Lesions Of Diabetic Nephropathy Research Articles

Modulation of single-nephron GFR in thedb/dbmouse model of type 2 diabetes mellitus. II. Effects of renal mass reduction

This study examines for the first time the effects of uninephrectomy (Nx) on modulation of whole kidney glomerular filtration rate (GFR), single-nephron GFR (SNGFR), and progression of diabetic nephropathy in the db/db mouse model of type 2 diabetes mellitus. To characterize SNGFR and tubuloglomerular feedback (TGF) responses to Nx and chronic neuronal nitric oxide synthase inhibition in the db/db mouse, we studied the effects of Nx on whole kidney GFR, SNGFR, and TGF characteristics in db/db and wild-type (WT) mice after Nx or sham Nx. We also documented progression of glomerular changes over a 6-mo period. Whole kidney GFR and SNGFR were significantly higher in db/db Nx than db/db sham mice, without change in proximal tubule reabsorptive rates. The TGF responses, determined as proximal-distal SNGFR differences, were brisk: 12.1 +/- 1.0 vs. 8.4 +/- 0.6 nl/min in WT sham (P < 0.05), 15.7 +/- 1.0 vs. 12.0 +/- 1.0 nl/min in WT Nx (P < 0.05), and 17.8 +/- 1.3 vs. 14.3 +/- 1.0 nl/min in db/db Nx (P < 0.05) mice. Chronic ingestion of the neuronal nitric oxide synthase inhibitor S-methylthiocitrulline for 2-3 wk after Nx had no effect on SNGFR or the TGF response. These studies show further elevations in whole kidney GFR and SNGFR in these hyperglycemic morbidly obese db/db mice, with an intact TGF system after Nx. In addition, in the db/db Nx mice, 4-6 mo after Nx, there was an exacerbation of the lesions of diabetic nephropathy, as quantified by a significant increase in the ratio of mesangial surface area to total glomerular surface area.

Having One Kidney Does Not Accelerate the Rate of Development of Diabetic Nephropathy Lesions in Type 1 Diabetic Patients

Reduced nephron number is hypothesized to be a risk factor for chronic kidney disease and hypertension. Whether reduced nephron number accelerates the early stages of diabetic nephropathy is unknown. This study investigated whether the rate of development of diabetic nephropathy lesions was different in type 1 diabetic patients with a single (transplanted) kidney compared with patients with two (native) kidneys. Three groups of volunteers were studied: 28 type 1 diabetic kidney transplant recipients with 8-20 years of good graft function, 39 two-kidney patients with duration of type 1 diabetes matched to the time since transplant in the one-kidney group, and 30 age-matched normal control subjects. Electron microscopic morphometry was used to estimate glomerular structural parameters on 3.0 +/- 1.4 glomeruli per biopsy. In the one- versus two-kidney diabetic subject groups, respectively, serum creatinine (means +/- SD 1.3 +/- 0.4 vs. 0.9 +/- 0.2 mg/dl; P < 0.001), systolic blood pressure (133 +/- 13 vs. 122 +/- 11 mmHg; P < 0.001), and albumin excretion rate (median [range] 32.1 microg/min [2-622] vs. 6.8 microg/min [2-1,495]; P = 0.006) were higher. There were no differences in the one- versus two-kidney diabetic subject groups, respectively, in glomerular basement membrane width (median [range] 511 nm [308-745] vs. 473 nm [331-814]), mesangial fractional volume (mean +/- SD 0.30 +/- 0.06 vs. 0.27 +/- 0.07), mesangial matrix fractional volume (0.16 +/- 0.05 vs. 0.16 +/- 0.06), and mesangial matrix fractional volume per total mesangium (0.61 +/- 0.07 vs. 0.64 +/- 0.09). However, these glomerular structural parameters were statistically significantly higher in both diabetic subject groups compared with normal control subjects. Results were similar when patients receiving ACE inhibitors were excluded from the analyses. Reduced nephron number is not associated with accelerated development of diabetic glomerulopathy lesions in type 1 diabetic patients.

