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Glycation
Kinds of Glycation Terms modified by Glycation Selected AbstractsTHERAPEUTIC EFFECT OF GREEN TEA EXTRACT ON ADVANCED GLYCATION AND CROSS-LINKING OF COLLAGEN IN THE AORTA OF STREPTOZOTOCIN DIABETIC RATSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 4 2006Pon Velayutham Anandh Babu SUMMARY 1The therapeutic effect of green tea extract (GTE) on the aortic collagen content and its characteristics were investigated in streptozotocin diabetic rats. 2Diabetes was induced in rats by a single intra peritoneal injection of streptozotocin (60 mg/kg bodyweight). Six weeks after diabetes induction, GTE was administered orally for four weeks (300 mg/kg bodyweight daily). Systolic blood pressure, blood glucose, anti-oxidant status, collagen content, extent of glycation, collagen linked fluorescence and aortic collagen solubility pattern were determined in experimental rats. 3At the end of the experimental period, there was a significant increase in the systolic blood pressure and blood glucose in diabetic rats. The lipid peroxides increased whereas glutathione and vitamin C levels were decreased in the serum of diabetic rats. The collagen content, extent of glycation, the advanced glycation end products (AGEs) and degree of cross-linking were increased in the aorta of diabetic rats. 4The oral administration of GTE to diabetic rats significantly reduced the systolic blood pressure and blood glucose. The level of lipid peroxides reduced and the content of glutathione and vitamin C increased in the serum of GTE treated diabetic rats. Green tea extract also impede the accumulation of aortic collagen, extent of glycation, formation of AGEs and cross-linking of collagen in diabetic rats. The antihyperglycemic, anti-oxidant and antiglycating effects of GTE ascribed for these beneficial effects. In conclusion, green tea may have therapeutic effect in the treatment of cardiovascular complications characterized by increased AGE accumulation and protein cross-linking associated with diabetes. [source] Advanced glycation endproducts: what is their relevance to diabetic complications?DIABETES OBESITY & METABOLISM, Issue 3 2007N. Ahmed Glycation is a major cause of spontaneous damage to proteins in physiological systems. This is exacerbated in diabetes as a consequence of the increase in glucose and other saccharides derivatives in plasma and at the sites of vascular complications. Protein damage by the formation of early glycation adducts is limited to lysine side chain and N-terminal amino groups whereas later stage adducts, advanced glycation endproducts (AGEs), modify these and also arginine and cysteine residues. Metabolic dysfunction in vascular cells leads to the increased formation of methylglyoxal which adds disproportionately to the glycation damage in hyperglycaemia. AGE-modified proteins undergo cellular proteolysis leading to the formation and urinary excretion of glycation free adducts. AGEs may potentiate the development of diabetic complications by activation of cell responses by AGE-modified proteins interacting with specific cell surface receptors, activation of cell responses by AGE free adducts, impairment of protein,protein and enzyme,substrate interactions by AGE residue formation, and increasing resistance to proteolysis of extracellular matrix proteins. The formation of AGEs is suppressed by intensive glycaemic control, and may in future be suppressed by thiamine and pyridoxamine supplementation, and several other pharmacological agents. Increasing expression of enzymes of the enzymatic defence against glycation provides a novel and potentially effective future therapeutic strategy to suppress protein glycation. [source] Glycation of low-density lipoprotein results in the time-dependent accumulation of cholesteryl esters and apolipoprotein B-100 protein in primary human monocyte-derived macrophagesFEBS JOURNAL, Issue 6 2007Bronwyn E. Brown Nonenzymatic covalent binding (glycation) of reactive aldehydes (from glucose or metabolic processes) to low-density lipoproteins has been previously shown to result in lipid accumulation in a murine macrophage cell line. The formation of such lipid-laden cells is a hallmark of atherosclerosis. In this study, we characterize lipid accumulation in primary human monocyte-derived macrophages, which are cells of immediate relevance to human atherosclerosis, on exposure to low-density lipoprotein glycated using methylglyoxal or glycolaldehyde. The time course of cellular uptake of low-density lipoprotein-derived lipids and protein has been characterized, together with the subsequent turnover of the modified apolipoprotein B-100 (apoB) protein. Cholesterol and cholesteryl ester accumulation occurs within 24 h of exposure to glycated low-density lipoprotein, and increases in a time-dependent manner. Higher cellular cholesteryl ester levels were detected with glycolaldehyde-modified low-density lipoprotein than with methylglyoxal-modified low-density lipoprotein. Uptake was significantly decreased by fucoidin (an inhibitor of scavenger receptor SR-A) and a mAb to CD36. Human monocyte-derived macrophages endocytosed and degraded significantly more 125I-labeled apoB from glycolaldehyde-modified than from methylglyoxal-modified, or control, low-density lipoprotein. Differences in the endocytic and degradation rates resulted in net intracellular accumulation of modified apoB from glycolaldehyde-modified low-density lipoprotein. Accumulation of lipid therefore parallels increased endocytosis and, to a lesser extent, degradation of apoB in human macrophages exposed to glycolaldehyde-modified low-density lipoprotein. This accumulation of cholesteryl esters and modified protein from glycated low-density lipoprotein may contribute to cellular dysfunction and the increased atherosclerosis observed in people with diabetes, and other pathologies linked to exposure to reactive carbonyls. [source] Functional Properties of Glycated Soy 11S GlycininJOURNAL OF FOOD SCIENCE, Issue 4 2005Allaoua Achouri ABSTRACT: 11S-rich glycinin fraction was extracted from