Writing in PLoS One, the Finnish research team noted that many population-based studies have suggested that vitamin D deficiency may increase the risk for chronic diseases and weaken the body's immune system. However, changes in serum vitamin D levels - measured as 25(OH)D3 concentrations - "can vary widely from person to person," they said.
"Based on this wide inter-individual response variation, it is obvious that a 'one-size-fits-all' approach will not work ideally for vitamin D supplementation," explained the study authors - led by Professor Carsten Carlberg from the University of Eastern Finland.
As a result, the team used a placebo controlled supplementation trial of vitamin D to identify genetic biomarkers that may be of use in identifying people who could benefit from supplementation.
" We present CD14 and THBD as transcriptomic biomarkers, from which straightforward conclusions on the benefits of a vitamin D3 supplementation can be obtained," said the team.
"These biomarkers allow the classification of subjects into those, who might benefit from a vitamin D3 supplementation, and others who do not."
Carlberg and his colleagues gave the participants a daily dose of either 40 or 80 micrograms of vitamin D, or a placebo, over a course of five months during Finnish winter. They monitored for changes in serum 25-hydroxyvitamin D3 (25(OH)D3) in addition to concentrations and the expression of primary vitamin D target genes in peripheral blood mononuclear cells and adipose tissue.
The results showed that the expression of vitamin D dependent genes in adipose tissue and monocytes (white blood cells) correlated only in half of the study participants with their vitamin D concentrations in the blood.
However, the genes CD14 and thrombomodulin (THBD) are up-regulated primary vitamin D targets and showed to be suitable gene expression markers for vitamin D signalling in both primary tissues.
The researchers therefore suggested that persons whose expression of the CD14 and thrombomodulin genes was not altered as a result of vitamin D supplementation already had a sufficiently high serum vitamin D concentration or their utilisation of vitamin D was disturbed, which calls for further study.
They said that studying the expression of vitamin D dependent genes in tissues is a novel way to identify individuals who might benefit from long-term vitamin D supplementation - an observation further supported by the fact that studying alterations in the expression of genes also made it possible to identify persons whose levels of interleukin 6, an inflammation marker, were reduced as their serum vitamin D levels increased.
Source: PLoS One
Published online ahead of print, doi:10.1371/journal.pone.0071042
"Primary Vitamin D Target Genes Allow a Categorization of Possible Benefits of Vitamin D3 Supplementation"
Authors: Carsten Carlberg, Sabine Seuter, et al