Vitamin C: update on physiology and pharmacology

Vitamin C in sepsis

PURPOSE OF REVIEW

This narrative review summarizes recent insights into the role of vitamin C in sepsis.

RECENT FINDINGS

Septic shock remains a major source of morbidity and mortality in critically ill patients. Although many nutritional supplements have previously been tested unsuccessfully, vitamins are still being explored as a therapeutic option in septic patients. In particular, vitamin C-containing regimens as adjunctive therapy in sepsis have received much attention.

SUMMARY

In-vitro evidence supports a critical role for vitamin C in cellular mechanisms relevant to the pathophysiology of sepsis. However, whether this justifies therapeutic use of vitamin C in septic patients remains uncertain.

Dysregulation of NRF2 in Cancer: from Molecular Mechanisms to Therapeutic Opportunities

Nuclear factor E2-related factor 2 (NRF2) plays an important role in redox metabolism and antioxidant defense. Under normal conditions, NRF2 proteins are maintained at very low levels because of their ubiquitination and proteasomal degradation via binding to the kelch-like ECH associated protein 1 (KEAP1)-E3 ubiquitin ligase complex. However, oxidative and/or electrophilic stresses disrupt the KEAP1-NRF2 interaction, which leads to the accumulation and transactivation of NRF2. During recent decades, a growing body of evidence suggests that NRF2 is frequently activated in many types of cancer by multiple mechanisms, including the genetic mutations in the KEAP1-NRF2 pathway. This suggested that NRF2 inhibition is a promising strategy for cancer therapy. Recently, several NRF2 inhibitors have been reported with anti-tumor efficacy. Here, we review the mechanisms whereby NRF2 is dysregulated in cancer and its contribution to the tumor development and radiochemoresistance. In addition, among the NRF2 inhibitors reported so far, we summarize and discuss repurposed NRF2 inhibitors with their potential mechanisms and provide new insights to develop selective NRF2 inhibitors.

cAMP signaling regulates DNA hydroxymethylation by augmenting the intracellular labile ferrous iron pool

It is widely accepted that cAMP regulates gene transcription principally by activating the protein kinase A (PKA)-targeted transcription factors. Here, we show that cAMP enhances the generation of 5-hydroxymethylcytosine (5hmC) in multiple cell types. 5hmC is converted from 5-methylcytosine (5mC) by Tet methylcytosine dioxygenases, for which Fe(II) is an essential cofactor. The promotion of 5hmC was mediated by a prompt increase of the intracellular labile Fe(II) pool (LIP). cAMP enhanced the acidification of endosomes for Fe(II) release to the LIP likely through RapGEF2. The effect of cAMP on Fe(II) and 5hmC was confirmed by adenylate cyclase activators, phosphodiesterase inhibitors, and most notably by stimulation of G protein-coupled receptors (GPCR). The transcriptomic changes caused by cAMP occurred in concert with 5hmC elevation in differentially transcribed genes. Collectively, these data show a previously unrecognized regulation of gene transcription by GPCR-cAMP signaling through augmentation of the intracellular labile Fe(II) pool and DNA hydroxymethylation.

Vitamin C and Immune Function

Vitamin C is an essential micronutrient for humans, with pleiotropic functions related to its ability to donate electrons. It is a potent antioxidant and a cofactor for a family of biosynthetic and gene regulatory enzymes. Vitamin C contributes to immune defense by supporting various cellular functions of both the innate and adaptive immune system. Vitamin C supports epithelial barrier function against pathogens and promotes the oxidant scavenging activity of the skin, thereby potentially protecting against environmental oxidative stress. Vitamin C accumulates in phagocytic cells, such as neutrophils, and can enhance chemotaxis, phagocytosis, generation of reactive oxygen species, and ultimately microbial killing. It is also needed for apoptosis and clearance of the spent neutrophils from sites of infection by macrophages, thereby decreasing necrosis/NETosis and potential tissue damage. The role of vitamin C in lymphocytes is less clear, but it has been shown to enhance differentiation and proliferation of B- and T-cells, likely due to its gene regulating effects. Vitamin C deficiency results in impaired immunity and higher susceptibility to infections. In turn, infections significantly impact on vitamin C levels due to enhanced inflammation and metabolic requirements. Furthermore, supplementation with vitamin C appears to be able to both prevent and treat respiratory and systemic infections. Prophylactic prevention of infection requires dietary vitamin C intakes that provide at least adequate, if not saturating plasma levels (i.e., 100–200 mg/day), which optimize cell and tissue levels. In contrast, treatment of established infections requires significantly higher (gram) doses of the vitamin to compensate for the increased inflammatory response and metabolic demand.

Latent scurvy with tiredness and leg pain in alcoholics: An underestimated disease three case reports

RATIONALE

Scurvy is often diagnosed at the state of well-established signs as, for example, skin and visceral purpura, gums involvement, loss of healthy teeth, which derive mostly from disturbance of collagen metabolism. Little is known about the state of latent scurvy, which symptoms are nonspecific and may mimic more common conditions such as weakness, leg pain, and muscle aching.

PATIENT CONCERNS

We report 3 cases of extreme lassitude and leg pain in alcoholics. In 2 of the 3 cases, discreet classic symptoms such as petechiae or hyperkeratosis of the legs involving collagen metabolism were also present.

DIAGNOSES

Latent scurvy has been diagnosed thanks to historical experimental data reporting and undetectable ascorbic acid levels.

INTERVENTIONS

In addition to the treatments recommended by the French Alcohol Society, patients were given oral vitamin C 500 mg to 1000 mg per day for at least three months.

OUTCOMES

Vitamin C supplementation allowed the regression of the symptoms, greatly improved the quality of life, and gave the possibility to return to work. Cartinine, requiring vitamin C for its hydroxylation, is an essential cofactor in the transport of long-chain fatty acid into mitochondrial matrix. Therefore, it plays an important role in energy production via beta-oxidation. It is thought that carnitine metabolism impairment is responsible for weakness or muscle aching.

LESSONS

We recommend being aware of the possibility of latent scurvy in chronic alcohol abusers. The vitamin C supplementation and dietetic recommendation eating fresh fruit and vegetables may help to cure tiredness and to return more easily to socialization and to work.

