Elevated plasma levels of free-form of TFPI antigen in
hypercholesterolemic patients
Eriko Morishita
a,b,*, Hidesaku Asakura
b, Masanori Saito
b, Masahide Yamazaki
b,
Yasuo Ontachi
b, Tomoe Mizutani
b, Minori Kato
b, Tamotsu Matsuda
b,
Shinji Nakao
baDepartment of Laboratory Sciences,School of Health Science,Kanazawa Uni
6ersity,13-1Takaramachi,Kanazawa920-8641,Japan bDepartment of Internal Medicine(III),School of Medicine,Kanazawa Uni
6ersity,13-1Takaramachi,Kanazawa920-8641,Japan Received 4 June 1999; received in revised form 25 February 2000; accepted 2 March 2000
Abstract
Several studies have previously reported high levels of total tissue factor pathway inhibitor (TFPI) antigen in patients with hypercholesterolemia. The relationship between serum lipid concentrations and total and free-form TFPI antigen in 32 patients with primary type II hypercholesterolemia and 38 age- and gender-matched normolipemic control subjects was studied (Study Group I). Plasma concentrations of total TFPI (tTFPI) antigen, free-form TFPI (fTFPI) antigen, tissue factor antigen, factor VII activity (FVIIc), and prothrombin fragment 1+2 (F1+2) were measured. The median levels of tTFPI, fTFPI, FVIIc, and F1+2 were higher in hyperlipidemic patients compared with those in healthy subjects. The effect of lowering total cholesterol on hypercoagulability in 25 patients with type II hyperlipoproteinemia (Study Group II) were also studied. The median levels of tTFPI, FVIIc, and F1+2 decreased significantly after 6 months of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor therapy in the hypercholesterolemic patients. On the other hand, fTFPI did not change after therapy. Plasma tTFPI was strongly correlated with total cholesterol and low density lipoprotein (LDL)-cholesterol in hyperlipidemic patients. In contrast to the strong correlation between tTFPI and total cholesterol, the correlation between plasma fTFPI and total cholesterol was relatively poor. These results suggest that the activation of the anticoagulant system as well as the activation of the coagulation system may occur in association with hypercholesterolemia. Furthermore, the results of this study may suggest that lowering of total cholesterol in hyperlipidemic patients reduces the thrombin generation in plasma and that down-regulation of LDL does not affect the anticoagulant potency of TFPI in plasma. © 2001 Elsevier Science Ireland Ltd. All rights reserved.
Keywords:Tissue factor pathway inhibitor; Hypercoagulability; Hypercholesterolemia; Anticoagulant; HMG-CoA reductase inhibitor
www.elsevier.com/locate/atherosclerosis
1. Introduction
Tissue factor pathway inhibitor (TFPI) is a vascular anticoagulant which inhibits the initial reaction of the tissue factor-mediated coagulation pathway [1,2]. TFPI is synthesized mainly by vascular endothelial cells [3] and is associated with these cells [4,5]. In plasma, TFPI can be separated by gel filtration into a free-form and low density lipoprotein/very low density lipoprotein (LDL/VLDL)-associated form and a high density lipo-protein (HDL)-associated form. The levels of the
free-form TFPI (fTFPI) may be important, since the endothelial cell-associated forms of TFPI is released as the free form by both heparin injection [4,5] and patho-logical stimuli [6]. Recently it has become possible to measure plasma concentrations of total TFPI (tTFPI) (free-form and lipoprotein-associated forms) [7] and fTFPI [8]. Then the levels of plasma tTFPI and plasma fTFPI have been demonstrated to vary in several pathophysiologic conditions [9 – 14]. The method for measuring free-form TFPI antigen can be used for assessing changes in the levels of endothelial cell-associ-ated TFPI antigen, which can be released by heparin injection [9]. Total plasma TFPI correlates significantly with plasma total cholesterol and LDL cholesterol lev-els both in normal subjects [13] and in hypercholes-* Corresponding author. Tel.: +81-762-658151; fax: +
81-762-344252.
