Vitamin K2 (Menaquinone-7) supplementation does not affect vitamin K-dependent coagulation factors activity in healthy individuals.

BACKGROUND: Vitamin K has long been regarded as a procoagulant drug by physicians, and concerns have been raised with regard to its effects on hemostasis. Although many studies have shown that vitamin K supplementation is safe for thrombotic events, the effect of vitamin K supplementation on the activities of vitamin K dependent procoagulation factors in healthy individuals is not available. OBJECTIVES: This study aimed to investigate whether vitamin K2 supplementation at recommended doses affects the activity of vitamin K dependent procoagulation factors in healthy individuals without any anticoagulation treatment. DESIGN: Forty healthy volunteers between 25 and 40 years of age were recruited. Menaquinone-7 (MK-7) was administrated at 90 µg for 30 days. Prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), and blood coagulation factors II, VII, IX, and X activities and Protein induced by vitamin K absence or antagonist-II (PIVKA-II) were measured on days 0 and 30 after MK-7 administration. RESULTS: PT, APTT, and TT showed no significant differences on day 30 when compared with baseline. The activities of coagulation factors II, VII, IX, and X on day 30 showed no significant differences with those at baseline. PIVKA-II levels were unchanged after 30 days of MK-7 supplementation. CONCLUSIONS: MK-7 supplementation at recommended dosage does not affect vitamin K-dependent coagulation factors' coagulation activity, and does not enhance the carboxylation of prothrombin in healthy individuals. This indicated that MK-7 administration does not alter hemostatic balance in healthy populations without anticoagulation treatment.

Effect of dietary omega-3 and omega-6 fatty acids on clotting activities of Factor V, VII and X in fatty liver haemorrhagic syndrome-susceptible laying hens.

1. The relationship between concentrations of omega-3 and omega-6 fatty acids in plasma and Factor V, VII and X clotting activities was determined using a crossover feeding trial with diets supplemented with either soy oil or flax oil. 2. Laying hens on the soy diet, which is high in omega-6 fatty acids, had substantially higher clotting activity for all three factors compared to laying hens on the flax diet that was high in omega-3 fatty acids. 3. Positive associations were seen between liver haemorrhage score and the percentage of liver weight and between the percentage of liver weight and the severity of haemorrhagic and fatty changes seen on histology. 4. These results support the hypothesis that concentrations of omega-6 and omega-3 fatty acids in plasma affect clotting activity; however, there was no relationship between the extent of liver haemorrhages and the composition of plasma fatty acids.

Folate deficiency-induced hyperhomocysteinemia attenuates, and folic acid supplementation restores, the functional activities of rat coagulation factors XII, X, and II.

Hyperhomocysteinemia (HH) constitutes a risk marker for thrombosis, but the pathophysiological mechanisms in thrombus formation are still unresolved. We investigated the influence of HH on single coagulation factor functions and evaluated the platelet GpIIb/IIIa receptor function in HH-induced changes in whole-blood coagulation profiles (WBCP). Three groups of 12 rats were investigated: control rats, folate deficient-HH (FD-HH) rats, and treated rats. Plasma total homocysteine was 7.1 micromol/L in controls, 31.3 micromol/L in FD-HH rats, and 7.6 micromol/L in treated rats. Factor (F) II:C, FX:C, and FXII:C were reduced in FD-HH rats compared with controls and normalized in treated rats (P < 0.05). FVII:C activity did not differ among the groups. Factor VIII:C activity was greater in FD-HH rats than in controls (P < 0.05). Blockage of the platelet GpIIb/IIIa receptor by Integrilin (Schering-Plough A/S) did not abolish the FD-HH-induced increase in whole-blood coagulation velocity, irrespective of the dosage of Integrilin. In conclusion, FD-HH reduced the functional activities of FXII:C, FX:C and FII:C, whereas FVII:C was unchanged and FVIII:C increased. These findings may partially explain the prolonged initiation phase of WBCP in FD-HH rats. The changes in single coagulation factor functions and WBCPs in FD-HH rats were reversed by treatment with folic acid.

