Plasminogen activator inhibitor-1 and apolipoprotein E gene polymorphisms and diabetic angiopathy.

BACKGROUND: A point mutation in the plasminogen activator inhibitor-1 (PAI-1) gene and a three-allelic variation in the apolipoprotein-E (ApoE) gene have been suggested as risk factors for the development of diabetic micro- and macrovascular complications. METHODS: We studied 198 type 1 diabetic patients with diabetic nephropathy [121 men, age (mean+/-SD) 41+/-10 years, diabetes duration 28+/-8 years] and 192 patients with persistent normoalbuminuria (118 men, age 43+/-10 years, diabetes duration 27+/-9 years). RESULTS: Male patients with nephropathy had elevated plasma PAI-1 levels [geometric mean (95% CI)], 70 (62-79) ng/ml, compared with normoalbuminuric men, 43 (38-47) ng/ml, P<0.001. Even though nephropathic patients with the 4G4G genotype tended to have higher plasma PAI-1 levels, P=0.06, no difference in allele frequency (4G/5G) was seen between patients with and without nephropathy: 0.538/0.462 vs 0.539/0.461, respectively. Nor did ApoE allele frequencies (epsilon2/epsilon3/epsilon4) differ between nephropathic and normoalbuminuric patients: 0.099/0.749/0. 152 vs 0.081/0.745/0.174, respectively. Genotype distributions were also similar, n.s. Coronary heart disease was more prevalent (36%) among nephropathic patients carrying the atherogenic epsilon4-allele compared with 12% in patients with the epsilon3,epsilon3 genotype, P<0.001. No associations between diabetic retinopathy and PAI-1 or ApoE polymorphisms were observed, n.s. CONCLUSIONS: The ApoE polymorphism may accelerate the development of coronary heart disease often seen in Caucasian patients with type 1 diabetes and diabetic nephropathy, a condition characterized by elevated plasma PAI-1 in men. Neither the PAI-1 nor the ApoE gene polymorphism contributes to the genetic susceptibility to diabetic nephropathy or retinopathy.     

Association of plasminogen activator inhibitor-1 gene polymorphism and type 2 diabetic nephropathy

Background: We investigated the relationship between plasminogen activator inhibitor-1 (PAI-1) 4G/5G insertion/deletion polymorphism and prevalence of diabetic nephropathy (DN) in Chinese patients. Methods: A total of 107 patients with type 2 diabetes were randomly recruited in the study, and 102 healthy subjects were selected as Control. Patients were divided into three groups according to their urinary albumin–creatinine ratio (UACR). Group A (n?=?44), had patients without DN (serum creatinine <106?µmol/L and UACR <30?µg/mg); Group B (n?=?30), had patients with micro-albuminuria (UACR 30–299?µg/mg), and Group C (n?=?33), had patients with macro-albuminuria (UACR ≥300?µg/mg and creatinine <200?µmol/L). Plasma level of PAI-1 was measured by ELISA. PAI-1 polymorphism was determined by a polymerase chain reaction (PCR) method and DNA sequencing. Results: (1) The plasma PAI-1 levels of group A (60.39?±?17.01?ng/L), group B (68.76?±?17.81?ng/L) and group C and (68.63?±?18.30?ng/L) are higher than that of controls (46.26?±?26.04?ng/L); (2) Patients with genotype 4G/4G tended to exhibit higher PAI-1 level; (3) The distribution frequency of genotype 4G/4G in group C was significantly higher than in group A (42.4% vs. 28.7%, p?Conclusions: (1) Plasma PAI-1 level was elevated in Type 2 diabetic patients; (2) The level of plasma PAI-1 is closely related to PAI-1 gene 4G/5G polymorphism and (3) PAI-1 4G/5G polymorphism is associated with the development and progression of predominant proteinuria diabetes nephropathy.     

Effect of tranilast in early-stage diabetic nephropathy.

