AGEs/sRAGE, a novel risk factor in the pathogenesis of end-stage renal disease

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.

Correlation between circulating advanced glycation end products and thioredoxin-interacting protein levels and renal fat content in type 2 diabetes mellitus patients

BACKGROUND

This study sought to explore the clinical relevance of the associations of serum levels of advanced glycation end products (AGEs), soluble receptor for AGEs (sRAGE), and thioredoxin-interacting protein (TXNIP) with the renal fat fraction (RFF) in individuals with type 2 diabetes mellitus (T2DM).

METHODS

A total of 133 patients with T2DM were enrolled in the study. RFF, which represents the renal fat level, was determined utilizing Dixon magnetic resonance imaging (MRI). Serum levels of AGEs, sRAGE, TXNIP, and other biochemical parameters were measured in patients who fasted.

RESULTS

RFF in T2DM patients was positively correlated with the fasting levels of C-peptide (CP), triglycerides (TG), AGEs, TXNIP, and sRAGE (P < 0.05) and negatively correlated with the high-density lipoprotein cholesterol (HDL-c) level (P < 0.05). Pearson's correlation analysis indicated that the serum levels of AGEs, sRAGE, and TXNIP were interrelated and positively correlated (P < 0.05). Then, all patients were assigned to four groups according to the RFF quartile. The HC, CP, TG, AGEs, sRAGE, TXNIP, and DKD percentages tended to increase as the RFF quartiles increased, while the HDL-c level tended to decrease (p for trend < 0.05). Next, multiple linear regression analysis was performed using RFF as the dependent variable. After controlling for covariates related to RFF, the results showed that the serum levels of AGEs and TXNIP were still significantly correlated with RFF.

CONCLUSION

These results suggest that circulating AGEs and TXNIP levels may be associated with ectopic fat accumulation in the kidneys of T2DM patients and may serve as indicators of the severity of renal fat deposition.

The RAGE/DIAPH1 axis: mediator of obesity and proposed biomarker of human cardiometabolic disease

Overweight and obesity are leading causes of cardiometabolic dysfunction. Despite extensive investigation, the mechanisms mediating the increase in these conditions are yet to be fully understood. Beyond the endogenous formation of advanced glycation endproducts (AGEs) in overweight and obesity, exogenous sources of AGEs accrue through the heating, production, and consumption of highly processed foods. Evidence from cellular and mouse model systems indicates that the interaction of AGEs with their central cell surface receptor for AGE (RAGE) in adipocytes suppresses energy expenditure and that AGE/RAGE contributes to increased adipose inflammation and processes linked to insulin resistance. In human subjects, the circulating soluble forms of RAGE, which are mutable, may serve as biomarkers of obesity and weight loss. Antagonists of RAGE signalling, through blockade of the interaction of the RAGE cytoplasmic domain with the formin, Diaphanous-1 (DIAPH1), target aberrant RAGE activities in metabolic tissues. This review focuses on the potential roles for AGEs and other RAGE ligands and RAGE/DIAPH1 in the pathogenesis of overweight and obesity and their metabolic consequences.

Soluble receptor for advanced glycation end-products (sRAGE) in childhood obesity: association with gene expression of RAGE and cardiometabolic markers

Introduction

Introduction: advanced glycation end-products (AGEs) interact with the receptor for AGEs (RAGE). Full-length RAGE is associated with intracellular signal transduction, and soluble-RAGE (sRAGE) lacks the transmembrane and cytoplasmic domains, acting as a competitive inhibitor of AGEs-RAGE binding. sRAGE levels in healthy children are associated with cell surface expression of RAGE. However, the expression of RAGE has not been explored in childhood obesity. Objective: the study aim was to evaluate the sRAGE levels and the gene expression of RAGE in children and its association with cardiometabolic markers. Methods: this is a cross-sectional study with 6-11-year children, 20 with overweight and 20 with obesity. Anthropometric measurements included waist circumference (cm) (WC), neck circumference (NC), weight (kg), fat mass (%), trunk fat (kg), muscular mass (kg), height (cm), and body mass index (BMI) (kg/m2). Blood samples following an overnight fast were collected to measure glucose (mg/dl) and lipid profile with colorimetric methods. sRAGE was determined in serum using the enzyme-linked immunosorbent assay (ELISA). Quantitative reverse transcription (RT-qPCR) was performed to analyze RAGE transcripts in peripheral blood mononuclear cells isolated by Ficoll®-Hypaque. Results: we found higher RAGE (p = 0.0315) and lower sRAGE (p = 0.0305) levels in the obesity group. sRAGE level showed a negative correlation with RAGE (r = -0.35) and BMI (r = -0.24), and positive with HDL-cholesterol (r = 0.29). Regression analysis suggests that HDL-C and RAGE levels are predictors of sRAGE levels. Conclusions: expression of RAGE is associated with lower sRAGE levels in childhood obesity. Moreover, obese children show higher cardiometabolic risk markers, and a positively associated with sRAGE.

Serum levels of high mobility group box-1 protein (HMGB1) and soluble receptors of advanced glycation end-products (RAGE) in depressed patients treated with electroconvulsive therapy

AIMS

High mobility group box-1 (HMGB1) is one of the damage-associated molecular patterns produced by stress and induces inflammatory responses mediated by receptors of advanced glycation end-products (RAGE) on the cell surface. Meanwhile, soluble RAGE (sRAGE) exhibits an anti-inflammatory effect by capturing HMGB1. Animal models have shown upregulation of HMGB1 and RAGE in the brain or blood, suggesting the involvement of these proteins in depression pathophysiology. However, there have been no reports using blood from depressed patients, nor ones focusing on HMGB1 and sRAGE changes associated with treatment and their relationship to depressive symptoms.

METHODS

Serum HMGB1 and sRAGE concentrations were measured by enzyme-linked immunosorbent assay in a group of patients with severe major depressive disorder (MDD) (11 males and 14 females) who required treatment with electroconvulsive therapy (ECT), and also in a group of 25 age- and gender-matched healthy subjects. HMGB1 and sRAGE concentrations were also measured before and after a course of ECT. Depressive symptoms were assessed using the Hamilton Rating Scale for Depression (HAMD).

