Endothelial dysfunction in small resistance arteries of patients with non-insulin-dependent diabetes mellitus

Determinants of arterial stiffness in patients with type 2 diabetes mellitus: a cross sectional analysis

In patients with type 2 diabetes mellitus (T2DM) arterial stiffness is associated with increased cardiovascular and total mortality. Little is known about determinants of arterial stiffness in clinical routine. Identification of potential determinants of arterial stiffness will help to address treatment targets for patients in the early state of T2DM. This is a cross-sectional analysis of arterial stiffness in 266 patients in the early stage of T2DM who did not have cardiovascular or renal complications. Parameters of arterial stiffness such as central systolic blood pressure (cSBP), central pulse pressure (cPP) and pulse wave velocity (PWV) were measured with the SphygmoCor System (AtCor Medical). We investigated the influence of parameters of glucose metabolism, lipid status, body constitution, blood pressure (BP) and inflammation on the stiffness parameters using multivariate regression analysis. The study cohort consisted of male and female patients aged 61 ± 8 years with mean diabetes duration of 6.4 ± 5.1 years, mean HbA1c 7.1 ± 0.9%, mean cSBP 121 ± 12 mmHg, mean cPP 44 ± 10 mmHg and mean PWV 8.9 ± 1.8 m/s. Multiple regression analysis identified waist circumference (WC) (beta = 0.411, p = 0.026), LDL-cholesterol (beta = 0.106, p = 0.006), systolic office BP (beta = 0.936, p < 0.001) and diabetes duration (beta = 0.233, p = 0.043) as potential determinants of cSBP. cPP was determined by sex (beta = 0.330, p = 0.008), age (beta = 0.383, p < 0.001), systolic office BP (beta = 0.370, p < 0.001) and diabetes duration (beta = 0.231, p = 0.028) whereas for PWV the following determinants could be identified: age (beta = 0.405, p < 0.001), systolic office BP (beta = 0.421, p < 0.001) and diabetes duration (beta = 0.073, p = 0.038). In addition to the known parameters age, sex and systolic office BP serum LDL-cholesterol, WC and diabetes duration have been identified as determinants of arterial stiffness in patients with T2DM. Treatment of patients in the early stage of T2DM should focus on these clinical parameters to prevent progression of arterial stiffness and as a consequence reduce cardiovascular mortality.Trial registration: The patients included in the analysis participated in one of the following clinical trials NCT02752113 (registered 26.4.2016), NCT02383238 (09.03.2015), NCT02471963 (15.06.2015), NCT01319357 (21.03.2011) ( http://www.clinicaltrials.gov ).

Intercellular adhesion molecule-1 (ICAM-1) associates with 24-hour ambulatory blood pressure variability in type 2 diabetes and controls

BACKGROUND AND AIM

Endothelial dysfunction is a common feature in hypertension and type 2 diabetes. Whether blood pressure (BP) variability is influencing serum intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) remains to be clarified. We aimed to assess the association between the circulating adhesion molecules and ambulatory blood pressure variability in patients with type 2 diabetes and controls.

PATIENTS AND METHODS

The study included data from type 2 diabetes with controlled BP (n = 55), type 2 diabetes with uncontrolled BP (n = 55) and control subjects (n = 28). ICAM-1 and VCAM-1 were measured with specific enzyme-linked immunosorbent assay method. BP variability was assessed using standard deviation of mean systolic and diastolic BP evaluated during 24-hour ambulatory BP monitoring.

RESULTS

The uncontrolled BP type 2 diabetes group had significantly higher serum ICAM-1 and VCAM-1 levels compared to controlled BP type 2 diabetes and control groups. In linear regression analysis, after adjustment, higher ICAM-1 was consistently associated with higher daytime and 24-hour diastolic BP variability, and daytime systolic BP variability in the study population. VCAM-1 was associated only with daytime systolic BP variability.

CONCLUSIONS

Our study evaluating the association of serum ICAM-1 and VCAM-1 with 24-hour ambulatory BP variability in patients with type 2 diabetes and controls might offer better understanding of the mechanisms generating endothelial dysfunction. Elevated 24-hour ambulatory BP variability might induce endothelial activation by increasing circulating adhesion molecules levels.

Coronary microvascular dysfunction after long-term diabetes and hypercholesterolemia

Coronary microvascular dysfunction (CMD) has been proposed as an important component of diabetes mellitus (DM)- and hypercholesterolemia-associated coronary artery disease (CAD). Previously we observed that 2.5 mo of DM and high-fat diet (HFD) in swine blunted bradykinin (BK)-induced vasodilation and attenuated endothelin (ET)-1-mediated vasoconstriction. Here we studied the progression of CMD after 15 mo in the same animal model of CAD. Ten male swine were fed a HFD in the absence (HFD, n = 5) or presence of streptozotocin-induced DM (DM + HFD, n = 5). Responses of small (∼300-μm-diameter) coronary arteries to BK, ET-1, and the nitric oxide (NO) donor S-nitroso-N-acetylpenicillamine were examined in vitro and compared with those of healthy (Normal) swine (n = 12). Blood glucose was elevated in DM + HFD (17.6 ± 4.5 mmol/l) compared with HFD (5.1 ± 0.4 mmol/l) and Normal (5.8 ± 0.6 mmol/l) swine, while cholesterol was markedly elevated in DM + HFD (16.8 ± 1.7 mmol/l) and HFD (18.1 ± 2.6 mmol/l) compared with Normal (2.1 ± 0.2 mmol/l) swine (all P < 0.05). Small coronary arteries showed early atherosclerotic plaques in HFD and DM + HFD swine. Surprisingly, DM + HFD and HFD swine maintained BK responsiveness compared with Normal swine due to an increase in NO availability relative to endothelium-derived hyperpolarizing factors. However, ET-1 responsiveness was greater in HFD and DM + HFD than Normal swine (both P < 0.05), resulting mainly from ET_B receptor-mediated vasoconstriction. Moreover, the calculated vascular stiffness coefficient was higher in DM + HFD and HFD than Normal swine (both P < 0.05). In conclusion, 15 mo of DM + HFD, as well as HFD alone, resulted in CMD. Although the overall vasodilation to BK was unperturbed, the relative contributions of NO and endothelium-derived hyperpolarizing factor pathways were altered. Moreover, the vasoconstrictor response to ET-1 was enhanced, involving the ET_B receptors. In conjunction with our previous study, these findings highlight the time dependence of the phenotype of CMD.

Increased plasma serotonin metabolite 5-hydroxyindole acetic acid concentrations are associated with impaired systolic and late diastolic forward flows during cardiac cycle and elevated resistive index at popliteal artery and renal insufficiency in type 2 diabetic patients with microalbuminuria

Although lower extremity arterial disease is frequently accompanied by diabetes mellitus, the association of circulating biomarkers with flow components during the cardiac cycle in lower-leg arteries has yet to be fully elucidated. We enrolled 165 type 2 diabetic patients with normal ankle-brachial index (ABI 1.0-1.4), comprising 106 normoalbuminuric and 59 microalbuminuric patients, and 40 age-matched nondiabetic subjects consecutively admitted to our hospital. Serum high sensitivity C-reactive protein (hsCRP) level and plasma von Willebrand factor ristocetin cofactor activity (VWF) and vasoconstrictor serotonin metabolite 5-hydroxyindole acetic acid (5-HIAA) concentrations were measured. An automatic device was used to measure ABI and brachial-ankle pulse wave velocity (baPWV). Flow components during the cardiac cycle, total flow volume, and resistive index at popliteal artery were evaluated using gated magnetic resonance imaging. Although estimated glomerular filtration rate (eGFR), early diastolic flow reversal, heart rate, and ABI were similar between the groups, diabetic patients had higher log hsCRP (p<0.001), VWF (p<0.001), 5-HIAA (p=0.002), resistive index (p<0.001) and baPWV (p<0.001) and lower systolic (p=0.026) and late diastolic (p<0.001) forward flows and total flow volume (p<0.001) than nondiabetic subjects. Multivariate analyses demonstrated that 5-HIAA in microalbuminuric patients showed higher associations with systolic and late diastolic forward flows during the cardiac cycle, total flow volume and resistive index at popliteal artery, and eGFR compared to normoalbuminuric patients. In microalbuminuric patients, 5-HIAA was a significant independent determinant among these factors. Thus, increased plasma 5-HIAA levels are involved in the pathogenesis of impaired blood flow in lower extremities and renal insufficiency in diabetic patients with microalbuminuria.

