The aromatic amino acid sensor GPR142 controls metabolism through balanced regulation of pancreatic and gut hormones.

OBJECTIVES: GPR142, which is highly expressed in pancreatic islets, has recently been deorphanized as a receptor for aromatic amino acids; however, its physiological role and pharmacological potential is unclear. METHODS AND RESULTS: We find that GPR142 is expressed not only in ß- but also in α-cells of the islets as well as in enteroendocrine cells, and we confirm that GPR142 is a highly selective sensor of essential aromatic amino acids, in particular Trp and oligopeptides with N-terminal Trp. GPR142 knock-out mice displayed a very limited metabolic phenotype but demonstrated that L-Trp induced secretion of pancreatic and gut hormones is mediated through GPR142 but that the receptor is not required for protein-induced hormone secretion. A synthetic GPR142 agonist stimulated insulin and glucagon as well as GIP, CCK, and GLP-1 secretion. In particular, GIP secretion was sensitive to oral administration of the GPR142 agonist an effect which in contrast to the other hormones was blocked by protein load. Oral administration of the GPR142 agonist increased [3H]-2-deoxyglucose uptake in muscle and fat depots mediated through insulin action while it lowered liver glycogen conceivably mediated through glucagon, and, consequently, it did not lower total blood glucose. Nevertheless, acute administration of the GPR142 agonist strongly improved oral glucose tolerance in both lean and obese mice as well as Zucker fatty rat. Six weeks in-feed chronic treatment with the GPR142 agonist did not affect body weight in DIO mice, but increased energy expenditure and carbohydrate utilization, lowered basal glucose, and improved insulin sensitivity. CONCLUSIONS: GPR142 functions as a sensor of aromatic amino acids, controlling GIP but also CCK and GLP-1 as well as insulin and glucagon in the pancreas. GPR142 agonists could have novel interesting potential in modifying metabolism through a balanced action of gut hormones as well as both insulin and glucagon.

Effects of FGF receptor peptide agonists on animal behavior under normal and pathological conditions.

Hexafins are recently identified low-molecular-weight peptide agonists of the fibroblast growth factor receptor (FGFR), derived from the beta6-beta7 loop region of various FGFs. Synthetic hexafin peptides have been shown to bind to and induce tyrosine phosphorylation of FGFR1, stimulate neurite outgrowth, and promote neuronal survival in vitro. Thus, the pronounced biological activities of hexafins in vitro make them attractive compounds for pharmacological studies in vivo. The present study investigated the effects of subcutaneous administration of hexafin1 and hexafin2 (peptides derived from FGF1 and FGF2, respectively) on social memory, exploratory activity, and anxiety-like behavior in adult rats. Treatment with hexafin1 and hexafin2 resulted in prolonged retention of social memory. Furthermore, rats treated with hexafin2 exhibited decreased anxiety-like behavior in the elevated plus maze. Employing an R6/2 mouse model of Huntington's disease (HD), we found that although hexafin2 did not affect the progression of motor symptoms, it alleviated deficits in activity related to social behavior, including sociability and social novelty. Thus, hexafin2 may have therapeutic potential for the treatment of HD.

An automatic procedure for evaluation of single cell motility.

BACKGROUND: Cell motility is vital in many physiological and pathological processes, such as embryogenesis, inflammation, wound healing, and metastasis. However, the time-consuming step in the evaluation of individual cell motility is the analysis of hundreds of recorded images of cell cultures in general consisting of retrieving images, one at a time, and marking the positions of individual cells by a computer mouse. Therefore, the aim of the present study was to develop a novel automatic procedure for the evaluation of cell motility. MATERIALS AND METHODS: The procedure was tested on fibroblasts and glioma and adenocarcinoma cells engineered to express the green fluorescent protein by either transient transfection or adenovirus transduction, allowing automatic recognition of cell coordinates on retrieved images. RESULTS: The effects of serum growth factors, teratogenic compounds, and overexpression of transcription factors on the motile behavior of cultured cells were determined. Cell motility was estimated by both manual and automatic marking of cell position and subsequently motility parameters were computed. The results obtained by the two procedures were found to correlate significantly. CONCLUSIONS: We developed a procedure allowing automatic video recording of sparsely seeded cells transfected with a plasmid or tranduced with a recombinant virus expressing the enhanced green fluorescent protein (EGFP).

Triple effect of mimetic peptides interfering with neural cell adhesion molecule homophilic cis interactions.

The neural cell adhesion molecule (NCAM) is pivotal in neural development, regeneration, and learning. Here we characterize two peptides, termed P1-B and P2, derived from the homophilic binding sites in the first two N-terminal immunoglobulin (Ig) modules of NCAM, with regard to their effects on neurite extension and adhesion. To evaluate how interference of these mimetic peptides with NCAM homophilic interactions in cis influences NCAM binding in trans, we employed a coculture system in which PC12-E2 cells were grown on monolayers of fibroblasts with or without NCAM expression and the rate of neurite outgrowth subsequently was analyzed. P2, but not P1-B, induced neurite outgrowth in the absence of NCAM binding in trans. When PC12-E2 cells were grown on monolayers of NCAM-expressing fibroblasts, the effect of both P1-B and P2 on neurite outgrowth was dependent on peptide concentrations. P1-B and P2 acted as conventional antagonists, agonists, and reverse agonists of NCAM at low, intermediate, and high peptide concentrations, respectively. The demonstrated in vitro triple pharmacological effect of mimetic peptides interfering with the NCAM homophilic cis binding will be valuable for the understanding of the actions of these mimetics in vivo.