a, Glucose utilization, lactate secretion and glutamine utilization in 143Bwt and 143Bcytb cells. b, Mass isotopomer analysis of citrate in cells cultured with D[U-13C]glucose and unlabeled glutamine. c,d, Mass isotopomer analysis of citrate and fumarate in cells cultured with L[U-13C]glutamine and unlabeled glucose. Data are the average ± S.D. for three independent cultures. * p<0.05; ** p<0.005, Student’s t-test. e, Schematic of glutamine metabolism in 143Bwt and 143Bcytb cells. Colored arrows follow the paths of glutamine-derived carbon. Abbreviations: Ac-CoA, acetyl-CoA; OAA, oxaloacetate; Gln, glutamine; Glu, glutamate; αKG, α-ketoglutarate; Succ-CoA, succinyl-CoA; Fum, fumarate; Mal, malate; PDH, pyruvate dehydrogenase; ACL, ATP-citrate lyase; IDH, isocitrate dehydrogenase; αKGDH, α-ketoglutarate dehydrogenase.