Effects of serotonin transporter promoter polymorphisms on serotonin function

Understanding the effects of serotonin in the brain through its role in the gastrointestinal tract

The neuromodulatory arousal system imbues the nervous system with the flexibility and robustness required to facilitate adaptive behaviour. While there are well-understood mechanisms linking dopamine, noradrenaline and acetylcholine to distinct behavioural states, similar conclusions have not been as readily available for serotonin. Fascinatingly, despite clear links between serotonergic function and cognitive capacities as diverse as reward processing, exploration, and the psychedelic experience, over 95% of the serotonin in the body is released in the gastrointestinal tract, where it controls digestive muscle contractions (peristalsis). Here, we argue that framing neural serotonin as a rostral extension of the gastrointestinal serotonergic system dissolves much of the mystery associated with the central serotonergic system. Specifically, we outline that central serotonin activity mimics the effects of a digestion/satiety circuit mediated by hypothalamic control over descending serotonergic nuclei in the brainstem. We review commonalities and differences between these two circuits, with a focus on the heterogeneous expression of different classes of serotonin receptors in the brain. Much in the way that serotonin-induced peristalsis facilitates the work of digestion, serotonergic influences over cognition can be reframed as performing the work of cognition. Extending this analogy, we argue that the central serotonergic system allows the brain to arbitrate between different cognitive modes as a function of serotonergic tone: low activity facilitates cognitive automaticity, whereas higher activity helps to identify flexible solutions to problems, particularly if and when the initial responses fail. This perspective sheds light on otherwise disparate capacities mediated by serotonin, and also helps to understand why there are such pervasive links between serotonergic pathology and the symptoms of psychiatric disorders.

Pharmacogenomics Factors Influencing the Effect of Risperidone on Prolactin Levels in Thai Pediatric Patients With Autism Spectrum Disorder

We investigated the association between genetic variations in pharmacodynamic genes and risperidone-induced increased prolactin levels in children and adolescents with autism spectrum disorder (ASD). In a retrospective study, variants of pharmacodynamic genes were analyzed in 124 ASD patients treated with a risperidone regimen for at least 3 months. To simplify genotype interpretation, we created an algorithm to calculate the dopamine D2 receptor (DRD2) gene genetic risk score. There was no relationship between prolactin levels and single SNPs. However, the H1/H3 diplotype (A2/A2-Cin/Cin-A/G) of DRD2/ankyrin repeat and kinase domain containing 1 (ANKK1) Taq1A, DRD2 -141C indel, and DRD2 -141A>G, which had a genetic risk score of 5.5, was associated with the highest median prolactin levels (23 ng/ml). As the dose-corrected plasma levels of risperidone, 9-OH-risperidone, and the active moiety increased, prolactin levels in patients carrying the H1/H3 diplotype were significantly higher than those of the other diplotypes. DRD2 diplotypes showed significantly high prolactin levels as plasma risperidone levels increased. Lower levels of prolactin were detected in patients who responded to risperidone. This is the first system for describing DRD2 haplotypes using genetic risk scores based on their protein expression. Clinicians should consider using pharmacogenetic-based decision-making in clinical practice to prevent prolactin increase.

Molecular imaging of the serotonin transporter availability and occupancy by antidepressant treatment in late-life depression

Patients with late-life depression (LLD) have a more variable response to pharmacotherapy relative to patients with mid-life depression. Degeneration of the serotonergic system and lower occupancy of the initial target for antidepressant medications, the serotonin transporter (5-HTT), may contribute to variability in treatment response. The focus of this study was to test the hypotheses that lower cortical and limbic serotonin transporter (5-HTT) availability in LLD patients relative to controls and less 5-HTT occupancy by antidepressant medications would be associated with less improvement in mood and cognition with treatment in LLD patients. Twenty LLD patients meeting DSM-IV criteria for a current major depressive episode and 20 non-depressed controls underwent clinical and neuropsychological assessments, magnetic resonance imaging to measure gray matter volumes and high-resolution positron emission tomography (PET) scanning to measure 5-HTT before and after 10-12 weeks of treatment with Citalopram or Sertraline (patients only). Prior to treatment, 5-HTT was lower in LLD patients relative to controls in mainly temporal cortical and limbic (amygdala and hippocampus) regions. Gray matter volumes were not significantly different between groups. 5-HTT occupancy was detected throughout cortical, striatal, thalamic and limbic regions. The magnitude of regional 5-HTT occupancy by antidepressants was 70% or greater across cortical and sub-cortical regions, consistent with the magnitude of 5-HTT occupancy observed in mid-life depressed patients. Greater regional 5-HTT occupancy correlated with greater improvement in depressive symptoms and visual-spatial memory performance. These data support the hypothesis that serotonin degeneration and variability in 5-HTT occupancy may contribute to heterogeneity in treatment response in LLD patients.

A comprehensive assessment of genetic variation in serotonin transporter gene (5-HTTLPR+rs25531) and the response to dapoxetine in Chinese patients with premature ejaculation

This study was to explore whether serotonin transporter gene-linked polymorphic region polymorphisms (5-HTTLPR+rs25531) influence the response to dapoxetine treatment in a Chinese population with premature ejaculation (PE). 112 patients with PE re-enrolled from our previous study received dapoxetine monotherapy. At the endpoint, patients with S'S' had a significant increased risk of nonresponse compared with L' carriers (p < .001). The improvement in S'S' genotype was significantly lower in premature ejaculation profile (PEP) items of 'control over ejaculation' (p = .035) and 'distress related to ejaculation' (p = .017) than that in L' carriers. As to clinical global impression of change (CGIC), results in S'S' subjects showed significantly lower scores (p = .008) and a less satisfaction rate reporting at least 'better' (p = .020) compared with L' carriers. Moreover, our findings suggested that patients with S'S' were more likely to develop adverse effects (AEs) compared with L' carriers (p = .040). This study suggests that PE patients bearing the S'S' genotype have an inferior comprehensive efficacy and safety of dapoxetine treatment, which consist of poorer response in IELTs, less improvement in patient-reported outcome (PRO) measures and greater incidence of AEs, than L' carriers. Variants of triallelic 5-HTTLPR may play a major role as a predictor of treatment response to dapoxetine.

Psychiatric risk and resilience: Plasticity genes and positive mental health

OBJECTIVE

The at-risk mental state (ARMS) for psychosis has long played a key role in diathesis-stress models of schizophrenia. More recent studies, however, have called for extending the boundaries of the ARMS construct beyond attenuated psychosis in nonhelp-seeking samples to include not only other vulnerability indicators but also protective factors related to genotype, mental health, personality, and cognition.

METHOD

Accordingly, we assessed in a sample of 100 college students, the ARMS construct with the Brief Prodromal Questionnaire (PQ-B) for psychosis, in conjunction with measures of positive mental health, childhood adversity, psychiatric symptoms, personality traits, social cognition, and genetic variables derived from assays of the serotonin transporter (5-HTTLPR) and the brain-derived neurotrophic factor (BDNF).

RESULTS

Higher PQ-B scores correlated positively with vulnerability indicators of childhood adversity and heightened levels of a wide variety of psychiatric symptoms but correlated negatively with protective factors of better overall mental health, social cognition as well as with a distinct NEO profile marked by reduced neuroticism and elevated agreeableness and conscientiousness. Multivariate analyses indicated that a composite ARMS measure comprised of PQ-B scores plus anxiety and depression symptoms revealed significant genotype differences, with lowest risk and highest resilience for allelic carriers of 5-HTTLPR-short and BDNF Met polymorphisms.

CONCLUSIONS

Results provided support for extending the ARMS construct, pointing to important contributions of personality, social cognition, and genes that support neural plasticity in mitigating vulnerability and enhancing resilience and well-being.

