Uncoupling of VEGF with NO as a mechanism for diabetic nephropathy

VEGF plays protective roles on a variety of non-diabetic renal diseases. However, in diabetes VEGF exhibits deleterious roles to mediate the development/progression of diabetic nephropathy in spite of high VEGF. The protective role of VEGF could be predominantly dependent on its ability to stimulate nitric oxide production in endothelial cell in non-diabetic renal disease. However, it has been known that nitric oxide bioavailability is reduced in diabetes, indicating that diabetic status does not allow high VEGF to lead to an increase in NO bioavailability. As a result, VEGF could engage to NO-independent pathway, and cause deleterious effects on vascular system. Thus, we have hypothesized that uncoupling of VEGF with endothelial NO can be a mechanism by which VEGF causes diabetic nephropathy. We found that diabetic eNOS knockout (KO) mice exhibit masangiolysis, glomerular capillary microaneurysm, Kimmelstiel-Wilson-like nodular lesions, abnormal angiogenesis and a marked macrophage infiltration in addition to mesangial expansion and thickening of GBM, all of that resemble human diabetic nephropathy. Interestingly these lesions were associated with an increase in renal VEGF expression, suggesting uncoupling of VEGF with endothelial NO could be a mechanism. Compatibly, our in vitro experiments demonstrated that VEGF-induced endothelial cell proliferation was enhanced by NO blocking (with LNAME) and suppressed by exogenous NO administration whereas macrophage migration in response to VEGF was inhibited by exogenous NO, suggesting that uncoupling condition could cause abnormal angiogenesis and macrophage infiltration.     

Association of VEGF-1499C-->T polymorphism with diabetic nephropathy in type 1 diabetes mellitus

Vascular endothelial growth factor (VEGF) is reported to be implicated in the development of diabetic nephropathy. We performed a case-control study to determine if VEGF-2578C-->A, VEGF-1499C-->T, and VEGF-635G-->C single-nucleotide polymorphisms (SNPs) in the VEGF gene are associated with predisposition to diabetic nephropathy in type 1 diabetes. Genomic DNA was obtained from Irish type 1 diabetic individuals with nephropathy (cases, n=242) and those without nephropathy (controls, n=301), in addition to 400 healthy control samples. These samples were genotyped for the three SNPs using TaqMan or Pyrosequencing technology. Chi-squared analyses revealed no significant differences in genotype or allele frequencies in cases versus controls for VEGF-2578C-->A (genotype, P=.58; allele, P=.52) and VEGF-635G-->C (genotype, P=.58; allele, P=.33). However, a positive association with diabetic nephropathy was observed for the VEGF-1499T allele in the Northern Ireland population (P <.001) and subsequently replicated in a separate population from the Republic of Ireland (P <.001; combined, P <.001). Carriage of the VEGF-1499T allele was associated with a twofold excess risk of developing diabetic nephropathy (OR=2.24, 95% CI=1.50-3.36, P <.0001). No significant differences were found between the healthy control population and the type 1 diabetic population. Our results suggest that the VEGF-1499T allele, or an allele in linkage disequilibrium with this allele, is associated with susceptibility to diabetic nephropathy in the Irish population.     

Plasma and urinary vascular endothelial growth factor and diabetic nephropathy in Type 2 diabetes mellitus.

