AGE-RAGE系统及氧化应激与糖尿病肾病

糖尿病肾病是糖尿病病人发病率及死亡率高的最主要原因之一,糖尿病肾病形成及发展的两大主要机制是:晚期糖基化及氧化应激.晚期糖基化受体(RAGE)与AGEs作用可激活多种信号转导级联及下传通路,其中包括活性氧族(ROS)的产生.当活性氧族产物与抗氧化剂作用失衡时就产生了氧化应激.氧化应激可通过多种途径促进糖尿病肾病的发生及发展.     

Glucose,glycation, and RAGE: implications for amplification of cellular dysfunction in diabetic nephropathy

Receptor for advanced glycation endproducts (RAGE) is a multi-ligand member of the immunoglobulin superfamily of cell surface molecules. Driven by rapid accumulation and expression of key ligands such as advanced glycation endproducts (AGE) and S100/calgranulins in diabetic tissues, upregulation and activation of RAGE magnifies cellular perturbation in tissues affected by hyperglycemia, such as the large blood vessels and the kidney. In the diabetic glomerulus, RAGE is expressed principally by glomerular visceral epithelial cells (podocytes). Blockade of RAGE in the hyperglycemic db/db mouse suppresses functional and structural alterations in the kidney, in the absence of alterations in blood glucose. Recent studies in homozygous RAGE null mice support a key role for RAGE in glomerular perturbation in diabetes. Importantly, beyond diabetes, studies in other settings of glomerulopathies support a critical RAGE-dependent pathway in podocytes linked to albuminuria, mesangial expansion, and glomerular sclerosis. A new paradigm is proposed in glomerular injury, and it is suggested that blockade of the RAGE axis may provide a novel means to prevent irreparable glomerular injury in diabetes and other sclerosing glomerulopathies.     

RAGE control of diabetic nephropathy in a mouse model: effects of RAGE gene disruption and administration of low-molecular weight heparin

Diabetic nephropathy is a major microvascular complication in long-standing diabetic patients who eventually undergo renal dialysis or transplantation. To prevent development of this disease and to improve advanced kidney injury, effective therapies directed toward the key molecular target are required. In this study, we examined whether inhibition of the receptor for advanced glycation end products (RAGE) could attenuate changes in the diabetic kidney. Here, we show that inactivation of the RAGE gene in a mouse model of diabetic nephropathy results in significant suppression of kidney changes, including kidney enlargement, increased glomerular cell number, mesangial expansion, advanced glomerulosclerosis, increased albuminuria, and increased serum creatinine compared with wild-type diabetic mice. The degree of kidney injury was proportional to RAGE gene dosage. Furthermore, we show that low-molecular weight heparin (LMWH) can bind RAGE at a mean equilibrium dissociation constant (K(d)) value of approximately 17 nmol/l and act as an antagonist to RAGE. LMWH treatment of mice significantly prevented albuminuria and increased glomerular cell number, mesangial expansion, and glomerulosclerosis in a dose-dependent manner; it also significantly improved the indexes of advanced-stage diabetic nephropathy. This study provides insight into the pathological role of RAGE in both early- and advanced-phase diabetic nephropathy and suggests that RAGE antagonists will be a useful remedy in the treatment of diabetic nephropathy.     

Gremlins, glomeruli and diabetic nephropathy

There have been major advances in our understanding of the pathogenetic mechanisms of diabetic nephropathy in recent years. Of particular interest is the emerging paradigm of the role that developmentally important genes may play in this process, representing recapitulation of the ontogenic process. This review examines the potential pathophysiological involvement of one such developmental gene gremlin in diabetic nephropathy.     

