Aspartic acid functions as carbonyl trapper to inhibit the formation of advanced glycation end products by chemical chaperone activity

2-Methoxy-4-formylphenol suppresses methylglyoxal glycation mediated structural alterations and esterase activity of hemoglobin - A multi spectroscopic, biophysical and in-silico study

Glycation is the non-enzymatic reaction of glucose or its metabolites to proteins, causing irreversible changes. Methylglyoxal, a dicarbonyl, affects the structure and function of physiologically important proteins. Being a major circulatory protein, hemoglobin is highly prone to glycation. Current research focuses on identifying potent glycation inhibitors to prevent glycation and their impact on protein structure and function. The present study investigates the Advanced Glycation Endproducts (AGEs) inhibitory effects of 2-methoxy-4-formylphenol (Vanillin) against methylglyoxal mediated glycation of hemoglobin. The hemoglobin-vanillin glycation model exhibited inhibition of AGE formation, amyloid fibrils, aggregates and reduction in esterase activity. The fluorescence spectroscopic technique revealed efficient binding of vanillin and hemoglobin, with Stern Volmer plot indicating the presence of static quenching. The conformational stability of the vanillin and hemoglobin interaction was also evident from the molecular docking and dynamics studies. The proximal orientation of residues (H2 and K82 associated in esterase activity) of hemoglobin β1 chain and vanillin, supports the noted effect of reduced esterase activity in the presence of vanillin in glycated hemoglobin and the inhibition of the overall formation of AGE of hemoglobin in the presence of vanillin.

Comparative analysis of the nutritional, physicochemical, and bioactive characteristics of Artemisia abyssinica and Artemisia arborescens for the evaluation of their potential as ingredients in functional foods

Artemisia abyssinica and Artemisia arborescens are unique plants that show significant bioactive properties and are used for the treatment of a variety of diseases. This study assessed the nutritional values, functional properties, chemical composition, and bioactive attributes of these plants as functional nutritional supplements. Compared to A. arborescens, A. abyssinica had higher fat (4.76%), fiber (16.07%), total carbohydrates (55.87%), and energy (302.15 kcal/100 g DW), along with superior functional properties, including higher water and oil absorption capacities (638.81% and 425.85%, respectively) and foaming capacity and stability (25.67% and 58.48%). The investigation of volatile compounds found that A. abyssinica had higher amounts of hotrienol (4.53%), yomogi alcohol (3.92%), caryophyllene (3.67%), and carvotanacetone (3.64%), which possess anti-inflammatory, antimicrobial, and antioxidant properties. Artemisia abyssinica contributed over 30% of the recommended dietary intake (RDI) of amino acids. It displayed superior levels of sodium (31.46 mg/100 g DW) and calcium (238.07 mg/100 g DW). It also exhibited higher levels of organic acids, particularly malic acid, butyric acid, and succinic acid, compared to A. arborescens. Fatty acid analysis revealed palmitic and linoleic acids as primary components in both plants, with A. abyssinica having a higher palmitic acid content. Artemisia abyssinica also had higher vitamin C and thiamine levels. Although A. arborescens showed the highest total phenolic content (TPC), antioxidant activity, and capacity, A. abyssinica demonstrated acceptable efficiency in TPC and antioxidant content. These findings highlight the potential of both Artemisia species, particularly A. abyssinica, as valuable sources of nutrients and bioactive compounds for various applications.

Optimizing glycation control in diabetes: An integrated approach for inhibiting nonenzymatic glycation reactions of biological macromolecules

Diabetes is a multifactorial disorder that increases mortality and disability due to its complications. A key driver of these complications is nonenzymatic glycation, which generates advanced glycation end-products (AGEs) that impair tissue function. Therefore, effective nonenzymatic glycation prevention and control strategies are urgently needed. This review comprehensively describes the molecular mechanisms and pathological consequences of nonenzymatic glycation in diabetes and outlines various anti-glycation strategies, such as lowering plasma glucose, interfering with the glycation reaction, and degrading early and late glycation products. Diet, exercise, and hypoglycemic medications can reduce the onset of high glucose at the source. Glucose or amino acid analogs such as flavonoids, lysine and aminoguanidine competitively bind to proteins or glucose to block the initial nonenzymatic glycation reaction. In addition, deglycation enzymes such as amadoriase, fructosamine-3-kinase, parkinson's disease protein, glutamine amidotransferase-like class 1 domain-containing 3A and terminal FraB deglycase can eliminate existing nonenzymatic glycation products. These strategies involve nutritional, pharmacological, and enzymatic interventions that target different stages of nonenzymatic glycation. This review also emphasizes the therapeutic potential of anti-glycation drugs for preventing and treating diabetes complications.

