Serotonin Transporter Genomic Biomarker for Quantitative Assessment of Ondansetron Treatment Response in Alcoholics

Paucity of sensitive biomarkers to quantify transient changes in alcohol consumption level remains a critical barrier for the development of efficacious therapeutic agents to treat alcoholism. Recently, in an 11-week, randomized, placebo-controlled, double-blind trial of 283 alcohol-dependent individuals, we demonstrated that ondansetron was efficacious at reducing the severity of drinking (measured as drinks per drinking day; DDD) in alcoholics carrying the LL compared with the LS/SS genotype of the serotonin transporter gene, 5′-HTTLPR. Using peripheral blood samples from a cohort of 41 of these subjects, we determined whether there was a relationship between mRNA expression level of the 5′-HTTLPR genotypes (measured at weeks 0, 4, and 11) and self-reported alcohol consumption following treatment with either ondansetron (4 μg/kg twice daily; N = 19) or placebo (N = 22). Using a mixed-effects linear regression model, we analyzed the effects of DDD and 5′-HTTLPR genotypes on mRNA expression levels within and between the ondansetron and placebo groups. We found a significant three-way interaction effect of DDD, 5′-HTTLPR genotypes, and treatment on mRNA expression levels (p = 0.0396). Among ondansetron but not placebo recipients, there was a significant interaction between DDD and 5′-HTTLPR genotype (p = 0.0385 and p = 0.7938, respectively). In the ondansetron group, DDD was associated positively with mRNA levels at a greater rate of expression alteration per standard drink in those with the LL genotype (slope = +1.1698 in ln scale). We suggest that the combination of the LL genotype and 5′-HTTLPR mRNA expression levels might be a promising and novel biomarker to quantify drinking severity in alcoholics treated with ondansetron

In silico Models of Alcohol Dependence and Treatment

In this paper we view alcohol dependence and the response to treatment as a recurrent bio-behavioral process developing in time and propose formal models of this process combining behavior and biology in silico. The behavioral components of alcohol dependence and treatment are formally described by a stochastic process of human behavior, which serves as an event generator challenging the metabolic system. The biological component is driven by the biochemistry of alcohol intoxication described by deterministic models of ethanol pharmacodynamics and pharmacokinetics to enable simulation of drinking addiction in humans. Derived from the known physiology of ethanol and the literature of both ethanol intoxication and ethanol absorption, the different models are distilled into a minimal model (as simple as the complexity of the data allows) that can represent any specific patient. We use these modeling and simulation techniques to explain responses to placebo and ondansetron treatment observed in clinical studies. Specifically, the response to placebo was explained by a reduction of the probability of environmental reinforcement, while the effect of ondansetron was explained by a gradual decline in the degree of ethanol-induced neuromodulation. Further, we use in silico experiments to study critical transitions in blood alcohol levels after specific average number of drinks per day, and propose the existence of two critical thresholds in the human – one at 5 and another at 11 drinks/day – at which the system shifts from stable to critical and to super critical state indicating a state of alcohol addiction. The advantages of such a model-based investigation are that (1) the process of instigation of alcohol dependence and its treatment can be deconstructed into meaningful steps, which allow for individualized treatment tailoring, and (2) physiology and behavior can be quantified in different (animal or human) studies and then the results can be integrated in silico

Impact of 5-HT3 receptor blockade on the subjective and behavioural effects of drugs of abuse in humans

