Tea and circulating estrogen levels in postmenopausal Chinese women in Singapore.
The role of tea in the etiology of breast cancer is controversial. We recently provided the first set of human evidence that breast cancer risk is significantly inversely associated with tea intake, largely confined to intake of green tea.
Since black tea and green tea possess comparable levels of the total tea polyphenols that possess antioxidative activities, reasons for the paradoxical effects of green tea and black tea on breast cancer protection are not apparent. Some limited evidence suggests that green tea may have downregulatory effects on circulating sex-steroid hormones, whereas
black tea may have upregulatory effects.
We therefore, investigated the relationship between tea intake, and plasma estrogen and androstenedione levels in a cross-sectional study of healthy postmenopausal Chinese women in Singapore.
In this group of 130 women, 84 were non or irregular (less than once a week) tea drinkers, 27 were regular (weekly/daily) green tea drinkers and 19 were regular (weekly/daily) black tea drinkers. Relative to plasma estrone levels in non- or irregular tea drinkers (29.5 pg/ml) the levels were 13% lower in regular green tea drinkers (25.8 pg/ml) and 19% higher in regular black tea drinkers (35.0 pg/ml).
These differences in estrone levels were statistically significant (P = 0.03) inspite of adjusting for age, body mass index, intake of soy, and other covariates. A similar pattern of differences between tea intake, and plasma levels of estradiol (P = 0.08) and androstenedione (P = 0.14) were found.
In addition, the tea-estrogen associations were observed irrespective of the genotype of catechol-O-methyltransferase (COMT), a major enzyme that aids in the excretion of tea polyphenols in humans.
Larger studies are needed to confirm results from this cross-sectional study and to better understand the potentially differing effect of black and green tea on circulating estrogen levels and ultimately on the risk of breast cancer.
Black tea and D. candidum extracts play estrogenic activity via estrogen receptor α-dependent signaling pathway
Prolonged BT and DC treatments increase the expression of ESR1 and PGR
Further, we analyzed the effects of long term exposure to BT/DC extracts on estrogen and progesterone receptors besides the acute treatments. Consistent with the above signaling, the estrogen receptor α (ESR1) and the progesterone receptor (PGR) were up-regulated in the protein expression after prolonged BT, DC and BT-DC treatments (Figure 6, P<0.001 each concentration vs. control). In parallel, the mRNA levels of ESR1 and PGR were determined by real-time qPCR. As shown in Figure 7, prolonged exposure to BT and DC extracts (included their combination) enhanced the mRNA expression of ESR1 and PGR (P<0.01 vs. control). Collectively, phytoestrogens induced estrogen and progesterone receptors expression via a prolonged activation.
![[Image: ajtr0010-0114-f6.jpg]](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5801351/bin/ajtr0010-0114-f6.jpg)
Figure 6
Prolonged Black tea and D. candidum treatments increase the expression of the estrogen receptor α (ERα) and progesterone receptor (PGR). A. ERα and PGR expression and statistical analysis in Black tea extract treated groups. B. ERα and PGR expression and statistical analysis in D. candidum extract treated groups. C. ERα and PGR expression and statistical analysis in Black tea and D. candidum extract treated groups. The ESR1 and PGR expression statistics are shown under the Western blot bands. *P<0.05, **P<0.01, ***P<0.001.
Best Wishes,
Pandora
The role of tea in the etiology of breast cancer is controversial. We recently provided the first set of human evidence that breast cancer risk is significantly inversely associated with tea intake, largely confined to intake of green tea.
Since black tea and green tea possess comparable levels of the total tea polyphenols that possess antioxidative activities, reasons for the paradoxical effects of green tea and black tea on breast cancer protection are not apparent. Some limited evidence suggests that green tea may have downregulatory effects on circulating sex-steroid hormones, whereas
black tea may have upregulatory effects.
We therefore, investigated the relationship between tea intake, and plasma estrogen and androstenedione levels in a cross-sectional study of healthy postmenopausal Chinese women in Singapore.
In this group of 130 women, 84 were non or irregular (less than once a week) tea drinkers, 27 were regular (weekly/daily) green tea drinkers and 19 were regular (weekly/daily) black tea drinkers. Relative to plasma estrone levels in non- or irregular tea drinkers (29.5 pg/ml) the levels were 13% lower in regular green tea drinkers (25.8 pg/ml) and 19% higher in regular black tea drinkers (35.0 pg/ml).
These differences in estrone levels were statistically significant (P = 0.03) inspite of adjusting for age, body mass index, intake of soy, and other covariates. A similar pattern of differences between tea intake, and plasma levels of estradiol (P = 0.08) and androstenedione (P = 0.14) were found.
In addition, the tea-estrogen associations were observed irrespective of the genotype of catechol-O-methyltransferase (COMT), a major enzyme that aids in the excretion of tea polyphenols in humans.
Larger studies are needed to confirm results from this cross-sectional study and to better understand the potentially differing effect of black and green tea on circulating estrogen levels and ultimately on the risk of breast cancer.
Black tea and D. candidum extracts play estrogenic activity via estrogen receptor α-dependent signaling pathway
Prolonged BT and DC treatments increase the expression of ESR1 and PGR
Further, we analyzed the effects of long term exposure to BT/DC extracts on estrogen and progesterone receptors besides the acute treatments. Consistent with the above signaling, the estrogen receptor α (ESR1) and the progesterone receptor (PGR) were up-regulated in the protein expression after prolonged BT, DC and BT-DC treatments (Figure 6, P<0.001 each concentration vs. control). In parallel, the mRNA levels of ESR1 and PGR were determined by real-time qPCR. As shown in Figure 7, prolonged exposure to BT and DC extracts (included their combination) enhanced the mRNA expression of ESR1 and PGR (P<0.01 vs. control). Collectively, phytoestrogens induced estrogen and progesterone receptors expression via a prolonged activation.
Figure 6
Prolonged Black tea and D. candidum treatments increase the expression of the estrogen receptor α (ERα) and progesterone receptor (PGR). A. ERα and PGR expression and statistical analysis in Black tea extract treated groups. B. ERα and PGR expression and statistical analysis in D. candidum extract treated groups. C. ERα and PGR expression and statistical analysis in Black tea and D. candidum extract treated groups. The ESR1 and PGR expression statistics are shown under the Western blot bands. *P<0.05, **P<0.01, ***P<0.001.
Best Wishes,
Pandora