For several years now, the microbiome increasingly at the centre 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 relationships are not yet fully understood, but one thing is certain: We live in a narrow Symbiosis with our bacteria.
The better we understand this interaction, the better we can use it to our advantage. For example, if we eat a lot of plant-based fiber our intestinal bacteria can convert these into short-chain fatty acids which are associated with several health benefits. Maintaining as much diversity as possible in the microbiome is also beneficial to health.
In old age, this symbiosis seems to increasingly become a dysbiosis to become. Fewer and fewer of the “good” bacteria live in our intestines and the “bad” ones take over. This cannot be easily broken down into one type of bacteria, as each microbiome is highly individual and depends on many factors (e.g. ethnic origin, living conditions, food choices, lifestyle, etc.). Changes in the microbiome are associated with some chronic diseases, such as diabetes, cardiovascular disease and cancerHere you can find out everything about the topic.
More than just bacteria – our microbiome
About the microbiome Entire books can be filled with this topic. Hardly a day goes by without a new study being published on the subject. 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 foodOur body does not have the right enzymes to break down every nutrient. And this is where the microbiome comes into play.
What would normally be considered “waste” for us, such as fiber, can be digested by our microbiome. The bacteria even depend 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 linked to our intestinal nervous system – a gigantic network of nerve cells that surround our intestines along their entire length. If you like, our second brain or our “gut feeling“And this enteric nervous system is of course also in communication with our central nervous system.
As you can see, the microbiome is complex and its connections and effects are even more complex. This does not always make it easy to conduct studies. Nevertheless, scientists have been able to find out a lot about aging. More on that in a moment.
Diversity is what matters – symbiosis instead of dysbiosis
Before we look at what happens when the microbiome does not work to our advantage, we have to ask ourselves what a healthy microbiome isThis question is more difficult to answer than one might think at first glance. There are countless studies on the subject and the findings can be defined as follows: The microbiome is very individual. What bacteria did we carry with us from early childhood? In which country were we born? What genes do we carry? What did our diet look like in childhood? Did we have serious intestinal infections? What do we eat? Do we eat a lot of fiber? And so on.
It is widely recognized that we develop our microbiome in early childhood and that it usually remains stable throughout our adulthood remains (unless you radically change your lifestyle or environment).
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-related diseases. A one-sided microbiome makes us susceptible to an excess of “bad” bacteria.
This can be seen impressively in the example of Clostridium difficile This small bacterium lives in our intestines and initially does not cause much of a stir. If we have a more serious infection, requires special antibiotic treatment, However, this bacterium has a survival advantageWhile most of the bacteria in our intestines die, C.difficile survives and begins to multiply rapidly because there are suddenly no more competitors. The result is a severe intestinal infection that often requires hospital treatment.
Dysbiosis can be triggered by an overpopulation of the bacterium Clostridium difficile. This is often caused by antibiotic therapy.
Dysbiosis using p-Cresol as an example
There are hundreds of metabolic processes, all of which have a potential impact on our health. To simplify things a little, 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 metabolites. It was found that participants with higher stool concentrations of p-cresol had increased frailty.
So what is p-cresol? This molecule is formed 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 does not seem to be a problem. However, when the filtration rate decreases and the p-cresol level in our blood increases, it seems 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 poor kidney function often have dysbiosis of the microbiomeThere is an increase in aerobic bacteria that promote the production of toxic metabolites, including p-cresol. Perhaps this is a possible starting point for the future.
Tryptophan Metabolism: From Symbiosis to Dysbiosis
Another important metabolic process in our intestine is the tryptophan pathway. Tryptophan is an amino acid that we absorb through food, for example. Our intestinal bacteria have various ways of metabolizing this amino acid. We will show you the three most important ones:
- kynurenine pathway (Kyn): About the enzyme I DO (indoleamine-2,3-dioxygenase) tryptophan is broken down to kynurenine
- serotonin pathway: Our intestinal bacteria can convert tryptophan into the “happiness hormone” serotonin. A full 90% of our serotonin is found in the intestines! Via this axis, tryptophan can also be melatonin, the sleep hormone
- indole pathway: The third way of tryptophan degradation is the indole pathway. Higher indole concentrations in older people could be increased fitness In mice, too, lifespan was increased by increasing indole metabolites
Dysbiosis as a Hallmark of Aging: It's all about balance
Some studies on tryptophan metabolism conclude that Disturbance of balance can contribute to illness. For example, the above-mentioned enzyme IDO (to be precise, the subclass IDO-1) is overactivated, We find more kynurenine compared to serotonin than is normal in the body. This excess of kynurenine is associated with some diseases. It has been shown that Depressed people often have 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 so easy to break down.
Chronic inflammation can increase IDO activity and thus the assumption can be formulated that inflammations In this way, they also contribute to the dysbiosis of our microbiome.
Inflammaging and dysbiosis – two hallmarks with close links
As we have just seen, a chronic inflammation can have a negative impact on our microbiomeBut it also seems to work the other way around, at least that is what experiments on mice suggest. Two populations of mice were used for this purpose.Once young and healthy mice and once older, sick mice. Now the microbiome of the older mice was transferred to the younger miceThe 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 its 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 AgingIn the future, we will certainly see some therapeutic approaches that reverse precisely this dysbiosis.
The next article in this series is about the twelfth hallmark of aging: Altered autophagy.
