Telmisartan improves insulin resistance in high renin nonmodulating salt-sensitive hypertensives.

BACKGROUND: Nonmodulating (NMHT) is a high-renin subtype of salt sensitive hypertension, which additionally develops insulin resistance and oxidative stress. Conversely, modulating hypertensives (MHT) normally regulates renal hemodynamics after high sodium intake without metabolic impairment. We postulate that telmisartan, an angiotensin receptor blocker with partial peroxisome proliferators-activated receptorgamma partial agonist, may improve insulin resistance compared with ramipril, an angiotensin-converting enzyme inhibitor (ACEI) in NMHT. METHODS: We studied 18 NMTH (32 +/- 5y nine men, BMI 29 +/- 3 kg/m2) and 16 MHT (34 +/- 4, 10 men, BMI 28 +/- 5 kg/m2) before and after the crossover administration of ramipril 10 mg (3 months) or telmisartan 80 mg (3 months). In each patient studied we measured, before and after each treatment period, office blood pressure, glycemia and insulinemia before and 60 and 120 min after a glucose overload (75 g), total cholesterol, high-density lipoprotein and low-density lipoprotein fractions, triglycerides and highly sensitive C-protein-reactive protein. After that, HOMA-IR Index was calculated. RESULTS: Plasma renin activity was higher in NMHT 4.4 +/- 0.5 than MHT 2.6 +/- 0.9 ng.ml.h; P < 0.01. Blood pressure was similarly reduced either in MHT or NMHT by ramipril (MHT: from 159 +/- 10/102 +/- 4 to 142 +/- 6/93 +/- 3 mmHg, P < 0.05; NMHT: from 162 +/- 12/97 +/- 4 to 139 +/- 7/89 +/- 2 mmHg, P < 0.05) or telmisartan (MHT: from 154 +/- 8/96 +/- 5 to 137 +/- 6/88 +/- 4 mmHg, P < 0.05; NMHT: from 161 +/- 9/96 +/- 5 to 137 +/- 5/86 +/- 3 mmHg, P < 0.05). In NMHT, fasting glycemia (99 +/- 10 mg%) and insulinemia (16 +/- 4 microU%) and 120 min glycemia (110 +/- 2 mg%) and insulinemia (57 +/- 9 microU%) were higher than in MHT (fasting: 92 +/- 8 mg% and 9.2 +/- 2 mU%; 120 min: 95 +/- 5 and 21 +/- 5 microU%, P < 0.05). In MHT, after 3 months treatment with either ramipril or telmisartan no changes were found in fasting and 120 min glycemia and insulinemia. In NMHT, telmisartan, after 3 months treatment, significantly reduced fasting and 120 min insulinemia (fasting: 8.4 +/- 2, 120 min: 25 +/- 10 microU%; P < 0.01) compared either to basal values or ramipril treatment. Similarly, only in NMHT, compared with basal values and ramipril treatment, telmisartan improved the HOMA-IR index in both MHT (2.76 +/- 0.16 to 2.24 +/- 0.18, P < 0.05) and NMHT (from: 4.4 +/- 1 to 2.3 +/- 0.7) and triglyceride plasma levels (MHT: from 139 +/- 1.85 to 122 +/- 2.4 mg%, P < 0.05; NMHT: from: 223 +/- 12 to 146 +/- 10 mg%, P < 0.01). Finally, highly sensitive C-protein-reactive protein values were higher in NMHT (0.33 +/- 0.07 mg.dl) than in MHT (0.14 +/- 0.06 mg.dl; P < 0.01). Both treatments reduced highly sensitive C-protein-reactive protein in NMHT. (ramipril from 0.32 +/- 0.05 mg.dl to 0.26 +/- 0.06 m.dl (P < 0.05) and telmisartan from 0.34 +/- 0.05+/- to 0.20 +/- 0.05 mg.dl (P < 0.01). CONCLUSION: Our data suggest that the improvement of the insulin sensitivity by telmisartan, instead of a similar effect on blood pressure shown by both drugs, could be ascribed to the PPAR agonistic action of telmisartan. This opens an interesting therapeutic approach for patients with hypertension and altered glycemic metabolism.

Vascular oxidative stress is associated with insulin resistance in hyper-reninemic nonmodulating essential hypertension.

