Ceramide and its metabolites (sphingosine, 4-hydroxy-dihydro sphingosine (phytosphingosine), sphingosine-1-phosphate (S1P) phytosphingosine-1-phosphate and ceramide-1-phosphate (C1P) are lipid mediators that modulate cellular function.
Ceramides and structural pseudo ceramides have been formulated in skin care products and medicine to treat xerosis, psoriasis, atopic dermatitis (AD). Topically applied ceramide, with appropriate chemical formulation, forms stable liquid crystal and bilayer structures, improving permeability barrier integrity on the skin surface. Ceramide may be incorporated into lamellar bilayer structures to enhance barrier integrity in the stratum corneum. It is noted that as changes in ceramide species occur in AD and psoriasis, ceramide species uses for topical agents must be carefully considered. Acylceramide is a ceramide species essential for forming a competent barrier. A suitable selection (and amount) of ceramide is required for the preparation of an effective topical formula. Topically applied ceramide can penetrate into nucleated layers of the epidermis, in particular in barrier-compromised skin. Absorbed ceramide is hydrolyzed to a sphingoid base and FA, which are utilized in endogenous ceramide synthesis.
Oral glycosylceramide and sphingomyelin derived from plants and milk are used (as nutraceuticals) to improve skin moisture and the epidermal permeability barrier. Some oral sphingolipids are hydrolyzed by digestive enzymes and enzymes derived from intestinal microbes and absorbed through the intestinal membrane. Sphingolipids could affect gut immunity. Absorbed sphingolipids are transferred to the liver where they are further metabolized and circulated to peripheral tissues, including skin.