Salt Sensitivity: Challenging and Controversial Phenotype of Primary Hypertension

Increases in life expectancy and cardiovascular adverse events in patients with hypertension highlight the need for new risk-reduction strategies to reduce the burden of degenerative diseases. Among the environmental factors, high salt consumption is currently considered the most important risk factor of hypertension. However, while high salt intake significantly raises blood pressure in some individuals, others do not show variation or even decrease their blood pressure. This heterogeneity is respectively classified as salt sensitivity and salt resistance. In this review, we propose salt sensitivity as a useful phenotype to unravel the mechanistic complexity of primary hypertension. The individual variability in blood pressure modification in response to salt intake changes derives from the combination of genetic and environmental determinants. This combination of random and non random determinants leads to the development of a personal index of sensitivity to salt. However, those genes involved in susceptibility to salt are still not completely identified, and the triggering mechanisms underlying the following development of hypertension still remain uncovered. One reason might be represented by the absence of a specific protocol, universally followed, for a standard definition of salt sensitivity. Another reason may be linked to the absence of common criteria for patient recruitment during clinical studies. Thus, the generation of a reliable approach for a proper recognition of this personal index of sensitivity to salt, and through it the identification of novel therapeutic targets for primary hypertension, should be one of the aspirations for the scientific community.