Effects of angiotensin II receptor blockers on diabetic nephropathy

Nephroprotective effects of Candesartan Cilexetil against Cyclosporine A-induced nephrotoxicity in a rat model

Cyclosporine A (CsA), a well-known immunosuppressive drug, has been prescribed after organ transplantation and in a variety of disorders with an immunological origin. Nephrotoxicity is one of the most frequently stated problems associated with CsA, and therefore the treatment with CsA remains a big challenge. This study sets out to assess the ameliorative influences of Candesartan Cilexetil (CC) on oxidative stress and the nephrotoxic effect of CsA in a rat model. Twenty-four Wister Albino rats, 7-8-week-old, weighing 150-250g, were randomly categorized into three groups (eight animals in each group). These groups were the (1) CsA-treated group, (2) vehicle-treated group, and (3) CC-treated group. Bodyweights were assessed at the start and end of experiments. Renal function test and levels of glutathione peroxidase 1 catalase -CAT (Gpx1), catalase (CAT), superoxide dismutase (SOD), interleukin -2 (IL-2), and malondialdehyde (MDA) were investigated in renal tissues. Histological changes in kidneys were also evaluated. Data showed that levels of urea and creatinine in serum and levels of IL-2 and MDA in renal tissues were elevated in the CsA-treated group, with severe histological changes compared with the control group. Furthermore, tissue levels of Gpx1, CAT, and SOD were significantly decreased in CsA-treated in comparison with the control group. Treatment with CC for the rats subjected to CSA resulted in a marked reduction in levels of serum urea and creatinine and tissue levels of IL-2 and MDA. Levels of Gpx1, CAT, and SOD in renal tissues were greater in the CC-treatment group compared with the CsA-treated group. CC treatment reduced the deterioration of renal morphology compared with CsA treatment. The findings of this study suggest that CC could prevent CSA-induced nephrotoxicity through its anti-inflammatory and antioxidant influences. Considerably more work needs to be done to determine the mechanistic insight behind the ameliorative effect of CC.

Probiotics ameliorates glycemic control of patients with diabetic nephropathy: A randomized clinical study

OBJECTIVE

This research aimed to explore the effects of probiotic administration on glycemic control and renal function in patients with diabetic nephropathy (DN).

METHODS

The 101 participants were randomly divided into two treatment groups and 76 patients were included in the final analysis. In 76 patients with diabetic nephropathy of type 2 diabetes, a randomized double-blind and placebo-controlled clinical trial was conducted to evaluate the administration of 3.2 × 109  CFU probiotic supplements per day (Bifidobacterium bifidum, 1.2 × 109  CFU, Lactobacillus acidophilus 4.2 × 109  CFU, Streptococcus thermophilus 4.3 × 109  CFU) for 12 weeks on glycemic control of patients, including fasting blood glucose, 2 h postprandial blood glucose, glycosylated hemoglobin (HbA1c), microalbuminuria/creatinine (mAlb/Cr) and estimated glomerular filtration rate (eGFR) levels. The placebo group daily received empty capsules filled with starch.

RESULTS

After 12 weeks, the administration of probiotics demonstrated a significant reduction in fasting blood glucose (10.68 ± 3.24 mmol/L before vs. 7.81 ± 2.77 mmol/L after, p < 0.05), HbA1c (8.19 ± 1.60% before vs. 7.32 ± 1.20% after, p < 0.05) and mAlb/Cr (101.60 ± 22.17 mg/g before vs. 67.53 ± 20.11 mg/g after, p < 0.05), while only mAlb/Cr level was significantly lower in the probiotic group than in the placebo group after intervention (67.53 ± 20.11 mg/g vs. 87.71 ± 23.01, p < 0.05). Meanwhile, there was no significant reduction of 2 h postprandial blood glucose level (18.95 ± 5.23 mmol/L vs. 17.35 ± 6.28 mmol/L, p = 0.24) and eGFR (84.34 ± 6.97 ml/min vs. 82.8 ± 8.72 ml/min, p = 0.45) in patients before and after probiotic intake. In addition, the placebo group failed to show any significant change of these parameters.

CONCLUSION

This clinical study revealed probiotic administration could ameliorate glycemic control of patients with diabetic nephropathy, potentiating its therapeutic potential in clinical application.

