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Diabetic kidney disease (DKD) is a major disease characterized by early albuminuria and heightened risk of renal deterioration. Increased reactive oxygen species (ROS) production, especially in glomeruli, plays an important role in the progression of DKD. ROS also cause activation of Apoptosis signal-regulating kinase 1 (ASK-1), which is implicated in various organ injuries. However, the detailed mechanisms remain unclear. This study investigates ASK-1 activation in advanced DKD and its underlying mechanisms using GS442172, an ASK-1 inhibitor. In the DKD mouse model, activation of ASK-1 was observed. Although inhibition of ASK-1 activation improved hyperpermeability in glomerular endothelial cells. ASK-1 inhibition significantly reduced glomerular injury and albuminuria, while also attenuating tubular damage and interstitial fibrosis. RNA-seq analysis revealed an aging phenotype associated with ASK-1 activation in DKD. In vitro experiments demonstrated ASK-1 activation-induced cellular senescence in tubular cells via redox signaling. These results suggested that the critical role of ASK-1 activation in DKD pathogenesis, implicating glomerular injury, tubular damage, and cellular senescence. ASK-1 inhibitors are promising therapeutic strategies to mitigate the progression of DKD., (© 2024. The Author(s).)

The mechanisms responsible for glomerular hemodynamic regulation with sodium-glucose co-transporter 2 (SGLT2) inhibitors in kidney disease due to type 2 diabetes remain unclear. Therefore, we investigated changes in glomerular hemodynamic function using an animal model of type 2 diabetes, treated with an SGLT2 inhibitor alone or in combination with a renin-angiotensin-aldosterone system inhibitor using male Zucker lean (ZL) and Zucker diabetic fatty (ZDF) rats. Afferent and efferent arteriolar diameter and single-nephron glomerular filtration rate (SNGFR) were evaluated in ZDF rats measured at 0, 30, 60, 90, and 120 minutes after the administration of a SGLT2 inhibitor (luseogliflozin). Additionally, we assessed these changes under the administration of the adenosine A1 receptor (A1aR) antagonist (8-cyclopentyl-1,3-dipropylxanthine), along with coadministration of luseogliflozin and an angiotensin II receptor blocker (ARB), telmisartan. ZDF rats had significantly increased SNGFR, and afferent and efferent arteriolar diameters compared to ZL rats, indicating glomerular hyperfiltration. Administration of luseogliflozin significantly reduced afferent vasodilatation and glomerular hyperfiltration, with no impact on efferent arteriolar diameter. Urinary adenosine levels were increased significantly in the SGLT2 inhibitor group compared to the vehicle group. A1aR antagonism blocked the effect of luseogliflozin on kidney function. Co-administration of the SGLT2 inhibitor and ARB decreased the abnormal expansion of glomerular afferent arterioles, whereas the efferent arteriolar diameter was not affected. Thus, regulation of afferent arteriolar vascular tone via the A1aR pathway is associated with glomerular hyperfiltration in type 2 diabetic kidney disease., (Copyright © 2024 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Aim: Sodium-glucose cotransporter 2 (SGLT2) inhibitors often cause a transient decrease in glomerular filtration rate (GFR) shortly after the initiation, referred to as the 'initial drop'. However, the clinical significance of this initial drop in real-world practice remains unclear., Materials and Methods: Using the nationwide Japan Chronic Kidney Disease Database, we examined factors that affected the initial drop, in patients with chronic kidney disease (CKD) and type 2 diabetes mellitus (T2DM). We also evaluated the effects of the initial drop on a composite kidney outcome (a decline in GFR of ≥50% or progression to end-stage kidney disease)., Results: Data from 2053 patients with CKD and T2DM newly prescribed an SGLT2 inhibitor were analysed. The follow-up period after SGLT2 inhibitor administration was 1015 days (interquartile range: 532, 1678). Multivariate linear regression models revealed that the concomitant use of the renin-angiotensin system inhibitors and diuretics, urinary protein levels ≥2+, and changes in GFR before the initiation of the SGLT2 inhibitor were associated with a larger initial GFR decline (β = -0.609, p = .039; β = -2.298, p < .001; β = -0.936, p = .048; β = -0.079, p < .001, respectively). Patients in the quartile with the largest initial GFR decline experienced a higher incidence of the subsequent composite kidney outcome than those in the other quartiles (p < .001)., Conclusions: The concomitant use of renin-angiotensin system inhibitors and diuretics, higher urine protein levels and pre-treatment GFR changes were associated with a larger initial GFR decline. Of these factors, the use of a diuretic had the largest effect. Furthermore, patients with CKD and T2DM experiencing an excessive initial GFR drop might be at a higher risk of adverse kidney outcomes., (© 2024 John Wiley & Sons Ltd.)

