Short and long term effects of antihypertensive therapy in the diabetic rat

Blocking angiotensin 2 receptor attenuates diabetic nephropathy via mitigating ANGPTL2/TL4/NF-κB expression

BACKGROUND

Diabetic nephropathy (DN) is a consequence of diabetes mellitus (DM) and is associated with early changes in renal angiotensin II (ANG II). These changes were evaluated using ANG II blocker valsartan early from week two of diabetes (experiment I, renoprotective) and late from week nine of diabetes (experiment II, renotherapeutic) to the end of both experiments at week twelve.

METHODS AND RESULTS

In both experiments, adult male Wister rats were divided into (i) vehicle group; (ii) valsartan received oral 30 mg/Kg/day; (iii) diabetic received single 50 mg/Kg intraperitoneal streptozotocin injection; (iv) renoprotection, diabetic rats received valsartan treated in experiments I and II. DM effects on urine albumin excretion, blood pressure, and renal ANG II were measured. Urinary nephrin, kidney injury molecule-1 (KIM-1), renal angiopoietin-like protein 2 (ANGPTL2), and toll-like receptor 4 (TLR 4) mRNA expression were tested. DM-initiated fibrotic markers integrin, α-smooth muscle actin expression, and collagen IV and apoptotic protein caspase 3 were tested. DM induced early changes starting from week four in the tested variables. At week twelve, in both experiments, valsartan intervention showed a significant reduction in ANG II, ANGPTL2, TLR 4 and integrin expression and improvement in albuminuria, blood pressure, urinary biomarkers, fibrotic and apoptotic markers.

CONCLUSIONS

Changes leading to DN starts early in the disease course and ANG II reduction decreased the expression of ANGPTL2 and integrin which preserve the glomerular barrier. Blocking ANG II was able to decrease TLR 4 and inflammatory cytokines leading to decreasing DN.

Efficacy of low-dose spironolactone on top of angiotensin receptor blockade in patients with glomerulonephritis

Background

Previous studies have shown that aldosterone antagonists have a proteinuria-lowering effect in patients with proteinuria and progressive proteinuric disease not adequately controlled by the use of angiotensin receptor blockers (ARBs). Aldosterone antagonists, in combination with ARBs, might improve proteinuria in patients with glomerulonephritis (GN).

Methods

In the present retrospective study, we evaluated the proteinuria-lowering effect and drug safety of low-dose spironolactone (12.5 mg/day) in 42 patients with GN being treated with an ARB.

Results

Proteinuria decreased from a mean total-protein-to-creatinine (TP/Cr) ratio of 592.3 ± 42.0 mg/g at baseline to 335.6 ± 43.3 mg/g after three months of treatment with spironolactone (P < 0.001). After the initial three months, the mean TP/Cr ratio increased progressively at six, nine, and 12 months; however, it was still less than the baseline value (P = 0.001, < 0.001, and < 0.001, respectively). Although serum Cr levels increased significantly at three and nine months compared with baseline (P = 0.036 and 0.026, respectively), there was no time effect of treatment (P = 0.071). Serum potassium levels tended to increase with time (P = 0.118), whereas systolic and diastolic blood pressures decreased with time (P = 0.122 and 0.044, respectively).

Conclusion

Low-dose spironolactone in combination with an ARB reduced proteinuria in patients with GN, which could represent a novel treatment option in individuals whose proteinuria is not optimally controlled by the use of ARBs alone.

Capillary Rarefaction Associates with Albuminuria: The Maastricht Study

Albuminuria may be a biomarker of generalized (i.e., microvascular and macrovascular) endothelial dysfunction. According to this concept, endothelial dysfunction of the renal microcirculation causes albuminuria by increasing glomerular capillary wall permeability and intraglomerular pressure, the latter eventually leading to glomerular capillary dropout (rarefaction) and further increases in intraglomerular pressure. However, direct evidence for an association between capillary rarefaction and albuminuria is lacking. Therefore, we examined the cross-sectional association between the recruitment of capillaries after arterial occlusion (capillary density during postocclusive peak reactive hyperemia) and during venous occlusion (venous congestion), as assessed with skin capillaroscopy, and albuminuria in 741 participants of the Maastricht Study, including 211 participants with type 2 diabetes. Overall, 57 participants had albuminuria, which was defined as a urinary albumin excretion ≥30 mg/24 h. After adjustment for potential confounders, participants in the lowest tertile of skin capillary recruitment during postocclusive peak reactive hyperemia had an odds ratio for albuminuria of 2.27 (95% confidence interval, 1.07 to 4.80) compared with those in the highest tertile. Similarly, a comparison between the lowest and the highest tertiles of capillary recruitment during venous congestion yielded an odds ratio of 2.89 (95% confidence interval, 1.27 to 6.61) for participants in the lowest tertile. In conclusion, lower capillary density of the skin microcirculation independently associated with albuminuria, providing direct support for a role of capillary rarefaction in the pathogenesis of albuminuria.

Renin-Angiotensin-Aldosterone System Blockade in Diabetic Nephropathy. Present Evidences

Diabetic Kidney Disease (DKD) is the leading cause of chronic kidney disease in developed countries and its prevalence has increased dramatically in the past few decades. These patients are at an increased risk for premature death, cardiovascular disease, and other severe illnesses that result in frequent hospitalizations and increased health-care utilization. Although much progress has been made in slowing the progression of diabetic nephropathy, renal dysfunction and the development of end-stage renal disease remain major concerns in diabetes. Dysregulation of the renin-angiotensin-aldosterone system (RAAS) results in progressive renal damage. RAAS blockade is the cornerstone of treatment of DKD, with proven efficacy in many arenas. The theoretically-attractive option of combining these medications that target different points in the pathway, potentially offering a more complete RAAS blockade, has also been tested in clinical trials, but long-term outcomes were disappointing. This review examines the “state of play” for RAAS blockade in DKD, dual blockade of various combinations, and a perspective on its benefits and potential risks.

A nonpeptide angiotensin II type 2 receptor agonist prevents renal inflammation in early diabetes

We hypothesized that direct AT2R stimulation improves albuminuria in diabetes by preventing renal inflammation and improving oxidative stress. Normoglycemic controls (NCs) and streptozotocin-induced diabetes Sprague-Dawley rats (DM) were treated for 4 weeks with vehicle (V) or the AT2R agonist Compound 21 (C21). At the end of study, we evaluated blood pressure, urinary albumin to creatinine ratio (UACR), renal interstitial fluid (RIF) levels of tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), nitric oxide (NO), cGMP, and 8-isoprostane, and renal expression of TNF-α, IL-6, and AT2R. There were no significant differences in blood pressure between different treatments. DM rats demonstrated increased UACR, RIF TNF-α, IL-6 and 8-isoprostane, and messenger RNA (mRNA) for TNF-α and IL-6. DM rats also had reduced RIF NO and cGMP. C21 treatment of DM rats limited the increase in UACR, normalized RIF TNF-α, IL-6 and 8-isoprostane, and in mRNA for TNF-α and IL-6, and increased RIF NO and cGMP. In NC rats, C21 treatment did not change these parameters. AT2R mRNA and protein expressions increased in DM rats compared with NC but were not influenced by C21 treatment. We conclude that direct AT2R stimulation in diabetic rats improves diabetic albuminuria through the prevention of renal inflammation and improved production of NO and cGMP.

