Junichi Kurokawa

Usefulness of flow-mediated dilation of the brachial artery and/or the intima-media thickness of the carotid artery in predicting coronary narrowing in patients suspected of having coronary artery disease.

It has been reported that flow-mediated dilation (FMD) of the brachial artery and the carotid intima-media thickness (IMT), markers of atherosclerosis, are altered in patients with coronary artery disease (CAD), but it is still not known if the presence of CAD can be detected using these markers. We examined whether the presence of CAD can be detected by FMD of the brachial artery and/or IMT. Eighty-one patients who underwent coronary angiography for the first time were enrolled. In each patient, brachial artery diameter responses to FMD and the administration of nitroglycerin spray, and carotid IMT were measured using high-resolution ultrasound (10 MHz) before coronary angiography. CAD was defined as >50% stenosis of a major coronary artery. Fifty-six patients had CAD. FMD was lower and IMT was greater in patients with CAD (FMD, 2.9 +/- 0.2% vs 9.4 +/- 0.5%; IMT, 1.09 +/- 0.05 vs 0.79 +/- 0.04 mm, both p <0.0001). Nitroglycerin-induced dilation did not differ in the 2 groups. Multivariate analysis showed that FMD was the only predictor of the presence of CAD (p = 0.0026). Receiver-operating characteristic analysis demonstrated that a cutoff value for FMD for detecting the presence of CAD was 6%, with a sensitivity of 0.93 (52 of 56) and a specificity of 0.88 (22 of 25). These findings suggest that FMD but not IMT may be used to detect the presence of CAD in patients with suspected CAD.

Effect of fluvastatin sodium (XU62-320), a new inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, on the induction of low-density lipoprotein receptor in HepG2 cells

The effect of fluvastatin sodium (XU62-320), a new type of inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A, on the induction of LDL receptor in the human liver-derived cell line HepG2 was investigated. Fluvastatin sodium produced marked inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity and induction of LDL receptor on HepG2 cells at a concentration of 0.1-1.0 microM. These results suggest that fluvastatin sodium has potential for use as a strong plasma cholesterol-lowering drug.

High dose of fluvastatin sodium (XU62-320), a new inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, lowers plasma cholesterol levels in homozygous Watanabe-heritable hyperlipidemic rabbits.

The effects of fluvastatin sodium (XU62-320), a new type of inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, on plasma cholesterol and triacylglycerol levels were investigated using homozygous Watanabe-heritable hyperlipidemic (WHHL) rabbit, an LDL-receptor-deficient animal which expresses a hepatic LDL receptor activity less than 5% that of control rabbits. Plasma levels of total, VLDL- and LDL-cholesterol were decreased profoundly after oral administration of fluvastatin at a dose of 50 mg/kg per day for 4 weeks. Plasma triacylglycerol levels were not affected by fluvastatin. Hepatic HMG-CoA reductase activity increased by 3-fold and hepatic LDL receptor activity increased by only 3.7-fold, as calculated by Scatchard plot analysis, with fluvastatin administration for 4 weeks, and the hepatic mRNA level for the rabbit LDL receptor was increased by 3-fold. Combined administration of fluvastatin (50 mg/kg per day) and cholestyramine, a bile acid sequestrant resin, at a level of 2% of the diet for 4 weeks more profoundly decreased plasma total, VLDL- and LDL-cholesterol levels with induction of hepatic cholesterol 7 alpha-hydroxylase and no further induction of the hepatic LDL receptor. Plasma triacylglycerol levels were increased by the combination treatment. These results suggest that high dose of fluvastatin sodium is effective in lowering plasma cholesterol levels in homozygous WHHL rabbits through the shared mechanisms involving decrease in production and secretion of cholesterol from the liver and the induction of hepatic LDL receptor. Additional effect of cholestyramine on decrease in plasma cholesterol levels seems to be due to the further decrease in hepatic cholesterol secretion by up-regulation of hepatic cholesterol 7 alpha-hydroxylase.

