GLP1R and obesity due to melanocortin 4 receptor deficiency: Additionally, circulating GLP-1 concentrations were increased in healthy normal-weight volunteers (LEAN), obese individuals with T2DM or impaired glucose tolerance (OB-DIAB), and obese nondiabetic control subjects (OB-CON) after glutamine intake (peak concentrations at 30 min: LEAN: 22.5 ± 3.4; OB-CON: 17.9 ± 1.1; OB-DIAB: 17.3 ± 3.4 pmol/L), which may represent a novel therapeutic approach to stimulating insulin secretion in obesity and T2DM [63].