Midori Fujishiro

The University of Tokyo, Tōkyō, Japan

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Publications (53)188.41 Total impact

  • Diabetology and Metabolic Syndrome 12/2015; 7(1). DOI:10.1186/s13098-015-0047-y · 2.50 Impact Factor
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    ABSTRACT: Prostate cancer initially develops in an androgen-dependent manner but, during its progression, transitions to being androgen-independent in the advanced stage. Pin1, one of the peptidyl-prolyl cis/trans isomerases, is reportedly overexpressed in prostate cancers and is considered to contribute to accelerated cell growth, which may be one of the major factors contributing to their androgen-independent growth. Thus, we investigated how Pin1 modulates the gene expressions in both androgen-dependent and androgen-independent prostate cancer cell lines using microarray analysis. In addition, the effects of Juglone, a commercially available Pin1 inhibitor were also examined. Two prostate cancer cell-lines, LNCaP (androgen-dependent) and DU145 (androgen-independent), were treated with Pin1 siRNA and its effects on gene expressions were analyzed by microarray. Individual gene regulations induced by Pin1 siRNA or the Pin1 inhibitor Juglone were examined using RT-PCR. In addition, the effects of Juglone on the growth of LNCaP and DU145 transplanted into mice were investigated. Microarray analysis revealed that transcriptional factors regulated by Pin1 differed markedly between LNCaP and DU145 cells, the only exception being that Nrf was regulated in the same way by Pin1 siRNA in both cell lines. Despite this marked difference in gene regulations, Pin1 siRNA and Juglone exert a strong inhibitory effect on both the LNCaP and the DU145 cell line, suppressing in vitro cell proliferation as well as tumor enlargement when transplanted into mice. Despite Pin1-regulated gene expressions differing between these two prostate cancer cell-lines, LNCaP (androgen-dependent) and DU145 (androgen-independent), Pin1 inhibition suppresses proliferation of both cell-lines. These findings suggest the potential effectiveness of Pin1 inhibitors as therapeutic agents for prostate cancers, regardless of their androgen sensitivity.
    PLoS ONE 06/2015; 10(6):e0127467. DOI:10.1371/journal.pone.0127467 · 3.53 Impact Factor
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    ABSTRACT: Dipeptidyl peptidase 4 (DPP-4) expression in visceral adipose tissue is reportedly increased in obese patients, suggesting an association of DPP-4 with inflammation. In this study, first, lipopolysaccharide (LPS)- or palmitate-induced elevations of inflammatory cytokine mRNA expressions in RAW264.7 macrophages were shown to be significantly suppressed by co-incubation with a DPP-4 inhibitor, anagliptin (10µM), despite low DPP-4 expression in the RAW264.7 cells. Regarding the molecular mechanism, LPS-induced degradation of IκBα and phosphorylations of p65, JNK and p38, as well as NF-κB and AP-1 promoter activities, were revealed to be suppressed by incubation with anagliptin, indicating suppressive effects of anagliptin on both NF-κB and AP-1 signaling pathways. Anagliptin also acted on 3T3-L1 adipocytes, weakly suppressing the inflammatory cytokine expressions induced by LPS and TNF-α. When 3T3-L1 and RAW cells were co-cultured and stimulated with LPS, the effects of anagliptin on the suppression of cytokine expressions in 3T3-L1 adipocytes were more marked, and became evident at the 10µM concentration. Anti-inflammatory effects of anagliptin were also observed in vivo on the elevated hepatic and adipose expressions and serum concentrations of inflammatory cytokines in association with the suppression of hepatic NF-κB transcriptional activity, in LPS-infused mice. Taking these observations together, the anti-inflammatory properties of anagliptin may be beneficial in terms of preventing exacerbation of diabetes and cardiovascular events. Copyright © 2015, American Journal of Physiology - Endocrinology and Metabolism.
