A team of scientists at the UNIGE (University of Geneva) in Switzerland, led by Dr. Mirko Trajkovski has shown a couple of weeks ago that the lack (or complete absence) of gut microbiota (the eco-community of pathogenic, symbiotic, and commensal microorganisms) can be related to the raised brown fat activation which occurs as a result of the body’s effort to stop obesity.
The aforementioned scientists have confirmed that mice affected by cold deal with the rapid shifts in microbiota composition, increasing their insulin sensitivity and making them leaner. Transferring cold-modified microbiota into mice free of germs makes them tolerant to cold. The reason is simple – this change raises the brown fat levels and ultimately enhances their insulin sensitivity even when they are not exposed to cold.
It is worth mentioning that lengthy cold exposure will also lead to accelerated weight loss because the body starts using more and more calories from the food we eat. Exposure to cold leads to the vanishing of a very important bacterium known as Akkermansiamuciniphila. This bacterium directly affects the way in which nutrients are processed and absorbed by the body. In case the bacterium is regulated artificially, the weight loss process continues. This revolutionary discovery revealed in reputed Cell magazine will definitely encourage scientists to come up with completely new methods that will help people eliminate obesity.
The body temperature in mammals is constant in most cases. However, when mammals are exposed to cold, the temperature in their body lowers for a few degrees, before it finally gets back to its optimal level. The body has a mechanism that allows mammals to normalize temperature and this is possible thanks to the brown fat. When exposed to cold, the body activates brown fat and this fat creates heat by burning calories faster.
So, cold, together with physical activity, leads to the emergence of adipose cells related to brown fat (the beige fat) inside white fat, which preserves the body’s healthy condition by fighting excess weight and the negative effects of excess weight.
But, how exactly this situation interacts with microbiota composition?
Is it possible for a cold to be used as a tool in activating this anti-obesity process? The researchers from UNIGE left a group of mice in cold temperatures for about 30 days. They were lowering the temperature gradually from 20 C to about 5 C and observed and analyzed the way in which mice’s microbiota altered. In addition, they transferred cold microbiota to mice free of germs.
According to Ozren Stojanovic and Claire Chevalier, who were part of this study, the modifications they noticed in the microbiota composition were more radical compared to microbiota differences analyzed in obese and healthy persons that were observed before. And what is even more interesting is that the mice free of germs that received cold microbiota became resistant to cold right away. The temperature of their body didn’t drop.
This study has shown that the microbiota itself can provide resistance to cold. In addition, the mice who received transplantation had an improved metabolic profile with extra beige fat and better insulin sensibility.
How does cold affect body weight?
When the conditions are normal, mice gain and lose weight regularly. However, when they are exposed to cold, they start losing weight faster because they must use the stored or taken calories to create heat. But, after a certain period of time, they continue to gain weight. In other words, there is a change in their system that alters the absorption of the nutrients.
According to Mirko Trajkovski, the team has expected to see the continuous loss of weight in mice exposed to cold because this is quite logical. However, they were stunned when they notices that microbiota changed during low-temperature exposure and supported increased microvilli and gut lengths.
It is good to know that microvilli represent small projections that extend from the intestinal wall which expand the gut’s surface used for absorption and in this way improve the usage of the nutrients from the food we take. In other words, the microbiota is also able to manage gut morphology.
An incredible bacterium is known as Akkermansiamuciniphila
In case the microbiota profile alters with cold, this is a result of the rapid reduction of the Akkermansiamuciniphila bacterium. But, when the aforementioned bacterium is regulated artificially, the length of the gut goes back to a standard size which means that it is a basic element of this mechanism that allows adjustment. This is what the study has confirmed. Once the mice exposed to cold were given Akkermansiamuciniphila, they continued losing weight. What is more interesting is that the microbiota of individuals dealing with obesity seems to miss this bacterium, which manages the absorption of nutrients. UNIGE researchers are planning to analyze and study the effects of Akkermansiamuciniphila in humans.
If they prove that this is a worthy anti-obesity technique, we will be able to come up with new ways to solve this problem. But, the study has given results that promise more things that are beneficial for our health. According to professor Trajkovski, the gut is the biggest endocrine tissue in the system which produces different hormones that act in different body parts. So, changing the gut morphology is one way for the microbiota to affect all bodily organs, even our brain. There is definitely room for more studies and we can expect these studies to take place very soon.