Abstract 081: Obesity-related Reductions in Cardiac Baroreflex Sensitivity and Higher 24-hour Blood Pressure Variability Are Not Related to Carotid Artery and Aortic Stiffness in Young And Middle-aged Adults

Abstract

Alterations in cardiac baroreflex sensitivity (BRS) and 24-hr blood pressure variability (24-hr BPV) are independent predictors of increased cardiovascular disease (CVD) risk, and occur in individuals with obesity. Obese humans are also likely to have a higher large elastic artery stiffness compared with normal-weight individuals. While an increase in stiffness of carotid and aortic arteries, the anatomical sites where baroreceptors reside, may likely be responsible in part for the decline in cardiac BRS with advancing age in adults, it remains unclear whether 1) elevated carotid and aortic stiffness are also directly associated with obesity-associated reductions in cardiac BRS in young/middle-aged individuals, and 2) if reduced BRS with obesity is associated with elevated 24hr BPV. We tested the hypothesis that lower BRS would be associated with higher carotid and aortic stiffness and 24hr BPV in young and middle-aged individuals with obesity. In a cross-sectional design, 22 normal-weight (body mass index, BMI 24.5 ± 0.6 kg/m 2 ; age 35±2 yrs; 8M/14F) and 22 obese (BMI 34.2 ± 1.1 kg/m 2 ; age 39 ± 2 yrs; 8M/14F) individuals underwent measures of spontaneous cardiac BRS (sequence technique), carotid artery β-stiffness (carotid tonometry and B-mode ultrasound of common carotid artery), aortic stiffness (carotid-femoral pulse wave velocity, CFPWV), and 24-hr-systolic BPV (24 hr ambulatory BP monitoring). A significant relation between cardiac BRS and 24-hr systolic BPV (r=-0.42, P<0.01) was corroborated by lower cardiac BRS (11.7±1.2 vs. 16.8±1.7 ms/mmHg, P<0.05) and higher 24-hr BPV (12.4±0.6 vs. 10.1±0.4 mmHg SD, P<0.05) among obese compared with normal-weight subjects. In contrast, carotid β-stiffness (7.8±0.6 vs. 6.9±0.4 U, P>0.05) and CFPWV (745±71 vs. 611±19 cm/s, P=0.07) were not significantly different between groups despite greater average 24-hr systolic BP in the obese vs. normal weight subjects (127±2 vs. 118±1 mmHg, P<0.05). These preliminary data suggest that an increase in carotid artery and aortic stiffness may not precede the decline in cardiac BRS and increase in 24hr BPV in young and middle-aged obese individuals, suggesting non-arterial stiffness related mechanisms for obesity-related reductions in cardiac BRS.