BACKGROUND: Tranilast is an antifibrotic drug known to suppress collagen synthesis by fibroblasts by interfering with the effects of TGF-beta. We recently reported that it slowed the progression rate of advanced diabetic nephropathy (DN) by reducing the accumulation of collagens in renal tissue. The present study was undertaken to examine the effect of tranilast on early-stage DN. METHODS: Among out-patients with diabetes mellitus, we selected patients with (i) urinary albumin excretion of 30-1000 mg/g creatinine (/gCr) in the first morning urine, (ii) serum creatinine (SCr) < or =1.2 mg/dl and no haematuria and (iii) currently taking an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker. Twenty patients fulfilled the criteria, of whom 10 were selected at random and commenced on tranilast [100 mg, 3 times daily; T(+) group]. The remaining 10 patients comprised the T(-) group. Excretion of both urinary type IV collagen (U-IV) and albumin (U-A) in the first morning urine was measured every 3 months. The follow-up period was 1 year. RESULTS: At baseline, no significant differences were observed in SCr, HbA(1c), blood pressure and U-A excretion between the T(+) and T(-) groups, but U-IV excretion in the T(+) group was higher than in the T(-) group (6.4 +/- 0.66 vs 3.7 +/- 0.36 microg/gCr, mean +/- SEM, P < 0.01). At 1 year, SCr was not different from the baseline in either group. In the T(+) group, however, excretion rates of both U-IV and U-A tended to decrease with time, and after 1 year, were significantly decreased compared with excretion at baseline (U-A: 279 +/- 78 to 191 +/- 62 mg/gCr; P = 0.049, U-IV: 6.4 +/- 0.66 to 4.4 +/- 0.99 microg/gCr; P = 0.02). In contrast, in the T(-) group, excretion of both U-A and U-IV tended to increase with time. The changes of both U-A and U-IV excretions in the two groups took statistically different trends through tranilast treatment (P = 0.01 and P = 0.04, respectively). CONCLUSIONS: Our results suggest that tranilast could be therapeutically beneficial in early-stage DN.     

Iron restriction prevents diabetic nephropathy in Otsuka Long-Evans Tokushima fatty rat

Abstract

High body iron levels are found in type 2 diabetes mellitus (DM). Iron excess leads to tissue injury through free radical formation. We investigated the effect of iron restriction on renal damage in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a model of type 2?DM. OLETF rats (n?=?18) were divided into three groups at 10 weeks of age: high fat diet containing 8% NaCl (HFS, n?=?6), HFS diet with iron restricted (HFS?+?IR, n?=?6), and HFS with hydralazine (HFS?+?Hyd, n?=?6). Long-Evans Tokushima (LETO) rats served as control. Iron restriction decreased hemoglobin levels, systolic blood pressure, and urinary excretion of protein and 8-hydroxy-2'-deoxyguanosine in the OLETF rats fed with HFS diet. Compared to the HFS group, the expression of desmin, renal glomerular injury marker and iron deposition in the renal tubules were attenuated in the HFS?+?IR group but not in the HFS?+?Hyd group at 26 weeks of age. Moreover, renal hypoxia (evaluated as pimonidazole adducts) was improved in the HFS?+?IR group compared to the HFS group in spite of anemia. Iron restriction prevented the production of reactive oxygen species and the development of early stage nephropathy in OLETF rats. Iron restriction may be beneficial in prevention of nephropathy in type 2?DM.     

VEGF and podocytes in diabetic nephropathy

Vascular endothelial growth factor-A (VEGF-A) is a protein secreted by podocytes that is necessary for survival of endothelial cells, podocytes, and mesangial cells. VEGF-A regulates slit-diaphragm signaling and podocyte shape via VEGF-receptor 2-nephrin-nck-actin interactions. Chronic hyperglycemia-induced excess podocyte VEGF-A and low endothelial nitric oxide drive the development and the progression of diabetic nephropathy. The abnormal cross-talk between VEGF-A and nitric oxide pathways is fueled by the diabetic milieu, resulting in increased oxidative stress. Recent findings on these pathogenic molecular mechanisms provide new potential targets for therapy for diabetic renal disease.     

Overexpression of thioredoxin1 in transgenic mice suppresses development of diabetic nephropathy.

