cyclic-gmp and Diabetic-Nephropathies

The aim of this study was to determine the influence of metabolic control of diabetes on natriuresis, the effect of natriuretic peptides and renal kallikrein on the kidney and the participation of proximal and distal tubules in natriuresis. The study was done in 41 individuals: 27 IDDM patients and 14 healthy controls. The patients were on insulin only, had normal blood pressure, and were prescribed a standard diabetic diet without sodium or protein restriction. Diabetic patients were assigned to subgroups, depending on the stage of nephropathy and level of metabolic control. Urine collection was done three times daily in all participants. The first collection was done after 500 mg lithium carbonate (p.o.) and was followed by 10 mg amilorid (Midamor, Thomas Morson Pharmaceuticals). The third collection of urine was used to evaluate excretion of cGMP. In addition to sodium, lithium, potassium and creatinine clearances, excretion of renal kallikrein, and levels of microalbuminuria, fructosamine and glycated hemoglobin were also determined. Lithium clearance was used to evaluate tubular sodium transport. The influence of diuretic peptides--ANP and urodilatin, on natriuresis was reflected by urinary cGMP excretion. Function of the kallikrein-kinin system was studied on the basis of excretion of kallikrein. Amilorid was used to test the effect of blocking amiloride-sensitive sodium channels in distal tubules on natriuresis (Tab. 1). A statistically significant decrease in mean lithium clearance was observed in IDDM patients as compared to healthy controls. Creatinine clearance was the same in both groups (Tab. 2). Lower lithium clearance was observed in the subgroup of diabetic patients with "silent" nephropathy. Diabetic patients with "silent" and early nephropathy had significantly higher levels of fractional sodium reabsorption in the proximal tubule when compared with controls (Tab. 3). Moreover, lower daily excretion of kallikrein was observed in patients with stage II nephropathy in comparison to the control group (Tab. 4). Amilorid uptake had no influence on urinary kallikrein. However, natriuresis after amilorid was significantly higher in diabetic patients than in controls. In conclusion, reabsorption in the proximal tubule is increased in patients with "silent" diabetic nephropathy, as revealed by decreased lithium clearance and unchanged creatinine clearance. Hyperactivity of the proximal tubule in stage II and III of diabetic nephropathy results in

Topics: Cyclic GMP; Diabetes Mellitus, Type 1; Diabetic Nephropathies; Female; Humans; Kallikreins; Kidney; Kidney Tubules, Proximal; Lithium; Male; Natriuresis; Sodium

To examine the impact of metabolic control on renal responses to human atrial natriuretic peptide (hANP) in type 1 diabetes mellitus, 13 patients with HbA1 less than 8.5%, nine patients with HbA1 greater than 8.5% and ten healthy volunteers were studied. According to a randomized, single-blind trial design, 0.5 and 2.0 micrograms/kg hANP-(95-126) (Urodilatin) (Bissendorf Peptide, Hannover) or placebo were given as iv bolus injections at 90-minute intervals. Patients with HbA1 greater than 8.5% differed from those with HbA1 less than 8.5% in longer diabetes duration, more prevalent retinopathy and neuropathy and increased somatomedin C levels and urinary albumin excretion (p less than 0.05). In response to hANP, patients with HbA1 greater than 8.5% had decreased responses of urinary volume and sodium excretion in comparison to patients with HbA1 less than 8.5% (p less than 0.05) in whom renal responses to hANP did not differ from controls. Despite similar hANP levels, hANP-stimulated urinary cGMP excretion in patients was higher than in controls (p less than 0.01). Impaired renal responses to hANP in diabetes patients with insufficient glycemic control apparently contribute to the mechanisms of diabetic sodium retention. Near-normoglycemia may prevent this phenomenon which is intimately involved into the pathogenesis of diabetic nephropathy.

Topics: Adult; Atrial Natriuretic Factor; Cyclic GMP; Diabetes Mellitus, Type 1; Diabetic Nephropathies; Diuretics; Dose-Response Relationship, Drug; Female; Glycated Hemoglobin; Humans; Male; Peptide Fragments; Single-Blind Method

