Salt sensitivity: genetic and physiological markers and its effects on salt taste perception and intake

Salt sensitivity is an independent cardiovascular disease and mortality risk factor, present in both hypertensive and normotensive population. It is genetically determined and it may affect the relationship between salt taste perception and salt intake. The aim of this study was to explore the genetic predisposition to salt sensitivity in young and middle-aged adult population and its effects on salt taste perception and salt intake. Salt sensitivity was investigated in 20 normotensive subjects and defined as the change in blood pressure (BP) after 7 days of low-salt (51.3 mmol sodium/day) and 7 days of high-salt diet (307.8 mmol sodium/day). Salt taste perception was identified using British Standards Institution sensory analysis method (BS ISO 3972:2011). Salt intake was assessed with a validated food frequency questionnaire. DNA was genotyped for single nucleotide polymorphisms in the SLC4A5, SCNN1B and TRPV1 genes coding for sodium and ion channels and transporters. The subjects with the rs7571842 (SLC4A5) AA genotype exhibited the highest increase in BP (systolic BP (∆SBP)=7.75 mmHg, p=0.002; diastolic BP (∆DBP)=6.25 mmHg, p=0.044; mean arterial pressure (∆MAP)=6.5 mmHg, p=0.014). There was an association between salt taste perception and salt sensitivity (rs=0.551, p=0.041) with salt intake being unaffected. There is a genetic predisposition to salt sensitivity and it is associated with salt taste perception. Unaffected salt intake suggests that factors other than taste sensitivity and/or other genetic variants may have more pronounced effects in healthy adults. Moreover, experiments are conducted in our laboratory to increase the understanding of the SLC4A5 effects on salt-sensitive changes in BP. Urine samples have been collected from subjects phenotyped for salt sensitivity to measure the expression of this co-transporter. If differently expressed in salt-sensitive and salt-resistant subjects, together with its genotype, it may serve as a personalised salt sensitivity biomarker.