Glycation Reaction Research Articles

Pharmacological Activities of Zingiber officinale Roscoe: Inhibition of HSA Protein Glycation, Structure Stability and Function Restoration.

Controlled non-enzymatic glycation reactions are common under normal physiological conditions. However, during elevated blood glucose conditions, the glycation reactions are accelerated, leading to the formation of toxic compounds such as advanced glycation end products (AGEs). Several natural products are now being investigated as protective agents against glycation to preserve blood protein structure and functions. Human serum albumin (HSA) was glycated with 0.05 M α-D-glucose alone or in the presence of Zingiber officinale Roscoe (ginger) extract (0.781-100 μg/mL) for 10 weeks, and biochemical, biophysical, and computational analyses were carried out. HSA glycated for 10 weeks (G-HSA-10W) resulted in significant production of ketoamines, carbonyl compounds, and AGE pentosidine. Notable structural alterations were observed in G-HSA-10W, ascertained by ultraviolet (UV), fluorescence, and circular dichroism (CD) studies. Antioxidant, anti-glycating, AGEs inhibitory, and antibacterial effects of ginger extracts were observed and attributed to the presence of various phytochemicals. Molecular docking studies suggested that the compounds 8-shagaol and gingerol exhibited strong and multiple interactions with HSA. Molecular simulation analysis suggests HSA attains a high degree of conformational stability with the compounds gingerol and 8-shogaol. These findings showed that ginger extract has an antioxidant function and can prevent glycation-induced biochemical and biophysical alterations in HSA. Thus, aqueous ginger extract can be utilized to combat glycation and AGE-related health issues, especially diabetes, neurological disorders, inflammatory diseases, etc.

Inhibitory effect of caffeic acid and dihydrocaffeic acid on the formation of advanced glycation end products: Mechanism analysis based on intermolecular interaction

The accumulation of advanced glycation end products (AGEs) generated from glycation reaction accelerates the development and deterioration of some diseases. Herein, the AGEs model of fructose-induced glycation of human serum albumin (HSA) was constructed and characterized. Both caffeic acid (CA) and dihydrocaffeic acid (DHCA) can inhibit the formation of AGEs, and the inhibitory effect of CA was more pronounced, as confirmed by fluorescence spectroscopy, gel electrophoresis, scanning electron microscopy, and carbonyl and thiol contents analysis. The binding of CA and DHCA to HSA was investigated by fluorescence spectroscopy and molecular docking. The primary inhibitory mechanism was the occupation of the glycation site LYS199 of HSA, and the more significant inhibitory effect of CA was related to its stronger binding affinity. Furthermore, the conformational changes caused by glycation and CA/DHCA binding were monitored using fluorescence, circular dichroism, and dynamic light scattering analysis. The results would help to elucidate the inhibitory mechanism of CA and DHCA on AGEs formation based on their different structures and inhibitory effects, and provide guidance for choosing natural inhibitors for diabetes.

The effects of ultrasound-assisted glycation on the allergenicity and functional properties of peanut proteins

This study investigated the effects of ultrasound-assisted glycation on the allergenicity and functional properties of peanut proteins. Results showed that ultrasound-assisted glycation increased the degree of glycation reaction of peanut proteins significantly (P < 0.05). ELISA results indicated that the binding of peanut allergens with serum immunoglobulin G (IgG) and immunoglobulin E (IgE) was significantly decreased (P < 0.05). Furthermore, secondary structure analysis revealed a significant increase in β-sheet content, alongside decreases in α-helix, β-turn, and random coil contents (P < 0.05). In addition, intrinsic fluorescence intensity, surface hydrophobicity, and ultraviolet (UV) spectra intensity were diminished (P < 0.05), indicating notable changes in both secondary and tertiary structures of peanut proteins. Moreover, emulsification property, antioxidant activity and in vitro digestibility of peanut proteins showed the most obvious improvements following ultrasound-assisted glycation, and the solubility was increased while turbidity was decreased significantly (P < 0.05). In conclusion, this study demonstrated that ultrasound-assisted glycation not only effectively reduced the allergenicity of peanut allergens, but also improved the overall functional properties of peanut proteins, and the changes in sensitization and functional properties might be closely related to structural changes. This study will provide a theoretical basis for the development of peanut products.

