Endogenous antioxidants predicted outcome and increased after treatment: A benzoate dose-finding, randomized, double-blind, placebo-controlled trial for Alzheimer's disease

Safety and efficacy of sodium benzoate for patients with mild Alzheimer's disease: a systematic review and meta-analysis

OBJECTIVE

Alzheimer's disease (AD) is the most common neurodegenerative disorder. A key factor in its pathogenesis is the dysfunction of the N-methyl-D-aspartate (NMDA) receptor due to D-serine degradation by D-amino acid oxidase. Benzoate has been suggested to enhance NMDA receptor function, potentially benefiting early-phase AD. This study aimed to synthesize evidence from randomized clinical trials (RCTs) on the safety and efficacy of sodium benzoate in AD patients.

METHODS

We followed PRISMA statement guidelines during the accommodation of this systematic review and meta-analysis. A computer literature search (PubMed, Scopus, Web of Science, and Cochrane Central) was conducted. We included RCTs that compared sodium benzoate with placebo regarding cognitive functions. The primary outcome measure was the Alzheimer's disease assessment scale-cognitive subscale, pooled as the mean difference between the two groups from baseline to the endpoint. The secondary outcomes measures are the clinician's interview-based impression of change plus caregiver input, catalase, and superoxide dismutase antioxidants.

RESULTS

Three RCTs (described in four articles) with 306 patients were included in this study. Sodium benzoate significantly improved the ADAS-cog score compared with placebo (MD -2.13 points, 95% CI [-3.35 to -0.90]; P= 0.0007).

CONCLUSION

Sodium benzoate is a safe drug that may improve cognitive function in patients with early-stage Alzheimer's disease. However, the significant effect arises primarily from one small study, highlighting the need for caution in interpretation. Further research with larger sample sizes and longer durations is necessary to validate these findings and assess safety and efficacy.

Sodium benzoate, a D-amino acid oxidase inhibitor, improved short-term memory in patients with mild cognitive impairment in a randomized, double-blind, placebo-controlled clinical trial

BACKGROUND

Previous studies have found that sodium benzoate (the pivotal D-amino acid oxidase [DAO] inhibitor) improved cognitive function in patients with mild Alzheimer disease; however, its efficacy for mild cognitive impairment (MCI) (especially its core feature, impaired short-term memory) remains uncertain. The aim of this study was to evaluate the efficacy and safety of sodium benzoate in treating amnestic MCI (aMCI).

METHODS

This study was a randomized, double-blind, placebo-controlled clinical trial conducted in a major medical center in Taiwan. Eighty-two patients with aMCI were recruited for 24-week treatment of 250 to 1500 mg/day of sodium benzoate or placebo. Overall, cognitive function was measured by Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-cog), and short-term memory was evaluated by the 'recall of test instructions' item in the ADAS-cog. The generalized estimating equation was applied to compare the two groups in efficacy.

RESULTS

Compared with placebo, sodium benzoate therapy, displayed a trend, albeit statistically insignificant, in improving overall cognitive function (P = 0.082), and significantly improved short-term memory (P = 0.044). Both benzoate and placebo were well tolerated and benzoate therapy produced no additional side effect.

CONCLUSIONS

With the moderate sample size of the current study, treatment using sodium benzoate, a DAO inhibitor, showed promise in improving cognition, especially short-term memory, in patients with aMCI. Of note, while the ADAS-cog total score has been regarded as insensitive in measuring aMCI, its 'recall of test instructions' item may be a more sensitive and clinically feasible tool. Further larger studies are warranted to confirm the preliminary finding.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier. NCT04736355.

Symptomatic and cognitive effects of D-amino acid oxidase inhibitors in patients with schizophrenia: a meta-analysis of double-blind randomized controlled trials

