Pharmacological Doses Of Vitamin Research Articles

Vitamin-C-dependent downregulation of the citrate metabolism pathway potentiates pancreatic ductal adenocarcinoma growth arrest.

In pancreatic ductal adenocarcinoma (PDAC), metabolic rewiring and resistance to standard therapy are closely associated. PDAC cells show enormous requirements for glucose-derived citrate, the first rate-limiting metabolite in the synthesis of new lipids. Both the expression and activity of citrate synthase (CS) are extraordinarily upregulated in PDAC. However, no previous relationship between gemcitabine response and citrate metabolism has been documented in pancreatic cancer. Here, we report for the first time that pharmacological doses of vitamin C are capable of exerting an inhibitory action on the activity of CS, reducing glucose-derived citrate levels. Moreover, ascorbate targets citrate metabolism towards the de novo lipogenesis pathway, impairing fatty acid synthase (FASN) and ATP citrate lyase (ACLY) expression. Lowered citrate availability was found to be directly associated with diminished proliferation and, remarkably, enhanced gemcitabine response. Moreover, the deregulated citrate-derived lipogenic pathway correlated with a remarkable decrease in extracellular pH through inhibition of lactate dehydrogenase (LDH) and overall reduced glycolytic metabolism. Modulation of citric acid metabolism in highly chemoresistant pancreatic adenocarcinoma, through molecules such as vitamin C, could be considered as a future clinical option to improve patient response to standard chemotherapy regimens.

Fasting and cancer: from yeast to mammals.

Fasting and fasting mimicking diets extend lifespan and healthspan in mouse models and decrease risk factors for cancer and other age-related pathologies in humans. Normal cells respond to fasting and the consequent decrease in nutrients by down-regulating proto-oncogene pathways to enter a stress-resistant mode, which protects them from different cancer therapies. In contrast, oncogene mutations and the constitutive activation of pathways including RAS, AKT, and PKA allow cancer cells to disobey fasting-dependent anti-growth signal. Importantly, in different tumor types, fasting potentiates the toxicity of various therapies by increasing reactive oxygen species and oxidative stress, which ultimately leads to DNA damage and cell death. This effect is not limited to chemotherapy, since periodic fasting/FMD cycles potentiate the effects of tyrosine kinase inhibitors, hormone therapy, radiotherapy, and pharmacological doses of vitamin C. In addition, the anticancer effects of fasting/FMD can also be tumor-independent and involve an immunotherapy-like activation of T cell-dependent attack of tumor cells. Supported by a range of pre-clinical studies, clinical trials are beginning to confirm the safety and efficacy of fasting/FMD cycles in improving the potential of different cancer therapies, while decreasing side effects to healthy cells and tissues.

The vitamin A transporter STRA6 adjusts the stoichiometry of chromophore and opsins in visual pigment synthesis and recycling

The retinal pigment epithelium of the vertebrate eyes acquires vitamin A from circulating retinol binding protein for chromophore biosynthesis. The chromophore covalently links with an opsin protein in the adjacent photoreceptors of the retina to form the bipartite visual pigment complexes. We here analyzed visual pigment biosynthesis in mice deficient for the retinol-binding protein receptor STRA6. We observed that chromophore content was decreased throughout the life cycle of these animals, indicating that lipoprotein-dependent delivery pathways for the vitamin cannot substitute for STRA6. Changes in the expression of photoreceptor marker genes, including a downregulation of the genes encoding rod and cone opsins, paralleled the decrease in ocular retinoid concentration in STRA6-deficient mice. Despite this adaptation, cone photoreceptors displayed absent or mislocalized opsins at all ages examined. Rod photoreceptors entrapped the available chromophore but exhibited significant amounts of chromophore-free opsins in the dark-adapted stage. Treatment of mice with pharmacological doses of vitamin A ameliorated the rod phenotype but did not restore visual pigment synthesis in cone photoreceptors of STRA6-deficient mice. The imbalance between chromophore and opsin concentrations of rod and cone photoreceptors was associated with an unfavorable retinal physiology, including diminished electrical responses of photoreceptors to light, and retinal degeneration during aging. Together, our study demonstrates that STRA6 is critical to adjust the stoichiometry of chromophore and opsins in rod and cone photoreceptors and to prevent pathologies associated with ocular vitamin A deprivation.

