Advanced Glycation End Products Modulate Structure and Drug Binding Properties of Albumin

Displacing the Burden: A Review of Protein-Bound Uremic Toxin Clearance Strategies in Chronic Kidney Disease

Uremic toxins (UTs), particularly protein-bound uremic toxins (PBUTs), accumulate in chronic kidney disease (CKD) patients, causing significant health complications like uremic syndrome, cardiovascular disease, and immune dysfunction. The binding of PBUTs to plasma proteins such as albumin presents a formidable challenge for clearance, as conventional dialysis is often insufficient. With advancements in the classification and understanding of UTs, spearheaded by the European Uremic Toxins (EUTox) working group, over 120 molecules have been identified, prompting the development of alternative therapeutic strategies. Innovations such as online hemodiafiltration aim to enhance the removal process, while novel adsorptive therapies offer a means to address the high affinity of PBUTs to plasma proteins. Furthermore, the exploration of molecular displacers, designed to increase the free fraction of PBUTs, represents a cutting-edge approach to facilitate their dialytic clearance. Despite these advancements, the clinical application of displacers requires more research to confirm their efficacy and safety. The pursuit of such innovative treatments is crucial for improving the management of uremic toxicity and the overall prognosis of CKD patients, emphasizing the need for ongoing research and clinical trials.

Insights into the conformational, secondary structural, dynamical and hydration pattern changes of glucose mediated glycated HSA: a molecular dynamics approach

The robust structural nature of human serum albumin (HSA) is responsible for its multifarious functional property. The site specific glycation of HSA due to hyperglycaemia (excess glucose) causes structural changes which have an impact on the functioning of the protein. This work investigates the effects of glucose-mediated glycation in the altered inter-domain motion, distorted binding site conformation and modified hydration patterns, Trp214 orientation, and secondary structure transition using simulation approach. Here we have observed an increase of turns in the helices of glycated HSA, which modulates the open-close conformation of Sudlow I & II. The secondary structure changes of glycated HSA indicate plausible reduction in the alpha helical content in the helices which participates in ligand binding. It also affects geometrical features of drug binding sites (Sudlow I and II) such as volume and hydration. We found that glycation disturbs domain specific mobility patterns of HSA, a substantial feature for albumin drug binding ability which is also correlated with changes in the local environment of Trp214.Communicated by Ramaswamy H. Sarma.

Conformational variation of site specific glycated albumin: A Molecular dynamics approach

Human serum albumin (HSA) is a major cargo protein, which undergoes glycation in hyperglycaemic conditions and results in impaired function. In physiological conditions, HSA plays a crucial role in pharmacological activities such as drug transport or delivery through its binding capacity and also by its enzymatic activity, which enables the translation of pro-drugs into active drugs. In this study, the impact of the methylglyoxal-mediated glycation on dynamic behaviour of inter-domain motion, Cys34 reactivity, binding site residual interaction and secondary structure transition were investigated through molecular dynamics simulation. The alteration in inter-domain motion reflects the effect of glycation-mediated changes on the structural conformation of albumin. The binding site residue interactions and volume analysis revealed the impact of glycation on the geometry of the binding site. We also found the correlation of Cys34 reactivity with increase of turns in the region between Ia-h4 and Ia-h5. The rise in turn formation in that region keeps Tyr84 farther away from Cys34 which could lead to higher Cys34 reactivity. In parallel, significant alterations in alpha helical content of helices in the binding sites were observed. These structural and conformational changes in glycated albumin could be the causative agents for functional impairment which leads to diabetic complications.

