Medical

Exciting insight into role gut bacteria play in obesity-related depression and anxiety

Exciting insight into role gut...
A new study has found gut bacteria may play a part in anxiety and depression seen to accompany conditions such as obesity and diabetes
A new study has found gut bacteria may play a part in anxiety and depression seen to accompany conditions such as obesity and diabetes
View 1 Image
A new study has found gut bacteria may play a part in anxiety and depression seen to accompany conditions such as obesity and diabetes
1/1
A new study has found gut bacteria may play a part in anxiety and depression seen to accompany conditions such as obesity and diabetes

A compelling new study from researchers at Joslin Diabetes Center has shed more light on the mysterious connection between our diet, gut bacteria and mood. The study found that mice given a high-fat diet displayed greater depressive behaviors until microbiome-altering antibiotics returned their behavior back to normal.

Microbiome research is undeniably one of the most exciting areas of medical research today. One of the most intriguing subsets in this field is the growing connections that link our gut bacteria and the brain. From PTSD to depression, researchers are finding interesting neurochemical effects stemming from the unique makeup of our gut microbiome.

It has long been known that people suffering from type 2 diabetes or obesity seem to be struck down with depression and anxiety at higher rates than the rest of the population. While this may seem like an obvious correlation, the psychological effects simply being a consequence of the disease, some researchers are beginning to suggest there may actually be more to it.

Several previous studies have found anxiety or stress-related behaviors in mice can be modulated through changes in the gut microbiome. This new work from the Joslin team set out to study how animals on high-fat diets can be behaviorally modified through microbiome alterations.

Earlier research from the same team established that mice fed a high-fat diet and bred to develop various metabolic diseases such as diabetes often had the onset of their diseases modulated by gut bacteria alterations. This new study set out to examine how a high-fat diet influences mood, and then how those mood changes can be subsequently disrupted through microbiome alterations.

The study initially showed that mice on a high-fat diet certainly displayed more clinical signs of depression and anxiety than those animals on a normal diet. But most interesting was the observation that when those mice on the high-fat diet were administered antibiotics they displayed behaviors that returned to normal.

The high-fat diet mice were administered two different broad antibiotics: vancomycin, to destroy gram positive gut bacteria, and metronidazole, which kills anaerobes. The antibiotics seemed to reverse any dietary induced negative behavior, but they also improved insulin-signaling in the brain, which was disrupted by the high-fat diet.

To confirm these changes were modulated through the microbiome, the researchers transferred gut bacteria from the experimental mice into a type of mouse engineered to have no gut bacteria of its own. In all cases the animals with the new, transplanted gut bacteria displayed behavior that mirrored the donor mice.

The research homed in on certain brain mechanisms that were being affected by these microbiome-alterations. It was discovered that many brain changes brought on by the high-fat diet were reversed when the antibiotics were administered.

"We demonstrated that, just like other tissues of the body, these areas of the brain become insulin resistant in mice on high-fat diets," says C. Ronald Kahn, senior author on the new study. "And this response to the high fat is partly, and in some cases almost completely, reversed by putting the animals [on] antibiotics. Again, the response is transferrable when you transfer the gut microbiome from mice on a high-fat diet to germ-free mice. So, the insulin resistance in the brain is mediated at least in part by factors coming from the microbiome."

At this stage, the researchers have not specifically targeted which bacteria could be causing the neurochemical changes, or what mechanism may be generating the effects. But it's a compelling beginning and yet another piece of strong evidence suggesting the bacteria in our gut has a more profound effect on our well being than we ever previously realized.

Kahn also suggests that antibiotics, such as those used in the study, that alter a broad spectrum of gut bacteria would never be an end result for human treatments.

"Antibiotics are blunt tools that change many bacteria in very dramatic ways," says Kahn. "Going forward, we want to get a more sophisticated understanding about which bacteria contribute to insulin resistance in the brain and in other tissues. 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."

The study was published in the journal Molecular Psychiatry.

Source: Joslin Diabetes Center via EurekAlert

5 comments
Bob
Just how does a depressed or anxiety afflicted mouse act? How do we know these aren't just Type A and Type B personality traits? Or in this case mouse-onality traits. Given the mouse's simple life and lack of speech, how do they interpolate this to human behavior? While I firmly believe they are on to something, I wish the results were less subjective.
IanWhiteley
High fat diets do not cause diabetes. High sugar and refined carbs diets cause both diabetes, and obesity, and indeed links to depression.
voluntaryist
Depression is not a disease. It, like pain, is a warning. The objective should be to find the cause of the depression/obesity/diabetes not give the patient something to remove a symptom. Of course, this would cure and reduce doctor visits, resulting in less revenue for the medical industry, therefore it won't happen until the public stop treating doctors like authority figures and start demanding "first, do no harm".
TK
From Molecular Psychiatry quoted in the post: "One week later both antibiotic-treated groups and one of the two control groups were challenged with a high fat diet (60% fat by calories) for 4 weeks, while the second control group remained on normal chow (22% fat by calories)." Well, the real high-fat diet, like the Optimal Diet, is no less than 80% fat by calories. The remainder is split between protein and low-glycemic carbs. It may have a different effect than 60% fat diet.
christopher
Interesting conundrum: if medical science shows that existent medical practice of widely prescribed antibiotics has caused widespread psychological and other ailments - that's a massive class action problem right there. It would seem that covering this up is in the best interests of practitioners, but not in the best interests of medicine...