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Articles by M Kobayashi
Total Records ( 9 ) for M Kobayashi
  Y Yamazaki , I Usui , Y Kanatani , Y Matsuya , K Tsuneyama , S Fujisaka , A Bukhari , H Suzuki , S Senda , S Imanishi , K Hirata , M Ishiki , R Hayashi , M Urakaze , H Nemoto , M Kobayashi and K. Tobe

Nonalcoholic fatty liver disease (NAFLD) is an abnormal liver metabolism often observed with insulin resistance and metabolic syndrome. Calorie restriction is a useful treatment for NAFLD and reportedly prolongs the life spans of several species in which sirtuin plays an important role. In this study, we examined whether the activation of SIRT1, a mammalian ortholog of sirtuin, may ameliorate the development of NAFLD. Monosodium glutamate (MSG) mice, which exhibited obesity and insulin resistance, were treated with SRT1720, a specific SIRT1 activator from the age of 6–16 wk. Sixteen-week-old MSG mice exhibited increased liver triglyceride content and elevated levels of aminotransferase. SRT1720 treatment significantly reduced these levels without affecting body weight or food intake. These results suggested that the administration of SRT1720 ameliorated the development of NAFLD in MSG mice. The expressions of lipogenic genes, such as sterol regulatory element-binding protein-1c, acetyl-CoA carboxylase, and fatty acid synthase, and the serum lipid profiles, including free fatty acids, were elevated in MSG mice and were reduced by SRT1720 treatment. SRT1720 treatment also reduced the expressions of lipogenic genes in cultured HepG2 cells. Furthermore, SRT1720 treatment decreased the expressions of marker genes for oxidative stress and inflammatory cytokines in the liver of MSG mice. Taken together, SRT1720 treatment may reduce liver lipid accumulation, at least in part, by directly reducing the expressions of lipogenic genes. The reduction of oxidative stress and inflammation may also be involved in the amelioration of NAFLD.

  T Okabayashi , I Nishimori , K Yamashita , T Sugimoto , H Maeda , T Yatabe , T Kohsaki , M Kobayashi and K. Hanazaki

Objective  To evaluate a closed-loop system providing continuous monitoring and strict control of perioperative blood glucose following pancreatic resection.

Design  Prospective, randomized clinical trial.

Patients  Thirty patients who had pancreatic resection for pancreatic neoplasm.

Interventions  Patients were prospectively randomized. Perioperative blood glucose levels were continuously monitored using an artificial endocrine pancreas (STG-22). Glucose levels were controlled using either the sliding scale method (sliding scale group, n = 13) or the artificial pancreas (artificial pancreas group, n = 17).

Main Outcome Measures  Incidence of severe hypoglycemia (<40 mg/dL) during the intensive care period following pancreatic resection in patients monitored with the artificial pancreas. The secondary outcome measure was the total amount of insulin required for glycemic control in the first 18 hours after pancreatic resection in each patient group.

Results  In the sliding scale group, postoperative blood glucose levels rose initially before reaching a plateau of approximately 200 mg/dL between 4 and 6 hours after pancreatectomy. The levels remained high for 18 hours postoperatively. In the artificial pancreas group, blood glucose levels reduced steadily, reaching the target zone (80-110 mg/dL) by 6 hours after surgery. The total insulin dose administered per patient during the first postoperative 18 hours was significantly higher in the artificial pancreas group (mean [SD], 107 [109] IU) than the sliding scale group (8 [6] IU; P < .01). Neither group showed hypoglycemia.

Conclusions  Perioperative use of an artificial endocrine pancreas to control pancreatogenic diabetes after pancreatic resection is an easy and effective way to maintain near-normal blood glucose levels. The artificial pancreas shows promise for use as insulin treatment for patients with pancreatogenic diabetes after pancreatic resection.

