Two new papers add to the growing evidence of the impact on health from gut microbes. The recent research identifies two new linkages – one good and one bad.
One of the studies suggests a common gut microbe, Helicobacter pylori (that is linked to stomach ulcers and cancer), might curb the risk of developing multiple sclerosis – at least in women.
The research, published online in the Journal of Neurology Neurosurgery & Psychiatry, is not entirely new, but the largest study of its kind and, if confirmed in other studies, might prove the hygiene hypothesis – that childhood infections help to prime and regulate the immune system and ward off autoimmune and allergic diseases in later life.
Cases of multiple sclerosis (MS) have increased worldwide, in tandem with other autoimmune diseases, but the reasons behind this rise are unclear. Some studies have suggested a link between early childhood infection and reduced MS risk, but the studies have all been small.
This one tested 550 people with confirmed MS and a comparison group of 299 healthy people, matched for age and sex, for the presence of antibodies to H. pylori, which is usually acquired before the age of two, and lasts for life in the stomach, unless treated.
The results showed that the prevalence of the infection was significantly lower in those with MS than in the comparison group, but only among women, in whom it was around 30% lower.
“Collectively, such an inverse correlation of H. pylori infection with MS in developing countries where MS and allergic disorders have increased, may support the ‘hygiene hypothesis,'” Professor Jun-ichi Kira, of the Neurological Institute at Kyushu University, Fukuoka, Japan writes in the journal.
“Although why the protective effects of H. pylori against MS were observed only in women remains to be elucidated, but might explain the recent increase in female to male ratio of MS in developed countries.”
In the second study, researchers also show a link between gut microbes acquired during youth may have long-term immune responses.
Scientists in Ghent, Belgium, investigated the colonisation of the gut of young mice by certain types of bacteria.
They found that increases in the levels of segmented filamentous bacteria can trigger changes in the lymphoid tissue of the mouse gut that result in the production of antibodies that attack components of the cell nucleus. This type of damage is a hallmark of autoimmune diseases like systemic lupus erythematosus and systemic sclerosis where organs throughout the body are damaged by wayward immune responses.
“Our results demonstrate how gut health in young animals may be linked to autoimmune disease in older animals,” says Dirk Elewaut, Professor at Ghent University Hospital in Belgium and VIB Inflammation Research Center, Ghent University, Ghent, Belgium who is one of the lead authors of the study.
“The microbiome of the young mouse impacts a loss of tolerance of the secondary immune system against proteins in the nucleus of the cell. The attack of certain proteins by the body’s own immune system can subsequently lead to tissue damage and disease.”