bluuebunny/crossref_metadata_2025 huggingface dataset:
Peptide Mapping of Human Serum Albumin Modified Minimally by Methylglyoxal in Vitro and in Vivo
Authors: AHMED NAILA , THORNALLEY PAUL J.
Published: July 2005

Abstract: Methylglyoxal is a potent glycating agent and important precursor of advanced glycation end products (AGEs) in physiological systems. Unlike glucose, methylglyoxal is predominantly an arginine‐directed glycating agent. Methylglyoxal reacts with proteins to form mainly the arginine‐derived hydroimidazolone AGE, Nδ‐(5‐hydro‐5‐methyl‐4‐imidazolon‐2‐yl)‐ornithine (MG‐H1), argpyrimidine, the lysine‐derived AGEs, Nε‐(1‐carboxyethyl)lysine (CEL), and methylglyoxal‐derived lysine dimer (MOLD). Sites within proteins susceptible to modification by methylglyoxal have not been identified. Here we show that modification of human serum albumin by methylglyoxal forms mainly hydroimidazolone MG‐H1 residues. The location of MG‐H1 residues was identified by mass spectrometric peptide mapping. This method identified a hot spot of hydroimidazolone formation at Arg‐410, with other minor MG‐H1 modifications at Arg‐114, Arg‐186, Arg‐218, and Arg‐428. Other extracellular and intracellular proteins are modified by methylglyoxal in physiological systems. Modification of arginine residues by methylglyoxal may be particularly damaging because arginine residues have a high frequency of occurrence in ligand and substrate recognition sites in receptor and enzyme active sites.
A Convenient Method for Preparation of High‐Purity, Amadori‐Glycated Phosphatidylethanolamine and Its Prooxidant Effect
Authors: MIYAZAWA TERUO , OAK JEONG‐HO , NAKAGAWA KIYOTAKA
Published: July 2005

Abstract: Phospholipid‐linked glycation has been implicated to play an important role in lipid peroxidation associated with several conditions, such as normal aging and diabetes. In this study, we established a convenient method for the preparation of a high‐purity, Amadori‐glycated phosphatidylethanolamine (Amadori‐PE) standard in a methanol system. We evaluated the prooxidant effect of the Amadori‐PE standard. When Amadori‐PE was incubated in a micellar and liposome system in the presence of metal ion, a remarkable increase of lipid peroxidation was observed in both systems. In addition, the Amadori‐PE‐induced lipid peroxidation was effectively inhibited by superoxide dismutase, mannitol, catalase, and EDTA. These results indicate that Amadori‐PE is a considerable risk factor that may cause membrane lipid peroxidation in the pathogenesis of diabetes and aging.
Proteomic Method for the Quantification of Methionine Sulfoxide
Authors: BROCK J W C , COTHAM W C , AMES J M , THORPE S R , BAYNES J W
Published: July 2005

Abstract: Glycoxidation and lipoxidation reactions contribute to the chemical modification of proteins during the Maillard reaction. Reactive oxygen species, produced during the oxidation of sugars and lipids in these processes, irreversibly oxidize proteins. Methionine is particularly susceptible to oxidation, yielding the oxidation product methionine sulfoxide (MetSO). Here we describe a method for the analysis of MetSO using proteomic techniques. Using these techniques, we measured MetSO formation on the model protein RNase during aerobic incubations with glucose and arachidonate. We also evaluated the susceptibility of MetSO to reduction by NaBH4, a commonly used reductant in the analysis of Maillard reaction products.
Simple Noninvasive Measurement of Skin Autofluorescence
Authors: MEERWALDT ROBBERT , LINKS THERA , GRAAFF REINDERT , THORPE SUZANNNE R. , BAYNES JOHN W. , HARTOG JASPER , GANS REINOLD , SMIT ANDRIES
Published: July 2005

Abstract:Accumulation of advanced glycation end products (AGEs) is thought to play a role in the pathogenesis of chronic complications of diabetes mellitus and renal failure. Several studies indicate that AGE accumulation in tissue may reflect the cumulative effect of hyperglycemia and oxidative stress over many years. Simple quantitation of AGE accumulation in tissue could provide a tool for assessing the risk of long‐term complications. Because several AGEs exhibit autofluorescence, we developed a noninvasive autofluorescence reader (AFR). Skin autofluorescence measured with the AFR correlates with collagen‐linked fluorescence and specific skin AGE levels from skin biopsy samples. Furthermore, skin autofluorescence correlates with long‐term glycemic control and renal function, and preliminary results show correlations with the presence of long‐term complications in diabetes. The AFR may be useful as a clinical tool for rapid assessment of risk for AGE‐related long‐term complications in diabetes and in other conditions associated with AGE accumulation.
Evaluation of the Maillard Reaction in Infant Formulas by Means of Front‐Face Fluorescence
Authors: BIRLOUEZ‐ARAGON I. , LOCQUET N , DE ST LOUVENT E , BOUVERESSE D JOUAN‐RIMBAUD , STAHL P
Published: July 2005

Abstract: Foods are complex mixtures of macro‐ and micronutrients, which interact, leading to oxidation, glycation, and hydrolysis upon heating (e.g., sterilization, cooking) and storage. Their nutritional quality and safety are consequently affected, justifying the need for accurate monitoring of the evolution of the food composition during processing and shelf life. Classical chromatographic analysis as well as newly proposed rapid methods based on fluorescence spectrometry analyses were applied on whey powder‐based models and commercial samples (in powdered form and ultrahigh temperature [UHT] sterilized), some of which had been previously submitted to protein hydrolysis. These samples were incubated for 48 h at 60°C to mimic accelerated storage. Fluorescence fingerprints addressing modifications in the product composition during processing were recorded and analyzed by chemometric methods. Carboxymethyllysine (Nε‐[carboxymethyl]lysine; CML) was measured using an ELISA method. Fluorescence, recorded in a front‐face mode on intact samples, is very sensitive to pertinent physicochemical changes induced by heat treatment, formulation (the moisture level in powders, presence of vitamin C and iron), and storage. Similar trends were observed between powders' fluorescence and CML—for example, a strong effect of protein hydrolysis and increasing water content. Addition of vitamin C was associated with an antioxidant effect despite the presence of iron. Good calibration models were obtained for predicting CML from fluorescence spectra both in food models and in commercial samples, although more work is needed to obtain accurate and robust calibration models. Results show the potential of nondestructively applied fluorescence spectrometry for measuring CML in formulas, a rapid, simple, and cost‐effective method to monitor formula quality.
Interplay between the Maillard Reaction and Lipid Peroxidation in Biochemical Systems
Authors: HIDALGO FRANCISCO J. , ZAMORA ROSARIO
Published: July 2005

