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

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

Increased expression of receptor for advanced glycation end-products worsens focal brain ischemia in diabetic rats

A rat model of diabetes mellitus was induced by a high fat diet, followed by focal brain ischemia induced using the thread method after 0.5 month. Immunohistochemistry showed that expression of receptor for advanced glycation end-products was higher in the ischemic cortex of diabetic rats compared with non-diabetic rats with brain ischemia. Western blot assay revealed increased phosphorylated c-Jun N-terminal kinase expression, and unchanged phosphorylated extracellular signal-regulated protein kinase protein expression in the ischemic cortex of diabetic rats compared with non-diabetic rats with brain ischemia. Additionally, phosphorylated p38 mitogen-activated protein kinase protein was not detected in any rats in the two groups. Severity of limb hemiplegia was worse in diabetic rats with brain ischemia compared with ischemia alone rats. The results suggest that increased expression of receptor for advanced glycation end-products can further activate the c-Jun N-terminal kinase pathway in mitogen-activated protein kinase, thereby worsening brain injury associated with focal brain ischemia in diabetic rats.

Comprehensive analysis of advanced glycation end-products in commonly consumed foods:presenting a database for dietary AGEs and associated exposure assessment

Advanced glycation end-products(AGEs)are a group of heterogeneous compounds formed in heatprocessed foods and are proven to be detrimental to human health.Currently,there is no comprehensive database for AGEs in foods that covers the entire range of food categories,which limits the accurate risk assessment of dietary AGEs in human diseases.In this study,we first established an isotope dilution UHPLCQq Q-MS/MS-based method for simultaneous quantification of 10 major AGEs in foods.The contents of these AGEs were detected in 334 foods covering all main groups consumed in Western and Chinese populations.Nε-Carboxymethyllysine,methylglyoxal-derived hydroimidazolone isomers,and glyoxal-derived hydroimidazolone-1 are predominant AGEs found in most foodstuffs.Total amounts of AGEs were high in processed nuts,bakery products,and certain types of cereals and meats(>150 mg/kg),while low in dairy products,vegetables,fruits,and beverages(<40 mg/kg).Assessment of estimated daily intake implied that the contribution of food groups to daily AGE intake varied a lot under different eating patterns,and selection of high-AGE foods leads to up to a 2.7-fold higher intake of AGEs through daily meals.The presented AGE database allows accurate assessment of dietary exposure to these glycotoxins to explore their physiological impacts on human health.

Advanced glycation end-products change placental barrier function and tight junction in rats with gestational diabetes mellitus via the receptor for advanced glycation end products/nuclear factor-κB pathway

The placenta plays an important role in nutrient transport to maintain the growth and development of the embryo.Gestational diabetes mellitus(GDM),the most common complication during pregnancy,highly affects placental function in late gestation.Advanced glycation end-products(AGEs),a complex and heterogeneous group of compounds engaged by the receptor for AGEs(RAGE),are closely associated with diabetes-related complications.In this study,AGEs induced a decrease in the expression of tight junction(TJ)proteins in BeWo cells and increased the paracellular permeability of trophoblast cells by regulating RAGE/NF-κB.Sprague-Dawley(SD)rats injected with 100 mg/kg AGEs-rat serum albumin(RSA)via the tail vein from embryo day 2 were set as the placental barrier dysfunction model group(n=10).The effect of AGEs on placental permeability was determined using the Evans-Blue dye extravasation method.The ultrastructure of the placenta samples was observed by transmission electron microscopy.The effects of AGEs on the placenta were confirmed by treating rats with RAGE antagonist FPS-ZM1 and soluble forms of RAGE(sRAGE).AGEs treatment increased placental permeability and disrupted the tight junctions in pregnant rat placenta,but has no effect on blood glucose.The expression of TJ-related proteins,including ZO-1,Occludin,and Claudin 5,were downregulated after AGEs treatment.Further,AGEs treatment increased the expression of RAGE and nuclear factor-κB in the placenta of rats and upregulated the levels of vascular endothelial growth factor.The effects of AGEs on the placenta were blocked by RAGE antagonist FPS-ZM1 and sRAGE.This study demonstrates the mechanism underlying AGEs-induced disturbance in placental function in pregnant rats and highlights the potential of AGEs in the treatment of GDM.

