Running Interference? Exercise and PCB-Induced Changes in the Gut

Trillions of diverse bacteria live in the gastrointestinal tract in a com-munity collectively known as the gut microbiome. Changes in the makeup of the gut microbiome have been implicated in a variety of diseases, including obesity and diabetes,1 both of which also are affected by exercise, diet, and other lifestyle behaviors.2 Likewise, exposure to the industrial pollutants polychlorinated biphenyls (PCBs) has been shown to impair glucose homeostasis in mice,3 suggesting it could increase the risk for diabetes, and obese people have been reported to have higher body burdens of PCBs than lean people.4 A novel study in EHP looks at the interaction among the gut microbiome, exercise, and PCB exposure in mice.5 The study showed that short-term oral exposure to an environ-mentally relevant mixture of PCBs was associated with reduced abun-dance and diversity of gut microbes. However, mice that exercised daily before PCB dosing began showed fewer changes to the gut microbiome than sedentary mice. The mice were about a year old, comparable to middle age for people. Half the mice exercised voluntarily on a running wheel, running an average of 10–12 km per day; the other half had locked wheels in their cages. After a five-week exercise period all mice were dosed with a mixture of PCB138, PCB153, and PCB180 for two days. These PCB congeners and the amounts given reflect those found in high concentra-tions in contaminated fish from the Great Lakes, according to senio