Comparison of Protective Effects of Phenolic Acids on Protein Glycation of BSA Supported by In Vitro and Docking Studies

Several diabetic complications are associated with forming advanced glycation end products (AGEs). Different chemical and natural compounds are able to prevent the development of these products. In this study, glycosylation was induced as a model by incubating bovine serum albumin (BSA) with glucose. Consequently, BSA was treated with glucose and different concentrations (1.25, 2.5, and 5 μM) of syringic acid, gallic acid, ellagic acid, ferulic acid, paracoumaric acid, and caffeic acid for 4 and 6 weeks. Biochemical experiments comprise measurements of fluorescent AGEs, protein carbonyl contents, total thiol, hemolysis tests, and also malondialdehyde (MDA) levels in RBC. These demonstrated the antiglycating mechanism of these phenolic acids. Most of the phenolic acids used in this study reduced MDA levels and protected thiol residues in protein structures. They also inhibited the formation of fluorescent AGEs and RBC lysis, except gallic acid. Moreover, ferulic acid, paracoumaric acid, and caffeic acid proteins significantly prevent carbonylation. Molecular docking and simulation studies showed that ellagic, caffeic, gallic, and syringic acids could interact with lysine and arginine residues in the active site of BSA and stabilize its structure to inhibit the formation of AGEs. Our results suggest that phenolic acid could be used as a potential phytochemical against protein glycation and related diabetic complications.

Glycation restrains open-closed conformation of Insulin

In hyperglycemic conditions, the level of reactive dicarbonyl metabolites concentration is found to be high, which plays a significant role in protein glycation. Despite decades of research, the effect of methylglyoxal on the structure and function of insulin is still unknown. Through a shift in conformation at the B-chain C-terminal (BT-CT) hinge from an "open" to a "wide-open" conformation, insulin binds to the receptor and activates the signal cascade. Insulin resistance, which is the main sign of Type 2 Diabetes, can be caused by a lack of insulin signaling. Methylglyoxal site-specific glycation in residue R22 at B chain forms AGE product Methylglyoxal-hydroimidazolone (MGH1) in insulin. In this work, we present molecular dynamics study of this glycated insulin R22MGH1, which revealed new insights into the conformational and structural changes. We find the following key results: 1) B-chain in insulin undergoes a closed conformational change upon glycation. 2) Glycated insulin shows secondary structure alteration. 3) Glycated insulin retains its closed shape due to an unusually strong hydrophobic contact between B-chain residues. 4) Wide open native conformation of insulin allows the B chain helix to be surrounded by more water molecules compared to the closed conformation of glycated insulin. The closed conformation of glycated insulin impairs its binding to insulin receptor (IR).

Revealing Advanced Glycation End Products Associated Structural Changes in Serum Albumin

Structural alterations in proteins have a significant impact on their function and body physiology. Glycation via nonenzymatic forms of cross-linking leads to proteins' conformational changes, the macromolecule being recognized as a stable fibrillary structure, oligomerization, and becoming advanced glycation end products (AGEs). Protein that undergoes glycation-related modifications, namely, β-sheet enriched structural changes, are recognized as amyloid. In the current study, we characterized a single protein modified in vitro under physiological conditions to represent a protein glycation model. The glycation altered the helical conformation of serum albumin (SA) and promoted the formation of a β-sheet enriched with amyloid fibrils detected at multidimensional levels. The nanoscale resolution by spectroscopy in the presence of thioflavin-T (ThT) and 8-anilinonaphthalene-1-sulfonic acid (8-ANS) showed binding of the fibrils formed in the presence of glucose (GLU) and the carbonyl metabolites methylglyoxal (MGO) and glycolaldehyde (GAD). In the presence of MGO and GAD, the SA becomes insoluble aggregates, demonstrated by TEM microscopy and dynamic light scattering (DLS). The protein oligomerization was visualized when separated via SDS gel electrophoresis and mass photometry (MP) assays. Following the glycation, eventually, the material polymerized and became stiffer. The level of stiffness was analyzed by a rheometer that revealed a quick alteration under MGO and GAD. This is the first study to combine multiple spectroscopy assays, imaging, and rheology measurements of SA and to demonstrate a resolution on a nanoscale structural toward better resolution of the conformational changes of glycated SA, oligomerization, and protein aggregations under physiological conditions.

