A review of 5-HT transporter linked promoter region (5-HTTLPR) polymorphism and associations with alcohol use problems and sexual risk behaviors

Changes in platelet serotonin concentration after four weeks of alcohol abstinence depending on the genotype of the serotonin transporter

BACKGROUND

Alcohol use disorder (AUD) is a psychiatric disorder characterized by excessive and uncontrolled drinking that causes distress and has damaging consequences for men and women of all ages. It is one of the four most disabling diseases and it affects approximately 14.6 million persons in Europe.

OBJECTIVES

Objective of this study is to investigate changes in platelet serotonin concentration after four weeks of alcohol abstinence in regards to the genotype of the serotonin transporter.

METHODS

A total of 154 patients with AUD were included in the study. Platelet serotonin concentrations were assessed by enzyme-linked immunosorbent assay. Genotype of serotonin transporter promoter polymorphism was determined by the polymerase chain reaction-based method.

RESULTS

We did not establish a statistically significant main effect of serotonin transporter polymorphism on platelet serotonin concentration after four weeks of abstinence.

CONCLUSION

Aforementioned finding is in line with previous research suggesting a complex relationship between serotonin transporter gene and platelet serotonin levels, and congruent with the well-established genotype interaction with numerous other factors, such as sex, ethnicity, education level, and stressful life events.

Personality as an intermediate phenotype for genetic dissection of alcohol use disorder

Genetic and environmental interactive influences on predisposition to develop alcohol use disorder (AUD) account for the high heterogeneity among AUD patients and make research on the risk and resiliency factors complicated. Several attempts have been made to identify the genetic basis of AUD; however, only few genetic polymorphisms have consistently been associated with AUD. Intermediate phenotypes are expected to be in-between proxies of basic neuronal biological processes and nosological symptoms of AUD. Personality is likely to be a top candidate intermediate phenotype for the dissection of the genetic underpinnings of different subtypes of AUD. To date, 38 studies have investigated personality traits, commonly assessed by the Cloninger's Tridimensional Personality Questionnaire (TPQ) or Temperament and Character Inventory (TCI), in relation to polymorphisms of candidate genes of neurotransmitter systems in alcohol-dependent patients. Particular attention has been given to the functional polymorphism of the serotonin transporter gene (5-HTTLPR), however, leading to contradictory results, whereas results with polymorphisms in other candidate monoaminergic genes (e.g., tryptophan hydroxylase, serotonin receptors, monoamine oxidases, dopamine receptors and transporter) are sparse. Only one genome-wide association study has been performed so far and identified the ABLIM1 gene of relevance for novelty seeking, harm avoidance and reward dependence in alcohol-dependent patients. Studies investigating genetic factors together with personality could help to define more homogenous subgroups of AUD patients and facilitate treatment strategies. This review also urges the scientific community to combine genetic data with psychobiological and environmental data to further dissect the link between personality and AUD.

Biological underpinnings of an internalizing pathway to alcohol, cigarette, and marijuana use

There is a limited understanding as to how specific genes impact addiction risk. Applying a developmental framework and research domain criteria (RDoC) to identify etiological pathways from genetic markers to addiction may have utility. Prior research has largely focused on externalizing pathways to substance use. Although internalizing mechanisms have received less attention, there is strong support that addiction is a longer term consequence of using substances to cope with internalizing as well as externalizing problems. This study tests whether temperament and depression mediate the association between specific genetic variants and substance use. The sample consisted of 426 adolescents from the Michigan Longitudinal Study (70.9% boys, 84.0% White). Four specific genetic variants were examined: SLC6A4 (5HTTLPR), BDNF (rs6265), NPY (rs3037354), and CRHBP (rs7728378). Childhood resiliency and behavioral control were examined as potential mediators, in addition to early adolescent depression, using a multiple-mediator path model. Resiliency and depression were supported as mediators in the association between genetic risk and later substance use. Important differences emerged across substances of abuse. Indirect effects via depression were not significant with the inclusion of aggression. Early difficulties with emotional coping may represent nonspecific neurobiological underpinnings for an internalizing pathway to addiction. (PsycINFO Database Record

Moderators of response to sertraline versus placebo among recently abstinent, cocaine dependent patients: A retrospective analysis of two clinical trials

BACKGROUND AND OBJECTIVES

Moderators of treatment response to serotonin reuptake inhibitor sertraline (SRT) for cocaine dependence were assessed in two randomized, double blind, placebo-controlled clinical trials.

