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Originally published November 11 2013

Researchers find probiotics help maintain intestinal homeostasis

by David Gutierrez, staff writer

(NaturalNews) One of the ways that probiotic bacteria help maintain intestinal health is by promoting the growth of the cells that line the intestine, according to a study conducted by researchers from Emory University and published in The EMBO Journal.

The researchers examined the activity of bacteria from the genus Lactobacillus in the intestines of mice and Drosophila fruit flies. They found that, even in these very distantly related animals, the same mechanism occurred: upon exposure to Lactobacillus, the epithelial (lining) cells of the intestine produced reactive oxygen species (ROS) which then stimulated the growth of intestinal stem cells and led to the regeneration of the intestinal lining. No ROS production was observed in animals whose intestines were free of Lactobacillus; those animals also had suppressed epithelial cell growth.

The researchers hypothesized that early life forms probably produced ROS for immune signaling and antibiotic functions, but that the function of ROS changed over time as animals and their intestinal flora coevolved.

"It is well-known that mammals live in a homeostatic symbiosis with their gut microbiota and that they influence a wide range of physiological processes. However, the molecular mechanisms of the symbiotic cross-talk in the gut are largely unrecognized," lead researcher Andrew S. Neish said. "In our study, we have discovered that Lactobacilli can stimulate reactive oxygen species that have regulatory effects on intestinal stem cells, including the activation of proliferation of these cells."

The findings have significant implications for human health, because they illuminate one mechanism through which probiotic bacteria maintain intestinal homeostasis. Scientists might soon be able to identify new species of probiotic microbes simply by looking for species that trigger certain ROS-mediated reactions.

Stress keeps the gut healthy

Although ROS, also known as free radicals, are commonly associated with cell damage, research into probiotics suggests that oxidative stress may be part of the way that certain bodily systems maintain their health.

In an earlier study published in the Proceedings of the National Academy of Sciences, the same Emory research team showed that, when exposed to Lactobacillus rhamnosus, the intestinal epithelial cells of mice produce ROS that actually stimulate healing. The ROS induce the epithelial cells to become more mobile, which causes them to fill in small gaps that naturally occur in the intestinal lining as a result of wear and tear from exposure to chemicals and microbes.

"Unlike most cell types that cannot tolerate bacterial contact, intestinal epithelial cells respond to Lactobacillus rhamnosus by increasing their motility," Neish said.

Notably, the researchers also found that the presence of antioxidants prevented epithelial cells from engaging in this wound healing activity. This proves that the role played by oxidative stress is essential in this particular healing pathway, and so is the role of probiotic bacteria.

"It's been known for years that probiotic bacteria can have these kinds of helpful effects, but it wasn't really clear how this worked," Neish said. "We've identified one example, among many, of how certain kinds of bacteria have specific biochemical functions in the body."

As scientists continue to uncover the ways in which humans and other animals live in a compulsory mutualistic relationship with their gut flora, it becomes increasingly clear that probiotics are not just beneficial for health, but essential.

Such research helps explain why an imbalance in the natural proportions of gut flora may actually produce autoimmune reactions in the intestines, leading to inflammatory bowel disease. Hopefully, it will also help scientists harness the power of probiotics to produce new treatments for these diseases, along with other metabolic, allergic and infectious disorders.

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