D-amino acid oxidase inhibitors (DAOI) have demonstrated potential therapeutic benefits for schizophrenia and cognitive impairment; however, existing studies present conflicting results. This meta-analysis aimed to assess the symptomatic and cognitive effects of DAOI on the treatment of schizophrenia. An electronic search was conducted using PubMed, Cochrane Systematic Reviews, and the Cochrane Central Register of Controlled Clinical Trials for double-blinded, randomized controlled trials evaluating DAOI for the treatment of schizophrenia. Published trials up to November 2024 were included in the analysis. A random-effects model was employed to pool data for comparing the treatment effects of DAOI. Participants diagnosed with schizophrenia were recruited. Clinical and cognitive improvements were compared between baseline and post-DAOI treatment using standardized mean differences (SMDs) with 95% confidence intervals (CIs). Heterogeneity across the trials was assessed through funnel plots and the I² statistic. A total of five trials with 530 participants met the inclusion criteria. Four trials utilized sodium benzoate, while one trial employed luvadaxistat. The Positive and Negative Syndrome Scale (PANSS) was used in all studies to evaluate clinical symptoms, with four studies also assessed cognitive function. This analysis highlighted that DAOI surpassed the comparator in reducing the scores of PANSS total (SMD = -0.270, P = 0.035), PANSS positive (SMD = -0.399, P = 0.022), PANSS negative (SMD = -0.171, P = 0.026), and PANSS general psychopathology (SMD = -0.180, P = 0.019). Subgroup analyses identified significant effects in trials using sodium benzoate (SMD = 0.368, P = 0.021). Moreover, DAOI showed greater improvements in cognitive functions (SMD = 0.359, P = 0.017), with a better effect correlated with more female participants. The findings of this meta-analysis suggest that DAOI may be effective in improving clinical symptoms and cognitive function in patients with schizophrenia. Further studies with larger sample sizes are needed to confirm these results.

Food additives for the central nervous system, useful or harmful? An evidence-based review

OBJECTIVES

This review examines how food additives impact the central nervous system (CNS) focusing on the effects of sugars, artificial sweeteners, colorings, and preservatives.

METHODS

A literature search of PubMed, Scopus, and Web of Science was conducted for studies published since 2010. Key search terms included, food additives, neurotoxicity, cognition, and behavior.

RESULTS

It summarizes research findings on additives such as aspartame, stevia, methylene blue, azo dyes, sodium benzoate, and monosodium glutamate. It also covers mechanisms such as oxidative stress, neuroinflammation, and disruptions in neurotransmitter systems. Furthermore, it emphasizes the properties of natural compounds such as garlic (Allium sativum), tetramethylpyrazine, curcumin, licorice root extract (glycyrrhizin), and polyphenols in mitigating CNS damage caused by food additives.

DISCUSSION

Although ongoing studies are expanding our knowledge on the effects of these additives, future CNS research should focus on long-term investigations involving subjects to provide a more comprehensive understanding of the cumulative impacts of different additives and update regulatory standards based on new scientific findings.

Overview of Novel Antipsychotic Drugs: State of the Art, New Mechanisms, and Clinical Aspects of Promising Compounds

Antipsychotic medications are a vast class of drugs used for the treatment of psychotic disorders such as schizophrenia. Although numerous compounds have been developed since their introduction in the 1950s, several patients do not adequately respond to current treatments, or they develop adverse reactions that cause treatment discontinuation. Moreover, in the past few decades, discoveries in the pathophysiology of psychotic disorders have opened the way for experimenting with novel compounds that have alternative mechanisms of action, with some of them showing promising results in early trials. The scope of this review was to summarize the novel antipsychotics developed, their current experimental status, and their mechanisms of action. In particular, we analyzed the main classes of investigational antipsychotics, such as monoamine, glutamate, acetylcholine, cannabinoid receptor modulators, enzyme inhibitors, ion channel modulators, and mixed receptor modulators. In addition, the safety profiles and adverse effects of these drugs were carefully evaluated, considering the relevance of these aspects for patients' drug adherence and quality of life, especially in the long-term treatment. Lastly, we tried to understand which compounds have greater potential to be approved by the principal drug regulatory agencies in the next years and if they could be used for diseases other than psychotic disorders.

Sex- and dose-dependent catalase increase and its clinical impact in a benzoate dose-finding, randomized, double-blind, placebo-controlled trial for Alzheimer's disease

BACKGROUND

Sex differences in Alzheimer's disease (AD) are gaining increasing attention. Previously research has shown that sodium benzoate treatment can improve cognitive function in AD patients, particularly in the female patients; and 1000 mg/day of benzoate appears more efficacious than lower doses. Catalase is a crucial endogenous antioxidant; and deficiency of catalase is regarded to be related to the pathogenesis of AD. The current study aimed to explore the role of sex and benzoate dose in the change of catalase activity among benzoate-treated AD patients.

