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Yuichi Nakagawa

Publications and source records attributed to Yuichi Nakagawa.

18 recordsLinked to original sources
PubMed2006

Liver X receptor agonist T0901317 inhibition of glucocorticoid receptor expression in hepatocytes may contribute to the amelioration of diabetic syndrome in db/db mice.

The glucocorticoid receptor (GR) is a crucial target gene for glucocorticoid-induced insulin resistance and hepatic gluconeogenesis linked to the development of type 2 diabetes. The liver X receptors (LXRs) are nuclear receptors that play an important role in the regulation of the metabolic gene linked to carbohydrate homeostasis. To assess the tissue-specific interaction of LXR with GR in the development of type 2 diabetes, we examined the possible effect of LXR agonist T0901317 on GR gene expression in vivo and in vitro in hepatocytes from db/db mice (a model of type 2 diabetes). Chronic ligand activation of LXR by a synthetic LXR T0901317 markedly decreased the expression of both GR mRNA and its protein in liver and improved the phenotype of type 2 diabetes in obese db/db mice. Suppression of hepatic GR expression was correlated with reduced levels of glucose and corresponded to the inhibition of phosphoenolpyruvate carboxykinase mRNA and 11beta-hydroxysteroid dehydrogenase type 1-mediated synthesis of active corticosterone from inactive 11-dehydrocorticosterone in liver. Treatment of db/db mouse primary hepatocytes with T0901317 resulted in dramatic suppression of GR mRNA and required ongoing protein synthesis. Addition of T0901317 to primary hepatocytes also suppressed the expression of both 11beta-hydroxysteroid dehydrogenase type 1 and phosphoenolpyruvate carboxykinase. These findings suggest that some of antidiabetic actions of LXR agonist T0901317 may be mediated, at least in part, through the suppression of hepatic GR gene expression.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗
PubMed2006

Differential effect of DHEA on mitogen-induced proliferation of T and B lymphocytes.

Dehydroepiandrosterone (DHEA) is the predominant steroid hormone secreted by adrenal gland, and it has been proposed in recent years that DHEA has significant effects on immune function. We investigated the effect of DHEA (1 x 10(-5) - 1 x 10(-8)M) on proliferation of human T cells and B cells and on immunoglobulin production, a representative function of B cells. High doses of DHEA (1 x 10(-5)) significantly inhibited proliferation of peripheral blood mononuclear cells (PBMCs) and T cells induced by T cell mitogens hemagglutinin (PHA) and concanavalin A (Con A). Proliferation of PBMCs induced by B cell mitogens pokeweed mitogen (PWM) was increased by 1 x 10(-7) - 1 x 10(-6)M DHEA. Proliferation of PBMCs and B cells induced by Staphylococcus aureus Cowan strain I (SAC) was not significantly changed at any concentrations of DHEA. However, a concentration of 1 x 10(-7)M DHEA tended to potentiate their proliferation. This study suggested that DHEA acted on T and B lymphocytes differentially in immune system.

Adult↗
PubMed2005

Directed evolution of Pseudomonas aeruginosa lipase for improved amide-hydrolyzing activity.

A lipase from Pseudomonas aeruginosa was subjected to directed molecular evolution for increased amide-hydrolyzing (amidase) activity. A single round of random mutagenesis followed by screening for hydrolytic activity for oleoyl 2-naphthylamide as compared with that for oleoyl 2-naphthyl ester identified five mutants with 1.7-2.0-fold increased relative amidase activities. Three mutational sites (F207S, A213D and F265L) were found to affect the amidase/esterase activity ratios. The combination of these mutations further improved the amidase activity. Active-site titration using a fluorescent phosphonic acid ester allowed the molecular activities for the amide and the ester to be determined for each mutant without purification of the lipase. A double mutant F207S/A213D gave the highest molecular activity of 1.1 min(-1) for the amide, corresponding to a 2-fold increase compared with that of the wild-type lipase. A structural model of the lipase indicated that the mutations occurred at the sites near the surface and remote from the catalytic triad, but close to the calcium binding site. This study is a first step towards understanding why lipases do not hydrolyze amides despite the similarities to serine proteases in the active site structure and the reaction mechanism and towards the preparation of a general acyl transfer catalyst for the biotransformation of amides.

