Angiotensin Receptor Blocker Added to Previous Antihypertensive Agents on Arteries of Diabetic Hypertensive Patients

Microcirculation in Hypertension: A Therapeutic Target to Prevent Cardiovascular Disease?

Arterial hypertension is a common condition worldwide and an important risk factor for cardio- and cerebrovascular events, renal diseases, as well as microvascular eye diseases. Established hypertension leads to the chronic vasoconstriction of small arteries as well as to a decreased lumen diameter and the thickening of the arterial media or wall with a consequent increased media-to-lumen ratio (MLR) or wall-to-lumen ratio (WLR). This process, defined as vascular remodeling, was firstly demonstrated in small resistance arteries isolated from subcutaneous biopsies and measured by micromyography, and this is still considered the gold-standard method for the assessment of structural alterations in small resistance arteries; however, microvascular remodeling seems to represent a generalized phenomenon. An increased MLR may impair the organ flow reserve, playing a crucial role in the maintenance and, probably, also in the progressive worsening of hypertensive disease, as well as in the development of hypertension-mediated organ damage and related cardiovascular events, thus possessing a relevant prognostic relevance. New non-invasive techniques, such as scanning laser Doppler flowmetry or adaptive optics, are presently under development, focusing mainly on the evaluation of WLR in retinal arterioles; recently, also retinal microvascular WLR was demonstrated to have a prognostic impact in terms of cardio- and cerebrovascular events. A rarefaction of the capillary network has also been reported in hypertension, which may contribute to flow reduction in and impairment of oxygen delivery to different tissues. These microvascular alterations seem to represent an early step in hypertension-mediated organ damage since they might contribute to microvascular angina, stroke, and renal dysfunction. In addition, they can be markers useful in monitoring the beneficial effects of antihypertensive treatment. Additionally, conductance arteries may be affected by a remodeling process in hypertension, and an interrelationship is present in the structural changes in small and large conductance arteries. The review addresses the possible relations between structural microvascular alterations and hypertension-mediated organ damage, and their potential improvement with antihypertensive treatment.

State of the Art Review: Vascular Remodeling in Hypertension

Although the gold-standard method for the assessment of structural alteration in small resistance arteries is the evaluation of the MLR by micromyography in bioptic tissues, new, noninvasive techniques are presently under development, focusing mainly on the evaluation of WLR in retinal arterioles. These approaches represent a promising and interesting future perspective. Appropriate antihypertensive treatment is able to prevent the development of microvascular alterations or to induce their regression. Also, conductance arteries may be affected by a remodeling process in hypertension, and a cross-talk may exist between structural changes in the small and large arteries. In conclusion, the evaluation of microvascular structure is ready for clinical prime time, and it could, in the future, represent an evaluation to be performed in the majority of hypertensive patients, to better stratify cardiovascular risk and better evaluate the effects of antihypertensive therapy. However, for this purpose, we need a clear demonstration of the prognostic relevance of noninvasive measures of microvascular structure, in basal conditions and during treatment. Vascular remodeling may be frequently observed in hypertension, as well as in obesity and diabetes mellitus. An increased media to lumen ratio (MLR) or wall to lumen ratio (WLR) in microvessels is the hallmark of hypertension, and may impair organ flow reserve, being relevant in the maintenance and, probably, also in the progressive worsening of hypertensive disease, as well as in the development of hypertension-mediated organ damage/cardiovascular events. The molecular mechanisms underlying the development of vascular remodeling are only partly understood.

Assessment and pathophysiology of microvascular disease: recent progress and clinical implications

The development of novel, non-invasive techniques and standardization of protocols to assess microvascular dysfunction have elucidated the key role of microvascular changes in the evolution of cardiovascular (CV) damage, and their capacity to predict an increased risk of adverse events. These technical advances parallel with the development of novel biological assays that enabled the ex vivo identification of pathways promoting microvascular dysfunction, providing novel potential treatment targets for preventing cerebral-CV disease. In this article, we provide an update of diagnostic testing strategies to detect and characterize microvascular dysfunction and suggestions on how to standardize and maximize the information obtained from each microvascular assay. We examine emerging data highlighting the significance of microvascular dysfunction in the development CV disease manifestations. Finally, we summarize the pathophysiology of microvascular dysfunction emphasizing the role of oxidative stress and its regulation by epigenetic mechanisms, which might represent potential targets for novel interventions beyond conventional approaches, representing a new frontier in CV disease reduction.

Oxidative Stress and Vascular Damage in the Context of Obesity: The Hidden Guest

The vascular system plays a central role in the transport of cells, oxygen and nutrients between different regions of the body, depending on the needs, as well as of metabolic waste products for their elimination. While the structure of different components of the vascular system varies, these structures, especially those of main arteries and arterioles, can be affected by the presence of different cardiovascular risk factors, including obesity. This vascular remodeling is mainly characterized by a thickening of the media layer as a consequence of changes in smooth muscle cells or excessive fibrosis accumulation. These vascular changes associated with obesity can trigger functional alterations, with endothelial dysfunction and vascular stiffness being especially common features of obese vessels. These changes can also lead to impaired tissue perfusion that may affect multiple tissues and organs. In this review, we focus on the role played by perivascular adipose tissue, the activation of the renin-angiotensin-aldosterone system and endoplasmic reticulum stress in the vascular dysfunction associated with obesity. In addition, the participation of oxidative stress in this vascular damage, which can be produced in the perivascular adipose tissue as well as in other components of the vascular wall, is updated.

Effect of direct renin inhibition on vascular function after long-term treatment with aliskiren in hypertensive and diabetic patients

OBJECTIVE

We tested the hypothesis that chronic treatment with the direct renin inhibitor aliskiren improves vascular function in resistance and conduit arteries of type two diabetic and hypertensive patients.

METHOD

Sixteen patients with mild essential hypertension and with a previous diagnosis of noninsulin-dependent diabetes mellitus were included in the study. Patients were then randomized to aliskiren (150 mg once daily, n = 9), or ramipril (5 mg once daily, n = 7). Each patient underwent a biopsy of the subcutaneous tissue and small arteries were dissected and mounted on a pressurized micromyograph to evaluate endothelium dependent vasorelaxation in response to acetylcholine ± N omega-nitro-L-arginine methyl ester hydrochloride in vessels precontracted with norepinephrine. Endothelial function has been quantified also in large conduit arteries by flow-mediated dilation.

