β-Cell Deletion of Hypoxia-Inducible Factor 1α (HIF-1α) Increases Pancreatic β-Cell Susceptibility to Streptozotocin.

Type 1 diabetes (T1D) is caused by the immune-mediated loss of pancreatic β-cells. Hypoxia-inducible factor 1α (HIF-1α) is a transcription factor which is crucial for cellular responses to low oxygen. Here, we investigate the role of β-cell HIF-1α in β-cell death and diabetes after exposure to multiple low-dose streptozotocin (MLDS). MDLS triggers auto-immunity in susceptible animal models, such as non-obese diabetic (NOD) mice. These experiments used a novel mouse model with β-cell-specific deletion of HIF-1α on a NOD background (BIN mice). Mice were given 20 mg/kg MLDS for 5 consecutive days. Following MLDS, 100% of BIN mice developed frank diabetes versus 33% of floxed-control (FC) littermates and 17% of NOD controls (p < 0.001). BIN mice had obvious loss of β-cell mass (p < 0.0001) and increased necrotic areas within islets (p < 0.001). To confirm that diabetes was T1D, adoptive transfers of splenocytes from diabetic BIN and FC mice were performed on NOD-SCID (Severe Combined ImmunoDeficiency) recipients. All mice receiving BIN-splenocytes developed frank diabetes, confirming that MLDS induced true T1D. Interestingly, diabetes developed significantly faster in BIN-adoptive transfer mice compared to mice which developed diabetes after receiving an FC-adoptive transfer. These studies demonstrate the importance of β-cell HIF-1α in the preservation of β-cell mass and avoidance of auto-immunity.