Hyperlipidaemia impairs the circadian clock and physiological homeostasis of vascular smooth muscle cells via the suppression of Smarcd1

Abstract

Many mammalian physiological processes show diurnal oscillation and are controlled by a circadian clock. Disruption of the circadian clock has been implicated in the pathogenesis of cardiovascular disorders, but the mechanism through which clock and vessel function are integrated is unclear. Here we show that the rhythmicity of key clock genes and Smarcd1, a member of the SWI/SNF chromatin remodelling complex family, is suppressed in the layer of vascular smooth muscle cells (VSMCs) of the thoracic aorta of hyperlipidaemic rats fed a high-fat diet (HFD). Smarcd1 stimulates the transcription of clock genes, notably bmal1, through co-activation of the nuclear orphan receptor RORα in VSMCs. The co-activation of Smarcd1 and RORα is dependent on the mediation of PGC-1α, a transcriptional co-activator. Pathophysiologically, Smarcd1 inhibits VSMC proliferation and migration by blocking cell cycle re-entry and via the activation of kinase signalling pathways. Our results demonstrate that Smarcd1 is a critical node integrating the circadian clock and VSMC physiological homeostasis.