Vitamin C function in the brain: vital role of the ascorbate transporter SVCT2

Vitamin C supplementation promotes mental vitality in healthy young adults: results from a cross-sectional analysis and a randomized, double-blind, placebo-controlled trial

Purpose

We aimed to investigate the link of vitamin C status with vitality and psychological functions in a cross-sectional study, and examine their causal relationship through a randomized controlled trial (RCT).

Methods

We first conducted a population-based cross-sectional investigation of healthy young adults (n = 214, 20–39 years), and analyzed the associations of serum vitamin C concentrations with vitality (fatigue and attention) and mood status (stress, depression, and positive and negative affect) using Pearson’s correlation and multiple linear regression analyses. Next, we performed a double-blind RCT in healthy subjects whose serum vitamin C concentrations were inadequate (< 50 μmol/L). Subjects were randomly allocated to receive 500 mg of vitamin C twice a day for 4 weeks (n = 24) or a placebo (n = 22). We assessed vitality, which included fatigue, attention, work engagement, and self-control resources, and measured mood status, including stress, depression, positive and negative affect, and anxiety. ELISA determined serum brain-derived neurotrophic factor (BDNF), and a Stroop color–word test evaluated attention capacity and processing speed.

Results

In the cross-sectional data, the serum vitamin C concentration was positively associated with the level of attention (r = 0.16, p = 0.02; standardized β = 0.21, p = 0.003), while no significant associations with the levels of fatigue and mood variables being found. In the RCT, compared to the placebo, the vitamin C supplementation significantly increased attention (p = 0.03) and work absorption (p = 0.03) with distinct tendency of improvement on fatigue (p = 0.06) and comprehensive work engagement (p = 0.07). The vitamin C supplementation did not affect mood and serum concentrations of BDNF. However, in the Stroop color–word test, the subjects supplemented with vitamin C showed better performance than those in the placebo group (p = 0.04).

Conclusion

Inadequate vitamin C status is related to a low level of mental vitality. Vitamin C supplementation effectively increased work motivation and attentional focus and contributed to better performance on cognitive tasks requiring sustained attention.

Trial registration number and date of registration

Cross-sectional study: KCT0005074 (cris.nih.go.kr)/1 June, 2020 (retrospectively registered). Intervention study: KCT0004276 (cris.nih.go.kr)/4 September, 2019.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-021-02656-3.

Mutation SVCT2 promotes cell proliferation, invasion and migration in colorectal cancer

The sodium-dependent vitamin C transporter 2 (SVCT2) surface glycoprotein regulates ascorbate accumulation in the plasma, often resulting in the induction of cancer cell death. Therefore, high expression of this gene associates with increased overall survival in several cancers. However, in colorectal cancer (CRC), high (likely mutated) SVCT2 expression relates to poor overall survival, and its functional significance has not been studied. Thus, we hypothesize that mutant SVCT2 expression could affect CRC patient survival. According to biological databases, SVCT2 has been found to be mutated frequently, and SVCT2 E264K has a particularly high pathogenic score (0.98), compared to other SVCT2 mutant sites, in CRC patients. Interestingly, our results reveal expression of SVCT2 E264K in many CRC tissues and cells. Also, we found wild-type SVCT2 expression to be largely localized to the cytoplasm and membrane, while SVCT2 E264K was restricted to the cytoplasm. We further found that SVCT2 E264K overexpression increases cell growth. By contrast, SVCT2 E264K knockdown significantly reduced cell proliferation and promoted cell apoptosis, resulting in inhibition of cell invasion and migration. Taken together, SVCT2 E264K plays a critical role in proliferation in CRC. Our results suggest that SVCT2 E264K could be a promising novel therapeutic target in CRC.

Neuroprotective Properties of Vitamin C: A Scoping Review of Pre-Clinical and Clinical Studies

There is a need for novel neuroprotective therapies. We aimed to review the evidence for exogenous vitamin C as a neuroprotective agent. MEDLINE, Embase, and Cochrane library databases were searched from inception to May 2020. Pre-clinical and clinical reports evaluating vitamin C for acute neurological injury were included. Twenty-two pre-clinical and 11 clinical studies were eligible for inclusion. Pre-clinical studies included models of traumatic and hypoxic brain injury, subarachnoid and intracerebral hemorrhage, and ischemic stroke. The median [IQR] maximum daily dose of vitamin C in animal studies was 120 [50-500] mg/kg. Twenty-one animal studies reported improvements in biomarkers, functional outcome, or both. Clinical studies included single reports in neonatal hypoxic encephalopathy, traumatic brain injury, and subarachnoid hemorrhage and eight studies in ischemic stroke. The median maximum daily dose of vitamin C was 750 [500-1000] mg, or ∼10 mg/kg for an average-size adult male. Apart from one case series of intracisternal vitamin C administration in subarachnoid hemorrhage, clinical studies reported no patient-centered benefit. Although pre-clinical trials suggest that exogenous vitamin C improves biomarkers of neuroprotection, functional outcome, and mortality, these results have not translated to humans. However, clinical trials used approximately one tenth of the vitamin C dose of animal studies.

Anxiolytic effects of essential oils may involve anti-oxidant regulation of the pro-oxidant effects of ascorbate in the brain

Essential oils (EOs) absorbed via inhalation are consistently reported to produce anxiolytic effects. The underlying neurochemical mechanisms, however, are not well understood. High concentrations of ascorbate in the human brain (~10 mM in neurons) implicates this compound as a key signaling molecule and regulator of oxidative stress. In this study, we demonstrate the significant in vitro capacity of ascorbate to produce H₂O₂ in the presence of oxygen at physiological pH values, peaking at ~400 μM for ascorbate levels of 1.0 mg/mL (5.6 mM). In comparison, individual EOs and selected neurotransmitters at similar concentrations produced <100 μM H₂O₂. Systematic studies with binary and ternary mixtures containing ascorbate indicated that EOs and neurotransmitters could variably enhance (pro-oxidant, POX) or suppress (anti-oxidant, AOX) the production of H₂O₂ versus the ascorbate control, depending on the concentration ratios of the components in the mixture. Moreover, the AOX/POX chemistry observed with binary mixtures did not necessarily predict effects with ternary mixtures, where the POX ascorbate chemistry tended to dominate. A model is proposed to account for the ability of compounds with electron-donating capacity to catalytically regenerate ascorbate from intermediate oxidized forms of ascorbate, thus driving H₂O₂ production and exerting a net POX effect; whilst compounds that irreversibly reacted with oxidized forms of ascorbate suppressed the production of H₂O₂ and produced an overall AOX effect. Since the anxiolytic effects of different EOs, including extracts of Lavendula angustifolia (lavender) and Salvia rosmarinus (rosemary), were associated with AOX regulation of H₂O₂ production by ascorbate, it can be concluded that these anxiolytic effects are potentially related to the AOX properties of EOs. In contrast, EOs driving POX effects (eg, Junipenus communis (Juniper) berry EO) are proposed to be more useful for their potential anti-microbial or cancer cytotoxic applications.

Variations in oxidative stress and antioxidant defense level during different phases of hibernation in common Asian toad, Duttaphrynus melanostictus

To assess redox status during hibernation with metabolic depression, oxidative stress parameters and antioxidant defense were assessed during different phases of hibernation including active period, hibernation, arousal, and post-arousal period, in the liver and brain tissues of Duttaphrynus melanostictus. We hypothesized low levels of oxidative stress and antioxidant defense during the hibernation period in comparison to the summer active period, due to hypometabolism and their subsequent increase during the arousal period following an increase in body temperature and metabolism. Contrary to our hypothesis, increased oxidative stress with significantly higher lipid peroxidation, protein carbonylation, oxidized glutathione (GSSG): glutathione (GSH) ratio, and elevated antioxidants defense consisting of higher catalase activity and high ascorbic acid content to control oxidative stress were found during hibernation. However, GSH and uric acid levels were found low with super oxide dismutase (SOD) activities at a steady level during hibernation. Supporting our hypothesis, increased oxidative stress with high lipid peroxidation and GSSG:GSH ratio were found during arousal from hibernation owing to increased oxygen consumption and rewarming. Augmented catalase and SOD activities and nonenzymatic antioxidants (GSH, ascorbic acid, and uric acid) level were found to counteract oxidative stress during arousal periods as it was expected. A steady level of protein carbonylation, indicating no oxidative damage during arousal from hibernation due to elevated antioxidant defense, shows the significance of hibernation to overcome food and water scarcity and cold climatic condition. Decrease in antioxidants levels accompanying coming down of lipid peroxidation, protein carbonylation, and GSSG:GSH ratio to their lower levels during the post-arousal period showing normalcy in redox status as it was during active period indicates controllability of oxidative stress in hibernating toads.

