Neural Responses to a Working Memory Task in Acute Depressed and Remitted Phases in Bipolar Patients.

(1) Cognitive impairments such as working memory (WM) deficits are amongst the most common dysfunctions characterizing bipolar disorder (BD) patients, severely contributing to functional impairment. We aimed to investigate WM performance and associated brain activation during the acute phase of BD and to observe changes in the same patients during remission. (2) Frontal brain activation was recorded using functional near-infrared spectroscopy (fNIRS) during n-back task conditions (one-back, two-back and three-back) in BD patients in their acute depressive (n = 32) and remitted (n = 15) phases as well as in healthy controls (n = 30). (3) Comparison of BD patients during their acute phase with controls showed a trend (p = 0.08) towards lower dorsolateral prefrontal cortex (dlPFC) activation. In the remitted phase, BD patients showed lower dlPFC and ventrolateral prefrontal cortex (vlPFC) activation (p = 0.02) compared to controls. No difference in dlPFC and vlPFC activation between BD patients' phases was found. (4) Our results showed decreased working memory performance in BD patients during the working memory task in the acute phase of disease. Working memory performance improved in the remitted phase of the disease but was still particularly attenuated for the more demanding conditions.

Influence of NOS1AP Risk Variants on the Corrected QT (QTc) Interval in the Pharmacotherapy of Schizophrenia.

INTRODUCTION: The variants of the gene for nitric oxide synthase 1 adaptor protein (NOS1AP) are associated with schizophrenia and cardiovascular deficits involving corrected QT (QTc) interval prolongation. Here, we investigated a possible pharmacogenetic effect of antipsychotic treatment on QTc length in interaction with two NOS1AP variants (rs12143842 and rs10494366) whose minor alleles are associated with increased QTc interval length. METHODS: We conducted a retrospective analysis of electrocardiographic (ECG) and genotype data of 239 patients diagnosed with schizophrenia. We converted antipsychotics dosage to chlorpromazine equivalents and defined daily doses. We analysed the effects of the minor (i. e. rs12143842-CT/TT and rs10494366-GT/GG) and major (i. e. rs12143842-CC and rs10494366-TT) allele genotypes to QTc interval for female and male participants separately. RESULTS: As expected, rs12143842 and rs10494366 exhibit strong linkage disequilibrium. Both polymorphisms had no direct effect on antipsychotic use or QTc interval. However, there was a continuous increase in QTc interval with increasing antipsychotic dosage in males. For both variants, positive correlation of QTc length with antipsychotic dosage was found in homozygous male carriers of the major alleles (i. e. rs12143842-CC and rs10494366-TT), but not in minor allele carriers. There was no significant interaction between antipsychotic dosage and QTc interval for either genotype in female patients. CONCLUSIONS: In this study, a significant interaction was found between both NOS1AP variants, rs12143842 and rs10494366, and antipsychotic treatment on the QTc interval in a sex-dependent manner. Our findings might be relevant for adequate antipsychotic treatment in rs12143842 and rs10494366 major allele carriers.

Is brain arousal regulation a predictor of response to psychostimulant therapy in adult ADHD patients?

We investigated whether baseline brain arousal instability during resting state EEG, using the Vigilance Algorithm Leipzig (VIGALL 2.1), can predict response to methylphenidate therapy in adult ADHD patients. An arousal stability score of the EEGs of 28 adult ADHD patients was calculated quantifying the extent of arousal decline. In logistic regression analysis, arousal stability score predicted response to MPH [odds ratio 1.28 (95% CI 1.0-1.65); p = 0.027]. In this pilot study, we demonstrated that arousal stability at baseline predicted methylphenidate treatment response, indicating that less stable arousal regulation during a 15-min EEG at rest increases the chance of treatment response.

The role of pre-, peri-, and postnatal risk factors in bipolar disorder and adult ADHD.

