Modulation of atherosclerosis, blood pressure and arterial elasticity by statins

Beneficial Effect of Statin Therapy on Arterial Stiffness

Arterial stiffness describes the increased rigidity of the arterial wall that occurs as a consequence of biological aging and several diseases. Numerous studies have demonstrated that parameters to assess arterial stiffness, especially pulse-wave velocity, are predictive of those individuals that will suffer cardiovascular morbidity and mortality. Statin therapy may be a pharmacological strategy to improve arterial elasticity. It has been shown that the positive benefits of statin therapy on cardiovascular disease is attributable not only to their lipid-lowering capacity but also to various pleiotropic effects, such as their anti-inflammatory, antiproliferative, antioxidant, and antithrombotic properties. Additionally, statins reduce endothelial dysfunction, improve vascular and myocardial remodeling, and stabilize atherosclerotic plaque. The aim of the present review was to summarize the evidence from human studies showing the effects of statins on arterial stiffness.

Blood pressure-lowering effects of statins: who benefits?

OBJECTIVES

To evaluate if the effect of statins on blood pressure is similar in patients grouped by use of antihypertensive medication, level of blood pressure, and high-density lipoprotein cholesterol (HDL-C).

METHODS

Blood pressure was compared in statins users (n = 995) and nonusers (n = 9536) from the National Health and Nutrition Examination Surveys. The overall effect of statins and their interactions with antihypertensive medication, blood pressure, and HDL-C were estimated using multiple linear and quantile regression.

RESULTS

Adjusted systolic blood pressure was on average 1.8 mmHg lower in statins users than in nonusers (P = 0.05). Although statins had no significant effect among nonusers, it decreased systolic blood pressure by 3.3 mmHg among users of antihypertensive medication (interaction P = 0.02). The effect of statins on systolic blood pressure was similar in individuals with HDL-C levels above and below the median (49 mg/dl). Statins also lowered diastolic blood pressure by an average of 1.9 mmHg (P < 0.01), regardless of antihypertensive medication use. Among individuals with high HDL-C statins did not lower diastolic blood pressure, whereas in those with low HDL-C diastolic blood pressure was reduced by 3.4 mmHg. The effect of statins on systolic and diastolic blood pressure increased with higher blood pressure and changed little with adjustment for total cholesterol.

CONCLUSION

Statins lower blood pressure by cholesterol-independent mechanisms, and the reduction is larger in individuals with higher blood pressure and those with low HDL-C. Statins may be beneficial in preventing hypertension and may contribute to better blood pressure control in hypertensive patients.

Measurement of arterial stiffness in subjects with vascular disease: Are vessel wall changes more sensitive than increase in intima-media thickness?

BACKGROUND AND AIMS

It is widely accepted that subjects with vascular disease have increased arterial stiffness and intima-media thickness (IMT) when compared with healthy controls. The aim of this study was to investigate indices of arterial stiffness and IMT in the common carotid arteries (CCAs) of subjects with and without peripheral arterial disease (PAD), in order to look for evidence of change in wall quality and quantity to explain increased stiffness that has been found in the arteries of subjects with vascular disease.

METHODS AND RESULTS

The arterial distension waveform (ADW), IMT, diameter and brachial blood pressure were measured to calculate Young's Modulus (E) and elastic modulus (Ep) in the common carotid arteries of subjects with and without PAD. 38 subjects with confirmed PAD were compared with 43 normal controls matched for age, sex, smoking and hypertension. The mean diameter (8.35mm [95% CI 7.93-8.77] vs. 6.93mm [6.65-7.20] P<0.001, increase 20%), IMT (0.99mm [0.92-1.07] vs. 0.88mm [0.82-0.93] P=0.020, increase 12.5%), Ep (315kPa [185-444] vs. 190kPa [164-216] P=0.034, increase 66%) and E (1383kPa [836-1930] vs. 744kPa [641-846] P=0.006, increase 86%) were all significantly higher in subjects with PAD.

CONCLUSIONS

This study suggests that increased stiffness observed in subjects with peripheral vascular disease is a result of change in both quantity and quality of the arterial wall. Changes in indices of arterial stiffness were much higher than changes in IMT and diameter. These preliminary observations may be an indication that indices of arterial stiffness are a sensitive early marker of atherosclerosis.

Angiotensin II AT1 receptor blockade normalizes CD11b+ monocyte production in bone marrow of hypercholesterolemic monkeys

The enhanced production of monocytes expressing pro-inflammatory markers such as the integrin CD11b in patients with hypercholesterolemia may promote vascular inflammation and exacerbate atherogenesis. The objective of the present study was to determine whether hypercholesterolemia stimulates the production of CD11b(+) monocytes in bone marrow, and whether the renin-angiotensin system participates in this process and thus provides a target for therapeutic intervention. The dietary induction of hypercholesterolemia in adult male cynomolgus monkeys was accompanied by increased bone marrow cellularity and elevated peripheral blood and bone marrow monocyte CD11b expression. Isolated bone marrow CD34(+) hematopoietic stem cells (HSCs) evaluated by in vitro functional assays exhibited enhanced myeloproliferative capacity and differentiation into CD11b(+) monocytes. Treatment of hypercholesterolemic monkeys with the angiotensin II AT(1) receptor blocker losartan for 15 weeks reduced bone marrow cellularity, suppressed peripheral blood and bone marrow monocyte CD11b expression, and normalized CD34(+) cell function assays. All variables returned to pretreatment levels 6 weeks after discontinuation of losartan treatment. Hypercholesterolemia was associated with increased CD34(+) cell AT(1) receptor expression and an exaggerated in vitro myeloproliferative response to angiotensin II stimulation that positively correlated to plasma LDL concentrations. In vitro exposure to native low-density lipoproteins (LDL) also increased CD34(+) cell AT(1) receptor expression and the myeloproliferative response to angiotensin II stimulation in a dose-dependent and receptor-mediated manner. Our data provide support for a positive regulatory role of plasma LDL on AT(1) receptor-mediated HSC differentiation and the production of pro-atherogenic monocytes. LDL-regulated HSC function may explain in part hypercholesterolemia-induced inflammation as well as the anti-inflammatory and anti-atherosclerotic effects of AT(1) receptor blockers.