Kefir peptides ameliorate osteoporosis in AKR1A1 knockout mice with vitamin C deficiency by promoting osteoblastogenesis and inhibiting osteoclastogenesis.

The AKR1A1 protein is a member of the aldo-keto reductase superfamily that catalyzes the transformation of D-glucuronate to L-gulonate in the synthesis of L-ascorbic acid (vitamin C, Vit C). We previously demonstrated that AKR1A1 knockout mice (AKR1A1eGFP/eGFP) with Vit C deficiency exhibited aberrant bone formation and osteoporosis. In this study, we aimed to evaluate the osteoprotective effects of kefir peptides (KPs) in AKR1A1eGFP/eGFP mice and uncover the underlying mechanism of KPs in the modulation of bone remodeling. Six male CD-1 mice and 24 male AKR1A1eGFP/eGFP mice were used in this study, in which the AKR1A1eGFP/eGFP mice were randomly divided into four groups (n = 6). KPs treatment for 12 weeks exerted several effects in AKR1A1eGFP/eGFP mice including the reduction of serum proinflammatory cytokines (IL-1ß, IL-6, TNF-α), bone resorption markers (CTX-1, RANKL), and the increase of serum bone formation markers (P1NP, OPG, OC). µ-CT analysis indicated that KPs prevented the bone loss in the femurs of AKR1A1eGFP/eGFP mice by significantly increasing the trabecular parameters of bone mineral density, bone volume and bone number. Nanoindentation analysis demonstrated that KPs enhanced the elasticity and hardness of femoral cortical bones in AKR1A1eGFP/eGFP mice. KPs promoted bone marrow mesenchymal stem cells (BMMSCs)-derived osteoblast differentiation and mineralization by upregulating positive regulators of osteoblastogenesis (Runx2, ß-catenin, BMP-2, NFATc1). Conversely, KPs inhibited bone marrow macrophages (BMMs)-derived osteoclast differentiation and bone resorption, which was demonstrated by the facts that KPs suppressed RANKL-induced p38, NF-κB, Akt, PLCγ2 and CREB-1 phosphorylation, decreased the nuclear translocation of NFATc1 and c-Fos. Our findings demonstrate the efficacy of KPs in the prevention of osteoporosis in AKR1A1eGFP/eGFP mice and also unveil the dual effects of KPs in osteogenic promotion and osteoclastic inhibition. This study supports the use of KPs as nutritional supplements for the prevention of osteoporosis.

Vitamin C deficiency induces hypoglycemia and cognitive disorder through S-nitrosylation-mediated activation of glycogen synthase kinase 3ß.

Vitamin C (VC, l-ascorbic acid) is an essential nutrient that plays a key role in metabolism and functions as a potent antioxidant in regulating the S-nitrosylation and denitrosylation of target proteins. The precise function of VC deprivation in glucose homeostasis is still unknown. In the absence of L-gulono-1,4-lactone oxidoreductase, an essential enzyme for the last step of VC synthesis, VC deprivation resulted in persistent hypoglycemia and subsequent impairment of cognitive functions in female but not male mouse pups. The cognitive disorders caused by VC deprivation were largely reversed when these female pups were given glucose. VC deprivation-induced S-nitrosylation of glycogen synthase kinase 3ß (GSK3ß) at Cys14, which activated GSK3ß and inactivated glycogen synthase to decrease glycogen synthesis and storage under the feeding condition, while VC deprivation inactivated glycogen phosphorylase to decrease glycogenolysis under the fasting condition, ultimately leading to hypoglycemia and cognitive disorders. Treatment with Nω-Nitro-l-arginine methyl ester (l-NAME), a specific inhibitor of nitric oxide synthase, on the other hand, effectively prevented S-nitrosylation and activation of GSK3ß in female pups in response to the VC deprivation and reversed hypoglycemia and cognitive disorders. Overall, this research identifies S-nitrosylation of GSK3ß and subsequent GSK3ß activation as a previously unknown mechanism controlling glucose homeostasis in female pups in response to VC deprivation, implying that VC supplementation in the prevention of hypoglycemia and cognitive disorders should be considered in the certain groups of people, particularly young females.

Patients with Community Acquired Pneumonia Exhibit Depleted Vitamin C Status and Elevated Oxidative Stress.

