Effects of anastrozole on lipid metabolism compared with tamoxifen in rats

Background. Anastrozole, a new aromatase inhibitor, has been used to treat postmenopausal metastatic breast cancer, and several clinical trials of adjuvant treatment using this agent are ongoing. However, the effects of anastrozole on lipid metabolism are unknown. The aim of this study was to evaluate the effect of anastrozole on lipid metabolism, especially lipoprotein lipase (LPL) activity, compared with tamoxifen in rats. Methods. Ovariectomized female rats were divided into six groups: C, controls; T, tamoxifen treatment; A, anastrozole treatment; CAT, combined anastrozole/tamoxifen treatment; NAT, no treatment after tamoxifen; and AAT, anastrozole treatment after tamoxifen. The agents were orally administered for 3 weeks. Serum total cholesterol, triglycerides, and LPL activity in postheparin plasma were measured at the end of the experiment. Results. Serum cholesterol levels were significantly lower in the T and CAT groups than in controls (P < 0.001). Serum triglyceride levels were significantly higher in the T group than in the other groups (P < 0.001). LPL activity was significantly lower in T and AAT groups (P < 0.01). There was no significant difference in any parameters in group A. Conclusions. Anastrozole does not affect lipid metabolism including LPL activity. There was little effect on lipid profiles during combination treatment or following treatment with tamoxifen. In a clinical setting, therefore, anastrozole might be safe for patients with abnormal triglyceride profiles during tamoxifen treatment.