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Biomedical subjects

Satoshi Kimura

Publications and source records attributed to Satoshi Kimura.

At least 19 recordsLinked to original sources
PubMed2003

Dilated cardiomyopathy in an adult human immunodeficiency virus type 1-positive patient treated with a zidovudine-containing antiretroviral regimen.

We describe an adult woman infected with human immunodeficiency virus type 1 (HIV-1) who developed dilated cardiomyopathy (DCM) with histologically confirmed mitochondrial damage while receiving anti-HIV-1 combination therapy that included nelfinavir, lamivudine, and zidovudine. DCM resolved after discontinuation of the regimen, and cardiac function remained normal after initiation of treatment with nelfinavir, lamivudine, and abacavir, which indicates that DCM was induced by mitochondrial toxicity, most likely caused by zidovudine.

Adult↗
PubMed2003

Raf1 plays a pivotal role in lipopolysaccharide-induced activation of dendritic cells.

Activation of extracellular-regulated kinases 1/2 (ERK) is involved in lipopolysaccharide (LPS)-induced cellular responses such as the increased production of proinflammatory cytokines. However, mitogen-activated protein kinases (MAPKs) such as p38 are also activated by LPS and have been postulated to be important in the control of these end points. Therefore, establishing the relative contribution of MAPKs in each cell type is important, as is elucidating the molecular mechanisms by which these MAPKs are activated in LPS-induced signaling cascades. We demonstrated in DC2.4 dendritic cells that ERK regulates tyrosine phosphorylation of phosphatidyl-inositol-3-kinase (PI3-K) and the production of TNF-alpha. We also demonstrated that Raf1 is phosphorylated and involved in the production of TNF-alpha and tyrosine phosphorylation of PI3-K via ERK. Raf1 also regulates the activation of NF-kappaB. We propose that Raf1 plays a pivotal role in LPS-induced activation of the dendritic cells.

Animals↗
PubMed2003

Impaired multimerization of human adiponectin mutants associated with diabetes. Molecular structure and multimer formation of adiponectin.

Adiponectin is an adipocyte-derived hormone, which has been shown to play important roles in the regulation of glucose and lipid metabolism. Eight mutations in human adiponectin have been reported, some of which were significantly related to diabetes and hypoadiponectinemia, but the molecular mechanisms of decreased plasma levels and impaired action of adiponectin mutants were not clarified. Adiponectin structurally belongs to the complement 1q family and is known to form a characteristic homomultimer. Herein, we demonstrated that simple SDS-PAGE under non-reducing and non-heat-denaturing conditions clearly separates multimer species of adiponectin. Adiponectin in human or mouse serum and adiponectin expressed in NIH-3T3 or Escherichia coli formed a wide range of multimers from trimers to high molecular weight (HMW) multimers. A disulfide bond through an amino-terminal cysteine was required for the formation of multimers larger than a trimer. An amino-terminal Cys-Ser mutation, which could not form multimers larger than a trimer, abrogated the effect of adiponectin on the AMP-activated protein kinase pathway in hepatocytes. Among human adiponectin mutations, G84R and G90S mutants, which are associated with diabetes and hypoadiponectinemia, did not form HMW multimers. R112C and I164T mutants, which are associated with hypoadiponectinemia, did not assemble into trimers, resulting in impaired secretion from the cell. These data suggested impaired multimerization and/or the consequent impaired secretion to be among the causes of a diabetic phenotype or hypoadiponectinemia in subjects having these mutations. In conclusion, not only total concentrations, but also multimer distribution should always be considered in the interpretation of plasma adiponectin levels in health as well as various disease states.

3T3 Cells↗
PubMed2003

Pdx1 expression in Irs2-deficient mouse beta-cells is regulated in a strain-dependent manner.

