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Ethnic differences in vitamin D and Interleukin-6 levels in healthy South Asian and Caucasian women revealed by the D2-D3 study

Published online by Cambridge University Press:  11 December 2017

A.L. Salter
Affiliation:
School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK, GU2 7XH
J. Elliott
Affiliation:
School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK, GU2 7XH
J. Sier
Affiliation:
School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK, GU2 7XH
O.A. Akinyemi
Affiliation:
School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK, GU2 7XH
J. Hunt
Affiliation:
School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK, GU2 7XH
S.A. Lanham-New
Affiliation:
School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK, GU2 7XH
D.J. Blackbourn
Affiliation:
School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK, GU2 7XH
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Abstract

Type
Abstract
Copyright
Copyright © The Authors 2017 

Vitamin D is most commonly known for its importance to bone health, but growing evidence suggests that it also has a role in regulating immune function and the inflammatory response. Vitamin D supplementation has recently been shown to reduce the risk of acute respiratory tract infection( Reference Martineau, Jolliffe and Hooper 1 ) and greater levels of circulating vitamin D are associated with a lower risk of chronic disease such as multiple sclerosis( Reference Munger, Levin and Hollis 2 ). Interleukin-6 (IL-6) is an immune function marker, released in the inflammatory response and has been shown to be inhibited by vitamin D( Reference Zhang, Leung and Richers 3 ). The present study aimed to determine any ethnic differences in IL-6 and serum 25-hydroxyvitamin D (25OHD) at baseline between South Asian and Caucasian women.

A total of 54 subjects (South Asian n = 22, Caucasian n = 32) were selected from the D2-D3 study( Reference Tripkovic, Wilson and Hart 4 ) based on the greatest 25OHD changes across the 12 week intervention period. Plasma samples were analysed from Visit 1 (baseline). IL-6 was quantified using high-sensitivity enzyme-linked immunosorbent assay (R&D Systems, Minneapolis, MN, USA) and all standards and samples were plated in duplicate. Serum 25OHD levels had previously been determined and were therefore available for use in this study. The D2-D3 study had ethical approval from both the South-East Coast (Surrey) NHS Research Ethics Committee (NHS REC No. 11/LO/0708) and the University of Surrey Ethics Committee (Fast-Track EC/2011/97/FHMS).

At baseline, IL-6 concentration was significantly higher in the South Asian women (1·83pg/mL IQR 0·85) compared to the Caucasian women (1·24pg/mL IQR 0·75) (P = 0·023) and serum 25OHD was significantly lower in the South Asian women (28·09 ± 15·8 nmol/L) compared to the Caucasian women (55·98 ± 24·8 nmol/L) (P < 0·001). No correlations (negative or positive) were found between serum 25OHD and IL-6 in either the South Asian (r −0·186, p = 0·407) or Caucasian (r −0·090, p = 0·625) women.

* P < 0·05 Independent Samples T-test, †P < 0·05 Mann Whitney U test, IQR, Interquartile Range.

The present study shows a significant ethnic difference in both IL-6 and serum 25OHD concentrations at baseline with South Asian women having greater IL-6 and lower 25OHD levels than Caucasian women. Very few studies have looked at IL-6 and vitamin D in a UK-based South Asian population, although a cross-sectional study carried out in West London found that IL-6 was significantly higher in South Asian women compared to European women( Reference Peters, Ghouri and McKeigue 5 ). An ethnic difference in serum 25OHD levels between South Asian and Caucasian women has previously been identified, with South Asian women being identified as vitamin D deficient( Reference Darling 6 ). The present study supports both of these previous findings. Further work is underway to investigate the effect of vitamin D supplementation, compared to placebo, on Interleukin-6 and serum 25OHD after 6 and 12 weeks intervention in the selected participants.

References

1. Martineau, AR, Jolliffe, DA, Hooper, RL et al. (2017) BMJ 356, i6583.Google Scholar
2. Munger, KL, Levin, LI, Hollis, BW et al. (2006) JAMA 296, 28322838.CrossRefGoogle Scholar
3. Zhang, Y, Leung, DYM, Richers, BN et al. (2012) J Immunol 188, 21272135.Google Scholar
4. Tripkovic, L, Wilson, L, Hart, K et al. (2015) Proc Nutr Soc 74, OCE1, E16.CrossRefGoogle Scholar
5. Peters, MJL, Ghouri, N, McKeigue, P et al. (2013) Cytokine 61, 2932.Google Scholar
6. Darling, AL et al. (2013) Osteoporos Int 24(2): 477488.Google Scholar