  M Goto , K Shinmura , H Igarashi , M Kobayashi , H Konno , H Yamada , M Iwaizumi , S Kageyama , T Tsuneyoshi , S Tsugane and H. Sugimura

A base excision repair enzyme, NTH1, has activity that is capable of removing oxidized pyrimidines, such as thymine glycol (Tg), from DNA. To clarify whether the NTH1 gene is involved in gastric carcinogenesis, we first examined the NTH1 expression level in eight gastric cancer cell lines, and the results showed that NTH1 expression was downregulated in all of them, including cell line AGS. Next, a comparison of excisional repair activity against Tg by empty vector-transfected AGS clones and FLAG-NTH1-expressing AGS clones showed that a low NTH1 expression level led to low capacity to repair the damaged base in the gastric epithelial cells. Reduced messenger RNA expression of NTH1 was also detected in 36% (18/50) of primary gastric cancers. Moreover, immunohistochemical analysis revealed that NTH1 was predominantly localized in the cytoplasm in 24% (12/50) of the primary gastric cancers in contrast to the nuclear localization in non-cancerous tissue, suggesting impaired excisional repair ability for nuclear DNA. No associations between clinicopathological factors and NTH1 expression level or localization pattern were detected in the gastric cancers. Next, we found two novel genetic polymorphisms, i.e. c.-163C>G and c.-241_-221del, in the NTH1 promoter region, and a luciferase assay showed that both were associated with reduced promoter activity. However, there were no associations between the polymorphisms and risk of gastric cancer in a gastric cancer case–control study. These findings suggested that downregulation of NTH1 expression and abnormal localization of NTH1 may be involved in the pathogenesis of a subset of gastric cancers.

  M Kobayashi and R. M. Costanzo

To investigate factors that influence the degree of neural regeneration and recovery, we studied 2 olfactory nerve injury models. Transection of the olfactory nerves along the surface of the olfactory bulb was performed in OMP-tau-lacZ mice using either a flexible Teflon blade (mild injury) or a stainless steel blade (severe injury). Histological assessment of recovery within the olfactory bulb was made at 5, 14, and 42 days after injury. We used X-gal staining to label the degenerating and regenerating olfactory nerve fibers and immunohistochemical staining to detect the presence of reactive astrocytes and macrophages. Areas of injury-associated tissue were significantly smaller in the mild injury model, and at 42 days, the regenerated nerves had reestablished connections to the glomerular layer of the bulb. With severe injury, there were larger areas of injury-associated tissue, more astrocytes and macrophages, and a decrease in regenerated nerve fibers. When dexamethasone (DXM) was injected after severe injury, there was a significant reduction in injury-associated tissue, better nerve recovery, and fewer astrocytes and macrophages. These results demonstrate that recovery in the olfactory system varies with the severity of injury and that DXM treatment may have therapeutic value by reducing injury-associated tissue and improving recovery outcome.

  H Nagaoka , T. H Tran , M Kobayashi , M Aida and T. Honjo

Activation-induced cytidine deaminase (AID) is essential and sufficient to accomplish class-switch recombination and somatic hypermutation, which are two genetic events required for the generation of antibody-mediated memory responses. However, AID can also introduce genomic instability, giving rise to chromosomal translocation and/or mutations in proto-oncogenes. It is therefore important for cells to suppress AID expression unless B lymphocytes are stimulated by pathogens. The mechanisms for avoiding the accidental activation of AID and thereby avoiding genomic instability can be classified into three types: (i) transcriptional regulation, (ii) post-transcriptional regulation and (iii) target specificity. This review summarizes the recently elucidated comprehensive transcriptional regulation mechanisms of the AID gene and the post-transcriptional regulation that may be critical for preventing excess AID activity. Finally, we discuss why AID targets not only Igs but also other proto-oncogenes. AID targets many genes but it is not totally promiscuous and the criteria that specify its targets are unclear. A recent finding that a non-B DNA structure forms upon a decrease in topoisomerase 1 expression may explain this paradoxical target specificity determination. Evolution has chosen AID as a mutator of Ig genes because of its efficient DNA cleavage activity, even though its presence increases the risk of genomic instability. This is probably because immediate protection against pathogens is more critical for species survival than complete protection from the slower acting consequences of genomic instability, such as tumor formation.

