COMT and 5-HT1A-receptor genotypes potentially affect executive functions improvement after cognitive remediation in schizophrenia

Importance of the dysregulation of the kynurenine pathway on cognition in schizophrenia: a systematic review of clinical studies

Schizophrenia is a chronic psychotic disease burdened by cognitive deficits which hamper daily functioning causing disability and costs for society. Biological determinants underlying cognitive impairment are only partially understood and there are no convincing pharmacological targets able to improve cognitive outcome. Mounting evidence has shown the involvement of the kynurenine pathway in the pathophysiology of schizophrenia, also concerning cognitive symptoms. Therefore, the action of specific metabolites of kynurenine could affects cognition in schizophrenia. To evaluate the impact of the metabolites of kynurenine pathway on cognitive functions in schizophrenia spectrum disorders, with a focus on the modulating role of gender, to identify predictors of cognitive functioning and hypothetical pharmacological targets able to resize disability by improving cognition, thus functioning and quality of life. A systematic review was performed in PubMed/MEDLINE and Embase according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses. All studies measuring the direct impact of kynurenine metabolites on cognitive performances in living individuals with schizophrenia spectrum disorders were included in the review. Six studies were included. The activation of the kynurenine pathway resulted associated with greater cognitive deficits in patients with schizophrenia and both elevations and reduction of metabolites seemed able to affect cognitive outcome. No modulating role of sex emerged. This systematic review provides evidence that the activation of the kynurenine pathway affects cognition in patients with schizophrenia and highlights this pathway as a possible future target for developing novel drugs toward this still unmet clinical need. However, evidence is still limited and future studies are needed to further clarify the relationship between kynurenine pathway and cognition in schizophrenia.

Associations Between a Polymorphism in the Rat 5-HT1A Receptor Gene Promoter Region (rs198585630) and Cognitive Alterations Induced by Microwave Exposure

The nervous system is a sensitive target of electromagnetic radiation (EMR). Chronic microwave exposure can induce cognitive deficits, and 5-HT system is involved in this effect. Genetic polymorphisms lead to individual differences. In this study, we evaluated whether the single-nucleotide polymorphism (SNP) rs198585630 of 5-HT_1A receptor is associated with cognitive alterations in rats after microwave exposure with a frequency of 2.856 GHz and an average power density of 30 mW/cm². Rats were exposed to microwaves for 6 min three times a week for up to 6 weeks. PC12 cells and 293T cells were exposed to microwaves for 5 min up to 3 times at 2 intervals of 5 min. Transcriptional activity of 5-HT_1A receptor promoter containing rs198585630 C/T allele was determined in vitro. Electroencephalograms (EEGs), spatial learning and memory, and mRNA and protein expression of 5-HT_1A receptor were evaluated in vivo. We demonstrated that transcriptional activity of 5-HT_1A receptor promoter containing rs198585630 C allele was higher than that of 5-HT_1A receptor promoter containing T allele. The transcriptional activity of 5-HT_1A receptor promoter was stimulated by 30 mW/cm² microwave exposure, and rs198585630 C allele was more sensitive to microwave exposure, as it showed stronger transcriptional activation. Rats carrying rs198585630 C allele exhibited increased mRNA and protein expression of 5-HT_1A receptor and were more susceptible to 30 mW/cm² microwave exposure, showing cognitive deficits and inhibition of brain electrical activity. These findings suggest SNP rs198585630 of the 5-HT_1A receptor is an important target for further research exploring the mechanisms of hypersensitivity to microwave exposure.

MiR-4763-3p targeting RASD2as a Potential Biomarker and Therapeutic Target for Schizophrenia

Existing diagnostic methods are limited to observing appearance and demeanor, even though genetic factors play important roles in the pathology of schizophrenia. Indeed, no molecular-level test exists to assist diagnosis, which has limited treatment strategies. To address this serious shortcoming, we used a bioinformatics approach to identify 61 genes that are differentially expressed in schizophrenia patients compared with healthy controls. In particular, competing endogenous RNA network revealed the important role of the gene RASD2, which is regulated by miR-4763-3p. Indeed, analysis of blood samples confirmed that RASD2 is downregulated in schizophrenia patients. Moreover, positron emission tomography data collected for 44 human samples identified the prefrontal and temporal lobes as potential key brain regions in schizophrenia patients. Mechanistic studies indicated that miR-4763-3p inhibits RASD2 by base-pairing with the 3’ untranslated region of RASD2 mRNA. Importantly, RASD2 has been shown to interact with β-arrestin2, which contributes to the regulation of the DRD2-dependent CREB response element-binding protein pathway in the dopamine system. Finally, results obtained with a mouse model of schizophrenia revealed that inhibition of miR-4763-3p function alleviated anxiety symptoms and improved memory. The dopamine transporters in the striatal regions were significantly reduced in schizophrenia model mice as compared with wild-type mice, suggesting that inhibition of miR-4763-3p can lessen the symptoms of schizophrenia. Our findings demonstrate that miR-4763-3p may target RASD2 mRNA and thus may serve as a potential biomarker and therapeutic target for schizophrenia, providing a theoretical foundation for further studies of the molecular basis of this disease.

