Evidence from preclinical and clinical metabolomics studies on the antidepressant effects of ketamine and esketamine

The antidepressant effects of ketamine and esketamine are well-documented. Nonetheless, most of the underlying molecular mechanisms have to be uncovered yet. In the last decade, metabolomics has emerged as a useful means to investigate the metabolic phenotype associated with depression as well as changes induced by antidepressant treatments. This mini-review aims at summarizing the main findings from preclinical and clinical studies that used metabolomics to investigate the metabolic effects of subanesthetic, antidepressant doses of ketamine and esketamine and their relationship with clinical response. Both animal and human studies report alterations in several metabolic pathways - including the tricarboxylic acid cycle, glycolysis, the pentose phosphate pathway, lipid metabolism, amino acid metabolism, the kynurenine pathway, and the urea cycle - following the administration of ketamine or its enantiomers. Although more research is needed to clarify commonalities and differences in molecular mechanisms of action between the racemic compound and its enantiomers, these findings comprehensively support an influence of ketamine and esketamine on mitochondrial and cellular energy production, membrane homeostasis, neurotransmission, and signaling. Metabolomics may thus represent a promising strategy to clarify molecular mechanisms underlying treatment-resistant depression and related markers of clinical response to ketamine and esketamine. This body of preclinical and clinical evidence, if further substantiated, has the potential to guide clinicians towards personalized approaches, contributing to new paradigms in the clinical management of depression.

Prevalence and correlates of manic/hypomanic and depressive predominant polarity in bipolar disorder: systematic review and meta-analysis

BACKGROUND

Identification of the predominant polarity, i.e. hypomanic/manic (mPP) or depressive predominant polarity (dPP), might help clinicians to improve personalised management of bipolar disorder.

AIMS

We performed a systematic review and meta-analysis to estimate prevalence and correlates of mPP and dPP in bipolar disorder.

METHOD

The protocol was registered in the Open Science Framework Registries (https://doi.org/10.17605/OSF.IO/8S2HU). We searched main electronic databases up to December 2023 and performed random-effects meta-analyses of weighted prevalence of mPP and dPP. Odds ratios and weighted mean differences (WMDs) were used for relevant correlates.

RESULTS

We included 28 studies, providing information on rates and/or correlates of mPP and dPP. We estimated similar rates of mPP (weighted prevalence = 30.0%, 95% CI: 23.1 to 37.4%) and dPP (weighted prevalence = 28.5%, 95% CI: 23.7 to 33.7%) in bipolar disorder. Younger age (WMD = -3.19, 95% CI: -5.30 to -1.08 years), male gender (odds ratio = 1.39, 95% CI: 1.10 to 1.76), bipolar-I disorder (odds ratio = 4.82, 95% CI: 2.27 to 10.24), psychotic features (odds ratio = 1.56, 95% CI: 1.01 to 2.41), earlier onset (WMD = -1.57, 95% CI: -2.88 to -0.26 years) and manic onset (odds ratio = 13.54, 95% CI: 5.83 to 31.46) were associated with mPP (P < 0.05). Depressive onset (odds ratio = 12.09, 95% CI: 6.38 to 22.90), number of mood episodes (WMD = 0.99, 95% CI: 0.28 to 1.70 episodes), history of suicide attempts (odds ratio = 2.09, 95% CI: 1.49 to 2.93) and being in a relationship (odds ratio = 1.98, 95% CI: 1.22 to 3.22) were associated with dPP (P < 0.05). No differences were estimated for other variables.

CONCLUSIONS

Despite some limitations, our findings support the hypothesis that predominant polarity might be a useful specifier of bipolar disorder. Evidence quality was mixed, considering effects magnitude, consistency, precision and publication bias. Different predominant polarities may identify subgroups of patients with specific clinical characteristics.

