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Abstract

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Limitations
  7. Conclusions
  8. Acknowledgments and disclosures:
  9. References

J Clin Hypertens (Greenwich). 2012;14:245–249. ©2012 Wiley Periodicals, Inc.

Atorvastatin is postulated to improve arterial stiffness in patients with diabetes mellitus or hypercholesterolemia; however, in elderly hypertensive patients, its effect on arterial stiffness and the possible mechanisms are unknown. A total of 73 elderly hypertensive patients were enrolled to receive atorvastatin for 6 months. Brachial-ankle pulse wave velocity (baPWV) and circulating biomarkers were measured before and after the intervention. After 6 months of treatment, the patients experienced a 19.66% reduction in low-density lipoprotein cholesterol (2.90±0.58 vs 2.33±0.56 mmol/L, P<.01) and a 10.63% reduction in baPWV (2100.89±513.21 vs 1877.56±432.06 cm/s, P=.01). In addition, a 21.79% reduction in circulating N-(epsilon)-carboxymethyl-lysine and a 20% reduction in Von Willebrand factor level were observed after treatment. Meanwhile, the activity of copper/zinc-containing superoxide dismutase (Cu/Zn SOD) was increased by 26.64% (5.04±1.01 vs 6.87±1.83 U/L, P<.001). Correlation analysis demonstrated that the increase of Cu/Zn SOD activity was related to the reductions of arterial stiffness (r=−0.340, P=.003). Taken together, these findings suggest that atorvastatin can improve arterial stiffness possibly by reducing oxidative stress levels in elderly hypertensive patients.

Large artery stiffness increases with age,1–3 which is amplified among individuals with hypertension and has now been recognized as the new treatment target for essential hypertension.4 Indeed, arterial stiffness has long been regarded as an independent predictor of cardiovascular events and mortality in both healthy and diseased populations.3,5,6

Previous studies demonstrate that structural components within the arterial wall, mainly collagen and elastin, together with transmural pressure, are key determinants of large arterial stiffness.3,7 However, smooth muscle tone also influences the stiffness of elastic and muscular arteries, suggesting functional regulation of stiffness by local and/or circulating vasoactive substances.8,9 Arterial stiffness alters the resting and stress-induced hemodynamics and energy expenditure,10 which results in widening of the arterial pulse pressure and profoundly influences blood vessel and heart biology. In arteries, the impact is related to changes to mechanical vascular stimulation, while in the heart, vascular stiffening influences the load imposed on the ventricles, the efficiency of cardiac ejection, and the perfusion of the heart itself.10 Therefore, in addition to being a measure of the cumulative influence of cardiovascular risk factors on target organ damage, changes of large artery phenotype may be causative in the pathogenesis of cardiovascular events.11 Consequently, numerous strategies have been used to reduce arterial stiffening. The major emphasis of pharmacologic destiffening strategies has focused on smooth muscle tone by enhancing nitric oxide bioavailability.10–12 Recently, there has been increasing interest in the use of statins as destiffening therapy.10,13–16 The interest goes beyond the ability of statins to lower serum cholesterol and extends to the increasingly recognized anti-inflammatory, antiproliferative, and immunomodulatory actions.

In elderly patients (older than 60 years), however, especially very elderly patients (older than 80 years), no information can be obtained on whether destiffening therapies such as statins have the ability to increase arterial elasticity. Accordingly, in the present study, we tested the hypothesis that 6 months of atorvastatin treatment would reduce large artery stiffness in elderly hypertensive patients, and we also intended to identify the possible mechanisms of atorvastatin on vascular destiffness.

Methods

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Limitations
  7. Conclusions
  8. Acknowledgments and disclosures:
  9. References

Study Population

The study population consisted of 73 consecutive patients with long-duration essential (>10 years) hypertension (45 men, 28 women), without coronary heart disease and diabetes mellitus, with a mean age of 79.94 years and mean duration of 12.1 hypertension years. All patients were found to have carotid atherosclerotic plaque by untrasound examination. Most patients had well-controlled blood pressure of <140/90 mm Hg while taking blood pressure–lowering medication before enrollment. Their baseline fasting serum low-density lipoprotein (LDL) cholesterol level were between 2.29 mmol/L and 4.46 mmol/L, with a fasting triglyceride <4.52 mmol/L. All patients were statin-naive, and those patients already taking lipid-lowering medication (eg, the traditional Chinese medicine such as Xuezhikang) required a 2-week washout period before enrollment. All of the patients were free from chronic disease, including liver or kidney disease and cancer, as assessed by medical history, physical examination, electrocardiography, complete blood cell count, blood chemistry, and urinalysis. Because all patients had caritod plaques and clinical trials have demonstrated substantially improved outcomes with statins, it was deemed ethically unacceptable to randomize these patients to placebo. Accordingly, all patients were assigned to an active treatment with 20 mg/d of atorvastatin. The institution’s ethical committee approved the study, and written informed consent was obtained from all participants. Patients were maintained on their other medications including aspirin, β-blockers, diuretics, and angiotensin-converting enzyme inhibitors or angiotensin receptor blocker, without change, throughout the study.

