Abstract: Objective To study the changes of serum retinol binding protein (RBP), microRNA-126 (miR-126) and silent information regulator1 (Sirt1) levels in patients with acute cerebral infarction (ACI) compared with healthy subjects, and to analyze the correlation between the changes of the three indexes and the stability of carotid atherosclerotic plaques in patients with ACI. 
Methods A total of 140 patients with ACI who presented to our hospital were selected as the case group, and 60 healthy physical examinees during the same period were selected as the control group. Patients in the case group underwent color Doppler ultrasonography and were divided into stable plaque group (n=78) and unstable plaque group (n=62) according to the ultrasound results. Clinical data of subjects were collected. The expression of serum RBP and Sirt1 was detected by enzyme-linked immunosorbent assay, and the expression of serum miR-126 was detected by real-time fluorescence quantitative PCR. Spearman was used to analyze the relationship between the expression of serum RBP, miR-126, Sirt1 and the stability of carotid atherosclerotic plaque. Receiver operating characteristic curve analysis was performed to evaluate the predictive value of serum RBP, miR-126, and Sirt1 expression on the stability of carotid atherosclerotic plaques in patients. 
Results Compared with control group, the expression of serum RBP in case group was increased, while the expression of miR-126 and Sirt1 was decreased (P＜0.05). The expression of serum RBP in unstable plaque group was increased compared with that in stable plaque group, while the expression of miR-126 and Sirt1 was decreased compared with that in stable plaque group (P＜0.05). The expression of serum RBP was positively correlated with the stability of carotid atherosclerotic plaque (r=0.423, P＜0.05), and the expression of serum miR-126 and Sirt1 was negatively correlated with the stability of carotid atherosclerotic plaque (r=-0.514, -0.366, P＜0.05). The AUC of RBP, miR-126, Sirt1 and their combination in prediction was 0.746, 0.798, 0.712, and 0.892, respectively, with a sensitivity of 59.7%, 75.8%, 75.8%, 74.2%, respectively, and specificity of 84.6%, 70.5%, 64.1%, and 92.3%, respectively. The combined prediction value of the three indexes was superior to that of the single one. 
Conclusion The increased expression of serum RBP and the decreased expression of miR-126 and Sirt1 in patients with ACI are correlated with the stability of carotid atherosclerotic plaque. Serum RBP, miR-126 and Sirt1 have good predictive value for the stability of carotid atherosclerotic plaque. 

Key words: brain infarction, plaque, atherosclerotic, retinol-binding proteins