defatted soy flakes and glycated using glucose (at a 1:44 molar ratio of protein to sugar) through the Maillard reaction. The glycation was done at 50°C and 65% relative humidity for varying incubation periods (6, 16, 24, and 48 h). Fluorescamine and trinitrobenzenesulfonic acid (TNBS) methods both revealed a gradual increase in % glycation from 34.8% to 39.6%, 42.6%, and 46.5%, as samples were glycated from 6 to 48 h. Functional studies of the glycated 11S-rich glycinin fraction showed an initial increase in solubility during the early stages of glycation and a decrease as glycation progressed beyond 24 h. Glycation in the 1st hour of incubation also decreased protein surface hydrophobicity and fat absorption capacity (FAC). This was mainly attributed to an increase in the net negative charge induced by the introduction of the sugar moiety. As the Maillard reaction progressed (24 h and 48 h of incubation), an increase in FAC and surface hydrophobicity was observed. The results further showed an increase in foaming properties and emulsifying activity of the 11S-rich glycinin fraction with glycation (compared with control), especially at the early and middles stages of the Maillard reaction. [source] Site-specific synthesis of Amadori-modified peptides on solid phaseJOURNAL OF PEPTIDE SCIENCE, Issue 6 2006Andrej Frolov Abstract Glycation of peptides and proteins is a slow chemical reaction of reducing sugars modifying the amino groups. The first intermediates of this nonenzymatic glycosylation are the Amadori products that can undergo further chemical reactions, finally leading to advanced glycation end products (AGEs). The formation of AGEs was not only linked to aging of tissues and organs in general but also to several diseases such as diabetes mellitus and Alzheimer's disease. Because of the importance of these modifications and their potential use as diagnostic markers, a global postsynthetic approach on solid phase was developed. The peptides were synthesized by Fmoc/tBu-chemistry, with the lysine residue to be modified being protected with the very acid-labile methyltrityl group. Incubation of the peptides with D -glucose in DMF at elevated temperatures resulted in product yields of 35%. Neighboring residues with bulky protecting groups reduced the yields only slightly. The major by-products were the unmodified peptide and an oxidation product. Whereas the unmodified peptide eluted before the glycated peptide, all other by-products eluted later in RP-HPLC, allowing simple purification. Copyright © 2005 European Peptide Society and John Wiley & Sons, Ltd. [source] Effects of Compounds Isolated from the Fruits of Rumex japonicus on the Protein GlycationCHEMISTRY & BIODIVERSITY, Issue 12 2008Sik Jang Abstract An anthraquinone, emodin (1), and five flavonoids, kaempferol-3- O - ,- D -glucoside (2), quercetin (3), quercitrin (4), isoquercitrin (5), and (+)-catechin (6), were isolated from an AcOEt-soluble extract of the fruits of Rumex japonicus. Their structures were determined by spectroscopic data interpretation. All the isolates were evaluated for their potential to inhibit AGEs (advanced glycation end products) formation and AGEs cross-linking, and to break already formed AGEs cross-links. [source] Recent Advances in the Recovery and Improvement of Functional Proteins from Fish Processing By-Products: Use of Protein Glycation as an Alternative MethodCOMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY, Issue 4 2009Esther Sanmartín ABSTRACT:, The recovery of proteins from fish by-products for their utilization as food ingredients is becoming of increasing interest in the food industry as they may possess good functional and nutritional properties. This article reviews the main processing methods, such as enzymatic hydrolysis, pH shifting, membrane filtration, and some emerging technologies, used for the recovery of proteins from fish processing by-products. The impact of these methods on the yield and, especially, on the functionality of the recovered proteins is discussed in detail. Considering that there is a huge amount of fish by-products destined for nonfood use, one of the current challenges of the food industry is the development of technologies that allow the recovery of ingredients from the fish processing by-products with potential to provide new and natural sources of high-value functional ingredients for human consumption. In this sense, this review explores the potential use of the glycation reaction to increase the yield of proteins extracted from fish by-products, as well as the effect of this reaction on their functional and biological properties. [source] The potential of cinnamon to reduce blood glucose levels in patients with type 2 diabetes and insulin resistanceDIABETES OBESITY & METABOLISM, Issue 12 2009S. Kirkham Aim: Cinnamon has a long history as an antidiabetic spice, but trials involving cinnamon supplementation have produced contrasting results. The aim of this review was to examine the results of randomized controlled clinical trials of cinnamon and evaluate the therapeutic potential amongst patients with diabetes and insulin-resistant patients, particularly the ability to reduce blood glucose levels and inhibit protein glycation. Methods: A systematic electronic literature search using the medical subject headings ,cinnamon' and ,blood glucose' was carried out to include randomized, placebo-controlled in vivo clinical trials using Cinnamomum verum or Cinnamomum cassia conducted between January 2003 and July 2008. Results: Five type 2 diabetic and three non-diabetic studies (total N = 311) were eligible. Two of the diabetic studies illustrated significant fasting blood glucose (FBG) reductions of 18,29% and 10.3% (p < 0.05), supported by one non-diabetic trial reporting an 8.4% FBG reduction (p < 0.01) vs. placebo, and another illustrating significant reductions in glucose response using oral glucose tolerance tests (p < 0.05). Three diabetic studies reported no significant results. Conclusions: Whilst definitive conclusions cannot be drawn regarding the use of cinnamon as an antidiabetic therapy, it