M. Aragues

Anatomical and functional brain variables associated with clozapine response in treatment-resistant schizophrenia

Clozapine alleviates the symptoms of a significant proportion of treatment-resistant schizophrenic patients. Previous studies suggest that the response to clozapine may be associated with prefrontal and temporal anatomy as well as with prefrontal, basal ganglia and thalamic metabolism. A sample of 25 treatment-resistant (TR) schizophrenic patients underwent magnetic resonance imaging (MRI) and 18F-deoxyglucose positron emission tomography (PET) before and after treatment with clozapine. We investigated the association between changes in positive, disorganized, and negative schizophrenic syndromes with clozapine treatment and a set of cerebral variables that included total intracranial volume (ICV); hippocampal, dorsolateral prefrontal (DLPF) and temporal gray-matter volume and metabolism; and metabolic activity of the thalamus, pallidum/putamen, and caudate head. Improvement in positive symptoms with clozapine was directly related to temporal gray-matter volume, whereas improvement of disorganization symptoms was inversely related to ICV and hippocampal volume. Patients with high baseline DLPF cortical volume and metabolic activity were more likely to experience improvement in their negative symptoms. We conclude that clinical improvement with clozapine may be related with the anatomy and metabolic activity of specific brain areas, with the structural integrity of the DLPF and temporal regions showing the maximum predictive capacity.

The ANKK1 Kinase Gene and Psychiatric Disorders

The TaqIA single nucleotide polymorphism (SNP, rs1800497), which is located in the gene that codes for the putative kinase ANKK1 (ANKK1) near the termination codon of the D2 dopamine receptor gene (DRD2; chromosome 11q22–q23), is the most studied genetic variation in a broad range of psychiatric disorders and personality traits. A large number of individual genetic association studies have found that the TaqIA SNP is linked to alcoholism and antisocial traits. In addition, it has also been related to other conditions such as schizophrenia, eating disorders, and some behavioral childhood disorders. The TaqIA A1 allele is mainly associated with addictions, antisocial disorders, eating disorders, and attention-deficit/hyperactivity disorders, while the A2 allele occurs more frequently in schizophrenic and obsessive-compulsive patients. Current data show that the TaqIA polymorphism may be a marker of both DRD2 and ANKK1 genetic variants. ANKK1 would belong to a family of kinases involved in signal transduction. This raises the question of whether signaling players intervene in the pathophysiology of psychiatric disorders. Basic research on the ANKK1 protein and its putative interaction with the D2 dopamine receptor could shed light on this issue.

Gender-specific COMT Val158Met polymorphism association in Spanish schizophrenic patients.

The functional Val158Met polymorphism (rs4680) located at the gene that codes for the catechol‐O‐methyltransferase (COMT) has been extensively investigated in schizophrenia although current data are still controversial. Since COMT activity is sexually dimorphic, we carried out two independent studies in homogeneous samples of male and female Spanish schizophrenic patients. In males, we found an association between the homozygous Val genotype and the disorder, which resembled a recessive model (P = 0.022; odds ratio [OR] = 1.67). This Val homozygotes overrepresentation is produced at the expense of the heterozygous individuals decrease, whilst the Met homozygotes showed no differences when compared controls and patients. As a consequence, the heterozygous genotype in this sample had a protective effect (P = 0.03; OR = 0.65) and a strong deviation from Hardy–Weinberg equilibrium in male cases was observed (P = 0.006). In addition, a 2‐SNP haplotype analysis (rs4818‐Val158Met) confirmed there is an overrepresentation of the different homozygous Val genotypes in the male schizophrenic sample. Regarding females, we did not find any statistically significant association between COMT SNP and schizophrenia. In the light of this we suggest that the Val158Met SNP is involved in risk and protective genotypes for the vulnerability to schizophrenia in Spanish male population.

Association in alcoholic patients between Psychopathic Traits and the additive effect of allelic forms of theCNR1 andFAAH endocannabinoid genes, and the 3′ Region of theDRD2 Gene

Little is known about the genetic factors that underlie the comorbidity between alcohol use disorder and antisocial personality disorder. Previous studies have associated both, dopaminergic and endocannabinoid systems to severe alcoholism with non-adaptive disrupted behaviours. In this work we have examined some gene variants involved in such systems in a sample of alcoholic patients to test whether there is a relationship with antisocial traits. The genetic analysis involved the genotyping of the single nucleotide polymorphism (SNP) TaqIA located nearby theDRD2 gene, the 10-repeat allele of a variable number tandem repeats (VNTR) of theSLC6A3 gene, the C385AFAAH SNP and the 3′-UTR microsatellite ofCNR1 gene. The clinical study was performed in 137 Spanish alcohol dependent males. Antisocial Personality Disorder (DSM-IV) diagnosis was made by applying the International Personality Disorder Examination, and psychopathic traits were evaluated by the Hare’s Psychopathy Checklist Revised (PCL-R). The genotype distribution indicates there is a relationship between the TaqIA SNP,CNR1 andFAAH genes and PCL-R’s Factor 1 in alcoholic patients. This relationship seems to be additive and independent and might be responsible for 11.4% of the variance in this PCL-R subscale. Our results suggest the implication of the dopaminergic and endocannabinoid systems in those processes leading to the comorbidity of alcoholism and antisocial behaviour.

C957T DRD2 polymorphism is associated with schizophrenia in Spanish patients

Objective:  The objective was to confirm whether a homozygous genotype for the C957 allele of the C957T DRD2 gene single nucleotide polymorphism (SNP) is associated with schizophrenia in an independent study population.

