2012-06-30 12:44:25
A few years ago I wrote in this section about the existence of a fifth type of flavor that was added to the four traditional flavors: sweet, salty, bitter and sour . This fifth flavor is called umami and is provided, in particular, by foods rich in proteins and amino acids. As surprising as it may seem, the list of flavors was not closed yet and we know today that there is a sixth type of flavor that some experience much better than others: the fatty flavor.
Without a doubt, the perception of flavors has been and is essential for our survival. We prefer tasty foods simply because they contain nutrients and energy sources necessary to stay alive. This perception depends on the presence of specific receptor proteins in the cells of the taste buds of the tongue, which detect the components of food and transmit signals to the brain that it interprets as flavors.
Since, in addition to carbohydrates (sweets) and proteins (umami), fats are also one of the most important nutrients, some researchers wondered if there might not be a particular receptor molecule that reacts to the presence of fats in foods and will provide us with a special flavor when tasting them. The search for this receptor molecule bore fruit and, in 2005, French researchers published the surprising discovery that this molecule was none other than an old one known to immunologists and hematologists, the one called CD36, produced by the activity of the gene of the same name.
CD HISTORY
The family of CD molecules is very diverse and has 247 members. These molecules were identified and numbered on the surface of blood cells, above all, so that they served to differentiate some cells from others. Thus, for example, a lymphocyte may have CD3 and CD4 on its surface, although not CD11, but a macrophage does not have CD3 or CD4, although it does have CD11. In this way, by analyzing what molecules are found on the surface of various cells, scientists and doctors can know what kind of cell it is. This is important, for example, to diagnose leukemias.
CD36 was identified as a molecule present on the surface of several blood cells, particularly platelets and macrophages, the latter being very important as the first line of defense against infection, and also for cleaning remains of dead cells. Our organism. It was also soon discovered that CD36 bound to a variety of molecules present in blood plasma, in particular to lipoproteins, which transport fats in the blood, and also to free fatty acids, which are part of the triglycerides of fats.
Subsequent studies also revealed that, surprisingly, CD36 was equally present in the tongue taste buds of laboratory mice and rats. This finding inspired the design of experiments that demonstrated that these animals show a preference for fatty foods, such as the famous cheese that rodents seem to like so much, because CD36 functions in the tongue as a taste receptor for fats, which probably It allows the animals that ingest them to experience a pleasant flavor. Would this also happen with humans? Would this have to do with abnormal eating behaviors, leading to obesity?
TASTY FATS
Researchers at Washington University, in St. Louis, USA, set out to start studies to find out. As it is well known that various sensory abilities are related to different variants of certain genes, the researchers decided to study which variants of the CD36 gene were present in obese people and check whether these variants produced proteins in the taste buds that increased or did not increase the sensation of pleasant taste. when eating fatty foods.
What the researchers found was that, despite being obese, the CD36 gene variants of the 21 people studied were different from each other. This meant that the various variants of the CD36 gene were not all associated with the development of obesity. However, by studying personal preferences for high-fat foods, such as hamburgers, mayonnaise or olive oil, the researchers found that those who possessed a CD36 gene variant that causes the production of higher levels of protein were able to detect fat in foods in a concentration eight times lower than those who had other variants of said gene. On the other hand, around 20% of those studied had a CD36 variant that produced less protein, which made them less sensitive to the presence of fats in food. These results have been published in the scientific journal Journal of Lipid Research.
Aside from the mystery that the same molecule functions in the cells of the blood and the tongue, which will have to be elucidated, it is possible that a different sensitivity to fats modifies our appetite for foods rich in these substances, which could affect our susceptibility to becoming obese. Drugs that modify the activity of CD36 could therefore be useful in the treatment of obesity. However, as always happens with newly acquired knowledge, we will have to wait several years to see if this can become a reality.
WORKS BY JORGE LABORDA.
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