Niacinamide and skin pigmentation: Hakozaki et al. have studied the effect of niacinamide on reducing skin pigmentation.1 Melanin production was measured in a purifi ed mushroom tyrosinase assay, cultured melanocytes, a keratinocyte/melanocyte culture model, and a pigmented reconstructed epidermis model (PREP). The clinical trials included 18 subjects with hyperpigmentation who used a moisturizing preparation containing 5% niacinamide. Their results showed that niacinamide had no effect on the catalytic activity of mushroom tyrosinase, or on melanogenesis in cultured melanocytes. However, niacinamide gave a 35% to 68% inhibition of melanosome transfer in the culture model and reduced cutaneous pigmentation in the PREP model. In the clinical studies, niacinamide signifi cantly reduced hyperpigmentation and increased skin lightness compared with the control vehicle after four weeks of use.
Protein-bound α-hydroxyceramides and atopic dermatitis: Macheleidt et al. have published on the defi ciency of epidermal protein-bound α-hydroxyceramides in atopic dermatitis. Atopic dermatitis is a common skin disease with an impaired permeability barrier function. The etiology of the disease is unknown. The permeability barrier is located in the stratum corneum (SC), the outermost layer of the epidermis, which consists of a densely packed system of corneocytes embedded in an intercellular multilamellar lipid matrix. The lipid composition in the SC varies with individuals, as well as with age and season; nevertheless, abnormal patient profi les are discernable and associated with defi cient barrier function in skin sites affected by atopic dermatitis.