Soluble levels of receptor for advanced glycation endproducts (sRAGE) and coronary artery disease: the next C-reactive protein?

The AGE-RAGE axis associates with chronic pulmonary diseases and smoking in the Rotterdam study

BACKGROUND

Chronic obstructive pulmonary disease (COPD) and asthma associate with high morbidity and mortality. High levels of advanced glycation end products (AGEs) were found in tissue and plasma of COPD patients but their role in COPD and asthma is unclear.

METHODS

In the Rotterdam Study (n = 2577), AGEs (by skin autofluorescence (SAF)), FEV1 and lung diffusing capacity (DLCOc and DLCOc /alveolar volume [VA]) were measured. Associations of SAF with asthma, COPD, GOLD stage, and lung function were analyzed using logistic and linear regression adjusted for covariates, followed by interaction and stratification analyses. sRAGE and EN-RAGE associations with COPD prevalence were analyzed by logistic regression.

RESULTS

SAF associated with COPD prevalence (OR = 1.299 [1.060, 1.591]) but not when adjusted for smoking (OR = 1.106 [0.89, 1.363]). SAF associated with FEV1% predicted (β=-3.384 [-4.877, -1.892]), DLCOc (β=-0.212 [-0.327, -0.097]) and GOLD stage (OR = 4.073, p = 0.001, stage 3&4 versus 1). Stratified, the association between SAF and FEV1%predicted was stronger in COPD (β=-6.362 [-9.055, -3.670]) than non-COPD (β=-1.712 [-3.306, -0.118]). Association of SAF with DLCOc and DLCOc/VA were confined to COPD (β=-0.550 [-0.909, -0.191]; β=-0.065 [-0.117, -0.014] respectively). SAF interacted with former smoking and COPD prevalence for associations with lung function. Lower sRAGE and higher EN-RAGE associated with COPD prevalence (OR = 0.575[0.354, 0.931]; OR = 1.778[1.142, 2.768], respectively).

CONCLUSIONS

Associations between SAF, lung function and COPD prevalence were strongly influenced by smoking. SAF associated with COPD severity and its association with lung function was more prominent within COPD. These results fuel further research into interrelations and causality between SAF, smoking and COPD.

TAKE-HOME MESSAGE

Skin AGEs associated with prevalence and severity of COPD and lung function in the general population with a stronger effect in COPD, calling for further research into interrelations and causality between SAF, smoking and COPD.

Combination of the biomarkers for aging and cancer? - Challenges and current status

The proportion of patients diagnosed with cancer has been shown to rise with the increasing aging global population. Advanced age is a major risk factor for morbidity and mortality in older adults. As individuals experience varying health statuses, particularly with age, it poses a challenge for medical professionals in the cancer field to obtain standardized treatment outcomes. Hence, relying solely on chronological age and disease-related parameters is inadequate for clinical decision-making for elderly patients. With functional, multimorbidity-related, and psychosocial changes that occur with aging, oncologic diseases may develop and be treated differently from younger patients, leading to unique challenges in treatment efficacy and tolerance. To overcome this challenge, personalized therapy using biomarkers has emerged as a promising solution. Various categories of biomarkers, including inflammatory, hematological, metabolic, endocrine, and DNA modification-related indicators, may display features related to both cancer and aging, aiding in the development of innovative therapeutic approaches for patients with cancer in old age. Furthermore, physical functional measurements as non-molecular phenotypic biomarkers are being investigated for their potential complementary role in structured multidomain strategies to combat age-related diseases such as cancer. This review provides insight into the current developments, recent discoveries, and significant challenges in cancer and aging biomarkers, with a specific focus on their application in advanced age.

Role of RAGE in obesity-induced adipose tissue inflammation and insulin resistance

Obesity is known to be associated with adipose tissue inflammation and insulin resistance. Importantly, in obesity, the accumulation of proinflammatory macrophages in adipose tissue correlates with insulin resistance. We hypothesized that the receptor for advanced glycation end products (RAGE) and associated ligands are involved in adipose tissue insulin resistance, and that the activation of the AGE–RAGE axis plays an important role in obesity-associated inflammation. C57BL/6J mice (WT) and RAGE deficient (RAGE^−/−) mice were fed a high fat diet (HFD) and subjected to glucose and insulin tolerance tests. Epdidymal adipose tissue (eAT) was collected and adipose stromal vascular cells isolated using flow cytometry. Visceral adipose tissue macrophage polarization was assessed by quantitative real time PCR. Immunoblotting was performed to evaluate the insulin signaling in adipose tissues. In additional studies, cell trafficking was assessed by injecting labeled blood monocytes into recipient mice. RAGE^−/− mice displayed improved insulin sensitivity and glucose tolerance, accompanied by decreased body weight and eAT mass. Exogenous methylglyoxal (MGO) impaired insulin-stimulated AKT signaling in adipose tissues from WT mice fed a normal chow diet, but not in RAGE^−/− mice. In contrast, in obese mice, treatment with MGO did not reduce insulin-induced phosphorylation of AKT in WT-HFD mice. Moreover, insulin-induced AKT phosphorylation was found to be impaired in adipose tissue from RAGE^−/−-HFD mice. RAGE^−/− mice displayed improved inflammatory profiles and evidence for increased adipose tissue browning. This observation is consistent with the finding of reduced plasma levels of FFA, glycerol, IL-6, and leptin in RAGE^−/− mice compared to WT mice. Collectively the data demonstrate that RAGE-mediated adipose tissue inflammation and insulin-signaling are potentially important mechanisms that contribute to the development of obesity-associated insulin resistance.

Assessment of Advanced Glycation End Products and Receptors and the Risk of Dementia

Importance

Advanced glycation end products (AGEs) and their receptor (RAGE) are implicated in the pathophysiological processes of dementia and potentially underlie the association of diabetes with neurodegeneration. However, longitudinal studies examining this association are lacking.

Objective

To determine whether markers of the AGE-RAGE system are associated with prevalent and incident dementia and with cognition.

Design, Setting, and Participants

In this population-based cohort study including participants from the prospective Rotterdam Study, extracellular newly identified RAGE binding protein (EN-RAGE) and soluble RAGE (S-RAGE) were measured in plasma collected between 1997 and 1999 in a random selection of participants, and additionally in participants with prevalent dementia. Participants without dementia were followed up for dementia until 2016. Skin AGEs, measured as skin autofluorescence, and cognition were measured between 2013 and 2016 in participants without dementia. Data analysis was performed from June 2019 to December 2019.

Exposures

EN-RAGE, S-RAGE, and skin autofluorescence.

Main Outcomes and Measures

Prevalent and incident dementia and cognition, adjusted for potential confounders, including age, sex, diabetes, educational level, APOE ε4 carrier status, smoking, and estimated glomerular filtration rate.

