Jun-ichi Iga

Brain-derived neurotrophic factor (BDNF) Val66Met polymorphism in schizophrenia is associated with age at onset and symptoms

Brain-derived neurotrophic factor (BDNF) is a neurotrophic factor that promotes several functions of neurons and modulates neurotransmissions. It has been reported that there are alterations of BDNF levels in schizophrenic brains and that BDNF gene expressional changes would be responsible for the etiology of schizophrenia. Recent studies have shown that a variation of BDNF gene (Val66Met polymorphism) affects the function of neurons, and is associated with several neurological and psychiatrical disorders. We investigated the relationship between BDNF Val66Met polymorphism and the onset age as well as levels of clinical symptoms in 159 of chronic schizophrenia in-patients diagnosed by DSM-IV. The mean onset ages were 27.5+/-9.5 for BDNF Val/Val, 25.5+/-7.4 for BDNF Val/Met and 22.9+/-6.0 for BDNF Met/Met and this polymorphism was significantly associated with age at onset (P=0.023). The mean Brief Psychiatric Rating Scale scores (BPRS) were significantly different among those three groups (P=0.003). No significant differences were demonstrated comparing the BDNF genotype distributions of positive and negative family history (P=0.21). Our investigation indicates that the BDNF gene Val66Met polymorphism is related to the onset age of schizophrenia and the levels of clinical symptoms that remain after long-term antipsychotic treatment.

GABA concentration in schizophrenia patients and the effects of antipsychotic medication: A proton magnetic resonance spectroscopy study

Gamma-amino butyric acid (GABA) is thought to play a role in the pathophysiology of schizophrenia. High magnetic field proton magnetic resonance spectroscopy ((1)H-MRS) provides a reliable measurement of GABA in specific regions of the brain. This study measured GABA concentration in the anterior cingulate cortex (ACC) and in the left basal ganglia (ltBG) in 38 patients with chronic schizophrenia and 29 healthy control subjects. There was no significant difference in GABA concentration between the schizophrenia patients and the healthy controls in either the ACC (1.36+/-0.45 mmol/l in schizophrenia patients and 1.52+/-0.54 mmol/l in control subjects) or the ltBG (1.13+/-0.26 mmol/l in schizophrenia patients and 1.18+/-0.20 mmol/l in control subjects). Among the right handed schizophrenia patients, the GABA concentration in the ltBG was significantly higher in patients taking typical antipsychotics (1.25+/-0.24 mmol/l) than in those taking atypical antipsychotics (1.03+/-0.24 mmol/l, p=0.026). In the ACC, the GABA concentration was negatively correlated with the dose of the antipsychotics (rs=-0.347, p=0.035). In the ltBG, the GABA concentration was positively correlated with the dose of the anticholinergics (rs=0.403, p=0.015). To the best of our knowledge, this is the first study to have directly measured GABA concentrations in schizophrenia patients using (1)H-MRS. Our results suggest that there are no differences in GABA concentrations in the ACC or the ltBG of schizophrenia patients compared to healthy controls. Antipsychotic medication may cause changes in GABA concentration, and atypical and typical antipsychotics may have differing effects. It is possible that medication effects conceal inherent differences in GABA concentrations between schizophrenia patients and healthy controls.

Gene expression and association analysis of vascular endothelial growth factor in major depressive disorder.

Vascular endothelial growth factor (VEGF) has been implicated in neuronal survival, neuroprotection, regeneration, growth, differentiation, and axonal outgrowth, which are known to be involved in the pathophysiology of major depressive disorder (MDD). Recently, the VEGF mRNA expression in the peripheral leukocytes from Alzheimers disease or cardiovascular disease was reported to be changed. We hypothesized that the expression of the VEGF mRNA in the peripheral leukocytes may be a good candidate for the biological marker for MDD. Thirty two patients with MDD and age- and sex-matched control subjects were included in this expression study. The VEGF mRNA levels in the peripheral leukocytes from drug-naive MDD patients were significantly higher than those from the control subjects and the magnitude of the decrease of VEGF mRNA after 8-week treatment significantly correlated with clinical improvement. Then, we genotyped two single nucleotide polymorphic markers of VEGF gene, which were reported to be associated with amyotrophic lateral sclerosis and Alzheimers disease, in patients with MDD and control subjects (n=154, each). We did not find any significant association between these markers and MDD or its clinical subtypes. Our investigation indicates that the higher expression levels of VEGF mRNA in the peripheral leukocytes are associated with the depressive state and their recovery after treatment may be associated with the clinical improvement.

