Maternal Myo-Inositol Deficiency Involved Autophagy Impairment by PI3K/Akt/mTOR Signaling in Neural Tube Defects During Pregnancy

Previous studies have demonstrated that peri-conceptional inositol supplementation could effectively ameliorate the recurrence of neural tube defects (NTDs); though, the mechanism remains unclear. In the current investigation, we detected the myo-inositol (MI) levels in maternal plasma and embryonic tissues in a Chinese population with high prevalence of NTDs and found maternal MI deficiency increased NTD susceptibility in this area. Pregnant mice were randomly divided into 2 groups. The control group was treated with 0.9% saline, while the experimental group was treated with IMPase inhibitor by intraperitoneal injection on E7.5 to generate the maternal MI-deficient mouse model, followed by comprehensive phenotypic and molecular analysis at E13.5. Corresponding in vitro experiments treated neural stem cells (NSCs) for 16 h with IMPase inhibitor, MI supplementation, or specific PI3K and mTOR inhibitors to systematically investigate the downstream signaling pathways. We observed aberrant activation PI3K/Akt/mTOR signaling and reduced autophagy in a maternal MI deficiency mouse model after ruling out the genetic perturbations. Further in vitro kinase assay showed that MI negatively regulated PI3K activity, in a dose-dependent manner, which possibly due to the hydrogen bond interactions between amino acid residues in the ATP-binding site of PI3K and inositol. MI deficiency NSCs also presented PI3K/AKT/mTOR pathway activation concurrent with reduced autophagy level; MI supplementation or inhibition of the PI3K/Akt/mTOR pathway could rescue MI deficiency-induced autophagy impairment. Finally, we validated decreased autophagy levels as well as hyperactivation of the PI3K/Akt/mTOR pathway by MI deficient human NTD embryonic neural tissues. Our results suggested that maternal MI deficiency might increase susceptibility to NTDs. Low levels of MI might impair autophagy in the developing neural tube involving upregulation of PI3K/Akt/mTOR pathway.