Fat Cells And The Skin Barrier?
What do fat cells have to do with the function of the epidermal permeability barrier? Before the recent International Investigative Dermatology Meeting in Orlando, we – although generally obsessed with all things related to the skin’s permeability barrier – would reluctantly have had to admit, “Alas, nothing.”
Therefore, we were most intrigued to learn of the discovery by Dr. S. Hong, of Dankook University in Cheonan, Korea, and his colleagues that some of our fat cells are at work, fine-tuning the permeability barrier. These particular fat cells are also unusual in their location. Rather than residing in the underlying subcutaneous fat layer, these barrier-regulatory fat cells hang out just under the epidermis, making them truly a part of the dermis.
Now traditionally, “subcutaneous fat” is thought of, as its name implies, as the under-layer of skin. It is not quite skin (that which surrounds and protects us), but rather it is a mostly unwanted repository of the excess calories that we consume, which just happens to take up residence below the ‘true’ skin. The fat in this under-layer is the stuff that we fret over, and try to get rid of through diet and exercise.
But now we are learning that there’s more to fat cells than merely the storage of calories for a rainy day.
These newly discovered, dermal fat cells generate a group of hormones, called ‘adipokines’, which influence epidermal functions, including its barrier function. Hong and colleagues found that administration of one of these adipokine hormones, ‘adiponectin’, stimulated the production of lipids by the epidermis, including ceramides, which are critical components of the barrier. Adiponectin also stimulated production of very-long-chain fatty acids, another class of critically important lipids for the skin barrier. These highly water repellant (or ‘hydrophobic’) very-long-chain fatty acids are incorporated into other complex lipids, where they largely account for the unique water-proofing capability of skin.
Only time will tell whether new types of therapy for skin barrier diseases, like atopic dermatitis and psoriasis, will be coming, based upon these new findings about our fat cells. Perhaps, at least, we can now consider some of our fat as our friend, and not just our enemy!