RESULTS

There was no significant difference in HMGB1 and sRAGE concentrations in the MDD group compared to healthy subjects. Although ECT significantly improved depressive symptoms, there was no significant change in HMGB1 and sRAGE concentrations before and after treatment. There was also no significant correlation between HMGB1 and sRAGE concentrations and the HAMD total score or subitem scores.

CONCLUSION

There were no changes in HMGB1 and sRAGE in the peripheral blood of severely depressed patients, and concentrations had no relationship with symptoms or ECT.

Anti-diabetic combination therapy with pioglitazone or glimepiride added to metformin on the AGE-RAGE axis: a randomized prospective study

Introduction

The ratio between advanced glycation end products (AGEs) and soluble form of receptor (s-RAGE) has been proposed as a risk marker for renal and cardiovascular diseases. The aim of this study was to evaluate in the diabetes condition the influence of two different oral anti-diabetic treatments on the AGE/s-RAGE ratio, during a 5-year observation period.

Methods

Seventy-three patients with type 2 diabetes mellitus were randomly assigned to a drug therapy with pioglitazone or glimepiride, combined to metformin. Each subject was evaluated at baseline and after 5 years of treatment.

Results

In both groups s-RAGE levels did not significantly vary, while the levels of AGE and AGE/s-RAGE were both significantly reduced, basal compared to 5-year values. Within pioglitazone group, as well within glimepiride group, significant variations (Δ, as difference between 5 years of treatment minus basal) were observed for AGE (Δ= -21.1±13.4 µg/ml, P<0.001 for pioglitazone; Δ= -14.4±11.4 µg/ml, P<0.001 for glimepiride) and in AGE/s-RAGE (Δ= -0.037±0.022 µg/pg, P<0.001 for pioglitazone; Δ= -0.024±0.020µg/pg, P<0.001 for glimepiride), suggesting an average decrease of the parameters by more than 50% in both treatments. Pioglitazone was more effective than glimepiride in reducing AGE/s-RAGE ratio after 5 years of therapy.

Conclusion

These data can help to explain the benefits of oral anti-diabetic therapy in relation to the reduction of cardiovascular risk, as suggested by variations in AGE/s-RAGE ratio as biochemical marker of endothelial function; in particular, treatment with pioglitazone seems to offer greater long-term benefit on AGE-RAGE axis.

Advanced glycosylation end products as metabolic predictors of systemic pro-inflammatory and prooxidant status in patients with end-stage renal disease

Controlling systemic proinflammatory and prooxidant effectors is essential for mitigating cardiovascular risk and mortality in patients with end-stage renal disease (ESRD). However, monitoring these processes is still challenging due to the high uncertainty about their determinants and predictors. Thus, we investigated the relationship between advanced glycosylation end products (AGE), proinflammatory and prooxidant effectors in ESRD patients undergoing hemodialysis (HD). In addition to nutritional profile and dialysis efficiency, AGE, cytokines, chemokines, C-reactive protein (CRP), total (TAC) and non-protein (npAC) antioxidant capacity, lipid and protein oxidation were analyzed in blood samples from 43 HD patients. AGE, CRP, cytokines, chemokines, protein carbonyl (PCn), and malondialdehyde (MDA) were upregulated, while TAC and npAC were down-regulated in HD patients compared to heath subjects. Dialysis efficiency, TAC and npAC were reduced, while leucocytes counting, pre- and post-HD urea, TNF, IL-6, IL-10, CCL-2, MIP-1β, PCn, and MDA were increased in patients with higher AGE accumulation compared to those with lower AGE levels. Serum levels of CRP, protein carbonyl, malondialdehyde, and all cytokines and chemokines analyzed were correlated with AGE circulating levels for patients with higher AGE accumulation. AGE was inversely correlated with IL-10, TAC and npAC in patients with higher AGE accumulation. AGE exhibited predictive value (determination coefficient) to explain CRP, cytokines, chemokines, PCN, MDA, TAC and npAC variability in patients with higher AGE levels. Taken together, our findings provide evidence that AGE accumulation is associated with important proinflammatory and prooxidant effectors in patients with ESRD undergoing hemodialysis. Thus, AGE monitoring may be relevant to predict systemic inflammatory stress and the balance between oxidant and antioxidant status in these patients.

RAGE pathways play an important role in regulation of organ fibrosis

Organ fibrosis is a pathological process of fibroblast activation and excessive deposition of extracellular matrix after persistent tissue injury and therefore is a common endpoint of many organ pathologies. Multiple cellular types and soluble mediators, including chemokines, cytokines and non-peptidic factors, are implicated in fibrogenesis and the remodeling of tissue architecture. The molecular basis of the fibrotic process is complex and consists of closely intertwined signaling networks. Research has strived for a better understanding of these pathological mechanisms to potentially reveal novel therapeutic targets for fibrotic diseases. In light of new knowledge, the receptor for advanced glycation end products (RAGE) emerged as an important candidate for the regulation of a wide variety of cellular functions related to fibrosis, including inflammation, cell proliferation, apoptosis, and angiogenesis. RAGE is a pattern recognition receptor that binds a broad range of ligands such as advanced glycation end products, high mobility group box-1, S-100 calcium-binding protein and amyloid beta protein. Although the link between RAGE and fibrosis has been established, the exact mechanisms need be investigated in further studies. The aim of this review is to collect all available information about the intricate function of RAGE and its signaling cascades in the pathogenesis of fibrotic diseases within different organs. In addition, to the major ligands and signaling pathways, we discuss potential strategies for targeting RAGE in fibrosis. We emphasize the functional links between RAGE, inflammation and fibrosis that may guide further studies and the development of improved therapeutic drugs.

