Ceramidu

Ceramidu, also called ceramide, is a class of lipid molecules formed by a fatty acid linked to a sphingoid base, typically sphingosine, through an amide bond. They are a central component of sphingolipids and are found in all eukaryotic cells, with especially high abundance in the skin.

In humans, ceramidu are a dominant constituent of the lipid matrix in the stratum corneum, where they, together with cholesterol and free fatty acids, form intercellular lipid lamellae that help maintain skin barrier integrity and regulate transepidermal water loss. Ceramidu also participate in signaling pathways related to cell differentiation, proliferation, and programmed cell death.

Biosynthesis occurs mainly by the de novo pathway in the endoplasmic reticulum: serine palmitoyltransferase condenses serine with palmitoyl-CoA to form 3-ketosphinganine, which is reduced and then N-acylated by ceramide synthases to yield dihydroceramide, and finally desaturated to ceramide. Ceramidu can also be generated by hydrolysis of sphingomyelin via sphingomyelinases or by processing other sphingolipids. Their catabolism yields sphingosine and free fatty acids or they can be remodeled into other sphingolipids.

The ceramidu family is highly diverse, with many molecular species differing in chain length, saturation, and hydroxylation. This diversity influences membrane biophysics and cellular signaling, and ceramidu levels are studied as biomarkers in metabolic and inflammatory diseases. In skincare, ceramidu are used to restore barrier function and reduce moisture loss, with deficiencies linked to conditions such as atopic dermatitis.