Vitamin C: update on physiology and pharmacology

Dynamics of ascorbic acid content in apple (Malus x domestica) during fruit development and storage

Vitamin C is a crucial antioxidant and cofactor for both plants and humans. Apple fruits generally contain low levels of vitamin C, making vitamin C content an interesting trait for apple crop improvement. With the aim of breeding high vitamin C apple cultivars it is important to get an insight in the natural biodiversity of vitamin C content in apple fruits. In this study, quantification of ascorbic acid (AsA), dehydroascorbic acid (DHA), and total AsA (AsA + DHA) in apple pulp of 79 apple accessions at harvest revealed significant variation, indicating a large genetic biodiversity. High density genotyping using an 8 K SNP array identified 21 elite and 58 local cultivars in this germplasm, with local accessions showing similar levels of total AsA but higher amounts of DHA compared to elite varieties. Out of the 79 apple cultivars screened, ten genotypes with either the highest or the lowest concentration of total AsA at harvest were used for monitoring vitamin C dynamics during fruit development and storage. For all these cultivars, the AsA/DHA ratio in both apple pulp and peel increased throughout fruit development, whereas the AsA/DHA balance always shifted towards the oxidized form during storage and shelf life, putatively reflecting an abiotic stress response. Importantly, at any point during apple fruit development and storage, the apple peel contained a higher level of vitamin C compared to the pulp, most likely because of its direct exposure to abiotic and biotic stresses.

On the physiological and cellular homeostasis of ascorbate

Recent interest in the role of ascorbate in crucial metabolic processes is driven by the growing number of medical reports that show beneficial effects of ascorbate supplementation for maintaining general well-being and recovery from a variety of medical conditions. The effect of ascorbate on the local body environment highly depends on its local concentration; at low concentrations it can cause the reduction of reactive oxygen and facilitate activities of enzymes, while at high concentrations it generates free radicals by reducing ferric ions. Ascorbate serving as an electron donor assists the iron-containing proteins and the iron transfer between various aqueous compartments. These functions require effective and adjustable mechanisms responsible for ascorbate biodistribution. In the paper we propose a new biophysical model of ascorbate redistribution between various aqueous body compartments. It combines recent experimental evidence regarding the ability of ascorbate to cross the lipid bilayer by unassisted diffusion, with active transport by well-characterized sodium vitamin C transporter (SVCT) membrane proteins. In the model, the intracellular concentration of ascorbate is maintained by the balance of two opposing fluxes: fast active and slow passive transport. The model provides a mechanistic understanding of ascorbate flux across the epidermal barrier in the gut as well as the role of astrocytes in ascorbate recycling in the brain. In addition, ascorbate passive diffusion across biological membranes, which depends on membrane electric potentials and pH gradients, provides the rationale for the correlation between ascorbate distribution and the transfer of iron ions inside a cell. The proposed approach provides, for the first time, a mechanistic account of processes leading to ascorbate physiological and cellular distribution, which helps to explain numerous experimental and clinical observations.

Strengthening the Immune System and Reducing Inflammation and Oxidative Stress through Diet and Nutrition: Considerations during the COVID-19 Crisis

The coronavirus-disease 2019 (COVID-19) was announced as a global pandemic by the World Health Organization. Challenges arise concerning how to optimally support the immune system in the general population, especially under self-confinement. An optimal immune response depends on an adequate diet and nutrition in order to keep infection at bay. For example, sufficient protein intake is crucial for optimal antibody production. Low micronutrient status, such as of vitamin A or zinc, has been associated with increased infection risk. Frequently, poor nutrient status is associated with inflammation and oxidative stress, which in turn can impact the immune system. Dietary constituents with especially high anti-inflammatory and antioxidant capacity include vitamin C, vitamin E, and phytochemicals such as carotenoids and polyphenols. Several of these can interact with transcription factors such as NF-kB and Nrf-2, related to anti-inflammatory and antioxidant effects, respectively. Vitamin D in particular may perturb viral cellular infection via interacting with cell entry receptors (angiotensin converting enzyme 2), ACE2. Dietary fiber, fermented by the gut microbiota into short-chain fatty acids, has also been shown to produce anti-inflammatory effects. In this review, we highlight the importance of an optimal status of relevant nutrients to effectively reduce inflammation and oxidative stress, thereby strengthening the immune system during the COVID-19 crisis.

Infantile scurvy: Still a relevant differential diagnosis in Western medicine

OBJECTIVE

Infantile scurvy or Moller-Barlow's disease appears to be of no further importance in Western countries; however, this is a careless assumption. In severely disabled children especially, this malady manifests itself in a broad range of symptoms such as delayed or suppressed bone healing, minor traumatization leading to bruises or fractures, and epiphysiolysis.

METHODS

The aim of this article was to present the required daily uptake of vitamin C and the biochemical pathways in the human body leading to the typical symptoms of scurvy. Two cases of chronic scurvy with prolonged bone healing and bleeding, epiphysiolysis, and gingival hyperplasia are presented. Both patients were chronically ill with one having cerebral palsy and the other a neuroblastoma of the adrenal gland.

RESULTS

After diagnosis, the substitution of vitamin C via percutaneous endoscopic gastrostomy in both patients was necessary to treat them. Both patients quickly achieved a full recovery.

CONCLUSION

The two patients presented show the importance of infantile scurvy in daily medical care. The prevalence of scurvy is often underestimated in severely disabled or chronically ill children.

The implications of vitamin content in the plasma in reference to the parameters of carbohydrate metabolism and hormone and lipid profiles in PCOS

So far, there have been no analyses of correlations between the level of water-soluble vitamins in women with polycystic ovary syndrome (PCOS) and hormone and lipid profiles as well as carbohydrate metabolism. The unpopular concept that PCOS may also be conditioned by a chronic infection leads to a suspicion that water-soluble vitamins may be involved in the struggle against PCOS. This is why the aim of this research was to determine whether there are any indications that could confirm this hypothesis. The study included 64 women of Caucasian race: 50 patients aged 29.52 ± 7.01 years with PCOS, diagnosed according to the Rotterdam criteria. The control group consisted of 14 women aged 30.23 ± 6.3 years with correct BMI. HPLC Infinity1260 Binary LC (Agilent Technologies, Waldbronn, Germany) was used to analyze nine vitamins. The vitamins were separated using the gradient method, a buffer of 25 mM HK2PO4 with pH equal to 7.0, and 100 % methanol buffer. The acquired results were compared using Statistica 12.0 (Statsoft, Tulsa, Oklahoma, USA). Non-parametric tests were used: Mann-Whitney tests for comparisons between groups (PCOS and control group, CG), in which p < 0.05 was considered statistically significant. Subsequently, we performed a correlation matrix of the biochemical parameters of blood with vitamins at p ≤ 0.05. Higher concentrations of ascorbic acid were observed in PCOS. The content of the remaining vitamins was higher in the control group, and the statistical differences were significant in reference to thiamine, riboflavin, pyridoxine and folic acid in comparison to the control group. A significant positive correlation was observed between vitamin C and testosterone/insulin, another between riboflavin and androstenedione/testosterone, next between biotin and thyrotropic hormone (TSH), between pantothenic acid and dehydroepiandrosteron (DHEA-SO4), and finally between pyridoxine and androstenedione. A negative correlation was observed in the case of niacin with sex hormone binding protein (SHBG) and high density lipoprotein (HDL). Water-soluble vitamins play an important role in the therapy of women with PCOS through the reduction of antioxidative stress and low-intensity inflammation caused by various factors, including chronic infection.

