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Biomedical subjects

H Shimano

Publications and source records attributed to H Shimano.

At least 55 records · Page 3Linked to original sources
PubMed1996

Transgenic mouse and gene therapy.

In the transgenic mouse, a specific gene can be transduced or deleted to study its function and relation to human diseases. Recently, various lines of transgenic mice that overexpress or lack a specific gene have been established and are available to study the pathophysiology of human diseases, including atherosclerosis, diabetes, and hyperlipidemia. We have established transgenic mouse lines with an integrated rat apolipoprotein (apo) E gene under control of the metallothionein promoter. Overexpression of apoE in the liver reduced plasma cholesterol and triglyceride levels and prevented diet-induced hypercholesterolemia. Another transgenic model with overexpression of apoE under control of the H2 Ld promoter in the arterial wall was established. In this model, the formation of fatty streak lesions was markedly inhibited, suggesting that apoE has antiatherogenic actions. Finally, we discuss gene therapy, which will be an important therapeutic approach to correct genetic abnormalities found in metabolic diseases.

Animals↗
PubMed1996

Dose-dependent effect of niceritrol on plasma lipoprotein-a.

Lipoprotein-a, Lp(a), is a variant form of low density lipoprotein (LDL) that contains apolipoprotein-a, whose structure has 75-85% homology with plasminogen. Elevated plasma levels of Lp(a) are considered to be one of the independent risk factors for cardiovascular disease. We studied the effects of niceritrol, a nicotinic acid derivative, on plasma Lp(a) levels in 72 patients with hypercholesterolaemia. The dose of niceritrol was increased every 4 weeks, from 750 to 1500 and then to 2250 mg day-1. The final dose was adjusted to obtain a plasma cholesterol level less than 5.69 mmol l-1. Niceritrol led to significant decreases in plasma levels of median Lp(a), from 16.1 mg dl-1 (interquartile intervals, 8.7 to 32.8) to 11.1 mg dl-1 (interquartile intervals, 6.6 to 21), the mean reduction rate being 17.6%. In the group with pretreatment Lp(a) levels of over 20 mg dl-1, Lp(a) decreased by 10.0, 22.0 and 31.8% at the doses of 750, 1500, and 2250 mg day-1, respectively. In the group with levels less than 20 mg dl-1, only the dose of 2250 mg day-1 was effective in the reduction of Lp(a). The results suggest that the reduction of Lp(a) was dependent on the dose of niceritrol and on the pretreatment level of Lp(a). In conclusion, niceritrol is effective, in a dose-dependent manner, for reducing Lp(a) levels.

Aged↗
PubMed1995

CTG triplet repeat in mouse growth inhibitory factor/metallothionein III gene promoter represses the transcriptional activity of the heterologous promoters.

Growth inhibitory factor/metallothionein III (GIF/MT-III) is expressed specifically in brain, and neither mRNA nor protein is detected in other organs. This tissue-specific expression might be regulated by negative elements as well as positive elements, such as tissue-specific enhancers. To investigate the repression mechanisms of this gene in organs other than the brain, transfection experiments were performed by using various deletion mutants. Interestingly, a 25 x CTG repeat in the promoter region seemed to contribute to the repression activity. Moreover, the repression activity of this 25 x CTG repeat was also observed in various promoters and in a direction and position independent manner, indicating that this element could act as a silencer. However, no binding protein was detected by gel-shift and footprint analyses. These results strongly suggest that the CTG repeat functions as a negative element, and that this effect is caused by unknown mechanisms, rather than by interactions between specific cis-elements and specific trans-acting factors as reported previously. It is also possible that the CTG repeat functions as a general silencer in many genes.

Alzheimer Disease↗
PubMed1995

Effects of platelet-derived growth factor on the synthesis of lipoprotein lipase in human monocyte-derived macrophages.

