The Gut Microbiome: An Overview
The gut microbiome is arguably one of the most important microbiomes of our body, describing the population of bacteria, fungi, viruses and other microbes which colonise our gastrointestinal tract. Over 100,000 billion microorganisms inhabit out gastrointestinal tract, the most dominant species being Bacteroides, Eubacterium and Clostridium amongst many others!
There are several factors (largely grouped into diet and lifestyle, antibiotic use, and environmental factors) which influence the gut microbiome. Some of these include:
- Diet: Diet plays a large role in determining the microbiota that live in your gastrointestinal tract. Following a Mediterranean diet, with an emphasis on vegetables, contributes towards a stable and thriving gut microbiome. On the other hand, the ‘western diet’, associated with the consumption of lots of carbohydrates, fast-food, and animal products, has been found to negatively affect the gut microbiome, promoting disease progression.
- Age: Your gut microbiota evolves throughout your life, diversifying into adulthood at which point it stabilises (although it will continue to change with age.)
- Genetics: Certain genetic traits affect the gut environment, determining how hospitable it is to specific microbes.
- Medications: Antibiotics, killing both harmful and beneficial bacteria, are well-known for disrupting the gut microbiota. Other medications, including nonsteroidal ant-inflammatory drugs (such as Ibuprofen) can also alter your gut microbiome.
- Environment: Factors such as sanitation and exposure to pathogens may influence your gut microbiome.
- Lifestyle: Particularly stress, sleep and physical activity levels can have influential roles on your gut microbiome. It has been found that both chronic stress and lack of sleep may negatively impact your microbiota.
Gut Bacteria and Health
As mentioned, your gut microbiome is crucial for various physiological processes. Understanding its beneficial roles, and the consequences of imbalances, is essential in order to appreciate its impact on health and disease. Some of the beneficial roles of gut bacteria have been highlighted below:
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Nutrient Absorption and Metabolism
Gut bacteria are integral to the digestion and absorption of nutrients. Without the gut bacteria we would be unable to digest certain food groups including complex carbohydrates, fibres and some proteins. The gut bacteria help to break down these food groups, producing short-chain fatty acids which are essential for other physiological functions.
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Immune System Modulation
The gut microbiota interacts with immune cells such as T cells, helping to regulate immune responses and ensuring homeostasis in the immune system.
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Protection Against Pathogens
The bacteria that make up the gut microbiome act as a barrier against harmful microorganisms. They inhibit pathogen colonisation via several means, notably direct killing, competition for limited nutrients within the gastrointestinal tract and enhancing the immune response against pathogens.
Gut Bacteria and Disease
As a result of the essential role that the gut microbiome plays in the human body, dysregulation of the gut microbiome is a major factor which underlies various disease conditions. Some imbalances in the gut microbiome and associated health conditions have been listed below:
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Dysbiosis and Gastrointestinal Disorders
Dysbiosis is often linked to gastrointestinal disorders such as irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), and celiac disease. Common symptoms of these conditions include abdominal pain, bloating, diarrhoea, and constipation. Importantly, when the microbiome is imbalanced, these symptoms are often exacerbated.
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Autoimmune Diseases
Dysbiosis is also implicated in the development of autoimmune diseases, such as rheumatoid arthritis, multiple sclerosis and type one diabetes. The gut microbiome dysregulation in these autoimmune diseases reveals the importance of the gut bacteria in modulating immune responses to prevent autoimmunity.
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Mental Health Disorders
Interestingly, more recent research has shown that there may be a connection between gut microbiota and mental health, termed the gut-brain axis. Dysbiosis can be associated with mental health disorders, including depression and anxiety. This is all of course emerging data, however, it has been suggested that gut bacteria produce neurotransmitters which may influence brain function and behaviour.
Association Between Gut Bacteria and Chronic Diseases
Not only does dysbiosis contribute to the disorders mentioned above, but it is also implicated in various chronic diseases, some of which include:
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Obesity and Metabolic syndrome
The composition of gut microbiota is very closely linked to obesity and metabolic syndrome. Interestingly, when looking and Bacteroidetes and Firmicutes divisions (which dominate the microbiota) patients who are obese have been found to have higher levels of Firmicutes. This dysbiosis has been associated with increased fat deposition, insulin resistance and systemic inflammation (all components of metabolic syndrome.)
2. Cardiovascular Diseases
Gut bacteria affects lipid metabolism and inflammation, thereby playing a role in cardiovascular health. Dysbiosis can exacerbate cardiovascular risk factors, such as hyperlipidaemia, contributing towards the development of diseases such as atherosclerosis.
The mechanisms underlying this gut bacteria-disease relationship can be largely attributed to metabolic disturbances and gut-brain axis communication.
Dysbiosis can disrupt the influence of the gut microbiota on host metabolism (through disruption of production of short chain fatty acids for example) leading to metabolic disturbances as well as disrupting neurotransmitter release within the gut-brain axis, thereby disrupting these communication networks essential for the maintenance of brain function and behaviour.
Research and Clinical Applications
Recent advances in microbiome research have significantly enhances our understanding of the gut microbiome and its impact on health and disease. Advances in microbiome research include high-throughput sequencing techniques, metagenomics and metatranscriptomics. These can be used to advance therapeutic interventions for diseases with underlying dysbiosis.
Therapeutic interventions targeting the gut microbiome have recently emerged as front-runners in medical treatment of numerous conditions. The use of probiotics (live beneficial bacteria) and prebiotics can help to restore and maintain a healthy gut microbiome, potentially alleviating symptoms of associated diseases.
Faecal microbiota transplantation is used less commonly, however it has shown promising results in treating certain conditions including Clostridium difficile infection and is therefore being explored for its potential in treating other gut-related diseases.
Finally, microbiome-based therapies, including the prescription of precision probiotics, is an emerging field with potential therapeutic advancements for a variety of diseases.
Potential Interview Questions: The Gut Microbiome
- Are there any ethical considerations that must be taken into account for future (or current) microbiome research?
- Is personalised medicine the way forward in the treatment approach to gut dysbiosis?
- What is the link between dysregulation of the gut microbiome and chronic conditions? Can you name an example of a chronic condition with underlying gut dysbiosis?
- What factors influence the gut microbiome? In your opinion, which is the most important and why?
- What does the gut microbiome refer to? Why is it essential for health?
- What are the clinical applications of gut microbiome research and which conditions may these be particularly important in?
Other medicine interview questions can be found on our website here.