We previously demonstrated that Irs2-/- mice develop diabetes due to beta-cell growth failure and insulin resistance; however, glucose-induced insulin secretion was increased in islets isolated from Irs2-/- mice. Pdx-1, a transcription factor important for maintenance of the beta-cell function, was recently reported to be severely reduced in Irs2-/- murine beta-cells. We report herein that Pdx-1 expression, including the amount of Pdx-1 localized in the nucleus, is not down-regulated in our Irs2-/- murine beta-cells with a C57BL/6 background. We have also demonstrated the expression of upstream genes of Pdx-1, such as HNF3beta and HNF1alpha, as well as its downstream genes, including insulin, Glut2, and Nkx6.1, to be well preserved. We have further demonstrated Pdx-1 expression to also be preserved in beta-cells of 30-week-old diabetic Irs2-/- mice. In addition, surprisingly, even in Irs2-/- mice on a high fat diet with markedly elevated blood glucose, exceeding 400 mg/dl, Pdx-1 expression was not reduced. Furthermore, we found Pdx-1 to be markedly decreased in certain severely diabetic Irs2-/- mice with a mixed C57BL/6J x 129Sv background. We conclude that 1) Pdx-1 expression in Irs2-/- mice is regulated in a strain-dependent manner, 2) Irs2-/- mice develop diabetes associated with beta-cell growth failure even when Pdx1 expression is preserved, and 3) Pdx-1 expression is preserved in severely hyperglycemic Irs2-/- mice with a C57BL/6 background on a high fat diet.

Animal Feed↗
PubMed2003

Involvement of Rho/Rho kinase pathway in regulation of apoptosis in rat hepatic stellate cells.

Hepatic stellate cells (HSCs) play a central role in the development of hepatic fibrosis. Recent evidence has revealed that HSCs also play a role in its resolution, where HSC apoptosis was determined. Moreover, induction of HSC apoptosis caused a reduction of experimental hepatic fibrosis in rats. Thus knowing the mechanism of HSC apoptosis might be important to clarify the pathophysiology and establish the therapeutic strategy for hepatic fibrosis. In HSCs, Rho and Rho kinase are known to regulate contraction, migration, and proliferation with modulation of cell morphology. Controversy exists as to the participation of Rho and Rho kinase on cell survival, and little is known regarding this matter in HSCs. In this study, we directed our focus on the role of the Rho pathway in the regulation of HSC survival. C3, an inhibitor of Rho, increased histone-associated DNA fragmentation and caspase 3 activity with enhanced condensation of nuclear chromatin in rat cultured HSCs. Moreover, Y-27632, an inhibitor of Rho kinase, had the same effects, suggesting that inhibition of the Rho/Rho kinase pathway causes HSC apoptosis. On the other hand, lysophosphatidic acid, which stimulates the Rho/Rho kinase pathway, decreased histone-associated DNA fragmentation in HSCs. Inhibition of the Rho/Rho kinase pathway did not affect p53, Bcl-2, or Bax levels in HSCs. Thus we concluded that the Rho/Rho kinase pathway may play a role in the regulation of HSC survival.

ADP Ribose Transferases↗
PubMed2003

p53 Activation in adipocytes of obese mice.

The tumor suppressor p53 is a transcription factor that activates or represses its target genes after various genotoxic stresses. We have previously shown that sterol regulatory element-binding protein-1 (SREBP-1), a key transcriptional regulator of triglyceride synthesis, and the lipogenic enzymes under its control are markedly suppressed in adipocytes from genetically obese ob/ob mice. Here we demonstrate that p53 and its target genes are highly induced in adipocytes of ob/ob mice in a fed state, leading to the negative regulation of SREBP-1 and thereby lipogenic genes. In fact, disruption of p53 in ob/ob mice completely suppressed the p53-regulated genes to wild-type levels and partially restored expression of lipogenic enzymes. Consistently, reporter gene analysis showed that p53 overexpression suppressed the promoter activity of the SREBP-1c gene and its downstream genes. Thus, the activation of p53 might constitute a negative feedback loop against excess fat accumulation in adipocytes. In conclusion, we discovered a novel role of p53 in the pathophysiology of obesity.

