However, weekly intra-amniotic IGF-1 treatment did result in significant up-regulation of mRNA levels of placental transporters for neutral (SLC38A4), cationic (SLC7A1), and branched-chain amino acids (SLC7A8), which could provide a mechanism for increased substrate supply to the IUGR fetus. The gene discussed is SLC38A4; the disease is fetal growth restriction.