Substance abuse is a major health problem world-wide. Whatever the treatment goal, be it abstinence, 'controlled' use, or relapse prevention, the outcome from both pharmacological and non-biological treatments remains disappointing. In recent years, animal experiments have suggested that the reinforcing properties of drugs of abuse are critical to drug-seeking behaviour. Dopaminergic fibres running from the ventral tegmental area to the nucleus accumbens play a central role in the mediation of alcohol-induced reinforcement. Notably, 5-hydroxytryptamine3 (5-HT3) receptor antagonists, which antagonize dopaminergic activity in the nucleus accumbens, have been shown to inhibit ethanol consumption in a free-choice paradigm, and to attenuate the reinforcing effects of amphetamine in some animal models. Obviously, the demonstration of a similar effect in humans would have important clinical implications for the treatment of substance abuse. In humans, however, reinforcement is difficult to measure directly. Nevertheless, the pleasurable subjective effects of drugs of abuse are important behavioural correlates of the reinforcement process. In the present thesis I investigated the effects of 5-HT3 receptor antagonists on the subjective positive effects of alcohol and amphetamine. In addition, the independent and interactive effects of a 5-HT3 antagonist and amphetamine on hunger, caloric intake and macronutrient selection, and cognitive performance was studied. The 5-HT3 antagonist, ondansetron, reliably reduced the pleasurable subjective effects and the desire to drink alcohol. In addition, evidence was provided to demonstrate that ondansetron did not simply reduce the absorption of alcohol, as it has the ability to slow gut motility. Thus, these experiments are the first clear evidence that 5-HT3 antagonists can decrease the reinforcing properties of alcohol in humans. It is, however, important to point out that alcohol consumption was not measured directly, and it is possible, as has been demonstrated with other drugs such as cocaine, that blockade of reinforcement can, paradoxically, increase consumption and the subject works harder to obtain the drug. While repeated dosing with ondansetron also attenuated some positive subjective effects and the anorexic properties of d-amphetamine; in contrast, a single dose of the second generation 5-HT3 antagonist, GR 68755, was without effect on mood, hunger, satiety, and food intake. This suggests that, as in recent electrophysiological studies, 5-HT3 antagonists may only influence the reinforcing properties of drugs which indirectly facilitate dopamine neurotransmission via 5-HT activity at excitatory pre-synaptic 5-HT3 receptors, and are not effective against drugs which, simply, cause the direct release of dopamine from nerve terminals and do not increase dopamine cell firing transynaptically. It is, therefore, possible that the successful attenuation of amphetamine-induced subjective state and hunger by ondansetron was due to kinetic effects, which presumably became more manifest with repeated rather than single dosing, possible post-synaptic effects at 5-HT3 receptors or interactions with other neurotransmitter systems which are, at present, poorly understood, or chance. Further studies are needed, however, to investigate the effectiveness of a pharmacological range of doses of 5-HT3 antagonists on amphetamine-induced behaviour. GR 68755 was without effect on the natural increase in subjective feelings of hunger over time following an overnight fast, and the pattern of caloric intake and macronutrient selection was similar to placebo. D-amphetamine reliably reduced hunger, and this was shown using a test meal to lead to a global decrease in caloric intake and no macronutrient was selectively spared or consumed. Interestingly, both GR 68755 and amphetamine alone improved cognitive performance but this effect was not additive suggesting different neurotransmitter systems may be involved. In future, I intend to extend this human laboratory work by uncovering the therapeutic range of ondansetron with respect to decreasing the positive subjective effects including the desire to drink in alcohol abusers, and to investigate what impact this has on alcohol consumption. If these experiments are successful a clinical trial would be warranted

A critical scientific evaluation of a purportedly negative data report - Response to Seneviratne et al. 2022

A core principle in the pursuit of scientific knowledge is that science is self-correcting and that important results should be replicable. Hypotheses need to be reinforced, adjusted, or rejected when novel results are obtained. Replication of results confirms hypotheses and enhances their integration into scientific practice. In contrast, publication of substantiated and replicated negative findings (i.e., non-significant or opposite findings) can be the basis to reject erroneous hypotheses or develop alternative strategies for investigation. Replication is a problem in all research fields. The Psychology Reproductivity Project reported that only 36% of \u27highly influential\u27 published research in highly ranked journals were reproduced. Similar to positive data, negative data can be flawed. Errors in a negative data set can be based on methodology, statistics, conceptual defects, and flawed peer review. The peer review process has received progressive scrutiny. A large-scale review of the peer review process of manuscripts submitted to the British Medical Journal group indicated that the process could be characterized as inconsistent, inaccurate, and biased. Further analysis indicated that the peer process is easily manipulated, indicative of a failed system, is a major factor behind the lack of replication in science (acceptance of flawed manuscripts), suppresses opposing scientific evidence and views, and causes gaps in and lack of growth of science. Complicating the integrity of scientific publication is the role of Editors/Researchers. Ethical guidelines exist for major publishing houses about editorial ethics, behavior, and practice

Being ‘Dissed’ and Abused: African American adolescent males’ ideas of unhealthy or harmful dating dynamics

While the prevalence of teen dating violence (TDV) is among the highest for African Americans (AA), the research and narrative surrounding this issue has been historically one-sided. This qualitative study was conducted to further explore the candid perspectives of adolescent AA males regarding healthy and unhealthy dating relationship dynamics. Convenience sampling and snowball sampling were utilized to recruit 19 AA males from schools and community youth groups around the greater Washington DC area. Semi-structured in-depth interviews were conducted. Analysis consisted of open coding, sorting, aggregation and synthesis of responses to the guiding question question: “How would you describe a dating relationship that was unhealthy or harmful?” Narratives provided multi-layered, descriptive characterizations of healthy and unhealthy dating dynamics. Through an iterative process, emergent themes and sub-themes were generated. The five emergent themes were: Amiss or Dissed Communication; Distrust, Dishonesty, Disloyalty; Fighting and Poor Conflict Resolution; and, Abuse. Adolescent AA males displayed a strong awareness of what constitutes unhealthy dating relationship characteristics, especially concerning conflict and abusive behaviors. Characterizations that addressed Communication and Distrust, Dishonesty, and Disloyalty may present areas that should be focused on in future prevention efforts. Prevention and intervention programs aimed at decreasing TDV within the African American community will benefit tremendously from these authentic perspectives. By building off of the knowledge and values already expressed among adolescent AA males, rather than perpetuated stereotypes, programs will more effectively connect with, educate, and empower them to build healthy dating relationship dynamics

