Endothelial and metabolic characteristics of patients with angina and angiographically normal coronary arteries: comparison with subjects with insulin resistance syndrome and normal controls

Higher fasting glucose is associated with poorer survival in non-diabetic subjects having ischemia with non-obstructive coronary arteries

Subjects who have ischemia with non-obstructive coronary arteries (INOCA) experience angina pectoris with evidence of myocardial ischemia but without coronary stenosis. Few studies have investigated factors associated with its survival, especially insulin resistance. In this study, subjects with angina pectoris, without known diabetes mellites (DM), and with non-invasive tests showing myocardial ischemia were admitted for coronary angiography (CAG). Those whose CAG did not reveal stenosis and agreed to receive an oral glucose tolerance test (OGTT) 2 weeks after hospital discharge were enrolled for analysis. All-cause mortality was recorded, which served as the outcome of the study. A total of 587 subjects with INOCA, without known DM, and with OGTT data were analyzed. After OGTT and HbA1c tests, 86 subjects (14.7%) were newly diagnosed with DM and 59.8% had pre-DM. The median duration of follow-up was 7.03 years. Thirty-nine subjects died during the follow-up period. The incidence rate of mortality was 9.9 /1000 person-year. Those who died had a higher fasting glucose (101 ± 17 vs. 94 ± 13 mg/dl, p = 0.003) but a lower estimated glomerular filtration rate (eGFR) (54 ± 22 vs. 87 ± 30 ml/min, p < 0.001). In the Cox survival analysis, a higher fasting glucose (hazard ratio 1.053, p = 0.007) was associated with worse mortality for INOCA without DM (N = 501). On the contrary, a higher eGFR (hazard ratio 0.967, p = 0.012) was protective of better survival for non-diabetic INOCA (N = 501). In conclusion, for non-diabetic INOCA, higher fasting glucose was associated with worse mortality and higher eGFR was protective for better survival.

Endothelin: 30 Years From Discovery to Therapy

Discovered in 1987 as a potent endothelial cell-derived vasoconstrictor peptide, endothelin-1 (ET-1), the predominant member of the endothelin peptide family, is now recognized as a multifunctional peptide with cytokine-like activity contributing to almost all aspects of physiology and cell function. More than 30 000 scientific articles on endothelin were published over the past 3 decades, leading to the development and subsequent regulatory approval of a new class of therapeutics-the endothelin receptor antagonists (ERAs). This article reviews the history of the discovery of endothelin and its role in genetics, physiology, and disease. Here, we summarize the main clinical trials using ERAs and discuss the role of endothelin in cardiovascular diseases such as arterial hypertension, preecclampsia, coronary atherosclerosis, myocardial infarction in the absence of obstructive coronary artery disease (MINOCA) caused by spontaneous coronary artery dissection (SCAD), Takotsubo syndrome, and heart failure. We also discuss how endothelins contributes to diabetic kidney disease and focal segmental glomerulosclerosis, pulmonary arterial hypertension, as well as cancer, immune disorders, and allograft rejection (which all involve ET_A autoantibodies), and neurological diseases. The application of ERAs, dual endothelin receptor/angiotensin receptor antagonists (DARAs), selective ET_B agonists, novel biologics such as receptor-targeting antibodies, or immunization against ET_A receptors holds the potential to slow the progression or even reverse chronic noncommunicable diseases. Future clinical studies will show whether targeting endothelin receptors can prevent or reduce disability from disease and improve clinical outcome, quality of life, and survival in patients.

Post-challenge insulin concentration is useful for differentiating between coronary artery disease and cardiac syndrome X in subjects without known diabetes mellitus

BACKGROUND

Cardiac syndrome X (CSX) is characterized by angina pectoris but with patent coronary arteries. Our previous study demonstrated that subjects with CSX had a higher fasting insulin-resistance (IR) than the controls. However, few studies have investigated the degree of IR, including oral glucose tolerance test (OGTT)-derived indices and profiles of metabolic abnormalities between CSX and coronary artery disease (CAD).

METHODS

Ninety-two CSX and 145 CAD subjects without known diabetes mellitus (DM) underwent coronary angiogram (CAG) for angina pectoris and also agreed to receive OGTT and glycated hemoglobin (HbA_1C) evaluations for screening abnormal glucose regulation and IR.

RESULTS

CAD group had more subjects with metabolically unhealthy obesity (52.4 vs. 31.5%, p < 0.001) than the CSX group. The CAD group had higher OGTT 2 h glucose and insulin (both p < 0.005) while fasting glucose, insulin and HOMA-IR were similar to those of CSX subjects. In the binary regression analysis, OGTT 2 h insulin and being metabolic unhealthy were significantly different between the CAD and CSX groups, but there were no significant differences in Matsuda index, fasting glucose, insulin, HOMA-IR, or HbA_1C.

CONCLUSIONS

Post challenge OGTT 2 h insulin and being metabolic unhealthy were useful parameters in differentiating between CAD and CSX in subjects without known DM but suffered from angina pectoris and underwent CAG. Different degrees of IR and metabolic abnormalities might be implicated in the pathogenesis of micro vs. macro vascular coronary diseases. Trial registration NCT01198730 at https://clinicaltrials.gov, Registered Sep. 8, 2010.

Circulating adipokines and insulin resistance in subjects with combined cardiac and metabolic syndrome X

BACKGROUND

Cardiac syndrome X (CSX) is characterized by angina pectoris but with patent coronary arteries. Our previous study showed that CSX subjects had decreased serum adiponectin but higher leptin and insulin resistance (IR). However, few studies have investigated circulating adipokines and IR in subjects with combined metabolic syndrome X (MetX) and CSX.

METHODS

Fifty-nine subjects with CSX were retrospectively enrolled from our cardiac catheterization patient databank. Fifty-four subjects with valvular heart disease or arrhythmia and with normal coronary angiograms were recruited as the non-CSX comparison group. The study subjects were reclassified according to the presence or absence of MetX. Circulating adipokines and degree of IR were measured.

RESULTS

Subjects with combined MetX and CSX had a significantly higher HOMA-IR, a higher circulating leptin level (median 8.7 vs. 3.3 ng/mL, p < 0.001), but a lower circulating adiponectin level (median 2.8 vs. 12.3 μg/mL, p < 0.001) than those without MetX and CSX. In pairwise comparisons, combined MetX and CSX subjects had a similar circulating adipokines and IR index as those who had only either one syndrome X. In a multivariate regression analysis, serum triglycerides (odds ratio 1.011, p = 0.024) and hypertension (odds ratio 14.453, p = 0.003) were independently associated with diagnosis of combined MetX and CSX.