Ascorbic Acid Sensitizes Colorectal Carcinoma to the Cytotoxicity of Arsenic Trioxide via Promoting Reactive Oxygen Species-Dependent Apoptosis and Pyroptosis

Arsenic trioxide (ATO) is an effective therapeutic agent against acute promyelocytic leukemia (APL); however, its anti-tumor effect on solid tumors such as colorectal cancer (CRC) is still in debate. Ascorbic acid (AA) also produces a selective cytotoxic activity against tumor cells. Here, we exploit the potential benefit of ATO/AA combination in generating cytotoxicity to CRC cells, which may lay the groundwork for the potential combinational chemotherapy of CRCs. According to the results, we found that ATO and AA effectively inhibited the viability of human CRC cells in a synergistic manner. AA and ATO corporately activated caspase-3 to trigger apoptosis and upregulated the expression of caspase-1 and promoted formation of inflammasomes to induce pyroptosis. Furthermore, the stimulation of reactive oxygen species (ROS) overproduction was demonstrated as a subcellular mechanism for apoptosis and pyroptosis induced by ATO/AA combination treatment. Our findings suggest that ATO combination with a conventional dosage of AA offers an advantage for killing CRC cells. The synergistic action of ATO/AA combination might be considered a plausible strategy for the treatment of CRC and perhaps other solid tumors as well.

Chrysin Reduces Oxidative Stress but Does Not Affect Polyol Pathway in the Lenses of Type 1 Diabetic Rats

Prolonged hyperglycemia is one of the main causes of reactive oxygen species and free radicals generation in diabetes which may affect various organs, including the eye. Oxidative damage to proteins and lipids in the eye lens could lead to cataract formation. To cope with oxidative stress, the endogenous antioxidative system may be supported by the supplementation of exogenous antioxidants. The aim of this study was to evaluate the effect of chrysin, a natural flavonoid, on oxidative stress and polyol pathway-related markers in the lenses of streptozotocin-induced type 1 male diabetic rats. Chrysin at doses of 50 and 100 mg/kg was administered by gavage for 28 days. This treatment resulted in a decrease in antioxidative enzymes activity and oxidative stress index. Moreover, chrysin administration elevated the reduced glutathione level in the lenses. A decrease in the markers linked to oxidative damage to proteins and lipids in the lenses was noted, especially after treatment with 50 mg/kg of chrysin. Neither of the chrysin doses affected glycemia-related markers in the serum or altered parameters related to the polyol pathway and advanced glycation end-products level in the lenses of diabetic rats. Upon obtaining results, it can be concluded that chrysin reveals antioxidative activity in the lenses but shows no antihyperglycemic or antiglycation properties.

Mitochondrial reactive oxygen species: the effects of mitochondrial ascorbic acid vs untargeted and mitochondria-targeted antioxidants

PREMISE

Mitochondria represent critical sites for reactive oxygen species (ROS) production, which dependent on concentration is responsible for the regulation of both physiological and pathological processes.

PURPOSE

Antioxidants in mitochondria regulate the redox balance, prevent mitochondrial damage and dysfunction and maintain a physiological ROS-dependent signaling. The aim of the present review is to provide critical elements for addressing this issue in the context of various pharmacological approaches using antioxidants targeted or non-targeted to mitochondria. Furthermore, this review focuses on the mitochondrial antioxidant effects of ascorbic acid (AA), providing clues on the complexities associated with the cellular uptake and subcellular distribution of the vitamin.

CONCLUSIONS

Antioxidants that are not specifically targeted to mitochondria fail to accumulate in significant amounts in critical sites of mitochondrial ROS production and may eventually interfere with the ensuing physiological signaling. Mitochondria-targeted antioxidants are more effective, but are expected to interfere with the mitochondrial ROS-dependent physiologic signaling. AA promotes multiple beneficial effects in mitochondria. The complex regulation of vitamin C uptake in these organelles likely contributes to its versatile antioxidant response, thereby providing a central role to the vitamin for adequate control of mitochondrial dysfunction associated with increased mitochondrial ROS production.

Vitamin C attenuates memory loss induced by post-traumatic stress like behavior in a rat model

Oxidative stress is associated with neuronal damage in many brain regions including the hippocampus; an area in the brain responsible of memory processing. Oxidative stress is also linked with many psychiatric conditions including post-traumatic stress disorder (PTSD). PTSD is triggered by traumatic experience and many PTSD patients show signs of memory impairment. Vitamin C is a water-soluble vitamin with antioxidant properties. Herein, we hypothesized that memory impairment observed during PTSD could be a result of oxidative stress in hippocampal tissues and that prophylactic vitamin C administration may reduce oxidative stress in the hippocampus and prevent memory impairment. The above hypothesis was tested in a rat model where PTSD-like behavior was induced through single prolonged stress (SPS). Short and long-term memory was tested using a radial arm water maze (RAWM). We found that SPS induced a significant increase in the oxidized glutathione levels of the hippocampus. This reduction was accompanied with a significant decrease in glutathione peroxidase and catalase enzyme activity, and a significant increase in lipid peroxidation. Intriguingly, vitamin C administration successfully attenuated memory impairment and all of the changes observed in oxidative stress markers. Our findings demonstrate that vitamin C could prevent oxidative stress and memory impairment induced by SPS model of PTSD-like behavior in rat.

Plasma ascorbic acid and the risk of islet autoimmunity and type 1 diabetes: the TEDDY study

AIMS/HYPOTHESIS

We studied the association of plasma ascorbic acid with the risk of developing islet autoimmunity and type 1 diabetes and examined whether SNPs in vitamin C transport genes modify these associations. Furthermore, we aimed to determine whether the SNPs themselves are associated with the risk of islet autoimmunity or type 1 diabetes.

METHODS

We used a risk set sampled nested case-control design within an ongoing international multicentre observational study: The Environmental Determinants of Diabetes in the Young (TEDDY). The TEDDY study followed children with increased genetic risk from birth to endpoints of islet autoantibodies (350 cases, 974 controls) and type 1 diabetes (102 cases, 282 controls) in six clinical centres. Control participants were matched for family history of type 1 diabetes, clinical centre and sex. Plasma ascorbic acid concentration was measured at ages 6 and 12 months and then annually up to age 6 years. SNPs in vitamin C transport genes were genotyped using the ImmunoChip custom microarray. Comparisons were adjusted for HLA genotypes and for background population stratification.

