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Background: Recent data suggest that the Pl(A2) allele of the platelet glycoprotein IIIa receptor may be a genetic risk factor for cardiovascular disease. We previously reported that the Pl(A2) allele was associated with increased platelet aggregability, as indicated by lower epinephrine threshold concentrations. Paradoxically, however, it has been reported that Pl(A2)-positive platelets have reduced fibrinogen binding. Because fibrinogen mediates platelet aggregability, we hypothesized that plasma fibrinogen levels may interact with Pl(A) genotype in modulating platelet aggregability. Methods and Results-- Glycoprotein IIIa Pl(A) genotype, fibrinogen level, and platelet aggregability were ascertained in 1340 subjects enrolled into the Framingham Offspring Study. Platelet aggregability was evaluated by the Born method. Higher fibrinogen levels were associated with increased epinephrine-induced aggregation (P=0.002) and a trend for ADP-induced aggregation (P=0.07). The fibrinogen effect was genotype specific, however, in that the increase in platelet aggregability with higher fibrinogen was present for the Pl(A1/A1) genotype (P=0.0005 and P=0.03 for epinephrine- and ADP-induced aggregation, respectively) but not for the Pl(A2)-positive genotype (P>0.90)., Conclusion: Higher fibrinogen levels were associated with increased platelet aggregability. However, the association between fibrinogen and platelet aggregability was genotype specific. This interaction may be responsible for the conflicting findings regarding Pl(A) genotype and platelet aggregability. Further study of this gene-environment interaction may provide insight into cardiovascular disease risk.

To determine whether the hypercoagulable state of patients with complications of diabetes can be reversed toward normal, a group of insulin-dependent individuals with proteinuria was treated with intensive insulin protocols. A statistically significant (P<.001) improvement in control of diabetes was achieved (mean +/- SEM glycosylated hemoglobin, 9.51% +/- 0.35% at baseline to 8.36% +/- 0. 39% at 12 months; and mean +/- SEM advanced glycosylated end products, 14.8 +/- 2.8 U/mL at baseline to 8.4 +/- 1.5 U/mL at 12 months). There were statistically significant decreases in 2 procoagulant factors: mean +/- SEM baseline elevated plasma factor VII, 128.69% +/- 5.63% at baseline to 106.24% +/- 3.43% at 12 months (P =.002); and mean +/- SEM plasma fibrinogen, 12.3 +/- 0.7 micromol/L (417.3 +/- 24.7 mg/dL) at baseline to 10.2 +/- 0.7 micromol/L (348.8 +/- 22.6 mg/dL) at 12 months (P =.04). Throughout the study, lipid fractions did not change significantly. Because plasma factor VII and fibrinogen concentrations were elevated while cholesterol and triglyceride concentrations were not, more attention should be paid to procoagulants as markers for thromboembolic complications in diabetic patients undergoing intensive insulin therapy.

Fibrinogen circulating in human blood is comprised of high molecular weight (HMW) and lower molecular weight (LMW) fractions. As previously documented by means of SDS-polyacrylamide gel electrophoresis (PAGE), LMW fraction was significantly increased in patients with cardiovascular disease and with diabetes mellitus (DM). We have recently observed that the values of fibrinogen measured by thrombin clotting time (the method of Clauss) were consistently lower in EDTA plasma than those obtained with citrated plasma. However, supplementation of EDTA plasma with magnesium (Mg) ions gave comparable results. In this study we documented by SDS-PAGE that fibrin formed with thrombin alone in EDTA plasma originated from HMW fibrinogen, whereas that formed after addition of Mg was derived from LMW fibrinogen. Thus, measurement of thrombin clotting time in EDTA plasma with and without Mg may serve as a quick method for the determination of HMW and LMW fibrinogens in human blood. Preliminary result obtained with this new method revealed that LMW fibrinogen was significantly increased in DM patients. We have therefore concluded that measurement of this fraction of fibrinogen may prove to be of clinical diagnostic significance.

Background: Fibrinogen has been identified as an independent risk factor for cardiovascular disease and associated with traditional cardiovascular risk factors. Also, the role of elevated fibrinogen in thrombosis suggests that it may be on the causal pathway for certain risk factors to exert their effect. These associations remain incompletely characterized. Moreover, the optimal fibrinogen assay for risk stratification is uncertain., Methods and Results: In 2632 subjects from cycle 5 of the Framingham Offspring Population, fibrinogen levels were determined with a newly developed immunoprecipitation test (American Biogenetic Sciences) and the functional Clauss method. With the immunoprecipitation method, there were significant linear trends across fibrinogen tertiles (P:<0.001) for age, body mass index, smoking, diabetes mellitus, total cholesterol, HDL cholesterol, and triglycerides in men and women. The Clauss method had significant results (P:<0.030), except for triglycerides in men. Fibrinogen levels were higher for those with compared with those without cardiovascular disease. After covariate adjustment, fibrinogen remained significantly higher in those with cardiovascular disease with the use of the immunoprecipitation test (P:=0.035 and P:=0.018 for men and women, respectively) but not with the Clauss method., Conclusions: Fibrinogen was associated with traditional cardiovascular risk factors. Elevation of fibrinogen may provide a mechanism for risk factors to exert their effect. Also, fibrinogen levels were higher among subjects with cardiovascular disease compared with those without disease. The immunoprecipitation test showed a stronger association with cardiovascular disease than the Clauss method, suggesting that it may be a useful screening tool to identify individuals at increased thrombotic risk.