Directed Design, Screening and Antiglycation Activity for 3-Substituted Thiazolium Derivatives, New Analogs of Alagebrium.

Preliminary abinitio calculations led to the synthesis of novel substituted thiazolium salts, analogs of Alagebrium, which were further explored invitro for their potential as inhibitors of the glycation reaction utilizing three distinct assays: inhibition of fluorescent AGEs formation, anticrosslinking, and deglycation. Despite the unidirectionality of the assays, distinct differences were observed in the mechanisms of interference and activity manifestation by the compounds. The gathered data permitted the formation of hypotheses about the molecular fragments of the studied antiglycators that are of utmost significance in each assay, thereby guiding future design endeavors. Potential mechanisms of actions are discussed therein. The compound 4-meth-yl-3-[2-(4-methylbiphenyl-4-yl)-2-oxoethyl] thiazolium bromide displayed high activity across all three assays, establishing it as a lead compound. The cytotoxicological properties of the compounds were evaluated using LDH and MTT assays. However, the lead compound exhibited cytotoxicity, indicating the need for additional investigations aimed at decreasing toxicity while maintaining activity. The targeted thiazolium salts were synthesized through an N-alkylation reaction between the corresponding thiazoles and phenacyl bromides.

Comparison of casein glycations induced by lactose and lactulose

Effects of lactose and lactulose on the casein glycation process at different times and specific glycation sites were investigated. Lactulose treatment generated higher levels of initial glycation products fructoselysine (1.160 μg/mL) and methylglyoxal (0.266 mg/mL) than lactose treatment which had 0.959 μg/mL and 0.140 mg/mL, respectively. The concentrations of intermediate products Nε‐(Carboxymethyl) lysine (0.654 μg/mL) and Nε‐(Carboxyethyl) lysine (0.154 μg/mL) in the lactulose treatment were approximately 2.5 and 1.1 times higher than these in the lactose treatment, respectively. The glycation induced by lactulose targeted Lys residues and had more glycated peptide fragments and wide‐ranging glycation sites in αs1‐casein. The high degree of casein glycation in lactulose treatment was attributed by the fructose on lactulose which had different pathways in the Maillard reaction, compared with the glucose on lactose. The findings revealed the differences of casein glycations by the two sugars and during thermal processing. The information could be helpful in developing potential approaches to monitor and control glycation reactions in dairy products.

Effects of glycation modifications of different glycosylating agents on the molecular structure and gel properties of sheep's hoof gelatin

In this study, we utilized sheep's hoof gelatin as a raw material to modify gelatin by non-enzymatic glycation reactions using five different monosaccharides (D-glucose, D-sorbose, D-fructose, D-ribose, and D-erythrose) and five different polysaccharides (pectin, inulin, carrageenan, xanthan gum, and konjac glucomannan) and comparatively analyzed the properties (rheological properties, textural properties, and thermal stability) of differently glycosylated sheep's hoof gelatin to determine the mechanism of different glycosylating agents on the molecular properties and gel performance of sheep's hoof gelatin. The results showed that the reactivity (DG value) and phase transition temperature (Td value) of gelatin modified with monosaccharide glycosylates were notably higher (p < 0.05) compared to those modified with polysaccharides, resulting in a micro-network structure with finer pore size. Conversely, polysaccharide glycosylation significantly enhanced the mechanical properties and rheological characteristics of gelatin (p < 0.05). The formation of a mosaic network structure in the polysaccharide-glycosylated gelatin group played a pivotal role in enhancing gel properties. Notably, the gel strength (584.62 ± 6.34 g), viscosity (η-value), and gel melting temperature (37.85 ± 0.20 °C) of the polysaccharide S-PEC were significantly higher than the other treatment groups (p < 0.05). This research not only provides a new perspective for modifying gelatin derived from sheep's hooves but also offers an important theoretical basis for the exploration and application of gelatin materials in the food industry.