RESULTS

A similar office blood pressure-lowering effect was observed with the two drugs, although changes in DBP were not statistically significant in the ramipril group. Aliskiren significantly improved endothelium-dependent relaxation in subcutaneous resistance arteries, as well as increased flow-mediated dilation in conduit arteries, whereas the effects induced by ramipril did not reach statistical significance. Only aliskiren significantly increased the expression of p1177-endothelial nitric oxide synthase in the endothelium. Both aliskiren and ramipril had a negligible effect on markers of oxidative stress.

CONCLUSION

Aliskiren restored endothelial function and induced a more prompt peripheral vasodilation in hypertensive and diabetic patients possibly through the increased production of nitric oxide via the enhanced expression and function of the active phosphorylated form of endothelial nitric oxide synthase.

Potential Protective Role of Blood Pressure-Lowering Drugs on the Balance between Hemostasis and Fibrinolysis in Hypertensive Patients at Rest and During Exercise

In patients with hypertension, the triad represented by endothelial dysfunction, platelet hyperactivity, and altered fibrinolytic function disturbs the equilibrium between hemostasis and fibrinolysis and translates into a hypercoagulable state, which underlies the risk of thrombotic complications. This article reviews the scientific evidence regarding some biological effects of antihypertensive drugs, which can protect patients from the adverse consequences of hypertensive disease, improving endothelial function, enhancing antioxidant activity, and restoring equilibrium between hemostatic and fibrinolytic factors. These protective effects appear not to be mediated through blood pressure reduction and are not shared by all molecules of the same pharmacological class.

Age- and Sex-Specific Reference Values for Media/Lumen Ratio in Small Arteries and Relationship With Risk Factors

Small-artery remodeling is an early feature of target organ damage in hypertension and retains a negative prognostic value. The aim of the study is to establish age- and sex-specific reference values for media/lumen in small arteries obtained in humans by biopsy. Data from 91 healthy individuals and 200 individuals with cardiovascular risk factors in primary prevention from 4 Italian centers were pooled. Sex-specific equations for media/lumen in the healthy subpopulation, with age as dependent variable, were calculated. These equations were used to calculate predicted media/lumen values in individuals with risk factors and Z scores. The association between classical risk factors and Z scores was then explored by multiple regression analysis. A second-degree polynomial equation model was chosen to obtain sex-specific equations for media/lumen, with age as dependent variable. In the population with risk factors (111 men, age 50.5±14.0 years, hypertension 80.5%), media/lumen Z scores were independently associated with body mass index (standardized β=0.293, P=0.0001), total cholesterol (β=0.191, P=0.031), current smoking (β=0.238, P=0.0005), fasting blood glucose (β=0.204, P=0.003), systolic blood pressure (β=0.233, P=0.023), and female sex (β=0.799, P=0.038). A significant interaction between female sex and total cholesterol was found (β=-0.979, P=0.014). Results were substantially similar in the hypertensive subgroup. A method to calculate individual values of remodeling and growth index based on reference values was also presented. Age- and sex-specific percentiles of media/lumen in a healthy population were estimated. In a predominantly hypertensive population, media/lumen Z scores were associated with major cardiovascular risk factors, including body mass index, cholesterol, smoking, glucose, and systolic blood pressure. Significant sex differences were observed.

Microvascular structure as a prognostically relevant endpoint

Remodelling of subcutaneous small resistance arteries, as indicated by an increased media-to-lumen ratio, is frequently present in hypertensive, obese, or diabetic patients. The increased media-to-lumen ratio may impair organ flow reserve. This may be important in the maintenance and, probably, also in the progressive worsening of hypertensive disease. The presence of structural alterations represents a prognostically relevant factor, in terms of development of target organ damage or cardiovascular events, thus allowing us a prediction of complications in hypertension. In fact, media-to-lumen ratio of small arteries at baseline, and possibly their changes during treatment may have a strong prognostic significance. However, new, non-invasive techniques are needed before suggesting extensive application of the evaluation of remodelling of small arteries for the cardiovascular risk stratification in hypertensive patients. Some new techniques for the evaluation of microvascular morphology in the retina, currently under clinical investigation, seem to represent a promising and interesting future perspective. The evaluation of microvascular structure is progressively moving from bench to bedside, and it could represent, in the near future, an evaluation to be performed in all hypertensive patients, to obtain a better stratification of cardiovascular risk, and, possibly, it might be considered as an intermediate endpoint in the evaluation of the effects of antihypertensive therapy, provided that a demonstration of a prognostic value of non-invasive measures of microvascular structure is made available.

c-Src Inhibition Improves Cardiovascular Function but not Remodeling or Fibrosis in Angiotensin II–Induced Hypertension

c-Src plays an important role in angiotensin II (Ang II) signaling. Whether this member of the Src family kinases is involved in the development of Ang II–induced hypertension and associated cardiovascular damage in vivo remains unknown. Here, we studied Ang II–infused (400 ng/kg/min) mice in which c-Src was partially deleted ( c-Src +/− ) and in wild-type (WT, c-Src +/+ ) mice treated with a c-Src inhibitor (CGP077675; 25 mg/kg/d). Ang II increased blood pressure and induced endothelial dysfunction in WT mice, responses that were ameliorated in c-Src +/− and CGP077675-treated mice. Vascular wall thickness and cross-sectional area were similarly increased by Ang II in WT and c-Src +/− mice. CGP077675 further increased cross-sectional area in hypertensive mice. Cardiac dysfunction (ejection fraction and fractional shortening) in Ang II–infused WT mice was normalized in c-Src +/− mice. Increased oxidative stress (plasma thiobarbituric acid–reactive substances, hydrogen peroxide, and vascular superoxide generation) in Ang II–infused WT mice was attenuated in c-Src–deficient and CGP077675-treated mice. Hyperactivation of vascular c-Src, ERK1/2 (extracellular signal–regulated kinase 1/2), and JNK (c-Jun N-terminal kinase) in hypertensive mice was normalized in CGP077675-treated and c-Src +/− mice. Vascular fibronectin was increased by Ang II in all groups and further augmented by CGP077675. Cardiac fibrosis and inflammation induced by Ang II were amplified in c-Src +/− and CGP-treated mice. Our data indicate that although c-Src downregulation attenuates development of hypertension, improves endothelial and cardiac function, reduces oxidative stress, and normalizes vascular signaling, it has little beneficial effect on fibrosis. These findings suggest a divergent role for c-Src in Ang II–dependent hypertension, where c-Src may be more important in regulating redox-sensitive cardiac and vascular function than fibrosis and remodeling.

