Beta-hydroxybutyrate (βOHB), along with acetoacetate and acetone, are liver-produced ketone bodies that are increased after fasting or prolonged exercise as an alternative fuel source to glucose. βOHB, as the main circulating ketone body, is not only a G-protein coupled receptor ligand but also a histone deacetylases inhibitor, prompting the reexamination of its role in health and disease. In this study, we compared the effects of two commercial βOHB formulations an enantiomer R βOHB and a racemic mixture ±βOHB on induced pluripotent stem cell cardiac myocytes (iPS-CMs) electrophysiology. Cardiac myocytes were cultured in R βOHB or ±βOHB for at least ten days after lactate selection. Flouvolt or Fluo-4 was used to assay iPS-CMs electrophysiology. We found that while both formulations increased the optical potential amplitude, R βOHB prolonged the action potential duration but ±βOHB shortened the action potential duration. Moreover, ±βOHB increased the peak calcium transient but R βOHB reduced the peak calcium transient. Co-culturing with glucose or fatty acids did not ameliorate the effects, suggesting that βOHB was more than a fuel source. The effect of βOHB on iPS-CMs electrophysiology is most likely stereoselective, and care must be taken to evaluate the role of exogenous βOHB in health and disease.
Keywords: beta-hydroxybutyrate (βOHB); electrophysiology; enantiomer; induced pluripotent stem cell-derived cardiac myocytes (iPS-CMs); racemic mixture.