Authors: Clayton Olinger, Mukundan Ragavan, Anthony Giacalone, and Matthew Merritt
Faculty Mentor: Dr. Matthew E. Merritt
College: College of Medicine
The use of isotopic tracers is an effective way to assess metabolic turnover, as well as various pathophysiologic perturbations of normal metabolic flux. The isolation and the perfusion of mice livers allow for measurements of hepatic citric acid cycle flux, as well as gluconeogenesis by tracking these isotopes in 2H and 13C NMR spectroscopy. Perfusions are performed by making an incision in the abdomen of the mice, allowing for a thin tube to be put into the portal vein of the liver. This liver is removed, cleaned and placed in a glass column where it is be perfused with a Krebs buffer, mixed fatty acids, lactate and pyruvate. These perfusions allow the liver to be metabolically active outside of the mouse. [U-13C]propionate, a labeled odd-chain fatty acid, has been used in the past to measure the oxidative capacity of the liver. Using NMR spectroscopy, we probe hepatic metabolism using [U-13C]glutamine and compare the results to the [U-13C]propionate method. Two different concentrations of [U-13C]glutamine are evaluated for its ability to report on gluconeogenesis and citric acid cycle turnover. Even at the lower concentration of 100 µM, glutamine can accurately report citric acid flux and gluconeogenesis activity in perfused mice livers.