Search

Exercise training lowers blood pressure and is a recommended nonpharmacological strategy and useful adjunctive therapy for hypertensive patients. Studies demonstrate that physical activity attenuates progression of hypertension. However, underlying mechanisms remain elusive. Vascular insulin resistance and endothelial dysfunction plays a critical role in the development of hypertension. The present study investigated whether long-term physical exercise starting during the prehypertensive period prevents the development of hypertension via improving vascular insulin sensitivity. Young (4 wk old) prehypertensive spontaneously hypertensive rats (SHRs) and their normotensive Wistar-Kyoto (WKY) control rats were subjected to a 10-wk free-of-loading swim training session (60 min/day, 5 days/wk). Blood pressure, mesenteric arteriolar vasorelaxation, G protein-coupled receptor kinase-2 (GRK2) expression and activity, and insulin-stimulated Akt/endothelial nitric oxide synthase (eNOS) activation were determined. SHRs had higher systolic blood pressure, systemic insulin resistance, and impaired vasodilator actions of insulin in resistance vessels when compared with WKY rats. Systolic blood pressure in SHRs postexercise was significantly lower than that in sedentary rats. Vascular insulin sensitivity in mesenteric arteries was improved after exercise training as evidenced by an increased vasodilator response to insulin. In addition, exercise downregulated vascular GRK2 expression and activity, which further increased insulin-stimulated vascular Akt/eNOS activation in exercised SHRs. Specific small interfering RNA knockdown of GRK2 in endothelium mimicked the effect of exercise-enhanced vascular insulin sensitivity. Likewise, upregulation of GRK2 by Chariot-mediated delivery opposed exercise-induced vascular insulin sensitization. Taken together, our results suggest that long-term exercise beginning at the prehypertensive stage improves vascular insulin sensitivity via downregulation of vascular GRK2 that may help to limit the progression of hypertension.

Background: We hypothesized that atorvastatin combined with amlodipine has additive beneficial vascular and metabolic effects that are superior to monotherapy in patients with hypertension., Methods: Forty-two patients were given atorvastatin 20mg/day and placebo, atorvastatin 20mg/day and amlodipine 10mg/day, or amlodipine 10mg/day and placebo during each 2-month treatment period of a randomized, single-blind, placebo-controlled cross-over trial with two 2-month washout periods., Results: Atorvastatin combined with amlodipine or amlodipine alone significantly reduced blood pressure to a greater extent than atorvastatin alone (all P < 0.001 by ANOVA). Atorvastatin combined with amlodipine significantly reduced plasma malondialdehyde and improved flow-mediated dilation to a greater extent than atorvastatin or amlodipine alone (all P < 0.001 by ANOVA). Atorvastatin therapy significantly increased insulin levels (P = 0.004) and decreased plasma adiponectin levels (P = 0.016) and insulin sensitivity (determined by QUICKI; P = 0.026) relative to baseline measurements. Amlodipine therapy significantly decreased insulin levels (P = 0.001) and increased adiponectin levels (P < 0.001) and insulin sensitivity (P = 0.003) relative to baseline measurements. Atorvastatin combined with amlodipine therapy significantly increased adiponectin levels (P < 0.001) and insulin sensitivity (P = 0.034) relative to baseline measurements. Effects of all three therapeutic arms on adiponectin levels and insulin sensitivity were statistically significant (P < 0.001 by ANOVA)., Conclusions: Atorvastatin combined with amlodipine therapy improves endothelial function and increases adiponectin levels and insulin sensitivity to a greater extent than monotherapy with either drug in hypertensive patients., (Copyright © 2009 Elsevier Ireland Ltd. All rights reserved.)