Assessment of vascular function in individuals with hyperglycemia: a cross-sectional study of glucose - induced changes in digital volume pulse

Background

Arterial stiffness is an independent risk factor for cardiovascular disease and its progression may be accelerated in the presence of hyperglycemia, either fasting or postprandial. The current study assessed vascular function in subjects with pre-diabetes hyperglycemia, using digital volume pulse analysis technique.

Methods

We conducted a cross-sectional study examining vascular function in the fasting and postprandial (glucose-induced) state in 44 adults, consisting of 17 subjects with pre-diabetic hyperglycemia and 27 normoglycemic volunteers. Photoplethysmography of the digital volume pulse (DVP) was used to determine stiffness index (SI) and reflective index (RI), as main measures of larger artery stiffness and vascular tone, respectively.

Results

Our results showed a significantly higher (Ln) fasting SI in the hyperglycemic group compared with the control group (2.19 ± 0.32 vs. 1.96 ± 0.22, P = 0.005). However, this pattern reversed after adjustment for potential confounders. In multiple linear regression analysis, (Ln) SI was related to age (β = 0.01, 95% CI: 0.01-0.02, P < 0.001) and systolic blood pressure (SBP) (β = 0.01, 95% CI: 0.00-0.01, P < 0.05), but not with W/H, diastolic blood pressure (DBP), fasting plasma glucose (FPG) or serum lipids. Furthermore, age (β = 0.02, 95% CI: 0.01-0.03, P < 0.001) and mean arterial pressure (MAP) (β = 0.01, 95% CI: 0.00-0.02, P < 0.05) were found as the strong predictors of fasting SI in hyperglycemic group. Neither FPG nor 2-h plasma glucose was a significant predictor for SI in hyperglycemic group, after accounting for age and MAP. Subjects with hyperglycemia had a 15% blunted change in postprandial AUCs for RI, adjusted for the respective baseline measurements (−9.40 ± 3.59 vs. -11.00 ± 2.84%) but these did not attain statistical significance.

Conclusion

Increased arterial stiffness in pre-diabetic subjects is strongly associated with age and MAP. The increased DVP-derived SI reported in patients with pre-diabetic hyperglycemia may result from different frequently accompanied risk factors not just glycemic changes in this range.

Elevated plasma B-type natriuretic peptide concentration and resistive index, but not decreased aortic distensibility, associate with impaired blood flow at popliteal artery in type 2 diabetic patients

Blood flow in lower extremity arteries is frequently impaired in diabetic patients even though they have a normal ankle-brachial index (ABI 1.0-1.4). Risk factors contributing to this lower extremity arterial disease have not been fully elucidated. We enrolled 52 type 2 diabetic patients with normal ABI and 30 age-matched nondiabetic subjects consecutively admitted to our hospital. Plasma B-type natriuretic peptide (BNP) concentrations were measured. Distensibility in ascending thoracic and abdominal aortas as well as total flow volume and resistive index at popliteal artery were evaluated by gated magnetic resonance imaging. An automatic device was used to measure ABI and brachial-ankle pulse-wave velocity (baPWV). Diabetic patients showed lower distensibility in ascending thoracic aorta (p<0.001) and total flow volume (p<0.001) and higher baPWV (p<0.001) and resistive index (p=0.005) and similar BNP and distensibility in abdominal aorta compared to nondiabetic subjects. Simple linear regression analyses revealed that distensibility in ascending thoracic (p=0.019) and abdominal (p=0.030) aortas positively as well as baPWV (p=0.020), resistive index (p<0.001) and BNP (p<0.001) negatively correlated with total flow volume. Stepwise multiple regression analysis demonstrated that increased BNP and resistive index were independent risk factors for total flow volume in diabetic patients (r(2)=0.639, p<0.001). These results indicate that increased plasma BNP levels and peripheral vascular resistance, but not decreased aortic distensibility, associate with impaired blood flow in lower extremity arteries in diabetic patients.

Mechanisms of diabetic complications

It is increasingly apparent that not only is a cure for the current worldwide diabetes epidemic required, but also for its major complications, affecting both small and large blood vessels. These complications occur in the majority of individuals with both type 1 and type 2 diabetes. Among the most prevalent microvascular complications are kidney disease, blindness, and amputations, with current therapies only slowing disease progression. Impaired kidney function, exhibited as a reduced glomerular filtration rate, is also a major risk factor for macrovascular complications, such as heart attacks and strokes. There have been a large number of new therapies tested in clinical trials for diabetic complications, with, in general, rather disappointing results. Indeed, it remains to be fully defined as to which pathways in diabetic complications are essentially protective rather than pathological, in terms of their effects on the underlying disease process. Furthermore, seemingly independent pathways are also showing significant interactions with each other to exacerbate pathology. Interestingly, some of these pathways may not only play key roles in complications but also in the development of diabetes per se. This review aims to comprehensively discuss the well validated, as well as putative mechanisms involved in the development of diabetic complications. In addition, new fields of research, which warrant further investigation as potential therapeutic targets of the future, will be highlighted.

Death by a thousand cuts in Alzheimer's disease: hypoxia--the prodrome

A wide range of clinical consequences may be associated with obstructive sleep apnea (OSA) including systemic hypertension, cardiovascular disease, pulmonary hypertension, congestive heart failure, cerebrovascular disease, glucose intolerance, impotence, gastroesophageal reflux, and obesity, to name a few. Despite this, 82 % of men and 93 % of women with OSA remain undiagnosed. OSA affects many body systems, and induces major alterations in metabolic, autonomic, and cerebral functions. Typically, OSA is characterized by recurrent chronic intermittent hypoxia (CIH), hypercapnia, hypoventilation, sleep fragmentation, peripheral and central inflammation, cerebral hypoperfusion, and cerebral glucose hypometabolism. Upregulation of oxidative stress in OSA plays an important pathogenic role in the milieu of hypoxia-induced cerebral and cardiovascular dysfunctions. Strong evidence underscores that cerebral amyloidogenesis and tau phosphorylation--two cardinal features of Alzheimer's disease (AD), are triggered by hypoxia. Mice subjected to hypoxic conditions unambiguously demonstrated upregulation in cerebral amyloid plaque formation and tau phosphorylation, as well as memory deficit. Hypoxia triggers neuronal degeneration and axonal dysfunction in both cortex and brainstem. Consequently, neurocognitive impairment in apneic/hypoxic patients is attributable to a complex interplay between CIH and stimulation of several pathological trajectories. The framework presented here helps delineate the emergence and progression of cognitive decline, and may yield insight into AD neuropathogenesis. The global impact of CIH should provide a strong rationale for treating OSA and snoring clinically, in order to ameliorate neurocognitive impairment in aged/AD patients.

The vascular phenotypes in hypertension: Relation with the natural history of hypertension

The different vascular phenotypes found in hypertension comprise different aspects. They may be clinical, diagnostic, structural, mechanical, functional, cellular and extracellular, signaling and molecular, proteomic, and gene expression phenotypes. In this manuscript the emphasis will be on the various structure, mechanics, dysfunction, and cell and signaling changes that can be demonstrated in hypertension, and particularly in human hypertension. The phenotype relates to the natural history of hypertension, increasingly elucidated on the basis of cohort studies. The evolution from pre-hypertension to diastolic, systolic, and systo-diastolic hypertension may have a vascular substratum that could explain, in part, the prevalence of each of these phenotypes. The potential for intervention to prevent the passage from pre-hypertension to hypertension thanks to therapies that modulate the development of vascular remodeling is highlighted.

