Glucocorticoid receptors in the brain

Molecular evidence of altered stress responsivity related to neuroinflammation in the schizophrenia midbrain

Stress and inflammation are risk factors for schizophrenia. Chronic psychosocial stress is associated with subcortical hyperdopaminergia, a core feature of schizophrenia. Hyperdopaminergia arises from midbrain neurons, leading us to hypothesise that changes in stress response pathways may occur in this region. To identify whether transcriptional changes in glucocorticoid and mineralocorticoid receptors (NR3C1/GR, NR3C2/MR) or other stress signalling molecules (FKBP4, FKBP5) exist in schizophrenia midbrain, we measured gene expression in the human brain (N = 56) using qRT-PCR. We assessed whether alterations in these mRNAs were related to previously identified high/low inflammatory status. We investigated relationships between stress-related transcripts themselves, and between FKBP5 mRNA, dopaminergic, and glial cell transcripts in diagnostic and inflammatory subgroups. Though unchanged by diagnosis, GR mRNA levels were reduced in high inflammatory compared to low inflammatory schizophrenia cases (p = 0.026). We found no effect of diagnosis or inflammation on MR mRNA. FKBP4 mRNA was decreased and FKBP5 mRNA was increased in schizophrenia (p < 0.05). FKBP5 changes occurred in high inflammatory (p < 0.001), whereas FKBP4 changes occurred in low inflammatory schizophrenia cases (p < 0.05). The decrease in mRNA encoding the main stress receptor (GR), as well as increased transcript levels of the stress-responsive negative regulator (FKBP5), may combine to blunt the midbrain response to stress in schizophrenia when neuroinflammation is present. Negative correlations between FKBP5 mRNA and dopaminergic transcripts in the low inflammatory subgroup suggest higher levels of FKBP5 mRNA may also attenuate dopaminergic neurotransmission in schizophrenia even when inflammation is absent. We report alterations in GR-mediated stress signalling in the midbrain in schizophrenia.

Neuroendocrinology of reward in anorexia nervosa and bulimia nervosa: Beyond leptin and ghrelin

The pathophysiology of anorexia nervosa (AN) and bulimia nervosa (BN) are still poorly understood, but psychobiological models have proposed a key role for disturbances in the neuroendocrines that signal hunger and satiety and maintain energy homeostasis. Mounting evidence suggests that many neuroendocrines involved in the regulation of homeostasis and body weight also play integral roles in food reward valuation and learning via their interactions with the mesolimbic dopamine system. Neuroimaging data have associated altered brain reward responses in this system with the dietary restriction and binge eating and purging characteristic of AN and BN. Thus, neuroendocrine dysfunction may contribute to or perpetuate eating disorder symptoms via effects on reward circuitry. This narrative review focuses on reward-related neuroendocrines that are altered in eating disorder populations, including peptide YY, insulin, stress and gonadal hormones, and orexins. We provide an overview of the animal and human literature implicating these neuroendocrines in dopaminergic reward processes and discuss their potential relevance to eating disorder symptomatology and treatment.

The potential of calibrated fMRI in the understanding of stress in eating disorders

Eating disorders (ED), including Anorexia Nervosa (AN), Bulimia Nervosa (BN), and Binge Eating Disorder (BED), are medically dangerous psychiatric disorders of unknown etiology. Accumulating evidence supports a biopsychosocial model that includes genetic heritability, neurobiological vulnerability, and psychosocial factors, such as stress, in the development and maintenance of ED. Notably, stress hormones influence appetite and eating, and dysfunction of the physiological stress response has been implicated in ED pathophysiology. Stress signals also appear associated with food reward neurocircuitry response in ED, providing a possible mechanism for the role of stress in appetite dysregulation. This paper provides a review of some of the interacting psychological, behavioral, physiological, and neurobiological mechanisms involved in the stress response among individuals with ED, and discusses novel neuroimaging techniques to address potential physiological confounds of studying neural correlates of stress in ED, such as calibrated fMRI.