Vitamin C activates pyruvate dehydrogenase (PDH) targeting the mitochondrial tricarboxylic acid (TCA) cycle in hypoxic KRAS mutant colon cancer.

Background: In hypoxic tumors, positive feedback between oncogenic KRAS and HIF-1α involves impressive metabolic changes correlating with drug resistance and poor prognosis in colorectal cancer. Up to date, designed KRAS-targeting molecules do not show clear benefits in patient overall survival (POS) so pharmacological modulation of aberrant tricarboxylic acid (TCA) cycle in hypoxic cancer has been proposed as a metabolic vulnerability of KRAS-driven tumors.Methods: Annexin V-FITC and cell viability assays were carried out in order to verify vitamin C citotoxicity in KRAS mutant SW480 and DLD1 as well as in Immortalized Human Colonic Epithelial Cells (HCEC). HIF1a expression and activity were determined by western blot and functional analysis assays. HIF1a direct targets GLUT1 and PDK1 expression was checked using western blot and qRT-PCR. Inmunohistochemical assays were perfomed in tumors derived from murine xenografts in order to validate previous observations in vivo. Vitamin C dependent PDH expression and activity modulation were detected by western blot and colorimetric activity assays. Acetyl-Coa levels and citrate synthase activity were assessed using colorimetric/fluorometric activity assays. Mitochondrial membrane potential (Δψ) and cell ATP levels were assayed using fluorometric and luminescent test.Results: PDK-1 in KRAS mutant CRC cells and murine xenografts was downregulated using pharmacological doses of vitamin C through the proline hydroxylation (Pro402) of the Hypoxia inducible factor-1(HIF-1)α, correlating with decreased expression of the glucose transporter 1 (GLUT-1) in both models. Vitamin C induced remarkable ATP depletion, rapid mitochondrial Δψ dissipation and diminished pyruvate dehydrogenase E1-α phosphorylation at Serine 293, then boosting PDH and citrate synthase activity.Conclusion: We report a striking and previously non reported role of vitamin C in the regulation of the pyruvate dehydrogenase (PDH) activity, then modulating the TCA cycle and mitochondrial metabolism in KRAS mutant colon cancer. Potential impact of vitamin C in the clinical management of anti-EGFR chemoresistant colorectal neoplasias should be further considered.

Differential sensitivities of triple-negative breast cancer stem cell towards various doses of vitamin C: An insight into the internal antioxidant systems.

Cancer stem cells (CSCs) are quiescent and self-renewing, having low levels of reactive oxygen species (ROS), and are responsible for cancer recurrence after chemotherapy and radiotherapy. However, the interplay between the ROS production and scavenging from the oxidative stress has never been studied in breast CSCs. In this present study, we have investigatedthe cellular energetics of two triple-negative breast cancer stem cells (MDA-MB-231 and MDA-MB-468) treated with two pharmacological doses of vitamin C (10 and 20 mM) that generated ROS. Our results indicate a differential behavior of ROS scavenging by both the CSCs. MDA-MB-468 CSCs exhibited higher resistance to ROS induced damage owing to the higher antioxidant activity, lower mitochondrial damage, and less decrease in membrane potential (ΔΨm ) as compared with MDA-MB-231 CSCs. Moreover, MDA-MB-231 CSCs exhibited an intrinsic apoptosis pathway by activating the cytochrome c, caspase-9, 3, 7, and cleaved PARP upon treatment with vitamin C. This data suggestsa possible strategy for targeting breast CSCs using vitamin C. Taken together, the CSCs from MDA-MB-231 could be easily targeted by high/pharmacological doses of vitamin C (≥20 mM) thereby indicating a less robust internal antioxidant machinery.

STRA6 is critical for cellular vitamin A uptake and homeostasis.