E-mail address: [email protected] (E. Morishita).
terolemic patients [14]. It is elucidated that the antico-agulant activity of lipoprotein-associated TFPI is markedly lower than that of fTFPI [15]. Therefore, fTFPI antigen was analyzed in plasma in hyperlipi-demic patients and the relation between fTFPI and lipoproteins was further investigated.
Moreover, it is also elucidated that TFPI activity and total TFPI antigen normalize during cholesterol-lower-ing therapy because of a specific drop in LDL-associ-ated TFPI in plasma [16]. Almus et al. have found that reducing plasma TFPI by 50% causes a similar increase in the factor VIIa-TF catalytic activity toward factor IX in an umbilical vein model of coagulation [17]. The question then arises whether the changes observed in tTFPI concentrations after cholesterol-lowering therapy should be considered beneficial or not. Therefore, in the present study, some parameters of the hemostatic sys-tem were monitored in order to determine whether decreases in tTFPI induced by cholesterol-lowering therapy reduce the anticoagulant potency of plasma in hyperlipidemic patients.
2. Subjects and methods
2.1. Subjects
2.1.1. Study Group I
Eighty-one subjects, 38 healthy controls and 32 pa-tients with type II primary hyperlipoproteinemia were recruited from a health center (Asanogawa Hospital, Kanazawa, Japan), to which they had been referred for a periodic health check-up. Twenty patients (19 men, 13 women) were classified as type IIa and 12 as type IIb hyperlipoproteinemia, according to the World Health Organization’s (WHO) classification for
hyperlipi-demia. They had never been treated. Patients with secondary hyperlipoproteinemia were excluded from the study. Familial hypercholesterolemia (FH) was clin-ically diagnosed according to the following criteria [18]; 1. Primary hypercholesterolemia of more than 260 mg/
dl with an increase in Achilles tendon thickness. 2. Primary hypercholesterolemia of more than 260 mg/
dl and the presence of one or more direct relatives with hypercholesterolemia of more than 260 mg/dl and an increase in Achilles tendon thickness. Achilles tendon thickness was determined by xerora-diography. A thickness of more than 9 mm was desig-nated as abnormal tendon thickening. In Japan, serum total cholesterol levels are lower than those in Western countries because the Japanese diet has far less fat than the Western diet. Therefore, patients with abnormal tendon thickening and hypercholesterolemia of more than 260 mg/dl are reported to have decreased LDL receptor activity [18].
The control subjects (22 men, 16 women), matched for age and gender, were apparently healthy according to their medical history and the results of periodic health check-up. Relevant characteristics of the control group and the hyperlipidemic patients are shown in Table 1. No subjects had clinical evidence of diabetes, hypertension, hypothyroidism, or cardiovascular, neu-rologic or renal diseases. None of them took drugs known to affect lipid metabolism or the coagulation system.
Overnight fasting, venous blood samples were ob-tained from patients after 24 h of abstaining from alcohol. The blood for the measurement of hemostatic parameters was collected into siliconized glass tubes containing 3.8% (w/v) trisodium citrate. Plasma was obtained from blood centrifuged at 2500×gfor 10 min at 4°C and stored frozen at −80°C until use the time
Table 1
Characteristics of patients with primary hyperlipidemia and normolipemic control subjectsa
Variable Controls (n=38) Hyperlipidemia
IIa (n=20) IIb (n=12)
44 (40–55) 51 (45–57) 46 (41–58)
Age (years)
22.5 (21.5–23.8)
Body mass index (kg/m2) 22.6 (21.5–23.8) 24.5 (23.4–26.0)*
6.35 (6.11–6.97)***
4.56 (4.14–5.15) 6.29 (6.16–7.38)***
Total cholesterol (mmol/l)
2.75 (2.36–3.20)
LDL-cholesterol (mmol/l) 4.55 (4.27–4.99)*** 3.94 (3.56–4.55)***
1.35 (1.11–1.58)
HDL-cholesterol (mmol/l) 1.37 (1.06–1.71) 1.32 (0.98–1.40)
0.91 (0.68–1.29)
Triglycerides (mmol/l) 1.14 (0.87–1.40)* 2.86 (2.31–3.97)***
Apoprotein AI (mg/dl) 102 (95–107) 107 (87–116) 122 (92–128)
70 (58–88)
Apoprotein B (mg/dl) 108 (94–122)*** 127 (107–169)***
Fasting blood sugar (mg/dl) 94 (89–98) 92 (90–98) 107 (99–113)**
Lipoprotein (a) (mg/dl) 16.4 (7.7–20.7) 22.9 (11.7–40.3) 15.1 (5.5–26.2)
aValues are shown as the median (25–75th percentiles). *PB0.05;
**PB0.01;
of assay. Serum was prepared by clotting of whole blood in glass tube at room temperature for 1 h and then centrifuging it at 1200×g for 10 min for the measurement of cholesterol and triglycerides.