Polyphenol binding disassembles glycation-modified bovine serum albumin amyloid fibrils

Glycation of protein results in the formation of advanced glycation end-products (AGEs) and leads to deposition as amyloid fibrils. Adhesive structural properties of polyphenols to aromatic amino acids draw significance in promoting, accelerating and/or stabilizing on-pathway and off-pathway folding intermediates, although the mechanistic action remains unclear. In this study, polyphenols remodeling mature AGEs modified amyloid fibrils were investigated through UV-visible spectroscopy, fluorescence spectroscopy, transmission electron microscopy, atomic force microscopy, circular dichroism spectroscopy, MALDI-MS/MS analysis and molecular docking studies. Our findings confirmed the glycation-mediated transformation of native protein into β-sheet rich amyloid fibrils. SDS-PAGE results suggested the presence of shorter peptide fragments ranging from ~10 kDa to ~40 kDa. MALDI-MS/MS results identified the plausible sequences to be His105-His181, Arg193-Lys242, Leu325-Tyr410, and Ala451-Tyr529. TEM and AFM results suggested that polyphenols binding mature amyloid fibrils remodel/disassemble them into distinct aggregate structures or non-amyloid fibrils. Circular dichroism studies suggested that polyphenols upon binding amyloid fibrils stabilizes and transforms the secondary structure towards helical or random coil-like conformation. Molecular modeling studies suggested high binding affinity and hydrophobic interaction to be the main driving force in remodeling perspective. Together, our findings suggest that polyphenols could differentially remodel mature AGEs-modified amyloid fibrils into distinct aggregate structures through non-covalent interactions and can alleviate AGEs-mediated amyloidosis.

Minimal invasive fluorescence methods to quantify advanced glycation end products (AGEs) in skin and plasma of humans

Advanced glycation end products (AGEs) are non-enzymatic modifications of proteins and lipids, which are spontaneously produced in the body in relation with several human diseases. Their relevance on protein functions alteration, either structural or enzymatic is under study, but their value as biomarkers or predictors of disease progression and clinical outcomes is unquestionable. The heterogeneity and amplitude of these modifications make their analysis difficult, although, different methods have been developed for specific AGEs based on colorimetric reactions, immunoassays or chromatography. However, for a massive application on human population, methods based on the autofluorescence of some AGEs stand out. Several qualities of these methods such as label-free measurement, rapidity, cost-effectiveness, and minimal invasiveness make them very useful for periodic measurements in critically ill patients and for the analysis of large populations. Here we explain the rationale of these methods, and we present a step-by-step protocol and the equipment requirements to carry out the estimation of AGE content in skin and plasma. AGE plasma content and skin accumulation are temporally related, so AGE plasmatic levels are a possible predictor of skin AGE content. On the other hand, AGE skin accumulation is a surrogate or an indicator of past AGE levels in plasma and in the rest of the body. AGE levels or their variations have shown to be related with prognosis of several diseases, so they can be used as predictor biomarkers for clinicians.

Polyphenols redirects the self-assembly of serum albumin into hybrid nanostructures

Chronic hyperglycemia results in the formation of advanced glycation end-products (AGEs) and triggers amyloid fibril formation. Molecules designed to inhibit amyloid fibrils function by eliminating toxic oligomers or reducing fibril formation. Here, the bioactivity of polyphenols in redirecting the self-assembly of amyloid fibrils was reported through microscopic, spectroscopic and molecular docking studies. Our findings illustrate that glycation causes BSA to self-assemble into amyloid fibrils. 17 Lys residues had modified to carboxy methyl lysine (CML) but only Lys523 was probable of modifying into carboxy ethyl lysine (CEL). In contrast, only 6 Arg residues are identified to be modified to Argpyrimidine (Arg-p). A simple polyphenol baicalein (BLN) redirect the self-assembly of amyloid fibrils into off-pathway hybrid nanostructures. Circular dichroism spectroscopic studies suggested that in the presence of BLN helical conformation was favored. Molecular modeling studies suggested that hydrogen bonding and hydrophobic interaction of polyphenols preferentially at crucial amyloidogenic regions can hinder amyloid fibrillation (Phe133, Lys136, Tyr137, Ile141, Tyr160 and Arg185). Mass spectrometric results illustrated that the presence of a simple polyphenol BLN several residues are unmodified to CML, CEL or Arg-p. Together, our findings suggest that polyphenols could have a protective effect and the redirection can help alleviate the amyloid fibril formation.

