Type 2 diabetes is associated with impaired endothelium-dependent, flow-mediated dilation, but impaired glucose metabolism is not; The Hoorn Study

The Protective Effect of Antioxidants Consumption on Diabetes and Vascular Complications

Obesity and diabetes is generally accompanied by a chronic state of oxidative stress, disequilibrium in the redox balance, implicated in the development and progression of complications such as micro- and macro-angiopathies. Disorders in the inner layer of blood vessels, the endothelium, play an early and critical role in the development of these complications. Blunted endothelium-dependent relaxation and/or contractions are quietly associated to oxidative stress. Thus, preserving endothelial function and oxidative stress seems to be an optimization strategy in the prevention of vascular complications associated with diabetes. Diet is a major lifestyle factor that can greatly influence the incidence and the progression of type 2 diabetes and cardiovascular complications. The notion that foods not only provide basic nutrition but can also prevent diseases and ensure good health and longevity is now attained greater prominence. Some dietary and lifestyle modifications associated to antioxidative supply could be an effective prophylactic means to fight against oxidative stress in diabesity and complications. A significant benefit of phytochemicals (polyphenols in wine, grape, teas), vitamins (ascorbate, tocopherol), minerals (selenium, magnesium), and fruits and vegetables in foods is thought to be capable of scavenging free radicals, lowering the incidence of chronic diseases. In this review, we discuss the role of oxidative stress in diabetes and complications, highlight the endothelial dysfunction, and examine the impact of antioxidant foods, plants, fruits, and vegetables, currently used medication with antioxidant properties, in relation to the development and progression of diabetes and cardiovascular complications.

Independent Association of Circulating Level of Chemerin With Functional and Early Morphological Vascular Changes in Newly Diagnosed Type 2 Diabetic Patients

There is growing evidence that chemerin, a novel adipokine elevated in obesity and metabolic syndromes, plays a crucial role in advanced atherosclerosis. This study aimed to determine the chemerin levels in diabetes and evaluate the effects of increased chemerin on early atherosclerosis.A total of 245 newly diagnosed diabetic patients and 148 age-matched, healthy, normal glucose tolerant (NGT) controls were enrolled. Anthropometric measurements and plasma parameters were examined, including body mass index (BMI), waist circumference, blood pressure, glucose, lipid profiles, inflammation markers, adipokines, and cell adhesion molecules. Vascular healthy was measured with brachial flow-mediated dilatation (FMD) and carotid intima-media thickness (IMT).Compared with NGT controls, plasma chemerin levels were higher in diabetic patients (P < 0.01) and higher chemerin level was an independent risk factor of occurrence of diabetes even after metabolic profiles were adjusted (odds ratio [OR] = 1.352, 95% CI: 1.181-1.543, P < 0.01). In patients with type 2 diabetes, chemerin was positively associated with intercellular adhesion molecule-1 (ICAM-1), E-selectin, but not vascular adhesion molecule-1 (VCAM-1) and P-selectin. We also explored that plasma chemerin level was negatively associated with brachial FMD and positively with carotid IMT. Chemerin also retained a strong association with ICAM-1, FMD, and IMT even after adjusted for age, sex, and other risk factors (ICAM-1: r = 0.150, P = 0.024; FMD: r = -0.126, P = 0.001; IMT: r = 0.325, P < 0.001). By multiple linear regression analysis, plasma chemerin levels were related to ICAM-1 even after adjustments for conventional cardiovascular risk factors (β = 0.192, P = 0.017). Moreover, logistic regression analysis showed that high chemerin level was an independent predictive variable for impaired endothelial function (OR = 1.066, 95% CI: 1.012-1.142, P = 0.048) and enhanced carotid vessel thickness (OR = 1.068, 95% CI: 1.021-1.148, P = 0.035) in diabetic patients.In summary, chemerin levels are independently associated with endothelial activation and early atherosclerosis in newly diagnosed type 2 diabetes.

BclI glucocorticoid receptor polymorphism in relation to cardiovascular variables: the Hoorn and CODAM studies

OBJECTIVE

Excess glucocorticoids are known to cause hypertension and cardiovascular disease (CVD). The BclI glucocorticoid receptor (GR) polymorphism increases glucocorticoid sensitivity and is associated with adverse metabolic effects. Previous studies investigating cardiovascular implications have shown inconsistent results. Therefore, the aim of the present study was to investigate the association of the BclI polymorphism with blood pressure, atherosclerosis, low-grade inflammation, endothelial dysfunction, and prevalent CVD.

DESIGN

Observational cohort study, combining two cohort studies designed to investigate genetic and metabolic determinants of CVD.

METHODS

We genotyped 1228 individuals (aged 64.7 years±8.5) from the Cohort on Diabetes and Atherosclerosis Maastricht (CODAM) study and Hoorn study for the BclI polymorphism. We measured blood pressure, ankle-brachial index (ABI), and carotid intima-media thickness (cIMT). Low-grade inflammation and endothelial dysfunction scores were computed by averaging Z-scores of six low-grade inflammation markers and four endothelial dysfunction markers respectively. Prevalent CVD was assessed with questionnaires, hospital records, ECG, and ABI.

RESULTS

Homozygous carriers (GG) had higher mean arterial pressure (103.8±12.4  mmHg vs 101.6±12.2  mmHg (mean±S.D.); P<0.05) compared with non-carriers (CC). Homozygous carriers had lower ABI compared with heterozygous carriers (CG) (1.08±0.13 vs 1.11±0.14; P<0.05). After adjustment for all covariates in the full model, the association with ABI was no longer significant. BclI was not associated with systolic blood pressure, cIMT, low-grade inflammation, endothelial dysfunction, and prevalent CVD.

CONCLUSIONS

The BclI polymorphism of the GR gene may contribute to an unfavorable cardiovascular profile; however, the effects on cardiovascular variables appear to be limited and partly mediated by the metabolic phenotype exerted by BclI.

A Comparison of the Effects of the GLP-1 Analogue Liraglutide and Insulin Glargine on Endothelial Function and Metabolic Parameters: A Randomized, Controlled Trial Sapporo Athero-Incretin Study 2 (SAIS2)

Objectives

GLP-1 improves hyperglycemia, and it has been reported to have favorable effects on atherosclerosis. However, it has not been fully elucidated whether GLP-1 is able to improve endothelial function in patients with type 2 diabetes. Therefore, we investigated the efficacy of the GLP-1 analogue, liraglutide on endothelial function and glycemic metabolism compared with insulin glargine therapy.

Materials and Methods

In this multicenter, prospective randomized parallel-group comparison study, 31 diabetic outpatients (aged 60.3 ± 10.3 years with HbA1c levels of 8.6 ± 0.8%) with current metformin and/or sulfonylurea treatment were enrolled and randomly assigned to receive liraglutide or glargine therapy once daily for 14 weeks. Flow mediated dilation (FMD), a comprehensive panel of hemodynamic parameters (Task Force Monitor), and serum metabolic markers were assessed before and after the treatment period.

Results

A greater reduction (worsening) in %FMD was observed in the glargine group, although this change was not statistically different from the liraglutide group (liraglutide; 5.7 to 5.4%, glargine 6.7 to 5.7%). The augmentation index, C-peptide index, derivatives of reactive oxygen metabolites and BMI were significantly improved in the liraglutide group. Central systolic blood pressure and NT-proBNP also tended to be improved in the liraglutide-treated group, while improvements in HbA1c levels were similar between groups. Cardiac index, blood pressure and most other metabolic parameters were not different.

Conclusions

Regardless of glycemic improvement, early liraglutide therapy did not affect endothelial function but may provide favorable effects on beta-cell function and cardioprotection in type 2 diabetics without advanced atherosclerosis.

Trial Registration

UMIN Clinical Trials Registry System as trial ID UMIN000005331.

