Association of baseline and longitudinal plasma retinol-binding protein 4 with all-cause mortality in maintenance hemodialysis patients

Introduction Elevated levels of retinol-binding protein 4 (RBP4) have been linked to conditions including cardiovascular disease, type 2 diabetes, obesity, and insulin resistance. However, the associations between baseline and longitudinal RBP4 levels with all-cause mortality in maintenance hemodialysis patients remain uncertain. The aim of this study was to investigate this issue. Methods A total of 342 consecutive patients undergoing maintenance hemodialysis at a single hemodialysis center between 2010 and 2022 were assessed. Enzyme-linked immunosorbent assay was used to quantify plasma RBP4 concentrations. Patient outcomes were assessed using Cox regression and Kaplan-Meier analyses. Results Non-survivors were associated with significantly lower baseline and longitudinal RBP4 levels compared to the survivors. A trend toward reduced all-cause mortality was found across quartiles of baseline and longitudinal RBP4 levels (p for trend < 0.0001). Multivariate analysis showed that the patients in the lowest quartiles (Quartile 1) of baseline and longitudinal RBP4 levels had hazard ratios of 2.22 (95% CI: 1.16-4.31) and 2.44 (95% CI: 1.30-4.84) for all-cause mortality, respectively, compared to those in the fourth quartile. In contrast to the non-survivors, the survivors had significantly higher plasma RBP4 levels during the 1-year follow-up period compared to the levels at the initiation of hemodialysis (p = 0.001). In addition, a positive association was observed between baseline RBP4 concentration and albumin level, while negative associations were observed between baseline RBP4 concentration and levels of aspartate aminotransferase, high-sensitivity C-reactive protein, and mean corpuscular volume. Structural equation model analysis confirmed the effect of RBP4 on mortality. Discussion Associations were identified between low baseline and longitudinal RBP4 plasma concentrations and all-cause mortality in our cohort of Taiwanese maintenance hemodialysis patients.