Treatment of FSGS in Children

Focal segmental glomerulosclerosis (FSGS) is a pathologic condition that represents many disease entities. The goals of therapy are to cure the disease. When this is not possible, the secondary goals are to reduce proteinuria to avoid the complications of nephrotic syndrome and to delay progression of kidney disease. Proteinuria remission is one of the most important independent predictors of kidney survival. Children with FSGS who do not achieve partial or complete remission have a 50% risk of progression to ESRD within 5 years whereas those who enter complete remission have a 5-year kidney survival rate of 90%. Treatment of idiopathic FSGS commonly involves immune-based and nonimmunologic therapy options. This manuscript will review the current state of FSGS therapy for children.

Involvement of heparan sulfate in the renoprotective effects of imidapril, an angiotensin-converting enzyme inhibitor, in diabetic db/db mice

We investigated the renoprotective effects of imidapril hydrochloride ((-)-(4 S)-3-[(2 S)-2-[[(1 S)-1-ethoxycarbonyl-3-phenylpropyl] amino] propionyl]-1-methyl-2-oxoimidazolidine-4-carboxylic acid hydrochloride, imidapril), an angiotensin-converting enzyme inhibitor, in a diabetic animal model. We used BKS.Cg-+Lepr(db)/+Lepr(db) (db/db) mice, a genetic animal model of obese type 2 diabetes. Diabetic db/db mice suffered from glomerular hyperfiltration, albuminuria and hypoalbuminemia. Oral administration of 5 mg/kg/day of imidapril for 3 weeks suppressed renal hyperfiltration, reduced albuminuria and normalized hypoalbuminemia. Imidapril did not influence body weights, blood pressure or blood glucose concentrations in db/db mice. Urinary excretion of heparan sulfate (HS) in non-treated 11-week-old db/db mice was significantly lower than that in age-matched non-diabetic db/+m mice. HS is a component of HS proteoglycans, which are present in glomerular basement membranes and glycocalyx of cell surfaces. Reduced urinary HS excretion indicated glomerular HS loss in db/db mice. Imidapril increased urinary excretion of HS to concentrations observed in db/+m mice, indicating that imidapril prevented the loss of renal HS. These results suggest that imidapril ameliorates renal hyperfiltration and loss of renal contents of HS. Improvement of filtration function and maintenance of HS, which is an important structural component of glomeruli, may contribute to renoprotective effects of imidapril.

Angiotensin receptor blockers shift the circadian rhythm of blood pressure by suppressing tubular sodium reabsorption

Recently, we found that an angiotensin II receptor blocker (ARB) restored the circadian rhythm of the blood pressure (BP) from a nondipper to a dipper pattern, similar to that achieved with sodium intake restriction and diuretics (Fukuda M, Yamanaka T, Mizuno M, Motokawa M, Shirasawa Y, Miyagi S, Nishio T, Yoshida A, Kimura G. J Hypertens 26: 583-588, 2008). ARB enhanced natriuresis during the day, while BP was markedly lower during the night, resulting in the dipper pattern. In the present study, we examined whether the suppression of tubular sodium reabsorption, similar to the action of diuretics, was the mechanism by which ARB normalized the circadian BP rhythm. BP and glomerulotubular balance were compared in 41 patients with chronic kidney disease before and during ARB treatment with olmesartan once a day in the morning for 8 wk. ARB increased natriuresis (sodium excretion rate; U(Na)V) during the day (4.5 ± 2.2 to 5.5 ± 2.1 mmol/h, P = 0.002), while it had no effect during the night (4.3 ± 2.0 to 3.8 ± 1.6 mmol/h, P = 0.1). The night/day ratios of both BP and U(Na)V were decreased. The decrease in the night/day ratio of BP correlated with the increase in the daytime U(Na)V (r = 0.42, P = 0.006). Throughout the whole day, the glomerular filtration rate (P = 0.0006) and tubular sodium reabsorption (P = 0.0005) were both reduced significantly by ARB, although U(Na)V remained constant (107 ± 45 vs. 118 ± 36 mmol/day, P = 0.07). These findings indicate that the suppression of tubular sodium reabsorption, showing a resemblance to the action of diuretics, is the primary mechanism by which ARB can shift the circadian BP rhythm into a dipper pattern.

Role of the renin angiotensin system in diabetic nephropathy

Diabetic nephropathy has been the cause of lot of morbidity and mortality in the diabetic population. The renin angiotensin system (RAS) is considered to be involved in most of the pathological processes that result in diabetic nephropathy. This system has various subsystems which contribute to the disease pathology. One of these involves angiotensin II (Ang II) which shows increased activity during diabetic nephropathy. This causes hypertrophy of various renal cells and has a pressor effect on arteriolar smooth muscle resulting in increased vascular pressure. Ang II also induces inflammation, apoptosis, cell growth, migration and differentiation. Monocyte chemoattractant protein-1 production responsible for renal fibrosis is also regulated by RAS. Polymorphism of angiotensin converting enzyme (ACE) and Angiotensinogen has been shown to have effects on RAS. Available treatment modalities have proven effective in controlling the progression of nephropathy. Various drugs (based on antagonism of RAS) are currently in the market and others are still under trial. Amongst the approved drugs, ACE inhibitors and angiotensin receptor blockers (ARBs) are widely used in clinical practice. ARBs are shown to be superior to ACE inhibitors in terms of reducing proteinuria but the combined role of ARBs with ACE inhibitors in diabetic nephropathy is under debate.

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.

Telmisartan lowers albuminuria in type 2 diabetic patients treated with angiotensin enzyme inhibitors

PURPOSE

Angiotensin-converting-enzyme inhibitors (ACEIs) provide renal protection in patients with type 2 diabetes and microalbuminuria.

MATERIAL AND METHODS

In the presented study we followed 34 stable, type 2 diabetic patients with persistent albuminuria treated with maximal doses of ACEIs as a part of their anti-hypertensive treatment. Telmisartan--an angiotensin receptor blocker (ARB)--in a dose of 40 mg was added to the treatment and the patients were observed for 12 weeks. We measured creatinine clearance, 24-hour urinary albumin excretion, before and after 12 weeks of combined therapy.

RESULTS

The addition of telmisartan resulted in a significant reduction of albuminuria from median 157 to 67 mg/24h. No change in creatinine clearance was observed (93 vs 97 ml/min).

CONCLUSION

The addition of telmisartan to a maximum dose of ACEI is safe and results in further albuminuria decrease in patients with type 2 diabetes and incipient nephropathy.

Changes seen in the aging kidney and the effect of blocking the renin—angiotensin system

Background: The objective was to evaluate structural changes of glomeruli during aging and the role of chronic renin—angiotensin system inhibition (RASi) on these changes; starting RASi on Wistar rats at two different moments: the first group after weaning and the second at the midpoint of their lifespan (12 months).

Methods: Thirty rats were divided, after weaning, into three groups of 10: group 1: control (C); group 2 : 30 mg/kg/day losartan (L); group 3 : 10 mg/kg/day enalapril (E). At 18 months, rats were placed in metabolic cages to evaluate proteinuria, then killed. Another group of 24 rats, 12 months old, were divided into three groups of eight: group 1: C; group 2: L; group 3: E. At 18 months the same procedure described above was carried out. Finally, a third group of 20 rats was studied as healthy controls and killed: 10 rats at 7 months and ten at 12 months of age. Tissue samples were collected after sacrifice. To evaluate glomerular fibrotic changes, both focal and periglomerular sclerosis, and mesangial matrix expansion, a scoring scale was established. We also evaluated anti-α-SM-actin and anti-collagen-III immunolabeling. Glomerular area was measured using an image analyzer.

