Regulatory role of peroxynitrite in advanced glycation end products mediated diabetic cardiovascular complications

The Advanced Glycation End Products(AGE)binding with its receptor can increase reactive oxygen species(ROS)generation through specific signaling mediators.The effect of superoxide(O2-)and O2-mediated ROS and reactive nitrogen species depends on their concentration and location of formation.Nitric oxide(NO)has anti-inflammatory and anticoagulant properties and a vasodilation effect,but NO can be deactivated by reacting with O_(2)^(-).This reaction between NO and O2-produces the potent oxidant ONOO−.Therefore,ONOO-'s regulatory role in AGEs in diabetic cardiovascular complications must considered as a regulator of cardiovascular complications in diabetes.

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.

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.

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.

Catalpol Prevents Glomerular Angiogenesis Induced by Advanced Glycation End Products via Inhibiting Galectin-3

Objective:The main characteristics of diabetic nephropathy(DN)at the early stage are abnormal angiogenesis of glomerular endothelial cells(GECs)and macrophage infiltration.Galectin-3 plays a pivotal role in the pathogenesis of DN via binding with its ligand,advanced glycation end products(AGEs).Catalpol,an iridoid glucoside extracted from Rehmannia glutinosa,has been found to ameliorate vascular inflammation,reduce endothelial permeability,and protect against endothelial damage in diabetic milieu.However,little is known about whether catalpol could exert an anti-angiogenesis and anti-inflammation effect induced by AGEs.Methods:Mouse GECs(mGECs)and RAW 264.7 macrophages were treated with different concentrations of AGEs(0,50,100,200 and 400μg/mL)for different time(0,6,12,24 and 48 h)to determine the optimal concentration of AGEs and treatment time.Cells were treated with catalpol(10μmol/L),GB1107(1μmol/L,galectin-3 inhibitor),PX-478(50μmol/L,HIF-1αinhibitor),adenovirus-green fluorescent protein(Ad-GFP)[3×10^(7)plaque-forming unit(PFU)/mL]or Ad-galectin-3-GFP(2×10^(8)PFU/mL),which was followed by incubation with 50μg/mL AGEs.The levels of galectin-3,vascular endothelial growth factor A(VEGFA)and pro-angiogenic factors angiopoietin-1(Ang-1),angiopoietin-2(Ang-2),tunica interna endothelial cell kinase-2(Tie-2)were detected by enzyme-linked immunosorbent assay(ELISA).Cell counting kit-8(CCK-8)assay was used to evaluate the proliferation of these cells.The expression levels of galectin-3,vascular endothelial growth factor receptor 1(VEGFR1),VEGFR2,and hypoxia-inducible factor-1α(HIF-1α)in mGECs and those of galectin-3 and HIF-1αin RAW 264.7 macrophages were detected by Western blotting and immunofluorescence(IF)staining.The rat DN model was established.Catalpol(100 mg/kg)or GB1107(10 mg/kg)was administered intragastrically once a day for 12 weeks.Ad-galectin-3-GFP(6×10^(7)PFU/mL,0.5 mL)or Ad-GFP(6×10^(6)PFU/mL,0.5 mL)was injected into the tail vein of rats 48 h before the sacrifice of the animals.The expression of galectin-3,VEGFR1,.VEGFR2,and HIF-1αin renal cortices was analyzed by Western blotting.The expression of galectin-3,F4/80(a macrophage biomarker),and CD34(an endothelium biomarker)in renal cortices was detected by IF staining,and collagen accumulation by Masson staining.Results:The expression levels of galectin-3 and VEGFA were significantly higher in mGECs and RAW 264.7 macrophages treated with 50μg/mL AGEs for 48 h than those in untreated cells.Catalpol and GB1107 could block the AGEs-induced proliferation of mGECs and RAW 264.7 macrophages.Over-expression of galectin-3 was found to reduce the inhibitory effect of catalpol on the proliferation of cells.Catalpol could significantly decrease the levels of Ang-1,Ang-2 and Tie-2 released by AGEs-treated mGECs,which could be reversed by over-expression of galectin-3.Catalpol could significantly inhibit AGEs-induced expression of galectin-3,HIF-1α,VEGFR1,and VEGFR2 in mGECs.The inhibitory effect of catalpol on galectin-3 in AGEs-treated mGECs was impaired by PX-478.Moreover,catalpol attenuated the AGEs-activated HIF-1α/galectin-3 pathway in RAW 264.7 macrophages,which was weakened by PX-478.Additionally,catalpol significantly inhibited the expression of galectin-3,macrophage infiltration,collagen accumulation,and angiogenesis in the kidney of diabetic rats.Over-expression of galectin-3 could antagonize these inhibitory effects of catalpol.Conclusion:Catalpol prevented the angiogenesis of mGECs and macrophage proliferation via inhibiting galectin-3.It could prevent the progression of diabetes-induced renal damage.

