Gender and sodium-ascorbate transporter isoforms determine ascorbate concentrations in mice

Vitamin C Deficiency Deteriorates Bone Microarchitecture and Mineralization in a Sex-Specific Manner in Adult Mice

Vitamin C (VitC) is essential for bone health, and low VitC serum levels increase the risk for skeletal fractures. If and how VitC affects bone mineralization is unclear. Using micro-computed tomography (μCT), histologic staining, as well as quantitative backscattered electron imaging (qBEI), we assessed the effects of VitC on femoral structure and microarchitecture, bone formation, and bone mineralization density distribution (BMDD) in the VitC incompetent Gulo-/- mouse model and wild-type mice. In particular, VitC-supplemented, 20-week-old mice were compared with age-matched counterparts where dietary VitC intake was excluded from week 15. VitC depletion in Gulo-/- mice severely reduced cortical thickness of the diaphyseal shaft and bone volume around the growth plate (eg, bone volume of the primary spongiosa -43%, p < 0.001). Loss of VitC also diminished the amount of newly formed bone tissue as visualized by histology and calcein labeling of the active mineralization front. BMDD analysis revealed a shift to higher calcium concentrations upon VitC supplementation, including higher average (~10% increase in female VitC deficient mice, p < 0.001) and peak calcium concentrations in the epiphyseal and metaphyseal spongiosa. These findings suggest higher bone tissue age. Importantly, loss of VitC had significantly more pronounced effects in female mice, indicating a higher sensitivity of their skeleton to VitC deficiency. Our results reveal that VitC plays a key role in bone formation rate, which directly affects mineralization. We propose that low VitC levels may contribute to the higher prevalence of bone-degenerative diseases in females and suggest leveraging this vitamin against these conditions. © 2023 American Society for Bone and Mineral Research (ASBMR).

Curcumin inhibits human cancer cell growth and migration through downregulation of SVCT2

Curcumin is a natural polyphenol that is extracted from the rhizomes of the turmeric plant (Curcuma longa), a member of the ginger family. It has been used for centuries in traditional Indian and Chinese medicine for its medicinal properties, including anti-inflammatory, antioxidant and antitumor effects. SVCT2 (Solute Carrier Family 23 Member 2, also known as SLC23A2) is a protein that plays a role in the transport of Vitamin C (Ascorbic Acid) into cells. SVCT2 plays an important role in tumor progression and metastasis, however, the molecular mechanisms of curcumin on SVCT2 have not been studied to date. Curcumin treatment inhibited proliferation and migration of cancer cells in a dose dependent manner. We found that curcumin reduced the expression of SVCT2 in cancer cells with a wild type p53, but not in those with a mutant type of p53. SVCT2 downregulation also reduced the MMP2 activity. Taken together, our results indicate that curcumin inhibited human cancer cell growth and migration by regulating SVCT2 through a downregulating p53. These findings provide new insights into the molecular mechanisms of curcumin's anticancer effects and potential therapeutic strategies for the treatment of metastatic migration.

Ascorbic acid is associated with favourable hormonal profiles among infertile males

Introduction

Infertility affects about 16% of North American couples, with the male factor contributing to ∼30% of cases. Reproductive hormones play an integral role in regulating the reproductive system and consequently, fertility. Oxidative stress reduces testosterone synthesis, and reduction in oxidative stress can improve hormone profiles. Ascorbic acid is a potent antioxidant that accounts for up to 65% of seminal antioxidant activity; however, its effects on reproductive hormones in humans are unknown.

Methods

The objective was to determine the association between serum ascorbic acid concentrations and male reproductive hormones. We conducted a cross-sectional study involving infertile males (n = 302) recruited from Mount Sinai Hospital, Toronto. Serum was analyzed for ascorbic acid, luteinizing hormone (LH), follicular stimulating hormone (FSH), total testosterone (TT), prolactin and estradiol. Statistical analyses included Spearman's rank correlations, linear regressions, logistic regressions, simple slope and Johnson-Neyman procedures.

Results

After adjusting for covariates, ascorbic acid was inversely associated with LH (P = 0.01). Ascorbic acid was positively associated with TT only among males over the age of 41.6 years (P = 0.01).

Discussion

Our findings show that ascorbic acid is associated with higher testosterone levels and improved androgenic status in infertile males, and some of the effects appear to be age dependent.

Cell signaling pathways based on vitamin C and their application in cancer therapy

Vitamin C, a small organic molecule, is widely found in fruits and vegetables and is an essential nutrient in the human body. Vitamin C is closely associated with some human diseases such as cancer. Many studies have shown that high doses of vitamin C have anti-tumor ability and can target tumor cells in multiple targets. This review will describe vitamin C absorption and its function in cancer treatment. We will review the cellular signaling pathways associated with vitamin C against tumors depending on the different anti-cancer mechanisms. Based on this, we will further describe some applications of the use of vitamin C for cancer treatment in preclinical and clinical trials and the possible adverse events that can occur. Finally, this review also assesses the prospective advantages of vitamin C in oncology treatment and clinical applications.

SVCT2-mediated ascorbic acid uptake buffers stress responses via DNA hydroxymethylation reprogramming of S100 calcium-binding protein A4 gene

Vitamin C, a key antioxidant in the central nervous system, cycles between ascorbic acid and dehydroascorbic acid under pathophysiological conditions. Clinical evidence supports that the absence of vitamin C may be linked to depressive symptoms, but much less is known about the mechanism. Herein, we show that chronic stress disrupts the expression of ascorbic acid transporter, sodium-dependent vitamin C transport 2, and induces a deficiency in endogenous ascorbic acid in the medial prefrontal cortex, leading to depressive-like behaviors by disturbing redox-dependent DNA methylation reprogramming. Attractively, ascorbic acid (100 mg/kg-1000 mg/kg, intraperitoneal injection, as bioequivalent of an intravenous drip dose of 0.48 g-4.8 g ascorbic acid per day in humans) produces rapid-acting antidepressant effects via triggering DNA demethylation catalyzed by ten-eleven translocation dioxygenases. In particular, the mechanistic studies by both transcriptome sequencing and methylation sequencing have shown that S100 calcium binding protein A4, a potentially protective factor against oxidative stress and brain injury, mediates the antidepressant activity of ascorbic acid via activating erb-b2 receptor tyrosine kinase 4 (ErbB4)-brain derived neurotrophic factor (BDNF) signaling pathway. Overall, our findings reveal a novel nutritional mechanism that couples stress to aberrant DNA methylation underlying depressive-like behaviors. Therefore, application of vitamin C may be a potential strategy for the treatment of depression.

Vitamin C modulates the levels of several proteins of the mitochondrial complex III and its activity in the mouse liver

Ascorbate is a crucial antioxidant and essential cofactor of biosynthetic and regulatory enzymes. Unlike humans, mice can synthesize ascorbate thanks to the key enzyme gulonolactone oxidase (Gulo). In the present study, we used the Gulo-/- mouse model, which cannot synthesize their own ascorbate to determine the impact of this vitamin on the liver proteome of specific subcellular organelles. We performed label-free Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) global quantitative proteomic profiling to identify and quantify proteins in microsomal enriched liver extracts (MEE) from Gulo-/- mice treated with 0-0.4% (w/v) ascorbate in drinking water until the age of four months. Using a principal component analysis on normalized and imputed data of the label-free protein quantifications, a sex-based difference in MEE proteome profiles was observed for all the different ascorbate treated mice. Suboptimal hepatic ascorbate concentrations affected the levels of more proteins and hence biochemical processes in females than in males. Nevertheless, Pearson correlation analyses revealed that the MS intensities of various proteins involved in complement activation inversely correlated with liver ascorbate concentrations in both Gulo-/- males and females. Moreover, the correlation analyses also indicated that several proteins in the mitochondrial complex III of the electron transport chain positively correlated with liver ascorbate concentrations in both Gulo-/- females and males. Consequently, the mitochondrial complex III activity in Gulo-/- female and male mice treated with suboptimal hepatic concentrations of ascorbate was significantly lower than Gulo-/- mice treated with optimal ascorbate concentration. Finally, the whole liver of ascorbate-deficient Gulo-/- mice exhibited lower ATP levels and increased reactive oxygen species. These findings provide new information on how ascorbate deficiency potentially induces mitochondrial dysfunction in the liver of mice.

