A polymorphism in the norepinephrine transporter gene alters promoter activity and is associated with attention-deficit hyperactivity disorder

Evaluation of SLC6A2 and CYP2D6 polymorphisms' effects on atomoxetine treatment in attention deficit and hyperactivity disorder

BACKGROUND

There is insufficient replicated data to establish a relationship between the polymorphisms of SLC6A2 and CYP2D6 and the treatment responses of atomoxetine (ATX) in ADHD. We focused on evaluating the effect of top-line single nucleotide polymorphisms (SNPs) in SLC6A2 and CYP2D6 on the ATX treatment response in attention deficit and hyperactivity disorder (ADHD).

METHODS

Of 160 patient records, 34 patients who met the inclusion criteria were evaluated to determine the relationship between genotypes of ten SNPs (six of SLC6A2 and four of CYP2D6) and ATX treatment response. Additionally, the connection between SNPs of CYP2D6 and the severity of side effects associated with ATX was analyzed in 37 patients, including the 34 study patients, and three patients discontinued because of ATX-dependent side effects.

RESULTS

All six polymorphisms we studied in SLC6A2 were associated with the treatment response of ATX. Clinical improvement in oppositional defiant disorder symptoms of patients with ADHD was only observed in carriers of the homozygous "C" allele of rs3785143 (podd = 0.026). We detected an association between higher CGI-side-effect severity scores and the "TT" genotype of rs1065852 polymorphism in CYP2D6 (p = 0.043).

CONCLUSIONS

The findings of this study suggest that genotypes of polymorphisms within the SLC6A2 and CYP2D6 may play an influential role in treatment response or the severity of side effects associated with ATX in ADHD patients.

Adaptive expansion of ERVK solo-LTRs is associated with Passeriformes speciation events

Endogenous retroviruses (ERVs) are ancient retroviral remnants integrated in host genomes, and commonly deleted through unequal homologous recombination, leaving solitary long terminal repeats (solo-LTRs). This study, analysing the genomes of 362 bird species and their reptilian and mammalian outgroups, reveals an unusually higher level of solo-LTRs formation in birds, indicating evolutionary forces might have purged ERVs during evolution. Strikingly in the order Passeriformes, and especially the parvorder Passerida, endogenous retrovirus K (ERVK) solo-LTRs showed bursts of formation and recurrent accumulations coinciding with speciation events over past 22 million years. Moreover, our results indicate that the ongoing expansion of ERVK solo-LTRs in these bird species, marked by high transcriptional activity of ERVK retroviral genes in reproductive organs, caused variation of solo-LTRs between individual zebra finches. We experimentally demonstrated that cis-regulatory activity of recently evolved ERVK solo-LTRs may significantly increase the expression level of ITGA2 in the brain of zebra finches compared to chickens. These findings suggest that ERVK solo-LTRs expansion may introduce novel genomic sequences acting as cis-regulatory elements and contribute to adaptive evolution. Overall, our results underscore that the residual sequences of ancient retroviruses could influence the adaptive diversification of species by regulating host gene expression.

Noradrenaline tracks emotional modulation of attention in human amygdala

The noradrenaline (NA) system is one of the brain's major neuromodulatory systems; it originates in a small midbrain nucleus, the locus coeruleus (LC), and projects widely throughout the brain.1,2 The LC-NA system is believed to regulate arousal and attention3,4 and is a pharmacological target in multiple clinical conditions.5,6,7 Yet our understanding of its role in health and disease has been impeded by a lack of direct recordings in humans. Here, we address this problem by showing that electrochemical estimates of sub-second NA dynamics can be obtained using clinical depth electrodes implanted for epilepsy monitoring. We made these recordings in the amygdala, an evolutionarily ancient structure that supports emotional processing8,9 and receives dense LC-NA projections,10 while patients (n = 3) performed a visual affective oddball task. The task was designed to induce different cognitive states, with the oddball stimuli involving emotionally evocative images,11 which varied in terms of arousal (low versus high) and valence (negative versus positive). Consistent with theory, the NA estimates tracked the emotional modulation of attention, with a stronger oddball response in a high-arousal state. Parallel estimates of pupil dilation, a common behavioral proxy for LC-NA activity,12 supported a hypothesis that pupil-NA coupling changes with cognitive state,13,14 with the pupil and NA estimates being positively correlated for oddball stimuli in a high-arousal but not a low-arousal state. Our study provides proof of concept that neuromodulator monitoring is now possible using depth electrodes in standard clinical use.

Norepinephrine system at the interface of attention and reward

Reward learning is key to survival for individuals. Attention plays an important role in the rapid recognition of reward cues and establishment of reward memories. Reward history reciprocally guides attention to reward stimuli. However, the neurological processes of the interplay between reward and attention remain largely elusive, due to the diversity of the neural substrates that participate in these two processes. In this review, we delineate the complex and differentiated locus coeruleus norepinephrine (LC-NE) system in relation to different behavioral and cognitive substrates of reward and attention. The LC receives reward related sensory, perceptual, and visceral inputs, releases NE, glutamate, dopamine and various neuropeptides, forms reward memories, drives attentional bias and selects behavioral strategies for reward. Preclinical and clinical studies have found that abnormalities in the LC-NE system are involved in a variety of psychiatric conditions marked by disturbed functions in reward and attention. Therefore, we propose that the LC-NE system is an important hub in the interplay between reward and attention as well as a critical therapeutic target for psychiatric disorders characterized by compromised functions in reward and attention.

Neural Correlates of Impaired Cognitive Control in Individuals with Methamphetamine Dependence: An fMRI Study

Impaired cognitive and behavioral control has often been observed in people who use methamphetamine (MA). However, a comprehensive understanding of the neural substrates underlying these impairments is still lacking. The goal of the present study was to study the neural correlates of impaired cognitive control in individuals with MA dependence according to DSM-IV criteria. Eighteen individuals with MA dependence and 21 healthy controls were investigated using Stroop task, fMRI, and an impulsivity questionnaire. Overall, patients were found to have significantly poorer accuracy on the Stroop task and higher self-rated impulsivity. Comparing brain activations during the task, decreased activation in the dorsolateral prefrontal cortex (DLPFC), anterior midcingulate cortex (aMCC), and dorsal striatum was observed in individuals with MA dependence, compared to healthy controls. Altered fMRI signal in DLPFC and aMCC significantly correlated with impaired behavioral task performance in individuals with MA dependence. Furthermore, significantly lower and pronounced brain activations in the MA group were additionally detected in several sensory cortical regions, i.e., in the visual, auditory, and somatosensory cortices. The results of the current study provide evidence for the negative impact of chronic crystal meth consumption on the proper functioning of the fronto-cingulate and striatal brain regions, presumably underlying the often-observed deficits in executive functions in individuals with MA use disorder. As a new finding, we also revealed abnormal activation in several sensory brain regions, suggesting the negative effect of MA use on the proper neural activity of these regions. This blunted activation could be the cause of the observed deficits in executive functions and the associated altered brain activation in higher-level brain networks.

Noradrenergic genes polymorphisms and response to methylphenidate in children with ADHD: A systematic review and meta-analysis

BACKGROUND

Attention-deficit hyperactivity disorder (ADHD) is the most common childhood-onset neurodevelopmental disorder, and methylphenidate (MPH) is considered one of the first-line medicine for ADHD. Unfortunately, this medication is only effective for some children with ADHD. This meta-analysis was conducted to evaluate whether noradrenergic gene polymorphisms impact the efficacy of MPH in children with ADHD.

METHODS

Candidate gene studies published in English until March 1, 2020, were identified through literature searches on PubMed, Web of Science, and Embase. Data were pooled from individual clinical trials considering MPH pharmacogenomics. According to the heterogeneity, the odds ratio and mean differences were calculated by applying fixed-effects or random-effects models.

