Mesangial Matrix Area Research Articles

Assessment of the impact of glyphosate and 2,4-D herbicides on the kidney injury and transcriptome changes in obese mice fed a Western diet

The development of chronic kidney disease has been associated with comorbidities resulting from the consumption of Westernized dietary (WD) patterns, including obesity and other metabolic dysfunctions. Kidneys also have a crucial role in the metabolism and excretion of xenobiotics, including herbicides. There is limited knowledge regarding the simultaneous exposure to WD and glyphosate (glypho) and 2,4-D, the most used herbicides globally. Thus, this study examined whether exposure to glypho and/or 2,4-D, either individually or in mixed, could impact the early effects of WD intake on kidney histology and gene expression in a rodent model. Male C57BL6J mice were fed a WD containing 20% lard, 0.2% cholesterol, 20% sucrose, and high sugar solution with 23.1 and 18.9 g/L of D-fructose and D-glucose for six months. During this period, the mice also received glypho (0.05 or 5 mg/kg/day), 2,4-D (0.02 or 2 mg/kg/day), or a mixture of both (0.05 +0.02, 5 +2 mg/kg/day) via intragastric administration five times per week. The doses were within or below the established regulatory limits. While single or mixed exposures did not alter WD-induced obesity, tubular lipid vacuolation, or increased serum creatinine levels; the exposure to higher doses of the mixture (5 +2) reduced the mesangial matrix area and tubular cell proliferation, while increasing the density of F4/80 macrophages in the renal interstitium. In terms of transcriptomic analysis, the herbicide mixture altered the expression of 415 genes in the kidney, which were found to be associated with immune response processes, particularly those related to phagocyte activity. While discrete, findings indicate that herbicide mixtures, rather than single exposures, might induce minor deleterious effects on the kidneys of obese mice under WD intake.

Characteristics of Serum Metabolites and Gut Microbiota in Diabetic Kidney Disease.

Disturbance of circulating metabolites and disorders of the gut microbiota are involved in the progression of diabetic kidney disease (DKD). However, there is limited research on the relationship between serum metabolites and gut microbiota, and their involvement in DKD. In this study, using an experimental DKD rat model induced by combining streptozotocin injection and unilateral nephrectomy, we employed untargeted metabolomics and 16S rRNA gene sequencing to explore the relationship between the metabolic profile and the structure and function of gut microbiota. Striking alterations took place in 140 serum metabolites, as well as in the composition and function of rat gut microbiota. These changes were mainly associated with carbohydrate, lipid, and amino acid metabolism. In these pathways, isomaltose, D-mannose, galactonic acid, citramalic acid, and prostaglandin B2 were significantly upregulated. 3-(2-Hydroxyethyl)indole, 3-methylindole, and indoleacrylic acid were downregulated and were the critical metabolites in the DKD model. Furthermore, the levels of these three indoles were restored after treatment with the traditional Chinese herbal medicine Tangshen Formula. At the genera level, g_Eubacterium_nodatum_group, g_Lactobacillus, and g_Faecalibaculum were most involved in metabolic disorders in the progression of DKD. Notably, the circulating lipid metabolites had a strong relationship with DKD-related parameters and were especially negatively related to the mesangial matrix area. Serum lipid indices (TG and TC) and UACR were directly associated with certain microbial genera. In conclusion, the present research verified the anomalous circulating metabolites and gut microbiota in DKD progression. We also identified the potential metabolic and microbial targets for the treatment of DKD.

Insulin Prevents Hyperfiltration and Proteinuria but Not Glomerular Hypertrophy and Increases Mesangial Matrix Expansion in Diabetic Rats

Objective: The aim of this work was to study the effect of 7 days of strict glycemic control with insulin on glomerular function and structure in streptozotocin (STZ)-diabetic rats. Materials and Methods: Three groups of adult male Fischer rats were studied: controls (n = 15), diabetics (n = 15), and insulin-treated diabetics (n = 15). Diabetes was induced by treating the rats with STZ (55 mg/kg i.p.). One week after the induction of diabetes, blood glucose, protein excretion rate (PER), glomerular filtration rate (GFR), and renal plasma flow (RPF) were estimated in each group. Furthermore, morphometric analysis was performed to estimate the tuft volume and changes in mesangial matrix area. The results are expressed as the mean ± SEM. Results: STZ diabetes caused significant increases in GFR (0.89 ± 0.1 to 1.21 ± 0.1 mL/min/100 g; p < 0.01) and RPF (1.78 ± 0.37 to 3.32 ± 0.6 mL/min/100 g; p < 0.05). Furthermore, the diabetic rats had higher glomerular volumes but mesangial matrix areas similar to controls. Insulin treatment prevented the increases in blood glucose (4.5 ± 0.2 m<smlcap>M</smlcap>), PER (66.1 ± 7.8 mg/day), GFR (0.6 ± 0.07 mL/min/100 g), and RPF (1.72 ± 0.36 mL/min/100 g), but did not prevent glomerular hypertrophy (21.7% increase), but induced mesangial matrix expansion (25% increase). Conclusions: Insulin prevented the diabetes-induced hyperfiltration and proteinuria, but did not prevent glomerular growth, and induced mesangial expansion. Hyperglycemic episodes could be partly responsible for persistent glomerular growth and accelerated mesangial growth.