Abstract: The Maillard reaction and lipid peroxidation are two of the most important chemical reactions that take place in biochemical systems. Both include a whole network of different reactions in which an extraordinarily complex mixture of compounds is produced in very different amounts, with both positive and negative consequences. In addition, both reactions are intimately interrelated, and the products of each reaction influence the other. Furthermore, there are common intermediates and products in both pathways; these products are usually known as advanced glycation end products (AGEs) and advanced lipoxidation end products (ALEs). Moreover, other AGE/ALEs are analogous and participate similarly in both amino acid degradation and amino phospholipid/protein polymerization by identical mechanisms. All these data suggest that the Maillard reaction and lipid peroxidation are so closely interrelated that both reactions should be considered simultaneously to understand the reaction mechanisms, kinetics, and products in the complex mixtures of carbohydrates, lipids, and proteins occurring in biochemical systems. In these systems, lipids and carbohydrates are competing in the chemical modification of amino phospholipids and proteins. Therefore, although there are significant differences between the Maillard reaction and lipid peroxidation, many aspects of both reactions can be better understood if they are included in only one general carbonyl pathway that can be initiated by both lipids and carbohydrates.
The Immunogenicity of Modified Lipoproteins
Authors: LOPES‐VIRELLA MARIA F. , THORPE SUZANNE R. , DERRICK M BROOKS , CHASSEREAU CHARLYNE , VIRELLA GABRIEL
Published: July 2005

Abstract: The immunogenicity of modified low‐density lipoprotein (mLDL) has been demonstrated both in laboratory animals and humans. Circulating human mLDL antibodies, purified by affinity chromatography, are predominantly of the IgG isotype, subclasses 1 and 3. The purified antibodies react with malondialdehyde‐lysine and carboxymethyl‐lysine epitopes, but also recognize minimally modified forms of LDL that do not contain significant amounts of those two epitopes. The quantitative assays of mLDL and mLDL antibodies in serum samples by enzymoimmunoassay (EIA) are unreliable owing to the interference of preformed circulating immune complexes (CICs). Isolation of CICs by precipitation with low concentrations of polyethylene glycol followed by analysis of antigens and antibodies contained in the precipitates is a technically complex approach, but one that yields valuable data. With this approach we have confirmed that the IgG antibodies involved in IC formation belong to the proinflammatory IgG1 and IgG3 isotypes, have a higher avidity than those that remain unbound in the supernatant after CIC precipitation, and are of higher avidity in diabetic patients with macroalbuminuria than in those with normal albuminuria. We have also developed capture assays for different forms of mLDL. These assays have shown a significant enrichment in mLDL of the precipitated ICs. The enrichment is also more pronounced in the CICs obtained from diabetic patients with macroalbuminuria. In conclusion, isolation and characterization of LDL‐ICs appears to yield information of significant value that is not derived from other approaches to measure LDL modifications and their corresponding antibodies in humans.
Effects of Modified Low‐Density Lipoproteins on Human Retinal Pericyte Survival
Authors: SONG WEIWEI , BARTH JEREMY L. , LU KANGMO , YU YONGXIN , HUANG YAN , GITTINGER CYNTHIA K. , ARGRAVES W SCOTT , LYONS TIMOTHY J.
Published: July 2005

Abstract: According to a current paradigm cardiovascular diseases can be initiated by exposure of vascular cells to qualitatively modified low‐density lipoproteins (LDL). Capillary leakage, an early feature of diabetic retinopathy, results in the exposure of retinal pericytes to modified LDL, including glycated (G‐LDL) and heavily oxidized glycated LDL (HOG‐LDL). We demonstrate here that modified LDL inhibits the proliferation and survival of cultured human retinal pericytes. Modified LDL also induced DNA fragmentation in bovine retinal pericytes. Overall, HOG‐LDL produced a significantly higher extent of cytotoxicity and apoptosis in retinal pericytes. These results indicate that exposure of pericytes to HOG‐LDL could be implicated in the development of diabetic retinopathy.
Acrolein Modifies Apolipoprotein A‐I in the Human Artery Wall
Authors: SHAO BAOHAI , O'BRIEN KEVIN D. , MCDONALD THOMAS O. , FU XIAOYUN , ORAM JOHN F. , UCHIDA KOJI , HEINECKE JAY W.
Published: July 2005

Abstract: Carbonyl stress is implicated in accelerated vascular disease, but little is known about the factors that control the reactions of carbonyls with proteins. Acrolein is a reactive carbonyl generated by the oxidation of lipids and amino acids. It also forms during cigarette smoking. We therefore investigated the possibility that acrolein might react with apolipoprotein A‐I (apoA‐I), the major protein of high‐density lipoprotein (HDL), which plays a critical role in mobilizing cholesterol from artery wall macrophages. Tandem mass spectrometric analysis demonstrated that lysine residues were the only amino acids in apoA‐I that were modified by acrolein. Immunohistochemical studies with a monoclonal antibody revealed that acrolein adducts colocalized with apoA‐I in human atherosclerotic lesions. Moreover, the ability of apoA‐I to remove cholesterol from cultured cells was impaired after exposure to acrolein, suggesting that the carbonyl might interfere with apoA‐I's normal function of promoting cholesterol efflux from artery wall cells. Our observations suggest that acrolein may interfere with normal HDL cholesterol transport by modifying apoA‐I. This structural damage might play a critical role in atherogenesis by impairing cholesterol removal from artery wall cells.
Lipid‐Derived Modifications of Plasma Proteins in Experimental and Human Diabetes
Authors: JANUSZEWSKI ANDRZEJ S. , JENKINS ALICIA J. , BAYNES JOHN W. , THORPE SUZANNE R.
Published: July 2005

