Protein Glycation Research Articles

DIABETES MELLITUS E SUAS IMPLICAÇÕES RENAIS: UMA REVISÃO BIBLIOGRÁFICA FOCADA NA NEFROPATIA DIABÉTICA E INSUFICIÊNCIA RENAL CRÔNICA

The article explores the renal complications of diabetes mellitus (DM), focusing on diabetic nephropathy (DN) and chronic renal failure (CRF). DN, considered one of the main causes of CRF in the world, results in high rates of morbidity and mortality in diabetic patients. The article addresses the pathophysiology of these diseases, highlighting how chronic hyperglycemia in DM leads to a series of structural and functional changes in the kidneys. Mechanisms such as advanced protein glycation, oxidative stress, activation of inflammatory cytokines, and endothelial dysfunction are central to the progression of DN. In addition to pathophysiology, the article extensively discusses treatments available to slow the progression of DN and prevent CKD. Strict control of glycemic levels, through medication and lifestyle changes, is essential. Furthermore, the use of drugs such as ACE inhibitors and angiotensin II receptor blockers has shown beneficial effects on renal protection. Other emerging treatments include SGLT2 and GLP-1 inhibitors, which demonstrate efficacy in both glycemic control and preservation of renal function. The article concludes that prevention and adequate management of these complications are fundamental to improving patients' quality of life and reducing rates of progression to CKD.

Protein glycation index and pro‑atherogenic indices from laboratory to bedside: Markers of prognostic significance in diabetes mellitus

Protein glycation index and pro‑atherogenic indices from laboratory to bedside: Markers of prognostic significance in diabetes mellitus

Glycation of sunnhemp protein with dextran via dry heating: Thermal, micro-structural characterization, and amino acid profiling.

This study aims to obtain sunnhemp protein isolate (SHPI) and dextran conjugates by dry heating method of Maillard conjugation. The effects of different incubation time (0, 1, 3, 5, 7, and 9 days) on the molecular flexibility, available lysine content, antioxidant properties, molecular structure, and thermal and micro-structural properties of conjugates were compared with SHPI (no conjugation) at 60°C and 79% relative humidity. The results indicated the formation of SHPI-dextran conjugates as confirmed by the change in molecular flexibility, lysine content, antioxidant activities, color, and water activity values. The molecular structure revealed the confirmation of covalent bonding between SHPI and dextran. Differential scanning calorimetry and thermo-gravimetric analysis results exhibited improvement in the thermal stability of SHPI when conjugated with dextran. The microstructural characterization showed that Maillard conjugation changed the surface structure of SHPI. The analysis of amino acid composition displayed that lysine, arginine, and phenylalanine were the dominant Maillard reaction sites of SHPI and dextran. Among all the conjugated samples, 5 days of incubation time was selected as an optimum condition for the development of SHPI-dextran conjugates on the basis of the aforementioned characterization. Overall, it was concluded that Maillard conjugation of sunnhemp protein with dextran via dry-heating technique could modify and improve its various attributes. PRACTICAL APPLICATION: The conjugation of plant proteins with polysaccharide through the Maillard reaction under dry heating conditions represents a natural and green technique for improving the techno-functional properties of proteins. The study has the potential to establish framework for the utilization of Sunnhemp protein isolate-dextran conjugates. This approach offers the potential for cost-effective production of emulsifiers and development of effective encapsulating matrices. The investigation expands on an underutilized plant protein source facilitating an alternative to animal-based proteins and contributing to the development of a sustainable circular bioeconomy.

Phytochemical Composition and Functional Properties of Brassicaceae Microgreens: Impact of In Vitro Digestion.