Ascorbate is a multifunctional micronutrient whose synthesis is lacking in primates

Ascorbate (vitamin C) is an essential micronutrient in primates, and exhibits multiple physiological functions. In addition to antioxidative action, ascorbate provides reducing power to α-ketoglutarate-dependent non-heme iron dioxygenases, such as prolyl hydroxylases. Demethylation of histones and DNA with the aid of ascorbate results in the reactivation of epigenetically silenced genes. Ascorbate and its oxidized form, dehydroascorbate, have attracted interest in terms of their roles in cancer therapy. The last step in the biosynthesis of ascorbate is catalyzed by l-gulono-γ-lactone oxidase whose gene Gulo is commonly mutated in all animals that do not synthesize ascorbate. One common explanation for this deficiency is based on the increased availability of ascorbate from foods. In fact, pathways for ascorbate synthesis and the detoxification of xenobiotics by glucuronate conjugation share the metabolic processes up to UDP-glucuronate, which prompts another hypothesis, namely, that ascorbate-incompetent animals might have developed stronger detoxification systems in return for their lack of ability to produce ascorbate, which would allow them to cope with their situation. Here, we overview recent advances in ascorbate research and propose that an enhanced glucuronate conjugation reaction may have applied positive selection pressure on ascorbate-incompetent animals, thus allowing them to dominate the animal kingdom.

The Role of Vitamin C in Reducing Pain Associated With Diabetic Neuropathy

Introduction: Neuropathic pain is a painful condition that arises after a lesion or an insult to the somatosensory nervous system, either in a central or peripheral location. The most common cause of neuropathic pain is diabetes. Controlled trials have been conducted on recent advancements in medicine to investigate the effect of vitamin C in the treatment of neuropathic pain. In this study, we aim to investigate the role of vitamin C in reducing pain associated with diabetic neuropathy.

Methods: This open-label, parallel-arm, interventional study was conducted in a public tertiary care hospital in Pakistan from April 2019 to March 2021. A total of 300 type II diabetic patients with newly diagnosed painful peripheral diabetic neuropathy, of either gender, were enrolled in the study. The intervention group received 60 mg duloxetine along with 200 mg oral vitamin C. The control group received 60 mg duloxetine without any additional intervention. Patients were asked to return for follow-up after 12 weeks.

Results: The mean visual analog score (VAS) was significantly lower in both, the intervention (5.54 ± 0.81 vs. 6.72 ± 0.90; p-value: <0.0001) and the control group (5.91 ± 0.80 vs. 6.79 ± 0.94; p-value: <0.0001), at week 12 compared to day 0. However, in comparison, VAS score in intervention at week 12 was significantly lower as compared to the control group (5.54 ± 0.81 vs. 5.91 ± 0.80; p-value: 0.0002).

Conclusion: The use of vitamin C could be cost-effective and would be a safe and useful adjunctive therapy for pain associated with diabetic peripheral neuropathy.

Scurvy mimicking as systemic lupus erythematosus

Scurvy is a disease caused by chronic vitamin C deficiency. The greater prevalence was found in the paediatric population with neurodevelopmental disorders such as autism spectrum disorders due to their restricted dietary intake. Our case reported a child with autism who presented with arthralgia and anaemia. Systemic lupus erythematosus was the first diagnostic impression, resulting in over investigation and delayed diagnosis of vitamin C deficiency. After the child was treated with ascorbic acid, the child's symptoms resolved. This case highlighted the importance of developmental and nutritional history taking in the paediatric population. Furthermore, parents and physicians should be concerned about nutritional status, especially in children with restrictive dietary intake.

Effect of dietary vitamins C and E on the risk of Parkinson's disease: A meta-analysis

BACKGROUND & AIMS

A neuroprotective effect of dietary vitamins C and E on Parkinson's disease (PD) has been suggested, however, several human studies have reported controversial results. Therefore, we conducted a meta-analysis on the effect of vitamins C and E on the risk of Parkinson's disease.

METHODS

A comprehensive literature search was conducted using the PubMed, EMBASE, Cochrane Library, and SCOPUS databases for studies published up to January 23, 2021. We included studies that reported (1) intake of vitamins C and E using validated methods; (2) assessment of odds ratio (OR), relative risk (RR), or hazard ratio (HR); and (3) patients with PD identified by a neurologist, hospital records, or death certificates. The Comprehensive Meta-Analysis Software 2 program was used for statistical analyses of the pooled data.

RESULTS

A total of 12 studies (four prospective cohort and eight case-control studies) were included in our meta-analysis. No significant risk reduction was observed in the high vitamin C intake group compared to low intake group. On the other hand, the high vitamin E intake group showed a significantly lower risk of development of PD than the low intake group (pooled OR = 0.799. 95% CI = 0.721 to 0.885).

CONCLUSIONS

We conclude that vitamin E might have a protective effect against PD, while vitamin C does not seem to have such an effect. However, the exact mechanism of the transport and regulation of vitamin E in the CNS remains elusive, and further studies would be necessary in this field.

Design, Preparation, and Characterization of Effective Dermal and Transdermal Lipid Nanoparticles: A Review

Limited permeability through the stratum corneum (SC) is a major obstacle for numerous skin care products. One promising approach is to use lipid nanoparticles as they not only facilitate penetration across skin but also avoid the drawbacks of conventional skin formulations. This review focuses on solid lipid nanoparticles (SLNs), nanostructured lipid nanocarriers (NLCs), and nanoemulsions (NEs) developed for topical and transdermal delivery of active compounds. A special emphasis in this review is placed on composition, preparation, modifications, structure and characterization, mechanism of penetration, and recent application of these nanoparticles. The presented data demonstrate the potential of these nanoparticles for dermal and transdermal delivery.

Vitamin C Deficiency in the Young Brain-Findings from Experimental Animal Models

Severe and long-term vitamin C deficiency can lead to fatal scurvy, which is fortunately considered rare today. However, a moderate state of vitamin C (vitC) deficiency (hypovitaminosis C)-defined as a plasma concentration below 23 μM-is estimated to affect up to 10% of the population in the Western world, albeit clinical hallmarks in addition to scurvy have not been linked to vitC deficiency. The brain maintains a high vitC content and uniquely high levels during deficiency, supporting vitC's importance in the brain. Actions include both antioxidant and co-factor functions, rendering vitamin C deficiency likely to affect several targets in the brain, and it could be particularly significant during development where a high cellular metabolism and an immature antioxidant system might increase sensitivity. However, investigations of a non-scorbutic state of vitC deficiency and effects on the developing young brain are scarce. This narrative review provides a comprehensive overview of the complex mechanisms that regulate vitC homeostasis in vivo and in the brain in particular. Functions of vitC in the brain and the potential consequences of deficiency during brain development are highlighted, based primarily on findings from experimental animal models. Perspectives for future investigations of vitC are outlined.

Parenteral high‑dose ascorbate - A possible approach for the treatment of glioblastoma (Review)

For glioblastoma, the treatment with standard of care therapy comprising resection, radiation, and temozolomide results in overall survival of approximately 14-18 months after initial diagnosis. Even though several new therapy approaches are under investigation, it is difficult to achieve life prolongation and/or improvement of patient's quality of life. The aggressiveness and progression of glioblastoma is initially orchestrated by the biological complexity of its genetic phenotype and ability to respond to cancer therapy via changing its molecular patterns, thereby developing resistance. Recent clinical studies of pharmacological ascorbate have demonstrated its safety and potential efficacy in different cancer entities regarding patient's quality of life and prolongation of survival. In this review article, the actual glioblastoma treatment possibilities are summarized, the evidence for pharmacological ascorbate in glioblastoma treatment is examined and questions are posed to identify current gaps of knowledge regarding accessibility of ascorbate to the tumor area. Experiments with glioblastoma cell lines and tumor xenografts have demonstrated that high-dose ascorbate induces cytotoxicity and oxidative stress largely selectively in malignant cells compared to normal cells suggesting ascorbate as a potential therapeutic agent. Further investigations in larger cohorts and randomized placebo-controlled trials should be performed to confirm these findings as well as to improve delivery strategies to the brain, through the inherent barriers and ultimately to the malignant cells.