AIMS: Vascular endothelial growth factor (VEGF) has been implicated in the pathogenesis of diabetes mellitus. We determined whether alterations of plasma and urinary VEGF levels are related to diabetic nephropathy in Type 2 diabetic patients. METHODS: One hundred and seven patients and 47 healthy controls were studied. Study subjects were divided into four groups using urinary albumin-to-creatinine ratio (ACR): a non-diabetic healthy control group (n = 47), a normoalbuminuric diabetic group (n = 37), a microalbuminuric diabetic group (n = 37) and an overt proteinuric diabetic group (n = 33). VEGF levels were measured by enzyme-linked immunosorbent assay. RESULTS: (i) Urinary VEGF concentrations were significantly higher in the diabetic groups, even at the normoalbuminuric stage (log VEGF/Cr, normoalbuminuria; 4.33 +/- 1.06 vs. control; 3.53 +/- 0.79, P = 0.009). Urinary VEGF excretions increased as diabetic nephropathy advanced. (ii) Plasma and urinary VEGF levels were higher in hypertensive diabetic patients than in the normotensive individuals with diabetes. (iii) In those with diabetes, plasma VEGF levels were found to be positively correlated with plasma urea (r = 0.398, P = 0.039) and urinary ACR (r = 0.251, P = 0.044), and urinary VEGF to be positively correlated with urinary ACR (r = 0.645, P < 0.001), and creatinine (r = 0.336, P = 0.009), and to be negatively correlated with serum albumin (r = -0.557, P < 0.001). Urinary VEGF and serum creatinine were independently correlated with urinary ACR. CONCLUSIONS: Urinary excretion of VEGF increased during the earlier stage of diabetic nephropathy and was significantly correlated with urinary albumin excretion. This suggests that urinary VEGF might be used as a sensitive marker of diabetic nephropathy and for predicting disease progression.     

Quantitave and qualitative changes in vascular endothelial growth factor gene expression in glomeruli of patients with type 2 diabetes

OBJECTIVE: Vascular endothelial growth factor (VEGF) exists in three main splice variants, characterized by 121, 165 and 189 amino acids (VEGF 121, VEGF 165 and VEGF 189) and acts via two specific receptors: VEGF-R1 or Flt-1 and VEGF-R2 or KDR. VEGF plays an important role in the pathogenesis of diabetic retinopathy. This study examined the relationship between VEGF and its isoforms and the severity of diabetic nephropathy in type 2 diabetes. DESIGN: We evaluated the glomerular gene expression of VEGF and its receptors and studied the relationships with renal functional and structural parameters in type 2 diabetic patients. METHODS: Glomeruli from 17 kidney biopsies were microdissected; 14 out of 17 biopsies were also subjected to electron microscopic morphometric analysis to estimate glomerular structural parameters. VEGF mRNA was studied by comparative kinetic RT-PCR and real-time RT-PCR in order to identify the three different isoforms and to quantify VEGF, VEGF-R1 and VEGF-R2 mRNA levels. RESULTS: (i) Glomerular VEGF mRNA levels were inversely related to albumin excretion rate (r=-0.66, P=0.004); (ii) both the degree of mesangial and mesangial matrix expansion were inversely related to VEGF 165 mRNA levels (r=-0.73, P=0.005 and r=-0.64, P=0.017), and directly to VEGF 121 mRNA levels (r=0.74, P=0.003 and r=0.73, P=0.004); and (iii) VEGF and VEGF-R2 mRNA levels were directly related (r=0.62, P=0.033). CONCLUSIONS: These findings suggested that quantitative and qualitative changes in VEGF expression are present in type 2 diabetic patients with nephropathy and might be involved in the pathogenesis and progression of diabetic glomerulopathy.     

Increases in Serum Lipids During Pregnancy in Type 1 Diabetic Women with Nephropathy

During pregnancy women with Type 1 diabetes do not differ from normal women with respect to pregnancy-associated changes in serum lipid levels. However influence of diabetic nephropathy on lipoprotein metabolism in pregnancy has not been described previously. Changes in lipids were compared during and after pregnancy in 10 Type 1 diabetic women without macroproteinuria as well as in 5 diabetic women with macroproteinuria due to diabetic nephropathy. In the pregnant women with macroproteinuria, compared to the diabetic women without macroproteinuria, we observed both significantly higher total and percent increases in serum levels of total cholesterol (97% versus 48%) and of LDL-cholesterol (137% versus 50%), which had risen progressively throughout gestation. The percent increases in serum triglycerides (115% versus 128%) were similar in both patient groups. Metabolic control was improved during pregnancy in both groups of women. Renal function remained normal throughout pregnancy in the diabetic women without nephropathy and worsened during pregnancy in the proteinuric women. The mean protein excretion showed a physiological rise from 0.107 ± 0.040 g 24 h^?1 before pregnancy to 0.336 ± 0.234 g 24 h^?1 in the third trimester in the non-proteinuric women, and an increase from 2.2 ± 1.0 to 7.1 ± 1.7 g 24 h^?1 during the same period in the women with macroproteinuria. Therefore, it is concluded that the greater increase in serum lipid levels during pregnancy in the women with pre-existing diabetic nephropathy can mainly be explained by the concomitant increase in proteinuria associated with development of the nephrotic syndrome in these patients.     

