Abstract 13458: Caspase Recruitment Domain-Containing Protein 9 Deficiency Mitigates Obesity-Induced Cardiac Dysfunction

Obesity has become an epidemic and is associated with cardiovascular anomalies. Obesity-induced low-grade chronic inflammation and macrophage infiltration into the heart plays a critical role in the development of cardiac dysfunction. Because the adaptor protein caspase recruitment domain-containing protein 9 (CARD9) regulates the innate immunity in macrophages via activation of pro-inflammatory cytokines, we hypothesized that CARD9 mediates chronic inflammation and plays a detrimental role in obesity-associated cardiac dysfunction. Male C57BL/6 wild-type (WT) and CARD9 knockout (CARD9-/-) mice were fed normal chow (ND, 12% fat) or a Western diet (WD, 45% fat) for 5 months starting at 4 weeks of age. At the end of 5-month WD feeding, cardiac geometry and function were evaluated using echocardiography. Immunofluorescence assay was performed to detect macrophage infiltration in the heart. Heart tissue homogenates, plasma, and supernatants from cultured macrophages were collected to measure the activities of pro-inflammatory cytokines by ELISA kits. Western immunoblotting analyses were performed on isolated peritoneal macrophages and heart tissue to dissect the pro-inflammatory signaling pathways. WD feeding induced insulin resistance and glucose intolerance in the WT mice and the effects were attenuated in the CARD9-/- mice. Myocardial fractional shortening and ejection fraction were significantly compromised in the WD-fed WT mice and CARD9 knockout preserved cardiac function. CARD9 knockout also significantly decreased the number of infiltrated macrophages in the heart. In addition, myocardium-, plasma- and macrophage-derived cytokines IL-6, IL-1β and TNFα were attenuated in the CARD9-/- mice compared to the WT mice. WD feeding resulted in increased protein phosphorylation levels of p38 MAPK in the heart and macrophages which were suppressed in the CARD9-/- mice. Taken together, these results suggest that CARD9 knockout ameliorates obesity-induced cardiac dysfunction, potentially through reduction of macrophage infiltration and suppression of p38 MAPK phosphorylation in the heart.