Lipoprotein lipase (LPL), which is secreted by the two predominant cell types in atherosclerotic plaque, macrophages and smooth muscle cells, may be involved in atherosclerosis by generating atherogenic remnant lipoproteins. We investigated the effects of platelet-derived growth factor (PDGF)-BB on the synthesis of LPL by human monocyte-derived macrophages. These cells were cultured in the presence of PDGF-BB for 8 days, after which the enzyme activity, mass, and mRNA levels of LPL were determined. The effect of PDGF-BB was time-dependent and dose-dependent at concentrations of 1 to 10 ng/mL. At 10 ng/mL PDGF-BB enhanced twofold to 2.3-fold the secretion of LPL, and a pulse-labeling study with [35S]methionine revealed that 10 ng/mL PDGF-BB significantly increased the synthesis of LPL. Northern blotting analysis showed that the LPL mRNA level increased dose dependently in macrophages treated with PDGF-BB, and 10 ng/mL PDGF-BB enhanced twofold the expression of LPL mRNA. The protein kinase C inhibitor staurosporine suppressed the effect of PDGF-BB on LPL activity. These results indicate that PDGF-BB stimulated transcription of the LPL gene in human monocyte-derived macrophages through protein kinase C activation and resulted in an increased synthesis of LPL. Therefore, we hypothesize that the augmented synthesis of LPL by PDGF-BB modulates atherosclerosis by influencing lipoprotein metabolism in the vascular wall.

Becaplermin↗
PubMed1995

Inhibition of diet-induced atheroma formation in transgenic mice expressing apolipoprotein E in the arterial wall.

Apolipoprotein E (apoE) plays a crucial role in lipoprotein metabolism both in plasma and in peripheral tissues. To test whether apoE in the vascular wall has a direct and local effect on atherogenesis, we established transgenic mice expressing human apoE under control of H2 Ld promoter. Studies on mRNA levels and immunohistochemistry demonstrated that this line was characterized by high expression of human apoE in the arterial wall while its expression was relatively low in other tissues as compared with the respective endogenous expression of mouse apoE. They showed no difference in plasma cholesterol levels and lipoprotein profile from controls when fed both normal and atherogenic diets. However, after 24 wk of an atherogenic diet, the formation of fatty streak lesions in proximal aorta was markedly inhibited in transgenic mice as compared with controls. Both lesion area and esterified cholesterol content were < 30% of those in controls. In a tissue cholesterol labeling study with 3H-cholesterol, the specific activity of aorta cholesterol was much less in transgenic mice, suggesting that apoE enhances cholesterol efflux from the aortic wall into plasma. Thus, apoE has anti-atherogenic action which is mediated via enhancing reverse cholesterol transport from arterial wall.

Animals↗
PubMed1995

Overexpression of apolipoprotein E prevents development of diabetic hyperlipidemia in transgenic mice.

To determine the role of apolipoprotein E (apoE) in diabetic hyperlipidemia, we induced diabetes in transgenic mice overexpressing apoE by intravenous injection of streptozotocin (STZ) and examined plasma lipoprotein metabolism in these mice. In STZ-induced diabetic mice, blood glucose levels were > 19 mmol/l (350 mg/dl) and plasma insulin levels were reduced to < 5 pmol/l (1 microU/ml). The diabetic nontransgenic mice developed hypercholesterolemia (plasma total cholesterol level: 4.55 +/- 1.32 vs. 1.97 +/- 0.13 mmol/l [176 +/- 51 vs. 76 +/- 5 mg/dl]) and hypertriglyceridemia (plasma triglyceride level: 0.82 +/- 0.29 vx. 0.42 +/- 0.11 mmol/l [73 +/- 26 vs. 37 +/- 10 mg/dl]) compared with values before induction of diabetes. In the diabetic nontransgenic mice, enhanced intestinal acylCoA:cholesterol acyltransferase activity was demonstrated, a factor that may contribute to the development of diabetic hyperlipidemia. Induction of apoE remarkably reduced the development of hyperlipidemia in diabetic transgenic mice compared with diabetic nontransgenic mice (plasma cholesterol level: 4.55 +/- 1.32 vs. 3.31 +/- 0.47 mmol/l [176 +/- 51 vs. 128 +/- 18 mg/dl], P < 0.01, and plasma triglyceride level: 0.82 +/- 0.29 vs. 0.17 +/- 0.11 mmol/l [73 +/- 26 vs. 15 +/- 10 mg/dl], P < 0.01). Plasma lipoprotein analysis by gel filtration chromatography showed that the reduction of plasma cholesterol and triglyceride levels was due to the disappearance of lipoproteins containing apoB. In these studies, we demonstrated the usefulness of STZ-induced diabetes in mice as an animal model for diabetic hyperlipidemia and demonstrated that endogenous induction of apoE in transgenic mice improved diabetic hyperlipidemia.