The effect of protein oxidation on the formation of advanced glycation end products after chicken myofibrillar protein glycation

Investigation that protein oxidation to the formation of advanced glycation end products(AGEs)after chicken myofibrillar protein glycation is limited.Models of protein oxidation induced by different concentrations of hydroxyl radicals(·OH)were developed after the chicken myofibrillar protein mild glycation(MPG).Results exhibited that levels of AGEs and surface hydrophobicity(H_(0))steadily increased with the a ddition of h ydrogen peroxide(H_(2)O_(2))concentration.However,levels of s ulfhydryl group,free amino group,and particle size gradually decreased with the H_(2)O_(2)concentration.The protein carbonyl value increased in H_(2)O_(2)concentration until 10 mmol/L.Pearson's correlation indicated that MPG structure modification(unfolding and degradation)induced by protein oxidation were significantly positively correlated with AGEs concentration(P<0.05).Finally,a mechanism was proposed to hypothesize t he effect of protein oxidation on the formation of AGEs under MPG conditions.

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.

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.

Management of Maillard reaction-derived reactive carbonyl species and advanced glycation end products by tea and tea polyphenols

Tea as the most consumed beverage in the world has received enormous attention for its promoting health benefits.The deleterious effect ofα-dicarbonyls and AGEs formed in Maillard reaction is also a longterm challenge.The connection between the two topics was the main aim of this review,to address and update the antiglycation effect and mechanism of tea and tea polyphenols.By analyzing recent publications,we have covered across chemistry models,cell lines and animal studies.Tea polyphenols,particularly catechins,showed outstanding antiglycation effect by trappingα-dicarbonyl compounds and impeding AGEs formation.Reduction of carbonyl stress brought alleviation to aging,diabetes,and collagen related diseases or complications through regulation of RAGE expression and subsequent MAPK and TGF-βpathway.Therefore,tea polyphenols can serve as promising natural candidates in the treatment and/or prevention of nephropathy,retinopathy,hepatopathy,hyperglycemia and obesity among others,by their potent antiglycation effect.Further studies need to address on aspects like exact mechanisms,solution of detection obstacles,balance of practical usage and harmful effects such as potential flavor damage and toxicity in food,to gain a comprehensive understanding of antiglycation activities of tea polyphenols and its actual application.

Fluorescent advanced glycation end-products (ages) detected by spectro-photofluorimetry, as a screening tool to detect diabetic microvascular complications

