Reduction in podocyte density as a pathologic feature in early diabetic nephropathy in rodents: Prevention by lipoic acid treatment

BACKGROUND: A reduction in the number of podocytes and podocyte density has been documented in the kidneys of patients with diabetes mellitus. Additional studies have shown that podocyte injury and loss occurs in both diabetic animals and humans. However, most studies in animals have examined relatively long-term changes in podocyte number and density and have not examined effects early after initiation of diabetes. We hypothesized that streptozotocin diabetes in rats and mice would result in an early reduction in podocyte density and that this reduction would be prevented by antioxidants. METHODS: The number of podocytes per glomerular section and the podocyte density in glomeruli from rats and mice with streptozotocin (STZ)-diabetes mellitus was determined at several time points based on detection of the glomerular podocyte specific antigens, WT-1 and GLEPP1. The effect of insulin administration or treatment with the antioxidant, α-lipoic acid, on podocyte number was assessed. RESULTS: Experimental diabetes resulted in a rapid decline in apparent podocyte number and podocyte density. A significant reduction in podocytes/glomerular cross-section was found in STZ diabetes in rats at 2 weeks (14%), 6 weeks (18%) and 8 weeks (34%) following STZ injection. Similar declines in apparent podocyte number were found in STZ diabetes in C57BL/6 mice at 2 weeks, but not at 3 days after injection. Treatment with α-lipoic acid substantially prevented podocyte loss in diabetic rats but treatment with insulin had only a modest effect. CONCLUSION: STZ diabetes results in reduction in apparent podocyte number and in podocyte density within 2 weeks after onset of hyperglycemia. Prevention of these effects with antioxidant therapy suggests that this early reduction in podocyte density is due in part to increased levels of reactive oxygen species as well as hyperglycemia

'Correction:' Serum transforming growth factor beta-1 (TGF-beta-1) levels in diabetic patients are not associated with pre-existent coronary artery disease

<p>Abstract</p> <p>Background</p> <p>The association between TGF-β1 levels and long-term major adverse cardiovascular events (MACE) in patients with coronary artery disease (CAD) is controversial. No study specifically addressed patients with CAD and diabetes mellitus (DM). The association between TGF-β1 levels and long-term major adverse cardiovascular events (MACE) in patients with coronary artery disease (CAD) is controversial. No study specifically addressed patients with CAD and diabetes mellitus (DM).</p> <p>Methods</p> <p>Patients (n = 135, 30–80 years) referred for coronary angiography were submitted to clinical and laboratory evaluation, and the coronary angiograms were evaluated by two operators blinded to clinical characteristics. CAD was defined as the presence of a 70% stenosis in one major coronary artery, and DM was characterized as a fasting glycemia > 126 mg/dl or known diabetics (personal history of diabetes or previous use of anti-hyperglycemic drugs or insulin). Based on these criteria, study patients were classified into four groups: no DM and no CAD (controls, C n = 61), DM without CAD (D n = 23), CAD without DM (C-CAD n = 28), and CAD with DM (D-CAD n = 23). Baseline differences between the 4 groups were evaluated by the χ²test for trend (categorical variables) and by ANOVA (continuous variables, post-hoc Tukey). Patients were then followed-up during two years for the occurrence of MACE (cardiac death, stroke, myocardial infarction or myocardial revascularization). The association of candidate variables with the occurrence of 2-year MACE was assessed by univariate analysis.</p> <p>Results</p> <p>The mean age was 58.2 ± 0.9 years, and 51% were men. Patients with CAD had a higher mean age (p = 0.011) and a higher percentage were male (p = 0.040). There were no significant baseline differences between the 4 groups regarding hypertension, smoking status, blood pressure levels, lipid levels or inflammatory markers. TGF-β1 was similar between patients with or without CAD or DM (35.1 ×/÷ 1.3, 33.6 ×/÷ 1.6, 33.9 ×/÷ 1.4 and 31.8 ×/÷ 1.4 ng/ml in C, D, C-CAD and D-CAD, respectively, p = 0.547). In the 2-year follow-ip, independent predictors of 2-year MACE were age (p = 0.007), C-reactive protein (p = 0.048) and systolic blood pressure (p = 0.008), but not TGF-β1.</p> <p>Conclusion</p> <p>Serum TGF-β1 was not associated with CAD or MACE occurrence in patients with or without DM.</p

