Oral anticoagulation reduces activated protein C less than protein C and other vitamin K-dependent clotting factors

Role of Noninvasive Urinary Prothrombin Fragment 1 + 2 to Measure Blood Coagulation Indices and Dose of Acenocoumarol

PF1 + 2 plasma levels are a crucial indicator for assessing anticoagulant action in individuals receiving anticoagulant treatment. Urine also has PF1 + 2 levels due to its molecular size. Hence, the present study aims to measure urinary prothrombin fragment 1 + 2 (uPF1 + 2) in patients taking anticoagulants in order to divulge a noninvasive surrogate marker of PT-INR of blood coagulopathy. A total of 205 people participated in the study: 104 patients on acenocoumarol (AC) and 101 healthy controls (HC). Clinical parameters, including PT-INR, urinary creatinine, etc., were measured in all subjects. To evaluate uPF1 + 2 in samples, MALDI-TOF-MS, Western blot analysis, and ELISA tests were used. The MALDI-TOF-MS results showed the presence of uPF1 + 2 in both AC and HC urine samples. The Western blot, ELISA experiment, and unpaired t test results displayed that the patients with AC had significantly increased levels of uPF1 + 2 compared to HC. A regression study showed a strong positive relation between blood-based PT-INR and uPF1 + 2. ROC validation also revealed the clinical efficacy of uPF1 + 2. For the goal to monitor anticoagulant medication, the present study highlights PF1 + 2, which describes the overall hemostatic capacity and might be utilized in addition to or instead of PT-INR.

Response of the critically endangered Przewalski's gazelle (Procapra przewalskii) to selenium deprived environment

Selenium (Se) is an essential mineral nutrient for animals. Se deprivation can lead to many disorders and even death. This study investigated the response of Przewalski's gazelle (P. przewalskii) to Se-deprived environment. We found that Se deprivation in soil and forage not only influenced the mineral contents of the blood and hair in P. przewalskii, but also severely disrupted their blood parameters. We identified significant changes in the abundance of 146 proteins and 25 metabolites (P < 0.05) in serum, including the selenoproteins L8IG93 (glutathione peroxidase) and F4YD09 (Cu/Zn superoxide dismutase). Furthermore, the major known proteins and metabolites associated with the Se stress response in P. przewalskii were Cu/Zn superoxide dismutase, the vitamin K-dependent protein C, the C4b-binding protein alpha chain, complement component C7, lipase linoleic acid, peptidase D, thymidine, pseudo-uridine, L-phenylalanine, L-glutamine, PGA1, and 15-deoxy-delta-12,14-PGJ2. The main signaling pathways involved included complement and coagulation cascades, metabolic pathways, and stress granule formation. Our results indicate that the intake of Se-deficient forage elicited an oxidative stress response in P. przewalskii. These findings provide insights into the response mechanisms of this threatened gazelle to Se stress, and enable the development of conservation strategies to protect populations on the Qinghai-Tibetan Plateau. SIGNIFICANCE: This study is the first to point out the presence of oxidative stress in P. przewalskii in selenium-deficient areas through proteomics and metabolomics studies. These findings should prove helpful for conservation efforts aimed at P. przewalskii populations and maintenance of the integrity of their ecological environment.

Effects of oral anticoagulant therapy and haplotype 1 of the endothelial protein C receptor gene on activated protein C levels

Oral anticoagulants (OACs) reduce activated protein C (APC) plasma levels less than those of protein C (PC) in lupus erythematosus and cardiac patients. Carriers of the H1 haplotype of the endothelial PC receptor gene (PROCR) have higher APC levels than non-carriers. We aimed to confirm these results in a large group of patients treated with OACs because of venous thromboembolism (VTE) and to assess whether the effect is influenced by the PROCR H1 haplotype. We evaluated APC, PC, and factor (F)II levels in 502 VTE patients (158 with and 344 without OACs) and in 322 healthy individuals. Mean APC, PC and FII levels were significantly lower in OAC patients than in patients not taking OACs. During anticoagulant therapy, the FII/PC ratios were independent of the PC values, whereas APC/FII and APC/PC ratios significantly increased when FII and PC levels decreased. Of the 22 OAC patients carrying the H1H1genotype, 11 (50%) showed APC/PCag ≥2.0 and 10 (45%) APC/ FIIag ratios ≥2.0, whereas for the 49 OAC patients non-carrying the H1 haplotype these figures were 6 (12%) and 4 (8%), respectively (p<0.001). Barium citrate adsorption of plasma from OAC patients showed that most of the circulating free and complexed APC, but only part of PCag, is fully carboxylated. In conclusion, during anticoagulant therapy VT patients have APC levels disproportionately higher than the corresponding PC levels, mainly due to the presence of the PROCR H1 haplotype. Furthermore, a sufficiently carboxylated PC Gla-domain seems to be essential for PC activation in vivo.