METHODS

This secondary analysis used data from a double-blind trial, in which 149 CE patients were randomized to receive placebo or one of three benzoate doses (500, 750, or 1000 mg/day) and measured with Alzheimer's disease assessment scale-cognitive subscale. Plasma catalase was assayed before and after treatment.

RESULTS

Benzoate treatment, particularly at 1000 mg/day, increased catalase among female patients, but not among male. The increases in the catalase activity among the benzoate-treated women were correlated with their cognitive improvements. In addition, higher baseline catalase activity was associated with more cognitive improvement after benzoate treatment among both female and male patients.

CONCLUSIONS

Supporting the oxidative stress theory and sex difference in AD, the finding suggest that sex (female) and benzoate dose co-determine catalase increase in benzoate-treated AD patients and the catalase increment contributes to cognitive improvement of benzoate-treated women.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03752463.

Physical Compatibility of Reduced Glutathione for Injection With 44 Intravenous Drugs During Simulated Y-site Administration

PURPOSE

Reduced glutathione (GSH) is extensively used in clinical therapeutics due to its antioxidative and cytoprotective properties. It is essential in the management of various chronic and acute conditions and serves as an adjunct therapy in oncology. Despite its widespread use, the physical compatibility of GSH with other intravenous drugs during Y-site administration has not been thoroughly investigated, posing risks such as reduced efficacy and adverse reactions. This study fills this critical gap by examining the physical compatibility of GSH with 44 commonly used intravenous drugs in simulated Y-site administration with 0.9% sodium chloride injection (NS) and 5% dextrose injection, aiming to enhance patient safety and clinical outcomes.

METHODS

Simulated Y-site administration was conducted in vitro by mixing 24 mg/mL of GSH with equal volumes of 44 diluted intravenous drugs. Physical compatibility was assessed by observing visual changes, checking for the Tyndall effect, measuring turbidity, and monitoring pH levels at 0, 0.5, 1, 2, and 4 hours post-mixing. Physical compatibility was defined as the absence of color changes, gas evolution, particulate formation, and the Tyndall effect within 4 hours, with turbidity changes of less than 0.5 nephelometric turbidity units from baseline and pH variations of less than 10% from initial values.

FINDINGS

GSH exhibited physical incompatibility with 11 of the 44 intravenous drugs evaluated, while it remained compatible with 33 drugs over 4 hours.

IMPLICATIONS

This study reveals that while GSH is physically compatible with the majority of tested intravenous drugs, incompatibilities with 11 drugs under simulated Y-site conditions necessitate rigorous compatibility testing prior to co-administration in clinical settings. These findings emphasize the importance of such testing to prevent potential treatment failures and adverse effects. Further research is needed to explore chemical stability and therapeutic efficacy in clinical settings, ensuring the safe and effective use of GSH in medical treatments.

Effects of sodium benzoate on cognitive function in neuropsychiatric disorders: a systematic review and meta-analysis

We performed a systematic review and meta-analysis on sodium benzoate's effects on cognitive function and other psychiatric symptoms in individuals with neuropsychiatric disorders. We searched PubMed, Embase, Cochrane Library, and PsychInfo databases until September 2023. A random-effects meta-analysis was performed within a frequentist framework. To investigate the potential sources of heterogeneity, we performed subgroup analyses based on sex, dose, diagnosis, and risk of bias of the included studies. Trial sequential analyses were performed to investigate the statistical power of the synthesized studies. The certainty in evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation approach. A total of 10 studies were included in the analysis. Sodium benzoate demonstrated a small-to-moderate positive effect on global cognitive function compared with placebo (standardized mean difference 0.40, 95% confidence interval 0.20 to 0.60, high certainty). Subgroup analyses suggested more pronounced effects in women; individuals receiving doses >500 mg/day; and individuals with early-phase Alzheimer's disease, chronic schizophrenia, or major depressive disorder. Sodium benzoate also demonstrated potential efficacy in enhancing the speed of processing, working memory, verbal learning and memory, visual learning and memory, and reasoning and problem solving. Furthermore, sodium benzoate was effective for positive psychotic symptoms but not for negative psychotic and depressive symptoms with moderate certainty. The current evidence strongly supports the positive effects of sodium benzoate on cognitive function in neuropsychiatric disorders. Further research is required to confirm its efficacy across different subtypes or stages of neurocognitive disorders and within specific cognitive domains.

