Scientists at the Science Foundation Ireland-funded APC Microbiome Institute at University College Cork, Ireland have shown that, at least in mice, gut bacteria play a key role in regulating abdominal pain and its associated changes in the brain and spinal cord.

Visceral pain is a global term used to describe pain originating from the internal organs of the body, which affects a significant proportion of the population and is a common feature of functional gastrointestinal disorders such as irritable bowel syndrome (IBS). Currently, the treatment strategies for visceral pain are unsatisfactory, with development of novel therapeutics hindered by a lack of detailed knowledge of the underlying mechanisms although alterations of the Gut-Brain axis has been implicated. The human gut is home to over 100 trillion bacteria and other microorganisms collectively known as the microbiota. The gut microbiota is involved in critical processes such as digestion, metabolism, immune responses, and absorption of nutrients. Until recently, little was known about how the microbiota influences the nervous system; however, it is becoming increasingly clear that gut microorganisms can influence the brain and behavior.

Profs. John Cryan and Ted Dinan along with postdoctoral fellow Dr. Monica Tramullas and research scientist Pauline Luczynski have unraveled a novel mechanism underlying how visceral pain can emerge. They have shown that mice that grow up without microbes (germ free mice) were more sensitive to visceral pain stimuli. These animals also showed corresponding changes in genes in their spinal cord. In the brain, germ-free mice had changes in areas involved in the descending pain modulation and its emotional regulation.

Of great interest, colonization of germ-free mice with gut bacteria reversed these changes which suggest that there is potential to reverse the changes with microbiota- based interventions. Prof. Cryan, says “we are very excited about these data, although the microbiota has long been thought to play a key role in pain modulation, the current study proves it categorically and offers insights into some of the potential neurobiological mechanisms at play” 
The data have implications for our understanding of IBS and supports the concept of targeting the microbiota to modulate pain symptoms in this and other gastrointestinal disorders.

The research is published today in the journal eLife. The research was co-authored by APC researchers at UCC, Maria Viola, Gerard Clarke and Fergus Shanahan, and funded by Science Foundation Ireland through a Research Centres Grant to the APC Microbiome Institute and through EU Grant 613979 MY NEWGUT FP7-KBBE-2013-7 (Timothy Dinan & John Cryan).

“Microbiota regulates visceral pain in the mouse”. eLife 20th June 2017

Full reference

Pauline Luczynski, Monica Tramullas, Maria Viola, Siobhain O’Mahony. Fergus Shanahan, Gerard Clarke, Timothy Dinan & John Cryan (2017)