Carbohydrate metabolism by murine ovarian follicles and oocytes grown in vitro

Abstract

Metabolic markers are potentially valuable for assessment of follicle development in vitro. Carbohydrate metabolism of murine preantral follicles grown to maturity over 13 days in vitro has been measured, and metabolism of resulting oocyte-cumulus complexes (OCCs) and denuded oocytes has been compared with in vivo ovulated control counterparts. Spent follicle culture media were analysed for glucose, lactate and pyruvate concentrations. During follicle in vitro growth, glycolysis accounted for a rise from w24 to 60% of all glucose consumed. Ovulation induction caused a significant increase in glucose uptake and lactate production by in vitrogrown follicles to 71.7G1.2 and 96.6G4.8 nmoles/day respectively. OCCs grown in vitro had significantly higher rates of glucose consumption and lactate and pyruvate production (110.1G3.5, 191.8G8.9 and 31.7G1.7 pmoles/h respectively) than in vivo ovulated controls (67.4G8.1, 113.9G17.1 and 20.2G4.0 pmoles/h respectively), but a reduced capacity for pyruvate consumption (1.13G0.06 vs 1.49G0.06 pmoles/h by in vivo ovulated oocytes). Metabolism of OCCs was affected by the quality of the original follicle. In vitro-grown oocytes had a reduced cytoplasmic volume when compared with controls (168.3G2.0 vs 199.0G3.2 proportionately respectively) but a similar rate of metabolism per unit volume. Meiotic status influenced metabolism of both OCCs and denuded oocytes. In conclusion, glucose consumption and lactate production by cultured follicles increased in tandem with developmental progression and were stimulated prior to ovulation. Additionally, the metabolic profiles of in vitro produced OCCs and the oocytes within them are affected by long-term exposure to the culture environment. Reproduction (2007) 134 415-424

The impact of obesity on egg quality

“…Previous work has shown that oocytes have low glycolytic activity [74] as well as low phosphofructokinase (PFK) activity [75]. As described above, the oocyte and cumulus cells exist together until after fertilization as the cumulus-oocyte-complex (COC).…”

Gonadotropins up-regulate the expression of enolase 2, but not enolase 1, in the rat ovary

“…Therefore, we suggest that endogenous gonadotropins, LH, FSH and CG, up-regulate expression of ENO2 in oocytes and theca cells of preantral and antral follicles, which would activate glycolysis in these cells. Glycolysis is a major contributor to energy production in ovarian follicles [6][7][8]. Thus, gonadotropin-stimulation of the glycolysis in oocytes and theca cells would activate ovarian functions such as follicle growth and maturation, and hormone production.…”

“…In addition, serum gonadotropin levels are low at metestrus [15, sure to hCG stimulates glycolytic activity in ovarian follicles [8,9] and that glycolysis in ovarian follicles is required for follicle growth and estradiol secretion [9]. In addition, the expression of ENOs varies according to the pathophysiological, metabolic or developmental conditions of cells [1,12], e.g., the levels of ovarian ral and antral follicles [12,[23][24][25], demonstrating that oocytes metabolize glucose via glycolysis.…”

“…Antibodies directed against ENO1 were found in 19.1% of sera obtained from 110 patients with POF [5]. It has been also reported that glycolysis is a major contributor to energy production in ovarian follicles [6][7][8] and glycolysis in ovarian follicles is required for follicle growth and estradiol secretion [9].…”

“…We found that the levels of ovarian ENO2 mRNA, but not ENO1, changed significantly during the estrus cycle. It is known that exposure to human CG (hCG) stimulates glycolytic activity in ovarian follicles [8,9]. These suggest that gonad-formed on each gene with ovarian RNA without reverse transcription.…”