Multiple sclerosis is a life-long, potentially disabling, neurological disease. We know that the human microbiome has a relationship with a variety of conditions and illnesses, such as asthma, allergies, diabetes, gut disorders and obesity, but at first-glance it seems hard to believe that the cause of MS has anything to do with the microbes in our digestive tract.
The latest research results, however, point to an intriguing link between the disease and the human microbiome. Two species of bacteria have been identified that seem to aggravate the condition and one species of bacteria has been shown to calm symptoms of the disorder. Taken together, this opens up the possibility that both the triggers and potential treatments have a bacterial component.
Multiple Sclerosis
Multiple Sclerosis is an auto-immune disease in which the protective covers on nerve receptors in the brain and spinal cord are degraded, impacting the communication of information within the brain and from the brain to the body. Because it is an auto-immune disease, the body itself attacks the myelin nerve sheath, a fatty substance that covers nerve fibers. Eventually, the nerves themselves may be damaged by the disease.
More than 2.3 million people world-wide have the disease. Those who have it experience a wide range of symptoms, ranging from mild to debilitating, depending on which nerves have been damaged and to what extent. The disease can come and go, with some people experiencing long periods of remission. Those affected can experience numbness and tingling, pain, vision loss, dizziness, slurred speech, lack of coordination or loss of movement and bowel or bladder problems, among other symptoms.
The causes and triggers of MS are not clearly understood. Genetics are not a perfect predictor of who will develop MS, although there is some heritable component. Even in identical twins who share the same genes, if one twin gets MS the other will develop it only 35% of the time. The current medical thinking is that there appears to be a genetic component, which combined with environmental triggers, seem to cause the body to turn its immune system against the nervous system.
The environmental triggers haven’t been definitively identified, but some associations have been observed. People are somewhat more likely to develop MS if they already have another auto-immune disease such as Type-1 diabetes, thyroid disease or inflammatory bowel disease. People who live further away from the equator are more likely to get MS. Smokers are at a higher risk of the disease. It may be that some herpes viruses trigger the disease. Women are at a higher risk for MS. These suspected environmental triggers are quite diverse and there does not seem to be a clear link between them.
Microbial Triggers of Multiple Sclerosis
The microbes living in our digestive tract can affect inflammation in the body. These gut microbes are an essential component of our immune system. Some microbes release metabolites (substances produced as part of their metabolic process) that calm inflammation and other produce compounds that trigger it. Auto-immune diseases, where the body mistakenly starts attacking itself, are diseases that can be related to chronic inflammation. Chronic inflammation is different than beneficial inflammation, which is a helpful response to pathogens or injury and that goes away once the threat goes away or the injury heals. Chronic inflammation persists in the absence of any need for it.
Scientists have known that the mix of microbes in people with MS are different and less diverse than what is found in their healthy peers, with the MS sufferers having higher levels of some microbes and lower levels of others.
More recent research has shed some light what role these particular microbes might play. A team of researchers at University of California, San Francisco led by Dr. Sergio Baranzini, aimed to investigate the significance of certain microbes is to the immune system and Multiple Sclerosis in particular.
They examined the gut microbiomes of 71 healthy people and 71 people with MS. First, they observed that the Acinetobacter and Akkermansia groups of bacteria were four times more numerous in the MS patients, whereas the group of Parabacteroides was four times as abundant in the disease-free group.
The team then decided to examine what, if anything, happened when they transferred a sample of the microbes from the MS patients into mice that had been raised to be germ-free (meaning they had no microbiome whatsoever). They transferred microbes from the healthy patients into a second group of germ-free mice. The scientists then triggered brain inflammation in both groups of the mice. In the group of mice with the microbes from the MS patients, the mice developed severe brain inflammation within 20 days, whereas the group with the disease-free subject microbes do not develop as extreme symptoms.
To further study the potential impact of the microbes found more frequently is MS patients on the immune system, the scientists exposed naïve immune cells (which become different types of immune cells depending on what type of bacteria they are exposed to) from healthy donors and exposed them to Acinetobacter and Akkermansia. In the presence of both microbes, the immune cells became a type of T helper cell that is know to trigger inflammation and assist in killing of invaders or diseased cells. Additionally, Acinetobacter had the effect of decreasing the immune system’s production of a type of T cell known to prevent auto-immune diseases, such as MS, by calming down the body’s immune response.
