Author: Eagle Biosciences

The MedFrontier Intact FGF-23 Assay is developed and manufactured by Minaris Medical! This assay kit is a reliable test that provides a simple and quick assay procedure that yields a broad dynamic range.

What is FGF-23?

FGF-23 (Fibroblast Growth Factor 23) is a protein belonging to the fibroblast growth factor family. FGF-23 is involved in the regulation of phosphorus metabolism. FGF-23 has a molecular weight of approximately 32 kDa. FGF-23 is produced in bone cells. In vivo, FGF-23 is secreted into circulation. A full-length active FGF-23 protein may undergo proteolytic cleavage to generate an inactive c-terminal fragment. The MedFrontier Intact FGF-23 Assay measures ONLY the full-length active form (intact form).

Why Measure FGF-23?

Phosphate plays a critical role in the formation and growth of bones in children and maintaining strength in adults. If there is an imbalance of FGF-23 within the bloodstream, it can cause hyper- and hypophosphatemia. These conditions have been linked to Rickets, osteomalacia, and impaired renal function to name a few.

About the MedFrontier Intact FGF-23 Assay Kit

This is a sandwich Chemiluminescence enzyme immunoassay (CLEIA) kit by using two anti-human FGF-23 mouse monoclonal antibodies. When serum is added to a plate well coated with anti-human FGF-23 mouse monoclonal antibodies, FGF-23 is captured by the immobilized antibodies (1st reaction). After the 1st reaction, the plate is washed. Then, ALP-labeled anti-human FGF-23 mouse monoclonal 2nd antibodies against FGF-23 react to FGF-23 antigens captured by the immobilized antibodies (2nd reaction). After the 2nd reaction, the plate is washed and light detection is performed after adding the luminescence reagent. Each active well of the plate is measured using a luminescence microplate reader and relative light units (RLU) are obtained. The concentration of FGF-23 in serum is calculated with a standard curve generated using the FGF-23 Standard 1 to 6.

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We are excited to bring you the newest addition to our line of Complement Assays, two new Factor P assays – one quantitative and one functional. Developed and Manufactured by Svar Life Science, these kits are designed to work optimally together. These assays are ideal for assisting in the development of next-generation complement therapies!

In addition to measuring the properdin (Factor P) concentration and determining its functionality, the Factor P assays can be easily adapted for more in-depth studies, granting a closer look at the amplification loop of the complement system.

About Factor P

Factor P (Complement P, Properdin, FP) is a positive regulator and an initiator of the alternative pathway (AP) for complement activation. It binds surface-bound C3 and C5 convertases and stabilizes them to amplify the activation cascade¹. Factor P binding increases the half-life of the convertase complex approximately 10-fold². It is suggested, however debated, that Factor P also can initiate complement activation by binding for example cell surfaces or certain biological substrates, recruiting C3b or C3(H2O) and Factor B and thus initiate the AP pathway^1,3. Factor P opposes the negative regulation of Factor H that enhances the dissociation of C3b and Bb and mediates Factor I cleavage of C3b to the inactive iC3b3 (Figure 1).

Figure 1: Factor P as stabilizer and initiator of the alternative complement pathway (left) and the opposing negative regulation by Factor H3 (right).

Factor P is not produced in hepatocytes as most complement proteins, but instead by several cell types including monocytes, macrophages, T-cells and granulocytes. It is likely that transient increased concentration of Factor P enhances the AP upon local stimuli4. For example, neutrophils have Factor P-containing granules that are secreted upon stimulation and can enhance the platelet-granulocyte aggregate formation¹. In plasma, Factor P is present in a concentration of approximately 4-25 µg/mL5. Factor P is an elongated 53 kDa glycoprotein that oligomerizes in vivo to dimers, trimers or tetramers (P2, P3 and P4) in a ratio of 26:54:20 (P2:P3:P4) in head to tail structures^5,6. Mutations, deficiencies, protein levels as well as protein deposits of Factor P are connected to diseases and disorders summarized by Chen et al 3. Deficiencies generally increase the susceptibility for meningococcal disease and other infectious diseases7. Altered serum levels have been associated with for example C3 glomerulopathy, Lupus Nephritis, sepsis and chronic heart failure and IgA nephropathy^8.

