Antibiotics, Immunity, and Obesity

Aug 19, 2014

By Jyoti Madhusoodanan


A brief, low dose of antibiotics shortly after birth can have long-lasting consequences on gut microbes in mice and lead to obesity once the rodents reach middle age. These findings, published today (August 14) in Cell, suggest that the gut microbiome may influence the development of metabolic pathways during a critical time window early in life.

Low doses of antibiotics have been used to promote animal growth in agriculture for several decades, although the mechanism underlying the drugs’ fattening effect was unclear. Martin Blaser of the New York University Langone Medical Center and his colleagues showed in a 2012 Nature paper that early-life antibiotic therapy in mice altered hormone levels and the activities of genes involved in carbohydrate and lipid metabolism.

For this latest study, Blaser and his colleagues aimed to better understand how the timing of such treatment might mediate microbial effects on host metabolism, he told The Scientist. The researchers treated two groups of mice with low doses of penicillin either shortly before pups were born or while they were weaning. A third group of pups received the antibiotic after they had been weaned. The low doses of penicillin used in the experiments were not strong enough to decrease the overall gut microbial population, although the treatment did lead to increased body fat and skewed the proportions of dominant bacterial species in the gut.

Treated mice had significantly lower levels of Lactobacillus in their guts than untreated mice;Candidatus and Allobaculum, two other bacteria that typically reach peak proportions early in life, were suppressed by the small penicillin doses.

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