Correlations found between the intestinal mycobiome and MS: study

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The study results highlight the potentially important role of the mycobiome in MS and its interactions with host immune and dietary factors, the authors write.

“Our data suggest that mycobiome diversity is an important predictor of gut microbial diversity in MS patients and may be more sensitive than bacterial diversity in response to changes in the gut microbiome associated with MS.”

They claim that modulation of the gut mycobiome through diet, environment, and exposure to different climates promotes fungal diversity and may optimize immune responses, which could help reduce the pathogenesis of MS.

Study protocol

Twenty-five MS and 22 healthy controls were recruited for the study at Washington University School of Medicine in St Louis.

Twenty-one of the MS subjects were diagnosed with relapsing-remitting MS, two with primary progressive MS, one with secondary progressive MS, and one with clinically isolated syndrome (CIS).

Stool and blood samples were collected at baseline and after six months for gut mycobiome and blood immune cell analyses, and a four-day food frequency questionnaire was recorded to provide qualitative dietary information.

Scientists performed ITS (gene) sequencing and characterized the gut mycobiome of MS subjects and healthy controls, at baseline and after six months, and found significantly higher alpha diversity in the MS group.

Results

The two dominant branches at the start were Ascomycetes and Basidiomycota​ in both MS and controls and accounted for more than 80% of the total mycobiome population.

On average, Saccharomyces ​composed of 23% and 42% gut mycobiome in control and MS, respectively.

A distinct pathogenic link has been identified between Saccharomycesabundance and MS.

While Saccharomycesis one of the major mycobiomes of the human gut, its biological role has been inconsistent in studies that have observed both protective and detrimental effects on gut inflammation.

Saccharomyces was​ overrepresented in the SP group, as well as Aspergillus, ​which is part of the respiratory and intestinal mycobiome and produces aflatoxins (toxins) that can cause opportunistic infections in humans.

The analyzes found a positive correlation between Saccharomyces​, consumption of “butter and milk”, a higher relative abundance in obese subjects and a negative correlation with Lachnospiraceae incertae sedis​ in MS, suggesting that the mycobiome may affect autoimmunity through the regulation of bacteria.

The fungus was also associated with increased circulation basophils (white blood cells) and a reduction in regulatory B cells (which modulate immune responses).

The authors note: “Mushrooms can have a direct impact on the immune response or indirectly through their interactions with bacteria. Our study revealed a disturbed correlation pattern between fungi and the peripheral immune profile in MS.

Different mycobiome profiles (or mycotypes) have been associated with different bacterial microbiomes and immune cells in the blood.

Meanwhile, disparities in mycobiome composition in MS and healthy controls have been attributed to higher between-subject variations in MS subjects.

Food intake analysis

The team’s PERMANOVA analysis identified four types of food groups potentially associated with the gut mycobiome community: butter and animal fats, nuts and seeds, refined grains and whole grains.

The results suggest that specific food types promote the abundance of different microbiomes. Notable findings included a moderate correlation between butter and animal fats and the relative abundance of the two Saccharomyces and Hannaella​. The relative abundance of the two was also significantly higher in obese subjects.

In MS subjects alone, there was a negative correlation between Saccharomycesand nuts and seeds, but a positive link between Hannaella and butter and animal fats were both stronger.

At the same time, a moderate increase in AspergillusAbundance was related to eggs and refined grains and was higher in the MS group.

The authors recommend further studies to assess any causal association of the mycobiome with MS and its direct or indirect interactions with bacteria and autoimmunity.

Source: EBioMedicine

Published online: doi.org/10.1016/j.ebiom.2021.1035572

Gut Mycobiome Alterations in MS Patients »

Authors: Saumya Shah et al.

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