Mitochondrial dysfunction in the APP/PSEN1 mouse model of Alzheimer's disease and a novel protective role for ascorbate

Mitochondrial dysfunction is elevated in very early stages of Alzheimer's disease and exacerbates oxidative stress, which contributes to disease pathology. Mitochondria were isolated from 4-month-old wild-type mice, transgenic mice carrying the APP_SWE and PSEN1_dE9 mutations, mice with decreased brain and mitochondrial ascorbate (vitamin C) via heterozygous knockout of the sodium dependent vitamin C transporter (SVCT2^+/-) and transgenic APP/PSEN1 mice with heterozygous SVCT2 expression. Mitochondrial isolates from SVCT2^+/- mice were observed to consume less oxygen using high-resolution respirometry, and also exhibited decreased mitochondrial membrane potential compared to wild type isolates. Conversely, isolates from young (4 months) APP/PSEN1 mice consumed more oxygen, and exhibited an increase in mitochondrial membrane potential, but had a significantly lower ATP/ADP ratio compared to wild type isolates. Greater levels of reactive oxygen species were also produced in mitochondria isolated from both APP/PSEN1 and SVCT2^+/- mice compared to wild type isolates. Acute administration of ascorbate to mitochondria isolated from wild-type mice increased oxygen consumption compared with untreated mitochondria suggesting ascorbate may support energy production. This study suggests that both presence of amyloid and ascorbate deficiency can contribute to mitochondrial dysfunction, even at an early, prodromal stage of Alzheimer's disease, although occurring via different pathways. Ascorbate may, therefore, provide a useful preventative strategy against neurodegenerative disease, particularly in populations most at risk for Alzheimer's disease in which stores are often depleted through mitochondrial dysfunction and elevated oxidative stress.

Ascorbic acid alters cell fate commitment of human neural progenitors in a WNT/β-catenin/ROS signaling dependent manner

Background

Improving the neuronal yield from in vitro cultivated neural progenitor cells (NPCs) is an essential challenge in transplantation therapy in neurological disorders. In this regard, Ascorbic acid (AA) is widely used to expand neurogenesis from NPCs in cultures although the mechanisms of its action remain unclear. Neurogenesis from NPCs is regulated by the redox-sensitive WNT/β-catenin signaling pathway. We therefore aimed to investigate how AA interacts with this pathway and potentiates neurogenesis.

Methods

Effects of 200 μM AA were compared with the pro-neurogenic reagent and WNT/β-catenin signaling agonist lithium chloride (LiCl), and molecules with antioxidant activities i.e. N-acetyl-L-cysteine (NAC) and ruthenium red (RuR), in differentiating neural progenitor ReNcell VM cells. Cells were supplemented with reagents for two periods of treatment: a full period encompassing the whole differentiation process versus an early short period that is restricted to the cell fate commitment stage. Intracellular redox balance and reactive oxygen species (ROS) metabolism were examined by flow cytometry using redox and ROS sensors. Confocal microscopy was performed to assess cell viability, neuronal yield, and levels of two proteins: Nucleoredoxin (NXN) and the WNT/β-catenin signaling component Dishevelled 2 (DVL2). TUBB3 and MYC gene responses were evaluated by quantitative real-time PCR. DVL2-NXN complex dissociation was measured by fluorescence resonance energy transfer (FRET).

Results

In contrast to NAC which predictably exhibited an antioxidant effect, AA treatment enhanced ROS metabolism with no cytotoxic induction. Both drugs altered ROS levels only at the early stage of the differentiation as no changes were held beyond the neuronal fate commitment stage. FRET studies showed that AA treatment accelerated the redox-dependent release of the initial pool of DVL2 from its sequestration by NXN, while RuR treatment hampered the dissociation of the two proteins. Accordingly, AA increased WNT/β-catenin signaling output i.e. MYC mRNA level, whereas RuR attenuated it. Moreover, AA improved neurogenesis as much as LiCl as both TUBB3-positive cell yield and TUBB3 mRNA level increased, while NAC or RuR attenuated neurogenesis. Markedly, the neurogenesis outputs between the short and the full treatment with either NAC or AA were found unchanged, supporting our model that neuronal yield is altered by events taking place at the early phase of differentiation.

Conclusions

Our findings demonstrate that AA treatment elevates ROS metabolism in a non-lethal manner prior to the NPCs commitment to their neuronal fate. Such effect stimulates the redox-sensitive DVL2 activation and WNT/β-catenin signaling response that would enhance the ensuing neuronal cell differentiation.

Electronic supplementary material

The online version of this article (10.1186/s12929-017-0385-1) contains supplementary material, which is available to authorized users.

Novel insights into ascorbate retention and degradation during the washing and post-harvest storage of spinach and other salad leaves

Post-harvest treatments of pre-packaged salad leaves potentially cause l-ascorbate loss, but the mechanisms of ascorbate degradation remain incompletely understood, especially in planta. We explored the extent and pathways of ascorbate loss in variously washed and stored salad leaves. Ascorbate was assayed by 2,6-dichlorophenolindophenol titration, and pathways were monitored by 14C-radiolabelling followed by high-voltage electrophoresis. All leaves tested showed ascorbate loss during storage: lettuce showed the greatest percentage loss, wild rocket the least. Spinach leaves were particularly prone to losing ascorbate during washing, especially with simultaneous mechanical agitation; however, washing in the presence of hypochlorite did not significantly increase ascorbate loss. In spinach, [14C]oxalate was the major product of [14C]ascorbate degradation, suggesting that commercial washing causes oxidative stress. This study highlights that ascorbate/dehydroascorbic acid are lost via the oxidative pathway during washing and post-harvest storage of salad leaves. Thus changes to washing procedures could potentially increase the post-harvest retention of ascorbate.

Combined effect of metformin with ascorbic acid versus acetyl salicylic acid on diabetes-related cardiovascular complication; a 12-month single blind multicenter randomized control trial

Background

We aimed to investigate the efficacy of ascorbic acid and acetylsalicylic acid among type II diabetes mellitus patients using metformin (only) for diabetes management therapy.