2.1.2. Study Group II
In addition, 25 consecutive outpatients were stud-ied, aged 35 – 71 years, including 14 men and 11 women with hyperlipidemia (12 had type IIa and 13 had type IIb hyperlipoproteinemia), not included in Study Group I. These patients were recruited in the Department of Internal Medicine, University Hospital of Kanazawa, Kanazawa, Japan. Five patients had hypertension; five had diabetes mellitus. The patients were followed for more than 6 months during treat-ment with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors. Eleven patients were treated with 5 mg/day simvastatin (Banyu, Tokyo, Japan), and 14 patients were treated with 10 mg/day atorvastatin (Yamanouchi, Tokyo, Japan). Fasting blood samples were obtained before and after 6 months of treatment. Informed consent was ob-tained from all patients.
2.2. Methods
Serum lipids were measured by standard enzymatic colorimetric methods using commercially available kits for total cholesterol (Kyowa Medex, Tokyo, Japan) and triglycerides (Toyobo, Osaka, Japan). HDL-cholesterol was measured using the same method after the VLDL and LDL were removed by precipitation with dextran sulphate and phospho-tungstic acid in the presence of magnesium ions (De-terminer HDL; Kyowa Medex). Plasma LDL cholesterol was calculated using the Friedewald equa-tion. If the triglyceride measurement was \4.52 mmol/l, LDL cholesterol was measured by enzymatic colorimetric method using commercially available kits (Daiichi Chemical, Tokyo, Japan). Apolipoprotein (apo) AI and apo B were measured using a nephelo-metric method (Eiken, Tokyo, Japan). Plasma concen-trations of lipoprotein (a) (Lp (a)) were assayed using an enzyme-linked immunosorbent assay (ELISA) (Biopool AB, Umea˚, Sweden). The inter-and intra-as-say coefficients of variation (CV) of serum lipids and apolipoproteins were as follows: total cholesterol,
0.9 and 0.9%; tryglyseride, 0.8 and 0.6%; HDL-cholesterol, 1.1 and 1.8%; LDL-choles-terol, 1.1 and 0.9%; apo AI, 0.6 and 0.3%; apo B, 0.6 and 0.5%; Lp (a), 1.2 and 1.4%, respectively.
