Molecular and Cellular Biochemistry

, Volume 313, Issue 1–2, pp 195–202 | Cite as

Anaplerosis from glucose, α-ketoisocaproate, and pyruvate in pancreatic islets, INS-1 cells and liver mitochondria

  • Michael J. MacDonald
  • Scott W. Stoker
  • Noaman M. Hasan
Article

Abstract

Methyl succinate (MS) and α-ketoisocaproate (KIC) when applied alone to cultured pancreatic islets or INS-1 832/13 cells do not stimulate insulin release. However, when the two metabolites are combined together they strongly stimulate insulin release. Studying the possible explanations for this complementarity has provided clues to the pathways involved in insulin secretion. MS increased carbon incorporation of KIC into acid-precipitable material and lipid in INS-1 cells. In isolated mitochondria, MS alone increased malate, but MS plus KIC increased citrate, α-ketoglutarate, and isocitrate. These data and the known pathways of their metabolism suggest that MS supplies the oxaloacetate component of citrate and KIC supplies the acetate component of citrate. Other citric acid cycle intermediates can be formed from citrate enabling anaplerosis to supply precursors for extramitochondrial pathways. In addition, KIC, glucose and pyruvate can be metabolized to acetoacetate. In an INS-1 cell line deficient in ATP citrate lyase, incorporation of carbon from pyruvate into acid-precipitable material and lipid was not lowered. This negative result is in agreement with our recent discovery that citrate is not the only carrier of acyl groups from the mitochondria to the cytosol in the beta cell and that acetoacetate can also transfer acyl carbon to the cytosol.

Keywords

Acetoacetate Methyl succinate Synergistic secretagogue combinations Pancreatic islets Anaplerosis 

Abbreviation

KIC

α-Ketoisocaproate

Notes

Acknowledgements

This work was supported by NIH Grant DK28348 and by a gift from the Oscar C. Rennebohm Foundation. The author thanks Julian Buss and Melissa Longacre for excellent technical assistance.

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Copyright information

© Springer Science+Business Media, LLC. 2008

Authors and Affiliations

  • Michael J. MacDonald
    • 1
  • Scott W. Stoker
    • 1
  • Noaman M. Hasan
    • 1
  1. 1.Childrens Diabetes Center, School of Medicine and Public HealthUniversity of WisconsinMadisonUSA

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