The Kynurenine Pathway in Attention-Deficit/Hyperactivity Disorder: A Systematic Review and Meta-Analysis of Blood Concentrations of Tryptophan and Its Catabolites

Preliminary evidence shows that the kynurenine pathway (KP) may be altered in attention-deficit/hyperactivity disorder (ADHD). We thus conducted a systematic review and meta-analysis exploring the peripheral blood concentrations of tryptophan catabolites (TRYCATs) in people with ADHD. We searched the main electronic databases up to 7th December 2023. Standardised mean differences (SMDs) with 95% confidence intervals (95%CIs) were used to compare TRYCAT concentrations between participants with ADHD and healthy controls (HCs). We included eight studies. Random-effects meta-analyses found higher kynurenine (SMD = 0.56; 95%CI: 0.04 to 1.08; p = 0.033; I2 = 90.3%) and lower kynurenic acid (SMD = -0.33; 95%CI: -0.49 to -0.17; p < 0.001; I2 = 0%) concentrations in people with ADHD compared to HCs. Additional analyses on drug-free children with ADHD showed higher tryptophan (SMD = 0.31; 95%CI: 0.11 to 0.50; p = 0.002; I2 = 0%) and kynurenine (SMD = 0.74; 95%CI: 0.30 to 1.17; p < 0.001; I2 = 76.5%), as well as lower kynurenic acid (SMD = -0.37; 95%CI: -0.59 to -0.15; p < 0.001; I2 = 0%) blood levels, as compared to HCs. Despite some limitations, our work provides preliminary evidence on KP alterations in ADHD that may suggest decreased neuroprotection. Further research is needed to clarify the role of the KP in ADHD.

Blood concentrations of anterior pituitary hormones in drug-naïve people with first-episode psychosis: A systematic review and meta-analysis

INTRODUCTION

The role of anterior pituitary hormones - i.e., adrenocorticotropic hormone (ACTH), luteinizing and follicle stimulating hormones (LH and FSH), growth hormone (GH), prolactin (PRL), and thyroid-stimulating hormone (TSH) - in early schizophrenia and psychoses unclear. We thus performed a systematic review and meta-analysis on the blood concentrations of ACTH, LH and FSH, GH, PRL, and TSH in drug-naïve people with first-episode psychosis (FEP) as compared with healthy controls.

METHODS

We searched Embase, MEDLINE, and PsycInfo for articles indexed until September 2022. Data quality was appraised. Random-effects meta-analyses were carried out, generating pooled standardized mean differences (SMDs). Between-study heterogeneity was estimated using the I2 statistic. Sensitivity and meta-regression analyses were performed.

RESULTS

Twenty-six studies were included. Drug-naïve people with FEP, compared to healthy subjects, had higher blood concentrations of ACTH (k = 7; N = 548; SMD = 0.62; 95%CI: 0.29 to 0.94; p < 0.001; I2 = 60.9%) and PRL (k = 17; N = 1757; SMD = 0.85; 95%CI: 0.56 to 1.14; p < 0.001; I2 = 85.5%) as well as lower levels of TSH (k = 6; N = 677; SMD = -0.34; 95%CI: -0.54 to -0.14; p = 0.001; I2 = 29.1%). Meta-regressions did not show any moderating effect of age (p = 0.78), sex (p = 0.21), or symptom severity (p = 0.87) on PRL concentrations in drug-naïve FEP. Available data were not sufficient to perform meta-analyses on FSH, LH, and GH.

CONCLUSIONS

Drug-naïve people with FEP have altered ACTH, PRL, and TSH blood concentrations, supporting the hypothesis that an abnormal anterior pituitary hormone secretion may be involved in the onset of schizophrenia and psychoses. Further research is needed to elucidate the role of pituitary hormones in FEP.

