Low Circulating Endogenous Secretory Receptor for AGEs Predicts Cardiovascular Mortality in Patients With End-Stage Renal Disease

RAGE in circulating immune cells is fundamental for hippocampal inflammation and cognitive decline in a mouse model of latent chronic inflammation

BACKGROUND

Latent chronic inflammation has been proposed as a key mediator of multiple derangements in metabolic syndrome (MetS), which are increasingly becoming recognized as risk factors for age-related cognitive decline. However, the question remains whether latent chronic inflammation indeed induces brain inflammation and cognitive decline.

METHODS

A mouse model of latent chronic inflammation was constructed by a chronic subcutaneous infusion of low dose lipopolysaccharide (LPS) for four weeks. A receptor for advanced glycation end products (RAGE) knockout mouse, a chimeric myeloid cell specific RAGE-deficient mouse established by bone marrow transplantation and a human endogenous secretory RAGE (esRAGE) overexpressing adenovirus system were utilized to examine the role of RAGE in vivo. The cognitive function was examined by a Y-maze test, and the expression level of genes was determined by quantitative RT-PCR, western blot, immunohistochemical staining, or ELISA assays.

RESULTS

Latent chronic inflammation induced MetS features in C57BL/6J mice, which were associated with cognitive decline and brain inflammation characterized by microgliosis, monocyte infiltration and endothelial inflammation, without significant changes in circulating cytokines including TNF-α and IL-1β. These changes as well as cognitive impairment were rescued in RAGE knockout mice or chimeric mice lacking RAGE in bone marrow cells. P-selectin glycoprotein ligand-1 (PSGL-1), a critical adhesion molecule, was induced in circulating mononuclear cells in latent chronic inflammation in wild-type but not RAGE knockout mice. These inflammatory changes and cognitive decline induced in the wild-type mice were ameliorated by an adenoviral increase in circulating esRAGE. Meanwhile, chimeric RAGE knockout mice possessing RAGE in myeloid cells were still resistant to cognitive decline and brain inflammation.

CONCLUSIONS

These findings indicate that RAGE in inflammatory cells is necessary to mediate stimuli of latent chronic inflammation that cause brain inflammation and cognitive decline, potentially by orchestrating monocyte activation via regulation of PSGL-1 expression. Our results also suggest esRAGE-mediated inflammatory regulation as a potential therapeutic option for cognitive dysfunction in MetS with latent chronic inflammation.

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.

Type 1 diabetes and hearing loss: Audiometric assessment and measurement of circulating levels of soluble receptor for advanced glycation end products

BACKGROUND

We examined the hearing function in adults with and without type 1 diabetes (T1D) to investigate whether an association exists between hearing loss and duration of diabetes, haemoglobin A1C level, diabetes complications and levels of select serum and urinary biomarkers.

METHODS

We measured pure tone audiometry (PTA) thresholds; serum levels of C-reactive protein (CRP), vascular endothelial growth factor (VEGF), soluble receptors for advanced glycation end-product (sRAGE); and urinary isoprostane in 30 adults with T1D (age 43.8 ± 11.4 years). We also measured PTA thresholds in 11 adults without diabetes (age 53 ± 5.5 years).

RESULTS

63.3% of adults with T1D had high-frequency hearing loss. Among adults with T1D, those with hearing loss were older (48.2 vs 36.2 years old, P < .01), had a longer duration of diabetes (30.7 vs 21.2 years, P = .02), a greater prevalence of peripheral neuropathy (57.9 vs 9.1%, P = .02) and significantly lower median levels of sRAGE (1054.27 vs 1306.83 pg/mL, P = .03) compared to those with normal hearing. Adults with T1D between the ages of 40 and 60 years old, who had diabetes for ≥35 years, had significantly higher PTA thresholds at both 500and 8000 Hz than age-matched adults without diabetes.

CONCLUSIONS

A significant proportion of adults with T1D have high-frequency hearing loss before age of 60 that is positively associated with age, duration of diabetes and presence of peripheral neuropathy. Our results are in support of previous studies suggesting a potential protective role of sRAGE against AGE toxicity and diabetes complications.

The Role of Nonenzymatic Post-translational Protein Modifications in Uremic Vascular Calcification

Considerable technological advances have enabled the identification and linkage of nonenzymatic post-translationally modified proteins to the pathogenesis of cardiovascular disease (CVD) in patients with kidney failure. Through processes such as the nonenzymatic carbamylation reaction as well as the formation of advanced glycation end products, we now know that protein modifications are invariably associated with the development of CVD beyond a mere epiphenomenon and this has become an important focus of nephrology research in recent years. Although the specific mechanisms by which protein modifications occurring in kidney failure that may contribute to CVD are diverse and include pathways such as inflammation and fibrosis, vascular calcification has emerged as a distinct pathological sequelae of protein modifications. In this review, we consider the biological mechanisms and clinical relevance of protein carbamylation and advanced glycation end products in CVD development with a focus on vascular calcification.

JNK and ATF4 as two important platforms for tumor necrosis factor-α-stimulated shedding of receptor for advanced glycation end products

Soluble receptor for advanced glycation end products (sRAGE), shed from cell surfaces, is found in human circulation and has been implicated in cardiovascular disease. Its pathophysiological regulation and underlying mechanisms are scarcely understood. In endothelium-specific human RAGE transgenic mice, human sRAGE was detected in circulation, whereas its level was markedly increased after LPS treatment. That increase was preceded by a rapid rise in TNF-α level. Treatment with TNF-α also significantly increased serum sRAGE. In human microvascular endothelial cells or human umbilical vein endothelial cells with RAGE overexpression, TNF-α markedly induced RAGE shedding, which was dependent on MMP9 and ADAM10. TNF-α-stimulated MMP9 expression was completely dependent on JNK activation, with its inhibition partially effective in suppressing TNF-α-induced RAGE shedding. In contrast, TNF-α transiently induced activation transcription factor (ATF)4, a major component in unfolded protein response (UPR), whereas knockdown of ATF4 abrogated TNF-α-stimulated RAGE shedding. Protein levels of the pro and activated forms of ADAM10 were also decreased by ATF4 knockdown, whereas inhibition of other components of UPR, including XBP1 and ATF6, failed to block TNF-α-stimulated RAGE shedding. Although the endoplasmic reticulum stressors thapsigargin and tunicamycin induced markedly and sustained expression of ATF4 and XBP-1, they did not induce RAGE shedding to the same level as TNF-α, suggesting that ATF4 is necessary but not sufficient alone for TNF-α-mediated RAGE shedding. ATF4 inhibition did not affect TNF-α-stimulated MMP9 expression, whereas inhibition of JNK activity did not influence ADAM10 activation. Thus, inflammatory cascades including TNF-α induced RAGE shedding in endothelial cells in vivo and in vitro. JNK and ATF4 may be 2 platforms for regulation of TNF-α-stimulated RAGE shedding.-Miyoshi, A., Koyama, S., Sasagawa-Monden, M., Kadoya, M., Konishi, K., Shoji, T., Inaba, M., Yamamoto, Y., Koyama, H. JNK and ATF4 as two important platforms for tumor necrosis factor-α-stimulated shedding of receptor for advanced glycation end products.

