Preconditioning with associated blocking of Ca2+ inflow alleviates hypoxia-induced damage to pancreatic β-cells

PLoS One. 2013 Jul 25;8(7):e67498. doi: 10.1371/journal.pone.0067498. Print 2013.


Objective: Beta cells of pancreatic islets are susceptible to functional deficits and damage by hypoxia. Here we aimed to characterize such effects and to test for and pharmacological means to alleviate a negative impact of hypoxia.

Methods and design: Rat and human pancreatic islets were subjected to 5.5 h of hypoxia after which functional and viability parameters were measured subsequent to the hypoxic period and/or following a 22 h re-oxygenation period. Preconditioning with diazoxide or other agents was usually done during a 22 h period prior to hypoxia.

Results: Insulin contents decreased by 23% after 5.5 h of hypoxia and by 61% after a re-oxygenation period. Preconditioning with diazoxide time-dependently alleviated these hypoxia effects in rat and human islets. Hypoxia reduced proinsulin biosynthesis ((3)H-leucine incorporation into proinsulin) by 35%. Preconditioning counteracted this decrease by 91%. Preconditioning reduced hypoxia-induced necrosis by 40%, attenuated lowering of proteins of mitochondrial complexes I-IV and enhanced stimulation of HIF-1-alpha and phosphorylated AMPK proteins. Preconditioning by diazoxide was abolished by co-exposure to tolbutamide or elevated potassium (i.e. conditions which increase Ca(2+) inflow). Preconditioning with nifedipine, a calcium channel blocker, partly reproduced effects of diazoxide. Both diazoxide and nifedipine moderately reduced basal glucose oxidation whereas glucose-induced oxygen consumption (tested with diazoxide) was unaffected. Preconditioning with diaxoxide enhanced insulin contents in transplants of rat islets to non-diabetic rats and lowered hyperglycemia vs. non-preconditioned islets in streptozotocin-diabetic rats. Preconditioning of human islet transplants lowered hyperglycemia in streptozotocin-diabetic nude mice.

Conclusions: 1) Prior blocking of Ca(2+) inflow associates with lesser hypoxia-induced damage, 2) preconditioning affects basal mitochondrial metabolism and accelerates activation of hypoxia-reactive and potentially protective factors, 3) results indicate that preconditioning by K(+)-ATP-channel openers has therapeutic potential for islet transplantations.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • AMP-Activated Protein Kinases / metabolism
  • Animals
  • Calcium / metabolism*
  • Calcium Channel Blockers / pharmacology*
  • Cell Hypoxia
  • Cells, Cultured
  • Diabetes Mellitus, Experimental / chemically induced
  • Diabetes Mellitus, Experimental / metabolism
  • Diabetes Mellitus, Experimental / pathology
  • Diabetes Mellitus, Experimental / therapy*
  • Diazoxide / pharmacology
  • Electron Transport Chain Complex Proteins / agonists
  • Electron Transport Chain Complex Proteins / metabolism
  • Humans
  • Hypoglycemic Agents / pharmacology
  • Hypoxia-Inducible Factor 1, alpha Subunit / agonists
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism
  • Insulin / metabolism
  • Insulin-Secreting Cells / cytology*
  • Insulin-Secreting Cells / drug effects*
  • Insulin-Secreting Cells / metabolism
  • Insulin-Secreting Cells / transplantation
  • Male
  • Mice
  • Nifedipine / pharmacology*
  • Oxygen / pharmacology*
  • Phosphorylation
  • Potassium / metabolism
  • Proinsulin / metabolism
  • Rats
  • Streptozocin
  • Tolbutamide / pharmacology


  • Calcium Channel Blockers
  • Electron Transport Chain Complex Proteins
  • HIF1A protein, human
  • Hypoglycemic Agents
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Insulin
  • Streptozocin
  • Proinsulin
  • Tolbutamide
  • AMP-Activated Protein Kinases
  • Nifedipine
  • Diazoxide
  • Potassium
  • Oxygen
  • Calcium