Serotonin transporter function is modulated by brain-derived neurotrophic factor (BDNF) but not nerve growth factor (NGF)

Dynamic changes of serotonin transporter expression in the prefrontal cortex evoked by aggressive social interactions

Aggression is a complex behavior influenced by developmental experiences, internal state, and social context, yet its neurobiological underpinnings remain insufficiently understood. The serotonergic system, particularly the serotonin transporter (SERT), plays a crucial role in aggression regulation. Here, we investigated region-specific, dynamic changes in SERT expression following aggressive interactions and in mice subjected to early-life social adversity. We found that aggressive encounters (resident-intruder test) triggered a significant, rapid increase in SERT immunoreactivity within 90 min, accompanied by neuronal activation in aggression-related brain regions, including the medial prefrontal cortex (mPFC), lateral septum (LS), medial amygdala (MeA), ventromedial hypothalamus (VMHvl), lateral habenula (LH), and dorsal raphe (DR), but not in the paraventricular thalamus (PVT). Notably, this SERT upregulation occurred across the aggression circuitry but was accompanied by a significant increase in 5-HT levels only in the mPFC, a key region in top-down regulation of social and aggressive behavior. This SERT upregulation was not observed following exposure to a non-social challenge, suggesting that it may be more specifically associated with social contexts. Using super-resolution microscopy, we identified an increased density of SERT localization points within serotonergic mPFC axons after an aggressive encounter. Social isolation during adolescence, a model of early social neglect, impaired this rapid SERT response, particularly in the ventral and medial orbitofrontal regions, and altered the relationship between SERT levels and aggression-related behaviors. These findings demonstrate that SERT expression undergoes rapid, experience-dependent plasticity in response to social aggression, and that early-life adversity disrupts this adaptive mechanism, providing new insights into the serotonergic regulation of aggression and its potential relevance for stress-related social dysfunctions.

The Influence of Serotonergic Signaling on Quality of Life, Depression, Insomnia, and Hypoxia in Obstructive Sleep Apnea Patients: Cross-Sectional Study

Background/Objectives: Serotonin and the serotonin transporter (SERT) may have a multifaceted, but not fully understood, role in obstructive sleep apnea (OSA) and its impact on mental health in this group of patients. This study aimed to investigate changes in serotonin and the serotonin transporter (SERT) and their association with depressive and insomnia symptoms. Methods: This study included 76 participants (OSA group: n = 36, control group (CG): n = 40) who underwent polysomnography, while venous blood samples (evening and morning) were analyzed for serotonin and the SERT using ELISA. SERT mRNA expression in peripheral leukocytes was measured via quantitative reverse-transcription polymerase chain reaction (qRT-PCR). Participants were evaluated for depression, insomnia, and quality of life (QoL). Results: This study found no significant differences in SERT mRNA or serotonin between the OSA group and CG. In the CG, individuals without mood disorders had higher baseline SERT levels and evening/morning SERT ratios than those with depression. Among the OSA participants, those with good QoL had elevated serotonin levels in the evening (p = 0.028) and morning (p = 0.043) compared to those with poor QoL. Baseline SERT protein levels were higher in the CG than in the OSA group for insomnia, while SERT mRNA expression was higher in the OSA group. Linear regression models showed 13.3% and 13.1% for non-rapid eye movement sleep (NREM) apnea/hypopnea index (AHI) and AHI variability, respectively, which was accounted for by the morning SERT level, while 30.8% of the arousal index variability was explained by the morning serotonin level. Conclusions: Serotonergic signaling may influence quality of life, depression, and insomnia in OSA, as well as the severity of the disease itself. Stratifying patients by clinical and laboratory phenotypes could enable more personalized treatment.

The dual roles of serotonin in antitumor immunity

Research has shown that a significant portion of cancer patients experience depressive symptoms, often accompanied by neuroendocrine hormone imbalances. Depression is frequently associated with decreased levels of serotonin with the alternate name 5-hydroxytryptamine (5-HT), leading to the common use of selective serotonin reuptake inhibitors (SSRIs) as antidepressants. However, the role of serotonin in tumor regulation remains unclear, with its expression levels displaying varied effects across different types of tumors. Tumor initiation and progression are closely intertwined with the immune function of the human body. Neuroimmunity, as an interdisciplinary subject, has played a unique role in the study of the relationship between psychosocial factors and tumors and their mechanisms in recent years. This article offers a comprehensive review of serotonin's regulatory roles in tumor onset and progression, as well as its impacts on immune cells in the tumor microenvironment. The aim is to stimulate further interdisciplinary research and discover novel targets for tumor treatment.

An insight into crosstalk among multiple signalling pathways contributing to the pathophysiology of PTSD and depressive disorders

Post-traumatic stress disorder (PTSD) and depressive disorders represent two significant mental health challenges with substantial global prevalence. These are debilitating conditions characterized by persistent, often comorbid, symptoms that severely impact an individual's quality of life. Both PTSD and depressive disorders are often precipitated by exposure to traumatic events or chronic stress. The profound impact of PTSD and depressive disorders on individuals and society necessitates a comprehensive exploration of their shared and distinct pathophysiological features. Although the activation of the stress system is essential for maintaining homeostasis, the ability to recover from it after diminishing the threat stimulus is also equally important. However, little is known about the main reasons for individuals' differential susceptibility to external stressful stimuli. The solution to this question can be found by delving into the interplay of stress with the cognitive and emotional processing of traumatic incidents at the molecular level. Evidence suggests that dysregulation in these signalling cascades may contribute to the persistence and severity of PTSD and depressive symptoms. The treatment strategies available for this disorder are antidepressants, which have shown good efficiency in normalizing symptom severity; however, their efficacy is limited in most individuals. This calls for the exploration and development of innovative medications to address the treatment of PTSD. This review delves into the intricate crosstalk among multiple signalling pathways implicated in the development and manifestation of these mental health conditions. By unravelling the complexities of crosstalk among multiple signalling pathways, this review aims to contribute to the broader knowledge base, providing insights that could inform the development of targeted interventions for individuals grappling with the challenges of PTSD and depressive disorders.

How Oxidative Stress Induces Depression?

Depression increasingly affects a wide range and a large number of people worldwide, both physically and psychologically, which makes it a social problem requiring prompt attention and management. Accumulating clinical and animal studies have provided us with substantial insights of disease pathogenesis, especially central monoamine deficiency, which considerably promotes antidepressant research and clinical treatment. The first-line antidepressants mainly target the monoamine system, whose drawbacks mainly include slow action and treatment resistant. The novel antidepressant esketamine, targeting on central glutamatergic system, rapidly and robustly alleviates depression (including treatment-resistant depression), whose efficiency is shadowed by potential addictive and psychotomimetic side effects. Thus, exploring novel depression pathogenesis is necessary, for seeking more safe and effective therapeutic methods. Emerging evidence has revealed vital involvement of oxidative stress (OS) in depression, which inspires us to pursue antioxidant pathway for depression prevention and treatment. Fully uncovering the underlying mechanisms of OS-induced depression is the first step towards the avenue, thus we summarize and expound possible downstream pathways of OS, including mitochondrial impairment and related ATP deficiency, neuroinflammation, central glutamate excitotoxicity, brain-derived neurotrophic factor/tyrosine receptor kinase B dysfunction and serotonin deficiency, the microbiota-gut-brain axis disturbance and hypothalamic-pituitary-adrenocortical axis dysregulation. We also elaborate on the intricate interactions between the multiple aspects, and molecular mechanisms mediating the interplay. Through reviewing the related research progress in the field, we hope to depict an integral overview of how OS induces depression, in order to provide fresh ideas and novel targets for the final goal of efficient treatment of the disease.

Prevalence of Common Alleles of Some Stress Resilience Genes among Adolescents Born in Different Periods Relative to the Socioeconomic Crisis of the 1990s in Russia

Social stress is common among people and is considered one of the causes of the declining birth rate. Predisposition to stress and stress-induced disorders is largely determined genetically. We hypothesized that due to differences in stress resistance, carriers of different genetic variants of genes associated with stress resilience and stress-induced diseases may have dissimilar numbers of offspring under conditions of long-term social stress. To test this hypothesis, a comparative analysis of frequencies of seven common polymorphic regions [exon 3 variable number of tandem repeats (VNTR) of the DRD4 gene, rs4680 of COMT, STin2 VNTR and the 5-HTTLPR (rs774676466) insertion/deletion polymorphism of SLC6A4, rs4570625 of TPH2, rs6265 of BDNF, and rs258747 of NR3C1] was performed on standardized groups of randomly selected adolescents born before, during, and after severe socioeconomic deprivation (the crisis of the 1990s in Russia). There were significant differences in frequencies of "long" alleles of the DRD4 gene (p = 0.020, χ² = 5.492) and rs4680 (p = 0.022, χ² = 5.289) in the "crisis" group as compared to the combined "noncrisis" population. It is possible that the dopaminergic system had an impact on the successful adaptation of a person to social stress.

