Investigation of Carcinogenic Impurities of N-Nitrosamines in Sartan Pharmaceutical Products Marketed in Brazil: Development and Validation of Method Based on High-Performance Liquid Chromatography-Tandem Mass Spectrometry.

N-nitrosamines (NA) impurities have unexpectedly been found in sartan products, angiotensin II receptor antagonists that are used to control hypertension, representing an urgent concern for industry, global regulators and for the patients. In this study, an HPLC-MS/MS method was developed and validated for the quantification of six NA (N-nitrosodimethylamine, N-Nitroso-N-methyl-4-aminobutyric acid, N-Nitrosodiethylamine, N-ethyl-N-nitroso-2-propanamine, N-nitroso-diisopropylamine and N-nitroso-di-n-butylamine) in losartan, valsartan, olmesartan, irbesartan, candesartan and telmisartan products. The method was validated in terms of sensitivity, linearity, accuracy, precision, robustness and stability. The limits of quantification were 100, 31.25, 250, 33, 312.5 and 125 µg kg-1 in losartan, valsartan, olmesartan, irbesartan, candesartan and telmisartan samples, respectively, which met the sensitivity requirements for the limits set by Food and Drug Administration of the United States. The standard curves showed good linearity. The recoveries ranged from 93.06 to 102.23% in losartan matrix, 83 to 85.9% in valsartan, 96.1 to 101.2% in olmesartan, 89.2 to 97.5% in irbesartan, 93.4 to 132.0% in candesartan and 62.3 to 106.2% in telmisartan matrix. The other parameters met the validation criteria, the good sensitivity and precision, high accuracy and simple and fast analysis provides a reliable method for quality control of NA in sartan pharmaceutical products. The developed method was successfully applied for the determination of N-nitrosamines in 71 sartan products marketed in Brazil.

Evaluation of Piperine as Natural Coformer for Eutectics Preparation of Drugs Used in the Treatment of Cardiovascular Diseases.

Piperine (PIP) was evaluated as a natural coformer in the preparation of multicomponent organic materials for enhancing solubility and dissolution rate of the poorly water-soluble drugs: curcumin (CUR), lovastatin (LOV), and irbesartan (IBS). A screening based on liquid assisted grinding technique was performed using 1:1 drug-PIP molar ratio mixtures, followed by differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) analyses. Three eutectic mixtures (EMs) composed of CUR-PIP, LOV-PIP, and IBS-PIP were obtained. Therefore, binary phase and Tamman's diagrams were constructed for each system to obtain the exact eutectic composition, which was 0.41:0.59, 0.29:0.71, and 0.31:0.69 for CUR-PIP, LOV-PIP, and IBS-PIP, respectively. Further, bulk materials of each system were prepared to characterize them through DSC, PXRD fully, Fourier transform infrared spectroscopy (FT-IR), and solution-state nuclear magnetic resonance (NMR) spectroscopy. In addition, the contact angle, solubility, and dissolution rate of each system were evaluated. The preserved characteristic in the PXRD patterns and FT-IR spectra of the bulk material of each system confirmed the formation of EM mixture without molecular interaction in solid-state. The formation of EM resulted in improved aqueous solubility and dissolution rate associated with the increased wettability observed by the decrease in contact angle. In addition, solution NMR analyses of CUR-PIP, LOV-PIP, and IBS-PIP suggested no significant intermolecular interactions in solution between the components of the EM. Hence, this study concludes that PIP could be an effective coformer to improve the solubility and dissolution rate of CUR, LOV, and IBS.

Hyperdynamic circulatory syndrome in a mouse model transgenic for SerpinB3.

