GLP1R and obesity due to melanocortin 4 receptor deficiency: Because of the new knowledge of the importance and complexity of GIP biology in α and β cell tones, and because DPP4 inhibition had additional beneficial effects compared to GLP-1R monoagonism, GIP has been reconsidered for the development of dual GLP-1/GIP agonists in the treatment of obesity and T2DM.