Human serum albumin (HSA) is the most abundant plasma protein in circulation. The three most important drug-binding sites on HSA are Sudlow’s Site I (subdomain IIA), Sudlow’s Site II (subdomain IIIA), and Heme site (subdomain IB). Heme site and Site I are allosterically coupled; therefore, their ligands may be able to allosterically modulate the binding affinity of each other. In this study, the effects of four Heme site ligands (bilirubin, biliverdin, hemin, and methyl orange) on the interaction of the Site I ligand warfarin with HSA were tested, employing fluorescence spectroscopic, ultrafiltration, and ultracentrifugation studies. Our major results/conclusions are the following. (1) Quenching studies indicated no relevant interaction, while the other fluorescent model used suggested that each Heme site ligand strongly decreases the albumin binding of warfarin. (2) Ultrafiltration and ultracentrifugation studies demonstrated the complex modulation of warfarin–HSA interaction by the different Heme site markers; for example, bilirubin strongly decreased while methyl orange considerably increased the bound fraction of warfarin. (3) Fluorescence spectroscopic studies showed misleading results in these diligand–albumin interactions. (4) Different Heme site ligands can increase or decrease the albumin binding of warfarin and the outcome can even be concentration dependent (e.g., biliverdin and hemin).

Mycotoxins are frequent food contaminants posing health risk to humans and animals. Since these interactions have been barely studied yet, we examined the potential complex formation of mycotoxins with human α₁-acid glycoprotein (AGP) and with bovine milk proteins (including casein (CSN), β-lactoglobulin (LG), and α-lactalbumin (LA)) based on fluorescence spectroscopic and ultracentrifugation techniques. Only weak interactions (logK = 2.7 to 3.5) of certain mycotoxins were observed with CSN, LG, and/or LA. Ultracentrifugation experiments demonstrated that aflatoxin M1, zearalenone, and α-zearalenol form more stable complexes with CSN than with LG or LA. These mycotoxins bound to bovine serum albumin with more than a tenfold higher affinity compared to CSN; nevertheless, it has likely limited importance due to the relatively low levels of BSA in bovine milk. Zearalenone, zearalenols, and sterigmatocystin showed strong interactions with AGP (logK = 5.5 to 6.4), suggesting that AGP may play an important role in the plasma protein binding of these mycotoxins.

Background: The actin-binding protein Flightless-I (Flii) has not been quantified in the human serum yet. We aimed to determine serum Flii levels in healthy individuals and to investigate Flii as a potential marker in patients with sepsis focusing on diagnosis, organ failures, and short-term mortality. Methods: A total of 30 controls and 64 septic and 22 non-septic patients were enrolled in this follow-up study. Serum Flii levels were quantified by using the capillary electrophoresis-based Simple Western™ system with chemiluminescent detection. The assay was calibrated by applying dilution series of a purified recombinant human Flii standard and a parallel internal standard. Results: Flii levels of healthy controls were found between 3.5 and 8.8 mg/L, while septic and non-septic patients showed significantly lower values (p < 0.001). First-day Flii could differentiate sepsis from the non-septic inflammatory state (AUC: 0.667; p < 0.05) and indicated acute respiratory distress syndrome (ARDS) among septic patients (AUC: 0.686; p < 0.05). Furthermore, a combination of Flii and other sepsis markers seemed to offer an improved diagnostic performance (sepsis vs. non-sepsis, AUC of Flii + gelsolin (GSN) + Gc-globulin + procalcitonin: 0.974; p < 0.001 and ARDS vs. non-ARDS, AUC of Flii + GSN + presepsin: 0.776; p < 0.001) compared with single markers even in the prediction of 14-day mortality (AUC of Flii + GSN + Gc-globulin: 0.76; p < 0.001). Conclusions: We adapted a properly precise and reproducible automated Western blot method to determine concentrations of Flii in human serum. Our results revealed the relationship between Flii and sepsis; however, Flii alone did not appear to be a prominent sepsis marker. When combined with other biomarkers, measurement of serum Flightless-I may provide additional value supporting patient care.

Background/Objectives: Intensive care unit-acquired weakness (ICUAW) is a frequent complication characterized by symmetrical and proximal limb muscle weakness. Its diagnosis is primarily based on clinical symptoms; however, ICUAW assessment can often be uncertain. Blood biomarkers have not yet been widely investigated for this purpose. Serum gelsolin (GSN) is synthesized by skeletal muscle cells. It plays a crucial role in binding extracellular actin filaments and pro-inflammatory cytokines. In sepsis-associated ICUAW, GSN levels might massively decrease due to their buffering activity and muscle wasting. We elucidated the predictive capacity of GSN regarding ICUAW and its additional diagnostic/prognostic potential in sepsis compared to classical parameters. Methods: We recruited septic and non-septic ICU patients for our follow-up study. Patients were retrospectively categorized into ICUAW positive (n = 26) and negative (n = 47) groups based on their clinical characteristics. Sera were collected on the 1st, 2nd and 3rd days of ICU stay. Ambulatory patients (n = 34) served as controls. GSN levels were measured by our previously developed automated immunoturbidimetric assay. Clinical and laboratory parameters were collected from our hospital information system. Results: Admission GSN levels were significantly reduced in ICU patients compared to controls (median: 11.60 vs. 75.99 mg/L). ICUAW positive patients had significantly lower admission GSN levels than ICUAW negative patients (median: 8.10 vs. 14.30 mg/L), and a similar tendency was observed during follow-up. GSN showed predictive capacity regarding ICUAW (ROC AUC: 0.711, p < 0.01), especially when combined with albumin (ROC AUC: 0.750, p < 0.01). The combination of admission GSN, albumin, and procalcitonin demonstrated significant diagnostic performance (ROC AUC: 0.803) regarding the requirement for invasive ventilation, and GSN had prognostic value for 28-day mortality as well. Conclusions: GSN might serve as an intriguing marker in the prediction of ICUAW, especially when combined with albumin. The parallel decline of GSN and albumin could reflect the combined effects of systemic inflammation and muscle wasting seen in ICUAW.