Abstract: Plasma from two diabetic rat models and human diabetic patients was analyzed to investigate the hypothesis that enhanced oxidative stress in diabetes promotes lipid‐derived protein modification. We evaluated the nonenzymatic modification of plasma protein by oxidized phospholipids, including measurement of protein‐bound pentanedioate, nonanedioate, and hexanoate, all derived from oxidation of phospholipid polyunsaturated fatty acids. Generally pentanedioate was higher in diabetic compared with nondiabetic control groups, and nonanedioate was also higher in the diabetic rat models. We conclude that diabetes is associated with higher levels of phospholipid‐derived protein modification in both animal models and human diabetes. Their role in the development of diabetes vascular complications warrants further research.
Angiogenic Potency of Amadori‐Glycated Phosphatidylethanolamine
Authors: NAKAGAWA KIYOTAKA , OAK JEONG‐HO , MIYAZAWA TERUO
Published: July 2005

Abstract: Glycation has been thought to participate in diabetic vascular diseases. However, there are no reports about the effects of lipid glycation on endothelial dysfunction. In this study, we have evaluated whether Amadori‐glycated phosphatidylethanolamine (Amadori‐PE), a lipid‐linked glycation compound, affected proliferation, migration, and tube formation of cultured human umbilical vein endothelial cells. These three factors involved in angiogenesis were significantly stimulated by Amadori‐PE at a low concentration of less than 5 μM. Furthermore, Amadori‐PE also stimulated the secretion of matrix metalloproteinase‐2 (MMP‐2), a pivotal enzyme in the initial step of angiogenesis. Our results indicated for the first time that Amadori‐PE would elicit vascular disease through angiogenic potency on endothelial cells, thereby playing an active part in the development and progression of diabetic microangiopathy.
Are Food Advanced Glycation End Products Toxic in Biological Systems?
Authors: CHUYEN N.V , ARAI H , NAKANISHI T , UTSUNOMIYA N.
Published: July 2005

Abstract: Model food advanced glycation end products (AGEs) were prepared as glycated casein (GC) and glycated soy protein (GS) by the reaction of casein or soy protein with glucose at 50°C, relative humidity 75% for seven days in a powder state. These browned proteins were used as materials for animal experiments. A mixture of 20% glycated proteins (GC:GS = 1:1) diet was fed to streptozotocin (STZ)‐diabetic rats for 11 weeks. The results showed that: (1) fructoselysine was observed in the hepatic portal veins, arteries, and femoral veins of rats fed with glycated proteins after 2 h of feeding; (2) blood sugar of glycated protein‐fed rats was lower than that of diabetic rats fed with intact protein, while HbA1C in blood and glucose in urine of both groups were similar; (3) lipid peroxidation status in serum, liver, and kidney of both groups was similar; (4) superoxide dismutase (SOD) and glutathione‐S‐transferase (GST) enzymatic activity in serum and liver of both groups were also similar; (5) there were no differences in degree of cataract formation and concentration of glucose, fructose, sorbitol, and lipid peroxide in the lenses of both groups. From the above results, it can be estimated that food AGEs are not toxic in biological systems, and reactive oxygen species increase in diabetic rats is not caused by glycated proteins but by other pathways.
Studies on Absorption and Elimination of Dietary Maillard Reaction Products
Authors: FÖRSTER ANKE , KÜHNE YVONNE , HENLE T.OMAS
Published: July 2005

Abstract: A nine‐day dietary study involving 18 healthy volunteers was performed in order to investigate the influence of nutrition on the urinary excretion of the Maillard reaction products (MRPs) fructoselysine, pyrraline, and pentosidine. From day two through day eight, most types of Maillard product‐containing food had to be avoided. On day five, participants were divided into four groups, three of them receiving a test meal (pretzel sticks, brewed coffee, or custard) containing defined amounts of MRPs. The fourth group served as a control. Urine samples taken over a 24‐h period were analyzed for MRPs using chromatographic means. As a result of the MRP‐free diet, urinary excretion of free pyrraline and fructoselysine, which was calculated from furosine analysis, were lowered about 90%. Excretion of pentosidine decreased about 40%. Consumption of pretzel sticks and coffee on day five resulted in increased amounts of pyrraline and pentosidine in urine samples on days five to seven. Related to the supplied amounts of pyrraline, about 50% were recovered in the urine samples after ingestion of the pretzel sticks. For pentosidine, 60% of the ingested free derivative from coffee brew and 2% of the peptide‐bound amino acid ingested with the bakery product were recovered in the urine samples, indicating a better bioavailability for free pentosidine compared to the protein‐bound form. For peptide‐bound Amadori products, no influence on the excretion was observed after ingestion of the test foods, indicating degradation in the intestine or plasma to yet‐unknown metabolites. In conclusion, differences concerning the excretion rate of individual MRPs point to individual resorption and metabolic pathways. These results are of importance for the discussion of a possible (patho)physiological role of dietary advanced glycation end products (AGEs).
Renal Effects of Oral Maillard Reaction Product Load in the Form of Bread Crusts in Healthy and Subtotally Nephrectomized Rats
Authors: ŠEBEKOVÁ KATARÍNA , HOFMANN THOMAS , BOOR PETER , ŠEBEKOVÁ KATARÍNA , ULICNÁ OL'GA , ERBERSDOBLER HELMUT F. , BAYNES JOHN W. , THORPE SUZANNE R. , HEIDLAND AUGUST , SOMOZA VERONIKA
Published: July 2005