Laboratory Paradigms of Impulsivity and Alcohol Dependence: A Review

Impulsivity can be defined as choosing a smaller, immediate reward over a larger, delayed reward. From this perspective, addictive behaviors such as substance abuse and pathological gambling reflect a series of impulsive choices. However, impulsivity is not a homogeneous construct. Laboratory measures of impulsivity reflect two types of processes. The first is related to behavioral inhibition and refers to an individual’s ability to appropriately inhibit thoughts or actions. The second is the delay of reward dimension, namely the degree to which immediate (rewarding) consequences have more control over an individual’s behavior than consequences that are delayed. In this review, we describe how alcohol is associated with significant impairments in these paradigms. We also suggest that they may have a role in the development of alcohol dependence. These results are in agreement with a model in which delay of gratification might be a marker for early use and/or abuse of alcohol, whereas impairment in behavioral inhibition might be a marker for maintained use in time and, therefore, for progression towards alcohol dependence.

From dopaminergic genes to psychiatric disorders

Individual vulnerability to develop neurological and psychiatric disorders is associated with both genetic and environmental factors. Association studies in patients have explored the contribution of gene variants in the dopaminergic system in these disorders. This system is involved in motor control, endocrinological function, the reward system and cognition. The diverse physiological functions of dopamine are mediated by five different dopamine receptors, encoded by the genesDRD1, DRD2, DRD3, DRD4 andDRD5. These genes have various types of polymorphisms that can produce changes in the genetic product or expression levels. In recent years, the development of new technologies for genetic analysis, and a wider comprehension of the genetic sequences of these genes have increased our understanding of the implications of the dopaminergic system in both health and pathological states. It has also allowed the identification of genetic variants that may represent risk or protection factors for a variety of psychiatric disorders.

Randomized trial of clozapine vs. risperidone in treatment-naïve first-episode schizophrenia: Results after one year

In first-episode patients with psychosis, clozapine may be potentially valuable as an initial treatment seeking to limit early on clinical and cognitive deterioration. Nevertheless, until recently its restricted use has limited the study of this possibility. Our research group is developing a non-commercial, multicentric and open label study on the differential efficacy between clozapine and risperidone in first-episode schizophrenia. In this paper, we present the results related to clinical variables after a one-year follow-up. So far, we have recruited 30 patients diagnosed with schizophrenia or schizophreniform disorder with illness duration of less than two years. The patients had not received any previous treatment and they were randomized to treatment with clozapine or risperidone. Our results indicate that on average, patients on clozapine adhered to their original treatment for a longer time period than patients on risperidone. By last observation carried forward (LOCF) analysis, patients on clozapine and risperidone displayed similar clinical improvements, although marginally greater improvements in positive and total symptoms scores were found in the clozapine group. At the 12-month point we observed a marginal improvement in negative symptom scores in patients on clozapine. Subjective secondary effects, as measured with the Udvalg for KliniskeUndersøgelser (UKU) scale, correlated negatively with negative symptoms at follow-up. Our data, although preliminary, suggest that clozapine may have a slightly superior efficacy in the initial year of treatment of first-episode treatment-naïve patients with schizophrenia, and this can be explained for the most part by greater adherence to this treatment.

Executive function in schizophrenia: Influence of substance use disorder history

Cognitive function in schizophrenia has been associated with different sociodemographic and clinical variables. Substance use disorder (SUD) history has also been associated with cognition in schizophrenia; however, contradictory results have been found regarding its influence on cognitive function. Our aim was to study the relationship between executive function and a) age, b) duration of illness, c) number of psychotic episodes, d) positive symptoms, and e) negative symptoms, in a sample of schizophrenic patients, and secondly to study whether these relationships persisted after stratification of the sample according to the presence or absence of SUD history. A final sample of 203 schizophrenic patients were evaluated for psychotic symptoms using the PANSS, and assessed using a neuropsychological battery to calculate a composite executive function score. Linear regression analyses were performed, with this executive score as the dependent variable, and age, duration of illness, number of psychotic episodes, positive PANSS score and negative PANSS score as independent variables. For the total sample, the regression model showed three variables to be significant predictors of the executive score: age (p=0.004), number of episodes (p=0.027), and PANSS negative score (p=0.003). However, once the sample was stratified, the regression model showed age (p=0.011) and number of episodes (p=0.011) to be predictor variables for the executive score in the group of schizophrenic patients with SUD history, while age (p=0.028) and PANSS negative score (p=0.006) were predictors in the group of schizophrenic patients without such history. These findings highlight the importance of considering SUD history in studies of cognitive function in schizophrenia.

DRD2 TaqIA polymorphism is associated with urinary homovanillic acid levels in a sample of spanish male alcoholic patients

TheTaqIA1 allele of the dopamine receptor gene D2 (DRD2) has been associated with alcoholism, as well as with other addictive behaviours. The exact nature of how the presence of this allele can be a vulnerability factor in the development of alcoholism remains unclear. In this study we found that the presence in theDRD2 genotype of theTaqIA1 allele in Spanish alcoholics is associated with higher levels of urine homovanillic acid (HVA) when compared to patients homozygous for theTaqIA2 allele.A sample of 142 Spanish male alcoholic patients was split into 2 groups on the basis of the presence or absence of the A1 allele in their genotype. The urine sample was analyzed by high performance liquid cromatography (HPLC), and the concentration of homovanillic acid (HVA), 5-hydroxyin-doleacetic acid (5-HIAA) and vanilylmandelic acid (VMA) was determined. We found a statistical difference in the concentration of HVA between the groups, that suggests this polymorphism could be related to the variance of urine HVA levels.