    AJP Endocrinology and Metabolism 05/2015; DOI:10.1152/ajpendo.00553.2014 · 4.09 Impact Factor
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    ABSTRACT: Xanthine oxidase (XO) is an enzyme involved in the production of uric acid (UA) from purine nucleotides. Numerous recent studies have revealed the prevalence of metabolic syndrome including non-alcoholic fatty liver disease (NAFLD) or steatohepatitis (NASH) to be related to hyperuricemia. However, it remains unclear whether elevated serum UA during the development of NAFLD or NASH is a cause or a consequence of these diseases. In this study, the XO inhibitor febuxostat was administered to two types of NASH model mice. Febuxostat exerted a strong protective effect against NASH development induced by a high fat diet containing trans fatty acid (HFDT). In contrast, methionine choline-deficient (MCD)-diet-induced NASH development not accompanied by hyperuricemia showed no UA normalization, suggesting that the ameliorating effect of febuxostat occurs via the normalization of hyperuricemia itself and/or accompanying molecular mechanism(s) such as oxidative stress. In the HFDT-fed mice, hyperuricemia, elevated alanine aminotransferase and increased Tunnel-positive cells in the liver were normalized by febuxostat administration. In addition, upregulation of fatty acid oxidation-related genes, fibrotic change and increases in collagen deposition, inflammatory cytokine expressions and lipid peroxidation in the HFDT-fed mice were also normalized by febuxostat administration. Taken together, these observations indicate that administration of febuxostat has a protective effect against HFDT-induced NASH development, suggesting the importance of XO in its pathogenesis. Thus, XO inhibitors are potentially potent therapies for patients with NASH particularly that associated with hyperuricemia. Copyright © 2014, American Journal of Physiology- Gastrointestinal and Liver Physiology.
    AJP Gastrointestinal and Liver Physiology 05/2015; DOI:10.1152/ajpgi.00443.2014 · 3.74 Impact Factor
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    ABSTRACT: Nonalcoholic steatohepatitis (NASH) is a disorder characterized by hepatic lipid accumulation followed by the inflammation-induced death of hepatocytes and fibrosis. In this process, oxidative stress contributes to the induction of several inflammatory cytokines including TNF-α and IL-1β in macrophages, while, in hepatocytes, NF-κB reportedly induces the expressions of cell survival genes for protection from apoptosis. Recently, it was reported that the new ubiquitin ligase complex termed linear ubiquitin chain assembly complex (LUBAC), composed of SHARPIN (SHANK-associated RH domain-interacting protein), HOIL-1L (longer isoform of heme-oxidized iron-regulatory protein 2 ubiquitin ligase-1), and HOIP (HOIL-1L interacting protein), forms linear ubiquitin on NF-κB essential modulator (NEMO) and thereby induces NF-κB pathway activation. In this study, we demonstrated the formation of LUBAC to be impaired in the livers of NASH rodent models produced by methionine and choline deficient (MCD) diet feeding, first by either gel filtration or Blue Native-PAGE, with subsequent confirmation by western blotting. The reduction of LUBAC is likely to be attributable to markedly reduced expression of SHARPIN, one of its components. Thus, impaired LUBAC formation, which would result in insufficient NF-κB activation, may be one of the molecular mechanisms underlying the enhanced apoptotic response of hepatocytes in MCD diet-induced NASH livers.
    Mediators of Inflammation 01/2015; 2015:1-10. DOI:10.1155/2015/125380 · 2.42 Impact Factor
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    ABSTRACT: Several lines of evidence have suggested a role of gut microbiota in the etiology of non-alcoholic steatohepatitis (NASH). NASH subjects reportedly showed a prolonged orocecal transit time coexistent with small intestinal bacterial overgrowth. We considered the possibility that enhanced gastrointestinal motility would influence gut microbiota and thus investigated the effects of the gastroprokinetic agent mosapride citrate (MC) on gut microbiota and the development of NASH using a methionine-choline deficient (MCD) diet-fed rodent model. Mice were divided into three groups, given the normal chow diet (NCD), the MCD diet or the MCD diet containing 10 mg/kg/day of MC (MCD plus MC) for 6 weeks. NASH development was evaluated based on hepatic histochemical findings, serum parameters and various mRNA and/or protein expression levels. MC treatment suppressed MCD diet-induced NASH development, with reduced serum lipopolysaccharide and increased plasma glucagon-like peptide-1 (GLP-1) concentrations. Calculation of the relative abundance of each strain based on gut microbiota analyses indicated lactic acid bacteria specifically, such as Bifidobacterium and Lactobacillus, in feces to be decreased in the MCD, as compared with the NCD group. Interestingly, the reduction in lactic acid bacteria in the MCD diet group was reversed in the MCD plus MC group. In addition, colon inflammation observed in the MCD diet group was reduced in the MCD plus MC group. Therefore, MC showed a protective effect against MCD diet-induced NASH development in our rodent model, with possible involvements of increased fecal lactic acid bacteria, protection against colon inflammation and elevated plasma GLP-1. Copyright © 2014, American Journal of Physiology- Gastrointestinal and Liver Physiology.