does possess antihyperglycaemic properties and potential to reduce postprandial blood glucose levels. Further research is required to confirm a possible correlation between baseline FBG and blood glucose reduction and to assess the potential to reduce pathogenic diabetic complications with cinnamon supplementation. [source] Advanced glycation endproducts: what is their relevance to diabetic complications?DIABETES OBESITY & METABOLISM, Issue 3 2007N. Ahmed Glycation is a major cause of spontaneous damage to proteins in physiological systems. This is exacerbated in diabetes as a consequence of the increase in glucose and other saccharides derivatives in plasma and at the sites of vascular complications. Protein damage by the formation of early glycation adducts is limited to lysine side chain and N-terminal amino groups whereas later stage adducts, advanced glycation endproducts (AGEs), modify these and also arginine and cysteine residues. Metabolic dysfunction in vascular cells leads to the increased formation of methylglyoxal which adds disproportionately to the glycation damage in hyperglycaemia. AGE-modified proteins undergo cellular proteolysis leading to the formation and urinary excretion of glycation free adducts. AGEs may potentiate the development of diabetic complications by activation of cell responses by AGE-modified proteins interacting with specific cell surface receptors, activation of cell responses by AGE free adducts, impairment of protein,protein and enzyme,substrate interactions by AGE residue formation, and increasing resistance to proteolysis of extracellular matrix proteins. The formation of AGEs is suppressed by intensive glycaemic control, and may in future be suppressed by thiamine and pyridoxamine supplementation, and several other pharmacological agents. Increasing expression of enzymes of the enzymatic defence against glycation provides a novel and potentially effective future therapeutic strategy to suppress protein glycation. [source] ,Lipoproteins, glycoxidation and diabetic angiopathy'DIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 5 2004Alicia J. Jenkins Abstract The chronic vascular complications of diabetes (nephropathy, retinopathy and accelerated atherosclerosis) are a major cause of morbidity and premature mortality. In spite of the more widespread availability of intensive diabetes management, approximately one in three people with diabetes develop aggressive complications and over 70% die of atherosclerosis-related diseases. Genetic and acquired factors are likely to be contributory. Potential mediators of vascular damage may include the interrelated processes of lipoprotein abnormalities, glycation, oxidation and endothelial dysfunction. Lipoprotein abnormalities encompass alterations in lipid concentrations, lipoprotein composition and subclass distribution and lipoprotein-related enzymes. Nonenzymatic glycation and oxidative damage to lipoproteins, other proteins and to vascular structures may also be deleterious. As atherosclerosis is a chronic condition commencing in youth, and because clinical events may be silent in diabetes, surrogate measures of vascular disease are important for early identification of diabetic patients with or at high risk of vascular damage, and for monitoring efficacy of interventions. The increasing array of biochemical assays for markers and mediators of vascular damage, noninvasive measures of vascular health, and therapeutic options should enable a reduction in the excessive personal and economic burden of vascular disease in type 1 and type 2 diabetes. Copyright © 2004 John Wiley & Sons, Ltd. [source] Fructose-mediated non-enzymatic glycation: sweet coupling or bad modificationDIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 5 2004Casper G. Schalkwijk Abstract The Maillard reaction is a process in which reducing sugars react spontaneously with amino groups in proteins to advanced glycation endproducts (AGEs). Although an elevated level of glucose had been thought to play a primary role in the Maillard reaction, on a molecular basis, glucose is among the least reactive sugars within biological systems. The formation of AGEs is now also known to result from the action of various metabolites other than glucose, which are primarily located intracellularly and participate in the non-enzymatic glycation reaction at a much faster rate, such as fructose, trioses and dicarbonyl compounds. In this review, we considered the glycation reaction with particular attention to the potential role of fructose and fructose metabolites. The two sources for fructose are an exogenous supply from the diet and the endogenous formation from glucose through the aldose reductase pathway. Despite its ,eightfold higher reactivity, the contribution of extracellular glycation by fructose is considerably less than that by glucose, because of the low plasma concentration of fructose (5 mmol/L glucose vs 35 µmol/L fructose). Intracellularly, fructose is elevated in a number of tissues of diabetic patients in which the polyol pathway is active. In the cells of these tissues, the concentrations of fructose and glucose are of the same magnitude. Although direct evidence is not yet available, it is likely that the high reactivity of fructose and its metabolites may substantially contribute to the formation of intracellular AGEs and may contribute to alterations of cellular proteins, dysfunction of cells and, subsequently, to vascular complications. Copyright © 2004 John Wiley & Sons, Ltd. [source] Diabetes control and complications: the role of glycated haemoglobin, 25 years onDIABETIC MEDICINE, Issue 7 2004S. L. Jeffcoate Abstract The long-term complications of diabetes have major consequences for individual subjects and growing healthcare delivery and cost implications for society. Evidence for the benefits of good glycaemic control, as monitored by glycated haemoglobin measurements, has been developed in the 25 years since they were introduced to the point where HbA1c assays play central roles in patient management, clinical guidance and audit, and clinical trial design. In this review this evidence is examined and three classes of uncertainty identified that diminish confidence in the effectiveness of these roles for HbA1c. 1Analytical variability between different methods for HbA1c has restricted the application of clinical targets and this problem has recently been addressed by reference method standardization. There are two approaches to this which result in different HbA1c values and this discrepancy needs to be resolved. 