nephrin and Hypertrophy

Diabetic kidney disease (DKD) is one of the leading pathological causes of decreased renal function and progression to end-stage kidney failure. To explore and characterize age-related changes in DKD and associated glomerular damage, we used a rat model of type 2 diabetic nephropathy (T2DN) at 12 wk and older than 48 wk. We compared their disease progression with control nondiabetic Wistar and diabetic Goto-Kakizaki (GK) rats. During the early stages of DKD, T2DN and GK animals revealed significant increases in blood glucose and kidney-to-body weight ratio. Both diabetic groups had significantly altered renin-angiotensin-aldosterone system function. Thereafter, during the later stages of disease progression, T2DN rats demonstrated a remarkable increase in renal damage compared with GK and Wistar rats, as indicated by renal hypertrophy, polyuria accompanied by a decrease in urine osmolarity, high cholesterol, a significant prevalence of medullary protein casts, and severe forms of glomerular injury. Urinary nephrin shedding indicated loss of the glomerular slit diaphragm, which also correlates with the dramatic elevation in albuminuria and loss of podocin staining in aged T2DN rats. Furthermore, we used scanning ion microscopy topographical analyses to detect and quantify the pathological remodeling in podocyte foot projections of isolated glomeruli from T2DN animals. In summary, T2DN rats developed renal and physiological abnormalities similar to clinical observations in human patients with DKD, including progressive glomerular damage and a significant decrease in renin-angiotensin-aldosterone system plasma levels, indicating these rats are an excellent model for studying the progression of renal damage in type 2 DKD.

Topics: Aging; Albuminuria; Animals; Blood Glucose; Diabetes Mellitus, Type 2; Diabetic Nephropathies; Disease Progression; Hypertrophy; Kidney Glomerulus; Male; Membrane Proteins; Organ Size; Polyuria; Rats; Rats, Wistar; Renin-Angiotensin System; Water-Electrolyte Imbalance

This study aimed to investigate the effects of aspirin on podocyte injury and its underlying mechanisms in diabetic nephropathy (DN).. Eight-week-old male Sprague-Dawley rats were divided into three groups: non-diabetic rats (Control), streptozotocin-induced diabetic rats (DM), and diabetic rats treated with aspirin (DM + Aspirin) for 12 weeks. Intracellular lipid accumulation was evaluated by Oil Red O staining and quantitative free cholesterol assays. Podocyte injury and the levels of COX-2, inflammatory cytokines, and low-density lipoprotein receptor (LDLr) pathway-related proteins were evaluated by electron microscopy, immunohistochemical staining, and Western blotting, respectively.. Lipid levels and urinary albumin-creatinine ratios were higher in the DM rats than in the Control rats. Periodic acid-Schiff staining showed glomerular hypertrophy and mild mesangial area widening in the DM rats. Electron microscopy showed that the podocyte foot processes were significantly flattened or absent in the DM rats. The protein expression levels of WT-1 and nephrin in the podocytes of DM rats were reduced. Interestingly, lipid accumulation in the kidneys of DM rats was significantly increased due to increased protein expression levels of LDLr, sterol regulatory element-binding protein (SREBP) cleavage-activating protein (SCAP), SREBP-2, cyclooxygenase-2 (COX-2), and inflammatory cytokines. Confocal immunofluorescent staining showed that COX-2 and WT-1 were co-expressed. Furthermore, COX-2 protein expression levels were positively correlated with LDLr protein expression levels. However, when COX-2 expression was inhibited by aspirin, these changes in the DM rats were significantly attenuated.. Aspirin attenuates podocyte injury in DN, which may be through COX-2-mediated dysregulation of LDLr pathway.