BACKGROUND: Advanced glycation end-products (AGEs) are one of the mechanisms related to diabetic vascular complications. However, since AGEs are multiple and heterogeneous moieties, there is no universally accepted method to measure them for clinical purposes. The aim of this work was to study the utility of a simple fluorimetric assay as predictor of complications. METHODS: Blood samples from 102 type 2 diabetic patients were obtained to assess glucose, glycosylated haemoglobin, creatinine, lipoproteins and C Reactive Protein (CRP), fluorescent AGES by spectrophotofluorimetry and non-fluorescent AGEs by measurement of N(ε)-carboxymethyl-Lysine (CML) using an ELISA kit in a subsample of 82 patients. Urinary fluorescent AGEs, albumin and creatinine were also measured in a morning urine sample. Microvascular complications were studied by ophthalmologic examination, albuminuria and peripheral nerve conduction velocity. RESULTS: Patients without microvascular complications had significantly lower levels of both serum and urinary AGEs. CML was associated with retinopathy. Multiple regression analysis confirmed that AGEs, length of diabetes and glycosylated haemoglobin were all variables associated with diabetic complications, in this sample. CONCLUSIONS: A simple fluorimetric assay to measure low molecular weight fluorescent AGEs, and CML could be employed as screening tools to predict diabetic complications, at a primary care setting. AGEs should probably be considered as another therapeutic target in diabetes management.

Individual and Combined Effects of Food Components in Attenuating the Formation of Advanced Glycation End Products (AGEs)

Advanced Glycation End Products (AGEs) have been associated as a possible cause in inflammation-mediated chronic diseases such as diabetes, Alzheimer’s and cardiovascular disorders. Thus, inhibition of AGE formation represents a prospective therapeutic target for the prevention and treatment of these complications. This study investigated the individual and combined effects of dietary ingredients, spices, on lowering AGEs formation in meat patties. In the study, Carboxymethyllysine (CML), a well-investigated AGE is used as a marker for AGEs and malondialdehyde (MDA) as an indicator for lipid peroxidation. Nine spices were selected based on their ability to inhibit the formation of AGEs at different stages of Maillard reactions. Individually, all the 9 selected spices significantly inhibited the formation of AGEs. Among the 33 combinations of spices, 26 combinations significantly inhibited the formation of AGEs. The highest reduction (84%) was found by the combination of Black Pepper-Rose-Cumin. The individual spices failed to significantly lower the MDA concentration;however, all 33 combinations were able to significantly reduce MDA concentration. The results of this study showed that spices when supplemented in combinations are more effective in inhibiting the formation of AGEs and in decreasing MDA concentration in meat patties.

Rosiglitazone inhibits expression of acyl-coenzyme A:cholesterol acyltransferase-1 in THP-1 macrophages induced by advanced glycation end-products

Objective： To investigate the effects of rosiglitazone, a synthetic ligand of peroxisome proliferators-activated receptor gamma （PPARγ）, on the expression of acyl-coenzyme A： cholesterol acyltransferase-1 （ACAT-1） in phorbol myristate acetate （PMA）-pretreated THP-1 cells after the inducement of advanced glycation end products （AGEs）. Methods： After THP-1 cells were cultured in the presence of 0.1 μmol/L PMA for 72 h to induce phagocytic differentiation, the obtained THP-1 macrophages were treated with rosiglitazone for 4 h at different concentrations （1, 5 or 10 μmol/L） and then exposed to AGEs-modified bovine serum albumin （AGEs-BSA） for 24 h at a concentration of 200 mg/L. Reverse transcription polymerase chain reaction （RT-PCR） and Western blot analysis were performed to detect the mRNA and protein expressions of ACAT-1 respectively. Results： Administration of AGEs-BSA （200 mg/L） into the THP-1 macrophages resulted in up-regulation of ACAT-1 at mRNA and protein levels when compared with the expressions in macrophages incubated with serum-free RPMI1640. Pretreatment of rosiglitazone inhibited significantly the increased expression of ACAT-1 induced by AGEs-BSA in a concentration-dependent manner. Conclusion： PPARy activation by rosiglitazone down-regulates ACAT-1 expression induced by AGEs in THP-1 macrophages, which might provide a new way for treating atherogenesis in diabetic patients.

