Gut: The Second Brain

Context: There have been numerous studies on how the environment, diseases, and our diets affect the composition of our gut microbiome. New studies based on genomic studies have suggested that differences in our genetic make-ups could also affect the diversity of gut microbes.

About the Human Gut (Digestive System)

The gut comprises digestive organs, including the mouth, oesophagus, stomach, small intestine, and colon. It is established at birth and continues to develop throughout our lifetime. 

Gut Microbiome

The gut microbiome refers to a collection of microorganisms—bacteria, viruses, fungi, and other microbes—living in the digestive system of animals, including humans.

1. These microbes play a crucial role in digestion, immune function, and brain health. 
2. Increased microbial exposure fosters greater diversity and a healthier immune system. 
3. No two people share the exact same microbiota due to unique life experiences. 
4. The microbiome is significantly influenced by childhood illnesses, antibiotic use, diet, age, genetics, and environmental factors, resulting in diversity among individuals.
5. Examples of common microorganisms found in the human gut: Bifidobacteria, Escherichia coli, Lactobacili.

Role of Gut Microbiome in Maintaining Health:

1. Communication and Cleansing: A healthy gut microbiome maintains gut health by communicating with intestinal cells, aiding in the digestion of certain foods, and preventing disease-causing bacteria from adhering to the intestinal walls.
2. Physiological function: contribute in digesting food and and absorbing essential nutrients which include the production of vitamins, the metabolism of bile acids, and the breakdown of complex carbohydrates.
3. Develop immunity: Some studies have shown that gut bacteria can direct the development of T-cells, a family of cells critical to immune function.
4. May Benefit Heart Health: The gut microbiome plays a crucial role in promoting "good" HDL cholesterol and triglycerides, contributing to heart health.
5. May Affect Weight: Having an imbalance between unhealthy and healthy gut microbiomes, referred to as gut dysbiosis, can contribute to weight gain.
6. May Affect Gut Health: An unhealthy microbiome in the gut may lead to conditions such as irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD), contributing to intestinal discomfort.
7. May Reduce Risk of Diabetes: The gut microbiome is involved in controlling blood sugar levels, reducing the occurrence of type 1 diabetes in children, which is associated with an unhealthy gut microbiome.
8. May Improve Brain Health: By producing brain chemicals and communicating with nerves connected to the brain, the gut microbiome, for example, produces serotonin, a neurotransmitter primarily synthesised in the gut.

Actions to Improve Gut Health

1. Diversify your food basket, as this will lead to a diverse microbiome—an indicator of good gut health. Legumes, beans, and other fibre-rich foods promote the growth of healthy bacteria.
2. Include fermented foods like yoghurt and Dahi (curd) in your diet, as they can reduce the presence of disease-causing species in the gut.
3. Limit the consumption of artificial sweeteners, such as aspartame, in your diet. Doing so may decrease blood sugar levels and, in turn, reduce the population of unhealthy bacteria like Enterobacteriaceae.
4. Take antibiotics only when recommended by a doctor, as antibiotics kill both good and bad gut microbiota, leading to antibiotic resistance

New Research in the field of Gut Microbiome 

Faecal Microbiota Transplant (FMT)

A faecal, or intestinal, microbiota transplant (FMT) is a medical procedure that involves transferring a small amount of stool from a healthy donor into the colon of a person with recurrent infections of a bacterium called Clostridium difficile.

1. The goal of FMT is to restore the balance of the gut microbiome and help the recipient fight off the infection.
2. FMT has been shown to be highly effective in treating Clostridium difficile infections that do not respond to antibiotics, with success rates of over 80%.
3. FMT is also considered to be safe, with few reported side effects or complications.

Metabolism of Urobilinogen and Genome Sequencing

Urobilinogen is produced in the body when the body metabolises bilirubin. Bilirubin is produced when the body metabolises haemoglobin in the blood. The yellow colour of urine comes from a pigment called urobilinogen. This is why a high level of bilirubin seen in the yellowing of the eyes is associated with jaundice.

1. Researchers have suggested that the human microbiome could be involved in the metabolism of urobilinogen.
2. Using biochemical analyses and comparative genomics, they identified a bacterial enzyme, called bilirubin reductase (BilR), to be responsible for reducing bilirubin to urobilinogen.
3. Through genome sequencing, the researchers observed that microorganisms belonging to the species Firmicutes predominantly encode the gene that teaches cells to make BilR.

Brain and Microbiome 

Some evidence in research has shown that the human microbiome can be associated with how neurons 'talk' to each other.

Gut microbes produce vitamin B12; researchers suggested the vitamin could influence neuronal signaling by influencing the availability of free choline, a molecule neuron used to make a neurotransmitter called acetylcholine.

Human Microbiome Project (HMP)

It was a research initiative by the United States National Institutes of Health (NIH) to improve understanding of the microbiota involved in human health and disease. 

1. It aimed to characterise the microbial communities that live in and on our bodies and the roles they play in human development, physiology, immunity, and nutrition. 
2. It generated a large amount of data and resources that are available for the scientific community to use and analyse.
3.  It also explored the ethical, legal, and social implications of human microbiome research. 

Phases of Human Microbiome Project (HMP)

The HMP consisted of two phases: 

1. The first phase (HMP1): It focused on identifying and characterising human microbiota from healthy adults and people with specific microbiome-associated diseases.
2. The second phase (iHMP): It focused on creating integrated datasets of multiple biological properties from both the microbiome and host over time in people with specific microbiome-associated diseases.