Pneumonia is a severe lower respiratory tract infection that is a common complication and a major cause of mortality of the vitamin C-deficiency disease scurvy. This suggests an important link between vitamin C status and lower respiratory tract infections. Due to the paucity of information on the vitamin C status of patients with pneumonia, we assessed the vitamin C status of 50 patients with community-acquired pneumonia and compared these with 50 healthy community controls. The pneumonia cohort comprised 44 patients recruited through the Acute Medical Assessment Unit (AMAU) and 6 patients recruited through the Intensive Care Unit (ICU); mean age 68 ± 17 years, 54% male. Clinical, microbiological and hematological parameters were recorded. Blood samples were tested for vitamin C status using HPLC with electrochemical detection and protein carbonyl concentrations, an established marker of oxidative stress, using ELISA. Patients with pneumonia had depleted vitamin C status compared with healthy controls (23 ± 14 µmol/L vs. 56 ± 24 µmol/L, p < 0.001). The more severe patients in the ICU had significantly lower vitamin C status than those recruited through AMAU (11 ± 3 µmol/L vs. 24 ± 14 µmol/L, p = 0.02). The pneumonia cohort comprised 62% with hypovitaminosis C and 22% with deficiency, compared with only 8% hypovitaminosis C and no cases of deficiency in the healthy controls. The pneumonia cohort also exhibited significantly elevated protein carbonyl concentrations compared with the healthy controls (p < 0.001), indicating enhanced oxidative stress in the patients. We were able to collect subsequent samples from 28% of the cohort (mean 2.7 ± 1.7 days; range 1-7 days). These showed no significant differences in vitamin C status or protein carbonyl concentrations compared with baseline values (p = 0.6). Overall, the depleted vitamin C status and elevated oxidative stress observed in the patients with pneumonia indicates an enhanced requirement for the vitamin during their illness. Therefore, these patients would likely benefit from additional vitamin C supplementation to restore their blood and tissue levels to optimal. This may decrease excessive oxidative stress and aid in their recovery.

Vitamin C Deficiency-Induced Pulmonary Arterial Hypertension.

We report a case of a man in his 60s who developed pulmonary arterial hypertension (PAH) in association with profound vitamin C deficiency. Decreased availability of endothelial nitric oxide and activation of the hypoxia-inducible family of transcription factors, both consequences of vitamin C deficiency, are believed to be mechanisms contributing to the pathogenesis of the pulmonary hypertension. The PAH resolved following vitamin C supplementation. The current case highlights the importance of testing for vitamin C deficiency in patients with PAH in the proper clinical setting.

Vitamin C deficiency aggravates tumor necrosis factor α-induced insulin resistance.

Chronic low-grade inflammation plays a major role in the development of insulin resistance. The potential role and underlying mechanism of vitamin C, an antioxidant and anti-inflammatory agent, was investigated in tumor necrosis factor-α (TNF-α)-induced insulin resistance. Gulonolactone oxidase knockout (Gulo-/-) mice genetically unable to synthesize vitamin C were used to induce insulin resistance by continuously pumping small doses of TNF-α for seven days, and human liver hepatocellular carcinoma cells (HepG2 cells) were used to induce insulin resistance by treatment with TNF-α. Vitamin C deficiency aggravated TNF-α-induced insulin resistance in Gulo-/- mice, resulting in worse glucose tolerance test (GTT) results, higher fasting plasma insulin level, and the inactivation of the protein kinase B (AKT)/glycogen synthase kinase-3ß (GSK3ß) pathway in the liver. Vitamin C deficiency also worsened liver lipid accumulation and inflammation in TNF-α-treated Gulo-/- mice. In HepG2 cells, vitamin C reversed the TNF-α-induced reduction of glucose uptake and glycogen synthesis, which were mediated by increasing GLUT2 levels and the activation of the insulin receptor substrate (IRS-1)/AKT/GSK3ß pathway. Furthermore, vitamin C inhibited the TNF-α-induced activation of not only the mitogen-activated protein kinase (MAPKs), but also nuclear factor-kappa B (NF-κB) signaling. Taken together, vitamin C is essential for preventing and improving insulin resistance, and the supplementing with vitamin C may be an effective therapeutic intervention for metabolic disorders.

Vitamin C and Immune Function.