Topics: Albuminuria; Animals; Aspirin; Creatinine; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Cytokines; Diabetes Mellitus, Experimental; Glomerular Mesangium; Hypertrophy; Male; Membrane Proteins; Podocytes; Rats; Rats, Sprague-Dawley; Receptors, LDL; Sterol Regulatory Element Binding Proteins; WT1 Proteins

Hypertrophy is a prominent feature of damaged podocytes in diabetic kidney disease (DKD). mTORC1 hyperactivation leads to podocyte hypertrophy, but the detailed mechanism of how mTORC1 activation occurs under pathological conditions is not completely known. Moreover, reduced nephrin tyrosine phosphorylation has been observed in podocytes under pathological conditions, but the molecular mechanism linking nephrin phosphorylation and pathology is unclear so far. In this study, we observed a significant increase in C1-Ten level in diabetic kidney and in high glucose-induced damaged podocytes. C1-Ten acts as a protein tyrosine phosphatase (PTPase) at the nephrin-PI3K binding site and renders PI3K for IRS-1, thereby activating mTORC1. Furthermore, C1-Ten causes podocyte hypertrophy and proteinuria by increasing mTORC1 activity in vitro and in vivo. These findings demonstrate the relationship between nephrin dephosphorylation and the mTORC1 pathway, mediated by C1-Ten PTPase activity. We suggest that C1-Ten contributes to the pathogenesis of DKD by inducing podocyte hypertrophy under high glucose conditions.

Topics: Animals; Diabetic Nephropathies; Glucose; HEK293 Cells; Humans; Hypertrophy; Insulin Receptor Substrate Proteins; Male; Mechanistic Target of Rapamycin Complex 1; Membrane Proteins; Mice; Phosphatidylinositol 3-Kinases; Phosphorylation; Podocytes; Protein Tyrosine Phosphatases; Proteinuria; Signal Transduction; Tensins

The predominant transcription factors regulating key genes in diabetic kidney disease have not been established. The transcription factor upstream stimulatory factor 1 (USF1) is an important regulator of glucose-mediated transforming growth factor (TGF)-β1 expression in mesangial cells; however, its role in the development of diabetic kidney disease has not been evaluated. In the present study, wild-type (WT; USF1 +/+), heterozygous (USF1 +/-), and homozygous (USF1 -/-) knockout mice were intercrossed with Akita mice (Ins2/Akita) to induce type 1 diabetes. Mice were studied up to 36 wk of age. The degree of hyperglycemia and kidney hypertrophy were similar in all groups of diabetic mice; however, the USF1 -/- diabetic mice had significantly less albuminuria and mesangial matrix expansion than the WT diabetic mice. TGF-β1 and renin gene expression and protein were substantially increased in the WT diabetic mice but not in USF1 -/- diabetic mice. The underlying pathway by which USF1 is regulated by high glucose was investigated in mesangial cell culture. High glucose inhibited AMP-activated protein kinase (AMPK) activity and increased USF1 nuclear translocation. Activation of AMPK with AICAR stimulated AMPK activity and reduced nuclear accumulation of USF1. We thus conclude that USF1 is a critical transcription factor regulating diabetic kidney disease and plays a critical role in albuminuria, mesangial matrix accumulation, and TGF-β1 and renin stimulation in diabetic kidney disease. AMPK activity may play a key role in high glucose-induced regulation of USF1.

Topics: Albuminuria; Alleles; AMP-Activated Protein Kinases; Animals; Cell Line; Cell Nucleus; Diabetes Mellitus, Type 1; Diabetic Nephropathies; Disease Progression; Extracellular Matrix; Female; Hyperglycemia; Hypertrophy; Kidney; Male; Membrane Proteins; Mice; Mice, Inbred C57BL; Mice, Knockout; Renin-Angiotensin System; RNA, Messenger; Transforming Growth Factor beta; Upstream Stimulatory Factors

