From stress to Alzheimer’s: the potential applications of microbiome research

Today, thanks to that research, we have a better understanding of the microbiome structure, its function, and its link to a whole range of diseases and other health problems. This knowledge is helping unlock vast opportunities to minimise the occurrence or reduce the severity of these diseases and conditions. Here are three ways microbiome research could revolutionise medicine and transform millions of lives.

Alzheimer’s disease

Alzheimer’s disease — a brain disorder that causes memory loss and other cognitive issues — was, with different forms of dementia, the leading cause of death in the UK in 2022. Demographic trends mean that, in the coming years, many more people will be affected.

Despite both its prevalence and severity, there is still no cure for Alzheimer’s, in part because of its complexity. However, recent microbiome research has been helping scientists better understand this disease. For example, a 2023 study revealed that the gut microbiomes of people in even the earliest stages of Alzheimer’s, before symptoms have appeared, differ from those of healthy people.

About a third of the study participants had signs of early Alzheimer’s. The bacterial species found in their guts and the biological or metabolic processes they are involved in were markedly different from healthy people. These changes correlated with the presence and levels of tau protein and beta-amyloid plaque formation, which are indicators of Alzheimer’s

It’s not clear yet which way causality runs — whether the gut affects the brain or the other way around. These findings, and other research on the relationship between the microbiome and Alzheimer’s disease, do, however, open the potential for early diagnosis, by analysing the bacteria present in stool samples, and microbiome-altering preventive therapies.

Cancer

While few microbes directly cause cancer, nascent research suggests the microbiome can affect both how cancer develops and progresses in patients. For example, studies involving mice have found that the microbiome contributes to tumour development by modulating the animals’ immune responses. 

The tumour microenvironment (TME) is the complex ecosystem that surrounds a tumour in the body. It has an important role in cancer progression, and the tumour microbiome is an integral part of this ecosystem that influences tumour growth and response to cancer treatments. Increased understanding of the TME and its resident microorganisms opens up new therapeutic opportunities through manipulating the tumour microbiome. 

Researchers have also found that the microbiome can affect how patients respond to immunotherapy. In 2021, scientists in China found that the microbiome can enhance or suppress the body’s immune response to cancerous tumours and modulate the metabolisation of antitumour agents administered to fight the disease. 

Research into the relationship between the microbiome and cancer is still in its infancy, but it could one day improve both diagnosis and treatment.

Stress and depression

Scientists have for a long time speculated on the link between the gastrointestinal system and mental health issues such as stress and depression. As far back as the early 19th century, English surgeon John Abernethy posited that the stomach and minds were connected, arguing in an 1829 book that all mental disorders had their roots in what he called ​“gastric derangement.”

More recent research corroborates these early hypotheses, and a growing body of research elucidates the link between the gut microbiome and depression. For example, in December 2023, researchers at the University of Oxford and the Erasmus Medical Centre in Rotterdam cross-referenced the faecal samples and self-reported depression scores of more than 1,000 study participants. 

They found that certain bacteria, such as those from the Eggerthella genus, were over-represented in the faecal samples of patients with higher depression scores. It is thought to be because Eggerthella and other bacteria are involved in the synthesis of depression-linked neurotransmitters like glutamate, butyrate, serotonin and gamma amino butyric acid (GABA). ​“This study provides some real-life evidence that you are what you eat,” one of the study’s authors told journalists.

Again, these recent scientific breakthroughs are not only helping us better understand the connection between the microbiome and mental health — they’re also paving the way for new treatments. For example, researchers looking into the link between gut bacteria and stress responsiveness think probiotic supplementation could help.

The future of microbiome research

As research develops, we’re only just beginning to appreciate the extent to which the human microbiome influences both our physical and mental health. Continued investment in research will help us better understand these connections and potentially lead to the development of innovative forms of diagnosis and treatments. 

From there, it becomes paramount to progress new microbiome therapeutics into pre-clinical and clinical trials. CPI can provide the facilities and expertise to support manufacturing process development and scale-up to support these goals.