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Lower cathelicidin concentrations in Irish athletes compared to controls: a role for vitamin D?

Published online by Cambridge University Press:  29 September 2017

J.J. Todd
Affiliation:
Northern Ireland Centre for Food and Health, Ulster University, Coleraine, BT52 1SA, Republic of Ireland
E.M. McSorley
Affiliation:
Northern Ireland Centre for Food and Health, Ulster University, Coleraine, BT52 1SA, Republic of Ireland
L.K. Pourshahidi
Affiliation:
Northern Ireland Centre for Food and Health, Ulster University, Coleraine, BT52 1SA, Republic of Ireland
S.M. Madigan
Affiliation:
Irish Institute of Sport, Sports Campus Ireland, Abbotstown, Dublin, Republic of Ireland
E. Laird
Affiliation:
School of Medicine, Trinity College Dublin, Republic of Ireland
R.R. Weir
Affiliation:
Northern Ireland Centre for Food and Health, Ulster University, Coleraine, BT52 1SA, Republic of Ireland
M. Healy
Affiliation:
Department of Biochemistry, St. James’ Hospital, Dublin, Republic of Ireland
M.B.E. Livingstone
Affiliation:
Northern Ireland Centre for Food and Health, Ulster University, Coleraine, BT52 1SA, Republic of Ireland
C. Beggan
Affiliation:
Northern Ireland Centre for Food and Health, Ulster University, Coleraine, BT52 1SA, Republic of Ireland
L. Beggan
Affiliation:
Northern Ireland Centre for Food and Health, Ulster University, Coleraine, BT52 1SA, Republic of Ireland
P.J. Magee
Affiliation:
Northern Ireland Centre for Food and Health, Ulster University, Coleraine, BT52 1SA, Republic of Ireland
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Abstract

Type
Abstract
Copyright
Copyright © The Authors 2017 

Despite strong in vitro evidence supporting pleiotropic actions of vitamin D in the immune system(Reference Baeke, Etten and Overbergh1), including synthesis of LL-37 antimicrobial peptide(Reference Vandamme, Landuyt and Luyten2), human studies have yielded inconsistent results. LL-37 has been linked with total 25-hydroxyvitamin D [25(OH)D] concentrations and the number of self-reported upper respiratory tract infection symptoms in endurance athletes(Reference He, Handzlik and Fraser3). This observational study investigated whether LL-37 concentration varied between athletes and a general population control group and also tested if total 25(OH)D was a positive predictor of LL-37 concentration.

Overall, 221 stored plasma samples from male and female athletes (n 101) and a healthy control group (n 120) were obtained from four previous studies and analysed for LL-37 using an ELISA. Total 25(OH)D concentration was quantified by LC-MS/MS during each original study. Prior to statistical analyses, outliers (n = 24) were removed.

BMI, body mass index; 25(OH)D, total 25-hydroxyvitamin D, PTH, parathyroid hormone; LL-37, biologically active cathelicidin antimicrobial peptide. a P < 0·001, b P < 0·05 versus healthy controls (independent t test).

Athletes had a significantly lower mean LL-37 concentration than controls. In contrast, the athlete group exhibited a higher mean total 25(OH)D concentration compared to the control group. Total 25(OH)D concentration did not predict LL-37 concentration overall (β = 0·073, P = 0·386), or in either group after adjusting for age, sex, BMI and season of sampling (athletes β = −0·033, P = 0·762; controls β = 0·145, P = 0·197). These findings question the purported link between vitamin D and LL-37 in vivo. Although significantly lower LL-37 concentrations were observed in athletes compared to controls, the clinical implications of this disparity require further investigation.

This study was funded by the Department of Employment and Learning, Northern Ireland and Translational Research Group: Diabetes, Endocrinology & Nutrition, HSC Research & Development Division, Public Health Agency, Belfast. Ethical approval was obtained from the University of Ulster Research Ethics Committee (REC/08/0044; REC/13/0235; REC/14/0087) or from the Office of Research Ethics Committees Northern Ireland (13/NI/0091) and the study was conducted according to the guidelines laid down in the Declaration of Helsinki.

References

1. Baeke, F, Etten, EV, Overbergh, L et al. (2007) Nutr Res Rev 20, 106118.Google Scholar
2. Vandamme, D, Landuyt, B, Luyten, W et al. (2012) Cell Immunol 280, 2235.Google Scholar
3. He, C, Handzlik, M, Fraser, WD et al. (2013) Exerc Immunol Rev 19, 86101.Google Scholar