Systematic Review Registration

PROSPERO, identifier CRD42023457462.

Elucidating the Mechanisms of Sodium Benzoate in Alzheimer Disease: Insights from Quantitative Proteomics Analysis of Serum Samples

BACKGROUND

N-methyl-D-aspartate receptors (NMDARs) are crucial components of brain function involved in memory and neurotransmission. Sodium benzoate is a promising NMDAR enhancer and has been proven to be a novel, safe, and efficient therapy for patients with Alzheimer disease (AD). However, in addition to the role of sodium benzoate as an NMDA enhancer, other mechanisms of sodium benzoate in treating AD are still unclear. To elucidate the potential mechanisms of sodium benzoate in Alzheimer disease, this study employed label-free quantitative proteomics to analyze serum samples from AD cohorts with and without sodium benzoate treatment.

METHODS

The serum proteins from each patient were separated into 24 fractions using an immobilized pH gradient, digested with trypsin, and then subjected to nanoLC‒MS/MS to analyze the proteome of all patients. The nanoLC‒MS/MS data were obtained with a label-free quantitative proteomic approach. Proteins with fold changes were analyzed with STRING and Cytoscape to find key protein networks/processes and hub proteins.

RESULTS

Our analysis identified 861 and 927 protein groups in the benzoate treatment cohort and the placebo cohort, respectively. The results demonstrated that sodium benzoate had the most significant effect on the complement and coagulation cascade pathways, amyloidosis disease, immune responses, and lipid metabolic processes. Moreover, Transthyretin, Fibrinogen alpha chain, Haptoglobin, Apolipoprotein B-100, Fibrinogen beta chain, Apolipoprotein E, and Alpha-1-acid glycoprotein 1 were identified as hub proteins in the protein‒protein interaction networks.

CONCLUSIONS

These findings suggest that sodium benzoate may exert its influence on important pathways associated with AD, thus contributing to the improvement in the pathogenesis of the disease.

d-Amino acids: new clinical pathways for brain diseases

Free d-amino acids (d-AAs) are emerging as a novel and important class of signaling molecules in many organs, including the brain and endocrine systems. There has been considerable progress in our understanding of the fundamental roles of these atypical messengers, with increasingly recognized implications in a wide range of neuropathologies, including schizophrenia (SCZ), epilepsy, Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), substance abuse, and chronic pain, among others. Research has enabled the discovery that d-serine, d-aspartate and more recently d-cysteine are essential for the healthy development and function of the central nervous system (CNS). We discuss recent progress that has profoundly transformed our vision of numerous physiological processes but has also shown how d-AAs are now offering therapeutic promise in clinical settings for several human diseases.

Adjunctive transcranial direct current stimulation (tDCS) plus sodium benzoate for the treatment of early-phase Alzheimer's disease: A randomized, double-blind, placebo-controlled trial

Previous studies found that an NMDA receptor (NMDAR) enhancer, sodium benzoate, improved cognitive function of patients with early-phase Alzheimer's disease (AD). Transcranial direct current stimulation (tDCS) induces NMDAR-dependent synaptic plasticity and strengthens cognitive function of AD patients. This study aimed to evaluate efficacy and safety of tDCS plus benzoate in early-phase dementia. In this 24-week randomized, double-blind, placebo-controlled trial, 97 patients with early-phase AD received 10-session tDCS during the first 2 weeks. They then took benzoate or placebo for 24 weeks. We assessed the patients using Alzheimer's disease assessment scale - cognitive subscale (ADAS-cog), Clinician's Interview-Based Impression of Change plus Caregiver Input, Mini Mental Status Examination, Alzheimer's disease Cooperative Study scale for ADL in MCI, and a battery of additional cognitive tests. Forty-seven patients received sodium benzoate, and the other 50 placebo. The two treatment groups didn't differ significantly in ADAS-cog or other measures. Addition of benzoate to tDCS didn't get extra benefit or side effect in this study. For more thoroughly studying the potential of combining tDCS with benzoate in the AD treatment, future research should use other study designs, such as longer-term benzoate treatment, adding benzoate in the middle of tDCS trial sessions, or administering benzoate then tDCS.

