Braz J Psychiatry. 2019 xxx-xxx;00(00):000-000 doi:10.1590/1516-4446-2019-0620 Brazilian Psychiatric Association 00000000-0002-7316-1185 ORIGINAL ARTICLE Association of BDNF, HTR2A, TPH1, SLC6A4, and COMT polymorphisms with tDCS and escitalopram efficacy: ancillary analysis of a double-blind, placebo-controlled trial Andre R. Brunoni0000-0000-0000-0000 ,1,2 Angel Carracedo,3 Olalla M. Amigo,3 Ana L. Pellicer,3 Leda Talib,2 Andre F. Carvalho0000-0000-0000-0000 ,4 Paulo A. Lotufo,1 Isabela M. Bensen˜ or,1 Wagner Gattaz,2 Carolina Cappi5 1Departamento de Medicina Interna, Faculdade de Medicina, Universidade de Sa˜o Paulo (USP), Sa˜o Paulo, SP, Brazil. 2Laborato´rio de Neurocieˆncias (LIM-27) and Instituto Nacional de Biomarcadores em Psiquiatria (INBION), Departamento e Instituto de Psiquiatria, Faculdade de Medicina, USP, Sa˜o Paulo, SP, Brazil. 3Grupo de Medicina Xeno´mica/Pharmacogenetics Research, Laboratorio SSL1, Centro Singular de Investigacio´n en Medicina Molecular y Enfermedades Cro´nicas (CiMUS), Santiago de Compostela, Spain. 4Department of Psychiatry, Faculty of Medicine, University of Toronto & Centre for Addiction & Mental Health (CAMH), Toronto, Canada. 5Programa Transtornos do Espectro Obsessivo-Compulsivo, Departamento e Instituto de Psiquiatria, Faculdade de Medicina, USP, Sa˜o Paulo, SP, Brazil. Objective: We investigated whether single nucleotide polymorphisms (SNPs) associated with neuroplasticity and activity of monoamine neurotransmitters, such as the brain-derived neurotrophic factor (BDNF, rs6265), the serotonin transporter (SLC6A4, rs25531), the tryptophan hydroxylase 1 (TPH1, rs1800532), the 5-hydroxytryptamine receptor 2A (HTR2A, rs6311, rs6313, rs7997012), and the catechol-O-methyltransferase (COMT, rs4680) genes, are associated with efficacy of transcranial direct current stimulation (tDCS) in major depression. Methods: Data from the Escitalopram vs. Electrical Current Therapy for Treating Depression Clinical Study (ELECT-TDCS) were used. Participants were antidepressant-free at baseline and presented with an acute, moderate-to-severe unipolar depressive episode. They were randomized to receive escitalopram/tDCS-sham (n=75), tDCS/placebo-pill (n=75), or placebo-pill/sham-tDCS (n=45). General linear models assessed the interaction between treatment group and allele-wise carriers. Additional analyses were performed for each group and each genotype separately. Results: Pairwise group comparisons (tDCS vs. placebo, tDCS vs. escitalopram, and escitalopram vs. placebo) did not identify alleles associated with depression improvement. In addition, exploratory analyses also did not identify any SNP unequivocally associated with improvement of depression in any treatment group. Conclusion: Larger, combined datasets are necessary to identify candidate genes for tDCS response. Keywords: Major depressive disorder; non-invasive brain stimulation; single-nucleotide polymorphism; selective serotonin reuptake inhibitors; randomized clinical trial Introduction speculated that, by stimulating the DLPFC, tDCS would increase the activity of the frontoparietal network, con- Transcranial direct current stimulation (tDCS) is a non- sequently leading to an improvement of depressive invasive brain stimulation intervention that consists of the symptoms.5 application of low-intensity electric currents over the scalp Clinically, tDCS excels in safety and tolerability6,7 and to modify brain activity and excitability according to the canevenbeusedathome.8 Nonetheless, tDCS has parameters selected for stimulation.1-3 For major depres- produced mixed outcomes in terms of antidepressant sive disorder (MDD), tDCS is applied over the dorsolateral efficacy.9-12 This may reflect a heterogeneous likelihood prefrontal cortex (DLPFC), a key hub of the frontopa- of response across participants. Therefore, identifying rietal network, which regulates several cognitive functions predictors of response may provide useful insights into and is hypoactive in depression.4 Although the exact anti- tDCS, such as clarifying its mechanisms of action, predic- depressant mechanisms of tDCS remain unclear, it is ting treatment outcomes, and designing better-tailored Correspondence: Andre´ R.Brunoni, Instituto de Psiquiatria, Servic¸o How to cite this article: Brunoni AR, Carracedo A, Amigo OM, Interdisciplinar de Neuromodulac¸a˜o, Rua Dr. Ovı´dio Pires de Campos, Pellicer AL, Talib L, Carvalho AF, et al. Association of BDNF, 785, 2o andar, Ala Sul, CEP 05403-000, Sa˜o Paulo, SP, Brazil. HTR2A, TPH1, SLC6A4, and COMT polymorphisms with tDCS and E-mail: [email protected] escitalopram efficacy: ancillary analysis of a double-blind, placebo- Submitted Jul 22 2019, accepted Aug 20 2019 controlled trial. Braz J Psychiatry. 2019;00:000-000. http://dx.doi.org/ . 