RESULTS

Childhood plasma ascorbic acid (mean ± SD 10.76 ± 3.54 mg/l in controls) was inversely associated with islet autoimmunity risk (adjusted OR 0.96 [95% CI 0.92, 0.99] per +1 mg/l), particularly islet autoimmunity, starting with insulin autoantibodies (OR 0.94 [95% CI 0.88, 0.99]), but not with type 1 diabetes risk (OR 0.93 [95% Cl 0.86, 1.02]). The SLC2A2 rs5400 SNP was associated with increased risk of type 1 diabetes (OR 1.77 [95% CI 1.12, 2.80]), independent of plasma ascorbic acid (OR 0.92 [95% CI 0.84, 1.00]).

CONCLUSIONS/INTERPRETATION

Higher plasma ascorbic acid levels may protect against islet autoimmunity in children genetically at risk for type 1 diabetes. Further studies are warranted to confirm these findings.

DATA AVAILABILITY

The datasets generated and analysed during the current study will be made available in the NIDDK Central Repository at https://www.niddkrepository.org/studies/teddy.

The Use of Antioxidants in the Treatment of Migraine

Despite numerous studies concerning the pathophysiology of migraine, the exact molecular mechanism of disturbances underlying migraine is still unknown. Furthermore, oxidative stress is considered to play a significant role in migraine pathogenesis. The notion of oxidative stress in migraine patients has been discussed for several decades. Over the past few years, among the substances that could potentially be used for migraine treatment, particular attention has been paid to the so-called nutraceutics, including antioxidants. Antioxidants supplied with food prevent oxidative stress by inhibiting initiation, propagation, and the oxidative chain reaction itself. Additionally, the agents used so far in the prevention of migraine indeed show some anti-oxidative action. The antioxidants discussed in the present paper are increasingly more often used by migraine patients not only due to mild or even a lack of side effects but also because of their effectiveness (decreased frequency of migraine episodes or shortening of an episode duration). The present review provides a summary of the studies on nutraceuticals with antioxidative properties.

Glut-1 explains the evolutionary advantage of the loss of endogenous vitamin C-synthesis: The electron transfer hypothesis

Introduction

During evolution, some species including humans, monkeys and fruit bats lost the ability for ascorbic acid (AA) biosynthesis due to inactivation of the enzyme l-gulono-lactone oxidase (GLO) and subsequently became dependent on dietary vitamin C. There are four current hypotheses in relation to the benefit of vitamin C dependence in the context of adaptation and reproduction. Here we advance and test a new ‘electron transfer hypothesis’, which focusses on the role of the expression of glucose transporter 1 (Glut-1) in red blood cells (RBCs) in recycling vitamin C, thereby increasing the efficiency of micronutrient uptake.

Methods

To evaluate the benefit of Glut-1 expression, we determined vitamin C uptake into RBCs and potential release from two different species, humans with l-Gulono-lactone-oxidase (GLO-loss) and pigs with functional GLO.

Results

The oxidized form of vitamin C (dehydroascorbate, DHA) was transported into human RBCs via Glut-1. There was no transport of either the reduced (AA) or the oxidized vitamin in pig erythrocytes.

Conclusion

We propose that the transport of vitamin C increases an intracellular electron pool, which transfers electrons from intracellular ascorbate to extracellular substances like ascorbyl free radical or DHA, resulting in 100-fold smaller daily requirement of this essential redox sensitive micronutrient. This would be an advantage during seasonal changes of the availability from food and may be the key for the survival of individuals without vitamin C biosynthesis.

Lay Summary

40 million years ago some individuals lost the ability to synthesize vitamin C. Why did they survive such as humans until now? Individuals with a specific glucose transporter Glut-1 on their erythrocytes which transports vitamin C need less and are protected from scarcity due to seasons and food competitors.

Temporal map of the pig polytrauma plasma proteome with fluid resuscitation and intravenous vitamin C treatment

BACKGROUND

Fluid resuscitation plays a prominent role in stabilizing trauma patients with hemorrhagic shock yet there remains uncertainty with regard to optimal administration time, volume, and fluid composition (e.g., whole blood, component, colloids) leading to complications such as trauma-induced coagulopathies (TIC), acidosis, and poor oxygen transport. Synthetic fluids in combination with antioxidants (e.g., vitamin C) may resolve some of these problems.

OBJECTIVES

We applied quantitative mass spectrometry-based proteomics [liquid chromatography-mass spectrometry (LC-MS/MS)] to map the effects of fluid resuscitation and intravenous vitamin C (VitC) in a pig model of polytrauma (hemorrhagic shock, tissue injury, liver reperfusion, hypothermia, and comminuted bone fracture). The goal was to determine the effects of VitC on plasma protein expression, with respect to changes associated with coagulation and trauma-induced coagulopathy (TIC).

METHODS

Longitudinal blood samples were drawn from nine male Sinclair pigs at baseline, 2 h post trauma, and 0.25, 2, and 4 h post fluid resuscitation with 500 mL hydroxyethyl starch. Pigs were treated intravenously (N = 3/treatment group) with saline, 50 mg VitC/kg (Lo-VitC), or 200 mg VitC/kg (Hi-VitC) during fluid resuscitation.

RESULTS

A total of 436 plasma proteins were quantified of which 136 changed following trauma and resuscitation; 34 were associated with coagulation, complement cascade, and glycolysis. Unexpectedly, Lo-VitC and Hi-VitC treatments stabilized ADAMTS13 levels by ~4-fold (P = .056) relative to saline and enhanced ADAMTS13/von Willebrand factor (VWF) cleavage efficiency based on LC-MS/MS evidence for the semitryptic VWF cleavage product (VWF1275-1286 ).

CONCLUSIONS

This study provides the first comprehensive map of trauma-induced changes to the plasma proteome, especially with respect to proteins driving the development of TIC.

Vitamin C in Plants: From Functions to Biofortification

Vitamin C (l-ascorbic acid) is an excellent free radical scavenger, not only for its capability to donate reducing equivalents but also for the relative stability of the derived monodehydroascorbate radical. However, vitamin C is not only an antioxidant, since it is also a cofactor for numerous enzymes involved in plant and human metabolism. In humans, vitamin C takes part in various physiological processes, such as iron absorption, collagen synthesis, immune stimulation, and epigenetic regulation. Due to the functional loss of the gene coding for l-gulonolactone oxidase, humans cannot synthesize vitamin C; thus, they principally utilize plant-based foods for their needs. For this reason, increasing the vitamin C content of crops could have helpful effects on human health. To achieve this objective, exhaustive knowledge of the metabolism and functions of vitamin C in plants is needed. In this review, the multiple roles of vitamin C in plant physiology as well as the regulation of its content, through biosynthetic or recycling pathways, are analyzed. Finally, attention is paid to the strategies that have been used to increase the content of vitamin C in crops, emphasizing not only the improvement of nutritional value of the crops but also the acquisition of plant stress resistance.