INTRODUCTION AND OBJECTIVES: SerpinB3 is a cysteine protease inhibitor involved in several biological activities. It is progressively expressed in chronic liver disease, but not in normal liver. The role in vascular reactivity of this serpin, belonging to the same family of Angiotensin II, is still unknown. Our aim was to evaluate the in vivo and in vitro effects of SerpinB3 on systemic and splanchnic hemodynamics. MATERIAL AND METHODS: Different hemodynamic parameters were evaluated by ultrasonography in two colonies of mice (transgenic for human SerpinB3 and C57BL/6J controls) at baseline and after chronic carbon tetrachloride (CCl4) treatment. In vitro SerpinB3 effect on mesenteric microvessels of 5 Wistar-Kyoto rats was analyzed measuring its direct action on: (a) preconstricted arteries, (b) dose-response curves to phenylephrine, before and after inhibition of angiotensin II type 1 receptors with irbesartan. Hearts of SerpinB3 transgenic mice and of the corresponding controls were also analyzed by morphometric assessment. RESULTS: In SerpinB3 transgenic mice, cardiac output (51.6±21.5 vs 30.1±10.8ml/min, p=0.003), hepatic artery pulsatility index (0.85±0.13 vs 0.65±0.11, p<0.001) and portal vein blood flow (5.3±3.2 vs 3.1±1.8ml/min, p=0.03) were significantly increased, compared to controls. In vitro, recombinant SerpinB3 had no direct hemodynamic effect on mesenteric arteries, but it increased their sensitivity to phenylephrine-mediated vasoconstriction (p<0.01). This effect was suppressed by inhibiting angiotensin II type-1 receptors. CONCLUSIONS: In transgenic mice, SerpinB3 is associated with a hyperdynamic circulatory syndrome-like pattern, possibly mediated by angiotensin receptors.

Highly Soluble Glimepiride and Irbesartan Co-amorphous Formulation with Potential Application in Combination Therapy.

One-third of the population of the USA suffers from metabolic syndrome (MetS). Treatment of patients with MetS regularly includes drugs prescribed simultaneously to treat diabetes and cardiovascular diseases. Therefore, the development of novel multidrug formulations is recommended. However, the main problem with these drugs is their low solubility. The use of binary co-amorphous systems emerges as a promising strategy to increase drug solubility. In the present study, irbesartan (IBS) and glimepiride (GMP), class II active pharmaceutical ingredients (API), widely used in the treatment of arterial hypertension and diabetes, were selected to develop a novel binary co-amorphous system with remarkable enhancement in the dissolution of both APIs. The phase diagram of IBS-GMP was constructed and co-amorphous systems were prepared by melt-quench, in a wide range of compositions. Dissolution profile (studied at pH 1.2 and 37°C for mole fractions 0.01, 0.1, and 0.5) demonstrated that the xGMP = 0.01 formulation presents the highest enhancement in its dissolution. GMP went from being practically insoluble to reach 3.9 ± 0.9 µg/mL, and IBS showed a 12-fold increment with respect to the dissolution of its crystalline form. Infrared studies showed that the increase in the dissolution profile is related to the intermolecular interactions (hydrogen bonds), which were dependent of composition. Results of structural and thermal characterization performed by XRD and DSC showed that samples have remained in amorphous state for more than 10 months of storage. This work contributes to the development of a highly soluble co-amorphous drugs with potential used in the treatment of MetS.

Experimental and DFT characterization, antioxidant and anticancer activities of a Cu(II)-irbesartan complex: structure-antihypertensive activity relationships in Cu(II)-sartan complexes.

The coordination compound of the antihypertensive ligand irbesartan (irb) with copper(II) (CuIrb) was synthesized and characterized by FTIR, FT-Raman, UV-visible, reflectance and EPR spectroscopies. Experimental evidence allowed the implementation of structural and vibrational studies by theoretical calculations made in the light of the density functional theory (DFT). This compound was designed to induce structural modifications on the ligand. No antioxidant effects were displayed by both compounds, though CuIrb behaved as a weak 1,1-diphenyl-2-picrylhydrazyl radical (DPPH(·)) scavenger (IC50 = 425 µM). The measurements of the contractile capacity on human mesangial cell lines showed that CuIrb improved the antihypertensive effects of the parent medication. In vitro cell growth inhibition against prostate cancer cell lines (LNCaP and DU 145) was measured for CuIrb, irbesartan and copper(II). These cell lines have been selected since the angiotensin II type 1 (AT1) receptor (that was blocked by the angiotensin receptor blockers, ARB) has been identified in them. The complex exerted anticancer behavior (at 100 µM) improving the activity of the ligand. Flow cytometry determinations were used to determine late apoptotic mechanisms of cell death. Experimental and DFT characterization of an irbesartan copper(II) complex has been performed. The complex exhibits low scavenging activity against DPPH(·) and significant growth inhibition of LNCaP and DU 145 prostate cancer cell lines. Flow cytometry determinations were used to determine late apoptotic mechanisms of cell death. This compound improved the antihypertensive effect of irbesartan. This effect was observed earlier for the mononuclear Cu-candesartan complex, but not in structurally modified sartans forming dinuclear or octanuclear Cu-sartan compounds.

