Clinical/Translational Aspects of Advanced Glycation End-Products

Development of a microarray microfluidic chip mass spectrometry platform based on UV curable 3D hepatocellular sphere bio-ink for rapid screening inhibitors of advanced glycosylation end products from natural compounds

Advanced glycation end products (AGEs) are the unwanted by-products of excessive sugar intake, and their generation and accumulation promote aging and disease occurrence. However, the lack of robust biology model and platform for fast evaluating AGE generation and accumulation under intervention of drugs hampers AGEs-targeted therapeutic development. This work described a novel biological high AGEs recombinant extracellular matrix 3D human hepatocellular spheres model was built, under the same cell numbers, this 3D hepatocellular spheres expressed more AGEs over an order of magnitude than monolayer culture cells. Combined with UV curable gelatin methacryloyl (GelMA), biological 3D human hepatocellular sphere were made into a extruded type bio-ink with high AGEs, simply encapsulated in a hepatic lobule shaped micro array polymethyl methacrylate (PMMA) microfluidic chip successfully. Due to this biomimetic fluid microreactor environment, our biological microfluidic chip enables effectively determine the inhibition capacity of compounds on endogenous AGE accumulation with a high sensitivity and in a short time, total determination workflow less than 2.5 h, it takes 1/200 of the time required by mainstream methods. The evaluation results showed that alisol B 23-monoacetate and chlorogenic acid were potential natural AGEs inhibitors. Moreover, the integration of high AGEs bio-ink and microfluidic chip provides a promising tool for AGE-related drug discovery and liver disease research.

Zn-Based Multi-Active Framework Nanoparticles TSA-CAN-Zn Inhibit Skin Glycation via Dual Blockade of HMGB1/RAGE and AGEs/RAGE Pathways

Receptor for advanced glycation end products (RAGE) plays an important role in skin glycation damage. High-mobility group 1B protein (HMGB1) and advanced glycation end products (AGEs) are key RAGE ligands. Simultaneous inhibition of HMGB1/RAGE and AGEs/RAGE pathways maybe an effective strategy to alleviate glycation induced skin damage. In this work, Theasinensin A (TSA) is identified as the active molecule inhibiting HMGB1-RAGE interaction through molecular docking. To simultaneously suppress HMGB1/RAGE and AGEs/RAGE pathways, Zn-based multi-active framework nanoparticles TSA-CAN-Zn are designed, which contain TSA and the active molecule L-carnosine (CAN) that inhibits AGEs production. In vitro studies demonstrated that TSA-CAN-Zn have radical scavenging activity and AGEs formation inhibition activity. TSA-CAN-Zn can not only inhibit ROS accumulation, cell apoptosis, and inflammatory factors production induced by glycation in HaCaT cells but also enhanced the lysosomal degradation of AGEs. TSA-CAN-Zn also mitigated the damage caused by glycation in mouse skin glycation model. Single-cell RNA sequencing results revealed the impact of TSA-CAN-Zn on different cell types of skin tissue, especially the basal cells of the epidermal layer and inflammation-related macrophages. And pathway analysis revealed that TSA-CAN-Zn mainly influences the downstream pathways of RAGE. Collectively, TSA-CAN-Zn is a promising therapeutic candidate for ameliorating glycation-induced skin damage.

Epimedium brevicornum Maxim alleviates diabetes osteoporosis by regulating AGE-RAGE signaling pathway

OBJECTIVES

Epimedium brevicornum Maxim (EP) has a history of utilization in Chinese traditional medicine for the treatment of bone diseases. However, the precise mechanism by which EP extract (EPE) operates in Diabetes osteoporosis (DOP) remains ambiguous. The study was aimed to explore the effects and underlying mechanisms of EPE on DOP, with particular emphasis on the AGE-RAGE pathway.

METHODS

The DOP model was induced through a combination of a high-sugar and high-fat diet along with streptozotocin injection. Following treatment with EPE, blood glucose levels, body weight, and serum biomarkers were measured. The trabecular microstructure of the femur was analyzed using micro-CT tomography and H&E staining. Bioinformatics techniques, including network pharmacology and molecular docking, were utilized to identify key targets of EP for DOP. The predicted targets and pathways were further validated through RT-PCR, TSA analysis ELISA, and western blotting (WB), respectively.

RESULTS

The findings from animal experiments indicate that EPE has a positive impact on weight and blood glucose levels, particularly in reversing the decrease and disordered arrangement of bone trabeculae. Bioinformatics analysis reveals the involvement of the AGE-RAGE pathways in the treatment of DOP with EPE. Subsequent animal validation experiments demonstrate that EPE can regulate key proteins AGE-RAGE pathway, resulting in reducing the inflammatory factors and apoptosis, including advanced Glycation End-products (RGEs), receptor for Advanced Glycation End-products (RAGE), Interleukin-6 (IL-6), Interleukin-1β (IL-1β), Nuclear Factor Kappa B (NF-κB), BCL2-Associated X protein (Bax), B-cell lymphoma 2(Bcl2), and etc. CONCLUSION: This study provides clear evidence that EPE mitigates DOP through enhancement of the AGE-RAGE pathways, offering innovative insights and approaches for clinical utilization.

Early and advanced glycation end product analysis from women with PCOS on metformin

In this cross-sectional study, we have analyzed advanced glycation end products (AGEs) in the plasma and follicular fluid of women with polycystic ovary syndrome (PCOS) taking metformin during in vitro fertilization (IVF) and control women undergoing IVF. Glucose, fructose, fructosamine, carboxymethyl lysine/ arginine (CML/R) proteins, and pentosidine were measured in the plasma and paired follicular fluid. Glycated proteins were characterized by mass spectrometry. Fasting serum glucose and fructosamine were comparable; however, follicular fluid glucose and fructosamine were higher in the PCOS group, and other AGEs remained unaltered. Fructose was lower in both serum and follicular fluid from the PCOS group. A positive correlation between some of these AGEs and sugars estimated was observed. Glucose and fructosamine in the follicular fluid correlated with the antral follicle count. The number of glycated peptides identified in the PCOS group by mass spectrometry was more. Glycated K75, K402 amino acid residues of albumin were detected in the PCOS group only. Additionally, some proteins involved in steroidogenesis and oocyte maturation as well as transporters, and extracellular matrix proteins, were found to be glycated in the PCOS group, which may affect their function. Elevated glucose and fructosamine in the follicular fluid of the PCOS group may contribute to abnormal folliculogenesis. The glycation of albumin should be validated in more samples to be considered as a marker for PCOS diagnosis.