CONCLUSIONS

Combined MetX and CSX had a significantly higher HOMA-IR, a higher circulating leptin but a lower circulating adiponectin level than those without MetX and CSX. Combined syndrome X did not confer more changes on adipokines or IR index comparing with those with only one syndrome X.

Coronary microvascular dysfunction in women: an overview of diagnostic strategies

Coronary microvascular dysfunction (CMD) also known as syndrome X, is characterized by typical anginal symptoms, evidence of myocardial ischemia on non-invasive testing and normal to minimal coronary disease on coronary angiography. It has a female preponderance and has been detected in up to 50% of women presenting with chest pain symptoms. Definitive diagnosis of CMD is critical as recent evidence suggests that women with this condition are at increased risk of cardiovascular events in the future. Invasive coronary reactivity testing on coronary angiography is considered to be the 'gold standard' for diagnosis of CMD. Non-invasive imaging techniques such as PET and cardiac magnetic resonance hold promise for detection of CMD in the future.

Vitamin D replacement therapy in patients with cardiac syndrome X

AIMS

The aim of present study was to assess whether vitamin D, with proven beneficial effects on the cardiovascular system, has any effect on angina and exercise-induced ischemia in patients with cardiac syndrome X and low serum vitamin D.

METHODS

Patients with cardiac syndrome X and low serum vitamin D3 were studied before and after treatment with an intramuscular injection of vitamin D3 (300,000 units, every other week for 2 months). We determined the angina episode (per day) and several indices of exercise capacity.

RESULTS

At the end of the treatment course (75±6 day), a significant increase of serum vitamin D3 occurred and was within the normal range (45±8 ng/ml) and the frequency of angina improved significantly (p=0.003). Exercise duration and maximal work capacity increased significantly (p<0.001). Maximal ST-segment depression (mm) decreased significantly (p=0.001). The calculated Duck treadmill score improved significantly (p=0.001).

CONCLUSIONS

Our findings show that vitamin D replacement therapy in patients with cardiac syndrome X and vitamin D deficiency dramatically improves symptoms and signs of ischemia.

Role of inflammation and endothelial dysfunction in the pathogenesis of cardiac syndrome X

Chest pain with normal coronary arteriograms represents a major diagnostic and therapeutic challenge to contemporary cardiology. Cardiac syndrome X (CSX), defined as typical angina-like chest pain, a positive response to exercise stress testing and normal coronary arteriograms, encompasses patients with a variety of pathogenic mechanisms. Cardiac ischemia has been documented in approximately 25% of CSX patients and is associated with endothelial dysfunction and microvascular vasodilator abnormalities. Increased endothelin-1, a powerful vasoconstrictor, has been suggested to play a pathogenic role. There is a high prevalence of postmenopausal women with CSX and thus estrogen deficiency has also been proposed to represent a possible pathogenic mechanism. Inflammatory mechanisms and endothelial dysfunction at the coronary microvascular level appear to be important in the pathogenesis of CSX. Treatment with agents that have protective effects on the vasculature and also anti-inflammatory properties, such as statins and angiotensin-converting enzyme inhibitors have been effective in improving both symptoms and electrocardiographic signs of myocardial ischemia in patients with CSX. This review discusses the roles for endothelial dysfunction and inflammation in the pathogenesis of CSX, as well as the potential therapeutic implications of these mechanisms.

Ultrasound measurement of peripheral endothelial dysfunction in type 2 diabetic patients: correlation with risk factors

The purpose of the study was to assess the endothelial dysfunction (ED) in type 2 diabetic patients ultrasonographically and estimate the correlation of ED with glycemia and other cardio-metabolic risk factors. 171 patient (age 60.0 + 8.5 years) with diagnosed type 2 diabetes and coronary artery disease (CAD) were randomly included in a cross sectional study. B-mode ultrasound system with a linear transducer of 7.5 MHz was used for evaluation of flow-mediated vasodilation in brachial artery (FMV). FMV was presented as a change of brachial artery diameter at rest and after limb ischemia, previously provoked by cuff inflation. Peripheral ED was found in 77.2% (132 patients). Multivariate logistic regression model defined: age (OR 1.071, 95% CI 1.003 1,143) and plasma cholesterol (OR 4.083 95% CI 1.080 17,017) as determinants for ED. Linear multivariate analysis presented duration of diabetes (Beta 0.173, Sig 0.024), and glycemia (Beta 0.132, Sig 0.044) to be associated independently with FMV value. Estimated factors influencing FMV, might be potential therapeutic targets for presented endothelial dysfunction in type 2 diabetic patients with coronary artery disease.

Serum ADMA concentration-- an independent factor determining FMD impairment in cardiac syndrome X

Mechanisms of decreased endogenous vascular reactivity in individuals with cardiac syndrome X (CSX) are not fully understood.

AIM

To evaluate the following serum markers: total nitric oxide (NO), asymmetric dimethylarginine (ADMA), platelet-derived growth factor (PDGF), and to establish their relation to ultrasound indexes of endothelial function and structural remodeling in CSX patients.

METHOD

The study group consisted of 43 CSX patients (mean age: 56.3 +/- 9 years), while the control group included 21 healthy subjects (mean age: 54.86 +/- 6.9 years). The high-resolution ultrasound was performed to measure: flow-mediated vasodilatation (FMD), nitroglycerine-mediated vasodilatation (NMD) and intima-media thickness (IMT) of carotid arteries.

RESULTS

In CSX patients, significantly lower FMD (9.06 +/- 3.2%) and significantly higher IMT (0.667 +/- 0.14 mm) values were observed compared to healthy individuals (17.42 +/- 8.4%, 0.571 +/- 0.2 mm; P < 0.05). Mean total NO serum concentration was significantly higher in the CSX group (48.2 +/- 18.2 micromol/L) as compared to controls (32.1 +/- 1.4 micromol/L; P < 0.0001). There were no differences in serum ADMA and PDGF levels. In CSX patients, FMD values correlated with NO (r = 0.323; P = 0.039) and ADMA (r = -0.387; P = 0.012) serum levels; however, there were no significant correlations between NO and ADMA concentrations.

CONCLUSION

Serum ADMA concentration is the only independent factor determining FMD impairment.

