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Science Snippet: Gut Flora, Obesity and Social Behavior

Obese mothers are 50 percent more likely to have children that become autistic than are mothers of normal weight. One theory is that the difference is due to gut bacteria. A recent study with mice did indeed show a relationship between gut flora, obesity and social behavior. Mice can exhibit autistic-appearing behavior, such as not interacting with other mice or inanimate objects, both of which can be measured. In a recent experiment, 100 female mice were divided into two groups. One group was fed a high-fat diet for eight weeks, and the other group was fed a normal diet. Mice in the high-fat group, of course, became obese, and their offspring showed deficits in behavior, such as avoiding other mice and remaining solitary. Mice in the group fed a normal diet gave birth to offspring that socialized and showed typical mouse behavior. When gut bacteria were assayed and compared between the two groups, it was found that one kind of bacterium, Lactobacillus reuteri, was nine times more abundant in the guts of offspring from normal mice. Since mice tend to eat their own feces, the researchers wondered what would happen if obese offspring were placed in the same cage as offspring from mothers fed a normal diet. Under such circumstances the obese mice began to behave normally and their Lactobacillus levels rose. Lactobacillus is known to promote release of oxytocin from the mother’s brain. This neurotransmitter enhances bonding between mother and offspring, suggesting that offspring from obese mothers receive less care (licking, nuzzling, etc.) than those from mothers of normal weight. This is another example of the resident bacteria of the intestine influencing behavior. Future research will determine the degree to which this mouse research is applicable to humans. (Buffington et al, 2016, Cell, June 16; The Economist, 2016, June 18; eurekalert.org/pub; other sources)

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