Results

Of 3889 included participants (mean [SD] age, 72.5 [8.9] years; 2187 [56.2%] women), 1021 participants had data on plasma markers (mean [SD] age 73.6 [7.8] years; 564 [55.2%] women), 73 participants had dementia at baseline, and during 10 711 person-years of follow-up, 161 participants developed incident dementia. Compared with low levels, high EN-RAGE level was associated with a higher prevalence of dementia (odds ratio [OR], 3.68 [95% CI, 1.50-8.03]; P = .003), while high S-RAGE level was associated with a lower prevalence of dementia (OR, 0.37 [95% CI, 0.17-0.78]; P = .01). These associations attenuated in a longitudinal setting, with hazard ratios of 0.65 (95% CI, 0.42-1.01) for high EN-RAGE (P = .05) and 1.22 (95% CI, 0.82-1.81) for high S-RAGE (P = .33). Among 2890 participants without dementia (mean [SD] age, 72.5 [9.4] years; 1640 [57%] women), higher skin autofluorescence was associated with lower global cognitive function (adjusted difference in z score per 1-SD higher skin autofluorescence, -0.07 [95% CI, -0.11 to -0.04]), especially among carriers of the APOE ε4 allele (adjusted difference in z score per 1-SD higher skin autofluorescence, -0.15 [95% CI, -0.22 to -0.07]).

Conclusions and Relevance

These findings suggest that the AGE-RAGE system is associated with cognitive decline and dementia cross-sectionally but not longitudinally. This indicates either a short-term association or reverse causality. Findings of cross-sectional associations between higher skin autofluorescence and lower cognitive function and an association with APOE status also warrant replication and prospective studies.

IL-12p40 and sRAGE in serum correlate with chemically induced cleft palate in mice

Cleft palate (CP), a congenital defect in the oral and maxillofacial regions, is difficult to detect prenatally. This study investigated the correlation between differentially expressed proteins in serum and CP induced by all-trans retinoic acid (atRA) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in mice. We studied 80 mice in the following groups: male mice (male; n = 6), nonpregnant female control mice (NP-CRL; n = 6), healthy pregnant controls (P-CRL; Con; n = 24), pregnant mice with CP induced by atRA (n = 24), or pregnant mice with CP induced by TCDD (TCDD; n = 20). Pregnant mice were given with atRA (100 mg/kg) or TCDD (40 μg/kg), or corn oil by oral gavage at E10.5. The serum samples were collected and eight proteins-including interleukin (IL)-12p40, IL-12p70, receptor for advanced glycation end products (RAGE), interferon (IFN)-γ, IFN-β, IL-10, leukemia inhibitory factor (LIF), and epiregulin-were detected by enzyme-linked immunosorbent assay. Placental tissues were immunostained for IL-12p40 and RAGE from stages E13.5 to E16.5. In P-CRL mice, serum IL-12p40 was significantly increased at E13.5 and declined over E14.5-E16.5. P-CRL had lower IFN-γ levels at E13.5 compared with NP-CRL. The CP groups showed lower concentrations of IL-12p40 at E13.5-E14.5 and clearly higher concentrations of soluble RAGE (sRAGE) at E13.5 when compared with P-CRL. IL-12p40 immunostaining clearly decreased in placental tissue sections obtained from E13.5 to E14.5 in both CP groups. These findings suggest that reduced levels of IL-12p40 and increased levels of sRAGE in serum may be correlated with chemically induced CP in mice, but further studies would be required to establish this.

The Relationship between Plasma Soluble Receptor for Advanced Glycation End Products and Coronary Artery Disease

Background

Inflammation is involved in the development and progression of coronary artery disease (CAD). The role of the receptor for advanced glycation end products (RAGE) in the development of CAD has been recognized. The expression of sRAGE and S100A12 in patients with coronary artery disease from different studies was inconsistent. We attempted to determine the expression of sRAGE and S100A12 and their relationship in the subjects with different severity levels of CAD.

Methods

A total of 259 patients undergoing coronary angiography were enrolled from the Department of Geriatric Cardiology in the First Affiliated Hospital of Nanjing Medical University from January 2014 to December 2016. Groups were divided as follows: normal coronary artery (control group), nonobstructive coronary atherosclerosis (<50% stenosis in all coronary vessels, NOCA group), stable angina (SAP group), and acute coronary syndrome (ACS group). During CAG or PCI, peripheral arterial blood was collected from all the patients. Plasma sRAGE and S100A12 levels were measured by ELISA. We calculated the SYNTAX score of each patient with CAD according to the result of CAG.

Results

The levels of sRAGE were significantly elevated in the ACS group compared with those in the control group, the NOCA group, and the SAP group. sRAGE levels were similar among the control group, the NOCA group, and the SAP group. Plasma S100A12 levels were significantly higher in the ACS group than in the control group and the NOCA group. Baseline correlations between plasma levels of sRAGE and plasma S100A12 in the ACS group were significant. Plasma sRAGE concentration was increasing in patients with ACS and was significantly positively correlated with the increasing SYNTAX score. ROC curve analysis revealed that the combination of sRAGE and S100A12 had a good performance in the prediction of high-risk CAD patients.

Conclusion

The plasma levels of sRAGE and S100A12 can be increased in patients with ACS. The elevated sRAGE concentration may be independently associated with the severity of CAD and the inflammatory process. sRAGE combined with S100A12 may be used as a predictor of severe coronary heart disease.

Therapeutic options to reduce advanced glycation end products in patients with diabetes mellitus: A review

Diabetes mellitus (DM) defines metabolic disorders, characterised by elevated levels of blood glucose. Chronic hyperglycaemic state promotes consequently the formation of advanced glycation end products (AGEs) and the expression of their receptor (RAGE) which aggravate many diabetic complications. Due to the relevant role of AGEs and RAGE, several therapeutic approaches with an anti-AGE or RAGE-antagonizing effect are investigated. These therapeutic options include AGE cross-link breakers, AGE inhibitors, RAGE antagonists, drugs clinically approved for various indications like antidiabetic, antihypertensive drugs or statins, as well as dietary and phytotherapeutic approaches. The aim of this review is to give an overview of these therapeutic approaches, their outcomes in clinical studies and their role in the management of diabetes and its complications.

Advanced glycation end products and risk of hypertension in Iranian adults: Tehran lipid and glucose study

Background:

Elevated blood pressure is still one of the major risk factors for diseases and disabilities and also a public health challenge worldwide. In the present longitudinal study, we aimed to evaluate the association between risk of hypertension and dietary advanced glycation end products (AGEs) as a recently discussed potential risk factor.

Materials and Methods:

Dietary assessment of 1775 participants in the third phase of Tehran lipid and glucose study to obtain dietary intake of AGEs was performed using a validated semi-quantitative food frequency questionnaire, and they were followed up for a mean duration of approximately 6 years. To determine the incidence of hypertension across quartiles of AGEs intake, logistic regression models with adjustment for potential confounding variables were used. All statistical analyses were conducted using SPSS, and P < 0.05 was considered statistically significant.

Results:

Higher hypertension occurrence risk was generally attributed to higher AGEs intake quartiles after adjusting for age in men (odds ratio [OR] = 1.48, 95% confidence interval [CI] = 1.11–1.52, P = 0.038) and additional adjustment for smoking, drugs, and physical activity in women (OR = 1.38%–95% CI = 1.09–1.42, P = 0.042). Moreover, across the increasing trend of dietary AGEs intake, the percentage of fat intake increased and that of carbohydrate significantly decreased (P < 0.0001).

Conclusion:

In conclusion, it is highly recommended to limit dietary AGEs consumption to prevent and manage hypertension and its complications.