Laboratory Tests

Blood samples for central laboratory assay of lipid profile and plasma circulating biomarkers were collected at months 0 and 6, at the same time as brachial-ankle pulse wave velocity (baPWV) measurement. Blood samples were drawn from the antecubital vein after an overnight fast. Patients were not allowed to engage in physical activity or take medications before the sample was collected. Blood samples were stored continuously at −70°C until the time of analysis of the circulating biomarkers.

LDL cholesterol fraction and serum biomarkers were separated from fresh serum by combined ultracentrifugation and precipitation. C-reactive protein (hs-CRP) was measured using high-sensitivity immunonephelometry (Dade Behring Diagnostics, Tarrytown, NY). Laboratory measurements serum levels of von Willebrand factor (vWF) were measured using an enzyme sandwich assay (Westang, Shanghai, China). The level of advanced glycation end products (AGEs) in this study was assessed by measuring the serum carboxymethyl-lysine (CML). CML is a dominant circulating AGE, the best characterized of all the AGEs, and a dominant AGE in tissue proteins.17 CML was measured in duplicate using a commercial competitive enzyme-linked immunosorbent assay kit (Westang, Shanghai, China). This assay has been validated, is specific, and shows no cross-reactivity with other compounds. The within-assay and between-assay coefficients of variation in the CML assay were both <5%. Serum copper/zinc-containing superoxide dismutase (Cu/Zn SOD) and mitochondrial manganese SOD (Mn SOD) activity measurement was assayed at 490 nm on a microplate reader using the commercial kit (Jiancheng, Nanjing, China). Briefly, the SOD activity was assayed by monitoring the inhibition of the rate of xanthine-mediated/xanthine oxidase–mediated reduction of cytochrome c (pH 7.4). To discriminate between Cu/Zn-SOD and Mn SOD activities, the assay was also performed after incubation in the presence of KCN, which selectively inhibits the Cu/Zn-SOD isoform.18

Pulse Wave Velocity Measurements

baPWV and oscillometric blood pressure were measured after the patients rested in the supine position in a quiet room for at least 10 minutes. Patients abstained from food and coffee or other caffeine-containing beverages for at least 45 minutes before performance of the pulse wave velocity (PWV) measurements. After simultaneous acquisition of pressure wave forms in the right common brachial artery and right ankle artery, pulse transit time between these two sites was automatically determined by the VP-2000 (Colin Medical Technology Co, Komaki, Japan), using the foot-to-foot method, as previously described and validated. PWV was calculated by dividing the pulse wave distance traveled by the pulse transit time. Measurements of PWV were made in triplicate and averaged for the analyses. The coefficient of variation for the measurement of PWV was 7.2%, and the intraclass correlation coefficient was 0.89.

Statistical Methods

Statistical analyses were performed using SPSS software version 13.0 (SPSS, Chicago, IL). All continuous variables were tested for normal distribution by the Shapiro–Wilk W test. All continuous variables are described as mean±standard deviation, or median (interquartile range), while categorical variables are non-normally distributed. Paired sample t test was used for comparison of the indices before and after atorvastatin treatment. Spearman rank correlation coefficients were calculated for examining bivariate associations between PWV, change in PWV before and after 6 months of treatment, and patient characteristics, as well as with markers of inflammation, endothelial function, and oxidative stress. P values of <.05 were considered significant.

Results

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Limitations
  7. Conclusions
  8. Acknowledgments and disclosures:
  9. References

Patient Characteristics

Patient characteristics at baseline are shown in the Table. At baseline, 75 patients with primary hypertension were enrolled in the study, of which 47 were men. Their age ranged from 60 to 93 years, with an average age of 79.94 years, and the blood pressure was 136±18/76±19 mm Hg. After 2 weeks of atorvastatin treatment, 2 male patients withdraw from the study because of alanine transaminase level >3 upper limitation. There were no significant changes in serum creatine kinase concentrations during the intervention in either group (data not shown).