Effect of aliskiren on vascular remodelling in small retinal circulation

BACKGROUND

In hypertension, changes in small arterial structure are characterized by an increased wall-to-lumen ratio (WLR). These adaptive processes are modulated by the rennin-angiotensin system. It is unclear whether direct renin inhibitors exert protective effects on small arteries in hypertensive patients.

METHODS

In this double-blind, randomized, placebo-controlled study (http://www.clinicaltrials.gov: NCT01318395), 114 patients with primary hypertension were randomized to additional therapy with either placebo or aliskiren 300 mg for 8 weeks after 4 weeks of standardized open-label treatment with valsartan 320 mg (run-in phase). Parameter of arteriolar remodelling was WLR of retinal arterioles (80 - 140 μm) assessed noninvasively and in vivo by scanning laser Doppler flowmetry (Heidelberg Engineering, Germany). In addition, pulse wave analysis (SphygmoCor, AtCor Medical, Australia) and pulse pressure (PP) amplification were determined.

RESULTS

In the whole study population, no clear effect of additional therapy with aliskiren on vascular parameters was documented. When analyses were restricted to patients with vascular remodelling, defined by a median of WLR more than 0.3326 (n = 57), WLR was reduced after 8 weeks by the treatment with aliskiren compared with placebo (-0.044 ± 0.07 versus 0.0043 ± 0.07, P = 0.015). Consistently, after 8 weeks of on-top treatment with aliskiren, there was an improvement of PP amplification compared with placebo (0.025 ± 0.07 versus -0.034 ± 0.08, P = 0.013), indicative of less stiff arteries in the peripheral circulation.

CONCLUSION

Thus, our data indicate that treatment with aliskiren, given on top of valsartan therapy, improves altered vascular remodelling in hypertensive patients.

The structural factor of hypertension: large and small artery alterations

Pathophysiological studies have extensively investigated the structural factor in hypertension, including large and small artery remodeling and functional changes. Here, we review the recent literature on the alterations in small and large arteries in hypertension. We discuss the possible mechanisms underlying these abnormalities and we explain how they accompany and often precede hypertension. Finally, we propose an integrated pathophysiological approach to better understand how the cross-talk between large and small artery changes interacts in pressure wave transmission, exaggerates cardiac, brain and kidney damage, and lead to cardiovascular and renal complications. We focus on patients with essential hypertension because this is the most prevalent form of hypertension, and describe other forms of hypertension only for contrasting their characteristics with those of uncomplicated essential hypertension.

Interactions between macro- and micro-circulation: are they relevant?

Macrovasculature, microvasculature, and the heart are the main determinants of the structure and function of the circulatory system. Due to viscoelastic properties of large arteries, the pulsatile pressure and flow that result from intermittent ventricular ejection are smoothed out, so that microvasculature mediates steadily the delivery of nutrients and oxygen to tissues. The disruption of this function, which occurs when microvascular structure develops, mainly in response to hypertension, leads to end-organ damage. Microvascular structure is not only the site of vascular resistance but probably also the origin of most of the wave reflections generating increased central systolic blood pressure in the elderly. Many data of the literature suggest that hypertension-related damage to the micro and macrovascular system may be corrected by pharmacological agents. Among them, β-blocking agents and diuretics have a negligible effect on microvascular structure, while renin-angiotensin system antagonists and calcium entry blockers have favorable actions, improving large artery mechanics and possibly reducing central wave reflections. Central pulse pressure, indicative of changes in large conduit arteries is an independent determinant of vascular remodelling in small resistance arteries and might represent a main target of antihypertensive treatment.

Effects of a Long-Term Treatment With Aliskiren or Ramipril on Structural Alterations of Subcutaneous Small-Resistance Arteries of Diabetic Hypertensive Patients

Structural alterations of subcutaneous small-resistance arteries are associated with a worse clinical prognosis in hypertension and non–insulin-dependent diabetes mellitus. The effects of the direct renin inhibitor aliskiren on microvascular structure were never previously evaluated. Therefore, we investigated the effects of aliskiren in comparison with those of an extensively used angiotensin-converting enzyme inhibitor, ramipril, on peripheral subcutaneous small-resistance artery morphology, retinal arteriolar structure, and capillary density in a population of patients with non–insulin-dependent diabetes mellitus. Sixteen patients with mild essential hypertension and with a previous diagnosis of non–insulin-dependent diabetes mellitus were included in the study. Patients were then randomized to 1 of the 2 active treatments (aliskiren 150 mg once daily, n=9; or ramipril 5 mg once daily, n=7). Each patient underwent a biopsy of the subcutaneous fat from the gluteal region, an evaluation of retinal artery morphology (scanning laser Doppler flowmetry), and capillary density (capillaroscopy), at baseline and after 1 year of treatment. Subcutaneous small arteries were dissected and mounted on a pressurized micromyograph, and the media-to-lumen ratio was evaluated. A similar office blood pressure–lowering effect and a similar reduction of the wall-to-lumen ratio of retinal arterioles were observed with the 2 drugs. Aliskiren significantly reduced media-to-lumen ratio of subcutaneous small-resistance arteries, whereas ramipril-induced reduction of media to lumen ratio was not statistically significant. No relevant effect on capillary density was observed. In conclusion, treatment with aliskiren or ramipril was associated with a correction of microvascular structural alterations in patients with non–insulin-dependent diabetes mellitus.