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

GDP-D-mannose epimerase regulates male gametophyte development, plant growth and leaf senescence in Arabidopsis.

Plant GDP-D-mannose epimerase (GME) converts GDP-D-mannose to GDP-L-galactose, a precursor of both L-ascorbate (vitamin C) and cell wall polysaccharides. However, the genetic functions of GME in Arabidopsis are unclear. In this study, we found that mutations in Arabidopsis GME affect pollen germination, pollen tube elongation, and transmission and development of the male gametophyte through analysis of the heterozygous GME/gme plants and the homozygous gme plants. Arabidopsis gme mutants also exhibit severe growth defects and early leaf senescence. Surprisingly, the defects in male gametophyte in the gme plants are not restored by L-ascorbate, boric acid or GDP-L-galactose, though boric acid rescues the growth defects of the mutants, indicating that GME may regulate male gametophyte development independent of L-ascorbate and GDP-L-galactose. These results reveal key roles for Arabidopsis GME in reproductive development, vegetative growth and leaf senescence, and suggest that GME regulates plant growth and controls male gametophyte development in different manners.

Bone Degeneration and Its Recovery in SMP30/GNL-Knockout Mice.

Senescence marker protein-30 (SMP30) decreases androgen-independently with aging and is a lactone-hydrolyzing enzyme gluconolactonase (GNL) that is involved in vitamin C biosynthesis. In the present study, bone properties of SMP30/GNL knockout (KO) mice with deficiency in vitamin C synthesis were investigated to reveal the effects of SMP30/GNL and exogenous vitamin C supplementation on bone formation. Mineral content (BMC) and mineral density (BMD) of the mandible and femur of SMP30/GNL KO and wild-type mice at 2 and 3 months of age with or without vitamin C supplementation were measured by dual-energy X-ray absorptiometry. Body and bone weight of both age groups decreased and became significantly lower than those of wild-type mice. The bones of SMP30/GNL KO mice were rough and porous, with BMC and BMD significantly below wild-type. Oral supplementation with vitamin C eliminated differences in body weight, bone weight, BMC, and BMD between SMP30/GNL KO and wild-type mice at each age. These results indicate that bone degeneration in SMP30/GNL KO mice was caused by lack of vitamin C, and that this mouse strain is an appropriate model for bone metabolism in humans, which have no ability to synthesize vitamin C.

Deficiency of vitamin D and vitamin C in the pathogenesis of bronchial asthma.

Epidemiology of bronchial asthma (BA) indicates a marked paradox: rapid rise in the prevalence.Simultaneous decline in mortality is mostly related to improvement in the diagnosis and therapy. In many economically developed countries the BA affects more than 10 per cent of the population, while mortality related to this respiratory disorder is below 1/100,000. Factors favorably influencing mortality of BA include new more effective medications, decline in smoking and also improved nutrition, based on awareness of protective role of vitamins. Vitamin D deficiency has a number of biological effects that are potentially instrumental in the pathogenesis and severity of BA. Increased number of randomized, controlled, interventional studies is showing positive effects of vitamin D supplementation in pediatric and in adult BA. Oxidative stress is potentially an important pathogenic factor in the progression of BA. Vitamin C (ascorbic acid) belongs to the most effective nutritional antioxidants. By counteracting oxidants, reducing generation of reactive oxygen species, vitamin C may inhibit external attacks in the respiratory tract, thus modulating the development of BA (Fig. 2, Ref. 15).

Vitamin D and/or calcium deficient diets may differentially affect muscle fiber neuromuscular junction innervation.

INTRODUCTION: There is evidence that supports a role for Vitamin D (Vit. D) in muscle. The exact mechanism by which Vit. D deficiency impairs muscle strength and function is not clear. METHODS: Three-week-old mice were fed diets with varied combinations of Vit. D and Ca2+ deficiency. Behavioral testing, genomic and protein analysis, and muscle histology were performed with a focus on neuromuscular junction (NMJ) -related genes. RESULTS: Vit. D and Ca2+ deficient mice performed more poorly on given behavioral tasks than animals with Vit. D deficiency alone. Genomic and protein analysis of the soleus and tibialis anterior muscles revealed changes in several Vit. D metabolic, NMJ-related, and protein chaperoning and refolding genes. CONCLUSIONS: These data suggest that detrimental effects of a Vit. D deficient or a Vit. D and Ca2+ deficient diet may be a result of differential alterations in the structure and function of the NMJ and a lack of a sustained stress response in muscles. Muscle Nerve 54: 1120-1132, 2016.

