Vitamin d deficiency in children with cancer.

A limited number of small studies have examined the vitamin D status of pediatric oncology patients, and the results indicate an increased prevalence of hypovitaminosis. We conducted a cross-sectional study with the primary aim of describing the vitamin D status of our pediatric cancer patients and any associations with demographic characteristics. Our secondary aim was to compare this prevalence to that of a healthy population. We collected data on children seen in our clinic and determined the overall prevalence of hypovitaminosis. We then compared this prevalence to that of healthy populations described in the literature. The prevalence of hypovitaminosis in our study population was 72%. Forty-three percent of our patients were considered deficient with 8% being severely deficient. Our analysis revealed a significant association between the outcome and age in that patients 6 years and above were more likely to have hypovitaminosis after adjustment for other characteristics (AOR = 3.23; 95% CI, 1.11-9.40). When compared with a healthy pediatric population, our patients had a significantly higher prevalence of hypovitaminosis (P-value = 0.003). Vitamin D deficiency is very common in children with cancer, representing a subpopulation of high-risk patients that could benefit most from early detection and supplementation.

A pilot study: effects of decreasing serum insulin with diazoxide on vitamin D levels in obese women with polycystic ovary syndrome.

INTRODUCTION: We conducted a pilot project to test the hypothesis that decreasing insulin concentrations with diazoxide would affect parameters of vitamin D in obese women with and without polycystic ovary syndrome (PCOS). MATERIALS AND METHODS: Eight obese women with PCOS and nine matched controls participated in the study. Diazoxide was administered orally 100 mg three times daily for 10 days, and parameters of vitamin D were measured at baseline and end-of-study. RESULTS: At baseline, women with polycystic ovary syndrome had significantly lower serum 25-hydroxyvitamin D (25[OH]D) levels than controls. After treatment with diazoxide, there were no significant changes in vitamin D parameters when PCOS and control women were evaluated separately. Diazoxide exhibited differential effects on 25(OH)D concentrations in PCOS as compared with normal women (P for interaction=0.045), and serum 25(OH)D levels converged after diazoxide treatment. CONCLUSIONS: Obese women with PCOS had significantly lower serum 25(OH)D levels at baseline than age- and body mass index-matched controls. Short-term administration with diazoxide seemed to have differential effects on 25(OH)D levels in PCOS as compared with control women. Further studies are necessary to confirm this finding.

PICquant: a quantitative platform to measure differential peptide abundance using dual-isotopic labeling with 12C6- and 13C6-phenyl isocyanate.

We have developed a complete system for the isotopic labeling, fractionation, and automated quantification of differentially expressed peptides that significantly facilitates candidate biomarker discovery. We describe a new stable mass tagging reagent pair, (12)C(6)- and (13)C(6)-phenyl isocyanate (PIC), that offers significant advantages over currently available tags. Peptides are labeled predominantly at their amino termini and exhibit elution profiles that are independent of label isotope. Importantly, PIC-labeled peptides have unique neutral-mass losses upon CID fragmentation that enable charge state and label isotope identification and, thereby, decouple the sequence identification from the quantification of candidate biomarkers. To exploit these properties, we have coupled peptide fractionation protocols with a Thermo LTQ-XL LC-MS(2) data acquisition strategy and a suite of automated spectrum analysis software that identifies quantitative differences between labeled samples. This approach, dubbed the PICquant platform, is independent of protein sequence identification and excludes unlabeled peptides that otherwise confound biomarker discovery. Application of the PICquant platform to a set of complex clinical samples showed that the system allows rapid identification of peptides that are differentially expressed between control and patient groups.