The primary objective is to evaluate the overarching hypothesis that obese and black individuals have relatively lower circulating natriuretic peptide levels compared with lean and white individuals. Conventional clinical assays for measurement of circulating natriuretic peptides display substantial overlap, precluding determination of the basis of the relative natriuretic peptide deficiency previously observed in these groups. We will study lean or obese, black or white, healthy adult subjects with intravenous (IV) saline infusion as a stimulus for natriuretic peptide production and release. We will measure circulating levels of natriuretic peptide isoforms using mass spectrometry that allows the specific identification of proBNP 1-108 and its cleavage product BNP 1-32.

Inclusion Criteria:

• Age between 18 and 65 years;
• BMI between 18 and 25 (lean) or 30 and 40 kg/m2 (obese);
• self-reported race of either black or white;
• otherwise healthy with no chronic comorbidities.

Exclusion Criteria:

• History of diabetes mellitus
• Currently pregnant
• History of cardiac disorder including heart failure, cardiomyopathy, myocardial infarction, coronary revascularization, abnormal stress test, uncontrolled arrhythmia or arrhythmia requiring treatment, congenital heart disease, pericardial disease.
• History of hypertension defined as taking anti-hypertensive medications or untreated hypertension with systolic blood pressure ≥ 140 mm Hg or diastolic blood pressure ≥ 90 mm Hg at most recent clinical visit or screening visit.
• Obstructive lung disease
• History of chronic kidney disease
• History of liver disease or cirrhosis
• Uncontrolled thyroid dysfunction
• History of solid organ transplant
• History of malignancy other than basal or squamous cell skin cancer
• Inability to lie flat for 6 hours

Only deidentified individual participant data will be provided to interested researchers with a data use agreement and confirmation that no protected health information will be shared, all data will be stored in password protected databases accessible to only key study personnel, and that data will be returned or destroyed after completion or 6 years, whichever is shorter.

No later than 1 year after completion of the study.

Only deidentified individual participant data will be provided to interested researchers with a data use agreement and confirmation that no protected health information will be shared, all data will be stored in password protected databases accessible to only key study personnel, and that data will be returned or destroyed after completion or 6 years, whichever is shorter.