Association of TGFβ1, TNFα, CCR2 and CCR5 gene polymorphisms in type-2 diabetes and renal insufficiency among Asian Indians

BACKGROUND: Cytokines play an important role in the development of diabetic chronic renal insufficiency (CRI). Transforming growth factor β1 (TGF β1) induces renal hypertrophy and fibrosis, and cytokines like tumor necrosis factor-alpha (TNFα), chemoattractant protein-1 (MCP-1), and regulated upon activation and normal T cell expressed and secreted (RANTES) mediate macrophage infiltration into kidney. Over expression of these chemokines leads to glomerulosclerosis and interstitial fibrosis. The effect of MCP-1 and RANTES on kidney is conferred by their receptors i.e., chemokine receptor (CCR)-2 and CCR-5 respectively. We tested association of nine single nucleotide polymorphisms (SNPs) from TGFβ1, TNFα, CCR2 and CCR5 genes among individuals with type-2 diabetes with and without renal insufficiency. METHODS: Type-2 diabetes subjects with chronic renal insufficiency (serum creatinine ≥ 3.0 mg/dl) constituted the cases, and matched individuals with diabetes of duration ≥ 10 years and normoalbuminuria were evaluated as controls from four centres in India. Allelic and genotypic contributions of nine SNPs from TGFβ1, TNFα, CCR2 and CCR5 genes to diabetic CRI were tested by computing odds ratio (OR) and 95% confidence intervals (CI). Sub-analysis of CRI cases diabetic retinopathy status as dependent variable and SNP genotypes as independent variable in a univariate logistic regression was also performed. RESULTS: SNPs Tyr81His and Thr263Ile in TGF β1 gene were monomorphic, and Arg25Pro in TGF β1 gene and Δ32 polymorphism in CCR5 gene were minor variants (minor allele frequency <0.05) and therefore were not considered for case-control analysis. A significant allelic association of 59029G>A SNP of CCR5 gene has been observed and the allele 59029A seems to confer predisposition to development of diabetic CRI (OR 1.39; CI 1.04–1.84). In CRI subjects a compound group of genotypes "GA and AA" of SNP G>A -800 was found to confer predisposition for proliferative retinopathy (OR 3.03; CI 1.08–8.50, p = 0.035). CONCLUSION: Of the various cytokine gene polymorphisms tested, allele 59029A of CCR5 gene is significantly associated with diabetic renal insufficiency among Asian Indians. Result obtained for 59029G>A SNP of CCR5 gene is in conformity with reports from a Japanese population but due to sub-optimal power of the sample, replication in larger sample set is warranted

SLC2A10 genetic polymorphism predicts development of peripheral arterial disease in patients with type 2 diabetes. SLC2A10 and PAD in type 2 diabetes

<p>Abstract</p> <p>Background</p> <p>Recent data indicate that loss-of-function mutation in the gene encoding the facilitative glucose transporter GLUT10 (<it>SLC2A10</it>) causes arterial tortuosity syndrome via upregulation of the TGF-β pathway in the arterial wall, a mechanism possibly causing vascular changes in diabetes.</p> <p>Methods</p> <p>We genotyped 10 single nucleotide polymorphisms and one microsatellite spanning 34 kb across the <it>SLC2A10 </it>gene in a prospective cohort of 372 diabetic patients. Their association with the development of peripheral arterial disease (PAD) in type 2 diabetic patients was analyzed.</p> <p>Results</p> <p>At baseline, several common SNPs of <it>SLC2A10 </it>gene were associated with PAD in type 2 diabetic patients. A common haplotype was associated with higher risk of PAD in type 2 diabetic patients (haplotype frequency: 6.3%, <it>P </it>= 0.03; odds ratio [OR]: 14.5; 95% confidence interval [CI]: 1.3- 160.7) at baseline. Over an average follow-up period of 5.7 years, carriers with the risk-conferring haplotype were more likely to develop PAD (<it>P </it>= 0.007; hazard ratio: 6.78; 95% CI: 1.66- 27.6) than were non-carriers. These associations remained significant after adjustment for other risk factors of PAD.</p> <p>Conclusion</p> <p>Our data demonstrate that genetic polymorphism of the <it>SLC2A10 </it>gene is an independent risk factor for PAD in type 2 diabetes.</p

