CARDIOVASCULAR JOURNAL OF AFRICA • Volume 34, No 2, May/June 2023 AFRICA 105 compared to mild stenosis in ischaemic stroke patients.11 A recent study identified that serum sLOX-1 concentrations were markedly elevated in patients with stable CAD, acute coronary syndrome and acute myocardial infarction.12 Circulatory sLOX-1 has been suggested as a predictive biochemical marker.12 However, the prospective clinical analytical value of sLOX-1 for patients with CAD has not yet been completely explored. This study investigated the clinical significance of sLOX-1 level as a biomarker for stable and unstable CAD patients and its correlation with aging in male and female subjects. Methods A total of 439 participants were recruited to participate in this study at Xiangya Hospital between June 2015 and September 2018. The institutional ethical review board of Xiangya Hospital Central South University approved this study. Written, informed consent was obtained from all the participants in accordance with the Declaration of Helsinki (World Medical Association) human clinical research protocols. This study prospectively enrolled 226 consecutive patients with stable CAD (male 145, female 81, median age 62 years) who underwent invasive coronary angiography at the same hospital. Blockage of a major coronary artery or its principal branches by more than 50% was considered CAD and the final diagnosis was confirmed by two experienced interventional cardiologists. One hundred and thirty-eight unstable CAD patients (male 78, female 60, median age 64 years) were included in the current research, following American College of Cardiology/ European Society of Cardiology diagnostic criteria.13 Patients with previously implanted coronary stents, acute myocardial infarction, heart failure, myocarditis or pericarditis were excluded from this study. The current study also enrolled 75 healthy volunteers (male 40, female 35, median age 55 years) from the health centre of the same institution. The inclusion criteria for the healthy subjects was no history of cardiovascular disease, ECG and echocardiography findings within normal limits, free from active inflammatory disease, autoimmune disorders, chronic or acute kidney and liver injury, and malignant disorders.14,15 Clinical data and medication information were obtained from all the participants’ record files. The study required a total sample size of 192 after calculating with GPower 3.1 software, considering an alpha error of 0.05, power (1-beta error) of 0.90, effect size of 0.5 and allocation (N2/N1) ratio of 2. Peripheral venous blood samples (3–5 ml) were collected from the stable CAD patients via an ante-cubital vein three days after coronary arteriography, if they had not developed any complications, within 30 to 60 minutes of diagnosis in the unstable CAD patients, and after an overnight fast (eight to 10 hours) in the healthy controls. Blood samples were first centrifuged at 15 000 revolutions per minute (rpm) for 10 minutes, followed by centrifuging at 10 000 rpm for five minutes, and the fresh plasma obtained was stored at –80°C for further use. The plasma was used for biochemical analysis of sLOX1. Enzyme-linked immunosorbent assay (ELISA) with multifunctional microplate reader was used to determine sLOX1 concentrations according to the American Bio-Rad Company instructions. WBC count, C-reactive protein and creatinine levels were determined with a Hitachi 7600 automated blood biochemical analyser (Hitachi, Tokyo, Japan). Statistical analysis Normally distributed continuous data are expressed as mean with standard error. The Student’s t-test, descriptive analysis and Mann–Whitney test were used for comparing differences between the two groups. One-way ANOVA was used for the comparison between more than two groups. Receiver operating characteristic (ROC) curves were performed to explore the biochemical diagnostic importance of sLOX-1. For analysis of the data, SPSS version 20 was used (Armonk, NY, USA: IBM Corp.). A p-value < 0.05 was regarded as statistically significant. Results A total of 439 participants (226 stable CAD, 138 unstable CAD, 75 healthy controls) were included in this study. The stable CAD group included 145 males and 81 females with an average age of 62.93 ± 9.7 years (range 30–84). Seventy-eight males and 60 females were included in the unstable CAD group and their median age was 64.95 ± 8.6 years. The control group comprised 40 males and 35 females and the mean age was 55.4 ± 10.1 years. Clinical information is shown in Table 1. Family history of CAD and WBC count were significantly higher in the stable and unstable CAD subjects than in the healthy participants. Inflammatory marker C-reactive protein expressions were significantly up-regulated in both the stable and unstable CAD patients than in the control group. Circulating concentrations of plasma sLOX-1 were markedly up-regulated (4.5-fold) in patients with stable CAD and 5.8-fold in patients with unstable CAD compared to the control group (p < 0.001). Moreover, the expression pattern of circulating sLOX-1 was also significantly different between the stable and unstable groups (Fig. 1A). Furthermore, the concentrations of peripheral Table 1. Clinical characteristics of the CAD patients and healthy subjects (n = 439). Characteristics Controls Stable CAD Unstable CAD P1 P2 P3 Participants, n 75 226 138 Age, years 55.4 ± 10.1 62.93 ± 9.7 64.95 ± 8.6 0.589 0.426 0.871 Gender, male/female 40/35 145/81 78/60 0.062 0.087 0.154 Tobacco smokers, % 57 69 77 0.063 0.085 0.450 Body mass index, kg/m2 20.4 ± 1.7 21.7 ± 2.9 22.9 ± 5.1 0.429 0.573 0.981 Hyperlipidaemia, % – 78 81 _ _ 0.770 Diabetes mellitus, % – 25 27 _ _ 0.979 Systemic hypertension, % – 74 79 _ _ 0.436 Family history of CAD, % 12 47 56 0.000 0.000 0.158 Heart rate, beats/min 73.18 ± 9.41 74.53 ± 11.27 76.24 ± 13.58 0.521 0.344 0.756 WBC, ×109 cells/l 6.2 ± 1.53 9.5 ± 2.69 10.4 ± 3.48 0.000 0.000 0.852 C-reactive protein, mg/l 1.27 ± 2.06 13.82 ± 11.3 21.5 ± 9.8 0.000 0.000 0.000 Creatinine, μmol/l 79.8 ± 10.21 81.8 ± 11.75 83.8 ± 9.94 0.648 0.532 0.759 Acetylsalicylic acid use – 54 60 _ _ 0.246 Lipid-lowering agents – 74 76 _ _ 0.817 Beta-2 receptor antagonist – 80 82 _ _ 0.898 CAD, coronary artery disease; WBC, white blood cells. P1: healthy subjects vs stable CAD, P2: healthy subjects vs unstable CAD, P3: stable and unstable CAD.
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