Effects of low-dose heparin infusion on arterial endothelin-1 release in humans

Progressive hyperglycemia across the glucose tolerance continuum in older obese adults is related to skeletal muscle capillarization and nitric oxide bioavailability

CONTEXT

Reduced tissue nutrient exposure may aid in the progression of glucose intolerance.

OBJECTIVE

The aim of the study was to examine peripheral tissue glucose disposal in relation to muscle capillarization and plasma nitric oxide bioavailability.

DESIGN

Participants were carefully matched for age, adiposity, and lipid status and stratified into normal (n = 20), impaired (n = 20), and type 2 diabetic (n = 20) glucose-tolerant groups.

SETTING

The study was conducted in an outpatient setting at a Clinical Research Unit.

PARTICIPANTS

Older, obese men and women (n = 60; age, 65 ± 1 yr; body mass index, 32.7 ± 0.5 kg/m(2)) participated in the study.

INTERVENTION

We performed a cross-sectional study.

MAIN OUTCOME MEASURES

Body composition, energy metabolism, aerobic fitness (maximum oxygen consumption), insulin sensitivity (glucose clamp), vastus lateralis muscle morphology, and plasma nitric oxide were assessed.

RESULTS

Although subjects were identical with respect to age, body composition, energy expenditure, and lipid status, insulin-stimulated glucose disposal and maximum oxygen consumption showed progressive decline with increasing glucose intolerance. Muscle fiber type composition and mitochondrial density were not different between groups. However, capillary density markedly declined with advancing glucose intolerance (1.86 ± 0.31, 1.70 ± 0.28, 1.42 ± 0.24 capillary/fiber; P < 0.05), a trend that was mirrored by fasting plasma nitric oxide concentrations (26.3 ± 3.6, 19.8 ± 2.3, 15.2 ± 2.1 μmol/liter; P < 0.05). Furthermore, skeletal muscle capillary density correlated with insulin sensitivity (r = 0.65; P < 0.001).

CONCLUSIONS

Impaired muscle capillarization and reduced nutrient exposure to the metabolizing tissue may play a major role in the progression of insulin resistance across the glucose tolerance continuum, independent of age, adiposity, lipid status, and resting energy metabolism. These data also highlight plasma nitric oxide as a potential surrogate marker of these impairments and may be indicative of the progression toward type 2 diabetes.

The impact of heparin compounds on cellular inflammatory responses: a construct for future investigation and pharmaceutical development

Atherosclerotic disease is recognized as a chronic inflammatory disorder with intermittent and widely variable phases of cellular proliferation and heightened thrombotic activity. The multi-tiered links between inflammation, atherogenesis and thrombogenesis provide a unique opportunity for research and development of pharmaceuticals which target one or more critical pathobiologic steps (Fig. 1). The purpose of the following review on heparin compounds is to comprehensively examine the multi-cellular, pleuripotential effects of a commonly used anticoagulant drug in the context of normal and disease-altered vascular responses and illustrate possible constructs for avenues of subsequent investigation in the field of atherothrombosis. The overview is divided into five integrated parts; antiinflammatory properties of the normal vessel wall, the relationship between glycosaminoglycans and inflammation, heparin-mediated effects on cellular inflammatory responses, association between molecular weight and antiinflammatory capabilities, and oral heparin compounds for achieving prolonged cell-based inhibition.

Modulation and roles of the endothelins in the pathophysiology of pulmonary embolism

Recent research on the endothelins (ETs) and their pathways in acute pulmonary embolism (APE) has led to significant advances in the understanding of this disease. ETs are potent vasoconstrictors and bronchoconstrictors found abundantly in the lung and can be released by stimuli such as endothelial injury, hypoxia, or thrombin, a key product in the coagulation cascade. Many studies using different approaches and methods of inducing pulmonary embolization, both in vitro and in vivo in various species, have mostly shown that ETs play an important role in the pathophysiology of APE. These results were obtained by comparing the hemodynamic data in the presence or absence of various ETs inhibitors, but also by assessing the modulation of the ET-related elements of this system by molecular, cell biology, and pharmacological methods. Based on the current understanding, a mechanism involving the ET pathway in the pathophysiology of APE is proposed for the reader's considerations. We postulate that ETs are primary mediators in APE based on the following: (i) their source from pulmonary endothelial cells where the primary injury takes place; (ii) their direct vasconstrictive, bronchoconstrictive, and promitogenic effects via distinct ET receptors; and (iii) their indirect effects associated with the secondary release of thromboxane and other mediators, which are released from inflammatory cells and platelets, which together can potentiate the overall hemodynamic response, most specifically the pulmonary vascular bed. Such combined effects of ETs on bronchomotor and vasomotor tone in the lung can adversely affect ventilation perfusion matching and lead to severe hypoxemia without causing significant changes in the chest X-ray of these patients. Thus, we may consider ET inhibitors as future current therapeutic agents in patients with PE.

Evaluation of unfractionated heparin and recombinant hirudin on survival in a sustained ovine endotoxin shock model

OBJECTIVE

To compare and evaluate the potential benefit of two different anticoagulation regimens during endotoxemia in an ovine model.

