Recent studies from 2023 [1] and 2022 [2] investigated the role of probiotics in the pathogenesis and clinical course of Myasthenia Gravis (MG), suggesting that regularly consuming probiotic and prebiotic foods may have positive impacts. This article summarize the key findings and recommendations from these studies.
The Human Microbiota
The human microbiome consists in a complex symbiosis of trillions of microorganisms, also called microbiota, of thousands of different species that reside in our body. Microbiome and microbiota are two different concepts. Microbiome is the whole system that contains the microbiota or, using a metaphor, the microbiome is the house and the microbiota are its inhabitants.
The human microbiota includes the entire population of microorganisms that live in the human body, which consists mainly of anaerobic organisms concentrated in the small and large intestine and in the stomach. The healthy bacteria that form our microbiota are primarily Firmicutes, Bacteroidetes and Actinobacteria, which account for more than 90% of the entire population.
Clostridia accounts for 95% of the Firmicutes phylum resident in gut microbiota, representing the main producers of short-chain fatty acids (SCFAs) through the fermentation of proteins and carbohydrates. SCFAs are the main source of nutrition for the cells in the colon and play a very important role for our health. [3]
The gut microbiota interconnection with the immune system regulates the production of immunoglobulins, in particular mucosal Immunoglobulin A (IgA). [1] IgA is the most important antibody class that act locally as a protection of the vast surfaces of the gastrointestinal, respiratory, and genitourinary tracts that are subject of attack by invading micro-organisms. IgA is also an important serum immunoglobulin, which mediates a variety of protective functions through interaction with specific receptors and immune mediators. [4] The human microbiota also plays an immunomodulatory function [5] and engages in bidirectional interactions with the central nervous system (CNS). [6]
In summary, the microbiome and its microbiota play a crucial role in developing and maintaining our health. The integrity of the gut microbiota guarantees many physiological processes such as intestinal barrier function, digestion, metabolism of dietary elements and vitamins biosynthesis, and plays a role in the modulation of our immune system.
How Dysbiosis Contributes To MG Pathogenesis And Clinical Course
An alteration of the normal composition of the human microbiome is called dysbiosis. Dysbiosis is characterized by the reduction in beneficial bacteria and the increase in pathogenetic bacteria, leading to increased permeabilization of the intestinal wall and an imbalance between lymphocytes able to regulate immunotolerance and prevent autoimmune diseases. Intestinal dysbiosis has been linked to chronic low-grade inflammation and has been described as a starting or aggravating factor in MG. [1] A 2023 study describes MG as an “autoimmune disease associated with the dysregulation in the composition and diversity of gut microbiome”. [2]
Recent studies observed that the Firmicutes/Bacteroidetes (F/B) ratio was lower in MG patients compared to healthy individuals of the same age. The decrease of the Firmicutes/Bacteroidetes ratio (F/B ratio) due to the increase in the Bacteroidetes phylum has been found to be associated with the pro-inflammatory shift of the gut microbiota in autoimmune diseases including MG. [1] [2].
MG patients showed a typical increase in Streptococcus and Bacteroidetes and also a reduction in Clostridia as well as short-chain fatty acid reduction. This reduction in Clostridia and the subsequent reduction in SCFAs in patients with MG has been hypothesized as one of the pathogenetic mechanisms contributing to MG onset. [1]
Early findings also suggest that dysbiosis may be involved in the progress of anxiety-like behaviors in MG. [1]
Factors That Influence The Composition Of The Gut Microbiota
Diet, aging, exercise and use of antibiotics can affect gut microbiota composition both in beneficial or in negative ways.
