16 results on '"Wataru, Ogawa"'
Search Results
2. O-GlcNAcylation of myocyte-specific enhancer factor 2D negatively regulates insulin secretion from pancreatic β-cells
- Author
-
Mai Yoshida, Norihide Yokoi, Harumi Takahashi, Naoya Hatano, Tomohide Hayami, Wataru Ogawa, and Susumu Seino
- Subjects
Proteomics ,Glucose ,Diabetes Mellitus, Type 2 ,MEF2 Transcription Factors ,Insulin Secretion ,Biophysics ,Humans ,Cell Biology ,Incretins ,Protein Processing, Post-Translational ,Molecular Biology ,Biochemistry ,Acetylglucosamine - Abstract
Patients with type 2 diabetes often exhibit impairments in both glucose-induced insulin secretion (GIIS) and incretin-induced insulin secretion (IIIS). These phenotypes are associated with altered glucose metabolism in pancreatic β-cells, although the molecular mechanisms remain unclear. Here, we used MIN6-K8 pancreatic β-cell lines as a model to examine the effect of O-linked N-acetylglucosamine glycosylation (O-GlcNAcylation), a glucose-induced protein posttranslational modification, on insulin secretion. O-GlcNAcylation was enhanced in high-glucose-treated MIN6-K8 cells, and high levels of O-GlcNAcylation attenuated PKA-dependent phosphorylation, suggesting that the two protein modifications may compete with each other. Immunoprecipitation proteomic analysis identified six candidate proteins that were O-GlcNAcylated by high-glucose treatment, whereas the O-GlcNAcylations were removed by treatment with an incretin mimetic, exendin-4. Among these proteins, knockdown of myocyte enhancer factor 2D (Mef2d) enhanced insulin secretion, and high-glucose treatment increased the level of O-GlcNAcylation of Mef2d in MIN6-K8 cells. Furthermore, knockout of Mef2d promoted GIIS in MIN6-K8 cells, whereas adenovirus-mediated rescue of Mef2d decreased GIIS in the knockout cells. These results suggest that Mef2d negatively regulates insulin secretion through O-GlcNAcylation.
- Published
- 2022
3. Canagliflozin ameliorates hepatic fat deposition in obese diabetic mice: Role of prostaglandin E2
- Author
-
Masakazu Shinohara, Makoto Imamori, Wataru Ogawa, Tetsuya Hosooka, Yusei Hosokawa, Kei Yoshino, and Chikako Aoki
- Subjects
0301 basic medicine ,medicine.medical_specialty ,Biophysics ,Prostaglandin E2 (PGE2) ,Biochemistry ,Palmitic acid ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Internal medicine ,Nonalcoholic fatty liver disease ,Lipidomics ,Medicine ,Prostaglandin E2 ,Canagliflozin ,Molecular Biology ,Nonalcoholic steatohepatitis (NASH) ,business.industry ,Fatty liver ,SGLT2 inhibitor ,Cell Biology ,medicine.disease ,030104 developmental biology ,Endocrinology ,chemistry ,Lipid mediator ,030220 oncology & carcinogenesis ,Animal studies ,business ,Resolvin ,medicine.drug ,Nonalcoholic fatty liver disease (NAFLD) - Abstract
Clinical and animal studies have suggested a possible beneficial effect of sodium-glucose cotransporter 2 (SGLT2) inhibitors on nonalcoholic fatty liver disease (NAFLD) including nonalcoholic steatohepatitis (NASH). Although SGLT2 inhibitors have been shown to reduce hepatic fat deposition in association with loss of body weight, the mechanism of this action has remained unknown. We here show that the SGLT2 inhibitor canagliflozin ameliorated fatty liver and hyperglycemia without affecting body weight or epididymal fat weight in obese diabetic KKAy mice. Lipidomics analysis based on liquid chromatography and tandem mass spectrometry revealed that canagliflozin treatment increased the amounts of prostaglandin E2 (PGE2) and resolvin E3 in the liver of these mice. We also found that PGE2 attenuated fat deposition in mouse primary hepatocytes exposed to palmitic acid. Our results thus suggest that PGE2 may play an important role in the amelioration of hepatic fat deposition by canagliflozin, with elucidation of its mechanism of action potentially providing a basis for the development of new therapeutics for NAFLD-NASH.
