I Kojima

Gunma University, Maebashi, Gunma Prefecture, Japan

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Publications (276)1156.13 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We reported recently that the taste type 1 receptor 3 (T1R3), a subunit of the sweet taste receptor, functions as a cell-surface glucose-sensing receptor in pancreatic β-cells. In the present study, we investigated the expression of T1R3 in pancreatic islets. mRNA for T1R2 and T1R3 was detected in mouse pancreatic islets. Quantitatively, the mRNA expression level of T1R2 was less than 1% of that of T1R3. Immunohistochemically, T1R3 was abundantly expressed in mouse islets whereas T1R2 was barely detected. Most immunoreactive T1R3 was colocalized with insulin and almost all β-cells were positive for T1R3. In addition, T1R3 was expressed in some portion of α-cells. Immunoreactivity of T1R3 in β-cells was markedly reduced in fed mice compared to those in fasting mice. In contrast, mRNA for T1R3 was not different in islets of fasting and fed mice. Glucose-induced insulin-secretion was higher in islets obtained from fasting mice compared to those from fed mice. The expression of T1R3 was markedly reduced in islets of ob/ob mice compared to those of control mice. Similarly, the expression of T1R3 was reduced in islet of db/db mice. In addition, the expression of T1R3 was markedly reduced in β-cells of fatty diabetic rats and GK rats, models of obese and non-obese type 2 diabetes, respectively. These results indicate that T1R3 is expressed mainly in β-cells and the expression levels are different depending upon the nutritional and metabolic conditions.
    Endocrine journal. 06/2014;
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    ABSTRACT: Androgen reduces fat mass, although the underlying mechanisms are unknown. Here, we examined the effect of testosterone on heat production and mitochondrial biogenesis. Testosterone-treated mice exhibited elevated heat production. Treatment with testosterone increased the expression level of PGC1α, ATP5B and Cox4 in skeletal muscle, but not that in brown adipose tissue and liver. mRNA levels of genes involved in mitochondrial biogenesis were elevated in skeletal muscle isolated from testosterone-treated male mice, but were down-regulated in androgen receptor deficient mice. These results demonstrated that the testosterone-induced increase in energy expenditure is derived from elevated mitochondrial biogenesis in skeletal muscle.
    FEBS letters 04/2014; · 3.54 Impact Factor
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    ABSTRACT: Thyroid hormone stimulates erythropoietic differentiation. However, severe anemia is sometimes seen in patients with hyperthyroidism, and the mechanisms have not been fully elucidated. Bone marrow is comprised about 2-8 % oxygen, and the characteristics of hematopoietic stem cells have been shown to be influenced under hypoxia. Hypoxia-inducible factor-1 is a critical mediator of cellular responses to hypoxia and an important mediator in signal transduction of thyroid hormone [triiodothyronine (T3)]. The aim of this study was to investigate the effect of T3 on erythropoiesis under hypoxia mimicking physiological conditions in the bone marrow. We maintained human erythroleukemia K562 cells under hypoxic atmosphere (2 % O2) and examined their cellular characteristics. Compared to that under normal atmospheric conditions, cells under hypoxia showed a reduction in the proliferation rate and increase in the hemoglobin content or benzidine-positive rate, indicating promotion of erythroid differentiation. T3 had no effect on hypoxia-induced erythroid differentiation, but significantly inhibited activin A/erythroid differentiation factor-induced erythroid differentiation. Moreover, GATA2 mRNA expression was suppressed in association with erythroid differentiation, while T3 significantly diminished that suppression. These results suggest that T3 has a direct suppressive effect on erythroid differentiation under hypoxic conditions.