Cardiovascular actions of insulin

Insulin has important vascular actions to stimulate production of nitric oxide from endothelium. This leads to capillary recruitment, vasodilation, increased blood flow, and subsequent augmentation of glucose disposal in classical insulin target tissues (e.g., skeletal muscle). Phosphatidylinositol 3-kinase-dependent insulin-signaling pathways regulating endothelial production of nitric oxide share striking parallels with metabolic insulin-signaling pathways. Distinct MAPK-dependent insulin-signaling pathways (largely unrelated to metabolic actions of insulin) regulate secretion of the vasoconstrictor endothelin-1 from endothelium. These and other cardiovascular actions of insulin contribute to coupling metabolic and hemodynamic homeostasis under healthy conditions. Cardiovascular diseases are the leading cause of morbidity and mortality in insulin-resistant individuals. Insulin resistance is typically defined as decreased sensitivity and/or responsiveness to metabolic actions of insulin. This cardinal feature of diabetes, obesity, and dyslipidemia is also a prominent component of hypertension, coronary heart disease, and atherosclerosis that are all characterized by endothelial dysfunction. Conversely, endothelial dysfunction is often present in metabolic diseases. Insulin resistance is characterized by pathway-specific impairment in phosphatidylinositol 3-kinase-dependent signaling that in vascular endothelium contributes to a reciprocal relationship between insulin resistance and endothelial dysfunction. The clinical relevance of this coupling is highlighted by the findings that specific therapeutic interventions targeting insulin resistance often also ameliorate endothelial dysfunction (and vice versa). In this review, we discuss molecular mechanisms underlying cardiovascular actions of insulin, the reciprocal relationships between insulin resistance and endothelial dysfunction, and implications for developing beneficial therapeutic strategies that simultaneously target metabolic and cardiovascular diseases.

Increased insulin-stimulated endothelin-1 release is a distinct vascular phenotype distinguishing Cushing's disease from metabolic syndrome

OBJECTIVE

Although much is known about the anti-inflammatory effects of an acute corticosteroid therapy, little is known about the effects on chronic hypercortisolism on endothelial dysfunction and proinflammatory alterations in patients with Cushing's disease (CD).

PATIENTS AND METHODS

We studied 9 patients with CD, 10 patients with metabolic syndrome and 27 normal controls. The tests consisted of an intravenous bolus of 0.1 U/kg insulin combined with a euglycaemic clamp technique with an arterialized forearm and assessment of the training parameters deep-venous balance of forearm glucose uptake (as an index of insulin sensitivity); NO(x) (nitric oxide end-products), c-GMP (second messenger of nitric oxide) and endothelin-1 release, as indices of endothelial function and proinflammatory systemic markers.

RESULTS

Forearm glucose uptake incremental area was significantly lower in Cushing's disease and in the metabolic syndrome than in controls, suggesting a state of severe insulin resistance. Compared to controls and to the metabolic syndrome, basal and insulin-stimulated NO(x) release incremental areas were significantly reduced in Cushing's disease, while forearm c-GMP release was similarly decreased in CD and metabolic syndrome. By contrast, endothelin-1 incremental areas after insulin bolus were significantly higher in CD than in controls and the metabolic syndrome, in the presence of increased TNF-alpha, IL-6 and CRP levels. Forearm glucose uptake incremental area significantly correlated with NO(x) incremental area, forearm c-GMP release incremental area, TNF-alpha levels and ET-1 incremental area.

CONCLUSIONS

In patients with CD, supraphysiological insulin levels are not able to overcome the insulin resistance due to chronic hypercortisolism. Furthermore, an increased proatherogenic risk profile is characterized by decreased nitric oxide synthesis and activity, enhanced endothelin-1 levels and increased proinflammatory markers.

Inhibition of free fatty acids metabolism as a therapeutic target in patients with heart failure

Recent studies have evidenced that alterations of cardiac metabolism can be present in several cardiac syndromes. In heart failure, wasting of subcutaneous fat and skeletal muscle is relatively common and suggests an increased utilisation of non-carbohydrate substrates for energy production. In fact, fasting blood ketone bodies as well as fat oxidation during exercise have been shown to be increased in patients with heart failure. This metabolic shift determines a reduction of myocardial oxygen consumption efficiency. A direct approach to manipulate cardiac energy metabolism consists in modifying substrate utilisation by the heart. To date, the most effective metabolic treatments include several pharmacological agents that directly inhibit fatty acid oxidation. Clinical studies have shown that these agents can substantially increase the ischaemic threshold in patients with effort angina. However, the results of current research is also supporting the concept that shifting the energy substrate preference away from fatty acid metabolism and towards glucose metabolism could be an effective adjunctive treatment in patients with heart failure, in terms of left ventricular function and glucose metabolism improvement. In fact, these agents have also been shown to improve overall glucose metabolism in diabetic patients with left ventricular dysfunction. In this paper, the recent literature on the beneficial therapeutic effects of modulation of cardiac metabolic substrates utilisation in patients with heart failure is reviewed and discussed.

Endothelin limits insulin action in obese/insulin-resistant humans

The normal action of insulin to vasodilate and redistribute blood flow in support of skeletal muscle metabolism is impaired in insulin-resistant states. Increased endogenous endothelin contributes to endothelial dysfunction in obesity and diabetes. Here, we test the hypothesis that increased endogenous endothelin action also contributes to skeletal muscle insulin resistance via impairments in insulin-stimulated vasodilation. We studied nine lean and seven obese humans, measuring the metabolic and hemodynamic effects of insulin (300 mU . m(-2) . min(-1)) alone and during femoral artery infusion of BQ123 (an antagonist of type A endothelin receptors, 1 micromol/min). Endothelin antagonism augmented skeletal muscle responses to insulin in obese subjects through changes in both leg blood flow (LBF) and glucose extraction. Insulin-stimulated LBF was significantly increased in obese subjects only. These changes, combined with differential effects on glucose extraction, resulted in augmented insulin-stimulated leg glucose uptake in obese subjects (54.7 +/- 5.7 vs. 107.4 +/- 18.9 mg/min with BQ123), with no change in lean subjects (103.7 +/- 11.4 vs. 88.9 +/- 16.3, P = 0.04 comparing BQ123 across groups). BQ123 allowed augmented leg glucose extraction in obese subjects even in the face of NOS antagonism. These findings suggest that increased endogenous endothelin action contributes to insulin resistance in skeletal muscle of obese humans, likely through both vascular and tissue effects.

Effects of Metformin on Microvascular Function and Exercise Tolerance in Women With Angina and Normal Coronary Arteries

OBJECTIVES

This study sought to determine whether metformin improves vascular function or myocardial ischemia in nondiabetic subjects.

BACKGROUND

Metformin prevents diabetes and may reduce coronary events in patients with diabetes, but effects on microvascular function and angina are not clear.

