Your eyes often betray how you’re feeling, the clearest example being tears. However, emotion is not the only insight your eyes offer. The health of your eyes may have a direct correlation on how long you will live, new research suggests.
A team from the US-based Buck Institute for Research on Aging has found a link between diet, circadian rhythms, eye health, and lifespan.
“Our study argues that it is more than correlation: dysfunction of the eye can actually drive problems in other tissues,” said senior author and Buck Institute Professor Pankaj Kapahi, PhD, whose lab has demonstrated for years that fasting and caloric restriction can improve many functions of the body.
“We are now showing that not only does fasting improve eyesight, but the eye actually plays a role in influencing lifespan.”
To gather their findings, the study authors examined the link between eyes health and lifespan among Drosophila — the common fruit fly.
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Lead author, Brian Hodge, PhD, said: “The finding that the eye itself, at least in the fruit fly, can directly regulate lifespan was a surprise to us.”
The explanation for this connection, Hodge said, lies in circadian “clocks,” the molecular machinery within every cell of every organism, which have evolved to adapt to daily stresses, such as changes in light and temperature caused by the rising and setting of the sun.
These 24-hour patterns – circadian rhythms – affect complex animal behaviours, such as predator-prey interactions and sleep/wake cycles, down to fine-tuning the temporal regulation of molecular functions of gene transcription and protein translation.
The new finding follows previous research conducted in Professor Kapahi’s lab in 2016.
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“That seemed very strange to us,” said Doctor Hodge. “We had thought flies needed the lighting cues to be rhythmic, or circadian.”
They then used bioinformatics to ask: Do the genes in the eye that are also rhythmic and responsive to dietary restriction influence lifespan? The answer was yes they do.
“We always think of the eye as something that serves us, to provide vision. We don’t think of it as something that must be protected to protect the whole organism,” said Professor Kapahi, who is also an associate adjunct professor of urology at UCSF.
Since the eyes are exposed to the outside world, he explained, the immune defences there are critically active, which can lead to inflammation, which, when present for long periods of time, can cause or worsen a variety of common chronic diseases. Additionally, light in itself can cause photoreceptor degeneration which can cause inflammation.
“Staring at computer and phone screens, and being exposed to light pollution well into the night are conditions very disturbing for circadian clocks,” Professor Kapahi said. “It messes up protection for the eye and that could have consequences beyond just the vision, damaging the rest of the body and the brain.”
There is much to be understood about the role the eye plays in the overall health and lifespan of an organism, including: How does the eye regulate lifespan, and does the same effect apply to other organisms?
The biggest question raised by this work as it might apply to humans is, simply, do photoreceptors in mammals affect longevity? Probably not as much as in fruit flies, said Doctor Hodge, noting that the majority of energy in a fruit fly is devoted to the eye.
But since photoreceptors are just specialised neurons, he said, “the stronger link I would argue is the role that circadian function plays in neurons in general, especially with dietary restrictions, and how these can be harnessed to maintain neuronal function throughout ageing”.
Once researchers understand how these processes are working, they can begin to target the molecular clock to decelerate ageing, said Doctor Hodge, adding that it may be that humans could help maintain vision by activating the clocks within our eyes. “It might be through diet, drugs, lifestyle changes… A lot of really interesting research lies ahead,” he said.Once researchers understand how these processes are working, they can begin to target the molecular clock to decelerate ageing, said Doctor Hodge, adding that it may be that humans could help maintain vision by activating the clocks within our eyes. “It might be through diet, drugs, lifestyle changes… A lot of really interesting research lies ahead,” he said.