bq-123 and Hypercholesterolemia

This study tested the hypothesis that pioglitazone reduces endothelin-1 activity in the forearm vasculature in non-diabetic patients with hypertension or hypercholesterolemia and variable degrees of insulin resistance.. We conducted a single center, randomized, double-blind, placebo controlled, cross-over trial in 80 patients with either hypertension or hypercholesterolemia and further classified as insulin-sensitive or insulin-resistant based on a published insulin sensitivity index. Participants received pioglitazone 45 mg daily or matching placebo for eight weeks. The main endpoint was the change in forearm vascular endothelin-1 activity, as assessed by intra-arterial infusion of the endothelin type A receptor blocker BQ-123, measured at the end of each 8-week treatment period.. Pioglitazone lowered plasma insulin (P < 0.001), improved insulin sensitivity (P < 0.001), increased HDL (P < 0.001), and reduced triglycerides (P = 0.003), free fatty acids (P = 0.005), and C-reactive protein (P = 0.001). However, pioglitazone did not affect the vasodilator response to BQ-123 in the whole group (P = 0.618) and in the diagnosis or insulin sensitivity subgroups. Hence, in non-diabetic patients with hypertension or hypercholesterolemia, PPARγ activation with pioglitazone does not affect endothelin-1 activity, despite enhancing insulin sensitivity and reducing plasma insulin and C-reactive protein levels.. In non-diabetic patients with hypertension or hypercholesterolemia, pioglitazone improves insulin sensitivity, lipid profile, and inflammation but does not affect endothelin activity. Our data suggest that the determinants of endothelin-1 vascular activity in vivo may differ and/or be more complex than those suggested by the results of previous in vitro studies.

Topics: Biomarkers; C-Reactive Protein; Cross-Over Studies; District of Columbia; Double-Blind Method; Endothelin A Receptor Antagonists; Endothelin-1; Endothelium, Vascular; Fatty Acids, Nonesterified; Forearm; Humans; Hypercholesterolemia; Hypertension; Insulin; Insulin Resistance; Lipoproteins, HDL; Peptides, Cyclic; Pioglitazone; PPAR gamma; Thiazolidinediones; Time Factors; Treatment Outcome; Triglycerides; Vasodilation

Endothelin blocking drugs have vasodilator effects mediated at least in part via the nitric oxide system. Hypercholesterolaemia is associated with vascular dysfunction manifest as impaired nitric oxide-mediated vasodilatation and arterial stiffness. Treatment with HMG CoA reductase inhibitors (statins) has proven mortality benefits in a range of patient populations. Subjects (n = 5) received either placebo or 800 mug cerivastatin for an 8-week period in a double-blind, placebo-controlled, cross-over study. Cerivastatin reduced the total plasma cholesterol compared with baseline by 27% (5.4 +/- 0.4 mmol/L versus 7.3 +/- 0.4 mmol/L, P = 0.04). Selective endothelin-A receptor blockade caused an increase in forearm blood flow (FBF) (18.0 +/- 7.2%, P = 0.04). Compared with placebo, cerivastatin therapy caused a trend towards a further increase in FBF (18.0 +/- 7.2% versus 52.0 +/- 19.0%, P = 0.06). Selective endothelin-B receptor blockade reduced FBF (-11.0 +/- 3.9%, P = 0.02) with no difference between placebo and cerivastatin therapy (-11.0 +/- 3.9% versus -13.0 +/- 3.6%, P = 0.9). Combined endothelin-A/endothelin-B receptor blockade increased FBF (39.8 +/- 13.4%, P < 0.01) with no difference between placebo and cerivastatin therapy (39.8 +/- 13.4% versus 42.4 +/- 19.0%, P = 0.7). There was a trend towards a reduction in the augmentation index between cerivastatin and placebo (6.2 +/- 2.7 versus 9.1 +/- 2.4, n = 5, P = 0.4) compared with baseline (7.2 +/- 1.0). In conclusion, statin therapy may decrease large artery stiffness and increase the vasodilating effects of endothelin-A receptor blockade.

Topics: Cholesterol, LDL; Compliance; Cross-Over Studies; Double-Blind Method; Down-Regulation; Drug Therapy, Combination; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Forearm; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Hypercholesterolemia; Oligopeptides; Peptides, Cyclic; Piperidines; Pyridines; Receptor, Endothelin A; Receptor, Endothelin B; Time Factors; Treatment Outcome; Vasodilation; Vasodilator Agents

Endothelin-1 (ET-1) is a potent vasoconstrictor that increases vascular tone in the resistance vessels of subjects with hypertension. It is unclear whether endogenous ET-1 affects resistance-vessel function equally in patients with other cardiovascular risk factors. Vasoconstriction to ET-1 is mediated principally via the endothelin-A (ETA) receptor on vascular smooth muscle cells. Accordingly, we used an ETA-specific antagonist, BQ-123, to test the hypothesis that endogenous ET-1 increases vascular resistance selectively in subjects with hypertension compared with other risk factors. BQ-123 was infused at 100 nmol/min for 80 minutes into the brachial artery of 10 subjects with hypertension (mean+/-SEM arterial pressure, 106+/-5 mm Hg), 12 subjects with hypercholesterolemia (mean+/-SEM total cholesterol, 7.1+/-0.2 mmol/L), 10 active smokers (mean+/-SEM, 42+/-11 pack-years), and 11 healthy, age-matched individuals. Forearm blood flow (FBF) was measured by venous occlusion plethysmography. BQ-123 dilated resistance arterioles in hypertensive subjects, with FBF's increasing by 46+/-7% from baseline (P<0.001). BQ-123 increased FBF to a lesser extent in hypercholesterolemic (24+/-5%, P<0.001) and healthy (20+/-8%, P=0.007) individuals but did not affect FBF significantly in smokers (10+/-8%, P=0.185). The vasodilator response in hypertensive subjects, but not in hypercholesterolemic patients or smokers, was significantly greater than that in healthy individuals (P=0.012). Endogenous ET-1, acting via the ETA receptor, increases resistance-vessel tone in subjects with hypertension more than in subjects with hypercholesterolemia or in smokers. These results indicate that ET-1 contributes more to the pathophysiology of hypertension than of other risk factors in subjects without overt atherosclerosis.

Topics: Arteriosclerosis; Endothelin Receptor Antagonists; Endothelin-1; Female; Forearm; Humans; Hypercholesterolemia; Hypertension; Male; Middle Aged; Peptides, Cyclic; Receptor, Endothelin A; Regional Blood Flow; Risk Factors; Smoking; Vascular Resistance; Vasodilation