Lifespan-extending effects of royal jelly and its related substances on the nematode Caenorhabditis elegans

Abstract

Background: One of the most important challenges in the study of aging is to discover compounds with longevity-promoting activities and to unravel their underlying mechanisms. Royal jelly (RJ) has been reported to possess diverse beneficial properties. Furthermore, protease-treated RJ (pRJ) has additional pharmacological activities. Exactly how RJ and pRJ exert these effects and which of their components are responsible for these effects are largely unknown. The evolutionarily conserved mechanisms that control longevity have been indicated. The purpose of the present study was to determine whether RJ and its related substances exert a lifespan-extending function in the nematode Caenorhabditis elegans and to gain insights into the active agents in RJ and their mechanism of action.

Principal findings: We found that both RJ and pRJ extended the lifespan of C. elegans. The lifespan-extending activity of pRJ was enhanced by Octadecyl-silica column chromatography (pRJ-Fraction 5). pRJ-Fr.5 increased the animals' lifespan in part by acting through the FOXO transcription factor DAF-16, the activation of which is known to promote longevity in C. elegans by reducing insulin/IGF-1 signaling (IIS). pRJ-Fr.5 reduced the expression of ins-9, one of the insulin-like peptide genes. Moreover, pRJ-Fr.5 and reduced IIS shared some common features in terms of their effects on gene expression, such as the up-regulation of dod-3 and the down-regulation of dod-19, dao-4 and fkb-4. 10-Hydroxy-2-decenoic acid (10-HDA), which was present at high concentrations in pRJ-Fr.5, increased lifespan independently of DAF-16 activity.

Conclusions/significance: These results demonstrate that RJ and its related substances extend lifespan in C. elegans, suggesting that RJ may contain longevity-promoting factors. Further analysis and characterization of the lifespan-extending agents in RJ and pRJ may broaden our understanding of the gene network involved in longevity regulation in diverse species and may lead to the development of nutraceutical interventions in the aging process.

Figure 1. The effects of RJ on the lifespan of C. elegans.

The survival curves of N2 hermaphrodites treated with RJ (0 (control), 1, 10 or 100 µg/ml) are shown. These substances were administered at 20°C, from the young adult stage until death. Day 0 corresponds to the L4 molt. The percentage of live worms is plotted against adult age. Detailed parameters are presented in Table S1.

Figure 2. The effects of pRJ on the lifespan of C. elegans.

The survival curves of N2 hermaphrodites treated with pRJ (0 (control), 1, 10 or 100 µg/ml) are shown. The experiment was performed as described in Figure 1 Legend. Detailed parameters are presented in Table S1.

Figure 3. The effects of pRJ-Fr.4 on the lifespan of C. elegans.

The survival curves of N2 hermaphrodites treated with pRJ Fr.4 (0 (control), 5, 10 or 25 µg/ml) are shown. The experiment was performed as described in Figure 1 Legend. Detailed parameters are presented in Table S1.

Figure 4. The effects of pRJ-Fr.5 on the lifespan of C. elegans.

Survival curves of N2 hermaphrodites treated with pRJ-Fr.5 (0 (control), 10, 25 or 100 µg/ml). The experiment was performed as described in Figure 1 Legend. Detailed parameters are presented in Table S1.

Figure 5. The effects of pRJ-Fr.5 treatment on gene expression in C. elegans.

Relative expression levels of genes (ins-9, dod-3, dod-19, dao-4, and fkb-4) in N2 hermaphrodites treated with pRJ-Fr.5 (0 (control) or 25 µg/ml) for 24 h starting at the L4 stage. Data are expressed as the mean ± S.E. (n = 3). *: p<0.05; **: p<0.01, compared with control (Student's t test).

Figure 6. The effects of pRJ-Fr.5 on the lifespan of daf-16(mu86) mutants.

The survival curves of daf-16(mu86) mutant hermaphrodites treated with pRJ-Fr.5 (0 (control) or 25 µg/ml). The experiment was performed as described in Figure 1 Legend. Detailed parameters are presented in Table S1.

Figure 7. The effects of 10-HDA on the lifespan of C. elegans.

The survival curves of N2 hermaphrodites incubated with 10-HDA (0 (control), 10, 25, 50 or 100 µM) are shown. The experiment was performed as described in Figure 1 Legend. Detailed parameters are presented in Table S3.

Figure 8. The effects of 10-HDA on the lifespan of daf-16(mu86) mutants.

The survival curves of daf-16(mu86) mutant hermaphrodites incubated with 10-HDA (0 (control), 10, 25, 50 or 100 µM) are shown. The experiment was performed as described in Figure 1 Legend. Detailed parameters are presented in Table S3.

Figure 9. The effects of 10-HDA and/or pRJ-Fr.5 on the lifespan of C. elegans.

The survival curves of N2 hermaphrodites incubated with 10-HDA (0 or 25 µM) and/or pRJ-Fr.5 (0 or 25 µg/ml) are shown. The experiment was performed as described in Figure 1 Legend. Detailed parameters are presented in Table S3.