August 30, 2013
Single Gene Adds 20 Percent To Mouse Lifespan
April Flowers for redOrbit.com - Your Universe Online
Researchers led by the National Institutes of Health (NIH) have extended the average lifespan of a group of mice by lowering the expression of a single gene. The lifespan of the mice was increased by about 20 percent, or the equivalent of raising the average human life span by 16 years, from 79 to 95. The researchers focused on a gene called mTOR, which is involved in metabolism and energy balance, and might be connected with an increase in lifespan associated with caloric restriction.
The study, published in the journal Cell Reports, revealed the gene-influenced lifespan extension did not affect every tissue and organ the same way. The mice retained better memory and balance as they aged, for example, but their bones deteriorated more quickly than normal.
"While the high extension in lifespan is noteworthy, this study reinforces an important facet of aging; it is not uniform," explained lead researcher Dr Toren Finkel at NIH's National Heart, Lung, and Blood Institute (NHLBI). "Rather, similar to circadian rhythms, an animal might have several organ-specific aging clocks that generally work together to govern the aging of the whole organism." Finkel is also the head of the NHLBI's Laboratory of Molecular Biology in the Division of Intramural Research.
He notes the findings of this study might help guide therapies for aging-related diseases that target specific organs, such as Alzheimer’s. The research team says further studies in these mice, as well as human cells, are required to identify exactly how aging in these different tissues is connected at the molecular level. The NHLBI research team was joined in this study by intramural researchers at the NIH's National Cancer Institute; National Institute of Diabetes and Digestive and Kidney Diseases; and National Institute on Aging.
The mice used in the study were engineered to produce about 25 percent of the normal amount of the mTOR protein. This is the minimal amount necessary for survival. These mice were slightly smaller than average but otherwise appeared normal.
The mTOR mice had a median lifespan of 28.0 months for males and 31.5 months for females. Normal males live 22.9 months and females live 26.5 months. Seven of the eight longest lived mice in this study were mTOR mice, meaning the mTOR mice had a longer maximal lifespan. The researchers report this lifespan increase is one of the largest observed in mice to date.
The mTOR mice aged better overall, however, they showed only selective improvement in specific organs. The mTOR mice generally outperformed normal mice of equivalent age in maze and balance tests, this indicates better memory retention and coordination. More muscle strength and posture were retained by older mTOR mice as well. However, the mTOR mice did show a greater loss in bone volume as they aged. They were also more susceptible to infections at old age, suggesting a loss of immune function.