Endogenous Secretory RAGE as a Novel Biomarker for Metabolic Syndrome and Cardiovascular Diseases

Receptor for advanced glycation end-products (RAGE) is known to be involved in both micro- and macrovascular complications in diabetes. Among numerous truncated forms of RAGE recently described, the C-terminally truncated form of RAGE has received much attention. This form of RAGE, carrying all of the extracellular domains but devoid of the trans-membrane and intracytoplasmic domains, is released outside from cells, binds ligands including AGEs, and is capable of neutralizing RAGE signaling on endothelial cells in culture. This form of RAGE is generated as a splice variant and is named endogenous secretory RAGE (esRAGE). Adenoviral overexpression of esRAGE reverses diabetic impairment of vascular dysfunction, suggesting that esRAGE may be an important inhibitor of RAGE signaling in vivo and potentially be useful for prevention of diabetic vascular complications. An ELISA system to measure plasma esRAGE was recently developed, and the pathophysiological roles of esRAGE have begun to be unveiled clinically. Plasma esRAGE levels are decreased in patients with several metabolic diseases including type 1 and type 2 diabetes, metabolic syndrome and hypertension. In cross-sectional analysis, plasma esRAGE levels are inversely correlated with carotid or femoral atherosclerosis. In an observational cohort of patients with end-stage renal disease, cumulative incidence of cardiovascular death was significantly higher in subjects with lower plasma esRAGE levels. These findings suggest that plasma esRAGE may act as a protective factor against and a novel biomarker for the occurrence of metabolic syndrome and cardiovascular diseases.

Polymorphisms of the receptor for advanced glycation end products and glyoxalase I and long-term outcome in patients with breast cancer

Receptor for advanced glycation end products and glyoxalase I metabolizing advanced glycation end product precursors may play important role in the pathogenesis and progression of cancer. Potential relation between soluble forms of receptor for advanced glycation end products (sRAGE), receptor for advanced glycation end products, glyoxalase I polymorphisms, and long-term outcome (median follow-up of 10.3 years) was studied in 116 patients with breast cancer. Gly82Ser and 2184 A/G RAGE polymorphisms were related to the mortality due to the breast cancer and -419 A/C glyoxalase I polymorphism was related to the overall mortality of the patients suggesting their role not only in the risk of breast cancer but also in the outcome of patients with breast cancer.

Functional food supplements to ameliorate the secondary complications in high fructose fed diabetic rats

Poly-herbal functional food supplements inhibited high fructose induced glycation in diabetic rats and showed promise for effective management of secondary complications of diabetes such as improved lipid profile, kidney function and reduction of oxidative stress.

The Receptor for Advanced Glycation End Products (Rage) and Its Ligands in Plasma and Infrainguinal Bypass Vein

OBJECTIVE

The aim was to investigate whether RAGE and its ligands are associated with infrainguinal bypass outcome in patients with and without diabetes.

METHODS

This was a prospective observational cohort. Patients (n = 68) with (n = 38) and without (n = 30) diabetes undergoing infrainguinal vein bypass for peripheral arterial disease were followed for 3 years. Endosecretory RAGE (esRAGE), S100A12, advanced glycation end products, and carboxymethyl-lysine (CML) were determined in plasma using ELISA. The influence of plasma levels on the main outcome (amputation free survival) was evaluated using Cox proportional hazard analysis. Plasma esRAGE, CML, and S100A12 in healthy controls (n = 30) without cardiovascular disease matched for sex and age were compared with patients, using the Mann-Whitney U test. Veins from bypass surgery procedures were stained and S100A12, RAGE, AGE, and CML were determined using immunohistochemistry.

RESULTS

Forty-six patients survived with an intact leg during follow up. Seventeen died (median survival time 702 days, IQR 188-899 day), and six had amputations. High plasma S100A12 was associated with reduced amputation free survival (hazard ratio [HR] 2.99; 95% CI 1.24-7.24) when comparing levels above the 75th percentile with levels below. The increased risk was unchanged adjusting for age, sex, and diabetes. Diabetic patients had higher plasma S100A12 (11.75 ng/mL; 95% CI 8.12-15.38 ng/mL) than non-diabetic patients (5.0141 ng/mL; 95% CI 3.62-6.41 ng/mL), whereas plasma CML, esRAGE, and AGE were similar. Plasma CML and S100A12 were higher in patients than in controls (1.25 μg/mL, 95% CI 1.18-1.32 μg/mL vs. 0.8925 μg/mL, 95% CI 0.82-0.96 μg/mL; and 8.7 μg/mL, 95% CI 6.52-10.95 μg/mL vs. 3.47 μg/mL, 95% CI 2.95-3.99 μg/mL, respectively). The proportion of vein tissue stained for AGE (21%), RAGE (5%), CML (9%) and S100A12 (3%), were similar in patients with and without diabetes.

CONCLUSIONS

Plasma S100A12 and CML are elevated in peripheral arterial disease and markers of RAGE and its ligands are found in vein used for bypass. This indicates a role for S100A12, CML, and RAGE in peripheral arterial disease complications by activation of the RAGE system.

The receptor for advanced glycation end products and risk of peripheral arterial disease, amputation or death in type 2 diabetes: a population-based cohort study

Background

Patients with type 2 diabetes have a high risk for early and extensive development of peripheral arterial disease (PAD) and this excess risk is not explained by increased burden of traditional atherosclerotic risk factors. Activation of the receptor for advanced glycation end products (RAGE) could be one additional mechanism for accelerated PAD and increased risk for amputation and death. We investigated the association between RAGE plasma components and the risk for PAD, amputation and death in patients with type 2 diabetes. We also estimated the rate of amputation-free survival and survival without PAD.

Methods

We investigated if plasma levels of carboxymethyl-lysine, S100A12 and endosecretory RAGE (esRAGE) were associated with two endpoints: survival without development of PAD and survival without amputation in a 12 years prospective population-based cohort of 146 patients with type 2 diabetes, free from PAD at inclusion. Influence of baseline plasma levels of RAGE ligands (individually and combined by a RAGE-score) were evaluated for both endpoints in the Cox-regression analysis.

Results

106 patients survived without amputation and 93 survived without signs of PAD during follow up. Higher levels of S100A12 and RAGE-score were associated with increased risk for amputation or death, hazard ratios (HR) 1.29; 95% confidence interval (CI) [1.04, 1.59] and 1.79; 95% CI [1.07, 2.99] and with increased risk for PAD or death, HR 1.22; 95% CI [1.00, 1.49] and 1.56; [1.00, 2.44] after adjustment for age and sex. The effect was decreased after adjustment for Framingham cardiovascular disease score: risk for amputation or death, HR 1.17; 95% CI [0.94, 1.46] and 1.54; [0.95, 2.49], and risk for PAD or death, HR 1.12; 95% CI [0.91, 1.38] and 1.38; [0.91, 2.11] for S100A12 and RAGE-score respectively. The incidence for amputation or death was 2.8 per 100 person-years; 95% CI [2.0, 3.7] and the incidence rate for PAD or death was 3.6 per 100 person-years; 95% CI [2.7, 4.8].

Conclusion

Higher plasma levels of S100A12 and the combined effect (RAGE-score) of esRAGE, carboxymethyl-lysine and S100A12 seem to be associated with shorter PAD- and amputation-free survival in patients with type 2 diabetes. This may indicate a role for S100A12 in PAD by activation of the RAGE system.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-015-0257-5) contains supplementary material, which is available to authorized users.