BACKGROUND: Nonmodulating hypertension (NMHT) is a high-renin subtype of salt-sensitive hypertension due to renal hemodynamic alterations. AIMS: To evaluate, in NMHT, whether the increased oxidative stress, which interferes with endothelial function, could be the consequence of an elevated renin-angiotensin activity and insulin resistance. METHODS: Fourteen patients with NMHT and 12 with modulating hypertension (MHT) were included. Plasma renin activity (PRA) and glucose/insulin tolerance test were performed and homeostasis model assessment (HOMA) index and areas under the curves (AUC) calculated. Urinary nitrites and nitrates (NOx), urinary cyclic guanosine monophosphate (cGMP) activity, urinary isoprostanes and plasma nitrotyrosine levels were also measured. RESULTS: PRA was higher in NMHT than MHT. In addition, L-arginine infusion increased effective renal plasma flow in MHT but not in NMHT. Insulin levels were higher in NMHT both at fasting and at 120 min, as were HOMA and AUC values. In MHT, NOx and cGMP significantly increased when moving from low to high Na+ intake, while nitrotyrosine mass and isoprostanes failed to show any change. On the contrary, in NMHT under low Na+ intake, urinary NOx levels were significantly higher than MHT under high Na+ intake, and failed to show any change under high Na intake; cGMP also failed to show any change when patients moved from low to high Na+ intake. Nitrotyrosine mass and isoprostanes, like to NOx, were significantly higher in NMHT under both low and high Na+ intake. CONCLUSIONS: It is suggested that, in NMHT, a possible association between higher renin-angiotensin system activity, insulin resistance and endothelial dysfunction, showed for the first time in the same subjects, might result in systemic vascular and renal endothelial dysfunction, salt-sensitive hypertension and high cardiovascular risk.

Mild hyperhomocysteinemia promotes renal hemodynamic dysfunction without histopathologic changes in adult rats.

BACKGROUND: Hyperhomocysteinemia is able to promote glomerular damage and generate tubulointerstitial lesions. These findings were reported in rats with unilateral nephrectomy or in weanling rats with normal function, two experimental models that are exposed to other concomitant vascular risk factors. The aim of this work is to study whether mild hyperhomocisteinemia per se can induce renal histopathologic changes in adults rats with normal renal function at either 10 or 44 weeks of hyperhomocysteinemia. METHODS: Two months old male Wistar rats (N= 52) were randomly allocated to either a normal control (N= 26) or hyperhomocysteinemic (N= 26) group. Control and hyperhomocysteinemic groups had free access to either tap water or homocysteine thiolactone 50 mg/kg/day, during 10 or 44 weeks. Plasma homocysteine levels were determined by a high-performance liquid chromatography (HPLC) method. Glomerular filtration rate (GFR) and renal plasma flow (RPF) were calculated from inulin and sodium para-aminohippurate (PAH) clearance determinations. Structural renal changes were investigated in kidneys fixed by perfusion. Histopathologic and morphometric analysis were carried out by standard methods. RESULTS: Plasma total homocysteine levels were 53% (10 weeks) and 56% (44 weeks) higher in hyperhomocysteinemic group compared to the control group. GFR and RPF were significantly lower in hyperhomocysteinemic than in control group. The histopathologic and morphometric studies did not show any differences between the control and hyperhomocysteinemic rats at 10 or 44 weeks. CONCLUSION: The present results show that mild hyperhomocysteinemia is able to induce renal functional and biochemical alterations in male adult rats that are not associated with renal histopathologic changes.

Hyperhomocysteinemia induces renal hemodynamic dysfunction: is nitric oxide involved?

Hyperhomocysteinemia is associated with endothelial dysfunction, although the underlying mechanism is unknown. Previous studies have shown that nitric oxide (NO) plays an important role in the regulation of systemic and renal hemodynamics. This study investigated whether hyperhomocysteinemia induces renal oxidative stress and promotes renal dysfunction involving disturbances of the NO-pathway in Wistar rats. During 8 wk, control (C) and hyperhomocysteinemic (HYC) groups had free access to tap water and homocysteine-thiolactone (HTL, 50 mg/kg per d), respectively. At 8 wk, plasma homocysteine concentration, renal superoxide anion (O(2)), nitrotyrosine, and nitrite+nitrate levels, and renal function were measured. To assess NO involvement, the responses to L-Arginine (L-Arg, 300 mg/kg) and N(G)-nitro-L-arginine-methyl-ester (L-NAME, 20 microg/kg per min for 60 min) were analyzed. The HYC group showed higher homocysteine concentration (7.6 +/- 1.7 versus 4.9 +/- 1.0 micromol/L; P < 0.001), (O(2) production (157.92 +/- 74.46 versus 91.17 +/- 29.03 cpm. 10(3)/mg protein), and nitrite+nitrate levels (33.4 +/- 5.1 versus 11.7 +/- 4.3 micro mol/mg protein; P < 0.001) than the control group. Western blot analyses showed a nitrotyrosine mass 46% higher in the HYC group than in the controls. Furthermore, the HYC group showed lower GFR, renal plasma flow (RPF), and higher renal vascular resistance (RVR) than the controls. After L-Arg administration, the responses of GFR, RPF, and RVR were attenuated by 36%, 40%, and 50%, respectively; after L-NAME, the responses of RPF and RVR were exaggerated by 79% and 112%, respectively. This suggests a reduced NO bioavailability to produce vasodilation and an enhanced sensitivity to NO inhibition. In conclusion, hyperhomocysteinemia induces oxidative stress, NO inactivation, and renal dysfunction involving disturbances on the NO-pathway.

