Human adrenal glands secrete vitamin C in response to adrenocorticotrophic hormone

The Role of Water-Soluble Vitamins and Vitamin D in Prevention and Treatment of Depression and Seasonal Affective Disorder in Adults

Depression is a major global health concern expected to worsen by 2030. In 2019, 28 million individuals were affected by depressive disorders. Dietary and supplemental vitamins show overall favorable preventative and therapeutic effects on depression. B vitamins are crucial for neurological function and mood regulation. Deficiencies in these vitamins are linked to depression. Studies on individual B vitamins show promise in improving depressive symptoms, particularly thiamin, riboflavin, niacin, and folate. Vitamin C deficiency may heighten depressive symptoms, but its exact role is not fully understood. Seasonal Affective Disorder (SAD) is associated with insufficient sunlight exposure and vitamin D deficiency. Vitamin D supplementation for SAD shows inconsistent results due to methodological variations. Further investigation is needed to understand the mechanisms of vitamins in depression treatment. Moreover, more research on SAD and light therapy's efficacy and underlying mechanisms involving photoreceptors, enzymes, and immune markers is needed. Although dietary and supplemental vitamins show overall favorable preventative and therapeutic effects on depression, dietitians treating psychiatric disorders face challenges due to diverse study designs, making direct comparisons difficult. Therefore, this article reviews the current literature to assess the role of dietary and supplemental vitamins in the prevention and treatment of depression. This review found that, although evidence supports the role of B vitamins and vitamins C and D in preventing and treating depression, further research is needed to clarify their mechanisms of action and determine the most effective intervention strategies.

Vitamin C supplementation alleviates hypercortisolemia caused by chronic stress

The aim of this study was to determine whether ascorbic acid (AA) supplementation can lower plasma levels of Cortisol and dehydroepiandrosterone-sulphate (DHEA-S) in patients diagnosed with functional hypercortisolemia due to unspecified chronic stress. Study includes data from 69 female with elevations in the cortisol and DHEA-S levels. Duration of follow-up was 2 months. Patients were divided into 3 groups. Group I included patients 23 with elevated cortisol, Group II-patients 24 with elevated levels of both hormones, Group III- patients 22 with normal cortisol and increased DHEA-S. Each group was randomly divided into two subgroups. The first subgroup was prescribed 1000 mg daily oral dose of AA. The diet of the second subgroup were left unaltered. All patients have their hormones levels re-examined 2 months later. After 2 months of AA supplementation the mean levels of elevated plasma cortisol and DHEA-S decreased. In Group I the level of cortisol fell from 780 ± 57-446 ± 26 nmol/L, p = 0.000065 in Group II from 657 ± 47-515 ± 29 nmol/L, p = 0.005. The elevated levels of DHEA-S have also declined in patients from AA-treated subgroups (from 13.9 ± 1.6-9.9 ± 1.2, p = 0.0007 in Group II, and from 12.8 ± 1.0-7.8 ± 1.4, p = 0.003 in Group III). In untreated subgroups changes in hormone levels were insignificant. The study shows that female patients with functional hypercortisolemia or elevated levels of DHEA-S can be treated with AA to bring level of these hormones closer to a normal range.

Exploring the role of antioxidants in sepsis-associated oxidative stress: a comprehensive review

Sepsis is a potentially fatal condition characterized by organ dysfunction caused by an imbalanced immune response to infection. Although an increased inflammatory response significantly contributes to the pathogenesis of sepsis, several molecular mechanisms underlying the progression of sepsis are associated with increased cellular reactive oxygen species (ROS) generation and exhausted antioxidant pathways. This review article provides a comprehensive overview of the involvement of ROS in the pathophysiology of sepsis and the potential application of antioxidants with antimicrobial properties as an adjunct to primary therapies (fluid and antibiotic therapies) against sepsis. This article delves into the advantages and disadvantages associated with the utilization of antioxidants in the therapeutic approach to sepsis, which has been explored in a variety of animal models and clinical trials. While the application of antioxidants has been suggested as a potential therapy to suppress the immune response in cases where an intensified inflammatory reaction occurs, the use of multiple antioxidant agents can be beneficial as they can act additively or synergistically on different pathways, thereby enhancing the antioxidant defense. Furthermore, the utilization of immunoadjuvant therapy, specifically in septic patients displaying immunosuppressive tendencies, represents a promising advancement in sepsis therapy.

Ascorbic Acid Protects Bone Marrow from Oxidative Stress and Transient Elevation of Corticosterone Caused by X-ray Exposure in Akr1a-Knockout Mice

Bone marrow cells are the most sensitive to exposure to X-rays in the body and are selectively damaged even by doses that are generally considered permissive in other organs. Ascorbic acid (Asc) is a potent antioxidant that is reported to alleviate damages caused by X-ray exposure. However, rodents can synthesize Asc, which creates difficulties in rigorously assessing its effects in such laboratory animals. To address this issue, we employed mice with defects in their ability to synthesize Asc due to a genetic ablation of aldehyde reductase (Akr1a-KO). In this study, concentrations of white blood cells (WBCs) were decreased 3 days after exposure to X-rays at 2 Gy and then gradually recovered. At approximately one month, the recovery rate of WBCs was delayed in the Akr1a-KO mouse group, which was reversed via supplementation with Asc. Following exposure to X-rays, Asc levels decreased in plasma, bone marrow cells, and the liver during an early period, and then started to increase. X-ray exposure stimulated the pituitary gland to release adrenocorticotropic hormone (ACTH), which stimulated corticosterone secretion. Asc released from the liver, which was also stimulated by ACTH, appeared to be recruited to the bone marrow. Since corticosterone in high doses is injurious, these collective results imply that Asc protects bone marrow via its antioxidant capacity against ROS produced via exposure to X-rays and the cytotoxic action of transiently elevated corticosterone.

Unwinding the potentials of vitamin C in COVID-19 and other diseases: An updated review

Background: The discovery of vitamin C (ascorbic acid) is related to the ancient history of persistent research on the origins of the haemorrhagic disease scurvy. Vitamin C is an important nutrient that aids in a variety of biological and physiological processes. Scientists have been researching the function of vitamin C in the prevention and ailment of sepsis and pneumonia for decades. This has created a potential platform for applying these results to individuals suffering from severe coronavirus infection (COVID-19). Vitamin C's ability to activate and enhance the immune system makes it a promising treatment in the present COVID-19 pandemic. Vitamin C also aids in the activation of vitamin B, the production of certain neurotransmitters, and the transformation of cholesterol into bile acids. Hence, vitamin C is used for the treatment of many diseases. Aim: This review highlights the Vitamin C investigations that are performed by various researchers on patients with COVID 19 infection, the clinical studies and their observations. The authors have additionally updated information on the significance of vitamin C insufficiency, as well as its relevance and involvement in diseases such as cancer, wound healing, iron deficiency anaemia, atherosclerosis and neurodegenerative disorders. Here, we discuss them with the references. Methods: The method used in order to perform literature search was done using SciFinder, PubMed and ScienceDirect. Results: There is a potential role of vitamin C in various diseases including neurodegenerative disorders, COVID-19 and other diseases and the results are highlighted in the review with the help of clinical and preclinical data. Conclusion: More research on vitamin C and the undergoing clinical trials might prove a potential role of vitamin C in protecting the population from current COVID-19 pandemic.

