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Articles by G. Y Koh
Total Records ( 3 ) for G. Y Koh
  H. K Sung , Y. W Kim , S. J Choi , J. Y Kim , K. H Jeune , K. C Won , J. K Kim , G. Y Koh and S. Y. Park
 

To test whether chronic enhanced blood flow alters insulin-stimulated glucose uptake, we measured skeletal muscle glucose uptake in chow-fed and high-fat-fed mice injected with adenovirus containing modified angiopoietin-1, COMP-Ang1, via euglycemic-hyperinsulinemic clamp. Blood flow rates and platelet endothelial cell adhesion molecule-1 positive endothelial cells in the hindlimb skeletal muscle were elevated in COMP-Ang1 compared with control LacZ. Whole body glucose uptake and whole body glycogen/lipid synthesis were elevated in COMP-Ang1 compared with LacZ in chow diet. High-fat diet significantly reduced whole body glucose uptake and whole body glycolysis in LacZ mice, whereas high-fat-fed COMP-Ang1 showed a level of whole body glucose uptake that was comparable with chow-fed LacZ and showed increased glucose uptake compared with high-fat-fed LacZ. Glucose uptake and glycolysis in gastrocnemius muscle of chow-fed COMP-Ang1 were increased compared with chow-fed LacZ. High-fat diet-induced whole body insulin resistance in the LacZ was mostly due to ~40% decrease in insulin-stimulated glucose uptake in skeletal muscle. In contrast, COMP-Ang1 prevented diet-induced skeletal muscle insulin resistance compared with high-fat-fed LacZ. Akt phosphorylation in skeletal muscle was increased in COMP-Ang1 compared with LacZ in both chow-fed and high-fat-fed groups. These results suggest that increased blood flow by COMP-Ang1 increases insulin-stimulated glucose uptake and prevents high-fat diet-induced insulin resistance in skeletal muscle.

  T Holopainen , H Huang , C Chen , K. E Kim , L Zhang , F Zhou , W Han , C Li , J Yu , J Wu , G. Y Koh , K Alitalo and Y. He
 

The angiopoietin-1 (Ang1)/Tie2 signaling pathway is known to play an important role in the regulation of vascular maturation and maintenance of vessel integrity. In this study, we have investigated the effect of systemic Tie2 activation or inhibition on tumor growth and metastasis. We found that treatment with Ang1 delivered via an adenoviral vector promoted s.c. implanted tumor metastasis to the lungs. Ang1 treatment did not significantly increase vascular density in the tumors but induced enlargement of blood vessels in both the tumor and normal tissues, which increased tumor cell dissemination into the blood circulation. Ang1 also enhanced the formation of metastatic foci in the lungs when tumor cells were injected into the circulation via the tail vein. The effect of Ang1 on metastasis was validated by a simultaneous treatment with a soluble form of Tie2 (sTie2), which led to the suppression of Ang1-induced increase of tumor metastasis. Furthermore, using a highly metastatic tumor model, we confirmed that systemic treatment with sTie2 suppressed tumor metastasis to the lungs and lymph nodes, whereas tumor-associated angiogenesis and lymphangiogenesis were not significantly affected. This suggests that the Ang1/Tie2 signals contribute to tumor progression by increasing vascular entry and exit of tumor cells to facilitate tumor dissemination and establishment of metastases. [Cancer Res 2009;69(11):4656–64]

  M. S Kim , C. S Lee , J Hur , H. J Cho , S. I Jun , T. Y Kim , S. W Lee , J. W Suh , K. W Park , H. Y Lee , H. J Kang , D. S Lee , G. Y Koh , H Nakagami , R Morishita , Y. B Park and H. S. Kim
 

Background— The low engraftment rate of stem/progenitor cells infused via the intracoronary route to the ischemic myocardium is one of the most important factors limiting the efficacy of cell therapy. We investigated the concept of priming peripheral blood stem cells enriched by granulocyte colony-stimulating factor mobilization and apheresis (mobPBSCs) with angiopoietin-1 (Ang1), to enhance the engraftment into the ischemic tissue and neovasculogenic potential.

Methods and Results— The expression of Tie2, the Ang1 receptor, was significantly higher in mobPBSCs than naïve peripheral blood mononuclear cells (19.2±3.0% versus 1.2±0.8% versus 1.2±0.2%; P<0.001 for mobPBSCs from acute myocardial infarction (AMI) patients with granulocyte colony-stimulating factor treatment for 3 days versus peripheral blood mononuclear cells from AMI patients versus peripheral blood mononuclear cells from stable angina patients). After 4 hours of cartilage oligomeric matrix protein (COMP)-Ang1 stimulation, mobPBSCs committed to the endothelial lineage with the induction of CD31 and VE-cadherin expression, mediated by Tie2/Ets-1 pathway. Priming of mobPBSCs with COMP-Ang1 induced the expression of 4β1 and 5β1 integrins, which are also Ets-1 downstream molecules, leading to enhanced adhesion to endothelial cells or fibronectin. In a rabbit ear ischemia/reperfusion model, priming of mobPBSCs with COMP-Ang1 improved first-pass engraftment to the distal vascular bed after intraarterial delivery. In a murine ischemic hind-limb model, intravascular delivery of primed mobPBSCs enhanced both engraftment and neovascularization.

Conclusions— The short-term priming with COMP-Ang1 may be a feasible and promising option to activate mobPBSCs by enhancing differentiation and adhesiveness and to improve the efficacy of cell therapy for ischemic diseases.

 
 
 
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