A functional polymorphism in the promoter region of the dopamine D2 receptor gene is associated with schizophrenia

Genetic susceptibility to caffeine intake and metabolism: a systematic review

BACKGROUND

Coffee and tea consumption account for most caffeine intake and 2-3 billion cups are taken daily around the world. Caffeine dependence is a widespread but under recognized problem.

OBJECTIVES

To conduct a systematic review on the genetic susceptibility factors affecting caffeine metabolism and caffeine reward and their association with caffeine intake.

METHODOLOGY

We conducted PubMed and Embase searches using the terms "caffeine", "reward", "gene", "polymorphism", "addiction", "dependence" and "habit" from inception till 2024. The demographics, genetic and clinical data from included studies were extracted and analyzed. Only case-control studies on habitual caffeine drinkers with at least 100 in each arm were included.

RESULTS

A total of 2552 studies were screened and 26 studies involving 1,851,428 individuals were included. Several genes that were involved with caffeine metabolism such as CYP1A2, ADORA2A, AHR, POR, ABCG2, CYP2A6, PDSS2 and HECTD4 rs2074356 (A allele specific to East Asians and monomorphic in Europeans, Africans and Americans) were associated with habitual caffeine consumption with effect size difference of 3% to 32% in number of cups of caffeinated drink per day per effect allele. In addition, ALDH2 was linked to the Japanese population. Genes associated with caffeine reward included BDNF, SLC6A4, GCKR, MLXIPL and dopaminergic genes such as DRD2 and DAT1 which had around 2-5% effect size difference in number of cups of caffeinated drink for each allele per day.

CONCLUSION

Several genes that were involved in caffeine metabolism and reward were associated with up to 30% effect size difference in number of cups of caffeinated drink per day, and some associations were specific to certain ethnicities. Identification of at-risk caffeine dependence individuals can lead to early diagnosis and stratification of at-risk vulnerable individuals such as pregnant women and children, and can potentially lead to development of drug targets for dependence to caffeine.

Discovering functional interactions among schizophrenia-risk genes by combining behavioral genetics with cell biology

Despite much progress in identifying risk genes for polygenic brain disorders, their core pathogenic mechanisms remain poorly understood. In particular, functions of many proteins encoded by schizophrenia risk genes appear diverse and unrelated, complicating the efforts to establish the causal relationship between genes and behavior. Using various mouse lines, recent studies indicate that alterations of parvalbumin-positive (PV+) GABAergic interneurons can lead to schizophrenia-like behavior. PV+ interneurons display fast spiking and contribute to excitation-inhibition balance and network oscillations via feedback and feedforward inhibition. Here, we first summarize different lines of genetically modified mice that display motor, cognitive, emotional, and social impairments used to model schizophrenia and related mental disorders. We highlight ten genes, encoding either a nuclear, cytosolic, or membrane protein. Next, we discuss their functional relationship in regulating fast spiking and other aspects of PV+ interneurons and in the context of other domains of schizophrenia. Future investigations combining behavioral genetics and cell biology should elucidate functional relationships among risk genes to identify the core pathogenic mechanisms underlying polygenic brain disorders.

D2 dopamine receptor expression, reactivity to rewards, and reinforcement learning in a complex value-based decision-making task

Different dopamine (DA) subtypes have opposing dynamics at postsynaptic receptors, with the ratio of D1 to D2 receptors determining the relative sensitivity to gains and losses, respectively, during value-based learning. This effective sensitivity to different reward feedback interacts with phasic DA levels to determine the effectiveness of learning, particularly in dynamic feedback situations where the frequency and magnitude of rewards need to be integrated over time to make optimal decisions. We modeled this effect in simulations of the underlying basal ganglia pathways and then tested the predictions in individuals with a variant of the human dopamine receptor D2 (DRD2; -141C Ins/Del and Del/Del) gene that associates with lower levels of D2 receptor expression (N = 119) and compared their performance in the Iowa Gambling Task to noncarrier controls (N = 319). Ventral striatal (VS) reactivity to rewards was measured in the Cards task with fMRI. DRD2 variant carriers made less effective decisions than noncarriers, but this effect was not moderated by VS reward reactivity as is hypothesized by our model. These results suggest that the interaction between DA receptor subtypes and reactivity to rewards during learning may be more complex than originally thought.

The Relationship Between Sexual Dysfunctions With Disease Prolactin and Genetic Polymorphisms in Schizophrenia and Bipolar Disorder Patients Receiving Pharmacotherapy

OBJECTIVE

The aim of this study is to investigate sexual dysfunctions (SDs) and related factors in patients with schizophrenia and bipolar disorder receiving pharmacotherapy.

METHODS

This study included 111 patients. The Scale for the Assessment of Positive Symptoms (SAPS), the Scale for the Assessment of Negative Symptoms (SANS), and the Calgary Depression Scale for Schizophrenia (CDSS) were applied to the schizophrenia, and the Young Mania Rating Scale (YMRS) and Hamilton Depression Rating Scale (HAM-D) to the bipolar patient group. The sociodemographic data form and the Arizona Sexual Experiences Scale (ASEX) were applied to both of the patient groups. Blood was drawn from all patients to evaluate the indicated gene polymorphisms and evaluate prolactin levels.

RESULTS

SD was detected in 45.9% (N = 34) of the schizophrenia group, and 59.5% (N = 22) in the bipolar disorder group. SD was significantly higher in elderly patients and patients with a high smoking amount and low education levels. The eNOS -786T>C T allele frequency was found to be significantly higher in patients with SD. The logistic regression analysis determined that eNOS -786T>C CT and TT genotypes increased the risk of SD.

CONCLUSION

In this study, the high rates of SD in patients with schizophrenia and bipolar disorder, and the presence of modifiable factors that influence the presence of SD, suggest that SD should be given more attention in these patient groups. On the other hand, the high rate of SD in patients with the eNOS -786T>C T allele indicates the importance of carrying out new studies investigating the factors affecting the enzyme activity in this genotype. There is a need for more studies on eNOS genotypes and enzyme activites in this area.

Association of 11 variants of the dopaminergic and cognitive pathways genes with major depression, schizophrenia and bipolar disorder in the Pakistani population

Background: The dopaminergic pathways control neural signals that modulate mood and behaviour along and have a vital role in the aetiology of major depression (MDD), schizophrenia (SHZ) and bipolar disorder (BD). Genome-wide association studies (GWAS) have reported several dopaminergic and cognitive pathway genes association with these disorders however, no such comprehensive data was available regarding the Pakistani population.Objective: The present study was conducted to analyse the 11 genetic variants of dopaminergic and cognitive system genes in MDD, SHZ, and BD in the Pakistani population.Methods: A total of 1237 subjects [MDD n = 479; BD n = 222; SHZ n = 146; and controls n = 390], were screened for 11 genetic variants through polymerase chain reaction (PCR) techniques. Univariant followed by multivariant logistic regression analysis was applied to determine the genetic association.Results: Significant risk associations were observed for rs4532 and rs1799732 with MDD; and rs1006737 and rs2238056 with BD. However, after applying multiple test corrections rs4532 and rs1799732 association did not remain significant for MDD. Moreover, a protective association was found for three variants; DRD4-120bp, rs10033951 and rs2388334 in the current cohort.Conclusions: The present study revealed the risk association of single nucleotide polymorphisms (SNPs) rs1006737 and rs2238056 with BD and the protective effect of the DRD4-120bp variant in MDD and BD, of rs2388334 in BD and of rs10033951 in MDD, BD, and SHZ in the current Pakistani cohort. Thus, the study is valuable in understanding the genetic basis of MDD, BD and SHZ in the Pakistani population, which may pave the way for future functional studies.

