糖尿病糖脂代谢紊乱与足细胞损害的实验研究

目的　观察糖脂代谢紊乱对糖尿病大鼠肾小球滤过屏障外层足细胞的影响 ,以探讨糖尿病肾病的发病机制。方法　采用链脲佐菌素诱导糖尿病大鼠模型 ,喂养 5周后 ,测定血糖、糖化血红蛋白、甘油三酯、总胆固醇、血肌酐、尿素氮和尿白蛋白排泄率 ,应用免疫组化检测肾小球足细胞损伤标志蛋白 -desmin的表达 ,同时利用透射电子显微镜观察肾小球足细胞超微结构。结果　糖尿病大鼠血糖、糖化血红蛋白、总胆固醇、血肌酐、尿素氮、尿白蛋白排泄率水平明显升高 (P <0 .0 5 ) ,肾小球内desmin蛋白表达上调 ,足细胞部分足突融合 ;同时 ,两组间血甘油三酯水平无显著性差异 (P >0 .0 5 )。结论　糖脂代谢紊乱可导致糖尿病大鼠肾小球滤过屏障外层足细胞明显损害 ,尿白蛋白排泄率增加 ,这可能是糖尿病肾脏损害、蛋白尿出现的机制之一     

足突细胞特异性过表达金属硫蛋白可减轻肾小球滤过屏障及肾小球组织结构相关的糖尿病并发症

前期研究表明,OVE26（OVE）转基因小鼠的肾小球血尿屏障的细胞内外结构对损伤十分敏感,并且该动物模型可反映尿白蛋白排泄率（UAE）,对研究人类糖尿病肾病具有重要价值。本研究旨在证实氧化应激对足突细胞的影响导致了OVE小鼠肾小球滤过屏障的损伤。     

足细胞与蛋白尿发病机制的研究进展

蛋白尿是肾脏疾病最常见的表现之一,其发生与肾小球滤过屏障的异常有密切关系。肾小球滤过屏障由毛细血管内皮细胞、肾小球基底膜(GBM)及脏层上皮细胞即足细胞组成。肾小球滤过膜具有电荷屏障和孔径屏障功能,任一屏障损伤均会产生蛋白尿。足细胞位于GBM最外侧,是避免机体蛋白丢     

足细胞损伤与糖尿病肾病

糖尿病肾病(diabetic nephropathy,DN)是糖尿病的主要并发症。1936年Kimmelstiel等[1]第一次描述DN时,系膜基质增多和肾小球基底膜(glomerular basement mem-brane,GBM)增厚就被描述为DN的主要病理表现。研究也证实,系膜增生与蛋白尿、肾功能恶化密切相关。但是,系膜增生并不能解释蛋白尿的发生,因为由肾小球内皮细胞、GBM、足细胞构成的肾小球滤过屏障的损伤才是蛋白尿的根源。事实上,肾小球内皮细胞和GBM参与了DN蛋白尿的发生,但两者均是有孔的,均允许某些蛋白通过[2]。因此,足细胞构成了蛋白滤过的最后一道屏障,但其在DN中的生物…     

足细胞和糖尿病及其肾病

肾小球足细胞损伤和丢失是肾小球硬化形成和发展的关键因素。糖尿病时足细胞可出现密度和数量减少、足突增宽、足细胞脱落等改变,且可从尿中丢失,继而导致糖尿病肾病的发生。高血糖、高血压、氧化应激及一氧化氮等可直接损伤足细胞,并抑制α3β1整合素、nephrin的表达,促进血管内皮生长因子、Ⅳ型胶原、糖基化终末产物受体、转化生长因子β等的表达而加重足细胞损伤。因而,探索足细胞损伤在糖尿病肾病发生、发展中的病理发展过程对糖尿病肾病的防治具有重要意义。     

