Remnant-like particle cholesterol in coronary artery disease: correlation with plasminogen activator inhibitor-1 activity

Postprandial Hyperlipidemia and Atherosclerosis

The development of the remnant like particle (RLP) method for conveniently measuring serum remnant lipoprotein levels in 1993 promoted much research on atherogenic significance and metabolism of remnant lipoproteins. This research brought about many results as the following. A novel apolipoprotein B48 receptor incorporating remnant lipoproteins into macrophages in arterial wall was discovered and the structure of the gene of the receptor was clarified. The expression of apolipoprotein B100 was recognized in the human small intestine, suggesting that dietary very low density lipoproteins (VLDL) might be synthesized in the human small intestine and converted into VLDL remnants and low density lipoproteins (LDL). It is recognized that the atherosclerotic risk of postprandial hyperlipidemia is derived from an increase of remnant lipoproteins and that measurement of serum RLP levels in postprandial state is more sensitive and necessary for evaluating an atherosclerotic risk because serum RLP levels remain high all day in patients with diabetes mellitus or coronary heart disease. The relation between postprandial hyperlipidemia and insulin resistance was clarified.

Relationship between insulin-resistance and remnant-like particle cholesterol

We investigated the relationship between insulin-resistance (IR) and remnant-like particle cholesterol (RLP-C) using 472 subjects (174 men and 298 women) randomly selected from inhabitants of two rural communities in Japan, Tanno and Sobetsu. The level of fasting immunoreactive insulin (FIRI), fasting blood glucose (FBS), total cholesterol (TC), triglyceride (TG), HDL cholesterol, LDL cholesterol, and RLP-C were measured in each subject. Homeostasis model assessment (HOMA-R) was used as an indicator of IR. The subjects were divided into two groups according to the value of HOMA-R: an IR group of subjects with HOMA-R > approximately equal to 1.73 and a normal (NR) group of subjects with HOMA-R <1.73. There was a significant positive correlation between HOMA-R and RLP-C. The value of RLP-C was higher in the IR group than in the NR group (7.1 vs. 3.9 mg/dl in men and 5.3 vs. 3.6 mg/dl in women). The frequency of hyper RLP cholesterolemia (RLP-C > approximately equal to 7.5 mg/dl) was higher in the IR than in the NR group (23.7 vs. 6.6% in men and 20.3 vs. 6.6% in women). The results of multiple regression analysis showed that HOMA-R was closely related to RLP-C. The results of this study suggest that RLP-C is closely associated with IR syndrome.

Plasminogen activator inhibitor type-1 in cardiovascular disease. Status report 2001

Plasminogen activator inhibitor type-1 (PAI-1) is known to contribute to thrombus formation and to the development and the clinical course of acute and chronic cardiovascular disease, as well as of other arterial and venous thromboembolic diseases. Recently, an important role of elevated pretreatment levels of PAI-1 for failure of thrombolytic therapy of acute myocardial infarction has been discussed. PAI-1 plasma levels depend on the one hand on gene regulation but are related on the other hand to known risk factors of atherosclerosis like insulin resistance, diabetes or hypertriglyceridemia, respectively. Furthermore, an activated renin-angiotensin-aldosterone system (RAAS) significantly contributes to the upregulation of PAI-1 concentration via a receptor-mediated mechanism. In accordance to the known mechanisms of regulation of PAI-1 plasma levels, the use of specific agents like antidiabetic drugs, fibrates, statins, ACE inhibitors and angiotensin II type-1 receptor-blockers may contribute to the downregulation of circulating PAI-1 and, therefore, increase the fibrinolytic capacity and consecutively counteract the thrombotic tendency. To further improve the efficacy of thrombolytic therapy, a PAI-1 resistant variant of t-PA, TNK-t-PA, has been developed and is now available for acute myocardial infarction.

Plasma level of triglyceride-rich lipoprotein remnants is closely associated with the activation of coagulation factor VII in patients with myocardial infarction

Remnant-like particles, which have been recognized to be atherogenic derivatives of chylomicrons and very low density lipoproteins, can be measured using a new assay kit. The purpose of the present study was to investigate the association of remnant-like particles with the coagulation system that has an important role in the pathogenesis of myocardial infarction. We assayed blood levels of total cholesterol, triglyceride, HDL-cholesterol, apolipoproteins, remnant-like particles-cholesterol, remnant-like particles-triglyceride, fibrinogen, factor VII antigen, activated factor VII, and tissue factor in 111 patients with a history of myocardial infarction and 128 control subjects. In simple regression analysis, plasma levels of remnant-like particles-cholesterol and remnant-like particles-triglyceride showed a significant positive correlation with the levels of activated factor VII (r=0.319, p<0. 001, and r=0.286, p=0.002, respectively) and the activated factor VII/factor VII antigen ratio (r=0.241, p=0.011, and r=0.249, p=0.008, respectively) in patients with myocardial infarction. In contrast, there were no significant differences between remnant-like particles and activated factor VII in control subjects. In stepwise multivariate regression analysis, the significant determinants of activated factor VII were remnant-like particles-cholesterol (10.2%), apolipoproteins A-I (5.1%), and E (7.1%); for the activated factor VII/factor VII antigen ratio, remnant-like particles-triglyceride (6. 2%), age at blood sampling (5.1%), and apolipoprotein A-I (4.0%) in patients with myocardial infarction. However, the significant determinants of activated factor VII and the activated factor VII/factor VII antigen ratio were HDL-cholesterol (9.9% and 9.2%, respectively) in control subjects. It is concluded that remnant-like particles may be a risk factor for myocardial infarction by activating the extrinsic coagulation pathway.