A prospective study of soluble receptor for advanced glycation end products and adipokines in association with pancreatic cancer in postmenopausal women

Advanced glycation end products (AGEs) dysregulate adipokines and induce inflammation by binding to their adipocyte receptor (RAGE). Soluble RAGE (sRAGE) prevents AGEs/RAGE signaling. We performed a nested case–control study of the association between sRAGE, adipokines, and incident pancreatic cancer risk in the prospective Women's Health Initiative Study. We individually matched controls (n = 802) to cases (n = 472) on age, race, and blood draw date. We evaluated serum concentrations of sRAGE, adiponectin, leptin, monocyte chemotactic protein 1 (MCP1), and plasminogen activator inhibitor‐1 (PAI1) using immunoassay. We used conditional logistic regression model to estimate adjusted odds ratios (aORs) and 95% confidence intervals (CIs) for pancreatic cancer over biomarker quartiles (Q1–Q4). We used principal component analysis to create two composite biomarkers and performed a confirmatory factor analysis to examine the association between composite biomarker scores (CBS) and pancreatic cancer risk. Baseline serum sRAGE concentrations were inversely associated with pancreatic cancer risk (aOR_{Q4 vs. Q1} = 0.70, 95% CI: 0.50–0.99). High MCP1 (aOR _{Q4 vs. Q1} = 2.55, 95% CI: 1.41–4.61) and the higher CBS including MCP1, PAI1, and leptin (aOR_{Q4 vs. Q1} = 1.82, 95% CI = 1.04–3.18) were also associated with increased pancreatic cancer risk among women with BMI <25 kg/m² (P values for interaction <0.05). We found an inverse association between prediagnostic sRAGE concentrations and risk of incident pancreatic cancer in postmenopausal women. A proinflammatory CBS was associated with increased risk only in women with normal BMI. MCP1 was not modulated by sRAGE.

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.

Glucagon-like peptide-1 analogue liraglutide ameliorates atherogenesis via inhibiting advanced glycation end product-induced receptor for advanced glycosylation end product expression in apolipoprotein-E deficient mice

Glucagon-like peptide-1 (GLP-1) can protect arteriosclerotic lesions in apolipoprotein-E deficient (ApoE-/-) mice. Advanced glycation end products (AGEs)/receptor for advanced glycation end products (RAGE) interaction serves a key role in the development of diabetic vascular complications. The present study examined whether the GLP-1 analogue liraglutide can ameliorate atherogenesis via inhibiting AGEs-induced RAGE expression. Male ApoE-/- mice (age, 10 weeks) were divided into control, GLP-1, AGEs and AGEs+GLP-1 group. All mice were fed a high-fat diet. The AGEs and AGEs+GLP-1 groups were treated with intraperitoneal injection of AGEs (30 mg/kg/day). The GLP-1 and AGEs+GLP-1 groups were treated with subcutaneous injections of liraglutide (0.4 mg/kg/day). After 9 weeks, blood was drawn and the aortas were rapidly procured. The serum levels of AGEs, soluble RAGE (sRAGE), stromal cell-derived factor-1α (SDF-1α), total cholesterol and triacylglycerol were measured. Atherosclerotic plaque area was determined by Sudan IV staining. The mRNA and protein expression levels of RAGE were determined using reverse transcription-quantitative polymerase chain reaction and western blotting, respectively. The results demonstrated that AGEs treatment increased serum AGEs levels, increased the expression of RAGE in the aorta, and aggravated atherosclerotic lesions compared with the control. Liraglutide treatment reduced serum AGEs levels, reduced the expression of RAGE in aorta, and relieved atherosclerotic lesions compared with the control. In conclusion, these data suggested that liraglutide serves an anti-atherosclerotic effect via inhibiting AGEs-induced RAGE expression in ApoE-/- mice. These findings provide novel evidence for the use of GLP-1-type agents for the treatment of diabetic vascular complications.

Serum soluble receptor of advanced glycation end products and risk of metabolic syndrome in Egyptian obese women

Obesity is one of the diagnostic criteria of metabolic syndrome (MS). It is correlated with insulin resistance (IR) and high vascular risk as well. Advanced glycation end products (AGEs) and their receptor (RAGE) play an important role in abnormal metabolic components in obese women. This study aimed to explore the serum levels of sRAGE in Egyptian obese women and compare with healthy non-obese controls and investigate the relationship between serum sRAGE, metabolic parameters, and obesity complications. The soluble form of receptor for advanced glycation end products (sRAGE), anthropometry, metabolic and biochemical biomarkers were measured in 100 obese women and 100 age-matched healthy control non-obese women. The homeostasis model assessment estimate of insulin resistance (HOMA-IR) has been determined from serum insulin and glucose values. Serum sRAGE levels were significantly lower in obese cases than controls and inversely correlated with obesity and metabolic parameters. Results of univariate and multivariate analyses for determinants of serum sRAGE levels in obese cases showed that parameters statistically and significantly related were body mass index (BMI), waist circumference (WC), LDL-C, TG, BP, HOMA-IR, ALT and AST. sRAGE is a novel biomarker for metabolic dysfunction in Egyptian obese women and might predict the future cardio-metabolic events.

Rutin Inhibits Neuroinflammation and Provides Neuroprotection in an Experimental Rat Model of Subarachnoid Hemorrhage, Possibly Through Suppressing the RAGE-NF-κB Inflammatory Signaling Pathway

As is known to all, neuroinflammation plays a vital role in early brain injury pathogenesis following subarachnoid hemorrhage (SAH). It has been shown that rutin have a property of inhibiting inflammation in many kinds of animal models. However, the effect of rutin on neuroinflammation after SAH remains uninvestigated. In this study, we investigated the potential effects of rutin on neuroinflammation and the underlying mechanism in an experimental rat model of SAH performed by endovascular perforation. Adult male SD rats were randomly divided into three groups, including sham group, SAH + vehicle group and SAH + rutin group (50 mg/kg) intraperitoneally (i.p.) administered at 30 min after SAH. After sacrificed at 24 h after SAH, all rats were examined by following tests, including neurologic scores, blood-brain barrier permeability, brain water content and neuronal cell death in cerebral cortex. The level of inflammation in brain was estimated by means of multiple molecules, including RAGE, NF-κB, and inflammation cytokines. Our results indicated that rutin could significantly downregulate the increased level of REGE, NF-κB and inflammatory cytokines in protein level. In addition, rutin could also ameliorate a series of secondary brain injuries such as brain edema, destruction of blood-brain barrier, neurological deficits and neuronal death. This study indicated that rutin administration had a neuroprotective effect in an experimental rat model of SAH, possibly through inhibiting RAGE-NF-κB mediated inflammation signaling pathway.

Dietary consumption of advanced glycation end products and risk of metabolic syndrome

Metabolic syndrome (MetS) is a complex disorder which has become one of the major public health challenges worldwide. This study was conducted to evaluate the association between dietary advanced glycation end products (AGEs) and risk of MetS and its components. This cross-sectional study was conducted in a representative sample of 5848 adults, aged 19-70 years. Daily consumption of carboxymethyl lysine, a major type of AGEs, was determined using a validated semi-quantitative food frequency questionnaire. Across increasing trend of AGEs consumption, the percentage of fat intake increased and that of carbohydrate significantly decreased (p < 0.001). Subjects in the highest (>10,506 kU/d) compared to the lowest (<6673 kU/d) quartile category of AGEs had higher risk of abdominal obesity (OR: 1.19, 95% CI: 1.01-1.39) and hypertriglyceridemia (OR: 1.26, 95% CI: 1.07-1.49). Therefore, recommendation on restriction of AGEs intake could be a practical approach to prevent metabolic abnormalities.