A decrease in intracellular levels of 3',5'-cyclic guanosine monophosphate (cGMP) has been implicated in the progression of diabetic nephropathy. Hyperglycemia significantly inhibits cGMP-dependent pathway activity in the kidney, leading to glomerular damage and proteinuria. The enhancement of activity of this pathway that is associated with an elevation of cGMP levels may be achieved by inhibition of the cGMP specific phosphodiesterase 5A (PDE5A) using selective inhibitors, such as tadalafil. Hyperglycemia decreased the insulin responsiveness of podocytes and impaired podocyte function. These effects were associated with lower protein amounts and activity of the protein deacetylase sirtuin 1 (SIRT1) and a decrease in the phosphorylation of adenosine monophosphate-dependent protein kinase (AMPK). We found that PDE5A protein levels increased in hyperglycemia, and PDE5A downregulation improved the insulin responsiveness of podocytes with reestablished SIRT1 expression and activity. PDE5A inhibitors potentiate nitric oxide (NO)/cGMP signaling, and NO modulates the activity and expression of SIRT1. Therefore, we investigated the effects of tadalafil on SIRT1 and AMPK in the context of improving the insulin sensitivity in podocytes and podocyte function in hyperglycemia. Our study revealed that tadalafil restored SIRT1 expression and activity and activated AMPK by increasing its phosphorylation. Tadalafil also restored stimulating effect of insulin on glucose transport in podocytes with high glucose-induced insulin resistance. Additionally, tadalafil improved the function of podocytes that were exposed to high glucose concentrations. Our results display novel mechanisms involved in the pathogenesis of glomerulopathies in diabetes, which may contribute to the development of more effective treatment strategies for diabetic nephropathy.

Topics: AMP-Activated Protein Kinases; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Diabetic Nephropathies; Glucose; Humans; Hyperglycemia; Insulin; Insulin Resistance; Podocytes; Sirtuin 1; Tadalafil

Diabetic nephropathy is the leading cause for end-stage renal disease worldwide. Until now, there is no specific therapy available. Standard treatment with inhibitors of the renin-angiotensin system just slows down progression. However, targeting the NO/sGC/cGMP pathway using sGC activators does prevent kidney damage. Thus, we investigated if the sGC activator cinaciguat was beneficial in a mouse model of diabetic nephropathy, and we analysed how mesangial cells (MCs) were affected by related conditions in cell culture.. Type 1 diabetes was induced with streptozotocin in wild-type and endothelial NOS knockout (eNOS KO) mice for 8 or 12 weeks.. Half of these mice received cinaciguat in their chow for the last 4 weeks. Kidneys from the diabetic mice were analysed with histochemical assays and by RT-PCR and western blotting. . Additionally, primary murine MCs under diabetic conditions were stimulated with 8-Br-cGMP or cinaciguat to activate the sGC/cGMP pathway.. The diabetic eNOS KO mice developed most characteristics of diabetic nephropathy, most marked at 12 weeks. Treatment with cinaciguat markedly improved GFR, serum creatinine, mesangial expansion and kidney fibrosis in these animals. We determined expression levels of related signalling proteins. Thrombospondin 1, a key mediator in kidney diseases, was strongly up-regulated under diabetic conditions and this increase was suppressed by activation of sGC/cGMP signalling.. Activation of the NO/sGC/PKG pathway with cinaciguat was beneficial in a model of diabetic nephropathy. Activators of sGC might be an appropriate therapy option in patients with Type 1 diabetes.. This article is part of a themed issue on cGMP Signalling in Cell Growth and Survival. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.11/issuetoc.

Topics: Animals; Benzoates; Cyclic GMP; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Diabetic Nephropathies; Female; Guanylate Cyclase; Humans; Kidney; Male; Mice; Nitric Oxide; Soluble Guanylyl Cyclase

Diabetic nephropathy (DN) ranks among the most detrimental long-term effects of diabetes, affecting more than 30% of all patients. Within the diseased kidney, intraglomerular mesangial cells play a key role in facilitating the pro-fibrotic turnover of extracellular matrix components and a progredient glomerular hyperproliferation. These pathological effects are in part caused by an impaired functionality of soluble guanylate cyclase (sGC) and a consequentially reduced synthesis of anti-fibrotic messenger 3',5'-cyclic guanosine monophosphate (cGMP). Bay 58-2667 (cinaciguat) is able to re-activate defective sGC; however, the drug suffers from poor bioavailability and its systemic administration is linked to adverse events such as severe hypotension, which can hamper the therapeutic effect. In this study, cinaciguat was therefore efficiently encapsulated into virus-mimetic nanoparticles (NPs) that are able to specifically target renal mesangial cells and therefore increase the intracellular drug accumulation. NP-assisted drug delivery thereby increased in vitro potency of cinaciguat-induced sGC stabilization and activation, as well as the related downstream signaling 4- to 5-fold. Additionally, administration of drug-loaded NPs provided a considerable suppression of the non-canonical transforming growth factor β (TGF-β) signaling pathway and the resulting pro-fibrotic remodeling by 50-100%, making the system a promising tool for a more refined therapy of DN and other related kidney pathologies.

