From January 2019 to March 2021, a total of 56 patients with T2DM and cerebral infarction admitted to our hospital were included in the diabetic cerebral infarction (DCI) group, which includes 14 patients with cardio-embolism, 25 cases of large artery atherosclerotic, 11 cases of small artery occlusion type, and 6 cases of unknown etiology. There were 27 cases of anterior circulation infarction and 29 cases of posterior circulation infarction. A total of 60 patients only with T2DM were included in the T2DM group, and healthy volunteers without a history of diabetes and cerebral infarction who were age- and sex-matched with the above two groups of patients were included in the control group (n = 60). The average age of the DCI group was 65.86 ± 8.74 (43–81 years), with 33 males and 23 females. The average age of the T2DM group was 65.17 ± 10.55 (41–81 years), with 36 males and 24 females. The average age of the control group was 65.18 ± 9.50 (44–82 years), with 34 males and 26 females. Inclusion criteria are as follows: (1) the diagnostic criteria for T2DM conform to the “China Guidelines for the Prevention and Treatment of Type 2 Diabetes (2017 Edition)” (7); (2) the diagnostic criteria for cerebral infarction conform to the “Chinese Guidelines for Diagnosis and Treatment of Cerebral Infarction with Integrated Traditional Chinese and Western Medicine (2017)” (8), and cerebral infarction has occurred within 1 month; (3) 18–85 years old; (4) patients in the T2DM group had no history of cerebral infarction and clinical symptoms and signs of diabetic cerebral infarction; and (5) the physical, electrocardiogram, ultrasound, and biochemical examinations of the volunteers in the control group were all normal. Exclusion criteria are as follows: patients with cerebral hemorrhage on head imaging, gestational diabetes mellitus, diabetic macrovascular (including cardiovascular accident and lower extremity arterial disease) and microvascular (including diabetic nephropathy, diabetic retinopathy, and diabetic neuropathy) complications, type 1 diabetes, infectious disease, chronic liver disease, chronic kidney disease, malignant tumor, or any hereditary disease that affects lipid metabolism. This study was approved by the Ethics Review Board of our institution, and all participants provided written informed consent prior to the study. All methods were performed according to approved guidelines and regulations.

General information about the patient was collected, including age, gender, body mass index (BMI), duration of T2DM, history of cardiovascular disease (history of hypertension, family history of coronary heart disease, history of arrhythmia, family history of hyperlipidemia or diabetes mellitus history), smoking history, drinking history, and biochemical indicators (fasting blood glucose [PBG], 2-h postprandial blood glucose [2-h PG], fasting insulin [Fins], total cholesterol, triglycerides, high-density lipoprotein cholesterol [HDL-C], low-density lipoprotein cholesterol [LDL-C], and glycosylated hemoglobin [hemoglobin A1C, HbA1c]).

The concentration of serum β2-GPI/oxLDL was determined by a sandwich enzyme-linked immunosorbent assay. First, blood samples were collected after 12 h of fasting, centrifuged at 1,500 r/min (radius: 8 cm) for 15 min, and stored at –80 °C. The polyclonal antibody against human β2-GPI was immobilized on a 96-well plate, and the polyclonal antibody against apolipoprotein B was used as the detection antibody. About 500 μl of serum was incubated at room temperature for 2 h, polyethylene glycol was added, and the samples were incubated overnight (4°C). The sample was centrifuged (10,000 r/min, radius: 8 cm, 20 min), and the obtained precipitate was resuspended in 0.01 mol/L PBS. β2-GPI antibody (2.5 μg/ml) was added to the samples, followed by incubation at 37°C for 2 h and then at 4°C overnight. The diluted samples (1:40) were added to the wells and blocked with 1% gelatin. BSA was added and incubated for 2 h. Standard β2-GPI/ox-LDL complexes were added to the wells and incubated overnight at 4°C to obtain a standard curve. Horseradish peroxidase-labeled goat antirabbit LDL polyclonal antibody was added to the wells, and TMBUS was added after incubation for 3 h (room temperature). The absorbance was read at 450 nm by using a microplate reader, and the serum oxLDL/β2-GPI complex concentration was calculated based on the standard curve.

An enzyme-linked immunosorbent assay kit (Diaclone, France) was used to detect tumor necrosis factor (TNF)-α and interleukin (IL)-6 in serum, the samples were detected by a Lablifeer/ew 2007, Varioskan LUX multimode microplate reader (CA, USA), and the concentrations of IL-6 and TNF-α in the sample were calculated based on the fitted concentration–absorbance curve. C-reactive protein (CRP) was detected by immuno-turbidimetry using a Hitachi 7020 automatic analyzer (Hitachi Kokusai Electric Inc., Tokyo, Japan).

SPSS 20.0 software was used for data analysis; the data were tested for normality first, and the continuous variables conforming to the normal distribution were expressed as x¯±s). Comparisons between groups were performed using an independent sample t-test or one-way ANOVA, and data with skewed normal distribution were expressed as M50 (P25, P75). Comparisons between groups were performed using the Mann–Whitney U or the Kruskal–Wallis test. The enumeration data were expressed in the form of cases (percentages), the comparison between groups was performed by the chi-square test, and Pearson’s analysis was used to measure the correlation of each index. Logistic model analysis of clinical factors affecting the risk of ischemic cerebral infarction in patients with T2DM was carried out, and the receiver operating characteristic (ROC) curve was used to analyze the diagnostic efficacy of serum β2-GPI/oxLDL for DCI. When P < 0.05, the data were statistically different.

There were no significant differences in age, gender, smoking history, drinking history, T2DM course, cardiovascular disease history, total cholesterol, triglyceride, and HDL-C among the three groups (P > 0.05). Compared with the control group, the BMI, LDL-C, PBG, 2-h PG, HbAlc, Fins, CRP, TNF-α, and IL-6 of the T2DM group and DCI group were significantly increased, with P values less than 0.05. Compared with those in the T2DM group, the TNF-α and CRP levels in the DCI group were significantly increased, and the P values were all less than 0.05, as shown in Table 1.

The level of serum β2-GPI/oxLDL in the control group, in the T2DM group, and in the DCI group was 0.79 (0.57, 1.03), 1.09 (0.88, 1.28), and 1.34 (1.03, 1.68) mmol/L, respectively. The difference was statistically significant among the three groups (Z = 53.504, P < 0.001). Compared with that in the control group, the concentration of serum β2-GPI/oxLDL in T2DM and DCI groups increased significantly (P < 0.001). Compared with that in the T2DM group, the level of serum β2-GPI/oxLDL in the DCI group was significantly increased (P < 0.05), as shown in Table 2.

The result of Pearson’s correlation analysis showed that serum β2-GPI/oxLDL was positively correlated with total cholesterol, triglyceride, PBG, 2hPG, HbAlc, IL-6, and TNF-α (P < 0.05), as shown in Table 3.

Taking cerebral infarction as a dependent variable (occurrence = 1, no occurrence = 0), the basic clinical data were included in the univariate logistic model analysis, and the results showed that HbAlc, serum TNF-α, and β2-GPI/oxLDL were closely related to the occurrence of DCI (P < 0.05). The above independent variables were included in the multivariate model analysis, and the results showed that elevated serum TNF-α and β2-GPI/oxLDL levels were independent risk factors for DCI (P < 0.05), as shown in Table 4.

According to the ROC curve analysis, the area under the curve of serum β2-GPI/oxLDL and their combination in the diagnosis of DCI was 0.680 (0.583–0.777), the sensitivity was 0.589, the specificity was 0.750, the cutoff value was 1.256, and the Youden index was 0.339 (P < 0.05), as shown in Figure 1.