Effect of Royal Jelly on Mouse Isolated Ileum and Gastrointestinal Motility

Royal jelly (RJ) is widely used as a cosmetic or dietary supplement to relieve various health disorders, such as dry skin, fatigue, and menopause. RJ has been recommended to improve constipation on a commercial basis. However, the detailed mechanisms by which RJ influences intestinal motility and whether RJ improves constipation remain unclear. Therefore, we investigated the effects of RJ on the motility of mouse ileum both in vitro and in vivo. Using myograph methods, RJ dose-dependently induced contractions of isolated ileal segments, which were inhibited by treatment with atropine. Eserine sulfate, a cholinesterase inhibitor, enhanced the RJ-induced contractions, whereas RJ treated with acetylcholinesterase did not result in ileum contraction. RJ-induced contractions were not affected by N^G-nitro-l-arginine methyl ester, a nitric oxide synthase inhibitor, although nicotine-induced contractions were significantly enhanced. In contrast, in a gastrointestinal (GI) transit model, single oral administration of 300 mg/kg RJ did not affect GI transit in both normal mice and the loperamide-induced constipation model mice. These results demonstrate that acetylcholine in RJ directly acted on the muscarinic receptors of the mouse intestinal smooth muscle, causing it to contract in vitro. In contrast, single oral administration of RJ did not improve constipation. This study is the first to evaluate the effects of RJ on the motility of mouse ileum in in vitro and in vivo experiments for the validation of application of RJ as a gentle laxative.