Inflammation and Vitamin C in Women with Prenatal Depression and Anxiety: Effect of Multinutrient Supplementation

Elevated inflammation has been associated with adverse mood states, such as depression and anxiety, and antioxidant nutrients, such as vitamin C, have been associated with decreased inflammation and improved mood. In the current study comprising a cohort of pregnant women with depression and anxiety, we hypothesised that elevated inflammation would be associated with adverse mood states and inversely associated with vitamin C status and that multinutrient supplementation would optimise vitamin concentrations and attenuate inflammation. Sixty-one participants from the NUTRIMUM trial had blood samples collected between 12 and 24 weeks gestation (baseline) and following 12 weeks of daily supplementation with a multinutrient formula containing 600 mg of vitamin C or active placebo. The samples were analysed for inflammatory biomarkers (C-reactive protein (CRP) and cytokines) and vitamin C content and were related to scales of depression and anxiety. Positive correlations were observed between interleukin-6 (IL-6) and all of the mood scales administered (p < 0.05), including the Edinburgh Postnatal Depression Scale, the Clinical Global Impressions-Severity Scale, the Montgomery and Åsberg Depression Rating Scale, the Depression Anxiety Stress Scale 21, and the Generalized Anxiety Disorder-7 (GAD-7). CRP correlated weakly with GAD-7 (p = 0.05). There was an inverse correlation between CRP and the vitamin C status of the cohort (p = 0.045), although there was no association of the latter with the mood scales (p > 0.05). Supplementation with the multinutrient formula resulted in a significant increase in the vitamin C status of the cohort (p = 0.007) but did not affect the inflammatory biomarker concentrations (p > 0.05). In conclusion, greater systemic inflammation was associated with worse mood states; however, 12-week multinutrient supplementation did not alter inflammatory biomarker concentrations. Nevertheless, the vitamin C status of the cohort was improved with supplementation, which may aid pregnancy and infant outcomes.

Case report: Pulmonary hypertensive crisis leading to cardiac arrest during endoscopic evaluation in a 6-year-old boy with autism, severe malnutrition, and undiagnosed scurvy

Pediatric gastroenterologists are often responsible for the evaluation of malnutrition in the setting of selective eating. Endoscopic evaluation for conditions including eosinophilic esophagitis and celiac disease can help to identify and treat mucosal disease contributing to food selectivity. However, undiagnosed micronutrient deficiencies can cause cardiovascular derangements that significantly increase a patient's anesthetic risk. Vitamin C deficiency in particular, alone or in combination with severe malnutrition, is associated with a severe but reversible form of pulmonary arterial hypertension that, while life threatening in the acute phase, may significantly improve within days of starting ascorbic acid replacement therapy. Here we present a case of a 6-year-old boy with autism spectrum disorder (ASD), severe malnutrition, and undiagnosed chronic vitamin C deficiency who developed a pulmonary hypertensive crisis after induction of general anesthesia leading to cardiac arrest during endoscopic evaluation. While the association between food selectivity among youth with neurodevelopmental differences and vitamin C deficiency is well-described, and pulmonary hypertension is a recognized rare complication of scurvy, extant literature has not addressed next steps to improve patient outcomes. Using this case report as a foundation, we discuss specific patient populations to screen and treat for micronutrient deficiencies prior to anesthesia and propose a novel clinical algorithm for pre-anesthesia risk stratification and mitigation in patients specifically at risk for scurvy and associated pulmonary hypertension.

Early ascorbic acid administration prevents vascular endothelial cell damage in septic mice

Oxidation of BH₄, a cofactor of nitric oxide synthase (NOS), produces reactive oxygen species (ROS) through uncoupling of NOS and affects vascular endothelial dysfunction. Ascorbic acid (AsA) inhibits the oxidation of BH₄ and reduces ROS. However, the kinetic changes of BH₄ in sepsis and its effect on the kinetic changes in AsA administration therapy, as well as the appropriate timing of AsA administration for AsA therapy to be effective, are unclear. Mice with sepsis, induced by cecal ligation and puncture (CLP), were examined for the effect of AsA administration (200 mg/kg) on vascular endothelial cell dysfunction at two administration timings: early group (AsA administered immediately after CLP) and late group (AsA administered 12 h after CLP). Survival rates were compared between the early and late administration groups, and vascular endothelial cell damage, indicated by the dihydrobiopterin/tetrahydrobiopterin ratio, serum syndecan-1, and endothelial nitric oxide synthase, as well as liver damage, were examined. The early group showed significantly improved survival compared to the non-treatment group (p < 0.05), while the late group showed no improved survival compared to the non-treatment group. Compared to the non-treated group, the early AsA group showed less oxidation of BH₄ in sepsis. Syndecan1, a marker of vascular endothelial cell damage, was less elevated and organ damage was reduced in the early AsA-treated group. In septic mice, early AsA administration immediately after CLP may protect vascular endothelial cells by inhibiting BH₄ oxidation, thereby reducing organ dysfunction and improving survival.

Vitamin therapy in sepsis

Vitamins are essential micronutrients with key roles in many biological pathways relevant to sepsis. Some of these relevant biological mechanisms include antioxidant and anti-inflammatory effects, protein and hormone synthesis, energy generation, and regulation of gene transcription. Moreover, relative vitamin deficiencies in plasma are common during sepsis and vitamin therapy has been associated with improved outcomes in some adult and pediatric studies. High-dose intravenous vitamin C has been the vitamin therapy most extensively studied in adult patients with sepsis and septic shock. This includes three randomized control trials (RCTs) as monotherapy with a total of 219 patients showing significant reduction in organ dysfunction and lower mortality when compared to placebo, and five RCTs as a combination therapy with thiamine and hydrocortisone with a total of 1134 patients showing no difference in clinical outcomes. Likewise, the evidence for the role of other vitamins in sepsis remains mixed. In this narrative review, we present the preclinical, clinical, and safety evidence of the most studied vitamins in sepsis, including vitamin C, thiamine (i.e., vitamin B₁), and vitamin D. We also present the relevant evidence of the other vitamins that have been studied in sepsis and critical illness in both children and adults, including vitamins A, B₂, B₆, B₁₂, and E. IMPACT: Vitamins are key effectors in many biological processes relevant to sepsis. We present the preclinical, clinical, and safety evidence of the most studied vitamins in pediatric sepsis. Designing response-adaptive platform trials may help fill in knowledge gaps regarding vitamin use for critical illness and association with clinical outcomes.

