A review of pharmacogenetic studies of substance-related disorders

Cocaine Use Disorder (CUD): Current Clinical Perspectives

Cocaine use disorder (CUD) is a devastating disorder, impacting both individuals and society. Individuals with CUD face many barriers in accessing treatment for CUD, and most individuals with CUD never receive treatment. In this review, we provide an overview of CUD, including risk factors for CUD, common co-occurring disorders, acute and chronic effects of cocaine use, and currently available pharmacological and behavioral treatments. There are no FDA-approved pharmacological treatments for CUD. Future studies with larger sample sizes and testing treatment combinations are warranted. However, individuals with CUD and co-occurring disorders (eg, a mood or anxiety disorder) may benefit from medication treatments. There are behavioral interventions that have demonstrated efficacy in treating CUD – contingency management (CM) and cognitive-behavioral therapy for substance use disorders (CBT-SUD) in particular – however many barriers remain in delivering these treatments to patients. Following the discussion of current treatments, we highlight some promising emerging treatments, as well as offer a framework that can be used in building a treatment plan for individuals with CUD.

Is Illicit Substance Use Gender-Specific? The Basic Points of Mental and Health Disorders

Among the groups of users of illicit substances, a high percentage are persons deprived of their liberty; at the same time, each social and age group is also affected, to one degree or another. The purpose of this study is to provide general data on the relationship between different psychostimulants, clinical and socio-demographic studies, and gender, both among the general population and in one of the most at-risk groups. This review identifies the use of illicit substances as gender-specific in the general population. A detailed study of the causal relationship between the use of illicit substances and gender was carried out. Electronic databases Academic Search Complete, PubMed, HealthCare, Web of Science, and Google Scholar were searched for relevant studies up to 2022 associated with drug abuse and mental and health disorders. The analysis indicated that the human population showed significant differences between the sex of the consumer as to the type of drug consumers, development of addiction, and relapse. We focus on the pathological changes caused by drug use, the personal and physiological individual traits that influence drug choice, and the extent of use in one of the most affected groups of individuals. The study may provide some guidance in developing gender-specific treatment and prevention, including response to some pharmacological and behavioral therapies. The review is intended for a wide audience of social workers, toxicologists, and pharmacologists.

The effects of acute oral naltrexone pretreatment on the abuse potential of intranasal methamphetamine, and the relationship between reward/punishment sensitivity and methamphetamine's effects

One potential medication for treating methamphetamine use disorder is the opioid antagonist naltrexone (NLTX). Despite encouraging preclinical findings, the results of clinical studies have been mixed. The primary aim of the current trial was to examine the effects of acute NLTX pretreatment on the subjective and reinforcing effects of intranasal methamphetamine. Nonmedical psychostimulant users completed outpatient testing sessions in which they received oral placebo (0 mg) or NLTX (50 mg) before intranasal methamphetamine (30 mg/70 kg). Primary outcome measures were peak positive subjective effects (e.g. drug 'Liking') assessed on a visual analog scale (0-100), and methamphetamine self-administration using an operant self-administration task. Participants also completed a probabilistic categorization task to assess reward and punishment learning sensitivity. Complete data were available from 13 male and 1 transgender (male-to-female) participant (age: 33.4 ± 7.6 years). Intranasal methamphetamine significantly increased subjective ratings of drug 'Liking', 'Good Effect' and 'High' from baseline (P's < 0.01), but did not significantly vary as a function of placebo or NLTX pretreatment. Similarly, methamphetamine self-administration did not vary between the placebo and NLTX pretreatment conditions. This sample did not demonstrate a significant 'bias' in learning from positive and negative outcomes (i.e. reward and punishment sensitivity), and reward/punishment sensitivity was not correlated with the effects of methamphetamine or the effects of NLTX on methamphetamine. The current study argues against the use of NLTX as a stand-alone medication for treating methamphetamine use disorder.

