Graph analysis of verbal fluency test discriminate between patients with Alzheimer's disease, mild cognitive impairment and normal elderly controls

Verbal fluency is the ability to produce a satisfying sequence of spoken words during a given time interval. The core of verbal fluency lies in the capacity to manage the executive aspects of language. The standard scores of the semantic verbal fluency test are broadly used in the neuropsychological assessment of the elderly, and different analytical methods are likely to extract even more information from the data generated in this test. Graph theory, a mathematical approach to analyze relations between items, represents a promising tool to understand a variety of neuropsychological states. This study reports a graph analysis of data generated by the semantic verbal fluency test by cognitively healthy elderly (NC), patients with Mild Cognitive Impairment-subtypes amnestic (aMCI) and amnestic multiple domain (a+mdMCI)-and patients with Alzheimer's disease (AD). Sequences of words were represented as a speech graph in which every word corresponded to a node and temporal links between words were represented by directed edges. To characterize the structure of the data we calculated 13 speech graph attributes (SGA). The individuals were compared when divided in three (NC-MCI-AD) and four (NC-aMCI-a+mdMCI-AD) groups. When the three groups were compared, significant differences were found in the standard measure of correct words produced, and three SGA: diameter, average shortest path, and network density. SGA sorted the elderly groups with good specificity and sensitivity. When the four groups were compared, the groups differed significantly in network density, except between the two MCI subtypes and NC and aMCI. The diameter of the network and the average shortest path were significantly different between the NC and AD, and between aMCI and AD. SGA sorted the elderly in their groups with good specificity and sensitivity, performing better than the standard score of the task. These findings provide support for a new methodological frame to assess the strength of semantic memory through the verbal fluency task, with potential to amplify the predictive power of this test. Graph analysis is likely to become clinically relevant in neurology and psychiatry, and may be particularly useful for the differential diagnosis of the elderly.

ADHD inattentive symptoms mediate the relationship between intelligence and academic performance in children aged 6-14

OBJECTIVE

Fluid intelligence and the behavioral problems of attention-deficit/hyperactivity disorder (ADHD) are related to academic performance, but how this association occurs is unclear. This study aimed to assess mediation and moderation models that test possible pathways of influence between these factors.

METHODS

Sixty-two children with ADHD and 33 age-matched, typically developing students were evaluated with Raven's Colored Progressive Matrices and the spelling and arithmetic subtests of the Brazilian School Achievement Test. Dimensional ADHD symptomatology was reported by parents.

RESULTS

Our findings suggest that fluid intelligence has a significant impact on academic tests through inattention. The inattentive dimension was the principal behavioral source of influence, also accounting for the association of hyperactive-impulsive manifestations with school achievement. This cognitive-to-behavioral influence path seems to be independent of diagnosis related group, and gender, but lower socioeconomic status might increase its strength.

CONCLUSION

Fluid intelligence is a relevant factor in the influence of ADHD behavioral symptoms on academic performance, but its impact is indirect. Therefore, early identification of both fluid intelligence and inattentive symptoms is of the utmost importance to prevent impaired academic performance and future difficulties in functioning.

Impaired generation of new subcategories and switching in a semantic verbal fluency test in older adults with mild cognitive impairment

The semantic verbal fluency task is broadly used in the neuropsychological assessment of elderly subjects. Even some studies have identified differences in verbal fluency clustering and switching measures between subjects with normal aging and a clinical condition such as mild cognitive impairment (MCI) and Alzheimer's disease, the results are not always consistent. This study aimed to compare clustering and switching measures of an animal's semantic verbal fluency task among normal controls (NC, n = 25), amnestic mild cognitive impairment (aMCI; n = 25), amnestic multiple domain Mild Cognitive Impairment (a+mdMCI; n = 25) and Alzheimer's disease (AD; n = 25) Brazilian subjects. The analyses were executed considering three (unifying the MCI subtypes) and four groups. As the data were not normally distributed, we carried out non-parametric tests (Kruskal-Wallis and Mann-Whitney tests) to evaluate the differences in performance in the measures of the verbal fluency test among the groups. The comparison demonstrated that the groups differed in the total of correct words produced, number of clusters and switching but the measure of new subcategories was the only with significant difference among the NC and all the clinical groups. The measure of new subcategories is the number of original subcategories inside the higher category of animals that the subject produced, such as farm, domestic, African animals. Our results indicate that semantic memory impairment is a visible and recent deficit that occurs even in non-demented subjects with very MCI and the implications of these findings are discussed.

