ECTS2014 Poster Presentations Bone development/growth and fracture repair (55 abstracts)
Associations among vitamin D binding protein polymorphisms and concentrations and total, free, and bioavailable serum 25-hydroxyvitamin D concentrations in finnish adults
Elisa Saarnio 1 , Minna Pekkinen 1, , Suvi Itkonen 1 , Virpi Kemi 1 , Heini Karp 1 , Merja Kärkkäinen 1 , Outi Mäkitie 3 & Christel Lamberg-Allardt 1
1University of Helsinki, Helsinki, Finland; 2Folkhälsan Institute of Genetics, Helsinki, Finland; 3Children’s Hospital, Helsinki University Central Hospital, Helsinki, Finland.
Vitamin D and its metabolites are bound to vitamin D binding protein (DBP) in the circulation. Only a small proportion is in unbound, free form. According to the ‘free-hormone-hypothesis’ only the free form is biologically active. DBP is a polymorphic protein and different variants of the protein differ in their ability to bind vitamin D. This may have an impact on the amount of free and bioavailable (free+albumin-bound) 25-hydroxyvitamin D (25(OH)D) in the circulation. We investigated the associations among DBP polymorphisms, total-, free- and bioavailable serum 25(OH)D in 617 healthy 37–47 year old Caucasian women and men in a cross-sectional study. Fasting blood samples were collected and concentrations of S-25(OH)D and DBP were determined from the blood. Dietary and supplement intake of vitamin D and calcium (Ca) as well as background data about lifestyle were collected. SNP’s 4588 and 7041 were genotyped based on polymorphisms in the DBP coding gene. They combine to form six common diplotypes and three haplotypes. The concentrations of free and bioavailable S-25(OH)D were calculated for the diplotypes and haplotypes according to published binding coefficients. The calculated amount of free and bioavailable S-25(OH)D was 0.02 and 8.8%, respectively, of the total measured S-25(OHD).
We found a significant difference in the DBP concentrations among the haplotypes and almost significant between the diplotypes. S-25(OH)D concentrations did not differ between the haplotypes but there was a significant difference among the diplotypes. When the haplotype and diplotype free and bioavailable S-25(OH) D concentrations were SNP adjusted, both the free and bioavailable S-25OHD among the genotypes differed significantly. In conclusion, DBP polymorphism affects the total, free and bioavailable concentrations. Free and bioavailable S-25(OH)D may bring new aspects to associations between vitamin D status and health outcomes.
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Bone Abstracts
ISSN 2052-1219 (online)
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