Eprosartan mesylate loaded bilosomes as potential nano-carriers against diabetic nephropathy in streptozotocin-induced diabetic rats

The objective of the present study was to formulate eprosartan mesylate loaded nano-bilosomes and investigates its potential for controlling streptozotocin induced diabetes nephropathy in Wistar rats. The eprosartan mesylate loaded nano-bilosomes comprising of various ratios of soybean phosphatidylcholine/sodium deoxycholate were prepared by thin film hydration technique. The prepared formulations were evaluated for vesicles size, polydispersity index, zeta potential and entrapment efficiency. Further the optimized formulation was characterized for vesicles morphology, and its efficacy for the management of diabetic nephropathy in Wistar rats. The optimized eprosartan mesylate loaded nano-bilosomes exhibited vesicles size, polydispersity index, zeta potential and entrapment efficiency of 63.88±3.46nm, 0.172±0.026, -30.40±2.75mV and 61.19±0.88% respectively. In vivo activity demonstrated that the prepared eprosartan mesylate loaded nano-bilosomes formulation demonstrated a nephro-protecting outcome as shown by the substantial decrease in serum creatinine, urea, lactate dehydrogenase, total albumin, and malondialdehyde. Additionally, an oral administration of eprosartan mesylate loaded nano-bilosomes decreases the raised expressions of Angiotensin II type 1 receptor, inducible nitric oxide synthase, and transforming growth factor-β1 in Wistar rats. Further, histopathological examination established the nephro-protective effect of prepared formulation. In conclusion, the research work in the paper suggests that the prepared eprosartan mesylate loaded nano-bilosomes could serve as a practical oral formulation for diabetic nephropathy in future therapy and may offer potential benefits in cases with hypertension and renal disease.

Abelmoschus esculentus fractions potently inhibited the pathogenic targets associated with diabetic renal epithelial to mesenchymal transition

Although Abelmoschus esculentus (AE) is known for anti-hyperglycemia, few reports have addressed its target. Our recent studies have focused on diabetic renal epithelial to mesenchymal transition (EMT), which plays a critical role in fibrosis that accompanies increasing vimentin and suggested signals DPP-4/AT-1/TGF-β1. This study aimed to investigate whether AE is useful for preventing diabetic renal EMT. We used a succession of extractions and obtained the corresponding fractions F1-F5, each with its own individual properties: F1 inhibits high glucose-stimulated vimentin, AT-1, TGF-β1, and DPP-4, and recovers E-cadherin in tubular cells; F2 decreases high glucose-induced vimentin, AT-1 and DPP-4; F3-F5 do not reduce the expression of vimentin. Chemical analysis revealed that F1 is rich of flavonoid glycosides especially quercetin glucosides, and pentacyclic triterpene ester. F2 contains a large amount of carbohydrates and polysaccharides composed of uronic acid, galactose, glucose, myo-inositol etc. In conclusion, AE has the potential to serve as an adjuvant for diabetic nephropathy, with F1 and F2 especially deserving further investigation and development.

Lipid disorder and intrahepatic renin-angiotensin system activation synergistically contribute to non-alcoholic fatty liver disease

BACKGROUND

This study aimed to investigate the possible synergistic effects of lipid disorder with renin-angiotensin system (RAS) activation in non-alcoholic fatty liver disease (NAFLD).

METHODS

Apolipoprotein E gene-knockout mice, angiotensin II (Ang II) type 1 receptor (AT1) gene-knockout mice and human hepatoblastoma cell line (HepG2) were used for experiments. Lipid accumulation was examined by Filipin staining and intracellular cholesterol quantitative assay. The gene and protein expression of molecules involved in RAS and low-density lipoprotein receptor (LDLr) pathway was examined by real-time PCR, immunofluorescent staining and Western blot.

