Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Growth hormone activates gene involved in healing damaged tissue

04.12.2003


Growth hormone is known to increase lean body mass and bone density in the elderly, but it does something else, too.

It activates a gene critical for the body’s tissues to heal and regenerate, says Robert Costa, professor of biochemistry and molecular genetics at the University of Illinois at Chicago and a member of the UIC Cancer Center.

That discovery could help explain why we age.



"Growth hormone levels decline as we grow older; as a result, the Foxm1b gene stops working and our bodies are less capable of repairing damage," Costa said.

In a paper published in the December issue of Hepatology, Costa and his colleagues report the results of studies on liver regeneration in aged (12-month-old) and young (2-month-old) mice -- a model system for studying the molecular mechanisms the body enlists to restore tissue damaged by injury or age. The liver is the only organ in the body capable of completely regenerating from mature cells.

The scientists focused on the Foxm1b gene, which is involved in the entire life cycle of the mammalian cell -- its proliferation, maturation and death. The gene’s activity is elevated in dividing cells in young mammals but diminishes in old age.

In previous studies, the researchers inserted the human Foxm1b gene in aged mice whose livers had been partially removed (the two species have virtually identical forms of the gene). The experiments showed that the gene restored levels of Foxm1b proteins and induced the animals’ livers to grow back at a rate typical of young mice. Further research detailed how the gene directs the busy molecular traffic inside cells to make them divide and multiply.

In the present study, the scientists tested the effects of human growth hormone because of its purported role in stimulating cell proliferation. Growth hormone, a substance secreted by the pituitary gland in the brain, is responsible for growth in children and young adults, but its levels decline during aging.

"The literature had suggested that growth hormone therapy in elderly men stimulates cells to divide," said Costa, leading to increases in muscle mass and skin thickness and greater bone density in the spine, while decreasing body fat.

"We wanted to find out how the hormone worked at a molecular level."

When aged mice whose livers had been partially removed were injected with human growth hormone, histological and other tests showed that the activity of the Foxm1b gene increased dramatically, as did levels of various enzymes and proteins that cause cells to divide. At the same time, the livers of these animals regenerated at a pace found in young mice. Cell proliferation peaked at just two days, and the liver was fully restored within a week.

By comparison, in aged mice that did not receive hormone injections, complete regeneration took a month or longer. Without growth hormone to turn on Foxm1b, the gene remained stuck at the low level of activity found in old age, and liver cells failed to multiply rapidly enough for a quick recovery.

Further tests were done with genetically engineered mice in whose liver cells the Foxm1b gene had been disabled. In these mice, growth hormone injections failed to stimulate recovery when the liver was partially removed.

"These results clearly demonstrate that Foxm1b is essential for growth hormone to spur liver regeneration," Costa said.

The study is apt to provide impetus for high-end clinics and spas already offering growth hormone injections to "treat" old age, but Costa is cautious about drawing any conclusions from his research about the merits of the therapy.

"Our liver regeneration studies tell us a great deal about how growth hormone works at a molecular level, but the injections occurred only over short periods of time, giving us no information about any long-term consequences," Costa said.

While several studies have shown that prolonged growth hormone therapy has dangerous side effects ranging from diabetes to carpal tunnel syndrome, Costa believes that short-term treatment with growth hormone could be used to speed repair after injuries or surgery in the elderly, shortening recovery time.


###
The National Institute of Diabetes and Digestive and Kidney Diseases and the National Institute on Aging provided funding for the study. Other UIC scientists involved in the research were Katherine Krupczak-Hollis, Xinhe Wang and Margaret Dennewitz.

Sharon Butler | EurekAlert!
Further information:
http://www.uic.edu/

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 >>>