Applicability of capillary electrophoresis-frontal analysis for displacement studies: Effect of several drugs on l-tryptophan and lidocaine binding to human serum albumin

The effective concentration of a drug in the blood, i.e. the concentration of a free drug in the blood, is influenced by the strength of drug binding onto plasma proteins. Besides its efficacy, these interactions subsequently influence the liberation, absorption, distribution, metabolism, excretion, and toxicological properties of the drug. It is important to not only determine the binding strength and stoichiometry, but also the binding site of a drug on the plasma protein molecule, because the co-administration of drugs with the same binding site can affect the above-mentioned concentration and as a result the pharmacological behavior of the drugs and lead to side effects caused by the change in free drug concentration, its toxicity. In this study, the binding characteristics of six drugs with human serum albumin, the most abundant protein in human plasma, were determined by capillary electrophoresis-frontal analysis, and the obtained values of binding parameters were compared with the literature data. The effect of several drugs and site markers on the binding of l-tryptophan and lidocaine to human serum albumin was investigated in subsequent displacement studies which thus demonstrated the usability of capillary electrophoresis as an automated high-throughput screening method for drug-protein binding studies.

Effect of advanced glycation end products on platelet activation and aggregation: a comparative study of the role of glyoxal and methylglyoxal

Advanced glycation end products (AGEs) arising from dietary intake have been associated with numerous chronic diseases including cardiovascular diseases. The interaction between platelets and AGEs has been proposed to play a role in the etiology of cardiovascular diseases. However, the effects of the interaction between platelets and Maillard reaction products generated from glyoxal (Gly) or methylglyoxal (MG) are poorly understood. In this work, the effects of AGEs generated by the reaction between Gly or MG with Lys or bovine serum albumin (BSA) on platelet activation and aggregation were assessed. AGEs were generated incubating Gly or MG with Lys or BSA during 5 hours or 14 days, respectively. AGEs generation were characterized by kinetic studies and by amino acid analysis. Human platelet-rich plasma (PRP) was incubated with different concentrations of AGEs from Lys-MG or Lys-Gly and BSA-MG or BSA-Gly. Platelet activation was determined quantifying the expression of CD62 (P-selectin) in PRP exposed to different AGEs concentrations. It was found that Lys-MG and Lys-Gly induced an increase in P-selectin expression (p < .05), being 33.9% higher for Lys-MG when compared to Lys-Gly. Platelets incubated in the presence of BSA-MG and BSA-Gly did not show an increase in the P-selectin expression. Platelet aggregation was significantly higher for the mixture Lys-MG (in all the range of concentrations evaluated), whereas for Lys-Gly it was only significant the highest concentration (Lys 168 µM/Gly 168 µM). It was observed a significant increase in platelet aggregation induced by ADP for samples BSA-Gly. AGEs formed with MG-Lys induce a higher activation and aggregation of platelets when compared to those formed from Gly-Lys.

Non-enzymatic glycation of human serum albumin modulates its binding efficacy towards bioactive flavonoid chrysin: A detailed study using multi-spectroscopic and computational methods

The non-enzymatic glycation of plasma proteins by reducing sugars have important consequences on the conformational and functional properties of protein. The formation of advanced glycation end products (AGEs) is responsible for cell death and other pathological conditions. We have synthesized the glycated human serum albumin (gHSA) and characterized the same by using differential spectroscopic measurements. The aim of the present study is to determine the effect of glycation on the binding of human serum albumin (HSA) with bioactive flavonoid chrysin, which possesses anti-cancer, anti-inflammatory and anti-oxidant activities. The interaction of chrysin with HSA and gHSA was studied using multi-spectroscopic, molecular docking and molecular dynamics (MD) simulation techniques. Chrysin quenched the intrinsic fluorescence of both HSA and gHSA by static quenching mechanism. The value of the binding constant (K_b) for the interaction of HSA-chrysin complex (4.779 ± 0.623 × 10⁵ M^-1 at 300 K) was found to be higher than that of gHSA-chrysin complex (2.206 ± 0.234 × 10⁵ M^-1 at 300 K). Hence, non-enzymatic glycation of HSA significantly reduced its binding affinity towards chrysin. The % α-helicity of HSA was found to get enhanced upon binding with chrysin, and minimal changes were observed for the gHSA-chrysin complex. Site marker probe studies indicated that chrysin binds to subdomain IIA and IIIA of both HSA and gHSA. The results from molecular docking and MD simulation studies correlated well with the experimental findings. Electrostatic interactions followed by hydrogen bonding and hydrophobic interactions played major roles in the binding process. These observations may have some useful insights into the field of pharmaceutics.

