The Microbiome, Its Circadian Rhythms…and Diabetes Risk

Not a day goes by that I don’t read something –  a synopsis, an article, an abstract, etc. – about the gut biome, and thus, every single day, I am astounded yet again at the incredible complexity.

Last November, I wrote about research looking at how gut bacteria may affect sleep quality and vice versa (how poor sleep negatively affects both the microbiome and leads to higher inflammation level).  What I have not as yet written about is that bacteria themselves have circadian rhythms, changing in quantity and function throughout the day.  (In fact, this is why people who do night shift work, or air crews who fly between time zones, often have health issues related to the disruption of the microbiome.  I posted an article about this on the Biome Buzz’ Facebook page last year.)

Researchers in New Zealand looked into microbiome circadian rhythms:  “Gut microbiota rhythmicity is expressed through the secretion of molecules at specific times of the day. At night, genes related to energy metabolism, DNA repair and cell growth are enacted, while during the day, bacteria produce molecules that consolidate their own colonization of the gut…According to the review in Microorganisms, sleep time controls the rhythmicity of our food intake through feeding and fasting actions. Any long disruption to this cycle may contribute to an unbalanced gut microbiota, which may lead to a higher risk of metabolic diseases such as diabetes and obesity.”[i]

Today’s article makes this topic all the more complex and interesting.  It turns out that this rhythmic pattern of gut bacteria may actually be useful in detecting risk factors for diseases before they start.[ii]  Researchers in Germany have just published a prospective cohort study, to look at how daytime fluctuations in the gut microbiome relate to the onset of type 2 diabetes. They followed thousands of people over time, observing them carefully, and then matching these observations to the future onset of disease.

Incredibly, it turned out that certain gut bacteria not following a normal day-night rhythm (that is, the number of them and their function does not change over the course of the day), is an indicator for potential type 2 diabetes:  “We demonstrate that in 1,976 subjects of a German population cohort…that specific microbiota members show 24-h oscillations in their relative abundance and identified 13 taxa with disrupted rhythmicity in type 2 diabetes.” This finding was replicated in in 2^nd cohort of 1,363 people.  And 5 years after the original sampling, this “arrhythmic risk signature” was able to predict type 2 diabetes in 699 people.  The predictive nature of the gut bacterial pattern was heightened when combined with body mass index (BMI) data, as excess weight is another major risk factor for the development of type 2 diabetes. Knowing someone is highly at risk can, of course, potentially lead to prophylactic measures to try to avoid the disease altogether.

As I’ve discussed multiple times before, and as they state in the opening sentence of this paper, “Increasing evidence links the human gut microbiome to metabolic health, and altered microbial profiles are associated with obesity, insulin resistance, and type 2 diabetes.”

As is so often the case, the scope of these findings have broad implications.  Firstly, in research conducted on other diseases that involve fecal sampling, it is now obvious that time of day is going to be critical in influencing findings.  Just what we needed was another factor adding to the complexity of all this!  Think about my post of last week on my experience with Thryve:  in hindsight, the results may mean more or less than I know, as time of day of collection is not taken into account by any of the personal biome testing companies.  (No blame assigned to them – we don’t yet know enough about this topic for them to make meaning of it anyway.)  Secondly, this finding, that the rhythmic pattern of bacteria is predictive of type 2 diabetes, probably does not apply to just that one disease.  In the near future, hopefully, we’ll be able to find similar patterns for other diseases which we can then learn to avoid.

Even what you eat at different points during the day will likely turn out to matter far more than we are currently aware.  As they found in the 2019 research noted above:  “Researchers highlighted that alcohol and fast food consumption at night lead to a disruption of gut microbiota rhythmicity through a fall in the number of Bacteroidetes, which may lead to intestinal inflammation and an increased risk of certain colorectal cancers. Furthermore, the higher fat content present in fast food promotes bacteria that can resist the molecules that come from digestion, and many of them are pathogenic or pro-inflammatory due to their ability to produce toxins.”

The article about that 2019 research on Gut Microbiota for Health concludes with the following, which is also a great way to wrap up today’s post because it’s something-you-can-do-now:  “…both your diet and your lifestyle can affect gut microbiota health and balance. A healthy diet that is high in fiber and a regular eating schedule during the day are tools we can easily access for improved gut microbiota rhythmicity, meanwhile behaviors that include eating late at night, alcohol consumption and sleep disruption need to be avoided.”

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[i] https://www.gutmicrobiotaforhealth.com/the-gut-microbiota-clock-the-close-connection-between-gut-microbiota-dietary-patterns-and-the-circadian-rhythm/

[ii] Sandra Reitmeier et al, Arrhythmic Gut Microbiome Signatures Predict Risk of Type 2 Diabetes, Cell Host & Microbe (2020). DOI: 10.1016/j.chom.2020.06.004