Nifedipine inhibits gene expression of receptor for advanced glycation end products (RAGE) in endothelial cells by suppressing reactive oxygen species generation

Advanced glycation end products (AGEs), the senescent macroprotein derivatives that form in increased amounts in diabetes, have been implicated in the pathogenesis of diabetic vascular complications. Indeed, AGEs elicit oxidative stress generation in vascular wall cells through an interaction with their receptor (RAGE), thus playing an important role in vascular inflammation and altered gene expression of growth factors and cytokines. We have previously shown that nifedipine, one of the most popular dihydropyridine-based calcium antagonists, blocked tumor necrosis factor-alpha-induced monocyte chemoattractant protein-1 expression in endothelial cells (ECs) through its antioxidative properties. However, the effects of nifedipine on AGE-exposed ECs remain to be elucidated. In this study we investigated whether nifedipine could inhibit the AGE-induced reactive oxygen species (ROS) generation and subsequent RAGE gene expression in human umbilical vein endothelial cells (HUVEC). Nifedipine completely inhibited AGE-induced ROS generation in HUVEC. Furthermore, nifedipine was found to prevent up-regulation of RAGE mRNA levels in AGE-exposed HUVEC. These results demonstrate that nifedipine can inhibit RAGE overexpression in AGE-exposed ECs by suppressing ROS generation. Our present study suggests that nifedipine may have therapeutic potential in the treatment of patients with AGE-related disorders such as diabetic vascular complications.     

Advanced glycation end products (AGEs) and their receptor (RAGE) system in diabetic retinopathy

Vascular complications are a leading cause of blindness, end-stage renal failure, a variety of neuropathies and accelerated atherosclerosis, which could account for disabilities and high mortality rates in patients with diabetes. There is a growing body of evidence that formation and accumulation of advanced glycation end products (AGEs) progress during normal aging, and at an extremely accelerated rate in diabetes, thus being involved in the pathogenesis of diabetic vascular complications. Furthermore, the interaction by AGEs of their receptor, RAGE, activates down-stream signaling and evokes inflammatory responses in vascular wall cells. Therefore, inhibition of AGE formation or blockade of the RAGE signaling may be a promising target for therapeutic intervention to prevent diabetic vascular complications. This review discusses the molecular mechanisms of diabetic retinopathy, especially focusing on the AGE-RAGE system. Several types of inhibitors of the AGE-RAGE system and their therapeutic implications are also reviewed here.     

Advanced glycation end product (age) inhibitors and their therapeutic implications in diseases

Nonenzymatic modification of proteins by reducing sugars, a process that is also known as the Maillard reaction, leads to the formation of advanced glycation end products (AGEs) in vivo. There is a growing body of evidence that formation and accumulation of AGEs progress during normal aging, and at an extremely accelerated rate under diabetes, and are thus involved in the pathogenesis of various diseases such as diabetic vascular complications and neurodegenerative diseases. Therefore, inhibition of AGE formation may be a promising target for therapeutic intervention in AGE-related disorders. In this review, we discuss several types of AGE inhibitors and their therapeutic implications in diseases.     

Agents that block advanced glycation end product (AGE)-RAGE (receptor for AGEs)-oxidative stress system: a novel therapeutic strategy for diabetic vascular complications

Background: Diabetic vascular complications are leading causes of acquired blindness, end-stage renal failure, a variety of neuropathies, and accelerated atherosclerosis, which together could account for disabilities and high mortality rates in patients with diabetes. Since there is accumulating evidence that the advanced glycation end product (AGE)–RAGE (receptor for AGEs)–oxidative stress axis is involved in diabetic vascular complications, inhibition of the AGE–RAGE system may be a promising target for therapeutic intervention in these devastating disorders. Objective: In this review, we discuss several types of agent that may be able to inhibit the AGE–RAGE–oxidative stress system, and their therapeutic implications in vascular complications in diabetes. Methods: We have analyzed currently available scientific literature in the field of AGE–RAGE to create a comprehensive review on novel therapeutic agents for vascular complications in diabetes. Results/conclusion: Inhibition of AGE formation, blockade of the AGE–RAGE interaction, and suppression of RAGE expression or its downstream pathways may be novel therapeutic strategies for the treatment of vascular complications in diabetes.     

