Renoprotective benefits of RAS inhibition: from ACEI to angiotensin II antagonists

Relationship between GFR and albuminuria in stage 1 hypertension

BACKGROUND AND OBJECTIVES

Whether glomerular hyperfiltration is implicated in the development of microalbuminuria in hypertension is not well known. This prospective study investigated the relationship between changes in GFR and microalbuminuria in hypertension.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study assessed 534 stage 1 hypertensive participants from the Hypertension and Ambulatory Recording Venetia Study (n=386 men) without microalbuminuria at baseline, who were recruited from 1990 to 1995 and followed for a median of 8.5 years. Mean age was 33.9±8.6 years and mean BP was 146.6±10.5/94.0±5.0 mmHg. Creatinine clearance and 24-hour urinary albumin were measured at study entry and end. Participants were defined as normofilterers (normo) or hyperfilterers (hyper) according to whether GFR was <150 or ≥150 ml/min per 1.73 m(2), respectively. Participants were divided into four groups based on GFR changes from baseline to follow-up end: normo→normo (n=395), normo→hyper (n=31), hyper→hyper (n=61), and hyper→normo (n=47).

RESULTS

Microalbuminuria progressively increased across the four groups and was 5.3% in normo→normo, 9.7% in normo→hyper, 16.4% in hyper→hyper, and 36.2% in hyper→normo (P<0.001). This association held true in a multivariable logistic regression in which several confounders, ambulatory BP, and other risk factors were taken into account (P<0.001). In particular, hyperfilterers whose GFR decreased to normal at study end had an adjusted odds ratio of 7.8 (95% confidence interval, 3.3-18.2) for development of microalbuminuria compared with participants with normal GFR throughout the study.

CONCLUSIONS

These data support the hypothesis for a parabolic association between GFR and urinary albumin in the early stage of hypertension.

Residual renal function in hemodialysis patients: the role of Angiotensin-converting enzyme inhibitor in its preservation

Residual Renal function (RRF) has an important role in the overall morbidity and mortality in hemodialysis patients. The role of angiotensin-converting enzyme inhibitor (ACEi) in preserving renal function in chronic proteinuric nephropathies is well documented. We test the hypothesis that enalapril (an ACEi) slows the rate of decline of RRF in patients starting hemodialysis. A prospective, randomized open-label study was carried out. 42 patients were randomized in two groups either in treatment with enalapril or no treatment at all. Our study has proven that enalapril has a significant effect on preserving residual renal function in patients starting dialysis at least during the first 12 months from the initiation of the hemodialysis. Further studies are necessary in order to investigate the potential long-term effect of ACEi on residual renal function and on morbidity and mortality in patients starting hemodialysis.

Proteinuria triggers renal lymphangiogenesis prior to the development of interstitial fibrosis

Proteinuria is an important cause of progressive tubulo-interstitial damage. Whether proteinuria could trigger a renal lymphangiogenic response has not been established. Moreover, the temporal relationship between development of fibrosis, inflammation and lymphangiogenesis in chronic progressive kidney disease is not clear yet. Therefore, we evaluated the time course of lymph vessel (LV) formation in relation to proteinuria and interstitial damage in a rat model of chronic unilateral adriamycin nephrosis. Proteinuria and kidneys were evaluated up to 30 weeks after induction of nephrosis. LVs were identified by podoplanin/VEGFR3 double staining. After 6 weeks proteinuria was well-established, without influx of interstitial macrophages and myofibroblasts, collagen deposition, osteopontin expression (tubular activation) or LV formation. At 12 weeks, a ∼3-fold increase in cortical LV density was found (p<0.001), gradually increasing over time. This corresponded with a significant increase in tubular osteopontin expression (p<0.01) and interstitial myofibroblast numbers (p<0.05), whereas collagen deposition and macrophage numbers were not yet increased. VEGF-C was mostly expressed by tubular cells rather than interstitial cells. Cultured tubular cells stimulated with FCS showed a dose-dependent increase in mRNA and protein expression of VEGF-C which was not observed by human albumin stimulation. We conclude that chronic proteinuria provoked lymphangiogenesis in temporal conjunction with tubular osteopontin expression and influx of myofibroblasts, that preceded interstitial fibrosis.

Mechanisms and treatment of CKD

As CKD continues to increase worldwide, along with the demand for related life-saving therapies, the financial burden of CKD will place an increasing drain on health care systems. Experimental studies showed that glomerular capillary hypertension and impaired sieving function with consequent protein overload play a pathogenic role in the progression of CKD. Consistently, human studies show that proteinuria is an independent predictor of progression and that its reduction is renoprotective. At comparable BP control, inhibitors of the renin-angiotensin system (RAS), including angiotensin converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs), more effectively than non-RAS inhibitor therapy reduce proteinuria, slow progression to ESRD, and even improve the kidney function achieving disease regression in some cases. In participants with diabetes, RAS inhibitors delay the onset of microalbuminuria and its progression to macroalbuminuria, and ACE inhibitors may reduce the excess cardiovascular mortality associated with diabetic renal disease. In addition to RAS inhibitors, however, multimodal approaches including lifestyle modifications and multidrug therapy will be required in most cases to optimize control of the several risk factors for CKD and related cardiovascular morbidity. Whether novel medications may help further improve the cost-effectiveness of renoprotective interventions is a matter of investigation.

The renin-angiotensin-aldosterone system in 2011: role in hypertension and chronic kidney disease

Over the past two decades, considerable advances have been made in our understanding of the renin-angiotensin-aldosterone system (RAAS) and its roles in various disease states. In this review, we will discuss the current state of knowledge of the many components of the RAAS, including new data on prorenin and its receptors, and important angiotensin fragments. The roles of these components of the RAAS in the pathogenesis of primary hypertension and the progression of chronic kidney disease (CKD) will also be highlighted. Given the new understanding of the many components and roles of the RAAS, it may be possible to develop improved therapies for hypertension and CKD.

Peptide-drug conjugate linked via a disulfide bond for kidney targeted drug delivery

Chronic kidney disease (CKD) is a worldwide public health problem, and unfortunately, the therapeutic index of clinically available drugs is limited. Thus, there is a great need to exploit effective treatment strategies, and the carrier-drug approach is an attractive method to improve the kidney specificity of the therapeutic agents. The aim of this present study is to develop a peptide-drug conjugate for the kidney targeted delivery of angiotensin-converting enzyme (ACE) inhibitor captopril (CAP), since G3-C12 peptide (ANTPCGPYTHDCPVKR) could specifically accumulate in the kidney after intravenous injection. Therefore, FITC labeled G3-C12 peptide (G3-C12-FITC) and peptide-drug conjugate (G3-C12-CAP) with a disulfide bond which can be cleaved by reduced glutathione in the kidney were prepared by solid-phase peptide synthesis. The fluorescence imaging of G3-C12-FITC revealed that the labeled peptide specifically accumulated in the kidney soon after i.v. injection to mice, and the accumulation is due largely to the reabsorption of the peptide by the proximal renal tubule cells. Furthermore, in comparison with the corresponding nonconjugated form, a 2.7-fold increase in renal area under concentration-time curve produced by the conjugate was observed in mice. Interestingly, the CAP entirely released in the kidney even at 0.05 h postinjection through disulfide reduction. As a consequence, the in vivo renal ACE inhibition was significantly increased. In conclusion, these findings suggest the potential of G3-C12 peptide serving as a suitable candidate carrier for kidney-targeted drug delivery.