A control systems approach to quantify wall shear stress normalization by flow-mediated dilation in the brachial artery

Flow-mediated dilation is aimed at normalization of local wall shear stress under varying blood flow conditions. Blood flow velocity and vessel diameter are continuous and opposing influences that modulate wall shear stress. We derived an index FMDv to quantify wall shear stress normalization performance by flow-mediated dilation in the brachial artery. In 22 fasting presumed healthy men, we first assessed intra- and inter-session reproducibilities of two indices pFMDv and mFMDv, which consider the relative peak and relative mean hyperemic change in flow velocity, respectively. Second, utilizing oral glucose loading, we evaluated the tracking performance of both FMDv indices, in comparison with existing indices [i.e., the relative peak diameter increase (%FMD), the peak to baseline diameter ratio (Dpeak/Dbase), and the relative peak diameter increase normalized to the full area under the curve of blood flow velocity with hyperemia (FMD/shearAUC) or with area integrated to peak hyperemia (FMD/shearAUC_peak)]. Inter-session and intra-session reproducibilities for pFMDv, mFMDv and %FMD were comparable (intra-class correlation coefficients within 0.521-0.677 range). Both pFMDv and mFMDv showed more clearly a reduction after glucose loading (reduction of ~45%, p≤0.001) than the other indices (% given are relative reductions): %FMD (~11%, p≥0.074); Dpeak/Dbase (~11%, p≥0.074); FMD/shearAUC_peak (~20%, p≥0.016) and FMD/shearAUC (~38%, p≤0.038). Further analysis indicated that wall shear stress normalization under normal (fasting) conditions is already far from ideal (FMDv << 1), which (therefore) does not materially change with glucose loading. Our approach might be useful in intervention studies to detect intrinsic changes in shear stress normalization performance in conduit arteries.

Flow Mediated Dilatation Is Reduced with the Progressive Stages of Glomerular Filtration Rate and Albuminuria in Type 2 Diabetic Patients without Coronary Heart Disease

We aimed to clarify the usefulness of measuring the flow mediated dilatation (FMD) in patients with type 2 diabetes mellitus without and with coronary heart disease (CHD). The FMD was measured in 480 patients with type 2 diabetes and in 240 nondiabetic subjects. The FMD was significantly lower in the subjects with CHD (n = 145, 5.4 ± 3.2%) than in those without CHD (n = 95, 6.9 ± 3.5%) among the nondiabetic subjects. The FMD was also lower in the subjects both with CHD (n = 161, 5.6 ± 2.8%) and without CHD (n = 319, 6.1 ± 3.3%) among the patients with diabetes compared to those without both diabetes and CHD. The FMD showed a significant positive correlation with the estimated glomerular filtration rate (eGFR) in the diabetic patients without CHD, while there was no significant association in those with CHD. The FMD was significantly lower with the progressive stages of the GFR or albuminuria in the patients without CHD among those with diabetes, although the FMD was not different in those with CHD. In conclusion, the FMD is considered to be useful for the detection of atherosclerosis in patients with type 2 diabetes, even if overt macroangiopathy is not diagnosed.

Functional and structural vascular adaptations following 8 weeks of low volume high intensity interval training in lower leg of type 2 diabetes patients and individuals at high risk of metabolic syndrome

We wished to investigate the effects of 8 weeks of low volume high intensity interval training (HIIT) on endothelial function of popliteal artery and circulating cell adhesion molecules in type 2 diabetes (T2D) patients and matched controls (CON).

METHODS

Over 8 weeks, non-active T2D patients and CONs cycled three times per week (10 × 60 sec HIIT). Pre- and post-HIIT measurements of endothelial function were conducted by applying flow-mediated dilation (FMD) along with taking venous blood samples.

RESULTS

Baseline diameter of popliteal artery increased significantly from an average of 5.53 mm to 5.97 mm (∼8%) in the CON-group (p = 0.006) and 5.32 mm to 5.61 mm (∼6%) in the T2D-group (p = 0.009). Peak diameter increased significantly from 5.82 mm to 6.36 mm (∼9%) in the CON-group (p = 0.001) and 5.57 mm to 5.93 mm (∼7%) in the T2D-group (p = 0.004). FMD% increased significantly from 5.12% to 6.58% in the CON-group (p = 0.004) and 4.84% to 5.66% in the T2D-group: (p = 0.045). The shear rate reduced significantly in both groups (CON-group: p = 0.04; T2D-group: p = 0.002). Circulating cell adhesion molecules remained unchanged (p > 0.05).

CONCLUSION

HIIT induced an improvement of endothelium-dependent FMD and significant outwards artery modelling. No changes in circulating cell adhesion molecules were observed.

High levels of mannose-binding lectin are associated with lower pulse wave velocity in uraemic patients

Background

Uraemia is associated with a highly increased risk of cardiovascular disease. Mannose-binding lectin (MBL) has been shown to be involved in cardiovascular pathophysiology and a protective effect of MBL is suggested. The purpose of the present study was to evaluate a potential impact of MBL on vascular parameters in uraemic patients.

Methods

A cohort of 98 patients with end stage renal disease (ESRD) awaiting kidney transplantation had pulse wave velocity (PWV) and augmentation index (AIX) examined by tonometry and endothelial dependent flow-mediated (FMD) and endothelial independent nitroglycerin-induced (NID) dilatory capacities of the brachial artery measured by ultrasound. An oral glucose tolerance test (OGTT) was performed and serum levels of MBL were measured using Luminex xMAP bead array technology.

Results

The cohort was divided in two groups according to MBL-concentration below or above the median concentration. These groups were comparable regarding age, BMI, and duration of ESRD. PWV was significantly lower in the group with high MBL levels compared to the group with low MBL levels and trends toward better AIX and higher insulin sensitivity (ISI) was also seen in the group with high MBL levels. No difference was seen in FMD and NID.

Conclusions

High levels of MBL are associated with lower PWV and the use of antihypertensive drugs in a cohort of patients with ESRD awaiting kidney transplantation suggesting a beneficial role of high levels of MBL on arterial stiffness in uraemia.

Metabolic syndrome components are associated with DNA hypomethylation

BACKGROUND

Disturbances of DNA methylation have been associated with multiple diseases, including cardiovascular disease, cancer and, as some have suggested, glucometabolic disturbances. Our aim was to assess the association of the metabolic syndrome and its individual components with DNA methylation in a population-based study.

MATERIALS AND METHODS

In a human population (n = 738) stratified by age, sex and glucose metabolism, we explored associations of the metabolic syndrome according to National Cholesterol Education Program/Adult Treatment Panel-III criteria and its individual components (fasting glucose, high-density lipoprotein cholesterol, triglycerides, blood pressure, waist circumference) with global leukocyte DNA methylation. DNA methylation was measured as the methylcytosine/cytosine ratio in peripheral leukocytes using liquid chromatography-tandem mass spectrometry.

RESULTS

Individuals with the metabolic syndrome had relative DNA hypomethylation compared to participants without the syndrome (β = -0.05; p = 0.01). This association was mainly attributable to linear associations of two metabolic syndrome components with DNA methylation: fasting plasma glucose (β = -0.02; p = 0.004) and high-density lipoprotein cholesterol (β = 0.07; p = 0.004). People with type 2 diabetes or impaired glucose metabolism had DNA hypomethylation compared to normoglycemic individuals (β = -0.05; p = 0.004).

CONCLUSIONS

DNA hypomethylation is independently associated with hyperglycemia and low high-density lipoprotein cholesterol, both essential components of the metabolic syndrome. The potential implications and direction of possible causality require further study.

Endothelial dysfunction is associated with a greater depressive symptom score in a general elderly population: the Hoorn Study

BACKGROUND

Endothelial dysfunction (ED), low-grade inflammation (LGI) and oxidative stress (OxS) may be involved in the pathobiology of depression. Previous studies on the association of these processes in depression have yielded contradictory results. We therefore investigated comprehensively, in a population-based cohort study, the association between ED, LGI and OxS on the one hand and depressive symptoms on the other.

METHOD

We used data from the Hoorn Study and determined biomarkers of ED [flow-mediated dilatation (FMD), von Willebrand factor, soluble intercellular adhesion molecule 1 (sICAM-1), soluble vascular cell adhesion molecule 1, soluble thrombomodulin and soluble endothelial selectin], LGI [C-reactive protein, tumour necrosis factor-α, interleukin 6, interleukin 8, serum amyloid A, myeloperoxidase (MPO) and sICAM-1] and OxS (oxidized low density lipoprotein and MPO). Depressive symptoms were quantified by the Center for Epidemiologic Studies Depression Scale (CES-D) questionnaire (n = 493; age 68 years; 49.9% female). Regression analyses were performed with the use of biomarker Z scores. Adjustments were made for age, sex and glucose metabolism status (cohort stratification variables) and prior cardiovascular disease, hypertension, waist-to-hip ratio, cholesterol levels, education level, physical activity, dietary habits, and the use of antihypertensive and/or lipid-lowering medication and/or metformin (potential confounders).