Results: Proteinuria and serum creatinine increased with age but were reduced in treated animals. Main glomerular changes present in 18-month-old rats were reduced by half in treated animals. Glomerular area showed significant increase with normal aging and all treatment strategies protected against it.

Conclusion: RAS plays a central role in natural process of renal aging, probably by producing effects influencing the biology of aging, the effects of which can be attenuated by RASi.

[Molecular bases of diabetic nephropathy]

The determinant of the diabetic nephropathy is hyperglycemia, but hypertension and other genetic factors are also involved. Glomerulus is the focus of the injury, where mesangial cell proliferation and extracellular matrix occur because of the increase of the intra- and extracellular glucose concentration and overexpression of GLUT1. Sequentially, there are increases in the flow by the poliol pathway, oxidative stress, increased intracellular production of advanced glycation end products (AGEs), activation of the PKC pathway, increase of the activity of the hexosamine pathway, and activation of TGF-beta1. High glucose concentrations also increase angiotensin II (AII) levels. Therefore, glucose and AII exert similar effects in inducing extracellular matrix formation in the mesangial cells, using similar transductional signal, which increases TGF-beta1 levels. In this review we focus in the effect of glucose and AII in the mesangial cells in causing the events related to the genesis of diabetic nephropathy. The alterations in the signal pathways discussed in this review give support to the observational studies and clinical assays, where metabolic and antihypertensive controls obtained with angiotensin-converting inhibitors have shown important and additive effect in the prevention of the beginning and progression of diabetic nephropathy. New therapeutic strategies directed to the described intracellular events may give future additional benefits.

Regression of glomerular injury by losartan in experimental diabetic nephropathy

Many features of chronic kidney disease may be reversed, but it is unclear whether advanced lesions, such as adhesions of sclerotic glomerular tufts to Bowman's capsule (synechiae), can resolve during treatment. We previously showed, using a renal ablation model, that the renoprotective effect of the AT-1 receptor blocker, losartan, is dose-dependent. Here we determined if moderate and advanced glomerular lesions, associated with streptozotocin-induced diabetes, regress with conventional or high-dose losartan treatment. Using daily insulin injection for 10 months, we maintained diabetic adult male Munich-Wistar rats in a state of moderate hyperglycemia. Following this period, some rats continued to receive insulin with or without conventional or high-dose losartan for an additional 2 months. Diabetic rats pretreated with insulin for 10 months and age-matched non-diabetic rats served as controls. Mesangial expansion was found in the control diabetic rats and was exacerbated in those rats maintained on only insulin for an additional 2 months. Conventional and high-dose losartan treatments reduced this mesangial expansion and the severity of synechiae lesions below that found prior to treatment; however, the frequency of the latter was unchanged. There was no dose-response effect of losartan. Our results show that regression of mesangial expansion and contraction of sclerotic lesions is feasible in the treatment of diabetes, but complete resolution of advanced glomerulosclerosis may be hard to achieve.

Angiotensin converting enzyme 2 in the kidney

1

Angiotensin converting enzyme 2 (ACE2) is an important homeostatic component of the renin angiotensin system (RAS). ACE2 both degrades the vasoconstrictor, angiotensin II and generates the potent vasodilator peptide, angiotensin 1–7. These actions counterbalance those of ACE.

2

ACE2 is highly expressed in the healthy kidney, particularly in the proximal tubules, where it colocalizes with ACE and angiotensin receptors.

3

Kidney disease and subtotal nephrectomy is associated with a reduction in renal ACE2 expression, possibly facilitating the damaging effects of angiotensin II in the failing kidney. Acquired or genetic ACE2 deficiency also appears to exacerbate renal damage and albuminuria in experimental models, supporting this hypothesis.

4

ACE2 also has an important role in blood pressure control. Many models of hypertension are associated with reduced ACE2 expression. Although ACE2 KO animals are normotensive, in states associated with activation of the RAS, ACE2 overexpression improves blood pressure control and reduces angiotensin responsiveness.

Products of 12/15-lipoxygenase upregulate the angiotensin II receptor

Angiotensin II and its type 1 receptor (AT1R) play important roles in the pathogenesis of renal disease and diabetic nephropathy. The 12/15-lipoxygenase pathway of arachidonate metabolism and its lipid products have also been implicated in diabetic nephropathy. However, it is unclear whether 12/15-lipoxygenase regulates expression of AT1R. In cultured rat mesangial cells, we found that the 12/15-lipoxygenase product 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE) increased AT1R mRNA and protein expression, primarily by stabilizing AT1R mRNA. Pretreatment with 12(S)-HETE also amplified the signaling effects of angiotensin II, likely due to the increased AT1R expression. Levels of AT1R protein expression decreased when 12/15-lipoxygenase was knocked down with specific short hairpin RNA (shRNA) compared with control cells. Similarly, levels of the AT1 receptor, but not the AT2 receptor, were significantly lower in mesangial cells and glomeruli derived from 12/15-lipoxygenase knockout mice compared with control mice. Reciprocally, stable overexpression of 12/15-lipoxygenase increased AT1R expression in cultured mesangial cells. In vivo, modified siRNA targeting 12/15-lipoxygenase reduced glomerular AT1R expression in a diabetic mouse model. Interestingly, angiotensin II induced greater levels of 12/15-lipoxygenase, TGF-beta1, and fibronectin (FN) in AT1R-overexpressing mesangial cells compared with control cells. Therefore, oxidized lipids generated by the 12/15-lipoxygenase-mediated metabolism of arachidonic acid can enhance AT1R expression in mesangial cells and augment the profibrotic effects of angiotensin II.

Dynamic blood pressure load and nephropathy in the ZSF1 (fa/facp) model of type 2 diabetes

Diabetes and increased blood pressure (BP) are believed to interact synergistically in the pathogenesis and progression of diabetic nephropathy. The present studies were performed to examine if there were differences in BP load and/or protective renal autoregulatory capacity between the obese diabetic Zucker fatty /spontaneously hypertensive heart failure F1 hybrid (ZSF1) ( fa/ facp) rats and their lean controls. By ∼26 wk of age, ZSF1 ( n = 13) but not their lean controls ( n = 16) had developed substantial proteinuria (180 ± 19 vs. 16 ± 1.4 mg/24 h) and glomerulosclerosis (19 ± 2.4 vs. 0.6 ± 0.2%; P < 0.001). However, average ambient systolic BP by radiotelemetry (12–26 wk of age) was modestly lower in ZSF1 than in lean controls (130 ± 1.4 vs. 137 ± 1.7 mmHg, P < 0.002), although the 24-h BP power spectra showed a mild increase at frequencies <0.1 Hz in the ZSF1. Autoregulatory capacity under anesthesia in response to step changes in perfusion pressure between 100 and 140 mmHg was similarly well preserved in both ZSF1 and lean controls at 16–18 wk of age [autoregulatory indexes (AI) <0.1]. Similarly, differences were not observed for dynamic autoregulation in conscious rats [transfer functions between BP (input) and renal blood flow (output) using chronic Transonic flow probes]. Collectively, these data indicate that the pathogenesis of nephropathy in the ZSF1 model of type 2 diabetic nephropathy is largely independent of differences in systemic BP and/or its potential renal transmission. However, these data do not exclude the possibility that the diabetic milieu may alter the glomerular capillaries in the ZSF1, such that there is an enhanced local susceptibility to injury with even normal glomerular pressures.