C-peptide as a Therapy for Kidney Disease: A Systematic Review and Meta-Analysis.

C-peptide has intrinsic biological activity and may be renoprotective. We conducted a systematic review to determine whether C-peptide had a beneficial effect on renal outcomes. MEDLINE, EMBASE, and the Cochrane Central Databases were searched for human and animal studies in which C-peptide was administered and renal endpoints were subsequently measured. We identified 4 human trials involving 74 patients as well as 18 animal studies involving 35 separate experiments with a total of 641 animals. In humans, the renal effects of exogenously delivered C-peptide were only studied in type 1 diabetics with either normal renal function or incipient nephropathy. Pooled analysis showed no difference in GFR (mean difference, -1.36 mL/min/1.73 m2, p = 0.72) in patients receiving C-peptide compared to a control group, but two studies reported a reduction in glomerular hyperfiltration (p<0.05). Reduction in albuminuria was also reported in the C-peptide group (p<0.05). In diabetic rodent models, C-peptide led to a reduction in GFR (mean difference, -0.62 mL/min, p<0.00001) reflecting a partial reduction in glomerular hyperfiltration. C-peptide also reduced proteinuria (mean difference, -186.25 mg/day, p = 0.05), glomerular volume (p<0.00001), and mesangial matrix area (p<0.00001) in diabetic animals without affecting blood pressure or plasma glucose. Most studies were relatively short-term in duration, ranging from 1 hour to 3 months. Human studies of sufficient sample size and duration are needed to determine if the beneficial effects of C-peptide seen in animal models translate into improved long-term clinical outcomes for patients with chronic kidney disease. (PROSPERO CRD42014007472)

NADPH oxidase NOX1 is involved in activation of protein kinase C and premature senescence in early stage diabetic kidney

Increased oxidative stress and activation of protein kinase C (PKC) under hyperglycemia have been implicated in the development of diabetic nephropathy. Because reactive oxygen species derived from nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, NOX1 accelerate the translocation of PKC isoforms, NOX1 is postulated to play a causative role in the development of diabetic nephropathy. Hyperglycemia was induced in wild-type and Nox1-deficient mice (KO) by two doses of streptozotocin injection. At 3 weeks after the induction of hyperglycemia, glomeruli and cortical tubules were isolated from kidneys. The mRNA level of Nox1 was significantly upregulated in the renal cortex at 3 weeks of hyperglycemia. Urinary albumin and expression of inflammatory or fibrotic mediators were similarly elevated in diabetic wild-type and KO; however, increases in glomerular volume and mesangial matrix area were attenuated in diabetic KO. Nox1 deficiency significantly reduced the levels of renal thiobarbituric acid-reacting substances and 8-hydroxydeoxyguanosine, membranous translocation of PKCα/β, activity of PKC, and phosphorylation of p38 mitogen-activated protein kinase in the diabetic kidney. Furthermore, increased staining of senescence-associated β-galactosidase in glomeruli and cortical tubules of diabetic mice was significantly suppressed in KO. Whereas the levels of cyclin-dependent kinase inhibitors, p16INK4A and p21Cip1, were equivalent between the genotypes, increased levels of p27Kip1 and γ-H2AX, a biomarker for DNA double-strand breaks, were significantly attenuated in isolated glomeruli and cortical tubules of diabetic KO. Taken together, NOX1 modulates the p38/p27Kip1 signaling pathway by activating PKC and promotes premature senescence in early stage diabetic nephropathy.