Participation of the Serotonergic System and Brain-Derived Neurotrophic Factor in the Antidepressant-like Effect of Flavonoids

Depressive disorders are among the most disabling diseases experienced around the world, and their incidence has significantly increased over the last few decades due to multiple environmental, social, and biological factors. The search for new pharmacological alternatives to treat depression is a global priority. In preclinical research, molecules obtained from plants, such as flavonoids, have shown promising antidepressant-like properties through several mechanisms of action that have not been fully elucidated, including crossing of the blood brain barrier (BBB). This review will focus on discussing the main findings related to the participation of the serotonergic system and brain-derived neurotrophic factor (BDNF) on the antidepressant-like effect of some flavonoids reported by behavioral, neurochemical, and molecular studies. In this sense, evidence shows that depressive individuals have low levels of serotonin and BDNF, while flavonoids can reverse it. Finally, the elucidation of the mechanism used by flavonoids to modulate serotonin and BDNF will contribute to our understanding of the neurobiological bases underlying the antidepressant-like effects produced by these natural compounds.

Coadministration of tianeptine alters behavioral parameters and levels of neurotrophins in a chronic model of Maple Syrup Urine disease

Maple Syrup Urine Disease (MSUD) is caused by the deficiency in the activity of the branched-chain α-ketoacid dehydrogenase complex (BCKDC), resulting in the accumulation of the branched-chain amino acids (BCAA) leucine, isoleucine, and valine, and their respective branched-chain α-keto acids. Patients with MSUD are at high risk of developing chronic neuropsychiatric disorders; however, the pathophysiology of brain damage in these patients remains unclear. We hypothesize that MSUD can cause depressive symptoms in patients. To test our hypothesis, Wistar rats were submitted to the BCAA and tianeptine (antidepressant) administration for 21 days, starting seven days postnatal. Depression-like symptoms were assessed by testing for anhedonia and forced swimming after treatments. After the last test, the brain structures were dissected for the evaluation of neutrophins. We demonstrate that chronic BCAA administration induced depressive-like behavior, increased BDNF levels, and decreased NGF levels, suggesting a relationship between BCAA toxicity and brain damage, as observed in patients with MSUD. However, the administration of tianeptine was effective in preventing behavioral changes and restoring neurotrophins levels.

Major Plant in Herbal Mixture Gan-Mai-Da-Zao for the Alleviation of Depression in Rat Models

Gan-Mai-Da-Zao (GMDZ) is a well-known product in Chinese traditional medicine and includes three major plants: blighted wheat (Fu Mai), licorice (Gan Cao), and jujube (Da Zao). GMDZ is widely used as an efficacious and well-tolerated prescription for depression in clinics. The present study was designed to investigate the main plant of GMDZ for its antidepressant-like effect using the unpredictable chronic mild stress (UCMS) model on rats who received an injection with p-chlorophenylalanine (PCPA) to produce the chemical model. In rats subjected to the UCMS model, forced swim tests, open field tests, and sucrose preference tests were applied to estimate the chronic effect of GMDZ. We found that the oral administration of GMDZ for 21 days significantly alleviated the behavior in rats with depression induced by either UCMS or PCPA. The expression levels of the serotonin transporter (5-HTT) and brain-derived neurotrophic factor (BDNF) in the hippocampus of the rats with depression were markedly increased by GMDZ. Additionally, rats that received the herbal mixture without licorice showed a markedly lower response than GMDZ. These results suggest that GMDZ may alleviate the depressive-like behaviors in depressive rats, possibly via licorice (Gan Cao), to increase 5-HTT and BDNF signals in the hippocampus. The present study confirmed the antidepressant-like effects of GMDZ. Additionally, licorice (Gan Cao) may play a key role in the effectiveness of GMDZ.

Crucial Role of Dopamine D2 Receptor Signaling in Nicotine-Induced Conditioned Place Preference

Nicotine in tobacco causes psychological dependence through its rewarding effect in the central nervous system (CNS). Although nicotine dependence is explained by dopamine receptor (DR) signaling together with nicotinic acetylcholine receptors (nAChRs), the synaptic molecular mechanism underlying the interaction between dopamine receptor and nAChRs remains unclear. Since reward signaling is mediated by dopamine receptors, we hypothesized that the dopamine D2 receptor (D2R), in part, mediates the synaptic modulation of nicotine-induced conditioned place preference (CPP) in addition to dopamine D1 receptor. To investigate the involvement of D2R, wild-type (WT) and dopamine D2 receptor knockout (D2RKO) mice were assessed using the CPP task after induction of nicotine-induced CPP. As expected, D2RKO mice failed to induce CPP behaviors after repeated nicotine administration (0.5 mg/kg). When kinase signaling was assessed in the nucleus accumbens and hippocampal CA1 region after repeated nicotine administration, both Ca²⁺/calmodulin-dependent protein kinase (CaMKII) and extracellular signal-regulated kinase (ERK) were upregulated in WT mice but not in D2RKO mice. Likewise, nicotine-induced CPP was associated with elevation of pro- brain-derived neurotropic factor (BDNF) and BDNF protein levels in WT mice, but not in D2RKO mice. Taken together, in addition to dopamine D1 receptor signaling, dopamine D2 receptor signaling is critical for induction of nicotine-induced CPP in mice.

Social isolation and social support at adulthood affect epigenetic mechanisms, brain-derived neurotrophic factor levels and behavior of chronically stressed rats

Epigenetic modulation of brain-derived neurotrophic factor (BDNF) provides one possible explanation for the dysfunctions induced by stress, such as psychiatric disorders and cognitive decline. Interestingly, social support can be protective against some of these effects, but the mechanisms of social buffering are poorly understood. Conversely, early isolation exacerbates the responses to stressors, although its effects in adulthood remain unclear. This study investigated the effects of social isolation and social buffering on hippocampal epigenetic mechanisms, BDNF levels and behavioral responses of chronically stressed young adult rats. Male Wistar rats (3 months) were assigned to accompanied (paired) or isolated housing. After one-month half of each group was submitted to a chronic unpredictable stress (CUS) protocol for 18 days. Among accompanied animals, only one was exposed to stress. Behavioral analysis encompassed the Open field, plus maze and inhibitory avoidance tasks. Hippocampal H3K9 and H4K12 acetylation, HDAC5 expression and BDNF levels were evaluated. Isolated housing increased HDAC5 expression, decreased H3K9 and H4K12 acetylation, reduced BDNF levels, and impaired long-term memory. Stress affected weight gain, induced anxiety-like behavior and decreased AcK9H3 levels. Interactions between housing conditions and social stress were seen only for HDAC5 expression, which showed a further increase in the isolated + CUS group but remained constant in accompanied animals. In conclusion, social isolation at adulthood induced epigenetic alterations and exacerbated the effects of chronic stress on HDAC5. Notwithstanding, social support counteracted the adverse effects of stress on HDAC5 expression.

BDNF mediates the protective effects of scopolamine in reserpine-induced depression-like behaviors via up-regulation of 5-HTT and TPH1

Reserpine treatment in rodents has been shown to induce depression-like behaviors that mimic monoamine dysfunction implicated in the development of depression. Herein, we aimed to demonstrate the antidepressant-like activities of scopolamine, the muscarinic receptor antagonist, in a reserpine-induced mouse model. Mice were injected with 1.5 mg/kg (i.p.) of reserpine for 10 days, and the depression-like state was confirmed via the open field test (OFT) and forced swimming test (FST). Then, the mice were treated with scopolamine (25 µg/kg, i.p.) or saline for 3 days. Ten days of reserpine treatment resulted in a significant decrease in locomotor activity and an increase in immobility time in the OFT and FST, respectively, indicating that ten days of reserpine administration significantly induced depression-like behaviors in mice. However, scopolamine rapidly ameliorated the increase in immobility time in the FST and had no effect on locomotor activity in the OFT. In addition, the reserpine-induced decreases in serotonin transporter (5-HTT), brain-derived neurotrophic factor (BDNF) and tryptophan hydroxylase 1 (TPH1) in mouse hippocampus and prefrontal cortex (PFC) were significantly reversed by scopolamine. Our study provides evidence that scopolamine rapidly attenuates reserpine-induced depression in mice partially by regulating 5-HTT, BDNF and TPH1 in the hippocampus and PFC of mice.