α3β1整合素与肾小球足细胞脱落的研究进展

肾小球是肾脏滤过单位,其滤过功能与滤过屏障密切相关.肾小球滤过屏障可有效阻止白蛋白等大分子量物质进入尿液,其结构和功能的改变是蛋白尿产生的病理生理基础.肾小球滤过屏障由内而外分为三层:①首先是带窗孔的肾小球内皮细胞;②其次为肾小球基底膜(GBM),这是一高度水化的胶原网,对白蛋白及其他血浆大分子物质兼有分子及电荷屏障作用,GBM含有紧密交联的层黏连蛋白(LN)、Ⅳ型胶原(Ⅳ-collagen)、纤维连接蛋白(FN)和硫酸乙酰肝素蛋白多糖(HSPG),GBM中主要的HSPG是集聚蛋白(agrin),这些HSPG构成GBM的高度阴电荷;③足突(FP)及覆盖于FP裂隙间的裂孔隔膜(SD).足细胞作为肾小球滤过膜的重要组成部分,在维持肾小球正常滤过方面具有至关重要的作用.足细胞从GBM上脱落会导致肾小球滤过屏障的完整性遭到破坏.足细胞通过许多分子锚定于GBM上,如:α3β1整合素、αβ蛋白聚糖复合体(αβdystroglycan complex)、辅肌动蛋白(α-actinin)、组织蛋白酶-L(cathepsin-L)、尿激酶纤维蛋白酶原激活剂受体(UPAR)、磷酸二酯酶抑制剂(B7-1)等[1～5],其中α3β1整合素与足细胞脱落之间的关系最近成为研究热点.本文就α3β1整合素与足细胞脱落的相互关系作一综述.     

足细胞病的治疗:免疫抑制剂,还是足细胞保护

蛋白尿,不仅是临床上肾脏损伤最显著的标志,大量蛋白尿的持续存在,也是导致肾组织损伤进行性加重的重要原因.因此,减少蛋白尿成为肾脏病治疗和对疗效进行判断的重要指标之一. 随着对肾小球滤过屏障结构和功能研究的深入,人们不再将其简单地理解为一个电荷屏障和机械屏障,现在认为肾小球滤过屏障至少由五层结构组成:内皮细胞表面膜结构,内皮细胞及内皮细胞窗孔,肾小球基底膜(GBM),足细胞下间隙和足细胞.     

Podocin与糖尿病肾病

Podocin是新近发现的肾小球裂隙隔膜上的一个蛋白，参与肾小球滤过屏障的形成并维持其正常功能。在糖尿病肾病(DN)患者中存在其编码基因nphs2的异常和podocin蛋白的表达下降。Podocin蛋白表达下降可使nephrin诱导的肾小球足细胞内信号转导功能障碍，肾小球足细胞减少，肾脏裂隙隔膜结构与屏障功能的完整性破坏，肾小球蛋白滤过增加。Podocin在DN的发生、发展中可能起关键作用。对podocin的进一步研究可能对DN的诊治有重要的指导意义。     

足细胞和糖尿病及其肾病

肾小球足细胞损伤和丢失是肾小球硬化形成和发展的关键因素。糖尿病时足细胞可出现密度和数量减少、足突增宽、足细胞脱落等改变，且可从尿中丢失，继而导致糖尿病肾病的发生。高血糖、高血压、氧化应激及一氧化氮等可直接损伤足细胞，并抑制α3β1整合素、nephrin的表达，促进血管内皮生长因子、Ⅳ型胶原、糖基化终末产物受体、转化生长因子β等的表达而加重足细胞损伤。因而，探索足细胞损伤在糖尿病肾病发生、发展中的病理发展过程对糖尿病肾病的防治具有重要意义。     

足细胞损伤及其应答

脏层上皮细胞即足细胞是位于肾小球基膜(GBM)外侧的一种终末期分化细胞 ,其构成了避免机体蛋白丢失的最后一道屏障 ,所以足细胞损伤必然伴随大量蛋白尿。目前研究也认为 ,各种类型的肾病综合征均特征性的表现为足细胞的异常。本文就近期发现的足突细胞损伤应答作一综述。1　足细胞损伤及其原因各种类型损伤包括足细胞膜抗原的抗原抗体反应 (膜性肾病、微小病变 ) ,血流动力学损伤 (肾单位数量减少、糖尿病、代谢性疾病 ) ,基因突变 (nephrin、α actinin、CD2AP) ,大量蛋白尿 ,毒素 (非类固醇类抗炎药、阿霉素 ) ,感染 (HIV)及一些目前…     

What is the mechanism of microalbuminuria in diabetes: a role for the glomerular endothelium?

