by American Physiological Society

Mean arterial pressure (MAP) and cosinor analysis. Credit: American Journal of Physiology-Heart and Circulatory Physiology (2024). DOI: 10.1152/ajpheart.00131.2024

High blood pressure disrupts natural day-and-night blood pressure dipping patterns in males and females, according to a new study from Tulane University School of Medicine. The findings are published in the American Journal of Physiology-Heart and Circulatory Physiology.

Nighttime blood pressure normally dips 10% to 20% below daytime levels. Physical activity and stress may reduce the reliability of daytime blood pressure measurements. Nondipping—when blood pressure stays at daytime levels—is a serious ailment linked to increased risk of cardiovascular diseases and organ damage. However, the mechanism behind nondipping is not fully explained.

Researchers from the Lindsey Lab at Tulane used an implantable, continuous monitoring method called radiotelemetry to determine how hypertension in male and female mice changed their blood pressure during the day and night. The researchers continuously measured the animals' blood pressure to learn how much it decreases during sleep.

Physiologists also collected blood vessel samples from the mice at various times of the day and night to examine how clock genes and estrogen receptors work together to regulate blood pressure. This was done using a highly accurate technique called droplet digital PCR. Additionally, the team studied how these vessels responded to drugs that cause them to dilate or constrict.

Credit: American Physiological Society

High blood pressure induced by high salt consumption, aging and poor sleep quality, among other factors, can lead to nondipping. This study also confirmed for the first time that estrogen receptors follow a daily cycle that aligns in the vessels with changes in a specific class of clock genes called period genes. This gene plays a key role in regulating the circadian rhythm. In addition, this study shows high blood pressure affects blood pressure rhythms. The expression of clock genes and estrogen receptors in the blood vessels is similar in both sexes.

"By understanding these changes, we can create better treatments that work specifically for men and women at different times of the day, which is a practice called 'chronotherapy,'" said Bruna Visniauskas, Ph.D., lead study author and instructor at Tulane. "This research could help us develop new strategies to lower the risk of high blood pressure and disruptions in daily rhythms in both sexes."

More information: Bruna Visniauskas et al, Hypertension disrupts the vascular clock in both sexes, American Journal of Physiology-Heart and Circulatory Physiology (2024). DOI: 10.1152/ajpheart.00131.2024

Provided by American Physiological Society