Expression of proinflammatory factors in renal cortex induced by methylmalonic acid

BACKGROUND

Methylmalonic aciduria is an inborn error of metabolism that causes renal failure and tubulointerstitial (TI) nephritis as complications. This study aimed to examine the levels of expression of several genes related to inflammation, oxidative stress, and mitochondrial function in the renal cortex of rats receiving methylmalonic acid (MMA).

METHODS

Rats received MMA subcutaneously for a month. Tumor necrosis factor alpha (TNFα), nuclear factor-kappa B, interleukin 1 beta (IL-1β), and cyclooxygenase 2 (COX-2) genes were examined by real-time polymerase chain reaction. We also examined transforming growth factor beta (TGF-β) related to TI fibrosis, c-FOS, belonging to the immediate early gene family of transcription factors, and expression of SIRT1, related to energy production.

RESULTS

There was significantly higher expression of TNFα and a trend toward a higher level of TGF-β transcripts in the methylmalonic model group compared with the controls. However, SIRT1 expression was not different among the groups. Urinary MMA excretion correlated positively with mRNA level of TGF-β. The expression of COX-2 was positively associated with the expression of c-FOS and inversely related to the expression of IL-1β.

CONCLUSIONS

The higher levels of TNFα and TGF-β transcripts suggest inflammation and differentiation processes in the renal cortex in rats because of MMA. After 1 month of MMA injections, expression levels of SIRT1 were not affected, suggesting mitochondrial preservation in early stages of the disease.

Bradykinin inhibits high glucose- and growth factor-induced collagen synthesis in mesangial cells through the B2-kinin receptor

Mesangial matrix expansion is an early lesion leading to glomeruloclerosis and chronic renal diseases. A beneficial effect is achieved with angiotensin I-converting enzyme inhibitors (ACEI), which also favor bradykinin (BK) B2 receptor (B2R) activation. To define the underlying mechanism, we hypothesized that B2R activation could be a negative regulator of collagen synthesis in mesangial cells (MC). We investigated the effect of BK on collagen synthesis and signaling in MC. Inflammation was evaluated by intercellular adhesion molecule-1 (ICAM-1) expression. BK inhibited collagen I and IV synthesis stimulated by high glucose, epithelial growth factor (EGF), and transforming growth factor-β (TGF-β) but did not alter ICAM-1. Inhibition of collagen synthesis was B2R but not B1R mediated. PKC or phosphatidylinositol 3-kinase (PI3K) inhibitors mimicked the BK effect. B2R activation inhibited TGF-β- and EGF-induced Erk1/2, Smad2/3, Akt S473, and EGFR phosphorylation. A phosphatase inhibitor prevented BK effects. The in vivo impact of B2R on mesangial matrix expansion was assessed in streptozotocin-diabetic rodents. Deletion of B2R increased mesangial matrix expansion and albuminuria in diabetic mice. In diabetic rats, matrix expansion and albuminuria were prevented by ACEI but not by ACEI and B2R antagonist cotreatment. Consistently, the lowered BK content of diabetic glomeruli was restored by ACEI. In conclusion, deficient B2R activation aggravated mesangial matrix expansion in diabetic rodents whereas B2R activation reduced MC collagen synthesis by a mechanism targeting Erk1/2 and Akt, common pathways activated by EGF and TGF-β. Taken together, the data support the hypothesis of an antifibrosing effect of B2R activation.

Involvement of glomerular renin-angiotensin system (RAS) activation in the development and progression of glomerular injury

Recently, there has been a paradigm shift away from an emphasis on the role of the endocrine (circulating) renin-angiotensin system (RAS) in the regulation of the sodium and extracellular fluid balance, blood pressure, and the pathophysiology of hypertensive organ damage toward a focus on the role of tissue RAS found in many organs, including kidney. A tissue RAS implies that RAS components necessary for the production of angiotensin II (Ang II) reside within the tissue and its production is regulated within the tissue, independent of the circulating RAS. Locally produced Ang II plays a role in many physiological and pathophysiological processes such as hypertension, inflammation, oxidative stress, and tissue fibrosis. Both glomerular and tubular compartments of the kidney have the characteristics of a tissue RAS. The purpose of this article is to review the recent advances in tissue RAS research with a particular focus on the role of the glomerular RAS in the progression of renal disease.

Glomerular hyperfiltration: definitions, mechanisms and clinical implications

Glomerular hyperfiltration is a phenomenon that can occur in various clinical conditions including kidney disease. No single definition of glomerular hyperfiltration has been agreed upon, and the pathophysiological mechanisms, which are likely to vary with the underlying disease, are not well explored. Glomerular hyperfiltration can be caused by afferent arteriolar vasodilation as seen in patients with diabetes or after a high-protein meal, and/or by efferent arteriolar vasoconstriction owing to activation of the renin-angiotensin-aldosterone system, thus leading to glomerular hypertension. Glomerular hypertrophy and increased glomerular pressure might be both a cause and a consequence of renal injury; understanding the renal adaptations to injury is therefore important to prevent further damage. In this Review, we discuss the current concepts of glomerular hyperfiltration and the renal hemodynamic changes associated with this condition. A physiological state of glomerular hyperfiltration occurs during pregnancy and after consumption of high-protein meals. The various diseases that have been associated with glomerular hyperfiltration, either per nephron or per total kidney, include diabetes mellitus, polycystic kidney disease, secondary focal segmental glomerulosclerosis caused by a reduction in renal mass, sickle cell anemia, high altitude renal syndrome and obesity. A better understanding of the mechanisms involved in glomerular hyperfiltration could enable the development of new strategies to prevent progression of kidney disease.