Gene-environment-development interactions are suggested to play a crucial role in psychiatric disorders. However, it is not clear if there are specific risk gene interactions with particular pre-, peri-, and postnatal risk factors for distinct disorders, such as adult attention-deficit-/hyperactivity disorder (aADHD) and bipolar disorder (BD). In this pilot study, the first aim was to investigate retrospective self-reports of pre-, peri-, and postnatal complications and risk factors from 126 participants (aADHD, BD, and healthy controls) and their mothers. The second aim was to investigate possible interaction between the previously published common risk gene variants of ADHD in the ADGRL3 (=LPHN3) gene (rs2305339, rs1397548, rs734644, rs1397547, rs2271338, rs6551665, and rs2345039) and shared risk gene variants of aADHD and BD in the DGKH gene (DGKH rs994856/rs9525580/rs9525584 GAT haplotype) and pre-, peri-, and postnatal risk factors in comparison to a healthy control group. After correction for multiple comparison, the following pre-, peri-, and postnatal risk factors remained statistically significant (p ≤ 0.0036) between healthy controls and ADHD and BD patients as one group: unplanned pregnancies, psychosocial stress of the mother during pregnancy, mode of delivery, shared decision-making regarding medical procedures during the delivery, perinatal bonding, number of crybabies, and quality of mother-child and father-child relationship. There were no significant environment-gene interactions. In our preliminary data, similar risk factors were found to be significantly associated with both disorders in comparison to healthy controls. However, larger and longitudinal studies and standardized and validated instruments to get a better understanding of the interaction of pre-, peri-, and postnatal complications and mental health in the offspring are needed.

Neural correlates of response inhibition in patients with bipolar disorder during acute versus remitted phase.

Objectives: Elevated behavioural impulsivity has been shown to be a core feature of bipolar disorder. However, no study has so far investigated impulsivity-related brain activation in patients with BD during acute versus remitted phase. To address the question whether elevated behavioural impulsivity and its differential neural pathways is a state or trait marker of BD, we employed a combined stop signal-go/no-go task in 30 controls, and 37 depressed and 15 remitted patients who were retested.Methods: Frontal brain activation was recorded using near-infrared spectroscopy.Results: Behaviourally, we found increased impulsivity as indexed by higher stop signal reaction time for patients in their depressed phase while remitted patients did not differ from controls in any measure. In contrast, brain activation measurements revealed an opposite pattern: compared to controls, depressed patients did not show significant differences, while the remitted group displayed significantly decreased activation in bilateral prefrontal cortex during successful inhibition. Analysis of the remaining conditions (go, no-go, unsuccessful inhibition) did not reveal significant differences.Conclusions: Therefore, behavioural impulsivity and prefrontal hypoactivation do not seem to be a trait marker of BD. As only successful inhibition differentiated between groups, a specific dysfunction of this inhibitory process and its neural pathway may be postulated in BD.

Reliable and efficient recording of the error-related negativity with a speeded Eriksen Flanker Task.

OBJECTIVE: There is accumulating evidence that the error-related negativity (ERN), an event-related potential elicited after erroneous actions, is altered in different psychiatric disorders and may help to guide treatment options. Thus, the ERN is a promising candidate as a psychiatric biomarker. Basic methodological requirements for a biomarker are that their measurements are standardised and reliable. The aim of the present study was to establish ERN acquisition in a reliable, time-efficient and patient-friendly way for use in clinical practice. METHODS: Healthy subjects performed a speeded Eriksen Flanker Task that increases the number of errors. In a test-retest design (N = 14) with two sessions separated by 28 days we assessed the reliability of the ERN. To ensure external validity, we aimed to replicate previously reported correlation patterns of ERN amplitude with (A) number of errors and (B) negative affect. In order to optimise the clinical use of the task, we determined to which extent the task can be shortened while keeping reliability >0.80. RESULTS: We found excellent reliability of the ERN (intraclass correlation coefficients = 0.806-0.947) and replicated ERN correlation patterns. The task can be halved to a patient-friendly length of 200 trials (recorded in 8 min) keeping reliability >0.80. CONCLUSIONS: The modified task provides reliable and efficient recording of the ERN, facilitating its use as a psychiatric biomarker.