Association between the catechol-O-methyltransferase (COMT) Val158Met polymorphism and manual aiming control in healthy subjects

BACKGROUND

Prefrontal dopamine is catabolized by the catechol-O-methyltransferase (COMT) enzyme. Current evidence suggests that the val/met single nucleotide polymorphism in the COMT gene can predict the efficiency of executive cognition in humans. Individuals carrying the val allele perform more poorly because less synaptic dopamine is available.

METHODOLOGY/PRINCIPAL FINDINGS

We investigated the influence of the COMT polymorphism on motor performance in a task that requires different executive functions. We administered a manual aiming motor task that was performed under four different conditions of execution by 111 healthy participants. Participants were grouped according to genotype (met/met, met/val, val/val), and the motor performance among groups was compared. Overall, the results indicate that met/met carriers presented lower levels of peak velocity during the movement trajectory than the val carriers, but met/met carriers displayed higher accuracy than the val carriers.

CONCLUSIONS/SIGNIFICANCE

This study found a significant association between the COMT polymorphism and manual aiming control. Few studies have investigated the genetics of motor control, and these findings indicate that individual differences in motor control require further investigation using genetic studies.

Sarcosine preconditioning induces ischemic tolerance against global cerebral ischemia

Brain ischemic tolerance is an endogenous protective mechanism activated by a preconditioning stimulus that is closely related to N-methyl-d-aspartate receptor (NMDAR). Glycine transporter type 1 (GlyT-1) inhibitors potentiate NMDAR and suggest an alternative strategy for brain preconditioning. The aim of this work was to evaluate the effects of brain preconditioning induced by sarcosine, a GlyT-1 inhibitor, against global cerebral ischemia and its relation to NMDAR. Sarcosine was administered over 7 days (300 or 500 mg/kg/day, ip) before the induction of a global cerebral ischemia model in Wistar rats (male, 8-week-old). It was observed that sarcosine preconditioning reduced cell death in rat hippocampi submitted to cerebral ischemia. Hippocampal levels of glycine were decreased in sarcosine-treated animals, which was associated with a reduction of [(3)H] glycine uptake and a decrease in glycine transporter expression (GlyT-1 and GlyT-2). The expression of glycine receptors and the NR1 and NR2A subunits of NMDAR were not affected by sarcosine preconditioning. However, sarcosine preconditioning reduced the expression of the NR2B subunits of NMDAR. In conclusion, these data demonstrate that sarcosine preconditioning induces ischemic tolerance against global cerebral ischemia and this neuroprotective state is associated with changes in glycine transport and reduction of NR2B-containing NMDAR expression.

Global pharmacogenomics: distribution of CYP3A5 polymorphisms and phenotypes in the Brazilian population

The influence of self-reported "race/color", geographical origin and genetic ancestry on the distribution of three functional CYP3A5 polymorphisms, their imputed haplotypes and inferred phenotypes was examined in 909 healthy, adult Brazilians, self-identified as White, Brown or Black ("race/color" categories of the Brazilian census). The cohort was genotyped for CYP3A5*3 (rs776746), CYP3A5*6 (rs10264272) and CYP3A5*7 (rs41303343), CYP3A5 haplotypes were imputed and CYP3A5 metabolizer phenotypes were inferred according to the number of defective CYP3A5 alleles. Estimates of the individual proportions of Amerindian, African and European ancestry were available for the entire cohort. Multinomial log-linear regression models were applied to infer the statistical association between the distribution of CYP3A5 alleles, haplotypes and phenotypes (response variables), and self-reported Color, geographical region and ancestry (explanatory variables). We found that Color per se or in combination with geographical region associates significantly with the distribution of CYP3A5 variant alleles and CYP3A5 metabolizer phenotypes, whereas geographical region per se influences the frequency distribution of CYP3A5 variant alleles. The odds of having the default CYP3A5*3 allele and the poor metabolizer phenotype increases continuously with the increase of European ancestry and decrease of African ancestry. The opposite trend is observed in relation to CYP3A5*6, CYP3A5*7, the default CYP3A5*1 allele, and both the extensive and intermediate phenotypes. No significant effect of Amerindian ancestry on the distribution of CYP3A5 alleles or phenotypes was observed. In conclusion, this study strongly supports the notion that the intrinsic heterogeneity of the Brazilian population must be acknowledged in the design and interpretation of pharmacogenomic studies, and dealt with as a continuous variable, rather than proportioned in arbitrary categories that do not capture the diversity of the population. The relevance of this work extrapolates the Brazilian borders, and extends to other admixed peoples of the Americas, with ancestral roots in Europe, Africa and the American continent.

