The power of sample size and homogenous sampling: association between the 5-HTTLPR serotonin transporter polymorphism and major depressive disorder

Genetic Landscape of Major Depressive Disorder: Assessment of Potential Diagnostic and Antidepressant Response Markers

BACKGROUND

The clinical heterogeneity in major depressive disorder (MDD), variable treatment response, and conflicting findings limit the ability of genomics toward the discovery of evidence-based diagnosis and treatment regimen. This study attempts to curate all genetic association findings to evaluate potential variants for clinical translation.

METHODS

We systematically reviewed all candidates and genome-wide association studies for both MDD susceptibility and antidepressant response, independently, using MEDLINE, particularly to identify replicated findings. These variants were evaluated for functional consequences using different in silico tools and further estimated their diagnostic predictability by calculating positive predictive values.

RESULTS

A total of 217 significantly associated studies comprising 1200 variants across 545 genes and 128 studies including 921 variants across 412 genes were included with MDD susceptibility and antidepressant response, respectively. Although the majority of associations were confirmed by a single study, we identified 31 and 18 replicated variants (in at least 2 studies) for MDD and antidepressant response. Functional annotation of these 31 variants predicted 20% coding variants as deleterious/damaging and 80.6% variants with regulatory effect. Similarly, the response-related 18 variants revealed 25% coding variant as damaging and 88.2% with substantial regulatory potential. Finally, we could calculate the diagnostic predictability of 19 and 5 variants whose positive predictive values ranges from 0.49 to 0.66 for MDD and 0.36 to 0.66 for response.

CONCLUSIONS

The replicated variants presented in our data are promising for disease diagnosis and improved response outcomes. Although these quantitative assessment measures are solely directive of available observational evidence, robust homogenous validation studies are required to strengthen these variants for molecular diagnostic application.

Tryptophan metabolites in depression: Modulation by gut microbiota

Clinical depression is a multifactorial disorder and one of the leading causes of disability worldwide. The alterations in tryptophan metabolism such as changes in the levels of serotonin, kynurenine, and kynurenine acid have been implicated in the etiology of depression for more than 50 years. In recent years, accumulated evidence has revealed that gut microbial communities, besides being essential players in various aspects of host physiology and brain functioning are also implicated in the etiology of depression, particularly through modulation of tryptophan metabolism. Therefore, the aim of this review is to summarize the evidence of the role of gut bacteria in disturbed tryptophan metabolism in depression. We summed up the effects of microbiota on serotonin, kynurenine, and indole pathway of tryptophan conversion relevant for understanding the pathogenesis of depressive behavior. Moreover, we reviewed data regarding the therapeutic effects of probiotics, particularly through the regulation of tryptophan metabolites. Taken together, these findings can open new possibilities for further improvement of treatments for depression based on the microbiota-mediated modulation of the tryptophan pathway.

Investigation of the Serotonergic Activity and the Serotonin Content in Serum and Platelet, and the Possible Role of the Serotonin Transporter in Patients with Depression

According to the monoamine hypothesis, the development of depression is associated with dysfunctions of the serotonergic system. Alterations in the serotonin transporter gene (5-HTTLPR), the serotonergic activity in the brain, and the content of serotonin (5-HT) have been related to depression and were examined separately by previous studies. This study investigates these parameters in 89 depressed patients and 89 healthy participants. We investigated the serotonergic activity measured by the loudness dependence of auditory evoked potentials (LDAEP). In addition to the examination of the serotonin content (serum and platelet), enzyme-linked immunosorbent assays (ELISA) were used and 5-HTTLPR genotypes were analyzed. We observed a lower serotonin content in patients compared to healthy participants. Further, we noticed a correlation between anxiety and depression-associated symptoms with serotonergic activity. Patients treated with SSRI/SNRI showed decreased contents of serum serotonin compared to patients without any psychotropic medication or other psychotropic medications. Since the serotonergic activity, peripheral serotonin content, and 5-HTTLPR were unrelated, the results suggest independent alterations of central and peripheral serotonergic systems in depression. In line with this finding, serotonergic activity was related to anxiety and depression symptoms. Furthermore, the applied medication seems to influence serum serotonin content in patients with depression.

Nature and nurture? A review of the literature on childhood maltreatment and genetic factors in the pathogenesis of borderline personality disorder

BACKGROUND

Borderline Personality Disorder (BPD) is a psychiatric disorder associated with significant morbidity and mortality. However, the neurobiological alterations underlying the condition remain poorly understood. As a result, existing treatments remain inadequate. One of the main risk factors for the development of BPD is a history of childhood maltreatment. However, it is considered neither causative nor specific to the condition. Current theory is therefore increasingly moving toward a 'Gene x Environment' (GxE) model of the condition. The purpose of the current work was to conduct a systematic literature review, which comprehensively identifies all published molecular level GxE studies that have explored the role of specific genetic loci, in influencing the risk of BPD following exposure to childhood abuse or neglect.

METHODS

Four electronic databases were used to systematically search for molecular level GxE studies of any design, which focused on the development of BPD following exposure to childhood abuse or neglect, without language or date restrictions. Articles were screened independently by two reviewers and results were synthesized narratively.

RESULTS

A total of 473 articles were screened of which sixteen were selected for inclusion in our review. Implicated genes were categorised according to their influence on; Neurotransmitter Systems, Neurodevelopment and Neuroendocrine Systems.

CONCLUSIONS

The identified studies have produced several relevant and statistically significant results. Of particular note, is the repeated finding that genes involved in HPA axis regulation, may be altered by exposure to childhood maltreatment, influencing subsequent susceptibility to BPD. This is both biologically plausible and of potential clinical significance.

Role of Tryptophan in Microbiota-Induced Depressive-Like Behavior: Evidence From Tryptophan Depletion Study

During the past decade, there has been a substantial rise in the knowledge about the effects of gut microbiota on host physiology and behavior, including depressive behavior. Initial studies determined that gut microbiota can regulate host tryptophan levels, which is a main serotonin precursor. A dysfunctional serotonergic system is considered to be one of the main factors contributing to the development of depression. Therefore, we hypothesized that regulation of brain tryptophan and serotonin can explain, at least partly, the effects of microbiota on depressive behavior. To test this hypothesis, we examined depressive-like behavior and brain levels of serotonin and tryptophan, of germ free (GF) and specific-pathogen free (SPF) mice under basal conditions, or after acute tryptophan depletion (ATD) procedure, which is a method to decrease tryptophan and serotonin levels in the brain. In basal conditions, GF mice exhibited less depressive-like behavior in sucrose preference, tail-suspension and forced swim tests, compared to SPF mice. In addition, in mice that were not subjected to ATD, GF mice displayed higher levels of tryptophan, serotonin and 5-hydroxyindoleacetic acid (the main degradation product of serotonin) in medial prefrontal cortex (mPFC) and hippocampus (HIPPO), compared to SPF mice. Interestingly, ATD increased depressive-like behavior of GF, but not of SPF mice. These behavioral changes were accompanied by a stronger reduction of tryptophan, serotonin and 5-hydroxyindoleacetic acid in mPFC and HIPPO in GF mice after ATD, when compared to SPF mice. Therefore, the serotonergic system of GF mice is more vulnerable to the acute challenge of tryptophan reduction, and GF mice after tryptophan reduction behave more similarly to SPF mice. These data provide functional evidence that microbiota affects depression-like behavior through influencing brain tryptophan accessibility and the serotonergic system.

