title: Vitamin D and respiratory infection in adults.
abstract: Vitamin D insufficiency is a global issue that has significant implications for health. The classical role of vitamin D in bone mineralisation is well known; vitamin D deficiency leads to rickets, osteomalacia or osteoporosis. The role of vitamin D in an immune system is less known. Vitamin D is not an actual vitamin but a secosteroid hormone produced in the skin from 7-dehydrocholesterol after exposure to sunlight UVB radiation. Nutrition and supplements are main sources of vitamin D in wintertime in northern countries as sunlight exposure is inadequate for the production. For activation vitamin D needs to be hydroxylated in liver to form 25-hydroxyvitamin D and in kidney to 1,25-dihydroxyvitamin D, the most active hormone in Ca absorption in the gut. For determination of vitamin D status serum 25-hydroxyvitamin D level, the major circulating form of the hormone is to be measured. Vitamin D regulates gene expression through binding with vitamin D receptors, which dimerises with retinoid X receptor. This complex binds to vitamin D-responsive elements inside the promoter regions of vitamin D-responsive genes. Vitamin D has a key role in innate immunity activation; the production of antimicrobial peptides (cathelicidin and defensins) following Toll-like receptor stimulation by pathogen lipopeptides is dependent on sufficient level of 25-hydroxyvitamin D. Clinically, there is evidence of the association of vitamin D insufficiency and respiratory tract infections. There is also some evidence of the prevention of infections by vitamin D supplementation. Randomised controlled trials are warranted to explore this preventive effect.
authors: Department of Cell Biology and Anatomy, Medical School, University of Tampere, Medisiinarinkatu 3, 33014 Tampere, Finland. ilkka.laaksi@uta.fi
authors: Ilkka
authors: I
authors: Laaksi
mesh_terms: D000328:Adult; D023181:Antimicrobial Cationic Peptides / Q000096:biosynthesis; D023082:Defensins / Q000096:biosynthesis; D019587:Dietary Supplements; D005786:Gene Expression Regulation; D006801:Humans; D007113:Immunity, Innate / Q000235:genetics / Q000502:physiology*; D018167:Receptors, Calcitriol / Q000378:metabolism; D012141:Respiratory Tract Infections / Q000209:etiology* / Q000517:prevention & control; D047488:Retinoid X Receptors / Q000378:metabolism; D014807:Vitamin D / Q000276:immunology* / Q000378:metabolism / Q000627:therapeutic use; D014808:Vitamin D Deficiency / Q000150:complications* / Q000188:drug therapy / Q000276:immunology; D054804:Cathelicidins
chemical_list: D023181:Antimicrobial Cationic Peptides; D023082:Defensins; D018167:Receptors, Calcitriol; D047488:Retinoid X Receptors; D014807:Vitamin D; D054804:Cathelicidins