PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Penn team elucidates evolution of bitter taste sensitivity

2013-11-12
(Press-News.org) Contact information: Katherine Unger Baillie
kbaillie@upenn.edu
215-898-9194
University of Pennsylvania
Penn team elucidates evolution of bitter taste sensitivity

It's no coincidence that the expression "to leave a bitter taste in one's mouth" has a double meaning; people often have strong negative reactions to bitter substances, which, though found in healthful foods like vegetables, can also signify toxicity. For this reason, the ability to sense bitterness likely played an important role in human evolution.

A new study by University of Pennsylvania scientists provides new evidence underlining the significance of bitter taste perception. Their work suggests that a genetic mutation that makes certain people sensitive to the taste of a bitter compound appears to have been advantageous for certain human populations in Africa. Yet the reason why this trait was selected may not have to do with just taste. Instead, the molecular receptor under study may also play important roles in immune response or metabolism.

"We're starting to understand that these taste receptors are involved in so many functions other than just oral sensory perception," said Michael Campbell, lead author on the study and a postdoctoral fellow in Penn's Perelman School of Medicine's Department of Genetics.

The study, published in the journal Molecular Biology and Evolution, represents the first time that this bitter-taste sensing gene, TAS2R16, was studied in a large set of ethnically and culturally diverse African populations.

"Because Africa is the site of origin of all modern humans," said Sarah Tishkoff, the study's senior author and a Penn Integrates Knowledge Professor with appointments in the School of Arts and Sciences' Department of Biology and Penn Medicine's Department of Genetics. "Africans are going to have a large amount of diversity and non-Africans are going to have a subset of that diversity. In Africa, you get an opportunity to observe how these genetic variants are influencing phenotypes that you wouldn't have if you were only studying non-Africans."

Campbell, Tishkoff and other Penn researchers collaborated with Paul Breslin of Rutgers University and Monell Chemical Senses Center, as well as scientists from Addis Ababa University, France's Musée de L'Homme, Integral Molecular Inc., the Kenya Medical Research Institutes, Cameroon's Ministry of Scientific Research and Innovation, Tanzania's Muhimbili University of Health and Allied Sciences and the National institute on Deafness and Other Communication Disorders.

The work builds on a previous study by the group, which explored the evolutionary history of a gene called TAS2R38, responsible for the ability to perceive the bitter tasting compound PTC. In that research, published in Molecular Biology and Evolution in 2011, the geneticists discovered that something other than taste perception must have driven the selection of that gene.

The current work examines the related gene TAS2R16, which codes for a molecular receptor that binds salicin. Salicin is a chemical found naturally in willow bark, the source of aspirin. It acts as an anti-inflammatory but in large doses can be toxic. It is also found in many nuts, fruits and vegetables.

To understand the patterns of variation at TAS2R16 in humans globally, the researchers collected DNA from 595 people in 74 populations across Africa with diverse lifestyles, such as pastoralism, hunting-gathering and agriculture. They sequenced the stretch of DNA encompassing the TAS2R16 gene in all of these individuals and also examined previously collected DNA from 94 non-Africans from the Middle East, Europe, East Asia and the Americas and found 15 variants total, most of which were only found in Africa.

In addition, the researchers asked 296 of the Africans sampled to perform "taste tests" of progressively more concentrated solutions of salicin and report when they could detect a bitter taste. The team also performed a cellular analysis, led by Integral Molecular scientists, to see the molecular effects of different TAS2R16 mutations.

The taste testing shows that the mutations in TAS2R16 had functional significance for the bitter taste perception system," Breslin said. "In this case, the mutation caused a gain of taste function.

When the researchers "mapped" individuals' genetic profiles onto their tasting ability, they found a strong correlation between one of the 15 variants and an increased sensitivity to salicin. The cell-based analysis offered an explanation for this sensitivity: cells with this genetic mutation had nearly twice as many receptors for salicin on their membranes as did cells with other forms of the TAS2R16 gene.

On a population level, the researchers found that the "high-sensitivity" variant for salicin was more prevalent in individuals from East Africa than in those from West Central or Central Africa, and non-Africans possessed only the "high-sensitivity" version of the gene. What's more, in East Africans this high-sensitivity variant, which arose roughly 1.1 million years ago, showed signs of being under a force of natural selection in humans, suggesting it conferred an evolutionary advantage at some point during our past.

"That's another sign that this variant must be tremendously important for human survival because it evolved in our human ancestors so long ago and carried over to us," Campbell said.

The geographic structure of TAS2R16 variants contrasts with the previous work on TAS2R38, variants of which did not appear to fall into any clear geographic pattern. These differences between two genes that both relate to bitter taste perception offer more support to the idea that taste was not the only force driving the evolution of this gene.

"The types of populations we're studying are diverse and they have diverse diets," Tishkoff said, "suggesting that there is likely something else going on here. By getting a handle on how much variation is in these populations, where it is located and what are the particular signatures of selection, it might start giving us clues as to what we should be looking at in terms of the biomedical or physiological significance of these genes."



INFORMATION:

Additional members of the team from Penn included Alessia Ranciaro, Daniel Zinshteyn, Renata Rawlings-Goss, Jibril Hirbo, Simon Thompson and Dawit Woldemeskel. Other collaborators included Alain Froment, Joseph B. Rucker, Sabah Omar, Jean-Marie Bodo, Thomas Nyambo, Gurja Belay and Dennis Drayna.

