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991.
992.
Seiji Nakamura Toshinari Takamura Naoto Matsuzawa-Nagata Hiroaki Takayama Hirofumi Misu Hiroyo Noda Satoko Nabemoto Seiichiro Kurita Tsuguhito Ota Hitoshi Ando Ken-ichi Miyamoto Shuichi Kaneko 《The Journal of biological chemistry》2009,284(22):14809-14818
Visceral adiposity in obesity causes excessive free fatty acid (FFA) flux
into the liver via the portal vein and may cause fatty liver disease and
hepatic insulin resistance. However, because animal models of insulin
resistance induced by lipid infusion or a high fat diet are complex and may be
accompanied by alterations not restricted to the liver, it is difficult to
determine the contribution of FFAs to hepatic insulin resistance. Therefore,
we treated H4IIEC3 cells, a rat hepatocyte cell line, with a monounsaturated
fatty acid (oleate) and a saturated fatty acid (palmitate) to investigate the
direct and initial effects of FFAs on hepatocytes. We show that palmitate, but
not oleate, inhibited insulin-stimulated tyrosine phosphorylation of insulin
receptor substrate 2 and serine phosphorylation of Akt, through c-Jun
NH2-terminal kinase (JNK) activation. Among the well established
stimuli for JNK activation, reactive oxygen species (ROS) played a causal role
in palmitate-induced JNK activation. In addition, etomoxir, an inhibitor of
carnitine palmitoyltransferase-1, which is the rate-limiting enzyme in
mitochondrial fatty acid β-oxidation, as well as inhibitors of the
mitochondrial respiratory chain complex (thenoyltrifluoroacetone and carbonyl
cyanide m-chlorophenylhydrazone) decreased palmitate-induced ROS
production. Together, our findings in hepatocytes indicate that palmitate
inhibited insulin signal transduction through JNK activation and that
accelerated β-oxidation of palmitate caused excess electron flux in the
mitochondrial respiratory chain, resulting in increased ROS generation. Thus,
mitochondria-derived ROS induced by palmitate may be major contributors to JNK
activation and cellular insulin resistance.Insulin is the major hormone that inhibits gluconeogenesis in the liver.
Visceral adiposity in obesity causes hepatic steatosis and insulin resistance.
In an insulin-resistant state, impaired insulin action allows enhancement of
glucose production in the liver, resulting in systemic hyperglycemia
(1) and contributing to the
development of type 2 diabetes. In addition, we have demonstrated
experimentally that insulin resistance accelerated the pathology of
steatohepatitis in genetically obese diabetic OLETF rats
(2). In contrast, lipid-induced
oxidative stress caused steatohepatitis and hepatic insulin resistance in mice
(3). In fact, steatosis of the
liver is an independent predictor of insulin resistance in patients with
nonalcoholic fatty liver disease
(4).It remains unclear whether hepatic steatosis causally contributes to
insulin resistance or whether it is merely a resulting pathology. Excessive
dietary free fatty acid
(FFA)2 flux into the
liver via the portal vein may cause fatty liver disease and hepatic insulin
resistance. Indeed, elevated plasma FFA concentrations correlate with obesity
and decreased target tissue insulin sensitivity
(5).Experimentally, lipid infusion or a high fat diet that increases
circulating FFA levels promotes insulin resistance in the liver. Candidate
events linking FFA to insulin resistance in vivo are the
up-regulation of SREBP-1c (6),
inflammation caused by activation of c-Jun amino-terminal kinase (JNK)
(7) or IKKβ
(8), endoplasmic reticulum (ER)
stress (9), ceramide
(10,
11), and TRB3
(12).However, which event is the direct and initial target of FFA in the liver
is unclear. Insulin resistance induced by lipid infusion or a high fat diet is
complex and may be accompanied by alterations not restricted to the liver,
making it difficult to determine the contribution of FFAs to hepatic insulin
resistance. For example, hyperinsulinemia and hyperglycemia secondary to the
initial event also may contribute to the development of diet-induced insulin
resistance in vivo
(6).To address the early event(s) triggering the development of high fat diet-
or obesity-induced insulin resistance, we investigated the molecular
mechanism(s) underlying the direct action of FFA on hepatocytes to cause
insulin resistance in vitro, using the rat hepatocyte cell line
H4IIEC3. We found that mitochondria-derived reactive oxygen species (ROS) were
a cause of palmitate-induced insulin resistance in hepatocytes. 相似文献
993.