BDNF gene and obsessive compulsive disorder risk, symptom dimensions and treatment response

AIM

Genetic etiology of Obsessive Compulsive Disorder (OCD) has been investigated extensively, with mixed results across candidate gene studies. The dimensional subtypes of OCD are shown to better correlate with brain imaging endophenotypes and thus could potentially enhance the power of genetic association. In this study, we perform a case control analysis of association of a single nucleotide polymorphism rs6265(Val66Met) in Brain Derived Neurotrophic Factor gene, that has been previously implicated in a variety of psychiatric syndromes, and examine its association with symptom dimensions of OCD.

METHODS

Individuals diagnosed to have OCD (n=377) and controls (n=449) of South Indian origin were genotyped for polymorphism rs6265 (196G/A, Val66Met). Detailed phenotypic assessment of the cases were carried out in the cases using structured instruments. The genotypic association was tested for clinical variables such as age of onset, gender, family history, co-morbidity, treatment response, and factor analyzed OCD symptom dimensions.

RESULTS

The allele 'A' frequency was found to be significantly higher in the controls, as compared to cases suggesting a protective effect. The contamination/washing symptom dimension score was significantly lower in carriers of 'A' allele which remained significant even after testing for confounding effects on linear regression.

CONCLUSIONS

Our results support findings from previous studies on a possible protective effect of the 'Met' allele at the Val66Met locus in OCD. Its association with lower scores on the contamination/washing dimension is a novel finding of this study.

The effects of 5-HTTLPR and BDNF Val66Met polymorphisms on neurostructural changes in major depressive disorder

The serotonin-transporter-linked polymorphic region (5-HTTLPR) and brain-derived neurotrophic factor (BDNF) Val66Met polymorphism have been implicated in the pathophysiology of major depressive disorder (MDD). We aimed to investigate the effects of genetic variants of the 5-HTTLPR and BDNF Val66Met polymorphisms and their interactions with MDD on cortical volume and white matter integrity. Ninety-five patients with MDD and 65 healthy participants aged 20-65 years were recruited. The subjects were genotyped for the 5-HTTLPR and BDNF Val66Met polymorphisms and scanned with T1-weighted and diffusion tensor imaging. The gray matter volumes of 24 gyri in the prefrontal and anterior cingulate cortices and the fractional anisotropy values of nine white matter tracts in both hemispheres were determined. In the pooled sample of subjects from both groups, 5-HTTLPR L-allele carriers had significantly decreased cortical volume in the right anterior midcingulate gyrus compared to S-allele homozygotes. A significant effect of the interaction of the BDNF Val66Met polymorphism and MDD on the fractional anisotropy values of the right uncinate fasciculus was observed. Our results suggested that these genetic polymorphisms play important roles in the neurostructural changes of emotion-processing regions in subjects with MDD.

Association of Brain-derived neurotrophic factor gene polymorphisms with body mass index: A systematic review and meta-analysis

BACKGROUND

Many studies with inconsistent results have assessed the association of Brain-derived neurotrophic factor (BDNF) gene polymorphisms with prevalence of obesity and overweight. This review aims to provide a summary of the literature evaluating the relation between BDNF genotype and body mass index (BMI).

METHODS

A systematic search through PubMed, Scopus, Science direct, Ovid and Cochrane was performed. We included observational studies with cross-sectional and case-control design, which investigated relationship between all kinds of BDNF polymorphisms with BMI, as a representative index of obesity and overweight. Newcastle-Ottawa Scale was used to assess the quality of included articles.

RESULTS

Thirty five studies were included in quantitative synthesis. Analyses were performed separately using OR, β coefficient and mean. Significant association were documented between rs925946 and BMI (OR=1.12, 95% CI=1.08-1.17, P heterogeneity=0.317), rs10501087 and BMI (OR=1.14, 95% CI=1.04-1.24, P heterogeneity=0.861), rs6265 and BMI (OR=1.13, 95% CI=1.07-1.19, P heterogeneity=0.406), rs988712 and BMI (OR=1.29, 95% CI=1.18-1.40, P heterogeneity=0.602). According to pooled β coefficient analysis, significant result was only observed in the rs925946 polymorphism subgroup. Pooled mean analysis showed that overall effects for the association between BDNF polymorphisms and BMI were not statistically significant.

CONCLUSION

This meta-analysis suggests that some polymorphisms in BDNF gene including rs925946, rs10501087, rs6265 and rs988712 can be considered as genetic determinants of obesity.

Methylene Blue (Tetramethylthionine Chloride) Influences the Mobility of Adult Neural Stem Cells: A Potentially Novel Therapeutic Mechanism of a Therapeutic Approach in the Treatment of Alzheimer's Disease

An interest in neurogenesis in the adult human brain as a relevant and targetable process has emerged as a potential treatment option for Alzheimer's disease and other neurodegenerative conditions. The aim of this study was to investigate the effects of tetramethylthionine chloride (methylene blue, MB) on properties of adult murine neural stem cells. Based on recent clinical studies, MB has increasingly been discussed as a potential treatment for Alzheimer's disease. While no differences in the proliferative capacity were identified, a general potential of MB in modulating the migratory capacity of adult neural stem cells was indicated in a cell mobility assay. To our knowledge, this is the first time that MB could be associated with neural mobility. The results of this study add insight to the spectrum of features of MB within the central nervous system and may be helpful for understanding the molecular mechanisms underlying a potential therapeutic effect of MB.

Prefrontal cortex modulates the correlations between brain-derived neurotrophic factor level, serotonin, and the autonomic nervous system

Top-down regulation in the human brain and anatomical connections between the prefrontal cortex (PFC) and specific catecholamine-related regions have been well-studied. However, the way in which the PFC modulates downstream neuro-networks in terms of serotonin and the autonomic nervous system (ANS) by variation in the level of brain-derived neurotrophic factor (BDNF) is still unclear. We recruited sixty-seven healthy subjects. Serotonin transporter (SERT) availability was examined by SPECT with [¹²³I]ADAM analysis; heart rate variability (HRV) testing was performed, and the BDNF level was measured. The Wisconsin card-sorting test (WCST), which assesses PFC activation, was also conducted. The interactions of BDNF level and SERT availability were significant in relation to the HRV indexes of low frequency, high frequency, total power, and mean heart rate range. Moderate to significant positive correlations between SERT availability and the above-mentioned HRV indexes existed only in subjects with a low BDNF level. Furthermore, in the low BDNF level group, only those with high WCST perseveration errors or low category completions exhibited significant positive correlations between SERT availability and HRV indexes. A lower BDNF level and poorer PFC function might modulate the synergistic effects of serotonergic and ANS systems in order to maintain brain physiological and psychological homeostasis.

Increased Serum G Protein-coupled Estrogen Receptor 1 Levels and Its Diagnostic Value in Drug Naïve Patients with Major Depressive Disorder

Objective

The facts that depression is more prevalent in females than in males and females are exposed to depression more commonly during certain hormonal fluctuating periods indicate the role of sex hormones in physiopathology. Estrogen acts over estrogen receptors alpha and beta and recently identified G protein-coupled estrogen receptor 1 (GPER1). The present study aimed, for the first time, to evaluate serum GPER1 levels in drug-naïve major depressive disorder (MDD) patients.

Methods

The study included 56 newly diagnosed drug-naïve MDD patients aged between 18 and 50 years and 42 age- and gender-matched healthy volunteers. Medical history was obtained and physical examinations, laboratory tests, and the Hamilton Depression Rating Scale (HAM-D), Hamilton Anxiety Rating Scale (HAM-A) were performed. The serum GPER1 levels were measured.

Results

The HAM-D score was significantly higher in the MDD patients than in the controls. The GPER1 level was significantly higher in the MDD patients than in the controls. A positive correlation was found with GPER1 levels and depression scores. The receiver operating characteristic analysis revealed sensitivity, specificity, positive predictive value, and negative predictive value as 82.1%, 90.5%, 92.0%, and 79.2%, respectively, for the presence of depression, when the serum GPER1 value was ≥0.16.

Conclusion

This study demonstrated significantly higher serum GPER1 levels in the MDD patients than in the controls, a positive correlation was found between GPER1 levels and depression scores and serum GPER1 level was valuable in predicting the presence of depression.