RESULTS

There was significantly increased expression of RAS components and extracellular matrix (ECM) in livers of high-fat-diet-fed apolipoprotein E gene-knockout mice compared with controls. Upregulation of RAS components was positively associated with increased plasma levels of lipid profile. The in vitro study further confirmed that cholesterol loading increased supernatant renin activity and Ang II level of HepG2 cells, accompanied by increased ECM production that was positively associated with increased expression of intracellular RAS components. Interestingly, Ang II treatment increased lipid accumulation in livers of C57BL/6 mice and HepG2 cells. Furthermore, Ang II treatment increased gene and protein expression of sterol regulatory element-binding protein (SREBP) cleavage activating protein (SCAP), SREBP-2 and LDLr, which were mediated by enhanced SCAP/SREBP-2 complex translocation from endoplasmic reticulum to Golgi. However, LDLr pathway was accordingly downregulated in livers of AT1 gene-knockout C57BL/6 mice or in HepG2 cells treated by telmisartan.

CONCLUSION

These findings demonstrate that lipid disorder and intrahepatic RAS activation synergistically accelerate NAFLD progression.

The association of ACE gene polymorphism with diabetic kidney disease and renoprotective efficacy of valsartan

Introduction:

To investigate the associations between the insertion/deletion (I/D) polymorphisms in the angiotensin converting enzyme (ACE) gene and susceptibility to diabetic kidney disease (DKD); and the efficacy of valsartan in reducing the urine protein in Type 2 diabetes mellitus (T2DM) patients.

Materials and methods:

We enrolled 128 T2DM patients in this study, including 54 cases with DKD (DKD+) and 74 controls (DKD–). The ACE polymorphism was assayed by polymerase chain reaction (PCR), and the genotype distribution and allele frequency were analyzed. The DKD+ group was subdivided into the DD, ID and II subgroups, based on their genotypes. In addition, patients with DKD received valsartan treatment for 12 weeks. We determined changes in the urinary albumin to creatinine ratio (ACR) and serum creatinine (SCr).

Results:

The frequencies of the genotypes DD and ID were higher in the DKD+ than in the DKD– group. The frequency of allele D was higher, and of allele I was lower, in the DKD+ than in DKD– group (p < 0.05). Following valsartan treatment, albuminuria was significantly decreased in subgroups DD and ID (p < 0.05).

Conclusions:

In T2DM patients, the ACE I/D polymorphism was associated with onset of DKD. Furthermore, the ACE I/D polymorphism influenced the renoprotective response to valsartan: Patients with the DD genotype benefitted the most from this treatment.

Oxidant Mechanisms in Renal Injury and Disease

SIGNIFICANCE

A common link between all forms of acute and chronic kidney injuries, regardless of species, is enhanced generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) during injury/disease progression. While low levels of ROS and RNS are required for prosurvival signaling, cell proliferation and growth, and vasoreactivity regulation, an imbalance of ROS and RNS generation and elimination leads to inflammation, cell death, tissue damage, and disease/injury progression.

RECENT ADVANCES

Many aspects of renal oxidative stress still require investigation, including clarification of the mechanisms which prompt ROS/RNS generation and subsequent renal damage. However, we currently have a basic understanding of the major features of oxidative stress pathology and its link to kidney injury/disease, which this review summarizes.

CRITICAL ISSUES

The review summarizes the critical sources of oxidative stress in the kidney during injury/disease, including generation of ROS and RNS from mitochondria, NADPH oxidase, and inducible nitric oxide synthase. The review next summarizes the renal antioxidant systems that protect against oxidative stress, including superoxide dismutase and catalase, the glutathione and thioredoxin systems, and others. Next, we describe how oxidative stress affects kidney function and promotes damage in every nephron segment, including the renal vessels, glomeruli, and tubules.

FUTURE DIRECTIONS

Despite the limited success associated with the application of antioxidants for treatment of kidney injury/disease thus far, preventing the generation and accumulation of ROS and RNS provides an ideal target for potential therapeutic treatments. The review discusses the shortcomings of antioxidant treatments previously used and the potential promise of new ones. Antioxid. Redox Signal. 25, 119-146.

Rationale, design, and baseline characteristics of ARTS-DN: a randomized study to assess the safety and efficacy of finerenone in patients with type 2 diabetes mellitus and a clinical diagnosis of diabetic nephropathy

BACKGROUND/AIMS

Finerenone decreases albuminuria in patients having heart failure with reduced ejection fraction and mild-to-moderate (stage 2-3) chronic kidney disease. The MinerAlocorticoid Receptor Antagonist Tolerability Study-Diabetic Nephropathy (ARTS-DN; NCT01874431) is a multicenter, randomized, double-blind, placebo-controlled, parallel-group, phase 2b study. ARTS-DN investigated whether the mineralocorticoid receptor antagonist finerenone reduces albuminuria without causing major alterations in serum potassium levels in patients with type 2 diabetes mellitus and a clinical diagnosis of DN who were receiving a renin-angiotensin-system (RAS) inhibitor.

