Effect of burn injury on relative anaplerosis and gluconeogenesis in rats by ^(13)C magnetic resonance spectrum

To introduce a safe and specific appr oach of 13 C magnetic resonance spectrum ( 13 C MRS) spectroscopy and investigate the alterations in hepatic anabolism. Methods: Relative anaplerotic, pyruvate recycling and gluconeog enic fluxes were measured by 13 C MRS isotopomer ana lysis of blood glucose from rats with 40% body surface area burn injury, and fro m rat s exposed to sham injury. A short chain fatty acid, [U 13 C] propionate which was avidly extracted by the liver, was infused intravenously to deliver 13 C into the citric acid cycle. Proton decoupled 13 C MRS of deproteinized plasma or extracts of the freeze clamped liver were used to determine the distribution of 13 C in blood or hepatic glucose.Results: There was no difference in the multiplets detected in the glucose carbon 2 anomer from blood or liver after 45 or 60 minutes of the i nfusion of the propionate, indicating that steady state isotopic conditions wer e achiev ed. Gluconeogenesis relative to citric acid cycle flux was not altered by burn i njury; in both sham and burn groups the rate of glucose production was about equ al to flux through citrate synthase. In the sham group of animals, the rate of e ntry of carbon skeletons into the citric acid cycle was about 4 times than that in the burn group. Similarly, flux through pyruvate kinase (again relative to ci trate synthase) was significantly increased after the burn injury. Conclusions: Since results from analysis of the blood glucose a re the same as that of the hepatic glucose, 13 C dis tribution in the glucose and hepatic metabolism can be assessed based on the 13 C MRS analysis of the blood glucose.