The epidermis is a very active site of lipid metabolism, and all peroxisome proliferator-
activated receptor (PPAR) and liver X receptor (LXR) isoforms are expressed in the
epidermis. Activation of PPARα,-β/δ, or-γ or LXRs stimulates keratinocyte differentiation.
Additionally, activation of these receptors also improves permeability barrier homeostasis by
a number of mechanisms, including stimulating epidermal lipid synthesis, increasing
lamellar body formation and secretion, and increasing the activity of enzymes required for …