    Molecular and Cellular Biochemistry 03/2014; · 2.33 Impact Factor
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    ABSTRACT: The sweet taste receptors present in the taste buds are heterodimers comprised of T1R2 and T1R3. This receptor is also expressed in pancreatic β-cells. When the expression of receptor subunits is determined in β-cells by quantitative reverse transcription polymerase chain reaction, the mRNA expression level of T1R2 is extremely low compared to that of T1R3. In fact, the expression of T1R2 is undetectable at the protein level. Furthermore, knockdown of T1R2 does not affect the effect of sweet molecules, whereas knockdown of T1R3 markedly attenuates the effect of sweet molecules. Consequently, a homodimer of T1R3 functions as a receptor sensing sweet molecules in β-cells, which we designate as sweet taste-sensing receptors (STSRs). Various sweet molecules activate STSR in β-cells and augment insulin secretion. With regard to intracellular signals, sweet molecules act on STSRs and increase cytoplasmic Ca(2+) and/or cyclic AMP (cAMP). Specifically, when an STSR is stimulated by one of four different sweet molecules (sucralose, acesulfame potassium, sodium saccharin, or glycyrrhizin), distinct signaling pathways are activated. Patterns of changes in cytoplasmic Ca(2+) and/or cAMP induced by these sweet molecules are all different from each other. Hence, sweet molecules activate STSRs by acting as biased agonists.
    Endocrinology and metabolism (Seoul, Korea). 03/2014; 29(1):12-19.
  • Article: Trpv2.
    Itaru Kojima, Masahiro Nagasawa
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    ABSTRACT: Transient receptor potential vanilloid type 2, TRPV2, is a calcium-permeable cation channel belonging to the TRPV channel family. This channel is activated by heat (>52 °C), various ligands, and mechanical stresses. In most of the cells, a large portion of TRPV2 is located in the endoplasmic reticulum under unstimulated conditions. Upon stimulation of the cells with phosphatidylinositol 3-kinase-activating ligands, TRPV2 is translocated to the plasma membrane and functions as a cation channel. Mechanical stress may also induce translocation of TRPV2 to the plasma membrane. The expression of TRPV2 is high in some types of cells including neurons, neuroendocrine cells, immune cells involved in innate immunity, and certain types of cancer cells. TRPV2 may modulate various cellular functions in these cells.
    Handbook of experimental pharmacology 01/2014; 222:247-72.
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    ABSTRACT: Activin, a member of the TGF-β superfamily, regulates cell growth and differentiation in various cell types. Activin A acts as a negative regulator of renal development as well as tubular regeneration after renal injury. However, it remains unknown whether activin A is involved in renal fibrosis. To clarify this issue, we utilized a rat model of unilateral ureteral obstruction (UUO). The expression of activin A was significantly increased in the UUO kidneys compared to that in contralateral kidneys. Activin A was detected in glomerular mesangial cells and interstitial fibroblasts in normal kidneys. In UUO kidneys, activin A was abundantly expressed by interstitial α-SMA-positive myofibroblasts. Administration of recombinant follistatin, an activin antagonist, reduced the fibrotic area in the UUO kidneys. The number of proliferating cells in the interstitium, but not in the tubules, was significantly lower in the follistatin-treated kidneys. Expression of α-SMA, deposition of type I collagen and fibronectin, and CD68-positive macrophage infiltration were significantly suppressed in the follistatin-treated kidneys. These data suggest that activin A produced by interstitial fibroblasts acts as a potent profibrotic factor during renal fibrosis. Blockade of activin A action may be a novel approach for the prevention of renal fibrosis progression.
    BioMed Research International 01/2014; 2014:376191. · 2.88 Impact Factor
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    ABSTRACT: Sweet taste receptor regulates GLP-1 secretion in enteroendocrine L-cells. We investigated the signaling system activated by this receptor using Hutu-80 cells. We stimulated them with sucralose, saccharin, acesulfame K and glycyrrhizin. These sweeteners stimulated GLP-1 secretion, which was attenuated by lactisole. All these sweeteners elevated cytoplasmic cyclic AMP ([cAMP]c) whereas only sucralose and saccharin induced a monophasic increase in cytoplasmic Ca2+ ([Ca2+]c). Removal of extracellular calcium or sodium and addition of a Gq/11 inhibitor greatly reduced the [Ca2+]c responses to two sweeteners. In contrast, acesulfame K induced rapid and sustained reduction of [Ca2+]c. In addition, glycyrrhizin first reduced [Ca2+]c which was followed by an elevation of [Ca2+]c. Reductions of [Ca2+]c induced by acesulfame K and glycyrrhizin were attenuated by a calmodulin inhibitor or by knockdown of the plasma membrane calcium pump. These results indicate that various sweet molecules act as biased agonists and evoke strikingly different patterns of intracellular signals.
