Endothelial Dysfunction: The Common Consequence in Diabetes and Hypertension:

Participation of nitric oxide pathway in the relaxation response induced by E-cinnamaldehyde oxime in superior mesenteric artery isolated from rats

For many years, nitric oxide (NO) has been studied as an important mediator in the control of vascular tone. Endothelial deficiencies that diminish NO production can result in the development of several future cardiovascular diseases, such as hypertension and arteriosclerosis. In this context, new drugs with potential ability to donate NO have been studied. In this study, 3 aromatic oximes [benzophenone oxime, 4-Cl-benzophenone oxime, and E-cinnamaldehyde oxime (E-CAOx)] induced vasorelaxation in endothelium-denuded and intact superior mesenteric rings precontracted with phenylephrine. E-CAOx demonstrated the most potent effect, and its mechanism of action was evaluated. Vascular reactivity experiments demonstrated that the effect of E-CAOx was reduced by the presence of 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, 1H[1,2,4,]oxadiazolo[4,3-a]quinoxalin-1-one, and (Rp)-8-(para-chlorophenylthio)guanosine-3',5'-cyclic monophosphorothioate, suggesting the participation of NO/sGC/PKG pathway. NO donation seems to be mediated through nicatinamide adenine dinucleotide phosphate-dependent reductases because 7-ethoxyresorufin decreased the effect of E-CAOx on vascular reactivity and reduced NO formation as detected by flow cytometry using the NO indicator diaminofluorescein 4,5-diacetate. Further downstream of NO donation, K+ subtype channels were also shown to be involved in the E-CAOx vasorelaxant effect. The present study showed that E-CAOx acts like an NO donor, activating NO/sGC/PKG pathway and thus K+ channels.

Treated effect of silymarin on vascular function of aged rats: Dependant on nitric oxide pathway

Abstract Context: Aging leads to endothelial dysfunction and vascular stiffness which are the main causes of many cardiovascular diseases. Previous reports have shown that the cell protective effect of silymarin (SM) is dependent on its antioxidant properties. Objectives: We investigated the effect of SM on vascular functions of aged rats and the involvement of nitric oxide or cyclooxygenase (COX) activity in this effect. Materials and methods: Isolated rat aortas were obtained from 22-month old rats. Each ring was incubated with SM (50 mg/L), SM/l-nitro-arginine methyl ester (100 μM, l-NAME) or SM/indomethacin (10 μM, INDO) in tissue bath. Three- to four-month-old rats were used as young controls. Endothelium-intact rings were precontracted with α-receptor agonist phenylephrine (0.001-30 µM) or voltage-dependent high potassium (40 mM), endothelium dependent/independent relaxant responses were obtained using acetylcholine (0.001-30 µM) and sodium nitroprusside (0.0001-3 µM), respectively. Results: Aging increased phenylephrine sensitivity (6.45 ± 0.08; 6.88 ± 0.09) and decreased KCl contraction (882 ± 118.4; 499 ± 80.4). SM treatment decreased the Emax of both agents (548 ± 109; 223 ± 48.9). Aging deteriorated acetylcholine relaxation (93.9 ± 2.09; 72.0 ± 2.56) and SM improved the response (86.3 ± 1.90). l-NAME prevented the SM effect whereas INDO was ineffective. Discussion and Conclusion: Immediate SM treatment partially restored endothelial dysfunction and vascular tone in aging. The possible mechanism might not be mediated by prostacyclin or the COX pathway in acute administration; the nitric oxide pathway and calcium antagonistic features of SM relate to its action on the vessel.

Correlates of nonalcoholic fatty liver among women receiving residential mental health care

PURPOSE

To review the risk factors for diagnosis of nonalcoholic fatty liver disease (NAFLD) in women in a mental health, dual diagnosis, treatment facility.

DATA SOURCES

A review of the literature and retrospective chart reviews of patients to identify factors within this population of women most closely associated with diagnosis of NAFLD.

CONCLUSIONS

NAFLD is a common diagnosis and as obesity rates increase in the United States the incidence for this disease is also increasing. Identifiable risk factors are associated with the presence of this disease. Advanced practice nurses, as prescribers, need to be aware that the presence of NAFLD may interfere with drug metabolism and toxin elimination in their patients.

IMPLICATIONS FOR PRACTICE

Numerous physical conditions, behavioral symptoms, and laboratory findings are identified as associated conditions of NAFLD. Patients seen in primary care practices have NAFLD, but patients in treatment centers for mental health disorders are also affected. This population is particularly at risk because of the hepatotoxic effects of many medications used in psychiatric-mental health settings.

Diabetes alters the expression of partial vasoactivators in cerebral vascular disease susceptible regions of the diabetic rat

BACKGROUND

The pathogenesis between cerebral vascular disease (CVD) and the endothelial dysfunction (ETD) remains elusive in diabetes. Therefore, we investigated the expression of partial vasoactivators which be closely relative to ETD in CVD susceptible brain regions in the diabetic rat. The aim was to search some possible pathogenesis.

METHODS

Diabetes was induced by a single intraperitoneal injection of streptozotocin and a high lipid/sugar diet. The expression of vasoactivators ET-1, CGRP, VCAM-1, ICAM-1 and P-selectin were assessed by immunohistochemical staining and measurement of optic density of positive cells in the frontal and temporal lobe, basal ganglia and thalamus at 4 weeks after establishment of the diabetic model.

RESULTS

The expression of ET-1, VCAM-1, ICAM-1 and P-selectin significantly increased and CGRP significantly decreased in the diabetic group, and the expression of these vasoactivators was significantly different among the frontal, temporal lobe, basal ganglia and thalamus, and among the emotion, splanchno-motor and neuroendocrine center in the diabetic group.

