Fabrication of nanocrystal forms of á´ -cycloserine and their application for transdermal and enteric drug delivery systems.

ᴅ-cycloserine (DCS), an FDA-approved medicine for the treatment of tuberculosis, is also a partial agonist at the glycine recognition site of N-methyl-ᴅ-aspartate (NMDA) receptor and has shown significant treatment efficacy for central nervous system (CNS) disorders including depression, schizophrenia, Alzheimer's disease, and post-traumatic stress disorder. The physicochemical properties of DCS, however, limit the options of formulation and medicinal applications of DCS, and warrants further investigation for the development of CNS therapeutics. Nanocrystals play an important role in pharmaceutic design and development. The properties of nanocrystals are remarkably different from their bulk material counterpart, attributed to the large surface-area-to-volume ratio which can improve the bioavailability. In this study, for the first time, DCS, a highly water-soluble compound, has formed nanocrystals and this was confirmed by scanning electronic microscopy and X-ray powder diffraction. Furthermore, DCS nanocrystals were applied to several formulations to test their stability and then to the in vitro Franz diffusion test with reservoir patch formulation as well as in vivo pharmacokinetics study with enteric capsules. We tested these formulations regarding their nanocrystal physical properties, size effect, and dissolution rate, respectively. We found that DCS nanocrystals showed good performance in the Franz diffusion test and rodent pharmacokinetic studies due to the nanoparticle size and faster dissolution as compared with the commercial DCS powder. These DCS nanocrystal formulations could offer a new approach for the development of an advanced drug delivery system for the treatment of CNS disorders.

The Development of a Regulator of Human Serine Racemase for N-Methyl-D-aspartate Function.

It is crucial to regulate N-methyl-D-aspartate (NMDA) function bivalently depending on the central nervous system (CNS) conditions. CNS disorders with NMDA hyperfunction are involved in the pathogenesis of neurotoxic and/or neurodegenerative disorders with elevated D-serine, one of the NMDA receptor co-agonists. On the contrary, NMDA-enhancing agents have been demonstrated to improve psychotic symptoms and cognition in CNS disorders with NMDA hypofunction. Serine racemase (SR), the enzyme regulating both D- and L-serine levels through both racemization (catalysis from L-serine to D-serine) and ß-elimination (degradation of both D- and L-serine), emerges as a promising target for bidirectional regulation of NMDA function. In this study, we explored using dimethyl malonate (DMM), a pro-drug of the SR inhibitor malonate, to modulate NMDA activity in C57BL/6J male mice via intravenous administration. Unexpectedly, 400 mg/kg DMM significantly elevated, rather than decreased (as a racemization inhibitor), D-serine levels in the cerebral cortex and plasma. This outcome prompted us to investigate the regulatory effects of dodecagalloyl-α-D-xylose (α12G), a synthesized tannic acid analog, on SR activity. Our findings showed that α12G enhanced the racemization activity of human SR by about 8-fold. The simulated and fluorescent assay of binding affinity suggested a noncooperative binding close to the catalytic residues, Lys56 and Ser84. Moreover, α12G treatment can improve behaviors associated with major CNS disorders with NMDA hypofunction including hyperactivity, prepulse inhibition deficit, and memory impairment in animal models of positive symptoms and cognitive impairment of psychosis. In sum, our findings suggested α12G is a potential therapeutic for treating CNS disorders with NMDA hypofunction.

Suicide attempts in French Polynesia during the era of COVID-19: a prospective analysis over three years.

