Objective: Menoprogen (MPG), a traditional Chinese medicine formula for menopause, improves menopausal symptoms; however, its mechanism remains unknown. Previous studies have shown that MPG is not directly estrogenic; thus, the goal of this study was to investigate the effects of MPG on insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-1 (IGFBP-1) levels in an aged female rat model of menopause.
Methods: In a six-arm study, 14-month-old female Sprague-Dawley rats (n = 8 per arm) were randomly divided into the following groups: untreated aged, 17β-estradiol-treated aged (estradiol [E2]), and three arms with increasing doses of MPG (162, 324, or 648 mg/kg/d). The sixth arm contained 4-month-old female Sprague-Dawley rats as a normal comparison group. Four weeks after MPG or E2 administration, animals were killed after blood draws, and ovarian tissues were excised. Levels of E2 and progesterone (P4) were determined by radioimmunoassay. Serum and ovarian tissue levels of IGF-1, IGFBP-1, and IGF-1 receptor were determined by enzyme-linked immunosorbent assay.
Results: Compared with the normal group, aged rats had significantly reduced serum levels of E2, P4, and IGF-1, and increased serum and ovarian tissue levels of IGFBP-1. MPG restored serum IGF-1 and IGFBP-1 levels and down-regulated ovarian levels of IGFBP-1, which were closely related to increases in E2 and P4 levels in aged rats. No significant differences in either IGF-1 or IGFBP-1 were observed between the three doses of MPG.
Conclusions: MPG exerts a direct in vivo effect on aged female rats by positively regulating serum and ovarian IGF-1 and IGFBP-1 levels.