The bioequivalence study design recommendations for immediate-release solid oral dosage forms in the international pharmaceutical regulators programme participating regulators and organisations: differences and commonalities

Bioequivalence (BE) studies are considered the standard for demonstrating that the performance of a generic drug product in the human body is sufficiently similar to that of its comparator product. The objective of this article is to describe the recommendations from participating Bioequivalence Working Group for Generics (BEWGG) members of the International Pharmaceutical Regulators Programme (IPRP) regarding the conduct and acceptance criteria for BE studies of immediate release solid oral dosage forms. A survey was conducted among BEWGG members regarding their BE recommendations and requirements related to study subjects, study design, sample size, single or multiple dose administration, study conditions (fasting or fed), analyte to be measured, selection of product strength, drug content, handling of endogenous substances, BE acceptance criteria, and additional design aspects. All members prefer conducting single dose cross-over designed studies in healthy subjects with a minimum of 12 subjects and utilizing the parent drug data to assess BE. However, differences emerged among the members when the drug's pharmacokinetics and pharmacodynamics become more complex, such that the study design (e.g., fasting versus fed conditions) and BE acceptance criteria (e.g., highly variable drugs, narrow therapeutic index drugs) may be affected. The survey results and discussions were shared with the ICH M13 Expert Working Group (EWG) and played an important role in identifying and analyzing gaps during the harmonization process. The draft ICH M13A guideline developed by the M13 EWG was endorsed by ICH on 20 December 2022, under Step 2.

Molecular Anatomy of the Class I Ligase Ribozyme for Elucidation of the Activity-Generating Unit

The class I ligase ribozyme consists of 121 nucleotides and shows a high catalytic rate comparable to that found in natural proteinaceous polymerases. In this study, we aimed to identify the smaller active unit of the class I ligase ribozyme comprising ~50 nucleotides, comparable to the estimated length of prebiotically synthesized RNA. Based on the three-dimensional structure of the class I ligase ribozyme, mutants were prepared and their ligation activities were analyzed. Sufficient ligation activity was maintained even when shortening to 94 nucleotides. However, because it would be difficult to approach the target of ~50 nucleotides by removing only the partial structure, the class I ligase ribozyme was then split into two molecules. The ligation activity was maintained even when splitting into two molecules of 55 and 39 nucleotides. Using a system with similar split ribozymes, we analyzed the ligation activity of mutants C30, C47, and A71, which have been previously identified as the positions that contribute to catalytic activity, and discussed the structural basis of the activity of these bases. Our findings suggest the rationale for the class I ligase ribozyme's assembling from multiple fragments that would be achievable with prebiotic synthesis.

First Approval of Generic Mometasone Furoate Nasal Suspension Spray in Japan: Similarities and Differences Between Japan and the USA

The Ministry of Health, Labour and Welfare (MHLW) in Japan approved the first generic version of Nasonex in February 2018. The Pharmaceuticals and Medical Devices Agency requires in vitro, pharmacokinetic, and pharmacodynamic or clinical endpoint data to approve generic nasal spray drug products. However, the MHLW has not published basic principle for approving nasal generic drug products. Therefore, this article summarizes the data used for the approval of the first generic Nasonex based on publicly available data. Additionally, we compare the bioequivalence evaluations regarding the human studies based on the generic version of Nasonex between Japan and the USA.

Requirements for Additional Strength Biowaivers for Modified Release Solid Oral Dosage Forms in International Pharmaceutical Regulators Programme Participating Regulators and Organisations: Differences and Commonalities

This article describes an overview of waivers of in vivo bioequivalence studies for additional strengths in the context of the registration of modified release generic products and is a follow-up to the recent publication for the immediate release solid oral dosage forms. The current paper is based on a survey among the participating members of the Bioequivalence Working Group for Generics (BEWGG) of the International Pharmaceutical Regulators Program (IPRP) regarding this topic. Most jurisdictions consider the extrapolation of bioequivalence results obtained with one (most sensitive) strength of a product series as less straightforward for modified release products than for immediate release products. There is consensus that modified release products should demonstrate bioequivalence not only in the fasted state but also in the fed state, but differences exist regarding the necessity of additional multiple dose studies. Fundamental differences between jurisdictions are revealed regarding requirements on the quantitative composition of different strengths and the differentiation of single and multiple unit dosage forms. Differences in terms of in vitro dissolution requirements are obvious, though these are mostly related to possible additional comparative investigations rather than regarding the need for product-specific methods. As with the requirements for immediate release products, harmonization of the various regulations for modified release products is highly desirable to conduct the appropriate studies from a scientific point of view, thus ensuring therapeutic equivalence.

Ras-related C3 botulinum toxin substrate 1 (RAC1) regulates glucose-stimulated insulin secretion via modulation of F-actin

AIMS/HYPOTHESIS

The small G-protein ras-related C3 botulinum toxin substrate 1 (RAC1) plays various roles in mammalian cells, such as in the regulation of cytoskeletal organisation, cell adhesion, migration and morphological changes. The present study examines the effects of RAC1 ablation on pancreatic beta cell function.

METHODS

Isolated islets from pancreatic beta cell-specific Rac1-knockout (betaRac1(-/-)) mice and RAC1 knockdown INS-1 insulinoma cells treated with small interfering RNA were used to investigate insulin secretion and cytoskeletal organisation in pancreatic beta cells.

RESULTS

BetaRac1(-/-) mice showed decreased glucose-stimulated insulin secretion, while there were no apparent differences in islet morphology. Isolated islets from the mice had blunted insulin secretion in response to high glucose levels. In RAC1 knockdown INS-1 cells, insulin secretion was also decreased in response to high glucose levels, consistent with the phenotype of betaRac1(-/-) mice. Even under high glucose levels, RAC1 knockdown INS-1 cells remained intact with F-actin, which inhibits the recruitment of the insulin granules, resulting in an inhibition of insulin secretion.

CONCLUSIONS/INTERPRETATION

In RAC1-deficient pancreatic beta cells, F-actin acts as a barrier for insulin granules and reduces glucose-stimulated insulin secretion.