    Molecular and Cellular Endocrinology 01/2014; · 4.04 Impact Factor
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    ABSTRACT: While insulin acutely stimulates glucose uptake by promotion of GLUT4 translocation from intracellular compartments to the plasma membrane in adipocytes and muscles, long-term insulin stimulation causes GLUT4 depletion particularly prominent in the insulin-responsive GLUT4-storage compartment (GSC). This effect is caused mainly by accelerated lysosomal degradation of GLUT4 although the mechanism is not fully defined. Here we show that insulin acutely induced dissociation of retromer components from the low-density microsomal (LDM) membranes of 3T3-L1 adipocytes, which was accompanied by disruption of the interaction of Vps35 with sortilin. This insulin effect was dependent on the activity of protein kinase CK2 but neither phosphatidylinositol 3-kinase nor extracellular signal-regulated kinase 1/2. Knockdown of Vps26 decreased GLUT4 to a level comparable to that with insulin stimulation for 4 hours. Vps35 with a mutation in the CK2 phosphorylation motif (Vps35-Ser7Ala) was resistant to insulin-induced dissociation from the LDM membrane and its overexpression attenuated GLUT4 downregulation with insulin. Furthermore, insulin-generated hydrogen peroxide was an upstream mediator of the insulin action on retromer and GLUT4. These results suggested that insulin-generated oxidative stress switches GLUT4 sorting direction to lysosomes through inhibition of the retromer function in a CK2-dependent manner.
    Journal of Biological Chemistry 11/2013; · 4.65 Impact Factor
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    ABSTRACT: A homodimer of taste type 1 receptor 3 (T1R3) functions as a sweet taste-sensing receptor in pancreatic β-cells. This receptor is activated by various sweet molecules including sugars such as glucose. To determine the role of this receptor in glucose-induced insulin secretion, we addressed whether or not this receptor modulates glucose metabolism in MIN6 cells. We measured changes in intracellular ATP ([ATP]i) in MIN6 cells expressing luciferase. Sucralose, an agonist of T1R3, induced immediate and sustained elevation of [ATP]i in the presence of 5.5 mM glucose. The effect of sucralose was dose-dependent and, at 5 mM, was greater than that induced by 25 mM glucose. In contrast, carbachol, GLP-1 or high concentration of potassium did not reproduce the sucralose action. Sucralose facilitated the increase in [ATP]i induced by a mitochondrial fuel methylsuccinate, and potentiated glucose-induced elevation of [ATP]i. Administration of a non-metabolizable glucose analogue, 3-O-methylglucose, which acts as an agonist of T1R3, induced a small and transient increase in [ATP]i. 3-O-Methylglucose augmented elevation of [ATP]i induced by methylsuccinate, and also enhanced glucose-induced increase in [ATP]i. Knock down of T1R3 by using shRNA attenuated [ATP]i-response to high concentration of glucose and also reduced the glucose-induced insulin secretion. These results indicate that activation of the homodimer of T1R3 facilitates the metabolic pathway in mitochondria and augments ATP production. The results obtained by using 3-O-methylglucose suggest that glucose, by acting on the homodimer of T1R3, promotes its own metabolism.