The Val66Met polymorphism of the brain‐derived neurotrophic factor gene is associated with psychotic feature and suicidal behavior in Japanese major depressive patients

Recent researches have suggested that brain‐derived neurotrophic factor (BDNF) may be implicated in the pathophysiology of mood disorder. This study examined the association between the BDNF Val66Met polymorphism and major depressive disorder (MDD) in a Japanese population. We genotyped the BDNF Val66Met polymorphism in 154 major depressive patients and 154 age‐ and sex‐matched control subjects. The genotypic distributions and allele frequencies were similar among the patients and control subjects. When the relationships of the polymorphism with several clinical variables (i.e., age, sex, age of onset, number of episode, presence of psychotic features, suicidal behavior, and family history) were examined, the dose of Met allele had significant effects on psychotic feature and suicidal behavior and family history. These results suggest that the BDNF Val66Met polymorphism is not related to the development of MDD but related to clinical features of MDD in a Japanese population.

Metabolite changes and gender differences in schizophrenia using 3-Tesla proton magnetic resonance spectroscopy (1H-MRS)

A change in the glutamatergic system is thought to play an important role in the pathophysiology of schizophrenia. The aim of this study was to investigate the changes in metabolites, including glutamate (Glu), in the anterior cingulate cortex (ACC) and the left basal ganglia (ltBG) of patients with chronic schizophrenia using proton magnetic resonance spectroscopy ((1)H-MRS). In addition, since gender differences in this illness were known, we examined the effects of gender on these metabolites. The (1)H-MRS was performed on the ACC and ltBG of 30 patients with schizophrenia and 25 healthy individuals who acted as the control group. The levels of Glu, glutamine (Gln), creatine plus phosphocreatine (Cre), myo-inositol (mI), N-acetylaspartate (NAA), and choline-containing compounds (Cho) were measured. Two-way analysis of variance revealed that the illness significantly affected the levels of Glu and mI in the ACC; both metabolites were lower in the patients with schizophrenia as compared to the control subjects. The results also revealed that gender significantly affected the level of Gln in the ACC and the levels of Cre and NAA in the ltBG; the level of Gln in the ACC were higher in male subjects versus female subjects, whereas Cre and NAA levels in the ltBG were lower in male subjects as compared to female subjects. These results confirmed a change in the glutamatergic system and suggested an involvement of mI in the pathophysiology of schizophrenia.

Predictors of subjective and objective quality of life in outpatients with schizophrenia

Aim:  In recent years, greater attention has been given to quality of life (QOL) in schizophrenia and several studies reported that negative and depressive symptoms and cognitive dysfunction are related to patient QOL. But because a variety of QOL measures have been used in the previous studies, there seems to be no unanimous predictors for subjective and objective QOL. The purpose of the present study was to elucidate the relationship between clinical variables and subjective and objective QOL in outpatients with schizophrenia, using schizophrenia disease‐specific QOL measures. Particular attention was paid to cognitive function as a predictor of QOL.

Serotonin transporter mRNA expression in peripheral leukocytes of patients with major depression before and after treatment with paroxetine

Serotonin transporter (5HTT) is thought to be involved in the pathophysiology of major depression and the target of antidepressants. We hypothesized that 5HTT mRNA levels in peripheral leukocytes may be associated with depressive states and the therapeutic response to antidepressant treatments. Fifteen patients with major depression and age-, sex-matched control subjects were studied. 5HTT mRNA levels were determined with quantitative real-time PCR method. 5HTT mRNA levels in leukocytes were significantly higher in depressive patients at baseline (before medication) than in control subjects. 5HTT mRNA levels were decreased significantly after 8 weeks of paroxetine medication compared with those at baseline. Our investigation suggested that the increased expression of 5HTT mRNA in peripheral leukocytes may be related with the pathophysiology of depression and its reduction after treatment may reflect the adaptive change induced by the antidepressant.

