Salt sensitivity in blacks. Salt intake and natriuretic substances.

Tozetto

et al. 2009

Braz J Med Biol Res

Salt sensitivity and insulin resistance are correlated with higher cardiovascular risk. There is no information about changes in salt sensitivity (SS) and insulin sensitivity (IS) after a chronic salt overload in humans. The aim of this study was to evaluate these parameters in the elderly. Seventeen volunteers aged 70.5 ± 5.9 years followed a low-salt diet (LSD) for 1 week and a high-salt diet (HSD) for 13 weeks. We evaluated SS after one week (HSD1) and after 13 weeks (HSD13), and subjects’ IS and lipids on their usual diet (UD) at HSD1, and at HSD13. Blood pressure (BP) was measured at each visit and ambulatory blood pressure monitoring (ABPM) was performed twice. SS was the same at HSD1 and HSD13. Systolic BP was lower on LSD than on UD (P = 0.01), HSD1 (P < 0.01) and HSD13 (P < 0.01). When systolic and diastolic BP were evaluated by ABPM, they were higher at HSD13 during the 24-h period (P = 0.03 and P < 0.01) and during the wakefulness period (P = 0.02 and P < 0.01) compared to the UD. Total cholesterol was higher (P = 0.04) at HSD13 than at HSD1. Glucose and homeostasis model assessment (HOMA) were lower at HSD1 (P = 0.02 and P = 0.01) than at HSD13. Concluding, the extension of HSD did not change the SS in an elderly group. The higher IS found at HSD1 did not persist after a longer HSD. A chronic HSD increased BP as assessed by ABPM

Section: Discussionsupporting

confidence: 88%

Salt and insulin sensitivity after short and prolonged high salt intake in elderly subjects

Tozetto

et al. 2009

Braz J Med Biol Res

“…11314 However, sodium sensitivity of blood pressure is not uniform throughout the population. 2 - 12 The present observations provide new evidence for a role of sodium sensitivity in the age-and time-related changes in blood pressure among both normotensive and hypertensive subjects. These studies also strengthen the validity and implications of one approach to the assessment of salt sensitivity and resistance of blood pressure in hypertensive as well as normotensive subjects.…”

Section: Study C: Change In Blood Pressure With Timementioning

confidence: 50%

Sodium and volume sensitivity of blood pressure. Age and pressure change over time.

1991

Salt sensitivity has been implicated in the age-related increase in blood pressure. We studied the reproducibility of a rapid method for assessing sodium sensitivity and resistance of blood pressure as well as the effect of age on this phenomenon. Blood pressure after volume expansion with 2 1 intravenous saline (0.9%) over 4 hours was compared with that after 1 day of 10 mmol sodium chloride intake and 3 and 40 mg oral doses of furosemide. Normal and hypertensive subjects (n=28) were studied twice within a year. Cross-sectional observations of the effect of age were made from studies in 230 hypertensive and 430 nonnotensive subjects. Longitudinal observations of blood pressure change over time were made 10 or more years after categorization of sodium responsivity in 31 subjects. The blood pressure response was reproducible in 28 subjects studied twice (r=0.56,p<0.002). Four subjects changed salt-responsiveness status and six were indeterminate on restudy. Sodium sensitivity of blood pressure increased significantly with increasing age in the entire population (n=660, r= -03S,p<0.001). The relation was more striking in hypertensive subjects (n=230, r= -031,p<0.00l) in whom a progressive increase in salt sensitivity with decades was seen than in the nonnotensive group (n=430, r=-0.19, /><0.01) in whom salt sensitivity was not observed until the sixth decade. Salt-sensitive subjects had a significantly greater increase in systolic (p<0.001) and diastolic (/?<0.01) pressure over time than those who were salt-resistant Salt sensitivity is a reproducible phenomenon that is related to the age-associated increase in blood pressure characteristic of industrialized societies. In addition, salt sensitivity can be shown to be a predictor of subsequent, age-related blood pressure increase. (Hypertension 1991;18:67-71) E pidemiological and interventional observations suggest a relation between dietary sodium chloride intake and blood pressure.

“…We found a 29% prevalence of low-renin hypertension among blacks and 11% among whites, consonant with earlier reports. 13 Black low-renin hypertensive patients also tended to show a blunted adrenal response to both posture and Ang II, although sample sizes were small and the results were not statistically significant. Previous studies have demonstrated normal aldosterone responses to Ang II infusion among low-renin hypertensive patients, suggesting heightened sensitivity of the adrenal gland to Ang II stimulation.…”

Section: Discussionmentioning

confidence: 83%

“…Dustan and coworkers 12 measured aldosterone excretion rate in hypertensive patients on a diet of 10 mmol sodium and also found no significant difference between blacks and whites. Sowers et al 13 found similar levels of plasma aldosterone among normotensive and hypertensive black men on a diet of 40 mmol sodium per day and concluded that salt-sensitive hypertension in blacks is not characterized by adrenal unresponsiveness. The discrepancy between their conclusion and ours may reflect the higher sodium intake used in that study.…”

Section: Discussionmentioning

confidence: 98%

Regulation of aldosterone secretion in hypertensive blacks.

et al. 1994

Hypertension in blacks is common, often severe, and largely unexplained. Recent studies have suggested that aldosterone secretion in blacks may be reduced, whereas older data demonstrate no racial differences in aldosterone excretion. We performed this study to examine adrenal responsiveness in black hypertensive patients under controlled metabolic conditions. Thirty-one black hypertensive patients and 7 black normotensive subjects were studied on intakes of 10 mmol/d sodium and 100 mmol/d potassium, with the renin-angiotensin-aldosterone system further stimulated by upright posture or infusion of angiotensin II (Ang II). Forty-six hypertensive and 14 normotensive whites underwent the same protocol as a comparison group. Hypertensive blacks and whites had similar mean basal plasma aldosterone levels on a low salt diet, lower in both groups than in normotensive subjects. '-4 In response to suggestions of an increased incidence of primary aldosteronism in blacks, 5 a comparative study found no difference in aldosterone excretion between black and white normotensive subjects or hypertensive patients. 6 Recently, a reduction in aldosterone secretion was documented in black children, with strong familial influences on the aldosterone excretion rate. 78 The following description results from a systematic assessment of adrenal responsiveness in blacks, using three stimuli known to increase aldosterone secretion: restriction of sodium intake, upright posture, and angiotensin II (Ang II) infusion. MethodsWe studied 31 black patients (14 men, 17 women) with hypertension and 7 black normotensive men. Race was determined by self-identification and supported by physical appearance. The term "black" is used instead of "African American" because not all of the patients were American. Forty-six white hypertensive patients, matched with the black patients for age, gender, and body mass index, served as the comparison group. Although this group consisted of proportionately fewer women (Table 1), the difference was not statistically significant (# 2 =1.26). Fourteen white normotensive men were also matched for comparative study.Hypertension was defined as a systolic blood pressure greater than 140 mm Hg and a diastolic blood pressure greater