Expert and self-assessment of lifetime symptoms and diagnosis of major depressive disorder in large-scale genetic studies in the general population: comparison of a clinical interview and a self-administered checklist

Supplemental Digital Content is available in the text.

Major depression disorder (MDD) is a complex neuropsychiatric disorder and an increasing number of genetic risk variants are being identified. Investigation of their influence in the general population requires accurate and efficient assessment of depressive symptoms. Here, clinical interviews conducted by clinicians are the gold standard. We investigated whether valid and reliable clinical phenotypes can be obtained efficiently using self-administered instruments. Lifetime depressive symptoms and lifetime MDD diagnosis were assessed in 464 population-based individuals using a clinical interview and a structured, self-administered checklist. Analyses were carried out of the following: (i) intraclass correlations (ICC) between checklist and interview; (ii) sensitivity/specificity of the checklist; and (iii) the association of interview and checklist with a positive family history of MDD (FH-MDD+). The correspondence of the self-administered checklist with the clinical interview was good for most depressive symptoms (ICC=0.60–0.80) and moderate for MDD diagnosis (ICC=0.45). With the consecutive inclusion of MDD diagnostic criteria, sensitivity decreased from 0.67 to 0.46, whereas specificity remained high (0.95). For checklist and interview, strong associations were found between FH-MDD+ and most depressive symptoms and MDD diagnosis (all odds ratio≥1.83). The self-administered checklist showed high reliability for both the assessment of lifetime depressive symptoms and screening for individuals with no lifetime diagnosis of MDD. However, attention is warranted when the aim is to identify MDD cases. The positive association between depressive symptomatology and FH-MDD+ indicates the usefulness of both instruments to assess patients in genetic studies. Our data suggest that the more time-efficient and cost-efficient self-administered instruments also allow for the assessment of depressive symptoms accurate enough to investigate the influence of MDD genetic risk variants in the general population.

Risk-seeking for losses is associated with 5-HTTLPR, but not with transient changes in 5-HT levels

RATIONALE

Serotonin (5-HT) plays a key role in different aspects of value-based decision-making. A recent framework proposed that tonic 5-HT (together with dopamine, DA) codes future average reward expectations, providing a baseline against which possible choice outcomes are compared to guide decision-making.

OBJECTIVES

To test whether high 5-HT levels decrease loss aversion, risk-seeking for gains, and risk-seeking for losses.

METHODS

In a first session, 611 participants were genotyped for 5-HTTLPR and performed a mixed gambles (MGA) task and two probability discounting tasks for gains and losses, respectively (PDG/PDL). Afterwards, a subsample of 105 participants (44 with S/S, 6 with S/L, 55 with L/L genotype) completed the pharmacological study using a crossover design with tryptophan depletion (ATD), loading (ATL), and balanced (BAL) conditions. The same decision constructs were assessed.

RESULTS

We found increased risk-seeking for losses in S/S compared to L/L individuals at the first visit (p = 0.002). Neither tryptophan depletion nor loading affected decision-making, nor did we observe an interaction between intervention and 5-HTTLPR genotype.

CONCLUSION

Our data do not support the idea that transient changes of tonic 5-HT affect value-based decision-making. We provide evidence for an association of 5-HTTLPR with risk-seeking for losses, independent of acute 5-HT levels. This indicates that the association of 5-HTTLPR and risk-seeking for losses is mediated via other mechanisms, possibly by differences in the structural development of neural circuits of the 5-HT system during early life phases.

Influence of demographic factors and serotonin transporter-linked polymorphic region (5-HTTLPR) variants on major depression in a northeastern Thai population

Background: Several lines of evidence suggest that the serotonergic system may be involved in the etiology of major depressive disorder (MDD). Objective: Investigate a potential association between the functional polymorphism in the serotonin transporter-linked polymorphic region (5-HTTLPR) and MDD in a northeastern Thai population, and explore the involvement of demographic characteristics in this disorder. Methods: One hundred eighty seven patients with MDD and 207 healthy controls were recruited from the same geographical area into the study. The 5-HTTLPR genotypes were determined using polymerase chain reaction (PCR) and analyzed statically. Results: Significant demographic differences between the two groups were observed, which included age, marital status, occupation, educational background, income, and alcohol use. The allele frequencies of the 5- HTTLPR polymorphism in our studied population were relatively near those of Asian populations, especially Chinese, which was regarded as enormously distinct from those of Caucasians. Nevertheless, our present study found no significant association between this polymorphism and MDD with respect to either genotype distributions or allele frequencies. Conclusion: No involvement of the 5-HTTLPR polymorphism was suggested, but demographic features in MDD were highlighted with respect to this studied population.

Serotonin transporter polymorphism, depressive symptoms, and emotional impulsivity among advanced breast cancer patients

PURPOSE

This study tested a theory linking a marker of low serotonergic function to both depression and impulsivity in a sample of advanced breast cancer patients, among whom elevated depressive symptoms and difficulty regulating emotions are commonly reported.

METHODS

A total of 95 patients provided blood samples for serotonin transporter polymorphic region of the gene (5-HTTLPR) and completed questionnaires that measured depressive symptoms and emotional impulsivity.

RESULTS

Structural equation modeling revealed that the s allele of 5-HTTLPR was related to greater depressive symptoms (β = .20, p < .042) but only marginally to greater emotional impulsivity (β = .19, p < .068). Depressive symptoms and emotional impulsivity were positively related (β = .33, p < .003). Further tests explored possible mediation from genotype to one psychological variable via the other. Results suggest that depressive symptoms, particularly perceived interpersonal rejection, may be a pathway linking genotype to emotional impulsivity.

CONCLUSIONS

Findings provide the first evidence that low serotonergic function contributes to both depression and impulsivity within a clinically meaningful sample. Furthermore, the link of s allele of 5-HTTLPR to emotional impulsivity was mediated by depressive symptoms, particularly perceptions of social rejection. Findings have implications for advanced breast cancer patients' treatment decision.

The interaction between 5-HTTLPR genotype and ruminative thinking on BMI

Negative affect or stress is often found to increase energy intake for high palatable energy-rich foods and hence weight gain. Reduced brain serotonin (5-HT) function is known to increase stress vulnerability and the risk for eating-related disturbances. A short (S) allele polymorphism in the serotonin transporter gene (5-HTTLPR) is associated with a less efficient functioning brain serotonin system and therefore higher stress vulnerability. It has been suggested that this genotype may be directly linked to an increased risk for weight gain and/or obesity. However, a high amount of variability has been apparent in replicating such a direct gene on weight gain relationship. A most recent suggestion is that this gene by weight relationship might be moderated by an additional (cognitive) vulnerability factor involving repetitive negative thinking (rumination). Our objective was to investigate whether the S-allele of 5-HTTLPR contributes to weight gain particularly in high cognitive ruminating individuals. A total of 827 healthy young male and female college students (aged 21·3 (sd 3·0) years; BMI 16–41·7 kg/m2) were genotyped for the 5-HTTLPR polymorphism and assessed for rumination (Event Related Ruminative Index) and body weight. In line with the hypothesis, a hierarchical regression model showed that higher BMI scores were observed in specifically high ruminating S'-carriers (P=0·031, f²=0·022). These results suggest that cognitive rumination may be a critical moderator of the association between 5-HTTLPR and body mass.

