High Plasma sRAGE (Soluble Receptor for Advanced Glycation End Products) Is Associated With Slower Carotid Intima-Media Thickness Progression and Lower Risk for First-Time Coronary Events and Mortality

The Gly82Ser polymorphism in the receptor for advanced glycation endproducts increases the risk for coronary events in the general population

The receptor for advanced glycation endproducts (RAGE) has pro-inflammatory and pro-atherogenic effects. Low plasma levels of soluble RAGE (sRAGE), a decoy receptor for RAGE ligands, have been associated with increased risk for major adverse coronary events (MACE) in the general population. We performed a genome-wide association study to identify genetic determinants of plasma sRAGE in 4338 individuals from the cardiovascular arm of the Malmö Diet and Cancer study (MDC-CV). Further, we explored the associations between these genetic variants, incident first-time MACE and mortality in 24,640 unrelated individuals of European ancestry from the MDC cohort. The minor alleles of four single nucleotide polymorphisms (SNPs): rs2070600, rs204993, rs116653040, and rs7306778 were independently associated with lower plasma sRAGE. The minor T (vs. C) allele of rs2070600 was associated with increased risk for MACE [HR 1.13 95% CI (1.02-1.25), P = 0.016]. Neither SNP was associated with mortality. This is the largest study to demonstrate a link between a genetic sRAGE determinant and CV risk. Only rs2070600, which enhances RAGE function by inducing a Gly82Ser polymorphism in the ligand-binding domain, was associated with MACE. The lack of associations with incident MACE for the other sRAGE-lowering SNPs suggests that this functional RAGE modification is central for the observed relationship.

Proteomic insights into the associations between obesity, lifestyle factors, and coronary artery disease

BACKGROUND

We aimed to investigate the protein pathways linking obesity and lifestyle factors to coronary artery disease (CAD).

METHODS

Summary-level genome-wide association statistics of CAD were obtained from the CARDIoGRAMplusC4D consortium (60,801 cases and 123,504 controls) and the FinnGen study (R8, 39,036 cases and 303,463 controls). Proteome-wide Mendelian randomization (MR) analysis was conducted to identify CAD-associated blood proteins, supplemented by colocalization analysis to minimize potential bias caused by linkage disequilibrium. Two-sample MR analyses were performed to assess the associations of genetically predicted four obesity measures and 13 lifestyle factors with CAD risk and CAD-associated proteins' levels. A two-step network MR analysis was conducted to explore the mediating effects of proteins in the associations between these modifiable factors and CAD.

RESULTS

Genetically predicted levels of 41 circulating proteins were associated with CAD, and 17 of them were supported by medium to high colocalization evidence. PTK7 (protein tyrosine kinase-7), RGMB (repulsive guidance molecule BMP co-receptor B), TAGLN2 (transgelin-2), TIMP3 (tissue inhibitor of metalloproteinases 3), and VIM (vimentin) were identified as promising therapeutic targets. Several proteins were found to mediate the associations between some modifiable factors and CAD, with PCSK9, C1S, AGER (advanced glycosylation end product-specific receptor), and MST1 (mammalian Ste20-like kinase 1) exhibiting highest frequency among the mediating networks.

CONCLUSIONS

This study suggests pathways explaining the associations of obesity and lifestyle factors with CAD from alterations in blood protein levels. These insights may be used to prioritize therapeutic intervention for further study.

Biomarkers of cellular senescence and risk of death in humans

A robust and heterogenous secretory phenotype is a core feature of most senescent cells. In addition to mediators of age-related pathology, components of the senescence associated secretory phenotype (SASP) have been studied as biomarkers of senescent cell burden and, in turn, biological age. Therefore, we hypothesized that circulating concentrations of candidate senescence biomarkers, including chemokines, cytokines, matrix remodeling proteins, and growth factors, could predict mortality in older adults. We assessed associations between plasma levels of 28 SASP proteins and risk of mortality over a median follow-up of 6.3 years in 1923 patients 65 years of age or older with zero or one chronic condition at baseline. Overall, the five senescence biomarkers most strongly associated with an increased risk of death were GDF15, RAGE, VEGFA, PARC, and MMP2, after adjusting for age, sex, race, and the presence of one chronic condition. The combination of biomarkers and clinical and demographic covariates exhibited a significantly higher c-statistic for risk of death (0.79, 95% confidence interval (CI): 0.76-0.82) than the covariates alone (0.70, CI: 0.67-0.74) (p < 0.001). Collectively, these findings lend further support to biomarkers of cellular senescence as informative predictors of clinically important health outcomes in older adults, including death.

