Satoshi Nishimura

The University of Tokyo, Edo, Tōkyō, Japan

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Publications (47)299.64 Total impact

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    ABSTRACT: Stretch-induced arrhythmias are multi-scale phenomena in which alterations in channel activities and/or calcium handling lead to the organ level derangement of the heart rhythm. To understand how cellular mechano-electric coupling (MEC) leads to stretch-induced arrhythmias at the organ level, we developed stretching devices and optical voltage/calcium measurement techniques optimized to each cardiac level. This review introduces these experimental techniques of (1) optical voltage measurement coupled with a carbon-fiber technique for single isolated cardiomyocytes, (2) optical voltage mapping combined with motion tracking technique for myocardial tissue/whole heart preparations and (3) real-time calcium imaging coupled with a laser optical trap technique for cardiomyocytes. Following the overview of each methodology, results are presented. We conclude that individual MEC in cardiomyocytes can be heterogeneous at the ventricular level, especially when moderate amplitude mechanical stretches are applied to the heart, and that this heterogeneous MEC can evoke focal excitation that develops into re-entrant arrhythmias.
    Progress in Biophysics and Molecular Biology 07/2014; · 2.91 Impact Factor
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    ABSTRACT: Body weight is tightly regulated by food intake and energy dissipation, and obesity is related to decreased energy expenditure (EE). Herein, we show that nucleotide pyrophosphatase/phosphodieseterase 2 (ENPP2, autotaxin) is an adipose-derived, secreted enzyme that controls adipose expansion, brown adipose tissue (BAT) function, and EE. In mice, Enpp2 was highly expressed in visceral white adipose tissue and BAT, and is downregulated in hypertrophied adipocytes/adipose tissue. Enpp2(+/-) mice and adipocyte-specific Enpp2 knockout mice fed a high-fat diet showed smaller body weight gains and less insulin resistance than control mice fed the same diet. BAT was functionally more active, and EE was increased in Enpp2-deficient mice. In humans, ENPP2 expression in subcutaneous fat and ENPP2 levels in serum were reduced in obese subjects. Taken together, our results establish ENPP2 as an adipose-derived, secreted enzyme that regulates adipose obesity and systemic metabolism. They also suggest ENPP2 could be a useful therapeutic target for the treatment of metabolic disease.
    Diabetes 06/2014; · 7.90 Impact Factor
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    ABSTRACT: The donor-dependent supply of platelets is frequently insufficient to meet transfusion needs. To address this issue, we developed a clinically applicable strategy for the derivation of functional platelets from human pluripotent stem cells (PSCs). This approach involves the establishment of stable immortalized megakaryocyte progenitor cell lines (imMKCLs) from PSC-derived hematopoietic progenitors through the overexpression of BMI1 and BCL-XL to respectively suppress senescence and apoptosis and the constrained overexpression of c-MYC to promote proliferation. The resulting imMKCLs can be expanded in culture over extended periods (4-5 months), even after cryopreservation. Halting the overexpression of c-MYC, BMI1, and BCL-XL in growing imMKCLs led to the production of CD42b(+) platelets with functionality comparable to that of native platelets on the basis of a range of assays in vitro and in vivo. The combination of robust expansion capacity and efficient platelet production means that appropriately selected imMKCL clones represent a potentially inexhaustible source of hPSC-derived platelets for clinical application.
    Cell stem cell 02/2014; · 23.56 Impact Factor
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    ABSTRACT: Distinct B cell populations, designated regulatory B (Breg) cells, are known to restrain immune responses associated with autoimmune diseases. Additionally, obesity is known to induce local inflammation within adipose tissue that contributes to systemic metabolic abnormalities, but the underlying mechanisms that modulate adipose inflammation remain poorly understood. We identified Breg cells that produce interleukin-10 constitutively within adipose tissue. B cell-specific Il10 deletion enhanced adipose inflammation and insulin resistance in diet-induced obese mice, whereas adoptive transfer of adipose tissue Breg cells ameliorated those effects. Adipose environmental factors, including CXCL12 and free fatty acids, support Breg cell function, and Breg cell fraction and function were reduced in adipose tissue from obese mice and humans. Our findings indicate that adipose tissue Breg cells are a naturally occurring regulatory B cell subset that maintains homeostasis within adipose tissue and that Breg cell dysfunction contributes pivotally to the progression of adipose tissue inflammation in obesity.