Pleiotropy of genetic variants on obesity and smoking phenotypes: Results from the Oncoarray Project of The International Lung Cancer Consortium

Obesity and cigarette smoking are correlated through complex relationships. Common genetic causes may contribute to these correlations. In this study, we selected 241 loci potentially associated with body mass index (BMI) based on the Genetic Investigation of ANthropometric Traits (GIANT) consortium data and calculated a BMI genetic risk score (BMI-GRS) for 17,037 individuals of European descent from the Oncoarray Project of the International Lung Cancer Consortium (ILCCO). Smokers had a significantly higher BMI-GRS than never-smokers (p = 0.016 and 0.010 before and after adjustment for BMI, respectively). The BMI-GRS was also positively correlated with pack-years of smoking (p<0.001) in smokers. Based on causal network inference analyses, seven and five of 241 SNPs were classified to pleiotropic models for BMI/smoking status and BMI/pack-years, respectively. Among them, three and four SNPs associated with smoking status and pack-years (p<0.05), respectively, were followed up in the ever-smoking data of the Tobacco, Alcohol and Genetics (TAG) consortium. Among these seven candidate SNPs, one SNP (rs11030104, BDNF) achieved statistical significance after Bonferroni correction for multiple testing, and three suggestive SNPs (rs13021737, TMEM18; rs11583200, ELAVL4; and rs6990042, SGCZ) achieved a nominal statistical significance. Our results suggest that there is a common genetic component between BMI and smoking, and pleiotropy analysis can be useful to identify novel genetic loci of complex phenotypes.

The role of 5-HT receptors in depression

Depression is a polygenic and highly complex psychiatric disorder that remains a major burden on society. Antidepressants, such as selective serotonin reuptake inhibitors (SSRIs), are some of the most commonly prescribed drugs worldwide. In this review, we will discuss the evidence that links serotonin and serotonin receptors to the etiology of depression and the mechanisms underlying response to antidepressant treatment. We will then revisit the role of serotonin in three distinct hypotheses that have been proposed over the last several decades to explain the pathophysiology of depression: the monoamine, neurotrophic, and neurogenic hypotheses. Finally, we will discuss how recent studies into serotonin receptors have implicated specific neural circuitry in mediating the antidepressant response, with a focus being placed on the hippocampus.

Association of brain-derived neurotrophic factor valine to methionine polymorphism with sexual dysfunction following selective serotonin reuptake inhibitor treatment in female patients with major depressive disorder

INTRODUCTION

The occurrence of female sexual dysfunction (FSD) in patients with major depressive disorder (MDD) receiving selective serotonin reuptake inhibitors (SSRIs) treatment gives negative impacts on patients' quality of life and causes treatment discontinuation. We aimed to investigate whether genetic polymorphism of identified candidate gene is associated with FSD in our study population.

METHODS

This is a cross-sectional study. A total of 95 female patients with MDD who met the criteria of the study were recruited and were specifically assessed on the sexual function by trained psychiatrists. Patients' DNA was genotyped for BDNF Val66Met polymorphism using real-time polymerase chain reaction.

RESULTS

The prevalence of FSD in this study is 31.6%. In the FSD group, patients with problematic marriage were significantly more frequent compared with patients who did not have problematic marriage (P = 0.009). Significant association was detected in the lubrication domain with BDNF Val66Met polymorphism (P = 0.030) using additive genetic model, with even stronger association when using the recessive model (P = 0.013).

DISCUSSION

This study suggested that there was no significant association between BDNF Val66Met with FSD. However, this polymorphism is significantly associated with lubrication disorder in patients treated with SSRIs.

Behavioral, morphometric, and gene expression effects in adult zebrafish (Danio rerio) embryonically exposed to PFOA, PFOS, and PFNA

Perfluoroalkylated substances (PFAS) are a class of persistent anthropogenic chemicals that have been detected worldwide. PFASs consist of fluorinated carbon chains of varying length, terminal groups, and have a number of industrial uses. A previous zebrafish study from our laboratory showed that acute (3-120h post fertilization, 0.02-2.0μM), waterborne embryonic exposure to these chemicals resulted in chemical specific alterations at 5days post fertilization (dpf), and some effects persisted up to 14 dpf. Using a gene battery consisting of 100 transcripts identified several genes that were up or down regulated. This current study looks at the long-term impacts of PFASs in adult zebrafish using the same exposure regimen. It was hypothesized that sub-lethal exposure of perfluorooctane sulfonate (PFOS), perfluorononanoic acid (PFNA), or perfluorooctane sulfonate (PFOA) in embryonic zebrafish (3-120 hpf) would result in permanent morphometric, gene expression, and behavioral changes in adult fish similar to those observed at 5 and 14 dpf. Zebrafish were exposed to PFOS, PFOA, and PFNA (Control 0μM, 2.0μM) for the first five days post fertilization. At six months post fertilization, no PFAS treatment resulted in a significant change in total body length or weight. In terms of behavior, PFNA males showed a reduction in total distance traveled and time of immobility, and an increase in thigmotaxis behavior, aggressive attacks, and preference for the bright section of the tank. PFOS treated males had a reduced aggression behavior, and PFOA females preferred the dark section of the tank. Gene expression of slco2b1, slco1d1, and tgfb1a were analyzed because these transcripts were previously found to be affected by PFAS exposure in 5dpf and 14 dpf zebrafish and resulted in: significant decrease in expression of slco2b1 for both sexes in PFNA and PFOS treated groups, significant decrease of slco1d1 in all treatment groups for females and PFOS and PFOA exposed males, significant increase of tgfb1a in males treated with PFOS and PFNA, and a significant increase of bdnf in all PFAS male groups. This study demonstrates that acute, embryonic exposure (5days) to individual PFASs result in significant biochemical and behavioral changes in young adult zebrafish 6 months after exposure. These three PFASs have long term and persistent impacts following short term embryonic exposure that persists into adulthood.

Do obsessive-compulsive disorder and Tourette syndrome share a common susceptibility gene? An association study of the BDNF Val66Met polymorphism in the Chinese Han population

OBJECTIVES

We explored the association between the BDNF Val66Met polymorphism and susceptibility to both obsessive-compulsive disorder (OCD) and Tourette syndrome (TS) in the Chinese Han population.

METHODS

Genotyping for the BDNF Val66Met polymorphism was performed in 321 OCD patients and 426 healthy control subjects and case-control association study data were analysed. Additionally, we evaluated the genetic contribution of this variant in 331 TS patients (including 267 TS trios) and 519 controls using the transmission disequilibrium test (TDT) and case-control study.

RESULTS

A statistically significant difference was found in the genetic contribution of the BDNF Val66Met polymorphism between both the OCD (χ(2) = 7.50, P = 0.023 by genotype; χ(2) = 6.67, P = 0.01 by allele) and TS (χ(2) = 6.76, P = 0.03 by genotype; χ(2) = 4.27, P = 0.04 by allele), and control groups. TDT and GHRR analysis for TS trios also showed a significant transform disequilibrium of this polymorphism (TDT: χ(2) = 3.96, P = 0.05; HHRR: χ(2) = 4.33 P = 0.04; GHRR: χ(2) = 5.74, P = 0.02; χ(2) = 0.98, P = 0.37). There was also a significant gender trend between patients and controls in female cases for OCD and in male cases for TS.

CONCLUSIONS

Our study supports the involvement of the BDNF Val66Met polymorphism as a common genetic susceptibility for OCD and TS in the Chinese Han population, showing specific gender trends.

Brain-Derived Neurotrophic Factor Gene Val66Met Polymorphism Is a Risk Factor for Attention-Deficit Hyperactivity Disorder in a Turkish Sample

OBJECTIVE

Attention-deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder that negatively affects different areas of life. We aimed to evaluate the associations between the Val66Met polymorphism of brain-derived neurotrophic factor (BDNF) and ADHD and to assess the effect of the BDNF polymorphism on the neurocognitive profile and clinical symptomatology in ADHD.

METHODS

Two hundred one ADHD cases and 99 typically developing subjects (TD) between the ages of 8 and 15 years were involved in the study. All subjects were evaluated using a complete neuropsychological battery, Child Behavior Checklist, the Teacher's Report Form (TRF) and the DSM-IV Disruptive Behavior Disorders Rating Scale-teacher and parent forms.

RESULTS

The GG genotype was significantly more frequent in the patients with ADHD than in the TD controls, and the GG genotype was also significantly more frequent in the ADHD-combined (ADHD-C) subtype patients than in the TDs. However, there were no significant associations of the BDNF polymorphism with the ADHD subtypes or neurocognitive profiles of the patients. The teacher-assessed hyperactivity and inattention symptom count and the total score were higher, and the appropriately behaving subtest score of the TRF was lower in the GG genotypes than in the GA and AA (i.e., the A-containing) genotypes.