Angiotensin converting enzyme 2, Angiotensin-(1-7), and receptor MAS axis in the kidney

In the past few years the understanding of the renin-angiotensin system (RAS) has improved, helping to better define the role of this system in physiological conditions and in human diseases. Besides Angiotensin (Ang) II, the biological importance of other Ang fragments was progressively evidenced. In this regard, Angiotensin- (Ang-) (1-7) was recognized as a biologically active product of the RAS cascade with a specific receptor, the G-protein-coupled receptor Mas, and that is mainly formed by the action of the angiotensin-converting enzyme (ACE) homolog enzyme, ACE2, which converts Ang II into Ang-(1-7). Taking into account the biological effects of these two mediators, Ang II and Ang-(1-7), the RAS can be envisioned as a dual function system in which the vasoconstrictor/proliferative or vasodilator/antiproliferative actions are primarily driven by the balance between Ang II and Ang-(1-7), respectively. In this paper, we will discuss our current understanding of the ACE2/Ang-(1-7)/Mas axis of the RAS in renal physiology and in the pathogenesis of primary hypertension and chronic kidney disease.

Effect of angiotensin type 2 receptor over-expression on the rat mesangial cell fibrotic phenotype: effect of gender

BACKGROUND AND AIM

The protective role of angiotensin type 2 receptors (AT2-Rs) is still controversial. As AT2-Rs are minimally expressed in adult tissues the aim of the current study was to over-express AT2-Rs in rat mesangial cells in order to ascertain their potential role in modulating renal scarring.

METHODS

Male and female mesangial cells were transiently transfected with AT2-R or control vector then 'injured' with macrophage-conditioned medium (MCM). Culture supernatants and extracted RNA were analysed for evidence of an anti-fibrotic phenotype.

RESULTS

Supernatant fibronectin levels in female mesangial cells treated with MCM were reduced in AT2-R transfected cells (p < 0.001) compared to controls. AT2-R transfected male cells showed a trend towards lower constitutive fibronectin levels. There was no effect of AT2-R transfection on TGF-β or TNF-α secretion; however, IL-1β levels were reduced in male cells treated with MCM. RT-PCR demonstrated that constitutive kallikrein mRNA levels were suppressed in both male and female AT2-R transfected cells. Bradykinin receptors (BkB2-R and BkB1-R) were unaffected in female cells although the BkB1-R was upregulated in male cells treated with MCM.

CONCLUSION

This data provides a case for AT2 receptors playing a protective role in rat mesangial cells independent of the effects of blood pressure control.

Early treatment with everolimus exerts nephroprotective effect in rats with adriamycin-induced nephrotic syndrome

BACKGROUND

Nephrotic syndrome (NS) is a clinical state characterized by massive proteinuria and excessive fluid retention. The effects of early versus late treatment with low or high doses of oral everolimus, a mammalian target of rapamycin inhibitor, on proteinuria in NS have not been previously described.

METHODS

The effects of early treatment (2 days prior to NS induction) versus late treatment (beginning 2 weeks following the establishment of NS) with a low (20 mg/L) or high (100 mg/L) dose of everolimus for 5-7 weeks on proteinuria and nephrin/podocin abundance were assessed in male adult SD rats with adriamycin-induced NS.

RESULTS

Adriamycin caused a significant increase in daily and cumulative proteinuria throughout the experimental period. Early, and to a lesser extent late treatment, with a low dose of everolimus, significantly decreased both daily and cumulative proteinuria and improved renal function. The anti-proteinuric effects of low-dose everolimus were associated with restoration of the disruptive glomerular nephrin/podocin abundance. In contrast, administration of a high dose of everolimus resulted in a decrease in proteinuria in NS rats, subsequently to deterioration of renal function.

CONCLUSIONS

Early, and to a lesser extent late treatment, with a low but not a high dose of everolimus is effective in reducing proteinuria in nephrotic rats. The mechanism may be via nephrin/podocin protection.

Angiotensin II type I receptor blockade suppresses glomerular renin-angiotensin system activation, oxidative stress, and progressive glomerular injury in rat anti-glomerular basement membrane glomerulonephritis

Excessive renin-angiotensin system (RAS) activation within the kidney induces not only renal oxidative stress but also renal scarring and dysfunction. This study examined the effects of an angiotensin II (Ang II) type I receptor (AT1R) blocker (ARB) on the progression of renal injury in rat anti-glomerular basement membrane glomerulonephritis (GN), with a particular focus on the participation of glomerular RAS activation in glomerular structural alterations, inflammation, and oxidative stress. Nephritic rats were divided into 2 groups and treated with vehicle or ARB until day 28. Treatment with ARB improved proteinuria significantly in nephritic rats. Vehicle-treated nephritic rats developed crescentic GN accompanied by marked macrophage infiltration and the enhanced expression of glomerular α-smooth muscle actin (α-SMA), angiotensinogen (AGT), Ang II, AT1R, and NADPH oxidase (Nox2) on days 7 and 28 of GN. ARB improved pathologic alterations such as crescent formation and glomerulosclerosis, and it had a significant inhibitory effect on the levels of these parameters on day 28 of GN. Enhanced superoxide production in nephritic glomeruli was decreased also by ARB. Moreover, Ang II and transforming growth factor beta (TGF-β) in the supernatant of cultured glomeruli was increased significantly in vehicle-treated nephritic rats whereas ARB inhibited the production of these compounds significantly on day 28. These results indicate that increased glomerular RAS activity and the resulting Ang II play important roles in progressive glomerular injury-the induction of oxidative stress and TGF-β expression, and they suggest that AT1R blockade attenuates proteinuria and progressive glomerular remodeling via the suppression of glomerular RAS activation in GN.

Functional evaluation of transplanted kidneys in normal function and acute rejection using BOLD MR imaging

In this study, we evaluated a large number of subjects using BOLD MRI to provide more information about oxygen metabolism in the normal function of transplanted kidneys and to distinguish acute graft rejection from normal function kidneys. This study included 122 subjects (20 volunteers, 72 patients with normal functioning transplants, and 21 patients with acute rejection), and 9 patients had normal function grafts received examination while grafts dysfunction occurred within 6 months during the follow-up. The R2 (1/s) values in the cortex and medulla as well as the R2 ratio of the medulla to cortex (R2 ratio of M/C) were recorded. The R2 values of the medulla were higher than those of the cortex in the normal function group and the volunteers which have a steep R2 ratio of M/C. All the R2 values in the acute rejection group were lower than those in the normal function grafts group (P<0.001). Moreover, in the 9 patients as normal function, the R2 values of the cortex and medulla were different from the normal function grafts, which was lower in 5 patients and was higher in the 4 remaining patients. Conversely, the R2 ratios of M/C of the 9 patients were similar to those in the normal function group. BOLD MRI shows that decreased R2 values of the cortex and medulla and R2 ratio of M/C suggest acute renal graft rejection; furthermore, a steep R2 ratio of M/C (>1.1) is an important reason for keeping clinical normal function.