Periodontitis was shown to have an impact on glucose levels in prediabetic and diabetic rats. The Zucker fatty rat (ZFR) is a well-characterized model of prediabetes presenting with impaired glucose tolerance, hyperinsulinemia, dyslipidemia, and moderate hypertension. The aim of the present study was to investigate whether periodontitis influences kidney changes in ZFRs.. Male adult ZFRs (N = 19) and their lean littermates (N = 18) were studied. Periodontitis was induced with ligatures in half of the ZFRs and lean rats, whereas the other half served as controls. After 4 weeks, the rats were sacrificed, and the kidneys, liver, and heart were removed and weighed. Kidneys were evaluated histologically for glomerular volume and renal mRNA levels of vascular endothelial growth factor (VEGF), VEGF receptor 2, transforming growth factor-beta, connective tissue growth factor, collagen IValpha1, fibronectin, and nephrin. Urinary albumin excretion and creatinine clearance were also evaluated.. In prediabetic ZFRs, periodontitis was associated with kidney hypertrophy (P = 0.03) and a tendency for increased glomerular volume (P = 0.06). In lean littermates, elevated fibronectin mRNA levels (P = 0.03) were noted in the presence of periodontitis.. Our findings suggest the participation of periodontitis in the development of early renal changes in ZFRs.

Topics: Albuminuria; Animals; Collagen Type IV; Connective Tissue Growth Factor; Creatinine; Fibronectins; Hypertrophy; Immediate-Early Proteins; Insulin-Like Growth Factor Binding Proteins; Intercellular Signaling Peptides and Proteins; Kidney; Kidney Diseases; Kidney Glomerulus; Male; Membrane Proteins; Organ Size; Periodontitis; Prediabetic State; Random Allocation; Rats; Rats, Zucker; RNA, Messenger; Transforming Growth Factor beta; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor Receptor-2

The protein kinase C (PKC)-beta isoform has been implicated to play a pivotal role in the development of diabetic kidney disease. We tested this hypothesis by inducing diabetic nephropathy in PKC-beta-deficient (PKC-beta(-/-)) mice. We studied nondiabetic and streptozotocin-induced diabetic PKC-beta(-/-) mice compared with appropriate 129/SV wild-type mice. After 8 weeks of diabetes, the high-glucose-induced renal and glomerular hypertrophy, as well as the increased expression of extracellular matrix proteins such as collagen and fibronectin, was reduced in PKC-beta(-/-) mice. Furthermore, the high-glucose-induced expression of the profibrotic cytokine transforming growth factor (TGF)-beta1 and connective tissue growth factor were significantly diminished in the diabetic PKC-beta(-/-) mice compared with diabetic wild-type mice, suggesting a role of the PKC-beta isoform in the regulation of renal hypertrophy. Notably, increased urinary albumin-to-creatinine ratio persisted in the diabetic PKC-beta(-/-) mice. The loss of the basement membrane proteoglycan perlecan and the podocyte protein nephrin in the diabetic state was not prevented in the PKC-beta(-/-) mice as previously demonstrated in the nonalbuminuric diabetic PKC-alpha(-/-) mice. In summary, the differential effects of PKC-beta deficiency on diabetes-induced renal hypertrophy and albuminuria suggest that PKC-beta contributes to high-glucose-induced TGF-beta1 expression and renal fibrosis, whereas perlecan, as well as nephrin, expression and albuminuria is regulated by other signaling pathways.

Topics: Albuminuria; Animals; Chromosome Deletion; Collagen Type IV; Creatinine; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Fibronectins; Fibrosis; Heparan Sulfate Proteoglycans; Hypertrophy; Kidney; Membrane Proteins; Mice; Mice, Knockout; Organ Size; Protein Isoforms; Protein Kinase C; RNA; Streptozocin; Transforming Growth Factor beta1; Vascular Endothelial Growth Factors