In search of positive mental health: Personality profiles and genetic polymorphisms

Individuals vary greatly in their mental health and these differences may play a critical role in stress resistance, risk reduction and illness recovery. Here we ask how these differences may be related to normal variation in personality and genotype. One hundred healthy college students completed measures of mental health (Mental Health Continuum-Short Form [MHC-SF]), personality (NEO Five Factor Inventory) and adverse childhood experiences. Participants also provided saliva samples, genotyped for both the serotonin transporter (5-HTTLPR) and the brain-derived neurotrophic factor (BDNF), each assayed for naturally occurring polymorphisms, 5-HTTLPR (short/long) and BDNF (valine/methionine). Mental health correlated strongly with the NEO triad of conscientiousness-extraversion-neuroticism, with largest contributions to MHC-SF scores for conscientiousness, followed by extraversion and then neuroticism. The personality trait interaction of extraversion × conscientiousness uniquely accounted for approximately 44.22% 44.62% of the variance in MHC-SF scores. Polygenic comparisons showed a significant gene × gene interaction, with highest mental health for 5-HTTLPR-S, Met carriers. Together these results provided support for distinct yet interacting roles of personality and genetics in the phenotypical expression of mental health.

Association between the serotonin transporter linked polymorphic region and lifelong premature ejaculation: An updated meta-analysis of case-control studies

Previous studies on the association between serotonin transporter linked polymorphic region (5-HTTLPR) polymorphism and premature ejaculation (PE) have led to inconsistent results. The purpose of the present meta-analysis was to examine whether 5-HTTLPR polymorphism is associated with PE susceptibility.All eligible studies were searched and acquired from PubMed, Embase, Science Direct, CNKI, and Wanfang databases according to inclusion and exclusion criteria. Odds ratios (ORs) with 95% confidence intervals (CIs) were computed to assess the strength of the association between 5-HTTLPR polymorphism and PE. In addition, heterogeneity test, publication bias and sensitivity analysis were also conducted.Firstly, the association were observed in 8 studies (L vs S: OR = 0.74, 95% CI = 0.63-0.87; LL vs SS: OR = 0.61, 95% CI = 0.44-0.83; SL vs SS: OR = 0.73, 95% CI = 0.55-0.96; LL + SL vs SS: OR = 0.67, 95% CI = 0.52-0.86; LL vs SL + SS: OR = 0.72, 95% CI = 0.55-0.92). When the 2 studies not in Hardy-Weinberg equilibrium (HWE) were omitted, a positive association could only be observed between the 5-HTTLPR polymorphism and PE in allele contrast model (L vs S: OR = 0.81, 95% CI = 0.67-0.98). In the stratified analysis by subgroup, significantly associations were also found between PE and 5-HTTLPR polymorphism in Caucasians but not Asians (L vs S: OR = 0.79, 95% CI = 0.63-0.98; LL + SL vs SS: OR = 0.67, 95% CI = 0.46-0.96).Our meta-analysis demonstrated that the 5-HTTLPR polymorphism was associated with the susceptibility to PE in the Caucasian population. Compared with S allele, L allele is likely to be less susceptible to PE.

Association between 5-hydroxytryptamine transporter gene-linked promoter region polymorphism and the susceptibility of lifelong premature ejaculation: a meta-analysis involving 1,604 subjects

The relationship between 5-hydroxytryptamine transporter-linked promoter region (5-HTTLPR) gene and lifelong premature ejaculation (LPE) risk was discussed widely for the last few years, which was still controversial and remained to be explored. We performed the meta-analysis with 8 reliable research, which were searched in the following databases: PubMed, Embase and Cochrane Library. We also performed random and fixed effects models to evaluate the odds ratios (ORs) and 95% confidence intervals respectively. By pooling all included studies, we found that SS genotype of 5-HTTLPR polymorphism was linked with significantly higher PE risk in Caucasian population (OR =0.635, 95% CI: 0.417–0.958, I²=0.311, P=0.035), and S-allele of 5-HTTLPR polymorphism increased the risk of LPE significantly in Asian population (OR =0.656, 95% CI: 0.539–0.799, I²=0.435, P<0.001). However, no significant was observed between 5-HTTLPR gene polymorphism and LPE risk in overall studies. Further studies were anticipated to be done.

The association between serotonin transporter availability and the neural correlates of fear bradycardia

Reduced expression of the serotonin transporter (5-HTT) is associated with susceptibility to stress-related psychopathology, but the underlying mechanisms remain elusive. We investigated whether an aberrant physiological and neural response to threat underlies this increased vulnerability. In a cross-species approach, we investigated the association between genetically encoded differences in 5-HTT expression and the neural correlates of fear bradycardia, a defensive response linked to vigilance. In both humans and rats, reduced 5-HTT expression was associated with exaggerated bradycardia or bradycardia-associated freezing, reduced activity of the medial prefrontal cortex, and increased threat-induced amygdala-periaqueductal grey connectivity and central amygdala somatostatin neuron activity. We have delineated a previously unknown neurogenetic mechanism underlying individual differences in the expression of anticipatory threat responses, contributing to stress sensitivity.

Susceptibility to stress-related psychopathology is associated with reduced expression of the serotonin transporter (5-HTT), particularly in combination with stress exposure. Aberrant physiological and neuronal responses to threat may underlie this increased vulnerability. Here, implementing a cross-species approach, we investigated the association between 5-HTT expression and the neural correlates of fear bradycardia, a defensive response linked to vigilance and action preparation. We tested this during threat anticipation induced by a well-established fear conditioning paradigm applied in both humans and rodents. In humans, we studied the effect of the common 5-HTT-linked polymorphic region (5-HTTLPR) on bradycardia and neural responses to anticipatory threat during functional magnetic resonance imaging scanning in healthy volunteers (n = 104). Compared with homozygous long-allele carriers, the 5-HTTLPR short-allele carriers displayed an exaggerated bradycardic response to threat, overall reduced activation of the medial prefrontal cortex (mPFC), and increased threat-induced connectivity between the amygdala and periaqueductal gray (PAG), which statistically mediated the effect of the 5-HTTLPR genotype on bradycardia. In parallel, 5-HTT knockout (KO) rats also showed exaggerated threat-related bradycardia and behavioral freezing. Immunohistochemistry indicated overall reduced activity of glutamatergic neurons in the mPFC of KO rats and increased activity of central amygdala somatostatin-positive neurons, putatively projecting to the PAG, which—similarly to the human population—mediated the 5-HTT genotype’s effect on freezing. Moreover, the ventrolateral PAG of KO rats displayed elevated overall activity and increased relative activation of CaMKII-expressing projection neurons. Our results provide a mechanistic explanation for previously reported associations between 5-HTT gene variance and a stress-sensitive phenotype.

Risk and protective effects of serotonin and BDNF genes on stress-related adult psychiatric symptoms

We focused on individual risk by examining childhood adversity and current psychiatric symptoms in a sample of 100 college students genotyped for both the serotonin transporter (5-HTTLPR) and the brain-derived neurotrophic factor (BDNF). Naturally occurring allelic variation in 5-HTTLPR (short/long) and BDNF (valine/methionine) have been strongly implicated in stress-related psychiatric risk, but the combined effects of these alleles on psychological functioning have yet to be fully elucidated. Univariate analysis revealed gene-environment correlations linking heightened psychiatric risk with past childhood adversity for short but not long 5-HTTLPR allelic carriers and for valine (Val) but not methionine (Met) BDNF allelic carriers. Multivariate analyses revealed a significant gene x gene interaction with results showing that risk varied systematically depending on both 5-HTTLPR and BDNF alleles, independent of childhood adversity. Hierarchical regression analyses indicated that approximately 11% of the variance in symptoms of depression could be specifically accounted for by the epistatic interaction of 5-HTTLPR and BDNF val66Met polymorphisms. Allelic group analyses indicated lowest risk, as measured by depression and anxiety, for allelic carriers of 5-HTTLPR-short and BDNF Met, followed by 5-HTTLPR-long and BDNF-Val, 5-HTTLPR-short and BDNF-Val, and 5-HTTLPR-long and BDNF-Met. Results suggest that protective or risk-enhancing effects on stress-related psychiatric functioning may depend on specific allelic combinations of 5-HTTLPR and BDNF.

