Prognostic significance of coronary collaterals in patients with coronary heart disease having percutaneous transluminal coronary angioplasty

We examined the presence and extent of coronary collaterals as a prognostic determinant of cardiovascular outcome in a prospective case-cohort study of 655 patients admitted for elective coronary angioplasty. In patients with ischemic heart disease, the angiographic presence of coronary collaterals may mark an unfavorable prognosis, particularly in relatively high-risk patients.

[The polypill: not an effective strategy for reduction of cardiovascular disease]

The implementation of the intriguing concept of the polypill to prevent cardiovascular events remains doubtful due to a lack of evidence, expected adherence problems, the inevitable overtreatment and undertreatment of individuals, and potential side effects. Lifestyle changes and individual interventions are more preferable strategies.

Presence of the metabolic syndrome does not impair coronary collateral vessel formation in patients with documented coronary artery disease

OBJECTIVE

The metabolic syndrome confers an increased risk for cardiovascular morbidity and mortality. The presence of coronary collaterals may have beneficial effects during myocardial ischemia and may improve cardiovascular outcome in patients with coronary artery disease. Impaired collateral formation could be one of the reasons for the increased cardiovascular risk in patients with the metabolic syndrome. The aim of the present study was to determine the influence of the metabolic syndrome and insulin resistance on the presence of coronary collaterals.

RESEARCH DESIGNS AND METHODS

We conducted a cross-sectional study in 227 patients referred for elective percutaneous transluminal coronary angioplasty to the University Medical Centre Utrecht. The metabolic syndrome was diagnosed according to Adult Treatment Panel III, and homeostasis model assessment of insulin resistance (HOMA-IR) and quantitative insulin sensitivity check index (QUICKI) were used to quantify insulin resistance. Coronary collaterals were graded with Rentrop's classification. Rentrop grade >/=1 indicated the presence of collaterals. Results were adjusted for age, sex, and severity of coronary artery disease.

RESULTS

A total of 103 patients (45%) were diagnosed with the metabolic syndrome. There was no association between the metabolic syndrome and the presence of coronary collateral formation (odds ratio [OR] 1.2 [95% CI 0.7-2.0]). Also, the degree of insulin resistance was not related to the presence of coronary collaterals. The OR for HOMA-IR (highest versus lowest tertile) was 0.7 (0.3-1.5) and for QUICKI (lowest versus highest tertile) 0.8 (0.4-1.6).

CONCLUSIONS

The metabolic syndrome and insulin resistance are not related to the presence of coronary collaterals in patients with documented coronary artery disease.

Progenitor cells in the kidney: Biology and therapeutic perspectives

The stem cell may be viewed as an engineer who can read the blue print and become the building. The role of this fascinating cell in physiology and pathophysiology has recently attracted a great deal of interest. The archetype of stem cells is the zygote: one cell capable of endless proliferation and differentiation into all tissue types in the human body. Historically, the differentiation of embryonic stem cells is seen as an irreversible process with restricting possibilities for differentiation leading finally to a terminally differentiated cell type. Stem cells have also been described in the adult. They were first defined in tissues with a high cell turnover like skin and gut. Today, stem cells have also been shown in tissues with no or low regenerative potential and turnover, like the kidney. Traditionally, adult stem cells were thought to be restricted in their differentiative and regenerative potential to the tissues in which they reside. However, the stem cell concept is changing rapidly as evidence is mounting that adult stem cells not only reside locally in specific niches, but may also be recruited from the circulation to actively participate in the regeneration of various tissues. Furthermore, reverse differentiation has been demonstrated. This means that highly specialized cell types are able to dedifferentiate and engage in stem cell like activities. Moreover, transdifferentiation of mature cells into different cell types has been reported. This paper will review our current knowledge on renal stem cells and progenitor cells. Specifically, it will discuss the role of progenitor cells and transdifferentiation in renal repair and maintenance. Finally, the potential clinical implications of these findings will be discussed.

[Pleiotropic effects of statins]

Statins safely and effectively reduce the morbidity and mortality due to cardiovascular disease. In the trials conducted so far, which have been carried out predominantly on high-risk patients, the observed risk reduction is probably completely attributable to the reduction of the cholesterol level. However, statins also influence the atherosclerotic disease process in a lipid-independent way. This includes beneficial effects on the early pathogenetic components of atherosclerosis, such as endothelial dysfunction and inflammation. These effects are probably not visible in the large clinical trials that usually follow up cohorts of patients with late stages of atherosclerosis during a relatively short period of time. These cholesterol-independent effects do affect intermediate factors in the atherosclerotic process, such as endothelial dysfunction. In clinical practice, where not only short-term effects in patients with manifest vascular disease but also the prevention of the long-term complications of atherosclerosis in high-risk patients is an important goal, these so-called pleiotropic effects may contribute to risk reduction.

