Sodium Storage in Singaporeans

Healthy, Hypertension

The overarching hypothesis of this study is that the kidney and the skin form an integrative network for water conservation, where Na+ storage is utilized to prevent body water loss, even at the expense of increased cardiovascular risk. The aim of this project is to characterise skin and muscle Na+ storage in a cohort designed to prospectively measure cardiovascular outcomes in Singaporeans, in order to determine whether humans with increased tissue Na+ storage have increased cardiovascular risk. To gain a better understanding of the mechanisms behind Na+ storage, the investigators will also test the hypothesis that participants with mutations of the skin protein filaggrin, who have increased water loss through the skin, will have increased skin Na+ storage and higher blood pressure levels.

Cardiovascular disease (CVD) occurs with increasing age and is the leading cause of death worldwide. A causal relationship between salt and CVD, although well established in animal models, has been difficult to prove in human populations. First, because humans do not live under the strict experimental conditions necessary to quantify sodium intake, and second, because tissue sodium stores cannot be detected with the available clinical methods, making reliable measurements of total body sodium extremely challenging. The investigators have previously implemented 23NaMRI technology to detect and quantify tissue Na+ stores in humans. Previous studies have sown that humans store large amounts of Na+ in their skin and muscle as they age and that skin Na+ storage is linked with hypertension, while muscle Na+ storage is coupled with insulin resistance and diabetes. More recent studies show that the adverse effect of Na+ on human health goes far beyond the well-established salt-blood pressure relationship. The investigators have found that urea and/or Na+ storage in barriers such as kidney or skin is a key principle of water conservation. This study aims to test the hypothesis that water conservation in the skin is essential for systemic fluid and blood pressure homeostasis, and that skin Na+ storage is utilized to prevent water loss, even at the expense of increased cardiovascular risk. This is a cross-sectional study design with one study visit and a recruitment period of 3 years. 600 participants will be recruited from the Biobank cohort and tissue Na+ will be measured using 23NaMRI. The study will test whether increased Na+ storage in the skin is coupled with transepidermal water loss at the expense of high blood pressure levels, and examine the association between tissue sodium storage and specific cardiovascular markers.

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Singapore