Biomedical subjects

H Mokuno

Publications and source records attributed to H Mokuno.

35 records · Page 2Linked to original sources

PubMed1997

Lipoprotein(a) phenotypes in Japanese children: a cohort study.

BACKGROUND: Elevated serum lipoprotein(a) [Lp(a)] concentrations have been demonstrated to be associated with cardiovascular diseases due to premature atherosclerosis. However, the association of Lp(a) phenotypes with the development of these diseases remains largely unexplored. METHODS: We analyzed the population-based frequencies of serum Lp(a) phenotypes in 269 Japanese children aged 8-13 years in one community. According to the different apolipoprotein(a) [apo(a)] electrophoretic mobilities, Lp(a) was classified into seven single-band and respective double-band phenotypes. Each individual expressed a single (homozygotic) or a double band (heterozygotic). RESULTS: The serum Lp(a) concentration frequency distribution was skewed toward lower levels with a mean +/- SD of 15.5 +/- 18.0 mg/dl and a median of 11.0 mg/dl. The Lp(a) phenotype frequencies revealed that the frequency of double-band phenotype expression (55%) was higher than that of single bands (44%) and that the frequency of phenotypes representative of low molecular weight apo(a) was very low (2%). The mean serum Lp(a) concentration of the double-band-expressing subjects was higher than that of subjects with the single-band phenotype (20.1 +/- 19.9 vs. 10.5 +/- 15.9 mg/dl, p < 0.01). CONCLUSIONS: These findings of Lp(a) phenotypes in children seemed to differ from those in Japanese adults in another study; contrary to expectation, the predominant Lp(a) phenotypes found in children were those frequently associated with cardiovascular diseases in adults. Thus, it is speculated that children whose Lp(a) phenotypes remain unchanged during the transition to adulthood may show an increased susceptibility to cardiovascular disease, although the nutritional effects on the Lp(a) phenotypes cannot be neglected.

Adolescent↗

PubMed1997

[Ultrasonographic assessment of carotid atherosclerosis emphasizing the variety of intimal-medial thickness and the relationship with coronary risk factors].

Intimal-medial thickness (IMT) of the extracranial carotid arteries measured by B-mode ultrasonography has been used as a marker of systemic and coronary atherosclerosis. Previous studies have indicated that maximum and mean carotid IMT are significantly correlated with the extent and severity of coronary artery disease (CAD), but the clinical usefulness of these markers is limited because they are neither specific nor sensitive enough to identify patients with or without significant CAD. The correlation of a new IMT marker, variance of IMT, with coronary risk factors and coronary atherosclerosis was investigated in 200 patients who underwent carotid ultrasonography and coronary angiography. IMT was measured in 16 sites of the extracranial carotid arteries for the calculation of mean, maximum and variance of IMT. Univariate analysis showed that these three indexes were significantly correlated with age, serum lipoprotein (a) and hypertension. However, age was correlated weakly with variance of IMT. There were significant gender differences in the mean and maximum IMT but not in the variance. There were also significant correlations of mean IMT with smoking, and maximum and variance of IMT with high-density lipoprotein. Multiple logistic regression analysis in 100 age and sex matched patients indicated that the only significant predictor for CAD in this subgroup was variance of IMT (odds ratio = 1.6). These results indicated that each risk factor causes different morphologic manifestations in the carotid atherosclerotic lesion. Variance of IMT, which represents the irregularity of carotid IMT, was correlated well with CAD and appears to be useful for assessing systemic and coronary atherosclerosis.

Aged↗

PubMed1996

Lack of increased coronary atherosclerotic risk due to elevated lipoprotein(a) in women > or = 55 years of age.