Advances in Novel Animal Vitamin C Biosynthesis Pathways and the Role of Prokaryote-Based Inferences to Understand Their Origin

Vitamin C (VC) is an essential nutrient required for the optimal function and development of many organisms. VC has been studied for many decades, and still today, the characterization of its functions is a dynamic scientific field, mainly because of its commercial and therapeutic applications. In this review, we discuss, in a comparative way, the increasing evidence for alternative VC synthesis pathways in insects and nematodes, and the potential of myo-inositol as a possible substrate for this metabolic process in metazoans. Methodological approaches that may be useful for the future characterization of the VC synthesis pathways of Caenorhabditis elegans and Drosophila melanogaster are here discussed. We also summarize the current distribution of the eukaryote aldonolactone oxidoreductases gene lineages, while highlighting the added value of studies on prokaryote species that are likely able to synthesize VC for both the characterization of novel VC synthesis pathways and inferences on the complex evolutionary history of such pathways. Such work may help improve the industrial production of VC.

Effects of the In Ovo and Dietary Supplementation of L-Ascorbic Acid on the Growth Performance, Inflammatory Response, and Eye L-Ascorbic Acid Concentrations in Ross 708 Broiler Chickens

Simple Summary

L-ascorbic acid (L-AA), known as vitamin C, is involved in several metabolic process, including bone formation, antioxidant activity, and inflammatory response. It is well documented that the antioxidant capacity and immunity of broilers are enhanced in response to the dietary or in ovo administration of L-AA. The aim of the current study was to determine the effects the in ovo or dietary administration of L-AA on the post hatch performance, plasma nitric oxide, and eye L-AA concentrations of Ross 708 broilers. At 17 days of incubation, the following treatments were administered: non-injected or sham-injected (100 μL of saline) controls, or the injection of either 12 or 25 mg of L-AA suspended in 100 μL of saline. In addition, chicks were fed a commercial diet with or without 200 mg/kg of supplemental L-AA. The results of the current study revealed that the eye concentrations of L-AA were higher in males in comparison to females. Additionally, 12 mg of L-AA decreased plasma nitric oxide levels in 14-day-old male broilers in comparison to all the other in ovo injection treatment groups. Compared to a commercial diet, dietary L-AA lowered feed conversion ratio during the second week of post hatch growth. In conclusion, the in ovo administration of L-AA was more effective in reducing inflammatory response, whereas the dietary source had a greater impact on the live performance of broilers. Further research is needed to determine the aforementioned effects throughout the entire growing phase.

Abstract

Effects of the dietary and in ovo administration of L-ascorbic acid (L-AA) on the performance, plasma nitric oxide, and eye L-AA concentrations of Ross 708 broilers were investigated. At 17 days of incubation, live embryonated hatching eggs were randomly assigned to a non-injected or sham-injected (100 μL of saline) control group, or a group injected with either 12 or 25 mg of L-AA suspended in 100 μL of saline. Chicks received a commercial diet with or without 200 mg/kg of supplemental L-AA and were randomly assigned to each of 6 replicate floor pens in each in ovo injection-dietary treatment combination. Weekly live performance variables through 14 days of post hatch age (doa) and the eye weights in both sexes at 0, 7, and 14 doa were determined. At 0 and 14 doa, plasma nitric oxide levels and eye L-AA concentrations of one bird of each sex in each pen were determined. Dietary supplemental L-AA decreased feed intake and growth between 0 and 7 doa, but from 8 to 14 doa; all birds fed supplemental L-AA had a lower feed conversion ratio. At 14 doa, male chicks had higher eye L-AA concentrations and lower plasma nitric oxide levels when treated in ovo with 12 mg of L-AA. In conclusion, dietary L-AA may be used to improve feed conversion in the second week of broiler post hatch growth. However, the in ovo administration of 12 mg of L-AA can increase male eye L-AA concentrations and is effective in reducing their general inflammatory response.

Identification of an exporter that regulates vitamin C supply from blood to the brain

Vitamin C (VC) distribution in our body requires VC transporters. However, mammalian VC exporters are yet to be identified. Herein, to unravel this long-standing mystery, we focused on the pathways whereby VC moves from blood to the brain, which should require a VC entrance and exit system composed of an importer and a latent exporter. Via cell-based transport analyses of VC efflux and using knockout mice generated via the CRISPR-Cas9 system, we identified GLUT12/SLC2A12 as a physiologically important VC efflux protein expressed in the choroid plexus; Glut12/Slc2a12 knockout halved the cerebral VC levels, markedly increased VC accumulation in the choroid plexus, and reduced the cerebrospinal fluid VC levels. These findings facilitate our understanding of VC regulation and the physiological impact of VC in our body.

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A long-standing mystery in vitamin C handling in mammalians was uncovered

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GLUT12 was identified as a physiologically important vitamin C efflux protein—VCEP

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GLUT12 is expressed in the choroid plexus and acts as a vitamin C exporter

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Glut12 knockout halved the cerebral vitamin C levels in mice

Dietary Vitamin C and Age-Induced Lipid and Hormonal Metabolic Changes in a Humanized Mouse Model Not Synthesizing Vitamin C and Producing Lipoprotein(a) [Gulo (-/-); Lp(a)+]

The lack of ability to produce vitamin C innately and the ability to synthesize human lipoprotein(a) (Lp(a)) are two unique metabolic features present in humans, compared with most other animal species. The Gulo (-/-) and Lp(a)+ mouse model displays these two features and is therefore suitable for the study of metabolic aspects relevant to human metabolism. It is a well-known fact that vitamin C is essential in collagen synthesis, and in maintaining extracellular matrix integrity, as well as being a powerful antioxidant and cofactor in many metabolic pathways, which makes it a critically important micronutrient for health and healthy aging. In this study, we investigated the effects of a long-term intake of high and low doses of vitamin C on age-related metabolic lipid and hormonal changes in young (eight to nine months), mid-aged (one year), and old (two years) Gulo (-/-) and Lp(a)+ mice. We observed that chronic vitamin C deficiency resulted in a less healthy metabolic lipid profile, impaired serum insulin-like growth factor (IGF-1), and sex-hormones secretion, all of which can accelerate the development of various pathological conditions in the aging process. The most susceptible to the negative impact of vitamin C deficiency were the young (eight to nine months) and old (two years) mice. Our study conducted in this humanized mouse model indicates that sustained adequate vitamin C intake is essential in maintaining a healthier metabolic profile, important in preventing age-related pathologies throughout the aging process.