- Published
- 2021
4. Canagliflozin ameliorates hepatic fat deposition in obese diabetic mice: Role of prostaglandin E
- Author
-
Kei, Yoshino, Tetsuya, Hosooka, Masakazu, Shinohara, Chikako, Aoki, Yusei, Hosokawa, Makoto, Imamori, and Wataru, Ogawa
- Subjects
Male ,Mice, Obese ,Diet, High-Fat ,Dinoprostone ,Diabetes Mellitus, Experimental ,Mice ,Liver ,Sodium-Glucose Transporter 2 ,Non-alcoholic Fatty Liver Disease ,Animals ,Obesity ,Canagliflozin ,Insulin Resistance ,Sodium-Glucose Transporter 2 Inhibitors ,Cells, Cultured - Abstract
Clinical and animal studies have suggested a possible beneficial effect of sodium-glucose cotransporter 2 (SGLT2) inhibitors on nonalcoholic fatty liver disease (NAFLD) including nonalcoholic steatohepatitis (NASH). Although SGLT2 inhibitors have been shown to reduce hepatic fat deposition in association with loss of body weight, the mechanism of this action has remained unknown. We here show that the SGLT2 inhibitor canagliflozin ameliorated fatty liver and hyperglycemia without affecting body weight or epididymal fat weight in obese diabetic KKAy mice. Lipidomics analysis based on liquid chromatography and tandem mass spectrometry revealed that canagliflozin treatment increased the amounts of prostaglandin E
- Published
- 2021
5. Modulation of lipid mediator profile may contribute to amelioration of chronic inflammation in adipose tissue of obese mice by pioglitazone
- Author
-
Wataru Ogawa, Masakazu Shinohara, Tetsuya Hosooka, and Kumiko Okada
- Subjects
0301 basic medicine ,Male ,medicine.medical_specialty ,Biophysics ,Adipose tissue ,Mice, Obese ,Inflammation ,Biochemistry ,03 medical and health sciences ,chemistry.chemical_compound ,Mice ,Internal medicine ,3T3-L1 Cells ,medicine ,Adipocytes ,Animals ,Hypoglycemic Agents ,Obesity ,Prostaglandin E2 ,Molecular Biology ,Pioglitazone ,Chemistry ,Gene Expression Profiling ,Interleukin ,Cell Biology ,Lipid signaling ,Lipid Metabolism ,Eicosapentaenoic acid ,Lipoxins ,030104 developmental biology ,Endocrinology ,Adipose Tissue ,Diabetes Mellitus, Type 2 ,Chronic Disease ,Cytokines ,medicine.symptom ,Resolvin ,medicine.drug - Abstract
Thiazolidinediones exert their antidiabetic effect in part by ameliorating chronic inflammation in adipose tissue. However, the precise mechanism of this anti-inflammatory action has remained unclear. We here investigated the effects of the TZD pioglitazone on the lipid mediator profile of adipose tissue in obese diabetic KKAy mice by metabololipidomics analysis based on liquid chromatography and tandem mass spectrometry. Pioglitazone treatment increased the amounts of pro-resolving lipid mediators including lipoxin B4 (LXB4), resolvin E2, and eicosapentaenoic acid as well as reduced those of prostaglandin E2 and 4-hydroxydocosahexaenoic acid in epididymal adipose tissue of KKAy mice. These effects were accompanied by increased expression of genes for the anti-inflammatory proteins arginase 1, interleukin (IL)–13, and IL-10 in this tissue. Pioglitazone also increased LXB4 production in cultured 3T3-L1 adipocytes. Finally, LXB4 increased IL-10 gene expression in adipose tissue explants from KKAy mice. Together, our results suggest that up-regulation of LXB4 may contribute to the anti-inflammatory effect of pioglitazone in obese adipose tissue.
