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Nutrition Research |
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Table of Contents
Introduction
Vitamin D has long been recognized as a required prohormone responsible for intestinal absorption of dietary calcium and phosphorus. At one time an image of a child with bowing femurs was a reminder of the vitamin D deficiency epidemic in starving populations of developing nations. In recent years, a cancer epidemiology graph is the new hallmark of vitamin D deficiency. Epidemiological studies dating back to 1941 report observations that people living in northern latitudes of the United States were more susceptible to death from cancer than people living in the lower latitudes. There has been increased interest in vitamin D and its relationship to cancer since 1980, when researchers proposed metabolites of sunlight derived vitamin D, through their influence on calcium metabolism, as protective factors against colon cancer based on the decreasing gradient of colon cancer mortality rates from northern to southern United States. Recent mainstream media attention regarding the evidence of vitamin D and its role in cancer prevention is encouraging the medical community to define recommended guidelines on circulating vitamin D levels from sunlight, fortified food, or supplemental sources. The synthesis, function, and role of vitamin D in disease prevention is explained in Vitamin D Deficiency and Prevention of Human Disease, while a complementary research article provides genomic evidence specifically documenting vitamin D as an environmental factor that influences the risk of multiple sclerosis, Expression of the Multiple Sclerosis-Associated MHC Class II Allele HLA-DRB1*1501 is Regulated by Vitamin D.
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Vitamin D and Prevention of Human Disease
Vitamin D2 (ergocalciferol) is naturally synthesized from ergosterol by invertebrates, fungi, and plants in response to ultraviolet B irradiation, while vitamin D3 synthesis (cholecalciferol) is uniquely initiated in the skin of vertebrates. During sun exposure, ultraviolet B photons are absorbed by 7-dehydrocholesterol, which is found within the plasma membranes of epidermal and dermal skin layers. This reaction yields an unstable derivative of 7-dehydrocholesterol, named precholecalcitrol, which rapidly rearranges to vitamin D3. Vitamin D binding protein (DBP) is a carrier protein responsible for drawing vitamin D3 from the plasma membrane into the dermal capillaries within the extracellular space. Vitamin D3 may be commercially synthesized from cholesterol extracted from the lanolin of sheep wool. The extracted cholesterol is converted to 7-dehydrocholesterol and then treated with UV light to produce vitamin D3. Both vitamin D2 and D3 are commercially used in fortified foods and supplements.Read MoreVitamin D, Multiple Sclerosis Connection
Sreeram V. Ramagopalan1,2#, Narelle J. Maugeri1#, Lahiru Handunnetthi1,2, Matthew R. Lincoln1,2, Sarah-Michelle Orton1,2, David A. Dyment1,2, Gabriele C. DeLuca1,2, Blanca M. Herrera1,2, Michael J. Chao1,2, A. Dessa Sadovnick3,4, George C. Ebers1,2*, Julian C. Knight1*
1 Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom, 2Department of Clinical Neurology, University of Oxford, John Radcliff e Hospital, Oxford, United Kingdom, 3 Department of Medical Genetics, Division of Neurology, University of British Columbia, UBC Hospital, Vancouver, British Columbia, Canada, 4 Faculty of Medicine, Division of Neurology, University of British Columbia, UBC Hospital, Vancouver, British Columbia, Canada
Multiple sclerosis (MS) is a complex trait in which allelic variation in the MHC class II region exerts the single strongest effect on genetic risk. Epidemiological data in MS provide strong evidence that environmental factors act at a population level to influence the unusual geographical distribution of this disease. Growing evidence implicates sunlight or vitamin D as a key environmental factor in aetiology. We hypothesised that this environmental candidate might interact with inherited factors and sought responsive regulatory elements in the MHC class II region. Sequence analysis localised a single MHC vitamin D response element (VDRE) to the promoter region of HLA-DRB1. Sequencing of this promoter in greater than 1,000 chromosomes from HLA-DRB1 homozygotes showed absolute conservation of this putative VDRE on HLA-DRB1*15 haplotypes. Read More Plant Bioactive Extraction and isolation
The extraction of plant material and isolation of plant constituents typically require tedious protocols that are essential to isolating biologically active compounds and understanding their role in disease prevention and treatment. Bioactives isolated from leaf, stem, root, bark, flower, fruit, seed, or other plant materials are often identified using a bioassay-guided approach. This type of approach is useful for the investigation of alkaloids, antioxidants, bioflavonoids, terpenoids, and other compounds as promising therapeutics from an immense pool of plant biodiversity. Sigma-Aldrich® offers many products for bioactive extraction, isolation, and purification:
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