Gla-Rich Protein (GRP): A Vitamin K-Dependent Regulator of Vascular Calcification, Inflammation, and Mineral Homeostasis.

Gla-rich protein (GRP), also known as UCMA, is a vitamin K-dependent protein that has emerged as an important regulator of pathological calcification and inflammation. Vascular calcification is a major complication of chronic kidney disease and cardiovascular disorders and is now recognized as an active and tightly regulated process rather than a passive accumulation of minerals. Increasing evidence indicates that GRP plays a protective role in mineral homeostasis through its strong calcium-binding capacity and its dependence on vitamin K-mediated gamma carboxylation. This work represents a comprehensive narrative review aimed at summarizing and critically discussing the current scientific knowledge on GRP. Available experimental and clinical data are analyzed with respect to gene expression, molecular regulation, vitamin K dependency, and underlying mechanisms of action. Particular emphasis is placed on the dual function of GRP in inhibiting ectopic calcification and modulating inflammatory responses. The evidence linking altered GRP levels or changes in its carboxylation status with chronic kidney disease, vascular calcification, calcific aortic valve disease, osteoarthritis, and tumor-associated microcalcifications is systematically examined. Current findings collectively support the concept that GRP is a multifunctional protein operating at the interface of mineral metabolism, inflammation, and tissue remodeling. Despite promising experimental data, important knowledge gaps remain, including the absence of standardized assays capable of distinguishing different GRP forms and the lack of longitudinal clinical studies evaluating its predictive value. This manuscript highlights the potential of GRP as a biomarker of disturbed mineral homeostasis and cardiovascular risk, while emphasizing the need for further research to clarify its precise biological functions and clinical relevance.