Green tea (Camellia sinensis) attenuates nephropathy by downregulating Nox4 NADPH oxidase in diabetic spontaneously hypertensive rats.
ABSTRACT: Green tea (GT), through its antioxidant properties, may be useful to treat or prevent human diseases. Because several lines of evidence suggest that oxidative stress contributes to the pathogenesis of diabetic nephropathy, we tested the hypothesis that GT prevents diabetes and hypertension-related renal oxidative stress, attenuating renal injury. Spontaneously hypertensive rats (SHR) with streptozotocin-induced diabetes and nondiabetic SHR were treated daily with tap water or freshly prepared GT (13.3 g/L). After 12 wk, the systolic blood pressure did not differ between treated and untreated nondiabetic or diabetic rats. However, body weight was less (P < 0.05) and glycemia was greater in diabetic SHR rats than in nondiabetic rats. Renal oxidative stress variables such as 8-hydroxy-2'-deoxyguanosine (8-OHdG) and nitrotyrosine expression, NADPH oxidase-dependent superoxide generation, and the expression of renal cortex Nox4 were greater (P < 0.05) in diabetic rats that received water (DW) than in nondiabetic rats that received water (CW). The 8-OHdG and NADPH oxidase-dependent superoxide generation were significantly less in rats treated with GT. Nitrotyrosine and Nox4 expression were significantly less in diabetic rats that received GT (DGT) than in DW. Likewise, the indices of renal injury, albuminuria, and renal expression of collagen IV were significantly greater in DW than in CW. These differences were significantly less in DGT than in DW. GT reestablished the redox state and reduced the indicators of nephropathy without altering glycemia and blood pressure levels in diabetic SHR. These findings suggest that the consumption of GT may ameliorate nephropathy in diabetic hypertensive patients.
Project description:Diabetic nephropathy (DN) and hypertension are prime causes for end-stage renal disease (ESRD) that often coexist in patients, but are seldom studied in combination. Kidney adenosine levels are markedly increased in diabetes, and the expression and function of renal adenosine receptors are altered in experimental diabetes. The aim of this work is to explore the impact of endogenous and exogenous adenosine on the expression/distribution profile of its receptors along the nephron of hypertensive rats with experimentally-induced diabetes. Using spontaneously hypertensive (SHR) rats rendered diabetic with streptozotocin (STZ), we show that treatment of SHR-STZ rats with an agonist of adenosine receptors increases A<sub>2A</sub> immunoreactivity in superficial glomeruli (SG), proximal tubule (PCT), and distal tubule (DCT). Differently, treatment of SHR-STZ rats with a xanthinic antagonist of adenosine receptors decreases adenosine A<sub>3</sub> immunoreactivity in SG, PCT, DCT, and collecting duct. There is no difference in the immunoreactivity against the adenosine A<sub>1</sub> and A<sub>2B</sub> receptors between the experimental groups. The agonist of adenosine receptors ameliorates renal fibrosis, probably via A<sub>2A</sub> receptors, while the antagonist exacerbates it, most likely due to tonic activation of A<sub>3</sub> receptors. The reduction in adenosine A<sub>3</sub> immunoreactivity might be due to receptor downregulation in response to prolonged activation. Altogether, these results suggest an opposite regulation exerted by endogenous and exogenous adenosine upon the expression of its A<sub>2A</sub> and A<sub>3</sub> receptors along the nephron of hypertensive diabetic rats, which has a functional impact and should be taken into account when considering novel therapeutic targets for hypertensive-diabetic nephropathy.
