The Bacterial Microbiome and (Male) Brain Development

A new study out of Singapore suggests that alterations in the microbiome affect the development of the brain’s immune system (the microglia) in males more than females.[i]

The microglia defend against pathogens in the brain, and clear out debris.  They are also partially responsible for brain development of neuronal connections.  Autism is known to be associated with microglia defects.

Maternal mice and their pups were raised in germ-free conditions, an extreme version of the biome depletion suffered by those of us in the industrialized world.  “The study reveals that the microglia increase in density and show significant changes in gene expression only in male fetal mice.”  Interestingly, this reversed in later in life: only the adult females showed large-scale changes in the microglia. Something about microbiome alterations early in life, starting even before birth, changes the male brain more than the female.  The reasons are unknown, but obviously, sex-specific hormones (which apparently diverge at the end of the embryonic phase of development) are a target for future research.

You do have to wonder if this is not why more boys have developmental disorders whereas, more adult females have depression and anxiety, for example.

????

Says the co-lead researcher on the study: “There’s a critical window during development where only males are very sensitive to the lack of a microbiome…”

Obviously, figuring out the mechanism that protects the neonatal female brain from microbiome alterations is a priority, and also, the researchers involved in this study do plan to look at “…how microglia respond to more realistic prenatal complications tied to autism risk, such as maternal infection and preterm birth.”  My two cents:  wouldn’t it be an even better idea to figure out how to stop the biome depletion issue from happening in the first place?

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[i] https://spectrumnews.org/news/early-changes-brain-immunity-may-underlie-sex-bias-autism/