Antibiotics are, in a sense, miraculous drugs. Thanks to them, many potentially debilitating or deadly diseases are now regarded as little more than a nuisance, and they allow a wide range of surgical procedures to be performed with a low risk of infection. But these drugs — and the way they’re often prescribed — also carry a number of substantial risks and drawbacks.
One aspect of antibiotics that researchers are still working to understand is the way they can affect a developing immune system. In early life, the immune system goes through an intensive “training period” in which it learns how to deal with countless types of cells, organisms, and molecules. What the immune system learns to recognize as a threat that should be attacked — and what it knows to leaves alone — can have a profound impact on your health for the rest of your life.
For a number of years, researchers have observed an association between taking antibiotics early in life and developing Type 1 diabetes. It’s not clear, though, exactly what doses of which antibiotics might lead to this increased risk — and it’s certainly not considered ethical to give children antibiotics for no reason to try to find out. So a recent study of mice may provide some useful insight into the relationship between these drugs and diabetes.
Changes in balance of bacteria, and more
In the latest study, published in July 2018 in the journal eLife, researchers at the NYU School of Medicine examined the effects of giving antibiotics to mice that were bred to be highly prone to developing Type 1 diabetes.
In a previous study, the research team had found that giving multiple courses of antibiotics to these mice sped up the onset of diabetes. For this study, they wanted to know if a single course of antibiotics could also have such an effect — and they found that it did. Mice that were given just one course of antibiotics were significantly more likely to have diabetes at various points in time over 20 weeks than those that weren’t given antibiotics.
But the study didn’t end there — it also looked at the composition of gut bacteria and other changes in the mice, to try to find out how antibiotics might raise the risk of Type 1 diabetes.
As noted in a press release on the study, the researchers found that four different groups of bacteria were more common in mice that were given the single course of antibiotics. Two of these groups (known as Blautia and Akkermansia) have been shown in studies of human children to increase the risk of Type 1 diabetes when they’re unusually abundant in gut bacteria.
Four other groups of bacteria were shown to be less common in the mice given the course of antibiotics.
The researchers also found that, as would be expected with a different balance of bacteria, the balance of chemical byproducts from bacteria was different in the mice given the antibiotic course.
And the consequences of the antibiotics went even further, with altered levels of various substances involved in metabolism seen in the mice’s blood and liver. There was also different expression of genes in their intestinal wall, which shows a way that immune system dysfunction may occur.
What does this study mean for people?
It’s important to note that a study of mice can’t lead to any direct recommendations for people, says Martin J. Blaser, MD, the study’s senior investigator and director of the Human Microbiome Program at the NYU School of Medicine.
“We study mice to understand the relevant biological principles,” says Blaser. But the results, he says, “are a model of the pervasive effects that antibiotic courses may have on children, causing immune systems to develop abnormally on the way to serious illness.”
The study’s lead author, Xuesong Zhang, PhD, an assistant professor of medicine at the NYU School of Medicine, notes that its findings “confirm earlier work showing that antibiotics can increase the risk for Type 1 diabetes.”
“Even a single early-life course,” says Zhang, “may perturb the intestinal microbiome in ways that lead to long-term consequences in the intestinal wall, including immune cell changes and damage to the pancreas.”
Blaser emphasizes that early life is a critical time for development in humans, so any disruption during this period is likely to have greater negative effects than a similar disruption would later on. “This has been recognized for a long time,” he notes. “What is new is that we now see the microbiome as an important participant in the development of healthy immunity, metabolism, and cognition.”
Want to learn more about antibiotics and diabetes? Read “Antibiotics and Diabetes: Do the Two Mix?” “Antibiotics Linked to Lows in People Taking Certain Diabetes Drugs,” and “Repeated Antibiotic Use Associated With Type 2 Diabetes Risk.”