Writing in Molecular Nutrition and Food Research, researchers from the Linus Pauling Institute, USA, tested the ability of more than 400 compounds for their ability to boost the innate immune system.
Using cell cultures in a lab setting, the team tested the compounds for their effect on the activity (expression) of a gene known as cathelicidin antimicrobial peptide (CAMP) - which produces proteins that can help defend against bacterial infection.
They found that two compounds in particular – resveratrol, which is found in red grapes, and pterostilbene, found in blueberries – appear to increase expression of the CAMP gene. The Linus Pauling team noted, however, that individually these effect was modest, but when used in combination with vitamin D3 there was a statistically significant increase in gene expression.
"Out of a study of hundreds of compounds, just these two popped right out," said Dr Adrian Gombart - senior author of the study. "Their synergy with vitamin D to increase CAMP gene expression was significant and intriguing. It's a pretty interesting interaction."
"Discovering additional small molecules that regulate its expression will identify new molecular mechanisms involved in CAMP regulation and increase understanding of how diet and nutrition can improve immune function," the authors added.
The research was supported by the US National Institutes of Health (NIH).
Gombart and his colleagues analysed the effects of 446 compounds for their the ability to boost the expression of CAMP.
"We discovered that two stilbenoids, resveratrol and pterostilbene, induced CAMP promoter-luciferase expression," explained the researchers.
"Although the induction of CAMP by resveratrol and pterostilbene was modest, they synergistically induced CAMP gene expression when combined with 1α,25(OH)2D3 [vitamin D3]. This synergy was observed in both monocyte and keratinocyte cell lines."
Stilbenoids are compounds produced by plants to fight infections, and in human biology appear to affect some of the signaling pathways that allow vitamin D to do its job, researchers said. It appears that combining these compounds with vitamin D has considerably more biological impact than any of them would separately.
However, the authors noted that their findings were made in laboratory cell cultures, and therefore do not prove that similar results would occur as a result of dietary intake.
However, Gombart and his team said the findings do add more interest to the potential of some foods to improve the immune response.
They added that continued research could lead to a better understanding of how diet and nutrition affect immune function, and possibly lead to the development of therapeutically useful natural compounds that could boost the innate immune response.
Source: Molecular Nutrition and Food Research
Published online ahead of print, doi: 10.1002/mnfr.201300266
" Synergistic induction of human cathelicidin antimicrobial peptide gene expression by vitamin D and stilbenoids"
Authors: Chunxiao Guo, Brian Sinnott, Brenda Niu, et al