Detect flavors not only with the mouth

Taste detection is carried out thanks to the presence in the oral cavity of specific receptors capable of detecting nutritional or non-nutritional components of food. There are 5 main tastes: sweet, salty, sour, bitter and umami, and each taste is detected by a type of receptor.

A research group from the Torre de la Sal Aquaculture Institute (IATS), of the Higher Council for Scientific Research (CSIC) in Spain, has found that fish also detect flavors in their gastrointestinal system.

The study characterizes a system of taste receptors in a type of fish, specifically sea bream, from the beginning of its embryonic development to adulthood, proving that these receptors could regulate intestinal physiology as occurs in mammals.

This discovery opens the door to the design of specific compounds based on the taste properties of the species to stimulate their intake and improve digestive processes.

The IATS Fish Intake Control group led by José Miguel Cerdá Reverter has studied the T1R family of receptors, responsible for detecting sweet flavors (sugars and sweeteners) and umami (protein), throughout the development of sea bream ( Sparus aurata), one of the main species of Mediterranean aquaculture.

His research is the most comprehensive to date on the development of taste in fish.

“We show for the first time that the receptors responsible for detecting taste information originally appear in the digestive tract before in the oral cavity,” explains José Miguel Cerdá. “At that time the fish still feed on the yolk [parte del cigoto que contiene elementos nutritivos]so we understand that it is part of a system programmed in development”.

A school of fish. (Photo: Dwayne Meadows/NOAA/NMFS/OPR)

The appearance of the expression of the family of T1R receptors in the oral tract coincides with the opening of the mouth when the sea bream begin to ingest food from outside (exogenous feeding), which is when they need taste to avoid harmful substances (toxins, poisons , food in poor condition…) or eating those that are nutritionally important.

“We show that when they are adults, these receptors are also expressed in enteroendocrine cells, that is, those responsible for hormone secretion from the gastrointestinal tract. This means that, in some way, flavors control intestinal physiology and hormonal secretion from the gastrointestinal tract in a process called gutsensing, something that has been proven in mammals and that we have demonstrated for the first time in fish”, remarks the CSIC researcher.

For José Miguel Cerdá, this implies that the fish could also detect flavors in the intestine, and communicate the information either through nerve impulses from the peripheral nerves or thanks to the modulation of the synthesis and secretion of gastrointestinal hormones. Experiments carried out on sea bream show that, indeed, these taste receptors of the T1R family are capable of modulating the secretion of hormones to improve digestive processes and the absorption of nutrients, as well as informing the brain to act accordingly, reducing or increasing intake or promoting behaviors aimed at increasing the selective intake of nutrients.

According to the CSIC researcher, knowing how edible fish species such as sea bream manage flavors, as well as the effects they have on their taste receptors, will make it possible to design specific compounds based on the taste properties of each species to stimulate their intake and improve the digestive processes by increasing nutrient absorption and feed efficiency.

The study is titled “Exploring the potential for an evolutionarily conserved role of the taste 1 receptor gene family in gut sensing mechanisms of fish”. And it has been published in the academic journal Animal Nutrition. (Source: Isidoro García / CSIC)