Amides↗
PubMed2005

Prevalence of antibodies against Simkania negevensis in a healthy Japanese population determined by the microimmunofluorescence test.

Simkania negevensis has been associated with bronchiolitis in infants and community-acquired pneumonia in adults. Reports of exposure to this microorganism are only available from Israel, North America and Western Europe. Currently, no standard method for diagnosis of S. negevensis infection has been established nor have prevalence rates been shown in Japan. For the first time we demonstrated the ability of the microimmunofluorescence (MIF) test to detect S. negevensis-specific immunoglobulin G and exposure to S. negevensis in Japan. The positive rate in healthy volunteers was 4.3% (25/588), with rates increasing with age. Results indicate the usefulness of the MIF test as a serological method for detecting S. negevensis-specific antibodies. A standard serological test for infection with S. negevensis is needed.

Adult↗
PubMed2005

Increased glucocorticoid receptor and 11{beta}-hydroxysteroid dehydrogenase type 1 expression in hepatocytes may contribute to the phenotype of type 2 diabetes in db/db mice.

Excess tissue glucocorticoid action may contribute to the hyperglycemia and insulin resistance associated with type 2 diabetes, but the associated mechanisms are poorly understood. 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) converts inactive 11-dehydrocorticosterone into active corticosterone, thus amplifying glucocorticoid receptor-mediated tissue glucocorticoid action, particularly in the liver. To examine the role of tissue glucocorticoid action in type 2 diabetes, we analyzed expression of glucocorticoid receptor and 11beta-HSD1 and their regulation by endogenous hormones in vivo and in vitro in hepatocytes from db/db mice (a model of type 2 diabetes). We observed positive relations between expression of both glucocorticoid receptor and 11beta-HSD1 in liver and insulin sensitivity and expression of PEPCK mRNA in db/db mice and db/+ controls. Increased expression of glucocorticoid receptor and 11beta-HSD1 in the liver of db/db mice was correlated with elevated circulating levels of corticosterone, insulin, and blood glu-cose. Treatment of db/db mice with glucocorticoid antagonist RU486 reversed the increases in the expression of glucocorticoid receptor and 11beta-HSD1 within the liver and attenuated the phenotype of type 2 diabetes. Addition of corticosterone to db/db mouse primary hepatocytes activated expression of glucocorticoid receptor, 11beta-HSD1, and PEPCK, and these effects were abolished by RU486. Incubation of primary hepatocytes with increasing concentrations of glucose caused dose-dependent increases in glucocorticoid receptor and 11beta-HSD1 expression, whereas insulin did not affect the expression of 11beta-HSD1 and glucocorticoid receptor in primary hepatocytes. These findings suggest that activation of glucocorticoid receptor and 11beta-HSD1 expression within the liver may contribute to the development of type 2 diabetes in db/db mice.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗
PubMed2004

Streptozotocin-induced diabetes in the pregnant rat reduces 11 beta-hydroxysteroid dehydrogenase type 2 expression in placenta and fetal kidney.

Several epidemiological and animal studies have shown that the offsprings of diabetic mothers have higher incidences of glucose intolerance, obesity, insulin resistance, and hypertension in later life. It is well known that glucocorticoid metabolism plays a crucial role on several adult disease originated from fetal environment. The aim of this study was to investigate the relation between diabetic pregnancy and glucocorticoid metabolism of both mother and fetus, focusing on the 11 beta-hydroxysteroid dehydrogenase (11beta-HSD) type 2. A model of diabetic pregnancy was made by intravenous injection of streptozotocin (35 mg/kg body weight) to Sprague-Dawley rats, and blood and tissue samples were collected on day 20 of pregnancy. In the diabetic group, expression of 11 beta-hydroxysteroid dehydrogenase type 2 in placentas and fetal kidneys was decreased remarkably. Corticosterone levels of diabetic mothers were lower than those of control rats. Despite the differences in maternal corticosterone levels, fetal levels of corticosterone did not differ between the groups. Our results lend support to the concept that diabetic pregnancy imprints glucocorticoid regulation in these fetuses, which may contribute to their increased incidence of higher blood pressure as adults.