Topics: Animals; Benzoates; Biomimetic Materials; Cells, Cultured; Cyclic GMP; Diabetic Nephropathies; Drug Delivery Systems; Enzyme Activation; Enzyme Stability; Fibrosis; Humans; Mesangial Cells; Models, Biological; Nanoparticles; Rats; Signal Transduction; Soluble Guanylyl Cyclase; Transforming Growth Factor beta

The use of iodine-based contrast agents entails the risk of contrast induced nephropathy (CIN). Radiocontrast agents elicit the third most common cause of nephropathy among hospitalized patients, accounting for 11-12% of cases. CIN is connected with clinically significant consequences, including increased morbidity, prolonged hospitalization, increased risk of complications, potential need for dialysis, and increased mortality rate. The number of in-hospital examinations using iodine-based contrast media has been significantly increasing over the last decade. In order to protect patients from possible complications of such examinations, new biomarkers are needed that are able to predict a risk of contrast-induced nephropathy. Urinary and plasma cyclic guanosine monophosphate (cGMP) concentrations are influenced by renal function. Urinary cGMP is primarily of renal cellular origin. Therefore, we assessed if urinary cGMP concentration may predict major adverse renal events (MARE) after contrast media exposure during coronary angiography.. Urine samples were prospectively collected from non-randomized consecutive patients with either diabetes or preexisting impaired kidney function receiving intra-arterial contrast medium (CM) for emergent or elective coronary angiography at the Charité Campus Mitte, University Hospital Berlin. Urinary cGMP concentration in spot urine was analyzed 24 hours after CM exposure. Patients were followed up over 90 days for occurrence of death, initiation of dialysis, doubling of plasma creatinine concentration or MARE.. In total, 289 consecutive patients were included into the study. Urine cGMP/creatinine ratio 24 hours before CM exposure expressed as mean±SD was predictive for the need of dialysis (no dialysis: 89.77±92.85 μM/mM, n = 277; need for dialysis: 140.3±82.90 μM/mM, n = 12, p = 0.008), death (no death during follow-up: 90.60±92.50 μM/mM, n = 280; death during follow-up: 169.88±81.52 μM/mM, n = 9; p = 0.002), and the composite endpoint MARE (no MARE: 86.02±93.17 μM/mM, n = 271; MARE: 146.64±74.68 μM/mM, n = 18, p<0.001) during the follow-up of 90 days after contrast media application. cGMP/creatinine ratio stayed significantly increased at values exceeding 120 μM/mM in patients who developed MARE, required dialysis or died.. Urinary cGMP/creatinine ratio ≥ 120 μM/mM before CM exposure is a promising biomarker for the need of dialysis and all-cause mortality 90 days after CM exposure in patients with preexisting renal impairment or diabetes.

Topics: Aged; Biomarkers; Cohort Studies; Contrast Media; Creatinine; Cyclic GMP; Diabetic Nephropathies; Female; Glomerular Filtration Rate; Humans; Kidney Diseases; Kidney Function Tests; Male; Middle Aged; Prognosis; ROC Curve; Time Factors

Decreased soluble guanylate cyclase activity and cGMP levels in diabetic kidneys were shown to influence the progression of nephropathy. The regulatory effects of soluble guanylate cyclase activators on renal signaling pathways are still unknown, we therefore investigated the renal molecular effects of the soluble guanylate cyclase activator cinaciguat in type-1 diabetic (T1DM) rats. Male adult Sprague-Dawley rats were divided into 2 groups after induction of T1DM with 60 mg/kg streptozotocin: DM, untreated (DM, n = 8) and 2) DM + cinaciguat (10 mg/kg per os daily, DM-Cin, n = 8). Non-diabetic untreated and cinaciguat treated rats served as controls (Co (n = 10) and Co-Cin (n = 10), respectively). Rats were treated for eight weeks, when renal functional and molecular analyses were performed. Cinaciguat attenuated the diabetes induced proteinuria, glomerulosclerosis and renal collagen-IV expression accompanied by 50% reduction of TIMP-1 expression. Cinaciguat treatment restored the glomerular cGMP content and soluble guanylate cyclase expression, and ameliorated the glomerular apoptosis (TUNEL positive cell number) and podocyte injury. These effects were accompanied by significantly reduced TGF-ß overexpression and ERK1/2 phosphorylation in cinaciguat treated diabetic kidneys. We conclude that the soluble guanylate cyclase activator cinaciguat ameliorated diabetes induced glomerular damage, apoptosis, podocyte injury and TIMP-1 overexpression by suppressing TGF-ß and ERK1/2 signaling.

