Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q8NEX9 (reductase)
 26,410 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The relationship between the inhibition of the vitamin K cycle and the inhibition of the vitamin K-dependent clotting factor synthesis was studied in the rat under a controlled rate of S-warfarin administration. Steady state of drug disposition was achieved from beyond day 2 and stable anticoagulation was achieved from beyond days 3 to 4. Doses up to 0.5 micrograms/kg/h were without effect, whereas 3 micrograms/kg/h reduced prothrombin complex activity to about 10%. Factor II and factor VII activity were equally suppressed as prothrombin complex activity. The concentration-effect relationship for steady-state S-warfarin plasma concentration and the inhibition of clotting factor synthesis revealed a steep sigmoidal response relationship (IC50 = 0.21 +/- 0.01 micrograms/ml, Hill slope = 2.07 +/- 0.3). Contrary to this, the target enzyme vitamin K1 2,3-epoxide reductase showed a dose-dependent response for the entire dose range. The sigmoidal effect relationship for plasma S-warfarin and enzyme inhibition showed a slope of 0.81 +/- 0.07 with IC50 = 16 +/- 1 ng/ml. The results demonstrate a reserve capacity for the coumarin-sensitive reductase; at least 70% of the hepatic vitamin K1 2,3-epoxide reductase activity has to be eliminated before the vitamin K-dependent carboxylation of the clotting factors objectively becomes compromised. In the study, the microsomal warfarin binding sites were compared with the vitamin K1 2,3-epoxide reductase activity, and a strict 1 to 1 relationship was found supporting the relationship between both.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The relationship between the vitamin K cycle inhibition and the plasma anticoagulant response at steady-state S-warfarin conditions in the rat. 154 79

We present a 6-year-old mentally retarded girl. Chromosome analysis showed an interstitial deletion of chromosome 8; 46,XX,del(8) (pter----p23.1::p21.3----qter). The proposita had normal activities of glutathione synthetase reductase (GSR) and factor VII. Parental chromosomes were normal.
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PMID:Interstitial deletion 8p21.3----p23.1 in a 6-year-old girl. 163 37

The clinical efficacy of the 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMGCoA) reductase inhibitor simvastatin in the treatment of hypercholesterolaemia in non-insulin-dependent diabetes (NIDDM), was examined in a double-blind placebo-controlled study of 6 months in 70 patients with NIDDM (age 25-70 years), of whom 57 were randomised to placebo (29 patients) or simvastatin for 6 months, following a 3-month run-in on diet. Patients were hypercholesterolaemic (7.8 (7.6-8.0) (mean (95% confidence intervals)) mmol/l simvastatin vs. 8.0 (7.7-8.5) mmol/l placebo) and mildly hypertriglyceridaemic (2.6 (2.2-3.0) simvastatin vs. 2.9 (2.3-3.5) placebo). Other lipid measures and estimates of glycaemic control and haemostasis were similar in both groups. There were no significant changes in lipids, haemostatic factors, or measures of glycaemic control in the placebo treatment group. Conversely by the end of 24 weeks, simvastatin produced a 28% reduction in cholesterol (to 5.6 (5.0-6.2) mmol/l (P < 0.001)), a 38% reduction in LDL cholesterol (from 5.5 (5.4-5.6) mmol/l to 3.4 (2.8-4.0) mmol/l, P < 0.001), a 15% reduction in triglyceride (to 2.2 (1.8-2.6) mmol/l, P < 0.05, and a 9% rise in HDL (from 1.16 (1.07-1.25) to 1.23 (1.14-1.32) mmol/l, P < 0.05). Improvements in apolipoprotein B (apo B) (-28%, P < 0.001), the LDL cholesterol to apo B ratio (-20%, P < 0.001), and apo A1 (+15%, P < 0.001) were recorded. There were no effects upon fibrinogen, factor VII activity, factor VIII activity, or measures of glycaemic control (fasting glucose, insulin, C-peptide, or HbA1).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Simvastatin in non-insulin-dependent diabetes mellitus: effect on serum lipids, lipoproteins and haemostatic measures. 807 Mar 2