Soluble RAGEs - Prospects for treating & tracking metabolic and inflammatory disease

Emerging evidence links the receptor for advanced glycation endproducts (RAGE) to the pathogenesis of tissue damage in chronic metabolic and inflammatory diseases. In human subjects, multiple reports suggest that in the plasma/serum, circulating levels of distinct forms of soluble RAGEs may be biomarkers of the presence or absence, and the extent of chronic disease. These considerations prompt us to consider in this review, what are soluble RAGEs; how are they formed; what might be their natural functions; and may they serve as biomarkers of inflammatory and metabolic disease activity? In this brief review, we seek to address what is known and suggest new areas for scientific investigation to uncover the biology of soluble RAGEs.

Do elevated plasma S100A12 levels predict atherosclerosis in peritoneal dialysis patients?

AIM

Atherosclerotic cardiovascular disease is one of the major causes of mortality and morbidity in peritoneal dialysis (PD) patients. S100A12 is an endogenous receptor ligand of advanced glycation end-products. It was shown to contribute to the development of atherosclerosis in animal models. The aim of this study was to evaluate the relationship between S100A12 levels and carotid atherosclerosis in PD patients.

METHODS

A cross-sectional study was performed in 56 PD patients and 20 control subjects. Plasma S100A12 levels were measured from all participants beside routine laboratory evaluation. All subjects underwent high-resolution B-mode ultrasonography to determine carotid intima media thickness (CIMT). S100A12 levels were compared between patient and control groups. Correlation analyses of S100A12 with other laboratory values and CIMT were also performed.

RESULTS

Plasma S100A12 levels were higher in PD patients compared with control subjects (129.5 ± 167.2 ng/mL vs. 48.5 ± 30.3 ng/mL, respectively, p < 0.001). In the patient group, CIMT was found to be positively correlated with age (r = 0.354; p = 0.007), CRP level (r = 0.269; p = 0.045), and S100A12 (r = 0.293; p = 0.028) level while it was found to be negatively correlated with hemoglobin concentration (r = -0.264; p = 0.049). In the linear regression analysis, the model, including CRP, S100A12, age, and Hgb, was found to be significant (F: 4.177, p: 0.005). When the parameters are analyzed age and S100A12 were found to be independent determinants of CIMT (β = 0.308, p = 0.018 and β = 0.248, p = 0.049, respectively).

CONCLUSIONS

This study suggests that an elevated plasma S100A12 level was closely associated with atherosclerosis. With aging elevated plasma S100A12 may show a powerful proatherogenic potential in patients undergoing PD.

Controlling the receptor for advanced glycation end-products to conquer diabetic vascular complications

Diabetic vascular complications, such as cardiovascular disease, stroke and microangiopathy, lead to high rates of morbidity and mortality in patients with long‐term diabetes. Extensive intracellular and extracellular formation of advanced glycation end‐products (AGE) is considered a causative factor in vascular injuries in diabetes. Receptor‐dependent mechanisms are involved in AGE‐induced cellular dysfunction and tissue damage. The receptor for AGE (RAGE), originally an AGE‐binding receptor, is now recognized as a member of pattern‐recognition receptors and a pro‐inflammatory molecular device that mediates danger signals to the body. Previous animal studies have shown RAGE dependent of diabetic vascular injuries. Prophylactic and therapeutic strategies focusing on RAGE and its ligand axis will be of great importance in conquering diabetic vascular complications. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2011.00191.x, 2012)

Comparison of effects of pioglitazone and glimepiride on plasma soluble RAGE and RAGE expression in peripheral mononuclear cells in type 2 diabetes: randomized controlled trial (PioRAGE)

OBJECTIVE

The receptor for advanced glycation end-products (RAGE) is involved in vascular complications in diabetic patients. Pioglitazone, in contrast to glimepiride, has been shown to be protective against atherosclerotic disorders. In this study, we directly compared the effects of those drugs on RAGE system.

METHODS

Sixty-three type 2 diabetic patients (age 20-80 years, hemoglobin A1c 6.4-10.3%) being treated with sulfonylurea (glimepiride 0.5-2.0 mg/day, glyclazide 20-80 mg/day, glibenclamide 1.25-5.0 mg/day), or with nateglinide or metiglynide were randomly assigned to receive either pioglitazone (n = 31) or glimepiride (n = 32). Levels in plasma of soluble RAGE (sRAGE) and endogenous secretory RAGE (esRAGE), and RAGE expression in peripheral mononuclear cells were determined at 0, 12, and 24 weeks.

RESULTS

Twenty-seven patients in the pioglitazone group (15-30 mg) and 30 in the glimepiride group (0.5-4 mg) completed the 24-week trial. Increases in plasma esRAGE were significantly greater in the pioglitazone group (12 weeks: 55 ± 15 pg/mL, p = 0.018; 24 weeks: 90 ± 14 pg/mL, p = 0.003) as compared to the glimepiride group (12 weeks: 12 ± 9 pg/mL; 24 weeks: 29 ± 14 pg/mL). Increases in plasma sRAGE were also significantly (p = 0.037) higher in the pioglitazone group at 24 weeks (170 ± 166 vs.74 ± 171 pg/mL). Furthermore, RAGE expression in mononuclear cells was significantly (p = 0.008) decreased to a greater degree in the pioglitazone group at 24 weeks (-7.39 ± 5.18 vs. -3.39 ± 5.72 MFI). Changes in HbA1c, IRI, and insulin resistance index (HOMA) at 24 weeks were not significantly different between the groups.

CONCLUSION

Pioglitazone suppresses RAGE expression and increases circulating sRAGE/esRAGE, and those activities are not necessarily dependent on plasma glucose or insulin resistance levels.

CLINICAL TRIAL NO

UMIN000002055.

Association of plasma sRAGE, but not esRAGE with lung function impairment in COPD

Rationale

Plasma soluble Receptor for Advanced Glycation End Product (sRAGE) is considered as a biomarker in COPD. The contribution of endogenous sRAGE (esRAGE) to the pool of plasma sRAGE and the implication of both markers in COPD pathogenesis is however not clear yet. The aim of the current study was therefore to measure plasma levels of esRAGE comparative to total sRAGE in patients with COPD and a control group. Further, we established the relations of esRAGE and total sRAGE with disease specific characteristics such as lung function and D_LCO, and with different circulating AGEs.

Methods

Plasma levels of esRAGE and sRAGE were measured in an 88 patients with COPD and in 55 healthy controls. FEV₁ (%predicted) and FEV₁/VC (%) were measured in both groups; D_LCO (%predicted) was measured in patients only. In this study population we previously reported that the AGE N^ϵ-(carboxymethyl) lysine (CML) was decreased, N^ϵ-(carboxyethyl) lysine (CEL) increased and pentosidine was not different in plasma of COPD patients compared to controls.

Results

Plasma esRAGE (COPD: 533.9 ± 412.4, Controls: 848.7 ± 690.3 pg/ml; p = 0.000) was decreased in COPD compared to controls. No significant correlations were observed between plasma esRAGE levels and lung function parameters or plasma AGEs. A positive correlation was present between esRAGE and total sRAGE levels in the circulation. Confirming previous findings, total sRAGE (COPD: 512.6 ± 403.8, Controls: 1834 ± 804.2 pg/ml; p < 0.001) was lower in patients compared to controls and was positively correlated FEV₁ (r = 0.235, p = 0.032), FEV₁/VC (r = 0.218, p = 0.047), and D_LCO (r = 0.308, p = 0.006). sRAGE furthermore did show a significant positive association with CML (r = 0.321, p = 0.003).