CONCLUSIONS

Diabetes alters the expression of partial vasoactivators in cerebral vascular disease susceptible regions of the diabetic rat. Therefore, we suggested that CVD complications in diabetes are partly caused by ETD via an imbalance expression of endothelial vasoactivators, which might be associated with dysfunction of emotion, autonomic nerve and endocrine center. However, further studies are warranted.

Bone morphogenic protein-4 contributes to venous endothelial dysfunction in patients with diabetes undergoing coronary revascularization

BACKGROUND

Hyperglycemia-induced venous endothelial dysfunction accelerates the progression of vein graft failure in patients with diabetes undergoing surgical coronary revascularization. Recent studies suggest the importance of bone morphogenic protein-4 (BMP4)-induced arterial endothelial dysfunction in the development of hypertension and atherosclerosis. The present study investigated the potential role of BMP4 in the pathogenesis of venous endothelial dysfunction in the setting of diabetes.

METHODS

Segments of saphenous vein from pigs and from patients with diabetes or patients without diabetes, as well as human umbilical venous endothelial cells (HUVECs), were used. The changes of BMP4 expression in veins from patients and in HUVECs cultured under hyperglycemic conditions were evaluated by Western blot assay. The effects of BMP4 on the production of reactive oxygen species (ROS) and endothelium-dependent venous relaxation were assessed by using dihydroethidium fluorescence and isometric tension measurements, respectively.

RESULTS

The impaired venous endothelium-dependent relaxations (2.9%±4.8% versus control group 74.1%±10%; p<0.01) accompanied by markedly increased BMP4 expression were observed in the diabetic group. The level of BMP4 expression in HUVECs treated with high levels of glucose were elevated in a glucose concentration-dependent manner. Ex vivo treatment with the BMP4 antagonist noggin significantly improved endothelium-dependent relaxations and inhibited accumulation of ROS in saphenous veins from patients with diabetes. Noggin treatment had no effect on the venous endothelium-dependent relaxations in individuals without diabetes. Meanwhile, BMP4 inhibited acetylcholine-induced relaxation (control group, 90%±7.1% versus BMP4-treated group, 52%±12.6%; p<0.05) and enhanced ROS production in porcine saphenous veins. Such harmful effects were again reversed by noggin.

CONCLUSIONS

The increased BMP4 expression and related ROS overproduction may play an important role in the development of hyperglycemia-induced venous endothelial dysfunction.

Salidroside improves homocysteine-induced endothelial dysfunction by reducing oxidative stress

Hyperhomocysteinemia is associated with an increased risk for cardiovascular diseases through increased oxidative stress. Salidroside is an active ingredient of the root of Rhodiola rosea with documented antioxidative, antihypoxia and neuroprotective properties. However, the vascular benefits of salidroside against endothelial dysfunction have yet to be explored. The present study, therefore, aimed to investigate the protective effect of salidroside on homocysteine-induced endothelial dysfunction. Functional studies on the rat aortas were performed to delineate the vascular effect of salidroside. DHE imaging was used to evaluate the reactive oxygen species (ROS) level in aortic wall and endothelial cells. Western blotting was performed to assess the protein expression associated with oxidative stress and nitric oxide (NO) bioavailability. Exposure to homocysteine attenuated endothelium-dependent relaxations in rat aortas while salidroside pretreatment rescued it. Salidroside inhibited homocystein-induced elevation in the NOX2 expression and ROS overproduction in both aortas and cultured endothelial cells and increased phosphorylation of eNOS which was diminished by homocysteine. The present study shows that salidroside is effective in preserving the NO bioavailability and thus protects against homocysteine-induced impairment of endothelium-dependent relaxations, largely through inhibiting the NOX2 expression and ROS production. Our results indicate a therapeutic potential of salidroside in the management of oxidative-stress-associated cardiovascular dysfunction.

Calcitriol restores renovascular function in estrogen-deficient rats through downregulation of cyclooxygenase-2 and the thromboxane-prostanoid receptor

Cardiovascular risks increase in postmenopausal women. While vitamin D is supplemented for osteoporosis, it is not known whether it protects renal arterial function during estrogen deficiency. Here we measured changes in renovascular reactivity induced by ovariectomy in rats and examined whether calcitriol, the most active form of vitamin D, was able to correct such changes. The impairment of endothelium-dependent relaxation in renal arteries from ovariectomized rats was effectively reversed by long-term calcitriol treatment. It was also corrected by acute exposure to cyclooxygenase-2 (COX-2) inhibitors and a thromboxane-prostanoid receptor antagonist, respectively. Calcitriol normalized the overexpression of COX-2 and thromboxane-prostanoid receptors in intralobal renal artery segments and aortic endothelial cells isolated from ovariectomized rats. In vitro exposure of the arterial segments to calcitriol for 12 h improved relaxation and downregulated thromboxane-prostanoid receptors. The attenuated nitric oxide production in ovariectomized rat aortic endothelial cells was restored following a 12-h treatment with calcitriol, COX-2 inhibition, or thromboxane-prostanoid receptor antagonism. Thus, impaired endothelium-dependent renal artery relaxation in ovariectomized rats is mediated largely through increased activity and expression of COX-2 and the thromboxane-prostanoid receptor. Calcitriol restores endothelial function through downregulating both signaling proteins during estrogen deficiency.

Serum uric acid predicts both current and future components of the metabolic syndrome

BACKGROUND

Uric acid (UA) is known to be associated with excess adiposity and insulin resistance. Our aim was to investigate the relationship between UA and the factors associated with the metabolic syndrome and type 2 diabetes mellitus (T2DM), both initially and longitudinally.

METHODS

Serum UA was assessed as a potential determinant of concurrent blood pressure, serum lipids, glucose regulation measured via an oral glucose tolerance test (OGTT), acute insulin response (AIR), and insulin action (M) measured with hyperinsulinemic-euglycemic clamps in 245 participants (72% Native American, 56% male). UA was also assessed as a predictor of the above variables in 60 participants with follow-up data available (median follow-up time=11.2 years [interquartile range (IQR)=8.1, 13.6 years]. The impact of UA on the risk of T2DM was determined as 36 of the 245 participants developed T2DM after the baseline visit.