玻璃体内注射抗血管内皮生长因子药物对糖尿病肾脏损害的影响

目的:观察玻璃体内抗血管内皮生长因子(VEGF)治疗对糖尿病患者肾脏损害的影响。方法:收集2016年6月至2019年9月收治的接受璃体内抗VEGF治疗糖尿病视网膜病变(DR)后肾脏损害明显加重的患者,回顾性分析其临床、病理特征及预后。结果:共9例DR分期Ⅲ~Ⅴ期患者纳入本研究。玻璃体内抗VEGF治疗后,1例基线仅有高血压无蛋白尿的患者临床病理表现符合血栓性微血管病(TMA);1例基线有蛋白尿、无高血压的患者出现血压明显升高,肾脏病理表现糖尿病肾病(DN)。另7例基线有蛋白尿和高血压的患者均表现为肾脏损害加速进展,尿蛋白定量、血清肌酐(SCr)和血压较基线明显升高(2例行肾脏病理符合DN),1例合并急性心肌梗死。9例均需增加降压药物种类或剂量以维持血压平稳,1例TMA患者同时给予小剂量糖皮质激素治疗。9例患者中位随访14.9(4.5,21.5)月,1例TMA患者蛋白尿转阴,肾功能部分恢复;1例新发高血压患者SCr保持稳定;余7例肾功能持续进展,多次用药的4例患者中3例进展为终末期肾病。结论:DR患者玻璃体内抗VEGF治疗可加重肾脏损害和高血压,故在治疗前后应密切监测尿蛋白、肾功能和血压,关注可能的不良事件。     

血管内皮细胞生长因子基因多态性与糖尿病肾病的相关性

目的研究血管内皮细胞生长因子（VEGF）基因多态性与糖尿病肾病（DN）的关系。方法单纯2型糖尿病（DM）组76例,DN组81例,健康对照（NC）组60例。UNIQ-10柱提取全血基因组DNA。标本基因型的判断用聚合酶链反应-限制性酶切片断长度多态性技术。Hardy-Weinberg平衡法检验各组基因频率的群体代表性。结果（1）DN组VEGF-460和＋405CC基因型频率和C等位基因频率明显高于DM组和NC组。（2）-460位点CC基因型DN患病率明显高于CT和TT基因型。＋405位点CC基因型DN患病率明显高于CG和GG基因型。（3）显示VEGF-460和＋405基因多态性均为DN发生的独立危险因素。结论（1）VEGF-460C/T基因多态性与DN发生有关。C等位基因可能是DN易感基因。（2）VEGF＋405G/C基因多态性与DN发生有关。C等位基因可能是DN的易感基因。     

血管内皮生长因子基因3'-非翻译区C936T多态性与2型糖尿病肾病相关

采用PCR-RFLP方法分析了194例2型糖尿病患者血管内皮生长因子(VECF)基因3'-非翻译区C936T变异与糖尿病肾病的关系.发现糖尿病肾病组C等位基因及CC基因型频率显著高于非肾病组和正常对照组,提示C等位基因及CC基因型患者可能是糖尿病易于发生肾病危险性的遗传标志.     

