Aim: 

The population of the developed world is ageing. Females live longer than males and these differences may be explained by estrogens. Our aim was to study the effect of the initiation of the estrogen replacement therapy (ERT) after the ovariectomy on oxidative stress parameters and in vivo glucose uptake.

Methods: 

We used 50 female Wistar rats. Thirty-eight were ovariectomiced and treated for 0, 3, 6 or 9 weeks with 17b-estradiol (1mg/kg/day) or vehicle subcutaneously. After 18F-fluordeoxyglucose (FDG) intravenous administration in vivo, brain glucose uptake was measured by positron emission tomography (PET). Oxidative stress parameters were measured by HPLC and spectrophotometric methods.

Results: 

We found that brain glucose uptake was lower in ovariectomized compared with control rats and similar to old rats. Immediate administration of ERT after ovariectomy prevented the loss of glucose uptake. However, implementation of ERT after 3, 5 or 9 weeks after ovariectomy did not recover glucose uptake. Similar results were obtained when measuring oxidative stress parameters. Ovariectomized rats had higher oxidative stress compared with control rats which was only prevented by immediate administration of ERT.

Conclusion: 

Immediate administration of estradiol after ovariectomy recovers brain glucose uptake and lowers oxidative stress parameters. However, ERT 3, 6 or 9 weeks after ovariectomy is not efficient to prevent detrimental ovariectomy effects. Therefore, we suggest that ERT is only effective if administrated immediately after menopause.

This work has been supported by BFU2007-65803/BFI and ISCIII2006-RED13-027 from the 'Red Temática de investigación cooperativa en envejecimiento y fragilidad' (RETICEF RD06/003–027) to J.V., by grant GV/2007/263 to C.B and by grant GVPRE/2008/138 to J. G.