Advanced glycation end products in gastric cancer:A promising future

In this editorial,we delve into the article and offer valuable insights into a crucial aspect of gastric cancer aetiology.Gastric cancer is a malignancy emanating from the epithelial lining of the gastric mucosa and one of the most prevalent forms of cancer worldwide.The development of gastric cancer is associated with multiple risk factors,including Helicobacter pylori infection,advanced age,a diet rich in salt,and suboptimal eating patterns.Despite notable reductions in morbidity and mortality rates,gastric cancer remains a formidable public health concern,impacting patients’lives.Advanced glycation end products(AGEs)are complex compounds arising from nonenzymatic reactions within living organisms,the accumulation of which is implicated in cellular and tissue damage;thus,the levels are AGEs are correlated with the risk of diverse diseases.The investigation of AGEs is of paramount importance for the treatment of gastric cancer and can provide pivotal insights into disease pathogenesis and preventive and therapeutic strategies.The reduction of AGEs levels and suppression of their accumulation are promising avenues for mitigating the risk of gastric cancer.This approach underscores the need for further research aimed at identifying innovative interventions that can effectively lower the incidence and mortality rates of this malignancy.

Contributions of the receptor for advanced glycation end products axis activation in gastric cancer

Compelling shreds of evidence derived from both clinical and experimental research have demonstrated the crucial contribution of receptor for advanced glycation end products(RAGE)axis activation in the development of neoplasms,including gastric cancer(GC).This new actor in tumor biology plays an important role in the onset of a crucial and long-lasting inflammatory milieu,not only by supporting phenotypic changes favoring growth and dissemination of tumor cells,but also by functioning as a pattern-recognition receptor in the inflammatory response to Helicobacter pylori infection.In the present review,we aim to highlight how the overexpression and activation of the RAGE axis contributes to the proliferation and survival of GC cells as and their acquisition of more invasive phenotypes that promote dissemination and metastasis.Finally,the contribution of some single nucleotide polymorphisms in the RAGE gene as susceptibility or poor prognosis factors is also discussed.

Nε-(carboxymethyl)lysine promotes lipid uptake of macrophage via cluster of differentiation 36 and receptor for advanced glycation end products

BACKGROUND Advanced glycation end products(AGEs)are diabetic metabolic toxic products that cannot be ignored.Nε-(carboxymethyl)lysine(CML),a component of AGEs,could increase macrophage lipid uptake,promote foam cell formation,and thereby accelerate atherosclerosis.The receptor for AGEs(RAGE)and cluster of differentiation 36(CD36)were the receptors of CML.However,it is still unknown whether RAGE and CD36 play key roles in CML-promoted lipid uptake.AIM Our study aimed to explore the role of RAGE and CD36 in CML-induced macrophage lipid uptake.METHODS In this study,we examined the effect of CML on lipid uptake by Raw264.7 macrophages.After adding 10 mmol/L CML,the lipid accumulation in macrophages was confirmed by oil red O staining.Expression changes of CD36 and RAGE were detected with immunoblotting and quantitative real-time polymerase chain reaction.The interaction between CML with CD36 and RAGE was verified by immunoprecipitation.We synthesized a novel N-succinimidyl-4-18Ffluorobenzoate-CML radioactive probe.Radioactive receptor-ligand binding assays were performed to test the binding affinity between CML with CD36 and RAGE.The effects of blocking CD36 or RAGE on CML-promoting lipid uptake were also detected.RESULTS The study revealed that CML significantly promoted lipid uptake by macrophages.Immunoprecipitation and radioactive receptor-ligand binding assays indicated that CML could specifically bind to both CD36 and RAGE.CML had a higher affinity for CD36 than RAGE.ARG82,ASN71,and THR70 were the potential interacting amino acids that CD36 binds to CML Anti-CD36 and anti-RAGE could block the uptake of CML by macrophages.The lipid uptake promotion effect of CML was significantly attenuated after blocking CD36 or RAGE.CONCLUSION Our results suggest that the binding of CML with CD36 and RAGE promotes macrophage lipid uptake.