    AJP Gastrointestinal and Liver Physiology 11/2014; 308(2):ajpgi.00198.2014. DOI:10.1152/ajpgi.00198.2014 · 3.74 Impact Factor
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    ABSTRACT: Hypoglycemia is a cause of considerable morbidity. Although septic shock produces hypoglycemia and has been associated with higher mortality, hypoglycemia in infection without sepsis has not been reported in the literature. A 72-year-old Japanese woman treated with high-dose glucocorticoids for autoimmune hemolytic anemia, as well as intensive insulin therapy for type 2 diabetes, presented with severe hypoglycemia. A lung abscess was diagnosed by imaging studies and treated with intravenous antibiotics. Hypoglycemia spontaneously recurred during lung abscess exacerbations, despite appropriate de-escalation of antidiabetic therapy. Only mild sporadic episodes of hypoglycemia occurred after the lung abscess was controlled. Infection accompanied with malnutrition and immunosuppression, although in the absence of sepsis, may have contributed to hypoglycemia. Caution is warranted in the management of hypoglycemia in patients with diabetes with the conditions described here, that is malnutrition and immunosuppression, as infection may be a contributing factor.
    Journal of Medical Case Reports 02/2014; 8(1):51. DOI:10.1186/1752-1947-8-51
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    ABSTRACT: Gut microbiota alternations are associated with various disorders. In this study, gut microbiota changes were investigated in a methionine-choline deficient (MCD) diet-induced non-alcoholic steatohepatitis (NASH) rodent model, and the effects of administering Lactobacillus casei strain Shirota (LcS) on the development of NASH were also investigated. Mice were divided into three groups, given the normal chow diet (NCD), MCD diet, or the MCD diet plus daily oral administration of LcS for 6 weeks. Gut microbiota analyses for the three groups revealed that lactic acid bacteria such as Bifidobacterium and Lactobacillus in feces were markedly reduced by the MCD diet. Interestingly, oral administration of LcS to MCD diet-fed mice increased not only the L.casei subgroup but also other lactic acid bacteria. Subsequently, NASH development was evaluated based on hepatic histochemical findings, serum parameters and various mRNA and/or protein expression levels. LcS intervention markedly suppressed MCD-diet induced NASH development, with reduced serum lipopolysaccharide concentrations, suppression of inflammation and fibrosis in the liver, and reduced colon inflammation. Therefore, reduced populations of lactic acid bacteria in the colon may be involved in the pathogenesis of MCD diet-induced NASH, suggesting normalization of gut microbiota to be effective for treating NASH.
