Stefano Porcelli

Meta-analysis of serotonin transporter gene promoter polymorphism (5-HTTLPR) association with antidepressant efficacy.

In the last decade the serotonin transporter gene promoter polymorphism (5-HTTLPR) was likely the most studied genetic variant as predictor of antidepressant response. Nevertheless results are not consistent across studies and previous meta-analysis, since various factors seem to modulate its effect on antidepressant response. With the aim of clarifying this issue, we systematically reviewed literature, selecting 33 studies for an exploratory analysis without any a priori hypothesis. Then we analyzed separately 19 studies performed on Caucasians and 11 on Asians. We tested two phenotypes--remission and response rates--and three genotype comparisons--ll versus ls/ss, ss versus ll/ls and ll versus ss - using the Cochrane review manager. Evaluations were performed separately for SSRIs and mixed/other drugs. Possible clinical modulators were investigated. In the exploratory analysis, we found an association between l allele and l/l genotype and remission. When the analysis was split for ethnic group, in Caucasians we found an association between l allele and both response (OR = 1.58, C.I. 1.16-2.16, p = 0.004), and remission (OR = 1.53, C.I. 1.14-2.04, p = 0.004) in the SSRI group. Only a marginal association between l allele and remission (OR = 1.41, C.I. 1.02-1.95, p = 0.04) survived pooling together mixed antidepressant treatments. In Asians, a small effect of 5-HTTLPR on remission for mixed antidepressants was detected (OR = 2.10, C.I. 1.15-3.84, p = 0.02). Gender, age and age at onset modulated the association in Caucasians. Gender, age and depression severity at baseline modulated the association in Asians. In conclusion, in Caucasians 5-HTTLPR may be a predictor of antidepressant response and remission, while in Asians it does not appear to play a major role.

Pharmacogenetics of antidepressant response

Personalized medicine - the adaptation of therapies based on an individuals genetic and molecular profile - is one of the most promising aspects of modern medicine. The identification of the relation between genotype and drug response, including both the therapeutic effect and side effect profile, is expected to deeply affect medical practice. In this paper, we review the current knowledge about the genes related to antidepressant treatment response and provide methodologic proposals for future studies. We have mainly focused on genes associated with pharmacodynamics, for which a list of promising genes has been identified despite some inconsistency across studies. We have also synthesized the main results for pharmacokinetic genes, although so far they seem less relevant than those for pharmaco dynamic genes. We discuss possible reasons for these inconsistent findings and propose new study designs.

Catechol-o-methyltransferase gene modulation on suicidal behavior and personality traits: review, meta-analysis and association study

Suicide is one of the leading causes of death among young adults. Both genetic and personality factors plausibly have a role on suicidal behavior. We focused on the catechol-O-methyltransferase gene (COMT) and we performed: a review of studies investigating the association between COMT and both suicidal behavior and personality; a meta-analysis of studies investigating the association between suicidal behavior and COMT rs4680 polymorphism; an association study investigating the link between seven COMT polymorphisms (rs737865, rs5844402, rs5993883, rs4680, rs4633, rs165599 and rs9332377) and both personality traits and suicidal behavior. For the review and the meta-analysis we performed an electronic search to identify studies focused on the association between COMT and both suicidal behavior and personality. The sample of the association study was composed of three groups: 289 German healthy controls, 111 German suicide attempters and 70 Italian mood disorder patients. From the review, the meta-analysis and the association study no relationship emerged between COMT and suicidal behavior. Nevertheless, from both review and association study several links were found between COMT and personality traits. In particular, in the association study we found a significant correlation between rs4633 and Reward Dependence (Temperament and Character Inventory). As secondary results we found an association between rs737865 and Angry Reaction (State-Trait Anger Expression Inventory) and between rs9332377 and Irritability (Questionnaire for Measuring Factors of Aggression). Our findings suggested that COMT variants may not be directly implicated in suicidal behavior, however evidence of a COMT role in the modulation of personality traits has been found.