Introduction: We compared the kidney outcomes between patients with diabetic kidney disease (DKD) aged ≥75 years initiating sodium-glucose cotransporter 2 (SGLT2) inhibitors versus other glucose-lowering drugs, additionally presenting with or without proteinuria., Research Design and Methods: Using the Japan Chronic Kidney Disease Database, we developed propensity scores, implementing a 1:1 matching protocol. The primary outcome included the decline rate in estimated glomerular filtration rate (eGFR), and secondary outcomes incorporated a composite of a 40% reduction in eGFR or progression to end-stage kidney disease., Results: At baseline, the mean age at initiation of SGLT2 inhibitors (n=348) or other glucose-lowering medications (n=348) was 77.7 years. The mean eGFR was 59.3 mL/min/1.73m 2 and proteinuria was 230 (33.0%) patients. Throughout the follow-up period, the mean annual rate of eGFR change was -0.80 mL/min/1.73 m 2 /year (95% CI -1.05 to -0.54) among SGLT2 inhibitors group and -1.78 mL/min/1.73 m 2 /year (95% CI -2.08 to -1.49) in other glucose-lowering drugs group (difference in the rate of eGFR decline between the groups was 0.99 mL/min/1.73 m 2 /year (95% CI 0.5 to 1.38)), favoring SGLT2 inhibitors (p<0.001). Composite renal outcomes were observed 38 in the SGLT2 inhibitors group and 57 in the other glucose-lowering medications group (HR 0.64, 95% CI 0.42 to 0.97). There was no evidence of an interaction between SGLT2 inhibitors initiation and proteinuria., Conclusions: The benefits of SGLT2 inhibitors on renal outcomes are also applicable to older patients with DKD aged≥75 years., Competing Interests: Competing interests: YY received research support from AstraZeneca, Bayer, and Daiichi Sankyo and lecture fee from Otsuka Pharmaceutical and Torii Pharmaceutical. NK received lecture fee from AstraZeneca, Otsuka Pharmaceutical, Novartis, Daiichi Sankyo, Takeda Pharmaceutical, Kyowa Kirin, Mitsubishi Tanabe Pharma, Astellas Pharma, and scholarship donations from Astellas Pharma, Teijin Pharma, AstraZeneca, Kyowa Kirin, Bayer Yakuhin, Chugai Pharmaceutical, Otsuka Pharmaceutical, Nippon Boehringer Ingelheim, Daiichi Sankyo, Takeda Pharmaceutical Company Limited, additionally, funded by Daiichi Sankyo, AstraZeneca, Bayer, and Nobelpharma. KT received research support from AstraZeneca, Ono, Bayer, Kyowa Kirin, Otsuka Pharmaceutical, Takeda Pharmaceutical, and Daiichi Sankyo and received lecture fee from Novartis, AstraZeneca, Ono, Daiichi Sankyo, Takeda Pharmaceutical, Otsuka Pharmaceutical, Bayer, and Kyowa Kirin. NC and HA are employees of AstraZeneca., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Aims/introduction: We aimed to clarify the effectiveness of the Diabetic Nephropathy Aggravation Prevention Program in Japan by comparing the diabetes-related medical visit behavior of individuals under the municipal national health insurance according to insurers' effort levels., Materials and Methods: We assessed changes in medical visit behavior according to insurers' effort levels, "Full Efforts," "Some Efforts" and "No Effort," using longitudinal data from the National Database of Health Insurance Claims and Specific Health Checkups before 2015 and after 2018 regarding the national health insurance programs in Japan. We analyzed the effect of the Diabetic Nephropathy Aggravation Prevention Program using a generalized linear mixed model for 208,388 participants with diabetes., Results: The additive effect on medical visit behavior was significantly higher for insurers with "Full Efforts" than for those with "No Effort;" the coefficient (log odds ratio) was 0.159 (95% confidence interval 0.063-0.256). The additive effects on medical visit behavior sizes for the people with hemoglobin A1c ≥7.0%, positive urinary protein and systolic blood pressure ≥140 mmHg were 0.508, 0.402 and 0.232, respectively, which were larger than the overall effect size (0.159) for insurers with "Full Efforts.", Conclusions: Our findings showed that insurer efforts had an additive effect on the increase in the number of medical visits, suggesting that this national program could reduce the number of end-stage renal failures or dialysis in Japan., (© 2023 The Authors. Journal of Diabetes Investigation published by Asian Association for the Study of Diabetes (AASD) and John Wiley & Sons Australia, Ltd.)

Background: Diabetic kidney disease (DKD) is the leading cause of end-stage kidney disease (ESKD), but currently available treatments do not improve kidney function or prevent the initiation of dialysis/kidney replacement therapy. A previous study demonstrated that bardoxolone methyl improves the estimated glomerular filtration rate (eGFR), but the study was prematurely terminated because of an imbalance in heart failure between treatment groups. The subsequent phase 2 TSUBAKI study demonstrated no incidence of heart failure and an improved eGFR and GFR as determined by inulin clearance in DKD patients., Methods: This randomized, double-blind, placebo-controlled multicentre phase 3 study was designed to assess the efficacy and safety of bardoxolone methyl in DKD patients with an eGFR ≥15.0-<60.0 ml/min/1.73 m2 and a urinary albumin:creatinine ratio (UACR) ≤3500 mg/g but without risk factors for heart failure. The primary endpoint is the time to onset of a ≥30% decrease in the eGFR or ESKD. Randomized patients (1:1) have been under treatment with once-daily oral bardoxolone methyl (5, 10 or 15 mg by intrapatient dose adjustment) or placebo for at least 3 years., Results: The mean age of the 1013 patients is 65.9 years, 21.5% are female, the mean eGFR is 37.84 ml/min/1.73 m2 and the median UACR is 351.80 mg/g., Conclusions: Appropriate patients are enrolled in this study. This study will investigate the long-term efficacy and safety of bardoxolone methyl in DKD patients covering a wider range of eGFR (≥15.0-<60.0 ml/min/1.73 m2) and albuminuria (≤3500 mg/g) compared with previous studies., (© The Author(s) 2022. Published by Oxford University Press on behalf of the ERA.)