Genetics of Tinnitus: Still in its Infancy

Tinnitus is the perception of a phantom sound that affects between 10 and 15% of the general population. Despite this considerable prevalence, treatments for tinnitus are presently lacking. Tinnitus exhibits a diverse array of recognized risk factors and extreme clinical heterogeneity. Furthermore, it can involve an unknown number of auditory and non-auditory networks and molecular pathways. This complex combination has hampered advancements in the field. The identification of specific genetic factors has been at the forefront of several research investigations in the past decade. Nine studies have examined genes in a case-control association approach. Recently, a genome-wide association study has highlighted several potentially significant pathways that are implicated in tinnitus. Two twin studies have calculated a moderate heritability for tinnitus and disclosed a greater concordance rate in monozygotic twins compared to dizygotic twins. Despite the more recent data alluding to genetic factors in tinnitus, a strong association with any specific genetic locus is lacking and a genetic study with sufficient statistical power has yet to be designed. Future research endeavors must overcome the many inherent limitations in previous study designs. This review summarizes the previously embarked upon tinnitus genetic investigations and summarizes the hurdles that have been encountered. The identification of candidate genes responsible for tinnitus may afford gene based diagnostic approaches, effective therapy development, and personalized therapeutic intervention.

Associations of 5HTTLPR polymorphism with major depressive disorder and alcohol dependence: A systematic review and meta-analysis

OBJECTIVE

The neurotransmitter serotonin is understood to control mood and drug response. Carrying a genetic variant in the serotonin transporter gene (5HTT) may increase the risk of major depressive disorder and alcohol dependence. Previous estimates of the association of the S allele of 5HTTLPR polymorphism with major depressive disorder and alcohol dependence have been inconsistent.

METHODS

For the systematic review, we used PubMed MEDLINE and Discovery of The University of Melbourne to search for all relevant case-control studies investigating the associations of 5HTTLPR polymorphism with major depressive disorder and alcohol dependence. Summary odds ratios (OR) and their 95% confidence intervals (CI) were estimated. To investigate whether year of publication, study population or diagnostic criteria used were potential sources of heterogeneity, we performed meta-regression analyses. Publication bias was assessed using Funnel plots and Egger's statistical tests.

RESULTS

We included 23 studies of major depressive disorder without alcohol dependence containing 3392 cases and 5093 controls, and 11 studies of alcohol dependence without major depressive disorder containing 2079 cases and 2273 controls. The summary OR for homozygote carriers of the S allele of 5HTTLPR polymorphism compared with heterozygote and non-carriers combined (SS vs SL+LL genotype) was 1.33 (95% CI = [1.19, 1.48]) for major depressive disorder and 1.18 (95% CI = [1.01, 1.38]) for alcohol dependence. The summary OR per S allele of 5HTTLPR polymorphism was 1.16 (95% CI = [1.08, 1.23]) for major depressive disorder and 1.12 (95% CI = [1.01, 1.23]) for alcohol dependence. Meta-regression models showed that the associations did not substantially change after adjusting for year of publication, study population and diagnostic criteria used. There was no evidence for publication bias of the studies included in our meta-analysis.

CONCLUSIONS

Our meta-analysis confirms that individuals with the homozygous S allele of 5HTTLPR polymorphism are at increased risks of major depressive disorder as well as alcohol dependence. Further studies are required to investigate the association between 5HTTLPR polymorphism and the comorbidity of major depressive disorder and alcohol dependence as well as gene × environmental interactions.

The ubiquitination of serotonin transporter in lymphoblasts derived from fluvoxamine-resistant depression patients

There is insufficient serotonergic neuronal function in the pathophysiology of major depressive disorder (MDD). Serotonin transporter (SERT) plays a critical role in terminating the function of serotoninergic neurons. SERT is linked to vulnerability to MDD and is an important target for antidepressants. The expression of SERT in lymphocytes and platelets is associated with their expression in central nervous system. Most of the clinical studies that have analyzed the role of SERT in depression have focused on absolute expression of SERT in the brain or peripheral tissue. Our study has shown that the SERT protein is ubiquitinated, which has been implicated through the SERT stability and depressive behaviors in mice. In our study, we have used lymphoblasts derived from the peripheral blood lymphocytes to quantitatively examine SERT protein expression and ubiquitination in fluvoxamine-responsive and fluvoxamine-resistant MDD patients. We found that the protein levels of SERT were higher in the fluvoxamine-resistant MDD patients. Ubiquitinated protein levels of SERT were lower in the fluvoxamine-resistant MDD patients. The proteasome inhibitor failed to increase the protein levels of SERT in both fluvoxamine-responsive and fluvoxamine-resistant MDD patients. In sum, these findings suggest that the downregulation of the ubiquitination of SERT protein induces insufficient degradation of SERT by proteasome, which resulted in the upregulation of SERT protein in fluvoxamine-resistant MDD patients. Although further studies with various populations will be required to generalize results, SERT protein expression, ubiquitination, and the responsiveness of SERT expression to proteasome inhibitor are potential biomarkers for the diagnosis of MDD and antidepressant efficacy.

[Association between anxiety-depression and 5-HTTLPR gene polymorphism in school-aged twins]

OBJECTIVE

To investigate the association between anxiety-depression and 5-HTTLPR gene polymorphism in school-aged twins.

METHODS

A total of 147 pairs of twins (47 pairs of monozygotic twins, 100 pairs of dizygotic twins) aged 8-12 years from Baotou and Hohhot were selected as respondents. The Achenbach Child Behavior Checklist (CBCL) was used to calculate the scores of anxiety-depression factors in school-aged twins. The DNA was extracted from oral epithelial cells, and polymerase chain reaction was applied for 5-HTTLPR genotyping. The generalized estimating equation (GEE) was used to analyze the effect of 5-HTTLPR polymorphism and family environment on anxiety-depression in school-aged twins.

RESULTS

The children with LS and SS genotypes had significantly higher scores of anxiety-depression factors than those with LL genotype (χ2=3.938, P<0.05). The interaction of 5-HTTLPR genotype with family cohesion and family rearing patterns had a significant impact on the scores of anxiety-depression factors in twins (χ2=6.129 and 7.665, both P<0.05).

CONCLUSIONS

5-HTTLPR genotype is significantly correlated with the scores of anxiety-depression factors in school-aged twins. In the family with high cohesion and an autocratic family rearing pattern, S allele may increase the possibility of anxiety-depression in twin children.

Personalized Medicine and Mood Disorders

Some of the latest advances in personalized psychiatry with future research directions are discussed in this article. Many factors contribute to the phenotypic psychiatric profile in individual patients. These overlapping factors include but are not limited to genetics, epigenetics, central nervous system circuit alterations, family history, past personal history, environmental influences including early life stress, and more recent life stressors. The authors discuss the role of pharmacogenomics, particularly in the cytochrome P450 enzyme system in relation to treatment response. Despite some promising advances in personalized medicine in psychiatry, it is still in its early phases of development.