Ascorbic acid insufficiency impairs spatial memory formation in juvenile AKR1A-knockout mice

AKR1A, an aldo-keto reductase, is involved in the synthesis of ascorbic acid as well as the reduction of a variety of aldehyde compounds. AKR1A^−/− mice produce considerably less ascorbic acid (about 10%) compared to AKR1A^+/+ mice and require ascorbic acid supplementation in order to breed. To elucidate the roles played by AKR1A in spatial memory, AKR1A^−/− male mice were weaned at 4 weeks of age and groups that received ascorbic acid supplementation and no supplementation were subjected to a Morris water maze test. Juvenile AKR1A^−/− mice that received no supplementation showed impaired spatial memory formation, even though about 70% of the ascorbic acid remained in the brains of the AKR1A^−/− mice at day 7 after weaning. To the contrary, the young adult AKR1A^−/− mice at 13–15 weeks of age maintained only 15% of ascorbic acid but showed no significant difference in the spatial memory compared with the AKR1A^+/+ mice or ascorbic acid-supplemented AKR1A^−/− mice. It is conceivable that juvenile mice require more ascorbic acid for the appropriate level of formation of spatial memory and that maturation of the neural system renders the memory forming process less sensitive to an ascorbic acid insufficiency.

Reprogramming the Epigenome With Vitamin C

The erasure of epigenetic modifications across the genome of somatic cells is an essential requirement during their reprogramming into induced pluripotent stem cells (iPSCs). Vitamin C plays a pivotal role in remodeling the epigenome by enhancing the activity of Jumonji-C domain-containing histone demethylases (JHDMs) and the ten-eleven translocation (TET) proteins. By maintaining differentiation plasticity in culture, vitamin C also improves the quality of tissue specific stem cells derived from iPSCs that are highly sought after for use in regenerative medicine. The ability of vitamin C to potentiate the activity of histone and DNA demethylating enzymes also has clinical application in the treatment of cancer. Vitamin C deficiency has been widely reported in cancer patients and has recently been shown to accelerate cancer progression in disease models. Therapies involving high-dose vitamin C administration are currently gaining traction in the treatment of epigenetic dysregulation, by targeting aberrant histone and DNA methylation patterns associated with cancer progression.

Plasma Vitamin C Levels: Risk Factors for Deficiency and Association with Self-Reported Functional Health in the European Prospective Investigation into Cancer-Norfolk

BACKGROUND

To investigate the demographic and lifestyles factors associated with vitamin C deficiency and to examine the association between plasma vitamin C level and self-reported physical functional health.

METHODS

A population-based cross-sectional study using the European Prospective Investigation into Cancer-Norfolk study. Plasma vitamin C level < 11 µmol/L indicated vitamin C deficiency. Unconditional logistic regression models assessed the association between vitamin C deficiency and potential risk factors. Associations between quartiles of vitamin C and self-reported functional health measured by the 36-item short-form questionnaire (SF-36) were assessed.

RESULTS

After adjustment, vitamin C deficiency was associated with older age, being male, lower physical activity, smoking, more socially deprived area (Townsend index) and a lower educational attainment. Compared to the highest, those in the lowest quartile of vitamin C were more likely to score in the lowest decile of physical function (adjusted odds ratio (aOR): 1.43 (95%CI: 1.21-1.70)), bodily pain (aOR: 1.29 (95% CI: 1.07-1.56)), general health (aOR: 1.4 (95%CI: 1.18-1.66)), and vitality (aOR: 1.23 (95%CI: 1.04-1.45)) SF-36 scores.

CONCLUSIONS

Simple public health interventions should be aimed at populations with risk factors for vitamin C deficiency. Poor self-reported functional health was associated with lower plasma vitamin C levels, which may reflect symptoms of latent scurvy.

Neurobiology of vitamin C: Expanding the focus from antioxidant to endogenous neuromodulator

Ascorbic acid (AA) is a water-soluble vitamin (C) found in all bodily organs. Most mammals synthesize it, humans are required to eat it, but all mammals need it for healthy functioning. AA reaches its highest concentration in the brain where both neurons and glia rely on tightly regulated uptake from blood via the glucose transport system and sodium-coupled active transport to accumulate and maintain AA at millimolar levels. As a prototype antioxidant, AA is not only neuroprotective, but also functions as a cofactor in redox-coupled reactions essential for the synthesis of neurotransmitters (e.g., dopamine and norepinephrine) and paracrine lipid mediators (e.g., epoxiecoisatrienoic acids) as well as the epigenetic regulation of DNA. Although redox capacity led to the promotion of AA in high doses as potential treatment for various neuropathological and psychiatric conditions, ample evidence has not supported this therapeutic strategy. Here, we focus on some long-neglected aspects of AA neurobiology, including its modulatory role in synaptic transmission as demonstrated by the long-established link between release of endogenous AA in brain extracellular fluid and the clearance of glutamate, an excitatory amino acid. Evidence that this link can be disrupted in animal models of Huntington´s disease is revealing opportunities for new research pathways and therapeutic applications (e.g., epilepsy and pain management). In fact, we suggest that improved understanding of the regulation of endogenous AA and its interaction with key brain neurotransmitter systems, rather than administration of AA in excess, should be the target of future brain-based therapies.

Differential Expression of CD3, TNF-α, and VEGF Induced by Olanzapine on the Spleen of Adult Male Albino Rats and the Possible Protective Role of Vitamin C

Olanzapine is an antipsychotic drug effective in the treatment of stress-associated psychiatric illnesses, but its effect on the spleen remains unclear. Vitamin C is essential for the optimum function of the immune system. We aim to investigate the effect of Olanzapine on spleen structures and to assess the protective effect of vitamin C. Forty adult male albino rats were divided into four groups: group (I), a control; group (II), rats were given vitamin C at 40 mg/kg body weight; group (III), rats were given Olanzapine at 2 mg/kg body weight; and group (IV), rats were given vitamin C and Olanzapine at the same dose of group (II) and group (III) for one month. The hematoxylin and eosin (H&E) of the olanzapine treated group showed focal areas of cellular depletion and a decrease in the size of the white pulp. The red pulp was expanded and showed marked congestion and dilatation of blood sinusoids. Cluster of differentiation 3 (CD3) was significantly reduced, however both tumor necrosis factor alpha (TNF-α), and vascular endothelial growth factor (VEGF) were significantly higher. The administration of vitamin C repaired structural and immunohistochemical changes via increased CD3 and decreased TNF-α and VEGF. Therefore, the oxidative and the inflammatory pathways may be the possible mechanisms underlying olanzapine immunotoxicity. Vitamin C exerted immune modulator and antioxidant effects against olanzapine.

