Metabolism of [3-¹³C]alanine in liver of mice infected with cysticerci of Taenia crassiceps

Carbon-13-decoupled proton spin-echo nuclear magnetic resonance (NMR) spectroscopy, with and without ¹³C population inversion, was used to study carbon flow between the host and the parasite in the mouse - Taenia crassiceps system. This NMR analysis revealed that 2 h after intraduodenal injection of [3-¹³C]alanine, livers from both uninfected mice and those infected with cysticerci of T. crassiceps contained ¹³C label in glycogen, glucose, succinate, glutamate, alanine, and lactate. Livers of infected animals had a lower percentage of ¹³C in alanine, indicating increased utilization of the substrate. In addition, infected mice had a lower concentration of total hepatic glucose and glutamate. The data are consistent with an increased rate of gluconeogenesis in the liver of infected animals. Cysticerci possessed ¹³C label in glucose, acetate, alanine, and lactate. Since these metacestodes are unable to make glucose de novo from pyruvate, labelled glucose found in cysticerci had to be newly synthesized via the host gluconeogenic pathway and then siphoned off by the parasite.