#215 - The gut-brain connection | Michael Gershon, M.D.

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Mike Gershon is a Professor of Pathology and Cell Biology at Columbia University and has been at the forefront of studying neural control of the gut for the past 60 years. In this episode, Mike gives a tour de force on the pathways of gut-brain communication but first sets the stage with an overview of gastrointestinal tract development and anatomy. He then explains how the gut communicates with the brain and vice versa, from early observations in physiology and anatomy up to our present understanding of what makes the GI tract so unique and complex relative to other organs. He talks about how the gut responds to meals of different food qualities and how that affects satiety signaling to the brain. Additionally, he explains how antidepressants and other drugs impact digestion through effects on serotonin signaling, and he discusses the effects of antibiotics, and what’s really going on with “leaky gut.” Finally, Mike offers his thoughts on the utility—or lack thereof—of gut microbiome diagnostic tests, and wraps up the discussion by considering how diet, probiotics, and prebiotics impact the microbiome and GI tract.

We discuss:

• The basics of the gastrointestinal (GI) system [3:45];
• The very early development of the GI system [9:30];
• The unique properties of the blood supply and portal system in the GI tract [12:45];
• An overview of gut anatomy and innervation [16:30];
• Turnover of the epithelial lining and why cancer rarely develops in the small intestine [26:45];
• Nutrient and water absorption in the small and large intestine [30:30];
• Ways in which the gut and brain communicate [34:30];
• The gut's role in the regulation of appetite [43:30];
• The impact of gastric bypass surgery on satiety signals [51:15];
• How varicella-zoster virus (VZV) can infect neurons in the gut and create issues later in life [54:30];
• The relationship between autism and gastrointestinal illness [1:02:45];
• The important role of serotonin in the gut, and the impact of SSRIs on serotonin in the gut [1:09:45];
• Defining “leaky gut” and its most common causes [1:16:45];
• The gut microbiome [1:30:45];
• Fecal transplants: use cases, limitations, and how they illustrate the importance of gut microbes [1:40:45];
• Gut microbiome diagnostic tests: why they aren’t useful outside of special cases such as cancer detection [1:50:30];
• Nutritional approaches to a maintain optimal flora in the gut [1:55:00];
• Prebiotics and probiotics, and getting your GI system back on track after a course of antibiotics [2:02:30];
• More.

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