New research out of the University of Massachusetts Medical School sheds light on how our stress responses, especially the “fight-or-flight” response, may be harming our health over the long term.
Specifically, Dr. Mark Alkema, professor of neurobiology, and his crew have been investigating the way in which the dynamic regulation of a stress neurohormone modulates and regulates the trade-off between long-term stress responses and acute ones.
To accomplish their task, the researchers studied stress responses in the nematode worm, c. elegans, which is a common research model. Their findings were published in Nature.
During human response to stressful situations, adrenaline, a powerful stress hormone, is released into the human body. Adrenaline increases heart rate, helps maximize blood flow to the muscles and brain and stimulates the production of sugar for fuel in the body. This is how the “fight-or-flight” response is initiated and is what gives you the ability to either fight the tiger (or your boss or who/whatever) or run away. Threats vary, but the primal response remains much the same.
In cooperation with the laboratory of Professor Diego Rayes at the National University of South in Argentina, Dr. Alkema repeatedly initiated the “fight-or-flight” response in the nematode c. elegans. He then observed the impact on the health of the critters. It may seem odd to study a worm to understand human neurohormonal response to stress, but c. elegans has already helped us answer a variety of fundamental biological questions, from those on disease to those on brain function.
There are a wide variety of potential stressors to which animals are exposed. They include abrupt, or acute stressors like being attacked or threatened by a predator or more progressive, or chronic stressors like high temperatures, chronic food shortages or exposure to disease.
“Much like in humans, repeated activation of the flight response in C. elegans drastically shortened lifespan,” said Jeremy Florman, PhD candidate in the Alkema lab. “The flight response is crucial for the worm to escape from predators. But we find there is a cost; the repeated activation of the flight response reduces the worm’s capacity to deal with other challenges it encounters in its environment.”
In the study, investigators found that the flight response in C. elegans triggers the activation of a single pair of neurons that release tyramine, the invertebrate analog of adrenaline. In contrast, exposure to environmental challenges such as heat and oxidative stress reduces tyramine release. This stress hormone thus provides a switch that regulates the animal’s response to either acute or long-term stressors.
Alkema and Rayes went on to show that tyramine stimulates the insulin pathway through the activation of an adrenergic-like receptor in the intestine. The activation of the insulin pathway can satisfy the animal’s energy demands of the flight response. On the other hand, the down-regulation of the insulin pathway is needed help to protect cells from environmental stress and extend lifespan.
“This shows how a dynamic regulation of a stress neurohormone regulates the trade-off between acute and long-term stress responses,” said Alkema. “The worm never ceases to amaze me; it keeps revealing fundamental molecular and neural mechanisms that may underlie even extremely complex human biology and disorders. Given the striking conservation of stress response mechanisms from worms to humans, it will be very interesting to see whether in humans the fight-or-flight response and stress neurohormones negatively impact health and aging through the activation of the insulin pathway.”
Whether you’re a worm or a human, it seems tyramine may play a key role in how stress may increase wear on the body and impede the proper function of the body’s systems.
Keep the faith and keep after it!