Abstract: The biological consequences of chronic consumption of Maillard reaction products (MRPs) on renal function in health and renal disease are still incompletely understood. We investigated the metabolic and renal effects of a diet with varying MRP content in healthy and subtotally nephrectomized rats. Male Wistar rats were subjected to sham operation (control, C, n= 12), or to 5/6 nephrectomy (5/6NX, n= 12). Both groups were randomized into subgroups and pair‐fed with either a MRP‐poor or ‐rich diet for six weeks. The diet was prepared by replacing 5% or 25% of wheat starch by bread crust (BC). In spite of pair‐feeding, the rats on the 25% BC diet gained more body weight (C: 183 ± 6 g; C + 5% BC: 197 ± 7 g; C + 25% BC: 229 ± 6 g [P < 0.05]; 5/6NX: 165 ± 10 g; 5/6NX + 5% BC: 202 ± 3 g; 5/6NX + 25% BC: 209 ± 8 g [P < 0.05]) and had a higher organ weight (heart, liver, lung, kidney/remnant kidney). Bread crust‐enriched diet induced proteinuria (C: 15 ± 5 mg/24 h; C + 5% BC: 19 ± 4; C + 25% BC: 26 ± 3 [P < 0.05]; 5/6NX: 30 ± 7 mg/24 h; 5/6NX + 5% BC: 47 ± 9; 5/6NX + 25% BC: 87 ± 19 [P < 0.01]) and a rise in urinary transforming growth factor β1 excretion (C: 0.4 ± 0.1 ng/24 h; C + 5% BC: 0.6 ± 0.1; C + 25% BC: 1.2 ± 0.3; 5/6NX: 0.5 ± 0.1 ng/24 h; 5/6NX + 5% BC: 0.9 ± 0.1; 5/6NX + 25% BC: 1.6 ± 0.2 [P < 0.01]). Plasma creatinine or creatinine clearance were not affected significantly. In conclusion, our data suggests that long‐term consumption of a diet rich in MRPs may lead to damage of the kidneys.
Dietary Bread Crust Advanced Glycation End Products Bind to the Receptor for AGEs in HEK‐293 Kidney Cells but Are Rapidly Excreted after Oral Administration to Healthy and Subtotally Nephrectomized Rats
Authors: SOMOZA VERONIKA , LINDENMEIER MICHAEL , HOFMANN THOMAS , FRANK OLIVER , ERBERSDOBLER HELMUT F. , BAYNES JOHN W. , THORPE SUZANNE R. , HEIDLAND AUGUST , ZILL HOLGER , BEK STEPHAN , HUBER JOCHEN , WEIGLE THOMAS , SCHEIDLER SABINE , BUSCH ANDREAS E. , ŠEBEKOVÁ KATARÍNA
Published: July 2005

Abstract: In renal HEK‐293 cells, the dietary Maillard reaction compounds casein‐linked Nε‐carboxymethyllysine (CML), CML, bread crust (BC), and pronyl‐glycine (a key compound formed in association with the process‐induced heat impact applied to bread dough) all showed activation of p38‐MAP kinase. Expression of the C‐terminus truncated receptor for advanced glycation end products (RAGE) resulted in a reduction of HEK‐293‐MAP kinase activation. As these findings suggested a RAGE‐mediated activating effect of CML, BC, and pronyl‐glycine on kidney cellular signal transduction pathways, an in vivo study was performed. Male Wistar rats were subjected to a sham operation (CTRL, n= 20) or to 5/6 nephrectomy (NX, n= 20). Both groups were randomized into two subgroups and fed 20 g of a diet containing either 25% by weight BC or wheat starch (WS). GC‐MS analyses of CML, carboxyethyllysine (CEL), and pentosidine revealed increased levels of CML and CEL in the liver but decreased levels of CML in the kidneys of CTRL and NX rats fed the BC diet compared to those on the WS diet. However, urinary levels of CML were also elevated in the CTRL and NX rats on the BC diet, pointing to enhanced excretion of AGEs after BC administration. Although renal insufficiency in the NX rats was reflected by proteinuria, the renal handling of CML and, presumably, other AGEs was not impaired.
Biological and Chemical Assessment of Antioxidant Activity of Sugar‐Lysine Model Maillard Reaction Products
Authors: KITTS DAVID D. , HU CHUN
Published: July 2005

Abstract: The antioxidant activity of Maillard reaction products (MRPs) is often associated with increased stability and shelf life of food systems vulnerable to oxidation reactions. In this study, nondialyzed, high‐molecular weight (HMW = >3500 Da) MRPs were recovered from three model sugar‐lysine (glucose‐lysine, Glc‐Lys; fructose‐lysine, Fru‐Lys; and ribose‐lysine, Rib‐Lys) reactions, heated at 121°C for one hour. Samples were characterized by UV and fluorescence spectra and assessed for antioxidant activity using both standard chemical methods (1,1‐diphenyl‐2‐picryl‐hydrazyl [DPPH] and oxygen radical absorbing capacity [ORAC]). In addition, biochemical (e.g., cell culture for intracellular oxidation in RAW264.7 cells and protection against metal ion‐induced cytotoxicity in C3H/10T1/2 mouse embryo fibroblast cells) assays were used. Patterns of change for fluorescence and multiple colorimetric parameters corresponded to the recovery yield of HMW MRPs and indicated that Rib was more (P < 0.05) reactive than Glc, which in turn was greater (P < 0.05) than Fru. These characteristics of rate of browning did not parallel the significant (P < 0.05) antioxidant activity noted for different sugar‐derived HMW MRPs to scavenge DPPH radical, or exhibit total antioxidant activity using the ORAC (e.g., 800‐1000 μmol Trolox/gm MRP) method. Antioxidant activity of Glc‐, Fru‐, and Rib‐Lys HMW‐MRPs (50 μg/mL) produced protection (P < 0.05) against both H2O2‐ and AAPH‐induced intracellular oxidation reactions in cultured RAW 264.7 cells. Metal chelating activity of all three sugar‐derived HMW MRPs (0.01% w/v) was attributed to similar protection (P < 0.05) against Fe2+ and Cu2+‐induced cytotoxicity in cultured mouse embryonic fibroblasts. The reducing activity of all three HMW‐MRPs indicated the potential for prooxidant activity that could explain enhanced cytotoxicity of Fe3+ in cultured cells.
Prevention of Oxidative Stress by Adenoviral Overexpression of Glutathione‐Related Enzymes in Pancreatic Islets
Authors: ROBERTSON R.PAUL , TANAKA YOSHITO , TAKAHASHI HIROKI , TRAN PHUONG OANH T. , HARMON JAMIE S.
Published: July 2005