Effect of long-acting injectable antipsychotics on 1-year hospitalization in bipolar disorder: a mirror-image study

Long-acting injectable (LAI) antipsychotics are often used for the long-term management also of bipolar disorder (BD). Nonetheless, evidence on their effect on pragmatic outcomes such as hospitalization risk in BD is inconsistent. We carried out a mirror-image study comparing rates and number of days of hospitalization, one year before and after the initiation of LAI treatment, in a sample of subjects with BD. Participants were selected from the STAR Network Depot Study, a pragmatic, observational, multicenter research involving a cohort of inpatients and outpatients consecutively started on LAI treatment. Variations in rates and in total number of days of hospitalization between the 12 months before and those after treatment initiation were analyzed. Among 461 individuals screened for eligibility, we included 71 adults with BD, initiated either on first- (FGA) or second-generation (SGA) LAIs. We found a significant decrease in terms of 12-month hospitalization rates (p < 0.001) and number of days (p < 0.001) after LAI initiation, without any effect by age, gender, alcohol/substance use disorders, and symptom severity. Subgroup analyses based on antipsychotic class, history of LAI treatment, and concomitant oral medications, confirmed the decreasing trend on both hospitalization rates and number of days. However, these reductions were not significant among participants who continued this treatment for less than 6 months. Comprehensively, this study supports the role of LAIs as effective maintenance treatment options for BD. Further research is needed to identify clinical characteristics of people with BD who would most benefit from long-acting formulations of antipsychotics.

The role of BDNF in major depressive disorder, related clinical features, and antidepressant treatment: insight from meta-analyses

The brain-derived neurotrophic factor (BDNF) has received considerable attention as a potential biomarker of major depressive disorder (MDD) and antidepressant response. We conducted an overview of meta-analyses investigating the relationship of BDNF with MDD, related clinical features, and antidepressant treatment. Based on a systematic screening on main electronic databases, 11 systematic reviews with meta-analyses were included. Available evidence suggests that people with MDD have peripheral and central BDNF levels lower than non-depressed individuals. A negative correlation between blood BDNF and symptom severity emerged, while no association with suicidality was detected. Moreover, an increase in blood BDNF levels after antidepressant treatment, proportional to symptom improvement, was reported. BDNF levels seem to be increased in both treatment responders and remitters, remaining stable in non-responders. Conversely, no variations of BDNF concentrations after non-pharmacological interventions (electroconvulsive therapy, repetitive transcranial magnetic stimulation, and physical activity) were found. The findings of this overview appear consistent with the neurotrophic hypothesis of depression, suggesting that BDNF may play a role in both MDD pathophysiology and pharmacological treatment response.

Blood concentrations of neopterin and biopterin in subjects with depression: A systematic review and meta-analysis

INTRODUCTION

Pteridines, such as neopterin, biopterin, and tetrahydrobiopterin (BH₄), may be involved in depression pathophysiology owing to their links to immune-inflammatory response, oxidative and nitrosative stress, and monoaminergic transmission. Nonetheless, studies assessing pteridines in depression are inconsistent. We conducted a systematic review and meta-analysis of observational studies comparing blood pteridine concentrations between subjects with depression and healthy controls (HCs).

METHODS

We searched Embase, MEDLINE, and PsycInfo for articles indexed through November 2021. Study quality was appraised, evaluating age and gender comparability between groups, sample representativeness, and methods to assess depression. Random-effects meta-analyses were carried out, generating pooled standardized mean differences (SMDs). Heterogeneity across studies was estimated using the I² statistic.

RESULTS

Twenty-four studies, involving 3075 subjects, were included. Individuals with depression showed blood neopterin concentrations higher than HCs (k = 19; SMD = 0.36; p < 0.001) with moderate heterogeneity across studies (I² = 58.2%). No moderating role of age, gender, or type of blood sample was found. Sensitivity analyses showed no impact of inconsistency and quality of studies on findings. Neopterin concentrations were higher among individuals with major depressive disorder compared to HCs (SMD = 0.44; p < 0.001). This held true also when considering only drug-free subjects (SMD = 0.68; p = 0.003). No differences in biopterin concentrations were found between subjects with depression and HCs (k = 5; SMD = -0.35; p = 0.086), though this result was limited by inconsistency of findings (I² = 77.9%) and quality of studies. Finally, no sufficient data were available for a meta-analysis on BH₄.