Studies in experimental animals and younger women suggest a protective role for estrogen; however, clinical trials may not substantiate this effect in older females. Therefore, the present study assessed the outcome of ovariectomy in older mRen2. Lewis rats subjected to a high-salt diet for 4 wk. Intact or ovariectomized (OVX, 15 wk of age) mRen2. Lewis rats were aged to 60 wk and then placed on a high-salt (HS, 8% sodium chloride) diet for 4 wk. Systolic blood pressures were similar between groups [OVX 169 +/- 6 vs. Intact 182 +/- 7 mmHg; P = 0.22] after the 4-wk diet; however, proteinuria [OVX 0.8 +/- 0.2 vs. Intact 11.5 +/- 2.6 mg/mg creatinine; P < 0.002, n = 6], renal interstitial fibrosis, glomerular sclerosis, and tubular casts were lower in OVX vs. Intact rats. Kidney injury molecule-1 mRNA, a marker of tubular damage, was 53% lower in the OVX HS group. Independent from blood pressure, OVX HS rats exhibited significantly lower cardiac (24%) and renal (32%) hypertrophy as well as lower C-reactive protein (28%). Circulating insulin-like growth factor-I (IGF-I) levels were not different between the Intact and OVX groups; however, renal cortical IGF-I mRNA and protein were attenuated in OVX rats [P < 0.05, n = 6]. We conclude that ovariectomy in the older female mRen2. Lewis rat conveys protection against salt-dependent increase in renal injury.

Topics: Aging; Angiotensin I; Angiotensin II; Animals; Animals, Congenic; Blood Pressure; C-Reactive Protein; Cell Adhesion Molecules; Disease Models, Animal; Female; Fibrosis; Hypertension; Hypertrophy; Insulin-Like Growth Factor I; Intracellular Signaling Peptides and Proteins; Kidney; Kidney Diseases; Membrane Proteins; Ovariectomy; Peptide Fragments; Proteinuria; Rats; Rats, Inbred Lew; Renin; Renin-Angiotensin System; RNA, Messenger; Sodium Chloride, Dietary

Congenital nephrotic syndrome of the Finnish type (NPHS1) is a rare genetic disease caused by mutations in the NPHS1 gene encoding a major podocyte slit-diaphragm protein, nephrin. Patients with NPHS1 have severe nephrotic syndrome from birth and develop renal fibrosis in early childhood. In this work, we studied the development of glomerular sclerosis in kidneys removed from 4- to 44-month-old NPHS1 patients. The pathological lesions and expression of glomerular cell markers were studied in nephrectomized NPHS1 and control kidneys using light and electron microscopy and immunohistochemistry. An analysis of 1528 glomeruli from 20 patients revealed progressive mesangial sclerosis and capillary obliteration. Although few inflammatory cells were detected in the mesangial area, paraglomerular inflammation and fibrosis was common. The podocytes showed severe ultrastructural changes and hypertrophy with the upregulation of cyclins A and D1. Podocyte proliferation, however, was rare. Apoptosis was hardly detected and the expression of antiapoptotic B-cell lymphoma-2 and proapoptotic p53 were comparable to controls. Moderate amounts of podocytes were secreted into the urine of NPHS1 patients. Shrinkage of the glomerular tuft was common, whereas occlusion of tubular opening or protrusion of the glomerular tuft into subepithelial space or through the Bowman's capsule were not detected. The results indicate that, in NPHS1 kidneys, the damaged podocytes induce progressive mesangial expansion and capillary obliteration. Podocyte depletion, glomerular tuft adhesion, and misdirected filtration, however, seem to play a minor role in the nephron destruction.

Topics: Apoptosis; Cell Proliferation; Child, Preschool; Disease Progression; Epithelium; Glomerular Mesangium; Humans; Hypertrophy; Infant; Kidney Glomerulus; Membrane Proteins; Mutation; Nephrotic Syndrome; Podocytes; Sclerosis

