Erythrocyte fatty acid composition does not influence levels of free, bioavailable, and total 25-hydroxy vitamin D

Abstract

In vitro, mono- and polyunsaturated fatty acids (FAs) may decrease the binding affinity of vitamin D metabolites for vitamin D-binding protein, which in turn may influence their bioavailability. FAs incorporated as phospholipids in erythrocyte (ery-) cell membranes reflect dietary intake. The purpose of this study was to investigate ery-FA composition in relation to markers for vitamin D. In healthy females (age 22.6 ± 2.0 years) total 25(OH)D was measured by LC-MS/MS (n = 78), free 25(OH)D with ELISA (n = 64 of 78), and bioavailable 25(OH)D was calculated. Analysis of ery-FA composition was by gas chromatography (n = 56 of 78). A strong correlation between total 25(OH)D and free 25(OH)D was seen (r = .66, p < .001), and between total-25(OH)D and bioavailable 25(OH)D (r = .68, p < .001). No correlations between 25(OH)D fractions and specific fatty acids were found, and in particular, no associations with mono- and poly-unsaturated FA compositions. All 25(OH)D fractions were correlated with leptin (total 25(OH)D (r = −.33, p < .003); bioavailable 25(OH)D (r = −.47, p < .001); free 25(OH)D (r = −.44, p < .001). Associations were found between PTH and total 25(OH)D (r = −.35, p = .002) and weaker between bioavailable 25(OH)D (r = −.35, p = .040) and free 25(OH)D (r = −.28, p = .079). All fractions of 25(OH)D appear to correlate in a similar way to PTH, BMI and body fat (leptin). No association was found between ery-FA composition and free/bioavailable 25(OH)D. It is unlikely that FAs are a strong uncoupling factor of DBP-bound 25(OH)D.

Keywords:

• Erythrocyte membrane
• fatty acids
• leptin
• lipids
• parathyroid hormone
• Vitamin D

Acknowledgements

We are indebted to nurse Ann-Britt Krondahl for her excellent assistance.

Ethical approval

This study was approved the Regional Ethical Committee, Linköping, Sweden (Dnr 2012/145-31).

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

Additional information

Funding

This work was supported by a Grant from the Medical Council of Southeast Sweden (FORSS).