Nephrin与糖尿病肾病

Nephrin是特异性表达于肾小球足细胞的一种跨膜蛋白,定位于肾小球足突细胞裂隙隔膜,在维持肾小球滤过屏障完整性及其正常功能过程中起关键作用。糖尿病肾病(DN)患者肾小球nephrin及其受体表达下降。破坏了肾小球足突细胞裂隙隔膜结构与其屏障功能的完整性,蛋白质从肾小球滤出增多,引起蛋白尿。Nephrin在DN的发病机制中起关键作用,深入研究nephrin可进一步了解DN的发病机制,对其诊断和治疗有重要的指导意义。     

Family-Based Association Analysis Confirms the Role of the Chromosome 9q21.32 Locus in the Susceptibility of Diabetic Nephropathy

A genome-wide association scan of type 1 diabetic patients from the GoKinD collections previously identified four novel diabetic nephropathy susceptibility loci that have subsequently been shown to be associated with diabetic nephropathy in unrelated patients with type 2 diabetes. To expand these findings, we examined whether single nucleotide polymorphisms (SNPs) at these susceptibility loci were associated with diabetic nephropathy in patients from the Joslin Study of Genetics of Nephropathy in Type 2 Diabetes Family Collection. Six SNPs across the four loci identified in the GoKinD collections and 7 haplotype tagging SNPs, were genotyped in 66 extended families of European ancestry. Pedigrees from this collection contained an average of 18.5 members, including 2 to 14 members with type 2 diabetes. Among diabetic family members, the 9q21.32 locus approached statistical significance with advanced diabetic nephropathy (P = 0.037 [adjusted P = 0.222]). When we expanded our definition of diabetic nephropathy to include individuals with high microalbuminuria, the strength of this association improved significantly (P = 1.42×10⁻³ [adjusted P = 0.009]). This same locus also trended toward statistical significance with variation in urinary albumin excretion in family members with type 2 diabetes (P = 0.032 [adjusted P = 0.192]) and in analyses expanded to include all relatives (P = 0.019 [adjusted P = 0.114]). These data increase support that SNPs identified in the GoKinD collections on chromosome 9q21.32 are true diabetic nephropathy susceptibility loci.     