Effect of pravastatin, a 3-hydroxy-3-methylglutaryl coenzyme a reductase inhibitor, on hepatic cholesterol 7α-hydroxylase, acyl-coenzyme A: cholesterol acyltransferase, and bile lipid secretion in the hamster with intact enterohepatic circulation

The effects of administration of pravastatin, a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, on hepatic cholesterol 7 alpha-hydroxylase and acyl-coenzyme A: cholesterol acyltransferase (ACAT) activities and bile lipid secretion were investigated in Syrian golden hamsters. Continuous administration of pravastatin induced no significant changes in hepatic cholesterol content, ACAT and cholesterol 7 alpha-hydroxylase activities, or bile lipid and acid composition. Abrupt withdrawal of pravastatin induced increases in hepatic cholesterol content and ACAT activity and no change in hepatic cholesterol 7 alpha-hydroxylase activity, and increased cholesterol saturation in bile. Hepatic cholesterol 7 alpha-hydroxylase activity paralleled hepatic mRNA levels of this enzyme. These results suggest that a change in hepatic cholesterol metabolism induced by continuous administration of pravastatin maintains a constant net balance of hepatic cholesterol content. In addition, the drug has no deleterious influence on metabolism of bile lipids and acids and related enzymes, except for a transient increase in cholesterol saturation in bile induced by an inappropriate increase in hepatic cholesterol content and a lack of response of cholesterol 7 alpha-hydroxylase activity to changes in hepatic cholesterol content upon abrupt withdrawal of pravastatin.

Amino Acid Transport System of the Guinea Pig Small Intestine is Injured by Hydroxyl Radicals

The mechanism for the damage to the alanine-preferring amino acid transport system (A system) of guinea pig intestinal brush border membrane vesicles induced by active oxygen species was studied in vitro. The transport activity of L-proline, which is a model amino acid for the A system, and the tryptophan fluorescence intensity of intestinal brush border membrane vesicles were decreased, and lipid peroxidation of these membrane vesicles was induced by ultraviolet irradiation, which generated active oxygen species. Thiourea (hydroxyl radical scavenger) protected L-proline transport activity and tryptophan fluorescence intensity of intestinal brush border membrane vesicles and also inhibited lipid peroxidation in these membrane vesicles in the presence of active oxygen radicals. alpha-Tocopherol (singlet oxygen radical scavenger) inhibited lipid peroxidation of intestinal brush border membrane vesicles but protected neither L-proline transport activity nor tryptophan fluorescence intensity in these membrane vesicles in the presence of active oxygen radicals. Catalase and superoxide dismutase showed no protective effect on L-proline transport activity, tryptophan fluorescence intensity, or lipid peroxide formation in intestinal brush border membrane vesicles in the presence of active oxygen radicals.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of a functional receptor differing from the LDL receptor that catabolizes chylomicron remnant in Hep G2 cells

We investigated types of lipoprotein receptors on Hep G2 cells using a monoclonal antibody against the LDL receptor. IgG-C7 inhibited the binding and internalization of 125I-labeled low density lipoprotein (LDL) in Hep G2 cells with upregulated and downregulated LDL receptors by 90% of control values. Binding and internalization of 125I-labeled chylomicron remnant in Hep G2 cells with upregulated and downregulated LDL receptors was 50% and 85%, respectively, of control values after exposure to IgG-C7. Excess unlabeled chylomicron remnant inhibited binding and internalization of 125I-labeled chylomicron remnant in Hep G2 cells with downregulated LDL receptors completely. Pronase treatment abolished binding and internalization of 125I-labeled LDL and 125I-labeled chylomicron remnant in Hep G2 cells. When solubilized fractions of Hep G2 cells were immunoprecipitated with IgG-C7, the binding activity of 125I-labeled chylomicron remnant to reconstituted vesicles was unchanged. 45Ca blotting analysis showed the presence of 45Ca binding protein (approximately 600 kDa) in Hep G2 cells. The amount of 45Ca binding protein was not affected by cholesterol and was abolished by pronase treatment. These results suggest the existence of a functional receptor other than the LDL receptor that catabolizes chylomicron remnant in Hep G2 cells and that this receptor may correspond to LDL receptor-related protein.

Metabolic changes in lipoprotein receptors after phorbol ester-induced differentiation of human monoblastic cells.

Mouse peritoneal macrophages accumulate cholesterol esters via receptors for the uptake of acetylated LDL (scavenger receptor) and ~-VLDL (1). A recent study has demonstrated that uptake of ~-VLDL, chylomicron remnants and LDL by mouse peritoneal macrophages or macrophage-like cell lines is mediated by LDL receptors (2-5), suggesting a mechanism whereby native lipoproteins may promote cholesterol accumulation in macrophages. Investigation of lipoprotein metabolism in U937 cells, which are of human origin and differentiate into monocyte-macrophage-like cells, might help explain cholesterol accumulation by macrophages. We therefore investigated metabolic changes in lipoprotein receptors and their characteristics after differentiation of U937 cells. 37 °C for 10 h, the cellular content of cholesteryl [14C]oleate was determined as described previously (1,6). The assays of cultures of U937 cells were performed as described previously (6).