Diabetic nephropathy: An update on renal structure

Abstract The renal lesions underlying renal dysfunction differ in type 1 and type 2 diabetes, although the clinical manifestations of diabetic nephropathy, proteinuria, decreased glomerular filtration rate and increasing blood pressure are similar. Indeed, in type 1 diabetes, although also tubular, interstitial and arteriolar lesions are present, the most important structural changes involve the glomerulus, while several type 2 diabetic patients, despite the presence of microalbuminuria or proteinuria, have normal glomerular structure with or without tubulo-interstitial and arteriolar abnormalities. The clinical manifestations of diabetic nephropathy are strongly related with the structural changes, especially with the degree of mesangial expansion in both type 1 and type 2 diabetes. In the last years it has been demonstrated that also changes in the structure and number of podocytes may be involved in the progression of diabetic nephropathy. Previous studies using light and electron microscopic morphometric analysis described the renal structural changes and the renal structural–functional relationships, documenting the contribution of kidney biopsy studies in understanding the pathogenesis of diabetic nephropathy and in identifying the patients with higher risk to progress to end stage renal disease. Finally this review will summarize studies in pancreas transplant recipients demonstrating that the lesions of diabetic nephropathy in humans are reversible, if normoglycemia is achieved and maintained for a long period of time.

Podocyte Detachment and Reduced Glomerular Capillary Endothelial Fenestration in Human Type 1 Diabetic Nephropathy

The aim of this study was to investigate the structural characteristics of podocytes and endothelial cells in diabetic nephropathy. We studied 18 patients with type 1 diabetes (seven normoalbuminuric, six microalbuminuric, and five proteinuric), and six normal control subjects. Groups were not different for age. Type 1 diabetic groups were not different for diabetes duration or age at diabetes onset. Podocyte foot process width (FPW), fraction of glomerular basement membrane (GBM) surface with intact nondetached foot processes (IFP), fraction of glomerular capillary luminal surface covered by fenestrated endothelium [S(S)(Fenestrated/cap)] and classic diabetic glomerulopathy lesions were morphometrically measured. Albumin excretion (AER) and glomerular filtration (GFR) rates were also measured. GFR correlated inversely and AER directly with GBM and mesangial measurements in diabetic patients. FPW correlated inversely with GFR (r = -0.71, P = 0.001) and directly with AER (r = 0.66, P = 0.003), GBM, and mesangial parameters. The GBM fraction covered by IFP was decreased in proteinuric versus control subjects (P = 0.001), normoalbuminuric patients (P = 0.0002) and microalbuminuric patients (P = 0.04) and correlated with renal structural and functional parameters, including AER (r = -0.52, P = 0.03). Only 78% of GBM was covered by IFP in proteinuric patients. S(S)(Fenestrated/cap) was reduced in normoalbuminuric (P = 0.03), microalbuminuric (P = 0.03), and proteinuric (P = 0.002) patients versus control subjects. S(S)(Fenestrated/cap) correlated with mesangial fractional volume per glomerulus (r = -0.57, P = 0.01), IFP (r = 0.61, P = 0.007), and FPW (r = -0.58, P = 0.01). These novel studies document that podocyte detachment and diminished endothelial cell fenestration are related to classical diabetic nephropathy lesions and renal function in type 1 diabetic patients and support a need for further studies of podocyte/GBM adherence and podocyte/endothelial cell functional interactions in diabetic nephropathy.

Histopathology of Diabetic Nephropathy

The clinical manifestations of diabetic nephropathy, proteinuria, increased blood pressure, and decreased glomerular filtration rate, are similar in type 1 and type 2 diabetes; however, the renal lesions underlying renal dysfunction in the 2 conditions may differ. Indeed, although tubular, interstitial, and arteriolar lesions are ultimately present in type 1 diabetes, as the disease progresses, the most important structural changes involve the glomerulus. In contrast, a substantial subset of type 2 diabetic patients, despite the presence of microalbuminuria or proteinuria, have normal glomerular structure with or without tubulointerstitial and/or arteriolar abnormalities. The clinical manifestations of diabetic nephropathy are strongly related with the structural changes, especially with the degree of mesangial expansion in both type 1 and type 2 diabetes. However, several other important structural changes are involved. Previous studies, using light and electron microscopic morphometric analysis, have described the renal structural changes and the structural-functional relationships of diabetic nephropathy. This review focuses on these topics, emphasizing the contribution of research kidney biopsy studies to the understanding of the pathogenesis of diabetic nephropathy and the identification of patients with a higher risk of progression to end-stage renal disease. Finally, evidence is presented that the reversal of established lesions of diabetic nephropathy is possible.

