The influence of 5-HTT and COMT genotypes on verbal fluency in ecstasy users

COMTVal158Met polymorphism is associated with ecstasy (MDMA)-induced psychotic symptoms in the Turkish population

OBJECTIVES

To investigate catechol-O-methyltransferase (COMT) Val158Met gene polymorphism in MDMA use disorder (MUD) by comparing genotype distributions between MUD patients and healthy controls considering clinical parameters.

METHODS

Eighty-two MUD patients' were consecutively admitted to the outpatient psychiatry clinic in May 2019-January 2020, and 95 healthy volunteers were included in the case-control study. We used the polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) to determine COMT Val158Met polymorphism.

RESULTS

The COMT Val158Met genotype distribution and allele frequencies of the MUD patient group were significantly different from the healthy control group. The Met/Met genotype (OR: 2.692; 95% Cl: 1.272-5.698; p=0.008) and Met allele frequencies (OR: 1.716; 95% Cl: 1.118-2.633; p=0.013) were significantly higher in the control group than in MUD patients. When the COMT Val158Met genotype and allele frequency distributions were compared between 2 groups according to the psychotic symptoms in the MUD patient group, the COMT Val158Met genotype distributions were significantly different between the groups of patients. The percentage of patients with the Val/Val genotype was significantly lower in MUD patients with a psychotic symptom than the MUD patients without a psychotic symptom (OR: 2.625; 95% Cl: 1.069-6.446; p=0.033).

CONCLUSION

The COMT Val158Met gene polymorphism was found to be related to the MUD-diagnosed Turkish patients and MDMA-induced psychotic symptoms.

Role of Serotonin Transporter and Receptor Gene Variations in the Acute Effects of MDMA in Healthy Subjects

Methylenedioxymethamphetamine (MDMA; ecstasy) is used recreationally and has been investigated as an adjunct to psychotherapy. Most acute effects of MDMA can be attributed to activation of the serotonin (5-hydroxytryptamine [5-HT]) system. Genetic variants, such as single-nucleotide polymorphisms (SNPs) and polymorphic regions in 5-HT system genes, may contribute to interindividual differences in the acute effects of MDMA. We characterized the effects of common genetic variants within selected genes that encode the 5-HT system (TPH1 [tryptophan 5-hydroxylase 1] rs1800532 and rs1799913, TPH2 [tryptophan 5-hydroxylase 2] rs7305115, HTR1A [5-HT_1A receptor] rs6295, HTR1B [5-HT_1B receptor] rs6296, HTR2A [5-HT_2A receptor] rs6313, and SLC6A4 [serotonin transporter] 5-HTTLPR and rs25531) on the physiological and subjective response to 125 mg of MDMA compared with placebo in 124 healthy subjects. Data were pooled from eight randomized, double-blind, placebo-controlled studies that were conducted in the same laboratory. TPH2 rs7305115, HTR2A rs6313, and SLC6A4 5-HTTLPR polymorphisms tended to moderately alter some effects of MDMA. However, after correcting for multiple comparisons, none of the tested genetic polymorphisms significantly influenced the response to MDMA. Variations in genes that encode key targets in the 5-HT system did not significantly influence the effects of MDMA in healthy subjects. Interindividual differences in the 5-HT system may thus play a marginal role when MDMA is used recreationally or therapeutically.

Depressive mood ratings are reduced by MDMA in female polydrug ecstasy users homozygous for the l-allele of the serotonin transporter

MDMA exerts its main effects via the serotonergic system and the serotonin transporter. The gene coding for this transporter determines the expression rate of the transporter. Previously it was shown that healthy individuals with the short allelic variant ('s-group') of the 5-HTTLPR-polymorphism displayed more anxiety and negative mood, and had a lower transcriptional efficiency compared to individuals who are homozygous for the l-allele ('l-group'). The present study aimed to investigate the role of the 5-HTTLPR polymorphism in MDMA-induced mood effects. Four placebo-controlled, within-subject studies were pooled, including in total 63 polydrug ecstasy users (N_s-group = 48; N_l-group = 15) receiving MDMA 75 mg and placebo on two test days, separated by minimally 7 days. Mood was assessed by means of the Profile of Mood States. Findings showed that MDMA induced -independent of sex- a positive mood state, and as a side effect also increased two negative affect states, anxiety and confusion. Anxiety ratings were higher in the l-group and independent of treatment or sex. Depression ratings were lowered by MDMA in the female l-group. Findings indicate that the MDMA-induced reduction in self-rated depressive feelings is sex- and genotype-dependent, with females homozygous for the l-allele showing this beneficial effect.