RESULTS

This meta-analysis includes 15 studies and 1382 patients. Four polymorphisms of the NET gene (rs5569, rs28386840, rs2242446, rs3785143) and 2 polymorphisms of the α2A-adrenergic receptor gene (ADRA2A) gene (MspI and DraI) were selected for the analysis. In the pooled data from all studies, T allele carriers of the rs28386840 polymorphism were significantly more likely to respond to MPH (P < .001, ORTcarriers = 2.051, 95% confidence interval [CI]:1.316, 3.197) and showed a relationship with significantly greater hyperactive-impulsive symptoms improvement (P < .001, mean difference:1.70, 95% CI:0.24, 3.16). None of the ADRA2A polymorphisms correlated significantly with MPH response as a whole. However, G allele carriers of the MspI polymorphism showed a relationship with significantly inattention symptoms improvement (P < .001, mean difference:0.31, 95% CI: 0.15, 0.47).

CONCLUSION

Our meta-analysis results indicate that the noradrenergic gene polymorphisms may impact MPH response. The NET rs28386840 is linked to improved MPH response in ADHD children. And the ADRA2A MspI is associated with inattention symptom improvements. Further investigations with larger samples will be needed to confirm these results.Registration: PROSPERO (no. CRD42021265830).

Atremorine in Parkinson's disease: From dopaminergic neuroprotection to pharmacogenomics

Atremorine is a novel bioproduct obtained by nondenaturing biotechnological processes from a genetic species of Vicia faba. Atremorine is a potent dopamine (DA) enhancer with powerful effects on the neuronal dopaminergic system, acting as a neuroprotective agent in Parkinson's disease (PD). Over 97% of PD patients respond to a single dose of Atremorine (5 g, p.o.) 1 h after administration. This response is gender-, time-, dose-, and genotype-dependent, with optimal doses ranging from 5 to 20 g/day, depending upon disease severity and concomitant medication. Drug-free patients show an increase in DA levels from 12.14 ± 0.34 pg/ml to 6463.21 ± 1306.90 pg/ml; and patients chronically treated with anti-PD drugs show an increase in DA levels from 1321.53 ± 389.94 pg/ml to 16,028.54 ± 4783.98 pg/ml, indicating that Atremorine potentiates the dopaminergic effects of conventional anti-PD drugs. Atremorine also influences the levels of other neurotransmitters (adrenaline, noradrenaline) and hormones which are regulated by DA (e.g., prolactin, PRL), with no effect on serotonin or histamine. The variability in Atremorine-induced DA response is highly attributable to pharmacogenetic factors. Polymorphic variants in pathogenic (SNCA, NUCKS1, ITGA8, GPNMB, GCH1, BCKDK, APOE, LRRK2, ACMSD), mechanistic (DRD2), metabolic (CYP2D6, CYP2C9, CYP2C19, CYP3A4/5, NAT2), transporter (ABCB1, SLC6A2, SLC6A3, SLC6A4) and pleiotropic genes (APOE) influence the DA response to Atremorine and its psychomotor and brain effects. Atremorine enhances DNA methylation and displays epigenetic activity via modulation of the pharmacoepigenetic network. Atremorine is a novel neuroprotective agent for dopaminergic neurons with potential prophylactic and therapeutic activity in PD.

Association between genetic variants of the norepinephrine transporter gene (SLC6A2) and bipolar I disorder

We aimed to investigate the associations between genetic variants of the norepinephrine transporter gene (NET, also known as SLC6A2) and diagnosis of bipolar I disorder. In addition, we examined the relationship between the genetic variants and manic and psychotic symptoms in patients with bipolar I disorder. The three SNPs rs28386840, rs2242446, and rs5569 were genotyped in 326 patients: patients with bipolar I disorder (n = 160) and a control group (n = 166). Subsequently, multivariate logistic regression analysis adjusting for age and sex was conducted to identify independent influences of the SNPs on diagnosis of bipolar I disorder. A possible association between manic and psychotic symptoms and variants of SLC6A2 was also investigated in patients with bipolar I disorder. The rs28836840 SNP in the 5'-UTR of SLC6A2 was significantly associated with bipolar I disorder and with severity of manic and psychotic symptoms in this disorder. Individuals carrying a T allele in the rs28836840 SNP were likely to have a lower risk of bipolar I disorder or lower severity of manic and psychotic symptoms in patients with bipolar I disorder (bipolar I disorder diagnosis: OR = 0.643, 95% Cl = 0.468-0.883, p = 0.006; manic symptoms: β = -2.457, 95% Cl = -4.674 ~ -0.239, p = 0.031; psychotic symptoms: β = -2.501, 95% Cl = -4.700 ~ -0.301, p = 0.027). For the rs2242446 and rs5569 SNPs, there were no significant differences between patients with bipolar I disorder and those without. Our results revealed associations of the rs28386840 SNP with bipolar I disorder diagnosis and with severity of manic and psychotic symptoms. However, the findings reported here require replication in larger samples and various ethnic groups.

Meta-Analysis: Hemodynamic Responses to Sub-anesthetic Doses of Ketamine in Patients With Psychiatric Disorders

Ketamine, a medication traditionally used as an anesthetic, has increasingly been recognized as an effective treatment for psychiatric disorders. At sub-anesthetic doses (defined here as ≤ 0.5 mg/kg), ketamine treatment has been studied in patients with treatment-resistant depression (TRD), obsessive-compulsive disorder (OCD), post-traumatic stress disorder (PTSD), and social anxiety disorder (SAD). Transient increases in hemodynamic activity have been reported during and after ketamine treatment, which may be desirable properties in some anesthesia settings, but are generally undesirable in psychiatric settings. While ketamine doses used in psychiatry are lower than those used in anesthesia, there are published instances of early termination of psychiatric ketamine infusions due to elevations in blood pressure and heart rate. No unifying study has been conducted to examine the impact of sub-anesthetic ketamine doses on hemodynamic parameters [systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR)] in psychiatric populations and to evaluate these changes across adult age groups. Here, data from 15 articles comprising a total N = 2,252 ketamine or esketamine treatments in adult participants were used to conduct a meta-analysis of treatment-induced hemodynamic changes. Ketamine/esketamine produced modest but significant increases in the variables of interest with an average SBP increase of 12.61 mm Hg (95% CI 10.40-14.82 mm Hg, z = 11.18, p < 0.0001), average DBP increase of 8.49 mm Hg (95% CI 6.89-10.09 mmHg, z = 10.41, p < 0.0001), and average heart rate increase of 4.09 beats per minute (95% CI 0.55-7.63 BPM), z = 2.27, p = 0.0235). Stratified subgroup analysis indicated no significant differences between ketamine and esketamine effects on blood pressure. Further analysis indicated that there was no significant effect of age on ketamine-induced changes in SBP, DBP, and HR. Taken together these data show that sub-anesthetic ketamine and esketamine induce small but significant increases in hemodynamic parameters that are transient in nature in adult psychiatric populations. While these data are reassuring, it is important for each treatment case to fully explore potential cardiovascular risks prior to initiating treatment.

The Association between Executive Functions and Body Weight/BMI in Children and Adolescents with ADHD

Despite the increasing body of research on Attention Deficit Hyperactivity Disorder (ADHD), the results of the studies assessing the relationship between executive function deficit and the risk of obesity in people with ADHD are incongruent. Our study aimed to assess the relationship between measures of executive functions and body weight and Body Mass Index (BMI) in children and adolescents with ADHD and control subjects. The study group consisted of 58 subjects aged from 8 to 17 years with ADHD. The Control group consisted of 62 healthy age and sex-matched participants from primary and secondary schools. Weight, height, and BMI measurements were standardized. The Sustained Attention to Response Test (SART) and the Attention Network Test (ANT) were used to assess executive functions. Based on the analysis of the correlation and analysis of moderation, we found that subjects with higher weight in the study group presented a lower efficiency of the inhibition processes and gave more impulsive and incorrect answers. The occurrence of impulsive reactions might contribute to the risk of excessive weight in children and adolescents with ADHD.