The research was supported by the National Science Foundation and the National Institutes of Health.



ELSE PRESS RELEASES FROM THIS DATE:

Understanding ourselves by studying the animal kingdom

2013-11-12
Understanding ourselves by studying the animal kingdom Researchers look to armadillos, fruit flies, nematodes, and other species to understand human brain function and vision loss SAN DIEGO — Research released today reveals a new model for a genetic eye disease, and ...

New study analyzes sharp rise in US drug poisoning deaths by county

2013-11-12
New study analyzes sharp rise in US drug poisoning deaths by county Investigators look at the link between geographic patterns and death rates in the new issue of the American Journal of Preventive Medicine San Diego, CA, November 12, 2013 – A new study published in ...

News media reinforce sexual exploitation stereotypes

2013-11-12
News media reinforce sexual exploitation stereotypes News stories about sexually exploited youth in Canada perpetuate unhelpful stereotypes, according to new research from the University of British Columbia. The study, recently published in the Canadian ...

Johns Hopkins research may improve early detection of dementia

2013-11-12
Johns Hopkins research may improve early detection of dementia Using scores obtained from cognitive tests, Johns Hopkins researchers think they have developed a model that could help determine whether memory loss in older adults is benign or a stop on the ...

You want fries with that? Don't go there

2013-11-11
You want fries with that? Don't go there New Dartmouth study of chronic dieters suggests brain disruptions weaken will power A new Dartmouth neuroimaging study suggests chronic dieters overeat when the regions of their brain that balance impulsive behavior and self-control ...

Hormones impact stress, memories, and understanding social cues

2013-11-11
Hormones impact stress, memories, and understanding social cues Research reveals new roles for estrogen and finds potential biomarker for maternal stress SAN DIEGO — Research released today demonstrates unexpected roles that sex hormones may play in the cognitive function ...

How zinc starves lethal bacteria to stop infection

2013-11-11
How zinc starves lethal bacteria to stop infection Australian researchers have found that zinc can 'starve' one of the world's most deadly bacteria by preventing its uptake of an essential metal. The finding, by infectious disease ...

Molecular interplay explains many immunodeficiencies

2013-11-11
Molecular interplay explains many immunodeficiencies Australian scientists have described an exquisitely balanced interplay of four molecules that trigger and govern antibody production in immune cells. As well as being an important basic science ...

Understanding immune system memory -- in a roundabout way

2013-11-11
Understanding immune system memory -- in a roundabout way While the principle of immune memory has been known for decades, the exact molecular mechanisms underpinning it have remained a mystery. Australian scientists have now unraveled part ...

Study finds key link responsible for colon cancer initiation and metastasis

2013-11-11
Study finds key link responsible for colon cancer initiation and metastasis Chronic inflammation has long been known as a key risk factor for cancer---particularly colon cancer---but the exact mechanisms of how inflammation heightens the immune response, ...

LAST 30 PRESS RELEASES:

Durham University scientists play key role in testing superconducting materials for world’s largest fusion energy project

Drug-resistant fungus Candidozyma auris confirmed to spread rapidly in European hospitals: ECDC calls for urgent action

New evidence of long-distance travelers in Seddin during the Bronze Age

Newly dated 85-million-year-old dino eggs could improve understanding of Cretaceous climate

From noise to power: A symmetric ratchet motor discovery

Family-based intervention programs are insufficient to prevent childhood obesity, major study finds

Emotions expressed in real-time barrage comments relate to purchasing intentions and imitative behavior

Your genes could prune your gut bugs and protect you from disease

EMBARGOED MEDIA RELEASE: Breathlessness increases long-term mortality risk, Malawi study finds

Permeable inspection of pharmaceuticals goes in-line

Warming rivers in Alaska threaten Chinook salmon populations and Indigenous food security

New multi-disciplinary approach sheds light on the role of mitochondrial DNA mutations in cancer

Worms reveal just how cramped cells really are

Alzheimer’s disease digital resources lacking for Latinos, Hispanics in Los Angeles years after COVID-19, study finds

Chronic disease deaths decline globally, but progress is slowing

The Lancet: Chronic disease deaths decline globally, but progress is slowing

The Lancet: Parent-focused programs insufficient to prevent obesity in toddlers, finds meta-analysis; authors call for a re-think of childhood obesity prevention approaches

Study sheds light on hurdles faced in transforming NHS healthcare with AI

Astrocytic “brake” that blocks spinal cord repair identified

As farm jobs decline, food industry work holds steady

Kennesaw State researcher aiming to move AI beyond the cloud

Revolutionizing impedance flow cytometry with adjustable microchannel height

Treating opioid addiction in jails improves treatment engagement, reduces overdose deaths and reincarceration

Can’t sleep? Insomnia associated with accelerated brain aging

Study links teacher turnover to higher rates of student suspensions, disciplinary referrals

How harmful bacteria hijack crops

Crowded conditions muddle frogs’ mating choices

A new way to guide light, undeterred

Researchers uncover how COVID-19 may linger in cancer patients and affect treatment outcomes

Tiny metal figurines from Sardinia's Nuragic civilization in around 1,000 BC reveal extensive ancient Mediterranean metal trading networks

[Press-News.org] Penn team elucidates evolution of bitter taste sensitivity