Implications of receptor for advanced glycation end products for progression from obesity to diabetes and from diabetes to cancer

Obesity and type 2 diabetes mellitus(T2DM)are chronic pathologies with a high incidence worldwide.They share some pathological mechanisms,including hyperinsulinemia,the production and release of hormones,and hyperglycemia.The above,over time,affects other systems of the human body by causing tissue hypoxia,low-grade inflammation,and oxidative stress,which lay the pathophysiological groundwork for cancer.The leading causes of death globally are T2DM and cancer.Other main alterations of this pathological triad include the accumulation of advanced glycation end products and the release of endogenous alarmins due to cell death(i.e.,damage-associated molecular patterns)such as the intracellular proteins high-mobility group box protein 1 and protein S100 that bind to the receptor for advanced glycation products(RAGE)-a multiligand receptor involved in inflammatory and metabolic and neoplastic processes.This review analyzes the latest advanced reports on the role of RAGE in the development of obesity,T2DM,and cancer,with an aim to understand the intracellular signaling mechanisms linked with cancer initiation.This review also explores inflammation,oxidative stress,hypoxia,cellular senescence,RAGE ligands,tumor microenvironment changes,and the“cancer hallmarks”of the leading tumors associated with T2DM.The assimilation of this information could aid in the development of diagnostic and therapeutic approaches to lower the morbidity and mortality associated with these diseases.

Intra-coronary administration of soluble receptor for advanced glycation end-products attenuates cardiac remodeling with decreased myocardial transforming growth factor-pl expression and fibrosis in minipigs with ischemia-reperfusion injury

Background The cardioprotective effects of soluble receptor for advanced glycation end-products （sRAGE） have not been evaluated in large animals and the underlying mechanisms are not fully understood. This study aimed to evaluate the effects of intra-coronary administration of sRAGE on left ventricular function and myocardial remodeling in a porcine model of ischemia-reperfusion （I/R） injury. Methods Ten male minipigs with I/R injury were randomly allocated to receive intra-coronary administration of sRAGE （sRAGE group, n=5） or saline （control group, n=5）. Echocardiography was performed before and 2 months after infarction. Myocardial expression of transforming growth factor （TGF）-β1 was determined by immunohistochemistry and fibrosis was evaluated by Sirius red staining. Results As compared with the baseline values in the control animals, left ventricular end-diastolic volume （from （19.5±5.1） to （32.3±5.6） ml, P 〈0.05） and end-systolic volume （from （8.3±3.2） to （15.2±4.1） ml, P 〈0.05） were significantly increased, whereas ejection fraction was decreased （from （61.6±13.3）% to （50.2±11.9）%, P 〈0.05）. No obvious change in these parameters was observed in the sRAGE group. Myocardial expression of TGF-β1 was significantly elevated in the infarct and non-infarct regions in the control group, as compared with sRAGE group （both P 〈0.01）. Fibrotic lesions were consistently more prominent in the infarct region of the myocardium in the control animals （P〈0.05）. Conclusion Intra-coronary sRAGE administration attenuates RAGE-mediated myocardial fibrosis and I/R injury through a TGF-β1-dependent mechanism, suggesting a clinical potential in treating RAGE/ligand-associated cardiovascular diseases.