Oral consumption of α-glucosyl-hesperidin could prevent lens hardening, which causes presbyopia

Presbyopia is one of the most well-known diseases of the eye, predominantly affecting the adult population after 50 years’. Due to hardening of the lens and failure of accommodative change, patients lose the ability to focus on near objects. This eye symptom is reported to be an early symptom of age-related nuclear cataract, and we have previously reported that hesperetin treatment could delay the onset of nuclear cataractogenesis induced by sodium selenite. In this study, we examined whether oral intake of α-glucosyl-hesperidin (G-Hsd), which has greater water solubility than hesperetin, could delay the onset of presbyopia. G-Hsd treatment protected lens elasticity, upregulated the mRNA expression of anti-oxidative enzymes like glutathione reductase and thioredoxin reductase 1 in the plasma and lens, and prevented premature cataract symptoms in selenite-induced cataract rat lens. Thus, the anti-presbyopic effects of G-Hsd were attributed, at least in part, to its antioxidant effects. G-Hsd represents the first oral treatment agent with anti-presbyopia and/or anti-cataract properties.

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G-Hsd prevents presbyopia by inhibiting aging-induced lens hardening.

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It reduces aging-induced oxidative stress in the lens and plasma.

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It ameliorates cataract development by preventing sclerosis of the eye.

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G-Hsd is the first oral supplement with anti-cataract and anti-presbyopia effects.

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

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

Dietary or supplemental fermentable fiber intake reduces the presence of Clostridium XI in mouse intestinal microbiota: The importance of higher fecal bacterial load and density

OBJECTIVES

Clostridium difficile infection is a public health concern. C. difficile was found in healthy human intestine as a member of Clostridium XI. Because soluble fermentable fiber ingestion affects intestinal microbiota, we used fiber-containing diets to determine the intestinal microbial condition that could reduce the presence of Clostridium XI.

METHODS

Newly weaned male mice were assigned to three published diets: Control AIN-93G purified diet with only poorly fermented cellulose; Control plus 5% purified fermentable fiber inulin; Chow with wheat, soybean and corn that provide a mixture of unpurified dietary fibers. Methods were developed to quantify 24-hour fecal microbial load and microbial DNA density. The relative abundance of bacterial genera and the bacterial diversity were determined through 16S rRNA sequence-based fecal microbiota analysis.

RESULTS

Mice adjusted food intake to maintain the same energy intake and body weight under these three moderate-fat (7% w:w) diets. Chow-feeding led to higher food intake but also higher 24-h fecal output. Chow-feeding and 1-8 wk ingestion of inulin-supplemented diet increased daily fecal microbial load and density along with lowering the prevalence of Clostridium XI to undetectable. Clostridium XI remained undetectable until 4 weeks after the termination of inulin-supplemented diet. Fermentable fiber intake did not consistently increase probiotic genera such as Bifidobacterium or Lactobacillus. Chow feeding, but not inulin supplementation, increased the bacterial diversity.

CONCLUSIONS

Increase fecal microbial load/density upon fermentable fiber ingestion is associated with a lower and eventually undetectable presence of Clostridium XI. Higher bacterial diversity or abundance of particular genera is not apparently essential. Future studies are needed to see whether this observation can be translated into the reduction of C. difficile at the species level in at-risk populations.

Vitamin C preferentially kills cancer stem cells in hepatocellular carcinoma via SVCT-2

Vitamin C (L-ascorbic acid, ascorbate, VC) is a potential chemotherapeutic agent for cancer patients. However, the anti-tumor effects of pharmacologic VC on hepatocellular carcinoma (HCC) and liver cancer stem cells (CSCs) remain to be fully elucidated. Panels of human HCC cell lines as well as HCC patient-derived xenograft (PDX) models were employed to investigate the anti-tumor effects of pharmacologic VC. The use of VC and the risk of HCC recurrence were examined retrospectively in 613 HCC patients who received curative liver resection as their initial treatment. In vitro and in vivo experiments further demonstrated that clinically achievable concentrations of VC induced cell death in liver cancer cells and the response to VC was correlated with sodium-dependent vitamin C transporter 2 (SVCT-2) expressions. Mechanistically, VC uptake via SVCT-2 increased intracellular ROS, and subsequently caused DNA damage and ATP depletion, leading to cell cycle arrest and apoptosis. Most importantly, SVCT-2 was highly expressed in liver CSCs, which promoted their self-renewal and rendered them more sensitive to VC. In HCC cell lines xenograft models, as well as in PDX models, VC dramatically impaired tumor growth and eradicated liver CSCs. Finally, retrospective cohort study showed that intravenous VC use was linked to improved disease-free survival (DFS) in HCC patients (adjusted HR = 0.622, 95% CI 0.487 to 0.795, p < 0.001). Our data highlight that pharmacologic VC can effectively kill liver cancer cells and preferentially eradicate liver CSCs, which provide further evidence supporting VC as a novel therapeutic strategy for HCC treatment.

Pharmacologic doses of vitamin C preferentially eradicate liver cancer stem cells and are associated with improved outcomes in patients. A team led by Hong-Yang Wang and Wen Yang from the Second Military Medical University in Shanghai, China, showed that clinically achievable concentrations of vitamin C effectively killed liver cancer cells and preferentially eradicated cancer stem cells in culture and in mouse transplant models. Cells with higher expression levels of a vitamin C transporter protein were more susceptible to the treatment, which explains why cancer stem cells, which highly express this transportor and use it for their own self-renewal, were especially sensitive to take in vitamin C, which led to a cascade that resulted in DNA damage, energy depletion, and ultimately cell death. A retrospective analysis of 613 patients with liver cancer showed that those who received intravenous vitamin C lived longer without disease relapse.

Sex Differences in Human and Animal Toxicology

Sex, the states of being female or male, potentially interacts with all xenobiotic exposures, both inadvertent and deliberate, and influences their toxicokinetics (TK), toxicodynamics, and outcomes. Sex differences occur in behavior, exposure, anatomy, physiology, biochemistry, and genetics, accounting for female-male differences in responses to environmental chemicals, diet, and pharmaceuticals, including adverse drug reactions (ADRs). Often viewed as an annoying confounder, researchers have studied only one sex, adjusted for sex, or ignored it. Occupational epidemiology, the basis for understanding many toxic effects in humans, usually excluded women. Likewise, Food and Drug Administration rules excluded women of childbearing age from drug studies for many years. Aside from sex-specific organs, sex differences and sex × age interactions occur for a wide range of disease states as well as hormone-influenced conditions and drug distribution. Women have more ADRs than men; the classic sex hormone paradigm (gonadectomy and replacement) reveals significant interaction of sex and TK including absorption, distribution, metabolisms, and elimination. Studies should be designed to detect sex differences, describe the mechanisms, and interpret these in a broad social, clinical, and evolutionary context with phenomena that do not differ. Sex matters, but how much of a difference is needed to matter remains challenging.

Gender Difference in Bacteria Endotoxin-Induced Inflammatory and Anorexic Responses

Inflammation-related anorexic response has been observed in systemic diseases as well as in localized infection and is an important issue in patient care. We tested the hypothesis that upon the same endotoxin exposure, males have more severe inflammatory responses and thus suffer from more negative effect on appetite. Ten-week old male and female mice were compared in their plasma levels of pro-inflammatory cytokines after a body weight-based i.p. injection of bacterial endotoxin lipopolysaccharide. Male mice consistently showed significantly higher levels of IL6 and TNFα than female mice. The difference was observed starting at 3 hours after the systemic endotoxin exposure. It was independent of the level of endotoxin dosage and of the genotype of the anti-inflammatory cytokine, IL10. Interestingly, endotoxin-injected male mice also had significantly higher plasma IL10 levels compared to the female mice. Pre-puberty young mice showed no gender differences in the plasma levels of IL6, TNFα and IL10. Their cytokine levels were mostly between that of the adult males and females. Consistent with the higher inflammatory response in male mice, the endotoxin exposure also led to significantly more appetite loss in male mice at a range of doses in two strains of mice. Saline injection in the absence of endotoxin affected neither the cytokine levels nor the appetite. Although a direct mechanistic link between inflammation parameters and appetite was not addressed here, the results support that male gender could be a risk factor for higher pro-inflammatory cytokines and anorexic response after the endotoxin exposure.