Endothelial progenitor cell dysfunction: a novel concept in the pathogenesis of vascular complications of type 1 diabetes

Type 1 diabetes is associated with reduced vascular repair, as indicated by impaired wound healing and reduced collateral formation in ischemia. Recently, endothelial progenitor cells (EPCs) have been identified as important regulators of these processes. We therefore explored the concept that EPCs are dysfunctional in diabetes. The number of EPCs obtained from type 1 diabetic patients in culture was 44% lower compared with age- and sex-matched control subjects (P < 0.001). This reduction was inversely related to levels of HbA(1c) (R = -0.68, P = 0.01). In addition, we demonstrated that patient EPCs were also impaired in function using an in vitro angiogenesis assay. Conditioned media from patient EPCs were significantly reduced in their capacity to support endothelial tube formation in comparison to control EPCs. Therefore, despite culturing the EPCs under normoglycemic conditions, functional differences between patient and control EPCs were maintained. Our findings demonstrate that adverse metabolic stress factors in type 1 diabetes are associated with reduced EPC numbers and angiogenicity. We hypothesize that EPC dysfunction contributes to the pathogenesis of vascular complications in type 1 diabetes.

Bone-marrow-derived cells contribute to glomerular endothelial repair in experimental glomerulonephritis

Glomerular endothelial injury plays an important role in the pathogenesis of renal diseases and is centrally involved in renal disease progression. Glomerular endothelial repair may help maintain renal function. We examined whether bone-marrow (BM)-derived cells contribute to glomerular repair. A rat allogenic BM transplant model was used to allow tracing of BM-derived cells using a donor major histocompatibility complex class-I specific mAb. In glomeruli of chimeric rats we identified a small number of donor-BM-derived endothelial and mesangial cells, which increased in a time-dependent manner. Induction of anti-Thy-1.1-glomerulonephritis (transient mesangial and secondary glomerular endothelial injury) caused a significant, more than fourfold increase in the number of BM-derived glomerular endothelial cells at day 7 after anti-Thy-1.1 injection compared to chimeric rats without glomerular injury. The level of BM-derived endothelial cells remained high at day 28. We also observed a more than sevenfold increase in the number of BM-derived mesangial cells at day 28. BM-derived endothelial and mesangial cells were fully integrated in the glomerular structure. Our data show that BM-derived cells participate in glomerular endothelial and mesangial cell turnover and contribute to microvascular repair. These findings provide novel insights into the pathogenesis of renal disease and suggest a potential role for stem cell therapy.

Impaired NO-dependent vasodilation in patients with Type II (non-insulin-dependent) diabetes mellitus is restored by acute administration of folate

AIMS/HYPOTHESIS

Patients with diabetes are characterised by endothelial dysfunction and cardiovascular mortality. In particular endothelium-derived nitric oxide has emerged as a first line mechanism against atherosclerosis. Hyperglycaemia causes oxygen radical stress but has also been associated with endothelial nitric oxide synthase uncoupling, both lead to decreased nitric oxide-availability. We recently showed that folate reverses eNOS uncoupling in vitro. Therefore we hypothesise that folate improves endothelial function in Type II (non-insulin-dependent) diabetes mellitus in vivo.

METHODS

Using forearm plethysmography, we evaluated the effect of local, intra-arterial administration of 5-methyltetrahydrofolate (5-MTHF, the active form of folic acid, 1 microg/100 ml FAV/min) on forearm blood flow in 23 patients with Type II diabetes and 21 control subjects, matched for age, sex, blood pressure, body mass index, weight and smoking habits. Serotonin as a stimulator of nitric oxide-dependent vasodilation and sodium nitroprusside as a stimulator of endothelium-independent vasodilation were infused.

RESULTS

Serotonin-induced vasodilation was blunted (53+/-30 vs 102+/-66 M/C%, p<0.005) and nitroprusside-induced vasodilation was mildly reduced (275+/-146 vs 391+/-203 M/C%, p<0.05) in patients with Type II diabetes compared to control subjects. 5-MTHF improved nitric oxide-mediated vasodilation (from 53+/-30 to 88+/-59 M/C%, p<0.05) in patients with Type II diabetes mellitus. As expected, 5-MTHF had no effect on forearm blood flow in control subjects.