Method

A 12-month single blinded multicenter randomized control trial was designed to investigate the measured variables [Glycated Hemoglobin (HbA1c), Renal function, Albumin Creatinine Ratio (ACR) etc.]. The trial was randomized into 2 experimental parallel arms (ascorbic acid vs acetylsalicylic acid) were blinded with study supplements in combination with metformin and findings were compared to control arm with metformin alone and blinded with placebo. Withdrawal criteria was defined to maintain the equity and balance in the participants in the whole trial.

Finding

Patients with metformin and ascorbic acid (parallel arm I) was twice more likely to reduce HbA1c than metformin alone (control arm) in a year (OR 2.31 (95% CI 1.87–4.42) p < 0.001). Also Parallel arm I was ten times more likely to reduced risk factors contributing to long-term diabetes complications than participants of arm II in a year (OR 10.38 (95% CI 6.91–15.77) p < 0.001). In contrast, parallel arm II patients were seven times more effective to reduce the risk of expected CVD development in 10 years than arm I (OR 7.54 (95% CI 3.76–10.32) p < 0.001).

Conclusions

The trial concluded that ascorbic acid with metformin is more effective against reducing risks for diabetes related long-term complications (including ACR).

TRIAL details Registration No: NTR-6100, Registry Name: Netherlands Trial Registry, URL: http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=6100, Date of Registration: 20th October, 2016, Date of first Enrollment: 1 November, 2015.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-017-0584-9) contains supplementary material, which is available to authorized users.

The Roles of Vitamin C in Skin Health

The primary function of the skin is to act as a barrier against insults from the environment, and its unique structure reflects this. The skin is composed of two layers: the epidermal outer layer is highly cellular and provides the barrier function, and the inner dermal layer ensures strength and elasticity and gives nutritional support to the epidermis. Normal skin contains high concentrations of vitamin C, which supports important and well-known functions, stimulating collagen synthesis and assisting in antioxidant protection against UV-induced photodamage. This knowledge is often used as a rationale for the addition of vitamin C to topical applications, but the efficacy of such treatment, as opposed to optimising dietary vitamin C intake, is poorly understood. This review discusses the potential roles for vitamin C in skin health and summarises the in vitro and in vivo research to date. We compare the efficacy of nutritional intake of vitamin C versus topical application, identify the areas where lack of evidence limits our understanding of the potential benefits of vitamin C on skin health, and suggest which skin properties are most likely to benefit from improved nutritional vitamin C intake.

Redox Control of Skeletal Muscle Regeneration

Skeletal muscle shows high plasticity in response to external demand. Moreover, adult skeletal muscle is capable of complete regeneration after injury, due to the properties of muscle stem cells (MuSCs), the satellite cells, which follow a tightly regulated myogenic program to generate both new myofibers and new MuSCs for further needs. Although reactive oxygen species (ROS) and reactive nitrogen species (RNS) have long been associated with skeletal muscle physiology, their implication in the cell and molecular processes at work during muscle regeneration is more recent. This review focuses on redox regulation during skeletal muscle regeneration. An overview of the basics of ROS/RNS and antioxidant chemistry and biology occurring in skeletal muscle is first provided. Then, the comprehensive knowledge on redox regulation of MuSCs and their surrounding cell partners (macrophages, endothelial cells) during skeletal muscle regeneration is presented in normal muscle and in specific physiological (exercise-induced muscle damage, aging) and pathological (muscular dystrophies) contexts. Recent advances in the comprehension of these processes has led to the development of therapeutic assays using antioxidant supplementation, which result in inconsistent efficiency, underlying the need for new tools that are aimed at precisely deciphering and targeting ROS networks. This review should provide an overall insight of the redox regulation of skeletal muscle regeneration while highlighting the limits of the use of nonspecific antioxidants to improve muscle function. Antioxid. Redox Signal. 27, 276-310.

Sustained blockade of ascorbic acid transport associated with marked SVCT1 loss in rat hepatocytes containing increased ascorbic acid levels after partial hepatectomy

The liver has an extraordinary regenerative capacity in response to partial hepatectomy (PHx), which develops with neither tissue inflammation response nor alterations in the whole organism. This process is highly coordinated and it has been associated with changes in glutathione (GSH) metabolism. However, there are no reports indicating ascorbic acid (AA) levels after partial hepatectomy. AA and GSH act integrally as an antioxidant system that protects cells and tissues from oxidative damage and imbalance observed in a variety of diseases that affect the liver. Although rat hepatocytes are able to synthesize AA and GSH, which are the providers of AA for the whole organism, they also acquire AA from extracellular sources through the sodium-coupled ascorbic acid transporter-1 (SVCT1). Here, we show that hepatocytes from rat livers subjected to PHx increase their GSH and AA levels from 1 to 7 days post hepatectomy, whose peaks precede the peak in cell proliferation observed at 3 days post-hepatectomy. The increase in both antioxidants was associated with higher expression of the enzymes involved in their synthesis, such as the modifier subunit of enzyme glutamine cysteine ligase (GCLM), glutathione synthetase (GS), gulonolactonase (GLN) and gulonolactone oxidase (GULO). Importantly, rat hepatocytes, that normally exhibit kinetic evidence indicating only SVCT1-mediated transport of AA, lost more than 90% of their capacity to transport it at day 1 after PHx without evidence of recovery at day 7. This observation was in agreement with loss of SVCT1 protein expression, which was undetectable in hepatocytes as early as 2h after PHx, with partial recovery at day 7, when the regenerated liver weight returns to normal. We conclude that after PHx, rat hepatocytes enhance their antioxidant capacity by increasing GSH and AA levels prior to the proliferative peak. GSH and AA are increased by de novo synthesis, however paradoxically hepatocytes from rat subjected to PHx also suppress their capacity to acquire AA from extracellular sources through SVCT1.

Ascorbic acid in the prevention and treatment of cancer

This review is aimed at the systematic mapping of ascorbic acid in the prevention and/or treatment of cancer in clinical and non-clinical studies from 2011 to 2015, in order to understand dose-response variations as well as its mechanisms of action as an antioxidant and antitumor agent. Seventy-eight articles were retrieved from the PubMed/Bireme database, of which only 30 included ascorbic acid in the prevention and/or treatment of cancer. However, there are controversies regarding doses and a lack of clinical studies featuring its mechanism of action more clearly. Other studies are needed to understand dose-response variations, as well as its targeting mechanisms of action, both as an antioxidant and antitumor agent, to assist treatment and prevention of cancer, aiming at better quality of life for both patients and the general population.

