There seems to be one surefire way to increase longevity in animals. It's caloric restriction, which means placing them on a near-starvation diet. We don't know if that could work on humans... but fruit flies might be able to give us the answer.
There's no reason to think that caloric restriction wouldn't work on humans, but it's not something that's easily tested. After all, an experiment designed to test the effectiveness of human caloric restriction would, by design, have to run at least a hundred years, and there are some thorny ethical questions about asking people to spend a century fasting if we're not even sure if they would get any longevity benefit out of it. And, of course, there's also the question of whether 150 years of caloric-restricted living is really better than 80 normal years.
But it would still be good to know just what caloric restriction could do for humans, or better yet to understand the underlying processes that make it so effective at increasing longevity. Now, researchers at the Salk Institute for Biological Studies may have found a way to get at an answer. They took some fruit flies and tweaked a gene in their intestinal stem cells. This gene, called PCG-1, is also found in humans. This tweak to their genes delayed the aging of their intestines and extended their lifespan by up to fifty percent.
Lead scientist Leanne Jones explains why this could be good news for humans:
"Fruit flies and humans have a lot more in common than most people think. There is a tremendous amount of similarity between a human small intestine and the fruit fly intestine."
One of the few things we know for certain about caloric restricted animals is that they have a greater quantity of mitochondria, which are the energy-producing powerhouses of the cells. Researchers think that this uptick in mitochondria might be a big part of why these animals can live twice as long as their peers. It's all the benefits of caloric restriction without actually having to bother with the whole caloric restriction bit.
The PCG-1 gene regulates how many mitochondria are created. Leanne Jones and her team seized on that by tweaking the fruit fly PCG-1 gene so that it went into overdrive, creating tons more mitochondria. The flies who received this genetic engineering enjoyed better health and longer lifespans, generally about 20 to 50% longer than those of their peers. Part of this may be because PCG-1 also stimulates the stem cells responsible for the intestinal tissues, which means boosting PCG-1 also keeps the intestine healthier.
Fellow researcher Christopher L. Koehler describes these flies and their guts:
"Their intestines were beautiful. The flies with the modified gene activity were much more active and robust than the other flies."
We're still a ways off from making use of this with humans — and even if we started tomorrow, it might not be until 2111 that we really know if PCG-1 can boost human longevity — but Leanne Jones sees way in which this could be adapted to help people in the near-term. She says PCG-1 could prove useful in slowing down the spread of age-related diseases:
Slowing the aging of a single, important organ — in this case the intestine — could have a dramatic effect on overall health and longevity. In a disease that affects multiple tissues, for instance, you might focus on keeping one organ healthy, and to do that you might be able to utilize PGC-1."