Aryl Hydrocarbon Receptor Nuclear Translocator/Hypoxia-inducible Factor-1β Plays a Critical Role in Maintaining Glucose-stimulated Anaplerosis and Insulin Release from Pancreatic β-Cells

Abstract

The metabolic pathways that are involved in regulating insulin secretion from pancreatic ␤-cells are still incompletely understood. One potential regulator of the metabolic phenotype of ␤-cells is the transcription factor aryl hydrocarbon receptor nuclear translocator (ARNT)/hypoxia-inducible factor (HIF)-1␤. ARNT/HIF-1␤ levels are profoundly reduced in islets obtained from type 2 diabetic patients. However, no study to date has investigated key pathways involved in regulating insulin release in ␤-cells that lack ARNT/HIF-1␤. In this study, we confirm that siRNA-mediated knockdown of ARNT/HIF-1␤ inhibits glucose-stimulated insulin secretion. We next investigated the metabolic consequence of the loss of ARNT/HIF-1␤ knockdown. We demonstrate that ␤-cells with reduced ARNT/ HIF-1␤ expression levels exhibit a 31% reduction in glycolytic flux without significant changes in glucose oxidation or the ATP:ADP ratio. Metabolic profiling of ␤-cells treated with siRNAs against the ARNT/HIF-1␤ gene revealed that glycolysis, anaplerosis, and glucose-induced fatty acid production were down-regulated, and all are key events involved in glucose-stimulated insulin secretion. In addition, both first and second phase insulin secretion in islets were significantly reduced after ARNT/HIF-1␤ knockdown. Together, our data suggest an important role for ARNT/HIF-1␤ in anaplerosis, and it may play a critical role in maintaining normal secretion competence of ␤-cells.

Distinct Role for ARNT/HIF-1β in Pancreatic Beta-Cell Function, Insulin Secretion and Type 2 Diabetes

“…It has been shown that down regulation of ARNT/HIF-1 in pancreatic beta-cells leads to loss of GSIS (Gunton et al, 2005;Pillai et al 2011). Our group has demonstrated that beta-cells with reduced ARNT/HIF-1 expression levels exhibit a 31% reduction in glycolytic flux without significant changes in glucose oxidation or the ATP/ADP ratio.…”

“…Studies in ARNT/HIF-1 deficient beta-cells suggest that it plays a crucial role in the regulation of key genes involved in glucose metabolism and insulin secretion (Gunton et al, 2005, Pillai et al, 2011. ARNT/HIF-1 target genes in beta-cells include the MODY1 and MODY3 genes HNF4 and HNF1 , glucose metabolism genes GK, G6PI, PFK, aldolase, PC, PDH, MEc, DIC, OGC and insulin signaling genes IR, IRS2 and AKT2.…”

Deletion of ARNT/HIF1β in pancreatic beta cells does not impair glucose homeostasis in mice, but is associated with defective glucose sensing ex vivo

“…A key player in the K ATP channel-independent pathway of insulin release is glucose-regulated anaplerosis. We have previously shown that ARNT/HIF1β regulates anaplerosis in clonal beta cells [3]. We next sought to rescue the defect in the K ATP channel-independent pathway in β-Arnt fl/fl/Cre islets using the anaplerotic substrates DMM and DMαKG.…”

“…Experiments involving human islets were approved by the local ethics committee. Mouse islets were isolated and cultured as previously described [3,6].…”

“…The cells were a gift from C. B. Newgard (Duke University, Durham, NC, USA) and were cultured as previously described [3,6,7,9].…”