Jean-Pierre Olié

Brain Derived Neurotrophic Factor (BDNF) gene variants association with age at onset and therapeutic response in schizophrenia

Schizophrenia is a heterogeneous disease involving genetic and environmental factors. The frequency of structural brain abnormalities1, 2 or physical anomalies3supports a neurodevelopmental etiology, especially in early onset schizophrenia.4Brain-Derived-Neurotrophic-Factor (BDNF) is involved in the neurodevelopment of dopaminergic (DA)-related systems5, 6 and interacts with the meso-limbic DA systems,7, 8, 9, 10 involved in the therapeutic response to antipsychotic drugs11 and substance abuse.12 In addition, BDNF promotes and maintains dopamine D3 receptor (DRD3) expression.13 In a French Caucasian population, we found no statistical difference in allele or genotype distribution of the BDNF gene dinucleotide repeat polymorphism (166–174 bp)14 between the whole group of schizophrenic patients and controls. By contrast, an excess of the 172–176 bp alleles was found in patients with late onset, in neuroleptic-responding patients and in non-substance-abusing patients. BDNF gene variants thus appear to be associated with developmental features of schizophrenia. In addition, this association with good treatment responding was independent from the association found with the DRD3 BalI gene polymorphism in the same population.15 These results suggest an independent contribution of each gene to a treatment-sensitive form of schizophrenia.

Prevalence of smoking in psychiatric patients

Compelling evidence that tobacco-smoking is a form of drug addiction exists. The aim of this study is to determine the following: (1) prevalence of tobacco-smoking and of nicotine dependence in French psychiatric patients; (2) rates and patterns of tobacco smoking and of nicotine dependence according to diagnosis; (3) relationship between current smoking status and antipsychotic medications; and (4) relationship between cigarette smoking and neurological side effects induced by neuroleptics. A population of 711 psychiatric in- and outpatients was assessed using: (1) a detailed smoking self-questionnaire for smoking history and nicotine dependence; and (2) a questionnaire for staff covering treatments and DSMIII-R diagnoses. Data were analyzed using chi2 analysis of variance (ANOVA) tests (one factor) for quantitative comparisons between groups of patients, and analysis of covariance (ANCOVA) test with age covariate was performed for age-dependent variables. Prevalence of smoking in the population of psychiatric patients was significantly higher than in the French general population. Diagnoses among current smokers were mainly substance-related disorder and schizophrenia. The authors established correlations between prevalence of smoking and age, sex, marital and socioeconomic status, alcohol use, coffee consumption and other psychoactive substance use or abuse. The authors did not find relationship between smoking prevalence and institutionalization. Neuroleptic neurological side effects were significantly fewer among smokers compared to nonsmokers. However, the rate of smokers was significantly higher in psychiatric patients receiving neuroleptic drugs. Nicotine abuse in psychiatric patients, and especially in schizophrenic patients, could support the hypothesis that smoking is consistent with self-medication.

Dopamine D3 receptor gene variants and substance abuse in schizophrenia

In an association study of the Bal I polymorphism in the dopamine D3 receptor (DRD3) gene in a French Caucasian population, global comparison of patients with schizophrenia (n = 89, DSM-III-R criteria) and controls (n = 52) led to non-significant differences. However, the homozygosity was significantly more frequent in schizophrenic patients with lifetime substance abuse comorbidity (n = 36) as compared to patients with no history of substance abuse (P = 0.010) or to controls (P = 0.047) and in neuroleptic responder patients as compared to treatment-refractory patients (n = 19; P = 0.037). The combined characteristics treatment response and lifetime substance abuse were strongly associated with homozygosity. We propose that homozygosity for the Bal I polymorphism DRD3 gene is associated with predisposition to substance abuse and/or the pharmacosensitive characteristic of schizophrenia rather than with schizophrenia itself, an hypothesis in agreement with the positive association of this polymorphism with opiate dependence (see companion article by Duaux et al) and the involvement of DRD3 in both pharmacodependence mechanisms and antipsychotic effects of neuroleptics.

5HTTLPR polymorphism in schizophrenic patients: Further support for association with violent suicide attempts

Previous studies testing the functional polymorphism in the promoter of the serotonin‐transporter gene (5HTTLPR) in various psychiatric conditions have suggested that the association could be with an intermediate phenotype, impulsivity and/or violence rather than with a diagnosis. Schizophrenia is associated with a high risk of suicide, especially in patients with high impulsivity. We examined whether this polymorphism could be associated with violent suicide and/or impulsivity in schizophrenic patients. We genotyped the 5HTTLPR polymorphism in 185 unrelated schizophrenic patients from a French Caucasian population. The genotype frequencies significantly differed between patients who made violent suicide attempts and both, those who attempted suicide with a non‐violent method (P = 0.013) and those who never attempted suicide (P = 0.026). The genotypes containing the low activity “short” allele was significantly more frequent in violent suicide attempters (P = 0.007) than in non‐violent suicide attempters. No evidence was found for an association either with schizophrenia itself, when compared to gender and ethnically matched controls (n = 159) or with impulsivity, assessed using Barratts Impulsivity Scale. Although replication studies are warranted, these results in schizophrenia further support the hypothesis that 5HTTLPR polymorphism is a risk factor for violent suicidal behavior.

Histamine H2 receptor gene variants: lack of association with schizophrenia.

A role of histaminergic neuronal systems in schizophrenia was suggested by an association with several polymorphisms located in the coding region of the histamine H2-receptor (H2R) gene (Orange et al, Mol Psychiatry 1996; 1: 466–469). Using either the reference method of direct sequencing or restriction endonuclease digestion of PCR products amplified from DNA, we could not confirm the existence of these polymorphisms in 53 Swedish controls, 52 French controls and 88 French schizophrenics. In contrast, we detected a G543A transition in the coding region of the gene that was not found in the British population. This allelic variation, which was observed in 15% of the controls with no homozygotes, did not change the amino acid sequence of the receptor. We also analyzed a 1.8-kb nucleotide sequence of the promoter region in which we detected two additional polymorphisms that may modulate the expression of the H2R gene. The first one was a A-592G transition located in the minimal promoter of the gene and found in ˜10% of controls with no homozygotes. The second one was a G-1018A transition located in an enhancer element of the promoter and was found in ˜20–30% of controls (with ˜2–4% homozygotes). DNA analysis of the 88 French schizophrenic subjects revealed that the incidence of the three polymorphisms was not significantly different in this population. In conclusion, the present findings may suggest a surprisingly high variability of the H2R gene polymorphisms in different geographical areas but do not support an association of these allelic variations with schizophrenia.

Prospects for anxiolytic therapy: a reflection from different viewpoints

Abstract Benzodiazepines are the most commonly used and effective treatment of symptoms of anxiety, but they have drawbacks. The current challenge is to discover partial agonists that do not cause the adverse effects characteristic of benzodiazepines. The authors discuss the main drugs that are used in the treatment of acute anxiety and some of the current or future alternatives and also highlight several problems that need to be resolved in the development of new anxiolytics.