Animals↗
PubMed1995

Role of apolipoprotein E in lipoprotein metabolism and in the process of atherosclerosis.

Apolipoprotein E (apoE) plays an important role in plasma lipoprotein metabolism through its high affinity binding to cell surface low density lipoprotein (LDL) receptor. To determine the role of apoE in plasma lipoprotein metabolism, transgenic mouse lines with integrated rat apoE gene under control of metallothionein promotor were established. The plasma level of rat apoE in homozygotes for the transgene was 17.4 mg/dl after zinc induction. In this group, plasma cholesterol and triglycerides levels were 43%, 68% reduced as compared with controls, respectively. Gel filtration chromatography showed that lipid reduction was mainly due to decreased both very low density lipoproteins (VLDL) and LDL. Furthermore, we studied the effects of apoE on the atherogenic process in Watanabe heritable hyperlipidemic (WHHL) rabbits. We administered 10 mg of purified apoE intravenously into five WHHL rabbits three times a week from their age of 2.5 months to 11 months for 8.5 months. After sustained administration of apoE, we found a significant reduction in the accumulation of cholesterol ester in aortae (1.55 +/- 0.07 mg/g tissue) as compared to control rabbits (4.32 +/- 0.61 mg/g tissue). Thus, apoE plays an important role not only in plasma lipoprotein metabolism but also in atherosclerotic process.

Animals↗
PubMed1994

Regulation of low density lipoprotein receptor activity in Chinese hamster ovary cells transfected with the c-fms gene.

Chinese hamster ovary (CHO) cells were transfected with the human c-fms gene, which encodes the receptor for macrophage colony-stimulating factor, to examine the effects on the low density lipoprotein (LDL) receptor activity. Degradation of [125I]LDL was significantly reduced in the transfected CHO cells as compared to non-transfected cells when incubated in lipoprotein-deficient serum. Quantitative analysis of LDL receptor mRNA using a competitive PCR method demonstrated that LDL receptor suppression occurred at transcription. These findings suggest that expression of the c-fms gene is involved in the regulation of LDL receptors on macrophages.

Animals↗
PubMed1994

Metabolism of chylomicron remnants in transgenic mice expressing apolipoprotein E in the intestine.

Apolipoprotein E (apoE) has high affinity for the cell surface low density lipoprotein (LDL) receptor. To determine the role of apoE in plasma chylomicron clearance, a transgenic mouse line which overexpresses apoE in the intestine was established. Immunohistochemistry demonstrated that considerable amounts of apoE were localized to mucosal cells of the intestine. In an oral retinyl palmitate challenge test, both the peak height and area under the curve in transgenic mice were less than 25% of those in controls. We speculate that the apoE molecules produced in the intestine of transgenic mice were incorporated onto newly synthesized chylomicron particles before their secretion into the plasma and thereby contributed to rapid plasma clearance of chylomicron remnants. Gene expression of apoE in the intestine would be a promising way to control postprandial hyperlipemia.

Administration, Oral↗
PubMed1994

Elevated serum and urinary thrombomodulin levels in patients with non-insulin-dependent diabetes mellitus.