The renin-angiotensin system in adipose tissue and its metabolic consequences during obesity

Obesity is a worldwide disease that is accompanied by several metabolic abnormalities such as hypertension, hyperglycemia and dyslipidemia. The accelerated adipose tissue growth and fat cell hypertrophy during the onset of obesity precedes adipocyte dysfunction. One of the features of adipocyte dysfunction is dysregulated adipokine secretion, which leads to an imbalance of pro-inflammatory, pro-atherogenic versus anti-inflammatory, insulin-sensitizing adipokines. The production of renin-angiotensin system (RAS) components by adipocytes is exacerbated during obesity, contributing to the systemic RAS and its consequences. Increased adipose tissue RAS has been described in various models of diet-induced obesity (DIO) including fructose and high-fat feeding. Up-regulation of the adipose RAS by DIO promotes inflammation, lipogenesis and reactive oxygen species generation and impairs insulin signaling, all of which worsen the adipose environment. Consequently, the increase of circulating RAS, for which adipose tissue is partially responsible, represents a link between hypertension, insulin resistance in diabetes and inflammation during obesity. However, other nutrients and food components such as soy protein attenuate adipose RAS, decrease adiposity, and improve adipocyte functionality. Here, we review the molecular mechanisms by which adipose RAS modulates systemic RAS and how it is enhanced in obesity, which will explain the simultaneous development of metabolic syndrome alterations. Finally, dietary interventions that prevent obesity and adipocyte dysfunction will maintain normal RAS concentrations and effects, thus preventing metabolic diseases that are associated with RAS enhancement.

Small artery structure during antihypertensive therapy is an independent predictor of cardiovascular events in essential hypertension

OBJECTIVE

Structural changes of small resistance arteries occur early in the disease process of essential hypertension and predict cardiovascular events in previously untreated patients. We investigated whether on-treatment small artery structure also identifies patients at elevated risk despite normalization of blood pressure (BP).

METHODS

We conducted a long-term follow-up survey of cardiovascular events in 134 moderate-risk patients with 9-12 months of well treated essential hypertension. All participants underwent subcutaneous biopsies with determination of small artery structure in terms of media to lumen ratio (M : L) before and during treatment.

RESULTS

After 9-12 months of treatment SBP was lowered from 164 ± 15 to 134 ± 14 mmHg (P < 0.01) and M : L reduced from 0.084 ± 0.028 to 0.075 ± 0.024 (P < 0.01). Mean follow-up hereafter was 15 years representing a total of 2035 years for the entire cohort. During this period 47 patients suffered a predefined cardiovascular event. For patients with on-treatment M : L above the mean value of the cohort (≥0.075), the hazard ratio was 2.14 [95% confidence interval (CI) 1.19-3.84, P = 0.01] and also those with M : L above mean +2SD of a normotensive population (≥0.098) had an elevated risk (hazard ratio 2.99, 95% CI 1.60-5.58, P < 0.01). Both results were adjusted for heart score (a 10-year mortality risk estimate integrating age, sex, smoking status, cholesterol level and SBP). Analysis of changes in M : L during treatment showed significantly higher event rates among patients with increased M : L and vice versa (hazard ratio 1.36 per 25% change, 95% CI 1.07-1.73, P = 0.013).

CONCLUSION

On-treatment small artery structure identifies individuals still at increased cardiovascular risk despite long-term BP normalization and may be an additional target for therapy to prevent cardiovascular events.

The direct renin inhibitor aliskiren improves vascular remodelling in transgenic rats harbouring human renin and angiotensinogen genes

In the present study, we tested the hypothesis that chronic treatment with the direct rennin inhibitor aliskiren improves the remodelling of resistance arteries in dTGR (double-transgenic rats). dTGR (5 weeks) were treated with aliskiren (3 mg/kg of body mass per day) or ramipril (1 mg/kg of body mass per day) for 14 days and compared with age-matched vehicle-treated dTGR. BP (blood pressure) was similarly reduced in both aliskiren-treated and ramipril-treated rats compared with control dTGR (167±1 and 169±2 mmHg compared with 197±4 mmHg respectively; P<0.05). The M/L (media-to-lumen) ratio assessed on pressurized preparations was equally reduced in aliskiren-treated and ramipril-treated rats compared with controls (6.3±0.5 and 6.4±0.2% compared with 9.8±0.4% respectively; P<0.05). Endothelium-dependent and -independent relaxations were similar among the groups. L-NAME (NG-nitro-L-arginine methyl ester) significantly reduced acetylcholine-induced dilation in drug-treated dTGR. This effect was significantly more prominent in aliskiren-treated rats. eNOS (endothelial NO synthase) expression showed a 2-fold increase only in aliskiren-treated dTGR as compared with controls (P<0.01) and ramipril-treated dTGR (P<0.05). Plasma nitrite, as an index of NO production, was significantly increased in dTGR treated with either aliskiren or ramipril compared with controls. Only aliskiren induced a 2-fold increase in plasma nitrite, which was significantly greater than that induced by ramipril (P<0.05). gp91phox expression and ROS (reactive oxygen species) production in aorta were significantly and similarly reduced by both drugs. In conclusion, equieffective hypotensive doses of aliskiren or ramipril reduced the M/L ratio of mesenteric arteries and improved oxidative stress in dTGR. However, only aliskiren increased further NO production in the vasculature. Hence, in dTGR, direct renin inhibition induces favourable effects similar to that induced by ACE (angiotensin-converting enzyme) inhibition in improving vascular remodelling through different mechanisms.

