Association study of the adrenergic receptors and childhood-onset mood disorders in Hungarian families

Association Study of the Beta-Adrenergic Receptor Genetic Variant Gly389Arg and Fluoxetine Response in Major Depression

Background

Pharmacogenetics has proven role in the treatment of different illnesses. Patients with special genotypes may achieve a better response to a specific drug. On the other hand, genetic parameters markedly contribute to the development of major depressive disorder (MDD). The significance of adrenergic system compartments in cognition and behavior, and their role in etiology of depression denote that adrenergic receptors beta gene polymorphism(s) might also have an association with drug response. Thus this study aims to evaluate the association between β1AR gene polymorphisms, G1165C, Arg389Gly and response to fluoxetine in MDD patients.

Materials and Methods

Among different antidepressants, we focused on fluoxetine as it is prescribed frequently in MDD and belongs to one of the most efficient antidepressant categories with minimum side effects. MDD was diagnosed at study entry using DSM-IV criteria. One hundred and one new MDD patients were treated with fluoxetine for a period of 6 weeks. A 50% decrease in Hamilton Rating Scale for Depression (HRSD) was considered as response to treatment. Genotyping of G1165C polymorphism was performed by PCR-RFLP method.

Results

Results of the study indicated no significant relationship between β1AR polymorphism and the patient's response to fluoxetine neither at genotypic nor allelic level (P=0.568).

Conclusion

Our study did not support the hypothesis of involvement of β1AR Arg389Gly polymorphism and response to fluoxetine in MDD patients.

Preliminary investigation of peripheral extracellular vesicles' microRNAs in bipolar disorder

BACKGROUND

The search for biomarkers of bipolar disorder (BD), including epigenetic alterations, has heavily relied on peripheral investigations that do not necessarily reflect brain-specific mechanisms. In this study we aimed to assess peripheral extracellular vesicles (EVs)' microRNAs and determine their use as a novel source of biomarkers in BD.

METHODS

We assessed peripheral blood EVs' microRNAs from 20 patients with BD type I and 21 age- and sex-matched healthy controls by microarray, and further explored the predicted biological functions of significantly differentially expressed microRNAs.

RESULTS

Our results identified 33 nominally significant microRNAs (p < 0.05 and fold-change >1.5) altered in BD patients, including miRNAs previously reported to be altered in post-mortem tissues of patients. Pathway analyses identified some brain-relevant mechanisms enriched in these miRNAs, including axon guidance by netrin and the serotonin receptor pathway.

LIMITATIONS

Relatively small sample size, potential confounding effects of mood states, medication use, and comorbidities, analysis of total rather than brain-specific EVs, and lack of validation of significant miRNAs by other methods.

CONCLUSIONS

This study provides important preliminary evidence of the potential use of EVs as a novel source of biomarkers in BD. Overall, our findings of brain-relevant mechanisms in these vesicles suggest their potential use in living patients as a peripheral window to the brain.

Positive autobiographical memory deficits in youth with depression histories and their never-depressed siblings

OBJECTIVES

Impaired positive autobiographical memory (AM) is closely linked to emotional disorders. AM impairments are often found in depressed adults and may be related to the difficulties such persons have in regulating their dysphoric mood. By contrast, less is known about AM disturbances among adolescents, or about the functional relationship of AM disturbances to early-onset depression.

DESIGN

A high-risk family design served to compare four groups of youth who differed in depression histories and familial depression risk.

METHODS

Thirty-one currently depressed probands, 185 remitted probands, 204 never-depressed siblings of probands, and 180 healthy control youth were induced into a negative mood prior to recalling positive AMs via a novel memory elicitation procedure. Several positive AM characteristics were assessed.

RESULTS

Relative to control youth, unaffected siblings and probands exhibited consistently impaired positive AMs. Moreover, we also found some evidence that probands were more impaired than siblings, who were in turn more impaired than controls, consistent with a gradient effect.

CONCLUSIONS

Positive AM disturbances may not only precede the onset of depression in vulnerable youth, but also continue to persist after remission of a depressive episode. Clinical and basic research implications of the findings are discussed.

PRACTITIONER POINTS

Positive AM impairments may be trait-like, persist in the euthymic phase of depression, and may serve as a risk marker for early-onset depression among vulnerable adolescents. Disturbances in positive AM may negatively impact the mood-regulatory functions of positive memory recall and contribute to persistent sadness and anhedonia, which are core features of depression. Our sample of currently depressed youth was relatively small, tempering our conclusions. Although we collected data on some important covariates (e.g., socioeconomic status), we lacked information on other relevant variables such as youths' executive functioning or IQ.

