y (NPY), somatostatin (SOM), substance P (SP), and vasoactive intestinal polypeptide (VIP) in selected clinically important brain sections and endocrine glands of the hypothalamic-pituitary-adrenal (HPA), -thyroid (HPT), -ovarian (HPO) axes. The study was conducted on ten immature crossbred female pigs. The brain peptides were extracted from the hypothalamus (medial basal hypothalamus, preoptic area, lateral hypothalamic area, mammillary bodies, and the stalk median eminence), and pituitary gland (adenohypophysis and neurohypophysis) sections and from the ovaries and adrenal and thyroid glands. There was no difference in health status between LPS and the control groups during the period of the experiment. Nevertheless, even a low single dose of LPS from S. Enteritidis that did not result in any clinical symptoms of disease induced dysregulation of various brain peptides, such as CRH, GnRH, TRH, GAL, NPY, SOM, SP, and VIP in selected brain sections of hypothalamus, pituitary gland and in the endocrine glands of the HPA, HPO, and HPT axes. In conclusion, the obtained results clearly show that subclinical LPS from S. Enteritidis can affect the brain chemistry structure and dysregulate bioactive substance from selected brain sections and glands of the neuroendocrine axes. The exact mechanisms by which LPS can influence major neuroendocrine axes are not fully understood and require further studies.

The effects of the urocortins on the hypothalamic-pituitary-adrenal axis - similarities and discordancies between rats and mice

The urocortins (Ucn I, Ucn II and Ucn III) are structural analogues of corticotropin-releasing factor (CRF). The aim of our present experiments was to compare the effects of the urocortins on the hypothalamic-pituitary-adrenal (HPA) axis in rats and mice, including the hypothalamic adrenocorticotropic hormone (ACTH) secretagogues, such as CRF and arginine vasopressin (AVP). Therefore, male CFLP mice and male Wistar rats were injected intracerebroventricularly (icv) with 0.5, 1, 2 and 5 μg/2 μl of Ucn I, Ucn II or Ucn III. After 30 min the animals were decapitated, and then, hypothalamic CRF and AVP concentrations and plasma ACTH and corticosterone (CORT) levels were measured. All measurements were performed by enzyme-linked immunosorbent assays (ELISA), except that of the plasma CORT level, which was determined by chemofluorescent assay. Ucn I increased significantly the hypothalamic CRF and AVP concentrations in both rats and mice. Ucn II and Ucn III influenced significantly only the hypothalamic CRF concentration in rats, without affecting the hypothalamic AVP concentration. In contrast, Ucn II and Ucn III increased significantly only the hypothalamic AVP concentration in mice, without affecting the hypothalamic CRF concentration. The hypothalamic changes were reflected more or less accurately by changes of the plasma ACTH and CORT levels. The present experiments demonstrate that the urocortins regulate the HPA axis centrally via modulation of the hypothalamic ACTH secretagogues and that there are some similarities and discordancies between rats and mice regarding this regulation.

Stability of diurnal cortisol measures across days, weeks, and years across middle childhood and early adolescence: Exploring the role of age, pubertal development, and sex

Effective regulation of the hypothalamic-pituitary-adrenal axis (HPA-axis) has been linked to numerous health outcomes. Within-person variation in diurnal measures of HPA-axis regulation assessed over days, months, and years can range between 50-73% of total variation. In this study of 59 youth (ages 8-13), we quantified the stability of the cortisol awakening response (CAR), the diurnal slope, and tonic cortisol concentrations at waking and bedtime across 8 days (2 sets of 4 consecutive days separated by 3 weeks), 3 weeks, and 3 years. We then compared the stability of these indices across three key developmental factors: age, pubertal status, and sex. Youth provided 4 saliva samples per day (waking, 30 min post-waking, before dinner, and before bedtime) for 4 consecutive days during the 3rd week of an ongoing 8-week daily diary study. Youth repeated this same sampling procedure 3 weeks and 3 years later. Using multi-level modeling, we computed the amount of variance in diurnal HPA-axis regulation that was accounted for by nesting an individual's diurnal cortisol indices within days, weeks, or years. Across days, diurnal slope was the most stable index, whereas waking cortisol and CAR were the least stable. All indices except bedtime cortisol were similarly stable when measured across weeks, and all indices were uniformly stable when measured across 3 years. Boys, younger participants, and youth earlier in their pubertal development at study enrollment exhibited greater HPA-axis stability overall compared with females and older, more physically mature participants. We conclude that important within- and between-subjects questions can be answered about health and human development by studying HPA-axis regulation, and selection of the index of interest should be determined in part by its psychometric characteristics. To this end, we propose a decision tree to guide study design for research in pediatric samples by longitudinal timeframe and sample characteristics.

