Shah A, Wang Y, Su X, Wondisford FE. Glycerol's contribution to lactate production outside of a glucose intermediate in fasting humans.
Metabolism 2022;
132:155214. [PMID:
35562085 DOI:
10.1016/j.metabol.2022.155214]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 04/27/2022] [Accepted: 05/05/2022] [Indexed: 10/18/2022]
Abstract
BACKGROUND
Glycerol is a well-recognized substrate for new glucose production via gluconeogenesis in the liver. However, its carbon contribution to the glycolytic intermediate lactate is not known in humans.
METHODS
Here we infused stable isotope tracers 13C3-glycerol and 6,6-D2-glucose into six metabolically healthy individuals after an overnight fast to study glycerol metabolism and measure glucose rate of appearance. Serum samples underwent liquid chromatography-mass spectrometry analysis.
RESULTS
Glycerol and glucose rates of appearance were 2.21 ± 1.42 μmol/kg/min and 7.81 ± 1.15 μmol/kg/min, respectively. Under steady-state conditions, the 13C enrichment for lactate was significantly higher than that of glucose (2.90 ± 0.52% versus 1.53 ± 0.78%, p = 0.017), suggesting direct glycerol to lactate metabolism. The percentage of lactate derived from glycerol was also significantly higher than the percentage of glucose (13.88 ± 2.69% versus 6.50 ± 2.59%, p = 0.005).
CONCLUSION
Given that lactate itself is a carbon source for gluconeogenesis and tricycarboxylic cycle intermediates, glycerol's ability to donate carbons to lactate may make it quantitatively more important to intermediary metabolism than currently appreciated.
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