Supplementation action with ascorbic acid in the morphology of the muscular layer and reactive acetylcholinesterase neurons of ileum of mdx mice

The Duchenne Muscular Dystrophy (DMD) is a genetic disorder characterized by the absence of dystrophin protein, causing severe myopathy from increases of oxidative stress. Injuries of intestinal muscle can compromise the myenteric plexus. This study aimed to evaluate the disorders occurred in the muscular layer and in the acetylcholinesterase myenteric neurons (ACHE-r) of ileum of mdx mice, and the effects of supplementation with ascorbic acid (AA) in both components. 30 male mice C57BL/10, and 30 male mice C57BL/10Mdx were separated according to the age and treatment (n=10/group): 30-days-old control group (C30); 30-days-old dystrophic group (D30); 60-days-old control group (C60); 60-days-old dystrophic group (D60); 60-days-old control group supplemented with AA (CS60); and 60-days-old dystrophic group supplemented with AA (DS60). The animals were euthanized and the ileum was collected and processed. Semi-serial sections were stained by Masson's trichrome, and acetylcholinesterase histochemical technique in whole-mounts preparations to identify the myenteric neurons. The muscular layer thickness and the area of smooth muscle of ileum were lower in dystrophic groups, especially in D30 group. The DS60 group showed the muscular layer thickness similar to C60. The density of ACHE-r neurons of myenteric plexus of ileum was lower in D30 animals; however, it was similar in animals of 60-days-old without treatment (C60 and D60) and, higher in DS60. The cell body profile area of ACHE-r neurons was similar in C30-D30 and C60-D60; however, it was higher in DS60. DMD caused damage to the ileum's musculature and myenteric plexus, and the AA prevented the ACHE-r neuronal loss.

Effects of vitamin C supplementation on glycaemic control: a systematic review and meta-analysis of randomised controlled trials

Randomised controlled trials (RCTs) have observed contrasting results on the effects of vitamin C on circulating biomarkers of glycaemic and insulin regulation. We conducted a systematic review and meta-analysis of RCTs testing the effect of vitamin C administration on glucose, HbA1c and insulin concentrations. Four databases (PubMed, Embase, Scopus and Cochrane Library) were used to retrieve RCTs published from inception until April 2016 and testing the effects of vitamin C in adult participants. The screening of 2008 articles yielded 22 eligible studies (937 participants). Overall, vitamin C did not modify glucose, HbA1c and insulin concentrations. However, subgroup analyses showed that vitamin C significantly reduced glucose concentrations (-0.44 mmol/l, 95% CI: -0.81, -0.07, P=0.01) in patients with type 2 diabetes and in interventions with a duration greater than 30 days (-0.53%, 95% CI: -0.79, -0.10, P=0.02). Vitamin C administration had greater effects on fasting (-13.63 pmol/l, 95% CI: -22.73, -4.54, P<0.01) compared to postprandial insulin concentration. Meta-regression analyses showed that age was a modifier of the effect of vitamin C on insulin concentration. Furthermore, the effect size was associated with baseline BMI and plasma glucose levels, and with the duration of the intervention. In conclusion, greater reduction in glucose concentrations observed in patients with diabetes, older individuals and with more prolonged supplementation. Personalised interventions with vitamin C may represent a feasible future strategy to enhance benefits and efficacy of interventions. Nevertheless, results need to be interpreted cautiously due to limitations in the primary studies analysed.

Pyruvate antioxidant roles in human fibroblasts and embryonic stem cells

Oxidative stress has been related to multiple diseases, especially during early embryonic development, when environmental alterations can lead to long-term deleterious effects. In vitro studies of oxidative stress have been mainly focused on somatic cells, but embryonic stem cells (ESCs) represent a promising model of early embryonic development as they are the in vitro equivalent to pluripotent cells in the embryo. Human fibroblasts and ESCs were exposed to different pro-oxidant agents (hydrogen peroxide, tert-butyl hydroperoxide (TBHP), and rotenone) and antioxidants (sodium pyruvate, N-acetylcysteine, Trolox, and sodium selenite) during a 72 h oxidative stress treatment. Then, cell viability, oxidative stress, mitochondrial activity, and gene expression were analyzed, focusing on the antioxidant effect of pyruvate. Pyruvate protected both somatic and pluripotent cells against different pro-oxidant agents, showing strong ROS scavenging capacity, protecting mitochondrial membrane potential, and regulating gene expression and cell metabolism through different mechanisms in fibroblasts and ESCs. In fibroblasts, pyruvate avoided NFKβ nuclear translocation and the upregulation of genes related to the oxidative stress response, while in ESCs pyruvate stimulated the expression of genes involved in anaerobic glycolysis. Fibroblasts and ESCs reacted in different ways to oxidative stress and antioxidant treatment, and pyruvate was the most complete antioxidant, protecting both cell types at different levels.

Magnetic nanocomposites of boron and vitamin C

Magnetic nanocomposites of boron and vitamin C for potential targeted delivery/therapy applications are reported here.

Purpura pigmentosa progressiva

Die Purpura pigmentosa progressiva (PPP) ist eine benigne, häufig chronisch rezidivierende Dermatose, die sich vor allem symmetrisch an den unteren Extremitäten, in ausgeprägten Fällen auch am Rumpf und den oberen Extremitäten, manifestiert. Auch einmalige Krankheitsverläufe sind beschrieben. Klinisch äußert sich die Purpura pigmentosa progressiva in der Akutphase in Form von meist asymptomatischen petechialen Einblutungen, in ihrem Verlauf mit bräunlich-orangenen Maculae. In einigen Fällen wird von einem geringen Juckreiz berichtet. Meist führt der ästhetische Aspekt zum Arztbesuch. Es werden in der Literatur verschiedene Ursachen diskutiert, der genaue Pathomechanismus ist jedoch unklar. Eine zugrundeliegende Systemerkrankung liegt nicht vor. Histologisch zeigen sich Erythrozytenextravasate, perivaskuläre Lymphozyteninfiltrate und Hämosiderinablagerungen ohne Zeichen einer Vaskulitis. Differenzialdiagnostisch kommen vor allem eine leukozytoklastische Vaskulitis oder Gerinnungsstörungen in Betracht. Therapeutisch empfiehlt sich die Gabe von Vitamin C in Kombination mit Rutosid.

