New link found between gut bacteria and age-related conditions

Gut bacteria from old mice induce age-related chronic inflammation in young mice, finds a study in Frontiers in Immunology

Gut microbiome (bacteria) linked to aging and inflammation

Strategies that alter the composition of the bacteria that make up the gut microbiome could promote healthy aging. Image: Shutterstock.

A new study suggests that chronic inflammation in the elderly — thought to be involved in many age-related diseases — is due to imbalances in gut bacteria

Scientists in the Netherlands have shed new light on how an imbalance of the gut microbiome may be the cause of so-called “inflammaging” in the elderly.

Inflammaging, or low-grade chronic inflammation, occurs with aging and is linked to life-limiting conditions such as stroke, dementia and cardiovascular disease.

The discovery was made as researchers transplanted bacteria from the gut of old conventional mice into young germ-free lab mice — and saw that the recipient mice showed the same inflammaging response as the elderly donors.

This news, published in Frontiers in Immunology, brings the hope of a potentially simple strategy to contribute to healthy aging, as the composition of bacteria in the gut is, at least in part, controlled by diet:

“Since inflammaging is thought to contribute to many diseases associated with aging, and we now find that the gut microbiome plays a role in this process, strategies that alter the gut microbiota composition in the elderly could reduce inflammaging and promote healthy aging,” explains Dr Fransen, who performed the research at the University Medical Center Groningen. “Strategies that are known to alter gut microbiota composition include changes in diet, probiotics, and prebiotics”.

Previous research has shown that the elderly tend to have a different composition of gut bacteria than younger people. It is also known that immune responses in the elderly tend to be compromised, resulting in inflammaging. Knowing this, Dr Fransen and his team set out to investigate a potential link.

The study looked at a variety to markers, using mice as a proxy for humans.

The scientists transferred gut microbiota from old and young conventional mice to young germ-free mice, and analysed immune responses in their spleen, lymph nodes and tissues in the small intestine. They also analysed whole-genome gene expression in the small intestine. All results showed an immune response to bacteria transferred from the old mice but not from the young mice.

The importance of a healthy gut microbiome

An imbalance, or “dysbiosis” of gut bacteria can have serious health implications: several disorders, such as inflammatory bowel disease, obesity, diabetes, cancer, anxiety and autism are already linked to the condition.

“Our gut is inhabited by a huge number of bacteria,” explains Dr Fransen. “Moreover, there are many different kinds of bacterial species, and the bacterial species that are present can vary a lot from person to person.”

Dysbiosis results in “bad” bacteria being more dominant than “good” bacteria.  An overgrowth of bad bacteria can make the lining of the gut becoming more permeable, allowing toxins to enter the bloodstream where they can travel around the body with various negative effects.

Maintaining a healthy gut microbiota is clearly important to a healthy body and healthy aging, but why the gut microbiome is different in the elderly is not fully understood.  Many people are aware of the effect a course of antibiotics can have on the digestive system for example, but as Dr Fransen explains, it may not be down to just one thing: “It is likely a combination of factors such as reduced physical activity, changes in diet, but also as part of a natural process.”

The future for elderly care?

Most, if not all, age-related diseases can be linked back to inflammaging. Despite the fact that this particular study was conducted on mice, it is clear that maintaining a healthy gut microbiota is key to a healthy lifestyle. However, more research is needed to confirm that the human body mirrors the mice in this study.

“Both in humans and mice there is a correlation between altered gut microbiota composition and inflammaging, but the link between the two remains to be proven in humans,” concludes Dr Fransen.

The article is part of the Frontiers Research Topic Immunomodulatory Functions of Nutritional Ingredients in Health and Disease.

Original research article: Aged Gut Microbiota Contributes to Systemical Inflammaging after Transfer to Germ-Free Mice

Corresponding author: Floris Fransen

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