The aim of this study was to compare the concentration of phenolic compounds, glucosinolates, proteins, sugars and vitamin C between kohlrabi (Brassica oleracea var. acephala gongylodes), Savoy cabbage (B. oleracea sabauda), Brussels sprouts (B. oleracea gemmifera), cauliflower (B. oleracea botrytis), radish (Raphanus sativus) and garden cress (Lepidium sativum) microgreens for their antioxidant and hypoglycemic potential. In addition, we applied an in vitro-simulated system of human digestion in order to track the bioaccessibility of the selected phenolic representatives, and the stability of the microgreens' antioxidant and hypoglycemic potential in terms of α-amylase and α-glucosidase inhibition after each digestion phase. Using spectrophotometric and RP-HPLC methods with statistical analyses, we found that garden cress had the lowest soluble sugar content, while Savoy cabbage and Brussels sprouts had the highest glucosinolate levels (76.21 ± 4.17 mg SinE/g dm and 77.73 ± 3.33 mg SinE/g dm, respectively). Brussels sprouts were the most effective at inhibiting protein glycation (37.98 ± 2.30% inhibition). A very high positive correlation (r = 0.830) between antiglycation potential and conjugated sinapic acid was recorded. For the first time, the antidiabetic potential of microgreens after in vitro digestion was studied. Kohlrabi microgreens best inhibited α-amylase in both initial and intestinal digestion (60.51 ± 3.65% inhibition and 62.96 ± 3.39% inhibition, respectively), and also showed the strongest inhibition of α-glucosidase post-digestion (19.22 ± 0.08% inhibition). Brussels sprouts, cauliflower, and radish had less stable α-glucosidase than α-amylase inhibitors during digestion. Kohlrabi, Savoy cabbage, and garden cress retained inhibition of both enzymes after digestion. Kohlrabi antioxidant capacity remained unchanged after digestion. The greatest variability was seen in the original samples, while the intestinal phase resulted in the most convergence, indicating that digestion reduced differences between the samples. In conclusion, this study highlights the potential of various microgreens as sources of bioactive compounds with antidiabetic and antiglycation properties. Notably, kohlrabi microgreens demonstrated significant enzyme inhibition after digestion, suggesting their promise in managing carbohydrate metabolism and supporting metabolic health.

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

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

Facile fabrication of redox nanoparticles loaded with exosomal-miRNAs and resveratrol as glycation inhibitor in alleviating the progression and development of diabetic cataract.

Diabetic cataract (DC) represents a highly prevalent ocular manifestation resulting from diabetes often culminating in vision impairment among individuals with diabetes. Regrettably, the armamentarium of pharmaceutical interventions capable of both delaying and thwarting the onset of DC remains conspicuously sparse. Based on contemporary investigations, the pathogenesis of DC is prominently influenced by oxidative harm to the crystalline lens and the nonenzymatic glycosylation of lens proteins. Consequently, we have developed self-regenerating cerium oxide nanoparticles (CeO2 NPs), enveloped with resveratrol (RSV) and exosomal-microRNA (miRNA) to alleviate the effects of DC in an in vitro model. Moreover, the inclusion of RSV within CeO2 NPs serves a dual purpose. It can act as an antioxidant, minimizing glycation, and induce oxidative stress by effectively neutralizing reactive oxygen species (ROS). Additionally, it serves as a glycation inhibitor effectively preventing the cross-linking. Consequently, it helps minimize the glucose level in hemoglobin and inhibits the formation of advanced glycation end products (AGEs). Likewise, the CeO2-exosomal-miRNA when treated alone found to slightly impede the viability of human lens epithelial cells (HLEC) and induce apoptosis by suppressing the expression of α-crystalline gene (CRYAA). Particularly, miRNAs target genes associated with oxidative stress pathways, protein glycation, and the generation of AGEs, hence preventing structural damage to lens proteins. Compared with CeO2, RSV-CeO2, and miRNA-RSV-CeO2, the presence of miRNA-RSV-CeO2 led to a significant decrease in hemoglobin glycation. Remarkably, miRNA-RSV-CeO2 NPs attenuate the formation of malondialdehyde (MDA) and conjugated dienes (CD) with a relative value of 14.63 and 11.37nmol/mg. As per the report, this method presents a promising opportunity to implement the proposed material combination for attenuating diabetic cataracts.

Skin senescence-from basic research to clinical practice.

