Prenatal alcohol exposure and maternal glutamine supplementation alter the mTOR signaling pathway in ovine fetal cerebellum and skeletal muscle.
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Prenatal alcohol exposure causes fetal neurodevelopmental damage and growth restriction. Among regions of the brain, the cerebellum is the most vulnerable to developmental alcohol exposure. Despite vast research in the field, there is still a need to identify specific mechanisms by which alcohol causes this damage in order to design effective therapeutic interventions. The mammalian target of rapamycin (mTOR) is known to be associated with axonal regeneration, dendritic arborization, synaptic plasticity, cellular growth, autophagy, and many other cellular processes. Glutamine and glutamine-related amino acids play a key role in fetal development and are known to alter the mTOR pathway; recent research has shown that disturbances in their bioavailability and signaling pathways may mediate adverse effects of prenatal alcohol exposure. This study investigated the role of the mTOR signaling pathway in the fetal cerebellum and skeletal muscle after third trimester-equivalent prenatal alcohol exposure and maternal l-glutamine (GLN) supplementation using a sheep model. Fetal cerebella and skeletal muscles were sampled for Western blot analysis of mTOR and its downstream targets S6 kinase and eukaryotic initiation factor 4E-bindin protein (4E-BP1). The expression of cerebellar phosphorylated mTOR relative to the total mTOR was elevated in the alcohol+GLN group compared to the saline and GLN groups. Alcohol exposure increased the ratio of phosphorylated S6K to total S6K in fetal cerebellum, and no significant effect of GLN supplementation was observed. On contrary, maternal GLN supplementation reduced the activation of mTOR and S6K in fetal skeletal muscle, possibly to make GLN and other amino acids available for use by other organs. These findings suggest prenatal alcohol exposure and maternal GLN supplementation during the third trimester-equivalent alter the mTOR signaling cascade, which plays a possible key role in alcohol-induced developmental damage.
