3.1 Baseline characteristics of patients
The baseline characteristics of the study population are shown in Table 1. There are no statistical differences among age, male, BMI, medical history, Gensini score, medication used before admission, laboratory value, and insulin sensitivity surrogate index. The age, BNP, and SPISE index levels had a higher tendency in group AD than those in group A (p > 0.05).
Table 1 Baseline clinical characteristics
|
AMI with T2DM (n=12)
|
AMI without T2DM (n=12)
|
p value
|
Age, years
|
61.42±4.29
|
58.75±8.71
|
0.352
|
Male gender
|
8(40.0%)
|
12(60.0%)
|
0.093
|
BMI, kg/m2
|
27.79±8.17
|
32.12±5.98
|
0.152
|
Medical history
|
Current/ex-Smoker, n (%)
|
4(33.3%)
|
8(66.7%)
|
0.220
|
Hypertension, n (%)
|
9(69.2%)
|
4(30.8%)
|
1.000
|
Dyslipidemia, n (%)
|
1(33.3%)
|
2(66.7%)
|
1.000
|
Gensini Score
|
34.25±19.35
|
38.75±9.97
|
0.482
|
Medication used before admission
|
Antiplatelet agent, n (%)
|
0(0.0%)
|
1(100%)
|
1.000
|
ACEI/ARB, n (%)
|
2(66.7%)
|
1(33.3%)
|
1.000
|
Beta-blocker, n (%)
|
2(66.7%)
|
1(33.3%)
|
1.000
|
Statins, n (%)
|
0
|
0
|
|
CCB, n (%)
|
4(80.0%)
|
1(20.0%)
|
0.317
|
Diuretic, n (%)
|
1(100.0%)
|
0(0.0%)
|
1.000
|
Laboratory value
|
BNP, pg/mL
|
959.70±762.12
|
516.51±603.63
|
0.129
|
Hemoglobin, g/L
|
142.17±20.28
|
140.17±11.57
|
0.769
|
TC, mg/dL
|
173.94±43.99
|
167.15±43.69
|
0.708
|
TGs, mg/dL
|
125.15±41.88
|
128.54±63.84
|
0.879
|
LDL-C, mg/dL
|
109.33±40.39
|
106.11±34.89
|
0.837
|
HDL-C, mg/dL
|
38.64±10.12
|
38.61±10.52
|
0.994
|
TNF-α, pg/mL
|
5.76±1.19
|
5.78±1.10
|
0.970
|
ALT, U/L
|
20.06±7.97
|
26.66±12.66
|
0.141
|
AST, U/L
|
22.72±11.57
|
33.70±20.61
|
0.122
|
Creatinine, umol/L
|
67.50±16.30
|
78.15±16.08
|
0.121
|
BUN, mmol/L
|
13.43±3.71
|
10.37±4.85
|
0.097
|
Insulin sensitivity surrogate index
|
TGs/HDL-C ratio
|
3.57±1.72
|
3.70±2.23
|
0.877
|
SPISE index
|
6.01±2.44
|
4.69±1.39
|
0.116
|
Data are presented as mean ± SD, median (IQR), or number (%)
BMI, body mass index; ACEI/ARB, angiotensin-converting enzyme inhibitor/angiotensin receptor blocker; CCB: calcium channel blockers; BNP, B‐type natriuretic peptide; TC, total cholesterol; LDL-C, low-density lipoprotein cholesterol; TGs, triglycerides; HDL-C, high-density lipoprotein cholesterol; TNF-α: tumor necrosis factor; ALT: glutamic-pyruvic transaminase ; AST: glutamic oxalacetic transaminase; BUN: blood urea nitrogen; SPISE index, Single Point Insulin Sensitivity Estimator.