Ferroptosis and traumatic brain injury

Traumatic brain injury (TBI) is a worldwide health problem contributing to significant economic burden. TBI is difficult to treat partly due to incomplete understanding of pathophysiology. Ferroptosis is a type of iron-dependent programmed cell death which has gained increasing attention due to its possible role in TBI. Current studies have demonstrated that ferroptosis is related to the pathology of TBI, and inhibition of ferroptosis may improve long term outcomes of TBI. Therefore, clarification of the exact association between ferroptosis and traumatic brain injury is necessary and may provide new targets for treatment. This review describes (1) the ferroptosis pathways following traumatic brain injury, (2) the role of ferroptosis during the chronic phase of traumatic brain injury, and (3) potential therapies targeting the ferroptosis pathways.

Micronutrients in Sepsis and COVID-19: A Narrative Review on What We Have Learned and What We Want to Know in Future Trials

Sepsis remains the leading cause of mortality in hospitalized patients, contributing to 1 in every 2–3 deaths. From a pathophysiological view, in the recent definition, sepsis has been defined as the result of a complex interaction between host response and the infecting organism, resulting in life-threatening organ dysfunction, depending on microcirculatory derangement, cellular hypoxia/dysoxia driven by hypotension and, potentially, death. The high energy expenditure driven by a high metabolic state induced by the host response may rapidly lead to micronutrient depletion. This deficiency can result in alterations in normal energy homeostasis, free radical damage, and immune system derangement. In critically ill patients, micronutrients are still relegated to an ancillary role in the whole treatment, and always put in a second-line place or, frequently, neglected. Only some micronutrients have attracted the attention of a wider audience, and some trials, even large ones, have tested their use, with controversial results. The present review will address this topic, including the recent advancement in the study of vitamin D and protocols based on vitamin C and other micronutrients, to explore an update in the setting of sepsis, gain some new insights applicable to COVID-19 patients, and to contribute to a pathophysiological definition of the potential role of micronutrients that will be helpful in future dedicated trials.

The Role of 2-Oxoglutarate Dependent Dioxygenases in Gliomas and Glioblastomas: A Review of Epigenetic Reprogramming and Hypoxic Response

Gliomas are a heterogeneous group of cancers that predominantly arise from glial cells in the brain, but may also arise from neural stem cells, encompassing low-grade glioma and high-grade glioblastoma. Whereas better diagnosis and new treatments have improved patient survival for many cancers, glioblastomas remain challenging with a highly unfavorable prognosis. This review discusses a super-family of enzymes, the 2-oxoglutarate dependent dioxygenase enzymes (2-OGDD) that control numerous processes including epigenetic modifications and oxygen sensing, and considers their many roles in the pathology of gliomas. We specifically describe in more detail the DNA and histone demethylases, and the hypoxia-inducible factor hydroxylases in the context of glioma, and discuss the substrate and cofactor requirements of the 2-OGDD enzymes. Better understanding of how these enzymes contribute to gliomas could lead to the development of new treatment strategies.

High-Dose Vitamin C: Preclinical Evidence for Tailoring Treatment in Cancer Patients

Simple Summary

Vitamin C is an indispensable micronutrient in the human diet due to the multiple functions it carries out in the body. Reports of clinical studies have indicated that, when administered at high dosage by the intravenous route, vitamin C may exert beneficial antitumor effects in patients with advanced stage cancers, including those refractory to previous treatment with chemotherapy. The aim of this article is to provide an overview of the current scientific evidence concerning the different mechanisms of action by which high-dose vitamin C may kill tumor cells. A special focus will be given to those mechanisms that provide the rationale basis for tailoring vitamin C treatment according to specific molecular alterations present in the tumor and for the selection of the most appropriate companion drugs.

Abstract

High-dose vitamin C has been proposed as a potential therapeutic approach for patients with advanced tumors who failed previous treatment with chemotherapy. Due to vitamin C complex pharmacokinetics, only intravenous administration allows reaching sufficiently high plasma concentrations required for most of the antitumor effects observed in preclinical studies (>0.250 mM). Moreover, vitamin C entry into cells is tightly regulated by SVCT and GLUT transporters, and is cell type-dependent. Importantly, besides its well-recognized pro-oxidant effects, vitamin C modulates TET enzymes promoting DNA demethylation and acts as cofactor of HIF hydroxylases, whose activity is required for HIF-1α proteasomal degradation. Furthermore, at pharmacological concentrations lower than those required for its pro-oxidant activity (<1 mM), vitamin C in specific genetic contexts may alter the DNA damage response by increasing 5-hydroxymethylcytosine levels. These more recently described vitamin C mechanisms offer new treatment opportunities for tumors with specific molecular defects (e.g., HIF-1α over-expression or TET2, IDH1/2, and WT1 alterations). Moreover, vitamin C action at DNA levels may provide the rationale basis for combination therapies with PARP inhibitors and hypomethylating agents. This review outlines the pharmacokinetic and pharmacodynamic properties of vitamin C to be taken into account in designing clinical studies that evaluate its potential use as anticancer agent.

One-Step Biosynthesis of Vitamin C in Saccharomyces cerevisiae

Vitamin C (VC) is comprehensively applied in foods, cosmetics, pharmaceuticals, and especially clinical medicine. Nowadays, the industrial production of VC mainly relies on the classic two-step fermentation route, and researchers have explored the way for one-step fermentation of VC in recent years. In this study, a VC biosynthesis pathway that directly produced VC from glucose was reconstructed in Saccharomyces cerevisiae, and the protein engineering and metabolic engineering strategies were adopted to improve it. First, five exogenous modules from Arabidopsis were introduced into the chassis cells by synthetic biology approaches to obtain the strain YLAA harboring VC biosynthesis. In addition, L-galactose dehydrogenase (L-GalDH) and L-galactono-1,4-lactone dehydrogenase (L-GLDH) were fused and expressed in S. cerevisiae cells for the first time, which increased the intracellular VC accumulation by 2.78-fold, reaching 9.97 ± 0.09 mg/L. Through copy number engineering, it was further confirmed that the last step catalyzed by L-GLDH is the rate-limiting step. GDP-L-galactose phosphorylase (GPP) encoded by vtc2 is another rate-limiting enzyme confirmed by GAL1p overexpression results. Finally, by balancing gene expression and cell growth, the highest production strain with overexpressing vtc2 by multicopy plasmids was constructed. The VC accumulation reached 24.94 ± 1.16 mg/L, which was currently the highest production from glucose in S. cerevisiae. The production of the recombinant strain reached nearly 44 mg/L with the exogenous addition of L-galactose or glutathione. The results further emphasized the importance of the step catalyzed by GPP. The investigation provided experience for the efficient biosynthesis of VC and the determination of rate-limiting steps.

Novel Multifunctional Ascorbic Triazole Derivatives for Amyloidogenic Pathway Inhibition, Anti-Inflammation, and Neuroprotection

Alzheimer's disease (AD) is a common neurodegenerative disorder. The number of patients with AD is projected to reach 152 million by 2050. Donepezil, rivastigmine, galantamine, and memantine are the only four drugs currently approved by the United States Food and Drug Administration for AD treatment. However, these drugs can only alleviate AD symptoms. Thus, this research focuses on the discovery of novel lead compounds that possess multitarget regulation of AD etiopathology relating to amyloid cascade. The ascorbic acid structure has been designated as a core functional domain due to several characteristics, including antioxidant activities, amyloid aggregation inhibition, and the ability to be transported to the brain and neurons. Multifunctional ascorbic derivatives were synthesized by copper (I)-catalyzed azide-alkyne cycloaddition reaction (click chemistry). The in vitro and cell-based assays showed that compounds 2c and 5c exhibited prominent multifunctional activities as beta-secretase 1 inhibitors, amyloid aggregation inhibitors, and antioxidant, neuroprotectant, and anti-inflammatory agents. Significant changes in activities promoting neuroprotection and anti-inflammation were observed at a considerably low concentration at a nanomolar level. Moreover, an in silico study showed that compounds 2c and 5c were capable of being permeated across the blood-brain barrier by sodium-dependent vitamin C transporter-2.