Integrated Biomarkers for Depression in Alzheimer's Disease: A Critical Review.

Depression is a common neuropsychiatric manifestation among Alzheimer's disease (AD) patients. It may compromise everyday activities and lead to a faster cognitive decline as well as worse quality of life. The identification of promising biomarkers may therefore help to timely initiate and improve the treatment of preclinical and clinical states of AD, and to improve the long-term functional outcome. In this narrative review, we report studies that investigated biomarkers for AD-related depression. Genetic findings state AD-related depression as a rather complex, multifactorial trait with relevant environmental and inherited contributors. However, one specific set of genes, the brain derived neurotrophic factor (BDNF), specifically the Val66Met polymorphism, may play a crucial role in AD-related depression. Regarding neuroimaging markers, the most promising findings reveal structural impairments in the cortico-subcortical networks that are related to affect regulation and reward / aversion control. Functional imaging studies reveal abnormalities in predominantly frontal and temporal regions. Furthermore, CSF based biomarkers are seen as potentially promising for the diagnostic process showing abnormalities in metabolic pathways that contribute to AD-related depression. However, there is a need for standardization of methodological issues and for replication of current evidence with larger cohorts and prospective studies.

Increase of Heart Rate and QTc by Amitriptyline, But Not by Venlafaxine, Is Correlated to Serum Concentration.

Electrocardiographic pathologies are a common problem during antidepressant treatment. The authors investigated the association of serum concentrations of antidepressants and heart rate, QT, and QTc. Polymorphisms of NOS1AP (nitric oxide synthase 1 adaptor protein) rs10494366 and rs12143842 as potential influence factors also were considered. In the amitriptyline sample (n = 59), significant Spearman ρ correlations were found between serum concentration and QTc (r = 0.333, P = 0.010), as well as heart rate (r = 0.407, P = 0.001). Patients with a serum concentration greater than the therapeutic range (>200 ng/mL) exhibit significantly higher heart rates (87.0 ± 13.3 vs 80.0 ± 13.9, U test P = 0.011) and higher QTc values (443.8 ± 28.8 vs 427.9 ± 20.6, U test P = 0.022). Excluding the 26 patients with a serum concentration greater than the therapeutic range, patients with rs12143842 risk alleles exhibit higher heart rates and as a trend lower QT intervals with no difference in QTc. In the venlafaxine sample (n = 81), no significant association between serum concentration and heart rate, QT, or QTc was revealed. In summary, the risk for relevant electrocardiographic alterations induced by tricyclic antidepressants, such as amitriptyline, is dependent on serum concentrations. NOS1AP polymorphisms may be a genetic vulnerability factor.

Reliance on functional resting-state network for stable task control predicts behavioral tendency for cooperation.

Humans display individual variability in cooperative behavior. While an ever-growing body of research has investigated the neural correlates of task-specific cooperation, the mechanisms by which situation-independent, stable differences in cooperation render behavior consistent across a wide range of situations remain elusive. Addressing this issue, we show that the individual tendency to behave in a prosocial or individualistic manner can be predicted from the functional resting-state connectome. More specifically, connections of the cinguloopercular network which supports goal-directed behavior encode cooperative tendency. Effects of virtual lesions to this network on the efficacy of information exchange throughout the brain corroborate our findings. These results shed light on the neural mechanisms underlying individualists' and prosocials' habitual social decisions by showing that reliance on the cinguloopercular task-control network predicts stable cooperative behavior. Based on this evidence, we provide a unifying framework for the interpretation of functional imaging and behavioral studies of cooperative behavior.

Neuropeptide S receptor gene variation and neural correlates of cognitive emotion regulation.