The role of AGEs in cardiovascular disease

Advanced glycation end-products (AGEs) are generated in the diabetic milieu, as a result of chronic hyperglycemia and enhanced oxidative stress. These AGEs, via direct and receptor dependent pathways promote the development and progression of cardiovascular disease. AGEs accumulate at many sites of the body including the heart and large blood vessels in diabetes. These modified proteins interact with receptors such as RAGE to induce oxidative stress, increase inflammation by promoting NFkappaB activation and enhance extracellular matrix accumulation. These biological effects translate to accelerated plaque formation in diabetes as well as increased cardiac fibrosis with consequent effects on cardiac function. Strategies to reduce the ligation of AGEs to their receptors such as agents which reduce AGE accumulation, soluble RAGE which acts as a competitive antagonist to the binding of AGEs to RAGE and genetic deletions of RAGE appear to attenuate diabetes associated atherosclerosis. Benefits on cardiac dysfunction with these inhibitors of the AGE/RAGE axis are not as well characterised. In conclusion, therapeutic strategies targeting AGEs appear to have significant clinical potential, often in combination with currently used agents such as inhibitors of the renin-angiotensin system, to reduce the major burden of diabetes, its associated cardiovascular complications.     

Selective inhibition by grape seed proanthocyanidin extracts of cell adhesion molecule expression induced by advanced glycation end products in endothelial cells

The interaction of advanced glycation end products (AGE) with their cell surface receptors for AGEs (RAGE) has been causally implicated in the pathogenesis of diabetic vascular complications and has been shown to stimulate cell adhesion molecule expression in endothelial cells via induction of reactive oxygen species (ROS). Alternatively, grape seed proanthocyanidin extracts (GSPE), which are naturally occurring polyphenolic compounds, have been reported to possess potent radical scavenging and antioxidant properties and to display significant cardiovascular protective action. In this study, we investigated whether GSPE could inhibit AGE-induced cell adhesion molecule expression through interference with ROS generations in human umbilical vein endothelial cells. AGE-modified bovine serum albumin (AGE-BSA) was prepared by incubating BSA with a high concentration of glucose. Stimulation of cultured human umbilical vein endothelial cells with 200 microg/mL of AGE-BSA significantly enhanced intracellular ROS formation and subsequently upregulated the expression of vascular cell adhesion molecule-1 (VCAM) and intercellular adhesion molecule-1 (ICAM-1), whereas both unmodified BSA and GSPE alone were without effect. However, preincubation of different concentrations of GSPE markedly downregulated AGE-BSA-induced VCAM-1 expression at the surface protein and mRNA level in a concentration-dependent manner, but the increased ICAM-1 expression was not affected by GSPE treatment. Meanwhile, the inhibition by GSPE of intracellular ROS generation was also observed at defined time periods. These results demonstrate that GSPE can inhibit the enhanced VCAM-1 expression but not ICAM-1 in AGE-exposed endothelial cells by suppressing ROS generation. Hence, GSPE may have therapeutic potential in the prevention and treatment of vascular complications in patients with diabetes.     