Vitamin A must be adequately distributed within the body to maintain the functions of retinoids in the periphery and chromophore production in the eyes. Blood transport of the lipophilic vitamin is mediated by the retinol-binding protein, RBP4. Biochemical evidence suggests that cellular uptake of vitamin A from RBP4 is facilitated by a membrane receptor. This receptor, identified as the Stimulated by retinoic acid gene 6 (Stra6) gene product, is highly expressed in epithelia that constitute blood-tissue barriers. Here we established a Stra6 knockout mouse model to analyze the metabolic basis of vitamin A homeostasis in peripheral tissues. These mice were viable when bred on diets replete in vitamin A, but evidenced markedly reduced levels of ocular retinoids. Ophthalmic imaging and histology revealed malformations in the choroid and retinal pigmented epithelium, early cone photoreceptor cell death, and reduced lengths of rod outer segments. Similar to the blood-retina barrier in the RPE, vitamin A transport through the blood-cerebrospinal fluid barrier in the brain's choroid plexus was impaired. Notably, treatment with pharmacological doses of vitamin A restored vitamin A transport across these barriers and rescued the vision of Stra6(-/-) mice. Furthermore, under conditions mimicking vitamin A excess and deficiency, our analyses revealed that STRA6-mediated vitamin A uptake is a regulated process mandatory for ocular vitamin A uptake when RBP4 constitutes the only transport mode in vitamin A deficiency. These findings identifying STRA6 as a bona fide vitamin A transporter have important implications for disease states associated with impaired blood vitamin A homeostasis.

Pharmacological doses of vitamin A deteriorate lupus-like disease in the MRL/lpr mouse model (THER5P.829)

Abstract The critical roles of retinoic acid (RA), a metabolite of vitamin A (VA), in both tolerogenic and immunogenic immune responses have been documented. However, how VA affects the development of autoimmunity is still unclear. Here we demonstrate that pharmacological doses of VA had adverse effects on the development of autoimmune lupus in the MRL/lpr mouse model. We administered, orally, RA (6 mg/kg body weight/day) or retinyl palmitate combined with 10% RA (VARA, a total of 6.6 mg/kg/day) to the mice starting from 6 weeks of age. At this age, the mice do not exhibit overt signs of lupus. However, the immunogenic environment preceding disease onset has been established that is evidenced by an increase of total IgM/IgG in the plasma and expansion of lymphocytes and dendritic cells in secondary lymphoid organs. After 8 weeks of RA or VARA treatment, significantly higher pathological scores in kidney, lung, and brain were observed, which were correlated with a marked increase in B-cell responses. In addition, although the number of T cells in the mesenteric lymph node decreased with RA that led to reduced tissue weight, the proportions of T-cell subsets did not change. Importantly, neither RA nor VARA affected regulatory T cells in these mice. Altogether, our results suggest that under the immunogenic environment in autoimmune lupus, VA can generate more severe disease rather than inducing tolerance. Thus, administration of VA in lupus treatment should be approached with caution.

STRA6: A gatekeeper of neuronal vitamin A homeostasis

Mutations in the STRA6 gene are associated with fatal Human Micro‐ophthalmic Syndrome 9. We generated a mouse model to elucidate the biochemical basis of this congenital disease. These mice failed to transport vitamin A across the blood‐retina and ‐ brain barrier and developed blindness, brain anomalies and hydrocephalus. Restriction of embryonic vitamin A supply extended malformations to extra‐neuronal tissues, whereas pharmacological doses of vitamin A mitigated anomalies of STRA6‐deficient offspring. Our study established a critical role of STRA6 for retinoid homeostasis of neuronal tissues and identified the vitamin as stochastic modulator of the phenotypic characteristics of this disease.

Medical foods: Inborn errors of metabolism and the reimbursement dilemma

PurposeMedical foods and pharmacological doses of vitamins are used to treat certain genetic diseases for the duration of a patient's lifetime, which necessitates life-long management of the condition and diet by the patient and a health care provider. However, payment for medical foods and health insurance coverage of medical foods is not uniform. MethodsA survey of states' newborn screening (NBS) representatives and a review of state policies (as of 2008) were conducted to ascertain payment and insurance coverage of medical foods. ResultsAccording to the NBS representatives, 61% of the states provided or guaranteed medical foods for all or a subset of the population detected by NBS, whereas 82% of states provided or guaranteed medical formulas for the same population. Policies for private health insurance coverage existed in 33/50 states, and range from providing medical food for one specific metabolic condition to providing it for any NBS disorder. In addition, there is variability among states in the specificity of defining what conditions qualify for medical foods. ConclusionThis article suggests four options, not mutually exclusive, options for addressing the patchwork of state policies regarding coverage of medical foods, ranging from amending Medicaid legislation to enacting federal legislation, or changing the Food and Drug Administration's stance on oversight of medical foods.