Involvement of AGE and Its Receptors in the Pathogenesis of Hypertension in Elderly People and Its Treatment

Both systolic and diastolic blood pressures increase with age up to 50 to 60 years of age. After 60 years of age systolic pressure rises to 84 years of age but diastolic pressure remains stable or even decreases. In the oldest age group (85-99 years), the systolic blood pressure (SBP) is high and diastolic pressure (DBP) is the lowest. Seventy percent of people older than 65 years are hypertensive. This paper deals with the role of advanced glycation end products (AGE) and its cell receptor (RAGE) and soluble receptor (sRAGE) in the development of hypertension in the elderly population. Plasma/serum levels of AGE are higher in older people as compared with younger people. Serum levels of AGE are positively correlated with age, arterial stiffness, and hypertension. Low serum levels of sRAGE are associated with arterial stiffness and hypertension. Levels of sRAGE are negatively correlated with age and blood pressure. Levels of sRAGE are lower in patients with arterial stiffness and hypertension than patients with high levels of sRAGE. AGE could induce hypertension through numerous mechanisms including, cross-linking with collagen, reduction of nitric oxide, increased expression of endothelin-1, and transforming growth factor-β (TGF-β). Interaction of AGE with RAGE could produce hypertension through the generation of reactive oxygen species, increased sympathetic activity, activation of nuclear factor-kB, and increased expression of cytokines, cell adhesion molecules, and TGF- β. In conclusion, the AGE-RAGE axis could be involved in hypertension in elderly people. Treatment for hypertension in elderly people should be targeted at reduction of AGE levels in the body, prevention of AGE formation, degradation of AGE in vivo, downregulation of RAGE expression, blockade of AGE-RAGE interaction, upregulation of sRAGE expression, and use of antioxidants.

Coexpression network analysis of human candida infection reveals key modules and hub genes responsible for host-pathogen interactions

Invasive fungal infections are a significant reason for morbidity and mortality among organ transplant recipients. Therefore, it is critical to investigate the host and candida niches to understand the epidemiology of fungal infections in transplantation. Candida albicans is an opportunistic fungal pathogen that causes fatal invasive mucosal infections, particularly in solid organ transplant patients. Therefore, identifying and characterizing these genes would play a vital role in understanding the complex regulation of host-pathogen interactions. Using 32 RNA-sequencing samples of human cells infected with C. albicans, we developed WGCNA coexpression networks and performed DESeq2 differential gene expression analysis to identify the genes that positively correlate with human candida infection. Using hierarchical clustering, we identified 5 distinct modules. We studied the inter- and intramodular gene network properties in the context of sample status traits and identified the highly enriched genes in the correlated modules. We identified 52 genes that were common in the most significant WGCNA turquoise module and differentially expressed genes in human endothelial cells (HUVEC) infection vs. control samples. As a validation step, we identified the differentially expressed genes from the independent Candida-infected human oral keratinocytes (OKF6) samples and validated 30 of the 52 common genes. We then performed the functional enrichment analysis using KEGG and GO. Finally, we performed protein-protein interaction (PPI) analysis using STRING and CytoHubba from 30 validated genes. We identified 8 hub genes (JUN, ATF3, VEGFA, SLC2A1, HK2, PTGS2, PFKFB3, and KLF6) that were enriched in response to hypoxia, angiogenesis, vasculogenesis, hypoxia-induced signaling, cancer, diabetes, and transplant-related disease pathways. The discovery of genes and functional pathways related to the immune system and gene coexpression and differential gene expression analyses may serve as novel diagnostic markers and potential therapeutic targets.

Circulating levels of AGEs and soluble RAGE isoforms are associated with all-cause mortality and development of cardiovascular complications in type 2 diabetes: a retrospective cohort study

BACKGROUND

Advanced glycation end-products (AGEs) and their interaction with the receptor for advanced glycation end-products (RAGE) play a pivotal role in the development and progression of type 2 diabetes. In this retrospective cohort study, we explored the association of circulating levels of soluble RAGE (sRAGE) isoforms, i.e., endogenous secretory esRAGE and cleaved cRAGE, AGEs and their respective ratios with 15-year all-cause mortality in type 2 diabetes.

METHODS

Baseline AGEs and sRAGE isoforms concentration were measured by ELISA in 362 patients with type 2 diabetes and in 125 age- and gender-matched healthy control subjects (CTR). Independent predictors of mortality were determined using Cox proportional-hazards models and used to build and validate a nomogram for all-cause mortality prediction in type 2 diabetes.

RESULTS

AGEs, total sRAGE, cRAGE and the AGEs/sRAGE and AGEs/esRAGE ratios were significantly increased in patients with type 2 diabetes compared to CTR (p < 0.001). In CTR subjects, but not in type 2 diabetes patients, a significant negative correlation between cRAGE and age was confirmed (p = 0.003), whereas the AGEs/sRAGE (p = 0.032) and AGEs/cRAGE (p = 0.006) ratios were positively associated with age. At an average follow-up of 15 years (4,982 person-years), 130 deaths were observed. The increase in the AGEs/cRAGE ratio was accompanied by a higher risk of all-cause mortality in patients with type 2 diabetes (HR per each SD increment = 1.30, 95% CI 1.15-1.47; p < 0.001). Moreover, sRAGE was associated with the development of major adverse cardiovascular events (MACE) in type 2 diabetes patients without previous MACE (OR for each SD increase: 1.48, 95% CI 1.11-1.89). A nomogram based on age, sex, HbA1c, systolic blood pressure, and the AGEs/cRAGE ratio was built to predict 5-, 10- and 15-year survival in type 2 diabetes. Patients were categorized into quartiles of the monogram scores and Kaplan-Meier survival curves confirmed the prognostic accuracy of the model (log-rank p = 6.5 × 10- 13).

CONCLUSIONS

The ratio between AGEs and the cRAGE isoform is predictive of 15-year survival in patients with type 2 diabetes. Our data support the assessment of circulating AGEs and soluble RAGE isoforms in patients with type 2 diabetes as predictors of MACE and all-cause mortality.

