To Define the Role of GLP-1 for Improving Glucose Homeostasis in Humans Following Gastric Bypass Surgery

Inclusion Criteria: * Individuals must be able to consent for their own participation (no mental impairment affecting cognition or willingness to follow study instructions). * Healthy, weight stable, with previous Roux-en-Y gastric bypass surgery and no clinical evidence of type 2 diabetes either before and after Roux-en-Y gastric bypass surgery. * Women of childbearing potential must be currently taking/using a method of birth control that is acceptable to the investigators. A pregnancy test will be done at the beginning of each visit. Any woman with a positive pregnancy test will be removed from the study. * Willingness to return have 8-10ml of blood drawn 25-30 days after the last Xenin infusion; to check for Xenin peptide antibodies that MAY develop. (All efforts will be made to complete this visit during study participation.) Exclusion Criteria: * Lacks cognitive ability to sign the consent \&/or follow the study directions for themselves. * Women unwilling to comply with using an acceptable method of contraception during the course of the study, or who are currently breast-feeding. * Volunteers with a history of Acute Pancreatitis. * Volunteers with a history of cancer (except for skin cancer). * Volunteer with a history of Chronic Pancreatitis and/or risk factors for chronic pancreatitis including hypertriglyceridemia (triglycerides \>400mg/ml) hypercalcemia (blood calcium level \>11.md/dl) and/or the presence of gallstones. * Subjects taking medications known to affect glucose tolerance. * Hematocrit from the lab is below 33% (or if the finger stick hemoglobin measured with the HemoCue 201+ is \<11.2 g/dl). * Any major medical conditions, or conditions that in the opinion of the PI make the subject unsuitable for the study. * Subjects with abnormal kidney function as measured by the Creatinine concentration will be excluded. * Subjects with a history of active liver disease or AST/ALT levels \>2X upper limit of normal will also be excluded. * Total Bilirubin levels should be \<2. * Subjects unwilling to allow the use of their own blood or albumin in the preparation of the peptides. (The blood will prevent sticking of the peptide to the tubing; an alternative method has been sought but not found.) * Unwillingness to return have 8-10ml of blood drawn 25-30 days after the last Xenin infusion; to check for Xenin peptide antibodies that MAY develop. (All efforts will be made to complete this visit during study participation.)