High glucose reduces Nrf2-dependent cRAGE release and enhances inflammasome-dependent IL-1βproduction in monocytes:the modulatory effects of EGCG

Soluble receptor for advanced glycation end products(sRAGE)acts as a decoy sequestering of RAGE ligands,thus preventing the activation of the ligand-RAGE axis linking human diseases.However,the molecular mechanisms underlying sRAGE remain unclear.In this study,THP-1 monocytes were cultured in normal glucose(NG,5.5 mmol/L)and high glucose(HG,15 mmol/L)to investigate the effects of diabetesrelevant glucose concentrations on sRAGE and interleukin-1β(IL-1β)secretion.The modulatory effects of epigallocatechin gallate(EGCG)in response to HG challenge were also evaluated.HG enhanced intracellular reactive oxygen species(ROS)generation and RAGE expression.The secretion of sRAGE,including esRAGE and cRAGE,was reduced under HG conditions,together with the downregulation of a disintegrin and metallopeptidase 10(ADAM10)and nuclear factor erythroid 2-related factor 2(Nrf2)nuclear translocation.Mechanistically,the HG effects were counteracted by siRAGE and exacerbated by siNrf2.Chromatin immunoprecipitation results showed that Nrf2 binding to the ADAM10 promoter and HG interfered with this binding.Our data reinforce the notion that RAGE and Nrf2 might be sRAGE-regulating factors.Under HG conditions,the treatment of EGCG reduced ROS generation and RAGE activation.EGCG-stimulated cRAGE release was likely caused by the upregulation of the Nrf2-ADAM10 pathway.EGCG inhibited HG-mediated NLRP3 inflammasome activation at least partly by stimulating sRAGE,thereby reducing IL-1βrelease.

Role of advanced glycation end products in cardiovascular disease

Advanced glycation end products (AGEs) are produced through the non enzymatic glycation and oxidation of proteins, lipids and nucleic acids. Enhanced formation of AGEs occurs particularly in conditions associated with hyperglycaemia such as diabetes mellitus (DM). AGEs are believed to have a key role in the development and progression of cardiovascular disease in patients with DM through the modification of the structure, function and mechanical properties of tissues through crosslinking intracellular as well as extracellular matrix proteins and through modulating cellular processes through binding to cell surface receptors [receptor for AGEs (RAGE)]. A number of studies have shown a correlation between serum AGE levels and the development and severity of heart failure. Moreover, some studies have suggested that therapies targeted against AGEs may have therapeutic potential in patients with heart failure (HF). The purpose of this review is to discuss the role of AGEs in cardiovascular disease and in particular in heart failure, focussing on both cellular mechanisms of action as well as highlighting how targeting AGEs may represent a novel therapeutic strategy in the treatment of HF.

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.

Advanced glycation end products induce neural tube defects through elevating oxidative stress in mice

Our previous study showed an association between advanced glycation end products （AGEs） and neural tube defects （NTDs）. To understand the molecular mechanisms underlying the effect of AGEs on neural tube development, C57BL/6 female mice were fed for 4 weeks with com- mercial food containing 3% advanced glycation end product bovine serum albumin （AGE-BSA） or 3% bovine serum albumin （BSA） as a control. After mating mice, oxidative stress markers including malondialdehyde and H202 were measured at embryonic day 7.5 （E7.5） of ges- tation, and the level of intracellular reactive oxygen species （ROS） in embryonic cells was determined at E8.5. In addition to evaluating NTDs, an enzyme-linked immunosorbent assay was used to determine the effect of embryonic protein administration on the N-（carboxymethyl） lysine reactivity of acid and carboxyethyl lysine antibodies at E10.5. The results showed a remarkable increase in the incidence of NTDs at El0.5 in embryos of mice fed with AGE-BSA （no hyperglycemia） compared with control mice. Moreover, embryonic protein administration resulted in a noticeable increase in the reactivity of N-（carboxymethyl） lysine and N（ε）-（carboxyethyl） lysine antibodies. Malondialdehyde and H2O2 levels in embryonic cells were increased at E7.5, followed by increased intracellular ROS levels at E8.5. Vitamin E supplementation could partially recover these phenomena. Collectively, these results suggest that AGE-BSA could induce NTDs in the absence of hyperglycemia by an underlying mechanism that is at least partially associated with its capacity to increase embryonic oxidative stress levels.