Autoantibodies to insulin receptors in man: immunological determinants and mechanism of action

The insulin receptor is a membrane glycoprotein of high Mr which binds insulin with high affinity and specificity and transmits some intracellular signal(s) that initiate(s) insulin action. Antibodies to the receptor have been identified in patients with a syndrome characterized by severe resistance to endogenous and exogenous insulin, varying degrees of glucose intolerance, and the skin lesion acanthosis nigricans. The syndrome is most common in non-Caucasian, middle-aged women, but occurs in patients of all races, both sexes, and spanning the ages of 12-62. Most patients have evidence of other autoimmune disease with increased erythrocyte sedimentation rate and gamma globulins, anti-DNA and anti-nuclear antibodies, leucopenia, and other signs and symptoms of autoimmune disease. Antibodies to the insulin receptor are detected by their ability to inhibit 125I-insulin binding or to immunoprecipitate solubilized insulin receptors. In vitro these antibodies acutely mimic most of insulin's metabolic effects. This insulin-like activity depends on antibody bivalence; monovalent Fab fragments block insulin binding and action but lack intrinsic activity. With prolonged exposure of cells to anti-receptor antibody the insulin-like effect is lost and a state of insulin resistance ensues. This is due to both a blockage of insulin binding and a form of post-receptor desensitization. The possible causation of anti-receptor antibodies in this condition is discussed.

Favorable genetic polymorphisms predictive of clinical outcome of chemoradiotherapy for stage II/III esophageal squamous cell carcinoma in Japanese

15088

Background: A 5-fluorouracil (5-FU)/cisplatin (CDDP)-based chemoradiotherapy (CRT) was proposed for esophageal cancer patients. Currently, there is an urgent need to establish a methodology to decide which is preferable for a patient, i.e., surgical treatment or CRT, especially for Stage II to III tumors defined as resectable. This study was performed to find the genetic factors predictive of clinical outcome to a 5-FU/ CDDP-based CRT in Japanese patients with locally advanced esophageal squamous cell carcinoma (ESCC). Methods: Thirty-one patients with Stage I-IVa ESCC (I/II/III/IVa = 7/7/14/3) were enrolled in this study. One course of treatment consisted of protracted venous infusions of 5-FU (400 mg/m2/24 h for day 1–5 and 8–12), CDDP (40 mg/m2/3 h on day 1 and 8) and radiation (2 Gy/day on day 1–5, 8–12 and 15–19), and a 2nd course was successively repeated after a 2-week interval. A total of 8 measurements of the plasma concentration of 5-FU were made using high performance liquid chromatography. Genetic polymorphisms examined herein included those in the genes coding thymidylate synthase (TS), glutathione S-transferase P1 (GSTP1) and multi-drug resistant transporter MDR1/P-glycoprotein. Results: The complete response rate depended on Stage (p = 0.001), but the analysis was not sufficiently powered to reach a level of statistical significance for the 2-year survival rate (p = 0.061). For Stage II/III patients, to have 2 or 3 polymorphisms of 3R/3R of 5’-TSER, a 6bp of 3’-TSUTR, and GSTP1-Leu105Val resulted in an extensively longer survival (p =0.0197), although no difference was found between 2 groups, with respect to the plasma concentrations of 5-FU and clinical or pathological characteristics. Conclusions: The genetic prognostic index may allow predictions of the clinical outcome of a 5- FU/CDDP-based CRT in Stage II/III ESCC patients. Now, we are analyzing the contribution of genetic polymorphisms of cytokines, including tumor necrosis factor a.

No significant financial relationships to disclose.

No significant difference in neutrophil activation found among three H2RAs

BACKGROUND

Even with the most effective treatment, Helicobacter pylori eradication is difficult in some patients. Therefore, patients sometimes require acid-suppressive therapy without H. pylori eradication. It has been reported that ranitidine inhibits neutrophil activation, whereas famotidine does not. However, few studies have been published concerning the activation of neutrophils before and after treatment using clinical doses of histamine-2 receptor antagonists in patients with H. pylori infection.

AIM

To examine the effects of neutrophil activation after treatment with three different histamine-2 receptor antagonists.

PATIENTS

This prospective, open-label, randomised, parallel-group study was conducted. Thirty patients with H. pylori infection were enrolled. These subjects were randomly assigned to receive one of the following treatments: (a) 150 mg ranitidine, (b) 20mg famotidine, or (c) 10 mg lafutidine b.d., for 4 weeks. Before and after histamine-2 receptor antagonist treatment, histological findings, myeloperoxidase activity, and interleukin-8 in the gastric mucosa were evaluated.

RESULTS

On the basis of the histological findings between before and after histamine-2 receptor antagonist treatment, no significant differences were found in any groups. Similarly, there were no significant differences in myeloperoxidase activity or interleukin-8 levels.

CONCLUSION

In patients with H. pylori, when used at clinical doses, any histamine-2 receptor antagonists can be used without concerning about inhibition of neutrophil activation.

Levofloxacin- versus metronidazole-based rescue therapy for H. pylori infection in Japan

BACKGROUND

The ideal second-line treatment regimens for Helicobacter pylori infection may differ between the areas, countries and races.

AIM

The aim was to confirm which was the better regimen for second-line therapy after treatment failure with a standard triple therapy in Japan, a high dosage of levofloxacin- or metronidazole-based therapy.

PATIENTS

Sixty outpatients with persistent H. pylori infection after a standard triple therapy were enrolled in this prospective, open-label and randomised trial.

METHODS

The subjects were randomly administered levofloxacin (300 mg b.d.)- or metronidazole (500 mg b.d.)-based therapy with lansoprazole (30 mg b.d.) and amoxicillin (1000 mg b.d.) for 7 days, and the cure rates and side effects were analysed. Antimicrobial susceptibility was also examined before second-line therapy using the E-test.

RESULTS

Good compliance was obtained without severe side effects in both the groups except for two patients. The cure rates, expressed as intention-to-treat and per-protocol analyses, respectively, were 70.0 and 72.4% in the levofloxacin group, and 96.7 and 100% in the metronidazole group. Each regimen often overcame even clarithromycin-resistant strains.

CONCLUSION

Metronidazole-based triple therapy is recommended as second-line therapy in Japan, and levofloxacin-based therapy can be an alternative treatment option.

Stomach regulates energy balance via acylated ghrelin and desacyl ghrelin

BACKGROUND/AIMS

The gastric peptide ghrelin, an endogenous ligand for growth-hormone secretagogue receptor, has two major molecular forms: acylated ghrelin and desacyl ghrelin. Acylated ghrelin induces a positive energy balance, while desacyl ghrelin has been reported to be devoid of any endocrine activities. The authors examined the effects of desacyl ghrelin on energy balance.

METHODS

The authors measured food intake, gastric emptying, c-Fos expression in the hypothalamus, and gene expression of hypothalamic neuropeptides in mice after administration of desacyl ghrelin. To explore the effects of long term overexpression of desacyl ghrelin, transgenic mice that overexpressed desacyl ghrelin were created.

