Increased plasma asymmetric dimethylarginine is associated with cognitive deficits in patients with schizophrenia

Neural dysfunction underlying working memory processing at different stages of the illness course in schizophrenia: a comparative meta-analysis

Schizophrenia, as a chronic and persistent disorder, exhibits working memory deficits across various stages of the disorder, yet the neural mechanisms underlying these deficits remain elusive with inconsistent neuroimaging findings. We aimed to compare the brain functional changes of working memory in patients at different stages: clinical high risk, first-episode psychosis, and long-term schizophrenia, using meta-analyses of functional magnetic resonance imaging studies. Following a systematic literature search, 56 whole-brain task-based functional magnetic resonance imaging studies (15 for clinical high risk, 16 for first-episode psychosis, and 25 for long-term schizophrenia) were included. The separate and pooled neurofunctional mechanisms among clinical high risk, first-episode psychosis, and long-term schizophrenia were generated by Seed-based d Mapping toolbox. The clinical high risk and first-episode psychosis groups exhibited overlapping hypoactivation in the right inferior parietal lobule, right middle frontal gyrus, and left superior parietal lobule, indicating key lesion sites in the early phase of schizophrenia. Individuals with first-episode psychosis showed lower activation in left inferior parietal lobule than those with long-term schizophrenia, reflecting a possible recovery process or more neural inefficiency. We concluded that SCZ represent as a continuum in the early stage of illness progression, while the neural bases are inversely changed with the development of illness course to long-term course.

Association between serum insulin-like growth factor 1 levels and the improvements of cognitive impairments in a subgroup of schizophrenia: Preliminary findings

BACKGROUND

Numerous studies have implicated abnormal insulin-like growth factor 1 (IGF-1) in the pathophysiology of schizophrenia, but findings have been inconsistent.

METHODS

We conducted a meta-analysis to compare IGF-1 levels in schizophrenia patients with healthy controls and explored factors contributing to variability between estimates. In an independent sample (58 chronic schizophrenia patients and 30 healthy controls), we investigated differences in IGF-1 levels among schizophrenia subgroups with distinct cognitive profiles, identified using k-means clustering based on five cognitive domains from The Repeatable Battery for the Assessment of Neuropsychological Status. Associations between serum IGF-1 levels and clinical and neurocognitive improvements were also examined.

RESULTS

The meta-analysis revealed significantly lower serum IGF-1 levels in schizophrenia patients compared to healthy controls, albeit with high heterogeneity. Medication status, BMI, and severity of negative symptoms were identified as potential contributors to this heterogeneity. In our independent study, antipsychotic treatment led to a significant increase in IGF-1 levels, and lower pre-treatment serum IGF-1 levels correlated with greater improvement in cognitive deficits, particularly in a subgroup with more severe cognitive symptoms.

CONCLUSIONS

Our findings support the "IGF-1 deficiency hypothesis" in the pathogenesis of schizophrenia. Further research is crucial to elucidate the role of IGF-1 in the cognitive impairments associated with schizophrenia.

Knock-out of the critical nitric oxide synthase regulator DDAH1 in mice impacts amphetamine sensitivity and dopamine metabolism

The enzyme dimethylarginine dimethylaminohydrolase 1 (DDAH1) plays a pivotal role in the regulation of nitric oxide levels by degrading the main endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA). Growing evidence highlight the potential implication of DDAH/ADMA axis in the etiopathogenesis of several neuropsychiatric and neurological disorders, yet the underlying molecular mechanisms remain elusive. In this study, we sought to investigate the role of DDAH1 in behavioral endophenotypes with neuropsychiatric relevance. To achieve this, a global DDAH1 knock-out (DDAH1-ko) mouse strain was employed. Behavioral testing and brain region-specific neurotransmitter profiling have been conducted to assess the effect of both genotype and sex. DDAH1-ko mice exhibited increased exploratory behavior toward novel objects, altered amphetamine response kinetics and decreased dopamine metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) level in the piriform cortex and striatum. Females of both genotypes showed the most robust amphetamine response. These results support the potential implication of the DDAH/ADMA pathway in central nervous system processes shaping the behavioral outcome. Yet, further experiments are required to complement the picture and define the specific brain-regions and mechanisms involved.