The most recognizable implications of tissue aging manifest themselves on the skin. Skin laxity, roughness, pigmentation disorders, age spots, wrinkles, telangiectasia or hair graying are symptoms of physiological aging. Development of the senescent phenotype depends on the interaction between aging cells and remodeling of the skin's extracellular matrix (ECM) that contains collagen and elastic fiber. Aging changes occur due to the combination of both endogenous (gene mutation, cellular metabolism or hormonal agents) and exogenous factors (ultraviolet light, environmental pollutants, and unsuitable diet). However, overproduction of mitochondrial reactive oxygen species (ROS) is a key factor driving cellular senescence. Aging theories have disclosed a range of diverse molecular mechanisms that are associated with cellular senescence of the body. Theories best supported by evidence include protein glycation, oxidative stress, telomere shortening, cell cycle arrest, and a limited number of cell divisions. Accumulation of the ECM damage is suggested to be a key factor in skin aging. Every cell indicates a functional and morphological change that may be used as a biomarker of senescence. Senescence-associated β-galactosidase (SA-β-gal), cell cycle inhibitors (p16INK4a, p21CIP1, p27, p53), DNA segments with chromatin alterations reinforcing senescence (DNA-SCARS), senescence-associated heterochromatin foci (SAHF), shortening of telomeres or downregulation of lamina B1 constitute just an example of aging biomarkers known so far. Aging may also be assessed non-invasively through measuring the skin fluorescence of advanced glycation end-products (AGEs). This review summarizes the recent knowledge on the pathogenesis and clinical conditions of skin aging as well as biomarkers of skin senescence.

5176 Time In Range Preferred Over A1c And Fructosamine To Monitor Glycemic Control In Sickle Cell Disease

Abstract Disclosure: A. Patel: None. B. Simon: None. Introduction: In sickle cell disease, hemoglobin A1c is unreliable due to anemia, hemolysis, transfusions, and increased red blood cell turnover. In this population, plasma glucose should be used to make a diagnosis of diabetes, but there are no reliable long-term measures of glycemic control. Measures of serum protein glycation such as fructosamine are often used as markers of short-term control[1]. Continuous glucose monitoring (CGM) time in range (TIR) may offer another more reliable metric of control in this population2. Case: A 58-year-old male presented to the office for uncontrolled type 2 diabetes mellitus. His medical history included sickle cell anemia (Hb SS disease), hypertension, monoclonal gammopathy, and priapism. He was diagnosed with type 2 diabetes mellitus approximately one year prior based on a fructosamine level of 470 umol/L (0-285 umol/L) and elevated fasting glucose level of 128 mg/dL. He started metformin 500 mg daily. Three months later, repeat fructosamine was 401 umol/L, and metformin was increased. Months later, fructosamine levels remained elevated at 419 umol/L; metformin was increased to 2 grams daily and he was referred to endocrinology. The patient was given a CGM (Freestyle Libre 2 system, Abbott Diabetes Care) as an additional method to assess control. CGM showed an excellent 2-week TIR (70-180mg/ dL) of 98%. Repeat fructosamine after 2 weeks of CGM wear was elevated at 500 umol/L. It was hypothesized that the history of IgG kappa monoclonal gammopathy was falsely elevating his fructosamine level. A glycated albumin level was 13.5% (10.7-13.5%). The patient was advised to discontinue his metformin. Four months later, his glycated albumin remained in range, and a 2-week TIR was 100%. Discussion: This case demonstrates how sickle cell disease and monoclonal gammopathy affect laboratory values typically used to diagnose and monitor type 2 diabetes. Fructosamine, a measure of non-enzymatic glycation of serum proteins, is non-specific2. Increased protein from monoclonal gammopathy (giving more protein glycation sites) was the probable cause of the persistently elevated fructosamine, leading to overtreatment of what may not have been a true diagnosis of diabetes. This case also demonstrates the value of CGM, with glucose values and TIR indicating near normoglycemia. Diagnostic CGM may be a useful measure of glucose control in patients with hemoglobinopathies.

8000 Intestinimonas Butyriciproducens As A New Preventive Therapy For Type 2 Diabetes: a Proof Of Concept Randomized Controlled Trial