    Cell metabolism 10/2013; · 17.35 Impact Factor
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    ABSTRACT: Hyaluronic acid (HA) has been implicated in the proliferation and metastasis of tumor cells. However, most previous studies were conducted on extracellular matrix or pericellular HA, and the role of circulating HA in vivo has not been studied. HA is rapidly cleared from the bloodstream. The scavenger receptor Stabilin-2 (Stab2) is considered a major clearance receptor for HA. Here we report a dramatic elevation in circulating HA levels in Stab2-deficient mice without any overt phenotype. Surprisingly, the metastasis of B16F10 melanoma cells to the lungs was markedly suppressed in the Stab2-deficient mice, whereas cell proliferation was not affected. Furthermore, administration of an anti-Stab2 antibody in Stab2(+) mice elevated serum HA levels and prevented the metastasis of melanoma to the lung, and also suppressed spontaneous metastasis of mammary tumor and human breast tumor cells inoculated in the mammary gland. Administration of the antibody or high-dose HA in mice blocked the lodging of melanoma cells to the lungs. Furthermore, HA at high concentrations inhibited the rolling/tethering of B16 cells to lung endothelial cells. These results suggest that blocking Stab2 function prevents tumor metastasis by elevating circulating HA levels. Stab2 may be a potential target in antitumor therapy.
    Proceedings of the National Academy of Sciences 02/2012; 109(11):4263-8. · 9.74 Impact Factor
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    ABSTRACT: The mechanism by which thrombotic vessel occlusion occurs independently of plaque development or endothelial cell (EC) disruption remains unclear, largely because of an inability to visualize the formation of thrombus, especially at the single-platelet level in real time. Here we demonstrate that rapidly developing thrombi composed of discoid platelets can be induced in the mesenteric capillaries, arterioles, and large-sized arteries of living mice, enabling characterization of the kinetics of thrombosis initiation and the multicellular interrelationships during thrombus development. Platelet aggregation without EC disruption was triggered by reactive oxygen species (ROS) photochemically induced by moderate power laser irradiation. The inflammatory cytokines TNF-α and IL-1 could be key components of the EC response, acting through regulation of VWF mobilization to the cell surface. Thrombus formation was then initiated by the binding of platelet GPIbα to endothelial VWF in our model, and this effect was inhibited by the ROS scavenger N-acetylcysteine. Actin linker talin-dependent activation of alphaIIb-beta3 integrin or Rac1 in platelets was required for late-phase thrombus stability. Our novel imaging technology illustrates the molecular mechanism underlying inflammation-based thrombus formation by discoid platelets on undisrupted ECs and suggests control of ROS could be a useful therapeutic target for the prevention of thrombotic diseases.
    Blood 11/2011; 119(8):e45-56. · 9.06 Impact Factor
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    ABSTRACT: In obese patients with type 2 diabetes, insulin delivery to and insulin-dependent glucose uptake by skeletal muscle are delayed and impaired. The mechanisms underlying the delay and impairment are unclear. We demonstrate that impaired insulin signaling in endothelial cells, due to reduced Irs2 expression and insulin-induced eNOS phosphorylation, causes attenuation of insulin-induced capillary recruitment and insulin delivery, which in turn reduces glucose uptake by skeletal muscle. Moreover, restoration of insulin-induced eNOS phosphorylation in endothelial cells completely reverses the reduction in capillary recruitment and insulin delivery in tissue-specific knockout mice lacking Irs2 in endothelial cells and fed a high-fat diet. As a result, glucose uptake by skeletal muscle is restored in these mice. Taken together, our results show that insulin signaling in endothelial cells plays a pivotal role in the regulation of glucose uptake by skeletal muscle. Furthermore, improving endothelial insulin signaling may serve as a therapeutic strategy for ameliorating skeletal muscle insulin resistance.