Heightened aggressive behavior in mice deficient in aldo-keto reductase 1a (Akr1a)

Aldehyde reductase (Akr1a) is involved in the synthesis of ascorbic acid (AsA) which may play a role in social behavior. In the current study, we performed analyses on Akr1a-deficient (Akr1a^-/-) mice that synthesize about 10% as much AsA as wild-type mice from the viewpoint of intermale aggression. The use of the resident-intruder test revealed that the Akr1a^-/- mice exhibited more aggressive phenotypes than wild-type control mice. Unexpectedly, however, the oral administration of additional AsA failed to reduce the aggressive behavior of Akr1a^-/- mice, suggesting that the heightened aggression was independent of AsA biosynthesis. The findings also show that the plasma levels of corticosterone, but not serotonin and testosterone, were increased in the absence of Akr1a in mice, suggesting that the mice were highly stressed. These results suggest that Akr1a might be involved in the metabolism of steroids and other carbonyl-containing compounds and, hence, the absence of Akr1a results in heightened aggression via a malfunction in a metabolic pathway.

Chemopreventive Agents and Inhibitors of Cancer Hallmarks: May Citrus Offer New Perspectives?

Fruits and vegetables have long been recognized as potentially important in the prevention of cancer risk. Thus, scientific interest in nutrition and cancer has grown over time, as shown by increasing number of experimental studies about the relationship between diet and cancer development. This review attempts to provide an insight into the anti-cancer effects of Citrus fruits, with a focus on their bioactive compounds, elucidating the main cellular and molecular mechanisms through which they may protect against cancer. Scientific literature was selected for this review with the aim of collecting the relevant experimental evidence for the anti-cancer effects of Citrus fruits and their flavonoids. The findings discussed in this review strongly support their potential as anti-cancer agents, and may represent a scientific basis to develop nutraceuticals, food supplements, or complementary and alternative drugs in a context of a multi-target pharmacological strategy in the oncology.

Development and implementation of an HPLC-ECD method for analysis of vitamin C in plasma using single column and automatic alternating dual column regeneration

Objectives

Vitamin C (l-ascorbic acid) is a water-soluble micronutrient necessary for human life. Inadequate intake can lead to the fatal disease scurvy. Measurement of vitamin C is used to assess nutritional status and to monitor supplementation. The goal of this study was to develop a chromatographic method for the quantitation of vitamin C in human plasma.

Design and methods

Samples were prepared by protein precipitation, addition of internal standard, and reduction with dithiothreitol. Separation of ascorbic acid was accomplished by isocratic elution on a reverse-phase column; concentration was determined by coulometry. The method was validated through studies of assay linearity, sensitivity, imprecision, accuracy, analytical specificity, and carryover.

Results

The new assay was developed using a single pump/single analytical column HPLC system. Results correlated well with our previously used spectrophotometric method. The analytical measurement range was 1.0–2500 µmol/L. The injection-to-injection time was 13 min. Subsequently, to increase method throughput and shorten turnaround time, a dual LC pump system with a 2-position/10-port switching valve capable of performing automatic alternating column regeneration was validated and implemented. The injection-to-injection time was reduced 2-fold to 6 min. The method was linear to 5000 µmol/L; limit of quantification was 1.9 µmol/L. Total imprecision was less than 5%.

Conclusions

We have developed a robust method suitable for routine clinical measurement of vitamin C in plasma specimens. The method incorporates a simplified sample preparation and a stable, non-endogenous internal standard to specifically quantify vitamin C. Faster throughput was achieved by employing an automatic alternating column regeneration system.

Vitamin C supplement intake and postmenopausal breast cancer risk: interaction with dietary vitamin C

BACKGROUND

Experimental and epidemiologic studies have yielded conflicting results on the relation between vitamin C intake and breast cancer risk.

OBJECTIVE

We investigated the relation between vitamin C supplement intake and breast cancer risk while considering dietary vitamin C intake.

DESIGN

Between 1995 and 2008, 2482 invasive breast cancer cases occurred in 57,403 postmenopausal women from the Etude Epidémiologique auprès de femmes de la Mutuelle Générale de l'Education Nationale (E3N) prospective cohort during 581,085 person-years. We estimated vitamin C intake from foods with the use of a validated food-frequency questionnaire that was sent to subjects in 1993-1995 and vitamin C supplement use via questionnaires sent in 1995, 2000, 2002, and 2005. Multivariable HRs (95% CIs) for primary invasive breast cancer were estimated with the use of Cox regression models. All statistical tests were 2-sided.

RESULTS

Vitamin C supplement use (ever compared with never) was not associated with breast cancer risk overall; it was associated with higher breast cancer risk in women in the fourth quartile of vitamin C intake from foods (HR: 1.32; 95% CI: 1.04, 1.67) but not in other quartiles of dietary vitamin C intake (P-interaction = 0.03).

CONCLUSIONS

We observed that vitamin C supplement use was associated with increased postmenopausal breast cancer risk in women with high vitamin C intake from foods. Our data suggest a potential U- or J-shaped relation between total vitamin C intake and postmenopausal breast cancer risk that deserves further investigation.

The epigenetic role of vitamin C in health and disease

Recent advances have uncovered a previously unknown function of vitamin C in epigenetic regulation. Vitamin C exists predominantly as an ascorbate anion under physiological pH conditions. Ascorbate was discovered as a cofactor for methylcytosine dioxygenases that are responsible for DNA demethylation, and also as a likely cofactor for some JmjC domain-containing histone demethylases that catalyze histone demethylation. Variation in ascorbate bioavailability thus can influence the demethylation of both DNA and histone, further leading to different phenotypic presentations. Ascorbate deficiency can be presented systematically, spatially and temporally in different tissues at the different stages of development and aging. Here, we review how ascorbate deficiency could potentially be involved in embryonic and postnatal development, and plays a role in various diseases such as neurodegeneration and cancer through epigenetic dysregulation.

