Katsuhisa Ioriya

Effect of SMP-500, a Novel Acyl-CoA:Cholesterol Acyltransferase Inhibitor, on the Cholesterol Esterification and Its Hypocholesterolemic Properties

We investigated the effects of SMP-500, a novel acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, on ACAT activities in the liver and intestine, and in macrophages. We measured its effects on the serum cholesterol levels and hepatic cholesterol content in mice, rabbits and hamsters. SMP-500 inhibited ACAT activities in rabbit liver and small intestine microsomes with IC50 values of 72 and 84 nmol/l, respectively, and acted as a competitive inhibitor of rabbit liver ACAT. SMP-500 potently inhibited cholesterol esterification in rat peritoneal macrophages (IC50 = 15 nmol/l). In high-fat and high-cholesterol diet-fed mice and in high-cholesterol diet-fed rabbits, SMP-500 reduced the serum cholesterol levels and the hepatic cholesterol content. SMP-500 also reduced the serum and hepatic cholesterol in normal chow-fed hamsters in a dose-dependent manner. In all the animal models, SMP-500 reduced the hepatic free cholesterol content as well as the total and esterified cholesterol. Administered orally, SMP-500 had a direct inhibitory effect on hepatic ACAT activity. These results indicate that SMP-500 is a potent and competitive ACAT inhibitor and may have a therapeutic potential for treating hypercholesterolemia and atherosclerosis.

Novel 1,4-diarylpiperidine-4-methylureas as anti-hyperlipidemic agents: Dual effectors on acyl-CoA:cholesterol O-acyltransferase and low-density lipoprotein receptor expression

A family of 1,4-diarylpiperidine-4-methylureas were designed and synthesized as novel dual effectors on ACAT and LDL receptor expression. We examined SAR of the synthesized compounds focusing on substitution at the three aromatic parts of the starting compound 1 and succeeded in identifying essential substituents for inhibition of ACAT and up-regulation of hepatic LDL receptor expression. Especially, we found that compound 12f, which can easily be prepared, has biological properties comparable to those of SMP-797, a promising ACAT inhibitor. In addition, the in vitro effects of 12f on lipid metabolism were substantially superior to those of a known ACAT inhibitor, Avasimibe.

A Novel Class of Antihyperlipidemic Agents with Low Density Lipoprotein Receptor Up-Regulation via the Adaptor Protein Autosomal Recessive Hypercholesterolemia

We have previously reported compound 2 as a inhibitor of acyl-coenzyme A:cholesterol O-acyltransferase (ACAT) and up-regulator of the low density lipoprotein receptor (LDL-R) expression. In this study we focused on compound 2, a unique LDL-R up-regulator, and describe the discovery of a novel class of up-regulators of LDL-R. Replacement the methylene urea linker in compound 2 with an acylsulfonamide linker kept a potent LDL-R up-regulatory activity, and subsequent optimization work gave compound 39 as a highly potent LDL-R up-regulator (39; EC(25) = 0.047 microM). Compound 39 showed no ACAT inhibitory activity even at 1 microM. The sodium salts of compound 39 reduced plasma total and LDL cholesterol levels in a dose-dependent manner in an experimental animal model of hyperlipidemia. Moreover, we revealed in this study using RNA interference that autosomal recessive hypercholesterolemia (ARH), an adaptor protein of LDL-R, is essential for compound 39 up-regulation of LDL-R expression.

Pharmacological profile of SMP-797, a novel acyl-coenzyme A : Cholesterol acyltransferase inhibitor with inducible effect on the expression of low-density lipoprotein receptor