Paeoniflorin Prevents Diabetic Nephropathy in Rats

The aim of this study was to test the hypothesis that paeoniflorin prevents the progression of diabetic nephropathy by modulating the inflammatory process. Sprague–Dawley rats were divided into 5 groups: nondiabetic control rats; untreated diabetic model (DM) rats; and DM rats treated with 5, 10, or 20 mg/kg paeoniflorin in drinking water once daily. Rats received a single intravenous injection of streptozotocin to induce diabetes; 9 wk after injection, rats began the 8-wk daily paeoniflorin treatment regimen. Compared with that of nonDM controls, the urinary albumin:creatinine ratio was increased significantly in untreated DM rats; this ratio was decreased in DM rats treated with 5, 10, or 20 mg/kg paeoniflorin compared with that of untreated DM rats. In addition, paeoniflorin treatment effectively suppressed glomerular hypertrophy; blood glucose; the expression of transforming growth factor β, type IV collagen, and intercellular adhesion molecule 1; and renal infiltration of macrophages compared with levels in untreated DM rats. Furthermore, renal nuclear factor κB activity was increased in untreated but not paeoniflorin-treated DM rats. In conclusion, our data suggest that the preventive effects of paeoniflorin may be mediated by its antiinflammatory actions.Abbreviations: DM, diabetic model; ECM, extracellular matrix; ICAM1, intercellular adhesion molecule 1; MCP1, monocyte chemoattractant protein 1; NFκB, nuclear factor κB; TGFβ, transforming growth factor βDiabetic nephropathy is the most common cause of endstage renal disease and high mortality in humans. Adequate control of blood glucose may slow the rate of its progression, but it is still difficult to achieve strict glycemic control for diabetic patients in the longer term, due at least in part to the limitations of available therapeutic approaches.³ Recent studies have suggested the emerging role of inflammatory processes in the pathogenesis of diabetic nephropathy in addition to other well-known mechanisms.In human renal disease, transforming growth factor β (TGFβ) may mediate the buildup of tissue extracellular matrix (ECM) proteins.¹⁷ This cytokine reportedly stimulated ECM protein accumulation in diabetic tissues by upregulating the production of ECM proteins or by downregulating the production of ECM-degrading enzymes.²⁶ Renal levels of TGFβ1 increase in both experimental and human diabetes. In addition, TGFβ1 induces the synthesis of ECM components including collagen types I, III, and IV and fibronectin.^2,5Intercellular adhesion molecule 1 (ICAM1) is a key adhesion molecules. In addition, the ICAM1-dependent infiltration of macrophages into the kidney is very important in the pathogenesis of diabetic nephropathy.¹⁸ In addition, the expression of ICAM1 is rapidly induced and maintained for a long time in renal tissues after induction of diabetes in experimental type 1 diabetic rats.^14,20 Macrophage infiltration was blocked by antiICAM1 antibody, confirming that ICAM1 mediates macrophage infiltration into the diabetic kidney.⁶ Furthermore, ICAM1-deficient mice were protected from renal injury after the induction of diabetes, suggesting that the inflammatory process is a critical factor for the development of diabetic nephropathy.²¹Despite the availability of treatments that lower blood glucose and blood pressure, many diabetic patients are still prone to developing kidney failure, which no currently available therapies can reverse.²⁴ Therefore a search is needed for new therapeutic approaches—based on novel mechanisms of action—to the treatment of diabetic nephropathy. Paeoniflorin is a monoterpene glucoside and a component of the total glucoside extract obtained from the root of Paeonia lactiflora.²⁸ This extract was approved for marketing in China in 1998.²³ As a disease-modifying drug, the total glucoside extract of peony has both antiinflammatory and immune-regulatory effects and is used in the treatment of rheumatoid arthritis, hepatitis, systemic lupus erythematosus, and mesenteric hyperplastic nephritis.^8,9,27 The goal of this study is to address whether paeoniflorin might prevent the progression of diabetic nephropathy through the inhibition of the inflammatory processes including TGFβ, type IV collagens, and ICAM1 expression, monocyte chemoattractant protein 1 (MCP1), nuclear factor κB (NFκB) activation, and macrophage infiltration.     

Diabetic Nephropathy and Extracellular Matrix

Diabetic nephropathy (DN) is a serious complication in diabetes. Major typicalmorphological changes are the result of changes in the extracellular matrix (ECM). Thus,basement membranes are thickened and the glomerular mesangial matrix and thetubulointerstitial space are expanded, due to increased amounts of ECM. One important ECMcomponent, the proteoglycans (PGs), shows a more complex pattern of changes in DN. PGs inbasement membranes are decreased but increased in the mesangium and the tubulointerstitialspace. The amounts and structures of heparan sulfate chains are changed, and such changesaffect levels of growth factors regulating cell proliferation and ECM synthesis, with cellattachment affecting endothelial cells and podocytes. Enzymes modulating heparan sulfatestructures, such as heparanase and sulfatases, are implicated in DN. Other enzyme classesalso modulate ECM proteins and PGs, such as matrix metalloproteinases (MMPs) and serineproteases, such as plasminogen activator, as well as their corresponding inhibitors. Thelevels of these enzymes and inhibitors are changed in plasma and in the kidneys in DN.Several growth factors, signaling pathways, and hyperglycemia per se affect ECM synthesisand turnover in DN. Whether ECM components can be used as markers for early kidney changesis an important research topic, whereas at present, the clinical use remains to beestablished.     

Cellular Cholesterol Transport Proteins in Diabetic Nephropathy

Background

Lipid accumulation has been shown to accelerate renal injury, and the intracellular accumulation of lipids may be caused by alterations in synthesis as well as lipid uptake and efflux. We have investigated the role of cellular cholesterol transport proteins including adenosine triphosphate binding cassette transporter A1 (ABCA1), G1 (ABCG1) and scavenger receptor class B type I (SR-BI) in diabetic nephropathy.