Conclusion

Although plasma esRAGE is decreased in COPD patients compared to controls, only total sRAGE showed a significant and independent association with FEV₁, FEV₁/VC and D_LCO, indicating that total sRAGE but not esRAGE may serve as marker of COPD disease state and severity.

Molecular strategies to prevent, inhibit, and degrade advanced glycoxidation and advanced lipoxidation end products

The advanced glycoxidation end products (AGEs) and lipoxidation end products (ALEs) contribute to the development of diabetic complications and of other pathologies. The review discusses the possibilities of counteracting the formation and stimulating the degradation of these species by pharmaceuticals and natural compounds. The review discusses inhibitors of ALE and AGE formation, cross-link breakers, ALE/AGE elimination by enzymes and proteolytic systems, receptors for advanced glycation end products (RAGEs) and blockade of the ligand-RAGE axis.

Soluble receptor for advanced glycation end-product levels are related to albuminuria and arterial stiffness in essential hypertension

BACKGROUND AND AIMS

Emerging evidence suggests that the soluble receptor for advanced glycation end-products (sRAGE) is implicated in the development of vascular disease. We investigated the interrelationships of sRAGE with albumin to creatinine ratio (ACR) and arterial stiffness in essential hypertension.

METHODS AND RESULTS

In 309 untreated non-diabetic hypertensives, ACR values were determined as the mean of three non-consecutive morning spot urine samples and aortic stiffness was evaluated on the basis of carotid to femoral pulse wave velocity (c-f PWV). In all subjects, venous blood sampling was performed for the estimation of sRAGE levels. Patients with low (n = 155) compared to those with high sRAGE values (n = 154) had greater 24-h systolic BP (140 ± 8 vs. 134 ± 7 mmHg, p < 0.0001), exhibited higher ACR (36.3 ± 51.6 vs. 17.2 ± 1.2 mg g(-1), p < 0.0001) and c-f PWV (8.3 ± 1.5 vs. 7.8 ± 1.1 m s(-1), p = 0.003), independently of confounding factors. Multiple regression analyses revealed that age, male sex, 24-h systolic BP and sRAGE were the 'independent correlates' of ACR (R(2) = 0.493, p < 0.0001), while age, 24-h systolic BP and sRAGE were the 'independent correlates' of c-f PWV (R(2) = 0.428, p < 0.0001).

CONCLUSION

In hypertensives, decreased sRAGE levels are accompanied by pronounced albuminuria and arterial stiffening. The association of sRAGE with ACR and c-f PWV suggests involvement of sRAGE in the progression of hypertensive vascular damage.

Meta-analysis of RAGE gene polymorphism and coronary heart disease risk

Background

Recent data from human and animal studies have shown an upregulated expression of advanced glycosylation end product–specific receptor (RAGE) in human atherosclerotic plaques 1 and in retina, messangial, and aortic vessels, suggesting an important role of RAGE in the pathogenesis of atherothrombotic diseases. In the past few years, the relationship between RAGE polymorphisms (−429T/C, −374T/A, and G82S) and coronary heart disease (CHD) has been reported in various ethnic groups; however, these studies have yielded contradictory results.

Methods

PubMed, ISI web of science, EMBASE and the Chinese National Knowledge Infrastructure databases were systematically searched to identify relevant studies. Data were abstracted independently by two reviewers. A meta-analysis was performed to examine the association between RAGE polymorphisms and susceptibility to CHD. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated.

Results

A total of 17 studies including 4343 patients and 5402 controls were involved in this meta-analysis. Overall, no significant results were observed for −429T/C (OR  = 1.01, 95% CI: 0.92–1.12, P  = 0.78), −374T/A (OR  = 1.11, 95% CI: 0.98–1.26, P  = 0.09) and G82S (OR  = 1.12, 95% CI: 0.86–1.45, P  = 0.41) polymorphism. In the stratified analyses according to ethnicity, sample size, CHD endpoint and Hardy-Weinberg status, no evidence of any gene-disease association was obtained.

Conclusions

This meta-analysis demonstrates that there is no association between the RAGE −429T/C, −374T/A and G82S polymorphisms and CHD.

Circulating soluble receptor for advanced glycation end product (sRAGE) and left ventricular hypertrophy in patients with chronic kidney disease (CKD)

BACKGROUND AND AIM

A decoy receptor for advanced glycation end product (soluble RAGE or sRAGE) is involved in left ventricular hypertrophy (LVH), and cardiomyopathy myocardial damage in experimental models and observational studies in patients with heart failure support the hypothesis that sRAGE attenuates the progression of heart disease and prevents death. Since sRAGE accumulates in patients with chronic kidney disease (CKD) we studied the relationship between plasma sRAGE with LVH in CKD patients.

METHODS AND RESULTS

We enrolled 142 patients with an average estimated glomerular filtration rate (eGFR) of 32 ml/min/1.73 m(2) and 49 healthy control individuals matched for age and gender. Plasma sRAGE was significantly higher in CKD patients than in healthy controls. Significant inverse relationships were found between sRAGE with left ventricular mass index (LVMI) and mean wall thickness (MWT) but no such associations were found in controls. A bootstrap re-sampling validation study confirmed the estimates of the link between sRAGE and these variables. On covariance analysis, the slopes of LVMI and MWT to sRAGE were significantly steeper in CKD patients than in the controls. On logistic regression analysis 1 log unit increase in sRAGE was associated with a 82% decrease in the odds for LVH in CKD patients.

CONCLUSIONS

sRAGE is an inverse marker of LVH in CKD patients. This association generates the hypothesis that the RAGE pathway could be a causal risk factor for LVH in this population and that blockade of this pathway by the endogenous decoy receptor sRAGE could attenuate LVH in the same population.

Plasma biomarkers of oxidative and AGE-mediated damage of proteins and glycosaminoglycans during healthy ageing: a possible association with ECM metabolism

The aim of this study was to examine whether oxidative and AGE-mediated processes correlates with the metabolic changes of proteoglycans (PGs) and proteins during physiological ageing. The age and gender-associated changes of PGs metabolism were evaluated by plasma chondroitin sulfates (CS), dermatan sulfates (DS) and heparan sulfates and heparin (HS/H). We found a linear age-related decline in CS, DS and HS/H, the first one being the predominant plasma GAG during ageing. The possible deleterious effect of oxidative phenomenon on proteins' and proteoglycans' metabolism during ageing process was analyzed by plasma carbonyls (PCO) and thiols (PSH) as well as by total antioxidant capacity (TAS). An age-dependent increase in PCO and decrease in PSH concentrations were found, both strongly correlated with decreasing with age plasma TAS. Intensity of glycation was assessed by circulating N(ε)-(carboxymethyl)lysine (CML) and endogenous secretory receptor for AGE (esRAGE), both of them founding associated with ageing. Moreover, all markers of oxidative and AGE-mediated damage correlated with CS and DS level and could be contributing factors to age-related changes of these GAG types. Thus, plasma CS and DS could become promising biomarkers of human ageing to date, owning to its close association with oxidative status and glycation processes.

[Protein glycation as a pathological mechanism in diabetes]

The incidence of diabetes has increased in the recent years. Diabetes is characterized by increased sugar concentrations in the blood. Due to this dysregulation, more carbohydrate-induced modification of proteins - so-called advanced glycation end products (AGEs) - are formed endogenously by non-enzymatic reactions. These are discussed to be at least in part responsible for diabetes-associated diseases. The accumulation of AGEs in the tissue can be used as a biomarker for patient outcome. In contrast, the effects of the uptake of AGEs from nutrition are still unclear.