Alpha-Lipoic Acid Treatment Reduces the Levels of Advanced End Glycation Products in Type 2 Diabetes Patients with Neuropathy

Background/Objectives: Type 2 diabetes mellitus (T2DM) and its macro- and microvascular complications are major health concerns with multiple factors, like advanced end glycation products (AGEs), in the background. AGEs induce long-lasting functional modification of the proteins and collagen in the vascular wall and nerve tissue. We investigated the effect of alpha-lipoic acid (ALA) treatment on AGEs, soluble AGE receptor (sRAGE), the AGE/sRAGE ratio, and the parameters of endothelial dysfunction and their correlations. Methods: In our 6-month intervention study, 54 T2DM patients with neuropathy treated according to the actual therapeutic guidelines with unchanged oral antidiabetic drugs were included and treated by daily oral administration of 600 mg ALA. A total of 24 gender and age-matched T2DM patients without neuropathy served as controls. Results: In our work, we first demonstrated the attenuating effect of alpha lipoic acid therapy on AGEs in humans (11.89 (9.44-12.88) to 10.95 (9.81-12.82) AU/μg (p = 0.017)). sRAGE levels or the AGEs/sRAGE ratio were not affected by ALA treatment or by the presence of neuropathy. We found a correlation between the changes of AGEs and the improvement of current perception threshold and progranulin levels, and an inverse correlation with the change of asymmetric dimethylarginine. Conclusions: According to our results, ALA decreases AGEs, which may contribute to the clinically well-known beneficial effect in diabetic neuropathy and improvement of endothelial function.

Leukocyte Extracellular Vesicles Predict Progression of Systolic Dysfunction in Heart Failure with Mildly Reduced Ejection Fraction (LYCHEE) - A Prospective, Multicentre Cohort Study

Risk stratification in heart failure with mildly-reduced ejection fraction (HFmrEF) remains challenging. We evaluated the predictive value of advanced glycation end products (AGEs) and plasma concentrations of extracellular vesicles (EVs) for the systolic and diastolic dysfunction progression in HFmrEF patients. Skin AGE accumulation was measured using AGE Reader. Plasma EV concentrations were measured using flow cytometry. Among 74 patients enrolled, 13 (18%) had systolic dysfunction progression and 5 (7%) had diastolic dysfunction progression during 6.5 months follow-up. Leukocyte EVs concentrations were higher in patients with systolic dysfunction progression (p = 0.002) and predicted the progression with 75.0% sensitivity and 58.3% specificity, independent of other clinical variables (OR 4.72, 95% CI 0.99-22.31). Skin AGE levels and concentrations of other EV subtypes were not associated with systolic or diastolic dysfunction progression. Increased leukocyte EVs concentrations are associated with 4.7-fold higher odds of systolic dysfunction progression in HFmrEF patients.

A Mediterranean diet improves glycation markers in healthy people and in those with chronic diseases: a systematic review of clinical trials

CONTEXT

Consumption of the Mediterranean diet (MedDiet) has beneficial effects on cardiometabolic health and aging.

OBJECTIVE

This systematic review aimed to critically investigate the effect of the MedDiet on glycation markers in healthy or overweight individuals with type 2 diabetes or cardiovascular disease.

DATA SOURCES

MEDLINE, EMBASE, Web of Science, and the Cochrane Library were searched, using the terms "Mediterranean diet" AND "glycation end products, advanced".

DATA EXTRACTION

Three randomized and 3 nonrandomized clinical trials, containing data on 2935 adult and elderly individuals with normal weight or overweight, were included. All extracted data were compiled, compared, and critically analyzed.

DATA ANALYSIS

The authors of most of the studies demonstrated a reduction in serum concentrations of advanced glycation end products (AGEs), such as εN-carboxymethyllysine and methylglyoxal, and in skin autofluorescence levels after at least 4 weeks of adherence to the MedDiet. The MedDiet also led to positive effects on gene expression of receptors for AGEs, as RAGE and AGER1, and an enzyme involved in detoxification (glyoxalase I). There is no evidence that short-term adherence affects glycation markers.

CONCLUSIONS

Glycation markers improved in response to the MedDiet. The possible mechanisms involved may be related to the low AGE and refined sugars content of the diet, as well as its high monounsaturated fatty acid, phenolic compound, and dietary fiber contents.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42021284006.

Extracellular Matrix-Mimicking Hydrogel with Angiogenic and Immunomodulatory Properties Accelerates Healing of Diabetic Wounds by Promoting Autophagy

The management of diabetic wounds faces significant challenges due to the excessive activation of reactive oxygen species (ROS), dysregulation of the inflammatory response, and impaired angiogenesis. A substantial body of evidence suggests that the aforementioned diverse factors contributing to the delayed healing of diabetic wounds may be associated with impaired autophagy. Impaired autophagy leads to endothelial and fibroblast dysfunction and impedes macrophage phenotypic transformation. This disruption hinders angiogenesis and extracellular matrix deposition, ultimately culminating in delayed wound healing. Therefore, biomaterials possessing autophagy regulatory functions hold significant potential for clinical applications in enhancing the healing of diabetic wounds. A hybrid multifunctional hydrogel (GelMa@SIS-Qu) has been developed, comprising methacrylamide gelatin (GelMa), a small intestine submucosal acellular matrix (SIS), and quercetin nanoparticles, which demonstrates the capability to promote autophagy. The promotion of autophagy not only reduces ROS levels in endothelial cells and enhances their antioxidant activity but also mitigates ROS-induced endothelial cell dysfunction and apoptosis, thereby promoting angiogenesis. Furthermore, the promotion of autophagy facilitates the phenotypic transformation of macrophages from the M1 phenotype to the M2 phenotype. This study investigates the distinctive mechanisms of the GelMa@SIS-Qu hydrogel and proposes a promising therapeutic strategy for treating diabetes-related wounds.

AGE-RAGE Axis and Cardiovascular Diseases: Pathophysiologic Mechanisms and Prospects for Clinical Applications

Advanced glycation end products (AGE), a diverse array of molecules generated through non-enzymatic glycosylation, in conjunction with the receptor of advanced glycation end products (RAGE), play a crucial role in the pathogenesis of diabetes and its associated complications. Recent studies have revealed that the AGE-RAGE axis potentially accelerated the progression of cardiovascular diseases, including heart failure, atherosclerosis, myocarditis, pulmonary hypertension, hypertension, arrhythmia, and other related conditions. The AGE-RAGE axis is intricately involved in the initiation and progression of cardiovascular diseases, independently of its engagement in diabetes. The mechanisms include oxidative stress, inflammation, alterations in autophagy flux, and mitochondrial dysfunction. Conversely, inhibition of AGE production, disruption of the binding between RAGE and its ligands, or silencing of RAGE expression could effectively impair the function of AGE-RAGE axis, thereby delaying or ameliorating the aforementioned diseases. AGE and the soluble receptor for advanced glycation end products (sRAGE) have the potential to be novel predictors of cardiovascular diseases. In this review, we provide an in-depth overview towards the biosynthetic pathway of AGE and elucidate the pathophysiological implications in various cardiovascular diseases. Furthermore, we delve into the profound role of RAGE in cardiovascular diseases, offering novel insights for further exploration of the AGE-RAGE axis and potential strategies for the prevention and management of cardiovascular disorders.

