Korekiyo Wakitani

A cholesteryl ester transfer protein inhibitor attenuates atherosclerosisin rabbits

Cholesteryl ester transfer protein (CETP) is a plasma protein that mediates the exchange of cholesteryl ester in high-density lipoprotein (HDL) for triglyceride in very low density lipoprotein (VLDL). This process decreases the level of anti-atherogenic HDL cholesterol and increases pro-atherogenic VLDL and low density lipoprotein (LDL) cholesterol, so CETP is potentially atherogenic. On the other hand, CETP could also be anti-atherogenic, because it participates in reverse cholesterol transport (transfer of cholesterol from peripheral cells through the plasma to the liver). Because the role of CETP in atherosclerosis remains unclear, we have attempted to develop a potent and specific CETP inhibitor. Here we describe CETP inhibitors that form a disulphide bond with CETP, and present one such inhibitor (JTT-705) that increases HDL cholesterol, decreases non-HDL cholesterol and inhibits the progression of atherosclerosis in rabbits. Our findings indicate that CETP may be atherogenic in vivo and that JTT-705 may be a potential anti-atherogenic drug.

Effects of peroxisome proliferator‐activated receptor‐α and ‐γ agonist, JTT‐501, on diabetic complications in Zucker diabetic fatty rats

This study has investigated the effects of JTT‐501, a peroxisome proliferator‐activated receptor (PPAR)‐α and PPAR‐γ agonist, on the pathogenesis of diabetic complications in the Zucker diabetic fatty (ZDF) rats, a model of type 2 diabetes. Comparison is made with troglitazone, a PPAR‐γ agonist. The ZDF rats exhibited hyperglycaemia and hyperlipidaemia, and developed diabetic complications such as cataract, nephropathy, and neuropathy. Treatment with JTT‐501 from the prediabetic stage controlled glycaemia and lipidaemia, and prevented the development of diabetic complications. Troglitazone was less effective in controlling serum cholesterol and neuropathy. ZDF rats developed diabetic osteopenia with reduced bone turnover, and this was prevented by JTT‐501 and troglitazone, possibly mediated by increased bone turnover and bone formation. Since JTT‐501 controlled glycaemia and lipidaemia in ZDF rats and prevented several diabetic complications, it is suggested that treatment with JTT‐501, which activates both PPAR‐α and PPAR‐γ, could provide a valuable therapeutic approach against diabetic complications in type 2 diabetes.

Pharmacological profiles of a novel oral antidiabetic agent, JTT-501, an isoxazolidinedione derivative.

JTT-501, 4-[4-[2-(5-methyl-2-phenyl-4-oxazolyl)ethoxy]benzyl]-3,5-isoxaz olidinedione, is an isoxazolidinedione derivative which is structurally distinct from thiazolidinediones such as pioglitazone and troglitazone. We investigated the effects of JTT-501 on insulin-sensitizing activity and in rodent diabetic models. JTT-501 enhanced insulin-stimulated cell differentiation of 3T3-L1 fibroblasts with an EC50 value of 110 nM. Furthermore, JTT-501 activated peroxisome proliferator-activated (PPA) gamma and alpha receptors with the EC5-fold values of 0.28 and 5.4 microM, respectively. In the non-insulin-dependent diabetes mellitus model KK-Ay mice, JTT-501 improved hyperglycemia, hyperinsulinemia and hypertriglyceridemia, and enhanced insulin-stimulated glucose oxidation in adipose tissues. JTT-501 was also effective in the non-insulin-dependent diabetes mellitus model Zucker diabetic fatty (ZDF) rats but not in the insulin-dependent diabetes mellitus model streptozotocin-induced diabetic mice. These observations suggest that JTT-501 enhances insulin sensitivity in peripheral tissues and improves hyperglycemia, hyperinsulinemia, and hypertriglyceridemia in non-insulin dependent diabetes mellitus models. In particular, the triglyceride-lowering activity of JTT-501 is a unique characteristic compared to the thiazolidinediones. Therefore, JTT-501 may be a promising antidiabetic agent for treating non-insulin-dependent diabetes mellitus patients with insulin resistance.