Neurocognitive Deficits in First-Episode and Chronic Psychotic Disorders: A Systematic Review from 2009 to 2022

Cognitive impairment in patients suffering from schizophrenia spectrum disorders has been discussed as a strong predictor for multiple disease outcome variables, such as response to psychotherapy, stable relationships, employment, and longevity. However, the consistency and severity of cognitive deficits across multiple domains in individuals with first-episode and chronic psychotic disorders is still undetermined. We provide a comprehensive overview of primary research from the years 2009 to 2022. Based on a Cochrane risk assessment, a systematic synthesis of 51 out of 3669 original studies was performed. Impairment of cognitive functioning in patients diagnosed with first-episode psychotic disorders compared with healthy controls was predicted to occur in all assessed cognitive domains. Few overall changes were predicted for chronically affected patients relative to those in the first-episode stage, in line with previous longitudinal studies. Our research outcomes support the hypothesis of a global decrease in cognitive functioning in patients diagnosed with psychotic disorders, i.e., the occurrence of cognitive deficits in multiple cognitive domains including executive functioning, memory, working memory, psychomotor speed, and attention. Only mild increases in the frequency of cognitive impairment across studies were observed at the chronically affected stage relative to the first-episode stage. Our results confirm and extend the outcomes from prior reviews and meta-analyses. Recommendations for psychotherapeutic interventions are provided, considering the broad cognitive impairment already observed at the stage of the first episode. Based on the risk of bias assessment, we also make specific suggestions concerning the quality of future original studies.

Recent advancements in biomarker research in schizophrenia: mapping the road from bench to bedside

Schizophrenia (SZ) is a severe progressive neurodegenerative as well as disruptive behavior disorder affecting innumerable people throughout the world. The discovery of potential biomarkers in the clinical scenario would lead to the development of effective methods of diagnosis and would provide an understanding of the prognosis of the disease. Moreover, breakthrough inventions for the treatment and prevention of this mysterious disease could evolve as a result of a thorough understanding of the clinical biomarkers. In this review, we have discussed about specific biomarkers of SZ an emphasis has been laid to delineate (1) diagnostic biomarkers like neuroimmune biomarkers, metabolic biomarkers, oligodendrocyte biomarkers and biomarkers of negative and cognitive symptoms, (2) therapeutic biomarkers like various neurotransmitter systems and (3) prognostic biomarkers. All the biomarkers were evaluated in drug-naïve (at least for 4 weeks) patients in order to achieve a clear comparison between schizophrenic patients and healthy controls. Also, an attempt has been made to elucidate the potential genes which serve as predictors and tools for the determination of biomarkers and would ultimately help in the prevention and treatment of this deadly illness.

Asymmetric dimethylarginine in psychiatric disorders

Serum concentrations of asymmetric dimethylarginine (ADMA) in patients with schizophrenia, schizoaffective disorder, bipolar disorder, and depression were determined and compared to serum concentrations in healthy individuals. In all psychiatric diseases investigated, the ADMA concentration was elevated compared to the control group. Patients with recurrent depressive disorder had higher ADMA levels than patients with only one depressive episode. No differences between women and men were found. The elevated ADMA levels suggest that ADMA is involved in the pathophysiology of psychiatric diseases.

Altered insulin-like growth factor-2 signaling is associated with psychopathology and cognitive deficits in patients with schizophrenia

BACKGROUND

Schizophrenia is linked with abnormal brain neurodevelopment, on which IGF-2 (insulin-like growth factor-2) has a great impact. The purpose of this study was to assess the levels of serum IGF-2 and its binding proteins IGFBP-3 and IGFBP-7 in schizophrenia patients and the associations of these proteins with schizophrenia psychopathology and cognitive deficits.

METHODS

Thirty-two schizophrenia patients and 30 healthy controls were recruited. The PANSS and a neurocognitive test battery were used to assess schizophrenic symptomatology and cognition, respectively. Serum IGF-2, IGFBP-3 and IGFBP-7 levels were determined using ELISA.

RESULTS

The schizophrenia patients had a much lower content of serum IGF-2, IGFBP-3 and IGFBP-7 than controls. For the patients, IGF-2 levels were negatively correlated with the PANSS negative scores and positively associated with working memory, attention, and executive function. The correlations between IGF-2 and the PANSS negative scores, working memory or executive function were still significant after controlling for age, sex, education level, BMI, illness history and age of onset. No significant associations of IGFBP-3 or IGFBP-7 with the PANSS scores and cognitive function were observed in the patients.

CONCLUSIONS

Our study demonstrates that serum IGF-2 was significantly correlated with negative and cognitive symptoms in patients with schizophrenia, suggesting that altered IGF-2 signaling may be implicated in the psychopathology and cognitive deficits in schizophrenia.