RESULTS

After adjustment for age, sex and glucose metabolism status, one standard deviation increase in the ED Z score was associated with a 1.9 [95% confidence interval (CI) 0.7-3.1] higher CES-D score. Additional adjustments did not materially change this result. LGI and OxS were not associated with the CES-D score.

CONCLUSIONS

ED, as quantified by an array of circulating biomarkers and FMD, was independently associated with depressive symptoms. This study supports the hypothesis that ED plays an important role in the pathobiology of depression.

Peroxynitrite disrupts endothelial caveolae leading to eNOS uncoupling and diminished flow-mediated dilation in coronary arterioles of diabetic patients

Peroxynitrite (ONOO(-)) contributes to coronary microvascular dysfunction in diabetes mellitus (DM). We hypothesized that in DM, ONOO(-) interferes with the function of coronary endothelial caveolae, which plays an important role in nitric oxide (NO)-dependent vasomotor regulation. Flow-mediated dilation (FMD) of coronary arterioles was investigated in DM (n = 41) and non-DM (n = 37) patients undergoing heart surgery. NO-mediated coronary FMD was significantly reduced in DM patients, which was restored by ONOO(-) scavenger, iron-(III)-tetrakis(N-methyl-4'pyridyl)porphyrin-pentachloride, or uric acid, whereas exogenous ONOO(-) reduced FMD in non-DM subjects. Immunoelectron microscopy demonstrated an increased 3-nitrotyrosine formation (ONOO(-)-specific protein nitration) in endothelial plasma membrane in DM, which colocalized with caveolin-1 (Cav-1), the key structural protein of caveolae. The membrane-localized Cav-1 was significantly reduced in DM and also in high glucose-exposed coronary endothelial cells. We also found that DM patients exhibited a decreased number of endothelial caveolae, whereas exogenous ONOO(-) reduced caveolae number. Correspondingly, pharmacological (methyl-β-cyclodextrin) or genetic disruption of caveolae (Cav-1 knockout mice) abolished coronary FMD, which was rescued by sepiapterin, the stable precursor of NO synthase (NOS) cofactor, tetrahydrobiopterin. Sepiapterin also restored coronary FMD in DM patients. Thus, we propose that ONOO(-) selectively targets and disrupts endothelial caveolae, which contributes to NOS uncoupling, and, hence, reduced NO-mediated coronary vasodilation in DM patients.

A short-term incubation with high glucose impairs VASP phosphorylation at serine 239 in response to the nitric oxide/cGMP pathway in vascular smooth muscle cells: role of oxidative stress

A reduction of the nitric oxide (NO) action in vascular smooth muscle cells (VSMC) could play a role in the vascular damage induced by the glycaemic excursions occurring in diabetic patients; in this study, we aimed to clarify whether a short-term incubation of cultured VSMC with high glucose reduces the NO ability to increase cGMP and the cGMP ability to phosphorylate VASP at Ser-239. We observed that a 180 min incubation of rat VSMC with 25 mmol/L glucose does not impair the NO-induced cGMP increase but reduces VASP phosphorylation in response to both NO and cGMP with a mechanism blunted by antioxidants. We further demonstrated that high glucose increases radical oxygen species (ROS) production and that this phenomenon is prevented by the PKC inhibitor chelerythrine and the NADPH oxidase inhibitor apocynin. The following sequence of events is supported by these results: (i) in VSMC high glucose activates PKC; (ii) PKC activates NADPH oxidase; (iii) NADPH oxidase induces oxidative stress; (iv) ROS impair the signalling of cGMP, which is involved in the antiatherogenic actions of NO. Thus, high glucose, via oxidative stress, can reduce the cardiovascular protection conferred by the NO/cGMP pathway via phosphorylation of the cytoskeleton protein VASP in VSMC.

The combined effect of hypertension and type 2 diabetes mellitus on aortic stiffness and endothelial dysfunction: an integrated study with high-resolution MRI

PURPOSE

The purpose of this study was to investigate the combined effect of hypertension and type 2 diabetes mellitus (DM2) on aortic stiffness and endothelial dysfunction by using an integrated MRI approach.

MATERIALS AND METHODS

A total of 31 non-hypertensive DM2 patients and 31 hypertensive DM2 patients underwent 3.0-T MRI. Aortic distensibility (AD), pulse wave velocity (PWV) and brachial artery flow-mediated dilation (FMD) were assessed. Student's t-test, Mann-Whitney U test, chi-squared test, Pearson correlation analysis, and univariable and multiple linear regression analyses were used for statistical analyses.

RESULTS

The hypertensive patients showed lower AD at multiple levels (ascending aorta [AA]: 2.07±0.98×10(-3)mm Hg(-1) vs. 3.21±1.70×10(-3)mm Hg(-1), p<0.01; proximal thoracic descending aorta [PDA]: 2.58±0.72×10(-3)mm Hg(-1) vs. 3.58±1.47×10(-3)mm Hg(-1), p<0.01; distal descending aorta [DDA]: 3.11±1.84×10(-3)mm Hg(-1) vs. 4.27±1.75×10(-3)mm Hg(-1), p<0.01); faster PWV (7.46±2.28m/s vs. 5.82±1.12m/s, p<0.05) and lower FMD (12.67%±6.49% vs. 20.66%±9.7%; p<0.01). Systolic blood pressure was an independent predictor of PWV, AA-AD, DDA-AD and FMD. FMD was statistically significantly associated with PWV (r=-0.37, p<0.01) and AD (p<0.01).

CONCLUSIONS

Hypertension has a contributive effect on aortic stiffness and endothelial dysfunction in DM2 patients.

Periodontitis is associated with endothelial dysfunction in a general population: a cross-sectional study

A large body of evidence underlines an association between periodontal disease and cardiovascular disease. In contrast, data on its relation with endothelial dysfunction as a marker of early subclinical atherosclerosis is inconclusive and limited to patient-cohort studies. We therefore investigated the association between periodontal disease and flow-mediated dilation of the brachial artery (FMD) as a measure of endothelial dysfunction in a general population, and also addressed a possible mediation via inflammation. The study population comprised 1,234 subjects (50.5% men) aged 25–85 years from the 5-year follow-up of the Study of Health in Pomerania, a population-based cohort study. Clinical attachment loss (CAL) and pocket probing depth (PPD) as measures of periodontal disease were assessed half-mouth at four sites per tooth. Subjects were classified according to the periodontitis case definition proposed by Tonetti and Claffey (2005). Measurements of FMD and nitroglycerin-mediated dilation (NMD) were performed using standardized ultrasound techniques. High-sensitive C-reactive protein, fibrinogen and leukocyte count were measured. Fully adjusted multivariate linear regression analyses revealed significant associations of the percentage of sites with PPD ≥6 mm with FMD (p_trend=0.048), with subjects within the highest category having a 0.74% higher FMD compared to subjects within the lowest category (p<0.05). Consistently, FMD values increased significantly across categories of the percentage of sites with CAL ≥6 mm (p_trend=0.01) and the periodontitis case definition (p_trend=0.006). Restrictions to subjects without antihypertensive or statin medication or current non-smokers confirmed previous results. Systemic inflammation did not seem to mediate the relation. Both PPD and CAL were not consistently associated with NMD. In contrast to previous studies, high levels of periodontal disease were significantly associated with high FMD values. This association was not mediated via systemic inflammation. This study revives the discussion on whether and how periodontitis contributes to endothelial dysfunction.

Do patients with type 1 and type 2 diabetes really have an impaired endothelial function? A population-based propensity score matching analysis

Background

Previous studies suggested an impaired endothelial function in patients with diabetes. However, the validity of this finding may be limited by the lack of adequate adjustment for further cardiovascular confounders. We assessed endothelial function as measured by flow-mediated dilation (FMD) of the brachial artery in patients with either type 1 or type 2 diabetes in comparison with non-diabetic controls.

