Glycerol carbon contributes to hepatic glucose production during the first eight hours in healthy term infants
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A Sunehag1, J Gustafsson, U Ewald
1Uppsala University Children's Hospital, Sweden.
Insights
Newborn infants utilize lipids for energy soon after birth. This study shows lipolysis and gluconeogenesis from glycerol are active within 8 hours of life in healthy term infants.
Area of Science:
- Neonatal physiology
- Metabolic adaptation in newborns
Background:
- Newborn infants rely on endogenous substrate stores for energy.
- Lipids, indicated by high free fatty acids and glycerol, are crucial fuels post-birth.
Purpose of the Study:
- To investigate the initiation of lipolysis and gluconeogenesis from glycerol in healthy, term, unfed infants.
Main Methods:
- Studied 8 infants from 3.5 to 7.4 hours postnatal age.
- Utilized stable isotope tracers ([6,6-2H2] glucose and [2-13C]glycerol).
- Analyzed samples using gas chromatography/mass spectrometry.
Main Results:
- Average plasma glucose: 2.9 mM, glycerol: 369 µM, insulin: 9.4 µU/mL.
- Hepatic glucose production averaged 25.0 µmol/kg/min.
- Glycerol conversion to glucose was 57.9%, contributing 11.1% to hepatic glucose output.
Conclusions:
- Lipolysis and gluconeogenesis from glycerol are established processes in term infants within the first 8 hours of life.
Abstract:
The newborn infant must mobilize endogenous substrate stores to meet the requirements of glucose-dependent organs. High concentrations of free fatty acids and glycerol, and a rapid decrease in the respiratory quotient, indicate that lipids are an important fuel soon after birth. The purpose of the present study was to determine the onset of lipolysis and gluconeogenesis from glycerol in healthy, term, unfed infants. Eight infants were studied from a postnatal age of 3.5 +/- 0.5 h to 7.4 +/- 0.2 h using [6,6-2H2] glucose and [2-13C]glycerol analysed by gas chromatography/mass spectrometry. Plasma concentrations of glucose, glycerol and insulin averaged 2.9 +/- 0.4 mM, 369 +/- 89 microM and 9.4 +/- 9.4 +/- 3.7 microU.ml-1, respectively. The hepatic glucose production rate averaged 25.0 +/- 3.5 mumol.kg-1 min-1 (4.5 +/- 0.6 mg.kg-1.min-1) and the endogenous plasma appearance rate of glycerol 8.7 +/- 1.2 mumol.kg-1.min. On average, 57.9 +/- 8.4% of the glycerol was converted to glucose, representing 11.1 +/- 2.3% of hepatic glucose output. Thus, lipolysis and gluconeogenesis from glycerol are established within the first 8 h of life in term infants.