RESULTS

Administration of desacyl ghrelin decreased food intake and gastric emptying rate through an action on the paraventricular nucleus and the arcuate nucleus in the hypothalamus. Gene expression of anorexigenic cocaine and amphetamine regulated transcript and urocortin in the hypothalamus was increased by desacyl ghrelin. Desacyl ghrelin overexpressing mice exhibited a decrease in body weight, food intake, and fat pad mass weight accompanied by moderately decreased linear growth. Gastric emptying was also decreased in desacyl ghrelin overexpressing mice.

CONCLUSIONS

These findings indicate that in contrast to acylated ghrelin, desacyl ghrelin induces a negative energy balance by decreasing food intake and delaying gastric emptying. The effect is mediated via the hypothalamus. Although derived from the same precursor, the inverse effects of these two peptides suggest that the stomach might be involved as an endocrine organ in the regulation of the energy balance.

Cell kinetic balance in gastric mucosa with intestinal metaplasia after Helicobacter pylori eradication: 2-year follow-up study

BACKGROUND

Proliferation and apoptosis events are altered in Helicobacter pylori infection. However, whether H. pylori eradication has an effect on the disturbed kinetics in metaplastic mucosa has not been well elucidated.

AIM

To investigate the effect of eradication on the gastric cell kinetics.

SUBJECTS AND METHODS

Initially, biopsies were obtained from 74 H. pylori-infected subjects and repeated 12 and 24 months after eradication. Biopsies were immunohistochemically stained for apoptosis by single-stranded DNA, for proliferation by Ki-67 antibodies and for intestinal metaplasia MUC2, MUC5AC, MUC6 and CD10.

RESULTS

While antral apoptosis in intestinal metaplasia was significantly lower than in non-intestinal metaplasia, proliferation was significantly higher (greater and lesser curvatures, P < 0.05, respectively). This resulted in a significantly lower apoptosis/proliferation ratio in intestinal metaplasia than in non-intestinal metaplasia (antrum greater and lesser curvatures and corpus greater curvature, P < 0.05). After successful eradication, apoptosis and proliferation decreased in both intestinal metaplasia and non-intestinal metaplasia. The pattern of reduction of apoptosis and proliferation differed in these two groups. However, in the corpus, the reduction resulted in a significant increase in the apoptosis/proliferation ratio in both.

CONCLUSION

Proliferation and apoptosis are unevenly and disproportionately altered in H. pylori infection leading to an imbalance in cell kinetics. Eradication of the organism improves the balance and may possibly play a role in the prevention of malignancy transformation in the metaplastic mucosa.

Levofloxacin based triple therapy as a second-line treatment after failure of helicobacter pylori eradication with standard triple therapy

BACKGROUND

Successful eradication of Helicobacter pylori infection after failure of standard triple therapy is difficult. The efficacy and safety of levofloxacin based triple therapy as a first-line therapy has-been studied.

AIMS

The aim was to evaluate the efficacy and tolerability of levofloxacin based therapy after a failed standard triple therapy.

PATIENTS

We conducted a prospective, uncontrolled study of a consecutive series of 33 patients who failed eradication with 1 week of lansoprazole-amoxicillin-clarithromycin triple therapy.

METHODS

The subjects were retreated with 1 week of LA-LVFX triple therapy (lansoprazole, 30 mg twice daily; amoxicillin, 1000 mg twice daily: levofloxacin, 200 mg twice daily). Cure of infection was defined as negative results from culture, histology and a urea breath test 4 to 8 weeks after the second-line therapy.

RESULTS

The eradication rate was 69.7% (23/33) by both intention-to-treat and per-protocol analyses (95% confidence interval=61-79%). Seven (21.2%) patients experienced mild side-effects, such as soft stools and taste disturbance. No patient stopped the medication on account of adverse effects.

CONCLUSIONS

Levofloxacin based triple therapy is an effective second-line treatment after a failed standard triple therapy.

Antagonism of ghrelin receptor reduces food intake and body weight gain in mice

BACKGROUND AND AIMS

Ghrelin, an endogenous ligand for growth hormone secretagogue receptor (GHS-R), is an appetite stimulatory signal from the stomach with structural resemblance to motilin. We examined the effects of the gastric peptide ghrelin and GHS-R antagonists on energy balance and glycaemic control in mice.

MATERIALS AND METHODS

Body weight, fat mass, glucose, insulin, and gene expression of leptin, adiponectin, and resistin in white adipose tissue (WAT) were measured after repeated administrations of ghrelin under a high fat diet. Gastric ghrelin gene expression was assessed by northern blot analysis. Energy intake and gastric emptying were measured after administration of GHS-R antagonists. Repeated administration of GHS-R antagonist was continued for six days in ob/ob obese mice.

RESULTS

Ghrelin induced remarkable adiposity and worsened glycaemic control under a high fat diet. Pair feeding inhibited this effect. Ghrelin elevated leptin mRNA expression and reduced resistin mRNA expression. Gastric ghrelin mRNA expression during fasting was increased by a high fat diet. GHS-R antagonists decreased energy intake in lean mice, in mice with diet induced obesity, and in ob/ob obese mice; it also reduced the rate of gastric emptying. Repeated administration of GHS-R antagonist decreased body weight gain and improved glycaemic control in ob/ob obese mice.

CONCLUSIONS

Ghrelin appears to be closely related to excess weight gain, adiposity, and insulin resistance, particularly under a high fat diet and in the dynamic stage. Gastric peptide ghrelin and GHS-R may be promising therapeutic targets not only for anorexia-cachexia but also for obesity and type 2 diabetes, which are becoming increasingly prevalent worldwide.

Dedifferentiation and decreased expression of adhesion molecules, E-cadherin and ZO-1, in colorectal cancer are closely related to liver metastasis

Carcinoma cells with high metastatic potential often show a dedifferentiated phenotype at the primary site. In this study, a total of 48 cases (24 primary tumors of colorectal cancer (Pr-CRC) with liver metastasis, 24 without) were examined for E-cadherin and ZO-1 expression by immunohistochemical staining, and for their dedifferentiated phenotype. The expression levels of E-cadherin and ZO-1 were markedly decreased in the cancer cells of tumors with liver metastasis. Moreover, dedifferentiation of cancer cells, which was evaluated by the modified Gleason score, was also related to liver metastasis. However, none of the conventional clinicopathologic parameters of invasion, except lymph node metastasis, showed any relationship with liver metastasis. These results indicate that dedifferentiation and a decreased expression of E-cadherin and ZO-1 are closely related to liver metastasis.