Influence of COMT (rs4680) and DRD2 (rs1076560, rs1800497) Gene Polymorphisms on Safety and Efficacy of Methylphenidate Treatment in Children with Fetal Alcohol Spectrum Disorders

Fetal alcohol spectrum disorders (FASD) in a course of high prenatal alcohol exposure (hPAE) are among the most common causes of developmental disorders. The main reason for pharmacological treatment of FASD children is attention deficit hyperactivity disorder (ADHD), and methylphenidate (MPH) is the drug of choice. The aim of the study was to assess whether children born of hPAE with ADHD, with or without morphological FASD, differ in terms of catechol-O-methyltransferase (COMT) and dopamine receptor D2 (DRD2) gene polymorphisms, and if genetic predisposition affects response and safety of MPH treatment. The polymorphisms of COMT (rs4680) and DRD2 (rs1076560, rs1800497) were analyzed in DNA samples. A borderline significance was found for the correlation between MPH side effects and the G allele of COMT (rs4680) (p = 0.04994) in all ADHD children. No effect of COMT (rs4680) and DRD2 (rs1076560, rs1800497) polymorphisms and the treatment efficacy was observed. The analyzed DRD2 and COMT gene polymorphisms seem to play no role in MPH efficacy in ADHD children with hPAE, while low-activity COMT (Met158) variant carriers may be more intolerant to MPH. The MPH treatment is effective in ADHD independent of FASD, although the ADHD-FASD variant requires higher doses to be successful. These results may help in optimization and individualization in child psychiatry.

The Streetlight Effect: Reappraising the Study of Addiction in Light of the Findings of Genome-wide Association Studies

Drug dependence has long been thought to have a genetic component. Research seeking to identify the genetic basis of addiction has gone through important transitions over its history, in part based upon the emergence of new technologies, but also as the result of changing perspectives. Early research approaches were largely dictated by available technology, with technological advancements having highly transformative effects on genetic research, but the limitations of technology also affected modes of thinking about the genetic causes of disease. This review explores these transitions in thinking about the genetic causes of addiction in terms of the "streetlight effect," which is a type of observational bias whereby people search for something only where it is easiest to search. In this way, the genes that were initially studied in the field of addiction genetics were chosen because they were the most "obvious," and formed current understanding of the biological mechanisms underlying the actions of drugs of abuse and drug dependence. The problem with this emphasis is that prior to the genomic era the vast majority of genes and proteins had yet to be identified, much less studied. This review considers how these initial choices, as well as subsequent choices that were also driven by technological limitations, shaped the study of the genetic basis of drug dependence. While genome-wide approaches overcame the initial biases regarding which genes to choose to study inherent in candidate gene studies and other approaches, genome-wide approaches necessitated other assumptions. These included additive genetic causation and limited allelic heterogeneity, which both appear to be incorrect. Thus, the next stage of advancement in this field must overcome these shortcomings through approaches that allow the examination of complex interactive effects, both gene × gene and gene × environment interactions. Techniques for these sorts of studies have recently been developed and represent the next step in our understanding of the genetic basis of drug dependence.

SNPs from BCHE and DRD3 genes associated to cocaine abuse amongst violent individuals from Sao Paulo, Brazil

Violence and drug abuse are highly destructive phenomena found world-wide, especially in Brazil. They seem to rise proportionally to one another and possibly related. Additionally, genetics may also play a role in drug abuse. This study has focused on identifying the use of cocaine within postmortem cases arriving at the Institute of Legal Medicine of Sao Paulo as well as the presence of certain single nucleotide polymorphisms (SNPs) to better understand one's susceptibility to abuse the drug. Both hair and blood samples have been extracted through a simple methanol overnight incubation or a rapid dilute-and-shoot method, respectively. The samples were then analyzed using an UPLC-ESI-MS/MS and genotyped through RT-PCR. Statistical analyses were performed via SPSS software. From 105 postmortem cases, 53% and 51% of the cases shown to be positive for cocaine in hair and blood, respectively. Genetic wise, a significant difference has been observed for SNP rs4263329 from the BCHE gene with higher frequencies of the genotypes A/G and G/G seen in cocaine users (OR=8.91; 95%CI=1.58-50.21; p=0.01). Likewise, also SNP rs6280 from the DRD3 gene presented a significant association, with both genotypes T/C and C/C being more frequent in users (OR=4.96; 95% CI=1.07-23.02; p=0.04). To conclude, a rather high proportion of cocaine has been found, which may suggest a connotation between the use of the drug and risky/violent behaviors. Additionally, significant associations were also found within two SNPs related to cocaine use, however, due to several inherent limitations, these must be confirmed.