Effects of fenofibrate on renal function in patients with type 2 diabetes mellitus: the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) Study

AIMS/HYPOTHESIS

Fenofibrate caused an acute, sustained plasma creatinine increase in the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) and Action to Control Cardiovascular Risk in Diabetes (ACCORD) studies. We assessed fenofibrate's renal effects overall and in a FIELD washout sub-study.

METHODS

Type 2 diabetic patients (n = 9,795) aged 50 to 75 years were randomly assigned to fenofibrate (n = 4,895) or placebo (n = 4,900) for 5 years, after 6 weeks fenofibrate run-in. Albuminuria (urinary albumin/creatinine ratio measured at baseline, year 2 and close-out) and estimated GFR, measured four to six monthly according to the Modification of Diet in Renal Disease Study, were pre-specified endpoints. Plasma creatinine was re-measured 8 weeks after treatment cessation at close-out (washout sub-study, n = 661). Analysis was by intention-to-treat.

RESULTS

During fenofibrate run-in, plasma creatinine increased by 10.0 μmol/l (p < 0.001), but quickly reversed on placebo assignment. It remained higher on fenofibrate than on placebo, but the chronic rise was slower (1.62 vs 1.89 μmol/l annually, p = 0.01), with less estimated GFR loss (1.19 vs 2.03 ml min(-1) 1.73 m(-2) annually, p < 0.001). After washout, estimated GFR had fallen less from baseline on fenofibrate (1.9 ml min(-1) 1.73 m(-2), p = 0.065) than on placebo (6.9 ml min(-1) 1.73 m(-2), p < 0.001), sparing 5.0 ml min(-1) 1.73 m(-2) (95% CI 2.3-7.7, p < 0.001). Greater preservation of estimated GFR with fenofibrate was observed with baseline hypertriacylglycerolaemia (n = 169 vs 491 without) alone, or combined with low HDL-cholesterol (n = 140 vs 520 without) and reductions of ≥ 0.48 mmol/l in triacylglycerol over the active run-in period (pre-randomisation) (n = 356 vs 303 without). Fenofibrate reduced urine albumin concentrations and hence albumin/creatinine ratio by 24% vs 11% (p < 0.001; mean difference 14% [95% CI 9-18]; p < 0.001), with 14% less progression and 18% more albuminuria regression (p < 0.001) than in participants on placebo. End-stage renal event frequency was similar (n = 21 vs 26, p = 0.48).

CONCLUSIONS/INTERPRETATION

Fenofibrate reduced albuminuria and slowed estimated GFR loss over 5 years, despite initially and reversibly increasing plasma creatinine. Fenofibrate may delay albuminuria and GFR impairment in type 2 diabetes patients. Confirmatory studies are merited.

TRIAL REGISTRATION

ISRCTN64783481.

TRPC6 enhances angiotensin II-induced albuminuria

Mutations in the canonical transient receptor potential cation channel 6 (TRPC6) are responsible for familial forms of adult onset focal segmental glomerulosclerosis (FSGS). The mechanisms by which TRPC6 mutations cause kidney disease are not well understood. We used TRPC6-deficient mice to examine the function of TRPC6 in the kidney. We found that adult TRPC6-deficient mice had BP and albumin excretion rates similar to wild-type animals. Glomerular histomorphology revealed no abnormalities on both light and electron microscopy. To determine whether the absence of TRPC6 would alter susceptibility to hypertension and renal injury, we infused mice with angiotensin II continuously for 28 days. Although both groups developed similar levels of hypertension, TRPC6-deficient mice had significantly less albuminuria, especially during the early phase of the infusion; this suggested that TRPC6 adversely influences the glomerular filter. We used whole-cell patch-clamp recording to measure cell-membrane currents in primary cultures of podocytes from both wild-type and TRPC6-deficient mice. In podocytes from wild-type mice, angiotensin II and a direct activator of TRPC6 both augmented cell-membrane currents; TRPC6 deficiency abrogated these increases in current magnitude. Our findings suggest that TRPC6 promotes albuminuria, perhaps by promoting angiotensin II-dependent increases in Ca(2+), suggesting that TRPC6 blockade may be therapeutically beneficial in proteinuric kidney disease.

Prevention of angiotensin II-mediated renal oxidative stress, inflammation, and fibrosis by angiotensin-converting enzyme 2

Angiotensin-converting enzyme 2 (ACE2) is a monocarboxypeptidase capable of metabolizing angiotensin (Ang) II into Ang 1 to 7. We hypothesized that ACE2 is a negative regulator of Ang II signaling and its adverse effects on the kidneys. Ang II infusion (1.5 mg/kg⁻¹/d⁻¹) for 4 days resulted in higher renal Ang II levels and increased nicotinamide adenine dinucleotide phosphate oxidase activity in ACE2 knockout (Ace2(-/y)) mice compared to wild-type mice. Expression of proinflammatory cytokines, interleukin-1β and chemokine (C-C motif) ligand 5, were increased in association with greater activation of extracellular-regulated kinase 1/2 and increase of protein kinase C-α levels. These changes were associated with increased expression of fibrosis-associated genes (α-smooth muscle actin, transforming growth factor-β, procollagen type Iα1) and increased protein levels of collagen I with histological evidence of increased tubulointerstitial fibrosis. Ang II-infused wild-type mice were then treated with recombinant human ACE2 (2 mg/kg⁻¹/d⁻¹, intraperitoneal). Daily treatment with recombinant human ACE2 reduced Ang II-induced pressor response and normalized renal Ang II levels and oxidative stress. These changes were associated with a suppression of Ang II-mediated activation of extracellular-regulated kinase 1/2 and protein kinase C pathway and Ang II-mediated renal fibrosis and T-lymphocyte-mediated inflammation. We conclude that loss of ACE2 enhances renal Ang II levels and Ang II-induced renal oxidative stress, resulting in greater renal injury, whereas recombinant human ACE2 prevents Ang II-induced hypertension, renal oxidative stress, and tubulointerstitial fibrosis. ACE2 is an important negative regulator of Ang II-induced renal disease and enhancing ACE2 action may have therapeutic potential for patients with kidney disease.