Therapeutic treatment with ascorbate rescues mice from heat stroke-induced death by attenuating systemic inflammatory response and hypothalamic neuronal damage

The impact of ascorbate on oxidative stress-related diseases is moderate because of its limited oral bioavailability and rapid clearance. However, recent evidence of the clinical benefit of parenteral vitamin C administration has emerged, especially in critical care. Heatstroke is defined as a form of excessive hyperthermia associated with a systemic inflammatory response that results in multiple organ dysfunctions in which central nervous system disorders such as delirium, convulsions, and coma are predominant. The thermoregulatory, immune, coagulation and tissue injury responses of heatstroke closely resemble those observed during sepsis and are likely mediated by similar cellular mechanisms. This study was performed by using the characteristic high lethality rate and sepsis-mimic systemic inflammatory response of a murine model of heat stroke to test our hypothesis that supra-physiological doses of ascorbate may have therapeutic use in critical care. We demonstrated that parenteral administration of ascorbate abrogated the lethality and thermoregulatory dysfunction in murine model of heat stroke by attenuating heat stroke-induced accelerated systemic inflammatory, coagulation responses and the resultant multiple organ injury, especially in hypothalamus. Overall, our findings support the hypothesis and notion that supra-physiological doses of ascorbate may have therapeutic use in critical care.

Improper Use of a Plant-Based Vitamin C-Deficient Beverage Causes Scurvy in an Infant

Scurvy is a rare disease in developed countries. Risk groups include children with restricted diets, mainly patients who are autistic or have cerebral palsy. Furthermore, consumption of plant-based beverages has increased in recent years, especially in developed countries. When plant-based beverages are the exclusive diet in the first year of life and not consumed as a supplement to formula or breastfeeding, it can result in severe nutritional problems. We report a case of scurvy after exclusive intake of almond beverages and almond flour from 2.5 to 11.0 months of life. The patient was referred for pathologic fractures of the femur, irritability, and failure to thrive. He had typical radiologic signs of scurvy, such as osteopenia, cortical thinning, Wimberger ring, Frankel line, fracture, and periosteal reaction. Moreover, his plasmatic vitamin C level was very low. The child was diagnosed with scurvy and was started on vitamin C replacement therapy at a dose of 300 mg per day. Over the following 3 months, his general condition, the pain in the legs, and the radiologic features improved; the plasmatic vitamin C level was normalized; and the child started walking. In summary, this case demonstrates that scurvy is a new and severe complication of improper use of almond drinks in the first year of life. Manufacturers should indicate that these beverages are inappropriate for infants who consume a vitamin C-deficient diet.

Vitamin C, a Multi-Tasking Molecule, Finds a Molecular Target in Killing Cancer Cells

Early work in the 1970s by Linus Pauling, a twice-honored Nobel laureate, led to his proposal of using high-dose vitamin C to treat cancer patients. Over the past several decades, a number of studies in animal models as well as several small-scale clinical studies have provided substantial support of Linus Pauling's early proposal. Production of reactive oxygen species (ROS) via oxidation of vitamin C appears to be a major underlying event, leading to the selective killing of cancer cells. However, it remains unclear how vitamin C selectively kills cancer cells while sparing normal cells and what the molecular targets of high-dose vitamin C are. In a recent article published in Science (2015 December 11; 350(6266):1391-6. doi: 10.1126/science.aaa5004), Yun et al. reported that vitamin C selectively kills KRAS and BRAF mutant colorectal cancer cells by targeting glyceraldehyde 3-phosphate dehydrogenase (GAPDH) through an ROS-dependent mechanism. This work by Yun et al. along with other findings advances our current understanding of the molecular basis of high-dose vitamin C-mediated cancer cell killing, which will likely give an impetus to the continued research efforts aiming to further decipher the novel biochemistry of vitamin C and its unique role in cancer therapy.

Effects of histidine and vitamin C on isoproterenol-induced acute myocardial infarction in rats

In the present study, we investigated the effects of histidine and vitamin C (alone or in combination) treatments against isoproterenol (a β-adrenergic receptor agonist)-induced acute myocardial infarction in rats. We used propranolol (a β-adrenergic receptor blocker) to compare the results. Rats were given intraperitoneal injections of histidine (40 mg kg(-1)) and vitamin C (40 mg kg(-1)) alone and combined daily for 21 days. Propranolol (10 mg kg(-1)) was orally administered daily for 10 days (from day 11 to day 21). Myocardial infarction was induced by subcutaneous injections of 150 mg kg(-1) of isoproterenol at an interval of 24 hr on days 20 and 21. Blood and tissue samples were taken for histopathological and biochemical evaluations following electrocardiography recording on day 21. Isoproterenol elevated ST segment, increased heart weight, heart rate, serum activities of aspartate transaminase, lactate dehydrogenase, creatine kinase-MB and heart tissue content of malondialdehyde, and decreased R wave amplitude and superoxide dismutase and catalase activities of heart tissue. Necrosis, edema and inflammatory cells infiltration were observed in myocardial tissue sections. Our results indicated that histidine and vitamin C alone, and especially in combination prevent isoproterenol-induced cardiotoxicity and have similar protective effects with propranolol. Cardioprotective effects of histidine and vitamin C may be associated with their ability to reduce free radical-induced toxic effects.

Antioxidant capacities and polyphenolics of Chinese cabbage (Brassica rapa L. ssp. Pekinensis) leaves

Chinese cabbage (Brassica rapa L. ssp. Pekinensis) is a green leafy vegetable used mainly in kimchi, salted and fermented dishes. Consumer preference for the leaf portion differs according to the type of dishes. In this study, Chinese cabbage was divided into three parts, and their antioxidant activities were investigated through in vitro assays. The total phenolic contents (TPC), total flavonoid contents (TFC), and vitamin C contents were also determined as indicators of antioxidant contents. The phenolic acids and flavonoids were separated and identified using high performance liquid chromatography (HPLC) and liquid chromatography/mass spectrometry (LC/MS). The outer leaf had the strongest antioxidant activity with the maximum antioxidant contents, followed by the mid- and inner leaves. Principal component analysis (PCA) revealed that outer leaf is positively related to caffeic acid, p-coumaric acid, ferulic acid, and myricetin contents, whereas the mid- and inner leaves are negatively related to sinapic acid contents.

