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Current Pharmaceutical Design Feb 2000Preformed vitamin A (all-trans-retinol and its esters) and provitamin A (beta-carotene) are essential dietary nutrients that provide a source of retinol. Both retinyl... (Review)
Review
Preformed vitamin A (all-trans-retinol and its esters) and provitamin A (beta-carotene) are essential dietary nutrients that provide a source of retinol. Both retinyl esters and beta-carotene are metabolized to retinol. The retinol-binding proteins on binding retinol provide a means for solubilizing retinol for delivery to target tissues and for regulating retinol plasma concentrations. Oxidation of retinol provides retinal, which is essential for vision, and retinoic acid, a transcription factor ligand that has important roles in regulating genes involved in cell morphogenesis, differentiation, and proliferation. The observations that vitamin A can produce cell and tissue changes similar to those found during neoplastic transformation and that vitamin supplementation can reverse this process indicated a potential role for vitamin A in cancer prevention. Thus far, correlative epidemiological studies on vitamin A use and cancer prevention have produced mixed results, as this review indicates. Apparently, in populations deficient in vitamin A (caused by an inadequate diet or tobacco use), supplementation programs appear to be effective in reducing cancer incidence. In groups already having sufficient dietary or supplemental vitamin A, cancer prevention by added vitamin A may not be particularly effective. The most likely reason for the low efficacy in the latter groups is that feedback mechanisms that increase retinol storage in the liver limit retinol plasma levels; whereas, supplementation at higher doses causes toxicity. In addition to serving as a metabolic source of retinol, beta-carotene, along with other dietary carotenoids, function as antioxidants that can prevent carcinogenesis by decreasing the levels of the free-radicals that cause DNA damage.
Topics: Animals; Anticarcinogenic Agents; Carotenoids; Diet; Dietary Supplements; Humans; Neoplasms; Nutritional Physiological Phenomena; Vitamin A
PubMed: 10637381
DOI: 10.2174/1381612003401190 -
Critical Reviews in Food Science and... Jul 2017The epigenetic phenomena refer to heritable changes in gene expression other than those in the DNA sequence, such as DNA methylation and histone modifications. Major... (Review)
Review
The epigenetic phenomena refer to heritable changes in gene expression other than those in the DNA sequence, such as DNA methylation and histone modifications. Major research progress in the last few years has provided further proof that environmental factors, including diet and nutrition, can influence physiologic and pathologic processes through epigenetic alterations, which in turn influence gene expression. This influence is termed nutritional epigenetics, and one prominent example is the regulation of gene transcription by vitamin A through interaction to its nuclear receptor. Vitamin A is critical throughout life. Together with its derivatives, it regulates diverse processes including reproduction, embryogenesis, vision, growth, cellular differentiation and proliferation, maintenance of epithelial cellular integrity and immune function. Here we review the epigenetic role of vitamin A in cancer, stem cells differentiation, proliferation, and immunity. The data presented here show that retinoic acid is a potent agent capable of inducing alterations in epigenetic modifications that produce various effects on the phenotype. Medical benefits of vitamin A as an epigenetic modulator, especially with respect to its chronic use as nutritional supplement, should rely on our further understanding of its epigenetic effects during health and disease, as well as through different generations.
Topics: Epigenesis, Genetic; Gene Expression Regulation; Humans; Vitamin A
PubMed: 26565606
DOI: 10.1080/10408398.2015.1060940 -
Lancet (London, England) Jan 1995
Review
Topics: Carotenoids; Child; Child Nutrition Disorders; Humans; Immunity; Neoplasms; Nutritional Requirements; Vitamin A; Vitamin A Deficiency
PubMed: 7799706
DOI: 10.1016/s0140-6736(95)91157-x -
Yakugaku Zasshi : Journal of the... 2021"Retinoid" is the general term for vitamin A derivatives and chemical compounds that act like vitamin A. Vitamin A are composed of four isoprene units and are named... (Review)
Review
"Retinoid" is the general term for vitamin A derivatives and chemical compounds that act like vitamin A. Vitamin A are composed of four isoprene units and are named according to their terminal functional group, such as retinol (OH, 1), retinal (CHO, 2), and retinoic acid (COH, 3). Vitamin A usually refers to retinol. In the past few decades, major advances in research on vitamin A have improved our understanding of its fundamental roles and physiological significance in living cells. In this review, three types of chemical biology studies using vitamin A analogs are described: (1) conformational studies of the chromophore in retinal proteins (rhodopsin, phoborhodopsin, and retinochrome), especially the conformation around the cyclohexene ring; (2) structure-activity relationship studies of retinoic acid analogs to create new signaling molecules for activating nuclear receptors; and (3) development of a new channelrhodopsin with an absorption maximum at longer wavelength to overcome the various demerits of channelrhodopsins used in optogenetics, as well as the stereoselective synthesis of retinoid isomers and their analogs using a diene-tricarbonyliron complex or a palladium-catalyzed cross-coupling reaction between vinyl triflates and stannyl olefins.
