Tag: Gut microbiome and human physiology

Science In Context

Role of gut-brain axis in the feeling of satiety

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It is a common knowledge that our brain influences each and every organ of our body, including our gut, but how strong is this connection? Also, is this connection between gut and brain, a unidirectional one or does the gut also have an influence on ‘the Master’-our brain?

The answers for these questions first came to light when a group of scientists conducted an experiment on two mice. One had all its gut microbiota removed while the other’s wasn’t. On keeping them in stress-inducing conditions, it was noted that the former one showed a greater response to stress. This and many other studies have shown that 50% of Dopamine- the pleasure inducing hormone and about 90% of Serotonin- the happiness hormone, are produced in our gut alone by the microbiota present in the gut.

The fact that our gut produces a variety of neurotransmitters and has more nerve endings than our spinal cord is more than enough to establish the exemplary control it has on our mental state.  No wonder then, that one feels depressed or anxious when one has indigestion. The connection that exists between our gut, its microbiota and the brain is mediated through Gut-Brain axis – have a look at some of the previous articles related to this topic here.

Our gut is lined throughout by glands that secrete a diversity of enzymes. One such hormone is Cholecystokinin (henceforth referred to as-CCK) which is released from our gut after we have a meal. While this hormone is mainly released to digest the fat and protein components in our food, it also makes sure that the stomach is kept relatively ‘full’ after a meal.

CCK does this by initiating a feedback loop through our gut, which sends a signal to the brain to stop eating food. Interestingly, this entire signaling is mediated with the help of receptors, which are present not only in our gut, but throughout the gut-brain axis as well as in the brain. Through this signal, an activation of the vagal afferent pathway takes place- this is the pathway in our body that integrates all the collected information from different organs in the hypothalamus region of the brain and results in modulating our eating behaviour.

Now you know how you get the feeling of ‘satiety’ after eating a full meal!

Now the next question that one could ask is- does the gut microbiome have any role to play in the production of this particular hormone? Well, not much has been explored regarding this topic… but with the way science is catching up, we may soon begin to understand their involvement better!
Malavika V Writer

Disclaimer: The content of this article is meant for educational and creative purposes only, and will not be directly used for generation of profits. All rights and responsibilities, including the authenticity of the information presented in this article belong to the original authors and their publications (listed below in the Bibliography section), and there is no copyright infringement intended.

Bibliography

Science In Context

Diving into the world of Probiotics

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‘Probiotics’ has become quite a buzz-word nowadays, especially in context of treating any kind of stomach/intestinal disorders. In this article, let us dive deeper into what they really are, and how they work.

Simply put- probiotics are a group of living microorganisms cultured in a laboratory setting to be used as a food supplement for human use. Before you begin to cringe, let us understand that these tiny organisms from the probiotics, that include bacteria and/or yeasts are actually very similar to the naturally residing microbes found in our body and more specifically, out gut. Thus, when probiotics are taken through diet, they add on to the ‘good microbe’ population in our gut.

(Read more about the gut microbiome and its influence on human physiology in the previous articles).

However, as we all know, every microbe consumed might not necessarily be beneficial to our body. And therefore, for a microbe to be called a ‘probiotic’, it must have certain characteristics-

  1. It should belong to one of the species of microbes that is isolated from humans and is easily cultivated in a lab setting
  2. It should be able to survive and thrive in the intestines after being consumed
  3. Last but not the least, it should be safe to consume

So, how to probiotics really work?

Imagine a scenario where the ‘bad bacteria’ in your gut have taken over the good ones. This is a common plot which plays out when one falls sick and the doctor has to prescribe antibiotics to fight off the infection. Now, while the antibiotics kill off all the ‘bad bacteria’ in your body, they may also accidentally end up destroying the ‘good bacteria’, since the good ones are now so few in number. In this scenario, not only is your digestion affected, but the other physiological parameters may also get disturbed.

This is one of the main reasons that your doctor prescribes probiotics along with antibiotics, in order to maintain a healthy composition of gut microbiome and to keep it neutral. Apart from carrying the microbes themselves, probiotic supplements influence the growth and development of ‘good’ microbiota by modulating the components released by the intestinal cells, thus creating a conducive atmosphere for the microbes to grow.