Abstract Disclosure: V. Antoniotti: None. M. Caputo: None. E. Mollero: None. A. Antonioli: None. S. Tini: None. M. Manfredi: None. S. Gul: None. N. Bui: None. J. Seegers: None. W. De Vos: None. G. Aimaretti: None. F. Prodam: None. Background. The incidence of type 2 Diabetes Mellitus (T2D) is increasing worldwide. Prevention is possible by changing lifestyle but it’s not effective alone in real life, due to poor compliance over time. New strategies are necessary, mostly for high-risk individuals. Therapeutic microbiology is a further proposed target, and butyrate-producing bacteria can improve metabolic parameters in obese patients. Our study aims to evaluate the effect of Intestinimonas butyriciproducens as a preventive therapy for T2D in prediabetes thanks to its effects in decreasing Advanced Glycation End Products (AGEs), converting sugars and proteins in butyrate, and increasing insulin sensitivity.Methods. The trial is a double-blind, randomized, placebo-controlled (phase 1) and open-label pilot study with two different doses (phase 2) of 26 weeks. I. butyriciproducens (105 CFU/day) or placebo were given for 12 weeks, then subjects in placebo will start the treatment (105 CFU/day), and the other group will increase the dose (108 CFU/day) for 14 weeks. Overweight or obese patients with impaired fasting glucose (IFG) or impaired glucose tolerance (IGT) were included. Patients were assessed for clinical, biochemical, and microbiota parameters at the time of recruitment (V1), after phase 1 (V7) and phase 2 (V10), during which the eating and lifestyle habits were also evaluated. No dietary advice was given. Results. Nineteen have completed the study. Treated patients during the first phase had a significant improvement in glucose-insulin metabolism demonstrated through the HOMA Disposition Index (p= 0.0075). Lipid profile also ameliorates in patients treated at a low dose and then at a high dose, particularly decreasing triglycerides (phase 1: p= 0.0212; phase 2: p= 0.0261). The weight and BMI of patients were stable throughout the period of study. Data from Flash glucose Monitoring (FGM) show a more stable glucose, mainly at the end of the study. Serum AGE concentrations showed a trend towards a decrease in treated patients, whereas IL-10 slowly increased without changes in IL-6 and IL-17.Lastly, 10 out of 19 patients after 26 weeks of treatment had a remission in IFG or IGT (52.6%). Conclusions. Intestinimonas butyriciproducens seems to improve insulin sensitivity and triglycerides in treated patients. Intestinimonas butyriciproducens could be a new strategy in the work-up of T2D prevention. Presentation: 6/1/2024

Milk protein glycation compromises post-prandial bioavailability of protein-derived lysine in vivo in men

Milk protein glycation compromises post-prandial bioavailability of protein-derived lysine in vivo in men

Monosaccharide-Mediated Glycoxidation of Bovine Serum Albumin and Its Prevention by Nigella sativa.

The substantial rise in metabolic illnesses that has occurred in both developed and developing countries over the last three decades has been linked to an increase in sugar-added foods and sweetened beverage intake. The significance of advanced glycation end products (AGEs) in the pathophysiology of metabolic diseases related to modern nutrition is an emerging issue. Spices and herbs can potentially be potent AGE production inhibitors due to their high polyphenol content. The inhibitory activity of an aqueous extract of Nigella sativa seeds (NS) on glucose- and fructose-mediated glycation of bovine serum albumin (BSA) was investigated. The glycation of proteins and its prevention using NS were assessed using spectrophotometry, spectrofluorometrics, and electrophoretic techniques. Additionally, the NBT assay, DNPH assay, Ellman assay, and thioflavin T assay were used to observe the biochemical alterations caused by glycated BSA. Molecular docking was employed to dock the BSA active site residues with inhibitors. Our data showed that NS protects against glucose- and fructose-mediated glycation and aggregation in vitro by inhibiting the formation of fructosamine, protein carbonyl content, free sulfhydryl groups, and fluorescent AGEs. Furthermore, NS also inhibited the production of β-cross-amyloid aggregates in proteins. It was interesting to note that the inhibition was found to be significantly higher in the Glu-BSA system, although the glycation product formed in the Fru-BSA system was higher compared to the Glu-induced protein system. It can be concluded that, by inhibiting AGE production, oxidation, and aggregation of the protein, NS may be an effective antiglycation drug for the prevention of diabetes complications.

