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Okayama Prefectural University

EducationSōja, Japan
About: Okayama Prefectural University is a education organization based out in Sōja, Japan. It is known for research contribution in the topics: Control theory & Control system. The organization has 826 authors who have published 1741 publications receiving 24370 citations. The organization is also known as: Okayama Kenritsu Daigaku.

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Journal ArticleDOI
TL;DR: The results suggest that the endothelial vasodilator dysfunction observed in hypercholesterolemia may be due to reduced degradation of ADMA, the endogenous inhibitor of NOS.
Abstract: Background—Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase (NOS). Plasma levels of ADMA are elevated in individuals with hypercholesterolemia or atherosclerosis. We postulated that reduced degradation of ADMA may play a role in the accumulation of ADMA in these individuals. Accordingly, we studied the effects of oxidized LDL (oxLDL) or tumor necrosis factor-α (TNF-α) on the accumulation of ADMA by transformed human umbilical vein endothelial cells (ECV304) and on the enzyme dimethylarginine dimethylaminohydrolase (DDAH), which degrades ADMA. Methods and Results—ECV304 were incubated with or without native LDL (100 μg/mL), oxLDL (100 μg/mL), or TNF-α (250 U/mL) for 48 hours. The concentration of ADMA in the conditioned medium was determined by high-performance liquid chromatography. Western blotting was performed to evaluate DDAH expression. We assayed DDAH activity by determining l-citrulline formation from ADMA. The addition of oxLDL or TNF-α to ECV304 significantly...

674 citations

Journal ArticleDOI
TL;DR: Homocysteine post-translationally inhibits DDAH enzyme activity, causing ADMA to accumulate and inhibit nitric oxide synthesis, which may explain the known effect of homocysteines to impair endothelium-mediated nitricoxide–dependent vasodilatation.
Abstract: Background—Hyperhomocysteinemia is a putative risk factor for cardiovascular disease, which also impairs endothelium-dependent vasodilatation. A number of other risk factors for cardiovascular disease may exert their adverse vascular effects in part by elevating plasma levels of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase. Accordingly, we determined if homocysteine could increase ADMA levels. Methods and Results—When endothelial or nonvascular cells were exposed to DL-homocysteine or to its precursor L-methionine, ADMA concentration in the cell culture medium increased in a dose- and time-dependent fashion. This effect was associated with the reduced activity of dimethylarginine dimethylaminohydrolase (DDAH), the enzyme that degrades ADMA. Furthermore, homocysteine-induced accumulation of ADMA was associated with reduced nitric oxide synthesis by endothelial cells and segments of pig aorta. The antioxidant pyrrollidine dithiocarbamate preserved DDAH activity and reduced ADMA accumulation. Moreover, homocysteine dose-dependently reduced the activity of recombinant human DDAH in a cell free system, an effect that was due to a direct interaction between homocysteine and DDAH. Conclusion—Homocysteine post-translationally inhibits DDAH enzyme activity, causing ADMA to accumulate and inhibit nitric oxide synthesis. This may explain the known effect of homocysteine to impair endothelium-mediated nitric oxide– dependent vasodilatation. (Circulation. 2001;104:2569-2575.)