Inhibitory effect of organogermanium compound 3-(trihydroxygermyl)propanoic acid on fructose-induced glycation of amino compounds

3-(Trihydroxygermyl)propanoic acid (THGP), a hydrolysate of poly-trans-[(2-carboxyethyl)germasesquioxane] (Ge-132, also known as repagermanium), can inhibit glycation between glucose/ribose and amino compounds. In addition, THGP may inhibit glycation by inhibiting reactions that occur after Amadori rearrangement and inducing the reversible solubilization of AGEs. In this study, we first investigated the effects and mechanisms on the glycation of fructose and amino compounds by THGP, as a greater reactivity was obtained with fructose than with glucose. Unlike other anti-glycation materials, THGP can form a complex with fructose, the initial compound of glycation. THGP also inhibited the production of AGEs and suppressed the reduction of fructose in a reaction between fructose and arginine. These results indicate that THGP forms a complex with cyclic fructose possessing a cis-diol structure at a reducing end, and that it suppresses the ring-opening of fructose and the progress of the initial glycation reaction. We next tried to evaluate the suppressive effect of glucosyl hesperidin (GHes) and THGP on the reaction of glycation between fructose and collagen. Both compounds effectively reduced the production of AGEs individually, and the combination of them led to a synergistic suppression. Therefore, through combination with other antiglycation materials, THGP may cooperatively exhibit glycation-inhibitory effects and be able to suppress the AGE production.

Glycation resistance and life-history traits: lessons from non-conventional animal models.

Glycation reactions play a key role in the senescence process and are involved in numerous age-related pathologies, such as diabetes complications or Alzheimer's disease. As a result, past studies on glycation have mostly focused on human and laboratory animal models for medical purposes. Very little is known about glycation and its link to senescence in wild animal species. Yet, despite feeding on high-sugar diets, several bat and bird species are long-lived and seem to escape the toxic effects of high glycaemia. The study of these models could open new avenues both for understanding the mechanisms that coevolved with glycation resistance and for treating the damaging effects of glycations in humans. Our understanding of glycaemia's correlation to proxies of animals' pace of life is emerging in few wild species; however, virtually nothing is known about their resistance to glycation, nor on the relationship between glycation, species' life-history traits and individual fitness. Our review summarizes the scarce current knowledge on the links between glycation and life-history traits in non-conventional animal models, highlighting the predominance of avian research. We also investigate some key molecular and physiological parameters involved in glycation regulation, which hold promise for future research on fitness and senescence of individuals.

In Vivo Behavior of Hydrolyzable Tannins after Oral Administration of the Trapa bispinosa Extract to Rats.

The pericarp extract of Trapa bispinosa (TBPE), which is rich in hydrolyzable tannins, has been reported to inhibit α-glucosidase and glycation reactions. We investigated the in vivo behavior of hydrolyzable tannins and related metabolites after administration of TBPE to rats. Using high pressure liquid chromatography-electrospray ionization-tandem mass spectroscopy (HPLC-ESI-MS/MS), 12 ellagitannin metabolites, such as urolithins and 6 gallotannin metabolites, produced in the collected plasma and urine were quantified. Urolithins and gallic acid metabolites reached their maximum blood concentration after 24 and 1 h of administration, respectively. Conversely, the excretion of urolithins in urine required up to 72 h and followed a sigmoidal curve, whereas gallic acid metabolites were rapidly excreted earlier after administration. The results suggest that the metabolites gallotannin and ellagitannin are responsible for the antiglycation effect of TBPE, which proceeds via different mechanisms and times. Our findings provide basic data demonstrating the functionality of hydrolyzable tannins as well as Trapa ingredients.