Type 2 diabetes mellitus worsens arterial stiffness in hypertensive patients through endothelial dysfunction

AIMS/HYPOTHESIS

Endothelium-derived factors are thought to be physiological modulators of large artery stiffness. The aim of the study was to investigate whether endothelial function could be a determinant of arterial stiffness in essential hypertensive patients, in relation with the concomitant presence of type 2 diabetes mellitus.

METHODS

The study included 341 participants (84 hypertensive patients with and 175 without type 2 diabetes mellitus, 82 matched controls). Brachial artery endothelium-dependent flow-mediated dilation (FMD) was determined by high-resolution ultrasound and computerised edge detection system. Applanation tonometry was used to measure carotid-femoral pulse wave velocity (PWV).

RESULTS

Hypertensive patients with diabetes had higher PWV (10.1 ± 2.3 m/s vs 8.6 ± 1.4 m/s, p < 0.001) and lower FMD (3.51 ± 2.07 vs 5.16 ± 2.96%, p < 0.001) than non-diabetic hypertensive patients, who showed impaired vascular function when compared with healthy participants (7.9 ± 1.6 m/s and 6.68 ± 3.67%). FMD was significantly and negatively correlated to PWV only in hypertensive diabetic patients (r = -0.456, p < 0.001), but not in hypertensive normoglycaemic patients (r = -0.088, p = 0.248) or in healthy participants (r = 0.008, p = 0.946). Multivariate analysis demonstrated that, in the diabetic group, FMD remained an independent predictor of PWV after adjustment for confounders (r(2) = 0.083, p = 0.003). Subgroup analysis performed in non-diabetic hypertensive patients revealed that neither obesity nor the metabolic syndrome affected the relationship between FMD and PWV.

CONCLUSIONS/INTERPRETATION

Endothelial dysfunction is a determinant of aortic stiffness in hypertensive diabetic patients but not in hypertensive patients without diabetes. These results suggest that type 2 diabetes mellitus on top of hypertension might worsen arterial compliance by endothelium-related mechanisms.

Associations of plasma von Willebrand factor ristocetin cofactor activity and 5-hydroxyindole acetic acid concentrations with blood flow in lower-leg arteries in Japanese type 2 diabetic patients with normal ankle-brachial index

AIMS

To evaluate the associations of circulating levels of proinflammatory molecules and endothelial factors with blood flow in lower-leg arteries in diabetic patients with normal ankle-brachial index (ABI>0.9).

METHODS

We enrolled 123 type 2 diabetic patients with normal ABI and 30 age-matched nondiabetic subjects consecutively admitted to our hospital. Flow volume and resistive index, an index of peripheral vascular resistance, at the popliteal artery were evaluated using gated two-dimensional cine-mode phase-contrast magnetic resonance imaging. An automatic device was used to measure ABI and brachial-ankle pulse-wave velocity (baPWV) for evaluation of arterial stiffness. Plasma soluble intercellular adhesion molecule-1 (sICAM-1) and monocyte chemoattractant protein-1 (MCP-1) concentrations, serum high-sensitivity C-reactive protein (hsCRP) levels, plasma von Willebrand factor ristocetin cofactor activity (VWF), and plasma vasoconstrictor serotonin metabolite 5-hydroxyindole acetic acid (5-HIAA) concentrations were measured.

RESULTS

Diabetic patients had higher baPWV (P<.0001), resistive index (P<.0001), sICAM-1 (P<.0001), MCP-1 (P=.0224), log hsCRP (P<.0001), VWF (P<.0001), 5-HIAA (P=.0015), and lower blood flow (P<.0001) than nondiabetic subjects. VWF (P=.0019) or 5-HIAA (P=.0011), but not sICAM-1, MCP-1, and log hsCRP, was negatively correlated with blood flow in diabetic patients. A multivariate analysis revealed that the significant independent determinants of blood flow were hypertension, use of renin-angiotensin system inhibitors, VWF and 5-HIAA (r(2)=0.198, P<.0001) in diabetic patients.

CONCLUSIONS

Plasma VWF and 5-HIAA concentrations are associated with blood flow and are involved in the pathogenesis of impaired peripheral circulation due to higher arterial stiffness and greater vascular resistance in lower-leg arteries in diabetic patients with normal ABI.

Small artery function 2 years postpartum in women with altered glycaemic distributions in their preceding pregnancy

GDM (gestational diabetes mellitus) is associated with later adverse cardiovascular risk. The present study examined the relationship between glycaemia during pregnancy and small artery function and structures approx. 2 years postpartum. Women were originally enrolled in the HAPO (Hyperglycaemia and Adverse Pregnancy Outcome) study from which they were classified by their glycaemic distribution during pregnancy as controls (in the lower half of the distribution), UQ (upper quartile; in the UQ of the glycaemic distribution) or having had overt GDM. Subcutaneous arteries from a gluteal fat biopsy taken at follow-up 2 years later were examined using wire myography. Small artery structure, stiffness and vasoconstrictor responses were similar across groups. Maximal endothelium-dependent dilation in response to carbachol was impaired in arteries from both GDM (43.3%, n=8 and P=0.01) and UQ (51.7%, n=13 and P=0.04) women despite generally 'normal' current glycaemia (controls, 72.7% and n=8). Inhibition of NOS (nitric oxide synthase) significantly reduced maximum endothelium-dependent dilation in controls but had no effect on arteries from UQ and GDM women, suggesting impaired NOS activity in these groups. Endothelium-independent dilation was unaffected in arteries from previous GDM and UQ women when compared with the control group. Multiple regression analysis suggested that BMI (body mass index) at biopsy was the most potent factor independently associated with small artery function, with no effect of current glycaemia. Overweight women with either GDM or marginally raised glycaemia during pregnancy (our UQ group) had normal vascular structure and stiffness, but clearly detectable progressively impaired endothelium-dependent function at 2 years follow-up. These results suggest that vascular pathology, which may still be reversible, is detectable very early in women at risk of decline into Type 2 diabetes mellitus.

Coronary microvascular dysfunction in a porcine model of early atherosclerosis and diabetes

Detailed evaluation of coronary function early in diabetes mellitus (DM)-associated coronary artery disease (CAD) development is difficult in patients. Therefore, we investigated coronary conduit and small artery function in a preatherosclerotic DM porcine model with type 2 characteristics. Streptozotocin-induced DM pigs on a saturated fat/cholesterol (SFC) diet (SFC + DM) were compared with control pigs on SFC and standard (control) diets. SFC + DM pigs showed DM-associated metabolic alterations and early atherosclerosis development in the aorta. Endothelium-dependent vasodilation to bradykinin (BK), with or without blockade of nitric oxide (NO) synthase, endothelium-independent vasodilation to an exogenous NO-donor (S-nitroso-N-acetylpenicillamine), and vasoconstriction to endothelin (ET)-1 with blockade of receptor subtypes, were assessed in vitro. Small coronary arteries, but not conduit vessels, showed functional alterations including impaired BK-induced vasodilatation due to loss of NO (P < 0.01 vs. SFC and control) and reduced vasoconstriction to ET-1 (P < 0.01 vs. SFC and control), due to a decreased ET(A) receptor dominance. Other vasomotor responses were unaltered. In conclusion, this model demonstrates specific coronary microvascular alterations with regard to NO and ET-1 systems in the process of early atherosclerosis in DM. In particular, the altered ET-1 system correlated with hyperglycemia in atherogenic conditions, emphasizing the importance of this system in DM-associated CAD development.

Mesenteric resistance arteries in type 2 diabetic db/db mice undergo outward remodeling

OBJECTIVE

Resistance vessel remodeling is controlled by myriad of hemodynamic and neurohormonal factors. This study characterized structural and molecular remodeling in mesenteric resistance arteries (MRAs) in diabetic (db/db) and control (Db/db) mice.

METHODS

Structural properties were assessed in isolated MRAs from 12 and 16 wk-old db/db and Db/db mice by pressure myography. Matrix regulatory proteins were measured by Western blot analysis. Mean arterial pressure and superior mesenteric blood flow were measured in 12 wk-old mice by telemetry and a Doppler flow nanoprobe, respectively.