Topics: Alkenes; Catalysis; Channelrhodopsins; Cyclohexenes; Eye Proteins; Isomerism; Mesylates; Molecular Conformation; Nuclear Reactors; Palladium; Retinoids; Stereoisomerism; Structure-Activity Relationship; Vinyl Compounds; Vitamin A
PubMed: 33790122
DOI: 10.1248/yakushi.20-00230 -
Nutrition (Burbank, Los Angeles County,... 2000
Review
Topics: Animals; History, 20th Century; Humans; Neoplasms; Receptors, Retinoic Acid; Vitamin A; Vitamin A Deficiency
PubMed: 10906560
DOI: 10.1016/s0899-9007(00)00347-6 -
Pharmacology & Therapeutics Feb 2022Vitamin A is an important micro-essential nutrient, whose primary dietary source is retinyl esters. In addition, β-carotene (pro-vitamin A) is a precursor of vitamin A... (Review)
Review
Vitamin A is an important micro-essential nutrient, whose primary dietary source is retinyl esters. In addition, β-carotene (pro-vitamin A) is a precursor of vitamin A contained in green and yellow vegetables that is converted to retinol in the body after ingestion. Retinol is oxidized to produce visual retinal, which is further oxidized to retinoic acid (RA), which is used as a therapeutic agent for patients with promyelocytic leukemia. Thus, the effects of retinal and RA are well known. In this paper, we will introduce (1) vitamin A circulation in the body, (2) the actions and mechanisms of retinal and RA, (3) retinoylation: another RA mechanism not depending on RA receptors, (4) the relationship between cancer and actions of retinol or β-carotene, whose roles in vivo are still unknown, and (5) anti-cancer actions of vitamin A derivatives derived from fenretinide (4-HPR). We propose that vitamin A nutritional management is effective in the prevention of cancer.
Topics: Cell Differentiation; Delivery of Health Care; Humans; Neoplasms; Receptors, Retinoic Acid; Tretinoin; Vitamin A
PubMed: 34175370
DOI: 10.1016/j.pharmthera.2021.107942 -
Cellular and Molecular Life Sciences :... Jul 2003Beyond their classical nutritional roles, nutrients modify gene expression and function in target cells and, by so doing, affect many fundamental biological processes.... (Review)
Review
Beyond their classical nutritional roles, nutrients modify gene expression and function in target cells and, by so doing, affect many fundamental biological processes. An emerging example, which is the focus of this review, is the involvement of vitamin A in the regulation of the level and functioning of body fat reserves. Retinoic acid, the carboxylic acid form of vitamin A, is a transcriptional activator of the genes encoding uncoupling proteins, and results in animals indicate that whole body thermogenic capacity is related to the vitamin A status. Retinoic acid also influences adipocyte differentiation and survival, with high doses inhibiting and low doses promoting adipogenesis of preadipose cells in culture. Moreover, vitamin A status can influence the development and function of adipose tissues in whole animals, with a low vitamin A status favouring increased fat deposition.