Functional single nucleotide polymorphisms in dopaminergic receptors D2 predict clinical response to Cariprazine

Cariprazine (CAR) is an antipsychotic drug for the treatment of schizophrenia (SCZ) and bipolar disorder (BD), and it acts as a partial agonist on the dopamine receptors (DR), D2, and D3. Although many single nucleotide polymorphisms (SNPs) in genes coding for these receptors are known to influence response to antipsychotics, to date, no study on CAR pharmacogenetics exists. In this pilot study, we investigated the relationship between SNPs in DRD2 (rs1800497 and rs6277) and DRD3 (rs6280), and response to CAR treatment, evaluated by the psychometric Brief Psychiatric Rating Scale (BPRS), in a cohort of Caucasian patients. We found a significant association between DRD2 rs1800497 and rs6277 and response to CAR treatment. When genotypes were combined into an arbitrary score, the receiver operating characteristic curve analysis showed that using a cut-off value of -2.5 the response to CAR treatment could be predicted with a positive likelihood ratio of 8.0. Our study report, for the first time, a correlation between SNPs in DRD2 and response to CAR treatment. After confirmation in a larger cohort of patients, our results could open the way for the identification of new tools for the provision of response to CAR treatment.

No association of the dopamine D2 receptor genetic bilocus score (rs1800497/rs1799732) on food addiction and food reinforcement in Chilean adults

Purpose: Different systems regulate food intake. In the reward system, dopamine (DA) is the main neurotransmitter, and a variety of genetic variants (rs1799732 and rs1800497) are associated with addiction. Addiction is a highly polygenic disease, where each allelic variant adds a small amount of vulnerability. Polymorphisms rs1799732 and rs1800497 are associated with eating behavior and hedonic hunger, but links to food addiction remain unclear.

Aim: To evaluate the association between the bilocus profile (rs1799732-rs1800497) of the dopaminergic pathway with food reinforcement and food addiction in Chilean adults.

Methods: A cross-sectional study recruited a convenience sample of 97 obese, 25 overweight, and 99 normal-weight adults (18–35 years). Anthropometric measurements were performed by standard procedures and eating behavior was assessed using the: Food Reinforcement Value Questionnaire (FRVQ) and Yale Food Addiction scale (YFAS). The DRD2 genotypes were determined by TaqMan assays (rs1800497 and rs1799732). A bilocus composite score was calculated.

Results: In the normal weight group, individuals who were heterozygous for the rs1977932 variant (G/del) showed higher body weight (p-value 0.01) and abdominal circumference (p-value 0.01) compared to those who were homozygous (G/G). When analyzing rs1800497, a significant difference in BMI was observed for the normal weight group (p-value 0.02) where heterozygous showed higher BMI. In the obese group, homozygous A1/A1 showed higher BMI in comparison to A1/A2 and A2/A2 (p-value 0.03). Also, a significant difference in food reinforcement was observed in the rs1800497, where homozygous for the variant (A1A1) show less reinforcement (p-value 0.01).In relation to the bilocus score in the total sample, 11% showed “very low dopaminergic signaling”, 24.4% were “under”, 49.7% showed “intermediate signaling”, 12.7% showed “high” and 1.4% showed “very high”. No significant genotypic differences were observed in food reinforcement and food addiction by bilocus score.

Conclusions: The results indicate that the genetic variants rs1799732 and rs1800497 (Taq1A) were associated with anthropometric measurements but not with food addiction or food reinforcement in Chilean university students. These results suggest that other genotypes, such as rs4680 and rs6277, which affect DA signaling capacity through a multilocus composite score, should be studied. Level V: Evidence obtained from a cross-sectional descriptive study.

Canonical and Non-Canonical Antipsychotics' Dopamine-Related Mechanisms of Present and Next Generation Molecules: A Systematic Review on Translational Highlights for Treatment Response and Treatment-Resistant Schizophrenia

Schizophrenia is a severe psychiatric illness affecting almost 25 million people worldwide and is conceptualized as a disorder of synaptic plasticity and brain connectivity. Antipsychotics are the primary pharmacological treatment after more than sixty years after their introduction in therapy. Two findings hold true for all presently available antipsychotics. First, all antipsychotics occupy the dopamine D2 receptor (D2R) as an antagonist or partial agonist, even if with different affinity; second, D2R occupancy is the necessary and probably the sufficient mechanism for antipsychotic effect despite the complexity of antipsychotics' receptor profile. D2R occupancy is followed by coincident or divergent intracellular mechanisms, implying the contribution of cAMP regulation, β-arrestin recruitment, and phospholipase A activation, to quote some of the mechanisms considered canonical. However, in recent years, novel mechanisms related to dopamine function beyond or together with D2R occupancy have emerged. Among these potentially non-canonical mechanisms, the role of Na²⁺ channels at the dopamine at the presynaptic site, dopamine transporter (DAT) involvement as the main regulator of dopamine concentration at synaptic clefts, and the putative role of antipsychotics as chaperones for intracellular D2R sequestration, should be included. These mechanisms expand the fundamental role of dopamine in schizophrenia therapy and may have relevance to considering putatively new strategies for treatment-resistant schizophrenia (TRS), an extremely severe condition epidemiologically relevant and affecting almost 30% of schizophrenia patients. Here, we performed a critical evaluation of the role of antipsychotics in synaptic plasticity, focusing on their canonical and non-canonical mechanisms of action relevant to the treatment of schizophrenia and their subsequent implication for the pathophysiology and potential therapy of TRS.

Examining how and why polygenic dopamine composite levels moderate adolescents' vulnerability to peer victimization

Extensive literature documents that dopaminergic genes play an important role in the link between adverse environments and adolescents' problem behavior. However, little is known about the potential mechanism underlying adolescents' vulnerability to peer victimization. The current study examined the effect of the interplay between a polygenic dopamine composite (i.e., COMT Val158Met and DRD2-141C Ins/Del polymorphisms) and peer victimization on adolescents' externalizing problems as well as the mediating role of emotion dysregulation in the interactive effects in a sample of 393 Chinese adolescents (Mean age = 14.71 years; 50.1% girls). A significant moderation of dopaminergic genetic composite was observed in girls but not in boys. In addition, emotion dysregulation partially explained the moderating effect of dopaminergic genes. Specifically, girls with genic composite indexing low dopamine activity reported a higher level of emotion dysregulation when faced with more peer victimization. More difficulties with emotion regulation, in turn, predicted more pronounced externalizing problems in girls. This study underscores polygenic underpinnings of adolescent vulnerability to negative peer experiences and suggests the importance of considering sex differences when investigating genic influence on the relationship between adverse environments and externalizing problems.

Cellular and neuronal mechanisms that underlie addiction - literature review

Introduction: Addictive substances act on a number of neurotransmitter systems, and the end result of this action is the activation of the reward system in the brain. The cellular and neuronal mechanisms that underlie addiction have long been searched for. One of such neurotransmitters is dopamine, a catecholamine synthesized in neurons located mainly in the midbrain.

Material and method: The available literature was reviewed on the Pubmed platform and from other sources. The analysis included original studies, reviews.

The aim of the study was to review the literature on the relationship between the DRD2 gene and the occurrence of substance addiction.

Discussion: This work presents several currently discussed biological mechanisms, especially at the molecular and genetic level, involved in the process of addiction to various psychoactive substances. They discovered the brain structures that are most at risk, as well as other neurotransmitter systems and receptor proteins through which they can exert their pathological effects. It has also been established that exposure to psychoactive substances causes significant changes in expression in over 100 genes (including genes for dopaminergic, serotonergic and signaling pathways). The DRD2 receptor (present, among others, in the nucleus accumbens) plays an important role in the reward system, in the transmission of information. The weakening of this conductivity is a significant risk factor for the onset of clinical features that are associated with reward system deficiency syndrome. The expression of the D2 receptor gene may take up to 2 isoforms: short D2S and long D2L.

