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.     

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。     

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.     

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)     

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。     

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.     

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.     

Urinary Exosomal MicroRNAs in Incipient Diabetic Nephropathy

MicroRNAs (miRNAs), a class of small non-protein-encoding RNAs, regulate gene expression via suppression of target mRNAs. MiRNAs are present in body fluids in a remarkable stable form as packaged in microvesicles of endocytic origin, named exosomes. In the present study, we have assessed miRNA expression in urinary exosomes from type 1 diabetic patients with and without incipient diabetic nephropathy. Results showed that miR-130a and miR-145 were enriched, while miR-155 and miR-424 reduced in urinary exosomes from patients with microalbuminuria. Similarly, in an animal model of early experimental diabetic nephropathy, urinary exosomal miR-145 levels were increased and this was paralleled by miR-145 overexpression within the glomeruli. Exposure of cultured mesangial cells to high glucose increased miR-145 content in both mesangial cells and mesangial cells-derived exosomes, providing a potential mechanism for diabetes-induced miR-145 overexpression. In conclusion, urinary exosomal miRNA content is altered in type 1 diabetic patients with incipient diabetic nephropathy and miR-145 may represent a novel candidate biomarker/player in the complication.     

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.     

线粒体功能障碍在糖尿病肾病进展的作用

糖尿病肾病是糖尿病微血管并发症之一,亦是引起终末期肾脏病的主要原因。目前各种临床治疗手段并没有阻止糖尿病肾病患者肾功能的进行性减退。因此,当务之急是进一步研究糖尿病肾病的发病机制,并从中寻找新的治疗靶点。大量研究结果显示线粒体功能障碍在糖尿病肾病的发生发展过程中具有重要作用。正常线粒体功能的维持依赖于多方面因素的共同参与,如线粒体质量控制机制、线粒体DNA等。这篇综述回顾了关于线粒体与糖尿病肾病相关文献,阐述线粒体功能障碍在糖尿病肾病进展中可能的作用。     

超声在糖尿病肾病诊断中的应用价值

由于快速变化的生活方式,我国糖尿病的患病率呈逐年上升趋势。糖尿病肾病(diabetic nephropathy,DN)是糖尿病最常见、最严重的微血管病变并发症之一,并且已经成为全球终末期肾病的最常见病因。因此,早期诊断、早期治疗是延缓DN进展的重点。超声是临床评价肾脏形态、功能常用的检查方法,与血、尿实验室检查相比,具有方便、快捷、无创、经济的优势。随着科学技术的发展,越来越多的超声新技术应用于临床,极大的丰富了诊断信息。本文就各项超声检查技术在检测DN患者肾脏体积、实质回声、血流动力学改变中的应用价值作一综述。得出结论:在DN早期血、尿实验室检查正常时超声已经可以发现肾脏体积、血流动力学发生了变化。因此,超声在DN的早期诊断、动态监测病程进展方面所发挥的作用是其他检查方法所不可替代的。三维超声技术和超声弹性成像在DN患者肾脏功能评价方面有着广泛研究空间及临床应用前景。     

糖尿病肾病发病分子机制

糖尿病肾病(DN)是高血糖所导致的一种主要的微血管并发症。在全世界糖尿病病人中,糖尿病肾病都有着非常高的发病率和致死率。并且在中国,糖尿病肾病已经成为一种常见的导致末期肾衰竭的因素。由于糖尿病肾病患者不断增多,传统的单纯通过控制血糖来控制糖尿病肾病并没有取得理想的效果,因此临床上迫切需要一些新的治疗方法来控制糖尿病肾病的发生和发展。最近的研究表明肾素-血管紧张素-醛固酮系统(RAAS)、蛋白激酶-C(PKC)、还原型烟酰胺腺嘌呤二核苷酸磷酸(NADPH)氧化酶、转化生长因子-β(TGF-β)等都单独的或共同的参与了DN的发生和发展过程。这些通路彼此交叉,十分复杂,因此需要对糖尿病肾病发病分子机制进行全面的综合的理解。这篇文章旨在讨论已发现的与糖尿病肾病密切相关的分子机制以及下调通路。     

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.     

糖尿病肾病致凝血异常的研究

糖尿病(DM)已成为世界性的常见病,其发病率高,并且随着生活水平的改善,其发病率必然还会进一步加剧。血管病变是DM的重要并发症之一,糖尿病肾病(DN)是糖尿病常见且严重的微血管并发症,与血栓形成密切相关。糖尿病肾病的进展伴随着体内凝血活性和抗凝活性的失调,同时激活自身免疫系统,发生炎症反应。炎症应答过程中释放的炎症因子损伤肾小球内皮细胞,导致抗凝活性减弱。DN患者体内血细胞激活,微粒形成增多会加强凝血活性。此外,纤溶酶抑制剂(PAI-1)与纤溶酶激活剂(t PA)的失衡会引起纤溶系统紊乱。这三个方面引起DN患者体内的高凝状态加重,并因此加速肾功能恶化,导致肾小球率过滤降低,系膜基质增多,最终引起肾小球硬化及终末期肾脏疾病。本文就糖尿病肾病致凝血异常的发生机制做一综述。     

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。     

Association and Linkage Analysis of Aluminum Tolerance Genes in Maize

Background

Aluminum (Al) toxicity is a major worldwide constraint to crop productivity on acidic soils. Al becomes soluble at low pH, inhibiting root growth and severely reducing yields. Maize is an important staple food and commodity crop in acidic soil regions, especially in South America and Africa where these soils are very common. Al exclusion and intracellular tolerance have been suggested as two important mechanisms for Al tolerance in maize, but little is known about the underlying genetics.

Methodology

An association panel of 282 diverse maize inbred lines and three F₂ linkage populations with approximately 200 individuals each were used to study genetic variation in this complex trait. Al tolerance was measured as net root growth in nutrient solution under Al stress, which exhibited a wide range of variation between lines. Comparative and physiological genomics-based approaches were used to select 21 candidate genes for evaluation by association analysis.

Conclusions

Six candidate genes had significant results from association analysis, but only four were confirmed by linkage analysis as putatively contributing to Al tolerance: Zea mays Alt_SB like (ZmASL), Zea mays aluminum-activated malate transporter2 (ALMT2), S-adenosyl-L-homocysteinase (SAHH), and Malic Enzyme (ME). These four candidate genes are high priority subjects for follow-up biochemical and physiological studies on the mechanisms of Al tolerance in maize. Immediately, elite haplotype-specific molecular markers can be developed for these four genes and used for efficient marker-assisted selection of superior alleles in Al tolerance maize breeding programs.