Background: ASCOT-BPLA study demonstrates that in hypertensive subjects, atenolol+bendroflumethiazide therapy is associated with higher incidence of adverse cardiovascular outcomes and developing diabetes than an amlodipine+perindopril regimen. This is not explained by changes in blood pressure alone. We hypothesized that distinct vascular and metabolic effects of anti-hypertensive drugs may explain these differential effects., Methods: Either placebo or one class of anti-hypertensive drug (atenolol 100 mg, amlodipine 10 mg, hydrochlorothiazide 50 mg, ramipril 10 mg, or candesartan 16 mg) was given daily during 8 weeks to 31 patients in each of 6 arms of a randomized, single-blind, placebo-controlled, parallel study., Results: Atenolol, amlodipine, and candesartan therapies significantly reduced systolic blood pressure when compared with ramipril (P<0.05 by ANOVA). Atenolol and thiazide therapies increased triglycerides levels greater than ramipril or candesartan (P=0.005 by ANOVA). Amlodipine significantly increased HDL cholesterol levels greater than atenolol (P=0.011 by ANOVA). Ramipril and candesartan therapies improved FMD and increased adiponectin levels and insulin sensitivity to a greater extent than atenolol or thiazide therapies (P<0.001 and P<0.015 by ANOVA). Amlodipine therapy increased adiponectin levels greater than atenolol therapy (P<0.05 by ANOVA). Ramipril, candesartan, and amlodipine therapies significantly decreased leptin levels to a greater extent when compared with atenolol or thiazide therapies (P<0.001 by ANOVA). Amlodipine therapies significantly decreased resistin levels greater than ramipril or candesartan therapies (P=0.001 by ANOVA)., Conclusions: We observed differential effects of anti-hypertensive drugs on endothelial dysfunction and plasma adipocytokines., (Copyright 2008 Elsevier Ireland Ltd. All rights reserved.)

Oxidative stress contributes to cardiovascular complications of diabetes, in part, by reducing the bioavailability of nitric oxide (NO). We investigated the mechanisms whereby the insulin sensitizer rosiglitazone may ameliorate oxidative stress in the vasculature of spontaneously hypertensive rats (SHR). Nine-week-old SHR were treated by gavage for 7 wk with rosiglitazone (5 mg x kg(-1) x day(-1)) or vehicle control. Treatment of SHR with rosiglitazone lowered systolic blood pressure, reduced fasting plasma insulin and asymmetrical dimethylarginine, and increased insulin sensitivity (when compared with vehicle treatment). In vessel homogenates and serum from rosiglitazone-treated SHR, SOD activity was enhanced, while 8-iso-PGF(2alpha) (lipid peroxidation product) was reduced (when compared with samples from vehicle-treated SHR). Moreover, expression of p22phox (catalytic subunit of NADPH oxidase) as well as nitrotyrosine and superoxide content were all reduced in the aortas of rosiglitazone-treated SHR. In mesenteric vascular beds (MVB) isolated ex vivo from rosiglitazone-treated SHR, NO-dependent vasodilator actions of insulin were improved when compared with MVB from vehicle-treated SHR. Acute pretreatment of MVB from vehicle-treated SHR with apocynin (NADPH oxidase inhibitor) enhanced vasodilator actions of insulin (results comparable to those in MVB from rosiglitazone-treated SHR). In Langendorff heart preparations from rosiglitazone-treated SHR, ischemia/reperfusion injury caused infarcts 40% smaller than in hearts from vehicle-treated SHR. Acute pretreatment of hearts from vehicle-treated SHR with apocynin produced similar results. Finally, rosiglitazone treatment of endothelial cells in primary culture reduced superoxide induced by insulin-resistant conditions. We conclude that rosiglitazone therapy in SHR increases SOD activity and decreases p22phox expression in the vasculature to reduce oxidant stress leading to an improved cardiovascular phenotype.

Background: Essential hypertension is characterized by reciprocal relations between endothelial dysfunction and insulin resistance. Cocoa flavanols stimulate production of the vasodilator nitric oxide from vascular endothelium., Objective: The objective was to test the hypothesis that consumption of cocoa may simultaneously lower blood pressure, improve endothelial dysfunction, and ameliorate insulin resistance in subjects with essential hypertension., Design: We conducted a randomized, placebo-controlled, double-blind, crossover trial of a flavanol-rich cocoa drink (150 mL twice a day, approximately 900 mg flavanols/d) in individuals with essential hypertension (n = 20). Antihypertensive medications were discontinued before study enrollment. After a 7-d cocoa-free run-in period, cocoa or flavanol-poor placebo (approximately 28 mg flavanols/d) treatment for 2 wk was followed by a 1-wk washout and then crossover to the other treatment arm. Blood pressure was measured thrice weekly. At baseline and after each treatment period, we assessed insulin sensitivity (hyperinsulinemic-isoglycemic glucose clamp) and insulin-stimulated changes in brachial artery diameter and forearm skeletal muscle capillary recruitment (Doppler ultrasound with or without microbubble contrast)., Results: Cocoa treatment for 2 wk increased insulin-stimulated changes in brachial artery diameter when compared with placebo [median percentage increase from baseline (25th-75th percentile): 8.3 (4.2-11.3) compared with 5.9 (-0.3 to 9.6); P < 0.04]. Nevertheless, cocoa treatment did not significantly reduce blood pressure or improve insulin resistance and had no significant effects on skeletal muscle capillary recruitment, circulating plasma concentrations of adipocytokines, or endothelial adhesion molecules., Conclusions: Daily consumption of flavanol-rich cocoa for 2 wk is not sufficient to reduce blood pressure or improve insulin resistance in human subjects with essential hypertension. This trial was registered at clinicaltrials.gov as NCT00099476.