Conclusions: Further research at the molecular level may result in the modification of psychotherapy and pharmacotherapy in terms of their personalization.

Association between Polymorphism rs1799732 of DRD2 Dopamine Receptor Gene and Personality Traits among Cannabis Dependency

Compared to other addictive substances, patients with cannabis addiction are significantly outnumbered by those who report dependence on other, more addictive substances. Unfortunately, most cannabis addiction goes untreated, and among those who choose treatment, the requirements are much higher for adolescents and young adults.

THE AIM OF THE STUDY

To examine the relationship of cannabinoid dependency in the genetic context-the association between the rs1799732 polymorphism of the DRD2 gene and psychological traits and anxiety.

METHODS

The study group consisted of 515 male volunteers. Of these, 214 patients were diagnosed with cannabis addiction and 301 were non-addicted. Patients were diagnosed with NEO Five-Factor Personality Inventory (NEO-FFI), and State-Trait Anxiety Inventory (STAI) questionnaires. The interactions between personality traits and polymorphisms in the DRD2 rs1799732 gene were investigated in a group of cannabis-addicted patients and non-addicted controls using the real-time PCR method.

RESULTS

Compared to the control group, the case group obtained significantly higher scores on the STAI State, STAI Trait, Neuroticism and Openness scales, as well as lower scores on the Extraversion, Agreeableness, and Conscientiousness scales. There was no statistically significant difference between addicts and the control group in the frequency of genotypes, but there was a statistically significant difference between addicts and the control group in the frequency of the DRD2 allele rs179973. The multivariate ANOVA analysis showed a statistically significant influence of the DRD2 rs1799732 genotype on the NEO-FFI agreeableness scale and a statistically significant effect of addiction to cannabinoids or its absence on the NEO-FFI agreeableness scale score.

CONCLUSIONS

Studying homogeneous subgroups-as in our study-seems reasonable, particularly when combined with genetic determinants and psychological traits. In multigenic and multifactorial entities, such a strategy has a future.

The Gender-Specific Association of DRD2 Polymorphism with Metabolic Syndrome in Patients with Schizophrenia

Background: Metabolic syndrome is widespread in patients with schizophrenia receiving long-term antipsychotic therapy. Dopamine D2 receptors play an important role in mediating both the therapeutic actions of antipsychotics and their side effects. The present study examined the association of two polymorphisms of the DRD2 gene with metabolic syndrome in patients with schizophrenia. Methods: We examined 517 patients from several regions of Siberia (Russia) with a clinical diagnosis of schizophrenia. Genotyping of two single nucleotide polymorphisms rs1799732 and rs4436578 of the dopamine D2 receptor gene (DRD2) was performed in a population of 471 patients. The results were analyzed using chi-square tests. Results: Functional polymorphism rs1799732 of the DRD2 gene is associated with drug-induced metabolic syndrome in women with schizophrenia. Conclusions: Our results show that the DRD2 gene may be involved in the pathogenesis of metabolic disorders in patients with schizophrenia. Further analysis of possible genetic markers will allow for personalized treatment with minimal side effects and optimal efficacy. This which seems relevant in light of the recent focus on improving the quality of life and ensuring a high level of social adaptation of patients with schizophrenia.

The role of genetic mutation in alcoholic liver disease

Background

Alcoholic liver disease (ALD) is the world’s most common type of liver disease caused due to overconsumption of alcohol. The liver supports the best level of tissue damage by hefty drinking since it is the binding site of ethanol digestion. This disease can progress to alcoholic steatohepatitis from alcoholic fatty liver, which implies steatosis has become the most punctual reaction to hefty drinking and is portrayed by the deposition of fat hepatocytes. In addition, steatosis can advance to steatohepatitis, a more extreme, provocative sort of liver damage described by hepatic inflammation. Constant and unnecessary liquor utilization delivers a wide range of hepatic sores, fibrosis and cirrhosis, and sometimes hepatocellular carcinoma. Most people consuming > 40 g of liquor each day create alcoholic fatty liver (AFL); notwithstanding, just a subset of people will grow further developed infection. Hereditary, epigenetic, and non-hereditary components may clarify the impressive interindividual variety in the ALD phenotype.

Main body

This systematic review is to classify new candidate genes associated with alcoholic liver disorders, such as RASGRF2, ALDH2, NFE2L2, ADH1B, PNPLA3, DRD2, MTHFR, TM6SF2, IL1B, and CYP2E1, MBOAT7 as well as to revise the functions of each gene in its polymorphic sequence. The information obtained from the previously published articles revealed the crucial relationship between the genes and ALD and discussed each selected gene’s mechanism.

Conclusion

The aim of this review is to highlight the candidate genes associated with the ALD, and the evidence of this study is to deliberate the part of genetic alterations and modifications that can serve as an excellent biological maker, risk predictors, and therapeutic targets for this disease.

Pharmacogenetics of Antipsychotic Treatment in Schizophrenia

Antipsychotics are the mainstay treatment for schizophrenia. There is large variability between individuals in their response to antipsychotics, both in efficacy and adverse effects of treatment. While the source of interindividual variability in antipsychotic response is not completely understood, genetics is a major contributing factor. The identification of pharmacogenetic markers that predict antipsychotic efficacy and adverse reactions is a growing area of research and holds the potential to replace the current trial-and-error approach to treatment selection in schizophrenia with a personalized medicine approach.In this chapter, we provide an overview of the current state of pharmacogenetics in schizophrenia treatment. The most promising pharmacogenetic findings are presented for both antipsychotic response and commonly studied adverse reactions. The application of pharmacogenetics to schizophrenia treatment is discussed, with an emphasis on the clinical utility of pharmacogenetic testing and directions for future research.

Altered Development of Mesencephalic Dopaminergic Neurons in SIDS: New Insights into Understanding Sudden Infant Death Pathogenesis

Sudden infant death syndrome (SIDS) is defined as the unexpected sudden death of an infant under 1 year of age that remains unexplained after a thorough case investigation. The SIDS pathogenesis is still unknown; however, abnormalities in brain centers that control breathing and arousal from sleep, including dramatic changes in neurotransmitter levels, have been supposed in these deaths. This is the first study focusing on mesencephalic dopaminergic neurons, so far extensively studied only in animals and human neurological diseases, in SIDS. Dopaminergic structures in midbrain sections of a large series of sudden infant deaths (36 SIDS and 26 controls) were identified using polyclonal rabbit antibodies against tyrosine hydroxylase, the rate-limiting enzyme in catecholamine biosynthesis, and the dopamine transporter, a membrane protein specifically expressed in dopaminergic cells. Dopamine-immunolabeled neurons were observed concentrated in two specific structures: the pars compacta of the substantia nigra and in the subnucleus medialis of the periaqueductal gray matter. Anatomical and functional degenerations of dopaminergic neurons in these regions were observed in most SIDS cases but never in controls. These results indicate that dopamine depletion, which is already known to be linked especially to Parkinson's disease, is strongly involved even in SIDS pathogenesis.

