Advanced Glycation End Products (AGEs): Biochemistry, Signaling, Analytical Methods, and Epigenetic Effects

Glucose addition and oven-heating of pork stimulate glycoxidation and protein carbonylation, while reducing lipid oxidation during simulated gastrointestinal digestion

In the present study, it was investigated if glucose addition (3 or 5%) to pork stimulates glycoxidation (pentosidine, PEN), glycation (Maillard reaction products, MRP), lipid oxidation (4-hydroxy-2-nonenal, 4-HNE; hexanal, HEX; thiobarbituric acid reactive substances, TBARS), and protein oxidation (protein carbonyl compounds, PCC) during various heating conditions and subsequent in vitro gastrointestinal digestion. An increase in protein-bound PEN level was observed during meat digestion, which was significantly stimulated by glucose addition (up to 3.3-fold) and longer oven-heating time (up to 2.5-fold) of the meat. These changes were accompanied by the distinct formation of MRP during heating and digestion of the meats. Remarkably, stimulated glyc(oxid)ation was accompanied by increased protein oxidation, whereas lipid oxidation was decreased, indicating these reactions are interrelated during gastrointestinal digestion of meat. Glucose addition generally didn't affect these oxidative reactions when pork was packed preventing air exposure and oven-heated until a core temperature of 75 °C was reached.

Decoding the role of aldosterone in glycation-induced diabetic complications

Diabetes-mediated development of micro and macro-vascular complications is a global concern. One of the factors is hyperglycemia induced the non-enzymatic formation of advanced glycation end products (AGEs). Accumulated AGEs bind with receptor of AGEs (RAGE) causing inflammation, oxidative stress and extracellular matrix proteins (ECM) modifications responsible for fibrosis, cell damage and tissue remodeling. Moreover, during hyperglycemia, aldosterone (Aldo) secretion increases, and its interaction with mineralocorticoid receptor (MR) through genomic and non-genomic pathways leads to inflammation and fibrosis. Extensive research on individual involvement of AGEs-RAGE and Aldo-MR pathways in the development of diabetic nephropathy (DN), cardiovascular diseases (CVDs), and impaired immune system has led to the discovery of therapeutic drugs. Despite mutual repercussions, the cross-talk between AGEs-RAGE and Aldo-MR pathways remains unresolved. Hence, this review focuses on the possible interaction of Aldo and glycation in DN and CVDs, considering the clinical significance of mutual molecular targets.

Exploring the composition and properties of Centella asiatica metabolites and investigating their impact on BSA glycation, LDL oxidation and α-amylase inhibition

Centella asiatica (L.) Urb. is a small herbaceous plant belonging to the Apiaceae family that is rich in triterpenes, such as asiaticoside and madecassoside. Centella asiatica finds broad application in promoting wound healing, addressing skin disorders, and boosting both memory and cognitive function. Given its extensive therapeutic potential, this study aimed not only to investigate the Centella asiatica ethanolic extract but also to analyze the biological properties of its organic fractions, such as antioxidant antiglycation capacity, which are little explored. We also identified the main bioactive compounds through spectrometry analysis. The ethanolic extract (EE) was obtained through a static maceration for seven days, while organic fractions (HF: hexane fraction; DF: dichloromethane fraction; EAF: ethyl acetate fraction; BF: n-butanol fraction and HMF: hydromethanolic fraction) were obtained via liquid-liquid fractionation. The concentration of phenolic compounds, flavonoids, and tannins in each sample was quantified. Additionally, the antiglycation (BSA/FRU, BSA/MGO, and ARG/MGO models) and antioxidant (FRAP, ORAC, and DPPH) properties, as well as the ability to inhibit LDL oxidation and hepatic tissue peroxidation were evaluated. The inhibition of enzyme activity was also analyzed (α-amylase, α-glycosidase, acetylcholinesterase, and butyrylcholinesterase). We also evaluated the antimicrobial and cytotoxicity against RAW 264.7 macrophages. The main compounds present in the most bioactive fractions were elucidated through ESI FT-ICR MS and HPLC-ESI-MS/MS analysis. In the assessment of antioxidant capacity (FRAP, ORAC, and DPPH), the EAF and BF fractions exhibited notable results, and as they are the phenolic compounds richest fractions, they also inhibited LDL oxidation, protected the hepatic tissue from peroxidation and inhibited α-amylase activity. Regarding glycation models, the EE, EAF, BF, and HMF fractions demonstrated substantial activity in the BSA/FRU model. However, BF was the only fraction that presented non-cytotoxic activity in RAW 264.7 macrophages at all tested concentrations. In conclusion, this study provides valuable insights into the antioxidant, antiglycation, and enzymatic inhibition capacities of the ethanolic extract and organic fractions of Centella asiatica. The findings suggest that further in vivo studies, particularly focusing on the butanol fraction (BF), may be promising routes for future research and potential therapeutic applications.

Assessment of EN-RAGE, sRAGE, and its isoforms: cRAGE, esRAGE in obese patients treated by moderate caloric restriction combined with physical activity conducted in hospital condition

BACKGROUND

AGEs, their receptor (RAGE), and the extracellular newly identified receptor for AGEs product-binding protein (EN-RAGE) are implicated in the pathogenesis of inflammation.

AIM

We analyzed serum EN-RAGE, soluble RAGE (sRAGE), and their isoforms: endogenous secretory - esRAGE and cleaved - cRAGE concentrations in lean controls (n = 74) and in patients with obesity (n = 71) treated for three weeks with moderate calorie restriction (CR) combined with physical activity in a hospital condition.

METHODS

Using the ELISA method, serum sRAGE, esRAGE, and EN-RAGE were measured before and after CR.

RESULTS

The serum level of sRAGE and esRAGE in patients with obesity was lower than that in non-obese individuals, contrary to cRAGE. EN-RAGE concentration was about three times higher in obese patients. Gradually, a rise in BMI resulted in sRAGE, esRAGE reduction, and EN-RAGE increase. The sRAGE concentration was sex-dependent, indicating a higher value in lean men. A moderate negative correlation was observed between BMI and all RAGE isoforms, whereas EN-RAGE displays a positive correlation. CR resulted in an expected decrease in anthropometric, metabolic, and proinflammatory parameters and EN-RAGE, but no RAGE isoforms. The ratio EN-RAGE/sRAGE was higher in obese humans than in control and was not modified by CR.

CONCLUSION

Obesity decreases sRAGE and esRAGE and increases EN-RAGE concentration. Moderate CR and physical activity by decreasing inflammation reduces EN-RAGE but is insufficient to increase sRAGE and esRAGE to the extent observed in lean patients. EN-RAGE instead of sRAGE could be helpful to indicate a better outcome of moderate dietary intervention in obese subjects.

Exploring anti-diabetic potential of compounds from roots of Dendrobium polyanthum Wall. ex Lindl. through inhibition of carbohydrate-digesting enzymes and glycation inhibitory activity

Eight compounds, including one anthraquinone, two bibenzyls, one phenanthrene, three dihydrophenanthrenes, and one flavonoid, were isolated from the roots of Dendrobium polyanthum Wall. ex Lindl. Among these, six compounds were investigated for inhibitory activities against alpha-glucosidase, alpha-amylase, and advanced glycation end products (AGEs) production. Additionally, molecular docking was conducted to analyze the interactions of the test compounds with alpha-glucosidase. Moscatin, the only isolated phenanthrene, displayed the strongest anti-alpha-glucosidase activity with an IC50 of 32.45 ± 1.04 μM, approximately 10-fold smaller than that of acarbose. Furthermore, moscatilin most strongly inhibited alpha-amylase and AGEs production with IC50 values of 256.94 ± 9.87 and 67.89 ± 9.42 μM, respectively. Molecular docking analysis revealed the effective binding of all substances to alpha-glucosidase with smaller lowest binding energy values than acarbose. Moscatin was selected for kinetics studies, and it was identified as a non-competitive inhibitor with approximately 9-fold greater inhibitory capability than acarbose. This study represents the first report on the phytochemical constituents and antidiabetic potential of compounds derived from the roots of D. polyanthum Wall. ex Lindl.

Galectin-3 protects distal convoluted tubules in rhabdomyolysis-induced kidney injury

Advanced glycation endproducts (AGEs) contribute to cellular damage of various pathologies, including kidney diseases. Acute kidney injury (AKI) represents a syndrome seldom characterized by a single, distinct pathophysiological cause. Rhabdomyolysis-induced acute kidney injury (RIAKI) constitutes roughly 15% of AKI cases, yet its underlying pathophysiology remains poorly understood. Using a murine model of RIAKI induced by muscular glycerol injection, we observed elevated levels of AGEs and the AGE receptor galectin-3 (LGALS3) in the kidney. Immunofluorescence localized LGALS3 to distal nephron segments. According to transcriptomic profiling via next-generation sequencing, RIAKI led to profound changes in kidney metabolism, oxidative stress, and inflammation. Cellular stress was evident in both proximal and distal tubules, as shown by kidney injury markers KIM-1 and NGAL. However, only proximal tubules exhibited overt damage and apoptosis, as detected by routine morphology, active Caspase-3, and TUNEL assay, respectively. In vitro, distal convoluted tubule (DCT) cells challenged with AGEs underwent apoptosis, which was markedly enhanced by Lgals3 siRNA treatment. Thus, in RIAKI, the upregulation of LGALS3 may protect the distal nephron from AGE-mediated damage, while proximal tubules lacking LGALS3 stay at risk. Thus, stimulating LGALS3 in the proximal nephron, if achievable, may attenuate RIAKI.