CONCLUSION

We found a positive association between the BDNF gene Val66Met polymorphism and ADHD, and this association was observed specifically in the ADHD-C subtype and not the ADHD-predominantly inattentive subtype. Our findings support that the Val66Met polymorphism of BDNF gene might be involved in the pathogenesis of ADHD. Furthermore Val66Met polymorphism of BDNF gene may be more closely associated with hyperactivity rather than inattention.

Human dermal fibroblasts in psychiatry research

In order to decipher the disease etiology, progression and treatment of multifactorial human brain diseases we utilize a host of different experimental models. Recently, patient-derived human dermal fibroblast (HDF) cultures have re-emerged as promising in vitro functional system for examining various cellular, molecular, metabolic and (patho)physiological states and traits of psychiatric disorders. HDF studies serve as a powerful complement to postmortem and animal studies, and often appear to be informative about the altered homeostasis in neural tissue. Studies of HDFs from patients with schizophrenia (SZ), depression, bipolar disorder (BD), autism, attention deficit and hyperactivity disorder and other psychiatric disorders have significantly advanced our understanding of these devastating diseases. These reports unequivocally prove that signal transduction, redox homeostasis, circadian rhythms and gene*environment (G*E) interactions are all amenable for assessment by the HDF model. Furthermore, the reported findings suggest that this underutilized patient biomaterial, combined with modern molecular biology techniques, may have both diagnostic and prognostic value, including prediction of response to therapeutic agents.

Meta-analysis of the association of brain-derived neurotrophic factor Val66Met polymorphism with obsessive-compulsive disorder

OBJECTIVE

Brain-derived neurotrophic factor (BDNF) plays an important role in neural survival and was proposed to be related to psychiatric disorders. Val66Met (also known as rs6265 or G196A), the only known functional polymorphism of the BDNF gene, has been widely studied and considered to be associated with risk of some psychiatric disorders such as bipolar disorder and schizophrenia. However, studies evaluating its association with obsessive-compulsive disorder (OCD) obtained inconsistent results. The purpose of this study was to derive a more precise estimation of the association between BDNF Val66Met polymorphism and OCD susceptibility by a meta-analysis.

METHOD

We carried a structured literature search in PubMed, Embase, PsycINFO and Chinese Biomedical Database up to December 2014; and retrieved all eligible case-control studies according to the including criteria. Meta-analysis was performed for four genetic models: allelic model: Met versus Val; additive model: Met/Met versus Val/Val; recessive model: Met/Met versus Val/Val+Val/Met; and dominant model: Val/Met+Met/Met versus Val/Val. Stratified analyses were performed by ethnicity and gender where appropriate.

RESULTS

A total of eight articles with nine studies including 1632 OCD cases and 2417 controls were identified. No significant association was detected in any comparison when the whole data were pooled together or stratified by ethnicity or gender in all four genetic models (p>0.05 for each comparison).

CONCLUSION

Despite some limitations, our meta-analysis suggests that no significant association exists between the BDNF Val66Met polymorphism and OCD susceptibility.

Harm avoidance involved in mediating the association between nerve growth factor (NGF) gene polymorphisms and antidepressant efficacy in patients with major depressive disorder

BACKGROUND

Antidepressants have variable efficacies in subjects with major depressive disorder (MDD). Nerve growth factor (NGF) has been suggested to play an important role in the pathogenesis of depressive symptoms and the response to antidepressant therapy. The aim of this study was to examine whether NGF gene polymorphisms are associated with the antidepressant therapeutic efficacy in subjects with MDD.

METHODS

A naturalistic follow-up study was carried out on 557 subjects with MDD. Of the enrolled patients, 304 completed the 8-week open-label antidepressant treatment. Seven single-nucleotide polymorphisms (SNPs) of the NGF gene were genotyped. The 21-item Hamilton Depression Rating Scale was used to assess depressive severity from baseline to endpoint. Tridimensional Personality Questionnaire was used to assess baseline personality traits. Single marker and haplotype analyses were conducted. Binary logistic regression was used to calculate odds ratios of remission. Structural equation modeling was used to analyze the predicted mediation effect.

RESULTS

A significant difference in genotype frequencies between remitters and non-remitters was observed in three NGF SNPs (rs12760036, rs7523654, and rs17033692). The haplotype analysis revealed that the CCC haplotype (rs2254527-rs6678788-rs12760036) was associated with a higher remission rate, while the CCA haplotype was associated with a lower remission rate. The harm avoidance psychological factor partially mediated the effect of NGF variants on antidepressant efficacy.

LIMITATIONS

The selected SNPs may not cover whole NGF gene.

CONCLUSIONS

NGF variants are associated with remission rates after 8-week antidepressant treatment, and harm avoidance partially mediated the effect of NGF variants on treatment outcomes.

The BDNF gene Val66Met polymorphism as a modifier of psychiatric disorder susceptibility: progress and controversy

Brain-derived neurotrophic factor (BDNF) has a primary role in neuronal development, differentiation and plasticity in both the developing and adult brain. A single-nucleotide polymorphism in the proregion of BDNF, termed the Val66Met polymorphism, results in deficient subcellular translocation and activity-dependent secretion of BDNF, and has been associated with impaired neurocognitive function in healthy adults and in the incidence and clinical features of several psychiatric disorders. Research investigating the Val66Met polymorphism has increased markedly in the past decade, and a gap in integration exists between and within academic subfields interested in the effects of this variant. Here we comprehensively review the role and relevance of the Val66Met polymorphism in psychiatric disorders, with emphasis on suicidal behavior and anxiety, eating, mood and psychotic disorders. The cognitive and molecular neuroscience of the Val66Met polymorphism is also concisely reviewed to illustrate the effects of this genetic variant in healthy controls, and is complemented by a commentary on the behavioral neuroscience of BDNF and the Val66Met polymorphism where relevant to specific disorders. Lastly, a number of controversies and unresolved issues, including small effect sizes, sampling of allele inheritance but not genotype and putative ethnicity-specific effects of the Val66Met polymorphism, are also discussed to direct future research.

Akt-mediated regulation of antidepressant-sensitive serotonin transporter function, cell-surface expression and phosphorylation

The present study is focused on the cellular basis for Akt-mediated SERT regulation. SERT has been implicated in mood disorders. SERT is a primary target for antidepressants used in the therapeutic intervention of psychiatric disorders.

Association between smoking, nicotine dependence, and BDNF Val66Met polymorphism with BDNF concentrations in serum

INTRODUCTION

Nicotine use is associated with the upregulation of brain-derived neurotrophic factor (BDNF) in serum. An association between smoking and the BDNF Val(66)Met polymorphism has also been found. The aim of this study is to examine the levels of serum BDNF in never-smokers, former smokers, and current smokers-with and without nicotine dependence-and to examine the interaction of the polymorphism and smoking status with serum BDNF.

METHODS

We used baseline serum and gene data of BDNF on 2,088 participants from the Netherlands Study of Depression and Anxiety (NESDA) to investigate smoking-BDNF association while controlling for potential confounding variables. Nicotine dependence was assessed with the Fagerstrom Test for Nicotine Dependence (FTND).

RESULTS

Smokers with and without nicotine dependence had higher levels of serum BDNF than former and never-smokers. Nicotine dependence and number of cigarettes smoked per day did not add to the prediction of serum BDNF; however, total number of smoking years was a significant predictor of serum BDNF. There was no association of BDNF Val(66)Met, nor an interaction of this polymorphism and smoking status, with serum BDNF.

CONCLUSIONS

Current smoking and higher number of smoking years are associated with higher levels of serum BDNF, and this is independent of the BDNF genotype. Nicotine dependence itself is not associated with a further increase or decrease of serum BDNF. Longitudinal investigations that address changes in serum BDNF in incident smokers and/or in quitters may be useful to understand the association of smoking with BDNF.

BDNF Val66Met and reward-related brain function in adolescents: role for early alcohol consumption

Changes in reward processing have been identified as one important pathogenetic mechanism in alcohol addiction. The nonsynonymous single nucleotide polymorphism in the brain-derived neurotrophic factor (BDNF) gene (rs6265/Val66Met) modulates the central nervous system activity of neurotransmitters involved in reward processing such as serotonin, dopamine, and glutamate. It was identified as crucial for alcohol consumption in healthy adults and, in rats, specifically related to the function in the striatum, a region that is commonly involved in reward processing. However, studies in humans on the association of BDNF Val66Met and reward-related brain functions and its role for alcohol consumption, a significant predictor of later alcohol addiction, are missing. Based on an intermediate phenotype approach, we assessed the early orientation toward alcohol and alcohol consumption in 530 healthy adolescents that underwent a monetary incentive delay task during functional magnetic resonance imaging. We found a significantly lower response in the putamen to reward anticipation in adolescent Met carriers with high versus low levels of alcohol consumption. During reward feedback, Met carriers with low putamen reactivity were significantly more likely to orient toward alcohol and to drink alcohol 2 years later. This study indicates a possible effect of BDNF Val66Met on alcohol addiction-related phenotypes in adolescence.

