Abstract 441: Role of the Mitochondrial Translocator Protein (TSPO) in the Proarrhythmic Vulnerability of the Diabetic Heart

• Published in: Circulation research Vol. 119; no. suppl_1
• Main Authors: Hu, Jun, Koh, Won-Joon, Xie, Chaoqin, Akar, Fadi G
• Format: Journal Article
• Language: English
• Published: 22.07.2016
• ISSN: 0009-7330; 1524-4571
• DOI: 10.1161/res.119.suppl_1.441

Abstract only In structurally normal hearts, inhibition of the mitochondrial translocator protein (TSPO) prevents ROS-mediated proarrhythmia. Whether and how TSPO modulates electrophysiological (EP) function of diabetic hearts, in which classically cardioprotective pathways are impaired, is unknown. We determined the EP effects of TSPO activation & inhibition in a rat model of type 2 diabetes mellitus (t2DM) and studied the mitochondrial pathway underlying TSPO-related proarrhythmia. Methods: TSPO expression & function were determined in Zucker Diabetic Fatty (ZDF) rats with established t2DM (N=16) compared to controls (ctrl, N=15). Optical mapping was performed before & after challenge of hearts with ischemia for 12 min followed by reperfusion. Hearts underwent TSPO activation (FGIN 4.6uM, N=10), blockade (DZP 64uM, N=7) or no treatment (N=14). Dependence of TSPO-related proarrhythmia on ROS and on the PTP a target of TSPO were also determined. Results: t2DM hearts exhibited markedly increased TSPO expression (mRNA & protein) compared to ctrl. TSPO activation did not alter EP properties at baseline in ctrl or t2DM. In contrast TSPO activation accelerated action potential (AP) shortening during ischemia in t2DM but not ctrl hearts. Following 8 min of ischemia, FGIN-mediated AP shortening was 2X greater in t2DM compared to ctrl (p=0.008). FGIN-treated t2DM (5/7) but not ctrl (0/5) hearts exhibited VT by 12min of ischemia (p=0.027). AP shortening and VT in FGIN-treated t2DM hearts were not prevented by the PTP blocker Cyclosporin A but rather by the ROS scavenger EUK implicating the inner membrane anion channel in the proarrhythmic activity of TSPO. Upon reperfusion, TSPO activation with FGIN caused VF in 100% of ctrl & t2DM hearts compared to ~50% of untreated hearts. DZP prolonged the AP in t2DM (by 53% p<0.01) but not ctrl (p=0.14) hearts consistent with heightened sensitivity of t2DM to TSPO ligands. DZP blunted AP shortening during ischemia and prevented VF upon reperfusion in ctrl and t2DM hearts. Conclusion: t2DM hearts exhibit heightened sensitivity to TSPO ligands. TSPO upregulation may be a key factor in the proarrhythmic vulnerability of the diabetic heart. The cardioprotective efficacy of TSPO inhibition against arrhythmias is preserved in t2DM.