Competent antioxidant and antiglycation properties of zinc oxide nanoparticles (ZnO-NPs) phyto-fabricated from aqueous leaf extract of Boerhaavia erecta L

During the present century, plant-based zinc oxide nanoparticles (ZnO-NPs) are exploited extensively for their vast biological properties due to their unique characteristic features and eco-friendly nature. Diabetes is one of the fast-growing human diseases/abnormalities worldwide, and the need for new/ novel antiglycation products is the need of the hour. The study deals with the phyto-fabrication of ZnO-NPs from Boerhaavia erecta, a medicinally important plant, and to evaluate their antioxidant and antiglycation ability in vitro. UV-visible spectroscopy (UV-Vis), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) were used to characterize the phyto-fabricated ZnO-NPs. The characterization of nanoparticles revealed that the particles showed an absorption peak at 362 nm and band gap energy of 3.2 eV, approximately 20.55 nm in size, with a ZnO elemental purity of 96.61%. The synthesized particles were found agglomerated when observed under SEM, and the FT-IR studies proved that the phyto-constituents of the extract involved during the different stages (reduction, capping, and stabilization) of nanoparticles synthesis. The antioxidant and metal chelating activities confirmed that ZnO-NPs could inhibit the free radicals generated, which was dose-dependent with an IC₅₀ value between 1.81 and 1.94 mg mL^-1, respectively. In addition, the phyto-fabricated nanoparticles blocked the formation of advanced glycation end products (AGEs) as noticed through inhibition of Amadori products, trapping of reactive dicarbonyl intermediate and breaking the cross-link of glycated protein. It was also noted that the phyto-fabricated ZnO-NPs significantly prevented the damage of red blood corpuscles (RBCs) induced by MGO. The present study's findings will provide an experimental basis for exploring ZnO-NPs in diabetes-related 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).

Protein aggregation as a consequence of non-enzymatic glycation: Therapeutic intervention using aspartic acid and arginine

Non-enzymatic glycation tempted AGEs of proteins are currently at the heart of a number of pathological conditions. Production of chemically stable AGEs can permanently alter the protein structure and function, concomitantly leading to dilapidated situations. Keeping in perspective, present study aims to report the glycation induced structural and functional modification of a cystatin type isolated from rai mustard seeds, using RSC-glucose and RSC-ribose as model system. Among the sugars studied, ribose was found to be most potent glycating agent as evident from different biophysical assays. During the course of incubation, RSC was observed to pass through a series of structural intermediates as revealed by circular dichroism, altered intrinsic fluorescence and high ANS binding. RSC incubation with ribose post day 36 revealed the possible buildup of β structures as observed in CD spectral analysis, hinting towards the generation of aggregated structures in RSC. High thioflavin T fluorescence and increased Congo red absorbance together with enhanced turbidity of the modified form confirmed the aggregation of RSC. The study further revealed anti-glycation and anti-aggregation potential of amino acids; aspartic acid and arginine as they prevented and/or slowed down the process of AGEs and β structure buildup in a concentration dependent manner with arginine proving to be the most effective one.