Effects of glycation reactions on the structure and immunological properties of sesame proteins

SummarySesame has been included in the top eight food allergens, and therefore reduction of sesame allergen potency is of great practical significance. Glycation reactions are extensively researched for their role in regulating the allergic properties of food allergens due to their distinct benefits. This study involved the glycation of sesame proteins with three different reducing sugars to generate reaction products. The structure of the reaction products was characterized by the use of spectroscopic and chromatographic techniques. The impact of glycation on the allergenic properties of sesame proteins was explored by in vitro simulated digestion tests combined with immunological techniques. The study results indicated that all three reducing sugars underwent glycation with sesame proteins, with D‐ribose showing the most significant level of glycation. During the glycation reaction of sesame proteins in this study, the proteins underwent precipitation as well as structural changes, leading to reduced immunoglobulin G (IgG) binding capacity. Glycation alters the digestive stability of sesame proteins and further reduces the ability to bind to IgG. Overall, glycation modification shows promise in decreasing the allergenicity of sesame.

Glycative stress inhibits hypertrophy and impairs cell membrane integrity in overloaded mouse skeletal muscle.

Glycative stress, characterized by the formation and accumulation of advanced glycation end products (AGEs) associated with protein glycation reactions, has been implicated in inducing a decline of muscle function. Although the inverse correlation between glycative stress and muscle mass and strength has been demonstrated, the underlying molecular mechanisms are not fully understood. This study aimed to elucidate how glycative stress affects the skeletal muscle, particularly the adaptive muscle response to hypertrophic stimuli and its molecular mechanism. Male C57BL/6NCr mice were randomly divided into the following two groups: the bovine serum albumin (BSA)-treated and AGE-treated groups. Mice in the AGE-treated group were intraperitoneally administered AGEs (0.5mg/g) once daily, whereas those in the BSA-treated group received an equal amount of BSA (0.5mg/g) as the vehicle control. After 7days of continuous administration, the right leg plantaris muscle of mice in each group underwent functional overload treatment by synergist ablation for 7days to induce muscle hypertrophy. In in vitro studies, cultured C2C12 myocytes were treated with AGEs (1mg/mL) to examine cell adhesion and cell membrane permeability. Continuous AGE administration increased the levels of fluorescent AGEs, Nε-(carboxymethyl) lysine, and methylglyoxal-derived hydroimidazolone-1 in both plasma and skeletal muscle. Plantaris muscle weight, muscle fibre cross-sectional area, protein synthesis rate, and the number of myonuclei increased with functional overload in both groups; however, the increase was significantly reduced by AGE treatment. Some muscles of AGE-treated mice were destroyed by functional overload. Proteomic analysis was performed to explore the mechanisms of muscle hypertrophy suppression and myofibre destruction by AGEs. When principal component analysis was performed on 4659 data obtained by proteomic analysis, AGE treatment was observed to affect protein expression only in functionally overloaded muscles. Enrichment analysis of the 436 proteins extracted using the K-means method further identified a group of proteins involved in cell adhesion. Consistent with this finding, dystrophin-glycoprotein complex proteins and cell adhesion-related proteins were confirmed to increase with functional overload; however, this was attenuated by AGE treatment. Additionally, the treatment of C2C12 muscle cells with AGEs inhibited their ability to adhere and increased cell membrane permeability. This study indicates that glycative stress may be a novel pathogenic factor in skeletal muscle dysfunctions by causing loss of membrane integrity and preventing muscle mass gain.

Glycation reactions of methylglyoxal during digestion in a dynamic, invitro model of the upper gastrointestinal tract (TIM-1).

The 1,2-dicarbonyl compound methylglyoxal (MGO) can react with and thereby impair the function of proteins and DNA, leading to pathophysiological pathways invivo. However, studies on the bioavailability of dietary MGO and its reactions during digestion have diverging results. Therefore, simulated digestion experiments of MGO, protein, and creatine were performed in the dynamic, invitro model of the upper gastrointestinal tract (TIM-1). This multicompartment model continuously adjusts pH values and has realistic gastrointestinal transit times while also removing water and metabolites by dialysis. Samples were analyzed with HPLC-UV for MGO and HPLC-MS/MS for creatine and glycated amino compounds. MGO reacted with creatine during simulated digestion in TIM-1 to form the hydroimidazolone MG-HCr in similar amounts as in a human intervention study. 28%-69% of MGO from the meal were passively absorbed in TIM-1, depending on the addition of creatine and protein. Simultaneous digestion of MGO with ovalbumin led to the formation of the lysine adduct N ε -carboxyethyllysine (CEL) and the methylglyoxal-derived hydroimidazolone of arginine (MG-H1). The formation of both compounds decreased with added creatine. Hence, glycation compounds are formed during digestion and significantly contribute to other ingested dietary glycation compounds, whose physiological consequences are critically discussed.