Now, because of their beneficial effect on our bodies, researchers have been trying to find out how the consumption of adequate probiotics can help fight against various gut-related medical conditions. A few conditions that might be helped by adding probiotics to our diet are inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), constipation, lactose intolerance, and antibiotic-associated diarrhoea. Studies have shown that apart from an improvement of the conditions themselves, there is also an enhancement of the working of the immune system by consumption of probiotics.

Considering the continuous bi-directional communication between the gut and the brain, it is not hard to predict that consumption of probiotics can influence our mental health in a positive manner. A few studies indicate the benefits of consuming probiotics or as they are called “psychobiotics” as future possibilities in the treatment of depression and anxiety. Psychobiotics are a sub-class of probiotics mainly containing specific families of bacteria, such as Lactobacilli, Bifidobacteria, Streptococci and Escherichia. Their presence in the gut influences the crosstalk between the brain and gastrointestinal system through the neurochemicals produced by the flourishing microbiota of the gut. Thus, psychobiotics have applications in mood and stress alleviation and even have remedial effects in the treatment of various neurodevelopment and neurodegenerative disorders.

While all this sounds interesting, one may ask themselves the very valid question- what are some easy-to-acquire sources of probiotics?

For a food item to be considered a probiotic, it should contain sufficient living bacteria (preferably in millions) that survive the food processing and the bacterial species present in the food item should have benefits to human health (such as Lactobacillus and Bifidobacterium). Thus, the largest source of probiotics are fermented dairy products, such as yoghurt, kimchi and sauerkraut. Apart from this, probiotic supplements can also be consumed through food, drinks or in the form of capsules or powders. Probiotic supplements are often consumed in combination with prebiotics – which are complex carbohydrates that feed the microbes in our gut. A combination of both means that not only are you supplying your gut with ‘good microbes’ but also providing the microbes with nutritious food so that it can thrive in your gut.

Now you know how to answer most of your stomach distress calls: just call upon your doctor and ask if you can have some probiotics!
Guneet Kaur Writer

Disclaimer: The content of this article is meant for educational and creative purposes only, and will not be directly used for generation of profits. All rights and responsibilities, including the authenticity of the information presented in this article belong to the original authors and their publications (listed below in the Bibliography section), and there is no copyright infringement intended.

Bibliography

Science In Context

Influence of gut microbiome on Serotonin

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Have you ever wondered why you always have a bad mood when something is wrong with your stomach? Well, recent research has thrown light upon the fact that all our body parts are largely affected by the ‘Gut Microbiome’- a haven of around 300 billion micro-organisms! These tiny creatures are known to play an important role in human development, right from the fetal stage. No wonder our gut is called the second brain

Although microbial colonization in the gut is a successive process, it is known to remain stable and resilient if there is an absence of stress-causing factors. Several factors are known to influence microbial composition at different stages of life- exercise, use of medication, diet and lifestyle.

Out of all the various body systems affected by our gut microbiota, the central nervous system stands out as the most interesting and hot research topic of this decade. Our gut and brain are connected via a bidirectional communication network called the Gut-Brain Axis.

Recent research has shown that our gut microbiome can alter the levels of Serotonin in our body, thus leading to episodes of anxiety, depression, panic attacks etc. And while this word has become common vocabulary nowadays, let us have a closer look at what exactly is serotonin. Serotonin is a neurotransmitter- which means that it carries messages between nerve cells in the brain and other parts of your body. Serotonin plays several roles in the body, including influencing learning, memory, happiness as well as regulating body temperature, sleep, sexual behavior and hunger.

Interestingly, about 90% of the Serotonin found in the body is produced in your gut itself! This serotonin is then released into the blood circulation and transported to other organs. Only about 10% is produced in the brain. Thus, you can now see how relevant and necessary it is to maintain the population of the gut microbiota producing serotonin.

Microbiome dysbiosis or in simpler words, the prevalence of bad bacteria over good ones, is associated with many diseases that lead to altered levels of serotonin. When researchers tried to replace the good bacteria in the gut with bacteria that led to swelling and inflammation, they observed that there was a slowing down of the serotonin secretion!