Adipose Tissue↗
PubMed2003

Janus kinase 2 is involved in lipopolysaccharide-induced activation of macrophages.

The mechanisms by which lipopolysaccharide (LPS) is recognized, and how such recognition leads to innate immune responses, are poorly understood. Stimulation with LPS induces the activation of a variety of proteins, including mitogen-activated protein kinases (MAPKs) and NF-kappaB. Activation of protein tyrosine kinases (PTKs) is also necessary for a number of biological responses to LPS. We used a murine macrophage-like cell line, RAW264.7, to demonstrate that Janus kinase (JAK)2 is tyrosine phosphorylated immediately after LPS stimulation. Anti-Toll-like receptor (TLR)4 neutralization antibody inhibits the phosphorylation of JAK2 and the c-Jun NH2-terminal protein kinase (JNK). Both the JAK inhibitor AG490 and the kinase-deficient JAK2 protein reduce the phosphorylation of JNK and phosphatidylinositol 3-kinase (PI3K) via LPS stimulation. Pharmacological inhibition of the kinase activity of PI3K with LY-294002 decreases the phosphorylation of JNK. Finally, we show that JAK2 is involved in the production of IL-1beta and IL-6. PI3K and JNK are also important for the production of IL-1beta. These results suggest that LPS induces tyrosine phosphorylation of JAK2 via TLR4 and that JAK2 regulates phosphorylation of JNK mainly through activation of PI3K. Phosphorylation of JAK2 via LPS stimulation is important for the production of IL-1beta via the PI3K/JNK cascade. Thus JAK2 plays a pivotal role in LPS-induced signaling in macrophages.

Animals↗
PubMed2003

Human plasma platelet-activating factor acetylhydrolase binds to all the murine lipoproteins, conferring protection against oxidative stress.

OBJECTIVE: Plasma platelet-activating factor (PAF) acetylhydrolase (AH) is an enzyme bound with lipoproteins that degrades not only PAF but also PAF-like oxidized phospholipids that are proposed to promote atherosclerosis. In this study, we investigated the distribution of PAF-AH protein among lipoprotein classes by using adenovirus-mediated gene transfer in mice, and we examined its effects on lipoprotein oxidation and foam cell formation of macrophages. METHODS AND RESULTS: Adenovirus-mediated overexpression of PAF-AH in mice resulted in a 76- to 140-fold increase in plasma PAF-AH activity. Contrary to the previous report, overexpressed human PAF-AH protein was bound to very low density lipoprotein, intermediate density lipoprotein, low density lipoprotein, and high density lipoprotein (HDL). All the lipoproteins with overexpressed human PAF-AH revealed more resistance against oxidative stress, which was associated with lower levels in autoantibody against oxidized low density lipoprotein in the plasma. In addition, HDL with human PAF-AH inhibited foam cell formation and facilitated cholesterol efflux in macrophages. CONCLUSIONS: These results suggest that human plasma PAF-AH exerts an antiatherogenic effect by binding to all the lipoproteins and thereby protecting them from oxidation, producing less proatherogenic lipoproteins and preserving HDL functions.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed2003

Glucose metabolism and glutamate analog acutely alkalinize pH of insulin secretory vesicles of pancreatic beta-cells.

We studied acute changes of secretory vesicle pH in pancreatic beta-cells with a fluorescent pH indicator, lysosensor green DND-189. Fluorescence was decreased by 0.66 +/- 0.10% at 149 +/- 16 s with 22.2 mM glucose stimulation, indicating that vesicular pH was alkalinized by approximately 0.016 unit. Glucose-responsive pH increase was observed when cytosolic Ca2+ influx was blocked but disappeared when an inhibitor of glycolysis or mitochondrial ATP synthase was present. Glutamate dimethyl ester (GME), a plasma membrane-permeable analog of glutamate, potentiated glucose-stimulated insulin secretion at 5 mM without changing cellular ATP content or cytosolic Ca2+ concentration ([Ca2+]). Application of GME at basal glucose concentration decreased DND-189 fluorescence by 0.83 +/- 0.19% at 38 +/- 2 s. These results indicated that the acutely alkalinizing effect of glucose on beta-cell secretory vesicle pH was dependent on glucose metabolism but independent of modulations of cytosolic [Ca2+]. Moreover, glutamate derived from glucose may be one of the mediators of this alkalinizing effect of glucose, which may have potential relevance to the alteration of secretory function by glutamate.