Sensitive colorimetric detection of ascorbic acid based on seed mediated growth of sodium alginate reduced/stabilized gold nanoparticles

A sensitive detection strategy for ascorbic acid (AA), using sodium alginate reduced/stabilized gold nanoparticles (SA-AuNPs) as the optical probe, is reported. The SA-AuNPs were prepared by mixing gold salt and SA under stirring for 2 h at room temperature, without any further steps. The mixture was aged at 4 °C overnight, after which a faint-purple colloidal solution of SA-AuNPs was obtained. Characterization shows that the synthesis is incapable of reducing all Au³⁺ to Au°, but rather to mixture of Au°/Au⁺. The addition of AA to the SA-AuNPs probe reduced completely all Au⁺ to new AuNPs which were deposited on the pre-formed SA-AuNPs seed, leading to size increment and absorption spectra enhancement. The assay exhibited a good linearity between 12.5 and 150.0 μM AA and low limit of quantification of 11.2 μM. It was further used for AA quantitation in vitamin C injection and fruit juice with satisfactory accuracy and precision.

Initial Evidence of Variation by Ethnicity in the Relationship between Vitamin C Status and Mental States in Young Adults

Higher fruit and vegetable intake has been associated with improved mood, greater vitality, and lower stress. Although the nutrients driving these benefits are not specifically identified, one potentially important micronutrient is vitamin C, an important co-factor for the production of peptide hormones, carnitine and neurotransmitters that are involved in regulation of physical energy and mood. The aim of our study was to investigate the cross-sectional relationship between blood plasma vitamin C status and mood, vitality and perceived stress. A sample of 419 university students (aged 18 to 35; 67.8% female) of various ethnicities (49.2% European, 16.2% East Asian, 8.1% Southeast/Other Asian, 9.1% Māori/Pasifika, 11.5% Other) provided a fasting blood sample to determine vitamin C status and completed psychological measures consisting of the Profile of Mood States Short Form (POMS-SF), the vitality subscale of the Rand 36-Item Short Form (SF-36), and the Perceived Stress Scale (PSS). Participants were screened for prescription medication, smoking history, vitamin C supplementation, fruit/juice and vegetable consumption, kiwifruit allergies, excessive alcohol consumption and serious health issues, and provided age, gender, ethnicity, and socioeconomic status information, which served as covariates. There were no significant associations between vitamin C status and the psychological measures for the sample overall. However, associations varied by ethnicity. Among Māori/Pasifika participants, higher vitamin C was associated with greater vitality and lower stress, whereas among Southeast Asian participants, higher vitamin C was associated with greater confusion on the POMS-SF subscale. These novel findings demonstrate potential ethnicity-linked differences in the relationship between vitamin C and mental states. Further research is required to determine whether genetic variation or cultural factors are driving these ethnicity differences.

Electrochemical Sensing of Ascorbate as an Index of Neuroprotection from Seizure Activity by Physical Exercise in Freely Moving Rats

Physical exercise (PE) has been drawing increasing attention to prevent and alleviate neural damage of brain diseases; however, in vivo sensing of the neuroprotection ability of PE remains a challenge. Here, we find that ascorbate can be used as a small molecular index for neuroprotective function of PE and the neuroprotection ability of PE can thus be in vivo monitored with an online electrochemical system (OECS) in freely moving animals. With the OECS as the sensing system, we find that the concentration of ascorbate in the microdialysate from the striatum increases greatly in kainic acid (KA)-induced seizure rats and reaches twice the basal level (i.e., 214.4 ± 32.7%, p < 0.001, n = 4) at a time point 90 min after KA microinjection. Such an increase of ascorbate is obviously attenuated (i.e., 153.6 ± 23.9% of the basal level, p < 0.05, n = 3) after PE, showing the neuroprotective activity of PE. This finding is believed to be significant in providing chemical insight into the neuroprotection ability of PE.

Frataxins Emerge as New Players of the Intracellular Antioxidant Machinery

Frataxin is a mitochondrial protein which deficiency causes Friedreich's ataxia, a cardio-neurodegenerative disease. The lack of frataxin induces the dysregulation of mitochondrial iron homeostasis and oxidative stress, which finally causes the neuronal death. The mechanism through which frataxin regulates the oxidative stress balance is rather complex and poorly understood. While the absence of human (Hfra) and yeast (Yfh1) frataxins turn out cells sensitive to oxidative stress, this does not occur when the frataxin gene is knocked-out in E. coli. To better understand the biological roles of Hfra and Yfh1 as endogenous antioxidants, we have studied their ability to inhibit the formation of reactive oxygen species (ROS) from Cu²⁺- and Fe³⁺-catalyzed degradation of ascorbic acid. Both proteins drastically reduce the formation of ROS, and during this process they are not oxidized. In addition, we have also demonstrated that merely the presence of Yfh1 or Hfra is enough to protect a highly oxidation-prone protein such as α-synuclein. This unspecific intervention (without a direct binding) suggests that frataxins could act as a shield to prevent the oxidation of a broad set of intracellular proteins, and reinforces that idea that frataxin can be used to prevent neurological pathologies linked to an enhanced oxidative stress.

Decreased content of ascorbic acid (vitamin C) in the brain of knockout mouse models of Na+,K+-ATPase-related neurologic disorders

Na⁺,K⁺-ATPase is a crucial protein responsible for maintaining the electrochemical gradients across the cell membrane. The Na⁺,K⁺-ATPase is comprised of catalytic α, β, and γ subunits. In adult brains, the α3 subunit, encoded by ATP1A3, is predominantly expressed in neurons, whereas the α2 subunit, encoded by ATP1A2, is expressed in glial cells. In foetal brains, the α2 is expressed in neurons as well. Mutations in α subunits cause a variety of neurologic disorders. Notably, the onset of symptoms in ATP1A2- and ATP1A3-related neurologic disorders is usually triggered by physiological or psychological stressors. To gain insight into the distinct roles of the α2 and α3 subunits in the developing foetal brain, whose developmental dysfunction may be a predisposing factor of neurologic disorders, we compared the phenotypes of mouse foetuses with double homozygous knockout of Atp1a2 and Atp1a3 (α2α3-dKO) to those with single knockout. The brain haemorrhage phenotype of α2α3-dKO was similar to that of homozygous knockout of the gene encoding ascorbic acid (ASC or vitamin C) transporter, SVCT2. The α2α3-dKO brain showed significantly decreased level of ASC compared with the wild-type (WT) and single knockout. We found that the ASC content in the basal ganglia and cerebellum was significantly lower in the adult Atp1a3 heterozygous knockout mouse (α3-HT) than in the WT. Interestingly, we observed a significant decrease in the ASC level in the basal ganglia and cerebellum of α3-HT in the peripartum period, during which mice are under physiological stress. These observations indicate that the α2 and α3 subunits independently contribute to the ASC level in the foetal brain and that the α3 subunit contributes to ASC transport in the adult basal ganglia and cerebellum. We propose that decreases in ASC levels may affect neural network development and are linked to the pathophysiology of ATP1A2- and ATP1A3-related neurologic disorders.

Two Distinct Faces of Vitamin C: AA vs. DHA

Historically, vitamin C has been associated with many regulatory processes that involve specific signaling pathways. Among the most studied signaling pathways are those involved in the regulation of aging, differentiation, neurotransmission, proliferation, and cell death processes in cancer. This wide variety of regulatory effects is due to the fact that vitamin C has a dual mechanism of action. On the one hand, it regulates the expression of genes associated with proliferation (Ccnf and Ccnb1), differentiation (Sox-2 and Oct-4), and cell death (RIPK1 and Bcl-2). At the same time, vitamin C can act as a regulator of kinases, such as MAPK and p38, or by controlling the activation of the NF-kB pathway, generating chronic responses related to changes in gene expression or acute responses associated with the regulation of signal transduction processes. To date, data from the literature show a permanent increase in processes regulated by vitamin C. In this review, we critically examine how vitamin C regulates these different cellular programs in normal and tumor cells.