PHARMACOLOGICAL PROFILE OF JTE-522, A NOVEL PROSTAGLANDIN H SYNTHASE-2 INHIBITOR, IN RATS

Abstract.Objective and Design: The antinociceptive, antipyretic, and anti-inflammatory effects of JTE-522, a novel selective prostaglandin H synthase (PGHS)-2 inhibitor, were examined in rats.¶Materials: Sheep seminal vesicle PGHS-1 and placenta PGHS-2 were used for in vitro assay, while for in vivo experiments, male rats (4–8 weeks old) were used.¶Treatment: JTE-522 and reference compounds (0.01–100 μM) were subjected to enzyme assay. JTE-522 (0.3–30 mg/kg) and indomethacin (0.3–10 mg/kg) were administered orally.¶Results: JTE-522 inhibited PGHS-2 (IC50: 0.64 μM) without affecting PGHS-1 activity at 100 μM. In rats with yeast-induced hyperalgesia, JTE-522 showed a dose-dependent antinociceptive effect (ED50: 4.4 mg/kg). In rats with yeast-induced pyrexia, JTE-522 significantly reversed the pyrexic response (ED50: 3.9 mg/kg). Orally administered JTE-522 dose-dependently inhibited carrageenin-induced rat paw edema (ED30: 4.7 mg/kg). In rats with adjuvant-induced arthritis, JTE-522 showed a significant inhibitory effect at daily doses of 0.3–3 mg/kg. JTE-522 did not cause severe gastric lesions at oral doses up to 300 mg/kg.¶Conclusions: Our results indicate that the selective PGHS-2 inhibitor JTE-522 may represent a novel type of anti-inflammatory drug without adverse effects on the gastrointestinal tract. JTE-522 may thus be a promising agent for treating both acute inflammatory diseases and chronic inflammatory diseases such as rheumatoid arthritis.

JTE-522 selectively inhibits cyclooxygenase-2-derived prostaglandin production in inflammatory tissues.

Abstract.Objective and Design: To investigate the effect of JTE-522, a selective cyclooxygenase (COX)-2 inhibitor, on prostaglandin (PG) production and COX expression in rats.¶Subjects: Male rats (4-8 weeks old) were used for in vivo experiments, while for in vitro assay, rat peritoneal macrophages were used.¶Treatment: JTE-522 (1-100mg/kg) and indomethacin (0.03-10mg/kg) were administered orally. JTE-522 and reference compounds (0.01-10 μM) were subjected to COX expression.¶Results: JTE-522 inhibited the development of carrageenin-induced paw edema and PGE2 production in inflammatory paws at a dose of 10mg/kg. On the other hand, JTE-522 (1-100 mg/kg) did not affect A23187-stimulated thromboxane B2 release from whole blood or the PGE2 level in gastric mucosa. JTE-522 did not suppress lipopolysaccharide-induced COX-2 expression in peritoneal macrophages.¶Conclusion: These results indicate that JTE-522 selectively inhibits PG production mediated by COX-2 in inflammatory tissues. JTE-522 may thus represent a novel type of anti-inflammatory drug without adverse effects on the gastrointestinal tract.

Effect of JTT-705 on cholesteryl ester transfer protein and plasma lipid levels in normolipidemic animals

This study evaluated JTT-705, S-[2-([[1-(2-ethylbutyl)cyclohexyl]carbonyl]amino)phenyl]2-methylpropanethioate, as a cholesteryl ester transfer protein (CETP) inhibitor in several animal species. In vitro, JTT-705 inhibited plasma CETP activities of humans, rabbits, hamsters, cynomolgus monkeys and marmosets with IC(50) values of 5.5, 1.0, 11.7, 2.4 and 6.3 microM, respectively. The thiol form (JTP-25203) also inhibited those activities with IC(50) values of 2.8, 0.44, 0.52, 1.3 and 1.1 microM, respectively. Following oral administration to normolipidemic animals (rabbits, hamsters and marmosets), JTT-705 reduced plasma CETP activity, increased high density lipoprotein cholesterol (HDL-cholesterol), and decreased the ratio of non-HDL-cholesterol to HDL-cholesterol (atherogenic index) in all species. In marmosets, JTT-705 increased slow alpha-migrating lipoprotein (apolipoprotein E-rich HDL) in agarose gel electrophoresis, indicating that HDL metabolism in JTT-705-treated marmosets is similar to that in CETP-deficient humans. These results indicate that JTT-705 can be expected to inhibit plasma CETP activity and improve plasma lipoprotein profiles in a wide range of animal species, including humans.

JTE-607, A NOVEL INFLAMMATORY CYTOKINE SYNTHESIS INHIBITOR WITHOUT IMMUNOSUPPRESSION, PROTECTS FROM ENDOTOXIN SHOCK IN MICE

