Impaired Blood Rheology and Elevated Remnant-like Lipoprotein Particle Cholesterol in Hypercholesterolaemic Subjects

M NARA 0 H SUMINO 0 M NARA 0 T MACHIDA 0 H AMAGAI 0 K NAKAJIMA 0 M MURAKAMI 0 0 Dr Masami Murakami Department of Clinical Laboratory Medicine, Gunma University Graduate School of Medicine , 3-39-15 Showa-machi, Maebashi, Gunma 371-8511, Japan - >> Version of Record - Mar 1, 2009 What is This? Downloaded from imr.sagepub.com by guest on October 16, 2014 The Journal of International Medical Research 2009; 37: 308 317 [first published online as 37(2) 12] Impaired Blood Rheology and Elevated Remnant-like Lipoprotein Particle Cholesterol in Hypercholesterolaemic Subjects Blood rheology, fasting serum concentrations of remnant-like lipoprotein particle cholesterol (RLP-C) and concentrations of other lipids were compared in 23 hypercholesterolaemic and 69 normocholesterolaemic subjects, and the relationship between red blood cell (RBC) deformability and RLP-C concentrations were studied in a different set of six hypercholesterolaemic and six normocholesterolaemic subjects. Passage time of whole blood and concentrations of total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and RLP-C were significantly higher in hypercholesterolaemic than in normocholesterolaemic subjects. Passage time of whole blood correlated positively with TC, TG, LDL-C and RLP-C and negatively with high-density lipoprotein cholesterol. Furthermore, the passage time of 10% haematocrit-adjusted RBCs in phosphatebuffered saline, which reflects RBC deformability, correlated positively with the passage time of whole blood and RLPC. Thus, hypercholesterolaemic subjects had impaired blood rheology and elevated RLP-C concentrations, which may be associated with the pathophysiology of atherosclerosis in hypercholesterolaemic subjects. Impaired RBC deformability may contribute to impaired blood rheology associated with elevated RLP-C in hypercholesterolaemic subjects. Introduction Epidemiological studies have established dyslipidaemia or dyslipoproteinaemia as important risk factors for atherosclerotic disease.1 High concentrations of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) and low concentrations of high-density lipoprotein cholesterol (HDL-C)1 result in increased risk of atherosclerosis. In addition, remnants of triglyceride (TG)-rich lipoproteins of both intestinal and liver origin are considered atherogenic.2,3 Remnant-like lipoprotein particle (RLP) cholesterol (RLP-C), i.e. chylomicron and very low-density Downloaded from imr.sagepu3b.c0om8by guest on October 16, 2014 lipoprotein cholesterol (VLDL-C) remnants, reflects the levels of remnants of TG-rich lipoprotein.4 The Framingham Heart Study5 demonstrated that RLP-C was a significant and independent risk factor for coronary heart disease, therefore elevated concentrations of TC, LDL-C and RLP-C are risk factors for cardiovascular disease. Despite new insights into the pathogenesis of atherosclerosis in recent years, the pathophysiology of the atherosclerotic process is not fully understood. Haemorheological parameters are considered to be related to the formation of atherosclerotic plaques and thrombi, because fibrinogen concentration,6,7 plasma viscosity8,9 and blood viscosity10,11 have been identified as independent atherosclerotic risk factors. Lipid and lipoprotein concentrations are associated with haemorheological parameters. Plasma viscosity is positively correlated with TC and TG levels and inversely correlated with HDL-C level.12,13 RLP-C is reported to promote platelet aggregation.14 The RLP-C level is increased and blood rheology is impaired in patients with fatty liver disease compared with normal healthy volunteers.15 A new microchannel method has been developed that makes it possible to view blood flow under a microscope connected to a visual display unit while evaluating blood rheology.15 20 This method may be useful in acquiring new insights into the pathophysiology of the atherosclerotic process in dyslipidaemic patients. It has been reported that blood rheology measured by the microchannel method is influenced by red blood cell (RBC) deformability, leucocyte adhesiveness, platelet aggregation, and whole blood and plasma viscosity.15 20 It remains unclear, however, which of these components is most strongly associated with blood rheology. To elucidate the possible effects of haemorheological abnormalities on the pathogenesis of atherosclerosis in patients with dyslipidaemia, blood rheology was measured using the microchannel method, and the concentrations of RLP-C and other lipids were measured in hypercholesterolaemic and normocholesterolaemic subjects. Since RBCs constitute a major component of the cells present in the blood and RBC deformability is an important factor in the microcirculatory system in patients with heart and diabetic conditions,21 RBC deformability was also measured in order to investigate the relationship between RBC deformability, blood rheology and RLP-C concentrations in hypercholesterolaemic and normocholesterolaemic subjects. Subjects and methods SUBJECTS Written informed consent was obtained from each participant in the two studies, which were approved by the Institutional Review Board of Gunma University Hospital. Study 1 For study 1 male and female Japanese volunteers with hypercholesterolaemia or normocholesterolaemia were recruited. Hypercholesterolaemia was defined as elevated TC ( 220 mg/dl) or elevated LDL-C ( 140 mg/dl) and normocholesterolaemia was defined as normal TC (< 220 mg/dl) and normal LDL-C (< 140 mg/dl), according to criteria of the Japanese Atherosclerosis Society.22 Exclusion criteria were diabetes mellitus, hypertension, thyroid disease, acute or severe chronic liver disease, coronary artery disease, thromboembolic disease, renal disease, and metabolic or other endocrine disease that could influence lipid metabolism. None of the subjects was receiving medication of any kind. Downloaded from imr.sagepu3b.c0om9by guest on October 16, 2014 Study 2 For study 2, Japanese men and women with hypercholesterolaemia or normocholesterolaemia, defined as in study 1, were recruited voluntarily. This cohort of volunteers was entirely different from that of study 1. None of the subjects had any diseases or disorders other than hypercholesterolaemia and none was receiving medication of any kind. STUDY PROTOCOLS Study 1 In the morning, after a fast of 12 h, anthropometric measurements were made and blood samples were collected into three polypropylene tubes for serum and plasma analyses, and for blood rheology measurements. Blood samples (2 ml) were obtained by puncture of an antecubital vein using 23 G needles whilst the subject was in a sitting position. Heparin solution (0.1 ml, 1000 IU/ml) was used as an anticoagulant. Rheology of whole blood samples was measured within 2 h of sample collection. Study 2 In the morning, after a fast of 12 h, anthropometric measurements were made and blood samples were collected into two po (...truncated)