Novel zebrafish behavioral assay to identify modifiers of the rapid, nongenomic stress response

When vertebrates face acute stressors, their bodies rapidly undergo a repertoire of physiological and behavioral adaptations, which is termed the stress response. Rapid changes in heart rate and blood glucose levels occur via the interaction of glucocorticoids and their cognate receptors following hypothalamic-pituitary-adrenal axis activation. These physiological changes are observed within minutes of encountering a stressor and the rapid time domain rules out genomic responses that require gene expression changes. Although behavioral changes corresponding to physiological changes are commonly observed, it is not clearly understood to what extent hypothalamic-pituitary-adrenal axis activation dictates adaptive behavior. We hypothesized that rapid locomotor response to acute stressors in zebrafish requires hypothalamic-pituitary-interrenal (HPI) axis activation. In teleost fish, interrenal cells are functionally homologous to the adrenocortical layer. We derived eight frameshift mutants in genes involved in HPI axis function: two mutants in exon 2 of mc2r (adrenocorticotropic hormone receptor), five in exon 2 or 5 of nr3c1 (glucocorticoid receptor [GR]) and two in exon 2 of nr3c2 (mineralocorticoid receptor [MR]). Exposing larval zebrafish to mild environmental stressors, acute changes in salinity or light illumination, results in a rapid locomotor response. We show that this locomotor response requires a functioning HPI axis via the action of mc2r and the canonical GR encoded by nr3c1 gene, but not MR (nr3c2). Our rapid behavioral assay paradigm based on HPI axis biology can be used to screen for genetic and environmental modifiers of the hypothalamic-pituitary-adrenal axis and to investigate the effects of corticosteroids and their cognate receptor interactions on behavior.

The dual nature of hypothalamic-pituitary-adrenal axis regulation in dyads of very preterm infants and their mothers

The co-regulation of the hypothalamic-pituitary-adrenal (HPA) axis in mother-infant dyads is thought to be key for infant and child development. Nonetheless, previous literature presents some inconsistencies that might at least partially be due to the presence of risk conditions and the use of different statistical approaches to measure HPA axis co-regulation. Very preterm (VPT) birth represents one of these risk conditions as the early foundation of mother-infant interaction is disrupted. Both VPT infants and their mothers present evidence of altered HPA axis regulation. Nonetheless, the comparison of mother-infant HPA axis co-regulation in VPT infants compared to full-term (FT) ones has not been previously investigated. In this study, 3-month-old (corrected age) VPT infants and FT counterparts with their mothers took part in a well-validated stress-inducing laboratory task (i.e., double Face-to-Face Still-Face, FFSF paradigm). Salivary cortisol samples were obtained before (Baseline) and after (Early reactivity, Late reactivity and Recovery) the FFSF procedure. Dyadic HPA axis co-regulation was assessed at each sample time-point (i.e., in-moment coupling) as well as across samples (i.e., in-time synchrony). Significant in-moment coupling emerged at Baseline, Late reactivity and Recovery for FT infants' dyads only. An overlying pattern of salivary cortisol trajectories emerged between mothers and infants in the VPT group, whereas a more complex pattern of reciprocal and complementary co-regulation was found for FT infants' dyads. Although both groups gave evidence of HPA axis co-regulation, dyads of VPT infants appear to be less able to adapt reciprocally and dynamically to stressful conditions. These findings suggest that multiple approaches to account for dyadic HPA axis co-regulation should be used in order to depict the complex pattern of biological rhythms coordination in mother-infant dyads.