Treatment of hypertension in patients with diabetes mellitus

Antihypertensive treatment in diabetes mellitus, especially in diabetics known to have cardiac autonomic neuropathy, may have to consider the status of the autonomic nervous system. In diabetic subjects with cardiac autonomic neuropathy, vagal activity during the night is often reduced. The reduction results in relative or absolute sympathetic activation, which could increase cardiovascular risk. Pathophysiological and clinical data suggests that antihypertensive treatment should reduce rather than induce sympathetic activity in this setting. Beta blocking agents, ACE inhibitors, calcium antagonists of verapamil or diltiazem type and selective imidazoline receptor agonists reduce sympathetic activity and, therefore, may have a beneficial effect in diabetic patients with disturbed sympathovagal balance.

Mineralocorticoid receptor antagonist reduces renal injury in rodent models of types 1 and 2 diabetes mellitus

To determine whether mineralocorticoid receptor (MR) activation plays a role in diabetic renal injury and whether this role differs in types 1 and 2 diabetes mellitus, we examined the effect of a MR antagonist on renal injury in rodent models of type 1 (streptozotocin-treated rat) and type 2 (db/db mouse) diabetes. We studied three groups of 8-wk-old, uninephrectomized Wistar rats for 4 wk: diabetic streptozotocin- (55 mg/kg) treated rats (n = 11), diabetic streptozotocin-treated rats receiving the MR antagonist eplerenone (n = 15), and nondiabetic rats (n = 9). In addition, we studied three groups of 8-wk-old mice for 16 wk: diabetic db/db mice (n = 10), diabetic db/db mice treated with eplerenone (n = 8), and nondiabetic, db/+ littermates (n = 11). Diabetic rats and mice developed albuminuria and histopathological evidence of renal injury, including glomerular hypertrophy, mesangial expansion, and tubulointerstitial injury as well as increased renal cortical levels of MR protein, MR mRNA, TGFbeta mRNA, and osteopontin mRNA. All of these changes were significantly reduced by treatment with eplerenone except for the elevated MR levels. The beneficial effects of eplerenone were not attributable to changes in blood pressure or glycemia. In summary, MR expression was increased in kidneys of diabetic rodents, and MR antagonists effectively reduced diabetic renal injury irrespective of the species or specific cause of the diabetes. Thus, these data suggest that MR activation is a critical factor in the early pathogenesis of renal disease in both type 1 and type 2 diabetes mellitus.

Spontaneously reduced blood pressure load in the rat streptozotocin-induced diabetes model: potential pathogenetic relevance

The rat streptozotocin (STZ)-induced diabetes model is widely used to investigate the pathogenesis of diabetic nephropathy. However, overt nephropathy is inexplicably slow to develop in this model compared with renal mass reduction (RMR) models. To examine whether blood pressure (BP) differences correlated with the time course of glomerulosclerosis (GS), BP was measured continuously throughout the course by radiotelemetry in control (n = 17), partially insulin-treated STZ-diabetes (average blood glucose 364 +/- 15 mg/dl; n = 15), and two normotensive RMR models (systolic BP <140 mmHg)--uninephrectomy (UNX; n = 16) and 3/4 RMR by surgical excision [right nephrectomy + excision of both poles of left kidney (RK-NX); n = 12] in Sprague-Dawley rats. Proteinuria and GS were assessed at approximately 16-20 wk (all groups) and at 36-40 wk (all groups except RK-NX). At 16 wk, significantly greater proteinuria and GS had developed in the RK-NX group compared with the other three groups (not different from each other). By 36-40 wk, substantial proteinuria and GS had also developed in the UNX group, but both the control and the STZ-diabetic rats exhibited comparable modest proteinuria and minimal GS. Systolic BP (mmHg) was significantly reduced in the STZ-diabetic rats (116 +/- 1.1) compared with both control (124 +/- 1.0) and RMR (128 +/- 1.2 and 130 +/- 3.0) groups (P < 0.01). Similarly, "BP load" as estimated by BP power spectral analysis was also lower in the STZ-diabetic rats. Given the known protective effects of BP reductions on the progression of diabetic nephropathy, it is likely that this spontaneous reduction in ambient BP contributes to the slow development of GS in the STZ-diabetes model compared with the normotensive RMR models.

Mechanisms for Renal Blood Flow Control Early in Diabetes as Revealed by Chronic Flow Measurement and Transfer Function Analysis

The purpose of this study was to establish the roles of the myogenic response and the TGF mechanism in renal blood flow (RBF) control at the very earliest stages of diabetes. Mean arterial pressure (MAP) and RBF were measured continuously, 18 h/d, in uninephrectomized control and diabetic rats, and transfer function analysis was used to determine the dynamic autoregulatory efficiency of the renal vasculature. During the control period, MAP averaged 91 +/- 0.5 and 89 +/- 0.4 mmHg, and RBF averaged 8.0 +/- 0.1 and 7.8 +/- 0.1 ml/min in the control and diabetic groups, respectively. Induction of diabetes with streptozotocin caused a marked and progressive increase in RBF in the diabetic rats, averaging 10 +/- 6% above control on day 1 of diabetes and 22 +/- 3 and 34 +/- 1% above control by the end of diabetes weeks 1 and 2. MAP increased approximately 9 mmHg during the 2 wk in the diabetic rats, and renal vascular resistance decreased. Transfer function analysis revealed significant increases in gain to positive values over the frequency ranges of both the TGF and myogenic mechanisms, beginning on day 1 of diabetes and continuing through day 14. These very rapid increases in RBF and transfer function gain suggest that autoregulation is impaired at the very onset of hyperglycemia in streptozotocin-induced type 1 diabetes and may play an important role in the increase in RBF and GFR in diabetes. Together with previous reports of decreases in chronically measured cardiac output and hindquarter blood flow, this suggests that there may be differential effects of diabetes on RBF versus nonrenal BF control.

Preventing end stage renal disease in diabetic patients--genetic aspect (part I)

Diabetic nephropathy is a major cause of diabetes- related morbidity and mortality; however the clinical course of the disease and the renal prognosis is highly variable among individuals. The current review will discuss the genetic influence on the development of end stage renal disease (ESRD) in diabetic patients and potential improvements to the current treatment strategy to slow the loss of kidney function in these patients. In this first part, the growing evidence that glucose-induced activation of the intra-renal and systemic renin-angiotensin systems plays an essential role in processes leading to destruction of renal function is summarised. Genetic variations, especially the angiotensin-converting enzyme (ACE)/ID polymorphisms in the gene coding for ACE, are involved in activation of the renin-angiotensin system and seem to influence the clinical course of diabetic nephropathy during treatment with ACE inhibitors. In addition, this polymorphism may interact with other polymorphisms within the renin-angiotensin system, leading to high risk of ESRD. As new genetic approaches and methods develop, further understanding of diabetic nephropathy will evolve and genotyping will help prevent ESRD in diabetic patients.

