Background and objectives: Cell longevity is linked to sirtuins (silent information regulators), which belong to a family of enzymes implicated in gene silencing, apoptosis, fatty acid metabolism, and regulation of cellular life spans of organisms. Sirtuins are associated with genes that coordinate and optimize the functions of cells as cells struggle to survive in a stressful environment, as it is the case for skin cells. This study focuses on 1) yeast Kluyveromyces biopetides in stimulating the expression of sirtuin in human cutaneous cells and 2) the benefit for the skin of an active skin care product containing yeast Kluyveromyces biopetides.
Methods: Silent mating type information regulation 2 homolog 1 (SIRT1) was investigated by immunostaining, Westem blotting, and cytometry on normal human skin cells in culture and on healthy skin samples ex vivo. SIRT7 are mammalian versions of the yeast SIR2 gene. Cellular integrity and aging was followed by comet assays measuring DNA fragmentation and beta galactosidase activity (a marker of senescence). The test product was yeast Kluyveromyces biopeptides. Thirty-three female subjects aged 37 to 64 years (mean 51.6 years) enrolled in the study. Subjects applied a formulation enriched in 1% of the yeast biopeptides SIRT1 activator once daily to the face and neck for 4 weeks. Dermatologists used a graded scale (1-9) to score fine lines and wrinkles, hydration, pigment color intensity, complexion radiance, skin density, firmness, complexion homogeneity, and texture of the skin before and after the first application and again after 4 weeks of use. A Pixel Skin method, based on an analysis of the gray-level variance and surface of imperfections (age-related parameters) from numerical pictures of the faces, was used to objectively measure the skin care efficacy.
Results: The yeast Kluyveromyces biopeptides 1) significantly increased SIRT1 expression in normal human dermal skin fibroblasts in vitro (+172%) and in epidermal cells of healthy human skin ex vivo and 2) decreased cell senescence and DNA fragmentation induced by ultraviolet-B (UVB) stress. At the end of the study, facial improvements could be seen on fine lines and wrinkles, hydration, pigmented spot color intensity, complexion radiance, firmness, complexion homogeneity, and texture. Improvement in hydration was significant immediately after the first application. Skin-pixel measurement and analysis show a significant reduction of the gray variance linked to pixel heterogeneity (-4.2%) and a significant reduction of the surface of skin imperfections (-30.4%). All the indicators from clinical evaluation to the objective measurements of the skin show a significant improvement of the aged skin.
Conclusion: These results demonstrate the efficacy of the yeast Kluyveromyces biopeptides in activating SIRT 1 of human skin cells, improving their DNA resistance and senescence, and of a formulation enriched in this ingredient in treating multiple skin aging signs.