Influence of dopamine, noradrenaline, and serotonin transporters on the pharmacogenetics of Atremorine in Parkinson's disease

Atremorine is a potent dopamine (DA) enhancer obtained by nondenaturing biotechnological processes from a genetic species of Vicia faba. Atremorine affects the neuronal dopaminergic system by acting as a neuroprotective agent against Parkinson's disease (PD). PD patients (N = 127) responded to a single dose of Atremorine (5 g, p.o.) 1 h after administration in a sex-, time-, dose-, and genotype-dependent fashion. Drug-free patients (N = 81) showed an increase in DA levels from 12.14 ± 0.34 pg/ml to 6463.21 ± 1306.90 pg/ml; and patients chronically treated with anti-PD drugs (N = 46) showed an increase in DA levels from 1321.53 ± 389.94 pg/ml to 16,028.54 ± 4783.98 pg/ml, indicating that Atremorine potentiates the dopaminergic effect of conventional anti-PD drugs. The variability in Atremorine-induced DA response is strongly attributable to pharmacogenetic factors. Polymorphic variants in pathogenic, mechanistic, metabolic, transporter, and pleiotropic genes influence the DA response to Atremorine. Genetic variation in the DA (SLC6A3; rs460000), noradrenaline (NA) (SLC6A2; rs12708954, rs3785143, rs5569), and serotonin (5-HT) transporter (SLC6A4; rs2020934, rs2020936, rs4251417, rs6354) genes exert a genotype-dependent Atremorine-induced DA response in PD, with potential impact on the DA-related pharmacogenetic outcome and minimum effects on NA and 5-HT levels.

Atomoxetine modulates the contribution of low-level signals during free viewing of natural images in rhesus monkeys

Visuo-spatial attentional orienting is fundamental to selectively process behaviorally relevant information, depending on both low-level visual attributes of stimuli in the environment and higher-level factors, such as goals, expectations and prior knowledge. Growing evidence suggests an impact of the locus-cœruleus-norepinephrine (LC-NE) system in attentional orienting that depends on taskcontext. Nonetheless, most of previous studies used visual displays encompassing a target and various distractors, often preceded by cues to orient the attentional focus. This emphasizes the contribution of goal-driven processes, at the expense of other factors related to the stimulus content. Here, we aimed to determine the impact of NE on attentional orienting in more naturalistic conditions, using complex images and without any explicit task manipulation. We tested the effects of atomoxetine (ATX) injections, a NE reuptake inhibitor, on four monkeys during free viewing of images belonging to three categories: landscapes, monkey faces and scrambled images. Analyses of the gaze exploration patterns revealed, first, that the monkeys spent more time on each fixation under ATX compared to the control condition, regard less of the image content. Second, we found that, depending on the image content, ATX modulated the impact of low-level visual salience on attentional orienting. This effect correlated with the effect of ATX on the number and duration of fixations. Taken together, our results demonstrate that ATX adjusts the contribution of salience on attentional orienting depending on the image content, indicative of its role in balancing the role of stimulus-driven and top-down control during free viewing of complex stimuli.

Atomoxetine improves attentional orienting in a predictive context

The role of norepinephrine (NE) in visuo-spatial attention remains poorly understood. Our goal was to identify the attentional processes influenced by atomoxetine (ATX) injections, a NE-reuptake inhibitor that boosts the level of NE in the brain, and to characterize these influences. We tested the effects of ATX injections, on seven monkeys performing a saccadic cued task in which cues and distractors were used to manipulate spatial attention. We found that when the cue accurately predicted the location of the upcoming cue in 80% of the trials, ATX consistently improved attentional orienting, as measured from reaction times (RTs). These effects were best accounted for by a faster accumulation rate in the valid trials, rather than by a change in the decision threshold. By contrast, the effect of ATX on alerting and distractor interference was more inconsistent. Finally, we also found that, under ATX, RTs to non-cued targets were longer when these were presented separately from cued targets. This suggests that the impact of NE on visuo-spatial attention depends on the context, such that the adaptive changes elicited by the highly informative value of the cues in the most frequent trials were accompanied by a cost in the less frequent trials.

Differential Genetic Effect of the Norepinephrine Transporter Promoter Polymorphisms on Attention Problems in Clinical and Non-clinical Samples

Among the monoaminergic modulatory neurotransmitters, norepinephrine is involved in task orienting, hence noradrenergic genetic variants have been studied in connection to attentional processes. The role of this catecholamine system is also highlighted by the selective norepinephrine transporter blocking atomoxetine, which has proved to be effective in the pharmacological treatment of Attention Deficit Hyperactivity Disorder (ADHD). In the present genetic association study three single nucleotide polymorphisms (rs28386840, rs2242446, rs3785143 SNPs) were analyzed from the 5′ region of the norepinephrine transporter (NET, SLC6A2) gene, which have been linked to ADHD previously. Attention problems scores of the mother-rated Child Behavior Checklist (CBCL) were used in separate analyses of 88 preschoolers (59.1% male, 6 years of age) recruited from the general population and 120 child psychiatry patients with ADHD diagnosis (85.8% male, age: 9.8 ± 2.9). The NET SNPs showed associations with attention problems, but the direction was different in the two groups. Regarding the promoter variant rs28386840, which showed the most consistent association, the T-allele-carrier patients with ADHD had lower CBCL attention problems scores compared to patients with AA genotype (p = 0.023), whereas T-allele-carriers in the community sample had more attention problems (p = 0.042). Based on previous reports of lower NE levels in ADHD children and the inverted-U shape effect of NE on cognitive functions, we propose that rs28386840 (-3081) T-allele, which is associated with lower NET expression (and potentially higher synaptic NE level) would support attention processes among ADHD patients (similarly as atomoxetine increases NE levels), whereas it would hinder cortical functions in healthy children.

Ketamine influences the locus coeruleus norepinephrine network, with a dependency on norepinephrine transporter genotype - a placebo controlled fMRI study

Background

Ketamine is receiving increasing attention as a rapid-onset antidepressant in patients suffering from major depressive disorder (MDD) with treatment resistance or severe suicidal ideation. Ketamine modulates several neurotransmitter systems, including norepinephrine via the norepinephrine transporter (NET), both peripherally and centrally. The locus coeruleus (LC), which has high NET concentration, has been attributed to brain networks involved in depression. Thus we investigated the effects of single-dose of racemic ketamine on the LC using resting state functional MRI.

Methods

Fifty-nine healthy participants (mean age 25.57 ± 4.72) were examined in a double-blind, randomized, placebo-controlled study with 7 Tesla MRI. We investigated the resting state functional connectivity (rs-fc) of the LC before and one hour after subanesthetic ketamine injection (0.5 mg/kg), as well as associations between its rs-fc and a common polymorphism in the NET gene (rs28386840).

Results

A significant interaction of drug and time was revealed, and post hoc testing showed decreased rs-fc between LC and the thalamus after ketamine administration compared with baseline levels, including the mediodorsal, ventral anterior, ventral lateral, ventral posterolateral and centromedian nuclei. The rs-fc reduction was more pronounced in NET rs28386840 [AA] homozygous subjects than in [T] carriers.

Conclusions

We demonstrated acute rs-fc changes after ketamine administration in the central node of the norepinephrine pathway. These findings may contribute to understanding the antidepressant effect of ketamine at the system level, supporting modes of action on networks subserving aberrant arousal regulation in depression.

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Ketamine decreased connectivity between locus coeruleus and bilateral thalamus in resting state fMRI.

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This reduction of rs-fc between LC and thalamus was dependent on norepinephrine transporter genotype.

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The central effects of ketamine involve norepinephrine and attention networks.

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Antidepressive effects of ketamine may involve LC attention system.

