Lipoprotein(a) and Oxidized Phospholipids Promote Valve Calcification in Patients With Aortic Stenosis

Figures

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  Figure 1. Study Diagram Study diagram of the study cohorts, describing the number of patients from the Ring of Fire and SALTIRE trials undergoing the different forms of baseline and repeat imaging. 18F-NaF PET = fluorine-18 sodium fluoride positron emission tomography; CT = computed tomography; Lp(a) = lipoprotein(a); OxPL-apoB = oxidized phospholipids on apolipoprotein B-100; SALTIRE = Scottish Aortic Stenosis and Lipid Lowering Trial, Impact on Regression.

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  Figure 2. Baseline Lp(a) and OxPL-apoB Levels in Our Cohort and Association With Baseline Aortic Valve CT Calcium Score and Peak Aortic Valve Jet Velocity on Echocardiography (A) Lp(a) and (B) OxPL-apoB distribution in 145 patients. Baseline aortic valve CT calcium scores for the top versus combined middle and bottom tertiles of (C) Lp(a) and (D) OxPL-apoB. Baseline peak aortic jet velocity for the top versus combined middle and bottom tertiles of (E) Lp(a) and (F) OxPL-apoB. Abbreviations as in Figure 1.

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  Figure 3. Baseline Calcification Activity and Aortic Stenosis Progression According to Patient Lp(a) and OxPL-apoB Levels At baseline, patients in the top Lp(a) and OxPL-apoB tertiles have increased valvular 18F-NaF uptake, as a marker of calcification activity, compared with the combined middle and bottom tertiles (A and B). (C) Two examples of increased valvular 18F-NaF PET uptake at baseline (left), which predicted progression to macrocalcification on CT after 2 years (right)(16). Patients in the top Lp(a) and OxPL-apoB tertiles also demonstrated faster progression in aortic valve CT calcium score (D and E), and faster hemodynamic progression, expressed as the annualized change in peak aortic jet velocity (ΔVmax) (F and G). Abbreviations as in Figure 1.

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  Figure 4. Aortic Valve Replacement or Death During Follow-Up According to Patient’s Lp(a) and OxPL-apoB Levels Kaplan-Meier curves show the composite endpoint of aortic valve replacement surgery and death. Patients in the top Lp(a) and OxPL-apoB tertiles had more events than those in the lower tertiles (A and B). Multivariate Cox proportional hazards analysis for aortic valve replacement surgery and death. Lp(a) and OxPL-apoB emerged as an independent predictor of events alongside the baseline peak aortic jet velocity (C and D). Hazard ratio for age is per 10 years, BMI per kg/m2, creatinine per 10 mg/dl; Vmax per m/s. BMI = body mass index; CI = confidence interval; CVD = cardiovascular disease; Vmax = peak aortic jet velocity; other abbreviations as in Figure 1.

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  Figure 5. Lp(a) Induces Osteogenic Differentiation in VICs (A to C) VICs in osteogenic media only conditions were used as the baseline comparator, while addition of TGF-β served as a positive calcification control. One week of exposure to Lp(a) (100 mg/dl) induced gene expression of the inflammatory mediator IL-6 and osteoblastic regulators BMP2 and RUNX2. Pre-incubation with the E06 antibody targeting OxPL reduced the transcriptional effect of Lp(a), suggesting that OxPL is intrinsic to the pro-calcific effects of Lp(a). The role of OxPL was further validated using 2 r-apo(a) constructs that differ in their lysine binding sites and consequently their capacity to bind OxPL. (D to F) Three days of exposure to r-apo(a) 17K-WT construct induced increased expression of osteogenic genes. This effect was reduced with the 17KΔLBS10 construct that lacks the ability to bind OxPL. (G and H) Bright-field microscopy images of VICs after stimulation with 17K constructs. 17K-WT induces an activated, rhomboid shape, whereas 17KΔLBS10 was characterized by a quiescent, spindle-shaped morphology. Data represent mean ± SEM for at least n = 3 independent experiments. *p < 0.05; **p < 0.01; ***p < 0.001…

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  Central Illustration. Lp(a) and OxPL Drive Disease Progression by Aggravating Calcification in Aortic Stenosis Patients Aortic stenosis patients with elevated levels of Lp(a) and OxPL-apoB demonstrate increased calcification activity in the valve as measured by 18F-NaF PET, compared with patients with low levels of Lp(a) and OxPL-apoB. During follow-up, this resulted in faster progression of CT calcium score and faster hemodynamic progression as measured by echocardiography. Ultimately, these patients have an increased risk of aortic valve replacement and death. Lp(a) = lipoprotein(a); OxPL-apoB = oxidized phospholipids on apolipoprotein B-100.