Peroxisome Proliferator-Activated Receptor-γ(PPAR-γ) Agonists Attenuate the Profibrotic Response Induced by TGF-β1 in Renal Interstitial Fibroblasts

Background. Studies have shown that peroxisome proliferator-activated receptor- (PPAR-) agonists could ameliorate renal fibrotic lesions in both diabetic nephropathy and nondiabetic chronic kidney diseases. In order to elucidate the antifibrotic mechanism of PPAR- agonists, we investigated the effects of PPAR- activation on TGF-1-induced renal interstitial fibroblasts. Methods. In rat renal interstitial fibroblasts (NRK/49F), the mRNA expression of TGF-1-induced -smooth muscle actin (-SMA), connective tissue growth factor (CTGF), fibronectin (FN) and collagen type III (Col III) were observed by reverse transcriptase-polymerase chain reaction (RT-PCR). The protein expressions of FN and Smads were observed by Western blot. Results. In NRK/49F, TGF-1 enhanced CTGF, FN and Col III mRNA expression in a dose- and time-dependent manner. -SMA, CTGF, FN and Col III mRNA and FN protein expression in 15-deoxy--prostaglandin J2 (15d-PGJ2)-troglitazone- and ciglitazone-pretreated groups, respectively, were significantly decreased compared with the TGF-1-stimulated group. TGF-1 (5 ng/mL) enhanced p-Smad2/3 protein expression in a time-dependent manner. Compared with the TGF-1-stimulated group, p-Smad2/3 protein induced by TGF-1 in PPAR- agonists-pretreated groups significantly decreased with no statistical difference amongst the three pretreated groups. Conclusion. PPAR- agonists could inhibit TGF-1-induced renal fibroblast activation, CTGF expression and ECM synthesis through abrogating the TGF-1/Smads signaling pathway.

Therapeutic Potential of (-)-Epigallocatechin 3-O-Gallate on Renal Damage in Diabetic Nephropathy Model Rats

Previous investigations have demonstrated that green tea polyphenols and partially hydrolyzed guar gum as dietary fiber have antioxidative and hypolipidemic activity, respectively, supporting their reduction of risk factors in the course of diabetic nephropathy via a hypoglycemic effect and ameliorating the decline of renal function through their combined administration to rats with subtotal nephrectomy plus streptozotocin (STZ) injection. As a further study, we examined whether (-)-epigallocatechin 3-O-gallate (EGCg), the main polyphenolic compound, could ameliorate the development of diabetic nephropathy. Rats with subtotal nephrectomy plus STZ injection were orally administrated EGCg at doses of 25, 50, and 100 mg/kg body weight/day. After a 50-day administration period, EGCg-treated groups showed suppressed hyperglycemia, proteinuria, and lipid peroxidation, although there were only weak effects on the levels of serum creatinine and glycosylated protein. Furthermore, EGCg reduced renal advanced glycation end-product accumulation and its related protein expression in the kidney cortex as well as associated pathological conditions. These results suggest that EGCg ameliorates glucose toxicity and renal injury, thus alleviating renal damage caused by abnormal glucose metabolism-associated oxidative stress involved in renal lesions of diabetic nephropathy.

Diabetic Nephropathy Is Associated With Gene Expression Levels of Oxidative Phosphorylation and Related Pathways

The in vitro behavior of skin fibroblasts from patients with or without diabetic nephropathy is associated with diabetic nephropathy risk. Here we compared skin fibroblast gene expression profiles from two groups of type 1 diabetic patients: 20 with very fast ("fast-track") versus 20 with very slow ("slow-track") rates of development of diabetic nephropathy lesions. Gene expression profiles of skin fibroblasts grown in 25 mmol/l glucose for 36 h were assessed by Affymetrix HG-U133A GeneChips to determine the proportion of genes in a given biological pathway that were directionally consistent in their group differences. Five pathways reached statistical significance. All had significantly greater proportions of genes with higher expression levels in the fast-track group. These pathways, the first four of which are closely related and have overlapping genes, included oxidative phosphorylation (P<0.001), electron transport system complex III (P=0.017), citrate cycle (P=0.037), propanoate metabolism (P=0.044), and transcription factors (P=0.046). These results support the concept that oxidative phosphorylation and related upstream pathways may be important in the pathogenesis of diabetic nephropathy. Whether these findings reflect inherent genetic cellular characteristics, "cell memory," or both requires further study.

