Cardiac-specific adipose triglyceride lipase overexpression protects from cardiac steatosis and dilated cardiomyopathy following diet-induced obesity.

BACKGROUND

Although obesity increases the risk of developing cardiomyopathy, the mechanisms underlying the development of this cardiomyopathy are incompletely understood. As obesity is also associated with increased intramyocardial triacylglycerol (TAG) deposition, also referred to as cardiac steatosis, we hypothesized that alterations in myocardial TAG metabolism and excess TAG accumulation contribute to obesity-induced cardiomyopathy.

OBJECTIVE

To test if increased TAG catabolism could ameliorate obesity-induced cardiac steatosis and dysfunction, we utilized wild-type (WT) mice and mice with cardiomyocyte-specific overexpression of adipose triglyceride lipase (MHC-ATGL mice), which regulates cardiac TAG hydrolysis. WT and MHC-ATGL mice were fed either regular chow (13.5 kcal% fat) or high fat-high sucrose (HFHS; 45 kcal% fat and 17 kcal% sucrose) diet for 16 weeks to induce obesity and mice were subsequently studied at the physiological, biochemical and molecular level.

RESULTS

Obese MHC-ATGL mice were protected from increased intramyocardial TAG accumulation, despite similar increases in body weight and systemic insulin resistance as obese WT mice. Importantly, analysis of in vivo cardiac function using transthoracic echocardiography showed that ATGL overexpression protected from obesity-induced systolic and diastolic dysfunction and ventricular dilatation. Ex vivo working heart perfusions revealed impaired cardiac glucose oxidation following obesity in both WT and MHC-ATGL mice, which was consistent with similar impaired cardiac insulin signaling between genotypes. However, hearts from obese MHC-ATGL mice exhibited reduced reliance on palmitate oxidation when compared with the obese WT, which was accompanied by decreased expression of proteins involved in fatty acid uptake, storage and oxidation in MHC-ATGL hearts.

CONCLUSIONS

These findings suggest that cardiomyocyte-specific ATGL overexpression was sufficient to prevent cardiac steatosis and decrease fatty acid utilization following HFHS diet feeding, leading to protection against obesity-induced cardiac dysfunction.