Royal jelly controls intestinal stem cell homeostasis via SIRT1/mTORC1 axis

Background and objectives: The homeostasis of the gut epithelium is maintained by the self-renewal and differentiation of intestinal stem cells (ISCs). As previous studies have described the aging-related deterioration of adult stem cell function, developing the interventions to increase the adult stem cell pool could be an efficient strategy to prevent the tissue decline during aging. On these backgrounds, we try to discover how royal jelly (RJ) affects the ISCs function. Methods: Mice were administered with RJ at 500 mg/kg/day or with 10-Hydroxydecanoic acid, which is an ingredient of RJ, at 10mg/kg/day by oral gavage for more than 6 weeks. Small intestine was isolated and used for immunohistochemistry. Proliferative function of ISCs was assessed by organoid culture from isolated crypts. ISCs and Paneth cells (stem cell niche) were isolated from Lgr5-EGFP-IRES-CreERT2 mice and were co-cultured for assessing the ISC and Paneth cell function. Results: RJ treatment of intestinal crypts (including ISCs and Paneth cells) promoted organoid formation from both young and old mice derived crypts. While RJ treatment of isolated Lgr5-positive ISCs did not promote organoid formation, Paneth cells isolated from RJ-treated mice stimulated organoid formation in co-culture with control ISCs. RJ treatment increased the number of ISCs and Paneth cells in vivo. Moreover, we found 10-Hydroxydecanoic acid, an ingrediend of RJ, mimiced the effect of RJ ex vivo and in vivo. In order to probe the mechanism of ISCs proliferation by RJ, ISCs and RJ-treated Paneth cells were co-cultured with the CAMKK inhibitor STO609, AMPK inhibitor Compound C, or the specific SIRT1 inhibitor EX527. STO609, Compound C or EX527 treatment blocked the promotion of organoid formation by RJ-treated Paneth cells. Moreover, mRNA of SIRT1 and Nampt was upregulated in RJ-treated ISCs. Finally, pS6 staining of intestine from RJ treated mice showed mTORC1 activation by RJ. These all results suggest that CaMKK-AMPK-Nampt-SIRT1-mTOCR1 pathway in ISCs mediates the effect of RJ like calorie restriction (Igarashi M et.al., Cell.2016) Conclusions: RJ expands the ISC pools though Paneth cell activation and mimics the effect of calorie restriction on ISCs. These results indicate that RJ could modify intestinal environment via Paneth cell and ISCs activation.