Fig. 1: In vivo labeling of mice using [U-¹³C]-glucose.

A Illustration of the approach used to label freely moving and unanesthetized mice with [U-¹³C]-glucose for up to 4 hours using catheters followed by MIMS-EM and spatial analysis. Figure created using biorender.com. B Blood glucose levels measured from mice continuously infused with 15 or 40 mg/min/kg of total body mass for up to 4 hours. Data from n = 4-17 mice per group. C Expelled ¹³CO₂ (in parts per million (ppm)) measured from the atmosphere of custom-made metabolic cages using gas mass spectrometers. ¹³C glucose was infused for the first 240 minutes and replaced with ¹²C glucose for an additional 120 minutes. AFE, atomic fractional enrichment. Data from n = 3 mice per group. D, E GC-MS analysis to determine the fractional ¹³C enrichment of circulating glucose molecules and of secondary metabolites pyruvate, citrate, and alpha ketoglutarate (aKG) generated from glucose metabolism. Each dot represents an animal, n = 6 animals per time point. In B, data shown as ± standard deviation of the mean. In C, the shaded region indicates the data range of ¹³CO₂ measurements. In D, E), ****p < 0.001 and *p < 0.05 using One-way ANOVA with Kruskal-Wallis tests.