Maintaining
sufficient vitamin D levels may help to prevent the onset of inflammatory
diseases like rheumatoid arthritis, research led by the University of
Birmingham has discovered.

The research
also found that while vitamin D can be effective at preventing the onset of
inflammation, it is less effective once inflammatory disease is established
because diseases such as rheumatoid arthritis leads to vitamin D insensitivity.

Another key
finding of the research was that the impact of vitamin D on inflammatory
disease cannot be predicted using cells from healthy individuals or even from
the blood of patients with inflammation as cells from the disease tissue are
very different.

The researchers
concluded that if vitamin D is to be used in patients with rheumatoid
arthritis, clinicians may need to prescribe much higher doses than currently
employed or provide a treatment that also corrects the vitamin D insensitivity
of immune cells within the joint.

In addition
to its well-established actions on the skeleton, vitamin D is a potent
modulator of the immune system. In particular, vitamin D can suppress
inflammation in autoimmune diseases such as rheumatoid arthritis. Patients with
rheumatoid arthritis are frequently vitamin D deficient and may receive vitamin
D supplementation.

The study,
published in the Journal of Autoimmunity,
involved using paired peripheral blood and synovial fluid from the inflamed
joint of patients with rheumatoid arthritis.

Prof Martin
Hewison, of the University of Birmingham’s Institute of Metabolism and Systems
Research, said: “Our current understanding of vitamin D and rheumatoid
arthritis is based on studies of patient blood which may not truly represent
the situation at the site of inflammation – the joints.

“We
therefore investigated responses to the active form of vitamin D in immune
cells from the inflamed joints of patients with rheumatoid arthritis.

“Compared to
blood from the same patients, the inflamed joint immune cells were much less
sensitive to active vitamin D.

“This
appears to be because immune cells from the joints of rheumatoid arthritis
patients are more committed to inflammation, and therefore less likely to
change, even though they have all the machinery to respond to vitamin D.”

Dr Louisa
Jeffery, also of the University of Birmingham, said: “Our research indicates
that maintaining sufficient vitamin D may help to prevent the onset of
inflammatory diseases like rheumatoid arthritis.

“However,
for patients who already have rheumatoid arthritis, simply providing vitamin D
might not be enough. Instead much higher doses of vitamin D may be needed, or
possibly a new treatment that bypasses or corrects the vitamin D insensitivity
of immune cells within the joint.”

Senior
author Prof Karim Raza, also of the University of Birmingham, said: “Our
findings were unexpected as we initially thought that cells from the inflamed
rheumatoid joint would respond just as well to vitamin D as cells from the
blood. The fact that they don’t has important implications for how we think
about using vitamin D to treat inflammation.

“Unlike
previous studies we isolated different immune cell types from the actual site
of disease to determine whether specific subsets of immune cells (specific T
cell groups) have equal sensitivity to vitamin D.”

This is the
first research of its kind to characterise the effects of vitamin D in both
peripheral blood and inflamed joints of patients with inflammatory disease.

Source: https://www.alphagalileo.org/ViewItem.aspx?ItemId=181115&CultureCode=en

Reference: Jeffery et al (2017). ‘Decreased
sensitivity to 1,25-dihydroxyvitamin D3 in T cells from the rheumatoid joint’.
Journal of Autoimmunity. Published 21 October 2017.