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

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

Receptor of advanced glycation end-products axis and gallbladder cancer:A forgotten connection that we should reconsider

Compelling evidence derived from clinical and experimental research has demonstrated the crucial contribution of chronic inflammation in the development of neoplasms,including gallbladder cancer.In this regard,data derived from clinical and experimental studies have demonstrated that the receptor of advanced glycation end-products(RAGE)/AGEs axis plays an important role in the onset of a crucial and long-lasting inflammatory milieu,thus supporting tumor growth and development.AGEs are formed in biological systems or foods,and food-derived AGEs,also known as dietary AGEs are known to contribute to the systemic pool of AGEs.Once they bind to RAGE,the activation of multiple and crucial signaling pathways are triggered,thus favoring the secretion of several proinflammatory cytokines also involved in the promotion of gallbladder cancer invasion and migration.In the present review,we aimed to highlight the relevance of the association between high dietary AGEs intakes and high risk for gallbladder cancer,and emerging data supporting that dietary intervention to reduce gallbladder cancer risk is a very attractive approach that deserves much more research efforts.

Advanced glycation end product signaling and metabolic complications:Dietary approach

Advanced glycation end products(AGEs)are a heterogeneous collection of compounds formed during industrial processing and home cooking through a sequence of nonenzymatic glycation reactions.The modern western diet is full of heat-treated foods that contribute to AGE intake.Foods high in AGEs in the contemporary diet include processed cereal products.Due to industrialization and marketing strategies,restaurant meals are modified rather than being traditionally or conventionally cooked.Fried,grilled,baked,and boiled foods have the greatest AGE levels.Higher AGE-content foods include dry nuts,roasted walnuts,sunflower seeds,fried chicken,bacon,and beef.Animal proteins and processed plant foods contain furosine,acrylamide,heterocyclic amines,and 5-hydroxymethylfurfural.Furosine(2-furoil-methyl-lysine)is an amino acid found in cooked meat products and other processed foods.High concentrations of carboxymethyl-lysine,carboxyethyl-lysine,and methylglyoxal-O are found in heat-treated nonvegetarian foods,peanut butter,and cereal items.Increased plasma levels of AGEs,which are harmful chemicals that lead to age-related diseases and physiological aging,diabetes,and autoimmune/inflammatory rheumatic diseases such as systemic lupus erythematosus and rheumatoid arthritis.AGEs in the pathophysiology of metabolic diseases have been linked to individuals with diabetes mellitus who have peripheral nerves with high amounts of AGEs and diabetes has been linked to increased myelin glycation.Insulin resistance and hyperglycemia can impact numerous human tissues and organs,leading to long-term difficulties in a number of systems and organs,including the cardiovascular system.Plasma AGE levels are linked to all-cause mortality in individuals with diabetes who have fatal or nonfatal coronary artery disease,such as ventricular dysfunction.High levels of tissue AGEs are independently associated with cardiac systolic dysfunction in diabetic patients with heart failure compared with diabetic patients without heart failure.It is widely recognized that AGEs and oxidative stress play a key role in the cardiovascular complications of diabetes because they both influence and are impacted by oxidative stress.All chronic illnesses involve protein,lipid,or nucleic acid modifications including crosslinked and nondegradable aggregates known as AGEs.Endogenous AGE formation or dietary AGE uptake can result in additional protein modifications and stimulation of several inflammatory signaling pathways.Many of these systems,however,require additional explanation because they are not entirely obvious.This review summarizes the current evidence regarding dietary sources of AGEs and metabolism-related complications associated with AGEs.