Effects of atorvastatin on progression of diabetic nephropathy and local RAGE and soluble RAGE expressions in rats

OBJECTIVE

Advanced glycation end-products (AGEs) exert inflammatory and oxidative stress insults to produce diabetic nephropathy mainly through the receptor for AGEs (RAGE). This study aimed to assess the effect of atorvastatin on diabetic nephropathy via soluble RAGE (sRAGE) and RAGE expressions in the rat kidney.

METHODS

Thirty-two male Sprague-Dawley rats were divided into four groups based on the presence or absence of streptozotocin-induced diabetes with or without atorvastatin treatment (10 mg/kg for 24 weeks). Serum sRAGE and glycated albumin (GA) levels were measured with enzyme-linked immunosorbent assay (ELISA) and improved bromocresol purple methods. Renal AGEs, RAGE, endogenous secretory RAGE (esRAGE), and sRAGE were determined with reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting.

RESULTS

Mesangial expansion and microalbuminuria were aggravated in diabetic rats, and improved with atorvastatin treatment. Serum sRAGE levels were lower in diabetic than in normal rats. After atorvastatin treatment, serum and renal sRAGE levels were up-regulated, while renal RAGE expression was decreased in diabetic rats, associated with a reduction in accumulation of AGEs, though renal esRAGE mRNA expression was not significantly increased.

CONCLUSIONS

Atorvastatin exerted a beneficial effect on diabetic nephropathy with reduced AGE accumulation, down-regulating RAGE expression and up-regulating sRAGE in the kidney.

Regulation of RAGE for attenuating progression of diabetic vascular complications

Diabetic angiopathy including micro- and macroangiopathy is concerned with high rate of morbidity and mortality in patients with long-standing diabetes. Receptor for advanced glycation end products (RAGE) and its ligands have been considered as important pathogenic triggers for the progression of the vascular injuries in diabetes. The deleterious link between RAGE and diabetic angiopathy has been demonstrated in animal studies. Preventive and therapeutic strategies focusing on RAGE and its ligand axis may be of great importance in relieving diabetic vascular complications and reducing the burden of disease.

Soluble receptor for AGE (RAGE) is a novel independent predictor of all-cause and cardiovascular mortality in type 1 diabetes

AIMS/HYPOTHESIS

Activation of the receptor for AGE (RAGE) is implicated in the development and progression of vascular complications of diabetes. In this study, we explore factors and mortality outcomes associated with soluble RAGE (sRAGE) in a multicentre nationwide cohort of Finnish adults with type 1 diabetes.

METHODS

Baseline sRAGE concentrations were estimated in 3,100 adults with type 1 diabetes. Clinical and biological variables independently associated with sRAGE were identified using multivariate regression analysis. Independent predictors of mortality were determined using Cox and Fine-Gray proportional-hazards models.

RESULTS

The main independent determinants of sRAGE concentrations were estimated glomerular filtration rate, albuminuria, body mass index, age, duration of diabetes, HbA(1c) and insulin dose (all p < 0.05). During a median of 9.1 years of follow-up there were 202 deaths (7.4 per 1,000 patient years). sRAGE was independently associated with all-cause (Cox model: HR 1.03) and cardiovascular mortality (Fine-Gray competing risks model: HR 1.06) such that patients with the highest sRAGE concentrations had the greatest risk of mortality, after adjusting for age, sex, macrovascular disease, HDL-cholesterol, HbA(1c), triacylglycerol, high-sensitivity C-reactive protein (hsCRP) and the presence and severity of chronic kidney disease. Although polymorphisms in the gene coding for RAGE were significantly associated with sRAGE concentrations, none were associated with mortality outcomes.

CONCLUSIONS/INTERPRETATION

Increased concentrations of sRAGE are associated with increased all-cause and cardiovascular mortality in type 1 diabetes, potentially reflecting the activation and production of RAGE in the context of accelerated vascular disease. These novel findings highlight the importance of the RAGE activation in the prevention and management of diabetic complications.

Susceptibility of LDL and its subfractions to glycation

PURPOSE OF REVIEW

To highlight the potential importance of glycation as an atherogenic modification of LDL, factors determining glycated apolipoprotein B in vivo and susceptibility of LDL to glycation in vitro. We also discuss the distribution of glycated apolipoprotein B across different LDL subfractions in healthy controls, patients with type 2 diabetes and metabolic syndrome.

RECENT FINDINGS

Small, dense LDL, which is known to be most closely associated with atherogenesis, is more preferentially glycated in vivo and more susceptible to glycation in vitro than more buoyant LDL. Glycation and oxidation of LDL appear to be intimately linked. In patients with type 2 diabetes, plasma glycated apolipoprotein B correlated with small, dense LDL apolipoprotein B, but not with HbA1c. Glycated apolipoprotein B is significantly lower in statin-treated type 2 diabetes compared with those not on statins.

SUMMARY

Glycation of LDL occurs chiefly because of the nonenzymatic reaction of glucose and its metabolites with the free amino groups of lysine of which apolipoprotein B is rich. Higher concentrations of glycated LDL are present in diabetes than in nondiabetic individuals and metabolic syndrome. Even in nondiabetic individuals, however, there is generally more circulating glycated LDL than oxidatively modified LDL. Probably, oxidation and glycation of LDL are partially interdependent and indisputably coexist, and both prevent LDL receptor-mediated uptake and promote macrophage scavenger receptor-mediated LDL uptake. The recognition that LDL glycation is at least as important as oxidation in atherogenesis may lead to improvements in our understanding of its mechanism and how to prevent it.

Advanced glycation end products, carotid atherosclerosis, and circulating endothelial progenitor cells in patients with end-stage renal disease

Numbers of endothelial progenitor cells (EPCs) have been shown to be decreased in subjects with end-stage renal disease (ESRD), the mechanism of which remained poorly understood. In this study, mutual association among circulating EPC levels, carotid atherosclerosis, serum pentosidine, and skin autofluorescence, a recently established noninvasive measure of advanced glycation end products accumulation, was examined in 212 ESRD subjects undergoing hemodialysis. Numbers of circulating EPCs were measured as CD34+ CD133+ CD45(low) VEGFR2+ cells and progenitor cells as CD34+ CD133+ CD45(low) fraction by flow cytometry. Skin autofluorescence was assessed by the autofluorescence reader; and serum pentosidine, by enzyme-linked immunosorbent assay. Carotid atherosclerosis was determined as intimal-medial thickness (IMT) measured by ultrasound. Circulating EPCs were significantly and inversely correlated with skin autofluorescence in ESRD subjects (R = -0.216, P = .002), but not with serum pentosidine (R = -0.079, P = .25). Circulating EPCs tended to be inversely associated with IMT (R = -0.125, P = .069). Intimal-medial thickness was also tended to be correlated positively with skin autofluorescence (R = 0.133, P = .054) and significantly with serum pentosidine (R = 0.159, P = .019). Stepwise multiple regression analyses reveal that skin autofluorescence, but not serum pentosidine and IMT, was independently associated with low circulating EPCs. Of note, skin autofluorescence was also inversely and independently associated with circulating progenitor cells. Thus, tissue accumulated, but not circulating, advanced glycation end products may be a determinant of a decrease in circulating EPCs in ESRD subjects.