Label-free visualization of unfolding and crosslinking mediated protein aggregation in nonenzymatically glycated proteins

Nonenzymatic glycation (NEG) unfolds and crosslinks proteins, resulting in aggregation. Label-free evaluation of such structural changes, without disturbing molecular integrity, would be beneficial for understanding the fundamental mechanisms of protein aggregation. The current study demonstrates the assessment of NEG-induced protein aggregation by combining autofluorescence (AF) spectroscopy and imaging. The methylglyoxal (MG) induced protein unfolding and the formation of cross-linking advanced glycation end-products (AGEs) leading to aggregation were evaluated using deep-UV-induced-autofluorescence (dUV-AF) spectroscopy in proteins with distinct structural characteristics. Since the AGEs formed on proteins are fluorescent, the study demonstrated the possibility of autofluorescence imaging of NEG-induced protein aggregates. Autofluorescence spectroscopy can potentially reveal molecular alterations such as protein unfolding and cross-linking. In contrast, AGE-based autofluorescence imaging offers a means to visually explore the structural arrangement of aggregates, regardless of whether they are amyloid or non-amyloid in nature.

METTL3-mediated NDUFB5 m6A modification promotes cell migration and mitochondrial respiration to promote the wound healing of diabetic foot ulcer

BACKGROUND

Diabetic foot ulcer (DFU) is the most devastating complication of diabetes mellitus (DM) and plays a major role in disability and death in DM patients. NADH: ubiquinone oxidoreductase subunit B5 (NDUFB5) plays an important role in maintaining mitochondrial respiration, but whether it is involved in regulating the progression of advanced glycation end products (AGEs)-mediated DFU is still unclear.

METHODS

Firstly, the role of AGEs on cell viability, migration, and mitochondrial respiration in human umbilical vein endothelial cells (HUVECs) was explored in vitro. Next, NDUFB5 expression was detected in human samples and AGEs-treated HUVECs, and NDUFB5's effect on AGEs-induced HUVECs injury and skin wound in diabetic mice was further clarified. In addition, the role of m6A modification mediated by methyltransferase-like 3 (METTL3) in regulating NDUFB5 expression and AGEs-induced HUVECs injury was investigated.

RESULTS

NDUFB5 promoted cell viability, migration, and mitochondrial respiration in AGEs-treated HUVECs, whereas mitochondrial fusion promoter M1 facilitated cell viability, migration, and mitochondrial oxiadative respiration in NDUFB5 knockdown HUVECs. Meanwhile, NDUFB5 promotes skin wound healing in diabetic mice. Besides, METTL3-mediated m6A modification and insulin like growth factor 2 mRNA binding protein 2 (IGF2BP2) enhanced NDUFB5 expression in HUVECs. Furthermore, METTL3 promoted cell viability, migration, and mitochondrial respiration in AGEs-treated HUVECs by increasing NDUFB5.

CONCLUSION

METTL3-mediated NDUFB5 m6A modification inhibits AGEs-induced cell injury in HUVECs. METTL3 and NDUFB5 might serve as potential targets for DFU therapy in the future.

Antiglycating Effects of Spirulina platensis Aqueous Extract on Glucose-Induced Glycation of Bovine Serum Albumin

Glucose, the predominant carbohydrate in the human body, initiates nonenzymatic reactions in hyperglycemia, potentially leading to adverse biochemical interactions. This study investigates the interaction between glucose and Bovine Serum Albumin (BSA), along with the protective effects of Spirulina platensis PCC 7345 aqueous extract. Phycobiliproteins (phycocyanin, phycoerythrin, and allophycocyanin) in the extract were quantified using spectrophotometry. The extract's anti-glycation potential was assessed by analyzing its effects on albumin glycation, fluorescent advanced glycation end products (AGEs), thiol group oxidation, and β-amyloid structure generation. Additionally, its antidiabetic potential was evaluated by measuring α-amylase and α-glucosidase enzyme inhibition. Results indicate that the Spirulina extract significantly mitigated ketoamine levels, fluorescence, and protein-carbonyl production induced by glucose, demonstrating a 67.81 % suppression of AGE formation after 28 days. Moreover, it effectively inhibited amyloid formation in BSA cross-linkages. These findings suggest the potential of S. platensis as an anti-glycation and antidiabetic agent, supporting its consideration for dietary inclusion to manage diabetes and associated complications.

Type 2 diabetes aggravates periodontitis-induced pathological changes in the dental pulp

OBJECTIVES

The inner mechanism of how diabetes affects dental pulp of patients with periodontitis has seldom been reported. We collected clinical samples and explored the influence of diabetes and periodontitis on the pathological change of dental pulp.

METHODS

Dental pulp from healthy individuals and patients with periodontitis with or without diabetes were collected based on strict inclusion and exclusion criteria. Dental pulp was morphologically observed; advanced glycation end products (AGEs) and lectin-like oxidized low-density lipoprotein receptor-1 (LOX1) were examined. Oxidative stress (OS), inflammatory indices, and apoptotic levels were assessed.

RESULTS

Morphologically, fibrous structure in the dental pulp of patients with diabetic periodontitis (DP) group was sparse and disordered, and the blood vessel wall was thickened. Diabetes related indexes as AGEs and LOX1 were upregulated. Superoxide dismutase 2 expression was decreased, and OS level was increased. Matrix metalloproteinase 3 and other relevant proinflammatory cytokines levels were increased. The elevated OS and inflammation contributed to upregulation of apoptotic levels in DP group.

CONCLUSIONS

Diabetes aggravates the pathological changes in the dental pulp of periodontitis patients possibly due to upregulated AGEs and LOX1. Our results highlight the importance of early oral intervention in patients with DP.

Development of a specific fluorescent probe to detect advanced glycation end products (AGEs)

Advanced glycation end products (AGEs) play a pivotal role in the aging process, regarded as a hallmark of aging. Despite their significance, the absence of adequate monitoring tools has hindered the exploration of the relationship between AGEs and aging. Here, we present a novel AGE-selective probe, AGO, for the first time. AGO exhibited superior sensitivity in detecting AGEs compared to the conventional method of measuring autofluorescence from AGEs. Furthermore, we validated AGO's ability to detect AGEs based on kinetics, demonstrating a preference for ribose-derived AGEs. Lastly, AGO effectively visualized glycation products in a collagen-based mimicking model of glycation. We anticipate that this study will enhance the molecular tool sets available for comprehending the physiological processes of AGEs during aging.

cGAS-ISG15-RAGE axis reprogram necroptotic microenvironment and promote lymphatic metastasis in head and neck cancer

BACKGROUND

Cancer cells frequently evolve necroptotic resistance to overcome various survival stress during tumorigenesis. However, we have previously showed that necroptosis is widespread in head and neck squamous cell carcinoma (HNSCC) and contributes to tumor progression and poor survival via DAMPs-induced migration and invasiveness in peri-necroptotic tumor cells. This implicated an alternative strategy that cancers cope with necroptotic stress by reprogramming a pro-invasive necroptotic microenvironment (NME). Here, we aim to decipher how necroptotic cells shape the NME and affect HNSCC progression.

METHODS

Both our pre-established cellular necroptotic model and newly established Dox-induce intratumoral necroptosis model were used to investigate how necroptosis affect HNSCC progression. Transcriptomic alterations in peri-necroptotic tumor cells were analyzed by RNA-seq and validated in the NME in mice and patients' samples. The differential DAMPs compositon among apopotosis. Necrosis, and necroptosis were analyzed by label-free proteomic technique, and the necroptosis-specific DAMPs were then identified and validated. The potential receptor for ISG15 were simulated using molecular docking and further validated by in vitro assays. Then the ISG15-RAGE axis was blocked by either knockdown of necroptotic-ISG15 release and RAGE inhibitor FPS-ZM1, and the impact on tumor progression were tested. Last, we further tested our findings in a HNSCC-patients cohort.

RESULTS

Necroptosis played a crucial role in driving tumor-cell invasiveness and lymphatic metastasis via tumor-type dependent DAMPs-releasing. Mechanistically, necroptotic DAMPs induced peri-necroptotic EMT via NF-κB and STAT3 signaling. Furthermore, intrinsic orchestration between necroptotic and cGAS-STING signaling resulted in producing a group of interferon stimulated genes (ISGs) as HNSCC-dependent necroptotic DAMPs. Among them, ISG15 played an essential role in reprogramming the NME. We then identified RAGE as a novel receptor for extracellular ISG15. Either blockage of ISG15 release or ISG15-RAGE interaction dramatically impeded necroptosis-driven EMT and lymphatic metastasis in HNSCC. Lastly, clinicopathological analysis showed high ISG15 expression in NME. Extensive necroptosis and high tumor-cell RAGE expression correlated with tumor progression and poor survival of HNSCC patients.