Abstract: Chronic exposure to supraphysiologic glucose concentrations causes functional damage to cells and tissues, a process known as glucose toxicity. Recent research indicates that one important mechanism for glucose toxicity is oxidative stress. Glucose has been shown to form reactive oxygen species through several metabolic pathways. The pancreatic islet is distinguished by its relatively low antioxidant enzyme content and activity, which render it especially susceptible to oxidative stress. Adenoviral overexpression of glutathione peroxidase as well as gamma‐glutamylcysteine ligase have been shown to protect the islet against oxidative stress. Antioxidants have been shown to brake the worsening of diabetes by improving beta cell function in animal models. These observations suggest that enhancing antioxidant defense mechanisms in pancreatic islets may be a valuable pharmacologic approach to managing diabetes.
A Common Pathway for Intracellular Reactive Oxygen Species Production by Glycoxidative and Nitroxidative Stress in Vascular Endothelial Cells and Smooth Muscle Cells
Authors: TANIGUCHI NAOYUKI , TAKAHASHI MOTOKO , SAKIYAMA HARUHIKO , PARK YONG SEEK , ASAHI MICHIO , MISONOU YOSHIKO , MIYAMOTO YASUHIDE
Published: July 2005

Abstract: A large body of evidence suggests that carbonyl compounds induce intracellular signaling by increasing oxidative stress in the cell; however, the mechanisms involved have not been fully described. The focus of our research is on the pathway in which antioxidative enzymes are modified and inactivated by carbonyl compounds, resulting in the accumulation of active oxygen species in the cell. A common pathway appears to exist for cellular signaling evoked by nitroxidative stress. It could be concluded that some glycoxidative stress and nitroxidative stress cause intracellular signaling via similar mechanisms. The elucidation of the pathway for extracellular stress‐induced reactive oxygen species (ROS) production would be important for our understanding of the role of ROS as signaling molecules.
An in Vitro Approach to the Chronological Aging of Skin by Glycation of the Collagen: The Biological Effect of Glycation on the Reconstructed Skin Model
Authors: PAGEON HERVÉ , ASSELINEAU DANIEL
Published: July 2005

Abstract: Glycation is a slow, nonenzymatic reaction that takes place between free amino groups in proteins primarily from lysine and a reducing sugar such as glucose or ribose. In skin, this reaction creates new residues or formations of cross‐links (advanced glycation end products, AGEs) in the extracellular matrix of the dermis. The formation of these bridges between dermal molecules is supposed to be responsible for loss of elasticity or other properties of the dermis observed during aging. Glycation may therefore play an important role in chronologic aging. In order to examine this hypothesis, we have developed a reconstructed skin model made of a modified dermal compartment that is a fibroblast‐contracted collagen lattice prepared with preglycated collagen. The presence of AGEs (glycoxidation products) in the skin equivalents was evidenced using specific antibodies against carboxymethyllysine (CML). Several changes were observed after collagen glycation: (1) fibroblast shape and distribution (vimentin staining) were modified; (2) extracellular matrix molecules and the dermal‐epidermal junction zone seemed to be enhanced (procollagen I and III, collagen IV and VII stainings); (3) stainings for β1 and α6 integrins were also increased in the epidermal cell layer; and (4) collagenase activity was increased. To verify the biological effect of glycation, we used the well‐known glycation inhibitor aminoguanidine. After aminoguanidine treatment, we found a low CML amount and decreased distribution of markers previously overexpressed in glycated skin constructs. These in vitro findings were at least in part related to aging in vivo and demonstrate an actual effect of glycation in skin aging.
Cross‐Linking of the Extracellular Matrix by the Maillard Reaction in Aging and Diabetes: An Update on “a Puzzle Nearing Resolution”
Authors: MONNIER VINCENT M. , MUSTATA GEORGIAN T. , BIEMEL KLAUS L. , REIHL OLIVER , LEDERER MARCUS O. , ZHENYU DAI , SELL DAVID R.
Published: July 2005

Abstract: The aging extracellular matrix is characterized by an age‐related increase in insolubilization, yellowing, and stiffening, all of which can be mimicked by the Maillard reaction in vitro. These phenomena are accelerated in metabolic diseases such as diabetes and end‐stage renal disease, which have in common with physiological aging the accumulation of various glycation products and cross‐links. Eight years ago we concluded that the evidence favored oxidative cross‐linking in experimental diabetes [Monnier, V.M. et al. 1996. The mechanism of collagen cross‐linking in diabetes: a puzzle nearing completion. Diabetes 45(Suppl. 3): 67‐72] and proposed a major role for a putative non‐UV active cross‐link derived from glucose. Below, we provide an update of the field that leads to the conclusion that, while oxidation might be important for Maillard reaction‐mediated cross‐linking via Strecker degradation and allysine formation, the single most important collagen cross‐link known to date in diabetes and aging is glucosepane, a lysyl‐arginine cross‐link that forms under nonoxidative conditions.
Oxidative Stress and Neurodegeneration
Authors: MOREIRA PAULA I. , SMITH MARK A. , ZHU XIONGWEI , NUNOMURA AKIHIKO , CASTELLANI RUDY J. , PERRY GEORGE
Published: July 2005

