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Regulation of blood–brain barrier integrity by microbiome-associated methylamines and cognition by trimethylamine N-oxide, 2021, Hoyles et al

Discussion in 'Other health news and research' started by Andy, Nov 27, 2021.

  1. Andy

    Andy Retired committee member

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    Location:
    Hampshire, UK
    In mice.

    Abstract

    Background
    Communication between the gut microbiota and the brain is primarily mediated via soluble microbe-derived metabolites, but the details of this pathway remain poorly defined. Methylamines produced by microbial metabolism of dietary choline and L-carnitine have received attention due to their proposed association with vascular disease, but their effects upon the cerebrovascular circulation have hitherto not been studied.

    Results
    Here, we use an integrated in vitro/in vivo approach to show that physiologically relevant concentrations of the dietary methylamine trimethylamine N-oxide (TMAO) enhanced blood-brain barrier (BBB) integrity and protected it from inflammatory insult, acting through the tight junction regulator annexin A1. In contrast, the TMAO precursor trimethylamine (TMA) impaired BBB function and disrupted tight junction integrity. Moreover, we show that long-term exposure to TMAO protects murine cognitive function from inflammatory challenge, acting to limit astrocyte and microglial reactivity in a brain region-specific manner.

    Conclusion
    Our findings demonstrate the mechanisms through which microbiome-associated methylamines directly interact with the mammalian BBB, with consequences for cerebrovascular and cognitive function.

    Open access, https://microbiomejournal.biomedcentral.com/articles/10.1186/s40168-021-01181-z
     
    Andy, Nov 27, 2021
    #1
    Midnattsol, Peter Trewhitt, shak8 and 2 others like this.
  2. Andy

    Andy Retired committee member

    Messages:
    23,839
    Location:
    Hampshire, UK
    Andy, Nov 29, 2021
    #2
    Midnattsol and Trish like this.
  3. Midnattsol

    Midnattsol Moderator Staff Member

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    I'm glad they mentioned the problems with previous research linking TMAO to cardiovascular disease. This link often comes up in studies of diet and TMAO, as TMAO increases after meat intake, and it makes a neat story that supports the "red meat is bad" argument. However, as mentioned here, fish intake also increases TMAO but is not linked to cardiovascular disease. There are also studies that have found increased TMAO in low-carb diets which have also been used to argue the potential dementrial effect of this type of diet on vascular health.

    I don't like that they are refering to the cochrane review on omega-3 supplements and cardiovascular disease though, this review does not take into account different types of omega-3 supplements (ratio of EPA to DHA, is there any DPA etc) and many if not all studies included do not account for diet intake of omega-3's, only the supplement. This means that a control group in such a study could have the same, or higher depending on the supplement, omega-3 intake than the supplement intervention group so comparing the two groups based on supplement status is not the same as omega-3 intake status.
     
    Midnattsol, Nov 29, 2021
    #3
    Trish likes this.

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