Abstract 210: PPARγ Activation Prevents Cardiac Dysfunction in Sepsis via Stimulation of Energy Production

Septic cardiac dysfunction has been attributed to either inflammation or suppression of fatty acid oxidation (FAO). We hypothesized that energy deprivation accounts for cardiac dysfunction in lipopolysaccharide (LPS)-induced sepsis. LPS compromised cardiac function, increased cardiac inflammatory markers (interleukin (IL)-1α, IL-6 and tumor necrosis factor (TNF)α) mRNA, and reduced FAO, ATP and FAO-related gene expression: Peroxisome proliferator activating receptor (PPAR)α, cluster of differentiation 36, lipoprotein lipase (LpL), fatty acid transport protein, carnitine palmitoyl-transferase (Cpt)1, PPARγ coactivator (PGC-1)α and PGC-1β in C57BL/6 mice. LC-MS/MS analysis of cardiac lipids showed that total ceramide, which might account for defective FAO and ceramide species were not modulated by LPS. Electron microscopy and ATPase6 DNA levels showed that LPS-treated animals had fewer and smaller cardiac mitochondria. PPARα agonist, WY-14643, did not prevent cardiac dysfunction and suppression of FAO-associated gene expression in LPS-treated mice. In contrast, LPS did not affect cardiac function of mice with cardiomyocyte-specific expression of PPARγ (αMHC-PPARg), although cardiac IL-1α, IL-6 and TNFα mRNA levels were increased. Despite a 77% reduction in PPARα, mRNA levels of FAO-associated genes, such as acyl-CoA oxidase, PGC-1α, PPARδ, Cpt1 increased over 10-fold as compared to saline-treated αMHC-PPARg mice. Similarly, cardiac FAO and ATP content was 2.6 and 5-fold greater in LPS-treated αMHC-PPARγ mice compared to LPS-treated C57BL/6 mice. Moreover, treatment of C57BL/6 mice with LPS and the PPARγ agonist, rosiglitazone, prevented cardiac dysfunction, increased FAO and relevant gene expression, while IL-1α, IL-6 and TNFα mRNA levels increased. Rosiglitazone prevented LPS-mediated reduction of PGC-1α and maintained the number and size of mitochondria. Treatment of C57BL/6 mice with a lethal dose of LPS (15 mg/kg) and repeated doses of rosiglitazone (30mg/kg/day for 72 hours) improved survival, mobility and overall appearance of LPS-treated mice. Thus, PPARγ activation stabilized cardiac energy and prevented cardiac dysfunction and mortality in septic animals despite cardiac inflammation and PPARα downregulation.