In Situ Modulation of Oxidative Stress: A Novel and Efficient Strategy to Kill Cancer Cells

Cancer cells show an up-regulation of glycolysis, they readily take up vitamin C, and they appear more susceptible to an oxidative stress than the surrounding normal cells. Here we compare, analyse and discuss these particular hallmarks by performing experiments in murine hepatomas (TLT cells) and freshly isolated mouse hepatocytes. The results show that rates of lactate formation are higher in TLT cells as compared to mouse hepatocytes, but their ATP content represents less than 25% of that in normal cells. The uptake of vitamin C is more important in hepatoma cells as compared to normal hepatocytes. This uptake mainly occurs through GLUT1 transporters. Hepatoma cells have less than 10% of antioxidant enzyme activities as compared to normal hepatocytes. This decrease includes not only the major antioxidant enzymes, namely catalase, superoxide dismutase and glutathione peroxidase, but also the GSH content. Moreover, catalase is almost not expressed in hepatoma cells as shown by western blot analysis. We explored therefore a selective exposure of cancer cells to an oxidative stress induced by pro-oxidant mixtures containing pharmacological doses of vitamin C and a redox active compound such as menadione (vitamin K(3)). Indeed, the combination of vitamin C (which accumulates in hepatoma cells) and a quinone undergoing a redox cycling (vitamin K(3)) leads to an oxidative stress that kills cancer cells in a selective manner. This differential sensitivity between cancer cells and normal cells may have important clinical applications, as it has been observed with other pro-oxidants like Arsenic trioxide, isothiocyanates, Adaphostin.

T1150 Efficacy of Two Different Weekly Doses of Vitamin D (400 Iu and 50,000 Iu) in Patients with Crohn's Disease in Improving Vitamin D Nutritional Status

Background: Vitamin D deficiency is prevalent among patients with Crohn's disease (CD). Factors predisposing to hypovitaminosis D in these patients may include lack of adequate vitamin D intake or supplementation and malabsorption. Since these factors have been poorly described in patients with CD, the aims of this study were to assess baseline serum vitamin D status and the efficacy of a standard pharmacologic dose of vitamin D in improving serum 25(OH)D levels.Methods: Consecutive adult patients with CD presenting for routine office visits to Boston Medical Center participated in the study from April 2007 to November 2007. Baseline serum 25(OH)D levels were measured by HPLC in 21 consecutive patients after which patients were randomized to receive either 50,000 IU (n = 14) or 400 IU (n = 7) of vitamin D2 q week for seven weeks. At the end of the study, changes in serum 25(OH)D from baseline were compared. As secondary endpoints, changes from baseline in serum calcium, hematocrit, ESR, CRP were measured. In addition, changes in serum levels of 12 cytokines (GMCSF, IFN-gamma, IL-10, IL-1beta, IL-s, IL-4, IL-5, IL-6, IL-8, MCP-1, MIP-1alpha, TNF-alpha) were evaluated by using multi-analyte profiling beads (Luminex, Toronto, ON). Results: Baseline serum levels of 25(OH)D were not significantly different between treatment arms (21.3 vs. 26.1 ng/ml). Both treatment arms significantly increased serum 25(OH)D levels over baseline. Those patients receiving 50,000 IU of vitamin D weekly had a mean increase of 25(OH)D of 61% (26.1 to 37 ng/ml, p=0.007) while those receiving 400 IU of vitamin D weekly had a mean increase of 25(OH)of 128% (21.3 to 41.6 ng/ml, p=0.035). There was no significant difference in end serum levels of 25(OH)D between the treatment arms (41.6 vs. 37.8 ng/ml). Neither a significant increase in serum 25(OH)D levels nor randomization to the 50,000 IU per week arm of the study had an effect any laboratory markers of disease activity (ESR, CRP, Hct) nor on serum cytokine levels. One patient in the high dose group discontinued the study medication after 4 doses secondary to increased diarrhea. Conclusions: 50,000 IU of vitamin D given once a week for 7 weeks was no more effective than 400 IU of vitamin D given once a week for 7 weeks in raising serum 25(OH)D levels. Hence, other variables that affect serum vitamin D levels such as sun exposure due to seasonal variation over the course of the study may be responsible for the significant increase in serum 25(OH)D in each group. The lack of difference in serum 25(OH)D levels between the two groups may be due to compromised absorption secondary to their Crohn's disease.