Preliminary Evidence for cue-induced Alcohol Craving Modulated by Serotonin Transporter Gene Polymorphism rs1042173

We previously have shown that cue-induced alcohol craving and propensity for higher drinking are modulated by allelic differences in SLC6A4 associated with serotonin transporter (5-HTT) expression level alterations. In an independent study, we characterized another polymorphism, SNP rs1042173, in 3′-untranslated region (3′-UTR) of the same gene, which also altered 5-HTT expression levels; the T allele of rs1042173 was associated with lower mRNA and protein levels. In subsequent analyses, the TT genotype was found to be associated with higher drinking intensity in alcohol-dependent (AD) individuals of Caucasian descent. Building upon these findings, we hypothesized that the low-expressing TT genotype associated with intense drinking would predict higher craving for alcohol in AD individuals. In this pilot study, we sought to test our hypothesis by examining 34 Hispanic AD volunteers (mean age, 34.8 years) for rs1042173 genotype-based [i.e., TT versus TG/GG (Gx)] differences in subjective response to alcohol. We employed a human laboratory paradigm and analyzed the data using a linear mixed-effects model (SAS® PROC MIXED) to assess treatment, cue procedures, and genotype main effects as well as the two-way interaction effects between them. On subjective “urge to drink” and “crave for a drink,” we found a significant main effect of the cue experiment (p ≤ 0.01) and an interaction effect between genotype and cue effects (p < 0.05). TT genotype was associated with higher urge to drink (p = 0.002) and crave for a drink (p = 0.005) when exposed to alcohol cue. Our results not only support the hypothesis that rs1042173 is a genetic marker for cue-induced alcohol craving among AD males but also are suggestive of a neurobiological mechanism associated with the rs1042173-TT genotype that triggers a disproportionate craving in response to alcohol consumption, which in turn may lead to more intense drinking. Future studies with larger sample sizes are needed to characterize the interactive effects of the serotonin transporter-linked polymorphic region (5′-HTTLPR)-L-allele reported in our previous study and of the rs1042173-TT genotype on cue-induced alcohol craving

Histomorphometric study of thyroid gland of female Wistar rats exposed to alcohol during pregnancy and/or lactation

The effect of alcohol on the histomorphology of thyroid gland of female rat offspring exposed to alcohol during pregnancy and/or lactation was studied. Previously published protocols for similar studies were followed. Data from both absolute and relative weights, coupled with histologic data from the thyroid glands of the alcohol-exposed rats suggest that alcohol consumption during pregnancy and/or lactation could be injurious to the thyroid glands of the female offspring

Association between Genotype of the Serotonin Transporter-Linked Polymorphic Region of the Serotonin Transporter Gene and Age of Onset of Methamphetamine Use: a Preliminary Analysis

Early-onset methamphetamine use increases the lifetime prevalence of methamphetamine dependence. An earlier onset of methamphetamine use leads to greater damage to the terminal ends of serotonin neurons, more reduction in serotonin transporter (5-HTT) density, and an increased propensity toward further methamphetamine use. Because the 5-HTT-linked polymorphic region (5′-HTTLPR) within the promoter region of the 5-HTT gene leads to differential expression of the 5-HTT, we examined, for the first time, whether there is a differential association between the long (L) and short (S) alleles of the 5′-HTTLPR and the age of first methamphetamine use (AMU). The study included 120 methamphetamine-dependent adults of European descent. Diagnosis of methamphetamine dependence and AMU were collected using structured questionnaires, and the 5′-HTTLPR genotypes were determined using the polymerase chain reaction–restriction fragment length polymorphism method. Statistical analysis with the general linear model detected a significant interactive effect of 5′-HTTLPR genotypes (SS vs. L-carriers) and gender, associated with AMU (F = 3.99; p = 0.048). Further analysis of 5′-HTTLPR effects on AMU in males and females separately showed that the SS genotype compared with L-carriers had about two times greater risk of an earlier onset of methamphetamine use in men (hazard ratio = 1.839; 95% confidence interval = 1.042–3.246; p = 0.036) but not in women. Together, our findings in this preliminary study suggest a greater risk for earlier onset methamphetamine use associated with the SS genotype of the 5′-HTTLPR among methamphetamine-dependent Caucasian males