Adenosine Triphosphate↗
PubMed2003

Isoform-dependent cholesterol efflux from macrophages by apolipoprotein E is modulated by cell surface proteoglycans.

OBJECTIVE: Apolipoprotein E (apoE) mediates cellular cholesterol efflux and plays a crucial role in the inhibition of atherogenesis. We investigated whether there is an isoform-specific difference in its function for cholesterol efflux from cholesterol-loaded RAW264.7 cells, a murine macrophage cell line that lacks endogenous apoE expression. METHODS AND RESULTS: When human apoE was expressed in RAW264.7 cells, apoE2 reduced cellular total cholesterol (TC) and esterified cholesterol (EC) levels significantly, whereas apoE3 and apoE4 had no effect. However, treatment of cells with 4-methylumbelliferyl-7-beta-D-xyloside (beta-DX) resulted in all 3 isoforms' reducing cellular TC and EC contents significantly. We also investigated the effect of exogenously derived apoE on cholesterol efflux by utilizing the medium harvested from HeLa cells expressing apoE. ApoE2 and E3 reduced both cellular TC and EC contents significantly, whereas apoE4 did not. However, treatment of the cells with beta-DX resulted in all 3 exogenously derived apoE isoforms' reducing TC and EC contents significantly. The binding ability of apoE to heparan sulfate proteoglycans examined by heparinase I treatment revealed less binding ability of apoE2 compared with that of apoE3 or apoE4. CONCLUSIONS: The present study clarified the differential cellular cholesterol-modulating effect of apoE isoforms in macrophages, which would be due to the difference in their binding to proteoglycans.

Adenoviridae↗
PubMed2003

Effect of constituting amino acid residue numbers on molecularly imprinted chiral recognition sites.

In the present study, the effect of constituting amino acid residue numbers of oligopeptide derivatives, which are candidate materials to construct molecular recognition sites, on chiral recognition ability was investigated. Chiral recognition sites were formed from oligopeptide derivatives, of which constituting amino acid residue numbers were three to six, by adopting an alternative molecular imprinting. It was made clear that the number four, in other words, the tetrapeptide derivative, is the best candidate material to form a chiral recognition site.

Amino Acids↗
PubMed2003

Evaluation of intra-aneurysmal blood flow by digital subtraction angiography: blood flow change after coil embolization.

BACKGROUND: The natural course of cerebral aneurysms is related to many factors, and it is very important that intra-aneurysmal blood flow is considered. Our group developed a method that allowed the simultaneous evaluation of blood flow in human cerebral aneurysms using digital subtraction angiography (DSA) with no special devices. The intra-aneurysmal blood flow measurement would also be very useful for coil embolization. Since the Guglielmi detachable coil (GDC) was developed, many patients with cerebral aneurysm have been treated with GDC, but coil compaction has sometimes caused a problem after the coil embolization of a cerebral aneurysm. We believed that an intra-aneurysmal flow measurement would suggest the final result of embolization during the procedure. METHODS: We performed DSA to examine 17 aneurysms in 17 patients. The video signal of serial DSA images was stored on a personal computer, and time-density curves were obtained for each individual pixel. The formula, determined by a two-exponential model, was fitted to the time-density curve 1000 times by least square approximation for each individual pixel. We indirectly substituted the coefficient of the flow-in curve for the blood flow. We were therefore able to display the distribution of intra-aneurysmal blood flow in color. We could compare the blood flow in each portion of the cerebral aneurysm and parent artery during coil embolization. RESULTS: The blood flow k(a) in a small aneurysm was faster than that in a large aneurysm, and it slowed in accordance with the coil embolization. The blood flow in a large aneurysm was sometimes accelerated by incomplete coil embolization. CONCLUSION: We can detect the flow distribution in cerebral aneurysms and the flow change during coil embolization, using existing equipment. Our method would be useful in elucidating the natural history of cerebral aneurysms, treating cerebral aneurysms with coils, and following patients after treatment.

