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: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.

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.

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.

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.

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 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.

HEPATOCYTE GROWTH FACTOR PROTECTS AGAINST APOPTOSIS INDUCED BY ADVANCED GLYCATION END PRODUCTS IN ENDOTHELIAL CELLS

Objective To investigate the effects of hepatocyte growth factor(HGF)on vascular endothelial cells apoptosis induced by advanced glycation end products(AGEs)and its possible mechanism. Methods Human umbilical vein endothelial cells(HUVECs)were cultured in vitro and intervened by different concentrations of AGEs and HGF.The cell inhibitory rates of each group with different culture time(12, 24, 48, and 72 hours)were measured by methyl thiazolyl tetrazolium(MTT)assay. The early stage apoptosis was detected by flow cytometry with Annexin V-FITC/PI double staining, morphology of cell apoptosis was observed by hoechst 33258 fluorescence staining, and the expression of apoptosis-associated genes Bax and Bcl-2 were determined by Western blotting.The activity of caspase-3 was detected by enzyme-linked immunosorbent assay (ELISA).Results Morphological observation indicated that high concentration of AGEs induced characteristic apoptotic changes in HUVECs.Within a certain concentration range, HUVECs apoptosis inducing rates by AGEs were in both dose- and time-dependent manners.HGF significantly inhibited the apoptosis of HUVECs induced by AGEs (P< 0.05).AGEs significantly promoted expression of Bax protein, but not Bcl-2.Whereas HGF significantly promoted the expression of Bcl-2(P<0.01)and decreased the activity of caspase-3(P<0.05)without affecting Bax level.Conclusions AGEs can induce the apoptosis of endothelial cells in vitro.HGF may effectively attenuate AGEs-induced endothelial cells apoptosis through upregulating Bcl-2 gene expression and inhibiting caspase-3 activation.

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.

Role of Protein Kinase C in Advanced Glycation End Products-induced Epithelial-Mesenchymal Transition in Renal Proximal Tubular Epithelial Cells

The role of protein kinase C （PKC） activation in advanced glycation end products （AGEs）-induced epithelial-mesenchymal transition in renal proximal tubular epithelial cells was investigated. HKC cells were divided into three groups： normal group, AGE-BSA group （100 mg/L AGE-BSA） and AGE-BSA＋PKC inhibitor （10 μmol/L chelerythrine chloride） group. PKC activity was measured by PKC assay kit. The expression of Vimentin, and phosphorylated β-catenin was detected by using Western blotting, and the content of TGF-β1 was examined by ELISA method. The intracellular disposition of Vimentin was observed by fluorescence microscopy. As compared with normal group, PKC activity was increased significantly in AGE-BSA group. The expression of Vimentin, phosphorylated β-catenin, and TGF-β1 was enhanced significantly in AGE-BSA group. The expression of Vimentin, phosphorylated β-catenin, and TGF-β1 was significantly blocked by chelerythrine chloride. High expression of Vimentin, phosphorylated β-catenin, and TGF-β1 induced by AGE-BSA may be mediated via the activation of PKC signal transduction pathway.

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.

Autophagy plays a protective role in advanced glycation end products-induced apoptosis of chondrocytes via regulation of tumor necrosis factor-α,nuclear factor-κ B and reactive oxygen species

Objective: To study the adverse effects of advanced glycation end products(AGEs) on chondrocytes and the role of autophagy in this process. Methods: Chondrocytes were harvested from the human articular cartilage tissues in surgery. AGEs were administered during chondrocytes culture. The rapamycin was used to induce autophagy. The cell viability was determined by 3-[4,5-dimethylthiazol2-yl]-2,5-diphenyl tetrazolium bromide(MTT) assay.The expression of tumor necrosis factor-α(TNF-α) and nuclear factor-κ B(NF-κ B) was detected by quantitative real-time polymerase chain reaction. The reactive oxygen species(ROS) production and apoptosis of the chondrocytes were determined by fluorescent probe and flow cytometer, respectively. Results: The chondrocytes viability was significantly reduced after 12 h incubation with AGEs(P<0.01)). In contrast, rapamycin pretreatment increased the chondrocytes viability through autophagy. AGEs increased TNF-α and NF-κ B mRNA expression of chondrocytes and autophagy receded or proceeded the change. AGEs increased intracellular ROS accumulation and autophagy reversed the change. AGEs accelerated chondrocytes apoptosis and autophagy suspended apoptosis. Conclusions: Accumulation of AGEs may have an adverse role for chondrocytes by increasing TNF-α and NF-κB expression, ROS accumulation and apoptosis; meanwhile, autophagy ameliorates the AGEsinduced adverse effects.

