Association of copy number polymorphisms at the promoter and translated region of COMT with Japanese patients with schizophrenia.

Chromosome 22q11.2 deletion syndrome and genetic variations including single-nucleotide polymorphism (SNP) and copy number variation (CNV) in catechol-O-methyltransferase (COMT) situated at 22q11.2 remains controversial. Here, the genetic relationship between COMT and Japanese patients with schizophrenia was investigated by examining whether the SNPs correlated with schizophrenia based on a common disease-common variant hypothesis. Additionally, 22q11.2DS were screened based on a common disease-rare variant hypothesis; low-frequency CNVs situated at two COMT promoters and exons were investigated based on the low-frequency variants with an intermediate effect; and positive findings from the first stage were reconfirmed using a second-stage replication study including a larger sample size. Eight SNPs and 10 CNVs were investigated using Taqman SNP and CNV quantitative real-time polymerase chain reaction method. For the first-stage analysis, 513 unrelated Japanese patients with schizophrenia and 705 healthy controls were examined. For the second-stage replication study, positive findings from the first stage were further investigated using a larger sample size, namely 1,854 patients with schizophrenia and 2,137 controls. The first-stage analysis showed significant associations among schizophrenia, intronic SNP rs165774, CNV6 situated at promoter 1, CNV8 at exon 6, and CNV9 at exon 7. The second-stage study showed that intronic SNP rs165774 (χ(2) = 8.327, P = 0.0039), CNV6 (χ(2) = 19.66, P = 0.00005), and CNV8 (χ(2) = 16.57, P = 0.00025) were significantly associated with schizophrenia. Large and rare CNVs as well as low-frequency CNVs and relatively small CNVs, namely <30 kb in COMT, may be genetic risk factors for schizophrenia.

Associations of common copy number variants in glutathione S-transferase mu 1 and D-dopachrome tautomerase-like protein genes with risk of schizophrenia in a Japanese population.

Oxidative-stress, genetic regions of interest (1p13 and 22q11), and common copy number variations (CNVs) may play roles in the pathophysiology of schizophrenia. In the present study, we confirmed associations between schizophrenia and the common CNVs in the glutathione (GSH)-related genes GSTT1, DDTL, and GSTM1 using quantitative real-time polymerase chain reaction analyses of 620 patients with schizophrenia and in 622 controls. No significant differences in GSTT1 copy number distributions were found between patient groups. However, frequencies of characterized CNVs and assumed gain alleles of DDTL and GSTM1 were significantly higher in patients with schizophrenia. In agreement with a previous report, the present data indicate that gains in the CNV alleles DDTL and GSTM1 are genetic risk factors in Japanese patients with schizophrenia, and suggest involvement of micro-inflammation and oxidative stress in the pathophysiology of schizophrenia.

Altered serum glyceraldehyde-derived advanced glycation end product (AGE) and soluble AGE receptor levels indicate carbonyl stress in patients with schizophrenia.

Recent cross-sectional and longitudinal studies indicate that measurements of peripheral blood carbonyl stress markers such as the advanced glycation end product (AGE) pentosidine and the reactive carbonyl-detoxifying B6 vitamin pyridoxal could be used as therapeutic biological markers in subpopulations of schizophrenia patients. Glyceraldehyde-derived AGEs (Glycer-AGE) have strong neurotoxicity, and soluble receptors for AGEs (sRAGE) may ameliorate the effects of AGEs. In the present study, we measured Glycer-AGEs and sRAGE levels to determine their potential as diagnostic, therapeutic, or clinical biological markers in patients with schizophrenia. After enrollment of 61 admitted Japanese patients with acute schizophrenia and 39 healthy volunteers, 54 patients were followed up from the acute stage to remission. Serum biomarkers were measured in blood samples taken before breakfast using competitive enzyme-linked immunosorbent assays, and Glycer-AGEs were significantly higher and sRAGE levels were significantly lower in patients with acute schizophrenia than in healthy controls. Glycer-AGEs/sRAGE ratios were also higher in schizophrenia patients and were stable during the clinical course. Furthermore, discriminant analyses confirmed that Glycer-AGEs and Glycer-AGEs/sRAGE ratios are significant diagnostic markers for schizophrenia, and distinguished between patients and healthy controls in 70.0% of cases. However, these markers of carbonyl stress were not correlated with clinical features, including disease severity, or with daily chlorpromazine doses. These data indicate the potential of Glycer-AGEs, RAGEs, and their relative ratios as diagnostic markers for patients with schizophrenia.