Impact of genetic background on nephropathy in diabetic mice

With the goal of identifying optimal platforms for developing better models of diabetic nephropathy in mice, we compared renal effects of streptozotocin (STZ)-induced diabetes among five common inbred mouse strains (C57BL/6, MRL/Mp, BALB/c, DBA/2, and 129/SvEv). We also evaluated the renal consequences of chemical and genetic diabetes on the same genetic background (C57BL/6). There was a hierarchical response of blood glucose level to the STZ regimen among the strains (DBA/2 > C57BL/6 > MRL/MP > 129/SvEv > BALB/c). In all five strains, males demonstrated much more robust hyperglycemia with STZ than females. STZ-induced diabetes was associated with modest levels of albuminuria in all of the strains but was greatest in the DBA/2 strain, which also had the most marked hyperglycemia. Renal structural changes on light microscopy were limited to the development of mesangial expansion, and, while there were some apparent differences among strains in susceptibility to renal pathological changes, there was a significant positive correlation between blood glucose and the degree of mesangial expansion, suggesting that most of the variability in renal pathological abnormalities was because of differences in hyperglycemia. Although the general character of renal involvement was similar between chemical and genetic diabetes, Akita mice developed more marked hyperglycemia, elevated blood pressures, and less variability in renal structural responses. Thus, among the strains and models tested, the DBA/2 genetic background and the Akita (Ins2(+/C96Y)) model may be the most useful platforms for model development.

Glomerular function reserve and sodium sensitivity

In clinical nephrology, the glomerular filtration rate (GFR) has been recognized as the golden standard to assess renal function. However, a normal GFR does not necessarily mean normal filtration capability of the kidneys, because impaired filtration capability can be compensated for by elevating glomerular hydraulic pressure. Therefore, an early phase of glomerular dysfunction cannot be detected by the baseline GFR alone. On the other hand, glomerular capillary hypertension is widely recognized as one of the strong risk factors for the progression of nephropathies. Now, it is very important to imagine glomerular hemodynamics in each patient with nephropathy for detecting early dysfunction, as well as for evaluating risk factors. Here, I would like to summarize the current status of how an early phase of renal dysfunction can be detected in clinical practice. I truly anticipate that new methods to assess glomerular hemodynamics in humans will be developed in the near future.

Renal synthesis of urokinase type-plasminogen activator, its receptor, and plasminogen activator inhibitor-1 in diabetic nephropathy in rats: modulation by angiotensin-converting-enzyme inhibitor

Plasmin is an important factor in the degradation of extracellular matrix. In the study reported here we examined the expression of plasminogen-activator inhibitor-1 (PAI-1), urokinase-type plasminogen activator (uPA), and uPA receptor (uPAR), as well as the relevance of such expression to the production of type IV collagen, a major component of extracellular matrix, in the renal tissue of rats with streptozotocin-induced diabetes. Because angiotensin II is involved in the synthesis of PAI-1 and uPA, we also examined the effect of benazepril, an angiotensin-converting-enzyme inhibitor, on the expression of PAI-1, uPA, and uPAR messenger RNAs (mRNAs) and type IV collagen protein. Rats with streptozocin-induced diabetes-some untreated and some treated with 30 mg/L benazepril-and nondiabetic control rats were sacrificed at 4, 12, or 24 weeks after induction of diabetes. We examined the expression of PAI-1, uPA, and uPAR mRNAs through the use of in situ hybridization and that of type IV collagen by means of immunohistochemical methods. In control rats, we detected weak signals for PAI-1, uPA, and uPAR mRNAs in glomeruli. Diabetic rats exhibited high levels of expression of PAI-1, uPA, and uPAR mRNAs and type IV collagen protein, mainly in mesangial cells. These mRNAs were synthesized in various renal cells (epithelial, mesangial, and endothelial cells and Bowman's capsule). Benazepril inhibited increases in all 3 mRNAs, especially in the mesangium; reduced type IV collagen expression; and attenuated mesangial expansion. Our results indicated that altered expression of PAI-1, uPA, and uPAR in diabetic nephropathy was associated with mesangial expansion and that the beneficial effects of ACE-I may be at least associated with such expression.

Calcium channel blockers and the kidney

Although end-stage renal disease (ESRD) currently affects only a small percentage (<0.2%) of the US population, its precursor, the mild and moderate forms of chronic kidney disease (CKD), affects 11% of the population, with significant growth in both ESRD and CKD anticipated in the rapidly aging US population. The primary diagnoses in the majority of ESRD patients are diabetes and hypertension. Results of clinical studies demonstrate that the level of proteinuria and sympathetic activation contribute to the progression of CKD to ESRD. There are sufficient clinical data to demonstrate that the dihydropyridine calcium channel blocker (DHP CCB) class of antihypertensives such as amlodipine and nifedipine, although effective in reducing systemic hypertension, lack activity in reducing proteinuria or attenuating sympathetic activity. Experimental studies and a limited number of clinical studies suggest that non-DHP CCBs, including verapamil and diltiazem, have a mechanism of action that differs from DHP CCBs. Non-DHP CCBs could potentially attenuate sympathetic activity and reduce protein excretion in patients with CKD.

A novel peroxisome proliferator-activated receptor (PPAR)gamma agonist, NIP-222, reduces urinary albumin excretion in streptozotocin-diabetic mice independent of PPARgamma activation

NIP-222 is a novel peroxisome proliferator-activated receptor (PPAR)gamma agonist. This study provides evidence that NIP-222 decreases urinary albumin excretion (UAE) in diabetic mice independent of its PPARgamma activation. We compared the effect of NIP-222 and another PPARgamma agonist, troglitazone, on UAE, plasma glucose level, blood pressure, and creatinine clearance (C(cr)) in streptozotocin (STZ)-induced diabetic mice. Treatment for 3 weeks with NIP-222 (30 mg/kg) was associated with a significant decrease in UAE without any change in blood pressure, creatinine clearance, or plasma glucose level. In contrast, UAE did not decrease in mice treated with troglitazone (300 mg/kg). These results indicate that NIP-222 has PPARgamma independent effects on UAE in diabetic mice and suggest that this agent may have potential to minimize the development and progression of diabetic nephropathy.

Angiotensin-converting enzyme inhibitors and type 2 diabetic nephropathy: a meta-analysis

OBJECTIVE

To perform a meta-analysis on studies evaluating the effect of angiotensin-converting enzyme (ACE) inhibitors on diabetic nephropathy in patients with type 2 diabetes mellitus.

METHODS

A computerized literature search was conducted for articles of studies comparing ACE inhibitors with a control in patients with diabetes, in which measurement of albuminuria or proteinuria was an outcome. Each article was abstracted by two of the authors. Data from the articles were presented as geometric or arithmetic means. The data were summarized separately by using standard techniques for meta-analysis.

MAIN RESULTS

Statistically significant reductions in albuminuria were observed regardless of whether data were described with geometric or arithmetic means. Both were associated with significant heterogeneity. When studies reporting geometric means were stratified and analyzed, the heterogeneity was lost and statistically significant reductions in albuminuria were observed. The same procedure was repeated for studies reporting arithmetic means, but heterogeneity remained.