Effects of uPA on mesangial matrix changes in the kidney of diabetic rats

Objective: To investigate the effect of urokinase-type plasminogen activator (uPA) on mesangial matrix in the kidney of diabetic rats and its related mechanisms. Methods: Diabetic Sprague-Dawley (SD) rats induced by intraperitoneal injection of streptozotocin (STZ) were randomly and evenly divided into two groups: DM + vehicle, and DM + uPA (2500 U kg−1 uPA via tail vein once a day for four weeks). The normal SD rats without diabetes were considered as control group. Rats in the three groups were executed and the heart blood was sampled for determination of blood glucose and serum creatinine. Meanwhile, kidney tissues of rats were also harvest for measurement of glomerular area, volume, and mesangial area by periodic acid silver methenamine (PASA) staining. The expression of urokinase-type plasminogen activator receptor (uPAR), plasminogen activator inhibitor-1 (PAI-1), and collagen IV in renal tissues was tested with immunohistochemistry. Results: Compared with control, the DM rats had obvious albuminuria, significantly (p < 0.01) increased glomerular volume and mesangial matrix area, and significantly (p < 0.05) higher expression of uPAR, PAI-1 and collagen IV in mesangial matrix, significantly up-regulated (p < 0.05) glomerular uPAR, PAI-1, and collagen IV expression. After treated with uPA, the diabetic rats had significantly (p < 0.05) reduced albuminuria, significantly (p < 0.01) improved glomerular volume and mesangial matrix, significantly (p < 0.05) down-regulated PAI-1 and collagen IV expression in mesangial matrix. However, the uPAR expression in renal tissues were unchangeable (p > 0.05) and PAI-1 and collagen IV expression were significantly (p < 0.05) reduced when diabetic rats were treated with uPA. Conclusion: uPA can down-regulate glomerular PAI-1 expression in the DM rats but not significantly influence uPAR expression, suggesting that uPA might regulate the mesangial cell (MC) and its matrix expression and improve diseased diabetic mesangial matrix via its combination with uPAR to uptake PAI-1 and accelerate its degradation.

The dipeptidyl peptidase-4 inhibitor sitagliptin protects against dyslipidemia-related kidney injury in Apolipoprotein E knockout mice.

The goal of this study was to investigate the possible protective effects of sitagliptin against dyslipidemia-related kidney injury in apolipoprotein E knockout (apoE−/−) mice. Eight-week-old male apoE−/− mice were randomized to receive either a high fat diet (HFD, apoE−/− group) or HFD mixed with sitagliptin (sita + apoE−/− group) for 16 weeks. A control group of age- and gender-matched C57BL/6J mice were fed a HFD. The apoE−/− group exhibited increases in body weight and serum lipid levels in addition to high-density lipoprotein, and increases in 24-h urinary 8-hydroxy-2-deoxyguanosine and albuminuria excretion. Decreased insulin sensitivity was also observed in the apoE−/− group. These mice additionally contained enlargements of the glomerular mesangial matrix area, lipid deposition area, and renal interstitium collagen area. The apoE−/− group also demonstrated down-regulation of phosphorylated AMP-activated protein kinase (AMPK), increases in renal mRNA expression of transforming growth factor-beta 1 (TGF-β1) and fibronectin (FN), and increased protein expression of Akt, TGF-β1, FN and p38/ERK mitogen-activated protein kinase (MAPK). Sitagliptin treatment successfully ameliorated all the deleterious effects of dyslipidemia tested. To our knowledge, this is the first time that sitagliptin has been shown to reverse the renal dysfunction and structural damage induced by dyslipidemia in apoE−/− mice. Our results suggest that the renoprotective mechanism of sitagliptin may be due to a reduction in Akt levels, a restoration of AMPK activity, and inhibition of TGF-β1, FN, and p38/ERK MAPK signaling pathways.

Up-regulation of glyoxalase 1 by mangiferin prevents diabetic nephropathy progression in streptozotocin-induced diabetic rats

