P. G. Unschuld

Polymorphisms in the FKBP5 gene region modulate recovery from psychosocial stress in healthy controls

Mood and anxiety disorders are considered stress‐related diseases characterized by an impaired function of mineralocorticoid and glucocorticoid receptors (MR and GR, respectively), the major regulatory elements of the hypothalamus–pituitary–adrenocortical (HPA) axis. A number of so‐called chaperone proteins moderate the function of these receptors. Genetic variations in one of these chaperones, FKBP5, were associated with antidepressant treatment response in depression and with a major risk‐factor for the development of posttraumatic stress disorder. To further investigate the effect of FKPB5 polymorphisms on corticosteroid receptor‐mediated HPA axis regulation we conducted the Trier Social Stress test, a standardized procedure to evaluate psychosocial stress response, in 64 healthy volunteers. We genotyped rs4713916, rs1360780 and rs3800737, the three single nucleotide polymorphisms (SNPs) in the FKBP5 region which had shown the strongest effect in previous studies. In addition, we evaluated the effects of the GR polymorphisms Bcl1 and N363S as well as the MR polymorphism I180V. Subjects homozygous for any of the FKBP5 variants displayed an incomplete normalization of the stress‐elicited cortisol secretion. This was also observed following a second test additionally accompanied by an increased self‐reported anxiety. Regarding GR and MR, only carriers of the Bcl1 variant displayed an altered cortisol response in the prognosticated direction. While Bcl1 was predominantly associated with anticipatory cortisol, homozygous carriers of the FKBP5 minor allele showed insufficient cortisol recovery and increased self‐reported anxiety after psychosocial stress. This reaction pattern suggests that subjects carrying these variants are at risk of displaying chronically elevated cortisol levels after repeated stress constituting a risk factor for stress‐related diseases.

Overweight and Obesity Affect Treatment Response in Major Depression

BACKGROUND Epidemiologic and clinical studies suggest comorbidity between major depressive disorder (MDD) and obesity. To elucidate the impact of weight on the course of depression beyond comorbidity, we investigated psychopathology, attention, neuroendocrinology, weight change, and treatment response in MDD patients, depending on their weight. METHODS Four hundred eight inpatients with MDD participated in the Munich Antidepressant Response Signature Study, designed to discover biomarkers and genotypes that are predictive for clinical outcome. Psychopathology and anthropometric parameters were monitored weekly in 230 patients. In subsamples, combined dexamethasone-corticotropin-releasing hormone and attention tests were conducted at admission and discharge. One thousand twenty-nine diagnosed matched controls served for morphometric comparisons. RESULTS Patients with MDD had a significantly higher body mass index (BMI) compared with healthy controls. Patients with high BMI (> or =25) showed a significantly slower clinical response, less improvement in neuroendocrinology and attention, and less weight gain than did patients with normal BMI (18.5 < or = BMI < 25) during antidepressant treatment. CONCLUSIONS Our findings suggest that overweight and obesity characterize a subgroup of MDD patients with unfavorable treatment outcome.

TMEM132D, a new candidate for anxiety phenotypes: evidence from human and mouse studies

The lifetime prevalence of panic disorder (PD) is up to 4% worldwide and there is substantial evidence that genetic factors contribute to the development of PD. Single-nucleotide polymorphisms (SNPs) in TMEM132D, identified in a whole-genome association study (GWAS), were found to be associated with PD in three independent samples, with a two-SNP haplotype associated in each of three samples in the same direction, and with a P-value of 1.2e−7 in the combined sample (909 cases and 915 controls). Independent SNPs in this gene were also associated with the severity of anxiety symptoms in patients affected by PD or panic attacks as well as in patients suffering from unipolar depression. Risk genotypes for PD were associated with higher TMEM132D mRNA expression levels in the frontal cortex. In parallel, using a mouse model of extremes in trait anxiety, we could further show that anxiety-related behavior was positively correlated with Tmem132d mRNA expression in the anterior cingulate cortex, central to the processing of anxiety/fear-related stimuli, and that in this animal model a Tmem132d SNP is associated with anxiety-related behavior in an F2 panel. TMEM132D may thus be an important new candidate gene for PD as well as more generally for anxiety-related behavior.