Vitamin C Can Shorten the Length of Stay in the ICU: A Meta-Analysis

A number of controlled trials have previously found that in some contexts, vitamin C can have beneficial effects on blood pressure, infections, bronchoconstriction, atrial fibrillation, and acute kidney injury. However, the practical significance of these effects is not clear. The purpose of this meta-analysis was to evaluate whether vitamin C has an effect on the practical outcomes: length of stay in the intensive care unit (ICU) and duration of mechanical ventilation. We identified 18 relevant controlled trials with a total of 2004 patients, 13 of which investigated patients undergoing elective cardiac surgery. We carried out the meta-analysis using the inverse variance, fixed effect options, using the ratio of means scale. In 12 trials with 1766 patients, vitamin C reduced the length of ICU stay on average by 7.8% (95% CI: 4.2% to 11.2%; p = 0.00003). In six trials, orally administered vitamin C in doses of 1⁻3 g/day (weighted mean 2.0 g/day) reduced the length of ICU stay by 8.6% (p = 0.003). In three trials in which patients needed mechanical ventilation for over 24 hours, vitamin C shortened the duration of mechanical ventilation by 18.2% (95% CI 7.7% to 27%; p = 0.001). Given the insignificant cost of vitamin C, even an 8% reduction in ICU stay is worth exploring. The effects of vitamin C on ICU patients should be investigated in more detail.

High doses of sodium ascorbate act as a prooxidant and protect gnotobiotic brine shrimp larvae (Artemia franciscana) against Vibrio harveyi infection coinciding with heat shock protein 70 activation

Ascorbate is an essential nutrient commonly regarded as an antioxidant. In this study, using axenic brine shrimp and pathogenic strain Vibrio harveyi as the host-pathogen model, we confirmed that pretreatment of sodium ascorbate (NaAs), at an optimum concentration, was a prooxidant by generation of hydrogen peroxide, inducing protective effects in the brine shrimp against V. harveyi infection. Such a protective effect could be neutralized by the addition of an antioxidant enzyme catalase. We further showed that generation of oxygen radicals is linked to the induction of heat shock protein 70 (Hsp70), which is involved in eliciting the antioxidant protection system including superoxidase dismutase (SOD) and possibly many other immune responses. Furthermore, using RNA interference technique, we found that the pretreatment of sodium ascorbate increased the survival significantly in the control knockdown groups (using green fluorescent protein, GFP) but not in Hsp70 knockdown groups and the result directly suggested that the up-regulated Hsp70 induced by sodium ascorbate pretreatment induced the protective effect. These results provide a mechanistic rationale for exploring the further use of ascorbate for antimicrobial therapy in aquaculture.

A Combination of Linalool, Vitamin C, and Copper Synergistically Triggers Reactive Oxygen Species and DNA Damage and Inhibits Salmonella enterica subsp. enterica Serovar Typhi and Vibrio fluvialis

Inappropriate and disproportionate use of antibiotics is contributing immensely to the development of antibiotic resistance in bacterial species associated with food contamination. The use of natural products in combination can be a potent alternative hurdle strategy to inactivate foodborne pathogens. Here, we explored the pro-oxidant properties of essential oil linalool and vitamin C in combination with copper (LVC) in combating the foodborne pathogens Vibrio fluvialis and Salmonella enterica subsp. enterica serovar Typhi using a three-dimensional (3D) checkerboard microdilution assay. Antibacterial activity in terms of the MIC revealed that the triple combination exerted a synergistic effect compared to the effects of the individual constituents. The bactericidal effect of the triple combination was confirmed by a live/dead staining assay. Reactive oxygen species (ROS) measurements with the terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling assay and scanning electron microscopy imaging strongly suggested that the increase in ROS production is the underlying mechanism of the enhanced antibacterial potency of the LVC combination (linalool [1.298 mM], vitamin C [8 mM], copper [16.3 μM]). In addition, the hypersensitivity of oxidative stress regulator mutants (oxyR, katG, ahpC, and sodA mutants) toward LVC corroborated the involvement of ROS in cell death. Live/dead staining and changes in cellular morphology revealed that oxidative stress did not transform the cells into the viable but nonculturable (VBNC) state; rather, killing was associated with intracellular and extracellular oxidative burst. Furthermore, the LVC combination did not display toxicity to human cells, while it effectively reduced the pathogen levels in acidic fruit juices by 3 to 4 log CFU/ml without adversely altering the organoleptic properties. This study opens a new outlook for combinatorial antimicrobial therapy.IMPORTANCE There is a need to develop effective antibacterial therapies for mitigating bacterial pathogens in food systems. We used a 3D checkerboard assay to ascertain a safe synergistic combination of food-grade components: vitamin C, copper, and the essential oil linalool. Individually, these constituents have to be added in large amounts to exert their antibacterial effect, which leads to unwanted organoleptic properties. The triple combination could exceptionally inhibit foodborne Gram-negative pathogens like Vibrio fluvialis and Salmonella enterica subsp. enterica serovar Typhi at low concentrations (linalool, 1.298 mM; vitamin C, 8 mM; copper, 16.3 μM) and displayed potent microbial inhibition in acidic beverages. We found increased susceptibility in deletion mutants of oxidative stress regulators (oxyR, katG, ahpC, and sodA mutants) due to ROS generation by Fenton's chemistry. The results of this study show that it may be possible to use plant-based antimicrobials in synergistic combinations to control microbial contaminants.

Scurvy, an old story in a new time: The hematologist's experience

BACKGROUND

Scurvy is a rare entity in developed countries and the diagnosis may often be delayed resulting in unnecessary investigations and/or potentially severe complications. A recent increase in the number of patients diagnosed with scurvy in our hematology clinics indicated the need to review the literature on the diagnosis and optimal management of similar patients.

METHODS

We conducted a retrospective chart review of patients referred to hematology at our tertiary care centre between 2010 and 2018, who were ultimately diagnosed with scurvy. Data collected from electronic medical records included baseline characteristics, clinical features on presentation, bloodwork results from initial consultation, treatment plan as well as response to treatment.

FINDINGS

Twenty-two adults patient had a diagnosis of scurvy with a mean vitamin C level of 6 μmol/L. Iron deficiency anemia (54%) and gastrointestinal disorders (54%) were the most common comorbidities noted in our cohort. Proton-pump inhibitors use was noted in 54% of patients. Bleeding (45%) and bruising (45%) were the most commonly reported clinical features. Eleven patients received oral supplementation, five had intravenous (IV) vitamin C and six were not treated. Two patients required a transition from oral to IV supplementation. Vitamin C dosing ranged between 250 and 2000 mg and the frequency varied from daily for oral therapy to every few weeks or months for IV.

INTERPRETATION

Awareness of scurvy and its associated risk factors and clinical presentation is important in the evaluation of a patient with bleeding tendency. Treatment plan should be individualized, and a careful review of patients' diet, medial history and medications is warranted.