Reduced frequency of T lymphocytes expressing CTLA-4 in frontotemporal dementia compared to Alzheimer's disease

Studies suggest that inflammation is involved in the neurodegenerative cascade of dementias. Immunological mechanisms may be part of the pathophysiological process in frontotemporal dementia (FTD), but up till now only vague evidence of such mechanisms has been presented. The B7- CD28/CTLA-4 pathway is an important immunological signaling pathway involved in modulation of T cell activation. The aim of this study was to compare the expression of molecules associated with co-stimulatory signaling in peripheral blood mononuclear cells (PBMC) of FTD to Alzheimer disease (AD) and control groups. Our results confirm the previous demonstrated increased expression of CD80 in CD14+ Alzheimer patients T cells but show, for the first time, a reduction in the expression of CTLA-4 in CD4+ FTD cells. As CTLA-4 is the most potent negative regulators of T-cell activation we speculated that peripheral T lymphocytes in FTD are more activated and this could be involved in the neurodegeneration observed in this dementia.

Genetic variations in FOXO3A are associated with Bipolar Disorder without confering vulnerability for suicidal behavior

BACKGROUND

Genetic variation plays an important role in Bipolar Disorder (BD) and suicide susceptibility. However, little is known about the genetic influence on the risk of suicide, particularly in BD patients. Since FOXO3A plays a role in distinct mood-relevant behavioral processes, this gene could be a novel gene candidate for BD. Thus, we investigated whether FOXO3A polymorphisms are associated with BD and suicidal behavior in BD patients.

METHODS

TaqMan genotyping was used to detect FOXO3A SNPs in 273 BD patients and 264 control subjects.

RESULTS

Three SNPs (rs1536057, rs2802292 and rs1935952) were associated with BD, but none was positively linked with suicidal behavior.

LIMITATION

A systematic evaluation within the whole FOXO3A gene and drug treatment in patients was not performed.

CONCLUSIONS

These data suggest that FOXO3A is a novel susceptibility locus for BD, but not for suicidal behavior in BD patients. These results may contribute to a better understanding of the BD genetics.

Lack of association of NALCN genetic variants with schizophrenia

NALCN (sodium leak channel, non-selective) is located on chromosome 13q (suggested linkage region for schizophrenia). We analyzed 21 polymorphisms in 464 schizophrenia subjects, 220 controls subjects and 119 small nuclear families. We observed nominal association with rs9518320 and rs9518331, suggesting that NALCN is not related to schizophrenia risk.

The genomic ancestry of individuals from different geographical regions of Brazil is more uniform than expected

Based on pre-DNA racial/color methodology, clinical and pharmacological trials have traditionally considered the different geographical regions of Brazil as being very heterogeneous. We wished to ascertain how such diversity of regional color categories correlated with ancestry. Using a panel of 40 validated ancestry-informative insertion-deletion DNA polymorphisms we estimated individually the European, African and Amerindian ancestry components of 934 self-categorized White, Brown or Black Brazilians from the four most populous regions of the Country. We unraveled great ancestral diversity between and within the different regions. Especially, color categories in the northern part of Brazil diverged significantly in their ancestry proportions from their counterparts in the southern part of the Country, indicating that diverse regional semantics were being used in the self-classification as White, Brown or Black. To circumvent these regional subjective differences in color perception, we estimated the general ancestry proportions of each of the four regions in a form independent of color considerations. For that, we multiplied the proportions of a given ancestry in a given color category by the official census information about the proportion of that color category in the specific region, to arrive at a "total ancestry" estimate. Once such a calculation was performed, there emerged a much higher level of uniformity than previously expected. In all regions studied, the European ancestry was predominant, with proportions ranging from 60.6% in the Northeast to 77.7% in the South. We propose that the immigration of six million Europeans to Brazil in the 19th and 20th centuries--a phenomenon described and intended as the "whitening of Brazil"--is in large part responsible for dissipating previous ancestry dissimilarities that reflected region-specific population histories. These findings, of both clinical and sociological importance for Brazil, should also be relevant to other countries with ancestrally admixed populations.