Methods

Protein expression and the ability to mediate cholesterol efflux of ABCA1, ABCG1 and SR-BI was determined in human renal mesangial cells and proximal tubular epithelial cells cultured under normal or high glucose conditions. Renal expression of these cholesterol transporters was examined in a murine model of streptozotocin-induced type 1 diabetes.

Results

ABCA1, ABCG1 and SR-BI were expressed in both human renal mesangial cells and proximal tubular epithelial cells, and mediated cholesterol efflux to apolipoprotein AI and HDL. In vitro, hyperglycemia reduced the expression and the ability to mediate cholesterol efflux of all three cholesterol transporters (p<0.05). In vivo studies showed that intra-renal accumulation of lipids was increased in diabetic mice, particularly in mice with nephropathy. This was associated with a significant reduction in the expression of ABCA1, ABCG1 and SR-BI in the kidneys. These changes were already seen in diabetic mice without nephropathy and preceded the development of nephropathy. Diabetic mice with nephropathy had the lowest level of these cholesterol transporters.

Conclusion

Inducing diabetes with streptozotocin significantly reduced renal expression of ABCA1, ABCG1 and SR-BI. Defects in cholesterol export pathway in renal cells could therefore promote cholesterol accumulation and might contribute to the development of diabetic nephropathy.     

BMP Signaling and Podocyte Markers Are Decreased in Human Diabetic Nephropathy in Association With CTGF Overexpression

Diabetic nephropathy is characterized by decreased expression of bone morphogenetic protein-7 (BMP-7) and decreased podocyte number and differentiation. Extracellular antagonists such as connective tissue growth factor (CTGF; CCN-2) and sclerostin domain-containing-1 (SOSTDC1; USAG-1) are important determinants of BMP signaling activity in glomeruli. We studied BMP signaling activity in glomeruli from diabetic patients and non-diabetic individuals and from control and diabetic CTGF^+/+ and CTGF^+/− mice. BMP signaling activity was visualized by phosphorylated Smad1, -5, and -8 (pSmad1/5/8) immunostaining, and related to expression of CTGF, SOSTDC1, and the podocyte differentiation markers WT1, synaptopodin, and nephrin. In control and diabetic glomeruli, pSmad1/5/8 was mainly localized in podocytes, but both number of positive cells and staining intensity were decreased in diabetes. Nephrin and synaptopodin were decreased in diabetic glomeruli. Decrease of pSmad1/5/8 was only partially explained by decrease in podocyte number. SOSTDC1 and CTGF were expressed exclusively in podocytes. In diabetic glomeruli, SOSTDC1 decreased in parallel with podocyte number, whereas CTGF was strongly increased. In diabetic CTGF^+/− mice, pSmad1/5/8 was preserved, compared with diabetic CTGF^+/+ mice. In conclusion, in human diabetic nephropathy, BMP signaling activity is diminished, together with reduction of podocyte markers. This might relate to concomitant overexpression of CTGF but not SOSTDC1. (J Histochem Cytochem 57:623–631, 2009)     

替米沙坦联合阿托伐他汀治疗糖尿病肾病的疗效分析

目的:探讨替米坦联合阿托伐他汀治疗糖尿病肾病(DN)的疗效及机制.方法:选择糖尿病肾病60例,随机分为治疗组和对照组各30例,对照组单用替米沙坦治疗,治疗组应用替米沙坦联合阿托伐他汀治疗,疗程6个月.治疗前后观察TC、TG、尿微量白蛋白(MALB)、24 h尿蛋白、Scr、BUN、C-反应蛋白、IL-6的值.结果:治疗前,两组TC、TG、尿微量白蛋白(MALB)、24 h尿蛋白、Scr、BUN、C-反应蛋白、IL-6的值比较无明显差异(P>0.05),治疗6月后,与治疗前比较,除TC、TG外,两组患者的尿微量白蛋 白(MALB)、24 h尿蛋白、Scr、BUN、C-反应蛋白、IL-6的值下降(P<0.01),治疗组的TC、TG、尿微量白蛋白(MALB)、24 h尿蛋白、Scr、BUN、C-反应蛋白、IL-6值较对照组低,差异有统计学意义(P<0.01).结论:采用替米沙坦和阿托伐他汀治疗糖尿病肾病具有降血脂、减少尿蛋白、改善肾功能、延缓病情进展的作用.     