2Biological variability in HbA1c values between individuals also restricts its predictive role when applied to populations. The correlations between HbA1c measurements and various components of glycaemia (overall, fasting, postprandial) are still uncertain and differences in protein glycation and de-glycation are greater between subjects than often thought. The influence of variability in erythrocyte life span is an area where research is needed, especially in diabetic subjects. 3Clinical variability is the most important and complex area of uncertainty. A predictive link between HbA1c and clinical outcomes is not as clear-cut as often stated. The correlation with the development of microvascular disease is well established in Type 1 diabetes, but in Type 2 subjects (90% of those with diabetes) the evidence that HbA1c monitoring is of value in predicting or preventing macrovascular disease is not strong, although it is the major cause of morbidity and early death in this group. It is recommended that, as a matter of urgency, these issues be examined, particularly within the context of self-care in diabetes. Diabet. Med. **, ***,*** (2003) [source] Advanced glycation end-products and the kidneyEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 8 2010Martin Busch Eur J Clin Invest 2010; 40 (8): 742,755 Abstract Background, Advanced glycation end-products (AGEs) are increased in situations with hyperglycemia and oxidative stress such as diabetes mellitus. They are products of nonenzymatic glycation and oxidation of proteins and lipids. The kidney plays an important role in clearance and metabolism of AGEs. Methods, Medline© and other relevant databases were searched. In addition, key review articles were scanned for relevant original publication. Finally, original data from our research group were also included. Results, Kidney podocytes and endothelial cells express specific receptors for AGEs. Their activation leads to multiple pathophysiological effects including hypertrophy with cell cycle arrest and apoptosis, altered migration, and generation of proinflammatory cytokines. AGEs have been primarily implicated in the pathophysiology of diabetic nephropathy and diabetic microvascular complications. AGEs are also involved in other primary renal diseases as well as in the development and progression of atherosclerosis. However, serum or plasma concentrations of AGEs do not correlate well with cardiovascular events in patients with chronic kidney disease (CKD). This is likely due to the fact that serum concentrations failed to correlate with AGEs deposited in target tissues. Several inhibitors of the AGE-RAGE axis are currently tested for various indications. Conclusion, AGEs and their receptors are involved in the pathogenesis of vascular and kidney disease. The role of circulating AGEs as biomarkers for cardiovascular risk estimation is questionable. Whether putative inhibitors of AGEs will get the maturity for its therapeutic use in the future remains open. [source] Advanced glycation and the immune system: stimulation, inhibition or both?EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 12 2001G. Glorieux [source] Glycation of low-density lipoprotein results in the time-dependent accumulation of cholesteryl esters and apolipoprotein B-100 protein in primary human monocyte-derived macrophagesFEBS JOURNAL, Issue 6 2007Bronwyn E. Brown Nonenzymatic covalent binding (glycation) of reactive aldehydes (from glucose or metabolic processes) to low-density lipoproteins has been previously shown to result in lipid accumulation in a murine macrophage cell line. The formation of such lipid-laden cells is a hallmark of atherosclerosis. In this study, we characterize lipid accumulation in primary human monocyte-derived macrophages, which are cells of immediate relevance to human atherosclerosis, on exposure to low-density lipoprotein glycated using methylglyoxal or glycolaldehyde. The time course of cellular uptake of low-density lipoprotein-derived lipids and protein has been characterized, together with the subsequent turnover of the modified apolipoprotein B-100 (apoB) protein. Cholesterol and cholesteryl ester accumulation occurs within 24 h of exposure to glycated low-density lipoprotein, and increases in a time-dependent manner. Higher cellular cholesteryl ester levels were detected with glycolaldehyde-modified low-density lipoprotein than with methylglyoxal-modified low-density lipoprotein. Uptake was significantly decreased by fucoidin (an inhibitor of scavenger receptor SR-A) and a mAb to CD36. Human monocyte-derived macrophages endocytosed and degraded significantly more 125I-labeled apoB from glycolaldehyde-modified than from methylglyoxal-modified, or control, low-density lipoprotein. Differences in the endocytic and degradation rates resulted in net intracellular accumulation of modified apoB from glycolaldehyde-modified low-density lipoprotein. Accumulation of lipid therefore parallels increased endocytosis and, to a lesser extent, degradation of apoB in human macrophages exposed to glycolaldehyde-modified low-density lipoprotein. This accumulation of cholesteryl esters and modified protein from glycated low-density lipoprotein may contribute to cellular dysfunction and the increased atherosclerosis observed in people with diabetes, and other pathologies linked to exposure to reactive carbonyls. [source] Diabetes, oxidative stress, and antioxidants: A reviewJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 1 2003A. C. Maritim Abstract Increasing evidence in both experimental and clinical studies suggests that oxidative stress plays a major role in the pathogenesis of both