We will investigate the effects of the hormone angiotensin-(1-7) on energy expenditure in patients with obesity.

This is an outpatient study that requires a screening visit, and if eligible, one study visit in the Clinical Research Center within the Penn State Health Milton S. Hershey Medical Center. The screening visit will take about one hour and includes a brief physical examination and medical history, urine pregnancy test if female and of childbearing potential, measurement of heart rhythm, collection of blood samples, and measurements of body composition. If eligible based on the results of the screening visit, participants will be invited to participate in one study visit that will take about four hours. Participants will complete food recall and activity questionnaires prior to the study visit and asked not to change eating or physical activity patterns. A urine pregnancy test will be given for females of childbearing potential. Participants will lie down on a bed and a catheter (small plastic tube) will be placed in a vein in each arm to draw blood samples and to give study medications. Equipment will then be placed to measure heart rate, blood pressure, breathing rate, and the amount of oxygen in the blood. After placing this equipment, participants will be allowed to rest for at least 20 minutes. Resting energy expenditure will then be measured by asking participants to breathe through a canopy placed over their head that is connected to a metabolic cart for 45 minutes. Blood samples will be taken to measure hormones influencing resting energy expenditure. Participants will then receive either angiotensin-(1-7) or normal saline (salt water) through the catheter in the arm for up to two hours. Angiotensin-(1-7) is a substance that the body produces naturally; however, in this form, it is considered experimental, which means the Food and Drug Administration has not approved it for this use. Participants will receive either angiotensin-(1-7) or normal saline. The treatment will be randomly assigned meaning that it is determined purely by chance, and neither the participant nor study investigators will know which treatment is received. Blood pressure, heart rate, breathing rate, and oxygen in the blood will be measured continuously while giving angiotensin-(1-7) or normal saline. During the last 45 minutes of the treatment, resting energy expenditure will be measured again and additional blood samples taken. Participants will also have the option of allowing for a small piece of fat to be taken from under the skin in the abdominal region (fat tissue biopsy). Participants will then be allowed to recover for at least 20 minutes and then all equipment will be removed. After the study visit, a nurse will contact participants to check on general well-being and answer any questions.

$25 per hour; additional $75 for fat tissue biopsy