RESULTS

Blood pressure was similar between groups. Lumen diameter and medial cross-sectional area were significantly increased in 16 wk-old db/db MRA compared to control, indicating outward hypertrophic remodeling. Moreover, wall stress and cross-sectional compliance were significantly larger in diabetic arteries. These remodeling indices were associated with increased expression of matrix regulatory proteins matrix metalloproteinase (MMP)-9, MMP-12, tissue inhibitors of matrix metalloproteinase (TIMP)-1, TIMP-2, and plasminogen activator inhibitor-1 (PAI-1) in db/db arteries. Finally, superior mesenteric artery blood flow was increased by 46% in 12 wk-old db/db mice, a finding that preceded mesenteric resistance artery remodeling.

CONCLUSIONS

These data suggest that flow-induced hemodynamic changes may supersede the local neurohormonal and metabolic milieu to culminate in hypertrophic outward remodeling of type 2 DM mesenteric resistance arteries.

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.

A review of endothelial dysfunction in diabetes: a focus on the contribution of a dysfunctional eNOS

Although the etiology of vascular dysfunction in diabetes has been extensively investigated in both humans as well as animal models of human diabetes, the relative importance of the cellular pathways involved is still not fully understood. In this review, we focus on reviewing the literature that provides insights into how an acute exposure to hyperglycemia results in a dysregulation of endothelial nitric oxide synthase function, the subsequent downstream effects of endothelial nitric oxide synthase dysregulation, and the development of endothelial dysfunction.

Alteration of vascular reactivity in diabetic human mammary artery and the effects of thiazolidinediones

Vascular reactivity was investigated in endothelium-denuded human internal mammary artery (IMA) rings from type 2 diabetic patients. It was also investigated whether insulin sensitizer thiazolidinedione drugs, pioglitazone and rosiglitazone, can directly affect the reactivity of IMA. Using organ bath techniques, cumulative concentration-response curves to phenylephrine (PE), KCl, cromakalim (CRO) and sodium nitroprusside (SNP) were constructed in diabetic and non-diabetic IMA rings. Means of maximal responses (% Emax) and pEC50 values (sensitivity) were compared. Emax values and the sensitivity to PE and KCl were increased while KATP-channel-mediated relaxations were reduced significantly in diabetic rings compared with non-diabetic rings (n = 5–12, P &lt; 0.05). No changes were observed for SNP responses (n = 5, P &gt; 0.05). Incubations with pioglitazone (1 and 10 μM) and rosiglitazone (1 and 20 μM), for 30 min, did not affect KATP-channel-mediated relaxations (n = 5 each, P &gt; 0.05). Pioglitazone partly inhibited pre-contractions of PE and KCl at 10 μM, rosiglitazone did not. Vascular dysfunction observed in diabetic IMA may be of specific importance since they are widely used as coronary bypass material. Thiazolidinedione drugs may not worsen arterial dilatation through KATP channels in ischaemic or hypoxic insults in diabetic patients who are prone to such conditions. Pioglitazone has vasorelaxant property in the grafts.

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.

Effects of pre- and periconceptional undernutrition on arterial function in adult female sheep are vascular bed dependent

The nutritional environment during development and even prior to conception may contribute to cardiovascular risk. In mature adult female sheep, we investigated the effect of preconceptional and periconceptional maternal nutritional restriction on the vascular reactivity of arteries from four vascular beds supplying the heart, thorax, kidney and hindlimb. Welsh Mountain ewes received 100% of nutrient requirements throughout gestation (control group, C, n = 18), or 50% of nutrient requirements for 30 days prior to conception (preconceptional group, PRE, n = 20) or for 15 days either side of conception (periconceptional group, PERI, n = 31) and 100% thereafter. In 3.5-year-old female offspring, the left anterior descending coronary (LAD), left internal thoracic (LITA), right renal and second and third order femoral arteries were dissected and their reactivity was assessed by organ bath or wire myography. Vasoconstrictor responses were greater in both LAD and LITA from PERI offspring compared with C (P < 0.01), while vasoconstriction was unaffected by maternal diet in arteries from the renal and femoral circulations (P = n.s.). Endothelium-dependent and -independent vasodilatation was attenuated in third order femoral arteries of PRE and PERI groups compared with C (P < 0.05). Endothelium-independent vasodilatation was attenuated in both the LAD and renal arteries in the PERI group compared with C (P < 0.05). These data show that moderate maternal undernutrition either prior to or around conception affects vascular function of adult offspring. The effect depends on the timing of the insult, but also on the vascular bed studied and vessel hierarchy in the vascular tree.

Higher arterial stiffness, greater peripheral vascular resistance and lower blood flow in lower-leg arteries are associated with long-term hyperglycaemia in type 2 diabetic patients with normal ankle-brachial index

BACKGROUND

Higher arterial stiffness and greater peripheral vascular resistance reduce blood flow in lower-leg arteries and contribute to the development of ischaemic limb in diabetic patients even without peripheral artery occlusive disease. The aim of this study was to clarify whether these vascular parameters are associated with long-term hyperglycaemia in diabetic patients.

METHODS

We examined 45 type 2 diabetic patients and 38 age-matched nondiabetic subjects without peripheral artery occlusive disease assessed by ankle-brachial index consecutively admitted to our hospital, and followed them over a 3-year period (3.7 +/- 0.7 years) with no vasodilative medication. Blood flow and resistive index, a measure of peripheral vascular resistance, at the popliteal artery were evaluated using gated two-dimensional cine-mode phase-contrast magnetic resonance imaging. Brachial-ankle pulse wave velocity was measured to assess arterial stiffness.

RESULTS

At baseline, consistent with our previous report, diabetic patients showed higher brachial-ankle pulse wave velocity (p < 0.0001) and resistive index (p < 0.0001) and lower flow volume (p = 0.0044) than those of nondiabetic subjects. Stepwise multiple regression analysis revealed that duration of diabetes, mean HbA(1c) during the study, use of renin-angiotensin system inhibitors and change per year in resistive index were identified as significant independent variables predicting change per year in blood flow (r(2) = 0.733, p < 0.0001) in diabetic patients. Mean HbA(1c) during the study was positively correlated with changes per year in brachial-ankle pulse wave velocity (p = 0.00007) and resistive index (p = 0.0014) and was negatively correlated with that in blood flow (p < 0.0001) in diabetic patients.

CONCLUSIONS

Long-term hyperglycaemia is a major cause of impaired peripheral circulation in lower-leg arteries in diabetic patients without peripheral artery occlusive disease.

Atorvastatin restores endothelial function in offspring of protein-restricted rats in a cholesterol-independent manner

Maternal protein restriction in rats leads to endothelial dysfunction and decreased NO bioavailability in the offspring. Statins (3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors) are recognized to have pleiotropic actions including increasing NO bioavailability and reducing inflammation and oxidative damage. This study assessed statin treatment on vascular function in a model of endothelial dysfunction, which is independent of dyslipidemia. Wistar rats were fed a control (18% casein) or protein-restricted (9% casein) diet throughout pregnancy. At weaning, a subset of the protein-restricted group was given atorvastatin (10 mg/kg per day) in the drinking water. At 145 days of age, offspring were euthanized by CO(2) inhalation. Plasma samples were collected for markers of inflammation, vascular reactivity of the thoracic aorta, and small mesenteric arteries were assessed on the wire myograph, and tissues were snap frozen for molecular biology analysis. Thoracic aorta endothelial-dependent vasodilatation was attenuated in the male offspring from both protein-restricted groups compared with controls (P<0.05) but was similar in females (P value not significant). Endothelial-dependent dilatation of mesenteric arteries was attenuated in male and female protein-restricted offspring (P<0.05) and was corrected by atorvastatin. Maternal protein restriction increased plasma inflammatory markers granulocyte chemotactic protein, lipocalin-2, and beta(2)-microglobulin in male and C-reactive protein in female offspring (P<0.05). Atorvastatin had no effect on inflammatory markers in the males but restored C-reactive protein to control levels in the females (P<0.05). Aortic and mesenteric artery mRNA levels of endothelial NO synthase, superoxide dismutase 1, and tumor necrosis factor-alpha were unchanged. These data suggest that atorvastatin can restore endothelial function in this model, but its effects are gender specific and dependent on the vascular bed.

