Exendin-4 Attenuates Remodeling in the Remote Myocardium of Rats After an Acute Myocardial Infarction by Activating β-Arrestin-2, Protein Phosphatase 2A, and Glycogen Synthase Kinase-3 and Inhibiting β-Catenin

Purpose This study tested if the protective anti-remodeling effect of GLP-1 agonist Exendin-4 after an acute myocardial infarction (MI) in rats involves inhibition of the Wnt1/beta-catenin signaling pathway. Methods Rats were divided into sham, sham + Exendin-4 (10 mu g/day, i.p), MI, and MI + Exendin-4. MI was introduced to rats by permanent left anterior descending coronary artery (LAD) ligation. Results On day 7 post-infraction, MI rats showed LV dysfunction with higher serum levels of cardiac markers. Their remote myocardia showed increased mRNA and protein levels of collagen I/III with higher levels of reactive oxygen species (ROS) and inflammatory cytokines, as well as protein levels of Wnt1, phospho-Akt, transforming growth factor (TGF-beta 1), Smad, phospho-Smad3, alpha-SMA, caspase-3, and Bax. They also showed higher protein levels of phospho-glycogen synthase kinase-3 beta (p-GSK3 beta), as well as total, phosphorylated, and nuclear beta-catenin with a concomitant decrease in the levels of cyclic adenosine monophosphate (cAMP), mRNA of manganese superoxide dismutase (MnSOD), and protein levels of Bcl-2, beta-arrestin-2, and protein phosphatase-2 (PP2A). Administration of Exendin-4 to MI rats reduced the infarct size and reversed the aforementioned signaling molecules without altering protein levels of TGF-1 beta and Wnt1 or Akt activation. Interestingly, Exendin-4 increased mRNA levels of MnSOD, protein levels of beta-arrestin-2 and PP2A, and beta-catenin phosphorylation but reduced the phosphorylation of GSK3 beta and Smad3, and total beta-catenin levels in the LV of control rats. Conclusion Exendin-4 inhibits the remodeling in the remote myocardium of rats following acute MI by attenuating beta-catenin activation and activating beta-arrestin-2, PP2A, and GSK3 beta.