Background: Past studies in French Polynesia have identified suicide as a significant concern, with a measured annual incidence of 79.4 attempts per 100,000 population during 2008-2010. In response to the COVID-19 pandemic, a monitoring system was established to track and investigate suicide attempts (SA). Methods: A prospective study was conducted between April 2020 and March 2023, including all patients referred to the French Polynesia Hospital Center for SA. Demographic factors as well as clinical parameters were analyzed. Findings: During the study period, 895 SAs were registered and confirmed, with a crude annual rate of 106.7 events and the adjusted rate at 113.2 per 100,000 population. Substantial majority of SA happened in the island of Tahiti. Half of the subjects did not have psychiatric diagnosis. There was a significant increase in SA from year 1 to year 3, with young people (female more than male) particularly at risk, especially in Tahiti. The normalized incidence among females younger than 20-year-old was as high as 310.4 per 100,000 population. Interpretation: Our data revealed an overall 34.4% increase in SA in French Polynesia, with a striking 54.9% increase during the third year of pandemic. The last year's record high incidence, is confirmed by increased activity on suicide hotlines, notably in Tahiti. A correlation between COVID exposure and suicidal behaviors, both at the individual and social level, is suspected with young female in Tahiti being the most vulnerable. These findings highlight the need for reinforced prevention and an efficient suicide monitoring system even after the public health emergency was declared over. Funding: The study is investigator-initiated without funding.

Acidic Microenvironment-Sensitive Core-Shell Microcubes: The Self-assembled and the Therapeutic Effects for Caries Prevention.

OBJECTIVES: The aim of this study was to develop a new material with integrated interface design that could achieve the purpose of environmental-sensing controlled release against cariogenic bacteria. Furthermore, this material can rebalance oral flora and serve as a preventive and reparative measure of dental caries. MATERIALS AND METHODS: NaF@PAA@HA@polyelectrolytes@HA@PAA particles were synthesized using the method of two-solution phases precipitation followed by biocompatible polymers coating layer by layer. The structure of the particles was confirmed by transmission electron microscope. The fluoride release profile was measured by fluoride ion electrode. Antimicrobial activity against the cariogenic microorganisms was analyzed by scanning electron microscopy and energy dispersive spectrum. The efficacy experiments were conducted on tooth enamel slides to evaluated fluoride absorption and antibacterial activity of the prototype toothpaste containing microcube particles RESULTS: The structure of NaF@PAA@HA@polyelectrolytes@HA@PAA particles showed a core surrounded by tooth-adhesion polymer layers in thin fin or filament structure. The loaded concentration of fluoride in the particles' core was 148,996 ± 28,484 ppm. NaF@PAA@HA@polyelectrolytes@HA@PAA particles showed selective inhibition of cariogenic microorganisms over probiotic strains and stronger fluoride adhesion on tooth enamel. A burst release (over 80%) of fluoride from the particle-containing toothpaste was observed under cariogenic acidic environment (pH < 5), while it remained extremely low under neutral environment. Compared with the best results of commercial toothpastes, our prototype toothpaste increased enamel fluoride uptake by 8-fold in normal enamel slides and by 11-fold in the slides with induced white spot lesions after either 1- or 7-day treatment. The prototype toothpaste also showed better inhibition of cariogenic microorganisms than the commercial brands. The coverage area of cariogenic bacteria under our toothpaste treatment was 73% on normal enamel slides compared with the commercial brands, while it was 69% in the induced white spot lesions. CONCLUSIONS: In our study, an intelligent toothpaste was developed that selectively inhibits cariogenic bacteria by microenvironment proton-triggered fluoride release. Such novel design would accomplish a favorable flora balance for optimal long-term oral health.

Lithium Benzoate Exerts Neuroprotective Effect by Improving Mitochondrial Function, Attenuating Reactive Oxygen Species, and Protecting Cognition and Memory in an Animal Model of Alzheimer's Disease.

Background: Alzheimer's disease (AD) is a multifactorial neurodegenerative disease affecting many cellular pathways, including protein aggregation, mitochondrial dysfunction, oxidative stress (OS), and neuroinflammation. Currently, no effective treatment for AD exists. Objective: We aim to determine the effect of lithium benzoate (LiBen) in protecting neurons from amyloid-ß (Aß) or other neurotoxin insults. Methods: Primary rat cortical neurons co-treated with neurotoxins and LiBen were used to examine its effect in cell viability, reactive oxygen species (ROS) clearance, and mitochondrial functions by MTT, CellRox fluorescence staining, and seahorse assay. Then, Barnes maze and prepulse inhibition test were performed in APP/PS1 mice that received chronic LiBen treatment to assess its effect on cognitive protection. Oral bioavailability of LiBen was also assessed by pharmacokinetic study in rat plasma. Results: In this study, we discovered that LiBen can attenuate cellular ROS level, improve mitochondrial function, increase cell viability against multiple different insults of mitochondrial dysfunction, Aß accumulation, and neuroinflammation, and promote neurogenesis. We demonstrated that LiBen has advantages over lithium or sodium benzoate alone as LiBen displays superior neuroprotective efficacy and oral bioavailability than the other two agents when being applied either alone or in combination. Furthermore, chronic administration of LiBen showed protection for cognition as well as spatial memory and reduced the senile plaque deposition in brains of AD animal models. Conclusion: LiBen stands as a promising therapeutic agent for improving cognition and delaying the progression of AD.