Effects of myricetin and its derivatives on nonenzymatic glycation: A mechanism study based on proteomic modification and fluorescence spectroscopy analysis

Myricetin and its derivatives, myricitrin and dihydromyricetin, are flavonoids widely presented in foods and phytomedicine that possess tremendous health potential. In this study, we compared the antiglycation activity of myricetin and its derivatives, then investigated the underlying mechanism using proteomic modification and fluorescence spectroscopy analysis. All three compounds exhibited thorough inhibition on nonenzymatic glycation process, with the inhibitory effects on AGEs reaching 85% at 40 μmol/L. They effectively protected bovine serum albumin (BSA) structure by inhibiting protein oxidation, preventing the conversion from α-helix to β-sheet, and reducing amyloid-like cross-β structure formation. Among the three compounds, myricetin showed a predominant antiglycation activity. Proteomic analysis identified the early glycated sites that were protected by myricetin, including lysine K235, 256, 336, 421, 420, 489, etc. Additionally, fluorescence spectroscopy revealed spontaneous interactions between BSA and myricetin. Overall, myricetin holds promise as an antiglycation agent in both the food and drug industries.

Evaluation of changes in carbonyl stress markers with treatment in male patients with bipolar disorder manic episode: A controlled study

BACKGROUND

Carbonyl stress, a metabolic state characterized by elevated production of reactive carbonyl compounds (RCCs), is closely related to oxidative stress and has been implicated in various diseases. This study aims to investigate carbonyl stress parameters in drug-free bipolar disorder (BD) patients compared to healthy controls, explore their relationship with clinical features, and assess the effect of treatment on these parameters.

METHODS

Patients with a primary diagnosis of a manic episode of BD and healthy controls were recruited. Exclusion criteria included intellectual disability, presence of neurological diseases, chronic medical conditions such as diabetes mellitus and metabolic syndrome, and clinical signs of inflammation. Levels of serum carbonyl stress parameters were determined using high-performance liquid chromatography.

RESULTS

Levels of glyoxal (GO) and methylglyoxal (MGO) did not differ between pre- and post-treatment patients, but malondialdehyde (MDA) levels decreased significantly post-treatment. Pre-treatment MGO and MDA levels were higher in patients compared to controls, and these differences persisted post-treatment. After adjusting for BMI and waist circumference, only MDA levels remained significantly higher in patients compared to controls.

LIMITATIONS

The study's limitations include the exclusion of female patients, which precluded any assessment of potential gender differences, and the lack of analysis of the effect of specific mood stabilizers or antipsychotic drugs.

CONCLUSIONS

This study is the first to focus on carbonyl stress markers in BD, specifically GO, MGO, and MDA. MDA levels remained significantly higher in patients, suggesting a potential role in BD pathophysiology. MGO levels were influenced by metabolic parameters, indicating a potential link to neurotoxicity in BD. Further research with larger cohorts is needed to better understand the role of RCCs in BD and their potential as therapeutic targets.

Advanced glycation end products and reactive oxygen species: uncovering the potential role of ferroptosis in diabetic complications

Advanced glycation end products (AGEs) are a diverse range of compounds that are formed when free amino groups of proteins, lipids, and nucleic acids are carbonylated by reactive carbonyl species or glycosylated by reducing sugars. Hyperglycemia in patients with diabetes can cause an overabundance of AGEs. Excess AGEs are generally acknowledged as major contributing factors to the development of diabetic complications because of their ability to break down the extracellular matrix directly and initiate intracellular signaling pathways by binding to the receptor for advanced glycation end products (RAGE). Inflammation and oxidative stress are the two most well-defined pathophysiological states induced by the AGE-RAGE interaction. In addition to oxidative stress, AGEs can also inhibit antioxidative systems and disturb iron homeostasis, all of which may induce ferroptosis. Ferroptosis is a newly identified contributor to diabetic complications. This review outlines the formation of AGEs in individuals with diabetes, explores the oxidative damage resulting from downstream reactions of the AGE-RAGE axis, and proposes a novel connection between AGEs and the ferroptosis pathway. This study introduces the concept of a vicious cycle involving AGEs, oxidative stress, and ferroptosis in the development of diabetic complications.

Soluble receptor of advanced glycation end product as a biomarker in neurocognitive and neuropsychiatric disorders: A meta-analysis of controlled studies

BACKGROUND & OBJECTIVES

Currently, there is a significant focus on the decrease of soluble receptor of advanced glycation end products (sRAGE) in neurocognitive and neuropsychiatric disorders. sRAGE plays a decoy role against the inflammatory response of advanced glycation end products (AGE), which has led to increased interest in its role in these disorders. This meta-analysis aimed to investigate the significant differences in sRAGE levels between neurocognitive and neuropsychiatric disorders compared to control groups.

METHOD

A systematic review was conducted using the PUBMED, Scopus and Embase databases up to October 2023. Two reviewers assessed agreement for selecting papers based on titles and abstracts, with kappa used to measure agreement and finally publications were scanned according to controlled studies. Effect sizes were calculated as weighted mean differences (WMD) and pooled using a random effects model. Heterogeneity was assessed using I2, followed by subgroup analysis and meta-regression tests. Quality assessment was performed using the Newcastle-Ottawa Quality Assessment Scale.

RESULTS

In total, 16 studies were included in the present meta-analysis. Subjects with neurocognitive (n = 1444) and neuropsychiatric (n = 444) disorders had lower sRAGE levels in case-control (WMD: -0.21, 95% CI: -0.33, -0.10; p <.001) and cross-sectional (WMD: -0.29, 95% CI = -0.44, -0.13, p <.001) studies with high heterogeneity and no publication bias. In subgroup analysis, subjects with cognitive impairment (WMD: -0.87, 95% CI: -1.61, -0.13, p =.000), and age >50 years (WMD: -0.39, 95% CI: -0.74, -0.05, p =.000), had lower sRAGE levels in case-control studies. Also, dementia patients (WMD: -0.41, 95% CI: -0.72, -0.10, p =.014) with age >50 years (WMD: -0.33, 95% CI: -0.54, -0.13, p = 0.000) and in Asian countries (WMD: -0.28, 95% CI: -0.42, -0.13, p =.141) had lower sRAGE levels in cross-sectional studies.

CONCLUSION

This meta-analysis revealed a significant reduction in sRAGE in neurocognitive and neuropsychiatric disorders particularly in Asians and moderate age.

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.

Endothelial β-catenin upregulation and Y142 phosphorylation drive diabetic angiogenesis via upregulating KDR/HDAC9

BACKGROUND

Diabetic angiogenesis is closely associated with disabilities and death caused by diabetic microvascular complications. Advanced glycation end products (AGEs) are abnormally accumulated in diabetic patients and are a key pathogenic factor for diabetic angiogenesis. The present study focuses on understanding the mechanisms underlying diabetic angiogenesis and identifying therapeutic targets based on these mechanisms.

METHODS

In this study, AGE-induced angiogenesis serves as a model to investigate the mechanisms underlying diabetic angiogensis. Mouse aortic rings, matrigel plugs, and HUVECs or 293T cells were employed as research objects to explore this pathological process by using transcriptomics, gene promoter reporter assays, virtual screening and so on.