Telomere length and salivary cortisol stress reactivity in very preterm infants

During the Neonatal Intensive Care Unit (NICU) stay, very preterm (VPT) infants are exposed to life-saving yet pain-inducing skin-breaking procedures (i.e., NICU pain-related stress) which contribute to the programming of hypo-responsive HPA axis development during the first months of life. Unfortunately, to date the mechanisms linking NICU pain-related stress and altered HPA axis regulation are only limitedly known. Telomere length (TL) regulation is an epigenetic mechanism previously shown to be affected by early stress exposures and capable of associating with HPA axis reactivity in children. In VPT infants, NICU pain-related stress was found to associate with decreased TL from birth to discharge, but there is no evidence for the association between TL and HPA axis in these infants. In this study, we prospectively examined the relationship between NICU pain-related stress and HPA axis reactivity to an age-appropriate socio-emotional condition (i.e., the Still-Face Procedure, SFP) in healthy VPT infants at 3-month corrected age. NICU pain-related stress was computed as the ratio between the number of skin-breaking procedures and length of NICU stay. A differential score (i.e., ∆TL) was obtained subtracting TL at birth from TL at discharge. A normalized (log10) cortisol reactivity index (CRI) was obtained by averaging post-stress (20 min after SFP) salivary cortisol sample on baseline value. A regression model controlling for neonatal and socio-demographic confounders showed that ∆TL was the only significant predictor of CRI. Although preliminary, these findings contribute to our knowledge of the mechanisms linking early exposures to adversity and later in life regulation of the HPA axis in VPT infants.

Chronic Suppression of Glucagon-Like Peptide-1 Receptor (GLP1R) mRNA Translation in the Rat Bed Nucleus of the Stria Terminalis Reduces Anxiety-Like Behavior and Stress-Induced Hypophagia, But Prolongs Stress-Induced Elevation of Plasma Corticosterone

The anterior lateral bed nucleus of the stria terminalis (alBST) expresses glucagon-like peptide-1 receptors (GLP1Rs) and receives input from caudal brainstem GLP1 neurons. GLP1 administered centrally reduces food intake and increases anxiety-like behavior and plasma corticosterone (cort) levels in rats, whereas central GLP1R antagonism has opposite effects. Anxiogenic threats and other stressors robustly activate c-fos expression in both GLP1-producing neurons and also in neurons within alBST subregions expressing GLP1R. To examine the functional role of GLP1R signaling within the alBST, adult male Sprague Dawley rats received bilateral alBST-targeted injections of an adeno-associated virus (AAV) vector expressing short hairpin RNA (shRNA) to knock down the translation of GLP1R mRNA (GLP1R-KD rats), or similar injections of a control AAV (CTRL rats). In situ hybridization revealed that GLP1R mRNA is expressed in a subset of GABAergic alBST neurons, and quantitative real-time PCR confirmed that GLP1R-KD rats displayed a significant 60% reduction in translatable GLP1R mRNA. Compared with CTRL rats, GLP1R-KD rats gained more body weight over time and displayed less anxiety-like behavior, including a loss of light-enhanced acoustic startle and less stress-induced hypophagia. Conversely, while baseline plasma cort levels were similar in GLP1R-KD and CTRL rats, GLP1R-KD rats displayed a prolonged stress-induced elevation of plasma cort levels. GLP1R-KD and CTRL rats displayed similar home cage food intake and a similar hypophagic response to systemic Exendin-4, a GLP1R agonist that crosses the blood-brain barrier. We conclude that GLP1R expressed within the alBST contributes to multiple behavioral responses to anxiogenic threats, yet also serves to limit the plasma cort response to acute stress.SIGNIFICANCE STATEMENT Anxiety is an affective and physiological state that supports threat avoidance. Identifying the neural bases of anxiety-like behaviors in animal models is essential for understanding mechanisms that contribute to normative and pathological anxiety in humans. In rats, anxiety/avoidance behaviors can be elicited or enhanced by visceral or cognitive threats that increase glucagon-like peptide-1 (GLP1) signaling from the caudal brainstem to the hypothalamus and limbic forebrain. Data reported here support a role for limbic GLP1 receptor signaling to enhance anxiety-like behavior and to attenuate stress-induced elevations in plasma cort levels in rats. Improved understanding of central GLP1 neural pathways that impact emotional responses to stress could expand potential therapeutic options for anxiety and other stress-related disorders in humans.