Significance of measurements of peripheral carbonyl stress markers in a cross-sectional and longitudinal study in patients with acute-stage schizophrenia.

Altered peripheral carbonyl stress markers, high levels of serum pentosidine, which accumulates following carbonyl stress, and low levels of pyridoxal (vitamin B6), which detoxifies reactive carbonyl compounds, have been reported in a cross-sectional study of chronic schizophrenia. However, changes in the levels of these compounds in patients with schizophrenia have not been investigated in a longitudinal study. To clarify whether these markers may be biological markers that reflect the clinical course of the disease, the serum levels of these compounds were investigated in a cross-sectional and a longitudinal study. One hundred and thirty-seven acute-stage Japanese patients were enrolled. Among these, 53 patients were followed from the acute stage to remission. A portion of patients in the acute stage (14 cases, 10.2%) showed extremely high pentosidine levels. These levels were not associated with the severity of symptoms but were associated with antipsychotic dose amounts. Pyridoxal levels were lower in schizophrenia and increased according to the clinical course of the illness. Furthermore, 18 patients with decreased pyridoxal levels according to the clinical course showed that the greater the decrease in pyridoxal levels, the lesser the improvement in symptoms. Thus, extremely high pentosidine levels in a portion of patients may be caused by higher daily antipsychotic doses, whereas pyridoxal levels were lower in schizophrenia and increased according to the clinical course. Patients with decreasing pyridoxal levels during the clinical course showed less improvement in symptoms. Carbonyl stress markers may also be therapeutic biological markers in some patients with schizophrenia.

No correlation between plasma NMDA-related glutamatergic amino acid levels and cognitive function in medicated patients with schizophrenia.

OBJECTIVE: Disrupted glutamatergic neurotransmission and cognitive functions are key components in the pathophysiology of schizophrenia. Changes in levels of serum/plasma glutamatergic amino acids, such as glutamate, glycine, and L- and D-serine may be possible clinical markers. Following our recent findings that peripheral blood levels of endogenous glycine, alanine, and especially D-serine may reflect the degree/change in symptoms in schizophrenia, here we investigated whether these plasma amino acid levels may also reflect the status of cognitive functions in schizophrenia. METHODS: One hundred eight Japanese patients with schizophrenia were evaluated with cognitive assessment batteries at the time that plasma glutamatergic amino acid levels were measured using high-performance liquid chromatography. For analyzing cognitive functions, batteries for reflection prefrontal cortex cognitive functions, verbal fluency tests, the Stroop test, and the digit span forward and backward tests were administered. RESULTS: Results failed to show a relationship between any plasma glutamatergic amino acid level and cognitive batteries. CONCLUSIONS: Our results suggest that plasma glutamatergic amino acid levels may be significant biological markers that reflect the condition or a dramatic change at the time of testing, especially in severely affected patients, but they do not reflect cognitive function.

No Associations Found between PGBD1 and the Age of Onset in Japanese Patients Diagnosed with Sporadic Alzheimer's Disease.

BACKGROUND/AIMS: PiggyBac transposable element derived 1 (PGBD1) encodes a molecule involved in epigenetic mechanisms that have been implicated in Alzheimer's disease (AD), and recent genome-wide association studies and meta-analyses have indicated that a single nucleotide polymorphism (SNP), rs3800324, in PGBD1 could be associated with AD and the age of onset. However, no Japanese patients were examined in these studies. The aim of the present study was to replicate the previous finding in Japanese AD cases. METHODS: We performed a case-control study (211 cases and 156 controls) to investigate the association between PGBD1 and Japanese AD using 4 tag SNPs including rs3800324. RESULTS: Single SNP and haplotype analysis showed no association between AD and age of onset, whereas genotypic and allelic frequencies of the ∊4 of apolipoprotein E (APOE) showed an association with AD as expected. CONCLUSION: In Japanese AD, we observed no influence of PGBD1, as either a risk factor or a modifier, even though APOE was associated with AD in this population.