糖尿病肾病发病机制研究进展

糖尿病肾病(DN)是糖尿病(DM)最常见的慢性并发症,也是终末期肾病(ESRD)的主要原因,其治疗费用巨大。其发病机制主要涉及遗传易感性、糖代谢紊乱、肾血流动力学的改变、细胞因子、炎症机制已及氧化应激等方面。本文就以上作用机制的最新研究进展作一综述。     

Hydrogen Sulfide Alleviates Diabetic Nephropathy in a Streptozotocin-induced Diabetic Rat Model

Accumulating evidence has demonstrated that hydrogen sulfide (H₂S) plays critical roles in the pathogenesis of chronic kidney diseases. This study was designed to investigate whether H₂S has protective effects against diabetic nephropathy. Diabetic rats were induced by intraperitoneal injection of streptozotocin and administrated with H₂S donor NaHS for 12 weeks. Rat glomerular mesangial cells were pretreated with NaHS or MAPK inhibitors (U0126, SP600125, and SB203580) prior to high glucose exposure, and cell proliferation was determined. Our findings suggest that H₂S can improve renal function and attenuate glomerular basement membrane thickening, mesangial matrix deposition, and renal interstitial fibrosis in diabetic rats. H₂S was found to reduce high glucose-induced oxidative stress by activating the Nrf2 antioxidant pathway and to exert anti-inflammatory effects by inhibiting NF-κB signaling. In addition, H₂S reduced high glucose-induced mesangial cell proliferation by blockade of MAPK signaling pathways. Moreover, H₂S was also found to inhibit the renin-angiotensin system in diabetic kidney. In conclusion, our study demonstrates that H₂S alleviates the development of diabetic nephropathy by attenuating oxidative stress and inflammation, reducing mesangial cell proliferation, and inhibiting renin-angiotensin system activity.     

G-CSF Prevents Progression of Diabetic Nephropathy in Rat

Background

The protective effects of granulocyte colony-stimulating factor (G-CSF) have been demonstrated in a variety of renal disease models. However, the influence of G-CSF on diabetic nephropathy (DN) remains to be examined. In this study, we investigated the effect of G-CSF on DN and its possible mechanisms in a rat model.

Methods

Otsuka Long-Evans Tokushima Fatty (OLETF) rats with early DN were administered G-CSF or saline intraperitoneally. Urine albumin creatinine ratio (UACR), creatinine clearance, mesangial matrix expansion, glomerular basement membrane (GBM) thickness, and podocyte foot process width (FPW) were measured. The levels of interleukin (IL)-1β, transforming growth factor (TGF)-β1, and type IV collagen genes expression in kidney tissue were also evaluated. To elucidate the mechanisms underlying G-CSF effects, we also assessed the expression of G-CSF receptor (G-CSFR) in glomeruli as well as mobilization of bone marrow (BM) cells to glomeruli using sex-mismatched BM transplantation.

Results

After four weeks of treatment, UACR was lower in the G-CSF treatment group than in the saline group (p<0.05), as were mesangial matrix expansion, GBM thickness, and FPW (p<0.05). In addition, the expression of TGF-β1 and type IV collagen and IL-1β levels was lower in the G-CSF treatment group (p<0.05). G-CSFR was not present in glomerular cells, and G-CSF treatment increased the number of BM-derived cells in glomeruli (p<0.05).