Renal disease in relatives of Indo-Asian Type 2 diabetic patients with end-stage diabetic nephropathy

AIMS/HYPOTHESIS: Indo-Asian immigrants in The Hague, The Netherlands, have a nearly 40-fold higher risk of end-stage diabetic nephropathy compared to the Caucasian population. To detect a genetic susceptibility for nephropathy within the Indo-Asian population, we assessed whether familial clustering of nephropathy occurs in families of Indo-Asian Type 2 diabetic patients. METHODS: We compared nephropathy prevalence between two groups of first-degree relatives of Indo-Asian patients with Type 2 diabetes; the first group (case relatives) consisted of 169 relatives of patients with end-stage diabetic nephropathy; the second group (control relatives) consisted of 161 relatives of diabetic patients who had no nephropathy. The case and control relatives were examined for diabetes, blood pressure, renal function, microalbuminuria and urine dipstick measurements. RESULTS: The mean age was 41 years and similar in the case and control relatives. Diabetes was distributed equally in both family groups. We did not find more nephropathy in first-degree relatives of Indo-Asian Type 2 diabetic patients with end-stage diabetic nephropathy in comparison with the control-relatives. CONCLUSION/INTERPRETATION: We could not detect a genetic susceptibility for diabetic nephropathy within the Indo-Asian population. The lack of familial clustering of renal disease in Indo-Asian diabetic patients points to a general genetic or environmental susceptibility for diabetic nephropathy in this population.     

Vascular endothelial growth factor and diabetic nephropathy

The field of vascular endothelial growth factor (VEGF) has recently witnessed a surge of research into its role in diabetic kidney disease. Based on its credentials as a potent inducer of vasopermeability and angiogenesis, podocyte-derived VEGF is believed to participate in the glomerular capillary hyperpermeability of macromolecules that potentially underlies the pathogenesis of diabetic albuminuria. The evidence for VEGF’s role is relatively straightforward in animal models of diabetes, establishing that VEGF is upregulated in the diabetic kidney, that VEGF alone reproduces some aspects of diabetic glomerulopathy, and that antagonism of VEGF attenuates diabetic albuminuria and other associated features of the podocytopathy. However, the promise shown in the animal studies has not carried over as convincingly into the realm of human studies, as some investigators find a negative or no relationship between VEGF and diabetic nephropathy, whereas others find a positive correlation between the two. If VEGF does play a role in diabetic renal disease, its observed effects and known mechanisms seem to point squarely at the podocyte as a central target of the maladaptive VEGF overactivity.     

VEGF和色素上皮衍生因子的表达失衡对糖尿病肾病的影响

建立链脲佐菌素诱导的糖尿病大鼠模型,用免疫组化法观察肾小管间质血管内皮生长因子(VEGF)和色素上皮衍生因子(PEDF)的表达变化;体外培养大鼠肾成纤维细胞(NRK),用RT-PCR检测高糖对VEGF和PEDF mRNA表达的影响.结果 显示糖尿病大鼠肾脏组织VEGF表达增加,而PEDF表达下降.在NRK细胞,高糖呈时间、剂量依赖性地增加VEGF和抑制PEDF的mRNA表达.提示VEGF和PEDF的表达失衡可能在糖尿病肾病的发生发展中起一定作用.     

No association between MTHFR gene polymorphism and diabetic nephropathy in Japanese type II diabetic patients with proliferative diabetic retinopathy

The development of diabetic nephropathy shows marked variation among individuals. Not only hyperglycemia, but also genetic factors may contribute to the development of diabetic nephropathy. Methylenetetrahydrofolate reductase (MTHFR) is involved in remethylation of homocysteine to methionine. Decreased activity of MTHFR which can result in hyperhomocysteinemia may lead to cerebrovascular disease and coronary artery disease. Recently, a common C to T mutation at nucleotide position 677 of the MTHFR gene (MTHFR677C>T) has been reported to be correlated with hyperhomocysteinemia and the severity of coronary artery disease as macroangiopathy. In the present study, we recruited 173 of Japanese type II diabetic patients with proliferative diabetic retinopathy who would be exposed to long-term hyperglycemia, and examined the contribution of the MTHFR gene polymorphism to the development of diabetic nephropathy as microangiopathy. The frequency of the mutated allele was 43.3% in patients with nephropathy (n = 105) versus 41.9% in those without nephropathy (n = 68). The genotype frequencies were +/+, 16.2%; +/−, 54.3%; −/−, 29.5% in patients with nephropathy versus +/+, 13.2%; +/−, 57.4%; −/−, 29.4% in those without nephropathy (+ indicates the presence of the mutation). The MTHFR genotype and allele frequencies were not significantly different between patients with and without nephropathy. Therefore, we conclude that the MTHFR gene polymorphism is not associated with the development of diabetic nephropathy in Japanese type II diabetic patients.     