Analyzing pathways from childhood maltreatment to internalizing symptoms and disorders in children and adolescents (AMIS): a study protocol

BACKGROUND

Effective interventions for maltreated children are impeded by gaps in our knowledge of the etiopathogenic mechanisms leading from maltreatment to mental disorders. Although some studies have already identified individual risk factors, there is a lack of large-scale multilevel research on how psychosocial, neurobiological, and genetic factors act in concert to modulate risk of internalizing psychopathology in childhood following maltreatment. To help close this gap, we aim to delineate gender-specific pathways from maltreatment to psychological disorder/resilience. To this end, we examine the interplay of specific maltreatment characteristics and psychological, endocrine, metabolomic, and (epi-)genomic stress response patterns as well as cognitive-emotional/social processes as determinants of developmental outcome. Specifically, we will explore endocrine, metabolomic, and epigenetic mechanisms leading from maltreatment to a higher risk of depression and anxiety disorders.

METHODS/DESIGN

Four large samples amounting to a total of N = 920 children aged 4-16 years will be assessed: Two cohorts with prior internalizing psychopathology and controls will be checked for maltreatment and two cohorts with substantiated maltreatment will be checked for internalizing (and externalizing) psychopathology. We will apply a multi-source (interview, questionnaires, official records), multi-informant strategy (parents, children, teachers) to assess maltreatment characteristics (e.g., subtypes, developmental timing, chronicity) and psychopathological symptoms, supplemented with multiple measurements of risk and protective factors and cutting-edge laboratory analyses of endocrine, steroid metabolomic and epigenetic factors. As previous assessments in the two largest samples are already available, longitudinal data will be generated within the three year study period.

DISCUSSION

Our results will lay the empirical foundation for (a) detection of early biopsychosocial markers, (b) development of screening measures, and

A functional 12T-insertion polymorphism in the ATP1A1 promoter confers decreased susceptibility to hypertension in a male Sardinian population

Identification of susceptibility genes for essential hypertension in humans has been a challenge due to its multifactorial pathogenesis complicated by gene-gene and gene-environment interactions, developmental programing and sex specific differences. These concurrent features make identification of causal hypertension susceptibility genes with a single approach difficult, thus requiring multiple lines of evidence involving genetic, biochemical and biological experimentation to establish causal functional mutations. Here we report experimental evidence encompassing genetic, biochemical and in vivo modeling that altogether support ATP1A1 as a hypertension susceptibility gene in males in Sardinia, Italy. ATP1A1 encodes the α1Na,K-ATPase isoform, the sole sodium pump in vascular endothelial and renal tubular epithelial cells. DNA-sequencing detected a 12-nucleotide long thymidine (12T) insertion(ins)/deletion(del) polymorphism within a poly-T sequence (38T vs 26T) in the ATP1A1 5’-regulatory region associated with hypertension in a male Sardinian population. The 12T-insertion allele confers decreased susceptibility to hypertension (P = 0.035; OR = 0.50 [0.28–0.93]) accounting for 12.1 mmHg decrease in systolic BP (P = 0.02) and 6.6 mmHg in diastolic BP (P = 0.046). The ATP1A1 promoter containing the 12T-insertion exhibited decreased transcriptional activity in in vitro reporter-assay systems, indicating decreased α1Na,K-ATPase expression with the 12T-insertion, compared with the 12T-deletion ATP1A1 promoter. To test the effects of decreased α1Na,K-ATPase expression on blood pressure, we measured blood pressure by radiotelemetry in three month-old, highly inbred heterozygous knockout ATP1A1+/− male mice with resultant 58% reduction in ATP1A1 protein levels. Male ATP1A1+/− mice showed significantly lower blood pressure (P < 0.03) than age-matched male wild-type littermate controls. Concordantly, lower ATP1A1 expression is expected to lower Na-reabsorption in the kidney thereby decreasing sodium-associated risk for hypertension and sodium-induced endothelial stiffness and dysfunction. Altogether, data support ATP1A1 as a hypertension susceptibility gene in a male Sardinian population, and mandate further investigation of its involvement in hypertension in the general population.

Evaluation of the promoter region polymorphism (5-HTTLPR) in the serotonin transporter gene in females with postpartum depression

The aim of the present study was to investigate the association between polymorphism in the serotonin transporter (5-HTT) gene-linked polymorphic region (5-HTTLPR) in the promoter region of the 5-HTT gene and the pathogenesis of postpartum depression (PPD). Blood samples were collected from 120 female patients with PPD and 140 age-matched normal controls. Polymerase chain reaction analysis was performed to detect the 5-HTTLPR polymorphism in these subjects, and the genotype and allele frequencies were compared between the two groups. The disease severity was evaluated using the Hamilton Depression Rating Scale (HAMD) score. The results showed that the frequency of the homozygous long/long (L/L) genotype was significantly lower in the PPD group than that in the control group; by contrast, the frequencies of the heterozygous long/short (L/S) and homozygous S/S genotypes were similar for the two groups, without significant differences. No significant differences were observed in the L and S allele frequencies between the two groups. Furthermore, compared with the L/S heterozygous and S/S homozygous genotypes, patients with PPD with the L/L homozygous genotype had a significantly lower HAMD score. The present results suggest that female patients with PPD carrying the homozygous L/L genotype may be less susceptible to depressive symptoms and that the L/L genotype may be associated with the reduced occurrence of PPD. These findings provide a theoretical basis for the clinical diagnosis and treatment of PPD.

The association of serotonin transporter gene polymorphism and geriatric depression: a meta-analysis

Serotonin-transporter-linked promoter region (5-HTTLPR) polymorphism is the genetic variant coding for the serotonin transporter and may play an important role in the etiology of depression. However, genetic studies examining the relationship between 5-HTTLPR polymorphism and geriatric depression have produced inconsistent results. We conducted a meta-analysis to compare the frequency of 5-HTTLPR variants in geriatric depression cases and non-depressed controls in the elderly. A total of 5 studies involving 579 geriatric cases and 1372 non-depressed controls met the inclusion criteria. With strong statistical power, pooled odds ratios (ORs) and 95% confidence intervals (CIs) for genotypic analyses (S carrier versus L/L, S/S versus L/L) were provided. The results of our analysis indicate statistically significant association between S allele and the risk of geriatric depression (OR ScarriervsS/S=1.29, 95% CI 1.01-1.66; OR S/SvsL/L=1.68, 95% CI 1.20-2.35). Our findings suggest that 5-HTTLPR polymorphism is of importance in the development of geriatric depression.

Serotonin and its implication in the side-effects of interferon-based treatment of patients with chronic viral hepatitis: Pharmacological interventions

Depression is a frequent side-effect of interferon-based treatment of patients with chronic viral hepatitis, that may lead to reduction or discontinuation of treatment. Clinical trials data showed the importance of therapy of psychiatric disorders for a successful antiviral treatment. Emerging evidence suggests that interferon may cause depression affecting serotonin synthesis via increased activity of indoleamine 2,3-dioxygenase. Serotonin reuptake inhibitors significantly improve mood disorders, but the use of these drugs requires caution because some studies reported the emergence of mania in patients treated for depression during antiviral therapy. Therefore, this review will examine and discuss the putative role of serotonin and its metabolism in the development of depression during antiviral therapy, focusing on pharmacological interventions to reduce side-effects.