BACKGROUND: Numerous studies have indicated that there is an association between lipoprotein(a) [Lp(a)] and coronary artery disease (CAD) in middle-aged men; however, few studies have addressed this issue in women or the elderly. METHODS AND RESULTS: Serum Lp(a) concentrations were determined in 354 women and 706 men with or without angiographically defined CAD (one or more coronary arteries with narrowing of > or = 75%). The age-specific impact of elevated Lp(a) (> or = 30 mg/dL) on CAD was examined in each sex. In the younger age group (< 55 years old), elevated Lp(a) was independently associated with CAD in both sexes (adjusted odds ratio [OR]: women, 6.90, P < .01; men, 2.63, P < .05). The age-specific ORs declined with age, and elevated Lp(a) no longer conferred an increased CAD risk in either elderly men or women > or = 65 years old. In the age group of 55 to 64 years, elevated Lp(a) was positively associated with CAD for men (adjusted OR: 2.45, P < .05) but not for women (adjusted OR: 0.56, P = NS). CONCLUSIONS: For both sexes, elevated Lp(a) appears to be an independent risk factor for premature CAD and the importance of Lp(a) appears to decrease with age. However, for women, the risk estimate of Lp(a) began to decline at an age approximately 10 years younger than for men. These data suggest that not only age- but also sex-specific factors such as menstrual status may interact with the association between Lp(a) and CAD.

Aged↗

PubMed1996

Effectiveness of probucol in preventing restenosis after percutaneous transluminal coronary angioplasty.

Lipid lowering therapies were employed to prevent restenosis following elective percutaneous transluminal coronary angioplasty (PTCA). The effect of probucol was compared to that of Pravastatin in 141 coronary atherosclerosis patients. Probucol (750 mg/day) was administered for at least 30 days prior to PTCA (34 patients, group P-1) or less than 14 days prior to PTCA (27 patients, group P-2). Pravastatin (10 mg/day) was administered for at least 30 days prior to PTCA (38 patients, group V-1) or less than 14 days prior to PTCA (42 patients, group V-2). In group P-1, the patient restenosis rate was 17.6% and lesion restenosis rate was 14%. These rates were significantly lower than those of group V-1, which were 44.7% and 40.4% respectively (p < 0.05). The respective values were 48.1% and 51.8% in group P-2 (p < 0.05, vs group P-1) and 35.7% and 34% (p < 0.05, vs group P-1) in group V-2. Probucol seems to work, not only by lowering cholesterol but also by its antioxidative properties when administered for a sufficient period prior to PTCA.

Angioplasty, Balloon, Coronary↗

PubMed1995

Relation of saphenous vein graft obstruction to serum cholesterol levels.

OBJECTIVES: To determine the potential of lipid-lowering therapy to reduce saphenous vein graft obstruction, we retrospectively studied the association between graft obstruction and serum cholesterol levels. BACKGROUND: Atherosclerosis is the major cause of vein graft obstruction. Approximately 50% of grafts are occluded by 10 years after operation. It remains to be established whether lipid control affects long-term graft survival. METHODS: We carried out a retrospective review of all 284 patients who had undergone coronary artery bypass graft surgery at Juntendo University Hospital between 1976 and 1991 and met the following additional criteria: at least one saphenous vein graft, repeat coronary arteriography at some point after coronary artery bypass graft surgery and a serum cholesterol level > or = 200 mg/dl before operation. Saphenous vein graft obstruction rates were compared among three groups classified by serum cholesterol levels at follow-up arteriography: group I < 200 mg/dl; group II 200 to 239 mg/dl; group III > or = 240 mg/dl. A vein graft was considered obstructed if it was narrowed by > or = 70%. RESULTS: In group I, 88% of grafts were not obstructed 7 years after operation. The respective rates were 61% in group II and 57% in group III (p < 0.005). This relation was true for vein grafts to the left anterior descending and other coronary arteries. CONCLUSIONS: Lower serum cholesterol levels are associated with lower rates of vein graft obstruction for up to 7 years. This suggests that cholesterol-lowering therapy may improve long-term saphenous vein graft survival after coronary artery bypass surgery.

Aged↗

PubMed1994

Effect of the 39-kDa receptor-associated protein on the hepatic uptake and endocytosis of chylomicron remnants and low density lipoproteins in the rat.