Advanced Glycation End Products Promote Differentiation of CD4^+ T Helper Cells toward Pro-inflammatory Response

This study investigated the effect of advanced glycation end products（AGEs） on differentiation of na ve CD4＋T cells and the role of the receptor of AGEs（RAGE） and peroxisome proliferator-activated receptors（PPARs） activity in the process in order to gain insight into the mechanism of immunological disorders in diabetes. AGEs were prepared by the reaction of bovine serum albumin（BSA） with glucose. Human na ve CD4＋T cells, enriched from blood of healthy adult volunteers with negative selection assay, were cultured in vitro and treated with various agents including AGEs, BSA, high glucose, PGJ2 and PD68235 for indicated time. In short hairpin（sh） RNA knock-down experiment, na ve CD4＋T cells were transduced with media containing shRNA-lentivirus generated from lentiviral packaging cell line, Lent-XTM293 T cells. Surface and intracellular cytokine stainings were used for examination of CD4＋T cell phenotypes, and real-time PCR and Western blotting for detection of transcription factor mRNA and protein expression, respectively. The suppressive function of regulatory T（Treg） cells was determined by a [3H]-thymidine incorporation assay. The results showed that AGEs induced higher pro-inflammatory Th1/Th17 cells differentiated from na ve CD4＋T cells than the controls, whereas did not affect anti-inflammatory Treg cells. However, AGEs eliminated suppressive function of Treg cells. In addition, AGEs increased RAGE mRNA expression in na ve CD4＋T cells, and RAGE knock-down by shRNA eliminated the effect of AGEs on the differentiation of CD4＋T cells and the reduction of suppressive function of Treg cells. Furthermore, AGEs inhibited the mRNA expression of PPARγ, not PPARα; PPARγ agonist, PGJ2, inhibited the effect of AGEs on na ve CD4＋T cell differentiation and reversed the AGE-reduced suppressive function of Treg cells; on the other hand, PPARγ antagonist, PD68235, attenuated the blocking effect of RAGE shRNA on the role of AGEs. It was concluded that AGEs may promote CD4＋T cells development toward pro-inflammatory state, which is associated with increased RAGE mRNA expression and reduced PPARγ activity. ＋

Injury of cortical neurons is caused by the advanced glycation end products-mediated pathway

Advanced glycation end products lead to cell apoptosis, and cause cell death by increasing endoplasmic reticulum stress. Advanced glycation end products alone may also directly cause damage to tissues and cells, but the precise mechanism remains unknown. This study used primary cultures of rat cerebral cortex neurons, and treated cells with different concentrations of glycation end products （50, 100, 200, 400 mg/L）, and with an antibody for the receptor of advanced glycation end products before and after treatment with advanced glycation end products. The results showed that with increasing concentrations of glycation end products, free radical content increased in neurons, and the number of apoptotic cells increased in a dose-dependent manner. Before and after treatment of advanced glycation end products, the addition of the antibody against advanced glycation end-products markedly reduced hydroxyl free radicals, malondialdehyde levels, and inhibited cell apoptosis. This result indicated that the antibody for receptor of advanced glycation end-products in neurons from the rat cerebral cortex can reduce glycation end product-induced oxidative stress damage by suppressing glycation end product receptors. Overall, our study confirms that the advanced glycation end products-advanced glycation end products receptor pathway may be the main signaling pathway leading to neuronal damage.

Increased plasma galectin-1 correlates with advanced glycation end products and interleukin-1β in patients with proliferative diabetic retinopathy

Dear Editor,Galectin-1, one of galactoside-binding lectin family proteins, has been shown to regulate cell growth, migration, and proliferation, where it binds many receptors depending on their glycosylation profile, rather than its specific receptors.