CONCLUSION/INTERPRETATION

These data imply that folate can be used to improve nitric oxide status and to restore endothelial dysfunction in patients with Type II diabetes. Our results provide a strong rationale for the initiation of studies that investigate whether supplementation with folic acid prevents future cardiovascular events in this patient group.

Folates and cardiovascular disease

It is increasingly recognized that folates may play a role in the prevention of cardiovascular disease. Over the last few years, several studies have reported beneficial effects of folates on endothelial function, a surrogate end point for cardiovascular risk. Consistently, observational studies have demonstrated an association between folate levels and cardiovascular morbidity and mortality. The exact mechanisms underlying the ameliorative effects of folates on the endothelium remain to be elucidated. Thus far, most studies have focused on the homocysteine-lowering effects of folates. However, recently, benefits of folates independent of homocysteine lowering have also been reported. Potential mechanisms include antioxidant actions, effects on cofactor availability, or direct interactions with the enzyme endothelial NO synthase. Obviously, beneficial effects of folates on cardiovascular risk would have important clinical and dietary consequences. However, for definite conclusions, the completion of ongoing randomized controlled trials will have to be awaited.

The endothelium: a gynecological and obstetric point of view

The endothelium, long considered merely an inert, semipermeable membrane between blood and the vessel wall, is now viewed as an important, large and highly active endocrine organ which is responsible for a number of vital physiological functions. In this editorial we will discuss the important role of the endothelium and endothelial (dys)function in health and disease, with particular focus on postmenopausal cardiovascular disease and preeclampsia.

Pharmacokinetics and pharmacodynamic effects of ABT-627, an oral ETA selective endothelin antagonist, in humans

AIMS

Endothelins (ETs) may play a role in the pathogenesis of a variety of cardiovascular diseases. The present study was designed to investigate the pharmacokinetic and pharmacodynamic effects of the orally active ETA selective receptor antagonist ABT-627 in healthy humans.

METHODS

Healthy volunteers were included in two studies with cross-over design. Subjects received single or multiple dose (an 8 day period) administration of oralABT-627 or matched placebo, in a dose range of 0.2-40 mg. The pharmacokinetics of ABT-627 were described and its effects on systemic haemodynamics under resting conditions and on forearm vasoconstriction in response to ET-1 were assessed.

RESULTS

ABT-627 was generally well tolerated in both studies, with transient headache being the most reported adverse event (in 62% vs 4% during placebo, P < 0.05, for Study 1 and in 42% vs 60%, P = 0.2, for Study 2). ABT-627 was rapidly absorbed, reaching maximum plasma levels at approximately 1 h post dose. Single dose ABT-627, at a dose of 20 and 40 mg, inhibited ET-1 induced forearm vasoconstriction at 8 h post dose. Eight days ABT-627 treatment, at a dose level of 5 mg and above, also effectively blocked forearm vasoconstriction to ET-1. ABT-627 caused a significant reduction in peripheral resistance as compared with placebo (16 +/- 1 vs 19 +/- 1, 18 +/- 2 vs 23 +/- 3, 15 +/- 1 vs 17 +/- 1 AU at 1, 5, 20 mg in Study 2) with only a mild decrease in blood pressure (79 +/- 2 vs 84 +/- 3, 80 +/- 4 vs 90 +/- 5, 75 +/- 3 vs 79 +/- 1 at 1, 5, 20 mg in Study 2). ABT-627 caused a moderate dose-dependent increase in circulating immunoreactive ET levels (a maximal increase of 50% over baseline at the 20 mg dose level).

CONCLUSIONS

The oral ETA receptor blocker ABT-627 is well tolerated, rapidly absorbed, effectively blocks ET-1 induced vasoconstriction and causes a decrease in total peripheral resistance and mean arterial pressure. Our data suggest that ABT-627 may be a valuable tool in treatment of cardiovascular disease.

Effects of oral folic acid supplementation on endothelial function in familial hypercholesterolemia. A randomized placebo-controlled trial

BACKGROUND

Folates have been suggested to be of benefit in reducing cardiovascular risk. The present study was designed to examine whether oral folic acid supplementation could improve endothelial function as an intermediate end point for cardiovascular risk in patients with increased risk of atherosclerosis due to familial hypercholesterolemia (FH).