The clinical significance of hyperfiltration in diabetes

Glomerular filtration rate is commonly elevated in early diabetes and patients with this symptom are arbitrarily considered to have hyperfiltration. The prevalence of hyperfiltration in type 1 diabetes varies from less than 25% to more than 75%. The corresponding figures in type 2 diabetes are significantly lower, ranging between 0% and more than 40%. Several factors, methodological and biological, may contribute to the wide variation in estimates of hyperfiltration prevalence. Methodological differences in measurement and evaluation of GFR apply in particular to the handling of plasma disappearance curves of filtration markers. Biological factors that may influence GFR in the hyperfiltration range include glycaemic control, diabetes duration, BMI, sex, pubertal status in type 1 diabetes and age in type 2 diabetes. Hyperglycaemia may influence GFR and albuminuria, and may therefore confound the evaluation of hyperfiltration as an independent risk factor for diabetic nephropathy. Adequate assessment of the relationship between glycaemic control, GFR and AER therefore requires serial measurements of all three variables followed by multivariate analysis. A recent meta-analysis of ten type 1 diabetes studies concluded that the presence of hyperfiltration at baseline more than doubled the risk of developing micro- or macroalbuminuria at follow-up. However, not all studies allowed for confounding factors or regression dilution bias. Future studies will therefore need to address the independent role of hyperfiltration, not only in the evolution of albuminuria, but also in the subsequent decline of GFR.

Angiotensin II blockade upregulates the expression of Klotho, the anti-ageing gene, in an experimental model of chronic cyclosporine nephropathy

BACKGROUND

The Klotho gene plays a role in suppressing ageing-related disorders. It is suggested that activation of renin-angiotensin system (RAS) or oxidative stress suppresses Klotho in the kidney. This study evaluated the association between Klotho expression and RAS in cyclosporine (CsA)-induced renal injury.

METHODS

Chronic CsA nephropathy was induced by administering CsA (30 mg/kg) to mice on a low-salt diet (LSD) for 4 weeks. A normal-salt diet (NSD) was used as the control. Reverse transcription-polymerase chain reaction, western blot and immunohistochemistry were performed for Klotho and intrarenal RAS activity was measured using immunohistochemistry for angiotensinogen and renin. Oxidative stress was measured with urinary excretion of 8-hydroxy-2'-deoxyguanosine (8-OHdG).

RESULTS

CsA treatment decreased Klotho mRNA and protein in mouse kidney in a dose-dependent and time-dependent manner, but a concurrent treatment with losartan, an angiotensin II type 1 (AT1) receptor blocker, reversed the decrease in Klotho expression with histological improvement. This finding was more marked in the LSD than the NSD. Klotho expression was correlated with angiotensinogen and renin expression, tubulointerstitial fibrosis score and urinary 8-OHdG excretion.

CONCLUSIONS

Angiotensin II may play a pivotal role in regulating Klotho expression in CsA-induced renal injury. AT1 receptor blocker may inhibit the ageing process by decreasing oxidative stress caused by CsA.

ANG II promotes autophagy in podocytes

Podocytes are an integral and important constituent of the glomerular filtration barrier (GFB) and are exposed to a higher concentrations of ANG II in diseased states; consequently, podocytes may accumulate oxidized proteins and damaged mitochondria. In the present study, we evaluated the effect of ANG II on the podocyte autophagic process, which is likely to be triggered in order to degrade unwanted proteins and damaged organelles. To quantitate the occurrence of autophagy, electron microscopic studies were carried out on control and ANG II-treated conditionally immortalized mouse podocytes (CIMPs). ANG II-treated cells showed a fivefold greater number of autophagosomes/field compared with control cells. This proautophagic effect of ANG II was inhibited by pretreatment with 3-methyladenine, an inhibitor of autophagy. ANG II also enhanced podocyte expression of autophagic genes such as LC3-2 and beclin-1. Since oxidative stress is often associated with the induction of autophagy, we examined the effect of ANG II on podocyte reactive oxygen species (ROS) generation. ANG II enhanced podocyte ROS generation in a time-dependent manner. To determine whether there is a causal relationship between ANG II-induced oxidative stress and induction of autophagy, we evaluated the effect of antioxidants on ANG II-induced autophagy. As expected, the proautophagic effect of ANG II was inhibited by antioxidants. We conclude that ANG II promotes podocyte autophagy through the generation of ROS.

A clinical comparative study of the management of chronic renal failure with Punarnavadi compound

India like any other country is facing a silent epidemic of chronic renal failure (CRF)- a facet of the health transition associated with industrialization partly fuelled by increase in sedentary lifestyle, low birth weight and malnutrition. Increasing figures by many folds seen is posing a difficult situation to overcome with respect to economy and health of the working and earning population of the nation. There is an urgent need to explore, highlight new interventions and modify modifiable risk factors as a basis for treatment strategies to prevent the development and progression of CRF. The present study was taken up to evaluate the role of trial formulation tab. Punarnavadi compound in the management of chronic renal failure. This was an open clinical comparative study in controlled circumstances wherein 67 patients were studied for two months in three groups- Group A (allopathic control), Group B (ayurvedic control) and Group C (ayurvedic test). It was a multi-centric study; patients were registered from Anandababa charitable dialysis centre, Jamnagar, Kayachikitsa O.P.D. of I.P.G.T. and R.A. Jamnagar and P. D. Patel Ayurveda hospital, Nadiad. Results were assessed on 15 parameters using Students (paired) 't' test. Group A patients showed comparatively better results in eight parameters- weight, platelet count, serum urea, serum uric acid, serum sodium, potassium, chloride and total proteins. Parameter Hemoglobin% showed better results in Group B patients and in Group C patients comparatively better results in six parameters viz.- quality of life (breathlessness, weakness, general functional capacity), total count, serum creatinine and serum calcium - were observed. Throughout the study, trial drug tab. Punarnavadi compound did not show any adverse drug reaction. The results of this study will help in developing a cheap and safe treatment for the management of CRF.

The mechanism of distinct diurnal variations of renin-angiotensin system in aorta and heart of spontaneously hypertensive rats

Diurnal variations in plasminogen activator inhibitor-1 mRNA expression are different between the spontaneously hypertensive rats (SHRs) and the Wistar-Kyoto (WKY) rats, and between the aorta and the heart. To elucidate the mechanisms, we examined diurnal changes in the circulating renin-angiotensin system in the SHR and WKY rats. Diurnal variations in plasma renin activity (PRA), plasma angiotensin I, and aldosterone concentrations were similar between the SHR and WKY rats. On the other hand, plasma angiotensin II (Ang II) concentration in the SHR was lower than that in the WKY rats at most time points, but increased to the level of the WKY rats in the late light phase. Treatment with AT1 receptor antagonist candesartan increased plasma Ang II concentration except at ZT 8 and lessened its diurnal variation in the SHR. At the peak in plasma Ang II in the SHR, Ang II regulated genes such as transforming growth factor-beta1 and p22phox were upregulated in the aorta. On the other hand, these genes were upregulated throughout the day in the heart of SHR. Candesartan treatment increased AT1a receptor mRNA expression in the heart but not in the aorta of SHR. These findings suggest that an AT1 receptor-mediated mechanism might cause a surge in plasma Ang II concentration at the late light phase in the SHR. Homologous down-regulation of AT1a receptor by Ang II may dampen the effect of a surge in plasma Ang II concentration in the heart of SHR.