    AJP Gastrointestinal and Liver Physiology 10/2013; 305(12). DOI:10.1152/ajpgi.00225.2013 · 3.74 Impact Factor
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    ABSTRACT: Pin1 and Par14 are parvulin-type peptidyl prolyl cis/trans isomerases. While numerous proteins have been identified as Pin1 substrates, the target proteins of Par14 remain largely unknown. Par14 expression levels are increased in the livers and embryonic fibroblasts of Pin1 KO mice, suggesting a compensatory relationship between the functions of Pin1 and Par14. In this study, first, the association of Par14 with IRS-1 was demonstrated in HepG2 cells overexpressing both as well as endogenously in the mouse liver. The analysis using deletion-mutated Par14 and IRS-1 constructs revealed the N-terminal portion containing the basic domain of Par14 and the two relatively C-terminal portions of IRS-1 to be involved in these associations, in contrast to the WW domain of Pin1 and the SAIN domain of IRS-1. Par14 overexpression in HepG2 markedly enhanced insulin-induced IRS-1 phosphorylation and its downstream events; PI 3-kinase binding with IRS-1 and Akt phosphorylation. In contrast, treating HepG2 cells with Par14 siRNA suppressed these events. In addition, overexpression of Par14 in the insulin-resistant ob/ob mouse liver by adenoviral transfer significantly improved hyperglycemia with normalization of hepatic PEPCK and G6Pase mRNA levels, and gene suppression of Par14 using shRNA adenovirus significantly exacerbated the glucose intolerance in Pin1 KO mice. Therefore, although Pin1 and Par14 associate with different portions of IRS-1, the prolyl cis-trans isomerization in multiple sites of IRS-1 by these isomerases appears to be critical for efficient insulin receptor-induced IRS-1 phosphorylation. This process is likely to be one of the major mechanisms regulating insulin sensitivity and also constitutes a potential therapeutic target for novel insulin-sensitizing agents.
    Journal of Biological Chemistry 05/2013; DOI:10.1074/jbc.M113.485730 · 4.60 Impact Factor
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    ABSTRACT: OBJECTIVE: Resistin-like molecule (RELM) β is a secretory protein homologous to resistin and reportedly contributes to local immune response regulation in gut and bronchial epithelial cells. However, we found that activated macrophages also express RELMβ and thus investigated the role of RELMβ in the development of atherosclerosis. APPROACH AND RESULTS: It was demonstrated that foam cells in atherosclerotic lesions of the human coronary artery abundantly express RELMβ. RELMβ knockout ((-/-)) and wild-type mice were mated with apolipoprotein E-deficient background mice. RELMβ(-/-) apolipoprotein E-deficient mice exhibited less lipid accumulation in the aortic root and wall than RELMβ(+/+) apolipoprotein E-deficient mice, without significant changes in serum lipid parameters. In vitro, RELMβ(-/-) peritoneal macrophages (PCPMs) exhibited weaker lipopolysaccharide-induced nuclear factor-κB classical pathway activation and inflammatory cytokine secretion than RELMβ(+/+), whereas stimulation with RELMβ upregulated inflammatory cytokine expressions and increased expressions of many lipid transporters and scavenger receptors in PCPMs. Flow cytometric analysis revealed inflammatory stimulation-induced RELMβ in F4/80(+) CD11c(+) PCPMs. In contrast, the expressions of CD11c and tumor necrosis factor were lower in RELMβ(-/-) PCPMs, but both were restored by stimulation with recombinant RELMβ. CONCLUSIONS: RELMβ is abundantly expressed in foam cells within plaques and contributes to atherosclerosis development via lipid accumulation and inflammatory facilitation.
    Arteriosclerosis Thrombosis and Vascular Biology 05/2013; 33(8). DOI:10.1161/ATVBAHA.113.301546 · 5.53 Impact Factor
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    ABSTRACT: The dynamic process of adipose differentiation involves stepwise expressions of transcription factors and proteins specific to the mature fat cell phenotype. In this study, it was revealed that expression levels of IntS6 and IntS11, subunits of the Integrator complex, were increased in 3T3-L1 cells in the period when the cells reached confluence and differentiated into adipocytes, while being reduced to basal levels after the completion of differentiation. Suppression of IntS6 or IntS11 expression using siRNAs in 3T3-L1 preadipocytes markedly inhibited differentiation into mature adipocytes, based on morphological findings as well as mRNA analysis of adipocyte-specific genes such as Glut4, perilipin and Fabp4. Although Pparγ2 protein expression was suppressed in IntS6 or IntS11-siRNA treated cells, adenoviral forced expression of Pparγ2 failed to restore the capacity for differentiation into mature adipocytes. Taken together, these findings demonstrate that increased expression of Integrator complex subunits is an indispensable event in adipose differentiation. Although further study is necessary to elucidate the underlying mechanism, the processing of U1, U2 small nuclear RNAs may be involved in cell differentiation steps.