Protein Interaction with Charged Macromolecules: From Model Polymers to Unfolded Proteins and Post-Translational Modifications

Interaction of proteins with charged macromolecules is involved in many processes in cells. Firstly, there are many naturally occurred charged polymers such as DNA and RNA, polyphosphates, sulfated glycosaminoglycans, etc., as well as pronouncedly charged proteins such as histones or actin. Electrostatic interactions are also important for "generic" proteins, which are not generally considered as polyanions or polycations. Finally, protein behavior can be altered due to post-translational modifications such as phosphorylation, sulfation, and glycation, which change a local charge of the protein region. Herein we review molecular modeling for the investigation of such interactions, from model polyanions and polycations to unfolded proteins. We will show that electrostatic interactions are ubiquitous, and molecular dynamics simulations provide an outstanding opportunity to look inside binding and reveal the contribution of electrostatic interactions. Since a molecular dynamics simulation is only a model, we will comprehensively consider its relationship with the experimental data.

Interaction of chlorpropamide with serum albumin: Effect on advanced glycated end (AGE) product fluorescence

Carrier proteins like bovine or human serum albumin (BSA and HSA, respectively) are prone to glycation as compared to the other available proteins. In this study, reducing sugars such as l-arabinose (ara), d-(-) galactose (gal) and d-(-) fructose (fru) were used to create model glycated serum albumins and binding ability of these with well-known antidiabetic drug chlorpropamide (CPM) was monitored. Fluorescence quenching experiment revealed that interaction of CPM with native as well as glycated albumins undergoes through a ground state complex formation. CPM binds strongly to glycated HSA with arabinose (gHSA_ara) as compared to other glycated systems and to the native proteins. CPM interacts through Van der Waals and hydrogen bonding interaction to glycated BSA by d-(-) fructose (gBSA_fru) and also with native HSA; whereas, it's interaction with BSA and others glycated systems like gBSA_ara, gBSA_gal and gHSA_ara occurs primarily through hydrophobic interaction. CPM showed an enhancement in the production of the advanced glycated end products (AGE) in all the glycated proteins. The difference in the binding capability of CPM to differently glycated albumins could be a major model to understand the drug carrying capacity of the glycated serum albumins.

Identification of differences in the formation of plasma glycated proteins between dogs and humans under diabetes-like glucose concentration conditions

Dogs have been proposed as a translational model and used for studying aging, diabetes, and diabetes-related complications in humans. However, no studies have ever compared the glycation of plasma proteins between dogs and humans under similar experimental conditions. Thus, the aim of this study was to fill this gap by comparing the plasma protein glycation patterns of dogs and humans in an ex-vivo system. Canine and human plasma samples were incubated with glucose at concentrations comparable to those observed in diabetic patients. The final glucose plasma concentration resulted in similar glucose:albumin ratios in both species. Glycated proteins were evaluated by measuring the content of fructosamine, protein carbonyls, and the formation of advanced glycation end-products (AGEs). The concentrations of fructosamine and protein carbonyls in canine and human plasma increased in a glucose concentration-dependent manner (P < 0.0001). Of note, the relative increment of fructosamine and protein carbonyl content and AGE formation was always higher in human than in dog plasma. Our results reveal that the plasma glycation processes in dogs and humans are not similar. These novel findings could contribute to improve our understating about canine and human diabetes as well as other condition associated in the glycation of proteins.