FKBP5 Gene Expression Predicts Antidepressant Treatment Outcome in Depression

Adverse experiences and chronic stress are well-known risk factors for the development of major depression, and an impaired stress response regulation is frequently observed in acute depression. Impaired glucocorticoid receptor (GR) signalling plays an important role in these alterations, and a restoration of GR signalling appears to be a prerequisite of successful antidepressant treatment. Variants in genes of the stress response regulation contribute to the vulnerability to depression in traumatized subjects. Consistent findings point to an important role of FKBP5, the gene expressing FK506-binding protein 51 (FKBP51), which is a strong inhibitor of the GR, and thus, an important regulator of the stress response. We investigated the role of FKBP5 and FKB51 expression with respect to stress response regulation and antidepressant treatment outcome in depressed patients. This study included 297 inpatients, who participated in the Munich Antidepressant Response Signature (MARS) project and were treated for acute depression. In this open-label study, patients received antidepressant treatment according to the attending doctor’s choice. In addition to the FKBP5 genotype, changes in blood FKBP51 expression during antidepressant treatment were analyzed using RT-PCR and ZeptoMARK^TM reverse phase protein microarray (RPPM). Stress response regulation was evaluated in a subgroup of patients using the combined dexamethasone (dex)/corticotropin releasing hormone (CRH) test. As expected, increased FKBP51 expression was associated with an impaired stress response regulation at baseline and after six weeks was accompanied by an elevated cortisol response to the combined dex/CRH test. Further, we demonstrated an active involvement of FKBP51 in antidepressant treatment outcome. While patients responding to antidepressant treatment had a pronounced reduction of FKBP5 gene and FKBP51 protein expression, increasing expression levels were observed in nonresponders. This effect was moderated by the genotype of the FKBP5 single nucleotide polymorphism (SNP) rs1360780, with carriers of the minor allele showing the most pronounced association. Our findings demonstrate that FKBP5 and, specifically, its expression product FKBP51 are important modulators of antidepressant treatment outcome, pointing to a new, promising target for future antidepressant drug development.

Conditioning cortisol in humans: design and pilot study of a randomized controlled trial

Background

Conditioning of physiological responses can be achieved by repeatedly pairing a previously neutral conditioned stimulus with the administration of a pharmacologically salient unconditioned stimulus. This type of conditioning has been effective for specific immune and endocrine responses, but results with regard to conditioning of cortisol, a key stress-regulatory parameter, are currently unclear. This paper describes a pharmacological conditioning design, optimized for the examination of effects of cortisol conditioning under both basal conditions and in response to stress.

Methods

A double-blind randomized controlled conditioning paradigm aimed at conditioning of cortisol is conducted in 48 healthy female volunteers. During the acquisition phase, a gustatory stimulus (conditioned stimulus) is paired with hydrocortisone (100 mg, capsulated, unconditioned stimulus) three times before being administered together with placebo during three evocation sessions. To investigate possible effects of cortisol conditioning in response to stress, participants are exposed to the Trier Social Stress Test during the third evocation session. Primary outcome measure of this study is the mean area under the curve of salivary cortisol during the first two evocation sessions. As secondary outcomes, self-reported affect and stress as well as alpha-amylase are investigated. A pilot study was conducted to ensure that this design is feasible to be used in a larger study.

Discussion

This study design provides an innovative opportunity to examine the conditioning of cortisol under basal conditions and in response to stress. Also, the possible effect of cortisol conditioning on secondary outcomes of self-reported affect and alpha-amylase can be investigated. If cortisol could successfully be conditioned, this would be of conceptual relevance, showing that hypothalamic pituitary adrenal (HPA) axis regulation can be influenced by associative learning processes. Eventually, this could also have important clinical implications for understanding and treating stress-related disorders in which HPA axis dysregulation might play a role.

Trial registration

Nederlands Trial Register, NTR4651. Registered on 29 July 2014

Electronic supplementary material

The online version of this article (10.1186/s40814-018-0382-5) contains supplementary material, which is available to authorized users.

The role of substance use, smoking, and inflammation in risk for suicidal behavior

BACKGROUND

Alcohol and substance use disorders are important predictors for suicidal behavior. However, the role of individual substances as proximal risk factors for suicidal behavior and the mechanisms through which substance use affect risk are not entirely clear. We examine whether the frequency of substance use and whether biological markers in the HPA axis and inflammatory pathways are associated with clinical risk factors of suicidal behavior of aggression, impulsivity, hopelessness, and poor sleep.

METHODS

The sample consisted of psychiatric inpatients, aged 15-30 years, admitted for suicide attempt (n = 38), suicidal ideation (n = 40); and healthy controls (n = 37). We measured hair cortisol concentrations, glucocorticoid receptor (GR) sensitivity, stimulated production of interleukin- or IL-6, C-reactive protein, and mRNA expression of GR, SKA2, FKBP5, TNF-α, and IL-1β.