Optimal Vitamin D Status for the Prevention and Treatment of Osteoporosis

Vitamin D(3) (cholecalciferol) sufficiency is essential for maximising bone health. Vitamin D enhances intestinal absorption of calcium and phosphorus. The major source of vitamin D for both children and adults is exposure of the skin to sunlight. Season, latitude, skin pigmentation, sunscreen use, clothing and aging can dramatically influence the synthesis of vitamin D in the skin. Very few foods naturally contain vitamin D or are fortified with vitamin D. Serum 25-hydroxyvitamin D [25(OH)D; calcifediol] is the best measure of vitamin D status. Vitamin D deficiency [as defined by a serum 25(OH)D level of <50 nmol/L (<20 ng/mL)] is pandemic. This deficiency is very prevalent in osteoporotic patients. Vitamin D deficiency causes osteopenia, osteoporosis and osteomalacia, increasing the risk of fracture. Unlike osteoporosis, which is a painless disease, osteomalacia causes aching bone pain that is often misdiagnosed as fibromyalgia or chronic pain syndrome or is simply dismissed as depression. Vitamin D deficiency causes muscle weakness, increasing the risk of falls and fractures, and should be aggressively treated with pharmacological doses of vitamin D. Vitamin D sufficiency can be sustained by sensible sun exposure or ingesting at least 800-1000 IU of vitamin D(3) daily. Patients being treated for osteoporosis should be adequately supplemented with calcium and vitamin D to maximise the benefit of treatment.

Efeito da administração de vitamina C sobre a colonização do estômago por Helicobacter pylori

The conventional treatment of Helicobacter pylori infection consists on antibiotics, to which a small but significant number of patients are non-responders. Alternative treatments to the infection have been suggested, including the use of antioxidants. There has been such increasing interest upon vitamin C since it was demonstrated vitamin C concentrations in the stomach of infected patients are significant lower compared to healthy subjects. Pharmacological doses of vitamin C have been investigated for eradication of H. pylori, with controversial results. To evaluate the effect of oral administration of vitamin C on H. pylori colonization in the stomach of patients with chronic gastritis and patients with peptic ulcer who had experienced antimicrobial treatment failures. Protocol I: randomized, double-blinded, placebo controlled study, with patients with chronic gastritis, with no previous treatment for eradication. Protocol II: open, uncontrolled study, with patients with peptic ulcer, with at least two previous treatments for eradication. Treatment consisted of 5 g vitamin C for 28 consecutive days. The effect of the treatment was evaluated by 14C-urea breath test concerning eradication rate, radioactivity variation and infection suppression. In Protocol I, 38 patients completed the study--21 received vitamin C and 17 received placebo 28 consecutive days. Eradication rates per-protocol analysis with vitamin C were 0, with 95% confidence interval of 0-15%. In Protocol II, eight patients completed treatment. Eradication rate was 0%, with 95% confidence interval of 0-12%. H. pylori load was not decreased. Administration of vitamin C, in a 5 g/day dosage during 28 days is neither effective for H. pylori eradication nor quantitatively alters the bacteria load in the stomach of infected patients.

