A group of Japanese scientists has found the answer to the puzzle, according to a study by researchers at Japanese universities in Tokyo and Saga, published by the online edition of the journal Human Reproduction.

The tests in mice indicate that paternal sperm is responsible for the shorter longevity of mammalian male versus females.

In their experiment, scientists have discovered that mice created using genetic material from two mothers and without the involvement of a parent living up to one third longer than normal mice with a mixture of maternal and paternal genes.

To explore this issue, researchers began to study the lifespan of mice produced no sperm. To this end, immature oocytes collected from mice one day old, manipulated the genetic material of these genes to behave like sperm and transplanted genes from this genetic material in unfertilized mature oocytes from adult mice that had eliminated the core.

These reconstructed oocytes became embryos which were transferred to a female mouse. The resulting pups had genetic material from two mothers but no father.

Furthermore, the authors created mice control through a natural pairing that were genetically identical mice from two mothers, irrespective of the fact that they were created in the normal way with genes of male and female mice. Both groups of mice were kept in the same environments without infections and with free access to food.

The study results were inconclusive. The mice created from two genomes women lived an average of 186 days longer than control mice created from the combination of a normal female and one male genome, whose life expectancy is between 600 and 700 days. These modified mice seemed to have a better immune system, with a significant increase in a type of white blood cell, eosinophils.

The study authors believe the reason for the difference in longevity may be related to a gene on chromosome 9, named Rasgrf1. “This gene is usually expressed from the chromosome inherited from the father and is a gene on chromosome 9 associated with postnatal growth,” said Tomohiro Kono of Tokyo University and co-author.

“Does not just genetics”

“This is very important genetic component in longevity of people,” agrees Mary Flora de Pablo, Professor, Biological Research Center of CSIC. The researchers say the study is “interesting model” which completes the analysis of the lifespan of mice on a type called “bimaternos” and on data that had already been published since 2004.

But longevity also “depends on environmental factors, modifiable,” explains De Paul. For example, “low-calorie diet, (without going to malnutrition) increases longevity and delays the onset of diseases associated with aging,” qualifies the teacher.

The end result of increased life expectancy in women than men in the developed world “is also a significant component derived from lower-risk behaviors in women than in men,” says the researcher, including appointment to a lower consumption of alcohol and drugs.

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