Orexin reverses cholecystokinin-induced reduction in feeding

AIM

This study was designed to investigate the effect of orexin on anorexia induced by cholecystokinin (CCK),a peripheral satiety signal.

METHODS

We administered orexin A (0.01-1 nmol/mouse) and CCK-8 (3 nmol/mouse) to mice. Food intake was measured at different time-points: 20 min, 1, 2 and 4 h post-intracerebroventricular (i.c.v.) or intraperitoneal (i.p.) administrations.

RESULTS

Intracerebroventricular-administered orexin significantly increased food intake in a dose-dependent manner. The inhibitory effect of i.p.-administered CCK-8 on food intake was significantly negated by the simultaneous i.c.v. injection of orexin in a dose-dependent manner.

CONCLUSIONS

Orexin reversed the CCK-induced loss of appetite. Our results indicate that orexin might be a promising target for pharmacological intervention in the treatment of anorexia and cachexia induced by various diseases.

Variation in MT expression in early-stage depressed-type and polypoid-type colorectal tumours

Metallothionein (MT) expression is observed in various carcinomas, but its role is not fully understood. To clarify the clinicopathological significance of MT, 87 colorectal adenomas and 128 early-stage carcinomas were immunohistochemically analysed for MT expression. The degree of MT immunostaining of a specimen was graded according to the proportion of MT-positive cells; negative (<5%) and positive (focally 5-50%, diffusely >50%). MT expression significantly decreased with tumour development. For carcinomas, MT-positivity was significantly associated with depth of invasion (T1 60% versus T2 33%; P<0.01), vascular involvement (positive 35% versus negative 61%; P<0.01) and morphology (polypoid 62% versus depressed 26%; P<0.01). Regarding MT-positive distribution, the diffuse-positive rate in MT-positive polypoid lesions was 28%, while MT-positive depressed lesions were all diffusely stained (P<0.01). In conclusion, our results suggested that decreasing MT expression is an early event in colorectal carcinogenesis and may reflect local invasion. Furthermore, MT-positive distribution may reflect genetic differences between the polypoid and depressed-type.

Identification of a single nucleotide polymorphism showing no insulin-mediated suppression of the promoter activity in the human insulin receptor substrate 2 gene

AIMS/HYPOTHESIS

To understand the transcriptional regulation and to investigate the pathological influence upon Type II (non-insulin-dependent) diabetes mellitus of insulin receptor substrate 2 ( IRS2), the 5' flanking region of the human IRS2 gene was cloned and screened in Japanese diabetic patients.

METHODS

Luciferase reporter assay and electrophoretic mobility shift assay (EMSA) were combined in HepG2, Fao, RINm5F, and HeLa cells to characterise the human IRS2 promoter region. Single nucleotide polymorphisms (SNPs) were identified in Japanese Type II diabetic patients by sequencing and were genotyped.

RESULTS

The proximal 2399 bp of the 5' flanking region of the human IRS2 gene was cloned. A core promoter region was extended between nucleotide positions -834 and -557 (relative to the translation initiation site). The region [(-758)AGGGGGAGGG(-749)] that appears important in the positive regulation of IRS2transcription was identified by EMSA with (32)P-labelled double-stranded oligonucleotides encompassing regions protected from DNase I digestion by nuclear extract of HepG2 cells. Two SNPs (-765 C/ T and -2062 T/ C), identified by screening Japanese Type II diabetic patients, were not associated with Type II diabetes. IRS2-driven reporter activity in the plasmid containing thymine at -765 was not suppressed by insulin when measured in Fao cells.

CONCLUSION/INTERPRETATION

The 5' flanking sequence of the human IRS2 was investigated and two SNPs were identified. The SNP at -765 was suggested to be involved in the insulin-mediated regulation of the transcriptional activity of IRS2.

Mosapride, a 5HT-4 receptor agonist, improves insulin sensitivity and glycaemic control in patients with Type II diabetes mellitus

AIMS/HYPOTHESIS

We investigated the potential role of mosapride, a 5HT-4 receptor agonist, in glycaemic control in Type II (non-insulin-dependent) diabetic mellitus patients without autonomic neuropathy.

METHODS

Thirty-four inpatients with Type II diabetes mellitus were randomly assigned to receive either mosapride (5 mg orally three times a day, n=17) or a placebo ( n=17) for 1 week (first study). Changes in blood glucose and insulin were determined basally as well as after intravenous glucose loading. Insulin sensitivity was evaluated during hyperinsulinaemic-normoglycaemic-clamp studies and by measuring the number of and the autophosphorylation of insulin receptors on the erythrocytes of patients ( n=9). Sixty-nine outpatients with Type II diabetes were similarly treated with mosapride or a placebo for 8 weeks (second study). Finally, tissue- specific expression of 5HT-4 receptors was examined by reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS

Mosapride lowered fasting blood glucose and fructosamine concentrations ( p<0.05) (first study). It significantly increased the number of (Mosapride 3323+/-518 vs 4481+/-786 [ p<0.05], Control 4227+/-761 vs 3275+/-554 per 300 microl erythrocytes) and the tyrosine autophosphorylation (Mosapride 3178+/-444 vs 4043+/-651 [ p<0.05], Control 3721+/-729 vs 3013+/-511 insulin receptor unit) of insulin receptors, as well as glucose utilisation (Mosapride 4.92+/-0.53 vs 5.88+/-0.72 [ p<0.05], Control 4.74+/-0.65 vs 4.70+/-0.31 mg/kg x min). Mosapride treatment for 8 weeks significantly reduced fasting glucose (9.91+/-0.34 vs 8.51+/-0.34 mmol/l, p<0.05), insulin (53.2+/-4.62 vs 40.8+/-5.52 pmol/l, p<0.05) and HbA(1c) (8.61+/-0.20 vs 7.67+/-0.19%, p<0.01) concentrations (second study). The RT-PCR analysis demonstrated specific expression of 5HT-4 receptors in the muscle, but not in the liver or fat tissues.

CONCLUSIONS/INTERPRETATION

Mosapride could improve insulin action at muscle and glycaemic control in Type II diabetic patients.

Vaginal symptoms in Japanese postmenopausal women: comparison with other climacteric symptoms

OBJECTIVES

This study was designed to investigate the current status of vaginal symptoms in Japanese postmenopausal women, and to clarify the significance of vaginal symptoms by analyzing their relationship to other climacteric symptoms.

METHODS

The complaints of 613 women attending a menopause clinic (mean age +/- standard deviation 53.5 +/- 7.2 years; time since menopause or bilateral oophorectomy 6.4 +/- 6.5 years) were evaluated according to the Keio modified menopause index.

