Changing the gut microbiome to beat illness really does hold great potential, said Vanderbilt University biologist Seth Bordenstein, but first scientists must answer what constitutes a healthy gut microbiome and in whom. By studying data on nearly 1,700 Americans of varying genders, ages, weights and ethnicities, they learned that gut microbiome differences among ethnicities are the most consistent factor.

That discovery holds promise in the burgeoning field of individualized medicine, because it is far easier to change a person’s microbiome than their genes — the other major markers for disease. In addition, many chronic diseases disproportionately affect ethnic minorities, with underlying causes of that difference unexplained. Perhaps some answers lie in the gut microbiome.

“Human genomes are 99.9 percent the same between any two people, so what we’re really interested in is what explains the marked variations in gut microbiomes between people,” said Bordenstein, associate professor of biological sciences. “What are the rules, and can we manipulate that microbiome in order to improve health and medicine in the long run? If you look at common factors associated with gut microbiome differences, such as gender, weight or age, you find many inconsistencies in the types of gut bacteria present. But when we compare differences by patients’ self-declared ethnicities, we find stable and consistent features of bacteria present in the gut.”

The work was done in collaboration with a team at the University of Minnesota, and the results, outlined in a paper titled “Gut Microbiota Diversity across Ethnicities in the United States,” appears today in the journal PLOS Biology.

The team discovered 12 particular types of bacteria that regularly vary in abundance by ethnicity. Because ethnicity captures many factors, ranging from diet to genetics, it’s difficult to say why this is, said Andrew Brooks, the Vanderbilt doctoral student in the Vanderbilt Genetics Institute who analyzed data provided by the American Gut Project and Human Microbiome Project. But it’s a baseline for understanding healthy microbiome differences among individuals.

Bordenstein is director of the Vanderbilt Microbiome Initiative, a collaboration among five Vanderbilt schools and colleges to advance microbial discoveries and, ultimately, get them into the hands of doctors for precision and preventative medicine.

“You may buy probiotics over the counter at a drugstore, but those are unlikely to affect your microbiome in a substantial way,” Bordenstein said. “They often are at too low a dose, and they may not even be viable bacteria. Moreover, one size may not fit all. But with more of this kind of research, we can hone in on the relevant differences and doses of bacteria that may reverse illness or prevent it from developing in the first place.”

Microbiome Initiative, funded by the Trans-Institutional Programs; and an Alfred P. Sloan Foundation Fellowship.

The 12 bacteria featured in this research are:

• Christensenellaceae
• Clostridiales
• Coriobacteriaceae
• Dehalobacteriaceae
• Odoribacter
• Odoribacteriaceae
• Peptococcaceae
• RF39
• Rikenellaceae
• Veillonella
• Verrucomicrobiaceae
• Victivallaceae

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Materials provided by Vanderbilt University. Original written by Heidi Nieland Hall. Note: Content may be edited for style and length.

Until now, research exploring how and why cute aggression occurs has been the domain of behavioral psychology, said Katherine Stavropoulos, an assistant professor of special education at the University of California, Riverside. But recently Stavropoulos, a licensed clinical psychologist with a background in neuroscience, has taken formal study of the phenomenon a few steps further.

In her research, Stavropoulos uses electrophysiology to evaluate surface-level electrical activity that arises from neurons firing in people’s brains. By studying that activity, she gauges neural responses to a range of external stimuli.

Stavropoulos said she first heard the term “cute aggression” after a team of Yale University psychologists released research related to the phenomenon in 2015. 

“The Yale researchers initially found that people reported feeling cute aggression more in response to baby animals versus adult animals,” Stavropoulos said. “But even beyond that, people reported feeling cute aggression more in response to picture of human babies that had been digitally enhanced to appear more infantile, and therefore ‘more cute,’ by enlarging features like their eyes, cheeks, and foreheads.”

After poring over the Yale research, Stavropoulos wondered whether there was a neural component to cute aggression. If people reported experiencing urges to squeeze, crush, or even bite creatures they found cute, would their brains also reflect patterns of activity that could be tied to those urges?

Stavropoulos hypothesized that the brains of people who reported experiencing cute aggression would, in fact, provide evidence of detectable activity. She suggested the activity might be related to the brain’s reward system, which deals with motivation, feelings of “wanting,” and pleasure, or to its emotion system, which handles emotional processing — or, more likely, to both. 

Stavropoulos and UCR doctoral student Laura Alba recruited 54 study participants between the ages of 18 and 40, all of whom agreed to wear caps outfitted with electrodes. While wearing the caps, participants looked at four blocks of 32 photographs divided into categories: 

• Cute (enhanced) babies
• Less cute (non-enhanced) babies
• Cute (baby) animals
• Less cute (adult) animals

After viewing each block on a computer screen, participants were then shown a set of statements and asked to rate how much they agreed with them on a scale of 1 to 10. 

The survey was designed to assess how cute participants found each block of photographs — known as “appraisal” — and how much cute aggression they were experiencing in response. Participants also rated how overwhelmed they felt after viewing the photos (“I can’t handle it!” and “I can’t stand it!”) and whether they felt compelled to take care of what they had just viewed (“I want to hold it!” and “I want to protect it!”). 

