Background: Transcription of the cathelicidin antimicrobial peptide (CAMP) gene is induced by binding of the bioactive form of vitamin D, 1,25-dihydroxyvitamin D, to the vitamin D receptor. Significant levels of the protein hCAP18/LL-37 are found in the blood and may protect against infection and/or sepsis. We hypothesized that serum vitamin D levels may modulate the circulating levels of hCAP18. Only three studies have shown a positive correlation between circulating 25-hydroxyvitamin D and hCAP18 levels. Here we provide additional evidence for such a correlation in healthy, middle-aged adults.
Findings: Serum levels of 25-hydroxyvitamin D [25(OH)D] and plasma levels of hCAP18 were determined in 19 healthy middle-aged (mean of 50.1 years) adult men and women. Plasma hCAP18 concentrations correlated with serum 25(OH)D concentrations in subjects with 25(OH)D levels ≤ 32 ng/ml (r = 0.81, p < 0.005) but not in subjects with concentrations > 32 ng/ml (r = 0.19, p = 0.63).
Conclusions: We conclude that plasma hCAP18 levels correlate with serum 25(OH)D levels in subjects with concentrations of 25(OH)D ≤ 32 ng/ml as opposed to those with concentrations > 32 ng/ml and that vitamin D status may regulate systemic levels of hCAP18/LL-37.