Interaction between the 5-HTTLPR genotype, impact of stressful life events, and trait neuroticism on depressive symptoms in healthy volunteers

INTRODUCTION

Recent biopsychological research on stress-related psychopathology shows promising evidence for the 5-hydroxytryptamine (5-HT) transporter linked polymorphic region (5-HTTLPR) genotype by life event interaction on depression. Yet, there appears to be variability in replicating such findings. From leading cognitive models of depression, it can be deduced that mainly high-impact events, particularly in stress-vulnerable, high trait neuroticism individuals who possess low coping abilities, can cause depression.

OBJECTIVE

The current study therefore examines the interaction between the 5-HTTLPR genotype, impact of life events, and trait neuroticism on depression symptoms.

PARTICIPANTS AND METHODS

A group of 771 healthy individuals, 595 women and 176 men aged 21.0±2.1 years, were genotyped for the 5-HTTLPR polymorphism and were rated for depressive symptoms, impact of life events, and neuroticism.

RESULTS

Only the low-allele expressing (S) 5-HTTLPR carriers showed vulnerability to depression exclusively when they also reported exposure to high-impact events and showed high neuroticism.

CONCLUSION

This suggests that cognitive vulnerabilities may mediate the 5-HTTLPR genotype by life event interaction on depression.

Longer telomere length in patients with schizophrenia

Previous studies have reported an association between shorter leukocyte telomere length and schizophrenia (SCZ). The aim of the present study was to replicate this finding in a large sample of SCZ patients (n=539) and population-based controls (n=519). In addition, the possible influence of SCZ severity on telomere length - as measured by age of onset, mode of onset, and course of the disorder - was investigated. Telomere length was negatively associated with age in both patients and controls. This is a consistently reported phenomenon, related to the problem of DNA end-replication. However, in contrast to previous findings, SCZ patients displayed longer telomeres compared to controls (p=0.015). No association was found with any SCZ-severity subphenotype. Interestingly, recent studies have reported associations between longer leukocyte telomere length and both smaller hippocampal volume, and poorer episodic memory performance. Both phenotypes are common in patients with SCZ. Further studies are warranted to investigate whether the present association between SCZ and increased telomere length was driven by such associations, or rather by association with the clinical disease per se or other associated phenotypes, endophenotypes or lifestyle factors.

Personalized medicine in psychiatry: problems and promises

The central theme of personalized medicine is the premise that an individual's unique physiologic characteristics play a significant role in both disease vulnerability and in response to specific therapies. The major goals of personalized medicine are therefore to predict an individual's susceptibility to developing an illness, achieve accurate diagnosis, and optimize the most efficient and favorable response to treatment. The goal of achieving personalized medicine in psychiatry is a laudable one, because its attainment should be associated with a marked reduction in morbidity and mortality. In this review, we summarize an illustrative selection of studies that are laying the foundation towards personalizing medicine in major depressive disorder, bipolar disorder, and schizophrenia. In addition, we present emerging applications that are likely to advance personalized medicine in psychiatry, with an emphasis on novel biomarkers and neuroimaging.

Genome-wide association data provide further support for an association between 5-HTTLPR and major depressive disorder

BACKGROUND

Dysfunctions of serotonergic neurotransmission are supposed to be involved in the pathogenesis of psychiatric disorders such as major depressive disorder (MDD). The concentration of serotonin (5-hydroxytryptamine, 5-HT) in the synaptic cleft is essentially regulated by the 5-HT transporter (5-HTT). A length polymorphism repeat in the 5-HTT promoter region, termed 5-HTTLPR, has been commonly investigated for an association with psychiatric disorders.

METHODS

Genotyping of the 5-HTTLPR is time-consuming and technically challenging. Recently, a two-SNP haplotype was identified that tags the 5-HTTLPR at r(2)=0.775. This allows extraction of 5-HTTLPR genotype information from large genome-wide association study (GWAS) data sets. In the present study we performed haplotype analysis using a German GWAS case-control dataset to test for an association between MDD and the two-SNP tagging haplotype for 5-HTTLPR.

RESULTS

We detected a significant association between the TA haplotype (tagging the S-allele of the 5-HTTLPR) and MDD. Our result is consistent with previous findings of an association between the 5-HTTLPR S-allele and MDD.

LIMITATIONS

Using the two-SNP tagging haplotype did not allow testing of the tri-allelic genotype (but only the two-allelic genotype). This and the fact that the haplotype tags the 5-HTTLPR with an imperfect linkage disequilibrium of r(2)=0.775 may lead to some loss of power.

CONCLUSIONS

Our results provide further support for an involvement of the 5-HTTLPR in MDD and represent the first example of demonstrating association between MDD and the S-allele of the length polymorphism repeat using common SNP information from SNP-array data.

Effect of gene, environment and maternal depressive symptoms on pre-adolescence behavior problems - a longitudinal study

BACKGROUND

Depression is a common and disabling condition with a high relapse frequency. Maternal mental health problems and experience of traumatic life events are known to increase the risk of behavior problems in children. Recently, genetic factors, in particular gene-by-environment interaction models, have been implicated to explain depressive etiology. However, results are inconclusive.

METHODS

Study participants were members of the SESBiC-study. A total of 889 mothers and their children were followed during the child's age of 3 months to 12 years. Information on maternal depressive symptoms was gathered postpartum and at a 12 year follow-up. Mothers reported on child behavior and traumatic life events experienced by the child at age 12. Saliva samples were obtained from children for analysis of 5-HTTLPR and BDNF Val66Met polymorphisms.

RESULTS

Multivariate analysis showed a significant association between maternal symptoms of depression and anxiety, and internalizing problems in 12-year-old children (OR 5.72, 95% CI 3.30-9.91). Furthermore, carriers of two short alleles (s/s) of the 5-HTTLPR showed a more than 4-fold increased risk of internalizing problems at age 12 compared to l/l carriers (OR 4.73, 95% CI 2.14-10.48). No gene-by-environment interaction was found and neither depressive symptoms postpartum or traumatic experiences during childhood stayed significant in the final model.

CONCLUSIONS

Concurrent maternal symptoms of depression and anxiety are significant risk factors for behavior problems in children, which need to be taken into account in clinical practice. Furthermore, we found a main effect of 5-HTTLPR on internalizing symptoms in 12-year-old children, a finding that needs to be confirmed in future studies.

Development × environment interactions control tph2 mRNA expression

Adverse early life experience is thought to increase an individual's susceptibility to mental health disorders, including anxiety and affective disorders, later in life. Our previous studies have shown that post-weaning social isolation of female rats during a critical period of development sensitizes an anxiety-related serotonergic dorsal raphe nucleus (DR) system in adulthood. Therefore, we investigated how post-weaning social isolation, in combination with a challenge with the anxiogenic drug, N-methyl-beta-carboline-3-carboxamide (FG-7142; a partial inverse agonist at the benzodiazepine allosteric site on the GABAA receptor), affects home cage behavior and serotonergic gene expression in the DR of female rats using in situ hybridization histochemistry. Juvenile female rats were reared in isolation or groups of three for a 3-week period from weaning (postnatal day (PD) 21 to mid-adolescence (PD42)), after which all rats were group-reared for an additional 16 days until adulthood. Among vehicle-treated rats, isolation-reared rats had decreased rodent tryptophan hydroxylase 2 (tph2) mRNA expression in ventral and ventrolateral subdivisions of the DR, a pattern observed previously in a rat model of panic disorder. Isolation-reared rats, but not group-reared rats, responded to FG-7142 with increased duration of vigilance and arousal behaviors. In addition, FG-7142 decreased tph2 expression, measured 4h following treatment, in multiple subregions of the DR of group-reared rats but had no effect in isolation-reared rats. No treatment effects were observed on 5-HT1A receptor or serotonin transporter gene expression. These data suggest that adolescent social isolation alters tph2 expression in specific subregions of the DR and alters the effects of stress-related stimuli on behavior and serotonergic systems.