Kidney involvement in a nongenetic rat model of type 2 diabetes

Rats fed a high fat diet and given a low dose of streptozotocin (STZ) (35 mg/kg) develop type 2 diabetes with insulin resistance, hyperinsulinemia, moderate hyperglycemia, hyperlipidemia, and salt-sensitive hypertension. We postulated that rats with noninsulinopenic (type 2) diabetes develop lesions of diabetic nephropathy significantly more prominent than those seen in classic insulinopenic (type 1) diabetic rats. Rats were fed regular chow or high fat diet (60% calories from fat and 70% animal fat). After 5 weeks, rats fed regular chow received vehicle (controls) or 55 mg/kg STZ (type 1 diabetes mellitus). Rats fed high fat diet received vehicle (high fat) or low dose STZ, 35 mg/kg (type 2 diabetes mellitus). Rats were sacrificed 14 weeks after STZ/vehicle injection. Blood glucose, systolic blood pressure, and urinary protein excretion were significantly higher in both diabetes groups than in controls. Serum insulin levels (ng/mL) were higher in type 2 diabetes than in type 1 diabetes groups (0.49 +/- 0.12 vs. 0.07 +/- 0.07) (P= 0.01). Percentage of sclerosed glomeruli was significantly higher in type 2 diabetes group than in control and type 1 diabetes groups. Fibronectin expression was significantly increased in high fat, type 1 and type 2 diabetes groups compared to controls. The expression of type IV collagen, connective tissue growth factor (CTGF), and transforming growth factor-beta (TGF-beta) was significantly increased in high fat and type 2 diabetes groups compared to controls. Rats fed a high fat diet and given a low dose of STZ developed diabetes (with normal/high insulin levels), hypertension, and proteinuria. Kidney lesions in this type 2 model appear to be more pronounced than in type 1 diabetic rats despite lower blood glucose levels and proteinuria. We present a nongenetic rat model of type 2 diabetes mellitus and nephropathy.

Hepatocyte Growth Factor Is a Downstream Effector that Mediates the Antifibrotic Action of Peroxisome Proliferator–Activated Receptor-γ Agonists

Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is a ligand-dependent transcription factor that plays an important role in the regulation of insulin sensitivity and lipid metabolism. Evidence shows that PPAR-gamma agonists also ameliorate renal fibrotic lesions in both diabetic nephropathy and nondiabetic chronic kidney disease. However, little is known about the mechanism underlying their antifibrotic action. This study demonstrated that PPAR-gamma agonists could exert their actions by inducing antifibrotic hepatocyte growth factor (HGF) expression. Incubation of mesangial cells with natural or synthetic PPAR-gamma agonists 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) or troglitazone and ciglitazone suppressed TGF-beta1-mediated alpha-smooth muscle actin, fibronectin, and plasminogen activator inhibitor-1 expression. PPAR-gamma agonists also induced HGF mRNA expression and protein secretion. Transfection studies revealed that 15d-PGJ2 stimulated HGF gene promoter activity, which was dependent on the presence of a novel peroxisome proliferator response element. Treatment of mesangial cells with 15d-PGJ2 induced the binding of PPAR-gamma to the peroxisome proliferator response element in the HGF promoter region. PPAR-gamma agonists also activated c-met receptor tyrosine phosphorylation, induced Smad transcriptional co-repressor TG-interacting factor expression, and blocked TGF-beta/Smad-mediated gene transcription in mesangial cells. Furthermore, ablation of c-met receptor through the LoxP-Cre system in mesangial cells abolished the antifibrotic effect of 15d-PGJ2. PPAR-gamma activation also induced HGF expression in renal interstitial fibroblasts and repressed TGF-beta1-mediated myofibroblast activation. Both HGF and 15d-PGJ2 attenuated Smad nuclear translocation in response to TGF-beta1 stimulation in renal fibroblasts. Together, these findings suggest that HGF may act as a downstream effector that mediates the antifibrotic action of PPAR-gamma agonists.