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) are unequivocally useful for lowering cholesterol levels in patients with dyslipidemias characterized by elevations in total and/or low-density lipoprotein cholesterol. The beneficial effects of statins to lower serum cholesterol translate into significant reductions in cardiovascular morbidity and mortality. In addition to lowering cholesterol levels, statins have other biological effects relevant to cardiovascular homeostasis including anti-inflammatory actions and downregulation of angiotensin type 1 receptor expression that contribute to improvements in endothelial function and arterial compliance. Since endothelial dysfunction and reduced arterial compliance are important pathophysiological determinants of essential hypertension, these actions of statins raise the possibility that statin therapy may be useful for simultaneously treating dyslipidemias and hypertension. However, it has been unclear whether statins are effective in lowering blood pressure. This controversy stems from a variety of methodological limitations including inadequate sample size, confounding effects of antihypertensive drugs, differences in blood pressure measurement techniques, and differences in patient populations. However, based on published results from both small clinical studies and large randomized clinical trials, statins modestly lower blood pressure in patients with high, but not normal, blood pressure, regardless of cholesterol level.

Aims: Ramipril and candesartan have distinct mechanisms of action to improve endothelial function. Therefore, we hypothesized that combination therapy has additive beneficial effects to simultaneously improve endothelial dysfunction and adipocytokine profiles in patients with hypertension., Methods and Results: Thirty-four patients were given ramipril 10 mg and placebo, ramipril 10 mg and candesartan 16 mg, or candesartan 16 mg and placebo daily in a randomized, double-blind, placebo-controlled cross-over trial with three treatment arms and two washout periods (each 2 months). Ramipril, candesartan, or combination therapy reduced blood pressure, improved flow-mediated dilation, and increased plasma adiponectin levels when compared with baseline values. However, combination therapy improved these outcome measures to a greater extent than either ramipril or candesartan alone (P < 0.001 and P = 0.016 for systolic and diastolic blood pressure, P < 0.001 and P = 0.048 for flow-mediated dilation and adiponectin levels by ANOVA). In addition, combination therapy reduced plasma leptin levels to a greater extent than either ramipril or candesartan alone (P = 0.042 by ANOVA). There were correlations between percent changes in adiponectin levels and percent changes in insulin sensitivity (determined by QUICKI) (r = 0.319, P = 0.066) following ramipril therapy, percent changes in QUICKI (r = 0.374, P = 0.029) following combination therapy, and percent changes in QUICKI (r = 0.607, P < 0.001) following candesartan therapy., Conclusion: Ramipril in combination with candesartan improves blood pressure, endothelial function, and adipocytokine profiles to a greater extent than monotherapy with either drug in hypertensive patients.

The proinflammatory mediator CD40 ligand plays an important role in atherogenesis. Biological mechanisms underlying statin and angiotensin II type 1 receptor blocker therapies differ. Therefore, we compared the effects of these therapies either alone or in combination on plasma soluble CD40 ligand (sCD40L). This was a randomized, double-blind, placebo-controlled cross-over trial with three treatment arms (each 2 months) and two washout periods (each 2 months). Forty-seven hypertensive, hypercholesterolemic patients were given simvastatin 20mg and placebo, simvastatin 20mg and losartan 100mg, or losartan 100mg and placebo daily during each 2 month treatment period. Simvastatin alone did not significantly reduce sCD40L levels relative to baseline measurements when the entire cohort was analyzed. However, simvastatin significantly reduced sCD40L levels from 5.10+/-0.34 to 3.07+/-0.43ng/ml (P=0.002) in a subgroup of 18 patients with high baseline sCD40L levels >2.95ng/ml. Combined therapy or losartan alone significantly decreased plasma sCD40L levels relative to baseline measurements by 14+/-7% (P=0.001) and 13+/-10% (P=0.001), respectively. These decreases were significantly greater than those observed with simvastatin alone (P=0.023 by ANOVA). Significant inverse correlations between baseline sCD40L levels and percent changes in sCD40L levels were observed (r=-0.456, P=0.001 after simvastatin alone; r=-0.476, P<0.001 after combined therapy; r=-0.451, P=0.002 after losartan alone). Losartan alone or combined therapy significantly reduced plasma sCD40L levels more than simvastatin alone in our subjects. Simvastatin, losartan and combined therapy significantly reduced sCD40L to the greatest extent in patients with high baseline sCD40L levels.

