31 May 2017 - St Louis Post-Dispatch - Of mice and men: a link between obesity and autism?

A recent column about a possible connection between obesity and the current trend for girls to first get their periods at increasingly early ages prompted a reader to send in a report that may be even more alarming.

Last year, the Economist magazine reported on a study showing a possible link between obesity and autism.

Before we go any further, I should point out that this is only one study (well, actually two, sort of), and that no one is stating it yet as proven fact. Much more work needs to be done.

Even so, the potential link between obesity and autism is at least intriguing. It begins with this fact: Obese mothers are 50 percent more likely than mothers of normal weight to give birth to a child who goes on to become autistic.

For obese women with diabetes, that probability shoots up to four times more likely. And even women with gestational diabetes — diabetes that begins with pregnancy and typically goes away after delivery — are three times more likely to have children who develop autism.

Knowing this, Baylor College of Medicine researchers Mauro Costa-Mattioli and Shelly Buffington did an experiment to see if the connection can have anything to do with bacteria in the stomach and intestinal tract.

For eight weeks, they fed a high-fat diet to 50 female mice and a normal diet to 50 other female mice. Then they got the mice pregnant and studied their offspring. They looked at how long the younger mice interacted with strangers and with inanimate objects.

The children of the normal mice played with other mice for an average of two minutes out of a 10-minute period. But the children of the obese mice interacted with others for an average of just 22 seconds.

And when the mice were given a choice between spending time with other mice or an empty cup, 55 percent of the obese-mouse children went to the empty cup. In contrast, all of the children of the normal-weight mice spent went to be with the other mice.

What was the difference? The scientists studied the gut bacteria of all the mice and determined that a particular bacterium, Lactobacillus reuteri, was found in only small numbers in the children of the obese mice. It was nine times more prevalent in the children of the normal mice.

A few years ago, L. reuteri was found to help release oxytocin, a hormone that, among many other things, affects social behavior and emotions. It can also be used to help treat people with autism.

The researchers next gave water that had L. reuteri in it to the children of both types of mothers. As a control, they gave either pure water or water with the bacterium in it to a control set of mice.

The children of the obese mice that drank the water with L. reuteri in it had normal social interactions. The control mice that did not get the water with the bacteria in it had social problems.

In other words, the link between obesity and social development— at least in mice — is caused by a deficit of L. reuteri, not by other factors of obesity.

It is not yet known whether there is a similar correlation between L. reuteri and autism in humans. If such a link can be made, the Economist suggests that it might be smart to give infants L. reuteri as a way to decrease the rate of autism.

It’s a promising idea.