Involvement of the TAGE-RAGE system in non-alcoholic steatohepatitis: Novel treatment strategies

Non-alcoholic fatty liver disease (NAFLD) is a major cause of liver disease around the world. It includes a spectrum of conditions from simple steatosis to non-alcoholic steatohepatitis (NASH) and can lead to fibrosis, cirrhosis, liver failure, and/or hepatocellular carcinoma. NAFLD is also associated with other medical conditions such as obesity, diabetes mellitus (DM), metabolic syndrome, hypertension, insulin resistance, hyperlipidemia, and cardiovascular disease (CVD). In diabetes, chronic hyperglycemia contributes to the development of both macro- and microvascular conditions through a variety of metabolic pathways. Thus, it can cause a variety of metabolic and hemodynamic conditions, including upregulated advanced glycation end-products (AGEs) synthesis. In our previous study, the most abundant type of toxic AGEs (TAGE); i.e., glyceraldehyde-derived AGEs, were found to make a significant contribution to the pathogenesis of DM-induced angiopathy. Furthermore, accumulating evidence suggests that the binding of TAGE with their receptor (RAGE) induces oxidative damage, promotes inflammation, and causes changes in intracellular signaling and the expression levels of certain genes in various cell populations including hepatocytes and hepatic stellate cells. All of these effects could facilitate the pathogenesis of hypertension, cancer, diabetic vascular complications, CVD, dementia, and NASH. Thus, inhibiting TAGE synthesis, preventing TAGE from binding to RAGE, and downregulating RAGE expression and/or the expression of associated effector molecules all have potential as therapeutic strategies against NASH. Here, we examine the contributions of RAGE and TAGE to various conditions and novel treatments that target them in order to prevent the development and/or progression of NASH.

Involvement of the TAGE-RAGE system in non-alcoholic steatohepatitis: Novel treatment strategies

Non-alcoholic fatty liver disease (NAFLD) is a major cause of liver disease around the world. It includes a spectrum of conditions from simple steatosis to non-alcoholic steatohepatitis (NASH) and can lead to fibrosis, cirrhosis, liver failure, and/or hepatocellular carcinoma. NAFLD is also associated with other medical conditions such as obesity, diabetes mellitus (DM), metabolic syndrome, hypertension, insulin resistance, hyperlipidemia, and cardiovascular disease (CVD). In diabetes, chronic hyperglycemia contributes to the development of both macro- and microvascular conditions through a variety of metabolic pathways. Thus, it can cause a variety of metabolic and hemodynamic conditions, including upregulated advanced glycation end-products (AGEs) synthesis. In our previous study, the most abundant type of toxic AGEs (TAGE); i.e., glyceraldehyde-derived AGEs, were found to make a significant contribution to the pathogenesis of DM-induced angiopathy. Furthermore, accumulating evidence suggests that the binding of TAGE with their receptor (RAGE) induces oxidative damage, promotes inflammation, and causes changes in intracellular signaling and the expression levels of certain genes in various cell populations including hepatocytes and hepatic stellate cells. All of these effects could facilitate the pathogenesis of hypertension, cancer, diabetic vascular complications, CVD, dementia, and NASH. Thus, inhibiting TAGE synthesis, preventing TAGE from binding to RAGE, and downregulating RAGE expression and/or the expression of associated effector molecules all have potential as therapeutic strategies against NASH. Here, we examine the contributions of RAGE and TAGE to various conditions and novel treatments that target them in order to prevent the development and/or progression of NASH.

Neuroprotection by the PARP inhibitor PJ34 modulates cerebral and circulating RAGE levels in rats exposed to focal brain ischemia

The receptor for advanced glycation end products (RAGE) has a potential role as a damage-sensing molecule; however, to date, its involvement in the pathophysiology of stroke and its modulation following neuroprotective treatment are not completely understood. We have previously demonstrated that expression of distinct RAGE isoforms, recognized by different antibodies, is differentially modulated in the brain of rats subjected to focal cerebral ischemia. Here, we focus on the full-length membrane-bound RAGE isoform, showing that its expression is significantly elevated in the striatum, whereas it is reduced in the cortex of rats subjected to transient middle cerebral artery occlusion (MCAo). Notably, the reduction of cortical levels of full-length RAGE detected 24 h after reperfusion is abolished by systemic administration of a neuroprotective dose of the poly(ADP-ribose) polymerase (PARP) inhibitor, N-(6-oxo-5,6-dihydrophenanthridin-2-yl)-N,N-dimethylacetamide (PJ34). More interestingly, a significant reduction of plasma soluble RAGE (sRAGE) occurs 24 h after reperfusion and this effect is reverted by a neuroprotective dose of PJ34. Soluble forms of RAGE, generated either by alternative splicing or by proteolysis of the full-length form, effectively bind advanced glycation end products, thereby competing with the cell surface full-length RAGE, thus providing a 'decoy' function that may counteract the adverse effects of receptor signaling in neurons and may possibly exert cytoprotective effects. Thus, our data confirm the important role of RAGE in ischemic cerebral damage and, more interestingly, suggest the potential use of sRAGE as a blood biomarker of stroke severity and of neuroprotective treatment efficacy.

Soluble receptor for advanced glycation end products independently predicts cardiometabolic syndrome in Latino youth

OBJECTIVE

The soluble receptor for advanced glycation end products (sRAGE) has anti-atherogenic properties in adults, however, little is known about the relationship between sRAGE and cardiometabolic disease risk in pediatric populations. Therefore, the purpose of this investigation is to examine the relationship between sRAGE and cardiometabolic risk factors in Latino youth.

RESEARCH DESIGN AND METHODS

Data from 133 Latino youth (58% female; age 16.3 ± 2.8 yr) enrolled in the Arizona Insulin Resistance Registry were analyzed. Cardiometabolic syndrome was determined using a continuous risk score normalized to the population. Components included waist circumference, high-density lipoprotein cholesterol (HDL-c), triglycerides, mean arterial pressure (MAP), and homeostatic assessment of insulin resistance (HOMA-IR). sRAGE levels were determined from fasting serum using an enzyme-linked immunosorbent assay.

RESULTS

In univariate analysis, sRAGE was inversely associated with waist circumference (r = -0.22, p = 0.01), MAP (r = -0.15, p = 0.09), and HOMA-IR (r = -0.29, p < 0.01) and positively associated with HDL-c (r = 0.19, p < 0.05). In multiple regression analysis with age, sex, and BMI, sRAGE remained an independent predictor of cardiometabolic syndrome risk score (R(2) = 0.55, p < 0.001).

CONCLUSIONS

These data suggest that sRAGE may be an early independent biomarker of cardiometabolic disease risk in youth. Prospective studies are needed to establish the predictive utility of sRAGE for long-term disease outcomes.

The alarmin functions of high-mobility group box-1 and IL-33 in the pathogenesis of systemic lupus erythematosus

'Alarmins' are a group of endogenous proteins or molecules that are released from cells during cellular demise to alert the host innate immune system. Two of them, high-mobility group box-1 (HMGB1) and IL-33 shared many similarities of cellular localization, functions and involvement in various inflammatory diseases including systemic lupus erythematosus (SLE). The expressions of HMGB1 and IL-33, and their corresponding receptors RAGE (receptor for advanced glycation end products) and ST2, respectively, are substantially upregulated in patients with lupus nephritis (LN). This review highlights the emerging roles of alarmin proteins in various pathologies of LN, by focusing on classical HMGB1 and a newly discovered alarmin IL-33.

