The bile acid sensor FXR regulates insulin transcription and secretion.
Farnesoid X Receptor plays an important role in maintaining bile acid, cholesterol homeostasis and glucose metabolism. Here we investigated whether FXR is expressed by pancreatic beta-cells and regulates insulin signaling in pancreatic beta-cell line and human islets. We found that FXR activation induces positive regulatory effects on glucose-induced insulin transcription and secretion by genomic and non-genomic activities. Genomic effects of FXR activation relay on the induction of the glucose regulated transcription factor KLF11. Indeed, results from silencing experiments of KLF11 demonstrate that this transcription factor is essential for FXR activity on glucose-induced insulin gene transcription. In addition FXR regulates insulin secretion by non-genomic effects. Thus, activation of FXR in betaTC6 cells increases Akt phosphorylation and translocation of the glucose transporter GLUT2 at plasma membrane, increasing the glucose uptake by these cells. In vivo experiments on Non Obese Diabetic (NOD) mice demonstrated that FXR activation delays development of signs of diabetes, hyperglycemia and glycosuria, by enhancing insulin secretion and by stimulating glucose uptake by the liver. These data established that an FXR-KLF11 regulated pathway has an essential role in the regulation of insulin transcription and secretion induced by glucose.
Renga
Barbara
B
Department of Experimental and Clinical Medicine, University of Perugia, Perugia, Italy. barbara.renga@unipg.it
Mencarelli
Andrea
A
Vavassori
Piero
P
Brancaleone
Vincenzo
V
Fiorucci
Stefano
S
D000818:Animals; D051017:Apoptosis Regulatory Proteins; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D005947:Glucose / Q000494:pharmacology; D051273:Glucose Transporter Type 2 / Q000235:genetics / Q000378:metabolism; D038321:Glycemic Index; D006801:Humans; D007124:Immunoenzyme Techniques; D007328:Insulin / Q000235:genetics* / Q000378:metabolism*; D000078790:Insulin Secretion; D007340:Insulinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D007515:Islets of Langerhans / Q000166:cytology / Q000378:metabolism*; D008114:Liver Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D051379:Mice; D016688:Mice, Inbred NOD; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
D051017:Apoptosis Regulatory Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C096916:FXR1 protein, human; C496283:Fxr1h protein, mouse; D051273:Glucose Transporter Type 2; D007328:Insulin; C115117:KLF11 protein, human; C506460:KLF11 protein, mouse; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D051057:Proto-Oncogene Proteins c-akt; D005947:Glucose