EGCG Modulation of Food Intake and Endocrine Systems

The mechanism by which EGCG suppresses prostate tumor growth may be very complex. Many in-vitro effects of EGCG, including inhibition of cancer cell mobility, inhibition of key enzymes and protein factors, induction of apoptosis, and inhibition of angiogenesis, have been shown (1). It is very difficult to assess whether these in-vitro observations are related to in-vivo effects because EGCG and other catechins can interact non-specifically with enzymes or other macromolecules as well as cellular membranes.

We have studied the effects of EGCG on endocrine systems (1, 26, 27) We found that EGCG, given to rats by ip injection, could within one week reduce body weight by about 20%. Other structurally related catechins, such as EC, EGC, or ECG were not effective at the same dose. Reduction ofbody weight appeared to be due to EGCG-induced reduction in food intake. EGCG, therefore, may influence neuropeptides and cause the loss of appetite.

After 7 days of daily ip treatment with EGCG, circulating levels of testosterone are reduced by about 75% in male rats and 17(3-estradiol levels by 34% in female rats. The weights of A-sensitive organs, such as ventral prostate and seminal vesicles and estrogen-sensitive organs, such as the uterus and ovary were reduced by about 50%. Other catechins were not as effective as EGCG. We also found that the serum level of LH is reduced by 40-50%, suggesting that low LH production led to the reduced blood levels of sex hormones. In both male and female rats, we observed significant reduction in blood levels of leptin, IGF-I, and insulin (1, 26). Some of these peptide hormones may modulate the levels of sex hormone and indirectly alter tumor growth in the animals.

In male rats treated with EGCG for one week, the serum level of protein, fatty acids, and glycerol were not altered, but significant reductions in serum glucose (-32%), lipids (-15%), triglycerides (-46%) and cholesterol (-20%) were observed. Based on proximate composition analysis, there was no change in % water and protein content, a moderate decrease in carbohydrate content, but a very large reduction in fat content, decreasing from 4.1% in control to 1.4% in EGCG-treated group. EGCG treatment also decreases subcutaneous fat by 40 to 70%, and abdominal fat by 20 to 35% in male rats (1, 26). Reduction of body fat may also influence the hormonal levels in animals and influence tumor growth.

Although orally administered EGCG is not as effective as ip injected EGCG (26), probably due to poor intestinal EGCG absorption, long-term oral use of green tea beverage or EGCG-containing drinks may mimic the effects of ip injected EGCG. This was clearly shown by Gupta, et. al. (28) who used a transgenic adenocarcinoma of the mouse prostate (TRAMP) model that mimics progressive forms ofhuman PCA. When these mice were orally infused with green tea polyphenols, in an amount equivalent to six cups of green tea per day in humans, PCA development was significantly inhibited and mice survival was increased. The green tea polyphenol infusion almost completely inhibited distant site metastasis.

0 0

Post a comment