CONCLUSION

The ACE inhibitors produce statistically significant reductions in albuminuria associated with significant heterogeneity of effect. Stratification reduces the heterogeneity and supports treatment with ACE inhibitors to reduce the progression of nephropathy in patients with type 2 diabetes mellitus.

Remission and regression of diabetic nephropathy

Diabetic nephropathy has become the single largest cause of end-stage renal disease (ESRD) worldwide. Until recently, it was thought that once a patient developed overt proteinuria, diabetic nephropathy was irreversible and inevitably progressed to ESRD. However, the reversal of lesions caused by diabetic nephropathy (e.g., glomerular basement membrane thickening and mesangial matrix increase) has been demonstrated in a series of patients who underwent a pancreas transplantation 10 years prior to the reversal. Remission of nephrotic range proteinuria has also been reported in some patients with type 1 diabetes from the Collaborative Study Group during a median follow-up of 3 years of angiotensin-converting enzyme (ACE) inhibitor administration; no deterioration of renal function was observed in these patients. Remission and regression in nephropathy of type 1 diabetes patients have also been reported when blood pressure was controlled aggressively. Recent clinical trials have demonstrated that angiotensin II receptor blocker (ARB) preserved renal function and slowed the progression of nephropathy to ESRD in patients with type 2 diabetes. Since many patients with type 2 diabetes manifest with a metabolic syndrome, multifactorial intensive treatment is necessary; such treatment includes behavior modifications, dietary intervention, exercise, and smoking cessation. In this population, pharmacological therapy targeting hyperglycemia, hypertension (including ARB/ACE inhibitor), and hyperlipidemia in cases of type 2 diabetes is also necessary.

Renoprotective effects of vasopeptidase inhibition in an experimental model of diabetic nephropathy

AIMS

Although ACE inhibitors slow progression of diabetic renal disease, the mortality and morbidity is still high. As other hormonal factors are involved, inhibition of vasopeptidases could further reduce progression. We studied dual inhibition of angiotensin converting enzyme and neutral endopeptidase in a model of progressive diabetic renal injury. The major endpoints were reductions in systemic blood pressure, albuminuria and renal structural injury.

METHODS

Diabetic spontaneously hypertensive rats were treated with the ACE inhibitor perindopril (mg.kg(-1).day(-1)) or the vasopeptidase inhibitor omapatrilat at doses of 10 (oma10) and 40 (oma40) mg.kg(-1).day(-1) for 32 weeks. In vivo ACE and NEP inhibition was quantitated by in vitro autoradiography. Renal structural injury was assessed by measurement of the glomerulosclerotic (GS) index and tubulointerstitial area (TI). The expression of transforming growth factor beta, beta-inducible gene-h3 and nephrin were also quantitated.

RESULTS

Despite a similar reduction in blood pressure by perindopril and oma10, greater attenuation of albuminuria was afforded by oma10, with a complete amelioration observed with oma40. Oma40 lead to a 33% reduction in renal NEP binding and this was associated with less albuminuria and prevention of GS, TI area and overexpression of TGFbeta and betaig-h3. Diabetes-associated reduction in nephrin expression was restored by both drugs.

CONCLUSION/INTERPRETATION

These findings suggest that other vasoactive mechanisms in addition to angiotensin II are important in the prevention of diabetic nephropathy, and that vasopeptidase inhibition might confer an advantage over blockade of the RAS alone in the treatment of diabetic renal disease.

Bone morphogenic protein-7 (BMP-7), a novel therapy for diabetic nephropathy

BACKGROUND

Bone morphogenic protein-7 (BMP-7), an essential developmental renal morphogen, is a secreted differentiation factor of the adult collecting duct. It activates receptors in the collecting duct, distal nephron, proximal tubule, and glomerulus. BMP-7 is therapeutic in tubulointerstitial nephritis raising the question of broader efficacy in chronic kidney disease (CKD).

METHODS

Diabetes was induced in 200 g rats by a single dose of streptozotocin. After 16 weeks, glomerular hypertrophy and proteinuria were established, and therapy with BMP-7 (10, 30, or 100 microg/kg intravenously twice a week), enalapril (20 mg/kg), or vehicle was begun and continued until 32 weeks. Kidney weight, glomerular filtration rate (GFR), urine albumin excretion, blood pressure, pathology, and BMP-7 expression were measured.

RESULTS

Diabetic vehicle-treated rats developed renal insufficiency by 32 weeks (GFR, 0.34 +/- 0.02 mL/min/100 g body weight vs. 0.55 +/- 0.02 in normal). In the diabetic BMP-7 high-dose-treated rats, GFR was preserved (0.70 +/- 0.08, P < 0.01 vs. vehicle), and higher than diabetic enalapril-treated rats (0.58 +/- 0.06). Kidney weights of vehicle-treated animals were not affected, but were reduced in all of the treatment groups (P < 0.001). Proteinuria was reversed to normal by BMP-7 in a dose-dependent manner. The reduction in proteinuria by the intermediate dose of BMP-7 was similar to the effect of enalapril therapy. Glomerular area and interstitial volume were significantly decreased in the BMP-7 and enalapril-treated animals. Glomerular sclerosis was prevented by BMP-7 therapy more effectively than by enalapril. Enalapril controlled hypertension throughout the course of therapy while BMP-7 did not affect blood pressure until the final 4 weeks of therapy. Diabetic vehicle-treated rats lost BMP-7 expression in the kidney. BMP-7 and enalapril therapy restored BMP-7 expression at high levels.

CONCLUSION

BMP-7 partially reversed diabetic-induced kidney hypertrophy, restoring GFR, urine albumin excretion, and glomerular histology toward normal. Restoration of BMP-7 expression was associated with a successful repair reaction and a reversal of the ill-fated injury response.

Characterization of renal angiotensin-converting enzyme 2 in diabetic nephropathy

ACE2, initially cloned from a human heart, is a recently described homologue of angiotensin-converting enzyme (ACE) but contains only a single enzymatic site that catalyzes the cleavage of angiotensin I to angiotensin 1-9 [Ang(1-9)] and is not inhibited by classic ACE inhibitors. It also converts angiotensin II to Ang(1-7). Although the role of ACE2 in the regulation of the renin-angiotensin system is not known, the renin-angiotensin system has been implicated in the pathogenesis of diabetic complications and in particular in diabetic nephropathy. Therefore, the aim of this study was to assess the possible involvement of this new enzyme in the kidney from diabetic Sprague-Dawley rats to compare and contrast it to ACE. ACE2 and ACE gene and protein expression were measured in the kidney after 24 weeks of streptozocin diabetes. ACE2 and ACE mRNA levels were decreased in diabetic renal tubules by approximately 50% and were not influenced by ACE inhibitor treatment with ramipril. By immunostaining, both ACE2 and ACE protein were localized predominantly to renal tubules. In the diabetic kidney, there was reduced ACE2 protein expression that was prevented by ACE inhibitor therapy. The identification of ACE2 in the kidney, its modulation in diabetes, and the recent description that this enzyme plays a biological role in the generation and degradation of various angiotensin peptides provides a rationale to further explore the role of this enzyme in various pathophysiological states including diabetic complications.

