Abstract 17827: Klf5 Mediates Glucose-driven Changes ofCcardiac Pparα in Diabetes

Abstract

Krüppel-like factors (KLF) affect metabolism. Lipopolysaccharide-induced sepsis reduced cardiac PPARα and increased KLF5 (8-fold) more than any cardiac KLF isoform detected by whole genome microarray analysis. In silico analysis of ppara gene promoter predicted two KLF5 binding sites that overlap with c-Jun (AP-1) binding sites: -792/-772 bp and -719/-698 bp. Infection of a mouse cardiomyocyte cell line (HL-1) with adenovirus expressing constitutively active c-Jun reduced, while Ad-KLF5 increased PPARα mRNA in a dose-dependent manner. Chromatin immunoprecipitation (ChIP) showed that c-Jun binds both -792/-772 bp and -719/-698 on ppara promoter while KLF5 binds on -792/-772 bp. ChIP on LPS-treated HL-1 cells showed that c-Jun binding on -792/-772 bp prohibits KLF5 binding. We generated a cardiomyocyte-specific KLF5 knockout mouse (αMHC-KLF5-/-), which had 50% normal cardiac function. Cardiomyocyte-specific KLF5 ablation reduced PPARα (50%) and several fatty acid metabolism-associated genes such as CD36 (40%), LpL (20%), PGC1α (45%), AOX (28%) and Cpt1 (45%). As PPARα regulates cardiac fatty acid metabolism, we tested whether cardiac KLF5 is modulated in diabetes, when cardiac PPARα and lipid changes occur. I.p. injection of streptozotocin (STZ) in C57BL/6 mice increased plasma glucose (2.9-fold) and reduced cardiac KLF5 and PPARα gene expression; similar to STZ-treated rats but unlike what had been found in a different mouse strain (C57BL/6 x DBA2) treated with STZ. Treatment of HL-1 cells with increased glucose-containing medium (1 mg/ml) reduced KLF5 (80%) and PPARα (65%), as well as fatty acid metabolism markers, such as AOX (85%), Cpt1β (70%), LCAD (80%) and VLCAD (85%). On the other hand GLUT1 and GLUT4 were increased (30% and 20%) and PDK4 was reduced (65%) indicating increased glucose utilization. A model of non-insulin dependent hyperglycemia (ob/ob mice) had reduced cardiac KLF5 (60%) and PPARα (65%). Correction of hyperglycemia in STZ-treated C57BL/6 mice by pharmacological (dapagliflozin) or antisense oligonucleotide inhibition of kidney’s sodium glucose transporter 2 (SGLT2), restored KLF5 and PPARα gene expression. Thus, KLF5 is a transcriptional regulator of cardiac PPARα that is driven by changes in plasma glucose levels