Limited evidence for a beneficial effect of vitamin C supplementation on biomarkers of cardiovascular diseases: an umbrella review of systematic reviews and meta-analyses

Vitamin C is an essential nutrient with important antioxidant properties. Higher vitamin C intake appears to be associated with positive effects on cardiovascular risk factors in cohort studies, whereas large randomized controlled clinical trials did not confirm the benefits of supplemental vitamin C on cardiovascular disease (CVD) outcomes. In this overview of systematic reviews and meta-analyses, an "umbrella review," we investigated the effects of vitamin C supplementation on biomarkers of cardiovascular risk, that is, arterial stiffness, blood pressure, endothelial function, glycemic control, and lipid profile. In addition, we assessed the strength of the evidence and the methodological qualities of available studies. Two independent investigators searched 4 databases (Medline, Embase, Scopus, and The Cochrane Library databases) from inception until February 2018. After full text examination, 10 systematic reviews and meta-analyses were included in the umbrella review which included 6409 participants. Three systematic reviews investigated the effects of vitamin C on endothelial function with contrasting results (2 reviews reported a significant effect, and all 3 showed a high heterogeneity [I2> 50%]); 1 systematic review reported significant improvement for each of the following risk factors: blood pressure, and blood concentrations of glucose, low-density lipoprotein cholesterol, and triglycerides. There were no overall effects of vitamin C on arterial stiffness and blood concentration of insulin, total cholesterol, and high-density lipoprotein cholesterol, but subgroup analyses revealed some evidence for significant improvements in subpopulations with higher body mass index, higher plasma concentrations of glucose or cholesterol, and low plasma concentration of vitamin C. Results from this umbrella review emphasize the weakness of the current evidence base about effects of vitamin C supplementation on markers of CVD risk. There is limited evidence that some population subgroups (older people, the obese, those with lower vitamin C status at baseline, and those at higher CVD risk) may be more responsive to vitamin C supplementation and offer opportunities for tailored nutritional interventions to improve cardiometabolic health. Future studies should implement a selective recruitment strategy that is informed by evidence-based literature synthesis.

The nutritional and health attributes of kiwifruit: a review

PURPOSE

To describe the nutritional and health attributes of kiwifruit and the benefits relating to improved nutritional status, digestive, immune and metabolic health. The review includes a brief history of green and gold varieties of kiwifruit from an ornamental curiosity from China in the 19th century to a crop of international economic importance in the 21st century; comparative data on their nutritional composition, particularly the high and distinctive amount of vitamin C; and an update on the latest available scientific evidence from well-designed and executed human studies on the multiple beneficial physiological effects. Of particular interest are the digestive benefits for healthy individuals as well as for those with constipation and other gastrointestinal disorders, including symptoms of irritable bowel syndrome. The mechanisms of action behind the gastrointestinal effects, such as changes in faecal (stool) consistency, decrease in transit time and reduction of abdominal discomfort, relate to the water retention capacity of kiwifruit fibre, favourable changes in the human colonic microbial community and primary metabolites, as well as the naturally present proteolytic enzyme actinidin, which aids protein digestion both in the stomach and the small intestine. The effects of kiwifruit on metabolic markers of cardiovascular disease and diabetes are also investigated, including studies on glucose and insulin balance, bodyweight maintenance and energy homeostasis.

CONCLUSIONS

The increased research data and growing consumer awareness of the health benefits of kiwifruit provide logical motivation for their regular consumption as part of a balanced diet. Kiwifruit should be considered as part of a natural and effective dietary strategy to tackle some of the major health and wellness concerns around the world.

Mitochondrial Uptake and Accumulation of Vitamin C: What Can We Learn from Cell Culture Studies?

SIGNIFICANCE

The mitochondrial fraction of l-ascorbic acid (AA) is of critical importance for the regulation of the redox status of these organelles and for cell survival. Recent Advances: Most cell types take up AA by the high-affinity sodium-dependent vitamin C transporter 2 (SVCT2) sensitive to inhibition by dehydroascorbic acid (DHA). DHA can also be taken up by glucose transporters (GLUTs) and then reduced back to AA. DHA concentrations, normally very low in biological fluids, may only become significant next to superoxide-releasing cells. Very little is known about the mechanisms mediating the mitochondrial transport of the vitamin.

CRITICAL ISSUES

Information on AA transport is largely derived from studies using cultured cells and is therefore conditioned by possible cell culture effects as overexpression of SVCT2 in the plasma membrane and mitochondria. Mitochondrial SVCT2 is susceptible to inhibition by DHA and transports AA with a low affinity as a consequence of the restrictive ionic conditions. In some cells, however, high-affinity mitochondrial transport of AA is observed. Mitochondrial uptake of DHA may take place through GLUTs, an event followed by its prompt reduction to AA in the matrix. Intracellular levels of DHA are, however, normally very low.

FUTURE DIRECTIONS

We need to establish, or rule out, the role and significance of mitochondrial SVCT2 in vivo. The key question for mitochondrial DHA transport is instead related to its very low intracellular concentrations.

Concentration Does Matter: The Beneficial and Potentially Harmful Effects of Ascorbate in Humans and Plants

SIGNIFICANCE

Ascorbate (Asc) is an essential compound both in animals and plants, mostly due to its reducing properties, thereby playing a role in scavenging reactive oxygen species (ROS) and acting as a cofactor in various enzymatic reactions. Recent Advances: Growing number of evidence shows that excessive Asc accumulation may have negative effects on cellular functions both in humans and plants; inter alia it may negatively affect signaling mechanisms, cellular redox status, and contribute to the production of ROS via the Fenton reaction.

CRITICAL ISSUES

Both plants and humans tightly control cellular Asc levels, possibly via biosynthesis, transport, and degradation, to maintain them in an optimum concentration range, which, among other factors, is essential to minimize the potentially harmful effects of Asc. On the contrary, the Fenton reaction induced by a high-dose Asc treatment in humans enables a potential cancer-selective cell death pathway.

FUTURE DIRECTIONS

The elucidation of Asc induced cancer selective cell death mechanisms may give us a tool to apply Asc in cancer therapy. On the contrary, the regulatory mechanisms controlling cellular Asc levels are also to be considered, for example, when aiming at generating crops with elevated Asc levels.

The Interrelationship of Pharmacologic Ascorbate Induced Cell Death and Ferroptosis

Pharmacologic ascorbate induced cell death and ferroptosis share common features such as iron dependency, production of ROS, lipid peroxidation, caspase independency and the possible involvement of autophagy. These observations lead us to hypothesize that ferroptosis may also be involved in cancer cell death due to pharmacologic ascorbate treatment. Thus cell death of HT-1080 cell line was induced by ferroptosis inducers and pharmacologic ascorbate then the mechanism of cell death was compared. The EC50 value of pharmacologic ascorbate on HT-1080 cell line was found to be 0.5 mM that is in the range of the most ascorbate sensitive cell lines. However either of the specific inhibitors of ferroptosis (ferrostatin-1 and liproxstatin-1) could not elevate the viability of pharmacologic ascorbate treated cells suggesting that ferroptosis was not involved in the pharmacologic ascorbate induced cell death. α-tocopherol that could effectively elevate the viability of erastin and RSL3 treated HT1080 cells failed to mitigate the cytotoxic effect of pharmacologic ascorbate further strengthened this assumption. Furthermore at lower concentrations (0.1-0.5 mM) ascorbate could avoid the effects of ferroptosis inducers. Our results indicate that pharmacologic ascorbate induced cytotoxicity and ferroptosis - albeit phenotypically they show similar traits - are governed by different mechanisms.