The long rather than the short allele of 5-HTTLPR predisposes Han Chinese to anxiety and reduced connectivity between prefrontal cortex and amygdala

The short allele of the serotonin-transporter gene is associated with higher risk for anxiety and depression in Caucasians, but this association is still unclear in Asians. Here, we addressed this issue using behavioral and multi-modal MRI approaches in a large group of healthy Han Chinese participants (n = 233). In contrast to findings in Caucasians, we found that long-allele (L) carriers had higher anxiety scores. In another group (n = 64) experiencing significant levels of depression or anxiety, the L-allele frequency was also significantly higher. In healthy participants, L-carriers had reduced functional and anatomical connectivity between the amygdala and prefrontal cortex (PFC), which was correlated with anxiety or depression scores. Our findings demonstrated that in Chinese Han participants, in contrast to Caucasians, the L-allele confers vulnerability to anxiety or depression and weakens top-down emotional control between the PFC and amygdala. Therefore, ethnic background should be taken into account in generelated studies and their potential clinical applications.

Enlarged thalamic volumes and increased fractional anisotropy in the thalamic radiations in veterans with suicide behaviors

Post-mortem studies have suggested a link between the thalamus, psychiatric disorders, and suicide. We evaluated the thalamus and anterior thalamic radiations (ATR) in a group of Veterans with and without a history of suicidal behavior (SB) to determine if thalamic abnormalities were associated with an increased risk of SB. Forty Veterans with mild traumatic brain injury (TBI) and no SB (TBI-SB), 19 Veterans with mild TBI and a history of SB (TB + SB), and 15 healthy controls (HC) underwent magnetic resonance imaging scanning including a structural and diffusion tensor imaging scan. SBs were evaluated utilizing the Columbia Suicide Rating Scale and impulsivity was measured using the Barratt Impulsiveness Scale (BIS). Differences in thalamic volumes and ATR fractional anisotropy (FA) were examined between (1) TBI + SB versus HC and (2) TBI + SB versus combined HC and TBI-SB and (3) between TBI + SB and TBI-SB. Left and right thalamic volumes were significantly increased in those with TBI + SB compared to the HC, TBI-SB, and the combined group. Veterans with TBI + SB had increased FA bilaterally compared to the HC, HC and TBI-SB group, and the TBI-SB only group. Significant positive associations were found for bilateral ATR and BIS in the TBI + SB group. Our findings of thalamic enlargement and increased FA in individuals with TBI + SB suggest that this region may be a biomarker for suicide risk. Our findings are consistent with previous evidence indicating that suicide may be associated with behavioral disinhibition and frontal-thalamic-limbic dysfunction and suggest a neurobiologic mechanism that may increase vulnerability to suicide.

Emerging risk factors for postpartum depression: serotonin transporter genotype and omega-3 fatty acid status

OBJECTIVE

Depression is a leading cause of disability and hospitalization. Women are at the highest risk of depression during their childbearing years, and the birth of a child may precipitate a depressive episode in vulnerable women. Postpartum depression (PPD) is associated with diminished maternal somatic health as well as health and developmental problems in their offspring. This review focuses on 2 PPD risk factors of emerging interest: serotonin transporter (5-HTT) genotype and omega-3 polyunsaturated fatty acid (n-3 PUFA) status.

METHOD

The MEDLINE, PubMed, and Web of Science databases were searched using the key words postpartum depression, nutrition, omega-3 fatty acids, and serotonin transporter gene. Studies were also located by reviewing the reference lists of selected articles.

RESULTS

Seventy-five articles were identified as relevant to this review. Three carefully conducted studies reported associations between the 5-HTT genotype and PPD. As well, there is accumulating evidence that n-3 PUFA intake is associated with risk of PPD. Preliminary evidence suggests that there could be an interaction between these 2 emerging risk factors. However, further studies are required to confirm such an interaction and to elucidate the underlying mechanisms.

CONCLUSIONS

Evidence to date supports a research agenda clarifying the associations between n-3 PUFAs, the 5-HTT genotype, and PPD. This is of particular interest owing to the high prevalence of poor n-3 PUFA intake among women of childbearing age and the consequent potential for alternative preventive measures and treatments for PPD.

Analysis of the normative conditions of oral health, depression and serotonin-transporter-linked promoter region polymorphisms in an elderly population

AIM

To investigate the association between depression, the normative conditions of oral health and serotonin-transporter-linked promoter region (5-HTTLPR) polymorphisms in a community-dwelling elderly sample.

METHODS

Elderly adults living in a community (n=200) were submitted to an oral clinical examination. Depression was assessed using the 15-item Geriatric Depression Scale. The 5-HTTLPR was analyzed by polymerase chain reaction-restriction fragment length polymorphism. Associations between the biomarkers and clinical covariates were assessed by bivariate and multivariate statistical tests. Statistical significance was set at P<0.05.

RESULTS

The prevalence of dental caries, periodontal disease, edentulism and oral mucosal lesions was 51.2%, 20.8%, 58.0% and 21.5%, respectively. The prevalence of depression was 21.5%. A higher frequency of the S allele was recorded in older individuals with depression (P=0.017). The present findings showed no significant association between depression and the normative conditions of oral health. The observed allelic polymorphisms were 44% S and 56% L, respectively. Genotypic variants were 33.5% LL, 45.0% SL and 21.5% SS. Individuals carrying the SS genotype showed a significantly high prevalence of periodontal disease (prevalence ratio=3.077, CI 95%=1.008-9.393, P=0.048).

CONCLUSION

The present findings suggest that depressive community-dwelling older individuals did not show any association with alterations of oral health normative conditions. However, the SS genotypic polymorphic variant of 5-HTTLPR seems to contribute to the occurrence of periodontal disease in the elderly.