Investigating the Molecular Mechanism of Quercetin Protecting against Podocyte Injury to Attenuate Diabetic Nephropathy through Network Pharmacology, MicroarrayData Analysis, and Molecular Docking

Quercetin (QUE), a health supplement, can improve renal function in diabetic nephropathy (DN) rats by ameliorating podocyte injury. Its clinical trial for renal insufficiency in advanced diabetes (NCT02848131) is currently underway. This study aimed to investigate the mechanism of QUE protecting against podocyte injury to attenuate DN through network pharmacology, microarray data analysis, and molecular docking. QUE-associated targets, genes related to both DN, and podocyte injury were obtained from different comprehensive databases and were intersected and analyzed to obtain mapping targets. Candidate targets were identified by constructing network of protein-protein interaction (PPI) of mapping targets and ranked to obtain key targets. The major pathways were obtained from Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) term enrichment analysis of candidate targets via ClueGO plug-in and R project software, respectively. Potential receptor-ligand interactions between QUE and key targets were evaluated via Autodocktools-1.5.6. 41. Candidate targets, of which three key targets (TNF, VEGFA, and AKT1), and the major AGE-RAGE signaling pathway in diabetic complications were ascertained and associated with QUE against podocyte injury in DN. Molecular docking models showed that QUE could closely bind to the key targets. This study revealed that QUE could protect against podocyte injury in DN through the following mechanisms: downregulating inflammatory cytokine of TNF, reducing VEGF-induced vascular permeability, inhibiting apoptosis by stimulating AKT1 phosphorylation, and suppressing the AGE-induced oxidative stress via the AGE-RAGE signaling pathway.

The RAGE/DIAPH1 Signaling Axis & Implications for the Pathogenesis of Diabetic Complications

Increasing evidence links the RAGE (receptor for advanced glycation end products)/DIAPH1 (Diaphanous 1) signaling axis to the pathogenesis of diabetic complications. RAGE is a multi-ligand receptor and through these ligand-receptor interactions, extensive maladaptive effects are exerted on cell types and tissues targeted for dysfunction in hyperglycemia observed in both type 1 and type 2 diabetes. Recent evidence indicates that RAGE ligands, acting as damage-associated molecular patterns molecules, or DAMPs, through RAGE may impact interferon signaling pathways, specifically through upregulation of IRF7 (interferon regulatory factor 7), thereby heralding and evoking pro-inflammatory effects on vulnerable tissues. Although successful targeting of RAGE in the clinical milieu has, to date, not been met with success, recent approaches to target RAGE intracellular signaling may hold promise to fill this critical gap. This review focuses on recent examples of highlights and updates to the pathobiology of RAGE and DIAPH1 in diabetic complications.

The Role of Advanced Glycation End Products and Its Soluble Receptor in Kidney Diseases

Patients with chronic kidney disease (CKD) are more prone to oxidative stress and chronic inflammation, which may lead to an increase in the synthesis of advanced glycation end products (AGEs). Because AGEs are mostly removed by healthy kidneys, AGE accumulation is a result of both increased production and decreased kidney clearance. On the other hand, AGEs may potentially hasten decreasing kidney function in CKD patients, and are independently related to all-cause mortality. They are one of the non-traditional risk factors that play a significant role in the underlying processes that lead to excessive cardiovascular disease in CKD patients. When AGEs interact with their cell-bound receptor (RAGE), cell dysfunction is initiated by activating nuclear factor kappa-B (NF-κB), increasing the production and release of inflammatory cytokines. Alterations in the AGE-RAGE system have been related to the development of several chronic kidney diseases. Soluble RAGE (sRAGE) is a decoy receptor that suppresses membrane-bound RAGE activation and AGE-RAGE-related toxicity. sRAGE, and more specifically, the AGE/sRAGE ratio, may be promising tools for predicting the prognosis of kidney diseases. In the present review, we discuss the potential role of AGEs and sRAGE as biomarkers in different kidney pathologies.

Does AGE-RAGE Stress Play a Role in the Development of Coronary Artery Disease in Obesity?

This article deals with the role of AGE (advanced glycation end products)-RAGE (receptor for AGE) stress (AGE/sRAGE) in the development of coronary artery disease (CAD) in obesity. CAD is due to atherosclerosis in coronary artery. The serum/plasma levels of AGE and sRAGE are reduced, while AGE-RAGE stress and expression of RAGE are elevated in obese individuals. However, the levels of AGE are elevated in obese individuals with more than one metabolic syndrome. The increases in the AGE-RAGE stress would elevate the expression and production of atherogenic factors, including reactive oxygen species, nuclear factor-kappa B, cytokines, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, endothelial leukocyte adhesion molecules, monocyte chemoattractant protein-1, granulocyte-macrophage colony-stimulating factor, and growth factors. Low levels of sRAGE would also increase the atherogenic factors. The increases in the AGE-RAGE stress and decreases in the levels of sRAGE would induce development of atherosclerosis, leading to CAD. The therapeutic regimen for AGE-RAGE stress-induced CAD in obesity would include lowering of AGE intake, prevention of AGE formation, degradation of AGE in vivo, suppression of RAGE expression, blockade of AGE-RAGE interaction, downregulation of sRAGE expression, and use of antioxidants. In conclusion, the data suggest that AGE-RAGE stress is involved in the development of CAD in obesity, and the therapeutic interventions to reduce AGE-RAGE would be helpful in preventing, regressing, and slowing the progression of CAD in obesity.

Role of advanced glycation end products on vascular smooth muscle cells under diabetic atherosclerosis

Atherosclerosis (AS) is a chronic inflammatory disease and leading cause of cardiovascular diseases. The progression of AS is a multi-step process leading to high morbidity and mortality. Hyperglycemia, dyslipidemia, advanced glycation end products (AGEs), inflammation and insulin resistance which strictly involved in diabetes are closely related to the pathogenesis of AS. A growing number of studies have linked AGEs to AS. As one of the risk factors of cardiac metabolic diseases, dysfunction of VSMCs plays an important role in AS pathogenesis. AGEs are increased in diabetes, participate in the occurrence and progression of AS through multiple molecular mechanisms of vascular cell injury. As the main functional cells of vascular, vascular smooth muscle cells (VSMCs) play different roles in each stage of atherosclerotic lesions. The interaction between AGEs and receptor for AGEs (RAGE) accelerates AS by affecting the proliferation and migration of VSMCs. In addition, increasing researches have reported that AGEs promote osteogenic transformation and macrophage-like transformation of VSMCs, and affect the progression of AS through other aspects such as autophagy and cell cycle. In this review, we summarize the effect of AGEs on VSMCs in atherosclerotic plaque development and progression. We also discuss the AGEs that link AS and diabetes mellitus, including oxidative stress, inflammation, RAGE ligands, small noncoding RNAs.