Transmission of raised blood pressure and endothelial dysfunction to the F2generation induced by maternal protein restriction in the F0, in the absence of dietary challenge in the F1generation

We have previously demonstrated that maternal protein restriction during pregnancy leads to raised blood pressure and endothelial dysfunction in the offspring (F1). Here we show that these characteristics are transmitted to the F2offspring through the maternal line, in the absence of any additional challenges to the F1. Female Wistar rats were fed either a control (18 % casein) or protein-restricted diet (PR; 9 % casein) throughout pregnancy. Female F1offspring, maintained on standard chow postpartum, were mated with breeding males to produce F2progeny. Systolic blood pressure (SBP) in male F2offspring was assessed by tail-cuff plethysmography at age 100 d and vascular function of small mesenteric arteries by wire myography at age 80 and 200 d. SBP was raised in PR F2offspring compared with controls (control 122·1 (sem2·3) mmHg,n7; PR 134·7 (sem3·2) mmHg,n6;P < 0·01) and endothelial function, assessed by vasodilatation to acetylcholine, was impaired at both age 80 d (% maximal response: control 89·7 (sem2·6),n14; PR 72·7 (sem4·4),n15;P < 0·01) and 200 d (effective concentration equal to 50 % of maximum (pEC50): control 7·67 (sem0·10),n10; PR 7·33 (sem0·07),n8;P < 0·05). The present study demonstrates that both raised blood pressure and endothelial dysfunction are passed via the maternal line to grand-offspring in the absence of any additional dietary challenges to their F1mothers. Risk factors for chronic disease may therefore be heritable by non-genomic processes.

Impaired peripheral circulation in lower-leg arteries caused by higher arterial stiffness and greater vascular resistance associates with nephropathy in type 2 diabetic patients with normal ankle-brachial indices

Diabetic nephropathy is a major cause of lower-limb amputation. We enrolled 250 type 2 diabetic patients without apparent occlusive peripheral arterial disease (ankle-brachial indices >0.9) and 40 age-matched nondiabetic subjects consecutively admitted to our hospital. Flow volume and resistive index (RI), an index of vascular resistance, at the popliteal artery were evaluated using gated two-dimensional cine-mode phase-contrast magnetic resonance imaging. Brachial-ankle pulse wave velocity (baPWV) was measured as an index of arterial distensibility. Flow volume was negatively correlated with both baPWV (p=0.0009) and RI (p<0.0001) among the patients. When the patients were grouped into four subgroups with or without albuminuria and renal insufficiency according to the levels of urinary albumin excretion rate (>or=20 or <20microg/min) and estimated glomerular filtration rate (eGFR) (<60 or >or=60ml/min/1.73m(2)), albuminuric patients with renal insufficiency (n=30) showed the lowest flow volume (p=0.0078) and the highest baPWV (p=0.0006) and RI (p=0.0274) among the groups. Simple linear regression analyses demonstrated that eGFR correlated positively with flow volume (p=0.0020) and negatively with baPWV (p=0.0258) and RI (p=0.0029) in patients with albuminuria (n=92), but not with normoalbuminuria (n=158). Impaired peripheral circulation in lower-leg arteries associates with nephropathy in diabetic patients even though they have normal ankle-brachial indices.

Maternal undernutrition leads to endothelial dysfunction in adult male rat offspring independent of postnatal diet

Increasing evidence suggests a role for prenatal environment in the onset of cardiovascular and metabolic disease in later life. In the rat, undernutritionin uteroand a postnatal high-fat diet gives rise to a phenotype similar to the metabolic syndrome. As endothelial dysfunction is a feature of both CVD and the metabolic syndrome we investigated the impact of maternal undernutrition and/or postnatal high-fat on endothelial function. Virgin Wistar rats were mated and randomly assigned to groups to receive food eitherad libitum(control) or at 30 % ofad libitumintake throughout gestation. At postnatal day 250, a cohort from each group was challenged with a high-fat diet (D12451, 45 % energy from fat; Research Diets, Inc., New Brunswick, NJ, USA) for the remainder of the study. At 1 year of age, small mesenteric arteries were dissected and mounted on a wire myograph and responses to phenylephrine, endothelin, acetylcholine, leptin and sodium nitroprusside assessed. Vasoconstriction to endothelin was significantly enhanced in all groups compared with controls (-log effective concentration equal to 50 % of the maximal response (pEC50);P < 0·001). Endothelium-dependent vasodilatation to acetylcholine was significantly blunted in all groups compared with controls (% maximum response;P < 0·01), while dilatation to leptin and sodium nitroprusside was similar in all groups. These data demonstrate that both maternal undernutrition and postnatal high fat lead to vascular alterations and suggest that maternal undernutrition alone is at least as detrimental to offspring endothelial function as a long-term exposure to a high-fat diet in the offspring.

Altered role of smooth muscle endothelin receptors in coronary endothelin-1 and α1-adrenoceptor-mediated vasoconstriction in Type 2 diabetes

Regulation of vascular tone and blood flow involves interactions between numerous local and systemic vascular control signals, many of which are altered by Type 2 diabetes (T2D). Vascular responses to endothelin-1 (ET-1) are mediated by endothelin type A (ETA) and type B (ETB) receptors that have been implicated in cross talk with α1-adrenoceptors (α1-AR). ETAand ETBreceptor expression and plasma ET-1 levels are elevated in T2D; however, whether this influences coronary α1-AR function has not been examined. Therefore, we examined the effect of ETAand ETBreceptor inhibition on coronary vasoconstriction to ET-1 and α1-AR activation in a mouse model of T2D. Coronary vascular responses were examined in isolated mouse hearts from control and diet-induced T2D C57BL/6J mice. Responses to ET-1 and the selective α1-AR agonist phenylephrine (PE) were examined alone and in the presence of the nitric oxide synthase inhibitor Nω-nitro-l-arginine methyl ester (l-NAME) alone or in combination with selective ETAor ETBreceptor inhibitors BQ-123 and BQ-788, respectively. Vasoconstriction to ET-1 was enhanced, whereas ETB, but not ETA, receptor blockade reduced basal coronary tone in T2D hearts. In the presence of l-NAME, ETAreceptor inhibition attenuated ET-1 vasoconstriction in both groups, whereas ETBinhibition abolished this response only in control hearts. In addition, ETAinhibition enhanced α1-AR-mediated vasoconstriction in T2D, but not control, hearts following l-NAME treatment. Therefore, in this model, enhanced coronary ET-1 responsiveness is mediated primarily through smooth muscle ETBreceptors, whereas the interaction with α1-ARs is mediated solely through the ETAreceptor subtype.

Folic acid: a marker of endothelial function in type 2 diabetes?

OBJECTIVES

Endothelial dysfunction is a common feature of type 2 diabetes. Recent studies suggest that the B-vitamin folic acid exerts direct beneficial effects on endothelial function, beyond the well known homocysteine lowering effects. Therefore, folic acid might represent a novel "biomarker" of endothelial function. We sought to determine whether plasma levels of folic acid determine endothelial-dependent vasodilation in patients with type 2 diabetes.

METHODS

Forearm arterial blood flow (FABF) was measured at baseline and during intra-brachial infusion of the endothelial-dependent vasodilator acetylcholine (15 microg/min) and the endothelial-independent vasodilator sodium nitroprusside (2 microg/min) in 26 type 2 diabetic patients (age 56.5 +/- 0.9 years, means +/- SEM) with no history of cardiovascular disease.

