Relationship of body composition to stress-induced pressure natriuresis in youth.

Background: The contribution of stress to obesity-related cardiovascular disease is uncertain. The purpose of this study was to examine the influence of body composition on stress-induced pressure natriuresis.

Methods: Dual energy x-ray absorptiometry was performed in 127 African American and white youths to assess lean body mass (LBM), fat mass (FM), and total percentage of body fat (%BF). The stress protocol was comprised of a 2-h baseline period, 1-h video game competition stressor, and 2-h recovery period. Blood and urine samples were collected hourly and blood pressure (BP) was obtained at 15-min intervals.

Results: Both BP and urinary sodium excretion(U(Na)V) increased from baseline to stress and returned to prestress levels after stress (P = .001 for each). The BP levels and changes were positively correlated with LBM. In contrast, levels and changes in sodium excretion U(Na)V were inversely correlated with FM and %BM. Multiple regression analyses that included ethnicity, sex, angiotensin II (Ang II), and measures of body composition in the models indicated the following: a) LBM was the best predictor of stress systolic BP and independently contributed with ethnicity to stress diastolic BP; b) ethnicity was the only independent predictor of the stress-related change in systolic and diastolic BP; c) LBM was the only independent predictor of the change in BP from stress to recovery for both systolic and diastolic BP; and d) total percent body fat accounted for 11.2% of the variance of stress U(Na)V, with Ang II contributing an additional 6.1%.

Conclusions: Based on the results of this study, ethnicity and body composition are related to stress-induced pressure natriuresis.