Serotonin transporter gene polymorphism and treatment response to serotonin reuptake inhibitor (escitalopram) in depression: An open pilot study

Pharmacogenetics of selective serotonin reuptake inhibitors (SSRI): A serotonin reuptake transporter (SERT)-based approach

Neuropsychiatric disorders are considered to be the most common cause of disability worldwide. Serotonin and its transporter is a prominent paradigm in mood disorders. Response to selective serotonin reuptake inhibitors (SSRI) is altered due to heterogeneity in the serotonin transporter gene, SLC6A4 (solute carrier family 6 member 4). The reported polymorphisms are found to be in different regions of the transporter gene: promoter region (5-HTTLPR and various single nucleotide polymorphisms within it), intron (STin2), and exon 9 (I425V). The long and short alleles of the 5-HTTLPR gene, which are prevalent among variations, may mediate differential effects. In long allelic variant carriers, an increased response to SSRI and timely recovery is due to increased availability of SERT. Whereas, SERT availability is significantly decreased in short allelic carriers, necessitating a reduction in SSRI dosage due to the increased risk of adverse drug reactions. Thus, pharmacogenetic investigations are required to understand the impact of functional variations on the efficacy and tolerability of SSRI. Identifying the carrier variants may aid in clear-decision making of the treatment regimen, aiding the approach of personalized medication.

Role of serotonin transporter and receptor gene polymorphisms in treatment response to selective serotonin reuptake inhibitors in major depressive disorder

OBJECTIVE

Significant challenges in the management of major depressive disorder include the lag period from treatment initiation to an evident response, low response rates and unpredictable disparities in outcome between patients. As a large part of these has been linked to genetic mechanisms, we tried to establish a relationship between genes associated with serotonin neurotransmission and outcome to selective serotonin reuptake inhibitor (SSRI) treatment.

METHODS

One hundred and twenty-five patients with moderate to severe depression [at least 15 on the Hamilton Depression (HAM-D) Rating Scale] being started on SSRI were recruited. Those with a reduction of at least 50% from baseline or an absolute score of 7 or less after 8 weeks of treatment were considered as responders. The serotonin transporter linked polymorphic region 5HTTLPR, serotonin transporter intron 2 (STin2) polymorphism and the 5-HT receptor 1A rs6295 polymorphisms were studied in association with outcome.

RESULTS

The l/l genotype of the 5HTTLPR was associated with greater likelihood of response (OR: 4.65, CI: 1.74-12.38, p = 0.003). Patients with the 12/12 repeat variant of the STin2 VNTR polymorphism showed a greater reduction in HAM-D score, compared to patients with the 10/10 genotype (OR: 0.12, CI: 0.03-0.44, p = 0.001). We found no association of the 5HTR1Ars6295 polymorphism with response.

CONCLUSIONS

The 5HTTLPR polymorphism and the SLC6A4 intron 2 polymorphism were associated with treatment response, with the l/l genotype and 12-copy allele showing a tendency towards better outcomes, respectively.

Association of serotonin transporter gene polymorphism with efficacy of the antidepressant drugs sertraline and mirtazapine in newly diagnosed patients with major depressive disorders

OBJECTIVE

We examined the association of serotonin receptor transporter gene polymorphism in patients with MDD with the clinical efficacy of mirtazapine (MZ) and sertraline (ST).

METHOD

Newly diagnosed, treatment naïve, 80 MDD patients (aged 18-45) diagnosed using DSM-5 criteria and with Beck's depression inventory score (BDI) score ≥21 were included and randomly divided into two groups of 40 participants and were administered MZ 15-45 mg/day or ST 25-200 mg/day respectively. Patients were followed up for 6 weeks for evaluation of BDI scores. Genotypic evaluation was done and three allele variants were identified based on the polymerase chain reaction fragment sizes: short (S; 486 bp), long (L; 529 bp), or extralong (XL; 612 or 654 bp) and classified into five genotypes: S/S,S/L, L/L, S/XL, and L/XL.

RESULT

We found that 32.5% patients belonged to the S/S genotype, suggesting that individuals with the SS genotype are at higher risk of developing MDD. No statistically significant association was seen with ST or MZ groups on the basis of genotypes. Clinically significant improvement was observed with a more than 50% reduction in BDI scores at 6 weeks of treatment with both drugs.

