Interview Summary from Shelley:
In the last 50 years, scientists have tracked an alarming increase in diseases such as arthritis and multiple sclerosis, and asthma and allergies. These autoimmune diseases have been rising the fastest in ‘modern‘ communities – those with better access to Western diets, health care and sanitation. As for why, some scientists suggest that “western life” is “too hygenic,” and this increases the chance of autoimmune diseases. Now a new study raises interesting possibilities about what’s going on. And while it offers no prescriptions for reducing the incidence of diabetes yet, it’s an important study for laying the foundation for a new “gut level” approach to improving health. Jayne Danska is a research scientist at the Hospital for Sick Children in Toronto. She’s been working with scientists at CU Health Sciences and CU Boulder to study three things: One, a special strain of mice at high risk for autoimmune diabetes; two, a sex hormone called testosterone, and three, microbes that live within the gut. Specifically, Danska’s team studied a mouse that’s bred to come down with Type 1 diabetes. Danska says the “hygiene” of the mouse colonies influences how often they get diabetes.
JANE DANSKA: A colony of these mice that has a higher burden of pathogenic viruses and bacteria will have a lower frequency of diabetes. And conversely a cleaner colony, that is, free of all pathogenic microbes, that we screen for, has has a higher frequency of diabetes. So we knew that the disease is influenced by hygiene status. So we knew that the disease was influenced by hygiene status.
Danska says the likelihood of diabetes in these diabetes-prone mice is also influenced by their sex. Male mice, who have higher levels of testosterone, have a 30-40% incidence of diabetes. Female mice, who have lower testosterone levels, have an 80-90 percent incidence of diabetes. Curious about how “hygiene” and sex hormones affect susceptibility to diabetes, Danska’s research team had male mouse pups grow up a completely sterile environment – no germs, no bacteria in their guts, none on their skin, none in their cages. Completely microbe free.
JANE DANSKA: What we observed was that the protection that males had, relative to females, for Type 1 diabetes, the lower frequency of diabetes in the males, that went away, when we put them in a sterile environment. So they were just as prone to the disease as the females were. They lost that benefit, and we immediately tested their testosterone levels, and we were very surprised to see that in the absence of normal bacterial components of their gut, their testosterone levels were significantly lower than the same strain of mouse, living with normal bacteria in their gut.
Danska says that to her knowledge, this is the first research to indicate a connection between an animal’s microbes and its level of a sex hormone, such as testosterone. Danska’s team decided to take the research one step further. They reasoned that something about the microbial community in male mices seems to regulate their testosterone levels. And something about that male hormone, testosterone, or the microbes themselves, protects the male mouse from getting as much diabetes. So the researchers took fecal samples of gut microbes from adult male mice, and they orally inoculated female mouse pups, with the gut microbes from an adult male. Among the female mice that did NOT get this microbial inoculation, roughly 90% went on to get diabetes. But among the females that got the microbial inoculation from the males, only about 30 to 40% of them ended up with diabetes, similar to their male counterparts. She adds that the females that got the male microbes did have higher testosterone levels.
JANE DANSKA: The male bacteria, when transferred into these females, provoked elevated levels of testosterone in the females that received this bacteria. But it was still far lower than you see in the males of this strain.
Danska adds that it’s possible that this same effect could have been achieved by injecting young female mice with testosterone but that approach has many risks of harmful side effects. She says her team plans to keep investigating what it is about a one-time, early on, inoculation of microbes from another mouse’s gut, that helped female mice avoid getting Type 1 diabetes. Danska adds that she’s especially excited about what her research might reveal about other autoimmune diseases and sex differences. For instance, women are more prone to diseases such as rheumatoid arthritis, multiple sclerosis, thyroid conditions and lupus than men are. She’s hopeful that her research will shed light on these conditions, and the role of healthy gut microbes.
JANE DANSKA: We’re just at the beginning of our understanding of the profound and intimate way that we are living with bacteria in our bodies. Ultimately the goal is to be partners with these bacteria. We are their partners. They help us to digest our food, they help to give us vitamins. They were, we know know over the past decade, essential in teaching and training our immune systems to develop properly, so they do an enormous amount of us. We need to behave in a way to benefit them as well.
This study about autoimmune disease, gut microbes and sex hormones was published in late January on line in the journal, Science Daily. And while its focus was on gut microbes, and basically a “stool transplant” between mice, it’s worth pointing out that how a person eats and exercises affects their gut microbes. Perhaps as more becomes understood about guts and microbes, and foot and so on, we’ll know about how to tailor diets to not only help our own health, but the health of the microbes in and on us. If you want to check out a neat project for doing just that, here’s a link to The American Gut. There’s still time to register for it, but hurry if you want to. That project closes out February 2nd. — Shelley