Abstract.Objective and Design: We investigated the effect of a novel N-benzoyl-L-phenylalanine derivative compound (JTE-607) on production of various cytokines and other immune responses in vitro and on endotoxin shock in vivo.¶Materials and Methods: Human, monkey, rabbit, mouse and rat peripheral blood mononuclear cells (PBMCs), and human fibroblasts, umbilical vein endothelial cells (HUVEC), mesangial cells and T cells were used in vitro. Endotoxin shock was induced by lipopolysaccharide (LPS) in Corynebacterium parvum (C. parvum) sensitized male C57BL/6 mice in vivo.¶Results: JTE-607 inhibited inflammatory cytokine production, including tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, IL-8 and IL-10, from LPS-stimulated human PBMCs, with IC50 values of 11, 5.9, 8.8, 7.3 and 9.1 nM, respectively. The inhibitory effects of JTE-607 were also seen in mRNA expression of those cytokines. The potency of JTE-607 on cytokine production from PBMCs of other species, and from other human cells were much lower than that on human PBMCs. JTE-607 did not affect either LPS-stimulated microbead phagocytosis or reactive oxygen species production at 1 μM in human PBMCs but slightly suppressed expression of major histocompatibility complex class II antigen at 1 μM, although it was 100-fold less active than it was as a cytokine inhibitor. JTE-607 (0.3-10 mg/kg, i.v.) showed dose dependent inhibition of mortality after LPS challenge in C. parvum sensitized mice in accordance with a decrease of plasma TNF-α.¶Conclusions: These results suggest that JTE-607 is a multiple cytokine inhibitor specific for human PBMCs. This compound may be useful for the treatment of various cytokine mediated diseases such as septic shock without causing immunosuppression.

JTT-608 controls blood glucose by enhancement of glucose-stimulated insulin secretion in normal and diabetes mellitus rats.

We investigated the pharmacological effects of a new anti-hyperglycemic agent, JTT-608 [trans-4-(4-methylcyclohexyl)-4-oxobutyric acid], in normal and neonatally streptozotocin-treated rats. In normal rats, JTT-608 improved glucose tolerance at 3-30 mg/kg, doses that did not cause a decrease in fasting blood glucose levels. In contrast, tolbutamide (10-100 mg/kg) and glibenclamide (1-3 mg/kg) caused a persistent decrease in fasting blood glucose levels, and tolbutamide only improved glucose tolerance at 10-100 mg/kg. Furthermore, JTT-608 (3-30 mg/kg) enhanced insulin secretion only with glucose stimulation, but tolbutamide (10-100 mg/kg) enhanced it both with and without glucose stimulation. In neonatally streptozotocin-treated rats, JTT-608 (10-100 mg/kg) improved glucose tolerance with enhanced insulin secretion in the oral glucose tolerance test and meal tolerance test. Additionally, JTT-608 improved glucose tolerance dose dependently, but the effect of tolbutamide reached a plateau. We conclude that JTT-608 is an enhancer of glucose-stimulated insulin secretion.

Effects of ONO-3708, an antagonist of the thromboxane A2/prostaglandin endoperoxide receptor, on platelet aggregation and thrombosis

The beneficial effects of an antagonist of the thromboxane A2/prostaglandin endoperoxide receptor, 7-[2 alpha,4 alpha-(dimethylmethano)-6 beta-(2-cyclopentyl-2 beta- hydroxyacetamido)-1 alpha-cyclohexyl]-5(Z)-heptenoic acid (ONO-3708) on thrombosis were examined. ONO-3708 at 0.1-3 microM inhibited the human platelet aggregation induced by thromboxane A2, prostaglandin H2, collagen, ADP (secondary phase) and epinephrine (secondary phase) without affecting prostanoid synthesis and the content of cyclic AMP in platelets. The in vivo effects, on coronary thrombosis in this case, were examined in two canine models. ONO-3708, 3 to 300 micrograms/kg i.v., prevented dose dependently the coronary thrombosis induced by partial obstruction of the coronary artery. ONO-3708, 3 micrograms/kg per min i.v., significantly prevented electrically stimulated coronary thrombosis without affecting systemic blood pressure and heart rate. These results indicate that the thromboxane A2/prostaglandin endoperoxide receptor could play an important role in the pathogenesis of thrombosis and that ONO-3708 may have therapeutic advantages in preventing thrombosis.

JTT-608 restores impaired early insulin secretion in diabetic Goto-Kakizaki rats.

We investigated the pharmacological effects of a new antidiabetic agent, JTT‐608, in comparison with the sulphonylurea tolbutamide, in Goto‐Kakizaki (GK) rats, a genetic model of non‐obese insulin‐dependent diabetes mellitus (NIDDM). In isolated perfused pancreas from GK rats, JTT‐608 (200 μM) enhanced 11.1 mM glucose‐stimulated insulin secretion in the first and second phases, but had little effect on insulin secretion at 2.8 mM glucose. In contrast, tolbutamide (100 μM) markedly stimulated insulin secretion at 2.8 mM glucose and enhanced the second phase of insulin secretion but not the first phase at 11.1 mM glucose. In vivo JTT‐608 also enhanced early insulin secretion only with glucose‐loading. In contrast, tolbutamide enhanced insulin secretion both with and without glucose‐loading. JTT‐608 (10–100 mg kg−1) improved oral glucose tolerance with enhanced insulin secretion in a meal tolerance test (MTT). In comparison with tolbutamide, JTT‐608 improved glucose tolerance more efficiently in GK rats than in Wistar rats. We conclude that in diabetic GK rats JTT‐608 suppressed postprandial glucose excursions with enhanced glucose‐stimulated insulin secretion, especially the first phase of insulin secretion.