Pharmacokinetics and Safety of Sodium Benzoate, a d-Amino Acid Oxidase (DAAO) Inhibitor, in Healthy Subjects: A Phase I, Open-label Study.

PURPOSE: N-methyl-d-aspartate receptor (NMDAR)-mediated neurotransmission plays a critical role in cognition and memory, and d-serine is a co-agonist of the receptor. d-serine is metabolized by d-amino acid oxidase (DAAO). Sodium benzoate is a DAAO inhibitor that leads to the elevation of d-serine levels and enhances NMDAR functions as a therapeutic for wide-spectrum central nervous system (CNS) disorders, including schizophrenia and dementia. For therapeutic application of sodium benzoate in CNS disorders, we conducted a Phase I study to evaluate its safety, tolerability, and pharmacokinetic profile after single-dose oral administration in healthy volunteers. In contrast to the accumulation in the CNS, sodium benzoate has a rapid pharmacokinetic profile when measured peripherally. METHODS: In this Phase I study, subjects were randomized into 4 different dose groups after a single oral administration. The pharmacokinetic parameters of sodium benzoate were assessed after exposure to 250, 500, 1000, and 2000 mg of sodium benzoate. All adverse events were investigated and recorded. FINDINGS: The Cmax and AUC of sodium benzoate exhibited a higher than dose-proportional increase within the dose range from 250 to 2000 mg under fasting conditions. The slopes were 1.78 and 2.61 and the 90% CIs were 1.41 to 2.15 and 2.20 to 3.03 for Cmax and AUC, respectively. Sodium benzoate was absorbed and converted to benzoic acid rapidly, reaching Cmax after ∼0.5 hour and elimination t1/2 after ∼0.3 hour. No subjects reported adverse events that were sodium benzoate related. IMPLICATIONS: The nonlinear pharmacokinetic response was observed within the dose range up to 2000 mg. Sodium benzoate treatment exhibited a favorable safety profile and was well tolerated at all dose levels. The study results serve as a foundation that should be useful for investigating efficacy and safety in the drug's subsequent clinical development. TRIAL REGISTRATION: TFDA-103607047.

Development of Ultrapure and Potent Tannic Acids as a Pan-coronal Antiviral Therapeutic.

The rampageous transmission of SARS-CoV-2 has been devastatingly impacting human life and public health since late 2019. The waves of pandemic events caused by distinct coronaviruses at present and over the past decades have prompted the need to develop broad-spectrum antiviral drugs against them. In this study, our Pentarlandir ultrapure and potent tannic acids (UPPTA) showed activities against two coronaviral strains, SARS-CoV-2 and HCoV-OC43, the earliest-known coronaviruses. The mode of inhibition of Pentarlandir UPPTA is likely to act on 3-chymotrypsin-like protease (3CLpro) to prevent viral replication, as supported by results of biochemical analysis, a 3CLpro assay, and a "gain-of-function" 3CLpro overexpressed cell-based method. Even in the 3CLpro overexpressed environment, Pentarlandir UPPTA remained its antiviral characteristic. Utilizing cell-based virucidal and cytotoxicity assays, the 50% effective concentrations (EC50) and 50% cytotoxicity concentration (CC50) of Pentarlandir UPPTA were determined to be ∼0.5 and 52.5 µM against SARS-CoV-2, while they were 1.3 and 205.9 µM against HCoV-OC43, respectively. In the pharmacokinetic studies, Pentarlandir UPPTA was distributable at a high level to the lung tissue with no accumulation in the body, although the distribution was affected by the food effect. With further investigation in toxicology, Pentarlandir UPPTA demonstrated an overall safe toxicology profile. Taking these findings together, Pentarlandir UPPTA is considered to be a safe and efficacious pancoronal antiviral drug candidate that has been advanced to clinical development.

