Effect of DPP4 Inhibition on Vasoconstriction

Inclusion Criteria: Type 2 Diabetes Mellitus, as defined by one or more of the following, * Hgb A1C ≥6.5%, or * Fasting plasma glucose ≥126mg/dL, or * Two hour plasma glucose ≥200 mg/dL following 75gr oral glucose load For female subjects the following conditions must be met: * Postmenopausal status for at least 1 year, or * Status post-surgical sterilization, or * If of childbearing potential, utilization of some form of birth control and willingness to undergo β-HCG testing prior to drug treatment and on every study day Exclusion Criteria: * Type 1 diabetes. * Poorly controlled T2DM, defined as Hgb A1C\>8.7%. * Use of anti-diabetic medications other than metformin. * Hypertension. * Subjects who have participated in a weight-reduction program during the last 6 months and whose weight has increased or decreased more than 5 kg over the preceding 6 months. * Pregnancy. Breast-feeding. * Treatment with any of the following drugs: cisapride, pimozide, terfenadine, astemizol * Clinically significant gastrointestinal impairment that could interfere with drug absorption * Cardiovascular disease that would pose risk for the subject to participate in the study, such as: myocardial infarction within 6 months prior to enrollment, presence of angina pectoris, significant arrhythmia, congestive heart failure (LV hypertrophy acceptable), deep vein thrombosis, pulmonary embolism, second- or third-degree AV block, mitral valve stenosis, or hypertrophic cardiomyopathy. * Impaired hepatic function (aspartate amino transaminase \[AST\] and/or alanine amino transaminase \[ALT\] \>2 x upper limit of normal range) * Impaired renal function (eGFR\< 60mL/min/1.73m2 as determined by the MDRD equation). * History or presence of immunological or hematological disorders. * History of pancreatitis or known pancreatic lesions. * History of angioedema or cough while taking an ACE inhibitor. * Hematocrit \<35%. * Treatment with anticoagulants. * Growth hormone deficiency. * Diagnosis of asthma requiring use of an inhaled β-2 agonist more than 1 time per week. * Any underlying or acute disease requiring regular medication which could possibly pose a threat to the subject or make implementation of the protocol or interpretation of the study results difficult * Treatment with systemic glucocorticoids within the last 6 months. * Treatment with lithium salts * Ongoing tobacco use or recreational drug use. * Treatment with any investigational drug in the 1 month preceding the study * Mental conditions rendering the subject unable to understand the nature, scope, or possible consequences of the study * Inability to comply with the protocol, e.g., uncooperative attitude, inability to return for follow-up visits, and unlikelihood of completing the study