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A reduction of 3 g/day from a usual 9 g/day salt diet improves endothelial function and decreases endothelin-1 in a randomised cross_over study in normotensive overweight and obese subjects

  • Kacie M. Dickinson
    Affiliations
    Commonwealth Scientific and Industrial Research Organisation, Animal, Food and Health Science, Adelaide, South Australia, Australia

    Discipline of Physiology, Faculty of Health Science, University of Adelaide, South Australia, Australia

    The National Health and Medical Research Council of Australia, Centre of Clinical Research Excellence in Nutritional Physiology, Interventions and Outcomes, Adelaide, South Australia, Australia
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  • Peter M. Clifton
    Affiliations
    The National Health and Medical Research Council of Australia, Centre of Clinical Research Excellence in Nutritional Physiology, Interventions and Outcomes, Adelaide, South Australia, Australia

    School of Pharmacy and Medical Sciences, Division of Health Sciences, University of South Australia, Adelaide, South Australia, Australia
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  • Jennifer B. Keogh
    Correspondence
    Corresponding author. School of Pharmacy and Medical Science, University of South Australia, GPO Box 2471, Adelaide, South Australia 5000, Australia. Tel.: +61 8 8302 2579; fax: +61 8 8302 2389.
    Affiliations
    School of Pharmacy and Medical Sciences, Division of Health Sciences, University of South Australia, Adelaide, South Australia, Australia
    Search for articles by this author

      Highlights

      • A diet containing 9 g salt/day impaired flow mediated dilatation (FMD) and increased endothelin-1.
      • A 3 g reduction in salt intake reversed the impaired FMD and improved serum endothelin-1.
      • Asymmetric dimethylarginine, plasma and urinary nitrate/nitrite concentrations did not change.
      • Aldosterone and renin were unchanged by salt reduction.

      Abstract

      Background and aim

      It is unclear if a modest reduction in dietary salt intake has beneficial effects on vascular function. The aim was to compare the effects of 9 g salt/day with 6 g salt/day intake on measures of vascular function and explore mechanisms of effect in overweight and obese adults.

      Methods

      Twenty-five overweight/obese subjects (BMI 27–40 kg/m2) completed a randomised cross-over study of 6 weeks each on a reduced salt (RS) (6 g/day) and usual salt diet (US) (9 g/day). Flow-mediated-dilatation (FMD), 24 h blood pressure (BP), augmentation index (AIx), pulse wave velocity (PWV), plasma and urinary nitrate/nitrite, asymmetric dimethylarginine (ADMA), renin, aldosterone and endothelin-1 and vascular adhesion molecules were measured after 2 days and 6 weeks. Adherence to the diets was determined from two 24 h urine collections.

      Results

      Urinary sodium excretion was 155 ± 58 mmol/24 h US vs 113 ± 45 mmol/24 h RS (p = 0.002). Following the RS diet there was a significant improvement in FMD from 3.5 ± 2.8% to 5.6 ± 2.8% (P < 0.001) and decrease in serum endothelin-1 from 1.45 ± 0.38 pg/ml to 1.25 ± 0.39 pg/ml (P < 0.05). Endothelium-independent vasodilatation was also significantly different between treatments (P < 0.05). AIx, PWV, serum ADMA and plasma and urinary nitrate/nitrite concentrations were not different between treatments. Change in FMD was related to the urinary sodium: creatinine ratio (r = −0.47, P < 0.05) and was independent of blood pressure. Aldosterone and renin were unchanged.

      Conclusions

      A small reduction in dietary salt intake of 3 g/day improves endothelial function in normotensive overweight and obese subjects. This response may be mediated by serum endothelin-1. This small reduction in salt had no effect on aldosterone and renin concentrations.
      This trial was registered with the Australian and New Zealand Clinical Trials Registry Unique Identifier: ACTRN12609000321246 http://www.anzctr.org.au/ACTRN12609000321246.aspx

      Keywords

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