Improved gastric emptying in diabetic rats by irbesartan via decreased serum leptin and ameliorated gastric microcirculation.

Diabetic gastroparesis (DG) is a common clinical complication of diabetes mellitus. Leptin may cause delayed gastric emptying in the central and peripheral pathways. Microcirculatory disturbances in the stomach make gastric smooth muscles and nerves hypoxic-ischemic, thereby impairing gastric motility. Irbesartan is an angiotensin II (ATII) receptor blocker that indirectly decreases serum leptin levels and improves blood vessel endothelia. This study examined the effect of irbesartan on DG and its relationship with serum leptin levels and microcirculatory disturbances of the stomach. Sprague-Dawley rats were injected with streptozotocin to induce diabetes and were then treated with or without 0.012 g·kg(-1)·d(-1) irbesartan by gavage. After six weeks of treatment, the gastric evacuation rate (GER) was measured using phenol red. Serum leptin levels were detected using enzyme-linked immunosorbent assays. Endothelin (ET) in the stomach tissue was examined using a radioimmunoassay, whereas chemical colorimetry was used to measure the nitric oxide synthase (NOS) activity of stomach tissues. The mRNA expression of the ATII receptor (AT1R) was assessed using reverse transcription-polymerase chain reaction. Treatment with irbesartan significantly increased the GER of diabetic rats and reduced the serum leptin levels, as well as decreased the ET content and AT1R mRNA expression in the stomach (P<0.05). Changes in the cNOS activity after irbesartan intervention were not significant (P>0.05), whereas iNOS activity was significantly decreased (P<0.05). Irbesartan can alleviate hyperglycemia-induced delayed gastric emptying, which is associated with decreased serum leptin levels and improved microcirculation in the stomach.

Maintaining goal blood pressures after switching from olmesartan to other angiotensin receptor blockers.

This study assessed blood pressure (BP) goal maintenance in patients controlled with olmesartan monotherapy after switching to another angiotensin type II receptor blocker (ARB). Hypertensive patients prescribed olmesartan monotherapy were identified from GE Healthcare's Centricity electronic medical record between 2007 and 2011. After documentation of BP goal (<140/90 mm Hg) attainment, patients were placed into the continuation cohort if olmesartan monotherapy was maintained or into the switch cohort if they were changed to irbesartan, losartan, or valsartan. Follow-up assessments were the first BP measurement 28 to 390 days after attaining BP goal (continuation cohort) or after prescribing an alternative ARB (switch cohort). Of 3412 patients included (3027 continuation cohort, 385 switch cohort), 52% were women and mean age was 58.0 years. In the switch cohort, 310 (80.5%) were switched to losartan (n=236), irbesartan (n=58), or valsartan (n=16) monotherapy and 75 (19.5%) were switched to combination antihypertensive therapy. Mean baseline and follow-up BP were 122.5/75.8 mm Hg and 126.6/77.6 mm Hg, respectively, in the continuation cohort (P<.001) and 123.5/75.4 mm Hg and 129.6/78.5 mm Hg, respectively, in the switch cohort (P<.001). BP goal maintenance was 78.7% and 72.2% in the continuation and switch cohort, respectively (odds ratio, 0.707; 95% confidence interval, 0.555-0.899). Patients who continued on olmesartan monotherapy after attaining BP goal had a higher percentage of BP goal maintenance than patients who switched therapy.

I-ADD study: assessment of efficacy and safety profile of irbesartan/amlodipine fixed-dose combination therapy compared with irbesartan monotherapy in hypertensive patients uncontrolled with irbesartan 150 mg monotherapy: a multicenter, phase III, prospective, randomized, open-label with blinded-end point evaluation study.