DESIGN

Animal prospective randomized and controlled study following preliminary dose-range study conforming with the Guide for the Care and Use of Laboratory Animals as promulgated by the Council of the American Physiologic Society and reviewed by the Ethical Committee for Animal Research of our institution.

SETTING

Laboratories of anesthesiological investigations and hemostasis, primary care university medical center.

SUBJECTS

Twenty-two adult sheep of either sex, weighing 29-42 kg (mean 35.8 kg), surgically instrumented for chronic studies and randomly allocated to receive three different treatment groups: unfractionated heparin (40 units.kg.hr; n = 7), recombinant hirudin (500 units.kg.hr; n = 7), or saline (nonanticoagulated controls; n = 8).

INTERVENTIONS

Ovine model of severe endotoxin shock induced by a continuous intravenous endotoxin infusion over 72 hrs (10 ng.kg.min ).

MEASUREMENTS AND MAIN RESULTS

Endotoxin infusion alone produced a progressive hypotensive, hyperdynamic shock state with right ventricle failure leading to the death of all animals of the control group within 44 hrs (median, 12 hrs). Heparin profoundly improved survival rate in this model, whereas effective anticoagulation with hirudin did not significantly increase the survival rate compared with controls. Animals in the control group died from disseminated intravascular coagulation, metabolic acidosis, and hemorrhagic pulmonary edema, whereas sheep treated with hirudin died from severe pulmonary edema (hypoxemia, increased alveoloarterial oxygen gradient associated with an increased wet/dry lung weight ratio) in the absence of disseminated intravascular coagulation.

CONCLUSIONS

We conclude that systemic anticoagulation with the thrombin inhibitor hirudin is without benefit in this sheep model of lethal endotoxemia, whereas anticoagulation with heparin affords not only effective prevention of endotoxin-induced coagulation disorders but also global protection with prevention of respiratory decompensation and thus markedly improves survival rate in this situation.

Oestrogen attenuates coronary vasoconstriction after angioplasty: role of endothelin-1

BACKGROUND AND AIMS

There were controversies as to whether endothelin-1 is released after coronary angioplasty. We sought to determine whether endothelin-1 is released after coronary angioplasty and whether oestrogen administration can affect coronary vasomotor tone by reducing endothelin-1 concentrations.

METHODS

The study was designed to prospectively investigate 24 consecutive patients scheduled for elective coronary angioplasty. Patients were randomized into two groups according to whether they did not (group 1, n = 12) or did (group 2, n = 12) have intracoronary treatment with oestrogen. Quantitative coronary angiography was monitored at baseline, immediately after successful angioplasty, and 15 min after the last deflation. Blood samples for measuring the levels of endothelin-1 were drawn from the ascending aorta and the coronary sinus simultaneously before angioplasty and 15 min after balloon dilatation.

RESULTS

The diameters of the coronary artery at the dilated segments were significantly reduced 15 min after dilation compared with those immediately after dilation in group 1 from 3.20 +/- 0.22 to 2.30 +/- 0.23 mm (P < 0.001), respectively. The vasoconstriction was significantly blunted in group 2. The endothelin-1 levels from the coronary sinus rose significantly, by 29%, 15 min after angioplasty in group 1, which was attenuated after administering oestrogen. Significant correlation was found between the changes of coronary vasomotion of the dilated segment and endothelin-1 levels (r = 0.70, P = 0.01).

CONCLUSION

Endothelin-1 is released into the coronary circulation after angioplasty, and this vasoactive substance may contribute to the occurrence of vasoconstriction. The vasoconstriction is attenuated by oestrogen by reducing the endothelin-1 levels. This finding provided a new strategy to treat coronary vasoconstriction after angioplasty.

Acute effects of heparin administration on the ischemic threshold of patients with coronary artery disease: evaluation of the protective role of the metabolic modulator trimetazidine

OBJECTIVES

We sought to assess the effects of heparin and the potential protective effects of trimetazidine (TMZ) on exercise performance, plasma nitric oxide (NO), endothelin-1 (ET-1) and free fatty acid (FFA) release in patients with stable coronary artery disease (CAD).

BACKGROUND

Heparin has been shown to reduce the ischemic threshold in patients with CAD. Trimetazidine may affect myocardial substrate utilization by shifting energy production from FFA to glucose oxidation.

METHODS

In four consecutive days, nine patients with CAD each received one of the following four regimens: 1) one tablet of placebo the evening before and at 8 AM and 4 PM on the day of the study, 10 ml of saline in a bolus 10 min before exercise, followed by an infusion of the same preparation; 2) placebo at the same times as in the first regimen, 5,000 IU of heparin 10 min before exercise, followed by 1,000 IU/h; 3) 20 mg TMZ at the same times as in the first regimen, 5,000 IU of heparin 10 min before exercise, followed by 1,000 IU/h; or 4) TMZ at the same times as in the first regimen, 10 ml of saline 10 min before exercise, followed by an infusion of the same preparation.

