Ellen Thiemann1, Anesa Isenova1, Margaret Nandudu1, Markus Heine2, Jörg Heeren2, Thomas Eschenhagen1, Paulus Kirchhof3, Friederike Cuello1,
(1) Department of Experimental Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. (2) Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg-Eppendorf, Hamburg , Germany. (3) Department of Cardiology, University Heart and Vascular Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
Aim:
Atrial fibrillation (AF) is the most common cardiac arrhythmia and is often driven by metabolic changes in the heart. Metabolic diseases such as obesity and diabetes are major risk factors for the development of AF. The expression of the transcription factor PITX2 has been shown to be altered in the atria in obesity and AF. Based on previous studies suggesting a role of PITX2 in cardiac metabolic function, we aimed to further investigate its role in atrial metabolism using atrial engineered heart tissue (aEHT).
Methods:
HiPSCs with CRISPR/Cas9-induced PITX2 knockout (PITX2KO) and isogenic control hiPSCs were differentiated into atrial cardiomyocytes and used for generating aEHTs. PITX2KO and isogenic control aEHTs were exposed to low- and high-glucose conditions to model physiological and hyperglycemic states. Contractile function was assessed, and media glucose and lactate levels were measured. Additionally, glucose and fatty acid uptake was analyzed using radioactively labeled metabolic tracers. Mitochondrial content was quantified and respiratory analysis was performed.
Results:
PITX2KO aEHTs showed a lower contractile force compared to isogenic control. Media glucose and lactate concentration was almost unchanged in PITX2KO after culture, while the isogenic control showed a decrease in glucose concentration and an increase in lactate levels. Under high-glucose conditions, glucose uptake increased in both isogenic control and PITX2KO aEHTs, with no effect on contractile function. The uptake of radiolabeled glucose was almost completely abolished in PITX2KO aEHTs, whereas the uptake of radiolabeled oleic acid was increased. PITX2KO aEHTs showed a lower ratio of mitochondrial to nuclear DNA and decreased mitochondrial respiratory activity.
Conclusion:
The data indicates a role of PITX2 in the regulation of glucose and fatty acid uptake. The diminished glucose uptake combined with the reduced mitochondrial respiration in PITX2KO aEHTs might promote the observed contractile dysfunction.