Extended Data Fig. 7. In vivo ¹³C tracing in support of figure 6.

LC-HRMS analysis of ¹³C₃ lactate generated from 8h continuous ¹³C₆ glucose infusion using an “insulin clamp”. Mice received a primed (42.5 mU/kg)/continuous (4.5 mU/kg/min) infusion of insulin and a variable infusion of 20% glucose (50% ¹³C₆-glucose : 50% ¹²C-glucose) to maintain euglycemia for 480 min. Mice were sacrificed and heart and liver were disrupted in liquid nitrogen. B cell populations were isolated as in Extended Data Fig. 1 and all samples were subjected to ¹³C₃-lactate detection by liquid chromatography-high resolution mass spectrometry.