To identify the mechanisms underlying muscle aging, we have undertaken a high-resolution differential proteomic analysis of gastrocnemius muscle in young adults, mature adults, and old LOU/c/jall rats. Two-dimensional gel electrophoresis and subsequent MALDI-ToF mass spectrometry analyses led to the identification of 40 differentially expressed proteins. Strikingly, most differences characterized old (30-month) animals, whereas young (7-month) and mature (18-month) adults exhibited similar patterns of expression. Important modifications in contractile (actin, myosin light-chains, troponins-T) and cytoskeletal (desmin, tubulin) proteins, and in essential regulatory proteins (gelsolin, myosin binding proteins, CapZ-beta, P23), likely account for dysfunctions in old muscle force generation and speed of contraction. Other features support decreases in cytosolic (triose-phosphate isomerase, enolase, glycerol-3-P dehydrogenase, creatine kinase) and mitochondrial (isocitrate dehydrogenase, cytochrome-c oxidase) energy metabolisms. Muscle aging is often associated with increased oxidative stress. Accordingly, we observed differential regulation of molecular chaperones (hsp20, hsp27, reticuloplasmin ER60) and of proteins implicated in reactive aldehyde detoxification (aldehyde dehydrogenase, glutathione transferase, glyoxalase). We further noticed up-regulation of proteins involved in transcriptional elongation (RNA capping protein) and RNA-editing (Apobec2). Most of these proteins were previously unrecognized as differentially expressed in old muscles, and they represent novel starting points for elucidating the mechanisms of muscle aging.

Hierarchical clustering methodology is a powerful data mining approach for a first exploration of proteomic data. It enables samples or proteins to be grouped blindly according to their expression profiles. Nevertheless, the clustering results depend on parameters such as data preprocessing, between-profile similarity measurement, and the dendrogram construction procedure. We assessed several clustering strategies by calculating the F-measure, a widely used quality metric. The combination, on logged matrix, of Pearson correlation and Ward's methods for data aggregation is among the best clustering strategies, at least with the data sets we studied. This study was carried out using PermutMatrix, a freely available software derived from transcriptomics.

24,25(OH)D is the product of 25(OH)D catabolism by CYP24A1. The measurement of serum 24,25(OH)D concentration may serve as an indicator of vitamin D catabolic status and the relative ratio with 25(OH)D can be used to identify patients with inactivating mutations in CYP24A1. We describe a LC-MS/MS method to determine: (1) the relationships between serum 24,25(OH)D and 25(OH)D; (2) serum reference intervals in healthy individuals; (3) the diagnostic accuracy of 24,25(OH)D measurement as an indicator for vitamin D status; 4) 24,25(OH)D cut-off value for clinically significant change between inadequate and sufficient 25(OH)D status. Serum samples of healthy participants (n=1996) from Army recruits and patients (n=294) were analysed. The LC-MS/MS assay satisfied industry standards for method validation. We found a positive, concentration-dependent relationship between serum 24,25(OH)D and 25(OH)D concentrations. The 25(OH)D:24,25(OH)D ratio was significantly higher (P<.001) at 25(OH)D<50 nmol/L. The reference interval for 25(OH)D:24,25(OH)D ratio in healthy subjects was 7-23. Measurement of serum 24,25(OH)D can be used as predictor of vitamin D status, a concentration of>4.2 nmol/L was identified as a diagnostic cut-off for 25(OH)D replete status. One patient sample with an elevated 25(OH)D:24,25(OH)D ratio of 32 and hypercalcaemia who on genetic testing confirmed to have a biallelic mutation of CYP24A1. Our study demonstrated the feasibility of a combined 24,25(OH)D and 25(OH)D assessment profile. Our established cut-off value for 24,25(OH)D and ratio reference ranges can be useful to clinicians in the investigation of patients with an impaired calcium/phosphate metabolism and may point towards the existence of CYP24A1 gene abnormalities.