CONCLUSION

Identification of risk population can be carried out by genotype testing. Prior genotyping in MDD patients might help to predict a better clinical outcome with antidepressants.

No Association Between SLC6A4 Gene Polymorphisms With Treatment Remission to Venlafaxine in Han Chinese Depressive Patients

OBJECTIVE

Major depressive disorder (MDD) is a heterogeneous psychiatric disorder and considered to be one of the most common mental diseases worldwide. The antidepressant venlafaxine, as a serotonin noradrenaline reuptake inhibitor, is applied to MDD relief. Solute carrier family 6 member 4 (SLC6A4) has been reported to promote the reuptake of serotonin and to be closely correlated to depression. The present study examined whether rs6354 and rs1487971 in SLC6A4 are associated with remission after venlafaxine treatment in MDD patients.

METHODS

This study consisted of 195 Han Chinese patients with MDD, who accepted a 6-week treatment with venlafaxine. Two SLC6A4 single-nucleotide polymorphisms (SNPs) were selected from database of SNP and genotyped by matrix-assisted laser desorption/ionization time of flight mass spectrometer in MassARRAY Analyzer 4 platforms. The 17-item Hamilton Depression Scale was used to access the severity of major depression. Allele and genotype frequencies between patients in remission and nonremission were calculated with online software SHEsis.

RESULTS

No significant differences in allele or genotype frequencies were observed in rs6354 and rs1487971. There were no significant associations between 2 SNPs and venlafaxine treatment outcome.

CONCLUSIONS

It suggested that rs6354 or rs1487971 within SLC6A4 appears not to be involved in the venlafaxine treatment outcome in Han Chinese patients with MDD.

5HTTLPR Genetic Variant and Major Depressive Disorder: A Review

Major Depressive Disorder (MDD) is a disease that involves biological, psychological, and social interactions. Studies have shown the importance of genetics contribution to MDD development. The SCL6A4 protein (5HTTLPR) functions transporting serotonin, a neurotransmitter linked to mood and emotion, to the synaptic cleft. Hence, this study seeks, through a literature review, a better comprehension of the 5HTTLPR genetic variant association with MDD. For this purpose, a search was performed on the Virtual Health Library Portal for articles that related 5HTTLPR to MDD. Most of the articles found were conducted in the American continent, with one (1) study implemented in Brazil. 5HTTLPR associations were found regarding changes in the nervous system, pharmacology, and risk factors seen in MDD patients. When verifying the allelic distribution, the S allele had a higher frequency in most of the studies analyzed. Despite not finding a commonality in the different studies, the tremendous genetic variation found demonstrates the MDD complexity. For this reason, further studies in diverse populations should be conducted to assist in the understanding and treatment of the disease.

A preliminary association study between serotonin transporter (5-HTTLPR), receptor polymorphisms (5-HTR1A, 5-HTR2A) and depression symptom-clusters in a north Indian population suffering from Major Depressive Disorder (MDD)

INTRODUCTION

Major Depressive Disorder (MDD) is a broad heterogeneous diagnostic construct. Previous studies have shown that it can be resolved into several symptom-clusters which are proposed to be associated with single nucleotide polymorphisms (SNPs) of the serotonergic pathway (5-HTTLPR, 5HTR1A, 5-HTR2A).

METHODS AND MATERIAL

In a cross-sectional study conducted at a tertiary level mental health care set-up in north India, 80 out-patients with MDD were evaluated with Montgomery Asberg Depression Rating Scale (MADRS) and then genotyping was done. The different clinical and genetic variables were compared across the factor structures of MADRS. Also, the comparison of the genetic data of cases was done with the pre-existing database of the non-blood related healthy ethnically-matched controls.

RESULTS

There was no significant association between age, gender, other clinical variables, SNPs like 5-HTTLPR SS/SL, rs6295 CC/CG/GG, rs6311GG/GA/AA, rs6313 CC/CT/TT and different factor-structures like 'detachment' consisting of items like concentration difficulty, lassitude, inability to feel; 'psychic anxiety' consisting of suicidal thoughts and inner tension; 'mood-pessimism' consisting of symptoms like apparent sadness, reported sadness, pessimistic thoughts and 'vegetative symptoms' like decreased sleep, poor appetite. Neither there was any association between genotype of the cases compared with the controls.

