Abstract
Renal tubular sodium (Na) handling plays a key role in blood pressure (BP) regulation. Several cross-sectional studies reported a positive association between higher proximal tubule fractional reabsorption of Na and BP, but no prospective investigation has been reported of this possible association. Hence, the purpose of this study was to estimate the predictive role of renal Na handling on the risk of incident hypertension and the changes in BP occurring in the 8-year follow-up observation of a sample of initially normotensive men (The Olivetti Heart Study). The study included 294 untreated normotensive non-diabetic men with normal renal function examined twice (1994–95 and 2002–04). Renal tubular Na handling was estimated by exogenous lithium clearance. Fractional reabsorption of Na in proximal and distal tubules was calculated and included in the analysis. At baseline, there was no association between BP and either proximal or distal fractional reabsorption of Na. At the end of the 8-year follow-up, direct associations were observed between baseline proximal (but not distal) Na fractional reabsorption and the changes occurred in systolic and diastolic BP over time (+2.79 and +1.53 mmHg, respectively, per 1SD difference in proximal Na-FR; p<0.01). Also multivariable analysis showed a direct association between baseline proximal Na fractional reabsorption and risk of incident hypertension, independently of potential confounders (OR: 1.34, 95%CI:1.06–1.70). The results of this prospective investigation strongly suggest a causal relationship between an enhanced rate of Na reabsorption in the proximal tubule and the risk of incident hypertension in initially normotensive men.
Highlights
The role of the kidney in blood pressure (BP) regulation was perceived since the early ‘40s [1] and comprehensively described over the last decades of the past century [2,3]
Data are expressed as means (SD), or as percentages; BP, Blood Pressure; 1 Geometric mean; 2Calculated by Tanaka’s formula. doi:10.1371/journal.pone.0171973.t001
Data are expressed as means ±SD; Δ, changes after 8 years were calculated as final minus basal measurements; SBP, systolic blood pressure; DBP, diastolic blood pressure. 1 p –value < 0.01
Summary
The role of the kidney in blood pressure (BP) regulation was perceived since the early ‘40s [1] and comprehensively described over the last decades of the past century [2,3]. In this general context, particular attention has been paid to renal tubular sodium handling [4]. Sodium handling and hypertension the Italian Nutritional Guidelines and an unpaid member of WASH (World Action in Salt and Health). FPC is Head of the World Health Organization Collaborating Centre for Nutrition, Vice-President and Trustee of the British Hypertension Society and unpaid member of CASH, WASH and the UH Health Forum. The remaining authors do not disclose any conflict of interest
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