Loss of smell saved the mice from becoming obese
Scientists from the University of California at Berkeley, found that mice lost their sense of smell to become resistant to obesity.
The reason for this was not a reduction of food intake, as you would think, and activation of the sympathetic nervous system and increased fat burning brown adipose tissue. The strengthening of the sense of smell, by contrast, has led to the fact that mice become prone to weight gain. A study published in the journal Cell Metabolism.
The connection between smell and food intake seems pretty obvious, because the aroma of food affects our appetite.
Indeed, it has been shown that people with impaired sense of smell suffered from weight loss and even anorexia because she did not feel the taste of food and losing interest in her. However, a study by American scientists shows that the relationship between smell and metabolism is much more complex. In their work, biologists have shown that the loss of olfactory activation of brown fat and increased energy consumption.
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In the first experiment, the authors used genetically modified line of mice with inactive olfactory neurons. The translation of such mice with a normal diet on high calorie high fat foods has led to the fact that the mice gained weight — however, to a much lesser extent than control mice with a normal sense of smell. Importantly, these mice ate the same as the control, that is off of smell did not affect their appetite. In the second experiment, normal mice that were on a high-calorie diet, temporarily disconnected sense of smell with a special toxin. After that the weight gain they have slowed down.
Studies have shown that mice with impaired olfaction began increased consumption of energy and oxygen due to the activation of brown fat. In addition, animals were observed “Browning” ordinary subcutaneous fat. In the blood of experimental animals was increased concentration of norepinephrine — a hormone of the sympathetic nervous system is activated in stressful reactions. Apparently, it is due to the release of noradrenaline, receptors which are on cells of brown adipose tissue was activated last.
Then scientists, by blocking certain receptors in the olfactory neurons, increased sense of smell in animals. Mouse with a keen sense of smell began to gain weight faster. It turned out that fat tissue they have lost the ability to dissipate energy, and fat is accumulating faster than ordinary mice.
In his article, the researchers do not offer any method for the treatment of obesity is based on the open of their mechanism, however the experts are willing to speculate on this topic (opinions you can read in the article in Science, giving an overview study).
For example, one can imagine the nasal spray, which temporarily would shut off the smell, and helped to normalize the metabolism of patients with obesity. News
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However, given that the basis of the mechanism is activation of the sympathetic nervous system, this method can be significant side effects, in fact we are dealing with a chronic stress reaction.
Brown fat is a type of adipose tissue, whose function is thermogenesis. Mitochondria, which are full of the brown fat, oxidize fatty acids and dissipate the resulting energy into heat. In humans, brown fat is represented in the body mainly in infants, but in adults also found a small amount. Since brown adipose tissue as a fuel actually uses fats, the conversion of white fat into brown researchers seem promising approach to the treatment of obesity (more on this can be read here). One of the easiest ways to activate brown fat is physical exercise. Muscles in response to the load is synthesized by a number of factors of protein nature (e.g., hormone irisin) that makes fat burn itself. However, recently we wrote about the fact that the muscles not only consume energy, but also involved in the creation of fat reserves.
Daria Spasskaya