Increased plasma levels of soluble thrombomodulin have been reported in several disorders as a marker for vascular endothelial damage. Serum and urinary thrombomodulin levels were measured in 79 patients with non-insulin-dependent diabetes mellitus. Both levels were significantly higher (23.5 +/- 6.1 ng/ml and 146.6 +/- 64.9 ng/ml, respectively) than those of normal healthy controls (18.8 +/- 3.1 ng/ml, P < 0.001, and 96.8 +/- 60.3 ng/ml, P < 0.01). Serum thrombomodulin levels increased in keeping with urinary albumin levels. In urine thrombomodulin was lower in the macroalbuminuria group than in the microalbuminuria group, suggesting two mechanisms: intravascular overproduction and impaired renal clearance. Both serum and urinary thrombomodulin levels in diabetic patients might be predictors for very early nephropathy.

Adult↗
PubMed1994

Dextran sulfate, a competitive inhibitor for scavenger receptor, prevents the progression of atherosclerosis in Watanabe heritable hyperlipidemic rabbits.

Dextran sulfate competes with binding of modified LDL to the scavenger receptor in macrophages. To elucidate the role of dextran sulfate in the atherosclerotic process, 100 mg of dextran sulfate in drinking water was given to 5 Watanabe heritable hyperlipidemic (WHHL) rabbits for 12 months starting at age 4 months. During the experimental period, there were no significant differences in plasma cholesterol levels between dextran sulfate-treated and untreated rabbits. After 12 months' treatment, accumulation of cholesterol ester in total aorta was significantly suppressed in dextran sulfate-treated rabbits as compared with untreated rabbits (71.4 +/- 22.3 vs. 42.7 +/- 16.5 mg/g dry weight, P < 0.05). Furthermore, lesion area with atherosclerotic plaques in treated rabbits was significantly less than that in untreated rabbits (59.7 +/- 24.5 vs. 30.4 +/- 14.4%, P < 0.05). These results indicate that dextran sulfate might prevent the progression of atherosclerosis by competitively inhibiting the binding of modified LDL to scavenger receptors.

Animals↗
PubMed1994

Overexpression of human lipoprotein lipase enhances uptake of lipoproteins containing apolipoprotein B-100 in transfected cells.

To investigate the role in lipoprotein metabolism of lipoprotein lipase (LPL) secreted by tissues, we established two cell lines. Fusion plasmids containing either human LPL cDNA or antisense LPL cDNA under control of the cytomegalovirus promoter were transfected into Chinese hamster ovary (CHO) cells, designated as CHO-LPL and CHO-anti-LPL, respectively. CHO-LPL constitutively produced a high level of LPL, whereas CHO-anti-LPL produced a minimal level. When very-low-density lipoprotein (VLDL) was incubated with CHO-LPL, VLDL triglycerides were hydrolyzed, intermediate-density lipoprotein (IDL) was produced, and apolipoprotein E contents increased. CHO-LPL took up and degraded 125I-VLDL at 37 degrees C four times more strongly than did CHO-anti-LPL. Whereas the degradation of apolipoprotein E-deficient VLDL was only 12% that of normal VLDL in CHO-LPL, structural changes of the lipoprotein, including apolipoprotein E expression on the lipoprotein surface, may be important for the cellular uptake of VLDL. Furthermore, we found that binding at 4 degrees C of VLDL and LDL to CHO-LPL was greater than to CHO-anti-LPL, and this binding difference was abolished by washing the cells with heparin. This suggests that cell surface LPL plays a role in the binding of lipoproteins to the cells. We conclude that both the composition of VLDL particles and their cellular binding are influenced by LPL secreted by cells, both of which may enhance the cellular uptake of VLDL.

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↗
PubMed1994

Secretion-recapture process of apolipoprotein E in hepatic uptake of chylomicron remnants in transgenic mice.