Downregulation of the cAMP/PKA pathway in PC12 cells overexpressing NCS-1

It is well known that dopamine imbalances are associated with many psychiatric disorders and that the dopaminergic receptor D₂ is the main target of antipsychotics. Recently it was shown that levels of two proteins implicated in dopaminergic signaling, Neuronal calcium sensor-1 (NCS-1) and DARPP-32, are altered in the prefrontal cortex (PFC) of both schizophrenic and bipolar disorder patients. NCS-1, which inhibits D₂ internalization, is upregulated in the PFC of both patients. DARPP-32, which is a downstream effector of dopamine signaling, integrates the pathways of several neurotransmitters and is downregulated in the PFC of both patients. Here, we used PC12 cells stably overexpressing NCS-1 (PC12-NCS-1 cells) to address the function of this protein in DARPP-32 signaling pathway in vitro. PC12-NCS-1 cells displayed downregulation of the cAMP/PKA pathway, with decreased levels of cAMP and phosphorylation of CREB at Ser133. We also observed decreased levels of total and phosphorylated DARPP-32 at Thr34. However, these cells did not show alterations in the levels of D₂ and phosphorylation of DARPP-32 at Thr75. These results indicate that NCS-1 modulates PKA/cAMP signaling pathway. Identification of the cellular mechanisms linking NCS-1 and DARPP-32 may help in the understanding the signaling machinery with potential to be turned into targets for the treatment of schizophrenia and other debilitating psychiatric disorders.

VKORC1 polymorphisms in Brazilians: comparison with the Portuguese and Portuguese-speaking Africans and pharmacogenetic implications

Aims: The heterogeneity of the Brazilian population renders the extrapolation of pharmacogenomic data derived from well-defined ethnic groups inappropriate. We investigated the influence of self-reported ‘race/color’, geographical origin and genetic ancestry on the distribution of four VKORC1 SNPs and haplotypes in Brazilians. Comparative data were obtained from two major ancestral roots of Brazilians: Portuguese and Africans from former Portuguese colonies. Materials & methods: A total of 1037 healthy adults Brazilians, recruited at four different geographical regions and self identified as white, brown or black (race/color categories), 89 Portuguese and 216 Africans from Angola and Mozambique were genotyped for the VKORC1 3673G>A (rs9923231), 5808T>G (rs2884737), 6853G>C (rs8050894) and 9041G>A (rs7294) polymorphisms using TaqMan® (Applied Biosystems, CA, USA) assays. VKORC1 haplotypes were statistically inferred using the haplo.stats software. We inferred the statistical association between the distribution of the VKORC1 polymorphisms among Brazilians and self-reported color, geographical region and genetic ancestry by fitting multinomial log linear models via neural networks. Individual proportions of European and African ancestry were used to assess the impact of genetic admixture on the frequency distribution of VKORC1 polymorphisms among Brazilians, and for the comparison of Brazilians with Portuguese and Africans. Results: The frequency distribution of the 3673G>A and 5808T>G polymorphisms, and VKORC1 haplotypes among Brazilians varies across geographical regions, within self-reported color categories and according to the individual proportions of European and African genetic ancestry. Notably, the frequency of the warfarin sensitive VKORC1 3673A allele and the distribution of VKORC1 haplotypes varied continuously as the individual proportion of European ancestry increased in the entire cohort, independently of race/color categorization and geographical origin. Brazilians with more than 80% African ancestry differ significantly from Angolans and Mozambicans in frequency of the 3673G>A, 5808T>G and 6853G>C polymorphisms and haplotype distribution, whereas no such differences are observed between Brazilians with more than 90% European ancestry and Portuguese individuals. Conclusion: The diversity of the Brazilian population, evident in the distribution of VKORC1 polymorphisms, must be taken into account in the design of pharmacogenetic clinical trials and dealt with as a continuous variable. Warfarin dosing algorithms that include ‘race’ terms defined for other populations are clearly not applicable to the heterogeneous and extensively admixed Brazilian population.