BACKGROUND: Oxidative stress has been suggested to play an important role in the pathogenesis of diabetic nephropathy. In the present study, the effects of thioredoxin1 (TRX1) overexpression, a small protein with antioxidant property, on the development of diabetic nephropathy in streptozotocin-induced diabetic animals were investigated using TRX1 transgenic mice (TRX1-Tg). METHODS: Eight-week-old male TRX1-Tg and wild-type mice littermates (WT) mice were treated either with streptozotocin (200 mg/kg) or vehicle alone. After 24 weeks of treatment, diabetic nephropathy and oxidative stress were assessed in these four groups of mice, by biochemical analyses of blood and urine, as well as by histological analyses of the kidneys. RESULTS: Haemoglobin A1c (HbA1c) levels of diabetic TRX1-Tg were not significantly different from those of the diabetic WT. Nevertheless, an augmented urinary albumin excretion observed in diabetic WT was significantly diminished in diabetic TRX1-Tg. Histological study revealed that pathological changes such as mesangial matrix expansion and tubular injury were significantly prevented in diabetic TRX1-Tg accompanied by a reduced tendency of expression of transforming growth factor-beta as compared with diabetic WT. In parallel, urinary excretion of 8-hydroxy-2'-deoxyguanosine and acrolein adduct and the immunostaining intensities of these markers in the kidney were significantly higher in diabetic WT compared with non-diabetic mice. The markers were significantly suppressed in diabetic TRX1-Tg, an indication of systemic and renal oxidative stress attenuation by TRX1 overexpression. CONCLUSION: These findings indicated the significant role of oxidative stress in the development of diabetic nephropathy and a potential inhibition of progression of nephropathy by TRX1.     

Glucose transporters in diabetic nephropathy

Changes in glucose transporter expression in glomerular cells occur early in diabetes. These changes, especially the GLUT1 increase in mesangial cells, appear to play a pathogenic role in the development of ECM expansion and perhaps other features of diabetic nephropathy. In addition, it appears that at least some diabetic patients may be predisposed to nephropathy because of polymorphisms in their GLUT1 genes. GLUT1 overexpression leads to increased glucose metabolic flux which in turn triggers the polyol pathway and activation of PKC and 1. Activation of these PKC isoforms can lead directly to AP-1 induced increases in fibronectin expression and ECM accumulation. Other, more novel effects of GLUT1 on cellular hypertrophy and injury could also promote changes of diabetic nephropathy. Strategies to prevent GLUT1 overexpression could ameliorate or prevent the progression of diabetic nephropathy.     

紫草素对糖尿病小鼠中性粒细胞胞外诱捕网表达的影响

目的:探讨紫草素对佛波酯(PMA)诱导的糖尿病小鼠骨髓来源的中性粒细胞胞外诱捕网（NETs）的影响,为其治疗糖尿病足溃疡提供依据。方法:采用链脲佐菌素腹腔注射构建糖尿病小鼠模型,密度梯度离心法提取小鼠骨髓来源的中性粒细胞,并进行体外培养,PMA刺激其诱导NETs模型,采用CCK-8法筛选紫草素的安全剂量;采用Sytox Green核酸荧光染料法定量检测NETs水平;PicoGreen荧光染料法定量检测dsDNA/NETs含量;荧光探针定量检测中性粒细胞活性氧(ROS)水平;荧光免疫组化法检测NETs标志物瓜氨酸化组蛋白H3(Cit-H3)的表达水平。结果：紫草素在0.125～1μg/mL浓度范围内对中性粒细胞活性无影响。与模型组比较,紫草素1、0.5、0.25μg/mL浓度组中性粒细胞NETs产生的荧光强度显著降低（P <0.01）,细胞外dsDNA水平显著降低（P <0.01）,细胞内ROS水平显著降低（P<0.01）,细胞Cit-H3表达显著下调（P <0.01）。结论:紫草素通过抑制糖尿病小鼠骨髓来源的中性粒细胞ROS水平和Cit-H3表达,从而抑制NET...     