RESULTS

UA was negatively associated with both concurrent and future M, such that for every 1 mg/dL increase in serum UA, M decreased 7.6% (P<0.001) and future M decreased 6.3% (P=0.02). However, UA was not associated with AIR (P=0.7). UA concentrations were a predictor of T2DM [hazard risk ratio (HRR)=1.5; P=0.02]. UA was positively associated with both concurrent blood pressure and lipids and also predicted future increases in blood pressure and total cholesterol.

CONCLUSIONS

Not only did UA associate with concomitant insulin action, blood pressure, and lipids, it also predicted future declines in insulin action and T2DM. UA is a potential target for preventing decreases in insulin sensitivity and rises in blood pressure and cholesterol.

Fo Shou San, an ancient Chinese herbal decoction, protects endothelial function through increasing endothelial nitric oxide synthase activity

Fo Shou San (FSS) is an ancient herbal decoction comprised of Chuanxiong Rhizoma (CR; Chuanxiong) and Angelicae Sinensis Radix (ASR; Danggui) in a ratio of 2:3. Previous studies indicate that FSS promotes blood circulation and dissipates blood stasis, thus which is being used widely to treat vascular diseases. Here, we aim to determine the cellular mechanism for the vascular benefit of FSS. The treatment of FSS reversed homocysteine-induced impairment of acetylcholine (ACh)-evoked endothelium-dependent relaxation in aortic rings, isolated from rats. Like radical oxygen species (ROS) scavenger tempol, FSS attenuated homocysteine-stimulated ROS generation in cultured human umbilical vein endothelial cells (HUVECs), and it also stimulated the production of nitric oxide (NO) as measured by fluorescence dye and biochemical assay. In addition, the phosphorylation levels of both Akt kinase and endothelial NO synthases (eNOS) were markedly increased by FSS treatment, which was abolished by an Akt inhibitor triciribine. Likewise, triciribine reversed FSS-induced NO production in HUVECs. Finally, FSS elevated intracellular Ca(2+) levels in HUVECs, and the Ca(2+) chelator BAPTA-AM inhibited the FSS-stimulated eNOS phosphorylation. The present results show that this ancient herbal decoction benefits endothelial function through increased activity of Akt kinase and eNOS; this effect is causally via a rise of intracellular Ca(2+) and a reduction of ROS.

Effect of short-term hyperglycemia on protein kinase C alpha activation in human erythrocytes

BACKGROUND

Diabetes mellitus, characterized by chronic hyperglycemia, is known to have a deleterious effect on erythrocyte structure and hemodynamic characteristics, which eventually contribute to diabetes-associated vascular complications. Protein kinase C alpha (PKCα) is a major regulator of many metabolic processes and structural changes in erythrocytes, and may play a significant role in the development of hyperglycemia-mediated cellular abnormalities.

AIM

We hypothesized that acute hyperglycemic stress may affect erythrocyte structure and metabolic properties through its effect on PKCα membrane content and activity.

RESULTS

Erythrocytes, from healthy individuals acutely exposed to a glucose enriched media, showed a significant decrease in the membranous fraction of PKCα and its phosphorylation (p = 0.005 and p = 0.0004, respectively). These alterations correlated with decreased affinity of PKCα to its membrane substrates (4.1R and GLUT1) and reduced RBC deformability (p = 0.017). Pre-activation of erythrocytes with PKC activator, PMA, minimized the effect of glucose on the membrane PKCα fraction and RBC deformability (p > 0.05).

CONCLUSIONS

Acute glycemia-induced inhibition of PKCα membranous translocation and activation is associated with reduced erythrocyte membrane deformability.

Cajaninstilbene acid relaxes rat renal arteries: roles of Ca2+ antagonism and protein kinase C-dependent mechanism

Cajaninstilbene acid (CSA) is a major active component present in the leaves of Cajanus cajan (L.) Millsp. The present study explores the underlying cellular mechanisms for CSA-induced relaxation in rat renal arteries. Vascular reactivity was examined in arterial rings that were suspended in a Multi Myograph System and the expression of signaling proteins was assessed by Western blotting method. CSA (0.1–10 µM) produced relaxations in rings pre-contracted by phenylephrine, serotonin, 9, 11-dideoxy-9α, 11α-epoxymethanoprostaglandin F_2α (U46619), and 60 mM KCl. CSA-induced relaxations did not show difference between genders and were unaffected by endothelium denudation, nor by treatment with N^G-nitro-L-arginine methyl ester, indomethacin, ICI-182780, tetraethylammonium ion, BaCl₂, glibenclamide, 4-aminopyridine or propranolol. CSA reduced contraction induced by CaCl₂ (0.01–5 mM) in Ca²⁺-free 60 mM KCl solution and by 30 nM (−)-Bay K8644 in 15 mM KCl solution. CSA inhibited 60 mM KCl-induced Ca²⁺ influx in smooth muscle of renal arteries. In addition, CSA inhibited contraction evoked by phorbol 12-myristate 13-acetate (PMA, protein kinase C agonist) in Ca²⁺-free Krebs solution. Moreover, CSA reduced the U46619- and PMA-induced phosphorylation of myosin light chain (MLC) at Ser19 and myosin phosphatase target subunit 1 (MYPT1) at Thr853 which was associated with vasoconstriction. CSA also lowered the phosphorylation of protein kinase C (PKCδ) at Thr505. In summary, the present results suggest that CSA relaxes renal arteries in vitro via multiple cellular mechanisms involving partial inhibition of calcium entry via nifedipine-sensitive calcium channels, protein kinase C and Rho kinase.