Advanced glycation endproducts (AGEs) and its precursor methylglyoxal are associated with diabetic nephropathy (DN). Mangiferin has many beneficial biological activities, including anti-inflammatory, anti-oxidative and anti-diabetic effects. We investigated the effect of mangiferin on DN and its potential mechanism associated with glyoxalase 1 (Glo-1), a detoxifying enzyme of methylglyoxal, in streptozotocin-induced rat model of DN. Diabetic rats were treated orally with mangiferin (15, 30, and 60mg/kg) or distilled water for 9 weeks. Kidney tissues were collected for morphologic observation and the determination of associated biochemical parameters. The cultured mesangial cells were used to measure the activity of Glo-1 in vitro. Chronic treatment with mangiferin significantly ameliorated renal dysfunction in diabetic rats, as evidenced by decreases in albuminuria, blood urea nitrogen, kidney weight index, periodic acid-schiff stain positive mesangial matrix area, glomerular extracellular matrix expansion and accumulation, and glomerular basement membrane thickness. Meanwhile, mangiferin treatment caused substantial increases in the enzymatic activity of Glo-1 in vivo and in vitro, and protein and mRNA expression of Glo-1, reduced levels of AGEs and the protein and mRNA expression of their receptor (RAGE) in the renal cortex of diabetic rats. Moreover, mangiferin significantly attenuated oxidative stress damage as reflected by the lowered malondialdehyde and the increased glutathione levels in the kidney of diabetic rats. However, mangiferin did not affect the blood glucose and body weight of diabetic rats. Therefore, mangiferin can remarkably ameliorate DN in rats through inhibiting the AGEs/RAGE aix and oxidative stress damage, and Glo-1 may be a target for mangiferin action.

Phenotypic change of macrophages in the progression of diabetic nephropathy; sialoadhesin-positive activated macrophages are increased in diabetic kidney

Inflammatory process is involved in pathogenesis of diabetic nephropathy, although the activation and phenotypic change of macrophages in diabetic kidney has remained unclear. Sialoadhesin is a macrophage adhesion molecule containing 17 extracellular immunoglobulin-like domains, and is an I-type lectin which binds to sialic acid ligands expressed on hematopoietic cells. The aim of this study is to clarify the activation and phenotypic change of macrophages in the progression of diabetic nephropathy. We examined the expression of surface markers for pan-macrophages, resident macrophages, sialoadhesin, major histocompatibility complex class II and α-smooth muscle actin in the glomeruli of diabetic rats using immunohistochemistry at 0, 1, 4, 12, and 24 weeks after induction of diabetes by streptozotocin. Expression of type IV collagen and the change of mesangial matrix area were also measured. The mechanism for up-regulated expression of sialoadhesin on macrophages was evaluated in vitro. The number of macrophages was increased in diabetic glomeruli at 1 month after induction of diabetes and the increased number was maintained until 6 months. On the other hand, sialoadhesin-positive macrophages were increased during the late stage of diabetes concomitantly with the increase of α-smooth muscle actin-positive mesangial cells, mesangial matrix area and type IV collagen. Gene expression of sialoadhesin was induced by stimulation with interleukin (IL)-1β and tumor necrosis factor-α but not with IL-4, transforming growth factor-β and high glucose in cultured human macrophages. The present findings suggest that sialoadhesin-positive macrophages may contribute to the progression of diabetic nephropathy.

Beneficial effects of C-peptide on renal morphology in diabetic rats

The study was undertaken to examine the effects of C-peptide on glomerular volume (V(GLOM)), mesangial matrix synthesis, and degradation in streptozotocin (STZ)-diabetic rats with poor or moderate glycemic control. Series 1 (poor glycemic control) included groups of healthy rats, hyperglycemic rats, diabetic insulin-treated rats and diabetic C-peptide-treated rats. Series 2 (moderate glycemic control) included groups of healthy rats, diabetic insulin-treated rats, diabetic insulin- and C-peptide-treated rats. After 8 weeks, the left kidney was excised for evaluation of V(GLOM) and mesangial matrix area via light microscopy. Mesangial cells were cultured for 48 h and type IV collagen expression and matrix metalloproteinase (MMP)-2 expression were measured by ELISA and RT-PCR. The results indicated that in Series 1, C-peptide administration suppressed the diabetes-induced increase in the V(GLOM) and the mesangial matrix area. In Series 2, C-peptide administration resulted in a similar decrease in the V(GLOM) and a greater decrease in the mesangial matrix area when compared with insulin therapy alone. Moreover, C-peptide (300 nM) completely inhibited the glucose-induced increase of the collagen IV mRNA expression and protein concentration in mesangial cells cultured in 30 mM glucose medium. MMP-2 mRNA expression was not influenced by C-peptide. In conclusion, C-peptide administration to STZ-diabetic rats for 8 weeks results in the inhibition of diabetes-induced expansion of the mesangial matrix. This effect is independent of the level of glycemic control and results from the inhibition of diabetes-induced excessive formation of mesangial type IV collagen.

