microbes

Hormones, Gut Bacteria, and Autoimmune Disease

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Women disproportionately suffer from autoimmune diseases at a rate of 3 to 1 compared to men. Most believe hormones influence the risk of autoimmune disease but determining the mechanisms has eluded researchers for some time. In animal research, when male rats are castrated, the incidence of autoimmune disease goes up, but when female rats are castrated – their ovaries are removed, the results are mixed. New research finds that the bacteria in the gut interact with hormones and provide the key to understanding the sex differences in the risks for and onset of autoimmune disease.

In a study published in the journal Immunity, Gender Bias in Autoimmunity is Influenced by Microbiota, researchers tested the potential signals between hormones and immune function, gut microbes and immune function, and hormones plus gut microbes and immune function in male and female mice. They wanted to delineate the relationship between hormones, specifically testosterone, gut bacteria and autoimmune factors. Is it solely the hormone signal that influences the types and distribution of gut bacteria that then initiates or regulates the immune response or do the gut microbes regulate the hormones which then influence the immune response, or is it some combination of the two? It appears to be the latter; hormones and gut microbiota interact synergistically to regulate the expression of various immune factors and each other.

In a series of experiments, researchers were able to show that the gut bacteria in post pubescent male mice, both quantitatively and qualitatively differed from those of the female mice and testosterone was the key. In male mice, there appeared to be a feedback loop in which testosterone increased gut bacteria and the gut bacteria in turn increased testosterone, to some degree. Once the minimum threshold was reached, higher concentrations of testosterone did not influence gut bacteria any longer. Because these bacteria in turn control the balance between inflammatory and anti-inflammatory factors researchers postulate that the relationship between gut microbiota and testosterone may be key in understanding the gender bias in autoimmune disease.

Questions remain. Testosterone is not the only androgen within the hormone pathway. There are other androgens that have noted and direct influence on immune factors. Moreover, while testosterone may be implicated that does not necessarily rule out a role for the estrogens, as testosterone is the precursor hormone for estrone, estradiol and the other estrogens. The downstream conversion from testosterone to estrone or estradiol may be an important consideration for future research. Nevertheless, this study highlights the importance of hormones in disease, and more specifically, the critical cross-talk between hormones, gut bacteria and inflammatory/anti-inflammatory factors.

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This article was originally published on September 12, 2013. 

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C-Sections Impact Vaginal Microorganisms

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Microorganisms Important to Our Health

Humans have trillions of microorganisms, which only make up 1 to 3% of our body’s mass, but play a large role in maintaining the health and well-being of the human body. We rely on the microbes in our body for a number of biological processes that are necessary for our survival.

Microorganisms produce vitamins and anti-inflammatories that the human body cannot produce alone. The microbes in our gastrointestinal tract (GI) also help with digesting food and absorbing nutrients; processes that rely on enzymes that the human body does not have.

Though microorganisms can cause illness, they usually live in harmony with the body. In fact, the National Institute of Health reported that most humans carry microorganisms that are known to cause disease, but these microorganisms do not make healthy individuals ill. Rather, they coexist with the other microbes in the body. Researchers still need to determine what triggers these disease-causing pathogens to negatively impact our health.

Reduced Exposure to Microbes Poses Health Risks

Now, Americans are bombarded with anti-bacterial products and triple-washed spinach that reduces our exposure to the bacteria that does the body good. The increased number of autoimmune disorders, a large majority of which are reported by women, may be partly due to society’s decreased exposure to bacteria, according to the New York Times.

Philosopher of Science at Oregon State University, Sharyn Clough, explained that emphasizing cleanliness to young girls may result in increased susceptibility to autoimmune diseases when they get older, since they are exposed to less bacteria than boys.

The New York Times explains that eating from our local farmers’ markets can reintroduce these microorganisms back into our systems, which may improve our microbial well-being, and therefore improve our own health.

Does C-Section Impact Microbial Makeup?

Researchers at the Baylor College of Medicine compared the changes in the vaginal microbiome of pregnant women to the vaginal microorganisms in women that were not pregnant, and discovered that the diversity of microbial species decreases significantly during pregnancy.

Babies are first exposed to bacteria while passing through the birth canal and absorb a significant amount of microbes from the vaginal microbiome. Researchers speculate that the reduction in vaginal bacterial species during pregnancy may be a means of creating a healthy bacterial environment for the baby when it begins to develop its own population of microbes.

If babies do not pass through the birth canal, however, the type and amount of bacteria they are exposed to changes dramatically and may possibly impact the baby’s health. In the United States, the rate of C-sections have risen from 4.5% in 1962 to 31.8% in 2009. This dramatic increase in cesarean sections means that there are a number of babies that are exposed to different bacteria at birth than those that pass through the birthing canal.

Researchers at Stanford University found that babies that passed through the birthing canal acquired bacteria that resemble their mothers’ vaginal microbiome, whereas babies delivered through C-section established a microbiome that is similar to the bacterial communities found on the skin’s surface.

Scientists have only just begun to research how differences in microbial makeup may impact an individual’s health, but reduced exposure to bacteria is tied to autoimmune disorders and allergies. In Germany, researchers have found that cesarean delivery is connected to celiac disease, a result of the lack of exposure to specific bacterial species.

We must be patient as researchers begin to sort through the trillions of microbes that live on our bodies, but in the meantime, fear not the bacteria that lurks all around; more often than not, it is our friend, not foe.

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