Abstract: Oxidative stress is a well‐studied early response in chronic neurodegenerative diseases, including Alzheimer's disease, where neuronal loss can exceed 90% in the vulnerable neuronal population. Oxidative stress affects all classes of macromolecules (sugar, lipids, proteins, and DNA), leading inevitably to neuronal dysfunction. We observed that Nε‐(carboxymethyl)lysine (CML), the predominant advanced glycation end product that accumulates in vivo, along with its glycation‐specific precursor hexitol‐lysine, are increased in neurons from cases of Alzheimer's disease, especially those containing intracellular neurofibrillary pathology. The increase in hexitol‐lysine and CML can result from either lipid peroxidation or advanced glycation, whereas hexitol‐lysine is solely a product of glycation, suggesting that two distinct oxidative processes act in concert in the neuropathology of the disease. Furthermore, using olfactory neurons as an experimental model, we observed an increase in glycation products in neurons derived from Alzheimer's disease patients. Our findings support the idea that aldehyde‐mediated modifications, in concert with oxyradical‐mediated modifications, are critical early pathogenic factors in Alzheimer's disease.
Receptor for Advanced Glycation End Products Is a Promising Target of Diabetic Nephropathy
Authors: YAMAMOTO YASUHIKO , DOI TOSHIO , KATO ICHIRO , SHINOHARA HARUMICHI , SAKURAI SHIGERU , YONEKURA HIDETO , WATANABE TAKUO , MYINT KIHN MAR , HARASHIMA AI , TAKEUCHI MASAYOSHI , TAKASAWA SHIN , OKAMOTO HIROSHI , HASHIMOTO NORIYOSHI , ASANO MASAHIDE , YAMAMOTO HIROSHI
Published: July 2005

Abstract: Advanced glycation end products (AGEs) and the receptor for AGE (RAGE) interactions have been implicated in the development of diabetic vascular complications, which cause various disabilities and shortened life expectancy, and reduced quality of life in patients with diabetes. Diabetes‐induced RAGE‐overexpressing transgenic mice exhibited the exacerbation of the indices of nephropathy, and this was prevented by the inhibition of AGE formation. We also created RAGE‐deficient mice by homologous recombination. They showed marked amelioration of diabetic nephropathy as compared with wild‐type mice. Through an analysis of vascular polysomal poly(A)+ RNA, we identified a novel splice variant coding for a soluble RAGE protein and named it endogenous secretory RAGE (esRAGE). esRAGE was able to protect AGE‐induced vascular cell injuries as a decoy receptor and was actually detected in human circulation. We conclude that RAGE plays an active role in the development of diabetic vascular complications, especially nephropathy, and is a promising target for overcoming this disease. The esRAGE, an endogenous decoy receptor, may be related to individual variations in resistance to the development of diabetic vascular complications.
Glycation Products as Markers and Predictors of the Progression of Diabetic Complications
Authors: MONNIER VINCENT M. , SELL DAVID R. , GENUTH SAUL
Published: July 2005

Abstract: The structure of a growing number of glycation and advanced glycation end products has been elucidated. Measuring these products can be used to assess cumulative glycemic and glycoxidative damage in diabetes and other chronic conditions. The predictive power of a given glycation product can be tested in large prospective studies that evaluate the risk of developing diabetic micro‐ and macrovascular disease over years following the quantitative determination of that marker. This article provides a comprehensive review of the field, comparing the merits of each marker, whether in skin, serum, or other tissue. Several conclusions are drawn, one of which identifies skin glycation products as powerful predictors of the risk of developing diabetic complications.
Localization of the Ezrin Binding Epitope for Glycated Proteins
Authors: McROBERT E ANNE , TIKOO ANJALI , GALLICCHIO MARISA A. , COOPER MARK E. , BACH LEON A.
Published: July 2005

Abstract: ERM proteins (ezrin, radixin, and moesin) have recently been identified as a new class of AGE‐binding proteins. ERM proteins link the plasma membrane with the actin cytoskeleton and regulate cell shape, motility, adhesion, and signal transduction. ERM proteins have three structural domains: the N‐terminal domain, a coiled midregion, and the C‐terminal domain. The N‐terminal domain binds to a number of plasma membrane ligands and is involved in signal transduction, while the C‐domain binds to actin filaments. Binding studies with isolated structural domains showed that glycated proteins bind to an epitope within the N‐terminal domain of ezrin (aa 1‐324). It is postulated that some of the cellular effects of AGEs leading to diabetic complications may be mediated by binding to this region of ezrin, thereby interrupting the cross‐linking between the plasma membrane and actin cytoskeleton and downstream signaling pathways. Indeed, changes in actin arrangement, cell shape, and adhesion have been described in diabetes, and AGE‐BSA inhibits ezrin‐dependent tubulogenesis of LLC‐PK1 proximal tubular cells. For future development of antagonists, further identification of the ezrin‐binding epitope for glycated proteins is required.
Significance of Proximal Tubular Metabolism of Advanced Glycation End Products in Kidney Diseases
Authors: SAITO AKIHIKO , TAKEDA TETSURO , SATO KIYOKO , HAMA HITOMI , TANUMA ATSUHITO , KASEDA RYOHEI , SUZUKI YOSHIKI , GEJYO FUMITAKE
Published: July 2005