Warfarin, like all the 4-hydroxycoumarin compounds, has an asymmetric carbon atom. The clinically available warfarin preparations consist of a racemic mixture of equal amounts of 2 distinct S and R isomers, the former being 4-times more potent as anticoagulant and more susceptible to drug interaction. Warfarin is highly water soluble and rapidly absorbed from the stomach and the upper gastrointestinal tract; its plasma concentrations peak 60 to 90 minutes after oral administration. Warfarin binds to the enzyme vitamin K 2,3-epoxide reductase in liver microsomes, stopping the cycle of vitamin K and reducing gamma-carboxylation of the precursors of vitamin D-dependent pro- and anticoagulant factors. A variable fraction of the binding with the target enzyme, albeit small, can be reversed by competitive displacers, such as dithiol-reducing agent activity. Differences in dithiol-reducing activity have been suggested as a contributing factor to the wide interindividual differences in sensitivity to oral anticoagulants. The anticoagulant effect is caused by a small fraction of the drug, since most (97 to 99%) is protein bound (mainly to albumin) and ineffective. Drugs that can displace the albumin binding will increase the action of warfarin, even though this effect is counteracted by a more rapid elimination of the drug. The elimination half-life of warfarin varies greatly among individuals, ranging from 35 to 45 hours; the S isomer has, however, an average half-life shorter than the R isomer. The plasma levels of vitamin K-dependent proteins are determined by a dynamic equilibrium between their synthesis and half-life times. The delay before warfarin takes effect reflects the half-life of the clotting proteins; the levels of factor VII and protein C (with shorter half-lives) are reduced earlier, reaching steady inhibited levels in about 1 day, whereas factor II takes more than 10 days. Oral anticoagulant therapy (OAT) with warfarin or other coumarin derivatives is increasingly administered to patients for primary or secondary prevention of various arterial or venous thromboembolic diseases. If in some clinical conditions OAT is given indefinitely, in others--such as venous thromboembolism or after tissue heart valve replacement--anticoagulants are usually given only for the high risk period of thrombotic complication. A recent large prospective study performed by the Italian Federation of Anticoagulation Clinics showed that about 30% of the patients who began OAT for various clinical indications stopped treatment at different times, confirming that withdrawal from OAT is an occurrence that affects a large number of patients. The expression 'rebound phenomenon' was adopted to indicate a hypercoagulant condition occurring after warfarin withdrawal. A possible more frequent recurrence of thromboembolism after cessation of anticoagulation became a matter of controversy and many clinical studies, mostly observational and noncontrolled, reported on the issue with inconsistent results. Most authoritative commentators agreed that rebound phenomenon, though possible, was not clinically relevant and did not differ in frequency and intensity according to mode of withdrawal. Scientific interest in the topic waned until more sensitive methods for investigating blood hypercoagulability became available. In recent years, many studies (reviewed in the text) have investigated the levels of different markers of hypercoagulability [fibrinopeptide A, activated factor VII, prothrombin fragments F1+2, thrombin-antithrombin complexes, D-dimers (DD)], consistently finding an increase in their values after cessation of anticoagulation. Changes in the levels of markers of activated blood coagulation were prospectively investigated by our group in 32 patients with venous thromboembolism who were randomly withdrawn abruptly or gradually from warfarin treatment. Our results indicate that interruption of anticoagulant treatment frequently elicits low grade acti
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PMID:Warfarin withdrawal. Pharmacokinetic-pharmacodynamic considerations. 898 60

The strong familial occurrence of venous and arterial thromboembolic disease has prompted ongoing research to identify novel risk factors. Polymorphisms in the factor VII and prothrombin genes are related to increased thrombosis, but the mechanism of increased risk remains to be elucidated. Elevated levels of plasma homocysteine and of the variant lipoprotein(a) particle also contribute to increased thrombotic risk, due in part to polymorphisms in the apolipoprotein(a) gene and the gene for methylene tetrahydrofolate reductase.
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PMID:Update on genetic risk factors for thrombosis and atherosclerotic vascular disease. 992 32

