Intestinal bacteria in disease

In today’s post, guest blogger and clinician-scientist Philip M. Sherman, MD, FRCPC, Scientific Director of the CIHR Institute of Nutrition, Metabolism and Diabetes, shares his perspectives on role of intestinal bacteria in disease:

When I was a young medical student, I quickly learned that there are many unanswered questions in the field of medicine.  I wanted to add a tiny piece of understanding to the complex jigsaw puzzle that is human health and disease. Now, as a clinician scientist, I work to answer some of these questions by translating laboratory research into improved treatments for patients.  My research focuses on explaining the role of intestinal bacteria in disease, which is a new frontier in human biology.

The human intestine is home to a complex community of bacteria referred to as the gut microbiome.  Each intestine contains approximately 100 trillion bacteria made up of roughly 1,000 different species. Everyone has a unique profile of bacterial species, which is influenced by diet and the use of antibiotics.  These bacteria help draw energy and vitamins from foods, keep the immune system in balance, and prevent the growth of harmful strains of bacteria. An altered gut microbiome can be seen in many conditions including obesity, diabetes, celiac disease, chronic inflammatory bowel diseases (Crohn’s disease, ulcerative colitis), and irritable bowel syndrome.  We know that the gut microbiome is different in patients with these diseases, but we don’t know whether these differences are the cause of the disease or if they are the result of the disease.

The brain and the gut are connected through a system of nerves and hormones as well as the immune system, which enables two-way communication between the brain and the gut. For example, when a person is nervous, the brain triggers activity in certain nerves that leads to feelings described as “butterflies in your stomach”.  It also appears that intestinal bacteria can influence the brain.  For example, my research group has found that mice that don’t have intestinal bacteria have poor memories compared to mice with normal intestinal bacteria. Other researchers have described an increase in risk-taking behaviour in mice without intestinal bacteria.  Together, these findings suggest a role for intestinal bacterial in brain development.

There is much more work to be done before we understand the role of intestinal bacteria in human health and disease.  CIHR- funded Canadian researchers are actively participating in the International Microbiome Project, an international effort to identify and describe the human microbiome.  While there are still many unanswered questions, initial research findings provide hope for the development of new treatments, such as the use of beneficial bacteria (also known as probiotics), to promote health and to manage diseases.

Photo #1 : In this photo, taken with an electron microscope,  Lactobacillus bacteria (rod-shaped cells) interact with cells from the immune system called neutrophils (large, round cells at the upper right corner and the extreme left).  Lactobacillus is one type of “friendly” bacteria that is commonly included in probiotics.  This photo was taken in Dr. Sherman’s lab by Dr. Linda Vong, PhD.

Photo #2 : Dr. Sherman (back row, far right) pauses for a photo with the technicians, postdocs and graduate students who work in his laboratory.

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