Index of Suspicion In the Nursery

A 9-day-old Hispanic boy presents to the emergency department with seizures and apnea. The seizure lasts for about 3 minutes and is characterized by stiffening of the body and laryngospasm. Laboratory evaluation reveals a serum calcium concentration of 6 mg/dL (1.5 mmol/L). Hypocalcemic tetany resolves after administration of intravenous calcium. The infant also has fever of 100.4°F (37.7°C). The infant was born at term, and his birthweight was 3.2 kg. He is the fifth child born of nonconsanguineous parentage. The antenatal period was uneventful. Because the family does not have insurance, the mother had not taken prenatal vitamins and supplements. The baby has been fed with human milk and formula. On physical examination upon admission to the hospital, his temperature is 99°F (36.9°C), pulse is 186 beats/min, respiratory rate is 54 breaths/min, blood pressure is 97/64 mm Hg, and weight is 3.83 kg. He has no dysmorphic features and is normocephalic, with an open and flat anterior fontanelle without craniotabes. No cataracts or Chvostek sign are present. Cardiovascular examination reveals a regular heart rate and rhythm, with no murmurs. The lungs are clear to auscultation bilaterally, and there is no hepatosplenomegaly. Neurologic findings are normal. Laboratory evaluation reveals: sodium, 136 mEq/L (136 mmol/L); potassium, 5.2 mEq/L (5.2 mmol/L); chloride, 101 mEq/L (101 mmol/L); bicarbonate, 26 mEq/L (26 mmol/L); blood urea nitrogen, 10 mg/dL (3.57 mmol/L); creatinine, 0.3 mg/dL (26.5 mcmol/L); glucose, 109 mg/dL (6.1 mmol/L); calcium, 6.6 mg/dL (1.65 mmol/L); phosphorous, 10.5 mg/dL (3.4 mmol/L); albumin, 3.0 g/dL (30 g/L); and magnesium, 2 mg/dL (0.82 mmol/L). The white blood cell count and differential count are normal. Findings on cerebrospinal fluid evaluation are normal. However, the 25-hydroxyvitamin D concentration is less than 7 ng/mL (17.5 nmol/L) (normal, 10 to 68 ng/mL [25 to 169.7 nmol/L]), the 1,25-dihydroxyvitamin D concentration is 45 …

Vitamin E, nuclear receptors and xenobiotic metabolism

Supplemental vitamin E (α-tocopherol) is taken daily by more than 35 million people in the US. Following absorption and liver uptake, the fate of vitamin E is largely unknown. Of potential importance are recent clinical studies that have reported adverse effects of vitamin E that may be directly related to its hepatic metabolism. In an in vitro system, both vitamin E and rifampicin, a known stimulator of xenobiotic metabolism, activated the pregnane X receptor (PXR), an orphan nuclear receptor. PXR as a heterodimer with the retinoid X receptor (RXR), binds to specific cis-elements in the promoter regions of genes. PXR/RXR regulates a constellation of genes involved in xenobiotic detoxification, including oxidation, conjugation, and transporters. Importantly, PXR/RXR regulates the cytochrome P450 (CYP), CYP3A, involved in the hepatic detoxification of more than 50% of prescription drugs. Vitamin E acting as a PXR ligand could alter these PXR-mediated reactions. Unfortunately, the extent to which pharmacologic doses of vitamin E modulate these pathways in vivo has not been determined.

Vitamin E supplementation for prevention of morbidity and mortality in preterm infants.