Adipocytokine levels mark endothelial function in normotensive individuals

Background

Endothelial dysfunction is an independent risk factor for cardiovascular events. Inflammatory mediators released by the adipose tissue can lead to local insulin resistance and endothelial dysfunction. This study addressed the relationship of adipocytokines with endothelial function and blood pressure.

Methods

In 92 newly diagnosed, drug-naïve essential hypertensive patients (HT, mean age 49 yrs) without organ damage and 66 normotensive subjects (NT, mean age 47 yrs), by an automated system, we measured endothelium-dependent and -independent vasodilation as brachial artery flow-mediated dilation before and after administration of glyceryl-trinitrate. Retinol binding protein-4 (RBP4) and resistin levels were determined by ELISA and RIA, respectively. Oxidative stress was evaluated by measuring serum malondyaldehyde (MDA).

Results

Flow-mediated dilation was significantly (p = 0.03) lower in HT (5.3 ± 2.6%) than NT (6.1 ± 3.1%), while response to glyceryl-trinitrate (7.5 ± 3.7% vs 7.9 ± 3.4%) was similar. RBP4 (60.6 ± 25.1 vs 61.3 ± 25.9 μg/ml), resistin (18.8 ± 5.3 vs 19.9 ± 6.1 ng/ml) and MDA levels (2.39 ± 1.26 vs 2.08 ± 1.17 nmol/ml) were not different in HT and NT.

RBP4 (r = −0.25; p = 0.04) and resistin levels (r = −0.29; p = 0.03) were related to flow-mediated dilation in NT, but not in HT (r = −0.03 and r = −0.10, respectively). In NT, multivariate analysis including RBP4 and confounders showed that only BMI or waist circumference remained related to flow- mediated dilation. In the multivariate model including resistin and confounders, BMI, age and resistin were significantly related to flow-mediated dilation, while only age significant correlated with this parameter when BMI was replaced by waist circumference.

Conclusions

Adipocytokine levels may be independent predictors of endothelial dysfunction in the peripheral circulation of healthy subjects, providing a pathophysiological link between inflammation from adipose tissue and early vascular alterations.

Dipeptidyl peptidase 4 inhibitor sitagliptin protects endothelial function in hypertension through a glucagon-like peptide 1-dependent mechanism

Sitagliptin, a selective dipeptidyl peptidase 4 inhibitor, inhibits the inactivation and degradation of glucagon like peptide 1 (GLP-1), which is used for the treatment of type 2 diabetes mellitus. However, little is known about the role of GLP-1 in hypertension. This study investigated whether the activation of GLP-1 signaling protects endothelial function in hypertension. Two-week sitagliptin treatment (10 mg/kg per day, oral gavage) improved endothelium-dependent relaxation in renal arteries, restored renal blood flow, and reduced systolic blood pressure in spontaneously hypertensive rats. In vivo sitagliptin treatment elevated GLP-1 and GLP-1 receptor expressions, increased cAMP level, and subsequently activated protein kinase A, liver kinase B1, AMP-activated protein kinase-α and endothelial NO synthase in spontaneously hypertensive rat renal arteries. Inhibition of GLP-1 receptor, adenylyl cyclase, protein kinase A, AMP-activated protein kinase-α, or NO synthase reversed the protective effects of sitagliptin. We also demonstrate that GLP-1 receptor agonist exendin 4 in vitro treatment had similar vasoprotective effects in spontaneously hypertensive rat renal arteries and increased NO production in spontaneously hypertensive rat aortic endothelial cells. Studies using transient expressions of wild-type and dominant-negative AMP-activated protein kinase-α2 support the critical role of AMP-activated protein kinase-α in mediating the effect of GLP-1 in endothelial cells. Ex vivo exendin 4 treatment also improved endothelial function of renal arteries from hypertensive patients. Our results elucidate that upregulation of GLP-1 and related agents improve endothelial function in hypertension by restoring NO bioavailability, suggesting that GLP-1 signaling could be a therapeutic target in hypertension-related vascular events.

Shockwave therapy in patients with peripheral artery disease

INTRODUCTION

Previous studies support the fact that extracorporeal shockwave (SW) induces angiogenesis and improves symptoms in patients affected by limb ischemia. The aim of this study was to evaluate the effects of SW therapy in patients with peripheral artery disease (PAD).

METHODS

Twenty-two patients were enrolled in this study and were randomly assigned into two groups: SW treatment (12 patients, 67 ± 9 years) and control (10 patients, 68 ± 12 years). The inclusion criteria were the following: age over 40 years, PAD diagnosis, optimal medical therapy, and ankle-brachial index less than 0.9. SW therapy was administered using the Minilith® SL1 litotriptor with an ultrasound guide able to detect the target area using a B-mode technique and a 7.5 MHz convex probe emitting 2,000 impulses with an energy flux density of 0.03 mJ/mm(2).

RESULTS

The variation in the degree of stenosis before and after treatment was statistically significant between the groups (-9% ± -10% vs. 0% ± 0%; P = 0.001). In addition, a significantly higher number of treated patients than controls showed a reduction in the Fontaine stage (12 [63%] vs. 0 [0%]; P < 0.001). This result was confirmed by analyzing the difference in patients' pain-free walking distance before and after SW therapy (76 ± 46 m vs. 0 ± 0 m for treated patients vs. controls; P < 0.001) and the difference in pain severity (measured on a pain scale; -1.4 ± 0.5 in the treated patients vs. -0.2 ± 0.4 in the controls; P < 0.001).

CONCLUSION

On the basis of these results the authors hypothesized a direct effect of SW on the ultrastructural composition of the vessel walls, inducing a reduction in artery stenosis. These data support the application of SW therapy as a new medical tool to improve the natural clinical course of PAD.