Assessing the contribution of opioid- and dopamine-related genetic polymorphisms to the abuse liability of oxycodone

BACKGROUND

Attempts to identify opioid users at increased risk of escalating to opioid use disorder have had limited success. Data from a variety of sources suggest that genetic variation may mediate the subjective response to opioid drugs, and therefore contribute to their abuse potential. The goal of the current study was to observe the relationship between select genetic polymorphisms and the subjective effects of oxycodone under controlled clinical laboratory conditions.

METHODS

Non-dependent, volunteers with some history of prescription opioid exposure (N = 36) provided a blood sample for analyses of variations in the genes that encode for the μ-, κ- and δ-opioid receptors, and the dopamine metabolizing enzyme, catechol-O-methyltransferase (COMT). Participants then completed a single laboratory test session to evaluate the subjective and analgesic effects of oral oxycodone (0, 10, and 20 mg, cumulative dose = 30 mg).

RESULTS

Oxycodone produced typical μ-opioid receptor agonist effects, such as miosis, and decreased pain perception. Oxycodone also produced dose-dependent increases in positive subjective responses such as: drug "Liking" and "Good Effect." Genetic variants in the μ- (rs6848893) and δ-opioid receptor (rs581111) influenced the responses to oxycodone administration. Additionally, self-reported "Stimulated" effects of oxycodone varied significantly as a function of COMT rs4680 genotype.

DISCUSSION

The current study shows that the euphoric and stimulating effects of oxycodone can vary as a function of genetic variation. Though the relationship between the stimulating effects of opioids and their abuse liability is not well established, we know that the ability of opioids to provide intense feelings of pleasure is a significant motivator for continued use. If replicated, specific genetic variants may be useful in predicting who is at increased risk of developing maladaptive patterns of use following medical exposure to opioid analgesics.

Current Understanding of Methamphetamine-Associated Metabolic Changes Revealed by the Metabolomics Approach

Metabolomics is a powerful tool used in the description of metabolic system perturbations caused by diseases or abnormal conditions, and it usually involves qualitative and/or quantitative metabolome determination, accompanied by bioinformatics assessment. Methamphetamine is a psychostimulant with serious abuse potential and due to the absence of effective pharmacotherapy and a high recurrence potential, methamphetamine addiction is a grave issue. Moreover, its addiction mechanisms remain unclear, probably due to the lack of experimental models that reflect personal genetic variances and environmental factors determining drug addiction occurrence. The metabolic approach is only recently being used to study the metabolic effects induced by a variety of methamphetamine exposure statuses, in order to investigate metabolic disturbances related to the adverse effects and discover potential methamphetamine addiction biomarkers. To provide a critical overview of methamphetamine-associated metabolic changes revealed in recent years using the metabolomics approach, we discussed methamphetamine toxicity, applications of metabolomics in drug abuse and addiction studies, biological samples used in metabolomics, and previous studies on metabolic alterations in a variety of biological samples—including the brain, hair, serum, plasma, and urine—following methamphetamine exposure in animal studies. Metabolic alterations observed in animal brain and other biological samples after methamphetamine exposure were associated with neuronal and energy metabolism disruptions. This review highlights the significance of further metabolomics studies in the area of methamphetamine addiction research. These findings will contribute to a better understanding of metabolic changes induced by methamphetamine addiction progress and to the design of further studies targeting the discovery of methamphetamine addiction biomarkers and therapeutic targets.