Treatment of inherited protein C deficiency by replacement therapy with the French purified plasma-derived protein C concentrate (PROTEXEL®)

BACKGROUND/OBJECTIVES

A multicentre retrospective study was performed to assess the efficacy/safety of a French purified plasma-derived protein C (PC) concentrate in inherited PC deficiency.

MATERIALS AND METHODS

Nine patients were enrolled, five children aged < 5 weeks, among whom four with a severe deficiency were homozygous, and four patients < 37 years with PC levels ranging 14-25%, including one compound heterozygous.

RESULTS

Thirty replacement therapy courses were recorded with mean PC dosages ranging between 24-90 IU/kg/day for prophylactic courses and 51-209 IU/kg/day for treatment courses. Recoveries varied between 0.8 and 1.12% IU/kg in preventive situations and between 1.09 and 1.91% IU/kg for treatment courses; 23 treatment courses were performed in patients aged 1 day to 18 years, 19 out of 23 treatments resulted in complete recovery with no sequelae. Treatment efficacy was difficult to assess in four out of 23 cases because the thrombotic event was not confirmed in one case and due to late treatment initiation in the three other cases. Seven prophylactic treatments were used either in association of vitamin K antagonists or to prevent thrombotic events due to vitamin K antagonist introduction or withdrawal. The safety assessed during 914 infusions was excellent. No abnormal bleeding was reported, including with high doses, during surgery, with heparin therapy.

CONCLUSIONS

Replacement therapy with this French PC concentrate is safe and effective in patients with inherited PC deficiency.

Effect of vitamin K intake on the stability of oral anticoagulant treatment: dose-response relationships in healthy subjects

Oral anticoagulants exert their effect by blocking the utilization of vitamin K, yet little is known about competitive aspects of their interaction with dietary vitamin K. We carried out systematic dose-response studies in healthy volunteers who had been stably anticoagulated and maintained on their individualized doses for 13 weeks. First, we studied the response to weekly incremental doses (50 μg-500 μg) of vitamin K1 supplements (K1) taken daily for 7 days. The threshold K1 dose causing a statistically significant lowering of the INR was 150 μg/day. In 25% of the participants the INR change was regarded as clinically relevant at a vitamin K intake of 150 μg/day. Circulating undercarboxylated osteocalcin did not decrease until 300 μg K1/day compared with 100 μg K1/day for undercarboxylated FII, suggesting differential antidotal effects on bone and hepatic γ-carboxylation. Next, we tested the response to vitamin K-rich food items. The short-lived response after meals of spinach and broccoli suggested an inefficient bioavailability from these 2 sources. We conclude that short-term variability in intake of K1 is less important to fluctuations in the international normalized ratio (INR) than has been commonly assumed and that food supplements providing 100 μg/day of vitamin K1 do not significantly interfere with oral anticoagulant therapy. (Blood. 2004;104:2682-2689)

A critical evaluation of the prothrombin time for monitoring oral anticoagulant therapy

The Quick prothrombin time is the most common clotting test performed, principally for monitoring oral anticoagulant therapy. The International Normalized Ratio (INR) for comparing patient results from prothrombin time measurements and the International Standardized Index (ISI) for achieving greater consistency of results using different thromboplastins have made it possible to compare the results of vitamin K antagonist drug therapy that was impossible before the introduction of the INR and ISI. However, INR values obtained from the same patient plasma sample using different thromboplastins are significantly different. This is so even when the thromboplastins have nearly the same ISI values. We suggest that investigation of patient-specific differences can provide a means by which the INR discrepancies can be identified and understood and thus lead to better methods for monitoring oral anticoagulant therapy.