RESULTS

FABF ratio (ie, the ratio between the infused and control forearm FABF) significantly increased during acetylcholine (1.10 +/- 0.04 vs 1.52 +/- 0.07, p < 0.001) and sodium nitroprusside (1.12 +/- 0.11 vs 1.62 +/- 0.06, p < 0.001) infusions. After correcting for age, gender, diabetes duration, smoking, hypertension, body mass index, microalbuminuria, glycated hemoglobin, low-density lipoprotein cholesterol, and homocysteine, multiple regression analysis showed that plasma folic acid concentration was the only independent determinant (p = 0.037, R2 = 0.22) of acetylcholine-mediated, but not sodium nitroprusside-mediated, vasodilatation.

CONCLUSIONS

Folic acid plasma concentrations determine endothelium-mediated vasodilatation in patients with type 2 diabetes. These results support the hypothesis of a direct effect of folic acid on endothelial function and the rationale for interventions aimed at increasing folic acid levels to reduce cardiovascular risk.

Circulating adhesion molecules levels in type 2 diabetes mellitus and hypertension

BACKGROUND

Risk factors for atherosclerosis such as hypertension, type 2 diabetes, obesity and dyslipidemia affect endothelial function and stimulate adhesion molecules expression. The aim of the study was to examine endothelial activation in type 2 diabetes and hypertension as indicated by adhesion molecule levels and further to investigate whether the coexistence of the above conditions has a different effect.

METHODS

Serum levels of soluble E-selectin, ICAM-1 and VCAM-1 were measured in 17 hypertensive type 2 diabetic patients (DM-HY), 32 normotensive type 2 diabetic patients (DM), 11 hypertensive nondiabetic patients (HY) and 15 healthy subjects.

RESULTS

In diabetic patients (either DM-HY or DM), soluble E-selectin levels were significantly increased compared to healthy subjects (p<0.001). In HY patients, both sE-selectin (66.44+/-71.59 vs. 29.42+/-15.56 ng/ml, p=0.033) and sVCAM-1 (1529+/-433.33 vs. 1027+/-243.56 ng/ml, p=0.03) levels were found significantly higher compared to healthy subjects (p<0.05). The coexistence of diabetes and hypertension (DM-HY) did not have an additive effect on circulating adhesion molecules levels compared with the levels observed in either diabetes or hypertension. Systolic and diastolic blood pressure (BP) were independent factors correlated respectively with sE-selectin and sVCAM-1 levels (R=0.454, p=0.034 and R=0.578, p=0.005) in nondiabetic subjects (hypertensive and normotensive).

CONCLUSIONS

Type 2 diabetes mellitus and hypertension induce endothelial activation as indicated by elevated levels of soluble adhesion molecules. This effect is not different when comorbidity is present.

Low blood flow estimates in lower-leg arteries predict cardiovascular events in Japanese patients with type 2 diabetes with normal ankle-brachial indexes

OBJECTIVE

To examine the association of baseline measures in lower-leg arteries and conventional cardiovascular risk factors with the incidence of cardiovascular disease (CVD) events in type 2 diabetic patients with normal ankle-brachial indexes (ABIs) (>0.9).

RESEARCH DESIGN AND METHODS

We studied 129 type 2 diabetic patients and 35 age-matched nondiabetic subjects with no apparent CVD consecutively admitted to our hospital. At baseline, total flow volume and resistive index, as an index of vascular resistance, at the popliteal artery was evaluated using gated two-dimensional cine-mode phase-contrast magnetic resonance imaging. Patients were followed 4.8 +/- 1.5 years (range 3.0-8.2) or until their first event of CVD.

RESULTS

On follow-up, 16 patients developed primary CVD events. Patients with CVD had lower blood flow (P < 0.01) and higher vascular resistance (P < 0.05) than patients without CVD. When the patients were grouped into tertiles according to their levels of total flow volume (129.6-85.5, 85.3-63.3, and 62.7-23.8 ml/min), Kaplan-Meier analysis showed a higher probability of developing CVD events in patients in the lowest than in patients in the highest (P = 0.0199, log-rank test) tertile. Multivariate Cox proportional hazards analysis revealed that the lowest tertile for flow volume (hazard ratio [HR] 8.60, 95% CI 1.61-45.97, P = 0.012), hypertension (3.99, 1.12-14.25, P = 0.033), and smoking status (12.01, 1.21-119.28, P = 0.034) were significant independent predictors of CVD events.

CONCLUSIONS

We have demonstrated that low blood flow estimates in lower-leg arteries may be predictive for CVD events among Japanese patients with type 2 diabetes even though they have a normal ABI.

Lack of prognostic role of endothelial dysfunction in subcutaneous small resistance arteries of hypertensive patients

OBJECTIVE

The presence of endothelial dysfunction in the coronary circulation or in the brachial artery has been found to be associated with a greater incidence of cardiovascular events. However, no data are presently available about the prognostic role of endothelial dysfunction in human small resistance arteries.

DESIGN AND METHODS

Ninety subjects were included in the present study. They were: 10 normotensive subjects, 36 patients with essential hypertension, 10 patients with phaeochromocytoma, 11 patients with primary aldosteronism, 10 patients with renovascular hypertension, and 13 normotensive patients with non-insulin-dependent diabetes mellitus (NIDDM). All subjects were submitted to a biopsy of subcutaneous fat from the gluteal or the anterior abdominal region. Small resistance arteries were dissected and mounted on an isometric myograph, and the concentration-response curves to acetylcholine (from 10 to 10 mol/l) (endothelium-dependent vasodilatation) and sodium nitroprusside (from 10 to 10 mol/l) (endothelium-independent vasodilatation) after precontraction of the vessels with norepinephrine were evaluated. The subjects were re-evaluated (by clinical visits or telephone interviews) after an average follow-up time of 5.5 years.

RESULTS

Twenty-nine subjects had a documented fatal or non-fatal cardiovascular event (5.87%/year). The endothelium-dependent vasodilatation in the subcutaneous small arteries was similar in subjects with or without cardiovascular events. Also, endothelium-independent vasodilatation to sodium nitroprusside was similar in the two groups. Similar results were obtained by subdividing patients in the different subgroups (essential hypertension, secondary hypertension, etc.).

CONCLUSIONS

Our results indicate that endothelial dysfunction in the microcirculation does not predict cardiovascular events. It is possible that a prognostic role of endothelial dysfunction may be observed when other vascular districts prone to atherosclerosis are evaluated, or it might be detected only in patients at low to medium cardiovascular risk, in whom endothelial dysfunction is less advanced.

Oxidative stress and diabetic cardiovascular complications

Diabetes diagnoses are increasing at an alarming rate worldwide. The majority of diabetes-related deaths arise from cardiovascular complications such as myocardial infarction, stroke, and peripheral vascular disease. Oxidative stress has been demonstrated to be present in animal models as well as in patients with diabetes and has been suggested as a possible contributor to the accelerated atherosclerosis seen in diabetics. The generation of reactive oxygen species in diabetes occurs via several mechanisms and is initiated not only by glucose, but also by other substances that are found at elevated levels in diabetic patients. The resulting oxidative stress leads to a number of proatherogenic events. The elucidation of the mechanisms of oxidative stress in diabetes and their relationship with atherosclerosis could potentially identify molecular targets of therapy for this condition and its cardiovascular consequences.

Abnormal peripheral circulation in type 2 diabetic patients with normal ankle-brachial index associates with coronary atherosclerosis, large artery stiffness, and peripheral vascular resistance

We tested the hypothesis that impaired peripheral circulation in diabetes arises from different aspects of vascular abnormalities even when accompanied by a normal ankle-brachial index (ABI>0.9). One hundred fourteen type 2 diabetic patients with normal ABI and 33 age-matched non-diabetic subjects consecutively admitted to our hospital were enrolled. The Agatston coronary artery calcium score (CACS), as a marker of coronary atherosclerosis, was obtained using electron-beam computed tomography. An automatic device was used to measure brachial-ankle pulse wave velocity (baPWV) as an index of arterial distensibility. Total flow volume and resistive index (RI), as a marker of peripheral vascular resistance, at the popliteal artery were evaluated using gated two-dimensional cine-mode phase-contrast magnetic resonance imaging. Diabetic patients had baPWV (P<0.001) and RI (P<0.001) higher than those in the non-diabetic subjects, indicating that those parameters are characteristically altered in diabetic patients. When diabetic patients were grouped into three subgroups according to their levels of total flow volume, those with the lowest range showed the highest log-transformed CACS (P<0.001), baPWV (P<0.001), and RI (P<0.001) among the groups. Total flow volume was negatively correlated with log-transformed CACS (P<0.001), baPWV (P<0.001), and RI (P<0.001). Waveform at the popliteal artery could be clearly separated into systolic and early and late diastolic blood flows, which were negatively correlated with log-transformed CACS (P<0.001), RI (P<0.001), and baPWV (P<0.001), respectively. These results suggest that impaired peripheral circulation in diabetes is attributable to coronary atherosclerosis, large artery stiffness, and peripheral vascular resistance even when ABI is normal.