Soluble form of receptor for advanced glycation end products is associated with obesity and metabolic syndrome in adolescents

The aim of this cross-sectional study was to investigate the relationship between soluble form of receptor for advanced glycation end products (sRAGE), obesity, and metabolic syndrome (MetS) in adolescents. A total of 522 male and 561 female adolescents were enrolled into the final analyses. Anthropometric parameters, blood pressure, blood biochemistry, fasting insulin, and plasma sRAGE levels were measured. In males, sRAGE was significantly and inversely correlated with waist circumference (WC), body mass index (BMI), systolic blood pressure, triglyceride (TG), low density lipoprotein cholesterol (LDL-C), and homeostasis model assessment-insulin resistance (HOMA-IR). Only WC and BMI were significantly and inversely correlated with sRAGE in females. Using linear regression analysis adjusting for age and gender, significant association was found between sRAGE and WC, BMI, TG, LDL-C, and HOMA-IR in adolescents of either gender (P < 0.05). This association was abolished when further adjusting BMI. In addition, sRAGE was significantly and inversely correlated with the increasing number of components of MetS in males (P for trend = 0.006) but not in females (P for trend = 0.422). In conclusion, plasma sRAGE is associated with obesity and MetS among adolescents. BMI may be the most important determinant of sRAGE levels in adolescents.

Efficacy of alogliptin, a dipeptidyl peptidase-4 inhibitor, on glucose parameters, the activity of the advanced glycation end product (AGE) - receptor for AGE (RAGE) axis and albuminuria in Japanese type 2 diabetes

BACKGROUND

To examine the effects of alogliptin, a dipeptidyl peptidase-4 inhibitor, on glucose parameters, the advanced glycation end product (AGE)-receptor for AGE (RAGE) axis and albuminuria in Japanese type 2 diabetes patients.

METHODS

Sixty-one patients whose HbAlc  ≥ 6.1% (mean age 64.7 years; 67% men; mean HbAlc 7.4%; 57% were pharmacologically treated) underwent blood and urine sampling and analysis before and after 12 weeks of treatment with alogliptin (25 mg once daily).

RESULTS

Alogliptin treatment significantly reduced fasting glucose (160.3 mg/dL at baseline versus 138.0 mg/dL at 12 weeks), glycoalbumin (21.1% at baseline versus 18.9% at 12 weeks), HbAlc (7.4% at baseline versus 6.9% at 12 weeks), circulating soluble form of RAGE concentrations (847.3 pg/mL at baseline versus 791.4 pg/mL at 12 weeks) and urine albumin to creatinine ratio (31.6 mg/g Cr at baseline versus 26.5 mg/g Cr at 12 weeks), whereas 1,5-anhydroglucitol concentrations were significantly increased (7.5 µg/mL at baseline versus 11.6 µg/mL at 12 weeks; all P < 0.05). Circulating AGEs concentrations were reduced only in patients with baseline AGEs ≥7 U/mL (n = 33, from 8.2 U/mL to 7.2U /mL; p < 0.01) after alogliptin treatment. The treatment-induced change of soluble form of sRAGE concentrations was associated with changes of 1,5-anhydroglucitol and HbAlc concentrations (rho = -0.32 and 0.29, respectively). Meanwhile, the treatment-induced change of urine albumin to creatinine ratio was associated with a change in the fasting glucose concentration (rho = 0.25; all p < 0.05). During the intervention, alogliptin treatment was well tolerated without any hypoglycemia or side effects.

CONCLUSION

Alogliptin treatment improved the AGE-RAGE axis and reduced albuminuria in Japanese type 2 diabetes patients.

Development of nonalcoholic hepatopathy: contributions of oxidative stress and advanced glycation end products

Advanced glycation end products (AGEs) are generated spontaneously in cells; however, under conditions of hyperglycemia and lipid peroxidation, their levels are higher than usual, which contribute to the development of diseases such as the nonalcoholic fatty liver disease (NAFLD). NAFLD is associated with oxidative stress (OS), which is linked to the transition of steatosis to steatohepatitis due to lipid peroxidation. The AGE-receptor interaction in hepatic stellate cells leads to an increase in reactive oxygen species and enhances the proliferation and activation of these cells, worsening liver fibrosis and disease progression. In this vicious cycle, there is production of (carboxymethyl)lysine, a biomarker for products of advanced glycation and lipid peroxidation, being a shared component between the two pathways. In this review, we aim to compile evidence to support the basic molecular mechanisms of AGEs and OS generation and their influence, independently or combined, on the evolution of NAFLD. The deeper understanding of the interrelations of AGEs + OS may help to elucidate the pathogenic pathways of NAFLD and to devise rational therapeutic interventions for this disease, with an expected positive impact on quality of life of patients.

Reasons to Investigate the Soluble Receptor for Advanced Glycation End-Product (sRAGE) Pathway in Aortic Disease

Aortic disease has a high rate of morbidity and mortality, and there are no documented screening methods to date. Yet biochemical research does show a significant link between soluble receptor for advanced glycation end-products (sRAGE) protein and cardiovascular disease. Therefore, it can be hypothesized that sRAGE plasma levels may help differentiate patients with aortic disease from the general population, which this paper will review and present.

Functional role of soluble receptor for advanced glycation end products in stroke

OBJECTIVE

Little is known about the involvement of the soluble form of receptor for advanced glycation end products (sRAGE) in acute ischemic stroke (IS). Here, we aim to identify the role of plasma sRAGE and high mobility group box 1 (HMGB1) in imaging-confirmed IS patients, as well as mice subjected to focal ischemic stroke.

METHODS AND RESULTS

IS patients were recruited and plasma samples were collected for the measurement of sRAGE and HMGB1 after stroke. The relation of sRAGE and HMGB1 with acute IS was also investigated in a C57BL/6J mouse model of focal ischemic stroke and primary cortical neurons subjected to oxygen and glucose deprivation. Plasma levels of sRAGE and HMGB1 were both significantly increased within 48 hours after IS, and the sRAGE level was an independent predictor of functional outcome at 3 months poststroke. Immunoprecipitation assays revealed that the binding of plasma HMGB1 to sRAGE increased progressively after IS both in patients and mice. Administration of recombinant sRAGE significantly reduced infiltrating immune cells and improved the outcome of injury in mice, protected cultured neurons against oxygen and glucose deprivation-induced cell death, and ameliorated the detrimental effect of recombinant HMGB1.

CONCLUSIONS

Early poststroke plasma sRAGE may play a protective role in IS by capturing HMGB1. Hence, recombinant sRAGE is a potential therapeutic agent in acute IS.

Association between serum endogenous secretory receptor for advanced glycation end products and risk of type 2 diabetes mellitus with combined depression in the Chinese population

OBJECTIVE

The role of the endogenous secretory receptor for advanced glycation end products (esRAGE) in depression of diabetes patients and its clinical significance are unclear. This study investigated the role of serum esRAGE in patients with type 2 diabetes mellitus with depression in the Chinese population.

PATIENTS AND METHODS

One hundred nineteen hospitalized patients with type 2 diabetes were recruited at Fujian Provincial Hospital (Fuzhou, China) from February 2010 to January 2011. All selected subjects were assessed with the Hamilton Rating Scale for Depression (HAMD). Among them, 71 patients with both type 2 diabetes and depression were included. All selected subjects were examined for the following: esRAGE concentration, glycosylated hemoglobin (HbA1c), blood lipids, C-reactive protein, trace of albumin in urine, and carotid artery intima-media thickness (IMT). Association between serum esRAGE levels and risk of type 2 diabetes mellitus with depression was also analyzed.