RESULTS

Here, we found that AGEs activated Wnt/β-catenin signaling pathway and enhanced the β-catenin protein level by affecting the expression of β-catenin degradation-related genes, such as FZDs (Frizzled receptors), LRPs (LDL Receptor Related Proteins), and AXIN1. AGEs could also mediate β-catenin Y142 phosphorylation through VEGFR1 isoform5. These dual effects of AGEs elevated the nuclear translocation of β-catenin and sequentially induced the expression of KDR (Kinase Insert Domain Receptor) and HDAC9 (Histone Deacetylase 9) by POU5F1 and NANOG, respectively, thus mediating angiogenesis. Finally, through virtual screening, Bioymifi, an inhibitor that blocks VEGFR1 isoform5-β-catenin complex interaction and alleviates AGE-induced angiogenesis, was identified.

CONCLUSION

Collectively, this study offers insight into the pathophysiological functions of β-catenin in diabetic angiogenesis.

Glucose transport, transporters and metabolism in diabetic retinopathy

Diabetic retinopathy (DR) is the most common reason for blindness in working-age individuals globally. Prolonged high blood glucose is a main causative factor for DR development, and glucose transport is prerequisite for the disturbances in DR caused by hyperglycemia. Glucose transport is mediated by its transporters, including the facilitated transporters (glucose transporter, GLUTs), the "active" glucose transporters (sodium-dependent glucose transporters, SGLTs), and the SLC50 family of uniporters (sugars will eventually be exported transporters, SWEETs). Glucose transport across the blood-retinal barrier (BRB) is crucial for nourishing the neuronal retina in the context of retinal physiology. This physiological process primarily relies on GLUTs and SGLTs, which mediate the glucose transportation across both the cell membrane of retinal capillary endothelial cells and the retinal pigment epithelium (RPE). Under diabetic conditions, increased accumulation of extracellular glucose enhances the retinal cellular glucose uptake and metabolism via both glycolysis and glycolytic side branches, which activates several biochemical pathways, including the protein kinase C (PKC), advanced glycation end-products (AGEs), polyol pathway and hexosamine biosynthetic pathway (HBP). These activated biochemical pathways further increase the production of reactive oxygen species (ROS), leading to oxidative stress and activation of Poly (ADP-ribose) polymerase (PARP). The activated PARP further affects all the cellular components in the retina, and finally resulting in microangiopathy, neurodegeneration and low-to-moderate grade inflammation in DR. This review aims to discuss the changes of glucose transport, glucose transporters, as well as its metabolism in DR, which influences the retinal neurovascular unit (NVU) and implies the possible therapeutic strategies for treating DR.

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.

Advanced Glycation End Products Upregulate CD40 in Human Retinal Endothelial and Müller Cells: Relevance to Diabetic Retinopathy

CD40 induces pro-inflammatory responses in endothelial and Müller cells and is required for the development of diabetic retinopathy (DR). CD40 is upregulated in these cells in patients with DR. CD40 upregulation is a central feature of CD40-driven inflammatory disorders. What drives CD40 upregulation in the diabetic retina remains unknown. We examined the role of advanced glycation end products (AGEs) in CD40 upregulation in endothelial cells and Müller cells. Human endothelial cells and Müller cells were incubated with unmodified or methylglyoxal (MGO)-modified fibronectin. CD40 expression was assessed by flow cytometry. The expression of ICAM-1 and CCL2 was examined by flow cytometry or ELISA after stimulation with CD154 (CD40 ligand). The expression of carboxymethyl lysine (CML), fibronectin, and laminin as well as CD40 in endothelial and Müller cells from patients with DR was examined by confocal microscopy. Fibronectin modified by MGO upregulated CD40 in endothelial and Müller cells. CD40 upregulation was functionally relevant. MGO-modified fibronectin enhanced CD154-driven upregulation of ICAM-1 and CCL2 in endothelial and Müller cells. Increased CD40 expression in endothelial and Müller cells from patients with DR was associated with increased CML expression in fibronectin and laminin. These findings identify AGEs as inducers of CD40 upregulation in endothelial and Müller cells and enhancers of CD40-dependent pro-inflammatory responses. CD40 upregulation in these cells is associated with higher CML expression in fibronectin and laminin in patients with DR. This study revealed that CD40 and AGEs, two important drivers of DR, are interconnected.

Discovery of Glycation Products: Unraveling the Unknown Glycation Space Using a Mass Spectral Library from In Vitro Model Systems

The nonenzymatic reaction between amino acids (AAs) and reducing sugars, also known as the Maillard reaction, is the primary source of free glycation products (GPs) in vivo and in vitro. The limited number of MS/MS records for GPs in public libraries hinders the annotation and investigation of nonenzymatic glycation. To address this issue, we present a mass spectral library containing the experimental MS/MS spectra of diverse GPs from model systems. Based on the conceptional reaction processes and structural characteristics of products, we classified GPs into common GPs (CGPs) and modified AAs (MAAs). A workflow for annotating GPs was established based on the structural and fragmentation patterns of each GP type. The final spectral library contains 157 CGPs, 499 MAAs, and 2426 GP spectra with synthetic model system information, retention time, precursor m/z, MS/MS, and annotations. As a proof-of-concept, we demonstrated the use of the library for screening GPs in unidentified spectra of human plasma and urine. The AAs with the C6H10O5 modification, fructosylation from Amadori rearrangement, were the most found GPs. With the help of the model system, we confirmed the existence of C6H10O5-modified Valine in human plasma by matching both retention time, MS1, and MS/MS without reference standards. In summary, our GP library can serve as an online resource to quickly screen possible GPs in an untargeted metabolomics workflow, furthermore with the model system as a practical synthesis method to confirm their identity.

Advanced glycation end products of dietary origin and their association with inflammation in diabetes - A minireview

Advanced glycation end products (AGEs) are a diverse group of compounds that are formed as a result of the non-enzymatic reaction between a reducing sugar such as glucose and the free NH2 groups of an amino acid in a protein or other biomolecule. The chemical reaction, by which these products are generated, is known as the Maillard reaction and occurs as a part of the body's normal metabolism. Such a reaction is enhanced during diabetes due to hyperglycemia, but it can also occur during the preparation, processing, and preservation of certain foods. Therefore, AGEs can also be obtained from the diet (d-AGE) and contribute to an increase of the total serum pool of these compounds. They have been implicated in a wide variety of pathological processes, mainly because of their ability to induce inflammatory responses and oxidative stress increase. They are extensively accumulated as a part of the normal aging, especially in tissues rich in long half-life proteins, which can compromise the physiology of these tissues. d-AGEs are abundant in diets rich in processed fats and sugars. This review is addressed to the current knowledge on these products and their impact on the immunomodulation of various mechanisms that may contribute to exacerbation of the diabetes pathophysiology.