Modulation of soluble receptor for advanced glycation end products isoforms and advanced glycation end products in long-living individuals

Background: Circulating levels of soluble receptor for advanced glycation end products (sRAGE) and advanced glycation end products (AGEs) correlate with aging/cardiovascular risk, which is delayed in long-living individuals (LLIs). AGEs/sRAGE isoforms (cleaved RAGE [cRAGE] and secretory RAGE [esRAGE]) ratio is a valuable marker for disease risk. Results: We evaluated circulating sRAGE isoforms, and AGEs in LLIs (n = 95; 90-105 years) and controls (n = 94; 11-89 years). cRAGE decreased with age in controls and further declined in LLIs. esRAGE increased in LLIs. AGEs rose with age in controls and decreased in LLIs that were characterized by a lower AGEs/sRAGE ratio. Notably, cRAGE and AGE/esRAGE ratio better discriminated controls from LLIs. Conclusion: circulating cRAGE could be considered a reliable marker of chronological age while esRAGE a protective factor for longevity.

AGE-RAGE Stress and Coronary Artery Disease

Coronary artery atherosclerosis and atherosclerotic plaque rupture cause coronary artery disease (CAD). Advanced glycation end products (AGE) and its cell receptor RAGE, and soluble receptor (sRAGE) and endogenous secretory RAGE (esRAGE) may be involved in the development of atherosclerosis. AGE and its interaction with RAGE are atherogenic, while sRAGE and esRAGE have antiatherogenic effects. AGE-RAGE stress is a ratio of AGE/sRAGE. A high AGE-RAGE stress results in development and progression of CAD and vice-versa. AGE levels in serum and skin, AGE/sRAGE in patients with CAD, and expression of RAGE in animal model of atherosclerosis were higher, while serum levels of esRAGE were lower in patients with CAD compared with controls. Serum levels of sRAGE in CAD patients were contradictory, increased or decreased. This contradictory data may be due to type of patients used, because the sRAGE levels are elevated in diabetics and end-stage renal disease. AGE/sRAGE ratio is elevated in patients with reduced or elevated levels of serum sRAGE. It is to stress that AGE, RAGE, sRAGE, or esRAGE individually cannot serve as universal biomarker. AGE and sRAGE should be measured simultaneously to assess the AGE-RAGE stress. The treatment of CAD should be targeted at reduction in AGE levels, prevention of AGE formation, degradation of AGE in vivo, suppression of RAGE expression, blockade of RAGE, elevation of sRAGE, and use of antioxidants. In conclusion, AGE-RAGE stress would initiate the development and progression of atherosclerosis. Treatment modalities would prevent, regress, and slow the progression of CAD.

Xueshuantong for Injection (Lyophilized, ) Alleviates Streptozotocin-Induced Diabetic Retinopathy in Rats

OBJECTIVE

To investigate the ameliorate effect and underlying mechanism of Xueshuantong for Injection (Lyophilized, , XST) in streptozocin (STZ)-induced diabetic retinopathy (DR) rats.

METHODS

Diabetes mellitus (DM) model was induced by intraperitoneal (i.p.) injection of STZ (60 mg/kg) in Sprague-Dawley rats. Diabetic rats were randomized into 3 groups (n=10) according to a random number table, including DM, XST50 and XST100 groups. XST treatment groups were daily i.p. injected with 50 or 100 mg/kg XST for 60 days, respectively. The control and DM groups were given i.p. injection with saline. Blood glucose level and body weight were recorded every week. Histological changes in the retina tissues were observed with hematoxylin-eosin staining. Apoptosis and inflammation related factors, including cleaved caspase-3, glial fifibrillary acidic protein (GFAP), tumor necrosis factor-α (TNF-α) and intercellular cell adhesion molecule-1 (ICAM-1) were detected by Western blot or real-time polymerase chain reaction. Then, the levels of advanced glycation end product (AGE) and its receptor (RAGE) were investigated. Tight junctions proteins (Zonula occludens-1 (ZO-1), Occludin and Claudin-5) of blood-retinal barrier were detected by Western blot. The levels of retinal fifibrosis, transforming growth factor-β1 (TGF-β1)-Smad2/3 signaling pathway were evaluated at last.

RESULTS

There was no signifificant difference in the body weight and blood glucose level between XST and DM groups (P>0.05). Compared with the DM group, XST treatment signifificantly increased the retinal thickness of rats (P<0.05 or P<0.01), and suppressed cleaved caspase-3 expression (P<0.01). XST increased the protein expressions of ZO-1, Occludin and Claudin-5 and decreased the mRNA expressions of matrix metalloproteinase 2 (MMP-2) and MMP-9 (P<0.05 or P<0.01). Moreover, XST signifificantly reduced the productions of AGE and RAGE proteins in the retina of rats (P<0.05 or P<0.01), suppressed the over-expression of TNF-α, and decreased the elevated level of ICAM-1 in retina of rats (P<0.05 or P<0.01). XST signifificantly reduced the levels of α-smooth muscle actin (α-SMA), connective tissue growth factor (CTGF), TGF-β1 and phosphorylation of Smad2/3 protein in rats (P<0.05 or P<0.01).

CONCLUSIONS

XST had protective effects on DR with possible mechanisms of inhibiting the inflammation and apoptosis, up-regulating the expression of tight junction proteins, suppressing the productions of AGE and RAGE proteins, and blocking the TGF-β/Smad2/3 signaling pathway. XST treatment might play a role for the future therapeutic strategy against DR.