Circulating endothelial progenitor cells, microvascular density and fibrosis in obesity before and after bariatric surgery

It is not known whether, in obesity, the capillary density or the number of circulating endothelial progenitor cells (EPCs) are reduced, or whether fibrosis of small vessels is also present. In addition, possible effects of weight reduction on these parameters have never been evaluated. Therefore, we investigated EPCs and capillary density in 25 patients with severe obesity, all submitted to bariatric surgery, and in 18 normotensive lean subjects and 12 hypertensive lean patients as controls. All patients underwent a biopsy of subcutaneous fat during bariatric surgery. In five patients, a second biopsy was obtained after consistent weight loss, about 1 year later, during a surgical intervention for abdominoplasty. EPCs and capillary density were reduced in obesity, and EPCs were significantly increased after weight reduction. Vascular collagen content was clearly increased in obese patients. No significant difference in vascular collagen was observed between normotensive obese patients and hypertensive obese patients. After pronounced weight reduction, collagen content was nearly normalized. No difference in stress-strain relation was observed among groups or before and after weight loss. In conclusion, our data suggest that microvascular rarefaction occurs in obesity. EPCs were significantly reduced in obese patients. Pronounced weight loss induced by bariatric surgery seems to induce a significant improvement of EPC number, but not of capillary rarefaction. A pronounced fibrosis of subcutaneous small resistance arteries is present in obese patients, regardless of the presence of increased blood pressure values. Consistent weight loss induced by bariatric surgery may induce an almost complete regression of microvascular fibrosis.

Increased inflammatory biomarkers in hypertensive type 2 diabetic patients: improvement after angiotensin II type 1 receptor blockade

Diabetes and hypertension increasingly are recognized as pro-inflammatory conditions. We tested the hypothesis that in patients with hypertension and type 2 diabetes, blood pressure (BP) reduction with an angiotensin receptor blocker (ARB), valsartan, or with a beta blocker, atenolol, is associated with a decreased inflammatory response. Normotensive subjects and hypertensive patients with type 2 diabetes (40 to 70 years of age) participated in the study. Patients (n = 28) were randomized to double-blind treatment for 1 year with valsartan (80-160 mg) or atenolol (50-100 mg) daily, added to previous therapy. Age-matched controls (n = 12) were also studied. Serum levels of cytokines (IL-6, IL-18), chemokines (MCP-1), and adhesion molecules (sICAM, sE-selectin) were measured by enzyme-linked immunosorbent assay (ELISA) as indices of systemic and vascular inflammation, before and 1 year after treatment. BP was similarly reduced by valsartan and atenolol. Glycemic control and lipid profiles were comparable in the two groups and did not change significantly with antihypertensive therapy. Serum levels of all inflammatory markers were increased in patients before treatment (by two- to four-fold vs. controls, P < .05). IL-6, IL-18, sICAM, and MCP-1 levels were reduced by valsartan (three-fold, P < .05). Only IL-18 was reduced by atenolol compared with pretreatment levels (P < .05). These data indicate that proinflammatory mediators are significantly increased in hypertensive type 2 diabetic patients and that despite similar BP lowering by valsartan and atenolol and similar glucose levels in both treated groups, global inflammatory status was improved only in the valsartan group. Our findings suggest that antihypertensive treatment, particularly with an ARB, ameliorates inflammatory processes in diabetic hypertensive patients. Such effects, which are independent of BP and glycemic control, may contribute to cardiovascular protection.

Endothelial dysfunction and cardiovascular disease in early-stage chronic kidney disease: cause or association?

Chronic kidney disease (CKD) is strongly associated with cardiovascular disease (CVD); a graded inverse relationship between estimated glomerular filtration rate (eGFR) and cardiovascular event rates has emerged from large-scale observational studies. Chronic kidney disease is also associated with endothelial dysfunction (ED) although the precise relationship with GFR and the "threshold" at which ED begins are contentious. Abnormal endothelial function is certainly present in late-stage CKD but data in early-stage CKD appear confounded by disease states such as diabetes and hypertension which themselves promote ED. Thus, the direct effect of a reduction in GFR on endothelial function and, therefore, cardiovascular (CV) risk is far from completely established. In human studies, the precise duration of kidney impairment is seldom known and the onset of CVD often insidious, making it difficult to determine exactly when CVD first appears in the context of CKD. Kidney donors provide a near-ideal experimental model of CKD; subjects undergo an acute change from normal to modestly impaired renal function at the time of nephrectomy and lack the confounding co-morbidity that has made observational studies of CKD patients so challenging to interpret. By examining changes in endothelial function in living kidney donors before and after nephrectomy, useful insight might be gained into the pathophysiology of CVD in CKD and help determine whether targeting ED or the renal disease itself has the potential to reduce CV risk.

Structural alterations in small resistance arteries in obesity

In cardiovascular and metabolic diseases, small resistance arteries may show the presence of structural alterations. In particular, in essential hypertension, an increased media-to-lumen ratio of subcutaneous small arteries with no change in the total amount of vascular wall tissue (eutrophic remodelling) has already been described several years ago. Similar alterations have been demonstrated also in patients with diabetes mellitus and obesity; in this case, however, a more evident contribution of vascular smooth muscle cell growth (hypertrophic remodelling) is present. This review addresses the effects of obesity on small resistance artery structure. Similar to diabetic patients, obese patients show an increased media-to-lumen ratio of subcutaneous small arteries, which appears associated with hypertrophic remodelling, as demonstrated by an increase in media cross-sectional area. Endothelial dysfunction evaluated as vasodilator response to acetylcholine has also been observed. Several studies have shown that increased media-to-lumen ratio of subcutaneous small resistance arteries possesses a prognostic significance in relation to cardiovascular outcome. Appropriate antihypertensive treatment may improve microvascular alterations both in essential hypertension and in type 2 diabetes mellitus. In obesity, a pronounced weight loss may improve microvascular structure. However, further studies are needed to elucidate the effects of other pharmacological and non-pharmacological interventions in obesity.

Small artery remodelling in diabetes

The aim of this article is to briefly review available data regarding changes in the structure of microvessels observed in patients with diabetes mellitus, and possible correction by effective treatment. The development of structural changes in the systemic vasculature is the end result of established hypertension. In essential hypertension, small arteries of smooth muscle cells are restructured around a smaller lumen and there is no net growth of the vascular wall, although in some secondary forms of hypertension, a hypertrophic remodelling may be detected. Moreover, in non-insulin-dependent diabetes mellitus a hypertrophic remodelling of subcutaneous small arteries is present. Indices of small resistance artery structure, such as the tunica media to internal lumen ratio, may have a strong prognostic significance in hypertensive and diabetic patients, over and above all other known cardiovascular risk factors. Therefore, regression of vascular alterations is an appealing goal of antihypertensive treatment. Different antihypertensive drugs seem to have different effect on vascular structure. In diabetic hypertensive patients, a significant regression of structural alterations of small resistance arteries with drugs blocking the renin–angiotensin system (angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers) was demonstrated. Alterations in the microcirculation represent a common pathological finding, and microangiopathy is one of the most important mechanisms involved in the development of organ damage as well as of clinical events in patients with diabetes mellitus. Renin–angiotensin system blockade seems to be effective in preventing/regressing alterations in microvascular structure.

