Visualizing Vascular Mechanisms of Salt Sensitivity
Condition: Obesity; Cardiovascular Risk Factor; Salt; Excess
MeSH terms: Obesity
Study type: Interventional

Summary: 
      This study aims to assess the salt sensitive blood pressure response to dietary salt load
      compared with radiological markers of salt handling.
    

Detailed description: 
      Hypertension is a major cause of heart disease, heart failure, and stroke. Hypertension, or
      high blood pressure, affects people differently and is related to the body's ability to
      maintain healthy circulation of salt. Some individuals may be affected by salt sensitive
      blood pressure (SSBP), when their blood pressure changes in response to dietary salt load.
      SSBP is a prevalent, independent risk factor for developing cardiovascular disease that
      preferentially affects black individuals. Current methods to assess SSBP require dietary salt
      loading over the course of days to weeks, and measurement of blood pressure following high
      salt diet and low salt diet. Such lengthy protocols are not feasible in a clinical setting to
      evaluate this risk factor for cardiovascular disease, and more importantly, these procedures
      provide incomplete information about mechanisms of salt sensitivity.

      Our knowledge regarding salt handling in the body is limited. While renal dysfunction is
      partly responsible for SSBP, recent research points to the role of lymphatic vascular
      clearance in regulating tissue salt storage and blood pressure control. To better understand
      these mechanisms in vivo, we have recently developed a noninvasive magnetic resonance (MR)
      lymphangiography method sensitive to lymphatic vasculature, and applied standardized MR
      protocols for measuring tissue sodium and fat storage in adults with impaired lymphatic
      clearance. We found evidence of lymph stasis and tissue salt deposition that correlated with
      local subcutaneous fat volume. Here, we will test whether similar lymphatic pathways are
      impaired in persons with SSBP, leading to tissue salt and fat storage, in comparison to the
      involvement of renal dysfunction in SSBP tissue profiles.

      The aims of this study are to improve our understanding of vascular mechanisms of human salt
      storage, and to provide standardized radiologic biomarkers sensitive to the SSBP phenotype.
      This study will test the primary hypothesis that the SSBP response is correlated with
      baseline tissue sodium storage, and elevated in persons with salt sensitivity. Secondary
      hypotheses will address whether the SSBP response is related to fat storage, lymphatic
      vascular function, renal vascular function, and impaired target organ responses to salt
      loading, including decreased urinary sodium excretion, and less suppression of plasma renin
      and serum aldosterone.
    

Intervention name(s): Low-salt diet; High-salt diet
Intervention type(s): Dietary Supplement; Dietary Supplement
Intervention description(s): The low-salt diet (7 days) will consist of meals, snacks and water provided by Vanderbilt's metabolic kitchen.; The high-salt diet (7 days) consists of each subject's typical diet, supplemented each day with 2 bullion broth packets, which will be provided to the subject by the study staff.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Basic Science
Keywords: salt sensitive, blood pressure, obesity, magnetic resonance imaging