BACKGROUND: Hypertension guidelines recommend the use of 2 agents with synergistic action when >1 agent is needed to achieve blood pressure goals. Newer antihypertensive treatment combinations include fixed-dose combinations of an angiotensin receptor blocker and a calcium channel blocker. OBJECTIVE: The I-ADD study aimed to demonstrate whether the antihypertensive efficacy of fixed-dose combination irbesartan 300 mg/amlodipine 5 mg (I300/A5) was superior to that of irbesartan (I300) monotherapy in lowering home systolic blood pressure after 10 weeks' treatment. METHODS: The I-ADD study was a 10-week, multicenter, Phase III, prospective, randomized, parallel-group, open-label with blinded-end point study. The main inclusion criterion was essential uncontrolled hypertension (systolic blood pressure ≥145 mm Hg at office after at least 4 weeks of irbesartan 150 mg [I150] monotherapy administered once daily). Patients continued to receive I150 for 7 to 10 days and were randomized to either monotherapy with I150 for 5 weeks then I300 for the next 5 weeks, or to a fixed-dose combination therapy (I150/A5, then I300/A5). Safety profile was assessed by recording adverse events reported by patients or observed by the investigator. RESULTS: Following enrollment, 325 patients were randomized to treatment, and 320 (mean [SD] age, 56.7 [11.4] years; 41% male) were included in the intention-to-treat analysis: 155 patients treated with I150/A5 then I300/A5, and 165 patients treated with I150 then I300. At randomization, mean home systolic blood pressure was similar in both groups: 152.7 (11.8) mm Hg in the I150/A5 group and 150.4 (10.1) mm Hg in the I150 group. At week 10, the adjusted mean difference in home systolic blood pressure between groups was -8.8 (1.1) mm Hg (P < 0.001). The percentage of controlled patients (mean home blood pressure <135 and 85 mm Hg) was nearly 2-fold higher in the I300/A5 group versus the I300 group (P < 0.001). Treatment-emergent adverse events were experienced by 10.5% of I300/A5-treated patients and 6.6% of I300-treated patients during the second 5-week period. Three serious adverse events were reported; 2 with monotherapy (1 with I150 and 1 with I300) and 1 with fixed-dose combination I300/A5. All patients affected by serious adverse events made a full recovery. CONCLUSIONS: These 10-week data from this patient population suggest a greater antihypertensive efficacy of the fixed-dose combination I300/A5 over I300 alone in lowering systolic blood pressure. Both treatments were well tolerated throughout the study. ClinicalTrials.gov identifier: NCT00957554.

I-COMBINE study: assessment of efficacy and safety profile of irbesartan/amlodipine fixed-dose combination therapy compared with amlodipine monotherapy in hypertensive patients uncontrolled with amlodipine 5 mg monotherapy: a multicenter, phase III, prospective, randomized, open-label with blinded-end point evaluation study.

BACKGROUND: Hypertension guidelines recommend the use of 2 agents with synergistic action when >1 agent is needed to achieve blood pressure goals. Newer antihypertensive treatment combinations include fixed-dose combinations of an angiotensin receptor blocker and a calcium channel blocker. OBJECTIVE: The I-COMBINE study aimed to determine whether the antihypertensive efficacy of the fixed-dose combination irbesartan 150 mg/amlodipine 5 mg (I150/A5) was superior to that of amlodipine 5 mg (A5) monotherapy in lowering home systolic blood pressure (HSBP) after 5 weeks' treatment. METHODS: The I-COMBINE study was a 10-week, multicenter, Phase III, prospective, randomized, parallel-group, open-label with blinded-endpoint study. The main inclusion criterion was essential uncontrolled hypertension (SBP ≥145 mm Hg at office, after at least 4 weeks of A5 monotherapy administered once daily). Patients continued to receive A5 for 7 to 10 days and were randomized to either monotherapy with A5 for 5 weeks then amlodipine 10 mg (A10) for the next 5 weeks or to a fixed-dose combination therapy (I150/A5 then I150/A10). Safety profile was assessed by recording adverse events reported by patients or observed by the investigator. RESULTS: Following enrollment, 290 patients were randomized to treatment, and 287 (mean [SD] age, 57.3 [11.2] years; 48% male) were included in the intention-to-treat analysis: 144 patients treated with I150/A5 then I150/A10, and 143 patients treated with A5 then A10. At randomization, mean HSBP was similar in both groups: 148.5 (10.3) mm Hg in the I150/A5 group and 149.2 (9.7) mm Hg in the A5 group. At week 5, the adjusted mean difference in HSBP between groups was -6.2 (1.0) mm Hg (P < 0.001). The proportion of controlled patients (mean home blood pressure <135 and 85 mm Hg) was significantly higher in the I150/A5 group than in the A5 group (P < 0.001). Treatment-emergent adverse events were experienced by 13.8% of I150/A5-treated patients and 11.9% of A5-treated patients during the first 5-week period, and by 15.8% of I150/A10-treated patients and 17.0% of A10-treated patients during the second 5-week period. Two serious adverse events were reported with the fixed-dose combination; both patients recovered. CONCLUSIONS: Data from this adult population with essential hypertension suggest greater efficacy with the fixed-dose combination I150/A5 over A5 monotherapy in lowering SBP after 5 weeks. Both treatment regimens were well tolerated throughout the study. ClinicalTrials.gov identifier: NCT00956644.