Spontaneously hypertensive rats (SHRs) exhibit endothelial dysfunction and insulin resistance. Reciprocal relationships between endothelial dysfunction and insulin resistance may contribute to hypertension by causing imbalanced regulation of endothelial-derived vasodilators (e.g., nitric oxide) and vasoconstrictors (e.g., endothelin-1 [ET-1]). Treatment of SHRs with rosiglitazone (insulin sensitizer) and/or enalapril (ACE inhibitor) may simultaneously improve hypertension, insulin resistance, and endothelial dysfunction by rebalancing insulin-stimulated production of vasoactive mediators. When compared with WKY control rats, 12-week-old vehicle-treated SHRs were hypertensive, overweight, and insulin resistant, with elevated fasting levels of insulin and ET-1 and reduced serum adiponectin levels. In mesenteric vascular beds (MVBs) isolated from vehicle-treated SHRs and preconstricted with norepinephrine (NE) ex vivo, vasodilator responses to insulin were significantly impaired, whereas the ability of insulin to oppose vasoconstrictor actions of NE was absent (versus WKY controls). Three-week treatment of SHRs with rosiglitazone and/or enalapril significantly reduced blood pressure, insulin resistance, fasting insulin, and ET-1 levels and increased adiponectin levels to values comparable with those observed in vehicle-treated WKY controls. By restoring phosphatidylinositol 3-kinase-dependent effects, rosiglitazone and/or enalapril therapy of SHRs also significantly improved vasodilator responses to insulin in MVB preconstricted with NE ex vivo. Taken together, our data provide strong support for the existence of reciprocal relationships between endothelial dysfunction and insulin resistance that may be relevant for developing novel therapeutic strategies for the metabolic syndrome.

Background: Angiotensin II type 1 (AT1) receptor blocker therapy prevented or retarded the progression of coronary heart disease. The mechanisms of this benefit may relate to the ability of AT1 receptor blockers to reduce inflammation and insulin resistance., Methods: We administered placebo or candesartan 16 mg daily during 2 months to 45 patients with mild to moderate hypertension. This study was randomized, double-blind, placebo-controlled, crossover in design., Results: Candesartan therapy significantly lowered both systolic and diastolic blood pressure. Compared with placebo, candesartan therapy significantly lowered plasma hsCRP levels relative to baseline measurements from 1.10 to 0.70 mg/l (P=0.024) and soluble CD40 ligand levels by 30+/-11% (P<0.001). There were significant inverse correlations between body mass index and baseline plasma adiponectin levels (r=-0.480, P=0.009). There were significant correlations between baseline adiponectin levels and baseline insulin (r=-0.317, P=0.034) or baseline Quantitative Insulin-Sensitivity Check Index (QUICKI), a surrogate index of insulin sensitivity (r=0.371, P=0.012). Compared with placebo, candesartan therapy significantly lowered fasting insulin levels (P=0.011) and increased plasma levels of adiponectin by 15+/-4% (P=0.012) and increased QUICKI by 8+/-2% (P=0.007). There were significant correlations between percent changes in adiponectin levels and percent changes in insulin (r=-0.340, P=0.022) or QUICKI (r=0.325, P=0.029)., Conclusions: Candesartan therapy significantly reduced inflammation and increased adiponectin levels and improved insulin sensitivity in hypertensive patients.