Table TABLE.   Baseline and Follow-Up Characteristics of the Study Patients
 BaselineAfter 6 MonthsP Value
  1. Abbreviations: baPWV, brachial-ankle pulse wave velocity; BMI, body mass index; CML, Cu/Zn SOD, copper/zinc-containing superoxide dismutase; hs-CRP, high-sensitivity C-reactive protein; LDL, low-density lipoprotein; Mn SOD, mitochondrial manganese superoxide dismutase; NS, not significant; vWF, von Willebrand factor.

Age, y 79.94±7.86  
Male:female 32:4  
Smoker, % 30.5  
BMI, kg/m223.8±4.4723.6±4.05NS
Heart rate, beats per min72.3±12.874.6±10.4NS
Systolic blood pressure, mm Hg136±18133±16NS
Diastolic blood pressure, mm Hg76±1973±15NS
baPWV, cm/s2100.89±513.211877.56±432.06<.01
Ankle-brachial index1.02±0.151.06±0.15NS
LDL cholesterol, mmol/L2.90±0.582.33±0.56<.01
vWF, ng/mL0.048±0.0170.041±0.016<.05
CML, mg/L189.65±142.96148.34±120.22<.01
Mn SOD, U/L2.98±2.304.21±0.70<.01
Cu/Zn SOD, U/L5.04±1.016.87±1.83<.01
hs-CRP, mg/L3.43±2.382.67±1.24<.05

Effects of Atorvastatin on Arterial Stiffness and Soluble Plasma Biomarkers in Elderly Hypertensive Patients

After 6 months of atorvastatin treatment, a fully significant regression in baPWV (2100.89±513.21 cm/s vs 1877.56±432.06 cm/s, P=.01) with almost unchanged ankle-brachial index (1.02±0.15 vs 1.06±0.15, P>.05) was observed in elderly hypertensive patients. In addition, the baseline and after-treatment values of lipids and soluble biomarkers were shown in the Table. As expected, atorvastatin induced a significant reduction in LDL cholesterol (2.90±0.58 mmol/L vs 2.33±0.56 mmol/L, P<.01). Furthermore, almost all soluble plasma biomarkers for inflammation and endothelial function decreased from baseline, with CML reduced by 21.79% (189.65±142.96 mg/L vs 148.34±120.22 mg/L, P<.001), hs-CRP reduced by 22.16% (3.43±2.38 mg/L vs 2.67±1.24 mg/L, P<.05), and vWF decreased by 20% (48±17 mg/L vs 41±16 ng/mL, P=.04). Moreover, the plasma levels of Cu/Zn SOD and Mn SOD increased by 26.64% (5.04±1.01 U/L vs 6.87±1.83 U/L, P<.001) and 29.22% (2.98±2.30 U/L vs 4.21±0.70 U/L, P<.001), respectively, after 6 months of atorvastatin treatment.

Correlation Between Changes in Arterial Elasticity Indices and Plasma Variable Before and After 6 Months of Atorvastatin Treatment

Pearson correlation analyses between PWV vs each plasma variable at baseline showed that positive correlation was observed between age (r=0.524, P<.0001) (Figure 1A), CML (r=0.431, P<.0001) (Figure 1B), and PWV. Then, all analyses evaluating the relationship between changes in PWV and changes in soluble markers were analyzed, and only the correlations between changes in Cu/Zn SOD (△Cu/Zn SOD) and PWV (△baPWV) reached the threshold value of P<.05 (r=−0.340, P=.003) (Figure 2A) after 6 months of atorvastatin treatment. Notably, no correlation was found between the changes of LDL (△LDL) and △baPWV (r=0.038, P=.748). Meanwhile, significant positive correlation was observed between age and vWF level (r=0.491, P<.0001) (Figure 1C) at baseline. Since vWF is a good biomarker for endothelial integrity, our results may indicate that the degree of endothelial dysfunction increases with age in old hypertensive patients. Because no correlation was found between △baPWV and improvement in endothelial function (defined as the vWF level change in our study) after 6 months of atorvastatin treatment, we then compared the correlation between the two variables in the patient with relative integrity endothelial function (aged younger than 80). Surprisingly, significant positive correlation between the △vWF and △baPWV was observed in those patients (r=0.608, P=.0008) (Figure 2B), meanwhile no correlation between the two variables was seen in patients older than 80 years.

image

Figure 1.  (A) Correlation between brachial-ankle pulse wave velocity (baPWV) and age. (B) Correlation between baPWV and carboxymethyl-lysine (CML). (C) Correlation between age and von Willebrand factor (vWF).