The Influence of L - Tryptophan Peroral Load on Glomerular Filtration Rate in Chronic Glomerulonephritis and Chronic Renal Failure

The results of our clinical observations of 102 patients with chronic glomerulonephritis with normal renal function and 10 patients with chronic renal failure, as well as 10 healthy individuals allow us to conclude that in patients with high proteinuria and impaired renal function the serum concentration of tryptophan is decreased, both before and after peroral L-tryptophan load. We have found a positive correlation between serum concentration of albumin and tryptophan in patients with normal kidney function, and negative correlations between serum concentration of albumin and intensity of proteinuria, as well as between serum concentration of tryptophan and proteinuria. Our studies have shown that L-tryptophan peroral load increases the glomerular filtration rate in healthy individuals, in patients with membronous proliferative glomerulonephritis with proteinuria 2 g/24 h and mesangioproliferative glomerulonephritis with proteinuria < 2 g/24 h. In patients with high proteinuria (> 2 g/24h) and decreased renal function L-tryptophan load does not influence the glomerular filtration rate.

Renoprotective effects of valsartan and enalapril in STZ-induced diabetes in rats

Effects of the angiotensin II type 1 (AT1) receptor antagonist valsartan and the angiotensin-converting enzyme (ACE) inhibitor enalapril were studied in streptozotocine (STZ)-induced diabetes in rats on the basis of microalbuminuria (Ma) and renal morphology. Five groups of Wistar rats were used, one group was the non-diabetic control, one group consisted of untreated STZ-diabetics and 3 groups of STZ-diabetics were treated with either enalapril and/or valsartan for 30 days. Blood glucose (BG) and Ma levels, body and kidney weight and glomerular size were measured. Immunohistochemical staining with an anti-transforming growth factor-beta1 (TGF-beta1) antibody was performed as well. In STZ-diabetics, BG and Ma levels were significantly increased when compared with the non-diabetic group. Although Ma levels in the valsartan-treated group was found to be higher than those in the non-diabetics group after 15 days of treatment, in all treated diabetic groups Ma levels were significantly decreased as compared with STZ-diabetics at the end of the experiment. Thickening of the glomerular and tubular basement membranes, increased mesangial matrix and glomerular size were found in the untreated diabetic group. All these changes were less in the treated groups. A significant increase in TGF-beta1 immunoreactivity was found in glomeruli of untreated STZ-diabetics as compared with non-diabetics. Again, TGF-beta1 expression was decreased in the treated groups as compared with untreated STZ-diabetics. We conclude that valsartan and enalapril have renoprotective effects in diabetic nephropathy. A combined therapy has an advantage because lower dosages of these drugs can be used. Their beneficial effects are related to a blockade of the renin-angiotensin system (RAS) and a decrease in TGF-beta1 expression in glomeruli.

Irbesartan reduces the albumin excretion rate in microalbuminuric type 2 diabetic patients independently of hypertension: a randomized double-blind placebo-controlled crossover study

OBJECTIVE

ACE inhibitors delay the progression from incipient to overt diabetic nephropathy and reduce albumin excretion rate (AER), independently of blood pressure. Angiotensin II type 1 receptor antagonists produce similar effects on microalbuminuria and mean arterial pressure. The aim of this study was to evaluate the effect of irbesartan on microalbuminuria and blood pressure in hypertensive and normotensive type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

Sixty-four microalbuminuric hypertensive (group 1) and 60 microalbuminuric normotensive (group 2) type 2 diabetic male patients, matched for age, BMI, HbA(1c), and diabetes duration, were enrolled. Each group was divided into two subgroups receiving either irbesartan (150 mg b.i.d. orally) or placebo for 60 days. After 15 days of washout, irbesartan was given to the subgroups who had received the placebo, and vice versa, in a randomized double-blind crossover study.

RESULTS

In microalbuminuric hypertensive type 2 diabetic subjects, irbesartan reduced 24-h mean systolic and diastolic pressure and AER. In microalbuminuric normotensive type 2 diabetic patients, irbesartan reduced AER.

CONCLUSIONS

These results indicate the beneficial effects of irbesartan on AER in type 2 diabetic subjects, independently of its antihypertensive effects.

The effects of losartan and fosinopril in hypertensive type 2 diabetic patients

The aim of this study is to evaluate the effects of losartan on blood pressure (BP), creatinine clearance (Ccr) and urinary albumin excretion (UAE), and to assess metabolic parameters in comparison with ACEI. Thirty-three type 2 diabetic hypertensive patients were enrolled in the study. Twenty patients were randomized to receive 50 mg/day losartan and 13 patients to 10 mg/day fosinopril. Patients were studied at baseline and after 1 and 6 months. BP was significantly decreased in both groups at the end of the 1st and 6th month to a similar extent. Ccr had fallen in both groups at the end of 1st and 6th months. The effect of each drug on Ccr was similar (64.2+/-70.6 and 42.8+/-53.8 ml/min, respectively, NS). In the subgroup with microalbuminuria at baseline, UAE rate was lower in both groups at the end of the 1st and 6th months. However, when compared with the end of 1st month, the antiproteinuric effect of losartan was slightly decreased at the end of 6th month. Metabolic parameters did not change with either drug. Both drugs were well tolerated. Thus the antihypertensive effects of the two drugs were comparable. In conclusion, this study confirms the efficacy and safety of losartan as an antihypertensive drug in diabetic patients.

Chronic angiotensin-converting enzyme inhibition and angiotensin II antagonism in rats with chronic renal failure

The current study was undertaken to compare the organ protective effects of an angiotensin-converting enzyme inhibitor, temocapril, with those of an angiotensin II type 1 receptor antagonist, CS-866 (olmesartan medoxomil), alone or combined, in the remnant kidney model of rats. Eight-week-old spontaneously hypertensive male rats were subjected to five-sixths nephrectomy. At the age of 10 weeks, the rats were randomly allocated to groups that received two doses of CS-866 (CS-L, 3 mg/kg/day; CS-H, 10 mg/kg/day), temocapril (TEM, 10 mg/kg/day), CS-866 (3 mg/kg/day) plus temocapril (10 mg/kg/day), or a vehicle alone (untreated control group). Systolic blood pressure (SBP) and urinary protein excretion (UprotV) were measured every 2 weeks. When the rats were 18 weeks old, biochemical measurement and histologic examination were performed. All the drug treatments significantly reduced SBP, UprotV, glomerular sclerosis index (GSI), relative interstitial volume (RIV), and heart weight. The hypotensive effects were on the order of combination therapy > CS-H = TEM > CS-L. Correlational analysis was based on the values for SBP and UprotV derived from the average of values obtained when the rats were 12 to 18 weeks of age. UprotV, GSI, and RIV were found to be highly correlated with SBP among the individual rats pooled from all the groups, and the correlation was maintained among the group means. A similar correlation was found between heart weight and SBP. The results suggest that the organ protective effects of temocapril, CS-866, and combination therapy are closely related to the magnitude of their antihypertensive effects.

