Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Food additive inhibits longevity enzyme in yeast, increases cell toxicity, new study finds

16.12.2005


A common additive found in food and cosmetics has been found to inhibit the activity of sirtuins, enzymes associated with lifespan control in yeast and other organisms, according to a new study led by researchers at the University of California, Berkeley.



The study, to be published Friday, Dec. 16, in the online journal Public Library of Science (PLoS) Genetics, found that in lab tests, dihydrocoumarin (DHC), a compound found naturally in sweet clover and synthetically manufactured for use in foods and cosmetics, inhibited the activity of Sir2p and SIRT1, forms of sirtuin found in yeast and humans, respectively.

Increased sirtuin activity is known to increase longevity in yeast, roundworms and fruit flies. The opposite effect in yeast has also been shown when the sirtuin enzyme is either deleted or reduced - the lifespan decreases by as much as 30 percent.


"Although studies on sirtuins and longevity have not been done in humans, there is reason to suspect that sirtuins play a role in the aging process of human cells, so identifying sirtuin inhibitors becomes important," said Martyn Smith, professor of toxicology at UC Berkeley’s School of Public Health and principal investigator of the study, which was funded by grants from the National Institute of Environmental Health Sciences and the National Institute of General Medical Sciences.

DHC is added as a flavoring agent to a wide variety of foods, including soft drinks, yogurt and muffins, and is used as a common fragrance in cosmetics, lotions and soaps. It can be found in concentrations as high as 100 parts per million in such foods as gelatins, puddings and frozen dairy products.

"It’s still a long jump from test tube to person, but our findings may imply that humans are exposed to chemicals in the diet and environment that block an important enzyme involved in longevity," said Smith.

Notably, there are five forms of sirtuins found in yeast, and seven forms of sirtuin in humans. "There is good reason to think that DHC would inhibit at least some of the functions of some of the other forms of sirtuins," said Jasper Rine, professor of genetics at UC Berkeley’s Department of Molecular and Cell Biology and co-author of the paper.

The UC Berkeley researchers collaborated with Dr. Eric Verdin, associate director and senior investigator at the Gladstone Institute of Virology and Immunology, which is affiliated with UC San Francisco. Verdin, who is also a professor of medicine at UCSF, is an expert on mammalian sirtuin enzymes.

"It’s important to note that the role of sirtuins in aging is conserved in distantly related organisms such as yeast, drosophila and the small roundworm, C. elegans," said Verdin. "So, it is not too much of a stretch to expect that sirtuins also control the aging process in mammals, including humans. In addition, sirtuins control many important cellular functions besides aging, and an agent that modulates sirtuins, such as DHC, could not only affect aging but also other critical functions, such as metabolism, neurodegeneration and cancer."

Sirtuin enzymes are histone deacetylases, which modify the structure of chromatins, complex substances made up of DNA and protein. Histone deacetylases keep chromatins packed and tightly coiled in such a way that enzymes cannot activate the DNA, keeping the gene from being expressed. This type of gene "silencing" is considered epigenetic, which means that it effectively controls the expression of a gene without altering the actual DNA molecules.

"Epigenetic mechanisms are crucial for nearly all aspects of development and have been implicated in a variety of human diseases," said Rine. "Hence, agents which disrupt epigenetic processes can have profound consequences."

Andrew Olaharski, UC Berkeley post-doctoral researcher in environmental health sciences and lead author of the paper, noted that toxicology testing routinely focuses on an agent’s ability to cause DNA mutations, chromosome alterations, or cell death, but does not currently test for chemical-induced epigenetic changes. While epigenetic changes do not alter the DNA structure, they can impact gene expression that may lead to disease.

"Identical twins with the exact same DNA may grow up to have different diseases because of epigenetic changes," said Olaharski. "The identification that a common additive to foods and cosmetics may interfere with these epigenetic processes is simply one more piece of evidence supporting the important role environmental agents may play in human health."

To screen for possible sirtuin inhibitors, the researchers used haploid strains of Saccharomyces cerevisiae yeast. The haploid yeast strains, like gametes or sex cells, contained only one set of chromosomes, and would not normally grow on the medium prepared in the lab.

However, if the haploid yeast strains were exposed to an agent that disrupted sirtuin activity, epigenetic silencing would be reversed, the strains would mate to become diploid cells, and the yeast would grow on the medium. Of the compounds tested thus far, DHC was the first environmental agent to have shown the ability to inhibit sirtuin enzymes.

The researchers further tested the role of DHC in apoptosis, a process that causes a cell to die. They exposed DHC to human white blood cells and found that increasing concentrations of the compound led to increases in cell toxicity, apoptosis, and the stability of p53, a tumor-suppressing protein associated with apoptosis.

"Our study raises some concern about the potential effects of DHC on humans," said Olaharski. "However, I would not be alarmed at this point, since we currently do not have any evidence that exposure to DHC in the diet accelerates the human aging process."

Olaharski said the findings highlight an emerging hypothesis regarding the delicate balance a cell must strike between tumor growth and aging. "Cancers and tumors are essentially cells that have uncontrolled or accelerated growth," he said. "In contrast, aging and apoptosis are processes involved in the halting of cell growth and eventually cell death. If there is too much tumor suppression, there may be no cancer, but the tissue may age more rapidly. It is interesting to speculate whether DHC present in the diet tips this balance towards enhanced tumor suppression, and on the potential ramifications this may have on human health."

The trick, researchers say, is to suppress tumor growth without triggering an acceleration of the aging process. The study suggests that properly functioning sirtuin enzymes - and the agents that inhibit or activate them - play a key role in that balance.

Sarah Yang | EurekAlert!
Further information:
http://www.berkeley.edu

More articles from Studies and Analyses:

nachricht The importance of biodiversity in forests could increase due to climate change
17.11.2017 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig

nachricht Win-win strategies for climate and food security
02.10.2017 | International Institute for Applied Systems Analysis (IIASA)

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Frictional Heat Powers Hydrothermal Activity on Enceladus

Computer simulation shows how the icy moon heats water in a porous rock core

Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Water cooling for the Earth's crust

23.11.2017 | Earth Sciences

Nano-watch has steady hands

23.11.2017 | Physics and Astronomy

Batteries with better performance and improved safety

23.11.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>