Resequencing of genes for transforming growth factor β1 (TGFB1) type 1 and 2 receptors (TGFBR1, TGFBR2), and association analysis of variants with diabetic nephropathy

BACKGROUND: Diabetic nephropathy is the leading cause of end stage renal failure in the western world. There is substantial epidemiological evidence supporting a genetic predisposition to diabetic nephropathy, however the exact molecular mechanisms remain unknown. Transforming growth factor (TGFβ1) is a crucial mediator in the pathogenesis of diabetic nephropathy. METHODS: We investigated the role of five known single nucleotide polymorphisms (SNPs) in the TGFB1 gene for their association with diabetic nephropathy in an Irish, type 1 diabetic case (n = 272) control (n = 367) collection. The activity of TGFβ1 is facilitated by the action of type 1 and type 2 receptors, with both receptor genes (TGFBR1 and TGFBR2) shown to be upregulated in diabetic kidney disease. We therefore screened TGFBR1 and TGFBR2 genes for genomic variants using WAVE™ (dHPLC) technology and confirmed variants by direct capillary sequencing. Allele frequencies were determined in forty-eight healthy individuals. Data for all SNPs was assessed for Hardy Weinberg equilibrium, with genotypes and allele frequencies compared using the χ(2 )test for contingency tables. Patterns of linkage disequilibrium were established and common haplotypes estimated. RESULTS: Fifteen variants were identified in these genes, seven of which are novel, and putatively functional SNPs were subsequently genotyped using TaqMan™, Invader™ or Pyrosequencing(® )technology. No significant differences (p > 0.1) were found in genotype or allele distributions between cases and controls for any of the SNPs assessed. CONCLUSION: Our results suggest common variants in TGFB1, TGFBR1 and TGFBR2 genes do not strongly influence genetic susceptibility to diabetic nephropathy in an Irish Caucasian population

Oral Administration of GW788388, an Inhibitor of Transforming Growth Factor Beta Signaling, Prevents Heart Fibrosis in Chagas Disease

Cardiac damage and dysfunction are prominent features in patients with chronic Chagas disease, which is caused by infection with the protozoan parasite Trypanosoma cruzi (T. cruzi) and affects 10–12 million individuals in South and Central America. Our group previously reported that transforming growth factor beta (TGFß) is implicated in several regulatory aspects of T. cruzi invasion and growth and in host tissue fibrosis. In the present work, we evaluated the therapeutic action of an oral inhibitor of TGFß signaling (GW788388) administered during the acute phase of experimental Chagas disease. GW788388 treatment significantly reduced mortality and decreased parasitemia. Electrocardiography showed that GW788388 treatment was effective in protecting the cardiac conduction system, preserving gap junction plaque distribution and avoiding the development of cardiac fibrosis. Inhibition of TGFß signaling in vivo appears to potently decrease T. cruzi infection and to prevent heart damage in a preclinical mouse model. This suggests that this class of molecules may represent a new therapeutic tool for acute and chronic Chagas disease that warrants further pre-clinical exploration. Administration of TGFß inhibitors during chronic infection in mouse models should be further evaluated, and future clinical trials should be envisaged

Mechanisms and consequences of TGF-ß overexpression by podocytes in progressive podocyte disease