Angiotensin II type 1 receptor-dependent oxidative stress mediates endothelial dysfunction in type 2 diabetic mice

The mechanisms underlying the effect of the renin-angiotensin-aldosterone system (RAAS) inhibition on endothelial dysfunction in type 2 diabetes are incompletely understood. This study explored a causal relationship between RAAS activation and oxidative stress involved in diabetes-associated endothelial dysfunction. Daily oral administration of valsartan or enalapril at 10 mg/kg/day to db/db mice for 6 weeks reversed the blunted acetylcholine-induced endothelium-dependent dilatations, suppressed the upregulated expression of angiotensin II type 1 receptor (AT(1)R) and NAD(P)H oxidase subunits (p22(phox) and p47(phox)), and reduced reactive oxygen species (ROS) production. Acute exposure to AT(1)R blocker losartan restored the impaired endothelium-dependent dilatations in aortas of db/db mice and also in renal arteries of diabetic patients (fasting plasma glucose level > or =7.0 mmol/l). Similar observations were also made with apocynin, diphenyliodonium, or tempol treatment in db/db mouse aortas. DHE fluorescence revealed an overproduction of ROS in db/db aortas which was sensitive to inhibition by losartan or ROS scavengers. Losartan also prevented the impairment of endothelium-dependent dilatations under hyperglycemic conditions that were accompanied by high ROS production. The present study has identified an initiative role of AT(1)R activation in mediating endothelial dysfunction of arteries from db/db mice and diabetic patients.

Cerebrovascular damage in late-life depression is associated with structural and functional abnormalities of subcutaneous small arteries

Late-life depression is increasingly viewed as a vascular illness because of patients exhibiting characteristic white matter brain lesions and in vivo large artery endothelial dysfunction. However, the "vascular depression" hypothesis pertains to the microvasculature, and this circulation has not been studied in this context. Our objective was to examine structure and function of small subcutaneous arteries in patients with late-life depression. Thus, 16 patients aged 71.8±4.0 years with late-life depression were compared with 15 control participants aged 72.1±5.9 years. There were similar cardiovascular profiles between the 2 groups. All of the participants underwent MRI brain scans and subcutaneous gluteal fat biopsy from which small arteries were isolated and studied using pressure myography. Cerebral microvascular damage in depressed patients was confirmed by assessment of basal ganglia Virchow-Robin space scores (depressed patients 3.9±1.7 versus controls: 2.5±1.6; P=0.01). Contractility to norepinephrine was equivalent in both groups, but relaxation of the small arteries to acetylcholine was significantly reduced in depressed patients (84.0±4.0%) compared with control participants (96.0±1.4%; P=0.012). This difference in arterial relaxation was reduced but not entirely eliminated when NO synthase was inhibited. Depressed patients also exhibited hypertrophic wall growth with an increase in medial cross-sectional area (P=0.035, multiple ANOVA and wall thickness; P=0.04, multiple ANOVA). In conclusion, despite similar cardiovascular profiles, depressed patients with cerebral microvascular damage show abnormalities of subcutaneous small artery structure and function.

Amlodipine-valsartan combination decreases central systolic blood pressure more effectively than the amlodipine-atenolol combination: the EXPLOR study

The beta-blocker atenolol is less effective than angiotensin-receptor blockers and calcium-channel blockers for reducing central blood pressure (BP). The trial was designed to determine whether the advantages of angiotensin-receptor blockers over atenolol remained significant when both were combined with the calcium-channel blocker amlodipine. A prospective, randomized, blinded endpoint (PROBE design) parallel group, multicenter trial including 393 patients with essential hypertension resistant to 4 weeks of 5 mg of amlodipine was set out. Central systolic BP, augmentation index (AIx; either rough or adjusted on heart rate), and carotid-to-femoral pulse wave velocity were measured with applanation tonometry (SphygmoCor) at inclusion and after 8 and 24 weeks of active treatment with an amlodipine-valsartan combination (5/80 mg and then 10/160 mg) or an amlodipine-atenolol combination (5/50 mg and then 10/100 mg). From baseline to week 24, central systolic BP decreased significantly more in the amlodipine-valsartan group (-13.70+/-1.15 mm Hg; P<0.0001) than in the amlodipine-atenolol group (-9.70+/-1.10 mm Hg; P<0.0001; difference: -4.00 mm Hg [95% CI: -7.10 to -0.90]; P=0.013), despite similar changes in brachial systolic BP. The difference in rough AIx reduction was -6.5% (95% CI: -8.3 to -4.7; P<0.0001) in favor of amlodipine-valsartan. AIx adjusted on heart rate was significantly reduced in favor of amlodipine-valsartan (-2.8% [95% CI: -4.92 to -0.68]; P<0.01). Heart rate decreased significantly more with amlodipine-atenolol (difference: -11 bpm [95% CI: -14 to -8 bpm]; P<0.001). Pulse wave velocity decreased by 0.95 m/s in both groups with no significant difference. Differences in central systolic BP and rough AIx remained significant after adjustment to the changes in heart rate. The amlodipine-valsartan combination decreased central (systolic and pulse) pressure and AIx more than the amlodipine-atenolol combination.