Objective: Mechanisms underlying fibric acid and angiotensin II type 1 receptor blocker therapies differ. Signaling from peroxisome proliferator-activated receptor alpha may cross-talk with the angiotensin II system. We investigated vascular and metabolic responses to these therapies either alone or in combination in hypertriglyceridemic hypertensive patients., Research Design and Methods: This was a randomized, double-blind, placebo-controlled, cross-over trial with three treatment arms (each 2 months) and two washout periods (each 2 months). Forty-four patients were given 200 mg fenofibrate and placebo, 200 mg fenofibrate and 16 mg candesartan, or 16 mg candesartan and placebo daily during each treatment period., Results: Fenofibrate, combined therapy, or candesartan therapy significantly reduced blood pressure. However, combined therapy significantly reduced blood pressure more than fenofibrate or candesartan alone (P < 0.001 by ANOVA). When compared with candesartan, fenofibrate or combined therapy significantly improved the lipoprotein profile. All three treatment arms significantly improved flow-mediated dilator response to hyperemia. Combined therapy significantly decreased plasma malondialdehyde, high-sensitivity C-reactive protein, and soluble CD40L levels relative to baseline measurements. Importantly, these parameters were changed to a greater extent with combined therapy when compared with monotherapy (P < 0.001, P = 0.002, P = 0.050, and P = 0.032 by ANOVA, respectively). Fenofibrate, combined therapy, and candesartan significantly increased plasma adiponectin levels and insulin sensitivity relative to baseline measurements. However, the magnitude of these increases were not significantly different among the three therapies (P = 0.246 and P = 0.153 by ANOVA, respectively)., Conclusions: Fenofibrate combined with candesartan improves endothelial function and reduces inflammatory markers to a greater extent than monotherapy in hypertriglyceridemic hypertensive patients.

Insulin stimulates production of NO in vascular endothelium via activation of phosphatidylinositol (PI) 3-kinase, Akt, and endothelial NO synthase. We hypothesized that insulin resistance may cause imbalance between endothelial vasodilators and vasoconstrictors (e.g., NO and ET-1), leading to hypertension. Twelve-week-old male spontaneously hypertensive rats (SHR) were hypertensive and insulin resistant compared with control Wistar-Kyoto (WKY) rats (systolic blood pressure 202 +/- 11 vs. 132 +/- 10 mmHg; fasting plasma insulin 5 +/- 1 vs. 0.9 +/- 0.1 ng/ml; P < 0.001). In WKY rats, insulin stimulated dose-dependent relaxation of mesenteric arteries precontracted with norepinephrine (NE) ex vivo. This depended on intact endothelium and was blocked by genistein, wortmannin, or N(omega)-nitro-l-arginine methyl ester (inhibitors of tyrosine kinase, PI3-kinase, and NO synthases, respectively). Vasodilation in response to insulin (but not ACh) was impaired by 20% in SHR (vs. WKY, P < 0.005). Preincubation of arteries with insulin significantly reduced the contractile effect of NE by 20% in WKY but not SHR rats. In SHR, the effect of insulin to reduce NE-mediated vasoconstriction became evident when insulin pretreatment was accompanied by ET-1 receptor blockade (BQ-123, BQ-788). Similar results were observed during treatment with the MEK inhibitor PD-98059. In addition, insulin-stimulated secretion of ET-1 from primary endothelial cells was significantly reduced by pretreatment of cells with PD-98059 (but not wortmannin). We conclude that insulin resistance in SHR is accompanied by endothelial dysfunction in mesenteric vessels with impaired PI3-kinase-dependent NO production and enhanced MAPK-dependent ET-1 secretion. These results may reflect pathophysiology in other vascular beds that directly contribute to elevated peripheral vascular resistance and hypertension.

The quantitative insulin-sensitivity check index (QUICKI) has an excellent linear correlation with the glucose clamp index of insulin sensitivity (SI(Clamp)) that is better than that of many other surrogate indexes. However, correlation between a surrogate and reference standard may improve as variability between subjects in a cohort increases (i.e., with an increased range of values). Correlation may be excellent even when prediction of reference values by the surrogate is poor. Thus, it is important to evaluate the ability of QUICKI to accurately predict insulin sensitivity as determined by the reference glucose clamp method. In the present study, we used a calibration model to compare the ability of QUICKI and other simple surrogates to predict SI(Clamp). Predictive accuracy was evaluated by both root mean squared error of prediction as well as a more robust leave-one-out cross-validation-type root mean squared error of prediction (CVPE). Based on data from 116 glucose clamps obtained from nonobese, obese, type 2 diabetic, and hypertensive subjects, we found that QUICKI and log (homeostasis model assessment [HOMA]) were both excellent at predicting SI(Clamp) (CVPE = 1.45 and 1.51, respectively) and significantly better than HOMA, 1/HOMA, and fasting insulin (CVPE = 3.17, P < 0.001; 1.67, P < 0.02; and 2.85, P < 0.001, respectively). QUICKI and log(HOMA) also had the narrowest distribution of residuals (measured SI(Clamp) - predicted SI(Clamp)). In a subset of subjects (n = 78) who also underwent a frequently sampled intravenous glucose tolerance test with minimal model analysis, QUICKI was significantly better than the minimal model index of insulin sensitivity (SI(MM)) at predicting SI(Clamp) (CVPE = 1.54 vs. 1.98, P = 0.001). We conclude that QUICKI and log(HOMA) are among the most accurate surrogate indexes for determining insulin sensitivity in humans.