The increasing number of patients undergoing dialysis due to diabetes mellitus (DM) is causing serious economic problems, and its reduction is an urgent policy issue in developed countries, including Japan. We aimed to assess the association between the annual rapid decline in renal function and health checkup measures, including blood pressure, to identify health guidance targets for preventing diabetic nephropathy (DN) and diabetic kidney disease (DKD) among individuals in a medical checkup system ("Tokuteikenshin" program) in 2018. This longitudinal analysis included 3,673,829 individuals who participated in the "Tokuteikenshin" program in 2018, had hemoglobin A1c (HbA1c) levels ≥5.6%, were available for follow-up, and underwent estimated glomerular filtration rate (eGFR) evaluation. We estimated the incidence of the relative annual decrease in eGFR ≥10% per 1000 person-years and odds ratios to evaluate the rapid decline in renal function and determine health guidance goals and their role in preventing DN and DKD. Overall, 20.83% of patients with DM had a rapid decline in renal function within the observation period. A rapid decline in renal function was associated with high systolic blood pressure, poor or strict DM control, increased urinary protein excretion, and decreased blood hemoglobin levels. The incidence of rapid decline in renal function is higher in DM, and appropriate systolic blood pressure and glycemic control are important to prevent the progression to DN or DKD. Our findings will be useful for researchers, clinicians, and other public health care members in establishing effective health guidance and guidelines for CKD prevention., (© 2023. The Author(s).)

Angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs) are recommended as first-line drugs for hypertension with diabetic nephropathy owing to their renoprotective effect; however, their effect beyond lowering blood pressure (BP) has not been confirmed. Recent studies have shown that aldosterone plays a key role in causing renal injury; therefore, it is likely that mineralocorticoid receptor (MR) blockers inhibit aldosterone-induced renal damage in different ways from ACE inhibitors and ARBs. Therefore, we investigated the mechanism of the effect of an MR blocker on reducing the urinary albumin-to-creatinine ratio (UACR) using data from a randomized, double-blind, placebo-controlled phase 3 study (ESAX-DN) of a new nonsteroidal MR blocker, esaxerenone. This post hoc analysis used a novel statistical method to quantitatively estimate the effect of esaxerenone on UACR reduction mediated, or not mediated, by changes in systolic BP (SBP) and/or estimated glomerular filtration rate (eGFR). The proportion of the mediated effect by SBP changes to the total effect on UACR reduction was 9.8-10.7%; the UACR was reduced to 0.903-0.911 times the baseline at the end of treatment through the SBP-related pathway and to 0.422-0.426 times the baseline through the non-SBP-related pathway. Even considering both SBP and eGFR simultaneously, the proportion of the mediated effect was 21.9-28.1%. These results confirm that esaxerenone has a direct UACR-lowering effect independent of BP lowering and that its magnitude is much larger than that of the BP-dependent effect. Thus, esaxerenone could be a UACR-reducing treatment option for patients with diabetic nephropathy., (© 2022. The Author(s).)

Aims/introduction: We evaluated the effect of co-administration of esaxerenone and a sodium-glucose cotransporter 2 (SGLT2) inhibitor on the magnitude of serum potassium elevation in Japanese patients with diabetic kidney disease., Materials and Methods: We carried out a prespecified subanalysis of data from two phase III studies: a multicenter, randomized, double-blind, placebo-controlled trial in patients with type 2 diabetes and microalbuminuria (J308); and a multicenter, single-arm, open-label trial in patients with type 2 diabetes and macroalbuminuria (J309). Changes in serum potassium levels during the studies and other measures were evaluated according to SGLT2 inhibitor use., Results: In both studies, time-course changes in serum potassium levels, and incidence rates of serum potassium elevation were lower in patients with co-administration of SGLT2 inhibitor in both the placebo and esaxerenone groups than those without the inhibitor. In contrast, time-course changes and mean percentage changes from baseline in urinary albumin-to-creatinine ratio, the proportion of patients with albuminuria remission and time-course changes in blood pressure did not change with or without SGLT2 inhibitor, whereas the albumin-to-creatinine ratio and blood pressure were reduced with esaxerenone. The blood glucose-lowering effect of SGLT2 inhibitor was not affected by esaxerenone., Conclusions: In Japanese patients with type 2 diabetes and albuminuria treated with esaxerenone, concomitant use of SGLT2 inhibitor reduced the magnitude of serum potassium elevation without any change of its antihypertensive and albuminuria-suppressing effects. Co-administration of esaxerenone and SGLT2 inhibitor might be a beneficial treatment option for patients with diabetic kidney disease., (© 2022 The Authors. Journal of Diabetes Investigation published by Asian Association for the Study of Diabetes (AASD) and John Wiley & Sons Australia, Ltd.)