Topics: Animals; Benzoates; Cyclic GMP; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Diabetic Nephropathies; Disease Models, Animal; Enzyme Activators; Kidney; Male; MAP Kinase Signaling System; Rats, Sprague-Dawley; Transforming Growth Factor beta; Treatment Outcome

The aim of this study was to identify sex-dependent expression of renal transporter mRNA in lean and obese Zucker spontaneously hypertensive fatty (ZSF1) rats and to investigate the interaction of the most altered transporter, organic anion transporter 2 (Oat2), with diabetes-relevant metabolites and drugs. Higher incidence of glomerulosclerosis, tubulointerstitial fibrosis, and protein casts in Bowman's space and tubular lumen was detected by PAS staining in obese male compared to female ZSF1 rats. Real-time PCR on RNA isolated from kidney cortex revealed that Sglt1-2, Oat1-3, and Oct1 were higher expressed in kidneys of lean females. Oct2 and Mrp2 were higher expressed in obese males. Renal mRNA levels of transporters were reduced with diabetic nephropathy in females and the expression of transcription factors Hnf1β and Hnf4α in both sexes. The highest difference between lean and obese ZSF1 rats was found for Oat2. Therefore, we have tested the interaction of human OAT2 with various substances using tritium-labeled cGMP. Human OAT2 showed no interaction with diabetes-related metabolites, diabetic drugs, and ACE-inhibitors. However, OAT2-dependent uptake of cGMP was inhibited by furosemide. The strongly decreased expression of Oat2 and other transporters in female diabetic ZSF1 rats could possibly impair renal drug excretion, for example, of furosemide.

Topics: Animals; Biological Transport; Blood Pressure; Cyclic GMP; Diabetes Mellitus; Diabetic Nephropathies; Female; Furosemide; Gene Expression Profiling; Gene Expression Regulation; HEK293 Cells; Humans; Kidney; Male; Obesity; Organic Anion Transporters, Sodium-Independent; Rats; Rats, Inbred SHR; Rats, Zucker; RNA, Messenger; Sex Factors; Transcription Factors

Aldosterone is increased in diabetes and contributes to the development of diabetic nephropathy. The authors hypothesized that reduction in aldosterone production in diabetes by amlodipine or aliskiren improves diabetic kidney disease by attenuating renal oxidative stress and fibrosis. Normoglycemic and streptozotocin-induced diabetic Sprague-Dawley rats were given vehicle, amlodipine, or aliskiren alone and combined for 6 weeks. At the end of study, we evaluated blood pressure (BP), 24-hour urinary sodium (UNaV) and aldosterone excretion rates, renal interstitial fluid (RIF) levels of nitric oxide (NO), cyclic guanosine 3',5'-monophosphate (cGMP), and 8-isoprostane, and renal morphology. BP was not significantly different between any of experimental groups. UNaV increased in diabetic animals and was not affected by different treatments. Urinary aldosterone excretion increased in diabetic rats receiving vehicle and decreased with amlodipine and aliskiren alone or combined. RIF NO and cGMP levels were reduced in vehicle-treated diabetic rats and increased with amlodipine or aliskiren given alone and combined. RIF 8-isoprostane levels and renal immunostaining for periodic acid-Schiff and fibronectin were increased in vehicle-treated diabetic rats and decreased with aliskiren alone or combined with amlodipine. The authors conclude that inhibition of aldosterone by amlodipine or aliskiren ameliorates diabetes induced renal injury via improvement of NO-cGMP pathway and reduction in oxidative stress and fibrosis, independent of BP changes.

Topics: Aldosterone; Amides; Amlodipine; Animals; Antihypertensive Agents; Blood Glucose; Blood Pressure; Cyclic GMP; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Dinoprost; Down-Regulation; Fibronectins; Fibrosis; Fumarates; Immunohistochemistry; Kidney; Male; Natriuresis; Nitric Oxide; Oxidative Stress; Rats; Rats, Sprague-Dawley; Time Factors

Diabetic nephropathy (DN) is characterized by podocyte damage and increased phosphodiesterase-5 (PDE-5) activity-exacerbating nitric oxide (NO)-cyclic 3',5' guanosine monophosphate (cGMP) pathway dysfunction. It has been shown that PDE-5 inhibition ameliorates DN. The role of podocytes in this mechanism remains unclear. We investigated how selective PDE-5 inhibition influences podocyte damage in streptozotocin (STZ) diabetic rats.. Male Sprague-Dawley rats (250-300 g) were injected with STZ and divided into two groups: (i) STZ control (non-treated, STZ, n=6) and (ii) STZ+vardenafil treatment (10 mg/kg/day, STZ-Vard, n=8). Non-diabetic rats served as negative controls (Control, n=7). Following 8 weeks of treatment, immunohistochemical and molecular analysis of the kidneys were performed.. Diabetic rats had proteinuria, increased renal transforming growth factor (TGF)-β1 expression and podocyte damage when compared with controls. Vardenafil treatment resulted in preserved podocyte cGMP levels, less proteinuria, reduced renal TGF-β1 expression, desmin immunostaining in podocytes and restored both nephrin and podocin mRNA expression. Diabetes led to increased glomerular nitrotyrosine formation and renal neuronal nitric oxide synthase and endothelial nitric oxide synthase mRNA expression, but vardenafil did not influence these parameters.. Our data suggest that a dysfunctional NO-cGMP pathway exacerbates podocyte damage in diabetes. In conclusion, vardenafil treatment preserves podocyte function and reduces glomerular damage, which indicates therapeutic potential in patients with DN.

