Quantifying contribution of Lipoprotein (a) to atherogenic lipoprotein burden: a novel particle-based approach

Background: Elevated lipoprotein (a) [Lp(a)] is an independent risk factor for atherosclerotic cardiovascular disease (ASCVD). As clinical LDL cholesterol [LDL-C] incorporates cholesterol from Lp(a) [Lp(a)-C], there is interest in quantifying the contribution of Lp(a)-C to LDL-C given implications for risk assessment, diagnosis, and treatment. Estimating Lp(a)-C is subject to inaccuracies; measuring Lp(a) particle number [Lp(a)-P] is more accurate. Objective: To capture how Lp(a) contributes to the atherogenic lipoprotein burden, we demonstrate a particle-based approach using readily available measures of Lp(a)-P and apolipoprotein B (apoB). Methods: Using the Very Large Database of Lipids (VLDbL), we compared Lp(a)-P (nmol/L) with all atherogenic particles (non-HDL-P). Non-HDL-P was calculated by converting apoB mass to molar concentration using the preserved molecular weight of apoB100 (512 kg/mol). We calculated the percentage of Lp(a)-P relative to non-HDL-P by Lp(a)-P deciles and stratified across sex, age, triglycerides, LDL-C, and non-HDL-C. Results: 158,260 patients from the VLDbL were included. The fraction Lp(a)-P/non-HDL-P increased with rising Lp(a)-P. Lp(a)-P comprised on average 3% of atherogenic particles among the study population and 15% at the highest Lp(a)-P decile. Findings were similar when stratified by sex. When stratified by age, Lp(a)-P/non-HDL-P was highest among the youngest and oldest patients. Lp(a)-P/non-HDL-P decreased at higher levels of triglycerides and LDL-C owing to larger contributions from VLDL and LDL. Conclusions: We demonstrate a particle-based approach to quantify the contribution of Lp(a) to total atherogenic particle burden using validated and widely available laboratory assays. Future research applying this method could define clinically meaningful thresholds and inform use in risk assessment and management.

P1521In a 36-week placebo-controlled phase 2 trial in patients with non-alcoholic steatohepatitis (NASH), treatment with MGL-3196 (resmetirom) significantly reduces atherogenic lipoprotein particles

Background MGL-3196 is a liver-directed, orally active, highly selective thyroid hormone receptor-β agonist being developed for the treatment of non-alcoholic steatohepatitis (NASH). In a 36-week Phase 2 NASH study, MGL-3196 treatment compared with placebo (PbO) resulted in significant reductions in hepatic fat, liver enzymes, NASH on liver biopsy, and atherogenic lipids including low-density lipoprotein cholesterol (LDL-C) and triglycerides. Most NASH patients die of cardiovascular disease (CVD), and, in NASH patients, CV risk correlates better with LDL particle than LDL-C levels. Purpose To determine the effects of MGL-3196 on lipoprotein particle concentrations in patients with NASH. Methods MGL-3196–05 (NCT02912260) is a 36-week multicenter, randomized, double-blind, placebo controlled study of NASH patients assessed with serial liver imaging and liver biopsies. Patients received 2:1 MGL-3196 80 mg (blinded ± 20 mg dose adjustment possible at Week 4 based on Week 2 pharmacokinetic data) or placebo once daily, for 36 weeks. Lipoprotein particle concentrations were assessed in fasting blood samples at baseline and Week (Wk) 36. Results As shown (Table), MGL-3196 significantly reduced the level of lipoprotein particles, with greater reductions in patients with baseline (BL) LDL-C ≥100 mg/dL and the patient group with higher MGL-3196 exposures (High exp). Lipoprotein particles Particles (by NMR) (nmol/L) Time Point Placebo, n=34 MGL-3196 (all), n=73 MGL-3196 BL LDL-C ≥100 mg/dL, n=44; High Exp, n=25 (PbO BL ≥100 mg/dL, n=23 mean data not shown) Total LDL, mean (SD) BL 1234 (276) 1275 (328) 1443 (290) 1407 (267) Wk 36 1251 (323) 1045 (264) 1155 (248) 1090 (216) % change from BL vs PbO (SE), p value −19.6 (4.2), <0.0001 −19.8 (5.6), 0.0008 −22.8 (6.3), 0.0006 Small LDL, mean (SD) BL 746 (295) 835 (294) 887 (329) 916 (314) Wk 36 749 (343) 641 (207) 641 (234) 618 (149) % change from BL vs PbO (SE), p value −27.7 (8.9), 0.002 −34.3 (13.1), 0.01 −39.4 (14.7), 0.009 Total VLDL and Chylomicron, mean (SD) BL 56.8 (23.9) 55.9 (22.9) 61.4 (24.5) 66.0 (24.8) Wk 36 58.8 (24.4) 46.0 (21.1) 47.6 (22.9) 47.4 (23.1) % change from BL vs PbO (SE), p value −22.7 (6.9), 0.001 −27.2 (7.5), 0.0006 −34.7 (8.3), <0.0001 Large VLDL and Chylomicron, mean (SD) BL 6.3 (4.3) 8.7 (5.8) 8.9 (6.1) 10.2 (6.8) Wk 36 7.2 (4.5) 6.6 (3.9) 6.7 (4.1) 7.2 (4.7) % change from BL vs PBO (SE), p value −52.5 (11.8), <0.0001 −65.6 (15.5), <0.0001 −71.3 (17.4), 0.0001 BL, baseline; High exp, high MGL-3196 exposure based on % increase from baseline in sex hormone binding globulin, BL LDL-C ≥100, a prespecified group. Conclusions MGL-3196 significantly reduced atherogenic lipoprotein particles, particularly in NASH patients with greater BL hypercholesterolemia. These findings are consistent with a potentially beneficial effect of MGL-3196 on the CV risk profile in NASH patients.