The role of sRAGE in cardiovascular diseases

Advanced glycation end products (AGEs), by-products of glucose metabolism, have been linked to the emergence of cardiovascular disorders (CVD). AGEs can cause tissue damage in four different ways: (1) by altering protein function, (2) by crosslinking proteins, which makes tissue stiffer, (3) by causing the generation of free radicals, and (4) by activating an inflammatory response after binding particular AGE receptors, such as the receptor for advanced glycation end products (RAGE). It is suggested that the soluble form of RAGE (sRAGE) blocks ligand-mediated pro-inflammatory and oxidant activities by serving as a decoy. Therefore, several studies have investigated the possible anti-inflammatory and anti-oxidant characteristics of sRAGE, which may help lower the risk of CVD. According to the results of various studies, the relationship between circulating sRAGE, cRAGE, and esRAGE and CVD is inconsistent. To establish the potential function of sRAGE as a therapeutic target in the treatment of cardiovascular illnesses, additional studies are required to better understand the relationship between sRAGE and CVD. In this review, we explored the potential function of sRAGE in different CVD, highlighting unanswered concerns and outlining the possibilities for further investigation.

Plasma AGE and Oxidation Products, Renal Function, and Preeclampsia in Pregnant Women with Type 1 Diabetes: A Prospective Observational Study

Aims

We aimed to determine whether plasma advanced glycation end products or oxidation products (AGE/oxidation-P) predict altered renal function and/or preeclampsia (PE) in pregnant women with type 1 diabetes.

Methods

Prospectively, using a nested case-control design, we studied 47 pregnant women with type 1 diabetes, of whom 23 developed PE and 24 did not. Nineteen nondiabetic, normotensive pregnant women provided reference values. In plasma obtained at ~12, 22, and 32 weeks' gestation (visits 1, 2, and 3; V1-V3), we measured five AGE products (carboxymethyllysine (CML), carboxyethyl-lysine (CEL), methylglyoxal-hydroimidazolone (MGH1), 3-deoxyglucosone hydroimidazolone (3DGH), and glyoxal-hydroimidazolone (GH1)) and four oxidation products (methionine sulfoxide (MetSO), 2-aminoadipic acid (2-AAA), 3-nitrotyrosine (3NT), and dityrosine (DT)), by liquid chromatography/mass spectroscopy. Clinical outcomes were "estimated glomerular filtration rate" (eGFR) at each visit and onset of PE.

Results

In diabetic women, associations between AGE/oxidation-P and eGFR were found only in those who developed PE. In this group, CEL, MGH1, and GH1 at V2 and CML, CEL, MGH1, and GH1 at V3 were inversely associated with contemporaneous eGFR, while CEL, MGH1, 3DGH, and GH1 at V2 were inversely associated with eGFR at V3 (all p < 0.05). There were no associations of plasma AGE or oxidation-P with pregnancy-related development of proteinuria or PE.

Conclusions

Inverse associations of second and early third trimester plasma AGE with eGFR among type 1 diabetic women who developed PE suggest that these patients constitute a subset susceptible to AGE-mediated injury and thus to cardiorenal complications later in life. However, AGE/oxidation-P did not predict PE in type 1 diabetic women.