Background: It is important to identify additional prognostic factors for diabetic kidney disease. Materials & methods: Baseline levels of ten cytokines (APRIL/TNFSF13, BAFF/TNFSF13B, chitinase 3-like 1, LIGHT/TNFSF14, TWEAK/TNFSF12, gp130/sIL-6Rβ, sCD163, sIL-6Rα, sTNF-R1, sTNF-R2) were measured in two cohorts of diabetic patients. In one cohort (n = 777), 156 individuals were randomly sampled after stratification and their plasma samples were analyzed; in the other cohort (n = 69), serum samples were analyzed in all the individuals. The levels of cytokines between rapid (estimated glomerular filtration rate decline >5 ml/min/1.73 m 2 /year) and non-rapid decliners were compared. Results: Multivariate analysis demonstrated significantly high levels of LIGHT/TNFSF14, TWEAK/TNFSF12 and sTNF-R2 in rapid decliners. Conclusion: These three cytokines can be potential biomarkers for the progression of diabetic kidney disease.

Background: Esaxerenone has potential renoprotective effects and reduces the urinary albumin-to-creatinine ratio (UACR) in patients with diabetic kidney disease and overt nephropathy. We investigated the efficacy and safety of esaxerenone in Japanese patients with type 2 diabetes (T2D) and macroalbuminuria (UACR ≥ 300 mg/g creatinine)., Methods: We conducted a multicenter, single-arm, open-label phase III study in 56 patients with T2D and UACR ≥ 300 mg/g creatinine with estimated glomerular filtration rate (eGFR) ≥ 30 mL/min/1.73 m 2 and treated with a renin-angiotensin system inhibitor. Patients received esaxerenone for 28 weeks at 1.25 mg/day initially with titration to 2.5 mg/day based on serum potassium (K + ) monitoring. Efficacy was evaluated as the change in UACR from baseline to week 28. Safety endpoints included adverse events (AEs), incidence of serum K + increase, and change in eGFR from baseline., Results: UACR decreased by 54.6% (95% CI 46.9%, 61.3%) on average from baseline (544.1 mg/g creatinine) to the end of treatment (246.8 mg/g creatinine); 51.8% of patients showed improvement to early nephropathy. AE incidence was 69.6%. Three patients (5.4%) had serum K + levels ≥ 6.0 mEq/L or ≥ 5.5 mEq/L on two consecutive occasions. Hyperkalemia in two patients was transient and resolved during the treatment period. One patient discontinued following two consecutive serum K + values ≥ 5.5 mEq/L. The maximum change from baseline in eGFR was - 8.3 mL/min/1.73 m 2 at week 24., Conclusions: Esaxerenone reduced UACR in Japanese patients with T2D and UACR ≥ 300 mg/g creatinine; more than half experienced a transition from UACR ≥ 300 mg/g creatinine to UACR < 300 mg/g creatinine., Clinical Trial Registration: JapicCTI-173696., (© 2021. The Author(s).)

Endothelial dysfunction represents a predominant early feature of diabetes, rendering patients with diabetes prone to renal complications, e.g., proteinuria. Recent studies have indicated a possible role for xanthine oxidase (XO) in the pathogenesis of vascular dysfunctions associated with diabetes. In the present study, we investigated the contribution of XO activation on the progression of diabetic nephropathy in a mouse model using selective XO inhibitors. Male Ins2 Akita heterozygous mice were used with wild-type mice as controls. Akita mice were treated with topiroxostat (Topi) or vehicle for 4 wk. Serum uric acid levels were significantly reduced in Akita + Topi mice compared with Akita + vehicle mice. The Akita + Topi group had a significant reduction in urinary albumin excretion compared with the Akita + vehicle group. Mesangial expansion, glomerular collagen type IV deposition, and glomerular endothelial injury (assessed by lectin staining and transmission electron microscopy) were considerably reduced in the Akita + topi group compared with the Akita + vehicle group. Furthermore, glomerular permeability was significantly higher in the Akita + vehicle group compared with the wild-type group. These changes were reduced with the administration of Topi. We conclude that XO inhibitors preserve glomerular endothelial functions and rescue compromised glomerular permeability, suggesting that XO activation plays a vital role in the pathogenesis of diabetic nephropathy.

