Study of Safety, Tolerability, Pharmacokinetics and Pharmacodynamics of Single Oral Doses of JTT-252

Inclusion Criteria: Healthy Subject Cohorts: * Healthy male or female subjects * Age 18 to 50 Years (inclusive) * Body Mass Index (BMI) between 19.0 and 31.0 kg/m2 (inclusive) Type 2 Diabetic Subject Cohorts: * Male or female Type 2 diabetic subjects who are currently being treated with a stable dose of metformin * Age 18 to 65 Years (inclusive) * BMI between 25.0 and 40.0 kg/m2 (inclusive) * Have a glycosylated hemoglobin (HbA1c) of \>7.0% to ≤9.5% * Have a fasting plasma glucose (FPG) \<240 mg/dL Exclusion Criteria: Healthy Subject Cohorts: * Known clinically relevant history or presence of significant respiratory, gastrointestinal, renal, hepatic, hematological, lymphatic, neurological, cardiovascular, psychiatric, musculoskeletal, genitourinary, immunological, metabolic and dermatological or connective tissue disease * Subjects with a systolic blood pressure \>140 mmHg and/or diastolic blood pressure \>90 mmHg Type 2 Diabetic Subject Cohorts: * Subjects with a known medical history or presence of type 1 diabetes mellitus * Subjects with known medical history of acute metabolic diabetic complications * Subjects with uncontrolled hypertension (systolic blood pressure \>150 mmHg and/or diastolic blood pressure \>95 mmHg