MAGE-D1 regulates expression of depression-like behavior through serotonin transporter ubiquitylation

The ubiquitin-proteasome system (UPS) controls the stability of most cellular proteins. The polymorphism of UPS-related genes is associated with major depression disorder, but less is known about the molecule that plays a role in depression by modulating the UPS. Melanoma antigen gene-D1 (MAGE-D1) interacts with RING E3 ubiquitin ligase and is implicated in protein degradation. MAGE-D1 may thus play an important role in the CNS via ubiquitylation. Here, we clarified a novel role of MAGE-D1 in emotional functions, namely its modulation of ubiquitylation to the serotonin transporter (SERT). The MAGE-D1 knock-out and knockdown by small interfering RNA (siRNA) in the prefrontal cortex showed depression-like behavior, such as a decrease in exploratory behavior in both the home cage and novel apparatus, a decrease in social interaction, increased immobility time during forced swimming and tail suspension, and a decrease in sucrose preference without any anxiety, or cognitive or motor dysfunction. Acute and chronic (28 d) administration of sertraline (10 mg/kg) and imipramine (20 mg/kg) reversed all or part of depression-like behavior in knock-out mice. In these mice, the serotonergic function in the prefrontal cortex and hippocampus was hypoactive, accompanied by hyperexpression of SERT attributable to a decrease in ubiquitylation. Furthermore, MAGE-D1 binds to SERT via the necdin homology domain. MAGE-D1 overexpression in cells resulted in a decrease in serotonin uptake activity and the protein level of SERT but an increase in ubiquitylated SERT. Together, the present findings suggest a novel role for MAGE-D1 in depressive behaviors: modulating SERT ubiquitylation.

5-HTTLPR polymorphism impacts task-evoked and resting-state activities of the amygdala in Han Chinese

Background

Prior research has shown that the amygdala of carriers of the short allele (s) of the serotonin transporter (5-HTT) gene (5-HTTLPR) have a larger response to negative emotional stimuli and higher spontaneous activity during the resting state than non-carriers. However, recent studies have suggested that the effects of 5-HTTLPR may be specific to different ethnic groups. Few studies have been conducted to address this issue.

Methodology/Principal Findings

Blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) was conducted on thirty-eight healthy Han Chinese subjects (l/l group, n = 19; s/s group, n = 19) during the resting state and during an emotional processing task. Compared with the s/s group, the l/l group showed significantly increased regional homogeneity or local synchronization in the right amygdala during the resting state (|t|>2.028, p<0.05, corrected), but no significant difference was found in the bilateral amygdala in response to negative stimuli in the emotional processing task.

Conclusions/Significance

5-HTTLPR can alter the spontaneous activity of the amygdala in Han Chinese. However, the effect of 5-HTTLPR on the amygdala both in task state and resting state in Asian population was no similar with Caucasians. They suggest that the effect of 5-HTTLPR on the amygdala may be modulated by ethnic differences.

Life stressors and 5-HTTLPR interaction in relation to midpregnancy depressive symptoms among African-American women

OBJECTIVE

In earlier analyses of nonHispanic White women we found a stronger relation between abuse history and midpregnancy elevated depressive symptoms in women with the serotonin transporter (5-HTTLPR) S/S genotype. Here, we focus on African-American women (N=698). Our inquiry is motivated by racial differences in depression diagnosis/treatment, stressors, and frequency of major 5-HTTLPR alleles (S, LA, LG).

MATERIALS AND METHODS

Stressful life events (lifetime) and depressive symptoms (current) were ascertained at 15-27 weeks gestation. A Center for Epidemiological Studies Depression Score of more than or equal to 18 was considered 'elevated'. Life events were scored together and separated into six subconstructs. 5-HTTLPR genotypes were grouped as follows: (i) L and S alleles, (ii) S-LG equivalence ('triallelic to biallelic'), and (iii) LA/LA, all others, S/S ('high/intermediate/low'). Odds ratios (OR) for 'elevated' depressive symptoms-life events (total and subconstructs) relations were calculated for each genotype grouping.

RESULTS

The prevalence of 'elevated' depressive symptoms did not vary by genotype. The relation between stressful life events and 'elevated' depressive symptoms was stronger in S/S compared with LA/LA genotype (interaction P=0.11). Of the six subconstructs, only abuse showed a statistically significant gene-environment interaction. The OR for the abuse-'elevated' depressive symptoms association was greater for S/S vs. LA/LA genotype (interaction P=0.03) and in the 'triallelic to biallelic' grouping (interaction P=0.04). In the 'high/intermediate/low' grouping, 'low' (S/S) had a higher OR (5.5) than both 'intermediate' and 'high' (ORs≤2.3) (interaction P=0.10).

CONCLUSIONS

These results show the importance of examining racial groups, specific stressful events, and different 5-HTTLPR genotype groupings when exploring gene-environment interactions in depression.

Fibromyalgia and depression

Fibromyalgia and depression might represent two manifestations of affective spectrum disorder. They share similar pathophysiology and are largely targeted by the same drugs with dual action on serotoninergic and noradrenergic systems. Here, we review evidence for genetic and environmental factors that predispose, precipitate, and perpetuate fibromyalgia and depression and include laboratory findings on the role of depression in fibromyalgia. Further, we comment on several aspects of fibromyalgia which support the development of reactive depression, substantially more so than in other chronic pain syndromes. However, while sharing many features with depression, fibromyalgia is associated with somatic comorbidities and absolutely defined by fluctuating spontaneous widespread pain. Fibromyalgia may, therefore, be more appropriately grouped together with other functional pain disorders, while psychologically distressed subgroups grouped additionally or solely with affective spectrum disorders.

Childhood adversity interacts separately with 5-HTTLPR and BDNF to predict lifetime depression diagnosis

The serotonin transporter polymorphism (5-HTTLPR) and the brain-derived neurotrophic factor (BDNF) val66met polymorphism have both been linked to depression symptoms and to depression diagnosis (MDD) in interaction with adversity; there have also been failures to find the effects. We reexamined both interactions for lifetime MDD in a college sample. Lifetime MDD was diagnosed by Structured Clinical Interview for DSM-IV in 133 undergraduates; genotypes for 5-HTTLPR and BDNF were assayed from blood, and self-reports were collected concerning childhood adversity (Risk). 5-HTTLPR interacted with Risk such that Risk predicted less likelihood of MDD among ll carriers and tended to predict greater likelihood of MDD among s carriers. BDNF interacted with Risk such that Risk predicted greater likelihood of MDD among met carriers and did not influence val/val carriers. These two interactions were additive: both were significant in a combined model.

P2RX7 gene is associated consistently with mood disorders and predicts clinical outcome in three clinical cohorts

We investigated the effect of nine candidate genes on risk for mood disorders, hypothesizing that predisposing gene variants not only elevate the risk for mood disorders but also result in clinically significant differences in the clinical course of mood disorders. We genotyped 178 DSM-IV bipolar I and II and 272 major depressive disorder patients from three independent clinical cohorts carefully diagnosed with semistructured interviews and prospectively followed up with life charts for a median of 60 (range 6-83) months. Healthy control subjects (n = 1322) were obtained from the population-based national Health 2000 Study. We analyzed 62 genotyped variants within the selected genes (BDNF, NTRK2, SLC6A4, TPH2, P2RX7, DAOA, COMT, DISC1, and MAOA) against the presence of mood disorder, and in post-hoc analyses, specifically against bipolar disorder or major depressive disorder. Estimates for time ill were based on life charts. The P2RX7 gene variants rs208294 and rs2230912 significantly elevated the risk for a familial mood disorder (OR = 1.35, P = 0.0013, permuted P = 0.06, and OR = 1.44, P = 0.0031, permuted P = 0.17, respectively). The results were consistent in all three cohorts. The same risk alleles predicted more time ill in all cohorts (OR 1.3, 95% CI 1.1-1.6, P = 0.0069 and OR 1.7, 95% CI 1.3-2.3, P = 0.0002 with rs208294 and rs2230912, respectively), so that homozygous carriers spent 12 and 24% more time ill. P2RX7 and its risk alleles predisposed to mood disorders consistently in three independent clinical cohorts. The same risk alleles resulted in clinically significant differences in outcome of patients with major depressive and bipolar disorder.