Predictors of response to cognitive remediation in patients with major psychotic disorders: A narrative review

BACKGROUND

Cognitive impairments are prominent features of individuals diagnosed with major psychotic disorders (MPD), negatively affecting occupational and social functioning. Over the past few years, several cognitive remediation (CR) interventions have been developed, with different foundation principles, targets, and mechanisms of action. The vast majority consists of drill and practice approaches that are grounded in the principle of neuropsychology. More recently, neuroplasticity-based cognitive training (NBCT) has shown promise. While several CR approaches have shown moderate efficacy, improving both cognition and real-world functioning, there is considerable variability in individual treatment response. Studies that have investigated factors that predict CR outcome and can be used to guide treatment have historically grouped all CR approaches together. Here, we aim to explore common and distinct predictors of response to neuroplasticity-based and neuropsychology-based CR.

METHODS

an electronic database search on MEDLINE/PubMed was conducted in February 2020 to identify articles investigating predictors of response to CR. We limited our queries to peer-reviewed, English-language journal articles describing trials of CR for adults with MPD.

RESULTS

a total of 58 articles were examined, and 14 different categories of CR predictors were identified. CR predictors that most stood out were age, shorter illness duration, lower symptoms severity, lower antipsychotic medications, and the delivery of CR in combination with other treatments. Although results are still mixed, demographical variables appear to be far less important for NBCT than they are for other CR programs. Clinical and genetic variables - such as symptoms severity, lower antipsychotic dose, serum BDNF and serum D-serine - seem to influence more significantly NBCT than neuropsychology-based CR.

CONCLUSIONS

Data on NBCT is relatively scarce, and further research is required to better understand which predictive factors uniquely pertain to it. The identification of predictors of response to CR will allow to implement a personalized medicine approach, in which each patient can receive a personalized cognitive remediation program according to their specific needs.

Free Thyroxine Concentrations Moderate the Response to a Cognitive Remediation Therapy in People With Early Psychosis: A Pilot Randomized Clinical Trial

INTRODUCTION

Cognitive deficits are a cause of functional disability in psychotic disorders. Cognitive remediation therapy (CRT) might be applied to improve these deficits. We conducted a pilot study to explore whether thyroid hormones might predict the response to CRT in patients with recent-onset psychosis (ROP).

METHODS

Twenty-eight stable ROP outpatients (9 women) were randomized to receive computerized CRT (N=14) or treatment as usual (TAU) (N=14), over three months. Both cognitive and thyroid functions were assessed at the baseline and after those three months to all patients. A full cognitive battery (CANTAB) was administered before and after the treatment. Serum levels of thyroid-stimulating hormone (TSH) and free thyroxine (FT4) were measured. FT4 concentrations were recoded into a dichotomic variable (FT4 group) based on the median of the sample (1.2 ng/dL). Data were analyzed on an intention-to-treat basis with linear mixed models. Afterwards, we offered CRT to all participants from the TAU group and seven enrolled CRT, reassessing them when finished. Secondary analyses were repeated in a sample of 14 participants who completed the CRT (either from the beginning or after the TAU period) and attended at least one third of the sessions.

RESULTS

The linear mixed models showed a significant time x CRT x FT4 group effect in two cognitive tasks dealing with executive functions and sustained attention (participants with higher FT4 concentrations worsened executive functions but improved sustained attention after CRT). In the secondary analysis including all patients assigned to CRT, higher FT4 concentrations were associated with a poorer response in verbal memory but a better response in spatial working memory.

CONCLUSIONS

Free thyroxine concentrations moderate the response to a CRT in patients with early psychosis.