Pharmacogenomics Factors Influencing the Effect of Risperidone on Prolactin Levels in Thai Pediatric Patients With Autism Spectrum Disorder

We investigated the association between genetic variations in pharmacodynamic genes and risperidone-induced increased prolactin levels in children and adolescents with autism spectrum disorder (ASD). In a retrospective study, variants of pharmacodynamic genes were analyzed in 124 ASD patients treated with a risperidone regimen for at least 3 months. To simplify genotype interpretation, we created an algorithm to calculate the dopamine D2 receptor (DRD2) gene genetic risk score. There was no relationship between prolactin levels and single SNPs. However, the H1/H3 diplotype (A2/A2-Cin/Cin-A/G) of DRD2/ankyrin repeat and kinase domain containing 1 (ANKK1) Taq1A, DRD2 -141C indel, and DRD2 -141A>G, which had a genetic risk score of 5.5, was associated with the highest median prolactin levels (23 ng/ml). As the dose-corrected plasma levels of risperidone, 9-OH-risperidone, and the active moiety increased, prolactin levels in patients carrying the H1/H3 diplotype were significantly higher than those of the other diplotypes. DRD2 diplotypes showed significantly high prolactin levels as plasma risperidone levels increased. Lower levels of prolactin were detected in patients who responded to risperidone. This is the first system for describing DRD2 haplotypes using genetic risk scores based on their protein expression. Clinicians should consider using pharmacogenetic-based decision-making in clinical practice to prevent prolactin increase.

Genetic differential susceptibility to the parent-child relationship quality and the life span development of compassion

The development of compassion for others might be influenced by the social experiences made during childhood and has a genetic component. No research has yet investigated whether the parent-child relationship quality interacts with genetic variation in the oxytocin and dopamine systems in predicting compassion over the life span. In the prospective Young Finns Study (N = 2099, 43.9% men), we examined the interaction between mother-reported emotional warmth and intolerance toward their child assessed in 1980 (age of participants, 3-18 years) and two established genetic risk scores for oxytocin levels and dopamine signaling activity. Dispositional compassion for others was measured with the Temperament and Character Inventory 1997, 2001, and 2012 (age of participants, 20-50 years). We found a gene-environment interaction (p = .031) that remained marginally significant after adjustment for multiple testing. In line with the differential susceptibility hypothesis, only participants who carry alleles associated with low dopamine signaling activity had higher levels of compassion when growing up with emotionally warm parents, whereas they had lower levels of compassion when their parents were emotionally cold. Children's genetic variability in the dopamine system might result in plasticity to early environmental influences that have a long-lasting effect on the development of compassion. However, our findings need replication.

Current strategies for predicting side effects from second generation antipsychotics in youth

Introduction: Antipsychotic medications are used to treat a number of conditions in children and adolescents. While side effect profiles from second generation antipsychotics (SGAs) may differ from older antipsychotics, they do not come without risk. Knowing which children may be at higher risk for specific outcomes is important clinical information for prescribers. Common side effects and toxicities of SGAs in children include movement disorders, weight gain, and hormonal changes. There are also rare, but potentially dangerous adverse events including neuroleptic malignant syndrome, hypersensitivity and suicidal ideation.Areas covered: This review will summarize and comment on clinical, pharmacological, and genetic factors having evidence as predictors of SGA-associated side effects and toxicities in children.Expert opinion: Observations across studies note that older children and those that do not respond early in treatment may be more at risk for movement disorders, while younger, antipsychotic naive children are at increased risk for weight gain. Relatively fewer studies have looked at pharmacogenetic relationships, although variations in pharmacokinetic and pharmacodynamic genes hold promise to advance drug dosing or selection strategies. Future efforts to assimilate multiple clinical, pharmacological, and genetic factors to facilitate predictive analytics and clinical decision support for prescribers will advance precision care to patients.

Influence of DRD2 Polymorphisms on the Clinical Outcomes of Opioiddependent Patients on Methadone Maintenance Therapy

Introduction:

Dopamine receptor D2 (DRD2) is one of the dopamine receptors that have been studied in relation to opioid dependence. It is possible, therefore, that DRD2 gene (DRD2) polymorphisms influence treatment outcomes of patients with opioid dependence. The objective of this study was to investigate the influence of DRD2 polymorphisms on the clinical outcomes of opioid-dependent patients on methadone maintenance therapy (MMT).

Materials and Methods:

Patients with opioid dependence (n = 148) were recruited from MMT clinics. Pain sensitivity, severity of the opiate withdrawal syndrome, and sleep quality were assessed using cold pressor test (CPT), Subjective Opiate Withdrawal Scale (SOWS-M), and Pittsburgh Sleep Quality Index (PSQI)-Malay, respectively. Deoxyribonucleic acid (DNA) was extracted from whole blood, and then was used for genotyping of Val96Ala, Leu141Leu, Val154Ile, Pro310Ser, Ser311Cys, TaqI A, -141C Ins/Del, and A-241G polymorphisms.

Results:

Among 148 patients, 8.1% (n = 12), 60.8% (n = 90), 27.7% (n = 41), and 29.1% (n = 43) had at least one risk allele for Ser311Cys, TaqI A, -141C Ins/Del, and A-241G polymorphisms, respectively. There were no significant differences in pain responses (pain threshold, tolerance, and intensity), SOWS, and PSQI scores between DRD2 polymorphisms.

Conclusion:

The common DRD2 polymorphisms are not associated with pain sensitivity, severity of the opiate withdrawal syndrome, and sleep quality in patients with opioid dependence on MMT. However, this may be unique for Malays. Additional research should focus on investigating these findings in larger samples and different ethnicity.

Polymorphisms of Dopamine Receptor Genes and Parkinson's Disease: Clinical Relevance and Future Perspectives

Parkinson’s disease (PD) is a neurodegenerative disease caused by loss of dopaminergic neurons in the midbrain. PD is clinically characterized by a variety of motor and nonmotor symptoms, and treatment relies on dopaminergic replacement. Beyond a common pathological hallmark, PD patients may present differences in both clinical progression and response to drug therapy that are partly affected by genetic factors. Despite extensive knowledge on genetic variability of dopaminergic receptors (DR), few studies have addressed their relevance as possible influencers of clinical heterogeneity in PD patients. In this review, we summarized available evidence regarding the role of genetic polymorphisms in DR as possible determinants of PD development, progression and treatment response. Moreover, we examined the role of DR in the modulation of peripheral immunity, in light of the emerging role of the peripheral immune system in PD pathophysiology. A better understanding of all these aspects represents an important step towards the development of precise and personalized disease-modifying therapies for PD.

Detection of altered methylation of MB-COMT promotor and DRD2 gene in cannabinoid or synthetic cannabinoid use disorder regarding gene variants and clinical parameters

This study aims to investigate the association between cannabinoid use disorder (CUD) or synthetic cannabinoid use disorder (SCUD) and methylation status of MB-COMT (membrane-bound catechol-O-methyltransferase) promotor or DRD2 gene considering gene variants and clinical parameters. Based on the DSM-5 criteria, 218 CUD/SCUD patients' diagnoses were confirmed with a positive urine test, and a control group consisting of 102 participants without substance use disorders was included. Methylation-specific PCR was used to identify the methylation of the MB-COMT promotor and DRD2 gene. DRD2-141C Ins/Del and COMT Val158Met gene variants were evaluated by using PCR-RFLP. When the DRD2 and MB-COMT promoter methylation of CUD/SCUD patients were compared with the control group, there was a significant difference between the MB-COMT promoter methylation status of the two groups. When comparing DRD2 gene methylation due to clinical parameters and DRD2 genotype distribution in patients, the methylation status was significantly different between the groups due to the family history. Again, comparing the MB-COMT promotor methylation due to the COMT Val158Met genotype distribution and clinical parameters in patients, the MB-COMT promoter methylation status was significantly different between the groups due to the presence of alcohol usage. In summary, whereas the MB-COMT promoter methylation may be associated with the CUD/SCUD, the methylation of the DRD2 gene was not related to CUD/SCUD.

Associations of the ANKK1 and DRD2 gene polymorphisms with overweight, obesity and hedonic hunger among women from the Northwest of Iran

BACKGROUND

Pleasure from palatable foods can stimulate hedonic eating and, therefore, might be a major culprit for obesity. Dopamine receptor polymorphisms, especially variants in the genes regulating the D2 receptor, including ANKK1 and DRD2, are the prime candidates for assessing the individual differences in hedonic eating. This study was carried out to investigate the possible associations of the T (rs1800497) and Del (rs1799732) alleles with body mass index (BMI) and hedonic hunger among Iranian Azeri women.