Reproducibilidad de la cuantificacion de la sensibilidad a la accion insulinica con el modelo minimo y comparacion con un test de tolerancia a bajas dosis de insulina / Repeatibility of insulin sensitivity estimation using the Minimal Model and comparison with a modified short low-dose insulin tolerance test

La hiperinsulinemia y la insulino-resistencia son disturbios metabólicos associados a obesidad central, hipertensión arterial, hipertrigliceridemia, sindrome polimetabólico, intolerancia a la glucosa y enfermedad aterosclerótica. La evaluación de los cambios en la sensibilidad a la acción insulínica in vivo (SAI in vivo) inducidos por intervenciones higiénico-dietéticas o farmacológicas requieren una técnica de adecuada reproducibilidad. En el presente estudio fue evaluada la reproducibilidad intra-individual de la SAI in vivo expresada como SI (par metro determinado utilizando el Modelo Mínimo de Bergman modificado con insulina [MMins]), em 11 sujetos con un amplio rango de SAI in vivo. SI (primer estudio) varió entre 0,82 y 8,48 x 10(-4) min(-1)/muU.mL (4,43 + 2,85 x 10(-4) min(-1)/muU.ml; média + DS) y presentó una correlación altamente significativa con SI (segundo estudio) (r = 0,89; p = 0,0002). El coeficiente de variación medio fue del 20,9 + 13,9 por ciento). La SAI in vivo fue também determinada analizando la tasa de caída de los niveles de glucemia luego del suministro IV de 0,025 U/kg de insulina cristalina humana (método de Bonora modificado o BBD), en 11 sujetos. La SAI in vivo determinada por BBD varió entre 21 y 234 mumol/ml/min (134 + 64,8 mumol/ml/min, média + DS). No se observaron hipoglucemias durante los estudios. La correlación entre los valores de SI obtenidos del MMins y los resultados del BBD fue altamente significativa ( r= 0,89, p = 0,0002). Los resultados del presente trabajo sugieren que el MMins tiene una adecuada reproducibilidad intra-sujeto y que el BBD constituye una medida aproximada de la SAI in vivo siendo particularmente aplicable cuando es necesaria la practica de un procedimiento de r pida ejecución y menor complejidad y costo.

Reproducibilidad de la cuantificacion de la sensibilidad a la accion insulinica con el modelo minimo y comparacion con un test de tolerancia a bajas dosis de insulina / Repeatibility of insulin sensitivity estimation using the Minimal Model and comparison with a modified short low-dose insulin tolerance test

La hiperinsulinemia y la insulino-resistencia son disturbios metabólicos associados a obesidad central, hipertensión arterial, hipertrigliceridemia, sindrome polimetabólico, intolerancia a la glucosa y enfermedad aterosclerótica. La evaluación de los cambios en la sensibilidad a la acción insulínica in vivo (SAI in vivo) inducidos por intervenciones higiénico-dietéticas o farmacológicas requieren una técnica de adecuada reproducibilidad. En el presente estudio fue evaluada la reproducibilidad intra-individual de la SAI in vivo expresada como SI (par metro determinado utilizando el Modelo Mínimo de Bergman modificado con insulina [MMins]), em 11 sujetos con un amplio rango de SAI in vivo. SI (primer estudio) varió entre 0,82 y 8,48 x 10(-4) min(-1)/muU.mL (4,43 + 2,85 x 10(-4) min(-1)/muU.ml; média + DS) y presentó una correlación altamente significativa con SI (segundo estudio) (r = 0,89; p = 0,0002). El coeficiente de variación medio fue del 20,9 + 13,9 por ciento). La SAI in vivo fue também determinada analizando la tasa de caída de los niveles de glucemia luego del suministro IV de 0,025 U/kg de insulina cristalina humana (método de Bonora modificado o BBD), en 11 sujetos. La SAI in vivo determinada por BBD varió entre 21 y 234 mumol/ml/min (134 + 64,8 mumol/ml/min, média + DS). No se observaron hipoglucemias durante los estudios. La correlación entre los valores de SI obtenidos del MMins y los resultados del BBD fue altamente significativa ( r= 0,89, p = 0,0002). Los resultados del presente trabajo sugieren que el MMins tiene una adecuada reproducibilidad intra-sujeto y que el BBD constituye una medida aproximada de la SAI in vivo siendo particularmente aplicable cuando es necesaria la practica de un procedimiento de r pida ejecución y menor complejidad y costo. (AU)