Abstract O-1: Klf5 Regulates Cardiac Pparα and Med13 and affects Cardiac Fatty Acid Metabolism And Obesity

Abstract

Krüppel-like factors (KLF) have been associated with metabolic phenotypes. Our study focused on the metabolic role of cardiac KLF5, as it showed the highest increase among all KLFs that were detected by whole genome microarrays of energy-starved hearts obtained from lipopolysaccharide (LPS)-treated mice. Analysis of ppara promoter indicated two potential binding sites for c-Jun (AP-1 sites), the transcriptional factor that is activated by LPS and reduces cardiac PPARα expression: −792/-772 bp and −719/-698 bp prior to the transcription initiation site. This analysis showed that both AP-1 sites overlap with potential KLF-binding sites. Adenovirus-mediated expression of constitutively active c-Jun in a mouse cardiomyocyte cell line (HL-1) reduced PPARα gene expression, while treatment with Ad-KLF5 had the opposite effect. Chromatin immunoprecipitation analysis (ChIP) showed that c-Jun binds both −792/-772 bp and −719/-698 sites of ppara promoter while KLF5 binds on −792/-772 bp. ChIP analysis also showed that LPS promotes c-Jun binding on −792/-772 bp, which prohibits occupation of this region by KLF5. A cardiomyocyte-specific KLF5 knockout mouse (αMHC-KLF5-/-) had normal cardiac function but reduced cardiac expression of PPARα (50%) and other fatty acid metabolism-associated genes such as CD36 (40%), LpL (20%), PGC1α (45%), AOX (28%) and Cpt1 (45%). High fat diet (HFD)-fed αMHC-KLF5-/- mice had a more profound body weight increase (35%) compared to HFD-fed WT mice (15%), as well as larger white adipocytes and brown adipocytes (H&E) and increased hepatic neutral lipid accumulation (Oil-Red-O). The obesogenic effect of cardiomyocyte-specific deletion of KLF5 resembles the phenotype of the αMHC-MED13-/- mice. We showed that KLF5 ablation reduced cardiac MED13 levels despite lack of changes in the expression levels of miR-208, a known regulator of MED13. Infection of HL-1 cells with Ad-KLF5 increased MED13 gene expression. ChIP identified a KLF5 binding site on med13 gene promoter region (-730/-714 bp). Thus, KLF5 regulates cardiac PPARα and MED13 and affects cardiac and systemic fatty acid metabolism and obesity, thus indicating KLF5 as a potential target for cardiac dysfunction associated with energetic complications, as well as for obesity