Jae-Hoon Shim

University of British Columbia - Vancouver, Vancouver, British Columbia, Canada

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Publications (5)5.94 Total impact

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    ABSTRACT: Lipid-laden peripheral tissue cells release cholesterol to an extracellular acceptor such as high-density lipoprotein (HDL). Foam cells are formed at the first stage of atherosclerosis development. This study investigated whether sage weed (Salvia plebeia) extract (SWE) influences cholesterol handling of J774A1 murine macrophages. A murine macrophage cell line, J774A1, was used in this study. Oxidized low-density lipoproteins (LDL) treatment was used for foam cell formation, which was confirmed using Oil red O staining. The oxidized LDL uptake and cholesterol efflux from lipid-laden foam cell-associated proteins were detected by western blot analysis. Also, transcriptional levels of these associated genes were examined using reverse transcription-PCR. Also, cholesterol efflux was measured using NBD-cholesterol efflux assay. Non-toxic SWE at ≥10 µg/ml attenuated scavenger receptor (SR)-B1 expression of macrophages induced by oxidized LDL for 6 h, which was achieved at its transcriptional levels. Consistently, SWE suppressed oxidized LDL-stimulated cellular lipid accumulation and foam cell formation due to downregulated SR-B1. SWE upregulated the protein expression and mRNA levels of ATP-binding cassette transporter A1 (ABCA1) and ATP-binding cassette transporter G1 (ABCG1) in lipid-laden foam cells, both responsible for cholesterol efflux. In addition, SWE promoted apolipoprotein E (apoE) secretion from oxidized LDL-induced foam cells. Cholesterol efflux was enhanced by ≥10 µg/ml SWE most likely through the induction of ABCA1 and ABCG1 and the secretion of apoE. Although 10 µM homoplantaginin, a compound mainly present in sage weeds, did not influence cellular expression of ABCA1 and ABCG1, it suppressed oxidized LDL-enhanced SR-B1 induction and foam cell formation. These results demonstrate that SWE antagonized oxidized LDL uptake and promoted cholesterol efflux in lipid-laden macrophages. Therefore, SWE may serve as a protective therapeutic agent against the development of atherosclerosis.
    International Journal of Molecular Medicine 08/2012; 30(5):1105-12. · 1.96 Impact Factor
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    ABSTRACT: Glycans bearing modified hydroxyl groups are common in biology but because these modifications are added after assembly, enzymes are not available for the transfer and coupling of hydroxyl-modified monosaccharide units. Access to such enzymes could be valuable, particularly if they can also introduce 'bio-orthogonal tags'. Glycosynthases, mutant glycosidases that synthesize glycosides using glycosyl fluoride donors, are a promising starting point for creation of such enzymes through directed evolution. Inspection of the active site of a homology model of the GH1 Agrobacterium sp. β-glycosidase, which has both glucosidase and galactosidase activity, identified Q24, H125, W126, W404, E411 and W412 as amino acids that constrain binding around the 3-OH group, suggesting these residues as targets for mutation to generate an enzyme capable of handling 3-O-methylated sugars. Site-directed saturation mutagenesis at these positions within the wild-type β-glycosidase gene and screening via an on-plate assay yielded two mutants (Q24S/W404L and Q24N/W404N) with an improved ability to hydrolyze 4-nitrophenyl 3-O-methyl-β-D-galactopyranoside (3-MeOGal-pNP). Translation of these mutations into the evolved glycosynthase derived from the same glucosidase (2F6) yielded glycosynthases (AbgSL-T and AbgNN-T, where T denotes transferase) capable of forming 3-O-methylated glucosides on multi-milligram scales at rates approximately 5 and 40 times greater, respectively, than the parent glycosynthase.
    Protein Engineering Design and Selection 08/2012; 25(9):465-72. · 2.59 Impact Factor
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    ABSTRACT: This study was conducted to evaluate the possible subacute toxicity of gamma-irradiated Tarakjuk. Tarakjuk was irradiated at a dose of 30 kGy at room temperature. For the animal study, AIN-93G as a control diet and 30 kGy irradiated and non-irradiated Tarakjuk diets were administered to male and female ICR mice (10 mice per group) for 3 months. During the experimental period, the group fed 30 kGy irradiated Tarakjuk did not show any changes in appearance, behavior, mortality, body weight, organ weight, or food consumption compared to control. Further, all biochemical parameters were in normal ranges. In the histopathological examination of liver and kidney tissues of ICR mice, there were no significant differences between the control and 30 kGy irradiated Tarakjuk groups. These results indicate that Tarakjuk irradiated at 30 kGy did not cause any toxic effects under these experimental conditions.
    Journal of the Korean Society of Food Science and Nutrition 01/2012; 41(11).
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    ABSTRACT: Prickly pear (Opuntia ficus-indica) is a longdomesticated crop plant of arid and semiarid parts of the world. The efficacy of extracts of prickly pear root for managing diabetes and diabetes complications was evaluated using a variety of in vitro bioassays. The ethyl acetate-soluble fraction was most effective in the prevention of diabetes and its complications via the inhibition of rat lens aldose reductase activity, the formation of advanced glycation end products, and α-glucosidase activity. MS and NMR were used to identify the bioactive compound from the ethyl acetate-soluble fraction as 3,5,7,4′-tetrahydroxyflavanone (aromadendrin).
    Food science and biotechnology 20(5). · 0.70 Impact Factor
  • Jae-Hoon Shim, Stephen G. Withers
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    ABSTRACT: To achieve high level expression of β-glucosidase from Agrobacterium sp. (Abg) in an Escherichia coli expression system, 6 rare codons at +3, +11, +158, +308, +314, and +318 of abg gene were replaced with favored codons using site-directed mutagenesis. The rare codon replacements of +3 (CCC) and +11 (CCC) positions enhanced the expression level of Abg by 2- and 3.6-fold, respectively. The double mutant, Abg-DM, where both of +3 and +11 rare codon positions were modified showed a 5.2-fold higher expression level than the original abg gene. Circular dichroism (CD) spectra of the over-expressed Abg and original Abg enzymes were identical, indicating that Abg was properly folded during over-expression.
    Food science and biotechnology 22(1). · 0.70 Impact Factor