METHODS

We conducted an 8-week double-blind, randomized, placebo-controlled study of metformin 500 mg twice a day in 33 nondiabetic women with a prior history of normal coronary angiography but two consecutive positive (ST-segment depression > or =1 mm) exercise tolerance tests. All parameters were measured at baseline and at 8 weeks, together with an in vivo assessment of forearm (skin) microvascular function using laser Doppler imaging combined with iontophoresis.

RESULTS

In comparison with placebo (n = 17), metformin recipients (n = 16) showed significant reductions in weight and in homeostatic model assessment for insulin resistance (p < 0.05, intention to treat). Endothelium-dependent microvascular responses improved significantly with metformin (2-way repeated analysis of variance, p = 0.0003), but responses with placebo were unchanged (p = 0.50). A comparison of change in acetylcholine responses between metformin and placebo recipients was significant, whether analyzed by a 2-way analysis of variance (p < 0.0001) or change in area under curves (mean change +392 perfusion units, 95% confidence interval [CI] 20 to 764). Endothelium-independent responses were not altered. Maximal ST-segment depression (-0.84 mm, 95% CI -1.49 to -0.20, p = 0.013), Duke score (6.1 U, 95% CI 1.8 to 10.5, p = 0.008), and chest pain incidence (-0.11 episodes/day, 95% CI -0.22 to 0.00, p = 0.056) improved in metformin relative to placebo recipients.

CONCLUSIONS

Metformin may improve vascular function and decrease myocardial ischemia in nondiabetic women with chest pain and angiographically normal coronary arteries. Larger controlled trials of longer duration are warranted.

Endothelin-1 impairs glucose transporter trafficking via a membrane-based mechanism

Endothelin-1 (ET-1) disrupts insulin-regulated glucose transporter GLUT4 trafficking. Since the negative consequence of chronic ET-1 exposure appears to be independent of signal disturbance along the insulin receptor substrate-1/phosphatidylinositol (PI) 3-kinase (PI3K)/Akt-2 pathway of insulin action, we tested if ET-1 altered GLUT4 regulation engaged by osmotic shock, a PI3K-independent stimulus that mimics insulin action. Regulation of GLUT4 by hyperosmotic stress was impaired by ET-1. Because of the mutual disruption of both insulin- and hyperosmolarity-stimulated GLUT4 translocation, we tested whether shared signaling and/or key phosphatidylinositol 4,5-bisphosphate (PIP2)-regulated cytoskeletal events of GLUT4 trafficking were targets of ET-1. Both insulin and hyperosmotic stress signaling to Cbl were impaired by ET-1. Also, plasma membrane PIP2 and cortical actin levels were reduced in cells exposed to ET-1. Exogenous PIP2, but not PI 3,4,5-bisphosphate, restored actin structure, Cbl activation, and GLUT4 translocation. These data show that ET-1-induced PIP2/actin disruption impairs GLUT4 trafficking elicited by insulin and hyperosmolarity. In addition to showing for the first time the important role of PIP2-regulated cytoskeletal events in GLUT4 regulation by stimuli other than insulin, these studies reveal a novel function of PIP2/actin structure in signal transduction.

Treating the metabolic syndrome using angiotensin receptor antagonists that selectively modulate peroxisome proliferator-activated receptor-γ

The metabolic syndrome, defined as a cluster of visceral obesity, insulin resistance, dyslipidemia and elevated blood pressure, is associated with pro-thrombotic, pro-atherogenic and inflammatory risk factors that predispose to cardiovascular disease. Although activators of the peroxisome proliferator-activated receptors (PPARalpha,gamma,delta) in various combinations are under development for treating the metabolic syndrome, they are hampered by adverse effects related to increased adipogenesis, weight gain, fluid overload and carcinogenesis. The recent discovery that telmisartan and irbesartan, antihypertensive angiotensin II type 1 receptor (AT1-R) blockers (ARBs), were uniquely capable of activating PPARgamma, has provided a novel approach to addressing the multifactorial components of the metabolic syndrome. Both drugs have established favorable safety profiles and can activate PPARgamma at concentrations potentially achievable at therapeutic doses. Emerging studies have revealed that both these drugs have beneficial metabolic profiles. This information provides a strategic rationale and pharmacological platform for the development of novel dual ARB/PPARgamma agonists to target the metabolic syndrome and its cardiovascular sequelae, for which therapy is presently insufficient or non-existent. Beneficial effects of these agents include increased energy expenditure, improved lipid profile, increased insulin sensitivity, blood pressure reduction, and amelioration of the associated pro-inflammatory and pro-atherogenic risk profiles. The potential benefit for treatment of the metabolic syndrome, cardiovascular protection, and prevention of related end-organ complications could be of immense clinical value.

Clinical implications of assessing coronary flow velocity reserve and plasma endothelin-1 in hypertensive patients

Previous reports have indicated that hypertensive patients who have angina-like chest pain and normal coronary arteriograms have reduced coronary flow velocity reserve (CFVR) levels. In addition, elevated plasma endothelin-1 (ET-1) levels have been reported to be associated with microvascular angina. The purpose of this study was to evaluate the plasma ET-1 levels and CFVR in patients with chest pain but without coronary artery disease (CAD). A total of 66 patients were included in this study. CAD was ruled out by exercise stress test or coronary angiogram. Plasma ET-1 and CFVR measurements were performed in patients with (n=35) and without (n=31) a history of angina-like chest pain. CFVR was measured using adenosine-triphosphate stress transthoracic Doppler echocardiography. The mean ET-1 level was significantly higher and the CFVR was significantly lower in patients in the symptomatic group than in those in the asymptomatic group (ET-1: 3.85 +/- 1.24 pg/ml vs. 2.98 +/- 1.27 pg/ml, CFVR: 2.26 +/- 0.48 vs. 2.77 +/- 0.11, respectively). Plasma ET-1 level and CFVR were significantly correlated with each other (-r = 0.265, p = 0.033). Age, blood pressure, cardiovascular risk factors, and left ventricular mass index were similar between the two groups. The results of multiple regression analysis indicate that age (p = 0.008) and plasma ET-1 concentration (p = 0.031) had statistically independent associations with CFVR. Attenuated CFVR in the symptomatic hypertensive patients was associated with endothelial dysfunction, which results in elevated plasma ET-1 levels. The link between these two parameters may play a role in the genesis of chest pain in hypertensive patients without CAD.

