Epicardial adipose tissue: A new cardiovascular risk marker?

MiR-21-3p Inhibits Adipose Browning by Targeting FGFR1 and Aggravates Atrial Fibrosis in Diabetes

A relationship between excess epicardial adipose tissue (EAT) and the risk of atrial fibrillation (AF) has been reported. Browning of EAT may be a novel approach for the prevention or treatment of AF by attenuating atrial fibrosis. Previous studies have identified microRNA-21 (miR-21) as a regulatory factor in atrial fibrosis. The present study examined the role of different subtypes of miR-21 in adipose browning and atrial fibrosis under hyperglycemic conditions. Wild type and miR-21 knockout C57BL/6 mice were used to establish a diabetic model via intraperitoneal injection of streptozotocin. A coculture model of atrial fibroblasts and adipocytes was also established. We identified miR-21-3p as a key regulator that controls adipocyte browning and participates in atrial fibrosis under hyperglycemic conditions. Moreover, fibroblast growth factor receptor (FGFR) 1, a direct target of miR-21-3p, decreased in this setting and controlled adipose browning. Gain and loss-of-function experiments identified a regulatory pathway in adipocytes involving miR-21a-3p, FGFR1, FGF21, and PPARγ that regulated adipocyte browning and participated in hyperglycemia-induced atrial fibrosis. Modulation of this signaling pathway may provide a therapeutic option for the prevention and treatment of atrial fibrosis or AF in DM.

Epicardial adipose tissue: an emerging biomarker of cardiovascular complications in type 2 diabetes?

Type 2 diabetes (T2D) is associated with an increased risk of cardiovascular disease and heart failure, which highlights the need for improved understanding of factors contributing to the pathophysiology of these complications as they are the leading cause of mortality in T2D. Patients with T2D have high levels of epicardial adipose tissue (EAT). EAT is known to secrete inflammatory factors, lipid metabolites, and has been proposed to apply mechanical stress on the cardiac muscle that may accelerate atherosclerosis, cardiac remodeling, and heart failure. High levels of EAT in patients with T2D have been associated with atherosclerosis, diastolic dysfunction, and incident cardiovascular events, and this fat depot has been suggested as an important link coupling diabetes, obesity, and cardiovascular disease. Despite this, the predictive potential of EAT in general, and in patients with diabetes, is yet to be established, and, up until now, the clinical relevance of EAT is therefore limited. Should this link be established, importantly, studies show that this fat depot can be modified both by pharmacological and lifestyle interventions. In this review, we first introduce the role of adipose tissue in T2D and present mechanisms involved in the pathophysiology of EAT and pericardial adipose tissue (PAT) in general, and in patients with T2D. Next, we summarize the evidence that these fat depots are elevated in patients with T2D, and discuss whether they might drive the high cardiometabolic risk in patients with T2D. Finally, we discuss the clinical potential of cardiac adipose tissues, address means to target this depot, and briefly touch upon underlying mechanisms and future research questions.

Epicardial adipose tissue predicts incident cardiovascular disease and mortality in patients with type 2 diabetes

Background

Cardiac fat is a cardiovascular biomarker but its importance in patients with type 2 diabetes is not clear. The aim was to evaluate the predictive potential of epicardial (EAT), pericardial (PAT) and total cardiac (CAT) fat in type 2 diabetes and elucidate sex differences.

Methods

EAT and PAT were measured by echocardiography in 1030 patients with type 2 diabetes. Follow-up was performed through national registries. The end-point was the composite of incident cardiovascular disease (CVD) and all-cause mortality. Analyses were unadjusted (model 1), adjusted for age and sex (model 2), plus systolic blood pressure, body mass index (BMI), low-density lipoprotein (LDL), smoking, diabetes duration and glycated hemoglobin (HbA_1c) (model 3).

Results

Median follow-up was 4.7 years and 248 patients (191 men vs. 57 women) experienced the composite end-point. Patients with high EAT (> median level) had increased risk of the composite end-point in model 1 [Hazard ratio (HR): 1.46 (1.13; 1.88), p = 0.004], model 2 [HR: 1.31 (1.01; 1.69), p = 0.038], and borderline in model 3 [HR: 1.32 (0.99; 1.77), p = 0.058]. For men, but not women, high EAT was associated with a 41% increased risk of CVD and mortality in model 3 (p = 0.041). Net reclassification index improved when high EAT was added to model 3 (19.6%, p = 0.035). PAT or CAT were not associated with the end-point.

Conclusion

High levels of EAT were associated with the composite of incident CVD and mortality in patients with type 2 diabetes, particularly in men, after adjusting for CVD risk factors. EAT modestly improved risk prediction over CVD risk factors.