METHODS

Patients were randomized to oral finerenone 1.25-20 mg or placebo once daily. The primary objectives were to assess the ratio of the urinary albumin-to-creatinine ratio at day 90 to that at baseline in patients receiving finerenone, and to compare it with that in the placebo group. Additional exploratory analyses included evaluating changes from baseline in serum potassium levels, efficacy and safety biomarkers, and health-related quality of life.

RESULTS

Of 1,501 patients screened, 821 (the sample population) received at least one dose of finerenone/placebo. Baseline characteristics included: male, 77.8%; white, 84.2%; very high albuminuria (formerly macroalbuminuria), 38.4%; high albuminuria (formerly microalbuminuria), 60.3%; median (range) estimated glomerular filtration rate, 66.3 (24.5-130.7) ml/min/1.73 m(2); and systolic blood pressure (mean ± standard deviation), 138.1 ± 14.4 mm Hg. There was a history of cardiovascular disease in 39.6%, diabetic neuropathy in 20.0%, and diabetic retinopathy in 19.9% of patients.

CONCLUSION

ARTS-DN is the first phase 2b trial of finerenone in combination with a RAS inhibitor in patients with type 2 diabetes mellitus and a clinical diagnosis of DN.

PTGER1 deletion attenuates renal injury in diabetic mouse models

We hypothesized that the EP1 receptor promotes renal damage in diabetic nephropathy. We rendered EP1 (PTGER1, official symbol) knockout mice (EP1(-/-)) diabetic using the streptozotocin and OVE26 models. Albuminuria, mesangial matrix expansion, and glomerular hypertrophy were each blunted in EP1(-/-) streptozotocin and OVE26 cohorts compared with wild-type counterparts. Although diabetes-associated podocyte depletion was unaffected by EP1 deletion, EP1 antagonism with ONO-8711 in cultured podocytes decreased angiotensin II-mediated superoxide generation, suggesting that EP1-associated injury of remaining podocytes in vivo could contribute to filtration barrier dysfunction. Accordingly, EP1 deletion in OVE26 mice prevented nephrin mRNA expression down-regulation and ameliorated glomerular basement membrane thickening and foot process effacement. Moreover, EP1 deletion reduced diabetes-induced expression of fibrotic markers fibronectin and α-actin, whereas EP1 antagonism decreased fibronectin in cultured proximal tubule cells. Similarly, proximal tubule megalin expression was reduced by diabetes but was preserved in EP1(-/-) mice. Finally, the diabetes-associated increase in angiotensin II-mediated constriction of isolated mesenteric arteries was blunted in OVE26EP1(-/-) mice, demonstrating a role for EP1 receptors in the diabetic vasculature. These data suggest that EP1 activation contributes to diabetic nephropathy progression at several locations, including podocytes, proximal tubule, and the vasculature. The EP1 receptor facilitates the actions of angiotensin II, thereby suggesting that targeting of both the renin-angiotensin system and the EP1 receptor could be beneficial in diabetic nephropathy.

Polyphenols of Hibiscus sabdariffa improved diabetic nephropathy via attenuating renal epithelial mesenchymal transition

We previously reported that Hibiscus sabdariffa polyphenol extracts (HPE) are beneficial for diabetic nephropathy. Since an epithelial to mesenchymal transition (EMT) is critical in renal fibrosis, the present study aimed to investigate whether HPE could prevent EMT of tubular cells. Treatment of HPE reduced angiotensin II receptors (AT)-1 and transforming growth factor β1 (TGF-β1) evoked by high glucose and recovered the increased vimentin and decreased E-cadherin. HPE decreased fibronectin, thus avoiding EMT and accompanying fibrosis. AT-1 was upstream to TGF-β1, while there were recruitment signals between AT-1 and TGF-β1. Scan electron microscopy (SEM) and immunohistochemistry (IHC) revealed that the interacting filaments of tubular cells disappeared when treated with high glucose, and type IV collagen of tubulointerstitial decreased in diabetic kidneys. Treatment of HPE recovered morphological changes of cell junction and basement membrane. We suggest that HPE has the potential to be an adjuvant for diabetic nephropathy by regulating AT-1/TGF-β1 and EMT.