Prenatal cannabinoid exposure and altered neurotransmission

Marijuana is one of the most commonly used illicit drugs worldwide. In addition, use of synthetic cannabinoids is increasing, especially among adolescents and young adults. Although human studies have shown that the use of marijuana during pregnancy leads to adverse behavioral effects, such as deficiencies in attention and executive function in affected offspring, the rate of marijuana use among pregnant women is steadily increasing. Various aspects of human behavior including emotion, learning, and memory are dependent on complex interactions between multiple neurotransmitter systems that are especially vulnerable to alterations during the developmental period. Thus, exploration of neurotransmitter changes in response to prenatal cannabinoid exposure is crucial to develop an understanding of how homeostatic imbalance and various long-term neurobehavioral deficits manifest following the abuse of marijuana or other synthetic cannabinoids during pregnancy. Current literature confirms that vast alterations to neurotransmitter systems are present following prenatal cannabinoid exposure, and many of these alterations within the brain are region specific, time-dependent, and sexually dimorphic. In this review, we aim to provide a summary of observed changes to various neurotransmitter systems following cannabinoid exposure during pregnancy and to draw possible correlations to reported behavioral alterations in affected offspring.

Genetic basis of psychopathological dimensions shared between schizophrenia and bipolar disorder

Shared genetic vulnerability between schizophrenia (SCZ) and bipolar disorder (BP) was demonstrated, but the genetic underpinnings of specific symptom domains are unclear. This study investigated which genes and gene sets may modulate specific psychopathological domains and if genome-wide significant loci previously associated with SCZ or BP may play a role. Genome-wide data were available in patients with SCZ (n = 226) or BP (n = 228). Phenotypes under investigation were depressive and positive symptoms severity, suicidal ideation, onset age and substance use disorder comorbidity. Genome-wide analyses were performed at gene and gene set level, while 148 genome-wide significant loci previously associated with SCZ and/or BP were investigated. Each sample was analyzed separately then a meta-analysis was performed. SH3GL2 and CLVS1 genes were associated with suicidal ideation in SCZ (p = 5.62e-08 and 0.01, respectively), the former also in the meta-analysis (p = .01). SHC4 gene was associated with depressive symptoms severity in BP (p = .003). A gene set involved in cellular differentiation (GO:0048661) was associated with substance disorder comorbidity in the meta-analysis (p = .03). Individual loci previously associated with SCZ or BP did not modulate the phenotypes of interest. This study provided confirmatory and new findings. SH3GL2 (endophilin A1) showed a role in suicidal ideation that may be due to its relevance to the glutamate system. SHC4 regulates BDNF-induced MAPK activation and was previously associated with depression. CLVS1 is involved in lysosome maturation and was for the first time associated with a psychiatric trait. GO:0048661 may mediate the risk of substance disorder through an effect on neurodevelopment/neuroplasticity.

Melatonin in drug addiction and addiction management: Exploring an evolving multidimensional relationship

Melatonin is a pleiotropic signalling molecule that regulates several physiological functions, and synchronises biological rhythms. Recent evidences are beginning to reveal that a dysregulation of endogenous melatonin rhythm or action may play a larger role in the aetiology and behavioural expression of drug addiction, than was previously considered. Also, the findings from a number of animal studies suggest that exogenous melatonin supplementation and therapeutic manipulation of melatonin/melatonin receptor interactions may be beneficial in the management of behavioural manifestations of drug addiction. However, repeated exogenous melatonin administration may cause a disruption of its endogenous rhythm and be associated with potential drawbacks that might limit its usefulness. In this review, we examine the roles of melatonin and its receptors in addictive behaviours; discussing how our understanding of melatonin’s modulatory effects on the brain rewards system and crucial neurotransmitters such as dopamine has evolved over the years. Possible indications(s) for melatonergic agents in addiction management, and how manipulations of the endogenous melatonin system may be of benefit are also discussed. Finally, the potential impediments to application of melatonin in the management of addictive behaviours are considered.