Spectroscopic and molecular modelling studies on glycation modified bovine serum albumin with cyanidin-3-O-glucoside

In this study, we report the glycation mediated effect of bovine serum albumin (BSA) on the molecular interaction mechanism of cyanidin-3-O-glucoside (C3G) by molecular modelling, Uv-visible spectroscopy, transmission electron microscopy (TEM), fluorescence spectroscopy, and circular dichroism spectroscopy studies. The structures of advanced glycation end-products (AGEs) modified BSA were modelled, energy minimized and analyzed for binding affinity by molecular docking studies using Autodock Vina. Glycation experiments are carried out using glucose and methylglyoxal to validate the molecular modelling results on the interaction of modified BSA with C3G. The modified structures were characterized by reduction in the binding pocket volume, surface, depth, hydrophobicity, and hydrogen bond donors/acceptors. Arg-194, Arg-196, Arg-198, Arg-217, Arg-409, Lys-114, Lys-116, Lys-204, Lys 221, and Lys-439 were found to be crucial in the context of glycation of BSA. TEM images represented the formation of unique globular aggregates in the event of glycation. Uv-visible spectroscopic studies showed the formation of new chromophores between 300 and 400 nm in the event of glycation. Fluorescence quenching was observed in a differential manner in the presence of C3G on glycation modified BSA. Circular dichroism studies suggested the loss of helical structure and formation of β-sheeted structure upon glycation, but subsequent C3G binding has resulted in the increase towards helical structure. Our findings suggested that drug binding affinity has been certainly impaired due to glycation and subsequent AGE modification. Arg-p modification has more austere impact on the structure and would affect the binding properties. We conclude that C3G had differential modulation of binding properties on glycated BSA which can help to protect the stability and bioavailability that has been impaired due to glycation mediated structural changes.

Noncovalent Interaction of Tilmicosin with Bovine Serum Albumin

Tilmicosin is a widely used antibiotic in veterinary applications. Its antimicrobial activity is ranged from Gram-positive and some Gram-negative bacteria towards activities against Mycoplasma and Chlamydia. Adsorption affinity of tilmicosin antibiotics towards bovine serum albumin was investigated by both spectroscopic (UV-vis, Photoluminescence) and calorimetric methods. The interaction was determined on the basis of quenching of albumin by tilmicosin. Results confirm noncovalent binding of tilmicosin on bovine serum albumin with 1:1 stoichiometry associated with pK = 4.5, highlighting possible removal of tilmicosin molecules from the albumin surface through exchange reactions by known competitor molecules. Calorimetric measurements have confirmed the weak interaction between tilmicosin and albumin and reflect enhanced denaturation of the albumin in the presence of tilmicosin antibiotic. This process is associated with the decreased activation energy of conformational transition of the albumin. It opens a new, very quick reaction pathway without any significant effect on the product by noncovalent binding the tilmicosin molecules to the protein molecules. Results highlight the medical importance of these investigations by considerable docking of the selected antibiotic molecules on serum albumins. Although the binding may cause toxic effects in living bodies, the strength of the binding is weak enough to find competitor molecules for effective removals from their surface.

Na+/K+-ATPase interaction with methylglyoxal as reactive metabolic side product

Proteins are subject to oxidative modification and the formation of adducts with a broad spectrum of reactive species via enzymatic and non-enzymatic mechanisms. Here we report that in vitro non-enzymatic methylglyoxal (MGO) binding causes the inhibition and formation of MGO advanced glycation end-products (MAGEs) in Na⁺/K⁺-ATPase (NKA). Concretely, MGO adducts with NKA amino acid residues (mainly Arg) and N^ε-(carboxymethyl)lysine (CML) formation were found. MGO is not only an inhibitor for solubilized NKA (IC₅₀=91±16μM), but also for reconstituted NKA in the lipid bilayer environment, which was clearly demonstrated using a DPPC/DPPE liposome model in the presence or absence of the NKA-selective inhibitor ouabain. High-resolution mass spectrometric analysis of a tryptic digest of NKA isolated from pig (Sus scrofa) kidney indicates that the intracellular α-subunit is naturally (post-translationally) modified by MGO in vivo. In contrast to this, the β-subunit could only be modified by MGO artificially, and the transmembrane part of the protein did not undergo MGO binding under the experimental setup used. As with bovine serum albumin, serving as the water-soluble model, we also demonstrated a high binding capacity of MGO to water-poorly soluble NKA using a multi-spectral methodology based on electroanalytical, immunochemical and fluorimetric tools. In addition, a partial suppression of the MGO-mediated inhibitory effect could be observed in the presence of aminoguanidine (pimagedine), a glycation suppressor and MGO-scavenger. All the results here were obtained with the X-ray structure of NKA in the E1 conformation (3WGV) and could be used in the further interpretation of the functionality of this key enzyme in the presence of highly-reactive metabolic side-products, glycation agents and generally under oxidative stress conditions.