To investigate the role of apoE in hepatic uptake of chylomicron remnants, we studied chylomicron metabolism in transgenic mice overexpressing apoE in the liver. Plasma clearance of injected 125I-labeled human chylomicrons was fivefold faster in transgenic mice than in controls. Immunohistochemistry demonstrated that apoE was specifically localized at the basolateral surface of hepatocytes from fasted transgenic mice. After injection of a large amount of chylomicrons, the density of the cell surface apoE was markedly reduced and vesicular staining was observed in the cytoplasm, suggesting that the cell surface apoE was used for hepatic endocytosis of chylomicrons and remnants. Polyacrylamide gel analysis of chylomicrons and remnants that had been reisolated from plasma and from liver membrane after the injection of chylomicrons showed the particles to be enriched with apoE mainly after their influx into the liver rather than during their residence in plasma. These results provide strong evidence for the secretion-recapture process of apoE, whereby chylomicron remnants enter the sinusoidal space, acquire apoE molecules, and subsequently are endocytosed. Data from experiments with very low density lipoprotein and LDL showed that this system is specific for chylomicron remnants.

Animals↗
PubMed1994

Increased risk factors for coronary artery disease in Japanese subjects with hyperinsulinemia or glucose intolerance.

OBJECTIVE: To understand the interrelationship of coronary artery disease (CAD) risk factors including hyperlipidemia, hypertension, and glucose intolerance to prevent and better manage this disease. RESEARCH DESIGN AND METHODS: We performed a 100-g oral glucose tolerance test in 2,113 subjects, and we evaluated their plasma lipid levels, blood pressure (BP), and plasma glucose and plasma insulin responses. RESULTS: Multiple regression analysis demonstrated a significant relationship of either BP, plasma triglyceride (TG), or high-density lipoprotein (HDL) cholesterol levels to plasma insulin and glucose response after the glucose load. Plasma cholesterol levels were related only to the plasma glucose response. In subjects matched for age, sex, and body mass index (BMI) with hyperinsulinemia or normoinsulinemia, the hyperinsulinemic subjects had a significantly higher mean BP and plasma TG level than the normoinsulinemic subjects (128.8/82.3 vs. 122.9/79.3 mmHg and 172.1 vs. 119.4 mg/dl), and the HDL-cholesterol level was significantly lower (43.9 vs. 47.8 mg/dl). Furthermore, subjects matched for age, sex, and BMI with glucose intolerance had a higher mean BP (128.4/81.8 vs. 123.5/78.7 mmHg) and higher plasma TG level (154.2 vs. 123.0 mg/dl) than those without glucose intolerance. CONCLUSIONS: Based on these findings, subjects with hyperinsulinemia or glucose intolerance should be carefully managed to prevent CAD, because they have more numerous and more severe risk factors than subjects with normal plasma insulin levels or subjects without glucose intolerance.

Blood Glucose↗
PubMed1994

Establishment of enzyme-linked immunosorbent assays for lipoprotein lipase with newly developed antibodies.

We developed eight new antibodies against lipoprotein lipase (LPL), which included polyclonal antibodies raised against recombinant human LPL produced by transformant cells and two synthetic peptides corresponding to either amino (N)- or carboxy (C)-terminus of human LPL. With these antibodies, we established three effective sandwich enzyme-linked immunosorbent assays (ELISAs) for LPL, which enabled us to examine LPL mass not only in the postheparin plasma from human, rat, mouse, and guinea pig but also in the media and lysates of cultured cells. All of the developed antibodies showed high affinities for LPL, but their binding to LPL did not always influence the lipolytic activity of the enzyme. Interestingly, although the anti-C-terminus antibody should bind to a common epitope of human and mouse LPL, its binding selectively suppressed only human LPL activity. Because amino acid sequence surrounding the epitope is common to both LPLs, difference in the sequence outside the epitope will contribute to the selective suppression of LPL activity by the antibody. Our results also suggested that both termini of LPL would be exposed on the surface of the molecule because they were fully accessible to antibodies and that the N-terminus of LPL would be functionally less important because binding of the anti-N-terminus antibody did not affect human LPL activity. The ELISAs were further utilized to demonstrate the presence of C-terminus truncated LPL protein in the postheparin plasma of an LPL-deficient patient, to map an epitope of the anti-C-terminus antibody within residues 433-436, and to gain insight into the structure-function relationship of the LPL molecule.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