Download {alpha}-Lipoic Acid Inhibits Adipocyte Differentiation by Regulating

{alpha}-Lipoic Acid Inhibits Adipocyte Differentiation by
Regulating Pro-adipogenic Transcription Factors via Mitogenactivated Protein Kinase Pathways.
Cho KJ, Moon HE, Moini H, Packer L, Yoon DY, Chung AS.
Department of Biological Sciences, Korea Advanced Institute of Science and
Technology, Daejeon 305-701, South Korea, Department of Molecular Pharmacology
and Toxicology, School of Pharmacy, University of Southern California, Los Angeles,
California 90089, and Laboratory of Cell Biology, Korea Research Institute of
Bioscience and Biotechnology, Daejeon 305-333, South Korea.
Obesity is associated with a number of pathological disorders such as non-insulindependent diabetes, hypertension, hyperlipidemia, and cardiovascular diseases. alphaLipoic acid (LA) has been demonstrated to activate the insulin signaling pathway and to
exert insulin-like actions in adipose and muscle cells. Based on this similarity LA is
expected to promote adipogenesis in pre-adipocytes. Here, however, we report that LA
inhibited differentiation of 3T3-L1 pre-adipocytes induced by a hormonal mixture or
troglitazone. Northern blot analysis of cells demonstrated that this inhibition was
accompanied with attenuated expression of adipocyte-specific fatty acid-binding
protein and lipoprotein lipase. Electrophoretic mobility shift assay and Western blot
analysis of cells demonstrated that LA modulates transcriptional activity and/or
expression of a set of anti- or pro-adipogenic transcription factors. LA treatment of
3T3-L1 pre-adipocytes also resulted in prolonged activation of major mitogenactivated protein kinase signaling pathways but showed little or no effect on the activity
of the insulin receptor/Akt signaling pathway. These findings suggest that LA inhibits
insulin or the hormonal mixture-induced differentiation of 3T3-L1 pre-adipocytes by
modulating activity and/or expression of pro- or anti-adipogenic transcription factors
mainly through activating the MAPK pathways.
PMID: 12837769 [PubMed - as supplied by publisher]
Development of ELISA for screening PPAR- modulators based on binding
affinity between PPAR and SRC-1 and the effect of a PPAR inhibitor WS31 on the differention of 3T3-L1 adipocyte cells
Peroxisome proliferator-activated receptors- (PPAR-) is an orphan
nuclear hormone receptor that is known to control the expression of genes
involved in lipid homeostasis and energy balance. PPAR- activates gene
transcription in response to a variety of compounds including hypolipidemic
drugs as well as natural fatty acids and synthetic drugs such as
thiazolidinediones (TZDs), indomethacin. Most of these compounds have high
affinity to PPAR ligand binding domain (LBD) and cause a conformational
change within PPAR. As results, the receptor is converted to an “activated
mode” that promotes the recruitment of co-activators such as steroid receptor
coactivator-1 (SRC-1). Based on the PPAR activation mechanism that ligand
binding to PPAR
would induces interactions of the receptor with
transcriptional co-activators, we primarily investigated binding of PPAR-
and SRC-binding by using of Western blot and enzyme-linked immunosorbent
assay. The Western blot showed that immobilized His-tagged SRC-1 on PVDF
membrane complexes with bacterially expressed glutathione S-transferasefused PPAR-2 (GST-fused PPAR-2) complexes. The indomethacin, PPAR-
agonist increased binding affinity of PPAR- and SRC-1 in a ligand dosedependent manner by immune-linked immunosorbent assay. These results
showed that in vitro conformation change of PPAR- by the ligands also
increased levels of ligand-dependent interaction with SRC-1. Collectivly, we
developed a novel PPAR-
screening enzyme-linked immunoassay (ELISA)
system, which is a useful system for the mass screening of potential drugs.
This screening system (based on the interaction between PPAR- and SRC-1)
can be a promising system in the development of drugs for metabolic disorders
such as type 2 diabetes, obesity, and inflammations. By using this ELISA system,
we screened WS3-1, a derivative of TZD, and the effects of WS3-1 on the
regulation of adipogenesis will be discussed. This work was supported by Korea
Research Council of Fundamental and technology (KRCF).