The following hemostatic parameters were mea-sured: tTFPI, fTFPI, tissue factor (TF) antigen, fac-tor VII activity (FVIIc) and prothrombin fragment
1+2 (F1+2). Plasma TF antigen was measured us-ing the IMUBIND Tissue Factor ELISA (American Diagnostica, Greenwich, CT) [19]. The test specimen was diluted 1:5 in 0.05 M Tris, pH7.5, with 2% bovine serum albumin and 0.05% Tween 20, to elimi-nate the matrix effect of undiluted plasma. The mon-oclonal antibody used in this kit was the murine immunoglobulin G1 raised against tissue factor from the human brain, which detects the TF – apoprotein complex, TF and TF – VIIa complex. Plasma tTFPI concentration was measured using an ELISA kit (American Diagnostica) [20]. The murine monoclonal antibody used in this assay binds near Kunitz domain 1, detecting native, complexed and truncated TFPI. Plasma fTFPI concentration was measured by the ELISA kit (Free TFPI ELISA kit ‘KAKETUKEN’; Chemo-Sera-Therapeutics Research Institute, Ku-mamoto, Japan), which was based on the one-step sandwich ELISA method. The kit uses two different monoclonal antibodies against human TFPI obtained by the cell fusion method [8]. FVIIc was determined with a one-stage clotting assay using Owren’s veronal buffer (Diagnostica Stago, Asnieres, France), human FVII deficient plasma (Baxter Diagnostics AG, Deerfield, IL) and thromboplastin reagent (Baxter Di-agnostics AG, Miami, FL). The FVIIc levels were expressed as percent activity compared with a com-mercially available standardized calibration plasma (Baxter Diagnostics AG). Plasma F1+2 was mea-sured using a commercially available ELISA kit (En-zygnost F1+2 micro, Behringwerke AG, Marburg, Germany) [21]. The inter-and intra-assay CV of he-matological parameters were as follows: tTFPI, 2.5 and 3%; fTFPI, 3.7 and 3.2%; TF antigen,
2.7 and 3.9%; FVIIc, 3.9 and 5%; F1+2,
5.6 and 5.3%, respectively.
2.3. Statistics
Data are presented as the median and interquartile ranges. Because normal distributions were not found for some parameters, statistical analysis was per-formed by nonparametric tests (the Mann – Whitney two-sample rank test and the Kruskal – Wallis one-way analysis of variance). The changes in the plasma concentrations of tTFPI, fTFPI, FVIIc, F1+2 and serum lipids were analyzed using the Wilcoxon’s signed-rank test for matched pairs. Correlations be-tween laboratory parameters were calculated using Spearman rank correlation coefficients. P valuesB
Table 2
Hemostatic parameters in patients with hyperlipidemic and normolipemic control subjectsa
Hyperlipidemia Controls (n=38)
Variable
IIa (n=20) IIb (n=12)
165 (130–206)***
Total TFPI (ng/ml) 113 (96–141) 151 (140–197)**
31 (27–34)**
Free-form TFPI (ng/ml) 21 (17–27) 41 (38–45)***
93 (77–130)
90 (50–116) 103 (70–147)
TF (pg/ml)
92 (79–100)
FVIIc (%) 112 (97–118)* 121 (109–128)**
1.00 (0.67–1.21)*
0.74 (0.56–0.92) 0.94 (0.79–1.71)*
F1+2 (nmol/l)
aTF, tissue factor; TFPI, tissue factor pathway inhibitor; FVIIc, factor VII activity; F1+2, prothrombin fragment 1+2. Values are shown as the median (25–75th percentiles).
*PB0.05; **PB0.01;
***PB0.001, compared to normolipemic control subjects.
Table 3
Serum lipids, apoprotein and hemostatic parameters in patients with hyperlipidemia before and after treatment with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitorsa
After treatment (n=25)
Variable Before treatment (n=25) Statistical significance
5.03 (4.66–5.49)
Total cholesterol (mmol/l) 7.07 (6.52–7.29) PB0.0001
2.75 (2.41–3.49)
LDL-cholesterol (mmol/l) 4.75 (3.96–5.14) PB0.0001
1.45 (1.28–1.77)
1.32 (1.17–1.68) PB0.05
HDL-cholesterol (mmol/l)
1.20 (0.91–2.23)
Triglycerides (mmol/l) 1.73 (1.31–2.59) PB0.01
142 (130–173)
138 (123–163) NS
Apoprotein AI (mg/dl)
157 (140–173)
Apoprotein B (mg/dl) 94 (89–122) PB0.001
21.0 (8.5–36.0)
Lipoprotein (a) (mg/dl) 30.0 (3.8–38.3) NS
162 (149–217)
200 (168–235) PB0.005
Total TFPI (ng/ml)
Free-form TFPI (ng/ml) 31 (28–39) 31 (27–37) NS
118 (105–124)
128 (112–150) PB0.005
FVIIc (%)
0.89 (0.72–1.21) PB0.05 F1+2 (nmol/l) 1.13 (0.94–1.27
aTFPI, tissue factor pathway inhibitor; FVIIc, factor VII activity; F1+2, prothrombin fragment 1+2. Values are shown as the median (25–75th percentiles).
