Glutamine released from the muscles to the blood by LAT1 (SLC7A5), ASCT1 (SLC1A4), and SNAT3 (SLC38A3) serves as a non-toxic form of ammonia transport for the synthesis of urea in the liver and ammonia in the kidneys, as preferred respiratory fuel and substrate for the synthesis of nucleic acids in rapidly proliferating cells, such as enterocytes, immune cells, and tumor cells, and as a precursor for glucose synthesis in the liver and kidneys [81,82,83,84,85,86]. The gene discussed is SLC7A5; the disease is neoplasm.