Contrasting effects of estradiol, testosterone and of a black cohosh extract on density, mechanical properties and expression of several genes in the metaphysis of the tibia and on fat tissue of orchidectomized rats

Abstract 

Objectives

Orchidectomy (orx) of rats increases bone metabolism, the activity of osteoclasts more than of osteoblasts which results in osteoporosis. As testosterone (T) may be metabolized to estrogens, the effects of a 3-month treatment of orx rats with an aqueous/ethanolic extract of black cohosh (Cimicifuga racemosa=CR) T, estradiol-17β (E2) on density of cortical and cancellous structures of the proximal tibia was determined. The CR preparation was tested, because it contains unidentified substances which appear also to be antiosteoporotic.

Methods

Bone density of the metaphysis of the tibia was measured by quantitative computer tomography. Stability of the tibia and expression of osteoblast- and osteoclast-specific genes in the metaphysis of the tibia were also studied.

Results

Cancellous density but not the total area of the cancellous metaphysis was significantly reduced in control animals and this effect could in part be prevented by E2, T and the CR extract. Cortical parameters were unaffected by T and the CR extract while E2 reduced the total cortical area. The mechanical stability was highest in the E2- and CR and low in orx and T-treated animals. Gene expression of osteocalcin, TGFβ1 and tartrate-resistant acid phosphatase was reduced by E2 and the CR extract whereas T treatment increased these parameters. Since orx results in increased bodyweight, the sizes of two fat depots as well as serum leptin concentrations were also determined. E2 and the CR extract but not T prevented the orx-induced fat accumulation largely, resulting in reduced leptin concentrations.

Conclusions

It is concluded that the effects of E2 and T in the bone and in fat tissue are dissimilar in that only E2 extract but not T increase bone stability and decrease fat accumulation. The CR extract BNO 1055 had mild antiosteoporotic and lipolytic or antilipotropic effects which may make these extracts useful to prevent osteoporosis in males.

Keywords: Cimicifuga racemosa, Bone, Fat tissue