RESULTS

Smoking was associated with increased aggression [β = 2.9, 95% CI (-0.03, 6), p = 0.05], impulsivity [β = 3.1, 95% CI (1.6, 4.6), p < 0.001], and poor sleep [β = 0.5, 95% CI (0.03, 0.95), p = 0.04] even after controlling for demographics and group. Similarly, TNF-α mRNA was associated with impulsivity [β = 0.07, 95% CI (0.01, 0.1), p = 0.02] and hopelessness [β = 0.03, 95% CI (0.004, 0.05), p = 0.03]. Smoking tobacco (r = 0.32, p < 0.001) was positively associated with TNF-α mRNA.

LIMITATIONS

Study limitations include the cross-sectional design, retrospective assessment, and relatively small sample size.

CONCLUSIONS

Future longitudinal studies are needed to test whether inflammatory markers mediate the relationships between smoking, clinical risk factors, and suicidal behavior; and to examine whether smoking cessation could reduce the risk for suicidal behavior in at-risk patients.

Sufficient intake of high-fat food attenuates stress-induced social avoidance behavior

AIMS

Psychosocial stress is a form of mental stress associated with human relationships that underlies the pathogenesis of mental disorders such as depression. Previous studies have suggested that intake of energy-dense foods, also known as "palatable foods," can relieve psychosocial stress. However, it remains unclear whether the volume of palatable food affects abnormal behavior induced by psychosocial stress. In the present study, we aimed to determine whether levels of high-fat food intake significantly influence psychosocial stress using the social-defeat stress (SDS) paradigm.

MAIN METHODS

Mice subjected to SDS ate either a high-fat or normal chow diet for 10 days. Behavioral tests were conducted following the completion of the SDS paradigm. The hypothalamus, liver, and blood were examined post-mortem.

KEY FINDINGS

Mice with sufficient intake of high-fat chow immediately following exposure to SDS did not exhibit social avoidance behavior, suggesting that a high-fat diet may improve social behavior. However, inadequate intake of high-fat food, which did not alter cholesterol metabolism or hypothalamic-pituitary-adrenal axis activity, was not associated with such benefits, instead increased anxiety-like behavior.

SIGNIFICANCE

The results of the present study demonstrate that eating a high-fat diet may attenuate stress, but that this benefit disappears with insufficient intake of high-fat foods. The benefits of a high-fat diet under SDS may be related to cholesterol metabolism in the liver.

Early life stress impairs fear memory and synaptic plasticity; a potential role for GluN2B

Programming of the brain by early life stress has been associated with alterations in structure and function of the dorsal hippocampus. Yet, the underlying molecular mechanisms remain largely elusive. In this study, we examined the effects of early life stress (ELS) - by housing mouse dams with limited nesting and bedding material from postnatal days 2-9 and examined in 6 month old offspring; 1) auditory fear conditioning, 2) expression of the hippocampal N-methyl-d-aspartate receptor (NMDA-R) subunits 2A and 2B (GluN2A, GluN2B), and expression of PSD-95 and synaptophysin, and 3) short- and long-term (LTP) synaptic plasticity. Given its critical role in NMDA receptor function and synaptic plasticity, we further examined the role of GluN2B in effects of ELS on synaptic plasticity and fear memory formation. We demonstrate that ELS impaired fear memory in 6 month old mice and decreased hippocampal LTP as well as the paired-pulse ratio (PPR). ELS also reduced hippocampal GluN2B expression. Interestingly, pharmacological blockade of GluN2B with the selective antagonist Ro25 6981 was less effective to reduce synaptic plasticity in ELS mice, and was also ineffective to impair memory retrieval in ELS mice. These studies suggest that ELS reduces hippocampal synaptic plasticity and fear memory formation and hampers GluN2B receptor function. As such, GluN2B may provide an important target for future strategies to prevent lasting ELS effects on cognition.

