Proteomic profiling of gamma-carboxylated proteins in horse plasma upon vitamin K supplementation

Proteomic profiling of gamma-carboxylated proteins in horse plasma upon vitamin K supplementation

Introduction: Vitamin K is a cofactor for γ-carboxyglutamase to convert glutamate (Glu) residues to γ-carboxyglutamic acid (Gla) residues in proteins. Few studies have investigated the relationship between vitamin K intake, and its effect on circulating vitamin K dependent proteins (VKDPs) in horses. It is suspected that vitamin K supplementation of mares may change the VKDP plasma proteome of foals. To date, no studies have investigated the applicability of a proteomics-based approach to evaluate this. The aim of this study was to facilitate the detection of carboxylated VKDPs in plasma by applying a novel method; Carboxylated Analysis by Ceramic Hydroxyapatite Enrichment (CACHE).

Method: 12 mares were allocated to a treatment; K1 and K2 (15mg) or control; blank paste. Treatments were administered orally, from parturition until 3 months post-parturition. Blood samples were collected from foals before suckling, at 12 h, 24 h and weekly up until 3 months. Plasma samples were analysed for vitamin K1 concentration by HPLC, and proteomic analysis by LC-MS/MS.

Results: This study applied the CACHE protocol to plasma samples collected from 14-day old foals, that showed a statistically significant difference in vitamin K1 concentration (P<0.05). While it was anticipated that supplementation would facilitate the detection of VKDPs by CACHE, no VKDPs of interest were identified in this preliminary study. Carboxylation however, was detected.

Conclusion: To the author’s knowledge, this is the first study to investigate a novel proteomics-based method to
decipher VKDPs in equine plasma. Further optimisation of this novel approach will facilitate future studies to investigate the function of VKDPs in the horse, and potentially other species.

Abstract #67.