The low density lipoprotein (LDL) receptor-related protein, which serves as the cell surface receptor for several proteins including alpha 2-macroglobulin-protease complexes, has been proposed to be a candidate hepatocytic receptor for chylomicron remnants through its recognition of apolipoprotein E. We have studied the effect of two ligands for this receptor, activated alpha 2-macroglobulin and the recently described 39-kDa protein that copurifies with the LDL receptor-related protein (receptor-associated protein), on the uptake and endocytosis of chylomicrons in intact rats and in isolated, perfused rat livers. Both of these ligands were rapidly taken up and endocytosed into the liver of rats. Chylomicrons from normal rats were injected in vivo and chylomicrons from estradiol-treated rats that were enriched in apolipoprotein E were added to liver perfusates. Prior administration of amounts of activated alpha 2-macroglobulin that saturated hepatic uptake mechanisms did not inhibit hepatic uptake or endocytosis of endogenously labeled cholesteryl esters of chylomicron particles in vivo or in perfused livers over a period of 15 min. By contrast, prior administration of saturating amounts of the receptor-associated protein (expressed in bacteria as a fusion protein with glutathione S-transferase) reduced hepatic uptake by about 30% and virtually abolished endocytosis. The receptor-associated protein inhibited hepatic uptake of human LDL in vivo by 70% and endocytosis by 81%. Our results show that receptor-associated protein-sensitive processes predominate in the overall pathways by which chylomicron remnants are endocytosed by rat liver. Furthermore, they show that the receptor-associated protein binds to and inhibits the function of the LDL receptor as well as the LDL receptor-related protein.

Animals↗

PubMed1994

Induction of LDL receptor-related protein during the differentiation of monocyte-macrophages. Possible involvement in the atherosclerotic process.

The low-density lipoprotein receptor-related protein (LRP) is a multifunctional receptor that binds to apolipoprotein E-rich lipoproteins, lipoprotein lipase, alpha 2-macroglobulin, lactoferrin, and tissue plasminogen activator. We studied the mRNA expression of LRP in human monocyte-derived macrophages and THP-1 cells. mRNA expression of LRP was induced during cell differentiation from human monocytes to macrophages or after incubation with phorbol ester (tetradecanoylphorbol acetate 100 ng/mL) in THP-1 cells, and the addition of 30 ng/mL macrophage colony-stimulating factor further enhanced LRP expression. These results indicated that the expression of LRP depended on the stage of differentiation and maturation of monocytic cells. mRNA expression of LRP was also enhanced in human monocyte-derived macrophages in the presence of acetylated low-density lipoprotein and in aorta of rabbits fed a high-cholesterol diet. We hypothesize that the LRP induced in monocyte-derived macrophages is involved in the initial process of atherosclerosis by interacting with its multiple ligands.

Animals↗

PubMed1993

[Ischemic heart disease].

During the progression of early atherosclerotic lesions, atherosclerotic plaque rupture, with intraluminal thrombosis superimposed, which is one of the principle mechanisms of evolving atherosclerosis, may lead to thrombotic occlusion and ischemic coronary syndrome. Pathologic studies suggest that plaque rupture and overlying thrombi, which are dynamic and repetitive may frequently occur. In most cases, healed ruptures and incorporation of thrombi produce plaque progression without manifestation of clinical symptoms. However, acute mural occlusive thrombi, overlying plaque ruptures, cause unstable angina and acute myocardial infarction. The different pathogenesis between unstable angina and acute myocardial infarction might depend on the composition and stability of the thrombus resulting from the degree of vessel injury and blood flow. Soft lipid-rich plaques appear more prone to rupture, particularly when the lipid pool is localized eccentrically within the intima. Macrophages in the plaque may also facilitate plaque rupture by releasing proteases.

Angioscopy↗

PubMed1991

The enhanced cellular uptake of very-low-density lipoprotein enriched in apolipoprotein E.