Activation of adenosine A3 receptors regulates vitamin C transport and redox balance in neurons

Adenosine is an important neuromodulator in the CNS, regulating neuronal survival and synaptic transmission. The antioxidant ascorbate (the reduced form of vitamin C) is concentrated in CNS neurons through a sodium-dependent transporter named SVCT2 and participates in several CNS processes, for instance, the regulation of glutamate receptors functioning and the synthesis of neuromodulators. Here we studied the interplay between the adenosinergic system and ascorbate transport in neurons. We found that selective activation of A3, but not of A1 or A2a, adenosine receptors modulated ascorbate transport, decreasing intracellular ascorbate content. Förster resonance energy transfer (FRET) analyses showed that A3 receptors associate with the ascorbate transporter SVCT2, suggesting tight signaling compartmentalization between A3 receptors and SVCT2. The activation of A3 receptors increased ascorbate release in an SVCT2-dependent manner, which largely altered the neuronal redox status without interfering with cell death, glycolytic metabolism, and bioenergetics. Overall, by regulating vitamin C transport, the adenosinergic system (via activation of A3 receptors) can regulate ascorbate bioavailability and control the redox balance in neurons.

Ascorbate kills breast cancer cells by rewiring metabolism via redox imbalance and energy crisis

The idea to use megadoses of ascorbate (vitamin C) for cancer treatment has recently been revived. Despite clear efficacy in animal experimentation, our understanding of the cellular and molecular mechanisms of this treatment is still limited and suggests a combined oxidative and metabolic mechanism behind the selective cytotoxicity of ascorbate towards cancerous cells. To gain more insight into the cellular effects of high doses of ascorbate, we performed a detailed analysis of metabolic changes and cell survival of both luminal and basal-like breast cancer cells treated with ascorbate and revealed a distinctive metabolic shift virtually reversing the Warburg effect and triggering a severe disruption of redox homeostasis. High doses of ascorbate were cytotoxic against MCF7 and MDA-MB231 cells representing luminal and basal-like breast cancer phenotypes. Cell death was dependent on ascorbate-induced oxidative stress and accumulation of ROS, DNA damage, and depletion of essential intracellular co-factors including NAD⁺/NADH, associated with a multifaceted metabolic rewiring. This included a sharp disruption of glycolysis at the triose phosphate level, a rapid drop in ATP levels, and redirection of metabolites toward lipid droplet accumulation and increased metabolites and enzymatic activity in the pentose phosphate pathway (PPP). High doses of ascorbate also inhibited the TCA cycle and increased oxygen consumption. Together the severe disruptions of the intracellular metabolic homeostasis on multiple levels "redox crisis and energetic catastrophe" consequently trigger a rapid irreversible cell death.

Grewia asiatica Berry Juice Diminishes Anxiety, Depression, and Scopolamine-Induced Learning and Memory Impairment in Behavioral Experimental Animal Models

Grewia asiatica L. fruit natively called phalsa is a popular berry of Pakistan and widely consumed in the form of fresh juices and carbonated drinks in the summer season. The berry is enriched with antioxidants such as phenols, flavonoids, anthocyanins, and vitamin C. Scientifically, it is the least explored berry in terms of neuromodulatory activities, and therefore, in the designed study, chronically fed rats with the different dilutions (5%-30%) of fruit juice were subjected to behavioral assessment for anxiety, depression, and cognition (spatial memory) followed by biochemical analysis of isolated brains. Results revealed a prominent impact of 20 and 30% dilutions of fruit exudate as treated animals showed anxiolytic behavior to central zone (P < 0.05) of open field test (OFT) and open arms of elevated plus maze (EPM) (P < 0.05) in anxiety models. Overall, immobility of rats treated with a higher concentration of exudate in forced swim test (FST) was reduced (P < 0.05) presenting antidepressant-like activity. Moreover, in learning and memory experimental models, the treated animals reversed scopolamine-induced amnesic effects as evident from improved step-through latencies (P < 0.05 vs. scopolamine; passive avoidance test), spontaneous alternation behavior (P < 0.05 vs. scopolamine; Y-maze test), discrimination index (P < 0.05 vs. scopolamine; novel object recognition test), and escape latencies (P < 0.05 vs. scopolamine; Morris water maze). Biochemical studies of isolated brains from treated rats demonstrated significantly elevated levels of superoxide dismutase and glutathione peroxidase (P < 0.05), whereas levels of acetylcholinesterase and malondialdehyde level (P < 0.05) were reduced, indicating its potential to reduce oxidative damage in the brain and modulation with the cholinergic system. The outcomes of studies support the benefits of phytoconstituents possessed by G. asiatica fruit in the amelioration of neurological disorders that could be due to their antioxidative capacity or due to interaction with GABAergic, serotonergic, and cholinergic systems in the brain.

Vitamin C deficient reduces proliferation in a human periventricular tumor stem cell-derived glioblastoma model

Glioblastoma multiforme (GBM) is the most common and aggressive brain tumor with a median survival of 14.6 months. GBM is highly resistant to radio- and chemotherapy, and remains without a cure; hence, new treatment strategies are constantly sought. Vitamin C, an essential micronutrient and antioxidant, was initially described as an antitumor molecule; however, several studies have shown that it can promote tumor progression and angiogenesis. Thus, considering the high concentrations of vitamin C present in the brain, our aim was to study the effect of vitamin C deficiency on the progression of GBM using a GBM model generated by the stereotactic injection of human GBM cells (U87-MG or HSVT-C3 cells) in the subventricular zone of guinea pig brain. Initial characterization of U87-MG and HSVT-C3 cells showed that HSVT-C3 are highly proliferative, overexpress p53, and are resistant to ferroptosis. To induce intraperiventricular tumors, animals received control or a vitamin C-deficient diet for 3 weeks, after which histopathological and confocal microscopy analyses were performed. We demonstrated that the vitamin C-deficient condition reduced the glomeruloid vasculature and microglia/macrophage infiltration in U87-MG tumors. Furthermore, tumor size, proliferation, glomeruloid vasculature, microglia/macrophage infiltration, and invasion were reduced in C3 tumors carried by vitamin C-deficient guinea pigs. In conclusion, the effect of the vitamin C deficiency was dependent on the tumor cell used for GBM induction. HSVT-C3 cells, a cell line with stem cell features isolated from a human subventricular GBM, showed higher sensitivity to the deficient condition; however, vitamin C deficiency displayed an antitumor effect in both GBM models analyzed.

(Ascorb)ing Pb Neurotoxicity in the Developing Brain

Lead (Pb) neurotoxicity is a major concern, particularly in children. Developmental exposure to Pb can alter neurodevelopmental trajectory and has permanent neuropathological consequences, including an increased vulnerability to further stressors. Ascorbic acid is among most researched antioxidant nutrients and has a special role in maintaining redox homeostasis in physiological and physio-pathological brain states. Furthermore, because of its capacity to chelate metal ions, ascorbic acid may particularly serve as a potent therapeutic agent in Pb poisoning. The present review first discusses the major consequences of Pb exposure in children and then proceeds to present evidence from human and animal studies for ascorbic acid as an efficient ameliorative supplemental nutrient in Pb poisoning, with a particular focus on developmental Pb neurotoxicity. In doing so, it is hoped that there is a revitalization for further research on understanding the brain functions of this essential, safe, and readily available vitamin in physiological states, as well to justify and establish it as an effective neuroprotective and modulatory factor in the pathologies of the nervous system, including developmental neuropathologies.

Impact of N-Truncated Aβ Peptides on Cu- and Cu(Aβ)-Generated ROS: CuI Matters!

In vitro Cu(Aβ_1-x )-induced ROS production has been extensively studied. Conversely, the ability of N-truncated isoforms of Aβ to alter the Cu-induced ROS production has been overlooked, even though they are main constituents of amyloid plaques found in the human brain. N-Truncated peptides at the positions 4 and 11 (Aβ_4-x and Aβ_11-x ) contain an amino-terminal copper and nickel (ATCUN) binding motif (H₂ N-Xxx-Zzz-His) that confer them different coordination sites and higher affinities for Cu^II compared to the Aβ_1-x peptide. It has further been proposed that the role of Aβ_4-x peptide is to quench Cu^II toxicity in the brain. However, the role of Cu^I coordination has not been investigated to date. In contrast to Cu^II , Cu^I coordination is expected to be the same for N-truncated and N-intact peptides. Herein, we report in-depth characterizations and ROS production studies of Cu (Cu^I and Cu^II ) complexes of the Aβ_4-16 and Aβ_11-16 N-truncated peptides. Our findings show that the N-truncated peptides do produce ROS when Cu^I is present in the medium, albeit to a lesser extent than the unmodified counterpart. In addition, when used as competitor ligands (i.e., in the presence of Aβ_1-16 ), the N-truncated peptides are not able to fully preclude Cu(Aβ_1-16 )-induced ROS production.

