Metabolic remodelling of cardiac myocytes during pregnancy: the role of mineralocorticoids.

BACKGROUND: Pregnancy is associated with significant cardiac adaptations. The regulatory mechanisms involved in functional cardiac adaptations during pregnancy are still largely unknown. In pathologic conditions, mineralocorticoids have been shown to mediate structural as well as functional remodelling of the heart. However, their role in cardiac physiological conditions is not completely understood. Here, we examined cardiac cell metabolic remodelling in the late stages of rat pregnancy, as well as mineralocorticoid involvement in this regulation. METHODS: We have applied rapid video imaging, echocardiography, patch clamp technique, confocal microscopy, and time-resolved fluorescence spectroscopy. RESULTS: Our results revealed that cardiac cells undergo metabolic remodelling in pregnancy. Inhibition of mineralocorticoid receptors during pregnancy elicited functional alterations in cardiac cells: blood levels of energy substrates, particularly lactate, were decreased. As a consequence, the cardiomyocyte contractile response to these substrates was blunted, without modifications of L-type calcium current density. Interestingly, this response was associated with changes in the mitochondrial metabolic state, which correlated with modifications of bound reduced nicotinamide adenine dinucleotide (phosphate) NAD(P)H levels. We also noted that mineralocorticoid receptor inhibition prevented pregnancy-induced decrease in transient outward potassium current. CONCLUSIONS: This study demonstrates that in pregnancy, mineralocorticoids contribute to functional adaptations of cardiac myocytes. By regulating energy substrate levels, in particular lactate, in the plasma and metabolic state in the cells, mineralocorticoids affect the contractility responsiveness to these substrates. In the future, understanding cardiac adaptations during pregnancy will help us to comprehend their pathophysiological alterations.