Down-regulation of angiogenic inhibitors: a potential pathogenic mechanism for diabetic complications

Diabetic retinopathy (DR) and diabetic nephropathy (DN) are the most common microvascular complications of diabetes. DR is a leading cause of blindness, and DN is a major cause of end-stage renal diseases. Diabetic macular edema (DME) resulting from increased vascular permeability in the retina and retinal neovascularization (NV) represent two major pathological changes in DR and are the primary causes of vision loss in diabetic patients. Previous studies have shown that angiogenic factors such as vascular endothelial growth factor (VEGF) play a key role in the development of DME and retinal NV. Studies in recent years have demonstrated that a number of endogenous angiogenic inhibitors are present in the normal retina and counter act the effect of VEGF in the regulation of angiogenesis and vascular permeability. Decreased levels of angiogenic inhibitors in the vitreous and retina have been found in diabetic patients and diabetic animal models. The decreased levels of angiogenic inhibitors shift the balance between angiogenic factors and angiogenic inhibitors and consequently, lead to the development of DME and retinal NV. Recently, we have found that these angiogenic inhibitors are expressed at high levels in the normal kidney and are down-regulated in diabetes. Moreover, these inhibitors inhibit the activity of VEGF and TGF-beta, two major pathogenic factors of DN. Therefore, decreased levels of these angiogenic inhibitors in diabetes may be associated with pathologies of DN. This review will summarize recent progress in these fields and therapeutic approaches to use angiogenic inhibitors for the treatment of diabetic complications.     

The DD genotype of the ACE gene polymorphism is associated with diabetic nephropathy in the type-1 diabetics.

Genetic factors are involved in the development of diabetic nephropathy in type-1 diabetes. We are examining the association of the angiotensin-converting enzyme (ACE), insertion/deletion (I/D) polymorphism with the presence of diabetic nephropathy in type-1 diabetic patients. 52 type-1 diabetic patients with diabetic nephropathy (30 with either microalbuminuria or macroalbuminuria and 22 with end stage renal disease on dialysis) were compared with 10 type-1 diabetic patients with normoalbuminuria and duration of disease longer than 15 years and 27 non-diabetic healthy subjects. We found that the D-allele frequency was higher in patients with nephropathy than in the healthy and normoalbuminuric controls. There was an association in the DD polymorphism of the ACE gene with patients with diabetic nephropathy and not with the control subjects. We conclude that the DD genotype of ACE gene polymorphism is associated with diabetic nephropathy in patients with type-1 diabetes mellitus.     

The Family Investigation of Nephropathy and Diabetes (FIND): design and methods

BACKGROUND: The Family Investigation of Nephropathy and Diabetes (FIND) is a multicenter study designed to identify genetic determinants of diabetic nephropathy. It is conducted in eight U.S. clinical centers and a coordinating center, and with four ethnic groups (European Americans, African Americans, Mexican Americans, and American Indians). Two strategies are used to localize susceptibility genes: a family-based linkage study and a case-control study using mapping by admixture linkage disequilibrium (MALD). METHODS: In the family-based study, probands with diabetic nephropathy are recruited with their parents and selected siblings. Linkage analyses will be conducted to identify chromosomal regions containing genes that influence the development of diabetic nephropathy or related quantitative traits such as serum creatinine concentration, urinary albumin excretion, and plasma glucose concentrations. Regions showing evidence of linkage will be examined further with both genetic linkage and association studies to identify genes that influence diabetic nephropathy or related traits. Two types of MALD studies are being done. One is a case-control study of unrelated individuals of Mexican American heritage in which both cases and controls have diabetes, but only the case has nephropathy. The other is a case-control study of African American patients with nephropathy (cases) and their spouses (controls) unaffected by diabetes and nephropathy; offspring are genotyped when available to provide haplotype data. CONCLUSIONS: Identification of genes that influence susceptibility to diabetic nephropathy will lead to a better understanding of how nephropathy develops. This should eventually lead to improved treatment and prevention.     