Comparison of plasma serotonin levels in patients with variant angina pectoris versus healed myocardial infarction

Patients with variant angina pectoris showed greater serotonin plasma levels than did control subjects and patients with healed myocardial infarction. The levels also tended to be greater in those with >1 episode/month than in those with fewer episodes. Moreover, patients with variant angina pectoris also had greater levels of nitrite and nitrate plasma levels than did control subjects or patients with healed myocardial infarction, partly, perhaps, as a compensatory mechanism.

Influence of coenzyme Q(10) and cerivastatin on the flow-mediated vasodilation of the brachial artery: results of the ENDOTACT study

AIM

Endothelial dysfunction (ED) is the functional prestep in atherosclerosis. Aim of the present study was to evaluate the effects of a potent antioxidant (coenzyme Q(10), CoQ(10)) and of cerivastatin on ED of the brachial artery.

METHODS AND RESULTS

Twenty-five male patients with manifest ED (flow-mediated vasodilation [FMD%]<4.5%) were included in this prospective, randomized, cross-over study. ED of the brachial artery was assessed by the use of high-resolution ultrasound. Each patient had to pass through three treatment phases ((1) single therapy with cerivastatin (C), (2) single therapy with CoQ(10), (3) combination therapy). FMD% significantly improved throughout all treatment phases ((1) 3.50+/-4.05% vs. 8.80+/-6.39%, p=0.009; (2) -0.25+/-4.0% vs. 7.06%+/-4.39%, p=0.004; (3) 3.14+/-3.54% vs. 8.82+/-5.78%, p=0.011). C led to a significant decrease of CoQ(10) plasma levels (1.23+/-0.34 vs. 0.87+/-0.39 microg/ml, p=0.004).

CONCLUSION

Our results indicate a positive influence of CoQ(10) supplementation on human ED, which appears to be independent of lipid lowering. Although large-scale studies evaluating other antioxidants failed to demonstrate a positive prognostic effect, Q(10) has never been evaluated in larger trials. Experimental as well as clinical results indicate that CoQ(10) warrants further attention in atherosclerosis research.

Increased plasma concentration of nitric oxide in type 2 diabetes but not in nondiabetic individuals with insulin resistance

OBJECTIVE

Insulin resistance (IR) is a key element in the pathogenesis of type 2 diabetes. The results of recent experiments on insulin-mediated vasodilatation have suggested that vascular insensitivity is a component of IR. However, it is still controversial that patients with type 2 diabetes have a decreased ability of insulin to increase endothelial nitric oxide (NO) release.

METHOD

Plasma concentration of NO was examined in 26 patients with type 2 diabetes and 78 nondiabetic volunteers during an insulin suppression test. The test measured the efficacy of insulin in promoting disposal of the infused glucose load, in which the steady state plasma glucose (SSPG) during the 150-180 min of the test was used as an index of IR. Plasma NO levels were assayed by measurement of the stable end products of their metabolism. Comparison of plasma NO levels between groups were performed by Mann-Whitney test and relationships between SSPG and different variables were analyzed by partial correlations.

RESULTS

Our results showed that the plasma NO levels were significantly higher in the diabetic group. When the nondiabetic subjects were analyzed according to their SSPG levels, there was no difference of plasma NO levels between those with SSPG>160 mg/dl and those with SSPG<160 mg/dl. There were also no difference of NO levels between those with a family history of type 2 diabetes and those without. In the nondiabetic group, SSPG correlated with BMI, fasting insulin, triglyceride and HDL-cholesterol, but neither with plasma NO levels nor fasting plasma glucose.

CONCLUSION

Our data suggests that the impairment of NO activity in patients with type 2 diabetes is due to an impaired effect rather than its production. This altered NO signaling pathway is not an early event in insulin resistant individuals. Any such changes will not be apparent until type 2 diabetes with overt hyperglycemia develops.

Insulin resistance as a contributor to myocardial ischaemia independent of obstructive coronary atheroma: a role for insulin sensitisation?

There is good evidence to suggest that insulin resistance and its surrogate markers are at least modest independent cardiovascular risk factors. However, as well as long term effects on atheromatous coronary disease, there is a well described correlation between markers of insulin resistance and endothelial dysfunction. In this review, the evidence for a relation between endothelial dysfunction and myocardial ischaemia is summarised. The evidence for a correlation between insulin resistance and endothelial dysfunction and the proposed cellular mechanisms are also examined. Finally, the potential role for insulin sensitising strategies is looked at and recent data examining their effects on both endothelial function and clinical symptoms is examined. In conclusion, it was found that insulin sensitising modalities have a potential role in the amelioration of angina and that randomised controlled studies are therefore warranted.

Myocardial insulin resistance associated with chronic hypertriglyceridemia and increased FFA levels in Type 2 diabetic patients

We evaluated the influence of chronic hypertriglyceridemia and endothelial dysfunction on myocardial glucose uptake (MGU) in Type 2 diabetic patients without coronary heart disease. Patients were divided into two groups according to fasting triglyceride (TG) levels: 5.4 ± 1.1 and 1.5 ± 0.3 mmol/l for high- and normal-TG groups, respectively. Five subjects were assigned to the high-TG group and 11 to the normal-TG group. Age, gender, body mass index, systolic and diastolic blood pressure, glucose, insulin, HbA1c, cholesterol, and HDL cholesterol were similar in the two groups, whereas free fatty acid (FFA) levels were higher in the high-TG group basally and at the end of the clamp. Furthermore, five healthy subjects were subjected to the same protocol and used as the control group. MGU was assessed by using 18F-labeled 2-fluoro-2-deoxy-d-glucose under hyperglycemic-hyperinsulinemic conditions. Basal endothelin-1 and nitric oxide levels were significantly higher in the high-TG group than in the normal-TG and control groups, and cGMP and maximal postischemic vasodilation were significantly decreased in the high-TG group compared with the normal-TG and control groups. However, significant alterations were found in the same parameters in the normal-TG group compared with the control group. By the end of the hyperglycemic clamp, in the high-TG group, MGU was ∼40 and 65% of that in the normal-TG and control groups. MGU negatively correlated with TG, FFA, and endothelin-1, whereas a positive correlation was found with cGMP and maximal postischemic vasodilation. In conclusion, increased TG and FFA levels are risks, in addition to Type 2 diabetes mellitus, for myocardial insulin resistance, endothelial dysfunction, and alteration of nitric oxide/cGMP levels.