Diabetes and the Kidney

Diabetes and the Kidney

Establishment of a Diabetic Mouse Model with Progressive Diabetic Nephropathy

Although diabetic animal models exist, no single animal model develops renal changes identical to those seen in humans. Here we show that transgenic mice that overexpress inducible cAMP early repressor (ICER Igamma) in pancreatic beta cells are a good model to study the pathogenesis of diabetic nephropathy. Although ICER Igamma transgenic mice exhibit extremely high blood glucose levels throughout their lives, they survive long enough to develop diabetic nephropathy. Using this model we followed the progress of diabetic renal changes compared to those seen in humans. By 8 weeks of age, the glomerular filtration rate (GFR) was already increased, and glomerular hypertrophy was prominent. At 20 weeks, GFR reached its peak, and urine albumin excretion rate was elevated. Finally, at 40 weeks, diffuse glomerular sclerotic lesions were prominently accompanied by increased expression of collagen type IV and laminin and reduced expression of matrix metalloproteinase-2. Nodular lesions were absent, but glomerular basement membrane thickening was prominent. At this point, GFR declined and urinary albumin excretion rate increased, causing a nephrotic state with lower serum albumin and higher serum total cholesterol. Thus, similar to human diabetic nephropathy, ICER Igamma transgenic mice exhibit a stable and progressive phenotype of diabetic kidney disease due solely to chronic hyperglycemia without other modulating factors.

Review Article: Dyslipidaemia, Lipid Oxidation, And Free Radicals In Diabetic Nephropathy: An Overview

Diabetes mellitus has assumed an epidemics proportion in most parts of the world including the developing countries, and one of its ominous complications, diabetic nephropathy represents today the leading cause of end-stage renal disease in USA, Europe, and Japan. However, there is a paucity of records of the magnitude in Africa and some parts of Asia. The pathophysiology of diabetic nephropathy can be viewed as a sequence of events evolving in a stepwise pattern starting with endothelial cell dysfunction (ECD) and end in end-stage renal failure ( Fig 1). Majority of diabetic associated metabolic syndromes, especially dyslipidaemia predispose to ECD, and therefore diabetic nephropathy. Diabetes mellitus is frequently associated with dyslipidaemia evidenced by high prevalence rate that range from 16%-40%, and chronically elevated level of plasma lipids, low-density lipoprotein in particular, leads to modification of structures, importantly through oxidative processes. Renal tissue particularly in diabetes milieu has been suggested to accelerate oxidation of lipids and lipoproteins. Lipids, particularly LDL oxidation are initiated by reactive oxygen species (ROS), but the rate of oxidation is usually suppressed in plasma by endogenous antioxidants. However, after ECD the lipid is sequested from the antioxidant milieu mainly in the glomerular wall intima and this accelerates its oxidation. The precise mechanism by which oxidized LDL promotes the development of ECD and diabetic nephropathy lesions remains to be elucidated. However, several lines of evidence suggest that oxidized LDL exerts many biological effects that may contribute to the initiation and progression of diabetic nephropathy. Therefore, oxidized lipids are a key early step in the pathogenesis of diabetic nephropathy. Importantly, trials of antioxidants in diseases where free radicals play an important role in their pathogenesis reveal satisfactory results,but results of trials of antioxidants in the management of chronic diabetic complications are inconclusive.Nonetheless, most, if not all, were instituted after a long-standing hyperlipidaemia and therefore oxidative stress, with already developed complications. This paper provides an overview on the involvement of oxidized lipids, lipoproteins and reactive oxygen species in initiation and progression of diabetic nephropathy. This will stimulate nephrologists to plan instituting the use of antioxidants as preventive measures at the diagnosis of the disease or even in those with impaired glucose tolerance. In addition, the use of lipid lowering agents in diabetics with hyperlipidaemia could become an additional cost-effective adjunct of the anti diabetic regimen. Highland Medical Research Journal Vol.2(1) 2004: 1-7