P4667Loss of function in PCSK9, atherogenic lipoprotein concentrations, and calcific aortic valve stenosis

Background Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition reduces plasma concentrations of most atherogenic lipoproteins such as low-density lipoprotein cholesterol (LDL-C), apolipoprotein B (apoB) and lipoprotein(a) [Lp(a)]. Atherogenic lipoprotein concentrations have also been linked with calcific aortic valve stenosis (CAVS). Purpose 1) To determine the association between genetic variants in PCSK9 and lipoprotein-lipid levels, 2) to determine whether loss of function (LOF) in PCSK9 is associated with CAVS and 3) to evaluate if PCSK9 could be implicated in aortic valve interstitial cells (VICs) calcification. Methods We built a weighted genetic risk score (wGRS) using 10 single nucleotide polymorphisms at the PCSK9 locus associated with LDL-C in the Global Lipids Genetics Consortium. We determined the association between the wGRS and LDL-C, apoB and Lp(a)] in 9692 participants of the EPIC-Norfolk study using linear regression. We investigated the association between the LOF PCSK9 R46L variant and CAVS risk in a meta-analysis of published (three Copenhagen studies, 1463 cases and 101,620 controls) and unpublished studies (UK Biobank, 1350 cases and 349,043 controls, Malmö Diet and Cancer study, 682 cases and 5963 controls and EPIC-Norfolk, 508 cases and 20,421 controls) prospective, population-based studies using logistic regression adjusted for age and sex. We evaluated PCSK9 expression and localization in explanted aortic valves by capillary Western blot and immunohistochemistry in patients with and without CAVS. Von Kossa staining was used to visualize aortic leaflet calcium deposits. We also assessed VICs calcification potential under oxidative stress condition. Results In EPIC-Norfolk, the wGRS was significantly associated with TC, LDL-C, and apoB (all p<0.0001), but not with VLDL-C, HDL-C, triglycerides apoA-I, or Lp(a). Carriers of the R46L variant were at lower CAVS risk (odds ratio=0.71 (95% CI, 0.57–0.88, p<0.001)). Aortic valves of patients with aortic sclerosis (n=12) and CAVS (n=8) presented elevated PCSK9 levels (log2 fold change [FC]=+28.6±5.1, p=0.008 and FC=+39.3±15.2, p=0.02, respectively) compared to controls (n=4).In calcified leaflets, PCSK9 expression co-localized with calcium deposits. PCSK9 expression in VICs was induced by oxidative stress (FC=+2.3±0.4, p=0.02), and subsequent increment in calcification potential was observed. Conclusion PCSK9LOF variants are associated with lifelong reductions in non-Lp(a) apoB-containing lipoprotein levels and a lower risk of coronary artery disease and CAVS. PCSK9 is abundant in fibrotic and calcified aortic leaflets. Oxidative stress increases PCSK9 expression in VICs. These results support randomized clinical trials of PCSK9 inhibition in the prevention of CAVS.