Inhibitory Effects of Aqueous Ethanol Extracts of Poplar-Type Propolis on Advanced Glycation End Products and Protein Oxidation

(1) Background: The non-enzymatic glycation of proteins is a significant contributor to the formation of advanced glycation end products (AGEs) and intermediates that are responsible for diabetic complications. It is imperative to explore effective inhibitors to prevent protein glycation. (2) Methods: This study aimed to investigate the inhibitory potential of various aqueous ethanol extracts of poplar-type propolis on AGEs and oxidative modifications in bovine serum albumin (BSA)-glucose and BSA-methylglyoxal models. (3) Results: The results revealed that these propolis extracts exhibited significant effectiveness in inhibiting the formation of total AGEs, pentosidine, and Nε-carboxymethyllysine (CML). Furthermore, the investigation discovered that these propolis extracts can effectively inhibit oxidative modification, based on measuring the levels of carbonyl and thiol groups and analyzing tryptophan fluorescence quenching. Notably, 75% ethanol extracts of propolis (EEP) exhibited the highest inhibitory activity, surpassing the chemical inhibitor aminoguanidine (AG). (4) Conclusions: The remarkable anti-glycation potency of aqueous ethanol extracts of poplar-type propolis can be attributed to their elevated contents of phenolic compounds, especially abundant flavonoids, which inhibit the formation of AGEs by scavenging free radicals, decreasing the levels of reactive oxygen species (ROS), and capturing reactive carbonyl species (RCS) in the protein glycation process. Our results indicate that poplar-type propolis may be a potential AGE inhibitor and could be used to develop functional foods and nutraceuticals to prevent diabetic complications.

Monascus pigments suppress fructose-mediated BSA glycation by trapping methylglyoxal and covalent binding to proteins

In this study, four Monascus pigments (ankaflavin, AK; monascin MS; rubropunctatin, O1; monascorubrin, O2) were proved to exhibit considerable anti-glycation properties in bovine serum albumin (BSA)-fructose model. AK (40.62 %) and MS (48.38 %) were found to exert lower inhibitory effects on the formation of fluorescent advanced glycation end products (AGEs) than aminoguanidine (59.4 %), while O1 (90.64 %) and O2 (93.82 %) displayed much stronger abilities. AK and MS could trap methylglyoxal (MGO) with maximum capture rates of 85.67 % and 84.90 %, respectively, and only mono-MGO adducts of them were detected. LC-Orbitrap MS/MS analysis revealed that four pigments significantly altered the type and reduced the number of the glycated sites and they all covalently bound to BSA, with O1 and O2 possessing high reactivity. Altogether, AK and MS suppressed fluorescent AGEs formation mainly via trapping MGO and covalently interacting with BSA, and blocking free amino groups was the dominant mechanism for O1 and O2. These findings presented new insights into Monascus pigments as dietary supplement for inhibiting protein glycation.

Testing AI predictions that hyperglycemia-induced non-enzymatic glycation of immune system proteins impairs diabetic immunity

People with type 1, type 2 and gestational diabetes, and newborns of diabetic mothers, have increased risks of contracting microbial infections such as SARS-CoV-2, amplifying comorbidity and mortality risks. Hyperglycemia and its associated hyperinflammation mediate these risks but by unknown mechanisms. We hypothesize that hyperglycemia results in glycation (non-enzymatic addition of sugars to free amino groups such as lysines) of antimicrobial and anti-inflammatory proteins and peptides that mediate innate and adaptive immunity. While glycation of hemoglobin A1c is used as a benchmark for glycemic control, studies of the effects of the glycation of immune system molecules are almost non-existent. Three AI protein-glycation prediction models demonstrate that immune system proteins and peptides such as serotransferrin, lactotransferrin, lysozyme, complement proteins, immunoglobulins, Toll-like receptors, etc., probably glycate at multiple sites affecting function. However, the AI-predicted glycation sites differed significantly among the three models employed. Therefore, three tests of these predictions were carried out. Predicted glycation sites were first evaluated in terms of clinically or experimentally identified glycation sites of homologous proteins and known effects of lysine substitutions at predicted glycation sites. Second, mass spectrometry was used to identify glycation sites on lactoferrin and human lysozyme. Third, the effects on the antimicrobial activity of lactotransferrin and lysozyme glycation were tested using a Candida albicans assay. Results of tests demonstrate that protein glycation occurs and interferes with immune function but that AI glycation prediction models are very inaccurate. Suggestions for improving AI accuracy are provided.