Microenvironmental dynamics of diabetic wounds and insights for hydrogel-based therapeutics

The rising prevalence of diabetes has underscored concerns surrounding diabetic wounds and their potential to induce disability. The intricate healing mechanisms of diabetic wounds are multifaceted, influenced by ambient microenvironment, including prolonged hyperglycemia, severe infection, inflammation, elevated levels of reactive oxygen species (ROS), ischemia, impaired vascularization, and altered wound physicochemical properties. In recent years, hydrogels have emerged as promising candidates for diabetic wound treatment owing to their exceptional biocompatibility and resemblance to the extracellular matrix (ECM) through a three-dimensional (3D) porous network. This review will first summarize the microenvironment alterations occurring in the diabetic wounds, aiming to provide a comprehensive understanding of its pathogenesis, then a comprehensive classification of recently developed hydrogels will be presented, encompassing properties such as hypoglycemic effects, anti-inflammatory capabilities, antibacterial attributes, ROS scavenging abilities, promotion of angiogenesis, pH responsiveness, and more. The primary objective is to offer a valuable reference for repairing diabetic wounds based on their unique microenvironment. Moreover, this paper outlines potential avenues for future advancements in hydrogel dressings to facilitate and expedite the healing process of diabetic wounds.

Tetrahedral Framework Nucleic Acids Based Small Interfering RNA Targeting Receptor for Advanced Glycation End Products for Diabetic Complications Treatment

Complications arising from diabetes can threaten multiple organs. Advanced glycation end products (AGEs) play a significant role in inducing these complications. Highly processed diets and hyperglycemia facilitate the accumulation of AGEs in the body. Interaction between AGEs and their main receptor (RAGE) initiates the transmission of intracellular inflammatory and cell death signals, which ultimately lead to complications. To counter AGEs-induced damage, we developed an siRNA-binding tetrahedral framework nucleic acids (TDN) system, termed Tsi, which combines the potent cell membrane penetrability and serum stability of TDN with the gene-targeting specificity of siRNA-RAGE. Tsi effectively and persistently downregulates the expression of RAGE, thereby suppressing inflammation by blocking the NF-κB pathway as well as exhibiting antioxidant functions. Furthermore, Tsi regulates the pyroptosis state of macrophages via the NLRP3/caspase-1 axis, which inhibits the spread of cell death signals and maintains homeostasis. This is of great significance for the synergistic treatment strategy for systemic complications in patients with refractory hyperglycemia. In summary, this study describes a nanomedicine that targets the RAGE and suppresses AGE-induced inflammation. This nucleic acid drug holds long-lasting efficacy and is independent of lowering hyperglycemia, which provides a strategy for the treatment of diabetic complications and age-related diseases.

Engineering of Therapeutic and Detoxifying Enzymes

Therapeutic enzymes present excellent opportunities for the treatment of human disease, modulation of metabolic pathways and system detoxification. However, current use of enzyme therapy in the clinic is limited as naturally occurring enzymes are seldom optimal for such applications and require substantial improvement by protein engineering. Engineering strategies such as design and directed evolution that have been successfully implemented for industrial biocatalysis can significantly advance the field of therapeutic enzymes, leading to biocatalysts with new-to-nature therapeutic activities, high selectivity, and suitability for medical applications. This minireview highlights case studies of how state-of-the-art and emerging methods in protein engineering are explored for the generation of therapeutic enzymes and discusses gaps and future opportunities in the field of enzyme therapy.

The Relationship between Resistant Hypertension and Advanced Glycation End-Product Levels Measured Using the Skin Autofluorescence Method: A Case-Control Study

Resistant hypertension is hypertension that cannot be controlled despite the use of three antihypertensive drugs, one of which is a diuretic. Resistant hypertension often coexists with advanced age, obesity, smoking, and diabetes. Advanced glycation end products (AGEs) are substances that are generated as a result of the glycation of proteins, lipids, and nucleic acids due to conditions such as hyperlipidemia, oxidative stress, and hyperglycemia. There are studies showing the relationships between AGE levels and aortic stiffness, hypertension, and microvascular and macrovascular complications in diabetes. In our study, we examined the relationship between resistant hypertension and AGE levels. Our study was planned as a case-control study, and 88 patients with resistant hypertension were included in the focus group, while 88 patients with controlled hypertension were included in the control group. The AGE levels of the patients were measured using the skin autofluorescence method. AGE levels were found to be significantly higher in patients with resistant hypertension than those recorded in the control group. A significant increase in AGE levels was also observed in patients with resistant hypertension and without diabetes compared with the control group. The levels of AGEs, which can be measured cheaply, noninvasively, and quickly with the skin autofluorescence method, may provide benefits in identifying these patients with resistant hypertension.

Advanced glycation end products: Key mediator and therapeutic target of cardiovascular complications in diabetes

The incidence of type 2 diabetes mellitus is growing in epidemic proportions and has become one of the most critical public health concerns. Cardiovascular complications associated with diabetes are the leading cause of morbidity and mortality. The cardiovascular diseases that accompany diabetes include angina, myocardial infarction, stroke, peripheral artery disease, and congestive heart failure. Among the various risk factors generated secondary to hyperglycemic situations, advanced glycation end products (AGEs) are one of the important targets for future diagnosis and prevention of diabetes. In the last decade, AGEs have drawn a lot of attention due to their involvement in diabetic patho-physiology. AGEs can be derived exogenously and endogenously through various pathways. These are a non-homogeneous, chemically diverse group of compounds formed non-enzymatically by condensation between carbonyl groups of reducing sugars and free amino groups of protein, lipids, and nucleic acid. AGEs mediate their pathological effects at the cellular and extracellular levels by multiple pathways. At the cellular level, they activate signaling cascades via the receptor for AGEs and initiate a complex series of intracellular signaling resulting in reactive oxygen species generation, inflammation, cellular proliferation, and fibrosis that may possibly exacerbate the damaging effects on cardiac functions in diabetics. AGEs also cause covalent modifications and cross-linking of serum and extracellular matrix proteins; altering their structure, stability, and functions. Early diagnosis of diabetes may prevent its progression to complications and decrease its associated comorbidities. In the present review, we recapitulate the role of AGEs as a crucial mediator of hyperglycemia-mediated detrimental effects in diabetes-associated complications. Furthermore, this review presents an overview of future perspectives for new therapeutic interventions to ameliorate cardiovascular complications in diabetes.

A Role for Advanced Glycation End Products in Molecular Ageing

Ageing is a composite process that involves numerous changes at the cellular, tissue, organ and whole-body levels. These changes result in decreased functioning of the organism and the development of certain conditions, which ultimately lead to an increased risk of death. Advanced glycation end products (AGEs) are a family of compounds with a diverse chemical nature. They are the products of non-enzymatic reactions between reducing sugars and proteins, lipids or nucleic acids and are synthesised in high amounts in both physiological and pathological conditions. Accumulation of these molecules increases the level of damage to tissue/organs structures (immune elements, connective tissue, brain, pancreatic beta cells, nephrons, and muscles), which consequently triggers the development of age-related diseases, such as diabetes mellitus, neurodegeneration, and cardiovascular and kidney disorders. Irrespective of the role of AGEs in the initiation or progression of chronic disorders, a reduction in their levels would certainly provide health benefits. In this review, we provide an overview of the role of AGEs in these areas. Moreover, we provide examples of lifestyle interventions, such as caloric restriction or physical activities, that may modulate AGE formation and accumulation and help to promote healthy ageing.

