This is an open-label prospective observation study. All patients in this study were recruited from Jiangxi Mental Hospital. The patients of schizophrenia were diagnosed by two trained research psychiatrists using modified sections of the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV). The age of recruited patients was between 18 and 50 years old and the Positive and Negative Syndrome Scale (PANSS) score need to be between 60 and 120 at the baseline interview. All the patients who were recruited in this study had acute exacerbation for their psychotic symptoms and were admitted into acute ward for assessment and treatment. All these patients were antipsychotic naive or had not taken any antipsychotic drug over the past 3 months. In order to reassure the drug compliance, only patients who stayed well for at least 8-weeks were included in the present study. Healthy individuals were recruited from the local community as controls, matched with the patients by age, gender, education, and body mass index (BMI). All participants were Han Chinese ethnicity.

Patients with neurological disorders, mental retardation, and drug/alcohol abuse or addiction were excluded from this study. Some diseases including metabolic syndrome, diabetes, hyperlipidemia, coronary artery disease, inflammatory disease, liver damage, and renal failure may lead to changes in plasma ADMA (18–23). Thus, besides any additional axis I or axis II DSM-IV diagnosis, the exclusion criteria also included acute or chronic infections, current pregnancy, autoimmune, endocrine, and neoplastic diseases, allergic asthma, and other acute physical disorders, including heart or brain infarction within the past 3 months. Both patient and control groups were assessed with a medical history, physical examination, electrocardiogram, and laboratory tests. They were screened for acute infectious diseases by measuring body temperature, erythrocyte sedimentation rate, serum creatinine, C-reactive protein (CRP), and urinary culture. Subjects with abnormal parameters were excluded, for example urea (Normal range: 2.14~7.85 mmol/L), creatinine (Normal range: 60~130 μmol/L), SGOT (Normal range: 0~40 U/L), SGPT (Normal range: 0~40 U/L), CRP (Normal range: 0~10 mg/L), cholesterol (Normal range: 3.38~6.47 mmol/L), triglycerides (Normal range: 0.4~1.81 mmol/L), systolic and diastolic blood pressure (Normal range: 140/90-90/60 mmHg), and BMI (Normal range: 18.5~24).

All procedures for this study were reviewed and approved by the Institutional Review Board at Jiangxi Mental Hospital. The research was carried out in accordance with the Declaration of Helsinki and other relevant national and international regulations. A written informed consent was obtained from each subject, or his or her legal guardians.

PANSS was used to assess the severity of the psychotic symptoms of patients. The evaluation was conducted by two psychiatrists who had both attended a training session of PANSS use before the study began. The inter-observer correlation coefficient for the PANSS total score was >0.80.

The cognitive function of subjects was measured by a comprehensive battery of neurocognitive tests (17, 24, 25). These tests are commonly used in China, and their clinical reliability and validity have been evaluated in Chinese populations. The battery consists of seven tests and can be grouped into six cognitive domains: processing speed (Trail making test part A: TMT-A; Brief assessment of cognition in schizophrenia-symbol coding: BACS-symbol coding), working memory (Wechsler memory scale-3rd edition-spatial span: WMS-III spatial span), visual memory (Brief visual-spatial memory test-revised: BVMT-R), verbal learning (Hopkins verbal learning test-revised: HVLT-R), attention (Continuous performance test-identical pairs: CPT-IP), and executive function (Stroop color-word test).

TMT-A: In this test, you are given a pencil and a piece of paper with numbered circles, and you are asked to draw a line and connect the circles in the sequence of their numbers. You should draw the lines as quickly and as accurately as you can, since the time taken for the drawing is used for grading.

BACS-symbol coding: In this test, you are given 133 pairs of digits and symbols, and asked to copy the specific symbol as soon as you are shown its paired number. You should do this quickly as the symbols you finish correctly within 120 s are used for the grading.