Possible participation of advanced glycation endproducts and their receptor system in the development of diabetic vascular complications

Diabetes causes vascular injuries in various organs and tissues, among which the lesions in retina and kidney are called retinopathy and nephropathy, respectively. As the number of diabetic patients is increasing in Japan, the population with the vascular complications is also elevating. For preventing diabetic complications, it is necessary to develop new drugs that target for key molecules in the development of this disease and useful animal models for the evaluation of their therapeutic potentials. We have focused on the non-enzymatic glycation reaction under prolonged hyperglycemia, which results in the formation and accumulation of advanced glycation endproducts (AGE). The interaction of AGE with the receptor for AGE (RAGE) has been implicated in the development of the vascular complications. AGE elicited vascular cell changes typical of diabetes, including angiogenic and thrombogenic responses of endothelial cells (EC), and a decrease in pericytes, the hallmarks of diabetic retinopathy. Our recent in vivo study revealed that transgenic mice overexpressing human RAGE in vascular EC developed advanced nephropathy when they were made diabetic. This mouse is thus regarded as a useful animal model of diabetic vascular disease. These results suggest that the AGE-RAGE system plays an active role in the development of diabetic vasculopathy and is a promising target in the prophylaxis and therapy of this disease. Recently, we identified three RAGE variants: novel C-terminally and N-terminally truncated forms and the known full-length form. The C-terminally truncated variant was found to be a soluble form and actually detected in human sera, and it was found to have neutralizing activities against AGE-induced EC injury. The endogenous soluble decoy against the AGE-RAGE system may contribute to the individual resistance to the development of diabetic vascular complications. The stimulation of secretion of this protein can be a new means for the prevention of chronic vascular disease in diabetes.     

Advanced glycation endproduct crosslinking in the cardiovascular system: potential therapeutic target for cardiovascular disease

Advanced glycation endproducts (AGEs) are formed by a reaction between reducing sugars and biological amines. Because of their marked stability, glycated proteins accumulate slowly over a person's lifespan, and can contribute to age-associated structural and physiological changes in the cardiovascular system such as increased vascular and myocardial stiffness, endothelial dysfunction, altered vascular injury responses and atherosclerotic plaque formation. The mechanisms by which AGEs affect the cardiovascular system include collagen crosslinking, alteration of low-density lipoprotein molecules and impairment of cellular nitric oxide signalling through their interaction with AGE receptors (RAGEs). Thus, the accumulation of AGEs may help to explain the increased cardiac risk associated with aging as well as diabetes mellitus and hypertension, two conditions that accelerate and enhance AGE formation. A variety of new pharmacological approaches are being developed to reduce the pathophysiological impact of AGEs. These agents can prevent AGE and AGE crosslink formation, break pre-existing AGE crosslinks, and block the interaction between AGEs and RAGEs. Such agents have been shown to reduce vascular and myocardial stiffness, inhibit atherosclerotic plaque formation and improve endothelial function in animal models. Improvement in vascular compliance has also been demonstrated with AGE crosslink breakers in clinical trials. These studies offer promise to reduce the cardiac risk associated with isolated systolic hypertension, diastolic dysfunction and diabetes.     

The AGE/RAGE axis in diabetes-accelerated atherosclerosis

1. There is increasing evidence that advanced glycation end-products (AGEs) and their interaction with the receptor RAGE play a pivotal role in atherosclerosis, in particular in the setting of diabetes. 2. Previous studies have shown that inhibition of AGE accumulation and RAGE expression in diabetes by either reduction of the formation of AGEs or cross-link breakers was associated with reduced atherosclerosis and renal disease. Advanced glycation end-products bind to RAGE, thereby leading to activation of a range of inflammatory and fibrotic pathways causing tissue injury. Different splice variants of RAGE exist, including a soluble form that lacks the intracellular domain and fails to induce signal transduction. Therapeutic approaches using soluble RAGE as a decoy binding protein for circulating AGE have been effective in preventing externally induced arterial injury and atherosclerosis in the absence and presence of diabetes. 3. In order to delineate the role of RAGE in vascular disease in more detail, it was necessary to create RAGE(-/-) mice, as well as transgenic mice overexpressing RAGE in endothelial cells. It was shown that RAGE overexpression was associated with increased vascular injury, nephropathy and retinopathy. 4. In contrast, RAGE deletion was associated with partial vascular protection, such as reduced neointima formation after arterial denudation, as well as protection from diabetic nephropathy. The present review summarizes the evidence for RAGE being a pro-inflammatory and pro-fibrotic receptor. 5. Further studies are needed to delineate the effect of RAGE deletion and overexpression in diabetic macrovascular disease. Based on these findings, RAGE could be a potential therapeutic target in combating inflammatory vascular diseases, including diabetes-associated atherosclerosis.     