Advanced glycation end products and their soluble receptor (sRAGE) in patients with Hashimoto's thyroiditis on levothyroxine substitution

Background

Advanced glycation end products (AGEs) are heterogenous group of irreversible chemical moieties originated from non-enzymatic glycation and oxidation of proteins, nucleic acids, and lipids. The engagement of AGEs with their chief cellular receptor (RAGE) activates a myriad of signaling pathways contributing to the progression of chronic diseases like autoimmune thyroiditis, type 2 diabetes mellitus and its complications. Soluble RAGE (sRAGE) prevents AGE-RAGE interaction in a competitive manner.

Objective

We investigated the association between serum AGE, sRAGE and thyroid function in 73 Hashimoto thyroiditis patients (HT) on levothyroxine substitution, and in 83 age, BMI and gender-matched healthy controls.

Methods

The serum AGEs levels were determined by autofluorescence on a multi-mode microplate reader, and the serum sRAGE levels by ELISA method.

Results

Mean AGE level was lower (10.71 vs 11.45 AU/µg protein; p=0.046), while mean sRAGE level was higher (923 vs 755 pg/mL; p<0.0005) in the serum of HT patients than the controls. AGE correlated with age, while sRAGE correlated negatively with BMI in both groups. We found negative correlation between AGE and fT3 levels (r=-0.32; p=0.006) and sRAGE and TSH levels (r=-0.27; p=0.022) in HT patients, while we failed to find association between AGE, sRAGE and parameters of thyroid function in the control group. Median AGE/sRAGE ratio was lower in HT patients than in controls (2.4, IQR 1.9 - 3.1 vs 3.3, IQR 2.3 - 4.1 AU/pg; p < 0.001). In HT patients, the AGE/sRAGE ratio correlated positively with BMI and correlated negatively with fT3.

Conclusion

According to our results in HT patients lower TSH and higher fT3 levels within the reference range is accompanied by a favorable AGE/RAGE balance. Further investigations are needed to confirm these results.

In Vitro Antiglycation Potential of Erva-Baleeira (Varronia curassavica Jacq.)

BACKGROUND

Varronia curassavica Jacq. (Boraginaceae) is traditionally used in the treatment of inflammatory processes. The ethanolic extract of its leaves (EEVc) showed anti-inflammatory properties and low toxicity. Medicinal plants have aroused interest for their antiglycation activities. The formation and accumulation of advanced glycation end products (AGEs) are associated with several chronic diseases. The objective of this study was to evaluate the antiglycation potential of EEVc and two isolated compounds.

METHODS

The compounds brickellin and cordialin A were obtained by chromatographic methods and identified by spectrometric techniques. Analysis of fluorescent AGEs, biomarkers of amino acid residue oxidation, protein carbonyl groups and crosslink formation were performed in samples obtained from an in vitro model system of protein glycation with methylglyoxal.

RESULTS

EEVc, brickellin and cordialin A significantly reduced the in vitro formation of AGEs, and reduced the damage caused by oxidative damage to the protein.

CONCLUSIONS

According to the results, EEVc, brickellin and cordialin A are potential candidates against AGEs formation, which opens the way to expand the therapeutic arsenal for many pathologies resulting from glycoxidative stress.

Extracellular Matrix Glycation and Crosslinking in Mammary Tumor Progression

Breast cancer progression is accompanied by profound extracellular matrix (ECM) remodeling. A greater abundance of aligned fibrillar collagen is characteristic of invasive and aggressive breast cancers and has been associated with elevated activity of collagen crosslinking enzymes, such as lysyl oxidase (LOX) and lysyl hydroxylases (LH) and the formation of more mature collagen matrix crosslinks. Aligned collagen fibers can facilitate metastatic dissemination of tumor cells, and LOX inhibitors have been used to inhibit tumor progression and metastasis in experimental models. Thus, a better understanding of how matrix crosslinking alters tumor cell phenotypes, and behaviors would improve our ability to effectively treat aggressive metastatic breast cancer. Herein described is an experimental approach to glycate and crosslink a collagen-I/basement membrane extract ECM to study the impact of ECM crosslinking on mammary tumor progression in vivo. Moreover, glycation of collagen by sugars to form advanced glycation end products naturally occurs during aging, extending the potential relevance of this approach to research on mechanisms of aging involved in disease progression.

Advanced glycation endproducts in diabetes-related macrovascular complications: focus on methylglyoxal

Diabetes is associated with vascular injury and the onset of macrovascular complications. Advanced glycation endproducts (AGEs) and the AGE precursor methylglyoxal (MGO) have been identified as key players in establishing the relationship between diabetes and vascular injury. While most research has focused on the link between AGEs and vascular injury, less is known about the effects of MGO on vasculature. In this review, we focus on the mechanisms linking AGEs and MGO to the development of atherosclerosis. AGEs and MGO are involved in many stages of atherosclerosis progression. However, more research is needed to determine the exact mechanisms underlying these effects. Nevertheless, AGEs and MGO could represent valid therapeutic targets for the macrovascular complications of diabetes.

HILIC-MS for Untargeted Profiling of the Free Glycation Product Diversity

Glycation products produced by the non-enzymatic reaction between reducing carbohydrates and amino compounds have received increasing attention in both food- and health-related research. Although liquid chromatography mass spectrometry (LC-MS) methods for analyzing glycation products already exist, only a few common advanced glycation end products (AGEs) are usually covered by quantitative methods. Untargeted methods for comprehensively analyzing glycation products are still lacking. The aim of this study was to establish a method for simultaneously characterizing a wide range of free glycation products using the untargeted metabolomics approach. In this study, Maillard model systems consisting of a multitude of heterogeneous free glycation products were chosen for systematic method optimization, rather than using a limited number of standard compounds. Three types of hydrophilic interaction liquid chromatography (HILIC) columns (zwitterionic, bare silica, and amide) were tested due to their good retention for polar compounds. The zwitterionic columns showed better performance than the other two types of columns in terms of the detected feature numbers and detected free glycation products. Two zwitterionic columns were selected for further mobile phase optimization. For both columns, the neutral mobile phase provided better peak separation, whereas the acidic condition provided a higher quality of chromatographic peak shapes. The ZIC-cHILIC column operating under acidic conditions offered the best potential to discover glycation products in terms of providing good peak shapes and maintaining comparable compound coverage. Finally, the optimized HILIC-MS method can detect 70% of free glycation product features despite interference from the complex endogenous metabolites from biological matrices, which showed great application potential for glycation research and can help discover new biologically important glycation products.

Research Advances on the Damage Mechanism of Skin Glycation and Related Inhibitors

Our skin is an organ with the largest contact area between the human body and the external environment. Skin aging is affected directly by both endogenous factors and exogenous factors (e.g., UV exposure). Skin saccharification, a non-enzymatic reaction between proteins, e.g., dermal collagen and naturally occurring reducing sugars, is one of the basic root causes of endogenous skin aging. During the reaction, a series of complicated glycation products produced at different reaction stages and pathways are usually collectively referred to as advanced glycation end products (AGEs). AGEs cause cellular dysfunction through the modification of intracellular molecules and accumulate in tissues with aging. AGEs are also associated with a variety of age-related diseases, such as diabetes, cardiovascular disease, renal failure (uremia), and Alzheimer's disease. AGEs accumulate in the skin with age and are amplified through exogenous factors, e.g., ultraviolet radiation, resulting in wrinkles, loss of elasticity, dull yellowing, and other skin problems. This article focuses on the damage mechanism of glucose and its glycation products on the skin by summarizing the biochemical characteristics, compositions, as well as processes of the production and elimination of AGEs. One of the important parts of this article would be to summarize the current AGEs inhibitors to gain insight into the anti-glycation mechanism of the skin and the development of promising natural products with anti-glycation effects.

