How hunger helps store fat
The hormone ghrelin, when it was first discovered in 1999, almost immediately received the name "hunger hormone" - getting from the stomach, where it is synthesized, into the pituitary gland, it triggers the synthesis of somatotropin (growth hormone) here and stimulates eating behavior, that is, stimulates the appetite. concentrates attention on food, etc. Quite quickly it was possible to establish that its level rises before eating, and laboratory animals after injections of ghrelin began to gain weight.
But further research revealed some oddities. For example, one would expect that if rats turn off ghrelin itself or a receptor for it, then the animals will turn into anorexic - they will simply no longer be interested in food. However, nothing of the kind happened.
This can be explained by the fact that in such a vital matter as nutrition and eating behavior, ghrelin signals have backup insurers, and that when ghrelin is completely turned off, some other molecules that support eating behavior come into play. To avoid such a compensatory effect, Jacques Pantel and his colleagues from the French research center INSERM tried to disable the ghrelin receptor not completely, but partially by removing a small part of it from the receptor gene.
It turned out that in this case, the sensitivity to the hormone only increased: both in cell culture and in animals, less ghrelin was required to turn on the receptor. At the same time, the effect itself remained the same: ghrelin stimulated appetite and triggered the synthesis of growth hormone.
True, this was the case when ghrelin was injected. But he is already synthesized in the body. And it turned out that the reaction to their own (or endogenous) ghrelin was different and very strange: animals with a modified receptor, which turned out to be more sensitive to the hormone, gained weight more actively than ordinary rats - but they ate both at the same time. The increase in weight was not due to an increase in food eaten, but due to the fact that body fat increased in the body - in other words, most of the food eaten was put aside.
That is, we repeat once again, with the strengthening of the signal chain associated with the "hunger hormone", the animals grew fat not due to overeating, but due to the accumulation of fat. Then it turns out that the increase in the level of ghrelin before a meal occurs not so much in order to tune the behavior to search for food, but in order to prepare the body for receiving and storing calories.
But what then about the first part of the work, in which hormone injections just stimulated eating behavior? The authors of the work suggest that the whole thing is in too much excess of ghrelin, which is formed in the body - after all, here an external portion is added to some of its internal level - and in this case, appetite stimulation is probably some kind of side and not quite natural reaction.
Other researchers admit that the new results on ghrelin, published in Science Signaling, are quite interesting, but in order to finally redefine the function of the "hunger hormone", additional experiments are needed. What interest in all this could be for those who are not involved in hormonal signals? Of course, we are talking here about food, about calories, but after all, no practical specifics can be extracted from this yet.
It should be noted here that, on the one hand, such studies are the best illustration of how a scientific search takes place and how many nuances are discovered when we try to clarify our ideas about a particular biological object (be it a hormone, a biochemical reaction, a cell or an animal) ... The interpretation of the results is not limited to a refutation or confirmation, and sometimes all confirmations or refutations remain in place, it just turns out that they relate to some kind of artificial or secondary manifestations.
On the other hand, the same "hunger hormone", as you might guess, is quite suitable as a target for some "means for losing weight", "drugs for normalizing metabolism", etc. But is it possible to use such means if we are still do not fully understand what exactly ghrelin does?
To summarize, we can say that when we suddenly suddenly discover some kind of gigantic economic prospect, we should always remind ourselves that the world is more complicated than it seems, especially when it comes to molecules, atoms, cells, etc.
Of course, someone will say that science never figures out anything to the end, and that how many people, so many opinions, and other similar pearls of folk wisdom, however, if things really were like this, we would still live in caves, not being able to figure out anything to the end and exchanging various opinions.