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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Abstract

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
Volume281
Issue number31
DOIs
StatePublished - Aug 4 2006

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Pyruvate Carboxylase
Islets of Langerhans
Insulin
Glucose
Pyruvic Acid
NADP
Rats
Cells
Acetylcarnitine
Fluxes
Acetyl Coenzyme A
Citric Acid Cycle
Adenoviridae
Small Interfering RNA

ASJC Scopus subject areas

  • Biochemistry

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Compensatory responses to pyruvate carboxylase suppression in islet β-cells : Preservation of glucose-stimulated insulin secretion. / Jensen, Mette V.; Joseph, Jamie W.; Ilkayeva, Olga; Burgess, Shawn; Lu, Danhong; Ronnebaum, Sarah M.; Odegaard, Matthew; Becker, Thomas C.; Sherry, A. Dean; Newgard, Christopher B.

In: Journal of Biological Chemistry, Vol. 281, No. 31, 04.08.2006, p. 22342-22351.

Research output: Contribution to journalArticle

Jensen, Mette V. ; Joseph, Jamie W. ; Ilkayeva, Olga ; Burgess, Shawn ; Lu, Danhong ; Ronnebaum, Sarah M. ; Odegaard, Matthew ; Becker, Thomas C. ; Sherry, A. Dean ; Newgard, Christopher B. / Compensatory responses to pyruvate carboxylase suppression in islet β-cells : Preservation of glucose-stimulated insulin secretion. In: Journal of Biological Chemistry. 2006 ; Vol. 281, No. 31. pp. 22342-22351.
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AU - Burgess, Shawn

AU - Lu, Danhong

AU - Ronnebaum, Sarah M.

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AB - 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.

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