Project description:OBJECTIVE:Chronic renal insufficiency and/or proteinuria in type 2 diabetes may stem from chronic renal diseases (CKD) other than classic diabetic nephropathy in more than one-third of patients. We interrogated urine proteomic profiles generated by surface-enhanced laser desorption/ionization-time of flight/mass spectrometry with the aim of isolating a set of biomarkers able to reliably identify biopsy-proven diabetic nephropathy and to establish a stringent correlation with the different patterns of renal injury. RESEARCH DESIGN AND METHODS:Ten micrograms of urine proteins from 190 subjects (20 healthy subjects, 20 normoalbuminuric, and 18 microalbuminuric diabetic patients and 132 patients with biopsy-proven nephropathy: 65 diabetic nephropathy, 10 diabetic with nondiabetic CKD [nd-CKD], and 57 nondiabetic with CKD) were run using a CM10 ProteinChip array and analyzed by supervised learning methods (Classification and Regression Tree analysis). RESULTS:The classification model correctly identified 75% of patients with normoalbuminuria, 87.5% of those with microalbuminuria, and 87.5% of those with diabetic nephropathy when applied to a blinded testing set. Most importantly, it was able to reliably differentiate diabetic nephropathy from nd-CKD in both diabetic and nondiabetic patients. Among the best predictors of the classification model, we identified and validated two proteins, ubiquitin and ?2-microglobulin. CONCLUSIONS:Our data suggest the presence of a specific urine proteomic signature able to reliably identify type 2 diabetic patients with diabetic glomerulosclerosis.
Project description:Esaxerenone is a novel selective mineralocorticoid receptor (MR) blocker that was recently approved in Japan to treat hypertension. In phase II and III studies, esaxerenone plus a renin-angiotensin system inhibitor markedly reduced the urinary albumin-to-creatinine ratio (UACR) in hypertensive patients with diabetic nephropathy. To evaluate a direct renoprotective effect by MR blockade independent of an antihypertensive effect in the context of diabetic nephropathy, esaxerenone (3?mg/kg), olmesartan (an angiotensin II receptor blocker; 1?mg/kg), or both were orally administered to KK-Ay mice, a type 2 diabetes model, once daily for 56 days. Urinary albumin (Ualb), UACR, and markers, such as podocalyxin, monocyte chemoattractant protein-1 (MCP-1), and 8-hydroxy-2'-deoxyguanosine (8-OHdG), were measured, along with systolic blood pressure (SBP), fasting blood glucose, and serum K<sup>+</sup> levels. Prior to the initiation of drug administration, KK-Ay mice showed higher blood glucose, insulin, Ualb excretion, and UACR levels than C57BL/6?J mice, a nondiabetic control, indicating the development of diabetic renal injury. Combined treatment with esaxerenone and olmesartan significantly reduced the change in UACR from baseline compared with the change associated with vehicle at week 8 (-1.750 vs. 0.339?g/gCre; P?<?0.002) and significantly inhibited the change in Ualb from baseline compared with the change associated with vehicle at week 8 (P?<?0.002). The combination treatment also reduced urinary excretion of podocalyxin and MCP-1, but did not influence 8-OHdG excretion, SBP, blood glucose, or serum K<sup>+</sup> levels. Overall, esaxerenone plus olmesartan treatment ameliorated diabetic nephropathy in KK-Ay mice without affecting SBP, suggesting that the renoprotective effects of esaxerenone could be exerted independently of its antihypertensive effect.
Project description:Diabetic nephropathy is a major cause of chronic kidney disease and end-stage kidney disease. However, so little is known about alterations of the glycopatterns in urine with the development of diabetic nephropathy. Presently, we interrogated glycopatterns in urine specimens using a lectin microarray. The results showed that expression levels of Sia<i>?</i>2-6Gal/GalNAc recognized by SNA exhibited significantly increased tendency with the development of diabetic nephropathy; moreover, SNA blotting indicated glycoproteins (90?kDa, 70?kDa, and 40?kDa) in urine may contribute to this alteration. Furthermore, the glycopatterns of (GlcNAc)<sub>2-4</sub> recognized by STL exhibited difference between diabetic and nondiabetic nephropathy. The results of urinary protein microarray fabricated by another 48 urine specimens also indicated (GlcNAc)<sub>2-4</sub> is a potential indictor to differentiate the patients with diabetic nephropathy from nondiabetic nephropathy. Furtherly, STL blotting showed that the 50?kDa glycoproteins were correlated with this alteration. In conclusion, our data provide pivotal information to monitor the development of diabetic nephropathy and distinguish between diabetic nephropathy and nondiabetic renal disease based on precise alterations of glycopatterns in urinary proteins, but further studies are needed in this regard.