Treating very low birth weight (VLBW) infants with pharmacologic doses of vitamin E as an antioxidant agent has been proposed for preventing or limiting retinopathy of prematurity, intracranial hemorrhage, hemolytic anemia, and chronic lung disease. However, excessive doses of vitamin E may result in side effects. The aim of this systematic review was to assess the effects of vitamin E supplementation on morbidity and mortality in preterm infants. We searched MEDLINE (October 2002), EMBASE (March 2002), the Cochrane Controlled Trials Register (CCTR) from the Cochrane Library, 2003, Issue 1, and personal files for clinical trials assessing vitamin E in preterm infants. We selected trials analyzing primary outcomes (mortality or combined long-term morbidity) or secondary outcomes (other morbidity) in infants with gestational age less than 37 weeks or birth weight less than 2500 grams. The intervention was allocation to routine supplementation with vitamin E in the treatment group versus placebo, no treatment or another type, dose or route of administration of vitamin E. We used standard methods of the Cochrane Collaboration and of the Cochrane Neonatal Review Group. Twenty-six randomized clinical trials fulfilled entry criteria. No study assessed combined long-term morbidity. Routine vitamin E supplementation significantly reduced the risk of germinal/intraventricular hemorrhage (typical relative risk [RR] 0.85, 95% confidence interval [CI] 0.73, 0.99), increased the risk of sepsis (typical RR 1.52, CI 1.13, 2.04) and increased hemoglobin concentration by a small amount, but did not significantly affect mortality and other morbidity. In VLBW infants, vitamin E supplementation increased the risk of sepsis, and reduced the risk of severe retinopathy and blindness among those examined. Subgroup analyses in VLBW infants showed (1) an association between serum tocopherol levels greater than 3.5 mg/dl and increased risk of sepsis and reduced risk for severe retinopathy among those examined; and (2) an association between intravenous, high-dose administration of vitamin E and increased risk of sepsis. Vitamin E supplementation in preterm infants reduced the risk of intracranial hemorrhage but increased the risk of sepsis. In very low birth weight infants it increased the risk of sepsis, and reduced the risk of severe retinopathy and blindness among those examined. Evidence does not support the routine use of vitamin E supplementation by intravenous route at high doses, or aiming at serum tocopherol levels greater than 3.5 mg/dl.

Deletion of deoxyribonucleic acid binding domain of the vitamin D receptor abrogates genomic and nongenomic functions of vitamin D.

The vitamin D hormone 1,25-dihydroxyvitamin D(3) [1,25-(OH)(2)D(3)], the biologically active form of vitamin D, is essential for an intact mineral metabolism. Using gene targeting, we sought to generate vitamin D receptor (VDR) null mutant mice carrying the reporter gene lacZ driven by the endogenous VDR promoter. Here we show that our gene-targeted mutant mice express a VDR with an intact hormone binding domain, but lacking the first zinc finger necessary for DNA binding. Expression of the lacZ reporter gene was widely distributed during embryogenesis and postnatally. Strong lacZ expression was found in bones, cartilage, intestine, kidney, skin, brain, heart, and parathyroid glands. Homozygous mice are a phenocopy of mice totally lacking the VDR protein and showed growth retardation, rickets, secondary hyperparathyroidism, and alopecia. Feeding of a diet high in calcium, phosphorus, and lactose normalized blood calcium and serum PTH levels, but revealed a profound renal calcium leak in normocalcemic homozygous mutants. When mice were treated with pharmacological doses of vitamin D metabolites, responses in skin, bone, intestine, parathyroid glands, and kidney were absent in homozygous mice, indicating that the mutant receptor is nonfunctioning and that vitamin D signaling pathways other than those mediated through the classical nuclear receptor are of minor physiological importance. Furthermore, rapid, nongenomic responses to 1,25-(OH)(2)D(3) in osteoblasts were abrogated in homozygous mice, supporting the conclusion that the classical VDR mediates the nongenomic actions of 1,25-(OH)(2)D(3).

Oral antioxidants counteract the negative effects of female aging on oocyte quantity and quality in the mouse.

This study aims to compare the effect of early and late onset administration of oral antioxidants on number and quality of oocytes retrieved from aged mice after exogenous ovarian stimulation. Control hybrid females were fed a standard diet supplemented or not supplemented with pharmacological doses of vitamins C and E either from the first day of weaning or from the age of 32 weeks until they were autopsied at the age 40-42, 50-52, or 57-62 weeks after exogenous ovarian stimulation. Analysis of chromosomal distribution, DNA organization and cellular morphology was performed in ovulated cumulus-enclosed and -free oocytes, ovarian non-germinal vesicle oocytes enclosed by or free of mucous cumulus cells and in vitro-matured ovarian germinal-vesicle oocytes. Both early and late onset administration of oral antioxidants counteracted the negative effects of female aging on number of ovarian oocytes and total percentage of oocytes retrieved from oviducts and ovaries exhibiting a normal distribution of chromosomes in the metaphase-II plate and/or morphological traits of apoptosis. Although both early and late onset administration of oral antioxidants can counteract the negative effects of female aging on number and quality of oocytes, transference of these results to human beings should be made with caution because of the potential side effects of high doses of vitamins on reproductive function as well as many other undesirable systemic disorders.