The Role of Proopiomelanocortin and α-Melanocyte-Stimulating Hormone in the Metabolic Syndrome in Psychiatric Disorders: A Narrative Mini-Review

The metabolic syndrome (MetS) comprises abdominal obesity, preclinical or full diabetes type 2, arterial hypertension, and dyslipidemia and affects a significant proportion of the general population with a remarkably higher prevalence in patients suffering from psychiatric disorders. However, studies exploring the pathogenetic link between MetS and psychiatric diseases are rare. Here, we aim to narrow this gap in knowledge by providing a narrative review on this topic that focuses on two psychiatric diseases, namely on schizophrenia and posttraumatic stress disorder (PTSD) since we assume them to be associated with two different main causalities of MetS: in schizophrenia, MetS evidently develops or aggravates in response to antipsychotic drug treatment while it assumingly develops in response to stress-induced endocrine and/or epigenetic alterations in PTSD. First, we compared the prevalences of MetS and associated pathologies (which we took from the latest meta-analyses) among different psychiatric disorders and were surprised that the prevalences of arterial hypertension and hyperglycemia in PTSD almost doubles those of the other psychiatric disorders. Next, we performed a literature search on the neurobiology of MetS and found numerous articles describing a role for proopiomelanocortin (POMC) in MetS. Thus, we concentrated further analysis on POMC and one of its downstream effector hormones, α-melanocyte-stimulating hormone (α-MSH). We found some evidence for a role of POMC in both PTSD and schizophrenia, in particular in antipsychotic-induced MetS, as well as for α-MSH in schizophrenia, but, surprisingly, no study on α-MSH in PTSD. Taken together, our synopsis reveals, first, a potential interaction between the POMC system and stress in the assumingly at least partially shared pathogenesis of psychiatric disorders and MetS, second, that modulation of the POMC system, in particular of the melanocortin 3 and 4 receptors, might be a promising target for the treatment of MetS and, third, that the DNA methylation status of POMC might speculatively be a promising biomarker for MetS in general and, possibly, in particular in the context of stress-related psychiatric conditions such as PTSD. To best of our knowledge, this is the first review on the role of the POMC system in MetS in psychiatric disorders.

A Major Role for the Lateral Habenula in Depressive Illness: Physiologic and Molecular Mechanisms

Emerging preclinical and clinical evidence indicate that the lateral habenula plays a major role in the pathophysiology of depressive illness. Aberrant increases in neuronal activity in the lateral habenula, an anti-reward center, signals down-regulation of brainstem dopaminergic and serotonergic firing, leading to anhedonia, helplessness, excessive focus on negative experiences, and, hence, depressive symptomatology. The lateral habenula has distinctive regulatory adaptive role to stress regulation in part due to its bidirectional connectivity with the hypothalamic-pituitary-adrenal (HPA) axis. In addition, studies show that increased lateral habenula activity affects components of sleep regulation including slow wave activity and rapid eye movement (REM), both disrupted in depressive illness. Lack of perceived reward experienced during the adverse outcomes also precipitates lateral habenula firing, while outcomes that meet or exceed expectations decrease lateral habenula firing and, in turn, increase midbrain dopaminergic and serotonergic neurotransmission. The ability to update expectations of the environment based on rewards and aversive stimuli reflects a potentially important survival mechanism relevant to the capacity to adapt to changing circumstances. What if one lives in a continuously aversive and invalidating environment or under the conditions of chronic stress? If there is a propensity of the habenula to release many burst discharges over time, an individual could habitually come to perceive the world as perpetually disappointing. Conceivably, the lateral habenula could learn to expect an adverse outcome systematically and communicate it more easily. Thus, if the lateral habenula fires more frequently, it may lead to a state of continuous disappointment and hopelessness, akin to depression. Furthermore, postmortem studies reveal that the size of the lateral habenula and total number of neurons are decreased in patients who had depressive illness. Novel research in the field shows that ketamine induces rapid and sustained antidepressant effect. Intriguingly, recent preclinical animal models show that ketamine abolishes N-methyl-D-aspartate receptor (NMDAR)-dependent lateral habenula bursting activity, leading to rapid resolution of depressive symptoms.

Interaction of HPA axis genetics and early life stress shapes emotion recognition in healthy adults

BACKGROUND

Early life stress (ELS) affects facial emotion recognition (FER), as well as the underlying brain network. However, there is considerable inter-individual variability in these ELS-caused alterations. As the hypothalamic-pituitary-adrenal (HPA) axis is assumed to mediate neural and behavioural sequelae of ELS, the genetic disposition towards HPA axis reactivity might explain differential vulnerabilities.