Biosynthesized ZnO-NPs from Morus indica Attenuates Methylglyoxal-Induced Protein Glycation and RBC Damage: In-Vitro, In-Vivo and Molecular Docking Study

The development of advanced glycation end-products (AGEs) inhibitors is considered to have therapeutic potential in diabetic complications inhibiting the loss of the biomolecular function. In the present study, zinc oxide nanoparticles (ZnO-NPs) were synthesized from aqueous leaf extract of Morus indica and were characterized by various techniques such as ultraviolet (UV)-Vis spectroscopy, Powder X-Ray Diffraction (PXRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Further, the inhibition of AGEs formation after exposure to ZnO-NPs was investigated by in-vitro, in-vivo, and molecular docking studies. Biochemical and histopathological changes after exposure to ZnO-NPs were also studied in streptozotocin-induced diabetic rats. ZnO-NPs showed an absorption peak at 359 nm with a purity of 92.62% and ~6-12 nm in size, which is characteristic of nanoparticles. The images of SEM showed agglomeration of smaller ZnO-NPs and EDS authenticating that the synthesized nanoparticles were without impurities. The biosynthesized ZnO-NPs showed significant inhibition in the formation of AGEs. The particles were effective against methylglyoxal (MGO) mediated glycation of bovine serum albumin (BSA) by inhibiting the formation of AGEs, which was dose-dependent. Further, the presence of MGO resulted in complete damage of biconcave red blood corpuscles (RBCs) to an irregular shape, whereas the morphological changes were prevented when they were treated with ZnO-NPs leading to the prevention of complications caused due to glycation. The administration of ZnO-NPs (100 mg Kg^-1) in streptozotocin(STZ)-induced diabetic rats reversed hyperglycemia and significantly improved hepatic enzymes level and renal functionality, also the histopathological studies revealed restoration of kidney and liver damage nearer to normal conditions. Molecular docking of BSA with ZnO-NPs confirms that masking of lysine and arginine residues is one of the possible mechanisms responsible for the potent antiglycation activity of ZnO-NPs. The findings strongly suggest scope for exploring the therapeutic potential of diabetes-related complications.

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.

Revisiting amino acids and peptides as anti-glycation agents

The importance of controlling or preventing protein glycation cannot be overstated and is of prime importance in the treatment of diabetes and associated complications including Alzheimer's disease, cataracts, atherosclerosis, kidney aliments among others. In this respect, simple molecules such as amino acids and peptides hold much promise both in terms of ease and scale-up of synthesis as well as in relation to negligible/low associated toxicity. In view of this, a comprehensive account of literature reports is presented, that documents the anti-glycation activity of natural and non-natural amino acids and peptides. This review also discusses the chemical reactions involved in glycation and the formation of advanced glycation end-products (AGEs) and possible/probable intervention sites and mechanism of action of the reported amino acids/peptides. This aspect of amino acids/peptides adds to their growing importance in medicinal and therapeutic applications.

Cyanidin-3-O-glucoside functions like chemical chaperone and attenuates the glycation mediated amyloid formation in albumin

In this study, chemical chaperone like function of cyanidin-3-O-glucoside (C3G) was investigated through fluorescence spectroscopy, UV-visible spectroscopy, circular dichroism spectroscopy, confocal microscopy, scanning electron microscopy and molecular docking studies. Early and advanced glycation inhibitory effect was evaluated by fluorescence spectroscopy and agarose gel electrophoresis. Amyloids were investigated based on their propensity to bind Congo Red (CR) and Thioflavin T (ThT) by multiple microscopic approaches. Circular dichroism studies were used to analyze the changes in the secondary structure due to glycation. C3G effectively inhibited early and advanced glycation by masking like function, carbonyl scavenging and chemical chaperone activity. C3G had molecular interaction with Glu186, Arg427, Ser428, Lys431, Arg435, and Arg458 of BSA. Based on the microscopic analysis, it is evident that C3G can inhibit protein aggregation and amyloid formation. Circular dichroism studies suggested that glycation had resulted in augmented β-sheet propensity, whereas C3G had a protective effect on the helical conformation of BSA. We conclude that C3G has a chemical chaperone like function on the event of glycation mediated amyloid formation in BSA.

Carbonyl scavenging and chemical chaperon like function of essential amino acids attenuates non-enzymatic glycation of albumin

Essential amino acids showed potent antiglycation activity by preventing formation of both early and advanced glycation end products (AGEs).

Silybin, a flavonolignan from milk thistle seeds, restrains the early and advanced glycation end product modification of albumin

Silybin exhibited a protective effect towards the non-enzymatic glycation mediated structure functional changes in albumin.