Topics: Animals; Blotting, Western; Cells, Cultured; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Diabetic Nephropathies; Imidazoles; Intracellular Signaling Peptides and Proteins; Male; Membrane Proteins; Nitric Oxide Synthase Type III; Oxidative Stress; Phosphodiesterase 5 Inhibitors; Piperazines; Podocytes; Proteinuria; Rats; Rats, Sprague-Dawley; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sulfones; Transforming Growth Factor beta1; Triazines; Vardenafil Dihydrochloride

Glomerular hyperfiltration plays a role in the pathophysiology of diabetic nephropathy. An increase in the glomerular filtration rate (GFR) could result from primary actions at the glomerular/vascular level or could be the consequence of a primary increase in proximal tubular sodium reabsorption resulting in systemic volume expansion. Recently it was hypothesized that an increase in sodium reabsorption may lead to glomerular hyperfiltration through the tubulo-glomerular feedback mechanism (tubular-hypothesis) without volume expansion.. We have studied 54 normoalbuminuric patients with type 1 diabetes. The GFR was measured by inulin clearance. Proximal and distal sodium reabsorption were calculated according to standard formulas using the free water clearance technique. Plasma volume, measured by the (125)I-albumin method, atrial natriuretic peptide (ANP) and the second messenger cyclic guanosine-3,5-monophosphate (c-GMP) were used as markers of extracellular volume expansion.. Glomerular hyperfiltration (GFR >or= 130 mL min(-1) 1.73 m(-2)) was present in 14 out of 55 patients with diabetes (25%). There were no differences in plasma volume between normo-(NF) and hyper-filtrating (HF) patients (2933 +/- 423 in NF vs. 3026 +/- 562 mL in HF, NS). Also plasma ANP and c-GMP levels were not significantly different between the groups. The fractional proximal reabsorption of sodium was significantly increased in HF [fPRNa(+) (%) 90.1 +/- 2.0 vs. 91.5 +/- 1.6, P = 0.02]. There were no differences in distal sodium reabsorption or distal sodium load (approximately macula densa concentration of NaCl) in both groups.. Our data suggest that the primary event in diabetic glomerular hyperfiltration is an increase in proximal tubular sodium reabsorption. They do not support the hypothesis that systemic volume expansion or ANP mediate glomerular hyperfiltration in patients with normoalbuminuric type 1 diabetes. As such, changes in tubular sodium handling most probably influence tubulo-glomerular feedback.

Topics: Absorption; Adolescent; Adult; Atrial Natriuretic Factor; Cyclic GMP; Diabetes Mellitus, Type 1; Diabetic Nephropathies; Female; Glomerular Filtration Rate; Humans; Kidney Tubules, Proximal; Male; Plasma Volume; Prospective Studies; Sodium

Renal interstitial fibrosis is believed to play a key role in the development of diabetic nephropathy (DN), and advanced glycation end-products (AGE) may contribute importantly to this. Recent reports have shown that nitric oxide (NO) is closely linked to the renal interstitial fibrosis of DN. In this study, the mechanisms by which NO and its downstream signals mediate the AGE-induced proliferative response in normal rat kidney fibroblasts (NRK-49F) are examined. AGE decreased NO production, cyclic guanosine 5'monophosphate (cGMP) synthesis, and cGMP-dependent protein kinase (PKG) activation time- and dose-dependently. These effects were not observed when cells were treated with nonglycated BSA. NO and inducible nitric oxide synthase (iNOS) stimulated by NO donors S-nitroso-N-acetylpenicillamine (SNAP)/sodium nitroprusside (SNP) and PKG activator 8-para-chlorophenylthio-cGMP (8-pCPT-cGMP) prevented both AGE-induced proliferation and Janus kinase 2 (JAK2)-signal transducers and activators of transcription 5 (STAT5) activation but not p42/p44 mitogen-activated protein kinase (MAPK) activation. The ability of NO-PKG to inhibit AGE-induced cell cycle progression was verified by the observation that SNAP, SNP, and 8-pCPT-cGMP inhibited both cyclin D1 and cdk4 activation. Furthermore, induction of NO-PKG significantly increased p21Waf1/Cip1 expression in AGE-treated NRK-49F cells. The data suggest that the NO-PKG pathway inhibits AGE-induced proliferation by suppressing activation of JAK2-STAT5 and cyclin D1/cdk4 and induction of p21Waf1/Cip1.

