The stomach of a house finch might hold secrets to how humans absorb nutrients, age and deal with the omniprescence of nighttime light pollution.
Pierce Hutton, doctoral candidate in Arizona State University’s School of Life SciencesThe School of Life Sciences is part of the College of Liberal Arts and Sciences., is studying the gut microbiome — the cocktail of microbes in the stomach that help digest food and promote health — of house finches to answer these questions.
His research is funded by ASU’s Center for Evolution and Medicine. Evolutionary medicine, also called Darwinian medicine, is the application of modern evolutionary theory to understanding health and disease. The goal is to understand why people and animals get sick, not simply how they get sick.
Human and animal common denominators can be used to diagnose, treat and heal all species. Human and veterinary medicine are the same, if examined from an evolutionary medicine standpoint.
Two years ago, the Center for Evolution and Medicine Venture Fund was launched to finance research projects that connect evolutionary biology and topics relevant to medicine or public health. The fund is open to all ASU, Mayo Clinic faculty and students.
Hutton had questions that arose from work in the behavioral ecology lab. Working along with postdoc Mathieu Giraudeau, he studied four questions relating to the gut biome of house finches: What do carotenoids tell us about overall health? What is the effect of light pollution? What role does the gut play in aging? What role does microbe diversity play in health?
The males have bright red breasts. Those plumage colors are made by chemicals called carotenoids, which they get from their diet. The intestine is a gatekeeper, so to speak.
“We think the males might vary in how well they absorb the carotenoids,” Hutton said. “One thing that might be helping them absorb them is the gut microbiome. It’s beneficial for them to absorb them, because the plumage colors they have are evaluated by females when they’re selecting mates. It could be some microbes in the gut are helping them become sexier. We wanted to manipulate their diet and see if certain microbes get more abundant. That would tell us which ones are beneficial for uptaking those carotenoids.”
Carotenoids are also linked to health. They have important health benefits in the forms of antioxidants and immune stimulants.
“You could make some extensions to human health and biology by saying, ‘Well, if we know these microbes are beneficial for taking in these key nutrients, then it might be the same case for humans as well,’” Hutton said. “There’s the medicine angle.”
Humans have carotenoids in their bodies, and it changes their appearance too. If Caucasians eat an excessive amount of carrots, they will take on an orange hue.
Hutton and Giraudeau added carotenoids to the birds’ diet. “We did find a major effect,” he said. “’We think these microbes might be related to the uptick of those.”
A second ongoing study is looking at how light pollution affects humans and wild animals. How does living with light in our homes and outside at night affect intestinal health?
“Light pollution is a global epidemic, so we were looking at how it affects the gut microbiome,” Hutton said.
They put birds in separate rooms, one with a blue light (blue light is more disruptive to sleep than any other wavelength) that switched on at night.
Hutton is also trying to manipulate the rate of aging in house finches by regulating their gut microbiome.
DNA has strands of non-coding DNA on the ends called telomeres. They protect DNA from damage.
“As you age and as your cells divide, those end caps shorten over time,” Hutton said. “It opens up DNA to becoming damaged more quickly. There are enzymes we can target to regrow these end caps. We can essentially slow or reverse biological aging in a way. We can do this by up-regulating this enzyme that does that. ... Intestinal health and the microbiome might change as people age. It might be helpful for medicine to know how it’s aging, if it does age, those sorts of things.”
The fourth experiment looked at how the cleanliness of bird feeders affects microbiome in birds. Many people neglect to clean their backyard bird feeders, and so birds are defecating on and eating from the same surface.
“This means that both pathogenic and beneficial microbes might have an easier time colonizing new hosts,” Hutton said.
They put up bird feeders in the wild. During some periods they allowed the feeders to accumulate dirt, and other periods they cleaned them daily.
“We are expecting to see a rise in the diversity of their gut microbe community when the feeder was dirty relative to when it was clean, which might also include more pathogenic bacteria,” Hutton said. “This might connect to humans because many human populations eat under less cleanly conditions, which could lead to similar effects. It also might help us understand how the process of urbanization, and feeding wildlife, affects their gastrointestinal health.”
Researchers are studying house finches because human and animal common denominators can be used to diagnose, treat and heal all species, according to evolutionary medicine. Photo courtesy of Creative Commons.
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