Profilin-1 is involved in macroangiopathy induced by advanced glycation end products via vascular remodeling and inflammation

BACKGROUND The accumulation of advanced glycation end products(AGEs)have been implicated in the development and progression of diabetic vasculopathy.However,the role of profilin-1 as a multifunctional actin-binding protein in AGEs-induced atherosclerosis(AS)is largely unknown.AIM To explore the potential role of profilin-1 in the pathogenesis of AS induced by AGEs,particularly in relation to the Janus kinase 2(JAK2)and signal transducer and activator of transcription 3(STAT3)signaling pathway.METHODS Eighty-nine individuals undergoing coronary angiography were enrolled in the study.Plasma cytokine levels were detected using ELISA kits.Rat aortic vascular smooth muscle cells(RASMCs)were incubated with different compounds for different times.Cell proliferation was determined by performing the MTT assay and EdU staining.An AGEs-induced vascular remodeling model was established in rats and histological and immunohistochemical analyses were performed.The mRNA and protein levels were detected using real-time PCR and Western blot analysis,respectively.In vivo,shRNA transfection was performed to verify the role of profilin-1 in AGEs-induced proatherogenic mediator release and aortic remodeling.Statistical analyses were performed using SPSS 22.0 software.RESULTS Compared with the control group,plasma levels of profilin-1 and receptor for AGEs(RAGE)were significantly increased in patients with coronary artery disease,especially in those complicated with diabetes mellitus(P<0.01).The levels of profilin-1 were positively correlated with the levels of RAGE(P<0.01);additionally,the levels of both molecules were positively associated with the degree of coronary artery stenosis(P<0.01).In vivo,tail vein injections of AGEs induced the release of proatherogenic mediators,such as asymmetric dimethylarginine,intercellular adhesion molecule-1,and the N-terminus of procollagen III peptide,concomitant with apparent aortic morphological changes and significantly upregulated expression of the profilin-1 mRNA and protein in the thoracic aorta(P<0.05 or P<0.01).Downregulation of profilin-1 expression with an shRNA significantly attenuated AGEs-induced proatherogenic mediator release(P<0.05)and aortic remodeling.In vitro,incubation of vascular smooth muscle cells(VSMCs)with AGEs significantly promoted cell proliferation and upregulated the expression of the profilin-1 mRNA and protein(P<0.05).AGEs(200μg/mL,24 h)significantly upregulated the expression of the STAT3 mRNA and protein and JAK2 protein,which was blocked by a JAK2 inhibitor(T3042-1)and/or STAT3 inhibitor(T6308-1)(P<0.05).In addition,pretreatment with T3042-1 or T6308-1 significantly inhibited AGEs-induced RASMC proliferation(P<0.05).CONCLUSION AGEs induce proatherogenic events such as VSMC proliferation,proatherogenic mediator release,and vascular remodeling,changes that can be attenuated by silencing profilin-1 expression.These results suggest a crucial role for profilin-1 in AGEs-induced vasculopathy.

Effect of thioltransferase on oxidative stress induced by high glucose and advanced glycation end products in human lens epithelial cells

AIM:To study the effect of thioltransferase(TTase)on oxidative stress in human lens epithelial cells(HLECs)induced by high glucose and advanced glycation end products(AGEs).METHODS:HLECs were treated with 35.5 mmol/L glucose or 1.5 mg/mL AGEs modified bovine serum albumin(AGEs-BSA)as the experimental groups,respectively.Cells were collected at the time point of 1,2,3,and 4 d.The TTase activity were measured accordingly.TTase mRNA levels were detected by quantitative reverse transcription polymerase chain response(qRT-RCR)and its protein level was detected by Western blot.The siRNA was used to knock down the expression of TTase.The activity of catalase(CAT)and superoxide dismutase(SOD),the content of reactive oxygen species(ROS)and the ratio of oxidized glutathione/total glutathione(GSSG/T-GSH)were assessed in different groups,respectively.RESULTS:The level of TTase mRNA gradually increased and reached the top at 2 d,then it decreased to the normal level at 4 d,and the TTase activity increased from 2 to 3 d in both high glucose and AGEs-BSA groups.The TTase expression elevated from 2 d in high glucose group,and it began to rise from 3 d in AGEs-BSA group.The activity of CAT and SOD showed a decrease and the content of ROS and the ratio of GSSG/T-GSH showed an increase in high glucose and AGEs-BSA group.These biochemical alterations were more prominent in the groups with TTase siRNA.CONCLUSION:High glucose and AGEs can increase ROS content in HLECs;therefore,it induces oxidative stress.This may result in the decreased GSH and increased GSSG content,impaired activity of SOD and CAT.The up-regulated TTase likely provides oxidation damage repair induced by high glucose and AGEs in the early stage.