The neuropeptide S (NPS) and its receptor NPSR have captured attention in the pathogenesis of anxiety disorders. Here, a functional polymorphism in the NPSR1 gene has been linked to deviant cortico-limbic interactions in response to negative stimuli. While healthy T allele carriers exhibited increased amygdala and prefrontal cortex activity, panic disorder patients carrying the T risk allele displayed hypofrontality possibly reflecting insufficient prefrontal inhibition of limbic reactivity. In order to study multi-level effects of genotype and anxiety, prefrontal cortex activity during an emotional n-back task was measured in 66 volunteers genotyped for the NPSR1 rs324981 A/T variant (AA homozygotes vs. T allele carriers) by means of functional near-infrared spectroscopy. For a high working memory load (3-back), T allele carriers showed a signal increase to negative pictures in the dorsolateral and medial prefrontal cortex while AA homozygotes displayed a signal decrease. Since groups did not differ on skin conductance level and behavioral parameters, this effect in the risk group in line with results from fMRI studies is speculated to represent an adaptive mechanism to compensate for presumably increased subcortical activity driven by an overactive NPS system. However, anxiety sensitivity correlated negatively with prefrontal activity in T allele carriers possibly suggesting a decompensation of the adaptive compensatory upregulation.

Electrophysiological evidence of a typical cognitive distortion in bipolar disorder.

Patients suffering from bipolar disorder often report negative thoughts and a bias towards negative environmental stimuli. Previous studies show that this mood-congruent attentional bias could mediated by dysfunctions in anterior limbic regions. The Error-Related Negativity (ERN), which originates in the anterior cingulate cortex (ACC), has been used to research this negativity bias in depressed patients, and could also help to better understand the underlying mechanisms causing the negativity bias in bipolar patients. In this study we investigated error processing in patients with bipolar disorder. Acute depressive bipolar patients (n = 20) and age-matched healthy controls (n = 20) underwent a modified Eriksen Flanker Task to assess test performance and two error-related event-related potentials (ERPs), i.e., the ERN and Error Positivity (Pe) were measured by EEG. Half of the patients were measured again in a euthymic state. We found similar ERN amplitudes in bipolar patients as compared to healthy controls, but significantly reduced Pe amplitudes. Moreover, acutely depressed bipolar patients displayed an ERN and Pe even if they responded accurately or too slow, which indicates that correct responses are processed in a way similar to wrong responses. This can be interpreted as a psychophysiological correlate of typical cognitive distortions in depression, i.e., an erroneous perception of personal failures. This biased error perception partially remained when patients were in a euthymic state. Together, our data indicate that aberrant error processing of bipolar patients may be regarded a trait marker possibly reflecting a risk factor for depressive relapses in bipolar disorder.

A preliminary study on methylphenidate-regulated gene expression in lymphoblastoid cells of ADHD patients.

OBJECTIVES: Methylphenidate (MPH) is a commonly used stimulant medication for treating attention-deficit/hyperactivity disorder (ADHD). Besides inhibiting monoamine reuptake there is evidence that MPH also influences gene expression directly. METHODS: We investigated the impact of MPH treatment on gene expression levels of lymphoblastoid cells derived from adult ADHD patients and healthy controls by hypothesis-free, genome-wide microarray analysis. Significant findings were subsequently confirmed by quantitative Real-Time PCR (qRT PCR) analysis. RESULTS: The microarray analysis from pooled samples after correction for multiple testing revealed 138 genes to be marginally significantly regulated due to MPH treatment, and one gene due to diagnosis. By qRT PCR we could confirm that GUCY1B3 expression was differential due to diagnosis. We verified chronic MPH treatment effects on the expression of ATXN1, HEY1, MAP3K8 and GLUT3 in controls as well as acute treatment effects on the expression of NAV2 and ATXN1 specifically in ADHD patients. CONCLUSIONS: Our preliminary results demonstrate MPH treatment differences in ADHD patients and healthy controls in a peripheral primary cell model. Our results need to be replicated in larger samples and also using patient-derived neuronal cell models to validate the contribution of those genes to the pathophysiology of ADHD and mode of action of MPH.

Multi-level biomarker analysis of nitric oxide synthase isoforms in bipolar disorder and adult ADHD.

