Brain protein linked to Alzheimer's found on tongue
The same protein in the brain that's involved in the tiny molecules linked to the plaques of Alzheimer's disease also exists on the tongue, where it governs the sense of taste, a Long Island researcher has discovered.
Philippe Marambaud of the Litwin-Zucker Center for Alzheimer's Disease in Manhasset has found that a protein, which stipples the tongue, could ultimately reveal an important link to health or disease in the brain -- but scientists are far from anything conclusive.
On the tongue the protein is intimately involved in the perception of sweet, sour, bitter, salty and umami tastes, Marambaud said. Umami, he explained, is a Japanese term that refers to savory-tasting substances.
Marambaud first discovered the protein, which he dubbed CALHM1, in 2008. But in the new round of research, which involved a group of collaborators on Long Island and beyond, the protein was found in a new and unexpected place.
"This is a critical regulator of the perception of taste," Marambaud said Tuesday. "We knew this protein was expressed in the brain and we had some clear evidence that it could be involved in Alzheimer's disease."
In the brain, Marambaud said, his evidence suggests the protein controls the development a key molecular structure known as the amyloid peptide. The peptide is a building block involved in senile plaques, the damaging deposits that clog the brain in Alzheimer's disease.
"That is still our main focus, how this protein controls the amyloid peptide," Marambaud said.
A question new to science -- which has not yet been answered -- is whether a declining perception of taste could somehow signal the onset of the progressive and incurable mind-crippling disease.
Scientists have long known that the perception of taste is a complex genetic trait that can differ from person to person, regardless of age.
High school students who have based science projects on PTC -- phenylthiocarbamide -- test strips are well aware of taste perception's complexity. Projects based on the strips have allowed students to divide classmates into distinct groups: those who carry a gene allowing them to perceive PTC as bitter and those who perceive it merely as bland.
Additionally, controversy has swirled among scientists over the sense of smell and whether its loss signals Alzheimer's.
A 2007 study reported in the Archives of Psychiatry suggested such was the case. Last year, Dr. Gordon Sun, a medical investigator at the Ann Arbor VA Medical Center and the University of Michigan, reviewed 1,200 previous studies and drew a less certain conclusion.
Sun said that though an association exists between the loss of smell and Alzheimer's, there isn't enough evidence to say it's a predictor of the disease.
Marambaud said it's equally important to proceed cautiously about making such assertions about taste perception.
"We need clear evidence to understand the disease process," he said.