Circadian rhythms and cardiac physiology: An essential interplay

Virtually every cell in the human body contains a molecular circadian clock that orchestrates the rhythmic oscillations of a multitude of tissue-specific functions. This is evident in the heart, where circadian rhythms are seen in various cardiac functions. Genetic disruption of clock genes has underscored their significance in regulating multiple aspects of cardiac physiology. In this review, we report the principal findings regarding the impact of clock gene manipulation (whole body or cardiomyocyte specific) on cardiac function. Furthermore, we present the current knowledge on the circadian clock in the different cell populations in the heart-cardiomyocytes, endothelial cells, fibroblasts, and immune cells. While increasing studies have shown mechanistic links between core clock components and cardiomyocytes-specific genes, the information of clock function within other cardiac cells in the heart is extremely limited. This review underlines the need to gain more information on the temporal segregation of clock processes in cardiac-especially in non-cardiomyocytes-cells, as clock-controlled mechanism may be target of chronotherapy to optimize current treatments for cardiovascular diseases.