MicroRNAs-141 and 200a regulate the SVCT2 transporter in bone marrow stromal cells

Vitamin C is a micro-nutrient which plays an important role in bone marrow stromal cell (BMSCs) differentiation to osteogenesis. This vitamin is transported into the BMSCs through the sodium dependent vitamin C transporter 2 (SVCT2). We previously reported that knockdown of the SVCT2 transporter decreases osteogenic differentiation. However, our understanding of the post-transcriptional regulatory mechanism of the SVCT2 transporter remains poor. MicroRNAs (miRNAs) are small non-coding RNAs that post-transcriptionally regulate the messenger RNAs of protein-coding genes. In this study, we aimed to investigate the impact of miR-141 and miR-200a on SVCT2 expression. We found that mouse BMSCs expressed miR-141 and miR-200a and repressed SVCT2 expression at the functional level by targeting the 3'-untranslated region of mRNA. We also found that miR-141 and miR-200a decreased osteogenic differentiation. Furthermore, miRNA inhibitors increased SVCT2 and osteogenic gene expression in BMSCs. Taken together, these results indicate that both miRNAs are novel regulators of the SVCT2 transporter and play an important role in the osteogenic differentiation of BMSCs.

Need for gender-specific pre-analytical testing: the dark side of the moon in laboratory testing

Many international organisations encourage studies in a sex-gender perspective. However, research with a gender perspective presents a high degree of complexity, and the inclusion of sex-gender variable in experiments presents many methodological questions, the majority of which are still neglected. Overcoming these issues is fundamental to avoid erroneous results. Here, pre-analytical aspects of the research, such as study design, choice of utilised specimens, sample collection and processing, animal models of diseases, and the observer's role, are discussed. Artefacts in this stage of research could affect the predictive value of all analyses. Furthermore, the standardisation of research subjects according to their lifestyles and, if female, to their life phase and menses or oestrous cycle, is urgent to harmonise research worldwide. A sex-gender-specific attention to pre-analytical aspects could produce a decrease in the time for translation from the bench to bedside. Furthermore, sex-gender-specific pre-clinical pharmacological testing will enable adequate assessment of pharmacokinetic and pharmacodynamic actions of drugs and will enable, where appropriate, an adequate gender-specific clinical development plan. Therefore, sex-gender-specific pre-clinical research will increase the gender equity of care and will produce more evidence-based medicine.

Genome wide analysis of sex difference in gene expression profiles of bone formations using sfx mice and BXD RI strains

The objective of this study is to identify sex differentially expressed genes in bone using a mouse model of spontaneous fracture, sfx, which lacks the gene for L-gulonolactone oxidase (Gulo), a key enzyme in the ascorbic acid (AA) synthesis pathway. We first identified the genes that are differentially expressed in the femur between female and male in sfx mice. We then analyzed the potential gene network among those differentially expressed genes with whole genome expression profiles generated using spleens of female and male mice of a total of 67 BXD (C57BL/6J X DBA/2J) recombinant inbred (RI) and other strains. Our result indicated that there was a sex difference in the whole genome profiles in sfx mice as measured by the proportion of up- and downregulated genes. Several genes in the pathway of bone development are differentially expressed between the male and female of sfx mice. Comparison of gene network of up- and downregulated bone relevant genes also suggests a sex difference.

Wild-type and IL10-null mice have differential colonic epithelial gene expression responses to dietary supplementation with synbiotic Bifidobacterium animalis subspecies lactis and inulin

Prebiotic plus probiotic (synbiotic) supplementations promote fermentation and have shown anti-inflammatory activity in colonic epithelium. However, in many instances, patients with inflammatory bowel disease (IBD) have demonstrated adverse effects after prebiotic supplementation at a dose well tolerated by normal individuals. To test the hypothesis that the host inflammation affects the colonic epithelial response to increased fermentation, the gene expression of colonic epithelium was analyzed. In a 1-way experimental design to test the effect of supplements in wild-type mice using the standard diet formulated by the American Institute of Nutrition (AIN-93G) as the control diet, fermentable fiber inulin (5%) in the absence or presence of the probiotic Bifidobacterium animalis subspecies lactis (Bb12) (10(8) CFU/kg diet) showed limited effects on gene expression as determined by whole-genome microarray. Bb12 supplementation alone was known not to increase fermentation and here instead significantly upregulated genes in nucleic acid metabolic processes. The effects of the synbiotic diet were then determined in mice exposed to LPS-induced inflammation in a 2-way experimental design testing the effect of diet and LPS. The microarray and quantitative reverse transcription-polymerase chain reaction analyses on the wild-type mice revealed that LPS-induced changes in the colonic epithelium were 4- to 10-fold less in the synbiotic diet group compared with the control diet group. Unlike the wild-type mice, anti-inflammatory cytokine interleukin 10 (IL10)-null mice (susceptible to IBD) given the synbiotic diet, compared with those given the control diet, had 3- to 40-fold increased expression of inflammation-related genes such as Cxcl1 (chemokine C-X-C motif ligand 1) and S100a9 (S100 calcium binding protein A9) in the absence and presence of LPS exposure. These contrasting intestinal epithelial responses to increased fermentation in wild-type and IL10-null mice are similar to the difference between healthy human individuals and those with IBD, suggesting that the host disease/genetic background should be considered before prebiotic/probiotic supplementation.

A comparative study of renal function in male and female spiny mice - sex specific responses to a high salt challenge

Background

There is a significant body of evidence to suggest that hormone levels, receptor density and structural differences between males and females can significantly alter renal hemodynamics. We compared the renal hemodynamic and excretory profile of female and male spiny mice under baseline conditions and in response to a high-NaCl diet.

Methods

Adult male and female spiny mice were fed either a normal or high salt diet for 7 days. Renal excretory profile was obtained from 24 h urine samples, and renal hemodynamic measurements using anaesthetised renal clearance techniques. Kidneys were excised, weighed and frozen for qPCR analysis.

Results

Under basal conditions, conscious and anaesthetised renal functions were similar between male and female spiny mice when adjusted for body weights. Male and female spiny mice on the high-NaCl diet had significantly greater GFR than sex matched controls (P_DIET < 0.001). However the magnitude of the effect of salt was sex dependent (P_SEX < 0.001; P_INT < 0.01). Male spiny mice showed a greater increase in GFR (84% higher than normal salt males) compared to females (33% higher than normal salt females), despite similar increases in renal plasma flow. In response to 7 days of high salt diet, female spiny mice showed a greater increase in 24-hour water consumption (45% more) and urinary output (50% more) compared to males (P_INT < 0.01). These sex differences could not be explained by differences in renal expression of the V2R or AQP3 channel.

Conclusion

These studies have identified major differences between male and female spiny mice in their renal response to a high-NaCl load suggesting that renal hemodynamics may be differentially regulated for the sexes.