Background: The Dapagliflozin and Prevention of Adverse outcomes in Chronic Kidney Disease (DAPA-CKD; NCT03036150) trial was designed to assess the effect of the sodium-glucose co-transporter 2 (SGLT2) inhibitor dapagliflozin on kidney and cardiovascular events in participants with CKD with and without type 2 diabetes (T2D). This analysis reports the baseline characteristics of those recruited, comparing them with those enrolled in other trials., Methods: In DAPA-CKD, 4304 participants with a urinary albumin:creatinine ratio (UACR) ≥200 mg/g and estimated glomerular filtration rate (eGFR) between 25 and 75 mL/min/1.73 m2 were randomized to dapagliflozin 10 mg once daily or placebo. Mean eGFR was 43.1 mL/min/1.73 m2 and median UACR was 949 mg/g (108 mg/mmol)., Results: Overall, 2906 participants (68%) had a diagnosis of T2D and of these, 396 had CKD ascribed to a cause other than diabetes. The most common causes of CKD after diabetes (n = 2510) were ischaemic/hypertensive nephropathy (n = 687) and chronic glomerulonephritis (n = 695), of which immunoglobulin A nephropathy (n = 270) was the most common. A total of 4174 participants (97%) were receiving an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker, 1882 (43.7%) diuretics, 229 (5.3%) mineralocorticoid receptor antagonists and 122 (2.8%) glucagon-like peptide 1 receptor agonists. In contrast to the Canagliflozin and Renal Events in Diabetes with Established Nephropathy Clinical Evaluation (CREDENCE), the DAPA-CKD trial enrolled participants with CKD due to diabetes and to causes other than diabetes. The mean eGFR of participants in the DAPA-CKD trial was 13.1 mL/min/1.73 m2 lower than in CREDENCE, similar to that in the Finerenone in Reducing Kidney Failure and Disease Progression in DKD (FIDELIO-DKD) trial and the Study Of diabetic Nephropathy with AtRasentan (SONAR)., Conclusions: Participants with a wide range of underlying kidney diseases receiving renin-angiotensin system blocking therapy have been enrolled in the DAPA-CKD trial. The trial will examine the efficacy and safety of dapagliflozin in participants with CKD Stages 2-4 and increased albuminuria, with and without T2D., (© The Author(s) 2020. Published by Oxford University Press on behalf of ERA-EDTA.)

Objective: Glomerular filtration rate (GFR) decreases without or prior to the development of albuminuria in many patients with diabetes. Therefore, albuminuria and/or a low GFR in patients with diabetes is referred to as diabetic kidney disease (DKD). A certain proportion of patients with diabetes show a rapid progressive decline in renal function in a unidirectional manner and are termed early decliners. This study aimed to elucidate the prevalence of DKD and early decliners and clarify their risk factors., Research Design and Methods: This combination cross-sectional and cohort study included 2385 patients with diabetes from 15 hospitals. We defined DKD as a urinary albumin to creatinine ratio (ACR) ≥30 mg/gCr and/or estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m². We classified patients into four groups based on the presence or absence of albuminuria and a decrease in eGFR to reveal the risk factors for DKD. We also performed a trajectory analysis and specified the prevalence and risk factors of early decliners with sequential eGFR data of 1955 patients in five facilities., Results: Of our cohort, 52% had DKD. Above all, 12% with a low eGFR but no albuminuria had no traditional risk factors, such as elevated glycated hemoglobin, elevated blood pressure, or diabetic retinopathy in contrast to patients with albuminuria but normal eGFR. Additionally, 14% of our patients were early decliners. Older age, higher basal eGFR, higher ACR, and higher systolic blood pressure were significantly associated with early decliners., Conclusions: The prevalence of DKD in this cohort was larger than ever reported. By testing eGFR yearly and identifying risk factors in the early phase of diabetes, we can identify patients at high risk of developing end-stage renal disease., Competing Interests: Competing interests: J-DREAMS is supported by Ministry of Health, Labour and Welfare, Japan Agency for Medical Research and Development, Japan Diabetes Society, Nippon Boehringer Ingelheim, Eli Lilly, Novo Nordisk Pharma, and Abbott Japan. KU reports lecture fees from Eli Lilly, Nippon Boehringer Ingelheim, Novo Nordisk, and Abbott Japan; grants and endowments from Eli Lilly, Nippon Boehringer Ingelheim, and Novo Nordisk., (© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Expression of klotho, the renoprotective anti-aging gene, is decreased in diabetic model kidneys. We hypothesized that klotho protein attenuates renal hypertrophy and glomerular injury in a mouse model of diabetic nephropathy., Methods: Klotho transgenic (KLTG) mice were crossed with spontaneously diabetic Ins2Akita (AKITA) mice. Glomerular morphology, macrophage infiltration, urinary albumin excretion and urinary 8-hydroxy-2-deoxy guanosine excretion were examined. In vitro, human glomerular endothelial cells were stimulated with high glucose with or without recombinant klotho, and calpain activity and proinflammatory cytokine expressions were measured., Results: We found that klotho protein overexpression attenuates renal hypertrophy and glomerular injury in this mouse model of diabetic nephropathy. Klotho overexpression attenuated renal hypertrophy, albuminuria, glomerular mesangial expansion, and endothelial glycocalyx loss in the AKITA mice. AKITA mice exhibit high levels of urinary 8-hydroxy-2-deoxy guanosine excretion. In the presence of klotho overexpression, this effect was reversed. In addition, the glomerular macrophage infiltration characteristic of AKITA mice was attenuated in KLTG-AKITA mice. In human glomerular endothelial cells, high glucose induced calpain activity. This effect was suppressed by expression of recombinant klotho, which also suppressed the induction of proinflammatory cytokines., Conclusion: Our data suggest klotho protein protects against diabetic nephropathy through multiple pathways.