Antibodies to advanced glycation end products in children with diabetes mellitus

The tissue accumulation of advanced glycation end products (AGE) alters the structure and function of long-lived proteins. A number of studies have shown that tissue accumulation of AGE correlates with the severity of diabetic complications. Proteins containing AGE are highly immunogenic and anti-AGE antibodies were found in sera of diabetic rats and human. Considering the potential use of anti-AGE antibodies as a marker of AGE deposition during diabetes, we have investigated, by competitive ELISA, the presence of anti-AGE antibodies in sera of 58 children with Type 1 diabetes mellitus. The patients were studied for the period of 5 years. Positive for anti-AGE antibodies were 19 children with diabetes. Fourteen of them showed initial data for vascular complications. Anti-AGE antibodies were related to age (r = .25, P = .024), duration of diabetes (r = .41, P = .0001), HbA1c (r = .27, P = .016), microalbuminuria (r = .41, P = .0001), retinopathy (r = .35, P = .001), triglycerides (r = .27, P = .016), and total cholesterol (r = .19, P = .05). In conclusion, our study showed that the investigation of the levels and dynamics of anti-AGE antibodies might give the possibility for early diagnosis and prognosis of the severity of diabetic late complications.     

Inhibitory effects of Terminalia chebula extract on glycation and endothelial cell adhesion

Terminalia chebula Retz. has been used in India for a long time to treat many diseases, and its extract was reported to have antidiabetic activity in vivo. In this study, T. chebula methanolic extract (TCE) containing 2.7 % chebulic acid was evaluated for its preventive effects against the formation of advanced glycation end products (AGEs) and endothelial cell dysfunction. When the effects of TCE on AGE formation and on protein crossing-linking by glycation with D-threose and lens crystallines were examined, TCE showed inhibitory activity in a dose-dependent manner, and the concentration of 1000 μg/mL presented an activity similar to that of 5 mM aminoguanidine as a positive control. Upon investigating the protective activity of TCE against AGE-induced vascular endothelium dysfunction, human umbilical vein endothelial cells (HUVEC) incubated with 100 μg/mL of AGEs had significantly enhanced reactive oxygen species (ROS) formation, whereas the treatment of T. chebula reduced AGE-induced ROS generation. The incubation of HUVEC with 100 μg/mL of AGEs caused a considerable increase in THP-1 monocytic cell adhesion, but this adhesion was reduced by the treatment of TCE. These results suggest that TCE is a potential agent for alleviating diabetic complications.     

