Epicardial fat, cardiac dimensions, and low-grade inflammation in young adult monozygotic twins discordant for obesity.

Epicardial fat with its close proximity to coronary arteries has been suggested to be a significant predictor of cardiovascular disease. We studied the relations among acquired obesity, low-grade inflammation, and genetic factors in the accumulation of epicardial fat. A rare sample (n = 15) of healthy monozygotic (MZ) twin pairs discordant for obesity (intrapair difference in body mass index ≥3 kg/m(2)) and 9 concordant MZ pairs 23 to 33 years old were examined for cardiac structure, function, epicardial fat thickness (echocardiography), abdominal subcutaneous tissue, and visceral adipose tissue (VAT), liver fat (magnetic resonance imaging/spectroscopy), and serum high-sensitivity C-reactive protein. In the entire sample, MZ cotwins were remarkably similar in most echocardiographic measurements including epicardial fat (intraclass correlation 0.63, p = 0.0004). However, in the discordant pairs, the obese cotwins (16.5 kg, 23% heavier) had 26% more epicardial fat (p = 0.0029) than nonobese cotwins. They also had significantly larger atrial and left ventricular dimensions. Epicardial fat correlated with VAT (r = 0.49, p = 0.02) in individual twins and when using intrapair differences of measurements within pairs (r = 0.39, p = 0.06). In multiple regression analyses including abdominal subcutaneous tissue, VAT, and liver fat, high-sensitivity C-reactive protein was the only factor that remained significantly associated with epicardial fat in individual twins and within pairs. In conclusion, subjects who share the same genes seem to have similar cardiac dimensions. However, acquired obesity increases epicardial fat independent of genetic factors. The close relation between epicardial fat and low-grade inflammation is likely to contribute to the development of cardiovascular disease in obesity.