Saturday July 21, 2018

Microbes May Be Stirring Up Anxiety And Depression In Obese People

To test the theory, Kahn and colleagues fed mice a high-fat diet and studied their behavior as the animals became obese

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Microbes May Be Stirring Up Anxiety And Depression In Obese People
Microbes May Be Stirring Up Anxiety And Depression In Obese People, Pixabay
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Microbes may be helping stir up anxiety and depression in obese people, if results from a new mouse study hold true in humans.

The authors link the effects to how the brain responds to insulin, the hormone that regulates sugar levels in the blood.

The research raises questions about whether changing gut microbes, or changing diet, could help treat these conditions.

Mood, microbes and metabolism

Obesity triggers changes in metabolism — for example, making liver, muscle, fat and other tissues less responsive to insulin. Left untreated, these changes can lead to diabetes.

Obese people also have higher rates of anxiety and depression.

“One could say, ‘Maybe that’s just because they’re obese,’ ” said Harvard Medical School diabetes researcher Ronald Kahn, “but others could say, ‘Maybe there’s a metabolic link.’ ”

“And we asked the question, ‘Maybe the metabolic link is at least partly fueled by the microbiome,’ ” the community of microbes living in a person’s gut, he added.

Those microbes change with diet, and Kahn said different microbes might respond differently to the foods we eat.

To test the theory, Kahn and colleagues fed mice a high-fat diet and studied their behavior as the animals became obese.

They used common tests to gauge anxious and depressed behavior in rodents — for example, how much time the animals spent hiding in a dark box versus exploring a brightly lit area. The more anxious the mouse, the less time it will spend in the light.

Obese mice spent about 25 percent less time in the light than animals on a normal diet, and they scored higher on the other anxiety and depression tests, too.

obesity
obesity, Pixabay

Return to normal

But those differences disappeared when obese mice were given antibiotics, even though their weight didn’t change much.

“That really says there’s probably something about the microbiome,” Kahn said.

The researchers then tested how the animals’ microbiomes affected mice raised in a sterile environment with no microbes of their own.

Bacteria from obese rodents made these germ-free mice more anxious than microbes from normal mice.

But when germ-free mice got microbes from obese animals that had been given antibiotics, they behaved like normal mice.

To see what parts of the brain might be responsible for the effects, the researchers focused on two regions involved in metabolism and responses to rewards. They found these regions were less responsive to insulin in the obese mice compared with normal-weight animals.

Again, antibiotics returned those responses to normal.

The research appears in the journal Molecular Psychiatry.

“It was actually quite a surprise,” Kahn said. “Even though we had seen some effects on metabolism in the rest of the body, I was very surprised how dramatic and how clear the effects were also on the brain and on behavior.”

Into the unknown

That doesn’t mean antibiotics are the cure for depression, Kahn warned. The drugs kill good and bad microbes indiscriminately, and taking the medication unnecessarily can contribute to the rising threat of antibiotic resistance.

Also, what happens in mice does not necessarily happen in humans, he added, or it may happen for only some people. So far, there is not much evidence that probiotics help anxious people.

scale
scale, Pixabay

“The difficulty is, both of these things — depression and obesity — are complicated things that have multiple, multiple factors influencing them,” said mental health researcher Gregory Simon at Kaiser Permanente Washington Health Research Institute, who was not part of the study.

Microbes are likely just one factor, along with environment, genetics, social influences and more, Simon added.

But Kahn said his group’s research raised interesting questions about how food affects our behavior.

“I think now we can get some idea that there are a lot of things that are being metabolized by gut bacteria that could affect brain function,” he said.

And he said there might be ways to change brain function by changing those bacteria, by eating helpful microbes or by eating foods that sustain them.

Also read: Two New Ways To Prevent Cholera: Microbes Fighting Microbes

He and his colleagues are working to figure out exactly which of the hundreds of species of gut bacteria are responsible. At the moment, it’s a mystery. (VOA)

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HIV Drug Is Not Linked to Depression: Study

A new study of a popular HIV drug could ease concerns about its link to depression

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A doctor draws blood from a man to check for HIV/AIDS at a mobile testing unit in Ndeeba, a suburb in Uganda's capital, Kampala.
A doctor draws blood from a man to check for HIV/AIDS at a mobile testing unit in Ndeeba, a suburb in Uganda's capital, Kampala. VOA

A new study of a popular HIV drug could ease concerns about its link to depression. Researchers in Uganda found that efavirenz, once feared to lead to depression and suicide, did not cause the expected negative side effects in their patients.

Efavirenz is an affordable, once-a-day pill used around the globe to treat and prevent HIV/AIDS. It’s “the treatment of choice” in most of the world, according to Africa Health Research Institute’s Mark Siedner, “especially [in] countries that depend on global aid to treat HIV.”

But some fear that efavirenz may come with a cost.

Some studies in the United States and Europe found the drug increased patients’ risk of depression or suicide, although other studies did not.

The mixed results prompted many doctors in the United States to prescribe more expensive but potentially safer drugs.

Siedner wanted to take another look at the risk of depression, this time in an African population. From 2005 until 2015, he and a team of Ugandan and U.S. doctors tracked 694 patients who took either efavirenz or another antiretroviral medication. They regularly asked the patients whether they experienced depression or suicidal thoughts.

No difference

Their analysis, published in the Annals of Internal Medicine, showed there was no difference between the two treatments. Siedner told VOA, “In other words, efavirenz was not associated with a risk of depression. If anything, there seems to be a signal that potentially it was associated with a decreased risk. But it wasn’t a strong enough [signal] for us to say that.”

The authors also reported that of the 17 participants who died in the course of the study, not a single death was a suicide.

Siedner has two possible explanations for why their findings differed from those in Western countries. “One potential cause is that every single ethnic group in the world, of course, is different, and different in many different ways — different socially, different environmentally, and in this case they may be different genetically.” His team is looking at whether the genes that control metabolism of the drug have a role to play in this story.

HIV Aids is a deadly disease.
HIV virus is Not Linked To Depression. Flickr

A second explanation could be the effectiveness of the drug. Because efavirenz is so potent, it could be keeping people healthier than they expected, so patients are less likely to report negative emotions.

The study is important, said Anthony Fauci, who heads the National Institute of Allergy and Infectious Diseases, because it pushes back against “the initial observation of suicidal ideation and suicide and depression” as caused by efavirenz. He told VOA, “I think now what you’re seeing is that with these conflicting reports, it’s likely someone will come in [with] the proposal to do a randomized study and take a look. So the story isn’t ended with this paper.”

As more research on the safety of efavirenz is conducted, new and cheaper drugs that might replace it are on the horizon. One of them, dolutegravir, might also pose a risk, however. A study in Botswana found dolutegravir was linked to neural tube defects in embryos, meaning it might not be safe for pregnant women. As always, further research is needed to confirm whether this is a common problem or specific to the population studied in Botswana.

Also read: UNAIDS : World Is At A “Defining Moment” In A Battle Against HIV/AIDS

“I think the whole field right now is in a bit of a holding pattern,” Siedner said when asked about dolutegravir and the future of HIV medication. (VOA)