Insula serotonin 2A receptor binding and gene expression contribute to serotonin transporter polymorphism anxious phenotype in primates

Genetic variation in the serotonin transporter gene (SLC6A4) is associated with vulnerability to affective disorders and pharmacotherapy efficacy. We recently identified sequence polymorphisms in the common marmoset SLC6A4 repeat region (AC/C/G and CT/T/C) associated with individual differences in anxiety-like trait, gene expression, and response to antidepressants. The mechanisms underlying the effects of these polymorphisms are unknown, but a key mediator of serotonin action is the serotonin 2A receptor (5HT_2A). Thus, we correlated 5HT_2A binding potential (BP) and RNA gene expression in 16 SLC6A4 genotyped marmosets with responsivity to 5HT_2A antagonism during the human intruder test of anxiety. Voxel-based analysis and RNA measurements showed a reduction in 5HT_2A BP and gene expression specifically in the right posterior insula of individuals homozygous for the anxiety-related variant AC/C/G. These same marmosets displayed an anxiogenic, dose-dependent response to the human intruder after 5HT_2A pharmacological antagonism, while CT/T/C individuals showed no effect. A voxel-based correlation analysis, independent of SLC6A4 genotype, revealed that 5HT_2A BP in the adjacent right anterior insula and insula proisocortex was negatively correlated with trait anxiety scores. Moreover, 5HT_2A BP in both regions was a good predictor of the size and direction of the acute emotional response to the human intruder threat after 5HT_2A antagonism. Our findings suggest that genetic variation in the SLC6A4 repeat region may contribute to the trait anxious phenotype via neurochemical changes in brain areas implicated in interoceptive and emotional processing, with a critical role for the right insula 5HT_2A in the regulation of affective responses to threat.

A Discrete Dorsal Raphe to Basal Amygdala 5-HT Circuit Calibrates Aversive Memory

Despite a wealth of clinical and preclinical data implicating the serotonin (5-HT) system in fear-related affective disorders, a precise definition of this neuromodulator's role in fear remains elusive. Using convergent anatomical and functional approaches, we interrogate the contribution to fear of basal amygdala (BA) 5-HT inputs from the dorsal raphe nucleus (DRN). We show the DRN→BA 5-HT pathway is engaged during fear memory formation and retrieval, and activity of these projections facilitates fear and impairs extinction. The DRN→BA 5-HT pathway amplifies fear-associated BA neuronal firing and theta power and phase-locking. Although fear recruits 5-HT and VGluT3 co-expressing DRN neurons, the fear-potentiating influence of the DRN→BA 5-HT pathway requires signaling at BA 5-HT1A/2A receptors. Input-output mapping illustrates how the DRN→BA 5-HT pathway is anatomically distinct and connected with other brain regions that mediate fear. These findings reveal how a discrete 5-HT circuit orchestrates a broader neural network to calibrate aversive memory.

Adaptive developmental plasticity in rhesus macaques: the serotonin transporter gene interacts with maternal care to affect juvenile social behaviour

Research has increasingly highlighted the role that developmental plasticity-the ability of a particular genotype to produce variable phenotypes in response to different early environments-plays as an adaptive mechanism. One of the most widely studied genetic contributors to developmental plasticity in humans and rhesus macaques is a serotonin transporter gene-linked polymorphic region (5-HTTLPR), which determines transcriptional efficiency of the serotonin transporter gene in vitro and modifies the availability of synaptic serotonin in these species. A majority of studies to date have shown that carriers of a loss-of-function variant of the 5-HTTLPR, the short (s) allele, develop a stress-reactive phenotype in response to adverse early environments compared with long (l) allele homozygotes, leading to the prevalent conceptualization of the s-allele as a vulnerability allele. However, this framework fails to address the independent evolution of these loss-of-function mutations in both humans and macaques as well as the high population prevalence of s-alleles in both species. Here we show in free-ranging rhesus macaques that s-allele carriers benefit more from supportive early social environments than l-allele homozygotes, such that s-allele carriers which receive higher levels of maternal protection during infancy demonstrate greater social competence later in life. These findings provide, to our knowledge, the first empirical support for the assertion that the s-allele grants high undirected biological sensitivity to context in primates and suggest a mechanism through which the 5-HTTLPR s-allele is maintained in primate populations.

Association of the functional serotonin transporter haplotype with familial form of obsessive compulsive disorder in Iranian patients

OBJECTIVE

Several polymorphisms have been reported in the 5-HTTLPR of the serotonin transporter gene (SLC6A4). Family-based evidences for the association of 5-HTTLPR polymorphisms with OCD were previously reported but results were controversial. The present study investigated the possible correlation of SLC6A4 polymorphisms (5-HTTLPR, rs25532, rs25531) in Iranian OCD patients considering gender, age of onset, family history of psychiatric disorders, obsessive and compulsive subtypes and severities.

METHODS

The included OCD patients fulfilled the criteria for DSM-IV-TR whom Y-BOCS score was more than 9. Blood samples (184 cases and 192 controls) were genotyped by means of PCR-RFLP.

RESULTS

Mean of Y-BOCS scores of included patients was 20.1 ± 0.69. Rs25532 CC genotype showed significant association with OCD in men and were detected more in the patients reported positive family history of psychiatric disorders but the other single loci (5-HTTLPR and rs25531) did not associate with OCD. Haplotype analysis showed significant association of 14-A variant with OCD and revealed the association of 14-A/14-A genotype with familial form of OCD.

CONCLUSIONS

The findings of this study showed the association of SLC6A4 variants with familial form of OCD and proposed stratified analyses in the genetic studies facilitate identification of genetic risk factors for this heterogeneous disorder.

Heightened amygdala responsiveness in s-carriers of 5-HTTLPR genetic polymorphism reflects enhanced cortical rather than subcortical inputs: An MEG study

Short allele carriers (S-carriers) of the serotonin transporter gene (5-HTTLPR) show an elevated amygdala response to emotional stimuli relative to long allele carriers (LL-homozygous). However, whether this reflects increased responsiveness of the amygdala generally or interactions between the amygdala and the specific input systems remains unknown. It is argued that the amygdala receives input via a quick subcortical and a slower cortical pathway. If the elevated amygdala response in S-carriers reflects generally increased amygdala responding, then group differences in amygdala should be seen across the amygdala response time course. However, if the difference is a secondary consequence of enhanced amygdala-cortical interactions, then group differences might only be present later in the amygdala response. Using magnetoencephalography (MEG), we found an enhanced amygdala response to fearful expressions starting 40-50 ms poststimulus. However, group differences in the amygdala were only seen 190-200 ms poststimulus, preceded by increased superior temporal sulcus (STS) responses in S-carriers from 130 to 140 ms poststimulus. An enhanced amygdala response to angry expressions started 260-270 ms poststimulus with group differences in the amygdala starting at 160-170 ms poststimulus onset, preceded by increased STS responses in S-carriers from 150 to 160 ms poststimulus. These suggest that enhanced amygdala responses in S-carriers might reflect enhanced STS-amygdala connectivity in S-carriers. Hum Brain Mapp 38:4313-4321, 2017. © 2017 Wiley Periodicals, Inc.

Biallelic and Triallelic 5-Hydroxytyramine Transporter Gene-Linked Polymorphic Region (5- HTTLPR) Polymorphisms and Their Relationship with Lifelong Premature Ejaculation: A Case-Control Study in a Chinese Population

BACKGROUND This study aimed to explore the relationship between premature ejaculation (PE) and the serotonin transporter gene-linked polymorphic region (5-HTTLPR) with respect to the biallelic and triallelic classifications. MATERIAL AND METHODS A total of 115 outpatients who complained of ejaculating prematurely and who were diagnosed as having lifelong premature ejaculation (LPE) and 101 controls without PE complaint were recruited. All subjects completed a detailed questionnaire and were genotyped for 5-HTTLPR polymorphism using PCR-based technology. We evaluated the associations between 5-HTTLPR allelic and genotypic frequencies and their association with LPE, as well as the intravaginal ejaculation latency time (IELT) of different 5-HTTLPR genotypes among LPE patients. RESULTS The patients and controls did not differ significantly in terms of any characteristic except age. The results showed no significant difference regarding biallelic 5-HTTLPR. According to the triallelic classification, no significant difference was found when comparing the genotypic distribution (P=0.091). However, the distribution of the S, LG, and LA alleles in the cases was significantly different from the controls (P=0.018). We found a significantly lower frequency of LA allele and higher frequency of LG allele in patients. Based on another classification by expression, we found a significantly lower frequency of the L'L' genotype (OR=0.37; 95%CI=0.15-0.91, P=0.025) in patients with LPE. No significant association was detected between IELT of LPE and different genotypes. CONCLUSIONS Contrary to the general classification based on S/L alleles, triallelic 5-HTTLPR was associated with LPE. Triallelic 5-HTTLPR may be a promising field for genetic research in PE to avoid false-negative results in future studies.