METHODS

A total of 372 healthy overweight/obese subjects (BMI ≥ 25 kg/m²) and 159 normal weight individuals (BMI 18.5-24.9 kg/m²) were genotyped for the polymorphisms of ANNK1 and DRD2 genes using PCR-RFLP. BMI and hedonic hunger were also evaluated.

RESULTS

Three hundred and sixty-three (68.36%), 152 (28.63%), and 16 (3.01%) of the participants had CC, CT, and TT genotypes for ANNK1 gene, respectively. Of 515 samples genotyped for DRD2 gene, 315 (60.51%), 173 (33.59%), and 27 (5.24%) had Ins/Ins, Ins/Del, and Del/Del genotypes, respectively. The genotype and genotype frequencies were significantly different between the groups (p = 0.04). Significant differences were observed between the T+ genotype (TT + TC) and the T- genotype (CC) regarding the BMI and hedonic hunger scores (p < 0.05). In addition, Del+ group (Del/Del + Ins/Del) had higher BMI and hedonic hunger scores compared to Del- group (Ins/Ins) (p < 0.05).

CONCLUSIONS

Our findings showed that the frequencies of T and Del alleles were greater in the overweight/obese individuals. Also, the polymorphism of ANKK1 (rs1800497) and polymorphism of the DRD2 gene (rs1799732) showed significant associations with BMI and hedonic hunger.

LEVEL OF EVIDENCE

Level III, case-control study.

Molecular genetics of neurotransmitters and neuropeptides involved in Internet use disorders including first insights on a potential role of hypothalamus' oxytocin hormone

This chapter covers the phenomenon of Internet use disorders (IUDs) and putative associations with different neurotransmitter and neuropeptide systems. Genes coding for such messengers can be seen as an important starting point in the complicated quest to understand human behavior including new phenomena such as IUDs. Therefore, a special focus of this chapter will lie on individual differences in molecular genetic underpinnings of neurotransmitter and neuropeptide systems and their associations with individual differences in tendencies towards IUDs. By shedding light on these associations, putative predisposing molecular genetic factors for the emergence and maintenance of IUDs can be carved out. Therefore, first an introduction to IUDs and a model that can guide research on putative associations of IUDs with different specific neurotransmitters and neuropeptides will be presented. Subsequently, twin studies on the heritability of IUDs are reviewed. Finally, studies on differences in molecular genetic predispositions and their associations with differences in IUDs will be presented and discussed, including targets related to the dopaminergic and serotonergic system as well as the hypothalamic neuropeptide oxytocin. The chapter closes with a conclusion about what is already known and what needs to be investigated in future studies to gain further insights into putative associations between molecular genetic markers and IUDs.

Association of DRD2 gene polymorphisms with schizophrenia in the young Bangladeshi population: A pilot study

Purpose

DRD2 gene is considered one of the most important candidate genes for the schizophrenia (SCZ) development due to its role in dopamine signaling and no genetic association study has been conducted yet on the Bangladeshi SCZ patients. The objective of the present study was to investigate the association of DRD2 genetic polymorphisms (rs4648317, rs4936270, and rs7131056) with SCZ in the Bangladeshi population.

Patients and methods

This case-control study consisted of 101 SCZ patients and 101 controls. Genotyping was performed by the polymerase chain reaction and restriction fragment length polymorphism (PCR–RFLP) method.

Results

The average ages were 22.15 and 22.09 years in patients and controls, respectively (p > 0.05). CT genotype of rs4936270 showed a significantly higher risk for the development of SCZ compared to CC genotype (OR = 2.0, p = 0.023), whereas no association was found for TT genotype. For the dominant model and T allele, rs4936270 showed a higher risk for the development of SCZ (OR = 2.01, p = 0.020; OR = 1.76, p = 0.021, respectively), while the recessive model had no association with SCZ. A statistically significant (OR = 2.70, p = 0.036) higher risk was found for the AA genotype, but no association was found for GA genotype of rs4648317 SNP compared to GG genotype. In case of dominant and recessive models, rs4648317 showed no association with SCZ. ‘A’ allele of rs4648317 SNP was found to be significantly associated with the elevated risk of SCZ (OR = 1.50, p = 0.044). No association with SCZ of rs7131056 SNP was found for AC, CC genotypes, dominant, recessive, and allele models. Furthermore, from the haplotyping analysis, we found that CAA and TAA haplotypes of rs4936270, rs7131056 and rs4648317 SNPs are associated with SCZ (χ2 = 8.26, p = 0.004; χ2 = 5.31, p = 0.021, respectively). After Bonferroni correction, the association of SCZ did not withstand with any genotype, allele and haplotype (p < 0.017) except CAA haplotype.

Conclusion

Our results suggest that DRD2 gene polymorphisms may be associated with the susceptibility of SCZ in the young Bangladeshi population.

A Behavioral Genetic Model of the Mechanisms Underlying the Link Between Obesity and Symptoms of ADHD

Objective: The ADHD-obesity link has been suggested to result from a shared underlying basis of suboptimal dopamine (DA); however, this theory conflicts evidence that an amplified DA signal increases the risk for overeating and weight gain. A model was tested in which ADHD symptoms, predicted by hypodopaminergic functioning in the prefrontal cortex, in combination with an enhanced appetitive drive, predict hedonic eating and, in turn, higher body mass index (BMI). Method: DRD2 and DRD4 markers were genotyped. The model was tested using structural equation modeling in a nonclinical sample (N = 421 adults). Results: The model was a good fit to the data. Controlling for education, all parameter estimates were significant, except for the DRD4-ADHD symptom pathway. The significant indirect effect indicates that overeating mediated the ADHD symptoms-BMI association. Conclusion: Results support the hypothesis that overeating and elevated DA in the ventral striatum-representative of a greater reward response-contribute to the ADHD symptom-obesity relationship.

Personality Traits or Genetic Determinants-Which Strongly Influences E-Cigarette Users?

Presently, a growing popularity of electronic cigarettes may be observed. Used as a means of obtaining nicotine they allow to substitute traditional cigarettes. The origins of substance use disorders are conditioned by dopaminergic signaling which influences motivational processes being elementary factors conditioning the process of learning and exhibiting goal-directed behaviors. The study concentrated on analysis of three polymorphisms located in the dopamine receptor 2 (DRD2) gene—rs1076560, rs1799732 and rs1079597 using the PCR method, personality traits determined with the Big Five Questionnaire, and anxiety measured with the State Trait Anxiety Inventory. The study was conducted on a group of 394 volunteers, consisting e-cigarette users (n = 144) and controls (n = 250). Compared to the controls the case group subjects achieved significantly higher scores in regard to the STAI state and the trait scale, as well as the NEO-FFI Neuroticism and Openness scale. Likewise, in the case of the STAI state for DRD2 rs1076560 significant differences were found. Furthermore, while comparing the groups (e-cigarette users vs. controls) we noticed interactions for the NEO FFI Neuroticism and DRD2 rs1076560. The same was observed in the case of interactions significance while comparing groups (e-cigarette users vs. controls) for the STAI trait/scale and DRD2 rs1799732. Findings from this study demonstrate that psychological factors and genetic determinants should be analyzed simultaneously and comprehensively while considering groups of addicted patients. Since the use, and rapid increase in popularity, of electronic cigarettes has implications for public health, e-cigarette users should be studied holistically, especially younger groups of addicted and experimenting users.