Is human cytomegalovirus infection associated with hypertension? The United States National Health and Nutrition Examination Survey 1999-2002

PURPOSE

Recent studies have implicated the human cytomegalovirus (HCMV) as a possible pathogen for causing hypertension. We aimed to study the association between HCMV infection and hypertension in the United States National Health and Nutrition Examination Survey (NHANES).

METHODS

We analyzed data on 2979 men and 3324 women in the NHANES 1999-2002. We included participants aged 16-49 years who had valid data on HCMV infection and hypertension.

RESULTS

Of the participants, 54.7% had serologic evidence of HCMV infection and 17.5% had hypertension. There were ethnic differences in the prevalence of HCMV infection (P<0.001) and hypertension (P<0.001). The prevalence of both increased with age (P<0.001). Before adjustment, HCMV seropositivity was significantly associated with hypertension in women (OR=1.63, 95% CI=1.25-2.13, P=0.001) but not in men. After adjustment for race/ethnicity, the association between HCMV seropositivity and hypertension in women remained significant (OR=1.55, 95% CI=1.20-2.02, P=0.002). Further adjustment for body mass index, diabetes status and hypercholesterolemia attenuated the association (OR=1.44, 95% CI=1.10-1.90, P=0.010). However, after adjusting for age, the association was no longer significant (OR=1.24, 95% CI=0.91-1.67, P=0.162).

CONCLUSIONS

In this nationally representative population-based survey, HCMV seropositivity is associated with hypertension in women in the NHANES population. This association is largely explained by the association of hypertension with age and the increase in past exposure to HCMV with age.

Dynamic contrast-enhanced MRI assessment of hyperemic fractional microvascular blood plasma volume in peripheral arterial disease: initial findings

Objectives

The aim of the current study was to describe a method that assesses the hyperemic microvascular blood plasma volume of the calf musculature. The reversibly albumin binding contrast agent gadofosveset was used in dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) to assess the microvascular status in patients with peripheral arterial disease (PAD) and healthy controls. In addition, the reproducibility of this method in healthy controls was determined.

Materials and Methods

Ten PAD patients with intermittent claudication and 10 healthy control subjects were included. Patients underwent contrast-enhanced MR angiography of the peripheral arteries, followed by one DCE MRI examination of the musculature of the calf. Healthy control subjects were examined twice on different days to determine normative values and the interreader and interscan reproducibility of the technique. The MRI protocol comprised dynamic imaging of contrast agent wash-in under reactive hyperemia conditions of the calf musculature. Using pharmacokinetic modeling the hyperemic fractional microvascular blood plasma volume (V_p, unit: %) of the anterior tibial, gastrocnemius and soleus muscles was calculated.

Results

V_p was significantly lower for all muscle groups in PAD patients (4.3±1.6%, 5.0±3.3% and 6.1±3.6% for anterior tibial, gastrocnemius and soleus muscles, respectively) compared to healthy control subjects (9.1±2.0%, 8.9±1.9% and 9.3±2.1%). Differences in V_p between muscle groups were not significant. The coefficient of variation of V_p varied from 10–14% and 11–16% at interscan and interreader level, respectively.

Conclusions

Using DCE MRI after contrast-enhanced MR angiography with gadofosveset enables reproducible assessment of hyperemic fractional microvascular blood plasma volume of the calf musculature. V_p was lower in PAD patients than in healthy controls, which reflects a promising functional (hemodynamic) biomarker for the microvascular impairment of macrovascular lesions.

Renoprotective effects of (+)-catechin in streptozotocin-induced diabetic rat model

Diabetic nephropathy is a complication of diabetes mellitus leading to end-stage renal disease. Oxidative stress and inflammation play a major role in the pathogenesis of diabetic nephropathy. Green tea, known for its antioxidant and anti-inflammatory properties, has been shown to be renoprotective. We hypothesized that (+)-catechin (CTN), a component of green tea, is responsible for the renoprotection. Our investigation of the therapeutic potential of CTN in streptozotocin-induced diabetic rats demonstrated for the first time that the effects of CTN treatment were comparable with the effects of an angiotensin-converting enzyme inhibitor (ACEi) enalapril for the treatment of albumin excretion. After 12 weeks of CTN treatment with 35 mg/d in the drinking water, urinary albumin excretion and plasma creatinine concentrations in all the diabetic treatment groups were reduced, compared with the diabetic group with no treatment. Urine creatinine and creatinine clearance were higher in diabetic groups treated with CTN and ACEi compared with the diabetic group with no treatment. Endothelin 1, lipid peroxidation, concentration of alanine transferase enzyme, and expression of fibronectin were lower in all the treatment groups compared with the diabetic group with no treatment. Concentrations of free thiols were higher in the CTN-treated group compared with the diabetic rats with no treatment. Our findings suggest that CTN has renoprotective properties comparable with ACEi, and coadministration of CTN and enalapril might be useful in reducing albumin excretion as well as improving endothelial function. (+)-Catechin might be successfully used in the future for clinical situations where ACEi is poorly tolerated or contraindicated.

Rosuvastatin improves endothelial function in db/db mice: role of angiotensin II type 1 receptors and oxidative stress

BACKGROUND AND PURPOSE

HMG-CoA reductase inhibitors, statins, with lipid-reducing properties combat against atherosclerosis and diabetes. The favourable modulation of endothelial function may play a significant role in this effect. The present study aimed to investigate the cellular mechanisms responsible for the therapeutic benefits of rosuvastatin in ameliorating diabetes-associated endothelial dysfunction.

EXPERIMENTAL APPROACH

Twelve-week-old db/db diabetic mice were treated with rosuvastatin at 20 mg·kg⁻¹ ·day⁻¹ p.o.for 6 weeks. Isometric force was measured in isolated aortae and renal arteries. Protein expressions including angiotensin II type 1 receptor (AT₁R), NOX4, p22(phox) , p67(phox) , Rac-1, nitrotyrosine, phospho-ERK1/2 and phospho-p38 were determined by Western blotting, while reactive oxygen species (ROS) accumulation in the vascular wall was evaluated by dihydroethidium fluorescence and lucigenin assay.