A Study on the Protective Effect of sRAGE-MSCs in a Rodent Reperfusion Model of Myocardial Infarction

Acute myocardial infarction (AMI) is one of the major leading causes of death in humans globally. Recently, increased levels of recruited macrophages and AGE-albumin were observed in the hearts of humans and animals with acute myocardial infarction. Thus, the purposes of this study were to investigate whether the elevated levels of AGE-albumin from activated macrophage cells are implicated in ischemia-induced cardiomyocyte death and to develop therapeutic strategies for AMI based on its underlying molecular mechanisms with respect to AGEs. The present study demonstrated that activated macrophages and AGE-albumin were observed in heart tissues obtained from humans and rats with AMI incidences. In the cellular model of AMI, it was found that increased expression of AGE-albumin was shown to be co-localized with macrophages, and the presence of AGE-albumin led to increased expression of RAGE through the mitogen-activated protein kinase pathway. After revealing cardiomyocyte apoptosis induced by toxicity of the AGE-RAGE system, sRAGE-secreting MSCs were generated using the CRISPR/Cas9 platform to investigate the therapeutic effects of sRAGE-MSCs in an AMI rat model. Gene-edited sRAGE-MSCs showed greater therapeutic effects against AMI pathogenesis in rat models compared to mock MSCs, and promising results of the functional improvement of stem cells could result in significant improvements in the clinical management of cardiovascular diseases.

Biomarkers in Systemic Juvenile Idiopathic Arthritis, Macrophage Activation Syndrome and Their Importance in COVID Era

Systemic juvenile idiopathic arthritis (sJIA) and its complication, macrophage activation syndrome (sJIA-MAS), are rare but sometimes very serious or even critical diseases of childhood that can occasionally be characterized by nonspecific clinical signs and symptoms at onset-such as non-remitting high fever, headache, rash, or arthralgia-and are biologically accompanied by an increase in acute-phase reactants. For a correct positive diagnosis, it is necessary to rule out bacterial or viral infections, neoplasia, and other immune-mediated inflammatory diseases. Delays in diagnosis will result in late initiation of targeted therapy. A set of biomarkers is useful to distinguish sJIA or sJIA-MAS from similar clinical entities, especially when arthritis is absent. Biomarkers should be accessible to many patients, with convenient production and acquisition prices for pediatric medical laboratories, as well as being easy to determine, having high sensitivity and specificity, and correlating with pathophysiological disease pathways. The aim of this review was to identify the newest and most powerful biomarkers and their synergistic interaction for easy and accurate recognition of sJIA and sJIA-MAS, so as to immediately guide clinicians in correct diagnosis and in predicting disease outcomes, the response to treatment, and the risk of relapses. Biomarkers constitute an exciting field of research, especially due to the heterogeneous nature of cytokine storm syndromes (CSSs) in the COVID era. They must be selected with utmost care-a fact supported by the increasingly improved genetic and pathophysiological comprehension of sJIA, but also of CSS-so that new classification systems may soon be developed to define homogeneous groups of patients, although each with a distinct disease.

Altered expression of a disintegrin and metalloproteinase 10 in peripheral blood mononuclear cells in type 2 diabetes mellitus patients with the acute coronary syndrome: a pilot study

PURPOSE

Advanced glycation end products (AGEs) are responsible for the complications in type 2 diabetes mellitus (T2DM) patients by acting via its receptor (RAGE). The soluble form of RAGE (sRAGE) prevents the harmful effects of AGE-RAGE signalling. The sRAGE is produced either by alternate splicing (esRAGE) or proteolytic RAGE cleavage by a disintegrin and metalloproteinase 10 (ADAM10). Hence, the study aimed to compare the expression of ADAM10 in peripheral blood mononuclear cell (PBMC), serum sRAGE and esRAGE levels in T2DM patients with and without acute coronary syndrome (ACS).

METHODS

Forty-five T2DM patients with ACS and 45 age, gender and duration of DM-matched T2DM patients without ACS were recruited. Serum sRAGE and esRAGE levels were measured by enzyme-linked immunosorbent assay. The expression of ADAM10 in PBMC was determined by quantitative reverse transcription-polymerase chain reaction.