types of diabetes mellitus. Free radicals are formed disproportionately in diabetes by glucose oxidation, nonenzymatic glycation of proteins, and the subsequent oxidative degradation of glycated proteins. Abnormally high levels of free radicals and the simultaneous decline of antioxidant defense mechanisms can lead to damage of cellular organelles and enzymes, increased lipid peroxidation, and development of insulin resistance. These consequences of oxidative stress can promote the development of complications of diabetes mellitus. Changes in oxidative stress biomarkers, including superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase, glutathione levels, vitamins, lipid peroxidation, nitrite concentration, nonenzymatic glycosylated proteins, and hyperglycemia in diabetes, and their consequences, are discussed in this review. In vivo studies of the effects of various conventional and alternative drugs on these biomarkers are surveyed. There is a need to continue to explore the relationship between free radicals, diabetes, and its complications, and to elucidate the mechanisms by which increased oxidative stress accelerates the development of diabetic complications, in an effort to expand treatment options. © 2003 Wiley Periodicals, Inc. J Biochem Mol Toxicol 17:24,38, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.10058 [source] Oxidative damage to DNA and lipids: correlation with protein glycation in patients with type 1 diabetesJOURNAL OF CLINICAL LABORATORY ANALYSIS, Issue 2 2010Mohammad Taghi Goodarzi Abstract Diabetic hyperglycemia is associated with increased production of reactive oxygen species (ROS). ROS reacts with DNA resulting in various products, such as 8-hydroxydeoxyguanosine (8-OHdG), that excrete in urine owing to DNA repair processes. Urinary 8-OHdG has been proposed as an indicator of oxidative damage to DNA. This study aimed to evaluate relationship between oxidative damage to DNA and protein glycation in patients with Type 1 diabetes. We measured urinary 8-OHdG level in diabetic patients and healthy subjects and discussed its relationship to glycated hemoglobin (HbA1c) and glycated serum protein (GSP) levels. Furthermore plasma malondialdehyde (MDA) level monitored as an important indicator of lipid peroxidation in diabetes. We studied 32 patients with Type 1 diabetes mellitus and compared the measured factors with those of 48 age-matched nondiabetic controls. GSP and MDA were measured bycolorimetric assay. Urinary 8-OHdG measurement was carried out using ELISA. In this study urinary 8-OHdG, HbA1c, plasma MDA, and GSP levels were progressively higher in diabetics than in control subjects (P<0.05). Furthermore we found significant correlation between urinary 8-OHdG and HbA1c (P<0.05) in diabetic group. Correlation between fasting blood sugar and GSP were significant. We also found significant correlation between fasting blood sugar and MDA. This case,control study in young diabetic patients showed increased blood glucose and related metabolic disorders result in oxidative stress and oxidative damage to DNA and lipids. Furthermore oxidative damage to DNA is associated to glycemic control level, whereas lipid peroxidation level was not significantly correlated with glycemic control level. J. Clin. Lab. Anal. 24:72,76, 2010. © 2010 Wiley-Liss, Inc. [source] Rapid method for the preparation of an AGE-BSA standard calibrator using thermal glycationJOURNAL OF CLINICAL LABORATORY ANALYSIS, Issue 1 2005A.D. Bhatwadekar Abstract Estimation of advanced glycation end products (AGEs) by determining fluorescence is based on the use of a standard calibrator prepared by incubating bovine serum albumin (BSA) and glucose at 37°C for 60 days. In the present study we attempted to reduce the duration of incubation to 4 days by increasing the temperature to 50°C. It is noteworthy that incubation at 50°C resulted in the rapid production of an AGE-BSA standard calibrator within 4 days. Aminoguanidine reduced the intensity of the glycation-induced fluorescence, while the addition of lysine intensified the reaction, as shown by the calibrator incubated at 37°C. The protein carbonyl content was shown to increase in the rapidly-formed standard calibrator. Thus we conclude that a simple increase in temperature and the addition of lysine (0.1M) can accelerate the process of glycation-induced fluorescence. This calibrator can be used effectively in fluorescence assays of AGEs. J. Clin. Lab. Anal. 19:11,15, 2005. © 2005 Wiley-Liss, Inc. [source] Protein modification and replicative senescence of WI-38 human embryonic fibroblastsAGING CELL, Issue 2 2010Emad K. Ahmed Summary Oxidized proteins as well as proteins modified by the lipid peroxidation product 4-hydroxy-2-nonenal (HNE) and by glycation (AGE) have been shown to accumulate with aging in vivo and during replicative senescence in vitro. To better understand the mechanisms by which these damaged proteins build up and potentially affect cellular function during replicative senescence of WI-38 fibroblasts, proteins targeted by these modifications have been identified using a bidimensional gel electrophoresis-based proteomic approach coupled with immunodetection of HNE-, AGE-modified and carbonylated proteins. Thirty-seven proteins targeted for either one of these modifications were identified by mass spectrometry and are involved in different cellular functions such as protein quality control, energy metabolism and cytoskeleton. Almost half of the identified proteins were found to be mitochondrial, which reflects a preferential accumulation of damaged proteins within the mitochondria during cellular senescence. Accumulation of AGE-modified proteins could be explained by the senescence-associated decreased activity of glyoxalase-I, the major enzyme involved in the detoxification of the glycating agents methylglyoxal and glyoxal, in both cytosol and mitochondria. This finding suggests a role of detoxification systems in the age-related build-up of damaged proteins. Moreover, the oxidized protein repair system methionine sulfoxide reductase was more affected in the mitochondria than