Enhanced glycolysis after maturation of bovine oocytes in vitro is associated with increased developmental competence

In vitro maturation of oocytes has enormous potential in assisted reproductive technology, but its use has been limited due to insufficient knowledge of oocyte physiology during this dynamic period and lack of an adequate maturation system. The aim of this study was to characterize the metabolic profiles of three groups of oocytes throughout maturation: cumulus -oocyte complexes (COCs), denuded oocytes, and denuded oocytes co-cultured with cumulus cells. Mouse oocytes were collected from 28-day-old unstimulated females and matured in a defined medium. Oocytes were matured individually and transferred into fresh 0.5 ml drops of medium at 4 h intervals until 16 h. Ultramicrofluorimetry was used to quantitate carbohydrate consumption from and metabolite release into the medium. Glucose consumption and lactate production of COCs increased (P < 0.001) over the maturation interval (0 -16 h). Glucose consumption by COCs that subsequently fertilized was higher between 8-12 h of maturation than by COCs that did not fertilize (38 versus 29 pmol/COC per h, respectively; P < 0.01). Lactate production by COCs that subsequently fertilized was higher between 8-16 h of maturation, than by oocytes that did not fertilize (8 -12 h, 66 versus 46 pmol/COC per h, P < 0.01; 12-16 h, 56 versus 40 pmol/COC per h, respectively; P < 0.05). These data indicate that the final hours of maturation may hold a unique marker of oocyte competence, as during this time fertilizable COCs take up more glucose and produce more lactate than those not subsequently fertilized.

Section: Discussionmentioning

confidence: 97%

Metabolic markers of developmental competence for in vitro-matured mouse oocytes

Preis¹,

Seidel²,

Gardner³

2005

“…And adding glucose to the culture medium enhanced glycolysis of oocytes, and a higher glycolysis rate in in vitro-maturated oocytes reflects a higher developmental competence (Krisher & Bavister 1999). Cumulus and oocyte complexes metabolize glucose through glycolysis and the pentose phosphate pathway, and metabolites of glucose are thought to regulate meiotic maturation (Rose-Hellekant et al 1995, Downs et al 1996, Krisher & Bavister 1999.…”

Section: Discussionmentioning

confidence: 99%

Effects of follicle size and electrolytes and glucose in maturation medium on nuclear maturation and developmental competence of bovine oocytes

Iwata¹,

Hashimoto²,

Ohota³

et al. 2004

The concentrations of electrolytes (Na, K, Cl, Mg and Ca) and glucose in small follicle (SF) follicular fluid (SFF) and large follicle (LF) follicular fluid (LFF) from slaughterhouse-derived ovaries were studied. Oocytes were matured in medium based on synthetic oviductal fluid. The effects of various concentrations of electrolytes (Na, K, Ca and Mg) and glucose in the maturation medium on the progression of nuclear maturation and subsequent development were also studied. K in SFF was significantly greater than that in LFF. The Mg concentration in follicular fluid (FF) is 2.0 -2.3 mM, which is greater than the concentration present in medium generally used for culture. The glucose concentration in FF is about 3.5 -3.9 mM and rapidly decreases during the preservation of ovaries. LF oocytes resumed nuclear maturation and progressed to the M2 stage significantly faster than those collected from SF oocytes. In addition, more LF oocytes developed to blastocysts than did SF oocytes. Changing the Na/K ratio in the maturation medium from 16 to 24 did not affect either the progression of nuclear maturation or the rate of development. A low concentration of Mg (0.5 mM) combined with a low Ca concentration (0.5 mM) inhibited the rate of development, but did not affect the progression of nuclear maturation. On the other hand, increasing the Mg concentration to 2.0 mM from 0.5 mM hastened the progression of nuclear maturation and improved the rate of blastulation, irrespective of the Ca concentration. The progression of nuclear maturation was faster and the rate of development was greater with 5.56 mM glucose than with 1.5 mM glucose. The difference in time needed to progress to M2 among the experiment was about 2-3 h. Therefore, prolonging the maturation periods from 21 to 24 h did not change the rate of development. Our results show that the concentrations of Mg and glucose in the maturation medium and the follicle size enveloping the oocyte affect the progression of nuclear maturation and subsequent development. The time requirement for oocytes to reach M2 is strongly related to the developmental competence of the oocytes.

“…However, numerous groups have demonstrated that despite the low glycolytic activity in the oocyte, there appears to be an important positive relationship between this relatively low glycolytic activity and developmental competence of oocytes (Krisher & Bavister 1999, Spindler et al 2000, Durkin et al 2001, Herrick et al 2006. For example, oocytes derived from pre-pubertal cattle and sheep (which have lower developmental competence) have delayed increases in glycolytic activity during maturation compared to oocytes derived from adult animals (higher developmental competence), with the rate of glucose metabolism in adult oocytes constantly increasing over a 24-h period, compared to increases in activity at the end of maturation in prepubertal derived oocytes (O'Brien et al 1996, Steeves & Gardner 1999.…”

Section: Glycolysismentioning

confidence: 99%

The pivotal role of glucose metabolism in determining oocyte developmental competence

Sutton‐McDowall

Gilchrist²,

Thompson³

2010

427

325

The environment that the cumulus oocyte complex (COC) is exposed to during either in vivo or in vitro maturation (IVM) can have profound effects on the success of fertilisation and subsequent embryo development. Glucose is a pivotal metabolite for the COC and is metabolised by glycolysis, the pentose phosphate pathway (PPP), the hexosamine biosynthesis pathway (HBP) and the polyol pathway. Over the course of oocyte maturation, a large proportion of total glucose is metabolised via the glycolytic pathway to provide substrates such as pyruvate for energy production. Glucose is also the substrate for many cellular functions during oocyte maturation, including regulation of nuclear maturation and redox state via the PPP and for the synthesis of substrates of extracellular matrices (cumulus expansion) and O-linked glycosylation (cell signalling) via the HBP. However, the oocyte is susceptible to glucose concentration-dependent perturbations in nuclear and cytoplasmic maturation, leading to poor embryonic development post-fertilisation. For example, glucose concentrations either too high or too low result in precocious resumption of nuclear maturation. This review will discuss the relevant pathways of glucose metabolism by COCs during in vivo maturation and IVM, including the relative contribution of the somatic and gamete compartments of the COC to glucose metabolism. The consequences of exposing COCs to abnormal glucose concentrations will also be examined, either during IVM or by altered maternal environments, such as during hyperglycaemia induced by diabetes and obesity.Reproduction (2010) 139 685-695