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      Vitamin C in Health and Disease: Its Role in the Metabolism of Cells and Redox State in the Brain

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          Abstract

          Ever since Linus Pauling published his studies, the effects of vitamin C have been surrounded by contradictory results. This may be because its effects depend on a number of factors such as the redox state of the body, the dose used, and also on the tissue metabolism. This review deals with vitamin C pharmacokinetics and its participation in neurophysiological processes, as well as its role in the maintenance of redox balance. The distribution and the concentration of vitamin C in the organs depend on the ascorbate requirements of each and on the tissue distribution of sodium-dependent vitamin C transporter 1 and 2 (SVCT1 and SVCT2). This determines the specific distribution pattern of vitamin C in the body. Vitamin C is involved in the physiology of the nervous system, including the support and the structure of the neurons, the processes of differentiation, maturation, and neuronal survival; the synthesis of catecholamine, and the modulation of neurotransmission. This antioxidant interacts with self-recycling mechanisms, including its participation in the endogenous antioxidant system. We conclude that the pharmacokinetic properties of ascorbate are related to the redox state and its functions and effects in tissues.

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          Most cited references77

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          The SLC2 (GLUT) family of membrane transporters.

          GLUT proteins are encoded by the SLC2 genes and are members of the major facilitator superfamily of membrane transporters. Fourteen GLUT proteins are expressed in the human and they are categorized into three classes based on sequence similarity. All GLUTs appear to transport hexoses or polyols when expressed ectopically, but the primary physiological substrates for several of the GLUTs remain uncertain. GLUTs 1-5 are the most thoroughly studied and all have well established roles as glucose and/or fructose transporters in various tissues and cell types. The GLUT proteins are comprised of ∼500 amino acid residues, possess a single N-linked oligosaccharide, and have 12 membrane-spanning domains. In this review we briefly describe the major characteristics of the 14 GLUT family members. Copyright © 2012 Elsevier Ltd. All rights reserved.
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            The pecking order of free radicals and antioxidants: lipid peroxidation, alpha-tocopherol, and ascorbate.

            Free radicals vary widely in their thermodynamic properties, ranging from very oxidizing to very reducing. These thermodynamic properties can be used to predict a pecking order, or hierarchy, for free radical reactions. Using one-electron reduction potentials, the predicted pecking order is in agreement with experimentally observed free radical electron (hydrogen atom) transfer reactions. These potentials are also in agreement with experimental data that suggest that vitamin E, the primary lipid soluble small molecule antioxidant, and vitamin C, the terminal water soluble small molecule antioxidant, cooperate to protect lipids and lipid structures against peroxidation. Although vitamin E is located in membranes and vitamin C is located in aqueous phases, vitamin C is able to recycle vitamin E; i.e., vitamin C repairs the tocopheroxyl (chromanoxyl) radical of vitamin E, thereby permitting vitamin E to function again as a free radical chain-breaking antioxidant. This review discusses: (i) the thermodynamics of free radical reactions that are of interest to the health sciences; (ii) the fundamental thermodynamic and kinetic properties that are associated with chain-breaking antioxidants; (iii) the unique interfacial nature of the apparent reaction of the tocopherol free radical (vitamin E radical) and vitamin C; and (iv) presents a hierarchy, or pecking order, for free radical electron (hydrogen atom) transfer reactions.
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              Physiological functions of thioredoxin and thioredoxin reductase.

              Thioredoxin, thioredoxin reductase and NADPH, the thioredoxin system, is ubiquitous from Archea to man. Thioredoxins, with a dithiol/disulfide active site (CGPC) are the major cellular protein disulfide reductases; they therefore also serve as electron donors for enzymes such as ribonucleotide reductases, thioredoxin peroxidases (peroxiredoxins) and methionine sulfoxide reductases. Glutaredoxins catalyze glutathione-disulfide oxidoreductions overlapping the functions of thioredoxins and using electrons from NADPH via glutathione reductase. Thioredoxin isoforms are present in most organisms and mitochondria have a separate thioredoxin system. Plants have chloroplast thioredoxins, which via ferredoxin-thioredoxin reductase regulates photosynthetic enzymes by light. Thioredoxins are critical for redox regulation of protein function and signaling via thiol redox control. A growing number of transcription factors including NF-kappaB or the Ref-1-dependent AP1 require thioredoxin reduction for DNA binding. The cytosolic mammalian thioredoxin, lack of which is embryonically lethal, has numerous functions in defense against oxidative stress, control of growth and apoptosis, but is also secreted and has co-cytokine and chemokine activities. Thioredoxin reductase is a specific dimeric 70-kDa flavoprotein in bacteria, fungi and plants with a redox active site disulfide/dithiol. In contrast, thioredoxin reductases of higher eukaryotes are larger (112-130 kDa), selenium-dependent dimeric flavoproteins with a broad substrate specificity that also reduce nondisulfide substrates such as hydroperoxides, vitamin C or selenite. All mammalian thioredoxin reductase isozymes are homologous to glutathione reductase and contain a conserved C-terminal elongation with a cysteine-selenocysteine sequence forming a redox-active selenenylsulfide/selenolthiol active site and are inhibited by goldthioglucose (aurothioglucose) and other clinically used drugs.
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                Author and article information

                Contributors
                Journal
                Front Physiol
                Front Physiol
                Front. Physiol.
                Frontiers in Physiology
                Frontiers Media S.A.
                1664-042X
                23 December 2015
                2015
                : 6
                : 397
                Affiliations
                Laboratorio de Estrés Oxidativo y Plasticidad Cerebral, Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México México, Mexico
                Author notes

                Edited by: Narasaiah Kolliputi, University of South Florida, USA

                Reviewed by: Lei Liu, University of Florida, USA; Khursheed Wani, Johns Hopkins University, USA

                *Correspondence: Selva Rivas-Arancibia srivas@ 123456unam.mx

                This article was submitted to Oxidant Physiology, a section of the journal Frontiers in Physiology

                Article
                10.3389/fphys.2015.00397
                4688356
                26779027
                a26a2dcb-4079-4273-addb-b10c445997f5
                Copyright © 2015 Figueroa-Méndez and Rivas-Arancibia.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

                History
                : 22 October 2015
                : 04 December 2015
                Page count
                Figures: 5, Tables: 0, Equations: 0, References: 96, Pages: 11, Words: 8733
                Funding
                Funded by: Universidad Nacional Autónoma de México 10.13039/501100005739
                Award ID: DGAPA N° IN221114
                Categories
                Physiology
                Review

                Anatomy & Physiology
                vitamin c,pharmacokinetics,neurophysiology,oxidative stress,learning and memory processes

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