WMS-III space span: In this test you are faced with a board with ten cubes on it spaced irregularly. An administrator will firstly show you combinations of the cubes in different ways and orders, forward and backward, and then ask you to recall the combinations. On each level of combination, you are given two trials. In the end you are graded in line with your recalled trials.

BVMT-R: In this test you will watch six geometric figures, which will appear three times, each time for 10 s. After that you are asked to draw the figures on a piece of paper in the layout as you watched. The more figures you draw correctly, the better you are rated.

HVLT-R: In this test, you will be presented with twelve Chinese words, which are listed in three categories. The list will be shown three times, followed by a delay time of 25–30 min. After that, you are asked to recall and speak out the words. Your performance is graded in accordance with the words you correctly recalled.

CPT-IP: In this test, you will see digital numbers of 2, 3, and 4 digits flashing on a computer screen. You are asked to immediately click the mouse after you see the same number flash on the screen in a row. In this test, you may hit 90 times in total, and possibly trigger false alarms 90 times in total. You will randomly respond about 270 times in total.

Stroop color-word test: In this test you're presented with three pages: firstly a word page, on which words of colors are black in color, secondly a color page, on which several rows of Xs are in different colors and thirdly a word-color page, on which the same words of colors on the first page are colored using the colors on the second page, though they are not colored in the color of themselves. In each trial you are presentedwith 100 words and you are asked to read them as fast as you can in a cycle time of 45 s. Your correct readings of the words are numbered for your grading.

Peripheral blood was collected from an antecubital vein between 07:00 and 09:00 a.m. following an overnight fasting at baseline and at the endpoint of the study. The blood samples were centrifuged at 3,000 rpm for 5 min at 4°C. The plasma was separated and stored at −80°C until analysis.

The concentration of plasma ADMA was measured by HPLC as described in our previous study (17). Briefly, we added 5 mg of 5-sulphosalici-licacid (SSA) to 1 mL of plasma and allowed them to mix for 10 min at −20°C. The sample was then centrifuged at 7,000 rpm for 5 min at temperature of 4°C. After that, 10 microliters of the supernatant was mixed with 100 μL of derivatization reagent (prepared by dissolving 10 mg of o-phthaldialdehyde in 0.5 mL of methanol, and adding 2 mL of 0.4 M borate buffer (pH 10.0) and 30 μL of 2-mercaptoethanol). The mixture was subsequently injected into the chromatographic system to determine the level of ADMA. The variability of this method was <7%, and the detection limit of the assay was 0.1 μm.

Demographic and clinical variables were compared between control and patient groups using Student's t-test or analysis of variance (ANOVA) for quantitative variables and chi-squared test for qualitative variables. An analysis of covariance (ANCOVA) was performed to compare the scores of cognitive tests between two groups, controlling for gender, age, years of education, and BMI by using these variables as covariates. To compare the levels of ADMA between the patient and control groups, ANCOVA was performed using gender, age, years of education, and BMI as covariates to minimize the potential effect of these factors on the expression of ADMA levels. A paired t-test was performed to analyze plasma concentrations of ADMA between two time points (at baseline and 8th-week after atypical antipsychotic treatment) in the same patients. A Non-parametric test (Kruskal-Wallis test) was used to test whether there was a difference in cognitive function and ADMA level among different atypical antipsychotics at the endpoint. Spearman's correlation analysis was used to examine the correlation between change of cognitive test scores and ADMA level. All statistical tests were two-tailed, and the significance level was set at p < 0.05.

A total of 41 schizophrenia patients with acute exacerbation consented to the study and received baseline assessments. During the study session, these patients only received one type of atypical antipsychotics. The type of atypical antipsychotic was chosen according to the demographic and clinical symptom characteristics of patients. Patients using clozapine met the criteria of refractory schizophrenia. Benzene hydrochloride was only used when patients developed a marked extrapyramidal response. Of these, 12 patients dropped out for the following reasons: four patients were discharged from hospital before the endpoint of study; five patients did not respond to atypical antipsychotic monotherapy and required a combined treatment with other antipsychotic drugs or modified electric convulsive treatment (MECT); three patients suffered severe impairment of liver function and need to receive liver-protecting therapy. All data reported here are based on the remaining 29 patients who completed this study.