New potential agents in treating diabetic kidney disease: the fourth act

Despite the worldwide epidemic of chronic kidney disease complicating diabetes mellitus, current therapies directed against nephroprogression are limited to angiotensin conversion or receptor blockade. Nonetheless, additional therapeutic possibilities are slowly emerging. The diversity of therapies currently in development reflects the pathogenic complexity of diabetic nephropathy. The three most important candidate drugs currently in development include a glycosaminoglycan, a protein kinase C (PKC) inhibitor and an inhibitor of advanced glycation. In targeting primary mechanisms by which hyperglycaemia contributes to diabetic complications, these drugs could provide risk reduction complementary to the partial reduction proven for ACE inhibitors and angiotensin II receptor antagonists (angiotensin receptor blockers). Glycosaminoglycans act to restore glycoproteins present in reduced amounts in the glomerular basement membrane and mesangium of diabetic animal models. Components of the drug sulodexide prevent pathological changes and proteinuria in diabetic rats. Reductions in albuminuria, a hallmark of early diabetic kidney disease, have been reported in initial human trials. In the US, a multicentre phase II study has been completed, with an interim analysis indicating reduction in urinary albumin losses. Pivotal phase II trials have begun in patients with type 2 diabetes. A second metabolic pathway of diabetic complications is overexpression of PKC. Several activators of this family of intracellular kinases have been identified and PKC activation may result in tissue damage through a variety of mechanisms. In animal models, the inhibitor ruboxistaurin reduces albuminuria, diabetic histological changes and kidney injury. Like sulodexide, drug development of ruboxistaurin has reached completion of a phase II evaluation with mixed results. The third metabolic target is the nonenzymatic formulation of advanced glycation end-products (AGEs) through well described biochemical pathways. Multiple pathways lead to AGE accumulation in tissues in diabetes and diverse AGE products are formed. AGE deposition has been implicated in animal models of diabetic nephropathy. The leading AGE inhibitor currently in development is pyridoxamine, which has multiple actions that inhibit glycation. Pyridoxamine is an efficient AGE inhibitor in experimental diabetes. A phase II study in diabetic patients with nephropathy reported mixed efficacy results and a favourable safety profile. Phase III evaluation of pyridoxamine has not begun. These three classes of potential therapies, if successfully developed, will confirm that diabetic kidney disease has entered the era of biochemical treatments.     

Kinetics, role and therapeutic implications of endogenous soluble form of receptor for advanced glycation end products (sRAGE) in diabetes

Reducing sugars can react non-enzymatically with amino groups of protein to form Amadori products. These early glycation products undergo further complex reaction such as rearrangement, dehydration, and condensation to become irreversibly cross-linked, heterogeneous fluorescent derivatives, termed advanced glycation end products (AGEs). The formation and accumulation of AGEs have been known to progress at an accelerated rate in diabetes. There is a growing body of evidence that AGEs and their receptor (RAGE) axis is implicated in the pathogenesis of diabetic vascular complications. Indeed, the engagement of RAGE with AGEs is shown to elicit oxidative stress generation and subsequently evoke inflammatory responses in various types of cells, thus playing an important role in the development and progression of diabetic micro- and macroangiopathy. Moreover, administration of a recombinant soluble form of RAGE (sRAGE), has been shown to suppress the development of accelerated atherosclerosis in diabetic apolipoprotein E-null mice. These observations suggest that exogenously administered sRAGE may capture and eliminate circulating AGEs, thus protecting against the AGEs-elicited tissue damage by acting as a decoy receptor. Recently, endogenous sRAGE has been identified in humans. However, there is few comprehensive review about the regulation and role of endogenous sRAGE in diabetes. In the former part of this paper, we review the role of the AGE-RAGE system in the pathogenesis of diabetic vascular complications. Then we summarize in the latter part of this review the kinetics and pathophysiological role of endogenous sRAGE in diabetes. We also discuss the possibility that endogenous sRAGE may be a therapeutic target for the prevention of diabetic vascular complications.     

Beneficial effects of metformin and irbesartan on advanced glycation end products (AGEs)-RAGE-induced proximal tubular cell injury

Advanced glycation end products (AGEs) and their receptor (RAGE) axis contributes to diabetic nephropathy. An oral hypoglycemic agent, metformin may have a potential effect on the inhibition of glycation reactions. Further, since a pathophysiological crosstalk between renin-angiotensin system (RAS) and AGEs-RAGE axis is involved in diabetic nephropathy, it is conceivable that metformin and irbesartan additively could protect against the AGEs-RAGE-induced tubular cell injury. In this study, we addressed the issues. Metformin dose-dependently inhibited the formation of AGEs modification of bovine serum albumin (BSA). Compared with AGEs-modified BSA prepared without metformin (AGEs-MF0), those prepared in the presence of 30 mM or 100 mM metformin (AGEs-MF30 or AGEs-MF100) significantly reduced RAGE mRNA level, reactive oxygen species (ROS) generation, apoptosis, monocyte chemoattractant protein-1 and transforming growth factor-β mRNA level in tubular cells. Irbesartan further inhibited the harmful effects of AGEs-MF0 or AGEs-MF30 on tubular cells. Our present study suggests that combination therapy with metformin and irbesartan may have therapeutic potential in diabetic nephropathy; it could play a protective role against tubular injury in diabetes not only by inhibiting AGEs formation, but also by attenuating the deleterious effects of AGEs via down-regulating RAGE expression and subsequently suppressing ROS generation.     