CONCLUSIONS

Our data revealed a previously unknown cGAS-ISG15-RAGE dependent reprogramming of the necroptotic microenvironment which converts the necroptotic stress into invasive force to foster HNSCC-cell dissemination. By demonstrating the programmatic production of ISG15 via necroptosis-cGAS orchestration and its downstream signaling through RAGE, we shed light on the unique role of ISG15 in HNSCC progression. Targeting such machineries may hold therapeutic potential for restoring intratumoral survival stress and preventing lymphatic metastasis in HNSCC.

Dietary Advanced Glycation End Products (AGEs) and Urinary Fluorescent AGEs in Children and Adolescents: Findings from the Italian I.Family Project

Advanced glycation end products (AGEs) have been implicated in chronic diseases in adults, but their role in paediatric populations remains uncertain. This study, conducted on the Italian sample of the I.Family project, aimed to investigate the relationship between dietary and urinary fluorescent AGEs in children and adolescents. The secondary objective was to investigate the sources of dietary AGEs (dAGEs) and their association with dietary composition and anthropometric parameters. Dietary data were collected from 1048 participants via 24 h dietary recall in 2013/2014 to estimate dAGEs intake, while urinary fluorescent AGE levels were measured in 544 individuals. Participants were stratified based on dAGEs intake and compared with respect to urinary fluorescent AGE levels, anthropometric measurements, and dietary intake. The results showed no significant correlation between dietary and urinary fluorescent AGE levels, nor between dAGEs and anthropometric parameters. Notably, higher dAGEs were associated with a diet richer in protein (especially from meat sources) and fat and lower in carbohydrates. In addition, the consumption of ultra-processed foods was lower in participants with a higher DAGE intake. This study highlights the lack of a clear association between dietary and urinary fluorescent AGEs in children, but suggests a distinctive dietary pattern associated with increased dAGEs intake. Further investigation is warranted to elucidate the potential health implications of dAGEs in paediatric populations.

An Intensive Culinary Intervention Programme to Promote Healthy Ageing: The SUKALMENA-InAge Feasibility Pilot Study

Dietary interventions are a key strategy to promote healthy ageing. Cooking skills training emerges as a promising approach to acquiring and maintaining healthy eating habits. The purpose was to evaluate the effectiveness of a culinary programme to improve healthy eating habits among overweight/obese adults (55-70 years old). A total of 62 volunteers were randomly (1:1) assigned to an culinary intervention group (CIG) or a nutritional intervention group (NIG). Dietary, cooking, and health-related outcomes, including body advanced glycation end product (AGE) levels, were evaluated at baseline and after four weeks. Mixed-effects linear models were used to assess the effects of the interventions within and between groups. Among the 56 participants who completed the trial, CIG participants achieved a significant improvement in Mediterranean diet adherence (1.2; 95%CI, 0.2 to 2.2) and a reduction in the use of culinary techniques associated with a higher AGE formation in foods (-2.8; 95%CI, -5.6 to -0.2), weight (-1.5; 95%CI, -2.5 to -0.5), body mass index (-0.5; 95%CI, -0.8 to -0.2), waist circumference (-1.4; 95%CI, -2.6 to -0.2), and hip circumference (-1.4; 95%CI, -2.4 to -0.4) compared with the NIG participants. Although a greater confidence in cooking in the CIG was found, attitudes and cooking habits did not improve. No significant differences in biochemical parameters or AGEs were found between groups. In conclusion, a culinary intervention could be successful in promoting healthy eating and cooking habits compared to a programme based on nutrition education alone. Nevertheless, further efforts are needed to strengthen attitudes and beliefs about home cooking, to address potential barriers and understand the impact of cooking interventions on biological parameters. Larger studies with longer follow-ups are needed to evaluate the relationship between cooking, diet, and health.

The dynamic roles of advanced glycation end products

Advanced glycation end products (AGEs) are a heterogeneous group of potentially harmful molecules that can form as a result of a non-enzymatic reaction between reducing sugars and proteins, lipids, or nucleic acids. The total body pool of AGEs reflects endogenously produced AGEs as well as exogeneous AGEs that come from sources such as diet and the environment. Engagement of AGEs with their cellular receptor, the receptor for advanced glycation end products (RAGE), which is expressed on the surface of various cell types, converts a brief pulse of cellular activation to sustained cellular dysfunction and tissue destruction. The AGEs/RAGE interaction triggers a cascade of intracellular signaling pathways such as mitogen-activated protein kinase/extracellular signal-regulated kinase, phosphoinositide 3-kinases, transforming growth factor beta, c-Jun N-terminal kinases (JNK), and nuclear factor kappa B, which leads to the production of pro-inflammatory cytokines, chemokines, adhesion molecules, and oxidative stress. All these events contribute to the progression of several chronic diseases. This chapter will provide a comprehensive understanding of the dynamic roles of AGEs in health and disease which is crucial to develop interventions that prevent and mitigate the deleterious effects of AGEs accumulation.

Early Stages of Ex Vivo Collagen Glycation Disrupt the Cellular Interaction and Its Remodeling by Mesenchymal Stem Cells-Morphological and Biochemical Evidence

Mesenchymal stem cells (MSCs), pivotal for tissue repair, utilize collagen to restore structural integrity in damaged tissue, preserving its organization through concomitant remodeling. The non-enzymatic glycation of collagen potentially compromises MSC communication, particularly upon advancing the process, underlying various pathologies such as late-stage diabetic complications and aging. However, an understanding of the impact of early-stage collagen glycation on MSC interaction is lacking. This study examines the fate of in vitro glycated rat tail collagen (RTC) upon exposure to glucose for 1 or 5 days in contact with MSCs. Utilizing human adipose tissue-derived MSCs (ADMSCs), we demonstrate their significantly altered interaction with glycated collagen, characterized morphologically by reduced cell spreading, diminished focal adhesions formation, and attenuated development of the actin cytoskeleton. The morphological findings were confirmed by ImageJ 1.54g morphometric analysis with the most significant drop in the cell spreading area (CSA), from 246.8 μm2 for the native collagen to 216.8 μm2 and 163.7 μm2 for glycated ones, for 1 day and 5 days, respectively, and a similar trend was observed for cell perimeter 112.9 μm vs. 95.1 μm and 86.2 μm, respectively. These data suggest impaired recognition of early glycated collagen by integrin receptors. Moreover, they coincide with the reduced fibril-like reorganization of adsorbed FITC-collagen (indicating impaired remodeling) and a presumed decreased sensitivity to proteases. Indeed, confirmatory assays reveal diminished FITC-collagen degradation for glycated samples at 1 day and 5 days by attached cells (22.8 and 30.4%) and reduced proteolysis upon exogenous collagenase addition (24.5 and 40.4%) in a cell-free system, respectively. The mechanisms behind these effects remain uncertain, although differential scanning calorimetry confirms subtle structural/thermodynamic changes in glycated collagen.

Developing a Portable Autofluorescence Detection System and Its Application in Biological Samples

Advanced glycation end-products (AGEs) are complex compounds closely associated with several chronic diseases, especially diabetes mellitus (DM). Current methods for detecting AGEs are not suitable for screening large populations, or for long-term monitoring. This paper introduces a portable autofluorescence detection system that measures the concentration of AGEs in the skin based on the fluorescence characteristics of AGEs in biological tissues. The system employs a 395 nm laser LED to excite the fluorescence of AGEs, and uses a photodetector to capture the fluorescence intensity. A model correlating fluorescence intensity with AGEs concentration facilitates the detection of AGEs levels. To account for the variation in optical properties of different individuals' skin, the system includes a 520 nm light source for calibration. The system features a compact design, measuring only 60 mm × 50 mm × 20 mm, and is equipped with a miniature STM32 module for control and a battery for extended operation, making it easy for subjects to wear. To validate the system's effectiveness, it was tested on 14 volunteers to examine the correlation between AGEs and glycated hemoglobin, revealing a correlation coefficient of 0.49. Additionally, long-term monitoring of AGEs' fluorescence and blood sugar levels showed a correlation trend exceeding 0.95, indicating that AGEs reflect changes in blood sugar levels to some extent. Further, by constructing a multivariate predictive model, the study also found that AGEs levels are correlated with age, BMI, gender, and a physical activity index, providing new insights for predicting AGEs content and blood sugar levels. This research supports the early diagnosis and treatment of chronic diseases such as diabetes, and offers a potentially useful tool for future clinical applications.

Label-Free Assessment of Key Biological Autofluorophores: Material Characteristics and Opportunities for Clinical Applications

Autofluorophores are endogenous fluorescent compounds that naturally occur in the intra and extracellular spaces of all tissues and organs. Most have vital biological functions - like the metabolic cofactors NAD(P)H and FAD+, as well as the structural protein collagen. Others are considered to be waste products - like lipofuscin and advanced glycation end products - which accumulate with age and are associated with cellular dysfunction. Due to their natural fluorescence, these materials have great utility for enabling non-invasive, label-free assays with direct ties to biological function. Numerous technologies, with different advantages and drawbacks, are applied to their assessment, including fluorescence lifetime imaging microscopy, hyperspectral microscopy, and flow cytometry. Here, the applications of label-free autofluorophore assessment are reviewed for clinical and health-research applications, with specific attention to biomaterials, disease detection, surgical guidance, treatment monitoring, and tissue assessment - fields that greatly benefit from non-invasive methodologies capable of continuous, in vivo characterization.