Distribution of vitamin C is tissue specific with early saturation of the brain and adrenal glands following differential oral dose regimens in guinea pigs.

Vitamin C (VitC) deficiency is surprisingly common in humans even in developed parts of the world. The micronutrient has several established functions in the brain; however, the consequences of its deficiency are not well characterised. To elucidate the effects of VitC deficiency on the brain, increased knowledge about the distribution of VitC to the brain and within different brain regions after varying dietary concentrations is needed. In the present study, guinea pigs (like humans lacking the ability to synthesise VitC) were randomly divided into six groups (n 10) that received different concentrations of VitC ranging from 100 to 1500 mg/kg feed for 8 weeks, after which VitC concentrations in biological fluids and tissues were measured using HPLC. The distribution of VitC was found to be dynamic and dependent on dietary availability. Brain saturation was region specific, occurred at low dietary doses, and the dose-concentration relationship could be approximated with a three-parameter Hill equation. The correlation between plasma and brain concentrations of VitC was moderate compared with other organs, and during non-scorbutic VitC deficiency, the brain was able to maintain concentrations from about one-quarter to half of sufficient levels depending on the region, whereas concentrations in other tissues decreased to one-sixth or less. The adrenal glands have similar characteristics to the brain. The observed distribution kinetics with a low dietary dose needed for saturation and exceptional retention ability suggest that the brain and adrenal glands are high priority tissues with regard to the distribution of VitC.

High dietary intake of vitamin C suppresses age-related thymic atrophy and contributes to the maintenance of immune cells in vitamin C-deficient senescence marker protein-30 knockout mice.

Vitamin C (VC) is an essential nutrient for humans and certain other animals. It has antioxidant properties and has been reported to ameliorate oxidative damage to lipids, DNA and proteins. However, the effects of VC on immune function are poorly understood, especially the influence of long-term high-dose VC intake on the number and function of immune cells. In the present study, to evaluate the immune effects of VC, VC-deficient senescence marker protein-30 knockout (SMP30KO) mice were fed a diet containing the recommended level of VC (20 mg/kg per d; 0·02 % VC) or a high level of VC (200 mg/kg per d; 0·2 % VC) for 1 year. The plasma VC concentration of the 0·02 % group was the same as that of age-matched C57BL/6 mice after 1 year of feeding; however, plasma VC concentration and thymus weight were significantly higher in the 0·2 % VC group than in the 0·02 % VC group. The total counts of leucocytes, lymphocytes, granulocytes and monocytes in the peripheral blood, as well as the number of splenocytes and thymocytes, were all significantly higher in the 0·2 % VC group than in the 0·02 % VC group. In addition, the number of naive T cells in peripheral blood lymphocytes, the number of memory T-cell populations in splenocytes, and the number of cluster of differentiation (CD)4⁺CD8⁺ or CD4⁺CD8⁻ or CD4⁻CD8⁺ T cells in thymocytes were all markedly higher in the 0·2 % VC group than in the 0·02 % VC group after 1 year of dietary treatment. These results suggest that a long-term high-dose intake of VC is effective in the maintenance of immune cells, partly through the suppression of age-related thymic involution in VC-deficient SMP30KO mice.

Ascorbic acid deficiency affects genes for oxidation-reduction and lipid metabolism in livers from SMP30/GNL knockout mice.