CONCLUSIONS

No significant association was obtained between the four-factor structures of depression in MADRS and serotonin transporter and receptor SNPs in a study with a small sample size. This study evaluates whether depression symptom-clusters have distinct genotypic determinants and necessitates more comprehensive studies for unravelling the genetic determinants of depression.

Translational Functional Neuroimaging in the Explanation of Depression

Translation as a notion and procedure is deeply embodied in medical science and education. Translation includes the possibility to translate data across disciplines to improve diagnosis and treatment procedures. The evidence accumulated using translation serves as a vehicle for reification of medical diagnoses. There are promising, established post hoc correlations between the different types of clinical tools (interviews and inventories) and neuroscience. The various measures represent statistical correlations that must now be integrated into diagnostic standards and procedures but this, as a whole, is a step forward towards a better understanding of the mechanisms underlying psychopathology in general and depression in particular. Here, we focus on functional magnetic resonance imaging studies using a trans-disciplinary approach and attempt to establish bridges between the different fields. We will selectively highlight research areas such as imaging genetics, imaging immunology and multimodal imaging, as related to the diagnosis and management of depression.

Evaluation of interleukin-6 and serotonin as biomarkers to predict response to fluoxetine

OBJECTIVE

Only 30% of major depressive disorder (MDD) patients achieve complete remission with a serotonergic antidepressant (selective serotonin reuptake inhibitor). We investigated the potential of serotonin (5-HT) and interleukin-6 (IL-6) to serve as functional biomarkers of fluoxetine response.

METHODS

Serum IL-6 and 5-HT were measured in 73 MDD patients (39 responders and 34 non-responders) pre- and 6 weeks post-treatment and in 44 normal controls with ELISA. Fluoxetine and norfluoxetine were measured using LC MS/MS.

RESULTS

IL-6 levels were significantly higher in MDD patients when compared with controls (p < 0.01), and 5-HT levels were significantly lower in non-responders compared with controls (p = 0.0131). Pre- and post-treatment levels of both biomarkers individually and in combination did not significantly differ between responders and non-responders. Area under the receiver operating characteristics curve for the biomarkers was 0.5. Significant correlation was seen between the percentage change in IL-6 and percentage change in Hamilton Rating Scale for Depression score in responders. Fluoxetine and norfluoxetine concentrations were not significantly different in responders and non-responders, and there was no correlation between fluoxetine concentrations and percentage reduction in 5-HT from week 0 to 6.

CONCLUSION

5-HT and IL-6 may not serve as useful markers of response to fluoxetine because of inconsistent results across different studies. Copyright © 2016 John Wiley & Sons, Ltd.

Association of serotonin transporter (SLC6A4) and receptor (5HTR1A, 5HTR2A) polymorphisms with response to treatment with escitalopram in patients with major depressive disorder: A preliminary study

Background & objectives:

Genetic factors have potential of predicting response to antidepressants in patients with major depressive disorder (MDD). In this study, an attempt was made to find an association between response to escitalopram in patients with MDD, and serotonin transporter (SLC6A4) and receptor (5HTR1A, 5HTR2A) polymorphisms.

Methods:

Fifty five patients diagnosed as suffering from MDD, were selected for the study. The patients were treated with escitalopram over a period of 6-8 wk. Severity of depression, response to treatment and side effects were assessed using standardised instruments. Genetic variations from HTR1A (rs6295), HTR2A (rs6311 and rs6313) and SLC6A4 (44 base-pair insertion/deletion at 5-HTTLPR) were genotyped. The genetic data of the responders and non-responders were compared to assess the role of genetic variants in therapeutic outcome.

Results:

Thirty six (65.5%) patients responded to treatment, and 19 (34.5%) had complete remission. No association was observed for genotype and allelic frequencies of single nucleotide polymorphisms (SNPs) among remitter/non-remitter and responder/non-responder groups, and six most common side-effects, except memory loss which was significantly associated with rs6311 (P =0.03).

Interpretation & conclusions:

No significant association was found between the SNPs analysed and response to escitalopram in patients with MDD though a significant association was seen between the side effect of memory loss and rs6311. Studies with larger sample are required to find out genetic basis of antidepressant response in Indian patients.