Do extremely old persons have a genetically favourable profile which has protected them from cardiovascular death? We have tried to answer this question by measuring DNA polymorphisms of selected cardiovascular risk indicators [factor VII, FVII (R/Q353, intron 7 (37bp)n, and -323ins10), beta fibrinogen (-455G/A), plasminogen activator inhibitor type 1, PAI-1 (-675(4G/5G)), tissue plasminogen activator, t-PA (intron 8 ins311), platelet receptor glycoprotein IIb/IIIa, GPIIb/IIIa (L/P33), prothrombin (20210G/A), methylene tetrahydrofolate reductase, MTHFR (A/V114), angiotensin converting enzyme, ACE (intron 16 ins287), and angiotensinogen (M/T235)]. Blood was collected from 187 unselected Danish centenarians, and 201 healthy Danish blood donors, aged 20-64 years (mean age 42 years). Genomic DNA was amplified using PCR and the genotype was determined by RFLP methods or allele-specific amplification followed by agarose gel electrophoresis. The frequencies of the high-risk alleles in centenarians were: for FVII R/Q353 0.91; for FVII intron 7 (37bp)n 0.67; for FVII-323 ins10 0.90; for fibrinogen 0.16; for PAI-1 0.52; for t-PA 0.59; for GPIIb/IIIa 0.16; for prothrombin 0.008; for MTHFR 0.33; for ACE 0.52; and for angiotensinogen 0.36. Comparable frequencies were observed in the blood donors. Subgroup analysis of men and women separately gave similar results. The genotype frequencies in the centenarians and the blood donors were similar for all polymorphisms, and this study suggests that common variations in genes associated with cardiovascular risk do not contribute significantly to longevity.
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PMID:Longevity is independent of common variations in genes associated with cardiovascular risk. 1049 71

Newborns are susceptible to hemorrhages (hemorrhagic disease of the newborn or HDN) due to vitamin K deficiency. Induction of cytochrome P450 in the fetal liver by maternal anticonvulsant therapy such as phenobarbital or phenytoin is considered to be a major cause. An observed increase in late hemorrhagic disease (LHD) in breast fed neonates gave rise to the hypothesis that PCBs and dioxins, P450-inducing contaminants present in human milk, might effect vitamin K-dependent blood coagulation. This hypothesis was studied in rats. Administration of a single oral dose of 0.003, 0.03, 0.3, 3 or 30 nmol 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) per kg bodyweight or 0.75, 4, 20, 100 or 500 micromol 2,2',4,4',5,5'-hexachlorobiphenyl/kg bw (HxCB) to female and male rats resulted in dose-related reductions of the vitamin K-dependent coagulation factor VII. The highest factor VII reduction in female rats was 44%, observed after TCDD exposure. The Lowest Observed Adverse Effect Level (LOAEL) of TCDD on female factor VII levels was 0.3 nmol/kg bw (96 ng/kg). There was a significant inverse correlation between Factor VII levels and induction of hepatic ethoxyresorufin O-deethylating (EROD) activity, reflecting CYP1A1, and total P450 content. HxCB had no effect on female coagulation factors. In contrast, in male rats only exposure to HxCB, which induces mainly CYP2B1 and 2B2, decreased both coagulation factors dramatically up to 88%. The LOAEL of HxCB on factor VII in male rats was 100 micromol/kg bw (36 mg/kg). In general, effects on coagulation factors in male rats exceeded those in females. In addition, sex-dependent differences of TCDD and HxCB were observed on the hepatic vitamin K cycle enzyme activities in female and male rats. Vitamin K-dependent (gamma-glutamyl carboxylase activity was mainly induced in female rats; 2.3-fold in the highest dose group of TCDD. In male rats only vitamin K 2,3-epoxide reductase (KO-reductase) activity was induced 1.7-fold by the highest dose of HxCB. KO-reductase activity in female rats was also increased by TCDD, however, less pronounced than the carboxylase activity. Concluding, the hepatic vitamin K cycle still functions and is not blocked by TCDD or HxCB, thus explaining the observed reduction in factor VII. Finally, the possible role of P450 in vitamin K deficiency is discussed. Based on these results it is suggested to investigate the possible role of PCBs and dioxin-like compounds in LHD in more detail.
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PMID:Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin or 2,2',4,4',5,5'-hexachlorobiphenyl on vitamin K-dependent blood coagulation in male and female WAG/Rij-rats. 1090 69