Microalbuminuria is an important risk factor for cardiovascular disease and progressive renal impairment. This holds true in the general population and particularly in those with diabetes, in whom it is common and marks out those likely to develop macrovascular disease and progressive renal impairment. Understanding the pathophysiological mechanisms through which microalbuminuria occurs holds the key to designing therapies to arrest its development and prevent these later manifestations. Microalbuminuria arises from the increased passage of albumin through the glomerular filtration barrier. This requires ultrastructural changes rather than alterations in glomerular pressure or filtration rate alone. Compromise of selective glomerular permeability can be confirmed in early diabetic nephropathy but does not correlate well with reported glomerular structural changes. The loss of systemic endothelial glycocalyx—a protein-rich surface layer on the endothelium—in diabetes suggests that damage to this layer represents this missing link. The epidemiology of microalbuminuria reveals a close association with systemic endothelial dysfunction and with vascular disease, also implicating glomerular endothelial dysfunction in microalbuminuria. Our understanding of the metabolic and hormonal sequelae of hyperglycaemia is increasing, and we consider these in the context of damage to the glomerular filtration barrier. Reactive oxygen species, inflammatory cytokines and growth factors are key players in this respect. Taken together with the above observations and the presence of generalised endothelial dysfunction, these considerations lead to the conclusion that glomerular endothelial dysfunction, and in particular damage to its glycocalyx, represents the most likely initiating step in diabetic microalbuminuria.     

艾塞那肽对糖尿病肾病小鼠足细胞的保护作用

目的:探讨艾塞那肽对糖尿病肾病小鼠足细胞的作用。方法:通过给予C57BL/6J小鼠高脂饮食并注射链脲佐菌素建立糖尿病肾病模型,按随机数字表法将其分为糖尿病肾病对照组(DN组, n＝8)、艾塞那肽干预组(DN＋Ex组, n＝8)。同时将普通饲料喂养的C57BL/6J小鼠作为正常对照组(NC组, ...     

Podocytes as a target of insulin

Diabetic nephropathy (DN) presents with a gradual breakdown of the glomerular filtration barrier to protein, culminating in widespread glomerular damage and renal failure. The podocyte is the central cell of the glomerular filtration barrier, and possesses unique architectural and signaling properties guided by the expression of key podocyte specific proteins. How these cellular features are damaged by the diabetic milieu is unclear, but what is becoming increasingly clear is that damage to the podocyte is a central event in DN. Here we present accumulating evidence that insulin action itself is important in podocyte biology, and may be deranged in the pathomechanism of early DN. This introduces a rationale for therapeutic intervention to improve podocyte insulin sensitivity early in the presentation of DN.     

High blood pressure is a major factor in progression of diabetic nephropathy

Arterial hypertension is a frequent finding, even early in the course of diabetic nephropathy. Systemic and glomerular hypertension enhance the development of diabetic glomerulopathy and accelerate the rate of decline in glomerular filtration rate in diabetic nephropathy. Conversely, effective antihypertensive treatment reduces albuminuria and diminishes the rate of decline in glomerular filtration rate, thereby postponing end-stage renal failure in diabetic nephropathy.     

Glomerular epithelial foot processes and filtration slits in IDDM patients

Summary Diabetic nephropathy is associated with functional changes in the glomerular filtration barrier but the structural counterpart remains unknown. Width of glomerular epithelial cell foot processes and of filtration slits were determined by morphometric methods in 11 non-diabetic kidney donors and in 28 diabetic patients with albumin excretion rates ranging from normal to proteinuria. Foot process width was estimated from the ratio of tuft surface density to length density of slits. At high magnification independently sampled, perpendicularly cut slits were classified. Foot process width on peripheral basement membrane was increased in microalbuminuric compared to normoalbuminuric diabetic patients (p<0.05) but showed no significant correlation with the level of albumin excretion when patients with increased barrier permeability were considered. Width of filtration slits in normo- and microalbuminuric diabetic patients exceeded that in non-diabetic control subjects (p<0.05). Filtration slits were narrower in patients with overt proteinuria than in patients with microalbuminuria (p<0.05) and correlated with glomerular filtration rate in all of the diabetic patients (r=0.65, p<0.005). The results show that insulin-dependent diabetic patients with nephropathy present changes of epithelial cells and filtration slits, demonstrable already in the stage of microalbuminuria. The mechanism of albumin leakage is not achieved by these measures. The dimension of filtration slits may play a contributing role in the level of glomerular filtration rate in diabetic patients.Abbreviations IDDM Insulin-dependent diabetes mellitus - GFR glomerular filtration rate - AER albumin excretion rate - HbA_1c glycated haemoglobin - ND non-diabetic control subjects - D_NA diabetic patients with normal albumin excretion rate - D_MI diabetic patients with microalbuminuria - D_P diabetic patients with proteinuria - CV coefficient of variation (SD/mean) - FPW_PBM width of foot processes on peripheral basement membrane - FPW_MES width of foot processes on glomerular mesangium - ANOVA analysis of variance - PBM peripheral basement membrane     