Role of the receptor for advanced glycation end products in hepatic fibrosis

AIM： To study the role of advanced glycation end products （AGE） and their specific receptor （RAGE） in the pathogenesis of liver fibrogenesis. METHODS： In vitro RAGE expression and extracellular matrix-related gene expression in both rat and human hepatic stellate cells （HSC） were measured after stimulation with the two RAGE ligands, advanced glycation end product-bovine serum albumin （AGE- BSA） and N＇-（carboxymethyl） lysine （CML）-BSA, or with tumor necrosis factor-α （TNF-α）. In vivo RAGE expression was examined in models of hepatic fibrosis induced by bile duct ligation or thioacetamide. The effects of AGE-BSA and CML-BSA on HSC proliferation, signal transduction and profibrogenic gene expression were studied in vitro. RESULTS： In hepatic fibrosis, RAGE expression was enhanced in activated HSC, and also in endothelial cells, inflammatory cells and activated bile duct epithelia. HSC expressed RAGE which was upregulated after stimulation with AGE-BSA, CML-BSA, and TNF-α.RAGE stimulation with AGE-BSA and CML-BSA did not alter HSC proliferation, apoptosis, fibrogenic signal transduction and fibrosis- or fibrolysis-related gene expression, except for marginal upregulation of procollagen α1（ I ） mRNA by AGE-BSA. CONCLUSION： Despite upregulation of RAGE in activated HSC, RAGE stimulation by AGE does not alter their fibrogenic activation. Therefore, RAGE does not contribute directly to hepatic fibrogenesis.

Advanced glycation end-product expression is upregulated in the gastrointestinal tract of type 2 diabetic rats

AIM:To investigate changes in advanced glycation end products(AGEs) and their receptor(RAGE) expression in the gastrointestinal(GI) tract in type 2 diabetic rats.METHODS:Eight inherited type 2 diabetic rats GotoKakizak(GK) and ten age-matched normal rats were used in the study.From 18 wk of age,the body weight and blood glucose were measured every week and 2 wk respectively.When the rats reached 32 wk,twocentimeter segments of esophagus,duodenum,jejunum,ileum,and colon were excised and the wet weight was measured.The segments were fixed in 10% formalin,embedded in paraffin and five micron sections were cut.The layer thickness was measured in Hematoxylin and Eosin-stained slides.AGE [N epsilon-(carboxymethyl) lysine and N epsilon-(carboxyethyl)lysine] and RAGE were detected by immunohistochemistry staining and image analysis was done using Sigmascan Pro 4.0 image analysis software.RESULTS:The blood glucose concentration(mmol/L) at 18 wk age was highest in the GK group(8.88 ± 1.87 vs 6.90 ± 0.43,P < 0.001),a difference that continued to exist until the end of the experiment.The wet weight per unit length(mg/cm) increased in esophagus,jejunum and colon from the normal to the GK group(60.64 ± 9.96 vs 68.56 ± 11.69,P < 0.05 for esophagus; 87.01 ± 9.35 vs 105.29 ± 15.45,P < 0.01 for jejunum; 91.37 ± 7.25 vs 97.28 ± 10.90,P < 0.05 for colon).Histologically,the layer thickness of the GItract was higher for esophagus,jejunum and colon in the GK group [full thickness(μm):575.37 ± 69.22 vs 753.20 ± 150.41,P < 0.01 for esophagus; 813.51 ± 44.44 vs 884.81 ± 45.31,P < 0.05 for jejunum; 467.12 ± 65.92 vs 572.26 ± 93.60,P < 0.05 for colon].In esophagus,the AGE and RAGE mainly distributed in striated muscle cells and squamous epithelial cells.The AGE distribution was much stronger in the GK group compared to the normal group both in the striated muscle layer and mucosa layer(immuno-positive area/ total measuring area %:4.52 ± 0.89 vs 10.96 ± 1.34,P < 0.01 for muscle; 8.90 ± 2.62 vs 22.45 ± 1.26,P < 0.01 for mucosa).No visible difference was found for RAGE distribution between the two groups.In the intestine AGE and RAGE distributed in epithelial cells of villi and crypt.RAGE was also found in neurons in the myenteric and submucosal plexus.The intensity of AGE staining in mucosa of all segments and RAGE staining in neurons in all segments were strongest in the diabetes group.Significant difference for AGE was found in the epithelial cells of villi and crypt in duodenum(immunopositive area/total measuring area %:13.37 ± 3.51 vs 37.48 ± 8.43,P < 0.05 for villi; 0.38 ± 0.12 vs 1.87 ± 0.53,P < 0.05 for crypt) and for RAGE in neurons of all segments(e.g.,for jejunum:no staining neurons% 0 vs 0,mild 36.0 ± 5.2 vs 28.7 ± 3.5,moderate 53.2 ± 4.8 vs 55.8 ± 5.4,strong 10.7 ± 1.1 vs 15.4 ± 2.0,P < 0.05).In the colon,RAGE was primarily found in neurons in the myenteric and submucosal plexus.It was stronger in the diabetes group than in the normal group(no staining neurons% 6.2 ± 0.2 vs 0.3 ± 0.04,mild 14.9 ± 2.1 vs 17.6 ± 1.5,moderate 53.1 ± 4.6 vs 44.7 ± 4.4,strong 25.6 ± 18 vs 43.6 ± 4.0,P < 0.05).In the rectum,RAGE was primarily found in the mucosa epithelial cells.CONCLUSION:The AGE and RAGE expression was upregulated in the GI tract of GK diabetic rats and may contribute to GI dysfunction in type 2 diabetic patients.