Pharmacogenetics predictors of methylphenidate efficacy in childhood ADHD

Stimulant medication has long been effective in treating attention-deficit/hyperactivity disorder (ADHD) and is currently the first-line pharmacological treatment for children. Both methylphenidate and amphetamine modulate extracellular catecholamine levels through interaction with dopaminergic, adrenergic and serotonergic system components; it is therefore likely that catecholaminergic molecular components influence the effects of ADHD treatment. Using meta-analysis, we sought to identify predictors of pharmacotherapy to further the clinical implementation of personalized medicine. We identified 36 studies (3647 children) linking the effectiveness of methylphenidate treatment with DNA variants. Pooled-data revealed a statistically significant association between single nucleotide polymorphisms (SNPs) rs1800544 ADRA2A (odds ratio: 1.69; confidence interval: 1.12-2.55), rs4680 COMT (odds ratio (OR): 1.40; confidence interval: 1.04-1.87), rs5569 SLC6A2 (odds ratio: 1.73; confidence interval: 1.26-2.37) and rs28386840 SLC6A2 (odds ratio: 2.93; confidence interval: 1.76-4.90), and, repeat variants variable number tandem repeat (VNTR) 4 DRD4 (odds ratio: 1.66; confidence interval: 1.16-2.37) and VNTR 10 SLC6A3 (odds ratio: 0.74; confidence interval: 0.60-0.90), whereas the following variants were not statistically significant: rs1947274 LPHN3 (odds ratio: 0.95; confidence interval: 0.71-1.26), rs5661665 LPHN3 (odds ratio: 1.07; confidence interval: 0.84-1.37) and VNTR 7 DRD4 (odds ratio: 0.68; confidence interval: 0.47-1.00). Funnel plot asymmetry among SLC6A3 studies was identified and attributed largely to small study effects. Egger's regression test and Duval and Tweedie's 'trim and fill' were used to examine and correct for publication bias. These findings have major implications for advancing our therapeutic approach to childhood ADHD treatment.

Association analysis of norepinephrine transporter polymorphisms and methylphenidate response in ADHD patients

AIMS

Methylphenidate (MPH) is the most frequently prescribed drug in Attention Deficit Hyperactivity Disorder (ADHD). Hitherto mostly the dopamine transporter gene has been studied in MPH-response and only a few studies analyzed the norepinephrine transporter (NET, SLC6A2) gene, although MPH is a potent inhibitor of both dopamine and norepinephrine transporters. We aimed to analyze this monoamine transporter gene in relation to ADHD per se and MPH-response in particular to gain further knowledge in ADHD pharmacogenetics using a Caucasian sample.

METHODS

Six single nucleotide polymorphisms (rs28386840, rs2242446, rs3785143, rs3785157, rs5569, rs7194256 SNP) were studied across the NET gene in 163 ADHD children (age: 9.3±2.6; 86.5% male) using ADHD-RS hyperactivity-impulsivity and inattention scales. For case-control analysis 486 control subjects were also genotyped. At the MPH-response analysis responders had minimum 25% decrease of ADHD-RS total score after 2months of treatment, and chi-square test compared 90 responders and 32 non-responders, whereas ANOVA was used to assess symptom improvement after the first month among the 122 ADHD patients.

RESULTS

The classical case-control analysis did not yield any association with ADHD diagnosis, which was supported by meta-analysis conducted on the available genetic data (combining previously published and the present studies). On the other hand, the intronic rs3785143 showed nominal association with inattention symptoms (p=0.01). The haplotype analysis supported this association, and indicated the importance of the first haploblock encompassing the intronic and 2 promoter SNPs. With MPH-response only the promoter rs28386840 showed nominal association: Those with at least one T-allele were overrepresented in the responder group (42% vs 19%, p=0.08), and they had better improvement on the hyperactivity-impulsivity scale compared to the AA genotype (p=0.04).

CONCLUSION

Although none of our single SNP findings remained significant after correcting for multiple testing, our results from the MPH-response analysis indicate the potential importance of promoter variants in the NET gene.

Pharmacogenetics of methylphenidate in childhood attention-deficit/hyperactivity disorder: long-term effects

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder in which a significant proportion of patients do not respond to treatment. The objective of this study was to examine the role of genetic risk variants in the response to treatment with methylphenidate (MPH). The effectiveness of MPH was evaluated based on variations in the CGI-S and CGAS scales over a 12-month treatment period using linear mixed effects models. A total of 208 ADHD patients and 34 polymorphisms were included in the analysis. For both scales, the response was associated with time, extended-release MPH/both formulations, and previous MPH treatment. For the CGI-S scale, response was associated with SLC6A3 rs2550948, DRD4 promoter duplication, SNAP25 rs3746544, and ADGRL3 rs1868790. Interactions between the response over time and SLC6A3 and DRD2 were found in the CGI-S and CGAS scales, respectively. The proportion of the variance explained by the models was 18% for the CGI-S and 22% for the CGAS. In this long-term study, the effects of SLC6A3, DRD4, SNAP25, and ADGRL3 on response to treatment reflect those observed in previous studies. In addition, 2 previously unreported interactions with response to treatment over a 12-month period were found (SLC6A3 and DRD2).

Factors Influencing the Cardiovascular Response to Subanesthetic Ketamine: A Randomized, Placebo-Controlled Trial

BACKGROUND

The increasing use of ketamine as a potential rapid-onset antidepressant necessitates a better understanding of its effects on blood pressure and heart rate, well-known side effects at higher doses. For the subanesthetic dose used for depression, potential predictors of these cardiovascular effects are important factors influencing clinical decisions. Since ketamine influences the sympathetic nervous system, we investigated the impact of autonomic nervous system-related factors on the cardiovascular response: a genetic polymorphism in the norepinephrine transporter and gender effects.

METHODS

Blood pressure and heart rate were monitored during and following administration of a subanesthetic dose of ketamine or placebo in 68 healthy participants (mean age 26.04 ±5.562 years) in a double-blind, randomized, controlled, parallel-design trial. The influences of baseline blood pressure/heart rate, gender, and of a polymorphism in the norepinephrine transporter gene (NET SLC6A2, rs28386840 [A-3081T]) on blood pressure and heart rate changes were investigated. To quantify changes in blood pressure and heart rate, we calculated the maximum change from baseline (ΔMAX) and the time until maximum change (TΔMAX).

RESULTS

Systolic and diastolic blood pressure as well as heart rate increased significantly upon ketamine administration, but without reaching hypertensive levels. During administration, the systolic blood pressure at baseline (TP0Sys) correlated negatively with the time to achieve maximal systolic blood pressure (TΔMAXSys, P<.001). Furthermore, women showed higher maximal diastolic blood pressure change (ΔMAXDia, P<.001) and reached this peak earlier than men (TΔMAXDia, P=.017) at administration. NET rs28386840 [T] carriers reached their maximal systolic blood pressure during ketamine administration significantly earlier than [A] homozygous (TΔMAXSys, P=.030). In a combined regression model, both genetic polymorphism and TP0Sys were significant predictors of TΔMAXSys (P<.0005).

CONCLUSIONS

Subanesthetic ketamine increased both blood pressure and heart rate without causing hypertensive events. Furthermore, we identified gender and NET rs28386840 genotype as factors that predict increased cardiovascular sequelae of ketamine administration in our young, healthy study population providing a potential basis for establishing monitoring guidelines.

Mechanisms underlying alterations in norepinephrine levels in the locus coeruleus of ovariectomized rats: Modulation by estradiol valerate and black cohosh

Hot flushes are common in menopause. Norepinephrine (NE), primarily synthesized in the locus coeruleus (LC), plays a major role in central thermoregulation. Furthermore, we previously observed decreased dopamine beta hydroxylase (DβH), a key enzyme in NE synthesis, in LC neurons following ovariectomy. In this study, we explore the mechanisms underlying decreased NE levels in the LC (LC-NE) in ovariectomized (OVX) rats, and the modulating effects of estradiol valerate (E2) and black cohosh (ICR). We used high-performance liquid chromatography to detect LC-NE in SHAM, OVX, OVX-E2, and OVX-ICR groups. Western blotting and immunohistochemistry were performed to investigate the expression of NE metabolic enzymes, the NE reuptake transporter (NET), and estrogen receptors (ERs) in the LC. We observed significant LC-NE decreases in the OVX group. E2 and ICR enhanced LC-NE but did not restore them to SHAM levels. Ovariectomy affected NE synthesis, degradation, and reuptake. Levels of NE catabolic enzymes monoamine oxidase A (MAOA) and catechol-O-methyltransferase (COMT) decreased, while NET expression increased. E2 restored MAOA and COMT to SHAM levels but had no effect on NET. ICR restored COMT and NET to SHAM levels but had no effect on MAOA. Moreover, the OVX group also exhibited decreased expression of ERα and ERβ. E2 enhanced the expression of ERα and ERβ, while ICR only enhanced ERβexpression. Taken together, reduced NE in OVX rats resulted from reduced synthesis and increased degradation and reuptake. E2 and ICR may regulate these processes in different ways through various ERs.

