Biomarkers for understanding the pathophysiology and risk assessment in subclinical and manifest coronary artery disease
Authors: Cederström Sofia 
Published: January 2025

<p dir="ltr"><b>Introduction</b></p><p dir="ltr">Coronary artery disease (CAD) is a progressive disease, and mechanisms of coronary atherosclerosis and plaque rupture are incompletely covered. This thesis aimed to examine biomarkers at different stages of CAD including evaluation of: (I) the relationships between high-sensitivity C-reactive protein (hsCRP) and coronary atherosclerosis, (II) the associations between protein and metabolite biomarkers and subclinical CAD in two groups with different cardiovascular disease (CVD) risk, (III) ST-elevation myocardial infarction (STEMI) mechanisms using gene expression (GE) techniques without the influence of the acute inflammatory response during the event and (IV) the importance of inflammatory biomarkers sampled in a stable phase for prediction of long-term CVD events in young MI patients.</p><p dir="ltr"><b>Methods and results</b></p><p dir="ltr">In study I, associations between hsCRP and coronary computed tomography angiography (CCTA)-detected CAD were examined in 25,408 participants from the Swedish CArdioPulmonary bioImage Study (SCAPIS). HsCRP >2.3 mg/L, compared to hsCRP <0.7 mg/L, was associated with presence of coronary atherosclerosis (odds ratio (OR) 1.15, 95% confidence interval (CI) 1.07-1.24) in a model adjusted for CVD risk factors. Results were attenuated when body mass index was added to the model, but hsCRP was still associated with noncalcified plaques (OR 1.16, 95% CI 1.02-1.32).</p><p dir="ltr">In study II, the relative importance of 409 biomarkers (184 proteins and 225 metabolites) for prediction of subclinical CAD, was evaluated by machine learning, random forest (RF), models. Two study groups from SCAPIS with different CVD risk were included: one low-risk group with a systematic coronary risk evaluation 2 (SCORE2) below 5% (n=2,063) and one high-risk group with SCORE2 above 7.5% (n=576). In the low-risk group, branched-chain amino acids (BCAAs) were predictive of subclinical CAD, while high-density lipoprotein (HDL) metabolites, except for phospholipids (PL), were protective biomarkers. In the high-risk group, proteins involved in inflammatory processes were negatively associated with subclinical CAD, while HDL metabolites did not have any protective effect. Renin and Matrix metalloproteinase (MMP)-12 were identified as risk markers of subclinical atherosclerosis in both CVD risk groups.</p><p dir="ltr">In study III, mixed linear models were used to examine GE in 51 STEMI patients sampled at three time points, in the acute phase before primary percutaneous coronary intervention (P1), after 24-48 hours (P2) and after three months (P3). Up- or downregulated genes between P1 and P2 were assumed to reflect the acute inflammatory response and therefore excluded. Seven genes had a differential GE at P1 compared to P3: ATP-binding cassette, sub-family G (WHITE), member 1 (ABCG1), RAB20, member RAS oncogene family (RAB20) and Transmembrane protein 2 (TMEM2) were upregulated, whereas four genes were downregulated: activin A receptor, type I (ACVR1), nuclear factor of activated T cells, cytoplasmic, calcineurin-dependent 2 interacting protein (NFATC2IP), Sad1 and UNC84 domain containing 1 (SUN1) and tetratricopeptide repeat domain 9C (TTC9C).</p><p dir="ltr">In study IV, nine inflammatory biomarkers (hsCRP, interleukin (IL)-6, IL-18, monocyte chemoattractant protein-1, MMP-1, MMP-3, MMP-9, serum amyloid A and tumor necrosis factor-alpha) were sampled in 382 MI patients below 60 years of age between 1996 and 2000. RF models were used to analyse the relative importance of biomarkers for prediction of CVD events after 20 years of follow-up. IL-6 was the most important biomarker for prediction of the composite endpoint of all-cause death, hospitalisation for MI or heart failure (HF) (hazard ratio (HR) 1.91, 95% CI 1.31-2.79), all-cause death (HR 2.38, 95% CI 1.42- 3.98) and HF hospitalisation (HR 2.70, 95% CI 1.32-5.50) after adjustment for CVD risk factors. IL-18 was the most important biomarker for MI hospitalisation.</p><p dir="ltr"><b>Conclusions</b></p><p dir="ltr">HsCRP was not associated with CCTA-detected coronary atherosclerosis in a large population-based cohort, although there was a weak association between hsCRP and noncalcified plaques, which are more prone to rupture. Different biomarker patterns were associated with subclinical CAD in a low versus a high CVD risk group. Increased BCAAs were associated with subclinical CAD, while HDL metabolites, with the exception of PL, were associated with less subclinical CAD in low-, but not in high-risk individuals. Renin and MMP-12 were associated with subclinical CAD regardless of the baseline CVD risk. ABCG1, involved in reversed cholesterol transport, was upregulated in the acute phase in STEMI patients and may be essential in initiation of an MI. IL-6 was the most important predictor of long-term CVD outcome, when nine inflammatory biomarkers were sampled in a stable clinical phase in young MI patients.</p><h3>List of scientific papers</h3><p dir="ltr">The present thesis is based on the following studies, which will be referred to by their Roman numerals.</p><p dir="ltr">I. <b>Sofia Cederström</b>, Pia Lundman, Joakim Alfredsson, Emil Hagström, Annica Ravn-Fischer, Stefan Söderberg, Troels Yndigegn, Per Tornvall, Tomas Jernberg. Association between high-sensitivity C-reactive protein and coronary atherosclerosis in a general middle-aged population. Scientific Reports. 2023;13(1):12171. <a href="https://doi.org/10.1038/s41598-023-39051-3" rel="noreferrer" target="_blank">https://doi.org/10.1038/s41598-023-39051-3</a></p><p dir="ltr">II. <b>Sofia Cederström</b>, Yunzhang Wang, Pia Lundman, Joakim Alfredsson, Göran Bergström, Gunnar Engström, Lars Lind, Stefan Söderberg, Per Tornvall, Tomas Jernberg. Different plasma biomarker patterns associated with coronary atherosclerosis in low- versus high-risk individuals. [Submitted]</p><p dir="ltr">III. <b>Sofia Cederström</b>, Pia Lundman, Lasse Folkersen, Gabrielle Paulsson-Berne, Glykeria Karadimou, Per Eriksson, Kenneth Caidahl, Anders Gabrielsen, Tomas Jernberg, Jonas Persson, Per Tornvall. New candidate genes for ST-elevation myocardial infarction. Journal of Internal Medicine. 2020;287(1):66-77. <a href="https://doi.org/10.1111/joim.12976" rel="noreferrer" target="_blank">https://doi.org/10.1111/joim.12976</a></p><p dir="ltr">IV. <b>Sofia Cederström</b>, Tomas Jernberg, Ann Samnegård, Fredrik Johansson, Angela Silveira, Per Tornvall, Pia Lundman. Inflammatory biomarkers and long-term outcome in young patients three months after a first myocardial infarction. Cytokine. 2024;182:156696. <a href="https://doi.org/10.1016/j.cyto.2024.156696" rel="noreferrer noopener" target="_blank">https://doi.org/10.1016/j.cyto.2024.156696</a></p>