However, the good news is that you can take care of your gut microbial population, by choosing the right kind of diet. Recent research has also come to the conclusion that intake of probiotics will improve the integrity of the gut lining and help in increasing serotonin production. With a 10.7% of the world population suffering from depression, Alzheimer’s and other mental disorders, probiotics is a ray of hope-towards a world free of anti-depressants and its side effects. Want to avoid such disorders in the future? Make your diet rich in Lactobacillus helveticus and Bifidobacterium longumin from now on and keep your natural serotonin levels at par!
Malavika V Writer

Disclaimer: The content of this article is meant for educational and creative purposes only, and will not be directly used for generation of profits. All rights and responsibilities, including the authenticity of the information presented in this article belong to the original authors and their publications (listed below in the Bibliography section), and there is no copyright infringement intended.

Bibliography

Science In Context

Changes in gut microbiome & its impact on mental health

Academia Plus

When one hears the term superorganisms”, the first thing that comes to mind is the Marvel Cinematic Universe Superheroes. But, did you know- that you yourself are a superorganism? Turns out, it’s not a necessity to get bitten by a radioactive spider to become a superorganism. Every human being is home to billions of microorganisms including bacteria, fungi, viruses, and many others which either live on or inside the human body. The number of microbiota present in human beings is almost 10 times the total number of human cells!

The most significant population of microorganisms, which make up to 1 kg, inhabit the digestive tract and they are collectively called the “gut microbiota” or the “gut microbiome”. The gut microbiota is actively involved in maintaining human physiology and communicates regularly with other body organs, including our brain.

A two-way communication system exists between the gut and the brain known as the gut-brain axis. There are two main pathways through which this bi-directional communication system operates:

  1. Neurologic pathway: The enteric nervous system (ENS), present in the intestine (also called the second brain), together with the Vagus nerve make up the neurologic pathway. Various neurotransmitters (GABA, serotonin, melatonin, histamine etc.) responsible for sending direct signals to the brain are produced by the sensory nerves present in the ENS.
  2. Metabolic pathway: The gut microbiota produce several components known as metabolites which have the ability to cross the blood-brain barrier and can affect the functioning of a special type of brain cells known as microglial cells which are necessary for the proper development of the brain as well as for modulation in the behavior in humans.

We have already touched upon these pathways in our previous article.

However, did you know that the population demographics of the gut microbiota changes rapidly with changes in the external environment? In this case- the gut or the digestive system.

For example, production of biologically active molecules such as peptides, or production of inflammatory molecules such as cytokines in the gut, directly affect the gut microbiota population. 

Now that we have had a quick look at how the gut and the brain communicate and what may cause disruptions in this communication (long distance is hard, phew!), we can move on to read about the various ways by which the microbiota residing in us impact our brain activities.

It has been found through various experiments that an imbalance in the gut microbiota (known as dysbiosis), can lead to clinical depression. Long-term swelling (also known as chronic inflammation) that occurs during stress-related disorders leads to changes in gut microbiota reduces serotonin production. The gut is responsible for providing 95% of the total serotonin which is known to play a beneficial role in several functions of the body. Inflammation in the gut can also cause stressful environments for the microbial population and can subsequently lead to symptoms of anxiety and depression.

On the other hand, changes in the gut microbiota can also be caused by on-going stress in an individual. In response to these changes, several metabolites, toxins, and neurohormones are released that can further impact an individual’s mood and eating behavior. The changes in eating behavior can further affect the gut microbiota population, creating a vicious cycle.

Therefore, it is evident that adapting a diet and lifestyle that promotes the growth of beneficial gut microbiota will lead to an optimal utilization of the gut-brain connection and help us maintain good mental health.

Probiotics such as yogurt, cheese, pickles, etc., are found to have species of microorganisms called – Lactobacillus and Bifidobacterium which are key components of a ‘healthy’ gut microbiota. A term called psychobiotic has been recently coined to show their importance in mental disorder therapies as they can act as  antidepressants and work against anxiety. Conversely, high-fat diets and highly-refined carbohydrate diets constitute an unhealthy diet that causes an unfavorable changes in the gut microbiota population and thereby can also affect our overall mental health.

Thus, one can safely say that the way to a ‘happy mind and heart’ is through a ‘happy gut’.
Sanjhi Sardana Writer

Disclaimer: The content of this article is meant for educational and creative purposes only, and will not be directly used for generation of profits. All rights and responsibilities, including the authenticity of the information presented in this article belong to the original authors and their publications (listed below in the Bibliography section), and there is no copyright infringement intended.