Identifying Synergistic Mechanisms of Multiple Ingredients in Shuangbai Tablets against Proteinuria by Virtual Screening and a Network Pharmacology Approach

Shuangbai Tablets (SBT), a traditional herbal mixture, has shown substantial clinical efficacy. However, a systematic mechanism of its active ingredients and pharmacological mechanisms of action against proteinuria continues being lacking. A network pharmacology approach was effectual in discovering the relationship of multiple ingredients and targets of the herbal mixture. This study aimed to identify key targets, major active ingredients, and pathways of SBT against proteinuria by network pharmacology approach combined with thin layer chromatography (TLC). Human phenotype (HP) disease analysis, gene ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, and molecular docking were used in this study. To this end, a total of 48 candidate targets of 118 active ingredients of SBT were identified. Network analysis showed PTGS2, ESR1, and NOS2 to be the three key targets, and beta-sitosterol, quercetin, and berberine were the three major active ingredients; among them one of the major active ingredients, quercetin, was discriminated by TLC. These results of the functional enrichment analysis indicated that the most relevant disease including these 48 candidate proteins is proteinuria, SBT treated proteinuria by sympathetically regulating multiple biological pathways, such as the HIF-1, RAS, AGE-RAGE, and VEGF signaling pathways. Additionally, molecular docking validation suggested that major active ingredients of SBT were capable of binding to HIF-1A and VEGFA of the main pathways. Consequently, key targets, major active ingredients, and pathways based on data analysis of SBT against proteinuria were systematically identified confirming its utility and providing a new drug against proteinuria.

Association between advanced glycation end products, their soluble receptor, and mortality in the general population: Results from the CARLA study

BACKGROUND

Advanced glycation end products (AGEs) in the plasma are associated with a number of age-related diseases that possibly lead to reduced longevity. However, previous studies showed large inconsistencies in the association between AGEs or their soluble receptor (sRAGE) and mortality. We studied this association in a cohort study of general population and assessed the potential changes in this association over time.

METHODS

We used data of 958 men and 802 women from the general population in Halle, Germany with a follow up of 12 years. The associations were assessed by means of Kaplan-Meyer survival curves and multivariable and time-varying Cox-regression.

RESULTS

AGEs and sRAGE were either not or only weakly (and in the other direction than expected) associated with all-cause mortality after 12 years follow-up in men and women (AGEs: Hazard ratio (HR) = 0.93, 95% confidence interval (95%CI) = 0.83-1.05 for men; HR = 0.88, 95%CI = 0.74-1.05 for women; sRAGE: HR = 1.08, 95%CI = 0.95-1.23 for men; HR = 1.10, 95%CI = 0.92-1.30 for women). There was no change of the predictive values over the follow up time. Sub-analyses with participants with and without AGEs-related conditions (diabetes mellitus and decreased renal function), with age stratified groups (younger (<65 years) and older (≥65 years) participants), with cardiovascular disease mortality as the outcome and the AGE/sRAGE ratio as predictor provided similar results.

CONCLUSIONS

Our findings suggest a lack of the expected association with mortality and contribute to the inconsistent findings for plasma-measured AGEs, sRAGE, and AGE/sRAGE ratio.

AGE-RAGE Stress in the Pathophysiology of Atrial Fibrillation and Its Treatment

Atrial fibrillation (AF) is the most common of cardiac arrhythmias. Mechanisms such as atrial structural remodeling and electrical remodeling have been implicated in the pathogenesis of AF. The data to date suggest that advanced glycation end products (AGEs) and its cell receptor RAGE (receptor for AGE) and soluble receptor (sRAGE) are involved in the pathogenesis of AF. This review focuses on the role of AGE-RAGE axis in the pathogenesis of AF. Interaction of AGE with RAGE generates reactive oxygen species, cytokines, and vascular cell adhesion molecules. sRAGE is a cytoprotective agent. The data show that serum levels of AGE and sRAGE, and expression of RAGE, are elevated in AF patients. Elevated levels of sRAGE did not protect the development of AF. This might be due to greater elevation of AGE than sRAGE. Measurement of AGE-RAGE stress (AGE/sRAGE) would be appropriate as compared with measurement of AGE or RAGE or sRAGE alone in AF patients. AGE and its interaction with RAGE can induce AF through alteration in cellular protein and extracellular matrix. AGE and its interaction with RAGE induce atrial structural and electrical remodeling. The treatment strategy should be directed toward reduction in AGE levels, suppression of RAGE expression, blocking of binding of AGE to RAGE, and elevation of sRAGE and antioxidants. In conclusion, AGE-RAGE axis is involved in the development of AF through atrial structural and electrical remodeling. The treatment modalities for AF should include lowering of AGE, suppression of RAGE, elevation of sRAGE, and use of antioxidants.

Stem Cells from Human Exfoliated Deciduous Teeth Ameliorate Diabetic Nephropathy In Vivo and In Vitro by Inhibiting Advanced Glycation End Product-Activated Epithelial-Mesenchymal Transition

Diabetic nephropathy (DN) is a major cause of chronic kidney disease. It has been proven that mesenchymal stem cells (MSCs) have therapeutic effects on kidney disease. Stem cells from human exfoliated deciduous teeth (SHED) are MSCs that are derived from dental pulps in exfoliated deciduous teeth from young patients and therefore have a high proliferation rate and an easy access. Hence, we aimed to explore the effect of SHED on DN in Goto-Kakizaki (GK) rats. SHED were administered via the tail vein. Blood glucose, serum triglycerides and cholesterol, body weight, and urinary albumin were measured before and after administration. At 8 weeks after administration, real-time PCR, immunohistochemistry (IHC), and electron microscopy were employed to examine pathological changes in glomerular and tubulointerstitial tissue. Kidney weight and serum IL-1, IL-10, TNF-α, TGF-β, and HGF levels were measured. SHED engraftment in the kidneys was detected by transfecting green fluorescence protein (GFP). Type II epithelial-mesenchymal transition (EMT) in the tubule-interstitial and arteriolar regions has been reported to be an important pathological characteristic of DN. This study is the first to apply a transwell system for coculture to explore the effects of MSCs on the EMT of human proximal tubular epithelial (HK-2) cells. The effects of SHED on advanced glycation end product- (AGE-) activated EMT in HK-2 cells were explored by real-time PCR and western blot. At 8 weeks after administration, renal injury, including hyperglycemia, hyperlipidemia, increased urinary albumin excretion, ECM accumulation, and a fractional mesangial area, was dramatically attenuated. The serum levels of IL-1, TNF-α, and TGF-β were significantly downregulated, whereas the serum levels of IL-10 and HGF were upregulated by SHED. GFP expression confirmed the engraftment of SHED in diabetic kidneys. In addition, cocultured SHED inhibited AGE-induced EMT in HK-2 cells. In conclusion, SHED offer a novel potential effective therapeutic approach for ameliorating DN.