in the cytosol during cellular senescence. Finally, in contrast to the proteasome, the activity of which is decreased in senescent fibroblasts, the mitochondrial matrix ATP-stimulated Lon-like proteolytic activity is increased in senescent cells but does not seem to be sufficient to cope with the increased load of modified mitochondrial proteins. [source] Aging induces cardiac diastolic dysfunction, oxidative stress, accumulation of advanced glycation endproducts and protein modificationAGING CELL, Issue 2 2005Shi-Yan Li Summary Evidence suggests that aging, per se, is a major risk factor for cardiac dysfunction. Oxidative modification of cardiac proteins by non-enzymatic glycation, i.e. advanced glycation endproducts (AGEs), has been implicated as a causal factor in the aging process. This study was designed to examine the role of aging on cardiomyocyte contractile function, cardiac protein oxidation and oxidative modification. Mechanical properties were evaluated in ventricular myocytes from young (2-month) and aged (24,26-month) mice using a MyoCam® system. The mechanical indices evaluated were peak shortening (PS), time-to-PS (TPS), time-to-90% relengthening (TR90) and maximal velocity of shortening/relengthening (± dL/dt). Oxidative stress and protein damage were evaluated by glutathione and glutathione disulfide (GSH/GSSG) ratio and protein carbonyl content, respectively. Activation of NAD(P)H oxidase was determined by immunoblotting. Aged myocytes displayed a larger cell cross-sectional area, prolonged TR90, and normal PS, ± dL/dt and TPS compared with young myocytes. Aged myocytes were less tolerant of high stimulus frequency (from 0.1 to 5 Hz) compared with young myocytes. Oxidative stress and protein oxidative damage were both elevated in the aging group associated with significantly enhanced p47phox but not gp91phox expression. In addition, level of cardiac AGEs was ,2.5-fold higher in aged hearts than young ones determined by AGEs-ELISA. A group of proteins with a molecular range between 50 and 75 kDa with pI of 4,7 was distinctively modified in aged heart using one- or two-dimension SDS gel electrophoresis analysis. These data demonstrate cardiac diastolic dysfunction and reduced stress tolerance in aged cardiac myocytes, which may be associated with enhanced cardiac oxidative damage, level of AGEs and protein modification by AGEs. [source] Functional Properties of Glycated Soy 11S GlycininJOURNAL OF FOOD SCIENCE, Issue 4 2005Allaoua Achouri ABSTRACT: 11S-rich glycinin fraction was extracted from defatted soy flakes and glycated using glucose (at a 1:44 molar ratio of protein to sugar) through the Maillard reaction. The glycation was done at 50°C and 65% relative humidity for varying incubation periods (6, 16, 24, and 48 h). Fluorescamine and trinitrobenzenesulfonic acid (TNBS) methods both revealed a gradual increase in % glycation from 34.8% to 39.6%, 42.6%, and 46.5%, as samples were glycated from 6 to 48 h. Functional studies of the glycated 11S-rich glycinin fraction showed an initial increase in solubility during the early stages of glycation and a decrease as glycation progressed beyond 24 h. Glycation in the 1st hour of incubation also decreased protein surface hydrophobicity and fat absorption capacity (FAC). This was mainly attributed to an increase in the net negative charge induced by the introduction of the sugar moiety. As the Maillard reaction progressed (24 h and 48 h of incubation), an increase in FAC and surface hydrophobicity was observed. The results further showed an increase in foaming properties and emulsifying activity of the 11S-rich glycinin fraction with glycation (compared with control), especially at the early and middles stages of the Maillard reaction. [source] Advanced glycation end product in familial amyloidotic polyneuropathy (FAP)JOURNAL OF INTERNAL MEDICINE, Issue 4 2000N. Nyhlin Abstract. Nyhlin N, Ando Y, Nagai R, Suhr O, El Sahly M, Terazaki H, Yamashita T, Ando M, Horiuchi S (Umeå University Hospital, Umeå, Sweden and Kumamoto University School of Medicine, Kumamoto, Japan). Advanced glycation end product in familial amyloidotic polyneuropathy (FAP). J Intern Med 2000; 247: 485,492. Objectives. Advanced glycation end products (AGE) are present in amyloid deposits in ,2 -microglobulin amyloidosis, and it has been postulated that glycation of ,2 -microglobulin may be involved in fibril formation. The aim of this paper was to ascertain whether AGE occur in amyloid deposits in familial amyloidotic polyneuropathy (FAP). Setting. Department of Medicine, Umeå University Hospital and First Department of Internal Medicine, Kumamoto University School of Medicine. Design. The presence of AGE was sought immunohistochemically and biochemically in amyloid-rich tissues from patients with FAP. Subjects. Biopsy specimens from nine patients and 10 controls were used for the immunohistochemical analysis. For amyloid preparation, vitreous samples from three FAP patients were used. Results. Immunohistochemical studies using a polyclonal anti-AGE antibody revealed positive immunoreactivity in intestinal materials, but the pattern of reactivity was unevenly distributed; it was often present in the border of amyloid deposits, or surrounding them. Non-amyloid associated immunoreactivity was also observed in a few regions of the specimens, although the AGE-positive structures were situated in areas containing amyloid deposits. Western blotting of purified amyloid from the vitreous body of FAP patients revealed a significant association of AGE with amyloid fibrils. Conclusion. The immunoreactivity for the AGE antibody suggests that AGE may be involved in fibril formation in FAP. [source] Solid-state glycation of ,-lactoglobulin by lactose and galactose: localization of the modified amino acids using mass spectrometric techniquesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 1 2004François Fenaille Abstract The Maillard reaction is commonly encountered during food processing or storage, and also in human nutrition, hence there is a need for analytical methodologies to identify and characterize the