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.

Effects of isoflavones on the coagulation and fibrinolytic system of postmenopausal women.

OBJECTIVE: We evaluated the effects of soy isoflavone supplementation on hemostasis in healthy postmenopausal women. METHODS: In this double-blinded, placebo-controlled study, 47 postmenopausal women 47-66 y of age received 40 mg of soy isoflavone (n = 25) or 40 mg of casein placebo (n = 22) once a day for 6 mo. Levels of factors VII and X, fibrinogen, thrombin-antithrombin complex, prothrombin fragments 1 plus 2, antithrombin, protein C, total and free protein S, plasminogen, plasminogen activator inhibitor-1, and D-dimers were measured at baseline and 6 mo. Urinary isoflavone concentrations (genistein and daidzein) were measured as a marker of compliance and absorption using high-performance liquid chromatography. Baseline characteristics were compared by unpaired Student's t test. Within-group changes and comparison between the isoflavone and casein placebo groups were determined by a mixed effects model. RESULTS: The levels of hemostatic variables did not change significantly throughout the study in the isoflavone group; however, the isoflavone group showed a statistically significant reduction in plasma concentration of prothrombin fragments 1 plus 2; both groups showed a statistically significant reduction in antithrombin, protein C, and free protein S levels. A significant increase in D-dimers was observed only in the isoflavone group. Plasminogen activator inhibitor-1 levels increased significantly in the placebo group. However, these changes were not statistically different between groups. CONCLUSION: The results of the present study do not support a biologically significant estrogenic effect of soy isoflavone on coagulation and fibrinolysis in postmenopausal women. However, further research will be necessary to definitively assess the safety and efficacy of isoflavone.

Anticoagulant modulation of blood cells and platelet reactivity by garlic oil in experimental diabetes mellitus.

Multiple blood cell types and metabolic pathways involved in the modulation of platelet reactivity were investigated in streptozotocin-induced diabetic rats treated with garlic oil. Platelet counts of diabetic rats treated with garlic oil were significantly (P<0.01) reduced as compared to diabetic control rats. Garlic oil also increased the leucocyte counts of diabetic rats as compared to diabetic control rats. The significant (P<0.001) decreases by garlic oil of plasma concentration factors, V, VII, VIII: C, IX and X in diabetic rats may be interpreted to mean that there was a modulation of factor VII similar to that brought about by thrombin on factors V and VIII: C. This reversal of hypercoagulation through integrated biochemical reaction is suggestive of multicellular modulation of platelet reactivity, erythrocytes and neutrophils and the functional interactions between plasma coagulation factors and platelet cofactors.

Poor correlation of supratherapeutic international normalised ratio and vitamin K-dependent procoagulant factor levels during warfarin therapy.

Patients with a supratherapeutic international normalised ratio (ST-INR) are at risk for bleeding. ST-INR is corrected by withholding warfarin therapy and often by supplementing vitamin K or providing vitamin K-dependent factors; the exact therapeutic decision is based on the extent of the prolonged INR. Currently, ST-INRs are frequently observed in clinical practice due to the use of sensitive recombinant tissue thromboplastin reagents and automation. However, there are scant data correlating an ST-INR with various vitamin K-dependent factors. This prospective cohort study, set in a large tertiary care teaching hospital for the University of Texas Southwestern Medical Center at Dallas, defined the relationship between ST-INR (>5.0) and measured vitamin K-dependent procoagulant factors. Prothrombin time, INR and vitamin K-dependent factors II, VII, IX and X were measured in 78 patients with an INR > 5.0 (ST-INR) who were on warfarin therapy for more than 2 months. There was no significant relationship between the ST-INR and levels of important vitamin K-dependent factors II and X. These data support the recent guidelines that the management of an INR > 5.0 should be driven by the clinical determinants rather than specific INR values per se.

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.

Decline of proteins C and S and factors II, VII, IX and X during the initiation of warfarin therapy.

Oral anticoagulants achieve an antithrombotic effect only several days after initiation of treatment. A rapid decline of the vitamin-K dependent natural anticoagulants (proteins C and S) during this period might result in a prothrombic phase. We addressed this question by measuring the rates of decline of these proteins, as well as the vitamin K dependent procoagulants, in two groups of patients: A "high dose group" (n = 7), who received a single 40 mg dose of warfarin, and a "low dose group" (n = 20), who received daily individually adjusted doses. In the high dose group an early and marked decline of factor VII:C and protein C antigen was observed, while levels of the other vitamin K dependent factors were still relatively high. In the low dose group, all these proteins declined more gradually. Mean +/- SD of protein C antigen level at 46 hr was 56 +/- 12% in the low dose group, and only 44 +/- 6% (p less than 0.05) in the high dose group. We conclude that during the initiation of warfarin therapy there is a transient prothrombotic phase, which is less marked in patients given daily adjusted doses.