👤 Anne-Marie Lund Winther

Risk factor-weighted clinical likelihood (RF-CL) estimates the probability of obstructive coronary artery disease (CAD) in patients without known CAD. We examined whether adding lipoprotein(a) [Lp(a)] measurements to the RF-CL model improves predictions of obstructive CAD. In a derivation cohort (N = 4262; 54% male; mean age 58 years), the prevalence of obstructive CAD at invasive angiography with fractional flow reserve was assessed by Lp(a)-strata. On the basis of initial results, an Lp(a)-adjusted model (RF-CLLp(a)) was developed: RF-CL was multiplied by 1.5 in patients with elevated Lp(a) (≥125 nmol/L) and otherwise unchanged. Discrimination, calibration, and reclassification were compared. Findings were validated in an external validation cohort (N = 1595; 49% male; mean age 60 years) using a comparative endpoint; significant stenosis at invasive angiography or coronary computed tomography.In the derivation cohort, 473 patients (11.1%) had obstructive CAD; in the validation cohort, 206 patients (12.9%) had significant stenosis. The relative risk in patients with elevated Lp(a) was 1.51 [95% confidence interval (CI) 1.23-1.86] and 1.19 (95% CI 0.88-1.60) in the derivation and validation cohort, respectively. In the derivation cohort, the RF-CLLp(a) model showed a higher area under the receiver operating curve than the RF-CL model [0.743 (standard error 0.011) vs. 0.740 (0.013)] and better calibration in patients with elevated Lp(a). Reclassification from RF-CL to RF-CLLp(a) improved likelihood stratification in the derivation cohort but not in the validation cohort. Adding elevated Lp(a) as a risk factor to the RF-CL model improves accuracy of obstructive CAD in patients with high Lp(a). Show less

High plasma lipoprotein(a) [Lp(a)] levels are associated with accelerated atherosclerosis and subsequent atherosclerotic cardiovascular disease (ASCVD), potentially through enhanced inflammatory signaling of monocytes. Given that monocytes are major players in ASCVD risk and the role of epigenetic changes in regulating their responsiveness, we propose that investigating changes in chromatin accessibility could reveal the underlying mechanisms of enhanced monocyte inflammation. In this observational case-control study, we collected blood from subjects with low (<25 nmol/L) and elevated (>350 nmol/L) plasma Lp(a) with and without a history of ASCVD, matched for age and sex. A total of 60 subjects were included in the study, comprising 60% males and a mean age of 62.8 ± 7.8 years. We assessed gene expression and chromatin accessibility of fluorescence-activated cell sorting (FACS)-sorted classical monocytes using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and bulk assay for transposase-accessible chromatin (ATAC)-sequencing and analyzed plasma cytokine levels. Subjects with high plasma Lp(a) showed significantly increased gene expression of IFIT3. At the plasma level, subjects with high Lp(a) without ASCVD were distinguished by higher concentrations of chemokine C-X-C motif ligand 10 (CXCL10). While these results are consistent with previous research demonstrating increased interferon-γ signaling in monocytes of individuals with elevated Lp(a), we did not detect differences in chromatin accessibility of monocytes between subjects with high or low Lp(a), irrespective of ASCVD status. While subjects with high Lp(a) levels showed enhanced monocyte inflammation, no differences in chromatin accessibility were detected. This suggests that the pro-inflammatory signature of Lp(a) and ASCVD on monocytes is regulated at a level other than chromatin accessibility. Show less

This study investigates the impact of perioperative tourniquet on skeletal muscle cells during total knee arthroplasty (TKA) and its effects on the gene expression of apoptotic, inflammatory, and angiogenic pathways. The randomized controlled trial included 44 patients undergoing TKA. The patients were randomized to undergo surgery with (n = 23) or without (n = 21) tourniquet. The tourniquet was inflated before skin incision and deflated before wound closure in the tourniquet group. Biopsies from the lateral vastus muscle were obtained from both groups before wound closure and 8 weeks after surgery. The messenger ribonucleic acid (mRNA) expression and protein levels of angiopoietin-like 4 (ANGPTL4), Hypoxia-inducible Factor 1α, and Vascular Endothelial Growth Factor Alpha (VEGF-A) in the biopsies were examined by reverse transcription-quantitative polymerase chain reaction and tissue microarray, respectively. Differences in mean values (ΔC Show less

The lipolytic processing of triglyceride-rich lipoproteins (TRLs) by lipoprotein lipase (LPL) is crucial for the delivery of dietary lipids to the heart, skeletal muscle, and adipose tissue. The processing of TRLs by LPL is regulated in a tissue-specific manner by a complex interplay between activators and inhibitors. Angiopoietin-like protein 4 (ANGPTL4) inhibits LPL by reducing its thermal stability and catalyzing the irreversible unfolding of LPL's α/β-hydrolase domain. We previously mapped the ANGPTL4 binding site on LPL and defined the downstream unfolding events resulting in LPL inactivation. The binding of LPL to glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 protects against LPL unfolding. The binding site on LPL for an activating cofactor, apolipoprotein C2 (APOC2), and the mechanisms by which APOC2 activates LPL have been unclear and controversial. Using hydrogen-deuterium exchange/mass spectrometry, we now show that APOC2's C-terminal α-helix binds to regions of LPL surrounding the catalytic pocket. Remarkably, APOC2's binding site on LPL overlaps with that for ANGPTL4, but their effects on LPL conformation are distinct. In contrast to ANGPTL4, APOC2 increases the thermal stability of LPL and protects it from unfolding. Also, the regions of LPL that anchor the lid are stabilized by APOC2 but destabilized by ANGPTL4, providing a plausible explanation for why APOC2 is an activator of LPL, while ANGPTL4 is an inhibitor. Our studies provide fresh insights into the molecular mechanisms by which APOC2 binds and stabilizes LPL-and properties that we suspect are relevant to the conformational gating of LPL's active site. Show less

The complex between lipoprotein lipase (LPL) and its endothelial receptor (GPIHBP1) is responsible for the lipolytic processing of triglyceride-rich lipoproteins (TRLs) along the capillary lumen, a physiologic process that releases lipid nutrients for vital organs such as heart and skeletal muscle. LPL activity is regulated in a tissue-specific manner by endogenous inhibitors (angiopoietin-like [ANGPTL] proteins 3, 4, and 8), but the molecular mechanisms are incompletely understood. ANGPTL4 catalyzes the inactivation of LPL monomers by triggering the irreversible unfolding of LPL's α/β-hydrolase domain. Here, we show that this unfolding is initiated by the binding of ANGPTL4 to sequences near LPL's catalytic site, including β2, β3-α3, and the lid. Using pulse-labeling hydrogen‒deuterium exchange mass spectrometry, we found that ANGPTL4 binding initiates conformational changes that are nucleated on β3-α3 and progress to β5 and β4-α4, ultimately leading to the irreversible unfolding of regions that form LPL's catalytic pocket. LPL unfolding is context dependent and varies with the thermal stability of LPL's α/β-hydrolase domain ( Show less

Lipopolysaccharide (LPS) decreases hepatic CETP (cholesteryl ester transfer protein) expression albeit that the underlying mechanism is disputed. We recently showed that plasma CETP is mainly derived from Kupffer cells (KCs). In this study, we investigated the role of KC subsets in the mechanism by which LPS reduces CETP expression. In CETP-transgenic mice, LPS markedly decreased hepatic Hepatic expression of CETP is exclusively confined to the resting KC subset (ie, F4/80 Show less