Expanded equine cumulus-oocyte complexes exhibit higher meiotic competence and lower glucose consumption than compact cumulus-oocyte complexes

Abstract

Equine cumulus-oocyte complexes (COCs) are classified as compact (cCOC) or expanded (eCOC) and vary in their meiotic competence. This divergence could be related to different glucose metabolism. To test this hypothesis eCOCs, cCOCs, and expanded or compact mural granulosa cells (EC and CC respectively) were matured in vitro for 30 hours and the maturation rate, glucose metabolism, and expression of genes involved in glucose transport, glycolysis, apoptosis and meiotic competence were determined. Significant differences were found between eCOCs and cCOCs maturation rates (50% vs. 21.7 %; n = 192 and 46 respectively, p < 0.001), glucose consumption (1.8 ± 0.5 vs. 27.9 ± 5.9 nmol/COC; mean ± SEM), pyruvate production (0.1 ± 0.0 vs. 2.4 ± 0.8 nmol/COC; mean ± SEM) and lactate production (4.7 ± 1.3 vs. 64.1 ± 20.6 nmol/COC; mean ± SEM) respectively (p < 0.05). Moreover, similar glucose consumption was observed for EC and CC. Hyaluronan binding protein (TNFAIP6) expression was increased in eCOCs and EC, solute carrier family 2 (facilitated glucose transporter) member 1 (SLC2A1) was increased in eCOCs, while glycolysis-related enzymes and solute carrier family 2 (facilitated glucose transporter) member 3 (SLC2A3) expression did not vary between COCs or mural granulosa cell type. Our data demonstrate that metabolic and genomic differences exist between eCOCs and cCOCs and mural granulosa cells in the horse.