Gene expression profiles of sodium-dependent vitamin C transporters in mice after alcohol consumption

Alcoholic liver disease (ALD) is a serious liver problem in western countries. Our previous study has demonstrated that vitamin C plays a protective role in ALD. The vitamin C homeostasis is tightly regulated by sodium-dependent vitamin C transporters (SVCTs) 1 and 2. But the role of two SVCTs in ALD is less understood. In this study, we examined the expression patterns of two SVCTs in mice after alcohol consumption. Our results suggested that alcohol consumption obviously increased the expression of two SVCTs in liver and SVCT1 in kidney and intestine, which is important for vitamin C absorption. Vitamin C supplement increased the sera vitamin C content and ameliorated the symptom of ALD. Intestinal absorption and renal re-absorption mediated by SVCT1 are key factors to increase the sera vitamin C content after alcohol consumption. We proposed that both reactive oxygen species and low vitamin C concentration regulate the expression of SVCTs, and the protective role of vitamin C is mediated by suppressing the stability of hypoxia-inducible factor-1α. Thus, our study is significant for the understanding of vitamin C homeostasis in ALD and for better use of other antioxidants in ALD therapy.

Regulation of vitamin C transporter in the type 1 diabetic mouse bone and bone marrow

A number of studies have revealed that Type I diabetes (T1D) is associated with bone loss and an increased risk of fractures. T1D induces oxidative stress in various tissues and organs. Vitamin C plays an important role in the attenuation of oxidative stress; however, little is known about the effect of T1D induced oxidative stress on the regulation of vitamin C transporter in bone and bone marrow cells. To investigate this, T1D was induced in mice by multiple low dose injections of streptozotocin. We have demonstrated that endogenous antioxidants, glutathione peroxidase (GPx) and superoxide dismutase (SOD) are down-regulated in the bone and bone marrow of T1D. The vitamin C transporter isoform SVCT2, the only known transporter expressed in bone and bone marrow stromal cells (BMSCs), is negatively regulated in the bone and bone marrow of T1D. The μCT imaging of the bone showed significantly lower bone quality in the 8 week T1D mouse. The in-vitro study in BMSCS showed that the knockdown of SVCT2 transporter decreases ascorbic acid (AA) uptake, and increases oxidative stress. The significant reversing effect of antioxidant vitamin C is only possible in control cells, not in knockdown cells. This study suggested that T1D induces oxidative stress and decreases SVCT2 expression in the bone and bone marrow environment. Furthermore, this study confirms that T1D increases bone resorption, decreases bone formation and changes the microstructure of bones. This study has provided evidence that the regulation of the SVCT2 transporter plays an important role not only in T1D osteoporosis but also in other oxidative stress-related musculoskeletal complications.

Regulation of vitamin C homeostasis during deficiency

Large cross-sectional population studies confirm that vitamin C deficiency is common in humans, affecting 5%–10% of adults in the industrialized world. Moreover, significant associations between poor vitamin C status and increased morbidity and mortality have consistently been observed. However, the absorption, distribution and elimination kinetics of vitamin C in vivo are highly complex, due to dose-dependent non-linearity, and the specific regulatory mechanisms are not fully understood. Particularly, little is known about how adaptive mechanisms during states of deficiency affect the overall regulation of vitamin C transport in the body. This review discusses mechanisms of vitamin C transport and potential means of regulation with special emphasis on capacity and functional properties, such as differences in the K_m of vitamin C transporters in different target tissues, in some instances demonstrating a tissue-specific distribution.

Liver metabolic/oxidative stress induces hepatic and extrahepatic changes in the expression of the vitamin C transporters SVCT1 and SVCT2

PURPOSE

Owing to its ability to inactivate harmful radicals, vitamin C plays a key role in antioxidant defense. The bioavailability of this vitamin depends upon the nutritional intake and its uptake by cells, mainly through the sodium-dependent transporters SVCT1/Svct1 and SVCT2/Svct2 (human/rat). Here, we investigated the effect of liver metabolic/oxidative stress on the expression of these transporters in extrahepatic tissues.

METHODS AND RESULTS

In Zucker rats, used here as a model of liver steatosis, Svct1-2 mRNA levels were similar in obese and lean animals, except for lung tissue, where Svct2 was up-regulated. Diabetes mellitus, developed by streptozotocin administration, was accompanied by a down-regulation of Svct1 in liver and kidney, together with a down-regulation of Svct2 in kidney and brain. Complete obstructive cholestasis due to bile duct ligation for 1 week induced a significant down-regulation of both Svct1 and Svct2 in ileum, whereas Svct2 was up-regulated in liver, and no significant changes in the expression of either transporter were found in kidney, brain or lung. In rat hepatoma Can-10 cells, bile acids, but not the FXR agonist GW4064, induced an up-regulation of Svct1 and Svct2. In human hepatoma Alexander cells transfected with FXR/RXRα/OATP1B1, neither GW4064 nor unconjugated or glycine-/taurine-conjugated major bile acids were able to up-regulate either SVCT1 or SVCT2.

CONCLUSIONS

Pathological circumstances characterized by the presence of metabolic/oxidative stress in the liver induce different responses in the expression of ascorbic acid transporters in intrahepatic and extrahepatic tissues, which may affect the overall bioavailability and cellular uptake of this vitamin.

Sodium-coupled vitamin C transporter (SVCT2): expression, function, and regulation in intervertebral disc cells

BACKGROUND CONTEXT

Vitamin C (ascorbic acid [AA]) is essential for the synthesis of collagen and also acts as an antioxidant in the intervertebral disc (IVD). However, there is very little information currently available on the identity of the transporter that facilitates AA entry into IVD cells and the factors that mediate the transport process.

PURPOSE

To investigate the expression of the two known isoforms of Na+ -coupled vitamin C transporter, SVCT1 and SVCT2, in IVD cells and its regulation by insulin-like growth factor 1 (IGF-1) and the steroid hormone dexamethasone.

STUDY DESIGN

To identify the expression and functional activity of the sodium-dependent vitamin C transporter (SVCT) in the IVD.

METHODS

Uptake studies were carried out with rabbit annulus fibrosis and nucleus pulposus cells in 24-well plates using [14C]-AA. To characterize SVCT transporter, uptake was done in the presence and absence of Na+ in the uptake buffer. Time dependency, Na+ activation kinetics, saturation kinetics, and substrate selectivity studies were performed. Regulatory studies were performed in the presence of IGF-1 and the steroid hormone dexamethasone. Gene expression was analyzed by quantitative polymerase chain reaction.

RESULTS

Our real-time polymerase chain reaction results showed the presence of SVCT2 but not SVCT1 in IVD cells. Uptake of vitamin C in IVD cells is Na+ dependent and saturable. The Michaelis constant for the process is 96±11 μM. The activation of vitamin C uptake by Na+ exhibits a sigmoidal relationship, indicating involvement of more than one Na+ in the activation process. The uptake system does not recognize any other water-soluble vitamin as a substrate. Immunocytochemical analysis shows robust expression of SVCT2 protein in IVD cells. The growth factors IGF-1 and the steroid hormone dexamethasone upregulate the expression of SVCT2 in IVD cells.

CONCLUSIONS

Our studies demonstrate that the active SVCT2 is expressed in IVD cells and that the expression of this transporter is regulated by growth factors IGF-1 and dexamethasone.