INTRODUCTION: Several studies have shown altered levels of nitric oxide (NO) and its stable metabolites (NOx (-)) in blood and cerebrospinal fluid of psychiatric patients. The aim of our study was to replicate previous findings and investigate the influence of the nitrinergic system in bipolar disorder and adult attention-deficit/hyperactivity disorder (aADHD) in particular. METHODS: The concentrations of NO2 (-) and NO3 (-) in peripheral blood in a sample of aADHD, bipolar disorder (BPD) and controls were analysed. The sample was genotyped for a three marker haplotype in the NOS3 gene (rs2070744, rs1799983 and Intron 4 VNTR) and for genetic variants of the NOS1 gene (NOS1 ex 1c, NOS1 ex 1f). Finally, qRT PCR was performed. RESULTS: We found significantly lower NOx (-) levels in BPD (p<0.001). rs2070744 T/T-carriers of the whole sample showed increased mRNA expression of NOS3 (p=0.05). Only in BPD an influence of rs2070744 was seen regarding NO metabolite levels; C/C carriers displayed lower NOx (-) levels (p=0.05). CONCLUSION: We could replicate and extend previous findings showing altered NOx (-) levels in BPD and an influence of NOS3 rs2070744 on NOS3 expression and NOx (-) concentration. Together, these data point to a role of the nitrinergic pathway in BPD.

Predominant polarity in bipolar disorder and validation of the polarity index in a German sample.

BACKGROUND: A large number of patients with bipolar disorder (BD) can be characterized by predominant polarity (PP), which has important implications for relapse prevention. Recently, Popovic et al. (EUR NEUROPSYCHOPHARM 22(5): 339-346, 2012) proposed the Polarity Index (PI) as a helpful tool in the maintenance treatment of BD. As a numeric expression, it reflects the efficacy of drugs used in treatment of BD. In the present retrospective study, we aimed to validate this Index in a large and well characterized German bipolar sample. METHODS: We investigated 336 bipolar patients (BP) according to their PP and calculated the PI for each patient in order to prove if maintenance treatment differs according to their PP. Furthermore, we analysed whether PP is associated with demographic and clinical characteristics of BP. RESULTS: In our sample, 63.9% of patients fulfilled criteria of PP: 169 patients were classified as depressive predominant polarity (DPP), 46 patients as manic predominant polarity (MPP). The two groups differed significantly in their drug regime: Patients with DPP were more often medicated with lamotrigine and antidepressants, patients with MPP were more often treated with lithium, valproate, carbamazepine and first generation antipsychotics. However, patients with DPP and MPP did not differ significantly with respect to the PI, although they received evidence-based and guideline-driven treatment. CONCLUSION: The reason for this negative finding might well be that for several drugs, which were used frequently, no PI value is available. Nevertheless we suggest PP as an important concept in the planning of BD maintenance treatment.

Further evidence for plasma progranulin as a biomarker in bipolar disorder.

BACKGROUND: A recent study suggested that progranulin (encoded by the fronto-temporal dementia risk gene GRN) plasma levels are decreased in bipolar disorder (BD). Replication of this finding is however lacking. METHODS: Progranulin plasma levels of bipolar patients (n=104) and healthy controls (n=80) were measured by enzyme-linked immunosorbent assay (ELISA). Participants were also genotyped for three single nucleotide polymorphisms (SNPs) in the GRN gene (rs2879096, rs4792938 and rs5848), and the effect of genetic variation on progranulin levels was examined. RESULTS: Plasma progranulin levels were decreased in BD (ANCOVA, p=0.001). Furthermore, age was significantly and positively correlated with plasma progranulin (Pearson׳s correlation, r=0.269, p<0.001). Also, lithium treatment but no other medication had a significant effect on progranulin plasma levels (ANCOVA, p=0.007). Specifically in BD, the GRN SNP rs5848 was associated with progranulin plasma levels (Kruskal-Wallis test, p<0.005). LIMITATIONS: Subgroup analysis regarding bipolar I vs. bipolar II subtype and polarity of the episode at sampling (manic vs. depressed vs. mixed vs. rapid cycling vs. euthymic) could only be performed with limited validity due to the relatively small sample size. The suitability of peripheral progranulin as a biomarker for BD is limited due to the overlap between patients and controls. CONCLUSION: The findings strengthen the evidence for progranulin being involved in pathomechanisms of bipolar disorder, and suggest a genetic determinant of progranulin concentrations that is relevant specifically in bipolar patients.