Physiological concentrations of insulin induce endothelin-dependent vasoconstriction of skeletal muscle resistance arteries in the presence of tumor necrosis factor-alpha dependence on c-Jun N-terminal kinase

OBJECTIVE

Tumor necrosis factor-alpha (TNF-alpha) has been linked to obesity-related insulin resistance and impaired endothelium-dependent vasodilatation, but the mechanisms have not been elucidated. To investigate whether TNF-alpha directly impairs insulin-mediated vasoreactivity in skeletal muscle resistance arteries and the role of c-Jun N-terminal kinase (JNK) in this interference.

METHODS AND RESULTS

Insulin-mediated vasoreactivity of isolated resistance arteries of the rat cremaster muscle to insulin (4 to 3400 microU/mL) was studied in the absence and presence of TNF-alpha (10 ng/mL). Although insulin or TNF-alpha alone did not affect arterial diameter, insulin induced dose-dependent vasoconstriction of cremaster resistance arteries in the presence of TNF-alpha, (-12+/-1% at 272 microU/mL). Blocking endothelin receptors in the absence of TNF-alpha uncovered insulin-mediated vasodilatation (18+/-6% at 272 microU/mL) but not in the presence of TNF-alpha (2+/-2% at 272 microU/mL), showing that TNF-alpha inhibits vasodilator effects of insulin. Using digital imaging microscopy, we discovered that TNF-alpha activates JNK in arterial endothelium, visible as an increase in phosphorylated JNK. Moreover, inhibition of JNK with the cell-permeable peptide inhibitor L-JNKI abolished insulin-mediated vasoconstriction in the presence of TNF-alpha, showing that JNK is required for interaction between TNF-alpha and insulin.

CONCLUSIONS

TNF-alpha inhibits vasodilator but not vasoconstrictor effects of insulin in skeletal muscle resistance arteries, resulting in insulin-mediated vasoconstriction in the presence of TNF-alpha. This effect of TNF-alpha is critically dependent on TNF-alpha-mediated activation of JNK.

Cytokines and vascular reactivity in resistance arteries

Cytokine levels are elevated in many cardiovascular diseases and seem to be implicated in the associated disturbances in vascular reactivity reported in these diseases. Arterial blood pressure is maintained within a normal range by changes in peripheral resistance and cardiac output. Peripheral resistance is mainly determined by small resistance arteries and arterioles. This review focuses on the effects of cytokines, mainly TNF-α, IL-1β, and IL-6, on the reactivity of resistance arteries. The vascular effects of cytokines depend on the balance between the vasoactive mediators released under their influence in the different vascular beds. Cytokines may induce a vasodilatation and hyporesponsiveness to vasoconstrictors that may be relevant to the pathogenesis of septic shock. Cytokines may also induce vasoconstriction or increase the response to vasoconstrictor agents and impair endothelium-dependent vasodilatation. These effects may help predispose to vessel spasm, thrombosis, and atherogenesis and reinforce the link between inflammation and vascular disease.

Effects of candesartan cilexetil and enalapril on inflammatory markers of atherosclerosis in hypertensive patients with non-insulin-dependent diabetes mellitus

OBJECTIVE

Circulating adhesion molecules may have a prognostic significance as markers of endothelial damage. Drugs which inhibit the renin-angiotensin system may be effective in reducing circulating or tissue adhesion molecules, albeit data available are scarce. The aim of the study was to investigate the effects of an angiotensin-converting enzyme (ACE) inhibitor, enalapril and a highly selective angiotensin receptor blocker, candesartan cilexetil, on circulating adhesion molecules in a large sample of patients with non-insulin-dependent diabetes mellitus (NIDDM). The study was comparative, multicenter, randomized and double blind, with two parallel groups.

PATIENTS AND METHODS

NIDDM patients with a diagnosis of mild (grade 1) essential hypertension were included in the study, at the end of a 2-week placebo run-in period. The primary end-point of the study was to evaluate changes of intercellular adhesion molecule-1 (ICAM-1) plasma levels during treatment. The secondary end-points were: changes in vascular cells adhesion molecule-1 (VCAM-1), von Willebrand factor (vWF), fibrinogen and plasminogen activator inhibitor-1 (PAI-1) circulating levels and of urinary albumin excretion rate (AER) as well; 129 patients were randomized: 66 in the candesartan group and 63 in the enalapril group, 118 of them completed the scheduled 24-week treatment period.

RESULTS

Candesartan and enalapril equally reduced circulating level of ICAM-1 and exerted comparable effects on changes of other adhesion molecules and coagulation factors. A similar blood pressure-lowering effect was observed with the two drugs (candesartan: from 148/90 +/- 11/8 to 132/82 +/- 12/7 mmHg, P < 0.01, enalapril: from 148/91 +/- 12/8 to 131/85 +/- 14/6 mmHg, P < 0.01). Candesartan was more effective than enalapril in the reduction of albuminuria (P < 0.05 between treatments), although urinary protein excretion can be considered normal in the majority of patients. The two drugs were comparable in terms of adverse events reported.

CONCLUSION

Candesartan and enalapril showed similar effects on blood pressure and on circulating adhesion molecules. In this study urinary protein excretion was reduced more by candesartan.

Brachial artery vasomotor function is inversely associated with 24-h ambulatory blood pressure

BACKGROUND

Impaired endothelial function has been reported in hypertensive individuals. The extent to which such changes reflect the co-existence of other cardiovascular disease risk factors rather than an independent association with blood pressure remains uncertain.

OBJECTIVE

To assess the relationship between brachial artery vasomotor function and ambulatory blood pressure in hypertensive individuals and normotensive controls.

METHODS

We assessed 24-h ambulatory blood pressure and brachial artery endothelial and smooth muscle function in 155 patients with hypertension and 40 normotensive controls. The vasomotor functions were determined by ultrasonographic assessment of vasodilator responses to flow and sublingual glyceryl trinitrate, respectively. Patients with hypertension were categorized as either treated (n = 85) or untreated (n = 70), and further subdivided on the basis of either no or at least one other cardiovascular risk factor. These included hyperlipidaemia, smoking, diabetes or a previous coronary or cerebrovascular event.

RESULTS

Age- and sex-adjusted flow-mediated and glyceryl trinitrate-mediated responses were not significantly different in hypertensive individuals with respect to treatment status or the presence of risk factors when compared with controls. However, when data from all 195 study participants were pooled, 24-h ambulatory systolic blood pressure was inversely related to flow-mediated response (P = 0.002), and both systolic and diastolic blood pressure were inversely related to glyceryl trinitrate response (P < 0.001 and P = 0.009, respectively). Observed relationships were largely unaltered after further adjustment for body mass index, antihypertensive treatment or the presence of other risk factors.

CONCLUSIONS

The finding of a direct and inverse relationship between the level of ambulatory blood pressure and flow-mediated and glyceryl trinitrate responses is consistent with a direct influence of blood pressure on conduit vessel vascular function.