modified proteins. This paper reports specific methods using mass spectrometric techniques to localize protein modifications induced by lactose and galactose on ,-lactoglobulin (,-Lg) under solid-state glycation conditions. The extent of glycation was first determined by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS). The specific identification of lactose-modified amino acid residues was realized using both NanoESI-MS, NanoESI-MS/MS (neutral loss scanning modes) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) (with and without guanidination of lysine residues) on unfractionated digests. The results indicated that, after 8.25 h of incubation, the lysine residues were the main targets of lactose-induced modification. In addition to the 15 lysine residues, Leu1 (NH2 terminal) and the Arg124 were also found to be modified, thus leading to a total of 17 different modified amino acid residues (versus 15 found by LC/ESI-MS measurement). In a second set of experiments, different strategies consisting of constant neutral loss and precursor ion scanning were compared to characterize galactose-induced modifications. Owing to the high level of ,-Lg glycation, the combined use of these different strategies appeared to be necessary for determining the galactose-modified sites after 8.25 h of incubation. Thus, among the 22 galactose adducts deduced from the LC/ESI-MS measurement, apart from the N-terminal and classical lysine residues, we also observed a few arginine residues (Arg40, Arg124 and Arg148) that were modified, and also dialkylations on specific lysine residues (Lys47, Lys75). Copyright © 2003 John Wiley & Sons, Ltd. [source] Non-enzymatic glycation of chondrocyte-seeded collagen gels for cartilage tissue engineeringJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 11 2008Rani Roy Abstract Collagen glycated with ribose (250 mM) in solution (pre-glycation) and as a gel (post-glycation) was seeded with chondrocytes and the effects of glycation on chondrocyte matrix assembly in culture were determined. Pre-glycation enhanced GAG accumulation significantly over controls at both 2 and 4 weeks (p,<,0.05), although at both time points there were no statistical differences in cell number between pre-glycated and control gels. The increased proteoglycan accumulation was shown to be in part due to significantly increased GAG retention by the pre-glycated constructs (p,<,0.05). Total collagen content in these pre-glycated gels was also significantly higher than unglycated gels at 4 weeks (p,<,0.05). With post-glycation of collagen gels, chondrocyte number and GAG accumulation were all significantly lower than controls (p,<,0.05). Post-glycation also inhibited GAG retention by the constructs (p,<,0.05). Given these results, pre-glycation may be an improved processing method for collagen gels for tissue engineering techniques. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1434,1439, 2008 [source] Diabetic neuropathies: components of etiologyJOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 2 2008David R. Tomlinson Abstract This review examines the putative role of glucose in the etiology of diabetic neuropathies. Excessive glucose generates several secondary metabolic anomalies , principally oxidative stress (via both the polyol pathway and glucoxidation) and non-enzymic glycation of macromolecules. The latter is also facilitated by glucoxidation. These metabolic deviations trigger cellular responses that are inappropriate to normal function. Principal among these are neurotrophic deficits and phosphorylation of mitogen-activated protein kinases (MAPK). Downstream of these events are aberrant ion channel function and disordered gene expression, leading to changes in cellular phenotype. This leads directly to disordered nerve conduction, a recognised early clinical sign, and indirectly, via as yet undisclosed links, to sensory loss and axonopathy. Recent work also links MAPK activation to the development of neuropathic pain. [source] REVIEW ARTICLE: Hyperglycemia: a prothrombotic factor?JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 8 2010B. A. LEMKES Summary., Diabetes mellitus is characterized by a high risk of atherothrombotic events. What is more, venous thrombosis has also been found to occur more frequently in this patient group. This prothrombotic condition in diabetes is underpinned by laboratory findings of elevated coagulation factors and impaired fibrinolysis. Hyperglycemia plays an important role in the development of these hemostatic abnormalities, as is illustrated by the association with glycemic control and the improvement upon treatment of hyperglycemia. Interestingly, stress induced hyperglycemia, which is often transient, has also been associated with poor outcome in thrombotic disease. Similar laboratory findings suggest a common effect of acute vs. chronic hyperglycemia on the coagulation system. Many mechanisms have been proposed to explain this prothrombotic shift in hyperglycemia, such as a direct effect on gene transcription of coagulation factors caused by hyperglycemia-induced oxidative stress, loss of the endothelial glycocalyx layer, which harbours coagulation factors, and direct glycation of coagulation factors, altering their activity. In addition, both chronic and acute hyperglycemia are often accompanied by hyperinsulinemia, which has been shown to have prothrombotic effects as well. In conclusion, the laboratory evidence of the effects of both chronic and acute hyperglycemia suggests a prothrombotic shift. Additionally, hyperglycemia is associated with poor clinical outcome of thrombotic events. Whether intensive treatment of hyperglycemia can prevent hypercoagulability and improve clinical outcome remains to be investigated. [source] Platelet activation in type 2 diabetes mellitusJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 8 2004P. Ferroni Summary., The abnormal metabolic state that accompanies diabetes renders arteries susceptible to atherosclerosis, being capable of altering the functional properties of multiple cell types, including endothelium and platelets. In