Background: Biological mechanisms underlying statin and angiotensin II type 1 receptor blocker therapies differ. Therefore, we compared vascular and metabolic responses to these therapies either alone or in combination in hypercholesterolemic, hypertensive patients., Methods and Results: This was a randomized, double-blind, placebo-controlled crossover trial with 3 treatment arms (each 2 months) and 2 washout periods (each 2 months). Forty-seven hypertensive, hypercholesterolemic patients were given simvastatin 20 mg and placebo, simvastatin 20 mg and losartan 100 mg, or losartan 100 mg and placebo daily during each 2-month treatment period. Losartan alone or combined therapy significantly reduced blood pressure compared with simvastatin alone. Compared with losartan alone, simvastatin alone or combined therapy significantly changed lipoproteins. All 3 treatment arms significantly improved flow-mediated dilator response to hyperemia and decreased plasma malondialdehyde and monocyte chemoattractant protein-1 levels relative to baseline measurements. However, these parameters were changed to a greater extent with combined therapy compared with simvastatin or losartan alone (both P<0.001 and P=0.030 for monocyte chemoattractant protein-1 by ANOVA). Combined therapy or losartan alone significantly increased plasma adiponectin levels and insulin sensitivity (determined by QUICKI) relative to baseline measurements. These changes were significantly greater than in the group treated with simvastatin alone (P<0.001 for adiponectin, P=0.029 for QUICKI by ANOVA)., Conclusions: Simvastatin combined with losartan improves endothelial function and reduces inflammatory markers to a greater extent than monotherapy with either drug in hypercholesterolemic, hypertensive patients.

Exercise training lowers blood pressure and is a recommended nonpharmacological strategy and useful adjunctive therapy for hypertensive patients. Studies demonstrate that physical activity attenuates progression of hypertension. However, underlying mechanisms remain elusive. Vascular insulin resistance and endothelial dysfunction plays a critical role in the development of hypertension. The present study investigated whether long-term physical exercise starting during the prehypertensive period prevents the development of hypertension via improving vascular insulin sensitivity. Young (4 wk old) prehypertensive spontaneously hypertensive rats (SHRs) and their normotensive Wistar-Kyoto (WKY) control rats were subjected to a 10-wk free-ofloading swim training session (60 min/day, 5 days/wk). Blood pressure, mesenteric arteriolar vasorelaxation, G protein-coupled receptor kinase-2 (GRK2) expression and activity, and insulin-stimulated Akt/ endothelial nitric oxide synthase (eNOS) activation were determined. SHRs had higher systolic blood pressure, systemic insulin resistance, and impaired vasodilator actions of insulin in resistance vessels when compared with WKY rats. Systolic blood pressure in SHRs postexercise was significantly lower than that in sedentary rats. Vascular insulin sensitivity in mesenteric arteries was improved after exercise training as evidenced by an increased vasodilator response to insulin. In addition, exercise downregulated vascular GRK2 expression and activity, which further increased insulin-stimulated vascular Akt/ eNOS activation in exercised SHRs. Specific small interfering RNA knockdown of GRK2 in endothelium mimicked the effect of exerciseenhanced vascular insulin sensitivity. Likewise, upregulation of GRK2 by Chariot-mediated delivery opposed exercise-induced vascular insulin sensitization. Taken together, our results suggest that long-term exercise beginning at the prehypertensive stage improves vascular insulin sensitivity via downregulation of vascular GRK2 that may help to limit the progression of hypertension. [ABSTRACT FROM AUTHOR]

