Author: Théophile Niyitegeka

{Lactobacillus affects mood, anxiety in mice; researchers optimistic findings should hold true in humans}

Researchers at the University of Virginia School of Medicine have reversed depression symptoms in mice by feeding them Lactobacillus, a probiotic bacteria found in live-cultures yogurt. Further, they have discovered a specific mechanism for how the bacteria affect mood, providing a direct link between the health of the gut microbiome and mental health.

Based on their findings, the researchers are optimistic that their discovery will hold true in people and are planning to confirm their findings in patients with depression.

“The big hope for this kind of research is that we won’t need to bother with complex drugs and side effects when we can just play with the microbiome,” explained lead researcher Alban Gaultier, PhD. “It would be magical just to change your diet, to change the bacteria you take, and fix your health — and your mood.”

Treating Depression

Depression is one of the most common mental health conditions in the United States, with up to 7 percent of people experiencing a major depressive episode, Gaultier noted. “It’s a huge problem and the treatments are not very good, because they come with huge side effects,” he said.

The role of the gut microbiome — the bacteria that live inside us — has been of tremendous interest to researchers studying depression and other health conditions, both mental and physical. Gaultier, of the UVA Department of Neuroscience and its Center for Brain Immunology and Glia, set out to see if he could find a concrete link between depression and gut health. “When you’re stressed, you increase your chance of being depressed, and that’s been known for a long, long time,” he said. “So the question that we wanted to ask is, does the microbiome participate in depression?”

The answer appears to be yes. Looking at the composition of the gut microbiome before and after mice were subjected to stress, Gaultier’s team found that the major change was the loss of Lactobacillus. With the loss of Lactobacillus came the onset of depression symptoms. Feeding the mice Lactobacillus with their food returned them to almost normal. “A single strain of Lactobacillus,” Gaultier observed, “is able to influence mood.”

He and his team then went on to determine the mechanism by which Lactobacillus influences depression. They found that the amount of Lactobacillus in the gut affects the level of a metabolite in the blood called kynurenine, which has been shown to drive depression. When Lactobacillus was diminished in the gut, the levels of kynurenine went up — and depression symptoms set in.

“This is the most consistent change we’ve seen across different experiments and different settings we call microbiome profiles,” explained researcher Ioana Marin, a graduate student who is finishing up her PhD. work. “This is a consistent change. We see Lactobacillus levels correlate directly with the behavior of these mice.”

Testing in Humans

Gaultier was careful to call the symptoms seen in mice as “depressive-like behavior” or “despair behavior,” as mice have no way to communicate that they are feeling depressed. But those symptoms are widely accepted as the best available model for looking at depression in creatures other than humans.

Based on the new findings, Gaultier plans to begin studying the effect in people as soon as possible. He intends to examine the effects of Lactobacillus on depression in patients with multiple sclerosis, a group in which the disorder is common. Promisingly, the same biological substances and mechanisms Lactobacillus uses to affect mood in mice are also seen in humans, suggesting the effect may be the same.

In addition to looking at the effects in people, the researchers are continuing to explore the important role of kynurenine. “There has been some work in humans and quite a bit in animal models talking about how this metabolite, kynurenine, can influence behavior,” Marin said. “It’s something produced with inflammation that we know is connected with depression. But the question still remains: How? How does this molecule affect the brain? What are the processes? This is the road we want to take.”

While there is no harm in people with depression eating yogurt, people receiving treatment for depression should not stop taking their medications without consulting their physicians. More studies, the researchers noted, are needed.

Source:Science Daily

{Just as a sprinter’s body and muscles are ready for action as they wait for the starting gun to fire, brain networks at rest appear to be waiting in a state of potentiation to execute even the simplest of behaviors.}

This evidence comes from a new paper published this week in the journal PLoS One, reporting on a study led by professors Vaibhav Diwadkar, Ph.D., at Wayne State University’s School of Medicine and Steven L. Bressler, Ph.D., interim director of Florida Atlantic University’s Center for Complex Systems and Brain Sciences.

In the study, “Potentiation of motor sub-networks for motor control but not working memory: Interaction of dACC and SMA revealed by resting-state directed functional connectivity,” the researchers used a simple experimental task, having each participant perform a simple motor control behavior (tapping their forefinger to a visual cue) that alternated between behavior and rest. Brain activity was acquired using functional MRI (fMRI), a technique that allows collection of dynamic signals from within the brain when the subject is doing a task as well as when they are at rest.

Using relatively complex modeling of fMRI signals, the team studied brain network interactions between two important brain regions: the dorsal anterior cingulate cortex (dACC), used for control, and the supplementary motor area (SMA), used for motor movements. In their previous studies, the team highlighted the importance of directional network interactions from the dACC to the SMA during simple motor behavior. In the PLoS One paper, they showed a compelling and opposite effect: during the rest periods that alternated between the motor behavior task, network interactions from the SMA to the dACC were now increased.

According to Diwadkar, who co-directs the Brain Imaging Research Division in the Department of Psychiatry & Behavioral Neurosciences, “These results suggest that directional interactions from the SMA to the dACC during the rest period may in fact potentiate task-related interactions in the opposite direction.” He further noted that the studies confirm what has been long suggested and independently demonstrated: that the brain’s networks are always in a state of potentiation for action, precisely because it is impossible to predict what they will be required to do at any given time. Therefore, it is unlikely that the brain can ever be at true rest.

This paper is one of the few attempts to systematically investigate directional interactions between brain networks in the resting state and show how this state might potentiate the opposite direction of the same network task-related processing.

“Our findings are compelling because brain networks are in patterns of incessantly complex directional interactions,” said Diwadkar. “Directionality is difficult to measure, and our complex analyses show that it is possible to estimate this from fMRI data.”

According to Diwadkar, the team’s findings reveal aspects not only of normative brain function but may also provide new directions for characterizing disordered network interactions in neuropsychiatric syndromes. They will be investigating these questions in obsessive-compulsive disorder with David Rosenberg, M.D., the Miriam L. Hamburger Endowed Chair of Child Psychiatry and chair of the Department of Psychiatry and Behavioral Neurosciences at Wayne State University; and in schizophrenia with Dr. Jeffrey Stanley, Ph.D., associate professor of psychiatry. Diwadkar and Bressler are continuing to collaborate on several directions of research focusing on brain network function and dysfunction.

Source:Science Daily