Roles of PDGF receptor-beta in the structure and function of postnatal kidney glomerulus

Mesangial cell functions are critically regulated by platelet-derived growth factor receptor (PDGFR)-β signals. In contrast to the well-established role of PDGFR-β in the development of kidney glomerulus, its role in adult kidney glomerulus remains controversial. We deleted the PDGFR-β gene postnatally using the Cre-loxP system and analysed the long-term effects of PDGFR-β inhibition on glomerular changes associated with ageing and subtotal nephrectomy. Mice depleted of PDGFR-β (Deletant) survived without showing apparent abnormalities. In glomerulus of Deletant, mesangial PDGFR-β expression was decreased. The glomerular cell numbers were low, and the ageing-associated increment of mesangial matrix area was suppressed in Deletant as compared with control mice with conserved PDGFR-β expression (Floxed) at 48weeks of age. At 2weeks after subtotal nephrectomy, albuminuria and the elevation of blood urea nitrogen were aggravated in Deletant. At this time, Deletant showed specific glomerular changes that included many hypertrophic podocytes and collapsed capillaries. At 12weeks after subtotal nephrectomy, the kidney function in Deletant restored to the level of Floxed; however, the Deletant glomeruli showed dilated capillaries, decreased cell number and reduced mesangial matrix area with less extended mesangial cell processes as compared with Floxed. The long-term inhibition of mesangial PDGFR-β prevented age-related mesangial expansion. On the other hand, the kidney glomeruli with decreased PDGFR-β showed increased vulnerability to the acute nephron loss, and showed mesangial insufficiency in the following adaptive process.

Histological assessment of the possible protective role of glimepiride against progression of experimentally induced diabetic nephropathy in rats

Introduction: little is known about the potential effects induced by sulphonylureas independently of their anti-hyperglycemic action. The present study examined the effect of glimepiride treatment on the progression of renal histological changes in diabetic rats to determine whether therapeutic intervention with these agents would prevent the onset and progression of renal complications or not. Material and methods: forty-eight adult male albino rats were equally divided into four groups; control, normal rats receiving glimepiride, streptozotocin induced diabetic non-treated rats and glimepiride-treated diabetic rats. Blood glucose level measurement and histological evaluation of renal tissue elements using H&E, Masson trichrome, and PAS reaction techniques at four and eight weeks after treatment were performed. Stained sections were subjected to some morphometric measurements namely, glomerular tuft area (GTA), mesangial matrix index (MMI) and area per cent of connective tissue (CT). Statistical analysis for significance of obtained data was performed using analysis of variance and student-T test. Results: Glimepiride did not cause any histological renal impairment when used solely. Induction of diabetes had a significant negative impact on renal structure. In addition to significant elevation of blood glucose levels, increased kidney and kidney to body weight ratio was estimated. A variety of histological changes affecting the glomerular and tubular elements of renal tissue were detected and were more intense in the eighth week of the experiment. A significant increase in GTA, MMI and area per cent of C.T. were also found in diabetic rats. All the tested parameters showed a significant improvement in the glimepiride-treated group. Conclusion: glimepiride could attenuate most of the histological changes produced in case of experimentally induced diabetic nephropathy in spite of persistent hyperglycemia. Recommendation: glimepiride could be used in Type I and type II diabetics to protect or slow down the progression of diabetic nephropathy.

Histological assessment of the possible protective role of glimepiride against progression of experimentally induced diabetic nephropathy in rats

Introduction: little is known about the potential effects induced by sulphonylureas independently of their anti-hyperglycemic action. The present study examined the effect of glimepiride treatment on the progression of renal histological changes in diabetic rats to determine whether therapeutic intervention with these agents would prevent the onset and progression of renal complications or not. Material and methods: forty-eight adult male albino rats were equally divided into four groups; control, normal rats receiving glimepiride, streptozotocin induced diabetic non-treated rats and glimepiride-treated diabetic rats. Blood glucose level measurement and histological evaluation of renal tissue elements using H&E, Masson trichrome, and PAS reaction techniques at four and eight weeks after treatment were performed. Stained sections were subjected to some morphometric measurements namely, glomerular tuft area (GTA), mesangial matrix index (MMI) and area per cent of connective tissue (CT). Statistical analysis for significance of obtained data was performed using analysis of variance and student-T test. Results: Glimepiride did not cause any histological renal impairment when used solely. Induction of diabetes had a significant negative impact on renal structure. In addition to significant elevation of blood glucose levels, increased kidney and kidney to body weight ratio was estimated. A variety of histological changes affecting the glomerular and tubular elements of renal tissue were detected and were more intense in the eighth week of the experiment. A significant increase in GTA, MMI and area per cent of C.T. were also found in diabetic rats. All the tested parameters showed a significant improvement in the glimepiride-treated group. Conclusion: glimepiride could attenuate most of the histological changes produced in case of experimentally induced diabetic nephropathy in spite of persistent hyperglycemia. Recommendation: glimepiride could be used in Type I and type II diabetics to protect or slow down the progression of diabetic nephropathy.