Precision medicine and pharmacogenetics: what does oncology have that addiction medicine does not?

BACKGROUND AND AIMS

Precision, personalized or stratified medicine, which promises to deliver the right treatment to the right patient, is a topic of international interest in both the lay press and the scientific literature. A key aspect of precision medicine is the identification of biomarkers that predict the response to medications (i.e. pharmacogenetics). We examined why, despite the great strides that have been made in biomarker identification in many areas of medicine, only in oncology has there been substantial progress in their clinical implementation. We also considered why progress in this effort has lagged in addiction medicine.

METHODS

We compared the development of pharmacogenetic biomarkers in oncology, cardiovascular medicine (where developments are also promising) and addictive disorders.

RESULTS

The first major reason for the success of oncologic pharmacogenetics is ready access to tumor tissue, which allows in-vitro testing and insights into cancer biology. The second major reason is funding, with cancer research receiving, by far, the largest allocation by the National Institutes of Health (NIH) during the past two decades. The second largest allocation of research funding has gone to cardiovascular disease research. Addictions research received a much smaller NIH funding allocation, despite the major impact that tobacco use, alcohol consumption and illicit drug use have on the public health and healthcare costs.

CONCLUSIONS

Greater support for research on the personalized treatment of addictive disorders can be expected to yield disproportionately large benefits to the public health and substantial reductions in healthcare costs.

Don't stress about CRF: assessing the translational failures of CRF1antagonists

BACKGROUND

Dr. Athina Markou sought treatments for a common neural substrate shared by depression and drug dependence. Antagonists of corticotropin-releasing factor (CRF) receptors, a target of interest to her, have not reached the clinic despite strong preclinical rationale and sustained translational efforts.

METHODS

We explore potential causes for the failure of CRF1 antagonists and review recent findings concerning CRF-CRF1 systems in psychopathology.

RESULTS

Potential causes for negative outcomes include (1) poor safety and efficacy of initial drug candidates due to bad pharmacokinetic and physicochemical properties, (2) specificity problems with preclinical screens, (3) the acute nature of screens vs. late-presenting patients, (4) positive preclinical results limited to certain models and conditions with dynamic CRF-CRF1 activation not homologous to tested patients, (5) repeated CRF1 activation-induced plasticity that reduces the importance of ongoing CRF1 agonist stimulation, and (6) therapeutic silencing which may need to address CRF2 receptor or CRF-binding protein molecules, constitutive CRF1 activity, or molecules that influence agonist-independent activity or to target structural regions other than the allosteric site bound by all drug candidates. We describe potential markers of activation towards individualized treatment, human genetic, and functional data that still implicate CRF1 systems in emotional disturbance, sex differences, and suggestive clinical findings for CRF1 antagonists in food craving and CRF-driven HPA-axis overactivation.

CONCLUSION

The therapeutic scope of selective CRF1 antagonists now appears narrower than had been hoped. Yet, much remains to be learned about CRF's role in the neurobiology of dysphoria and addiction and the potential for novel anti-CRF therapies therein.

Histopathological study of cardiac lesions in methamphetamine poisoning-related deaths

BACKGROUND

Methamphetamine abuse is a worldwide health concern. Methamphetamine causes health hazards in many vital organs. It can cause damage to cardiac tissue via catecholamines release. Methamphetamine related deaths are becoming one of the most important problems in Iran. The purpose of the present study was to determine cardiac pathology in methamphetamine poisoning-related deaths.

METHODS

The study included 100 cases of methamphetamine poisoning-related deaths and 100 cases as control group. Toxicology analysis of liver, gastric content, bile, urine, blood and vitreous humor were conducted to detect drugs, poisons and alcohols using thin layer chromatography, gas chromatography/mass spectrometry, and high performance liquid chromatography. Positive toxicology analysis results except for amphetamine and methamphetamine were excluded from the study in order to omit interfering factors. The most striking features of cardiac damage were observed by light microscopy.