Association between DRD2 and ANKK1 polymorphisms with the deficit syndrome in schizophrenia

BACKGROUND

The clinical course of schizophrenia varies among patients and is difficult to predict. Some patient populations present persistent negative symptoms, referred to as the deficit syndrome. Compared to relatives of non-deficit schizophrenia patients, family members of this patient population are at an increased risk of developing schizophrenia. Therefore, the aim of this study was to search for genetic underpinnings of the deficit syndrome in schizophrenia.

METHODS

Three SNPs, i.e., rs1799732 and rs6276 located within DRD2, and rs1800497 within ANKK1, were identified in the DNA samples of 198 schizophrenia probands, including 103 patients with deficit (DS) and 95 patients with non-deficit schizophrenia (NDS). Results: No significant differences concerning any of the analyzed polymorphisms were found between DS and NDS patients. However, significant links were observed between family history of schizophrenia and the deficit syndrome, G/G genotype and rs6276 G allele. In a separate analysis, we identified significant differences in frequencies of rs6276 G allele between DS and NDS patients with family history of schizophrenia. No significant associations were found between DRD2 and ANKK1 SNPs and the age of onset or schizophrenia symptom severity.

CONCLUSIONS

The results of our preliminary study fail to provide evidence of associations between DRD2 and ANKK1 polymorphisms with the deficit syndrome or schizophrenia symptom severity, but suggest potential links between rs6276 in DRD2 and the deficit syndrome in patients with hereditary susceptibility to schizophrenia. However, further studies are necessary to confirm this observation.

No Effect of Genome-Wide Significant Schizophrenia Risk Variation at the DRD2 Locus on the Allelic Expression of DRD2 in Postmortem Striatum

A genome-wide significant association has been reported between non-coding variants at the dopamine D2 receptor (DRD2) gene locus and schizophrenia. However, effects of identified schizophrenia risk alleles on DRD2 function are yet to be demonstrated. Using highly sensitive measures of allele-specific expression, we have assessed cis-regulatory effects associated with genotype at lead SNP rs2514218 on DRD2expression in the adult human striatum. No significant differences were observed in the extent of allelic expression imbalance between samples that were genomic heterozygotes for rs2514218 (where cis-regulatory effects of the risk allele are compared with those of the non-risk allele within individual subjects) and samples that were homozygous for rs2514218 (where cis-regulatory effects of this SNP on each expressed DRD2 allele will be equal). We therefore conclude that rs2514218 genotype is not associated with large effects on overall DRD2 RNA expression, at least in postmortem adult striatum. Alternative explanations for the genetic association between this variant and schizophrenia include effects on DRD2 that are transcript specific, restricted to minor DRD2-expressing cell populations or elicited only under certain physiological circumstances, or mediation through effects on another gene (or genes) at the locus.

DRD2 and ANKK1 genes associate with late-onset heroin dependence in men

Objectives: Dopamine plays an important role in reward system of heroin dependence (HD), and dopaminergic D2 receptor (DRD2) gene is a candidate for the aetiology of HD. Ankyrin repeat and kinase domain containing 1 (ANKK1) gene is proximal to DRD2 and may influence its expression. We explored whether DRD2 and ANKK1 associate with occurrence of HD, and whether the genetic variants influence personality traits in male patients with HD.Methods:DRD2/ANKK1 polymorphisms were analysed in 950 unrelated Han Chinese male participants (601 HD patients and 349 healthy controls). All participants were screened using the same assessment tools and all patients met the diagnostic criteria of HD. Personality traits were assessed in 274 patients and 142 controls using the Tridimensional Personality Questionnaire.Results: According to the allele, genotype and haplotype frequency analysis, we observed an association between HD and several DRD2/ANKK1 polymorphisms (rs1800497, rs1800498, rs1079597 and rs4648319); this was most notable in the late-onset HD subgroup. However, these DRD2/ANKK1 polymorphisms did not associate with specific personality traits in HD patients and controls.Conclusions:DRD2/ANKK1 may play an important role in occurrence of late-onset HD, but does not mediate the relationship between personality traits and HD in Han Chinese male population.

Analysis of methylation and -141C Ins/Del polymorphisms of the dopamine receptor D2 gene in patients with schizophrenia

The gene for dopamine receptor D2 (DRD2) is associated with schizophrenia (SCZ). Epigenetic changes may be related to SCZ pathology. The -141C Ins/Del polymorphism in DRD2 (rs1799732) is functional and associated with SCZ. Fifty SCZ patients and 50 control subjects were newly recruited and analyzed in addition to 50 previously reported SCZ samples and 50 previously reported control samples. Genomic DNA from peripheral leukocytes was analyzed. We replicated analysis of DNA methylation rates at seven CpG sites (CpG 1-1 to 1-7) and also analyzed five additional sites (CpG 2-1 to 2-5) in the upstream region of DRD2. We also performed genotyping of -141C IIns/Del and analyzed the effects of -141C Ins/Del on methylation of DRD2. Methylation rates were significantly lower in SCZ patients compared to control subjects, respectively. In control subjects, the methylation rates were significantly lower in individuals with the Ins/Ins genotype than in Del allele carriers. We replicated hypomethylation of the DRD2 promoter region in SCZ patients compared to age-matched control subjects. The -141C Ins/Del polymorphism affected the methylation rates in regions of DRD2. Hypomethylation and the -141C Ins/Del polymorphism of DRD2 may be biomarkers for SCZ.

No association between polymorphisms in the promoter region of dopamine receptor D2 gene and schizophrenia in the northern Chinese Han population: A case-control study

BACKGROUND

Epidemiological studies found that genetic factors are among the causes of schizophrenia, exclusively the genes involved in the dopamine system. Prior to this, the role of dopamine receptor D2 (DRD2) gene promoter polymorphisms and schizophrenia has been studied extensively, but there are still some uncertainties about these associations. The present study is focusing on the association between the DRD2 gene promoter region polymorphisms and schizophrenia in the northern Chinese Han population.

METHODS

We sequenced 2,111-bp fragment of DRD2 gene promoter region in 306 schizophrenic patients and 324 healthy controls to find association between DRD2 and schizophrenia. SPSS version 18 0.0 was used to calculate odds ratios (OR), 95% confidence intervals (CIs).The Hardy-Weinberg equilibrium test and the confirmation of haplotypes were calculated using Haploview version 4.1. The association of schizophrenic risk of DRD2 genotypes, alleles, and haplotypes between case and control groups was calculated using the chi-squared test. PS program was used to calculate the Power analysis.

RESULTS

The genotype frequencies of rs7116768 (p = 0.025) and rs1799732 (p = 0.042) were associated meagerly. After Bonferroni correction, there was no association found between DRD2 gene promoter region with schizophrenia risk in the northern Chinese Han population.

CONCLUSIONS

In this study, we did not find any significant difference between schizophrenia and the polymorphisms of DRD2 gene promoter region. A more forceful conclusion remains to be verified by further confirmatory experiments.

Molecular Imaging of Opioid and Dopamine Systems: Insights Into the Pharmacogenetics of Opioid Use Disorders

Opioid use in the United States has steadily risen since the 1990s, along with staggering increases in addiction and overdose fatalities. With this surge in prescription and illicit opioid abuse, it is paramount to understand the genetic risk factors and neuropsychological effects of opioid use disorder (OUD). Polymorphisms disrupting the opioid and dopamine systems have been associated with increased risk for developing substance use disorders. Molecular imaging studies have revealed how these polymorphisms impact the brain and contribute to cognitive and behavioral differences across individuals. Here, we review the current molecular imaging literature to assess how genetic variations in the opioid and dopamine systems affect function in the brain's reward, cognition, and stress pathways, potentially resulting in vulnerabilities to OUD. Continued research of the functional consequences of genetic variants and corresponding alterations in neural mechanisms will inform prevention and treatment of OUD.

