Association of prothrombin and protein S with plasma triglyceride-rich lipoproteins in humans after test meals rich in milk fat or soybean oil

Abstract

Introduction: Prothrombin can associate with rat chylomicrons in vitro. This enhances a platelet factor Xa mediated prothrombin activation when the chylomicron–prothrombin complex is exposed to platelets. Vitamin K-dependent pro- and anti-coagulation proteins are associated with TG-rich lipoproteins obtained from human plasma. In the present study, we examined the effects of saturated and unsaturated fat meals on the association of prothrombin and protein S with TG-rich lipoproteins in vivo. Materials and Methods: Human EDTA plasma was separated from normal subjects after overnight fasting and 2.5 h after ingestion of either a saturated fat meal (butter and cream) or an unsaturated fat meal (soybean oil) containing 54–80 g fat (60.2 E%). The prothrombin and protein S in delipidated lipoproteins were determined by SDS-PAGE combined with Western blotting. Results: Both prothrombin and protein S associated with TG-rich lipoproteins in fasting and in postprandial samples. The levels of prothrombin and protein S in postprandial TG-rich lipoproteins, especially after ingestion of a saturated fat meal, were higher than those in fasting TG-rich lipoproteins. Conclusions: The levels of both prothrombin and protein S in TG-rich lipoproteins in plasma increased after a single fat meal. This association is more pronounced after saturated fat meals and one may hypothesize that it can be linked to atherogenic properties of TG-rich lipoproteins.