Background: Given the importance of thrombosis in causation of acute coronary syndromes, it is possible that the beneficial effect of low lipid levels on the risk of coronary events is achieved by lowering thrombotic potential of the blood. Hypobetalipoproteinemia is characterized by plasma concentrations of apolipoprotein B and LDL cholesterol that are one third of those observed in the general population. The aim of this study was to utilize subjects with hypobetalipoproteinemia to examine the relation between thrombotic potential and low levels of LDL cholesterol., Methods and Results: Hemostatic risk factors were measured in 1878 individuals (1003 women and 875 men) participating in cycle 5 of the Framingham Offspring Study. The subjects were divided into five groups on the basis of LDL cholesterol level. Subjects with hypobetalipoproteinemia (LDL cholesterol < 70 mg/dL) had the lowest levels of fibrinogen, plasminogen activator inhibitor-1 antigen, and tissue plasminogen activator antigen. As LDL cholesterol increased, there was a significant increase in the levels of the hemostatic risk factors, with the exception of von Willebrand factor antigen. Adjustment with multivariate regression analyses for the covariates age, sex, body mass index, diabetes mellitus, smoking, alcohol intake, triglyceride level, and use of antihypertensive medication did not materially alter the results., Conclusions: Decreasing levels of LDL cholesterol are associated with decreasing levels of hemostatic risk factors. Subjects with hypobetalipoproteinemia have the lowest levels of hemostatic risk factors and may be protected against thrombotic complications of atherosclerotic cardiovascular disease because of reduced thrombotic potential. One mechanism by which lipid-lowering therapy may decrease clinical cardiac events is through a reduction in thrombotic tendency.

Electrophoresis in 3.5% polyacrylamide gel was used to determine the patterns of fibrinogen heterogeneity in healthy subjects, in postoperative patients and in patients with cancer or occlusive vascular disease. Two major and one minor fibrinogen fractions, differing in molecular weight, were identified, and their concentrations in blood determined. The high-molecular-weight (HWM) fraction was found in greatest concentration after operation, during the period of hyperfibrinogenemia, whereas no simultaneous increase of lower-molecular-weight (LMW and LMW') fractions occurred, suggesting that these were derivatives of HMW ("native") fibrinogen. No correlation between the concentrations of the LMW and LMW' fractions and fibrinolytic activity was found, suggesting that direct degradation of HMW fibrinogen by plasmin was unlikely. The high fibrinogen level in cancer patients was related to increased concentrations of HMW and LMW fractions, whereas in the vascular-disease patients it was due exclusively to increased concentrations of LMW and LMW' fibrinogen. Serial observations indicated little fluctuation in the concentration of these fractions, indicating a persistently accelerated rate of conversion of HMW to LMW and LMW' fibrinogen in occlusive vascular disease. Possible pathogenic implications are discussed.

The present study demonstrates that the fibrinolytic activity is significantly increased and the level of plasminogen antiactivator diminished in the blood of patients with advanced liver cirrhosis and chronic aggressive hepatitis as compared with the values for healthy subjects. Total fibrinogen concentration was similar in patients and controls. However, electrophoresis of plasma with the use of SDS-polyacrylamide gel (3.5%) showed considerable differences in the composition of fibrinogen fractions. Lower molecular weight (LMW and LMW1) clottable protein was significantly (p less than 0.01) increased in the patients. In two out of 22 patients the higher molecular weight (HMW) fraction was virtually absent. In vitro incubation (37 degrees C for 48 hr) of diluted (1:10) plasma from a patient resulted in extensive degradation of a low-solubility fibrinogen fraction (HMW) previously added to the sample. No degradation was observed in any undiluted plasma samples. It is concluded that the increased concentration of lower-molecular-weight forms of clottable protein in the blood of patients with liver disease is probably related to increased in vivo degradation rather than abnormal synthesis. An association rather than a direct correlation with fibrinolytic activity was found.

Plasma lipids, lipoproteins, fibrinogen and fibrinolytic activity (FA) were measured in 202 consecutive patients undergoing coronary angiography. Twenty-one patients, 13 men and 8 women with a mean age of 52.8 years and 56.7 years respectively, were found to be angiographically free of coronary artery disease (CAD) and served as the principal control group. Since this group contained a disproportionate number of subjects with risk factors such as family history, hypertension and smoking, a second control group of clinically healthy subjects selected for age was also tested. Their laboratory results were not used in the statistical calculations. The group with angiographic CAD consisted of 130 men (mean age 57.6 years) and 51 women (mean age 61.5 years). Abnormal angiograms were graded according to the number of major vessels with more than 50% stenosis involved. The laboratory variables which were significantly (p less than .01-.001) associated with the presence of CAD were: High density lipoprotein (HDL) when determined by polyacrylamide gel electrophoresis (PAGE) and expressed as a percentage of total lipoproteins rather than concentration, presence of Intermediate Density Lipoprotein (IDL), percent of Very Low Density Lipoprotein (VLDL), fibrinogen concentration and FA. The HDL2 subfraction was significantly inversely correlated only in women. The total plasma cholesterol was normal and virtually identical in both groups. Within the CAD group, only two of the laboratory results were significantly correlated with the extent of disease. By univariate analysis, the FA showed the closest association with the score for severity of CAD (p less than .001) followed by the presence of IDL (p less than .01). In conclusion, lipoprotein analysis by a method which measures not only HDL, but also LDL, VLDL and IDL, together with the determination of fibrinogen and FA provides information useful in the identification of individuals at risk for CAD.