The strengths of our study are as follows: this was the first randomized controlled trial directly comparing DPP-4 inhibitors and an SGLT2 inhibitor on glucose fluctuation in insulin therapy; there were no significant biases in the pre-treatment for type 2 diabetes mellitus in both study arms; and we could assess the relationship between glucose fluctuations and other metabolic parameters. This evidence concerns the gene SLC5A2 and type 2 diabetes mellitus.