KEY RESULTS

Rosuvastatin treatment of db/db mice reversed the impaired ACh-induced endothelium-dependent dilatations in both renal arteries and aortae and prevented the exaggerated contractions to angiotensin II and phenylephrine in db/db mouse renal arteries and aortae. Rosuvastatin reduced the elevated expressions of AT₁R, p22(phox) and p67(phox) , NOX4, Rac1, nitrotyrosine and phosphorylation of ERK1/2 and p38 MAPK and inhibited ROS production in aortae from db/db mice.

CONCLUSIONS AND IMPLICATIONS

The vasoprotective effects of rosuvastatin are attributed to an increase in NO bioavailability, which is probably achieved by its inhibition of ROS production from the AT₁R-NAD(P)H oxidase cascade.

Vascular dysfunction as target organ damage in animal models of hypertension

Endothelial dysfunction is one of the main characteristics of chronic hypertension and it is characterized by impaired nitric oxide (NO) bioactivity determined by increased levels of reactive oxygen species. Endothelial function is usually evaluated by measuring the vasodilation induced by the local NO production stimulated by external mechanical or pharmacological agent. These vascular reactivity tests may be carried out in different models of experimental hypertension such as NO-deficient rats, spontaneously hypertensive rats, salt-sensitive rats, and many others. Wire myograph and pressurized myograph are the principal methods used for vascular studies. Usually, increasing concentrations of the vasodilator acetylcholine are added in cumulative manner to perform endothelium-dependent concentration-response curves. Analysis of vascular mechanics is relevant to identify arterial stiffness. Both endothelial dysfunction and vascular stiffness have been shown to be associated with increased cardiovascular risk.

Exogenous hydrogen sulfide (H2S) reduces blood pressure and prevents the progression of diabetic nephropathy in spontaneously hypertensive rats

The coexistence of hypertension and diabetes results in the rapid development of nephropathy. Hydrogen sulfide (H2S) is claimed to control the vascular and renal functions. This study tested the hypothesis that exogenous H2S lowers the blood pressure and decreases the progression of nephropathy in spontaneously hypertensive rats (SHR) that were diabetic. Eighteen SHR were divided into three groups: SHR, SHR diabetic, and SHR diabetic treated with a group of Wistar-Kyoto rats serving as normotensive nondiabetic control. Diabetes was induced with streptozotocin (STZ) in two groups and one diabetic group received sodium hydrosulfide (NaHS), a H2S donor for 5 weeks. Blood pressure was measured in conscious and anesthetized states and renal cortical blood perfusion in acute studies. Plasma and urinary H2S levels, creatinine concentrations, and electrolytes were measured on three different occasions throughout the 35-day period. Diabetic SHR had higher blood pressure, lower plasma and urinary H2S levels, and renal dysfunction as evidenced by increased plasma creatinine, creatinine clearance, and decreased urinary sodium-to-potassium ratio and renal cortical blood perfusion. NaHS reduced blood pressure, increased H2S levels in plasma and urinary excretion, and reversed the STZ-induced renal dysfunction. The findings of this study suggest that the administration of exogenous H2S lowers the blood pressure and confers protection against the progression of STZ-induced nephropathy in SHR.

Renalase gene polymorphisms in patients with type 2 diabetes, hypertension and stroke

Renalase is a novel, recently identified, flavin adenine dinucleotide-dependent amine oxidase. It is secreted by the kidney and metabolizes circulating catecholamines. Renalase has significant hemodynamic effects, therefore it is likely to participate in the regulation of cardiovascular function.The aim of our study was to investigate the involvement of renalase gene polymorphisms in hypertension in type 2 diabetes patients. A total of 892 patients and 400 controls were genotyped with three SNPs in the renalase gene. The C allele of rs2296545 SNP was associated with hypertension (P < 0.01). For rs2576178 SNP, frequencies in hypertensive patients differed from controls, but not from normotensive patients. For rs10887800 SNP, the differences in the G allele frequencies were observed in hypertensive patients with stroke, with 66% of patients being GG homozygotes. To confirm observed association we later genotyped 130 stroke patients without diabetes. The OR for risk allele was 1.79 (95% CI 1.33-2.41). In conclusion, the renalase gene polymorphism was associated with hypertension in type 2 diabetes patients. The most interesting result is a strong association of the rs10887800 polymorphism with stroke in patients with and without diabetes. The G allele of this polymorphism might thus be useful in identifying diabetes patients at increased risk of stroke.

Raloxifene improves vascular reactivity in pressurized septal coronary arteries of ovariectomized hamsters fed cholesterol diet

Although vascular effects of selective estrogen receptor modulators (SERMs) have been extensively examined in conduit arteries, whether SERMs could favorably modulate myogenic response in resistance arteries is unknown. The impact of raloxifene therapy and cholesterol diet on myogenic constriction during estrogen deficiency is unresolved. This study investigated changes in vascular reactivity and myogenic responses in female ovariectomized (Ovx) hamsters fed high-cholesterol diet (HCD) with and without chronic treatment of raloxifene. Functional studies were performed on hamster septal coronary arteries cannulated in a pressure myograph. Acetylcholine (ACh)-induced dilatation was reduced in arteries from cholesterol-fed Ovx hamsters, but not in those from cholesterol-fed hamsters, while pressure-induced myogenic constriction was unaffected. Chronic treatment with raloxifene restored ACh-induced dilatation in cholesterol-fed Ovx hamsters. U46619-induced constriction was increased in arteries from cholesterol-fed Ovx hamsters but not from cholesterol-fed control hamsters, which was normalized by chronic raloxifene treatment. The pressure-diameter relationship is presented as normalized diameter versus intraluminal pressure, while the effect of ACh or U46619 is expressed as percentage of tone at 80 mm Hg. Two-way analysis of variance (ANOVA) followed by Bonferroni post-tests were used for statistical evaluation among different treatment groups. P<0.05 was taken as statistically significant. The present results show that chronic treatment with raloxifene could benefit myogenically active coronary arteries by (i) restoring ACh-induced dilatation and (ii) reducing U46619-induced constriction without affecting pressure-induced myogenic responses in cholesterol-fed hamsters during estrogen deficiency. If such benefit can be observed in humans, raloxifene and other SERMs may be useful to preserve endothelial function and curtail vascular hypersensitivity in resistance coronary arteries in post-menopausal women with hypercholesterolemia or hyperlipidemia, a lipid condition implicated in the pathogenesis of myocardial infarction.