Glyoxal induced advanced glycation end products formation in chicken meat emulsion instead of oxidation

Advanced glycation end products(AGE) are potential harmful substances formed in the advanced Maillard reaction and increasingly investigated in muscle foods. However, the contribution of oxidation to the AGE formation is controversial. Moreover, reports on glyoxal(GO) induced AGE formation in chicken meat emulsion(CME) are limited. Thus, the effects of GO on emulsifying properties, rheological behavior and AGE formation in CME were investigated. Our findings exhibited that levels of Nε-carboxymethyllysine(CML) and Nε-carboxyethyllysine(CEL) were associated with lipid oxidation but not significantly(P > 0.05). Levels of AGE peaked when GO concentration ranged from 5 mmol/L(CML) to 10 mmol/L(CEL). The droplets’ aggregation associated with the disulfide bond when the concentration of GO was at 0.5–30 mmol/L while non-disulfide bond association occurred at 30–50 mmol/L GO concentration. In conclusion, compared to the effect of oxidation, GO exhibited the main role in the AGE formation of CME. This study will provide theoretical significance for further understanding and controlling the formation of AGE in CME.

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.

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.

Effects of advanced glycation end products on renal fibrosis and oxidative stress in cultured NRK-49F ceils

Background Advanced glycation end products （AGEs） play a critical role in the development of diabetic nephropathy. Reactive oxygen species （ROS） may play a critical role in AGEs induced growth factor expression. In this study, the effects of AGEs on transforming growth factor β1 （TGF-β1）, connective tissue growth factor （CTGF） and fibronectin （Fn） mRNA expression and oxidative stress in cultured NRK-49F cells were examined. Methods NRK-49F cells were incubated with medium containing different doses of AGEs （50, 100 or 200 μg/ml） for 24 hours, or with AGEs 100 μg/ml for different times （0, 12, 24 or 48 hours）. Cells in the serum-free medium or medium containing 25 mmol/L glucose were controls. Cells were treated with 25 mmol/L glucose and 100 μg/ml AGEs for 24 hours to determine the effects between AGEs and glucose. We clarified the role of antioxidant by pretreating cells with N-acetylcysteine （10 mmol/L）, ginkgo biloba extract （50 or 100 mg/L） for 24 hours and with 100 μg/ml AGEs for further 24 hours. Alamarblue dye assay was used to analyze cell growth; intracellular ROS generation was measured by flow cytometry; intracellular glutathione by fluorescence spectrophotometry; expressions of TGF-β1, CTGF and Fn mRNA by semiquantitative RT-PCR. Results AGEs significantly increased the expressions of TGF-β1, CTGF, Fn mRNA and intracellular ROS generation, and decreased the glutathion level in NRK-49F cells in dose- and time-dependent manners. High glucose and AGEs together significantly increased the expression of TGF-β1, CTGF and Fn mRNA, compared with AGEs and high glucose separately. Preincubation with N-acetylcysteine or ginkgo biloba extract increased GSH level, suppressed AGEs-induced oxidative stress and TGF-β1, CTGF and Fn mRNA overexpression. Conclusions AGEs can significantly increase expression of TGF-β1, CTGF, Fn mRNA in NRK-49F cells through enhancement of oxidative stress. The accumulation of AGEs may play a pivotal role in the pathogenesis of tubulointerstitial fibrosis in diabetic nephropathy. Suppression of AGEs induced TGF-β1, CTGF and Fn mRNA overexpression in renal fibroblasts through inhibition of oxidative stress may be a mechanism underlying effect of ginkgo biloba extract in diabetic nephropathy. In addition, antioxidant therapy may help prevent AGEs accumulation and its induced damage.