We investigated the pharmacological profile of SMP-797, a novel hypocholesterolemic agent. SMP-797 showed inhibitory effects on acyl-coenzyme A: cholesterol acyltransferase (ACAT) activities in various microsomes and in human cell lines, and hypocholesterolemic effects in rabbits fed a cholesterol-rich diet and hamsters fed a normal diet. In hamsters, the reduction of total cholesterol level by SMP-797 was mainly due to the decrease of low-density lipoprotein (LDL) cholesterol level rather than that of very low-density lipoprotein (VLDL) cholesterol level. Interestingly, SMP-797 increased the hepatic low-density lipoprotein receptor expression in vivo when it decreased the low-density lipoprotein cholesterol level. SMP-797 also increased low-density lipoprotein receptor expression in HepG2 cells like atorvastatin, an HMG-CoA reductase inhibitor, although other acyl-coenzyme A: cholesterol acyltransferase inhibitor had no effect. In addition, SMP-797 had no effect on cholesterol synthesis in HepG2 cells. These results suggested that the increase of low-density lipoprotein receptor expression by SMP-797 was independent of its acyl-coenzyme A: cholesterol acyltransferase inhibitory action and did not result from the inhibition of hepatic cholesterol synthesis. In conclusion, these results suggest that SMP-797 is a novel hypocholesterolemic agent showing a cholesterol-lowering effect in which the increase of hepatic low-density lipoprotein receptor expression as well as the inhibition of acyl-coenzyme A: cholesterol acyltransferase is involved.

Effect of SMP-500, a novel ACAT inhibitor, on hepatic cholesterol disposition in rats

The effects of SMP-500, a novel ACAT inhibitor, on serum lipid levels, hepatic lipid secretion rate, and hepatic lipid disposition in rats were studied to clarify its lipid-lowering action. SMP-500 reduced the serum cholesterol level in a dose-dependent manner in rats fed a hypercholesterolemic diet. SMP-500 also reduced hepatic free cholesterol content in addition to hepatic total and esterified cholesterol contents. Biliary concentrations of cholesterol and bile acid were increased by SMP-500; however, the bile flow and lithogenic index were not affected. SMP-500 increased cholesterol 7α-hydroxylase mRNA level. Therefore, it is suggested that the increase in concentrations of cholesterol and bile acid in bile is due to both the increase of bile acid production through the increase of cholesterol 7α-hydroxylase and the decrease of hepatic free cholesterol content. An inhibitory effect of SMP-500 both on the cholesterol secretion and on the TG secretion from liver was observed. SMP-500 reduced the serum TG level in sucrose-fed rats. From these results, one may hypothesize that the suppression of hepatic VLDL secretion probably plays an important role on both cholesterol- and TG-lowering effects of SMP-500.

Effect of SMP-500, a novel acyl-CoA:cholesterol acyltransferase inhibitor, on serum cholesterol level and LDL cholesterol clearance in hamsters with induced hyperlipidemia.

The effect of SMP-500, a novel acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, on serum cholesterol levels was investigated in hyperlipidemic hamsters whose condition had been preestablished by diet. SMP-500 reduced the total serum cholesterol level in a dose-dependent manner. SMP-500 also reduced the hepatic free cholesterol content and markedly reduced the esterified cholesterol content compared with the control group. Interestingly, SMP-500 at a dose of 30 mg/kg increased LDL clearance in vivo. As SMP-500 at this dose potently lowered the total serum cholesterol level, the increased LDL clearance was identified as another mechanism for the cholesterol-lowering effect of SMP-500. However, unlike HMG CoA reductase inhibitors, SMP-500 did not affect cholesterol biosynthesis in HepG2 cells. Therefore the etiology of the increased LDL clearance is not yet clear, but the reduced hepatic free cholesterol may play an important role in this process. These results suggest that the cholesterol-lowering effect of SMP-500 is due, not only to the inhibition of ACAT, but also to the increase in cholesterol clearance from the blood. This finding supports the therapeutic potential of SMP-500 for the treatment of human hypercholesterolemia.

Synthesis and structure―activity relationships of N-(4-amino-2,6-diisopropylphenyl)-N'-(1,4-diarylpiperidine-4-yl)methylureas as anti-hyperlipidemic agents

Based on 1,4-diarylpiperidine-4-methylureas, a new class of ACAT inhibitors, we examined in the study the SAR of a series of compounds prepared by replacing the substituent at the three aromatic parts. Introduction of long alkoxy group onto the phenyl moiety at the B-part was effective in improving both the inhibitory activity for ACAT and the up-regulatory activity for LDL-R expression. Particularly, 3-hydroxypropoxy group (43) on the phenyl moiety of B-part led to improved solubility, while keeping both biological activities. Compound 43 inhibited ACAT activity with an IC(50) value of 18 nM, which is superior to that of a known ACAT inhibitor, CI-1011. In addition, compound 43 revealed an LDL-R up-regulatory activity comparable to that of SMP-797. We therefore expect this compound to be a novel ACAT inhibitor.