Of the 16 diagnostic only proteins, 4 were higher in T2D: Kallikrein-4 (214 ± 9 vs. 181 ± 3, T2D vs. control, p = 0.001), Aminoacylase-1 (4616 ± 514 vs. 2956 ± 346 RFU, T2D vs. control, p = 0.001), Insulin-like growth factor-binding protein-4 (IGFBP4) (7334 ± 212 vs. 6658 ± 255 RFU, T2D vs. control, p < 0.05) and Reticulon-4 receptor (RTN4R) (1872 ± 93 vs. 1474 ± 53, T2D vs. control, p < 0.001) (Figure 2A–D). This evidence concerns the gene IGFBP4 and type 2 diabetes mellitus.