CONCLUSIONS

As a whole, our work partly supports the hypothesis of an imbalance of pteridine metabolism in depression.

Long-acting injectable antipsychotics for the treatment of bipolar disorder: evidence from mirror-image studies

Clinical trials and real-world data have shown that long-acting injectable antipsychotics (LAIs) might be an effective therapeutic option also for people with bipolar disorder (BD). However, complementing evidence from mirror-image studies investigating LAIs in BD is scattered and has not been systematically evaluated so far. We thus performed a review of observational mirror-image studies testing the effectiveness of LAI treatment on clinical outcomes in people with BD. Embase, MEDLINE, and PsycInfo electronic databases were systematically searched (via Ovid) up to November 2022. We included six mirror-image studies that compared relevant clinical outcomes between the 12-months after (post-treatment period) and the 12-months before (pre-treatment period) the initiation of a LAI treatment in adults with BD. We found that LAI treatment is associated with a significant reduction in days spent in hospital and number of hospitalizations. Moreover, LAI treatment seems to be associated with a significant decrease in the proportion of individuals with at least one hospital admission, even though data on this outcome were reported by just two studies. In addition, studies consistently estimated a significant reduction of hypo-/manic relapses after LAI treatment initiation, while the effect of LAIs for depressive episodes is less clear. Finally, LAI treatment initiation was associated with a lower number of emergency department visits in the year after LAI initiation. The findings of this review seem to suggest that the use of LAIs is an effective strategy to improve major clinical outcomes in people with BD. Nonetheless, additional research, based on standardized assessments of prevalent polarity and relapses, is needed to identify the clinical characteristics of individuals with BD who are most likely to benefit from a LAI treatment.

Clinical correlates of comorbid attention deficit hyperactivity disorder in adults suffering from bipolar disorder: A meta-analysis

OBJECTIVE

Attention deficit hyperactivity disorder is a frequent comorbid condition in adults with bipolar disorder. We performed a meta-analysis aimed at assessing sociodemographic and clinical correlates of attention deficit hyperactivity disorder in bipolar disorder.

METHOD

We searched main electronic databases up to June 2021. Random-effects meta-analyses, with relevant meta-regression and quality-based sensitivity analyses, were carried out to estimate the association between attention deficit hyperactivity disorder and putative correlates, grading the quality of evidence.

RESULTS

We included 43 studies, based on 38 independent samples. Attention deficit hyperactivity disorder participants were more likely to be males (odds ratio = 1.46; p < 0.001) and unemployed (odds ratio = 1.45; p = 0.045), and less likely to be married (odds ratio = 0.62; p = 0.014). They had an earlier onset of bipolar disorder (standardized mean difference = -0.36; p < 0.001); more mood episodes (standardized mean difference = 0.35; p = 0.007), particularly depressive (standardized mean difference = 0.30; p = 0.011) and mixed (standardized mean difference = 0.30; p = 0.031) ones; higher odds of using antidepressants (odds ratio = 1.80; p = 0.024) and attempted suicides (odds ratio = 1.83; p < 0.001) and lower odds of psychotic features (odds ratio = 0.63; p = 0.010). Moreover, they were more likely to have generalized anxiety disorder (odds ratio = 1.50; p = 0.019), panic disorder (odds ratio = 1.89; p < 0.001), social phobia (odds ratio = 1.61; p = 0.017), eating disorders (odds ratio = 1.91; p = 0.007), antisocial personality disorder (odds ratio = 3.59; p = 0.004) and substance (odds ratio = 2.29; p < 0.001) or alcohol (odds ratio = 2.28; p < 0.001) use disorders. Quality of the evidence was generally low or very low for the majority of correlates, except for bipolar disorder onset and alcohol/substance use disorders (high), and suicide attempts (moderate).

