Lack of linkage between the corticotropin-releasing hormone (CRH) gene and bipolar affective disorder

Integrative Analysis of DiseaseLand Omics Database for Disease Signatures and Treatments: A Bipolar Case Study

Transcriptomics technologies such as next-generation sequencing and microarray platforms provide exciting opportunities for improving diagnosis and treatment of complex diseases. Transcriptomics studies often share similar hypotheses, but are carried out on different platforms, in different conditions, and with different analysis approaches. These factors, in addition to small sample sizes, can result in a lack of reproducibility. A clear understanding and unified picture of many complex diseases are still elusive, highlighting an urgent need to effectively integrate multiple transcriptomic studies for disease signatures. We have integrated more than 3,000 high-quality transcriptomic datasets in oncology, immunology, neuroscience, cardiovascular and metabolic disease, and from both public and internal sources (DiseaseLand database). We established a systematic data integration and meta-analysis approach, which can be applied in multiple disease areas to create a unified picture of the disease signature and prioritize drug targets, pathways, and compounds. In this bipolar case study, we provided an illustrative example using our approach to combine a total of 30 genome-wide gene expression studies using postmortem human brain samples. First, the studies were integrated by extracting raw FASTQ or CEL files, then undergoing the same procedures for preprocessing, normalization, and statistical inference. Second, both p-value and effect size based meta-analysis algorithms were used to identify a total of 204 differentially expressed (DE) genes (FDR < 0.05) genes in the prefrontal cortex. Among these were BDNF, VGF, WFS1, DUSP6, CRHBP, MAOA, and RELN, which have previously been implicated in bipolar disorder. Finally, pathway enrichment analysis revealed a role for GPCR, MAPK, immune, and Reelin pathways. Compound profiling analysis revealed MAPK and other inhibitors may modulate the DE genes. The ability to robustly combine and synthesize the information from multiple studies enables a more powerful understanding of this complex disease.

Genetic influences on hormonal markers of chronic hypothalamic-pituitary-adrenal function in human hair

BACKGROUND

Cortisol is the primary output of the hypothalamic-pituitary-adrenal (HPA) axis and is central to the biological stress response, with wide-ranging effects on psychiatric health. Despite well-studied biological pathways of glucocorticoid function, little attention has been paid to the role of genetic variation. Conventional salivary, urinary and serum measures are strongly influenced by diurnal variation and transient reactivity. Recently developed technology can be used to measure cortisol accumulation over several months in hair, thus indexing chronic HPA function.

METHOD

In a socio-economically diverse sample of 1070 twins/multiples (ages 7.80-19.47 years) from the Texas Twin Project, we estimated effects of sex, age and socio-economic status (SES) on hair concentrations of cortisol and its inactive metabolite, cortisone, along with their interactions with genetic and environmental factors. This is the first genetic study of hair neuroendocrine concentrations and the largest twin study of neuroendocrine concentrations in any tissue type.

RESULTS

Glucocorticoid concentrations increased with age for females, but not males. Genetic factors accounted for approximately half of the variation in cortisol and cortisone. Shared environmental effects dissipated over adolescence. Higher SES was related to shallower increases in cortisol with age. SES was unrelated to cortisone, and did not significantly moderate genetic effects on either cortisol or cortisone.

CONCLUSIONS

Genetic factors account for sizable proportions of glucocorticoid variation across the entire age range examined, whereas shared environmental influences are modest, and only apparent at earlier ages. Chronic glucocorticoid output appears to be more consistently related to biological sex, age and genotype than to experiential factors that cluster within nuclear families.

The HPA axis in bipolar disorder: Systematic review and meta-analysis

OBJECTIVES

To provide a quantitative and qualitative synthesis of the available evidence on the role of Hypothalamic-Pituitary-Adrenal (HPA) axis in the pathophysiology of Bipolar Disorder (BD).

METHODS

Meta-analysis and meta-regression of case-control studies examining the levels of cortisol, ACTH, CRH levels. Systematic review of stress reactivity, genetic, molecular and neuroimaging studies related to HPA axis activity in BD.

RESULTS

Forty-one studies were included in the meta-analyses. BD was associated with significantly increased levels of cortisol (basal and post-dexamethasone) and ACTH, but not of CRH. In the meta-regression, case-control differences in cortisol levels were positively associated with the manic phase (p=0.005) and participants' age (p=0.08), and negatively with antipsychotics use (p=0.001). Reviewed studies suggest that BD is associated with abnormalities of stress-related molecular pathways in several brain areas. Variants of HPA axis-related genes seem not associated with a direct risk of developing BD, but with different clinical presentations. Also, studies on unaffected relatives suggest that HPA axis dysregulation is not an endophenotype of BD, but seems related to environmental risk factors, such as childhood trauma. Progressive HPA axis dysfunction is a putative mechanism that might underlie the clinical and cognitive deterioration of patients with BD.

CONCLUSIONS

BD is associated with dysfunction of HPA axis activity, with important pathophysiological implications. Targeting HPA axis dysfunctions might be a novel strategy to improve the outcomes of BD.

SRD5A2 is associated with increased cortisol metabolism in schizophrenia spectrum disorders

OBJECTIVE

Dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis is documented in bipolar disorder and schizophrenia, but the mechanism is unclear; recently, increased activity of cortisol metabolizing enzymes was indicated in these disorders. We investigated whether five genes involved in cortisol metabolism were associated with altered activity of cortisol metabolizing enzymes in bipolar disorder (BD) and schizophrenia spectrum disorders (SCZ).