Retinopathy, hematuria, and diabetic nephropathy

We have retrospectively analyzed the incidence of diabetic nephropathy in 21 diabetic patients who underwent renal biopsy between 1985 and 1995 for microscopic hematuria and/or proteinuria >2.5 g/day without retinopathy. Diabetic nephropathy was observed in 13 of 21 patients (62%). 50% of our patients with diabetic nephropathy had hematuria, the incidence being higher in type I as compared with type II diabetic patients (30 vs. 20%). Diabetic nephropathy without retinopathy but with hematuria was noted in 5 of 13 patients, and diabetic nephropathy without retinopathy and hematuria was also noted in 5 of 13 patients. We suggest from our retrospective analysis that renal-retinal diabetic syndrome really exists.     

Specifics of diabetic nephropathy, viewpoint in diabetology: trends of diabetic nephropathy in diabetes

The evolution of diabetic nephropathy has been studied by Peter Rossing on a cohort of diabetic patients followed at the Steno hospital of Copenhagen during more than 20 years. In the diabetics of type 1, existence of albuminuria at the upper threshold of the normal range, male gender, high blood pressure and poor glycemic control with a very high HbAlc are the main predictive factors of nephropathy evolution. In this population, nephropathy clearly increases the risks of mortality and cardiovascular morbidity. However, the comparison with older studies showed that better control of glycemia, blood pressure and cholesterol, reduction of tobacco consumption and improvement of proteinuria due to antihypertensive treatments, were able to sharply decrease mortality and cardiovascular morbidity with a relative risk reduction of 60%. In type 2 diabetics, besides factors observed in type 1 diabetic patients, the presence of anemia is a predictive criterion of nephropathy progression. In these patients, prevention keys lie not only in the control of glycemia and blood pressure as in type 1 diabetics, but also in that of anemia.     

Blocking RAGE improves wound healing in diabetic pigs

Receptor for Advanced Glycated End-products (RAGE) is highly expressed in diabetes and impairs wound healing. We proposed that administering an antibody that blocks RAGE will hasten the healing of dorsal wounds in diabetic pigs compared with a non-immune IgG. Two purpose-bred diabetic (D) Yucatan minipigs (Sinclair, Auxvasse MO) each underwent 12 2 × 2 cm full thickness dorsal wounds: four wounds received decellularized porcine skin patches (Xylyx Bio, Bklyn NY): four anti-RAGE Ab (CR-3) infused patches, four saline infused patches and four wounds were left open. One pig received anti-RAGE Ab (CR-3) 1 mg/kg IM q 10 days and other received non-immune IgG. Wounds were measured at 2 and 4 weeks followed by euthanasia and wound harvesting. At 2 weeks few of the patches appeared to be incorporated into the wound. By 4 weeks all patches in pigs treated systemically with CR-3 were detached and the wounds almost healed. For all 24 wounds for both pigs regardless of presence of patch or type of patch, the average IgG treated pig wound size at 4 weeks was 69.2 ± 14.6% of initial size and the average CR-3 treated pig wound size was 40.9 ± 11.3% of initial size (P = 0.0002). Quantitative immunohistology showed greater staining for collagen in the CR-3 treated wounds compared with IgG treated. Staining was positive for RAGE, Mac, and IL-6 in the IgG treated wounds and negative in the CR-3 treated wounds. From these pilot experiments, we conclude that a RAGE blocking antibody given parenterally improved wound healing in a diabetic pig while patches were not effective.     

Association between the RAGE gene -374T/A, -429T/C polymorphisms and diabetic nephropathy: a meta-analysis

