Identification of DEGs
Two datasets, GSE78721 and GSE12288, were utilized for bioinformatics analysis in this study. In GSE78721, a total of 2,266 DEGs were identified between T2DM patients and normal samples, comprising 1,209 upregulated and 1,057 downregulated genes (Figure 1A). In GSE12288, 924 DEGs were verified between ASCVD patients and controls, including 403 genes that were overexpressed and 521 that were downregulated (Figure 1C). The top 50 DEGs identified in both datasets are represented in heat maps shown in Figure 1B,D. By intersecting these two datasets, 32 C-DEGs were identified, consisting of 20 upregulated and 12 downregulated genes (Figure 2A,B).
GO and KEGG enrichment of the C-DEGs
To elucidate the biological functions and key pathways associated with the 32 C-DEGs, GO and KEGG analyses were performed. The top ten terms related to biological process (BP), cellular component (CC), and molecular function (MF) among the C-DEGs are presented in Figure 3A. The BP functions predominantly include regulation of plasminogen activation, regulation of fibrinolysis, positive regulation of cardiocyte differentiation, negative regulation of protein binding, and cardioblast differentiation. The CC functions pertain to the serine-type endopeptidase complex, protein complexes involved in cell-matrix adhesion, condensed chromosome, specific granule membrane, and PML body. The MF encompasses structural constituents of the cytoskeleton, superoxide-generating NADPH oxidase activator activity, intramolecular transferase activity (phosphotransferases), serine-type exopeptidase activity, and IgG binding (Figure 3A). In terms of KEGG analysis, the C-DEGs were primarily involved in critical pathways, including viral myocarditis, arrhythmogenic right ventricular cardiomyopathy, complement and coagulation cascades, prostate cancer, hypertrophic cardiomyopathy, dilated cardiomyopathy, apoptosis, phagosome, and protein processing in the endoplasmic reticulum (Figure 3B).
Construction of PPI networks and hub gene screening
Among the 32 C-DEGs, three genes exhibited no known interactions with other C-DEGs in the STRING database and were therefore excluded from the PPI network construction. The STRING platform was employed for PPI analysis of the remaining 29 C-DEGs, revealing a network consisting of 29 nodes and 39 edges, which was visualized using Cytoscape (Figure 4A). Subsequently, eight hub C-DEGs (HSP90B1, PLAU, SLPI, TOP3A, NCF4, PRF1, TUBA1C, and CS) were identified based on their connectivity degree (Figure 4B).
Differences in immune cell infiltration and their correlation with hub C-DEGs
This analysis focused exclusively on the T2DM dataset (GSE78721) to preliminarily investigate changes in the immune microenvironment in the context of T2DM and their relationship with hub genes. Violin plots were utilized to visualize the relationship between the T2DM dataset and the infiltration levels of 22 immune cell types (Figure 5A; details in Supplementary Table 3). The immune cell infiltration analysis indicated a higher proportion of activated dendritic cells in the T2DM group compared to the control group (P = 0.049), while the proportion of resting dendritic cells was significantly lower in the T2DM group (P = 0.023). Furthermore, the relationship between the expression levels of the eight hub C-DEGs and the infiltration levels of the 22 different immune cell types was visualized using a heatmap (Figure 5B). Notably, TOP3A expression exhibited a strong positive correlation with the infiltration level of regulatory T cells (Tregs) (P < 0.001), while SLPI expression was strongly positively correlated with gamma delta T cell infiltration (P < 0.001). Conversely, NCF4 expression showed a strong negative correlation with the infiltration level of activated NK cells (P < 0.001), PRF1 expression was strongly negatively correlated with the infiltration level of M2 macrophages (P < 0.001), and PLAU expression was strongly negatively related to the infiltration level of naive B cells (P < 0.001).
Candidate drug-target network for hub C-DEGs
Among the eight identified hub C-DEGs, CS and TOP3A were not listed as known drug targets in the DGIdb database and were thus excluded from the subsequent candidate drug-target network analysis. To identify drugs with potential therapeutic roles in T2DM and ASCVD, the remaining six hub C-DEGs were submitted to the DGIdb database (details in Supplementary Table 4). Subsequently, Cytoscape was employed to construct a candidate drug-target network illustrating the associations between hub C-DEGs and candidate targeted drugs (Figure 6). This network comprised six hub C-DEGs, 136 molecular drugs, and 137 edges. Specifically, 82, 5, 3, 4, 1, and 42 candidate target drugs were identified for TUBA1C, NCF4, PRF1, SLPI, HSP90B1, and PLAU, respectively, with the majority classified as antineoplastic agents, anti-inflammatory agents, and antithrombotic agents.
Validation of hub C-DEGs expression
Due to the absence of CS and TOP3A as candidate drug targets in the DGIdb database and their biological functions being less directly related to therapeutic strategies in the context of T2DM and ASCVD research, the study focused on the remaining six hub C-DEGs (HSP90B1, PLAU, SLPI, NCF4, PRF1, and TUBA1C) for experimental validation. To further explore the roles of these hub C-DEGs, qRT-PCR and western blot assays were conducted to assess the expression levels of core genes across different groups (Figure 7 and Figure 8). The expression levels of TUBA1C, NCF4, SLPI, HSP90B1, and PLAU were significantly upregulated in patients with T2DM and ASCVD compared to corresponding healthy control groups, while PRF1 expression was downregulated. These findings suggest that these core genes may play a significant role in the progression of patients with T2DM and ASCVD.
DATA AVAILABILITY:The gene expression datasets GSE78721 and GSE12288 used for bioinformatics analysis in this study are available from the public NCBI GEO database. The raw data from the experimental validation part generated in this study are provided in Supplementary File 1.