particular, an altered platelet metabolism and changes in intraplatelet signaling pathways may contribute to the pathogenesis of atherothrombotic complications of diabetes. A variety of mechanisms may be responsible for enhanced platelet aggregation. Among them, hyperglycemia may represent a causal factor for in vivo platelet activation, and may be responsible for nonenzymatic glycation of platelet glycoproteins, causing changes in their structure and conformation, as well as alterations of membrane lipid dynamics. Furthermore, hyperglycemia-induced oxidative stress is responsible for enhanced peroxidation of arachidonic acid to form biologically active isoprostanes, which represents an important biochemical link between impaired glycemic control and persistent platelet activation. Finally, increased oxidative stress is responsible for activation of transcription factors and expression of redox-sensitive genes leading to a phenotypic switch of endothelium toward an adhesive, pro-thrombotic condition, initial platelet activation, adhesion and subsequent platelet aggregate formation. All this evidence is strengthened by the results of clinical trials documenting the beneficial effects of metabolic control on platelet function, and by the finding that aspirin treatment may even be more beneficial in diabetic than in high-risk non-diabetic patients. Attention to appropriate medical management of diabetic patients will have great impact on long-term outcome in this high-risk population. [source] Monitoring of blood proteins glycation by refractive index and spectral measurementsLASER PHYSICS LETTERS, Issue 6 2008O.S. Zhernovaya Abstract Monitoring of blood glucose and glycated proteins level is an urgent requirement for diabetic patients. The amount of glycated hemoglobin and glycated albumin depends on blood glucose concentration and reflects the mean glycemia. The purpose of this study is to investigate the effect of presence of glucose and glycation of proteins on optical properties of water solutions of hemoglobin and albumin with different glucose concentrations. We present the results of feasibility study of the refractive index measurements for water solutions of hemoglobin and albumin with glucose by Abbe refractometer. In addition, absorbance spectrum of water solutions of hemoglobin and albumin with different glucose concentrations has been studied. The experimental results show that the changes of optical properties caused by glycation of proteins can be observed by refractive index and spectral measurements. The refractive index measurements can be potentially applied for evaluation of glycated hemoglobin and glycated albumin amount in blood. (© 2008 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Mass spectrometry for the study of protein glycation in diseaseMASS SPECTROMETRY REVIEWS, Issue 5 2006Toshimitsu Niwa Abstract The structural elucidation of advanced glycation end-product (AGE)-modified proteins and quantitative analysis of free AGEs have been successfully performed, by use of mass spectrometry (MS) in plasma and tissues of patients with AGE-related diseases, such as diabetes mellitus, uremia, cataract, and liver cirrhosis. Matrix-assisted laser desorption/ionization (MALDI)-MS made it possible to directly analyze the AGE-modified proteins such as albumin and IgG. However, because the direct structural analysis of intact AGE-modified proteins is often not easy due to the formation of broad and poorly resolved peaks, peptide mapping after enzymatic hydrolysis was introduced into the analysis of AGE-modified proteins and the site-specific analysis of defined AGEs by MALDI-MS. Liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) has been employed not only for the structural elucidation of enzymatically hydrolyzed AGEs-modified peptides but also for simultaneous quantification of free AGEs in plasma and tissues of patients. Based on many studies that use MS for the analysis of AGEs, there is no doubt as to the important role of protein-linked AGEs in several diseases. © 2006 Wiley-Liss, Inc. [source] Hyperglycemia Stimulates a Sustained Increase in Hydraulic Conductivity In Vivo without Any Change in Reflection CoefficientMICROCIRCULATION, Issue 7 2007RACHEL M. PERRIN ABSTRACT Objective: Increased microvascular permeability contributes to the development of diabetic microvascular complications and diabetic vasculopathy is correlated with blood glucose levels. The mechanisms underlying increased permeability, however, are poorly understood. Methods: The Landis-Michel technique was used to measure water permeability (hydraulic conductivity, Lp) and macromolecular permeability (reflection coefficient, ,) of exchange capillaries in frogs and rats. Results: Dialysed normoglycemic plasma from diabetic patients had no effect on Lp. The same plasma with 20 mM glucose increased hydraulic conductivity from (mean ± SEM × 10,7 cm · s,1· cm H2O,1) 5.73 ± 2.01 to 13.09 ± 2.67 (P < .01). Nondiabetic control plasma did not affect Lp, but addition of 20 mM glucose increased Lp to a similar degree. The effect of glucose alone was examined. Glucose at 20 mM increased Lp, from 2.82 ± 0.61 to 4.71 ± 1.35 × 10, 7 cm · s, 1· cm H2O,1 (P = .002, n = 13). A similar increase was seen in rat mesenteric microvessels, from 1.04 ± 0.40 in control perfusions to 2.18 ± 0.56, P < .05. The microvascular macromolecular reflection coefficient in all the above experiments was unaltered. The use of specific inhibitors indicated that the glucose-induced increased Lp did not appear to be mediated through protein kinase C (PKC), free radical generation, glucose metabolism, or albumin glycation. Conclusions: These data suggest that hyperglycemia induced increased apparent protein permeability may be secondary to a glucose-mediated change in macromolecular convective flux rather than any change in protein permeability per se. The authors speculate that the increased microvascular permeability to water in vivo is mediated by direct interaction of glucose with the endothelial cells (perhaps with the glycocalyx). [source] | |||||||||||||||||||||||||||||||||||||