Involvement of extracellular signal-regulated kinase and p38 in human diabetic nephropathy

The involvement of mitogen-activated protein kinase (MAPK) in human diabetic nephropathy has not been fully investigated. The presence of cells positive for the phosphorylated MAPK family (phosphorylated extracellular signal-regulated kinase [p-ERK], phosphorylated p38MAPK [p-p38MAPK]) was investigated immunohistochemically in kidneys of 30 patients with diabetic nephropathy. In addition, 10 patients with minimal change nephrotic syndrome, 10 patients with thin basement membrane disease, and 5 patients with benign nephrosclerosis were studied as disease controls. The presence of activated nuclear factor-kappaB (p65)-positive cells also was evaluated in kidney specimens. In patients with diabetic nephropathy, p-ERK, p-p38MAPK, and p65 were observed in mesangial cells, endothelial cells, podocytes, tubular epithelial cells, and mononuclear infiltrates in interstitium. Numbers of p-ERK-, p-p38MAPK-, and p65-positive cells in both glomeruli and interstitium in patients with diabetic nephropathy were higher than those in controls. In particular, the number of glomerular p-ERK-positive cells in patients with diabetic nephropathy increased in accordance with the progression of glomerular lesions and correlated well with the number of glomerular p65-positive cells (r = 0.654; P < 0.01; n = 30). Conversely, the number of p-p38MAPK-positive cells in glomeruli did not correlate with glomerular lesions. However, the number of tubulointerstitial p-p38MAPK-positive cells in patients with diabetic nephropathy reflected the severity of tubulointerstitial lesions, and numbers of those in the interstitium increased with good correlation to numbers of tubulointerstitial p65-positive cells (r = 0.757; P < 0.01; n = 30) and interstitial CD68-positive macrophages (r = 0.647; P < 0.05; n = 30) and urinary monocyte chemoattractant protein-1 levels (r = 0.605; P < 0.05; n = 30). These results suggest that MAPK phosphorylation contributes to human diabetic nephropathy. In particular, ERK and p38MAPK may be distinctly involved in glomerular and tubulointerstitial lesions in human diabetic nephropathy.

Rapidly Progressive Renal Failure in Type 2 Diabetes in the Tropical Environment: A Clinico-Pathological Study

Background. Rapid decline of renal function in a diabetic suggests the presence of a nondiabetic kidney disease (NDKD). We designed a prospective study to evaluate the factors associated with a rapid decline in renal function in patients with type 2 diabetes. Methods. Over a 2 and a half year period, all patients with type 2 diabetes who presented with documented doubling of serum creatinine in less than 4 weeks or recently diagnosed advanced renal failure were identified. Patients with prerenal causes, urinary tract obstruction, or systemic disease causing renal failure were not included. Renal histology was studied in all cases. Results. A total of 26 patients satisfied the inclusion criteria. Over 75% had serum creatinine > 4 mg/dL at presentation and 62% were dialysis dependent. Renal histology showed mixed lesions of diabetic nephropathy (DN) and NDKD in 11 cases, only DN in nine, and pure NDKD in six. Diffuse proliferative glomerulonephritis (DPGN) was the commonest NDKD (27% cases), all on a background of DN. History of preceding cutaneous or pharyngeal infection was available in five cases. The proportion of postinfectious glomerulonephritis in diabetics with rapidly progressive renal failure was over six times that of the nondiabetic adult RPRF population during the study period. Four patients had acute interstitial nephritis and three showed crescentic glomerulonephritis. Other lesions included amyloidosis, atheroembolic disease, and renal papillary necrosis (one each). The frequency of microscopic hematuria and retinopathy was similar in those with pure DN and NDKD. Four out of seven cases with DPGN showed partial recovery whereas the other three remained unchanged. Conclusions. About two-thirds of patients with type 2 diabetes presenting with rapid decline of renal function in a tropical environment show NDKD. The high incidence of postinfectious glomerulonephritis in this group is possibly related to the high prevalence of skin and soft tissue infections; and could contribute to progressive kidney disease.

