Compensatory responses to pyruvate carboxylase suppression in islet β-cells: Preservation of glucose-stimulated insulin secretion

Mette V. Jensen, Jamie W. Joseph, Olga Ilkayeva, Shawn Burgess, Danhong Lu, Sarah M. Ronnebaum, Matthew Odegaard, Thomas C. Becker, A. Dean Sherry, Christopher B. Newgard

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We have previously reported that glucose-stimulated insulin secretion (GSIS) is tightly correlated with pyruvate carboxylase (PC)-catalyzed anaplerotic flux into the tricarboxylic acid cycle and stimulation of pyruvate cycling activity. To further evaluate the role of PC in β-cell function, we constructed a recombinant adenovirus containing a small interfering RNA (siRNA) specific to PC (Ad-siPC). Ad-siPC reduced PC mRNA levels by 83 and 64% andPCprotein by 56 and 35% in INS-1-derived 832/13 cells and primary rat islets, respectively. Surprisingly, this manipulation did not impair GSIS in rat islets. In Ad-siPC-treated 832/13 cells, GSIS was slightly increased, whereas glycolytic rate and glucose oxidation were unaffected. Flux through PC at high glucose was decreased by only 20%, suggesting an increase in PC-specific activity. Acetyl carnitine, a surrogate for acetyl-CoA, an allosteric activator of PC, was increased by 36% in Ad-siPC-treated cells, suggesting a mechanism by which PC enzymatic activity is maintained with suppressed PC protein levels. In addition, the NADPH:NADP ratio, a proposed coupling factor for GSIS, was unaffected in Ad-siPC-treated cells. We conclude that β-cells activate compensatory mechanisms in response to suppression of PC expression that prevent impairment of anaplerosis, pyruvate cycling, NAPDH production, and GSIS.

Original languageEnglish (US)
Pages (from-to)22342-22351
Number of pages10
JournalJournal of Biological Chemistry
Issue number31
Publication statusPublished - Aug 4 2006


ASJC Scopus subject areas

  • Biochemistry

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