Methods

The study population comprised 1487 subjects including 122 subjects with type 2 diabetes, aged 25 to 85, from the population-based Study of Health in Pomerania, and 65 outpatients, aged 23 to 75, with type 1 diabetes. FMD measurements were performed using standardized ultrasound techniques. Subjects with type 1 and type 2 diabetes were matched 1:4 to healthy controls using propensity score matching.

Results

Neither type 1 diabetes (β = 0.142; SE = 0.568, p = 0.803) nor type 2 diabetes (β = 0.107; SE = 0.340, p = 0.752) were significantly associated with FMD in comparison with their non-diabetic controls after adjustment for major cardiovascular confounders like age, gender, body mass index, smoking status, hypertension, antihypertensive medication, LDL and HDL cholesterol levels.

Conclusions

In this population-based study comparing adjusted FMD values of diabetic individuals with adequately matched controls, propensity score analyses revealed no association between diabetes and endothelial function. Since these findings are in discordance with the majority of previous reports, we suggest performing similar analyses using data from other population-based studies.

Hemoglobin A1C in non-diabetic patients: an independent predictor of coronary artery disease and its severity

AIMS

To determine the association between glycated hemoglobin (HbA1c) and angiographically proven coronary artery disease (CAD) and its severity in nondiabetic individuals.

METHODS

We enrolled 299 consecutive individuals undergoing coronary angiography for suspected ischemia. Patients were included if they had no history of prior revascularization or diabetes mellitus and had fasting blood glucose<126mg/dl (7.0mmol/l) and HbA1c<6.5% (47mmol/mol). The severity of the CAD was also evaluated using the Gensini score. Serum HbA1c (NGSP certified Method), highly sensitive C-reactive protein (hsCRP), lipid profile, insulin and APO lipoprotein A1 and B100 levels were measured.

RESULTS

Mean age was 58.8±10.4 year; 60.9% men. One hundred forty seven patients had significant CAD (≥50% stenosis in any major vessel). With increasing HbA1c levels, there was a significant increase in the prevalence of CAD and number of vessels involved. In multivariate analysis, HbA1c emerged as an independent predictor of significant CAD (OR: 2.8, 95% CI: 1.3-6.2, p=0.009). Adjusted ORs for the occurrence of CAD were highest in subjects with both hsCRP and HbA1c in the upper 2 quartiles (OR: 4.183; 95% CI: 1.883-9.290, p<0.0001). There was a significant association between Gensini score and increasing HbA1c tertiles (p=0.038). The ideal cut-off value of HbA1c for prediction of the occurrence of CAD was 5.6% 38mmol/mol) (sensitivity: 60.5%, specificity: 52%).

CONCLUSIONS

In non-diabetic subjects, HbA1c could be utilized for risk stratification of CAD and its severity, independent of traditional cardiovascular risk factors, insulin resistance and inflammatory markers.

Endothelial dysfunction in diabetes: pathogenesis, significance, and treatment

Type 2 diabetes (T2D) markedly increases the risk of cardiovascular disease. Endothelial dysfunction (ED), an early indicator of diabetic vascular disease, is common in T2D and independently predicts cardiovascular risk. Although the precise pathogenic mechanisms for ED in T2D remain unclear, at inception they probably involve uncoupling of both endothelial nitric oxide synthase activity and mitochondrial oxidative phosphorylation, as well as the activation of vascular nicotinamide adenine dinucleotide phosphate oxidase. The major contributing factors include dyslipoproteinemia, oxidative stress, and inflammation. Therapeutic interventions are designed to target these pathophysiological factors that underlie ED. Therapeutic interventions, including lifestyle changes, antiglycemic agents and lipid-regulating therapies, aim to correct hyperglycemia and atherogenic dyslipidemia and to improve ED. However, high residual cardiovascular risk is seen in both research and clinical practice settings. Well-designed studies of endothelial function in appropriately selected volunteers afford a good opportunity to test new therapeutic interventions, paving the way for clinical trials and utilization in the care of the diabetic patient. However, based on the results from a recent clinical trial, niacin should not be added to a statin in individuals with low high-density lipoprotein cholesterol and very well controlled low-density lipoprotein cholesterol.

Diabetic retinopathy and endothelial dysfunction in patients with type 2 diabetes mellitus

BACKGROUND

We investigated the relationship between endothelial dysfunction and diabetic retinopathy (DR) in patients with type 2 diabetes.

METHODS

We used a cross-sectional design to examine 167 patients with type 2 diabetes mellitus. All patients underwent biochemical and ophthalmological examination. We assessed endothelial dysfunction by a flow-mediated vasodilation method of the brachial artery. Changes in vasodilation (flow-mediated vasodilatation, %FMD) were expressed as percent change over baseline values.

RESULTS

The mean±standard deviation of patient age was 54.1±8.6 years. The %FMD was significantly lower in patients with DR than without DR. The prevalence of retinopathy decreased across increasing tertiles of %FMD. After adjusting for patients' age, sex, diabetes duration, use of insulin, use of antihypertensive, antiplatelet, and lipid lowering medications, systolic blood pressure, fasting plasma glucose, 2-hour plasma glucose, glycated hemoglobin, and urinary albumin excretion, participants with a reduced %FMD were more likely to have DR (odds ratio, 11.819; 95% confidence interval, 2.201 to 63.461; P=0.004, comparing the lowest and highest tertiles of %FMD).

CONCLUSION

Endothelial dysfunction was associated with DR, which was most apparent when the endothelial dysfunction was severe. Our study provides insights into the possible mechanism of the influence of endothelial dysfunction on the development of DR.

Effect of dietary nitrate on blood pressure, endothelial function, and insulin sensitivity in type 2 diabetes

Diets rich in green, leafy vegetables have been shown to lower blood pressure (BP) and reduce the risk of cardiovascular disease. Green, leafy vegetables and beetroot are particularly rich in inorganic nitrate. Dietary nitrate supplementation, via sequential reduction to nitrite and NO, has previously been shown to lower BP and improve endothelial function in healthy humans. We sought to determine if supplementing dietary nitrate with beetroot juice, a rich source of nitrate, will lower BP and improve endothelial function and insulin sensitivity in individuals with type 2 diabetes (T2DM). Twenty-seven patients, age 67.2±4.9 years (18 male), were recruited for a double-blind, randomized, placebo-controlled crossover trial. Participants were randomized to begin, in either order, a 2-week period of supplementation with 250ml beetroot juice daily (active) or 250ml nitrate-depleted beetroot juice (placebo). At the conclusion of each intervention period 24-h ambulatory blood pressure monitoring, tests of macro- and microvascular endothelial function, and a hyperinsulinemic isoglycemic clamp were performed. After 2 weeks administration of beetroot juice mean ambulatory systolic BP was unchanged: 134.6±8.4mmHg versus 135.1±7.8mmHg (mean±SD), placebo vs active-mean difference of -0.5mmHg (placebo-active), p=0.737 (95% CI -3.9 to 2.8). There were no changes in macrovascular or microvascular endothelial function or insulin sensitivity. Supplementation of the diet with 7.5mmol of nitrate per day for 2 weeks caused an increase in plasma nitrite and nitrate concentration, but did not lower BP, improve endothelial function, or improve insulin sensitivity in individuals with T2DM.

An ethanolic extract of Lindera obtusiloba stems, YJP-14, improves endothelial dysfunction, metabolic parameters and physical performance in diabetic db/db mice

Lindera obtusiloba is a medicinal herb traditionally used in Asia for improvement of blood circulation, treatment of inflammation, and prevention of liver damage. A previous study has shown that an ethanolic extract of Lindera obtusiloba stems (LOE) has vasoprotective and antihypertensive effects. The possibility that Lindera obtusiloba improves endothelial function and metabolic parameters in type 2 diabetes mellitus (T2DM) remains to be examined. Therefore, the aim of the present study was to determine the potential of LOE to prevent the development of an endothelial dysfunction, and improve metabolic parameters including hyperglycemia, albuminuria and physical exercise capacity in db/db mice, an experimental model of T2DM. The effect of LOE (100 mg/kg/day by gavage for 8 weeks) on these parameters was compared to that of an oral antidiabetic drug, pioglitazone (30 mg/kg/day by gavage). Reduced blood glucose level, body weight and albumin-creatinine ratio were observed in the group receiving LOE compared to the control db/db group. The LOE treatment improved endothelium-dependent relaxations, abolished endothelium-dependent contractions to acetylcholine in the aorta, and normalized the increased vascular oxidative stress and expression of NADPH oxidase, cyclooxygenases, angiotensin II, angiotensin type 1 receptors and peroxynitrite and the decreased expression of endothelial NO synthase in db/db mice. The angiotensin-converting enzyme (ACE) activity was reduced in the LOE group compared to that in the control db/db group. LOE also inhibited the activity of purified ACE, COX-1 and COX-2 in a dose-dependent manner. In addition, LOE improved physical exercise capacity. Thus, the present findings indicate that LOE has a beneficial effect on the vascular system in db/db mice by improving endothelium-dependent relaxations and vascular oxidative stress most likely by normalizing the angiotensin system, and also on metabolic parameters, and these effects are associated with an enhanced physical exercise capacity.