Poor replication of candidate genes for major depressive disorder using genome-wide association data

Data from the Genetic Association Information Network (GAIN) genome-wide association study (GWAS) in major depressive disorder (MDD) were used to explore previously reported candidate gene and single-nucleotide polymorphism (SNP) associations in MDD. A systematic literature search of candidate genes associated with MDD in case-control studies was performed before the results of the GAIN MDD study became available. Measured and imputed candidate SNPs and genes were tested in the GAIN MDD study encompassing 1738 cases and 1802 controls. Imputation was used to increase the number of SNPs from the GWAS and to improve coverage of SNPs in the candidate genes selected. Tests were carried out for individual SNPs and the entire gene using different statistical approaches, with permutation analysis as the final arbiter. In all, 78 papers reporting on 57 genes were identified, from which 92 SNPs could be mapped. In the GAIN MDD study, two SNPs were associated with MDD: C5orf20 (rs12520799; P=0.038; odds ratio (OR) AT=1.10, 95% CI 0.95-1.29; OR TT=1.21, 95% confidence interval (CI) 1.01-1.47) and NPY (rs16139; P=0.034; OR C allele=0.73, 95% CI 0.55-0.97), constituting a direct replication of previously identified SNPs. At the gene level, TNF (rs76917; OR T=1.35, 95% CI 1.13-1.63; P=0.0034) was identified as the only gene for which the association with MDD remained significant after correction for multiple testing. For SLC6A2 (norepinephrine transporter (NET)) significantly more SNPs (19 out of 100; P=0.039) than expected were associated while accounting for the linkage disequilibrium (LD) structure. Thus, we found support for involvement in MDD for only four genes. However, given the number of candidate SNPs and genes that were tested, even these significant may well be false positives. The poor replication may point to publication bias and false-positive findings in previous candidate gene studies, and may also be related to heterogeneity of the MDD phenotype as well as contextual genetic or environmental factors.

A topographical map of the causal network of mechanisms underlying the relationship between major depressive disorder and coronary heart disease

OBJECTIVE

Major depressive disorder (MDD) and coronary heart disease (CHD) are both clinically important public health problems. Depression is linked with a higher incidence of ischaemic cardiac events and MDD is more prevalent in patients with CHD. No single comprehensive model has yet described the causal mechanisms linking MDD to CHD. Several key mechanisms have been put forward, comprising behavioural mechanisms, genetic mechanisms, dysregulation of immune mechanisms, coagulation abnormalities and vascular endothelial dysfunction, polyunsaturated omega-3 free fatty acid deficiency, and autonomic mechanisms. It has been suggested that these mechanisms form a network, which links MDD and CHD. The aim of this review is to examine the causal mechanisms underlying the relationship between MDD and CHD, with the aim of constructing a topological map of the causal network which describes the relationship between MDD and CHD.

METHODS

The search term 'depression and heart disease' was entered into an electronic multiple database search engine. Abstracts were screened for relevance and individually selected articles were collated.

RESULTS

This review introduces the first topological map of the causal network which describes the relationship between MDD and CHD.

CONCLUSIONS

Viewing the causal pathways as an interdependent network presents a new paradigm in this field and provides fertile ground for further research. The causal network can be studied using the methodology of systems biology, which is briefly introduced. Future research should focus on the creation of a more comprehensive topological map of the causal network and the quantification of the activity between each node of the causal network.

Influence of 5-HTTLPR polymorphism on resting state perfusion in patients with major depression

Neuroimaging studies in major depressive disorder (MDD) have indicated dysregulation in a network involving prefrontal cortex, subgenual cingulate and the amygdalae, which is known to be modulated by serotonin. The serotonergic system is the principal target for pharmacological treatment in MDD and the functional variable serotonin promoter polymorphism (5-HTTLPR) influences susceptibility, course and treatment response of MDD. Using data from a previously published sample of 89 MDD-patients, we examined post hoc the effect of 5-HTTLPR status on resting state perfusion, as measured with (99m)Tc-HMPAO-SPECT. MDD patients were stratified according to receptor polymorphism, both using a bi-allelic (group A: L/L vs. group B: S/S and S/L genotype) and a tri-allelic approach (Group A': LA/LA vs. Group B': non-LA/LA genotype). There were no significant differences between both subgroups regarding age, gender, severity of depression, medication, or treatment response (p > 0.1). Using the bi-allelic approach, Group B, compared to group A, revealed a significantly higher resting state perfusion in medial prefrontal cortex (p(voxel) (FWE) < 0.05). Additional ROI analyses showed relative overactivity of the amygdalae in group B (p(voxel) (FWE) < 0.05). Similar effects were observed in the tri-allelic approach. The opposite contrasts (Group A > Group B) revealed no significant effects. We demonstrate that in patients with MDD, 5-HTTLPR gene polymorphism modulates resting state perfusion in key structures of mood processing. While the clinical impact of these findings will need to be further investigated in larger cohort studies, the necessity to monitor and to account for individual 5-HTTLPR-status in future MDD imaging studies is highly recommended.

Risk factors for the development of depression in patients with hepatitis C taking interferon-α

Interferon-α, currently used for the treatment of hepatitis C, is associated with a substantially elevated risk of depression. However, not everyone who takes this drug becomes depressed, so it is important to understand what particular factors may make some individuals more 'at risk' of developing depression than others. Currently there is no consensus as to why interferon-induced depression occurs and the range of putative risk factors is wide and diverse. The identification of risk factors prior to treatment may allow identification of patients who will become depressed on interferon, allowing the possibility of improved treatment support and rates of treatment adherence. Here, we consolidate and review the literature on risk factors, and we discuss the potential confounds within the research examined in order to better isolate the risk factors that may be important in the development of depression in these patients and which might help predict patients likely to become depressed on treatment. We suggest that interactions between psychobehavioral, genetic, and biological risk factors are of particular importance in the occurrence of depression in patients with hepatitis C taking interferon-α.

Association between 5-HTTLPR and Borderline Personality Disorder Traits among Youth

This study provides the first genetic association examination of borderline personality disorder (BPD) traits in children and adolescents (ages 9-15) using two independent samples of youth recruited from the general community. We tested the a priori hypothesis that the serotonin transporter promoter gene (5-HTTLPR) would relate specifically to BPD traits in youth. This association was hypothesized based on prior genetic association research with BPD adults and theory positing that emotion dysregulation may be a core risk process contributing to BPD. Youth provided DNA via buccal cells. Both youth and a parent completed self-report measures assessing youth's BPD traits and depressive symptoms. Results from both Study 1 (N = 242) and an independent replication sample of Study 2 (N = 144) showed that carriers of the short allele of 5-HTTLPR exhibited the highest levels of BPD traits. This relation was observed even after controlling for the substantial co-occurrence between BPD traits and depressive symptoms. This specific association between 5-HTTLPR and BPD traits among youth supports previous genetic associations with adults diagnosed with BPD and provides preliminary support for a developmental extension of etiological risk for BPD among youth.