Albuminuria and Renal Histopathology in Hyperlipidemic, Insulin Resistant Swine

Human diabetic nephropathy is characterized by progressive renal insufficiency, albuminuria, and characteristic histopathology. Both insulin resistance (IR) without overt diabetes as well as hyperglycemia in diabetes are risk factors for chronic renal disease in humans.ObjectiveTo determine the extent of renal dysfunction and histopathology in hypercholesterolemic IR pigs and if these changes mirror the nephropathy seen in IR humans.Methods18 adult IR pigs were fed a high fat diet and 6 adult FH insulin sensitive (IS) pigs were fed a low fat diet for 12 months. Urine was analyzed for albumin/creatinine ratio (UA/C) and kidneys for histopathology.ResultsAll pigs had comparable hypercholesterolemia. One IR pig died with renal failure after 3 months on diet (serum creatinine 9.4 mg/dl). No other pig had an increase in serum creatinine. 9/18 IR pigs that completed 12 months of diet had UA/C &gt;30 and only these 9 had higher blood pressure and renal histopathology: glomerulosclerosis, increased mesangial matrix area, tubulointerstitial fibrosis, and arteriolar hyalinosis (p &lt; 0.05). 0/6 IS FH pigs had a UA/C&gt; 30 or renal histopathology.ConclusionRenal histopathology in IR pigs appears to mirror the phenotype of a diabetic nephropathy when albuminuria is present. These data also suggest that IR is necessary but insufficient for nephropathogenesis in pigs. Research support: NCBC 2008‐MRG‐1101, R01 HL069364.

Pathological Roles of Advanced Glycation End Product Receptors SR‐A and CD36

The pathological significance of advanced glycation end product (AGE)-modified proteins deposited in several lesions is generally accounted for by their cellular interaction via the AGE receptors and subsequent acceleration of the inflammatory process. In this study, we focused on two AGE receptors-specifically, the role of SR-A in pathogenesis of diabetic nephropathy and the role of CD36 in AGE-induced downregulation of leptin by adipocytes. In terms of SR-A, diabetic wild-type mice exhibited increased urinary albumin excretion, glomerular hypertrophy, and mesangial matrix expansion, whereas SR-A-knockout mice showed reduced glomerular size and mesangial matrix area. In these diabetic SR-A-knockout mice, the number of macrophages that infiltrated into glomeruli was remarkably reduced (P < 0.05), suggesting that SR-A-dependent glomerular migration of macrophages plays an important role in the pathogenesis of diabetic nephropathy. In terms of CD36, incubation of glycolaldehyde-modified bovine serum albumin (GA-BSA) with 3T3-L1 adipocytes reduced leptin secretion by these cells. The binding of GA-BSA to these cells and subsequent endocytic degradation were effectively inhibited by a neutralizing anti-CD36 antibody. AGE-induced downregulation of leptin was protected by N-acetyl-cysteine, an antioxidant. These results indicate that the interaction of AGE ligands with 3T3-L1 adipocytes via CD36 induces oxidative stress and leads to inhibition of leptin expression by these cells, suggesting a potential link of this phenomenon to exacerbation of the insulin sensitivity in metabolic syndrome.

Vascular endothelial growth factor gene expression is correlated with glomerular neovascularization in human diabetic nephropathy

In diabetic nephropathy (DN) small vessels are frequently observed around the glomerular vascular pole in addition to normal afferent and efferent arterioles; this is regarded as neovascularization . Because vascular endothelial growth factor (VEGF) promotes vascular generation, the authors investigated the relationship between glomerular VEGF gene expression and structural glomerular changes in the early stage of human DN. Kidney specimens were obtained from 18 type 2 DN patients by open renal biopsy. Additional vessels were distinguished by light microscopy as either afferent or efferent arterioles. Glomerular VEGF messenger RNA expression was determined by using in situ hybridization. The mesangial matrix area was quantified, and the ratio of the mesangial matrix area to the whole glomerular area was calculated to determine the mesangial matrix index (MMI). There were significantly more glomeruli with extra vessels in DN than in normal kidneys. The degree of neovascularization was significantly increased in DN and correlated with the magnitude of VEGF messenger RNA expression (r 2 = 0.46, P = 0.010) and MMI (r 2 = 0.45, P = 0.0093). These findings suggest that glomerular VEGF may be involved in structural changes in human DN at an early stage.