Vulnerable combinations of functional dopaminergic polymorphisms to late-onset treatment resistant schizophrenia

Background

A significant portion of patients with schizophrenia who respond to initial antipsychotic treatment acquire treatment resistance. One of the possible pathogeneses of treatment-resistant schizophrenia (TRS) is antipsychotic-induced dopamine supersensitivity psychosis (Ai-DSP). Patients with this disease progression might share some genetic vulnerabilities, and thus determining individuals with higher risks of developing Ai-DSP could contribute to preventing iatrogenic development of TRS. Therefore, we decided to examine whether combinations of functional single nucleotide polymorphisms (SNPs) known to affect dopaminergic functions are related to Ai-DSP development.

Methods

In this case-control study, 357 Japanese participants diagnosed with schizophrenia or schizoaffective disorder were recruited and divided into two groups, those with and without Ai-DSP. As functional SNPs, we examined rs10770141 of the tyrosine hydroxylase gene, rs4680 of the catechol-O-methyltransferase gene, and rs1799732 and rs1800497 of the DRD2 genes, which are known to possess strong directional ties to dopamine synthesis, dopamine degradation and post-synaptic DRD2 prevalence, respectively.

Results

Among the 357 Japanese patients with schizophrenia or schizoaffective disorder, 130 were classified as Ai-DSP(+) and the other 227 as Ai-DSP(-). Significantly higher proportions of Ai-DSP(+) patients were found to have the SNP combinations of rs10770141/rs4680 (57.9%, OR2.654, 95%CI1.036–6.787, P = 0.048) and rs10770141/rs4680/ rs1800497 (64.3%, OR4.230, 95%CI1.306–13.619, P = 0.029). However, no single SNP was associated with Ai-DSP.

Conclusions

We preliminarily found that carrying particular combinations of functional SNPs, which are related to relatively higher dopamine synthesis and dopamine degradation and lower naïve DRD2, might indicate vulnerability to development of Ai-DSP. However, further studies are needed to validate the present results.

Age-Related Changes in Topological Degradation of White Matter Networks and Gene Expression in Chronic Schizophrenia

Current hypotheses stipulate core symptoms of schizophrenia (SZ) result from the brain's incapacity to integrate neural processes. Converging diffusion magnetic resonance imaging and graph theory studies provide evidence of macrostructural alterations in SZ. However, age-related topological changes within and between white matter (WM) networks and its relationship to gene expression with disease progression remain incompletely understood. This cross-sectional study uses network modeling to investigate changes in WM network organization with disease progression in chronic SZ as well its relationship with gene expression in healthy brains. First, we replicate prior findings demonstrating altered global WM network topology in SZ. Novel results show significantly altered age-related network degradation patterns in patients compared with controls. Specifically, controls show stereotyped, linear global network decline with age. In contrast, patients show nonlinear network decline with age. Further analysis reveals lack of significant topological decline in younger adult patients, which is subsequently followed by stereotyped linear decline in older adult patients. Node-specific analyses show significant topological differences in frontal and limbic regions of younger adult patients compared with age-matched controls, which become less pronounced with age in older adult patients compared with age-matched controls. Lastly, we show several gene expression profiles, including DISC1, are associated with age-related changes in WM disconnectivity. Together, these findings provide novel WM topological and genetic evidence supporting neurodevelopmental models of SZ, suggesting that network remodeling continues throughout the third decade of life before stabilizing.

Evaluation of association of DRD2 TaqIA and -141C InsDel polymorphisms with food intake and anthropometric data in children at the first stages of development

The reward sensation after food intake may be different between individuals and variants in genes related to the dopaminergic system may indicate a different response in people exposed to the same environmental factors. This study investigated the association of TaqIA (rs1800497) and -141C InsDel (rs1799732) variants in DRD2/ANKK1 gene with food intake and adiposity parameters in a cohort of children. The sample consisted of 270 children followed until 7 to 8 years old. DNA was extracted from blood and polymorphisms were detected by PCR-RFLP analysis. Food intake and nutritional status were compared among individuals with different SNP genotypes. Children carrying the A1 allele (TaqIA) had higher energy of lipid dense foods (LDF) when compared with A2/A2 homozygous children at 7 to 8 years old (GLM p=0.004; Mann Whitney p=0.005). No association was detected with -141C Ins/Del polymorphism. To our knowledge, this is the first association study of the DRD2 TaqIA and -141C Ins/Del polymorphism with food intake and anthropometric parameters in children. DRD2 TaqIA polymorphism has been associated with a reduction in D₂ dopamine receptor availability. Therefore, the differences observed in LDF intake in our sample may occur as an effort to compensate the hypodopaminergic functioning.

Effects of the -141C insertion/deletion polymorphism in the dopamine D2 receptor gene on the dopamine system in the striatum in patients with schizophrenia

The relationships between -141C insertion/deletion (Ins/Del) polymorphisms in the dopamine D2 receptor gene and the two dopamine system integrators, i.e., dopamine- and cAMP-regulated phosphoprotein of molecular weight 32 kDa (DARPP-32) and calcineurin (CaN), are still unclear. In this study, we assessed the effect of this polymorphism on DARPP-32 and CaN protein expression in the postmortem striatum of patients with schizophrenia and control individuals. The expression levels of truncated DARPP and CaN were lower in Del allele carriers. These findings provide important insights into the mechanism by which this genotype could result in a poor response to antipsychotic drugs.

DRD2/ANKK1 gene polymorphisms in forensic autopsies of methamphetamine intoxication fatalities

Dopamine D2 receptor/ankyrin repeat and kinase domain containing 1 (DRD2/ANKK1) gene polymorphisms have been associated with responses to psychotropic drugs and addiction. We analyzed two DRD2/ANKK1 polymorphisms, Taq1A and -141C Ins/Del, in 37 fatal methamphetamine (MA) intoxication cases and 235 control cases in which MA and psychotropic drugs were not detected. The association among polymorphism, cause of death, and cerebrospinal fluid (CSF) dopamine concentration was evaluated. The Taq1A polymorphism distribution in the fatal MA intoxication cases differed from in the controls (P = 0.030) with a significantly high A1/A1 + A1/A2 genotype frequency. No significant associations were observed between -141C Ins/Del polymorphisms and MA intoxication cases or between DRD2/ANKK1 polymorphisms and CSF dopamine concentrations. Our findings suggest that the DRD2/ANKK1 Taq1A polymorphism is associated with susceptibility to fatal MA intoxication.

Role of the Sympathetic Nervous System and Its Modulation in Renal Hypertension

The kidneys are densely innervated with renal efferent and afferent nerves to communicate with the central nervous system. Innervation of major structural components of the kidneys, such as blood vessels, tubules, the pelvis, and glomeruli, forms a bidirectional neural network to relay sensory and sympathetic signals to and from the brain. Renal efferent nerves regulate renal blood flow, glomerular filtration rate, tubular reabsorption of sodium and water, as well as release of renin and prostaglandins, all of which contribute to cardiovascular and renal regulation. Renal afferent nerves complete the feedback loop via central autonomic nuclei where the signals are integrated and modulate central sympathetic outflow; thus both types of nerves form integral parts of the self-regulated renorenal reflex loop. Renal sympathetic nerve activity (RSNA) is commonly increased in pathophysiological conditions such as hypertension and chronic- and end-stage renal disease. Increased RSNA raises blood pressure and can contribute to the deterioration of renal function. Attempts have been made to eliminate or interfere with this important link between the brain and the kidneys as a neuromodulatory treatment for these conditions. Catheter-based renal sympathetic denervation has been successfully applied in patients with resistant hypertension and was associated with significant falls in blood pressure and renal protection in most studies performed. The focus of this review is the neural contribution to the control of renal and cardiovascular hemodynamics and renal function in the setting of hypertension and chronic kidney disease, as well as the specific roles of renal efferent and afferent nerves in this scenario and their utility as a therapeutic target.