Diet And The Gut Microbiota
Certain eating habits, such as these of the so-called Mediterranean Diet, promote microbial diversity and increase the amount of beneficial bacterial. For example, fruits and vegetables are able to reduce the growth of potentially harmful bacteria; while polyunsaturated fatty acids (PUFAs) can reduce the Firmicutes/Bacteroidetes ratio while increasing SCFA-producing bacteria (e.g., Bifidobacterium, Lachnospira, Roseburia and Lactobacillus). On the other end, diets rich in animal-based proteins and saturated fatty acids, and low in vitamin D intake, such as the so-called Western Diet, reduce microbial diversity and increase the abundance of the potentially pathogenic and pro-inflammatory bacteria. [1] [9]
Exercise And The Gut Microbiota
Exercise has beneficial effects on the composition of the microbiota. In both animal models and humans, physical exercise can increase butyrate-producing bacteria. [1] Butyrate is a SCFA that has an important role in human health. [10]
Antibiotics And Other Drugs And Their Impact On The Gut Microbiota
The excessive use of antibiotics can rapidly cause dysbiosis, which is then long to be reversed. Antibiotics reduce both the amount and the functional differentiation of healthy bacteria in the colon. The incidence of autoimmune diseases has increased in parallel with the increased use of antibiotics. Dysbiosis may be also sustained by proton pump inhibitors (PPIs) and consumption of other drugs. [1]
What Probiotics And Prebiotics Are
Probiotics (PRO-biotics) are foods or supplements that directly contain live microorganisms that can maintain or even improve the “good” bacteria that form the microbiota in our body.
Prebiotics (PRE-biotics) are foods that nourish the “good bacteria” that live in our microbiota, and are primarily represented by dietary fiber. In other words, prebiotics are foods not only for us but also for our microbiota.
Probiotics And Prebiotics Can Mitigate MG Severity
The restoration of gut microbiota though probiotics and lifestyle interventions, such as our eating habits and physical activity, might prevent MG onset and mitigate disease severity. According to a 2023 study “the administration of probiotics was able to restore the gut perturbation and improvement of symptoms in MG patients.” [1]
The combined use of prebiotics and probiotics may have a synergistic effect to improve the microbial balance of the gastro intestinal tract, and modify the composition of colonic microflora leading to the predominance of some of the potentially health-promoting bacteria, particularly, bifidobacteria and lactobacilli. [2]
The following figure summarizes how the gut microbiome is associated with the manifestation of Myasthenia Gravis (MG). [2]
The role of probiotics in MG has also been explored in a number of studies in animal models. These studies found that administration of probiotics was able to improve progression of Experimental Autoimmune Myasthenia Gravis (EAMG). [7] [8]
Further Studies Are Needed. In The Meantime, Consuming Pre- And Probiotics Is Still A Good Idea.
The studies referenced in this article provide initial evidence supporting the use of probiotics and prebiotics to treat MG. However, more studies are needed to provide further evidence. In fact, it is reasonable to assume that microbiota alterations may also be an indirect effect of MG because patients take a higher number of medications which overall may alter microbiota composition. In addition, the modification of eating habits and physical activity in patients with MG may also play a role in the microbiota perturbation. For these reasons, further studies are needed to clarify the direction of this close relationship that has been observed between MG and microbiota alteration. Finally, more research is needed to determine the specific microbial species that can constitute a novel targeted treatment for MG.
In the meantime, it is still a good idea to regularly consume pre- and probiotics, which in any case bring numerous health benefits. Learn more about The Surprising Health Benefits of Eating Probiotic Foods.
References
[1] The Role of Human Microbiota in Myasthenia Gravis: A Narrative Review
[2] Exploring the Gut Microbiome in Myasthenia Gravis
[3] Intestinal Short Chain Fatty Acids and their Link with Diet and Human Health
[4] The function of immunoglobulin A in immunity
[5] Interaction between microbiota and immunity in health and disease
[6] Gut Microbiota Interaction with the Central Nervous System throughout Life
[7] Prophylactic effect of probiotics on the development of experimental autoimmune myasthenia gravis
[9] Role of “Western Diet” in Inflammatory Autoimmune Diseases