Temporal Profile of Diabetic Nephropathy Pathologic Changes

Diabetic nephropathy, by far, is the most common cause of end stage renal disease in the US and many other countries. In type 1 diabetes, the natural history of diabetic nephropathy is tightly linked to evolution of classic lesions of the disease, namely glomerular basement membrane thickening, increased mesangial matrix, and reduced glomerular filtration surface density. These lesions progress in parallel and correlate with increased albumin excretion rate and reduced glomerular filtration rate across a wide range of renal function. In fact, the vast majority of the variances of albumin excretion and glomerular filtration rates can be explained by these glomerular lesions alone in type 1 diabetic patients. Although, classic lesions of diabetic nephropathy, indistinguishable from those of type 1 diabetes, also occur in type 2 diabetes, renal lesions are more heterogeneous in type 2 diabetic patients with some patients developing more advanced vascular or chronic tubulointerstitial lesions than diabetic glomerulopathy. More research biopsy longitudinal studies, especially in type 2 diabetic patients, are needed to better understand various pathways of renal injury in diabetic nephropathy.     

The salt paradox and its possible implications in managing hypertensive diabetic patients

Diabetes mellitus is one of the leading causes of end-stage renal disease. The pathogenesis of diabetic nephropathy is still poorly understood, but glomerular injury has been ascribed, at least in part, to glomerular hyperfiltration, which occurs early in the course of diabetes mellitus. Therefore, a better understanding of the early dysfunctions observed in the diabetic kidney may permit the development of new strategies to prevent diabetic nephropathy. In this review, we discuss the pathophysiology for the paradoxical relationship between dietary salt and glomerular filtration rate observed in early diabetes mellitus and possible implications in managing diabetic patients.     

Cell biology of diabetic nephropathy: Roles of endothelial cells,tubulointerstitial cells and podocytes

Diabetic nephropathy is the major cause of end‐stage renal failure throughout the world in both developed and developing countries. Diabetes affects all cell types of the kidney, including endothelial cells, tubulointerstitial cells, podocytes and mesangial cells. During the past decade, the importance of podocyte injury in the formation and progression of diabetic nephropathy has been established and emphasized. However, recent findings provide additional perspectives on pathogenesis of diabetic nephropathy. Glomerular endothelial damage is already present in the normoalbuminuric stage of the disease when podocyte injury starts. Genetic targeting of mice that cause endothelial injury leads to accelerated diabetic nephropathy. Tubulointerstitial damage, previously considered to be a secondary effect of glomerular protein leakage, was shown to have a primary significance in the progression of diabetic nephropathy. Emerging evidence suggests that the glomerular filtration barrier and tubulointerstitial compartment is a composite, dynamic entity where any injury of one cell type spreads to other cell types, and leads to the dysfunction of the whole apparatus. Accumulation of novel knowledge would provide a better understanding of the pathogenesis of diabetic nephropathy, and might lead to a development of a new therapeutic strategy for the disease.     

Podocyte foot process broadening in experimental diabetic nephropathy: amelioration with renin-angiotensin blockade

Aims/hypothesis. Changes in podocyte number and morphology have been implicated in the pathogenesis of proteinuria and the progression of human and experimental kidney disease. This study sought to examine podocyte foot process and slit pore architecture in experimental diabetic nephropathy and to determine whether such changes were modified with renoprotective intervention by blockade of the renin-angiotensin system. Methods. The number of filtration slits per 100 μm of glomerular basement membrane was assessed by transmission electron microscopy and quantitated histomorphometrically in control animals and in rats with 24 weeks of streptozotocin-induced diabetes. Diabetic rats were either untreated or received the angiotensin converting enzyme inhibitor ramipril, or the angiotensin II type 1 receptor antagonist, valsartan. Results. When compared with control animals, diabetes was associated with a decrease in the number of slit pores per unit length of glomerular basement membrane, indicative of podocyte foot process broadening. Both ramipril and valsartan attenuated these ultrastructural changes to a similar degree. These differences remained after correcting for glomerular volume as a possible confounding variable. Conclusion/interpretation. Preservation of podocyte architecture could contribute to the renoprotective effects of renin-angiotensin system blockade in diabetic nephropathy. [Diabetologia (2001) 44: 878–882] Received: 19 January 2001 and in revised form: 28 March 2001