Glycemic associations with endothelial function and biomarkers among 5 ethnic groups: the Multi-Ethnic Study of Atherosclerosis and the Mediators of Atherosclerosis in South Asians Living in America studies

Background

The association of prediabetic states with endothelial dysfunction measured by flow‐mediated dilation (FMD) or endothelial biomarker levels remains controversial. We examined data from 5 ethnic groups to determine the association between glucose categories and FMD or endothelial biomarkers. We determined whether these associations vary by ethnic group or body mass index.

Methods and Results

We used data from 3516 participants from 5 race/ethnic groups with brachial FMD, endothelial biomarkers, and glucose category (normal, impaired fasting glucose [IFG], and diabetes) measures. There were significant ethnic differences in FMD, biomarker levels, and the prevalence of IFG and diabetes. However, all 5 ethnic groups showed similar patterns of higher FMD for the IFG group compared with the normal glucose and diabetes groups, which was most significant among whites and Asian Indians. Associations between glucose categories and endothelial biomarkers were more uniform, with the IFG and diabetes groups having higher biomarker levels than the normal glucose group. These associations did not change with further adjustment for fasting insulin levels. Whites with normal BMI had higher FMD values with higher glucose levels, but those with BMI in the overweight or obese categories had the inverse association (P for interaction=0.01).

Conclusions

The discordance of IFG being associated with higher FMD but more abnormal endothelial biomarker levels is a novel finding. This higher FMD for the IFG group was most notable in whites of normal BMI. The higher FMD among those with impaired fasting glucose may reflect differences in insulin signaling pathways between the endothelium and skeletal muscle.

Determinants of vascular function in patients with type 2 diabetes

Background

Type 2 diabetes mellitus (T2DM) is independently associated with an increased risk for cardiovascular diseases that is primarily due to the early development of advanced atherosclerotic vascular changes. The aim of our study was to investigate the predictors of vascular dysfunction in T2DM patients.

Methods

We studied 165 T2DM patients without known macrovascular or microvascular disease. Standard demographic (age, gender, cardiovascular risk factors, medications), clinical (body mass index, blood pressure) and laboratory (glucose, glycated hemoglobin, lipids, renal function) parameters were included in analyses. Brachial artery flow-mediated dilation (FMD), nitrate mediated dilation (NMD) and Carotid-Femoral Pulse Wave Velocity (PWV) were measured.

Results

Median age was 66 years and duration since T2DM diagnosis was 10 years, 70% were females and 79% hypertensives, while only 10% had a glycated hemoglobin <7%. FMD was positively associated with NMD (r 0.391, P < 0.001), while PWV was inversely associated with FMD (r -0.218, P = 0.014) and NMD (r -0.309, P < 0.001). Time since diagnosis of diabetes was the single independent predictor of FMD (β -0.40, P = 0.003). Increased age and fasting glucose and the presence of hypertension were independent predictors of decreased NMD (P < 0.001). Increased age and systolic blood pressure were independently associated with increased PWV (P < 0.001).

Conclusions

In T2DM patients, impairment of endothelium-dependent vasodilation was independently associated only with longer diabetes duration while no association with other established risk factors was found. Vascular smooth muscle dysfunction and increased arterial stiffness were more prominent in older T2DM patients with hypertension. Worse glycemic control was associated with impaired vascular smooth muscle function.

Hyperfiltration and effect of nitric oxide inhibition on renal and endothelial function in humans with uncomplicated type 1 diabetes mellitus

Studies of experimental diabetes mellitus (DM) suggest that increased nitric oxide (NO) bioactivity contributes to renal hyperfiltration. However, the role of NO in mediating hyperfiltration has not been fully elucidated in humans. Our aim was to examine the effect of NO synthase inhibition on renal and peripheral vascular function in normotensive subjects with uncomplicated type 1 DM. Renal function and brachial artery flow-mediated vasodilatation (FMD) were measured before and after an intravenous infusion of the NO synthase inhibitor N(G)-nitro-l-arginine methyl ester (l-NMMA) in 21 healthy control and 37 type 1 DM patients. Measurements in DM participants were made under clamped euglycemic conditions. The effect of l-NMMA on circulating and urinary NO metabolites (NO(x)) and cGMP and on urinary prostanoids was also determined. Baseline characteristics were similar in the two groups. For analysis, the DM patients were divided into those with hyperfiltration (DM-H, n = 18) and normal glomerular filtration rate (GFR) levels (DM-N, n = 19). Baseline urine NO(x) and cGMP were highest in DM-H. l-NMMA led to a decline in GFR in DM-H (152 ± 16 to 140 ± 11 ml·min(-1)·1.73 m(-2)) but not DM-N or healthy control participants. The decline in effective renal plasma flow in response to l-NMMA (806 ± 112 to 539 ± 80 ml·min(-1)·1.73 m(-2)) in DM-H was also exaggerated compared with the other groups (repeated measures ANOVA, P < 0.05), along with declines in urinary NO(x) metabolites and cGMP. Baseline FMD was lowest in DM-H compared with the other groups and did not change in response to l-NMMA. l-NMMA reduced FMD and plasma markers of NO bioactivity in the healthy control and DM-N groups. In patients with uncomplicated type 1 DM, renal hyperfiltration is associated with increased NO bioactivity in the kidney and reduced NO bioactivity in the systemic circulation, suggesting a paradoxical state of high renal and low systemic vascular NO bioactivity.

Association between diabetic retinopathy and flow-mediated vasodilation in type 2 DM

OBJECTIVE

Retinal endothelial dysfunction is a key in the etiogenesis of diabetic retinopathy (DR), in patients with type 2 diabetes mellitus (DM). Brachial artery flow-mediated vasodilation (FMD) is a marker of endothelial function associated with production of endogenous nitric oxide. Using FMD, we investigated the relationship between macrovascular function and DR.

METHODS

We studied 74 patients with type 2 DM, including non-DR (NDR) (n = 30); mild nonproliferative DR (NPDR) (n = 16); moderate NPDR (n = 10); severe NPDR (n = 10); and proliferative DR (PDR) (n = 8); and 21 age-matched controls. We measured FMD in each group. Retinal blood flow and pulsatility ratios were measured using laser Doppler velocimetry.

RESULTS

FMD decreased significantly in patients with DM compared with healthy control subjects. No significant differences were found in FMD among the NDR, mild NPDR, and moderate NPDR groups. FMD decreased significantly in the severe NPDR and PDR groups compared with the NDR group. FMD was significantly and negatively correlated with duration of DM and pulsatility ratio.

CONCLUSION

Systemic endothelial dysfunction appears to be associated with DR and vascular abnormalities in patients with type 2 DM.

Low-grade inflammation, but not endothelial dysfunction, is associated with greater carotid stiffness in the elderly: the Hoorn Study

OBJECTIVE

Biomarkers of low-grade inflammation and endothelial dysfunction are associated with cardiovascular disease. Arterial stiffening may be a mechanism through which low-grade inflammation and (or) endothelial dysfunction lead to cardiovascular disease. Therefore, we investigated whether low-grade inflammation and endothelial dysfunction were associated with greater carotid stiffness in a population-based cohort of elderly individuals.