Inhibitory effect of chlorogenic acid and vanillic acid on fluorescent advanced glycation end products formation in low-temperature-processed pork meat

This work aimed to investigate the effects of chlorogenic acid (CA) and vanillic acid (VA) on structural changes in myofibrillar protein (MP) and fluorescent advanced glycation end products (fAGEs) formation in low-temperature-processed pork meat. Raw pork was prepared, different concentrations (0, 0.005%, 0.010%, 0.020%, 0.040%) of CA or VA were added, and then heated at 50 °C for 12 h. The results suggested that the degree of lipid oxidation significantly declined with increase in amounts of CA (from 12.166 ± 0.469 to 4.661 ± 0.333) or VA (from 11.771 ± 0.355 to 5.451 ± 0.362), and carbonyls, surface hydrophobicity, tryptophan fluorescence intensity, and protein oxidation products also showed a significant downward trend (p < 0.05). Compared with the control (498.183 ± 10.849), there were marked decrease of fAGEs intensity in samples containing CA (70.958 ± 4.114) or VA (76.667 ± 3.882). Besides, mitigating capacity of CA on fAGEs accumulation was just greater than that of VA. Therefore, CA and VA can impede MP and lipid oxidation of raw pork, which further reduce fAGEs formation in low-temperature-processed pork meat. This study is expected to provide a new strategy to prevent the oxidation of MP and reduce fAGEs contents in the meat industry.

Identification of genes contributing to attenuation of rat model of galactose-induced cataract by pyruvate.

Cataracts are a disease that reduces vision due to opacity formation of the lens. Diabetic cataracts occur at young age and progress relatively quickly, so the development of effective treatment has been awaited. Several studies have shown that pyruvate inhibits oxidative stress and glycation of lens proteins, which contribute to onset of diabetic cataracts. However, detailed molecular mechanisms have not been revealed. In this study, we attempted to reduce galactose-induced opacity by pyruvate with rat ex vivo model. Rat lenses were extracted and cultured in galactose-containing medium to induce lens opacity. After opacity had developed, continued culturing with pyruvate in the medium resulted in a reduction of lens opacity. Subsequently, we conducted microarray analysis to investigate the genes that contribute to the therapeutic effect. We performed quantitative expression measurements using RT-qPCR for extracted genes that were upregulated in cataract-induced lenses and downregulated in pyruvate-treated lenses, resulting in the identification of 34 candidate genes. Functional analysis using the STRING database suggests that metallothionein-related factors (Mt1a, Mt1m, and Mt2A) and epithelial-mesenchymal transition-related factors (Acta2, Anxa1, Cd81, Mki67, Timp1, and Tyms) contribute to the therapeutic effect of cataracts.

Glypred: Lysine Glycation Site Prediction via CCU-LightGBM-BiLSTM Framework with Multi-Head Attention Mechanism.

Glycation, a type of posttranslational modification, preferentially occurs on lysine and arginine residues, impairing protein functionality and altering characteristics. This process is linked to diseases such as Alzheimer's, diabetes, and atherosclerosis. Traditional wet lab experiments are time-consuming, whereas machine learning has significantly streamlined the prediction of protein glycation sites. Despite promising results, challenges remain, including data imbalance, feature redundancy, and suboptimal classifier performance. This research introduces Glypred, a lysine glycation site prediction model combining ClusterCentroids Undersampling (CCU), LightGBM, and bidirectional long short-term memory network (BiLSTM) methodologies, with an additional multihead attention mechanism integrated into the BiLSTM. To achieve this, the study undertakes several key steps: selecting diverse feature types to capture comprehensive protein information, employing a cluster-based undersampling strategy to balance the data set, using LightGBM for feature selection to enhance model performance, and implementing a bidirectional LSTM network for accurate classification. Together, these approaches ensure that Glypred effectively identifies glycation sites with high accuracy and robustness. For feature encoding, five distinct feature types─AAC, KMER, DR, PWAA, and EBGW─were selected to capture a broad spectrum of protein sequence and biological information. These encoded features were integrated and validated to ensure comprehensive protein information acquisition. To address the issue of highly imbalanced positive and negative samples, various undersampling algorithms, including random undersampling, NearMiss, edited nearest neighbor rule, and CCU, were evaluated. CCU was ultimately chosen to remove redundant nonglycated training data, establishing a balanced data set that enhances the model's accuracy and robustness. For feature selection, the LightGBM ensemble learning algorithm was employed to reduce feature dimensionality by identifying the most significant features. This approach accelerates model training, enhances generalization capabilities, and ensures good transferability of the model. Finally, a bidirectional long short-term memory network was used as the classifier, with a network structure designed to capture glycation modification site features from both forward and backward directions. To prevent overfitting, appropriate regularization parameters and dropout rates were introduced, achieving efficient classification. Experimental results show that Glypred achieved optimal performance. This model provides new insights for bioinformatics and encourages the application of similar strategies in other fields. A lysine glycation site prediction software tool was also developed using the PyQt5 library, offering researchers an auxiliary screening tool to reduce workload and improve efficiency. The software and data sets are available on GitHub: https://github.com/ZBYnb/Glypred.

