Have you ever noticed that fluctuating emotions can cause a reaction in your stomach? You may feel butterflies with love, nausea with anxiety and gut-wrenching fear. This is because the brain has a direct effect on the gastrointestinal system. This also means that when you are experiencing stress — chronic stress or ongoing tension from daily stressors, such as quizzes or that next homework assignment — your gastrointestinal health is impacted.
Adam Moeser, assistant professor of swine medicine and gastrointestinal physiology in the department of population health and pathobiology, received a five-year, $1.5 million grant from the National Institutes of Health to further his research studying the physiological changes in the GI tracts of pigs that have undergone early life stress. Pigs and humans experience stress in similar ways, which often causes internal complaints.
“There was a specific call for proposals that had dual benefits,” Moeser said. “Dual purpose and dual benefit for projects that had impact or relevance to human health while at the same time they could have impact to animal health.”
According to Moeser, his research program was the perfect fit, with stress having a major role in GI disease in humans and animals.
“In humans, there’s an increasing prevalence of stress-related GI diseases such as irritable bowel syndrome and inflammatory bowel diseases as well as a number of other diseases,” Moeser said. “We know that stress is playing a major role in either increasing the susceptibility of a person to become sick with these disorders, or if a person has these disorders [stress] heightens the disease or exasperates it.”
According to Moeser, increasing evidence has shown that early-life stressful events in humans, whether they’re infections or psychological or traumatic stresses, are more likely to cause inflammatory diseases later on in life.
“Based on our previous research in the lab, we’ve shown that when stresses occur early in life or early in development they can have lasting effects on the development of the GI system that makes the animal more susceptible to diseases later in life,” Moeser said.
Moeser said his research concentrates specifically on early-life stress as well as the interest of gender in the process.
“We are really interested in how gender plays a role in this,” Moeser said. “With stress-related disorders there seems to be … a gender-specific effect where females are actually more susceptible to developing more stress related gastrointestinal diseases. We’re finding the same thing in the lab and in our research and in our animal models.”
Using swine as a model for GI stress, Moeser said using pigs as models for GI stress is appropriate because pigs are the best mirrors for research and can eventually translate to humans.
“The pig is more similar to the human as far as anatomy, physiology and development — in particular, the GI system,” Moeser said. “Pigs have long been known to be appropriate model for human diseases but we’re learning more about the gastrointestinal tract and how they’re very similar to humans and they may better predict the diseases in humans.”
In order to research the effect early-life stress can have on the GI tract, Moeser had to decide upon an event that was significantly stressful in an animal’s life.
“We felt that weaning was an event we should focus on,” Moeser said. “The weaning is very stressful especially for pigs because they’re removed from their mom and they’re often removed from their littermates. There’s a lot of social anxiety as you can imagine that would take place in these animals. Right after weaning the animal is actually more susceptible to disease.”
Similar to humans, the psychosocial stresses pigs go through during the weaning process cause the physiological pathways to become activated during the stress response.
“It’s difficult, obviously, to ask an animal if they’re stressed or not,” Moeser said. “We use biological markers for stress because the stress response in animals is well conserved all the way from lower species to humans. There are key biological pathways that we can measure like the corticotrophin-releasing factor system is activated in stress in mice, pigs and humans.”
According to Moeser, one of the key measurements he has studied is the permeability of the intestinal tract.
“We found a link between stress and intestinal permeability,” Moeser said. “Once that permeability becomes increased, it can lead to diseases. We’re trying to understand the biology behind that. What does stress do to increase something like leaky gut and then how can we circumvent that?”
Moeser said the biggest curiosity within the recent research is the previously unstudied gender effect.
“We would expect there would be a gender influence, but what we didn’t expect was that we would see changes at such an early age before sexual maturity,” Moeser said. “It’s always been thought that sexual maturity and sex related hormones like estrogen and testosterone would be contributed to gender differences. We’re finding that that’s not the full story. There are actually potentially innate genetic differences that could be contributing to disease and to the stress response. It seems like every day we find something that’s interesting.”