References

1. Blatt, A. Z.; Pathan, S.; Ferreira, V. P. Properdin: A Tightly Regulated Critical Inflammatory Modulator. Immunol Rev 2016, 274 (1), 172–190. https://doi.org/10.1111/imr.12466.
2. Fearon, D. T.; Austen, K. F. Properdin: Binding to C3b and Stabilization of the C3b-Dependent C3 Convertase. J Exp Med 1975, 142 (4), 856–863.
3. Chen, J. Y.; Cortes, C.; Ferreira, V. P. Properdin: A Multifaceted Molecule Involved in Inflammation and Diseases. Mol. Immunol. 2018, 102, 58–72. https://doi.org/10.1016/j.molimm.2018.05.018.
4. Cortes, C.; Ohtola, J. A.; Saggu, G.; Ferreira, V. P. Local Release of Properdin in the Cellular
   Microenvironment: Role in Pattern Recognition and Amplification of the Alternative Pathway of Complement. Front Immunol 2013, 3. https://doi.org/10.3389/fimmu.2012.00412.
5. Pangburn, M. K. Analysis of the Natural Polymeric Forms of Human Properdin and Their Functions in Complement Activation. The Journal of Immunology 1989, 142 (1), 202–207.
6. Smith, C. A.; Pangburn, M. K.; Vogel, C. W.; Müller-Eberhard, H. J. Molecular Architecture of Human Properdin, a Positive Regulator of the Alternative Pathway of Complement. J. Biol. Chem. 1984, 259 (7), 4582–4588.
7. Fijen, C. A. P.; van den Bogaard, R.; Schipper, M. Properdin Defciency: Molecular Basis and Disease Association. Molecular Immunology 1999, 36, 863–867.
8. Michels, M. A. H. M.; Volokhina, E. B.; van de Kar, N. C. A. J.; van den Heuvel, L. P. W. J. The Role of Properdin in Complement-Mediated Renal Diseases: A New Player in Complement-Inhibiting Therapy? Pediatr Nephrol 2019, 34 (8), 1349–1367. https://doi.org/10.1007/s00467-018-4042-z.

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Circulating DKK-1 levels predict disease outcomes and mirror metabolic adaptations in patients with Covid-19

Individuals with low serum levels of DKK-1 (Dickkopf-1) are twice as likely to die from Covid-19 than those with high levels according to new research published by Nikolai Jaschke and colleagues in the Journal of Clinical Endocrinology & Metabolism.

The researchers found that circulating DKK1 levels vary in humans and change as a function of time during SARS-CoV-2 infection. The infection promotes metabolic adaptations that resembles fasting, which are mirrored by circulating DKK1 levels. DKK-1 levels predict disease outcomes in Covid-19 individuals.

The results of the study suggest a potential use of measuring circulating DKK1 as an indicator of disease severity in COVID-19 patients.

Abstract

Context and aims: Coronavirus disease 19 (COVID-19) trajectories show high interindividual variability, ranging from asymptomatic manifestations to fatal outcomes, the latter of which may be fueled by immunometabolic maladaptation of the host. Reliable identification of patients who are at risk of severe disease remains challenging. We hypothesized that serum concentrations of Dickkopf1 (DKK1) indicate disease outcomes in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected individuals.

Methods: We recruited hospitalized patients with PCR-confirmed SARS-CoV-2 infection and included 80 individuals for whom blood samples from 2 independent time points were available. DKK1 serum concentrations were measured by ELISA in paired samples. Clinical data were extracted from patient charts and correlated with DKK1 levels. Publicly available datasets were screened for changes in cellular DKK1 expression on SARS-CoV-2 infection. Plasma metabolites were profiled by nuclear magnetic resonance spectroscopy in an unbiased fashion and correlated with DKK1 data. Kaplan-Meier and Cox regression analysis were used to investigate the prognostic value of DKK1 levels in the context of COVID-19.

Results: We report that serum levels of DKK1 predict disease outcomes in patients with COVID-19. Circulating DKK1 concentrations are characterized by high interindividual variability and change as a function of time during SARS-CoV-2 infection, which is linked to platelet counts. We further find that the metabolic signature associated with SARS-CoV-2 infection resembles fasting metabolism and is mirrored by circulating DKK1 abundance. Patients with low DKK1 levels are twice as likely to die from COVID-19 than those with high levels, and DKK1 predicts mortality independent of markers of inflammation, renal function, and platelet numbers.

Conclusion: Our study suggests a potential clinical use of circulating DKK1 as a predictor of disease outcomes in patients with COVID-19. These results require validation in additional cohorts.

Check out the full article here.

Circulating DKK-1 levels were measured with the DKK-1 ELISA from Biomedica

• Small sample volume – 20µl serum/well
• Reliable –international validation guidelines
• Easy – direct measurement
• Widely cited in +170 publications

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