Redox Properties of Human Erythrocytes Are Adapted for Vitamin C Recycling

Ascorbic acid (AA; or vitamin C) is an important physiological antioxidant and radical scavenger. Some mammalian species, including homo sapiens, have lost the ability to synthetize AA and depend on its nutritional uptake. Erythrocytes from AA-auxotroph mammals express high amounts of the glucose transporter GLUT1. This isoform enables rapid uptake of glucose as well as dehydroascorbate (DHA), the fully oxidized form of AA. Here, we explored the effects of DHA uptake on the redox metabolism of human erythrocytes. DHA uptake enhanced plasma membrane electron transport (PMET) activity. This process is mediated by DCytb, a membrane bound cytochrome catalyzing extracellular reduction of Fe³⁺ and ascorbate free radical (AFR), the first oxidized form of AA. DHA uptake also decreased cellular radical oxygen species (ROS) levels. Both effects were massively enhanced in the presence of physiological glucose concentrations. Reduction of DHA to AA largely depleted intracellular glutathione (GSH) and induced the efflux of its oxidized form, GSSG. GSSG efflux could be inhibited by MK-571 (IC₅₀ = 5 μM), indicating involvement of multidrug resistance associated protein (MRP1/4). DHA-dependent GSH depletion and GSSG efflux were completely rescued in the presence of 5 mM glucose and, partially, by 2-deoxy-glucose (2-DG), respectively. These findings indicate that human erythrocytes are physiologically adapted to recycle AA both intracellularly via GLUT1-mediated DHA uptake and reduction and extracellularly via DCytb-mediated AFR reduction. We discuss the possibility that this improved erythrocyte-mediated AA recycling was a prerequisite for the emergence of AA auxotrophy which independently occurred at least twice during mammalian evolution.

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

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

Developmental retardation in neonates of aldehyde reductase (AKR1A)-deficient mice is associated with low ascorbic acid and high corticosterone levels

Aldehyde reductase encoded by the Akr1a gene catalyzes the NADPH-dependent reduction of a variety of aldehyde compounds, and it plays a role in the biosynthesis of ascorbic acid (AsA) by converting D-glucuronate to L-gulonate. Although supplementing drinking water with AsA (1.5 mg/mL) ameliorates the fertility of Akr1a^-/- (KO) female mice, litter sizes in the KO mice are typically smaller than those for Akr1a^+/+ (WT) mice, and about one-third of the neonates have a reduced stature. Half of the neonates in the smallest, developmentally retarded group died before weaning, and the remaining half (less than 6 g in weight) also barely grew to adulthood. While no difference was found in the number of fetuses between the KO and WT mice at 14.5-embryonic days, the sizes of the KO fetuses had already diverged. Among the organs of these retarded KO neonates at 30 d, the spleen and thymus were characteristically small. While an examination of spleen cells showed the normal proportion of immune cells, apoptotic cell death was increased in the thymus, which would lead to thymic atrophy in the retarded KO neonates. Plasma AsA levels were lower in the small neonates despite the fact that their mothers had received sufficient AsA supplementation, and the corticosterone levels were inversely higher compared to wild-type mice. Thus, insufficient AsA contents together with a defect in corticosterone metabolism might be the cause of the retarded growth of the AKR1A-deficient mice embryos and neonates.

Vitamin C-An Adjunctive Therapy for Respiratory Infection, Sepsis and COVID-19

There are limited proven therapies for COVID-19. Vitamin C's antioxidant, anti-inflammatory and immunomodulating effects make it a potential therapeutic candidate, both for the prevention and amelioration of COVID-19 infection, and as an adjunctive therapy in the critical care of COVID-19. This literature review focuses on vitamin C deficiency in respiratory infections, including COVID-19, and the mechanisms of action in infectious disease, including support of the stress response, its role in preventing and treating colds and pneumonia, and its role in treating sepsis and COVID-19. The evidence to date indicates that oral vitamin C (2-8 g/day) may reduce the incidence and duration of respiratory infections and intravenous vitamin C (6-24 g/day) has been shown to reduce mortality, intensive care unit (ICU) and hospital stays, and time on mechanical ventilation for severe respiratory infections. Further trials are urgently warranted. Given the favourable safety profile and low cost of vitamin C, and the frequency of vitamin C deficiency in respiratory infections, it may be worthwhile testing patients' vitamin C status and treating them accordingly with intravenous administration within ICUs and oral administration in hospitalised persons with COVID-19.

On a Novel, Simplified Model Framework Describing Ascorbic Acid Concentration Dynamics

Ascorbic acid is an essential aminoacid which interacts in several parts of the human body metabolism. The ascorbic acid concentration is controlled by homeostasis, a biological, autonomous control function in the body. Humans are not able to produce ascorbic acid, and the ascorbic acid concentration is maintained by daily oral digestion. Ascorbic acid is buffered in various tissues, such as the adrenal glands, brain, muscles, and other. Excessive ascorbic acid is extracted from the body through urine and intestines. Measuring ascorbic acid concentration in the body is challenging, and special procedures must be followed when extracting a blood sample and performing a concentration analysis. This paper presents a novel, simplified model framework of the ascorbic acid homeostasis in the human body plasma and tissues, including tissues such as adrenal glands, brain, liver, muscles and bone marrow. These tissues also act as ascorbic acid concentration buffers, in case of low oral supply. The dynamic model framework is based on mass balances of ascorbate acid in various tissues, including tissue buffer terms involving the intestine, kidney, adrenal glands, and other critical and noncritical tissues. The interaction between buffer tissues and fluids is maintained by the body homeostasis using chemical transport protein molecules. Additional usage terms describing energy metabolism, body growth, and immune system response are also included. This dynamic model framework, including the ascorbic acid concentration control system, is simulated with assumed parameters based on available literature. The results indicates that further investigations using experiments, in addition to adaptive model parameter estimation schemes and additional model verification tests are needed in order to identify the various model framework parameters to fit the human body ascorbic acid homeostasis and pharmacokinetics.

Vitamin C: an essential "stress hormone" during sepsis

The stress response is a preserved evolutionary response that functions to enhance the survival of the species. In mammals, the stress response is characterized by activation of the HPA axis and sympathoadrenal system (SAS) as well as the increased synthesis and secretion of vitamin C. Cortisol, catecholamines, and vitamin C act synergistically to increase hemodynamic reserve, maintain immune function and protect the host against excessive oxidant injury. Humans (and anthropoid apes) have lost the ability to synthesize vitamin C and therefore have an impaired stress response. The inability to produce vitamin C has serious implications in septic humans. Treatment with vitamin C appears to restore the stress response and improve the survival of stressed humans.

Attenuation of sleep deprivation dependent deterioration in male fertility parameters by vitamin C

PURPOSE

Male fertility is multifaceted and its integrity is as well multifactorial. Normal spermatogenesis is dependent on competent testicular function; namely normal anatomy, histology, physiology and hormonal regulation. Lifestyle stressors, including sleep interruption and even deprivation, have been shown to seriously impact male fertility. We studied here both the effects and the possible underlying mechanisms of vitamin C on male fertility in sleep deprived rats.