No genetic association between SLC7A10 and Japanese patients with schizophrenia.

Disrupted glutamatergic neurotransmission may be a pathophysiological feature in the brains from patients with schizophrenia, and glutamatergic amino acids including D-serine have been found to be involved in pathophysiology. Endogenous and exogenous D-serine have shown potential as biological markers for the pathophysiology of schizophrenia and especially as a therapeutic strategy in treatment-resistant schizophrenia (TRS). This is the first study investigating whether SLC7A10, a d-serine transporter gene, is associated with schizophrenia in Japanese patients. We investigated the association between schizophrenia in Japanese patients with SLC7A10 using six tag single nucleotide polymorphisms (SNPs). Results failed to show any association between Japanese schizophrenia and each individual SNP or with two-, three-, or four-window haplotype analyses. We also investigated whether SLC7A10 contributes to TRS in Japanese participants. Results showed no association. In conclusion, SLC7A10 had no apparent degree of association with schizophrenia as a candidate susceptibility gene in the disease per se.

Association study between Disrupted-in-Schizophrenia-1 (DISC1) and Japanese patients with treatment-resistant schizophrenia (TRS).

Treating the 20-30% of patients with schizophrenia whose symptoms are resistant to antipsychotic treatment, a condition known as treatment-resistant schizophrenia (TRS), can be problematic. Recently, an association between Disrupted-in-Schizophrenia-1 (DISC1), a candidate susceptibility gene for schizophrenia, and TRS was reported. Associations between three missense SNPs, rs3738401 (Q264R), rs6675281 (L607F), and rs821616 (S704C) in DISC1, especially rs3738401, showed strong significance. Thus, the main aim of our current study was to examine if the reported possible functional polymorphisms in DISC1 were related to Japanese TRS. First, DISC1 was re-investigated in 485 Japanese patients with schizophrenia and 660 healthy controls with a case-control study using four candidate SNPs, rs751229, rs3738401, rs821597, and rs821616. DISC1 was not associated with schizophrenia in the Japanese population. Second, we investigated whether these SNPs contributed to TRS in 127 inpatients with schizophrenia (35 patients; TRS and 92 patients; non-TRS). The genotypic distributions of these four SNPs were not significantly different between TRS and non-TRS in either genotypic or recessive models of minor alleles. In addition, clinical variables, such as improvement in clinical symptoms, duration of hospitalization, and total antipsychotics dose amounts, were not different among the genotypes of these SNPs. Taken together, results showed that DISC1 had no apparent degree of association with Japanese patients with schizophrenia as a candidate susceptibility gene for disease per se or TRS.

No association between glutathione-synthesis-related genes and Japanese schizophrenia.

AIMS: Schizophrenia is a major psychiatric disorder with complex genetic, environmental, and psychological causes, and oxidative stress may be involved in the pathogenesis of the disease. Glutathione (GSH), one of the main cellular non-protein antioxidants and redox regulators, and altered GSH levels have been reported in various regions in patients with schizophrenia. Three enzymes are responsible for GSH synthesis: glutamate cysteine ligase modifier (GCLM), glutamate cysteine ligase catalytic subunit (GCLC), and glutathione synthetase (GSS). Previously, positive associations between GCLM and schizophrenia were reported in Europeans, but not in the Japanese population. Thus, in this study, we investigated the association between the GSH synthesis genes (GCLM, GCLC, and GSS) and schizophrenia in Japanese individuals. METHODS: Seventeen single-nucleotide polymorphisms (SNP) in GCLM, GCLC, and GSS were genotyped in 358 patients with schizophrenia and in 359 controls. RESULTS: No SNP showed a significant association between their allelic or genotypic frequencies and schizophrenia. Case-control haplotype association analysis using windows of two or three SNP showed no significant associations with schizophrenia. The case-control haplotype analyses based on the ascertained linkage disequilibrium blocks also showed no significant associations in any genes with schizophrenia. CONCLUSIONS: The three primary GSH synthesis genes do not have an apparent degree of association with schizophrenia in the Japanese population.

Plasma alanine levels increase in patients with schizophrenia as their clinical symptoms improve-Results from the Juntendo University Schizophrenia Projects (JUSP).