Topics: Animals; Blotting, Western; Cell Cycle; Cell Line; Cell Nucleus; Cell Proliferation; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Cyclin D; Cyclin-Dependent Kinase 4; Cyclin-Dependent Kinase Inhibitor p21; Cyclins; Diabetic Nephropathies; Dose-Response Relationship, Drug; Enzyme Activation; Fibroblasts; Flow Cytometry; Glycation End Products, Advanced; Immunoprecipitation; Janus Kinase 2; Kidney; Models, Biological; Nitric Oxide; Nitric Oxide Synthase Type II; Nitroprusside; Oligonucleotides; Oxidative Stress; Penicillamine; Phosphorylation; Protein-Tyrosine Kinases; Proto-Oncogene Proteins; Rats; S-Nitroso-N-Acetylpenicillamine; Signal Transduction; STAT5 Transcription Factor; Thionucleotides; Time Factors

The effects of overexpression of Cu(2+)/Zn(2+) superoxide dismutase-1 (SOD-1) on indexes of renal injury were compared in 5-month-old nontransgenic (NTg) db/db mice and db/db mice hemizygous for the human SOD-1 transgene (SOD-Tg). Both diabetic groups exhibited similar hyperglycemia and weight gain. However, in NTg-db/db mice, albuminuria, glomerular accumulation of immunoreactive transforming growth factor-beta, collagen alpha1(IV), nitrotyrosine, and mesangial matrix were all significantly increased compared with either nondiabetic mice or SOD-Tg-db/db. SOD-1 activity and reduced glutathione levels were higher, whereas malondialdehyde content was lower, in the renal cortex of SOD-Tg-db/db compared with NTg-db/db mice, consistent with a renal antioxidant effect in the transgenic mice. Inulin clearance (C(IN)) and urinary excretion of guanosine 3',5'-cyclic monophosphate (U(cGMP)) were increased in SOD-Tg-db/db mice compared with corresponding values in nondiabetic mice or NTg-db/db mice. C(IN) and U(cGMP) were suppressed by Nomega-nitro-L-arginine methyl ester in SOD-Tg-db/db but not in NTg-db/db mice, implying nitric oxide (NO) dependence of these increases and enhanced renal NO bioactivity in SOD-Tg-db/db. Studies of NO-responsive cGMP in isolated glomeruli supported greater quenching of NO in glomeruli from NTg-db/db compared with SOD-Tg-db/db mice. Evidence of increased NO responsiveness and the suppression of glomerular nitrotyrosine may both reflect reduced NO-superoxide interaction in SOD-Tg-db/db mice. The results implicate superoxide in the pathogenesis of diabetic nephropathy.

Topics: Animals; Base Sequence; Cyclic GMP; Diabetic Nephropathies; DNA Primers; Humans; Immunohistochemistry; Inulin; Kidney; Kidney Glomerulus; Mice; Mice, Transgenic; NG-Nitroarginine Methyl Ester; Nitric Oxide; Reverse Transcriptase Polymerase Chain Reaction; Superoxide Dismutase; Superoxide Dismutase-1; Superoxides; Transforming Growth Factor beta

Dipyridamole stimulates nitric oxide action via inhibition of phosphodiesterase and also has an antioxidant effect. ACE inhibitor reduces glomerular pressure and enhances NO action via increased bradykinin. Thus, we evaluated the effect of the combination of dipyridamole and ACE inhibitor in diabetic nephropathy.. Streptozotocin-induced diabetic rats at 2 weeks were treated with dipyridamole, quinapril or both. The expression of NOS and NAD(P)H oxidase p47phox was investigated using immunohistochemistry and western blot, and urinary albumin, cGMP and lipid peroxidation products (LPO) were measured at 4 weeks.. NAD(P)H oxidase and urinary LPO were significantly enhanced in diabetes, and suppressed by each treatment to the same extent. The nNOS expression in macula densa and eNOS increased significantly with combination therapy compared to quinapril treatment alone contributing to an enhanced urinary excretion of cGMP and to maintain the creatinine clearance. Increased albuminuria in diabetes was reduced more effectively with combination therapy to the control level than with single treatments.. Combination therapy with dipyridamole and quinapril suppressed urinary LPO via reduction of NAD(P)H oxidase increase in diabetes. The combination therapy reduced microalbuminuria to the control level and maintained creatinine clearance with enhanced nNOS and eNOS expression compared to quinapril alone.