Endothelin-induced changes in blood flow in STZ-diabetic and non-diabetic rats: relation to nitric oxide synthase and cyclooxygenase inhibition

In this study, using the microsphere method, the hemodynamic response to endothelin-1 (ET-1) in healthy and streptozotocin (STZ)-diabetic rats was evaluated as well as the influences of inhibition of nitric oxide (NO)-synthase using L-NAME (Nω-nitro-L: -arginine methyl ester) and the cyclooxygenase inhibitor indomethacin. Blood flow (Q) was measured in tissues of interest for vascular complications in diabetes such as kidney, eye, brain, heart and skeletal muscle with the main focus on ophthalmic circulation. Under resting conditions, evidence for renal vasoconstriction was found in diabetic animals. In both groups, administration of L-NAME reduced Q in all investigated tissues indicating a basal NO influence. In the normal rats, ET-1 induced a significant increase in blood pressure and intense vasoconstriction in all tissues except in the choroid of the eye and in the brain, where it induced an increased Q. In the STZ-diabetic rats, effects of ET-1 were less pronounced. Pretreatment with L-NAME, but not the cyclooxygenase inhibitor, abolished the ET-1-induced vasodilation in the choroid of both groups. Administration of ET A receptor antagonist BQ-123 reduced the ET-1-induced vasodilation in the choroid only in diabetic animals. In conclusion, evidence for altered vascular endothelial response to ET-1 in STZ-diabetic animals was found particularly in the ophthalmic circulation. The findings suggest differential involvement of receptors in the response to ET-1 in normal and STZ-diabetic animals.

Endothelial nitric oxide synthase enhancer reduces oxidative stress and restores endothelial function in db/db mice

AIMS

Endothelial dysfunction is caused by reduced nitric oxide (NO) bioavailability and/or over-produced reactive oxygen species (ROS). The present study investigated a vascular benefit of AVE3085, an endothelial nitric oxide synthase (eNOS) enhancer, in preserving endothelial function in diabetic mice and the mechanisms involved.

METHODS AND RESULTS

Male db/db and db/m(+) mice were orally administered AVE3085 for 7 days (10 mg kg(-1) day(-1)). Vascular reactivity of arteries was studied via myography under both isometric and isobaric conditions. ROS levels in aortas were determined using dihydroethidium fluorescence dye and electron paramagnetic resonance spin trapping. Chronic treatment with AVE3085 reduced blood pressure, enhanced endothelium-dependent relaxations (EDR) to acetylcholine in aortas, mesenteric, and renal arteries, lowered oxidative stress, and augmented the attenuated flow-dependent dilatation in mesenteric resistance arteries from db/db mice. Incubation of aortas from C57BL/6J mice in high glucose (30 mmol L(-1)) culture medium for 48 h impaired EDR and elevated ROS generation, and these effects were reversed by co-treatment with AVE3085 (1 µmol L(-1)). Benefits of AVE3085 were abolished by the transcription inhibitor actinomycin D, the NOS inhibitor N(G)-nitro-L-arginine methyl ester, and in eNOS(-/-) mice. NO production in primary endothelial cells from mouse aortas was detected with a NO-sensitive fluorescence dye. Protein expression was assayed by western blotting. Treatment with AVE3085 enhanced NO production in endothelial cells and eNOS expression in aortas.

CONCLUSION

AVE3085 ameliorates endothelial dysfunction in db/db mice through increased NO bioavailability, which reduces oxidative stress in the vascular wall. Targeting eNOS and NO production may be a promising approach to combat diabetic vasculopathy.

Angiotensin II and the vascular phenotype in hypertension

Hypertension is associated with vascular changes characterised by remodelling, endothelial dysfunction and hyperreactivity. Cellular processes underlying these perturbations include altered vascular smooth muscle cell growth and apoptosis, fibrosis, hypercontractility and calcification. Inflammation, associated with macrophage infiltration and increased expression of redox-sensitive pro-inflammatory genes, also contributes to vascular remodelling. Many of these features occur with ageing, and the vascular phenotype in hypertension is considered a phenomenon of ‘premature vascular ageing’. Among the many factors involved in the hypertensive vascular phenotype, angiotensin II (Ang II) is especially important. Ang II, previously thought to be the sole effector of the renin–angiotensin system (RAS), is converted to smaller peptides [Ang III, Ang IV, Ang-(1-7)] that are biologically active in the vascular system. Another new component of the RAS is the (pro)renin receptor, which signals through Ang-II-independent mechanisms and might influence vascular function. Ang II mediates effects through complex signalling pathways on binding to its G-protein-coupled receptors (GPCRs) AT1R and AT2R. These receptors are regulated by the GPCR-interacting proteins ATRAP, ARAP1 and ATIP. AT1R activation induces effects through the phospholipase C pathway, mitogen-activated protein kinases, tyrosine kinases/phosphatases, RhoA/Rhokinase and NAD(P)H-oxidase-derived reactive oxygen species. Here we focus on recent developments and new research trends related to Ang II and the RAS and involvement in the hypertensive vascular phenotype.