UNLABELLED: Since oral administration of d-alanine, an agonist that binds to the glycine site of N-methyl-d-aspartate (NMDA) receptors, improves the positive and cognitive symptoms of patients with schizophrenia, measurement of endogenous plasma alanine levels could serve as a clinical marker for schizophrenia severity and improvement. Mean plasma alanine levels were compared in healthy controls and patients with schizophrenia during the clinical course of the disease. METHODS: eighty-one Japanese patients with schizophrenia and 50 age- and gender-matched healthy controls were studied. Plasma alanine levels were measured twice, during the acute stage and during the remission stage, using high-performance liquid chromatography. On admission, lower plasma alanine levels in patients with schizophrenia were accompanied by more severe schizophrenic symptoms, especially positive symptoms. The plasma alanine levels in patients with schizophrenia increased significantly from the time of admission to discharge, when they were significantly higher than control levels. An increase in plasma alanine levels from the acute stage to the remission stage of schizophrenia was correlated with improvement in symptoms. Drug-naïve patients did not show a significant difference in plasma alanine levels when compared with healthy controls. The measurement of plasma alanine levels may be a therapeutic marker for schizophrenia.

Association analysis between functional polymorphism of the rs4606 SNP in the RGS2 gene and antipsychotic-induced Parkinsonism in Japanese patients with schizophrenia: results from the Juntendo University Schizophrenia Projects (JUSP).

Antipsychotic-induced extrapyramidal symptoms (AIEPSs) are commonly recognized side effects of typical 1st generation antipsychotics, and considerable variability is seen in the susceptibility of individual patients to AIEPSs. Regulator of G-protein signaling 2 (RGS2) proteins regulate intracellular signaling and second messenger activation of molecules including dopamine, serotonin, and acetylcholine receptors, all of which appear to be involved in the pathophysiology of AIEPSs. Previous studies have shown an association between AIEPSs in schizophrenia and RGS2, especially the minor G allele of single nucleotide polymorphism (SNP) rs4606 (+2971C>G) in RGS2, and have suggested a possible protective effect by the G allele on AIEPSs. In this study, we investigated whether the rs4606 SNP in RGS2 alone also showed an effect on AIEPSs by utilizing the Drug-Induced Extrapyramidal Symptom Scale (DIEPSS) in 103 Japanese patients with schizophrenia. In the assumed G allele recessive model, sialorrhea and total Parkinsonism scores were significantly higher in subjects with the GG genotype than in subjects with other genotypes. Other clinical variables were not significantly different among the various genotype groups. Controlling for clinical variables as covariates, a one-way analysis of covariance found no association between rs4606 genotypes and DIEPSS scores. Taken together, these results, although preliminary, suggest that rs4606 does not affect AIEPSs in Japanese subjects.

No genetic association between the SLC1A2 gene and Japanese patients with schizophrenia.

Glutamatergic dysfunction may be a pathophysiological feature in the brains of schizophrenic patients. In addition to glutamate receptors, excitatory amino acid transporters (EAATs) have received much attention because they directly affect glutamatergic neurotransmission by excluding excessive glutamate from the synaptic cleft. Among these, EAAT2 (also known as solute carrier family 1, member 2; SLC1A2) has been widely studied in schizophrenia pathophysiology. During the last decade, we reported significant decreases in EAAT2 mRNA expression in the prefrontal cortex and parahippocampal gyrus in postmortem schizophrenic brains. Previously, a haplotype association between SLC1A2 and Japanese patients with schizophrenia was reported. In this study, we reinvestigated the association between SLC1A2 and schizophrenia by performing a case-control association study with twice as many subjects (401 cases and 407 controls) as compared to a previous study, and especially focused on the region where a previous association with schizophrenia had been shown. Our current results failed to show any significant association with schizophrenia in individual single nucleotide polymorphisms (SNPs), two- and three-SNP-based haplotypes, or with possible pairwise haplotype analysis. SCL1A2 appears not to be a genetic risk factor for schizophrenia.

Association analysis of glycine- and serine-related genes in a Japanese population of patients with schizophrenia.