Pharmacological treatments for methamphetamine addiction: current status and future directions

INTRODUCTION

Methamphetamine (MA) abuse remains a global health challenge despite intense research interest in the development of pharmacological treatments. This review provides a summary of clinical trials and human studies on the pharmacotherapy of methamphetamine use disorder (MUD). Areas covered: We summarize published clinical trials that tested candidate medications for MUD and also conducted PubMed and Google Scholar searches to identify recently completed clinical trials using the keywords 'methamphetamine' 'addiction' 'pharmacotherapy' and 'clinical trial.' To determine the status of ongoing clinical trials targeting MUD, we also searched the ClinicalTrials.gov online database. We conclude this review with a discussion of current research gaps and future directions. Expert commentary: Clinical trials examining the potential for pharmacotherapies of MUD have largely been negative. Future studies need to address several limitations to reduce the possibility of Type II errors: small sample sizes, high dropout rates or multiple comorbidities. Additionally, new treatment targets, such as MA-induced disruptions in cognition and in the neuroimmune system, merit trials with agents that selectively modulate these processes.

Role of GNB3, NET, KCNJ11, TCF7L2 and GRL genes single nucleotide polymorphism in the risk prediction of type 2 diabetes mellitus

Type 2 diabetes (T2DM) is a polygenic metabolic disorder characterized by hyperglycemia occurring as a result of impaired insulin secretion or insulin resistance. Various environmental and genetic factors interact and increase the risk of T2DM and its complications. Among the various genetic factors associated with T2DM, single nucleotide polymorphism in different candidate genes have been studied intensively and the resulting genetic variants have been found to have either positive or negative association with T2DM thereby increasing or decreasing the risk of T2DM, respectively. In this review, we will focus on Guanine nucleotide-binding protein subunit beta 3 (GNB3), Norepinephrine Transporter (NET), Potassium Channel gene (KCNJ11), Transcription Factor 7-Like 2 (TCF7L2) and Glucocorticoid receptor (GRL) genes and their association with T2DM studied in different ethnic groups. The products of these genes are involved in the biochemical pathway leading to T2DM. Polymorphisms in these genes have been intensively studied in individuals of different ethnic origins. Results show that genetic variants of TCF7L2 and KCNJ11 genes have potential to emerge as a risk biomarker for T2DM whereas results of GNB3, GRL and NET genes have been controversial when studied in individuals of different ethnicities. We have tried to summarize the results generated globally in context to the selected genes which could possibly help researchers working in this field and would eventually help in understanding the mechanistic pathways of T2DM leading early diagnosis and prevention.

Association of norepinephrine transporter gene polymorphisms in attention-deficit/hyperactivity disorder in Korean population

We investigated the association of three single nucleotide polymorphisms(SNP) of the norepinephrine transporter (NET) gene SLC6A2, T-182C (rs2242446), A-3081T (rs28386840), and G-1287A (rs5569) with the prevalence of attention-deficit/hyperactivity disorder (ADHD), its clinical severity, and other disease-related characteristics in a Korean population. The genotype, allele frequency and haplotype of 103 ADHD patients and 173 controls were analyzed for these three SNPs. All participants completed the Korean version of the ADHD Rating Scale (K-ARS). The ADHD group also completed the Korean Educational Development Institute-Wechsler Intelligence Scale for Children (KEDI-WISC) and the Continuous Performance Test (CPT) in a drug-naive state. The χ2 test and logistic regression analysis revealed no significant differences in the genotype distribution or allele frequencies of each SNP between the ADHD group and the control. In the haplotype analysis, the most common T-A-G haplotype was related to an increased risk of ADHD in females (P=0.002). There was no statistical significance between clinical features of ADHD and any specific allele of each SNP after multiple test correction except lower omission error in non-A girl carriers (GG type) of G-1287A (carrier 76.75±18.74, non-carrier 55.00±9.26, t=3.026, P=0.007, Bonferroni-corrected P=0.042). Some values related A-3081 and G-1287A showed a trend approaching the significance level when analyzed separately by gender. Even though it was not statistically meaningful after multiple test correction, G allele might have some protective effect against development of ADHD symptoms and this finding was consistent with previous studies.

Investigating the genetic basis of attention to facial expressions: the role of the norepinephrine transporter gene

OBJECTIVE

Levels of norepinephrine (NE) in the brain are related to attention ability in animals and risk of attention-deficit hyperactivity disorder in humans. Given the modulation of the norepinephrine transporter (NET) on NE levels in the brain and the link between NE and attention impairment of attention-deficit hyperactivity disorder, it was possible that the NET gene underpinned individual differences in attention processes in healthy populations.

METHODS

To investigate to what extent NET could modulate one's attention orientation to facial expressions, we categorized individuals according to the genotypes of the -182 T/C (rs2242446) polymorphism and measured individuals' attention orientation with the spatial cueing task.

RESULTS

Our results indicated that the -182 T/C polymorphism significantly modulated attention orientation to facial expressions, of which the CC genotype facilitated attention reorientation to the locations where cued faces were previously presented. However, this polymorphism showed no significant effects on the regulations of emotional cues on attention orientation.

CONCLUSION

Our findings suggest that the NET gene modulates the individual difference in attention to facial expressions, which provides new insights into the roles of NE in social interactions.

Kinase-dependent Regulation of Monoamine Neurotransmitter Transporters

Modulation of neurotransmission by the monoamines dopamine (DA), norepinephrine (NE), and serotonin (5-HT) is critical for normal nervous system function. Precise temporal and spatial control of this signaling in mediated in large part by the actions of monoamine transporters (DAT, NET, and SERT, respectively). These transporters act to recapture their respective neurotransmitters after release, and disruption of clearance and reuptake has significant effects on physiology and behavior and has been linked to a number of neuropsychiatric disorders. To ensure adequate and dynamic control of these transporters, multiple modes of control have evolved to regulate their activity and trafficking. Central to many of these modes of control are the actions of protein kinases, whose actions can be direct or indirectly mediated by kinase-modulated protein interactions. Here, we summarize the current state of our understanding of how protein kinases regulate monoamine transporters through changes in activity, trafficking, phosphorylation state, and interacting partners. We highlight genetic, biochemical, and pharmacological evidence for kinase-linked control of DAT, NET, and SERT and, where applicable, provide evidence for endogenous activators of these pathways. We hope our discussion can lead to a more nuanced and integrated understanding of how neurotransmitter transporters are controlled and may contribute to disorders that feature perturbed monoamine signaling, with an ultimate goal of developing better therapeutic strategies.