The role of genetics in cognitive remediation in schizophrenia: A systematic review

The role of genetics in cognitive remediation therapies in schizophrenia has not been completely understood yet. Different genes involved in neurotrophic, dopaminergic and serotonin systems have reported to influence cognitive functioning in schizophrenia. These genetic factors could also be contributing to the variability in responsiveness to cognitive treatments. No comprehensive synthesis of the literature of the role of genetics in the context of cognitive remediation has been conducted until now. We aimed to systematically review the published works through three electronic database searches: PubMed, Scopus, and the Cochrane Library. Eligible studies revealed a rising interest in the field although the number of published studies was rather small (n = 10). Eventually, promising results showing a relationship between some phenotypic variations based on different polymorphisms and different levels of responsivity to cognitive remediation therapies have been described although results are still inconclusive. In case those findings will be replicated, they could be guiding future research and informing clinical decision-making in the next future.

A systematic review of factors that influence the efficacy of cognitive remediation therapy in schizophrenia

OBJECTIVE

Cognitive remediation therapy is a moderately effective intervention for ameliorating cognitive deficits in individuals with schizophrenia-related disorders. With reports of considerable variability in individual response to cognitive remediation therapy, we need to better understand factors that influence cognitive remediation therapy efficacy to realise its potential. A systematic review was conducted to identify and evaluate predictors of cognitive outcome.

METHODS

An electronic database search was conducted identifying peer-reviewed articles examining predictors of cognitive response to cognitive remediation therapy.

RESULTS

A total of 40 articles accounting for 1681 cognitive remediation therapy participants were included; 81 distinct predictors of cognitive response were identified. Data synthesis and discussion focused on 20 predictors examined a minimum three times in different studies. Few of the examined predictors of cognitive outcome following cognitive remediation therapy were significant when examined through systematic review. A strong trend was found for baseline cognition, with reasoning and problem solving and working memory being strongly predictive of within-domain improvement. Training task progress was the most notable cross-domain predictor of cognitive outcome.

CONCLUSION

It remains unclear why a large proportion of participants fail to realise cognitive benefit from cognitive remediation therapy. However, when considering only those variables where a majority of articles reported a statistically significant association with cognitive response to cognitive remediation therapy, three stand out: premorbid IQ, baseline cognition and training task progress. Each of these relates in some way to an individual's capacity or potential for change. There is a need to consolidate investigation of potential predictors of response to cognitive remediation therapy, strengthening the evidence base through replication and collaboration.

hsa-miR-3177-5p and hsa-miR-3178 Inhibit 5-HT1A Expression by Binding the 3'-UTR Region in vitro

Abnormal expression of the 5-HT1A receptor, which is encoded by the HTR1A gene, leads to susceptibilities to neuropsychiatric disorders such as depression, anxiety, and schizophrenia. miRNAs regulate gene expression by recognizing the 3'-UTR region of mRNA. This study evaluated the miRNAs that might identify and subsequently determine the regulatory mechanism of HTR1A gene. Using the HEK-293, U87, SK-N-SH and SH-SY5Y cell lines, we determined the functional sequence of the 3'-UTR region of the HTR1A gene and predicted miRNA binding. Dual luciferase reporter assay and Western Blot were used to confirm the effect of miRNA mimics and inhibitors on endogenous 5-HT1A receptors. In all cell lines, gene expression of the -17 bp to +443 bp fragment containing the complete sequence of the 3'-UTR region was significantly decreased, although mRNA quantification was not different. The +375 bp to +443 bp sequence, which exhibited the most significant change in relative chemiluminescence intensity, was recognized by hsa-miR-3177-5p and hsa-miR-3178. In HEK-293 and U87 cells, hsa-miR-3177-5p significantly inhibited the 5-HT1A receptor expression, while a hsa-miR-3178 inhibitor up-regulated HTR1A gene expression in SK-N-SH and SH-SY5Y cells. By constructing the pmirGLO-vector with the mutated HTR1A gene, we further confirmed that hsa-miR-3177-5p recognized the HTR1A gene tgtacaca at +377 bp to +384 bp, and the +392 bp to +399 bp fragment cgcgccca was identified by hsa-miR-3178. hsa-miR-3177-5p and hsa-miR-3178 had significant inhibitory effects on expression of the HTR1A gene and 5-HT1A receptor and may directly participate in the development of neuropsychiatric diseases.

