(Essential) Fatty Acids (oil) And Lipids In Anti-Aging Cream

– Ceramides

Ceramides are a family of lipid molecules. A ceramide is composed of sphingosine and a fatty acid. Ceramides are found in high concentrations within the cell membrane of cells. They are one of the component lipids that make up sphingomyelin, which is one of the major lipids in the lipid bilayer of cell membrane.

Skin Ceramides – exceptionally, the stratum corneum of the skin in which the outer-most layer consists of dead cells contains relatively high levels of ceramides (as much as 50% of the total lipids), including O-acylceramides. These are present mainly in the extracellular matrix (interstices) and are accompanied by nearly equimolar amounts of cholesterol, and free fatty acids. This ratio is believed to be essential for the normal organization of the tissue into the membrane structures that are responsible for functioning of the epidermal barrier. Ceramides exist both in the free form and linked by ester bonds to structural proteins. The lipid organization in the membranes of skin is different from that of other biological membranes in that two lamellar phases are present, which form crystalline lateral phases mainly, with repeat distances of approximately 6 and 13 nm. Small sub-domains of lipids in a liquid phase may also exist.

Some of these skin ceramides have distinctive structures not seen in other tissues, and eleven forms are commonly recognized. They can contain the normal range of longer-chain fatty acids (some with hydroxyl groups in position 2), linked both to dihydroxy bases with trans-double bonds in position 4 or to trihydroxy bases. In addition, there are O-acyl ceramides in which the long-chain fatty acid component (typically C30) has a terminal hydroxyl group, which may be in the free form or esterified with either linoleic acid or a 2-hydroxy acid; the sphingoid base can be either di- or trihydroxy; the latter is not a common feature in sphingolipids of animal origin, and can include phytosphingosine and the unique 6-hydroxy-4-sphingenine in human epidermis. In addition, several molecular forms of glucosylceramide, based on similar ceramide structures, have been characterized in skin, and these are also essential for its proper function. Some ceramides with a terminal omega-hydroxy group also bind covalently to the proteins of the cornified envelope, especially to involucrin.

Depending on the particular layer of the skin (stratum corneum, etc.), the lipid composition can vary. These lipids have an obvious role in the barrier properties of the skin, limiting loss of water and solutes and at the same time preventing ingress of harmful substances. As the aliphatic chains in the ceramides and the fatty acids are mainly non-branched long-chain saturated compounds with a high melting point and a small polar head group, the lipid chains are mostly in a solid crystalline or gel state, which exhibits low lateral diffusional properties with low permeability at physiological temperatures. There is a report that the stratum corneum layer of the skin has a water permeability only one thousandth that of other biomembranes. Natural and synthetic ceramides are now commonly added to cosmetics and other skin care preparations.

Skin as a barrier system inhibits water movement via its extracellular matrix. Ceramides are necessary for the skin’s water-retention capacity as well as for cell regulation. Adding ceramides to skin-care products can help to restore the skin’s barrier system.