Researchers based at the Buck Institute for Research on Aging, in San Francisco, California, have reported results on the impact of dietary restriction, circadian rhythms and lifespan, at least in the context of Drosophila research. Results of their research, published in Nature Communications (2022, Vol. 13, 1, 3156), reported that dietary restriction (DR) may extend lifespan by promoting circadian homeostatic processes and protecting the visual system from age- and light-associated damage. According to a senior author on the paper, Professor Pankaj Kapahi commented that, “our study argues that [work] is more than correlation: dysfunction of the eye can actually drive problems in other tissues. We are now showing that not only does fasting improve eyesight, but the eye actually plays a role in influencing lifespan.”
In the research study, circadian processes appeared to show highly elevated gene expression in the context of dietary restriction (DR). In particular, DR enhanced the “rhythmic expression of genes that encode proteins that are involved in light adaptation (i.e., calcium handling and deactivation of rhodopsin-mediated signalling)”, reported in their journal. In follow up to this observation, the researchers showed that the majority of circadian phototransduction genes were transcriptionally regulated by “CLK” (transcription factors Clock), and turning off this transcription factor appeared to accelerate visual decline with age. In addition, disrupting photoreceptor homeostasis appeared to increase systemic immune responses and shortened lifespan. From evaluating the outcome of the experiments, eye-specific CLK-output genes were upregulated in expression in response to dietary response, and this DR approach may slow visual senescence and extend lifespan.
One observation in terms of human activity may suggest how modern lifestyles might impact on biology. Professor Kapahi commented that, “staring at computer and phone screens, and being exposed to light pollution well into the night are conditions very disturbing for circadian clocks. 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.” Add into a sedentary lifestyle with an “ad libitum” food consumption habit, eye health and lifespan impacts negatively. In the their study, the researchers indicated that reducing specific nutrients or total calories, is the most “robust mechanism for delaying disease and extending lifespan. The mechanisms by which DR promotes health and lifespan may be integrally linked with circadian function, as DR enhances the circadian transcriptional output of the molecular clock and preserves circadian function with age”. In contrast, high-nutrient diets, including excess consumption of protein, fats, or total calories may repress circadian rhythms and shortening organismal lifespan.