Effect of vitamins C and E on insulin resistance in diabetes: a meta-analysis study

BACKGROUND

Data regarding the effect of vitamin C (VC) and vitamin E (VE) supplementation on insulin resistance in type 2 diabetes mellitus (T2DM) are controversial. We aimed to systematically review the current data on this topic.

MATERIALS AND METHODS

All randomized controlled trials (RCTs) conducted to assess the effect of VC and/or VE on insulin resistance in diabetes published in Google Scholar and PubMed web databases until January 2014 were included. Exclusion criteria were studies conducted in animal, type 1 DM, children or pregnant women. Main outcome measure was insulin resistance by homoeostasis model assessment (HOMA) index. According to degree of heterogeneity, fixed- or random-effect model was employed by stata software (11.0).

RESULTS

We selected 14 RCTs involving 735 patients with T2DM. VE or mixture-mode supplementation did not have any significant effect on HOMA with a standardized mean difference (SMD): 0·017, 95% CI: -0·376 to 0·411 (P = 0·932); and SMD: -0·035, 95% CI: -0·634 to 0·025 (P = 0·070), respectively, by random-effect model. VC supplement alone did not improve insulin resistance with a SMD: -0·150, 95% CI: -0·494 to 0·194 (P = 0·391), by fixed-effect model. Meta-regression test demonstrated that HOMA index may have not been influenced by the year of publication, dosage or duration of treatment.

CONCLUSIONS

The sole intake of VC, VE or their combination with other antioxidants could not improve insulin resistance in diabetes.

Early treatment with rutoside and ascorbic acid is highly effective for progressive pigmented purpuric dermatosis

BACKGROUND AND OBJECTIVES

Progressive pigmented purpuric dermatosis (PPPD, Schamberg disease) is a rare benign, but chronic dermatosis frequently misdiagnosed as vasculitis or bleeding disorder. Although affected patients experience significant impairment in quality of life no effective treatment has been established. The aim of our two center case series was to evaluate efficacy and tolerability of the antioxidants rutoside and ascorbic acid as combination treatment for PPPD.

PATIENTS AND METHODS

A retrospective review was performed on 35 patients with PPPD treated with 2 × 50 mg rutoside and 1,000 mg ascorbic acid daily between 2004 until 2011. The mean treatment duration was 8.2 months.

RESULTS

71.4% of the participants experienced complete clearance and 20.0% an improvement of more than 50%, accompanied by increased quality of life. Nine participants (25.1%) relapsed after discontinuation. In seven, rutoside and ascorbic acid was re-initiated, and all responded again. Only three participants reported mild adverse effects. Participants with shorter disease duration showed better therapeutic success, shorter time to response and lower risk of recurrence.

CONCLUSION

Oral rutoside and ascorbic acid may be an efficient and well tolerated treatment for PPPD. Early treatment is recommended to achieve best clinical outcome.

Melatonin, minocycline and ascorbic acid reduce oxidative stress and viral titers and increase survival rate in experimental Venezuelan equine encephalitis

Venezuelan equine encephalitis (VEE) virus causes an acute central nervous system infection in human and animals. Melatonin (MLT), minocycline (MIN) and ascorbic acid (AA) have been shown to have antiviral activities in experimental infections; however, the mechanisms involved are poorly studied. Therefore, the aim of this study was to determine the effects of those compounds on the viral titers, NO production and lipid peroxidation in the brain of mice and neuroblastoma cultures infected by VEE virus. Infected mouse (10 LD50) were treated with MLT (500 μg/kg bw), MIN (50mg/kg bw) or AA (50mg/kg bw). Infected neuroblastoma cultures (MOI: 1); MLT: 0.5, 1, 5mM, MIN: 0.1, 0.2, 2 μM or AA: 25, 50, 75 μM. Brains were obtained at days 1, 3 and 5. In addition, survival rate of infected treated mice was also analyzed. Viral replication was determined by the plaque formation technique. NO and lipid peroxidation were measured by Griess׳ reaction and thiobarbituric acid assay respectively. Increased viral replication, NO production and lipid peroxidation were observed in both, infected brain and neuroblastoma cell cultures compared with uninfected controls. Those effects were diminished by the studied treatments. In addition, increased survival rate (50%) in treated infected animals compared with untreated infected mice (0%) was found. MLT, MIN and AA have an antiviral effect involving their anti-oxidant properties, and suggesting a potential use of these compounds for human VEE virus infection.

Ascorbic acid and protein glycation in vitro

The aim of the study was to compare the effects of ascorbic acid (AA) in vitro in the absence and in the presence of cell-dependent recycling. In a cell-free system, AA enhanced glycoxidation of bovine serum albumin (BSA) by glucose and induced BSA glycation in the absence of sugars. On the other hand, AA did not affect erythrocyte hemolysis, glycation of hemoglobin and erythrocyte membranes, and inactivation of catalase, protected against inactivation of acetylcholinesterase of erythrocytes incubated with high glucose concentrations and enhanced the loss of glutathione. These results can be explained by assumption that AA acts as a proglycating agent in the absence of recycling while is an antiglycating agent when metabolic recycling occurs.

Systematic review and meta-analysis of randomised controlled trials testing the effects of vitamin C supplementation on blood lipids

BACKGROUND & AIMS

Randomised controlled trials (RCTs) in humans revealed contradictory results regarding the effect of vitamin C supplementation on blood lipids. We aimed to conduct a systematic review and meta-analysis of RCTs investigating the effect of vitamin C supplementation on total cholesterol, low-density lipoprotein-cholesterol (LDL-C), high-density lipoprotein-cholesterol (HDL-C) and triglycerides and to determine whether the effects are modified by the participants' or intervention characteristics.

METHODS

Four databases (PubMed, Embase, Scopus and Cochrane Library) were searched from inception until August 2014 for RCTs supplementing adult participants with vitamin C for ≥ 2 weeks and reporting changes in blood lipids.