Genetic association of the GDNF alpha-receptor genes with schizophrenia and clozapine response

GDNF (glial-cell-line derived neurotrophic factor) is a potent neurotrophic factor for dopaminergic neurons. Neuropsychiatric diseases and their treatments are associated with alterations in the levels of both GDNF and its receptor family (GDNF family receptor alpha or GFRA). GFRA1, GFRA2 and GFRA3 are located in chromosomal regions with suggestive linkage to schizophrenia. In this study we analyzed polymorphisms located in all four known GFRA genes and examined association with schizophrenia and clozapine response. We examined SNPs across the genes GFRA1-4 in 219 matched case-control subjects, 85 small nuclear families and 140 schizophrenia patients taking clozapine for 6months. We observed that GFRA3 rs11242417 and GFRA1 rs11197557 variants were significantly associated with schizophrenia after combining results from both schizophrenia samples. Furthermore, we found an overtransmission of the G-C GFRA1 rs7920934-rs730357 haplotype to subjects with schizophrenia and association of A-T-G-G GFRA3 rs10036665-rs10952-rs11242417-rs7726580 with schizophrenia in the case-control sample. On the other hand, GFRA2 variants were not associated with schizophrenia diagnosis but subjects carrying T-G-G rs1128397-rs13250096-rs4567028 haplotype were more likely to respond to clozapine treatment. The statistical significance of results survived permutation testing but not Bonferroni correction. We also found nominally-significant evidence for interactions between GFRA1, 2 and 3 associated with schizophrenia and clozapine response, consistent with the locations of these three genes within linkage regions for schizophrenia.

Lack of effects of typical and atypical antipsychotics in DARPP-32 and NCS-1 levels in PC12 cells overexpressing NCS-1

Background

Schizophrenia is the major psychiatry disorder, which the exact cause remains unknown. However, it is well known that dopamine-mediated neurotransmission imbalance is associated with this pathology and the main target of antipsychotics is the dopamine receptor D₂. Recently, it was described alteration in levels of two dopamine signaling related proteins in schizophrenic prefrontal cortex (PFC): Neuronal Calcium Sensor-1 (NCS-1) and DARPP-32. NCS-1, which is upregulated in PFC of schizophrenics, inhibits D₂ internalization. DARPP-32, which is decreased in PFC of schizophrenics, is a key downstream effector in transducing dopamine signaling. We previously demonstrated that antipsychotics do not change levels of both proteins in rat's brain. However, since NCS-1 and DARPP-32 levels are not altered in wild type rats, we treated wild type PC12 cells (PC12 WT) and PC12 cells stably overexpressing NCS-1 (PC12 Clone) with antipsychotics to investigate if NCS-1 upregulation modulates DARPP-32 expression in response to antipsychotics treatment.

Results

We chronically treated both PC12 WT and PC12 Clone cells with typical (Haloperidol) or atypical (Clozapine and Risperidone) antipsychotics for 14 days. Using western blot technique we observed that there is no change in NCS-1 and DARPP-32 protein levels in both PC12 WT and PC12 Clone cells after typical and atypical antipsychotic treatments.

Conclusions

Because we observed no alteration in NCS-1 and DARPP-32 levels in both PC12 WT and Clone cells treated with typical or atypical antipsychotics, we suggest that the alteration in levels of both proteins in schizophrenic's PFC is related to psychopathology but not with antipsychotic treatment.

Lack of association of GPX1 and MnSOD genes with symptom severity and response to clozapine treatment in schizophrenia subjects

Abnormal activities of critical antioxidant enzymes and other indices of lipid peroxidation in plasma and red blood cells were detected in patients with schizophrenia. Other results have shown that oxidative stress may be modulated by clozapine. Based on that and some studies already found different clinical relations between reactive oxygen species and negative and positive symptoms, we evaluated association between clinical response and the polymorphism in the human glutathione peroxidase (GPX1) (Pro200Leu, rs1050450) and manganese SOD (MNSOD) (Ala16Val, rs4880) gene in 216 clozapine-treated patients with schizophrenia. No association was found with these two functional polymorphisms and clozapine response and symptom change after 6 months. No correlations were found between positive/negative symptoms score and both polymorphisms. Our results present that GPX1 (Pro200Leu) and MNSOD (Ala16Val) polymorphisms seem do not play a central role in the clozapine response, although studies in larger and independent samples are necessary to confirm our findings.

