With increasing age, the number of differentiated melanocytes and melanocyte stem cells decreases over time, and the probability of melanocyte proliferation and local aggregation occurring increases.
Additionally, age-related increases in oxidative stress can promote melanogenesis that stimulates remaining active melanocytes, making skin more susceptible to pigmentation problems. The main types of pigmentation seen in aging skin include sun spots, seborrheic keratosis, and melasma.
Studies have found that NMN supplementation can significantly reduce melanin production in aging melanocytes by interfering with cAMP/Wnt signaling in melanin production by regulating gene expression levels.
In the experiment, the researchers continuously subcultured young melanocytes in a culture dish until the melanocytes stopped dividing. This means that melanocytes lose their ability to divide and enter the aging stage. During this process, the researchers found that the shape of young melanocytes is regular and has 2-3 branches, but the shapes of aging melanocytes are diverse, with different cell widths and flattening degrees, and the cells have multiple branches.
Comparison of morphology of young and aged melanocytes
The researchers then treated melanocytes with NMN for 3 months and measured the amount of melanin produced by the melanocytes using spectrophotometry. It was found that compared with senescent melanocytes not treated with NMN, the relative content of melanin produced by senescent melanocytes treated with NMN was reduced by approximately 20%.
To explore the mechanism by which NMN supplementation reduces melanin production, the researchers conducted gene expression profiling on NMN-treated senescent melanocytes. The results found that compared with senescent melanocytes without NMN treatment, the expression levels of 420 genes were increased and the expression levels of 832 genes were decreased in senescent melanocytes treated with NMN. Among them, the genes with increased expression levels are all genes involved in cell proliferation and metabolism, and the genes with decreased expression levels are all related genes involved in melanin production.
Especially in the cAMP/Wnt pathway, which plays a key role in melanin production, supplementing NMN can significantly reduce the expression levels of "signaling proteins" ADCY5, ADCY9, FZD10, and WNT4. This suggests that NMN supplementation can reduce melanin production by interfering with signaling in the cAMP/Wnt pathway in melanin production by regulating gene expression levels.
.Brito, S., Baek, J.-M., Cha, B., Heo, H., Lee, S.-H., Lei, L., Jung, S.Y., Lee, S.M., Lee, S.H., Kwak, B.-M., Chae, S., Lee, M.-G. and Bin, B.-H. (2022). Nicotinamide Mononucleotide reduces melanin production in aged melanocytes by inhibiting cAMP/Wnt signaling. Journal of Dermatological Science, [online] 106(3), pp.159–169. doi:10.1016/j.jdermsci.2022.05.002.
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