The five diagnostic genes, namely, inter-trypsin inhibitor heavy chain 3 (ITIH3), fibroblast growth factor 1 (FGF1), neuron cell adhesion molecule (NRCAM), advanced glycosylation end-product-specific receptor (AGER), and CACNA1C, were identified when the lambda min = 0.0106 via LASSO analysis (Figure 3A), and they were all downregulated in T2DM samples of the GSE21321 dataset (Supplementary Figure S2). The gene discussed is CACNA1C; the disease is type 2 diabetes mellitus.