RESULTS

There were statistically significant differences in gender, age, body mass index, waist circumference, and treatment methods between the group with depression and the group without depression (P<0.05). Multiple linear regression analysis showed that HAMD scores were negatively correlated with esRAGE levels (standard regression coefficient -0.270, P<0.01). HAMD-17 scores were positively correlated with IMT (standard regression coefficient 0.183, P<0.05) and with HbA1c (standard regression coefficient 0.314, P<0.01).

CONCLUSIONS

Female gender, younger age, obesity, poor glycemic control, complications, and insulin therapy are all risk factors of type 2 diabetes mellitus with combined depression in the Chinese population. Inflammation and atherosclerosis play an important role in the pathogenesis of depression. esRAGE is a protective factor of depression among patients who have type 2 diabetes.

Inverse Association between Cardiac Troponin-I and Soluble Receptor for Advanced Glycation End Products in Patients with Non-ST-Segment Elevation Myocardial Infarction

Interaction of advanced glycation end products (AGEs) with the receptor for advanced AGEs (RAGE) results in activation of nuclear factor kappa-B, release of cytokines, expression of adhesion molecules, and induction of oxidative stress. Oxygen radicals are involved in plaque rupture contributing to thromboembolism, resulting in acute coronary syndrome (ACS). Thromboembolism and the direct effect of oxygen radicals on myocardial cells cause cardiac damage that results in the release of cardiac troponin-I (cTnI) and other biochemical markers. The soluble RAGE (sRAGE) compete with RAGE for binding with AGE, thus functioning as a decoy and exerting a cytoprotective effect. Low levels of serum sRAGE would allow unopposed serum AGE availability for binding with RAGE, resulting in the generation of oxygen radicals and proinflammatory molecules that have deleterious consequences and promote myocardial damage. sRAGE may stabilize atherosclerotic plaques. It is hypothesized that low levels of sRAGE are associated with high levels of serum cTnI in patients with ACS. The main objective of the study was to determine whether low levels of serum sRAGE are associated with high levels of serum cTnI in ACS patients. The serum levels of sRAGE and cTnI were measured in 36 patients with non-ST-segment elevation myocardial infarction (NSTEMI) and 30 control subjects. Serum levels of sRAGE were lower in NSTEMI patients (802.56 ± 39.32 pg/mL) as compared with control subjects (1311.43 ± 66.92 pg/mL). The levels of cTnI were higher in NSTEMI patients (2.18 ± 0.33 μg/mL) as compared with control subjects (0.012 ± 0.001 μg/mL). Serum sRAGE levels were negatively correlated with the levels of cTnI. In conclusion, the data suggest that low levels of serum sRAGE are associated with high serum levels of cTnI and that there is a negative correlation between sRAGE and cTnI.

Low levels of soluble receptor for advanced glycation end products in non-ST elevation myocardial infarction patients

BACKGROUND

Interaction of the receptors for advanced glycation end products (RAGEs) with advanced glycation end products (AGEs) results in expression of inflammatory mediators (tumor necrosis factor-alpha [TNF-α] and soluble vascular cell adhesion molecule-1 [sVCAM-1]), activation of nuclear factor-kappa B and induction of oxidative stress - all of which have been implicated in atherosclerosis. Soluble RAGE (sRAGE) acts as a decoy for the RAGE ligand and is protective against atherosclerosis.

OBJECTIVES

To determine whether levels of serum sRAGE are lower, and whether levels of serum AGEs, TNF-α and sVCAM-1 are higher in non-ST elevation myocardial infarction (NSTEMI) patients than in healthy control subjects; and whether sRAGE or the ratio of AGEs to sRAGE (AGEs/sRAGE) is a predictor/biomarker of NSTEMI.

METHODS

Serum levels of sRAGE, AGEs, TNF-α and sVCAM-1 were measured in 46 men with NSTEMI and 28 age- and sex-matched control subjects. Angiography was performed in the NSTEMI patients.

RESULTS

sRAGE levels were lower, and levels of AGEs, TNF-α, sVCAM-1 and AGEs/sRAGE were higher in NSTEMI patients than in control subjects. sRAGE levels were negatively correlated with the number of diseased coronary vessels, serum AGEs, AGEs/sRAGE, TNF-α and sVCAM-1. The sensitivity of the AGEs/sRAGE test is greater than that of the sRAGE test, while the specificity and predictive values of the sRAGE test are greater than those of the AGEs/sRAGE test for identifying NSTEMI patients.

CONCLUSIONS

Serum levels of sRAGE were low in NSTEMI patients, and were negatively correlated with extent of lesion, inflammatory mediators, AGEs and AGEs/sRAGE. Both sRAGE and AGEs/sRAGE may serve as biomarkers/predictors for identifying NSTEMI patients.

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.

Do statins have a role in reduction/prevention of post-PCI restenosis?

The pathophysiology of post-PCI restenosis involves neointimal formation that consists of three phases: thrombosis (within 24 h), recruitment (3-8 days), and proliferation, which starts on day 8 of PCI. Various factors suggested to be predictors/risks for restenosis include C-reactive protein (CRP), inflammatory mediators (cytokines and adhesion molecules), oxygen radicals, advanced glycation end products (AGEs) and their receptors (RAGE), and soluble RAGE (sRAGE). The earlier noted factors produce thrombogenesis, vascular smooth muscle cell proliferation, and extracellular matrix formation. Statins have pleiotropic effects. Besides lowering serum cholesterol, they have various other biological effects including antiinflammatory, antithrombotic, CRP-lowering, antioxidant, antimitotic, and inhibition of smooth muscle cell proliferation. They inhibit matrix metalloproteinase and cyclooxygenase-2, lower AGEs, decrease expression of RAGE and increase levels of serum sRAGE. They also increase the synthesis of nitric oxide (NO) by increasing endothelial NO synthase expression and activity. Preprocedural statin therapy is known to reduce peri- and post-PCI myonecrosis and reduce the need for repeat revascularization. There is evidence that statin-eluting stents inhibit in-stent restenosis in animal models. It is concluded that because of the above attributes of statins, they are suitable candidates for reduction of post-PCI restenosis and post-PCI myonecrosis. The future directions for the use of statins in reduction of post-PCI restenosis and myonecrosis have been discussed.

Low plasma levels of the soluble receptor for advanced glycation end products in HIV-infected patients with subclinical carotid atherosclerosis receiving combined antiretroviral therapy

OBJECTIVE

Combined antiretroviral therapy (cART) has significantly improved the survival rate and quality of life for HIV-infected subjects, but it contributes to the development of metabolic complications including coronary artery disease (CAD). Recent studies have reported that high plasma levels of the soluble receptor for advanced glycation end products (sRAGE) were associated with a lower incidence of CAD in non-HIV infected patients. However, there has been no report of an association of sRAGE and subclinical carotid atherosclerosis in HIV-infected patients receiving cART.

METHODS

We examined the association of circulating sRAGE in HIV-infected patients with carotid intima-media thickness (IMT) and other metabolic variables. We prospectively enrolled 76 HIV-infected patients receiving cART for ≥ 6 months.