Circulatory therapeutics: use of antihypertensive agents and their effects on the vasculature

This review addresses the use of the different antihypertensive agents currently available and some in development, and their effects on the vasculature. The different classes of agents used in the treatment of hypertension, and the results of recent large clinical trials, dosing protocols and adverse effects are first briefly summarized. The consequences on blood vessels of the use of antihypertensive drugs and the differential effects on the biology of large and small arteries resulting in modulation of vascular remodelling and dysfunction in hypertensive patients are then described. Large elastic conduit arteries exhibit outward hypertrophic remodelling and increased stiffness, which contributes to raise systolic blood pressure and afterload on the heart. Small resistance arteries undergo eutrophic or hypertrophic inward remodelling, and impair tissue perfusion. By these mechanisms both large and small arteries may contribute to trigger cardiovascular events. Some antihypertensive agents correct these changes, which could contribute to improved outcome. The mechanisms that at the level of the vascular wall lead to remodelling and can be beneficially affected by antihypertensive agents will also be addressed. These include vasoconstriction, growth and inflammation. The molecular pathways contributing to growth and inflammation will be summarily described. Further identification of these signalling pathways should allow identification of novel targets leading to development of new and improved medications for the treatment of hypertension and cardiovascular disease.

Vascular remodeling, macro- and microvessels: therapeutic implications

Macrovasculature and microvasculature are deeply interrelated, since microvascular structure is not only the site of vascular resistance but probably also the origin of most of the wave reflections generating increased central systolic blood pressure. In fact, preliminary data suggest that some index of large artery stiffness is related with the media to lumen ratio of subcutaneous small resistance arteries of hypertensive patients. Microvascular structural alterations and changes in the mechanical properties of the macrovessels represent potent predictors of prognosis. Hypertension-related damage to the micro- and macrovascular system may be corrected by pharmacological agents. Among them, beta-blocking agents and diuretics have a negligible effect on microvascular structure, while renin-angiotensin system antagonists and calcium entry blockers have favorable actions, improving large artery mechanics and possibly reducing central wave reflections.

Mineralocorticoid receptor inhibits CREB signaling by calcineurin activation

We investigated the interaction of MR with cAMP-response element binding protein (CREB) and provide a mechanistic explanation and insights into the cellular relevance. MR --> CREB crosstalk was assessed in vascular smooth muscle cells and heterologous expression systems. Experiments were designed in a way that only one variable changed at a time and the respective vehicles served as controls. MR, but not GR, activation (aldosterone or hydrocortisone, IC(50), approximately 0.3 nM) inhibits CREB transcriptional activity induced by stimulation of beta1/2-adrenoceptors and adenylyl cyclase or addition of membrane-permeable cAMP up to 70% within 2 h after addition. The MR DNA-binding domain is not required for this inhibition. cAMP formation is virtually unchanged, whereas MR exerts a robust inhibition of CREB(S133) phosphorylation via calcineurin/PP2B activation without changes in PP2B-Aalpha or beta expression. In parallel, the PP2B-sensitive NFaT-pathway is activated. The inhibitory crosstalk attenuates CREB-induced glucose-6-phosphate dehydrogenase expression. Overall, transcriptional relevant MR --> CREB crosstalk occurs at the level of CREB phosphorylation by enhanced calcineurin activity, enables GRE-independent genomic signaling of MR, and is of potential pathophysiological relevance.

Structural and functional alterations of subcutaneous small resistance arteries in severe human obesity

Obese persons are at increased cardiovascular risk and exhibit increased arterial stiffness and impaired endothelial function of large- and medium-size arteries. We hypothesized that normotensive subjects suffering from severe obesity would also present remodeling and endothelial dysfunction of small resistance arteries. A total of 16 lean (age: 49.6 +/- 2.9 years, BMI: 22.9 +/- 0.3 kg/m(2), mean +/- s.e.m.) and 17 age-matched severely obese (BMI: 41.1 +/- 2.3 kg/m(2)) normotensive subjects were investigated. None had glucose or lipid metabolic abnormalities except for insulin resistance. Resistance arteries, dissected from abdominal subcutaneous tissue, were assessed on a pressurized myograph. For superimposable blood pressure, the media thickness, media cross-sectional area (CSA), and media-to-lumen ratio values of resistance arteries were markedly and significantly greater in obese compared to lean subjects (media thickness 26.3 +/- 0.6 vs. 16.2 +/- 0.6 microm, CSA 22,272 +/- 1,339 vs. 15,183 +/- 1,186 microm(2), and media-to-lumen ratio 0.113 +/- 0.006 vs. 0.059 +/- 0.001, respectively, P < 0.01). Acetylcholine-induced relaxation was impaired in vessels from obese subjects compared to the lean individuals (-40.4 +/- 1.3%, P < 0.01), whereas endothelium-independent vasorelaxation was similar in all groups. Stiffness of small arteries as assessed by the stress/strain relationship was similar in lean and severely obese subjects. We conclude that severe human obesity is associated with profound alterations in structural and functional characteristics of small arteries, which may be responsible for the presence of elevated cardiovascular risk and increased incidence of coronary, cerebrovascular and renal events reported in obesity.

Renal protective effect of RAAS blockade across the renal continuum, with a review of the efficacy and safety of valsartan

Abstract Objective: The purpose of this report is to review key data on the angiotensin receptor blocker (ARB) valsartan, along with data from several pivotal studies with other ARBs and angiotensin-converting enzyme (ACE) inhibitors, to highlight the beneficial class effects of renin-angiotensin-aldosterone system (RAAS) blockade throughout the renal continuum.

METHODS

The selection of articles was based on a search of PubMed for clinical trials published between 1997 (the year in which valsartan was approved for sale in the US) and 2009 that involved valsartan and reported effects on renal function, plus a select range of articles on other agents acting on the RAAS, including key guidance documents issued during this time.

SUMMARY

Valsartan has been studied extensively and is widely used for the management of hypertension. Data from clinical studies involving valsartan and other ARBs and ACE inhibitors provide evidence of an additional renal protective effect. This renal protection apparently arises from hemodynamic, endothelial, and anti-inflammatory actions.

LIMITATIONS

Given the extent of the available literature on this topic, this review included only a subset of available publications. This report may reflect inherent heterogeneity between patient populations from these studies and also incorporate the limitations of these individual publications. The inclusion of guidance documents from several organizations may have resulted in apparent minor conflicts in the approaches of the different groups.

Small artery remodeling in diabetes mellitus

AIMS

To briefly review available data regarding changes in the structure of microvessels observed in patients with diabetes mellitus, and possible correction by effective treatment.

