Racial Differences in the Natriuretic Peptide Response to Glucose Challenge

Previous studies have shown an association between reduced levels of circulating natriuretic
peptides (NPs) and obesity in humans. This association is especially pronounced in those with
metabolic syndrome traits and elevated plasma insulin. As previously conducted study has
shown that an increase in NPs with weight loss in obese individuals is "primary" and not
secondary to alteration in cardiac structure or function.

Previous experimental data suggests that Atrial NP (ANP) has a wide range of favorable
metabolic effects including that activation of brown fat and improvement in skeletal muscle
oxidative capacity and glucose utilization. New evidence suggests that ANP activation
directly modulates insulin sensitivity and energy homeostasis, suggesting that ANP
suppression could promote more obesity/insulin resistance. Moreover, ANP exerts potent
lipolytic effects in vitro and in vivo. The previous study has shown that a high-carbohydrate
challenge in healthy volunteers is associated with a reduction in N-terminal-proANP
(NTproANP) but not N-terminal-proB-type NP (NTproBNP) levels. Nonetheless our outcomes were
predominantly in Caucasians and warrants replication in other racial groups.

There is no data on the ANP response to high-carbohydrate challenge in African Americans, a
racial group with disproportionately greater rates of obesity, insulin resistance, and
diabetes as compared to Caucasians. So the investigators have proposed to conduct a pilot
study in otherwise healthy, normotensive subjects to examine NP system, especially the
effects on MRproANP in response of high-carbohydrate challenge.

Inclusion Criteria:

- Age 18-40 years

- Blood pressure less than 140/90

- Estimated creatinine clearance >60cc/min

- Willingness to comply with the study diet

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% in men and <35% in women

- Abnormal serum sodium or potassium

- Urine β-HCG consistent with pregnancy

- Abnormal liver function tests (>3x upper limit of normal)

- Women taking hormonal birth control

- Current smokers

- Regular users of non-steroid anti-inflammatory medications