Effect of oral L-arginine on blood pressure and symptoms and endothelial function in patients with systemic hypertension, positive exercise tests, and normal coronary arteries

Thirteen hypertensive patients with microvascular angina were studied before and after receiving oral L-arginine (4 weeks, 2 g, 3 times daily). L-arginine significantly improved angina class, systolic blood pressure at rest, and quality of life. Maximal forearm blood flow, plasma L-arginine, L-arginine:asymmetric dimethyl arginine ratio, and cyclic guanylate monophosphate increased significantly after treatment. In medically treated hypertensive patients with micro-vascular angina, oral L-arginine may represent a useful therapeutic option.

Association of insulin resistance, hyperleptinemia, and impaired nitric oxide release with in-stent restenosis in patients undergoing coronary stenting

BACKGROUND

Previously undiagnosed diabetes, impaired glucose tolerance, and insulin resistance are common in patients with acute myocardial infarction and coronary heart disease (CHD) and might be involved in early restenosis after stent implantation. To evaluate whether markers of insulin resistance syndrome, including leptin, and endothelial dysfunction are related to increased rate of early restenosis, we studied nondiabetic patients with CHD after successful coronary stenting.

METHODS AND RESULTS

Both patients with CHD undergoing coronary stenting (120 patients) and control subjects (58 patients) were submitted to an oral glucose tolerance test (OGTT). Fasting leptin levels and fasting and postglucose load insulin sensitivity were assessed. Endothelial function was measured by nitrite and nitrate release (NOx) during OGTT. More than 50% of patients treated with stent implantation presented impaired glucose tolerance or type 2 diabetes, which was previously undiagnosed. These patients also had higher glucose, insulin, and leptin levels than control subjects. Among the stented patients, insulin and leptin levels were higher in patients with restenosis than in patients without restenosis. A significant increase in NOx levels was found during OGTT both in patients without restenosis and in control subjects. On the contrary, NOx profiles were blunted in patients with restenosis. At multiple regression analysis, only DeltaAUC-NOx areas and insulin sensitivity index showed an independent correlation with the minimal lumen diameter at follow-up.

CONCLUSIONS

We demonstrated that insulin resistance and endothelial dysfunction are independent predictors of early restenosis after coronary stenting.

Chronic endothelin-1 treatment leads to insulin resistance in vivo

We determined whether chronic endothelin-1 (ET-1) treatment could lead to in vivo insulin resistance. Like insulin, ET-1 acutely stimulated glucose transport in isolated soleus muscle strips of WKY rats. ET-1 pretreatment (1 h) decreased insulin-stimulated glucose transport in muscle strips (-23%). Both ET-1-mediated effects were generated through ET(A) receptors, because a specific ET(A) receptor antagonist (BQ610) blocked these effects of ET-1. Osmotic minipumps were used to treat normal rats with ET-1 for 5 days. Subsequent hyperinsulinemic-euglycemic clamps showed that ET-1 treatment led to an approximately 30% decrease in insulin-stimulated glucose disposal rates in male and female rats. In addition, ex vivo study of soleus muscle strips showed decreased glucose transport into muscle from ET-1-treated animals. With respect to insulin signaling, chronic in vivo ET-1 treatment led to a 30-40% decrease in IRS-I protein content, IRS-I-associated p110(alpha), and AKT activation. In summary, 1) in vitro ET-1 pretreatment leads to decreased insulin-stimulated glucose transport in skeletal muscle strips; 2) chronic ET-1 administration in vivo leads to whole-body insulin resistance, with decreased skeletal muscle glucose transport and impaired insulin signaling; and 3) elevated ET-1 levels may be a cause of insulin resistance in certain pathophysiologic states.

[Cardiovascular syndrome X and endothelial dysfunction]

Up to 30% of patients with chest pain who undergo coronary arteriography, have completely normal coronary angiograms. The subgroup with typical angina and a positive response to stress testing is generally included under the diagnosis of cardiovascular syndrome X. Several causes and mechanisms have been investigated in the past twenty years, to explain both chest pain and ischemic angina-like ST segment depression that are commonly observed in these patients. Clinical and pathogenic heterogeneity appears to be the main features of the syndrome. Among the suggested pathophysiological mechanisms, endothelial dysfunction of the coronary microcirculation features prominently. In this review, we present the available evidence regarding endothelial dysfunction in cardiovascular syndrome X.

Acute intravenous L-arginine infusion decreases endothelin-1 levels and improves endothelial function in patients with angina pectoris and normal coronary arteriograms: correlation with asymmetric dimethylarginine levels

BACKGROUND

We tested the hypothesis that asymmetric dimethylarginine (ADMA) levels could be elevated and influence endothelin-1 and nitric oxide release and action in patients with cardiac syndrome X (CSX). In addition, we evaluated whether an intravenous infusion of L-arginine would improve endothelial function in these subjects.

METHODS AND RESULTS

Nine patients with CSX and 14 control subjects underwent a continuous infusion of L-arginine (0.125 g/min) or saline for 120 minutes. Sixty minutes after L-arginine or saline infusions, an intravenous insulin bolus (0.1 U/kg) combined with a euglycemic clamp was performed. Basal ADMA and endothelin-1 levels were higher in patients with CSX than in controls. At the end of the first hour of infusion, compared with saline, L-arginine infusion increased basal forearm blood flow, nitrite and nitrate (NOx), and forearm cGMP release and decreased endothelin-1. After insulin bolus, during saline, insulin-induced NOx, endothelin-1, and forearm cGMP release was almost abolished. Conversely, L-arginine restored a physiological profile of all endothelial variables compared with control subjects. In control subjects, compared with saline infusion, L-arginine infusion did not modify any parameter. ADMA levels were positively correlated with basal endothelin-1 levels and negatively correlated with insulin-induced incremental levels of NOx and forearm cGMP release.

CONCLUSIONS

Plasma ADMA levels are increased in patients with CSX, and they are correlated with increases in endothelin-1 and reductions in insulin-induced increments in plasma NOx and cGMP, effects that are reversed by intravenous L-arginine. These data suggest that increased ADMA levels play a role in the abnormal vascular reactivity that is observed in patients with CSX.

