TY - JOUR
T1 - Compensatory responses to pyruvate carboxylase suppression in islet β-cells
T2 - Preservation of glucose-stimulated insulin secretion
AU - Jensen, Mette V.
AU - Joseph, Jamie W.
AU - Ilkayeva, Olga
AU - Burgess, Shawn
AU - Lu, Danhong
AU - Ronnebaum, Sarah M.
AU - Odegaard, Matthew
AU - Becker, Thomas C.
AU - Sherry, A. Dean
AU - Newgard, Christopher B.
PY - 2006/8/4
Y1 - 2006/8/4
N2 - 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.
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.
UR - http://www.scopus.com/inward/record.url?scp=33746847686&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33746847686&partnerID=8YFLogxK
U2 - 10.1074/jbc.M604350200
DO - 10.1074/jbc.M604350200
M3 - Article
C2 - 16740637
AN - SCOPUS:33746847686
SN - 0021-9258
VL - 281
SP - 22342
EP - 22351
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 31
ER -