Increased generation of reactive oxygen species (ROS) is a common denominative pathogenic mechanism underlying vascular and renal complications in diabetes mellitus. Endothelial NAD(P)H oxidase is a major source of vascular ROS, and it has an important role in endothelial dysfunction. We hypothesized that activation of endothelial NAD(P)H oxidase initiates and worsens the progression of diabetic nephropathy, particularly in the development of albuminuria. We used transgenic mice with endothelial-targeted overexpression of the catalytic subunit of NAD(P)H oxidase, Nox2 (NOX2TG). NOX2TG mice were crossed with Akita insulin-dependent diabetic (Akita) mice that develop progressive hyperglycemia. We compared the progression of diabetic nephropathy in Akita versus NOX2TG-Akita mice. NOX2TG-Akita mice and Akita mice developed significant albuminuria above the baseline at 6 and 10 weeks of age, respectively. Compared with Akita mice, NOX2TG-Akita mice exhibited higher levels of NAD(P)H oxidase activity in glomeruli, developed glomerular endothelial perturbations, and attenuated expression of glomerular glycocalyx. Moreover, in contrast to Akita mice, the NOX2TG-Akita mice had numerous endothelial microparticles (blebs), as detected by scanning electron microscopy, and increased glomerular permeability. Furthermore, NOX2TG-Akita mice exhibited distinct phenotypic changes in glomerular mesangial cells expressing α-smooth muscle actin, and in podocytes expressing increased levels of desmin, whereas the glomeruli generated increased levels of ROS. In conclusion, activation of endothelial NAD(P)H oxidase in the presence of hyperglycemia initiated and exacerbated diabetic nephropathy characterized by the development of albuminuria. Moreover, ROS generated in the endothelium compounded glomerular dysfunctions by altering the phenotypes of mesangial cells and compromising the integrity of the podocytes.

In diabetes, endothelial nitric oxide synthase (eNOS) produces superoxide anion rather than nitric oxide, referred to as "eNOS uncoupling," which may contribute to endothelial dysfunction, albuminuria, and diabetic nephropathy. Reduced levels of endothelium-derived tetrahydrobiopterin (BH4), an essential cofactor for eNOS, promote eNOS uncoupling. Accelerated degradation of guanosine triphosphate cyclohydrolase I (GTPCH I), the rate-limiting enzyme in BH4 biosynthesis, also occurs in diabetes, suggesting that GTPCH I may have a role in diabetic microvascular disease. Here, we crossed endothelium-dominant GTPCH I transgenic mice with Ins2(+/Akita) diabetic mice and found that endothelial overexpression of GTPCH I led to higher levels of intrarenal BH4 and lower levels of urinary albumin and reactive oxygen species compared with diabetic control mice. Furthermore, GTPCH I overexpression attenuated the hyperpermeability of macromolecules observed in diabetic control mice. In addition, we treated Ins2(+/Akita) mice with metformin, which activates AMP-activated protein kinase (AMPK) and thereby slows the degradation of GTPCH I; despite blood glucose levels that were similar to untreated mice, those treated with metformin had significantly less albuminuria. Similarly, in vitro, treating human glomerular endothelial cells with AMPK activators attenuated glucose-induced reductions in phospho-AMPK, GTPCH I, and coupled eNOS. Taken together, these data suggest that maintenance of endothelial GTPCH I expression and the resulting improvement in BH4 biosynthesis ameliorate diabetic nephropathy.

Purpose: Calcium channel blockers (CCBs) are recommended second-line antihypertensives for renin-angiotensin system (RAS) inhibitor-treated patients with chronic kidney disease (CKD), but they do not always ameliorate the progression of CKD. However, small clinical studies suggest that sympatholytic CCBs may protect against kidney injury. Therefore, a clinical trial was designed to test whether the sympatholytic CCB azelnidipine decreases the urinary albumin levels of CKD patients treated with the angiotensin receptor blocker olmesartan more potently than the widely-used non-sympatholytic CCB amlodipine., Methods: A multi-center, open-labeled, randomized clinical intervention trial was designed to compare the antialbuminuric effect of azelnidipine (8-16 mg/day) and amlodipine (2.5-5 mg/day) in olmesartan-treated hypertensive (blood pressure 130-180/80-110 mmHg) patients with type 2 diabetes (fasting blood sugar ≥126 mg/dL or treatment with antidiabetic agents) and albuminuria (urinary albumin/creatinine ratio ≥30 mg/g). The primary study endpoint is the change in the urinary albumin/creatinine ratio after 12 months of treatment., Conclusions: The present trial is expected to clarify whether the sympatholytic CCB azelnidipine is a beneficial second-line choice for RAS inhibitor-treated hypertensive patients with CKD, such as diabetic nephropathy.

Diabetic nephropathy is a leading cause of end-stage renal failure worldwide. Its morphologic characteristics include glomerular hypertrophy, basement membrane thickening, mesangial expansion, tubular atrophy, interstitial fibrosis and arteriolar thickening. All of these are part and parcel of microvascular complications of diabetes. A large body of evidence indicates that oxidative stress is the common denominator link for the major pathways involved in the development and progression of diabetic micro- as well as macro-vascular complications of diabetes. There are a number of macromolecules that have been implicated for increased generation of reactive oxygen species (ROS), such as, NAD(P)H oxidase, advanced glycation end products (AGE), defects in polyol pathway, uncoupled nitric oxide synthase (NOS) and mitochondrial respiratory chain via oxidative phosphorylation. Excess amounts of ROS modulate activation of protein kinase C, mitogen-activated protein kinases, and various cytokines and transcription factors which eventually cause increased expression of extracellular matrix (ECM) genes with progression to fibrosis and end stage renal disease. Activation of renin-angiotensin system (RAS) further worsens the renal injury induced by ROS in diabetic nephropathy. Buffering the generation of ROS may sound a promising therapeutic to ameliorate renal damage from diabetic nephropathy, however, various studies have demonstrated minimal reno-protection by these agents. Interruption in the RAS has yielded much better results in terms of reno-protection and progression of diabetic nephropathy. In this review various aspects of oxidative stress coupled with the damage induced by RAS are discussed with the anticipation to yield an impetus for designing new generation of specific antioxidants that are potentially more effective to reduce reno-vascular complications of diabetes.