RESULTS

The expression of ADAM10 in PBMC and serum sRAGE levels were significantly lower in T2DM patients with ACS than in T2DM patients without ACS (p < 0.001). Serum sRAGE levels and expression of ADAM10 in PBMC were positively correlated with each other and negatively correlated with markers of cardiac injury and glycaemic status (p < 0.05). Simple logistic regression showed that the models containing the expression of ADAM10 and serum sRAGE level could predict the ACS risk among T2DM patients. ROC analysis showed that both might be used for ACS diagnosis in T2DM patients.

CONCLUSION

Reduced expression of ADAM10 in PBMC might be responsible for lower serum sRAGE levels, predisposing T2DM patients to high ACS risk.

Receptor for Advanced Glycation End Products (RAGE): A Pivotal Hub in Immune Diseases

As a critical molecule in the onset and sustainment of inflammatory response, the receptor for advanced glycation end products (RAGE) has a variety of ligands, such as advanced glycation end products (AGEs), S100/calcium granule protein, and high-mobility group protein 1 (HMGB1). Recently, an increasing number studies have shown that RAGE ligand binding can initiate the intracellular signal cascade, affect intracellular signal transduction, stimulate the release of cytokines, and play a vital role in the occurrence and development of immune-related diseases, such as systemic lupus erythematosus, rheumatoid arthritis, and Alzheimer’s disease. In addition, other RAGE signaling pathways can play crucial roles in life activities, such as inflammation, apoptosis, autophagy, and endoplasmic reticulum stress. Therefore, the strategy of targeted intervention in the RAGE signaling pathway may have significant therapeutic potential, attracting increasing attention. In this paper, through the systematic induction and analysis of RAGE-related signaling pathways and their regulatory mechanisms in immune-related diseases, we provide theoretical clues for the follow-up targeted intervention of RAGE-mediated diseases.

Differential Regulation of Circulating Soluble Receptor for Advanced Glycation End Products (sRAGEs) and Its Ligands S100A8/A9 Four Weeks Post an Exercise Intervention in a Cohort of Young Army Recruits

Apart from its beneficial effects on cardiovascular risk factors, an anti-inflammatory effect of exercise is strongly implicated. Yet, data regarding the effect of an exercise intervention on healthy individuals are limited and contradictory. The present study aimed to investigate the effects of a physical activity intervention on the soluble form of the receptor for advanced glycation end products (sRAGEs) and its ligands S100A8/A9. A total of 332 young army recruits volunteered and 169 completed the study. The participants underwent the standard basic training of Greek army recruits. IL-6, IL-1β, S100A8/A9, and sRAGEs were measured at the beginning and at the end of the training period. Primary rodent adult aortic smooth muscle cells (ASMCs) were analyzed for responsiveness to direct stimulation with S100A8/A9 alone or in combination with sRAGEs. At the end of the training period, we observed a statistically significant reduction in S100A8/A9 (630.98 vs. 472.12 ng/mL, p = 0.001), IL-1β (9.39 [3.8, 44.14] vs. 5.03 [2.44, 27.3] vs. pg/mL, p = 0.001), and sRAGEs (398.38 vs. 220.1 pg/mL, p = 0.001). IL-6 values did not change significantly after exercise. S100A8/A9 reduction was positively correlated with body weight (r = 0.236 [0.095, 0.370], p = 0.002) and BMI (r = 0.221 [0.092, 0.346], p = 0.004). Direct stimulation of ASMCs with S100A8/A9 increased the expression of IL-6, IL-1β, and TNF-α and, in the presence of sRAGEs, demonstrated a dose-dependent inhibition. A 4-week military training resulted in significant reduction in the pro-inflammatory cytokines IL-1β and S100A8/A9 complex. The observed reduction in sRAGEs may possibly reflect diminished RAGE axis activation. Altogether, our findings support the anti-inflammatory properties of physical activity.

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.

