It's an age-old search: the secret to eternal youth. For centuries, the dream of a single factor that may increase our lifespan has been at the forefront of many legends, excursions, and of course, advertising campaigns. But while this search has been fruitless for the majority of us, there is hope for a future in which we could all live beyond the current life expectancy.
The answer, however, may lie not in water, food or lifestyle, but in our relationship with germs.
Research into longevity is not entirely new and has been the life work of many a scientist. Perhaps the most important discovery happened some 20 years ago with the identification of small proteins in the cell called Forkhead Box (FOX) transcription factors. These proteins are diverse -- there are more than 100 of them -- and they help to control the cell's life...and death. But one of them, known as FOXO, held an even greater potential as a possible cellular fountain of youth.
Unfortunately, while there was interest, little was understood about how FOXO was manipulated to improve longevity. The only clue came from a study performed four years earlier, in 2001, when a team of researchers from the University of Dundee discovered a significant difference between the gut microbiota of the young and elderly.
Based on their findings, the microbial diversity inside the gastrointestinal tract decreased with age, leaving the elderly with a higher number of bacteria known to be associated with chronic diseases. However, while this was a good start, there was still little evidence to suggest that this could be linked to longevity.
It wasn't until 2012 when a multinational team based in Uruguay decided to find out whether there was a possible link between microbes and FOXO. Instead of humans, they performed their tests on a small worm, Caenorhabditis elegans, which are known to have a similar FOXO protein. The experiments were rather simple in that they fed the creatures a known probiotic, Lactobacillus rhamnosus, and determined if there was any change in lifespan. They were rather surprised at the extent of the change. On average, a worm fed the probiotic lived about 20 per cent longer. What was even more impressive was that the results suggested that the key to a longer life was dependent on the amount of low level inflammation. When inflammation was reduced, life was extended.
The data gave an Italian group of researchers the incentive to determine whether there was a difference between people that lived to a normal age and those who lived beyond 100 years of age. Once again, the results from the study showed centenarians possessed a very different gut microbiota composition. The most remarkable detail was that much like the study in worms, the majority of bacteria were known to be involved in controlling inflammation.
But while there was a circumstantial link between the microbiome, FOXO and longevity, there was still no concrete evidence to show that germs were indeed a contributing factor to living longer. But this week, a team of researchers from California and New York State may have finally shown the link. However, as their paper suggests, the answers are far from simple.
The team worked with another model organism, the fruit fly. Using genetic engineering, the researchers developed flies that either could not express FOXO or expressed too much of the protein. They also looked at the microbial composition of the gut to see if there were any changes and whether that was associated with lifespan. The experiments were somewhat complicated but the results revealed an incredible interaction between FOXO, microbes and longevity.
The natural process of aging leads to changes in the gut microbiome. Without proper supplementation of good germs, the change will continue to move away from health towards disease. As that happens, FOXO leads the body towards a state of inflammation. Once that has happened, a vicious cycle happens that can lead to a reduced lifespan and poorer health.
However, if good germs are continually supplemented -- including probiotics -- then the cycle is disrupted allowing for improved health and longer life. In essence, as the body ages, it turns against itself to move towards death. This may then be stopped by bringing in the good germs.
Although the data presented is at the moment limited to fruit flies, the results offer some hope for future research into the future of human longevity. We already know probiotics have anti-inflammatory effects and help to balance the gut against dysbiosis; it would be simple to hypothesize that the work in flies may be applicable to humans.
Yet without clinical trials, the real answer may never be known. Still, for those searching for the real fountain of youth, turning to good germs, while perhaps not being the true means for eternal life, may still offer some great benefits to health and happiness, regardless of lifespan.
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