RESULTS

In total, 56.4% of subjects had at least one vaginal symptom. The most frequent vaginal symptom was dyspareunia, followed by vaginal dryness, discharge and itching, and the mean prevalence of the four symptoms was 31.7%. The peak intensity of vaginal symptoms occurred in the sixth decade, or 3-5 years after menopause or oophorectomy. Vaginal symptoms were usually associated with other climacteric symptoms, but some occurred independently.

CONCLUSIONS

A moderate proportion of Japanese postmenopausal women experience vaginal symptoms, which can occur independently of other climacteric symptoms. Vaginal symptoms therefore warrant careful attention during the treatment of postmenopausal women.

Significance of serum matrix metalloproteinases and their inhibitors on the antifibrogenetic effect of interferon-alfa in chronic hepatitis C patients

OBJECTIVE AND METHODS

The imbalance between matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) is considered to be an important determination of deposition and breakdown of the extracellular matrix. To investigate the antifibrogenetic effect of interferon-alpha (IFN-alpha) treatment on factors regulating hepatic fibrosis, serum MMP-1, MMP-2, TIMP-1 and TIMP-2 levels were measured by the one-step sandwich enzyme immunoassay in 27 patients with chronic hepatitis C and compared with the histological status of the patients before and at the end of treatment.

RESULTS

After 6 months of IFN-alpha treatment, the histological status of liver fibrosis showed improvement in 9 patients (IF group) and no change or a worsening in 18 patients (NIF group). Compared with pretreatment levels, in the IF group, IFN treatment caused a significant increase in the MMP-1/TIMP-1 ratio. In the NIF group, however, the MMP-1/TIMP-1 ratio tended towards a decrease; moreover, there was not only a significant increase in TIMP-2 levels but also a tendency towards an increase in TIMP-1 levels.

CONCLUSION

These results suggested that an elevated MMP-1/TIMP-1 ratio may ameliorate liver fibrosis by interferon in cases of chronic hepatitis C, whereas elevated levels of TIMP-1 and TIMP-2 might impede improvement.

Insulin regulation of gene expression through the forkhead transcription factor Foxo1 (Fkhr) requires kinases distinct from Akt

Insulin inhibits expression of certain liver genes through the phosphoinositol (PI) 3-kinase/Akt pathway. However, whether Akt activity is both necessary and sufficient to mediate these effects remains controversial. The forkhead proteins (Foxo1, Foxo3, and Foxo4, previously known as Fkhr or Afx) are transcriptional enhancers, the activity of which is inhibited by insulin through phosphorylation-dependent translocation and nuclear exclusion. Others and we have previously shown that the forkhead protein Foxo1 is phosphorylated at three different sites: S(253), T(24), and S(316). We have also shown that T(24) fails to be phosphorylated in hepatocytes lacking insulin receptors, and we have suggested that this residue is targeted by a kinase distinct from Akt. In this study, we have further analyzed the ability of Akt to phosphorylate different Foxo1 sites in control and insulin receptor-deficient hepatocytes. Expression of a dominant negative Akt (Akt-AA) in control hepatocytes led to complete inhibition of endogenous Akt, but failed to inhibit Foxo1 T(24) phosphorylation and, consequently, insulin suppression of IGFBP-1 promoter activity. Conversely, expression of a constitutively active Akt (Akt-Myr) in insulin receptor-deficient hepatocytes led to an overall increase in the level of Foxo1 phosphorylation, but failed to induce T(24) and S(316) phosphorylation. These data indicate that the Foxo1 T(24) and S(316) kinases are distinct from Akt, and suggest that the pathways required for insulin regulation of hepatic gene expression diverge downstream of PI 3-kinase.

MDR1 genotype-related pharmacokinetics of digoxin after single oral administration in healthy Japanese subjects

PURPOSE

To evaluate the MDR1 genotype frequency in the Japanese population and to study the relationship between the MDR1 genotype and the pharmacokinetics of digoxin after single oral administration in healthy subjects.

METHODS

The MDR1 genotype at exon 26 was determined in 114 healthy volunteers by polymerase chain reaction-restriction fragment length polymorphism. The serum concentration-time profile of digoxin was examined after single oral administration at a dose of 0.25 mg.

RESULTS

It was found that 35.1 % (40/114) of subjects were homozygous for the wild-type allele (C/C). 52.6% (60/114) were compound heterozygotes with a mutant T-allele (C3435T) (C/T), and 12.3% (14/114) were homozygous for the mutant allele (T/T). There was no effect of gender or age on the distribution. The serum concentration of digoxin after a single oral administration increased rapidly, attaining a steady state in all subjects; however, it was lower in the subjects harboring the T-allele. AUC0-4 h values (+/-SD) were 4.11 +/- 0.57, 3.20 +/- 0.49. and 3.27 +/- 0.58 ng h/ml, respectively, with a significant difference between C/C and C/T or T/T.

CONCLUSIONS

The serum concentration of digoxin after single oral administration was lower in the subjects harboring a mutant allele (C3435T) at exon 26 of the MDR1 gene.

N-Acetyltransferase 2 genotype correlates with sulfasalazine pharmacokinetics after multiple dosing in healthy Japanese subjects

Sulfapyridine (SP) is metabolized by polymorphic N-acetyltransferase 2 (NAT2) [EC 2.3.1.5]. In this study, the correlation between the NAT2 genotype and the pharmacokinetics of SP after multiple oral dosing of sulfasalazine (SASP) was examined to elucidate the effect of multiple dosing on the predictability of the phenotype by NAT2 genotyping. Seven healthy subjects were classified into two groups; the homozygotes for the wild-type allele, NAT2*4/*4 (Group I) and the compound heterozygotes for the mutant allele (NAT2*4/*6A or NAT2*4/*7B) (Group II). All received once-daily 1 g of SASP (Salazopyrin) orally for 8 d. Plasma concentrations and urinary recoveries of SASP, SP and N-acetylsulfapyridine (AcSP) were monitored for 8 d. At 24 h on Day 1, the plasma concentration of SASP was lower and those of SP and AcSP were higher in Group II compared with Group I, but there was no significant difference. The plasma concentration ratio of AcSP to SP (AcSP/SP) tended to be lower in Group II. Urinary recoveries of SP and AcSP were increased in Group II, and their ratio was slightly reduced in Group II. Multiple dosing for 8 d resulted in an increase in the plasma concentrations of SASP, SP and AcSP. The difference between Group I and II was marked compared with single dosing, resulting in a significant difference in the plasma concentration of SP and the ratio of AcSP/SP. The simple input-output pharmacokinetic model applied for the analysis of plasma concentrations and urinary recoveries of SP and AcSP suggested the acetylation of SP into AcSP was 2.7-fold reduced in Group II (p=0.064).