Conclusions

G-CSF can prevent the progression of DN in OLETF rats and its effects may be due to mobilization of BM cells rather than being a direct effect.     

缬沙坦治疗糖尿病肾病疗效观察

目的观察血管紧张素Ⅱ1型受体拮抗剂(AT1Ra)缬沙坦(Valsartan)对伴大量白蛋白尿的临床糖尿病肾病的治疗作用.方法 32例2型糖尿病患者,24h尿白蛋白排泄率(24hUAER)＞200μg/min,均伴高血压,维持原糖尿病治疗不变,分组比较应用缬沙坦(80 mg/d)或贝那普利(10 mg/d)治疗8周前后平均动脉压(MAP)、24h UAER、HbA1c、尿酸(UA)等指标的变化.结果缬沙坦治疗组和贝那普利治疗组24h UAER分别由(703.2±987.9)μg/min降至(664.2±970.6)μg/min(P＜0.01)和由(778.6±1005.0)μg/min降至(734.9±996.0)μg/min(P＜0.01).二者疗效相似,且均与血压变化不相关.结论AT1Ra缬沙坦可以降低临床糖尿病肾病的尿蛋白,其肾脏保护作用除了与降血压有关,还有不依赖降压效应的其他机制.     

法尼酯衍生物X受体（FXR）在糖尿病肾病中的研究进展

糖尿病肾病（DN）是糖尿病常见的慢性微血管并发症,最初是由高血糖引起的肾脏适应性高滤过率,进而导致肾脏细胞的代偿性增生、炎症以及纤维化。法尼酯X受体（FXR）被证明对糖尿病肾病有负性调节的作用,FXR可以通过不同的方面（血糖、血脂、炎症以及纤维化）对糖尿病肾病进行调控,从而有效的控制糖尿病肾病的发生和发展。本文将对FXR以及FXR调控糖尿病肾病的不同方面予以综述。     

Resveratrol Attenuates Diabetic Nephropathy via Modulating Angiogenesis

Angiogenesis plays an important role in the pathogenesis of diabetic nephropathy (DN). In the present study, we investigated the therapeutic potential of resveratrol, a polyphenol with antiangiogenic activity in DN. In a type 1 diabetic rat model, resveratrol treatment blunted the increases of urine albumin excretion, kidney weight and creatinine clearance rate. The increases of glomerular diameter, mesangium accumulation, glomerular basement membrane thickness and renal fibrosis in diabetic rats were also reduced by resveratrol treatment. In the diabetic kidney, increased expression of vascular endothelial growth factor (VEGF), Flk-1 and angiopoietin 2, and reduced expression of Tie-2 were observed. These changes in angiogenic hormones and associated receptors were attenuated by resveratrol treatment. No changes in angiopoietin 1 expression were detected among each group of rats. Resveratrol also significantly downregulated high glucose-induced VEGF and Flk-1 expressions in cultured mouse glomerular podocytes and endothelial cells, respectively. These effects were attenuated by knocking-down silent information regulator 1 (Sirt1) expression. In contrast, upregulation of Sirt1 in cultured endothelial cells reduced Flk-1 expression. Increased permeability and cellular junction disruption of cultured endothelial cells caused by VEGF were also inhibited by resveratrol pretreatment. Taken together, the present study demonstrated that resveratrol may attenuate DN via modulating angiogenesis.     

Albumin Antioxidant Response to Stress in Diabetic Nephropathy Progression

Background

A new component of the protein antioxidant capacity, designated Response Surplus (RS), was recently described. A major feature of this component is the close relationship between protein antioxidant capacity and molecular structure. Oxidative stress is associated with renal dysfunction in patients with renal failure, and plasma albumin is the target of massive oxidation in nephrotic syndrome and diabetic nephropathy. The aim of the present study was to explore the albumin redox state and the RS component of human albumin isolated from diabetic patients with progressive renal damage.

