Role of sympathetic activity in blood pressure reduction with low calorie regimen

Abstract

To investigate the effects of a low calorie regimen on sympathetic function and its relation to blood pressure response, 22 untreated obese essential hypertensive patients (50±2 years, body mass index 29±1 kg/m2) were hospitalized and a diet was prescribed of 2,000 kcal/day for 5 days (control period) followed by 800 kcal/day for 21 days without changing salt intake (8-10 g/day). The dose of intravenous phenylephrine infusion needed to elevate systolic blood pressure 20 mm Hg (CD20) and the 24-hour urinary excretion of norepinephrine (UNE) were measured. During the low calorie period, blood pressure normalized in 14 patients (responder group, 124±3/79±4 mm Hg) and eight remained hypertensive (poor responder group, 158±6/103±3 mm Hg). At the control period, blood pressure and body mass index were similar, but the responder group had higher UNE (134±15 μg/day) and CD20 (127±11 μg) than the poor responder group (89±6 μg/day and 79±13 μg, respectively). During the low calorie period, both UNE (87±15 μg/day) and CD20 (74±10 μg) decreased in the responder group; no change was seen in the poor responder group. Changes in UNE and systolic blood pressure were correlated (r=0.6, p<0.05). In conclusion, suppression of sympathetic activity plays a role in blood pressure reduction during moderate caloric restriction.