Differential Impacts of Endogenous Antioxidants on Clinical Symptoms and Cognitive Function in Acute and Chronic Schizophrenia Patients

BACKGROUND

Impaired antioxidant defense is implicated in the pathophysiology of schizophrenia, and superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) are 3 first-line endogenous antioxidants. Various cognitive functions decline differently during the schizophrenia course. The characteristic roles of the 3 antioxidants in clinical and cognitive profiles in acute and chronic phases of schizophrenia require study.

METHODS

We recruited 311 patients with schizophrenia, including 92 acutely exacerbated patients who had been off antipsychotics for at least 2 weeks and 219 chronic patients who had been stable on medication for at least 2 months. Blood SOD, CAT, and GSH levels; clinical symptoms; and 9 cognitive test scores were measured.

RESULTS

Blood CAT levels were higher in the acute patients than in the chronic patients, whereas SOD and GSH levels were similar to one another. Higher CAT levels were correlated with less positive symptoms, better working memory and problem solving in the acute phase, and less negative symptoms, less general psychopathology, better global assessment of function, and better cognitive function (in speed of processing, attention, problem solving) in the chronic period. Higher SOD levels were correlated with better global assessment of function in the acute phase and better speed of processing, working memory, and verbal learning and memory in the chronic period. GSH influenced neither clinical nor cognitive manifestations.

CONCLUSIONS

This study showed that blood CAT affected different clinical and cognitive domains between acute and chronic stages of schizophrenia, SOD influenced cognitive functions in chronic state, but GSH affected none. Further studies are needed to explore the underlying mechanisms.

Differential relationships of NMDAR hypofunction and oxidative stress with cognitive decline

NMDAR hypofunction and oxidative stress are implicated in the pathogenesis of Alzheimer's disease. D-amino acid oxidase (DAO) regulates NMDAR function. Glutathione, superoxide dismutase, and catalase are three first-line endogenous antioxidants. This study explored the associations of these potential biomarkers with mild cognitive impairment. Cognitive function and blood levels of DAO, glutathione, superoxide dismutase, and catalase were measured in 63 mild cognitive impairment patients and 24 healthy individuals every 6 months for 2 years. Among the patients, DAO and glutathione levels at baseline contributed to the cognitive decline 2 years later. Among the healthy individuals, only glutathione levels were associated with cognitive change. The four biomarkers differed in change directions (upward vs. downward) in the patients and in the healthy individuals. Among patients, glutathione levels were negatively correlated with superoxide dismutase and positively correlated with catalase, and DAO levels were negatively correlated with superoxide dismutase. To our knowledge, this is the first study to demonstrate the differential associations of NMDAR hypofunction and oxidative stress with cognitive change between the mild cognitive impairment patients and healthy people. Glutathione may be regarded as an aging marker for both mild cognitive impairment and normal aging; and DAO, a biomarker exclusively for mild cognitive impairment.

Mapping new pharmacological interventions for cognitive function in Alzheimer's disease: a systematic review of randomized clinical trials

Background and Objective: Alzheimer's disease (AD) is a progressive neurodegenerative disorder, that is, characterized by cognitive decline. To date, there are no effective treatments for AD. Therefore, the objective of this study was to map new perspectives on the effects of pharmacological treatment on cognitive function and the overall psychological state in patients with AD. Methods: Two independent researchers searched for randomized clinical trials (RCTs) exploring new pharmacological approaches related to cognition in Alzheimer's disease in adults from 2018 to 2023 in PubMed, Web of Science, Scopus, and Cochrane Library databases. A total of 17 RCTs were included in this review. Results: The results show that in recent years, new drugs have been tested in patients with Alzheimer's disease, including masitinib, methylphenidate, levetiracetam, Jiannao Yizhi, and Huannao Yicong formulas. Most studies have been conducted in populations with mild to moderate Alzheimer's disease. Conclusion: Although some of the drugs found suggested improvement in cognitive function, the scarcity of available studies highlights the need for further research in this area. Systematic review registration: [www.crd.york.ac.uk/prospero], identifier [CRD42023409986].