Differential Internalization Rates and Postendocytic Sorting of the Norepinephrine and Dopamine Transporters Are Controlled by Structural Elements in the N Termini

The norepinephrine transporter (NET) mediates reuptake of synaptically released norepinephrine in central and peripheral noradrenergic neurons. The molecular processes governing availability of NET in the plasma membrane are poorly understood. Here we use the fluorescent cocaine analogue JHC 1-64, as well as several other approaches, to investigate the trafficking itinerary of NET in live noradrenergic neurons. Confocal imaging revealed extensive constitutive internalization of JHC 1-64-labeled NET in the neuronal somata, proximal extensions and presynaptic boutons. Phorbol 12-myristate 13-acetate increased intracellular accumulation of JHC 1-64-labeled NET and caused a parallel reduction in uptake capacity. Internalized NET strongly colocalized with the "long loop" recycling marker Rab11, whereas less overlap was seen with the "short loop" recycling marker Rab4 and the late endosomal marker Rab7. Moreover, mitigating Rab11 function by overexpression of dominant negative Rab11 impaired NET function. Sorting of NET to the Rab11 recycling compartment was further supported by confocal imaging and reversible biotinylation experiments in transfected differentiated CATH.a cells. In contrast to NET, the dopamine transporter displayed markedly less constitutive internalization and limited sorting to the Rab11 recycling compartment in the differentiated CATH.a cells. Exchange of domains between the two homologous transporters revealed that this difference was determined by non-conserved structural elements in the intracellular N terminus. We conclude that NET displays a distinct trafficking itinerary characterized by continuous shuffling between the plasma membrane and the Rab11 recycling compartment and that the functional integrity of the Rab11 compartment is critical for maintaining proper presynaptic NET function.

Attention deficit hyperactivity disorder: genetic association study in a cohort of Spanish children

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) has a strong genetic component. The study is aimed to test the association of 34 polymorphisms with ADHD symptomatology considering the role of clinical subtypes and sex in a Spanish population.

METHODS

A cohort of ADHD 290 patients and 340 controls aged 6-18 years were included in a case-control study, stratified by sex and ADHD subtype. Multivariate logistic regression was used to detect the combined effects of multiple variants.

RESULTS

After correcting for multiple testing, we found several significant associations between the polymorphisms and ADHD (p value corrected ≤0.05): (1) SLC6A4 and LPHN3 were associated in the total population; (2) SLC6A2, SLC6A3, SLC6A4 and LPHN3 were associated in the combined subtype; and (3) LPHN3 was associated in the male sample. Multivariable logistic regression was used to estimate the influence of these variables for the total sample, combined and inattentive subtype, female and male sample, revealing that these factors contributed to 8.5, 14.6, 2.6, 16.5 and 8.5 % of the variance respectively.

CONCLUSIONS

We report evidence of the genetic contribution of common variants to the ADHD phenotype in four genes, with the LPHN3 gene playing a particularly important role. Future studies should investigate the contribution of genetic variants to the risk of ADHD considering their role in specific sex or subtype, as doing so may produce more predictable and robust models.

Effects of norepinephrine transporter gene variants on NET binding in ADHD and healthy controls investigated by PET

Attention deficit hyperactivity disorder (ADHD) is a heterogeneous disorder with a strong genetic component. The norepinephrine transporter (NET) is a key target for ADHD treatment and the NET gene has been of high interest as a possible modulator of ADHD pathophysiology. Therefore, we conducted an imaging genetics study to examine possible effects of single nucleotide polymorphisms (SNPs) within the NET gene on NET nondisplaceable binding potential (BPND ) in patients with ADHD and healthy controls (HCs). Twenty adult patients with ADHD and 20 HCs underwent (S,S)-[18F]FMeNER-D2 positron emission tomography (PET) and were genotyped on a MassARRAY MALDI-TOF platform using the Sequenom iPLEX assay. Linear mixed models analyses revealed a genotype-dependent difference in NET BPND between groups in the thalamus and cerebellum. In the thalamus, a functional promoter SNP (-3081 A/T) and a 5'-untranslated region (5'UTR) SNP (-182 T/C), showed higher binding in ADHD patients compared to HCs depending on the major allele. Furthermore, we detected an effect of genotype in HCs, with major allele carriers having lower binding. In contrast, for two 3'UTR SNPs (*269 T/C, *417 A/T), ADHD subjects had lower binding in the cerebellum compared to HCs depending on the major allele. Additionally, symptoms of hyperactivity and impulsivity correlated with NET BPND in the cerebellum depending on genotype. Symptoms correlated positively with cerebellar NET BPND for the major allele, while symptoms correlated negatively to NET BPND in minor allele carriers. Our findings support the role of genetic influence of the NE system on NET binding to be pertubated in ADHD.

No Evidence for Association Between Norepinephrine Transporter-3081 (A/T) Polymorphism and Attention Deficit Hyperactivity Disorder in Iranian Population

Background:

Attention Deficit Hyperactivity Disorder (ADHD) can lead to drastic problems for the patient and its worldwide prevalence is 5%-12%. It also has many comorbidities with other disorders, and the genetic contribution seems the most significant cause.

Objectives:

The current study was conducted to investigate the association between norepinephrine transporter-3081 (A/T) polymorphisms and ADHD in Iranian population.

Patients and Methods:

Participants were chosen from children and adolescents diagnosed with ADHD referred to Imam Hoseyn Hospital. A child and adolescent psychiatrist confirmed the diagnosis using the Kiddie-Sads-Present and Lifetime Version (K-SADS-PL) semi-structural interview. The control group was from pupils of schools in Tehran (capital city of Iran) who had no history or presence of psychiatric and medical complications. Also, a child and adolescent psychiatrist confirmed their health using the K-SADS-PL semi-structural interview. Genetic examinations were DNA distraction, Polymerase Chain Reaction (PCR), and Restricted Fragment Length Polymorphism (RFLP), which were conducted according to standard protocols. The statistical analysis was performed using chi-square and Fisher's exact test in SPSS version 21.

Results:

The percentages of ADHD subtypes for combined, inattentive, and hyperactive/impulsive were 72.2%, 17.2%, and 11.9%, respectively. There was no significant association between norepinephrine transporter polymorphism and ADHD (P = 0.81). Moreover, no significant relationship was found between gender [male (P = 0.92) and female (P = 0.63)] and polymorphism. No significant association was found between subtypes of ADHD [combined (P = 0.46), inattentive (P = 0.41), hyperactive/impulsive (P = 0.32)] and polymorphism SCL6A2. This lack of association can also be seen in gender in every subtype.

Conclusions:

The results of the study show no significant association between norepinephrine transporter polymorphism SCL6A2 and ADHD.

Analysis of Association between Norepinephrine Transporter Gene Polymorphisms and Personality Traits of NEO-FFI in a Japanese Population

OBJECTIVE

Norepinephrine is an important chemical messenger that is involved in mood and stress in humans, and is reabsorbed by the norepinephrine transporter (NET). According to Cloninger's theory, the noradrenergic system mediates the personality trait of reward dependence. Thus far, although association studies on NET gene polymorphisms and Cloninger's personality traits have been reported, they yielded inconsistent results. Therefore, in the present study we investigated whether or not the 1287G/A, -182T/C and -3081A/T polymorphisms of the NET gene (SLC6A2) are associated with reward dependence-related traits, as assessed by the five-factor model.

METHODS

After written informed consent was obtained from participants, the three NET gene polymorphisms were analyzed by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP), and personality was assessed by the Neuroticism Extraversion Openness-Five Factor Inventory (NEO-FFI) in 270 Japanese university students.

RESULTS

A significant relation was found between the -3081A/T functional promoter polymorphism and NEO-FFI scores: those with the T allele exhibited a lower extraversion (E) score than those without the T allele (Mann-Whitney U-test: z=-3.861, p<0.001). However, there was no correlation between the other NET gene polymorphisms and E score, and no association with other dimensions and these three polymorphisms.

CONCLUSION

We conclude that the -3081A/T functional polymorphism in the NET gene may affect the extraversion of reward dependence-related traits, as measured by NEO-FFI. However, we used only the shortened version of NEO-PI-R in this study. Further investigations are necessary using the full version of self-rating personality questionnaires.