BACKGROUND: We sought to elucidate the effect of an ascorbic acid (AA) deficiency on gene expression, because the water soluble antioxidant AA is an important bioactive substance in vivo. METHODS: We performed microarray analyses of the transcriptome in the liver from senescence marker protein-30 (SMP30)/gluconolactonase (GNL) knockout (KO) mice, which are unable to synthesize AA in vivo. RESULTS: Our microarray analysis revealed that the AA deficiency increased gene expression related to the oxidation-reduction process, i.e., the nuclear factor, erythroid derived 2, like 2 (Nrf2) gene, which is a reactive oxygen species-sensitive transcriptional factor. Moreover, this AA deficiency increased the expression of genes for lipid metabolism including the cytochrome P450, family 7, subfamily a, polypeptide 1 (Cyp7a1), which is a late-limiting enzyme of the primary bile acid biosynthesis pathway. Although an AA deficiency increased the Cyp7a1 protein level, bile acid levels in the liver and gallbladder decreased. Since Cyp7a1 has a heme iron at the active site, AA must function as a reductant of the iron required for the continuous activation of Cyp7a1. CONCLUSIONS: This experimental evidence strongly supports a role for AA in the physiologic oxidation-reduction process and lipid metabolism including bile acid biosynthesis. GENERAL SIGNIFICANCE: Although many effects of AA supplementation have been reported, no microarray analysis of AA deficiency in vivo is available. Results from using this unique model of AA deficiency, the SMP30/GNL-KO mouse, now provide new information about formerly unknown AA functions that will implement further study of AA in vivo.

Chronic vitamin C insufficiency aggravated thioacetamide-induced liver fibrosis in gulo-knockout mice.

Given the involvement of oxidative stress in liver-disease- or hepato-toxicant-induced hepatic damage and fibrosis, antioxidants are an effective preventive and therapeutic tool. The beneficial results of vitamin C, one of the physiological antioxidants, have been observed both in experimental animals and in humans. However, most of these studies have been concerned with supplementary vitamin C; the effects of under vitamin C insufficiency, which humans sometimes confront, have not been substantially investigated. In the present study, we established a vitamin C-insufficient animal model (half-to-normal serum vitamin C concentration) with gulo(-/-) mice that cannot synthesize vitamin C, and induced hepatotoxicity by means of thioacetamide (TAA) injections twice a week for 18 weeks. Additionally, we explored the direct effects of vitamin C both on immortalized human hepatic stellate LX-2 cells and on rat primary hepatic stellate cells. Vitamin C insufficiency resulted in a decreased survival rate and increased serum markers for hepatocyte damage, such as alanine aminotransferase and aspartate aminotransferase. Concomitantly, the levels of reactive oxygen species (ROS) and lipid peroxides in the liver were increased. Histological examinations of the vitamin C-insufficient liver revealed increases in collagen fiber deposition and activated-hepatic-stellate-cell number. Vitamin C, when directly applied to the LX-2 cells as well as the rat primary hepatic stellate cells, suppressed not only proliferation but hydrogen peroxide-induced collagen expression as well. In conclusion, vitamin C insufficiency exacerbated TAA-induced hepatotoxicity. These effects seem to be mainly from insufficient scavenging of ROS in the liver, and possibly in part, by directly affecting hepatic stellate cells.

Recent applications of engineered animal antioxidant deficiency models in human nutrition and chronic disease.

Dietary antioxidants are essential nutrients that inhibit the oxidation of biologically important molecules and suppress the toxicity of reactive oxygen or nitrogen species. When the total antioxidant capacity is insufficient to quench these reactive species, oxidative damage occurs and contributes to the onset and progression of chronic diseases, such as neurodegenerative diseases, cardiovascular diseases, and cancer. However, epidemiological studies that examine the relationship between antioxidants and disease outcome can only identify correlative associations. Additionally, many antioxidants also have prooxidant effects. Thus, clinically relevant animal models of antioxidant function are essential for improving our understanding of the role of antioxidants in the pathogenesis of complex diseases as well as evaluating the therapeutic potential and risks of their supplementation. Recent progress in gene knockout mice and virus-based gene expression has potentiated these areas of study. Here, we review the current genetically modified animal models of dietary antioxidant function and their clinical relevance in chronic diseases. This review focuses on the 3 major antioxidants in the human body: vitamin C, vitamin E, and uric acid. We examine genetic models of vitamin C synthesis (guinea pig, Osteogenic Disorder Shionogi rat, Gulo(-/-) and SMP30(-/-) mouse mutants) and transport (Slc23a1(-/-) and Slc23a2(-/-) mouse mutants), vitamin E transport (Ttpa(-/-) mouse mutant), and uric acid synthesis (Uox(-/-) mouse mutant). The application of these models to current research goals is also discussed.

Tolerance to nitroglycerin through proteasomal down-regulation of aldehyde dehydrogenase-2 in a genetic mouse model of ascorbate deficiency.