METHODS

A case-control sample of subjects with BD (N=213), SCZ (N=274) and healthy controls (N=370) from Oslo, Norway, were included and genotyped from 2003 to 2008. A sub-sample (healthy controls: N=151; SCZ: N=40; BD: N=39) had estimated enzyme activities based on measurements of urinary free cortisol, urinary free cortisone and metabolites. A total of 102 single nucleotide polymorphisms (SNPs) in the SRD5A1, SRD5A2, AKR1D1, HSD11B1 and HSD11B2 genes were genotyped, and significant SNPs analyzed in the sub-sample.

RESULTS

There was a significant association of rs6732223 in SRD5A2 (5α-reductase) with SCZ (p=0.0043, Bonferroni corrected p=0.030, T risk allele). There was a significantly increased 5α-reductase activity associated with rs6732223 (T allele) within the SCZ group (p=0.011).

CONCLUSIONS

The present data suggest an interaction between SCZ and SRD5A2 variants coding for the enzyme 5α-reductase, giving rise to increased 5α-reductase activity in SCZ. The findings may have implications for cortisol metabolizing enzymes as possible drug targets.

The CRF system, stress, depression and anxiety-insights from human genetic studies

A concatenation of findings from preclinical and clinical studies support a preeminent function for the corticotropin-releasing factor (CRF) system in mediating the physiological response to external stressors and in the pathophysiology of anxiety and depression. Recently, human genetic studies have provided considerable support to several long-standing hypotheses of mood and anxiety disorders, including the CRF hypothesis. These data, reviewed in this report, are congruent with the hypothesis that this system is of paramount importance in mediating stress-related psychopathology. More specifically, variants in the gene encoding the CRF(1) receptor interact with adverse environmental factors to predict risk for stress-related psychiatric disorders. In-depth characterization of these variants will likely be important in furthering our understanding of the long-term consequences of adverse experience.

G protein-coupled receptors in major psychiatric disorders

Although the molecular mechanisms underlying psychiatric illnesses such as depression, bipolar disorder and schizophrenia remain incompletely understood, there is increasing clinical, pharmacologic, and genetic evidence that G protein-coupled receptors (GPCRs) play critical roles in these disorders and their treatments. This perspectives paper reviews and synthesizes the available data. Dysfunction of multiple neurotransmitter and neuropeptide GPCRs in frontal cortex and limbic-related regions, such as the hippocampus, hypothalamus and brainstem, likely underlies the complex clinical picture that includes cognitive, perceptual, affective and motoric symptoms. The future development of novel agents targeting GPCR signaling cascades remains an exciting prospect for patients refractory to existing therapeutics.

Association and linkage studies of CRH and PENK genes in bipolar disorder: a collaborative IGSLI study

Corticotropin-releasing hormone (CRH) and proenkephalin (PENK) are hypothalamic peptides involved in the stress response and hypothalamic-pituitary axis regulation. Previous research has implicated these peptides in the pathogenesis of affective disorders. In this study we investigated two polymorphisms located in the genes that code for CRH and PENK by means of association and linkage analyses. A total of 138 bipolar patients and 108 controls were included in the association study. In addition, 24 families were available for linkage analysis, including six families of probands with documented periodic positivity of dexamethasone suppression tests (DST) during remission. We found no association of bipolar disorder with either gene. Similarly, we did not find any evidence of linkage (P = 0.56 for CRH and 0.52 for PENK) in the entire sample or in the subsample of families of DST positive probands. In conclusion, our study does not support the hypothesis that genes coding for CRH or PENK contribute to the genetic susceptibility to bipolar disorder. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:178-181, 2000.

The dexamethasone/corticotropin-releasing hormone test in depression in bipolar and unipolar affective illness

The combined dexamethasone/corticotropin-releasing hormone (DEX/CRH) test was performed in forty patients with depression (12 male, 28 female), aged 20-68 years, in the course of affective illness (16 bipolar, 24 unipolar) both during acute depressive episode and in remission. The results were compared with those of 20 healthy control subjects (10 male, 10 female), aged 22-52 years. During acute depressive episode, cortisol concentration at 16 h after dexamethasone, 1.5 mg, and cortisol release after subsequent infusion of CRH, 100 microg, were significantly elevated in bipolar patients compared with unipolar ones and with control subjects. Patients with multiple episodes of unipolar depression exhibited greater cortisol levels after CRH than control subjects. In remission, significantly higher cortisol concentrations measured at 30 min(-1) h after CRH infusion were found in bipolar than in unipolar patients. Male bipolar patients had significantly higher cortisol level than bipolar females before and at 1.5 h after CRH. First episode unipolar patients during remission had lower levels of cortisol than control subjects before and at 1.5 h after CRH. Correlation between the magnitude of cortisol response and age was found within unipolar depressed patients but not in bipolar ones. On the other hand, correlation of test results with intensity of depression measured by Hamilton scale as well as with insomnia and anxiety subscales was more robust in bipolar subjects than in unipolar ones. It is concluded that the dysregulation of hypothalamic-pituitary-adrenal (HPA) axis activity, detected by DEX/CRH test is significantly more marked in patients with depression in the course of bipolar affective illness than in unipolar depression. Within unipolar depression, this dysregulation may increase with the time course of the illness.