Glucose production, gluconeogenesis, and hepatic tricarboxylic acid cycle fluxes measured by nuclear magnetic resonance analysis of a single glucose derivative

A triple-tracer method was developed to provide absolute fluxes contributing to endogenous glucose production and hepatic tricarboxylic acid (TCA) cycle fluxes in 24-h-fasted rats by ²H and ¹³C nuclear magnetic resonance (NMR) analysis of a single glucose derivative. A primed, intravenous [3,4-¹³C₂]glucose infusion was used to measure endogenous glucose production; intraperitoneal ²H ₂O (to enrich total body water) was used to quantify sources of glucose (TCA cycle, glycerol, and glycogen), and intraperitoneal [U- ¹³C₃] propionate was used to quantify hepatic anaplerosis, pyruvate cycling, and TCA cycle flux. Plasma glucose was converted to monoacetone glucose (MAG), and a single ²H and ¹³C NMR spectrum of MAG provided the following metabolic data (all in units of μmol/kg/min; n=6): endogenous glucose production (40.4±2.9), gluconeogenesis from glycerol (11.5±3.5), gluconeogenesis from the TCA cycle (67.3±5.6), glycogenolysis (1.0±0.8), pyruvate cycling (154.4±43.4), PEPCK flux (221.7±47.6), and TCA cycle flux (49.1±16.8). In a separate group of rats, glucose production was not different in the absence of ²H₂O and [U- ¹³C]propionate, demonstrating that these tracers do not alter the measurement of glucose turnover.