Advances in Medications and Tailoring Treatment for Alcohol Use Disorder

Alcohol use disorder (AUD) is a chronic heritable brain disorder with a variable clinical presentation. This variability, or heterogeneity, in clinical presentation suggests complex interactions between environmental and biological factors, resulting in several underlying pathophysiological mechanisms in the development and progression of AUD. Classifying AUD into subgroups of common clinical or pathological characteristics would ease the complexity of teasing apart underlying molecular mechanisms. Genetic association analyses have revealed several polymorphisms-small differences in DNA-that increase a person's vulnerability to develop AUD and other alcohol-related intermediate characteristics, such as severity of drinking, age of AUD onset, or measures of craving. They also have identified polymorphisms associated with reduced drinking. Researchers have begun utilizing these genetic polymorphisms to identify alcoholics who might respond best to various treatments, thereby enhancing the effectiveness of currently tested medications for treating AUD. This review compares the efficacy of medications tested for treatment of AUD with and without incorporating genetics. It then discusses advances in pre-clinical genetic and genomic studies that potentially could be adapted to clinical trials to improve treatment efficacy. Although a pharmacogenetic approach is promising, it is relatively new and will need to overcome many challenges, including inadequate scientific knowledge and social and logistic constraints, to be utilized in clinical practice.

5-Hydroxy tryptamine transporter (5HTT) gene promoter region polymorphism in anxiety and depressive disorders

BACKGROUND

5HTTLPR polymorphism (5- Hydroxy tryptamine transporter linked promoter region polymorphism) is the most widely studied genetic variant in psychiatry. The present study is a modest effort at ascertaining the role of 5HT transporter linked promoter region polymorphism (5HTTLPR) in anxiety and depressive disorders in Kashmir (India).The aim of this study was to examine 5-Hydroxy tryptamine transporter (5HTT) gene promoter region polymorphism in anxiety and depressive disorders.

METHODS

Thirty patients with unipolar depressive disorders, 30 patients with anxiety disorders and 40 healthy volunteers (controls) were studied on a case control design, using polymerase chain reaction (PCR) and agarose gel electrophoresis after digestion with endonuclease enzyme. Genotypes and allele frequencies were compared using chi square tests, and p value of < 0.05 was considered as statistically significant.

RESULTS

The mean (±sd) HAM-A (Hamilton rating scale for anxiety) scores for anxiety and depressive groups were 28.2±5.14 and 17±5.61, respectively (P < 0.001). The mean (±sd) HAM-D (Hamilton rating scale for depression) scores for depressive and anxiety groups were 25±5.58 and 15±6.13, respectively. (p< 0.001). The frequency of S allele was significantly high (83.3% vs 60%) in the group with anxiety (p< 0.05) compared to the control group (p> 0.05).

CONCLUSION

The genetic studies are still evolving as pathogenesis of anxiety and depressive disorders and involve the interaction of environmental factors with various genes. Genetic variation in different populations and hence different environments is important for elucidation of the mechanisms of these disorders. However, the study concludes that the locus under study is not shared between the two disorders.

Altered response to the selective serotonin reuptake inhibitor escitalopram in mice heterozygous for the serotonin transporter: an electrophysiological and neurochemical study

A serotonin (5-HT) transporter (5-HTT; SERT) polymorphism has been associated with depressive states and poor responses to selective serotonin reuptake inhibitors (SSRIs). Given the similar attenuation of SERT activity in SERT+/- mice and in humans with short allele(s) of SERT in its promoter region, it is conceivable that SERT+/- mice offer an adequate model to mimic the human subpopulation with respect to their altered response to SSRIs. This study investigated the effects of the most selective SSRI escitalopram, in heterozygous SERT+/- mice using a combined electrophysiological and neurochemical approach. Results indicated that administration of escitalopram for 2 d resulted in a 72% and 63% decrease in dorsal raphe 5-HT neuronal firing rate in SERT+/+ and SERT+/- mice, respectively. In contrast, administration of escitalopram for 21 d produced a gradual recovery of 5-HT neuronal firing rate to basal level in SERT+/+, but not in SERT+/- mice. In the hippocampus, microdialysis revealed that sustained administration of escitalopram produced a greater increase in extracellular 5-HT ([5-HT]ext) outflow in SERT+/- than in the wild-types with or without a washout of the SSRI. Nevertheless, the ability of microiontophoretically applied 5-HT to inhibit the firing rate of CA3 pyramidal neurons was not different between SERT+/+ and SERT+/- mice given escitalopram for 21 d. The data indicate that the poor response to SSRIs of depressive patients with short allele(s) of SERT is not attributable to a lesser increase in 5-HT transmission in the hippocampus.

