Diabetic vascular complication is a leading cause of end-stage renal failure, acquired blindness, a variety of neuropathies and accelerated atherosclerosis, which could account for disabilities and high mortality rates in patients with diabetes. Recent large prospective clinical studies have shown that intensive glucose control reduces effectively microvascular complications among patients with diabetes, and insulin resistance and postprandial hyperglycemia seem to be involved in diabetic macrovascular complications. Chronic hyperglycemia is a major initiator of diabetic vascular complications. Indeed, high glucose, via various mechanisms such as increased production of advanced glycation end products, activation of protein kinase C, stimulation of the polyol pathway and enhanced reactive oxygen species generation, regulates vascular inflammation, altered gene expression of growth factors and cytokines, and platelet and macrophage activation, thus playing a central role in the development and progression of diabetic vascular complications. This article summarizes the molecular mechanisms of diabetic vascular complications and the potential therapeutic interventions that may prevent these disorders even in the presence of hyperglycemia, control of which is often difficult with current therapeutic options.

About 246 million people worldwide had diabetes in 2007. The global figure of people with diabetes is projected to increase to 370 million in 2030. As the prevalence of diabetes has risen to epidemic proportions worldwide, diabetic nephropathy has become one of the most challenging health problems. Therapeutic options such as strict blood glucose and blood pressure controls are effective for preventing diabetic nephropathy, but are far from satisfactory, and the number of diabetic patients on end‐stage renal disease is still increasing. Therefore, a novel therapeutic strategy that could halt the progression of diabetic nephropathy should be developed. There is accumulating evidence that advanced glycation end products (AGEs), senescent macroprotein derivatives formed at an accelerated rate under diabetes, play a role in diabetic nephropathy via oxidative stress generation. In this paper, we review the pathophysiological role of AGEs and their receptor (RAGE)‐oxidative stress system in diabetic nephropathy.

Advanced glycation end products (AGE) have been implicated in the pathogenesis of glomerulosclerosis in diabetes. However, their involvement in the development of the early phase of diabetic nephropathy has not been fully elucidated. We investigated the effects of AGE on growth and on vascular endothelial growth factor (VEGF) and monocyte chemoattractant protein-1 (MCP-1) expression in human cultured mesangial cells. We prepared three immunochemically distinct AGE by incubating bovine serum albumin (BSA) with glucose, glyceraldehyde, or glycolaldehyde. When human mesangial cells were cultured with various types of AGE-BSA, viable cell numbers as well as DNA syntheses were significantly decreased. All of the AGE-BSA were found to significantly increase p53 and Bax protein accumulations and subsequently induce apoptotic cell death in mesangial cells. An antioxidant, N-acetylcysteine, significantly prevented the AGE-induced apoptotic cell death in mesangial cells. Human mesangial cells stimulated prostacyclin production by co-cultured glomerular endothelial cells. Furthermore, various types of AGE-BSA were found to up-regulate the levels of mRNAs for VEGF and stimulate the secretion of VEGF and MCP-1 proteins in mesangial cells. The results suggest that AGE disturbed glomerular homeostasis by inducing apoptotic cell death in mesangial cells and elicited hyperfiltration and microalbuminuria by stimulating the secretion of VEGF and MCP-1 proteins, thereby being involved in the pathogenesis of the early phase of diabetic nephropathy.

We previously have found that advanced glycation end products (AGE), senescent macroproteins formed at an accelerated rate in diabetes, arise in vivo not only from glucose but also from reducing sugars. Furthermore, we recently have shown that glyceraldehyde‐ and glycolaldehyde‐derived AGE (glycer‐ and glycol‐AGE) are mainly involved in loss of pericytes, the earliest histopathological hallmark of diabetic retinopathy. However, the effects of these AGE proteins on angiogenesis, another vascular derangement in diabetic retinopathy, remain to be elucidated. In this study, we investigated whether these AGE proteins elicit changes in cultured endothelial cells that are associated with angiogenesis. When human skin microvascular endothelial cells (EC) were cultured with glycer‐AGE or glycol‐AGE, growth and tube formation of EC, the key steps of angiogenesis, were significantly stimulated. The AGE‐induced growth stimulation was significantly enhanced in AGE receptor (RAGE)‐overexpressed EC. Furthermore, AGE increased transcriptional activity of nuclear factor‐κB (NF‐κB) and activator protein‐1 (AP‐1) and then up‐regulated mRNA levels of vascular endothelial growth factor (VEGF) and angiopoietin‐2 (Ang‐2) in EC. Cerivastatin, a hydroxymethylglutaryl CoA reductase inhibitor; pyrrolidinedithiocarbamate; or curcumin was found to completely prevent the AGE‐induced increase in NF–κB and AP‐1 activity, VEGF mRNA up‐regulation, and the resultant increase in DNA synthesis in microvascular EC. These results suggest that the AGE‐RAGE interaction elicited angiogenesis through the transcriptional activation of the VEGF gene via NF‐κB and AP‐1 factors. By blocking AGE‐RAGE signaling pathways, cerivastatin might be a promising remedy for treating patients with proliferative diabetic retinopathy.