Extracellular matrix molecules: potential targets in pharmacotherapy

The extracellular matrix (ECM) consists of numerous macromolecules classified traditionally into collagens, elastin, and microfibrillar proteins, proteoglycans including hyaluronan, and noncollagenous glycoproteins. In addition to being necessary structural components, ECM molecules exhibit important functional roles in the control of key cellular events such as adhesion, migration, proliferation, differentiation, and survival. Any structural inherited or acquired defect and/or metabolic disturbance in the ECM may cause cellular and tissue alterations that can lead to the development or progression of disease. Consequently, ECM molecules are important targets for pharmacotherapy. Specific agents that prevent the excess accumulation of ECM molecules in the vascular system, liver, kidney, skin, and lung; alternatively, agents that inhibit the degradation of the ECM in degenerative diseases such as osteoarthritis would be clinically beneficial. Unfortunately, until recently, the ECM in drug discovery has been largely ignored. However, several of today's drugs that act on various primary targets affect the ECM as a byproduct of the drugs' actions, and this activity may in part be beneficial to the drugs' disease-modifying properties. In the future, agents and compounds targeting directly the ECM will significantly advance the treatment of various human diseases, even those for which efficient therapies are not yet available.

ERK5 activation enhances mesangial cell viability and collagen matrix accumulation in rat progressive glomerulonephritis

The mitogen-activated protein kinase (MAPK) cascade plays an important role in the regulation of various cellular functions in glomerulonephritis (GN). Here, we investigated whether extracellular signal-regulated kinase 5 (ERK5), a member of the MAPK family, is involved in the pathogenesis of chronic mesangioproliferative GN, using a rat model induced by uninephrectomy and anti-Thy-1 antibody injection. Immunostaining of kidneys obtained at different time points revealed that phospho-ERK5 was weakly expressed in control glomeruli but dramatically increased in a typical mesangial pattern after 28 and 56 days of GN. A semiquantitative assessment indicated that glomerular phospho-ERK5 expression closely paralleled the accumulation of extracellular matrix (ECM), collagen type I, as well as glomerular expression of reactive oxygen species (ROS) and ANG II. On the other hand, phospho-ERK1/2 expression increased on day 7 during the phase of enhanced mesangial cell (MC) proliferation and decreased thereafter. H(2)O(2) and ANG II each induced ERK5 phosphorylation by cultured rat MCs. Costimulation with both H(2)O(2) and ANG II synergistically increased ERK5 phosphorylation in MCs. Cultured MCs transfected with ERK5-specific small interference RNA showed a significant decrease in H(2)O(2) or ANG II-induced cell viability and soluble collagen secretion compared with control cells. Treatment of GN rats with an ANG II type 1 receptor blocker resulted in significant decreases in phospho-ERK5 expression and collagen accumulation accompanied by remarkable histological improvement. Taken together, these results suggest that MC ERK5 phosphorylation by ANG II or H(2)O(2) enhances cell viability and ECM accumulation in an experimental model of chronic GN.

Astragalus mongholicus ameliorates renal fibrosis by modulating HGF and TGF-beta in rats with unilateral ureteral obstruction

Astragalus mongholicus (AM) derived from the dry root of Astragalus membranaceus Bge. var. mongolicus (Bge.) Hsiao is a widely used traditional Chinese medicine. The present study investigated the potential role of AM on renal fibrosis on a rat model of unilateral ureteral obstruction (UUO). We divided 48 Sprague-Dawley rats randomly into 4 groups: sham-operated group (Sham), untreated UUO group, AM-treated (10 g/(kg x d)) UUO group, and losartan-treated (20 mg/(kg x d)) UUO group as positive control. Haematoxylin & eosin (HE) and Masson staining were used to study the dynamic histological changes of the kidneys 7 and 14 d after operation. The expressions of fibronectin (FN), type I collagen (colI), hepatocyte growth factor (HGF), transforming growth factor-beta1 (TGF-beta1), and alpha-smooth muscle actin (alpha-SMA) were analyzed by real-time polymerase chain reaction (PCR), immunohistochemistry staining, and Western blot. Results show that, similar to losartan, AM alleviated the renal damage and decreased the deposition of FN and colI from UUO by reducing the expressions of TGF-beta1 and alpha-SMA (P<0.05), whereas HGF increased greatly with AM treatment (P<0.05). Our findings reveal that AM could retard the progression of renal fibrosis. The renoprotective effect of AM might be related to inhibition of myofibroblast activation, inducing of HGF and reducing of TGF-beta1 expression.

Long-term antiproteinuric effect of dual renin-angiotensin system blockade

We evaluated the long-term changes on overt proteinuria induced by dual blockade of the renin-angiotensin system (RAS). Dual blockade was produced by adding an angiotensin II receptor blocker (ARB) to treatment with maximal recommended doses of an angiotensin converting enzyme (ACE) inhibitor in proteinuric patients. A total of 28 patients (19 men and 9 women) with proteinuria higher than 1 g/24 h were enrolled in this trial of treatment with the ARB candesartan (from 4 up to 32 mg daily) added to existing treatment with an ACE inhibitor. At 6, 12, 24, and 36 months, we evaluated proteinuria in 24-h urinary collections, office blood pressure (BP), plasmatic creatinine (Cr), serum potassium (K), and 24 h urine collection creatinine clearance (CrC). During monoblockade of the RAS by ACE inhibitor treatment, albuminuria was 2.94 +/- 1.92 mg/24 h; BP was 137/76 mmHg; K+ was 4.8 +/- 0.5 mmol/l, Cr was 1.76 +/- 0.67 mg/dL, and CrC was 62 +/- 31.9 mL/min. After 6 months, dual blockade of the RAS albuminuria was 2.18 +/- 2.29 mg/24 h (P < 0.01 vs. baseline) and BP was 133/75 mmHg (not significant). At 36 months, albuminuria was 2.21 +/- 2.20 mg/24 h (P < 0.05 vs. baseline); BP was 133/73 mmHg (not significant). CrC was not changed along the follow up. A small increment of Cr was detected at 24 months (2.11 +/- 1.06 mg/mL, P < 0.05). The antiproteinuric effect of dual renin-angiotensin system blockade combining candesartan and ACE inhibitors remain after 36 months without losing its initial effect. Blood pressure changes seem not to explain this long-term antiproteinuric effect.

Low-dose angiotensin II receptor antagonists and angiotensin II-converting enzyme inhibitors alone or in combination for treatment of primary glomerulonephritis

OBJECTIVE

The renin-angiotensin system is thought to be involved in the progression of chronic renal diseases of both diabetic and non-diabetic origin. It has been confirmed that angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs) reduce urinary protein excretion and attenuate the development of renal injury. Clinical data comparing the renal effects of ACEIs and ARBs, either singly or in combination, are scarce and usually concern the use of standard or high doses.