Circulating Advanced Glycation End Products and Their Soluble Receptors in Relation to All-Cause and Cardiovascular Mortality: A Systematic Review and Meta-analysis of Prospective Observational Studies

Advanced glycation end products (AGEs) are involved in the development of several age-related complications. The protective role of soluble receptors for AGEs (sRAGE) against deleterious effects of AGEs has been indicated in several studies. However, findings on the association of AGEs or sRAGE with mortality are equivocal. In this meta-analysis we aimed to present a quantitative estimation of the association between circulating AGEs or sRAGE and all-cause or cardiovascular disease (CVD) mortality. A comprehensive literature search was performed to determine relevant publications through the online databases including PubMed, Scopus, and Web of Science up to 29 November 2020. Prospective observational studies assessing the association between circulating AGEs or sRAGE and all-cause or CVD mortality were included. Seven studies with a total of 3718 participants and 733 mortality cases (345 CVD deaths) were included in the meta-analysis for assessing the association between circulating AGEs and mortality. Our results showed that higher circulating AGEs were associated with increased risk of all-cause (pooled effect measure: 1.05; 95% CI: 1.01, 1.09; P = 0.018, I2 = 77.7%) and CVD mortality (pooled effect measure: 1.08; 95% CI: 1.01, 1.14; P = 0.015, I2 = 80.2%), respectively. The association between sRAGE and mortality was assessed in 14 studies with a total of 16,335 participants and 2844 mortality cases (419 CVD deaths). Serum concentrations of sRAGE were not associated with the risk of all-cause mortality (pooled effect measure: 1.01; 95% CI: 1.00, 1.01; P = 0.205, I2 = 75.5%), whereas there was a significant link between sRAGE and the risk of CVD mortality (pooled effect measure: 1.02; 95% CI: 1.00, 1.04; P = 0.02, I2 = 78.9%). Our findings showed that a higher serum AGE concentration was associated with increased risk of all-cause and CVD mortality. In addition, higher circulating sRAGE was related to increased risk of CVD mortality. This review was registered at PROSPERO as CRD42021236559.

Soluble Receptor for Advanced Glycation End-products regulates age-associated Cardiac Fibrosis

Myocardial aging increases the cardiovascular risk in the elderly. The Receptor for Advanced Glycation End-products (RAGE) is involved in age-related disorders. The soluble isoform (sRAGE) acts as a scavenger blocking the membrane-bound receptor activation. This study aims at investigating RAGE contribution to age-related cardiac remodeling.

We analyzed the cardiac function of three different age groups of female Rage-/- and C57BL/6N (WT) mice: 2.5- (Young), 12- (Middle-age, MA) and 21-months (Old) old. While aging, Rage-/- mice displayed an increase in left ventricle (LV) dimensions compared to age-matched WT animals, with the main differences observed in the MA groups. Rage-/- mice showed higher fibrosis and a larger number of α-Smooth Muscle Actin (SMA)+ cells with age, along with increased expression of pro-fibrotic Transforming Growth Factor (TGF)-β1 pathway components. RAGE isoforms were undetectable in LV of WT mice, nevertheless, circulating sRAGE declined with aging and inversely associated with LV diastolic dimensions. Human cardiac fibroblasts stimulated with sRAGE exhibited a reduction in proliferation, pro-fibrotic proteins and TGF-beta Receptor 1 (TGFbR1) expression and Smad2-3 activation. Finally, sRAGE administration to MA WT animals reduced cardiac fibrosis.

Hence, our work shows that RAGE associates with age-dependent myocardial changes and indicates sRAGE as an inhibitor of cardiac fibroblasts differentiation and age-dependent cardiac fibrosis.

Receptor for advanced glycation end-products axis and coronavirus disease 2019 in inflammatory bowel diseases: A dangerous liaison?

