Fig. 4.

PDA tumors of the obese have enhanced nitrogen flux into the urea cycle. a ¹⁵N enrichment in plasma glutamine in 19–21 week old male Rag1 ^−/− mice bearing orthotopic AsPC1-shScr and AspC1-shARG2 PDA tumors that were infused with ¹⁵N(amine) glutamine (n  = 3). b Schematic of the urea cycle with red arrows indicating increases in ¹⁵N-labeling of the urea cycle metabolites in tumors of the obese; CPS-1, Carbamoyl phosphate synthase 1; OTC, Ornithine transcarbamylase; ASL, Argininosuccinate lyase. c, d Relative abundance of ¹⁵N-labeled metabolites (n = 3 except for Lean-shScr n = 4) outside c, or within d the urea cycle. e Relative abundance of derivatized ¹⁵N-ammonia. Data indicate the mean ± s.d. in a, c–e, and are representative of two independent experiments. *P ≤ 0.05, **P ≤ 0.01, ***P  ≤ 0.001, ****P ≤ 0.0001, by one-way ANOVA followed by Tukey test