CONCLUSION

Comorbid bipolar disorder/attention deficit hyperactivity disorder may have some distinctive clinical features including an earlier onset of bipolar disorder and higher comorbid alcohol/substance use disorder rates. Further research is needed to identify additional clinical characteristics of this comorbidity.

Practical Guidance for the Use of Long-Acting Injectable Antipsychotics in the Treatment of Schizophrenia

Schizophrenia is a severe mental illness causing a high degree of disability. First- and second-generation antipsychotics (FGAs and SGAs) represent key resources for its acute and long-term management. Since a poor adherence to oral treatments may negatively impact the course of the disorder, long-acting injectable antipsychotics (LAIs) are often used to reduce clinical relapses. Notwithstanding their potential beneficial features, LAIs use in clinical practice remains somewhat hampered by the limited amount of relevant systematic information. This review thus aims at providing a clinical, practical guidance for the use of LAIs in the treatment of schizophrenia. We synthetized main information on indications, dosage, and administration of LAIs approved by the US Food and Drug Administration (FDA) and/or in EU countries, as well as evidence from the most recent systematic reviews and meta-analyses. Currently available information, though heterogeneous, shows that LAIs can prevent relapses and rehospitalizations, improving clinical outcomes and favouring sustained remission among people with schizophrenia. The use of SGA LAIs is supported by more robust evidence than FGA LAIs. Along with their positive impact on the prevention of treatment discontinuation, some LAIs might also enhance individual global functioning and quality of life, without additional adverse events or health-care costs, as compared with oral antipsychotics. Although which LAIs can be considered a first-choice option, as well as their superiority over oral antipsychotics, remain unclear issues, this review offers a comprehensive overview of information available on the use of LAIs for people with schizophrenia, providing clinicians with practical guidance in terms of efficacy and acceptability of single agents. Literature gaps and future research needs are also described.

The association of kynurenine pathway metabolites with symptom severity and clinical features of bipolar disorder: An overview

BACKGROUND

The balance between neurotoxic and neuroprotective effects of kynurenine pathway (KP) components has been recently proposed as a key element in the pathophysiology of bipolar disorder (BD) and related mood episodes. This comprehensive overview explored the link of KP with symptom severity and other clinical features of BD.

METHODS

We searched Medline, Embase, and PsycInfo electronic databases for studies assessing the association of peripheral and/or central concentrations of KP metabolites with putative clinical features, including symptom severity and other clinical domains in BD.

RESULTS

We included the findings of 13 observational studies investigating the possible variations of KP metabolites according to symptom severity, psychotic features, suicidal behaviors, and sleep disturbances in BD. Studies testing the relationship between KP metabolites and depression severity generated mixed and inconsistent findings. No statistically significant correlations with manic symptoms were found. Moreover, heterogeneous variations of the KP across different clinical domains were shown. Few available studies found (a) higher levels of cerebrospinal fluid kynurenic acid and lower of plasma quinolinic acid in BD with psychotic features, (b) lower central and peripheral picolinic acid levels in BD with suicide attempts, and (c) no significant correlations between KP metabolites and BD-related sleep disturbances.

CONCLUSIONS

An imbalance of KP metabolism toward the neurotoxic branches is likely to occur in people with BD, though evidence on variations according to specific clinical features of BD is less clear. Additional research is needed to clarify the role of KP in the etiopathogenesis of BD and related clinical features.

Repurposed drugs as adjunctive treatments for mania and bipolar depression: A meta-review and critical appraisal of meta-analyses of randomized placebo-controlled trials

