Inflammatory Response to Salt in Essential Hypertension

Salt is a main environmental risk factor involved in atherosclerotic complications and in the high risk of a variety of cardiovascular (CV) diseases including hypertension, left ventricular hypertrophy (LVH), chronic kidney disease (CKD) and heart failure. The link between sodium and cardiovascular disease is complex and involves blood pressure (BP) dependent and independent mechanisms. Among the latter, inflammation is suspected to be a major effector of arterial damage brought about by the salt excess in animal models. In humans, C-Reactive Protein (CRP) associated directly with dietary salt intake in a population-based survey but such a link was not confirmed in other studies. This apparent discrepancy may depend on the observational (i.e., open to confounding) nature of these studies. Inflammatory cytokines are essential for the short term systemic response to environmental stressors. For example it is well established that TNF-α, a cytokine that modulates renin gene expression by signalling via TNF-receptor 2, exerts a protective effect for the myocardium in a stressful condition like experimental cardiac ischemia while low levels of adiponectin have a detrimental effect in the same setting. Thus, the inflammation-sodium relationship may be non-linear and severe salt restriction may actually trigger inflammation, a hypothesis suggested by the observation that biomarkers of inflammation rose in response to salt depletion in a sequential study in essential hypertensives. However, the lack of randomization in this study leaves open the question whether the observed pro-inflammatory effect was due to change in salt intake or to other, unmeasured time-dependent effect(s). With this background in mind the investigators setup a randomized, single masked, cross-over study to assess the effect of a short term very low salt diet on biomarkers of innate immunity in patients with uncomplicated essential hypertension.