Adjunctive sarcosine plus benzoate improved cognitive function in chronic schizophrenia patients with constant clinical symptoms: A randomised, double-blind, placebo-controlled trial.

Objectives Hypofunction of NMDA receptor is implicated in the pathophysiology, particularly cognitive impairment, of schizophrenia. Sarcosine, a glycine transporter I (GlyT-1) inhibitor, and sodium benzoate, a d-amino acid oxidase (DAAO) inhibitor, can both enhance NMDA receptor-mediated neurotransmission. We proposed simultaneously inhibiting DAAO and GlyT-1 may be more effective than inhibition of either in improving the cognitive and global functioning of schizophrenia patients. Methods This study compared add-on sarcosine (2 g/day) plus benzoate (1 g/day) vs. sarcosine (2 g/day) for the clinical symptoms, as well as the cognitive and global functioning, of chronic schizophrenia patients in a 12-week, double-blind, randomised, placebo-controlled trial. Participants were measured with the Positive and Negative Syndrome Scale and the Global Assessment of Functioning Scale every 3 weeks. Seven cognitive domains, recommended by the Measurement and Treatment Research to Improve Cognition in Schizophrenia Committee, were measured at weeks 0 and 12. Results Adjunctive sarcosine plus benzoate, but not sarcosine alone, improved the cognitive and global functioning of patients with schizophrenia, even when their clinical symptoms had not improved. Conclusions This finding suggests N-methyl-d-aspartate receptor-enhancement therapy can improve the cognitive function of patients with schizophrenia, further indicating this pro-cognitive effect can be primary without improvement in clinical symptoms.

Sarcosine treatment for oppositional defiant disorder symptoms of attention deficit hyperactivity disorder children.

Methylphenidate, a stimulant that activates dopaminergic and noradrenergic function, is an important agent in the treatment of attention deficit hyperactivity disorder (ADHD). Sarcosine, a glycine transporter-1 inhibitor, may also play a role in treating ADHD by modulating the glutamatergic neurotransmission system through activating N-methyl-D-aspartate type glutamate receptors. This study aimed to assess the efficacy of sarcosine in treating children with ADHD. We conducted a six-week, randomized, double-blind, placebo-controlled clinical trial. The primary outcome measures were those on the Inattention, Hyperactivity/impulsivity, and oppositional defiant disorder (ODD) subscales of the Swanson, Nolan, and Pelham, version IV scale. Efficacy and safety were measured bi-weekly. A total of 116 children with ADHD were enrolled. Among them, 48 (83%) of the 58 sarcosine recipients and 44 (76%) of the 58 placebo recipients returned for the first post-treatment visit. The missing data values were imputed by the last observation carry forward method. From a multiple linear regression analysis, using the generalized estimating equation approach, and an intention to treat analysis, the efficacy of sarcosine marginally surpassed that of placebo at weeks 2, 4, and 6, with p-values=0.01, 0.026, and 0.012, respectively, although only for ODD symptoms. Treatment of ADHD by sarcosine (0.03 g/kg/day) was well tolerated. Sarcosine could possibly be a novel agent for managing ODD symptoms in the context of ADHD. However, future larger-scale studies are warranted to optimize its dosage.

Assessing the construct validity of the Chinese-Version Schizotypal Personality Questionnaire-Brief on male and female undergraduate students.

