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Dietary salt loading produced significant increases in PWV and BP in hypertensive volunteers. Correlations between BP and PWV suggest that salt loading may have a BP-independent effect on vascular wall function. This further supports the importance of dietary sodium restriction in the management of hypertension. This trial was registered with the Australian and New Zealand Clinical Trials Registry as ACTRN12609000161224.

Dietary salt loading did not produce significant increases in PWV and blood pressure in normotensive subjects with systolic blood pressure <130 mmHg. The lack of an observed effect supports Guyton's pressure-natriuresis hypothesis with appropriate renal excretion of the excess sodium load.

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BackgroundIntravenous iron affects serum levels of intact fibroblast growth factor-23 (iFGF23) and its cleavage product c-terminal FGF23 (cFGF23) in iron-deficient people with normal renal function. We hypothesized that intravenous iron modulates iFGF23 and cFGF23 in haemodialysis patients differently according to the type of iron used.MethodsPrevalent, stable haemodialysis patients requiring protocol-based intravenous iron therapy were randomized to a single 200 mg dose of either ferric carboxymaltose (FCM) or iron sucrose (IS). The primary outcome was change in iFGF23 and cFGF23 from pre-infusion to Day 2 post-infusion. Serum hepcidin, ferritin and phosphate were also measured. Pair-wise comparisons utilised the Wilcoxon rank sum test; linear mixed models with an interaction term for treatment and time evaluated between-group effects.ResultsForty-two participants completed the study. In those randomized to FCM (n = 22), median (interquartile range) values pre-infusion and Day 2, respectively, were 843 pg/mL (313–1922) and 576 pg/mL (356–1296, p = 0.05) for iFGF23, 704RU/mL (475–1204) and 813RU/mL (267–1156, p = 0.04) for cFGF23, and 1.53 mmol/L (1.14–1.71) and 1.37 (1.05–1.67, p = 0.03) for phosphate. These parameters did not change following IS. Both serum ferritin (p < 0.001) and hepcidin (p < 0.001) increased in both groups, and the increase in hepcidin was greater in the FCM group (p = 0.03 for between-group difference).ConclusionsContrary to iron-deficient people with normal renal function, haemodialysis patients given protocol-driven intravenous FCM demonstrated a fall in iFGF23 and a rise in cFGF23, changes not evident with IS. This suggests a differential effect of intravenous iron treatment according to both formulation and renal function.Trial registrationAustralian and New Zealand Clinical Trials Register ACTRN12614000548639. Registered 22 May 2014 (retrospectively registered).Electronic supplementary materialThe online version of this article (doi:10.1186/s12882-016-0391-7) contains supplementary material, which is available to authorized users.