Topics: Albuminuria; Angiotensin-Converting Enzyme Inhibitors; Animals; Blood Glucose; Blotting, Western; Creatinine; Cyclic GMP; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Dipyridamole; Drug Therapy, Combination; Female; Immunohistochemistry; Isoquinolines; Kidney; Lipid Peroxides; NADH, NADPH Oxidoreductases; NADPH Oxidases; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Phosphodiesterase Inhibitors; Phosphoproteins; Quinapril; Random Allocation; Rats; Rats, Sprague-Dawley; Tetrahydroisoquinolines

Brain natriuretic peptide (BNP) is released into circulation in response to ventricular dilatation and pressure overload. Plasma BNP concentration correlates with left ventricular mass and dysfunction, which is prevalent in hemodialysis (HD) patients.. To evaluate the potential of BNP level for determination of hydration status, we measured inferior vena caval diameter (IVCD) and BNP levels and performed bioimpedance analysis in 49 HD patients.. Pre-HD BNP levels remained unchanged after HD. Agreement between IVCD and pre-HD BNP level in overhydration was significant (kappa = 0.304). The area under the receiver operating characteristic (ROC) curve for overhydration was 0.819 for pre-HD BNP level. When extracellular fluid/total-body water (ECF/TBW) ratios of HD patients were compared with those of 723 controls, pre- and post-HD BNP levels were significantly greater in overhydrated patients. The area under the ROC curve for overhydration by ECF/TBW ratio was 0.781 for pre-HD BNP level. However, there was no significance for pre- or post-HD BNP levels on assessment of normohydration or underhydration. Pre-HD BNP level correlated significantly with post-HD BNP level, post-HD diastolic blood pressure, pulse pressure, and ECF/TBW ratio. IVCD correlated significantly with post-HD BNP level.. BNP level seems to have a limited potential for assessment of overhydration in HD patients.

Topics: Adult; Aged; Atrial Natriuretic Factor; Biomarkers; Body Water; Cyclic GMP; Diabetic Nephropathies; Electric Impedance; Extracellular Fluid; Female; Humans; Kidney Failure, Chronic; Male; Middle Aged; Natriuretic Peptide, Brain; Renal Dialysis; ROC Curve; Sensitivity and Specificity; Ultrasonography; Vena Cava, Inferior; Ventricular Dysfunction, Left; Water Intoxication

To study the mechanism of preventing proteinuria by traditional Chinese medicine YSGJD in early diabetic nephropathy (DN) in rats.. The male Sprague-Dawley (SD) rats were randomly divided into three groups: normal control, untreated control and treated groups. Experimental diabetes mellitus (DM) was induced in untreated control and treated rats with streptozotocin (STZ), and the normal group was given equal buffer solution. The treated rats were given YSGJD daily. The other two groups were given running water. Eight weeks later, the rats were raised in metabolic cages for 24 hours. Then, the 24 h urinary protein, serum glucose and nitric oxide (NO) were measured. In the renal cortex, the levels of iNOS mRNA and cGMP were determined by reverse transcription-polymerase chain reaction (RT-PCR) and radioimmunoassay separately.. Compared with normal control, in DN rats, the 24 h urine protein, the levels of renal cortex iNOS mRNA and cGMP were increased significantly (P<0.01). All above in treated group were reduced than in untreated control (P<0.05). The serum glucose and NO were increased in DN rats than in normal control (P<0.01), and had a little decrease in the treated group, with no significance between untreated and treated groups.. This recipe can diminish the urine protein in early DN without the significant decrease of serum sugar, can correct the abnormal levels of iNOS mRNA and cGMP in renal cortex. Interfering with the function of NO may be one of its mechanisms.

Topics: Animals; Cyclic GMP; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Drugs, Chinese Herbal; Male; Nitric Oxide Synthase Type II; Phytotherapy; Proteinuria; Rats; Rats, Sprague-Dawley

Adrenomedullin (AM) is a potent vasodilating peptide and is involved in cardiovascular and renal disease. In the present study, we investigated the role of AM in cardiac and renal function in streptozotocin (STZ)-induced diabetic rats. A single tail-vein injection of adenoviral vectors harboring the human AM gene (Ad.CMV-AM) was administered to the rats 1-wk post-STZ treatment (65 mg/kg iv). Immunoreactive human AM was detected in the plasma and urine of STZ-diabetic rats treated with Ad.CMV-AM. Morphological and chemical examination showed that AM gene delivery significantly reduced glycogen accumulation within the hearts of STZ-diabetic rats. AM gene delivery improved cardiac function compared with STZ-diabetic rats injected with control virus, as observed by decreased left ventricular end-diastolic pressure, increased cardiac output, cardiac index, and heart rate. AM gene transfer significantly increased left ventricular long axis (11.69 +/- 0.46 vs. 10.31 +/- 0.70 mm, n = 10, P < 0.05) and rate of pressure rise and fall (+6,090.1 +/- 597.3 vs. +4,648.5 +/- 807.1 mmHg/s), (-4,902.6 +/- 644.2 vs. -3,915.5 +/- 805.8 mmHg/s, n = 11, P < 0.05). AM also significantly attenuated renal glycogen accumulation and tubular damage in STZ-diabetic rats as well as increased urinary cAMP and cGMP levels, along with increased cardiac cAMP and Akt phosphorylation. We also observed that delivery of the AM gene caused an increase in body weight along with phospho-Akt and membrane-bound GLUT4 levels in skeletal muscle. These results suggest that AM plays a protective role in hyperglycemia-induced glycogen accumulation and cardiac and renal dysfunction via Akt signal transduction pathways.