We have recently reported an increased clearance of plasma very-low-density lipoprotein (VLDL) after intravenous injection of apolipoprotein (apo) E in Watanabe heritable hyperlipidemic (WHHL) rabbits. In the present study, we have investigated the cellular uptake of VLDL enriched in apo E (VLDL-E) which had been incubated with purified rabbit apo E. VLDL-E was taken up approx. 2-fold more than VLDL in human skin fibroblast, human monocyte-derived macrophage and Hep G2 cell and its degradation was least in macrophage. To characterize the binding of VLDL-E, we performed a binding assay using hepatic endosome isolated from estradiol-treated rats and we observed both increased EDTA-sensitive and -resistant binding of VLDL-E on endosome. Ligand blotting of hepatic endosome demonstrated two major bands of LDL receptor (130 and 260 kDa protein) and a minor band of LDL receptor-related protein (580 kDa protein) with a ligand of VLDL-E. These results suggested that VLDL-E was endocytosed in liver through a similar pathway among three cell types, and enrichment of apo E in VLDL enhanced the uptake of VLDL not only via an EDTA-sensitive binding site (classical LDL receptor) but also via other binding sites including an EDTA-resistant binding site and an LDL receptor-related protein.

Animals↗

PubMed1991

Characterization of monoclonal anti-rabbit apolipoprotein E antibodies and chemical composition of lipoproteins separated by anti-apolipoprotein E immuno-affinity chromatography.

Six mouse monoclonal antibodies against rabbit apolipoprotein E (apo E) have been developed. Of these monoclonal antibodies, clone 5 revealed a high affinity for purified apo E, very low density lipoprotein (VLDL) and beta-VLDL. This monoclonal antibody was used to prepare an immunoaffinity column. Coupled to Sepharose 4B, this antibody allowed complete removal of lipoproteins containing apo E from plasma of New Zealand white (NZW) rabbits; 62, 46, 14, and 3% of VLDL-, IDL-, LDL-, and HDL-protein, respectively, were bound to the anti-apo E affinity column. The bound VLDL was significantly rich in free cholesterol (FC) and cholesteryl esters (CE) relative to the unbound VLDL, whereas bound IDL, LDL and HDL were significantly rich in FC only. All of the bound fractions were characterized by significantly increased ratios of FC/phospholipids (PL). These results indicate that the two lipoprotein populations with and without apo E have different lipid compositions. The relatively high content of cholesterol in lipoproteins containing apo E suggests a contribution of apo E to plasma cholesterol transport.

Animals↗

PubMed1991

Oxidation-labile subfraction of human plasma low density lipoprotein isolated by ion-exchange chromatography.

We isolated subfractions of human plasma low density lipoprotein (LDL) using ion-exchange chromatography. Plasma LDL from normolipidemic subjects were applied to a DEAE Sepharose 6B column. After elution of the bulk of LDL at 150 mM NaCl (the major fraction), the residual LDL was eluted at 500 mM NaCl and designated as the minor fraction. The minor fraction, only less than 1% of total LDL, tended to be somewhat similar in certain properties to oxidized LDL, e.g., an increased negative charge, higher protein/cholesterol ratio, and a higher flotation density than native LDL. These results were consistent with data reported by Avogaro et al. (1988. Arteriosclerosis. 8: 79-87). However, assays of 125I-labeled LDL binding activity for LDL receptors equal to that of the major fraction. Incorporation of [14C]oleate into cholesteryl ester [acyl-CoA:cholesterol acyltransferase (ACAT) activity] in mouse peritoneal macrophages incubated with the minor fraction was only slightly greater than that with the major fraction. Incubation of the minor fraction with 0.5 microM Cu2+ caused a remarkable stimulation of ACAT activity, while stimulation by the major fraction required incubation with 5 microM Cu2+, suggesting that the minor fraction was relatively labile to oxidation. The minor but definite presence of a plasma LDL subfraction more negative and susceptible to oxidation implicates the possibility of its association with atherogenesis.

Arteriosclerosis↗

PubMed1990

Monocyte colony-stimulating factor enhances uptake and degradation of acetylated low density lipoproteins and cholesterol esterification in human monocyte-derived macrophages.