- Published
- 2018
6. Protective role of AgRP neuron's PDK1 against salt-induced hypertension
- Author
-
Masanori Nakata, Boyang Zhang, Takashi Okada, Toshihiko Yada, Ming Lu, Jun Nakae, and Wataru Ogawa
- Subjects
0301 basic medicine ,Leptin ,medicine.medical_treatment ,Blood Pressure ,Biochemistry ,Energy homeostasis ,Mice ,Norepinephrine ,Insulin ,Agouti-Related Protein ,Mice, Knockout ,Neurons ,Chemistry ,digestive, oral, and skin physiology ,DNA-Binding Proteins ,medicine.anatomical_structure ,Hypertension ,hormones, hormone substitutes, and hormone antagonists ,medicine.drug ,Signal Transduction ,medicine.medical_specialty ,Biophysics ,Nerve Tissue Proteins ,Protein Serine-Threonine Kinases ,03 medical and health sciences ,Arcuate nucleus ,Orexigenic ,Internal medicine ,FLOX ,medicine ,Animals ,Nucleobindins ,RNA, Messenger ,Sodium Chloride, Dietary ,Molecular Biology ,Calcium-Binding Proteins ,Arcuate Nucleus of Hypothalamus ,Pyruvate Dehydrogenase Acetyl-Transferring Kinase ,Cell Biology ,Feeding Behavior ,Disease Models, Animal ,030104 developmental biology ,Endocrinology ,nervous system ,Gene Expression Regulation ,Neuron ,Energy Intake ,Hormone ,Paraventricular Hypothalamic Nucleus - Abstract
In the hypothalamic arcuate nucleus (ARC), orexigenic agouti-related peptide (AgRP) neurons regulate feeding behavior and energy homeostasis. The 3-phosphoinositide-dependent protein kinase-1 (PDK1) in AgRP neurons serves as a major signaling molecule for leptin and insulin, the hormones regulating feeding behavior, energy homeostasis and circulation. However, it is unclear whether PDK1 in AGRP neurons is also involved in regulation of blood pressure. This study explored it by generating and analyzing AgRP neuron-specific PDK1 knockout (Agrp-Pdk1flox/flox) mice and effect of high salt diet on blood pressure in KO and WT mice was analyzed. Under high salt diet feeding, systolic blood pressure (SBP) of Agrp-Pdk1flox/flox mice was significantly elevated compared to Agrp-Cre mice. When the high salt diet was switched to control low salt diet, SBP of Agrp-Pdk1flox/flox mice returned to the basal level observed in Agrp-Cre mice within 1 week. In Agrp-Pdk1flox/flox mice, urinary noradrenalin excretion and NUCB2 mRNA expression in hypothalamic paraventricular nucleus (PVN) were markedly upregulated. Moreover, silencing of NUCB2 in the PVN counteracted the rises in urinary noradrenalin excretions and SBP. These results demonstrate a novel role of PDK1 in AgRP neurons to counteract the high salt diet-induced hypertension by preventing hyperactivation of PVN nesfatin-1 neurons.
- Published
- 2018
7. Casein kinase 2 phosphorylates and stabilizes C/EBPβ in pancreatic β cells
- Author
-
Wataru Ogawa, Yoshiaki Kido, Tomokazu Matsuda, Maki Kimura-Koyanagi, Ayumi Kanno, Yuki Matsuura, Tomoko Takai, Kaho Inoue, Naoya Hatano, Emi Suzuki, and Shun-ichiro Asahara
- Subjects
0301 basic medicine ,Biophysics ,Biochemistry ,Cell Line ,03 medical and health sciences ,Mice ,AMP-Activated Protein Kinase Kinases ,Insulin-Secreting Cells ,Animals ,Phosphorylation ,Protein kinase A ,Casein Kinase II ,Molecular Biology ,030102 biochemistry & molecular biology ,Chemistry ,Endoplasmic reticulum ,CCAAT-Enhancer-Binding Protein-beta ,AMPK ,Cell Biology ,Endoplasmic Reticulum Stress ,Molecular biology ,030104 developmental biology ,Cell culture ,Apoptosis ,Unfolded protein response ,Casein kinase 2 ,Protein Kinases - Abstract
During the development of type 2 diabetes, endoplasmic reticulum (ER) stress leads to pancreatic β cell failure. CCAAT/enhancer-binding protein (C/EBP) β is highly induced by ER stress and AMP-activated protein kinase (AMPK) suppression in pancreatic β cells, and its accumulation reduces pancreatic β cell mass. We investigated the phosphorylation state of C/EBPβ under these conditions. Casein kinase 2 (CK2) was found to co-localize with C/EBPβ in MIN6 cells. It phosphorylated S222 of C/EBPβ, a previously unidentified phosphorylation site. We found that C/EBPβ is phosphorylated by CK2 under AMPK suppression and ER stress, which are important from the viewpoint of the worsening pathological condition of type 2 diabetes, such as decreased insulin secretion and apoptosis of pancreatic β cells.