Preparation of magnetic nanoparticle integrated nanostructured lipid carriers for controlled delivery of ascorbyl palmitate

Most cancer treatments can cause vital side effects on healthy tissues. Ascorbic acid (AA) is a water-soluble antioxidant molecule and possesses a variety of functions such as prevention of tumor proliferation and treatment of cancer. However, AA, is very sensitive to air, heat and light. Its high hydrophilicity also makes the controlled delivery difficult. To overcome these problems, AA can be chemically-modified and made more hydrophobic by the esterification. Palmitic acid is one of the most common long-chain fatty acids that can be used for this purpose. It is known that Ascorbyl palmitate (AP) which is a lipopihilic derivative of AA, can inhibit cell proliferation and DNA synthesis in many types of cancer. Although AP has higher stability, its bioavailability and therapeutic effect is low due to its lipophilicity and low release capacity.•

In this study, nanostructured lipid carriers (NLC) which are colloidal nanoparticles with high biocompatibility, low crystallinity and high hydrophobic-drug encapsulation capacity was prepared to increase the bioavailability of AP.

•

To provide triggered drug release via hyperthermia, magnetic nanoparticles (MNps) were integrated into the NLCs besides AP.

•

The synthesis of biocompatible NLCs with controlled and triggered release ability, is successfully completed and controlled release of AP as an antitumor agent is achieved.

Fluorescent Diagnostic Probes in Neurodegenerative Diseases

Neurodegenerative diseases are debilitating disorders that feature progressive and selective loss of function or structure of anatomically or physiologically associated neuronal systems. Both chronic and acute neurodegenerative diseases are associated with high morbidity and mortality along with the death of neurons in different areas of the brain; moreover, there are few or no effective curative therapy options for treating these disorders. There is an urgent need to diagnose neurodegenerative disease as early as possible, and to distinguish between different disorders with overlapping symptoms that will help to decide the best clinical treatment. Recently, in neurodegenerative disease research, fluorescent-probe-mediated biomarker visualization techniques have been gaining increasing attention for the early diagnosis of neurodegenerative diseases. A survey of fluorescent probes for sensing and imaging biomarkers of neurodegenerative diseases is provided. These imaging probes are categorized based on the different potential biomarkers of various neurodegenerative diseases, and their advantages and disadvantages are discussed. Guides to develop new sensing strategies, recognition mechanisms, as well as the ideal features to further improve neurodegenerative disease fluorescence imaging are also explored.

Pretreatment of Ascorbic Acid Inhibits MPTP-Induced Astrocytic Oxidative Stress through Suppressing NF-κB Signaling

Astrocytes are a major constituent of the central nervous system (CNS). Astrocytic oxidative stress contributes to the development of Parkinson's disease (PD). Maintaining production of antioxidant and detoxification of reactive oxygen and nitrogen species (ROS/RNS) in astrocytes is critical to prevent PD. Study has illuminated that ascorbic acid (AA) stimulates dopamine synthesis and expression of tyrosine hydroxylase in human neuroblastoma cells. However, the role and regulatory mechanisms of AA on detoxification of astrocytes are still unclear. The purpose of our study is in-depth study of the regulatory mechanism of AA on detoxification of astrocytes. We found that AA pretreatment decreased the expression of ROS and inducible nitric oxide synthase (iNOS) in MPP⁺-treated astrocytes. In contrast, the expression levels of antioxidative substances—including superoxide dismutase (SOD), glutathione (GSH), and glutamate-cysteine ligase modifier (GCLM) subunit—were upregulated after AA pretreatment in MPP⁺-treated astrocytes. However, inhibition of NF-κB prevented such AA induced increases in antioxidative substances following MPP⁺ treatment in astrocytes, suggesting that AA improved antioxidative function of astrocytes through inhibiting NF-κB-mediated oxidative stress. Furthermore, in vivo studies revealed that AA preadministration also suppressed NF-κB and upregulated the expression levels of antioxidative substances in the midbrain of MPTP-treated mice. Additionally, pretreatment of AA alleviated MPTP-induced PD-like pathology in mice. Taken together, our results demonstrate that preadministration of AA improves the antioxidative function of astrocytes through suppressing NF-κB signaling, following alleviated the pathogenesis of PD which induced by MPTP. Hence, our findings elucidate a novel protective mechanism of AA in astrocytes.

Ascorbic acid improves extrapyramidal syndromes and corpus striatal degeneration induced by dopamine-2 receptor inhibition in Wistar rats

Objectives The prolonged uses of fourth-generation antipsychotics have been implicated in inducing extrapyramidal syndromes characterized by the motor deficit. This was attributed to the loss of dopamine-2 receptor (D2R) signaling. However, ascorbic acid (SVCT2R stimulation) in the brain is proposed to modulate D2R activity. We, therefore, investigated the beneficial roles of ascorbic acid in improving the extrapyramidal symptoms seen in D2R loss. Methods Twenty adult male Wistar rats of average weight 200 g were distributed randomly into four groups. The control (NS) received normal saline for 28 days, Untreated D2R inhibition group (-D2R) received normal saline for seven days and then subsequently received chlorpromazine for 21 days, D2R inhibition group treated with ascorbic acid (-D2R+SVCT2R) received chlorpromazine for 21 days and was subsequently treated with ascorbate for seven days while the withdrawal group (WG) received chlorpromazine for 21 days and subsequently received normal saline for seven days. Motor deficits were assessed using a rotarod and cylinder test. The corpus striatum was harvested, processed, and stained using H&E and Nissl stains. Cellular density was analyzed using Image J software 1.8.0. Results Motor deficit was observed in -D2R animals administered chlorpromazine with less improvement in WG compared to control (p<0.05) in both rotarod and cylinder test. Ascorbic acid (SVCT2R stimulation) significantly (p<0.001) improved the latency of fall and climbing attempts observed in -D2R animals. The density of basophilic trigoid bodies was significantly (p<0.001) restored in -D2R+SVCT2R group, suggesting recovery of neural activity in the corpus striatum. Moreover, the hallmarks of neuronal degeneration were less expressed in the ascorbic acid treatment groups. Conclusions Ascorbic acid putatively ameliorates extrapyramidal symptoms observed in D2R blockage by chlorpromazine in Wistar rats.

Measuring stimulation and inhibition of intracellular nitric oxide production in SIM-A9 microglia using microfluidic single-cell analysis

Chronic neuroinflammation has long been considered to be a central factor in accelerating the progression of neurodegenerative diseases such as Alzheimer's diseases, Parkinson's disease and chronic traumatic encephalopathy. Under pathological conditions microglia produce inflammatory signaling molecules, such as nitric oxide (NO), that can damage DNA and proteins and ultimately induce neuronal apoptosis. One strategy for treating neurodegenerative diseases is to specifically target NO production through inhibition of inducible nitric oxide synthase (iNOS). However, accurately measuring changes in microglial NO production in response to potential therapeutics is challenging due to NO's short half-life and microglial heterogeneity. In this paper we report the application of a microfluidic device for the high-throughput measurement of intracellular NO in SIM-A9 microglial cells. NO production was measured in response to treatment with lipopolysaccharides (LPS) and interferon gamma (IFN-γ) with and without a potent iNOS inhibitor (1400 W dihydrochloride). Cells were labeled with a fluorogenic NO probe, 4-amino-5-methylamino-2',7'-difluorofluoescein diacetate (DAF-FM DA), and 6-carboxyfluorescein diacetate (6-CFDA) as an internal standard. Separation and quantitation of intracellular NO was achieved using microchip electrophoresis and laser induced fluorescence detection (LIF). Statistical analysis suggests that the populations fit a lognormal distribution and are better represented by their geometric mean values. Comparison of the geometric means indicated a 1.6-fold increase in NO production between untreated and stimulated cells and a decrease by a factor of approximately 0.5 comparing stimulated and inhibited cells. Additionally, we report experimental data demonstrating the improvement in the sensitivity of our integrated optical fiber-based detection system through the use of refractive index matching gel.

