September 2021 • Vol. 27 • Issue 7
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Cholesterol and Its Derivatives: Underutilized Ingredients for Skincare …by Frank Schmidtmann
holesterol is one of the most well-known molecules to the average person, but it is almost always referred to with negative connotations. When most people mention cholesterol, they are often discussing how to reduce their dietary intake or control blood cholesterol levels. Most people ultimately associate cholesterol with heart disease (atherosclerosis). However, what is not always understood is that cholesterol and its derivatives are essential for all animal life. Cholesterol is found in every cell and is necessary for proper membrane stability/fluidity, and acts as a precursor for other extremely important molecules, such as vitamin D3.1 Even less well known, cholesterol components account for over one third of the intercellular lipids in human skin.2, 3 The level of cholesterol both in cells and exterior to the cells is extremely important for maintaining healthy, properly functioning skin. By extension, the use of cholesterol and its derivatives in skincare products can offer many benefits, not just in the formulation aesthetics, but for the barrier function and natural biological processes as well.
Cholesterol Function
Cholesterol is one of the main components of cell membranes and is essential for their function. It is a small, semi-rigid aliphatic (lipid) molecule consisting of multiple fused rings and is classified as a sterol (modified steroid).4 The function of cholesterol in the membrane is to increase membrane fluidity and elasticity, and control small molecule diffusion.1 The level of cholesterol present in a bilipid layer can affect the packing of membrane components, creating less voids and ultimately helping to reduce both transmembrane and lateral diffusion while still maintaining fluidity.5-7 The result is membrane barrier function. In fact, without cholesterol, membranes would be rigid, brittle, and unable to create viable barriers for cellular functions. This function in cellular membranes is directly related to the utilization of cholesterol in the skin. The extracellular lipid matrix (material between skin cells) in the stratum corneum consists of approximately 35% cholesterol and cholesterol sulfate.2, 3 Cholesterol works to create fluid lamellar layers in the lipid matrix, very similar to the functions in the cell membrane. This has been visualized frequently with a “brick and mortar” model, but a deeper look into the “mortar” illustrates the structure consists of stacks of bilayers containing ceramides, fatty acids, and the cholesterols.8 Cholesterol is again responsible for matrix fluidity, proper packing of functional components, and controlling small molecule diffusion in the extracellular lipid matrix. This structure is the basis for true barrier function—the lipid matrix keeps water in and the external environment out. Fluctuation in the composition of the lipid matrix can compromise its function, which could have detrimental effects on skin health, ranging from excessive water loss to atopic dermatitis or even bacterial infections.9 Thus, cholesterol and cholesterol sulfate are truly essential components of skin. (continued on Page 14)
SKIN, HYGIENE, AND THE MICROBIOME • SEPTEMBER 14th ...see pages 10-12 for more information.