Daniel Rosen Alexander M. Lewis Akiko Mizote Justyn M. Thomas Parvinder K. Aley Sridhar R. Vasudevan Raman Parkesh Antony Galione Minoru Izumi A. Ganesan Grant C. Churchill 《The Journal of biological chemistry》2009,284(50):34930-34934
Nicotinic acid adenine dinucleotide phosphate (NAADP) is a Ca2+-releasing messenger. Biological data suggest that its receptor has two binding sites: one high-affinity locking site and one low-affinity opening site. To directly address the presence and function of these putative binding sites, we synthesized and tested analogues of the NAADP antagonist Ned-19. Ned-19 itself inhibits both NAADP-mediated Ca2+ release and NAADP binding. A fluorometry bioassay was used to assess NAADP-mediated Ca2+ release, whereas a radioreceptor assay was used to assess binding to the NAADP receptor (only at the high-affinity site). In Ned-20, the fluorine is para rather than ortho as in Ned-19. Ned-20 does not inhibit NAADP-mediated Ca2+ release but inhibits NAADP binding. Conversely, Ned-19.4 (a methyl ester of Ned-19) inhibits NAADP-mediated Ca2+ release but cannot inhibit NAADP binding. Furthermore, Ned-20 prevents the self-desensitization response characteristic of NAADP in sea urchin eggs, confirming that this response is mediated by a high-affinity allosteric site to which NAADP binds in the radioreceptor assay. Collectively, these data provide the first direct evidence for two binding sites (one high- and one low-affinity) on the NAADP receptor. 相似文献
994.
Yukie Iwabu Hideaki Fujita Masanobu Kinomoto Keiko Kaneko Yukihito Ishizaka Yoshitaka Tanaka Tetsutaro Sata Kenzo Tokunaga 《The Journal of biological chemistry》2009,284(50):35060-35072
Bone marrow stromal antigen 2 (BST-2, also known as tetherin) is a recently identified interferon-inducible host restriction factor that can block the production of enveloped viruses by trapping virus particles at the cell surface. This antiviral effect is counteracted by the human immunodeficiency virus type 1 (HIV-1) accessory protein viral protein U (Vpu). Here we show that HIV-1 Vpu physically interacts with BST-2 through their mutual transmembrane domains and leads to the degradation of this host factor via a lysosomal, not proteasomal, pathway. The degradation is partially controlled by a cellular protein, β-transducin repeat-containing protein (βTrCP), which is known to be required for the Vpu-induced degradation of CD4. Importantly, targeting of BST-2 by Vpu occurs at the plasma membrane followed by the active internalization of this host protein by Vpu independently of constitutive endocytosis. Thus, the primary site of action of Vpu is the plasma membrane, where Vpu targets and internalizes cell-surface BST-2 through transmembrane interactions, leading to lysosomal degradation, partially in a βTrCP-dependent manner. Also, we propose the following configuration of BST-2 in tethering virions to the cell surface; each of the dimerized BST-2 molecules acts as a bridge between viral and cell membranes. 相似文献
995.
Minetaka Sugiyama Kazuo Yamagishi Yeon-Hee Kim Yoshinobu Kaneko Masafumi Nishizawa Satoshi Harashima 《Applied microbiology and biotechnology》2009,84(6):1045-1052
A fundamental issue in biotechnology is how to breed useful strains of microorganisms for efficient production of valuable
biomaterials. On-going and more recent developments in gene manipulation technologies and chromosomal and genomic modifications
in particular have facilitated important contributions in this area. “Chromosome manipulation technology” as an outgrowth
of “gene manipulation technology” may provide opportunities for creating novel strains of organisms with a variety of genomic
constitutions. A simple and rapid chromosome splitting technology called “PCR-mediated chromosome splitting” (PCS) that we
recently developed has made it possible to manipulate chromosomes and genomes on a large scale in an industrially important
microorganism, Saccharomyces cerevisiae. This paper focuses on recent advances in molecular methods for altering chromosomes and genome in S. cerevisiae featuring chromosome splitting technology. These advances in introducing large-scale genomic modifications are expected to
accelerate the breeding of novel strains for biotechnological purposes, and to reveal functions of presently uncharacterized
chromosomal regions in S. cerevisiae and other organisms. 相似文献
996.
Y. Takeuchi F. Kaneko C. Hashizume K. Masuda N. Ogata T. Maki M. Inoue-Murayama B. L. Hart Y. Mori 《Animal genetics》2009,40(5):616-622
The relationships between behavioural trait data and the genotype of 15 polymorphisms in eight neurotransmitter-related genes were analysed in 77 dogs of the Shiba Inu breed, an indigenous Japanese dog. The data were obtained from a 26-item questionnaire on the dog's behaviour, distributed to the dog's owners, through veterinary hospitals and the Shiba Inu breed magazine. A factor analysis of the questionnaire items extracted eight factors accounting for 66.8% of the variance. An association analysis between these factors and genetic polymorphisms indicated that the polymorphism of c.471T>C in the solute carrier family 1 ( neuronal/epithelial high-affinity glutamate transporter ) member 2 ( SLC1A2 ) gene was significantly associated with Factor 1, referred to as 'aggression to strangers'. This association remained stable in separate analyses of data from surveys obtained from the hospitals and those obtained from the magazine. The results suggest that the c.471T>C polymorphism is associated with some types of aggressive behaviour in the Shiba Inu. Further studies using other dog breeds are necessary to extend these findings to dogs in general. 相似文献
997.