RESULTS

During placebo (test 2), heparin reduced the time to 1-mm ST-segment depression and prolonged the recovery time, as compared with the results of test 1. When heparin was administered after TMZ (test 3), the time to 1-mm ST-segment depression and the recovery time were similar to those recorded during saline (test 1). Finally, compared with all study phases, TMZ during saline (test 4) prolonged the time to 1 mm. No changes in NO release were found, whereas ET-1 was decreased at peak exercise and during recovery, when the patients were receiving TMZ (tests 3 and 4). Free fatty acids increased after heparin, both with placebo and TMZ.

CONCLUSIONS

In patients with CAD, heparin reduces the ischemic threshold. Trimetazidine reduces the effects of heparin, probably by inhibiting FFA oxidation and enhancing glucose metabolism. The concomitant novel observation of reduced ET-1 release is likely to be also dependent on TMZ-induced improvement of endothelial metabolism or reduction of myocardial ischemia.

Rationales for treating IgA nephropathies

An outline is given of the pathophysiology of IgA nephropathy (IgA) in order to emphasize the role of eicosanoids, angiotensin II, and reactive oxygen species. ACE inhibitors and early corticosteroid usage are prime therapies. Tonsillectomy is to be considered, certainly for individual cases. It is logical that other components of a cocktail could be (i) thromboxane antagonists, (ii) leukotriene antagonists, or (iii) PAF antagonist. In theory there should be benefit from antioxidants. Fish oils have not come up to expectation. PDGF aptamers look promising for the prevention of mesangial cell proliferation. Heparins are not used in the way that they could be. Various other agents could help reduce decline.

Heparin-induced vasodilation in human hand veins

OBJECTIVE

To investigate whether heparin produces vasodilation in human veins and to explore the underlying mechanisms.

METHODS

Eleven healthy volunteers were studied with the dorsal hand vein compliance technique. Dose-response curves to heparin and enoxaparin were generated. Dose-response curves to heparin were also constructed before and after heparin was infused with the nitric oxide synthase inhibitor N(G)-monomethyl-l-arginine (L-NMMA) or combined histamine H1- and H2-receptor blockade.

RESULTS

Heparin but not enoxaparin caused significant dose-dependent relaxation with an average apparent maximal response (at an infusion rate of 20 IU/min) of 47% +/- 23%. L-NMMA attenuated heparin-induced relaxation (P < .001). The combination of H1-and H2-receptor antagonists attenuated heparin-induced relaxation to a lesser extent (P < .05). Heparin-induced relaxation decreased by 52%, 73%, and 35% in the presence of L-NMMA, indomethacin (INN, indometacin) plus L-NMMA, and combined H1- and H2-receptor blockade, respectively.

CONCLUSION

Heparin is an endothelium-dependent venodilator in humans. The mechanism of heparin-induced relaxation involves an increased availability of nitric oxide, possibly partially related to local release of histamine.

Effects of acute euglycemic hyperinsulinemia on urinary nitrite/nitrate excretion and plasma endothelin-1 levels in men with essential hypertension and normotensive controls

Insulin stimulates the production of endothelin-1 (ET-1) and nitric oxide (NO) by isolated endothelial cells. Additionally, insulin-dependent glucose transport and insulin-mediated NO production partially share common elements in signal transduction. There are discordant data on plasma ET-1 levels during acute euglycemic systemic hyperinsulinemia in normotensive men and men with essential hypertension (EH) (known to be insulin-resistant), as well as on the relations between insulin sensitivity and vascular function. Our aim was to assess the response of approximate measures of whole-body generation of NO and ET-1 to acute euglycemic hyperinsulinemia in EH patients and controls. We studied 17 newly diagnosed untreated men with uncomplicated EH and 10 normotensive controls. Plasma ET-1 and urinary excretion of nitrite plus nitrate, stable NO metabolites (Uno(x)), were measured before and during a 3-hour hyperinsulinemic-euglycemic clamp. Both in hypertensives and normotensives, plasma ET-1 levels were reduced after 2 hours of the clamp (EH: baseline, 3.1+/-1.9 pg/mL; 2 hours, 1.9+/-1.2 pg/mL, P = .04 v baseline; controls: baseline, 4.2+/-2.6 pg/mL; 2 hours, 2.8+/-1.4 pg/mL, P = .04 v baseline). No significant changes in Uno(x) during the clamp were observed. Changes in Uno(x) during the clamp (deltaUno(x)) and differences in plasma ET-1 measured before the end and before the beginning of the clamp (deltaET-1) were correlated in the controls (r = .75, P = .01) but not in EH (r = -.01, P = .97). No parameter of glucose metabolism correlated with basal Uno(x), basal plasma ET-1, deltaUno(x), and deltaET-1, whether absolute or percent values, in either group. Thus, acute euglycemic hyperinsulinemia produces a decrease in plasma ET-1 in both EH patients and controls. The lack of correlation between deltaUno(x) and deltaET-1 under these conditions in EH may suggest an impairment of systems governing interactions between the NO-dependent pathway and ET-1. In addition, insulin actions on glucose metabolism and on the endothelial mediators appear dissociated.