    Endocrine Journal 11/2013; · 2.23 Impact Factor
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    ABSTRACT: Conophylline (CnP) is a vinca alkaloid purified from a tropical plant and inhibits activation of pancreatic stellate cells. We investigated the effect of CnP on hepatic stellate cells (HSC) in vitro. We also examined whether CnP attenuates hepatic fibrosis in vivo. We examined the effect of CnP on the expression of α-smooth muscle actin (α-SMA) and collagen-1, DNA synthesis and apoptosis in rat HSC and Lx-2 cells. We also examined the effect of CnP on hepatic fibrosis induced by thioacetamide (TAA). In rat HSC and Lx-2 cells, CnP reduced the expression of α-SMA and collagen-1. CnP inhibited DNA synthesis induced by serum. CnP also promoted activation of caspase-3 and induced apoptosis as assessed by DNA ladder formation and TUNEL assay. In contrast, CnP did not induce apoptosis in AML12 cells. We then examined the effect of CnP on TAA-induced cirrhosis. In TAA-treated rats, the surface of the liver was irregular and multiple nodules were observed. Histologically, formation of pseudolobules surrounded by massive fibrous tissues was observed. When CnP was administered together with TAA, the surface of the liver was smooth and liver fibrosis was markedly inhibited. Collagen content was significantly reduced in CnP-treated liver. Conophylline suppresses HSC and induces apoptosis in vitro. CnP also attenuates formation of the liver fibrosis induced by TAA in vivo.
    Liver international: official journal of the International Association for the Study of the Liver 09/2013; · 3.87 Impact Factor
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    ABSTRACT: The sweet taste receptor is expressed in the taste bud and is activated by numerous sweet molecules with diverse chemical structures. It is, however, not known whether these sweet agonists induce a similar cellular response in target cells. Using MIN6 cells, a pancreatic β-cell line expressing endogenous sweet taste receptor, we addressed this question by monitoring changes in cytoplasmic Ca(2+) ([Ca(2+)]i) and cAMP ([cAMP]i) induced by four sweet taste receptor agonists. Glycyrrhizin evoked sustained elevation of [Ca(2+)]i but [cAMP]i was not affected. Conversely, an artificial sweetener saccharin induced sustained elevation of [cAMP]i but did not increase [Ca(2+)]i. In contrast, sucralose and acesulfame K induced rapid and sustained increases in both [Ca(2+)]i and [cAMP]i. Although the latter two sweeteners increased [Ca(2+)]i and [cAMP]i, their actions were not identical: [Ca(2+)]i response to sucralose but not acesulfame K was inhibited by gurmarin, an antagonist of the sweet taste receptor which blocks the gustducin-dependent pathway. In addition, [Ca(2+)]i response to acesulfame K but not to sucralose was resistant to a Gq inhibitor. These results indicate that four types of sweeteners activate the sweet taste receptor differently and generate distinct patterns of intracellular signals. The sweet taste receptor has amazing multimodal functions producing multiple patterns of intracellular signals.
    Endocrine Journal 08/2013; · 2.23 Impact Factor
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    ABSTRACT: Recent evidence indicates that low oxygen tension or hypoxia alters the characteristics of stem cells. The actions of hypoxia are mediated through the hypoxia-inducible factor, a critical mediator of the cellular response to hypoxia. Adipose tissue-derived stromal cells (ASCs) are one of the most promising cell sources for tissue engineering applications. This study investigated the effect of hypoxia on ASCs in terms of the ability to proliferate and differentiate. ASCs were extracted from mice and maintained under hypoxic atmosphere (2% O2) for up to eight in vitro passages. The proliferation rate was examined as a growth curve, and the potency of differentiation was evaluated. To investigate the cell characteristics, we checked several stem-cell markers and growth factors. Compared with the normoxic state (20% O2), hypoxia enhances proliferation with an approximately six- to sevenfold higher ASC expansion over 6 weeks. The expression of Oct3/4 and Nanog (stem-cell marker) and the amount of secreted growth factors were increased under the hypoxic condition. These results suggest that low oxygen tension enhances proliferation and maintains stemness of ASCs. Thus, this study emphasizes the profitability of hypoxic culture for expansion of ASCs and maintenance of their undifferentiated state for further therapeutic use.
    BioResearch open access. 06/2013; 2(3):199-205.
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    ABSTRACT: Microorganisms and plants produce bioactive metabolites that are potentially useful in the treatment of disease. We have designed and synthesized DHMEQ as a specific inhibitor of NF-κB based on the structure of epoxyquinomicin. It directly binds to NF-κB components to inhibit DNA-binding and was shown to be endowed with inhibiting activity in various inflammatory and cancer models in experimental animals. It was also effective to improve the success of islet transplantation especially when administered to donor mice. We have also isolated from the leaves of Ervatamia microphylla conophylline, a compound that induces differentiation of beta cells from the precursor cells and was recently found to suppress islet fibrosis in diabetes model rats.