A link has been suggested between blood lipids and hemostatic activation. Factor VII (FVII) is a coagulation factor which plays a pivotal role in fibrin generation and thrombus formation. Clinical trials have demonstrated that inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase greatly reduce cardiovascular events in patients with and without coronary artery disease but few data, at this time, are available on the effects of lipid-lowering treatment on factor VII levels. We studied thirty-six IIA and IIB type hyperlipidemic patients who, after a preliminary period of lipid-lowering diet, added atorvastatin (20 mg/daily) or continued dietary treatment alone until they achieved LDL-C recommended levels (<4 mmol/L). Four to six weeks of lipid lowering treatment with diet plus atorvastatin, produced a significant reduction in FVII coagulant activity (FVIIc) and antigen (FVIIAg). No significant changes were observed in activated FVII (FVIIa). The lipid-lowering treatment with diet alone induced an improved lipid pattern, but no significant changes in FVII profile. Our study suggests a significant effect of lipid-lowering treatment on FVII levels. A possibile nonlipid mechanism that modifies FVII pathway may be suggested.
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PMID:Effect of lipid-lowering treatment on factor VII profile in hyperlipidemic patients. 1112 57

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.
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PMID:Elevated plasma levels of free-form of TFPI antigen in hypercholesterolemic patients. 1113 1

Inflammation and thrombosis are important mechanisms in cardiovascular disease, as illustrated by the consistent association between inflammatory and hemostatic variables and the risk of cardiovascular events in epidemiological studies. However, the relationship between plasma concentrations of inflammatory and hemostatic markers and the severity of atherosclerosis is not yet well studied. We have evaluated 325 men and 370 women of 60 years, participating in the Danish Glostrup study. We diagnosed atherosclerosis by ultrasonographic measurement of intima-media thickness (IMT) of the right carotid artery and the assessment of plaque occurrence. Plasma samples were analyzed for the concentration of C-reactive protein (CRP), fibrinogen, d-dimer, plasminogen activator inhibitor type-1 (PAI-1) antigen and activity, tissue-type plasminogen activator (t-PA) antigen and activity, factor VII (FVII) antigen, FVII coagulant activity (FVII:C) and activated FVII (FVIIa). DNA variations were determined for fibrinogen, PAI-1, t-PA, FVII, factor XIII and methylene tetrahydrofolate reductase (MTHFR). Subjects with high IMT (upper 10% of distribution, n = 63) had higher CRP levels [2.2 mg L-1 (SE 0.3)] than subjects with IMT in the lowest tertile (n = 217) [1.7 mg L-1 (SE 0.1), P = 0.04], whereas there was no association between the hemostatic variables and IMT. There was an association between fibrinogen and d-dimer concentrations and number of plaques (P < 0.01), whereas there were no associations between CRP and the other hemostatic variables and the number of plaques. Genetic variation in the t-PA and MTHFR gene was associated with IMT. In conclusion, in the Glostrup population study, thrombosis and inflammation are associated with the severity of atherosclerosis, as reflected by IMT and plaque occurrence.
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PMID:Inflammation, thrombosis and atherosclerosis: results of the Glostrup study. 1287 60


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