Taken together, the effects of the microbes show that the microbes found in higher numbers in the microbiome of people with MS have a pro-inflammatory effect on the immune system – both increasing T-cells that cause inflammation and reducing T-cells that calm the body’s immune response. When the microbes that exist in the gut are pro-inflammatory they can create chronic, disease-causing inflammation. This is significant because chronic inflammation can cause harmful effects to the body and trigger disease, such as MS, to appear over time.
This could be an explanation for why MS is more common in people who have another auto-immune disease, because like MS, those other auto-immune diseases may also be set off by chronic inflammation.
The microbe studies may also shed some light on how the disease develops over time. The study showed that the presence of certain microbes cause the worsening of brain inflammation. Having a higher than normal number of microbes that promote brain inflammation may lead to a worsening of MS symptoms.
This opens up very interesting areas for further scientific inquiry into the microbial causes and triggers of MS.
Bacterial Treatments for MS?
We have known for some time that metabolites produced in the gut can calm inflammation. A May 2018 study published in the journal, Nature, demonstrated how microbes in the digestive tract can directly impact the progression of neurological disease such as MS.
There are two types of cells in the brain that play an important role in the central nervous system (brain and spinal cord) – microglia and astrocytes. Microglia can clean up plaques and damaged cells. Astrocytes are brain cells that regulate the transmission of electrical impulses in nerve cells, facilitating communication. The microglia produce a chemical, as a byproduct of their metabolism, that damages astrocytes. It is thought that damage to the astrocytes contributes to MS and other neurological diseases.
Researchers at Brigham and Women’s Hospital have conducted the first study that shows how microbial byproducts can directly affect the microglia and reduce inflammation. They demonstrated that the byproduct the microbes produce when digesting dietary tryptophan can reduce brain inflammation by its effect on the microglia. Tryptophan is found in high levels in turkey. It is also found in other poultry, cheese, eggs and fish.
They observed how dietary changes impacted functioning in mice with a rodent version of MS.
The researchers determined that the microbial byproduct of tryptophan was capable of crossing the blood-brain barrier. Inside the brain, the compound activated an anti-inflammatory pathway that reduced neurodegeneration, such as is seen in MS. After studying brain samples of MS patients, they observed that the same pathways and cells were implicated.
Understanding that this pathway between the gut and the brain exists is only the first step. There are likely to be others. Much more work needs to be done to learn how to control this pathway to reduce MS symptoms or to stop the disease.
What Should I Do Now?
Although this research is very exciting, we still haven’t had human trials to further understand how the microbiome can either trigger MS or reduce its symptoms. The researchers have declined to give any advice on dietary changes or other therapies related to their findings. Eventually interventions such as fecal transplants (where fecal samples from a healthy donor are introduced into the large intestine) or drugs based on microbial byproducts may become standard treatment for MS.
In the meantime, taking steps to maintain or improve gut health are always a good idea to promote overall health and for improved immune function, whether one has MS or not. There is zero risk (other than food allergies) to making these dietary and lifestyle changes. Whether these might improve the proregression of MS, is unknown at this point. However, they have been shown to improve weight control mood and support the immune system to fight off sickness and a myriad of other benefits.
Eating to support gut health involves increasing dietary fiber and roughage, that our healthy microbes need to survive and thrive. Fermented foods introduce healthy gut bugs into the digestive tract.
There are chemicals in our foods that can harm our microbes. Preservatives, artificial sweeteners and colors, alcohol and Roundup (glyphosate) have all been demonstrated to impact gut health.
Whether eating more turkey (or chicken, duck, cheese, eggs or fish) could help MS symptoms or slow the disease’s progression is entirely speculative at this point. However, these foods are a good source of dietary protein and micronutrients. If you like these foods, indulge yourself! Make the Thanksgiving Turkey a more than once a year treat. And please do let us know if you observe any changes.