    Cell metabolism 03/2011; 13(3):294-307. · 17.35 Impact Factor
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    ABSTRACT: Human (h) induced pluripotent stem cells (iPSCs) are a potentially abundant source of blood cells, but how best to select iPSC clones suitable for this purpose from among the many clones that can be simultaneously established from an identical source is not clear. Using an in vitro culture system yielding a hematopoietic niche that concentrates hematopoietic progenitors, we show that the pattern of c-MYC reactivation after reprogramming influences platelet generation from hiPSCs. During differentiation, reduction of c-MYC expression after initial reactivation of c-MYC expression in selected hiPSC clones was associated with more efficient in vitro generation of CD41a(+)CD42b(+) platelets. This effect was recapitulated in virus integration-free hiPSCs using a doxycycline-controlled c-MYC expression vector. In vivo imaging revealed that these CD42b(+) platelets were present in thrombi after laser-induced vessel wall injury. In contrast, sustained and excessive c-MYC expression in megakaryocytes was accompanied by increased p14 (ARF) and p16 (INK4A) expression, decreased GATA1 expression, and impaired production of functional platelets. These findings suggest that the pattern of c-MYC expression, particularly its later decline, is key to producing functional platelets from selected iPSC clones.
    Journal of Experimental Medicine 12/2010; 207(13):2817-30. · 13.21 Impact Factor
  • Satoshi Nishimura, Mika Nagasaki
    Seikagaku. The Journal of Japanese Biochemical Society 09/2010; 82(9):832-6. · 0.04 Impact Factor
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    ABSTRACT: CLEC-2 has been described recently as playing crucial roles in thrombosis/hemostasis, tumor metastasis, and lymphangiogenesis. The snake venom rhodocytin is known as a strong platelet activator, and we have shown that this effect is mediated by CLEC-2 (Suzuki-Inoue, K., Fuller, G. L., García, A., Eble, J. A., Pöhlmann, S., Inoue, O., Gartner, T. K., Hughan, S. C., Pearce, A. C., Laing, G. D., Theakston, R. D., Schweighoffer, E., Zitzmann, N., Morita, T., Tybulewicz, V. L., Ozaki, Y., and Watson, S. P. (2006) Blood 107, 542-549). Podoplanin, which is expressed on the surface of tumor cells, is an endogenous ligand for CLEC-2 and facilitates tumor metastasis by inducing platelet aggregation. Mice deficient in podoplanin, which is also expressed on the surface of lymphatic endothelial cells, show abnormal patterns of lymphatic vessel formation. In this study, we report on the generation and phenotype of CLEC-2-deficient mice. These mice are lethal at the embryonic/neonatal stages associated with disorganized and blood-filled lymphatic vessels and severe edema. Moreover, by transplantation of fetal liver cells from Clec-2(-/-) or Clec-2(+/+) embryos, we were able to demonstrate that CLEC-2 is involved in thrombus stabilization in vitro and in vivo, possibly through homophilic interactions without apparent increase in bleeding tendency. We propose that CLEC-2 could be an ideal novel target protein for an anti-platelet drug, which inhibits pathological thrombus formation but not physiological hemostasis.
    Journal of Biological Chemistry 08/2010; 285(32):24494-507. · 4.65 Impact Factor
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    ABSTRACT: CLEC-2 has been described recently as playing crucial roles in thrombosis/hemostasis, tumor metastasis, and lymphangiogenesis. The snake venom rhodocytin is known as a strong platelet activator, and we have shown that this effect is mediated by CLEC-2 (Suzuki-Inoue, K., Fuller, G. L., García, A., Eble, J. A., Pöhlmann, S., Inoue, O., Gartner, T. K., Hughan, S. C., Pearce, A. C., Laing, G. D., Theakston, R. D., Schweighoffer, E., Zitzmann, N., Morita, T., Tybulewicz, V. L., Ozaki, Y., and Watson, S. P. (2006) Blood 107, 542–549). Podoplanin, which is expressed on the surface of tumor cells, is an endogenous ligand for CLEC-2 and facilitates tumor metastasis by inducing platelet aggregation. Mice deficient in podoplanin, which is also expressed on the surface of lymphatic endothelial cells, show abnormal patterns of lymphatic vessel formation. In this study, we report on the generation and phenotype of CLEC-2-deficient mice. These mice are lethal at the embryonic/neonatal stages associated with disorganized and blood-filled lymphatic vessels and severe edema. Moreover, by transplantation of fetal liver cells from Clec-2−/− or Clec-2+/+ embryos, we were able to demonstrate that CLEC-2 is involved in thrombus stabilization in vitro and in vivo, possibly through homophilic interactions without apparent increase in bleeding tendency. We propose that CLEC-2 could be an ideal novel target protein for an anti-platelet drug, which inhibits pathological thrombus formation but not physiological hemostasis.