    Biochemical and Biophysical Research Communications 03/2013; 434(2). DOI:10.1016/j.bbrc.2013.03.029 · 2.28 Impact Factor
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    ABSTRACT: Inflammation involving adipose tissue is regarded as one of the major molecular mechanisms underlying obesity-related insulin resistance. Recent studies have suggested a series of angiotensin II receptor blockers (ARBs) to improve insulin resistance or protect against the development of diabetes mellitus. We previously demonstrated that valsartan suppresses the inflammatory response of macrophages. Interestingly, however, this effect did not occur via peroxisome proliferator-activated receptor (PPAR) γ or the AT1a receptor. This suppression appears to secondarily lead to amelioration of insulin resistance and reductions in abnormal gene expressions in adipocytes. In addition to these in vitro findings, we herein demonstrate the in vivo effects of valsartan, using mice constitutively infused with lipopolysaccharide (LPS) for 4 weeks. Oral administration of valsartan to LPS-infused mice normalized the increased expressions of inflammatory cytokines in adipose and liver tissues. These results raise the possibility that valsartan not only contributes to normalization of obesity-related insulin resistance, but is also beneficial for the treatment of other diseases with inflammation related to the metabolic syndrome such as atherosclerosis and non-alcoholic steatohepatitis. Further study is necessary to clarify these issues.
    01/2013; 2(1):28-32. DOI:10.4161/adip.21837
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    ABSTRACT: Non-alcoholic steatohepatitis (NASH) is a disorder characterized by simultaneous fat accumulation and chronic inflammation in the liver. In this study, Pin1 expression was revealed to be markedly increased in the livers of mice with MCDD (Methionine choline-deficient diet)-induced NASH, a rodent model of NASH. In addition, Pin1 KO mice were highly resistant to MCDD-induced NASH, based on a series of data showing simultaneous fat accumulation, chronic inflammation and fibrosis in the liver. In terms of Pin1-induced fat accumulation, it was revealed that the expression levels of PPARα and its target genes were higher in the livers of Pin1 KO mice than in controls. Thus, resistance of Pin1 KO mice to hepatic steatosis is partially attributable to lack of Pin1-induced down-regulation of PPARα, although multiple other mechanisms are apparently involved. Another mechanism involves the enhancing effect of hematopoietic Pin1 on the expressions of inflammatory cytokines such as tumor necrosis factorαand monocyte chemoattractant protein 1 through NF-κB activation, eventually leading to hepatic fibrosis. Finally, to distinguish the roles of hematopoietic or non-hematopoietic Pin1 in NASH development, mice lacking Pin1 in either non-hematopoietic or hematopoietic cells were produced by bone marrow transplantation between wild-type and Pin1 KO mice. The mice having non-hematopoietic Pin1 exhibited fat accumulation without liver fibrosis on the MCD diet. Thus, hepatic Pin1 appears to be directly involved in the fat accumulation in hepatocytes, while Pin1 in hematopoietic cells contribute to inflammation and fibrosis. In summary, this is the first study to demonstrate that Pin1 plays critical roles in NASH development. This report also raises the possibility that hepatic Pin1 inhibition to the appropriate level might provide a novel therapeutic strategy for NASH.