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.

Structural changes in hemoglobin and glycation

Hemoglobin (Hb) is a hemeprotein found inside erythrocytes and is crucial in transporting oxygen and carbon dioxide in our bodies. In erythrocytes (Ery), the main energy source is glucose metabolized through glycolysis. However, a fraction of Hb can undergo glycation, in which a free amine group from the protein spontaneously binds to the carbonyl of glucose in the bloodstream, resulting in the formation of glycated hemoglobin (HbA1c), widely used as a marker for diabetes. Glycation leads to structural and conformational changes, compromising the function of proteins, and is intensified in the event of hyperglycemia. The main changes in Hb include structural alterations to the heme group, compromising its main function (oxygen transport). In addition, amyloid aggregates can form, which are strongly related to diabetic complications and neurodegenerative diseases. Therefore, this chapter discusses in vitro protocols for producing glycated Hb, as well as the main techniques and biophysical assays used to assess changes in the protein's structure before and after the glycation process. This more complete understanding of the effects of glycation on Hb is fundamental for understanding the complications associated with hyperglycemia and for developing more effective prevention and treatment strategies.

Vitamin B6 and diabetes and its role in counteracting advanced glycation end products

Naturally occurring forms of vitamin B6 include six interconvertible water-soluble compounds: pyridoxine (PN), pyridoxal (PL), pyridoxamine (PM), and their respective monophosphorylated derivatives (PNP, PLP, and PMP). PLP is the catalytically active form which works as a cofactor in approximately 200 reactions that regulate the metabolism of glucose, lipids, amino acids, DNA, and neurotransmitters. Most of vitamers can counteract the formation of reactive oxygen species and the advanced glycation end-products (AGEs) which are toxic compounds that accumulate in diabetic patients due to prolonged hyperglycemia. Vitamin B6 levels have been inversely associate with diabetes, while vitamin B6 supplementation reduces diabetes onset and its vascular complications. The mechanisms at the basis of the relation between vitamin B6 and diabetes onset are still not completely clarified. In contrast more evidence indicates that vitamin B6 can protect from diabetes complications through its role as scavenger of AGEs. It has been demonstrated that in diabetes AGEs can destroy the functionality of macromolecules such as protein, lipids, and DNA, thus producing tissue damage that result in vascular diseases. AGEs can be in part also responsible for the increased cancer risk associated with diabetes. In this chapter the relationship between vitamin B6, diabetes and AGEs will be discussed by showing the acquired knowledge and questions that are still open.

Associations between Skin Autofluorescence Levels with Cardiovascular Risk and Diabetes Complications in Patients with Type 2 Diabetes

Advanced Glycation End Products (AGEs) contribute to the pathophysiology of type 2 diabetes mellitus (T2DM) and cardiovascular (CV) diseases (CVDs), making their non-invasive assessment through skin autofluorescence (SAF) increasingly important. This study aims to investigate the relationship between SAF levels, cardiovascular risk, and diabetic complications in T2DM patients. We conducted a single-center, cross-sectional study at Consultmed Hospital in Iasi, Romania, including 885 T2DM patients. The assessment of SAF levels was performed with the AGE Reader™, (Diagnoptics, Groningen, The Netherlands). CVD prevalence was 13.9%, and according to CV risk category distribution, 6.1% fell into the moderate-risk, 1.13% into the high-risk, and 92.77% into the very-high-risk category. The duration of DM averaged 9.0 ± 4.4 years and the mean HbA1c was 7.1% ± 1.3. After adjusting for age and eGFR, HbA1c values showed a correlation with SAF levels in the multivariate regression model, where a 1 SD increase in HbA1c was associated with a 0.105 SD increase in SAF levels (Nagelkerke R2 = 0.110; p < 0.001). For predicting very high risk with an SAF cut-off of 2.35, sensitivity was 67.7% and specificity was 56.2%, with an AUC of 0.634 (95% CI 0.560-0.709, p = 0.001). In T2DM, elevated SAF levels were associated with higher CV risk and HbA1c values, with 2.35 identified as the optimal SAF cut-off for very high CV risk.

Unravelling the Influence of Chlorogenic Acid on the Antioxidant Phytochemistry of Avocado (Persea americana Mill.) Fruit Peel

Oxidative stress is pivotal in the pathology of many diseases. This study investigated the antioxidant phytochemistry of avocado (Persea americana Mill.) peel. Different solvent extracts (dichloromethane, ethyl acetate, methanol, and water) of avocado peel were subjected to total phenol and flavonoid quantification, as well as in vitro radical scavenging and ferric reducing evaluation. The methanol extract was subjected to gradient column chromatographic fractionation. Fraction 8 (eluted with hexane:chloroform:methanol volume ratio of 3:6.5:0.5, respectively) was subjected to LC-MS analysis. It was assessed for cellular inhibition of lipid peroxidation and lipopolysaccharide (LPS)-induced ROS and NO production. The DPPH radical scavenging mechanism of chlorogenic acid was investigated using Density Functional Theory (DFT). The methanol extract and fraction 8 had the highest phenol content and radical scavenging activity. Chlorogenic acid (103.5 mg/mL) and 1-O-caffeoylquinic acid (102.3 mg/mL) were the most abundant phenolics in the fraction. Fraction 8 and chlorogenic acid dose-dependently inhibited in vitro (IC50 = 5.73 and 6.17 µg/mL) and cellular (IC50 = 15.9 and 9.34 µg/mL) FeSO4-induced lipid peroxidation, as well as LPS-induced ROS (IC50 = 39.6 and 28.2 µg/mL) and NO (IC50 = 63.5 and 107 µg/mL) production, while modulating antioxidant enzyme activity. The fraction and chlorogenic acid were not cytotoxic. DFT analysis suggest that an electron transfer, followed by proton transfer at carbons 3'OH and 4'OH positions may be the radical scavenging mechanism of chlorogenic acid. Considering this study is bioassay-guided, it is logical to conclude that chlorogenic acid strongly influences the antioxidant capacity of avocado fruit peel.

The effects of advanced glycation end-products on skin and potential anti-glycation strategies

The advanced glycation end-products (AGEs) are produced through non-enzymatic glycation between reducing sugars and free amino groups, such as proteins, lipids or nucleic acids. AGEs can enter the body through daily dietary intake and can also be generated internally via normal metabolism and external stimuli. AGEs bind to cell surface receptors for AGEs, triggering oxidative stress and inflammation responses that lead to skin ageing and various diseases. Evidence shows that AGEs contribute to skin dysfunction and ageing. This review introduces the basic information, the sources, the metabolism and absorption of AGEs. We also summarise the detrimental mechanisms of AGEs to skin ageing and other chronic diseases. For the potential strategies for counteracting AGEs to skin and other organs, we summarised the pathways that could be utilised to resist glycation. Chemical and natural-derived anti-glycation approaches are overviewed. This work offers an understanding of AGEs to skin ageing and other chronic diseases and may provide perspectives for the development of anti-glycation strategies.

An overview on glycation: molecular mechanisms, impact on proteins, pathogenesis, and inhibition

The formation of a heterogeneous set of advanced glycation end products (AGEs) is the final outcome of a non-enzymatic process that occurs in vivo on long-life biomolecules. This process, known as glycation, starts with the reaction between reducing sugars, or their autoxidation products, with the amino groups of proteins, DNA, or lipids, thus gaining relevance under hyperglycemic conditions. Once AGEs are formed, they might affect the biological function of the biomacromolecule and, therefore, induce the development of pathophysiological events. In fact, the accumulation of AGEs has been pointed as a triggering factor of obesity, diabetes-related diseases, coronary artery disease, neurological disorders, or chronic renal failure, among others. Given the deleterious consequences of glycation, evolution has designed endogenous mechanisms to undo glycation or to prevent it. In addition, many exogenous molecules have also emerged as powerful glycation inhibitors. This review aims to provide an overview on what glycation is. It starts by explaining the similarities and differences between glycation and glycosylation. Then, it describes in detail the molecular mechanism underlying glycation reactions, and the bio-molecular targets with higher propensity to be glycated. Next, it discusses the precise effects of glycation on protein structure, function, and aggregation, and how computational chemistry has provided insights on these aspects. Finally, it reports the most prevalent diseases induced by glycation, and the endogenous mechanisms and the current therapeutic interventions against it.