3. Results
3.1. Patient characteristics
Table 1 summarizes the clinical characteristics and clinical data in patients with hypercholesterolemia and age- and sex-matched normolipemic control subjects (Study Group I). There were no statistically significant differences in age among the two patient groups and control subjects. At base line, serum levels of total cholesterol, LDL-cholesterol, triglycerides, and apo B were significantly higher in the two patients groups than in the control subjects. Patients with type IIb hyperlipoproteinemia exhibited significantly higher body mass indices (PB0.05) and fasting blood sugar (PB0.05) than control subjects.
3.2. Assessment of hemostatic parameters
Table 2 summarizes the hemostatic parameters in the patients with hyperlipoproteinemia and in the age- and sex-matched normolipemic control group. The plasma concentrations of tTFPI antigen were significantly
higher in the patients with type IIa and type IIb hyper-lipidemia compared with the control group (PB0.0001, PB0.001, respectively). Compared with the control group, fTFPI antigen was 2-fold higher in type IIb hyperlipidemia (PB0.0001) and 1.5-fold higher in type IIa hyperlipidemia (PB0.001). With respect to the control group, the patients with type IIa and IIb hyper-lipidemia had significantly higher levels of FVIIc (PB
0.05, PB0.001, respectively). F1+2 was significantly higher in the two hyperlipidemic groups than in the control group (type IIa; PB0.05, type IIb; PB0.05). Although the median TF antigen was slightly higher in the patients with type IIb than in the control group, this increase did not reach statistical significance.
3.3. Effects of HMG-CoA reductase inhibitor on plasma hemostatic parameters
LDL-choles-terol (PB0.0001), and apo B (PB0.005) decreased significantly, and HDL-cholesterol increased signifi-cantly (PB0.05). However, serum apo AI and plasma Lp (a) did not show any significant change during therapy. After therapy, the median value for plasma tTFPI (162 ng/ml) decreased significantly compared to the value before therapy (200 ng/ml, PB0.005) (Fig. 1A), although the plasma levels of fTFPI did not change (Fig. 1B). Significantly lower values for FVIIc (Fig. 2) and F1+2 (Fig. 3) were also observed follow-ing therapy (PB0.005, PB0.05, respectively).
Fig. 2. Changes in plasma levels of factor VII (FVII) activity in subjects taking 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors.
Fig. 1. Changes in plasma concentrations of (A) total tissue factor pathway inhibitor (tTFPI) antigen and (B) free-form TFPI (fTFPI) antigen in subjects taking 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors.
Fig. 3. Changes in plasma concentrations of fragment 1+2 (F1+2) in subjects taking 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors.
3.4. Relationships between serum lipids and tTFPI, fTFPI, and FVIIc
correlation between plasma fTFPI and total cholesterol was relatively poor (r=0.31, PB0.05; Fig. 5A). The correlation between plasma fTFPI and LDL-cholesterol was also poor (r=0.30,PB0.05; Fig. 5B). The plasma level of FVIIc correlated with total cholesterol (r=
0.35, PB0.05; Fig. 6A) and triglycerides (r=0.36, PB0.05; Fig. 6D), whereas no significant associations were found with LDL-cholesterol (r=0.03; Fig. 6B) or HDL-cholesterol (r=0.23; Fig. 6C). On the other hand, no correlations were found between plasma F1+
2 and serum lipids (data not shown). There were also no significant correlations between Lp (a) concentra-tions and any of the hemostatic parameters (data not shown).
