A gel‐based proteomic analysis of green tea polyphenols effects on ovariectomized rats

Abstract

Our recent study has demonstrated the protective action of green tea polyphenols (GTP) against bone loss in rats with ovariectomy through their antioxidant activities 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 ovariectomized rats after GTP treatment by a gel‐based proteomic approach, which could lead to understand the mechanisms of GTP in promoting bone health. Liver samples were obtained from 14‐month‐old female ovariectomized rats treated with no GTP (OVX) or 0.5% GTP (OVX+GTP) in drinking water for 16 weeks (n=10/group). Two‐dimensional difference in gel electrophoresis combined with mass spectrometry, was used to compare the liver protein profiles of pooled samples from OVX and OVX+GTP. Liver proteins from OVX and OVX+GTP were labeled in duplicate by reversing the fluorescent dyes. Among approximately 800 reproducible protein spots detected, the level of superoxide dismutase 1 (SOD1) was 2‐fold higher in OVX+GTP versus OVX, while the level of catechol‐O‐methyltransferase (COMT) was 1.5‐fold lower in OVX+GTP versus OVX. The changes of SOD1 and COMT in individual liver sample were confirmed by Western blot. As a result, our data provide evidences for the benefits of GTP on bone health through the antioxidant role in increasing SOD1 and the estrogen‐like effect in decreasing COMT.