Breath of fresh air: Investigating the link between AGEs, sRAGE, and lung diseases

Advanced glycation end products (AGEs) are compounds formed via non-enzymatic reactions between reducing sugars and amino acids or proteins. AGEs can accumulate in various tissues and organs and have been implicated in the development and progression of various diseases, including lung diseases. The receptor of advanced glycation end products (RAGE) is a receptor that can bind to advanced AGEs and induce several cellular processes such as inflammation and oxidative stress. Several studies have shown that both AGEs and RAGE play a role in the pathogenesis of lung diseases, such as chronic obstructive pulmonary disease, asthma, idiopathic pulmonary fibrosis, cystic fibrosis, and acute lung injury. Moreover, the soluble form of the receptor for advanced glycation end products (sRAGE) has demonstrated its ability to function as a decoy receptor, possessing beneficial characteristics such as anti-inflammatory, antioxidant, and anti-fibrotic properties. These qualities make it an encouraging focus for therapeutic intervention in managing pulmonary disorders. This review highlights the current understanding of the roles of AGEs and (s)RAGE in pulmonary diseases and their potential as biomarkers and therapeutic targets for preventing and treating these pathologies.

Potential application of Nardostachyos Radix et Rhizoma-Rhubarb for the treatment of diabetic kidney disease based on network pharmacology and cell culture experimental verification

BACKGROUND

Diabetic kidney disease (DKD) is one of the serious complications of diabetes mellitus, and the existing treatments cannot meet the needs of today's patients. Traditional Chinese medicine has been validated for its efficacy in DKD after many years of clinical application. However, the specific mechanism by which it works is still unclear. Elucidating the molecular mechanism of the Nardostachyos Radix et Rhizoma-rhubarb drug pair (NRDP) for the treatment of DKD will provide a new way of thinking for the research and development of new drugs.

AIM

To investigate the mechanism of the NRDP in DKD by network pharmacology combined with molecular docking, and then verify the initial findings by in vitro experiments.

METHODS

The Traditional Chinese Medicine Systems Pharmacology (TCMSP) database was used to screen active ingredient targets of NRDP. Targets for DKD were obtained based on the Genecards, OMIM, and TTD databases. The VENNY 2.1 database was used to obtain DKD and NRDP intersection targets and their Venn diagram, and Cytoscape 3.9.0 was used to build a "drug-component-target-disease" network. The String database was used to construct protein interaction networks. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis and Gene Ontology analysis were performed based on the DAVID database. After selecting the targets and the active ingredients, Autodock software was used to perform molecular docking. In experimental validation using renal tubular epithelial cells (TCMK-1), we used the Cell Counting Kit-8 assay to detect the effect of NRDP on cell viability, with glucose solution used to mimic a hyperglycemic environment. Flow cytometry was used to detect the cell cycle progression and apoptosis. Western blot was used to detect the protein expression of STAT3, p-STAT3, BAX, BCL-2, Caspase9, and Caspase3.

RESULTS

A total of 10 active ingredients and 85 targets with 111 disease-related signaling pathways were obtained for NRDP. Enrichment analysis of KEGG pathways was performed to determine advanced glycation end products (AGEs)-receptor for AGEs (RAGE) signaling as the core pathway. Molecular docking showed good binding between each active ingredient and its core targets. In vitro experiments showed that NRDP inhibited the viability of TCMK-1 cells, blocked cell cycle progression in the G0/G1 phase, and reduced apoptosis in a concentration-dependent manner. Based on the results of Western blot analysis, NRDP differentially downregulated p-STAT3, BAX, Caspase3, and Caspase9 protein levels (P < 0.01 or P < 0.05). In addition, BAX/BCL-2 and p-STAT3/STAT3 ratios were reduced, while BCL-2 and STAT3 protein expression was upregulated (P < 0.01).

CONCLUSION

NRDP may upregulate BCL-2 and STAT3 protein expression, and downregulate BAX, Caspase3, and Caspase9 protein expression, thus activating the AGE-RAGE signaling pathway, inhibiting the vitality of TCMK-1 cells, reducing their apoptosis. and arresting them in the G0/G1 phase to protect them from damage by high glucose.

Evaluation of the effects of dietary advanced glycation end products on inflammation

Advanced glycation end products (AGEs) are a large number of heterogeneous compounds formed by the glycation of proteins, fats or nucleic acids. Endogenous AGEs have been associated with various health problems such as obesity, type 2 diabetes mellitus and cardiovascular disease. Inflammation is thought to be one of the main mechanisms in the development of these disorders. Although AGEs are produced endogenously in the body, exogenous sources such as smoking and diet also contribute to the body pool. Therefore, when the AGE pool in the body rises above physiological levels, different pathological conditions may occur through various mechanisms, especially inflammation. While the effects of endogenous AGEs on the development of inflammation have been studied relatively extensively, and current evidence indicates that dietary AGEs (dAGEs) contribute to the body's AGE pool, it is not yet known whether dAGEs have the same effect on the development of inflammation as endogenous AGEs. Therefore, this review aimed to evaluate the results of cross-sectional and intervention studies to understand whether dAGEs are associated with inflammation and, if there is an effect on inflammation, through which mechanisms this effect might occur.

How dietary advanced glycation end products could facilitate the occurrence of food allergy

BACKGROUND

Food allergy (FA) is one of the most common chronic conditions in children with an increasing prevalence facilitated by the exposure to environmental factors in predisposed individuals. It has been hypothesized that the increased consumption of ultra-processed foods, containing high levels of dietary advanced glycation end products (AGEs), could facilitate the occurrence of FA.

OBJECTIVE

We sought to provide preclinical and clinical evidence on the potential role of AGEs in facilitating the occurrence of FA.

METHODS

Human enterocytes, human small intestine organ culture, and PBMCs from children at risk for allergy were used to investigate the direct effect of AGEs on gut barrier, inflammation, TH2 cytokine response, and mitochondrial function. Intake of the 3 most common glycation products in Western diet foods, Nε-(carboxymethyl) lysine, Nε-(1-carboxyethyl) lysin, and Nδ-(5-hydro-5- methyl-4-imidazolone-2-yl)-ornithine (MG-H1), and the accumulation of AGEs in the skin were comparatively investigated in children with FA and in age-matched healthy controls.

RESULTS

Human enterocytes exposed to AGEs showed alteration in gut barrier, AGE receptor expression, reactive oxygen species production, and autophagy, with increased transepithelial passage of food antigens. Small intestine organ cultures exposed to AGEs showed an increase of CD25+ cells and proliferating crypt enterocytes. PBMCs exposed to AGEs showed alteration in proliferation rate, AGE receptor activation, release of inflammatory and TH2 cytokines, and mitochondrial metabolism. Significant higher dietary AGE intake and skin accumulation were observed children with FA (n = 42) compared with age-matched healthy controls (n = 66).

CONCLUSIONS

These data, supporting a potential role for dietary AGEs in facilitating the occurrence of FA, suggest the importance of limiting exposure to AGEs children as a potential preventive strategy against this common condition.

P75NTR regulates autophagy through the YAP-mTOR pathway to increase the proliferation of interfollicular epidermal cells and promote wound healing in diabetic mice

Wound healing is delayed in diabetic patients. Increased autophagy and dysfunction of interfollicular epidermal (IFE) cells are closely associated with delayed healing of diabetic wounds. Autophagy plays an important role in all stages of wound healing, but its role in diabetic wound healing and the underlying molecular mechanisms are not clear. Here, we found that diabetic mice had delayed wound healing and increased autophagy in wounds compared with normal mice and that chloroquine, an inhibitor of autophagy, decreased the level of autophagy, improved the function of IFE cells, and accelerated wound healing in diabetic mice. Treatment of IFE cells with advanced glycosylation end products (AGEs) resulted in increased microtubule-associated protein chain (LC3) expression and decreased prostacyclin-62 (P62) expression, indicating increased autophagy in AGE-treated IFE cells. Moreover, P75NTR reduced autophagy in IFE cells in the presence of AGEs and significantly increased the proliferation of IFE cells. In addition, P75NTR participated in regulating autophagy in IFE cells and in wounds in diabetic mice through the YAP-mTOR signalling pathway, which increased the functional activity of the cells and the healing rate of wounds in diabetic mice. Thus, our study suggests that P75NTR protects IFE cells against AGEs by affecting autophagy and accelerating wound healing in diabetic mice, providing a basis for understanding the role of autophagy in diabetic wound healing.

Disturbed Follicular Microenvironment in Polycystic Ovary Syndrome: Relationship to Oocyte Quality and Infertility

Polycystic ovary syndrome (PCOS) is a common endocrine disorder associated with infertility and poor reproductive outcomes. The follicular fluid (FF) microenvironment plays a crucial role in oocyte development. This review summarizes evidence elucidating the alterations in FF composition in PCOS. Various studies demonstrated a pronounced proinflammatory milieu in PCOS FF, characterized by increased levels of cytokines, including but not limited to interleukin-6 (IL-6), tumor necrosis factor α, C-reactive protein, and IL-1β, concomitant with a reduction in anti-inflammatory IL-10. T lymphocytes and antigen-presenting cells are dysregulated in PCOS FF. PCOS FF exhibit heightened reactive oxygen species production and the accumulation of lipid peroxidation byproducts, and impaired antioxidant defenses. Multiple microRNAs are dysregulated in PCOS FF, disrupting signaling critical to granulosa cell function. Proteomic analysis reveals changes in pathways related to immune responses, metabolic perturbations, angiogenesis, and hormone regulation. Metabolomics identify disturbances in glucose metabolism, amino acids, lipid profiles, and steroid levels with PCOS FF. Collectively, these pathological alterations may adversely affect oocyte quality, embryo development, and fertility outcomes. Further research on larger cohorts is needed to validate these findings and to forge the development of prognostic biomarkers of oocyte developmental competence within FF. Characterizing the follicular environment in PCOS is key to elucidating the mechanisms underlying subfertility in this challenging disorder.