G protein beta3 gene variant, vascular function, and insulin sensitivity in type 2 diabetes

A common polymorphism (825 C/T) in exon 10 of the GNB3 gene, that encodes for the beta-3 subunit, has been associated with different degrees of activation of heterotrimeric guanine nucleotide binding proteins (G proteins). Many hormones and neurotransmitters use specific receptors that interact noncovalently with G proteins in the transmembrane signaling process. Among them, insulin uses an inhibitory G protein-sensitive mechanism that is involved in metabolic and vascular events, leading to enhanced glucose transport and vasodilation. We hypothesized differences in peripheral and vascular insulin sensitivity according to GNB3 gene polymorphism in type 2 diabetic patients. To address this issue, we used an intervention-optimization protocol to examine whether diabetic patients with the variant show a different response in terms of insulin-sensitivity. Interindividual differences in baseline insulin sensitivity and vascular dysfunction (vasodilatory response to glyceryl trinitrate) were not attributable to this polymorphism of the GNB3 gene. However, in contrast to normal homozygotes, insulin sensitivity (S(I)) significantly improved (P=0.01) in carriers of the 825T variant. Parallel to these findings, stimulated C-peptide tended to decrease, and the response to glyceryl trinitrate significantly improved (P=0.004) among 825T carriers. Body mass index, systolic and diastolic blood pressure, heart rate, or serum lipid levels did not significantly change in either group. Our findings suggest an effect of GNB3 gene polymorphism on important phenotypic variations in type 2 diabetes mellitus. The GNB3 gene polymorphism might be an example of pharmacogenetics, with the underlying etiological genetic defect altering the response to treatment.

Can the premises of the spasm of resistance vessel concept permit improvement in the treatment and prevention of ischemic heart disease?

In this communication, the spasm of resistance vessel (S-RV) concept of ischemic heart disease (IHD) and other ischemic will be reviewed and updated, and evidence will be presented that principles of the hypothesis might improve the treatment and prevention of IHD. The S-RV concept provides a different basic pathogenetic framework for IHD, and suggestions for treatment and prevention stem from its different basic conceptualization of this disorder. The concept asserts that S-RV directly induces symptoms in IHD, and this position challenges the accepted pathogenetic mechanism for this disorder, i.e., that symptoms in IHD are due directly to obstructive occlusions of epicardial arteries secondary to coronary artery disease. The S-RV concept avers that ischemia-induced S-RV is a major factor in IHD, and evidence supporting this position is provided. Another major position of the hypothesis is that no-reflow (reduced flow after infarction and severe myocardial ischemia in the absence of infarction) is due to ischemic injury-induced S-RV, and a variety of evidences to support this position are offered.Proposed improvement in the treatment of IHD is based mainly on treating ischemia-induced S-RV. alpha-Adrenergic sympathetic blockade reverses ischemia-induced S-RV, and alpha-adrenergic blockade is suggested as therapy for acute coronary syndromes and to prevent complications of percutaneous coronary interventions. Also, angiotensin-converting enzyme inhibition, which has actions similar to alpha-adrenergic blockade, is also suggested. Proposals for the prevention of IHD are based the prevention of S-RV, and special emphasis is given to preventing exercise- and stress-related IHD.

The lipids that matter from infant nutrition to insulin resistance

Breast-fed infants showed decreased incidence of obesity, hypertension, diabetes mellitus, and coronary heart disease in later life and higher cognitive function. Breast milk is rich in long-chain polyunsaturated fatty acids (LCPUFAs) and brain preferentially accumulates LCPUFAs during the last trimester of pregnancy and the first few months of life. Breast-fed infants showed significantly lower plasma glucose levels and higher percentage of docosahexaenoic acid and total percentages of LCPUFAs in their skeletal muscle biopsies compared with formula fed. LCPUFAs suppress the production of pro-inflammatory cytokines, regulate the function of several neurotransmitters, enhance the number of insulin receptors in the brain and other tissues, and decrease insulin resistance. LCPUFAs may enhance the production of bone morphogenetic proteins (BMPs), which participate in neurogenesis. It is proposed that the beneficial effects of breast feeding in later life can be attributed to its rich LCPUFA content. It is likely that inadequate breast feeding results in marginal deficiency of LCPUFAs during the critical stages of development, which can lead to insulin resistance. Hence, promoting prolonged breast feeding and/or supplementing LCPUFAs during the critical stages of development may be beneficial in preventing insulin resistance.

Shedding of TNF-alpha receptors, blood pressure, and insulin sensitivity in type 2 diabetes mellitus

Tumor necrosis factor-alpha (TNF-alpha) is increasingly recognized as a key component in the development of insulin resistance and increased blood pressure. In a sample of 368 individuals, the ratio of soluble TNF-alpha receptors (sTNFR2/sTNFR1) correlated positively with systolic and diastolic blood pressure (P < 0.01). This ratio was significantly greater in type 2 diabetic subjects (DM-2) than in type 1 diabetic patients and was greater than in control nondiabetic subjects (P < 0.00001). The TNF-alpha receptor 1 (TNFR1) density in peripheral blood monocytes was similar in DM-2 patients and in nondiabetic subjects. After phorbol 12-myristate 13-acetate, TNFR1 shedding was significantly decreased in DM-2 compared with control subjects, and it was directly associated with insulin sensitivity (r = 0.54, P = 0.03). Serum sTNFR1 concentration was also linked to the vasodilatory response to glyceryltrinitrate (P = 0.01). Conversely, TNF-alpha receptor 2 shedding was negatively associated with insulin sensitivity (r = -0.54, P = 0.03), whereas shedding of L-selectin showed no significant association. After exercise-induced lowering of blood pressure, a parallel decrease in sTNFR2/sTNFR1 was observed in DM-2 patients. Our findings suggest that insulin resistance and blood pressure are linked to altered shedding of TNF-alpha receptors in DM-2. The latter seems reversible and is not genetically determined.

Left ventricular hypertrophy in hypertension as a predictor of coronary events: relation to geometry

The present review examines epidemiological evidence for a relation of left ventricular hypertrophy with coronary heart disease, and mechanisms that may represent pathophysiological links between left ventricular hypertrophy and coronary events. Left ventricular hypertrophy has been demonstrated to be a powerful predictor of coronary heart disease, and when geometry is concentric the relation is even stronger. In addition to its association with risk factors for atherosclerosis and mechanisms that precipitate acute heart attacks, left ventricular hypertrophy also directly predisposes to and aggravates clinical presentation of coronary heart disease through a number of biological mechanisms. These include the following: increase in oxygen requirement related to left ventricular geometry; coronary hypertension, with endothelial dysfunction and reduced coronary reserve; diastolic dysfunction; and structural remodelling of myocardium and vascular bed. Some of these alterations are also worsened by underlying coronary heart disease, and can potentially be maintained by loop mechanisms. A recognizable stage of abnormal coronary haemodynamics in the context of left ventricular hypertrophy is probably that at which coronary reserve is impaired in the absence of any other sign of heart disease; in many circumstances, this may occur early in the disease process.