Several drugs previously tested in clinical trials and approved for different indications have been repurposed for bipolar disorder. We carried out a systematic meta-review of meta-analyses of randomized placebo-controlled trials investigating repurposed drugs as adjunctive treatments for mania and bipolar depression. We performed a critical appraisal using 'A MeaSurement Tool to Assess systematic Reviews' Version 2 (AMSTAR 2). We synthesized results on efficacy, tolerability, and safety, assessing evidence quality according to the 'Grading of Recommendations, Assessment, Development and Evaluations' (GRADE) approach. Our systematic search identified nine eligible studies investigating 12 drugs, four for mania and eight for bipolar depression. The quality of reporting was heterogeneous according to AMSTAR 2. In mania, allopurinol (for symptoms reduction and remission at 4-8 weeks) and tamoxifen (for response and symptoms reduction at 4-6 weeks) showed higher efficacy than placebo, with low and very low quality of evidence, respectively. Concerning bipolar depression, modafinil/armodafinil (for response, remission, and symptoms reduction at 6-8 weeks) and pramipexole (for response and symptoms reduction at 6 weeks) were superior to placebo, despite the low quality of evidence. Results on the efficacy of celecoxib and N-acetylcysteine were of low quality and limited to certain outcomes. Overall, the lack of evidence of high and moderate quality does not allow us to draw firm conclusions on the clinical utility of repurposed drugs as adjunctive treatments for mania and bipolar depression, highlighting the need for additional research.

Pre-Discharge Predictors of 1-Year Rehospitalization in Adolescents and Young Adults with Severe Mental Disorders: A Retrospective Cohort Study

Background and objectives: Readmissions of youths hospitalized for a severe mental disorder are common events and bear a remarkable human, social, and economic burden. The current study aimed at evaluating predictors of 1-year rehospitalization in a sample of adolescents and young adults with severe mental disorders. Materials and Methods: Data for ≤25-year-old inpatients with a severe mental disorder and consecutively admitted between 1 January 2016 and 30 June 2019 were collected. Subjects were retrospectively assessed over a follow-up period of one year after the index discharge to track readmissions—i.e., the primary outcome variable. Standard descriptive statistics were used. The association between variables and 1-year rehospitalization was estimated using the univariate Cox proportional hazards regression model. We then carried out a multivariable Cox regression model, also estimating the covariate-adjusted survivor function. Hazard ratios (HRs) with related 95% confidence intervals (95% CIs) were provided. Results: The final sample included 125 individuals. The multivariable Cox regression model estimated that co-occurring substance use disorders (HR = 2.14; 95% CI: 1.08 to 4.26; p = 0.029) and being admitted for a suicide attempt (HR = 2.49; 95% CI: 1.13 to 5.49; p = 0.024) were both significant predictors of 1-year rehospitalization. Conclusions: Our study showed that comorbid substance use disorders and being admitted for a suicide attempt were predictors of early readmission in youths with severe mental disorders. Although their generalizability is limited, our findings could contribute to improve the quality of young patients’ mental health care by identifying vulnerable subjects who may benefit from tailored interventions to prevent rehospitalizations.

Anticonvulsant properties of BIBP3226, a non-peptide selective antagonist at neuropeptide Y Y1 receptors

Several lines of evidence indicate that neuropeptide Y (NPY)-mediated neurotransmission in the hippocampus is altered by limbic seizures. The functional consequences of this change are still unresolved and clearly depend on the type of NPY receptors involved. We have investigated the role of NPY Y1 receptor subtypes, which are enriched in the dentate area of the hippocampus, on EEG seizures induced by a local injection of 0.04 microg kainic acid in rats. Intrahippocampal administration of 10 microg BIBP3226 (N2- (diphenylacetyl)-N-[(4-hydroxyphenyl)methyl]D-arginamide), a non-peptide selective antagonist at the NPY Y1 receptors, increased threefold on average (P < 0.01) the time to onset of seizures and reduced the number of seizures and the total time in seizures three- and fourfold, respectively (P < 0.01). Its inactive S-enantiomer BIBP3435 was ineffective on seizure activity. One microgram [Leu31,Pro34]NPY, an agonist at Y1 receptors, did not modify per se the EEG sequelae induced by kainic acid but it antagonized the anticonvulsant effect of BIBP3226. These results indicate that NPY Y1 receptors in the hippocampus are involved in epileptic phenomena and suggest that selective Y1 receptor antagonists may be of value for attenuating limbic seizures.