Cux-1 transgenic mice develop glomerulosclerosis and interstitial fibrosis

Cux-1 is a murine homeobox gene that is highly expressed in the nephrogenic zone of the developing kidney. Transgenic mice ectopically expressing Cux-1 develop renal hyperplasia associated with down-regulation of the cyclin kinase inhibitor p27. Because the reduction of p27 has been associated with mesangial cell proliferation and glomerular disease, we evaluated glomerular changes in Cux-1 transgenic mice. Adult kidneys from Cux-1 transgenic mice were analyzed morphologically for changes in glomerular cell number and for changes in mesangial and interstitial extracellular matrix deposition. Mesangial matrix expansion was identified by light microscopy. Glomerular cell number was performed following immunohistochemistry. Type IV collagen deposition was analyzed by immunofluoresence and Western blotting. Renal function was evaluated by serum protein, blood urea nitrogen (BUN), creatinine, and electrolyte analysis, and by urine protein and creatinine analysis. In adult transgenic glomeruli, Cux-1 was ectopically expressed in mesangial cells, and this was associated with an increase in mesangial cell number, resulting from an increase in proliferation. There was a marked increase in mesangial matrix area in transgenic mice compared to non-transgenic littermates, related to an increase in type IV collagen. Podocyte foot process effacement was observed in transgenic mice, and this was related to an increase in urinary albumin. Interstitial fibrosis was also observed in transgenic kidneys. These observations indicate that increased expression of Cux-1 in mesangial cells results in cell proliferation and mesangial expansion. In addition, these changes are potentially related to disruption of podocyte architecture leading to loss of filtration. These results suggest that expression of Cux-1 is sufficient to induce the early events of mesangioproliferative glomerulonephritis.

Heminephrectomy causes the progression of glomerulosclerosis and apoptosis in high IgA strain of ddY (HIGA) mice

Background: The nephron reduction in IgA nephropathy is critical for the newly established prognosis of this disease. A high immunoglobulin A inbred strain of ddY mouse (HIGA mouse) showed progressive mesangial sclerosis with elevated renal expression of transforming growth factor (TGF)‐β,1 however, the progression of the renal lesion of this mouse is relatively mild with rare association of active crescentic glomerulonephritis. However, although nephron reduction causes progressive renal injury, the modifications of glomerular lesions by nephron reduction are dependent upon the pathological background of each strain. Thus, we investigated the influence of nephron reduction by heminephrectomy on the renal lesions of the HIGA mouse.Methods: Five‐week‐old HIGA mice were heminephrectomized (Nx), and were evaluated in comparison with a sham‐operated group (S) at 40 weeks old. Measurements of renal function, blood pressure and serum levels of immunoglobulins (IgG, IgA, and IgM) were performed. Histological findings, including glomerular enlargement, matrix expansion, immunoglobulin depositions (IgG, IgA, and IgM), expressions of cytokines (TGF‐β, TNF‐α, and IL‐6) and extracellular matrix proteins were analysed. PCNA and TUNEL stainings were performed. In addition, mRNA expressions of renin‐angiotensin systems (RAS; angiotensinogen and angiotensin converting enzyme (ACE)) were also investigated.Results: The physiological and serological data showed no significant difference between Nx and S. In Nx, the glomerular tuft area and ratio of mesangial matrix area for one tuft were significantly increased and glomerular IgG and IgM deposits were significantly expanded in the paramesangium. However, IgA was not significantly increased. The glomerular expressions of cytokines (TGF‐β, TNF‐α, and IL‐6) and extracellular matrix proteins (fibronectin, collagen type I and IV) were significantly increased in this group. In contrast to the significant decrease of PCNA‐positive cells, TUNEL‐positive cells were significantly increased in Nx. The total mRNA expression of ACE was also significantly increased in the renal cortex of Nx.Conclusion: Heminephrectomy of HIGA mice may be a potential model for the research into the progressive glomerulosclerosis of human IgA nephropathy. The pathological role of apoptosis is apparently involved in these disease processes, possibly through up‐regulated RAS.

Overexpression of Cu2+/Zn2+ superoxide dismutase protects against early diabetic glomerular injury in transgenic mice.