Human skeletal muscle ascorbate is highly responsive to changes in vitamin C intake and plasma concentrations

BACKGROUND

Vitamin C (ascorbate) is likely to be essential for skeletal muscle structure and function via its role as an enzyme cofactor for collagen and carnitine biosynthesis. Vitamin C may also protect these metabolically active cells from oxidative stress.

OBJECTIVE

We investigated the bioavailability of vitamin C to human skeletal muscle in relation to dietary intake and plasma concentrations and compared this relation with ascorbate uptake by leukocytes.

DESIGN

Thirty-six nonsmoking men were randomly assigned to receive 6 wk of 0.5 or 2 kiwifruit/d, an outstanding dietary source of vitamin C. Fasting blood samples were drawn weekly, and 24-h urine and leukocyte samples were collected before intervention, after intervention, and after washout. Needle biopsies of skeletal muscle (vastus lateralis) were carried out before and after intervention.

RESULTS

Baseline vastus lateralis ascorbate concentrations were ~16 nmol/g tissue. After intervention with 0.5 or 2 kiwifruit/d, these concentrations increased ~3.5-fold to 53 and 61 nmol/g, respectively. There was no significant difference between the responses of the 2 groups. Mononuclear cell and neutrophil ascorbate concentrations increased only ~1.5- and ~2-fold, respectively. Muscle ascorbate concentrations were highly correlated (P < 0.001) with dietary intake (R = 0.61) and plasma concentrations (R = 0.75) in the range from 5 to 80 μmol/L.

CONCLUSIONS

Human skeletal muscle is highly responsive to vitamin C intake and plasma concentrations and exhibits a greater relative uptake of ascorbate than leukocytes. Thus, muscle appears to comprise a relatively labile pool of ascorbate and is likely to be prone to ascorbate depletion with inadequate dietary intake. This trial was registered at the Australian New Zealand Clinical Trials Registry (www.anzctr.org.au) as ACTRN12611000162910.

Sodium-dependent vitamin C transporter SVCT2: expression and function in bone marrow stromal cells and in osteogenesis

Ascorbic acid (Vitamin C) has a critical role in bone formation and osteoblast differentiation, but very little is known about the molecular mechanisms of ascorbic acid entry into bone marrow stromal cells (BMSCs). To address this gap in knowledge, we investigated the identity of the transport system that is responsible for the uptake of ascorbic acid into bone marrow stromal cells (BMSCs). First, we examined the expression of the two known isoforms of the sodium-coupled ascorbic acid transporter, namely SVCT1 and SVCT2, in BMSCs (Lin-ve Sca1+ve) and bone at the mRNA level. Only SVCT2 mRNA was detected in BMSCs and bone. Uptake of ascorbic acid in BMSCs was Na(+)-dependent and saturable. In order to define the role of SVCT2 in BMSC differentiation into osteoblasts, BMSCs were stimulated with osteogenic media for different time intervals, and the activity of SVCT2 was monitored by ascorbic acid uptake. SVCT2 expression was up-regulated during the osteogenic differentiation of BMSCs; the expression was maximal at the earliest phase of differentiation. Subsequently, osteogenesis was inhibited in BMSCs upon knock-down of SVCT2 by lentivirus shRNA. We also found that the expression of the SVCT2 could be negatively or positively modulated by the presence of oxidant (Sin-1) or antioxidant (Ascorbic acid) compounds, respectively, in BMSCs. Furthermore, we found that this transporter is also regulated with age in mouse bone. These data show that SVCT2 plays a vital role in the osteogenic differentiation of BMSCs and that its expression is altered under conditions associated with redox reaction. Our findings could be relevant to bone tissue engineering and bone related diseases such as osteoporosis in which oxidative stress and aging plays important role.

Cellular phenotype-dependent and -independent effects of vitamin C on the renewal and gene expression of mouse embryonic fibroblasts

Vitamin C has been shown to delay the cellular senescence and was considered a candidate for chemoprevention and cancer therapy. To understand the reported contrasting roles of vitamin C: growth-promoting in the primary cells and growth-inhibiting in cancer cells, primary mouse embryonic fibroblasts (MEF) and their isogenic spontaneously immortalized fibroblasts with unlimited cell division potential were used as the model pair. We used microarray gene expression profiling to show that the immortalized MEF possess human cancer gene expression fingerprints including a pattern of up-regulation of inflammatory response-related genes. Using the MEF model, we found that a physiological treatment level of vitamin C (10⁻⁵ M), but not other unrelated antioxidants, enhanced cell growth. The growth-promoting effect was associated with a pattern of enhanced expression of cell cycle- and cell division-related genes in both primary and immortalized cells. In the immortalized MEF, physiological treatment levels of vitamin C also enhanced the expression of immortalization-associated genes including a down-regulation of genes in the extracellular matrix functional category. In contrast, confocal immunofluorescence imaging of the primary MEF suggested an increase in collagen IV protein upon vitamin C treatment. Similar to the cancer cells, the growth-inhibitory effect of the redox-active form of vitamin C was preferentially observed in immortalized MEF. All effects of vitamin C required its intracellular presence since the transporter-deficient SVCT2−/− MEF did not respond to vitamin C. SVCT2−/− MEF divided and became immortalized readily indicating little dependence on vitamin C for the cell division. Immortalized SVCT2−/− MEF required higher concentration of vitamin C for the growth inhibition compared to the immortalized wildtype MEF suggesting an intracellular vitamin C toxicity. The relevance of our observation in aging and human cancer prevention was discussed.

Sodium-dependent vitamin C transporter 2 deficiency causes hypomyelination and extracellular matrix defects in the peripheral nervous system

Ascorbic acid (vitamin C) is necessary for myelination of Schwann cell/neuron cocultures and has shown beneficial effects in the treatment of a Charcot-Marie-Tooth neuropathy 1A (CMT1A) mouse model. Although clinical studies revealed that ascorbic acid treatment had no impact on CMT1A, it is assumed to have an important function in peripheral nerve myelination and possibly in remyelination. However, the transport pathway of ascorbic acid into peripheral nerves and the mechanism of ascorbic acid function in peripheral nerves in vivo remained unclear. In this study, we used sodium-dependent vitamin C transporter 2-heterozygous (SVCT2(+/-)) mice to elucidate the functions of SVCT2 and ascorbic acid in the murine peripheral nervous system. SVCT2 and ascorbic acid levels were reduced in SVCT2(+/-) peripheral nerves. Morphometry of sciatic nerve fibers revealed a decrease in myelin thickness and an increase in G-ratios in SVCT2(+/-) mice. Nerve conduction velocities and sensorimotor performance in functional tests were reduced in SVCT2(+/-) mice. To investigate the mechanism of ascorbic acid function, we studied the expression of collagens in the extracellular matrix of peripheral nerves. Here, we show that expression of various collagen types was reduced in sciatic nerves of SVCT2(+/-) mice. We found that collagen gene transcription was reduced in SVCT2(+/-) mice but hydroxyproline levels were not, indicating that collagen formation was regulated on the transcriptional and not the posttranslational level. These results help to clarify the transport pathway and mechanism of action of ascorbic acid in the peripheral nervous system and may lead to novel therapeutic approaches to peripheral neuropathies by manipulation of SVCT2 function.