METHODS

We determined biomarkers of low-grade inflammation (C-reactive protein, serum amyloid A, interleukin 6, interleukin 8, tumour necrosis factor α and soluble intercellular adhesion molecule 1), and of endothelial dysfunction (von Willebrand factor, soluble vascular cell adhesion molecule 1, soluble endothelial selectin, soluble thrombomodulin, soluble intercellular adhesion molecule 1 and flow-mediated dilation), and combined these into mean z-scores (n = 572; women = 286; age 67.5 ± 6.6 years). Additionally, we determined by ultrasonography carotid diameter, distension, pulse pressure and intima-media thickness. Carotid stiffness indices were determined by calculation of the distensibility and compliance coefficient, Young's elastic modulus and β stiffness index.

RESULTS

The study population was characterized by a high prevalence of cardiovascular disease (46%), hypertension (66%) and the use of lipid-lowering (16%) and antihypertensive (34%) medication. After adjustment for the above in addition to sex, age, glucose tolerance status and current smoking, the low-grade inflammation z-score was positively associated with Young's elastic modulus [β (95% confidence interval) 0.080 (0.021-0.139), P = 0.008]. This association was primarily driven through greater diameter. After adjustment for the variables above, the endothelial dysfunction z-score was not associated with carotid stiffness.

CONCLUSION

These data suggest that low-grade inflammation, in the elderly, plays an important role in carotid artery remodelling and stiffening.

Albuminuria and cognitive functioning in an older population: the Hoorn study

BACKGROUND/AIMS

Markers of vascular disease elsewhere in the body may reflect vascular abnormalities in the brain relevant to age-related cognitive decline and dementia. We examined the association between albuminuria, as a marker of microvascular damage, and cognition in older individuals.

METHODS

380 individuals (age 73 ± 6 years), participating in the population-based Hoorn Study, underwent extensive neuropsychological examination in 2005-2008, and urinary albumin-to-creatinine ratios measurements in 2000-2001 (n = 378) and/or 2005-2008 (n = 346). Cognition was expressed in z-scores on 6 domains.

RESULTS

In 2000-2001, 42 participants were with and 336 without albuminuria, and in 2005-2008 51 were with and 295 were without. In age-, sex- and premorbid IQ-adjusted analyses, participants with albuminuria 5-7 years earlier had slightly lower z-scores for the domains attention and executive functioning [mean difference: -0.21 (95% CI -0.40 to -0.02)] and language [-0.36 (95% CI -0.63 to -0.09)]. No statistically significant differences in cognition were found between participants with and without albuminuria at the time of neuropsychological testing.

CONCLUSION

Albuminuria predicts future modest cognitive decrements, but concurrent albuminuria is unrelated to cognitive functioning. The link between albuminuria and cognitive dysfunction may convey an etiological message, but because effect sizes were modest its value in prognostic models for cognitive decline may be limited.

Cardiovascular Risk Assessment with Vascular Function, Carotid Atherosclerosis and the UKPDS Risk Engine in Korean Patients with Newly Diagnosed Type 2 Diabetes

BACKGROUND

Patients with type 2 diabetes have an increased risk of cardiovascular disease. Few studies have evaluated the cardiovascular disease (CVD) risk simultaneously using the United Kingdom Prospective Diabetes Study (UKPDS) risk engine and non-invasive vascular tests in patients with newly diagnosed type 2 diabetes.

METHODS

Participants (n=380; aged 20 to 81 years) with newly diagnosed type 2 diabetes were free of clinical evidence of CVD. The 10-year coronary heart disease (CHD) and stroke risks were calculated for each patient using the UKPDS risk engine. Carotid intima media thickness (CIMT), flow mediated dilation (FMD), pulse wave velocity (PWV) and augmentation index (AI) were measured. The correlations between the UKPDS risk engine and the non-invasive vascular tests were assessed using partial correlation analysis, after adjusting for age, and multiple regression analysis.

RESULTS

The mean 10-year CHD and 10-year stroke risks were 14.92±11.53% and 4.03±3.95%, respectively. The 10-year CHD risk correlated with CIMT (P<0.001), FMD (P=0.017), and PWV (P=0.35) after adjusting for age. The 10-year stroke risk correlated only with the mean CIMT (P<0.001) after adjusting for age. FMD correlated with age (P<0.01) and systolic blood pressure (P=0.09). CIMT correlated with age (P<0.01), HbA1c (P=0.05), and gender (P<0.01).

CONCLUSION

The CVD risk is increased at the onset of type 2 diabetes. CIMT, FMD, and PWV along with the UKPDS risk engine should be considered to evaluate cardiovascular disease risk in patients with newly diagnosed type 2 diabetes.

Endothelial function and carotid intima-medial thickness in adolescents with type 2 diabetes mellitus

OBJECTIVE

We assessed the effect of type 2 diabetes mellitus and obesity on flow-mediated dilation (FMD) and endothelial-dependent vasodilation and carotid intima-medial thickness (cIMT) in young people.

STUDY DESIGN

Adolescents were recruited in 3 groups: subjects with type 2 diabetes mellitus (n = 15), subjects who were obese and non-insulin resistant (n = 13), and lean control subjects (n = 13). Body mass index was similar in subjects with obesity and subjects with type 2 diabetes mellitus, but higher compared with that of lean control subjects (both P < .001). Brachial artery FMD and cIMT were assessed by using Duplex ultrasound scanning imaging.

RESULTS

There were no significant differences in brachial or common carotid arterial diameters in the groups. cIMT was significantly greater in the group with type 2 diabetes mellitus (0.54 ± 0.01mm) compared with both the lean control (0.46 ± 0.02 mm, P < .001) and obese control (0.46 ± 0.02 mm, P < .01) groups. FMD was significantly decreased in the group with type 2 diabetes mellitus (7.98% ± 0.54%) compared with the lean group (10.40% ± 1.00%, P < .05).

CONCLUSIONS

Measures of vascular health were impaired in adolescents with type 2 diabetes mellitus compared with lean and obese adolescents who were not insulin resistant. Measures of arterial function and structure may provide pre-clinical measures of cardiovascular disease in young people at elevated risk.

Ethnic differences in macrovascular and microvascular function in systolic heart failure

BACKGROUND

Endothelial dysfunction is implicated in the pathophysiological features of heart failure (HF), and ethnic differences in the presentation of cardiovascular disease are evident, with an excess seen among South Asians (SAs). However, data on ethnic differences in endothelial function in HF are limited.

METHODS AND RESULTS

In a cross-sectional study, we recruited 128 subjects with systolic HF: 50 SAs, 50 whites, and 28 African Caribbeans (ACs). In addition, SAs with systolic HF were compared with 40 SAs with coronary artery disease without HF ("disease controls") and 40 SA healthy controls. Macrovascular endothelial function was assessed by measurement of flow-mediated dilation (FMD) in response to hyperemia, arterial stiffness was assessed by the pulse-wave velocity, and microvascular endothelial function was assessed by forearm laser Doppler flowmetry. CD144-expressing endothelial microparticles were measured by flow cytometry. When compared with disease controls and healthy controls, SAs with HF had an impaired microvascular response to acetylcholine (P=0.001) and reduced FMD (P<0.001). In comparing ethnic groups, SAs with HF had an impaired response to acetylcholine (123±95.5%) compared with whites (258±156%) and ACs (286±173%, P<0.001 for both). Whites had a higher FMD (8.49±4.63%) than SAs (4.76±4.78%, P<0.001) and ACs (4.55±3.56%, P=0.01). No difference in endothelial-independent response was observed between study groups or in pulse-wave velocity. Ethnicity remained associated with microvascular endothelial function even after adjustment for age, presence of hypertension and diabetes mellitus, blood pressure, and glucose levels (P=0.003). There were no differences in numbers of endothelial microparticles.

CONCLUSIONS

The SAs with HF have impaired microvascular and macrovascular endothelial function but preserved arterial elastic properties. Significant ethnic differences in endothelial function are evident in subjects with HF, with ethnicity being associated with microvascular endothelial dysfunction in this disorder.

Dynamic evaluation of renal resistive index in normoalbuminuric patients with newly diagnosed hypertension or type 2 diabetes

AIM/HYPOTHESIS

Renal resistive index is a useful measure for quantifying alterations in renal blood flow. In the present study we evaluated resistive index at baseline and after vasodilation induced by nitroglycerine in normoalbuminuric patients with type 2 diabetes or essential hypertension, relating the values to indices of systemic vascular dysfunction.