Topics: Adenoviridae; Adrenomedullin; Animals; Blood Glucose; Body Weight; Cyclic AMP; Cyclic GMP; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Disease Models, Animal; Gene Expression; Genetic Therapy; Genetic Vectors; Glucose Transporter Type 4; Glycogen; Heart; Heart Function Tests; Humans; Kidney; Male; Monosaccharide Transport Proteins; Muscle Proteins; Muscle, Skeletal; Myocardium; Peptides; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Rats; Rats, Sprague-Dawley; Streptozocin; Ventricular Function, Left

The findings that circulating levels of atrial natriuretic peptide (ANP) are elevated in diabetic nephropathy and that the magnitude of the urinary excretion rate of cGMP in response to hypervolemia-induced ANP release is blunted have recently been reported. The purpose of this study was to determine whether these abnormalities are associated with the down-regulation of ANP receptors. Because biologically active (A) ANP receptors in the kidney are inaccessible, we have examined the binding of (125I alpha)ANP to clearance (C) receptors on platelets obtained from patients with diabetic nephropathy. Scatchard analysis revealed a reduction in such binding sites compared with those in healthy controls: 12 +/- 2 versus 19 +/- 2 per platelet, respectively (P less than 0.001). The dissociation constant, Kd, was higher: 66.7 +/- 33.1 versus 38.5 +/- 11 pM, respectively (P less than 0.02). The reduced number of receptors could reflect the down-regulation of ANP C receptors in response to an elevation of plasma levels of ANP, the median value of which was 10.6 versus 7.1 pmol/L in controls (P less than 0.05). Alternatively, the findings could represent a primary adaptation by C receptors to elevate plasma ANP levels and increase the availability of the peptide to biologically active renal receptors. The latter adaptation would serve to mitigate the sodium retention that attends diabetic nephropathy.

Topics: Adult; Atrial Natriuretic Factor; Blood Platelets; Cyclic GMP; Diabetic Nephropathies; Guanosine Monophosphate; Humans; Middle Aged; Receptors, Atrial Natriuretic Factor

We evaluated the renal and hormonal responses to volume expansion induced by water immersion in subjects with diabetic nephropathy (n = 12) and in healthy control subjects (n = 9). Immersion induced similar average increments in sodium excretion (+/- 223 vs. 176 mumol/min) and comparable decrements in renovascular resistance (RVR; -15 vs. -16 U). However, whereas the control subjects responded uniformly, the response among diabetic subjects was highly variable, with a subset of patients exhibiting paradoxical antinatriuresis and vasoconstriction. Immersion was associated with marked elevation of atrial natriuretic peptide (ANP) in plasma of diabetic versus control subjects (61 +/- 9 vs. 19 +/- 2 pM, respectively; P less than 0.001). Yet for each picomolar increment in plasma ANP during immersion, the corresponding increases in urinary excretion of cyclic guanosine monophosphate (26 vs. 279 pmol/min) and sodium (9 vs. 47 mumol/min) and the reciprocal lowering of RVR (0.7 vs. 1.9 U) were blunted in the diabetic versus control group. Volume contraction in the postimmersion period was associated with disproportionate antinatriuresis and renal vasoconstriction in the diabetic group, despite a persistent elevation of ANP (29 +/- 2 vs. 16 +/- 2 pM, P less than 0.01). We propose that renal insensitivity to ANP in diabetic nephropathy could contribute to altered vasoreactivity and abnormal excretory responsiveness to changing plasma volume. Blunted natriuresis in response to ANP release and enhanced sodium retention during volume contraction could account for the expanded extracellular fluid volume that has consistently been reported to accompany the development of diabetic nephropathy.

Topics: Adult; Atrial Natriuretic Factor; Blood Glucose; Blood Pressure; Blood Proteins; Cyclic GMP; Diabetic Nephropathies; Glomerular Filtration Rate; Hematocrit; Humans; Immersion; Middle Aged; Plasma Volume; Reference Values; Renal Circulation; Renin; Sodium; Vascular Resistance