• Oncology Microbiota diversity improves response to hematopoietic stem cell transplantation

  • Well-being This is how what happens in your gut alters your mood

The presence of a group of intestinal bacteria has been associated with depressive symptoms.

This is stated in two articles published in

Nature Communications

.

The discoveries made by the researchers

have identified specific microorganisms present in the digestive system

that are involved in the synthesis of key chemical messengers related to depression.

Despite being a leading cause of mortality and economic disparity, the biological origins of depression remain poorly understood, as the causes are unclear and treatment options are limited.

The gut microbiome is thought to play a role in depressive disorders, but

the underlying biological mechanisms are poorly studied

.

In addition, it is known that both the microbiome and the levels of depressive symptoms vary substantially between ethnic groups.

Therefore, any future microbiome-targeted depression interventions require an understanding of microbiome-depression associations across races.

"In the two studies

, relatively large populations of subjects are analyzed

and this is one of their main strengths. In one of them, it is done with a multiethnic population, which helps to analyze the consistency of the observations in different populations," he points out to

Science .

Media Center

(SMC) José Manuel Fernández-Real, Head of the Nutrition, Eumetabolism and Health group at IDIBGI and CIBEROBN, Professor of Medicine at the University of Girona and Head of the Endocrinology Section at the Dr. Josep Trueta Hospital.

Jos Bosch, Anja Lok, Susanne de Rooij, and colleagues studied a group of 3,211 people from the HELIUS study microbiome cohort, which consists of six ethnic groups living in urban Amsterdam, including Dutch, Surinamese from southern Asian, African Surinamese, Ghanaian, Turkish and Moroccan.

By linking microbiota data with demographic, behavioral, and depression data,

the authors identified a predictive microbial signature of depressive symptoms

that was largely invariant across ethnic groups studied.

About this work, Eduard Vieta, scientific director of the Mental Health Network Biomedical Research Center (Cibersam), head of the Psychiatry and Psychology Service of the Hospital Clínic de Barcelona and professor at the University of Barcelona, ​​comments to SMC that "this

is a very interesting topic and in full progression

The results are not extraordinarily novel (only in a small part), but

they confirm the changes in the microbiome already described

and they do so in one of the largest samples to date. measuring the severity of depressive symptoms and controlling for the coexistence of other pathologies and the effects of treatment".

In the other paper, a paper co-edited by Najaf Amin, Robert Kraaij, and Djawad Radjabzadeh, they compared the gut microbiota characteristics of 1,054 participants from a separate cohort in the Netherlands, called the

Rotterdam Cohort

, and found 13 associated microbial taxa. with depressive symptoms, such as

Eggerthella

,

Subdoligranulum

, and

Coprococcus

.

These findings were then replicated in the HELIUS study cohort.

The authors found that these

bacteria are involved in the synthesis of chemical messengers known

to be associated with depression, such as

glutamate, butyrate, serotonin, and gamma aminobutyric acid

(GABA).

The fecal microbiome was studied as a proxy for the gut microbiome in both studies.

"Changes are identified

in the bacterial populations of people with depression

related to microorganisms that produce glutamate and serotonin, among other neurotransmitters, which are precisely of great relevance in depression. In addition,

these changes are maintained beyond cultural differences, genetics and lifestyle of different ethnic groups

Despite the large sample, some analyzes could not be replicated but, in my opinion, it represents a step forward in understanding the inflammatory changes associated with depression and the connection between our digestive flora and brain function", explains the scientific director of Cibersam.

Rosa del Campo, a researcher at the Ramón y Cajal Hospital, in Madrid, and a member of the Specialized Group for the Study of the Human Microbiota of the Spanish Society of Infectious Diseases and Clinical Microbiology (Seimc-Gembiota), in statements collected by SMC, points out : "The implication of these works is that we must

add the intestinal microbiota as one more factor in the cause of depression

. It is suggested that it is an organic cause related to the production/degradation of neurotransmitters by bacteria in the intestinal tract. Despite the fact that these theories have existed for a long time, for the moment

the study of the microbiota has not been incorporated into clinical practice, also because the tools we have to modulate it are scarce.

.

At the moment we cannot use antibiotics due to the high pressure of resistance, probiotics have a dubious utility and fecal transplantation is not authorized for this type of pathology".

Del Campo points out a 'hack' to these works: "They are based on the composition of the microbiota. Through the data they have obtained, the production/degradation of neurotransmitters is inferred, but

the concentration of said neurotransmitters in feces has not been determined or in serum, which would be essential to prove

it. All these studies are based on the DNA of the feces to know the composition of the bacteria and from this data the functionality of these bacteria is inferred, but it is necessary to know the final metabolome" .

Although the clinical impacts of these findings need to be confirmed experimentally, the two studies together further strengthen the link between gut microbiome composition and depression, and suggest that it may be a useful target for future therapies.

"It is still too early to talk about treatments. On the one hand,

there are indications that a balanced diet (for example, the Mediterranean diet) can improve mental health

, although it is not an adequate treatment by itself for major depression. For another, it would be premature and fanciful today to consider fecal transplantation as a therapeutic alternative", concludes Vieta.

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