    Journal of Biological Chemistry 08/2010; 285(32):24494-24507. · 4.65 Impact Factor
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    ABSTRACT: Voltage-gated Ca(2+) channels (Ca(V)) are ubiquitously expressed in various cell types and play vital roles in regulation of cellular functions including proliferation. However, the molecular identities and function of Ca(V) remained unexplored in preadipocytes. Therefore, whole cell voltage-clamp technique, conventional/quantitative real-time RT-PCR, Western blot, small interfering RNA (siRNA) experiments, and immunohistochemical analysis were applied in mouse primary cultured preadipocytes as well as mouse 3T3-L1 preadipocytes. The effects of Ca(V) blockers on cell proliferation and cell cycle were also investigated. Whole cell recordings of 3T3-L1 preadipocytes showed low-threshold Ca(V), which could be inhibited by mibefradil, Ni(2+) (IC(50) of 200 muM), and NNC55-0396. Dominant expression of alpha(1G) mRNA was detected among Ca(V) transcripts (alpha(1A)-alpha(1I)), supported by expression of Ca(V)3.1 protein encoded by alpha(1G) gene, with immunohistochemical studies and Western blot analysis. siRNA targeted for alpha(1G) markedly inhibited Ca(V). Dominant expression of alpha(1G) mRNA and expression of Ca(V)3.1 protein were also observed in mouse primary cultured preadipocytes. Expression level of alpha(1G) mRNA and Ca(V)3.1 protein significantly decreased in differentiated adipocytes. Mibefradil, NNC55-0396, a selective T-type Ca(V) blocker, but not diltiazem, inhibited cell proliferation in response to serum. NNC55-0396 and siRNA targeted for alpha(1G) also prevented cell cycle entry/progression. The present study demonstrates that the Ca(V)3.1 T-type Ca(2+) channel encoded by alpha(1G) subtype is the dominant Ca(V) in mouse preadipocytes and may play a role in regulating preadipocyte proliferation, a key step in adipose tissue development.
    AJP Cell Physiology 06/2010; 298(6):C1414-23. · 3.71 Impact Factor
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    ABSTRACT: The nature of the in vivo cellular events underlying thrombus formation mediated by platelet activation remains unclear because of the absence of a modality for analysis. Lymphocyte adaptor protein (Lnk; also known as Sh2b3) is an adaptor protein that inhibits thrombopoietin-mediated signaling, and as a result, megakaryocyte and platelet counts are elevated in Lnk-/- mice. Here we describe an unanticipated role for Lnk in stabilizing thrombus formation and clarify the activities of Lnk in platelets transduced through integrin alphaIIbbeta3-mediated outside-in signaling. We equalized platelet counts in wild-type and Lnk-/- mice by using genetic depletion of Lnk and BM transplantation. Using FeCl3- or laser-induced injury and in vivo imaging that enabled observation of single platelet behavior and the multiple steps in thrombus formation, we determined that Lnk is an essential contributor to the stabilization of developing thrombi within vessels. Lnk-/- platelets exhibited a reduced ability to fully spread on fibrinogen and mediate clot retraction, reduced tyrosine phosphorylation of the beta3 integrin subunit, and reduced binding of Fyn to integrin alphaIIbbeta3. These results provide new insight into the mechanism of alphaIIbbeta3-based outside-in signaling, which appears to be coordinated in platelets by Lnk, Fyn, and integrins. Outside-in signaling modulators could represent new therapeutic targets for the prevention of cardiovascular events.