Project description:Nephropathy frequently co-occurs with metabolic syndrome in humans. Metabolic syndrome is a cluster of metabolic diseases including obesity, diabetes, hypertension, and dyslipidemia, and some previous studies revealed that dyslipidemia contributes to the progression of kidney dysfunction. To establish a new nephropathy model with metabolic syndrome, we produced human apolipoprotein B (apoB) transgenic (Tg.) SHR/NDmcr-cp (SHR-cp/cp) rats, in which dyslipidemia is exacerbated more than in an established metabolic syndrome model, SHR-cp/cp rats. Human apoB Tg. SHR-cp/cp rats showed obesity, hyperinsulinemia, hypertension, and severe hyperlipidemia. They also exhibited exacerbated early-onset proteinuria, accompanied by increased kidney injury and increased oxidative and inflammatory markers. Histological analyses revealed the characteristic features of human apoB Tg. SHR-cp/cp rats including prominent glomerulosclerosis with lipid accumulation. Our newly established human apoB Tg. SHR-cp/cp rat could be a useful model for the nephropathy in metabolic syndrome and for understanding the interaction between dyslipidemia and renal dysfunction in metabolic syndrome.
Project description:Familial clustering of disparate kidney diseases including clinically diagnosed hypertensive and diabetic nephropathy, idiopathic focal segmental glomerulosclerosis, and HIV-associated nephropathy are often observed in African Americans. Admixture mapping recently identified the nonmuscle myosin heavy chain 9 gene (MYH9) as a susceptibility factor strongly associated with several nondiabetic etiologies of end-stage renal disease in African Americans, less strongly with diabetes-associated end-stage renal disease. MYH9-associated nephropathies reside in the spectrum of focal segmental glomerulosclerosis/focal global glomerulosclerosis. The renal histology in proteinuric African Americans homozygous for MYH9 risk variants with longstanding type 2 diabetes mellitus is unknown. We report a case of coincident idiopathic focal segmental glomerulosclerosis collapsing variant and diabetic nephropathy in an African American homozygous for the MYH9 E1 risk haplotype. This case demonstrates that diabetic African Americans with overt proteinuria can have mixed renal lesions, including those in the spectrum of MYH9-associated nephropathy. Careful interpretation of kidney biopsies in proteinuric African Americans with diabetes is necessary to exclude coincident nondiabetic forms of nephropathy, precisely define etiologies of kidney disease, and determine the natural history and treatment response in mixed lesions of diabetes-associated and MYH9-associated kidney disease.
Project description:In nondiabetic rat models of renal disease, angiotensin II (Ang II) perpetuates podocyte injury and promotes progression to end-stage kidney disease. Herein, we wanted to explore the role of Ang II in diabetic nephropathy by a translational approach spanning from in vitro to in vivo rat and human studies, and to dissect the intracellular pathways involved. In isolated perfused rat kidneys and in cultured human podocytes, Ang II down-regulated nephrin expression via Notch1 activation and nuclear translocation of Snail. Hairy enhancer of split-1 was a Notch1-downstream gene effector that activated Snail in cultured podocytes. In vitro changes of the Snail/nephrin axis were similar to those in renal biopsy specimens of Zucker diabetic fatty rats and patients with advanced diabetic nephropathy, and were normalized by pharmacological inhibition of the renin-angiotensin system. Collectively, the present studies provide evidence that Ang II plays a relevant role in perpetuating glomerular injury in experimental and human diabetic nephropathy via persistent activation of Notch1 and Snail signaling in podocytes, eventually resulting in down-regulation of nephrin expression, the integrity of which is crucial for the glomerular filtration barrier.
