English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Background   Adequate concentrations of vitamin D are required to ensure bone health and minimize the incidence of multiple extraskeletal diseases. Although total 25-hydroxyvitamin D (25OHD) remains the recommended biomarker for assessing vitamin D status, it has been speculated that free 25OHD correlates better with clinical outcomes. The calculation of free 25OHD depends on the concentrations of vitamin D binding protein (DBP), the determination of which involves different immunoassays and has led to varying results and conclusions. We developed a liquid chromatography–tandem mass spectrometry (LC-MS/MS) method for simultaneous identification and relative quantification of DBP isoforms.Methods   We used serum samples from healthy children ( n = 79), mainly Caucasian (88%). Proteins were denatured, reduced, alkylated and digested with trypsin. Purified peptides were analysed by LC-MS/MS. The DBP phenotype was established by using the combinations of tryptic peptides associated with each of the three isoforms and one peptide common to all of them to perform relative quantification. The genotyping of volunteers ( n = 7) facilitated verification of the ability of our method to correctly identify the DBP phenotype.Results   The DBP phenotype was correctly established in all samples from volunteers, based on the 100% correlation observed with the genotype. The most common DBP phenotype in Caucasian children was 2/1S (34%) and the rarest 1F/1F (2%). The relative quantification of DBP concentrations did not show statistically significant differences between phenotypes ( P = 0.11).Conclusions   LC-MS/MS enabled simultaneous phenotyping and relative quantification of DBP, while avoiding the analytical limitations of immunoassays and confirming similar concentrations of DBP in all phenotypes.

annals of clinical biochemistry

Phenotyping and relative quantification of vitamin D binding protein in a paediatric population by using liquid chromatography–tandem mass spectrometry