Pancreatic β-cells secrete insulin in a biphasic manner via KATP-channel dependent and independent pathways. The KATP-channel independent pathway produces a rise in the NADPH/NADP+ ratio and cytosolic α-ketoglutarate (α-KG). Prolyl hydroxylase domain proteins (PHDs) belong to the α-KG-dependent dioxygenase superfamily and regulates stability of hypoxia-inducible factor α (HIF-α). Prolyl hydroxylation of HIF-α for ubiquitin-mediated proteasomal degradation requires sufficient levels of oxygen, iron and α-KG. We have previously shown pharmacological inhibition of PHDs reduces glucose-stimulated insulin secretion (GSIS), glucose utilization, and mitochondrial function in clonal β-cells. Glucose-induced changes in cytosolic α-KG may regulate PHD and thus β-cell function. In mouse pancreatic β-cells, PHD isoforms express unique subcellular localization: PHD1 is expressed exclusively in the cytosol, PHD2 is expressed in the cytosol and nucleus, and PHD3 is mainly expressed in the nucleus. To further explore the isoform-specific roles of PHD, we employed a β-cell specific knockout (β-PHD KO) mouse model for each of the PHD isoforms. β-PHD1 KO, β-PHD2 KO and β-PHD3 KO. β-PHD KO mice show no significant in vivo defects associated with glucose tolerance and insulin resistance; however, β-PHD1 KO and β-PHD2 KO mice have significantly increased plasma insulin compared to wild type (WT) controls (p<0.05). Consistent with our cell culture model of PHD knockdown, PHD1 and PHD3 regulate insulin secretion as both β-PHD1 KO and β-PHD3 KO mice show impaired GSIS. Only β-PHD1 KO mice have reduced beta-cell mass (p<0.01).

In conclusion, there are significant and unique effects observed with isoform-specific suppression of PHD.


M. Hoang: None. S.M. Janssen: None. J.W. Joseph: None.


Natural Sciences and Engineering Research Council of Canada; Canadian Institutes of Health Research

Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. More information is available at