3.2 Proteomics
3.2.1 Data quality control of quantitative proteomics
To further investigate the biomarkers associated with T2DM in AMI patients, the overall protein levels of the two groups were assessed using DIA. A total of 416 non-redundant proteins were quantified, but there were missing values in the raw data, Figure 2A shows the completeness of the data, the number of proteins in group A and AD were (385.2±9.79) and (379.4±10.85) respectively, and the data completeness was higher in group A (p>0.05). T2DM may elevate the complexity of the protein composition of serum from AMI patients. Raw quantitative data for proteins are provided in Supplementary Table S1.
The distribution of the coefficient of variation (CV) shows the repeatability of the quantitative data. The data was log-transformed to fit a normal distribution before calculation. Figure 2B provides a detailed analysis of the CV distribution in the 2 groups, with median CV values of 0.053 and 0.060 and mean CV values of 0.083 and 0.080 for groups A and AD, respectively. The data of both groups have a majority distribution in the lower CV interval that showed excellent intragroup agreement.
3.2.2 Identification of differentially regulated proteins
In total, 14 differentially expressed proteins (DEPs) were screened according to the preset parameters, of which 6 proteins were up-regulated and 8 were down-regulated (Figure 2C). Volcano plots were further drawn based on significance levels and fold change values, red dots represent up-regulated proteins, blue dots represent down-regulated proteins, and grey dots represent non-differentially expressed genes. Hierarchical clustering analysis of expression patterns showed that 14 DEPs were induced or inhibited by T2DM stimulation in AMI patients, which could be significantly stratified in the 2 groups (Figure 2D). Furthermore, subcellular localization of these DEPs revealed their distribution in the extracellular (64.3%), plasma membrane (21.4%), mitochondrion (7.1%), and endoplasmic reticulum (7.1%) (Figure 2E).
3.2.3 Functional classification of differentially regulated proteins
According to the Go ontology (GO) enrichment, 14 DEPs covered a wide range of biological processes (BP), molecular functions (MF), and cellular components (CC). BP included regulation of body fluid levels, with SERPINF2, ApoE, and SERPINA10 participating in the entry; No results were obtained in MF; CC focused on endocytic vesicle lumen, platelet alpha granule, blood microparticle, endoplasmic reticulum lumen, collagen-containing extracellular matrix, extracellular vesicle (Table 2).
Table 2 GO enrichment analysis of DEPs
GO entries
|
GO
categories
|
Fold enrichment
|
p value
|
Regulation of body fluid levels (GO:0050878)
|
BP
|
20.95
|
2.64E-06
|
-
|
MF
|
-
|
-
|
Endocytic vesicle lumen (GO:0071682)
|
CC
|
> 100
|
1.17E-04
|
Platelet alpha granule (GO:0031091)
|
CC
|
48.48
|
3.23E-05
|
Blood microparticle (GO:0072562)
|
CC
|
30.85
|
1.20E-04
|
Endoplasmic reticulum lumen (GO:0005788)
|
CC
|
28.01
|
3.69E-08
|
Collagen-containing extracellular matrix (GO:0062023)
|
CC
|
13.94
|
1.53E-04
|
Extracellular vesicle (GO:1903561)
|
CC
|
6.23
|
1.66E-06
|
BP: biological process; MF: molecular function; CC: cellular component.
3.2.4 Enrichment analysis of DEPs
To explain the biological significance represented by the DEPs between the two groups, DAVID and KOBAS were used to analyze KEGG pathways, as shown in Figure 3A, fourteen DEPs were enriched for four functional clusters, the horizontal axis represents significance and the vertical axis represents the degree of enrichment, with the larger the bubble the higher the degree of enrichment. Biological differences between the two groups included the NF-kappa B signaling pathway, toll-like receptor signaling pathway, Notch signaling pathway, Th1 and Th2 cell differentiation, thyroid hormone signaling pathway, cholesterol metabolism, oxidative phosphorylation, complement and coagulation cascades, and so on. hormone signaling pathway, cholesterol metabolism, oxidative phosphorylation, complement and coagulation cascades, and so on.