RESULTS

sRAGE had a significantly negative correlation with body mass index (r = -0.324, p = 0.005), waist-to-hip ratio (r = -0.335, p = 0.003), systolic blood pressure (BP) (r=-0.359, p=0.002), diastolic BP (r = -0.343, p = 0.004), total cholesterol (r = -0.240, p = 0.037), low-density lipoprotein-cholesterol (r=-0.284, p=0.024), log(homeostasis model assessment of insulin resistance [HOMA-IR]) (r = -0.380, p = 0.002) and carotid IMT including max-IMT and mean-IMT (r = -0.358, p = 0.001 and r = -0.329, p = 0.004, respectively). By the use of multiple stepwise regression analyses, systolic BP (p=0.001) and log[HOMA-IR] (p = 0.001) remained significant independently.

CONCLUSIONS

These results suggest that sRAGE may have a protective effect against subclinical atherosclerosis by preventing inflammatory responses mediated by the activation of cell surface RAGE in HIV-infected patients receiving cART.

Atorvastatin exerts its anti-atherosclerotic effects by targeting the receptor for advanced glycation end products

Recent studies demonstrated the beneficial role of atorvastatin in reducing the risk of cardiovascular morbidity and mortality in patients with diabetes mellitus and/or metabolic syndrome. To investigate the mechanisms underlying the anti-atheroscleroic action of atorvastatin, we examined the expression of the receptor for advanced glycation end products (RAGE) and its downstream target gene, monocyte chemoattractant protein-1 (MCP-1) using real-time PCR. In in vitro studies, exposure to high glucose or AGE induced oxidative stress and activation of the AGE/RAGE system in human umbilical vein endothelial cells. Treatment of the cells with atorvastatin significantly released the oxidative stress by restoring the levels of glutathione and inhibited the RAGE upregulation. In diabetic Goto Kakisaki (GK) rats fed with a high-fat diet for 12weeks, RAGE and MCP-1 were upregulated in the aortas, and there was a significant correlation between RAGE and MCP-1 mRNA abundance (r=0.482, P=0.031). Treatment with atorvastatin (20mg/kg qd) significantly downregulated the expression of RAGE and MCP-1. These data thus demonstrate a novel "pleiotropic" activity of atorvastatin in reducing the risk of cardiovascular diseases by targeting RAGE expression.

Advanced glycation end products, soluble receptor for advanced glycation end products, and risk of colorectal cancer

BACKGROUND

Advanced glycation end products (AGE) accumulate in human tissue proteins during aging, particularly under hyperglycemia conditions. AGEs induce oxidative stress and inflammation via the receptor for AGEs (RAGE) and soluble RAGE (sRAGE) can neutralize the effects mediated by RAGE-ligand engagement.

METHODS

We examined the association between N(ε)-(carboxymethyl)lysine (CML), a prominent AGE, and sRAGE and colorectal cancer risk in a prospective case-cohort study nested within a cancer prevention trial among 29,133 Finnish male smokers. Among study subjects who were alive without cancer 5 years after baseline (1985-1988), we identified 483 incident colorectal cancer cases and randomly sampled 485 subcohort participants as the comparison group with the follow-up to April 2006. Baseline serum levels of CML-AGE, sRAGE, glucose and insulin were determined. Weighted Cox proportional hazard regression models were used to calculate relative risks (RR) and 95% CI.

RESULTS

Comparing highest with lowest quintile of sRAGE, the RR for incident colorectal cancer was 0.65 (95% CI, 0.39-1.07; P(trend) = 0.03), adjusting for age, years of smoking, body mass index, and CML-AGE. Further adjustment for serum glucose strengthened the association (RR = 0.52; 95% CI, 0.30-0.89; P(trend) = 0.009). Highest quintile of CML-AGE was not associated with an increased risk of colorectal cancer (multivariate RR = 1.20; 95% CI, 0.64-2.26).

CONCLUSIONS

Higher prediagnostic levels of serum sRAGE were associated with lower risk of colorectal cancer in male smokers.

IMPACT

This is the first epidemiologic study to implicate the receptor for AGEs in colorectal cancer development.

Soluble receptors for advanced glycation end products (sRAGE) as a predictor of restenosis following percutaneous coronary intervention

BACKGROUND

Interaction of advanced glycation end products (AGEs) with their receptor (RAGE) increases expression of inflammatory mediators (tumor necrosis factor alpha [TNF-α] and soluble vascular cell adhesion molecule-1 [sVCAM-1]) and induces oxygen radicals that are implicated in atherosclerosis. Balloon-injury-induced atherosclerosis is associated with increased expression of AGEs and RAGE. The soluble receptor for AGE (sRAGE), which acts as a decoy for RAGE ligands (AGEs), prevents atherosclerosis in this model.

HYPOTHESIS

We evaluated: 1) whether post-percutaneous coronary intervention (PCI) restenosis is associated with low pre-PCI serum sRAGE, high serum AGEs, TNF-α, and sVCAM-1, and high AGE/sRAGE ratio; 2) whether pre-PCI and post-PCI levels of these markers are similar in patients with or without restenosis; and 3) whether sRAGE and AGE/sRAGE ratio have predictive value for post-PCI restenosis.

METHODS

Angiography was performed in 46 patients with non-ST-segment elevation myocardial infarction for assessment of restenosis. Serum sRAGE, AGEs, TNF-α, and sVCAM-1 were measured in these patients and 20 control subjects.

RESULTS

: Nineteen of the 46 patients developed post-PCI restenosis, which was associated with lower sRAGE and higher TNF-α and sVCAM-1 levels, and higher AGE/sRAGE ratio compared with patients without restenosis. Pre-PCI and post-PCI levels of these biomarkers were similar in both groups, except in patients with restenosis, in whom the post-PCI level of sRAGE was lower and TNF-α was higher than the pre-PCI levels. The sensitivity and negative predictive value of sRAGE were 100%, and were higher than those of AGE/sRAGE ratio in identifying post-PCI restenosis.

CONCLUSIONS

Both low serum sRAGE levels and high AGE/sRAGE ratio have predictive value for post-PCI restenosis.

Low maternal serum matrix metalloproteinase (MMP)-2 concentrations are associated with preterm labor and fetal inflammatory response

OBJECTIVES

to assess the relationship between maternal and umbilical serum concentrations of matrix metalloproteinases (MMP)-2,8,9, the soluble receptor for advanced glycation end products (sRAGE) and IL-10 and premature delivery and fetal inflammation.

METHODS

maternal serum levels of MMPs, sRAGE, IL-10 and C-reactive protein (CRP) were determined in 67 women with preterm labor and in 38 healthy pregnant women of similar gestational age (GA). In the group with preterm labor we also determined umbilical concentrations of MMPs, IL-6 and sRAGE. The group with preterm labor was additionally divided based on the presence of funisitis and elevations of fetal umbilical IL-6 concentrations.

RESULTS

maternal serum levels of MMP-2 and sRAGE were significantly lower in women with preterm labor compared to women with normal pregnancy. Additionally, within the group of women with preterm labor, maternal serum MMP-2 concentrations were significantly lower in the subgroup with funisitis and in the subgroup with elevated umbilical concentration of IL-6.

CONCLUSION

our results demonstrate significantly different serum concentrations of MMP-2 and sRAGE in women with preterm labor compared to healthy pregnant patients of the same GA.

