Impact of renal denervation on circadian variations of blood pressure and clock gene expression in spontaneously hypertensive rats

Background: Hypertension is often associated with elevated nighttime blood pressure and is a significant risk factor for cardiovascular and cerebrovascular diseases. This study explored the effects of renal denervation (RDN) on circadian blood pressure rhythms and clock gene expression in spontaneously hypertensive rats (SHRs). Methods: Ten-week-old SHRs were randomized into RDN and sham surgery (Sham) groups, with Wistar-Kyoto (WKY) rats as controls. Blood pressure was measured at rest (14:00) and during activity (02:00) biweekly, and blood pressure variability was analyzed. Results: RDN significantly reduced BP and enhanced circadian BP variation, particularly during the resting phase. The Sham group displayed minimal circadian variations in plasma and renal norepinephrine levels, whereas the RDN group exhibited an overall reduction in norepinephrine levels, with lower levels at rest than during activity. Furthermore, the Sham group showed no significant circadian variation in the renin-angiotensin-aldosterone system (RAS), whereas RDN restored circadian rhythms in ACE1, Ang II, ACE2, and Ang1-7. Additionally, the Sham group demonstrated consistently high renal BMAL1 protein expression throughout the day, whereas RDN reduced BMAL1 expression during the resting phase, indicating restored circadian variation. Conclusions: These findings suggest that RDN not only lowers blood pressure but also improves circadian rhythm, likely through the modulation of sympathetic nervous activity, the RAS system, and the circadian clock gene BMAL1.