The ability to achieve meiotic maturation in the dog oocyte is linked to glycolysis and glutamine oxidation

Abstract

We tested the hypothesis that meiotic competence of dog oocytes was tightly linked with donor follicle size and energy metabolism. Oocytes were recovered from small (< 1 mm diameter, n = 327), medium (1 – < 2 mm, n = 292) or large (≥ 2 mm, n = 102) follicles, cultured for 0, 24 or 48 h, assessed for glycolysis, glucose oxidation, pyruvate uptake, glutamine oxidation and then nuclear status. More oocytes (P < 0.05) from large follicles (37%) reached the metaphase II (MII) stage than from the small group (11%), with the medium size class being intermediate (18%; P > 0.05). Glycolytic rate increased (P < 0.05) as oocytes progressed from the germinal vesicle (GV) to MII stage. At 48 h of culture, oocytes completing nuclear maturation had higher (P < 0.05) glycolytic rate than those arrested at earlier stages. GV oocytes recovered from large follicle oocytes had higher (P < 0.05) metabolism than those from smaller counterparts at culture onset. MII oocytes from large follicles oxidized more (P < 0.05) glutamine than the same stage gametes recovered from smaller counterparts. In summary, larger size dog follicles contain a more metabolically-active oocyte with a greater chance of achieving nuclear maturation in vitro. These findings demonstrate a significant role of energy metabolism in promoting dog oocyte maturation, information that will be useful for improving culture systems for rescuing intraovarian genetic material.

Metabolic control of oocyte development: linking maternal nutrition and reproductive outcomes

“…1; Table 1). Interestingly, dog and pig oocytes seem to utilize glucose as the primary energy substrate at a much higher rate than that of other species [32, 49], implying the species-specific differences in metabolic pattern of glucose in oocytes.…”

Energy Metabolism Regulating Mammalian Oocyte Maturation

“…Thus, most mammalian species appear to rely on cumulus cells that contain an additional GLUT with high affinity to this substrate and high phosphofructokinase activity to convert glucose into readily utilized substrates (i.e., pyruvate, NADPH; (Sutton-McDowall et al, 2010;Biggers, et al, 1967). However, we have recently found that dog oocytes utilize glucose at a much higher rate than that of other species (Songsasen et al, 2012). This finding indicates that dog gamete may contain additional GLUT or high levels of glycolytic enzyme compared to those in other species.…”

“…In order to correctly reference this scholarly work, feel free to copy and paste the following: N. Songsasen (2012). Energy Metabolism Regulating Mammalian Oocyte Maturation, Meiosis -Molecular Mechanisms and Cytogenetic Diversity, Dr. Andrew Swan (Ed.…”

Structural Changes of Zona Pellucida Surface of Immature, In vivo and In Vitro Matured Canine Oocytes Using Scanning Electron Microscopy

“…Nuclear status assessments were carried out as previously described (Songsasen et al 2012). In brief, oocytes were fixed by placement into wells containing 1:3 acetic acid:ethanol solution for 48 h, then stained using aceto-orcein (1%…”