Topics: Adipocytes; Adipose Tissue; Animals; Body Temperature Regulation; Homeostasis; Humans; Models, Biological; Receptors, Retinoic Acid; Vitamin A
PubMed: 12943220
DOI: 10.1007/s00018-003-2290-x -
Experimental Biology and Medicine... May 2021Vitamin A is a fat-soluble vitamin involved in essential functions including growth, immunity, reproduction, and vision. The vitamin A Dietary Reference Intakes (DRIs)... (Review)
Review
Vitamin A is a fat-soluble vitamin involved in essential functions including growth, immunity, reproduction, and vision. The vitamin A Dietary Reference Intakes (DRIs) for North Americans suggested that a minimally acceptable total liver vitamin A reserve (TLR) is 0.07 µmol/g, which is not explicitly expressed as a vitamin A deficiency cutoff. The Biomarkers of Nutrition for Development panel set the TLR cutoff for vitamin A deficiency at 0.1 µmol/g based on changes in biological response of several physiological parameters at or above this cutoff. The criteria used to formulate the DRIs include clinical ophthalmic signs of vitamin A deficiency, circulating plasma retinol concentrations, excretion of vitamin A metabolites in the bile, and long-term storage of vitamin A as protection against vitamin A deficiency during times of low dietary intake. This review examines the biological responses that occur as TLRs are depleted. In consideration of all of the DRI criteria, the review concludes that induced biliary excretion and long-term vitamin A storage do not occur until TLRs are >0.10 µmol/g. If long-term storage is to continue to be part of the DRI criteria, vitamin A deficiency should be set at a minimum cutoff of 0.10 µmol/g and should be set higher during times of enhanced requirements where TLRs can be rapidly depleted, such as during lactation or in areas with high infection burden. In population-based surveys, cutoffs are important when using biomarkers of micronutrient status to define the prevalence of deficiency and sufficiency to inform public health interventions. Considering the increasing use of quantitative biomarkers of vitamin A status that indirectly assess TLRs, i.e. the modified-relative-dose response and retinol-isotope dilution tests, setting a TLR as a vitamin A deficiency cutoff is important for users of these techniques to estimate vitamin A deficiency prevalence. Future researchers and policymakers may suggest that DRIs should be set with regard to optimal health and not merely to prevent a micronutrient deficiency.
Topics: Biomarkers; Humans; Liver; Reference Values; Vitamin A; Vitamin A Deficiency
PubMed: 33765844
DOI: 10.1177/1535370221992731 -
Food and Nutrition 1980The availability of synthetic vitamin A and its esters in unlimited quantities, has enabled populations around the world, consuming inadequate amounts of this vital... (Review)
Review
The availability of synthetic vitamin A and its esters in unlimited quantities, has enabled populations around the world, consuming inadequate amounts of this vital micro-nutrient and hence subject to potential loss of sight or other manifestations of vitamin A deficiency, to have hope for a better future life. A technology exists for the preparation of synthetic vitamin A in various application forms. Many commonly-consumed foods may be used as carriers or vehicles of vitamin A to assure deficient populations of a sufficient intake of this antixerophthalmic and anti-infective vitamin.
Topics: Animals; Dietary Fats; Diterpenes; Edible Grain; Food, Fortified; Global Health; Humans; Margarine; Milk; Palmitates; Retinyl Esters; Sodium Chloride; Sodium Glutamate; Sucrose; Tea; Technology, Pharmaceutical; Vitamin A; Vitamin A Deficiency
PubMed: 7002640
DOI: No ID Found -
The Journal of Nutrition Apr 1999In the last fifteen years, a large series of controlled clinical trials showed that vitamin A supplementation reduces morbidity and mortality of children in developing... (Review)
Review
In the last fifteen years, a large series of controlled clinical trials showed that vitamin A supplementation reduces morbidity and mortality of children in developing countries. It is less well known that vitamin A underwent two decades of intense clinical investigation prior to World War II. In the 1920s, a theory emerged that vitamin A could be used in "anti-infective" therapy. This idea, largely championed by Edward Mellanby, led to a series of at least 30 trials to determine whether vitamin A--usually supplied in the form of cod-liver oil--could reduce the morbidity and mortality of respiratory disease, measles, puerperal sepsis, and other infections. The early studies generally lacked such innovations known to the modern controlled clinical trial such as randomization, masking, sample size and power calculations, and placebo controls. Results of the early trials were mixed, but the pharmaceutical industry emphasized the positive results in their advertising to the public. With the advent of the sulfa antibiotics for treatment of infections, scientific interest in vitamin A as "anti-infective" therapy waned. Recent controlled clinical trials of vitamin A from the last 15 y follow a tradition of investigation that began largely in the 1920s.
Topics: Child; Child Welfare; Communicable Disease Control; History, 19th Century; History, 20th Century; Humans; Infant; Infant Mortality; Nutritional Physiological Phenomena; United States; Vitamin A
PubMed: 10203551
DOI: 10.1093/jn/129.4.783