Epigallocatechin gallate: friend or foe of stallion spermatozoa? (#280)
Epigallocatechin gallate (EGCG) is a major ingredient of several antioxidant horse feed supplements. To date, there is no literature on the effects of the nutritional supplementation of EGCG on stallion spermatozoa in vivo. The aim of this experiment was twofold, firstly, to determine the effects of EGCG on stallion spermatozoa in vitro, and secondly to observe whether gallocatechin gallate (GCG), the major epimerization breakdown product of EGCG following digestion, would produce the same effects. For both experiments, semen was collected from stallions (n=3) and incubated in BWW media with or without 250 µM EGCG (experiment 1) or 250 µM GCG (experiment 2) at 37°C for 24 h. Motility (CASA), vitality (eosin), mitochondrial ROS production (MitoSOX™ Red) and mitochondrial membrane potential (JC-1) were assessed after 24 h. The results of the first experiment revealed that total motility was significantly lower in EGCG than the control (1.5 vs. 57%), while vitality was significantly higher in EGCG compared to the control (85 vs. 58%). Mitochondrial ROS was significantly higher in EGCG treatment compared to the control (72.3 vs. 53.3%), and mitochondrial membrane potential was significantly reduced by incubation with EGCG (10.2 vs. 77.8%). Exposure of spermatozoa to GCG during experiment 2 produced similar results to those observed in experiment 1. Total motility was significantly lower in GCG than in the control (0.33 vs. 52.67%). Mitochondrial ROS was significantly higher in GCG compared to the control (84.32 vs. 32.67%), and mitochondrial membrane potential was significantly reduced by incubation with GCG (0.33 vs. 75.05%). In contrast to experiment 1, GCG had no effect on vitality (42 vs. 44% for GCG and control respectively). In conclusion, the deleterious effects of both EGCG and GCG on spermatozoa at 37°C suggest that feeding EGCG based feed supplements to stallions may be contraindicated and warrants further investigation in vivo.