Factors Associated With Response and Resistance to Cognitive Remediation in Schizophrenia: A Critical Review

Cognitive impairment is a central feature of schizophrenia and has shown to play a crucial role in the psychosocial function of the disorder. Over the past few years, several cognitive remediation (CR) interventions have been developed for schizophrenia, whose effectiveness has also been widely demonstrated by systematic reviews and meta-analysis studies. Despite these evidences, many questions remain open. In particular, the identification of CR response predictors in patients with schizophrenia is still a topic with equivocal findings and only a few studies have looked for the relationship between CR response or resistance and the biological, socio-demographic, clinical and cognitive features in schizophrenia. The current knowledge on positive or negative response predictors to CR treatment in schizophrenia include: age, duration of illness, premorbid adjustment, baseline cognitive performance, intrinsic motivation, hostility, disorganized symptoms, neurobiological reserve, genetic polymorphisms, the amounts of antipsychotics, the type of CR, etc. The aim of this review is to identify neurobiological, psychopathological, cognitive, and functional predictors of CR response or resistance in schizophrenia, taking into account both cognitive and functional outcome measures. The information obtained could be very useful in planning integrated and personalized interventions, also with a better use of the available resources.

BDNF as a marker of response to cognitive remediation in patients with schizophrenia: A randomized and controlled trial

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is considered to be a putative biomarker for cognitive recovery in schizophrenia. However, current evidence is still scarce for pharmacological treatments, and the use of BDNF as a biomarker has only been tested once with cognitive remediation treatment (CRT).

METHODS

A randomized and controlled trial (NCT02341131) with 70 schizophrenia outpatients and 15 healthy volunteers was conducted. The participants with schizophrenia were randomly assigned to either CRT or the control group. All the participants were assessed in terms of cognition, quality of life, and their serum BDNF levels at both baseline and after the intervention. Additionally, comparisons of the effects of the different genotypes of the Val66Met polymorphism at the BDNF gene on the outcome variables were also performed.

RESULTS

The patients in the CRT group presented with improvements in both cognition and quality of life. However, no significant changes were detected in the serum levels of BDNF. Interestingly, we found a significant positive interaction effect between the serum BDNF levels and the different BDNF genotypes. The Val/Val group showed significantly higher serum levels after the CRT treatment. However, the interaction among the serum BDNF levels, the BDNF genotypes and the treatment condition was not statistically significant.

CONCLUSIONS

The replication of the previous finding of increased serum BDNF levels after cognitive remediation in clinically stable individuals with schizophrenia was not achieved. However, our data indicated that genetic variability may be mediating serum BDNF activity in the context of CRT.

The role of premorbid adjustment in schizophrenia: Focus on cognitive remediation outcome

Premorbid adjustment has been associated with several outcomes in schizophrenia and has been proposed as an index of cognitive reserve. This study aims to comprehensively analyse the relation between premorbid adjustment and clinical, neurocognitive, socio-cognitive and functional assessments, as well as to investigate the effect of premorbid adjustment on cognitive improvements after a cognitive remediation therapy protocol. Seventy-nine clinically stabilised outpatients with schizophrenia underwent a combined intervention consisting of cognitive remediation therapy added to standard rehabilitation therapy. All patients were assessed at baseline for psychopathology, premorbid adjustment, intellectual level, cognition and functioning. Cognitive evaluations were also repeated after the intervention. At baseline, significant correlations were observed between premorbid adjustment and working memory. The global cognitive improvement after treatment was significantly predicted by age and premorbid adjustment. This study confirms the association between premorbid adjustment and cognitive impairment and is the first to highlight the possible role of premorbid adjustment on the capacity to recover from cognitive deficits through a cognitive remediation therapy protocol. The data suggest that cognitive remediation may be particularly effective for people in the early course and that the assessment of premorbid adjustment could be of value to design individualised interventions.

Improving Cognition to Increase Treatment Efficacy in Schizophrenia: Effects of Metabolic Syndrome on Cognitive Remediation's Outcome

