ABCA1 and ABCG1 DNA methylation in epicardial adipose tissue of patients with coronary artery disease

Abstract

Background: Recent studies have focused on the potential role of epicardial adipose tissue (EAT) in the development of coronary artery disease (CAD). ABCA1 and ABCG1 transporters regulate cell cholesterol content and reverse cholesterol transport. We aimed to determine whether DNA methylation and mRNA levels of the ABCA1 and ABCG1 genes in EAT and subcutaneous adipose tissue (SAT) were associated with CAD.

Methods: Paired EAT and SAT samples were collected from 82 patients undergoing elective cardiac surgery either for coronary artery bypass grafting (CAD group, N = 66) or valve surgery (NCAD group, N = 16). ABCA1 and ABCG1 mRNA levels in EAT and SAT samples were analyzed using real time polymerase chain reaction, ABCA1 protein levels in EAT samples were assessed by western blotting. ABCA1 and ABCG1 DNA methylation analysis was performed in 24 samples from the CAD group and 9 samples from the NCAD group via pyrosequencing.

Results: DNA methylation levels in the ABCA1 promoter and ABCG1 cg27243685 and cg06500161 CpG sites were higher in EAT samples from patients with CAD compared with NCAD (21.92% vs 10.81%, p = 0.003; 71.51% vs 68.42%, p = 0.024; 46.11% vs 37.79%, p = 0.016, respectively). In patients with CAD, ABCA1 and ABCG1 DNA methylation levels were higher in EAT than in SAT samples (p < 0.05). ABCA1 mRNA levels in EAT samples were reduced in the subgroup of patients with CAD and concomitant carotid artery disease or peripheral artery disease compared with the NCAD group (p = 0.024). ABCA1 protein levels in EAT samples tended to be lower in CAD patients than in the NCAD group (p = 0.053). DNA methylation levels at the ABCG1 cg27243685 site positively correlated with plasma triglyceride concentration (r = 0.510, p = 0.008), body mass index (r = 0.556, p = 0.013) and waist-to-hip ratio (r = 0.504, p = 0.012) in SAT samples.

Conclusion: CAD is associated with ABCA1 and ABCG1 DNA hypermethylation in EAT. CAD with concomitant carotid artery disease or peripheral artery disease is accompanied by decreased ABCA1 gene expression in EAT. DNA methylation levels at the ABCG1 cg27243685 locus in SAT are associated with hypertriglyceridemia and obesity.

Keywords: ABCA1 and ABCG1 transporters; Coronary artery disease; DNA methylation; Epicardial adipose tissue.

Fig. 1

A Mean ABCA1 DNA methylation levels in EAT and SAT; B ABCA1 mRNA levels in EAT and SAT samples from the CAD and NCAD groups; C ABCA1 mRNA levels in EAT and SAT samples from the subgroup of patients with CAD and concomitant carotid artery disease or peripheral artery disease compared to the NCAD group; D ABCA1 protein levels in EAT samples from the CAD and NCAD groups and representative western blot. The origin bands of WB are presented in Additional file 5. Note: The CAD+ subgroup includes patients with CAD and concomitant carotid artery disease or peripheral artery disease

Fig. 2

A ABCG1 cg06500161 locus methylation levels in EAT and SAT; B ABCG1 cg27243685 locus methylation levels in EAT and SAT; C ABCG1 mRNA levels in EAT and SAT samples from the CAD and NCAD groups; D ABCG1 mRNA levels in EAT and SAT samples from the subgroup of patients with CAD and concomitant carotid artery disease or peripheral artery disease compared to the NCAD group. Note: The CAD+ subgroup includes patients with CAD and concomitant carotid artery disease or peripheral artery disease

Fig. 3

Spearman’s correlation analysis of ABCG1 locus 1 methylation levels and (A, B) plasma triglyceride concentration; (C, D) body mass index; and (E, F) waist-to-hip ratio, if available