October 9, 2012
Ability To Taste Linked To Better Respiratory Health
April Flowers for redOrbit.com - Your Universe Online
A person's ability to taste certain bitter flavors might just be directly related to their ability to fight off upper respiratory tract infections, especially chronic sinus infections, a new study led by the University of Pennsylvania finds.The study, published in the Journal of Clinical Investigation, includes researchers from the Perelman School of Medicine at the University of Pennsylvania, the Monell Chemical Senses Center, and the Philadelphia VA Medical Center.
The majority of people experience five basic types of tastes: sweet, salty, sour, bitter and savory. The receptor cells bundled in our taste buds mediate the sense of taste. The body is alerted to harmful foods that have spoiled or are toxic by the tastes of "sour" and "bitter." Based on genetics, it is known that approximately 25 percent of the population cannot detect certain bitter flavors. They are known as non-tasters. Another 25 percent are sensitive to an extremely small quantitative of such flavors and are known as super-tasters. The rest of us fall somewhere in between these two poles.
What could chronic sinus infections, known to account for 18-22 million doctor visits a year in the U.S., have to do with a cup of bitter coffee?
The new study shows that the taste receptors (T2Rs) are also found in both upper and lower human respiratory tissue. This likely signals a connection between activation of bitter tastes and the need for the body to launch an immune response in these areas when exposure to potentially harmful bacteria and viruses occur.
"With this information in mind, we wanted to better understand the exact role that bitter taste receptors play in the upper airway, especially between these super and non-tasters," says Noam Cohen, MD, PhD, assistant professor of Otorhinolaryngology: Head and Neck Surgery, staff physician at the Philadelphia VAMC.
The research team formulated three hypotheses around this possible connection.
"(1) Bitter taste receptors are functional in the nose (upper respiratory tract), and each receptor detects a specific type of bacteria. (2) Upon activation by a specific bacterial product, the bitter taste receptor initiates a local defensive response to combat the attacking bacteria. (3) Genetic variability of the bitter taste receptors alters the vigorousness of the response, thus leaving certain individuals with very strong defenses and others with weak defenses against a specific bacteria."
To test the hypotheses, they then grew cell cultures of sinus and nasal tissues. The tissues used were collected during sinus surgical procedures. The cell cultures develop cilia, produce mucus, and reflect many of the defensive workings found inside the nose and sinuses.
What the team found was that one of the bitter taste receptors functioning in the upper airway cells (T2R38) acts as a "security guard," so to speak. It detects molecules of a certain class of bacteria secretes.
"These molecules instruct other bacteria to form a biofilm, which helps harbor the bacteria. From previous work, we know that these biofilms spur the immune system to mount an over-exuberant inflammatory response that can lead to sinusitis symptoms. When the T2R38 receptor detects these molecules, it activates local defensive maneuvers to increase mucus clearance and kill the invading bacteria. It's really like modern warfare — intercept the enemies' early communications to thwart their plans and win the battle," Cohen said.
Using the data collected from the cultures, the team demonstrated that super-tasters detect very small concentrations of the offending molecules. Non-tasters and middle-ground individuals, on the other hand, require 100 times more of the molecule for detection. Examinations of the patients' original samples were collected and revealed that none of the super-tasters were infected with the specific type of bacteria that T2R38 detects, known as the gram-negative bacteria.
"Based on these findings, we believe that other bitter taste receptors in the airway perform the same "guard duty" function for early detection of attack by different types of bacteria, and we hope to translate these findings into personalized diagnostics for patients with chronic rhinosinusitis," Cohen says.
The team hopes to use this research to develop a simple "taste-test" protocol to be conducted during clinical visits.
"We're optimistic that a test of this nature will help us predict who is at risk to develop biofilms based on their ability to taste various bitter compounds. Additionally, we are looking at therapeutic outcomes, both surgical and medical, based on the taster/non-taster genetic status to determine whether knowing this status will stratify patients to either surgical or medical interventions."