Association between advanced glycation end products and uveitis/scleritis activity in patients with active immune-mediated ocular inflammatory diseases

PURPOSE

To investigate for association between skin autofluorescence (SAF) advanced glycation end products (AGEs) and uveitis/scleritis activity in systemic inflammatory disease-related active non-infectious uveitis/scleritis patients.

METHODS

This cross-sectional study was conducted at Siriraj Hospital during October 2019 to March 2020. AGEs were measured by SAF method in systemic immune-related disease patients with active uveitis/scleritis, and those results were compared with those of healthy age-matched controls.

RESULTS

Thirty-one active non-infectious uveitis/scleritis patients and 31 age-matched controls were enrolled. The mean age of patients was 40.0 ± 12.8 years, and most were female (55.0%). The most common associated systemic immune-related disease was Vogt-Koyanagi-Harada disease (n = 14). Mean SAF AGE level in the study group compared to the control group was 2.38 ± 0.66 arbitrary units (AU) versus 2.58 ± 0.56 AU, respectively (p = 0.20). Multivariate analysis showed decreased SAF AGE level to be significantly associated with active ocular inflammation, (odds ratio: 0.01, 95% confidence interval: 0.00004-0.81; p = 0.04).

CONCLUSIONS

SAF AGE level was not so far found to be a reliable biomarker for indicating uveitis/scleritis activity in systemic immune-related disease patients with active ocular inflammation.

CLINICAL TRIAL REGISTRATION

Thai Clinical Trials Registry, https://www.thaiclinicaltrials.org/ . (Reg. No. TCTR20200114004, registered date 01/01/2020, beginning date of the trial 10/01/2019).

Structures of Toxic Advanced Glycation End-Products Derived from Glyceraldehyde, A Sugar Metabolite

Advanced glycation end-products (AGEs) have recently been implicated in the onset/progression of lifestyle-related diseases (LSRDs); therefore, the suppression of AGE-induced effects may be used in both the prevention and treatment of these diseases. Various AGEs are produced by different biological pathways in the body. Glyceraldehyde (GA) is an intermediate of glucose and fructose metabolism, and GA-derived AGEs (GA-AGEs), cytotoxic compounds that accumulate and induce damage in mammalian cells, contribute to the onset/progression of LSRDs. The following GA-AGE structures have been detected to date: triosidines, GA-derived pyridinium compounds, GA-derived pyrrolopyridinium lysine dimers, methylglyoxal-derived hydroimidazolone 1, and argpyrimidine. GA-AGEs are a key contributor to the formation of toxic AGEs (TAGE) in many cells. The extracellular leakage of TAGE affects the surrounding cells via interactions with the receptor for AGEs. Elevated serum levels of TAGE, which trigger different types of cell damage, may be used as a novel biomarker for the prevention and early diagnosis of LSRDs as well as in evaluations of treatment efficacy. This review provides an overview of the structures of GA-AGEs.

Effect of enzymolysis combined with Maillard reaction treatment on functional and structural properties of gluten protein

In this work, the modified gluten was prepared by enzymolysis combined with Maillard reaction (MEG), and its functional and structural properties were investigated. The result showed that the maximum foamability of MEG was 19.58 m2/g, the foam stability was increased by 1.8 times compared with gluten, and the solubility and degree of graft were increased to 44.4 % and 28.1 % at 100 °C, whereas the content of sulfhydryl group decreased to 0.81 μmol/g. The scavenging ability on ABTS+radical and DPPH radical of MEG was positively correlated with reaction temperature, and the maximum values were 86.57 % and 71.71 % at 140 °C, respectively. Furthermore, the fluorescence quenching effect of tryptophan and tyrosine residues was enhanced, while the fluorescence intensity decreased with the temperature increase. Scanning electron microscopy revealed that the surface of enzymatically hydrolyzed-gluten became smooth and the cross section became straightened, while MEG turned smaller and irregular approaching a circular structure. FT-IR spectroscopy showed that enzymatic hydrolysis promoted the occurrence of more carbonyl ammonia reactions and the formation of precursors of advanced glycosylation end products. These results provide a feasible method for improving the structure and functional properties of gluten protein.

Women suffering from systemic lupus erythematosus are characterized by low blood levels of α-dicarbonyl compounds

Introduction

Systemic lupus erythematosus (SLE) is a chronic, autoimmune disease, often characterised by severe course and unclear etiopathogenesis. The reaction of protein glycoxidation, also known as glycation, may be linked to etiopathogenesis of SLE. Advanced glycation end-products (AGEs) exhibit cytotoxic properties, affect cellular signalling, impair functions of extracellular proteins, and may act as neoepitopes. Glucosone (GS), glyoxal (GO), and methylglyoxal (MGO) are examples of α-dicarbonyl compounds (α-DCs) partaking in glycoxidation. The study aimed to evaluate concentrations of these three compounds in blood serum of SLE patients, and to compare the results with healthy individuals.

Material and methods

31 women suffering from SLE and 26 healthy individuals were included in the study. High-performance liquid chromatography with fluorescence detection was applied to evaluate concentrations of α-DCs in their serum samples. Correlations between the results and parameters such as disease duration time, age, glomerular filtration rate (GFR), Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K), and creatinine were analysed.

Results

The SLE patients exhibited lower concentrations of glucosone, glyoxal, and methylglyoxal than the control group. Analysis of correlations showed a difference between the examined groups.

Conclusions

In women suffering from SLE the course of α-DCs metabolism is altered. SLE patients are characterised by low serum levels of α-DCs. We hypothesise that either hindered proteasomal degradation or fast consumption of α-DCs in oxidative conditions may cause the observed low concentration of these compounds.

D-ribose metabolic disorder and diabetes mellitus

D-ribose, an ubiquitous pentose compound found in all living cells, serves as a vital constituent of numerous essential biomolecules, including RNA, nucleotides, and riboflavin. It plays a crucial role in various fundamental life processes. Within the cellular milieu, exogenously supplied D-ribose can undergo phosphorylation to yield ribose-5-phosphate (R-5-P). This R-5-P compound serves a dual purpose: it not only contributes to adenosine triphosphate (ATP) production through the nonoxidative phase of the pentose phosphate pathway (PPP) but also participates in nucleotide synthesis. Consequently, D-ribose is employed both as a therapeutic agent for enhancing cardiac function in heart failure patients and as a remedy for post-exercise fatigue. Nevertheless, recent clinical studies have suggested a potential link between D-ribose metabolic disturbances and type 2 diabetes mellitus (T2DM) along with its associated complications. Additionally, certain in vitro experiments have indicated that exogenous D-ribose exposure could trigger apoptosis in specific cell lines. This article comprehensively reviews the current advancements in D-ribose's digestion, absorption, transmembrane transport, intracellular metabolic pathways, impact on cellular behaviour, and elevated levels in diabetes mellitus. It also identifies areas requiring further investigation.

Cosmetic application of the stem-bark extract of Bertholletia excelsa H.B.K

OBJECTIVE

The Amazon has a rich biodiversity where many different plant species can be found. This diversity is an important source of bioactive substances, mainly due to the different structural components of their phytometabolites. Research for natural products is a strategy for the development of new agents in therapeutic applications, especially cosmetic applications, that have better pharmacological potential. Within this perspective, the objective of the study was to investigate the cosmetic application (anti-aging potential) of the stem-bark extract of Bertholletia excelsa H.B.K - (SBEBE), popularly known as the Brazil nut tree, here called SBEBE, a noble plant species of the Amazon that is rich in selenium.

METHODS

Enzymatic, glycation, proliferation, cell-healing, collagen quantification, toxicity and genotoxicity assays were used.

RESULTS

Among the enzymes involved in the extracellular matrix of the skin, SBEBE was able to inhibit only elastase (62.67 ± 3.75) when compared to the standard sivelestat (89.04 ± 0.53), and the extract was also able to inhibit both the oxidative and the non-oxidative pathway. When cell toxicity in fibroblasts (MRC-5) and keratinocytes (HACAT) was evaluated, SBEBE did not present toxicity in 24 h of incubation. After this period, the extract showed average cytotoxicity in 48 and 72 h, but not enough to reach the concentration of 50% of MRC-5 fibroblasts. In the trypan blue assay, the extract promoted fibroblast proliferation in 24, 48 and 72 h of incubation, which was evaluated through exponential cell growth, with emphasis mainly on the lowest concentration with results higher than the standard. When the cell healing capacity was evaluated, in 48 h of exposure to fibroblast, SBEBE was able to induce a cell carpet (cell film) in the cell monolayer scratch assay.

CONCLUSIONS

SBEBE stimulated collagen production at all concentrations tested. In the alkaline comet assay, at the lowest concentration, the extract did not induce DNA damage when compared to the reference drug doxorubicin. This study proved that SBEBE extract can be considered an ally in the treatment of skin anti-ageing as a possible biotechnological, phytocosmetic product.

