Lower Cathelicidin Concentrations In Irish Athletes Compared To Healthy Controls: A Role For Vitamin D?

The biologically active vitamin D metabolite (1[alpha]-dihydroxyvitamin D) has been linked to regulation of human cathelicidin antimicrobial peptide (LL-37) in vitro. Recent studies in athletes indicate that vitamin D inadequacy is associated with lower concentrations of LL-37 and that this may increase risk of upper respiratory tract infection (URTI). PURPOSE: To compare circulating LL-37 concentrations between athletes and healthy controls and to establish if total 25-hydroxyvitamin D (25[OH]D) was a significant determinant of this antimicrobial peptide.METHODS: A total of 221 stored, fasted plasma samples from male and female athletes (elite rugby n=12, elite boxing n=12, Gaelic football n=77) and age and sex-matched healthy controls (n=120) were analysed in duplicate for LL-37 concentrations using an enzyme-linked immunosorbent assay. Total 25(OH)D concentrations were quantified by liquid chromatography-tandem mass spectrometry as part of the previous studies. Comparison of 25(OH)D and LL-37 concentrations between athletes and controls was made using Mann-Whitney U tests. Linear regression was used to test if 25(OH)D concentration was a significant determinant of LL-37 concentration after adjusting for season of sampling.RESULTS: Median [IQR] 25(OH)D concentrations were 49.76[39.37] and 28.90[23.55] nmol/L for athletes and healthy controls respectively, P