The Herbal Bitter Drug Gentiana lutea Modulates Lipid Synthesis in Human Keratinocytes In Vitro and In Vivo

Int J Mol Sci. 2017 Aug 22;18(8). pii: E1814. doi: 10.3390/ijms18081814. Wölfle U1, Haarhaus B2, Seiwerth J3, Cawelius A4, Schwabe K5, Quirin KW6, Schempp CM7. Author information 1 Department of Dermatology, Medical Center, Faculty of Medicine, University of Freiburg, 79085 Breisgau, Germany. ute.woelfle@uniklinik-freiburg.de. 2 Department of Dermatology, Medical Center, Faculty of Medicine, University of Freiburg, 79085 Breisgau, Germany. birgit.haarhaus@uniklinik-freiburg.de. 3 Department of Dermatology, Medical Center, Faculty of Medicine, University of Freiburg, 79085 Breisgau, Germany. Jasmin.Seiwerth@t-online.de. 4 Flavex Naturextrakte GmbH, 66780 Rehlingen, Germany. ac@flavex.com. 5 BSI-Beauty Science Intelligence GmbH, 30855 Langenhagen, Germany. K.Schwabe@bsi-cosmetics.de. 6 Flavex Naturextrakte GmbH, 66780 Rehlingen, Germany. wq@flavex.com. 7 Department of Dermatology, Medical Center, Faculty of Medicine, University of Freiburg, 79085 Breisgau, Germany. Christoph.schempp@uniklinik-freiburg.de. Abstract Gentiana lutea is a herbal bitter drug that is used to enhance gastrointestinal motility and secretion. Recently we have shown that amarogentin, a characteristic bitter compound of Gentiana lutea extract (GE), binds to the bitter taste receptors TAS2R1 and TAS2R38 in human keratinocytes, and stimulates the synthesis of epidermal barrier proteins. Here, we wondered if GE also modulates lipid synthesis in human keratinocytes. To address this issue, human primary keratinocytes were incubated for 6 days with GE. Nile Red labeling revealed that GE significantly increased lipid synthesis in keratinocytes. Similarly, gas chromatography with flame ionization detector indicated that GE increases the amount of triglycerides in keratinocytes. GE induced the expression of epidermal ceramide synthase 3, but not sphingomyelinase. Lipid synthesis, as well as ceramide synthase 3 expression, could be specifically blocked by inhibitors of the p38 MAPK and PPARγ signaling pathway. To assess if GE also modulates lipid synthesis in vivo, we performed a proof of concept half side comparison on the volar forearms of 33 volunteers. In comparison to placebo, GE significantly increased the lipid content of the treated skin areas, as measured with a sebumeter. Thus, GE enhances lipid synthesis in human keratinocytes that is essential for building an intact epidermal barrier. Therefore, GE might be used to improve skin disorders with an impaired epidermal barrier, e.g., very dry skin and atopic eczema. KEYWORDS: Gentiana lutea; PPARγ; ceramide synthase 3; keratinocytes; lipid synthesis; p38 MAPK PMID: 28829355 DOI: 10.3390/ijms18081814 Free full text