Meta-analysis of executive functioning in ecstasy/polydrug users

Ecstasy/3,4-methylenedioxymethamphetamine (MDMA) use is proposed to cause damage to serotonergic (5-HT) axons in humans. Therefore, users should show deficits in cognitive processes that rely on serotonin-rich, prefrontal areas of the brain. However, there is inconsistency in findings to support this hypothesis. The aim of the current study was to examine deficits in executive functioning in ecstasy users compared with controls using meta-analysis. We identified k = 39 studies, contributing 89 effect sizes, investigating executive functioning in ecstasy users and polydrug-using controls. We compared function-specific task performance in 1221 current ecstasy users and 1242 drug-using controls, from tasks tapping the executive functions - updating, switching, inhibition and access to long-term memory. The significant main effect demonstrated overall executive dysfunction in ecstasy users [standardized mean difference (SMD) = -0.18, 95% confidence interval (CI) -0.26 to -0.11, Z = 5.05, p < 0.001, I 2 = 82%], with a significant subgroup effect (χ 2 = 22.06, degrees of freedom = 3, p < 0.001, I 2 = 86.4%) demonstrating differential effects across executive functions. Ecstasy users showed significant performance deficits in access (SMD = -0.33, 95% CI -0.46 to -0.19, Z = 4.72, p < 0.001, I 2 = 74%), switching (SMD = -0.19, 95% CI -0.36 to -0.02, Z = 2.16, p < 0.05, I 2 = 85%) and updating (SMD = -0.26, 95% CI -0.37 to -0.15, Z = 4.49, p < 0.001, I 2 = 82%). No differences were observed in inhibitory control. We conclude that this is the most comprehensive analysis of executive function in ecstasy users to date and provides a behavioural correlate of potential serotonergic neurotoxicity.

Semantic Verbal Fluency Pattern, Dementia Rating Scores and Adaptive Behavior Correlate With Plasma Aβ42 Concentrations in Down Syndrome Young Adults

Down syndrome (DS) is an intellectual disability (ID) disorder in which language and specifically, verbal fluency are strongly impaired domains; nearly all adults show neuropathology of Alzheimer’s disease (AD), including amyloid deposition by their fifth decade of life. In the general population, verbal fluency deficits are considered a strong AD predictor being the semantic verbal fluency task (SVFT) a useful tool for enhancing early diagnostic. However, there is a lack of information about the association between the semantic verbal fluency pattern (SVFP) and the biological amyloidosis markers in DS. In the current study, we used the SVFT in young adults with DS to characterize their SVFP, assessing total generated words, clustering, and switching. We then explored its association with early indicators of dementia, adaptive behavior and amyloidosis biomarkers, using the Dementia Questionnaire for Persons with Intellectual Disability (DMR), the Adaptive Behavior Assessment System-Second Edition (ABAS-II), and plasma levels of Aβ peptides (Aβ₄₀ and Aβ₄₂), as a potent biomarker of AD. In DS, worse performance in SVFT and poorer communication skills were associated with higher plasma Aβ₄₂ concentrations, a higher DMR score and impaired communication skills (ABAS–II). The total word production and switching ability in SVFT were good indicators of plasma Aβ₄₂ concentration. In conclusion, we propose the SVFT as a good screening test for early detection of dementia and amyloidosis in young adults with DS.

5-HTTLPR Genotype Moderates the Effects of Past Ecstasy Use on Verbal Memory Performance in Adolescent and Emerging Adults: A Pilot Study

OBJECTIVE

Ecstasy use is associated with memory deficits. Serotonin transporter gene (5-HTTLPR) polymorphisms have been linked with memory function in healthy samples. The present pilot study investigated the influence of 5-HTTLPR polymorphisms on memory performance in ecstasy users, marijuana-using controls, and non-drug-using controls, after a minimum of 7 days of abstinence.

METHOD

Data were collected from 116 young adults (18-25 years-old), including 45 controls, 42 marijuana users, and 29 ecstasy users, and were balanced for 5-HTTLPR genotype. Participants were abstinent seven days prior to completing memory testing. Three MANCOVAs and one ANCOVA were run to examine whether drug group, 5-HTTLPR genotype, and their interactions predicted verbal and visual memory after controlling for gender, past year alcohol use, other drug use, and nicotine cotinine levels.

RESULTS

MANCOVA and ANCOVA analysis revealed a significant interaction between drug group and genotype (p = .03) such that ecstasy users with the L/L genotype performed significantly worse on CVLT-2 total recall (p = .05), short (p = .008) and long delay free recall (p = .01), and recognition (p = .006), with the reverse pattern found in controls. Ecstasy did not significantly predict visual memory. 5-HTTLPR genotype significantly predicted memory for faces (p = .02); short allele carriers performed better than those with L/L genotype.

CONCLUSIONS

5-HTTLPR genotype moderated the effects of ecstasy on verbal memory, with L/L carriers performing worse compared to controls. Future research should continue to examine individual differences in ecstasy's impact on neurocognitive performance as well as relationships with neuronal structure. Additional screening and prevention efforts focused on adolescents and emerging adults are necessary to prevent ecstasy consumption.