Stress induced neural reorganization: A conceptual framework linking depression and Alzheimer's disease

Chronic stress is a risk factor for a number of physiological disorders including cardiovascular disease, obesity and gastrointestinal disorders, as well as psychiatric and neurodegenerative disorders. There are a number of underlying molecular and cellular mechanisms altered in the course of chronic stress, which may increase the vulnerability of individuals to develop psychiatric disorders such as depression, and neurodegenerative disorders such as Alzheimer's Disease (AD). This is evident in the influence of stress on large-scale brain networks, including the resting state Default Mode Network (DMN), the effects of stress on neuronal circuitry and architecture, and the cellular and molecular adaptations to stress, which may render individuals with stress related psychiatric disorders more vulnerable to neurodegenerative disease later in life. These alterations include decreased negative feedback inhibition of the hypothalamic pituitary axis (HPA) axis, decreased dendritic arborization and spine density in the prefrontal cortex (PFC) and hippocampus, and the release of proinflammatory cytokines, which may suppress neurogenesis and promote neuronal cell death. Each of these factors are thought to play a role in stress-related psychiatric disease as well as AD, and have been observed in clinical and post-mortem studies of individuals with depression and AD. The goal of the current review is to summarize clinical and preclinical evidence supporting a role for chronic stress as a putative link between neuropsychiatric and neurodegenerative disease. Moreover, we provide a rationale for the importance of taking a medical history of stress-related psychiatric diseases into consideration during clinical trial design, as they may play an important role in the etiology of AD in stratified patient populations.

The attention network changes in breast cancer patients receiving neoadjuvant chemotherapy: Evidence from an arterial spin labeling perfusion study

To investigate the neural mechanisms underlying attention deficits that are related to neoadjuvant chemotherapy in combination with cerebral perfusion. Thirty one patients with breast cancer who were scheduled to receive neoadjuvant chemotherapy and 34 healthy control subjects were included. The patients completed two assessments of the attention network tasks (ANT), neuropsychological background tests, and the arterial spin labeling scan, which were performed before neoadjuvant chemotherapy and after completing chemotherapy. After neoadjuvant chemotherapy, the patients exhibited reduced performance in the alerting and executive control attention networks but not the orienting network (p < 0.05) and showed significant increases in cerebral blood flow (CBF) in the left posterior cingulate gyrus, left middle occipital gyrus, bilateral precentral gyrus, inferior parietal gyrus, supramarginal gyrus, angular gyrus, precuneus, cuneus, superior occipital gyrus, calcarine cortex, and temporal gyrus (p < 0.01 corrected) when compared with patients before chemotherapy and healthy controls. A significant correlation was found between the decrease performance of ANT and the increase in CBF changes in some brain regions of the patients with breast cancer. The results demonstrated that neoadjuvant chemotherapy influences hemodynamic activity in different brain areas through increasing cerebral perfusion, which reduces the attention abilities in breast cancer patients.

Long-term cognitive effects of glucocorticoid excess in Cushing's syndrome

CONTEXT AND OBJECTIVE

We previously found that patients with Cushing's syndrome (CS) scored lower than controls in several domains of cognitive function and that correction of hypercortisolism is not necessarily correlated with short-term improvement in intellectual performance. Here, we examined the long-term outcome in patients treated for CS by assessing the extent to which the detrimental effects of glucocorticoid (GC) excess on cognition can be reversed three years after corrective surgery.

DESIGN

A battery of neuropsychological tests, including tests of attention, visuospatial processing, learning and memory, and executive functioning were administered pre-treatment and 12, 24 and 36 months post-treatment.

PATIENTS AND CONTROL SUBJECTS

We included 18 patients with endogenous CS recruited before surgical treatment and 18 controls matched for age, sex and education.

RESULTS

CS patients performed worse than controls on tests of attention, executive functioning and nonverbal aspects of memory. Moreover, at 36 months following eucortisolism, executive function performance and, to a lesser extent, attention tasks showed limited change compared to pre-treatment testing.

CONCLUSION

Chronic hypercortisolism is accompanied by a deleterious impact on aspects of cognitive function. This negative effect on attention, executive performance and nonverbal memory seen in patients with CS suggests a differential effect of excess GCs upon different brain areas and networks. This influence persists years after the return to normal cortisol secretion levels.

Increased hypothalamic-pituitary-adrenal drive is associated with decreased appetite and hypoactivation of food-motivation neurocircuitry in anorexia nervosa

OBJECTIVE

Corticotrophin-releasing hormone (CRH)-mediated hypercortisolemia has been demonstrated in anorexia nervosa (AN), a psychiatric disorder characterized by food restriction despite low body weight. While CRH is anorexigenic, downstream cortisol stimulates hunger. Using a food-related functional magnetic resonance imaging (fMRI) paradigm, we have demonstrated hypoactivation of brain regions involved in food motivation in women with AN, even after weight recovery. The relationship between hypothalamic-pituitary-adrenal (HPA) axis dysregulation and appetite and the association with food-motivation neurocircuitry hypoactivation are unknown in AN. We investigated the relationship between HPA activity, appetite, and food-motivation neurocircuitry hypoactivation in AN.