Maillard reaction: formation, advantage, disadvantage and control. A review

The Maillard reaction (MR) is often known as the amino-carbonyl reaction, nonenzymatic browning, or protein glycation reaction. The non-enzymatic browning reaction is influenced by several factors like period, quantity of H2O, temperature, involved reactants, pH, and metal ions in food. During the production, processing, and storage of food, the MR is a crucial chemical process. While Maillard reaction products (MRPs) can enhance food quality during processing, some unfavorable reactions can also result in undesirable food effects. There are two sides to MRPs. The positive side is that these products have several advantages such as improvement in color, odor, flavor, and antioxidant ability. On the other hand, the negative side represents decreasing food quality and the nutritional value of some foods, as well as some health-related problems. The review involves several strategies by which MR could be controlled or prevented. These strategies were divided into two parts, the first is non-enzymatic which is done by adding functional ingredients that work to modify reducing sugars and amino groups and/or trapping of α-dicarbonyl compounds. The second is enzymatic, by using enzymes for example, fructosamine kinase, fructosamine oxidase, and lactose oxidase.

A novel approach has been developed to produce pure plant-based gel soy yogurt by combining soy proteins (7S/11S), high pressure homogenization, and glycation reaction

This research sought to examine how the physicochemical characteristics of soy globulins and different processing techniques influence the gel properties of soy yogurt. The goal was to improve these gel properties and rectify any texture issues in soy yogurt, ultimately aiming to produce premium-quality plant-based soy yogurt. In this research study, the investigation focused on examining the impact of 7S/11S, homogenization pressure, and glycation modified with glucose on the gel properties of soy yogurt. A plant-based soy yogurt with superior gel and texture properties was successfully developed using a 7S/11S globulin-glucose conjugate at a 1:3 ratio and a homogenization pressure of 110 MPa. Compared to soy yogurt supplemented with pectin or gelatin, this yogurt demonstrated enhanced characteristics. These findings provide valuable insights into advancing plant protein gels and serve as a reference for cultivating new soybean varieties by soybean breeding experts.

Fabrication of high-preformance emulsifier from conjugating maltodextrin onto myofibrillar protein peptide with microwave- ultrasound synergy

In this study, we systematically investigated the emulsifying capabilities of myofibrillar protein (MP)- and MP peptide (MPP)-based conjugates synthesized through intensification techniques: water bath (WB), microwave, ultrasound, and the combined ultrasound-microwave (UM) methods. Compared with WB, microwave, and ultrasound treatments, the combined UM treatment greatly promoted the glycation reaction because ultrasound and microwave mutually reinforced modification effects. The resultant conjugate structure tended to unfold with more flexible conformation and homogeneous morphology. Moreover, the emulsifying properties of conjugates developed with single and combined ultrasound-assisted glycation displayed substantial improvement, and pre-hydrolysis further enhanced these performances, as observed in the Principal Component Analysis as well. Remarkably, MPP grafted by maltodextrin with the assistance of a combined UM field produced the smallest and most uniform emulsion system, positioning it as the most efficient emulsifier among all the fabricated glycoconjugates. Our study highlighted the potential of synergistically applying ultrasound and microwave techniques to develop a well-performance glycation with an ideal conjugate structure, in which they would be associated into a strong film that provided the robust physical barrier, creaming stability, heat retention, and oxidation resistance. These findings offered a basis for better utilizing complex ultrasonic technology to develop novel and improved MP-based food products.

