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Background Carbonyl stress in patients with schizophrenia has been reported to be reflected by an increase in peripheral pentosidine levels. This cohort study tested whether the accumulation of pentosidine was related to the disease severity or the treatment (routine administration of high antipsychotic doses). Methods We followed up our original investigation using a new group of 137 patients with acute schizophrenia and 45 healthy subjects, and then pooled the two cohorts to conduct the following analysis on a total of 274 patients. The associations of serum pentosidine and pyridoxal levels with duration of education, estimated duration of medication, the severity of symptoms, and daily doses of antipsychotics, antiparkinsonian drugs, and anxiolytics were evaluated by multiple linear regression analysis. Results The combined cohort of 274 patients exhibited abnormally high serum levels of pentosidine, were associated with a higher daily dose of antipsychotic drugs and a longer estimated duration of medication without statistical significance of diagnosis. This was also observed in the patients treated with antipsychotic polypharmacy, but the serum pentosidine levels of patients treated with first- or second-generation antipsychotic monotherapy showed no relationship with these two variables. Conclusion High levels of serum pentosidine were associated with high daily doses of antipsychotic drugs and a longer estimated duration of medication in patients treated with antipsychotic polypharmacy.

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.

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.

Inflammation may be involved in the pathophysiology of schizophrenia. However, few cross-sectional or longitudinal studies have examined changes in biomarker expression to evaluate diagnostic and prognostic efficacy in acute-stage schizophrenia. We compared serum inflammatory biomarker concentrations in 87 patients with acute-stage schizophrenia on admission to 105 age-, sex-, and body mass index (BMI)-matched healthy controls. The measured biomarkers were soluble tumor necrosis factor receptor 1 (sTNFR1) and adiponectin, which are associated with inflammatory responses, and pigment epithelium-derived factor (PEDF), which has anti-inflammatory properties. We then investigated biomarker concentrations and associations with clinical factors in 213 patients (including 42 medication-free patients) and 110 unmatched healthy controls to model conditions typical of clinical practice. Clinical symptoms were assessed using the Brief Psychiatric Rating Scale and Global Assessment of Function. In 121 patients, biomarker levels and clinical status were evaluated at both admission and discharge. Serum sTNFR1 was significantly higher in patients with acute-stage schizophrenia compared to matched controls while no significant group differences were observed for the other markers. Serum sTNFR1 was also significantly higher in the 213 patients compared to unmatched controls. The 42 unmedicated patients had significantly lower PEDF levels compared to controls. Between admission and discharge, sTNFR1 levels decreased significantly; however, biomarker changes did not correlate with clinical symptoms. The discriminant accuracy of sTNFR1 was 93.2% between controls and patients, showing no symptom improvement during care. Inflammation and a low-level anti-inflammatory state may be involved in both schizophrenia pathogenesis and acute-stage onset. High serum sTNFR1 in the acute stage could be a useful prognostic biomarker for treatment response in clinical practice.

Studies have reported that cognitive decline occurs after the onset of schizophrenia despite heterogeneity in cognitive function among patients. The aim of this study was to investigate the degree of estimated cognitive decline in patients with schizophrenia by comparing estimated premorbid intellectual functioning and current intellectual functioning.A total of 446 patients with schizophrenia (228 male, 218 female), consisting of three sample sets obtained from 11 psychiatric facilities, and 686 healthy controls participated in this study. The Wechsler Adult Intelligence Scale-III (WAIS-III) was used to measure the participants' current full-scale IQ (FSIQ). The premorbid IQ was estimated using the Japanese Adult Reading Test-25. Estimated cognitive decline (difference score) was defined as the difference between the estimated premorbid IQ and the current FSIQ.Patients with schizophrenia showed greater estimated cognitive decline, a lower FSIQ, and a lower premorbid IQ compared with the healthy controls. The mean difference score, FSIQ, and estimated premorbid IQ were -16.3, 84.2, and 100.5, respectively, in patients with schizophrenia. Furthermore, 39.7% of the patients had a difference score of 20 points or greater decline. A discriminant analysis showed that the difference score accurately predicted 81.6% of the patients and healthy controls.These results show the distribution of difference score in patients with schizophrenia. These findings may contribute to assessing the severity of estimated cognitive decline and identifying patients with schizophrenia who suffer from cognitive decline.

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.

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.

Objectives Photosensitivity to ultraviolet A (UVA) radiation from sunlight is an important side effect of treatment with antipsychotic agents. However, the pathophysiology of drug-induced photosensitivity remains unclear. Recent studies demonstrated the accumulation of advanced glycation end products (AGEs), annotated as carbonyl stress, to be associated with the pathophysiology of schizophrenia. In this study, we investigated the relationship among skin AGE levels, minimal response dose (MRD) with UVA for photosensitivity, and the daily dose of antipsychotic agents in patients with schizophrenia and healthy controls. Methods We enrolled 14 patients with schizophrenia and 14 healthy controls. Measurement of skin AGE levels was conducted with AGE scanner, a fluorometric method for assaying skin AGE levels. Measurement of MRD was conducted with UV irradiation device. Results Skin AGE levels and MRD at 24, 48, and 72 hr in patients with schizophrenia showed a higher tendency for photosensitivity than in the controls, but the difference was statistically insignificant. Multiple linear regression analysis using skin AGE levels failed to show any influence of independent variables. MRD did not affect skin AGE levels. Conclusions Photosensitivity to UVA in patients with schizophrenia receiving treatment with antipsychotic agents might not be affected by skin AGE levels.

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

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. © 2015 Wiley Periodicals, Inc.

Recent GWAS demonstrated an association between candidate genes located at region 6p22.1 and schizophrenia. This region has been reported to house certain candidate SNPs, which may be associated with schizophrenia at HIST1H2BJ, PRSS16, and PGBD1. These genes may presumably be associated with pathophysiology in schizophrenia, namely epigenetics and psychoneuroimmunology. A three-step study was undertaken to focus on these genes with the following aims: (1) whether these genes may be associated in Japanese patients with schizophrenia by performing a 1st stage case–control study (514 cases and 706 controls) using Japanese tagging SNPs; (2) if the genetic regions of interest for the disease from the 1st stage of analyses were found, re-sequencing was performed to search for new mutations; (3) finally, a replication study was undertaken to confirm positive findings from the 1st stage were reconfirmed using a larger number of subjects (2,583 cases and 2,903 controls) during a 2nd stage multicenter replication study in Japan. Genotyping was performed using TaqMan PCR method for the selected nine tagging SNPs. Although three SNPs situated at the 3′ side of PGBD1; rs3800324, rs3800327, and rs2142730, and two-window haplotypes between rs3800327 and rs2142730 showed positive associations with schizophrenia, these associations did not have enough power to sustain significance during the 2nd stage replication study. In addition, re-sequencing for exons 5 and 6 situated at this region did not express any new mutations for schizophrenia. Taken together these results indicate that the genes HIST1H2BJ, PRSS16, and PGBD1 were not associated with Japanese patients with schizophrenia. © 2012 Wiley Periodicals, Inc.

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.Seventeen single-nucleotide polymorphisms (SNP) in GCLM, GCLC, and GSS were genotyped in 358 patients with schizophrenia and in 359 controls.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.The three primary GSH synthesis genes do not have an apparent degree of association with schizophrenia in the Japanese population.