Factor VII activation and oral contraceptives

Risk Factors for Heart Attack, Stroke, and Venous Thrombosis Associated With Hormonal Contraceptive Use

The search for a safe and effective method of contraception has been ongoing for centuries. During the last century, a variety of hormonal contraceptives, including combined hormonal oral contraceptives (COCs), have been introduced into the market. COCs have evolved through modifications of different hormonal components to minimize the risk of thrombotic events including stroke, myocardial infarction, and venous thrombosis. The evolution of COC development led to the reduction in the estrogen dose, in an attempt to lower the risk of vascular diseases. Although the risk of thrombotic events due to COC use has been substantially reduced since their inception, the quest for developing safer methods of birth control continues. It is of great interest to study coagulation effects of newer COCs, as well as progestin only, as rigorously as older COCs.

Effect of four oral contraceptives on hemostatic parameters

This is the first double-blind, controlled, randomized study comparing the effect of different estrogen components in oral contraceptives (OCs) on hemostasis variables. Four groups of 25 women each were treated for six cycles with monophasic combinations containing 21 tablets with either 30 microg ethinylestradiol (EE) + 2 mg dienogest (DNG) (30EE/DNG), 20 microg EE + 2 mg DNG (20EE/DNG), 10 microg EE + 2 mg estradiol valerate (EV) + 2 mg DNG (EE/EV/DNG) or 20 microg EE + 100 microg levonorgestrel (LNG) (EE/LNG). Blood samples were taken on Days 21-26 of the control cycle and on Days 18-21 of the first, third and sixth treatment cycle. Treatment with all four OCs caused an increase in levels of fibrinogen, prothrombin fragment 1+2, D-dimer, plasminogen, plasmin-antiplasmin complex and an increase in protein C activity, a decrease in antithrombin activity, tissue-plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI), and a slight decrease in the sensitivity to activated protein C, but no significant change in that of the thrombin-antithrombin complex. In users of the DNG-containing OCs, the reduction in total and free protein S, and in t-PA and PAI was dependent on the EE dose, while factor VII activity was elevated, but not significantly different from EE/LNG. The results are in agreement with those of previous studies. The effects of EE/EV/DNG on total and free protein S and on t-PA and PAI were lower than those of 20EE/DNG, suggesting that the impact of 2 mg EV on several hemostasis variables is less than that of 10 microg EE. The results show an antagonistic effect of LNG on the EE-induced rise of factor VII activity and fragment 1+2 and on the EE-dependent reduction of total and free protein S.

Plasma concentrations of blood coagulation factor VII measured by immunochemical and amidolytic methods

Ever since the coagulant activity of blood coagulation factor VII (FVII:C) was identified as a risk indicator of cardiac death, a large number of studies have measured FVII protein concentrations in plasma. FVII protein concentrations are either measured immunologically with an ELISA method (FVII:Ag) or estimated with an amidolytic method (FVII:Am). We have investigated whether FVII:Am is a valuable alternative to FVII:Ag. FVII:Ag and FVII:Am were measured in 147 plasma samples from blood donors, patients on oral anticoagulant therapy, postmenopausal women on hormone replacement therapy, in postprandial plasma, in cold activated plasma and in FVII deficient plasma. There was a positive correlation (r=0.96) between FVII:Ag and FVII:Am with slightly but significantly higher values for FVII:Ag (FVII:Ag= 106 U/ml and FVII:Am=100 U/ml; p <0.001). A significant correlation (r=0.93) was still observed after omitting the data from patients on oral anticoagulant therapy, with mean values of 113 U/ml for FVII:Ag and 110 U/ml for FVII:Am (p < 0.01). In a linear regression analysis, the intercept (alpha=-21.50) was different from zero (p < 0.0001) and the slope (beta=1.16) was different from 1.0 (p < 0.001). Only a few points (3.1%) in a difference plot were present outside the expected 95% interval calculated from the analytical imprecision of the two methods. Therefore, we consider the amidolytic method an acceptable alternative to the ELISA method when analysing citrated plasma samples containing only enzymatically functional FVII protein, but the results cannot be directly transferred from one method to the other.

Oral contraceptives highlight the genotype-specific association between serum phospholipids and activated factor VII

The present analysis was undertaken to study the effect of oral contraceptive (OC) use on activated factor VII (FVIIa) in subjects characterized by FVII genotypes, with the further aim of evaluating the role of lipids in this pharmacological interaction. In OC users (n=42) and nonusers (n=130) of comparable age, we examined the FVII phenotypic variables (FVII coagulant activity [FVIIc], FVII antigen, and FVIIa), FVII genotypes (the 353R/Q and 5'F7 polymorphisms analyzed in combination; alleles M1/M2 and A1/A2, respectively), and a number of lipid and lipoprotein parameters: serum concentrations of total cholesterol (chol), low density lipoprotein and high density lipoprotein-chol, triglycerides, phospholipids (PhLs), apolipoprotein A1, and lipoprotein(a). PhLs, triglycerides, apolipoprotein A1, chol, FVII antigen, FVIIc, and high density lipoprotein-chol levels were shown to be statistically higher in users than nonusers. FVII levels, particularly those of FVIIa and FVIIc, were much higher in homozygotes for the A1 and M1 alleles (A11 M11), especially in OC users. A strong association was found between PhL and FVIIa: in the multiple regression analysis, women taking OCs who had elevated PhL concentrations also had very high levels of FVIIa, but only if their genotype was A11 M11. These results indicate that the increased FVII levels in OC users depend on the FVII genotype and that high PhL concentrations predict very high levels of FVIIa and FVIIc.