The association between serum insulin-like growth factor 1 and cognitive impairments in patients with schizophrenia

Accumulating evidence has shown that insulin-like growth factors (IGFs) are implicated in schizophrenia. Altered serum levels of IGF-1 have been found in schizophrenia patients and are associated with psychopathological symptoms. However, whether there is a relationship between IGF-1 and cognitive impairment in schizophrenia remains unknown. Thirty schizophrenia patients and 26 healthy controls were recruited for this study. The Positive and Negative Syndrome Scale was adopted to assess schizophrenic symptoms, and a battery of neuropsychological tests was employed to evaluate cognitive function. Serum IGF-1 content was determined by enzyme-linked immunosorbent assay (ELISA). We found that patients with schizophrenia performed more poorly than healthy controls in most cognitive tasks, excluding visual memory. The serum IGF-1 concentrations in schizophrenia patients were much lower than those in controls. Correlation analyses revealed that the levels of serum IGF-1 were positively correlated with executive function and attention scores in patients. Furthermore, IGF-1 was an independent contributor to deficits in executive function and attention among schizophrenia patients. Collectively, serum IGF-1 levels were significantly correlated with cognitive performance in schizophrenia patients, indicating that decreased IGF-1 levels might contribute to the pathophysiology of schizophrenia-associated cognitive impairments. The regulation of IGF-1 signaling might be a potential treatment strategy for cognitive impairments in schizophrenia.

Decreased plasma levels of gasotransmitter hydrogen sulfide in patients with schizophrenia: correlation with psychopathology and cognition

OBJECTIVE

Aberrant N-methyl-D-aspartate receptor (NMDAR) function has been implicated in the pathophysiology of schizophrenia. Hydrogen sulfide (H₂S) is an endogenous gasotransmitter that regulates NMDAR function. The current study investigated the relationship between plasma H₂S levels and both psychopathological and cognitive symptoms in schizophrenia.

MATERIALS AND METHODS

Forty-one patients with schizophrenia and 40 healthy control subjects were recruited in present study. Schizophrenic symptomatology was assessed using the Positive and Negative Syndrome Scale (PANSS). Cognitive function was evaluated with a neuropsychological battery including seven neurocognitive tests. Plasma H₂S levels were measured by reversed-phase high-performance liquid chromatography (RP-HPLC).

RESULTS

Patients with schizophrenia performed worse in all of the cognitive tests than the healthy controls except for the visual memory. Plasma H₂S levels were significantly lower in patients with schizophrenia relative to healthy control subjects (F = 3.821, p = 0.007). Correlation analysis revealed a significant negative correlation between the H₂S levels and the PANSS general scores (r = - 0.413, p = 0.007). Additionally, a positive association was observed between plasma H₂S levels and working memory (r = 0.416, p = 0.007), visual memory (r = 0.363, p = 0.020), or executive function (r = 0.344, p = 0.028) in patients. Partial correlation analysis showed that the correlations between the H₂S levels and the PANSS general scores, working memory, visual memory, or executive function were still significant when controlling for age, gender, years of education, BMI, duration of illness, and age of onset.

CONCLUSION

The significant relations observed in the current study between H₂S and the general psychopathological as well as cognitive symptoms suggest that decreased H₂S is involved in the psychopathology and cognitive deficits of schizophrenia, and it might be a promising peripheral biomarker of schizophrenia.

Treatment Responses of Cognitive Function and Plasma Asymmetric Dimethylarginine to Atypical Antipsychotic in Patients With Schizophrenia

Cognitive deficits represent a core feature of schizophrenia. Previous studies have demonstrated that plasma asymmetric dimethylarginine (ADMA) was increased in patients with schizophrenia and correlated with cognitive impairments. Atypical antipsychotics can produce cognitive benefits in schizophrenia patients. In this study, we conducted a prospective observation trial to explore whether plasma ADMA may serve as an indicator for evaluating cognitive improvements induced by atypical antipsychotics in patients with schizophrenia. A total of 41 schizophrenia patients with acute exacerbation were enrolled and 29 patients completed this study. These recruited patients were drug-naive or had no exposure to antipsychotics for at least 3 months. Thirty healthy individuals were recruited as a control group. Positive and Negative Syndrome Scale (PANSS) and a neuropsychological battery were used to evaluate schizophrenic symptoms and cognitive function, respectively. Plasma ADMA was measured by high-performance liquid chromatography (HPLC). We found that schizophrenia patients with acute exacerbation had significantly poorer cognitive performances and higher plasma ADMA levels than control individuals (p < 0.05). After 2 months of atypical antipsychotic treatment, patients showed significant improvements in processing speed, working memory, attention, and executive function (all p < 0.01). Plasma ADMA levels in patients after treatment were significantly decreased compared to baseline (2.42 ± 0.84 vs. 1.55 ± 0.34 μmol/L; t = 6.491, p < 0.001). Correlation analysis reveals that there is a significant correlation of the decrease in ADMA with improvements in working memory (r = -0.413, p = 0.026) and attention (r = -0.417, p = 0.025). Collectively, our results suggest that atypical antipsychotics improve cognitive function in schizophrenia patients with acute exacerbation, in parallel with decreased plasma ADMA levels. Plasma ADMA levels may be an indicator of cognitive recovery in schizophrenia.