Impact of 5-HTTLPR on hippocampal subregional activation in older adults

Studies have shown that a functional polymorphism of the serotonin transporter gene (5-HTTLPR) impacts performance on memory-related tasks and the hippocampal structures that subserve these tasks. The short (s) allele of 5-HTTLPR has been linked to greater susceptibility for impaired memory and smaller hippocampal volume compared to the long allele (l). However, previous studies have not examined the associations between 5-HTTLPR allele and activation in subregions of the hippocampus. In this study, we used functional magnetic resonance imaging (fMRI) to measure activation in hippocampal and temporal lobe subregions in 36 elderly non-clinical participants performing a face-name encoding and recognition task. Although there were no significant differences in task performance between s allele carriers and l homozygotes, right CA1 and right parahippocampal activation during recognition errors was significantly greater in individuals bearing the s allele. In an exploratory analysis, we determined that these effects were more pronounced in s allele carriers with the apolipoprotein ɛ4 allele. Our results suggest that older individuals with the s allele inefficiently allocate neural resources while making errors in recognizing face-name associations, which could negatively impact memory performance during more challenging tasks.

The Association of 5-HTTLPR XLL Genotype with Higher Cortisol Levels in African Americans

Genetic variants of the human serotonin transporter (SERT) may contribute to HPA axis dysregulation. SERT has two promoter region polymorphisms (5-HTTLPR: VNTR and SNP: rs25531), which may alter levels of SERT protein and its function. Combining these polymorphisms creates a functional polymorphism (FN) which may modulate mRNA expression. This study examines the relationship between these genetic variants and morning and evening salivary samples of both cortisol and dehydroepiandrosterone sulfate (DHEAS) concentrations in 269 African American (AA) adults. Resultant allele frequencies for the VNTR, SNP, and FN genotypes were 70% L (2% XLL), 84% A, and 54% LA (2% XLLA), respectively. The XLL genotype was associated with significantly higher concentrations of cortisol (~3X) and DHEAS (~2X) for both VNTR and FN polymorphisms. No significant differences were found for SNP genotypes. Conclusions were that persons with VNTR and FN XLL polymorphisms had significantly higher cortisol and DHEAS concentrations than other genotypes. AAs also appear to have a higher frequency of the rare XL allele than Caucasians. Whether the XLL genotype predisposes AAs to greater health challenges will require further research to determine the implications of these findings.

Mood disorders

Mood disturbances, especially depressive disorders, are the most frequent neuropsychiatric complication of traumatic brain injury (TBI). These disorders have a complex clinical presentation and are highly comorbid with anxiety, substance misuse, and other behavioral alterations such as impulsivity and aggression. Furthermore, once developed, mood disorders tend to have a chronic and refractory course. Thus, the functional repercussion of these disorders is huge, affecting the rehabilitation process and the long-term outcome of TBI patients. The pathophysiology of mood disorders involves the interplay of factors that precede trauma (e.g., genetic vulnerability and previous psychiatric history), factors that pertain to the traumatic injury itself (e.g., type, extent, and location of brain damage) and factors that influence the recovery process (e.g., family and social support). It is hardly surprising that mood disorders are associated with structural and functional changes of neural circuits linking brain areas specialized in emotional processing such as the prefrontal cortex, basal ganglia, and amygdala. In turn, the onset of mood disorders may contribute to further prefrontal dysfunction among TBI patients. Finally, in spite of the prevalence and impact of these disorders, there have been relatively few rigorous studies of therapeutic options. Development of treatment strategies constitutes a priority in this field of research.

Serotonin: a never-ending story

The neurotransmitter serotonin is an evolutionary ancient molecule that has remarkable modulatory effects in almost all central nervous system integrative functions, such as mood, anxiety, stress, aggression, feeding, cognition and sexual behavior. After giving a short outline of the serotonergic system (anatomy, receptors, transporter) the author's contributions over the last 40 years in the role of serotonin in depression, aggression, anxiety, stress and sexual behavior is outlined. Each area delineates the work performed on animal model development, drug discovery and development. Most of the research work described has started from an industrial perspective, aimed at developing animals models for psychiatric diseases and leading to putative new innovative psychotropic drugs, like in the cases of the SSRI fluvoxamine, the serenic eltoprazine and the anxiolytic flesinoxan. Later this research work mainly focused on developing translational animal models for psychiatric diseases and implicating them in the search for mechanisms involved in normal and diseased brains and finding new concepts for appropriate drugs.

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.

Candidate SNP associations of optimism and resilience in older adults: exploratory study of 935 community-dwelling adults

OBJECTIVE

Optimism and resilience promote health and well-being in older adults, and previous reports suggest that these traits are heritable. We examined the association of selected single-nucleotide polymorphisms (SNPs) with optimism and resilience in older adults.

DESIGN

Candidate gene association study that was a follow-on at the University of California, San Diego, sites of two NIH-funded multi-site longitudinal investigations: Women's Health Initiative (WHI) and SELenium and vitamin E Cancer prevention Trial (SELECT).

PARTICIPANTS

426 women from WHI older than age 50 years, and 509 men older than age 55 years (age 50 years for African American men) from SELECT.

MEASUREMENTS

65 candidate gene SNPs that were judged by consensus, based on a literature review, as being related to predisposition to optimism and resilience, and 31 ancestry informative marker SNPs, genotyped from blood-based DNA samples and self-report scales for trait optimism, resilience, and depressive symptoms.

RESULTS

Using a Bonferroni threshold for significant association (p = 0.00089), there were no significant associations for individual SNPs with optimism or resilience in single-locus analyses. Exploratory multi-locus polygenic analyses with p <0.05 showed an association of optimism with SNPs in MAOA, IL10, and FGG genes, and an association of resilience with a SNP in MAOA gene.

CONCLUSIONS

Correcting for Type I errors, there were no significant associations of optimism and resilience with specific gene SNPs in single-locus analyses. Positive psychological traits are likely to be genetically complex, with many loci having small effects contributing to phenotypic variation. Our exploratory multi-locus polygenic analyses suggest that larger sample sizes and complementary approaches involving methods such as sequence-based association studies, copy number variation analyses, and pathway-based analyses could be useful for better understanding the genetic basis of these positive psychological traits.

Connectivity underlying emotion conflict regulation in older adults with 5-HTTLPR short allele: a preliminary investigation

OBJECTIVE

The serotonin transporter polymorphism short (s) allele is associated with heightened emotional reactivity and reduced emotion regulation, which increases vulnerability to depression and anxiety disorders. We investigated behavioral and neural markers of emotion regulation in community-dwelling older adults, contrasting s allele carriers and long allele homozygotes.

METHODS

Participants (N = 26) completed a face-word emotion conflict task during functional magnetic resonance imaging, in which facilitated regulation of emotion conflict was observed on face-word incongruent trials following another incongruent trial (i.e., emotional conflict adaptation).

RESULTS

There were no differences between genetic groups in behavioral task performance or neural activation in postincongruent versus postcongruent trials. By contrast, connectivity between dorsal anterior cingulate cortex (ACC) and pregenual ACC, regions previously implicated in emotion conflict regulation, was impaired in s carriers for emotional conflict adaptation.

CONCLUSION

This is the first demonstration of an association between serotonin transporter polymorphism and functional connectivity in older adults. Poor dorsal ACC-pregenual ACC connectivity in s carriers may be one route by which these individuals experience greater difficulty in implementing effective emotional regulation, which may contribute to their vulnerability for affective disorders.