    Internal and Emergency Medicine 03/2013; · 2.35 Impact Factor
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    ABSTRACT: The mechanism that initiates regeneration of pancreatic β-cells is not clear at present. The vagal nerve is implicated in the regulation of gastrointestinal functions, glucose metabolism and proliferation of pancreatic β-cells under physiological conditions. To elucidate the triggering mechanism of the regeneration of pancreatic β-cells, we examined the involvement of the vagal nerve. To this end, we employed a rat pancreatic duct ligation (DL) model, in which profound β-cell neogenesis and β-cell proliferation were observed within a week. We administered atropine to block the vagal nerve. Administration of atropine inhibited proliferation of β-cells in both islets and islet-like cell clusters (ICC), without affecting ductal cell proliferation in the ligated pancreas. The numbers of PDX-1 and MafB-positive cells in or attaching to the ducts were significantly reduced by atropine. MafB/glucagon and MafB/insulin double-positive cells were also decreased by atropine. Finally, atropine reduced the number of MafA-positive ductal cells, all of which were positive for insulin, by 50% on day 5. These results strongly suggest that the vagal nerve is involved in β-cell proliferation, induction of endocrine progenitors and neogenesis of α- and β-cells.
    Endocrine Journal 02/2013; · 2.23 Impact Factor
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    ABSTRACT: BACKGROUND: Sweet taste receptor is expressed not only in taste buds but also in nongustatory organs such as enteroendocrine cells and pancreatic beta-cells, and may play more extensive physiological roles in energy metabolism. Here we examined the expression and function of the sweet taste receptor in 3T3-L1 cells. METHODOLOGY/PRINCIPAL FINDINGS: In undifferentiated preadipocytes, both T1R2 and T1R3 were expressed very weakly, whereas the expression of T1R3 but not T1R2 was markedly up-regulated upon induction of differentiation (by 83.0 and 3.8-fold, respectively at Day 6). The α subunits of Gs (Gαs) and G14 (Gα14) but not gustducin were expressed throughout the differentiation process. The addition of sucralose or saccharin during the first 48 hours of differentiation considerably reduced the expression of peroxisome proliferator activated receptor γ (PPARγ and CCAAT/enhancer-binding protein α (C/EBPα at Day 2, the expression of aP2 at Day 4 and triglyceride accumulation at Day 6. These anti-adipogenic effects were attenuated by short hairpin RNA-mediated gene-silencing of T1R3. In addition, overexpression of the dominant-negative mutant of Gαs but not YM-254890, an inhibitor of Gα14, impeded the effects of sweeteners, suggesting a possible coupling of Gs with the putative sweet taste-sensing receptor. In agreement, sucralose and saccharin increased the cyclic AMP concentration in differentiating 3T3-L1 cells and also in HEK293 cells heterologously expressing T1R3. Furthermore, the anti-adipogenic effects of sweeteners were mimicked by Gs activation with cholera toxin but not by adenylate cyclase activation with forskolin, whereas small interfering RNA-mediated knockdown of Gαs had the opposite effects. CONCLUSIONS: 3T3-L1 cells express a functional sweet taste-sensing receptor presumably as a T1R3 homomer, which mediates the anti-adipogenic signal by a Gs-dependent but cAMP-independent mechanism.