Effect of vitamin C on forearm blood flow and glucose metabolism in essential hypertension.

In 9 patients with essential hypertension, we tested whether a high-dose (12 mg. min(-1)) vitamin C infusion into the brachial artery, by improving endothelium-dependent vasodilatation, would also attenuate the insulin resistance of deep forearm tissues. We measured the effect of vitamin C on acetylcholine (Ach)-induced vasodilatation and on forearm glucose uptake during systemic hyperinsulinemia; in all studies, the contralateral forearm served as the control. Intrabrachial Ach infusion produced a stable increase in forearm blood flow, from 2.6+/-0.3 to 10.6+/-2.1 mL. min(-1). dL(-1); when vitamin C was added, a further rise in forearm blood flow (to 13.4 mL. min(-1). dL(-1); P<0.03 vs Ach alone) was observed. In response to insulin, blood flow in both the infused and control forearms did not significantly change from baseline values (+10+/-16% and +2+/-11%, respectively). In contrast, when vitamin C was added, blood flow in the infused forearm increased significantly (to 3.7+/-0.7 mL. min(-1). dL(-1); P<0.02 vs 2.8+/-0.6 mL. min(-1). dL(-1) in the control forearm). Insulin stimulated whole-body glucose disposal to 20+/-2 micromol. min(-1). kg(-1), compatible with the presence of marked insulin resistance. Forearm glucose uptake was similarly stimulated after 80 minutes of insulin infusion (to 2.11+/-0.42 and 2.06+/-0.43 micromol. min(-1). dL(-1), infused and control, respectively). When intrabrachial vitamin C was added, no difference in glucose uptake was observed between the 2 forearms (infused, 2.37+/-0.44 micromol. min(-1). dL(-1)and control, 2.36+/-0. 53 micromol. min(-1). dL(-1)). Forearm O(2) uptake at baseline was also similar in the 2 forearms (infused, 9.7+/-0.7 micromol. min(-1). dL(-1) and control, 9.6+/-1.1 micromol. min(-1). dL(-1)) and was not changed by either insulin or vitamin C. We conclude that in the deep forearm tissues of patients with essential hypertension and insulin resistance, an acute improvement in endothelial function, obtained with pharmacological doses of vitamin C, restores insulin-mediated vasodilatation but does not improve insulin-mediated glucose uptake. Thus, the endothelial dysfunction of essential hypertension is unlikely to be responsible for their metabolic insulin resistance.

Decreased bioavailability of vitamin D in obesity

Obesity is associated with vitamin D insufficiency and secondary hyperparathyroidism. This study assessed whether obesity alters the cutaneous production of vitamin D(3) (cholecalciferol) or the intestinal absorption of vitamin D(2) (ergocalciferol). Healthy, white, obese [body mass index (BMI; in kg/m(2)) > or = 30] and matched lean control subjects (BMI </= 25) received either whole-body ultraviolet radiation or a pharmacologic dose of vitamin D(2) orally. Obese subjects had significantly lower basal 25-hydroxyvitamin D concentrations and higher parathyroid hormone concentrations than did age-matched control subjects. Evaluation of blood vitamin D(3) concentrations 24 h after whole-body irradiation showed that the incremental increase in vitamin D(3) was 57% lower in obese than in nonobese subjects. The content of the vitamin D(3) precursor 7-dehydrocholesterol in the skin of obese and nonobese subjects did not differ significantly between groups nor did its conversion to previtamin D(3) after irradiation in vitro. The obese and nonobese subjects received an oral dose of 50000 IU (1.25 mg) vitamin D(2). BMI was inversely correlated with serum vitamin D(3) concentrations after irradiation (r = -0.55, P: = 0.003) and with peak serum vitamin D(2) concentrations after vitamin D(2) intake (r = -0.56, P: = 0.007). Obesity-associated vitamin D insufficiency is likely due to the decreased bioavailability of vitamin D(3) from cutaneous and dietary sources because of its deposition in body fat compartments.