Acute Administration of Branched-Chain Amino Acids Increases the Pro-BDNF/Total-BDNF Ratio in the Rat Brain

Maple syrup urine disease (MSUD) is caused by an inborn error in metabolism resulting from a deficiency in the branched-chain α-keto acid dehydrogenase complex activity. This blockage leads to accumulation of the branched-chain amino acids (BCAA) leucine, isoleucine and valine, as well as their corresponding α-keto acids and α-hydroxy acids. High levels of BCAAs are associated with neurological dysfunction and the role of pro- and mature brain-derived neurotrophic factor (BDNF) in the neurological dysfunction of MSUD is still unclear. Thus, in the present study we investigated the effect of an acute BCAA pool administration on BDNF levels and on the pro-BDNF cleavage-related proteins S100A10 and tissue plasminogen activator (tPA) in rat brains. Our results demonstrated that acute Hyper-BCAA (H-BCAA) exposure during the early postnatal period increases pro-BDNF and total-BDNF levels in the hippocampus and striatum. Moreover, tPA levels were significantly decreased, without modifications in the tPA transcript levels in the hippocampus and striatum. On the other hand, the S100A10 mRNA and S100A10 protein levels were not changed in the hippocampus and striatum. In the 30-day-old rats, we observed increased pro-BDNF, total-BDNF and tPA levels only in the striatum, whereas the tPA and S100A10 mRNA expression and the immunocontent of S100A10 were not altered. In conclusion, we demonstrated that acute H-BCAA administration increases the pro-BDNF/total-BDNF ratio and decreases the tPA levels in animals, suggesting that the BCAA effect may depend, at least in part, on changes in BDNF post-translational processing.

The role of the brain-derived neurotrophic factor genotype and parenting in early life in predicting externalizing and internalizing symptoms in children with attention-deficit hyperactivity disorder

BACKGROUND

We aimed to determine whether early parenting is associated with externalizing and internalizing symptoms in children with attention-deficit hyperactivity disorder (ADHD) and whether such an association is affected by the brain-derived neurotrophic factor (BDNF) val66met polymorphism.

METHODS

The participants included 92 patients with ADHD aged 6-15 years. Measures of parenting in early life and externalizing and internalizing symptoms and the genotype of the BDNF Val66Met polymorphism were obtained.

RESULTS

The degree to which the baby's autonomy was allowed was significantly and negatively correlated with the CDI scores in ADHD children (r = -0.38, p = 0.005). After adjusting for the child's gender, the child's age, the family's gross annual income, and the maternal education level, there was a significant interaction for the BDNF genotype and mother's positive feelings about caring in relation to the development of childhood anxiety/depression in ADHD children (F = 2.51, p = 0.011).

CONCLUSIONS

Our results provide evidence of an interaction between the BDNF met allele and early parenting on the development of depression/anxiety symptoms.

SLC6A4 polymorphisms and age of onset in late-life depression on treatment outcomes with citalopram: a Sequenced Treatment Alternatives to Relieve Depression (STAR*D) report

OBJECTIVE

Age at onset of first major depressive episode (MDE) does not necessarily translate into different treatment outcomes to antidepressants in late-life depression. The influence of genetic variants may affect this relationship.

DESIGN

Post hoc data set analysis of the association between variants in the promoter region (indel, rs25531) and within intron 2 (Stin2 VNTR) of the SCL6A4 gene and treatment outcomes among older participants in the first treatment arm of the Sequenced Treatment Alternatives to Relieve Depression trial (STAR*D).

SETTING

Participants were enrolled from 23 psychiatric and 18 primary care settings.

PARTICIPANTS

Two hundred twenty-one, white non-Hispanic subjects, aged 60 to 75 years, with 16-item Quick Inventory of Depressive Symptomatology-Clinician Rating (QIDS-CR16) initial score ≥10, and who remained in the study for at least 6 weeks, were genotyped.

INTERVENTION

Citalopram treatment for up to 14 weeks.

MEASUREMENTS

Main outcome was remission rate defined as a score of ≤5 on the QIDS-CR16. Response was a secondary outcome defined as a reduction of ≥50% of baseline QIDS-CR16.

RESULTS

Polymorphism in the indel promoter region was associated with remission among subjects whose first lifetime episode of major depression occurred later than age 55. In this group, subjects with L/L genotype had significantly higher remission (80% versus 43%) compared to those subjects with any other indel promoter genotype. Multivariate analysis demonstrated that the genetic effect of the indel promoter region on remission increases along with age at onset of MDE.

CONCLUSIONS

Variants in the indel promoter region of the SLC6A4 gene have a more robust effect to antidepressant outcome among older subjects who experienced their first MDE at a later age. The mechanism of action of these variants remains to be determined.

Effects of lithium and valproic acid on BDNF protein and gene expression in an in vitro human neuron-like model of degeneration

One of the common effects of lithium (Li) and valproic acid (VPA) is their ability to protect against excitotoxic insults. Neurodegenerative and neuropsychiatric diseases may be also associated with altered trophic support of brain-derived neurotrophic factor (BDNF), the most widely distributed neurotrophin in the central nervous system. However, despite these evidences, the effect of Li-VPA combination on BDNF after excitoxic insult has been inadequately investigated. We address this issue by exposing a human neuroblastoma cell line (SH-SY5Y) to neurotoxic concentration of L-glutamate and exploring whether the neuroprotective action of Li-VPA on these cells is associated with changes in BDNF protein and mRNA levels. The results showed that pre-incubation of Li-VPA abolished the toxic effect of glutamate on SH-SY5Y cell survival and this neuroprotective effect was associated with increased synthesis and mRNA expression of BDNF after 24 and 48 h of incubation. In conclusion, this study demonstrates that the neuroprotective effects of Li-VPA against glutamate-induced neurotoxicity in SH-SY5Y neuroblastoma cells is associated with increased synthesis and mRNA expression of BDNF. These data further support the idea that these two drugs can be used for prevention and/or treatment of glutamate-related neurodegenerative disorders.

An update on the interaction between the serotonin transporter promoter variant (5-HTTLPR), stress and depression, plus an exploration of non-confirming findings

In the three years since the most recent meta-analysis of the association between the serotonin transported promoter polymorphism (5-HTTLPR), stress and the development of depression, another 27 studies have been published on this issue, which is an increase of 50% more studies than were previously reviewed. In addition, previous findings of inconsistency of results across studies argued for further exploration of this relationship. From the 81 studies identified to June 2013, the significant relationship between the short form of the 5-HTTLPR was confirmed (p=.0000009), which is stronger than the relationship reported in the most recent meta-analysis in 2011. However, nearly 26% of the 81 studies reviewed failed to show any significant association between the 5-HTTLPR, stress and depression, and four studies found opposite results to those expected. Examination of the methodologies of all studies failed to indicate any flaws in the opposite or unequivocal studies, and the latter had larger sample sizes than those studies which supported the expected association, arguing that the null results were not an outcome of insufficient statistical power. The need to consider aspects of samples and measures of depression, particularly the presence of subtypes of depression in future research is discussed.

Epigenetic and epistatic interactions between serotonin transporter and brain-derived neurotrophic factor genetic polymorphism: insights in depression

Epidemiological studies have shown significant results in the interaction between the functions of brain-derived neurotrophic factor (BDNF) and 5-HT in mood disorders, such as major depressive disorder (MDD). The latest research has provided convincing evidence that gene transcription of these molecules is a target for epigenetic changes, triggered by stressful stimuli that starts in early childhood and continues throughout life, which are subsequently translated into structural and functional phenotypes culminating in depressive disorders. The short variants of 5-HTTLPR and BDNF-Met are seen as forms which are predisposed to epigenetic aberrations, which leads individuals to a susceptibility to environmental adversities, especially when subjected to stress in early life. Moreover, the polymorphic variants also feature epistatic interactions in directing the functional mechanisms elicited by stress and underlying the onset of depressive disorders. Also emphasized are works which show some mediators between stress and epigenetic changes of the 5-HTT and BDNF genes, such as the hypothalamic-pituitary-adrenal (HPA) axis and the cAMP response element-binding protein (CREB), which is a cellular transcription factor. Both the HPA axis and CREB are also involved in epistatic interactions between polymorphic variants of 5-HTTLPR and Val66Met. This review highlights some research studying changes in the epigenetic patterns intrinsic to genes of 5-HTT and BDNF, which are related to lifelong environmental adversities, which in turn increases the risks of developing MDD.