Mood disorders after TBI

In this article, we examine the epidemiology and risk factors for the development of the most common mood disorders observed in the aftermath of TBI: depressive disorders and bipolar spectrum disorders. We describe the classification approach and diagnostic criteria proposed in the fifth edition of the Diagnostic and Statistical Manual for Mental Disorders. We also examine the differential diagnosis of post-TBI mood disorders and describe the mainstay of the evaluation process. Finally, we place a special emphasis on the analysis of the different therapeutic options and provide guidelines for the appropriate management of these conditions.

The evolutionary history of SLC6A4 and the role of plasticity in Macaca

Serotonin has been repeatedly indicated as a biological marker of behavior. In particular, the serotonin transporter gene, SLC6A4, has been the focus of a large body of research. Interestingly, both rhesus macaques (Macaca mulatta) and humans have independently evolved a number of shared polymorphisms for this gene, which is indicative of parallel evolution between the two species. However, little is known about the evolution of this gene, particularly within macaques. Although there are several hypotheses as to the adaptive values of various polymorphisms, few authors have gone beyond theoretical discussion. Here, we examined the genetic variation in SLC6A4 within and between several species of macaques and investigate whether selection has played a significant role in its evolutionary history. In addition, we assayed the promoter region polymorphism, 5-HTTLPR, which is known to play a significant role in regulating both serotonin turnover and behavior. In examining the distribution of the 5-HTTLPR polymorphism, we identified significant differences between Indian and Chinese populations of Macaca mulatta; furthermore, we discovered its presence in Macaca cyclopis, which has not been described before. In regard to the evolutionary history of SLC6A4, we found little evidence for selection and conclude that SLC6A4 largely evolved through neutral processes, possibly due to its potential role in regulating behavioral plasticity. However, we also found very low levels of linkage between the coding regions and 5-HTTLPR. Because we limited evolutionary analyses to the coding regions, it is possible that the promoter region shows a distinct evolutionary history from SLC6A4.

Acute responsivity of the serotonergic system to S-citalopram and positive emotionality-the moderating role of the 5-HTTLPR

According to the idea that the central serotonergic system has a modulatory function on behavior and personality in general, we aimed to highlight its association to habitual positive emotionality. In a placebo-controlled double-blind and randomized cross-over neuroendocrine challenge design (n = 72 healthy males) we investigated the association of the central serotonergic responsivity, 5-HTTLPR-genotype as well as their combined effects on positive emotionality. Regression analyses revealed an involvement of the serotonergic system in positive emotionality. There was, however, no direct association between positive emotionality and cortisol responses to S-citalopram; rather 5-HTTLPR-genotype showed an association (p < 0.05). That is, positive emotionality scores increased with the number of s-alleles carried by the individuals. Most notable was the moderating role of 5-HTTLPR-genotype (p < 0.05) on the association between acute serotonergic responsivity and positive emotionality. Indeed, this association was only found in ss-homozygotes, in which the acute responsivity of the serotonergic system additionally seems to contribute to the level of positive emotionality (r = 0.70, p < 0.05). The findings correspond to previous research demonstrating that the 5-HTTLPR is not only involved in the negative-emotional aspects of behavior and temperament, but is associated, moreover, with positive affectivity-supporting the assumption of its valence-neutrality. In addition, our data are in line with the idea of possible influences of the 5-HTTLPR-genotype on early neuronal development. They also indicate the need for further studies in order to clearly elucidate the role of the serotonergic system and its subcomponents in the regulation of positive emotionality.

Social stress and the polymorphic region of the serotonin reuptake transporter gene modify oestradiol-induced changes on central monoamine concentrations in female rhesus monkeys

Psychosocial stress exposure is linked to the disruption of emotional regulation that can manifest as anxiety and depression. Women are more likely to suffer from such psychopathologies than men, indicating that sex-based differences in gonadal steroids may be a key factor in the aetiology of stress-induced adverse health outcomes. Oestradiol (E2 ) positively influences mood and cognition in females, an effect likely related to the ability of E2 to modulate the serotonin and dopamine neurotransmitter systems. Furthermore, genetic variation as a result of the polymorphism in the promoter region of the gene (SLC6A4) encoding the serotonin transporter (5HTTLPR) also can influence the ability of E2 to modulate behaviour and physiology. However, it remains uncertain whether exposure to social stress interacts with the 5HTTLPR to influence E2 -induced changes in behaviour and physiology. The present study used ovariectomised adult female rhesus monkeys to investigate acute and chronic effects of E2 on central monoamine metabolite concentrations using cerobrospinal fluid sampling. We further assessed how E2 -induced changes in monoamine metabolite levels are modified by the unpredictable stress of social subordination and the 5HTTLPR polymorphism. Levels of the serotonin metabolite 5-hydroxyindoleacetic acid decreased significantly during chronic E2 treatment only in dominant females with the long promoter length of SLC6A4. Chronic administration of E2 decreased levels of the dopamine metabolite dihydrophenylacetic acid in a manner independent of the social status, 5HTTLPR genotype, or their interactions. Overall levels of dopamine and serotonin metabolites were increased in subordinate females, although this effect of social stress was not influenced by 5HTTLPR genotype. Together, these data emphasise how E2 can modulate central neurotransmitter systems and indicate that social subordination in female monkeys is a valid model for examining how chronic psychosocial stress alters sensitivity to E2 . Future studies are necessary to elaborate how changes in central neurotransmitter metabolism affect behaviour and physiology as a result of E2 and prolonged exposure to stress.

Aging and Clinical Pharmacology: Implications for Antidepressants

The elderly frequently have changes in pharmacokinetics, sensitivity to medications, homeostatic reserve (ability to tolerate physiological challenges), exposure to multiple medications, and adherence. All of these age-associated factors can potentially influence total exposure to medication, adverse effects, and subsequent treatment outcome. Most clinical trials are performed with healthy, younger adults. Extrapolating the results of these trials to the elderly may be inappropriate, particularly for the antidepressant treatment of depression. The authors review these age-associated differences and discuss their implications for antidepressant use in older adults.

A meta-analysis of the effects of the 5-hydroxytryptamine transporter gene-linked promoter region polymorphism on susceptibility to lifelong premature ejaculation

Objective

Premature ejaculation (PE) has been reported as the most common male sexual dysfunction with global prevalence rates estimated at approximately 30%. The neurobiogenesis of ejaculation is very complex and involves the serotoninergic (5-hydroxytryptamine, 5-HT) system. Recently, genetic polymorphisms located on SLC6A4 gene codifying for 5-HT transporter (5-HTT), the major regulator of serotonic neurotransmission, have been linked with the pathogenesis and risk of PE. Apparently studies of this type of polymorphism in PE have show conflicting results.

Methods

A meta-analysis was performed that are available in relation with 5-HTT gene-linked promoter region (5-HTTLPR) polymorphism and the risk of lifelong PE (LPE) in men to clarify this relationship. We searched Pubmed and Embase (last search updated on Aug 2012) using ‘premature ejaculation’, ‘polymorphism or variant’, ‘genotype’, ‘ejaculatory function’, and ‘rapid ejaculation’ as keywords and reference lists of studies corresponded to the inclusion criteria for meta-analysis. These studies involved the total number of 481 LPE men and 466 health control men subjects. Odds ratio (OR) and 95% confidence intervals (CIs) were used to evaluate this relationship.

Results

In the overall analysis, significant associations between LPE risk and 5-HTTLPR polymorphism were found (L-allele vs. S-allele OR = 0.86, 95% CI = 0.79–0.95, P = 0.002; LL vs. SS: OR = 0.80, 95% CI = 0.68–0.95, P = 0.009; LS vs. SS: OR = 0.85, 95% CI = 0.76–0.97, P = 0.012 and LL+LS vs. SS: OR = 0.88, 95% CI = 0.81–0.95, P = 0.002). Moreover, in subgroup analysis based on ethnicity, similar significant associations were detected. The Egger’s test did not reveal presence of a publication bias.

Conclusions

Our investigations demonstrate that 5-HTTLPR (L>S) polymorphism might protect men against LPE risk. Further studies based on larger sample size and gene-environment interactions should be conducted the role of 5-HTTLPR polymorphism and LPE risk.