Association between serotonin transporter gene promoter-region polymorphism and 4- and 12-week treatment response to sertraline in posttraumatic stress disorder

BACKGROUND

We examined the association between serotonin transporter (5HTTLPR) genotype (SS vs SL vs LL) and sertraline treatment outcome in posttraumatic stress disorder (PTSD).

METHODS

Outpatients (n=330) with PTSD underwent 5HTTLPR genotyping. All patients received sertraline (100 mg/day) for 12 weeks. Patients were assessed using the Clinician-Administered PTSD Scale (CAPS) and other instruments. Patients and rater were blind to the genotyping results. The primary outcome was completer sample CAPS improvement at 12 weeks. Response was defined as ≥30% improvement in CAPS total score with a CGI-I score of 1 or 2.

RESULTS

The discontinuation rate was 31.5%. Adverse events led to drop out in 18.1%, 15.3%, and 5.9% of SS, SL, and LL patients, respectively (P=0.038). Among completers, there were 95, 43, and 88 patients with the SS, SL, and LL genotypes, respectively. At endpoint, CAPS total scores improved by 26% vs 46%, respectively, in SS and SL vs LL patients (P<0.001); much of this improvement (15% vs 31% in SS and SL vs LL patients, respectively; P<0.001) was apparent by week 4. The findings were largely similar for the other outcome measures. The response rate was 0%, 0%, and 47.7% in the SS, SL, and LL groups, respectively (P<0.001).

LIMITATIONS

We administered a fixed dose of sertraline. For sociopolitical reasons, we planned a completer analysis only.

CONCLUSIONS

Relative to the SS and SL 5HTTLPR genotypes, the LL genotype is associated with greater responsiveness of PTSD to sertraline (100mg/day) and with lower drop out due to adverse events. The S allele is associated with a striking specificity for treatment nonresponse, as defined in this study.

Serotonin transporter gene polymorphism and psychiatric disorders: is there a link?

Though still in infancy, the field of psychiatric genetics holds great potential to contribute to the development of new diagnostic and therapeutic options to treat these disorders. Among a large number of existing neurotransmitter systems, the serotonin system dysfunction has been implicated in many psychiatric disorders and therapeutic efficacy of many drugs is also thought to be based on modulation of serotonin. Serotonin transporter gene polymorphism is one of the most extensively studied polymorphisms in psychiatric behavioral genetics. In this article, we review the status of evidence for association between the serotonin gene polymorphism and some common mental disorders like affective disorders, post-traumatic stress disorder, obsessive-compulsive disorder, suicide, autism, and other anxiety and personality disorders. Going beyond traditional association studies, gene-environment interaction, currently gaining momentum, is also discussed in the review. While the existing information of psychiatric genetics is inadequate for putting into practice genetic testing in the diagnostic work-up of the psychiatric patient, if consistent in future research attempts, such results can be of great help to improve the clinical care of a vast majority of patients suffering from such disorders.

Berberine and evodiamine influence serotonin transporter (5-HTT) expression via the 5-HTT-linked polymorphic region

The aim of this study was to investigate the effect of berberine and evodiamine on serotonin transporter (5-HTT) expression and then test how allelic variations previously identified in the promoter region could modulate that effect in the serotonergic neuronal cell line RN46A. Both berberine and evodiamine, alone and in combination, increased 5-HTT mRNA and protein expression significantly across the various alleles. When tested against the S, XS(11), L(G), L(A), XL(17), and XL(18) alleles, respectively, 100 μM berberine increased 5-HTT promoter activities by 67%, 128.7%, 106.9%, 100.4%, 26.2% and 82%, 2 μM evodiamine increased 5-HTT promoter activities by 216.7%, 81.6%, 305.6%, 181.5%, 175.3% and 102.2%. Berberine and evodiamine increased 5-HTT promoter activity differently depending on the genetic variation of the 5-HTTLPR polymorphism. This study has provided a convincing example of how herbal compounds influence the expression of one of the most intensively studied psychiatric candidate genes, the serotonin transporter.