MATERIAL AND METHODS

This was a prospective, randomized, 9-month study of the effects of low doses of losartan (25 mg; n = 18) versus enalapril (10 mg; n = 18) versus the combination of losartan (25 mg) and enalapril (10 mg) (n = 16) on proteinuria, kidney function and metabolic profile in 54 patients with biopsy-proven chronic glomerulonephritis, hypertension and normal or slightly impaired kidney function. The clinical evaluation and laboratory tests were performed before treatment (baseline) and after 3 and 9 months of therapy.

RESULTS

After 3 months, significant decreases in proteinuria were observed in all groups: losartan, 22.6% (p = 0.02); enalapril, 43% (p = 0.012); and combined therapy, 63% (p = 0.001). This anti-proteinuric effect was even greater after 9 months of therapy: losartan, 44.2% (p = 0.02); enalapril, 49.6% (p = 0.02); and combined therapy, 51% (p = 0.003). There was no significant difference between losartan and enalapril with respect to their impact on proteinuria level. Proteinuria reduction was significantly greater in patients receiving combined therapy in comparison with losartan treatment after 3 months of therapy (p = 0.02). Creatinine clearance and serum creatinine were stable during the entire study period in all patients. No significant changes in lipids, serum uric acid or protein levels were observed.

CONCLUSIONS

These results indicate that proteinuria is reduced by low doses of losartan or enalapril. The combination of these drugs seems to be beneficial and may offer an additional renoprotective effect. This needs to be confirmed in a study with a larger sample size.

Low-dose dual blockade of the renin–angiotensin system improves tubular status in non-diabetic proteinuric patients

OBJECTIVE

Treatment with agents that inhibit the renin-angiotensin system is commonly regarded as a gold standard renoprotective strategy in patients with chronic kidney diseases. For maximum antiproteinuric effect, the dose titration of these agents is recommended. This therapeutic strategy is not used for proteinuric patients who are not able to receive high doses of angiotensin-converting enzyme inhibitor or angiotensin II receptor antagonists.

MATERIAL AND METHODS

In patients with primary glomerulonephritis (n=24), a randomized, triple-treatment, triple-period, cross-over study was performed to compare the effects of combined therapy with benazepril 5 mg and losartan 25 mg and monotherapy with either agent alone at a two-fold higher dose on the extent of tubular injury as assessed by alpha1-microglobulin (alpha1-m) excretion and the plasma level of transforming growth factor-beta1 (TGF-beta1).

RESULTS

Combination therapy significantly reduced alpha1-m excretion compared to either agent used alone: 178.29+/-27.36 to 99.63+/-13.03 mg/g creatinine for losartan + benazepril vs 178.29+/-27.36 to 161.59+/-23.22 mg/g creatinine for benazepril alone (p<0.05; ANOVA) and 178.29+/-27.36 to 99.63+/-13.03 mg/g creatinine for losartan + benazepril vs 178.29+/-27.36 to 173.45+/-27.69 mg/g creatinine for losartan alone (p<0.05; ANOVA). There was a significant correlation between change in alpha1-m excretion and reduction in proteinuria (r=0.704; p=0.023). There were no differences in TGF-beta1 level between the studied treatments. Systemic blood pressure reduction did not differ among the therapies.

CONCLUSIONS

Combination therapy with angiotensin-converting enzyme inhibitor and angiotensin II subtype 1 receptor antagonists at very small doses may be superior to monotherapy with these agents at higher doses as far as tubular injury is concerned. We speculate that such a therapeutic strategy may be a useful approach for patients who are known not to be capable of receiving optimal renoprotective doses of these regimens.

Position of fixed‐dose combinations containing an AT1‐receptor blocker and a thiazide diuretic

Treatment of hypertension remains a difficult task despite the availability of different types of medications lowering blood pressure by different mechanisms. In order to reach the target blood pressures recommended today combination therapy is required in most patients. The co-administration of two drugs with different impacts on the cardiovascular system markedly increases the antihypertensive effectiveness without altering adversely tolerability. Fixed low-dose combinations are becoming a valuable option not only as second-line, but also as first-line therapy. In this respect the co-administration of thiazide diuretic with an AT(1)-receptor blocker is particularly appealing. The diuretic-induced decrease in total body sodium activates the renin-angiotensin system, thus rendering blood pressure maintenance angiotensin II-dependent. During blockade of the renin-angiotensin system low doses of thiazides generally suffice, allowing the prevention of undesirable metabolic effects. Also, blockade of the AT(1)-receptor, particularly when angiotensin II production is enhanced in response to diuretic therapy, is expected to be beneficial, since angiotensin II seems to contribute importantly to the pathogenesis of cardiovascular and renal complications of hypertension.

Beneficial effect of triple treatment plus immunoglobulin in experimental nephrotic syndrome

Combinations of antiproteinurics, including angiotensin I-converting enzyme inhibitors + angiotensin II receptor antagonist + statins, are promising choices in the treatment of steroid-resistant nephrotic syndrome. We aimed to investigate the effects of high doses of immunoglobulin in addition to these combinations in rats with adriamycin-induced nephrosis. The study included 40 rats allocated into five groups: control, nephrotic syndrome without treatment, dual therapy (DT) with enalapril + losartan, triple therapy (TT) with enalapril + losartan + simvastatin, and quadruple therapy (QT) with enalapril + losartan + simvastatin + a high dose of immunoglobulin. The proteinuria levels were not statistically different between DT, TT and QT groups at weeks 5, 8, 12 and 16. At week 16, serum creatinine levels in the QT group were significantly lower than those in the control, DT and TT groups. The glomerulosclerosis index in the DT group was significantly lower than in the TT and QT groups. The scores for interstitial fibrosis and TGF-beta staining were similar among treatment groups. In conclusion, we showed that quadruple therapy including immunoglobulin had a beneficial effect on renal function in the late phase, but it had no additional effects in reducing proteinuria or in glomerulosclerosis score in experimental nephrotic syndrome. Further studies with angiotensin I-converting enzyme inhibitors (ACEIs), angiotensin II receptor antagonists (AIIRAs) and immunoglobulin combinations would offer some benefits in the treatment of nephrotic syndrome.

