http://www.sciencedaily.com/releases/2011/05/110517110315.htmMay 17, 2011
For the first time, researchers at McMaster University have conclusive evidence that bacteria residing in the gut influence brain chemistry and behaviour.
The findings are important because several common types of gastrointestinal disease, including irritable bowel syndrome, are frequently associated with anxiety or depression. In addition there has been speculation that some psychiatric disorders, such as late onset autism, may be associated with an abnormal bacterial content in the gut. . . .
Working with healthy adult mice, the researchers showed that disrupting the normal bacterial content of the gut with antibiotics produced changes in behaviour; the mice became less cautious or anxious. This change was accompanied by an increase in brain-derived neurotrophic factor (BDNF), which has been linked to depression and anxiety.
When oral antibiotics were discontinued, bacteria in the gut returned to normal. "This was accompanied by restoration of normal behaviour and brain chemistry," Collins said.
http://www.physorg.com/news/2011-02-gut-bacteria-functions.htmlFebruary 28, 2011
Claus and her colleagues exposed germ-free mice to bedding that had previously been used by conventional mice with normal microbiota and followed their metabolic profiles for 20 days to observe changes as they became colonized with gut bacteria.
Over the first 5 days after exposure, the mice exhibited a rapid increase in weight (4%). Colonization also triggered a number of processes in the liver in which sugars (glucose) are converted to starch (glycogen) and fat (triglycerides) for short-term and long-term energy storage. Statistical modeling between liver metabolic functions and microbial populations determined that the levels of glucose, glycogen and triglycerides in the liver were strongly associated with a single family of bacteria called Coriobacteriaceae. . . .
Another important finding in the paper, according to Claus, is that gut colonization strongly stimulated the expression and activity of the cytochrome P450 3A11, an essential enzyme in drug-detoxification pathways.