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Lipoprotein(a) in plasma, arterial wall, and thrombus from patients with aortic aneurysm
E Papagrigorakis1, D Iliopoulos, P J Asimacopoulos
1Department of Medicine, The Methodist Hospital and Baylor College of Medicine, Houston, Texas 77030, USA.
Insights
Lipoprotein(a) [Lp(a)] levels increase after aortic aneurysm surgery, suggesting a role in tissue repair. Lp(a) is significantly higher in aneurysmal thrombus, indicating its involvement in clot formation and aortic wall reinforcement.
Area of Science:
- Cardiovascular Research
- Biochemistry
- Vascular Biology
Background:
- Elevated lipoprotein(a) [Lp(a)] is linked to cardiovascular disease.
- The precise physiological function of Lp(a) remains unclear, but elevated levels suggest roles in tissue repair.
Purpose of the Study:
- To investigate the hypothesis that Lp(a) contributes to the repair and reinforcement of the aorta.
Main Methods:
- Measured plasma Lp(a) levels in 38 patients before and after aortic aneurysm surgery.
- Analyzed Lp(a) protein concentration in resected aortic aneurysm wall and thrombus specimens.
- Correlated Lp(a) levels in plasma with concentrations found in aortic tissues.
Main Results:
- Plasma Lp(a) levels were significantly higher in patients with aortic aneurysms compared to normal subjects (10.7 mg/dl vs. 6.4 mg/dl).
- Post-surgery plasma Lp(a) levels increased significantly.
- Lp(a) concentration was substantially higher in aortic thrombus (69.6 ng/mg) than in the aortic wall (14.6 ng/mg), with both strongly correlating with pre-surgery plasma Lp(a).
Conclusions:
- Lp(a) plays a significant role in thrombus formation within aortic aneurysms.
- Lp(a) is involved in reinforcing the weakened aortic wall in patients with aneurysms.
Abstract:
The plasma concentration of lipoprotein(a) [Lp(a)] is highly correlated with the incidence of cardiovascular and peripheral vascular disease. A positive physiological role for Lp(a) has not yet been clearly identified, although elevated plasma levels in pregnant women, long-distance runners, subjects given growth hormone, patients after cardiovascular surgery, and patients with cancer, diabetes, or renal disease suggest its involvement in tissue synthesis and repair. The hypothesis that Lp(a) is involved in repair/reinforcement of the aorta was tested in 38 patients undergoing surgery for aortic aneurysm. In 29 patients 1 day before surgery, the mean plasma Lp(a) protein level was 10.7 mg/dl. At about 1, 2, and 8 weeks after surgery, the level was 14.1, 15.1, and 15.2 mg/dl, respectively. These levels are significantly higher than those of a comparable group of normal subjects (6.4 mg/dl; n = 274). Specimens of resected aortic aneurysm showed extensive medial degeneration, discontinuous elastic fibers, and deposition of mucopolysaccharides; these specimens were treated with a detergent-containing buffer to extract entrapped lipoproteins. The mean Lp(a) protein level in aortic wall extracts was 14.6 ng/mg tissue; these individual values were significantly associated with plasma Lp(a) levels before surgery (r2 = 0.31, p = 0.0003). The mean Lp(a) protein level in aortic thrombus extracts was substantially higher at 69.6 ng/mg tissue; these individual levels also were significantly associated with plasma Lp(a) concentrations before surgery (r2 = 0.68, p < 0.0001). The observations that: (i) plasma Lp(a) protein is about 1.7-fold higher in patients with aortic aneurysms than in normal subjects; and (ii) that Lp(a) protein in the aneurysmic thrombus is about 4.8-fold higher than in the aortic wall suggest that this lipoprotein plays a significant and direct role in thrombus formation and in reinforcement of the aneurysmic aortic wall.