Pathogenesis of diabetic nephropathy

Diabetic nephropathy is one of the most serious complications among patients with long-standing diabetes mellitus. In recent years, nearly one third of the patients newly admitted to dialysis therapy in Japan suffer from diabetic nephropathy. Hyperglycemia appears to play a major role in the pathogenesis of this disease, probably via glomerular hemodynamic changes, as well as via metabolic alterations in glomerular cells, although both pathways may interact with each other. Recently, an activation of protein kinase C has been advocated to be a critical mediator between hyperglycemia and diabetic nephropathy. Protein kinase C is known to induce the production of various extracellular matrix proteins, which may cause the expansion of glomerular mesangium. Administration of a specific inhibitor of the β isoform of protein kinase C corrected glomerular hyperfiltration in diabetic rats. In addition, genetic factors may be involved in the progression of diabetic nephropathy, since various clinical studies have indicated the familial clustering of this complication in diabetes mellitus. Although the association with gene polymorphism of angiotensin-converting enzyme has been extensively studied by several individual research groups, a decisive conclusion has not been obtained. Further research using multicenter studies enrolling large numbers of patients may be needed to detect nephropathic gene(s).     

Antioxidants ameliorate the expression of vascular endothelial growth factor mediated by protein kinase C in diabetic podocytes.

BACKGROUND: The increased production of reactive oxygen species (ROS) may be involved in the onset or development of diabetic vascular complications. The release of ROS from podocytes plays a role in the pathogenesis of glomerular damage in various experimental glomerular diseases. Although it is assumed that the podocyte injury also plays an important role in diabetic nephropathy, the mechanism is still unknown. METHODS: Using a differentiated mouse podocyte cell line, we investigated: (1) whether a high level of ambient glucose increases the level of ROS, (2) whether the protein kinase C (PKC) pathway is involved in a high-glucose-induced generation of ROS and vascular endothelial growth factor (VEGF) and (3) whether antioxidants ameliorate PKC-mediated VEGF expression in diabetic milieu. RESULTS: Intracellular ROS generation was significantly higher in high glucose than in control conditions in cultured podocytes. High ambient glucose also increased VEGF mRNA and protein expression. The high-glucose-induced increases in ROS and VEGF mRNA and protein by podocytes were effectively inhibited by pretreatment with various antioxidants and were completely restored by PKC inhibition. The results show that cultured mouse podocytes produce ROS in response to high glucose, and that PKC is involved in high-glucose-induced ROS and VEGF production by podocyte. CONCLUSION: Increased ROS in podocytes may play a role in the pathogenesis of podocyte injury in diabetic nephropathy.     

Evolving spectrum of diabetic nephropathy

Diabetes remains an important health issue as more patients with chronic and uncontrolled diabetes develop diabetic nephropathy(DN), which classically presents with proteinuria followed by a progressive decrease in renal function.However, an increasing proportion of DN patients have a decline in kidney function and vascular complications without proteinuria, known as nonproteinuric DN(NP-DN). Despite the increased incidence of NP-DN, few clinical or experimental studies have thoroughly investigated the pathophysiological mechanisms and targeted treatment for this form of DN. In this review, we will examine the differences between conventional DN and NP-DN and consider potential pathophysiological mechanisms, diagnostic markers, and treatment for both DN and NP-DN. The investigation of the pathophysiology of NP-DN should provide additional insight into the cardiovascular factors influencing renal function and disease and provide novel treatments for the vascular complications seen in diabetic patients.     

GLUT1 and TGF-beta: the link between hyperglycaemia and diabetic nephropathy.

Recent experimental work implicates transforming growth factor-beta (TGF-beta) as an aetiologic mediator of diabetic nephropathy and the ubiquitous glucose transporter GLUT1 as an important permissive factor for the tissue injury caused by hyperglycaemia. High ambient glucose increases GLUT1 expression and glucose transport activity when compared with physiologic glucose concentrations. Treatment of rat mesangial cells with TGF-beta up-regulates GLUT1 mRNA and protein levels and significantly increases glucose uptake. Addition of neutralizing anti-TGF-beta antibody prevents the stimulatory effects of high glucose on GLUT1 expression. Cultured rat mesangial cells transduced with the human GLUT1 gene and thus overexpressing the GLUT1 protein show marked increase in glucose uptake and the synthesis of extracellular matrix molecules, even when grown in normal ambient glucose concentrations. Thus, TGF-beta and GLUT1, two proteins that are up-regulated in glomerular mesangial cells in a hyperglycaemic milieu, can influence the expression of one another. It is therefore fair to conclude that, with successful interruption of the TGF-beta-GLUT1 axis, the beneficial effects of strict glucose control on the development of diabetic nephropathy could likely be augmented.     