Baseline demographic and clinical characteristics for the patient and control groups are shown in Table 1. There was no significant difference in age, gender, years of education, or BMI between the two groups (all p > 0.05). Cognitive tests revealed that schizophrenia patients with acute exacerbation demonstrated significantly poorer cognitive performance than control individuals except for the BVMT-R controlling for age, gender, years of education, and BMI (all p < 0.05). We then measured the levels of plasma ADMA in both patient and control groups. The data of 29 patients and 30 healthy controls were included in the analysis of baseline ADMA levels. As previously reported (16, 17), patients with schizophrenia showed higher levels of plasma ADMA relative to the controls (2.42 ± 0.84 vs. 1.41 ± 0.14 μmol/L; F = 42.947, p < 0.001). ANCOVA analysis revealed that the difference between two groups still existed (F = 10.098, p < 0.001) when age, gender, years of education, and BMI were used as covariates.

The primary endpoint was the change from baseline to 8-weeks in PANSS and cognitive test scores. The number of patients treated with risperidone, olanzapine, clozapine, and aripiprazole was 10, 5, 7, and 7, respectively. The final median dose of risperidone, olanzapine, clozapine, and aripiprazole was 3.12 ± 1.05, 16.27 ± 5.33, 292.75 ± 115.63, and 14.66 ± 3.81 mg/day, respectively. Table 2 shows the clinical efficacy and neurocognitive effect of atypical antipsychotics in schizophrenia patients with acute exacerbation. A significant improvement in PANSS total score and each subscore was observed when the patients completed this study (Paired t-tests; all p < 0.01). According to the proposed criteria for symptomatic remission in patients with schizophrenia (26), the rate of symptomatic remission at the endpoint was 82.75% (24/29). Additionally, patients given an 8-week period of atypical antipsychotic treatment showed significant improvements in the test scores of TAM-A, BACS-SC, WMS-III, CPT-IP, and Stroop color-word test (all p < 0.01). Furthermore, Kruskal-Wallis test showed that there was no difference in PANSS total score, each subscore, or the cognitive tests mentioned above, among risperidone, olanzapine, clozapine, and aripiprazole-treated groups at the endpoint (p > 0.05).

Together with clinical improvement, plasma ADMA levels after 8-week atypical antipsychotic monotherapy were also significantly decreased compared with baseline (2.42 ± 0.84 vs. 1.55 ± 0.34 μmol/L; t = 6.491, p < 0.001) (Figure 1). There was no significant difference in plasma ADMA levels between the patients after atypical antipsychotic treatment and the controls (1.55 ± 0.34 vs. 1.41 ± 0.14 μmol/L; p > 0.05). Furthermore, all these atypical antipsychotics could lead to a significant decrease in the levels of plasma ADMA (p < 0.05), and there was no significant difference between groups in plasma ADMA levels at the study endpoint (Kruskal-Wallis test, χ² = 4.255, p = 0.235) (Table 3).

Spearman's correlation analysis was conducted to explore whether the change in plasma ADMA levels was correlated with clinical improvements. Similar to a previous study (16), we did not find any relationship between the reduction of plasma ADMA and the change of PANSS total score (r = 0.028, p = 0.886), positive subscore (r = −0.021, p = 0.913), negative subscore (r = −0.044, p = 0.821), or general psychopathology (r = 0.055, p = 0.776). Then we further analyzed the relationship between the change of plasma ADMA levels and cognitive improvement. As shown in Figure 2, there is a significant correlation between the decrease of ADMA and the change in WMS-III (r = −0.413, p = 0.026) or CPT subscore (r = −0.417, p = 0.025), indicating that the decrease in plasma ADMA was correlated with the improvements of working memory and attention in patients treated with atypical antipsychotic.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.