An intricate relationship between the gastrointestinal (GI) tract and the part of the brain that senses smell contributes to human longevity, a new study shows. The middleman that facilitates this relationship? Autophagy.
Autophagy is the cellular process of removing debris and delivering it to an organelle called a lysosome to be degraded, like recycling or taking out the trash to keep your house clean of things you don’t need anymore. The goal of autophagy is simple, but its effects are complicated and diverse. Many studies on autophagy have shown that the process is vital for tumor suppression, targeting microorganisms in the body, and inhibiting the aging process.
In a new study from Florida Atlantic University published in the journal PLOS Genetics, researchers unveil how autophagy, nutrient absorption, and olfactory neurons are intertwined to influence natural human aging.
"If you want to extend the lifespan of any animal, after limiting their diet, you have to have functional autophagy in this animal otherwise you won't see this lifespan extending effect," explained corresponding author Kailiang Jia, PhD. In the new study, Jia and the other study authors found that autophagy is closely linked to lifespan because of its influence over nutrient absorption and olfaction.
"Autophagy can be activated and enhanced when you restrict calories, and we can actually see the autophagy process activated through caloric restriction," Jia explained. "With disease, when you decrease autophagy the disease process is exacerbated, and when you increase it you get the opposite effect."
Jia and the research team first realized the anti-aging role of smelling food in an experiment with fruit flies. Put simply, the flies on a restricted diet who were allowed to smell their food lived longer than the flies who couldn’t smell their food. Now, the researchers turn to model organism C. elegans to learn more about how autophagy, both in the nervous system and the GI tract, is connected to the aging process.
They found that autophagy is required for a neuroendocrine pathway that facilitates the conversation between sensory neurons and nutrient levels in the GI tract. When olfactory neurons sense a food’s smell, they secrete neuron signals, which influence aging. This pathway is mediated by autophagy.
In the GI tract, autophagy is regulated by nutrients that are consumed through food and absorbed in the gut. Together, autophagy in the brain and in the GI tract influence aging.
This current study sets the groundwork for an intriguing cellular relationship between the food we eat, the food we smell, and how are body’s cells break down and recycle cellular debris. Along with continued work on the application to anti-aging, the study’s authors plan to apply these findings to potential treatments for cancer, obesity, and neurodegenerative diseases.