Exercise causes changes to some of the body's metabolites, research finds

New research finds that exercise causes changes to some of the body's metabolites-;small molecules the body produces during metabolism. These changes to the global metabolome-;the entire group of metabolites found throughout the body in the blood, tissues or urine-;may help scientists better understand the body's response to exercise. The study, published ahead of print in the American Journal of Physiology-;Endocrinology and Metabolism, was chosen as an APSselect article for November.

The human global metabolome includes hundreds to thousands of xenometabolites, "non-self" chemicals that the body does not produce, but that are the byproducts of organisms that live in the digestive tract (gut microbiome) and of the foods we consume. "It is believed that many of the xenometabolites impact health and enable cross-talk and signaling between the microbiome and the host," explained Sean Adams, PhD, corresponding author of the study.

Adams' research team studied the global metabolome of sedentary women with obesity and insulin resistance before and after exercise. The women followed a reduced-calorie diet and exercise regimen for 14 weeks that led to weight loss and improved cardiovascular fitness. They walked on a treadmill or used a stationary bicycle for 30-minute workouts at least four days a week for a month, after which each exercise session was extended to 40 minutes. The intensity level of the workouts increased incrementally throughout the trial. The researchers took blood samples every five minutes throughout the exercise sessions.

Levels of select carbohydrates, fats and amino acids in the blood dropped with acute exercise, while surprisingly, concentrations of some xenometabolites increased. The finding that "an exercise bout can change blood concentrations of xenometabolites that originally come from the gut is an emerging concept, and very exciting," Adams said. More research needs to be done to understand why this happens, "but [it] may involve exercise-associated changes to digestion or to storage and release of the molecules."

"Future studies should address the tissue‐specific origins of exercise‐related metabolite changes, how the metabolome responds across the entire spectrum of low‐to‐modest‐to‐high intensity exercise, which pathways and metabolites link to exertion and fatigue signaling and the potential interrelationships between exercise, fitness and the xenometabolome," the researchers wrote.