Modulation of muscarinic signaling in PC12 cells overexpressing neuronal Ca2+ sensor-1 protein

It has been suggested that overexpression of neuronal Ca2+ sensor-1 (NCS-1) protein is implicated in the pathophysiology of neurodisorders such as schizophrenia, bipolar disturbance and X-linked mental retardation. The mechanism by which NCS-1 would be involved in the causes and/or consequences of these neurodisorders is still far from elucidation. Independent evidence has pointed NCS-1 as a key regulator of synaptic efficacy by altering the expression and activity of voltage-gated channels, inhibiting internalization of dopaminergic receptors, and altering phosphoinositide metabolism. In this study, we examined the possible participation of NCS-1 protein in signal transmission dependent on muscarinic receptor activation, using PC12 cells stably expressing NCS-1 (PC12-NCS-1). Carbachol (CCH; 300 microM) was able to evoke glutamate release more efficiently from PC12-NCS-1 (15.3+/-1.0nmol/mg of protein) than wild type cells (PC12-wt; 8.3+/-0.9nmol/mg of protein). This increase of glutamate release induced by CCH was independent on extracellular Ca2+ influx. Additionally, a larger increase of cytoplasmic levels of InsP3 (663.0+/-63.0 and 310.0+/-39.0% of fluorescence in A.U.) and [Ca2+]i (766.4+/-40.0 and 687.8+/-37.1nmol/L) was observed after CCH stimulus of PC12-NCS-1 compared with PC12-wt. Clearly distinction between intracellular Ca2+ dynamics was also observed in PC12-NCS-1 and PC12-wt. A larger increase followed by fast decay of [Ca2+]i was observed in PC12-NCS-1. A plateau with a delayed decay of [Ca2+]i was characteristic of PC12-wt [Ca2+]i response. Both enhancement of InsP3 production and glutamate release observed in PC12-NCS-1 were blocked by atropine (10 microM). Together, our data show that overexpression of NCS-1 in PC12 cells induces an enhancement of intracellular second messenger and transmitter release dependent on CCH response, suggesting that muscarinic signaling is "up-regulated" in this cell model.

The leukocytes expressing DARPP-32 are reduced in patients with schizophrenia and bipolar disorder

Bipolar disorder (BPD) and schizophrenia (SCZ) are severe disorders representing an enormous social, familiar and individual burden, being SCZ the most disabling psychiatric disorder characterized by psychosis and cognitive impairment. It is well known that SCZ and BPD are associated with abnormalities in dopamine signaling pathway. Recent data in the literature have demonstrated altered expression levels of some proteins involved in the modulation of this pathway in both brain and peripheral tissues. It was shown that protein and mRNA levels of dopamine and cAMP regulated phosphoprotein (DARPP-32) were downregulated in dorsolateral prefrontal cortex (DLPFC) of patients with SCZ or BPD when compared to controls. Due to the difficulty to access brain tissue and the absence of objective laboratory tests for bio-markers, we measured DARPP-32 expression in blood cell sub-populations (CD4+ T lymphocytes, CD56+ NK cells, CD19+ B lymphocytes and CD14+ monocytes) taking advantage of the close relation of nervous and immune systems. Using flow cytometry as the analytical method, our results have shown that the DARPP-32 expression was diminished in CD4+ T lymphocytes, CD19+ B lymphocytes and CD14+ monocytes of BPD patients and was also decreased in CD4+ T lymphocytes and CD56+ NK cells of SCZ patients. These results showed that DARPP-32 expression in immune cells agrees with reports of reduced DARPP-32 protein in the DLPFC of BPD or SCZ patients. Our data suggest that DARPP-32 expression in PBMC could be used as a source of bio-markers to help in the treatment response of neuropsychiatry disorders as a window to the changes in the brain of those patients.