Maintenance of blood-pressure-lowering effect following a missed dose of aliskiren, irbesartan or ramipril: results of a randomized, double-blind study.

Most patients inadvertently miss an occasional dose of antihypertensive therapy, and hence drugs that provide sustained blood-pressure (BP) reduction beyond the 24-h dosing interval are desirable. The primary objective of this study was to compare the 24-h mean ambulatory BP reductions from baseline after a simulated missed dose of the direct renin inhibitor aliskiren, irbesartan or ramipril. In this double-blind study, 654 hypertensive patients (24-h mean ambulatory diastolic BP (MADBP) >or=85 mm Hg) were randomized 1:1:1 to once-daily aliskiren 150 mg, irbesartan 150 mg or ramipril 5 mg. Doses were doubled after 2 weeks. At day 42, patients were again randomized equally within each group to receive 1 day of placebo ('missed dose') on either day 42 or day 49. Patients with a successful 24-h ambulatory BP measurement at baseline and on day 42/49 were included in the analyses. The 24-h mean ambulatory systolic BP (MASBP)/MADBP reductions from baseline after a missed dose of aliskiren 300 mg (9.3/7.0 mm Hg) were similar to irbesartan 300 mg (9.5/7.3 mm Hg) and significantly larger than ramipril 10 mg (7.1/5.0 mm Hg, P

Long-term treatment with an angiotensin II receptor blocker decreases adipocyte size and improves insulin signaling in obese Zucker rats.

BACKGROUND: Angiotensin II (Ang II) has been shown to contribute to the pathogenesis of hypertension and insulin resistance. In addition, administration of selective Ang II type-1 receptor blockers has been shown to improve insulin sensitivity. However, only a few studies have addressed the molecular mechanisms involved in this association. OBJECTIVE AND DESIGN: The current study was undertaken to determine whether an Ang II receptor blocker (irbesartan) is effective in improving insulin resistance in adipose tissue from obese Zucker rats, a model of metabolic syndrome. METHODS: Ten-week-old male obese Zucker rats (fa/fa) were treated daily with either vehicle or 50 mg/kg irbesartan for 6 months, and their age-matched lean (+/?) (lean Zucker rats) was used as a control. We determined systolic blood pressure (SBP), together with plasma levels of insulin, triglycerides, cholesterol and glucose. In addition, we evaluated insulin signaling through the insulin receptor/insulin receptor substrate-1/phosphatidylinositol 3 kinase/Akt/glucose transporter 4 pathway as well as the inflammatory status of adipose tissue. RESULTS: Obese Zucker rats displayed hyperglycemia, hypertriglyceridemia, hyperinsulinemia and hypercholesterolemia and increased SBP together with decreased activation of insulin signaling through the insulin receptor/insulin receptor substrate-1/phosphatidylinositol 3 kinase/Akt pathway in adipose tissue as well as increased adipocytes size, macrophage infiltration and augmented levels of inflammatory mediators such tumor necrosis factor-alpha, monocyte chemoattractant protein-1 and Ang II. Chronic irbesartan treatment resulted in an improvement of all alterations. CONCLUSION: The present study provides substantial information that demonstrates that long-term selective Ang II blockade ameliorates insulin resistance in adipose tissue from a model of metabolic syndrome via a mechanism that could involve the modulation of insulin signaling.