Abstract

Aim: The investigations into the association between the receptor for advanced glycation end products (RAGE) gene -374T/A, -429T/C polymorphisms and diabetic nephropathy (DN) in several case–control studies have rendered conflicting results. To shed light on these inconclusive findings, a meta-analysis of all the eligible studies relating these two polymorphisms to the risk of DN was conducted. Methods: The databases were searched for relevant articles up to July 2014. A pooled estimate of the genetic association, the heterogeneity between studies, and the publication bias were investigated. Results: Eight studies with 1725 cases and 1857 controls were enrolled in -374T/A polymorphism analysis. The main analysis indicated no association for the allele contrast, the recessive model and the dominant model. Subgroup analyses in Caucasians and in type 2 diabetes also showed no association between -374T/A polymorphism and DN. Five studies with 1019 cases and 792 controls were enrolled in -429T/C polymorphism analysis. The main analysis revealed heterogeneity and no association for the allele contrast and the dominant model. However, the recessive model for -429C allele diminished the heterogeneity and showed a marginal association overall [fixed-effects OR?=?2.83 (1.33–6.00) and random effects OR?=?2.50 (1.00–6.24), respectively]. Conclusions: Our meta-analysis indicated that the RAGE gene -429CC genotype might be a risk factor for DN in patients with type 2 diabetes.     

不规则趋化因子与糖尿病肾病

不规则趋化因子(Fractalkine.Fkn)是趋化因子家族CX3C的一种新型趋化因子,具有CX3C基序、跨膜区、黏液样结构域的特殊结构,它可趋化并激活肾脏中单核/巨噬细胞,导致细胞外基质大量堆积,在糖尿病肾病的发生、发展中起着重要作用.     

Proteomics and diabetic nephropathy

Proteomic methods have found broad applications in kidney disease research and more specifically in diabetic nephropathy (DN) research. Proteomic methods such as 2-dimensional gel electrophoresis have been used to gain insight into glomerular and tubular nephropathies including DN. At the protein level, differences in high-abundant proteins in DN have been shown to reflect primarily differentially posttranslationally modified plasma proteins. Higher-sensitivity proteomic methods (eg, liquid chromatography-mass spectrometry) have pushed the boundaries on the known urinary proteome to include more than 1,500 proteins. These same high-sensitivity methods have been applied toward profiling urinary peptides, which has resulted in methods to diagnostically screen urine to differentiate between type-2 diabetes mellitus and type-1 diabetes mellitus urine, normal versus microalbuminuria, or by angiotensin II receptor blocker treatment. Proteomic methods are being used to show response to insulin gene therapy in an animal model or alterations in the renal cortex mitochondrial proteome with the development of the diabetic phenotype. Proteomic methods continue to aid in the discovery of new mechanisms of diabetic pathology and understanding of the etiology of diabetic complications.     

Angiogenesis in diabetic nephropathy

Angiogenesis, the formation of new blood vessels from pre-existing vasculature, plays a key role in both physiologic and pathologic events, including wound healing, cancer, and diabetes. Neovascularization has been implicated in the genesis of diverse diabetic complications such as retinopathy, impaired wound healing, neuropathy, and, most recently, diabetic nephropathy. Diabetic nephropathy is one of the major microvascular-associated complications in diabetes and is the leading cause of end-stage renal disease worldwide. In this review we describe the major factors involved in the pathologic glomerular microvascular alterations in response to hyperglycemia and the possible use of anti-angiogenic therapies for the treatment of diabetic nephropathy.     

足细胞和糖尿病肾病

近年来精尿病发病率逐年上升,因而探讨糖尿病肾病治疗新进展具有非常重要的意义.足细胞受损与糖尿病肾病发病机制密切相关,因而近年来足细胞成为糖尿病肾病研究的一个热点和前沿,探讨足细胞在糖尿病肾病中的作用将为糖尿病肾病的治疗提供新的理论依据.     

Combined AGE inhibition and ACEi decreases the progression of established diabetic nephropathy in B6 db/db mice

