Because I know how to have a good time, I spent a lot of time yesterday reading incredibly depressing articles, one after another, about the gut: paper after paper about the differences in the gut microbiota of those on the autism spectrum, subsequent differences in the short-chain fatty acids of those on the autism spectrum, how changes in the gut biome affect the development of the amygdala (the emotion center of the brain), and yet-another paper on how unbelievably detrimental is the administration of antibiotics early in life.
I’ve picked this last one for today’s post because there is an interesting finding that should be shared. The paper was written by a researchers from around the world including Australia, Thailand, and the USA.[i] There were two experimental groups in their study: one group of mice consisted of newborns and a second group had just been weaned. Both were given vancomycin, a non-systemic (i.e. it stays in the gut) antibiotic. As expected, the antibiotic induced dysbiosis in both groups and, as I also would have expected, this dysbiotic effect differed in the mice depending on their age. The second group, who were older and already weaned, had had time for their gut microbiota to mature a little more, as opposed to the newborn mice.
Previous research has shown that “…oral vancomycin administered to mice during the neonatal period profoundly affects the gut microbiota and ENS [enteric nervous system (i.e. the gut’s nervous system)] function.” The shift in gut flora of the weaned mice caused “…disrupted colonic migrating motor complexes” and changes in the circuitry of the enteric nervous system. In other words, the ability of the digestive system to normally propel food through itself was altered, leading to constipation. In contrast, vancomycin administered to neonatal mice caused an increase in colonic contractions – so diarrhea: “The differential effects of vancomycin on colonic contractions may be due to the different effects on microbiota communities in the neonatal compared with the postweaning period.”
This was a first for me: the diarrhea versus constipation, depending on when the antibiotics were administered to the babies. And of course, intestinal transit time has a major effect on the “…gut microbiota composition, diversity, metabolism, and clearance, as well as nutrient and water absorption.” That is, disrupt the transit time of food through the gut early in life, you alter the physiology of the gut biome and the host organism…and thereby, alter development, including that of the brain.
(A good read (NOT) for a mom whose child was administered 5 days of round-the-clock antibiotics starting at 1 day old…whose child then suffered from inflammatory bowel disease and autism…)
To sum up: the article concludes the following: “…antibiotics administered during critical developmental windows have greater consequences on host physiology than antibiotic exposure during maturity.” That is, “…changes in communication between the microbiota and the enteric nervous system that arise from early-life antibiotic treatment could have lasting effects on gastrointestinal function.”[ii] And of course, changes in gastrointestinal function affect everything, including brain development.
If you remember, I have written multiple times before about biome alterations affecting the development of the amygdala, which is the emotion center of the brain. In January, I wrote this post (on how both too much or too little of various short chain fatty acids affect the brain and the development of disease), which included covering a 2019 article that showed that the short-chain fatty acid, propionic acid, affects the structure of the amygdala. The take-away message from that post: in the right amounts at the right times, SCFAs, including propionic acid, are crucially important for good health.
Included in my readings of yesterday was another paper confirming these effects of early life biome alterations affecting the development of the amygdala in those on the autism spectrum: “Recent work shows alterations in the gut microbiome to have a significant impact on amygdala development in infancy, suggesting that the alterations in the gut microbiome may act to modulate not only amygdala development but how the amygdala modulates the development of the frontal cortex and other brain regions.”[iii]
I began reading about the early introduction of antibiotics being problematic well over 2 decades ago. I wonder if medical practices have as yet substantially changed in light of all this research. ????
[i] Lin Y. Hung et al. Antibiotic exposure postweaning disrupts the neurochemistry and function of enteric neurons mediating colonic motor activity, American Journal of Physiology-Gastrointestinal and Liver Physiology (2020). DOI: 10.1152/ajpgi.00088.2020
[iii] Seo M, Anderson G. Gut-Amygdala Interactions in Autism Spectrum Disorders: Developmental Roles via regulating Mitochondria, Exosomes, Immunity and microRNAs. Curr Pharm Des. 2019;25(41):4344-4356. doi:10.2174/1381612825666191105102545