Dietary advanced glycation end-products aggravate non-alcoholic fatty liver disease

AIM To determine if manipulation of dietary advanced glycation end product(AGE), intake affects nonalcoholic fatty liver disease(NAFLD) progression and whether these effects are mediated via RAGE. METHODS Male C57Bl6 mice were fed a high fat, high fructose, high cholesterol(HFHC) diet for 33 wk and compared with animals on normal chow. A third group were given a HFHC diet that was high in AGEs. Another group was given a HFHC diet that was marinated in vinegar to prevent the formation of AGEs. In a second experiment, RAGE KO animals were fed a HFHC diet or a high AGE HFHC diet and compared with wildtype controls. Hepatic biochemistry, histology, picrosirius red morphometry and hepatic mR NA were determined. RESULTS Long-term consumption of the HFHC diet generated significant steatohepatitis and fibrosis after 33 wk. In this model, hepatic 4-hydroxynonenal content(a marker of chronic oxidative stress), hepatocyte ballooning, picrosirius red staining, α-smooth muscle actin and collagen type 1A gene expression were all significantly increased. Increasing the AGE content of the HFHC diet by baking further increased these markers of liver damage, but this was abrogated by pre-marination in acetic acid. In response to the HFHC diet, RAGE-/-animals developed NASH of similar severity to RAGE+/+ animals but were protected from the additional harmful effects of the high AGE containing diet. Studies in isolated Kupffer cells showed that AGEs increase cell proliferation and oxidative stress, providing a likely mechanism through which these compounds contribute to liver injury. CONCLUSION In the HFHC model of NAFLD, manipulation of dietary AGEs modulates liver injury, inflammation, and liver fibrosis via a RAGE dependent pathway. This suggests that pharmacological and dietary strategies targeting the AGE/RAGE pathway could slow the progression of NAFLD.

Role of the advanced glycation end products receptor in Crohn's disease inflammation