Development of simultaneous quantitation method for 20 free advanced glycation end products using UPLC–MS/MS and clinical application in kidney injury

Advanced glycation end products (AGEs), derived from the non-enzymatic glycation reaction, are defined as glycotoxins in various diseases including aging, diabetes and kidney injury. Exploring AGEs as potential biomarkers for these diseases holds paramount significance. Nevertheless, the high chemical structural similarity and great heterogeneity among AGEs present a formidable challenge when it comes to the comprehensive, simultaneous, and accurate detection of multiple AGEs in biological samples. In this study, an UPLC/MS/MS method for simultaneous quantification of 20 free AGEs in human serum was firstly established and applied to quantification of clinical samples from individuals with kidney injury. Simple sample preparation method through protein precipitation without derivatization was used. Method performances including imprecision, accuracy, sensitivity, linearity, and carryover were systematically validated. Intra- and inter- imprecision of 20 free AGEs were 1.93–5.94 % and 2.30–8.55 %, respectively. The method accuracy was confirmed with good recoveries ranging from 96.40 % to 103.25 %. The LOD and LOQ were 0.1–3.13 ng/mL and 0.5–6.25 ng/mL, respectively. Additionally, the 20 free AGEs displayed excellent linearity (R2 >0.9974) across a wide linear range (1.56–400 ng/mL). Finally, through simultaneous quantitation of 20 Free AGEs in 100 participants including kidney injury patient and healthy controls, we identified six free AGEs, including N6-carboxyethyl-L-arginine (CEA), N6-carboxymethyl-L-lysine (CML), methylglyoxal-derived hydroimidazolones (MG-H), N6-formyl-lysine, N6-carboxymethyl-L-arginine (CMA), and glyoxal-derived hydroimidazolone (G-H), could well distinguish kidney injury patients and healthy individuals. Among them, the levels of four free AGEs including CML, CEA, MG-H, and G-H strongly correlate with traditionally clinical markers of kidney disease. The high area under the curve (AUC) values (AUC=0.965) in receiver operating characteristic (ROC) curve indicated that these four free AGEs can be served as combined diagnostic biomarkers for the diagnosis of kidney disease.

Metabolization of the Amadori Product N-ε-Fructosyllysine by Probiotic Bacteria.

Glycation reactions in food lead to the formation of the Amadori rearrangement product (ARP) N-ε-fructosyllysine (fructoselysine, FL), which is taken up with the daily diet and comes into contact with the gut microbiota during digestion. In the present study, nine commercially available probiotic preparations as well as single pure strains thereof were investigated for their FL-degrading capability under anaerobic conditions. One of the commercial preparations as well as three single pure strains thereof was able to completely degrade 0.25 mM FL within 72 h. Three new deglycating lactic acid bacteria species, namely, Lactobacillus buchneri DSM 20057, Lactobacillus jensenii DSM 20557, and Pediococcus acidilactici DSM 25404, could be identified. Quantitative experiments showed that FL was completely deglycated to lysine. Using 13C6-labeled FL as the substrate, it could be proven that the sugar moiety of the Amadori product is degraded to lactic acid, showing for the first time that certain lactic acid bacteria can utilize the sugar moiety as a substrate for lactic acid fermentation.

Effect of Total Hemoglobin on Glycated Hemoglobin (HbA1c) in Type 2 Diabetes Mellitus