Beneficial effects of ascorbic acid to treat lung fibrosis induced by paraquat

Paraquat (PQ) is one of the most widely employed herbicides that is used worldwide and it causes severe toxic effects in humans and animals. A PQ exposition can lead to pulmonary fibrosis (PF) and the mechanisms seem to be linked to oxidative stress, although other pathways have been suggested. Antioxidants can be useful as a therapy, although interventions with this kind of system are still controversial. Hence, this study has investigated the role of ascorbic acid (vitamin C) post-treatment on PQ-induced PF in male C57/BL6 mice. Pulmonary fibrosis was induced by a single PQ injection (10mg/kg; i.p.). The control group received a PQ vehicle. Seven days after the PQ or vehicle injections, the mice received vitamin C (150 mg/kg, ip, once a day) or the vehicle, over the following 7 days. Twenty-four hours after the last dose of vitamin C or the vehicle, the mice were euthanized and their bronchoalveolar lavage fluid (BALF) and their lungs were collected. The data obtained showed that vitamin C reduced the cellular recruitment, the secretion of IL-17 –a cytokine involved in neutrophils migration, TGF-β–a pro-fibrotic mediator and the collagen deposition. Moreover, vitamin C elevated the superoxide dismutase (SOD) and catalase levels, both antioxidant enzymes, but it did not alter the tracheal contractile response that was evoked by methacholine. Therefore, the researchers have highlighted the mechanisms of vitamin C as being non-invasive and have suggested it as a promising tool to treat lung fibrosis when it is induced by a PQ intoxication.

Antioxidative effect of flavonoid naringenin in the lenses of type 1 diabetic rats

Oxidative stress arising during diabetes may lead to cataract formation. Thus, in order to prevent oxidative stress development, antioxidants could be considered helpful agents. Naringenin, a flavonoid with a well-documented antioxidative activity, can be found in many plant-derived products, especially citrus fruits. The aim of the study was to examine the effect of naringenin on oxidative stress markers in the lenses of type 1 diabetic rats. The study was conducted on 3-month-old male Wistar rats with streptozotocin-induced type 1 diabetes. The rats were treated orally with naringenin at the doses of 50 and 100 mg/kg for 4 weeks. In the lenses obtained from the animals, enzymatic and non-enzymatic parameters connected with oxidative stress were measured. The enzymatic parameters included superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glucose-6-phosphate dehydrogenase activity. For non-enzymatic parameters, the total thiol groups, reduced and oxidized glutathione, protein carbonyl groups, advanced oxidation protein products, malondialdehyde and vitamin C level were assayed. Oral administration of naringenin counteracted most of the unfavorable changes induced by diabetes, including reduction of elevated antioxidative enzymes activity and amelioration of oxidative damage in proteins and lipids. Naringenin administered orally reduces oxidative stress markers in the lenses of type 1 diabetic rats.

Characterization of a L-Gulono-1,4-Lactone Oxidase Like Protein in the Floral Nectar of Mucuna sempervirens, Fabaceae

Floral nectar plays important roles in the interaction between animal-pollinated plants and pollinators. Its components include water, sugars, amino acids, vitamins, and proteins. Growing empirical evidence shows that most of the proteins secreted in nectar (nectarines) are enzymes that can tailor nectar chemistry for their animal mutualists or reduce the growth of microorganisms in nectar. However, to date, the function of many nectarines remains unknown, and very few plant species have had their nectar proteome thoroughly investigated. Mucuna sempervirens (Fabaceae) is a perennial woody vine native to China. Nectarines from this species were separated using two-dimensional gel electrophoresis, and analyzed using mass spectrometry. A L-gulonolactone oxidase like protein (MsGulLO) was detected, and the full length cDNA was cloned: it codes for a protein of 573 amino acids with a predicted signal peptide. MsGulLO has high similarity to L-gulonolactone oxidase 5 (AtGulLO5) in Arabidopsis thaliana, which was suggested to be involved in the pathway of ascorbate biosynthesis; however, both MsGulLO and AtGulLO5 are divergent from animal L-gulonolactone oxidases. MsGulLO was expressed mainly in flowers, and especially in nectary before blooming. However, cloning and gene expression analysis showed that L-galactonolactone dehydrogenase (MsGLDH), a vital enzyme in plant ascorbate biosynthesis, was expressed in all of flowers, roots, stems, and especially leaves. MsGulLO was purified to near homogeneity from raw MS nectar by gel filtration chromatography. The enzyme was determined to be a neutral monomeric protein with an apparent molecular mass of 70 kDa. MsGulLO is not a flavin-containing protein, and has neither L-galactonolactone dehydrogenase activity, nor the L-gulonolactone activity that is usual in animal GulLOs. However, it has weak oxidase activity with the following substrates: L-gulono-1,4-lactone, L -galactono-1,4-lactone, D-gluconic acid-δ-lactone, glucose, and fructose. MsGulLO is suggested to function in hydrogen peroxide generation in nectar but not in plant ascorbate biosynthesis.

Role of vitamin C in wound healing after dental implant surgery in patients treated with bone grafts and patients with chronic periodontitis

BACKGROUND

Postoperative wound healing is an important part of the success of the dental implant surgery. However, in case of complex surgery or unfavorable factors, wound healing is often unsatisfactory.

OBJECTIVE

The aim of this study was to explore the effects of vitamin C supplementation in wound healing, following the placement of dental implants with or without bone grafts and patients with chronic periodontitis.

METHODS

This randomized controlled clinical trial included 128 patients requiring dental implants to replace missing teeth. Patients were divided into four groups, group A received dental implants supported by guided bone regeneration (GBR) technique, group B received dental implants with Bio-Oss Collagen, group C received dental implants in patients with chronic periodontitis, and group D received dental implants without any bone grafting or periodontal disease. Each group was divided into an experimental subgroup, who received vitamin C, and a control subgroup. Follow-up appointments were performed at day 3, day 7, and day 14 postsurgery, during which soft tissue healing and pain response scores were evaluated using the Landry index and visual analogue scale, respectively.

RESULTS

The experimental subgroups had significantly higher healing indices than the controls (P < .05) at day 7 postsurgery for group B and day 14 postsurgery for groups A, B, and C. Group D displayed no difference between the experimental and control groups at any time point. In reference to vitamin C for pain relief, there were no statistically significant differences between the study groups.

CONCLUSION

Using vitamin C supplementation improves postoperative healing following dental implant surgery in patients with chronic periodontitis and patients treated with GBR or Bio-Oss Collagen grafts. However, vitamin C supplementation does not decrease the postoperative pain associated with dental implant surgery.