Genetic variation in alpha2-adrenoreceptors and heart rate recovery after exercise

Heart rate recovery (HRR) after exercise is an independent predictor of adverse cardiovascular outcomes. HRR is mediated by both parasympathetic reactivation and sympathetic withdrawal and is highly heritable. We examined whether common genetic variants in adrenergic and cholinergic receptors and transporters affect HRR. In our study 126 healthy subjects (66 Caucasians, 56 African Americans) performed an 8 min step-wise bicycle exercise test with continuous computerized ECG recordings. We fitted an exponential curve to the postexercise R-R intervals for each subject to calculate the recovery constant (kr) as primary outcome. Secondary outcome was the root mean square residuals averaged over 1 min (RMS1min), a marker of parasympathetic tone. We used multiple linear regressions to determine the effect of functional candidate genetic variants in autonomic pathways (6 ADRA2A, 1 ADRA2B, 4 ADRA2C, 2 ADRB1, 3 ADRB2, 2 NET, 2 CHT, and 1 GRK5) on the outcomes before and after adjustment for potential confounders. Recovery constant was lower (indicating slower HRR) in ADRA2B 301-303 deletion carriers (n = 54, P = 0.01), explaining 3.6% of the interindividual variability in HRR. ADRA2A Asn251Lys, ADRA2C rs13118771, and ADRB1 Ser49Gly genotypes were associated with RMS1min. Genetic variability in adrenergic receptors may be associated with HRR after exercise. However, most of the interindividual variability in HRR remained unexplained by the variants examined. Noncandidate gene-driven approaches to study genetic contributions to HRR in larger cohorts will be of interest.

Association of norepinephrine transporter (NET, SLC6A2) genotype with ADHD-related phenotypes: findings of a longitudinal study from birth to adolescence

Variation in the gene encoding for the norepinephrine transporter (NET, SLC6A2) has repeatedly been linked with ADHD, although there is some inconsistency regarding the association with specific genes. The variants for which most consistent association has been found are the NET variants rs3785157 and rs28386840. Here, we tested for their association with ADHD diagnosis and ADHD-related phenotypes during development in a longitudinal German community sample. Children were followed from age 4 to age 15, using diagnostic interviews to assess ADHD. Between the ages of 8 and 15 years, the Child Behavior Checklist (CBCL) was administered to the primary caregivers. The continuous performance task (CPT) was performed at age 15. Controlling for possible confounders, we found that homozygous carriers of the major A allele of the functional promoter variant rs28386840 displayed a higher rate of ADHD lifetime diagnosis. Moreover, homozygous carriers of the minor T allele of rs3785157 were more likely to develop ADHD and showed higher scores on the CBCL externalizing behavior scales. Additionally, we found that individuals heterozygous for rs3785157 made fewer omission errors in the CPT than homozygotes. This is the first longitudinal study to report associations between specific NET variants and ADHD-related phenotypes during the course of development.

The co-occurrence of zinc deficiency and social isolation has the opposite effects on mood compared with either condition alone due to changes in the central norepinephrine system

Nutritional and social environmental problems during the early stages of life are closely associated with the pathophysiology of mood disorders such as depression. Disruption or dysfunction of the central norepinephrine (NE) system is also considered to play a role in mood disorders. Therefore, we evaluated the effects of zinc deficiency and/or social isolation on mood and changes in the central NE system using rats. Compared with the controls, the rats subjected to zinc deficiency or social isolation alone exhibited increased anxiety-related behavior in the elevated plus maze and greater depression-like behavior in the forced swim test. However, the co-occurrence of zinc deficiency and social isolation resulted in decreased anxiety-related behavior and control levels of depression-like behavior. Social isolation alone decreased the rats' cerebral NE concentrations. The expression of the NE transporter was not affected by social isolation alone, but its expression in the locus coeruleus was markedly decreased by the co-occurrence of social isolation and zinc deficiency, and this change was accompanied by an increase in the blood concentration of 3-methoxy-4-hydroxyphenylglycol, which is a marker of central NE system activity. These findings suggest that zinc deficiency or social isolation alone induce anxious or depressive symptoms, but the presence of both conditions has anxiolytic or antidepressive effects. Furthermore, these opposing effects of mood-related behaviors were found to be associated with changes in the central NE system.

SLC6A2 variants may predict remission from major depression after venlafaxine treatment in Han Chinese population

OBJECTIVE

Venlafaxine, an antidepressant of the serotonin-norepinephrine reuptake inhibitor (SNRI) type, is used to treat patients with major depressive disorder (MDD). Much evidence suggests that genetic polymorphisms may modulate serotonergic and noradrenergic function, thereby affecting the treatment efficacy of venlafaxine. The aim of this study was to examine whether polymorphisms in the norepinephrine transporter gene (SLC6A2) associate with remission after venlafaxine treatment for MDD.

METHOD

An 8-week naturalistic treatment study with venlafaxine was carried out in 243 Han Chinese patients with MDD. The patients were screened for seven single-nucleotide polymorphisms of the SLC6A2 gene. Of the enrolled patients, 161 completed the 8-week treatment. The 21-item Hamilton Depression Rating Scale (HDRS) was used to assess the improvement of depressive symptoms in each subject from baseline to the endpoint. For better presentation of time-course change of remission status, a Cox regression analysis for remission incidence during the 8-week treatment was conducted.

RESULTS

Between remitters and non-remitters, significant differences in genotype frequencies were observed in five of the investigated SLC6A2 variants (rs28386840, rs1532701, rs40434, rs13333066, rs187714). GCG haplotype (rs40434 - rs13333066 - rs187714) in the SLC6A2 gene showed a association with non-remission. A Cox regression analysis for remission incidence during the 8-week treatment course significantly depends on SLC6A2 variants (rs28386840, rs40434, and rs187714).

CONCLUSION

Our results suggest that the variation of the SLC6A2 gene is associated with treatment remission after venlafaxine in patients with MDD.

Synthesis and in silico evaluation of novel compounds for PET-based investigations of the norepinephrine transporter

Since the norepinephrine transporter (NET) is involved in a variety of diseases, the investigation of underlying dysregulation-mechanisms of the norepinephrine (NE) system is of major interest. Based on the previously described highly potent and selective NET ligand 1-(3-(methylamino)-1-phenylpropyl)-3-phenyl-1,3-dihydro-2H-benzimidaz- ol-2-one (Me@APPI), this paper aims at the development of several fluorinated methylamine-based analogs of this compound. The newly synthesized compounds were computationally evaluated for their interactions with the monoamine transporters and represent reference compounds for PET-based investigation of the NET.

The possible involvement of genetic variants of NET1 in the etiology of attention-deficit/hyperactivity disorder comorbid with oppositional defiant disorder

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD) often coexist and shared some genetic influences. Evidence from the existing literature indicated that comorbid with ODD may increase the heterogeneity of ADHD genetics. Our present study sought to investigate the role of norepinephrine transporter gene (NET1) for ADHD comorbid with ODD.

METHODS

Six single nucleotide polymorphisms (SNPs) of NET1 were genotyped for a total of 1,815 ADHD cases, including 587 subjects (32.3%) with ODD. Chi-square tests were conducted for pseudo case-control study comparing allelic and genotypic distributions between ADHD with and without ODD. Among them, there were 1,249 probands together with their parents composing trios for family-based association studies using transmission disequilibrium tests (TDTs). In addition, 1,337 ADHD probands have detailed information of ODD symptoms and were included for quantitative analyses with genotypes using analyses of covariance (ANCOVA). To consider the overlap and correlation of other comorbidities with ODD and eliminate their potential confounding effect, we further repeated above analyses for 'pure ADHD+ODD' versus 'ADHD-only' after excluding other comorbidities except for ODD.

RESULTS

The pseudo case-control study showed different allelic and genotypic distributions of SNP rs3785143 between ADHD with ODD and those without ODD. Family-based association tests indicated overtransmission of the T allele of rs3785143 in ADHD with ODD trios, but no biased transmission in those without ODD. ANCOVA showed association between genotypes of rs3785143 with ODD symptoms in ADHD probands, especially with 'Argumentative/Defiant Behavior (ADB)' dimension after controlling gender, age, clinical subtypes and intelligence. Above association still existed after removing the samples with other comorbidities.

