Estimation of gluconeogenesis in newborn infants

The rate of glucose turnover (R-a) and gluconeogenesis (GNG) via pyruvate w ere 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 [C-1 3(6)]glucose and (H2O)-H-2. The preterm babies were receiving parenteral al imentation of either glucose or glucose plus amino acid with or without lip ids. The contribution of GNG to glucose production was measured by the appe arance of H-2 on C-6 of glucose. Glucose R-a in full-term babies was 30 +/- 1.7 (SD) mu mol.kg(-1).min(-1). GNG via pyruvate contributed similar to 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 inf ants receiving low rates of exogenous glucose infusion. In an additional gr oup of infants of normal and diabetic mothers, lactate turnover and its inc orporation into glucose were measured within 4-24 h of birth by use of [C-1 3(3)] lactate tracer. The rate of lactate turnover was 38 mu mol.kg(-1).min (-1), and lactate C, not corrected for loss of tracer in the tricarboxylic acid cycle, contributed similar to 18% to glucose C. Lactate and glucose ki netics were similar in infants that were small for their gestational age an d in normal infants or infants of diabetic mothers. These data show that gl uconeogenesis is evident soon after birth in the newborn infant and that, e ven after a brief fast (5 h), GNG via pyruvate makes a significant contribu tion to glucose production in healthy full-term infants. These data may hav e important implications for the nutritional support of the healthy and sic k newborn infant.