Estimation of gluconeogenesis in newborn infants

Abstract

The rate of glucose turnover (R(a)) and gluconeogenesis (GNG) via pyruvate were quantified in seven full-term healthy babies between 24 and 48 h after birth and in twelve low-birth-weight infants on days 3 and 4 by use of [(13)C(6)]glucose and (2)H(2)O. The preterm babies were receiving parenteral alimentation of either glucose or glucose plus amino acid with or without lipids. The contribution of GNG to glucose production was measured by the appearance of (2)H on C-6 of glucose. Glucose R(a) in full-term babies was 30 +/- 1.7 (SD) micromol. kg(-1). min(-1). GNG via pyruvate contributed approximately 31% to glucose R(a). In preterm babies, the contribution of GNG to endogenous glucose R(a) was variable (range 6-60%). The highest contribution was in infants receiving low rates of exogenous glucose infusion. In an additional group of infants of normal and diabetic mothers, lactate turnover and its incorporation into glucose were measured within 4-24 h of birth by use of [(13)C(3)]lactate tracer. The rate of lactate turnover was 38 micromol. kg(-1). min(-1), and lactate C, not corrected for loss of tracer in the tricarboxylic acid cycle, contributed approximately 18% to glucose C. Lactate and glucose kinetics were similar in infants that were small for their gestational age and in normal infants or infants of diabetic mothers. These data show that gluconeogenesis is evident soon after birth in the newborn infant and that, even after a brief fast (5 h), GNG via pyruvate makes a significant contribution to glucose production in healthy full-term infants. These data may have important implications for the nutritional support of the healthy and sick newborn infant.

Metabolic and Genomic Response to Dietary Isocaloric Protein Restriction in the Rat

“…The rate of production of glucose was measured in a separate group of animals using [6,6-2 H 2 ]glucose tracer as described previously (17). Gluconeogenesis from pyruvate was quantified by measuring the incorporation of 2 H in C-6 of glucose following the 2 H labeling of the total body water (18).…”

Measuring gluconeogenesis using a low dose of2H2O: advantage of isotope fractionation during gas chromatography

“…H 2 O method is not subject to such artifacts, and it has been widely used to measure gluconeogenesis (2)(3)(4)(5)(6)(7)(8)12). The principle of the 2 H 2 O method is straightforward.…”

“…The principle of the 2 H 2 O method is straightforward. Briefly, after an oral bolus of 2 H 2 O is administered, the contribution of gluconeogenesis to glucose production is determined by measuring the ratio of 2 H that is bound to carbon-5 vs. carbon-2 of glucose (2)(3)(4)(5)(6)(7)(8)12).…”

An Update on Neonatal Hypoglycemia

“…It is metabolized via oxidation by lactate www.intechopen.com dehydrogenase in the brain. Although the lactate pool is small (2.4 mM), the concentrations tend to be higher in the crucial first 2-3 postnatal hours (Kalhan et al, 2001). In the post-natal life, blood glucose concentrations depend upon the feeding practices.…”

“…The levels of these proteins are relatively low in immature neonates and are a limiting step for glucose transfer and utilization Volpe, 2008). GLUT1 is expressed in the blood-brain barrier endothelial cells, astrocytes, oligodendrocytes and choroid plexus while GLUT3 is expressed primarily in neurons and their synaptic membranes (Mantych et al, 1993;Kalhan et al, 2001). The brain glucose transporter is concentrated in capillaries and the concentration increases with maturity.…”