A Key Micronutrient Identified in Breast Milk Promotes Synaptic Growth
Post by Lani Cupo
The takeaway
Myo-inositol (MYO) is a micronutrient identified in human milk from around the world which helps establish synaptic connections between neurons early in life.
What's the science?
Diet can have a big impact on brain development early in life and preservation later in life, however, it is unclear what micronutrients are important in contributing to connectivity between neurons. This week in PNAS, Paquette and colleagues analyzed samples of human breast milk from around the world to identify a micronutrient MYO that is present during periods when neuronal connections are formed. They then validate the ability of MYO to promote synapse formation in cultured neurons and mouse models.
How did they do it?
First, the authors collected samples of breast milk from women from Mexico City (N = 10), Shanghai (N = 10), and Cincinnati (N = 10) at 5 time points throughout the first year postpartum. Focusing on inositol, a sugar that is elevated in human milk compared to cow’s milk, the authors quantified the amount of MYO, a form of inositol not bound in other molecules, across time. Second, using human induced pluripotent stem cells the authors cultivated human glutamatergic neurons to examine the impact of MYO on synaptic sites.
Next, the authors cultivated hippocampus neurons from rats in vitro (in a Petri dish) and exposed them to differing dosages of MYO to examine the impact on the synapses between neurons. Then, the authors conducted an analysis in mice by supplementing them with MYO from birth to 35 days old and examining synaptic sites in the visual cortex. Finally, they examined the impact of MYO in mature tissue - aging neurons from the mouse hippocampus - before exposing them to the sugar.
What did they find?
First, the authors found that MYO levels are highest in the first weeks of lactation, a time period associated with dramatic increases in synaptic density in babies. Second, introducing MYO to cultured neurons increased post-synaptic staining intensity, an indicator of increased sites for synaptic connections.
Next, the authors found that MYO increased synapse formation in a dose-dependent manner with higher dosages leading to an increased impact. These results provided further evidence of MYO’s role in promoting synapse formation for both excitatory and inhibitory neurons. Then, the authors found enlarged synaptic sites in the visual cortex of mice exposed to supplements of MYO after giving birth. This further emphasizes the role of MYO across species and brain regions. Finally, the authors found evidence of increased synapses in mature tissue as well, suggesting a potential preservative effect of MYO in adults.
What's the impact?
The authors highlight the importance of the micronutrient MYO in synapse formation and neuronal connectivity, both in development and mature tissue. Their results provide avenues to improve pediatric nutrition products, and may, in time, promote synapse protection in aging.