Multivariate relationships between international normalized ratio and vitamin K-dependent coagulation-derived parameters in normal healthy donors and oral anticoagulant therapy patients

Background and objectives

International Normalized Ratio (INR) is a world-wide routinely used factor in the monitoring of oral anticoagulation treatment (OAT). However, it was reported that other factors, e. g. factor II, may even better reflect therapeutic efficacy of OAT and, therefore, may be potentialy useful for OAT monitoring. The primary purpose of this study was to characterize the associations of INR with other vitamin K-dependent plasma proteins in a heterogenous group of individuals, including healthy donors, patients on OAT and patients not receiving OAT. The study aimed also at establishing the influence of co-morbid conditions (incl. accompanying diseases) and co-medications (incl. different intensity of OAT) on INR.

Design and Methods

Two hundred and three subjects were involved in the study. Of these, 35 were normal healthy donors (group I), 73 were patients on medication different than OAT (group II) and 95 were patients on stable oral anticoagulant (acenocoumarol) therapy lasting for at least half a year prior to the study. The values of INR and activated partial thromboplastin time (APTT) ratio, as well as activities of FII, FVII, FX, protein C, and concentration of prothrombin F1+2 fragments and fibrinogen were obtained for all subjects. In statistical evaluation, the uni- and multivariate analyses were employed and the regression equations describing the obtained associations were estimated.

Results

Of the studied parameters, three (factors II, VII and X) appeared as very strong modulators of INR, protein C and prothrombin fragments F1+2 had moderate influence, whereas both APTT ratio and fibrinogen had no significant impact on INR variability. Due to collinearity and low tolerance of independent variables included in the multiple regression models, we routinely employed a ridge multiple regression model which compromises the minimal number of independent variables with the maximal overall determination coefficient. The best-fitted two-component model included FII and FVII activities and explained 90% of INR variability (compared to 93% in the 5-component model including all vitamin K-dependent proteins). Neither the presence of accompanying diseases nor the use of OAT nor any other medication (acetylsalicylic acid, statins, steroids, thyroxin) biased significantly these associations.

Conclusion

Among various vitamin K-dependent plasma proteins, the coagulation factors II, VII and X showed the most significant associations with INR. Of these variables, the two-component model, including factors II and VII, deserves special attention, as it largely explains the overall variability observed in INR estimates. The statistical power of this model is validated on virtue of the estimation that the revealed associations are rather universal and remain essentially unbiased by other compounding variables, including clinical status and medical treatment. Further, much broader population studies are needed to verify clinical usefulness of methods alternate or compounding to INR monitoring of OAT.

Recombinant human activated protein C (rhAPC; drotrecogin alfa [activated]) has minimal effect on markers of coagulation, fibrinolysis, and inflammation in acute human endotoxemia

Inflammatory and procoagulant host responses are closely related in sepsis. The protein C pathway serves as a regulatory pathway with anti-inflammatory and anticoagulant properties. Recently, recombinant human activated protein C (rhAPC) was shown to reduce mortality in severe sepsis. Nevertheless, the effects of rhAPC in humans are still ill defined. The infusion of low endotoxin doses into humans provides a standardized model to study inflammatory and hemostatic mechanisms. Thus, we investigated whether rhAPC acts as an anticoagulant or anti-inflammatory drug in human endotoxemia. There were 24 volunteers randomized to receive either 24 microg/kg per hour rhAPC or placebo intravenously for 8 hours. Lipopolysaccharide (LPS, 2 ng/kg) was administered 2 hours after starting the infusions. rhAPC decreased basal tissue factor (TF)-mRNA expression, and thrombin formation and action. In contrast, rhAPC did not significantly blunt LPS-induced thrombin generation. Consistently, rhAPC did not reduce LPS-induced levels of TF-mRNA or D-dimer and had no effect on fibrinolytic activity or inflammation. Finally, endogenous APC formation was enhanced during endotoxemia and appeared to be associated with inflammation rather than thrombin formation. In conclusion, even low-grade endotoxemia induces significant protein C activation. Infusion of rhAPC decreases "spontaneous" activation of coagulation but does not blunt LPS-induced, TF-mediated coagulation in healthy volunteers, which is in contrast to a number of anticoagulants.