METHODS

Thirty male Wistar albino rats were used in the present study. Rats were divided (10/group) into: control (remained in their cages with free access to food and water), sleep deprivation (SD) group (subjected to paradoxical sleep deprivation for 5 consequent days, rats received intra-peritoneal injections of vehicle daily throughout the sleep deprivation), and sleep deprivation vitamin C-treated (SDC) group (subjected to sleep deprivation for 5 consequent days with concomitant intra-peritoneal injections of 100 mg/kg/day vitamin C). Sperm analysis, hormonal assay, and measurement of serum oxidative stress and inflammatory markers were performed. Testicular gene expression of Nrf2 and NF-κβ was assessed. Structural changes were evaluated by testicular histopathology, while PCNA immunostaining was conducted to assess spermatogenesis.

RESULTS

Sleep deprivation had significantly altered sperm motility, viability, morphology and count. Serum levels of cortisol, corticosterone, IL-6, IL-17, MDA were increased, while testosterone and TAC levels were decreased. Testicular gene expression of Nrf2 was decreased, while NF-κβ was increased. Sleep deprivation caused structural changes in the testes, and PCNA immunostaining showed defective spermatogenesis. Administration of vitamin C significantly countered sleep deprivation induced deterioration in male fertility parameters.

CONCLUSION

Treatment with vitamin C enhanced booth testicular structure and function in sleep deprived rats. Vitamin C could be a potential fertility enhancer against lifestyle stressors.

Treating sepsis with vitamin C, thiamine, and hydrocortisone: Exploring the quest for the magic elixir

The administration of ascorbic acid (vitamin C) alone or in combination with thiamine (vitamin B1) and corticosteroids (VCTS) has recently been hypothesized to improve hemodynamics, end-organ function, and may even increase survival in critically ill patients. There are several clinical studies that have investigated the use of vitamin C alone or VCTS in patients with sepsis and septic shock or are ongoing. Some of these studies have demonstrated its safety and potential benefit in septic patients. However, many questions remain regarding the optimal dosing regimens and plasma concentrations, timing of administration, and adverse effects of vitamin C and thiamine. These questions exist because the bulk of research regarding the efficacy of vitamin C alone or in combination with thiamine and corticosteroids in sepsis is limited to a few randomized controlled trials, retrospective before-and-after studies, and case reports. Thus, although the underlying rationale and mechanistic pathways of vitamin C and thiamine in sepsis have been well described, the clinical impact of the VCTS regimen is complex and remains to be determined. This review aims to explore the current evidence and potential benefits and adverse effects of the VCTS regimen for the treatment of sepsis.

Plasma Vitamin C Concentrations and Cognitive Function: A Cross-Sectional Study

Vitamin-C is a water soluble molecule that humans have lost the ability to produce. Vitamin-C plays a role in CNS functions such as neuronal differentiation, maturation, myelin formation and modulation of the catecholaminergic systems. A recent systematic review by our team indicated the need for further research into the relationship between plasma vitamin C and cognition in cognitively intact participants using plasma vitamin C concentrations instead of estimates derived from food-frequency-questionnaires (FFQ), and more sensitive cognitive assessments suitable for cognitive abilities vulnerable to aging. It was hypothesized that higher plasma vitamin C concentrations would be linked with higher cognitive performance. This cross-sectional trial was conducted on healthy adults (n = 80, Female = 52, Male = 28, 24-96 years) with a range of plasma Vitamin C concentrations. Cognitive assessments included The Swinburne-University-Computerized-Cognitive-Assessment-Battery (SUCCAB) and two pen and paper tests, the Symbol-Digits-Modalities-Test (SDMT) and Hopkins-Verbal-Learning-Test-Revised (HVLT-R). The pen and paper assessments were conducted to establish whether their scores would correlate with the computerized tasks. Plasma-Vitamin C concentrations were measured using two biochemical analyses. Participants were grouped into those with plasma vitamin-C concentrations of adequate level (≥28 μmol/L) and deficient level (<28 μmol/L). The SUCCAB identified a significantly higher performance ratio (accuracy/reaction-time) in the group with adequate vitamin-C levels vs. deficient vitamin-C on the choice reaction time (M = 188 ± 4 vs. 167 ± 9, p = 0.039), immediate recognition memory (M = 81 ± 3 vs. 68 ± 6, p = 0.03), congruent Stroop (M = 134 ± 3 vs. 116 ± 7, p = 0.024), and delayed recognition tasks (M = 72 ± 2 vs. 62 ± 4, p = 0.049), after adjusting for age (p < 0.05). Significantly higher scores in immediate recall on the HVLT-R (M = 10.64 ± 0.16 vs. 9.17 ± 0.37, p = 0.001), delayed recall (M = 9.74 ± 0.22 vs. 7.64 ± 0.51, p < 0.001), total recall (M = 27.93 ± 0.48 vs. 24.19 ± 1.11, p = 0.003) were shown in participants with adequate plasma Vitamin-C concentrations, after adjusting for vitamin-C supplementation dose (p < 0.05). Similarly, higher SDMT scores were observed in participants with adequate plasma Vitamin-C concentrations (M = 49.73 ± 10.34 vs. 41.38 ± 5.06, p = 0.039), after adjusting for age (p < 0.05). In conclusion there was a significant association between vitamin-C plasma concentrations and performance on tasks involving attention, focus, working memory, decision speed, delayed and total recall, and recognition. Plasma vitamin C concentrations obtained through vitamin C supplementation did not affect cognitive performance differently to adequate concentrations obtained through dietary intake. Clinicaltrials.gov Unique Identifier: ACTRN 12615001140549, URL: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=369440.

Vitamin C supplementation in the critically ill: A systematic review and meta-analysis

BACKGROUND

Low plasma levels of vitamin C are associated with adverse outcomes, including increased mortality, in critically ill patients. Several trials have suggested that the administration of intravenous vitamin C in this setting may have beneficial effects, such as reducing the incidence of organ failure and improving survival. However, these studies have generally involved combination therapies consisting of vitamin C along with other antioxidants, confounding the effects of vitamin C alone. The primary objective of this meta-analysis is to investigate the effects of isolated intravenous supplementation of vitamin C in adults with critical illness.

METHODS

A database search was conducted for studies on the use of intravenous vitamin C in adult patients with critical illness. The primary outcome assessed was mortality at the longest follow-up time available. Secondary outcomes were the duration of mechanical ventilation, duration of vasopressor support, fluid requirements, and urine output in the first 24 h of intensive care unit admission.

RESULTS

Five studies (four randomized controlled trials and one retrospective review) enrolling a total of 142 patients were included in this meta-analysis. Compared with controls, the administration of intravenous vitamin C was associated with a decreased need for vasopressor support (standardized mean difference -0.71; 95% confidence interval (-1.16 to -0.26); p = 0.002) and decreased duration of mechanical ventilation (standardized mean difference -0.5; 95% confidence interval (-0.93 to -0.06); p = 0.03), but no difference was found in mortality (odds ratio 0.76; 95% confidence interval (0.27 to 2.16); p = 0.6). Trends were also noted toward decreased fluid requirements and increased urine output. No adverse effects were reported.

