Fetal and Neonatal Responses to Maternal Canine Starvation: Circulating Fuels and Neonatal Glucose Production

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Abstract
Summary: Pregnant dogs were starved for 72 hr while controls were fasted overnight. Maternal starvation significantly reduced fetal birth weight (269 ± 7.2 versus 294 ± 4.4 g). Total caloric deprivation had no effect on maternal or fetal blood glucose concentrations at the time of delivery; however, fasting neonatal blood glucose levels were depressed during the first 9 hr of life. Starvation produced a large elevation of maternal free fatty acids (1.68 ± 0.39 versus 0.74 ± 0.2 mM) and ketone bodies (2.99 ± 0.70 versus 1.04 ± 0.48). Although fetal free fatty acids increased minimally (0.39 ± 0.03 versus 0.22 ± 0.07), ketone body levels were markedly elevated (2.53 ± 0.35 versus 1.01 ± 0.32). After birth, plasma-free fatty acid and β-hydroxybutyrate levels were lower in pups of starved mothers at 3 hr, and acetoacetate was lower at 6 and 9 hr. Other alternate fuels such as amino acids demonstrated lower levels of glutamine in pups of starved mothers throughout the day (except 3 hr), whereas alanine levels declined significantly only at 24 hr (114.9 ± 15 versus 187.6 ± 26 μM. Glucose production was significantly depressed in pups of starved mothers at 3 (13.7 ± 1.4 versus 22.7 ± 3) and 9 hr (17.5 ± 2.2 versus 26.0 ± 2.8 μmoles/kg/min), whereas glucose clearance rates were elevated at 3, 6, and 9 hr of age. Lactate carbon incorporation into glucose increased throughout the day but was not significantly affected by prior maternal starvation. Speculation: Because glucose concentration and turnover were depressed whereas glucose clearance was elevated early during neonatal fasting, diminished oxidation of alternate fuels (such as fatty acids) may necessitate enhanced glucose consumption. Diminished intrahepatic oxidation of fatty acids may limit the energy source for sufficient glucose production from gluconeogenic precursors.