Association of placental nutrient sensing pathways with birth weight.

Birth weight (BW) is an important indicator for newborn health. Both high and low BW is associated with increased risks for adult metabolic diseases. AMPK (AMP-activated protein kinase), mTOR (mechanistic target of rapamycin), and insulin/IGF1 (insulin-like growth factor 1) pathways may function as placental sensors of maternal hormonal and nutritional status. However, the physiological role of these pathways in placenta has not been completely elucidated. To evaluate expression and activation of AMPK, mTOR, and insulin/IGF1 pathways and its association with placental weight (PW), BW, and maternal hormonal and metabolic status, we performed a cross-sectional study in placentas from non-obese mothers with SGA (n = 17), AGA (n = 19) and LGA (n = 10) newborns. We analyzed placental expression of total and phosphorylated key proteins from the AMPK, mTOR and insulin/IGF1 pathways. Maternal and cord blood hormones were determined by ELISA. AMPK and LKB1 activation correlated negatively with PW and BW, cord leptin, and pregestational BMI. Placental SIRT1 inversely correlated with BW, cord leptin, neonatal HOMA-IR, and maternal IGF1. PGC1α correlated negatively with PW and BW. Phosphorylated mTOR positively correlated with maternal glucose, PW and BW. IGF1R was lower in SGA. No changes in p-IGF1R, INSRb, total AKT or p-AKT were found, and pPDK1 was lower in SGA and LGA. These results suggest that placental AMPK, insulin/IGF1, and mTOR pathways may influence fetal growth, perhaps regulating placental physiology, even in metabolically healthy pregnancies. Our study highlights these nutrient sensing pathways as potential molecular mechanisms modulating placental adaptations and, thus, long-term metabolic health.