Serotonin modulation of cerebral glucose metabolism: sex and age effects

The serotonin system is implicated in a variety of psychiatric disorders whose clinical presentation and response to treatment differ between males and females, as well as with aging. However, human neurobiological studies are limited. Sex differences in the cerebral metabolic response to an increase in serotonin concentrations were measured, as well as the effect of aging, in men compared to women. Thirty-three normal healthy individuals (14 men/19 women, age range 20-79 years) underwent two resting positron emission tomography studies with the radiotracer [18F]-2-deoxy-2-fluoro-D-glucose ([(18)F]-FDG) after placebo and selective serotonin reuptake inhibitor (SSRI, citalopram) infusions on two separate days. Results indicated that women demonstrated widespread areas of increased cortical glucose metabolism with fewer areas of decrease in metabolism in response to citalopram. Men, in contrast, demonstrated several regions of decreased cortical metabolism, but no regions of increased metabolism. Age was associated with greater increases in women and greater decreases in men in most brain regions. These results support prior studies indicating that serotonin function differs in men and women across the lifespan. Future studies aimed at characterizing the influences of age and sex on the serotonin system in patients with psychiatric disorders are needed to elucidate the relationship between sex and age differences in brain chemistry and associated differences in symptom presentation and treatment response.

5-HTTLPR short allele, resilience, and successful aging in older adults

OBJECTIVE

Resilience is proposed as a significant component of successful aging. Young adult carriers of the Serotonin Transporter Polymorphism (5-HTTLPR) short(s) allele appear to have reduced resilience to stress. We examined whether the presence of the short allele was associated with poorer emotional resilience in older adults.

METHODS

In a cross-sectional study of 99 healthy, community-dwelling, older adults, we determined 5-HTTLPR genotype status and administered the Connor-Davidson Resilience Scale and self-reported measures of successful aging, cognition, and health.

RESULTS

There was no significant association between the 5-HTTLPR s allele and resilience. S allele carriers had worse cognition and self-report ratings of successful aging.

CONCLUSION

These findings suggest that the impact of the 5-HTTLPR s allele on stress-related outcomes may attenuate with older age. However, s allele status appears to be a biomarker of poorer self-rated successful aging, and cognitive performance in older adults.

Estradiol and progesterone modify the effects of the serotonin reuptake transporter polymorphism on serotonergic responsivity to citalopram

Individual vulnerability to psychopathologies is linked to a number of genetic polymorphisms including the serotonin transporter (5HTT) promoter polymorphic region (5HTTLPR). A single copy of the short variant (s-variant) allele of 5HTTLPR confers increased susceptibility to anxiety disorders and depression and decreased efficacy of serotonin-releasing agents in pharmacotherapy compared to the homozygous long 5HTTLPR variant (l/L). The data suggesting that the 5HTTLPR polymorphism modulates the efficacy of serotonin-releasing agents in pharmacotherapy is inconsistent. Other factors such as age, gender, and hormonal status could interact with 5HTTLPR genotype to affect individual physiological and behavioral responses to serotonin reuptake inhibitors such as citalopram. Indeed, estradiol and progesterone, the primary female steroid hormones, exert an array of effects on the serotonergic system, including 5HTT expression. The present study used ovariectomized female rhesus monkeys to determine the interaction between the 5HTTLPR polymorphism and the effects of midfollicular levels of estradiol and luteal levels of progesterone on serotonergic responsivity to acute citalopram administration. The increase in serum prolactin, a surrogate measure of serotonin activity, following citalopram administration was significantly larger in l/L females than in s-variant females over the course of two hours during concurrent estradiol and progesterone hormone replacement only. These data suggest that ovarian function and the 5HTTLPR polymorphism interact to gate serotonergic reactivity in females, suggesting that clinicians should be aware of the ovarian status and 5HTTLPR genotype of women when considering serotonergic pharmacotherapy in women.

Variants of the serotonin transporter gene, selective serotonin reuptake inhibitors, and bone mineral density in risperidone-treated boys: a reanalysis of data from a cross-sectional study with emphasis on pharmacogenetics

OBJECTIVE

Selective serotonin reuptake inhibitors (SSRIs) may reduce bone mineral density (BMD). Here, we investigate whether variants of the serotonin transporter-linked polymorphic region (5-HTTLPR) of the serotonin transporter gene moderate this association in boys.

METHOD

Between November 2005 and August 2009, medically healthy boys, aged 7 to 17 years, were enrolled in a cross-sectional study exploring the effect of risperidone-induced hyperprolactinemia on BMD. Volumetric BMD of the ultradistal radius was measured using peripheral quantitative computed tomography, and areal BMD of the lumbar spine was estimated using dual energy x-ray absorptiometry. Multiple linear regression analysis tested whether the 5-HTTLPR genotypes interacted with SSRI treatment status to affect BMD, adjusting for relevant confounders. Participant enrollment was conducted at the University of Iowa, Iowa City.

RESULTS

Of 108 boys (mean ± SD age = 11.7 ± 2.8 years), with DSM-IV clinical diagnoses based on chart review, 52% (n = 56) had been taking an SSRI for a median duration of 2.8 years. After adjusting for pubertal development, anthropometric measures, physical activity, calcium intake, and prolactin concentration, there was a significant 5-HTTLPR genotype × SSRI treatment interaction effect on total lumbar spine BMD z score (P < .05) in non-Hispanic whites. The interaction effect on BMD at the ultradistal radius failed to reach statistical significance. Among LS genotype carriers, those treated with SSRIs had lower lumbar BMD z score and trabecular BMD at the radius compared to those not treated (P < .02 and P < .008, respectively).

CONCLUSIONS

These findings add to the growing evidence implicating the serotonin system in bone metabolism. They suggest the potential use of 5-HTTLPR genotypes to guide the safer long-term prescribing of SSRIs in youths. However, prospective confirmation in a controlled matched population is warranted.

The impact of serotonin transporter (5-HTTLPR) genotype on the development of resting-state functional connectivity in children and adolescents: a preliminary report

A fundamental component of brain development is the formation of large-scale networks across the cortex. One such network, the default network, undergoes a protracted development, displaying weak connectivity in childhood that strengthens in adolescence and becomes most robust in adulthood. Little is known about the genetic contributions to default network connectivity in adulthood or during development. Alterations in connectivity between posterior and frontal portions of the default network have been associated with several psychological disorders, including anxiety, autism spectrum disorders, schizophrenia, depression, and attention-deficit/hyperactivity disorder. These disorders have also been linked to variants of the serotonin transporter linked polymorphic region (5-HTTLPR). The LA allele of 5-HTTLPR results in higher serotonin transporter expression than the S allele or the rarer LG allele. 5-HTTLPR may influence default network connectivity, as the superior medial frontal region has been shown to be sensitive to changes in serotonin. Also, serotonin as a growth factor early in development may alter large-scale networks such as the default network. The present study examined the influence of 5-HTTLPR variants on connectivity between the posterior and frontal structures and its development in a cross-sectional study of 39 healthy children and adolescents. We found that children and adolescents homozygous for the S allele (S/S, n=10) showed weaker connectivity in the superior medial frontal cortex compared to those homozygous for the LA allele (LA/LA, n=13) or heterozygotes (S/LA, S/LG, n=16). Moreover, there was an age-by-genotype interaction, such that those with LA/LA genotype had the steepest age-related increase in connectivity between the posterior hub and superior medial frontal cortex, followed by heterozygotes. In contrast, individuals with the S/S genotype had the least age-related increase in connectivity strength. This preliminary report expands our understanding of the genetic influences on the development of large-scale brain connectivity and lays down the foundation for future research and replication of the results with a larger sample.

Behavioral and molecular genetics of dissociation: the role of the serotonin transporter gene promoter polymorphism (5-HTTLPR)

We evaluated the role of the serotonin transporter gene promoter polymorphism (5-HTTLPR) in the etiology of dissociation. Adult twin pairs (N = 184 pairs; mean age 33.0 years, SD = 10.8) completed measures for dissociation and trauma. The DNA samples were genotyped for 5-HTTLPR adjusted for rs25531 alleles. Behavioral genetic analyses showed that genetic factors explained 45% of the variance in dissociative symptoms, while 55% of the variance was explained by unique environment and measurement error. Participants with the SS genotype of 5-HTTLPR reported more dissociative symptoms compared to participants with the other genotypes (p = .02), and they showed more pathological dissociative symptoms than the other participants (p = .04) when they reported more depressive symptoms and when they had experienced trauma.

