title: 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.
authors.affiliation: a Department of Clinical Chemistry , County Hospital of Kalmar , Kalmar , Sweden.|b Department of Medicine and Optometry , Linnaeus University , Kalmar , Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Carlsson
authors.affiliation: a Department of Clinical Chemistry , County Hospital of Kalmar , Kalmar , Sweden.
authors.forename: Ingela
authors.initials: I
authors.lastname: Nilsson
authors.affiliation: c Department of Clinical Physiology , County Hospital of Kalmar , Kalmar , Sweden.|d Department of Medicine and Health Sciences , University Hospital Linkoping , Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Brudin
authors.affiliation: a Department of Clinical Chemistry , County Hospital of Kalmar , Kalmar , Sweden.
authors.forename: Siv-Ping
authors.initials: SP
authors.lastname: Von
authors.affiliation: e Department of Internal Medicine, Section of Endocrinology , County Hospital of Kalmar , Kalmar , Sweden.
authors.forename: Pär
authors.initials: P
authors.lastname: Wanby
mesh_terms: D015652:25-Hydroxyvitamin D 2 / Q000097:blood*; D000273:Adipose Tissue / Q000378:metabolism; D000293:Adolescent; D000328:Adult; D001782:Blood Donors; D015992:Body Mass Index; D002112:Calcifediol / Q000097:blood*; D002853:Chromatography, Liquid; D004912:Erythrocytes / Q000737:chemistry* / Q000378:metabolism; D005227:Fatty Acids / Q000097:blood*; D005231:Fatty Acids, Unsaturated / Q000097:blood*; D005260:Female; D006801:Humans; D012044:Regression Analysis; D053719:Tandem Mass Spectrometry; D014809:Vitamin D-Binding Protein / Q000097:blood*
chemical_list: D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D014809:Vitamin D-Binding Protein; D015652:25-Hydroxyvitamin D 2; D002112:Calcifediol
keywords: Erythrocyte membrane; Vitamin D; fatty acids; leptin; lipids; parathyroid hormone