BACKGROUND: Screening for the schizotypal personality trait is one strategy to identify people who may be susceptible to early psychosis or be at high risk for prodromal psychosis. The Schizotypal Personality Questionnaire-Brief (SPQ-B) has been widely used to assess the schizotypal personality and has been translated into Chinese. However, the psychometric properties of the Chinese-version scale have yet to be evaluated. PURPOSE: This study evaluates the construct validity of the Chinese-version SPQ-B on a sample of male and female undergraduate students in Taiwan. METHODS: A cross-sectional design with convenient sampling was used for this study. The data were collected using the Chinese-version SPQ-B between October 2008 and June 2009. Participants included 513 male and 675 female undergraduate students in Taiwan. The factor construct validity of the scale was examined by confirmatory factor analysis using structural equation modeling with SPSS AMOS version 17 software. RESULTS: The results show that the three-factor model fits the data better than the one-factor model for both male and female participants. The male participants scored significantly higher than their female counterparts in terms of total scale, interpersonal subscales, and disorganized subscales. CONCLUSIONS/IMPLICATIONS FOR PRACTICE: The Chinese version of the SPQ-B adequately achieves three-factor construct validity for undergraduate students. The scale may be used to screen for the schizotypal personality trait in both male and female college students to identify those at an elevated risk for mental illness.

Effectiveness of aripiprazole, olanzapine, quetiapine, and risperidone augmentation treatment for major depressive disorder: a nationwide population-based study.

OBJECTIVE: Previous studies suggested that antidepressants augmented with second-generation antipsychotics (SGAs), including aripiprazole, olanzapine, quetiapine, and risperidone, resulted in better treatment response or higher rates of remission in patients with major depressive disorder (MDD). However, population-based study on SGA augmentation for patients with MDD remains limited. The purpose of this study was to investigate the effectiveness of SGA augmentation for treatment of MDD using the National Health Insurance Research Database in Taiwan. METHOD: The subjects were patients with MDD (ICD-9-CM code: 296.2 and 296.3) who were initially admitted to psychiatric inpatient settings for the first time between January 1, 1996, and December 31, 2007, and could be tracked until December 31, 2011. To assess the treatment effect of SGA augmentation, 993 MDD patients who received aripiprazole, olanzapine, quetiapine, or risperidone augmentation treatment for 8 weeks or more were included in this 1-year mirror-image study. Outcome measures included length of psychiatric hospitalization and number of psychiatric admissions and emergency room (ER) visits. RESULTS: After patients received SGA augmentation treatment, key psychiatric service use (including length of psychiatric hospitalization [P < .0001], number of psychiatric admissions [P < .0001], and ER visits [P = .0006]) due to MDD diagnosis was significantly reduced. Subgrouping analysis for each SGA drug also showed significant reduction in number of psychiatric admissions for MDD patients who received aripiprazole (P < .0001), olanzapine (P = .003), quetiapine (P < .0001), and risperidone (P < .0001). CONCLUSIONS: The study provides support that aripiprazole, olanzapine, quetiapine, and risperidone augmentation therapy could be effective in reducing psychiatric service utilization among MDD patients.

Nuclear receptor TLX stimulates hippocampal neurogenesis and enhances learning and memory in a transgenic mouse model.

The role of the nuclear receptor TLX in hippocampal neurogenesis and cognition has just begun to be explored. In this study, we generated a transgenic mouse model that expresses TLX under the control of the promoter of nestin, a neural precursor marker. Transgenic TLX expression led to mice with enlarged brains with an elongated hippocampal dentate gyrus and increased numbers of newborn neurons. Specific expression of TLX in adult hippocampal dentate gyrus via lentiviral transduction increased the numbers of BrdU(+) cells and BrdU(+)NeuN(+) neurons. Furthermore, the neural precursor-specific expression of the TLX transgene substantially rescued the neurogenic defects of TLX-null mice. Consistent with increased neurogenesis in the hippocampus, the TLX transgenic mice exhibited enhanced cognition with increased learning and memory. These results suggest a strong association between hippocampal neurogenesis and cognition, as well as significant contributions of TLX to hippocampal neurogenesis, learning, and memory.

NMDA pathology and treatment of schizophrenia.