We have investigated effects of monocyte colony-stimulating factor (M-CSF) on the uptake of acetylated low density lipoproteins (acetyl-LDL) and the activity of cholesterol esterification in human monocyte-derived macrophage. The cells were cultured with M-CSF for 10 days and then incubated with acetyl-LDL for 24 h. M-CSF (128 ng/ml) enhanced the uptake and degradation of 10 micrograms/ml of 125I-acetyl LDL 7.5-fold (n = 6) and the effect of M-CSF was dose-dependent at the concentrations of 0.5-32 ng/ml. The binding experiments at 4 degrees C demonstrated that the number of acetyl-LDL receptor was increased by the addition of M-CSF. Supporting this, ligand blotting analysis revealed a significant increase in a receptor protein for acetyl-LDL (240 kDa). Binding of LDL was also enhanced by M-CSF but less significantly than that of acetyl-LDL. Cellular cholesterol esterification in the presence of 10 micrograms/ml acetyl-LDL was enhanced 24.1-fold (n = 13) by 128 ng/ml M-CSF. It was evident that M-CSF enhanced cholesterol esterification to a greater extent than the cellular uptake of acetyl-LDL (24.1- versus 7.5-fold). Cholesterol esterification was also enhanced by the addition of granulocyte-macrophage colony-stimulating factor and interleukin 1. We conclude that M-CSF enhances the uptake of both acetyl-LDL and LDL by increasing their receptor number, and further enhances the process of cholesterol esterification, resulting in a remarkable increase in cholesterol esterification in macrophages. These findings strongly suggest the significant involvement of cytokines such as M-CSF in cholesterol metabolism of macrophages.

Biological Transport↗

PubMed1990

Apolipoprotein E and lipoprotein lipase secreted from human monocyte-derived macrophages modulate very low density lipoprotein uptake.

We investigated the roles of lipoprotein lipase and apolipoprotein E (apoE) secreted from human monocyte-derived macrophages in the uptake of very low density lipoproteins (VLDL). ApoCII-deficient VLDL were isolated from a patient with apoCII deficiency. The lipolytic conversion to higher density and the degradation of the apoCII-deficient VLDL by macrophages were very slight, whereas the addition of apoCII enhanced both their conversion and degradation. This suggests that the lipolysis and subsequent conversion of VLDL to lipoproteins of higher density are essential for the VLDL uptake by macrophages. VLDL incubated with macrophages obtained from subjects with E3/3 phenotype (E3/3-macrophages) showed a 17-fold greater affinity in inhibiting the binding of 2 micrograms/ml 125I-low density lipoprotein (LDL) to fibroblasts than native VLDL, whereas the incubation of VLDL with macrophages obtained from a subject with E2/2 phenotype (E2/2-macrophages) did not cause any increase in their affinity. Furthermore, 3 micrograms/ml 125I-VLDL obtained from a subject with E3/3 phenotype were degraded by E3/3-macrophages to a greater extent than by E2/2-macrophages (2-fold), indicating that VLDL uptake is influenced by the phenotype of apoE secreted by macrophages. From these results, we conclude that both lipolysis by lipoprotein lipase and incorporation of apoE secreted from macrophages alter the affinity of VLDL for the LDL receptors on the cells, resulting in facilitation of their receptor-mediated endocytosis.

Apolipoprotein C-II↗

PubMed1990

Cholesterol-free diet with a high ratio of polyunsaturated to saturated fatty acids in heterozygous familial hypercholesterolemia: significant lowering effect on plasma cholesterol.

We have studied the effect of diet therapy on plasma lipoprotein metabolism in heterozygous familial hypercholesterolemia. Seven patients with a mean plasma cholesterol concentration of 323 +/- 67 mg/dl were hospitalized and kept on a cholesterol-free diet for as long as 11 days without any medication. The content of dietary cholesterol was approximately 1.4 mg a day, and dietary fat, carbohydrate and protein comprised 18.0, 69.2 and 12.8% of calories, respectively. The ratio of polyunsaturated to saturated fatty acids (P/S) was 3.1. At the end of the study period, plasma cholesterol was lowered by 14.2%, from 323 to 277 mg/dl, and low density lipoprotein (LDL) cholesterol by 17.5% from 229 to 189 mg/dl. Using density gradient ultracentrifugation, the major change in LDL cholesterol was found to be in those fractions with a mean density between 1.034 and 1.042, where cholesterol concentrations decreased from 132 to 87 mg/dl (34%). These results indicate that diet therapy with free-cholesterol and a high ratio of P/S is highly effective in controlling plasma cholesterol levels in heterozygous familial hypercholesterolemia.

