Effects of royal jelly and its extracts on endometrial receptivity and MCF-7 cell growth in rats with thin endometrium

• RJ, protein extract, and fatty acid extracts may regulate estrogen-like effects. • High protein and fatty acid extract doses promoted breast cancer cell growth. Therefore, the presence of estrogen-dependent growth diseases in the body should be considered when administering protein and fatty acid extracts. • RJ plays an estrogen-like role in regulating cell growth and estrogen receptor expression; however, its components are complex. The estrogen-like effect is not determined by a single component, and a deeper regulatory mechanism needs to be explored. Royal jelly (RJ) is rich in various nutrients, including proteins and amino acids. RJ consumption improves sexual and urinary function in postmenopausal women, possibly owing to its hormone-like effects. Currently, hormone regulation and assisted reproductive technologies are widely used to treat thin endometria; however, high doses of these drugs can add to liver burden. In this study, RJ proteins and fatty acids were isolated, and their therapeutic effects on thin endometria were investigated in vivo and in vitro to verify their hormone-like regulatory effects. The results showed that RJ and its extracts could regulate endometrial receptivity-related factor expression levels in rats with a thin endometrium, accelerate MCF-7 cell apoptosis, and increase estrogen receptor expression in MCF-7 cells wherein. The estrogen-like effects of RJ and the fatty acids may be the main contributors. RJ may be a potential natural hormone replacement therapy.