Partial Regulation of Ketone Metabolism by Hypoxia in H9C2 Cardiomyocytes.

Abstract

Objective: Hypoxia plays a critical role in the pathophysiology of cardiomyopathy, myocardial infarction, and heart failure. Promoting ketone metabolism has been shown to be beneficial for myocardial cells under hypoxic conditions. However, the expression and regulatory mechanisms of key enzymes in the ketone pathway under hypoxic conditions are still unclear. This study aimed to investigate the effects of hypoxia on the expression of key enzymes in the ketone metabolic pathway and the underlying regulatory mechanisms involved.

Methods: H9C2 myocardial cells were cultured for 6 h in an oxygen-glucose-deprived state, and the expression of various genes was detected by quantitative real-time PCR. ELISA and lactate dehydrogenase (LDH) cytotoxicity assay were used to measure CoAs, itaconic acid, and LDH levels, respectively, and the dependence of gene expression on hypoxia-inducible factor-1 alpha (HIF-1α) was evaluated using the inhibitor LW6.

Results: H9C2 cardiomyocytes exhibited increased ketone body metabolism in response to hypoxia. Hypoxia induced the expression of the ketone body enzymes succinyl-CoA:3-oxoacid CoA transferase (SCOT/OXCT1), 3-hydroxybutyrate dehydrogenase 2 (BDH2), and acyl-CoA: cholesterol acyltransferase 1 (ACAT1) in cardiomyocytes, with a concomitant increase in the level of acyl-CoA and a decrease in the level of succinyl-CoA. The HIF-1α inhibitor LW6 could partially reverse the expression of BDH2 and ACAT1, as well as the levels of succinyl-CoA. Interestingly, however, hypoxia-induced SCOT/OXCT1 expression was not regulated by the HIF-1α inhibitor. In addition, hypoxia promoted the expression of inflammatory factors.

Conclusion: These data confirm the critical role of ketone metabolism in myocardial hypoxia and help to elucidate the pathophysiology of cardiomyopathy, myocardial infarction and heart failure.