Abstract: Advanced glycation end products (AGEs) are formed by the nonenzymatic Maillard reaction between sugars and proteins. Low‐molecular weight AGEs are filtered by renal glomeruli and then reabsorbed and metabolized by proximal tubule cells (PTCs). High‐molecular weight AGEs are also delivered to PTCs in proteinuric states. In patients with diabetes, AGE generation is increased, and the actions of AGEs on PTCs are likely involved in the pathogenesis of diabetic nephropathy. In patients with chronic renal failure (CRF), reduced renal metabolism of AGEs likely accounts for the accumulation of AGEs in serum, leading to uremic complications including dialysis‐related amyloidosis. AGE precursors such as reactive carbonyl compounds also accumulate in the sera of patients with CRF. It is likely that PTCs take up AGEs and AGE precursors via specific endocytotic receptors or transporters. Megalin is a multiligand endocytotic receptor that is abundantly expressed on PTCs. There is evidence that megalin is involved in the cellular uptake and degradation of AGEs. We previously reported a cell therapy model involving implantation of megalin‐expressing cells into experimental mice with renal failure for elimination of uremic toxin proteins. Further studies are needed to clarify the molecular mechanisms of the metabolism of AGEs and their precursors to develop a strategy for the treatment of diabetic nephropathy and uremic complications of CRF.
Low‐Molecular Weight Advanced Glycation End Products: Markers of Tissue AGE Accumulation and More?
Authors: THOMAS MERLIN C. , FORBES JOSEPHINE M. , MacISAAC RICHARD , JERUMS GEORGE , COOPER MARK E.
Published: July 2005

Abstract: Incomplete digestion of advanced glycation end product (AGE)‐modified protein results in the formation of low‐molecular weight degradation products incorporating AGE modifications (LMW‐AGEs). In addition to being biomarkers of AGE modification, LMW‐AGEs may have a high toxic potential, being free to interact with AGE receptors at distant sites via the circulation. Several free AGEs have been identified, including pentosidine, Nε‐(carboxymethyl)lysine (CML), and free‐imidazole AGEs. In addition, fluorescence (370 nm [excitation]/440 nm [emission]) in the LMW phase of serum correlates with tissue fluorescence, an established marker for AGE modification. In experimental diabetes, LMW fluorescence increases with duration of disease and is normalized with the AGE inhibitor aminoguanidine. LMW fluorescence is also higher in patients with diabetes, in whom it is associated with glomerular filtration rate and hemoglobin. Patients with hyperfiltration have lower LMW fluorescence than those with normal renal function, which may protect them from AGE accumulation in the short term. These findings provide clinical support for the association between AGEs and progressive renal injury in diabetes.
Plasma Levels of AGE Peptides in Type 1 Diabetic Patients Are Associated with Serum Creatinine and Not with Albumin Excretion Rate: Possible Role of AGE Peptide‐Associated Endothelial Dysfunction
Authors: SCHALKWIJK CASPER G. , TER WEE PIET M. , STEHOUWER COEN D. A.
Published: July 2005

Abstract: Patients with renal impairment have an increased risk for cardiovascular disease, which may be the result of advanced glycation end products (AGEs). The aim of this study was to investigate the levels of AGE peptides in relation to kidney function and to study the relationship of AGE peptides with endothelial function and inflammation in type 1 diabetic patients. We measured plasma levels of AGE peptides with a simple fluorescent analytical procedure in patients with end‐stage renal disease with or without diabetes and in 60 type 1 diabetic patients categorized as having normo‐, micro‐, or macroalbuminuria. Using enzyme‐linked immunosorbent assays, we determined vascular cell adhesion molecule 1 (sVCAM‐1), sE‐selectin, plasminogen activator inhibitor 1 (PAI‐1), tissue type‐specific plasminogen activator (tPA), von Willebrand factor (vWF), and soluble thrombomodulin (sTM) to be markers of endothelial function and determined C‐reactive protein (CRP) to be a marker of inflammation. AGE peptides were increased approximately fivefold in patients with end‐stage renal disease, without difference between patients with or without diabetes. In type 1 diabetic patients, the increase of AGE peptides across the groups normo‐, micro‐, and macroalbuminuria (with medians [range] of 12.6% [7.8‐27.2%], 12.1% [7.8‐162%], and 46.5% [9.0‐248.9%]) was associated with serum creatinine level and not with albumin excretion rate (AER). The relationship with serum creatinine decreased but remained significant after adjusting for age, sex, diabetes duration, hemoglobin A1c (HbA1c), AER, systolic and diastolic blood pressure (BP), and CRP in multiple linear‐regression analysis. AGE peptide levels were significantly associated with sVCAM‐1 and sTM, independently of serum creatinine. However, these relationships were no longer significant after adjusting for age, sex, diabetes duration, HbA1c, AER, systolic and diastolic BP, and CRP. This study shows that plasma levels of AGE peptides rise with renal impairment, as determined by serum creatinine. AGE peptides are associated with some markers of endothelial activation, which may suggest an involvement of AGE peptides in the acceleration of cardiovascular complications in type 1 diabetic patients with renal impairment.
Pathological Roles of Advanced Glycation End Product Receptors SR‐A and CD36
Authors: HORIUCHI SEIKOH , UNNO YUKA , USUI HITOMI , SHIKATA KENICHI , TAKAKI KAORI , KOITO WAKAKO , SAKAMOTO YU‐ICHIRO , NAGAI RYOJI , MAKINO KENJI , SASAO AKIRA , WADA JUN , MAKINO HIROFUMI
Published: July 2005