A polymorphism in the serotonin transporter gene moderates cardiovascular reactivity to psychosocial stress

OBJECTIVE

To examine whether a polymorphism (5-HTTLPR: serotonin transporter linked polymorphic region) in the promoter of the serotonin transporter gene (SLC6A4) moderates cardiovascular reactivity to social threat.

METHODS

Psychologically healthy young adults delivered a speech and performed mental arithmetic in one of three conditions: a) an evaluative audience condition that gave disapproving and negative nonverbal social signals (n = 59); b) an evaluative audience condition that provided supportive social signals (n = 60); or c) a no audience condition (n = 65). Heart rate (HR) and systolic and diastolic blood pressures (DBP) were measured before, during, and after the stress tasks to assess cardiovascular reactivity and recovery.

RESULTS

In the negative audience condition, there was a significant association between the 5-HTTLPR and systolic blood pressure, DBP, and HR reactivity. Individuals with the short/short genotype showed the greatest reactivity. The DBP and HR reactivity of short/short individuals in the negative audience condition was also greater than that of individuals with the short/short genotype in the no audience condition. These associations of the 5-HTLPR with HR reactivity were moderated by gender, being limited to females. With respect to cardiovascular recovery, short/short individuals in the negative audience condition exhibited impaired DBP recovery relative to other genotypes in the same condition, as well as short/short individuals in the no audience condition.

CONCLUSIONS

The 5-HTTLPR moderates cardiovascular reactivity to stress in a threatening evaluative social context, which suggests that the serotonin system may be involved in the processes by which stressful, conflict-ridden social environments affect risk for cardiovascular-related health outcomes.

Serotonin transporter polymorphism as a predictor for escitalopram treatment of major depressive disorder comorbid with alcohol dependence

The aim of this study was to determine whether the serotonin transporter gene polymorphism (5-HTTLPR) is associated with the treatment outcomes of escitalopram for patients with comorbid major depression and alcohol dependence. Eighty treatment-seeking patients were randomly assigned to either receive 20mg of escitalopram or a control of 20mg of the non-serotonergically acting memantine. Depression was measured by the Montgomery-Asberg Depression Rating Scale (MADRS) and alcoholism by the Alcohol Use Disorders Identification Test (AUDIT). Twenty-nine participants in each treatment group completed the study, and from those DNA was given by 27 in the escitalopram group and 21 in the memantine group. In the escitalopram group linear regression showed that LL genotype predicted greater decrease in MADRS scores compared with the SS/SL genotypes (p=0.04) after a 3month treatment period. Moreover, each L allele associated with MADRS score decrease by 15% (p=0.04) in the escitalopram group. In the memantine group, however, no association between LL genotype and MADRS decrease was detected. AUDIT decrease was not associated with the 5-HTTLPR genotype for either medication. This is the first study in the treatment of depression in dual diagnosis patients to report a significant association between outcomes with escitalopram and the 5-HTTLPR gene polymorphism.

The roles of dopamine and serotonin in decision making: evidence from pharmacological experiments in humans

Neurophysiological experiments in primates, alongside neuropsychological and functional magnetic resonance investigations in humans, have significantly enhanced our understanding of the neural architecture of decision making. In this review, I consider the more limited database of experiments that have investigated how dopamine and serotonin activity influences the choices of human adults. These include those experiments that have involved the administration of drugs to healthy controls, experiments that have tested genotypic influences upon dopamine and serotonin function, and, finally, some of those experiments that have examined the effects of drugs on the decision making of clinical samples. Pharmacological experiments in humans are few in number and face considerable methodological challenges in terms of drug specificity, uncertainties about pre- vs post-synaptic modes of action, and interactions with baseline cognitive performance. However, the available data are broadly consistent with current computational models of dopamine function in decision making and highlight the dissociable roles of dopamine receptor systems in the learning about outcomes that underpins value-based decision making. Moreover, genotypic influences on (interacting) prefrontal and striatal dopamine activity are associated with changes in choice behavior that might be relevant to understanding exploratory behaviors and vulnerability to addictive disorders. Manipulations of serotonin in laboratory tests of decision making in human participants have provided less consistent results, but the information gathered to date indicates a role for serotonin in learning about bad decision outcomes, non-normative aspects of risk-seeking behavior, and social choices involving affiliation and notions of fairness. Finally, I suggest that the role played by serotonin in the regulation of cognitive biases, and representation of context in learning, point toward a role in the cortically mediated cognitive appraisal of reinforcers when selecting between actions, potentially accounting for its influence upon the processing salient aversive outcomes and social choice.

Serotonin transporter triallelic genotype and response to citalopram and risperidone in dementia with behavioral symptoms

The risk/benefit ratio of pharmacotherapy for behavioral symptoms of dementia is questionable: second-generation antipsychotics are poorly tolerated, and the efficacy of alternative treatments, for example, selective serotonin-reuptake inhibitors (SSRIs), is uncertain. Biomarkers of treatment response may improve this risk/benefit ratio. The length polymorphism of the serotonin transporter promoter gene (5-HTTLPR/SLC6A4) may moderate tolerability of SSRIs and expression of behavioral symptoms in dementia. We assessed the effect of 5-HTTLPR on tolerability and efficacy of citalopram and risperidone in a 12-week randomized controlled trial, which included nondepressed patients with dementia hospitalized for behavioral or psychotic symptoms. Genotypes including the A/G polymorphism of the L allele (rs25531) were determined in 92 of 103 participants. We used pattern-mixture models to account for dropout. Low-expression alleles (S and Lg) predicted greater early and overall side effects of citalopram and early treatment discontinuation. These results remained unchanged after excluding African-American participants and in covariate analyses. Unexpectedly, low-expression alleles seemed to predict greater early side effects of risperidone (but not early discontinuation) and poorer early response of psychosis symptoms to risperidone. In conclusion, 5-HTTLPR may be a useful biomarker of SSRI intolerance in dementia. Our findings of intolerance of a second-generation antipsychotics and persistence of psychosis in patients with low-expression alleles needs to be replicated.

Serotonin transporter polymorphisms, microstructural white matter abnormalities and remission of geriatric depression

OBJECTIVE

This study compared microstructural abnormalities in depressed elders and controls and studied the association of the serotonin transporter gene status to white matter abnormalities and to remission of depression.

METHODS

The subjects were Caucasians with non-psychotic major depression and normal elders. Depressed subjects received escitalopram 10 mg daily for 12 weeks. Remission was defined as a HDRS score of 7 or below for 2 consecutive weeks. Diffusion tensor imaging was performed and voxel-based analysis of fractional anisotropy (FA) was conducted using age and mean diffusivity as covariates.

RESULTS

Depressed elders (N=27) had lower FA than controls (N=27) in several frontolimbic areas. Depressed elderly S-allele carriers also had lower FA than L homozygotes in frontolimbic brain areas, including the dorsal and rostral anterior cingulate, posterior cingulate, dorsolateral prefrontal and medial prefrontal regions, thalamus, and in other regions. S-allele carriers had a lower remission rate than L homozygotes.

LIMITATIONS

Small number of subjects, lack of random sampling, fixed antidepressant dose, short follow-up.

CONCLUSIONS

Lower FA was observed in several frontolimbic and other regions in depressed elders compared to controls. Depressed S-allele carriers had both microstructural white matter abnormalities in frontolimbic networks and a low remission rate. It remains unclear whether the risk for chronicity of geriatric depression in S-allele carriers is mediated by frontolimbic compromise. However, these observations set the stage for studies aiming to identify the relationship of S allele to impairment in specific frontolimbic functions interfering with response of geriatric depression to antidepressants.

