Development Of Cell-Free Assay System For The Screening Of PPAR Ligands From Natural Products : In Search For Positive Therapeutic Agents For Type 2 Diabetes

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dc.contributor.authorLau, Wai Kwan
dc.date.accessioned2017-10-20T07:50:20Z
dc.date.available2017-10-20T07:50:20Z
dc.date.issued2013-10
dc.description.abstractPeroxisome proliferator-activated receptor-(PPAR) is an essential regulator of glucose metabolic genes, of which upon activation by ligands, enhances the actions of cellular insulin to promote glucose uptake to overcome insulin resistance in Type 2 diabetes patients. Thiazolidinediones (TZD) is a common class of drugs for type 2 diabetes and they function as synthetic ligands for PPAR. However, many adverse effects are associated with these synthetic ligands. Therefore there is an urgent need to find alternatives to TZD such as natural ligands from plant source. In this study, a cell-free assay system was developed in order to be used as a platform to screen for plant extracts with compounds that had the ability to bind to PPAR as ligands which in turn, increased the binding of PPAR to its coactivator. Truncated recombinant plasmids of PPAR and p300 coactivator were constructed and their His-tagged recombinant proteins were expressed and column purified. An ELISA-based PPAR ligand binding assay system was adopted to evaluate the presence of potential PPAR ligand in plants. With Rosiglitazone, a known synthetic ligand for PPAR as control, the extracts of six local plants found in Malaysia namely Ficus deltoidea, Garcinia mangostana, Momordica charantia, Swietenia macrophylla, Orthosiphon stamineus and Tinospora crispa were screened for their activity as natural ligands for PPAR. It was found that methanol extracts of F. deltoidea, G. mangostana, M. charantia, S. macrophylla and O. Stamineus increased the binding rate of PPAR to its coactivator which indicate that these extracts may contain potential PPAR ligands. Further anti-diabetic studies were performed on S. macrophylla seed extracts which were previously examined tocontain the putative PPAR activating components. Three isolated natural compounds from S. macrophylla namely 6-O-acetylswietenolide, diacetyl swietenolide and swietenine, were shown to possess PPAR ligand characteristics interms of PPAR binding, recruitment of coactivator as well as activation of PPAR to regulate downstream adipocyte differentiation and the expression of genes responsible for adipocyte differentiation. Moreover, the compounds also induced GLUT4 expression in muscle cells and increased GLUT4 translocation to plasma membrane. Their potential in modulating glucose uptake activity by enhancing 2- NBDG uptake partly via AMPK activation in muscle cells were also demonstrated in the study. Thus, these natural compounds in S. macrophylla seeds may have vast potential to be developed and used as therapeutic agents against type 2 diabetes.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/5037
dc.language.isoenen_US
dc.publisherUniversiti Sains Malaysiaen_US
dc.subjectdiabetesen_US
dc.subjectliganden_US
dc.titleDevelopment Of Cell-Free Assay System For The Screening Of PPAR Ligands From Natural Products : In Search For Positive Therapeutic Agents For Type 2 Diabetesen_US
dc.typeThesisen_US
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