674 citations

Journal ArticleDOI
TL;DR: The similarities and differences of these two incretin hormones in secretion and metabolism, their insulinotropic action on pancreatic β cells, and their non‐insulinotropic effects are summarized and their potential in treatment of type 2 diabetes is discussed.
Abstract: Gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are the two primary incretin hormones secreted from the intestine on ingestion of glucose or nutrients to stimulate insulin secretion from pancreatic b cells. GIP and GLP-1 exert their effects by binding to their specific receptors, the GIP receptor (GIPR) and the GLP-1 receptor (GLP-1R), which belong to the G-protein coupled receptor family. Receptor binding activates and increases the level of intracellular cyclic adenosine monophosphate in pancreatic b cells, thereby stimulating insulin secretion glucose-dependently. In addition to their insulinotropic effects, GIP and GLP-1 play critical roles in various biological processes in different tissues and organs that express GIPR and GLP-1R, including the pancreas, fat, bone and the brain. Within the pancreas, GIP and GLP-1 together promote b cell proliferation and inhibit apoptosis, thereby expanding pancreatic b cell mass, while GIP enhances postprandial glucagon response and GLP-1 suppresses it. In adipose tissues, GIP but not GLP-1 facilitates fat deposition. In bone, GIP promotes bone formation while GLP-1 inhibits bone absorption. In the brain, both GIP and GLP-1 are thought to be involved in memory formation as well as the control of appetite. In addition to these differences, secretion of GIP and GLP-1 and their insulinotropic effects on b cells have been shown to differ in patients with type 2 diabetes compared to healthy subjects. We summarize here the similarities and differences of these two incretin hormones in secretion and metabolism, their insulinotropic action on pancreatic b cells, and their non-insulinotropic effects, and discuss their potential in treatment of type 2 diabetes. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2010.00022.x, 2010)

484 citations

Journal ArticleDOI
TL;DR: The results strongly suggested that the fatty acid inhibition of glucose-induced l-PK transcription resulted from AMPK phosphorylation of ChREBP at Ser568, which inactivated the DNA binding activity.
Abstract: Carbohydrate-responsive element-binding protein (ChREBP) is a new transcription factor that binds to the carbohydrate-responsive element of the l-type pyruvate kinase gene (l-PK). The aim of this study was to investigate the mechanism by which feeding high fat diets results in decreased activity of ChREBP in the liver (Yamashita, H., Takenoshita, M., Sakurai, M., Bruick, R. K., Henzel, W. J., Shillinglaw, W., Arnot, D., and Uyeda, K. (2001) Proc. Natl. Acad. Sci. U. S. A. 98, 9116–9121). We cloned the rat liver ChREBP gene for use throughout this study. Acetate, octanoate, and palmitate inhibited the glucose-induced activation of l-PK transcription in ChREBP-overexpressed hepatocytes. In these hepatocytes, the cytosolic AMP concentration increased 30-fold and AMP-activated protein kinase activity was activated 2-fold. Similarly to the fatty acids, 5-amino-4-imidazolecarboxamide ribotide, a specific activator of AMP-activated protein kinase (AMPK) also inhibited the l-PK transcription activity in ChREBP-overexpressed hepatocytes. Using as a substrate a truncated ChREBP consisting of the C-terminal region, we demonstrated that phosphorylation by AMPK resulted in inactivation of the DNA binding activity. AMPK specifically phosphorylated Ser568 of ChREBP. A S568A mutant of the ChREBP gene showed tight DNA binding and lost its fatty acid sensitivity, whereas a S568D mutant showed weak DNA binding and inhibited l-PK transcription activity even in the absence of fatty acid. These results strongly suggested that the fatty acid inhibition of glucose-induced l-PK transcription resulted from AMPK phosphorylation of ChREBP at Ser568, which inactivated the DNA binding activity. AMPK was activated by the increased AMP that was generated by the fatty acid activation.

391 citations

Journal ArticleDOI
TL;DR: DDAH I overexpression increases NOS activity in vitro and in vivo and provides compelling evidence that the elaboration and metabolism of endogenous ADMA plays an important role in regulation of NOSActivity.
Abstract: Background— NO is a major regulator of cardiovascular physiology that reduces vascular and cardiac contractility. Accumulating evidence indicates that endogenous inhibitors may regulate NOS. The NO...

339 citations


Showing all 827 results

Hiroshi Itoh9089734839
Hiroshi Kiyama5733313449
Jianbo Xiao522909923
Hideyuki Ito502027135
Tsuneo Morishima452288722
Shigeru Utsumi441616461
Koichi Hayashi411495012
Seiya Kato391154916
Seiji Ueda391075817
Toshio Miwatani381755276
Mitsuo Fukushima381435065
Kaoru Nakamura372205132
Shu Wakino361484951
Ning Sun341213561
Chiaki Kamei332544296
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