DESIGN

Cross-sectional study of 36 women (13 AN, ten weight-recovered AN (ANWR), and 13 healthy controls (HC)).

METHODS

Peripheral cortisol and ACTH levels were measured in a fasting state and 30, 60, and 120 min after a standardized mixed meal. The visual analog scale was used to assess homeostatic and hedonic appetite. fMRI was performed during visual processing of food and non-food stimuli to measure the brain activation pre- and post-meal.

RESULTS

In each group, serum cortisol levels decreased following the meal. Mean fasting, 120 min post-meal, and nadir cortisol levels were high in AN vs HC. Mean postprandial ACTH levels were high in ANWR compared with HC and AN subjects. Cortisol levels were associated with lower fasting homeostatic and hedonic appetite, independent of BMI and depressive symptoms. Cortisol levels were also associated with between-group variance in activation in the food-motivation brain regions (e.g. hypothalamus, amygdala, hippocampus, orbitofrontal cortex, and insula).

CONCLUSIONS

HPA activation may contribute to the maintenance of AN by the suppression of appetitive drive.

Factors influencing cortisol level and slope among community dwelling older adults in Minnesota

Cortisol has frequently been used as a stress marker and has been shown to be elevated in response to laboratory stressors, severe real-life stressors, and daily hassles. Furthermore, variation in cortisol rhythms has been observed in some disease states and may be related to health outcomes. The majority of cortisol and stress research has been conducted on young adults. This study examines factors associated with cortisol level and slope in healthy older adults. Forty-eight older adults from the Twin Cities, MN (age = 76.4 +/- 5.8) were interviewed regarding health, stress, affect, and social networks. Participants collected saliva every two hours over a three-day period while keeping a record of their emotions and activities. Cortisol was assayed by radioimmunoassay. Data were analyzed using a random mixed effects model and linear regression. In univariate models cortisol was associated with age (p < 0.0001), time of day (p < 0.001), stress level (p = 0.01), positive affect measured in interview (p = 0.005), positive mood state (p < 0.0001), negative mood state (p = 0.09), and morningness (p = 0.0006). In multivariate models, affect was no longer significantly associated with cortisol. Age (p < 0.001), morningness (p = 0.014), physical activity (p = 0.017), and hours slept (p < 0.001) predicted cortisol slope. These results suggest that while cortisol reactivity to current mood and daily stressors may be diminished in older adults, perception of average stress on a trait level is predictive of cortisol level. As such, salivary cortisol might not be a good marker of acute stress in older adults, while still valuable to measure stress over a longer period of time.

Diurnal cycles of salivary cortisol in older adults

Cortisol has a well-documented circadian pattern. However, recent studies have demonstrated that individual variation in diurnal cortisol patterns occurs in young adult populations. Since older adults experience altered sleep-wake cycles and changes in circadian rhythmicity, we may see even greater variations in diurnal cortisol patterns in older adults. This study examined salivary cortisol patterns in 48 community dwelling older adults. Participants (mean age 76+/-6) collected saliva every 2 h over a three-day period. Cortisol was assayed by using RIA. Cortisol cycles were defined as inconsistent, typical or flat based on the slopes of two sequential daily cortisol patterns. Demographic, physical, psychological and behavioral measures were tested for group differences using t-tests and chi-square analyses. Forty-eight percent of the sample had inconsistent cycles, 50% had typical cycles and 2% had flat cycles. This sample had a higher percentage of inconsistent cycles and fewer flat cycles than reported for young adults (p=0.008) (Psychoneuroendocrinology 22 (1997) 89). Those with inconsistent cycles were younger and reported higher caffeine and food intake than those with typical cycles. This study demonstrates that normal diurnal rhythms of cortisol can be maintained in older adults, while day-to-day variation may increase.