METHODS AND RESULTS

In a prospective, randomized, double-blind, placebo-controlled study with crossover design, we evaluated the effects of 4 weeks of treatment with oral folic acid (5 mg PO) on endothelial function in FH. In 20 FH patients, forearm vascular function was assessed at baseline, after 4 weeks of folic acid treatment, and after 4 weeks of placebo treatment by venous occlusion plethysmography, with serotonin and sodium nitroprusside used as endothelium-dependent and -independent vasodilators. In addition, we examined the vasoconstrictor response to the NO synthase inhibitor N(G)-monomethyl-L-arginine to assess basal NO activity. In FH patients, folic acid supplementation restored the impaired endothelium-dependent vasodilation, whereas it did not significantly influence endothelium-independent vasodilation or basal forearm vasomotion. There was a trend toward improvement in basal NO activity.

CONCLUSIONS

These data demonstrate that oral supplementation of folic acid can improve endothelial function in patients with increased risk of atherosclerotic disease due to hypercholesterolemia, without changes in plasma lipids.

Nifedipine improves endothelial function in hypercholesterolemia, independently of an effect on blood pressure or plasma lipids

OBJECTIVE

Dihydropyridine calcium antagonists have been shown to retard atherogenesis in animal models and to prevent the development of early angiographic lesions in human coronary arteries. Endothelial dysfunction is an early event in the pathogenesis of cardiovascular disease. We investigated whether nifedipine could improve endothelial function in hypercholesterolemia, independently of changes in blood pressure or plasma lipids.

METHODS

First, we compared in vivo forearm vascular responses to the endothelium-dependent and independent vasodilators serotonin (5-HT) and sodium nitroprusside (SNP) in 11 patients with familial hypercholesterolemia before and after 6-weeks treatment with nifedipine GITS (60 mg, OD) and in 12 matched controls. In a subgroup of six control subjects forearm vascular function was also assessed before and after 6-weeks nifedipine GITS treatment. In vitro, we subsequently explored possible mechanisms underlying the effect of nifedipine on endothelial function. We investigated the effects of nifedipine on both NO production by recombinant endothelial NO synthase (eNOS) and endothelial cells, using 3H-arginine conversion, as well as on superoxide generation by endothelial cell lysates, using lucigenin enhanced chemiluminescence.

RESULTS

In hypercholesterolemia 5-HT-induced vasodilation was impaired (47 +/- 9% increase in forearm bloodflow vs. 99 +/- 8% in controls). Treatment with nifedipine completely restored 5-HT-induced vasodilation (113 +/- 13%), whereas it did not influence basal forearm vasomotion or SNP-induced vasodilation. Nifedipine did not alter forearm vascular responses in control subjects and did not alter blood pressure or plasma lipids. In vitro, we found no direct effect of nifedipine on NO production by recombinant eNOS or endothelial cells. However, we did observe a reduction in endothelial superoxide generation.

CONCLUSIONS

Our data show that nifedipine improves endothelial function in hypercholesterolemia. It is suggested from our in vitro experiments that this effect is due to reduced NO degradation.

Endothelial function: strategies for early intervention

Assessment of endothelial function appears to be a valuable additional tool for diagnosing and therapeutic monitoring of coronary artery disease. The first part of this review discusses the biosynthesis, degradation, and antiatherosclerotic properties of nitric oxide, a major determinant of endothelial function. In the second part methods for assessing endothelial function and strategies for reversal of endothelial dysfunction are reviewed. Improvement of endothelial function may be obtained by lifestyle modifications, such as cessation of smoking, better blood glucose regulation, exercise, dietary measures, and pharmacological interventions, such as lipid lowering, antioxidant therapy, angiotensin-converting enzyme inhibition, and calcium channel blockers.

Endothelin-A receptor antagonist-mediated vasodilatation is attenuated by inhibition of nitric oxide synthesis and by endothelin-B receptor blockade

BACKGROUND

The role of endothelin (ET)-1 in maintenance of basal vascular tone has been demonstrated by local and systemic vasodilatation to endothelin receptor antagonists in humans. Although the constrictor effects mediated by the vascular smooth muscle ET(A) receptors are clear, the contribution from endothelial and vascular smooth muscle ET(B) receptors remains to be defined. The present study, in human forearm resistance vessels in vivo, was designed to further investigate the physiological function of ET(A) and ET(B) receptor subtypes in human blood vessels and determine the mechanism underlying the vasodilatation to the ET(A)-selective receptor antagonist BQ-123.

METHODS AND RESULTS

Two studies were performed, each in groups of eight healthy subjects. Brachial artery infusion of BQ-123 caused significant forearm vasodilatation in both studies. This vasodilatation was reduced by 95% (P=.006) with inhibition of the endogenous generation of nitric oxide and by 38% (P<.001) with coinfusion of the ET(B) receptor antagonist BQ-788. In contrast, inhibition of prostanoid generation did not affect the response to BQ-123. Infusion of BQ-788 alone produced a 20% reduction in forearm blood flow (P<.001).