In patients with progressive podocyte disease, such as focal segmental glomerulosclerosis (FSGS) and membranous nephropathy, upregulation of transforming growth factor-ß (TGF-ß) is observed in podocytes. Mechanical pressure or biomechanical strain in podocytopathies may cause overexpression of TGF-ß and angiotensin II (Ang II). Oxidative stress induced by Ang II may activate the latent TGF-ß, which then activates Smads and Ras/extracellular signal-regulated kinase (ERK) signaling pathways in podocytes. Enhanced TGF-ß activity in podocytes may lead to thickening of the glomerular basement membrane (GBM) by overproduction of GBM proteins and impaired GBM degradation in podocyte disease. It may also lead to podocyte apoptosis and detachment from the GBM, and epithelial-mesenchymal transition (EMT) of podocytes, initiating the development of glomerulosclerosis. Furthermore, activated TGF-ß/Smad signaling by podocytes may induce connective tissue growth factor and vascular endothelial growth factor overexpression, which could act as a paracrine effector mechanism on mesangial cells to stimulate mesangial matrix synthesis. In proliferative podocytopathies, such as cellular or collapsing FSGS, TGF-ß-induced ERK activation may play a role in podocyte proliferation, possibly via TGF-ß-induced EMT of podocytes. Collectively, these data bring new mechanistic insights into our understanding of the TGF-ß overexpression by podocytes in progressive podocyte disease

Geldanamycin Derivative Ameliorates High Fat Diet-Induced Renal Failure in Diabetes

Diabetic nephropathy is a serious complication of longstanding diabetes and its pathogenesis remains unclear. Oxidative stress may play a critical role in the pathogenesis and progression of diabetic nephropathy. Our previous studies have demonstrated that polyunsaturated fatty acids (PUFA) induce peroxynitrite generation in primary human kidney mesangial cells and heat shock protein 90β1 (hsp90β1) is indispensable for the PUFA action. Here we investigated the effects of high fat diet (HFD) on kidney function and structure of db/db mice, a widely used rodent model of type 2 diabetes. Our results indicated that HFD dramatically increased the 24 h-urine output and worsened albuminuria in db/db mice. Discontinuation of HFD reversed the exacerbated albuminuria but not the increased urine output. Prolonged HFD feeding resulted in early death of db/db mice, which was associated with oliguria and anuria. Treatment with the geldanamycin derivative, 17-(dimethylaminoehtylamino)-17-demethoxygeldanamycin (17-DMAG), an hsp90 inhibitor, preserved kidney function, and ameliorated glomerular and tubular damage by HFD. 17-DMAG also significantly extended survival of the animals and protected them from the high mortality associated with renal failure. The benefit effect of 17-DMAG on renal function and structure was associated with a decreased level of kidney nitrotyrosine and a diminished kidney mitochondrial Ca2+ efflux in HFD-fed db/db mice. These results suggest that hsp90β1 is a potential target for the treatment of nephropathy and renal failure in diabetes

Connective tissue growth factor(CCN2), a pathogenic factor in diabetic nephropathy. What does it do? How does it do it?

Connective tissue growth factor (CTGF/CCN2) is a member of the CCN family of matricellular proteins. Its expression is induced by a number of factors including TGF-β. It has been associated with fibrosis in various tissues including the kidney. Diabetic nephropathy (DN) develops in about 30% of patients with diabetes and is characterized by thickening of renal basement membranes, fibrosis in the glomerulus (glomerulosclerosis), tubular atrophy and interstitial fibrosis, all of which compromise kidney function. This review examines changes in CTGF expression in the kidney in DN, the effects they have on glomerular mesangial and podocyte cells and the tubulointerstitium, and how these contribute to driving fibrotic changes in the disease. CTGF can bind to several other growth factors modifying their function. CTGF is also able to interact with receptors on cells, including integrins, tyrosine receptor kinase A (TrkA), low density lipoprotein receptor-related protein (LRP) and heparan sulphate proteoglycans. These interactions, the intracellular signalling pathways they activate, and the cellular responses evoked are reviewed. CTGF also induces the expression of chemokines which themselves have pharmacological actions on cells. CTGF may prompt some responses by acting through several different mechanisms, possibly simultaneously. For example, CTGF is often described as an effector of TGF-β. It can promote TGF-β signalling by binding directly to the growth factor, promoting its interaction with the TGF-β receptor; by triggering intracellular signalling on binding the TrkA receptor, which leads to the transcriptional repression of Smad7, an inhibitor of the TGF-β signalling pathway; and by binding to BMP-7 whose own signalling pathway opposing TGF-β is inhibited, leading to enhanced TGF-β signalling