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Measurement by a Novel LC-MS/MS Methodology Reveals Similar Serum Concentrations of Vitamin D-Binding Protein in Blacks and Whites.

ABSTRACT: BACKGROUND:Vitamin D deficiency is associated with poor bone health and other adverse health outcomes; however, the associations are greatly attenuated in black vs white individuals. One possible explanation for this attenuation is different concentrations of bioavailable vitamin D metabolites in plasma, which are estimated with equations that include the total concentration of vitamin D binding globulin (VDBG) and haplotype-specific dissociation constants. METHODS:We developed a method to quantify VDBG with LC-MS/MS that could also identify the haplotypes/isoforms of VDBG present. We validated the method according to recent recommendations for publications of biomarker studies. We determined serum VDBG concentrations in samples from the Atherosclerosis Risk in Communities cohort and compared the results with a widely used monoclonal immunoassay. RESULTS:With 10 ?L of serum or plasma, the lower limit of quantification for the assay (<20% CV) was 71 ?g/mL. The assay was linear from 62 to 434 ?g/mL, with total imprecision of 7.3-9.0% CV at approximately 250 ?g/mL. Significant hemolysis interfered with quantification. The identification of isoforms was 97% concordant with genotyping (? coefficient). Method comparison with immunoassay revealed significant isoform-specific effects in the immunoassay. Mean concentrations (SD) of VDBG by mass spectrometry were similar in whites and blacks [262 (25) vs 266 (35) ?g/mL, respectively; P = 0.43]. CONCLUSIONS:Validated mass spectrometric methods for the quantification of proteins in human samples can provide additional information beyond immunoassay. Counter to prior observations by immunoassay, VDBG concentrations did not vary by race.

SUBMITTER: Henderson CM

PROVIDER: S-EPMC4698095 | biostudies-literature | 2016 Jan

REPOSITORIES: biostudies-literature

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Measurement by a Novel LC-MS/MS Methodology Reveals Similar Serum Concentrations of Vitamin D-Binding Protein in Blacks and Whites.

Henderson Clark M CM Lutsey Pamela L PL Misialek Jeffrey R JR Laha Thomas J TJ Selvin Elizabeth E Eckfeldt John H JH Hoofnagle Andrew N AN

Clinical chemistry 20151009 1

<h4>Background</h4>Vitamin D deficiency is associated with poor bone health and other adverse health outcomes; however, the associations are greatly attenuated in black vs white individuals. One possible explanation for this attenuation is different concentrations of bioavailable vitamin D metabolites in plasma, which are estimated with equations that include the total concentration of vitamin D binding globulin (VDBG) and haplotype-specific dissociation constants.<h4>Methods</h4>We developed a ...[more]

PMID: 26453697

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Project description:The indiscriminate use of antibiotics in agriculture has raised concerns about antibiotic residues in food products, necessitating robust analytical methods for detection and quantification. In this study, our primary aim was to develop a robust and advanced liquid chromatography-tandem mass spectrometry (LC-MS/MS) methodology specifically designed for the accurate quantification of ticarcillin degradation products in tomato leaves. The choice of ticarcillin as the target analyte stems from its frequent use in agriculture and the potential formation of degradation products, which can pose a threat to food safety. The use of tomatoes as the target sample matrix in this study is justified by their significance in human diets, their widespread cultivation, and their suitability as a model for assessing antibiotic residue dynamics in diverse agricultural environments. By optimizing the MS/MS parameters, the study successfully demonstrates the practicality and reliability of the employed LC-MS/MS method in accurately assessing ticarcillin degradation product (Thiophene-2-Acetic acid and Thiophene-3-Acetic acid) levels. The chromatographic separation was achieved using a specialized column, ensuring high resolution and sensitivity in detecting analytes. Multiple reaction monitoring (MRM) data acquisition was employed to enhance the selectivity and accuracy of the analysis. The developed method exhibited excellent linearity and precision, meeting the stringent requirements for antibiotic residue analysis in complex matrices. Key outcomes of this study include the successful identification and quantification of ticarcillin and its degradation products in tomato leaves, providing crucial insights into the fate of this antibiotic in agricultural settings. The methodology's applicability was further demonstrated by analyzing real-world samples, highlighting its potential for routine monitoring and ensuring food safety compliance. In summary, our study constitutes a noteworthy advancement in the domain of antibiotic residue analysis, offering a reliable method for quantifying ticarcillin degradation products in tomato leaves. The optimized parameters and MRM-based LC-MS/MS approach enhance the precision and sensitivity of the analysis, opening up opportunities for further studies in the assessment of antibiotic residues in agricultural ecosystems.

Project description:BackgroundBisphenol A (BPA) is typically measured in urine using an indirect method that involves enzymatic deconjugation and extraction. In contrast, the direct method measures free and conjugated BPA concurrently and sums them to estimate urinary BPA concentrations. Statistical comparison of total BPA results using the direct and indirect methods is necessary to accurately interpret biomonitoring data for risk assessments.ObjectivesTo compare urinary BPA concentrations estimated from the indirect and direct methods in duplicate first trimester urine samples collected from 1879 pregnant women from the MIREC Study.MethodsFor the indirect method, we measured urinary BPA concentrations using GC-MS/MS. For the direct method, we summed free and conjugated BPA concentrations measured using LC-MS/MS. We evaluated deviation between the two methods using the Bland-Altman analysis in the total sample and stratified (1) by specific gravity and (2) at the limit of quantification (LOQ).ResultsMedian urinary BPA concentrations for the direct and indirect methods were 0.89 µg BPA equivalents/L and 0.81 µg/L respectively. Concentrations from the direct method were, on average, 8.6% (95% CI: 6.7%, 10.5%) higher than the indirect method in a Bland-Altman analysis. The percent differences between the two methods was 4.0% in urines with specific gravities < 1.02 (n = 1348, 72%) and 20.3% in urine with specific gravity ≥ 1.02. In values below the LOQ (n = 663, 35%), we observed smaller average percent deviation (4.8%) between the two methods but wider limits of agreement.DiscussionResults from this study, based on the largest statistically rigorous comparison of the direct and indirect methods of BPA measurement, contrast previous findings reporting that the indirect method underestimates total BPA exposure. The difference in urinary BPA concentrations we observed with the indirect and direct methods is unlikely to alter the interpretation of health outcome data.

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Measurement by a Novel LC-MS/MS Methodology Reveals Similar Serum Concentrations of Vitamin D-Binding Protein in Blacks and Whites.

Publications

Measurement by a Novel LC-MS/MS Methodology Reveals Similar Serum Concentrations of Vitamin D-Binding Protein in Blacks and Whites.

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