title: Role of prolyl hydroxylase domain proteins in the regulation of insulin secretion.
abstract: Type 2 diabetes is associated with impaired nutrient-regulated anaplerosis and insulin secretion in pancreatic β-cells. One key anaplerotic substrate that may be involved in regulating insulin release is α-ketoglutarate (αKG). Since prolyl hydroxylase domain proteins (PHDs) can metabolize cytosolic αKG, we sought to explore the role of this enzyme in the regulation of β-cell function. The oxygen-sensing PHDs regulate the stability of hypoxia-inducible factor 1α (HIF1α) as well as other proline-containing proteins by catalyzing the hydroxylation of proline residues. This reaction is dependent on sufficient levels of oxygen, iron, and αKG. In the present study, we utilized both pharmacological and genetic approaches to assess the impact of inhibiting PHD activity on β-cell function. We demonstrate that ethyl-3,4-dihydroxybenzoate (EDHB), a PHD inhibitor, significantly blunted glucose-stimulated insulin secretion (GSIS) from 832/13 clonal cells, rat, and human islets. EDHB reduced glucose utilization, ATP/ADP ratio, and key TCA cycle intermediates such as pyruvate, citrate, fumarate, and malate. siRNA-mediated knockdown of PHD1 and PHD3 inhibited GSIS, whereas siRNA-mediated knockdown of PHD2 had no effect on GSIS. Taken together, the current results demonstrate an important role for PHDs as mediators of islet insulin secretion.
authors.affiliation: School of Pharmacy, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Mei
authors.initials: M
authors.lastname: Huang
authors.affiliation: School of Pharmacy, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Sabina
authors.initials: S
authors.lastname: Paglialunga
authors.affiliation: School of Pharmacy, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Julia M-K
authors.initials: JM
authors.lastname: Wong
authors.affiliation: School of Pharmacy, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Monica
authors.initials: M
authors.lastname: Hoang
authors.affiliation: School of Pharmacy, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Renjitha
authors.initials: R
authors.lastname: Pillai
authors.affiliation: School of Pharmacy, University of Waterloo, Waterloo, Ontario, Canada j3joseph@uwaterloo.ca.
authors.forename: Jamie W
authors.initials: JW
authors.lastname: Joseph
mesh_terms: D000818:Animals; D002460:Cell Line; D055785:Gene Knockdown Techniques / Q000379:methods; D006801:Humans; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases / Q000502:physiology*; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000502:physiology; D051381:Rats
chemical_list: D007328:Insulin; C490190:EGLN1 protein, human; C447780:EGLN2 protein, human; C488894:EGLN3 protein, human; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases
keywords: ethyl‐3,4‐dihydroxybenzoate; insulin release; islets; metabolism; pancreas; prolyl hydroxylase; α‐ketoglutarate