AIMS/HYPOTHESIS: Adipocytes secrete signalling molecules that elicit responses from target cells, including pancreatic beta cells. Wnt signalling molecules have recently been identified as novel adipocyte-derived factors. They also regulate insulin secretion in pancreatic beta cells and the cell cycle. The aim of this study was to investigate the effect of adipocyte-derived Wnt signalling molecules on insulin secretion and beta cell proliferation. METHODS: Human adipocytes were isolated to generate fat cell-conditioned medium (FCCM). Ins-1 cells were stimulated with FCCM and transiently transfected with reporter genes. Proliferation assays using [3H]thymidine incorporation were carried out in Ins-1 cells and primary islet cells. Insulin secretion from primary islets was assessed by radioimmunoassay. Gene expression in primary islets was assessed by Taqman PCR. RESULTS: Treatment with human FCCM increased the transcription of a T cell-specific transcription factor reporter gene (TOPFLASH) in Ins-1 cells (241%, p < 0.05). FCCM induced the proliferation of Ins-1 cells (1.8 fold, p < 0.05) and primary mouse islet cells (1.6 fold, p < 0.05). Antagonizing Wnt signalling with secreted Frizzled-related protein 1 (FRP-1) inhibited the proliferative effect induced by Wnt3a and FCCM on Ins-1 cells by 49 and 41%, respectively. In addition, FCCM led to a twofold (p < 0.05) induction of cyclin D1 promoter activity in Ins-1 cells. Furthermore, FCCM stimulated insulin secretion (204% of controls, p > 0.05) in primary mouse islets, and this stimulation was inhibited by sFRP-1. At a molecular level, canonical Wnt signalling induced glucokinase gene transcription in a peroxisome proliferator-activated receptor gamma-dependent fashion, thereby defining the glucokinase gene as a novel Wnt target gene. CONCLUSIONS/ INTERPRETATION: Taken together, these data show that adipocyte-derived Wnt signalling molecules induce beta cell proliferation and insulin secretion in vitro, suggesting a novel mechanism linking obesity to hyperinsulinaemia.
AIMS/HYPOTHESIS: Adipocytes secrete signalling molecules that elicit responses from target cells, including pancreatic beta cells. Wnt signalling molecules have recently been identified as novel adipocyte-derived factors. They also regulate insulin secretion in pancreatic beta cells and the cell cycle. The aim of this study was to investigate the effect of adipocyte-derived Wnt signalling molecules on insulin secretion and beta cell proliferation. METHODS:Human adipocytes were isolated to generate fat cell-conditioned medium (FCCM). Ins-1 cells were stimulated with FCCM and transiently transfected with reporter genes. Proliferation assays using [3H]thymidine incorporation were carried out in Ins-1 cells and primary islet cells. Insulin secretion from primary islets was assessed by radioimmunoassay. Gene expression in primary islets was assessed by Taqman PCR. RESULTS: Treatment with humanFCCM increased the transcription of a T cell-specific transcription factor reporter gene (TOPFLASH) in Ins-1 cells (241%, p < 0.05). FCCM induced the proliferation of Ins-1 cells (1.8 fold, p < 0.05) and primary mouse islet cells (1.6 fold, p < 0.05). Antagonizing Wnt signalling with secreted Frizzled-related protein 1 (FRP-1) inhibited the proliferative effect induced by Wnt3a and FCCM on Ins-1 cells by 49 and 41%, respectively. In addition, FCCM led to a twofold (p < 0.05) induction of cyclin D1 promoter activity in Ins-1 cells. Furthermore, FCCM stimulated insulin secretion (204% of controls, p > 0.05) in primary mouse islets, and this stimulation was inhibited by sFRP-1. At a molecular level, canonical Wnt signalling induced glucokinase gene transcription in a peroxisome proliferator-activated receptor gamma-dependent fashion, thereby defining the glucokinase gene as a novel Wnt target gene. CONCLUSIONS/ INTERPRETATION: Taken together, these data show that adipocyte-derived Wnt signalling molecules induce beta cell proliferation and insulin secretion in vitro, suggesting a novel mechanism linking obesity to hyperinsulinaemia.
Authors: Struan F A Grant; Gudmar Thorleifsson; Inga Reynisdottir; Rafn Benediktsson; Andrei Manolescu; Jesus Sainz; Agnar Helgason; Hreinn Stefansson; Valur Emilsson; Anna Helgadottir; Unnur Styrkarsdottir; Kristinn P Magnusson; G Bragi Walters; Ebba Palsdottir; Thorbjorg Jonsdottir; Thorunn Gudmundsdottir; Arnaldur Gylfason; Jona Saemundsdottir; Robert L Wilensky; Muredach P Reilly; Daniel J Rader; Yu Bagger; Claus Christiansen; Vilmundur Gudnason; Gunnar Sigurdsson; Unnur Thorsteinsdottir; Jeffrey R Gulcher; Augustine Kong; Kari Stefansson Journal: Nat Genet Date: 2006-01-15 Impact factor: 38.330
Authors: R Scott Heller; Darwin S Dichmann; Jan Jensen; Chris Miller; Gordon Wong; Ole D Madsen; Palle Serup Journal: Dev Dyn Date: 2002-11 Impact factor: 3.780
Authors: Jose C Florez; Kathleen A Jablonski; Nick Bayley; Toni I Pollin; Paul I W de Bakker; Alan R Shuldiner; William C Knowler; David M Nathan; David Altshuler Journal: N Engl J Med Date: 2006-07-20 Impact factor: 91.245
Authors: Xi Chen; Iriscilla Ayala; Chris Shannon; Marcel Fourcaudot; Nikhil K Acharya; Christopher P Jenkinson; Sami Heikkinen; Luke Norton Journal: Diabetes Date: 2018-01-09 Impact factor: 9.461