The study conducted by researchers at Washington University School of Medicine in St. Louis was published online in the Journal of Lipid Research.
They found that people with a particular variant of the CD36 gene are far more sensitive to the presence of fat than others.
"The ultimate goal is to understand how our perception of fat in food might influence what foods we eat and the quantities of fat that we consume," says senior investigator Nada A. Abumrad, PhD, the Dr. Robert A. Atkins Professor of Medicine and Obesity Research.
"In this study, we've found one potential reason for individual variability in how people sense fat. It may be, as was shown recently, that as people consume more fat, they become less sensitive to it, requiring more intake for the same satisfaction. What we will need to determine in the future is whether our ability to detect fat in foods influences our fat intake, which clearly would have an impact on obesity."
People who made more CD36 protein could easily detect the presence of fat. In fact, study subjects who made the most CD36 were eight times more sensitive to the presence of fat than those who made about 50 percent less of the protein.
The researchers studied 21 people with a body mass index (BMI) of 30 or more, which is considered to be obese. Some participants had a genetic variant that led to the production of more CD36. Others made much less. And some were in between.
Participants were asked to taste solutions from three different cups. One contained small amounts of a fatty oil. The other two contained solutions that were similar in texture to the oil but were fat-free. Subjects were asked to choose the cup that was different.
"We did the same three-cup test several times with each subject to learn the thresholds at which individuals could identify fat in the solution," explains first author M. Yanina Pepino, PhD, research assistant professor of medicine. "If we had asked, 'does it taste like fat to you?' that could be very subjective. So we tried to objectively measure the lowest concentration of fat at which someone could detect a difference."
Her team masked input that might help participants identify fat by sight or smell. To eliminate visual cues, they lit the testing area with a red lamp. Study subjects also wore nose clips so that they could not smell the solutions.
Fat is an important component of the diet, and both humans and animals usually prefer high-fat, energy-dense foods. Scientists have believed that people identify those high-fat foods mainly by texture, but this study suggests that the presence of fat can change the way our tongues perceive the food, just as it does for the tastes sweet, sour, bitter, salty and savory (umami).
The CD36 discovery follows research that had identified a role for the gene in rats and mice. Scientists had learned that when animals are genetically engineered without a working CD36 gene, they no longer display a preference for fatty foods. In addition, animals that can't make the CD36 protein have difficulty digesting fat.
Up to 20 percent of people are believed to have the variant in the CD36 gene that is associated with making significantly less CD36 protein. That, in turn, could mean they are less sensitive to the presence of fat in food.
Abumrad was the first to identify CD36 as the protein that facilitates the uptake of fatty acids. She says better understanding of how the protein works in people could be important in the fight against obesity.
People with obesity are at an elevated risk for cardiovascular disease, stroke, type 2 diabetes, certain cancers, arthritis and other problems. Obesity rates have risen dramatically over the past 30 years as more people have become sedentary, and diets incorporate more hamburgers, French fries, fried chicken and other high-fat foods.
"Diet can affect sensitivity to fat, and in animals, diet also influences the amount of CD36 that's made," Pepino says. "If we follow the results in animals, a high-fat diet would lead to less production of CD36, and that, in turn, could make a person less sensitive to fat. From our results in this study, we would hypothesize that people with obesity may make less of the CD36 protein. So it would seem logical that the amounts of the protein we make can be modified, both by a person's genetics and by the diet they eat."
제6의 맛 있다
인간의 혀가 감지할 수 있는 제6의 맛이 있으며 이는 기름(지방)맛이라는 연구결과가 나왔다.
미국 워싱턴 대학 의과대학의 나다 아붐라드(Nada Abumrad) 박사는 사람의 혀가 느낄 수 있는 기본적인 미각은 단맛, 신맛, 짠맛, 쓴맛, 감칠맛(우마미) 등 5가지 외에 기름맛이 있으며 이 제6의 맛에 대한 민감도가 비만과 연관이 있는 것으로 보 인다고 밝힌 것으로 영국의 데일리 텔레그래프와 데일리 메일 인터넷판이 15일(현지시간) 보도했다.
아붐라드 박사는 혀에 분포하는 미뢰(taste bud)에는 지방분자를 인지하는 CD36 이라는 수용체가 있으며 이 수용체의 많고 적음에 따라 기름맛에 대한 민감도가 사 람마다 차이가 있다고 밝혔다.
기름맛에 대한 민감도가 높은 사람은 지방을 많이 먹어 민감도가 낮아지며 이를 보상하기 위해 더 많은 지방을 섭취해 결국은 과체중-비만에 이르게 된다고 그는 말 했다.
그의 연구팀은 과체중인 21명에게 기름이 소량 함유된 액체가 들어있는 컵 하나 와 감촉은 기름과 비슷하지만 기름은 전혀 들어있지 않은 액체가 들어있는 2개의 컵 을 주면서 맛을 보고 3컵 중 맛이 다른 하나를 고르게 했다.
그 결과 기름맛에 대한 민감도가 8배나 높은 사람들이 있었으며 이들은 미뢰의
CD36 수용체가 가장 많은 것으로 밝혀졌다. 다른 사람들은 이 수용체가 이들의 절반 밖에 되지 않았다.
연구팀은 이 수용체를 만드는 유전자를 검사한 결과 기름맛에 대한 민감성이 낮 은 사람들은 이 유전자가 변이되어 있었다.
결국 이 유전자가 변이된 사람은 음식 속에 들어있는 지방에 덜 민감해 더 많은 지방을 섭취하게 됨으로서 과체중-비만에 이르는 것으로 생각된다고 아붐라드 박사 는 말했다.
사람 중 약20%는 이 변이유전자를 가지고 있는 것으로 믿어진다고 그는 덧붙였 다.
이 연구논문의 공동저자 중 한 사람인 야니나 페피노(Yanina Pepino) 연구원은 동물실험에서는 지방 과다섭취가 CD36 수용체 감소로 이어지고 이것이 다시 지방에 대한 민감성을 떨어뜨리는 것으로 나타났다면서 이로 미루어 비만인 사람은 CD36 수 용체가 다른 사람보다 적다고 추정할 수 있다고 말했다.
이 연구결과는 '지질연구 저널(Journal of Lipid Research)' 최신호에 발표되었다. (연합뉴스)