Background: Glycated hemoglobin (HbA1c) is a pivotal marker in the diagnosis, prognosis, and therapeutic monitoring of diabetes mellitus. Given the involvement of hemoglobin in non-enzymatic glycation reactions, it is hypothesized that total hemoglobin concentration might impact HbA1c levels alongside blood glucose concentrations. Objectives: This study aimed to estimate and compare plasma fasting glucose level and total hemoglobin level in type 2 diabetes mellitus (T2DM) patients with and without anemia. The study also aimed to estimate HbA1C and compare with calculated HbA1C using formula in T2DM patients with and without anemia and to correlate between total hemoglobin levels with directly measured HbA1c in T2DM patients with and without anemia. Methodology: This cross-sectional study, employing purposive sampling, investigated 30 anemic and 30 non-anemic Type 2 Diabetes Mellitus (T2DM) patients at the Central Diagnostic Laboratory. Total Hemoglobin, HbA1C, and Fasting Plasma Glucose were measured for the patients and the data was analyzed. Results: Independent 't' tests revealed significant differences (p &lt; 0.0001) in estimated HbA1c, fasting blood sugar, calculated HbA1c, and Hb levels between the two groups. Subgroup analyses exhibited significant differences in estimated HbA1c for both groups individually (p = 0.003 for T2DM without anemia and p&lt;0.0001 for T2DM with anemia). Pearson's correlation analysis indicated no significant correlation between HbA1c and hemoglobin in either subgroup. Similarly linear regression analysis treating HbA1c as the dependent variable yielded a non-significant p-value, suggesting that hemoglobin levels do not significantly influence HbA1c. Conclusion: In conclusion, regardless of anemia status, our findings suggest that hemoglobin is not a significant predictor of HbA1c levels in T2DM patients, offering valuable insights into factors influencing HbA1c variability in diabetic populations.

Glycation-induced Amyloid Formation in Proteins: An Emerging Perspective to Explore Diabetes Associated Onset of Neurodegenerative Symptoms

Abstract: Non-enzymatic protein glycation occurs spontaneously via the formation of sugarprotein Schiff adducts. The end products of this pathway are terminally misfolded proteins popularly known as Advanced Glycation End (AGE) Products. Glycated proteins account for a diverse spectrum of physiological maladies including arteriosclerosis, renal failure, diabetic complications, obesity, and neurological disorders. AGEs not only jeopardise the functionality of modified proteins but also induce the formation of Covalent protein cross-links. Glycation has the potential to induce the unfolding and refolding of globular proteins into cross-β structures thus resembling many amyloid deposits like amyloid beta, tau protein, and prions. However, glycation-induced amyloid formation is not a generic property of proteins; instead, it is guided by the nature and conformation of the protein, the type of glycation agent as well as the solution conditions governing the glycation reaction. The half-lives of AGE adducts are prolonged by their impaired proteasomal clearance since glycation modifies the lysine residues and renders them unavailable for ubiquitination. AGEs are cleared via sequestration with specific cell surface receptors (RAGE); subsequently, downstream signalling events involving MAPK and NF-κB result in the activation of inflammatory response or the apoptotic pathway. This perspective article discusses the current developments in understanding the various facets of glycationassociated protein aggregation and the corresponding development of amyloid-like entities.

Chemical synthesis of site-selective advanced glycation end products in α-synuclein and its fragments.

Advanced glycation end products (AGEs) arise from the Maillard reaction between dicarbonyls and proteins, nucleic acids, or specific lipids. Notably, AGEs are linked to aging and implicated in various disorders, spanning from cancer to neurodegenerative diseases. While dicarbonyls like methylglyoxal preferentially target arginine residues, lysine-derived AGEs, such as N(6)-(1-carboxymethyl)lysine (CML) and N(6)-(1-carboxyethyl)lysine (CEL), are also abundant. Predicting protein glycation in vivo proves challenging due to the intricate nature of glycation reactions. In vitro, glycation is difficult to control, especially in proteins that harbor multiple glycation-prone amino acids. α-Synuclein (aSyn), pivotal in Parkinson's disease and synucleinopathies, has 15 lysine residues and is known to become glycated at multiple lysine sites. To understand the influence of glycation in specific regions of aSyn on its behavior, a strategy for site-specific glycated protein production is imperative. To fulfill this demand, we devised a synthetic route integrating solid-phase peptide synthesis, orthogonal protection of amino acid side-chain functionalities, and reductive amination strategies. This methodology yielded two disease-related N-terminal peptide fragments, each featuring five and six CML and CEL modifications, alongside a full-length aSyn protein containing a site-selective E46CEL modification. Our synthetic approach facilitates the broad introduction of glycation motifs at specific sites, providing a foundation for generating glycated forms of synucleinopathy-related and other disease-relevant proteins.