Study of the Effects of Xenin-25 in Humans With and Without Type 2 Diabetes Mellitus

Inclusion Criteria: * Individuals must be able to consent for their own participation (no mental impairment affecting cognition or willingness to follow study instructions). * Healthy volunteers with no clinical evidence of T2DM. * Otherwise healthy volunteers that have impaired glucose tolerance. * Otherwise healthy volunteers with diet controlled T2DM. * Otherwise healthy volunteers with T2DM that take oral agents only if the subject's pre-existing oral anti-diabetic agents can be safely discontinued for 48-hours. * Persons with HbA1c less than 9%. * Women of childbearing potential must be currently taking/using an acceptable method of birth control. 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 complete all required visits. Exclusion Criteria: * Lacks cognitive ability to sign the consent or follow the study directions. * Women unwilling to use an acceptable method of contraception during the course of the study, or who are currently breast-feeding. * Any subject whose screening HbA1c is \>9.0%. * Type 2 diabetes requiring the use of supplemental insulin at home. * 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. * Volunteers with a history of gastrointestinal disorders, particularly related to gastric motility/emptying such as gastric bypass, documented gastro-paresis in diabetic volunteers. * 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% mg/dlL). * Diabetics that have the potential to have a low blood sugar without them being aware that their blood sugar is low (hypoglycemia unawareness). * Significant systemic illness including heart, kidney, inflammatory, liver, or malignant disease requiring medications. * Subjects will be excluded if their liver or kidney function is outside the upper limits of normal by \> 3%. Total Bilirubin levels should be \<2. * Subjects unwilling to allow the use of human albumin in the preparation of the peptides. * Unwillingness to allow blood glucose level adjustment (if needed) with IV insulin