Protective effect of green tea polyphenols on bone loss in middle-aged female rats.
Recent studies have suggested that green tea polyphenols (GTP) are promising agents for preventing bone loss in women. Findings that GTP supplementation resulted in increased urinary GTP concentrations and bone mass via an increase of antioxidant capacity and/or a decrease of oxidative stress damage suggest a significant role of GTP in bone health of women.


BACKGROUND
Recent studies suggested that green tea polyphenols (GTP) are promising agents for preventing bone loss in women. However, the mechanism related to the possible protective role of GTP in bone loss is not well understood.


METHODS
This study evaluated bioavailability, mechanisms, bone mass, and safety of GTP in preventing bone loss in middle-aged rats without (sham, SH) and with ovariectomy (OVX). A 16-week study of 2 (SH vs. OVX) x 3 (no GTP, 0.1% GTP, and 0.5% GTP in drinking water) factorial design using 14-month-old female rats (n = 10/group) was performed. An additional 10 rats in baseline group were euthanized at the beginning of study to provide baseline parameters.


RESULTS
There was no difference in femur bone mineral density between baseline and the SH+0.5% GTP group. Ovariectomy resulted in lower values for liver glutathione peroxidase activity, serum estradiol, and bone mineral density. GTP supplementation resulted in increased urinary epigallocatechin and epicatechin concentrations, liver glutathione peroxidase activity and femur bone mineral density, decreased urinary 8-hydroxy-2'-deoxyguanosine and urinary calcium levels, but no effect on serum estradiol and blood chemistry levels.


CONCLUSIONS
We conclude that a bone-protective role of GTP may contribute to an increase of antioxidant capacity and/or a decrease of oxidative stress damage.
Shen
C-L
CL
Department of Pathology, Texas Tech University Health Sciences Center, BB 198, 3601 4th street, Lubbock, TX, 79430-9097, USA. leslie.shen@ttuhsc.edu
Wang
P
P
Guerrieri
J
J
Yeh
J K
JK
Wang
J-S
JS
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D015519:Bone Density / Q000187:drug effects*; D002118:Calcium / Q000652:urine; D002392:Catechin / Q000031:analogs & derivatives / Q000494:pharmacology / Q000652:urine; D004958:Estradiol / Q000097:blood; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000187:drug effects*; D005979:Glutathione Peroxidase / Q000008:administration & dosage / Q000652:urine*; D015675:Osteocalcin / Q000097:blood / Q000494:pharmacology; D010024:Osteoporosis / Q000378:metabolism / Q000517:prevention & control*; D010052:Ovariectomy; D028321:Plant Preparations / Q000494:pharmacology*; D011859:Radiography; D051381:Rats; D017207:Rats, Sprague-Dawley; D013662:Tea
D000975:Antioxidants; D028321:Plant Preparations; D013662:Tea; D015675:Osteocalcin; D004958:Estradiol; D002392:Catechin; D005979:Glutathione Peroxidase; C057580:gallocatechol; D002118:Calcium