Increased expression of glucagon‐like peptide‐1 receptors in psoriasis plaques

Recent case reports suggest that treatment with glucagon‐like peptide‐1 (GLP‐1) agonists results in clinical improvement of psoriasis. The purpose of this study was to determine whether GLP‐1 receptors (GLP‐1Rs) are found in the skin of healthy volunteers and psoriasis patients and if so, whether GLP‐1Rs are located on keratinocytes or immune cells. Three mm‐punch skin biopsies were taken for gene expression analysis from six healthy volunteers and from affected and unaffected skin of six psoriasis patients. In addition, a blood sample was obtained from all participants. Cultured human keratinocytes were either untreated or incubated with tumor necrosis factor‐ α (TNF‐α), interferon‐γ (IFN‐γ) or a combination of TNF‐α and IFN‐γ for 48 h. Total RNA was extracted from all the samples, reversely transcribed and analysed for the expression of GLP‐1R using real‐time PCR. Gene expression analysis showed expression of GLP‐1Rs in five of six skin biopsies from psoriasis plaques, in one of six biopsies from unaffected psoriatic skin and in one of six biopsies from healthy skin. GLP‐1R expression was found in the blood of both healthy volunteers and psoriasis patients. No GLP‐1R expression was found in either stimulated or unstimulated cultured human keratinocytes. Our results show increased presence of GLP‐1Rs in psoriasis plaques and that this most likely is due to infiltration with immune cells. This offers a possible explanation for the positive effect of treatment with GLP‐1R agonists in patients with psoriasis.