METHODS

Generalized estimating equation modeling was performed on data from cocaine-dependent volunteers randomized to receive SRT or placebo (N = 126) who completed >2-week drug-free residential portions of the 12-week trials, in which subsequent outpatient treatment (weeks 3-12) included weekly cognitive behavioral therapy and thrice-weekly supervised urine toxicology.

PRIMARY OUTCOME MEASURE

Relapse (2 consecutive cocaine-positive or missing urines) following residential stay. Potential moderators included treatment, sex, age, race, depression measures, baseline cocaine urine result, and alcohol dependence diagnosis (ADDx).

RESULTS

Odds ratios (OR) for relapse showed placebo-treated participants were significantly more likely to relapse than SRT participants. Regardless of treatment condition, participants more likely to relapse were male, and those with lower Hamilton depression ratings, or baseline cocaine-negative urines. Older subjects or those with current ADDx had higher relapse risk than those without ADDx; however, treating older or ADDx participants with SRT reduced cocaine relapse more than placebo.

DISCUSSION AND CONCLUSIONS

Women or those with more severe cocaine use or depressive symptoms may have fewer cocaine relapses regardless of medication treatment. SRT at 200 mg reduced cocaine relapse more than placebo, especially in older participants or in those with comorbid ADDx.

SCIENTIFIC SIGNIFICANCE

SRT may be efficacious to support relapse prevention among cocaine-dependent patients in the context of brief residential followed by outpatient treatment, especially in older participants or those with comorbid alcohol/cocaine dependence. (Am J Addict 2017;26:807-814).

The serotonin transporter polymorphism (5-HTTLPR) and coping strategies influence successful emotion regulation in an acute stress situation: Physiological evidence

INTRODUCTION

Emotion regulation is an important everyday-life skill to reduce harm and stress. Consequently, research shows associations between psychopathologies and emotional dysregulation. The serotonin transporter polymorphism (5-HTTLPR) has repeatedly been associated to phenotypes and syndromes related to emotional dysregulation. However, there is no study showing any direct effects of 5-HTTLPR genotype and emotion regulation. Hence, the aim of the present study was to draw a link between 5-HTTLPR to emotion regulation.

METHOD

N=91 healthy participants filled in a coping questionnaire, provided gene samples and participated in an emotion regulation experiment. In a within-subject design they viewed emotional pictures and were either instructed to suppress their emotions or not. During the emotion regulation task, skin conductance responses (SCR) were recorded.

RESULTS

Emotion regulation abilities measured by SCR were influenced by 5-HTTLPR and coping strategies, together explaining 30% of variance. S-allele carriers showed increased SCRs when watching aversive stimuli in the uninstructed condition. However, when receiving an emotion regulation instruction, they were able to downregulate their arousal resulting in comparable SCRs as observed in LL-carriers.

DISCUSSION

This is the first study showing an impact of 5-HTTLPR on physiological emotion regulation. Results show that S-allele carriers have the same emotional arousal as L-allele carriers, when they get a supportive instruction to suppress unwanted feelings. These findings have implications for psychotherapeutic treatments.

Serotonin's Complex Role in Alcoholism: Implications for Treatment and Future Research

Current pharmacological treatments for alcohol dependence have focused on reducing alcohol consumption, but to date there are few treatments that also address the negative affective symptoms during acute and protracted alcohol withdrawal which are often exacerbated in people with comorbid anxiety and depression. Selective serotonin reuptake inhibitors (SSRIs) are sometimes prescribed to ameliorate these symptoms but can exacerbate anxiety and cravings in a select group of patients. In this critical review, we discuss recent literature describing an association between alcohol dependence, the SERT linked polymorphic region (5-HTTLPR), and pharmacological response to SSRIs. Given the heterogeneity in responsiveness to serotonergic drugs across the spectrum of alcoholic subtypes, we assess the contribution of specific 5-HT circuits to discrete endophenotypes of alcohol dependence. 5-HT circuits play a distinctive role in reward, stress, and executive function which may account for the variation in response to serotonergic drugs. New optogenetic and chemogenetic methods for dissecting 5-HT circuits in alcohol dependence may provide clues leading to more effective pharmacotherapies. Although our current understanding of the role of 5-HT systems in alcohol dependence is incomplete, there is some evidence to suggest that 5-HT3 receptor antagonists are effective in people with the L/L genotype of the 5-HTTLPR polymorphism while SSRIs may be more beneficial to people with the S/L or S/S genotype. Studies that assess the impact of serotonin transporter polymorphisms on 5-HT circuit function and the subsequent development of alcohol use disorders will be an important step forward in treating alcohol dependence.