Tsutomu Shibata

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.

JTT-501, a novel oral antidiabetic agent, improves insulin resistance in genetic and non-genetic insulin-resistant models.

We investigated whether JTT‐501 (4‐[4‐[2‐(5‐methyl‐2‐phenyl‐4‐oxazolyl)ethoxy]benzyl]‐3,5‐isoxazolidinedione) would improve insulin resistance in genetic (Zucker fatty rats) and non‐genetic (high‐fat fed rats) rodent models of obesity. JTT‐501 (10–100 mg kg−1 day−1) was administered orally to Zucker fatty rats for 7–21 days. In the high‐fat fed rat model, JTT‐501 (100 mg kg−1 day−1) was administered orally for 7 days. In both models, JTT‐501 improved metabolic abnormalities by enhancing insulin action during the glucose tolerance test and the euglycaemic‐hyperinsulinaemic clamp study. In ex vivo assays, JTT‐501 ameliorated the impaired insulin‐sensitive glucose oxidation and lipid synthesis in peripheral tissues. Furthermore, JTT‐501 enhanced insulin receptor autophosphorylation in hindlimb muscle. JTT‐501 reduced serum leptin concentrations in both models, but did not affect body weight or epididymal fat weight. Our observations indicate that JTT‐501 improves the metabolic abnormalities in both genetic and non‐genetic insulin‐resistant models by enhancing insulin action in peripheral tissues. These effects of JTT‐501 are due, at least in part, to enhanced insulin receptor autophosphorylation. In addition, JTT‐501 is able to reduce serum leptin concentrations in hyperleptinaemia of the insulin‐resistant model. We expect JTT‐501 to show promise for treating non‐insulin dependent diabetes mellitus patients with insulin resistance.

Induction of late airway response was involved in serum antigen-specific immunoglobulin G in rats.

The antigen-induced immediate airway response (IAR) has been considered a form of bronchoconstriction mainly provoked by histamine and leukotriene C4/D4/E4, which are released by stimulation by antigen-specific IgE. However, the pathophysiological features of the antigen-induced late airway response (LAR) are not yet fully understood. In the present study, sensitized rats were repeatedly exposed to ovalbumin (OVA) to induce IAR and LAR, and the immunological profiles of IAR and LAR were examined. The first antigen inhalation induced only IAR but not LAR. However, the second antigen inhalation 7 days after IAR induced LAR but not IAR. Tumor necrosis factor (TNF)-alpha level in BALF in LAR was significantly higher than that in IAR, although there were no differences in histamine, leukotriene C4/D4/E4, interleukin (IL)-1beta, or IL-13 levels between IAR and LAR. Serum antigen-specific IgE titer was high in both IAR and LAR, but serum antigen-specific IgG, IgG1, and IgG2a titers were dramatically high in LAR but not IAR. There were significant correlations between antigen-specific IgG, IgG1, and IgG2a titers and LAR. Interestingly, LAR could be induced in normal rats by transfer of serum from LAR rats, which exhibited high antigen-specific IgG, IgG1, and IgG2a titers. In conclusion, these findings suggest that repeated antigen inhalation converts IAR to LAR, and that LAR is a reaction triggered by antigen-specific IgG and involving TNF-alpha. This is the first study to directly suggest the involvement of antigen-specific IgG in the induction of LAR.

Triglyceride-lowering effect of a novel insulin-sensitizing agent, JTT-501

JTT-501, 4-[4-[2-(5-methyl-2-phenyl-4-oxazolyl)ethoxy]benzyl]-3, 5-isoxazolidinedione, is a novel insulin-sensitizing agent. We investigated the triglyceride-lowering activity of JTT-501 in a high-fat (HF) rat model. The HF rats showed insulin resistance with elevation of fasting insulin levels and reduction of insulin-stimulated glucose oxidation. There was also a tendency towards increased basal insulin and triglyceride levels. Oral administration of JTT-501 (3-30 mg kg(-1) day(-1) for 7 days) reduced basal triglyceride levels dose dependently with a minimum effective dose of 3 mg kg(-1) day(-1). Furthermore, regarding triglyceride metabolism, JTT-501 (30 mg kg(-1) day(-1) for 15 days, p.o.) decreased hepatic triglyceride output rate and serum triglyceride half-life (T1/2). In contrast, pioglitazone (30 mg kg(-1) day(-1) for 15 days, p.o.) reduced T1/2, but did not affect hepatic triglyceride output rate. We conclude that JTT-501 possesses potent triglyceride-lowering activity due to its inhibition of triglyceride secretion from the liver and enhancement of triglyceride disposal in peripheral tissues.

JTK-853, a Novel Non-Nucleoside Hepatitis C Virus Polymerase Inhibitor, Demonstrates a High Genetic Barrier to Resistance in vitro

JTK-853 is a novel, non-nucleoside, palm site-binding hepatitis C virus (HCV) polymerase inhibitor that has demonstrated antiviral activity in HCV-infected patients during 3 days of treatment. To estimate the genetic barrier of JTK-853 to resistance in vitro, colony formation assays were conducted using HCV replicon cells (genotypes 1a and 1b). The colony formation assays revealed that the numbers of resistant colonies for JTK-853 were much lower than those for other direct-acting antivirals, including palm site- or thumb pocket-binding non-nucleoside HCV polymerase inhibitors (NNIs), an NS5A inhibitor (NS5Ai), and a protease inhibitor (PI). Furthermore, the numbers of resistant colonies for JTK-853 in combination with the NS5Ai or PI were lower than those for other combinations of NS5Ai + NNI, and NS5Ai + PI. Our findings demonstrate that JTK-853 has a high genetic barrier to resistance, and suggest that its combination therapies will be potent in suppressing the emergence of drug resistance in HCV-infected patients.

Genotypic and Phenotypic Analyses of Hepatitis C Virus from Patients Treated with JTK-853 in a Three-Day Monotherapy

ABSTRACT JTK-853, a palm site-binding NS5B nonnucleoside polymerase inhibitor, shows antiviral activity in vitro and in hepatitis C virus (HCV)-infected patients. Here, we report the results of genotypic and phenotypic analyses of resistant variants in 24 HCV genotype 1-infected patients who received JTK-853 (800, 1,200, or 1,600 mg twice daily or 1,200 mg three times daily) in a 3-day monotherapy. Viral resistance in NS5B was investigated using HCV RNA isolated from serum specimens from the patients. At the end of treatment (EOT) with JTK-853, the amino acid substitutions M414T (methionine [M] in position 414 at baseline was replaced with threonine [T] at EOT), C445R (cysteine [C] in position 445 at baseline was replaced with arginine [R] at EOT), Y448C/H (tyrosine [Y] in position 448 at baseline was replaced with cysteine [C] or histidine [H] at EOT), and L466F (leucine [L] in position 466 at baseline was replaced with phenylalanine [F] at EOT), which are known to be typical resistant variants of nonnucleoside polymerase inhibitors, were observed in a clonal sequencing analysis. These substitutions were also selected by a treatment with JTK-853 in vitro, and the 50% effective concentration of JTK-853 in the M414T-, C445F-, Y448H-, and L466V-harboring replicons attenuated the susceptibility by 44-, 5-, 6-, and 21-fold, respectively, compared with that in the wild-type replicon (Con1). These findings suggest that amino acid substitutions of M414T, C445R, Y448C/H, and L466F are thought to be viral resistance mutations in HCV-infected patients receiving JTK-853 in a 3-day monotherapy.