Positive association of the PDE4B (phosphodiesterase 4B) gene with schizophrenia in the Japanese population

The phosphodiesterase 4B (PDE4B) gene is located at 1p31, a susceptibility region for schizophrenia (SZ). Moreover, PDE4B interacts with DISC1, which is a known genetic risk factor for SZ. Recently, it was reported that the PDE4B gene is associated with SZ in Caucasian and African American populations. In this study, case-controlled association analyses were performed in the Japanese population to determine if the PDE4B gene is implicated in SZ. Thirteen single nucleotide polymorphisms (SNPs) were analyzed in 444 schizophrenic patients and 452 control subjects. Three SNPs (rs2180335, rs910694 and rs472952) were significantly associated with SZ after applying multiple test correction (p=0.039, 0.004 and 0.028). In addition, a significant association was found between specific haplotypes (rs2180335 and rs910694) and SZ (permutation p=0.001). Our result suggests that variations at the PDE4B locus may play a significant role in the etiology of SZ in the Japanese population.

Blood diagnostic biomarkers for major depressive disorder using multiplex DNA methylation profiles: discovery and validation.

Aberrant DNA methylation in the blood of patients with major depressive disorder (MDD) has been reported in several previous studies. However, no comprehensive studies using medication-free subjects with MDD have been conducted. Furthermore, the majority of these previous studies has been limited to the analysis of the CpG sites in CpG islands (CGIs) in the gene promoter regions. The main aim of the present study is to identify DNA methylation markers that distinguish patients with MDD from non-psychiatric controls. Genome-wide DNA methylation profiling of peripheral leukocytes was conducted in two set of samples, a discovery set (20 medication-free patients with MDD and 19 controls) and a replication set (12 medication-free patients with MDD and 12 controls), using Infinium HumanMethylation450 BeadChips. Significant diagnostic differences in DNA methylation were observed at 363 CpG sites in the discovery set. All of these loci demonstrated lower DNA methylation in patients with MDD than in the controls, and most of them (85.7%) were located in the CGIs in the gene promoter regions. We were able to distinguish patients with MDD from the control subjects with high accuracy in the discriminant analysis using the top DNA methylation markers. We also validated these selected DNA methylation markers in the replication set. Our results indicate that multiplex DNA methylation markers may be useful for distinguishing patients with MDD from non-psychiatric controls.

Gene expression and association analyses of the phosphodiesterase 4B (PDE4B) gene in major depressive disorder in the Japanese population

The phosphodiesterase 4B (PDE4B) interacts with disrupted‐in‐schizophrenia 1 (DISC1), which is a known genetic risk factor for schizophrenia, bipolar disorder and major depressive disorder (MDD). PDE4B is also important in the regulation of cAMP signaling, a second messenger implicated in learning, memory, and mood. In this study, we determined mRNA expression levels of the PDE4B gene in the peripheral blood leukocytes of patients with MDD and control subjects (n = 33, each). Next we performed two‐stage case‐controlled association analyses (first set; case = 174, controls = 348; second set; case = 481, controls = 812) in the Japanese population to determine if the PDE4B gene is implicated in MDD. In the leukocytes, a significantly higher expression of the PDE4B mRNA was observed in the drug‐naïve MDD patients compared with control subjects (P < 0.0001) and the expression of the MDD patients significantly decreased after antidepressant treatment (P = 0.030). In the association analysis, we observed significant allelic associations of four SNPs (the most significant, rs472952; P = 0.002) and a significant haplotypic association (permutation P = 0.019) between the PDE4B gene and MDD in the first‐set samples. However, we could not confirm these significant associations in the following independent second‐set of samples. Our results suggest that the PDE4B gene itself does not link to MDD but the elevated mRNA levels of PDE4B might be implicated in the pathophysiology of MDD.