Insulin resistance and endothelial dysfunction in atherosclerosis: implications and interventions

Current research suggests that insulin resistance is associated with endothelial dysfunction, which is considered an early but significant step in the pathogenesis of atherosclerosis. Both insulin resistance and endothelial dysfunction appear to precede the development of overt hyperglycemia in patients with type 2 diabetes. Therefore, in patients with diabetes or insulin resistance, endothelial dysfunction may be a critical early target for preventing atherosclerosis and cardiovascular disease. Insulin-sensitizing agents--specifically, thiazolidinediones (TZDs)--may be useful for preventing or mitigating endothelial dysfunction. In vitro and clinical data show that TZDs can limit thrombotic, inflammatory, and oxidative changes that contribute to endothelial dysfunction. For example, TZDs have been shown to lower blood levels of plasminogen activator inhibitor-1, a prothrombotic substance, in patients with diabetes or insulin resistance. In obese patients, TZD treatment can improve vascular reactivity and reduce monocyte expression of nuclear factor kappa-B, a transcription factor that contributes to inflammation and oxidative damage. In patients with overt diabetes or insulin resistance, TZD treatment can lower blood levels of C-reactive protein and interleukin-6, markers of inflammation and cardiovascular risk. These beneficial effects of TZDs may help to decrease the risk of vascular damage and atherosclerosis in patients with insulin resistance or diabetes.

Hypercholesterolemia impairs myocardial perfusion and permeability: role of oxidative stress and endogenous scavenging activity

OBJECTIVES

We intended to study the effect of hypercholesterolemia (HC) on myocardial perfusion and permeability response to increased cardiac demand.

BACKGROUND

Hypercholesterolemia is associated with increased incidence of cardiac events and characterized by impaired coronary vascular function, possibly mediated partly through increased pro-oxidative conditions in plasma and tissue. However, it is yet unclear whether HC is also associated with impaired myocardial perfusion and vascular permeability responses in vivo.

METHODS

For 12 weeks pigs were fed a normal, HC or HC diet supplemented daily with antioxidants (HC + AO, 100 IU/kg vitamin E and 1 g vitamin C). Myocardial perfusion and vascular permeability were measured in vivo using electron beam computed tomography before and after cardiac challenge with intravenous adenosine. Plasma and tissue oxidative status was determined ex vivo.

RESULTS

Plasma cholesterol increased in all cholesterol-fed pigs but was associated with increased markers of oxidative stress only in HC pigs. Myocardial perfusion increased in response to adenosine in normal and HC + AO (+37 +/- 13% and +58 +/- 22%, respectively, p < 0.05 vs. baseline) but not in HC, whereas vascular permeability index increased only in HC pigs (+ 92 +/- 25%, p = 0.002). In HC animals, tissue endogenous oxygen radical scavengers and antioxidant vitamins were depleted and LDL oxidizability enhanced, but both were normalized in HC + AO pigs. Myocardial perfusion response was directly, and permeability inversely, associated with plasma and tissue vitamin concentrations.

CONCLUSIONS

This study demonstrates that experimental HC is associated with blunted myocardial perfusion and increased vascular permeability responses in vivo to increased cardiac demand, which may be partly mediated by a shift in oxidative status.

Endothelial activation in patients with cardiac syndrome X

BACKGROUND

The presence of endothelial dysfunction with increased endothelin-1 plasma concentrations in patients with cardiac syndrome X is still under debate. The aim of the present study was to evaluate the presence of endothelial dysfunction in patients with cardiac syndrome X.

METHODS AND RESULTS

++Endothelin-1 levels were evaluated with a sensitive radioimmunoassay with previous purification through reverse phase HPLC in 24 patients (3 men and 21 women, mean age 54+/-7 years) with typical angina, instrumental evidence of ischemia, and normal coronary angiograms both under baseline conditions and after oral glucose load (75 g D-glucose). We also measured plasma nitrite-plus-nitrate levels, a sharp index of endothelial nitric oxide production, and circulating concentrations of the soluble fraction of the endothelial adhesion molecule vascular cell adhesion molecule-1, a well-recognized marker of early endothelial dysfunction. Fourteen healthy subjects (1 man and 13 women, mean age 47+/-15 years) served as controls. There were no significant differences in baseline plasma endothelin-1 concentrations between patients and control subjects (0.55+/-0.34 versus 0.48+/-0.22 pg/mL, P=0.503). Plasma nitrite-plus-nitrate and soluble vascular cell adhesion molecule-1 concentrations were also similar between the 2 groups. After glucose ingestion, circulating endothelin-1 concentrations were significantly higher in patients with cardiac syndrome X than in control subjects (P<0.03 at 60, 90, and 120 minutes).

CONCLUSIONS

Our findings show that no basal endothelial damage is present in patients with cardiac syndrome X. Nevertheless, increased responsiveness of endothelin-1 to glucose loading suggests that patients with cardiac syndrome X present an increased susceptibility to releasing endothelin-1 under stressful circumstances.

Influence of vessel size, age and body mass index on the flow-mediated dilatation (FMD%) of the brachial artery

BACKGROUND

The non-invasive determination of the endothelial dysfunction (ED) of the brachial artery is a widely used method in clinical research. It remained, however, unclear, whether the test-results are influenced by the anatomical vessel size, the patients age, body mass index (BMI) or gender.

METHODS

The flow-mediated vasodilatation (FMD%) of the brachial artery was determined in 122 consecutive (88 male, 34 female) patients. FMD% was measured using high resolution ultrasound (13 Mhz) at rest, during reactive hyperaemia and after the sublingual administration of glycerolnitrate (GTN%).

RESULTS

Lumen diameters at rest varied from 2.48 mm to 6.33 mm (4.46+/-0.74 mm). The extent of FMD% as well as of GTN% showed an inverse correlation to the resting lumen diameters (r=-0.33, P<0.001/r=-0.51, P<0.001). This correlation was even more distinct in females (females: FMD% r=-0.54, P<0.001; GTN% r=-0.64, P<0.001 vs. males: FMD% -0.23, P<0.001; GTN% -0.59, P<0. 001). No significant influence of age (61+/-9 years, FMD%: r=-0.04, P=0.68, GTN%: r=-0.18, P=0.05) and BMI (27.03+/-3.43 kg/m(2), FMD%: r=0.16, P=0.08, GTN%: r=0.09, P=0.3) on the test results were found.

CONCLUSIONS

FMD% was found to be rather independent of age or BMI. The anatomical vessel size had an influence on the test results, which was more obvious in female patients. Our data indicate the necessity of further methodological studies, in larger, community-based populations. In particular, it needs to be clarified, whether vessel size or even gender-specific correction factors are required when using this technique in routine clinical practice.