The Diurnal Rhythm in Natriuretic Peptide Levels
Condition: Natriuretic Peptides; Obesity; Nocturnal Blood Pressure
Study type: Interventional

Summary: 
      The purpose of the study to assess the diurnal rhythm in natriuretic peptide levels and its
      temporal relationship with nocturnal blood pressure in obese and African-American individuals
      as compared with lean and white individuals.
    

Detailed description: 
      Obese and African-American individuals are at greater risk for cardiovascular morbidity and
      mortality than lean and white individuals. One of the key reasons for this health disparity
      is a higher risk of hypertension among obese and African-American individuals. The reasons
      for why these disparities develop are not well understood.

      Natriuretic peptides are hormones produced by the heart and have a wide range of favorable
      cardiovascular effects such as natriuresis (sodium excretion), vasodilation, and direct
      inhibition of the renin-angiotensin-aldosterone system. Human studies showed the existence of
      24-hour (diurnal) variations in the circulating natriuretic peptide levels.

      Prior work from the investigators and others demonstrated that individuals with
      genetically-determined lower circulating natriuretic peptides levels have higher blood
      pressure and greater risk of hypertension. Further, the investigators have shown that obesity
      and African-American race are associated with lower natriuretic peptide levels, suggesting
      that relatively low natriuretic peptide levels may be a biologic determinant contributing to
      health disparities.

      Obese and African-American individuals have a greater prevalence of nocturnal hypertension
      [nighttime blood pressure >120/80 mmHg], which is an independent risk factor for
      cardiovascular events. The underlying reasons for 24-hour variations in blood pressure are
      unknown.

      The investigators hypothesize that loss of the natural 24-hour rhythm of natriuretic peptide
      levels plays a role in the development of nocturnal hypertension in obese and
      African-American individuals. The aims of this study are:

        1. to examine whether there is a presence of a 24-hour rhythm in natriuretic peptide levels
           among normotensive obese and African-American individuals and whether there is a
           difference in the rhythmicity of natriuretic peptide levels between obese and lean as
           well as in African-Americans and whites;

        2. to examine whether there is an existence of a relationship between 24-hour variability
           of natriuretic peptide levels and 24-hour patterns of blood pressure and whether this
           relationship of rhythmicity of natriuretic peptide levels and nocturnal blood pressure
           differed in obese and lean individuals and by race.
    

Intervention name(s): standardized Study Diet
Intervention type(s): Other
Intervention description(s): Standardized diet consisted with eucaloric meals with 4.5 gm of sodium per day for 5 days.
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Other
Keywords: Diurnal Rhythm; Race