Preliminary evidence for a role of the adrenergic nervous system in generalized anxiety disorder

Generalized anxiety disorder (GAD) is a common chronic condition that is understudied compared to other psychiatric disorders. An altered adrenergic function has been reported in GAD, however direct evidence for genetic susceptibility is missing. This study evaluated the associations of gene variants in adrenergic receptors (ADRs) with GAD, with the involvement of stressful events. Data were obtained from 844 French community-dwelling elderly aged 65 or over. Anxiety disorders were assessed using the Mini-International Neuropsychiatry Interview, according to DSM-IV criteria. Eight single-nucleotide polymorphisms (SNPs) involved with adrenergic function were genotyped; adrenergic receptors alpha(1A) (ADRA1A), alpha(2A) (ADRA2A), and beta2 (ADRB2) and transcription factor TCF7L2. Questionnaires evaluated recent stressful life events as well as early environment during childhood and adolescence. Using multivariate logistic regression analyses four SNPs were significantly associated with GAD. A 4-fold modified risk was found with ADRA1A rs17426222 and rs573514, and ADRB2 rs1042713 which remained significant after Bonferroni correction. Certain variants may moderate the effect of adverse life events on the risk of GAD. Replication in larger samples is needed due to the small case number. This is the first study showing that ADR variants are susceptibility factors for GAD, further highlighting the critical role of the adrenergic nervous system in this disorder.

Positive Affectivity is Dampened in Youths with Histories of Major Depression and Their Never-Depressed Adolescent Siblings

While hedonic capacity is diminished during clinical depression, it is unclear whether that deficit constitutes a risk factor and/or persists after depression episodes remit. To examine these issues, adolescents with current/past major depression (probands; n=218), never depressed biological siblings of probands (n=207), and emotionally-well controls (n=183) were exposed to several positively valenced probes. Across baseline and hedonic probe conditions, controls consistently reported higher levels of positive affect than high-risk siblings, and siblings reported higher levels of positive affect than probands (remitted and depressed probands' reports were similar). Extent of positive affect across the protocol predicted adolescents' self-reports of social support network and parental reports of offspring's use of various adaptive mood repair responses in daily life. Attenuated hedonic responding among youths remitted from depression offers partial support for anhedonia as a trait, while its presence among never depressed high-risk siblings argues for anhedonia as a potential diathesis for clinical depression.

Alpha2C-adrenoceptor Del322-325 polymorphism and risk of psychiatric disorders: significant association with opiate abuse and dependence

Objectives α2C-adrenoceptors (α2C-AR) are involved in behavioural responses relevant to psychiatric disorders and suicide completion. The genetic polymorphism α2CDel322-325-AR confers a loss-of-function phenotype. Functional human studies have associated α2CDel322-325-AR polymorphism with major depression pathophysiology. The aim of this study was to analyse, for the first time, the association of α2CDel322-325-AR polymorphism with suicide completion and with related psychiatric disorders: major depression, schizophrenia, opiate and alcohol abuse and dependence. Methods Post-mortem brain DNA was extracted (n = 516) and genotyping performed by HaeIII restriction endonuclease digestion of PCR products and DNA fragment analysis on capillary sequencer. Amplified products were sequenced to confirm the presence of the polymorphism. Results The frequency of α2CDel322-325-AR in suicide (9%, n = 236) and non-suicide victims (11%, n = 280) was similar. Genotype frequencies for the α2CDel322-325-AR polymorphism in depressed (15%, n = 39) and schizophrenic subjects (18%, n = 39) were higher than in controls (7%, n = 187), but these differences did not reach statistical significance (P = 0.125 and P = 0.063, respectively). A selective and significant association of α2CDel322-325-AR polymorphism with opiate abuse and dependence was found (23%, n = 35, P = 0.011). Conclusions Our results indicate that α2CDel322-325-AR may play a role in the pathophysiology of opiate abuse and dependence and raise the interest for larger genetic associative studies.

The current state of play on the molecular genetics of depression

BACKGROUND

It has been well established that both genes and non-shared environment contribute substantially to the underlying aetiology of major depressive disorder (MDD). A comprehensive overview of genetic research in MDD is presented. Method Papers were retrieved from PubMed up to December 2011, using many keywords including: depression, major depressive disorder, genetics, rare variants, gene-environment, whole genome, epigenetics, and specific candidate genes and variants. These were combined in a variety of permutations.

RESULTS

Linkage studies have yielded some promising chromosomal regions in MDD. However, there is a continued lack of consistency in association studies, in both candidate gene and genome-wide association studies (GWAS). Numerous factors may account for variable results including the use of different diagnostic approaches, small samples in early studies, population stratification, epigenetic phenomena, copy number variation (CNV), rare variation, and phenotypic and allelic heterogeneity. The conflicting results are also probably, in part, a consequence of environmental factors not being considered or controlled for.

CONCLUSIONS

Each research group has to identify what issues their sample may best address. We suggest that, where possible, more emphasis should be placed on the environment in molecular behavioural genetics to identify individuals at environmental high risk in addition to genetic high risk. Sequencing should be used to identify rare and alternative variation that may act as a risk factor, and a systems biology approach including gene-gene interactions and pathway analyses would be advantageous. GWAS may require even larger samples with reliably defined (sub)phenotypes.