Endogenous secretory receptor for advanced glycation end products and chronic kidney disease in the elderly population

BACKGROUND/AIMS

The relationship of circulating endogenous secretory receptor for advanced glycation end products (esRAGE) and chronic kidney disease (CKD) has not been well characterized. The aim of the study was to determine whether plasma esRAGE is associated with CKD and is predictive of developing CKD in older adults.

METHODS

The relationship between plasma esRAGE and CKD (more than stage 3 of the National Kidney Foundation classification; estimated glomerular filtration rate <60 ml/min/1.73 m(2)) and CKD over 6 years of follow-up was examined in a cross-sectional and prospective study design in 1,016 men and women, ≥65 years, in the InCHIANTI study, a population-based cohort study of aging in Tuscany, Italy.

RESULTS

At enrollment, 158 (15.5%) had CKD. Mean (SD) plasma esRAGE was 0.45 (0.24) ng/ml. Plasma esRAGE (ng/ml) was associated with CKD (odds ratio per 1 SD = 1.30; 95% CI 1.1-1.6; p < 0.005) in a multivariable logistic regression model, adjusting for potential confounders. Plasma esRAGE was an independent predictor of incident CKD over 6 years of follow-up (hazard ratio per 1 SD = 1.37; 95% CI 1.1-1.7; p < 0.008) in a multivariable Cox proportional hazards model, adjusting for potential confounders.

CONCLUSIONS

Elevated plasma esRAGE is independently associated with CKD and is an independent predictor of incident CKD in older community-dwelling adults.

Endogenous secretory receptor for advanced glycation end products is associated with low serum interleukin-1 receptor antagonist and elevated IL-6 in older community-dwelling adults

BACKGROUND

Advanced glycation end products (AGEs) are thought to cause inflammation through interaction with the receptor for AGEs (RAGE), therefore contributing to adverse aging-related processes. The relationship between AGEs, RAGE, and inflammation has not been well characterized.

METHODS

We examined the relationship of plasma endogenous secretory RAGE (esRAGE); carboxymethyl-lysine (CML), a circulating AGE; and inflammatory mediators in 1,298 adults, 20-97 years, who participated in the InCHIANTI study in Tuscany, Italy. Blood levels of esRAGE, CML, interleukin-1 receptor antagonist (IL-1RA), IL-1β, tumor necrosis factor-α (TNF-α), IL-6, IL-6 receptor (IL-6R), IL-18, C-reactive protein (CRP), transforming growth factor-β (TGF-β), and fibrinogen were measured.

RESULTS

Log plasma esRAGE was associated with log IL-1RA (β = -0.069, SE = 0.036, p = .05) and log IL-6 (β = 0.077, SE = 0.035, p = .03), respectively, in separate multivariable linear regression models, adjusting for potential confounders. Log plasma esRAGE was also negatively associated with log TGF-β but did not reach statistical significance (β = -0.091, SE = 0.053, p = .09). Log plasma esRAGE was not significantly associated with log IL-1β, log TNF-α, IL-6R, log IL-18, or CRP. Log plasma CML was not associated with any of the inflammatory mediators except for IL-6R (β = -14.10, SE = 5.94, p = .02) and fibrinogen (β = 13.95, SE = 7.21, p = .05) in separate multivariable models, adjusting for potential confounders.

CONCLUSIONS

Plasma esRAGE is correlated with higher IL-6 and lower IL-1RA. These findings suggest that plasma esRAGE plays a role in modulating inflammation, although the exact mechanisms remain to be elucidated.

Plasma S100A12 level is associated with cardiovascular disease in hemodialysis patients

BACKGROUND AND OBJECTIVES

S100A12 is an endogenous receptor ligand for advanced glycation end products. Cardiovascular disease remains a major cause of morbidity and mortality in patients with chronic kidney disease. In this study, we report cross-sectional data on 550 hemodialysis patients and assess the relationship between plasma S100A12 level and cardiovascular disease.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A cross-sectional study of 550 maintenance hemodialysis patients was conducted. We investigated the past history of cardiovascular disease and quantified the plasma level of S100A12 protein in all participants.

RESULTS

Plasma S100A12 level was higher in hemodialysis patients with cardiovascular disease (n=197; 33.8 ± 28.1 ng/ml) than in those without it (n=353; 20.2 ± 16.1 ng/ml; P<0.001). In multivariate logistic regression analysis, the plasma S100A12 level (odds ratio [OR], 1.28; 95% confidence interval [CI], 1.13 to 1.44; P<0.001) was identified as an independent factor associated with the prevalence of cardiovascular disease. The other factors associated with the prevalence of cardiovascular diseases were the presence of diabetes mellitus (OR, 2.81; 95% CI, 1.79 to 4.41; P < 0.001) and high-sensitivity CRP level (OR, 1.02; 95% CI, 1.00 to 1.05; P=0.046). Furthermore, the plasma S100A12 level (OR, 1.30; 95% CI, 1.09 to 1.54; P=0.004) was significantly associated with cardiovascular disease even in hemodialysis patients without diabetes mellitus (n=348).

CONCLUSIONS

These results suggest that the plasma S100A12 protein level is strongly associated with the prevalence of cardiovascular disease in hemodialysis patients.

Effect of circulating soluble receptor for advanced glycation end products (sRAGE) and the proinflammatory RAGE ligand (EN-RAGE, S100A12) on mortality in hemodialysis patients

BACKGROUND AND OBJECTIVES

The soluble receptor of advanced glycation end products (sRAGE) may exert anti-inflammatory protective roles on the vasculature. In contrast, the RAGE ligand S100A12 (also known as EN-RAGE) contributes to inflammation and the development of atherosclerosis in animal models. Whether alterations at this level contribute to the increased mortality observed in patients on dialysis is currently unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Prospective study including 184 prevalent hemodialysis patients and 50 healthy controls matched for age and gender. Plasma concentrations of S100A12 and sRAGE were studied in relation to risk profile and mortality after a median follow-up period of 41 months.

RESULTS

S100A12 and sRAGE levels were significantly elevated in hemodialysis patients compared with healthy controls. S100A12 had a strong positive correlation with C-reactive protein and IL-6, whereas sRAGE negatively associated with C-reactive protein. S100A12, but not sRAGE, was independently and positively associated with clinical cardiovascular disease (CVD). During follow-up, 85 (33 cardiovascular-related) deaths occurred. Whereas sRAGE did not predict mortality, S100A12 was associated with both all-cause (per log(10) ng/ml hazard ratio [HR] 1.93, 95% confidence interval [CI] 1.18 to 3.15) and CVD-related (HR 3.23, 95% CI 1.48 to 7.01) mortality, even after adjustment for age, sex, vintage, and comorbidities. Further adjustment for inflammation made the predictive value of S100A12 disappear for all-cause mortality, but still persisted in CVD-related mortality.

CONCLUSIONS

Circulating S100A12 and sRAGE are both elevated in hemodialysis patients. However, only S100A12 associates with mortality, partly explained by its links with inflammation.

AGEs/RAGE in CKD: irreversible metabolic memory road toward CVD?

