Association of SLC38A4 and system A with abnormal fetal birth weight.

In this study, we aimed to explore the correlation between solute carrier family 38 member 4 (SLC38A4) and system A activity in human placentas from pregnancies with abnormal fetal birth weight. We collected placentas from consenting women immediately after their full-term babies were born, with normal, low birth weight or macrosomia, and used real-time PCR and Western blot analysis to detect the levels of SLC38A4 mRNA and protein [also known as sodium-coupled neutral amino acid transport protein 4 (SNAT4)]. Isotope incorporation assay was applied to measure system A activity in the placentas. Compared to the normal birth weight (NBW) group, placentas from the fetal macrosomia (FM) group had significantly increased levels of SLC38A4 mRNA and SNAT4 (both were increased by almost 2-fold; P<0.05), while no significant changes were detected in the placentas from the low birth weight (LBW) group. In addition, system A activity in the placentas from the FM and LBW groups was significantly different from that in the NBW group (1.2±0.20, 0.6±0.14 vs. 1.0±0.18, P<0.05). The data suggest that SNAT4 and system A have a strong association with abnormal fetal birth weight and that they may play a crucial role in fetal growth and development.