Molecular characterization and transcriptional regulation of the sodium-dependent vitamin C transporter genes (slc23a1 and slc23a2) in a teleost fish, the Senegalese sole (Solea senegalensis)

Vitamin C (ascorbic acid, AA) is an antioxidant that acts as a free radical scavenger and cofactor for several important enzymatic reactions, thus being important for normal cellular functions, growth and development. Accumulation of AA in cells depends on two types of sodium-dependent vitamin C transporters (SVCTs), designed as SVCT1 and SVCT2. In human, they are the products of SLC23A1 and SLC23A2 genes, respectively. In the present work, the molecular cloning of the cDNAs corresponding to slc23a1 and slc23a2 in a teleost fish, the Senegalese sole (Solea senegalensis Kaup, 1858) is first described. Sequence analysis of the predicted polypeptides revealed a conserved topology with those of mammals with important motifs involved in structure and function, being also present in svct1 and svct2. Phylogenetic analyses including a range of vertebrate SVCTs suggest that both transporters are the result of an ancient gene duplication event that occurred prior to the divergence of tetrapods and teleosts, which took place 450 million years ago. Expression profiles in juvenile tissues and during larval development were analyzed using a real-time PCR approach. In juvenile fish, slc23a1 was strongly expressed in intestine, whereas slc23a2 exhibited a widespread distribution in tissues. Transcripts of both genes were detected at early developmental stages, probably representing mRNAs of maternal origin. A possible regulation by their own substrate was detected after first uptakes of AA from diet in both genes. During metamorphosis, both slc23a1 and slc23a2 were down-regulated, the former in a thyroid hormone (TH) dependent way. This pattern coincided with a significant reduction in the AA content of larvae during metamorphosis. These results are interpreted in a physiological context of general reduction in the metabolism of metamorphic larvae. Data presented here provide the first step toward a better understanding of the physiological role of SVCTs in teleost fish.

Hepatic expression of sodium-dependent vitamin C transporters: ontogeny, subtissular distribution and effect of chronic liver diseases

Ascorbic acid uptake is a key step in determining the overall bioactivity of this vitamin. Expression of Na-dependent vitamin C transporters (SVCT; SLC23A1 and SLC23A2) during long-term oxidative stress occurring in several chronic liver diseases may determine the antioxidant defence in this organ. In patients with hepatocellular cholestasis, primary biliary cirrhosis, haemochromatosis and non-alcoholic steatohepatitis, using real-time RT-PCR, an enhanced hepatic expression of both SLC23A1 and SLC23A2, but not other organic anions transporters, such as OATP1A2, OATP1B1 and OATP1B3, was found. To further investigate these findings, we used secondary biliary cirrhosis induced in rats by long-term biliary obstruction as a model of chronic liver disease accompanied by oxidative stress because of bile acid accumulation. In control rat liver, expression of Slc23a1 was low at birth, increased progressively up to adulthood and decreased in senescence, whereas expression of Slc23a2 did not change significantly after birth. In 8-week-old rats, immunohistochemistry and confocal microscopy studies revealed the expression in hepatocytes and bile duct cells of mainly Slc23a1, whereas both Slc23a1 and Slc23a2 were expressed in endothelial, stellate and Kupffer cells. In adult rats, when obstructive cholestasis was maintained for 8 weeks, a significant up-regulation of Slc23a2 accompanied by a down-regulation of Slc23a1 was found. In sum, there is a selective cell-type distribution of SVCT in the liver tissue, which, in addition to differential control in the expression of both isoforms, may play a role in the ability of different liver cell types to take up vitamin C under physiological and pathological conditions.

Vitamin C: Overview and Update

Vitamin C functions in enzyme activation, oxidative stress reduction, and immune function. There is considerable evidence that vitamin C protects against respiratory tract infections and reduces risk for cardiovascular disease and some cancers. Current trials are examining the efficacy of intravenous vitamin C as cancer therapy. Many experts believe that the recommended intakes for vitamin C (45 to 90 mg daily) are several orders of magnitude too low to support optimal vitamin C functionality. Also, there is a misperception that vitamin C deficiency disease (scurvy) is largely historical and rarely observed in developed nations. Physical symptoms of scurvy include swelling of the lower extremities, bleeding gums, fatigue, and hemorrhaging, as well as psychological problems, including depression, hysteria, and social introversion. The long-term safety of vitamin C supplementation seems evident as large investigations have noted reduced risk of mortality in vitamin C supplementing populations and in those with elevated plasma vitamin C concentrations.

Alterations in hepatic mRNA expression of phase II enzymes and xenobiotic transporters after targeted disruption of hepatocyte nuclear factor 4 alpha

Hepatocyte nuclear factor 4 alpha (HNF4a) is a liver-enriched master regulator of liver function. HNF4a is important in regulating hepatic expression of certain cytochrome P450s. The purpose of this study was to use mice lacking HNF4a expression in liver (HNF4a-HNull) to elucidate the role of HNF4a in regulating hepatic expression of phase II enzymes and transporters in mice. Compared with male wild-type mice, HNF4a-HNull male mouse livers had (1) markedly lower messenger RNAs (mRNAs) encoding the uptake transporters sodium taurocholate cotransporting polypeptide, organic anion transporting polypeptide (Oatp) 1a1, Oatp2b1, organic anion transporter 2, sodium phosphate cotransporter type 1, sulfate anion transporter 1, sodium-dependent vitamin C transporter 1, the phase II enzymes Uridine 5'-diphospho (UDP)-glucuronosyltransferase (Ugt) 2a3, Ugt2b1, Ugt3a1, Ugt3a2, sulfotransferase (Sult) 1a1, Sult1b1, Sult5a1, the efflux transporters multidrug resistance-associated protein (Mrp) 6, and multidrug and toxin extrusion 1; (2) moderately lower mRNAs encoding Oatp1b2, organic cation transporter (Oct) 1, Ugt1a5, Ugt1a9, glutathione S-transferase (Gst) m4, Gstm6, and breast cancer resistance protein; but (3) higher mRNAs encoding Oatp1a4, Octn2, Ugt1a1, Sult1e1, Sult2a2, Gsta4, Gstm1-m3, multidrug resistance protein (Mdr) 1a, Mrp3, and Mrp4. Hepatic signaling of nuclear factor E2-related factor 2 and pregnane X receptor appear to be activated in HNF4a-HNull mice. In conclusion, HNF4a deficiency markedly alters hepatic mRNA expression of a large number of phase II enzymes and transporters, probably because of the loss of HNF4a, which is a transactivator and a determinant of gender-specific expression and/or adaptive activation of signaling pathways important in hepatic regulation of these phase II enzymes and transporters.

Low vitamin C and increased oxidative stress and cell death in mice that lack the sodium-dependent vitamin C transporter SVCT2

The sodium-dependent vitamin C transporter (SVCT2) is responsible for the transport of vitamin C into cells in multiple organs, from either the blood or the cerebrospinal fluid. Mice null for SVCT2 (SVCT2(-/-)) do not survive past birth but the cause of death has not yet been ascertained. After mating of SVCT2(+/-) males and SVCT2(+/-) females, fewer SVCT2(-/-) and SVCT2(+/-) progeny were observed than would be expected according to Mendelian ratios. Vitamin C levels in SVCT2(-/-), SVCT2(+/-), and SVCT2(+/+) were genotype-dependent. SVCT2(-/-) fetuses had significantly lower vitamin C levels than littermates in placenta, cortex, and lung, but not in liver (the site of vitamin C synthesis). Low vitamin C levels in placenta and cortex were associated with elevations in several markers of oxidative stress: malondialdehyde, isoketals, F(2)-isoprostanes, and F(4)-neuroprostanes. Oxidative stress was not elevated in fetal SVCT2(-/-) lung tissue despite low vitamin C levels. In addition to the expected severe hemorrhage in cortex, we also found hemorrhage in the brain stem, which was accompanied by cell loss. We found evidence of increased apoptosis in SVCT2(-/-) mice and disruption of the basement membrane in fetal brain. Together these data show that SVCT2 is critical for maintaining vitamin C levels in fetal and placental tissues and that the lack of SVCT2, and the resulting low vitamin C levels, results in fetal death and, in SVCT2(-/-) mice that survive the gestation period, in oxidative stress and cell death.