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image

Figure 2.  (A) Correlation between the change of brachial-ankle pulse wave velocity (△baPWV) and Cu/Zn SOD (△Cu/Zn SOD). (B) Correlation between △baPWV and vWF (△vWF) in patients younger than 80 years.

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Discussion

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Limitations
  7. Conclusions
  8. Acknowledgments and disclosures:
  9. References

Decreased arterial stiffness with time, as assessed by PWV, was observed in elderly patients treated with atorvastatin after 6 months of therapy in our study. These results are compatible with previous studies.13,19,20 However, the mechanisms mediating the large artery destiffening effects of atorvastatin treatment remain largely unknown. The current prevailing view of arterial stiffness is focused on structural alterations of the arterial wall with the aging process,21,22 which was confirmed by us that the age was a strong predictor for arterial PWV velocity in aging hypertensive patients. Previous studies have revealed that CML is a dominant circulating AGE, which modifies the arterial structure and increases the arterial stiffness.23 In our study, we found that serum circulating CML level was correlated with PWV before atorvastatin treatment, and significant decreased serum CML level was observed after 6 months of atorvastatin therapy, which may indicate that atorvastatin treatment might be an effective approach to decrease the arterial stiffness by modifying the structure of the arterial wall in a long-term intervention period.

However, as the structural changes occur with the aging process, it is unlikely that short-term intervention, such as in the present study, would result in favorable structural modifications to the arterial wall in elderly patients. Accordingly, although decreased CML level was observed in our study, no correlation was found between the change of PWV and decrease in circulating CML level after 6 months of statin intervention. Thus, a more plausible explanation for our findings is that statin therapy may reduce arterial stiffness by regulating local and/or circulating vasoactive substance expression in vascular and improving endothelial function. We, therefore, investigated the oxidative stress by measuring SOD activity before and after atorvastatin therapy. SOD is the primary cellular defense against ROS, which plays a critical role in the progression of atheroclerosis.24 Three SOD isoforms have been identified: cytosolic, Cu/Zn SOD; Mn SOD; and the extracellular SOD.19 Our study revealed that atorvastatin treatment significantly increased circulating Cu/Zn SOD and Mn SOD activity, and the change of Cu/Zn SOD activity was negatively correlated with decrease in PWV velocity. Previously, Cu/Zn SOD has been shown to attenuate vascular remodeling and alter vascular responsiveness.25,26 Therefore, atorvastatin may exert an inhibition of the increase in aortic stiffness in elderly hypertensive patients, by restoring Cu/Zn SOD activity, resulting in the reduction of ROS in the vascular wall independent of the lipid-lowering action. Furthermore, the vWF, a good biomarker for endothelial integrity, was also measured in our study. Our results demonstrated that circulating vWF increased with age, which may indicate that the impairment of endothelial function increases with age. Furthermore, we found that 6 months of statin therapy significantly decreased circulating vWF level in hypertensive patients, which coincides with previous studies stating that statins have advantages in improving endothelial function in vascular patients. However, this improvement was significantly correlated with the change in arterial stiffness only in patients with relative integrity endothelial function (aged younger than 80). Therefore, we may conclude that atorvastatin improves arterial stiffness partially by attenuating endothelial dysfunction in elderly patients with relative integrity endothelial function (younger than 80).

Limitations

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Limitations
  7. Conclusions
  8. Acknowledgments and disclosures:
  9. References

There are some limitations of our study that warrant discussion. First, our sample size was relatively small, especially the sample size for relative integrity endothelial function hypertensive patients (only 27), and thus, larger studies are needed in more individuals to extend the generalizability of our findings. Second, although observed change in PWV and oxidative stress demonstrated an association in this study, future intervention studies specifically on lower oxidative stress are needed to prove the causality between them.

Conclusions

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Limitations
  7. Conclusions
  8. Acknowledgments and disclosures:
  9. References

These findings suggest that atorvastatin reduces arterial stiffness by reducing oxidative stress damage and/or improving endothelial function in elderly hypertensive patients. In light of the present findings, future studies on statins focusing on the mechanisms of arterial destiffening are needed.

Acknowledgments and disclosures:

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Limitations
  7. Conclusions
  8. Acknowledgments and disclosures:
  9. References

This work was supported by the National Natural Science Foundation of China (NSFC 30900602) to Dr Wang Junhong and National Natural Science Foundation of Jiangsu Province (BK2011382) to Professor Guo Yan. The authors declare that they have no relevant financial interests.

References

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Limitations
  7. Conclusions
  8. Acknowledgments and disclosures:
  9. References
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