Persistent cognitive impairment following surgical treatment of Cushing's syndrome

Chronic exposure to elevated glucocorticoid (GC) levels in Cushing's syndrome (CS) is associated with deficits in cognitive function. It has already been shown that CS patients scored significantly lower than controls on several aspects of cognitive function (J. Int. Neuropsychol. Soc. 6 (2000) 20). In the present study, 13 subjects who presented with CS were investigated one year after surgical treatment to determine the extent to which the effects of hypercortisolism on cognitive function are reversible. Subjects were evaluated with a battery of tasks, similar to the original battery of a year earlier and including tests of attention, visuospatial processing, memory, reasoning and verbal fluency. Except for one task of visual organization, the results showed little change in performance, suggesting that prolonged exposure to high levels of GC can cause long-lasting deleterious effects on cognitive function. The data suggest that correction of hypercortisolism is not necessarily correlated with short-term improvement in cognitive function.

Brain metabolic alterations in Cushing's syndrome as monitored by proton magnetic resonance spectroscopy

Proton magnetic resonance spectroscopy ((1)H MRS) was used to evaluate changes in cerebral metabolites in 13 patients with Cushing's syndrome (including seven with pituitary corticotroph adenomas and six with primary adrenal disease) as compared to 40 normal subjects. Data were recorded in the frontal, thalamic and temporal areas; quantification of the MRS signals demonstrated a statistically significant decrease of the Cho/Cr ratio in the frontal and thalamic areas but not in the temporal area for patients with Cushing's syndrome. The largest decrease in Cho/Cr was measured in the thalamic area of patients with a Cushing's syndrome secondary to an adrenal disease. No statistically significant changes in the NAA/Cr ratio were measured in any of the areas studied. These results suggest that the quantification of choline levels could be helpful for monitoring the cerebral metabolite alterations in patients with hypercortisolism.

Memory improvement following induced hyperinsulinemia in Alzheimer's disease

Dementia of the Alzheimer type (DAT) is accompanied by disruption in glucose regulation and utilization that may contribute to its characteristic memory impairment. Increasing glucose availability by raising plasma glucose improves memory in patients with DAT. Such memory improvement is associated with a secondary elevation in plasma insulin levels, raising the question of whether improvement is due to changes in insulin levels, independent of hyperglycemia. Distributions of insulin receptors in the hippocampus and insulin-mediated increases in glucose utilization in entorhinal cortex provide potential mechanisms for such improvement. We show that raising plasma insulin through intravenous infusion while keeping plasma glucose at a fasting baseline level produces striking memory enhancement for patients with DAT. Previous findings of hyperglycemic memory enhancement were also replicated. Patients with DAT also showed abnormal plasma levels of glucoregulatory hormones and metabolites at baseline and during metabolic manipulations. Our findings suggest that neuroendocrine factors play an important role in the pathophysiology of DAT.

The effects of olfactory bulbectomy and chronic psychosocial stress on serum glucocorticoids and sexual behavior in female rats

The effects of olfactory bulb removal (OBX) and chronic psychosocial stress on serum glucocorticoids and sexual behavior were assessed in female rats primed with a subthreshold level of estradiol (E2). Ovariectomized females underwent either OBX or sham surgery. Half of the OBX and half of the sham animals were exposed to chronic psychosocial stress (crowding, strobe light, and intermittent noise) for one-half h per day for 27 days. On day 22, three blood samples were collected from each animal for serum corticosterone analysis; 1) before, 2) during, and 3) after acute stress (one-half h restraint). On day 28, females were exposed to either 4 or 24 h of E2. On day 29, all females received 500 micrograms progesterone (P) 4 h prior to sexual behavior testing. Sexual receptivity was measured using the lordosis quotient (LQ = [number of lordotic responses/10 mounts] x 100). Sexual proceptivity (dart and ear wiggling sequences) and rejection (number of nonlordotic responses to mount attempts) were measured throughout a 10-min test period. Results showed that chronic psychosocial stress dramatically increased sexual receptivity and proceptivity while decreasing sexual rejection in female rats primed with a subthreshold level of E2. Chronic psychosocial stress also elevated serum glucocorticoids and significantly exacerbated the glucocorticoid response to acute stress. OBX, while increasing sexual receptivity and decreasing sexual rejection, had no effect on serum glucocorticoids. These findings support the hypothesis that OBX potentiates female sexual behavior directly through an increase in neural sensitivity to E2. In contrast, the enhancing effect of chronic psychosocial stress on female sexual behavior may result from alterations of the hypothalamo-pituitary-adrenal system.