Methods/Principal Findings

Serum aliquots were collected and albumin isolated from 125 diabetic patients divided into 5 groups according to their estimated glomerular filtration rate (GFR). In addition to clinical and biochemical variables, the albumin redox state, including antioxidant capacity, thiol group content, and RS component, were evaluated. The albumin antioxidant capacity and thiol group content were reciprocally related to the RS component in association with GFR reduction. The GFR decline and RS component were significantly negatively correlated (R = –0.83, p<0.0001). Age, creatinine, thiol groups, and antioxidant capacity were also significantly related to the GFR decline (R = –0.47, p<0.001; R = –0.68, p<0.0001; R = 0.44, p<0.001; and R = 0.72, p<0.0001).

Conclusion/Significance

The response of human albumin to stress in relation to the progression of diabetic renal disease was evaluated. The findings confirm that the albumin molecular structure is closely related to its redox state, and is a key factor in the progression of diabetes nephropathy.     

Association of Polymorphic Markers of the Antioxidant Enzyme Genes with Diabetic Polyneuropathy in Type 1 Diabetes Mellitus

The allele and genotype frequency distributions of polymorphic markers of genes coding for antioxidant enzymes were compared for type 1 diabetes mellitus patients with or without diabetic polyneuropathy (DPN). The groups (total 180 patients) had nonoverlapping (polar) phenotypes. Group DPN+ included 86 patients with DPN and diabetic record no more than 5 years. Control group DPN– included patients without DPN and diabetic record of at least 10 years. Comparative analysis with Fisher's exact test revealed a significant difference in allele and genotype frequency distributions of the (–262) polymorphic marker of the CAT gene. Polymorphic markers C1167T of the CAT gene, Pro/Leu of the GPX1 gene, 0/+ of the GSTT1 gene, and 0/+ of the GSTM1 gene showed no significant difference in allele or genotype frequency distribution. On this evidence, these markers were not associated with DPN in the sample examined.     

Effective Delivery of Endogenous Antioxidants Ameliorates Diabetic Nephropathy

Background

Diabetic nephropathy (DN) is thought to be partially due to the injury of renal cells and the renal micro-environment by free radicals. Free radial scavenging agents that inhibit free radical damage may well prevent the development of underlying conditions such as mesangial expansion (by inhibiting extracellular matrix expression) in these patients.

Methods

Using techniques for intra-cellular delivery of peptides, we made metallothionein (MT) and superoxide dismutase (SOD), potent endogenous antioxidants, readily transducible into cell membrane and tested their protective effect against the development of DN in OLETF rats. Herein, we study antioxidant peptides for their ability to prevent oxidative damage to primary rat mesangial cells (MCs), which are important constituents of renal glomeruli.

Results

Intraperitoneal administration of these antioxidants resulted in delivery to the kidney and decreased ROS and the expression of downstream signals in renal cells and postponed the usual progression to DN. In in vitro experiments, MT and SOD were efficiently transferred to MCs, and the increased removal of ROS by MT and SOD was proportional to the degree of scavenging enzymes delivered. MT and SOD decreased three major oxidative injuries (hyperglycemia, AGE and ROS exposure) and also injuries directly mediated by angiotensin II in MCs while changing downstream signal transduction.

Conclusions

The protective effects of MT and SOD for the progression of DN in experimental animals may be associated with the scavenging of ROS by MT and SOD and correlated changes in signal transduction downstream. Concomitant administration of these antioxidant peptides may prove to be a new approach for the prevention and therapy of DN.     

糖尿病肾病动物模型的研究进展

糖尿病肾病是终末期肾衰的主要原因,也是糖尿病致命的重要原因。但是糖尿病肾病的致病机制迄今尚不完全明了,理想的动物模型无疑可对糖尿病肾病的研究提供重要线索。糖尿病肾病动物模型包括诱发性、自发性和转基因等多种类型的动物模型,各种类型的动物模型在疾病的发生发展、病理生理变化等多个方面与人类糖尿病肾病具有相似的特征。应用这些模型有助于开展对糖尿病肾病的防治、发病机理、相关药物的开发等多方面的研究。