Ceramidi

Ceramidi, in English often referred to as ceramides, are a family of lipid molecules consisting of a fatty acid linked to a sphingoid base by an amide bond. They are a major component of the lipid matrix that makes up cell membranes, and in mammals they are especially abundant in the stratum corneum, the outermost layer of the skin. Ceramidi are also found in other tissues where they participate in signaling processes.

Structurally, ceramidi are sphingolipids. The common backbone is sphingosine, to which a fatty acid is attached. Variants differ in the length and hydroxylation of the fatty acid and in the sphingoid base, leading to multiple ceramide species. In biological membranes, ceramidi interact with cholesterol and free fatty acids to form the lipid lamellae that contribute to barrier properties.

Biosynthesis occurs mainly in the endoplasmic reticulum via the de novo pathway, beginning with serine and palmitoyl-CoA and proceeding through ceramide synthases to generate various ceramide species. Ceramidi can be further metabolized into complex sphingolipids such as sphingomyelin and glycosphingolipids, or degraded by ceramidases to release sphingosine.

Functionally, ceramidi are critical for maintaining skin barrier integrity and regulating transepidermal water loss. Reduced ceramide levels are linked to dry skin, aging, and certain disorders such as ichthyosis and atopic dermatitis. Because of their barrier-enhancing properties, ceramidi are widely used in cosmetic and dermatological products to restore or support skin hydration and resilience.