A review of micronutrients in sepsis: the role of thiamine, l-carnitine, vitamin C, selenium and vitamin D

Sepsis is defined as the dysregulated host response to an infection resulting in life-threatening organ dysfunction. The metabolic demand from inefficiencies in anaerobic metabolism, mitochondrial and cellular dysfunction, increased cellular turnover, and free-radical damage result in the increased focus of micronutrients in sepsis as they play a pivotal role in these processes. In the present review, we will evaluate the potential role of micronutrients in sepsis, specifically, thiamine, l-carnitine, vitamin C, Se and vitamin D. Each micronutrient will be reviewed in a similar fashion, discussing its major role in normal physiology, suspected role in sepsis, use as a biomarker, discussion of the major basic science and human studies, and conclusion statement. Based on the current available data, we conclude that thiamine may be considered in all septic patients at risk for thiamine deficiency and l-carnitine and vitamin C to those in septic shock. Clinical trials are currently underway which may provide greater insight into the role of micronutrients in sepsis and validate standard utilisation.

Potential Mechanisms of Action for Vitamin C in Cancer: Reviewing the Evidence

Whether vitamin C (ascorbate) has a role to play as an anti-cancer agent has been debated for decades. Ascorbate has been used by cancer patients in an unregulated environment, either as a dietary supplement or in pharmacological doses administered by infusion, with numerous reports of clinical benefit, but in the absence of rigorous clinical trial data. The design of appropriate clinical trials has been hindered by a lack of understanding of the mechanism(s) of action that would inform the choice of effective dose, timing of administration and likely responsive cancer models. More recently, expanded understanding of the biological activities of ascorbate has led to a number of plausible hypotheses for mechanisms of anti-cancer activity. Prominent among these are the generation of significant quantities of hydrogen peroxide by the autoxidation of supra-physiological concentrations of ascorbate and stimulation of the 2-oxoglutarate-dependent dioxygenase family of enzymes (2-OGDDs) that have a cofactor requirement for ascorbate. Hydrogen peroxide generation is postulated to generate oxidative stress that preferentially targets cancer cells. The 2-OGDDs include the hydroxylases that regulate the hypoxic response, a major driver of tumor survival, angiogenesis, stem cell phenotype and metastasis, and the epigenetic histone and DNA demethylases. The latter are of particular interest, with recent studies suggesting a promising role for ascorbate in the regulation of the ten-eleven translocase (TET) DNA demethylases in hematological cancers. Support for these proposed mechanisms has come from many in vitro studies, and xenograft animal models have consistently shown an anti-cancer effect of ascorbate administration. However, decisive evidence for any particular mechanism(s) of action is not yet available from an in vivo setting. With a number of early phase clinical trials currently underway, evidence for potential mechanism(s) of action is required to inform the most appropriate study design and choice of cancer model. Hopefully such information will result in sound clinical data that will avert adding any further controversy to this already contentious debate.

Characterization of a Novel Mitochondrial Ascorbate Transporter From Rat Liver and Potato Mitochondria

The Mitochondrial Ascorbic Acid Transporter (MAT) from both rat liver and potato mitochondria has been reconstituted in proteoliposomes. The protein has a molecular mass in the range of 28–35 kDa and catalyzes saturable, temperature and pH dependent, unidirectional ascorbic acid transport. The transport activity is sodium independent and it is optimal at acidic pH values. It is stimulated by proton gradient, thus supporting that ascorbate is symported with H⁺. It is efficiently inhibited by the lysine reagent pyridoxal phosphate and it is not affected by inhibitors of other recognized plasma and mitochondrial membranes ascorbate transporters GLUT1(glucose transporter-1) or SVCT2 (sodium-dependent vitamin C transporter-2). Rat protein catalyzes a cooperative ascorbate transport, being involved two binding sites; the measured K_0.5 is 1.5 mM. Taking into account the experimental results we propose that the reconstituted ascorbate transporter is not a GLUT or SVCT, since it shows different biochemical features. Data of potato transporter overlap the mammalian ones, except for the kinetic parameters non-experimentally measurable, thus supporting the MAT in plants fulfills the same transport role.

Lifestyle behaviors and serum vitamin C in the Thai population in Bangkok Metropolitan

This study aimed to investigate the influence of lifestyle behaviors on the vitamin C levels in the circulating blood of the Thai population in Bangkok Metropolitan. The participants (n=250) included community workers (i.e., construction and business office workers) from the Bangkok Metropolitan, and the participants were placed in various behavior and lifestyle groups (Group I: reference; Group II: alcohol drinkers; Group III: outdoor workers; Group IV: smokers; and Group V: combined). The results showed that the lowest and highest vitamin C intakes were 7 and 27 mg/day in Groups IV and III, respectively. Group I (indoor workers free of smoking and drinking), had the highest total serum vitamin C level (39.7 µmol/L), while Group V (outdoor workers with smoking and drinking), had the lowest value (12.5 µmol/L). Furthermore, Group V had the highest prevalence (44 %) of total serum vitamin C deficiency (<11 µmol/L), while Group I had the lowest deficient indication (8 %). The vitamin C dietary intake and total serum levels were positively correlated in the reference group (Spearman's correlation=0.402, p < 0.05) but not in the other four groups. The significant adjusted odds ratio of inadequate total serum vitamin C (< 23 µmol/L) was 2.90 (CI: 1.15, 7.31) in Group IV and 3.73 (CI: 1.42, 9.81) in Group V. Moreover, the tendency to have an inadequate total serum vitamin C level was demonstrated in the following order: Group I < II < III < IV < V. Our results indicated that outdoor workers (Group III) and smokers (Group IV) had a greater likelihood of having a vitamin C deficiency than the reference group. A high percentage of deficiency was clearly observed among the outdoor workers with smoking and drinking behaviors (Group V).

Intravenous vitamin C in the supportive care of cancer patients: a review and rational approach

This article reviews intravenous vitamin C (IV C) in cancer care and offers a rational approach to enable medical oncologists and integrative practitioners to safely provide IV C combined with oral vitamin C to patients. The use of IV C is a safe supportive intervention to decrease inflammation in the patient and to improve symptoms related to antioxidant deficiency, disease processes, and side effects of standard cancer treatments. A proposed rationale, together with relevant clinical safety considerations for the application of IV C in oncologic supportive care, is provided.

Affinity resins as new tools for identifying target proteins of ascorbic acid

l-Ascorbic acid (AA) has diverse physiological functions, but little is known about the functional mechanisms of AA. In this study, we synthesized two types of affinity resin on which AA is immobilized in a stable form to identify new AA-targeted proteins, which can provide important clues for elucidating unknown functional mechanisms of AA. To our knowledge, an affinity resin on which AA as a ligand is immobilized has not been prepared, because AA is very unstable and rapidly degraded in an aqueous solution. By using the affinity resins, cytochrome c (cyt c) was identified as an AA-targeted protein, and we showed that oxidized cyt c exhibits specific affinity for AA. These results suggest that two kinds of AA-affinity resin can be powerful tools to identify new target proteins of AA.