title: Back to the future: a new look at 'old' vitamin D.
abstract: Our perception of the vitamin D system continues to evolve. Recent studies have re-evaluated the parameters for adequate vitamin D status in humans, revealing a high prevalence of insufficiency in many populations throughout the world. Other reports have highlighted the potential consequences of vitamin D insufficiency beyond established effects on bone homeostasis. Most notably, there is now strong evidence of a role for vitamin D in modulating innate and adaptive immunities, with insufficiency being linked to infectious disease and other immune disorders. To date, signaling pathways for these new responses to vitamin D have been based on established endocrine models for active 1,25-dihydroxyvitamin D, despite present evidence for more localized, intracrine modes of action. In the following review, we provide a fresh perspective on vitamin D signaling in non-classical target cells such as macrophages by highlighting novel factors associated with the transport and action of this pluripotent secosteroid.
authors.affiliation: Department of Orthopaedic Surgery, David Geffen School of Medicine, UCLA, 615 Charles E Young Drive South, Los Angeles, California 90095, USA.
authors.forename: Rene F
authors.initials: RF
authors.lastname: Chun
authors.forename: John S
authors.initials: JS
authors.lastname: Adams
authors.forename: Martin
authors.initials: M
authors.lastname: Hewison
mesh_terms: D000818:Animals; D006801:Humans; D007113:Immunity, Innate / Q000502:physiology; D008264:Macrophages / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D014807:Vitamin D / Q000378:metabolism* / Q000502:physiology*; D014808:Vitamin D Deficiency / Q000503:physiopathology
chemical_list: D014807:Vitamin D