Epigallocatechin gallate (EGCG), a bioactive polyphenol in green tea, may augment metabolic and vascular actions of insulin. Therefore, we investigated effects of EGCG treatment to simultaneously improve cardiovascular and metabolic function in spontaneously hypertensive rats (SHR; model of metabolic syndrome with hypertension, insulin resistance, and overweight). In acute studies, EGCG (1-100 µM) elicited dose-dependent vasodilation in mesenteric vascular beds (MVB) isolated from SHR ex vivo that was inhibitable by Nω-nitro-L-arginine methyl ester (L-NAME; nitric oxide synthase antagonist) or wortmannin [phosphatidylinositol (PI) 3-kinase inhibitor]. In chronic studies, 9-wk-old SHR were treated by gavage for 3 wk with EGCG (200 mg·kg-1·day-1), enalapril (30 mg·kg-1·day-1), or vehicle. A separate group of SHR receiving L-NAME (80 mg/I in drinking water) was treated for 3 wk with either EGCG or vehicle. Vasodilator actions of insulin were significantly improved in MVB from EGCG- or enalapril-treated SHR (when compared with vehicle-treated SHR). Both EGCG and enalapril therapy significantly lowered systolic blood pressure (SBP) in SHR. EGCG therapy of SHR significantly reduced infarct size and improved cardiac function in Langendorff-perfused hearts exposed to ischemia-reperfusion (I/R) injury. In SHR given L-NAME, beneficial effects of EGCG on SBP and I/R were not observed. Both enalapril and EGCG treatment of SHR improved insulin sensitivity and raised plasma adiponectin levels. We conclude that acute actions of EGCG to stimulate production of nitric oxide from endothelium using PI 3-kinase-dependent pathways may explain, in part, beneficial effects of EGCG therapy to simultaneously improve metabolic and cardiovascular pathophysiology in SHR. These findings may be relevant to understanding potential benefits of green tea consumption in patients with the metabolic syndrome. [ABSTRACT FROM AUTHOR]

Abstract: Background: Angiotensin II type 1 (AT1) receptor blocker therapy prevented or retarded the progression of coronary heart disease. The mechanisms of this benefit may relate to the ability of AT1 receptor blockers to reduce inflammation and insulin resistance. Methods: We administered placebo or candesartan 16 mg daily during 2 months to 45 patients with mild to moderate hypertension. This study was randomized, double-blind, placebo-controlled, crossover in design. Results: Candesartan therapy significantly lowered both systolic and diastolic blood pressure. Compared with placebo, candesartan therapy significantly lowered plasma hsCRP levels relative to baseline measurements from 1.10 to 0.70 mg/l (P =0.024) and soluble CD40 ligand levels by 30±11% (P <0.001). There were significant inverse correlations between body mass index and baseline plasma adiponectin levels (r =−0.480, P =0.009). There were significant correlations between baseline adiponectin levels and baseline insulin (r =−0.317, P =0.034) or baseline Quantitative Insulin-Sensitivity Check Index (QUICKI), a surrogate index of insulin sensitivity (r =0.371, P =0.012). Compared with placebo, candesartan therapy significantly lowered fasting insulin levels (P =0.011) and increased plasma levels of adiponectin by 15±4% (P =0.012) and increased QUICKI by 8±2% (P =0.007). There were significant correlations between percent changes in adiponectin levels and percent changes in insulin (r =−0.340, P =0.022) or QUICKI (r =0.325, P =0.029). Conclusions: Candesartan therapy significantly reduced inflammation and increased adiponectin levels and improved insulin sensitivity in hypertensive patients. [Copyright &y& Elsevier]

OBJECTIVE -- Mechanisms underlying fibric acid and angiotensin 11 type 1 receptor blocker therapies differ. Signaling from peroxisome proliferator-activated receptor α may cross-talk with the angiotensin II system. We investigated vascular and metabolic responses to these therapies either alone or in combination in hypertriglyceridemic hypertensive patients. RESEARCH DESIGN AND METHODS-- This was a randomized, double-blind, placebo-controlled, cross-over trial with three treatment arms (each 2 months) and two washout periods (each 2 months). Forty-four patients were given 200 mg fenofibrate and placebo, 200 mg fenofibrate and 16 mg candesartan, or 16 mg candesartan and placebo daily during each treatment period. RESULTS-- Fenofibrate, combined therapy, or candesartan therapy significantly reduced blood pressure. However, combined therapy significantly reduced blood pressure more than fenofibrate or candesartan alone (P < 0.001 by ANOVA). When compared with candesartan, fenofibrate or combined therapy significantly improved the lipoprotein profile. All three treatment arms significantly improved flow-mediated dilator response to hyperemia. Combined therapy significantly decreased plasma malondialdehyde, high-sensitivity C-reactive protein, and soluble CD40L levels relative to baseline measurements. Importantly, these parameters were changed to a greater extent with combined therapy when compared with monotherapy (P < 0.001, P = 0.002, P = 0.050, and P = 0.032 by ANOVA, respectively). Fenofibrate, combined therapy, and candesartan significantly increased plasma adiponectin levels and insulin sensitivity relative to baseline measurements. However, the magnitude of these increases were not significantly different among the three therapies (P = 0.246 and P = 0.153 by ANOVA, respectively). CONCLUSIONS-- Fenofibrate combined with candesartan improves endothelial function and reduces inflammatory markers to a greater extent than monotherapy in hypertriglyceridemic hypertensive patients. [ABSTRACT FROM AUTHOR]

