Effects of estradiol (E2) and some phytoestrogens (PEs) containing plant extracts on differentiated 3T3-L1 fat cells

Adipose tissue expresses both E2-receptors (ERα+β) and a variety of proteins that may be associated with diabetes type II and other obesity-related diseases. Little information is available about effects of PEs on fat tissue. Therefore, we investigated the effects of PE containing extracts of Vitex Agnus castus (AC) BNO 1095, of Belamcanda chinensis (BC) BNO 1420, of Cimicifuga racemosa (CR) BNO 1055, of silymarin a purified extract of Silybum marianum and of a soy extract at concentrations of 20µg/ml on differentiated mouse 3T3-L1 cells as a model of adipocytes. E2 (10–7 M) served as positive control. After 48 hs incubation in steroid free medium glycerol release was measured as an index of cellular lipolytic activity. E2, SM, soy, and CR but not AC and BC reduced lipolytic activity. (P<0.05). Leptin release reflecting the amount of fat stored in 3T3-L1 was decreased by all tested compounds, this effect was significant for E2 and SM (<60% vs. control). Resistin plays a role in development of insulin resistance. Its gene expression determined by real-time PCR was reduced by SM (P<0.05) while E2, AC, and CR were ineffective. In contrast a 2-fold increase (P<0.05) of mRNA levels were found in soy- and BC-treated 3T3-L1 cells. Adipose tissue is a prominent source of the plasminogen activator inhibitor-1 a major regulator of the fibrinolytic system of which gene expression was 5-fold higher in SM-treated cells than in controls while E2 caused a significant reduction. All other tested extracts were without effects. ER-α mRNA of 3T3-L1 cells was significantly reduced in E2-treated cells while BC had a reverse effect (1.8-fold increase, P<0.05). Proliferation experiments performed with undifferentiated 3T3-L1 preadipocytes revealed a significant, dose-dependent inhibition after SM-, CR-, and soy-treatment assessed with BrdU while E2, AC, and BM had minor effects. In conclusion, results show that PEs of plant extracts which are discussed as an alternative for HRT have pronounced but not consistently estrogenic effects in fat tissue.