CONCLUSION

The administration of intravenous vitamin C may lead to vasopressor sparing effects and a reduced need for mechanical ventilation in the critically ill, without affecting overall mortality. However, these results should be interpreted in light of the limitations of the primary literature and should serve as a preview of upcoming trials in this area.

Vitamin C Pharmacokinetics in Critically Ill Patients: A Randomized Trial of Four IV Regimens

BACKGROUND

Early high-dose IV vitamin C is being investigated as adjuvant therapy in patients who are critically ill, but the optimal dose and infusion method are unclear. The primary aim of this study was to describe the dose-plasma concentration relationship and safety of four different dosing regimens.

METHODS

This was a four-group randomized pharmacokinetic trial. Patients who were critically ill with multiple organ dysfunction were randomized to receive 2 or 10 g/d vitamin C as a twice daily bolus infusion or continuous infusion for 48 h. End points were plasma vitamin C concentrations during 96 h, 12-h urine excretion of vitamin C, and oxalate excretion and base excess. A population pharmacokinetic model was developed using NONMEM.

RESULTS

Twenty patients were included. A two-compartment pharmacokinetic model with creatinine clearance and weight as independent covariates described all four regimens best. With 2 g/d bolus, plasma vitamin C concentrations at 1 h were 29 to 50 mg/L and trough concentrations were 5.6 to 16 mg/L. With 2 g/d continuous, steady-state concentrations were 7 to 37 mg/L at 48 h. With 10 g/d bolus, 1-h concentrations were 186 to 244 mg/L and trough concentrations were 14 to 55 mg/L. With 10 g/d continuous, steady-state concentrations were 40 to 295 mg/L at 48 h. Oxalate excretion and base excess were increased in the 10 g/d dose. Forty-eight hours after discontinuation, plasma concentrations declined to hypovitaminosis levels in 15% of patients.

CONCLUSIONS

The 2 g/d dose was associated with normal plasma concentrations, and the 10 g/d dose was associated with supranormal plasma concentrations, increased oxalate excretion, and metabolic alkalosis. Sustained therapy is needed to prevent hypovitaminosis.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT02455180; URL: www.clinicaltrials.gov.

Metformin and ascorbic acid combination therapy ameliorates type 2 diabetes mellitus and comorbid depression in rats

Diabetes mellitus and depression are the common comorbid disorders affecting humans worldwide. There is an unmet need to develop therapeutic strategies to treat both diabetes mellitus and comorbid depression. The present study evaluated the effectiveness of metformin and ascorbic acid against type 2 diabetes mellitus and comorbid depression in rats. Four groups of diabetic rats were orally administered with vehicle (1mL/kg), metformin (25mg/kg), ascorbic acid (25mg/kg), or combination of metformin (25mg/kg) and ascorbic acid (25mg/kg) for 11 consecutive days. Diabetes was induced by single-dose administration of streptozotocin (65mg/kg, i.p.) with nicotinamide (120mg/kg, i.p.). Comorbid depression was induced by five inescapable foot-shocks (2mA, 2ms duration) at 10s intervals on days 1, 5, 7, and 10. One group of healthy rats received only vehicles to serve as nondiabetic control group. On day 11, animals were sacrificed, and blood and brain samples were collected from each rat following forced swim test. Plasma glucose, insulin, and corticosterone levels were estimated in plasma. The levels of monoamines, proinflammatory cytokines, and oxidative stress were measured in prefrontal cortex. The combination therapy significantly reduced immobility period, glucose, and corticosterone levels relative to diabetes with comorbid depression group. Furthermore, the combination therapy increased the levels of insulin and monoamines, and caused a significant reductions in oxidative stress and proinflammatory cytokines. In conclusion, the present study revealed that metformin and ascorbic acid combination therapy could be a potential strategy to treat type 2 diabetes mellitus and comorbid depression.

Effect of smoking on acute phase reactants, stress hormone responses and vitamin C in pulmonary tuberculosis

BACKGROUND

Chronic inflammation, possibly exacerbated by cigarette smoking, is considered to be the primary cause of pulmonary damage in patients with tuberculosis (TB). However, the mechanisms which underpin these harmful inflammatory responses, have not been well documented.

OBJECTIVES

The current study was undertaken to determine possible associations between systemic biomarkers of inflammation (acute phase reactants, stress hormones, leukocyte vitamin C) and smoking status in patients (n=71, 20 smokers) with newly-diagnosed pulmonary TB presenting at a tertiary hospital, Johannesburg, South Africa.

METHODS

Plasma concentrations of C-reactive protein (CRP), ferritin, cortisol, epinephrine, norepinephrine, dopamine and leukocyte vitamin C were measured using a combination of immunonephelometric, radioimmunoassay, immunochromatographic and spectrophotometric procedures. Demographic, clinical and laboratory data was captured and analysed by parametric and non-parametric analyses where appropriate.

RESULTS

Smokers were predominantly males (P<0.0001), of older age (P<0.0003) with a significantly lower body mass index (P<0.03). Plasma levels of CRP, ferritin and dopamine were higher in the group of smokers in the setting of lower levels of epinephrine, and leukocyte vitamin C, with CRP and vitamin C attaining statistical significance (P<0.04 and P<0.02 respectively). Those of cortisol and norepinephrine were comparable to those of non-smokers, as were radiographic changes and clinical indices of disease activity.

CONCLUSION

Cigarette smoking is associated with an exaggerated systemic inflammatory response in pulmonary TB in the setting of decreased concentrations of leukocyte vitamin C. Although no significant associations with radiographic changes and most clinical indices of disease activity were evident on presentation, these pro-inflammatory interactions may have prognostic significance.

The impact of essential fatty acid, B vitamins, vitamin C, magnesium and zinc supplementation on stress levels in women: a systematic review

BACKGROUND

Women juggling multiple roles in our complex society are increasingly experiencing psychological stress. Dietary supplementation to manage stress is widespread despite limited supporting evidence. A systematic review of the available literature was undertaken to investigate the efficacy of specific dietary supplements in managing female stress and anxiety.

OBJECTIVES

To identify the impact of essential fatty acids (EFAs), B vitamins, vitamin C, magnesium and/or zinc, consumed as dietary supplements to the daily diet, on female stress and anxiety levels.

INCLUSION CRITERIA TYPES OF PARTICIPANTS

Women aged 18 years and over, who had participated in a study where stress and/or anxiety were assessed.

TYPES OF INTERVENTION(S)

Dietary supplementation with EFAs, B vitamins, vitamin C, magnesium and/or zinc.

TYPES OF COMPARATORS

Supplements, either alone or combined, were compared with either no intervention or placebo.

TYPES OF STUDIES

Randomized controlled and pseudo-randomized trials were included.

OUTCOMES

Stress and anxiety were assessed using self-report or physiological outcome measures.

SEARCH STRATEGY

Published and unpublished studies were sought via MEDLINE (via PubMed), Embase, Scopus, CINAHL, PsycINFO, PsycARTICLES, MedNar, National Institute of Mental Health and the International Association for Women's Mental Health.