Molecular biology research in neuropsychiatry: India's contribution

Neuropsychiatric disorders represent the second largest cause of morbidity worldwide. These disorders have complex etiology and patho-physiology. The major lacunae in the biology of the psychiatric disorders include genomics, biomarkers and drug discovery, for the early detection of the disease, and have great application in the clinical management of disease. Indian psychiatrists and scientists played a significant role in filling the gaps. The present annotation provides in depth information related to research contributions on the molecular biology research in neuropsychiatric disorders in India. There is a great need for further research in this direction as to understand the genetic association of the neuropsychiatric disorders; molecular biology has a tremendous role to play. The alterations in gene expression are implicated in the pathogenesis of several neuropsychiatric disorders, including drug addiction and depression. The development of transgenic neuropsychiatric animal models is of great thrust areas. No studies from India in this direction. Biomarkers in neuropsychiatric disorders are of great help to the clinicians for the early diagnosis of the disorders. The studies related to gene-environment interactions, DNA instability, oxidative stress are less studied in neuropsychiatric disorders and making efforts in this direction will lead to pioneers in these areas of research in India. In conclusion, we provided an insight for future research direction in molecular understanding of neuropsychiatry disorders.

Initiatives in biological research in Indian psychiatry

Biological psychiatry is an exploratory science for mental health. These biological changes provide some explicit insight into the complex area of 'brain-mind and behavior'. One major achievement of research in biological field is the finding to explain how biological factors cause changes in behavior. In India, we have a clear history of initiatives in research from a biological perspective, which goes back to 1958. In the last 61 years, this field has seen significant evolution, precision and effective utilization of contemporary technological advances. It is a matter of great pride to see that in spite of difficult times in terms of challenges of practice and services, administration, resource, funding and manpower the zest for research was very forthcoming. There was neither dedicated time nor any funding for conducting research. It came from the intellectual insight of our fore fathers in the field of mental health to gradually grow to the state of strategic education in research, training in research, international research collaborations and setting up of internationally accredited centers. During difficult economic conditions in the past, the hypothesis tested and conclusions derived have not been so important. It is more important how it was done, how it was made possible and how robust traditions were established. Almost an entire spectrum of biological research has been touched upon by Indian researchers. Some of these are electroconvulsive therapy, biological markers, neurocognition, neuroimaging, neuroendocrine, neurochemistry, electrophysiology and genetics. A lot has been published given the limited space in the Indian Journal of Psychiatry and other medical journals published in India. A large body of biological research conducted on Indian patients has also been published in International literature (which I prefer to call non-Indian journals). Newer research questions in biological psychiatry, keeping with trend of international standards are currently being investigated by the younger generation with great enthusiasm. What we have achieved so far is the foundation work in last 60 years. Our main challenge in development of biological psychiatry research in India remains resources in terms of manpower, funding and dedicated time for research psychiatrists. Developing basic sciences laboratories, discrete research questions, high quality methodology, and logistical support are some of the essentials. In the present time the culture of research has changed. It is specific and evidence-based. We have time-tested examples of International collaborative research. We need to get more resources, develop education, collaboration and effective leadership. In times to come, India will provide international leadership in basic and clinical biological psychiatry. There is hope.

Research on antidepressants in India

Data suggests that antidepressants are useful in the management of depressive disorders, anxiety disorders, sexual dysfunction, eating disorders, impulse control disorders, enuresis, aggression and some personality disorders. Research focusing on the usefulness of antidepressants in India has more or less followed the trends seen in the West. Most of the studies conducted in India have evaluated various antidepressants in depression. In this article, we review studies conducted in India on various antidepressants. The data suggests that antidepressants have been evaluated mainly in the acute phase treatment and rare studies have evaluated the efficacy in continuation phase treatment.

An overview of Indian research in depression

Depression as a disorder has always been a focus of attention of researchers in India. Over the last 50-60 years, large number of studies has been published from India addressing various aspects of this commonly prevalent disorder. The various aspects studied included epidemiology, demographic and psychosocial risk factor, neurobiology, symptomatology, comorbidity, assessment and diagnosis, impact of depression, treatment related issues and prevention of depression in addition to the efficacy and tolerability of various antidepressants. Here, we review data on various aspects of depression, originating from India.