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Background/Objectives: Vascular calcification and arterial stiffness are common in chronic kidney disease (CKD). Gla-rich protein (GRP) is a vitamin K-dependent protein implicated in mineral biology, but clinical evidence across CKD stages is limited. We evaluated associations of serum GRP with vascular calcification (VC) burden and arterial stiffness across CKD stages, including hemodialysis, compared with controls. Methods: In this prospective observational study, 185 adults were enrolled: controls (n = 61), individuals with CKD stage IIIb–IV (n = 61), and individuals with CKD stage V on hemodialysis (HD) (n = 63). Abdominal aortic calcification was assessed by the Kauppila score, and arterial stiffness was assessed by oscillometric pulse wave velocity (PWV). Serum GRP, FGF-23, and β-Klotho (KLb) were measured by ELISA. Non-parametric group comparisons and Bonferroni-corrected Spearman correlations were used. Results: GRP differed across groups (p < 0.001), showing a non-linear pattern with the lowest values in CKD IIIb–IV. PWV and Kauppila score increased across CKD stages (both p < 0.001). After Bonferroni correction, GRP correlated with KLb (ρ = 0.720) and FGF-23 (ρ = 0.625), but not with PWV or Kauppila score. In multivariable analyses, GRP showed a statistically significant but modest association with PWV and Kauppila score. Conclusions: In this CKD spectrum cohort, serum GRP was associated with CKD-MBD biochemical markers (KLb and FGF-23) much more strongly than with vascular phenotypes; its associations with vascular calcification burden and arterial stiffness were modest in multivariable modelling, supporting GRP as a marker of the CKD-MBD biochemical profile rather than a strong surrogate of vascular phenotype.
Lončarić et al. (Tue,) studied this question.