Submitted on July 5, 2005
Accepted on November 8, 2005
Stimulation of gluconeogenesis by intravenous lipids in preterm infants: response depends on fatty acid profile
A.M.W. van Kempen1*, Saskia N van der Crabben2, Mariette T Ackermans3, Erik Endert3, Joke H Kok4, and Hans P Sauerwein2
1 Metabolism Unit, Department of Endocrinology and Metabolism, Academic Medical Center, Amsterdam, The Netherlands; Department of Neonatology, Academic Medical Center, Amsterdam, The Netherlands
2 Metabolism Unit, Department of Endocrinology and Metabolism, Academic Medical Center, Amsterdam, The Netherlands
3 Metabolism Unit, Department of Endocrinology and Metabolism, Academic Medical Center, Amsterdam, The Netherlands; Department of Clinical Chemistry, Lab of Endocrinology and Radiochemistry, Academic Medical Center, Amsterdam, The Netherlands
4 Department of Neonatology, Academic Medical Center, Amsterdam, The Netherlands
* To whom correspondence should be addressed. E-mail: a.vankempen{at}amc.uva.nl.
Background: In preterm infants both hypo- and hyperglycemia are a frequent problem. Intravenous lipids can affect glucose metabolism by stimulation of gluconeogenesis by providing glycerol, a gluconeogenic precursor, and/or by providing free fatty acids (FFA), stimulants of the rate of gluconeogenesis.
Methods: In 25 preterm infants glucose production and gluconeogenesis were measured using stable isotope techniques, during a six-hour infusion of glucose only, glucose plus glycerol, or glucose plus an intravenous lipid emulsion. Two lipid emulsions differing in FFA composition were used: Intralipid® (~60% polyunsaturated FFA) and Clinoleic® (~60% monounsaturated FFA). The rate of glucose infusion was 22 µmol.kg-1.min-1 in all groups.
Results: During the study-infusion the FFA concentrations were higher in both lipid groups compared to the glycerol group (p<0.001). Compared to baseline, the glucose production rate increased in the Intralipid® group, whereas it decreased in the other groups (p=0.002), due to a significant increase in gluconeogenesis in the Intralipid® group (p=0.016). The plasma glucose concentration was significantly higher during Intralipid® infusion compared to the other groups (p=0.046).
Conclusion: Intralipid® enhanced glucose production by increasing gluconeogenesis in preterm infants. This can be ascribed to the stimulatory effect of FFA in addition to any effect of glycerol alone. The lack of stimulation of gluconeogenesis in the Clinoleic® compared to the Intralipid® group suggests that different classes of fatty acids exert different effects on glucose kinetics in preterm infants.
