Abstract 504: 23Na Magnetic Resonance Imaging-Determined Tissue Sodium Increases With Age.
Hypertension is the most common cardiovascular risk factor and systolic blood pressure increases continuously with age. Increased vascular stiffness, nitric oxide, renin-angiotensin aldosterone system and salt intake have been implicated. We have developed 23Na magnetic resonance imaging (23Na MRI) and showed that aldosterone influences tissue Na+ storage. We reasoned that Na+ might accumulate in tissues with age. We investigated tissue Na+ of the lower leg in 113 subjects with 3T 23Na MRI. Tissue Na+ concentration was calibrated by solutions containing 10 to 40 mmol/l of Na+. Prior to 23Na MRI measurements, a medical history was taken, blood and urine samples were obtained and blood pressure was analyzed in seated position. The age of the 113 subjects analyzed by 23Na MRI ranged from 22 to 90 years. We studied 44 women and 69 men. Hypertension was diagnosed in 46 subjects (29 men and 17 women). Men showed an exponential increase in tissue Na+ with age (muscle R2 = 0.54, skin R2= 0.33). In contrast, tissue Na+ in women was only slightly affected by age and increased linearly (skin R2 = 0.40, muscle R2= 0.13). To compare subpopulations, we allocated the participants into three different age groups <50, 50-65 and >65 years. A gender difference in skin tissue Na+ could be found throughout all groups with higher levels in men (14.3 vs. 18.1 (<50 yrs), 19.0 vs. 24.5 (50-65 yrs), 20.1 vs. 27.4 mmol/l (>65 yrs); p < 0.05). Skin Na+ content was elevated in hypertensive women compared to age-matched controls (17.2, n = 12 vs. 21.0 mmol/l, n = 17; p<0.05). We could not identify such a difference in hypertensive versus normotensive men. In line with our previous results, older hypertensive patients receiving an aldosterone antagonist revealed muscle Na+ values below age-matched subjects (17.6, n = 6 vs. 21.3 mmol/l, n = 24; p < 0.05). We conclude that aging is associated with Na+ tissue accumulation with a pronounced gender difference. Skin Na+ overload occurs in hypertensive women but not in men. Aldosterone antagonists may reset the age-dependent muscle Na+ overload to levels of young healthy controls.
- © 2012 by American Heart Association, Inc.