Vitamin C: historical perspectives and heart failure

Vitamin C (Vit C) is an ideal antioxidant as it is easily available, water soluble, very potent, least toxic, regenerates other antioxidants particularly Vit E, and acts as a cofactor for different enzymes. It has received much attention due to its ability in limiting reactive oxygen species, oxidative stress, and nitrosative stress, as well as it helps to maintain some of the normal metabolic functions of the cell. However, over 140 clinical trials using Vit C in different pathological conditions such as myocardial infarction, gastritis, diabetes, hypertension, stroke, and cancer have yielded inconsistent results. Such a divergence calls for new strategies to establish practical significance of Vit C in heart failure or even in its prevention. For a better understanding of Vit C functioning, it is important to revisit its transport across the cell membrane and subcellular interactions. In this review, we have highlighted some historical details of Vit C and its transporters in the heart with a particular focus on heart failure in cancer chemotherapy.

Brain foods - the role of diet in brain performance and health

The performance of the human brain is based on an interplay between the inherited genotype and external environmental factors, including diet. Food and nutrition, essential in maintenance of brain performance, also aid in prevention and treatment of mental disorders. Both the overall composition of the human diet and specific dietary components have been shown to have an impact on brain function in various experimental models and epidemiological studies. This narrative review provides an overview of the role of diet in 5 key areas of brain function related to mental health and performance, including: (1) brain development, (2) signaling networks and neurotransmitters in the brain, (3) cognition and memory, (4) the balance between protein formation and degradation, and (5) deteriorative effects due to chronic inflammatory processes. Finally, the role of diet in epigenetic regulation of brain physiology is discussed.

Neuroprotective Effect of Antioxidants in the Brain

The brain is vulnerable to excessive oxidative insults because of its abundant lipid content, high energy requirements, and weak antioxidant capacity. Reactive oxygen species (ROS) increase susceptibility to neuronal damage and functional deficits, via oxidative changes in the brain in neurodegenerative diseases. Overabundance and abnormal levels of ROS and/or overload of metals are regulated by cellular defense mechanisms, intracellular signaling, and physiological functions of antioxidants in the brain. Single and/or complex antioxidant compounds targeting oxidative stress, redox metals, and neuronal cell death have been evaluated in multiple preclinical and clinical trials as a complementary therapeutic strategy for combating oxidative stress associated with neurodegenerative diseases. Herein, we present a general analysis and overview of various antioxidants and suggest potential courses of antioxidant treatments for the neuroprotection of the brain from oxidative injury. This review focuses on enzymatic and non-enzymatic antioxidant mechanisms in the brain and examines the relative advantages and methodological concerns when assessing antioxidant compounds for the treatment of neurodegenerative disorders.

Positive Association of Ascorbate and Inverse Association of Urate with Cognitive Function in People with Parkinson's Disease

Oxidative stress is thought to contribute to the aetiology of neurological disorders such as Parkinson’s disease. Ascorbate (vitamin C) is a potent antioxidant and is associated with neurological and cognitive function. In this study we assessed the ascorbate status of a cohort of people with Parkinson’s disease (n = 215), aged 50–90 years, compared with a cohort of age matched healthy controls (n = 48). The study sample’s cognitive status ranged from normal to mild cognitive impairment and dementia. There was no difference between the Parkinson’s disease and healthy control groups with respect to mean ascorbate status, however, a higher proportion of participants with Parkinson’s disease had hypovitaminosis C (i.e., <23 μmol/L) compared with healthy controls (20% vs. 8%, respectively). Within the Parkinson’s disease group, Montreal Cognitive Assessment (MoCA) scores correlated positively with ascorbate concentrations, with higher ascorbate status associated with better cognitive function (r = 0.14, p = 0.045). Participants with hypovitaminosis C had significantly lower MoCA scores relative to participants with ascorbate concentrations >23 µmol/L (p = 0.014). Ascorbate concentrations were significantly lower in the cognitively impaired subgroup compared with the normal cognition subgroup in the Parkinson’s disease cohort (p = 0.03). In contrast, urate showed an inverse correlation with cognitive function (r = −0.19, p = 0.007), with higher urate concentrations observed in the cognitively impaired subgroup compared with the normal cognition subgroup (p = 0.015). There was an inverse association between ascorbate status and urate concentrations (r = −0.15, p = 0.017). Plasma protein carbonyls, a measure of systemic oxidative stress, were not significantly different between the Parkinson’s disease cohort and healthy controls, and there was no association with cognitive function (r = 0.09, p = 0.19) or with ascorbate status (r = −0.05, p = 0.45). Overall, our study showed ascorbate status was positively associated with cognitive function in Parkinson’s disease, suggesting that longitudinal studies investigating the temporal sequence of cognitive decline and ascorbate status are warranted.

KiwiC for Vitality: Results of a Randomized Placebo-Controlled Trial Testing the Effects of Kiwifruit or Vitamin C Tablets on Vitality in Adults with Low Vitamin C Levels

Consumption of vitamin C-rich fruit and vegetables has been associated with greater feelings of vitality. However, these associations have rarely been tested in randomized controlled trials. The aim of the current study was to test the effects of eating a vitamin C-rich food (kiwifruit) on subjective vitality and whether effects are driven by vitamin C. Young adults (n = 167, 61.1% female, aged 18-35) with plasma vitamin C <40 µmol/L were randomized into three intervention conditions: kiwifruit (2 SunGold™ kiwifruit/day), vitamin C (250 mg tablet/day), placebo (1 tablet/day). The trial consisted of a two-week lead-in, four-week intervention, and two-week washout. Plasma vitamin C and vitality questionnaires (total mood disturbance, fatigue, and well-being) were measured fortnightly. Self-reported sleep quality and physical activity were measured every second day through smartphone surveys. Nutritional confounds were assessed using a three-day food diary during each study phase. Plasma vitamin C reached saturation levels within two weeks for the kiwifruit and vitamin C groups. Participants consuming kiwifruit showed significantly improved mood and well-being during the intervention period; improvements in well-being were sustained during washout. Decreased fatigue and increased well-being were observed following intake of vitamin C alone, but only for participants with consistently low vitamin C levels during lead-in. Diet records showed that participants consuming kiwifruit reduced their fat intake during the intervention period. Intervention effects remained significant when adjusting for age and ethnicity, and were not explained by sleep quality, physical activity, BMI, or other dietary patterns, including fat intake. There were no changes in plasma vitamin C status or vitality in the placebo group. Whole food consumption of kiwifruit improved subjective vitality in adults with low vitamin C status. Similar, but not identical, changes were found for vitamin C tablets suggesting that additional properties of kiwifruit may contribute to improved vitality.

The Contribution of Plasma and Brain Vitamin C on Age and Gender-Related Cognitive Differences: A Mini-Review of the Literature

There is increasing evidence that sex differences in the brain may contribute to gender-related behavioral differences, including cognitive function. Literature has revealed gender dimorphisms in cognitive function between males and females. Additionally, several risk factors associated with cognitive decline depend on chronological age. It is well recognized that the process of aging is associated with a decline in cognitive ability and brain function. Various explanations may account for these gender-related cognitive differences and age-associated cognitive changes. Recent investigations have highlighted the importance of vitamin C in maintaining brain health and its association with cognitive function in both cognitively intact and impaired cohorts. The present review explores previous literature that has evaluated differences in plasma/brain vitamin C between genders and during aging. It then assesses whether these age and gender-related differences may affect the relationship between plasma/brain vitamin C and cognition. The purpose of this review was to examine the evidence for a link between plasma/brain vitamin C and cognition and the impact of gender and age on this relationship. Epidemiological studies have frequently shown higher vitamin C plasma concentrations in women. Similarly, aging has been systematically associated with reductions in plasma vitamin C levels. A range of animal studies has demonstrated potential gender and age-related differences in vitamin C brain distribution and utilization. The reviewed literature suggests that gender differences in plasma and brain vitamin C may potentially contribute to differences in gender-associated cognitive ability, particularly while females are pre-menopausal. Additionally, we can propose that age-associated differences in plasma and brain vitamin C may be potentially linked to age-associated cognitive differences, with older cohorts appearing more vulnerable to experience declines in plasma vitamin C concentrations alongside compromised vitamin C brain regulation. This review encourages future investigations to take into account both gender and age when assessing the link between plasma vitamin C concentrations and cognitive function. Further large scale investigations are required to assess whether differences in cognitive function between genders and age groups may be causally attributed to plasma vitamin C status and brain distribution and utilization.

