Anders Bröijersén

Lipoprotein profiles in plasma and interstitial fluid analyzed with an automated gel‐filtration system

Background  High‐quality methods for lipoprotein characterization are warranted in studies on various metabolic diseases.

Atorvastatin reduces thrombin generation and expression of tissue factor, P-selectin and GPIIIa on platelet-derived microparticles in patients with peripheral arterial occlusive disease

We investigated the effects of statin treatment on platelet-derived microparticles (PMPs) and thrombin generation in atherothrombotic disease. Nineteen patients with peripheral arterial occlusive disease were randomised to eight weeks of treatment with atorvastatin or placebo in a cross-over fashion. Expression of GPIIIa (CD61), P-selectin (CD62P), tissue factor (TF, CD142) and phosphatidylserine (PS; annexin-V or lactadherin binding) was assessed on PMPs. Thrombin generation in vivo was assessed by measurement of prothrombin fragment 1+2 in plasma (F1+2) and ex vivo by using the calibrated automated thrombogram (CAT). During atorvastatin treatment, expression of TF, P-selectin and GPIIIa was significantly reduced vs. placebo (p<0.001 for all). No effect on annexin-V or lactadherin binding was seen. Thrombin generation was significantly reduced during atorvastatin as assessed by both the CAT assay (p<0.001) and by measurements of F1+2 (p<0.01). Subsequent in vitro experiments showed that when TF on microparticles (MPs) was blocked by antibodies, the initiation of thrombin generation was slightly but significantly delayed. Blocking PS on MPs using annexin-V or lactadherin resulted in almost complete inhibition of thrombin generation. In conclusion, atorvastatin reduces thrombin generation and expression of TF, GPIIIa and P-selectin on PMPs in patients with peripheral vascular disease. Microparticle-bound TF slightly enhances initiation of thrombin generation whereas negatively charged surfaces provided by MPs or lipoproteins could reinforce thrombin generation. Statins may inhibit initiation of thrombin generation partly through a microparticle dependent mechanism but the main effect is probably through reduction of lipoprotein levels.

No Influence of Simvastatin Treatment on Platelet Function In Vivo in Patients With Hypercholesterolemia

Hypercholesterolemia is associated with platelet activation. Reduction of plasma cholesterol levels by the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor simvastatin has been found to improve certain aspects of platelet function in vitro and in vivo, but controlled trials are largely lacking. The present randomized, double-blind, crossover study was performed to evaluate whether 10- to 12-week treatment with simvastatin or placebo affects platelet function in vivo in 23 hypercholesterolemic men. Measurements were performed at rest and during mental stress. Simvastatin treatment reduced plasma total cholesterol levels by 18 +/- 2% and low density lipoprotein cholesterol levels by 26 +/- 2% (P < .001 for both), whereas high density lipoprotein cholesterol levels increased slightly (6 +/- 2%, P < .05). Platelet aggregability as assessed by filtragometry ex vivo was unaffected by simvastatin treatment both at rest and during mental stress. Plasma beta-thromboglobulin levels, which reflect platelet secretion, were also unaltered by simvastatin treatment both at rest (antilog of the mean: 20.2 versus 20.0 ng/mL during placebo) and during mental stress. Moreover, nocturnal excretion of 11-dehydrothromboxane B2 in urine did not differ between placebo and active treatment: 218 versus 216 ng/mmol creatinine, respectively. The corresponding values for urinary excretion of high-molecular-weight beta-thromboglobulin were 1.78 versus 1.92 ng/mmol creatinine. Thus, simvastatin treatment had no clear-cut effect on platelet function, as assessed by four different in vivo related platelet function variables, in hypercholesterolemic men.

Angiotensin II infusion in man is proinflammatory but has no short-term effects on thrombin generation in vivo.

BACKGROUND Angiotensin (Ang) II may be involved in the development of cardiovascular disease. We examined the potential proinflammatory and prothrombotic effects of Ang II in 16 healthy subjects and in 16 subjects with familial combined hyperlipidemia (FCHL), a condition associated with an increased risk of cardiovascular complications. METHODS We studied the effects of a three hour intravenous infusion of Ang II (10 ng/kg/min) on plasma concentrations of interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-alpha), circulating leukocyte count, tissue plasminogen activator/plasminogen activator inhibitor-1 (t-PA/PAI-1) complexes, prothrombin fragment 1+2 (F1+2), and thrombin-antithrombin (TAT) complexes. Blood was collected before, during and 1 h after Ang II infusion. RESULTS IL-6 was higher in subjects with FCHL at rest (P < 0.05) and increased (P < 0.001) similarly in both groups by Ang II infusion. Also leukocyte count was higher in subjects with FCHL at rest (P < 0.001) and increased (P < 0.001) similarly in both groups by Ang II infusion. T-PA/PAI-1 complexes were higher in subjects with FCHL at rest (P < 0.001) and decreased (P < 0.001) similarly in both groups during Ang II infusion. TNF-alpha, F1+2 and TAT complexes were similar in the two groups at rest and did not change during or after the Ang II infusion. CONCLUSIONS A three hour Ang II infusion increases inflammation and may enhance fibrinolysis but does not affect short term thrombin generation. Subjects with FCHL have signs of increased inflammation and impaired fibrinolysis.