Genetic, transcriptomic, and epigenetic studies of HIV-associated neurocognitive disorder

The Human Genome Project, coupled with rapidly evolving high-throughput technologies, has opened the possibility of identifying heretofore unknown biological processes underlying human disease. Because of the opaque nature of HIV-associated neurocognitive disorder (HAND) neuropathogenesis, the utility of such methods has gained notice among NeuroAIDS researchers. Furthermore, the merging of genetics with other research areas has also allowed for application of relatively nascent fields, such as neuroimaging genomics, and pharmacogenetics, to the context of HAND. In this review, we detail the development of genetic, transcriptomic, and epigenetic studies of HAND, beginning with early candidate gene association studies and culminating in current "omics" approaches that incorporate methods from systems biology to interpret data from multiple levels of biological functioning. Challenges with this line of investigation are discussed, including the difficulty of defining a valid phenotype for HAND. We propose that leveraging known associations between biology and pathology across multiple levels will lead to a more reliable and valid phenotype. We also discuss the difficulties of interpreting the massive and multitiered mountains of data produced by current high-throughput omics assays and explore the utility of systems biology approaches in this regard.

The longitudinal and interactive effects of HIV status, stimulant use, and host genotype upon neurocognitive functioning

Both human immunodeficiency virus (HIV)-1 infection and illicit stimulant use can adversely impact neurocognitive functioning, and these effects can be additive. However, significant variability exists such that as-of-yet unidentified exogenous and endogenous factors affect one's risk for neurocognitive impairment. Literature on both HIV and stimulant use indicates that host genetic variants in immunologic and dopamine-related genes are one such factor. In this study, the individual and interactive effects of HIV status, stimulant use, and genotype upon neurocognitive functioning were examined longitudinally over a 10-year period. Nine hundred fifty-two Caucasian HIV+ and HIV- cases from the Multicenter AIDS Cohort Study were included. All cases had at least two comprehensive neurocognitive evaluations between 1985 and 1995. Pre-highly active antiretroviral therapy (HAART) data were examined in order to avoid the confounding effect of variable drug regimens. Linear mixed models were used, with neurocognitive domain scores as the outcome variables. No four-way interactions were found, indicating that HIV and stimulant use do not interact over time to affect neurocognitive functioning as a function of genotype. Multiple three-way interactions were found that involved genotype and HIV status. All immunologically related genes found to interact with HIV status affected neurocognitive functioning in the expected direction; however, only C-C chemokine ligand 2 (CCL2) and CCL3 affected HIV+ individuals specifically. Dopamine-related genetic variants generally affected HIV-negative individuals only. Neurocognitive functioning among HIV+ individuals who also used stimulants was not significantly different from those who did not use stimulants. The findings support the role of immunologically related genetic differences in CCL2 and CCL3 in neurocognitive functioning among HIV+ individuals; however, their impact is minor. Being consistent with findings from another cohort, dopamine (DA)-related genetic differences do not appear to impact the longitudinal neurocognitive functioning of HIV+ individuals.

Psychophysiology of dissociated consciousness

Recent study of consciousness provides an evidence that there is a limit of consciousness, which presents a barrier between conscious and unconscious processes. This barrier likely is specifically manifested as a disturbance of neural mechanisms of consciousness that through distributed brain processing, attentional mechanisms and memory processes enable to constitute integrative conscious experience. According to recent findings a level of conscious integration may change during certain conditions related to experimental cognitive manipulations, hypnosis, or stressful experiences that can lead to dissociation of consciousness. In psychopathological research the term dissociation was proposed by Pierre Janet for explanation of processes related to splitting of consciousness due to traumatic events or during hypnosis. According to several recent findings dissociation of consciousness likely is related to deficits in global distribution of information and may lead to heightened levels of "neural complexity" that reflects brain integration or differentiation based on numbers of independent neural processes in the brain that may be specifically related to various mental disorders.

Allele-specific expression of the serotonin transporter and its transcription factors following lamotrigine treatment in vitro

Lamotrigine, a mood stabilizer used clinically in the treatment of bipolar disorder, is thought to exert actions on the serotonin system. However lamotrigine's exact mechanism of action remains unclear. The current study investigated whether lamotrigine might exert its effects through altering the expression of the serotonin transporter (5-HTT) gene and its regulatory transcription factors Y box binding protein 1 (YB-1) and CCCTC-binding factor (CTCF). We further considered whether functional variable number tandem repeat (VNTR) polymorphisms in the promoter region of 5-HTT, (5-HTTLPR) and within intron 2 (Stin2) of the gene, moderated any putative gene expression changes. The study employed an in vitro design carried out in human lymphoblastoid cell lines (LCLs) to investigate the effects of lamotrigine treatment at 0.04, 0.2, and 0.4 mM doses for 24 hr on the mRNA expression of 5-HTT, YB-1, and CTCF. LCLs were selected based on combinations of haplotypes of the two VNTRs in the serotonin transporter gene; creating low-expressing and high-expressing LCL groups. Ubiquitin C (UBC) and topoisomerase I (TOP1) genes were found to be the most stably expressed housekeeping genes in drug-treated LCLs. Subsequently, quantitative PCR revealed that higher doses of lamotrigine significantly lowered 5-HTT expression and increased CTCF expression. Haplotype-specific differences in CTCF expression were found in response to lamotrigine, with strongest expression changes observed in the high-expressing LCLs. These data provide an allele-specific in vitro model for examining the molecular targets of lamotrigine, and support the important role of the serotonin transporter gene in its clinical mechanism of action.

Interaction between novelty seeking and the aldehyde dehydrogenase 2 gene in heroin-dependent patients

OBJECTIVES

Heroin dependence is a multifactor disorder. We investigated the association of genetic factors and heroin-dependent temperaments to determine whether a temperament-gene interaction is involved in the pathogenesis of heroin dependence.

METHODS

Three hundred seventy participants (259 heroin-dependent patients and 111 healthy controls) were recruited and finished the Tridimensional Personality Questionnaire to assess personality traits (temperament). The genotypes of the aldehyde dehydrogenase 2 (ALDH2) gene and the Val66Met polymorphism of the brain-derived neurotrophic factor (BDNF) gene using polymerase chain reactions plus restriction fragment length polymorphism analysis.

RESULTS

Multiple logistic regression analysis showed significant main effects for novelty seeking (P ≤ 0.001) and harm-avoidance (P = 0.001) scores, and a significant interaction effect between novelty seeking and ALDH2 genotypes (P = 0.016) in heroin-dependent patients compared with controls. When stratified by the ALDH2 genotypes, only heroin-dependent patients with the *1*2 and *2*2 genotypes at ALDH2 had higher novelty-seeking scores than did controls (heroin dependence = 15.94, controls = 12.46; P ≤ 0.001).

CONCLUSIONS

Our results provide initial evidence that the ALDH2 gene interacted with novelty seeking in heroin-dependent Han Chinese patients in Taiwan.

Brain-derived neurotrophic factor serum levels and genotype: association with depression during interferon-α treatment

Depression has been associated with inflammation, and inflammation may both influence and interact with growth factors such as brain-derived neurotrophic factor (BDNF). Both the functional Val66Met BDNF polymorphism (rs6265) and BDNF levels have been associated with depression. It is thus plausible that decreased BDNF could mediate and/or moderate cytokine-induced depression. We therefore prospectively employed the Beck Depression Inventory-II (BDI-II), the Hospital Anxiety and Depression Scale (HADS), and the Montgomery-Asberg Depression Rating Scale (MADRS) in 124 initially euthymic patients during treatment with interferon-alpha (IFN-α), assessing serum BDNF and rs6265. Using mixed-effect repeated measures, lower pretreatment BDNF was associated with higher depression symptoms during IFN-α treatment (F144,17.2=6.8; P<0.0001). However, although the Met allele was associated with lower BDNF levels (F1,83.0=5.0; P=0.03), it was only associated with increased MADRS scores (F4,8.9=20.3; P<0.001), and not the BDI-II or HADS. An exploratory comparison of individual BDI-II items indicated that the Met allele was associated with suicidal ideation, sadness, and worthlessness, but not neurovegetative symptoms. Conversely, the serotonin transporter promoter polymorphism (5-HTTLPR) short allele was associated with neurovegetative symptoms such as insomnia, poor appetite and fatigue, but not sadness, worthlessness, or suicidal ideation. IFN-α therapy further lowered BDNF serum levels (F4,37.7=5.0; P=0.003), but this decrease occurred regardless of depression development. The findings thus do not support the hypothesis that decreasing BDNF is the primary pathway by which IFN-α worsens depression. Nonetheless, the results support the hypothesis that BDNF levels influence resiliency against developing inflammatory cytokine-associated depression, and specifically to a subset of symptoms distinct from those influenced by 5-HTTLPR.