BACKGROUND AND PURPOSE: L-gulonolactone oxidase-deficient (Gulo((-/-))) mice were used to study the effects of ascorbate deficiency on aortic relaxation by nitroglycerin (GTN) with focus on changes in the expression and activity of vascular aldehyde dehydrogenase-2 (ALDH2), which catalyses GTN bioactivation. EXPERIMENTAL APPROACH: Ascorbate deficiency was induced in Gulo((-/-)) mice by ascorbate deprivation for 4 weeks. Some of the animals were concomitantly treated with the proteasome inhibitor bortezomib and effects compared with ascorbate-supplemented Gulo((-/-)), untreated or nitrate-tolerant wild-type mice. Aortic relaxation of the experimental groups to GTN, ACh and a NO donor was studied. Changes in mRNA and protein expression of vascular ALDH2 were quantified by qPCR and immunoblotting, respectively, and aortic GTN denitration rates determined. KEY RESULTS: Like GTN treatment, ascorbate deprivation induced vascular tolerance to GTN that was associated with markedly decreased rates of GTN denitration. Ascorbate deficiency did not affect ALDH2 mRNA levels, but reduced ALDH2 protein expression and the total amount of ubiquitinated proteins to about 40% of wild-type controls. These effects were largely prevented by ascorbate supplementation or treating Gulo((-/-)) mice with the 26S proteasome inhibitor bortezomib. CONCLUSIONS AND IMPLICATIONS: Our data indicate that ascorbate deficiency results in vascular tolerance to GTN via proteasomal degradation of ALDH2. The results support the view that impaired ALDH2-catalysed metabolism of GTN contributes significantly to the development of vascular nitrate tolerance and reveal a hitherto unrecognized protective effect of ascorbate in the vasculature.

Ascorbate supplementation inhibits growth and metastasis of B16FO melanoma and 4T1 breast cancer cells in vitamin C-deficient mice.

Degradation of the extracellular matrix (ECM) plays a critical role in the formation of tumors and metastasis and has been found to correlate with the aggressiveness of tumor growth and invasiveness of cancer. Ascorbic acid, which is known to be essential for the structural integrity of the intercellular matrix, is not produced by humans and must be obtained from the diet. Cancer patients have been shown to have very low reserves of ascorbic acid. Our main objective was to determine the effect of ascorbate supplementation on metastasis, tumor growth and tumor immunohistochemistry in mice unable to synthesize ascorbic acid [gulonolactone oxidase (gulo) knockout (KO)] when challenged with B16FO melanoma or 4T1 breast cancer cells. Gulo KO female mice 36-38 weeks of age were deprived of or maintained on ascorbate in food and water for 4 weeks prior to and 2 weeks post intraperitoneal (IP) injection of 5x105 B16FO murine melanoma cells or to injection of 5x105 4T1 breast cancer cells into the mammary pad of mice. Ascorbate-supplemented gulo KO mice injected with B16FO melanoma cells demonstrated significant reduction (by 71%, p=0.005) in tumor metastasis compared to gulo KO mice on the control diet. The mean tumor weight in ascorbate supplemented mice injected with 4T1 cells was reduced by 28% compared to tumor weight in scorbutic mice. Scorbutic tumors demonstrated large dark cores, associated with increased necrotic areas and breaches to the tumor surface, apoptosis and matrix metalloproteinase-9 (MMP-9), and weak, disorganized or missing collagen I tumor capsule. In contrast, the ascorbate-supplemented group tumors had smaller fainter colored cores and confined areas of necrosis/apoptosis with no breaches from the core to the outside of the tumor and a robust collagen I tumor capsule. In both studies, ascorbate supplementation of gulo KO mice resulted in profoundly decreased serum inflammatory cytokine interleukin (IL)-6 (99% decrease, p=0.01 in the B16F0 study and 85% decrease, p=0.08 in the 4T1 study) compared to the levels in gulo KO mice deprived of ascorbate. In the B16FO study, ascorbate supplementation of gulo KO mice resulted in profoundly decreased serum VEGF (98% decrease, p=0.019 than in the scorbutic gulo KO mice). As expected, mean serum ascorbate level in ascorbate-restricted mice was 2% (p<0.001) of the mean ascorbate levels in supplemented mice. In conclusion, ascorbate supplementation hinders metastasis, tumor growth and inflammatory cytokine secretion as well as enhanced encapsulation of tumors elicited by melanoma and breast cancer cell challenge in gulo KO mice.

