Fetuin-A – Alpha2-Heremans-Schmid Glycoprotein: From Structure to a Novel Marker of Chronic Diseases Part 2. Fetuin-A – A Marker of Insulin Resistance and Related Chronic Diseases

Polydopamine modification of polydimethylsiloxane for multifunctional biomaterials: Immobilization and stability of albumin and fetuin-A on modified surfaces

The surface of polydimethylsiloxane (PDMS) can be modified to immobilize proteins; however, most existing approaches are limited to complex reactions and achieving multifunctional modifications is challenging. This work applies a simple technique to modify PDMS using polydopamine (PDA) and investigates immobilization of multiple proteins. The surfaces were characterized in detail and stability was assessed, demonstrating that in a buffer solution, PDA modification was maintained without an effect on surface properties. Bovine serum albumin (BSA) and bovine fetuin-A (Fet-A) were used as model biomolecules for simultaneous or sequential immobilization and to understand their use for surface backfilling and functionalization. Based on 125I radiolabeling, amounts of BSA and Fet-A on PDA were determined to be close to double that were obtained on control PDMS surfaces. Following elution with sodium dodecyl sulfate, around 67% of BSA and 63% of Fet-A were retained on the surface. The amount of immobilized protein was influenced by the process (simultaneous or sequential) and surface affinity of the proteins. With simultaneous modification, a balanced level of both proteins could be achieved, whereas with the sequential process, the initially immobilized protein was more strongly attached. After incubation with plasma and fetal bovine serum, the PDA-modified surfaces maintained over 90% of the proteins immobilized. This demonstrates that the biological environments also play an important role in the binding and stability of conjugated proteins. This combination of PDA and surface immobilization methods provides fundamental knowledge for tailoring multifunctional PDMS-based biomaterials with applications in cell-material interactions, biosensing, and medical devices.

A novel method for multiplex protein biomarker analysis of human serum using quantitative MALDI mass spectrometry

In this work, we have extended our previously proposed approach for determining protein concentrations in human serum (using MALDI-TOF mass spectrometry) to include simultaneous analysis of several proteins associated with acute inflammation (alpha-2-macroglobulin, fetuin-A, serum amyloid A1). This technique can be used to diagnose systemic inflammation and provides results in 4-5 h. The developed approach was verified using standard immunological methods (ELISA). Samples from 87 individuals, in specific groups, were used for testing and validation: control; inflammatory soft tissue disease accompanied by sepsis; influenza A infection; or COVID-19. The feasibility of differentiating patient groups with the aforementioned conditions was analyzed using a combination of the inflammatory markers described. For fetuin-A and serum amyloid A1, diagnostically significant concentration ranges were established.

Quench me if you can: Alpha-2-macroglobulin trypsin complexes enable serum biomarker analysis by MALDI mass spectrometry

One of the main functions of alpha-2-macroglobulin (A2M) in human blood serum is the binding of all classes of protease. It is known that trypsin, after such interaction, possesses modified proteolytic activity. Trypsin first hydrolyzes two bonds in A2M's 'bait region', and the peptide ⁷⁰⁵VGFYESDVMGR⁷¹⁵ is released from A2M. In this work, specifics of the A2M-trypsin interaction were used to determine A2M concentration directly in human blood serum using MALDI mass-spectrometry. Following exogenous addition of trypsin to human blood serum in vitro, the concentration of the VGFYESDVMGR peptide was measured, using its isotopically-labeled analogue (¹⁸O), and A2M concentration was calculated. The optimized mass spectrometric approach was verified using a standard method for A2M concentration determination (ELISA) and the relevant statistical analysis methods. It was also shown that trypsin's modified proteolytic activity in the presence of serum A2M can be used to analyze other serum proteins, including potential biomarkers of pathological processes. Thus, this work describes a promising approach to serum biomarker analysis that can be technically extended in several useful directions.

Effects of fetuin-A with diverse functions and multiple mechanisms on human health

Fetuin-A (Alfa 2-Heremans-Schmid) is a glycoprotein that is mainly synthesized by hepatocytes and then released into the bloodstream. While fetuin-A, a multifunctional protein, has inhibitory effects on health in the processes of calcification, mineralization, coronary artery calcification (CAC), and kidney stone formation by various mechanisms, it has such stimulatory effects as obesity, diabetes, and tumor progression processes. Fetuin-A produces these effects on the organism mainly by playing a role in the secretion levels of some inflammatory cytokines and exosomes, preventing unwanted calcification, inhibiting the autophosphorylation of tyrosine kinase, suppressing the release of adiponectin and peroxisome proliferator-activated receptor-γ (PPARγ), activating the toll-like receptor 4 (TLR-4), triggering the phosphatidylinositol 3 (PI3) kinase/Akt signaling pathway and cell proliferation, and mimicking the transforming growth factor-beta (TGF-β) receptor. In the present review, fetuin-A was examined in a wide perspective from the structure and release of fetuin-A to its effects on health.