Cheng-Shiun He

Measurement of circulating 25-hydroxy vitamin d using three commercial enzyme-linked immunosorbent assay kits with comparison to liquid chromatography: tandem mass spectrometry method.

Aim. The purpose of this study was to compare the accuracy and clinical implications of three commercial enzyme-linked immunosorbent assay (ELISA) kits (Eagle Biosciences, Immundiagnostik, and MicroVue) with a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the measurement of serum 25(OH)D concentration. Methods. Blood samples were obtained from 225 healthy individuals who were recruited as subjects from Loughborough University, UK. Plasma samples were measured for 25(OH)D concentration by means of LC-MS/MS and ELISA kits from Eagle Biosciences, Immundiagnostik, and MicroVue. Results. The 25(OH)D concentration measured by the Eagle Biosciences, Immundiagnostik, and MicroVue ELISAs biased −50.9 ± 79.1 nmol/L, −14.2 ± 91.0 nmol/L, and −7.2 ± 18.9 nmol/L (bias ± SD) from the LC-MS/MS method, respectively. We found that 52% (Eagle Biosciences), 48% (Immundiagnostik), and 38% (MicroVue) of participants were misclassified, and the results showed the poor agreement (Kappa: −0.201~0.251) in classification of participants defined as vitamin D sufficiency and insufficiency between each method and LC-MS/MS. Conclusions. The present study demonstrated that there were negative biases and considerable misclassification of participants using the cut-off point (50 nmol/L) for vitamin D insufficiency and sufficiency using the Eagle Biosciences, Immundiagnostik, and MicroVue ELISAs compared with the LC-MS/MS assay.

The effect of 14 weeks of vitamin D3 supplementation on antimicrobial peptides and proteins in athletes

Abstract Heavy training is associated with increased respiratory infection risk and antimicrobial proteins are important in defence against oral and respiratory tract infections. We examined the effect of 14 weeks of vitamin D3 supplementation (5000 IU/day) on the resting plasma cathelicidin concentration and the salivary secretion rates of secretory immunoglobulin A (SIgA), cathelicidin, lactoferrin and lysozyme in athletes during a winter training period. Blood and saliva were obtained at the start of the study from 39 healthy men who were randomly allocated to vitamin D3 supplement or placebo. Blood samples were also collected at the end of the study; saliva samples were collected after 7 and 14 weeks. Plasma total 25(OH)D concentration increased by 130% in the vitamin D3 group and decreased by 43% in the placebo group (both P = 0.001). The percentage change of plasma cathelicidin concentration in the vitamin D3 group was higher than in the placebo group (P = 0.025). Only in the vitamin D3 group, the saliva SIgA and cathelicidin secretion rates increased over time (both P = 0.03). A daily 5000 IU vitamin D3 supplement has a beneficial effect in up-regulating the expression of SIgA and cathelicidin in athletes during a winter training period, which could improve resistance to respiratory infections.

Influence of vitamin D metabolites on plasma cytokine concentrations in endurance sport athletes and on multiantigen stimulated cytokine production by whole blood and peripheral blood mononuclear cell cultures.

Aim. Our aims were to determine the influence of plasma total 25-hydroxy vitamin D (25(OH)D) status on the plasma cytokine concentrations in athletes and the in vitro effects of different doses of 1, 25 dihydroxyvitamin D3 (1, 25(OH)2D3) on multiantigen stimulated cytokine production by whole blood and peripheral blood mononuclear cell (PBMC) cultures. Methods. Plasma samples from 43 athletes with high and low levels of 25(OH)D were assayed for the concentrations of cytokines. The whole blood samples and PBMCs from healthy subjects were incubated in vitro with a multi-antigen vaccine and different doses of added 1, 25(OH)2D3. The circulating cytokines and stimulated whole blood and PBMC culture production of cytokines were determined using a biochip assay. Results. The circulating interleukin-(IL-)10 and interferon-(IFN-) γ concentrations were significantly higher in the vitamin D sufficient athletes. Furthermore, the production of tumour necrosis factor-(TNF-) α, IL-6, IFN-γ, IL-2, and IL-10 by whole blood culture was significantly inhibited by 1, 25(OH)2D3 concentrations of 1000 pmol/L or 10000 pmol/L. Conclusions. We found that the influence of vitamin D on circulating cytokines might be different in athletes compared with nonathletes and cytokines production by whole blood culture was not influenced by 1, 25(OH)2D3 in concentrations within the normal healthy range.