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!
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