ACE inhibition and AT1 receptor blockade prevent fatty liver and fibrosis in obese Zucker rats.

OBJECTIVE: Non-alcoholic steatohepatitis (NASH), which is a common liver disease in industrialized countries, is associated with obesity, hypertension, and type-2 diabetes (metabolic syndrome). Since angiotensin II (ANG II) has been suggested to play an important role in liver inflammation and fibrosis, the purpose of this study was to investigate whether therapy against renin-angiotensin system (RAS) may provide some beneficial effect in liver of an animal model of metabolic syndrome. METHODS AND PROCEDURES: For 6 months, obese Zucker rats (OZRs) were treated as follows: OZR-group, OZR + Perindopril (P) group, OZR + Irbesartan (IRB) group, OZR + Amlodipine (AML) group, and lean Zucker rats (LZRs) group as a control. Livers were evaluated by immunohistochemistry techniques using corresponding antibodies. RESULTS: All treated groups showed a similar reduction in blood pressure compared to untreated OZR. Therapy either with IRB or P improves insulin sensitivity and reduces hepatic enzyme level with respect to untreated OZR. Conversely, AML failed to modify both parameters. Untreated OZR displayed higher hepatic ANG II levels and steatosis together with a marked increase in tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and transforming growth factor-beta1 (TGF-beta1) level compared to LZR. Following RAS inhibition either by P or IRB, a significant reduction (P < 0.01) in the immunostaining of TNF-alpha, IL-6 and TGF-beta1 compared to untreated OZR was observed. DISCUSSION: These results indicate that ANG II expression is increased in the liver of these animals with steatohepatitis. Furthermore, RAS control by either angiotensin-converting enzyme inhibition or AT1 receptor blockade seems to provide a beneficial modulation concerning the inflammatory response to liver injury in this model. Consequently, blockade of RAS could be a new approach to prevent or to treat patients with NASH.

Hypothalamic angiotensinergic-noradrenergic systems interaction in fructose induced hypertension.

OBJECTIVE: Several studies suggest the importance of the interaction between the renin angiotensin and sympathetic nervous systems in blood pressure control, especially in clinical situations such as the metabolic syndrome. Previously, we have demonstrated changes in noradrenergic hypothalamic control of blood pressure in an animal model of insulin resistance and hypertension. The aim of the present study was to evaluate the effects of the interaction between the noradrenergic and angiotensinergic systems on hypothalamic blood pressure regulation in fructose hypertensive rats. METHODS: In control (C) and fructose-fed hypertensive (F) rats, we studied: 1) the effects of hypothalamic perfusion of irbesartan (AT(1) angiotensin receptor antagonist, 50 and 500 microg ml(-1)) and metoprolol (beta(1) adrenergic receptor antagonist, 10 and 100 microg ml(-1)) on blood pressure, heart rate and noradrenaline intrahypothalamic levels, by means of the microdialysis technique; and 2) the effects of intrahypothalamic microinjection of angiotensin II alone or after metoprolol pre-administration, on blood pressure and heart rate. RESULTS: Meanwhile irbesartan perfusion did not modify neither mean arterial pressure (MAP) nor heart rate or noradrenaline hypothalamic levels in the C group, its highest dose diminished MAP (DeltaMAP: F: - 16.3+/-1 mm Hg, p<0.05) and noradrenaline levels (% of basal levels: 58+/-7%, p<0.05) in the F group, without affecting heart rate. Intrahypothalamic perfusion of metoprolol diminished MAP only in the F group (DeltaMAP: F: -12.1+/-1.1 mm Hg, p<0.05), but did not modify heart rate in both groups. On the other hand, it diminished noradrenaline hypothalamic levels in C (% of basal levels: 53+/-6%, p<0.05) but not in the F group. The pressor response to angiotensin II microinjection was increased in F rats (DeltaMAP: F: 13.3+/-1.5 mm Hg vs. C: 6.9+/-1.8 mm Hg; p<0.05). Previous administration of metoprolol markedly abolished this increment. CONCLUSIONS: Our results suggest the existence of an increase in AT(1) and beta(1) adrenergic receptors tone in the hypothalamus of F rats, which could be related to the increase in blood pressure present in this experimental model. On the other hand, considering that the enhanced pressor response to angiotensin II intrahypothalamic injection in F rats was abolished by previous administration of a beta(1) adrenergic receptor antagonist, these results would indicate that beta(1) adrenergic receptors activation participates in the pressor response to angiotensin II in this experimental model of insulin resistance and hypertension.