Soluble receptor for advanced glycation end products (sRAGE) in tracheobronchial aspirate fluid and cord blood of very low birth weight infants with chorioamnionitis and funisitis

BACKGROUND

A systemic fetal inflammatory response, reflected by histological funisitis is associated with pulmonary morbidity and increased mortality after premature birth. The receptor for advanced glycation end products (RAGE) is a membrane-bound multiligand receptor with a key role in inflammation. Soluble RAGE (sRAGE) is created by alternative mRNA splicing or shedding of the receptor's extracellular domain and can inhibit RAGE-activation.

AIMS

To assess the association of funisitis with airway and systemic concentrations of sRAGE in very premature infants.

METHODS

Forty-two ventilated infants (gestational age: 27.4 +/- 1.8weeks, birth weight: 1017 +/- 229 g [mean +/- SD]) were studied. sRAGE concentrations were measured in tracheobronchial aspirate fluid (TAF) on days of life 1, 3, 5, 7 and 10 and in umbilical cord serum of 28 infants by ELISA. The secretory component for IgA (SC) served as reference protein in TAF. Placental tissue, membranes and umbilical cords were examined microscopically to distinguish three groups: chorioamnionitis (n=9), funisitis (n=17) and controls (n=16).

RESULTS

The funisitis group had lower sRAGE concentrations than both other groups in cord blood serum (median: 0.52 ng/ml [25th-75th centile: 0.32-0.91]; control, 1.72 [1.02-2.69]; chorioamnionitis, 1.44 [0.92-1.63], p<0.01) and TAF on day 1 (290 ng/ngSC [140-400]; control, 2750 [1470-28920]; chorioamnionitis, 2150 [1220-7140], p<0.01). sRAGE in TAF remained lower in the funisitis than in the chorioamnionitis group on days 3 and 10, p<0.01 respectively.

CONCLUSIONS

Decreased sRAGE in airways and circulation after funisitis may contribute to an imbalance between pro- and anti-inflammatory factors priming very premature infants for pulmonary injury and increasing the risk of adverse outcome.

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.

Involvement of TAGE-RAGE System in the Pathogenesis of Diabetic Retinopathy

Diabetic complications are a leading cause of acquired blindness, end-stage renal failure, and accelerated atherosclerosis, which are associated with the disabilities and high mortality rates seen in diabetic patients. Continuous hyperglycemia is involved in the pathogenesis of diabetic micro- and macrovascular complications via various metabolic pathways, and numerous hyperglycemia-induced metabolic and hemodynamic conditions exist, including increased generation of various types of advanced glycation end-products (AGEs). Recently, we demonstrated that glyceraldehyde-derived AGEs, the predominant structure of toxic AGEs (TAGE), play an important role in the pathogenesis of angiopathy in diabetic patients. Moreover, recent evidence suggests that the interaction of TAGE with the receptor for AGEs (RAGE) elicits oxidative stress generation in numerous types of cells, all of which may contribute to the pathological changes observed in diabetic complications. In this paper, we discuss the pathophysiological role of the TAGE-RAGE system in the development and progression of diabetic retinopathy.

Comparative effects of pioglitazone and rosiglitazone on plasma levels of soluble receptor for advanced glycation end products in type 2 diabetes mellitus patients

Low levels of soluble receptor for advanced glycation end products (sRAGE) have been associated with the occurrence of vascular complications in patients with type 2 diabetes mellitus. Preliminary evidence has suggested that thiazolidinediones have the ability to modulate circulating levels of this molecule in the hyperglycemic milieu. The aim of this pilot study was to assess the differential effect of 2 different thiazolidinediones-pioglitazone and rosiglitazone-on plasma levels of sRAGE in type 2 diabetes mellitus patients. Sixty type 2 diabetes mellitus subjects were randomly assigned to receive pioglitazone (30 mg/d, n = 19), rosiglitazone (4 mg/d, n = 20), or placebo (medical nutrition therapy, n = 21) for 12 weeks. Changes in plasma glucose, glycosylated hemoglobin, insulin resistance (homeostasis model assessment), total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, and sRAGE were evaluated at baseline and after 12 weeks. At 12 weeks, the pioglitazone (P < .001) group had a significant increase from baseline in sRAGE values that was not seen in the medical nutrition therapy and rosiglitazone groups. We conclude that, in type 2 diabetes mellitus patients, pioglitazone-but not rosiglitazone-significantly raised sRAGE, which may contribute to its antiatherogenic effects.

High plasma levels of the soluble receptor for advanced glycation endproducts in patients with symptomatic carotid atherosclerosis

BACKGROUND

Advanced glycation endproducts (AGEs), particularly carboxymethyl(lysine)-adducts (CML), exert part of their cellular effects by binding to a receptor, named receptor for AGEs (RAGE). The soluble form of this receptor (sRAGE) has been shown to have an athero-protective role. We hypothesized the existence of a relationship between the AGE-RAGE axis and the occurrence of symptoms related to carotid atherosclerosis in nondiabetic conditions.

MATERIALS AND METHODS

We evaluated plasma levels of CML and sRAGE (by ELISA), and tissue levels (tAGEs and tRAGE, semiquantitatively, by immunohistochemistry) in endarterectomy carotid plaque tissue in 29 nondiabetic patients. At the time of surgery, 10 patients were asymptomatic and 19 were symptomatic.

RESULTS

Plasma levels of sRAGE were higher in symptomatic patients than in asymptomatic patients [median (interquartile range): 676 (394-858) pg mL(-1) vs. 347 (284-479) pg mL(-1), P = 0.009]. In symptomatic patients, plasma levels of sRAGE correlated positively with CML (r = 0.60, P < 0.01), C-reactive protein (CRP) (r = 0.618, P < 0.01) and fibrinogen (r = 0.522, P<0.005), while in asymptomatic patients, no correlation was observed. Although tissue and plasma levels of AGEs and RAGE did not correlate between each other, tAGEs and tRAGE were also positively correlated only in symptomatic patients (chi(2) = 8.93, P = 0.003).

CONCLUSIONS

Plasma levels of sRAGE are higher in symptomatic than asymptomatic carotid atherosclerosis. Higher levels of sRAGE in symptomatic patients may be markers of a higher degree of vascular inflammation in such patients.

Circulating levels of a soluble form of receptor for advanced glycation end products and high-mobility group box chromosomal protein 1 in patients with acute pancreatitis

OBJECTIVES

To study in patients with acute pancreatitis (AP) the plasma soluble form of the receptor for advanced glycation end products (sRAGE) and high-mobility group box chromosomal protein 1 (HMGB1) levels, followed-up for 12 days after hospitalization, in relation to the occurrence of organ failure and mortality.

METHODS

Thirty-eight patients with severe AP and organ failure (grade 2). A control group (127 patients) consisted of 38 patients with severe AP without organ failure (grade 1) and 89 patients with mild AP (grade 0). Plasma samples for determination of HMGB1 and sRAGE levels were collected on admission and on days 1 and 2, days 3 and 4, and days 7 and 12 after admission.

RESULTS

The median of the highest sRAGE levels was higher in grade 2 patients (472 pg/mL; interquartile range [IQR], 259-912) than in grade 0 plus grade 1 patients (349 pg/mL; IQR, 209-544; P = 0.024). Among the patients with detectable HMGB1, the median of the highest HMGB1 levels was 117 ng/mL (IQR, 56-212; n = 24) in grade 2 patients and 87 ng/mL (IQR, 54-161; n = 62) in grade 0 plus grade 1 patients (P = 0.310).

CONCLUSIONS

We demonstrate that sRAGE level, but not HMGB1 level, is significantly higher in AP patients who develop organ failure than in AP patients without organ failure who recover.