WASHINGTON, June 17 (Xinhua) -- American researchers found the bacteria in the gut might be a potential contributor to depression and anxiety for people in obesity.
Mice on a high-fat diet showed significantly more signs of anxiety, depression and obsessive behavior than animals on standard diets, according to a study published on Sunday in the journal Molecular Psychiatry.
"But all of these behaviors are reversed or improved when antibiotics that will change the gut microbiome were given with the high fat diet," said the paper's senior author C. Ronald Kahn, professor of medicine at Harvard Medical School.
Researchers identified the effect of the microbiome by transferring gut bacteria from these experimental mice to germ-free mice, who did not have any bacteria of their own.
The animals who received bacteria from mice on a high-fat diet began to show increased levels of activity associated with anxiety and obsessive behavior.
However, those who received microbes from mice on a high-fat diet plus antibiotics did not, even though they did not receive the antibiotics themselves.
The researchers looked for clues in two areas of the brain, the hypothalamus (which helps to control whole body metabolism) and the nucleus accumbens (which is important for mood and behavior).
"We demonstrated that, just like other tissues of the body, these areas of the brain become insulin resistant in mice on high-fat diets," Kahn said.
"This response to the high fat is partly, and in some cases almost completely, reversed by putting the animals by antibiotics," Khan said."So, the insulin resistance in the brain is mediated at least in part by factors coming from the microbiome."
They also linked the microbiome alterations to the production of certain neurotransmitters, which are the chemicals that transfer signals across the brain.
Kahn and his colleagues are now working to identify specific populations of bacteria involved in these processes, and the molecules that the bacteria produce.
"Antibiotics are blunt tools that change many bacteria in very dramatic ways," Kahn said, adding that their eventual goal is to find drugs or supplements that can help to achieve healthier metabolic profiles in the brain.
"If we could modify those bacteria, either by putting in more beneficial bacteria or reducing the number of harmful bacteria, that might be a way to see improved behavior."