Rodent models of streptozotocin-induced diabetic nephropathy

Streptozotocin-induced pancreatic injury is commonly used for creating rodent models of type 1 diabetes which develop renal injury with similarities to human diabetic nephropathy. This model can be established in genetically modified rodents for investigating the role of molecular mechanisms and genetic susceptibility in the development of diabetic nephropathy. In this report, the authors describe and compare the current protocols being used to establish models of diabetic nephropathy in rat and mouse strains using streptozotocin. The authors also list some of the histological criteria and biochemical measurements which are being used to validate these models. In addition, our review explains some of the key aspects involved in these models, including the impact of streptozotocin-dosage, uninephrectomy, hypertension and genetically modified strains, which can each affect the development of disease and the interpretation of findings.     

PC-1 amino acid variant (K121Q) has no impact on progression of diabetic nephropathy in type 1 diabetic patients.

BACKGROUND: Recently, an amino acid variant (K121Q) in the glycoprotein PC-1 (Q allele) has been associated with faster progression of diabetic nephropathy, as estimated by calculated creatinine clearance. We tested the impact of the PC-1 (K121Q) variant on loss of glomerular filtration rate (GFR) measured by the [(51)Cr]EDTA plasma clearance technique. METHODS: We performed an observational follow-up study of 295 (182 males) type 1 patients with diabetic nephropathy [mean age 37 (SE 0.7) years, mean duration of diabetes 23 (SE 0.5) years]. All patients were followed for at least 3 years, median 8 years (range 3-17), with at least three measurements of GFR using [(51)Cr]EDTA (median 11 measurements (range 3-32)). Two hundred and seventeen patients had the KK genotype and 78 carried the Q allele (71 KQ and 7 QQ). RESULTS: Patients carrying the Q allele had a mean rate of decline in GFR during follow-up of 3.6 ml/min per year (SE 0.4) compared with 4.0 ml/min per year (SE 0.3) in patients with the KK genotype. Other risk factors for progression of diabetic nephropathy were similar in Q carriers and KK carriers. When dividing patients in tertiles based on rate of decline in GFR, we found no difference in distribution of K121Q genotypes. No difference in the number of patients who died or reached end-stage renal disease during follow-up according to K121Q genotype were found. A multiple linear regression analysis revealed that albuminuria, mean arterial blood pressure, haemoglobin A(1C) and serum cholesterol during follow-up predicted a steeper decline in GFR [R(2) (adjusted)=0.27], whereas the PC-1 genotype did not contribute. CONCLUSIONS: Our study did not reveal an association between the PC-1 amino acid variant K121Q and progression of diabetic nephropathy.     

The endothelium in diabetic nephropathy

The long-term complications of diabetes are characterized by pathologic changes in both the microvasculature and conduit vessels. Although the fenestrated glomerular endothelium classically has been viewed as providing little in the way of an impediment to macromolecular flow, increasing evidence illustrates that this is not the case. Rather, hyperglycemia-mediated endothelial injury may predispose to albuminuria in diabetes both through direct effects and through bidirectional communication with neighboring podocytes. Although neo-angiogenesis of the glomerular capillaries may be a feature of early diabetes, particularly in the experimental setting, loss of capillaries in the glomerulus and in the interstitium are key events that each correlate closely with declining glomerular filtration rate in patients with diabetic nephropathy. The hypoxic milieu that follows the microvascular rarefaction provides a potent stimulus for fibrogenesis, leading to the glomerulosclerosis and tubulointerstitial fibrosis that characterize advanced diabetic kidney disease. Given the pivotal role the endothelium plays in both the development and the progression of diabetic nephropathy we need effective strategies that prevent its loss or accelerate its regeneration. Such advances likely will lead not only to improved tissue oxygenation and reduced fibrosis, but also to improved long-term renal function.