TY - JOUR
T1 - Normal flux through ATP-citrate lyase or fatty acid synthase is not required for glucose-stimulated insulin secretion
AU - Joseph, Jamie W.
AU - Odegaard, Matthew L.
AU - Ronnebaum, Sarah M.
AU - Burgess, Shawn C.
AU - Muehlbauer, Jeffrey
AU - Sherry, A. Dean
AU - Newgard, Christopher B.
PY - 2007/10/26
Y1 - 2007/10/26
N2 - It has been proposed that de novo synthesis of long-chain acyl-CoA (LC-CoA) is a signal for glucose-stimulated insulin secretion (GSIS). Key enzymes involved in synthesis of fatty acids from glucose include ATP-citrate lyase (CL) and fatty acid synthase (FAS). An inhibitor of CL, hydroxycitrate (HC), has been reported to inhibit insulin secretion in some laboratories but not in others. Here we show that high concentrations of NaCl created during preparation of HC by standard methods explain the inhibition of GSIS, and that removal of the excess NaCl prevents the effect. To further investigate the role of CL, two small interfering RNA adenoviruses (Ad-siCL2 and Ad-siCL3) were generated. Ad-siCL3 reduced CL mRNA levels by 92 ± 6% and CL protein levels by 75 ± 4% but did not affect GSIS in 832/13 cells compared with cells treated with a control adenovirus (Ad-siControl). Similar results were obtained with Ad-siCL2. Ad-siCL3-treated cells also exhibited a 52 ± 7% reduction in cytosolic oxaloacetate, an 83 ± 4% reduction in malonyl-CoA levels, and inhibition of [U-14C]glucose incorporation into lipid by 43 ± 4%, all expected metabolic outcomes of CL suppression. Similarly, treatment of 832/13 cells with a recombinant adenovirus specific to FAS (Ad-siFAS) reduced FAS mRNA levels by 81 ± 2% in 832/13 cells, resulting in a 59 ± 4% decrease in[U-14C]glucose incorporation into lipid, without affecting GSIS. Finally, treatment of primary rat islets with Ad-siCL3 or Ad-siFAS reduced CL and FAS mRNA levels by 65 ± 4% and 52 ± 3%, respectively, but had no effect on GSIS relative to Ad-siControl-treated islets. These findings demonstrate that a normal rate of flux of glucose carbons through CL and FAS is not required for GSIS in insulinoma cell lines or rat islets.
AB - It has been proposed that de novo synthesis of long-chain acyl-CoA (LC-CoA) is a signal for glucose-stimulated insulin secretion (GSIS). Key enzymes involved in synthesis of fatty acids from glucose include ATP-citrate lyase (CL) and fatty acid synthase (FAS). An inhibitor of CL, hydroxycitrate (HC), has been reported to inhibit insulin secretion in some laboratories but not in others. Here we show that high concentrations of NaCl created during preparation of HC by standard methods explain the inhibition of GSIS, and that removal of the excess NaCl prevents the effect. To further investigate the role of CL, two small interfering RNA adenoviruses (Ad-siCL2 and Ad-siCL3) were generated. Ad-siCL3 reduced CL mRNA levels by 92 ± 6% and CL protein levels by 75 ± 4% but did not affect GSIS in 832/13 cells compared with cells treated with a control adenovirus (Ad-siControl). Similar results were obtained with Ad-siCL2. Ad-siCL3-treated cells also exhibited a 52 ± 7% reduction in cytosolic oxaloacetate, an 83 ± 4% reduction in malonyl-CoA levels, and inhibition of [U-14C]glucose incorporation into lipid by 43 ± 4%, all expected metabolic outcomes of CL suppression. Similarly, treatment of 832/13 cells with a recombinant adenovirus specific to FAS (Ad-siFAS) reduced FAS mRNA levels by 81 ± 2% in 832/13 cells, resulting in a 59 ± 4% decrease in[U-14C]glucose incorporation into lipid, without affecting GSIS. Finally, treatment of primary rat islets with Ad-siCL3 or Ad-siFAS reduced CL and FAS mRNA levels by 65 ± 4% and 52 ± 3%, respectively, but had no effect on GSIS relative to Ad-siControl-treated islets. These findings demonstrate that a normal rate of flux of glucose carbons through CL and FAS is not required for GSIS in insulinoma cell lines or rat islets.
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U2 - 10.1074/jbc.M706080200
DO - 10.1074/jbc.M706080200
M3 - Article
C2 - 17823126
AN - SCOPUS:35748952524
SN - 0021-9258
VL - 282
SP - 31592
EP - 31600
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 43
ER -