Angiotensin converting enzyme inhibitors or angiotensin receptor blockers in nephropathy from type 2 diabetes

Type 2 diabetes is the most common cause of end-stage renal disease in the United States, and type 2 diabetes has been shown to be a myocardial infarction equivalent in regard to risk of death from a cardiovascular event. Proteinuria is a surrogate marker for renal disease progression, and although data favor both the angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) in reducing proteinuria, data for renal outcomes, such as time to dialysis, only exist for the ARBs, which clearly increase the duration to dialysis. Conversely, ACE inhibitors have overwhelming data that show substantial risk reduction from cardiovascular events and death in people with type 2 diabetes. Similar data on cardiovascular risk reduction are not yet available with ARBs, although two trials of renal disease progression did have cardiovascular endpoints as secondary outcomes. There were no significant differences between the ARB and control group except for first hospitalization with heart failure, where losartan reduced the risk by 32%, but there was a trend, albeit not significant, toward reduction of myocardial infarction. The first information regarding ARB effects on cardiovascular events as primary outcomes will come from the Losartan Intervention for Endpoint (LIFE) Reduction in Hypertension study. Therefore, as of this writing, all patients with type 2 diabetes and no evidence of nephropathy, ie, proteinuria and an elevated creatinine > 1.5 mg/dL, should be placed on an ACE inhibitor for cardiovascular risk reduction. If nephropathy is present, the evidence would support an ARB for therapy in concert with a b-blocker for cardiovascular risk reduction and renoprotection.

Rationale and design of diabetics exposed to telmisartan and enalapril (DETAIL) study

The DETAIL (diabetics exposed to telmisartan and enalapril) study will compare the long-term renal outcome of treatment with the angiotensin II receptor antagonist (ARA) telmisartan versus the angiotensin-converting enzyme (ACE) inhibitor enalapril in patients with mild-to-moderate hypertension and diabetic nephropathy. In short-term clinical studies, ACE inhibitors reduce microalbuminuria and, in the longer term, they are superior to conventional therapies in maintaining normal renal function. ARAs also appear to be renoprotective in diabetic animals. In this double-blind, parallel-group study, 252 patients with Type 2 diabetes and concurrent hypertension (mean seated systolic blood pressure < or = 180 mm Hg, on treatment seated diastolic blood pressure < or = 95 mm Hg) have been randomised to once-daily telmisartan 40 mg or enalapril 10 mg; doses are mandatorily titrated to 80 and 20 mg once daily, respectively, after 4 weeks. The primary endpoint will be the change from baseline in glomerular filtration rate (GFR) after 5 years of therapy, using the iohexol method and central laboratory analysis. The secondary endpoints to be evaluated will be: changes in GFR in relation to baseline after 1-4 years of therapy; percentage changes in albumin excretion rate after 1-5 years; and incidences of end-stage renal disease, cardiovascular events, all-cause mortality, and adverse events. The planned date for the completion of the study is 2005.

Role of ACE inhibitors in patients with diabetes mellitus

The adjective 'epidemic' is now attributed to the rapidly growing number of patients with diabetes mellitus, mainly type 2. and the specific complications linked to this disorder. Provided they are recognised early enough, these different complications can be treated; in some patients the evolutive course of these complications can be slowed or even stopped. Furthermore, some recent observations suggest that specific tissular lesions may be prevented or even reversed. Although glycaemic control is essential, other therapeutic measures that must also be taken include those to control blood pressure and to lower lipid levels. Of the agents available to control the complications of diabetes mellitus, cardiovascular drugs, and particularly ACE inhibitors, have a pre-eminent place. Experimental and epidemiological data suggest that activation of the renin-angiotensin-aldosterone system plays an important role in increasing in the micro- and macrovascular complications in patients with diabetes mellitus. Not only are ACE inhibitors potent antihypertensive agents but there is a growing body of data indicating that also they have a specific 'organ-protective' effect. For the same degree of blood pressure control, compared with other antihypertensive agents, ACE inhibitors demonstrate function and tissue protection of considered organs. ACE inhibitors have been reported to improve kidney, heart, and to a lesser extent, eye and peripheral nerve function of patients with diabetes mellitus. These favourable effects are the result of inhibition of both haemodynamic and tissular effects of angiotensin II. Finally, there are a growing number of arguments favouring the use of ACE inhibitors very early in patients with diabetes mellitus.

Effects of low-dose and early versus late perindopril treatment on the progression of severe diabetic nephropathy in (mREN-2)27 rats

It was previously reported that transgenic (mRen-2)27 rats with streptozotocin-induced diabetes mellitus progressively develop advanced nephropathy in 12 wk. These lesions are largely prevented when the angiotensin-converting enzyme inhibitor perindopril is administered from the time of induction of diabetes mellitus. This study aimed to determine the lowest dose of early perindopril treatment required for substantial improvement of renal function and structure and to investigate whether late intervention prevents or reverses the progression of established renal lesions. At 6 wk of age, female heterozygous Ren-2 rats were randomized to receive either streptozotocin (diabetic) or citrate buffer (control). Rats were gavaged, beginning early after the induction of diabetes mellitus or the administration of control vehicle, with 0, 0.02, 0.2, or 2 mg/kg per d perindopril for 12 wk. A separate group of diabetic Ren-2 rats received late treatment with 2 mg/kg per d perindopril throughout week 8 to week 12, when rats were hypertensive and albuminuric and exhibited increased kidney weight and glomerulosclerotic index (GSI). Among diabetic rats, early 0.02 mg/kg per d perindopril treatment reduced systolic BP, GSI, and renal collagen staining but had no effect on albuminuria or kidney hypertrophy. Early 0.2 or 2 mg/kg per d perindopril treatment further reduced systolic BP, GSI, and renal collagen staining and decreased albuminuria and kidney hypertrophy. Late intervention was as antihypertensive and antialbuminuric as early 0.2 or 2 mg/kg per d perindopril treatment but did not prevent a moderate increase in GSI. In conclusion, early treatment with 0.2 mg/kg per d perindopril was the lowest dosage to largely prevent severe diabetic nephropathy in transgenic Ren-2 rats. Late-onset perindopril treatment of diabetic rats with established nephropathy was as efficacious as early treatment with respect to various renal parameters, such as albuminuria, but was associated with moderate progression of glomerulosclerosis.

Role of intrarenal angiotensin-converting enzyme in nephropathy of type II diabetic rats

To examine the mechanism of nephropathy in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a recently developed type II diabetic model, we compared the long-term effect of angiotensin-converting enzyme (ACE) inhibitor (imidapril, 1 mg/kg/day), calcium channel blocker (amlodipine, 10 mg/kg/day), and insulin (5-10 U/kg/day) on nephropathy of OLETF rats. Both imidapril and amlodipine, but not insulin, significantly reduced blood pressure of OLETF rats. Imidapril treatment significantly decreased urinary albumin excretions and improved glomerulosclerosis of OLETF rats, while amlodipine failed to improve nephropathy of OLETF rats despite lowering of blood pressure. Insulin treatment, which significantly decreased HbA1c throughout the treatment period, did not ameliorate nephropathy of OLETF rats. Serum ACE activity in OLETF rats was significantly lower than that in genetic control nondiabetic Long-Evans Tokushima Otsuka (LETO) rats. However, glomerular and aortic ACE activities in OLETF rats were significantly higher than those in LETO rats, and were significantly decreased by treatment with imidapril. Furthermore, immunohistochemical analysis of ACE in the kidney using specific antibodies indicated greater ACE immunostaining in the glomeruli and renal vessels of OLETF rats than in those of LETO rats. These observations demonstrate that ACE is involved in the development of nephropathy of OLETF rats and provide evidence that intrarenal ACE rather than circulating ACE may play an important role in nephropathy of this type II diabetic model.