Background: Recent studies showed that angiotensin II type 1 receptor blocker (ARB) slows progression of chronic renal disease in patients with type 2 diabetes, regardless of changes in blood pressure. We showed that the imbalance of nitric oxide (NO) and reactive oxygen species (ROS) due to endothelial NO synthase (eNOS) uncoupling contributed to renal dysfunction in the diabetic nephropathy. The aim of this study was to determine the effects of ARB on uncoupled eNOS in rat diabetic nephropathy., Methods: Diabetes was induced in Sprague-Dawley rats with streptozotocin (65 mg/ kg body weight). After 6 weeks, rats were divided into saline (DM; n = 11) and ARB, losartan groups (DM+Los; n = 11). After 2-week treatment, glomerular ROS production was assessed by 2',7'-dichlorofluorescin diacetate (DCFH-DA)-derived chemiluminescence. Renal NO and ROS production were imaged by confocal laser microscopy after renal perfusion with DCFH-DA and diaminorhodamine-4M acetoxymethyl ester with L-arginine. The dimeric form of eNOS was measured by low-temperature sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Serum tetrahydrobiopterin (BH4) concentrations were determined by high-performance liquid chromatography. Protein and mRNA expression of GTP cyclohydrolase 1 (GTPCH1), key enzyme of BH4 synthesis, were examined., Results: Losartan attenuated glomerular ROS production in DM. Accelerated ROS production and diminished bioavailable NO caused by NOS uncoupling were noted in DM glomeruli. Losartan reversed the decreased GTPCH1 and decreased dimeric form of eNOS and glomerular NO production by increased BH4 bioavailability., Conclusions: ARB improved the NOS uncoupling in diabetic nephropathy by increasing BH4 bioavailability.

Background: Serotonin (5-HT) is involved in vascular inflammation and atherosclerogenesis. Serum 5-HT concentrations are elevated in diabetes, and 5-HT is involved in diabetic vasculopathies. Sarpogrelate hydrochloride, a 5-HT2A receptor antagonist, has renoprotective effects, but its effect in diabetic nephropathy is not elucidated. The aim of this study was to examine the effects of sarpogrelate on endothelial dysfunction in rats with streptozotocin (STZ)-induced diabetes., Methods: Rats with STZ-induced diabetes were either untreated or treated with sarpogrelate (30 mg/kg P.O.) for 8 weeks. At the end of the experiment, we measured urinary albumin excretion, serum adiponectin concentration and platelet-derived microparticles. Intraglomerular coagulation was detected by immunostaining for platelets. Production of renal reactive oxygen species (ROS) and nitric oxide (NO) was investigated by confocal laser microscopy and used as an index of glomerular endothelial dysfunction., Results: Diabetic nephropathy was associated with enhanced production of ROS and diminished bioavailable NO in the glomeruli. Treatment with sarpogrelate improved ROS/NO imbalance in glomeruli, suppressed platelet aggregation in glomeruli, reduced platelet-derived microparticles, increased serum adiponectin level and reduced the level of albuminuria, compared with non-treated diabetic rats., Conclusions: Our results indicate that sarpogrelate improves endothelial function in rats with STZ-induced diabetes through a reduction of glomerular platelet activation and an increase in serum adiponectin concentrations and suggest that sarpogrelate is potentially useful for the treatment of diabetic nephropathy.

Background: Angiotensin II (AII) and transforming growth factor-beta (TGF-beta) are closely involved in the pathogenesis of diabetic nephropathy (DN). AII is known to induce TGF-beta production in resident renal cells, including glomerular mesangial cells and tubular epithelial cells. TGF-beta receptor types I and II (TGF-betaRI, II) are up-regulated in the diabetic kidney. The aim of this study was to clarify the role of AII in the regulation of the TGF-beta system in the early stage of DN using AII type1a receptor-deficient(AT1a(-/-)) mice., Methods: We investigated the expression of TGF-beta1, TGF-betaRI, II, and Smad signaling in AT1a(-/-) mice with streptozotocin (STZ)-induced DN. Mice were killed 10 and 20 days after the induction of hyperglycemia. The expression of TGF-beta receptors was analyzed by immunohistochemical staining and reverse transcriptase-polymerase chain reaction (RT-PCR). TGF-beta-specific Smad signaling was analyzed by electrophoretic mobility shift assay and Western blotting., Results: The expression of both TGF-betaRI and RII was up-regulated in the glomerular tufts and vasculature in diabetic AT1a(+/+) mice kidney by immunohistochemistry. RT-PCR revealed that mRNAs for TGF-betaRI and RII were also up-regulated. Smad2 and 4 protein levels were reduced in the renal cortex after the induction of diabetes, with an increase of Smad 3/4 complex in the nucleus. The expression of TGF-beta receptors increased in both diabetic AT1a(-/-) and AT1a(+/+) mice. Smad signaling in AT1a(-/-) mice was also enhanced., Conclusions: Our results suggest that the complete blockade of the AT1a-mediated pathway has a minimal effect on the enhanced TGF-beta/Smad signaling in the early stage of DN, at least in the AT1a(-/-) model.