Diabetic nephropathy is one of the major microvascular complications in diabetes and is the leading cause of end-stage renal disease worldwide. Among various factors, angiogenesis-associated factors such as vascular endothelial growth factor (VEGF)-A and angiopoietin (Ang)-2 are involved in the development of diabetic nephropathy. We previously reported the therapeutic efficacy of antiangiogenic tumstatin peptide in the early diabetic nephropathy model. Here, we examine the effect of endostatin peptide, a potent inhibitor of angiogenesis derived from type XVIII collagen, in preventing progression in the type 1 diabetic nephropathy mouse model. Endostatin peptide did not affect hyperglycemia induced by streptozotocin (STZ). Glomerular hypertrophy, hyperfiltration, and albuminuria were significantly suppressed by endostatin peptide (5 mg/kg) in STZ-induced diabetic mice. Glomerular mesangial matrix expansion, the increase of glomerular type IV collagen, endothelial area (CD31(+)), and F4/80(+) monocyte/macrophage accumulation were significantly inhibited by endostatin peptide. Increase in the renal expression of VEGF-A, flk-1, Ang-2, an antagonist of angiopoietin-1, transforming growth factor-beta1, interleukin-6, and monocyte chemoattractant protein-1 was inhibited by endostatin peptide in diabetic mice. Decrease of nephrin mRNA and protein in diabetic mice was suppressed by treatment with endostatin peptide. The level of endostatin in the renal cortex and sera was increased in diabetic mice. Endogenous renal levels of endostatin were decreased in endostatin peptide-treated groups in parallel with VEGF-A. Although serum levels of endostatin were decreased in the low-dose endostatin-peptide group, high-dose administration resulted in elevated serum levels of endostatin. These results demonstrate the potential use of antiangiogenic endostatin peptide as a novel therapeutic agent in diabetic nephropathy.

Topics: Albuminuria; Amino Acid Sequence; Animals; Blood Glucose; Body Weight; Collagen Type IV; Creatinine; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Diabetic Nephropathies; Endostatins; Female; Hyperglycemia; Hypertrophy; Immunohistochemistry; Integrin alpha5beta1; Kidney; Kidney Glomerulus; Membrane Proteins; Mice; Mice, Inbred C57BL; Molecular Sequence Data; Organ Size; Peptide Fragments; RNA, Messenger; Transforming Growth Factor beta; Transforming Growth Factor beta1; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor Receptor-2

In the early stage of diabetic nephropathy (one of the major microvascular complications of diabetes) glomerular hyperfiltration and hypertrophy are observed. It is clinically important to regulate glomerular hypertrophy for preventing glomerulosclerosis. The number of glomerular endothelial cells is known to be increased in diabetic nephropathy associated with enlarged glomerular tufts, suggesting that the mechanism is similar to that of angiogenesis. Tumstatin peptide is an angiogenesis inhibitor derived from type IV collagen and inhibits in vivo neovascularization induced by vascular endothelial growth factor (VEGF), one of the mediators of glomerular hypertrophy in diabetic nephropathy. Here, we show the effect of tumstatin peptide in inhibiting alterations in early diabetic nephropathy. Glomerular hypertrophy, hyperfiltration, and albuminuria were suppressed by tumstatin peptide (1 mg/kg) in streptozotocin-induced diabetic mice. Glomerular matrix expansion, the increase of total glomerular cell number and glomerular endothelial cells (CD31 positive), and monocyte/macrophage accumulation was inhibited by tumstatin peptide. Increase in renal expression of VEGF, flk-1, and angiopoietin-2, an antagonist of angiopoietin-1, was inhibited by tumstatin treatment in diabetic mice. Alteration of glomerular nephrin expression, a podocyte protein crucial for maintaining glomerular filtration barrier, was recovered by tumstatin in diabetic mice. Taken together, these results demonstrate the potential use of antiangiogenic tumstatin peptide as a novel therapeutic agent in early diabetic nephropathy.

Topics: Albuminuria; Angiogenesis Inhibitors; Animals; Autoantigens; Blood Glucose; Collagen Type IV; Creatinine; Diabetes Mellitus, Experimental; Diabetic Neuropathies; Female; Hypertrophy; Kidney Glomerulus; Macrophages; Membrane Proteins; Mice; Mice, Inbred C57BL; Monocytes; Neovascularization, Pathologic; Platelet Endothelial Cell Adhesion Molecule-1; Proteins; RNA, Messenger