    The Journal of clinical investigation 01/2010; 120(1):179-90. · 15.39 Impact Factor
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    ABSTRACT: Fibroblasts, which are the most numerous cell type in the heart, interact with cardiomyocytes in vitro and affect their function; however, they are considered to play a secondary role in cardiac hypertrophy and failure. Here we have shown that cardiac fibroblasts are essential for the protective and hypertrophic myocardial responses to pressure overload in vivo in mice. Haploinsufficiency of the transcription factor-encoding gene Krüppel-like factor 5 (Klf5) suppressed cardiac fibrosis and hypertrophy elicited by moderate-intensity pressure overload, whereas cardiomyocyte-specific Klf5 deletion did not alter the hypertrophic responses. By contrast, cardiac fibroblast-specific Klf5 deletion ameliorated cardiac hypertrophy and fibrosis, indicating that KLF5 in fibroblasts is important for the response to pressure overload and that cardiac fibroblasts are required for cardiomyocyte hypertrophy. High-intensity pressure overload caused severe heart failure and early death in mice with Klf5-null fibroblasts. KLF5 transactivated Igf1 in cardiac fibroblasts, and IGF-1 subsequently acted in a paracrine fashion to induce hypertrophic responses in cardiomyocytes. Igf1 induction was essential for cardioprotective responses, as administration of a peptide inhibitor of IGF-1 severely exacerbated heart failure induced by high-intensity pressure overload. Thus, cardiac fibroblasts play a pivotal role in the myocardial adaptive response to pressure overload, and this role is partly controlled by KLF5. Modulation of cardiac fibroblast function may provide a novel strategy for treating heart failure, with KLF5 serving as an attractive target.
    The Journal of clinical investigation 01/2010; 120(1):254-65. · 15.39 Impact Factor
  • Satoshi Nishimura, Mika Nagasaki
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    ABSTRACT: Obese visceral adipose tissue remodeling and dysfunction, based on chronic inflammation and local immunological changes, play major roles in the metabolic syndrome. Therefore, an in vivo visualization technique has been developed to assess the dynamic interplay between multiple cell types in obese adipose. In vivo imaging revealed close spatial and temporal interrelationships between angiogenesis and adipogenesis, which were augmented in obese adipose tissue. In addition, increased leukocyte–platelet–endothelial cell interactions were observed in the microcirculation, a hallmark of inflammation. Upregulated expression of adhesion molecules contribute to the local activation of inflammatory processes. We also found that large numbers of CD8+ effector T cells infiltrated into the obese adipose tissue, playing major roles in inflammatory macrophage infiltration into obese adipose tissue, the induction and maintenance of inflammation, and systemic insulin resistance. Our results demonstrate the power of our imaging technique to analyze multi-cellular interactions in inflammation in vivo and to evaluate new therapeutic interventions. KeywordsInflammation-Metabolic diseases-Adipose tissue-In vivo molecular imaging method- Angiogenesis-Adipogenesis
    Journal of Biorheology 01/2010; 24(1):11-15.
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    ABSTRACT: Mechanical stress is known to alter the electrophysiological properties of the myocardium and may trigger fatal arrhythmias when an abnormal load is applied to the heart. We tested the hypothesis that the structural heterogeneity of the ventricular wall modulates globally applied stretches to create heterogeneous strain distributions that lead to the initiation of arrhythmias. We applied global stretches to arterially perfused rabbit right ventricular tissue preparations. The distribution of strain (determined by marker tracking) and the transmembrane potential (measured by optical mapping) were simultaneously recorded while accounting for motion artifacts. The 3D structure of the preparations was also examined using a laser displacement meter. To examine whether such observations can be translated to the physiological condition, we performed similar measurements in whole heart preparations while applying volume pulses to the right ventricle. At the tissue level, larger stretches (> or = 20%) caused synchronous excitation of the entire preparation, whereas medium stretches (10% and 15%) induced focal excitation. We found a significant correlation between the local strain and the local thickness, and the probability for focal excitation was highest for medium stretches. In the whole heart preparations, we observed that such focal excitations developed into reentrant arrhythmias. Global stretches of intermediate strength, rather than intense stretches, created heterogeneous strain (excitation) distributions in the ventricular wall, which can trigger fatal arrhythmias.