Ex vivo and in vitro observations implicate superoxide as a mediator of cell injury in diabetes, but in vivo evidence is lacking. In the current studies, parameters of glomerular injury were examined in hemizygous nondiabetic transgenic mice (SOD) and streptozotocin-diabetic (D) transgenic mice (D-SOD), which overexpress human cytoplasmic Cu2+/Zn2+ superoxide dismutase (SOD-1), and in corresponding wild-type littermates (WT, D-WT) after 4 months of diabetes. In both SOD and D-SOD mice, renal cortical SOD-1 activity was twofold higher than values in the WT mice; blood glucose and glycosylated hemoglobin (GHb) levels did not differ in the two diabetic groups. Urinary albumin excretion, fractional albumin clearance, urinary transforming growth factor-beta (TGF-beta) excretion, glomerular volume, glomerular content of immunoreactive TGF-beta, and collagen alpha1 (IV) and renal cortical malondialdehyde (MDA) levels were significantly higher in D-WT mice compared with corresponding values in D-SOD mice. Glomerular volume, glomerular content of TGF-beta and collagen IV, renal cortical MDA, and urinary excretion of TGF-beta in D-SOD mice did not differ significantly from corresponding values in either the nondiabetic SOD or WT mice. In separate groups of mice studied after 8 months of diabetes, mesangial matrix area, calculated as a fraction of total glomerular tuft area, and plasma creatinine were significantly higher in D-WT but not in D-SOD mice, compared with corresponding values in the nondiabetic mice. In vitro infection of mesangial cells (MC) with a recombinant adenovirus encoding human SOD-1 increased SOD-1 activity threefold over control cells and prevented the reduction of aconitase activity, an index of cellular superoxide, and the increase in collagen synthesis that otherwise occurred in control MC in response to culture with 300 or 500 mg/dl glucose. Thus, increases in cellular SOD-1 activity attenuate diabetic renal injury in vivo and also prevent stimulation of MC matrix protein synthesis induced in vitro by high glucose.

Effect of chronic and progressive aortic constriction on renal function and structure in rats

The purpose of this study was to evaluate the functional and structural renal damage observed in aortic-constricted hypertensive rats and to identify their possible relationship with transforming growth factor β (TGF-β) expression. Progressive renovascular hypertension was induced by progressive aortic constriction between the two renal arteries. Three months after constriction, the glomerular filtration rate (GFR), effective renal blood flow (ERBF), perfusion pressure (PP), urinary protein excretion (UPE) and urinary electrolyte excretion (UNaV and UKV) in the kidney above (right kidney, RK) and below the ligature (left kidney, LK) were measured. The cross-sectional corpuscular, capillary tuft and mesangial matrix area and tubulo-interstitial fibrosis were measured in tissue sections stained with Syrius Red using a computer-assisted image analysis system. TGF-β was detected by immunohistochemistry. The functional parameters were similar in the two kidneys of aortic-constricted hypertensive rats (GFR-RK, 1.33 ± 0.08 vs. LK, 1.18 ± 0.08 mL/min; ERBF-RK, 9.23 ± 1.32 vs. LK, 8.18 ± 0.91 mL/min; RVR-RK, 28.3 ± 3.9 vs. LK, 21.7 ± 3.2 mmHg·min/mL). The RK was subject to a higher PP than the LK (176 ± 7 vs. 128 ± 5 mmHg, P &lt; 0.05). UPE, UNaV, and UKV were greater in the RK than in the LK (UPE-RK, 512 ± 61 vs. LK, 361 ± 38 µg/30 min, P &lt; 0.05; UNaV-RK, 0.056 ± 0.012 vs. LK, 0.022 ± 0.006 mEq/30 min, P &lt; 0.05; UKV-RK, 0.042 ± 0.006 vs. LK, 0.029 ± 0.003 mEq/30 min, P &lt; 0.05). Morphometric analysis revealed that the RK capillary tuft area and mesangial matrix area were higher than those in the LK. The LK had a higher degree of interstitial fibrosis than the RK. No significant differences in TGF-β immunostaining were observed between the RK and the LK. In conclusion, the RK (subjected to hypertension) of aortic-constricted hypertensive animals developed glomerular fibrosis, only in the outer glomeruli whereas the LK developed mild interstitial fibrosis. Neither glomerular nor interstitial fibrosis seem to be responsible for the proteinuria observed in both kidneys.Key words: renovascular hypertension, renal fibrosis, rats, TGF-β.