Aldosterone escape with diuretic or angiotensin-converting enzyme inhibitor/angiotensin II receptor blocker combination therapy in patients with mild to moderate hypertension.

Renin-angiotensin-aldosterone system (RAAS) hyperactivity is implicated in the development of hypertension and progressive damage in target organs. Chronic inhibition of the RAAS or use of thiazide-type diuretics may trigger an aldoster-one escape. The aim of this study was to assess this phenomenon in hypertensive patients treated with thiazide-type diuretics (hydrochlorothiazide [HCTZ]) or single or double blockade of the RAAS (irbesartan [IRBE], quinapril [QUIN], and IRBE+QUIN). Blood pressure levels were obtained by 24-hour ambulatory blood pressure monitoring. Plasma renin activity and aldosterone levels were determined by immunoradiometric assay. Blood pressure level was normalized in the 4 treatment groups; the HCTZ and IRBE+QUIN groups showed an increased plasma aldosterone level after 12 weeks (9.1+/-2.2 to 14.1+/-1.4 and 6.9+/-1.9 to 12.9+/-2.3 ng/dL, respectively; P<.05), whereas plasma renin activity was increased only in the HCTZ group (0.9+/-0.2-1.7+/-0.2 ng/mL/h; P<.05). The increase in plasma aldosterone level after 12 weeks of HCTZ and IRBE+QUIN therapy suggests early aldosterone escape.

Irbesartan restores the in-vivo insulin signaling pathway leading to Akt activation in obese Zucker rats.

BACKGROUND: Angiotensin II (AII) has been shown to contribute to the pathogenesis of hypertension and insulin resistance. In addition, the administration of selective AII type 1 receptor blockers has been shown to improve insulin sensitivity. However, only a few studies have addressed the molecular mechanisms involved in this association. Furthermore, in a previous study we illustrated that obese Zucker rats (OZR) present increased serine 994 (Ser994) phosphorylation of hepatic insulin receptor, and this event seems to be implicated in the regulation of the intrinsic IRK in this model of insulin resistance. OBJECTIVE AND DESIGN: We examined the effects of chronic treatment with irbesartan (50 mg/kg a day for 6 months) on the hepatic insulin signaling system of OZR. METHODS: The extent of phosphorylation of several components of the insulin signaling system was assessed by immunoprecipitation, followed by immunoblotting with phosphospecific antibodies. In addition, liver AII levels and fat deposits were determined by immunohistochemistry and Oil red O, respectively. RESULTS: OZR displayed a marked attenuation in the in-vivo phosphorylation of several components of the insulin signaling pathways in the liver, together with significantly higher hepatic AII levels and hepatic steatosis when compared with lean Zucker rats. We found that in the livers of OZR long-term administration of irbesartan is associated with: (i) increased insulin-stimulated insulin receptor tyrosine phosphorylation; (ii) decreased insulin receptor Ser994 phosphorylation; (iii) augmented insulin receptor substrate (IRS) 1 and 2 abundance and tyrosine phosphorylation; (iv) augmented association between IRS and the p85 regulatory subunit of phosphatidylinositol 3-kinase; (v) increased insulin-induced Akt phosphorylation; and (vi) decreased hepatic steatosis. CONCLUSION: The present study provides substantial information that demonstrates that long-term selective AII blockade by irbesartan improves insulin signaling and is associated with decreased insulin receptor Ser994 phosphorylation in the liver of a representative animal model of the human metabolic syndrome.

Angiotensin II antagonists: clinical experience in the treatment of hypertension, prevention of cardiovascular outcomes and renal protection in diabetic nephropathy and proteinuria.