ACE insertion/deletion (I/D) polymorphism and diabetic nephropathy

CONTEXT

Angiotensin converting enzyme (ACE) gene encodes ACE, a key component of renin angiotensin system (RAS), plays an important role in blood pressure homeostasis by generating the vasoconstrictor peptide angiotensin II.

EVIDENCE ACQUISITIONS

Directory of Open Access Journals (DOAJ), Google Scholar, Pubmed (NLM), LISTA (EBSCO) and Web of Science have been searched.

RESULTS

The presence of ACE insertion/deletion (I/D) polymorphism affects the plasma level of ACE. ACE DD genotype is associated with the highest systemic and renal ACE levels compared with the lowest ACE activity in carriers of II genotype.

CONCLUSIONS

In this review focus has been performed on the study of ACE I/D polymorphism in various populations and its influence on the risk of onset and progression of diabetic nephropathy. Also, association between ACE I/D polymorphism and response to ACE inhibitor and angiotensin II receptor antagonists will be reviewed. Further, synergistic effect of this polymorphism and variants of some genes on the risk of development of diabetic nephropathy will be discussed.

Clinical features and outcomes of 98 children and adults with dense deposit disease

BACKGROUND

Dense deposit disease (DDD) is an ultra-rare renal disease.

METHODS

In the study reported here, 98 patients and their families participated in a descriptive patient-centered survey using an online research format. Reports were completed by patients (38%) or their parents (62%). Age at diagnosis ranged from 1.9 to 38.9 years (mean 14 years).

RESULTS

The majority of patients presented with proteinuria and hematuria; 50% had hypertension and edema. Steroids were commonly prescribed, although their use was not evidence-based. One-half of the patients with DDD for 10 years progressed to end-stage renal disease (ESRD), with young females having the greatest risk for renal failure. Of first allografts, 45% failed within 5 years, most frequently due to recurrent disease (70%). Type 1 diabetes (T1D) was present in over 16% of families, which represents a 116-fold increase in incidence compared with the general population (p < 0.001).

CONCLUSIONS

Based on these findings, we suggest that initiatives are needed to explore the high incidence of T1D in family members of DDD patients and the greater risk for progression to ESRD in young females with DDD. These efforts must be supported by sufficient numbers of patients to establish evidence-based practice guidelines for disease management. An international collaborative research survey should be implemented to encourage broad access and participation.

Combination of direct renin inhibition with angiotensin type 1 receptor blockade improves aldosterone but does not improve kidney injury in the transgenic Ren2 rat

Enhanced renin-angiotensin-aldosterone system (RAAS) activation contributes to proteinuria and chronic kidney disease by increasing glomerular and tubulointerstitial oxidative stress, promotion of fibrosis. Renin activation is the rate limiting step in angiotensin (Ang II) and aldosterone generation, and recent work suggests direct renin inhibition improves proteinuria comparable to that seen with Ang type 1 receptor (AT(1)R) blockade. This is important as, even with contemporary use of AT(1)R blockade, the burden of kidney disease remains high. Thereby, we sought to determine if combination of direct renin inhibition with AT(1)R blockade in vivo, via greater attenuation of kidney oxidative stress, would attenuate glomerular and proximal tubule injury to a greater extent than either intervention alone. We utilized the transgenic Ren2 rat with increased tissue RAS activity and higher serum levels of aldosterone, which manifests hypertension and proteinuria. Ren2 rats were treated with renin inhibition (aliskiren), AT(1)R blockade (valsartan), the combination (aliskiren+valsartan), or vehicle for 21days. Compared to Sprague-Dawley controls, Ren2 rats displayed increased systolic pressure (SBP), circulating aldosterone, proteinuria and greater urine levels of the proximal tubule protein excretory marker beta-N-acetylglucosaminidase (β-NAG). These functional and biochemical alterations were accompanied by increases in kidney tissue NADPH oxidase subunit Rac1 and 3-nitrotyrosine (3-NT) content as well as fibronectin and collagen type III. These findings occurred in conjunction with reductions in the podocyte-specific protein podocin as well as the proximal tubule-specific megalin. Further, in transgenic animals there was increased tubulointerstitial fibrosis on light microscopy as well as ultrastructural findings of glomerular podocyte foot-process effacement and reduced tubular apical endosomal/lysosomal activity. Combination therapy led to greater reductions in SBP and serum aldosterone, but did not result in greater improvement in markers of glomerular and tubular injury (i.e. β-NAG) compared to either intervention alone. Further, combination therapy did not improve markers of oxidative stress and podocyte and proximal tubule integrity in this transgenic model of RAAS-mediated kidney damage despite greater reductions in serum aldosterone and BP levels.

