Factors associated with Gla-rich protein serum concentrations in healthy adults

Introduction: Gla-rich protein (GRP) is a vitamin K-dependent protein involved in the regulation of ectopic calcification and inflammatory processes.However, data on circulating GRP concentrations in healthy adults remain limited. Materials and methods:This cross-sectional observational study evaluated serum total GRP (tGRP) concentrations in 254 healthy adult blood donors (48% male), aged 18-65 years, using a sandwich enzyme-linked immunosorbent assay (ELISA) (GenoGla Diagnostics, Faro, Portugal).Participants were stratified by age tertiles, and associations between serum tGRP concentrations and demographic and laboratory parameters were assessed using non-parametric statistical tests, Spearman correlation, and stepwise linear regression.Results: The median serum tGRP concentration in the overall population was 1809.5 pg/mL (interquartile range: 1197.4-2476.0pg/mL).Serum tGRP concentrations differed significantly across age tertiles (P = 0.038), with higher concentrations observed in younger adults.Serum tGRP concentrations showed a weak but statistically significant inverse correlation with age (r = -0.30,P = 0.001), while no significant differences were observed between sexes (P = 0.420).In multivariable analysis, age and serum calcium concentration remained independently associated with serum tGRP concentrations, jointly explaining approximately 7% of their variability. Conclusion:This study establishes robust reference data for circulating tGRP concentrations in healthy adults, providing a foundation for the interpretation of GRP measurements in future clinical and epidemiological research.