A gel-based proteomic analysis of the effects of green tea polyphenols on ovariectomized rats.
OBJECTIVE
Our recent study demonstrated the protective action of green tea polyphenols (GTPs) against bone loss in ovariectomized (OVX) rats through their antioxidant capacities to scavenge reactive oxygen species. The objective of the present study was to evaluate the alterations of liver protein profiles in estrogen-deficient middle-aged rats after GTP treatment by a gel-based proteomic approach. This may lead to understanding the mechanisms of GTPs in promoting bone health.


METHODS
Liver samples were obtained from 14-mo-old female OVX rats treated with no GTPs (OVX) or 0.5% (w/v) GTPs (OVX + GTP) in drinking water for 16 wk (n = 10/group). Two-dimensional difference gel electrophoresis combined with mass spectrometry was used to compare the liver protein profiles of pooled samples from the OVX and OVX + GTP groups. Liver proteins were labeled in duplicate by reversing the fluorescent dyes.


RESULTS
Approximately 800 protein spots were detected. The expression levels of superoxide dismutase-1 and adenosine triphosphate synthase were 2.0-fold and 1.5-fold higher in the OVX + GTP group versus the OVX group, respectively, whereas the expression level of catechol-O-methyltransferase was 1.5-fold lower in the OVX + GTP group versus the OVX group. The changes of superoxide dismutase-1 and catechol-O-methyltransferase in individual liver samples were confirmed by western blots.


CONCLUSIONS
Our data provide further evidence for the antioxidant role of GTPs by increasing superoxide dismutase-1 and adenosine triphosphate synthase and the estrogen-associated effect of GTPs by decreasing catechol-O-methyltransferase.
Shao
Changxia
C
Department of Environmental Toxicology, The Institute of Environmental and Human Health, Texas Tech University, Lubbock, Texas, USA.
Chen
Lixia
L
Lu
Chuanwen
C
Shen
Chwan-Li
CL
Gao
Weimin
W
D000818:Animals; D000975:Antioxidants / Q000627:therapeutic use; D050071:Bone Density Conservation Agents / Q000737:chemistry / Q000627:therapeutic use*; D028241:Camellia sinensis / Q000737:chemistry; D002394:Catechol O-Methyltransferase / Q000378:metabolism; D019587:Dietary Supplements / Q000032:analysis; D005260:Female; D005419:Flavonoids / Q000032:analysis / Q000627:therapeutic use*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D015663:Osteoporosis, Postmenopausal / Q000378:metabolism / Q000517:prevention & control*; D010052:Ovariectomy; D010446:Peptide Fragments / Q000378:metabolism; D010636:Phenols / Q000032:analysis / Q000627:therapeutic use*; D018515:Plant Leaves / Q000737:chemistry; D059808:Polyphenols; D040901:Proteomics / Q000379:methods*; D011897:Random Allocation; D051381:Rats; D011916:Rats, Inbred F344; D013482:Superoxide Dismutase / Q000378:metabolism; D013662:Tea / Q000737:chemistry*; D057825:Two-Dimensional Difference Gel Electrophoresis
D000975:Antioxidants; D050071:Bone Density Conservation Agents; D005419:Flavonoids; D007527:Isoenzymes; D010446:Peptide Fragments; D010636:Phenols; D059808:Polyphenols; D013662:Tea; D013482:Superoxide Dismutase; D002394:Catechol O-Methyltransferase