    Journal of Biological Chemistry 10/2012; 287(53). DOI:10.1074/jbc.M112.397133 · 4.60 Impact Factor
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    ABSTRACT: Macrophages in adipose tissue reportedly play a major role in the development of insulin resistance and chronic inflammation associated with obesity. On the other hand, several clinical trials have revealed angiotensin II receptor blockers (ARBs) to improve insulin resistance. In this study, we analyzed the gene expression profile of 3T3-L1 adipocytes co-cultured with LPS-treated RAW264.7 macrophages in the presence or the absence of the angiotensin receptor 1 blocker valsartan, for 4, 8, 12 and 24 h. The genes of which expressions were affected by LPS-treated RAW macrophages but normalized by co-addition of valsartan were analyzed using KeyMolnet Lite. They included many NF-κB, thyroid receptor and AP-1 target transcripts. In addition, the expression patterns of caspases, integrins, matrix metallopeptidases and adipogenic genes, altered by co-culture with LPS-treated RAW cells, were generally normalized by valsartan treatment. In light of these data, it is reasonable to consider valsartan to normalize altered gene expression patterns in adipose tissue infiltrated by macrophages, and to ameliorate inflammation, apoptosis and fibrotic changes of adipose tissue. Although there may be multiple mechanisms by which ARBs ameliorate insulin resistance, for example, through effects on muscle or other tissues via the circulatory system, this is the first report demonstrating that a favorable effect of valsartan involves normalization of the interaction between adipocytes and macrophages. This mechanism of valsartan action holds promise for developing treatments for obesity-related insulin resistance.
    Obesity Research & Clinical Practice 10/2012; 6(4):e288–e297. DOI:10.1016/j.orcp.2012.05.005 · 0.70 Impact Factor
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    ABSTRACT: LST8 is a component of both mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2). Herein, to examine the role of LST8, a common component of mTOR complexes, in the regulation of mTORC1 and mTORC2, first, we showed over-expression of LST8 in HepG2 to markedly enhance basal phosphorylation levels of not only p70 S6 kinase but also Akt. In contrast, LST8 knockdown by siRNA in HepG2 decreased phosphorylation levels of both p70 S6 kinase and Akt. These results indicate the LST8 expression level to determine basal mTORC1 and mTORC2 activities, since LST8 appears to be the component present at the lowest level in both mTORC1 and mTORC2 complexes. Previously, we reported S6 kinase phosphorylation to be reduced by over-expression of the Cterminally deleted Raptor mutant (Raptor-ΔCT) not binding to mTOR or LST8, while phosphorylation levels of Akt were markedly enhanced with no alteration in IRS-1 phosphorylation or PI 3-kinase activity. Using Raptor-ΔCT, we investigated the competition for association with LST8 between mTORC1 and mTORC2. Over-expression of Raptor-ΔCT abolished formation of the Raptor, S6 kinase, mTOR and LST8 complex, while the amount of LST8 in the Rictor-mTOR complex was increased. Therefore, it is likely that Raptor-mTOR and Rictor-mTOR complexes compete for association with LST8, and this mechanism may contribute to the reciprocal negative regulations of mTORC1 and mTORC2 activities, in terms of their LST8 components.:
    Obesity Research & Clinical Practice 07/2012; 6(3):e175-e262. DOI:10.1016/j.orcp.2011.10.002 · 0.70 Impact Factor
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    ABSTRACT: Hyperuricemia is common in patients with metabolic syndrome. We investigated the role of xanthine oxidoreductase (XOR) in atherosclerosis development, and the effects of the XOR inhibitor allopurinol on this process. Oral administration of allopurinol to ApoE knockout mice markedly ameliorated lipid accumulation and calcification in the aorta and aortic root. In addition, allopurinol treatment or siRNA-mediated gene knockdown of XOR suppressed transformation of J774.1 murine macrophage cells, treated with acetylated LDL or very low density lipoprotein (VLDL) into foam cells. This inhibitory effect of allopurinol was also observed in primary cultured human macrophages. In contrast, overexpression of XOR promoted transformation of J774.1 cells into foam cells. Interestingly, SR-A1, SR-B1, SR-B II, and VLDL receptors in J774.1 cells were reduced by XOR knockdown, and increased by XOR overexpression. Conversely, expressions of ABCA1 and ABCG1 were increased by XOR knockdown and suppressed by XOR overexpression. Finally, productions of inflammatory cytokines accompanied by foam cell formation were also reduced by allopurinol administration. These results strongly suggest XOR activity and/or its expression level to contribute to macrophage foam cell formation. Thus, XOR inhibitors may be useful for preventing atherosclerosis.
