Nicotinamide (NAM) is a NAM adenine dinucleotide precursor that benefits skin health in numerous ways. Under standard culture conditions, it slows down the differentiation and boosts the proliferation of human primary keratinocytes, causing the maintenance of stem cells. 

Tan et al, in their recent study, investigated the effects of NAM on photoaging in two-dimensional human primary keratinocyte cultures and three-dimensional organotypic epidermal models. They observed that both models showed that ultraviolet B (UVB) irradiation and hydrogen peroxide induce premature terminal differentiation and senescence in human primary keratinocytes. In three-dimensional organotypic, they characterized phenotype by thickening the granular layer expressing filaggrin and loricrin, but thinning the epidermis overall. NAM showed to restrict premature differentiation and decrease senescence by maintaining lamin B1 levels in both models. It also showed decreased lipofuscin staining and reduced interleukin (IL)-6/IL-8 secretion in three-dimensional models contrasting those in UVB-only controls. The DNA damage after irradiation also included a decline in energy metabolism, which NAM partially prevented. 

These data indicate the protective effects of NAM against photoaging and oxidative stress in the human epidermis and pinpoint DNA repair and energy metabolism as crucial underlying mechanisms.

Source: Tan CYR, Tan CL, Chin T, et al. Nicotinamide prevents UVB- and oxidative stress-induced photoaging in human primary keratinocytes. J Invest Dermatol. 2022;142(6):P1670-81.e12.