Endothelial dysfunction is a hallmark of Type 2 diabetes related to hyperglycemia and oxidative stress. Nitric oxide-dependent vasodilator actions of insulin may augment glucose disposal. Thus endothelial dysfunction may worsen insulin resistance. Intra-arterial administration of vitamin C improves endothelial dysfunction in diabetes. In the present study, we investigated effects of high-dose oral vitamin C to alter endothelial dysfunction and insulin resistance in Type 2 diabetes. Plasma vitamin C levels in 109 diabetic subjects were lower than healthy (36 ± 2 µM) levels. Thirty-two diabetic subjects with low plasma vitamin C (<40 µM) were subsequently enrolled in a randomized, double-blind, placebo-controlled study of vitamin C (800 mg/day for 4 wk). Insulin sensitivity (determined by glucose clamp) and forearm blood flow in response to ACh, sodium mitroprusside (SNP), or insulin (determined by plethysmography) were assessed before and after 4 wk of treatment. In the placebo group (n = 17 subjects), plasma vitamin C (22 ± 3 µM), fasting glucose (159 ± 12 mg/dl), insulin (19 ± 7 µU/ml), and SIclamp [2.06 ± 0.29 × 10-4 dl·kg-1·min-1/(µU/ml)] did not change significantly after placebo treatment. In the vitamin C group (n = 15 subjects), basal plasma vitamin C (23 ± 2 µM) increased to 48 ± 6 µM (P < 0.01) after treatment, but this was significantly less than that expected for healthy subjects (>80 µM). No significant changes in fasting glucose (156 ± 11 mg/dl), insulin (14 ± 2 µU/ml), SIclamp [2.71 ± 0.46 × 10-4 dl·kg-1· min-1/(µU/ml)], or forearm blood flow in response to ACh, SNP, or insulin were observed after vitamin C treatment. We conclude that high-dose oral vitamin C therapy, resulting in incomplete replenishment of vitamin C levels, is ineffective at improving endothelial dysfunction and insulin resistance in Type 2 diabetes. [ABSTRACT FROM AUTHOR]

Insulin resistance may link disorders of metabolic homeostasis such as diabetes and obesity with disorders of hemodynamic homeostasis such as hypertension. Thus it is of interest to validate simple methods for quantifying insulin sensitivity in hypertensive patients. The quantitative insulin-sensitivity check index (QUICKI) is a novel mathematical transformation of fasting blood glucose and insulin levels. In obese and diabetic subjects, QUICKI has a significantly better linear correlation with glucose clamp determinations of insulin sensitivity than minimal-model estimates. To determine whether QUICKI is also useful in hypertensive subjects, we performed glucose clamps and frequently sampled intravenous glucose tolerance tests (FSIVGTT) on 27 hypertensive subjects taken off antihypertensive medication. Indexes of insulin sensitivity derived from glucose clamp studies (SI[sub Clamp]) were compared with QUICKI, minimal-model analysis of FSIVGTTs (SI[sub MM]), and homeostasis model assessment (HOMA). The correlation between QUICKI and SI[sub Clamp] (r = 0.84) was significantly better than that between SI[sub MM] and SI[sub Clamp] (r = 0.65; P < 0.028). The correlation between QUICKI and SI[sub Clamp] was comparable to that between 1/HOMA and SI[sub Clamp] (r = 0.82). When studies were repeated in 14 subjects who had resumed antihypertensive medications, the percent changes in SI[sub Clamp] for each of these patients were significantly correlated with percent changes in QUICKI (r = 0.61) and HOMA (r = -0.54) but not SI[sub MM] (r = -0.18). We conclude that QUICK is a simple, robust index of insulin sensitivity that is useful for evaluating and following the insulin resistance of hypertensive subjects in both research studies and clinical practice. [ABSTRACT FROM AUTHOR]