Changes in serotonin transporter (5-HTT) gene expression in peripheral blood cells after MDMA intake

RATIONALE

3,4-Methylenedioxymethamphetamine (MDMA, ecstasy) is an amphetamine derivative abused worldwide. Although data report that relatively high doses of MDMA deplete serotonin (5-HT) content and decrease the availability of serotonin transporters (5-HTT), there is no available evidence as to the adaptive mechanisms taking place in 5-HTT gene expression following MDMA intake in humans.

OBJECTIVE

To evaluate the pharmacological effects of MDMA on 5-HTT gene expression, using peripheral mononuclear cells as a biomarker of the central nervous system, and study whether an association exists between 5-HTT gene expression and psychobiological scores.

METHODS

A randomized, double-blind, controlled trial was conducted in 18 (nine women) healthy recreational MDMA users. Subjects were genotyped for 5-HTT linked polymorphism region (5-HTTLPR). MDMA 75 mg or placebo was administered; Profile of Mood States (POMS) and 5-HTT gene expression measures were performed at baseline, 90, and 165 min post administration. POMS scores were correlated with changes in gene expression.

RESULTS

The administration of 75 mg MDMA induced a significant twofold increase in 5-HTT gene expression after 165 min of drug administration. Significant associations were found between gene expression and POMS scores after MDMA administration. Results for each gender and 5-HTTLPR genotype are also reported.

CONCLUSIONS

Preliminary results show that MDMA causes substantial regulatory changes in the expression of serotonergic markers, likely being modulated by the 5-HTTLPR polymorphism. Changes in 5-HTT gene expression may play an important role in the regulation of mood state.

Behavioral effects and pharmacokinetics of (±)-3,4-methylenedioxymethamphetamine (MDMA, Ecstasy) after intragastric administration to baboons

(±)-3,4-Methylenedioxymethamphetamine (MDMA, "Ecstasy") is a popular drug of abuse. We aimed to characterize the behavioral effects of intragastric MDMA in a species closely related to humans and to relate behavioral effects to plasma MDMA and metabolite concentrations. Single doses of MDMA (0.32-7.8 mg/kg) were administered via an intragastric catheter to adult male baboons (N = 4). Effects of MDMA on food-maintained responding were assessed over a 20-hour period, whereas untrained behaviors and fine-motor coordination were characterized every 30 minutes until 3 hours postadministration. Levels of MDMA and metabolites in plasma were measured in the same animals (n = 3) after dosing on a separate occasion. MDMA decreased food-maintained responding over the 20-hour period, and systematic behavioral observations revealed increased frequency of bruxism as the dose of MDMA was increased. Drug blood level determinations showed no MDMA after the lower doses of MDMA tested (0.32-1.0 mg/kg) and modest levels after higher MDMA doses (3.2-7.8 mg/kg). High levels of 3,4-dihydroxymethamphetamine (HHMA) were detected after all doses of MDMA, suggesting extensive first-pass metabolism of MDMA in the baboon. The present results demonstrate that MDMA administered via an intragastric catheter produced behavioral effects that have also been reported in humans. Similar to humans, blood levels of MDMA after oral administration may not be predictive of the behavioral effects of MDMA. Metabolites, particularly HHMA, may play a significant role in the behavioral effects of MDMA.

Clinical pharmacology of 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy"): the influence of gender and genetics (CYP2D6, COMT, 5-HTT)

The synthetic psychostimulant MDMA (±3,4-methylenedioxymethamphetamine, ecstasy) acts as an indirect serotonin, dopamine, and norepinephrine agonist and as a mechanism-based inhibitor of the cytochrome P-450 2D6 (CYP2D6). It has been suggested that women are more sensitive to MDMA effects than men but no clinical experimental studies have satisfactorily evaluated the factors contributing to such observations. There are no studies evaluating the influence of genetic polymorphism on the pharmacokinetics (CYP2D6; catechol-O-methyltransferase, COMT) and pharmacological effects of MDMA (serotonin transporter, 5-HTT; COMT). This clinical study was designed to evaluate the pharmacokinetics and physiological and subjective effects of MDMA considering gender and the genetic polymorphisms of CYP2D6, COMT, and 5-HTT. A total of 27 (12 women) healthy, recreational users of ecstasy were included (all extensive metabolizers for CYP2D6). A single oral weight-adjusted dose of MDMA was administered (1.4 mg/kg, range 75–100 mg) which was similar to recreational doses. None of the women were taking oral contraceptives and the experimental session was performed during the early follicular phase of their menstrual cycle. Principal findings show that subjects reached similar MDMA plasma concentrations, and experienced similar positive effects, irrespective of gender or CYP2D6 (not taking into consideration poor or ultra-rapid metabolizers) or COMT genotypes. However, HMMA plasma concentrations were linked to CYP2D6 genotype (higher with two functional alleles). Female subjects displayed more intense physiological (heart rate, and oral temperature) and negative effects (dizziness, sedation, depression, and psychotic symptoms). Genotypes of COMT val158met or 5-HTTLPR with high functionality (val/val or l/*) determined greater cardiovascular effects, and with low functionality (met/* or s/s) negative subjective effects (dizziness, anxiety, sedation). In conclusion, the contribution of MDMA pharmacokinetics following 1.4 mg/kg MDMA to the gender differences observed in drug effects appears to be negligible or even null. In contrast, 5-HTTLPR and COMT val158met genotypes play a major role.

