The body is heavily
colonised by microorganisms, known collectively as the human microbiome. The
microbiome has a number of health benefits: it helps us digest food, helps
prevent other microbes from causing infection and is essential for the proper
development of the immune system. Sometimes, however, the composition of the
microbiome can change to one that is associated with disease, a condition know
as dysbiosis. Whether a dysbiotic microbiome can cause disease or whether the
composition of the microbiome changes because of the disease is the major
question which microbiome researchers are trying to answer.
Two recent papers (1)(2) have compared the gut microbiome in individuals
with multiple sclerosis with healthy controls. Both found the microbiome in MS
to be different from that of controls although, interestingly, the changes in
bacterial composition observed were different in the two studies. The authors
suggest that MS may be associated with gut dysbiosis and that improved
understanding of this relationship might lead to the development of new
treatments.
These studies need
to be interpreted with caution, however. Both studies investigated stool
samples. It has been shown that the primary factor affecting the microbial
composition of faecal samples is stool consistency (3). Since MS is known to cause gastrointestinal
disturbance, it is possible that this could be the reason for the differences
seen. Alternatively, there could be a number of other confounding factors such
as diet or inflammation of the gut which may have affected the microbiome of the
MS patients studied.
These studies
included relatively small numbers of subjects. Further work on larger numbers
of patients and carefully selected control subjects is needed to confirm if the
gut microbiome is different in MS and whether this occurs as a result of the
disease or contributes to its cause.
1. Chen J, Chia
N, Kalari KR, Yao JZ, Novotna M, Soldan MMP, et al. Multiple sclerosis patients
have a distinct gut microbiota compared to healthy controls. Sci Rep
[Internet]. 2016;6:28484. Available from:
http://www.nature.com/articles/srep28484
2. Jangi S,
Gandhi R, Li N, Glehn F, Yan R, Melo K, et al. Alterations of the human gut
microbiome in multiple sclerosis. Mult Scler J [Internet]. 2015;21(11 Suppl):168–168.
Available from: http://msj.sagepub.com/cgi/doi/10.1177/1352458515602642
3. Falony G,
Joossens M, Vieira-Silva S, Wang J, Darzi Y, Faust K, et al. Population-level
analysis of gut microbiome variation. Science [Internet]. 2016 Apr 29 [cited
2016 Jul 7];352(6285):560–4.