- Published
- 2018
8. Compensatory hyperinsulinemia in high-fat diet-induced obese mice is associated with enhanced insulin translation in islets
- Author
-
Katsuhisa Masuda, Shun-ichiro Asahara, Susumu Seino, Wataru Ogawa, Tomokazu Matsuda, Maki Kimura-Koyanagi, Ayumi Kanno, and Yoshiaki Kido
- Subjects
Male ,medicine.medical_specialty ,Transcription, Genetic ,medicine.medical_treatment ,Biophysics ,Mice, Obese ,Biology ,Diet, High-Fat ,Biochemistry ,Cell Line ,Mice ,Insulin resistance ,Hyperinsulinism ,Insulin-Secreting Cells ,Internal medicine ,medicine ,Animals ,Insulin ,Obesity ,Molecular Biology ,geography ,geography.geographical_feature_category ,Translation (biology) ,Cell Biology ,medicine.disease ,Islet ,Insulin oscillation ,Mice, Inbred C57BL ,Endocrinology ,Protein Biosynthesis ,Animal studies ,Compensatory Hyperinsulinemia - Abstract
A high-fat diet (HF) is associated with obesity, insulin resistance, and hyperglycemia. Animal studies have shown compensatory mechanisms in pancreatic β-cells after high fat load, such as increased pancreatic β-cell mass, enhanced insulin secretion, and exocytosis. However, the effects of high fat intake on insulin synthesis are obscure. Here, we investigated whether insulin synthesis was altered in correlation with an HF diet, for the purpose of obtaining further understanding of the compensatory mechanisms in pancreatic β-cells. Mice fed an HF diet are obese, insulin resistant, hyperinsulinemic, and glucose intolerant. In islets of mice fed an HF diet, more storage of insulin was identified. We analyzed insulin translation in mouse islets, as well as in INS-1 cells, using non-radioisotope chemicals. We found that insulin translational levels were significantly increased in islets of mice fed an HF diet to meet systemic demand, without altering its transcriptional levels. Our data showed that not only increased pancreatic β-cell mass and insulin secretion but also elevated insulin translation is the major compensatory mechanism of pancreatic β-cells.
- Published
- 2015
9. The Krüppel-like factor KLF15 inhibits transcription of the adrenomedullin gene in adipocytes
- Author
-
Kazuhiro Takahashi, Wataru Ogawa, Hiroshi Sakaue, Yasushi Matsuki, Hideyuki Gomi, Mototsugu Takashima, Eijiro Watanabe, Ryuji Hiramatsu, Masato Kasuga, and Tomoki Nagare
- Subjects
Chromatin Immunoprecipitation ,Transcription, Genetic ,Kruppel-Like Transcription Factors ,Biophysics ,Down-Regulation ,Adipose tissue ,KLF15 ,Biology ,Biochemistry ,Adrenomedullin ,Mice ,chemistry.chemical_compound ,Transcription (biology) ,Adipocyte ,Gene expression ,Adipocytes ,Animals ,Humans ,Promoter Regions, Genetic ,Molecular Biology ,Gene ,Oligonucleotide Array Sequence Analysis ,3T3 Cells ,Cell Biology ,Molecular biology ,DNA-Binding Proteins ,Gene Expression Regulation ,chemistry ,Chromatin immunoprecipitation ,hormones, hormone substitutes, and hormone antagonists ,Transcription Factors - Abstract
KLF15 (Kruppel-like factor 15) plays a key role in adipocyte differentiation and glucose transport in adipocytes through activation of its target genes. We have now identified six target genes regulated directly by KLF15 in 3T3-L1 mouse adipocytes with the use of a combination of microarray-based chromatin immunoprecipitation and gene expression analyses. We confirmed the direct regulation by KLF15 of one of these genes, that for adrenomedullin, with the use of a luciferase reporter assay in 3T3-L1 preadipocytes and adipocytes. Such analysis revealed that the most proximal CACCC element in the promoter of the human adrenomedullin gene (located in the region spanning nucleotides −70 and −29) is required for trans-inhibition by KLF15. Furthermore, chromatin immunoprecipitation showed that KLF15 binds to this region of the human adrenomedullin gene promoter in cultured human adipocytes. These results thus implicate KLF15 in the regulation of adrenomedullin expression in adipose tissue.