Pharmacokinetics and pharmacodynamics of 3,4-methylenedioxymethamphetamine (MDMA): interindividual differences due to polymorphisms and drug-drug interactions

Clinical outcome following 3,4-methylenedioxymethamphetamine (MDMA) intake ranges from mild entactogenic effects to a life-threatening intoxication. Despite ongoing research, the clinically most relevant mechanisms causing acute MDMA-induced adverse effects remain largely unclear. This complicates the triage and treatment of MDMA users needing medical care. The user's genetic profile and interactions resulting from polydrug use are key factors that modulate the individual response to MDMA and influence MDMA pharmacokinetics and dynamics, and thus clinical outcome. Polymorphisms in CYP2D6, resulting in poor metabolism status, as well as co-exposure of MDMA with specific substances (e.g. selective serotonin reuptake inhibitors (SSRIs)) can increase MDMA plasma levels, but can also decrease the formation of toxic metabolites and subsequent cellular damage. While pre-exposure to e.g. SSRIs can increase MDMA plasma levels, clinical effects (e.g. blood pressure, heart rate, body temperature) can be reduced, possibly due to a pharmacodynamic interaction at the serotonin reuptake transporter (SERT). Pretreatment with inhibitors of the dopamine or norepinephrine reuptake transporter (DAT or NET), 5-HT(2A) or α-β adrenergic receptor antagonists or antipsychotics prior to MDMA exposure can also decrease one or more MDMA-induced physiological and/or subjective effects. Carvedilol, ketanserin and haloperidol can reduce multiple MDMA-induced clinical and neurotoxic effects. Thus besides supportive care, i.e. sedation using benzodiazepines, intravenous hydration, aggressive cooling and correction of electrolytes, it is worthwhile to investigate the usefulness of carvedilol, ketanserin and haloperidol in the treatment of MDMA-intoxicated patients.

The influence of genetic and environmental factors among MDMA users in cognitive performance

This study is aimed to clarify the association between MDMA cumulative use and cognitive dysfunction, and the potential role of candidate genetic polymorphisms in explaining individual differences in the cognitive effects of MDMA. Gene polymorphisms related to reduced serotonin function, poor competency of executive control and memory consolidation systems, and high enzymatic activity linked to bioactivation of MDMA to neurotoxic metabolites may contribute to explain variations in the cognitive impact of MDMA across regular users of this drug. Sixty ecstasy polydrug users, 110 cannabis users and 93 non-drug users were assessed using cognitive measures of Verbal Memory (California Verbal Learning Test, CVLT), Visual Memory (Rey-Osterrieth Complex Figure Test, ROCFT), Semantic Fluency, and Perceptual Attention (Symbol Digit Modalities Test, SDMT). Participants were also genotyped for polymorphisms within the 5HTT, 5HTR2A, COMT, CYP2D6, BDNF, and GRIN2B genes using polymerase chain reaction and TaqMan polymerase assays. Lifetime cumulative MDMA use was significantly associated with poorer performance on visuospatial memory and perceptual attention. Heavy MDMA users (>100 tablets lifetime use) interacted with candidate gene polymorphisms in explaining individual differences in cognitive performance between MDMA users and controls. MDMA users carrying COMT val/val and SERT s/s had poorer performance than paired controls on visuospatial attention and memory, and MDMA users with CYP2D6 ultra-rapid metabolizers performed worse than controls on semantic fluency. Both MDMA lifetime use and gene-related individual differences influence cognitive dysfunction in ecstasy users.

Serotonin transporter and memory

The serotonin transporter (SERT) has been associated to diverse functions and diseases, though seldom to memory. Therefore, we made an attempt to summarize and discuss the available publications implicating the involvement of the SERT in memory, amnesia and anti-amnesic effects. Evidence indicates that Alzheimer's disease and drugs of abuse like d-methamphetamine (METH) and (+/-)3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") have been associated to decrements in the SERT expression and memory deficits. Several reports have indicated that memory formation and amnesia affected the SERT expression. The SERT expression seems to be a reliable neural marker related to memory mechanisms, its alterations and potential treatment. The pharmacological, neural and molecular mechanisms associated to these changes are of great importance for investigation.