Bibliography

Science In Context

Exploring the gut-brain connection

Academia Plus

Gutsy: Hey Mindy! What’s up? I see that you are not keeping well these days. It’s really difficult for me to move things fast when you are ill!

Mindy: I’ve kind of started feeling anxious quite often.

Gutsy: Oh, that’s bad! Is there anything I can do to help you with your anxiety?

Mindy: Umm. I might need my medicines. I am running out of stock!

Gutsy: Well, send me the list, and I’ll deliver them to you.

Mindy: 4 tablets of Serotonin, 2 tablets each of Dopamine and Oxytocin, and maybe a tablet of Endorphin!

Gutsy: Ah! All the happy hormones! I got it, friend. Your order will be delivered.

Mindy: Thank you Gutsy! You’ve always been my savior.

Gutsy: No worries, my friend. Which delivery system would you like to opt for? The courier or the fax?

Mindy: Any one will do, as long as they are here!

Gutsy: You are all set, buddy. Your order will be delivered soon! I hope you feel better and then we can get back to work smoothly once again.

Mindy: Great! Waiting for it.

Gutsy: Take care till then. Bye!

Wondering who this hormone dealer Gutsy is? Well, it is none other than our Gut! And Mindy, who is desperately in need of happy hormones, is our Brain.

Our brain cells (neurons) constantly require different types of hormones to communicate with one another, which is an important process of brain and body functioning. More than 30 such hormones, known as neurotransmitters are closely associated with our gut- the microbiota residing in our gut are able to regulate the production of neurotransmitters. These neurotransmitters are capable of directly or indirectly modulating the brain function.

Isn’t it interesting how the remotely residing gut microbiota influences brain functions? This can only happen when there is a concrete connection between the brain and the gut. In our previous article, we briefly touched upon this connection; in this article, we shall explore the connection more.

We know that our gut/intestine is home to many different types of bacteria. These bacteria while thriving in our gut, utilise the nutrients that we consume and produce metabolic waste products/metabolites. Even though these metabolites are waste for the bacteria, they are useful to humans!

Eeuu! So, are we saying that bacterial poop is useful to humans? Oh yes! Certain bacterial metabolites stimulate a special type of cells in the gut which leads to an increased production of selective neurotransmitters, including the happy hormones that Mindy requires.

Hmm.. so now Gutsy must send across these neurotransmitters or at least the information encoded in these neurotransmitters to Mindy to reduce the anxiety. But, how will she do that?

Well, she can use two different types of delivery systems- the fax delivery system or the courier delivery system.

We have learnt about the Vagus nerve in our previous blog, which is the longest nerve that connects the brain and the gut. The ends of the Vagus nerves that are spread onto the gut wall have receptors that can sense specific neurotransmitters. These terminal receptors bind to the neurotransmitters present in the gut lumen, and a signal transduction through the vagus nerve is initiated. Depending on the neurotransmitter produced in the body, different signals can be sent to the Brain through the Vagus nerve.

This works just like the fax delivery system- where the original document is just scanned through the fax machine and the information is decoded at the other end and an exactly similar copy gets printed. When signal transduction takes place through neural pathway, the neurotransmitters from the gut lumen do not reach the brain physically, but simply transmit the relevant information (nerve impulse) to the brain.

Ta-da! Aren’t you impressed by how wisely our body has been constructed? Efficiency increases with the complexity it seems.

How does the courier delivery service work then?

This is the most popular system of our body, functioning continuously that connects each and every body part to one another a.k.a. the circulatory system. It not only provides a constant supply of oxygen-rich blood to all body organs, but also provide nutrients and hormones and is responsible for removing waste products from the different parts of our body.

Now, can you guess how Gutsy uses this system to deliver the neurotransmitters to Mindy? The capillary network in the gut wall absorbs the neurotransmitters and they travel all the way through our blood to the brain, much like a parcel (courier) is physically delivered to the designated address. And just like a courier must be signed off by the recipient upon delivery, the delivered neurotransmitters too must be approved by a special type of cells of the Blood Brain Barrier (BBB) – which is the shield or a gate, around our brain. It is only upon approval that the neurotransmitters are able to cross the blood brain barrier and modulate the brain activity.