High expression of PKC-MAPK pathway mRNAs correlates with glomerular lesions in human diabetic nephropathy

Activation of protein kinase C (PKC) is a major signaling pathway for transforming growth factor (TGF)-beta to induce extracellular matrix (ECM) production in diabetic nephropathy (DN). PKC also activates mitogen-activated protein kinase (MAPK), which is called the PKC-MAPK pathway. The PKC-MAPK pathway is probably responsible for PKC-related abnormalities in diabetic glomeruli. To confirm the involvement of this pathway, we determined the localization and expression of mRNAs in glomeruli by in situ hybridization method. In the present study, we examined expression of PKCbeta1, MAPK/ERK kinase (MEK) 1, MEK2, extracellular signal-regulated protein kinase (ERK) 1, ERK2, and TGF-beta1 mRNAs using renal tissue samples from kidneys affected by DN (N= 21) and from normal human kidney (NHK; N= 6). We also performed an immunohistochemical study using anti-phosphorylated MEK1/2 (P-MEK) and ERK1/2 (P-ERK) antibodies. The glomerular severity of DN was classified into three groups according to mesangial expansion: D1 (N= 4), D2 (N= 13), and D3 (N= 4). We analyzed differences and correlations between variables. In the glomeruli, the number of cells that stained for these mRNAs in DN was significantly higher than in NHK. The expression of PKC-MAPK pathway mRNAs tended to be inversely proportional to the degree of mesangial expansion. The P-MEK and P-ERK signal intensity were parallel to its mRNA expression pattern. Furthermore, there were significant correlations among the P-MEK, P-ERK signal intensity, PKCbeta1 mRNA expression. Our results suggest that high expression of PKC-MAPK pathway mRNAs plays an important role in the development and/or progression of early tissue damage in DN.

Progression of diabetic nephropathy

Background: Diabetic nephropathy, a kidney disease caused by diabetes, is the most devastating and money-consuming complication in patients with diabetes throughout the world. The cardinal lesion of diabetic nephropathy resides in renal glomeruli and is called diabetic glomerulosclerosis. Hyperglycemia is responsible for the development and progression of diabetic nephropathy through metabolic derangements, including increased oxidative stress, renal polyol formation, activation of protein kinase C (PKC)-mitogen-activated protein kinases (MAPKs), and accumulation of advanced glycation end products, as well as such hemodynamic factors as systemic hypertension and increased intraglomerular pressure. Methods: We examined whether inhibition of the PKC-MAPK pathway could inhibit functional and pathological abnormalities in glomeruli from diabetic animal models and cultured mesangial cells exposed to high glucose condition and/or mechanical stretch. Results: Direct inhibition of PKC by PKC β inhibitor prevented albuminuria and mesangial expansion in db/db mice, a model of type 2 diabetes. We also found that inhibition of MAPK by PD98059, an inhibitor of MAPK, or mitogen-activated extracellular regulated protein kinase kinase prevented enhancement of activated protein-1 (AP-1) DNA binding activity and fibronectin expression in cultured mesangial cells exposed to mechanical stretch in an in vivo model of glomerular hypertension. Conclusion: These findings highlight the important role of PKC-MAPK pathway activation in mediating the development and progression of diabetic nephropathy. Am J Kidney Dis 41 (S1):S19-S21. © 2003 by the National Kidney Foundation, Inc.

Urinary Albumin as an Indicator of Diabetic Nephropathy Lesions in Japanese Type 2 Diabetic Patients

Caucasian type 2 diabetic patients with microalbuminuria (MA) or overt nephropathy (ON) show greater heterogeneity of renal lesions than type 1 diabetic patients. We examined whether a similar situation exists in 30 Japanese type 2 diabetic patients [21 male, age 48 ± (SD) 8 years, known duration 11 ± (SD) 8 years] without definable renal disease other than diabetic nephropathy. Six patients were normoalbuminuric (NA), 11 MA, and 13 had ON. Normal controls were 9 age-matched Japanese living-related renal transplant donors. Electron microscopic morphometry was performed on renal biopsy specimens and related to renal function. Glomerular basement membrane width and mesangial fractional volume [Vv(Mes/glom)] were increased in all type 2 diabetic patients groups (NA, MA, ON) as compared with normal controls. The Vv(Mes/glom) correlated directly with urinary albumin/creatinine. However, Vv(Mes/glom) as well as glomerular basement membrane width overlapped among the three functional categories (NA, MA, ON) and normal controls. In conclusion: (1) similar to Caucasian type 2 diabetic patients, Japanese type 2 diabetic patients have greater heterogeneity of renal structure than Caucasian type 1 diabetic patients, and (2) urinary albumin is not a reliable indicator of underlying renal structure in Japanese type 2 diabetic patients.