Schizophrenia, a multifactorial mental disorder with polygenic inheritance as well as environmental influences, encompasses a characteristic group of symptoms. Negative and cognitive symptoms which respond poorly to currently available antipsychotics remain a great clinical challenge. Aggressive studies are ongoing to explore the etiological mechanisms of this disease. Among them, one of the primary causal factors is dysfunction of the N-methyl-D-aspartate (NMDA)-type glutamate receptors. This article reviews the clinical manifestations of the disease, limitations of current antipsychotics and reconceptualization of the nature of disease and treatment modalities based on the evidence provided by drug models, genetic studies, and clinical trials. The NMDA receptor (NMDAR) model plays a critical role in the revolution of pharmaceutical industry as a new set of drug targets is proposed. Investigations on the modulation of glutamatergic system, particularly the intrinsic NMDA glycine modulatory site, exhibit encouraging results. A group of "NMDA-enhancing agents" either acts directly or indirectly on the glycine modulatory site, showing therapeutic efficacy in preclinical and early clinical trials. A new generation of therapeutic agents targeting the NMDAR shows promise as the next wave of drug development for schizophrenia.

Assessing and treating cognitive impairment in schizophrenia: current and future.

Schizophrenia is a serious neuropsychiatric disease characterized by positive symptoms, negative symptoms and cognitive impairment. Evidence have shown that cognitive impairment sustains in every clinical stage, may relate with the liability, may predict functional outcome in schizophrenia and could be the core symptom of schizophrenia. The treatment of cognitive impairment in schizophrenia could alleviate the burden of the illness and has become the subject of intensive research. In this review, we synthesize current advances of assessing strategies, pharmacological and non-pharmacological treatments of cognitive impairment in schizophrenia. According to the registered records of ClinicalTrials.gov, the most widely studied strategies have aimed at modifying neurochemical mechanisms of dopamine metabolism, glutamate metabolism, γ-aminobutyric acid (GABA) metabolism, serotonin metabolism, acetylcholine metabolism, and oxytocin. Despite preclinical data for putative pro-cognitive drugs, their clinical benefits for schizophrenia patients have been limited. The small sample sizes and the short treatment duration could be related with the suboptimal results. Evidence supported the short-term benefits of cognitive remediation therapy on cognitive domains with small to moderate effects; however, the small sample sizes and the characteristics of subjects limited the generalization of the positive results and the long-term functional outcome is not clear. Combination therapy is promising, by integrating pro-cognitive agents and cognitive rehabilitation programs or combining two kinds of pro-cognitive agents via different mechanisms. Future studies should investigate the pro-cognitive drugs' long-term efficacy, rebound deterioration in psychosis/cognition following discontinuation, and related biomarkers of functional outcome.

NMDA neurotransmission dysfunction in mild cognitive impairment and Alzheimer's disease.

The prevalence of Alzheimer's disease (AD) in the elderly is growing rapidly worldwide, and the deteriorating clinical course of AD places a heavy burden on both the patients and their families. Early detection and intervention of mild cognitive impairment in the early phase of AD is vital for the purpose of improving the cognitive performance of patients and preventing the existing deficits from worsening. However, the main compounds currently used to treat early AD, acetylcholinesterase inhibitors (AChEIs), are unsatisfactory in efficacy and safety. Moreover, evidence indicates that AChEIs are ineffective in treating AD at extremely early stages, which implies that mechanisms other than those targeted by AChEIs underlie the pathogenesis of AD. Dysfunctional glutamatergic neurotransmission, particularly that mediated by the N-methyl-D-aspartate (NMDA) receptor, has been reported to play a role in the pathophysiology of AD. The NMDA receptor (NMDAR) regulates synaptic plasticity, memory, and cognition, and the attenuation of NMDAR-mediated neurotransmission can result in impaired neuroplasticity and cognitive deficits in the aging brain. Furthermore, NMDARs also interact with amyloid beta peptide/amyloid precursor protein and tau protein, whose production represents the main manifestations of AD. In this paper, we review the evidence supporting NMDA dysfunction in both animal models of AD and patients afflicted with AD, and we also review the literature that suggests that NMDA-enhancing agents such as glycine and D-cycloserine can improve cognitive functions. The benefits and limitations of NMDAR antagonists that can diminish the excitatory neurotoxicity triggered by glutamate are also addressed in relation to AD. We propose that enhancing glutamatergic neurotransmission by activating the NMDAR may be effective in treating the cognitive decline that occurs in AD. Prospective studies on AD in which NMDA-enhancing agents are used are required to verify this hypothesis and confirm the long-term efficacy and safety of the treatment agents.

