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Nat Chem Biol. 2016 May;12(5):345-52. doi: 10.1038/nchembio.2047. Epub 2016 Mar 21.

Malic enzyme tracers reveal hypoxia-induced switch in adipocyte NADPH pathway usage.

Liu L1,2,3, Shah S4,3, Fan J1,2, Park JO1,5, Wellen KE4,3, Rabinowitz JD1,2,3.

Author information

1
Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, USA.
2
Department of Chemistry, Princeton University, Princeton, New Jersey, USA.
3
Diabetes Research Center, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
4
Department of Cancer Biology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
5
Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey, USA.

Abstract

The critical cellular hydride donor NADPH is produced through various means, including the oxidative pentose phosphate pathway (oxPPP), folate metabolism and malic enzyme. In growing cells, it is efficient to produce NADPH via the oxPPP and folate metabolism, which also make nucleotide precursors. In nonproliferating adipocytes, a metabolic cycle involving malic enzyme holds the potential to make both NADPH and two-carbon units for fat synthesis. Recently developed deuterium ((2)H) tracer methods have enabled direct measurement of NADPH production by the oxPPP and folate metabolism. Here we enable tracking of NADPH production by malic enzyme with [2,2,3,3-(2)H]dimethyl-succinate and [4-(2)H]glucose. Using these tracers, we show that most NADPH in differentiating 3T3-L1 mouse adipocytes is made by malic enzyme. The associated metabolic cycle is disrupted by hypoxia, which switches the main adipocyte NADPH source to the oxPPP. Thus, (2)H-labeled tracers enable dissection of NADPH production routes across cell types and environmental conditions.

PMID:
26999781
PMCID:
PMC4891982
DOI:
10.1038/nchembio.2047
[Indexed for MEDLINE]
Free PMC Article

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