Advanced glycation end products and their ratio to soluble receptor are associated with limitations in physical functioning only in women: results from the CARLA cohort

BACKGROUND

Advanced glycation end products (AGEs), modifications of proteins or amino acids, are increasingly produced and accumulated with age-related diseases. Recent studies suggested that the ratio of AGEs and their soluble receptor (sRAGE) is a more accurate biomarker for age-related diseases than each separately. We aim to investigate whether this also applies for physical functioning in a broad age-spectrum.

METHODS

AGE and sRAGE levels, and physical functioning (SF-12 questionnaire) of 967 men and 812 women (45-83 years) were measured in the CARLA study. We used ordinal logistic regression to examine associations between AGEs, sRAGE, and AGE/sRAGE ratio with physical functioning in sex- and age-stratified models.

RESULTS

Higher levels of AGEs and AGE/sRAGE ratio were associated with lower physical functioning only in women, even after consideration of classical lifestyle and age-related factors (education, BMI, smoking, alcohol consumption, diet, creatinine clearance, diabetes mellitus, lipid lowering and antihypertensive drugs) (odds ratio (OR) =0.86, 95%confidence interval = 0.74-0.98 and OR = 0.86, 95%CI = 0.75-0.98 for AGEs and AGE/sRAGE ratio respectively). We could not demonstrate a significant difference across age.

CONCLUSIONS

We showed a sex-specific association between physical functioning and AGEs and AGE/sRAGE, but no stronger associations of the latter with physical functioning. Further investigation is needed in the pathophysiology of this association.

[Mechanism of Shenbing decoction Ⅲ in the treatment of proteinuria in chronic kidney disease: a network pharmacology-based study]

OBJECTIVE

To identify the main active components in Shenbing decoction Ⅲ and their targets and explore the mechanism by which Shenbing decoction Ⅲ alleviates proteinuria in chronic kidney disease (CKD) based on network pharmacology.

METHODS

The active components of Shenbing decoction Ⅲ and their potential targets, along with the oral bioavailability and drug-like properties of each component were searched in the TCMSP database. The proteinuria-related targets were searched in the GeneCards database. The active component-target network was constructed using Cytoscape software, and the acquired information of the targets from ClueGO was used for enrichment analysis of the gene pathways.

RESULTS

A total of 102 active components were identified from Shenbing decoction Ⅲ. These active components acted on 126 targets, among which 69 were related to proteinuria. Enrichment analysis revealed fluid shear stress- and atherosclerosisrelated pathways as the highly significant pathways in proteinuria associated with CKD.

CONCLUSIONS

We preliminarily validated the prescription of Shenbing decoction Ⅲ and obtained scientific evidence that supported its use for treatment of proteinuria in CKD. The findings in this study provide a theoretical basis for further study of the mechanism of Shenbing decoction Ⅲ in the treatment of proteinuria in CKD.

The ratio of AGE to sRAGE independently associated with albuminuria in hypertensive patients

BACKGROUND

Soluble receptor for advanced glycation end-products (sRAGE) and advanced glycation end-products (AGE) have been associated with risks of cardiovascular disease. Because sRAGE is regarded as a scavenger to AGE, we hypothesized that the ratio of AGE to sRAGE (AGE/sRAGE) is associated with albuminuria in hypertensive patients.

METHODS

In this cross-sectional study, a total of 104 patients with essential hypertension were recruited. Hypertension was defined as a systolic blood pressure ≥ 140 mmHg, a diastolic blood pressure ≥ 90 mmHg, or use of antihypertensive treatment. Albuminuria was defined as albumin excretion rate ≧ 20 μg/min. Multivariate logistic regression analyses were performed to evaluate the association between AGE/sRAGE and albuminuria.

RESULTS

Among the 104 patients, 30 (28.8%) patients had albuminuria and 74 (71.2%) patients did not. Patients with albuminuria had higher AGE (2.15 vs. 1.71 μg/mL), lower sRAGE (424.5 vs. 492.5 pg/ml) and higher AGE/sRAGE (3.79 vs. 3.29 μg/pg) than those without albuminuria. Multivariate logistic regression model revealed that AGE/sRAGE (OR = 1.131, 95% CI = 1.001-1.278, P = 0.048) was independently associated with albuminuria. There was no significant relationship between AGE and sRAGE alone with albuminuria.

CONCLUSION

This study suggests that the ratio of AGE to sRAGE may be a surrogate biomarker for microvascular injury. Further prospective studies of the prognostic value of the ratio in relation to microvasular injury are needed.

