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Quercki : gut   3

Is eating behavior manipulated by the gastrointestinal microbiota? Evolutionary pressures and potential mechanisms
Abstract

Microbes in the gastrointestinal tract are under selective pressure to manipulate host eating behavior to increase their fitness, sometimes at the expense of host fitness. Microbes may do this through two potential strategies: (i) generating cravings for foods that they specialize on or foods that suppress their competitors, or (ii) inducing dysphoria until we eat foods that enhance their fitness. We review several potential mechanisms for microbial control over eating behavior including microbial influence on reward and satiety pathways, production of toxins that alter mood, changes to receptors including taste receptors, and hijacking of the vagus nerve, the neural axis between the gut and the brain. We also review the evidence for alternative explanations for cravings and unhealthy eating behavior. Because microbiota are easily manipulatable by prebiotics, probiotics, antibiotics, fecal transplants, and dietary changes, altering our microbiota offers a tractable approach to otherwise intractable problems of obesity and unhealthy eating.
Keywords: cravings, evolutionary conflict, host manipulation, microbiome, microbiota, obesity
diet  health  mood  obesity  microbes  gut  brain 
7 weeks ago by Quercki
Joint Pain, From the Gut - The Atlantic
Several recent studies have found intriguing links between gut microbes, rheumatoid arthritis, and other diseases in which the body’s immune system goes awry and attacks its own tissue.  

A study published in 2013 by Jose Scher, a rheumatologist at New York University, found that people with rheumatoid arthritis were much more likely to have a bug called Prevotella copri in their intestines than people that did not have the disease. In another study published in October, Scher found that patients with psoriatic arthritis, another kind of autoimmune joint disease, had significantly lower levels of other types of intestinal bacteria.

"This is frontier stuff. With the microbiome, we’ve added a new player to the game."
This work is part of a growing effort by researchers around the world to understand how the microbiome—the mass of microbes that live in the gastrointestinal tract—affects our overall health. The gut contains up to a thousand different bacteria species, which together weigh between one and three pounds. This mass contains trillions of cells, more than the number of cells that make up our own bodies. Over the past several years, scientists have compiled a growing collection of evidence that many of these bugs may have a major effect on our well-being, with some triggering chronic, non-infectious ailments such as rheumatoid arthritis, and others protecting against such diseases.
microbes  gut  arthritis 
april 2015 by Quercki
Complex and Hidden Brain in Gut Makes Stomachaches and Butterflies - New York Times
Details of how the enteric nervous system mirrors the central nervous system have been emerging in recent years, said Dr. Gershon, who is considered one of the founders of a new field of medicine called neurogastroenterology.

Nearly every substance that helps run and control the brain has turned up in the gut, Dr. Gershon said. Major neurotransmitters like serotonin, dopamine, glutamate, norepinephrine and nitric oxide are there. Two dozen small brain proteins, called neuropeptides, are in the gut, as are major cells of the immune system. Enkephalins, one class of the body's natural opiates, are in the gut. And in a finding that stumps researchers, the gut is a rich source of benzodiazepines -- the family of psychoactive chemicals that includes such ever popular drugs as Valium and Xanax.

In evolutionary terms, it makes sense that the body has two brains, said Dr. David Wingate, a professor of gastrointestinal science at the University of London and a consultant at Royal London Hospital. The first nervous systems were in tubular animals that stuck to rocks and waited for food to pass by, Dr. Wingate said. The limbic system is often referred to as the "reptile brain."

As life evolved, animals needed a more complex brain for finding food and sex and so developed a central nervous system. But the gut's nervous system was too important to put inside the newborn head with long connections going down to the body, Dr. Wingate said. Offspring need to eat and digest food at birth. Therefore, nature seems to have preserved the enteric nervous system as an independent circuit inside higher animals. It is only loosely connected to the central nervous system and can mostly function alone, without instructions from topside.
gut  brain  bacteria  neuroscience 
may 2011 by Quercki

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