Ogasawara D Hachiya NS Kaneko K Sode K Ikebukuro K 《Biosensors & bioelectronics》2009,24(5):1372-1376
Aptamers are good molecular recognition elements for biosensors. Especially, their conformational change, which is induced by the binding to the target molecule, enables the development of several types of useful detection systems. We applied this property to bound/free separation, which is a crucial process for highly sensitive detection. We designed aptamers which change their conformation upon binding to the target molecule and thereby expose a single-strand bearing the complementary sequence to the capture probe immobilized onto the support. We named the designed aptamers "capturable aptamers" and the capture probe "capture DNA". Three capturable aptamers were designed based on the PrP aptamer, which binds to prion protein. One of these capturable aptamers was demonstrated to recognize prion protein and change its conformation upon binding to it. A detection system using this designed capturable aptamer for prion protein was developed. Capturable aptamers and capture DNA allow us to perform simple bound/free separation with only one target ligand. 相似文献
998.
Naokazu Kumura Hirotaka Furukawa Arnold N. Onyango Minoru Izumi Shuhei Nakajima Hideyuki Ito Tsutomu Hatano Hye-Sook Kim Yusuke Wataya Naomichi Baba 《Chemistry and physics of lipids》2009,160(2):114-120
The reaction of trioxane and tetraoxane endoperoxides with unsaturated phospholipid 1 in the presence of Fe(II) was investigated in the absence of oxygen by means of tandem ESI-MS analysis. The spectral analyses for the reaction mixtures showed that artemisinin 2 with a trioxane structure gave no peak except that for the remaining intact phospholipid 1 (m/z 758.9), indicating that there was no structural change to 1. On other hand, the reaction mixture of 1 with tetraoxanes 3 and 4 afforded a number of new peaks (m/z 620–850) that were presumably assigned to oxidative degradation products originating from phospholipid 1. Since this reaction was completely inhibited by the addition of a phenolic antioxidant, the process was considered to involve some free radical species. The newly discovered marked differences in reactivity between the trioxane and the tetraoxanes possibly reflects their different anti-malarial mechanisms, and this reactivity may contribute to the classification of a number of anti-malarial endoperoxides whose mode of action is based on phospholipid oxidation. 相似文献
999.
Ryosaku Tomioka Ai Kushida Ippei Izumi Keiko Fukushima Hiroko Ideo Katsuko Yamashita Shigehisa Hirose Yuji Saito 《Biochemical and biophysical research communications》2009,389(1):122-127
GOTO cells, a neuroblastoma cell line retaining the ability to differentiate into neuronal or Schwann cells, were found to be rich in membrane rafts containing ganglioside GM2 and hypersensitive to lipid raft-disrupting methyl-β-cyclodextrin (MβCD); the GM2-rich rafts and sensitivity to MβCD were markedly diminished upon their differentiation into Schwann cells. We first raised a monoclonal antibody that specifically binds to GOTO cells but not to differentiated Schwann cells and determined its target antigen as ganglioside GM2, which was shown to be highly concentrated in lipid rafts by its colocalization with flotillin, a marker protein of rafts. Disturbance of normal structure of the lipid raft by depleting its major constituent, cholesterol, with MβCD resulted in acute apoptotic cell death of GOTO cells, but little effects were seen on differentiated Schwann cells. Until this study, GM2-rich rafts are poorly characterized and MβCD hypersensitivity, which may have clinical implications, has not been reported. 相似文献
1000.
Keiichi Miyamoto Masaki Atarashi Hideki Kadozono Masakazu Shibata Yoshihiro Koyama Masanori Okai Akinobu Inakuma Eiichi Kitazono Hiroaki Kaneko Takafumi Takebayashi Takashi Horiuchi 《International journal of biological macromolecules》2009,45(1):33-41
Effective application of elastin materials for vascular grafts in tissue engineering requires these materials to retain the elastic and biological properties of native elastin. To clarify the influence of soluble elastin isotypes on vascular smooth muscle cells (VSMCs), soluble elastin was prepared from insoluble elastin by hydrolysis with oxalic acid. Its fractions were separated and classified into three isotypes. Elastin retaining 2.25 mol% of cross-linked structures exhibited significant differentiation of VSMCs, which adhered to the elastin with contraction phenotypes similar to that of native elastin, causing proliferation to cease. This trend was more strongly demonstrated in cotton-like elastin fibers with a new cross-linker. The results suggest that elastin isotypes could be applied as new effective biomaterials for suppressing intimal hyperplasia in vascular grafts. 相似文献