    Circulation Research 11/2009; 106(1):176-84. · 11.86 Impact Factor
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    ABSTRACT: Inflammation is increasingly regarded as a key process underlying metabolic diseases in obese individuals. In particular, obese adipose tissue shows features characteristic of active local inflammation. At present, however, little is known about the sequence of events that comprises the inflammatory cascade or the mechanism by which inflammation develops. We found that large numbers of CD8(+) effector T cells infiltrated obese epididymal adipose tissue in mice fed a high-fat diet, whereas the numbers of CD4(+) helper and regulatory T cells were diminished. The infiltration by CD8(+) T cells preceded the accumulation of macrophages, and immunological and genetic depletion of CD8(+) T cells lowered macrophage infiltration and adipose tissue inflammation and ameliorated systemic insulin resistance. Conversely, adoptive transfer of CD8(+) T cells to CD8-deficient mice aggravated adipose inflammation. Coculture and other in vitro experiments revealed a vicious cycle of interactions between CD8(+) T cells, macrophages and adipose tissue. Our findings suggest that obese adipose tissue activates CD8(+) T cells, which, in turn, promote the recruitment and activation of macrophages in this tissue. These results support the notion that CD8(+) T cells have an essential role in the initiation and propagation of adipose inflammation.
    Nature medicine 09/2009; 15(8):914-20. · 27.14 Impact Factor
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    ABSTRACT: Use of short interfering RNA (siRNA) is a promising new approach thought to have a strong potential to lead to rapid development of gene-oriented therapies. Here, we describe a newly developed, systemically injectable siRNA vehicle, the "wrapsome" (WS), which contains siRNA and a cationic lipofection complex in a core that is fully enveloped by a neutral lipid bilayer and hydrophilic polymers. WS protected siRNA from enzymatic digestion, providing a long half-life in the systemic circulation. Moreover, siRNA/WS leaked from blood vessels within tumors into the tumor tissue, where it accumulated and was subsequently transfected into the tumor cells. Because the transcription factor KLF5 is known to play a role in tumor angiogenesis, we designed KLF5-siRNA to test the antitumor activity of siRNA/WS. KLF5-siRNA/WS exhibited significant antitumor activity, although neither WS containing control scrambled-siRNA nor saline containing KLF5-siRNA affected tumor growth. KLF5-siRNA/WS inhibited Klf5 expression within tumors at both mRNA and protein levels, significantly reducing angiogenesis, and we detected no significant acute or long-term toxicity. Our findings support the idea that siRNA/WS can be used to knock down specific genes within tumors and thereby exert therapeutic effects against cancers.
    Cancer Research 09/2009; 69(16):6531-8. · 8.65 Impact Factor
  • Satoshi Nishimura, Ichiro Manabe, Ryozo Nagai
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    ABSTRACT: Metabolic syndrome is a major risk factor for cardiovascular and metabolic diseases. Playing a central role in the development of metabolic syndrome and in its clinical consequences is visceral obesity. Adipose tissue is now considered to be an active endocrine organ that secretes various humoral factors (adipokines), and its shift to production of proinflammatory cytokines in obesity likely contributes to the low-level systemic inflammation that is seen in metabolic syndrome-associated chronic pathologies such as atherosclerosis. Recent studies have shown that obesity induces chronic local inflammation in adipose tissue, and that cells of the innate immune system, particularly macrophages, are crucially involved in adipose inflammation and systemic metabolic abnormalities. Moreover, we and others recently revealed that T cells are key regulators of adipose inflammation, and that the adaptive immune system is also crucially important. In mouse models modulation of T cell function ameliorated not only adipose inflammation but also systemic insulin resistance induced by obesity. Thus clarification of the inflammatory processes ongoing in obese adipose tissue would seem essential for the understanding of metabolic syndrome and for developing novel therapeutic strategies to treat it.
    Discovery medicine 08/2009; 8(41):55-60. · 2.97 Impact Factor
  • Journal of Clinical Investigation - J CLIN INVEST. 01/2009; 119(12).