PFKFB3 Depletion Activates β-Cell Replication by Cell Competitive Culling of Compromised β-Cells Under Stress

Abstract

ABSTRACTHighly conserved hypoxia-inducible factor 1 alpha (HIF1α) and its target 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) play a critical role in the survival of damaged β-cells in type 2 diabetes (T2D) while rendering β-cells non-responsive to glucose stimulation by mitochondrial suppression. HIF1α-PFKFB3 is activated in 30-50% of all β-cells in diabetic islets, leaving an open question of whether targeting this pathway may adjust β-cell mass and function to the specific metabolic demands during diabetogenic stress.Our previous studies of β-cells under amyloidogenic stress by human islet amyloid polypeptide (hIAPP) revealed that PFKFB3 is a metabolic execution arm of the HIF1α pathway with potent implications on Ca2+ homeostasis, metabolome, and mitochondrial form and function.To discriminate the role of PFKFB3 from HIF1α in vivo, we generated mice with conditional β-cell specific disruption of the Pfkfb3 gene on a hIAPP+/- background and a high-fat diet (HFD) [PFKFB3βKO + diabetogenic stress (DS)].PFKFB3 disruption in β-cells under diabetogenic stress led to selective purging of hIAPP-damaged β-cells and the disappearance of bihormonal insulin- and glucagon-positive cells, thus compromised β-cells. At the same time, PFKFB3 disruption led to a three-fold increase in β-cell replication resembling control levels as measured with minichromosome maintenance 2 protein (MCM2). PFKFB3 disruption depleted bihormonal cells while increased β-cell replication that was reflected in the increased β-/α-cell ratio and maintained β-cell mass. Analysis of metabolic performance indicated comparable glucose intolerance and reduced plasma insulin levels in PFKFB3βKO DS relative to PFKFB3WT DS mice. In the PFKFB3βKO DS group, plasma glucagon levels were reduced compared to PFKFB3WT DS mice and were in line with increased insulin sensitivity. Glucose intolerance in PFKFB3βKO DS mice could be explained by the compensatory expression of HIF1α after disruption of PFKFB3. Our data strongly suggest that the replication and functional recovery of β-cells under diabetogenic stress depend on selective purification of HIF1α and PFKFB3-positive β-cells. Thus, HIF1α-PFKFB3-dependent activation of cell competition and purging of compromised β-cells may yield functional competent β-cell mass in diabetes.