Behavioral and monoamine changes following severe vitamin C deficiency.

Severe vitamin C deficiency (ascorbic acid; AA) was induced in gulo-/- mice incapable of synthesizing their own AA. A number of behavioral measures were studied before and during the deprivation period, including a scorbutic period, during which weight loss was observed in the mice. Mice were then resuscitated with AA supplements. During the scorbutic period, gulo-/- mice showed decreased voluntary locomotor activity, diminished physical strength, and increased preference for a highly palatable sucrose reward. These behaviors all returned to control levels following resuscitation. Altered trial times in subordinate mice in the tube test for social dominance in the AA-deprived mice persisted following resuscitation and may signify a depressive-like behavior in these mice. Biochemical analyses were undertaken following a second deprivation period. AA deficiency was accompanied by decreased blood glucose levels, oxidative damage to lipids and proteins in the cortex, and decreases in dopamine and serotonin metabolites in both the cortex and striatum. Given the reasonably high proportions of the population that do not consume sufficient AA in the diet, these data have important implications for physical and psychological function in the general population.

Nitroso-redox status and vascular function in marginal and severe ascorbate deficiency.

UNLABELLED: Marginal vitamin C (ascorbic acid) deficiency is a prevalent yet underappreciated risk factor for cardiovascular disease. Along with glutathione, ascorbate plays important roles in antioxidant defense and redox signaling. Production of nitric oxide (NO) and reactive oxygen species and their interaction, giving rise to nitroso and nitrosyl product formation, are key components of the redox regulation/signaling network. Numerous in vitro studies have demonstrated that these systems are interconnected via multiple chemical transformation reactions, but little is known about their dynamics and significance in vivo. AIMS: We sought to investigate the time-course of changes in NO/redox status and vascular function during ascorbate depletion in rats unable to synthesize vitamin C. RESULTS: We here show that both redox and protein nitros(yl)ation status in blood and vital organs vary dynamically during development of ascorbate deficiency. Prolonged marginal ascorbate deficiency is associated with cell/tissue-specific perturbations in ascorbate and glutathione redox and NO status. Scurvy develops earlier in marginally deficient compared to adequately supplemented animals, with blunted compensatory NO production and a dissociation of biochemistry from clinical symptomology in the former. Paradoxically, aortic endothelial reactivity is enhanced rather than impaired, irrespective of ascorbate status. Innovation/Conclusion: Enhanced NO production and protein nitros(yl)ation are integral responses to the redox stress of acute ascorbate deprivation. The elevated cardiovascular risk in marginal ascorbate deficiency is likely to be associated with perturbations of NO/redox-sensitive signaling nodes unrelated to the regulation of vascular tone. This new model may have merit for the future study of redox-sensitive events in marginal ascorbate deficiency.

Vitamin C deficiency activates the purine nucleotide cycle in zebrafish.

Vitamin C (ascorbic acid, AA) is a cofactor for many important enzymatic reactions and a powerful antioxidant. AA provides protection against oxidative stress by acting as a scavenger of reactive oxygen species, either directly or indirectly by recycling of the lipid-soluble antioxidant, α-tocopherol (vitamin E). Only a few species, including humans, guinea pigs, and zebrafish, cannot synthesize AA. Using an untargeted metabolomics approach, we examined the effects of α-tocopherol and AA deficiency on the metabolic profiles of adult zebrafish. We found that AA deficiency, compared with subsequent AA repletion, led to oxidative stress (using malondialdehyde production as an index) and to major increases in the metabolites of the purine nucleotide cycle (PNC): IMP, adenylosuccinate, and AMP. The PNC acts as a temporary purine nucleotide reservoir to keep AMP levels low during times of high ATP utilization or impaired oxidative phosphorylation. The PNC promotes ATP regeneration by converting excess AMP into IMP, thereby driving forward the myokinase reaction (2ADP → AMP + ATP). On the basis of this finding, we investigated the activity of AMP deaminase, the enzyme that irreversibly deaminates AMP to form IMP. We found a 47% increase in AMP deaminase activity in the AA-deficient zebrafish, complementary to the 44-fold increase in IMP concentration. These results suggest that vitamin C is crucial for the maintenance of cellular energy metabolism.