Increased production of reactive oxygen species (ROS) in diabetes may be a common pathway linking diverse pathogenic mechanisms of diabetic vascular complications, including nephropathy. Assessment of the oxidative stress production pathway is therefore important for the prediction and prevention of diabetic complications. However, ROS production mechanisms remain unclear in diabetic glomeruli. To identify the source and determine the mechanisms of ROS production in the diabetic kidney, diabetes was induced with streptozotocin in rats. After 6 wk, glomerular ROS production had increased in the streptozotocin rat kidney, as assessed by dihydroethidium-derived chemiluminescence. ROS production was increased by the addition of NADH or L-arginine and was partially reduced by the addition of diphenylene iodonium or N(G)-nitro-L-arginine methyl ester, identifying NAD(P)H oxidase and nitric oxide (NO) synthase (NOS) as ROS sources. The mRNA and protein expression of endothelial NOS (eNOS), as measured by real-time RT-PCR and Western blotting, increased significantly (mRNA level, 1.3-fold; protein level, 1.8-fold). However, the dimeric form of eNOS was decreased in diabetic glomeruli, as measured by low-temperature SDS-PAGE. Production of renal ROS and NO by uncoupled NOS was imaged by confocal laser microscopy after renal perfusion of 2',7'-dichlorofluorescein diacetate (a ROS marker) and diaminorhodamine-4M AM (a NO marker) with L-arginine. Accelerated ROS production and diminished bioavailable NO caused by NOS uncoupling were noted in the diabetic kidney. Administration of tetrahydrobiopterin (BH4), a cofactor for eNOS, reversed the decreased dimeric form of eNOS and glomerular NO production. Our results indicate that NAD(P)H oxidase and uncoupling of eNOS contribute to glomerular ROS production, mediated by the loss of BH4 availability. These mechanisms are potential key targets for therapeutic interventions.

The phenotypic change of the mesangial cell is considered to play a pivotal role in the accumulation of extracellular matrix in diabetic nephropathy. This investigation was undertaken to evaluate the expression of the various isoforms of contractile proteins in the streptozocin (STZ)-induced diabetic rat kidney and in renal biopsy specimens from patients with diabetic nephropathy. Specific antibodies to myosin heavy chain isoforms (SM1, SM2, SMemb), caldesmon, and alpha-smooth muscle actin and cDNAs for SMemb were used. Increased expression of SMemb at the mRNA and protein levels was demonstrated at 1 week after STZ administration in the rat. Both levels were increased at 4 weeks. Mesangial staining of caldesmon was observed at 4 weeks and that of alpha-smooth muscle actin at 24 weeks. Immunohistochemical mesangial staining of the contractile proteins was pronounced in patients with diabetic nephropathy in contrast to the trace mesangial staining in normal control subjects. These results indicate that the phenotypic change in mesangial cells occurs in the early stages of diabetes and that several stages in phenotypic changes may exist. Expression of the contractile protein isoforms, especially SMemb, should serve as a new marker for the subsequent glomerular hypertrophy and sclerosis.

In diabetic nephropathy there is accumulation of matrix proteins. Overproduction of these matrix proteins considered to be due to the phenotypic change of mesangial cell. In order to detect the phenotypic change of the mesangial cell, renal biopsy specimens from patients with diabetic nephropathy were stained with antibodies against various types of collagens and contractile-associated protein, caldesmon. Type III collagen was not stained in the glomerulus and type VI collagen showed mesangial pattern from normal controls. In diabetes, mesangial staining of type III collagen and increases in type VI collagen were observed in the mesangium. Increased mesangial staining of caldesmon was noted in the glomerulus from diabetic nephropathy in contrast to only vessel staining from normal controls. These results indicate that phenotypic changes are noted in the mesangium in diabetes. Expression of contractile-associated protein such as caldesmon, would serve as a useful marker to predict glomerulosclerosis.

Collagen is one of the major components of the extracellular matrices of the kidney. Basement membrane collagen, type IV collagen, is the major component in normal glomeruli. Fibril and interstitial collagen such as type III collagen, type V collagen, and type VI collagen are minor components of glomerular extracellular matrices and are localized mainly in the interstitium. Diabetic glomerulosclerosis is characterized by the expansion of the glomerular mesangial matrix as well as by thickening of the glomerular basement membrane. In order to clarify the roles of these various types of collagen in the development of diabetic glomerulosclerosis, immunohistochemical studies were performed in kidney specimens from patients with Type 2 diabetes. Early glomerulosclerosis is characterized by expansion of mesangial matrix with basement membrane collagen. However, in later stages glomerulosclerosis is characterized by an increase in the minor collagen components, such as type V and type VI collagen or collagens not normally present, such as type III collagen. Mesangial cells are known to synthesize all these types of collagen. In diabetes, phenotypic change in mesangial cells might produce excess amounts of fibril and interstitial collagen such as type III, type V, and type VI collagen, thus, leading to glomerulosclerosis.