CONCLUSIONS

Selective ET(A) receptor antagonism causes vasodilatation of human forearm resistance vessels in vivo. This response appears to result in major part from an increase in nitric oxide generation. ET(B) receptor antagonism either alone or on a background of ET(A) antagonism causes local vasoconstriction, indicating that ET(B) receptors in blood vessels respond to ET-1 predominantly by causing vasodilatation.

5-methyltetrahydrofolate, the active form of folic acid, restores endothelial function in familial hypercholesterolemia

BACKGROUND

Impaired nitric oxide (NO) activity is an early event in the pathogenesis of cardiovascular disease, resulting from either reduced NO formation or increased NO degradation. Administration of tetrahydrobiopterin (BH4), an essential cofactor for NO production, could restore NO activity in familial hypercholesterolemia (FH). Because folates have been suggested to stimulate endogenous BH4 regeneration, we hypothesized that administration of 5-methyltetrahydrofolate (5-MTHF, the active circulating form of folate) might improve NO formation in FH.

METHODS AND RESULTS

We studied the effects of 5-MTHF on NO bioavailability in vivo in 10 patients with FH and 10 matched control subjects by venous occlusion plethysmography, using serotonin and nitroprusside as endothelium-dependent and -independent vasodilators. In vitro, we investigated the effect of 5-MTHF on NO production by recombinant endothelial NO synthase (eNOS) by use of [3H]arginine to [3H]citrulline conversion. We also studied the effects of 5-MTHF on superoxide generation by eNOS and xanthine oxidase (XO) by use of lucigenin chemiluminescence. The impaired endothelium-dependent vasodilation in FH (63% versus 90% in control subjects) could be reversed by coinfusion of 5-MTHF (117% vasodilation), whereas 5-MTHF had no significant effect on endothelium-dependent vasodilation in control subjects. 5-MTHF did not influence basal forearm vasomotion or endothelium-independent vasodilation. 5-MTHF had no direct effect on in vitro NO production by eNOS. However, we did observe a dose-dependent reduction in both eNOS- and XO-induced superoxide generation.

CONCLUSIONS

These results show that the active form of folic acid restores in vivo endothelial function in FH. It is suggested from our in vitro experiments that this effect is due to reduced catabolism of NO.

Progressive vascular damage in hypertension is associated with increased levels of circulating P-selectin

OBJECTIVE

To assess whether increased shedding of adhesion molecules in plasma provides an index for endothelial damage in hypertension.

DESIGN AND METHODS

Three groups of hypertensive patients with increasing severity of vascular damage were studied: 20 essential hypertensives, 21 atherosclerotic, renovascular hypertensives and four malignant hypertensives. Twenty healthy subjects were included as a control group. Levels of P-selectin, E-selectin, intracellular adhesion molecule 1, vascular cell adhesion molecule and von Willebrand factor in venous blood were measured, using sandwich-type enzyme-linked immunosorbent assay.

RESULTS

For essential hypertensives a trend for increased P-selectin and E-selectin values compared with those in controls was observed (159+/-44 versus 132+/-40 ng/ml, P = 0.062 and 40+/-13 versus 34+/-17 ng/ml, P = 0.055, respectively). P-selectin (210+/-84 ng/ml, P = 0.0021) and E-selectin (42+/-12 ng/ml, P = 0.012) levels in renovascular hypertensives were significantly higher than those in healthy controls. There were no significant increases in circulating levels of intracellular adhesion molecule 1, vascular cell adhesion molecule and von Willebrand factor either in essential hypertensives or in renovascular hypertensives. Marked increases in circulating levels of adhesion molecules and von Willebrand factor relative to those in controls were observed in malignant hypertensives (P-selectin 634+/-332 versus 132+/-40 ng/ml, P = 0.0004; vascular cell adhesion molecule 968+/-187 versus 493+/-139 ng/ml, P = 0.0004; and von Willebrand factor 259+/-75 versus 130+/-72 U/dl, P = 0.016).

CONCLUSIONS

Progression of vascular damage in essential, renovascular and malignant hypertension is associated with a rise in circulating levels of P-selectins and, to a lesser extent, E-selectins, whereas levels of intracellular adhesion molecule 1, vascular cell adhesion molecule and von Willebrand factor are elevated only in diseases associated with acute severe vascular damage, including malignant hypertension. Our data suggest that selectins may be useful as indicators of vascular damage in hypertension.