METHODOLOGICAL QUALITY

Methodological quality was evaluated using standardized critical appraisal instruments from the Joanna Briggs Institute.

DATA EXTRACTION

Data were extracted using the standardized data extraction instruments from the Joanna Briggs Institute.

DATA SYNTHESIS

Due to heterogeneity of the included studies, narrative synthesis was performed.

RESULTS

Fourteen studies were included in this review. Essential fatty acids were effective in reducing perceived stress and salivary cortisol levels during pregnancy and anxiety in premenstrual women, and anxiety during menopause in the absence of depression, but were ineffective when depression was disregarded. Disregarding the hormonal phase, EFAs were ineffective in reducing stress or anxiety in four groups of women. Combined magnesium and vitamin B6 supplementation reduced premenstrual anxiety but had no effect when used in isolation and did not affect stress in women suffering from dysmenorrhea when combined or used in isolation. Older women experienced anxiety reduction using vitamin B6, but not folate or vitamin B12. High-dose sustained-release vitamin C was effective in reducing anxiety and blood pressure in response to stress.

CONCLUSION

The current review suggests that EFAs may be effective in reducing prenatal stress and salivary cortisol and may reduce anxiety during premenstrual syndrome and during menopause in the absence of depression. Magnesium and vitamin B6 may be effective in combination in reducing premenstrual stress, and vitamin B6 alone may reduce anxiety effectively in older women. High-dose sustained-release vitamin C may reduce anxiety and mitigate increased blood pressure in response to stress.

IMPLICATIONS FOR PRACTICE

Essential fatty acids may be effective in reducing prenatal stress and salivary cortisol levels, and premenstrual or menopausal anxiety in the absence of depression. Combining magnesium and vitamin B6 may reduce premenstrual anxiety and vitamin B6 may reduce anxiety in older women. High-dose sustained-release vitamin C may reduce anxiety and mitigate increased blood pressure in response to stress.

IMPLICATIONS FOR RESEARCH

Investigating supplementation in longer term studies is warranted and should include compliance testing, the use of inert substances as controls and reliable outcome measures.

Effects of exercise on alterations in redox homeostasis in elite male and female endurance athletes using a clinical point-of-care test

Exercise causes alterations in redox homeostasis (ARH). Measuring ARH in elite athletes may aid in the identification of training tolerance, fatigued states, and underperformance. To the best of our knowledge, no studies have examined ARH in elite male and female distance runners at sea level. The monitoring of ARH in athletes is hindered by a lack of reliable and repeatable in-the-field testing tools and by the rapid turnaround of results. We examined the effects of various exercise intensities on ARH in healthy (non-over-reached) elite male and female endurance athletes using clinical point-of-care (POC) redox tests, referred to as the free oxygen radical test (FORT) (pro-oxidant) and the free oxygen radical defence (FORD) (antioxidant). Elite male and female endurance athletes (n = 22) completed a discontinuous incremental treadmill protocol at submaximal running speeds and a test to exhaustion. Redox measures were analyzed via blood sampling at rest, warm-up, submaximal exercise, exhaustion, and recovery. FORD was elevated above rest after submaximal and maximal exercise, and recovery (p < 0.05, d = 0.87–1.55), with only maximal exercise and recovery increasing FORT (p < 0.05, d = 0.23–0.32). Overall, a decrease in oxidative stress in response to submaximal and maximal exercise was evident (p < 0.05, d = 0.46). There were no gender differences for ARH (p > 0.05). The velocity at lactate threshold (vLT) correlated with the FORD response at rest, maximal exercise, and recovery (p < 0.05). Using the clinical POC redox test, an absence of oxidative stress after exhaustive exercise is evident in the nonfatigued elite endurance athlete. The blood antioxidant response (FORD) to exercise appears to be related to a key marker of aerobic fitness: vLT.

Determination of plasma and leukocyte vitamin C concentrations in a randomized, double-blind, placebo-controlled trial with Ester-C(®)

Background

Rapid uptake of vitamin C into blood and retention in tissues are important indicators of the efficacy of vitamin C supplementation and its immune-supporting role. The objective of this study was to evaluate the bioavailability of vitamin C in plasma (reflective of recent intake) and leukocytes (reflective of tissue stores and influences on immune function) from a novel vitamin C formulation, Ester-C^®.

Methods

The study was a double-blind, placebo-controlled, crossover trial. Thirty-six subjects, 18–60 years of age, were randomized to receive placebo (PL, 0 mg vitamin C), ascorbic acid (AA, 1000 mg vitamin C), and Ester-C^® (EC, 1000 mg vitamin C). Plasma and leukocyte vitamin C were measured baseline and at 2, 4, 8 and 24 h postdose.

Results

The concentration and percent change from baseline in plasma were significantly higher with EC at all time points when compared to PL. No significant differences between EC and AA were observed in plasma concentration. Maximum plasma concentration was higher for EC compared to AA (P = 0.039) and PL (P < 0.001). Plasma area under the curve (AUC_0–24h) was higher for EC (P < 0.001) compared to PL. The concentration change from baseline in leukocyte vitamin C was increased with EC at 24 h post-dose (P = 0.036) while no significant within-group changes were observed in AA or PL at any time point. The percent change in leukocyte vitamin C concentration was higher for EC at 8 and 24 h compared to AA (P = 0.028 and P = 0.034, respectively) and PL (P = 0.042 and P = 0.036, respectively).

Conclusions

A single dose of EC resulted in favorable percent change in leukocyte vitamin C concentration compared to AA and PL, indicating EC is retained longer within leukocytes.

Trial registration ClinicalTrials.gov Identifier NCT01852903

Vitamin C: the known and the unknown and Goldilocks

Vitamin C (Ascorbic Acid), the antiscorbutic vitamin, cannot be synthesized by humans and other primates, and has to be obtained from diet. Ascorbic acid is an electron donor and acts as a cofactor for fifteen mammalian enzymes. Two sodium-dependent transporters are specific for ascorbic acid, and its oxidation product dehydroascorbic acid is transported by glucose transporters. Ascorbic acid is differentially accumulated by most tissues and body fluids. Plasma and tissue vitamin C concentrations are dependent on amount consumed, bioavailability, renal excretion, and utilization. To be biologically meaningful or to be clinically relevant, in vitro and in vivo studies of vitamin C actions have to take into account physiologic concentrations of the vitamin. In this paper, we review vitamin C physiology; the many phenomena involving vitamin C where new knowledge has accrued or where understanding remains limited; raise questions about the vitamin that remain to be answered; and explore lines of investigations that are likely to be fruitful.