RESULTS

Overall, vitamin C supplementation did not change blood lipids concentration significantly. However, supplementation reduced total cholesterol in younger participants (≤52 years age) (-0.26 mmol/L, 95% CI: -0.45, -0.07) and LDL-C in healthy participants (-0.32 mmol/L, 95% CI: -0.57, -0.07). In diabetics, vitamin C supplementation reduced triglycerides significantly (-0.15 mmol/L, 95% CI: -0.30, -0.002) and increased HDL-C significantly (0.06 mmol/L, 95% CI: 0.02, 0.11). Meta-regression analyses showed the changes in total cholesterol (β: -0.24, CI: -0.36, -0.11) and in triglycerides (β: -0.17, CI: -0.30, -0.05) following vitamin C supplementation were greater in those with higher concentrations of these lipids at baseline. Greater increase in HDL-C was observed in participants with lower baseline plasma concentrations of vitamin C (β: -0.002, CI: -0.003, -0.0001).

CONCLUSIONS

Overall, vitamin C supplementation had no significant effect on lipid profile. However, subgroup and sensitivity analyses showed significant reductions in blood lipids following supplementation in sub-populations with dyslipidaemia or low vitamin C status at baseline. PROSPERO Database registration: CRD42014013487, http://www.crd.york.ac.uk/prospero/.

mtDNA Mutagenesis Disrupts Pluripotent Stem Cell Function by Altering Redox Signaling

mtDNA mutagenesis in somatic stem cells leads to their dysfunction and to progeria in mouse. The mechanism was proposed to involve modification of reactive oxygen species (ROS)/redox signaling. We studied the effect of mtDNA mutagenesis on reprogramming and stemness of pluripotent stem cells (PSCs) and show that PSCs select against specific mtDNA mutations, mimicking germline and promoting mtDNA integrity despite their glycolytic metabolism. Furthermore, mtDNA mutagenesis is associated with an increase in mitochondrial H₂O₂, reduced PSC reprogramming efficiency, and self-renewal. Mitochondria-targeted ubiquinone, MitoQ, and N-acetyl-L-cysteine efficiently rescued these defects, indicating that both reprogramming efficiency and stemness are modified by mitochondrial ROS. The redox sensitivity, however, rendered PSCs and especially neural stem cells sensitive to MitoQ toxicity. Our results imply that stem cell compartment warrants special attention when the safety of new antioxidants is assessed and point to an essential role for mitochondrial redox signaling in maintaining normal stem cell function.

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mtDNA mutagenesis affects reprogramming and stemness through redox signaling

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Altered redox signaling can be pharmacologically rescued by NAC or MitoQ

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Stem cells are sensitive to mitochondria-targeted ubiquinone toxicity

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Pluripotent stem cells show active selection against mtDNA mutations

Qualitative and quantitative proteomic analysis of Vitamin C induced changes in Mycobacterium smegmatis

Vitamin C is a critical dietary nutrient in human which has a wide range of regulatory effects on gene expression and physiology of Mycobacterium tuberculosis that leads to a dormant drug-tolerant phenotype. In the presence of iron, vitamin C shows a high bactericidal activity even in the drug resistant phenotype of M. tuberculosis. The regulatory mechanisms underlying vitamin C induced adaptations are largely unknown due to lack of functional genomics data in this field. In this study, we attempt to characterize the direct effect of vitamin C treatment on the physiology of actively growing Mycobacterium smegmatis. The study chose M. smegmatis as it is a fast-growing bacterium and a non-pathogenic model system which shares many physiological features with the pathogenic M. tuberculosis including dormancy and its regulation. The proteomic adaptation of M. smegmatis on vitamin C treatment demonstrates the important changes in cellular and metabolic process such as reversal of tricarboxylic acid cycle, decrease in ATP synthesis, decrease in iron acquisition and storage, and induction of dormancy regulators WhiB3, PhoP, and Lsr2.

Regulation of the Epigenome by Vitamin C

Emerging evidence suggests that ascorbate, the dominant form of vitamin C under physiological pH conditions, influences activity of the genome via regulating epigenomic processes. Ascorbate serves as a cofactor for Ten-eleven translocation (TET) dioxygenases that catalyze the oxidation of 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC), and further to 5-formylcytosine (5fC) and to 5-carboxylcytosine (5caC), which are ultimately replaced by unmodified cytosine. The Jumonji C (JmjC)-domain-containing histone demethylases also require ascorbate as a cofactor for histone demethylation. Thus, by primarily participating in the demethylation of both DNA and histones, ascorbate appears to be a mediator of the interface between the genome and environment. Furthermore, redox status has a profound impact on the bioavailability of ascorbate in the nucleus. In order to bridge the gap between redox biology and genomics, we suggest an interdisciplinary research field that can be termed redox genomics to study dynamic redox processes in health and diseases. This review examines the evidence and potential molecular mechanism of ascorbate in the demethylation of the genome, and it highlights potential epigenetic roles of ascorbate in various diseases.

A cross-kingdom history

The enzyme that catalyses the last step in the synthesis of ascorbate has been repeatedly lost and replaced during the evolution of the different kingdoms of eukaryotes.

Blood markers of oxidative stress predict weaning failure from mechanical ventilation

Patients undergoing mechanical ventilation (MV) often experience respiratory muscle dysfunction, which complicates the weaning process. There is no simple means to predict or diagnose respiratory muscle dysfunction because diagnosis depends on measurements in muscle diaphragmatic fibre. As oxidative stress is a key mechanism contributing to MV-induced respiratory muscle dysfunction, the aim of this study was to determine if differences in blood measures of oxidative stress in patients who had success and failure in a spontaneous breathing trial (SBT) could be used to predict the outcome of MV. This was a prospective analysis of MV-dependent patients (≥72 hrs; n = 34) undergoing a standard weaning protocol. Clinical, laboratory and oxidative stress analyses were performed. Measurements were made on blood samples taken at three time-points: immediately before the trial, 30 min. into the trial in weaning success (WS) patients, or immediately before return to MV in weaning failure (WF) patients, and 6 hrs after the trial. We found that blood measures of oxidative stress distinguished patients who would experience WF from patients who would experience WS. Before SBT, WF patients presented higher oxidative damage in lipids and higher antioxidant levels and decreased nitric oxide concentrations. The observed differences in measures between WF and WS patients persisted throughout and after the weaning trial. In conclusion, WF may be predicted based on higher malondialdehyde, higher vitamin C and lower nitric oxide concentration in plasma.