Clozapine resistance: Augmentation strategies

BACKGROUND Clozapine (CLZ) is not effective in more than 50% of treatment-resistant schizophrenic patients. In these cases, several pharmacological strategies are used in clinical practice, with different levels of evidence for both safety and efficacy. OBJECTIVES In the present paper we critically reviewed literature data regarding the efficacy and safety of adjunctive agents in CLZ-resistant schizophrenics. The following classes of agents were considered: 1) antipsychotics, 2) antidepressants, 3) mood stabilizers, 4) other agents (e.g. fatty acid supplement and glutamatergic agents), 5) electroconvulsive therapy (ECT). For lamotrigine and risperidone sufficient data were available to perform a meta-analysis. METHODS A Medline literature search covering a 20-year period was performed. For the meta-analysis, data were entered and analyzed with the Cochrane Collaboration Review Manager Software (RevMan version 5). RESULTS 62 pertinent studies were identified, including 1556 schizophrenic or schizoaffective patients. Among treatments investigated, there is evidence for CLZ augmentation with 1) amisulpride and aripiprazole, 2) mirtazapine and 3) ethyl eicosapentaenoic acid (E-EPA). Although promising, ECT augmentation needs further validation. The meta-analyses did not support either the use of risperidone or lamotrigine as CLZ adjunct. CONCLUSION Overall, there is scarce evidence of efficacy and safety as regards adjunctive strategies for CLZ-resistant patients. However, several limitations do not allow to draw any definitive conclusion; among these we underline the small sample size of clinical trials, the variable definitions of CLZ resistance, the heterogeneity of outcome measures and methodological designs.

Pharmacogenetics of Antidepressants

Up to 60% of depressed patients do not respond completely to antidepressants (ADs) and up to 30% do not respond at all. Genetic factors contribute for about 50% of the AD response. During the recent years the possible influence of a set of candidate genes as genetic predictors of AD response efficacy was investigated by us and others. They include the cytochrome P450 superfamily, the P-glycoprotein (ABCB1), the tryptophan hydroxylase, the catechol-O-methyltransferase, the monoamine oxidase A, the serotonin transporter (5-HTTLPR), the norepinephrine transporter, the dopamine transporter, variants in the 5-hydroxytryptamine receptors (5-HT1A, 5-HT2A, 5-HT3A, 5-HT3B, and 5-HT6), adrenoreceptor beta-1 and alpha-2, the dopamine receptors (D2), the G protein beta 3 subunit, the corticotropin releasing hormone receptors (CRHR1 and CRHR2), the glucocorticoid receptors, the c-AMP response-element binding, and the brain-derived neurotrophic factor. Marginal associations were reported for angiotensin I converting enzyme, circadian locomotor output cycles kaput protein, glutamatergic system, nitric oxide synthase, and interleukin 1-beta gene. In conclusion, gene variants seem to influence human behavior, liability to disorders and treatment response. Nonetheless, gene × environment interactions have been hypothesized to modulate several of these effects.

Genetic polymorphisms of cytochrome P450 enzymes and antidepressant metabolism

Introduction: The cytochrome P450 (CYP) enzymes are the major enzymes responsible for Phase I reactions in the metabolism of several substances, including antidepressant medications. Thus, it has been hypothesized that variants in the CYP network may influence antidepressant efficacy and safety. Nonetheless, data on this field are still contradictory. The authors aim to give an overview of the published studies analyzing the influence of CYP highly polymorphic loci on antidepressant treatment in order to translate the acquired knowledge to a clinical level. Areas covered: The authors collected and compared experimental works and reviews published from the 1980s to the present and included in the Medline database. The included studies pertain to the effects of CYP gene polymorphisms on antidepressant pharmacokinetic parameters and clinical outcomes (response and drug-related adverse effects), with a focus on applications in clinical practice. The authors focused mainly on in vivo studies in humans (patients or healthy volunteers). Expert opinion: Great variability in antidepressant metabolism among individuals has been demonstrated. Thus, with the current interest in individualized medicine, several genetic tests to detect CYP variants have been produced. They provide a potentially useful way to anticipate some clinical outcomes of antidepressant treatment, although they will only be extensively used in clinical practice if precise and specific treatment options and guidelines based on genetic tests can be provided.

Influence of BDNF variants on diagnosis and response to treatment in patients with major depression, bipolar disorder and schizophrenia.