11-beta-Hydroxysteroid Dehydrogenase Type 2↗
PubMed2004

A novel mutation in the renal V2 receptor gene in a boy with trisomy 21.

We describe for the first time an infant with Down syndrome and congenital nephrogenic diabetes insipidus (NDI). The 11-day-old Japanese boy was admitted with failure to thrive and fever. Polyuria (3,000-3,500 ml/m(2) per day), low urine specific gravity (1.001-1.002), and high plasma arginine vasopressin (AVP) (18.2 pg/ml) suggested NDI. Gene analysis confirmed the diagnosis of congenital NDI due to a novel mutation of the V2 receptor gene (L309P). He also had symptoms of Down syndrome and karyotype analysis of the peripheral lymphocytes revealed trisomy 21. The relationship between pyelectasis and a risk of Down syndrome is discussed.

Diabetes Insipidus, Nephrogenic↗
PubMed2004

Different responsiveness in body weight and hepatic 11beta-hydroxysteroid dehydrogenase (11beta-HSD) type 1 mrna to 11beta-HSD inhibition by glycyrrhetinic acid treatment in obese and lean zucker rats.

Tissue-specific dysregulation of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) activity in obese humans and animals may be associated with obesity and the metabolic syndrome. We investigated the effect of inhibition of 11beta-HSD with glycyrrhetinic acid (GE), an effective 11beta-HSD inhibitor, on body weight regulation in obese Zucker rats, which have a defect in the leptin receptor gene. GE (280 mg/kg/d) was administered in drinking water to 8-week-old male Zucker rats for 14 weeks. GE had no effect on food intake or weight gain, and did not affect hepatic 11beta-HSD1 and renal 11beta-HSD2 mRNA levels in obese rats. In contrast, average daily food intake and body weight on week 14 were significantly reduced by GE in lean rats (both P <.0001). Hepatic 11beta-HSD1 and renal 11beta-HSD2 mRNA levels were also significantly decreased by GE in lean rats (both P <.05). GE had no significant effect on plasma corticosterone levels in obese rats but lowered them in lean rats (P <.05). Plasma leptin levels declined in both GE-treated obese and lean rats (both P <.01). In conclusion, long-term GE treatment decreased weight gain in lean Zucker rats but not in obese Zucker rats. These findings suggest that the differing responses of 11beta-HSD1 to GE in obese and lean Zucker rats are closely associated with the different weight-gain responses. Furthermore, the weight-lowering effect of GE may require intact leptin receptors.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed2004

Factors improving the propagation of Simkania negevensis strain Z in cell culture.

The purpose of the present study was to develop an optimal method for culturing Simkania negevensis. Centrifugation was effective for the propagation of S. negevensis, but sonication was not effective. The addition of cycloheximide to the culture medium significantly decreased the number of inclusions. Pretreatment of host monolayers with diethylaminoethyl-dextran or polyethylene glycol was detrimental. The most optimal conditions were centrifugation of the inocula onto untreated Vero cells, and culture in RPMI 1640 medium containing 10% fetal calf serum without cycloheximide or antimicrobial agents.

Animals↗
PubMed2003

Hepatic steatosis is a risk factor for hepatocellular carcinoma in patients with chronic hepatitis C virus infection.

BACKGROUND: Hepatic steatosis is one of the histopathologic features of chronic hepatitis C. It was reported recently that the expression of hepatitis C virus (HCV) core protein in transgenic mice induced hepatocellular carcinoma (HCC) in association with steatosis. The objective of this study was to determine the relation between hepatic steatosis and hepatocarcinogenesis in patients with chronic HCV infection. METHODS: The authors studied 161 patients with chronic HCV infection who were diagnosed at Nagasaki University Hospital, Nagasaki, Japan, between January 1980 and December 1999. Age, gender, body mass index (BMI), habitual drinking, diabetes mellitus, serum alanine aminotransferase (ALT) level, HCV serotype, serum level of HCV core protein, interferon (IFN) treatment, hepatic fibrosis inflammation, and hepatic steatosis were studied with regard to their significance in the development of HCC using univariate and multivariate analyses. RESULTS: The cumulative incidence rates of HCC were 24%, 51%, and 63% at 5 years, 10 years, and 15 years, respectively. Multivariate analysis identified hepatic steatosis, together with aging, cirrhosis, and no IFN treatment, as independent and significant risk factors for HCC (P = 0.0135, P = 0.0390, P = 0.0068, and P = 0.0142, respectively). In addition, hepatic steatosis was correlated with BMI, serum ALT levels, and triglyceride levels. CONCLUSIONS: The findings of the current study indicate that hepatic steatosis is a risk factor for HCC in patients with chronic HCV infection. Patients with chronic HCV and hepatic steatosis should be monitored carefully for HCC.