The effect of emotional content on brain activation and the late positive potential in a word n-back task.

INTRODUCTION: There is mounting evidence for the influence of emotional content on working memory performance. This is particularly important in light of the emotion processing that needs to take place when emotional content interferes with executive functions. In this study, we used emotional words of different valence but with similar arousal levels in an n-back task. METHODS: We examined the effects on activation in the prefrontal cortex by means of functional near-infrared spectroscopy (fNIRS) and on the late positive potential (LPP). FNIRS and LPP data were examined in 30 healthy subjects. RESULTS: BEHAVIORAL RESULTS SHOW AN INFLUENCE OF VALENCE ON THE ERROR RATE DEPENDING ON THE DIFFICULTY OF THE TASK: more errors were made when the valence was negative and the task difficult. Brain activation was dependent both on the difficulty of the task and on the valence: negative valence of a word diminished the increase in activation, whereas positive valence did not influence the increase in activation, while difficulty levels increased. The LPP also differentiated between the different valences, and in addition was influenced by the task difficulty, the more difficult the task, the less differentiation could be observed. CONCLUSIONS: Summarized, this study shows the influence of valence on a verbal working memory task. When a word contained a negative valence, the emotional content seemed to take precedence in contrast to words containing a positive valence. Working memory and emotion processing sites seemed to overlap and compete for resources even when words are carriers of the emotional content.

Progranulin gene variability and plasma levels in bipolar disorder and schizophrenia.

Basing on the assumption that frontotemporal lobar degeneration (FTLD), schizophrenia and bipolar disorder (BPD) might share common aetiological mechanisms, we analyzed genetic variation in the FTLD risk gene progranulin (GRN) in a German population of patients with schizophrenia (n = 271) or BPD (n = 237) as compared with 574 age-, gender- and ethnicity-matched controls. Furthermore, we measured plasma progranulin levels in 26 German BPD patients as well as in 61 Italian BPD patients and 29 matched controls.A significantly decreased allelic frequency of the minor versus the wild-type allele was observed for rs2879096 (23.2 versus 34.2%, P<0.001, OR:0.63, 95%CI:0.49-0.80), rs4792938 (30.7 versus 39.7%, P = 0.005, OR: 0.70, 95%CI: 0.55-0.89) and rs5848 (30.3 versus 36.8, P = 0.007, OR: 0.71, 95%CI: 0.56-0.91). Mean±SEM progranulin plasma levels were significantly decreased in BPD patients, either Germans or Italians, as compared with controls (89.69±3.97 and 116.14±5.80 ng/ml, respectively, versus 180.81±18.39 ng/ml P<0.001) and were not correlated with age.In conclusion, GRN variability decreases the risk to develop BPD and schizophrenia, and progranulin plasma levels are significantly lower in BPD patients than in controls. Nevertheless, a larger replication analysis would be needed to confirm these preliminary results.

NOS1 ex1f-VNTR polymorphism affects prefrontal oxygenation during response inhibition tasks.