Aim: The present study aimed to explore whether some single nucleotide polymorphisms (SNPs) within the BDNF gene could be associated with major depression (MD), bipolar disorder (BD) and schizophrenia, and whether they could predict clinical outcomes in Korean inpatients treated with antidepressants, mood stabilizers and antipsychotics, respectively. Methods: One hundred and forty-five patients with MD, 132 patients with BD, 221 patients with schizophrenia and 170 psychiatrically healthy controls were genotyped for 5 BDNF SNPs (rs2030324, rs7103873, rs10835210, rs11030101 and rs6265). Baseline and final clinical measures – including the Montgomery-Asberg Depression Rating Scale, Young Mania Rating Scale and Positive and Negative Symptoms Scale for patients with MD, BD and schizophrenia, respectively – were recorded. Results: rs10835210 CA and rs11030101 AT genotype frequencies were higher in BD and schizophrenia patients than in healthy and MD subjects. No significant association was found with clinical improvement. Discussion: Our findings provide evidence of an association between BDNF and BD and schizophrenia. However, taking into account the several limitations of our study, including the moderately small sample size, further research is needed to draw more definitive conclusions.

Mechanisms of antidepressant action: an integrated dopaminergic perspective.

The molecular mechanisms that cause and maintain the major depressive disorder (MDD) are currently unknown. Consistently, antidepressant treatments are characterized by insufficient success rates. This causes high social costs and severe personal sufferings. In the present review we analyze some of the paradigms that are used to explain MDD, particularly from the perspective of the dopaminergic (DA) system. DA has been more classically associated with psychosis and substance abuse disorders, even though a role of DA in MDD has been proposed as well and some antidepressants with DA profile exist. In the present work, we review some of the molecular mechanisms that underpin MDD from the perspective of the dopaminergic system, in the hope of unifying some of the major theories of MDD - the monoaminergic, inflammatory, epigenetics, neurotrophin and anti-apoptotic theories. Several shared components of these theories are highlighted, partially accounted by the functions of the DA system (see supplementary video).

From Pharmacogenetics to Pharmacogenomics: The Way toward the Personalization of Antidepressant Treatment

Objective: Major depressive disorder is the most common psychiatric disorder, worldwide, yet response and remission rates are still unsatisfactory. The identification of genetic predictors of antidepressant (AD) response could provide a promising opportunity to improve current AD efficacy through the personalization of treatment. The major steps and findings along this path are reviewed together with their clinical implications and limitations. Method: We systematically reviewed the literature through MEDLINE and Embase database searches, using any word combination of “antidepressant,” “gene,” “polymorphism,” “pharmacogenetics,” “genome-wide association study,” “GWAS,” “response,” and “adverse drug reactions.” Experimental works and reviews published until March 2012 were collected and compared. Results: Numerous genes pertaining to several functional systems were associated with AD response. The more robust findings were found for the following genes: solute carrier family 6 (neurotransmitter transporter), member 4; serotonin receptor 1A and 2A; brain-derived neurotrophic factor; and catechol-O-methyltransferase. Genome-wide association studies (GWASs) provided many top markers, even if none of them reached genome-wide significance. Conclusions: AD pharmacogenetics have not produced any knowledge applicable to routine clinical practice yet, as results were mainly inconsistent across studies. Despite this, the rising awareness about methodological deficits of past studies could allow for the identication of more suitable strategies, such as the integration of the GWAS approach with the candidate gene approach, and innovative methodologies, such as pathway analysis and study of depressive endophenotypes.

Influence of TPH2 variants on diagnosis and response to treatment in patients with major depression, bipolar disorder and schizophrenia

The present study is aimed at exploring whether some single nucleotide polymorphisms (SNPs) within the tryptophan hydroxylase 2 gene (TPH2) could be associated with major depression (MD), bipolar disorder (BD) and schizophrenia and whether they could predict clinical outcomes in Korean in-patients treated with antidepressants, mood stabilizers and antipsychotics, respectively. One hundred forty-five patients with MD, 132 patients with BD, 221 patients with schizophrenia and 170 psychiatrically healthy controls were genotyped for six TPH2 SNPs (rs4570625, rs10748185, rs11179027, rs1386498, rs4469933, and rs17110747). Baseline and final clinical measures, including the Montgomery-Åsberg Depression Rating Scale (MADRS), Young Mania Rating Scale and Positive and Negative Syndrome Scale, for patients with MD, BD and schizophrenia, respectively were recorded. None of the SNPs under investigation were associated with MD, BD and schizophrenia. However, in patients with MD, the rs4570625-rs10748185 G-A haplotype was significantly associated with higher endpoint MADRS severity, though not with response. Our results suggest that TPH2 variants neither have a major role in MD, BD and schizophrenia nor in response to treatments.