Adult↗
PubMed2003

Interferon-alpha sensitizes human hepatoma cells to TRAIL-induced apoptosis through DR5 upregulation and NF-kappa B inactivation.

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), a member of the TNF superfamily, induces apoptosis in a variety of cancer cells with little or no effect on normal cells. Human hepatoma cells, however, are resistant to TRAIL-induced apoptosis. Since interferon-alpha (IFN-alpha) is capable of enhancing TNF-alpha-induced apoptosis in certain cancer cells, we evaluated the effect of IFN-alpha on TRAIL-induced apoptosis of human hepatoma cells. IFN-alpha pretreatment enhanced TRAIL-induced apoptosis of HuH-7 and Hep3B cells, in which IFN-alpha upregulated the expression of DR5, a death receptor of TRAIL, and downregulated the expression of survivin, which has an antiapoptotic function. In contrast, IFN-alpha did not enhance TRAIL-induced apoptosis of HepG2 cells, in which expression of DR5 and survivin was not affected by IFN-alpha. On the other hand, TRAIL activated NF-kappa B composed of RelA-p50 heterodimer, a key transcription factor regulating cell survival, in HuH-7 and HepG2 cells. However, IFN-alpha pretreatment repressed the TRAIL-mediated activation of NF-kappaB and decreased its transcriptional activity in HuH-7 but not in HepG2 cells. Moreover, IFN-alpha pretreatment clearly augmented TRAIL-mediated caspase-8 activation in HuH-7 cells. Our results suggest that IFN-alpha could sensitize certain human hepatoma cells to TRAIL-induced apoptosis by stimulating its death signaling and by repressing the survival function in these cells.

Apoptosis↗
PubMed2003

Leptin activation of corticosterone production in hepatocytes may contribute to the reversal of obesity and hyperglycemia in leptin-deficient ob/ob mice.

Glucocorticoids have been implicated as pathophysiological mediators of obesity and insulin resistance and are regulated by 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1). This enzyme regenerates active corticosterone from inactive 11-keto forms. To assess the role of 11beta-HSD1-mediated synthesis of active corticosterone in leptin-related obesity and diabetes, we examined the peripheral effect of leptin on 11beta-HSD1 activity and gene expression in vivo and in vitro in hepatocytes from ob/ob mice and in liver of streptozotocin (STZ)-treated ob/ob mice. We observed an inverse relationship between hepatic 11beta-HSD1 expression and body weight in ob/ob mice and lean littermates. Leptin treatment of ob/ob mice markedly increased hepatic 11beta-HSD1 activity and mRNA expression. This induction of 11beta-HSD1 expression corresponded to reduced levels of circulating corticosterone and weight loss in ob/ob mice treated with leptin, indicating that impaired hepatic 11beta-HSD1 expression may contribute to the pathogenesis of obesity in ob/ob mice. In addition, leptin treatment of STZ-treated ob/ob mice caused marked increases in hepatic 11beta-HSD1 levels associated with decreased body weight and a significant reduction in hyperglycemia due to pancreatic beta-cell damage. Addition of leptin to ob/ob mouse primary hepatocytes led to a dose-dependent increase in 11beta-HSD1 mRNA expression. In contrast, leptin did not influence 11beta-HSD1 expression in primary hepatocytes from db/db mice, indicating that leptin regulation of 11beta-HSD1 expression is probably mediated by the functional leptin receptor. Thus, leptin appears to be an important metabolic signal that directly activates intrahepatic corticosterone production. These findings suggest that the liver-specific interaction of leptin with 11beta-HSD1 is involved in the development of obesity and insulin resistance in ob/ob mice.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