BACKGROUND

Cardiovascular disease is the major cause of death in patients with renal insufficiency, accounting for 50% of all deaths in renal replacement therapy patients. Mortality from cardiovascular diseases in these patients is approximately 9% per year, which is about 30 times the risk in the general population. So far, intensive interventions to the general risk factors, such as high LDL-cholesterol or C-reactive protein, have not been successful in improving their cardiovascular outcomes, suggesting that the beneficial effect of risk reduction may be overwhelmed by accumulated risk memorized by long-term exposure to oxidative stress during the progression of renal failure.

DESIGN

In this review, we propose that this irreversible memory effect in renal failure may be mediated by advanced glycation end-products (AGEs).

RESULTS

The generation of AGEs has been implicated to be deeply associated with increased oxidative stress. Moreover, interaction of the receptor for AGEs (RAGE) with AGEs leads to crucial biomedical pathway generating intracellular oxidative stress and inflammatory mediators, which could result in further amplification of the pathway involved in AGE generation. Several lines of evidence suggest that AGEs/RAGE axis can profoundly be involved in cardiovascular diseases. Recent advances in AGEs and RAGE measurements led us to be capable of understanding more about the role of AGEs/RAGE axis as a risk for cardiovascular diseases in patients with renal failure.

CONCLUSION

AGEs/RAGE axis could be a crucial mediator of oxidative stress in renal failure. RAGE could be not only a useful biomarker, but also a potentially therapeutic target to overcome the accumulated adverse metabolic memory in renal failure.

Alternatively spliced RAGEv1 inhibits tumorigenesis through suppression of JNK signaling

Receptor for advanced glycation end products (RAGE) and its ligands are overexpressed in multiple cancers. RAGE has been implicated in tumorigenesis and metastasis, but little is known of the mechanisms involved. In this study, we define a specific functional role for an alternate splice variant termed RAGE splice variant 1 (RAGEv1), which encodes a soluble endogenous form of the receptor that inhibits tumorigenesis. RAGEv1 was downregulated in lung, prostate, and brain tumors relative to control matched tissues. Overexpressing RAGEv1 in tumor cells altered RAGE ligand stimulation of several novel classes of genes that are critical in tumorigenesis and metastasis. Additionally, RAGEv1 inhibited tumor formation, cell invasion, and angiogenesis induced by RAGE ligand signaling. Analysis of signal transduction pathways underlying these effects revealed marked suppression of c-jun-NH(2)-kinase (JNK) pathway signaling, and JNK inhibition suppressed signaling through the RAGE pathway. Tumors expressing RAGEv1 were significantly smaller than wild-type tumors and displayed prominently reduced activation of JNK. Our results identify RAGEv1 as a novel suppressor, the study of which may offer new cancer therapeutic directions.

Circulating soluble receptor of advanced glycation end product inversely correlates with atherosclerosis in patients with chronic kidney disease

The soluble receptor of advanced glycation end product (sRAGE) prevents vascular damage in experimental animal models, and observational studies in the general population support the hypothesis that sRAGE may exert a protective role on the vasculature. To test this in patients with chronic kidney disease, we determined the relationship between plasma sRAGE and carotid atherosclerosis in 142 patients with an average estimated glomerular filtration rate (eGFR) of 32 ml/min per 1.73 m(2) and 49 healthy control individuals matched for age and gender. Plasma sRAGE was significantly higher in patients with chronic kidney disease than in the control cohort. In an aggregate analysis of the patients and controls, there was a significant inverse relationship between eGFR and sRAGE, with a breakpoint in the regression line at 64 ml/min per 1.73 m(2). Significant inverse relationships were found for sRAGE to intima-media thickness and plaque number in the patients with chronic kidney disease, but no such associations were found in the controls. On covariance analysis, the slopes of intima-media thickness and plaque number to sRAGE were significantly steeper in patients with chronic kidney disease than in the controls. Furthermore, a significant interaction was found between sRAGE and smoking for predicting atherosclerotic plaques in patients with chronic kidney disease. The pathophysiological significance of this correlation will have to await more mechanistic studies.

Proteomic profiling reveals comprehensive insights into adrenergic receptor-mediated hypertrophy in neonatal rat cardiomyocytes

Myocardial adrenergic receptors (ARs) play important roles in cardiac hypertrophy. However, the detailed molecular mechanism of AR-mediated cardiac hypertrophy remains elusive to date. To gain full insight into how ARs are involved in the regulation of cardiac hypertrophy, protein expression profiling was performed with comparative proteomics approach on neonatal rat cardiomyocytes. Forty-six proteins were identified as differentially expressed in hypertrophic cardiomyocytes induced by AR stimulation. To better understand the biological significance of the obtained proteomic data, we utilized the ingenuity pathway analysis tool to construct biological networks and analyze function and pathways that might associate with AR-mediated cardiac hypertrophy. Pathway analysis strongly suggested that ROS may be involved in the development of AR-mediated cardiac hypertrophy, which was then confirmed by further experimentation. The results showed that a marked increase in ROS production was detected in AR-mediated cardiac hypertrophy and blocking of ROS production significantly inhibited AR-mediated cardiac hypertrophy. We further proved that the ROS production was through NADPH oxidase or the mitochondrial electron transport chain and this ROS accumulation resulted in activation of extracellular signal-regulated kinase 1/2 leading to AR-mediated cardiac hypertrophy. These experimental results support the hypothesis, from the ingenuity pathway analysis, that AR-mediated cardiac hypertrophy is associated with the dysregulation of a complicated oxidative stress-regulatory network. In conclusion, our results provide a basis for understanding the detailed molecular mechanisms of AR-mediated cardiac hypertrophy.

Soluble forms of RAGE in internal medicine

The receptor for advanced glycation end-products (RAGE) and its ligands are intimately involved in the pathobiology of a wide range of diseases that share common features, such as enhanced oxidative stress, immune/inflammatory responses, and altered cell functions. Soluble forms of RAGE (sRAGE), including the splice variant endogenous secretory (es)RAGE, have been found circulating in plasma and tissues. Experimental data suggest that these isoforms may neutralize the ligand-mediated damage by acting as a decoy. Moreover, evidence is mounting to support a role for both sRAGE and esRAGE as biomarkers or endogenous protection factors against RAGE-mediated pathogenesis. In this review, we will focus on clinical and therapeutical implications arising from studies investigating the significance of soluble RAGE isoforms in several clinical settings, including cardiovascular disease, diabetes mellitus, hypercholesterolemia, chronic renal failure, immune/inflammatory diseases, pulmonary diseases, neurodegeneration, and cancer.

Advanced glycation end products and their circulating receptors predict cardiovascular disease mortality in older community-dwelling women

AIMS

To characterize the relationship between advanced glycation end products (AGEs) and circulating receptors for AGEs (RAGE) with cardiovascular disease mortality.

METHODS

The relationships between serum AGEs, total RAGE (sRAGE), and endogenous secretory RAGE (esRAGE), and mortality were characterized in 559 community-dwelling women, double dagger 65 years, in Baltimore, Maryland.