Combined Effects of Exonic Polymorphisms in CRHR1 and AVPR1B Genes in a Case/Control Study for Panic Disorder

Accumulating evidence from animal studies suggests that the corticotropin releasing hormone (CRH) and arginine vasopressin (AVP) neuropeptide systems, contribute to anxiety behavior. To investigate whether polymorphisms in the genes regulating these two systems may alter susceptibility to anxiety disorders in humans, we genotyped 71 single nucleotide polymorphisms (SNPs) in CRH, CRHR1, CRHR2, AVP, AVPR1A, AVPR1B in a German sample from Munich with patients suffering from panic disorder and matched healthy controls (n = 186/n = 299). Significant associations were then replicated in a second German sample with 173 patients with panic disorder and 495 controls. In both samples separately and the combined sample, SNPs within CHRH1 and AVPR1B were nominally associated with panic disorder. We then tested two locus multiplicative and interaction effects of polymorphisms of these two genes on panic disorder. Fifteen SNP pairs showed significant multiplicative effects in both samples. The SNP pair with the most significant association in the combined sample (P = 0.00057), which withstood correction for multiple testing, was rs878886 in CRHR1 and rs28632197 in AVPR1B. Both SNPs are of potential functional relevance as rs878886 is located in the 3′ untranslated region of the CRHR1 and rs28632197 leads to an arginine to histidine amino acid exchange at position 364 of AVPR1B which is located in the intracellular C‐terminal domain of the receptor. These data suggest that polymorphisms in the AVPR1B and the CRHR1 genes alter the susceptibility to panic disorder.

Regulation of the hypothalamic-pituitary-adrenocortical system in patients with panic disorder

Anxiety and depressive disorders are among the most common psychiatric disorders with a high number of hospital admissions and a lifetime prevalence of up to 25%. So far, the pathophysiological mechanisms for anxiety disorders remain to be found. Preclinical studies suggest that changes in hypothalamic–pituitary–adrenocortical (HPA) system function are causally related to the expression of anxiety-related behavior. The findings on HPA system function in patients with anxiety disorders are, however, heterogeneous. Both hypo- and hyperresponsiveness of HPA response in various anxiety disorders under different experimental conditions were found. In order to characterize putative case/control differences in HPA system function, we performed a Dex-CRH test, a widely used test to pick up changes in HPA system regulation with high sensitivity, in 30 patients with panic disorder, 35 patients with major depressive episode and in 30 controls individually matched for ethnicity, age and gender. The results indicate a similar dysregulation of the HPA system response in the Dex-CRH test in both patient groups. This finding further underlines the hypothesis that both, depression and panic disorder, share impaired HPA system regulation, supporting the notion that the impairment is involved in the pathophysiology of these clinical conditions. However, differences in the suppression effects and psychopathological correlation patterns between depressed and panic patients suggest different biological mechanisms of HPA system dysregulation in both disorders.

Polymorphisms in the serotonin receptor gene HTR2A are associated with quantitative traits in panic disorder

Anxiety disorders and specifically panic disorder (PD) are caused by complex interactions of environmental and genetic factors. The latter comprise many different genes, from which those involved in serotonergic neurotransmission have received particular attention. Here we report the results from an association candidate‐gene approach, where we analyzed 15 single nucleotide polymorphisms (SNPs) within the gene coding for the serotonin‐receptor 2A (HTR2A) in patients suffering from PD and a control sample. We found that the SNP rs2296972 shows an association between the number of T‐alleles and severity of symptoms in PD. By performing tests according to the Fisher product method (FPM), an association between HTR2A and the personality trait reward dependence could be shown. Most pronounced effects were observable for the SNPs rs2770304, rs6313, and rs6311. Furthermore, the polymorphisms rs3742278, rs2296972, and rs2770292 form a haplotype, which may be associated with higher susceptibility for PD. These results further underline a possible important role of genetic variations within the system controlling serotonergic neurotransmission for the development and course of disease in PD.

Prefrontal Brain Network Connectivity Indicates Degree of Both Schizophrenia Risk and Cognitive Dysfunction

OBJECTIVE Cognitive dysfunction is a core feature of schizophrenia, and persons at risk for schizophrenia may show subtle deficits in attention and working memory. In this study, we investigated the relationship between integrity of functional brain networks and performance in attention and working memory tasks as well as schizophrenia risk. METHODS A total of 235 adults representing 3 levels of risk (102 outpatients with schizophrenia, 70 unaffected first-degree relatives of persons with schizophrenia, and 63 unrelated healthy controls [HCs]) completed resting-state functional magnetic resonance imaging and a battery of attention and working memory tasks (Brief Test of Attention, Hopkins Verbal Learning Test, and Brief Visuospatial Memory Test) on the same day. Functional networks were defined based on coupling with seeds in the dorsal anterior cingulate cortex, dorsolateral prefrontal cortex (DLPFC), medial prefrontal cortex (MPFC), and primary visual cortex. Networks were then dissected into regional clusters of connectivity that were used to generate individual interaction matrices representing functional connectivity within each network. RESULTS Both patients with schizophrenia and their first-degree relatives showed cognitive dysfunction compared with HCs. First canonicals indicated an inverse relationship between cognitive performance and connectivity within the DLPFC and MPFC networks. Multivariate analysis of variance revealed multivariate main effects of higher schizophrenia risk status on increased connectivity within the DLPFC and MPFC networks. CONCLUSIONS These data suggest that excessive connectivity within brain networks coupled to the DLPFC and MPFC, respectively, accompany cognitive deficits in persons at risk for schizophrenia. This might reflect compensatory reactions in neural systems required for cognitive processing of attention and working memory tasks to brain changes associated with schizophrenia.