RESULTS

Methamphetamine and amphetamine were detected in either urine or gastric content samples. In all of the cases methamphetamine toxicity was determined to be a direct cause of death by forensic medicine practitioner. Cardiovascular pathology was noted in 68% of studied cases. The most common histopathologic features were myocardial fiber hypertrophy, mild, moderate to severe atherosclerosis and focal degeneration/necrosis.

CONCLUSION

The results of the present study indicate that cardiotoxicity is one of the major contributing factors in methamphetamine poisoning related deaths. Overall, the current study highlights the fact that cardiotoxic effects of methamphetamine can explain increasing reports of heart failure and consequently death in young abusers.

TRIAL REGISTRATION

Not applicable. Histopathological study of cardiac lesions in methamphetamine poisoning-related deaths.

Single nucleotide polymorphism near CREB1, rs7591784, is associated with pretreatment methamphetamine use frequency and outcome of outpatient treatment for methamphetamine use disorder

Although stimulant dependence is highly heritable, few studies have examined genetic influences on methamphetamine dependence. We performed a candidate gene study of 52 SNPs and pretreatment methamphetamine use frequency among 263 methamphetamine dependent Hispanic and Non-Hispanic White participants of several methamphetamine outpatient clinical trials in Los Angeles. One SNP, rs7591784 was significantly associated with pretreatment methamphetamine use frequency following Bonferroni correction (p < 0.001) in males but not females. We then examined rs7591784 and methamphetamine urine drug screen results during 12 weeks of outpatient treatment among males with treatment outcome data available (N = 94) and found rs7591784 was significantly associated with methamphetamine use during treatment controlling for pretreatment methamphetamine use. rs7591784 is near CREB1 and in a linkage disequilibrium block with rs2952768, previously shown to influence CREB1 expression. The CREB signaling pathway is involved in gene expression changes related to chronic use of multiple drugs of abuse including methamphetamine and these results suggest that variability in CREB signaling may influence pretreatment frequency of methamphetamine use as well as outcomes of outpatient treatment. Medications targeting the CREB pathway, including phosphodiesterase inhibitors, warrant investigation as pharmacotherapies for methamphetamine use disorders.

Searching for evidence of genetic mediation of opioid withdrawal by opioid receptor gene polymorphisms

BACKGROUND

Previous research has identified many genetic polymorphisms that appear to mediate the effects of opioid drugs. However, the relationship between genetic polymorphisms and the severity of opioid withdrawal has not yet been characterized.

METHODS

Data were collected from 48 daily heroin users who previously completed a standardized abstinence-induced or naloxone-precipitated withdrawal procedure to assess opioid dependence. The total withdrawal severity score (based on the COWS) from this procedure was correlated with genotype information for variants of OPRM1 (rs1799971; rs6848893), OPRD1 (rs10753331; rs2234918; rs581111; rs678849; rs1042114), and OPRK1 (rs6473797; rs963549). Genotype and other participant variables (age, race, sex, duration of drug use, concomitant drug use, route of opioid use) were used as predictors.

RESULTS

Of these variables, those individually correlated with a p < .2 were entered into a multivariate regression in order to identify the most predictive model. Three polymorphisms were significantly associated with severity of abstinence-induced withdrawal (n = 19) in the bivariate analysis (R): OPRM1 rs6848893 (.45), OPRD1 rs10753331 (.03), and rs678849 (.08), but only the OPRM1 rs6848893 was retained in the multivariate model (p < .001). For participants who underwent naloxone-precipitated withdrawal (n = 29) only OPRK1 rs6473797 (-.23) was significant in the bivariate analysis, though not retained in the final model.

CONCLUSIONS

These data provide evidence for genetic modulation of opioid withdrawal severity, and suggest there may be qualitative differences between withdrawal resulting from abstinence and antagonist-precipitated withdrawal.

SCIENTIFIC SIGNIFICANCE

This study demonstrates the importance and feasibility of incorporating genetic information into clinical addiction research.