Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Turning Back the Clock: Fasting Prolongs Reproductive Life Span

31.08.2009
Scientific dogma has long asserted that females are born with their entire lifetime’s supply of eggs, and once they’re gone, they’re gone. New findings by researchers at Fred Hutchinson Cancer Research Center, published online Aug. 27 in Science, suggest that in nematode worms, at least, this does not hold true.

Molecular physiologist Marc Van Gilst, Ph.D., and colleagues report that during starvation, sexually mature adult worms stop ovulating and the germline component of their reproductive system – the sex cells, including mature and maturing eggs – dies off and leaves behind nothing but a few stem cells.

However, once normal food conditions resume, the conserved stem cells can produce a brand new crop of sex cells, complete with youthful and fertile eggs.

This turning back of the reproductive clock all takes place in tiny C. elegans soil worms that are up to15 times older than normally fed worms in their reproductive prime.

“For many, it has been assumed that cells and organs remain relatively stable during periods of starvation or caloric restriction,” said Van Gilst, an assistant member of the Hutchinson Center’s Basic Sciences Division, who authored the study with postdoctoral research fellow Giana Angelo, Ph.D. “The idea that an entire system would kill itself off during starvation and then regenerate upon food restoration was very surprising. The fact that extremely old worms could generate new eggs and produce healthy offspring long after their normally fed counterparts had reproduced and died was also unexpected,” he said.

The mechanism behind the preservation and extension of fertility long past the worms’ normal reproductive prime, Van Gilst suspects, is a signaling receptor protein in the cell nucleus called NHR-49, which promotes a major metabolic response to dietary restriction and fasting. While it has been hypothesized that this protein may interface with calorie restriction to extend life span, until now its role in protecting and extending reproductive longevity in the face of starvation had not been known. “In worms that contained an inactive NHR-49 gene, reproductive recovery and fertility after starvation were severely impaired,” he said. “We found that reproductive arrest and recovery are highly dependent on a functioning NHR-49 gene.”

NHR-49 in worms is analogous to various proteins in humans, all of which belong to a family of proteins called nuclear receptors. Nuclear receptors, such as estrogen receptors and androgen receptors, are particularly good targets for pharmaceutical intervention. “The identification of a nuclear receptor that turns on and off the beneficial response to nutrient deprivation would be of great interest because it would be a candidate for drugs aimed at tricking the body, or specifically the reproductive system, into thinking they are calorically restricted or starved, even when food intake is normal,” Van Gilst said.

The biomedical implications of model organisms such as flies and worms cannot be overlooked, he said. “Many paradigm-shifting discoveries in C. elegans have since been replicated in humans. Therefore, the idea that our findings will be relevant to human reproduction is a possibility that certainly needs exploration,” he said.

However, Van Gilst is quick to point out that even if this mechanism is conserved in humans, it is still unknown what degree of caloric restriction would be required to impact egg production in humans. “If such a process exists in humans, it likely evolved to help our ancestors preserve fertility during periods of famine or food shortage. We certainly don’t have a prescription for famine. Consequently, our study should not be used to promote potentially dangerous interventions such as severe caloric restriction and starvation as a means to restore a woman’s fertility,” he said.

In the meantime, Van Gilst and colleagues will continue to study the tiny worm to better understand the basic mechanisms that control fertility. One question their research may help address is how in some cases women recovering from radiation and bone marrow transplantation – which damages or destroys much of the germline, including mature and immature eggs – can regain their fertility.

“There is controversy over how this occurs,” Van Gilst said. “On the one hand, it has been argued that new eggs are generated from the woman’s germline stem cells through a process that may mirror the germline regeneration we observed in C. elegans. In fact, there is controversy over whether or not germline stem cells exist in adult women. We believe that our work in C. elegans throws another hat in the ring, raising the possibility that germline stem cells may indeed be present in women and that their activity may surface under conditions of nutrient deprivation or stress,” he said.

This work may also shed new light on cancer. “Cancer cells, when starved, are very susceptible to cell death. However, cancer stem cells, or progenitor cells, often thrive and flourish during starvation in cell-culture experiments. When nutrition is restored, these cells can trigger rapid regrowth. Consequently, understanding how germline stem cells in C. elegans survive starvation may help appreciate how cancers survive treatments aimed at starving tumors,” he said.

For the study, the researchers withheld food from two types of nematodes: those that were genetically normal and those that lacked a functioning NHR-49 gene. The worms were monitored every few days by microscopy to observe changes in their reproductive system, including ovulation, cell death and germline stem cell survival. After different periods of starvation, food was restored and the worms were again monitored by microscopy to assess the recovery of their reproductive system. Fertility was determined by counting offspring after mating.

The research was supported by a National Institutes of Health Ruth L. Kirschstein National Research Service Award, the American Diabetes Association and the National Institute of Diabetes and Digestive and Kidney Diseases.

At Fred Hutchinson Cancer Research Center, our interdisciplinary teams of world-renowned scientists and humanitarians work together to prevent, diagnose and treat cancer, HIV/AIDS and other diseases. Our researchers, including three Nobel laureates, bring a relentless pursuit and passion for health, knowledge and hope to their work and to the world. For more information, please visit fhcrc.org.

Kristen Lidke Woodward | Newswise Science News
Further information:
http://www.fhcrc.org

More articles from Life Sciences:

nachricht How brains surrender to sleep
23.06.2017 | IMP - Forschungsinstitut für Molekulare Pathologie GmbH

nachricht A new technique isolates neuronal activity during memory consolidation
22.06.2017 | Spanish National Research Council (CSIC)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>