Factors Associated with Serum Vitamin D Metabolites and Vitamin D Metabolite Ratios in Premenopausal Women

Role of rs2282679 in 25-hydroxyvitamin D levels and insulin resistance after a sleeve gastrectomy

BACKGROUND & AIMS

Some studies have reported links between 25-hydroxyvitamin D levels and the presence of obesity and some genetic variants. The aim of our design was to evaluate the effects of rs2282679 genetic variant of CG gene on 25-hydroxyvitamin D levels, weight loss and metabolic parameters after a robotic sleeve gastrectomy in premenopausal females with obesity.

METHODS

76 participants were enrolled. 25-hydroxyvitamin D levels, biochemical evaluation and anthropometric parameters were registered before surgery and after 3, 6 and 12 months follow up. Genotype of rs2282679 CG gene was evaluated.

RESULTS

The improvements in anthropometric parameters, blood pressure and lipid profile were similar in both genotypes (TT vs TG + GG). Basal insulin levels and HOMA-IR were greater in G allele carriers than non-carriers (Delta: 6.7 ± 1.2 mUI/L; p = 0.01) and (Delta: 1.3 ± 0.1 units; p = 0.02). 25-hydroxyvitamin D levels were lower in G allele carriers than non-carriers (Delta: 8.1 ± 1.1 ng/dl; p = 0.03). The levels of insulin and HOMA-IR remained greater in G allele carriers than non-carriers throughout all the visits. The levels of 25-hydroxyvitamin D remained lower in G allele carriers than non-G allele. The average level of 25-hydroxyvitamin D at 12 months in non-G allele carriers were above 30 ng/dl (36.0 ± 3.1 ng/dl) and the level in G allele carriers were below (24.9 ± 4.9 ng/dl).

CONCLUSIONS

rs 2282679 (GC) was related with low 25 hydroxyvitamin D levels and insulin resistance. In addition, the presence of G allele produced a decrease in the improvement of 25-hydroxyvitamin D levels and insulin resistance after weight loss during 12 months.

24,25-Dihydroxy Vitamin D and Vitamin D Metabolite Ratio as Biomarkers of Vitamin D in Chronic Kidney Disease

The appropriate management of vitamin D deficiency and hyperparathyroidism is essential to prevent metabolic bone disorder (MBD) and cardiovascular diseases in chronic kidney disease (CKD). Recently, the 24,25-dihydroxyvitamin D [24,25(OH)₂D] and vitamin D metabolite ratio (VMR), i.e., the ratio of 24,25(OH)₂D to 25-hydroxyvitamin D [25(OH)D], have emerged as biomarkers of vitamin D level. We analyzed the usefulness of vitamin D biomarkers for the evaluation of MBD in patients with CKD. We analyzed blood and urine samples from 208 outpatients with CKD stage G2-G5. 25(OH)D showed a poor correlation with the estimated glomerular filtration rate (eGFR). Conversely, the 24,25(OH)₂D level and VMR were significantly correlated with eGFR and the intact parathyroid hormone level. In conclusion, 24,25(OH)₂D and VMR have the potential to be vitamin D biomarkers for the detection of MBD in CKD patients.

Simultaneous determination of vitamin D metabolites 25(OH)D3 and 1α,25(OH)2D3 in human plasma using liquid chromatography tandem mass spectrometry

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LC-MS/MS method development and optimization for simultaneous determination of 25(OH)D₃ and 1α,25(OH)₂D₃ in human plasma.

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Lowest concentration of 25(OH)D₃ and 1α,25(OH)₂D₃ was 1000 and 20 pg/mL, respectively.

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The validated method was applied to a pharmacokinetic study in humans.

Background

Although measurement of 25(OH)D₃ is a routine analytical method to determine plasma vitamin D status, 1α,25(OH)₂D₃ is the biologically active form. Hence, simultaneous measurement of 25(OH)D₃ and 1α,25(OH)₂D₃ could provide better insight into vitamin D status and pharmacokinetics. However, 1α,25(OH)₂D₃ has a low plasma concentration, making its quantification challenging for most analytical techniques. Here, we demonstrate use of liquid chromatography tandem mass spectrometry (LC-MSMS) for the development of a simple and rapid method for the simultaneous quantification of 25(OH)D₃ and 1α,25(OH)₂D₃.

Methods

Samples were purified from 250 µL human plasma. Chromatography was performed on an analytical column, under gradient conditions using a mobile phase consisting of methanol-lithium acetate. The mass detector was operated in positive multiple reaction monitoring mode. The established method was validated according to the guidance issued by ICH and FDA. Furthermore, a clinical study was performed using this method to detect the plasma concentrations of 1α,25(OH)₂D₃ after oral administration of calcitriol.

Results and conclusion

The method was acceptably linear over the concentration ranges of 20–1200 pg/mL for 1α,25(OH)₂D₃ and 1–60 ng/mL for 25(OH)D₃, respectively, with correlation coefficients of r² > 0.993. Both the inter-assay and intra-assay precision was < 15%, and the analytical recoveries were within 100% ± 10%, with no significant matrix effect or carryover. Thereby, we, provide a facile method for the simultaneous detection of vitamin D metabolites in plasma.

Biomarkers of vitamin D status in healthy adults: Associations with serum lipid parameters: A pilot study

Vitamin D deficiency is among important healthcare challenges today. Traditionally, vitamin D status is assessed through determination of 25-hydroxy metabolite (25(OH)D), but novel data point to 24,25(OH)2D and 25(OH)D/24,25(OH)2D ratio (VDMR) as promising biomarkers. It is widely accepted that the biological role of vitamin D exceeds its well-known contribution to bone turnover. However, its effects on overall energy metabolism and lipid status alterations are not completely understood. In this study, we analyzed the relationship of vitamin D status assessed as concentrations of 25(OH)D3 and 24,25(OH)2D3 determined by liquid chromatography-tandem mass spectrometry, as well as VDMR with advanced lipid status parameters. Vitamin D status biomarkers, routine parameters of lipid status and size and distribution of lipoprotein subclasses were determined in 89 healthy adults (35 with adequate vitamin D status and 54 with vitamin D deficiency). Our results indicated a preponderance of proatherogenic small, dense LDL particles (sdLDL) in vitamin D deficient subjects. Both 25(OH)D and 24,25(OH)2D were associated with a relative proportion of sdLDL (B: -0.410; SE: 0.154; P=0.010; and B: -2.041; SE: 0.969; P=0.039, respectively). Positive correlation was found for VDMR and relative proportion of HDL 3a particles (r=0.251; P=0.024). VDMR value was decreased in subjects with vitamin D deficiency (P=0.001), thus implying its usefulness as a biomarker. A thorough investigation of novel vitamin D biomarkers and advanced lipid status parameters can be useful in the estimation of individual risk for the development of cardiometabolic alterations.