AIM:To investigate the level of mucosal expression and the involvement of the receptor for the advanced glycation end products(RAGE)in delayed apoptosis and tumor necrosis factor(TNF)-αproduction in Crohn’s disease(CD).METHODS:Surgical and endoscopic specimens from both inflamed and non-inflamed areas of the ileum and/or colon were collected from 20 and 14 adult CD patients,respectively,and used for the assessment of RAGE expression by means of immunohistochemistry and western blotting analysis.Normal tissues from 21 control subjects were used for comparison.The same polyclonal anti-human RAGE antibody(R and D System)was used in all experimental conditions.RAGE staining was quantized by a score including both the amount of positive cells and intensity of immunoreactivity;cellular pattern was also described.The effects of RAGE blocking on apoptotic rate and TNF-αproduction were investigated on immune cells freshly isolated from CD mucosa and incubated both with and without the muramyl dipeptide used as antigenic stimulus.Statistical analysis was performed via the test for trend,with regression models to account for intra-patient correlations.A 2-sided P<0.05 was considered significant.RESULTS:In inflamed areas,RAGE expression in both the epithelial and lamina propria compartments was higher than control tissues(P=0.001 and 0.021,respectively),and a cluster of positive cells were usually found in proximity of ulcerative lesions.Similar results were obtained in the lamina propria compartment of non-inflamed areas(P=0.025).The pattern of staining was membranous and granular cytosolic at the epithelial level,while in the lamina propria it was diffuse cytosolic.When evaluating the amount of protein expression by immunoblotting,a significant increase of both surface area and band intensity(P<0.0001 for both)was observed in CD inflamed areas compared to control tissue,while in non-inflamed areas a significant increase was found only for band intensity(P<0.005).Moreover,a significantly lower expression in noninflamed areas in comparison with inflamed areas was found for both surface area and band intensity(P<0.0006 for both).Finally,RAGE blocking largely affects both the apoptotic rate of mucosal cells(towards an increase in both non-inflamed and inflamed areas of P<0.001 and<0.0001,respectively)and TNF-αsecretion(towards a decrease in both non-inflamed and inflamed areas of P<0.05 and<0.01,respectively),mainly in the presence of antigenic stimulation.CONCLUSION:RAGE is up-regulated in CD,especially in inflamed areas,and it appears to play a role in the mechanisms involved in chronic inflammation.

Association of vascular endothelial growth factor-634G/C and receptor for advanced glycation end products G82S gene polymorphisms with diabetic retinopathy

AIMTo investigate the association of receptor for advanced glycation end products (RAGE) G82S and vascular endothelial growth factor (VEGF) -634 G/C gene polymorphisms with diabetic retinopathy (DR).METHODSOur cross-sectional study included 61 diabetic patients, 12 of them had proliferative diabetic retinopathy (PDR), 15 had non proliferative diabetic retinopathy (NPDR), 34 had no diabetic retinopathy (NDR) and 61 healthy controls. Participants were tested for RAGE G82S and VEGF -634 G/C polymorphisms by polymerase chain reaction-restriction fragment length polymorphism.RESULTSWe found a significant association between VEGF -634 G/C polymorphism and PDR as PDR patients had increased incidence of VEGF -634 CC genotype compared to NDR patients [odds ratio for CC vs (GC+GG)=6.5, 95% CI=1.5-27.8, P=0.021]. Also VEGF -634 CC genotype and C allele were significantly higher in the PDR than in NPDR patients, which is a novel finding in our study (P=0.024, 0.009 respectively). The mean triglycerides level was significantly higher in diabetic patients with CC genotype (P=0.01) as compared to patients with other genotypes. All cases and control subjects were of the same heterozygous RAGE 82G/S genotype.CONCLUSIONPatients carrying VEGF -634 C polymorphism have a higher risk of PDR development, so VEGF -634 G/C polymorphism could be used as a predictive marker for PDR in diabetic patients. We could not find a significant association between RAGE G82S polymorphism and DR.

Correlation between soluble receptor for advanced glycation end products levels and coronary artery disease in postmenopausal nondiabetic women