A Novel Approach for Managing Protein-Energy Wasting in People With Kidney Failure Undergoing Maintenance Hemodialysis: Rationale and Call for Trials

Protein-energy wasting (PEW) is a unique presentation of protein-energy malnutrition in people with kidney disease that is characterized by body protein catabolism exceeding anabolism. PEW is especially common in patients undergoing maintenance hemodialysis (HD) treatment. Dietary guidelines for managing PEW in HD patients primarily focus on protein adequacy and typically promote the intake of animal-based protein foods. Although intake of protein and essential amino acids is important for protein synthesis, the emphasis on protein adequacy largely fails to address-and may actually exacerbate-many of the root causes of PEW. This perspective examines the dietary determinants of PEW in people undergoing HD treatment, with an emphasis on upstream disease-related factors that reduce dietary protein utilization and impair dietary intakes. From this, we present a theoretical diet model for managing PEW that includes etiology-based dietary strategies to address barriers to intake and treat disease-related factors, as well as supportive dietary strategies to promote adequate energy and protein intakes. Given the complexity of diet-disease interactions in the pathogenesis of PEW, and its ongoing burden in HD patients, interventional trials are urgently needed to evaluate alternative diet therapy approaches for PEW in this population.

Endophytes, a Potential Source of Bioactive Compounds to Curtail the Formation–Accumulation of Advanced Glycation End Products: A Review

Endophytes, microorganisms that live in the internal tissues and organs of the plants, are known to produce numerous bioactive compounds, including, at times, some phytochemicals of their host plant. For such reason, endophytes have been quoted as a potential source for discovering bioactive compounds, particularly, of medical interest. Currently, many non-communicable diseases are threatening global human health, noticeably: diabetes, neurodegenerative diseases, cancer, and other ailment related to chronic inflammation and ageing. Intriguingly, the pathogenesis and development of these diseases have been linked to an excessive formation and accumulation of advanced glycation end products (AGEs). AGEs are a heterogeneous group of compounds that can alter the conformation, function, and lifetime of proteins. Therefore, compounds that prevent the formation and consequent accumulation of AGEs (AntiAGEs compounds) could be useful to delay the progress of some chronic diseases, and/or harmful effects of undue AGEs accumulation. Despite the remarkable ability of endophytes to produce bioactive compounds, most of the natural antiAGEs compounds reported in the literature are derived from plants. Accordingly, this work covers 26 plant antiAGEs compounds and some derivatives that have been reported as endophytic metabolites, and discusses the importance, possible advantages, and challenges of using endophytes as a potential source of antiAGEs compounds.

Advanced Glycation End-Products (AGEs): Formation, Chemistry, Classification, Receptors, and Diseases Related to AGEs

Advanced glycation end-products (AGEs) constitute a non-homogenous, chemically diverse group of compounds formed either exogeneously or endogeneously on the course of various pathways in the human body. In general, they are formed non-enzymatically by condensation between carbonyl groups of reducing sugars and free amine groups of nucleic acids, proteins, or lipids, followed by further rearrangements yielding stable, irreversible end-products. In the last decades, AGEs have aroused the interest of the scientific community due to the increasing evidence of their involvement in many pathophysiological processes and diseases, such as diabetes, cancer, cardiovascular, neurodegenerative diseases, and even infection with the SARS-CoV-2 virus. They are recognized by several cellular receptors and trigger many signaling pathways related to inflammation and oxidative stress. Despite many experimental research outcomes published recently, the complexity of their engagement in human physiology and pathophysiological states requires further elucidation. This review focuses on the receptors of AGEs, especially on the structural aspects of receptor-ligand interaction, and the diseases in which AGEs are involved. It also aims to present AGE classification in subgroups and to describe the basic processes leading to both exogeneous and endogeneous AGE formation.

Protein Modification with Ribose Generates Nδ-(5-hydro-5-methyl-4-imidazolone-2-yl)-ornithine

Advanced glycation end products (AGEs) are associated with diabetes and its complications. AGEs are formed by the non-enzymatic reactions of proteins and reducing sugars, such as glucose and ribose. Ribose is widely used in glycation research as it generates AGEs more rapidly than glucose. This study analyzed the AGE structures generated from ribose-modified protein by liquid chromatography-quadrupole time-of-flight mass spectrometry. Among these AGEs, N^δ-(5-hydro-5-methyl-4-imidazolone-2-yl)-ornithine (MG-H1) was the most abundant in ribose-glycated bovine serum albumin (ribated-BSA) among others, such as N^ε-(carboxymethyl) lysine, N^ε-(carboxyethyl) lysine, and N^ω-(carboxymethyl) arginine. Surprisingly, MG-H1 was produced by ribated-BSA in a time-dependent manner, whereas methylglyoxal levels (MG) were under the detectable level. In addition, Trapa bispinosa Roxb. hot water extract (TBE) possesses several anti-oxidative compounds, such as ellagic acid, and has been reported to inhibit the formation of MG-H1 in vivo. Thus, we evaluated the inhibitory effects of TBE on MG-H1 formation using ribose- or MG-modified proteins. TBE inhibited MG-H1 formation in gelatin incubated with ribose and ribated-BSA, but not in MG-modified gelatin. Furthermore, MG-H1 formation was inhibited by diethylenetriaminepentaacetic acid. These results demonstrated that ribose reacts with proteins to generate Amadori compounds and form MG-H1 via oxidation.

Analysis of 19 urinary biomarkers of oxidative stress, nitrative stress, metabolic disorders, and inflammation using liquid chromatography–tandem mass spectrometry

Environmental chemical exposures have been associated with cancer, diabetes, hormonal and immunological disorders, and cardiovascular diseases. Some direct effects of chemical exposure that are precursors to adverse health outcomes, including oxidative stress, nitrative stress, hormonal imbalance, neutrophilia, and eosinophilia, can be assessed through the analysis of biomarkers in urine. In this study, we describe a novel methodology for the determination of 19 biomarkers of health effects: malondialdehyde (MDA), 8-isoprostaglandin-F_2α (8-PGF_2α), 11-β-prostaglandin-F_2α (11-PGF_2α), 15-prostaglandin-F_2α (15-PGF_2α), 8-iso-15-prostaglandin-F_2α (8,15-PGF_2α), 8-hydroxy-2′-deoxyguanosine (8-OHdG), 8-hydroxyguanosine (8-HdG), 8-hydroxyguanine (8-HG), dityrosine (diY), allantoin (Alla), and two metabolic products of 4-hydroxynonenal (HNE), namely 4-hydroxy-2-nonenal glutathione (HNE-GSH) and 4-hydroxy-2-nonenal mercapturic acid (HNE-MA) (in total, 12 oxidative stress biomarkers, OSBs); 8-nitroguanosine (8-NdG), 8-nitroguanine (8-NG), and 3-nitrotyrosine (NY) (3 nitrative stress biomarkers, NSBs); chlorotyrosine (CY) and bromotyrosine (BY) (2 inflammatory biomarkers); and the advanced glycation end-products (AGEs) N^ε-carboxymethyllysine (CML) and N^ε-carboxyethyllysine (CEL) (2 metabolic disorder biomarkers). Since these biomarkers are trigged by a variety of environmental insults and produced by different biomolecular pathways, their selective and sensitive determination in urine would help broadly elucidate the pathogenesis of diseases mediated by environmental factors.