DATA SYNTHESIS

The development of structural changes in the systemic vasculature is the end result of established hypertension. In essential hypertension, small arteries' smooth muscle cells are restructured around a smaller lumen and there is no net growth of the vascular wall, while in some secondary forms of hypertension, hypertrophic remodeling may be detected. Moreover, in non-insulin-dependent diabetes mellitus hypertrophic remodeling of subcutaneous small arteries is present. Indices of small resistance artery structure, such as the tunica media to internal lumen ratio, may have a strong prognostic significance in hypertensive and diabetic patients, over and above all other known cardiovascular risk factors. Therefore, regression of vascular alterations is an appealing goal of antihypertensive treatment. Different antihypertensive drugs seem to have different effects on vascular structure. In diabetic hypertensive patients, a significant regression of structural alterations to the small resistance arteries with drugs blocking the renin-angiotensin system (ACE inhibitors, angiotensin II receptor blockers) was demonstrated.

CONCLUSION

Alterations in the microcirculation represent a common pathological finding, and microangiopathy is one of the most important mechanisms involved in the development of organ damage as well as of clinical events in patients with diabetes mellitus. Renin-angiotensin system blockade seems to be effective in preventing and/or regressing alterations in the microvascular structure.

Role of renin-angiotensin system blockade in patients with diabetes mellitus

The investigators review the evidence of the potential role of renin-angiotensin system (RAS) blockers in delaying or preventing the onset and progression of diabetes mellitus (DM) and cardiovascular disease and the suggested mechanisms by which these agents exert their favorable metabolic and cardiovascular effects. Data from clinical trials suggest that RAS blockade not only reduces cardiovascular risk in patients with DM but also may prevent or delay DM onset in at-risk subjects. These observations set the stage for further studies evaluating the risk for developing DM as a primary end point: the Diabetes Reduction Approaches With Ramipril And Rosiglitazone Medications (DREAM) trial, in which ramipril significantly increased regression to normoglycemia (although it did not reduce the primary end point of new-onset DM or death), and the ongoing Nateglinide and Valsartan in Impaired Glucose Tolerance Outcomes Research (NAVIGATOR) trial, the only DM prevention trial also powered to evaluate whether a reduced risk for DM is associated with a reduction in cardiovascular disease events. In conclusion, overwhelming evidence suggests that the RAS plays an important role in the pathogenesis of DM and its associated cardiovascular risks.

Altered structure of small cerebral arteries in patients with essential hypertension

OBJECTIVE

Structural alterations in the microcirculation may be considered an important mechanism of organ damage. An increased media-to-lumen ratio of subcutaneous small resistance arteries has been demonstrated to predict the development of cardiocerebrovascular events in hypertensive patients. Alterations in the structure of small cerebral arteries have been demonstrated in animal models of experimental or genetic hypertension. However, no evaluation with reliable techniques has ever been performed in humans.

DESIGN AND METHODS

Twenty-eight participants were included in the present study: they were 13 hypertensive patients and 15 normotensive individuals. All participants underwent a neurosurgical intervention for benign or malign tumors. A small portion of morphologically normal cerebral tissue was excised from surgical samples and examined. Cerebral small resistance arteries (relaxed diameter around 200 mum) were dissected and mounted on an isometric and isobaric myograph, and the tunica media to internal lumen ratio was measured. In addition, cerebral cortical microvessel density (MVD) was also evaluated. The tissue was sectioned and stained for CD31, and MVD was measured with an automated image analyzer (percentage of area stained). Blood pressure values were evaluated, before surgical intervention, by standard sphygmomanometry.

RESULTS

M/L was significantly greater and MVD significantly lower in hypertensive patients than that in normotensive individuals. No difference between groups in collagen content or mechanical properties of cerebral small arteries was observed.

CONCLUSION

Our results indicate that structural alterations of small cerebral vessels are present in hypertensive patients compared with normotensive individuals, similar to those previously observed in subcutaneous small arteries.

Angiotensin II and the development of insulin resistance: implications for diabetes

Angiotensin II (Ang II), the major effector hormone of the renin-angiotensin system (RAS), has an important role in the regulation of vascular and renal homeostasis. Clinical and pharmacological studies have recently shown that Ang II is a critical promoter of insulin resistance and diabetes mellitus type 2. Ang II exerts its actions on insulin-sensitive tissues such as liver, muscle and adipose tissue where it has effects on the insulin receptor (IR), insulin receptor substrate (IRS) proteins and the downstream effectors PI3K, Akt and GLUT4. The molecular mechanisms involved have not been completely identified, but the role of serine/threonine phosphorylation of the IR and IRS-1 proteins in desensitization of insulin action has been well established. The purpose of this review is to highlight recent advances in the understanding of Ang II actions which lead to the development of insulin resistance and its implications for diabetes.

PPARgamma and its ligands: therapeutic implications in cardiovascular disease

The relevance of PPARgamma (peroxisome-proliferator-activated receptor gamma) as an important therapeutic target for the treatment of diabetes arises from its hypoglycaemic effects in diabetic patients and also from the critical role in the regulation of cardiovascular functions. From a clinical perspective, differences between current FDA (Food and Drug Administration)-approved PPARgamma drugs have been observed in terms of atherosclerosis and cardiac and stroke events. The adverse effects of PPARgamma-specific treatments that hamper their cardiovascular protective roles, affirm the strong need to evaluate the efficacy of the current drugs. Therefore active research is directed towards high-throughput screening and pharmacological testing of a plethora of newly identified natural or synthetic compounds. In the present review we describe the rationale behind drug design strategies targeting PPARgamma, based on current knowledge regarding the effects of such drugs in experimental animal models, as well as in clinical practice. Regarding endogenous PPARgamma ligands, several fatty acid derivatives bind PPARgamma with different affinities, although the physiological relevance of these interactions is not always evident. Recently, NO-derived unsaturated fatty acids were found to be potent agonists of PPARs, with preferential affinity for PPARgamma, compared with oxidized fatty acid derivatives. Nitroalkenes exert important bioactivities of relevance for the cardiovascular system including anti-inflammatory and antiplatelet actions, and are important mediators of vascular tone. A new generation of insulin sensitizers with PPARgamma function for the treatment of diabetes may serve to limit patients from the increased cardiovascular burden of this disease.