Salt-regulating hormones in young normotensive obese subjects. Effects of saline load.

Abstract

To investigate whether the response of salt-regulating hormones to volume expansion is impaired in obese subjects, we assessed the effects of saline load (0.25 mL/kg.min.120 min) in 9 young, healthy, normotensive obese subjects (body mass index, > 30 kg/m2) and in 10 lean control subjects (body mass index, < 25 kg/m2) matched for age, gender, height, and mean blood pressure. Hematocrit, plasma renin activity (PRA), plasma aldosterone (PA), atrial natriuretic factor (ANF), and urinary sodium excretion (UNaV) were evaluated. Saline load increased ANF levels significantly (P < .001) in lean subjects at both 60 and 120 minutes, whereas they decreased in obese subjects. Such decreases became significant (P < .01) at 120 minutes. Suppression of PRA and PA by saline load were more marked in lean than obese subjects. Hematocrit decreased in both groups, and UNaV increased more in lean than obese subjects during saline load. Comparisons of percent changes in ANF, PRA, and PA after saline load showed that the responses of lean and obese subjects were significantly different (P < .001 for ANF at both 60 and 120 minutes; P < .05 for PRA and PA at both 60 and 120 minutes). In conclusion, the lack of ANF response and the reduced suppression of PRA and PA to saline load indicate a dysfunction of these systems in obese subjects. This alteration may be involved in the higher susceptibility of obese subjects to developing hypertension.

N-Terminal Pro Brain Natriuretic Peptide Is Inversely Related to Metabolic Cardiovascular Risk Factors and the Metabolic Syndrome

“…This is also supported by previous observations that hyperinsulinemic 22 or obese 23 subjects are more sensitive to sodium load because of reduced effect of atrial natriuretic peptide, 24 -26 partly attributable to an increased clearance in adipose tissue. 27,28 This may also relate to Nt-proBNP, but the importance of the natriuretic clearance receptor C for clearance of Nt-proBNP is unknown.…”

“…14,22-24 LV mass was considered as an unadjusted variable and also after traditional normalizations for body surface area (BSA). 4,23 LV mass/BSA partition values of 116 g/m 2 in men and 104 g/m 2 in women were used as the upper gender-specific normal 95% confidence intervals, as described previously. 4,15 Relative wall thickness (RWT) was calculated as 2ϫ end-diastolic PWT/LV internal dimension.…”

Visceral Obesity and Insulin Resistance Are Associated with Plasma Aldosterone Levels in Women

“…One published report suggested that obese subjects have relatively low levels of atrial natriuretic peptide, especially after a salt load (33). Increased aldosterone secretion could be explained by a direct effect of circulating insulin on the adrenal, an effect we have been unable to confirm (34).…”

Renal and cardiovascular considerations for the nonpharmacological and pharmacological therapies of obesity-hypertension

“…36 Obese subjects were reported to have delayed urinary sodium excretion and a blunted response of plasma ANP to saline load. 37 Weight loss induced by caloric restriction led to significant natriuresis and diuresis, together with an early increase of circulating ANP levels. 38 Dessi-Fulgheri et al 39 reported that after caloric restriction for 4 days in obese hypertensive patients, ANP infusion caused more profound diuresis, natriuresis, reduction of BP, than ANP infusion did before caloric restriction.…”