Persistent Remodeling of Resistance Arteries in Type 2 Diabetic Patients on Antihypertensive Treatment

We hypothesized that resistance arteries from diabetic patients with controlled hypertension have less remodeling than vessels from untreated hypertensive subjects. Eight normotensive subjects (aged 44±3 years, 3 men; values are mean±SEM), 19 untreated hypertensive subjects (46±2 years, 9 men), and 23 hypertensive subjects with type 2 diabetes mellitus under antihypertensive treatment (58±1 years, 15 men) were studied. Resistance arteries dissected from gluteal subcutaneous tissue were assessed on a pressurized myograph. Most diabetic patients (70%) were being treated with angiotensin-converting enzyme inhibitors. Although systolic blood pressure was still above the normotensive range in these patients (144±2 versus 150±3 mm Hg in hypertensive and 114±4 mm Hg in normotensive subjects), diastolic blood pressure was well controlled (83±2 mm Hg) and significantly lower compared with that in untreated hypertensives (100±1 mm Hg; P <0.001) but higher than in normotensives (76±3 mm Hg; P <0.05). Thus, pulse pressure was higher in diabetic patients ( P <0.05). The media-to-lumen ratio of resistance arteries was greater in hypertensives (0.083±0.002) compared with normotensive controls (0.059±0.003; P <0.05) and was even higher in diabetic hypertensive subjects (0.105±0.004; P <0.001 versus normotensive controls). The medial cross-sectional area was greater in diabetic and hypertensive patients compared with normotensive controls ( P <0.001). Acetylcholine-induced relaxation was impaired in vessels from hypertensive patients and from patients with both diabetes mellitus and hypertension ( P <0.05 versus normotensive controls), whereas endothelium-independent vasorelaxation was similar in all groups. Despite effective antihypertensive treatment, resistance arteries from hypertensive diabetic patients showed marked remodeling, greater than that of vessels from untreated, nondiabetic, hypertensive subjects, in agreement with the high cardiovascular risk of subjects suffering from both diabetes and hypertension.

Augmented Contractile Response of Vascular Smooth Muscle in a Diabetic Mouse Model

The vasomotor properties of isolated aortae and mesenteric arteries of insulin-resistant ob/ob and 57CBL/6J mice were compared in organ bath studies. Vessels from ob/ob mice were more sensitive to phenylephrine. Pretreatment with L-NAME caused similar leftward shifts of the phenylephrine concentration response curves in diabetic and non-diabetic vessels. The ob/ob aortae contracted in response to phenylephrine with roughly twice the force while they were not stiffer than control aortae. L-NAME caused a greater percentage increase in maximal force in the control than in the ob/ob tissue. Denudation potentiated force in the control aortae, but not in the ob/ob aortae. Endothelium-dependent relaxation in the ob/ob aortae and mesenteric arteries was impaired as manifested by a decreased sensitivity and maximal relaxation to acetylcholine, while the aortic basal eNOS mRNA levels did not differ between the two strains. In addition, ob/ob aortae were less sensitive to the nitric oxide donor sodium nitroprusside. Inhibition of endogenous prostaglandin synthesis with indomethacin (10 microM) partly normalized the contractile response of the ob/ob aortae and enhanced their endothelium-dependent relaxation. Neither blockade of endothelin-1 receptors (bosentan, 10 microM) nor PKC inhibition (calphostin, 1 microM) affected the contractile response to phenylephrine in the mouse aortae of either strain. In conclusion, vascular dysfunction in the aorta and mesenteric artery of ob/ob mice are due to increased smooth muscle contractility and impaired dilation but not to changes in elasticity of the vascular wall. Endothelium-produced prostaglandins contribute to the increased vasoconstriction.

Circulating adhesion molecules and carotid artery structural changes in patients with noninsulin-dependent diabetes mellitus

Hypertension and non insulin-dependent diabetes mellitus (NIDDM) are well-known risk factors for atherosclerotic disease. Intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) may exert a relevant role in the pathogenesis of atherosclerosis; their prognostic relevance has been recently demonstrated. The aim of the study was to investigate possible inter-relation between circulating adhesion molecule levels, carotid artery structure and endothelial function in 15 patients with NIDDM, as well as in 15 patients with both NIDDM and essential hypertension (NIDDM+EH) compared with 15 normal subjects (NS) and 15 euglycaemic patients with EH, matched for age, sex and body weight. All subjects were submitted to a biopsy of the gluteal subcutaneous fat. Small arteries were dissected and mounted on a micromyograph, and the media-to-lumen (M/L) ratio was then calculated. Carotid artery structure was investigated by Doppler ultrasound. Endothelial function was evaluated by investigation of the flow-mediated dilatation (FMD) of the brachial artery. ICAM-1 and VCAM-1 plasma levels were measured by ELISA. ICAM-1 and VCAM-1 plasma levels were significantly greater and FMD smaller in EH, NIDDM and NIDDM+EH than in NS, but no difference was observed among the three pathological groups. Carotid artery structural changes were more pronounced in NIDDM+EH. No significant difference was observed among NIDDM, EH and NS. The M/L ratio of subcutaneous small resistance arteries was significantly greater in NIDDM+EH than in NIDDM or EH. NS had a smaller M/L ratio than the other groups. Significant correlations were observed between ICAM-1 plasma levels and indices of carotid artery structure in diabetic patients. However, the relations were close only in NIDDM+EH. In conclusion, our data suggest that NIDDM+EH may present more pronounced vascular structural alterations than NIDDM, and that adhesion molecules plasma levels are closely inter-related with carotid artery structural alterations, at least in NIDDM+EH, but not with M/L ratio of small resistance arteries.

Effects of severe hypertension on endothelial and platelet microparticles

The molecular mechanisms by which extreme blood pressure elevation leads to vascular injury are not defined. To explore the hypothesis that activation of endothelium and platelets as manifested by increased concentrations of circulating endothelial microparticles and platelet microparticles could play a role in this target organ injury, we conducted a cross-sectional study of these markers in 3 groups: (1) untreated patients referred specifically for treatment of severe uncontrolled hypertension; (2) untreated patients with established mild hypertension; and (3) normotensive volunteer subjects. By ANOVA, endothelial (P=0.002) and platelet (P=0.01) microparticles were greatest in the severely hypertensive group. There was a significant correlation between both of these markers and blood pressure, even in the setting of multiple risk factors. Our results suggest that these markers may be useful and specific for pressure-induced endothelial and platelet activation in hypertension. Furthermore, because of the combined effects of endothelial and platelet microparticles on coagulation, leukocytes, and endothelium, it is possible that they may play a pathogenic role in mediating target organ injury in severe hypertension.

Effects of severe, uncontrolled hypertension on endothelial activation: soluble vascular cell adhesion molecule-1, soluble intercellular adhesion molecule-1 and von Willebrand factor

OBJECTIVES

The molecular mechanisms whereby severe, uncontrolled hypertension (SHT) is translated into acute vascular target organ dysfunction have not been completely defined. We sought to determine whether SHT is associated with pressure-dependent endothelial activation as assessed by soluble vascular cell adhesion molecule-1 (sVCAM-1), soluble intercellular adhesion molecule-1 (sICAM-1) and von Willebrand Factor (vWF).

METHODS

We determined sVCAM-1, sICAM-1 and vWF in three groups: (i) untreated patients referred specifically for treatment of SHT [diastolic blood pressure (DBP) > or = 120 mm Hg; n = 24]; (ii) untreated patients with established mild hypertension (MHT; DBP 95-100 mmHg; n = 19); and (iii) normotensive volunteers (DBP < or = 90; n = 16).

RESULTS

By analysis of variance, sVCAM-1 (P = 0.002), sICAM-1 (P = 0.02) and vWF (P = 0.009) were greater in SHT and MHT than in normotensives but did not differ between SHT and MHT. We observed a significant positive correlation between blood pressure and soluble activation markers at lower blood pressures (normotensives and MHT considered together) that was not present in SHT.

CONCLUSIONS

Even mild elevation of blood pressure may be sufficient to activate the expression of adhesion molecules. Mechanisms other than the endothelial expression of adhesion molecules may be important in mediating the accelerated target organ injury produced by SHT in humans. Concentrations of soluble adhesion molecules and vWF may depend more strongly upon factors in the hypertensive microenvironment other than the absolute level of blood pressure.