In addition, Figure 3C shows the GSEA analyses of the top-ranked Reactome and KEGG according to enrichment sore, which provides a more comprehensive interpretation of the biological processes involved in the pathogenesis of T2DM in AMI patients. It contains the PI3K pathway, complement cascade, GPCR signaling pathway, regulation of IGF transport and uptake by IGFBPs, phosphodiesterase D signaling pathway, NF-kappaB signaling pathway, and a large number of phosphorylation pathways.
Table 3 Results of Reactome pathways
Reactome pathways
|
Fold enrichment
|
Raw p-value
|
Protein/gene details
|
Post-translational protein phosphorylation (R-HSA-8957275)
|
68.72
|
8.35E-09
|
CALU
F5
ApoE
SERPINA10
IGFBP7
|
Regulation of Insulin-like Growth Factor (IGF) transport and uptake by Insulin-like Growth Factor Binding Proteins (IGFBPs) (R-HSA-381426)
|
59.3
|
1.70E-08
|
CALU
F5
ApoE
SERPINA10
IGFBP7
|
Binding and Uptake of Ligands by Scavenger Receptors (R-HSA-2173782)
|
43.25
|
4.49E-05
|
HYOU1
IGLV3-25
ApoE
|
Platelet degranulation (R-HSA-114608)
|
34.74
|
8.49E-05
|
CALU
SERPINF2
F5
|
Response to elevated platelet cytosolic Ca2+ (R-HSA-76005)
|
33.42
|
9.50E-05
|
CALU
SERPINF2
F5
|
3.2.5 Protein-protein interaction (PPI) analysis of DEPs
We further constructed the PPI network using the STRING database and identified hub genes. A confidence level of 0.15 was set to obtain more interactions. Figure 3B shows that the input 14 DEPs matched 13 nodes, among which the top-ranked node proteins included LBP, ApoE, SERPINF2, SERPINA10, IGFBP7, HYOU1, LUM, and most of the proteins were up-regulated. These proteins share nodes of biological pathways through a complex network, informing subsequent laboratory studies and targeted biomarker validation projects.
3.2.6 ROC curve
To assess the discriminative ability of 14 DEPs, we constructed ROC and calculated AUC, of which 6 met statistical differences (Figure 4A). These proteins also had top-ranked importance in the PPI network based on literature information and public databases. All the AUC values showed favorable diagnostic performance with a mean AUC of 0.77±0.03.
3.2.7 Text-mined and validation by ELISA analysis
When candidate biomarkers were text-mined using the method of Pletscher-Frankild et al[16], relevant clinical associations were generated, with the majority of candidate proteins associated with heart disease and diabetes (Table 4). LBP, ApoE, SERPINF2, SERPINA10, IGFBP7, and HYOU1 were selected for validation based on AUC values, PPI network, and enrichment results. ELISA results showed higher concentrations of LBP, ApoE, SERPINF2, SERPINA10, and IGFBP7 in AD patients, and low concentrations of HYOU1 in AD patients, all changes were consistent with statistical differences. Figure 4B shows a concordance of ELISA results and MS data for candidate biomarkers.
Table 4 Correlation and confidence level of target proteins mined from the literature with diabetes
protein
|
disease
|
Z-score
|
confidience
|
ApoE
|
Type 2 diabetes mellitus
|
6.9
|
4
|
LBP
|
Type 2 diabetes mellitus
|
4.6
|
3
|
SERPINF2
|
Diabetes mellitus
|
4
|
2
|
IGFBP7
|
Diabetes mellitus
|
4
|
2
|
HYOU1
|
Type 2 diabetes mellitus
|
3.6
|
2
|
SERPINA10
|
Diabetes mellitus
|
1.8
|
1
|
The Z-score and confidence level corresponding to each protein were determined using the text-mining database. In statistics, the Z-score denotes how many standard deviations an element or datum is from the mean whereas the confidence level refers to the likelihood of all possible samples that can be expected to include the true population parameter.