Abstract: The pathological significance of advanced glycation end product (AGE)‐modified proteins deposited in several lesions is generally accounted for by their cellular interaction via the AGE receptors and subsequent acceleration of the inflammatory process. In this study, we focused on two AGE receptors—specifically, the role of SR‐A in pathogenesis of diabetic nephropathy and the role of CD36 in AGE‐induced downregulation of leptin by adipocytes. In terms of SR‐A, diabetic wild‐type mice exhibited increased urinary albumin excretion, glomerular hypertrophy, and mesangial matrix expansion, whereas SR‐A‐knockout mice showed reduced glomerular size and mesangial matrix area. In these diabetic SR‐A‐knockout mice, the number of macrophages that infiltrated into glomeruli was remarkably reduced (P < 0.05), suggesting that SR‐A‐dependent glomerular migration of macrophages plays an important role in the pathogenesis of diabetic nephropathy. In terms of CD36, incubation of glycolaldehyde‐modified bovine serum albumin (GA‐BSA) with 3T3‐L1 adipocytes reduced leptin secretion by these cells. The binding of GA‐BSA to these cells and subsequent endocytic degradation were effectively inhibited by a neutralizing anti‐CD36 antibody. AGE‐induced downregulation of leptin was protected by N‐acetyl‐cysteine, an antioxidant. These results indicate that the interaction of AGE ligands with 3T3‐L1 adipocytes via CD36 induces oxidative stress and leads to inhibition of leptin expression by these cells, suggesting a potential link of this phenomenon to exacerbation of the insulin sensitivity in metabolic syndrome.
Advanced Glycation End Products: A Possible Link to Angiotensin in an Animal Model
Authors: BOHLENDER JÜRGEN , FRANKE SYBILLE , SOMMER MANFRED , STEIN GÜNTER
Published: July 2005

Abstract: Advanced glycation end products (AGEs) have been associated with progressive vascular and renal damage in a variety of pathological conditions such as renal failure and diabetes mellitus. The formation of AGEs is generally attributed to increased oxidative and carbonyl stress or hyperglycemia. Activation of the cellular receptor of AGE (RAGE) leads to subsequent cellular activation and proinflammatory responses. Angiotensin (Ang) produces cellular oxidative stress and similarly promotes end organ damage via its type 1 receptor. We investigated the interrelation between these two systems in a new transgenic rat (TGR) model with Ang II‐dependent hypertension and renal damage and in nontransgenic controls. TGR showed increased systolic blood pressure (∼210 mmHg), proteinuria, and increased renal collagen I mRNA expression compared with normotensive nontransgenic controls. Immunohistochemical staining of kidney sections showed colocalization for Nε‐carboxy(methyl)lysine, RAGE, and NF‐κB in TGR glomeruli. These features were absent in nontransgenic controls. Our observations suggest a possible link between Ang II‐dependent end‐organ damage and the AGE/RAGE axis in vivo. TGRs provide an excellent model to study the interrelation between the renin‐angiotensin system and the AGE/RAGE axis in promoting cardiovascular end‐organ damage, which would otherwise not be possible in humans.
Genotoxicity of Advanced Glycation End Products: Involvement of Oxidative Stress and of Angiotensin II Type 1 Receptors
Authors: SCHUPP NICOLE , SCHINZEL REINHARD , HEIDLAND AUGUST , STOPPER HELGA
Published: July 2005

Abstract: In patients with chronic renal failure, cancer incidence is increased. This may be related to an elevated level of genomic damage, which has been demonstrated by micronuclei formation as well as by comet assay analysis. Advanced glycation end products (AGEs) are markedly elevated in renal failure. In the comet assay, the model AGEs methylglyoxal‐ and carboxy(methyl)lysine‐modified bovine serum albumin (BSA) induced significant DNA damage in colon, kidney, and liver cells. The addition of antioxidants prevented AGE‐induced DNA damage, suggesting enhanced formation of reactive oxygen species (ROS). The coincubation with dimethylfumarate (DMF), an inhibitor of NF‐κB translocation, reduced the genotoxic effect, thereby underscoring the key role of NF‐κB in this process. One of the genes induced by NF‐κB is angiotensinogen. The ensuing proteolytic activity yields angiotensin II, which evokes oxidative stress as well as proinflammatory responses. A modulator of the renin‐angiotensin system (RAS), the angiotensin II (Ang II) receptor 1 antagonist, candesartan, yielded a reduction of the AGE‐induced DNA damage, connecting the two signal pathways, RAS and AGE signaling. We were able to identify important participants in AGE‐induced DNA damage: ROS, NF‐κB, and Ang II, as well as modulators to prevent this DNA damage: antioxidants, DMF, and AT1 antagonists.
Glycolaldehyde‐Modified Bovine Serum Albumin Downregulates Leptin Expression in Mouse Adipocytes via a CD36‐Mediated Pathway
Authors: UNNO YUKA , SAKAI MASAKAZU , SAKAMOTO YU‐ICHIRO , KUNIYASU AKIHIKO , NAGAI RYOJI , NAKAYAMA HITOSHI , HORIUCHI SEIKOH
Published: July 2005

Abstract: Previous observations by us have clarified that proteins modified by advanced glycation end products (AGEs) are recognized as effective ligands by CD36‐overexpressed CHO cells and undergo receptor‐mediated endocytosis. CD36, a member of the class B scavenger receptor family, also acts as a fatty acid transporter in adipocytes. Oxidized low‐density lipoprotein (Ox‐LDL), a ligand for CD36, is known to upregulate CD36 by activating peroxisome proliferator‐activated receptor γ (PPAR‐γ) in macrophages, whereas PPAR‐γ ligands such as troglitazone and 15‐deoxy‐delta12,14‐prostaglandin J2 decrease leptin secretion from adipocytes. The purpose of this study was to examine effects of AGE ligands on leptin expression in adipocytes. Glycolaldehyde‐modified bovine serum albumin (GA‐BSA) decreased leptin expression at both the protein and mRNA levels in 3T3‐L1 adipocytes and mouse epididymal adipocytes. The binding to and subsequent endocytic degradation of GA‐BSA by 3T3‐L1 adipocytes were effectively inhibited by a neutralizing anti‐CD36 antibody. These results indicate that the ligand interaction of GA‐BSA with CD36 leads to downregulation of leptin expression in 3T3‐L1 adipocytes, suggesting that AGE‐induced leptin downregulation is linked to reduction of the insulin sensitivity in metabolic syndrome.