Off the beaten renin-angiotensin-aldosterone system pathway: new perspectives on antiproteinuric therapy

CKD is a major public health problem in the developed and the developing world. The degree of proteinuria associated with renal failure is a generally well accepted marker of disease severity. Agents with direct antiproteinuric effects are highly desirable therapeutic strategies for slowing, or even halting, progressive loss of kidney function. We review progress on therapies acting further downstream of the renin-angiotensin-aldosterone system pathway (e.g., transforming growth factor-beta antagonism, endothelin antagonism) and on those acting independent of the renin-angiotensin-aldosterone system pathway. In all, we discuss 26 therapeutic targets or compounds and 2 lifestyle changes (dietary modification and weight loss) that have been used clinically for diabetic or nondiabetic kidney disease. These therapies include endogenous molecules (estrogens, isotretinoin), biologic antagonists (monoclonal antibodies, soluble receptors), and small molecules. Where mechanistic data are available, these therapies have been shown to exert favorable effects on glomerular cell phenotype. In some cases, recent work has indicated surprising new molecular pathways for some therapies, such as direct effects on the podocyte by glucocorticoids, rituximab, and erythropoietin. It is hoped that recent advances in the basic science of kidney injury will prompt development of more effective pharmaceutical and biologic therapies for proteinuria.

Angiotensin II activation of mTOR results in tubulointerstitial fibrosis through loss of N-cadherin

BACKGROUND/AIMS

Angiotensin (Ang) II contributes to tubulointerstitial fibrosis. Recent data highlight mammalian target of rapamycin (mTOR)/S6 kinase 1 (S6K1) signaling in tubulointerstitial fibrosis; however, the mechanisms remain unclear. Thereby, we investigated the role of Ang II on mTOR/S6K1-dependent proximal tubule (PT) injury, remodeling, and fibrosis.

METHODS

We utilized young transgenic Ren2 rats (R2-T) and Sprague-Dawley rats (SD-T) treated with the Ang type 1 receptor (AT(1)R) blocker telmisartan (2 mg · kg(-1) · day(-1)) or vehicle (R2-C; SD-C) for 3 weeks to examine PT structure and function.

RESULTS

Ren2 rats displayed increased systolic blood pressure, proteinuria and increased PT oxidant stress and remodeling. There were parallel increases in kidney injury molecule-1 and reductions in neprilysin and megalin with associated ultrastructural findings of decreased clathrin-coated pits, endosomes, and vacuoles. Ren2 rats displayed increased Serine(2448) phosphorylation of mTOR and downstream S6K1, in concert with ultrastructural basement membrane thickening, tubulointerstitial fibrosis and loss of the adhesion molecule N-cadherin. Telmisartan treatment attenuated proteinuria as well as the biochemical and tubulointerstitial structural abnormalities seen in the Ren2 rats.

CONCLUSIONS

Our observations suggest that Ang II activation of the AT(1)R contributes to PT brush border injury and remodeling, in part, due to enhanced mTOR/S6K1 signaling which promotes tubulointerstitial fibrosis through loss of N-cadherin.

Effects of angiotensin receptor blocker on phenotypic alterations of podocytes in early diabetic nephropathy

BACKGROUND

Emerging evidence suggests that podocyte injury is a crucial event in the stage of diabetic nephropathy (DN), a process in which angiotensin II is implicated. In this study, the authors investigated the influence of irbesartan, an angiotensin receptor blocker, on the phenotypic alterations of podocytes in experimental DN.