Cardioprotective effect of an endothelin receptor antagonist during ischaemia/reperfusion in the severely atherosclerotic mouse heart

1 Endothelin (ET) receptor antagonists are cardioprotective during myocardial ischaemia and reperfusion through a nitric oxide (NO)‐dependent mechanism. The aim of the present study was to investigate whether the ET receptor antagonist, bosentan, is cardioprotective in atherosclerotic mice. 2 Buffer‐perfused hearts from apolipoprotein E/LDL receptor double knockout (KO) and wild‐type (WT) mice were subjected to global ischaemia and reperfusion. 3 Following reperfusion, the recovery of rate–pressure product (RPP; left ventricular developed pressure (LVDP) × heart rate) was equally impaired in WT and KO mice given vehicle (34±8 and 29±9%, respectively). The ETA/ETB receptor antagonist bosentan (10 μmol l−1) improved recoveries to 57±10% in WT and to 68±10% in KO mice (P<0.01). Similar effects were observed for the recovery of left ventricular end‐diastolic pressure (LVEDP), developed pressure and dP/dt. 4 Bosentan improved the recovery of coronary flow in both KO and WT mice. Recovery of coronary flow was significantly higher in the KO mice given bosentan (135±15%) than in the WT group (111±12%; P<0.01). ET‐1 (1 nmol l−1) impaired recovery of coronary flow in both WT and KO mice though this effect was more pronounced in the KO mice (P<0.01). 5 Coronary outflow of NO during reperfusion was enhanced in both KO and WT mice following bosentan administration. 6 The ETA/ETB receptor antagonist bosentan protects the atherosclerotic mouse heart from ischaemia/reperfusion injury. The observation that ET receptor blockade and stimulation have a greater effect on coronary flow in atherosclerotic hearts indicates an increased activation of the ET system in atherosclerotic coronary arteries.

Altered vascular responses to circulating angiotensin II in familial combined hyperlipidemia.

Objectives Patients with familial combined hyperlipidemia (FCHL) are at increased risk of hypertension and cardiovascular disease. We examined if patients with FCHL have altered microvascular and macrovascular responses to angiotensin II, a principal mediator of the renin–angiotensin–aldosterone system. Methods Sixteen patients with FCHL and 16 healthy controls were investigated before, during and after a 3 h intravenous infusion of angiotensin II (10 ng/kg/min). Forearm skin microcirculation was studied by laser Doppler fluxmetry during rest and local heating to 44°C (microvascular hyperemia). Results Baseline systolic blood pressures were 129 ± 13 and 123 ± 12 mmHg in FCHL patients and controls (P = 0.11), respectively. Angiotensin II elicited a greater systolic blood pressure response in the FCHL group (+32 ± 13 mmHg) than in the control group (+20 ± 11 mmHg; P < 0.001). At 3 h angiotensin II infusion, microvascular hyperemia increased in the controls (P < 0.001), whereas microvascular hyperemia was unchanged in the FCHL patients (P < 0.01, between groups). Conclusion In healthy individuals, a 3 h intravenous infusion of angiotensin II enhances heat-induced microvascular hyperemia. In FCHL, this microvascular hyperemia is impaired and the systolic blood pressure response is increased. A reduced microvascular dilatation capacity in FCHL may contribute to the observed blood pressure elevation and promote development of micro- and macrovascular complications.

Levels of atherogenic lipoproteins are unexpectedly reduced in interstitial fluid from type 2 diabetes patients

At a given level of serum cholesterol, patients with T2D have an increased risk of developing atherosclerosis compared with nondiabetic subjects. We hypothesized that T2D patients have an increased interstitial fluid (IF)-to-serum gradient ratio for LDL, due to leakage over the vascular wall. Therefore, lipoprotein profiles in serum and IF from 35 T2D patients and 35 healthy controls were assayed using fast performance liquid chromatography. The IF-to-serum gradients for VLDL and LDL cholesterol, as well as for apoB, were clearly reduced in T2D patients compared with healthy controls. No such differences were observed for HDL cholesterol. Contrary to our hypothesis, the atherogenic VLDL and LDL particles were not increased in IF from diabetic patients. Instead, they were relatively sparser than in healthy controls. The most probable explanation to our unexpected finding is that these lipoproteins are more susceptible to retainment in the extravascular space of these patients, reflecting a more active uptake by, or adhesion to, tissue cells, including macrophages in the vascular wall. Further studies are warranted to further characterize the mechanisms underlying these observations, which may be highly relevant for the understanding of why the propensity to develop atherosclerosis is increased in T2D.