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Background In the initial stages of the SARS-CoV-2 (COVID-19) pandemic a plethora of new serology tests were developed and introduced to the global market. Many were not evaluated rigorously and there is a significant lack of concordance in results across methods. To enable meaningful clinical decisions to be made, robustly evaluated, quantitative serology methods are needed. These should be harmonized to a primary reference material, allowing for the comparison of trial data and improved clinical decision making. Methods A comprehensive evaluation of the new Abbott IgG II anti-SARS-CoV-2 IgG method was undertaken using CLSI based protocols. Two different candidate primary reference materials and verification panels were assessed with a goal to moving towards harmonization. Results The Abbott IgG II method performs well across a wide range of parameters with excellent imprecision (<3.5%) and is linear throughout the positive range (tested to 38,365 AU/mL). The sensitivity (based on ≥14 day post positive RT-PCR samples) and specificity are 98.3% [90.6-100.0%] and 99.5% [97.1-100%] respectively. The candidate reference materials showed poor correlation across methods with mixed responses noted in methods that use the spike protein versus the nucleocapsid proteins as their binding antigen. Conclusions The Abbott IgG II anti-SARS-CoV-2 measurement appears to be the first linear method potentially capable of monitoring the immune response to natural infection, including from new emerging variants. The candidate reference materials assessed do not generate uniform results across several methods and further steps are needed to enable the harmonization process.

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Sclerostin, bone formation antagonist is in the spotlight as a potential biomarker for diseases presenting with associated bone disorders such as chronic kidney disease (CDK-MBD). Accurate measurement of sclerostin is therefore important. Several immunoassays are available to measure sclerostin in serum and plasma. We compared the performance of three commercial ELISA kits. We measured sclerostin concentrations in serum and EDTA plasma obtained from healthy young (18–26 years) human subjects using kits from Biomedica, TECOmedical and from R&D Systems. The circulating sclerostin concentrations were systematically higher when measured with the Biomedica assay (serum: 35.5 ± 1.1 pmol/L; EDTA: 39.4 ± 2.0 pmol/L; mean ± SD) as compared with TECOmedical (serum: 21.8 ± 0.7 pmol/L; EDTA: 27.2 ± 1.3 pmol/L) and R&D Systems (serum: 7.6 ± 0.3 pmol/L; EDTA: 30.9 ± 1.5 pmol/L). We found a good correlation between the assay for EDTA plasma (r > 0.6; p < 0.001) while in serum, only measurements obtained using TECOmedical and R&D Systems assays correlated significantly (r = 0.78; p < 0.001). There was no correlation between matrices results when using the Biomedica kit (r = 0.20). The variability in values generated from Biomedica, R&D Systems and TECOmedical assays raises questions regarding the accuracy and specificity of the assays. Direct comparison of studies using different kits is not possible and great care should be given to measurement of sclerostin, with traceability of reagents. Standardization with appropriate material is required before different sclerostin assays can be introduced in clinical practice.

A better understanding of primary school teachers' practices and representations toward health education (HE), and identification of individual or structural resistance as well as the partnership and training needs all constitute important goals in HE research. A quantitative study was conducted between April and December 2001 on a representative sample of the population of primary school teachers (n = 673) in the Auvergne region. The results demonstrate that the majority of teachers declare practicing and implementing HE. The approach is primarily thematic, essentially limited to a few lessons since it is only integrated into a broader project 20% of the time. 30% of teachers work in partnership, mainly with partners in school health; however, parents are rarely involved in HE activities. Parameters which influence the teachers' practices and representations are: (1) prioritizing work within an educational network and an inter-communal pedagogical regrouping, with the advantage that there are a greater number of teachers to do HE in these schools than in others, and (2) receiving initial or in-service training. These results suggest that a policy aiming to generalize the inclusion of HE in French primary schools must develop teacher training as well as support and accompany the collective dynamics within schools.