The effect of hormone replacement therapy of the age-related rise of factor VIIc, and its activity state

Although hormone replacement therapy (HRT) appears to protect women from ischaemic heart disease (IHD), its use is associated with increased factor clotting activity (VIIc), an independent risk factor for IHD. The nature of this factor VII rise was therefore examined in a cross-sectional study of 279 women aged between 40 and 65 years. Ninety-four were pre-menopausal, 44 were post-menopausal and taking HRT, whilst 141 were post-menopausal non-users. For those women on oestrogen-only HRT, the mean factor VIIc was 144%, compared to 130% for post-menopausal non-users, and 116% for those on combined HRT. These differences were significant (p = 0.01). Oestrogen-only users also had significantly higher mean levels of factor VIIa (3.3 ng/ml) compared to non-users (2.2 ng/ml) and those on oestrogen-progestogen HRT (2.2 ng/ml-p = 0.015). In contrast for factor VII antigen the mean values of the three groups were similar. Analysis of the age-regression slopes showed a significant age-related rise in factor VIIc of 1.2% per annum (p < 0.01) for post-menopausal non-users. There was a similar increase in factor VII antigen (2.1%) but no rise in factor VIIa. For all HRT users there was no change with age for any of the factor VII measures. Thus the age-related rise in factor VIIc appears to be due to an increase in factor VII zymogen alone, and taking HRT seems to abolish such a rise. In contrast, the increased factor VIIc seen with oestrogen-only HRT appears to be secondary to factor VII activation.

Population correlates of coagulation factor VII. Importance of age, sex, and menopausal status as determinants of activated factor VII

Factor VII coagulant activity (FVIIc) has been found to be related to cardiovascular risk factors and may be an independent predictor of coronary heart disease (CHD). Whether these associations are due to changes in FVII activation rather than FVII concentration remain unclear. Therefore, we investigated the relationships between activated factor VII (FVIIa) and CHD risk factors in healthy subjects (336 men and 348 women) aged 25 to 64 years. In addition to direct quantitation of FVIIa by use of a recombinant, truncated tissue factor, FVIIc and factor VII antigen (FVII:Ag) levels were measured by standard procedures. There were highly significant correlations between the three techniques of FVII assay (r > + .55). Plasma FVIIc and FVIIa levels increased with age in both sexes, but the rate of rise was significantly greater in women than men. At younger ages, mean values of FVIIc and FVIIa were significantly lower in women than men, whereas at older ages the reverse was observed. After adjustment for age, postmenopausal women had significantly higher mean levels of FVIIc and FVIIa than did premenopausal women. Hormone replacement therapy significantly reversed the rise in FVIIc in postmenopausal women, and a similar trend in FVIIa was also observed. Age-, sex-, and menopause-related changes in FVIIc were partly explained by a higher proportion of fully active FVII molecules, as indicated by significant differences in the FVIIa-to-FVII:Ag ratio. Oral contraceptive use was associated with high FVIIc levels, and this effect was mainly due to an increase in FVII:Ag. Levels of FVIIa were positively correlated with serum cholesterol concentrations in both sexes. There were no strong associations between FVIIa levels and other CHD risk factors, including smoking habits, alcohol consumption, blood pressure, obesity, glucose, triglycerides, and serum lipoprotein(a) concentrations. Multiple regression analysis showed independent effects of age and cholesterol levels on FVIIa in men, whereas age and menopausal status were the main predictors of FVIIa in women. Our results show that FVII activation is associated with CHD risk factors. These findings are consistent with a possible role for FVII in the pathogenesis of CHD. Furthermore, our data suggest that the dramatic rise in CHD incidence in postmenopausal women as well as the cardioprotective effect of estrogen may be mediated through FVII and blood coagulation.

The protein concentration of blood coagulation factor VII can be measured equally well in plasma and serum

In the Northwick Park Heart Study, the coagulant activity of factor VII (FVII:C) has been identified as a risk marker of ischaemic heart disease. In the fasting state, the protein concentration of FVII (FVII:Ag) might be an even better risk marker, because of the low coefficient of variation of the antigen assay. Today, most analyses are performed in plasma samples, as it is unknown whether FVII, to some extent, is consumed during coagulation. In the present study, we have investigated, whether FVII:Ag can be measured equally well in plasma and serum. FVII:Ag was measured in 88 plasma and serum samples. Results were compared by means of linear regression, where y = 0.984 x +0.770, r = 0.96. No systematic variation existed between FVII:Ag in plasma and serum. The mean difference in FVII:Ag between plasma and serum was -1.17 (SD 11.92) arbitrary units, compared with a mean difference of 0.18 (SD 8.31) arbitrary units between duplicate measurements of the same plasma dilution. Our findings indicate that there is a good agreement between FVII:Ag in plasma and serum.