METHODS

An additive genetic profile score (GPS) of HPA axis reactivity was built from 6 SNPs in 3 HPA axis-related genes (FKBP5, CRHR1, NR3C1). We studied two independent samples. As a proof of concept, GPS was tested as a predictor of cortisol increase to a psychosocial challenge (MIST) in a healthy community sample of n = 40. For the main study, a sample of n = 170 completed a video-based FER task and retrospectively reported ELS experiences in the Childhood Trauma Questionnaire (CTQ).

RESULTS

GPS positively predicted cortisol increase in the stress challenge over and above covariates. CTQ and genetic profile scores interacted to predict facial emotion recognition, such that ELS had a detrimental effect on emotion processing only in individuals with higher GPS. Post-hoc moderation analyses revealed that, while a less stress-responsive genetic profile was protective against ELS effects, individuals carrying a moderate to high GPS were affected by ELS in their ability to infer emotion from facial expressions.

DISCUSSION

These results suggest that a biologically informed genetic profile score can capture the genetic disposition to HPA axis reactivity and moderates the influence of early environmental factors on facial emotion recognition. Further research should investigate the neural mechanisms underlying this moderation. The GPS used here might prove a powerful tool for studying inter-individual differences in vulnerability to early life stress.

Fast Feedback Inhibition of Adrenocorticotropic Hormone Secretion by Endogenous Cortisol in Humans

BACKGROUND

Using high-frequency blood sampling, we demonstrate glucocorticoid fast feedback (FF) mediated by endogenous cortisol in 6 normal humans.

METHODS

We stimulated adrenocorticotropic hormone (ACTH) secretion by ovine corticotropin-releasing hormone (oCRH) with the experimental paradigm in which a high-frequency blood sampling was designed for plasma ACTH and cortisol determinations.

RESULTS

We saw previously unrecognized variability in the timing of key events such as onsets of ACTH and cortisol secretion, onset and offset of FF, and in FF duration. This variability mandated analyses referenced to case-wise event times rather than referenced simply to time since oCRH administration. The mean time of FF onset was 4.0 min (range 0-9; median 3) after cortisol secretion began, and the mean FF duration was 7.5 min (range 3-18; median 6.0). The FF effect was rate-sensitive and does not reflect level-sensitive cortisol feedback. In agreement with previous estimates using hydrocortisone infusions, the rate of rise of cortisol that triggered FF was approximately 44 nmol/L/min or 1.6 µg/dL/min. FF onset followed the trigger cortisol slope with an average lag of 1 min (range 0-3; median 0). Unexpectedly, this trigger cortisol slope quickly declined within the FF period.

CONCLUSIONS

This experimental design may enable new physiological studies of human FF that is mediated by endogenous cortisol, including mechanisms, reproducibility, and generalizability to other activating stimuli.

The use of hair cortisol for the assessment of stress in animals

The hair cortisol concentration (HCC) is assumed to be a retrospective marker of integrated cortisol secretion and stress over longer periods of time. Its quantification is increasingly used in psychoneuroendocrinological studies in humans, but also in animal stress and welfare research. The measurement of HCCs for the assessment of stress offers many considerable benefits for use in domesticated and wild animals, especially due to the easy and minimally invasive sampling procedure and the representation of longer time periods in one sample. This review aims to outline the different fields of application and to assess the applicability and validity of HCC as an indicator for chronic stress or long-term activity of the hypothalamic-pituitary-adrenal axis in wild and domesticated animals. Specific hair characteristics are presented and the advantages and limitations of using HCC are discussed. An overview of findings on the impact of stress- and health-related factors on HCCs and of diverse influencing factors causing variation in hair cortisol levels in different species is given. Recommendations for the use of hair cortisol analysis are proposed and potential fields of future research are pointed out. The studies indicate an effect of age and pregnancy on HCCs, and cortisol incorporation into hair was also found to depend on hair colour, body region, sex and season of year, but these results are less consistent. Furthermore, the results in animals show that a wide array of stressors and pathological conditions alters the cortisol concentrations in hair and that HCC thereby provides a reliable and valid reflection of long-term cortisol secretion in many species. However, more research is necessary to investigate the underlying mechanisms of cortisol incorporation into the hair and to explore the hair growth characteristics in the species of interest. To overcome confounding influences, the use of standardized sampling protocols is strongly advised.