Glucagon Suppression by Hyperglycemia in the Presence and Absence of Amino Acid Infusion

Inclusion Criteria - Obese Subjects with Type 2 Diabetes: * HbA1c ≤ 8.5% (type 2 diabetic subjects). * HbA1c ≤ 6.5% (obese and lean subjects). * BMI ≥ 28 Kg/M\^2 (Obese subjects with and without type 2 diabetes). * BMI ≤ 25 Kg/M\^2 (Lean subjects without type 2 diabetes). * Use of sulfonylureas or metformin only (type 2 diabetec subjects). * For female subjects: negative pregnancy test at the time of enrollment or study. * No history of prior upper abdominal surgery such as adjustable gastric banding, pyloroplasty and vagotomy. * No active systemic illness or malignancy. * No symptomatic macrovascular or microvascular disease. * No contraindications to MRI (e.g., metal implants, claustrophobia). * Hematocrit \> 35%. * TSH \> 0.4 or \< 5.5. * Consumption of \< 2 alcohol drinks per day or \< 14 per week or a negative AUDIT questionnaire. Exclusion Criteria - Obese Subjects with Type 2 Diabetes: * HbA1c ³ 8.5% * BMI ≤ 28 Kg/M2 * Use of insulin or agents other than sulfonylureas or metformin. * For female subjects: positive pregnancy test at the time of enrollment or study * History of prior upper abdominal surgery such as adjustable gastric banding, pyloroplasty and vagotomy. * Active systemic illness or malignancy. * Symptomatic macrovascular or microvascular disease. * Contraindications to MRI (e.g., metal implants, claustrophobia). * Hematocrit \< 35% * TSH \< 0.4 or \> 5.5. * Consumption of \> 2 alcohol drinks per day or \> 14 per week or a positive AUDIT questionnaire. Inclusion Criteria - Obese Subjects without Type 2 Diabetes: * BMI ≥ 28 Kg/M2. * \> 5% liver fat content, as determined by MRI using the proton density fat fraction (PDFF) technique. Exclusion Criteria - Obese Subjects without Type 2 Diabetes: * HbA1c ≥ 6.5% * BMI ≤ 28 Kg/M2 * Use of any glucose-lowering agents including metformin or sulfonylureas. * For female subjects: positive pregnancy test at the time of enrollment or study * History of prior upper abdominal surgery such as adjustable gastric banding, pyloroplasty and vagotomy. * Active systemic illness or malignancy. * Symptomatic macrovascular or microvascular disease. * Contraindications to MRI (e.g., metal implants, claustrophobia). * Hematocrit \< 35% * TSH \< 0.4 or \> 5.5. * Consumption of \> 2 alcohol drinks per day or \> 14 per week or a positive AUDIT questionnaire. Inclusion Criteria - Lean subjects without Diabetes: \- BMI ≤ 25 Kg/M\^2). Exclusion Criteria - Lean Subjects without Diabetes: * HbA1c ≥ 6.5%. * BMI ≥ 25 Kg/M\^2. * Use of any glucose-lowering agents including metformin or sulfonylureas. * For female subjects: positive pregnancy test at the time of enrollment or study. * History of prior upper abdominal surgery such as adjustable gastric banding, pyloroplasty and vagotomy. * Active systemic illness or malignancy. * Symptomatic macrovascular or microvascular disease. * Contraindications to MRI (e.g., metal implants, claustrophobia). * Hematocrit \< 35%. * TSH \< 0.4 or \> 5.5. * Consumption of \> 2 alcohol drinks per day or \> 14 per week or a positive AUDIT questionnaire. * Liver fat content ≥ 5% as determined by MRI using the proton density fat fraction (PDFF) technique.