The GABA transporter 1 (SLC6A1): a novel candidate gene for anxiety disorders

Recent evidence suggests that the GABA transporter 1 (GAT-1; SLC6A1) plays a role in the pathophysiology and treatment of anxiety disorders. In order to understand the impact of genetic variation within SLC6A1 on pathological anxiety, we performed a case–control association study with anxiety disorder patients with and without syndromal panic attacks. Using the method of sequential addition of cases, we found that polymorphisms in the 5′ flanking region of SLC6A1 are highly associated with anxiety disorders when considering the severity of syndromal panic attacks as phenotype covariate. Analysing the effect size of the association, we observed a constant increase in the odds ratio for disease susceptibility with an increase in panic severity (OR ~ 2.5 in severely affected patients). Nominally significant association effects were observed considering the entire patient sample. These data indicate a high load of genetic variance within SLC6A1 on pathological anxiety and highlight GAT-1 as a promising target for treatment of anxiety disorders with panic symptoms.

Gender-Specific Association of Galanin Polymorphisms with HPA-Axis Dysregulation, Symptom Severity, and Antidepressant Treatment Response

Galanin (GAL) is an estrogen-inducible neuropeptide, highly expressed in brain regions reported to be involved in regulation of mood and anxiety. GAL possibly has a direct modulatory effect on hypothalamic–pituitary–adrenal (HPA)-axis regulation. Recent data from pharmacological and genetic studies indicate a significant function of GAL in stress-related disorders. By using a tag SNP approach covering the locus encoding preprogalanin (PPGAL), earlier findings of female-specific associations of polymorphisms in this locus with panic disorder were expanded to a larger sample of 268 outpatients with anxiety disorders (ADs). Within a larger sample of 541 inpatients with major depressive disorder (MDD), we then tested associations of one PPGAL tag SNP with specific depression symptom clusters and HPA-axis activity assessed by the combined dexamethasone-suppression/CRH-stimulation test both at inpatient admission and discharge (n=298). Gender specificity as well as dependence of the association on levels of circulating estrogens was analyzed. Genotyping revealed high linkage disequilibrium in the promoter area of the PPGAL gene, which includes several estrogen-response elements. Confirming earlier results, rs948854, tagging this promoter region, was associated with more severe anxiety pathology in female AD patients, but not in males. In premenopausal female MDD patients, the same allele of rs948854 was associated with more severe vegetative but not cognitive depressive symptoms at discharge and worse treatment response on antidepressant medication. Furthermore, this allele was associated with higher HPA-axis activity at admission. No significant case–control associations could be observed. However, because of power limitations of both patient samples, small effects cannot be excluded. The reported associations in independent samples of AD and MDD support an estrogen-dependent function of GAL in pathophysiology of anxiety and depression, affecting response to antidepressant treatment.

Polymorphisms in the GAD2 gene-region are associated with susceptibility for unipolar depression and with a risk factor for anxiety disorders†

Glutamate decarboxylase (GAD) is the rate limiting enzyme for conversion of glutamic acid to gamma‐aminobutyric acid (GABA). The GAD 65 kDa isoform is encoded by the gene GAD2 and is mainly expressed in synaptic terminals. It serves as an apoenzyme, which shows enhanced availability in situations of stress, responding to short‐term demands for GABA. We analyzed 18 single nucleotide polymorphisms (SNPs) in the GAD2‐gene region for associations with psychiatric diagnosis and behavioral inhibition (BI) derived from the personality traits neuroticism and extraversion as defined by the Eysenck Personality Questionaire (EPQ). A total of 268 patients with anxiety disorder (AD), 541 with unipolar depression (MD), and 541 healthy controls were included. We observe associations for five tag‐SNPs with BI in the AD‐ and control samples as well as two additional case–control associations in the MD‐sample. The associated SNPs lie within a 16KB linkage disequilibrium‐block, including putative 5′ GAD2‐promoter‐elements as well as the 3′ end of the gene MYO3A. Using open access mRNA‐expression data, we could show that BI‐associated SNPs appear to be associated with differences in MYO3A‐ but not GAD2 lymphoblastoid‐mRNA expression levels. These results support earlier studies that suggest associations of polymorphisms within the GAD2 locus with anxiety and affective disorders. However, data from expression studies imply that these polymorphisms could tag functional effects on the neighboring gene MYO3A, which is also expressed in the brain, including the cingulate cortex and the amygdala.