Cocaine-amphetamine-regulated transcript influences energy metabolism, anxiety and gastric emptying in mice

This study was designed to investigate the effects of cocaine-amphetamine-regulated transcript (CART), a recently discovered hypothalamic neuropeptide, on food intake, anxiety, oxygen consumption and gastric emptying in mice. Intracerebroventricular (i. c. v.) injection of CART (1 - 100 pmol) markedly reduced food intake in a dose-related manner. A significant decrease was observed 20 min after i. c. v. injection of CART and continued for four hours. In the elevated plus maze test, i. c. v. CART injection significantly raised the normal preference for the closed arms. Furthermore, the i. c. v. injection of CART significantly reduced oxygen consumption and gastric emptying rate. These results suggest that CART modulates feeding, emotion, and autonomic functions in mice.

Various scoring systems evaluating histologic features of chronic hepatitis C treated with interferon

Various scoring systems for chronic hepatitis have been proposed; however, there is no standard scoring system for studies of interferon (IFN) therapy in patients with chronic hepatitis C. The aims of this study were to determine the most useful system reflecting histologic changes in biopsy specimens from complete responders and predicting the efficacy of IFN therapy. Patients with chronic hepatitis C were administered IFN-alpha for 6 months. Forty-six patients were included in this study and categorized as complete responders (n = 15), partial responders (n = 24), and nonresponders (n = 7) according to viral and biochemical responses to the therapy. Biopsy specimens obtained from each patient before and after treatment were evaluated under 3 different systems: Histological Activity Index (HAI), modified HAI, and Scheuer classification. Complete responders showed considerable improvement in both grade and stage on the modified HAI and Scheuer classifications. On the HAI, a considerable improvement was observed in grade but not in stage. No significant change was observed in partial responders or nonresponders on any system. Prediction of complete response was not possible under any system, but the pretreatment score reflecting piecemeal necrosis on any 1 of the 3 classifications and the fibrosis score on Scheuer classification were predictors of nonresponse. The modified HAI system and Scheuer classification were amply useful in evaluating histologic changes in complete responders. Scores higher than 4 of the categories reflecting piecemeal necrosis on any system and fibrosis scores of 3 or 4 on Scheuer classification predicted nonresponse to IFN therapy.

A role of ghrelin in neuroendocrine and behavioral responses to stress in mice

Ghrelin, an endogenous ligand of the growth hormone secretagogue receptor, was recently identified in the rat stomach. Previous studies have shown that ghrelin potently increases growth hormone release and food intake. We examined the effects of the gastric peptide ghrelin on anxiety-like behavior in association with the hypothalamic-pituitary-adrenal axis in mice. Both intra-third cerebroventricular and intraperitoneal administration of ghrelin potently and significantly induced anxiogenic activities in the elevated plus maze test. Ghrelin gene expression in the stomach was increased by tail pinch stress as well as by starvation stress. Administration of a corticotropin-releasing hormone (CRH) receptor antagonist significantly inhibited ghrelin-induced anxiogenic effects. Peripherally administered ghrelin significantly increased CRH mRNA, but not urocortin mRNA expression in the hypothalamus. Furthermore, intraperitoneal injection of ghrelin produced a significant dose- dependent increase in serum corticosterone levels. These findings suggest that ghrelin may have a role in mediating neuroendocrine and behavioral responses to stressors and that the stomach could play an important role, not only in the regulation of appetite, but also in the regulation of anxiety.

Hyperosmolality activates Akt and regulates apoptosis in renal tubular cells

BACKGROUND

The novel serine-threonine kinase Akt is a critical enzyme in cell survival. We investigated the roles of the Akt pathway and apoptotic signals in (1) Madin-Darby canine kidney (MDCK) cells in a hyperosmotic condition in vitro and (2) in the inner medulla of dehydrated rat in vivo.

METHODS

The in vivo experiments were performed in 24- and 48-hour water-restricted rats. Hyperosmolality-stimulated Akt phosphorylation was examined in MDCK cells. Phosphatidylinositol 3-kinase (PI3-K) inhibitors, the dominant-negative mutant of PI3-K, the dominant-negative mutant of Akt, and the dominant-active form of Akt were used to examine the roles of the PI3-K/Akt pathways in renal tubular cell apoptosis.

RESULTS

The amount of phosphorylated Akt protein was increased in the inner medulla of dehydrated rats. Hyperosmolality induced by the addition of NaCl, urea, and raffinose phosphorylated Akt in MDCK cells in an osmolality-dependent manner. PI3-K inhibitors and the dominant-negative mutant of PI3-K inhibited the hyperosmolality-induced phosphorylation of Akt. Raising the media osmolality from a normal level to 500 or 600 mOsm/kg H2O final osmolality elicited apoptotic changes such as nucleosomal laddering of DNA and an increment of caspase-3 activity and increased activity in the cell death enzyme-linked immunosorbent assay. Dominant-active Akt prevented the mild hyperosmolality-induced apoptosis, while inhibition of the PI3-K/Akt pathways promoted apoptosis.

CONCLUSION

The Akt pathway is activated by hyperosmolality in vitro and in vivo, and activation of Akt prevents the mild hyperosmolality-induced apoptotic changes in MDCK cells. PI3-K/Akt pathways are involved in a hypertonic condition that confers the balance between cell survival and apoptosis.

Inhibition of the motility and growth of B16F10 mouse melanoma cells by dominant negative mutants of Dok-1

Dok-1 (p62(Dok)) is a multiple-site docking protein that acts downstream of receptor and nonreceptor tyrosine kinases. Although it has been proposed to contribute to the control of cell growth and migration through association with the Ras GTPase-activating protein and the adapter protein Nck, the role of Dok-1 remains largely unknown. The functions of Dok-1 have now been investigated by the generation of two different COOH-terminal truncation mutants of this protein: one (DokPH+PTB) containing the pleckstrin homology and phosphotyrosine-binding domains, and the other (DokPH) composed only of the pleckstrin homology domain. Both of these mutant proteins were shown to act in a dominant negative manner. Overexpression of each of the mutants in highly metastatic B16F10 mouse melanoma cells thus both inhibited the tyrosine phosphorylation of endogenous Dok-1 induced by cell adhesion as well as reduced the association of the endogenous protein with cellular membranes and the cytoskeleton. Overexpression of DokPH+PTB in these cells also markedly reduced both the rates of cell spreading, migration, and growth as well as the extent of Ras activation. The effects of DokPH on these processes were less pronounced than were those of DokPH+PTB, indicating the importance of the phosphotyrosine-binding domain. These results suggest that at least in B16F10 cells, Dok-1 positively regulates not only cell spreading and migration but also cell growth and Ras activity.

