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Health News Archive 259 - Tuberculosis
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Vitamin D Has Antimicrobial Actions that Protect Against Tuberculosis

A new study indicates vitamin D3 has antimicrobial actions that can protect against bacterial infections such as tuberculosis.  Published in the journal Science, vitamin D3 triggered a key antimicrobial response in humans against Mycobacterium tuberculosis (TB).

In innate immune responses, activation of Toll-like receptors (TLRs) triggers direct antimicrobial activity against intracellular bacteria. The researchers in the current study have discovered that when TLR activates human macrophages, the expression of the vitamin D receptor is upregulated within these immune cells. Also upregulated in the immune cells was a gene that activates the enzyme that converts vitamin D to its active form. When vitamin D’s active form was added to the immune cells, this triggered the action of an antimicrobial peptide that helps kill intracellular TB. However, when the vitamin D receptor and vitamin D activating enzyme were inhibited, the antimicrobial peptide remained dormant.

In addition, the researchers observed that blood serum from African-American individuals, known to have increased susceptibility to tuberculosis, had low vitamin D levels. The serum from the African Americans was less efficient in triggering the antimicrobial peptide that kills TB. However, when researchers added vitamin D to serum samples from African-American subjects, it restored the antibacterial properties of the peptide that kills TB.

Based on these results, the study authors believe that “differences in ability of human populations to produce vitamin D may contribute to susceptibility to microbial infection.”

The findings also may help explain why African-Americans, who are often deficient in vitamin D, are more susceptible to TB.

Source: Liu PT, Stenger S, Li H, Wenzel L, Tan BH, Krutzik S, Ochoa MT, Schauber J, et al. Toll-Like Receptor Triggering of a Vitamin D-Mediated Human Antimicrobial Response. Science. Published Online February 23, 2006.