Effect of Dietary Vitamin E Supplementation on Liver Oxidative Damage in Rats with Water-Immersion Restraint Stress

We examined how dietary supplementation of vitamin E protects against liver oxidative damage in rats with water-immersion restraint stress (WIRS). Before WIRS exposure, rats received a normal diet (ND) or vitamin E-supplemented diet (VESD) (500 IU α-tocopherol/kg diet) at a mean dose of 15 g/animal/d for 4 wk. The two diet groups had serum transaminases and lactate dehydrogenase activities and adrenocorticotropic hormone, corticosterone, and glucose levels to a similar extent. VESD-fed rats had higher liver α-tocopherol concentrations and lower liver ascorbic acid, total coenzyme Q9 (CoQ9), reduced CoQ9, reduced CoQ10, and lipid peroxide (LPO) concentrations than ND-fed rats. When the two diet groups were exposed to 6 h of WIRS, the serum liver cell damage index enzyme activities increased more greatly in ND-fed rats than in VESD-fed rats but the serum stress marker levels increased to a similar extent. The WIRS exposure caused no change in liver LPO concentration with the further increase in liver α-tocopherol concentration in VESD-fed rats but increased liver LPO concentration without changing liver α-tocopherol concentration in ND-fed rats. Upon the WIRS exposure, liver reduced glutathione concentration decreased with the further decrease in liver ascorbic acid concentration in VESD-fed rats and those concentrations decreased in ND-fed rats. The WIRS exposure recovered the decreased liver total CoQ9 and reduced CoQ9 concentrations in VESD-fed rats but decreased liver total CoQ9, reduced CoQ9, and reduced CoQ10 concentrations in ND-fed rats. These results indicate that dietary vitamin E supplementation protects against liver oxidative damage without affecting the stress response in rats with WIRS.

Ascorbate-dependent vasopressor synthesis: a rationale for vitamin C administration in severe sepsis and septic shock?

Severe systemic inflammatory response to infection results in severe sepsis and septic shock, which are the leading causes of death in critically ill patients. Septic shock is characterised by refractory hypotension and is typically managed by fluid resuscitation and administration of catecholamine vasopressors such as norepinephrine. Vasopressin can also be administered to raise mean arterial pressure or decrease the norepinephrine dose. Endogenous norepinephrine and vasopressin are synthesised by the copper-containing enzymes dopamine β-hydroxylase and peptidylglycine α-amidating monooxygenase, respectively. Both of these enzymes require ascorbate as a cofactor for optimal activity. Patients with severe sepsis present with hypovitaminosis C, and pre-clinical and clinical studies have indicated that administration of high-dose ascorbate decreases the levels of pro-inflammatory biomarkers, attenuates organ dysfunction and improves haemodynamic parameters. It is conceivable that administration of ascorbate to septic patients with hypovitaminosis C could improve endogenous vasopressor synthesis and thus ameliorate the requirement for exogenously administered vasopressors. Ascorbate-dependent vasopressor synthesis represents a currently underexplored biochemical mechanism by which ascorbate could act as an adjuvant therapy for severe sepsis and septic shock.

Vitamin E depletion enhances liver oxidative damage in rats with water-immersion restraint stress

We examined the effect of vitamin E depletion on liver oxidative damage in rats with water-immersion restraint stress (WIRS). Male Wistar rats were fed a normal diet (N) or vitamin E-depleted diet (VE-D) for 4 wk. N- and VE-D-fed rats were exposed to WIRS for 6 h. The activities of serum transaminases and lactate dehydrogenase and serum ascorbic acid concentration were similar in both diet groups. WIRS exposure increased these serum enzyme activities and the serum ascorbic acid concentration in both diet groups but the ratios of these increases were higher in VE-D-fed rats than in N-fed rats. Serum and liver α-tocopherol concentrations in VE-D-rats were approximately 50% and 30% of those in N-fed rats, respectively. WIRS exposure reduced liver α-tocopherol concentration in VE-D-fed rats, but not in N-fed rats. Liver ascorbic acid and reduced glutathione concentrations were higher in the VE-D-fed group than in the N-fed group. WIRS exposure reduced liver ascorbic acid and reduced glutathione concentrations in both diet groups. There were no differences in liver concentrations of coenzyme Q9 or coenzyme Q10 in the reduced form between the N- and VE-D-fed groups. WIRS exposure reduced liver concentrations of coenzyme Q9 and coenzyme Q10 in the reduced form in both diet groups. Liver lipid peroxide concentration was higher in the VE-D-fed group than in the N-fed group. WIRS exposure raised liver lipid peroxide concentration more in the VE-D-fed group than in the N-fed group. These results indicate that vitamin E depletion enhances liver oxidative damage in rats with WIRS.

Effect of dietary antioxidants, training, and performance correlates on antioxidant status in competitive rowers

The beneficial effects of exercise and a healthy diet are well documented in the general population but poorly understood in elite athletes. Previous research in subelite athletes suggests that regular training and an antioxidant-rich diet enhance antioxidant defenses but not performance.

PURPOSE

To investigate whether habitual diet and/or exercise (training status or performance) affect antioxidant status in elite athletes.

METHODS

Antioxidant blood biomarkers were assessed before and after a 30-min ergometer time trial in 28 male and 34 female rowers. The antioxidant blood biomarkers included ascorbic acid, uric acid, total antioxidant capacity (TAC), erythrocyte- superoxide dismutase, glutathione peroxidase (GPx), and catalase. Rowers completed a 7-d food diary and an antioxidant-intake questionnaire. Effects of diet, training, and performance on resting biomarkers were assessed with Pearson correlations, and their effect on exercise-induced changes in blood biomarkers was assessed by a method of standardization.

RESULTS

With the exception of GPx, there were small to moderate increases with exercise for all markers. Blood resting TAC had a small correlation with total antioxidant intake (correlation .29; 90% confidence limits, ±.27), and the exercise-induced change in TAC had a trivial to small association with dietary antioxidant intake from vitamin C (standardized effect .19; ±.22), vegetables (.20; ±.23), and vitamin A (.25; ±.27). Most other dietary intakes had trivial associations with antioxidant biomarkers. Years of training had a small inverse correlation with TAC (-.32; ±.19) and a small association with the exercise-induced change in TAC (.27; ±.24).

CONCLUSION

Training status correlates more strongly with antioxidant status than diet does.

Dynamic expression of the sodium-vitamin C co-transporters, SVCT1 and SVCT2, during perinatal kidney development

Isoform 1 of the sodium-vitamin C co-transporter (SVCT1) is expressed in the apical membrane of proximal tubule epithelial cells in adult human and mouse kidneys. This study is aimed at analyzing the expression and function of SVCTs during kidney development. RT-PCR and immunohistochemical analyses revealed that SVCT1 expression is increased progressively during postnatal kidney development. However, SVCT1 transcripts were barely detected, if not absent, in the embryonic kidney. Instead, the high-affinity transporter, isoform 2 (SVCT2), was strongly expressed in the developing kidney from E15; its expression decreased at postnatal stages. Immunohistochemical analyses showed a dynamic distribution of SVCT2 in epithelial cells during kidney development. In renal cortex tubular epithelial cells, intracellular distribution of SVCT2 was observed at E19 with distribution in the basolateral membrane at P1. In contrast, SVCT2 was localized to the apical and basolateral membranes between E17 and E19 in medullary kidney tubular cells but was distributed intracellularly at P1. In agreement with these findings, functional expression of SVCT2, but not SVCT1 was detected in human embryonic kidney-derived (HEK293) cells. In addition, kinetic analysis suggested that an ascorbate-dependent mechanism accounts for targeted SVCT2 expression in the developing kidney during medullary epithelial cell differentiation. However, during cortical tubular differentiation, SVCT1 was induced and localized to the apical membrane of tubular epithelial cells. SVCT2 showed a basolateral polarization only for the first days of postnatal life. These studies suggest that the uptake of vitamin C mediated by different SVCTs plays differential roles during the ontogeny of kidney tubular epithelial cells.