Differences in the levels of the glutamate-related amino acids glycine and serine in brain/plasma between schizophrenic patients and normal subjects and changes in the plasma concentrations of these amino acids according to the clinical course have been reported. It has been hypothesized that glycine and serine metabolism may be altered in schizophrenia. In fact, some genes related to the metabolism of these amino acids have been suggested to be candidate genes for schizophrenia. Thus, we performed a genomic case-control analysis of amino acid metabolism-related genes in Japanese patients with schizophrenia. Case-control genetic association analysis of PHGDH, SHMT1, SRR, and DAO was performed. In addition, the effect of the various genotypes resulting from these four genes on changes in plasma amino acid levels in schizophrenia was assessed. The genetic case-control analysis showed that no individual single-nucleotide polymorphism (SNP) in any of the four genes was associated with schizophrenia; only the two (rs3918347-rs4964770, P=0.0009) and three (rs3825251-rs3918347-rs4964770, P=0.002) SNP-based haplotype analysis of the DAO gene showed an association with schizophrenia even after correction for multiple testing. None of the genotypes studied was associated with changes in the plasma glycine and l- and d-serine levels during the schizophrenic clinical course. The DAO gene may be a susceptibility locus for schizophrenia.

Changes in plasma glycine, L-serine, and D-serine levels in patients with schizophrenia as their clinical symptoms improve: results from the Juntendo University Schizophrenia Projects (JUSP).

OBJECTIVES: Based on the hypothesis of NMDA receptor hypofunction in schizophrenia, plasma glycine, L-serine, and D-serine levels have been studied, since they could serve as biological markers. However, changes over time in the levels of these amino acids in schizophrenic patients have not been investigated. To clarify the mean plasma glycine, L-serine, and D-serine levels in patients with schizophrenia, levels of these amino acids were compared between healthy controls and patients with schizophrenia. The plasma levels of these amino acids during the clinical course of schizophrenia were also compared. METHODS: Eighty-nine Japanese patients with schizophrenia and 50 age- and gender-matched healthy controls were studied. Plasma glycine, L-serine, and D-serine levels and their ratios were measured twice, during the acute stage and during the remission stage, using high-performance liquid chromatography. RESULTS: The admission plasma glycine, L-serine, and D-serine levels of schizophrenic patients were higher than those of healthy controls. There were no significant differences between drug-naïve patients and healthy controls in the admission levels of the plasma amino acids, but chronically medicated patients had higher admission plasma glycine and D-serine levels. Only the D-serine level and the D-/L-serine ratio were markedly significantly increased in schizophrenic patients from the time of admission to the time of discharge as their clinical symptoms improved. In addition, the increase in the plasma D-serine levels of drug-naïve patients was correlated with improvements in positive symptoms. CONCLUSIONS: Plasma amino acid levels, especially D-serine levels, could be useful as a "therapeutic" or "clinical state" marker in patients with acute schizophrenia.

The relationship between the response of clinical symptoms and plasma olanzapine concentration, based on pharmacogenetics: Juntendo University Schizophrenia Projects (JUSP).

The monitoring of plasma olanzapine concentrations has been found to be an important and useful tool for optimizing psychiatric treatment. The present study investigated the effect that clinical factors, such as smoking and age, and functional polymorphisms of UGT1A4, CYP1A2, and CYP2D6 genes have on plasma olanzapine concentration, as well as the effects of plasma olanzapine concentrations on Japanese schizophrenic patients' clinical symptoms. The subjects included 51 chronic schizophrenic patients whose symptoms were not controlled with chronic conventional antipsychotics and therefore were switched to olanzapine. Male smokers had a significantly lower olanzapine concentration-dose ratio and olanzapine/4'-N-desmethyl olanzapine ratio (which reflects CYP1A2 activity) than male nonsmokers and female nonsmokers. The results of a 2-way analysis of covariance showed that smoking had the main effect, rather than gender or age. The functional gene polymorphisms that were studied had no effect on the plasma olanzapine and metabolite concentrations. An improved total Brief Psychiatric Rating Scale (BPRS) score was not correlated with the plasma olanzapine concentration, but individual BPRS scores related to improvement of suspiciousness, hallucinations, and blunted affect were significantly correlated with plasma olanzapine concentration. Clinical factors, especially smoking, were more important modulators of olanzapine metabolism than the functional genotypes. Long-term olanzapine treatment with adequate plasma olanzapine concentrations could be more effective in improving some symptoms than treatment with conventional antipsychotics.