PEDF对人肾小球系膜细胞VEGF表达及活性氧簇产生的影响

观察不同浓度高糖培养下及人重组色素上皮衍生因子(PEDF)干预后人肾小球系膜细胞活性氧簇水平、血管内皮生长因子(VEGF)mRNA和蛋白的改变.结果 显示活性氧簇水平、VEGF mRNA和蛋白的表达随糖浓度的升高而增加;PEDF干预后,高糖环境下活性氧簇水平及VEGF的表达明显下降,且呈浓度依赖性.提示PEDF可能通过改善血管通透性和抑制氧化应激延缓糖尿病肾病的进展.     

High serum TNF-alpha level in Type 2 diabetic patients with microangiopathy is associated with eNOS down-regulation and apoptosis in endothelial cells

A high dose of tumor necrosis factor (TNF)-alpha induces endothelial dysfunction and enhances apoptosis in vitro. The present study was conducted to examine whether incubating human umbilical vein endothelial cells (HUVECs) with serum from Type 2 diabetic patients complicated with retinopathy and/or microalbuminemia demonstrate endothelial dysfunction. Serum levels of TNF-alpha and vascular endothelial growth factor (VEGF) were elevated in diabetic patients. Plasma levels of TNF-alpha, two soluble TNF-alpha receptors (sTNFR), and VEGF were assessed in diabetic patients (CD, n=21) complicated with retinopathy and/or nephropathy, uncomplicated diabetic patients (UD, n=18), and in healthy normal participants (NS, n=16). In HUVECs incubated with patient's serum, endothelial constitutive nitric oxide synthase (eNOS) protein expressions were measured by Western blot analysis. Apoptosis in HUVECs was determined by optical microscopy, DNA fragmentation, and CPP32-like protease activity. Serum TNF-alpha, sTNFR-I, and asymmetric dimethylarginine (ADMA), an endogenous inhibitor of NOS, in CD were significantly higher than in UD or NS. While, serum sTNFR-I and VEGF levels were significantly increased in the both diabetic patients, compared with those of NS, no difference was observed in the serum TNF-alpha, sTNFR-II, and ADMA levels between UD and NS. eNOS down-regulation and apoptosis were seen in HUVECs incubated with serum from CD for 24 h, but those observations were completely counteracted in the incubation by the addition of the antihuman TNF-alpha antibody. These results imply that eNOS down-regulation in CD is associated with high serum TNF-alpha levels despite of high serum of VEGF levels. Therefore, endothelial dysfunction in diabetic patients complicated with microangiopathy may, in part, be attributed to high serum TNF-alpha levels.     

Putative pathophysiological role of growth factors and cytokines in experimental diabetic kidney disease

The development of diabetic nephropathy in patients with Type I (insulin-dependent) and Type II (non-insulin-dependent) diabetes mellitus is still a huge clinical problem associated with increased morbidity and mortality. The mechanisms underlying the development of diabetic kidney disease are extremely complex and yet not completely understood. Among many potential pathogenic mechanisms responsible for the development of diabetic kidney disease, various growth factors have been suggested to be important players. In particular, growth hormone (GH)/insulin-like growth factors (IGFs), transforming growth factor β (TGF-β), vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF) have measurable effects on the development of experimental diabetic kidney disease through complex intra-renal systems. Recent findings that these growth factors might initiate the early diabetic renal changes have provided insight into processes that might be relevant for future development of new drugs useful in the treatment of diabetic kidney disease. As will appear from the present review, enhanced understanding of the cellular mechanisms responsible for the development of diabetic kidney disease has already allowed the design of specific antagonists of pathophysiologically increased growth factors. Recent studies have shown that treating experimental diabetic models with such antagonists is followed by renoprotection. [Diabetologia (2000) 43: 1205–1223]