Angiotensin II antagonists (AIIAs) were introduced to treat hypertension about 10 years ago. During this period they were evaluated not only in terms of efficacy and safety but also in several large studies with clinical outcomes. They are efficacious in all clinical forms of hypertension and are effective also in all ethnic groups. Cardiovascular and renal protection in proteinuric diabetic nephropathy beyond blood pressure reduction was proved in major clinical studies: Losartan Intervention For Endpoint reduction in hypertension study (LIFE), Reduction of Endpoint in Non-Insulin dependent Diabetes Mellitus with the AII Antagonist Losartan (RENAAL) and Irbesartan Type 2 Diabetic Nephropathy Trial (IDNT). Their blood pressure independent protective effect is also mentioned by the blockade of AT1 receptor. As a class AIIs have a tolerability profile similar to placebo.

Effects of dual blockade of the renin angiotensin system in hypertensive type 2 diabetic patients with nephropathy.

AIM: To evaluate the effects of combined treatment of an ACE inhibitor and an angiotensin II receptor antagonist on parameters related to the progression of renal disease in type 2 diabetic patients. METHODS: 20 hypertensive type 2 diabetic patients with non-nephrotic proteinuria (0.5 - 3.0 g/day) and estimated creatinine clearance > or = 40 ml/min/1.73m2 were randomly assigned to be treated with perindopril 8 mg/day (Per), irbesartan 300 mg/day (Irb) or a combination of both with the same doses (Per + Irb). Each treatment phase lasting 16 weeks was preceded by a four-week washout period. Diuretics, clonidine and hydralazine were used as supplementary drugs for blood pressure control. Patients were evaluated at baseline and at the end of each treatment phase. RESULTS: 15 (3M/12F) patients completed all the phases. Use of Per, Irb and Per + Irb led to a reduction in 24-hour mean blood pressure of 6 mmHg, 4 mmHg and 4 mmHg, respectively. Changes in glomerular filtration rate were not significant at any phase. Renal plasma flow was significantly more elevated with Irb than Per. Treatment with both Irb and Per + Irb induced similar plasma renin elevation, but treatment with Per did not, suggesting escape. Plasma aldosterone was reduced only by treatment with Per + Irb (-36%, p < 0.02). Reduction in proteinuria during Per + Irb (-33%) was not significantly different from Per (-34%) or Irb (-22%). Urinary transforming growth factor beta1 (TGF-beta1) excretion was significantly reduced with both Irb (-24%, p < 0.05) and Per + Irb (-36%, p < 0.05) but not with Per (-11%, p = 0.60). CONCLUSION: Only combined therapy with irbesartan plus perindopril concurrently reduces plasma aldosterone, proteinuria and urinary TGF-beta1.

Irbesartan reduces creatinine clearance in type 1 diabetic children with renal hyperfunction: a randomized, double-blind, placebo-controlled trial.

BACKGROUND: Previous studies in type 2 diabetes have demonstrated the renoprotective effect of AT(1)-receptor antagonist drugs, but data on type 1 diabetic (T1DM) children are scarce. The aim of this study was to evaluate the effectiveness of the AT(1)-receptor antagonist irbesartan in reducing creatinine clearance rate (CCR) in non-hypertensive T1DM children with renal hyperfunction. METHODS: In this randomized, double-blind, placebo-controlled trial we enrolled 20 T1DM children aged 6-16 years and randomly allocated them to receive either irbesartan (1 mg/kg body weight) or placebo daily for 12 weeks. Children were eligible to participate if they had renal hyperfunction, defined as a CCR >20 ml/min/1.73 m(2) body surface area. In addition, the participants could not have high blood pressure or renal failure and they could not be receiving diuretics or angiotensin-converting enzyme inhibitors. The primary endpoint of the trial was the change in CCR. RESULTS: There were no significant differences in age, duration of diabetes or body mass index between the two groups. No subject dropped out, withdrew consent or had side effects or adverse events attributable to irbesartan or the placebo. In the irbesartan group, CCR decreased from 155.0+/-6.6 to 86.2+/-7.4 ml/min (P<0.0001); CCR did not change significantly in the control group (154.1+/-13.1 to 172.0+/-15.5 ml/min; P = 0.86). Blood pressures at baseline and throughout the study were similar in both groups. CONCLUSIONS: Irbesartan significantly reduces CCR in non-hypertensive, non-controlled T1DM children; the clinical significance of this finding, however, remains to be established.