For several years now, the microbiome has been moving more and more into the center of public interest. The billions of bacteria that live in our bodies have a previously underestimated influence on whether we are healthy or sick. The exact connections are not yet fully understood, but one thing is certain: We live in a close symbiosis with our bacteria.
The better we understand this interaction, the better we can make use of it. Let's eat a lot e.g.b vegetable fiber our intestinal bacteria can convert it into short-chain fatty acids which are associated with some health benefits. It is also beneficial to health to maintain as much diversity as possible in the microbiome.
As we get older, this symbiosis increasingly seems to become a dysbiosis . Fewer and fewer of the “good” bacteria live in our intestines and the “bad” ones are taking over. This cannot be easily broken down into one type of bacteria, as each microbiome is highly individual and depends on many factors. For example, ethnic origin, living conditions, food choices, lifestyle, etc.). Changes in the microbiome are associated with some chronic diseases, such as diabetes, cardiovascular disease and cancer. Here you can find out everything about the topic.
More than just bacteria – our microbiome
Entire books can be filled about the microbiome . Hardly a day goes by without a new study being published on the topic. And the research interest is more than justified. The microbiome depends on us and vice versa. How exactly this symbiosis works is gradually being revealed. Roughly speaking, we need the microbiome to get some nutrients from food. Our body does not have the right enzymes to break down every nutrient. And this is exactly where the microbiome comes into play.
What would normally be just “waste” for us, such as:b Fiber, can be digested by our microbiome. The bacteria even rely on us to “feed” them. In return, they produce some substances that are beneficial to our health. These include secondary bile acids, vitamins, amino acid derivatives and short-chain fatty acids.
In addition, the microbiome appears to be closely related to our intestinal nervous system – a gigantic network of nerve cells that surround our entire intestine. If you will, our second brain or our “gut feeling”. And of course this enteric nervous system also communicates with our central nervous system.
So you can see that the microbiome is complex and its networks or Effects even more complex. This does not always make it easy to conduct studies. Nevertheless, scientists were able to find out a lot about aging. More on that in a moment.
It's diversity that counts - symbiosis instead of dysbiosis
Before we look at what happens when the microbiome doesn't work to our advantage, we have to ask ourselves what a healthy microbiome actually is. This question is more difficult to answer than one might think at first glance. There are countless studies on this and the findings from them can be defined as follows: The microbiome is very individual. Which bacteria did we take with us from our youngest childhood? In which country were we born? What genes do we carry within us? What did our food look like in childhood? Did we have severe intestinal infections
It is widely accepted that we develop our microbiome in early childhood and that it typically remains stable as we progress into adulthood t6> (unless you change your lifestyle or his environment is radical).
The older we get, the more the diversity of bacteria in our intestines decreases. The researchers see this as one of the main reasons for age-associated diseases. A biased microbiome makes us susceptible to an excess of “bad” bacteria.
This can be seen impressively using the example of Clostridium difficile . This small bacterium lives in our intestines and initially doesn't cause much of a stir there. If we have a more severe infection that requires special antibiotic treatment, this bacterium does have a survival advantage. While most of the bacteria in our intestines die, C. survives.difficile and begins to multiply rapidly because suddenly there are no more competitors. The result is a serious intestinal infection, which often has to be treated in hospital.
Dybiosis can be triggered by the overpopulation of the bacterium Clostridium difficile. Antibiotic therapy is often responsible for this.
Dysbiosis using the example of p-cresol
There are hundreds of metabolic processes, all of which have a possible impact on our health. To simplify things a bit, we'll show you an example of a fairly well-researched metabolite: p-cresol
In the ELDERMET study 500 people, all over 65, were tested for their microbiome and possible metabolic products. This showed that participants with higher stool concentrations of p-cresol had increased frailty.
What is p-cresol? This molecule is created by the fermentation of the amino acid tyrosine in our intestines. The sulfated version of the molecule is excreted through our kidneys. As long as our kidneys are healthy, this doesn't seem to be a problem. However, if the filtration rate decreases and the p-cresol level in our blood increases, things seem to become problematic.
High p-cresol levels are associated with the development of cardiovascular diseases and they have a toxic effect on the filter system in our kidneys. This seems to be a vicious circle. People with poorer kidney function often have dysbiosis of the microbiome. There are increasing numbers of aerobic bacteria that promote the production of toxic metabolites, including p-cresol. Maybe there is a possible starting point for the future.
Tryptophan metabolism: From symbiosis to dysbiosis
Another important metabolic process in our intestines is the tryptophan pathway. Tryptophan is an amino acid that we use, for example.b absorb through food. Our intestinal bacteria have various ways to further metabolize this amino acid. We'll show you the three most important ones:
- Kynurenine pathway (Kyn): Tryptophan is broken down into kynurenine via the enzyme IDO (indoleamine 2,3-dioxygenase). t225>
- Serotonin pathway: Our intestinal bacteria can convert tryptophan into the “happiness hormone” serotonin. A full 90% of our serotonin is located in the intestine! Through this axis, tryptophan can also be converted into Melatonin, the sleep hormone, can be converted
- Indole pathway: The third way to break down tryptophan is the indole pathway. Higher indole concentrations in older people were associated with increased fitness . The lifespan of mice could also be increased through an increase in indole metabolites
Dysbiosis as a hallmark of aging: It's all about balance
Some studies on tryptophan metabolism come to the conclusion that a disruption of the balance can contribute to illness. Is e.g.b The above-mentioned enzyme IDO (to be precise, the subclass IDO-1) overactivates, so we find more kynurenine compared to serotonin than normal in the body . This excess of kynurenine is associated with some diseases. It has been shown that Depressed people often have an overactivation of IDO-1, which results in lower serotonin levels. One of the hypotheses is that this contributes to depression.
Note: The hypothesis, long accepted in science, that low serotonin levels are the trigger for depression is not entirely correct. Serotonin plays a role in the disease, but it is not easily broken down.
Chronic inflammation can increase IDO activity and thus it can be hypothesized that inflammation also contribute to the dysbiosis of our microbiome via this pathway.
Inflammaging and dysbiosis – two hallmarks with a close connection
As we have just seen, chronic inflammation can have a negative impact on our microbiome. But it also seems to work the other way around, at least that's what experiments on mice suggest. For this purpose, two populations of mice were taken. One was young, healthy mice and the other was older, sick mice. Now the microbiome from the older mice was transferred to the younger mice. The result was that the younger mice showed significantly more signs of inflammation, i.e. higher inflammatory markers.
Conclusion
The microbiome is one of the most exciting fields of research and the disruption of the balance seems to contribute to some diseases in old age. We are losing the diversity of bacteria that keep us healthy and that is why dysbiosis has been included as one of the Hallmarks of Aging. In the future we will certainly see some therapeutic approaches that reverse exactly this dysbiosis.
The next article in this series will focus on the twelfth hallmark of aging: Altered autophagy.
