Scientists at University College London are exploring why some mice live longer. They have shown that mice who do not have the insulin receptor substrate (IRS)-1 tend to live longer than normal mice. There has been a lot of research that has shown that insulin signaling pathways play a part in animals, and possibly in humans
Im the study, they used mice who had been engineered one or the other of two insulin receptor substrates, IRS-1 or IRS-2, which are proteins that are activated by insulin.
The study showed that the mice without the IRS-1 had an increased life span of 20% when compared with the life span of normal mice. And the females did better than the males, averaging 30%. The life expectancy of a mouse is about 25 months. One of the mice without the IRS-1 actually lived for 38 months, 66% longer.
Living longer was not the only difference. The mice also had better health as they got older, for instance, their eyes were brighter, they were more alert and just healthier overall.
But the mice that did not have the IRS-2 did not do so well. They actually lived shorter lives than the normal mice and have symptoms of obesity and type 2 diabetes.
The results show that mice without IRS-1, and especially female mice, not only live longer, but are resistant to signs of aging such as skin, bone, immune, and motor dysfunction
Furthermore they achieved this results in spite of the fact that by removing the IRS-1, they made the mice resistant to insulin and that lasted for their entire lifetime. This indicates that IRS-1 is a pathway designed by evolution to regulate the lifespan in mammals and it may be an indicator that the same thing can happen in humans.
They are looking for the reason why, but one possible reason could be that it only makes them mildly resistant to insulin and instead of having a negative effect, it helps increase resistance to stress, protects the cells from damage, and acts as a trigger for other reactions that extend life without having any negative effects of health.
There have been other studies done that have shown mutations in individual genes in the insulin pathway are also able to give animals a longer lifespan. But, this is the first one that shown that, in addition to making the animals live longer, it also gives them a better quality of life.
The lead author on the project is Professor Dominic Withers, who works with the UCL Centre for Research on Aging
Source: University College London http://www.ucl.ac.uk/