Scientists talked about the connection of intestinal bacteria with the age of the brain

The composition of the intestinal microbiota and the metabolic products found in the intestine are related to the estimated age of the brain in young people and middle-aged adults. A higher score was also accompanied by poorer cognitive test scores and more pronounced symptoms of depression. How scientists estimated the age of the brain and why the results do not yet allow us to predict its aging by analyzing the microbiota — in the Izvestia material.

How scientists determine the age of the brain

A person's age does not always match the age that a computer model determines based on data about their brain. For this assessment, researchers analyze the characteristics of the images and compare them with age patterns in a large sample.

Previously, a higher estimated brain age was associated with memory impairment, cognitive abilities, and mood changes. However, most of these studies concerned the elderly or patients with already identified neurological diseases.

A team from the University of California at Los Angeles (UCLA) decided to find out whether similar connections are found in young people and middle-aged adults, including those without diagnosed diseases.

What the study showed was almost 1.5 thousand people

The researchers used data from functional magnetic resonance imaging at rest. This method allows you to assess how consistently the activity of different areas of the brain changes while a person is not performing a special task.

In total, the researchers analyzed data from 1,462 participants from three groups. The first one included 674 people, the other two included 444 and 344. We developed an age assessment model for the first sample, then tested it on the rest.

The computer model calculated age based on functional connections between brain regions. The difference between the predicted and calendar age, adjusted for the age bias of the model, was used to determine the Brain Aging Index, or BAI.

A higher index meant that the features of functional connections corresponded to an older age than the actual age of the participant.

How brain age is related to memory and mood

Increased BAI was associated with poorer measures of cognitive functions, primarily working memory and executive functions. Working memory allows you to temporarily hold and use information, and executive functions help you plan actions, manage attention, and organize work.

Participants with a higher index also reported more severe symptoms of depression. The general pattern was reproduced in different groups. The index-related features affected areas of the brain involved in memory and the processes by which a person thinks about themselves and their own experiences.

However, these connections do not mean that the estimated age of the brain alone explains all the differences in memory or mood. In the article, the authors note that the magnitude of the detected effects was moderate.

How is the intestinal microbiota related to this?

For some of the participants in one of the groups, the scientists additionally studied stool samples. The composition of the microbiota was studied in 212 people, and metabolic products were studied in 215 samples. A higher brain aging index was associated with certain bacterial groups and a metabolic profile.

Among the compounds found were ceramides, a type of lipid, cholesterol derivative 24-hydroxycholesterol, and dicarboxylic acids. A higher BAI was also associated with a lower content of the hormone estherol in the samples studied.

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An analysis of the biological pathways associated with these signs indicated the possible involvement of immune processes, vascular function, signal transmission between nerve cells, and cellular energy metabolism.

These results help to determine the directions for further research on the interaction of the intestine and the brain. However, the origin and role of each discovered compound require a separate study.

Can these data help with early prevention

Senior author of the study Arpana Church believes that the work can help to better understand the changes that occur long before noticeable cognitive impairment.

According to Church, comparing early brain changes with the microbiota and metabolites allows us to look for biological pathways that may become targets for prevention in the future.

So far, the work describes the relationships between the indicators measured in a cross-sectional study. This approach does not allow us to determine what changed first, or to determine the rate of aging of a particular person's brain. This requires long-term observations with repeated measurements.

The authors also note that the microbiota analysis was carried out in a relatively small subgroup, mainly consisting of women. The found relationships should be checked in larger and more gender-balanced samples.