Advanced glycation endproducts and diabetes. Beyond vascular complications

Advanced Glycation Endproducts (AGEs) are a group of heterogeneous compounds formed by the non enzymatic reactions between aldehydic group of reducing sugars with proteins, lipids or nucleic acids. Formation and accumulation of AGEs is related with the aging process and is accelerated in diabetes. Type 2 diabetes, the most common form of diabetes, is characterized by hyperglycaemia and insulin resistance associated to a progressive deterioration of beta cell function and mass. The pathogenic role of AGEs in vascular diabetic complications is widely recognised. Recently other aspects of the detrimental effects of AGEs in type 2 diabetes are emerged: AGEs interfere with the complex molecular pathway of insulin signaling, leading to insulin resistance; AGEs modify the insulin molecule, and, consequently, its function; AGEs decrease insulin secretion and insulin content. In this article we review the role of AGEs in type 2 diabetes, beyond their involvement in vascular complications.     

Crocetin prevents AGEs-induced vascular endothelial cell apoptosis.

Advanced glycation end products (AGEs) are causally correlated with diabetic vascular complications. AGEs triggered oxidative reaction then accelerated endothelial cell apoptosis is a critical event in the process of vascular complications. Crocetin, a carotenoid has been previously shown to have strong antioxidant activates. Therefore, this study was designed to investigate the role of crocetin on the prevention of AGEs-mediated cell apoptosis in bovine aortic endothelial cells (BEC) and the mechanisms involved. Exposure of BEC to 200 microg/ml AGEs for 48 h results in a significant increase in apoptotic rate, compared with control. AGEs-induced DNA fragmentation preferentially occurred in the S phase cells. Crocetin prevented AGEs-induced BEC apoptosis, which correlates with crocetin attenuation of AGEs mediated increase of intracellular reactive oxygen species (ROS) formation and elevation of intracellular Ca2+ concentration ([Ca2+]i) level (P<0.01 versus AGEs group). These results demonstrate that crocetin prevents AGEs-induced BEC apoptosis through ROS inhibition and [Ca2+]i stabilization and suggest that crocetin may exert a beneficial effect in preventing diabetes-associated vascular complications.     

Role of advanced glycation end products (AGEs) and their receptor (RAGE) in the pathogenesis of diabetic microangiopathy

Diabetic vascular complication is a leading cause of acquired blindness, end-stage renal failure, a variety of neuropathies and accelerated atherosclerosis, which could account for disabilities and high mortality rates in patients with diabetes. Chronic hyperglycemia is essentially involved in the pathogenesis of diabetic micro- and macrovascular complications via various metabolic derangements. In this review, we discuss the molecular mechanisms of diabetic retinopathy and nephropathy, especially focusing on advanced glycation end products (AGEs) and their receptor (RAGE) system. Several types of AGE inhibitors and their therapeutic implications in diseases, including diabetic microangiopathy, will be discussed in the next review article.     