The early natural history of nephropathy in type 1 diabetes: II. Early renal structural changes in type 1 diabetes.

Renal structural abnormalities are known to precede the development of proteinuria, hypertension, and reduced renal function in patients with type 1 diabetes. The determinants of these early structural abnormalities are, however, largely unknown. The International Diabetic Nephropathy Study (IDNS) has recruited 243 children and adults (aged 10-40 years) in Montreal, Minneapolis, and Paris to identify and quantify these determinants. All study subjects were normotensive and had normal-to-high glomerular filtration rates (GFRs) and urinary albumin excretion rates (AERs) <100 microg/min at study entry. Only 8 of 243 had an AER > or =20 microg/min (microalbuminuria). Two renal biopsies are obtained at a 5-year intervals, with baseline and follow-up measures of renal function, blood pressure (BP), HbA(1c), plasma lipids, and AER. Herein, we examine the baseline renal biopsy morphometric findings in these subjects and in 87 kidney donor control subjects and explore the associations between findings and clinical and demographic variables. The principal morphometric abnormalities were increased glomerular basement membrane (GBM) width and fractional volume of mesangium [Vv(Mes/glom)] and mesangial matrix [Vv(MM/glom)]. The frequency of these abnormalities increased with increasing duration of diabetes but was observed as early as 2-8 years after onset. Diastolic BP (DBP), but not HbA(1c), was directly associated with these abnormalities. Elevated GFR was associated with only a small increase in peripheral glomerular capillary basement membrane filtration surface density. Center differences were detected in renal structural, renal functional, and BP parameters, especially between the Paris and North American centers. GBM width, Vv(Mes/glom), and Vv(MM/glom) are significantly increased even within a few years of onset of type 1 diabetes. These changes are detectable in normoalbuminuric patients and are related to duration, BP, and study site. Changes in these and other morphometric measures over 5-year follow-up should help clarify the roles of glycemia and other determinants of the rates of development of diabetic nephropathy lesions, as well as their relationships to early changes in BP, albumin excretion, and renal function.

Glycoxidation-modified macrophages and lipid peroxidation products are associated with the progression of human diabetic nephropathy

The aim of this study is to investigate the role of glomerular macrophages activated by glycoxidation and lipid peroxidation products in the progression of glomerular lesions in diabetic nephropathy. Renal biopsy samples from 43 patients with diabetes (age, 54 ± 14 years) and 10 control cases were immunohistochemically examined for the expression of carboxymethyllysine (CML), a representative glycoxidative product; oxidized phosphatidylcholine (Ox-PC), a representative lipid peroxidation product; leukocyte common antigen (LCA); CD68; and macrophage scavenger receptor (MSR) class A. The severity of the diffuse lesions in each glomerulus was histologically graded from 0 to IV. When grade II and III lesions had Kimmelstiel-Wilson (KW) nodules, they were placed in a new category called grade III with KW nodules. The number of cells positive for CML, Ox-PC, LCA, CD68, and MSR was compared in different grades. The number of macrophages per glomerulus increased with the glomerular lesion grade and was highest in grade III with KW nodules. Conversely, the number of lymphocytes did not parallel the grade of glomerular lesions. Almost 50% of macrophages contained CML, and more than 40% of those were observed in exudative lesions, tuft adhesions, and at the periphery of KW nodules. Ox-PC accumulated in 50% of CML-positive macrophages, which coexpress MSR. Macrophages positive for CML and Ox-PC increased with the grade. Glomerular macrophages may be activated by glycoxidative and lipid peroxidation products through MSR and may have a role in the development of human diabetic glomerulosclerosis. © 2001 by the National Kidney Foundation, Inc.