Evaluation by functional MRI about the rat brain activity change at the sweetness stimulation with the difference sweeteners

抄録

Non-nutritive artificial sweeteners have been used for the aim of diminishing the calories of the foods and beverages, instead of sugar. Artificial sweeteners are also used for suppression of weight gain in patients with obesity or diabetes. However, from the results of animal experiments, excess intake of artificial sweeteners suggested a cause of overeating, weight gain, increase in body fat percentage and increase in diabetes risk. In addition, even the results of human studies, excessive intake of artificial sweeteners caused weight gain, increase in visceral fat and obesity, and had been reported to increase in high blood pressure, diabetes, metabolic syndrome and depression as a result. However, it is not clear whether artificial sweetener intake really causes these events. Therefore, we examined the time course of weight gain of mice fed by foods with sweetened water. We used acesulfame K and sucrose as a sweetener. The acesulfame K is artificial sweetener with 200 times as much as sweetness as sugar and is a zero calorie. It is also one of the artificial sweeteners that are used in many foods and beverages currently. As a result, the mice were found to prefer acesulfame K or sucrose than water. It was suggested that the rats like also acesulfame K as much as sucrose, up to a certain fixed concentration. There was no little difference in weight gain between mice that ingested sucrose or acesulfame K.

　In this time, we also examined brain activity of rats by functional magnetic resonance imaging (fMRI) when rat tongue was stimulated with sweeteners. The experiment objects were the rats which did not gave sweetness at all and the rats which gave both sweeteners of sugar and acesulfame K.

　From the results of fMRI in rats, it was shown that cerebral activation area changed considerably with each sweetener stimuli. In addition, the rat brain activation area changes were clearly different whether a rat knew the sweetness.

　These results suggested the possibility that the preference formation of the rat sweetness changed by memory and reward system participated.