Role of the Soluble Receptor for Advanced Glycation End Products (sRAGE) as a Prognostic Factor for Mortality in Hemodialysis and Peritoneal Dialysis Patients

End-stage renal disease patients on dialysis (CKD-G5D) have a high mortality rate due to cardiovascular diseases (CVD). In these patients, inflammation, oxidative stress, and uremia increase the production of glycation products (AGEs) which in turn accelerate CVD onset and progression. Recently, attention has been given to the soluble receptor for AGEs (sRAGE) as a marker of inflammation, oxidative stress, atherosclerosis, and heart failure in CKD-G5D. However, its association with patient outcomes is still under debate. Our aim is to explore whether sRAGE may be a predictor of mortality in CKD-G5D. We studied 123 CKD-G5D for 24 months. Of these patients, 56 were on hemodialysis (HD) and 67 on peritoneal dialysis (PD). Demographic, anthropometric, biochemical, and clinical data were recorded. sRAGE was quantified by enzyme-linked immunosorbent assay. sRAGE was a predictor of mortality at 2-year follow-up. Each increase of 100 pg/mL in sRAGE levels was associated with an approximately 7% increased risk of mortality. Furthermore, in the entire study group, as well as in PD and HD patient subgroups, sRAGE was positively correlated with brain natriuretic peptide (BNP) levels. Mortality rates as well as sRAGE levels in patients who died did not differ between PD and HD patients. In conclusion, the positive association observed with BNP levels suggests a role for sRAGE as a prognostic factor for mortality in CKD-G5D patients displaying an active process of cardiac remodeling.

Is there any evidence that AGE/sRAGE is a universal biomarker/risk marker for diseases?

Advanced glycation end products (AGE) and its cell-bound receptor called receptor for AGE (RAGE) are implicated in the pathogenesis of numerous diseases. Soluble receptor for AGE (sRAGE) counteracts the adverse effects of AGE-RAGE interaction by competing with RAGE for binding with AGE. Low levels of serum sRAGE have been proposed as a biomarker for diseases. However, the serum levels of sRAGE in diabetes and end-stage renal disease (ESRD) are elevated. Thus, low levels of sRAGE cannot be a universal biomarker. An elevated ratio of AGE/sRAGE was then proposed as a universal biomarker. However, evidence was not provided for this new biomarker. The objective of this paper is to provide evidence in support of elevated AGE/sRAGE being a universal biomarker. The data for serum levels of AGE, sRAGE, and ratio of AGE/sRAGE were collected from patients with low serum sRAGE [non-ST-elevation myocardial infarction (NSTEMI), hyperthyroidism (HT), thoracic aortic aneurysm (TAA),and hypercholesterolemia (HC)], and with high serum levels of sRAGE [type-2 diabetes (T2D) and ESRD], and control subjects. The serum levels of AGE and ratio of AGE/sRAGE were higher in all types of patients irrespective of low or high serum sRAGE as compared to control subjects. Reasons are provided as to why AGE or sRAGE individually cannot be considered as a universal biomarker. In conclusion, the evidence supports the validity of the high ratio AGE/sRAGE as a universal biomarker/risk marker for diseases.

AGE-RAGE Stress, Stressors, and Antistressors in Health and Disease

Adverse effects of advanced glycation end-products (AGEs) on the tissues are through nonreceptor- and receptor-mediated mechanisms. In the receptor-mediated mechanism, interaction of AGEs with its cell-bound receptor of AGE (RAGE) increases generation of oxygen radicals, activates nuclear factor-kappa B, and increases expression and release of pro-inflammatory cytokines resulting in the cellular damage. The deleterious effects of AGE and AGE-RAGE interaction are coined as "AGE-RAGE stress." The body is equipped with defense mechanisms to counteract the adverse effects of AGE and RAGE through endogenous enzymatic (glyoxalase 1, glyoxalase 2) and AGE receptor-mediated (AGER1, AGER2) degradation of AGE, and through elevation of soluble receptor of AGE (sRAGE). Exogenous defense mechanisms include reduction in consumption of AGE, prevention of AGE formation, and downregulation of RAGE expression. We have coined AGE and RAGE as "stressors" and the defense mechanisms as "anti-stressors." AGE-RAGE stress is defined as a shift in the balance between stressors and antistressors in the favor of stressors. Measurements of stressors or antistressors alone would not assess AGE-RAGE stress. For true assessment of AGE-RAGE stress, the equation should include all the stressors and antistressors. The equation for AGE-RAGE stress, therefore, would be the ratio of AGE + RAGE/sRAGE + glyoxalase1 + glyoxalase 2 + AGER1 +AGER2. This is, however, not practical in patients. AGE-RAGE stress may be assessed simply by the ratio of AGE/sRAGE. A high ratio of AGE/sRAGE indicates a relative shift in stressors from antistressors, suggesting the presence of AGE-RAGE stress, resulting in tissue damage, initiation, and progression of the diseases and their complications.

Do Advanced Glycation End Products and Its Receptor Play a Role in Pathophysiology of Hypertension?

There is a close relationship between arterial stiffness and blood pressure. The studies suggest that the advanced glycation end products (AGEs) and its cell receptor (RAGE) are involved in the arterial stiffness in two ways: changes in arterial structure and vascular function. Plasma levels of AGEs and expression of RAGE are elevated, while the levels of soluble RAGE (sRAGE) and endogenous secretory RAGE (esRAGE) are lowered in patients with hypertension (HTN). There is a positive correlation between plasma levels of AGEs and arterial stiffness, and an inverse association between arterial stiffness/HTN, and serum levels of sRAGE and esRAGE. Various measures can reduce the levels of AGEs and expression of RAGE, and elevate sRAGE. Arterial stiffness and blood pressure could be reduced by lowering the serum levels of AGEs, and increasing the levels of sRAGE. Levels of AGEs can be lowered by reducing the consumption of AGE-rich diet, short duration of cooking in moist heat at low temperature, and cessation of cigarette smoking. Drugs such as aminoguanidine, vitamins, angiotensin-converting enzyme (ACE) inhibitors, angiotensin-II receptor blockers, statins, and metformin inhibit AGE formation. Alagebrium, an AGE breakers reduces levels of AGEs. Clinical trials with some drugs tend to reduce stiffness. Systemic administration of sRAGE has beneficial effect in animal studies. In conclusion, AGE-RAGE axis is involved in arterial stiffness and HTN. The studies suggest that inhibition of AGEs formation, reduction of AGE consumption, blockade of AGE-RAGE interaction, suppression of RAGE expression, and exogenous administration of sRAGE may be novel therapeutic strategies for treatment of arterial stiffness and HTN.