The Diurnal Rhythm in Natriuretic Peptide Levels

Study Overview
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Brief Summary
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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
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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: 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; 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.

Official Title
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The Diurnal Rhythm in Natriuretic Peptide Levels and Relationship With Nocturnal Blood Pressure

Conditions
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Obesity, Natriuretic Peptides, Nocturnal Blood Pressure

Intervention / Treatment
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* Other: standardized Study Diet


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age 18 to 40 years Blood pressure less than 140/90 Body Mass Index between 18.5 to 25 kg/m2 (lean) or 30 to 45 kg/m2 (obese) Self identified African-American or white individuals Willingness to comply with the study diet Provide informed consent Exclusion Criteria: History of hypertension History of cardiovascular, renal, or liver disease Diabetes or use of glucose-lowering medications Use of vasoactive or diuretic medications Atrial fibrillation Anemia (Hematocrit <41%) Abnormal serum sodium or potassium Abnormal liver function tests (>3x upper limit of normal) Current smokers Regular users of non-steroid anti-inflammatory medications

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 40 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Other
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: Study Individuals<br>Healthy self-identified African-American and white male participants will be screened. Study consent will be obtained, medical history and physical examination administered, and study eligibility determined based on the inclusion and exclusion criteria. Eligible subjects will meet a bio-nutritionist who will explain the 5 days of standardized diet at the screening visit and will review instructions for complying with the diet. If the subject agrees to adhere to the study diet, they will then be enrolled in the study (stratified by race). | Other: standardized Study Diet<br>* Standardized diet consisted with eucaloric meals with 4.5 gm of sodium per day for 5 days.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Plasma MRproANP | Assess the diurnal rhythm in circulating MRproANP levels among obese individuals and compared it with lean individuals | About 24 hours on the in-patient study visit day after consuming study meals for 5 days | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Acrophase Difference in Hours Between the MR-proANP and Systolic BP Rhythm | Assess relationship between 24-hour variability of MRproANP levels and 24-hour patterns of blood pressure and whether this relationship of rhythmicity of MRproANP levels and nocturnal blood pressure differed in obese and lean individuals and by race | About 24 hours on the in-patient study visit day after consuming study meals for 5 days | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Race, Diurnal Rhythm