10.1590/1516-4446-2019-0620 2 AR Brunoni et al trials within the framework of precision psychiatry.2,13,14 In Methods this context, the investigation of genomic variants, such as common single nucleotide polymorphisms (SNPs), Trial design has been considered a promising avenue to tailor anti- depressant strategies.15-17 Furthermore, compared to This is an ancillary study of the Escitalopram versus Electrical Current Therapy for Treating Depression other biological markers such as magnetic resonance imaging (MRI) and electroencephalography (EEG), Clinical Study (ELECT-TDCS), a non-inferiority, placebo- controlled trial in which the efficacy of tDCS, escitalopram, SNPs are relatively more available and affordable to 19,31 18 and placebo were evaluated. The ELECT-TDCS collect and analyse. 19,31 In the present study, we investigated whether specific trial (clinicaltrials.gov number NCT01894815) took SNPs involved in MDD pathophysiology were associated place from 2013 to 2016 at the Universidade de 19 Sa˜o Paulo, the capital of the state of Sa˜o Paulo, Brazil. with tDCS response. According to our study protocol, Participants were randomized to receive escitalopram- the following genes and SNPs associated with treatment response in MDD, neuroplasticity, and serotonin metabo- pill/sham-tDCS (henceforth, escitalopram), placebo-pill/ active-tDCS (tDCS), or placebo-pill/sham-tDCS (placebo) lism were investigated: in a 3:3:2 ratio. ELECT-TDCS was designed to demonstrate noninfer- a) brain-derived neurotrophic factor (BDNF, rs6265, chro- iority of escitalopram vs. tDCS. Specifically, noninferiority mosome 11p13): the BDNF gene was chosen because would be proven if the improvement in the tDCS vs. placebo the factor it encodes plays a key role in synaptic plasticity, groups was at least 50% of the improvement achieved in the depression and antidepressant response.20 The most escitalopram vs. placebo groups at the primary endpoint frequent BDNF genetic variation is the 196G/A (rs6265) 0 (week 10) on our primary outcome scale, the Hamilton SNP, which causes a change from Val to Met at the 5 -pro Depression Rating Scale, 17 items (HDRS-17). Briefly, the protein site. This polymorphism disrupts cellular traffick- original study showed a mean (standard deviation [SD]) ing, processing, and BDNF secretion,21 and impairs depression improvement in HDRS-17 of 11.3 (6.5) for synaptic transmission and cortical plasticity.22 Although escitalopram, 9 (7.1) for tDCS, and 5.8 (7.9) for placebo. we did not observe an influence of rs6265 on tDCS res- The main findings showed that tDCS was not noninferior ponse in an earlier study,23 our analyses might have been to escitalopram, as the lower boundary of the confidence underpowered. interval for the difference in the decrease of tDCS vs. b) solute carrier family 6 member 4 (SLC6A4, rs25531, escitalopram, a difference of -2.3 (95% confidence inter- chromosome 17q11.1-q12): SLC6A4 codifies the presy- val [95%CI] -4.3 to -0.4), was lower than the noninferiority naptic serotonin reuptake transporter (SERT) and is margin of -2.75. Secondary analyses showed that esci- characterized by a functional 44-bp insertion/deletion talopram and tDCS were both superior to placebo, and polymorphism (5HTTLPR) in its promoter region.24 This confirmed that escitalopram was superior to tDCS. More- SNP was chosen because it has been consistently asso- over, moderator analyses did not identify any clinical ciated with selective serotonin reuptake inhibitor (SSRI) or demographic predictor associated with treatment res- antidepressant response25; ponse for any intervention group. c) tryptophan hydroxylase 1 (TPH1, rs1800532, chromo- In ELECT-TDCS, we additionally investigated several some 11p15.3-p14) polymorphism: the TPH enzyme biological markers that could be associated with clinical metabolizes L-tryptophan to 5-HTP, which is then metab- depression outcomes, such as plasma biomarkers and olized to serotonin by the enzyme 5-HTP decarboxylase. motor cortical excitability.31,32 Here, we report data from TPH regulates the activity of this metabolic pathway and, the participants who finished the study and had at least therefore, the availability of serotonin. Although the TPH1 one blood sample collected at baseline for genotyping. isoform is less expressed in the brain than TPH2, the TPH1 gene has been particularly associated with anti- depressant effects17; Subjects d) 5-hydroxytryptamine receptor 2A (HTR2A, rs6311, rs6313, rs7997012, chromosome 13q14-q21) genes: this Participants with unipolar depression aged 18 to 75 years G protein-coupled receptor triggers long-term, intracellu- were included. Diagnoses were established by certified lar effects when activated and therefore plays a critical psychiatrists using the DSM-5