- Published
- 2009
10. Role of Krüppel-like factor 15 in PEPCK gene expression in the liver
- Author
-
Kazuaki Miyake, Wataru Ogawa, Kiyoshi Teshigawara, Masato Kasuga, Ryuji Hiramatsu, Hiroshi Sakaue, Yasushi Matsuki, Eijiro Watanabe, Toshiyuki Mori, and Hiroshi Inoue
- Subjects
medicine.medical_specialty ,medicine.medical_treatment ,Kruppel-Like Transcription Factors ,Biophysics ,Down-Regulation ,KLF15 ,Biochemistry ,Dexamethasone ,Gene Expression Regulation, Enzymologic ,Mice ,Phosphatidylinositol 3-Kinases ,chemistry.chemical_compound ,Internal medicine ,Gene expression ,Cyclic AMP ,medicine ,Animals ,Insulin ,Phosphatidylinositol ,Molecular Biology ,Transcription factor ,Gene ,Cells, Cultured ,Phosphoinositide-3 Kinase Inhibitors ,Cell Biology ,Rats ,DNA-Binding Proteins ,Endocrinology ,Liver ,chemistry ,Glucose Clamp Technique ,Hepatocytes ,Electrophoresis, Polyacrylamide Gel ,Phosphoenolpyruvate Carboxykinase (GTP) ,Phosphoenolpyruvate carboxykinase ,Transcription Factors ,Hormone - Abstract
Regulation of hepatic gene expression is important for energy homeostasis. We now show that hepatic expression of the gene for the transcription factor Kruppel-like factor 15 (KLF15) is increased by food deprivation and reduced by feeding in mice. Expression of the KLF15 gene in mouse liver was also down-regulated by a euglycemic–hyperinsulinemic clamp and was increased by inhibition of phosphatidylinositol 3-kinase. In cultured rat hepatocytes, KLF15 gene expression was induced by dexamethasone and a non-hydrolyzing analog of cAMP, and this effect was inhibited by insulin in a manner dependent on phosphatidylinositol 3-kinase signaling. Forced expression of KLF15 in cultured hepatocytes increased both the expression and the promoter activity of the gene for phosphoenolpyruvate carboxykinase (PEPCK). These results suggest that insulin and its counteracting hormones regulate the hepatic expression of KLF15, and that this transcription factor contributes to the regulation of PEPCK gene expression in the liver.