BACKGROUND The established cardiovascular risk factors cannot explain the overall risk of coronary artery disease(CAD),especially in women.Therefore,there is a growing need for the assessment of novel biomarkers to identify women at risk.The receptor for advanced glycation end products(RAGE)and its interaction with the advanced glycation end product(AGE)ligand have been associated with atherogenesis.The soluble fraction of RAGE(sRAGE)antagonizes RAGE signaling and exerts an antiatherogenic effect.AIM The study aim was to explore the association between plasma levels of sRAGE and CAD in nondiabetic postmenopausal women.METHODS This case-control study included 110 nondiabetic postmenopausal women who were enrolled in two groups.Group I included 55 angiographically proven CAD subjects with>50%stenosis in at least one of the major coronary arteries and Group II included 55 healthy control women who did not have CAD or had<50%stenosis of the coronary arteries.Stenosis was confirmed by invasive angiography.Plasma sRAGE was determined by an enzyme-linked immunosorbent assay.RESULTS We observed significantly lower plasma sRAGE concentrations in subjects with CAD vs healthy controls(P<0.05).Univariate and multivariate logistic regression analysis also revealed a significant correlation between plasma sRAGE levels and CAD(P=0.01).Multivariate odds ratios for CAD revealed that subjects with sRAGE concentrations below 225 pg/mL(lowest quartile)had a 6-fold increase in CAD prevalence independent of other risk factors.CONCLUSION Our findings indicated that low sRAGE levels were independently associated with CAD in nondiabetic postmenopausal women.Risk assessment of CAD in postmenopausal women can be improved by including sRAGE along with other risk factors.

Lactobacillus fermentum as a new inhibitor to control advanced glycation end-product formation during vinegar fermentation

The inhibitory activity of lactic acid bacteria(LAB)toward advanced glycation end-products(AGEs)during vinegar fermentation was studied,and its relationships with the substrate consumption,antioxidant capacity,total phenolic content,total flavonoid compounds,α-glucosidase,andα-amylase activity inhibition were evaluated.The vinegar was made from rice powder flour by liquid-state fermentation(LSF).The selected LAB strains were separately co-cultivated with Saccharomyces cerevisiae and Acetobacter pasteurianus 1.41 in alcoholic and acetic acid fermentation,respectively.Among 3 strains,Lactobacillus fermentum showed the strongest inhibitory effect on the formation of total fluorescent AGEs and carboxymethyl lysine(CML)/carboxyethyl lysine(CEL)in the fermentation process.The corresponding mechanisms included the acceleration of substrate consumtion,improvement of antioxidant activities,and inhibition ofα-glucosidase andα-amylase.In addition,the fluorescent AGEs and the CML/CEL were negatively correlated with the antioxidant activities,while theα-glucosidase andα-amylase activities were positively correlated with the total phenols and total flavonoids.Moreover,the variety of main flavor compounds increased,including esters,alcohols,phenols and acids.The results of the study support the potential use of screened LAB strains to inhibit the formation of fluorescent AGEs,CML and CEL on fermented products and in the food processing industry,without associated risks to consumers.

Novel Inhibitory Effects of Glycyrrhizic Acid on the Accumulation of Advanced Glycation End Product and Its Receptor Expression

Beneficial effects of glycyrrhizic acid(GA),a bioactive extract of licorice root,in the prevention of metabolic syndrome have been consistently reported while advanced glycation end products(AGE)and receptor for advanced glycation end product(RAGE)are the leading factors in the development of diabetes mellitus.The aim of this study was to investigate the effects of GA on the AGE-RAGE axis using high-fat/high-sucrose(HF/HS)diet-induced metabolic syndrome rat models.Twenty four male Sprague–Dawley rats were randomly assigned into three groups for 4 weeks:(1)Group A,normal diet with standard rat chow;(2)Group B,HF/HS diet;(3)Group C,HF/HS diet and oral administration of 100 mg/kg GA per day.The results showed that HF/HS diet elevated the fasting blood glucose level and insulin resistance index which was prevented by GA supplementation.GA treatment significantly lowered the circulating AGE independent of its glucose-lowering effect.HF/HS diet also triggered RAGE upregulation in the abdominal muscles while GA administration downregulated RAGE expression in the abdominal muscles,aorta and subcutaneous adipose tissues.In conclusion,HF/HS diet could cause glucose intolerance,insulin resistance and upregulation of RAGE expression while GA ameliorated the metabolic dysregulation besides exhibiting inhibitory effects on the AGE-RAGE axis.