Serotonin uptake is largely mediated by platelets versus lymphocytes in peripheral blood cells

The serotonin transporter (SERT), a primary target for many antidepressants, is expressed in the brain and also in peripheral blood cells. Although platelet SERT function is well accepted, lymphocyte SERT function has not been definitively characterized. Due to their small size, platelets often are found in peripheral blood mononuclear cell preparations aimed at isolating lymphocytes, monocytes, and macrophages. The presence of different cells makes it difficult to assign SERT expression and function to specific cell types. Here, we use flow cytometry and IDT307, a monoamine transporter substrate that fluoresces after uptake into cells, to investigate SERT function in lymphocyte and platelet populations independently, as well as simultaneously without prior isolation. We find that murine lymphocytes exhibit temperature-dependent IDT307 transport but uptake is independent of SERT. Lack of measurable SERT function in lymphocytes was corroborated by chronoamperometry using serotonin as a substrate. When we examined rhesus and human mixed blood cell populations, we found that platelets, and not lymphocytes, were primary contributors to SERT function. Overall, these findings indicate that lymphocyte SERT function is minimal. Moreover, flow cytometry, in conjunction with the fluorescent transporter substrate IDT307, can be widely applied to investigate SERT in platelets from populations of clinical significance.

Association of the Brain-derived Neurotrophic Factor Gene and Clinical Features of Bipolar Disorder in Korea

Objective

Brain-derived neurotrophic factor (BDNF) plays an important role in cell survival, differentiation, and cell death as well as in neural plasticity. Recent studies have suggested that BDNF is involved in the pathogenesis of bipolar disorder. The aim of this study was to investigate the association of the genetic variations of the BDNF gene with bipolar disorder in Korea. We also studied the possible association of these genetic variants with clinical features.

Methods

The allelic and genotypic distributions of Val66Met polymorphism of the BDNF gene were analyzed using a polymerase chain reaction-based method in 184 bipolar patients and 214 controls. Analysis was performed to investigate an association of the Val66Met polymorphism of the BDNF gene and the clinical features in bipolar patients.

Results

No significant difference was found between bipolar patients and controls in the genotype and allele frequencies for the investigated BDNF polymorphism. However, the age of onset of bipolar disorder among the Val/Val (25.57), Val/Met (30.42) and Met/Met (32.45) genotype groups were significantly different (p=0.037).

Conclusion

This study suggests that Val66Met polymorphisms are unlikely to contribution to the genetic predisposition to bipolar disorder as a whole. But Val66Met polymorphism may be associated with age of onset of the disorder, further studies designed to investigate the relationship in a larger population may be warranted.

Is Altered BDNF Biosynthesis a General Feature in Patients with Cognitive Dysfunctions?

Severe cognitive deficits are a frequent outcome of both neurodegenerative and neurodevelopmental disorders. In the attempt to define new clinical biomarkers, current research trends aim at the identification of common molecular features in these pathologies rather than searching for differences. Brain-derived neurotrophic factor (BDNF) has attracted great interest as possible biomarker because of its key role in synaptic remodeling during cognitive processes. BDNF undergoes proteolytic processing and studies in animal models have highlighted that different forms of learning and memory require either the proBDNF precursor or the mature BDNF form. Significantly, an altered expression of BDNF forms was found in postmortem brains and serum from patients with schizophrenia, Alzheimer’s disease and mood disorders. Based on these studies, this review puts forward the hypothesis that abnormalities in proBDNF or mBDNF biosynthesis may correspond to different cognitive dysfunctions in these brain diseases, while the role of truncated BDNF remains unknown.

Interaction of the DRD3 and BDNF gene variants in subtyped bipolar disorder

OBJECTIVES

Bipolar disorder is a severe mental disorder with prominent genetic etiologic factors. Dopaminergic dysfunction has been implicated in the pathogenesis of bipolar disorder, which suggests that the dopamine D3 receptor gene (DRD3) is a strong candidate gene. The brain-derived neurotrophic factor (BDNF) gene has been implicated in the etiology of bipolar disorder. We examined the association between the BDNF Val66Met and DRD3 Ser9Gly polymorphisms with two subtypes of bipolar disorder: bipolar-I and -II. Because BDNF regulates DRD3 expression (1), we also examined possible interactions between these genes.

METHODS

We recruited 964 participants: 268 with bipolar-I, 436 with bipolar-II, and 260 healthy controls. The genotypes of the BDNF Val66Met and DRD3 Ser9Gly polymorphisms were determined using polymerase chain reactions plus restriction fragment length polymorphism analysis.

RESULTS

Logistic regression analysis showed a significant main effect for the Val/Val genotype of the BDNF Val66Met polymorphism (P=0.020), which predicted bipolar-II patients. Significant interaction effects for the BDNF Val66Met Val/Val genotype and both DRD3 Ser9Gly Ser/Ser and Ser/Gly genotypes were found only in bipolar-II patients (P=0.027 and 0.006, respectively).

CONCLUSION

We provide initial evidence that the BDNF Val66Met and DRD3 Ser9Gly genotypes interact only in bipolar-II disorder and that bipolar-I and bipolar-II may be genetically distinct.

The functional epistasis of 5-HTTLPR and BDNF Val66Met on emotion processing: a preliminary study

An epistatic interaction of 5-HTTLPR and BDNF Val66Met polymorphisms has been implicated in the structure of rostral anterior cingulate cortex (rACC) and amygdala (AMY): key regions associated with emotion processing. However, a functional epistasis of 5-HTTLPR and BDNF Val66Met on overt emotion processing has yet to be determined. Twenty-eight healthy, Caucasian female participants provided saliva samples for genotyping and underwent functional magnetic resonance imaging (fMRI) during which an emotion processing protocol were presented. Confirming the validity of this protocol, we observed blood oxygen level-dependent (BOLD) activity consistent with fMRI meta-analyses on emotion processing. Region-of-interest analysis of the rACC and AMY revealed main effects of 5-HTTLPR and BDNF Val66Met, and an interaction of 5-HTTLPR and BDNF Val66Met. The effect of the BDNF Met66 allele was dependent on 5-HTTLPR alleles, such that participants with S and Met alleles had the greatest rACC and AMY activation during the presentation of emotional images relative to other genetic groupings. Increased activity in these regions was interpreted as increased reactivity to emotional stimuli, suggesting that those with S and Met alleles are more reactive to emotional stimuli relative to other groups. Although limited by a small sample, this study contributes novel and preliminary findings relating to a functional epistasis of the 5-HTTLPR and BDNF Val66Met genes in emotion processing and provides guidance on appropriate methods to determine genetic epistasis in fMRI.

COMT and BDNF interacted in bipolar II disorder not comorbid with anxiety disorder

Bipolar disorder (BP), especially bipolar II disorder (BP-II), is highly comorbid with anxiety disorder (AD). Monoaminergic dysfunction has been implicated in the pathogenesis of BP, it may be important to investigate genes such as the catechol-O-methyltransferase (COMT), involved in monoamine metabolism and brain-derived neurotrophic factor (BDNF) genes, modulating the monoamine system. We therefore examined the association of the COMT Val158Met and BDNF Val66Met polymorphisms with BP-II with and without comorbidity of AD, and possible interactions between these genes. Seven hundred and seventy-one participants were recruited: 314 with bipolar-II without AD, 117 with bipolar-II with AD, and 340 healthy controls. The genotypes of the COMT and BDNF polymorphisms were determined using polymerase chain reactions plus restriction fragment length polymorphism analysis. Logistic regression analysis showed a significant effect of the COMT and the BDNF polymorphisms, and a significant interaction effect for the Val/Val genotypes of the BDNF Val66Met polymorphism and the COMsT Val158Met Val/Met and Met/Met genotypes (P=0.007, 0.048) discriminated between BP-II without AD patients and controls. Our findings provide initial evidence that the COMT and BDNF genes interact in bipolar-II without AD. Our findings suggest the involvement of dopaminergic pathway in the pathogenesis of bipolar-II.