Dopamine receptor D2 genetic variations is associated with the risk and clinicopathological variables of urothelial cell carcinoma in a Taiwanese population

Dopamine receptor D2 (DRD2) is overexpressed in several kinds of cancers and was correlated with the prognosis of these cancers. Polymorphisms within the DRD2 gene were shown to be associated with lung and colon cancers. The purpose of this study was to explore effects of DRD2 gene polymorphisms on the susceptibility to and clinicopathological characteristics of urothelial cell carcinoma (UCC). In total, 369 patients diagnosed with UCC and 738 healthy controls were enrolled to analyze DRD2 genotypes at four loci (rs1799732, -141C>del; rs1079597, TaqIB; rs6277, 957C>T; and rs1800497, TaqIA) using a TaqMan-based real-time polymerase chain reaction (PCR). We found a significantly lower risk for UCC in individuals with the DRD2 rs6277 CT genotype compared to those with the wild-type CC genotype (adjusted odds ratio (AOR)=0.405, 95% confidence interval (CI): 0.196~0.837, p=0.015). In 124 younger patients (aged < 65 years) of the recruited UCC cohort, patients who carried at least one T allele of DRD2 rs1800497 were at higher risk (AOR=2.270, 95% CI: 1.060~4.860, p=0.033) of developing an invasive stage (pT2~pT4). In 128 female patients of the recruited UCC cohort, patients who carried at least one deletion allele of DRD2 rs1799732 showed a higher incidence of having an invasive stage (AOR=2.585, 95% CI: 1.066~6.264, p=0.032) and a large tumor (AOR=2.778, 95% CI: 1.146~6.735, p=0.021). Further analyses of The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) datasets revealed correlations of the expression of DRD2 with an invasive tumor, tumor metastasis, and the lower survival rate in patients with UCC. Our findings suggest that DRD2 levels might affect the progression of UCC, and the polymorphisms rs6277, rs1800497, and rs1799732 of DRD2 are probably associated with the susceptibility and clinicopathologic development of UCC in a Taiwanese population.

Pharmacogenetic tests for antipsychotic medications: clinical implications and considerations

Optimizing antipsychotic pharmacotherapy is often challenging due to significant variability in effectiveness and tolerability. Genetic factors influencing pharmacokinetics and pharmacodynamics may contribute to some of this variability. Research studies have characterized these pharmacogenetic relationships, and some genetic markers are now available as clinical tests. These advances in pharmacogenetics research and test availability have great potential to improve clinical outcomes and quality of life in psychiatric patients. For clinicians considering using pharmacogenetics, it is important to understand the clinical implications and also the limitations of markers included in currently available tests. This review focuses on pharmacokinetic and pharmacodynamic gene variants that are currently available in commercial genetic testing panels. Associations of these variants with clinical efficacy and adverse effects, as well as other clinical implications, in antipsychotic pharmacotherapy are discussed.

High-Coverage Whole-Exome Sequencing Identifies Candidate Genes for Suicide in Victims with Major Depressive Disorder

We carried out whole-exome ultra-high throughput sequencing in brain samples of suicide victims who had suffered from major depressive disorder and control subjects who had died from other causes. This study aimed to reveal the selective accumulation of rare variants in the coding and the UTR sequences within the genes of suicide victims. We also analysed the potential effect of STR and CNV variations, as well as the infection of the brain with neurovirulent viruses in this behavioural disorder. As a result, we have identified several candidate genes, among others three calcium channel genes that may potentially contribute to completed suicide. We also explored the potential implication of the TGF-β signalling pathway in the pathogenesis of suicidal behaviour. To our best knowledge, this is the first study that uses whole-exome sequencing for the investigation of suicide.

Pharmacogenetic evaluation to assess breakthrough psychosis with aripiprazole long-acting injection: a case report

BACKGROUND

Given the complex nature of symptom presentation and medication regimens, psychiatric clinics may benefit from additional tools to personalize treatments. Utilizing pharmacogenetic information may be helpful in assessing unique responses to therapy. We report herein a case of wearing-off phenomena during treatment with aripiprazole long-acting injectable (LAI) and a proof of concept strategy of how pharmacogenetic information may be used to assess possible genetic factors and also hypothesize potential mechanisms for further study.

CASE PRESENTATION

A 51-year-old African American male with schizoaffective disorder was referred to a psychiatric clinic for medication management. After unsuccessful trials of multiple antipsychotics, oral aripiprazole was initiated (up to 30 mg/day) and transitioned to aripiprazole LAI with symptom improvement. At a high dose of aripiprazole LAI (400 mg Q3wks), the patient experienced breakthrough symptoms approximately 3 days prior to his next injection. Various considerations were examined to explain his atypical dose requirements, including but not limited to pharmacogenetic influences. Pharmacogenetic testing ruled out genetic influences on drug metabolism but noted a -141C Del variant in the dopamine-D2 receptor (DRD2) gene associated in prior studies of poor-response to antipsychotics. At this time, a new formulation, aripiprazole lauroxil, was explored due to its availability in higher dose options. Transition to the new formulation (882 mg Q4wks) greatly improved and stabilized the patient's symptoms with no breakthrough psychosis. Comparable daily dose equivalents were achieved with two different formulations due to the Q3wks vs Q4wks dosing strategies, although the two agents have some differences in pharmacokinetic profiles.

CONCLUSIONS

We report a case of a patient experiencing wearing-off symptoms with aripiprazole LAI who benefited from switching to aripiprazole lauroxil. Pharmacogenetic testing revealed normal activity for relevant metabolism pathways but a DRD2 -141C variant that may influence brain D2 expression and antipsychotic responsiveness. The clinical utility of DRD2 information and what to do with genotyping results has not been previously addressed, despite availability on clinical test panels. Our case report suggests further investigations of altered dosing strategies and receptor genotype sensitivities to pharmacokinetic factors may be helpful in understanding symptom re-emergence observed in some patients taking LAI antipsychotics.

Pharmacogenomics and Efficacy of Risperidone Long-Term Treatment in Thai Autistic Children and Adolescents

The purpose of this study was to evaluate the association of pharmacogenomic factors and clinical outcome in autistic children and adolescents who were treated with risperidone for long periods. Eighty-two autistic subjects diagnosed with DSM-IV and who were treated with risperidone for more than 1 year were recruited. Pharmacogenomics and clinical outcome (CGI-I, aggressive, overactivity and repetitive score) were evaluated. Almost all patients showed stable symptoms on aggressive behaviour (89.02%), overactivity (71.95%), repetitive (70.89%) behaviour and all clinical symptoms (81.71%). Only 4.48% of patients showed minimally worse CGI-I score. Patients in the non-stable symptom group had DRD2 Taq1A non-wild-type (TT and CT) frequencies higher than the clinically stable group (p = 0.04), whereas other gene polymorphisms showed no significant association. Haplotype ACCTCAT (rs6311, rs1045642, rs1128503, rs1800497, rs4436578, rs1799978, rs6280) showed a significant association with non-stable clinical outcome (χ²  = 6.642, p = 0.010). Risperidone levels showed no association with any clinical outcome. On the other hand, risperidone dose, 9-OH risperidone levels and prolactin levels were significantly higher in the non-stable compared to the stable symptom group (p = 0.013, p = 0.044, p = 0.030). Increased appetite was the most common adverse drug reaction and associated with higher body-weight, whereas it was not significantly associated with genetic variations and non-genetic information. In conclusion, risperidone showed efficacy to control autism, especially aggressive symptoms in long-term treatment. However, Taq1A T - carrier of dopamine 2 receptor gene - is associated with non-stable response in risperidone-treated patients. This study supports pharmacogenomics testing for personalized therapy with risperidone in autistic children and adolescents.