Water-immersion restraint stress disrupts nonenzymatic antioxidant defense systems through rapid and continuous ascorbic acid depletion in the adrenal gland of rats

We examined whether water-immersion restraint stress (WIRS) disrupts nonenzymatic antioxidant defense systems through ascorbic acid depletion in the adrenal gland of rats. Rats were exposed to WIRS for 0.5, 1.5, 3 or 6 h. WIRS increased serum adrenocorticotropic hormone, corticosterone and glucose concentrations and adrenal corticosterone content at each time point. WIRS increased adrenal lipid peroxide content at 3 and 6 h, and the increase was twofold higher than the unstressed level at 6 h. WIRS decreased adrenal ascorbic acid content at each time point, and the decrease reached one-third of the unstressed level at 6 h. WIRS increased adrenal reduced glutathione content at 0.5 and 6 h but reduced that content to half of the unstressed level at 6 h. WIRS increased adrenal α-tocopherol content at 1.5 h but returned that content to the unstressed level thereafter. When rats with 6 h of WIRS was orally preadministered with l-ascorbic acid (250 mg/kg), WIRS-induced changes in adrenal lipid peroxide, ascorbic acid and reduced glutathione contents were attenuated without any change in stress response. These results indicate that WIRS disrupts nonenzymatic antioxidant defense systems through rapid and continuous ascorbic acid depletion in the adrenal gland of rats.

Scurvy: historically a plague of the sailor that remains a consideration in the modern intensive care unit

We report the case of the case of a 56 year old female with sepsis on a background of rheumatoid arthritis and steroid use manifesting with overt clinical features of scurvy. Ascorbic acid assays were able to demonstrate severe deficiency and confirm a diagnosis of scurvy. Clinical resolution of signs and symptoms following commencement of vitamin C replacement was rapid. The intensivist and dietitian need to consider this diagnosis even in the first world setting, particularly in the presence of sepsis, inflammatory conditions, steroid use and importantly malnutrition.

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

Ascorbate (vitamin C) is a vital antioxidant molecule in the brain. However, it also has a number of other important functions, participating as a cofactor in several enzyme reactions, including catecholamine synthesis, collagen production, and regulation of HIF-1 alpha. Ascorbate is transported into the brain and neurons via the sodium-dependent vitamin C transporter 2 (SVCT2), which causes accumulation of ascorbate within cells against a concentration gradient. Dehydroascorbic acid, the oxidized form of ascorbate, is transported via glucose transporters of the GLUT family. Once in cells, it is rapidly reduced to ascorbate. The highest concentrations of ascorbate in the body are found in the brain and in neuroendocrine tissues such as adrenal, although the brain is the most difficult organ to deplete of ascorbate. Combined with regional asymmetry in ascorbate distribution within different brain areas, these facts suggest an important role for ascorbate in the brain. Ascorbate is proposed as a neuromodulator of glutamatergic, dopaminergic, cholinergic, and GABAergic transmission and related behaviors. Neurodegenerative diseases typically involve high levels of oxidative stress and thus ascorbate has been posited to have potential therapeutic roles against ischemic stroke, Alzheimer's disease, Parkinson's disease, and Huntington's disease.

Mechanisms and regulation of vitamin C uptake: studies of the hSVCT systems in human liver epithelial cells

Humans use two sodium-ascorbate cotransporters (hSVCT1 and hSVCT2) for transporting the dietary essential micronutrient ascorbic acid, the reduced and active form of vitamin C. Although the human liver plays a pivotal role in regulating and maintaining vitamin C homeostasis, vitamin C transport physiology and regulation of the hSVCT systems in this organ have not been well defined. Thus, this research used a human hepatic cell line (HepG2), confirming certain results with primary human hepatocytes and determined the initial rate of ascorbic acid uptake to be Na(+) gradient, pH dependent, and saturable as a function of concentration over low and high micromolar ranges. Additionally, hSVCT2 protein and mRNA are expressed at higher levels in HepG2 cells and native human liver, and the cloned hSVCT2 promoter has more activity in HepG2 cells. Results using short interfering RNA suggest that in HepG2 cells, decreasing hSVCT2 message levels reduces the overall ascorbic acid uptake process more than decreasing hSVCT1 message levels. Activation of PKC intracellular regulatory pathways caused a downregulation in ascorbic acid uptake not mediated by a single predicted PKC-specific amino acid phosphorylation site in hSVCT1 or hSVCT2. However, PKC activation causes internalization of hSVCT1 but not hSVCT2. Examination of other intracellular regulatory pathways on ascorbic acid uptake determined that regulation also potentially occurs by PKA, PTK, and Ca(2+)/calmodulin, but not by nitric oxide-dependent pathways. These studies are the first to determine the overall ascorbic acid uptake process and relative expression, regulation, and contribution of the hSVCT systems in human liver epithelial cells.

Vitamin C metabolites, independent of smoking status, significantly enhance leukocyte, but not plasma ascorbate concentrations

INTRODUCTION

The objective of this study was to test the effects of acute doses of vitamin C alone, calcium ascorbate with vitamin C metabolites, and placebo, on total plasma and leukocyte vitamin C concentrations over 24 hours.

METHODS

A double-blind, placebo-controlled, four-way crossover study was performed consisting of four separate phases lasting 24 hours each and utilizing one of four oral 1000-mg preparations within each phase (one of vitamin C alone, two separate vitamin C formulations of calcium ascorbate with vitamin C metabolites, and placebo). There was a 7-day washout between phases, and blood draws at seven time points within each phase of the study for a total of 28 serologic measurements per subject and 420 total measurements for the entire clinical trial. Vitamin C concentration in plasma and leukocytes were measured by high-performance liquid chromatography at baseline and at six sequential time periods over 24 hours.

RESULTS

Fifteen healthy males were enrolled, aged 18-39 years; nine were had never smoked and six were chronic smokers. No significant difference in plasma vitamin C levels was observed when comparing the different preparations. However, at 24 hours, calcium ascorbate with metabolites resulted in significantly higher concentrations of vitamin C in leukocytes (P<0.0001) compared with vitamin C alone. These results were similar for both metabolite formulations, and independent of smoking status.

CONCLUSION

Regardless of smoking status, vitamin C metabolites may enhance leukocyte utilization of vitamin C itself, despite no consistent difference in plasma levels among the different preparations. A larger clinical investigation is warranted to confirm these preliminary findings, and to determine the clinical relevance of this impact on overall immune function.