METHODS

DN was induced by combination of high-sucrose, high-fat diet and intraperitoneal injection of low dose of streptozotocin (35 mg/kg) in spontaneously hypertensive rats. Diabetic rats were treated with irbesartan (50 mg/kg/d) by gavage for 8 weeks. Nondiabetic normotensive Wistar-Kyoto rats, which have the same genetic background as spontaneously hypertensive rat, were used as controls. The renal histological changes were investigated by light and electron microscopy. The epithelial marker of nephrin and mesenchymal marker of desmin were detected by real-time reverse transcriptase-polymerase chain reaction and Western blotting.

RESULTS

Compared with controls, diabetic rats were associated with mesangial matrix deposition, thickening of glomerular basement membrane, albuminuria, loss of podocytes and effacement of foot processes. Furthermore, the expression of nephrin was significantly reduced whereas desmin was increased. Irbesartan treatment not only lowered blood pressure and albuminuria but also attenuated podocyte loss, maintenance of nephrin expression and inhibition of desmin expression.

CONCLUSIONS

This study demonstrates that early irbesartan intervention attenuates the podocyte damage and ameliorates phenotypic alterations of podocytes, which provides a novel insight for the early application of angiotensin receptor blocker to prevent the development of DN.

Angiotensin II blockade: a strategy to slow ageing by protecting mitochondria?

Protein and lipid oxidation-mainly by mitochondrial reactive oxygen species (mtROS)-was proposed as a crucial determinant of health and lifespan. Angiotensin II (Ang II) enhances ROS production by activating NAD(P)H oxidase and uncoupling endothelial nitric oxide synthase (NOS). Ang II also stimulates mtROS production, which depresses mitochondrial energy metabolism. In rodents, renin-angiotensin system blockade (RAS blockade) increases survival and prevents age-associated changes. RAS blockade reduces mtROS and enhances mitochondrial content and function. This suggests that Ang II contributes to the ageing process by prompting mitochondrial dysfunction. Since Ang II is a pleiotropic peptide, the age-protecting effects of RAS blockade are expected to involve a variety of other mechanisms. Caloric restriction (CR)-an age-retarding intervention in humans and animals-and RAS blockade display a number of converging effects, i.e. they delay the manifestations of hypertension, diabetes, nephropathy, cardiovascular disease, and cancer; increase body temperature; reduce body weight, plasma glucose, insulin, and insulin-like growth factor-1; ameliorate insulin sensitivity; lower protein, lipid, and DNA oxidation, and mitochondrial H(2)O(2) production; and increase uncoupling protein-2 and sirtuin expression. A number of these overlapping effects involve changes in mitochondrial function. In CR, peroxisome proliferator-activated receptors (PPARs) seem to contribute to age-retardation partly by regulating mitochondrial function. RAS inhibition up-regulates PPARs; therefore, it is feasible that PPAR modulation is pivotal for mitochondrial protection by RAS blockade during rodent ageing. Other potential mechanisms that may underlie RAS blockade's mitochondrial benefits are TGF-β down-regulation and up-regulation of Klotho and sirtuins. In conclusion, the available data suggest that RAS blockade deserves further research efforts to establish its role as a potential tool to mitigate the growing problem of age-associated chronic disease.

PPARs in the Renal Regulation of Systemic Blood Pressure

Recent research has revealed roles for the peroxisome proliferator activated receptor (PPAR) family of transcription factors in blood pressure regulation, expanding the possible therapeutic use of PPAR ligands. PPARalpha and PPARgamma modulate the renin-angiotensin-aldosterone system (RAAS), a major regulator of systemic blood pressure and interstitial fluid volume by transcriptional control of renin, angiotensinogen, angiotensin converting enzyme (ACE) and angiotensin II receptor 1 (AT-R1). Blockade of RAAS is an important therapeutic target in hypertension management and attenuates microvascular damage, glomerular inflammation and left ventricular hypertrophy in hypertensive patients and also show antidiabetic effects. The mechanisms underlying the benefits of RAAS inhibition appear to involve PPARgamma-regulated pathways. This review summarizes current knowledge on the role of PPARs in the transcriptional control of the RAAS and the possible use of PPAR ligands in the treatment of RAAS dependent hypertension.