We now know that the Neural Pathway (fax delivery system) and Circulatory Pathway (courier delivery system) are the two main routes through which the Gut-Brain connection manifests. But which system is more efficient for the different types of neurotransmitters? And does Gutsy always use the same system for delivering the hormones to Mindy? We shall reflect upon these questions and also talk about the specific influence that neurotransmitters have on our brain activity, in the upcoming articles.

In the meanwhile, rest assured- Mindy might have surely received her order of happy hormones by now! Hurray!
Payal Lonkar Writer
Aaqifa Shaikh Sci-Artist

Disclaimer: The content of this article is meant for educational and creative purposes only, and will not be directly used for generation of profits. All rights and responsibilities, including the authenticity of the information presented in this article belong to the original authors and their publications (listed below in the Bibliography section), and there is no copyright infringement intended.

Bibliography

Science In Context

Introducing the second brain

Academia Plus

What? Do we have a second brain?
Yes, you read that right. Your gut has a brain of its own!

Have you ever experienced changes in your mood after having your favourite meal? Or sensed butterflies in your stomach when you are too excited or anxious? Also, you must have noticed how your tummy rumbles when you are hungry and your mouth waters just by the sight of your favourite food.

Well, these are not merely illusions created by your mind. Science is now catching up to reveal what might be causing these sensations in your stomach. There exists a bidirectional communication system between your brain and your gut. This is termed as the Gut-Brain Axis (GBA). In simple terms, GBA is the communication network that connects your gut to your brain. Thus, our gut has a direct influence on our brain and vice versa.

What causes this bi-directional communication to occur?

Well, perhaps a better question would be – who causes this bidirectional communication to occur? And the answer lies in the trillions of microbial cells (even outnumbering our own human cells), collectively known as the Human Microbiota. The human gut microbiota forms an essential component of human gut. It has been reported that the gut microbiota composition of an individual considerably influences how their brain functions, thereby creating an impact on the overall health.

You might think, how can a microbe send and even receive signals? Well, let’s dive into the basics to understand this.

Neurons, the cells present in your Central Nervous System (Brain), instruct your body how to behave by sending and receiving information to and from all parts of the body. The human brain is thought to have approximately 100 billion such neurons. Interestingly, 500 million neurons are found to be present in the ‘Gastro-Intestinal Tract’ or gut. These neurons connect the gut to the brain, through nerves present in your nervous system. This is specifically termed as the Enteric Nervous System (ENS). In other words, it is the nervous system of the gut. One of the biggest nerves of ENS that connects the brain and the gut physically as well as biochemically is the Vagus Nerve. It has the ability to send signals in both directions at the same time. The ends of the Vagus nerves that are spread on to the gut wall can sense certain chemicals called ‘Neurotransmitters’ and ‘Hormones’. These form chemical connections between the brain and the body parts.

Interesting! Isn’t it? Voila! Now it must be clear how the gut and the brain swap messages.

But what do they talk about? And is it important?

The gut wall encloses a complex environment and contains millions of neurons, hormone producing cells (endocrine cells) and most of our immune cells. That being so, the gut becomes central to hormone production and a place where most of the body reactions ensue. The gut, being the part of our digestive system is also involved in digestion of food and absorption of nutrients. While this is happening, the brain on the other hand, needs to direct and co-ordinate the sequence of activities taking place there. Accordingly, the brain and gut continuously exchange information and influence each other’s performances.

What’s the role of gut microbiota then?

Well, most of the hormones and neurotransmitters are made in the gastro-intestinal tract by the gut microbiota. For example, the neurotransmitter called gamma-aminobutyric acid (GABA) produced by gut microbes is the main regulator of emotions such as fear and anxiety. Similarly, several neurotransmitters like serotonin, dopamine, norepinephrine, acetylcholine etc. that communicate with the brain to stimulate and regulate other set of emotions are also produced by the gut microbiota.

Profuse right!!

We will reflect over these compounds and their cycle of production and regulation in our upcoming articles.
Payal Lonkar Writer
Ramya Ganesan Sci-Artist
Aaqifa Shaikh Sci-Artist

Disclaimer: The content of this article is meant for educational and creative purposes only, and will not be directly used for generation of profits. All rights and responsibilities, including the authenticity of the information presented in this article belong to the original authors and their publications (listed below in the Bibliography section), and there is no copyright infringement intended.

Bibliography