Cholecystokinin activation of 70-kDa S6 kinase in exocrine pancreas

Cholecystokinin (CCK), a known mitogen for the exocrine pancreas, is shown to activate 70-kDa S6 kinase in isolated pancreatic acini. In this study, we examined the kinetics and cellular mechanisms of CCK-induced p70 S6 kinase activation in vivo and in vitro. Fasted mice were intraperitoneally injected with 0.01-10 microg/kg CCK analoge cerulein. Cerulein caused a concentration-dependent activation of p70 S6 kinase, with the maximal effect at 1-10 microg/kg. After 1 microg/kg cerulein administration, the kinase activity was increased at 5 min, peaked at 10 min, and subsequently decreased. Cerulein also caused a rapid and transient activation of Src. Prior administration of the tyrosine kinase inhibitor herbimycin A compeletely inhibited cerulein-induced Src activation, while the inhibition of p70 S6 kinase activity was partial. Similar results were obtained with pancreatic acinar cell line AR42J cells. These results suggest that tyrosine kinases, including Src as a possible candidate, are partly implicated in the signaling pathway of CCK-induced p70 S6 kinase activation in the exocrine pancreas.

CYP2C19 genotype and pharmacokinetics of three proton pump inhibitors in healthy subjects

PURPOSE

To predict the CYP2C19 genotype-dependence in anti-Helicobacter pylori (H. pylori) therapy when lansoprazole or rabeprazole was used instead of omeprazole as a proton pump inhibitor (PPI).

METHODS

A comparative pharmacokinetic study with each PPI was designed as an open, randomized, and crossover study of 18 Japanese healthy volunteers who were classified into the homozygous, heterozygous extensive metabolizer and the poor metabolizer based on the CYP2C19 genotype determined by PCR-RFLP method. Each subject received a single oral dose of 20 mg omeprazole, 30 mg lansoprazole, or 20 mg sodium rabeprazole, with at least 1 week washout period between treatments. Plasma concentrations of PPIs and their metabolites were monitored until 12 h after medication.

RESULTS

Pharmacokinetic profiles of omeprazole and lansoprazole were well correlated with the CYP2C19 genotype. The heterozygous extensive metabolizer was slightly different from the homozygote, but there was no statistically significant difference. The CYP2C19 genotype dependence found for lansoprazole was not obvious compared with omeprazole. As for rabeprazole, the pharmacokinetic profile was independent of the CYP2C19 genotype.

CONCLUSIONS

CYP2C19 genotype dependence will be found in the anti-H. pylori therapy even when lansoprazole is used as the PPI.

Bilateral interstitial pneumonic shadows caused by perivascular fibrosis and extramedullary megakaryopoiesis of the lung in a case of advanced agnogenic myeloid metaplasia and myelofibrosis

A 59-year-old man with progressive and advanced agnogenic myeloid metaplasia, also called idiopathic myelofibrosis, had complications showing bilateral interstitial pneumonic shadows. Pathological assessment of transbronchial biopsy revealed pulmonary perivascular fibrosis and infiltration of megakaryocytes. Autopsy 3 months later showed extramedullary megakaryopoiesis and fibrosis in lung, pleura, kidney, liver and spleen. Histopathological analysis for platelet-derived growth factor (PDGF) and PDGF-receptor revealed an abnormally high expression of the PDGF-receptor-beta gene in pulmonary fibroblasts. This is the first description of an association between pulmonary fibrosis and PDGF in idiopathic myelofibrosis.

Inhibition of cell growth and spreading by stomach cancer-associated protein-tyrosine phosphatase-1 (SAP-1) through dephosphorylation of p130cas

SAP-1 (stomach cancer-associated protein-tyrosine phosphatase-1) is a transmembrane-type protein-tyrosine phosphatase that is abundant in the brain and certain cancer cell lines. With the use of a "substrate-trapping" approach, p130(cas), a major focal adhesion-associated phosphotyrosyl protein, has now been identified as a likely physiological substrate of SAP-1. Expression of recombinant SAP-1 induced the dephosphorylation of p130(cas) as well as that of two other components of the integrin-signaling pathway (focal adhesion kinase and p62(dok)) in intact cells. In contrast, expression of a substrate-trapping mutant of SAP-1 induced the hyperphosphorylation of these proteins, indicating a dominant negative effect of this mutant. Overexpression of SAP-1 induced disruption of the actin-based cytoskeleton as well as inhibited various cellular responses promoted by integrin-mediated cell adhesion, including cell spreading on fibronectin, growth factor-induced activation of extracellular signal-regulated kinase 2, and colony formation. Finally, the enzymatic activity of SAP-1, measured with an immunocomplex phosphatase assay, was substantially increased by cell-cell adhesion. These results suggest that SAP-1, by mediating the dephosphorylation of focal adhesion-associated substrates, negatively regulates integrin-promoted signaling processes and, thus, may contribute to contact inhibition of cell growth and motility.

CYP2C19 genotype related effect of omeprazole on intragastric pH and antimicrobial stability

PURPOSE

A combination of proton pump inhibitors and antimicrobials has been applied as an anti-Helicobacter pylori (H. pylori) therapy. Omeprazole, one of the proton pump inhibitors, is metabolized by CYP2C19. which exhibits genetic polymorphism. It was reported previously that the overall anti-H. pylori efficacy can be related to the CYP2C19 genotype. The main aim of the present study was to obtain a rational explanation for the relationship between the overall anti-H. pylori efficacy and the CYP2C19 genotype.

METHODS

Six healthy volunteers were classified as extensive metabolizers and poor metabolizers, according to their CYP2C19 genotypes. Plasma concentrations and intragastric pH were monitored prior to and until 24 h after the administration of 20 mg omeprazole. The stability of amoxicillin, clarithromycin, and metronidazole was examined using buffer solutions with monitored intragastric pH, and their remaining percentage in the intragastric space was simulated.

RESULTS

The poor metabolizers, classified by the CYP2C19 genotypes, showed the higher effectiveness in anti-H. pylori therapy, via the higher plasma concentration of omeprazole and the higher intragastric pH, and possibly the higher stability of antimicrobials in the higher intragastric pH.