Methylglyoxal promotes oxidative stress and endothelial dysfunction

Modern diets can cause modern diseases. Research has linked a metabolite of sugar, methylglyoxal (MG), to the development of diabetic complications, but the exact mechanism has not been fully elucidated. The present study was designed to investigate whether MG could directly influence endothelial function, oxidative stress and inflammation in Wistar and Goto-Kakizaki (GK) rats, an animal model of type 2 diabetes. Wistar and GK rats treated with MG in the drinking water for 3 months were compared with the respective control rats. The effects of MG were investigated on NO-dependent vasorelaxation in isolated rat aortic arteries from the different groups. Insulin resistance, NO bioavailability, glycation, a pro-inflammatory biomarker monocyte chemoattractant protein-1 (MCP-1) and vascular oxidative stress were also evaluated. Methylglyoxal treated Wistar rats significantly reduced the efficacy of NO-dependent vasorelaxation (p<0.001). This impairment was accompanied by a three fold increase in the oxidative stress marker nitrotyrosine. Advanced glycation endproducts (AGEs) formation was significantly increased as well as MCP-1 and the expression of the receptor for AGEs (RAGE). NO bioavailability was significantly attenuated and accompanied by an increase in superoxide anion immunofluorescence. Methylglyoxal treated GK rats significantly aggravated endothelial dysfunction, oxidative stress, AGEs accumulation and diminished NO bioavailability when compared with control GK rats. These results indicate that methylglyoxal induced endothelial dysfunction in normal Wistar rats and aggravated the endothelial dysfunction present in GK rats. The mechanism is at least in part by increasing oxidative stress and/or AGEs formation with a concomitant increment of inflammation and a decrement in NO bioavailability. The present study provides further evidence for methylglyoxal as one of the causative factors in the pathogenesis of atherosclerosis and development of macrovascular diabetic complication.     

The AGE of the matrix: chemistry, consequence and cure

Accumulation of advanced glycation endproducts (AGEs) plays a crucial part in the development of age-related diseases and diabetic complications. AGEs are formed in vivo via the so-called Maillard reaction: a reducing sugar reacts with a protein to form a labile Amadori product that is subsequently stabilized, producing an irreversible, non-enzymatic post-translational modification of the protein involved. Recently, it has become clear that, in addition to sugars, lipids play an important role in the initiation of AGE formation, and that genetic factors contribute to an individual's AGE levels. The highest AGE levels are found in tissues with slow turnover, such as tendon, skin, bone, amyloid plaques and cartilage. AGEs exert their effects by adversely affecting the mechanical properties of the matrix and by modulating tissue turnover. In cartilage, these detrimental effects result in tissue that is more prone to the development of osteoarthritis. As such, the accumulation of AGEs provides the first molecular mechanism explaining the age-related increase in the incidence of osteoarthritis. Ongoing research into anti-AGE-ing therapies, such as pyrodoxamine and thiazolium compounds, which are often developed to prevent AGE-induced diabetic complications, might also prove beneficial for the prevention of osteoarthritis.     

Regulation of advanced glycation end product (AGE)-receptor (RAGE) system by PPAR-gamma agonists and its implication in cardiovascular disease

Non-enzymatic modification of proteins by reducing sugars leads to the formation of advanced glycation end products (AGEs), whose process has been reported to progress under physiological aging, oxidative stress or diabetic conditions. There is a growing body of evidence that AGEs and their receptor (RAGE) axis is involved in the pathogenesis of cardiovascular disease (CVD). Indeed, engagement of RAGE with AGEs is shown to elicit oxidative stress generation and subsequently evoke inflammatory and thrombogenic responses in various types of cells, including endothelial cells, smooth muscle cells, macrophages and renal cells, thus playing an important role in the development and progression of vascular injury in both diabetes and non-diabetes. These observations suggest that the inhibition of AGE formation, down-regulation of RAGE expression or blockade of the RAGE downstream signaling may be a promising therapeutic target for preventing CVD. Recently, peroxisome proliferator-activated receptor-γ (PPARγ) is involved in not only adipocyte differentiation, but also vascular homeostasis. Therefore, in this study, we review effects of PPARγ agonists on the AGE–RAGE system and their implication in CVD.