RESULTS

During 4.5 years of follow-up, 123 (22%) women died, of whom 54 died with cardiovascular disease. The measure of serum AGEs was carboxymethyl-lysine (CML), a dominant AGE. Serum CML predicted cardiovascular disease mortality (Hazards Ratio [HR] for highest vs lower three quartiles, 1.94, 95% Confidence Interval [CI] 1.08-3.48, p=0.026), after adjusting for age, race, body mass index, and renal insufficiency. Serum sRAGE (ng/mL) and esRAGE (ng/mL) predicted cardiovascular disease mortality (HR per 1 Standard Deviation [SD] 1.27, 95% CI 0.98-1.65, p=0.07; HR 1.28, 95% CI 1.02-1.63, p=0.03), after adjusting for the same covariates. Among non-diabetic women, serum CML, sRAGE, and esRAGE, respectively, predicted cardiovascular disease mortality (HR for highest vs lower three quartiles, 2.29, 95% CI 1.21-4.34, p=0.01; HR per 1 SD, 1.24, 95% CI 0.92-1.65, p=0.16; HR per 1 SD 1.45, 95% CI 1.08-1.93, p=0.01), after adjusting for the same covariates.

CONCLUSIONS

High circulating AGEs and RAGE predict cardiovascular disease mortality among older community-dwelling women. AGEs are a potential target for interventions, as serum AGEs can be lowered by change in dietary pattern and pharmacological treatment.

RAGE (Receptor for Advanced Glycation Endproducts), RAGE ligands, and their role in cancer and inflammation

The Receptor for Advanced Glycation Endproducts [RAGE] is an evolutionarily recent member of the immunoglobulin super-family, encoded in the Class III region of the major histocompatability complex. RAGE is highly expressed only in the lung at readily measurable levels but increases quickly at sites of inflammation, largely on inflammatory and epithelial cells. It is found either as a membrane-bound or soluble protein that is markedly upregulated by stress in epithelial cells, thereby regulating their metabolism and enhancing their central barrier functionality. Activation and upregulation of RAGE by its ligands leads to enhanced survival. Perpetual signaling through RAGE-induced survival pathways in the setting of limited nutrients or oxygenation results in enhanced autophagy, diminished apoptosis, and (with ATP depletion) necrosis. This results in chronic inflammation and in many instances is the setting in which epithelial malignancies arise. RAGE and its isoforms sit in a pivotal role, regulating metabolism, inflammation, and epithelial survival in the setting of stress. Understanding the molecular structure and function of it and its ligands in the setting of inflammation is critically important in understanding the role of this receptor in tumor biology.

RAGE: a novel biological and genetic marker for vascular disease

RAGE [receptor for AGEs (advanced glycation end-products)] plays an important role in the development and progression of vascular disease. Studies in cultured cells and small animal models of disease have clearly demonstrated that RAGE is central to the pathogenesis of vascular disease of the macro- and micro-vessels in both the diabetic and non-diabetic state. Emerging results from human clinical studies have revealed that levels of circulating soluble RAGE in the plasma may reflect the presence and/or extent of vascular disease state. Additionally, genetic variants of the RAGE gene (AGER in HUGO nomenclature) have been associated with vascular disease risk. Combining RAGE circulating protein levels and the presence of particular RAGE polymorphisms may be a useful clinical tool for the prediction of individuals at risk for vascular disease. Therapeutic intervention targeted at the RAGE gene may therefore be a useful means of treating pathologies of the vasculature.

Receptor for AGE (RAGE) and its ligands-cast into leading roles in diabetes and the inflammatory response

The actors in the pathogenesis of diabetes and its complications are many and multifaceted. The effects of elevated levels of glucose are myriad; among these is the generation of advanced glycation end products (AGEs), the products of nonenzymatic glycoxidation of proteins and lipids. The finding that AGEs stimulate signal transduction cascades through the multiligand receptor RAGE unveiled novel insights into diabetes and its complications. Inextricably woven into AGE-RAGE interactions in diabetes is the engagement of the innate and adaptive immune responses. Although glucose may be the triggering stimulus to draw RAGE into diabetes pathology, consequent cellular stress results in release of proinflammatory RAGE ligands S100/calgranulins and HMGB1. We predict that once RAGE is engaged in the diabetic tissue, a vicious cycle of ligand-RAGE perturbation ensues, leading to chronic tissue injury and suppression of repair mechanisms. Targeting RAGE may be a beneficial strategy in diabetes, its complications, and untoward inflammatory responses.

Receptor for advanced glycation end-products (RAGE) and soluble RAGE (sRAGE): cardiovascular implications

Disorders of glucose metabolism are associated with increased risk for cardiovascular disease (CVD) complications, including coronary, peripheral and cerebral arterial disease, that account for the majority of morbidity and mortality among patients with diabetes mellitus (DM). These associations between glucose and CVD risk extend continuously well below the glycaemic thresholds established for the diagnosis of diabetes, including significantly increased risk associated with impaired fasting glucose, impaired glucose tolerance, and even high normal glucose concentrations. While these epidemiological observations have established a clear association between cardiovascular disease and dysglycaemia and suggest a direct causal link, the mechanisms by which hyperglycaemia may contribute to the development, progression and instability of atherosclerosis remain unclear. A number of recent advances in the realm of vascular biology have identified several novel, plausible pathways that might link hyperglycaemia with atherosclerosis, individually or in aggregate. Key among them are the interaction between advanced glycation end-products (AGEs) and the receptor for AGEs (RAGE), which exists as a trans-membrane signalling receptor and as a circulating form, soluble RAGE (sRAGE). The purpose of this review is to provide an overview of the present understanding of RAGE and sRAGE, their plausible role linking perturbed glucose metabolism with the development, progression and instability of atherosclerosis, and the potential therapeutic implications of modulation of this biological system.

A look inside the diabetic brain: Contributors to diabetes-induced brain aging

Central nervous system (CNS) complications resulting from diabetes is a problem that is gaining more acceptance and attention. Recent evidence suggests morphological, electrophysiological and cognitive changes, often observed in the hippocampus, in diabetic individuals. Many of the CNS changes observed in diabetic patients and animal models of diabetes are reminiscent of the changes seen in normal aging. The central commonalities between diabetes-induced and age-related CNS changes have led to the theory of advanced brain aging in diabetic patients. This review summarizes the findings of the literature as they relate to the relationship between diabetes and dementia and discusses some of the potential contributors to diabetes-induced CNS impairments.

Skin autofluorescence, a marker for advanced glycation end product accumulation, is associated with arterial stiffness in patients with end-stage renal disease

Elevated cardiovascular mortality has been shown to be associated with increased arterial stiffness. However, the contribution of tissue accumulation of advanced glycation end products (AGEs) to increased arterial stiffness is unclear. We examined whether skin autofluorescence, a recently developed marker of tissue accumulation of AGEs, is associated with arterial stiffness in 120 Japanese patients with end-stage renal disease (ESRD) and 110 age- and sex-matched control subjects. The ESRD patients had significantly higher pulse wave velocity (PWV), a noninvasive measure of arterial stiffness, and skin autofluorescence than the control subjects. Skin autofluorescence was significantly associated with age in the group of all subjects (R(s) = 0.255, Spearman rank correlation test) and that of control subjects (R(s) = 0.493), but not in the group of ESRD subjects (R(s) = 0.046). The PWV was significantly and positively associated with skin autofluorescence in the group of all subjects (R(s) = 0.335), controls (R(s) = 0.246), and ESRD subjects (R(s) = 0.205). Multiple regression analyses showed that, in the group of all subjects, association of skin autofluorescence with PWV was significant even after adjustment for other covariates including the presence of ESRD and age. Moreover, for ESRD subjects, a significant association between skin autofluorescence and PWV was found, independent of age. Our findings demonstrate the potential usefulness of skin autofluorescence in people of color and demonstrate clinically for the first time the potential involvement of tissue accumulation of AGEs in the pathophysiology of arterial stiffness.