Figure 1: Identification of DEGs in the datasets GSE78721 and GSE12288. (A,C) The volcano plots of DEGs in GSE78721 and GSE12288, respectively. |logFC|≥ 0.5 and P < 0.05 were established as the screening threshold; the upregulated genes were marked as red, and the downregulated genes were marked as green. (B,D) Heatmaps of the top 50 DEGs in GSE78721 and GSE12288, respectively. Please click here to view a larger version of this figure.

Figure 2: Venn diagram of C-DEGs from two datasets. (A) Venn diagram of upregulated C-DEGs from T2DM and ASCVD in GSE78721 and GSE12288 datasets. (B) Venn diagram of downregulated C-DEGs from T2DM and ASCVD in GSE78721 and GSE12288 datasets. Please click here to view a larger version of this figure.

Figure 3: Functional and pathway enrichment analysis of C-DEGs. Bar graphs of GO (A) and KEGG (B) enrichment analyses. Vertical coordinates indicate the description of different GO items or KEGG pathways, and horizontal coordinates indicate the number of enriched C-DEGs. Please click here to view a larger version of this figure.

Figure 4: PPI network and hub gene screening of C-DEGs. (A) The PPI network of C-DEGs. Red and blue represent the upregulated and downregulated C-DEGs, respectively. (B) Eight hub genes were identified among the C-DEGs. Nodes represent a C-DEG, and edges represent the interaction between C-DEGs. Please click here to view a larger version of this figure.

Figure 5: Immune cell infiltration analysis. (A) Differences in the infiltration of 22 immune cell types between the T2DM group and the control group. Horizontal axis: immune cell subtypes; Vertical axis: relative infiltration level of immune cells. (B) Correlation heatmap of the expression of 8 hub C-DEGs and the infiltration levels of 22 immune cell types. Red squares: positive correlation; Blue squares: negative correlation. Darker colors indicate stronger correlations. Please click here to view a larger version of this figure.

Figure 6: Candidate drug-target network for six hub C-DEGs. Red nodes represent hub C-DEGs, green nodes represent candidate targeted drugs, and the edges between them represent interaction pairs. Please click here to view a larger version of this figure.

Figure 7: Validation of core gene expression in the patients with T2DM and ASCVD by qRT-PCR. The mRNA expression levels of HSP90B1 (A), PLAU (B), SLPI (C), NCF4 (D), PRF1 (E), and TUBA1C (F) were detected by qRT-PCR. Please click here to view a larger version of this figure.

Figure 8: Validation of core gene expression in patients with T2DM and ASCVD by Western blot. The protein expression levels of HSP90B1 (A), PLAU (B), SLPI (C), NCF4 (D), PRF1 (E), and TUBA1C (F) were detected by Western blot assays. Please click here to view a larger version of this figure.
Supplementary Table 1. Gene expression matrix for the GSE78721 dataset, used for the T2DM transcriptomic analysis in this study.Please click here to download this file.
Supplementary Table 2. Gene expression matrix for the GSE12288 dataset, used for the ASCVD transcriptomic analysis in this study.Please click here to download this file.
Supplementary Table 3: Immune cell infiltration analysis in the GSE78721 dataset.Please click here to download this file.
Supplementary Table 4: Candidate drug-target interactions for hub common differentially expressed genes.Please click here to download this file.
Supplementary File 1: The raw data from the experimental validation part generated in this study.Please click here to download this file.