β-Endorphins are not responsible for delayed gastric emptying of digestible solids after exercise in professional cyclists. A preliminary study

Objective: It has been reported that professional cyclists had an accelerated solid gastric emptying which decreased by increasing the exercise intensity. That could be explained by a predominance of stress-dependent motility inhibitors such gastrointestinal hormones, neurotransmitters and or the predominance of the gastric inhibitory vagal motor circuit. The aim of this preliminary study was to evaluate the role of beta-endorphins, inhibitors of gastric motility, in these findings. Methods: Gastric emptying of solids marked with Tc-99 while resting and plasmatic levels of beta-endorphins were evaluated in 27 healthy controls and 19 professional cyclists (day 1). Besides, gastric emptying of solids was also assessed in cyclists when they reached 50% (day 1) and 75% (day 2) of the maximum oxygen consumption (low and high, respectively), during exercise on the cycle-ergometer. The third day, naloxone was administered in cyclists in order to block the beta-endorphins receptors and gastric emptying was measured when they reached 75% of the maximum oxygen consumption. Results: Basal beta-endorphin levels were lower in cyclists vs controls (p < 0.05) and they increased with the exercise intensity (p < 0.001). There were no significant differences in gastric emptying of solids with or without naloxone when 75% of the maximum oxygen consumption was reached. Conclusions: The inhibitory effect of the exercise in the gastric emptying of solids does not seem to be secondary to the action of beta-endorphins, that leaves the gastric inhibitory vagal motor circuit a more likely predominant role. (c) 2022 Elsevier Espana, S.L.U. All rights reserved.