Abstract 9807: Sirt1 Ameliorates High Fat Diet-Induced Diastolic Heart Failure

Abstract

Approximately half of heart failure patients are diagnosed with diastolic heart failure. Sirt1 is a protein deacetylase that inhibits cardiac fibrosis and diastolic dysfunction. We investigated how Sirt1 inhibits cardiac fibrosis and diastolic dysfunction using a high fat diet (HFD)-induced obesity model with cardiac-specific Sirt1 knockout (Sirt1cKO) and overexpression (Sirt1cTG) mice. In addition to diastolic dysfunction, HFD (3 months)-induced cardiac fibrosis was promoted in Sirt1cKO (Relative fibrosis: wild-type mice (WT) Normal Diet (ND): 1.0; WT HFD: 2.4; Sirt1cKO ND: 1.2; Sirt1cKO HFD: 6.2*, p<0.05 vs WT HFD) but inhibited in Sirt1cTG mice. Cardiomyocyte-specific gene expression analysis with Ribo-tag mice revealed that TGFβ1 mRNA is increased in Sirt1cKO mice during HFD consumption (relative TGFβ1 mRNA: WT ND: 1.0; WT HFD: 1.3; Sirt1cKO ND: 1.1; Sirt1cKO HFD: 1.9*, p<0.05 vs WT HFD). A TGFβ1 receptor inhibitor inhibited HFD-induced cardiac fibrosis and diastolic dysfunction in Sirt1cKO mice, suggesting that loss of Sirt1 promotes cardiac fibrosis and diastolic dysfunction partly though TGFβ1. ChIP-sequencing revealed that Sirt1 localized to the TGFβ1 promoter, overlapping with Smad binding elements. Co-immunoprecipitation assays showed that Sirt1 bound to Smad3 in the heart. Reporter gene assays showed that Sirt1 inhibited the TGFβ1 promoter activity through Smad3 (Relative activity: control 1.0; Sirt1 overexpression: 0.35; Sirt1 overexpression with Smad3 knockdown: 0.89*, p<0.05 vs Sirt1). DNA binding assays with the TGFβ1 promoter region showed that Sirt1 binds to the TGFβ1 promoter, which was inhibited by Smad3 knockdown (relative binding to TGFβ1 promoter: Control: 1.0; Smad3 knockdown: 0.45*, p<0.05 vs Control). Taken together, the data show that Sirt1 binds to the TGFβ1 promoter through Smad3, thereby suppressing TGFβ1 expression and subsequent cardiac fibrosis and diastolic dysfunction.