    Arteriosclerosis Thrombosis and Vascular Biology 11/2011; 32(2):291-8. DOI:10.1161/ATVBAHA.111.234559 · 5.53 Impact Factor
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    ABSTRACT: Macrophages are integrated into adipose tissues and interact with adipocytes in obese subjects, thereby exacerbating adipose insulin resistance. This study aimed to elucidate the molecular mechanism underlying the insulin-sensitizing effect of the angiotensin II receptor blocker (ARB) valsartan, as demonstrated in clinical studies. Insulin signaling, i.e., insulin receptor substrate-1 and Akt phosphorylations, in 3T3-L1 adipocytes was impaired markedly by treatment with tumor necrosis factor-α (TNFα) or in the culture medium of lipopolysaccharide (LPS)-stimulated RAW 264.7 murine macrophages, and valsartan had no effects on these impairments. However, in contrast, when cocultured with RAW 264.7 cells using a transwell system, the LPS-induced insulin signaling impairment in 3T3-L1 adipocytes showed almost complete normalization with coaddition of valsartan. Furthermore, valsartan strongly suppressed LPS-induced productions of cytokines such as interleukin (IL)-1β, IL-6, and TNFα with nuclear factor-κB activation and c-Jun NH(2)-terminal kinase phosphorylation in RAW 264.7 and primary murine macrophages. Very interestingly, this effect of valsartan was also observed in THP-1 cells treated with angiotensin II type 1 (AT1) siRNA or a peroxisome proliferator-activated receptor-γ (PPARγ) antagonist as well as macrophages from AT1a receptor-knockout mice. We conclude that valsartan suppresses the inflammatory response of macrophages, albeit not via PPARγ or the AT1a receptor. This suppression appears to secondarily improve adipose insulin resistance.
    AJP Endocrinology and Metabolism 11/2011; 302(3):E286-96. DOI:10.1152/ajpendo.00324.2011 · 4.09 Impact Factor
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    ABSTRACT: Peptidyl-prolyl cis/trans isomerase NIMA-interacting 1 (Pin1) is a unique enzyme that associates with the pSer/Thr-Pro motif and catalyzes cis-trans isomerization. We identified Pin1 in the immunoprecipitates of overexpressed IRS-1 with myc and FLAG tags in mouse livers and confirmed the association between IRS-1 and Pin1 by not only overexpression experiments but also endogenously in the mouse liver. The analysis using deletion- and point-mutated Pin1 and IRS-1 constructs revealed the WW domain located in the N terminus of Pin1 and Ser-434 in the SAIN (Shc and IRS-1 NPXY binding) domain of IRS-1 to be involved in their association. Subsequently, we investigated the role of Pin1 in IRS-1 mediation of insulin signaling. The overexpression of Pin1 in HepG2 cells markedly enhanced insulin-induced IRS-1 phosphorylation and its downstream events: phosphatidylinositol 3-kinase binding with IRS-1 and Akt phosphorylation. In contrast, the treatment of HepG2 cells with Pin1 siRNA or the Pin1 inhibitor Juglone suppressed these events. In good agreement with these in vitro data, Pin1 knock-out mice exhibited impaired insulin signaling with glucose intolerance, whereas adenoviral gene transfer of Pin1 into the ob/ob mouse liver mostly normalized insulin signaling and restored glucose tolerance. In addition, it was also demonstrated that Pin1 plays a critical role in adipose differentiation, making Pin1 knock-out mice resistant to diet-induced obesity. Importantly, Pin1 expression was shown to be up-regulated in accordance with nutrient conditions such as food intake or a high-fat diet. Taken together, these observations indicate that Pin1 binds to IRS-1 and thereby markedly enhances insulin action, essential for adipogenesis.