    PLoS ONE 01/2013; 8(1):e54500. · 3.73 Impact Factor
  • Masahiro Nagasawa, Itaru Kojima
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    ABSTRACT: The present study was conducted to investigate localization and function of TRPV2 channel in a mouse macrophage cell line, TtT/M87. We infected an adenovirus vector encoding TRPV2 tagged with c-Myc in the extracellular domain. Immunoreactivity of c-Myc epitope exposed to the cell surface formed a ring structure, which was colocalized with markers of the podosome, namely β-integrin, paxillin and Pyk2. The ring structure was also observed in TRPV2-GFP-expressing cells using total internal reflection fluorescent microscopy. Addition of formyl-Met-Leu-Phe (fMLP) increased the number of podosome and increased the intensity of the TRPV2 signal associated with the podosome. Measurement of subplasmalenmal free calcium concentration ([Ca(2+)](pm)) revealed that [Ca(2+)](pm) was elevated around the podosome. fMLP further increased [Ca(2+)](pm) in this region, which was abolished by a TRPV2 inhibitor ruthenium red. Phosphorylated Pyk2 was detected in fMLP-treated cells, and knockdown of TRPV2 reduced the expression of phospho-Pyk2. Introduction of dominant-negative Pyk2 or knockdown of TRPV2 increased the number of podosome. Conversely, elevation of [Ca(2+)](pm) by the addition of ionomycin reduced the number of podosome. These results indicate that TRPV2 is localized abundantly in the podosome and increases [Ca(2+)](pm) by the podosome. The elevation of [Ca(2+)](pm) is critical to regulate assembly of the podosome.
    Cell calcium 02/2012; 51(2):186-93. · 4.29 Impact Factor
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    ABSTRACT: Activin A is a differentiation factor for β-cells and is effective to promote β-cell neogenesis. Activin A is also an autocrine activator of pancreatic stellate cells, which play a critical role in fibrogenesis of the pancreas. Conophylline (CnP) is a natural compound, which reproduces the effect of activin on β-cell differentiation and promotes β-cell neogenesis when administered in vivo. However, its effect on stellate cells is not known. We therefore investigated the effect of CnP on stellate cells both in vitro and in vivo. Unlike activin A, CnP inhibited activation of cultured stellate cells and reduced the production of collagen. We then analyzed the involvement of stellate cells in islet fibrosis in Goto-Kakizaki (GK) rats, a model of type 2 diabetes mellitus. In pancreatic sections obtained from 6-wk-old GK rats, CD68-positive macrophages and glial fibrillary acidic protein- and α-smooth muscle actin-positive stellate cells infiltrated into islets. Later, the number of macrophages was increased, and the α-smooth muscle actin staining of stellate cells became stronger, indicating the involvement of stellate cells in islet fibrosis in GK rats. When CnP was administered orally for 4 wk, starting from 6 wk of age, invasion of stellate cells and macrophages was markedly reduced and islet fibrosis was significantly improved. The insulin content was twice as high in CnP-treated rats. These results indicate that CnP exerts antifibrotic actions both in vitro and in vivo and improves islet fibrosis in Goto-Kakizaki rats.
    Endocrinology 12/2011; 153(2):621-30. · 4.72 Impact Factor
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    ABSTRACT: GPR119 is one of the G-protein-coupled receptors expressed in pancreatic β-cells and intestinal endocrine cells. Since agonists to GPR119 stimulate glucose-dependent insulin secretion, GPR119 agonists are anticipated to promote anti-diabetic effects and control of glucose homeostasis. Here, we reported that an omega-3 unsaturated fatty acid metabolite, 5-hydroxy-eicosapentaenoic acid (5-HEPE), was a potent agonist for GPR119 and enhanced glucose-dependent insulin secretion. 5-HEPE stimulated cAMP accumulation in mouse MIN6 insulinoma cells and human HuTu80 intestinal adenocarcinoma cells. These effects were blunted by GPR119-specific siRNA. Recombinant GPR119 also responded to 5-HEPE as well as authentic agonists. Several previous reports have indicated the beneficial biological effects of omega-3 unsaturated fatty acids, and epidemiological studies have suggested that these fatty acids plays a protective role against diabetes. However, the molecular pharmacology and receptor identifications of omega-3 unsaturated fatty acids and their metabolites have not yet been well investigated. It is hoped that our findings will encourage novel investigations into the molecular relationships between omega-3 fatty acids and diabetes.