4. Discussion
The present study demonstrates, as previously re-ported by other authors [14,22], that plasma levels of
tTFPI increase in the patients with type II hyperlipi-demia and that cholesterol-lowering therapy reduces this increase. However, the results showed that plasma levels of fTFPI also increased and fTFPI levels did not change after therapy. Furthermore, the plasma F1+2 concentrations and FVIIc were higher in hypercholes-terolemic patients than in normal controls and the plasma levels of F1+2 and FVIIc were significantly decreased after therapy.
4.1. Extrinsic coagulation pathway in hypercholesterolemia
TF is synthesized in perturbed endothelial cells, and can be found in the cores of atherosclerotic plaques [23]. At sites of vascular injury, exposed subendothe-lium, or plaque rupture, TF comes in contact with circulating FVII, forming a bimolecular complex and, thus, plays a central role as the initiator of the extrinsic coagulation pathway [24]. The expression of TF by
Fig. 5. Correlations between free-form tissue factor pathway inhibitor (fTFPI) antigen and total cholesterol (A), low density lipoprotein (LDL)-cholesterol (B), high density lipoprotein (HDL)-cholesterol (C), and triglyceride (D) in hypercholesterolemic patients at baseline () and after treatment with simvastatin () and atorvastatin ().
endothelial cells and macrophages is stimulated by min-imally oxidized LDL and acetyl-modified LDL respec-tively [25,26]. Transient exposure of TF at the surface of atherosclerotic plaques or pertubated endothelial cells may cause low-grade triggering of blood coagulation. Actually, the results show elevated plasma levels of F1+2 in the patients with type II hyperlipidemia. Because F1+2 is a very sensitive and specific marker of thrombin generation and activation of the coagulation system [27], the data indicate that there may be an activation of thrombin generation in hypercholes-terolemic patients. However, plasma concentrations of TF antigen in the patients with hyperlipidemia were not significantly increased in the present study. Since TF is cell-associated, plasma TF antigen may not reflect blood circulating levels of TF. So it should be experimentally demonstrated that topical expression of TF at the surface of macrophages and endothelial cells actually results in activation of the extrinsic coagulation system.
4.2. Plasma tTFPI antigen and fTFPI antigen in hypercholesterolemic patients
As in other recent studies [13,14], the findings show that plasma levels of tTFPI antigen increase in hyperc-holesterolemic patients and that tTFPI antigen in plasma is positively correlated with serum total choles-terol and LDL-cholescholes-terol. However, the findings show that plasma levels of fTFPI antigen were also signifi-cantly higher in those patients than in normal subjects. This result of this study is contrary to those of Kokawa’s [9], although Kokawa et al. and plasma levels of fTFPI antigen were measured using the same ELISA kit. In their study, hyperlipidemic patients were found to have higher plasma levels of lipoprotein-bound TFPI and lower levels of fTFPI, in comparison to control subjects. These opposite results observed between two studies may be likely to be due to differ-ences in patient groups, baseline levels of cholesterol, or the extent of atherosclerosis and the endothelial injury. The patients in their study contained some FH and had higher levels of total cholesterol than those in this
study. Therefore their patients would promote athero-genesis and have severe endothelial injury, so that the endothelial cell-associated TFPI might decrease.
On the other hand, the mechanism of increase in the plasma fTFPI in the patients with hypercholesterolemia remains unknown. It was speculated that at least the endothelial cell-associated TFPI would not decrease in the hyperlipidemic patients, as the patients would have mild endothelial injury, and that the increase in fTFPI in plasma of the patients may have been caused by the following: (1) reflection to increased endothelial cell-as-sociated TFPI (hypercoagulability activates the produc-tion of TFPI in endothelial cells and bind to surface of them); or (2) release from the endothelial cells by thrombin stimulation. Clinical studies have demon-strated that the inhibition of the coagulation system by the administration of recombinant TFPI prevents reoc-clusion [28]. Moreover, Lindahl et al. suggest that the anticoagulant potential of plasma TFPI is restricted to
carrier-free TFPI [15]. If this assumption is correct, the increased fTFPI levels may inhibit the blood coagula-tion in the hyperlipidemic patients. It may be hypothe-sized that the elevated plasma fTFPI concentrations (and/or lipoprotein-associated TFPI concentrations) seen in hypercholesterolemia represent a compensatory mechanism to prevent activation of the blood coagula-tion system by TF and FVII.