The accumulation of advanced glycation end products (AGE) is a key factor in diabetic nephropathy (DN). Pyridoxamine inhibits AGE formation and protects against type I DN. Herein we tested: (1) whether C57BL6 db/db mice as a model of established type II DN resembled patients treated with drugs which inhibit angiotensin II action; (2) whether pyridoxamine was effective as a single therapy; and (3) whether pyridoxamine would add to the benefit of angiotensin-converting enzyme inhibition (ACEi) by enalapril. In first set of experiments mice were treated with ACEi (benazepril) and an angiotensin II receptor blocker (valsartan) combination for 16 weeks after the onset of diabetes. In second group, mice with established DN were treated with pyridoxamine for 8 weeks. In a third set, mice with established DN were treated with pyridoxamine and enalapril combination for 16 weeks. Benazepril and valsartan combination partially prevented the development and progression of DN. Pyridoxamine treatment, as single therapy, decreased the progression of albuminuria and glomerular lesions. The combination of pyridoxamine with enalapril reduced both mortality and the progression of DN. In conclusion, (1) C57 BL6 db/db mice are a model of progressive type II DN; (2) The combination of pyridoxamine with enalapril decreased progression of type 2 DN and overall mortality. Thus, pyridoxamine could be a valuable adjunct to the current treatment of established type II DN.     

RAGE and modulation of ischemic injury in the diabetic myocardium

OBJECTIVE—Subjects with diabetes experience an increased risk of myocardial infarction and cardiac failure compared with nondiabetic age-matched individuals. The receptor for advanced glycation end products (RAGE) is upregulated in diabetic tissues. In this study, we tested the hypothesis that RAGE affected ischemia/reperfusion (I/R) injury in the diabetic myocardium. In diabetic rat hearts, expression of RAGE and its ligands was enhanced and localized particularly to both endothelial cells and mononuclear phagocytes.RESEARCH DESIGN AND METHODS—To specifically dissect the impact of RAGE, homozygous RAGE-null mice and transgenic (Tg) mice expressing cytoplasmic domain-deleted RAGE (DN RAGE), in which RAGE-dependent signal transduction was deficient in endothelial cells or mononuclear phagocytes, were rendered diabetic with streptozotocin. Isolated perfused hearts were subjected to I/R.RESULTS—Diabetic RAGE-null mice were significantly protected from the adverse impact of I/R injury in the heart, as indicated by decreased release of LDH and lower glycoxidation products carboxymethyl-lysine (CML) and pentosidine, improved functional recovery, and increased ATP. In diabetic Tg mice expressing DN RAGE in endothelial cells or mononuclear phagocytes, markers of ischemic injury and CML were significantly reduced, and levels of ATP were increased in heart tissue compared with littermate diabetic controls. Furthermore, key markers of apoptosis, caspase-3 activity and cytochrome c release, were reduced in the hearts of diabetic RAGE-modified mice compared with wild-type diabetic littermates in I/R.CONCLUSIONS—These findings demonstrate novel and key roles for RAGE in I/R injury in the diabetic heart.Cardiac complications remain a leading cause of morbidity and mortality in subjects with diabetes (1–3). Although many factors contribute to depressed cardiac function in diabetes, innate disturbances within the diabetic heart contribute importantly to progressive dysfunction, which often leads to irreversible failure and death (3). Alterations in substrate metabolism and increased levels of oxygen free radicals have been observed in diabetic tissues. Inflammatory cytokines may exert direct negative inotropic effects on cardiac myocytes and contribute to aberrant remodeling in the failed heart (4–8). The pathophysiology of diabetes-associated cardiac complications is complex and involves a host of factors linked to metabolic and immune/inflammatory cell activation.The accumulation of late-stage glycoxidation adducts of proteins, termed advanced glycation end products (AGEs), occurs in diabetic tissues. AGEs modify long-lived molecules in the blood vessel wall and structural tissues of the heart considerably earlier than symptomatic cardiac dysfunction occurs (9). A major way in which AGEs exert their cellular effects is by ligation of the multiligand receptor for AGE (RAGE) (10–13).We tested the role of RAGE in rodent models of type 1 diabetes, and we show that pharmacological blockade of ligand-RAGE interaction or genetic modulation of RAGE suppresses ischemia/reperfusion (I/R) injury in the isolated perfused heart, at least in part secondary to critical contributions evoked from RAGE-expressing endothelial cells and mononuclear phagocytes in the diabetic heart.