GLP1R and type 2 diabetes mellitus: Although numerous clinical studies have proven the benefit of sitagliptin in reducing glucose excursion after glucose or meal tolerance tests (MTT) (4,11,12), researchers need to clarify how different macronutrient composition meals could impact the effect of sitagliptin on glucose, insulin, C-peptide, glucagon and GLP-1 excursion in early T2DM.