Structural basis for FN3K-mediated protein deglycation

Protein glycation is a universal, non-enzymatic modification that occurs when a sugar covalently attaches to a primary amine. These spontaneous modifications may have deleterious or regulatory effects on protein function, and their removal is mediated by the conserved metabolic kinase fructosamine-3-kinase (FN3K). Despite its crucial role in protein repair, we currently have a poor understanding of how FN3K engages or phosphorylates its substrates. By integrating structural biology and biochemistry, we elucidated the catalytic mechanism for FN3K-mediated protein deglycation. Our work identifies key amino acids required for binding and phosphorylating glycated substrates and reveals the molecular basis of an evolutionarily conserved protein repair pathway. Additional structural-functional studies revealed unique structural features of human FN3K as well as differences in the dimerization behavior and regulation of FN3K family members. Our findings improve our understanding of the structure of FN3K and its catalytic mechanism, which opens new avenues for therapeutically targeting FN3K.

Multi-target anti-diabetic styrylpyrones from Phellinus igniarius: Inhibition of α-glucosidase, protein glycation, and oxidative stress

Bioactivity screening revealed that the EtOAc extract from the culture broth of Phellinus igniarius SY489 exhibited remarkable α-glucosidase inhibitory activity, with an IC50 value of 1.92 μg/mL. Activity- and ultraviolet (UV) profile-guided isolation led to the discovery of four anti-diabetic styrylpyrones (1–4), including two novel compounds, phelignidins A (1) and B (2). Compounds 1 and 2 represent a rare structural type of styrylpyrone dimer, in which one of the pyrone moieties exists in an open-ring state. The absolute configurations of the new compounds 1 and 2, as well as the previously unresolved compound 3, were established. Compounds 1–4 were effective in α-glucosidase inhibition, anti-glycation, and antioxidant assays, surpassing or being comparable to the positive control drugs, with minimal cytotoxicity. Furthermore, studies on α-glucosidase inhibition mechanisms suggested that these compounds interact with α-glucosidase at a single binding site, causing secondary structure unfolding and exerting inhibitory activity via a mixed-type mechanism. These results provide an important basis for developing novel, low-toxicity, multi-target anti-diabetic drugs from edible and medicinal fungi.

Region-selective and site-specific glycation of influenza proteins surrounding the viral envelope membrane

Analysis of protein modifications is critical for quality control of therapeutic biologics. However, the identification and quantification of naturally occurring glycation of membrane proteins by mass spectrometry remain technically challenging. We used highly sensitive LC MS/MS analyses combined with multiple enzyme digestions to determine low abundance early-stage lysine glycation products of influenza vaccines derived from embryonated chicken eggs and cultured cells. Straightforward sequencing was enhanced by MS/MS fragmentation of small peptides. As a result, we determined a widespread distribution of lysine modifications attributed by the region-selectivity and site-specificity of glycation toward influenza matrix 1, hemagglutinin and neuraminidase. Topological analysis provides insights into the site-specific lysine glycation, localizing in the distinct structural regions of proteins surrounding the viral envelope membrane. Our finding highlights the proteome-wide discovery of lysine glycation of influenza membrane proteins and potential effects on the structural assembly, stability, receptor binding and enzyme activity, demonstrating that the impacts of accumulated glycation on the quality of products can be directly monitored by mass spectrometry-based structural proteomics analyses.