CONCLUSIONS

CYP2C19 genotyping is a very useful method to determine the effective and safe dosage regimen including the selection of the dual and triple therapy in anti-H. pylori therapy.

The effects of brain-derived neurotrophic factor on insulin signal transduction in the liver of diabetic mice

AIM/HYPOTHESIS

We previously reported that repeated subcutaneous or intracerebroventricular injection of brain-derived neurotrophic factor (BDNF) reduces blood glucose concentrations in obese diabetic C57BL/KsJ-db/db mice. In this study, we assessed the effects of BDNF on insulin action in peripheral tissues of diabetic mice.

METHODS

First, brain-derived neurotrophic factor (20 mg/kg) was subcutaneously given to male db/db mice for 14 days and then the insulin-stimulated tyrosine phosphorylation of insulin receptors and insulin-stimulated phosphatidylinositol (PI) 3-kinase activity in peripheral tissues was assessed. Second, we examined the effects of a single subcutaneous or intracerebroventricular brain-derived neurotrophic factor injection on insulin responsiveness in liver and skeletal muscle of streptozotocin (STZ)-induced diabetic mice. Third, the effects of brain-derived neurothrophic factor on insulin action were also examined in cultured cells.

RESULTS

Repeated injection of BDNF to db/db mice for 14 days enhanced insulin-stimulated tyrosine phosphorylation of insulin receptors in liver and insulin-stimulated PI 3-kinase activity in liver, skeletal muscle and interscapular brown adipose tissue. We then examined the rapid effect of BDNF on insulin signalling in vivo. A single subcutaneous or intracerebroventricular injection of BDNF rapidly increased insulin-stimulated tyrosine phosphorylation of insulin receptors and PI 3-kinase activity in liver of STZ-mice. No direct effect of brain-derived neurothrophic factor was observed on insulin signalling in primary cultured hepatocytes, L6 muscle cells or 3T3-L1 adipocytes. Brain-derived neurothrophic factor did not affect either glucose uptake or gluconeogenesis in these cells.

CONCLUSION/INTERPRETATION

These data indicate that brain-derived neurothrophic factor rapidly enhances insulin signal transduction in liver and shows hypoglycaemic action in diabetic mice.

Urocortin reduces oxygen consumption in lean and ob/ob mice

A vast number of intensive studies have been undertaken to clarify the mechanisms of energy balance. This study was undertaken to investigate the effect of urocortin, an endogenous ligand for corticotropin-releasing factor (CRF) type 2 receptor, on oxygen consumption in lean and genetically obese (ob/ob) mice. Oxygen consumption was measured after intraperitoneal injection in unrestrained mice at an environmental temperature of 22 degrees C of one of the following: urocortin, deamidated form of urocortin (urocortin OH) or CRF. The intraperitoneal injection of urocortin (0.3-3 nmol) dose-dependently decreased oxygen consumption in lean mice. The inhibitory effect induced by urocortin was more potent than that induced by CRF or urocortin OH. The ranking potency was urocortin > urocortin OH > CRF. Urocortin significantly reduced oxygen consumption in ob/ob mice as well as in lean mice. These results suggest that urocortin decreases oxygen consumption, and that the CRF type 2 receptor may influence energy balance in lean and ob/ob mice.

Modest overexpression of neuropeptide Y in the brain leads to obesity after high-sucrose feeding

Neuropeptide Y (NPY), one of the most abundant peptide transmitters in the mammalian brain, is assumed to play an important role in feeding and body weight regulation. However, there is little genetic evidence that overexpression or knockout of the NPY gene leads to altered body weight regulation. Previously, we developed NPY-overexpressing mice by using the Thy-1 promoter, which restricts NPY expression strictly within neurons in the central nervous system, but we failed to observe the obese phenotype in the heterozygote. Here we report that in the homozygous mice, overexpression of NPY leads to an obese phenotype, but only after appropriate dietary exposure. NPY-overexpressing mice exhibited significantly increased body weight gain with transiently increased food intake after 50% sucrose--loaded diet, and later they developed hyperglycemia and hyperinsulinemia without altered glucose excursion during 1 year of our observation period.

Differential control of cellular gene expression by diffusible and non-diffusible EGF

Cell gene expression is affected by both the kind and mode of growth factor stimulation (diffusive vs. non-diffusive). Epidermal growth factor (EGF) was pattern-immobilized on a polystyrene plate. Although the growth of the rat phaeochromocytoma cell line PC12 is stimulated by diffusible EGF, and differentiation is stimulated by diffusible nerve growth factor (NGF), immobilized (non-diffusible) EGF stimulated PC12 differentiation. The immobilized EGF caused a long-lasting stimulation of the intracellular signal protein mitogen-associated protein MAP kinase (MAPK, also known as ERK) and p38 (a subfamily of the MAPK superfamily) in cells, as did diffusible NGF. The switching between growth stimulation and differentiation is considered to be due to the duration of the stimulus. The function of the biosignal conjugate was regulated using conjugation methodology.

Inhibition of insulin-induced activation of Akt by a kinase-deficient mutant of the epsilon isozyme of protein kinase C

Akt, also known as protein kinase B, is a protein-serine/threonine kinase that is activated by growth factors in a phosphoinositide (PI) 3-kinase-dependent manner. Although Akt mediates a variety of biological activities, the mechanisms by which its activity is regulated remain unclear. The potential role of the epsilon isozyme of protein kinase C (PKC) in the activation of Akt induced by insulin has now been examined. Expression of a kinase-deficient mutant of PKCepsilon (epsilonKD), but not that of wild-type PKCepsilon or of kinase-deficient mutants of PKCalpha or PKClambda, with the use of adenovirus-mediated gene transfer inhibited the phosphorylation and activation of Akt induced by insulin in Chinese hamster ovary cells or L6 myotubes. Whereas the epsilonKD mutant did not affect insulin stimulation of PI 3-kinase activity, the phosphorylation and activation of Akt induced by a constitutively active mutant of PI 3-kinase were inhibited by epsilonKD, suggesting that epsilonKD affects insulin signaling downstream of PI 3-kinase. PDK1 (3'-phosphoinositide-dependent kinase 1) is thought to participate in Akt activation. Overexpression of PDK1 with the use of an adenovirus vector induced the phosphorylation and activation of Akt; epsilonKD inhibited, whereas wild-type PKCepsilon had no effect on, these actions of PDK1. These results suggest that epsilonKD inhibits the insulin-induced phosphorylation and activation of Akt by interfering with the ability of PDK1 to phosphorylate Akt.