Carbamylated Proteins in Renal Disease: Aggravating Factors or Just Biomarkers?

Carbamylation is a nonenzymatic post-translational modification resulting from the reaction between cyanate, a urea by-product, and proteins. In vivo and in vitro studies have demonstrated that carbamylation modifies protein structures and functions, triggering unfavourable molecular and cellular responses. An enhanced formation of carbamylation-derived products (CDPs) is observed in pathological contexts, especially during chronic kidney disease (CKD), because of increased blood urea. Significantly, studies have reported a positive correlation between serum CDPs and the evolutive state of renal failure. Further, serum concentrations of carbamylated proteins are characterized as strong predictors of mortality in end-stage renal disease patients. Over time, it is likely that these modified compounds become aggravating factors and promote long-term complications, including cardiovascular disorders and inflammation or immune system dysfunctions. These poor clinical outcomes have led researchers to consider strategies to prevent or slow down CDP formation. Even if growing evidence suggests the involvement of carbamylation in the pathophysiology of CKD, the real relevance of carbamylation is still unclear: is it a causal phenomenon, a metabolic consequence or just a biological feature? In this review, we discuss how carbamylation, a consequence of renal function decline, may become a causal phenomenon of kidney disease progression and how CDPs may be used as biomarkers.

Chrysophyllum cainito. L alleviates diabetic and complications by playing antioxidant, antiglycation, hypoglycemic roles and the chemical profile analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Chrysophyllum cainito L. (C. cainito) is a traditional folk medicine in tropical area which can be an alternative agent for diabetes mellitus. Although the antioxidant and antidiabetic activity of the extracts are reported, little is known on the antiglycation activity and effects on diabetic complications.

AIM OF THE STUDY

This work was aimed to investigate the chemical profile, antidiabetic, antioxidant activities of C. cainito. Especially, the antiglycation potential as well as the relationships between components and activities were evaluated.

MATERIALS AND METHODS

The content of the primary components (polyphenols, flavonoids, steroids, and triterpenes), antioxidant, and hypoglycemic effects of ethanolic extracts from C. cainito leaves (CCE-1, 2, 3, 4) and stems (CSE-1, 2, 3, 4) were analyzed and detected. The chemical profiles of CCE-2 were characterized by HPLC-Q-TOF-MS/MS. The antiglycation and protection against oxidative stress effects were determined by in vitro assays. Relationship between bioactivities and components was analyzed by principal component analysis (PCA), heatmap analysis, and Pearson correlation analysis.

RESULTS

The composition was diverse between leaves and stem extracts with different activities. CCE-2 possessed the highest DPPH scavenging activity. CSE-2 displayed the highest ABTS scavenging activity and ferric reducing power. While CCE-3 showed the most effective inhibition on α-amylase and α-glucosidase activity (IC50 4.103 ± 0.332 μg/mL and 0.180 ± 0.006 mg/mL, respectively). PCA analysis showed that the most important variables in PC1 (60.7%) were total polyphenol and antioxidant activities. The hypoglycemic activity and contents of steroids showed important correlation. Advanced glycation end products formation was effectively inhibited by CCE-2 with myricetin 3-O-rhamnoside as the main constituent. CCE-3 displayed the highest protection effect against L02 cell line oxidation damage.

CONCLUSIONS

C. cainito leaves might be a promising candidate for antioxidant, hypoglycemic and antiglycation dietary supplement or potential agent against diabetes associated chronic diseases.

Comparison of metabolic fate, target organs, and microbiota interactions of free and bound dietary advanced glycation end products

Increased intake of Western diets and ultra-processed foods is accompanied by increased intake of advanced glycation end products (AGEs). AGEs can be generated exogenously in the thermal processing of food and endogenously in the human body, which associated with various chronic diseases. In food, AGEs can be divided into free and bound forms, which differ in their bioavailability, digestion, absorption, gut microbial interactions and untargeted metabolites. We summarized the measurements and contents of free and bound AGE in foods. Moreover, the ingestion, digestion, absorption, excretion, gut microbiota interactions, and metabolites and metabolic pathways between free and bound AGEs based on animal and human studies were compared. Bound AGEs were predominant in most of the selected foods, while beer and soy sauce were rich in free AGEs. Only 10%-30% of AGEs were absorbed into the systemic circulation when orally administered. The excretion of ingested free and bound AGEs was approximately 90% and 60%, respectively. Dietary free CML has a detrimental effect on gut microbiota composition, while bound AGEs have both detrimental and beneficial impacts. Free and bound dietary AGEs changed amino acid metabolism, energy metabolism and carbohydrate metabolism. And besides, bound dietary AGEs altered vitamin metabolism, and glycerolipid metabolism.

Elevated glucose increases genomic instability by inhibiting nucleotide excision repair

Exposure to chronic, elevated glucose inhibits nucleotide excision repair, which leads to accumulation of DNA glycation adducts, increased DNA strand breaks, and activation of the DNA damage response.

We investigated potential mechanisms by which elevated glucose may promote genomic instability. Gene expression studies, protein measurements, mass spectroscopic analyses, and functional assays revealed that elevated glucose inhibited the nucleotide excision repair (NER) pathway, promoted DNA strand breaks, and increased levels of the DNA glycation adduct N²-(1-carboxyethyl)-2ʹ-deoxyguanosine (CEdG). Glycation stress in NER-competent cells yielded single-strand breaks accompanied by ATR activation, γH2AX induction, and enhanced non-homologous end-joining and homology-directed repair. In NER-deficient cells, glycation stress activated ATM/ATR/H2AX, consistent with double-strand break formation. Elevated glucose inhibited DNA repair by attenuating hypoxia-inducible factor-1α–mediated transcription of NER genes via enhanced 2-ketoglutarate–dependent prolyl hydroxylase (PHD) activity. PHD inhibition enhanced transcription of NER genes and facilitated CEdG repair. These results are consistent with a role for hyperglycemia in promoting genomic instability as a potential mechanism for increasing cancer risk in metabolic disease. Because of the pleiotropic functions of many NER genes beyond DNA repair, these results may have broader implications for cellular pathophysiology.

In vitro chronic glycation induces AGEs accumulation reducing insulin-stimulated glucose uptake and increasing GLP1R in adipocytes

Intracellular AGEs accumulation increases RAGE and GLP1R and reduces glucose uptake in adipocytes.