Impulsivity is a trait shared by many psychiatric disorders and therefore a suitable intermediate phenotype for their underlying biological mechanisms. One of the molecular determinants involved is the NOS1 ex1f-VNTR, whose short variants are associated with a variety of impulsive behaviors. Fifty-six healthy controls were stratified into homozygous long (LL) (30 probands) and short (SS) (26 probands) allele groups. Subjects completed a combined stop-signal go/nogo task, while the oxygenation in the prefrontal cortex was measured with functional near-infrared spectroscopy. Electromyography was recorded to control for differences in muscle activity in the two inhibition tasks. Two questionnaires on impulsive traits were completed. Differences between the two tasks are shown by distinct activation patterns within the prefrontal cortex. The nogo task resulted mainly in the activation of the dorsolateral prefrontal cortex (dlPFC), whereas successful and unsuccessful inhibition in the stop-signal task elicited the predicted activity in the inferior frontal cortex (IFC). Although significant differences were found in neither the scores obtained on impulsivity-related questionnaires nor the behavioral data, the LL group displayed increased dlPFC activity during nogo trials and the predicted activation in the IFC during successful inhibition in the stop-signal task, while no significant activation was found in the SS group. Our data confirm an influence of NOS1 ex1f-VNTR on impulsivity, as carriers of the short risk allele exhibited diminished activity of (pre-)frontal brain regions during the inhibition in a stop-signal task. Impairment of prefrontal control with consecutive failure of inhibitory processes might underlie association findings reported previously.

Cross-disorder analysis of bipolar risk genes: further evidence of DGKH as a risk gene for bipolar disorder, but also unipolar depression and adult ADHD.

Recently, several genome-wide association studies (GWAS) on bipolar disorder (BPD) suggested novel risk genes. However, only few of them were followed up and further, the specificity of these genes is even more elusive. To address these issues, we genotyped SNPs in ANK3, CACNA1C, CMTM8, DGKH, EGFR, and NPAS3, which were significantly associated with BPD in previous GWAS, in a sample of 380 BPD patients. Replicated SNPs were then followed up in patients suffering from unipolar depression (UPD; n=387) or adult attention-deficit/hyperactivity disorder (aADHD; n=535). While we could not confirm an association of ANK3, CACNA1C, and EGFR with BPD, 10 SNPs in DGKH, CMTM8, and NPAS3 were nominally associated with disease, with two DGKH markers surviving correction for multiple testing. When these were followed up in UPD and aADHD, seven DGKH SNPs were also associated with UPD, while one SNP each in NPAS3 and CMTM8 and four in DGKH were linked to aADHD. Furthermore, a DGKH haplotype consisting of rs994856/rs9525580/rs9525584 GAT was associated with all disorders tested, while the complementary AGC haplotype was protective. The corresponding haploblock spans a 27-kb region covering exons coding for amino acids 65-243, and thus might include functional variants yet to be identified. We demonstrate an association of DGKH with BPD, UPD, and aADHD by applying a two-stage design. These disorders share the feature of mood instability, so that this phenotype might be associated with genetic variation in DGKH.

NOS1 ex1f-VNTR polymorphism influences prefrontal brain oxygenation during a working memory task.

Nitric oxide (NO) synthase produces NO, which serves as first and second messenger in neurons, where the protein is encoded by the NOS1 gene. A functional variable number of tandem repeats (VNTR) polymorphism in the promoter region of the alternative first exon 1f of NOS1 is associated with various functions of human behavior, for example increased impulsivity, while another, non-functional variant was linked to decreased verbal working memory and a heightened risk for schizophrenia. We therefore investigated the influence of NOS1 ex 1f-VNTR on working memory function as reflected by both behavioral measures and prefrontal oxygenation. We hypothesized that homozygous short allele carriers exhibit altered brain oxygenation in task-related areas, namely the dorsolateral and ventrolateral prefrontal cortex and the parietal cortex. To this end, 56 healthy subjects were stratified into a homozygous long allele group and a homozygous short allele group comparable for age, sex and intelligence. All subjects completed a letter n-back task (one-, two-, and three-back), while concentration changes of oxygenated (O(2)Hb) hemoglobin in the prefrontal cortex were measured with functional near-infrared spectroscopy (fNIRS). We found load-associated O(2)Hb increases in the prefrontal and parts of the parietal cortex. Significant load-associated oxygenation differences between the two genotype groups could be shown for the dorsolateral prefrontal cortex and the parietal cortex. Specifically, short allele carriers showed a significantly larger increase in oxygenation in all three n-back tasks. This suggests a potential compensatory mechanism, with task-related brain regions being more active in short allele carriers to compensate for reduced NOS1 expression.