Project description:<h4>Background and objectives</h4>Presumed genetic risk for diabetic and nondiabetic end stage renal disease is strong in African Americans.<h4>Design, setting, participants, & measurements</h4>Exome sequencing data from African Americans with type 2 diabetic end stage renal disease and nondiabetic, non-nephropathy controls in the T2D-GENES study (Discovery, n=529 patients and n=535 controls) were evaluated, focusing on missense variants in NPHS1. Associated variants were then evaluated in independent type 2 diabetic end stage renal disease (Replication, n=1305 patients and n=760 controls), nondiabetic end stage renal disease (n=1705), and type 2 diabetes-only, non-nephropathy samples (n=503). All participants were recruited from dialysis facilities and internal medicine clinics across the southeastern United States from 1991 to present. Additional NPHS1 missense variants were identified from exome sequencing resources, genotyped, and sequence kernel association testing was then performed.<h4>Results</h4>Initial analysis identified rs35238405 (T233A; minor allele frequency=0.0096) as associated with type 2 diabetic end stage renal disease (adjustment for admixture P=0.042; adjustment for admixture+APOL1 P=0.080; odds ratio, 2.89 and 2.36, respectively); with replication in independent type 2 diabetic end stage renal disease samples (P=0.018; odds ratio, 4.30) and nondiabetic end stage renal disease samples (P=0.016; odds ratio, 4.48). In a combined analysis (all patients with end stage renal disease versus all controls), T233A was associated with all-cause end stage renal disease (P=0.0038; odds ratio, 2.82; n=3270 patients and n=1187 controls). A P-value of <0.001 was obtained after adjustment for admixture and APOL1 in sequence kernel association testing. Two additional variants (H800R and Y1174H) were nominally associated with protection from end stage renal disease (P=0.036; odds ratio, 0.44; P=0.0084; odds ratio, 0.040, respectively) in the locus-wide single-variant association tests.<h4>Conclusions</h4>Coding variants in NPHS1 are associated with both risk for and protection from common forms of nephropathy in African Americans.
Project description:Krüppel-like factor 2 (KLF2), a shear stress-inducible transcription factor, has endoprotective effects. In streptozotocin-induced diabetic rats, we found that glomerular Klf2 expression was reduced in comparison with nondiabetic rats. However, normalization of hyperglycemia by insulin treatment increased Klf2 expression to a level higher than that of nondiabetic rats. Consistent with this, we found that Klf2 expression was suppressed by high glucose but increased by insulin in cultured endothelial cells. To determine the role of KLF2 in streptozotocin-induced diabetic nephropathy, we used endothelial cell-specific Klf2 heterozygous knockout mice and found that diabetic knockout mice developed more kidney/glomerular hypertrophy and proteinuria than diabetic wild-type mice. Glomerular expression of Vegfa, Flk1, and angiopoietin 2 increased, but expression of Flt1, Tie2, and angiopoietin 1 decreased, in diabetic knockout mice compared with diabetic wild-type mice. Glomerular expression of ZO-1, glycocalyx, and eNOS was also decreased in diabetic knockout compared with diabetic wild-type mice. These data suggest knockdown of Klf2 expression in the endothelial cells induced more endothelial cell injury. Interestingly, podocyte injury was also more prominent in diabetic knockout compared with diabetic wild-type mice, indicating a cross talk between these two cell types. Thus, KLF2 may play a role in glomerular endothelial cell injury in early diabetic nephropathy.
Project description:Diabetic kidney disease (DKD) is a common complication of diabetes, which frequently leads to end-stage renal failure and increases cardiovascular disease risk. Hyperglycemia promotes renal pathologies such as glomerulosclerosis, tubular hypertrophy, microalbuminuria, and a decline in glomerular filtration rate. Importantly, recent clinical data have demonstrated distinct sexual dimorphism in the pathogenesis of DKD in people with diabetes, which impacts both severity- and age-related risk factors. This study aimed to define sexual dimorphism and renal function in a nonobese type 2 diabetes model with the spontaneous development of advanced diabetic nephropathy (T2DN rats). T2DN rats at 12- and over 48-wk old were used to define disease progression and kidney injury development. We found impaired glucose tolerance and glomerular hyperfiltration in T2DN rats to compare with nondiabetic Wistar control. The T2DN rat displays a significant sexual dimorphism in insulin resistance, plasma cholesterol, renal and glomerular injury, urinary nephrin shedding, and albumin handling. Our results indicate that both male and female T2DN rats developed nonobese type 2 DKD phenotype, where the females had significant protection from the development of severe forms of DKD. Our findings provide further evidence for the T2DN rat strain's effectiveness for studying the multiple facets of DKD.