- Published
- 2005
11. Role of S6K1 in regulation of SREBP1c expression in the liver
- Author
-
Aki Emi, Kumiko Hayashi, Wataru Ogawa, Masato Kasuga, Kazuhiro Nomura, Kenta Hara, Yoko Senga, Shuying Li, and De-Min Yu
- Subjects
Morpholines ,Biophysics ,P70-S6 Kinase 1 ,Mice, Inbred Strains ,mTORC1 ,Biology ,Mechanistic Target of Rapamycin Complex 1 ,Biochemistry ,Ribosomal Protein S6 Kinases, 90-kDa ,Cell Line ,Small hairpin RNA ,chemistry.chemical_compound ,Mice ,Gene expression ,Animals ,Obesity ,RNA, Small Interfering ,Molecular Biology ,Transcription factor ,PI3K/AKT/mTOR pathway ,Hypertriglyceridemia ,Sirolimus ,Fatty acid metabolism ,Effector ,TOR Serine-Threonine Kinases ,Proteins ,Cell Biology ,Molecular biology ,Fatty Liver ,chemistry ,Gene Expression Regulation ,Liver ,Chromones ,Multiprotein Complexes ,Hepatocytes ,Sterol Regulatory Element Binding Protein 1 - Abstract
The transcription factor sterol regulatory element-binding protein 1c (SREBP1c) plays an important role in the control of fatty acid metabolism in the liver. Evidence suggests that mammalian target of rapamycin (mTOR) complex 1 (mTORC1) contributes to the regulation of SREBP1c expression, but signaling downstream of mTORC1 remains unclear. We have now shown that medium rich in branched-chain amino acids stimulates expression of the SREBP1c gene in cultured hepatocytes in a manner sensitive both to rapamycin, a pharmacological inhibitor of mTORC1, and to a short hairpin RNA (shRNA) specific for S6 kinase 1 (S6K1), a downstream effector of mTORC1. The phosphorylation of S6K1 was increased in the liver of obese db/db mice. Furthermore, depletion of hepatic S6K1 in db/db mice with the use of an adenovirus vector encoding S6K1 shRNA resulted in down-regulation of SREBP1c gene expression in the liver as well as a reduced hepatic triglyceride content and serum triglyceride concentration. These results thus suggest that S6K1 regulates SREBP1c expression both in cultured hepatocytes and in mouse liver, and that increased hepatic activity of S6K1 contributes at least in part to the pathogenesis of obesity-induced hepatic steatosis and hypertriglyceridemia.
- Published
- 2011
12. Identification and characterization of an alternative promoter of the human PGC-1alpha gene
- Author
-
Tetsuya Hosooka, Yasushi Matsuki, Eijiro Watanabe, Ryuji Hiramatsu, Tetsuya Noguchi, Masato Kasuga, Haruhisa Iguchi, Toyo Yoshioka, Wataru Ogawa, Mashito Sakai, and Kenjiro Inagaki
- Subjects
Transcriptional Activation ,Transcription, Genetic ,Response element ,Molecular Sequence Data ,Biophysics ,E-box ,P300-CBP Transcription Factors ,CREB ,MyoD ,Biochemistry ,Cyclic AMP ,Humans ,p300-CBP Transcription Factors ,Protein kinase A ,Cyclic AMP Response Element-Binding Protein ,Muscle, Skeletal ,Promoter Regions, Genetic ,Molecular Biology ,Transcription factor ,Heat-Shock Proteins ,biology ,Base Sequence ,Promoter ,Cell Biology ,Molecular biology ,Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha ,biology.protein ,Calcium ,Muscle Contraction ,Transcription Factors - Abstract
The transcriptional regulator peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha) controls mitochondrial biogenesis and energy homeostasis. Although physical exercise induces PGC-1alpha expression in muscle, the underlying mechanism of this effect has remained incompletely understood. We recently identified a novel muscle-enriched isoform of PGC-1alpha transcript (designated PGC-1alpha-b) that is derived from a previously unidentified first exon. We have now cloned and characterized the human PGC-1alpha-b promoter. The muscle-specific transcription factors MyoD and MRF4 transactivated this promoter through interaction with a proximal E-box motif. Furthermore, either forced expression of Ca(2+)- and calmodulin-dependent protein kinase IV (CaMKIV), calcineurin A, or the p38 mitogen-activated protein kinase (p38 MAPK) kinase MKK6 or the intracellular accumulation of cAMP activated the PGC-1alpha-b promoter in cultured myoblasts through recruitment of cAMP response element (CRE)-binding protein (CREB) to a putative CRE located downstream of the E-box. Our results thus reveal a potential molecular basis for isoform-specific regulation of PGC-1alpha expression in contracting muscle.