METHODS

Newly diagnosed treatment-naïve type 2 diabetic (n = 32) and hypertensive patients (n = 49) were compared with 27 age- and sex-matched healthy controls. Renal resistive index was obtained by duplex ultrasound at baseline and after 25 μg sublingual nitroglycerine. Endothelium-dependent (flow-mediated dilation) and -independent (response to nitroglycerine) vasodilation in the brachial artery was assessed by computerised edge detection system. Carotid-femoral pulse-wave velocity and augmentation index were assessed by applanation tonometry. Nitrotyrosine levels, an index of oxidative stress, were also measured.

RESULTS

Resistive index was higher in diabetic than in hypertensive patients and controls (p < 0.001), while changes in resistive index induced by nitroglycerine were lower in hypertensive patients compared with controls (p < 0.01), and were further reduced in type 2 diabetic patients. Hypertensive and diabetic patients showed significantly increased arterial stiffness, nitrotyrosine levels and reduced endothelial function than controls (p < 0.05). Changes in resistive index induced by nitroglycerine were independently related to serum glucose, reactive hyperaemia and aortic pulse-wave velocity in the overall population.

CONCLUSIONS/INTERPRETATION

These results support the dynamic evaluation of renal resistive index as an early detector of renal vascular alterations in the presence of type 2 diabetes and hypertension, even before the onset of microalbuminuria.

Inflammatory effects of blood leukocytes: association with vascular function in neuropeptide Y proline 7-genotyped type 2 diabetes patients

OBJECTIVE

We investigated the associations of inflammatory blood cell activation with vascular parameters in patients with type 2 diabetes to elucidate the possible mechanisms of accelerated atherosclerosis observed in subjects with the Leucine 7 to Proline 7 polymorphism (Leu7Pro) in the neuropeptide Y (NPY).

METHODS

Our study included 31 Caucasian patients with type 2 diabetes; 12 of them had the Leu7Pro7 (heterozygous), and 19 had the Leu7Leu7 (wild type) genotype. Vascular parameters were determined by ultrasound methods. Leukocyte analyses were performed from blood samples using flow cytometry. NPY concentrations were determined in plasma.

RESULTS

The amount of platelet-granulocyte complexes was positively correlated with NPY concentration (p=0.008) and carotid intima-media thickness (p=0.035) in the Leu7Pro7 group. Interferon gamma (IFN-γ) expression in monocytes correlated negatively with brachial artery flow-mediated dilatation also in the Leu7Pro7 group (p=0.037). The expression of tissue factor on monocytes correlated negatively with brachial artery diameter in the Leu7Pro7 patients as well (p=0.019).

CONCLUSION

The results indicate significant associations between inflammatory cell activation in blood and vascular atherosclerosis in genetically prone subjects, and provide possible mechanistic information about the role of NPY and the Leu7Pro polymorphism in the development of atherosclerosis.

Impaired endothelium mediated vascular reactivity in endogenous Cushing's syndrome

Endogenous Cushing's syndrome (CS) is associated with a high incidence of cardiovascular morbidity and mortality resulting from the co-existence of multiple cardiovascular risk factors which probably induce a state of endothelial dysfunction. Recently, studies conducted in vitro as well as in normal human subjects suggest a direct role of cortisol in the causation of vascular dysfunction in this disorder. We non-invasively assessed the vascular reactivity and its potential association with elevated cortisol levels in patients of CS. A single time point observational study was conducted in 18 patients of CS and 15 age and gender matched healthy subjects. Vascular reactivity was assessed non-invasively by measuring the peripheral pulse wave form changes during reactive hyperemia (RH) using digital photoplethysmography (PPG). Parameters measured were pulse wave form amplitude (PWA), slope and pulse transit time (PTT). Maximal percentage changes in PWA during RH with reference to baseline were significantly lower in the patients as compared to controls [23.19% (13.19-53.54) vs 61.71% (38.21-95.36); p=0.0079]. Normalized PTT responses during the 1(st) minute of RH were blunted in the patients as compared to controls (1.036 ± 0.026 vs 1.056 ± 0.029; p=0.0425). Percentage changes in PTT during the 2(nd) minute of RH were negatively correlated to the morning cortisol levels in patients (r = -0.6328; p=0.0064). The present study showed that endothelium mediated vascular reactivity along with myogenic regulation of vascular tone is impaired in CS. Hypercortisolism possibly plays an important role in the causation of impaired vascular reactivity and endothelial dysfunction in CS.

Effect of long-term and high-dose allopurinol therapy on endothelial function in normotensive diabetic patients

OBJECTIVES

Endothelial dysfunction is a well known risk factor for atherosclerosis. Uric acid levels are associated with endothelial dysfunction and atherosclerosis even if in physiological range. Xanthine oxidase inhibition with allopurinol decreases uric acid levels and oxidative stress and improves endothelial function. We have investigated the effect of high-dose and long-term allopurinol therapy on endothelial function in diabetic normotensive patients.

METHODS

This study is a randomized, single-blind, placebo-controlled trial. Both treatment and placebo groups consisted of 50 patients. In the treatment group, daily oral 900 mg allopurinol was started after randomization and maintained for 12 weeks. Brachial artery flow-mediated dilatation (FMD) and nitrate-induced dilatation (NID) were measured at baseline and after the allopurinol therapy to evaluate endothelial function.

RESULTS

HbA1c and uric acid levels decreased after allopurinol therapy (6.1 ± 2.1 vs 5.5 ± 1.0%, 5.0 ± 0.8 vs 3.3 ± 0.5 mg/dl, respectively, p = 0.01) but no change was observed in the placebo group (7.7 ± 1.9% vs 7.6 ± 2.0%, 5.3±2.1 vs 5.6 ± 0.8 mg/dl, respectively, p > 0.05). FMD and NID increased significantly in the treatment group (5.6 ± 2.1% vs 8.5 ± 1.2%, 10 ± 7.4% vs 14 ± 4.0%, 10 ± 7.4% vs 14 ± 4.0%, respectively, p = 0.01), whereas no change was observed in the placebo group (5.8 ± 1.8% vs 6.1 ± 0.8%, 12 ± 9.5 vs 10 ± 3.8%, respectively, p > 0.05).

CONCLUSION

Long-term and high-dose allopurinol therapy significantly improved endothelial function in diabetic normotensive patients. In addition, allopurinol therapy contributes to the lower HbA1c levels.

Plasma myeloperoxidase is inversely associated with endothelium-dependent vasodilation in elderly subjects with abnormal glucose metabolism

Myeloperoxidase (MPO), a biomarker related to inflammation, oxidative stress, and nitric oxide scavenging, has been shown to impair endothelium-dependent vasodilation. Because elevated hydrogen peroxide concentrations in diabetic vessels may enhance MPO activity, we hypothesized that a stronger association of MPO with flow-mediated dilation (FMD) may be found in subjects with abnormal glucose metabolism. Myeloperoxidase concentrations were measured in EDTA plasma samples from participants of a population-based cohort study, including 230 subjects with normal glucose metabolism and 386 with abnormal glucose metabolism. Vascular function was expressed as FMD and nitroglycerin-mediated dilation of the brachial artery. In subjects with abnormal glucose metabolism, MPO was negatively associated with FMD (-20.9 [95% confidence interval {CI}, -41.7 to -0.2] -μm change in FMD per SD increment of MPO). This association remained significant after adjustment for nitroglycerin-mediated dilation (-31.1 [95% CI, -50.0 to -12.3]) and was not attenuated after further adjustment for established risk factors. In subjects with normal glucose metabolism, MPO was not significantly associated with FMD (2.0 [95% CI, -16.0 to 20.0]). In conclusion, in subjects with abnormal glucose metabolism, plasma levels of MPO are inversely associated with endothelium-dependent vasodilation, possibly reflecting enhancement of MPO activity by vascular oxidative stress.

Hypotheses, rationale, design, and methods for prognostic evaluation in type 2 diabetic patients with angiographically normal coronary arteries. The MASS IV-DM Trial

Background

The MASS IV-DM Trial is a large project from a single institution, the Heart Institute (InCor), University of São Paulo Medical School, Brazil to study ventricular function and coronary arteries in patients with type 2 diabetes mellitus.