  K Abe , K Osakabe , Y Ishikawa , A Tagiri , H Yamanouchi , T Takyuu , T Yoshioka , T Ito , M Kobayashi , K Shinozaki , H Ichikawa and S. Toki

BRCA2 is a breast tumour susceptibility factor with functions in maintaining genome stability through ensuring efficient double-strand DNA break (DSB) repair via homologous recombination. Although best known in vertebrates, fungi, and higher plants also possess BRCA2-like genes. To investigate the role of Arabidopsis BRCA2 genes in DNA repair in somatic cells, transposon insertion mutants of the AtBRCA2a and AtBRCA2b genes were identified and characterized. atbrca2a-1 and atbrca2b-1 mutant plants showed hypersensitivity to genotoxic stresses compared to wild-type plants. An atbrca2a-1/atbrca2b-1 double mutant showed an additive increase in sensitivity to genotoxic stresses compared to each single mutant. In addition, it was found that atbrca2 mutant plants displayed fasciation and abnormal phyllotaxy phenotypes with low incidence, and that the ratio of plants exhibiting these phenotypes is increased by -irradiation. Interestingly, these phenotypes were also induced by -irradiation in wild-type plants. Moreover, it was found that shoot apical meristems of the atbrca2a-1/atbrca2b-1 double mutant show altered cell cycle progression. These data suggest that inefficient DSB repair in the atbrca2a-1/atbrca2b-1 mutant leads to disorganization of the programmed cell cycle of apical meristems.

  D Albinsky , M Kusano , M Higuchi , N Hayashi , M Kobayashi , A Fukushima , M Mori , T Ichikawa , K Matsui , H Kuroda , Y Horii , Y Tsumoto , H Sakakibara , H Hirochika , M Matsui and K. Saito

Plant metabolomics developed as a powerful tool to examine gene functions and to gain deeper insight into the physiology of the plant cell. In this study, we screened Arabidopsis lines overexpressing rice full-length (FL) cDNAs (rice FOX Arabidopsis lines) using a gas chromatography–time-of-flight mass spectrometry (GC–TOF/MS)-based technique to identify rice genes that caused metabolic changes. This screening system allows fast and reliable identification of candidate lines showing altered metabolite profiles. We performed metabolomic and transcriptomic analysis of a rice FOX Arabidopsis line that harbored the FL cDNA of the rice ortholog of the Lateral Organ Boundaries (LOB) Domain (LBD)/Asymmetric Leaves2-like (ASL) gene of Arabidopsis, At-LBD37/ASL39. The investigated rice FOX Arabidopsis line showed prominent changes in the levels of metabolites related to nitrogen metabolism. The transcriptomic data as well as the results from the metabolite analysis of the Arabidopsis At-LBD37/ASL39-overexpressor plants were consistent with these findings. Furthermore, the metabolomic and transcriptomic analysis of the Os-LBD37/ASL39-overexpressing rice plants indicated that Os-LBD37/ASL39 is associated with processes related to nitrogen metabolism in rice. Thus, the combination of a metabolomics-based screening method and a gain-of-function approach is useful for rapid characterization of novel genes in both Arabidopsis and rice.

  T Kakita , K Nagatoya , T Mori , M Kobayashi and T. Inoue

We present the case of a woman with IgA nephropathy and concomitant Fabry’s disease. She was referred to our hospital with proteinuria and haematuria. A renal biopsy showed findings indicating IgA nephropathy under light and immunofluorescence microscopy. Electron microscopy, however, showed laminated inclusion bodies characteristic of Fabry’s disease. The -galactosidase activity in her serum was low, and the diagnosis of Fabry’s disease was confirmed by genetic analysis. Fabry’s disease in a patient with IgA nephropathy is a very rare occurrence, and Fabry’s disease diagnosed only by electron microscopy has not been previously reported.

  M Kobayashi , N Hirawa and S. Umemura
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