University of Zagreb

School of Medicine

Mitochondrial dysfunction plays important role in diabetic cardiomyopathy. Mitochondrial unfolded protein response (UPRmt) is one of key mechanisms involved in regulation of proper mitochondrial function. However, the role of UPRmt is not investigated in diabetic cardiomyopathy. This proposal is designed to investigate the role of UPRmt in diabetic cardiomyopathy, focusing on the proposed Yme1L-Oma1 molecular switch.

Our preliminary data show that high glucose downregulates Yme1L protein, a trigger and effector of UPRmt. mitoTEMPO, a mitochondria-targeted antioxidant restores Yme1L protein expression. This indicates involvement of ROS in glucose-induced Yme1L downregulation. Preliminary data also show that high glucose accelerates mPTP opening and increases ROS generation.

Our experiments will be conducted on isolated cardiomyocytes, diabetic rat hearts and failing human myocardium. The role of UPRmt in diabetes-induced cardiomyopathy will be investigating by several approaches. We will be testing the expression of UPRmt markers and proposed molecular switch that regulates activation of UPRmt by qPCR and western blot. mPTP opening and ROS generation will be tested by confocal microscopy, while cell apoptosis and mitochondrial calcium will be tested by fluorimetric approaches. The mPTP opening time and ROS generation will be also analyzed in previously identified mitochondrial subpopulations, subsarcolemmal and interfibrilar mitochondria. The extent of heart damage will be tested immunopathohistologically. We will apply Yme1L overexpression, Oma1 silencing and mitoTEMPO treatment to restore Yme1L-Oma1 balance, restore UPRmt and ameliorate diabetic cardiomyopathy.

PI: Filip Sedlić, MD, PhD, Associate Professor

Vesna Kušec, MD, PhD, Professor

Ana Kulić, PhD Assistant Professor

Ana Šepac, MD, PhD, Postdoctoral Fellow

Sunčana Sikirić, Graduate Student

Tomo Svaguša, MD, Graduate Student

Fran Seiwerth, MD, Graduate Student

Svaguša T, Martinić M, Martinić M, Kovačević L, Šepac A, Miličić D, Bulum J, Starčević B, Sirotković-Skerlev M, Seiwerth F, Kulić A, Sedlić F. Mitochondrial unfolded protein response, mitophagy and other mitochondrial quality control mechanisms in heart disease and aged heart. Croat Med J. 2020 Apr 30;61(2):126-138.