Plasma reactive carbonyl species: Potential risk factor for hypertension

To study the role of oxidative stress in hypertension and pre-hypertension, this study analysed plasma levels of reactive carbonyl species (RCS) in 1204 Chinese Han adults. Results showed a statistically significant positive correlation (p < 0.001) between blood pressure and plasma RCS levels with or without being adjusted for covariates. Multivariate-adjusted odds ratio (OR) illustrated that, compared with the lowest quartile of plasma RCS levels, the highest quartile subjects had a 59% and a 130% increase in the risk for developing pre-hypertension and hypertension, respectively. The multi-interaction analysis manifested that the underlying mechanism of the increase of hypertensive risk or pre-hypertensive risk by overweight and unhealthy lifestyles might, at least in part, be through oxidative stress. In conclusion, these findings suggest that oxidative stress, as indicated by plasma RCS levels, are not the necessary consequence of pre-hypertension or hypertension, but reliable risk factors for developing pre-hypertension or hypertension in Chinese Han adults.

Coronary artery endothelial dysfunction associated with sleep apnea

There is little information about coronary artery endothelial dysfunction in patients with sleep apnea. We evaluated relation between severity of sleep apnea and coronary artery endothelial dysfunction. In all, 26 patients without significant coronary stenoses were enrolled. Endothelial function was estimated by measuring coronary vasoreactivity in response to acetylcholine infusion (10(-7) mol/L) into coronary arteries. Vasoconstriction rate was defined as ([lumen diameter after isosorbide dinitrate injection - lumen diameter after acetylcholine injection]/lumen diameter after isosorbide dinitrate injection × 100). Vasoconstriction rate was calculated at each major coronary artery and the highest value was used for that patient. Overnight sleep study was performed and the apnea-hypopnea index (AHI) was calculated as the mean number of apneas and hypopneas per hour of sleep. There was significant correlation between AHI and vasoconstriction rate (P = .04). There is significant correlation between severity of sleep apnea and endothelial function of coronary arteries.

Salt modulates vascular response through adenosine A(2A) receptor in eNOS-null mice: role of CYP450 epoxygenase and soluble epoxide hydrolase

High salt (HS) intake can change the arterial tone in mice, and the nitric oxide (NO) acts as a mediator to some of the receptors mediated vascular response. The main aim of this study was to explore the mechanism behind adenosine-induced vascular response in HS-fed eNOS(+/+) and eNOS(-/-) mice The modulation of vascular response by HS was examined using aortas from mice (eNOS(+/+) and eNOS(-/-)) fed 4% (HS) or 0.45% (NS) NaCl-diet through acetylcholine (ACh), NECA (adenosine-analog), CGS 21680 (A(2A) AR-agonist), MS-PPOH (CYP epoxygenase-blocker; 10(-5) M), AUDA (sEH-blocker; 10(-5) M), and DDMS (CYP4A-blocker; 10(-5) M). ACh-response was greater in HS-eNOS(+/+) (+59.3 ± 6.3%) versus NS-eNOS(+/+) (+33.3 ± 8.0%; P < 0.05). However, there was no response in both HS-eNOS(-/-) and NS-eNOS(-/-). NECA-response was greater in HS-eNOS(-/-) (+37.4 ± 3.2%) versus NS-eNOS(-/-) (+7.4.0 ± 3.8%; P < 0.05). CGS 21680-response was also greater in HS-eNOS(-/-) (+45.4 ± 5.2%) versus NS-eNOS(-/-)(+5.1 ± 5.0%; P < 0.05). In HS-eNOS(-/-), the CGS 21680-response was reduced by MS-PPOH (+7.3 ± 3.2%; P < 0.05). In NS-eNOS(-/-), the CGS 21680-response was increased by AUDA (+38.2 ± 3.3%; P < 0.05) and DDMS (+30.1 ± 4.1%; P < 0.05). Compared to NS, HS increased CYP2J2 in eNOS(+/+) (35%; P < 0.05) and eNOS(-/-) (61%; P < 0.05), but decreased sEH in eNOS(+/+) (74%; P < 0.05) and eNOS(-/-) (40%; P < 0.05). Similarly, CYP4A decreased in HS-eNOS(+/+) (35%; P < 0.05) and HS-eNOS(-/-) (34%; P < 0.05). These data suggest that NS causes reduced-vasodilation in both eNOS(+/+) and eNOS(-/-) via sEH and CYP4A. However, HS triggers possible A(2A)AR-induced relaxation through CYP epoxygenase in both eNOS(+/+) and eNOS(-/-).

Obesity and the development of type 2 diabetes: the effects of fatty tissue inflammation

Obesity is a worldwide epidemic with multiple obesity-associated health problems including type 2 diabetes, hypertension, and cardiovascular disease. Adipose tissue serves as a fuel storage depot, but also plays a pivotal role in homeostasis of energy expenditure, appetite regulation, glucose regulation, and immunity. Both genetics and environment play important roles in adipose tissue function and dysfunction. Obesity represents an abnormal accumulation of adipose tissue resulting from chronic overnutrition and reduced physical activity. The nature of this increased accumulation of fat tissue, whether hyperplasia or hypertrophy, local or ectopic, is associated with deleterious perturbations including excess fatty acid secretion, increased production of inflammatory cytokines, and abnormal adipocyte hormone signaling resulting in insulin resistance. In the setting of obesity, insulin resistance and chronic inflammation is postulated to play a role in development of type 2 diabetes and other obesity-related comorbidities including obstructive sleep apnea, hepatic steatosis, polycystic ovarian syndrome, hypertension and cardiovascular disease. Although the exact mechanism of these relationships are complex and not completely understood, the ability to store and limit fatty acid deposition to adipose tissue is a common component to remaining insulin sensitive, controlling the inflammatory cascade and reducing the risk of developing obesity-related comorbidities.