Red Pandas Reveal an Unexpected (Artificial) Sweet Tooth
ScienceDaily (Apr. 16, 2009)

Scientist researchers from the Monell centre have discovered the red panda’s affection for the artificial sweetener, aspartame, may be explained through structural variation of its sweet taste receptor.
The researchers studied six different species that were closely related but differed in their diet selection and taste preference - red panda, ferret, genet, meerkat, mongoose and lion. They studied the sweet preferences of these species by exposing the animals to six natural sugars and six artificial sugars one by one with water present as an alternative. The animal was said to prefer the sweet solution if it drank more of it than of water in a 24 hour period. They then related this data to the genetics of sweet receptor structure of each species. Sweet taste receptors contain binding sites for a variety of different natural and artificial sweeteners and these are said to vary between species. The sweet receptor gene Tas1r2 was looked at, which codes for T1R2, one of two taste receptors that join together to recognize sweetness.
The lion and cat, which did not prefer any of the sweet solutions, were found to have a defective Tas1r2 gene and therefore, do not have sweet taste receptors to be able to detect sweet compounds. The researchers were surprised when the red panda drank large amounts of the artificial sweeteners as this behavior had only been previously seen in primates. They tried to explain this behavior by comparing the Tas1r2 genes from various species that can and cannot taste artificial sweeteners and were surprised to find that there were no differences in the gene. However, the red panda’s sweet receptor was found to have a different structure compared to all the other species examined. This may explain why the red panda can taste these artificial compounds, which may demonstrate the past evolution of this sweet receptor to help the panda detect some natural compound that is similar in structure to the sweeteners.
The implications of this research point to further studies that may help in finding a link between different individual’s taste receptor structures and their dietary choices. Further studies will look at protein structure of taste receptor genes and how this predicts stimulus binding and ultimately affects taste, food choice and diet.


http://www.sciencedaily.com/releases/2009/04/090415120959.htm

Picture: http://www.wildlifearchives.com/images/red-panda.jpg