Correlation of mild cognitive impairment with the thickness of retinal nerve fiber layer and serum indicators in type 2 diabetic patients

Background

Cognitive Impairment arising from type 2 diabetes mellitus (T2DM) has garnered significant attention in recent times. However, there are few studies on the identification and diagnosis of markers of cognitive impairment. Notably, alterations in the Retinal Nerve Fiber Layer's (RNFL) thickness can potentially serve as an indicative measure of central nervous system changes. Further investigations have indicated that the decline in cognitive function within T2DM patients is intricately linked to persistent systemic inflammation and the accumulation of advanced glycosylation end products. Comprehensive studies are warranted to unveil these complex associations.

Objective

This study aims to explore the potential of utilizing the RNFL thickness and serological concentrations of IL-18, irisin, CML, and RAGE as diagnostic indicators for Mild Cognitive Impairment (MCI) among individuals with T2DM.

Methods

The thickness of RNFL were determined in all patients and controls using optical coherence tomography (OCT). The serum levels of IL-18, irisin, CML and RAGE were detected by ELISA kit. In addition, Cognitive assessment was performed by the Mini-Mental State Examination (MMSE) and the Montreal Cognitive assessment (MoCA).

Results

The average RNFL thickness in the right eye were decreased in T2DM and T2DM combined with MCI (T2DM-MCI) patients and were positively correlated with MoCA and MMSE scores. The serum levels of IL-18, CML and RAGE in T2DM and T2DM-MCI increased significantly (p<0.05) and were negative correlated with MoCA and MMSE scores. The level of irisin in T2DM and T2DM-MCI decreased significantly (p<0.05) and were positively correlated with MoCA and MMSE scores. The area under the ROC curve of T2DM-MCI predicted by the average RNFL thickness in the right eye, CML and RAGE were 0.853, 0.874 and 0.815. The diagnostic efficacy of the combination of average RNFL thickness in the right eye, CML, and RAGE for the diagnosis of T2DM-MCI was 0.969.

Conclusion

The average RNFL thickness in the right eye, CML and RAGE have possible diagnostic value in T2DM-MCI patients.

Multiphoton imaging of the monosachharide induced formation of fluorescent advanced glycation end products in tissues

We studied the in vitro rate of fluorescent advanced glycation end products (fAGEs) formation with multiphoton microscopy in different porcine tissues (aorta, cornea, kidney, dermis, and tendon). These tissues were treated with d-glucose, d-galactose, and d-fructose, three primary monosaccharides found in human diets. We found that the use of d-fructose resulted in the highest glycation rate, followed by d-galactose and then d-glucose. Moreover, compared to non-collagen tissue constituents such as elastic fibers and cells, the rate of tissue glycation was consistently higher in collagen, suggesting that collagen is a more sensitive target for fAGE formation. However, we also found that collagen in different tissues exhibits different rates of fAGE formation, with slower rates observed in tightly packed tissues such as cornea and tendon. Our study suggests that for fAGE to be developed into a long-term glycemic biomarker, loosely organized collagen tissues located in the proximity of vasculature may be the best targets.

Plasma/Serum Proteomics based on Mass Spectrometry

Human blood is a window of physiology and disease. Examination of biomarkers in blood is a common clinical procedure, which can be informative in diagnosis and prognosis of diseases, and in evaluating treatment effectiveness. There is still a huge demand on new blood biomarkers and assays for precision medicine nowadays, therefore plasma/serum proteomics has attracted increasing attention in recent years. How to effectively proceed with the biomarker discovery and clinical diagnostic assay development is a question raised to researchers who are interested in this area. In this review, we comprehensively introduce the background and advancement of technologies for blood proteomics, with a focus on mass spectrometry (MS). Analyzing existing blood biomarkers and newly-built diagnostic assays based on MS can shed light on developing new biomarkers and analytical methods. We summarize various protein analytes in plasma/serum which include total proteome, protein post-translational modifications, and extracellular vesicles, focusing on their corresponding sample preparation methods for MS analysis. We propose screening multiple protein analytes in the same set of blood samples in order to increase success rate for biomarker discovery. We also review the trends of MS techniques for blood tests including sample preparation automation, and further provide our perspectives on their future directions.

Role of advanced glycation end products in diabetic vascular injury: molecular mechanisms and therapeutic perspectives

BACKGROUND

In diabetic metabolic disorders, advanced glycation end products (AGEs) contribute significantly to the development of cardiovascular diseases (CVD).

AIMS

This comprehensive review aims to elucidate the molecular mechanisms underlying AGE-mediated vascular injury.

CONCLUSIONS

We discuss the formation and accumulation of AGEs, their interactions with cellular receptors, and the subsequent activation of signaling pathways leading to oxidative stress, inflammation, endothelial dysfunction, smooth muscle cell proliferation, extracellular matrix remodeling, and impaired angiogenesis. Moreover, we explore potential therapeutic strategies targeting AGEs and related pathways for CVD prevention and treatment in diabetic metabolic disorders. Finally, we address current challenges and future directions in the field, emphasizing the importance of understanding the molecular links between AGEs and vascular injury to improve patient outcomes.

Fish oil supplementation counteracts the effect of high-fat and high-sucrose diets on the carbonylated proteome in the rat cerebral cortex

High daily intake of saturated fats and refined carbohydrates, which often leads to obesity and overweight, has been associated with cognitive impairment, premature brain aging and the aggravation of neurodegenerative diseases. Although the molecular pathology of obesity-related brain damage is not fully understood, the increased levels of oxidative stress induced by the diet seem to be definitively involved. Being protein carbonylation determinant for protein activity and function and a main consequence of oxidative stress, this study aims to investigate the effect of the long-term high-fat and sucrose diet intake on carbonylated proteome of the cerebral cortex of Sprague-Dawley rats. To achieve this goal, the study identified and quantified the carbonylated proteins and lipid peroxidation products in the cortex, and correlated them with biometrical, biochemical and other redox status parameters. Results demonstrated that the obesogenic diet selectively increased oxidative damage of specific proteins that participate in fundamental pathways for brain function, i.e. energy production, glucose metabolism and neurotransmission. This study also evaluated the antioxidant properties of fish oil to counteract diet-induced brain oxidative damage. Fish oil supplementation demonstrated a stronger capacity to modulate carbonylated proteome in the brain cortex. Data indicated that fish oils did not just decrease carbonylation of proteins affected by the obesogenic diet, but also decreased the oxidative damage of other proteins participating in the same metabolic functions, reinforcing the beneficial effect of the supplement on those pathways. The results could help contribute to the development of successful nutritional-based interventions to prevent cognitive decline and promote brain health.

Oral proniosomal amitriptyline and liraglutide for management of diabetic neuropathy: Exceptional control over hyperglycemia and neuropathic pain

Exploitation of nanocarriers provides a compartment for enclosing drugs to protect them from degradation and potentiate their therapeutic efficiency. In the current study, amitriptyline- and liraglutide-loaded proniosomes were constructed for management of diabetic neuropathy, a serious complication associated with diabetes, that triggers spontaneous pain in patients and results in impaired quality of life. The developed therapeutic proniosomes were extensively characterized via dynamic light scattering, scanning electron microscopy, transmission electron microscopy, and Fourier transform-infrared spectroscopy. High entrapment efficiency could be attained for both drugs in the proniosomes, and the reconstituted amitriptyline- and liraglutide-loaded niosomes possessed spherical morphology and particle sizes of 585.3 nm and 864.4 nm, respectively. In a diabetic neuropathy rat model, oral administration of the developed amitriptyline- and liraglutide-loaded proniosomes significantly controlled blood glucose levels, reduced neuropathic pain, oxidative stress and inflammatory markers, and improved histological structure of the sciatic nerve as compared to the oral and subcutaneous administration of amitriptyline and liraglutide, respectively. Loading of the tricyclic antidepressant amitriptyline and the antidiabetic peptide liraglutide into proniosomes resulted in exceptional control over hyperglycemia and neuropathic pain, and thus could provide an auspicious delivery system for management of neuropathic pain and control of blood glucose levels.

New Insights into Cardiovascular Diseases Treatment Based on Molecular Targets

Cardiovascular diseases (CVDs) which consist of ischemic heart disease, stroke, heart failure, peripheral arterial disease, and several other cardiac and vascular conditions are one of the most common causes of death worldwide and often co-occur with diabetes mellitus and lipid disorders which worsens the prognosis and becomes a therapeutic challenge. Due to the increasing number of patients with CVDs, we need to search for new risk factors and pathophysiological changes to create new strategies for preventing, diagnosing, and treating not only CVDs but also comorbidities like diabetes mellitus and lipid disorders. As increasing amount of patients suffering from CVDs, there are many therapies which focus on new molecular targets like proprotein convertase subtilisin/kexin type 9 (PCSK9), angiopoietin-like protein 3, ATP-citrate lyase, or new technologies such as siRNA in treatment of dyslipidemia or sodium-glucose co-transporter-2 and glucagon-like peptide-1 in treatment of diabetes mellitus. Both SGLT-2 inhibitors and GLP-1 receptor agonists are used in the treatment of diabetes, however, they proved to have a beneficial effect in CVDs as well. Moreover, a significant amount of evidence has shown that exosomes seem to be associated with myocardial ischaemia and that exosome levels correlate with the severity of myocardial injury. In our work, we would like to focus on the above mechanisms. The knowledge of them allows for the appearance of new strategies of treatment among patients with CVDs.