Adult↗

PubMed1990

Effect of exogenous apo E on the cellular binding of lipoproteins.

It is well known that apolipoprotein E (apo E) has a significant role in the metabolism of plasma cholesterol through receptor-mediated endocytosis of lipoproteins containing apo B 100. We have reported that intravenous administration of apo E increases the clearance of lipoproteins containing apo B 100, resulting in reduced plasma cholesterol levels in WHHL rabbits. In the present study, we investigated the effects of exogenous apo E on lipoprotein binding to cell surface receptors. Lipoproteins were enriched in apo E by the incubation with purified apo E. Among lipoproteins enriched in apo E, VLDL and intermediate-density lipoprotein demonstrated higher binding affinity to cell surface receptor on fibroblast than respective unmodified lipoproteins. In competitive binding study, VLDL enriched by apo E (VLDL + E) completely suppressed 125I-LDL binding to human skin fibroblasts and showed the greatest binding activity among different lipoprotein classes, whereas both VLDL and LDL incompletely suppressed a binding of 125I-VLDL + E. This result indicated that apo-E-rich VLDL can bind not only to LDL receptor but to binding sites other than LDL receptors.

Animals↗

PubMed1989

Increased clearance of plasma cholesterol after injection of apolipoprotein E into Watanabe heritable hyperlipidemic rabbits.

Apolipoprotein E (apoE) is known to play an important role in lipoprotein metabolism. We have studied the effect of apoE on the metabolism of plasma cholesterol by injecting apoE intravenously into rabbits deficient in low density lipoprotein receptors [Watanabe heritable hyperlipidemic (WHHL) rabbits]. Approximately 30 mg of apoE was injected per rabbit; a total of five WHHL rabbits were used. One hour later, plasma cholesterol levels fell 8.3% (from 488 +/- 192 to 446 +/- 174 mg/dl). After 3 hr, cholesterol levels had fallen by 19% (to 392 +/- 152 mg/dl). The reduced levels were maintained for at least 8 hr after injection of apoE. Cholesterol in very low density lipoproteins (VLDLs) and intermediate density lipoproteins fell rapidly during the first 2 hr after injection, followed by a reduction in the low density lipoprotein cholesterol level. Changes in apolipoprotein B levels in each lipoprotein fraction were very similar to those of cholesterol. Plasma apoE levels 3 min after injection were elevated 3-fold to 22.8 +/- 6.3 mg/dl and returned to initial levels 8 hr after injection. The rate of removal of intravenously injected 125I-labeled VLDL that had been incubated with apoE was 3-fold higher than that of unmodified VLDL. From these results, we conclude that the injected apoE is incorporated into VLDLs and that VLDL particles carrying more apoE are removed from the blood more rapidly, resulting in reduced formation of low density lipoprotein and lowered cholesterol levels.

Animals↗

PubMed1988

Down-regulation of hepatic LDL receptor protein and messenger RNA in fasted rabbits.

Rabbits fasted for 9 and 14 d exhibited 6- and 8-fold increase in plasma cholesterol level, respectively. As one of the mechanisms causing hypercholesterolemia in fasted rabbits, the decreased activity of hepatic low-density lipoproteins (LDL) receptor has been reported (Stoudemire, J.B., Renaud, G., Shames, D.M., & Havel, R.J. (1984) J. Lipid Res. 25, 33-39). In order to demonstrate the down-regulation of hepatic LDL receptor on a molecular basis, we carried out immunoblotting of the liver membranes with a specific antibody against LDL receptors and blot hybridization of hepatic RNAs with cDNA of LDL receptor. Immunoblotting showed that LDL receptors in fasted rabbits were markedly decreased, and blot hybridization of RNAs showed a significant decrease in mRNA level of hepatic LDL receptor in fasted rabbits. Further, significant decreases both in LDL binding to liver membrane and in hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in fasted rabbits were demonstrated. From these results, we concluded that hypercholesterolemia in fasted rabbits is caused by the impaired catabolism of LDL due to down-regulated biosynthesis of hepatic LDL receptor.

Animals↗