Multiple sclerosis, intestinal bacteria linked

Scientists have discovered a connection between gut bacteria – the bacteria that live in our intestines – and multiple sclerosis, a disease of the brain and spinal cord. EarthSky spoke with Dr. Sarkis Mazmanian, a biologist at CalTech.

Sarkis Mazmanian: I wouldn’t go as far as saying that gut bacteria cause MS. I would say that gut bacteria contribute to the inflammatory symptoms that promote MS.

In other words, bacteria might help along the symptoms of MS, or multiple sclerosis – symptoms like paralysis and lethargy. Dr. Mazmanian published his research in July of 2010 in the Proceedings of the National Academy of Sciences. He said he observed the progression of MS in two different groups of mice – mice with normal gut bacteria, and mice with no gut bacteria at all.

Sarkis Mazmanian: The animals with the gut bacteria had an inflammatory response in the brain and central nervous system consistent with disease.

They got sick with MS, that is. But the mice without intestinal bacteria showed no symptoms. Dr. Mazmanian said his results suggest that some kinds of gut bacteria might contribute heavily to MS. But, he added, scientists still don’t know which bacteria, or combination of bacteria, might be causing problems. Research is ongoing, and Mazmanian looks to a future in which patients might be able to alter their gut bacteria through diet or medication to prevent or cure MS, and possibly other diseases. Dr. Mazmanian clarified that gut bacteria are normal and necessary for all mammals’ digestion, but the role they play in our immune response is just now getting attention from scientists.

Sarkis Mazmanian: Unless you believe these organism have an effect, then there’s no incentive to study them.

Dr. Mazmanian explained that all mammals have pretty similar gut bacteria – up to 1,000 different species live inside of us., and also in mice. (When he says “gut”, by the way, he’s mostly talking about the lower intestine and colon.)

Sarkis Mazmanian: These are not harmful organisms, these are not infectious agents such as those that cause strep throat or tuberculosis. These are organisms that help our digestion and help our immune response.

He said that’s true in all mammals, and why the study of MS in mice could eventually help humans.

Sarkis Mazmanian: Our study does not cure MS in animals, it helps us understand the cause of MS. And by understanding what those causes are, we can think of ways of manipulating gut bacteria to help prevent the symptoms that they’re causing. In other words, if a patient with MS has a change not just in their DNA, but also in the numbers or the types of the organism in their intestine, based on lifestyle, diet, antibiotic use, hygiene, what have you, then one can imagine that in the future, we can manipulate gut bacteria to restore a “correct” set of organisms

He also explained the paradox of not knowing what causes MS, yet being able to induce it in a laboratory in mice. He said that, basically, it’s the main physiological symptom that’s introduced at will – the demyelation of the spinal cord. He said that he uses mice because there’s no way to do this experiment in humans; it’s not possible to induce MS in humans, or possible to test a group of humans with zero gut bacteria (no such group exists).