- Published
- 2009
13. Natural regulatory mechanisms of insulin degradation by insulin degrading enzyme
- Author
-
Wataru Ogawa, Shigeaki Baba, Kozui Shii, Masato Kasuga, Hiroyuki Akiyama, Hiroshi Taniguchi, and Koichi Yokono
- Subjects
Male ,Immunoprecipitation ,medicine.medical_treatment ,Radioimmunoassay ,Biophysics ,Biology ,Insulysin ,Biochemistry ,medicine ,Insulin-degrading enzyme ,Animals ,Molecular Biology ,Pancreatic hormone ,chemistry.chemical_classification ,Kidney ,Insulin ,Antibodies, Monoclonal ,Rats, Inbred Strains ,Cell Biology ,Metabolism ,Rats ,Enzyme ,medicine.anatomical_structure ,chemistry ,Intracellular ,Peptide Hydrolases - Abstract
Insulin-degrading enzyme (IDE) accounts for most of the insulin degrading activity in extracts of several tissues and plays an important role in the intracellular degradation of insulin. Using newly developed sandwich radioimmunoassay for rat IDE, this enzyme was detectable in all tissues we examined and liver had the highest level of IDE. The ratio of insulin degrading activity to IDE concentration was roughly the same in liver, brain and muscle, however, twice as high in kidney as compared with other tissues. On the contrary, its degrading activity in these tissue extracts, including kidney, was completely lost after immunoprecipitation of IDE. These results suggest that IDE degrades insulin in the initial step of cleavage and that there are some mechanisms to regulate insulin degrading activity by IDE in the tissues.
- Published
- 1990
14. A novel IKKbeta inhibitor stimulates adiponectin levels and ameliorates obesity-linked insulin resistance
- Author
-
Yusuke Hada, Yusuke Ito, Toshimasa Yamauchi, Wataru Ogawa, Susumu Muto, Junji Kamon, Sato Takekawa, Akiko Itai, Kazuyuki Tobe, Masato Kasuga, and Takashi Kadowaki
- Subjects
Blood Glucose ,Leptin ,Time Factors ,medicine.medical_treatment ,Adipose tissue ,Mice, Obese ,Biochemistry ,Mice ,Phosphatidylinositol 3-Kinases ,Adipocytes ,Insulin ,Adiponectin secretion ,Enzyme Inhibitors ,Genes, Dominant ,Phosphoinositide-3 Kinase Inhibitors ,I-kappa B Kinase ,Up-Regulation ,Benzamides ,Intercellular Signaling Peptides and Proteins ,Adiponectin ,medicine.medical_specialty ,Morpholines ,Biophysics ,Down-Regulation ,Biology ,Carbohydrate metabolism ,Protein Serine-Threonine Kinases ,Models, Biological ,Insulin resistance ,Downregulation and upregulation ,Internal medicine ,3T3-L1 Cells ,Proto-Oncogene Proteins ,medicine ,Diabetes Mellitus ,Animals ,Obesity ,Molecular Biology ,Protein kinase B ,Dose-Response Relationship, Drug ,Body Weight ,Cell Biology ,medicine.disease ,Disease Models, Animal ,Endocrinology ,Glucose ,Gene Expression Regulation ,Chromones ,Insulin Resistance ,Proto-Oncogene Proteins c-akt - Abstract
Adiponectin is an anti-diabetic and anti-atherogenic hormone that is exclusively secreted from fat cells. Serum adiponectin levels are reduced in obese patients and obese model mice, despite increased adipose tissue mass. Elucidation of the mechanism(s) by which plasma adiponectin levels are decreased in obese and diabetic patients would provide insight into the cause of obesity-induced diabetes and the development of therapeutic advances. In the present study, the regulation of adiponectin secretion was investigated using 3T3-L1 adipocytes and a diabetic-/obese-mouse model. A novel insulin sensitizer, IkappaB kinase beta (IKKbeta) inhibitor, ameliorated insulin resistance and up-regulated plasma levels of adiponectin without producing a significant change in body weight in KKAy mice that were fed a high-fat diet. The IKKbeta inhibitor cancelled the TNFalpha-mediated down-regulation of adiponectin secretion and simultaneously up-regulated the phosphorylation of Akt in 3T3-L1 adipocytes. Using dominant-negative mutants of Akt or PKClambda (downstream effectors of phosphoinositide 3-kinase), insulin-stimulated Akt activity was found to be important in the regulation of adiponectin secretion by insulin in 3T3-L1 adipocytes. These observations suggest that "insulin-stimulated Akt activity in adipocytes" may play an important role in the regulation of adiponectin secretion.