    Journal of Biological Chemistry 06/2011; 286(23):20812-20822. · 4.60 Impact Factor
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    ABSTRACT: Glucose transporter 1 (GLUT1) is widely distributed throughout various tissues and contributes to insulin-independent basal glucose uptake. Using a split-ubiquitin membrane yeast two-hybrid system, we newly identified 4F2 heavy chain (4F2hc) as a membrane protein interacting with GLUT1. Though 4F2hc reportedly forms heterodimeric complexes between amino acid transporters, such as LAT1 and LAT2, and regulates amino acid uptake, we investigated the effects of 4F2hc on GLUT1 expression and the associated glucose uptake. First, FLAG-tagged 4F2hc and hemagglutinin-tagged GLUT1 were overexpressed in human embryonic kidney 293 cells and their association was confirmed by coimmunoprecipitation. The green fluorescent protein-tagged 4F2hc and DsRed-tagged GLUT1 showed significant, but incomplete, colocalization at the plasma membrane. In addition, an endogenous association between GLUT1 and 4F2hc was demonstrated using mouse brain tissue and HeLa cells. Interestingly, overexpression of 4F2hc increased the amount of GLUT1 protein in HeLa and HepG2 cells with increased glucose uptake. In contrast, small interfering RNA (siRNA)-mediated 4F2hc gene suppression markedly reduced GLUT1 protein in both cell types, with reduced glucose uptake. While GLUT1 mRNA levels were not affected by overexpression or gene silencing of 4F2hc, GLUT1 degradation after the addition of cycloheximide was significantly suppressed by 4F2hc overexpression and increased by 4F2hc siRNA treatment. Taken together, these observations indicate that 4F2hc is likely to be involved in GLUT1 stabilization and to contribute to the regulation of not only amino acid but also glucose metabolism.
    AJP Cell Physiology 04/2011; 300(5):C1047-54. DOI:10.1152/ajpcell.00416.2010 · 3.67 Impact Factor
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    ABSTRACT: Peptidyl-prolyl cis/trans isomerase NIMA-interacting 1 (Pin1) is a unique enzyme that associates with the pSer/Thr-Pro motif and catalyzes cis-trans isomerization. We identified Pin1 in the immunoprecipitates of overexpressed IRS-1 with myc and FLAG tags in mouse livers and confirmed the association between IRS-1 and Pin1 by not only overexpression experiments but also endogenously in the mouse liver. The analysis using deletion- and point-mutated Pin1 and IRS-1 constructs revealed the WW domain located in the N terminus of Pin1 and Ser-434 in the SAIN (Shc and IRS-1 NPXY binding) domain of IRS-1 to be involved in their association. Subsequently, we investigated the role of Pin1 in IRS-1 mediation of insulin signaling. The overexpression of Pin1 in HepG2 cells markedly enhanced insulin-induced IRS-1 phosphorylation and its downstream events: phosphatidylinositol 3-kinase binding with IRS-1 and Akt phosphorylation. In contrast, the treatment of HepG2 cells with Pin1 siRNA or the Pin1 inhibitor Juglone suppressed these events. In good agreement with these in vitro data, Pin1 knock-out mice exhibited impaired insulin signaling with glucose intolerance, whereas adenoviral gene transfer of Pin1 into the ob/ob mouse liver mostly normalized insulin signaling and restored glucose tolerance. In addition, it was also demonstrated that Pin1 plays a critical role in adipose differentiation, making Pin1 knock-out mice resistant to diet-induced obesity. Importantly, Pin1 expression was shown to be up-regulated in accordance with nutrient conditions such as food intake or a high-fat diet. Taken together, these observations indicate that Pin1 binds to IRS-1 and thereby markedly enhances insulin action, essential for adipogenesis.
    Journal of Biological Chemistry 03/2011; 286(23):20812-22. DOI:10.1074/jbc.M110.206904 · 4.60 Impact Factor

Publication Stats

1k Citations
188.41 Total Impact Points

Institutions

  • 2001–2015
    • The University of Tokyo
      • Division of Internal Medicine
      Tōkyō, Japan
  • 2008–2011
    • Hiroshima University
      • School of Medicinal Sciences
      Hiroshima-shi, Hiroshima-ken, Japan
  • 2004
    • University of Tsukuba
      Tsukuba, Ibaraki, Japan
  • 2002
    • Saitama Medical University
      Saitama, Saitama, Japan