CONCLUSION

NET1 was associated with comorbidity of ODD and ODD symptoms in ADHD probands. Our findings emphasize the importance of considering the comorbidity of ODD in ADHD genetic studies, especially ADHD with ADB. However, further replication in independent sample or different populations is still needed.

Attention Deficit/Hyperactivity Disorder (ADHD) Is Associated With Altered Heart Rate Asymmetry

Attention deficit/hyperactivity disorder (ADHD) is associated with complex neurocardiac integrity. We aimed to study heart rate time asymmetry as a nonlinear qualitative feature of heart rate variability indicating complexity of cardiac autonomic control at rest and in response to physiological stress (orthostasis) in children suffering from ADHD. Twenty boys with ADHD and 20 healthy age-matched boys at the age of 8 to 12 years were examined. The continuous ECG was recorded in a supine position and during postural change from lying to standing (orthostasis). Time irreversibility indices – Porta’s (P%), Guzik’s (G%) and Ehlers’ (E) – were evaluated. Our analysis showed significantly reduced heart rate asymmetry indices at rest (P%: 49.8 % vs. 52.2 %; G%: 50.2 % vs. 53.2 %; p<0.02), and in response to orthostatic load (P%: 52.4 % vs. 54.5 %, G%: 52.3 % vs. 54.5 %; p<0.05) associated with tachycardia in ADHD children compared to controls. Concluding, our study firstly revealed the altered heart rate asymmetry pattern in children suffering from ADHD at rest as well as in response to posture change from lying to standing (orthostasis). These findings might reflect an abnormal complex cardiac regulatory system as a potential mechanism leading to later cardiac adverse outcomes in ADHD.

Future pharmacological treatments for substance use disorders

Substance use disorders represent a serious public health and social issue worldwide. Recent advances in our understanding of the neurobiological basis of the addictive processes have led to the development of a growing number of pharmacological agents to treat addictions. Despite this progress, there are no approved pharmacological treatments for cocaine, methamphetamine and cannabis addiction. Moving treatment development to the next stage will require novel ways of approaching substance use disorders. One such novel approach is to target individual vulnerabilities, such as cognitive function, sex differences and psychiatric comorbidities. This review provides a summary of promising pharmacotherapies for alcohol, opiate, stimulant and nicotine addictions. Many medications that target positive and negative reinforcement of drugs, as well as individual vulnerabilities to addiction, are in different phases of development. Clinical trials testing the efficacy of these medications for substance use disorder are warranted.

ADHD pharmacogenetics across the life cycle: New findings and perspectives

Attention-deficit/hyperactivity disorder (ADHD) is a complex and heterogeneous disorder, affecting individuals across the life cycle. Although its etiology is not yet completely understood, genetics plays a substantial role. Pharmacological treatment is considered effective and safe for children and adults, but there is considerable inter-individual variability among patients regarding response to medication, required doses, and adverse events. We present here a systematic review of the literature on ADHD pharmacogenetics to provide a critical discussion of the existent findings, new approaches, limitations, and recommendations for future research. Our main findings are: first, the number of studies continues to grow, making ADHD one of the mental health areas with more pharmacogenetic studies. Second, there has been a focus shift on ADHD pharmacogenetic studies in the last years. There is an increasing number of studies assessing gene-gene and gene-environment interactions, using genome-wide association approaches, neuroimaging, and assessing pharmacokinetic properties. Third and most importantly, the heterogeneity in methodological strategies employed by different studies remains impressive. The question whether pharmacogenetics studies of ADHD will improve clinical management by shifting from trial-and-error approach to a pharmacological regimen that takes into account the individual variability remains unanswered. © 2014 Wiley Periodicals, Inc.

An evaluation of the pharmacokinetics of methylphenidate for the treatment of attention-deficit/ hyperactivity disorder

INTRODUCTION

Methylphenidate (MPH) plays a principal role in the multimodal treatment of attention-deficit/hyperactivity disorder (ADHD). Controlled studies have demonstrated an effective reduction in the core symptoms of the disorder following MPH therapy, although long-term studies also demonstrate that the therapeutic benefits dissipate in the absence of combined psychosocial interventions.

AREAS COVERED

This review article focuses on the pharmacological characteristics of MPH, examining its effects on brain metabolism and the neurotransmitter system. Neuropsychological and clinical effects of different immediate and extended release MPH formulations are discussed to aid clinicians in choosing the appropriate formulation. The drug's addictive potency and abuse potential is also discussed. Data came from a literature search of relevant studies performed using the PubMed database up to June 2013.

EXPERT OPINION

MPH is effective in the treatment of the core symptoms of ADHD. Considerable clinical expertise is required to identify an individually well-adapted dosage which will produce the optimal clinical effects with potential side effects minimized. Due to low adherence to medication, especially in adolescents, motivation to treatment and attentive clinical monitoring is mandatory, as is the consideration of risks of abuse or the presence of a comorbid addictive disorder.

Association between norepinephrine transporter gene (SLC6A2) polymorphisms and suicide in patients with major depressive disorder

BACKGROUND

Although several studies have investigated possible associations between norepinephrine neurotransmitter transporter gene (SLC6A2) polymorphisms and depression, few studies have examined associations between SLC6A2 polymorphisms and suicide.

METHODS

Three single-nucleotide polymorphisms (rs2242446, rs28386840, and rs5569) were measured in 550 patients: 201 with major depressive disorder (MDD) and suicide attempt/s, 160 with MDD without suicide attempts, and 189 healthy controls. Analysis of single-nucleotide polymorphisms (SNPs) and haplotype was conducted for the three groups. Subsequently, multivariate logistic regression analysis adjusting for age and gender was conducted to identify independent influences of each SNP. A possible association between suicide lethality and SLC6A2 polymorphisms was also investigated.

RESULTS

In the genotype and allele frequency analysis, there were significant differences in rs28386840 between suicidal MDD patients and healthy controls. In the haplotype analysis, TAA (rs2242446-rs28386840-rs5569, from left to right) was associated with suicide attempts in MDD, although the significance (p=0.043) disappeared after Bonferroni correction. There were no relationships between lethality scores and SLC6A2 polymorphisms in suicidal MDD.

LIMITATIONS

Modest sample size and a single type of neurotransmitter analyzed (norepinephrine) are the primary limitations.

CONCLUSION

Our results suggest that SLC6A2 polymorphisms were associated with suicide risk in patients with MDD. Future studies are warranted to elucidate possible mechanisms by which SLC6A2 polymorphisms influence suicide risk.

Norepinephrine transporter heterozygous knockout mice exhibit altered transport and behavior

The norepinephrine (NE) transporter (NET) regulates synaptic NE availability for noradrenergic signaling in the brain and sympathetic nervous system. Although genetic variation leading to a loss of NET expression has been implicated in psychiatric and cardiovascular disorders, complete NET deficiency has not been found in people, limiting the utility of NET knockout mice as a model for genetically driven NET dysfunction. Here, we investigate NET expression in NET heterozygous knockout male mice (NET(+/-) ), demonstrating that they display an approximately 50% reduction in NET protein levels. Surprisingly, these mice display no significant deficit in NET activity assessed in hippocampal and cortical synaptosomes. We found that this compensation in NET activity was due to enhanced activity of surface-resident transporters, as opposed to surface recruitment of NET protein or compensation through other transport mechanisms, including serotonin, dopamine or organic cation transporters. We hypothesize that loss of NET protein in the NET(+/-) mouse establishes an activated state of existing surface NET proteins. The NET(+/-) mice exhibit increased anxiety in the open field and light-dark box and display deficits in reversal learning in the Morris water maze. These data suggest that recovery of near basal activity in NET(+/-) mice appears to be insufficient to limit anxiety responses or support cognitive performance that might involve noradrenergic neurotransmission. The NET(+/-) mice represent a unique model to study the loss and resultant compensatory changes in NET that may be relevant to behavior and physiology in human NET deficiency disorders.