4.3. Effect of HMG-CoA reductase inhibitor on plasma hemostatic parameters
As expected, total cholesterol was reduced in the 25 patients receiving HMG CoA-reductase inhibitors in the present study. Interestingly, recent clinical trials have documented that intensive lipid lowering therapy, especially employing HMG-CoA reductase inhibitors, significantly reduces ischemia-related clinical cardiac events despite only minimal regression of coronary artery stenosis, as measured angiographically [29,30]. Plaque stabilization due to decreased lipid content of lesions [31], improved endothelial function [32,33] and decreased tendency to form platelet thrombi [34] are three direct mechanisms that may account for the re-duction in coronary events associated with this lower-ing of cholesterol.
Lipids and lipoproteins modulate hemostasis by al-tering the expression and function of thrombotic and fibrinolytic factors. Consequently additional beneficial effects of HMG-CoA reductase inhibitors on coronary events may involve secondary mechanisms that modify thrombus formation. This study shows that cholesterol-lowering treatment induces a significant reduction in plasma levels of F1+2 and FVIIc. These changes suggest that there may be an improvement in the hypercoagulable state with reduction of serum choles-terol levels. Although the reduction in these parameters of hypercoagulation did not correlate with reduction in serum cholesterol concentrations and may have resulted in part from the lowered fat intake or a non specific effect of the drug, the reduction in F1+2 and FVIIc during lipid-lowering treatment may, in part, be respon-sible for a decreased risk of thrombosis.
4.4. Effect of HMG-CoA reductase inhibitor on plasma tTFPI and fTFPI le6els
The present study also demonstrated that therapeutic lowering of total cholesterol in patients with type II hyperlipoproteinemia was paralleled by a decrease in plasma concentrations of tTFPI but did not effect the plasma concentrations of fTFPI. The fall in tTFPI is believed to be due mainly to a lowering of the amount of circulating LDL – TFPI complexes [16]. If the as-sumption that the anticoagulant activity of fTFPI is markedly higher than that of lipoprotein-associated
TFPI [15] is correct, HMG-CoA reductase inhibitor treatment, which caused a specific drop in LDL – TFPI complexes and maintained fTFPI levels, would not affect the anticoagulant potency of TFPI in plasma. Recently, Hansen et al. have also demonstrated that a specific and prominent decrease in the amount of LDL – TFPI complexes by the HMG-CoA reductase inhibitor, lovastatin, did not affect the anticoagulant potency of TFPI either in human plasma or in the vascular endothelium [22].
5. Conclusions
In conclusion, it has been shown that patients with type IIa or IIb hyperlipoproteinemia have elevated concentrations of plasma tTFPI and fTFPI compared with the healthy individuals and that total cholesterol and LDL-cholesterol are correlated with tTFPI antigen in plasma. It may be hypothesized that the elevated plasma fTFPI concentrations (and/or lipoprotein-asso-ciated TFPI concentrations) seen in hypercholes-terolemia represent a compensatory mechanism to prevent activation of the blood coagulation system by TF and FVII, but the pathogenic mechanism is as yet unknown.
In addition, therapeutic lowering of total cholesterol in the patients with type II hyperlipoproteinemia was accompanied by decreases in plasma F1+2, FVIIc, and tTFPI concentrations, and maintenance of plasma fTFPI concentrations. These results may imply that lowering of total cholesterol in hyperlipidemic patients improve the hypercoagulability and that downregula-tion of LDL does not affect the anticoagulant potency of TFPI in plasma. However, because of the uncon-trolled nature of the cholesterol-lowering treatment study, the effects of HMG-CoA reductase inhibitor-in-duced inhibition of hypercoagulability requires confir-mation in a properly conducted placebo-controlled study.
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