Research Fellows Directory
Professor Martin Hewison
University of Birmingham
The over-arching aim of my research is to define the role of vitamin D in human health. Over the last five years my group has identified new immunomodulatory effects of vitamin D that are mediated via local, tissue-specific mechanisms independent of classical skeletal vitamin D. We have shown that antibacterial and anti-inflammatory effects of vitamin D correlate better with serum levels of inactive 25-hydroxyvitamin D (25D) than active 1,25-dihydroxyvitamin D (1,25D). 25D is the major circulating form of vitamin D so that vitamin D status (serum 25D concentration) can potently influence immune function.
Using human material we have shown that infection and/or immune challenge triggers expression of 1alpha-hydroxylase and the vitamin D receptor to support tissue-specific immune responses to 25D. We have shown that these antibacterial responses are impaired under conditions of vitamin D (25D)-deficiency and can be enhanced following vitamin D supplementation to elevate 25D levels. Our studies have endorsed the local model for vitamin D-induced immunity, but have also identified key factors that can promote or corrupt this model. These include the vitamin D binding protein (DBP), which carries vitamin D in blood, and we have developed a new hypothesis actions of vitamin D are dependent on 25D that is not bound to DBP but is, instead, bioavailable or free. This has profound implications for our definition of vitamin D status, and has led to our current work using DBP knockout mice.
Interests and expertise (Subject groups)