Orally administered sphingomyelin in bovine milk is incorporated into skin sphingolipids and is involved in the water-holding capacity of hairless mice.

BACKGROUND: We previously reported that dietary sphingomyelin (SM) concentrate from bovine milk improves epidermal functions. SM is a known precursor of ceramide (Cer) in the stratum corneum (SC). Neither the uptake nor distribution of orally administered SM nor its effects on epidermal functions have been demonstrated. OBJECTIVE: We evaluated the effects of dietary SM on epidermal functions, and the distribution and fate of its radiolabeled metabolites in mice orally administered [4,5-(3)H-sphinganyl] sphingomyelin ((3)H-SM). METHODS: Bovine milk SM (98% purity) was administered orally to 13-week-old hairless mice at 142 mg/kg per day for eight weeks. Their SC hydration, transepidermal water loss (TEWL), and SC Cer content were measured. (3)H-SM was then administered orally to 10-week-old hairless mice. Its distribution and metabolites in the skin were evaluated with whole-body autoradiography, liquid scintillation counting, and thin-layer chromatography. RESULTS: SC hydration in the SM-administered mice was higher than that in control mice, whereas their TEWL and Cer contents did not differ. Radioactivity was distributed extensively in the bodies of the experimental mice and decreased gradually with time. In contrast, the radioactivity in the SC remained constant after its administration, and radiolabeled SM and Cer were detected in the skin. This suggests that dietary SM is transferred to the skin and then converted to Cer in the SC. CONCLUSIONS: Orally administered SM is incorporated into skin SM and converted to SC Cer, which is involved in the water-holding capacity of the SC.

Investigation into the dosage of dietary sphingomyelin concentrate in relation to the improvement of epidermal function in hairless mice.

We previously found that dietary sphingomyelin (SPM) concentrate from bovine milk improved epidermal function. In this study, we investigated the dosage of dietary SPM concentrate from bovine milk in relation to the improvement of epidermal function. Thirteen-week-old hairless male mice were separated into four experimental groups, each fed one of four types of experimental diet: the control group, the low SPM group, the medium SPM group and the high SPM group. The mice were each fed the experimental diet for 6 weeks. The stratum corneum hydration and the transepidermal water loss (TEWL) were measured using a Corneometer and a Tewameter at 3 weeks and 6 weeks. After the feeding period, ceramides in the stratum corneum were analyzed. We found that the stratum corneum hydration in all the SPM groups was significantly higher than that in the control group, whereas TEWL in all the SPM groups was significantly lower than that in the control group. Ceramides increased significantly in mice fed the medium SPM diet and statistically tended to increase in mice fed the high SPM diet. Our results indicate that a daily intake of 17 mg SPM concentrate is enough to improve epidermal function in hairless mice.