The role of serotonin in nonnormative risky choice: the effects of tryptophan supplements on the "reflection effect" in healthy adult volunteers

Risky decision-making involves weighing good and bad outcomes against their probabilities in order to determine the relative values of candidate actions. Although human decision-making sometimes conforms to rational models of how this weighting is achieved, irrational (or nonnormative) patterns of risky choice, including shifts between risk-averse and risk-seeking choices involving equivalent-value gambles (the "reflection effect"), are frequently observed. In the present experiment, we investigated the role of serotonin in decision-making under conditions of uncertainty. Fifteen healthy adult volunteers received a treatment of 3 g per day of the serotonin precursor, tryptophan, in the form of dietary supplements over a 14-day period, whereas 15 age- and IQ-matched control volunteers received a matched placebo substance. At test, all participants completed a risky decision-making task involving a series of choices between two simultaneously presented gambles, differing in the magnitude of their possible gains, the magnitude of their possible losses, and the probabilities with which these outcomes were delivered. Tryptophan supplements were associated with alterations in the weighting of gains and small losses perhaps reflecting reduced loss-aversion, and a marked and significant diminution of the reflection effect. We conclude that serotonin activity plays a significant role in nonnormative risky decision-making under conditions of uncertainty.

Gender moderates the relationship between mania spectrum and serotonin transporter polymorphisms in depression

The short (s) variant of the serotonin transporter gene linked functional polymorphic region (5-HTTLPR) is associated with depression. Stressful life events, gender, and race have been shown to moderate this association. Because features of mania/hypomania seem to constitute an indicator of higher severity of depression, we examined the relationship between 5-HTTLPR genotype and symptoms of mania-hypomania spectrum occurring over the lifetime in patients with major depression. The possible moderating role of gender in this relationship was taken into account. Two hundred twenty-two patients with unipolar major depression were genotyped for 5-HTTLPR and nine other representative polymorphisms, and were administered the Mood Spectrum Questionnaire, Lifetime Version (MOODS-SR). The manic-hypomanic (MH) component score was used for analysis. Using a linear model of the MH score as a function of genotypes and gender, controlling for age, severity of depression, and site, we found significant effects of gender (F = 8.003, df = 1, P = 0.005), of the interaction gender x genotype (F = 4.505, df = 2, P = 0.012), and of the baseline Hamilton score (F = 5.404, df = 1, P = 0.021), non-significant effects of genotype (F = 1.298, df = 2, P = 0.275), age (F = 0.310, df = 1, P = 0.578) site (F = 0.504, df = 1, P = 0.479). Significant associations were also detected at three other SNPs. The association between the manic/hypomanic component of the MOODS-SR and the polymorphisms of the 5-HTTLPR is moderated by gender. This finding is intriguing from a clinical point of view because women with unipolar disorder and the "ss" genotype seem to constitute a sub-group with higher severity of depression. These results should be considered tentative pending replication in other samples.

The interaction of reward genes with environmental factors in contribution to alcoholism in mexican americans

BACKGROUND

Alcoholism is a polygenic disorder resulting from reward deficiency; polymorphisms in reward genes including serotonin transporter (5-HTT)-linked polymorphic region (5-HTTLPR), A118G in opioid receptor mu1 (OPRM1), and -141C Insertion/Deletion (Ins/Del) in dopamine receptor D2 (DRD2) as well as environmental factors (education and marital status) might affect the risk of alcoholism. Objective of the current study was to examine the main and interacting effect of these 3 polymorphisms and 2 environmental factors in contribution to alcoholism in Mexican Americans.

METHODS

Genotyping of 5-HTTLPR, OPRM1 A118G, and DRD2-141C Ins/Del was performed in 365 alcoholics and 338 nonalcoholic controls of Mexican Americans who were gender- and age-matched. Alcoholics were stratified according to tertiles of MAXDRINKS, which denotes the largest number of drinks consumed in one 24-hour period. Data analysis was done in the entire data set and in each alcoholic stratum. Multinomial logistic regression was conducted to explore the main effect of 3 polymorphisms and 2 environmental factors (education and marital status); classification tree, generalized multifactor dimensionality reduction (GMDR) analysis, and polymorphism interaction analysis version 2.0 (PIA 2) program were used to study factor interaction.

RESULTS

Main effect of education, OPRM1, and DRD2 was detected in alcoholic stratum of moderate and/or largest MAXDRINKS with education < or =12 years, OPRM1 118 A/A, and DRD2 -141C Ins/Ins being risk factors. Classification tree analysis, GMDR analysis, and PIA 2 program all supported education*OPRM1 interaction in alcoholics of largest MAXDRINKS with education < or =12 years coupled with OPRM1 A/A being a high risk factor; dendrogram showed synergistic interaction between these 2 factors; dosage-effect response was also observed for education*OPRM1 interaction. No definite effect of marital status and 5-HTTLPR in pathogenesis of alcoholism was observed.

CONCLUSIONS

Our results suggest main effect of education background, OPRM1 A118G, and DRD2 -141C Ins/Del as well as education*OPRM1 interaction in contribution to moderate and/or severe alcoholism in Mexican Americans. Functional relevance of these findings still needs to be explored.

The serotonin transporter gene and disease modification in psychosis: evidence for systematic differences in allelic directionality at the 5-HTTLPR locus

A 44 base pair insertion ("l")/deletion ("s") polymorphism (called 5-HTTLPR) in the 5' promoter region of the human serotonin transporter gene (SLC6A4) modulates expression and has been associated to anxiety and depressive traits in otherwise healthy individuals. In individuals with psychiatric diagnoses, including schizophrenia, it seems to modulate symptom severity. Thus, it may be a disease modifying gene. In this study, 92 patients with psychosis (including schizophrenia, schizoaffective disorder, bipolar psychosis, and major depression) were assessed at their first hospital admission. Symptom ratings, including SANS negative symptoms, SAPS positive symptoms, and SCID depressive symptoms, were obtained. Stress was also assessed. Bi-allelic genotyping at the 5-HTTLPR locus was done. Using multiple regression models, we found that 5-HTTLPR genotype (especially in dominant models) accounted for a significant portion of the variance in SCID Depression and SANS (about 5%). In particular we found that the l allele was associated with greater psychopathology. This is consistent with our review of the literature and is at variance with findings in healthy controls that the s allele is associated with greater anxiety and depression levels. We believe that this set of findings argues for principled reversal of directionality in associations at the 5-HTTLPR locus and raises the possibility that allelic variation may have very different consequences for personality traits or psychiatric symptoms depending on epistasis or epigenetic context. Furthermore, these results also imply that categorical diagnostic distinctions may still be relevant in understanding some genetic effects.

Association between triallelic polymorphism of the serotonin transporter and [18F]MPPF binding potential at 5-HT1A receptors in healthy subjects

Previous [(11)C]WAY100-635 PET studies have demonstrated that the short (S) and long (L) alleles of the serotonin transporter gene-linked polymorphic region (5-HTTLPR) were associated with distinct patterns of 5-HT(1A) receptor distribution in human. However, these studies reported discordant findings and did not take into account the recent description of two functional variants of the L allele (L(A)/L(G)). To further explore this issue, we investigated the triallelic functional polymorphism of the 5-HTTLPR in 38 healthy volunteers who underwent a [(18)F]MPPF PET study of 5-HT1A receptors. We used a simplified reference tissue model to generate parametric images of [(18)F]MPPF binding potential (BP(ND)), and compared these data among the different genotypes using statistical parametric mapping and region of interest of the raphe nuclei. Homozygote carriers of the S allele demonstrated greater [(18)F]MPPF BP(ND) than carriers of the L(A) allele, but this association was only found in women. Differences in [(18)F]MPPF BP(ND) between women with and without L(A) allele were observed over large clusters encompassing the right and left temporal lobes, cingulate and perisylvian regions, as well as the right precuneus and frontal dorso-lateral cortex, and the left orbitofrontal cortex. In contrast, no difference was found between groups in the raphe nuclei. The greater [(18)F]MPPF BP(ND) observed in women homozygote carriers of the S allele could either reflect a greater 5-HT1A receptor density or a lower extracellular concentration of 5-HT. Our data suggest that any future PET studies of 5-HT1A receptors should incorporate the 5-HTTLPR polymorphism status of the population studied.