Attention deficit hyperactivity disorder and N-methyl-D-aspartate (NMDA) dysregulation.

Attention deficit hyperactivity disorder (ADHD) is a long recognized and common childhood disorder. ADHD adolescents tend to encounter more difficulties in school and peer relationships, whereas ADHD adults have more occupational and interpersonal difficulties. However, with the treatment of central nervous system (CNS) stimulants, 10-20 % of the patients still remain poor responders to treatment. Among hypotheses for ADHD, dysfunction of N-methyl-D-aspartate (NMDA)-type glutamate receptors has recently been suggested by accumulating genetic and animal studies. This article systemically reviews evidence supporting NMDA dysfunction as a potential ADHD pathogenesis from perspectives of neurodevelopment, attentional circuitry, and impulse inhibition. The review also addresses the development of novel treatments for ADHD via modulation of glutamatergic system, particularly the NMDA/glycine site. These so-called NMDA enhancers may provide a new treatment option for patients with ADHD.

Benzoate, a D-amino acid oxidase inhibitor, for the treatment of early-phase Alzheimer disease: a randomized, double-blind, placebo-controlled trial.

BACKGROUND: N-methyl-D-aspartate receptor (NMDAR)-mediated neurotransmission is vital for learning and memory. Hypofunction of NMDAR has been reported to play a role in the pathophysiology of Alzheimer disease (AD), particularly in the early phase. Enhancing NMDAR activation might be a novel treatment approach. One of the methods to enhance NMDAR activity is to raise the levels of NMDA coagonists by blocking their metabolism. This study examined the efficacy and safety of sodium benzoate, a D-amino acid oxidase inhibitor, for the treatment of amnestic mild cognitive impairment and mild AD. METHODS: We conducted a randomized, double-blind, placebo-controlled trial in four major medical centers in Taiwan. Sixty patients with amnestic mild cognitive impairment or mild AD were treated with 250-750 mg/day of sodium benzoate or placebo for 24 weeks. Alzheimer's Disease Assessment Scale-cognitive subscale (the primary outcome) and global function (assessed by Clinician Interview Based Impression of Change plus Caregiver Input) were measured every 8 weeks. Additional cognition composite was measured at baseline and endpoint. RESULTS: Sodium benzoate produced a better improvement than placebo in Alzheimer's Disease Assessment Scale-cognitive subscale (p = .0021, .0116, and .0031 at week 16, week 24, and endpoint, respectively), additional cognition composite (p = .007 at endpoint) and Clinician Interview Based Impression of Change plus Caregiver Input (p = .015, .016, and .012 at week 16, week 24, and endpoint, respectively). Sodium benzoate was well-tolerated without evident side-effects. CONCLUSIONS: Sodium benzoate substantially improved cognitive and overall functions in patients with early-phase AD. The preliminary results show promise for D-amino acid oxidase inhibition as a novel approach for early dementing processes.

The C-terminal region of G72 increases D-amino acid oxidase activity.

The schizophrenia-related protein G72 plays a unique role in the regulation of D-amino acid oxidase (DAO) in great apes. Several psychiatric diseases, including schizophrenia and bipolar disorder, are linked to overexpression of DAO and G72. Whether G72 plays a positive or negative regulatory role in DAO activity, however, has been controversial. Exploring the molecular basis of the relationship between G72 and DAO is thus important to understand how G72 regulates DAO activity. We performed yeast two-hybrid experiments and determined enzymatic activity to identify potential sites in G72 involved in binding DAO. Our results demonstrate that residues 123-153 and 138-153 in the long isoform of G72 bind to DAO and enhance its activity by 22% and 32%, respectively. A docking exercise indicated that these G72 peptides can interact with loops in DAO that abut the entrance of the tunnel that substrate and cofactor must traverse to reach the active site. We propose that a unique gating mechanism underlies the ability of G72 to increase the activity of DAO. Because upregulation of DAO activity decreases d-serine levels, which may lead to psychiatric abnormalities, our results suggest a molecular mechanism involving interaction between DAO and the C-terminal region of G72 that can regulate N-methyl-d-aspartate receptor-mediated neurotransmission.