Synergistic effect of mycophenolate mofetil and angiotensin-converting enzyme inhibitor in patients with chronic allograft nephropathy

Experimental data and few clinical non-randomized studies have shown that inhibition of the renin-angiotensin system by angiotensin-converting enzyme (ACE) associated or not with the use of mycophenolate mofetil (MMF) could delay or even halt the progression of chronic allograft nephropathy (CAN). In this retrospective historical study, we investigated whether ACE inhibition (ACEI) associated or not with the use of MMF has the same effect in humans as in experimental studies and what factors are associated with a clinical response. A total of 160 transplant patients with biopsy-proven CAN were enrolled. Eighty-one of them were on ACE therapy (G1) and 80 on ACEI_free therapy (G2). Patients were further stratified for the use of MMF. G1 patients showed a marked decrease in proteinuria and stabilized serum creatinine with time. Five-year graft survival after CAN diagnosis was more frequent in G1 (86.9 vs 67.7%; P < 0.05). In patients on ACEI-free therapy, the use of MMF was associated with better graft survival. The use of ACEI therapy protected 79% of the patients against graft loss (OR = 0.079, 95%CI = 0.015-0.426; P = 0.003). ACEI and MMF or the use of MMF alone after CAN diagnosis conferred protection against graft loss. This finding is well correlated with experimental studies in which ACEI and MMF interrupt the progression of chronic allograft dysfunction and injury. The use of ACEI alone or in combination with MMF significantly reduced proteinuria and stabilized serum creatinine, consequently improving renal allograft survival.

Genetic deletion of the angiotensin-(1-7) receptor Mas leads to glomerular hyperfiltration and microalbuminuria

Angiotensin-(1-7), an active fragment of both angiotensins I and II, generally opposes the vascular and proliferative actions of angiotensin II. Here we evaluated effects of the angiotensin-(1-7) receptor Mas on renal physiology and morphology using Mas-knockout mice. Compared to the wild-type animals, Mas knockout mice had significant reductions in urine volume and fractional sodium excretion without any significant change in free-water clearance. A significantly higher inulin clearance and microalbuminuria concomitant with a reduced renal blood flow suggest that glomerular hyperfiltration occurs in the knockout mice. Histological analysis found reduced glomerular tuft diameter and increased expression of collagen IV and fibronectin in the both the mesangium and interstitium, along with increased collagen III in the interstitium. These fibrogenic changes and the renal dysfunction of the knockout mice were associated with an upregulation of angiotensin II AT1 receptor and transforming growth factor-beta mRNA. Our study suggests that Mas acts as a critical regulator of renal fibrogenesis by controlling effects transduced through angiotensin II AT1 receptors in the kidney.

Deterioration of atherosclerosis in mice lacking angiotensin II type 1A receptor in bone marrow-derived cells

The renin-angiotensin system (RAS) modulates end-organ damages, resulting in cardiovascular and kidney diseases. Experiments both in vitro and in vivo demonstrate that the angiotensin II (Ang II) type 1 (AT1) receptor pathway also exerts pro-inflammatory and pro-atherogenic effects on bone marrow-derived cells (BMDCs). Here, we investigated how AT1 receptor expression by BMDCs contributes to atherosclerosis and kidney injury in vivo by transplanting BM into RAS-activated transgenic mice. There was no difference in the extent of kidney damage between mice receiving BM transplants from mutant mice lacking the angiotensin II type 1a receptor (AT1a) gene and mice receiving transplants from wild-type (WT) mice. However, mice receiving transplants from AT1a 'knockout' (KO) mice displayed accelerated lethality and atherosclerotic lesions. These results indicated that the effects of AT1a receptor on BMDCs are organ dependent. Microarray expression profiling of macrophages from AT1a-KO mice revealed significant changes in the mRNA levels for a number of genes implicated in atherosclerosis. In accordance with the in vivo atherosclerosis results, AT1a-KO macrophages exhibited greater uptake of modified lipoproteins relative to macrophages from WT mice. We propose that the expression of AT1a receptor by BMDCs limits atherosclerosis in vivo.

The effects of candesartan on diabetes glomerulopathy: a double-blind, placebo-controlled trial

Our objective was to study the effects of candesartan on diabetic glomerulopathy in young normoalbuminuric and normotensive patients with type 1 diabetes in a double-blind, placebo-controlled trial. In 13 patients aged 24 years at baseline, we evaluated blood pressure, kidney biopsies and kidney function tests at baseline and after 5 years of treatment. Kidney biopsies were examined with light and electron microscopy, glomerular filtration rate and effective renal plasma flow determined with inulin and para-aminohippuric acid clearances. Two patients in the placebo group needed antihypertensive treatment because they developed microalbuminuria and/or hypertension, but no patient in the candesartan group did. A significant reduction in mesangial matrix volume and mesangial volume occurred in the candesartan group, although changes in morphological parameters were similar between groups. Office blood pressure was significantly lower in the candesartan group at follow-up than in the placebo group. Deterioration in morphological parameters observed in earlier studies of our patients did not become worse during treatment with candesartan or placebo. The effects of candesartan, with reduction in morphological parameters and lowering of blood pressure, might influence future treatment of glomerulopathy in type 1 diabetes patients.

Renal and metabolic disorders depend on the renin-angiotensin system in Lyon hypertensive rats associated with diabetes

BACKGROUND

In Lyon genetically hypertensive (LH) rats with diabetes, the effects of angiotensin converting enzyme (ACE) inhibition with perindopril on the prevention of dyslipidemia and proteinuria were evaluated by comparison with a nonspecific antihypertensive treatment.

METHODS

Diabetes was induced in 2-day-old male LH rats by intraperitoneal injection of streptozotocin (75 mg/kg). Glucose tolerance (glucose 2 g/kg by gavage), blood pressure (BP), plasma lipids, and urinary protein excretion were studied in: (i) untreated diabetic LH rats, (ii) diabetic LH rats treated from 8 to 16 weeks of age with oral perindopril at a low dose (0.01 mg/kg/day), (iii) similar rats treated with oral perindopril for the same duration at a high dose (1 mg/kg/day), and (iv) similar rats treated for the same duration with a triple therapy regimen consisting of hydralazine, hydrochlorothiazide, and reserpine (75, 15, and 0.75 mg/kg/day, respectively).

RESULTS

The neonatal administration of streptozotocin in LH rats increased nonfasting glycemia and induced a marked glucose intolerance which was accompanied by further increases in BP, plasma cholesterol, and urinary protein excretion. None of the treatments was able to modify glucose tolerance in diabetic LH rats. The low dose of perindopril was ineffective in the prevention of hypertension, dyslipidemia, and proteinuria in diabetic LH rats, while the high dose of perindopril normalized the BP, reduced the plasma lipids, and lowered the proteinuria. However, in spite of significant reduction in BP, the triple therapy failed to improve dyslipidemia and proteinuria; on the contrary, the therapy worsened these two conditions.

CONCLUSIONS

In diabetic LH rats, only ACE inhibition is of benefit to the kidney and lipidemia, thereby demonstrating that antihypertensive regimens may differ in their capacity to protect the target organs and lipid metabolism in a diabetic setting.