Living well into their senior years is a dream for many people. As animals age, their mitochondria progressively become less functional; they produce less energy in the form of adenosine triphosphate (ATP) and more inflammatory compounds such as reactive oxygen species (ROS). Keeping active and continuing your favourite activities for the majority of your golden years is tricky, but a new study using the model species fruit fly Drosophila melanogaster suggests that exposure to near-infrared light – that's red light on the very end of the visible spectrum – might help out.
Cytochrome c oxidase is a key enzyme in the electron transport chain in the mitochondria, responsible for pumping protons across the mitochondrial membrane to provide a proton gradient to help other enzymes produce ATP. Researchers in the past have also found that absorbing near-infrared light improves cytochrome c oxidase's proton pumping efficiency, which helps the mitochondria produce more ATP. As ageing animals produce less ATP, Rana Begum from University College London, UK, and colleagues from Universidade Federal Fluminense, Brazil, and Moorfields Eye Hospital, UK, decided to investigate whether exposure to near-infrared light improved activity later in life in D. melanogaster.
The researchers housed newly metamorphosed adult flies in small containers that had a rack of built-in ‘heat lamps’ – LED lights that produced a small dose of radiation at the near-infrared wavelength of 670 nm – that the flies were exposed to for 20 min each day. Then, as the flies aged over a period of 3 months, the researchers assessed the insects’ climbing ability, survival and the amount of available energy in ATP.
While the extent of the very longest lifespans did not differ between the groups, flies that had a daily sunning session lived longer on average. They also produced much more ATP and less of a protein marker of inflammation, which suggested they were producing fewer inflammatory compounds like ROS. Finally, the senior citizen flies that had been bathing in the lamps’ warmth were able to climb much better than their control counterparts – a key marker of activity level. So, even a short dose of daily near-infrared light allowed geriatric flies to have much more active lives and extended their health span.
As promising as these results are, the researchers note this type of whole-body exposure would not work with mammals because near-infrared radiation would not pass through their larger bodies as it does with flies. Instead, their study suggests that ageing is at least partially due to ATP limitation and that this might be why fast-ageing tissues that can absorb in the 670 nm range – like the retina – are treatable with near-infrared light. While we're a long way off providing humans with the benefits that the flies received from their glowing infrared lamps, understanding the mechanisms behind the effects of ageing could lead to treatments that might give a better quality of life to seniors of all species.