Influence of glyco-oxidation on complexes between fibrin(ogen) and insulin-like growth factor-binding protein-1 in patients with diabetes mellitus type 2

Fibrinogen and insulin-like growth factor-binding protein-1 (IGFBP-1) are tightly connected to metabolic changes and complications in patients with diabetes mellitus (DM), and since they mutually interact to form complexes in plasma, we investigated whether and to what extent IGFBP-1/fibrinogen complexes change due to glyco-oxidative processes in DM and whether they participate in fibrin clot formation. These complexes were determined by immunoblotting in plasma samples from healthy adults and patients with DM type 2 (DM2). The influence of glyco-oxidation in vitro on the complexes was also investigated. Amounts of IGFBP-1/fibrinogen complexes in plasma from patients with DM2 were slightly but not significantly lower than in healthy persons. Such complexes in patients' samples participated in fibrin clot formation to a significantly decreased extent. In vitro experiments with glucose or methylglyoxal (MGO) as reactive agents demonstrated that the complexes underwent glyco-oxidative modification leading to reduced formation and/or stability. Extensively oxidized fibrinogen almost completely lost its ability to bind IGFBP-1. The reduced affinity of fibrinogen for IGFBP-1 accompanying diabetes may potentially shift the equilibrium to liberate more IGFBP-1 (and possibly insulin-like growth factor (IGF)-I) able to activate platelets during coagulation, so contributing to the hypercoagulation state together with other factors. This hypothesis, however, needs further examination.

Glycated albumin: from biochemistry and laboratory medicine to clinical practice

This review summarizes current knowledge about glycated albumin. We review the changes induced by glycation on the properties of albumin, the pathological implications of high glycated albumin levels, glycated albumin quantification methods, and the use of glycated albumin as a complementary biomarker for diabetes mellitus diagnosis and monitoring and for dealing with long-term complications. The advantages and limits of this biomarker in different clinical settings are also discussed.

Combined computational and experimental studies of molecular interactions of albuterol sulfate with bovine serum albumin for pulmonary drug nanoparticles

Albumin-based nanoparticles (NPs) are a promising technology for developing drug-carrier systems, with improved deposition and retention profiles in lungs. Improved understanding of these drug–carrier interactions could lead to better drug-delivery systems. The present study combines computational and experimental methods to gain insights into the mechanism of binding of albuterol sulfate (AS) to bovine serum albumin (BSA) on the molecular level. Molecular dynamics simulation and surface plasmon resonance spectroscopy were used to determine that there are two binding sites on BSA for AS: the first of which is a high-affinity site corresponding to AS1 and the second of which appears to represent the integrated functions of several low-affinity sites corresponding to AS2, AS3, and AS8. AS1 was the strongest binding site, established via electrostatic interaction with Glu243 and Asp255 residues in a hydrophobic pocket. Hydrogen bonds and salt bridges played a main role in the critical binding of AS1 to BSA, and water bridges served a supporting role. Based upon the interaction mechanism, BSA NPs loaded with AS were prepared, and their drug-loading efficiency, morphology, and -release profiles were evaluated. Successful clinical development of AS-BSA-NPs may improve therapy and prevention of bronchospasm in patients with reversible obstructive airway disease, and thus provide a solid basis for expanding the role of NPs in the design of new drug-delivery systems.

Non-enzymatic glycation mediated structure–function changes in proteins: case of serum albumin

Albumin, a major plasma protein with extraordinary ligand binding properties, transports various ligands ranging from drugs, hormones, fatty acids, and toxins to different tissues and organs in the body.