Compelling evidence supports the crucial role of the receptor for advanced glycation end-products (RAGE) axis activation in many clinical entities. Since the beginning of the coronavirus disease 2019 pandemic, there is an increasing concern about the risk and handling of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in inflammatory gastrointestinal disorders, such as inflammatory bowel diseases (IBD). However, clinical data raised during pandemic suggests that IBD patients do not have an increased risk of contracting SARS-CoV-2 infection or develop a more severe course of infection. In the present review, we intend to highlight how two potentially important contributors to the inflammatory response to SARS-CoV-2 infection in IBD patients, the RAGE axis activation as well as the cross-talk with the renin-angiotensin system, are dampened by the high expression of soluble forms of both RAGE and the angiotensin-converting enzyme (ACE) 2. The soluble form of RAGE functions as a decoy for its ligands, and soluble ACE2 seems to be an additionally attenuating contributor to RAGE axis activation, particularly by avoiding the transactivation of the RAGE axis that can be produced by the virus-mediated imbalance of the ACE/angiotensin II/angiotensin II receptor type 1 pathway.

The use of the soluble receptor for advanced glycation-end products (sRAGE) as a potential biomarker of disease risk and adverse outcomes

The soluble receptor for advanced glycation end-products (sRAGE) has been classically considered a sink for pro-inflammatory RAGE ligands and as such has been associated with protection from inflammatory stress and disease. An alternative, though not mutually exclusive view is that high levels of sRAGE in circulation reflect the overstimulation of cell surface RAGE which if persistent, lead to the amplification of pro-inflammatory processes and the exacerbation of pathological states. With these two scenarios in mind this review focuses on the potential role of sRAGE as a prospective biomarker of disease risk and adverse outcomes.

•

The prognostic value of measuring sRAGE levels in blood is subjected to debate.

•

Raised sRAGE levels may result from the overstimulation of cell surface RAGE.

•

Raised sRAGE may reflect chronic inflammation and multimorbidity rather than a healthy state.

•

sRAGE is a promising biomarker of disease risk and adverse outcomes.

Higher sRAGE Levels Predict Mortality in Frail Older Adults with Cardiovascular Disease

INTRODUCTION

The evidence that blood levels of the soluble receptor for advanced glycation end products (sRAGE) predict mortality in people with cardiovascular diseases (CVD) is inconsistent. To clarify this matter, we investigated if frailty status influences this association.

METHODS

We analysed data of 1,016 individuals (median age, 75 years) from 3 population-based European cohorts, enrolled in the FRAILOMIC project. Participants were stratified by history of CVD and frailty status. Mortality was recorded during 8 years of follow-up.

RESULTS

In adjusted Cox regression models, baseline serum sRAGE was positively associated with an increased risk of mortality in participants with CVD (HR 1.64, 95% CI 1.09-2.49, p = 0.019) but not in non-CVD. Within the CVD group, the risk of death was markedly enhanced in the frail subgroup (CVD-F, HR 1.97, 95% CI 1.18-3.29, p = 0.009), compared to the non-frail subgroup (CVD-NF, HR 1.50, 95% CI 0.71-3.15, p = 0.287). Kaplan-Meier analysis showed that the median survival time of CVD-F with high sRAGE (>1,554 pg/mL) was 2.9 years shorter than that of CVD-F with low sRAGE, whereas no survival difference was seen for CVD-NF. Area under the ROC curve analysis demonstrated that for CVD-F, addition of sRAGE to the prediction model increased its prognostic value.

CONCLUSIONS

Frailty status influences the relationship between sRAGE and mortality in older adults with CVD. sRAGE could be used as a prognostic marker of mortality for these individuals, particularly if they are also frail.

Higher levels of the soluble receptor for advanced glycation end products and lower levels of the extracellular newly identified receptor for advanced glycation end products were associated with lipid-lowering drugs in patients with type 1 diabetes: a comparative cross-sectional study

Background

The receptors for advanced glycation end products (RAGE) are increased in atherosclerotic plaques. Soluble (s)RAGE decreases, whereas the extracellular newly identified receptor for advanced glycation end products (EN-RAGE) increases inflammatory responses mediated by RAGE. The aims were to explore whether sRAGE, EN-RAGE and the EN-RAGE/sRAGE ratio, were associated with the use of lipid-lowering drugs (LLD) and/or antihypertensive drugs (AHD) in patients with type 1 diabetes (T1D).