Cognitive impairment, typically more severe in treatment resistant patients, is considered a hallmark of schizophrenia and the prime driver of functional disability. Recent evidence suggests that metabolic syndrome may contribute to cognitive deficits in schizophrenia, possibly through shared underlying mechanisms. However, results are still contradictory and no study has so far examined the influence of metabolic syndrome on cognitive outcome after cognitive remediation therapy (CRT). Based on these premises, this study aims to investigate the relationship between metabolic syndrome and cognition, specifically considering cognitive outcome after treatment. Secondary objectives include the analysis of the association between cognitive impairment and psychopathological status and, in a subgroup of patients, the evaluation of the effect of Sterol Regulatory Element Binding Transcription Factor 1 (SREBF-1) rs11868035 genetic polymorphism, previously associated with metabolic alterations, on both cognition and metabolic syndrome. One-hundred seventy-two outpatients with schizophrenia were assessed for metabolic parameters and neurocognitive measures and 138 patients, who completed CRT, were re-evaluated for cognition. A subsample of 51 patients was also genotyped for rs11868035 from peripheral blood sample. Results show a negative impact of metabolic syndrome on executive functions and global cognitive outcome after CRT. Data also revealed a significant effect of SREBF-1 polymorphism, with a higher prevalence of metabolic syndrome and worse processing speed performance among G/G homozygous subjects, compared the A allele carriers. Overall these findings support the hypothesis that metabolic alterations may hamper the capacity to restore cognitive deficits, as well as they highlight the need to further explore possible converging mechanisms underlying both cognitive and metabolic dysfunction. At the clinical level, results point to the importance of a comprehensive assessment including the metabolic status of patients and of individualized strategies addressing metabolic dysfunction in order to potentiate treatment outcome in schizophrenia.

COMT genotype and response to cognitive remediation in schizophrenia

BACKGROUND

A functional polymorphism of the catechol-O-methyltransferase (COMT) gene (Val158Met) partially appears to influence cognitive performance in schizophrenia subjects and healthy controls by modulating prefrontal dopaminergic activity. This study evaluated the association of the COMT Val108/158 Met genotype with response to computerized neurocognitive remediation (CRT).

METHOD

145 subjects with DSM-IV-TR schizophrenia or schizoaffective disorder were genotyped via saliva sampling. Subjects were evaluated on neurocognitive assessments (MATRICS) and clinical symptoms (PANSS) at baseline and endpoint after 12weeks of CRT. "Improvement" was defined as ≥67% of cognitive domains (≥4) showing performance increases. If ≤67% (≤2) of domains improved, the change was defined as "minimal improvement." A general linear model was conducted for change of each cognitive domain.

RESULTS

Of 145 subjects, data from 138 subjects were usable. Distribution of COMT genotype: Met/Met: 28 (20.29%), Val/Met: 61 (44.20%), and Val/Val: 49 (35.51%). No significant differences were seen among genotype groups at baseline or across genotype group for "Improvement" vs. "Minimal Improvement." GLM analysis showed significant differences in Verbal Learning (p=0.003), Visual Learning (p=0.014) and Attention/Vigilance (p=0.011) favoring Met/Met and Val/Met groups.

CONCLUSIONS

The low activity Met allele (Met/Met; Val/Met) was associated with significantly greater improvements in the MATRICS domains of Verbal Learning, Visual Learning and Attention/Vigilance after CRT.

COMT Val158Met and 5-HT1A-R -1019 C/G polymorphisms: effects on the negative symptom response to clozapine

Aim: Clozapine is still considered the gold standard for treatment-resistant schizophrenia patients; however, up to 40% of patients do not respond adequately. Identifying potential predictors of clinical response to this last-line antipsychotic could represent an important goal for treatment. Among these, functional polymorphisms involved in dopamine system modulation, known to be disrupted in schizophrenia, may play a role. We examined the COMT Val158Met polymorphism, which plays a key role in dopamine regulation at the prefrontal level, and the 5-HT1A-R -1019 C/G polymorphism, a target of clozapine activity involved in the interaction between the serotonin and dopamine systems. Materials & methods: 107 neuroleptic-refractory, biologically unrelated Italian patients (70 males and 37 females) with a DSM-IV diagnosis of schizophrenia who were being treated with clozapine were recruited. Psychopathology was assessed by the Positive and Negative Symptoms Scale (PANSS) at the beginning of treatment, and at weeks 8 and 12. Genomic DNA was extracted from venous blood samples. COMT rs4680 (Val158Met) and 5-HT1A-R rs6295 (-1019 C/G) polymorphisms were analyzed by PCR-based restriction fragment length and direct sequencing, respectively. Results: We found a significant effect of COMT and 5-HT1A-R on the PANSS Negative Subscale variation, with greater improvement among COMT Val/Val and 5-HT1A-R G/G subjects. Conclusion: The findings support the hypothesis that COMT rs4680 and 5-HT1A-R rs6295 polymorphisms could influence the negative symptom response to clozapine, probably through modulation of the dopaminergic system.

Original submitted 26 February 2014; Revision submitted 15 October 2014