Pathogenesis of Youth Onset Type 2 Diabetes and Prediabetes

Inclusion Criteria: * Good general health, taking no medication on a chronic basis; * Age 12 to 18 yrs, in puberty (girls and boys: Tanner stage II - IV), * BMI (BMI \>85th%) indicating obesity, * Girls who are menstruating must have a negative pregnancy test during the study and, when possible, be in the follicular phase during infusion study visits (The follicular phase will be identified according to the last menstrual period record and/or according to the oral contraceptive assumption schedule. The investigators will not perform ovulation testing or hormonal assays); * Subject must have normal liver and kidney function, amylase and lipase levels. * Pre-IGT or IGT * TT or CC genotype. Exclusion Criteria: * Baseline creatinine \>1.0 mg; * Pregnancy; * Presence of endocrinopathies (e.g. Cushing syndrome); * Cardiac, renal or pulmonary or other chronic illness; * Adolescents with psychiatric disorder or with substance abuse history and taking the drugs that affect glucose metabolism, such as any form of steroids, antipsychotics, progesterone preparations, and others.