In vitro effects of poly-N-acetyl glucosamine on the activation of platelets in platelet-rich plasma with and without red blood cells.

BACKGROUND: This study was performed to assess the effect of poly-N-acetyl glucosamine fiber slurry on plasma clotting proteins, platelets, and red blood cells in the clotting of the blood. METHODS: Citrate phosphate dextrose whole blood was stored at 22degreesC for 48 hours to prepare platelet-poor plasma, platelet-rich plasma (PRP), and PRP plus red blood cells with hematocrit values of 20%, 35%, and 45% with and without an equal volume of poly-N-acetyl glucosamine fibers (1 mg/mL 0.9% NaCl). RESULTS: Thromboelastogram data show that poly-N-acetyl glucosamine fibers (p-GlcNAc) significantly reduced the R time in platelet-poor plasma, PRP, and PRP supplemented with red blood cells. Poly-N-acetyl glucosamine fibers increased, but not significantly, Annexin V and factor X binding to platelets, platelet microparticles, and red blood cell Annexin V binding. Poly-N-acetyl glucosamine fibers increased the production of thromboxane B2 by PRP. CONCLUSION: Poly-N-acetyl glucosamine slurry activates platelets.

Activation and inactivation of human factor X by proteases derived from Ficus carica.

We investigated the effect of proteases derived from Ficus carica (common fig) on human blood coagulation. The milky sap (latex) of several Ficus (F.) species contain ficin, which is a mixture of proteases. Ficin derived from Ficus carica shortened the activated partial thromboplastin time and the prothrombin time of normal plasmas and plasmas deficient in coagulation factors, except plasma deficient in factor X (FX) and generated activated FX (FXa) in defibrinated plasma. Chromatographic separation of ficin from Ficus carica yielded six proteolytic fractions with a different specificity towards FX. We isolated two factor X activators with molecular masses of 23.2 and 23.5 kDa, and studied their action on purified human FX. Factor X was converted to activated FXbeta by consecutive proteolytic cleavage in the heavy chain between Leu178 and Asp179, Arg187 and Gly188, and Arg194and Ile195 (FX numbering system) with concomitant release of a carboxy-terminal peptide. The cleavage pattern of FXa degradation products in the light chain was influenced by Ca2+ and Mn2+. These data suggest the haemostatic potency of Ficus proteases is based on activation of human coagulation factor X.

The influence exerted by a restricted phospholipid microenvironment on the expression of tissue factor activity at the cell plasma membrane surface.

Phosphatidylserine (PhtdSer) is an anionic aminophospholipid necessary for the development of optimal tissue factor (TF) activity at the cell surface. This study investigates the implication of a restricted lipid environment with respect to PhtdSer availability on TF expression and activity. K562 cells, showing a reduced ability to externalize PhtdSer, were transfected with human TF cDNA. PhtdSer exposure and TF activity were examined in transfected cells and compared to monocytic THP-1 cells expressing constitutive and inducible TF or megakaryocytic HEL cells showing a high PhtdSer externalization potency. TF expression was evidenced by flow cytometry and its activity measured using functional assays. PhtdSer exposure was monitored by enzymatic prothrombinase assay. One clone (DC9) expressed a stable amount of TF antigen without global modification of its membrane status. Despite a noticeable TF expression level, clone DC9 presented only a weak TF activity even after ionophore stimulation. The apparent Km, relative to factor X (FX) activation by TF-factor VIIa (FVIIa) complex, was 335 nM versus 70 nM for THP-1 cells. The velocity of the reaction was found 3-fold slower in DC9 than THP-1 cells. Ionophore treatment resulting in slightly enhanced amounts of available PhtdSer abolished this difference. The DC9 clone appears suitable for further investigations on the biology of TF expressed at the surface of cells where the contribution of PhtdSer is significantly attenuated. Such cells should enable further assessment of the role of TF as a receptor coupled to intracellular signaling pathways and its fate during apoptotic cell death.