Aged↗
PubMed2003

"All-in-One Assay", a direct phenotypic anti-human immunodeficiency virus type 1 drug resistance assay for three-drug combination therapies that takes into consideration in vivo drug concentrations.

A novel phenotypic anti-human immunodeficiency virus type 1 (HIV-1) drug resistance assay is described. Three drugs at concentrations equivalent to those determined in in vivo pharmacokinetics, were mixed in a well, serially diluted by 10-folds, and added to incubations of clinical HIV-1 isolates and CCR-5 expressing HeLa/CD4+ cells which was previously reported as the MAGIC-5 cells (Antimicrob. Agents Chemother. 45 (2001) 495) to determine the 95% inhibitory dilution (ID(95)) of the combination regimens. The ID(95) of efavirenz (EFV)-containing regimens was ten-times lower than that of nevirapine (NVP)-containing regimens against HIV-1 isolated from antiviral therapy naive patients. However, the difference was not apparent by the conventional fold resistance measurement based on the 50% inhibitory concentration. Furthermore, the synergistic effects of drug combinations against clinical HIV-1 isolates can be evaluated by our assay. The ID(95)s of EFV- and nelfinavir (NFV)- containing regimens against HIV-1 from naive patients were less than 0.01 whereas those against resistant viruses were over 0.05, although the clinical cut-off values are to be determined in larger clinical studies. Our assay, designated "All-in-One Assay", that can examine resistance to three drugs simultaneously under consideration of in vivo drug concentrations described above might be useful in practice.

Anti-HIV Agents↗
PubMed2003

A case showing an association between type 1 diabetes mellitus and Kabuki syndrome.

The case of a 31-year-old female suffering from type 1 diabetes mellitus (DM) and Kabuki syndrome is presented. The patient was diagnosed as having impaired glucose tolerance (IGT) at age 18; secondary amenorrhea occurred at age 20, following acute body weight loss. Extensive examination revealed the patient to have a slowly progressive form of type 1 DM and, based on the physical findings, including her facial features, she was diagnosed as also having congenital Kabuki syndrome. Since then, this patient has experienced several episodes of diabetic ketoacidosis, all of which were brought about by prolonged bronchial infection. Although it is perhaps reasonable at present to consider this case to represent a chance association, further clinical investigations will be carried out to clarify whether or not Kabuki syndrome and type 1 DM have any common pathogenic features.

Adult↗
PubMed2003

Serum lipid profile of patients with genotype 1b hepatitis C viral infection in Japan.

Hepatitis C virus (HCV) infection is associated with the development of steatosis in the liver. Recently, infection with genotype 3a HCV has been reported to have a closer association with hepatic steatosis than that with genotype 1 or 2 HCV. Moreover, infection with genotype 3a HCV but not with genotype 1 has been shown to be associated with serum hypocholesterolemia or hypobetalipoproteinemia in European countries. We conducted a case control study to characterize the serum lipid profile in patients infected with genotype 1b HCV, which is the most prevalent HCV genotype in Japan. These patients had significantly lower serum cholesterol levels than those infected with HBV or genotype 2a HCV who had similar liver disease progression and body mass index. Further analysis of serum apolipoproteins revealed that not only apolipoprotein B but also apolipoprotein CII and apolipoprotein CIII levels were significantly reduced, while apolipoprotein AI, AII and E levels were similar in patients infected with genotype 1b HCV and those with HBV or genotype 2a HCV. These results indicate that, in Japan, infection with genotype 1b HCV is a cause of lipid metabolism disturbances, which may be associated with the pathogenesis of hepatitis C liver disease.