    Biochemical and Biophysical Research Communications 11/2011; 416(1-2):58-63. · 2.41 Impact Factor
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    Itaru Kojima, Yuko Nakagawa
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    ABSTRACT: The sweet taste receptor is expressed in taste cells located in taste buds of the tongue. This receptor senses sweet substances in the oral cavity, activates taste cells, and transmits the taste signals to adjacent neurons. The sweet taste receptor is a heterodimer of two G protein-coupled receptors, T1R2 and T1R3. Recent studies have shown that this receptor is also expressed in the extragustatory system, including the gastrointestinal tract, pancreatic β-cells, and glucose-responsive neurons in the brain. In the intestine, the sweet taste receptor regulates secretion of incretin hormones and glucose uptake from the lumen. In β-cells, activation of the sweet taste receptor leads to stimulation of insulin secretion. Collectively, the sweet taste receptor plays an important role in recognition and metabolism of energy sources in the body.
    Diabetes & metabolism journal 10/2011; 35(5):451-7.
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    ABSTRACT: Pancreatic acinar cells are used to study regulated exocytosis. We investigated the role of interferon regulatory factor-2 (IRF2) in exocytosis in pancreatic acinar cells. Pancreas tissues from Irf2⁺/⁺, Irf2⁺/⁻), and Irf2⁻/⁻ mice were examined by microscopy, immunohistochemical, and immunoblot analyses; amylase secretion was quantified. We also compared salivary glands and pancreatic islets of Irf2⁻/⁻ mice with those of Irf2⁺/⁻ mice. To examine the effects of increased signaling by type I interferons, we studied pancreatic acini from Irf2⁻/⁻Ifnar1⁻/⁻ mice. The effect of IRF2 on amylase secretion was studied using an acinar cell line and a retroviral system. We studied expression of IRF2 in wild-type mice with cerulein-induced pancreatitis and changes in pancreatic tissue of Irf2⁻/⁻ mice, compared with those of Irf2⁺/⁻ mice. Irf2⁻/⁻ pancreas was white and opaque; numerous and wide-spread zymogen granules were observed throughout the cytoplasm, along with lack of fusion between zymogen granules and the apical membrane, lack of secretagogue-stimulated amylase secretion, and low serum levels of amylase and elastase-1, indicating altered regulation of exocytosis. The expression pattern of soluble N-ethylmaleimide-sensitive factor attachment protein receptors changed significantly, specifically in pancreatic acini, and was not rescued by disruption of type I interferon signaling. Down-regulation of IRF2 decreased amylase secretion in an acinar cell line. In mice with pancreatitis, levels of IRF2 were reduced. Irf2⁻/⁻ acini were partially resistant to induction of pancreatitis. IRF2 regulates exocytosis in pancreatic acinar cells; defects in this process might be involved in the early phases of acute pancreatitis.
    Gastroenterology 06/2011; 141(3):1102-1113.e1-8. · 12.82 Impact Factor

Publication Stats

5k Citations
1,156.13 Total Impact Points

Institutions

  • 1970–2014
    • Gunma University
      • • Institute for Molecular and Cellular Regulation
      • • Department of Anatomy and Cell Biology
      • • Department of Medicine and Molecular Science
      Maebashi, Gunma Prefecture, Japan
  • 2007–2010
    • Tokyo Gakugei University
      Koganei, Tōkyō, Japan
    • Boca Raton Regional Hospital
      Boca Raton, Florida, United States
  • 1982–2005
    • The University of Tokyo
      • • Department of Internal Medicine
      • • Faculty & Graduate School of Medicine
      • • Division of Internal Medicine
      Tokyo, Tokyo-to, Japan
    • National Institute of Radiological Sciences
      Tiba, Chiba, Japan
  • 2003
    • University Hospital Medical Information Network
      Edo, Tōkyō, Japan
  • 2002
    • Osaka University
      • Graduate School of Medicine
      Suika, Ōsaka, Japan
  • 1987–1988
    • Shinshu University
      • Department of Medicine
      Shonai, Nagano, Japan
  • 1984–1986
    • Yale-New Haven Hospital
      New Haven, Connecticut, United States
  • 1983
    • Mito Red Cross Hospital
      Mito-shi, Ibaraki, Japan