Cellular pathways for transport and efflux of ascorbate and dehydroascorbate

The mechanisms allowing the cellular transport of ascorbic acid represent a primary aspect for the understanding of the roles played by this vitamin in pathophysiology. Considerable research effort has been spent in the field, on several animal models and different cell types. Several mechanisms have been described to date, mediating the movements of different redox forms of ascorbic acid across cell membranes. Vitamin C can enter cells both in its reduced and oxidized form, ascorbic acid (AA) and dehydroascorbate (DHA), utilizing respectively sodium-dependent transporters (SVCT) or glucose transporters (GLUT). Modulation of SVCT expression and function has been described by cytokines, steroids and post-translational protein modification. Cellular uptake of DHA is followed by its intracellular reduction to AA by several enzymatic and non-enzymatic systems. Efflux of vitamin C has been also described in a number of cell types and different pathophysiological functions were proposed for this phenomenon, in dependence of the cell model studied. Cellular efflux of AA is mediated through volume-sensitive (VSOAC) and Ca(2+)-dependent anion channels, gap-junction hemichannels, exocytosis of secretory vesicles and possibly through homo- and hetero-exchange systems at the plasma membrane level. Altogether, available data suggest that cellular efflux of ascorbic acid - besides its uptake - should be taken into account when evaluating the cellular homeostasis and functions of this important vitamin.

Vitamin C acts indirectly to modulate isotype switching in mouse B cells

Vitamin C, one of essential micronutrients, has been reported to modulate the humoral immune responses in some mammals. We investigated whether vitamin C might modulate this response in mice by directly affecting B cells. Splenic B cells were isolated and activated by CD40- and B cell receptor-ligation in vitro. The cells were cultured with a pretreatment of vitamin C from 0 to 1 mM of concentrations. Vitamin C slightly increased apoptosis of B cells dose-dependently and behaved as an antioxidant. We found that in vivo administration of vitamin C by intraperitoneal injection affected isotype switching as previously reported: the titer of antigen-specific IgG1 antibody was decreased, while that of IgG2a was unaffected. Somewhat different from those observed in vivo, in vitro exposure to vitamin C slightly decreased isotype switching to IgG1 and increased isotype switching to IgG2a. Pretreatment with vitamin C in the safe range did not affect either proliferation of cultured B cells or the expression of CD80 and CD86 in those cells. Taken together, in vivo results suggest that vitamin C acts to modulate isotype switching in the mouse. However, because of our in vitro results, we suggest that the modulation exerted by vitamin C in vivo is by indirectly affecting B cells, perhaps by directly influencing other immune cells such as dendritic cells.

Vitamin C restores healthy aging in a mouse model for Werner syndrome

Werner syndrome (WS) is a premature aging disorder caused by mutations in a RecQ-like DNA helicase. Mice lacking the helicase domain of the WRN homologue exhibit many phenotypic features of WS, including a prooxidant status and a shorter mean life span compared to wild-type animals. Here, we show that Wrn mutant mice also develop premature liver sinusoidal endothelial defenestration along with inflammation and metabolic syndrome. Vitamin C supplementation rescued the shorter mean life span of Wrn mutant mice and reversed several age-related abnormalities in adipose tissues and liver endothelial defenestration, genomic integrity, and inflammatory status. At the molecular level, phosphorylation of age-related stress markers like Akt kinase-specific substrates and the transcription factor NF-kappaB, as well as protein kinase Cdelta and Hif-1alpha transcription factor levels, which are increased in the liver of Wrn mutants, were normalized by vitamin C. Vitamin C also increased the transcriptional regulator of lipid metabolism PPARalpha. Finally, microarray and gene set enrichment analyses on liver tissues revealed that vitamin C decreased genes normally up-regulated in human WS fibroblasts and cancers, and it increased genes involved in tissue injury response and adipocyte dedifferentiation in obese mice. Vitamin C did not have such effect on wild-type mice. These results indicate that vitamin C supplementation could be beneficial for patients with WS.

Effect of vitamin C depletion on age-related hearing loss in SMP30/GNL knockout mice

Using senescence marker protein 30 (SMP30)/gluconolactonase (GNL) knockout (KO) mice, which cannot synthesize vitamin C (VC), we examined whether modulating VC level affects age-related hearing loss (AHL). KO and wild-type (WT) C57BL/6 mice were given water containing 1.5 g/L VC [VC(+)] or 37.5mg/L VC [VC(-)]. At 10 months of age, KO VC(-) mice showed significant reduction in VC level in the inner ear, plasma, and liver, increase in auditory brainstem response (ABR) thresholds, and decrease in the number of spiral ganglion cells compared to WT VC(-), WT VC(+), and KO VC(+) mice. There were no differences in VC level in the inner ear, ABR thresholds, or the number of spiral ganglion cells among WT VC(-), WT VC(+), and KO VC(+) mice. These findings suggest that VC depletion can accelerate AHL but that supplementing VC may not increase VC level in the inner ear or slow AHL in mice.

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.

Polymorphisms in the estrogen receptor 1 and vitamin C and matrix metalloproteinase gene families are associated with susceptibility to lymphoma

BACKGROUND

Non-Hodgkin lymphoma (NHL) is the fifth most common cancer in the U.S. and few causes have been identified. Genetic association studies may help identify environmental risk factors and enhance our understanding of disease mechanisms.

METHODOLOGY/PRINCIPAL FINDINGS

768 coding and haplotype tagging SNPs in 146 genes were examined using Illumina GoldenGate technology in a large population-based case-control study of NHL in the San Francisco Bay Area (1,292 cases 1,375 controls are included here). Statistical analyses were restricted to HIV- participants of white non-Hispanic origin. Genes involved in steroidogenesis, immune function, cell signaling, sunlight exposure, xenobiotic metabolism/oxidative stress, energy balance, and uptake and metabolism of cholesterol, folate and vitamin C were investigated. Sixteen SNPs in eight pathways and nine haplotypes were associated with NHL after correction for multiple testing at the adjusted q<0.10 level. Eight SNPs were tested in an independent case-control study of lymphoma in Germany (494 NHL cases and 494 matched controls). Novel associations with common variants in estrogen receptor 1 (ESR1) and in the vitamin C receptor and matrix metalloproteinase gene families were observed. Four ESR1 SNPs were associated with follicular lymphoma (FL) in the U.S. study, with rs3020314 remaining associated with reduced risk of FL after multiple testing adjustments [odds ratio (OR) = 0.42, 95% confidence interval (CI) = 0.23-0.77) and replication in the German study (OR = 0.24, 95% CI = 0.06-0.94). Several SNPs and haplotypes in the matrix metalloproteinase-3 (MMP3) and MMP9 genes and in the vitamin C receptor genes, solute carrier family 23 member 1 (SLC23A1) and SLC23A2, showed associations with NHL risk.

CONCLUSIONS/SIGNIFICANCE

Our findings suggest a role for estrogen, vitamin C and matrix metalloproteinases in the pathogenesis of NHL that will require further validation.