Interaction of carbohydrate metabolism and rat liquid gastric emptying in sustained running

Abstract

Moderate to severe running usually leads to gastrointestinal dysmotility and critical energy exhaustion. It is unknown whether the carbohydrate metabolism of runners can influence gastric emptying (GE). Using a running rat model, the present study explored the impact of exercise/carbohydrate metabolism on liquid GE. Rats were put on the runways of a moving treadmill for 1 h. Trained rats underwent daily running 5 days a week for 4 weeks. Untrained rats were those put on a quiet treadmill to serve as sham exercise. On the motility study day, trained and untrained rats ran for 45 min. After orogastric feeding of radiochromium marker, they resumed running for an additional 15 min and were then killed in order to measure GE. Another group of trained and untrained rats received lactate infusion for 1 h in the quiet condition to measure their GE. The third group of rats received glucose infusion during running to measure GE. Running of untrained (P < 0.05) and trained (P < 0.01) rats enhanced GE compared to sham exercise. Running for the untrained rats rather than the trained counterparts had diminished plasma glucose level (P < 0.05). Running also elevated plasma lactate levels for both untrained (P < 0.001) and trained rats (P < 0.01). Lactate infusion delayed GE in untrained (P < 0.01) and trained rats (P < 0.05). Glucose infusion of untrained rats during running was not only to correct hypoglycemia (P < 0.01) but also to restore their enhanced GE (P < 0.01). Running-induced hypoglycemia, rather than lactate accumulation, is one of the essential factors leading to enhanced liquid GE in untrained rats.