Association between serum retinol-binding protein and lower limb atherosclerosis risk in type 2 diabetes mellitus

BACKGROUND Serum retinol-binding protein (RBP) is the primary transport protein of circulating vitamin A. RBP has a crucial role in maintaining nutrient metabolism and physiologic homeostasis. Several studies have indicated that serum RBP participates in the progression of diabetes and diabetes-related complications. However, the impact of serum RBP on lower limb atherosclerosis has not been determined in individuals with type 2 diabetes mellitus (T2DM). AIM To determine the association between serum RBP and lower limb atherosclerosis in individuals with T2DM. METHODS This retrospective study enrolled 4428 eligible T2DM patients and divided the patients into non-lower limb atherosclerosis (n = 1913) and lower limb atherosclerosis groups (n = 2515) based on lower limb arterial ultrasonography results. At hospital admission, baseline serum RBP levels were assessed, and all subjects were categorized into three groups (Q1-Q3) based on RBP tertiles. Logistic regression, restricted cubic spline regression, subgroup analysis, and machine learning were used to assess the association between RBP levels and lower limb atherosclerosis risk. RESULTS Among 4428 individuals with T2DM, 2515 (56.80%) had lower limb atherosclerosis. Logistic analysis showed that lower limb atherosclerosis risk increased by 1% for every 1 unit rise in serum RBP level (odds ratio = 1.01, 95% confidence interval: 1.00-1.02, P = 0.004). Patients in the highest tertile group (Q3) had a higher lower limb atherosclerosis risk compared to the lowest tertile group (Q1) (odds ratio = 1.36, 95% confidence interval: 1.12-1.67, P = 0.002). The lower limb atherosclerosis risk gradually increased with an increase in RBP tertile (P for trend = 0.005). Restricted cubic spline analysis indicated a linear correlation between serum RBP levels and lower limb atherosclerosis risk (non-linear P < 0.05). Machine learning demonstrated the significance and diagnostic value of serum RBP in predicting lower limb atherosclerosis risk. CONCLUSION Elevated serum RBP levels correlate with an increased lower limb atherosclerosis risk in individuals with T2DM.