TGFB1 and obesity due to melanocortin 4 receptor deficiency: - Sustained obesity (vs. lean): ↑ LA pressure, ↑ inflammation, ↑ atrial TGF-β, ↑ endothelin-B receptor expression, ↑ atrial fibrosis, ↑ epicardial fat infiltration, ↓ ERP, ↓ Cx43 and ↓ CV, ↑ CV heterogeneity, ↑ duration of induced AF- 30% weight loss (vs. obese) had ↓ LA pressure, ↓ inflammation, ↓ endothelin-B receptor expression, ↓ atrial fibrosis, ↑ ERP, ↑ Cx43 and ↑ CV, ↓ CV heterogeneity, ↓ duration of induced AF