June 16, 2016

expert reaction to gut bacteria and social behaviour in mice

Publishing in the journal Cell a group of scientists have published their research working on mice which reports that a high fat diet of the mother can bring about a shift in gut microbes that negatively impacts the social behaviour of the offspring mice.

Dr Jaleel Miyan, Senior Lecturer in Neurobiology, University of Manchester, said:

“This is a really excellent study demonstrating clear effect on abnormal behaviour of changing the gut microbiome.

“Most experimental studies have used genetic models or maternal insult models to obtain ASD-like behaviours in rodent models. In humans there are clear distinctions between different classes of ASD-like behaviours. In some cases unbalanced or increased presence of bad gut bugs are associated with ASD like behaviours and some recent evidence from various labs suggests that manipulating the gut microbiome can improve the symptoms.

“What one has to understand is that where there is poor development of the brain there is undoubtedly poor development of the peripheral nervous system and therefore consequential effects on the balance and functions of any/all peripheral organs and systems affected. A major target of such poor development is the gut and thus any abnormality in gut nerve development (the gut contains more neurones than the spinal cord) would have a significant effect not only on gut functions and probably gut microbiome, but also on information flowing back to the brain that may cause interference in normal brain functions, perhaps precipitating ASD-like behaviour in a developmentally challenged brain.

“The two go together in other words. A bad microbiome is unlikely to ‘cause’ ASD like behaviour unless the brain is also affected in development to be susceptible to the changes in peripheral neural information arriving from the gut and other places.

“Some questions remain: is there also a brain developmental issue making the mice susceptible to the gut bug change? Can one get a similar behavioural change by changing the gut microbiome of a normal mouse (different to the germ-free mice that the authors used)? And what is the mechanism of changing the microbiome through maternal obesity? For example, it is well known that neonates pick up their microbiome during birth through the birth canal. Has the mother’s own microbiome been changed to ‘cause’ the change in the offspring or what other mechanism could explain this?”

Dr Payam Rezaie, Reader in Neuropathology, The Open University and Co-editor of Researching the Autism Spectrum, said:

“We are only now beginning to understand what constitutes a ‘normal’ gut microbiome and the consequences that an imbalanced microbial community may have for the individual. Diet clearly plays an important role in the establishment, growth and maintenance of microbial diversity in the gut ecosystem, and feeding practices from birth help to modulate this.

“Recent experimental data suggest that the microbial make-up of the gut can influence the development of the immune and nervous systems and influence behaviour. This has given rise to various speculation as to mechanisms involved, focusing on an interaction between the gut and the brain. Emerging data, however, have raised more questions than answers.

“This study entertains the possibility that probiotic treatment can be beneficial in ‘restoring’ certain behaviours in autism and other neurodevelopmental conditions, based on experimental evidence in rodents. While this study goes some way towards establishing a causal relationship between the gut microbiome and social behaviour in rodents, the extent to which these findings can relate to human neurodevelopmental conditions remains to be established.

“The results of this experimental study suggest a need to more closely examine the relationship between the gut microbiome, brain development and human behaviour.”

‘Microbial reconstitution reverses maternal diet-induced social and synaptic deficits in offspring’ by Buffington et al. published in Cell on Thursday 16^th June. 

Declared interests

Dr Miyan: None received

Dr Rezaie: “None”