No evidence of an association between two genes, EDN1 and ACE, and childhood-onset mood disorders

Recent evidence supports a pathological link between heart disease and depressive symptoms, suggesting that depression is both etiologic and prognostic to heart disease. Thus, biological molecules which are at the interface between heart and mind are plausible candidate genes for depressive disorders. To investigate this line of enquiry we have investigated two genes, Endothelin 1 (EDN1) and Angiotensin-converting enzyme (ACE) in a family-based sample with childhood-onset mood disorders (COMDs). EDN1 is highly expressed in endothelium where it acts as a potent vasoconstrictor, and is also expressed in the brain where it exhibits neurotransmitter characteristics. ACE acts as a potent vasopressor, and interacts with the hypothalamic-pituitary-adrenocortical (HPA) system, which is often dysregulated in mood disorders. Furthermore, ACE has recently been found to be associated with major depression. Polymorphisms were selected to best capture the genetic variation at the two loci, and to replicate previous associations. The markers were genotyped across EDN1 and ACE in a sample comprised of 382 Hungarian nuclear families ascertained through affected probands diagnosed with a mood disorders before the age of 15. We found no evidence of association between either of these genes and COMD. Consequently, we were unable to support our hypothesis that these two genes, which are involved in both vascular and brain functions are contributing to the susceptibility to mood disorders of children/adolescents.

Further genetic evidence implicates the vasopressin system in childhood-onset mood disorders

Studies in both animals and humans advocate a role for the vasopressin (AVP) system in the aetiology of depressive symptoms. Attention has particularly focused on the role of AVP in the overactivation of the hypothalamic-pituitary-adrenal (HPA)-axis in mood disorders. Elevated AVP plasma levels have been found in mood disorder patients, which are often positively correlated with the severity of symptoms. We recently reported an association between childhood-onset mood disorders (COMD) and polymorphisms in the receptor responsible for the AVP-mediated activation of the HPA-axis (AVPR1B). As genetic variation in the vasopressinergic system could provide a mechanism to explain the endocrine alterations observed in mood disorders, we investigated other genes in this system. The gene encoding AVP is the strongest candidate, particularly as genetic variation in this gene in rodents is associated with anxiety-related behaviours. Six single-nucleotide polymorphisms (SNPs) were genotyped across the AVP gene in a sample comprised of 586 Hungarian nuclear families ascertained through affected probands with a diagnosis of COMD. In addition, AVP coding and putative regulatory regions were screened for mutations using denaturing high-performance liquid chromatography. One SNP, 3' to the AVP, gene reached significance (P = 0.03), as did the overtransmission of a five-marker haplotype with a frequency of 22% (P = 0.0001). The subsequent mutation screen failed to identify any putative functional polymorphisms. The outcome of this study, combined with our previous association between COMD and AVPR1B, implicates genetic variation in vasopressinergic genes in mediating vulnerability to COMD.

Genome scan in sibling pairs with juvenile-onset mood disorders: Evidence for linkage to 13q and Xq

Mood disorders (bipolar and depressive disorders) in children and adolescents are associated with significant morbidity and mortality. Twin and family studies, for the most part, indicate higher familiality and heritability for mood disorders that onset in childhood/adolescence than those that onset in adulthood. To identify the genetic contribution to mood disorders that onset in childhood/adolescence, we performed a genome scan on 146 nuclear families from Hungary containing an affected proband and affected siblings. In total, the pedigrees contained 303 affected children: 146 probands, 137 siblings with a first episode of mood disorder before 14.9 years of age, and 20 siblings with onset of their first episode after 14.9 years of age but before the age of 18. The results of the genome scan using 405 microsatellite markers did not provide evidence for linkage at the recommended genome wide significance level for any novel loci. However, markers on two chromosomes, 13q and Xq, provided evidence for linkage in regions previously identified as linked to bipolar disorder in multiple studies. For the marker on chromosome 13q the peak non-parametric multipoint LOD score was at the marker D13S779 (LOD = 1.5, P = 0.004). On chromosome Xq, evidence for linkage was observed across a large region spanning two regions previously linked to bipolar disorder; Xq24 to Xq28, with a peak at marker TTTA062 (LOD 2.10, P = 0.0009) in Xq28. Results for these regions exceed the recommended P-value for a replication study of P < 0.01 and thus provide evidence for these two loci as contributing to mood disorders with juvenile onset.

GPR50 is not associated with childhood-onset mood disorders in a large sample of Hungarian families

We investigated the relationship of the gene for the X-linked orphan G protein-coupled receptor (GPR50) to childhood-onset mood disorders in a sample of 384 families with 468 affected children and adolescents collected in Hungary. Our choice of this gene for study was based on a previous report of an association of GPR50 with bipolar disorder and major depressive disorder. A significant association with the deletion allele of an insertion/deletion polymorphism (Delta502-505) located in exon 2 had been reported in a sample of 226 patients with major depressive disorder and 264 patients with bipolar disorder. The association was more significant in females compared with males in those samples. We used for this study a polymorphism in complete linkage disequilibrium with the Delta502-505 polymorphism, Thr532Ala (rs561077), and two additional polymorphisms, Val606Ile (rs13440581) and an intronic polymorphism (rs2072621). We found no evidence for an association for the markers analyzed individually, nor for haplotypes of these markers. Further, we found no evidence of association when the results were analyzed in girls only (n=215). We, therefore, failed to replicate the previous association of this gene with mood disorders.