Impaired intracellular trafficking of sodium-dependent vitamin C transporter 2 contributes to the redox imbalance in Huntington's disease

Huntington's disease (HD) is a neurodegenerative disorder caused by a glutamine expansion at the first exon of the huntingtin gene. Huntingtin protein (Htt) is ubiquitously expressed and it is localized in several organelles, including endosomes. HD is associated with a failure in energy metabolism and oxidative damage. Ascorbic acid is a powerful antioxidant highly concentrated in the brain where it acts as a messenger, modulating neuronal metabolism. It is transported into neurons via the sodium-dependent vitamin C transporter 2 (SVCT2). During synaptic activity, ascorbic acid is released from glial reservoirs to the extracellular space, inducing an increase in SVCT2 localization at the plasma membrane. Here, we studied SVCT2 trafficking and localization in HD. SVCT2 is decreased at synaptic terminals in YAC128 male mice. Using cellular models for HD (STHdhQ7 and STHdhQ111 cells), we determined that SVCT2 trafficking through secretory and endosomal pathways is altered in resting conditions. We observed Golgi fragmentation and SVCT2/Htt-associated protein-1 mis-colocalization. Additionally, we observed altered ascorbic acid-induced calcium signaling that explains the reduced SVCT2 translocation to the plasma membrane in the presence of extracellular ascorbic acid (active conditions) described in our previous results. Therefore, SVCT2 trafficking to the plasma membrane is altered in resting and active conditions in HD, explaining the redox imbalance observed during early stages of the disease.

Interplay between Metabolism, Nutrition and Epigenetics in Shaping Brain DNA Methylation, Neural Function and Behavior

Gene expression in the brain is dramatically regulated by a variety of stimuli. While the role of neural activity has been extensively studied, less is known about the effects of metabolism and nutrition on transcriptional control mechanisms in the brain. Extracellular signals are integrated at the chromatin level through dynamic modifications of epigenetic marks, which in turn fine-tune gene transcription. In the last twenty years, it has become clear that epigenetics plays a crucial role in modulating central nervous system functions and finally behavior. Here, we will focus on the effect of metabolic signals in shaping brain DNA methylation, both during development and adulthood. We will provide an overview of maternal nutrition effects on brain methylation and behavior in offspring. In addition, the impact of different diet challenges on cytosine methylation dynamics in the adult brain will be discussed. Finally, the possible role played by the metabolic status in modulating DNA hydroxymethylation, which is particularly abundant in neural tissue, will be considered.

Vitamin C is a source of oxoaldehyde and glycative stress in age-related cataract and neurodegenerative diseases

Oxoaldehyde stress has recently emerged as a major source of tissue damage in aging and age-related diseases. The prevailing mechanism involves methylglyoxal production during glycolysis and modification of arginine residues through the formation of methylglyoxal hydroimidazolones (MG-H1). We now tested the hypothesis that oxidation of vitamin C (ascorbic acid or ASA) contributes to this damage when the homeostatic redox balance is disrupted especially in ASA-rich tissues such as the eye lens and brain. MG-H1 measured by liquid chromatography mass spectrometry is several fold increased in the lens and brain from transgenic mice expressing human vitamin C transporter 2 (hSVCT2). Similarly, MG-H1 levels are increased two- to fourfold in hippocampus extracts from individuals with Alzheimer's disease (AD), and significantly higher levels are present in sarkosyl-insoluble tissue fractions from AD brain proteins than in the soluble fractions. Moreover, immunostaining with antibodies against methylglyoxal hydroimidazolones reveals similar increase in substantia nigra neurons from individuals with Parkinson's disease. Results from an in vitro incubation experiment suggest that accumulated catalytic metal ions in the hippocampus during aging could readily accelerate ASA oxidation and such acceleration was significantly enhanced in AD. Modeling studies and intraventricular injection of 13 C-labeled ASA revealed that ASA backbone carbons 4-6 are incorporated into MG-H1 both in vitro and in vivo, likely via a glyceraldehyde precursor. We propose that drugs that prevent oxoaldehyde stress or excessive ASA oxidation may protect against age-related cataract and neurodegenerative diseases.

Dual-Sensitive Nanomicelles Enhancing Systemic Delivery of Therapeutically Active Antibodies Specifically into the Brain

Delivering therapeutic antibodies into the brain across the blood-brain barrier at a therapeutic level is a promising while challenging approach in the treatment of neurological disorders. Here, we present a polymeric nanomicelle (PM) system capable of delivering therapeutically effective levels of 3D6 antibody fragments (3D6-Fab) into the brain parenchyma for inhibiting Aβ aggregation. PM assembly was achieved by charge-converting 3D6-Fab through pH-sensitive citraconylation to allow complexation with reductive-sensitive cationic polymers. Brain targeting was achieved by functionalizing the PM surface with glucose molecules to allow interaction with recycling glucose transporter (Glut)-1 proteins. Consequently, 41-fold enhanced 3D6-Fab accumulation in the brain was achieved by using the PM system compared to free 3D6-Fab. Furthermore, therapeutic benefits were obtained by successfully inhibiting Aβ_1-42 aggregation in Alzheimer's disease mice systemically treated with 3D6-Fab-loaded glucosylated PM. Hence, this nanocarrier system represents a promising method for effectively delivering functional antibody agents into the brain and treating neurological diseases.

The neuropsychiatric effects of vitamin C deficiency: a systematic review

BACKGROUND

Vitamin C deficiency may be more common than is generally assumed, and the association between vitamin C deficiency and adverse psychiatric effects has been known for centuries. This paper aims to systematically review the evidence base for the neuropsychiatric effects of vitamin C deficiency.

METHODS

Relevant studies were identified via systematic literature review.

RESULTS

Nine studies of vitamin C deficiency, including subjects both with and without the associated physical manifestations of scurvy, were included in this review. Vitamin C deficiency, including scurvy, has been linked to depression and cognitive impairment. No effect on affective or non-affective psychosis was identified.

CONCLUSIONS

Disparate measurement techniques for vitamin C, and differing definitions of vitamin C deficiency were apparent, complicating comparisons between studies. However, there is evidence suggesting that vitamin C deficiency is related to adverse mood and cognitive effects. The vitamin C blood levels associated with depression and cognitive impairment are higher than those implicated in clinical manifestations of scurvy. While laboratory testing for ascorbic acid can be practically difficult, these findings nonetheless suggest that mental health clinicians should be alerted to the possibility of vitamin C deficiency in patients with depression or cognitive impairment. Vitamin C replacement is inexpensive and easy to deliver, although as of yet there are no outcome studies investigating the neuropsychiatric impact of vitamin C replacement in those who are deficient.

Role of PTA in the prevention of Cu(amyloid-β) induced ROS formation and amyloid-β oligomerisation in the presence of Zn

Metal-targeting drugs are being widely explored as a possible treatment for Alzheimer's disease, but most of these ligands are developed to coordinate Cu(ii). In a previous communication (E. Atrián-Blasco, E. Cerrada, A. Conte-Daban, D. Testemale, P. Faller, M. Laguna and C. Hureau, Metallomics, 2015, 7, 1229-1232) we showed another strategy where Cu(i) was targeted with the PTA (1,3,5-triaza-7-phosphaadamantane) ligand that is able to target Cu(ii) as well, reduce it and keep it in a safe complexed species. Removal of Cu(ii) from the amyloid-β peptide prevents the stabilization of oligomers and protofibrils and the complexation of Cu(i) also stops the formation of reactive oxygen species. Besides, zinc, which is found in the synaptic cleft at a higher concentration than copper, can hamper the ability of metal-targeting drug candidates, an issue that is still poorly considered and studied. Here we show that PTA fully retains the above described properties even in the presence of zinc, thus fulfilling an additional pre-requisite for its use as a model of Cu(i)-targeting drug candidates in the Alzheimer's disease context.