Methods

Cross-sectional design. T1D patients were consecutively recruited from one diabetes clinic. Blood samples were collected, supplemented with data from electronic health records. sRAGE and EN-RAGE were analysed by enzyme linked immunosorbent assays. An EN-RAGE/sRAGE ratio was calculated. Adjustments were performed with inflammatory and metabolic variables, s-creatinine, depression, smoking, physical inactivity, medication, and cardiovascular complications. Multiple regression analyses were performed.

Results

In this study 283 T1D patients (men 56%, 18–59 years) were included. One-hundred and thirty LLD users compared to 153 non-users had lower levels of the EN-RAGE/sRAGE ratio (P = 0.009), and 89 AHD users compared to 194 non-users had lower levels of sRAGE (P = 0.031). The use of LLD (inversely) (B coefficient − 0.158, P = 0.033) and the use of AHD (B coefficient 0.187, P = 0.023) were associated with the EN-RAGE/sRAGE ratio. sRAGE (Lg10) (per unit) (adjusted odds ratio (AOR) = 3.5, 95% CI = 1.4–9.1, P = 0.009), EN-RAGE (Lg10) (per unit) (inversely) (AOR 0.4, 95% CI = 0.2–1.0, P = 0.046), age (P <  0.001), and triglycerides (P <  0.029), were associated with LLD. sRAGE (Lg10) (per unit) (inversely) (AOR = 0.2, 95% CI = 0.1–0.5, P = 0.001), diabetes duration, triglycerides, s-creatinine, and systolic BP (all P values < 0.043), were associated with AHD.

Conclusions

Higher sRAGE levels and lower EN-RAGE levels were linked to the use of LLD, whereas lower sRAGE levels were linked to the use of AHD. No other variables but the use of LLD and the use of AHD were linked to the EN-RAGE/sRAGE ratio. This may be of major importance as sRAGE is an inhibitor and EN-RAGE is a stimulator of inflammatory processes mediated by RAGE.

The role of soluble receptor for advanced glycation end-products (sRAGE) in the general population and patients with diabetes mellitus with a focus on renal function and overall outcome

Isoforms of the receptor for advanced glycation end-product (RAGE) protein, which lack the transmembrane and the signaling (soluble RAGE or sRAGE) domains are hypothesized to counteract the detrimental action of the full-length receptor by acting as a decoy, and they provide a potential tool to treat RAGE-associated diseases. Multiple studies have explored the relationship between sRAGE and endogenous secretory RAGE and its polymorphism and obesity, metabolic syndrome, atherosclerosis, kidney function, and increased mortality in the general population. In addition, sRAGE may be a key player in the pathogenesis of diabetes mellitus and its microvascular (e.g. kidney disease) as well as macrovascular (e.g. cardiovascular disease) complications. In this review, we focus on the role of sRAGE as a biomarker in these specific areas. As there is a lack of an underlying unifying hypothesis about how sRAGE changes according to the disease condition or risk factor, there is a call to incorporate all three players of the AGE-RAGE axis into a new universal biomarker/risk marker: (AGE + RAGE)/sRAGE. However, the measurement of RAGE in humans is not practical as it is a cell-bound receptor for which tissue is required for analysis. A high AGE/sRAGE ratio may be a valuable alternative and practical universal biomarker/risk marker for diseases associated with the AGE-RAGE axis, irrespective of low or high serum sRAGE concentrations.

Accumulation of advanced glycation end products (AGEs) is associated with the severity of aortic stenosis in patients with concomitant type 2 diabetes

BACKGROUND

Accumulation of advanced glycation end products (AGEs) leads to chronic glycation of proteins and tissue damage, particularly in patients with diabetes mellitus (DM). We aimed to evaluate whether increased accumulation of AGEs in patients with aortic stenosis (AS) and concomitant type 2 diabetes (DM) is associated with AS severity.

