The Effect of Weight Loss on the Sensitivity of Blood Pressure to Sodium in Obese Adolescents

Abstract

To clarify the role of sodium intake in the regulation of blood pressure in obese subjects, we measured blood pressure in 60 obese and 18 nonobese adolescents after successive two-week periods of a high-salt diet (greater than 250 mmol of sodium per day) and a low-salt diet (less than 30 mmol per day). When they were changed from a high-salt to a low-salt diet, the obese group had a significantly larger mean change (+/- SE) in mean arterial pressure (-12 +/- 1 mm Hg) than did the nonobese group (+1 +/- 2 mm Hg; P less than 0.001). The variables that best predicted the degree of sodium sensitivity were the fasting plasma insulin level, the plasma aldosterone level while the low-salt diet was being given, the plasma norepinephrine level while the high-salt diet was being given, and the percentage of body weight made up by fat. Fifty-one of the obese adolescents were also studied before and after a 20-week weight-loss program. After the weight-loss program, the 36 subjects who lost more than 1 kg of body weight had a reduced sensitivity of blood pressure to sodium (difference from value during high-salt diet to that during low-salt diet, -1 +/- 1 mm Hg). The blood pressure of the remaining 15 adolescents was still sensitive to sodium intake (-11 +/- 3 mm Hg). These results support the hypothesis that the blood pressure of obese adolescents is sensitive to dietary sodium intake and that this sensitivity may be due to the combined effects of the hyperinsulinemia, hyperaldosteronism, and increased activity of the sympathetic nervous system that are characteristic of obesity.

Effects of lifestyle changes and metformin on salt sensitivity and nitric oxide metabolism in obese salt-sensitive Hispanics

“…In addition, we do not know which of the changes, that is reduced weight, improved insulin sensitivity, correction of dyslipidemia, or others, is directly or indirectly responsible for the correction of salt sensitivity. Since weight loss simply achieved by caloric restriction corrected salt sensitivity in obese adolescents, 6 it is feasible that reduced adiposity would also be the main factor by which the lifestyle-metformin treatment corrected salt sensitivity in our study. However, how reduced adiposity translates into decreased salt sensitivity is unclear.…”

“…6 In largely obese teenagers, weight reduction (8% of basal weight) achieved through a 20-week program of caloric restriction was found to correct salt sensitivity. These two observations (Rocchini et al 6 and current study) indicate that correctable acquired factors play an important role in the pathogenesis of salt sensitivity associated with obesity. The present study was not designed to compare the effects of lifestyle changes versus metformin in improving salt sensitivity.…”

“…[1][2][3][4][5] Although the pathogenesis of salt sensitivity is unknown, both genetic and environmental factors appear to interact to determine the exaggerated BP response to changes in salt intake. [6][7][8][9][10][11][12][13][14][15] Increased reactivity of BP to salt is commonly observed in subjects with obesity and associated cardiovascular risk factors. [6][7][8][9][10] Insulin resistance, hypertension, increased sympathetic activity, endothelial dysfunction and abnormal nitric oxide (NO) bioactivity are among the list of factors that have been proposed to directly or indirectly lead to salt sensitivity related to obesity.…”

“…[6][7][8][9][10][11][12][13][14][15] Increased reactivity of BP to salt is commonly observed in subjects with obesity and associated cardiovascular risk factors. [6][7][8][9][10] Insulin resistance, hypertension, increased sympathetic activity, endothelial dysfunction and abnormal nitric oxide (NO) bioactivity are among the list of factors that have been proposed to directly or indirectly lead to salt sensitivity related to obesity. 2,4,6,[16][17][18] NO is involved in renal sodium homeostasis and inhibition of NO synthesis is associated with impaired natriuresis and salt sensitivity.…”

“…[6][7][8][9][10] Insulin resistance, hypertension, increased sympathetic activity, endothelial dysfunction and abnormal nitric oxide (NO) bioactivity are among the list of factors that have been proposed to directly or indirectly lead to salt sensitivity related to obesity. 2,4,6,[16][17][18] NO is involved in renal sodium homeostasis and inhibition of NO synthesis is associated with impaired natriuresis and salt sensitivity. 19 Impairment in NO production has been observed in salt-sensitive subjects when exposed to a high sodium diet.…”