Journal Article↗
PubMed2003

Primary nelfinavir (NFV)-associated resistance mutations during a follow-up period of 108 weeks in protease inhibitor naïve patients treated with NFV-containing regimens in an HIV clinic cohort.

BACKGROUND: Nelfinavir (NFV) is a widely prescribed HIV-1 specific protease inhibitor (PI). However, there are only a few reports that have described the long-term effects of NFV-containing regimens, especially with regard to the emergence of drug resistance in inner-city clinics. OBJECTIVES: The aim of this study was to investigate the clinical and virologic responses to treatment with NFV-containing regimens for up to 108 weeks and determine the timing and rate of emergence of primary NFV-resistance associated mutations in daily clinical practice. STUDY DESIGN: A cohort study in an inner-city clinic. Our study included 51 consecutive patients who were PI-nai;ve and commenced therapy in February 1997 through April 1999. RESULTS AND CONCLUSIONS: The proportions of patients who continued the same therapeutic regimen and showed virologic success (viral load <400 copies/ml) up to 108 weeks were 78 and 63%, respectively, based on intent-to-treat analysis. Among patients with a viral load persistently >400 copies/ml at week 12 (n=30), 11 developed primary NFV-resistance associated mutations by 108 weeks (stratified log-rank test; P<0.05). The Cox proportional hazard model showed that prior use of reverse transcriptase inhibitors (n=22) (relative hazard (RH); 2.10, 95% CI; 0.67-6.62), prior AIDS diagnosis (n=6) (RH; 1.70, 95% CI; 0.37-7.77), CD4 < 200/microl at baseline (n=19) (RH; 2.48, 95% CI; 0.78-7.81) and viral load >30,000 copies/ml at baseline (n=21) (RH; 2.10, 95% CI; 0.67-6.62) were not independent predictors of the NFV-resistance, although some tendency was noted. In total, 77% of the patients continued NFV-containing treatment without the NFV-resistance for 108 weeks. The viral load at week 12 could be used as a predictor of treatment success in our cohort study.

Adult↗
PubMed2003

Cytoskeletal reorganization induced by insulin: involvement of Grb2/Ash, Ras and phosphatidylinositol 3-kinase signalling.

BACKGROUND: Cytoskeletal reorganization is important for a wide variety of insulin-mediated biological actions, including cell growth, migration and metabolism, but the intracellular signalling pathways leading to insulin-induced cytoskeletal reorganization have largely been unknown. We therefore investigated the involvement of Grb2/Ash-Ras and phosphatidylinositol (PI) 3-kinase in the insulin-induced morphological changes in fibroblasts over-expressing human insulin receptors (HIRcB cells). RESULTS: Insulin, as well as 12-O-tetradecanoylphorbol-13-acetate (TPA) and 8-bromo-cAMP, induced a unique morphological change associated with actin cytoskeletal reorganization characterized by the disruption of actin stress fibres and thicker actin bundle formation. Microinjection of an anti-Grb2/Ash antibody, but not control IgG, inhibited the insulin-induced actin reorganization, whereas the TPA- and 8-bromo-cAMP-induced morphological changes were not inhibited by microinjection of the anti-Grb2/Ash antibody. In addition, microinjection of dominant negative ras p21 protein, but not the heat-treated protein, inhibited insulin-induced cytoskeletal reorganization. Microinjection of activated p21ras protein resulted in very similar cytoskeletal reorganization with actin bundle formation in the cytoplasm. The PI3-kinase inhibitor wortmannin inhibited insulin-induced cytoskeletal reorganization, but not the TPA- nor 8-bromo-cAMP-induced reorganization. Interestingly, wortmannin also inhibited the activated p21ras-induced morphological change. CONCLUSIONS: We concluded that Grb2/Ash-Ras activation and probably Ras-associated PI3-kinase activation are involved in the insulin-induced morphological change.

8-Bromo Cyclic Adenosine Monophosphate↗