METHODS

We prospectively enrolled 76 patients with severe AS (47.1% males; nonDM), aged 68 [66-72] years, and 50 age-matched DM patients with a median blood glucose level of 7.5 [5.9-9.1] mM and glycated hemoglobin (HbA1c) of 6.8 [6.3-7.8]%, scheduled for aortic valve replacement. Valvular expression of AGEs, AGEs receptor (RAGE), interleukin-6 (IL-6), and reactive oxygen species (ROS) induction were evaluated ex vivo by immunostaining and calculated as the extent of positive immunoreactive areas/total sample area. Plasma levels of AGEs and soluble RAGE (sRAGE) were assessed by ELISAs.

RESULTS

Subjects with DM had increased valvular expression of both AGEs (6.6-fold higher, 15.53 [9.96-23.28]%) and RAGE (1.8-fold higher, 6.8 [4.9-8.45]%) compared to nonDM patients (2.05 [1.21-2.58]% and 2.4 [1.56-3.02]%, respectively; both p < 0.001). Plasma levels of AGEs (12-fold higher) and sRAGE (1.3-fold higher) were elevated in DM patients, compared to nonDM (both p < 0.0001). The percentage of valvular ROS-positive (2.28 [1.6-3.09] vs. 1.15 [0.94-1.4]%, p < 0.0001) but not IL-6-positive areas was higher within DM, compared to nonDM valves. In DM patients, the percentage of valvular AGEs- and RAGE-positive areas correlated with HbA1c (r = 0.77, p < 0.0001 and r = 0.30, p = 0.034). Similarly, plasma AGEs and sRAGE levels were associated with HbA1c in the DM group (r = 0.32, p = 0.024 and r = 0.33, p = 0.014, respectively). In all DM patients, we found an association between the amount of valvular AGEs and the disease severity measured as aortic valve area (AVA; r = 0.68, p < 0.0001). Additionally, in DM patients with HbA1c > 7% (n = 24, 48%) we found that valvular expression of AGEs correlated with mean transvalvular pressure gradient (PG_mean; r = 0.45, p = 0.027). Plasma AGEs levels in the whole DM group correlated with AVA (r = - 0.32, p = 0.02), PG_mean (r = 0.31, p = 0.023), and PG_max (r = 0.30, p = 0.03).

CONCLUSIONS

Our study suggests that poorly-controlled diabetes leads to increased AGEs and RAGE valvular accumulation, which at least partially, might result in AS progression in DM patients.

The role of advanced glycation end products in vascular aging: which parameter is the most suitable as a biomarker?

Advanced glycation end products (AGEs) are involved in several pathophysiologic processes in vascular diseases, including progressive loss of elasticity of the vessel wall (arterial stiffness). Circulating soluble receptors for AGEs (sRAGE) act as a decoy and counterbalanced the harmful properties of AGEs as the natural protective factor. We compared the role of circulating or skin-deposed AGEs and sRAGE regarding the natural course of arterial stiffening. In a prospective cohort study, we longitudinally followed 536 general population-based subjects (subsample of Czech post-MONICA study). Aortic pulse-wave velocity (PWV) was measured twice (at baseline and after ~8 years of follow-up) using a SphygmoCor device (AtCor Medical Ltd), and the intraindividual change in PWV per year (∆PWV/year) was calculated. Concentrations of sRAGE and carboxymethyl lysine (circulating AGEs) were assessed at the follow-up visit by ELISA, while skin AGEs were measured using the autofluorescence-based device AGE Reader. Using multiple regressions, we found significant association between ∆PWV/year as a dependent variable, and both, sRAGE and skin AGEs as independent ones (each on its own model). However, the closest associations to ∆PWV/year were found for the ratio of these two factors (skin AGEs/sRAGE) [β coeff = 0.0747 (SE 0.0189), p < 0.0001]. In a categorized manner, subjects with skin AGEs/sRAGE ratio ≥ 3.3 showed about twofold higher risk having ΔPWV/year ≥ 0.2 m/s [adjusted odds ratio was 2.09 (95% CI: 1.35-3.22), p = 0.001]. In contrast, neither circulating AGEs nor circulating AGEs/sRAGE showed any significant relation to ΔPWV/year. In conclusion, skin AGEs/sRAGE ratio seems to be a more sensitive biomarker of vascular aging than these single factors themselves or circulation status of AGEs.