Methods/Design

The study will enroll 600 patients with type 2 diabetes who have angiographically normal ventricular function and coronary arteries. The goal of the MASS IV-DM Trial is to achieve a long-term evaluation of the development of coronary atherosclerosis by using angiograms and coronary-artery calcium scan by electron-beam computed tomography at baseline and after 5 years of follow-up. In addition, the incidence of major cardiovascular events, the dysfunction of various organs involved in this disease, particularly microalbuminuria and renal function, will be analyzed through clinical evaluation. In addition, an effort will be made to investigate in depth the presence of major cardiovascular risk factors, especially the biochemical profile, metabolic syndrome inflammatory activity, oxidative stress, endothelial function, prothrombotic factors, and profibrinolytic and platelet activity. An evaluation will be made of the polymorphism as a determinant of disease and its possible role in the genesis of micro- and macrovascular damage.

Discussion

The MASS IV-DM trial is designed to include diabetic patients with clinically suspected myocardial ischemia in whom conventional angiography shows angiographically normal coronary arteries. The result of extensive investigation including angiographic follow-up by several methods, vascular reactivity, pro-thrombotic mechanisms, genetic and biochemical studies may facilitate the understanding of so-called micro- and macrovascular disease of DM.

Endothelial function in individuals with coronary artery disease with and without type 2 diabetes mellitus

The goal of this study was to determine if individuals with coronary artery disease (CAD) and type 2 diabetes mellitus (T2DM) had greater endothelial dysfunction (ED) than individuals with only CAD. Flow-mediated dilation (FMD), calculated as percentage increase in brachial artery diameter in response to postischemic blood flow, was measured after an overnight fast in 2 cohorts. The first cohort included 76 participants in the Northern Manhattan Study with CAD; 25 also had T2DM. The second cohort was composed of 27 individuals with both T2DM and CAD who were participants in a study of postprandial lipemia. Combined, we analyzed 103 patients with CAD: 52 with T2DM (T2DM+) and 51 without T2DM (T2DM-). The 52 CAD T2DM+ subjects had a mean FMD of 3.9% +/- 3.2%, whereas the 51 CAD T2DM- subjects had a greater mean FMD of 5.5% +/- 4.0% (P < .03). An investigation of various confounders known to affect FMD identified age and body mass index as the only significant covariates in a multiple regression model. Adjusting for age and body mass index, we found that FMD remained lower in T2DM+ subjects compared with T2DM- subjects (difference, -1.99%; P < .03). In patients with CAD, the concomitant presence of T2DM is independently associated with greater ED, as measured by FMD. This finding may be relevant to the greater early and late morbidity and mortality observed in patients with both CAD and T2DM.

Deterioration of glomerular endothelial surface layer induced by oxidative stress is implicated in altered permeability of macromolecules in Zucker fatty rats

AIMS/HYPOTHESIS

The glomerular endothelial layer is coated by the endothelial surface layer (ESL), which is suggested to play a role in regulation of the permselectivity of macromolecules. Production of heparanase, a degrading enzyme of the ESL, is induced by reactive oxygen species (ROS). We hypothesised that oxidative stress could cause deterioration of the glomerular ESL by induction of heparanase, resulting in increased glomerular permeability.

METHODS

Male Zucker fatty (ZF) rats with albuminuria and Zucker lean (ZL) rats were used in this study. Some of the ZF rats were treated with the angiotensin II receptor blocker, irbesartan. We determined the amount of ESL by wheat germ agglutinin staining and heparan sulphate proteoglycan production by western blot analysis. Glomerular hyperfiltration of macromolecules was visualised using in vivo microscopy. We used 2',7'-dichlorofluorescein diacetate-derived chemiluminescence staining to assess ROS production, and heparanase production and expression were determined by western blot analysis and quantitative real-time polymerase chain reaction respectively.

RESULTS

By 18 weeks of age, ZF rats had developed albuminuria. The glomerular endothelial cell glycocalyx was significantly decreased in ZF compared with ZL rats. Glomerular filtration and the permeability of macromolecules were increased in ZF, but not in ZL rats. Glomerular ROS and heparanase production were significantly increased in ZF compared with ZL rats. These changes in ZF rats were reversed by irbesartan treatment.

CONCLUSIONS/INTERPRETATION

Increased oxidative stress induces glomerular ESL deterioration in part through increased heparanase levels, resulting in exacerbation of glomerular permselectivity and development of albuminuria.

Diabetes impairs arteriogenesis in the peripheral circulation: review of molecular mechanisms

Patients suffering from both diabetes and PAD (peripheral arterial disease) are at risk of developing critical limb ischaemia and ulceration, and potentially requiring limb amputation. In addition, diabetes complicates surgical treatment of PAD and impairs arteriogenesis. Arteriogenesis is defined as the remodelling of pre-existing arterioles into conductance vessels to restore the perfusion distal to the occluded artery. Several strategies to promote arteriogenesis in the peripheral circulation have been devised, but the mechanisms through which diabetes impairs arteriogenesis are poorly understood. The present review provides an overview of the current literature on the deteriorating effects of diabetes on the key players in the arteriogenesis process. Diabetes affects arteriogenesis at a number of levels. First, it elevates vasomotor tone and attenuates sensing of shear stress and the response to vasodilatory stimuli, reducing the recruitment and dilatation of collateral arteries. Secondly, diabetes impairs the downstream signalling of monocytes, without decreasing monocyte attraction. In addition, EPC (endothelial progenitor cell) function is attenuated in diabetes. There is ample evidence that growth factor signalling is impaired in diabetic arteriogenesis. Although these defects could be restored in animal experiments, clinical results have been disappointing. Furthermore, the diabetes-induced impairment of eNOS (endothelial NO synthase) strongly affects outward remodelling, as NO signalling plays a key role in several remodelling processes. Finally, in the structural phase of arteriogenesis, diabetes impairs matrix turnover, smooth muscle cell proliferation and fibroblast migration. The review concludes with suggestions for new and more sophisticated therapeutic approaches for the diabetic population.

Endothelial dysfunction in metabolic syndrome: prevalence, pathogenesis and management

The metabolic syndrome (MetS) is characterized by the presence of central obesity, impaired glucose metabolism, dyslipidemia and hypertension. Several studies showed that MetS is associated with increased risk for type 2 diabetes mellitus (T2DM) and vascular events. All components of MetS have adverse effects on the endothelium. Endothelial dysfunction plays a role in the pathogenesis of atherosclerosis and might also increase the risk for insulin resistance and T2DM. We review the prevalence and pathogenesis of endothelial dysfunction in MetS. We also discuss the potential effects of lifestyle measures and pharmacological interventions on endothelial function in these patients. It remains to be established whether improving endothelial function in MetS will reduce the risk for T2DM and vascular events.

Effect of rosiglitazone, metformin and medical nutrition treatment on arterial stiffness, serum MMP-9 and MCP-1 levels in drug naive type 2 diabetic patients

The aim of the study was to evaluate the long-term effect of rosiglitazone and metformin monotherapy with medical nutrition treatment (MNT) and of MNT alone on arterial stiffness, serum monocyte chemoattractant protein (MCP)-1 and matrix metalloproteinase (MMP)-9 in drug naive patients with type 2 diabetes mellitus. Fifty type 2 diabetic patients were randomized to receive rosiglitazone 4 mg/day (n=19) or metformin 850 mg/day (n=16) with MNT or MNT alone (n=15), for 52 weeks. Arterial stiffness was assessed by using large and small artery elasticity index (SAEI and LAEI, respectively). SAEI, LAEI, serum MCP-1 and MMP-9 levels were measured at baseline and following 52 weeks of treatment. SAEI was improved only in the rosiglitazone group, and the difference was still statistically significant when the three groups were compared (p=0.024). There were no differences in LAEI in inter- and intragroup comparisons at the end of the study. Serum MMP-9 levels were decreased in the metformin (-13.5+/-34.8%, p=0.02) and rosiglitazone (-27.2+/-51.0%, p=0.023) groups compared with baseline values, whereas no significant change was seen in serum MCP-1 levels. These results suggest that rosiglitazone monotherapy has favorable effects on arterial stiffness compared with metformin monotherapy independent of glycemic control.