Stavropoulos said the statements were the same ones used in Yale researcher Oriana Aragón’s groundbreaking 2015 study of cute aggression.

Overall, participants self-reported more significant feelings of cute aggression, being overwhelmed, appraisal, and caretaking toward cute (baby) animals than toward less cute (adult) animals. Among the two categories of babies — cute (enhanced) and less cute (non-enhanced) — the researchers did not observe the same pattern. 

Using electrophysiology, Stavropoulos also measured study participants’ brain activity before, during, and after viewing the sets of images. To her knowledge, the study’s results, published this week in the journal Frontiers in Behavioral Neuroscience, are the first to confirm a neural basis for cute aggression. 

Based on the neural activity she observed in participants who experienced cute aggression, Stavropoulos’s findings offer direct evidence of both the brain’s reward system and emotion system being involved in the phenomenon.

“There was an especially strong correlation between ratings of cute aggression experienced toward cute animals and the reward response in the brain toward cute animals,” Stavropoulos said. “This is an exciting finding, as it confirms our original hypothesis that the reward system is involved in people’s experiences of cute aggression.” 

Another result that Stavropoulos said lends weight to prior theories: The relationship between how cute something is and how much cute aggression someone experiences toward it appears to be tied to how overwhelmed that person is feeling.

“Essentially, for people who tend to experience the feeling of ‘not being able to take how cute something is,’ cute aggression happens,” Stavropoulos said. “Our study seems to underscore the idea that cute aggression is the brain’s way of ‘bringing us back down’ by mediating our feelings of being overwhelmed.”

Stavropoulos likened this process of mediation to an evolutionary adaptation. Such an adaptation may have developed as a means of ensuring people are able to continue taking care of creatures they consider particularly cute.  

“For example, if you find yourself incapacitated by how cute a baby is — so much so that you simply can’t take care of it — that baby is going to starve,” Stavropoulos said. “Cute aggression may serve as a tempering mechanism that allows us to function and actually take care of something we might first perceive as overwhelmingly cute.”

In the future, Stavropoulos hopes to use electrophysiology to study the neural bases of cute aggression in a variety of populations and groups, such as mothers with postpartum depression, people with autism spectrum disorder, and participants with and without babies or pets. 

“I think if you have a child and you’re looking at pictures of cute babies, you might exhibit more cute aggression and stronger neural reactions,” she said. “The same could be true for people who have pets and are looking pictures of cute puppies or other small animals.”

A new study from UT Southwestern Medical Center shows neurons in mice that influence metabolism are active for up to two days after a single workout. The research offers new insight into the brain’s potential role in fitness and — in the longer term — may provide a target for developing therapies that improve metabolism.

“It doesn’t take much exercise to alter the activity of these neurons,” said Dr. Kevin Williams, a neuroscientist at UT Southwestern. “Based on our results, we would predict that getting out and exercising even once in a semi-intense manner can reap benefits that can last for days, in particular with respect to glucose metabolism.”

The study, published in the December edition of Molecular Metabolism, measured the effects of short- and long-term exercise on two types of neurons that comprise the melanocortin brain circuit, which is shared by both humans and mice. One of the neuron types (POMC) is associated with reduced appetite, lower blood glucose levels, and higher energy burning when activated; the other type (NPY/AgRP) increases appetite and diminishes metabolism when activated.

The study found that a single bout of exercise can boost the activity of POMC neurons and inhibit the counterpart NPY/AgRP neuron for up to two days. Those changes last longer with more training.

The findings expand the scientific understanding of the melanocortin circuit, which previous studies showed could be altered through feeding or fasting but had not yet been linked to exercise.

The results also provide another avenue to research potential treatments to improve glucose metabolism in patients with conditions such as diabetes. More than 30 million Americans have diabetes, accounting for nearly 10 percent of the population. Another 84 million have prediabetes, which can lead to diabetes within five years, according to the Centers for Disease Control and Prevention.

“It is possible that activating melanocortin neurons may hold therapeutic benefits for patients one day, especially for diabetics who need improved blood-glucose regulation,” Dr. Williams said.

The study measured brain circuit activity in mice given training regiments that lasted from zero to 10 days. Scientists found that a single workout (consisting of three 20-minute treadmill runs) caused a decrease in appetite that lasted up to six hours. “This result may explain at the neural circuit level why many people don’t feel hungry immediately after exercise,” Dr. Williams said.

The longer-term effects of exercise were seen in the POMC neurons, which improve glucose metabolism when activated. These neurons remained active longer if they also expressed a protein called the leptin receptor.

Dr. Williams’ lab is preparing a second study to establish the mechanisms by which exercise triggers changes in melanocortin neurons. The planned study will also record more data on how those changes correlate with biological functions such as glucose metabolism and energy balance.

“This research is not just for improving fitness,” Dr. Williams said. “A better understanding of neural links to exercise can potentially help a number of conditions affected by glucose regulation.”

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Materials provided by UT Southwestern Medical Center. Note: Content may be edited for style and length.