- Published
- 2004
15. Requirement of the serine-threonine kinase Akt for heat treatment-induced activation of p70 S6 kinase
- Author
-
Tadahiro Kitamura, Masato Kasuga, Wataru Ogawa, Shoji Kuroda, Hiroaki Konishi, and Ushio Kikkawa
- Subjects
Hot Temperature ,Genetic Vectors ,Biophysics ,CHO Cells ,Mitogen-activated protein kinase kinase ,Protein Serine-Threonine Kinases ,Biochemistry ,MAP2K7 ,Adenoviridae ,TANK-binding kinase 1 ,Cricetinae ,Proto-Oncogene Proteins ,Animals ,ASK1 ,Phosphorylation ,Molecular Biology ,Protein kinase B ,Platelet-Derived Growth Factor ,Binding Sites ,MAP kinase kinase kinase ,biology ,Chemistry ,Akt/PKB signaling pathway ,Ribosomal Protein S6 Kinases ,Cyclin-dependent kinase 2 ,Cell Biology ,Molecular biology ,Recombinant Proteins ,Rats ,Enzyme Activation ,Mutation ,biology.protein ,Mutagenesis, Site-Directed ,Tetradecanoylphorbol Acetate ,Proto-Oncogene Proteins c-akt - Abstract
p70 S6 kinase plays an important role in growth factor-induced translational control and in cell cycle progression. Although the mechanism of p70 S6 kinase regulation is not fully understood, phosphorylation of serine and threonine residues of the enzyme is essential for its activation. The possible role of the serine-threonine kinase Akt in the activation of p70 S6 kinase induced by exposure of cells to heat has now been investigated. Overexpression of a mutant Akt1 (Akt-AA) in which the phosphorylation sites (Thr 308 and Ser 473 ) targeted by growth factors are replaced by alanine was shown to exert a dominant negative effect on Akt activation induced by platelet-derived growth factor (PDGF) or by heat treatment in CHO cells. Akt-AA also inhibited p70 S6 kinase activation induced by these stimuli. However, Akt-AA had no effect on the activation of p70 S6 kinase induced by 12- O -tetradecanoylphorbol 13-acetate, which did not stimulate Akt activity in these cells. These data suggest that Akt is required for heat treatment-induced activation of p70 S6 kinase.
- Published
- 1998
16. Molecular cloning of p125Nap1, a protein that associates with an SH3 domain of Nck
- Author
-
Ivan Gout, Wataru Ogawa, Kazuyoshi Yonezawa, Nick Totty, Yukari Kitamura, Kenshiro Hara, Waterfield, Tadahiro Kitamura, Masato Kasuga, and Morito Sakaue
- Subjects
Molecular Sequence Data ,Biophysics ,Biology ,Molecular cloning ,Transfection ,Biochemistry ,DNA-binding protein ,Polymerase Chain Reaction ,Homology (biology) ,SH3 domain ,Cell Line ,src Homology Domains ,Complementary DNA ,Chlorocebus aethiops ,Animals ,Humans ,Amino Acid Sequence ,Cloning, Molecular ,Molecular Biology ,Peptide sequence ,Adaptor Proteins, Signal Transducing ,Glutathione Transferase ,Oncogene Proteins ,Binding Sites ,Cell Biology ,Molecular biology ,Fusion protein ,Rats ,Molecular Weight ,biology.protein ,GRB2 ,Carrier Proteins ,Plasmids - Abstract
Binding proteins to the Src homology 3 (SH3) domains of Nck were screened by the use of glutathione S-transferase fusion proteins. Two proteins of 140 and 125 kDa were detected, both of which associated preferentially with the first SH3 domain of Nck. The 125-kDa protein, designated as Nap1 for Nck-associated protein 1, was purified and the corresponding rat cDNA was isolated. The predicted amino acid sequence revealed that p125 Nap1 dose not contain any known functional motif but shows sequence homology to Hem family gene. Using specific antibodies, p125 Nap1 was shown to associate with Nck both in vitro and in intact cells. Further characterization of p125 Nap1 may clarify the protein-protein interaction in the downstream signaling of Nck.
- Published
- 1996
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.