Novel Fluorometric Assay of Antiglycation Activity Based on Methylglyoxal-Induced Protein Carbonylation

Advanced glycation end products (AGEs), which can have multiple structures, are formed at the sites where the carbonyl groups of reducing sugars bind to the free amino groups of proteins through the Maillard reaction. Some AGE structures exhibit fluorescence, and this fluorescence has been used to measure the formation and quantitative changes in carbonylated proteins. Recently, fluorescent AGEs have also been used as an index for the evaluation of compounds that inhibit protein glycation. However, the systems used to generate fluorescent AGEs from the reaction of reducing sugars and proteins used for the evaluation of antiglycation activity have not been determined through appropriate research; thus, problems remain regarding sensitivity, quantification, and precision. In the present study, using methylglyoxal (MGO), a reactive carbonyl compound to induce glycation, a comparative analysis of the mechanisms of formation of fluorescent substances from several types of proteins was conducted. The analysis identified hen egg lysozyme (HEL) as a protein that produces stronger fluorescent AGEs faster in the Maillard reaction with MGO. It was also found that the AGE structure produced in MGO-induced in HEL was argpyrimidine. By optimizing the reaction system, we developed a new evaluation method for compounds with antiglycation activity and established an efficient evaluation method (HEL-MGO assay) with greater sensitivity and accuracy than the conventional method, which requires high concentrations of bovine serum albumin and glucose. Furthermore, when compounds known to inhibit glycation were evaluated using this method, their antiglycation activities were clearly and significantly measured, demonstrating the practicality of this method.

Albumin from sera of rheumatoid arthritis patients share multiple biochemical, biophysical and immunological properties with in vitro generated glyco-nitro-oxidized-albumin

The purpose of the present study is to explore the effects of endogenous stressors on structure and function of rheumatoid arthritis (RA) patients' albumin. In contrast to glycated-albumin or nitro-oxidized-albumin, high titre antibodies against glyco-nitro-oxidized-albumin were found in the sera of RA patients. Also, compared to the other two modified forms of albumin, glyco-nitro-oxidized-albumin showed highest percent inhibition. Albumin isolated from RA patients' sera displayed hyperchromicity and quenching of tyrosine and tryptophan fluorescence. Fluorescence spectroscopy studies also revealed the presence of dityrosine and advanced glycation end products in RA patient's albumin. RA patients' albumin showed weaker binding with 1-anilinonaphthalene-8-sulfonic acid dye. Secondary structure alterations were demonstrated by circular dichroism and Fourier transform infrared spectroscopy. Biochemical investigations revealed substantial decline in the availability of free side chains of amino acid residues; increased carbonyls and decreased sulfhydryls in RA patients' albumin. The functional impairment in RA patients' albumin was revealed by their low binding with bilirubin and cobalt. Liquid chromatography mass spectrometry analysis revealed the presence of Nε-(carboxymethyl) lysine and 3-nitrotyrosine in RA patients' albumin. The amyloidogenic aggregation of RA patients' albumin was confirmed by Congo red absorption and thioflavin-T fluorescence assays. The morphology of the aggregates was visualized under scanning and transmission electron microscope. From the above findings, we inferred that endogenous stress in RA patients have modified albumin and produce structural/functional abnormalities. Also, the presence of anti-glyco-nitro-oxidized-albumin antibodies along with other clinical features may be used as biomarker for the diagnosis and assessment of treatment responses in RA patients.Communicated by Ramaswamy H. Sarma.

Pathophysiological Aspects and Therapeutic Armamentarium of Alzheimer's Disease: Recent Trends and Future Development

Alzheimer's disease (AD) is the primary cause of dementia and is characterized by the death of brain cells due to the accumulation of insoluble amyloid plaques, hyperphosphorylation of tau protein, and the formation of neurofibrillary tangles within the cells. AD is also associated with other pathologies such as neuroinflammation, dysfunction of synaptic connections and circuits, disorders in mitochondrial function and energy production, epigenetic changes, and abnormalities in the vascular system. Despite extensive research conducted over the last hundred years, little is established about what causes AD or how to effectively treat it. Given the severity of the disease and the increasing number of affected individuals, there is a critical need to discover effective medications for AD. The US Food and Drug Administration (FDA) has approved several new drug molecules for AD management since 2003, but these drugs only provide temporary relief of symptoms and do not address the underlying causes of the disease. Currently, available medications focus on correcting the neurotransmitter disruption observed in AD, including cholinesterase inhibitors and an antagonist of the N-methyl-D-aspartate (NMDA) receptor, which temporarily alleviates the signs of dementia but does not prevent or reverse the course of AD. Research towards disease-modifying AD treatments is currently underway, including gene therapy, lipid nanoparticles, and dendrimer-based therapy. These innovative approaches aim to target the underlying pathological processes of AD rather than just managing the symptoms. This review discusses the novel aspects of pathogenesis involved in the causation of AD of AD and in recent developments in the therapeutic armamentarium for the treatment of AD such as gene therapy, lipid nanoparticles, and dendrimer-based therapy, and many more.

Advances and Perspectives in Relation to the Molecular Basis of Diabetic Retinopathy-A Review

Diabetes mellitus (DM) is a growing problem nowadays, and diabetic retinopathy (DR) is its predominant complication. Currently, DR diagnosis primarily relies on fundoscopic examination; however, novel biomarkers may facilitate that process and make it widely available. In this current review, we delve into the intricate roles of various factors and mechanisms in DR development, progression, prediction, and their association with therapeutic approaches linked to the underlying pathogenic pathways. Specifically, we focus on advanced glycation end products, vascular endothelial growth factor (VEGF), asymmetric dimethylarginine, endothelin-1, and the epigenetic regulation mediated by microRNAs (miRNAs) in the context of DR.

The Roles of NFR2-Regulated Oxidative Stress and Mitochondrial Quality Control in Chronic Liver Diseases

Chronic liver disease (CLD) affects a significant portion of the global population, leading to a substantial number of deaths each year. Distinct forms like non-alcoholic fatty liver disease (NAFLD) and alcoholic fatty liver disease (ALD), though they have different etiologies, highlight shared pathologies rooted in oxidative stress. Central to liver metabolism, mitochondria are essential for ATP production, gluconeogenesis, fatty acid oxidation, and heme synthesis. However, in diseases like NAFLD, ALD, and liver fibrosis, mitochondrial function is compromised by inflammatory cytokines, hepatotoxins, and metabolic irregularities. This dysfunction, especially electron leakage, exacerbates the production of reactive oxygen species (ROS), augmenting liver damage. Amidst this, nuclear factor erythroid 2-related factor 2 (NRF2) emerges as a cellular protector. It not only counters oxidative stress by regulating antioxidant genes but also maintains mitochondrial health by overseeing autophagy and biogenesis. The synergy between NRF2 modulation and mitochondrial function introduces new therapeutic potentials for CLD, focusing on preserving mitochondrial integrity against oxidative threats. This review delves into the intricate role of oxidative stress in CLD, shedding light on innovative strategies for its prevention and treatment, especially through the modulation of the NRF2 and mitochondrial pathways.

Crosstalk between Aldosterone and Glycation through Rac-1 Induces Diabetic Nephropathy

Background: Advanced glycation end products (AGEs) interaction with its receptor (RAGE) and aldosterone (Aldo) through the mineralocorticoid receptor (MR) activates Rac-1 and NF-κB independently in diabetic nephropathy (DN). However, the crosstalk of Aldo with AGEs-RAGE is still unresolved. Our study examined the impact of the AGEs-Aldo complex on renal cells and its effect on the RAGE-MR interaction. Methods and results: Glycation of human serum albumin (HSA) (40 mg/mL) with methylglyoxal (10 mM) in the presence of Aldo (100 nM) and aminoguanidine (AG) (100 nM) was performed. Glycation markers such as fructosamine and carbonyl groups and fluorescence of AGEs, pentosidine, and tryptophan followed by protein modification were measured. Renal (HEK-293T) cells were treated with the glycated HSA-Aldo (200 μg/mL) along with FPS-ZM1 and spironolactone antagonists for RAGE and Aldo, respectively, for 24 h. Glycation markers and esRAGE levels were measured. Protein and mRNA levels of RAGE, MR, Rac-1, and NF-κB were estimated. Glycation markers were enhanced with Aldo when albumin was only 14-16% glycated. AGEs-Aldo complex upregulated RAGE, MR, Rac-1 and NF-κB expressions. However, FPS-ZM1 action might have activated the RAGE-independent pathway, further elevating MR, Rac-1, and NF-κB levels. Conclusion: Our study concluded that the presence of Aldo has a significant impact on glycation. In the presence of AGEs-Aldo, RAGE-MR crosstalk exerts inflammatory responses through Rac-1 in DN. Insights into this molecular interplay are crucial for developing novel therapeutic strategies to alleviate DN in the future.