Nutrient pathways regulating the nuclear maturation of mammalian oocytes

Abstract

Oocyte maturation is defined as that phase of development whereby a fully grown oocyte reinitiates meiotic maturation, completes one meiotic division with extrusion of a polar body, then arrests at MII until fertilisation. Completion of maturation depends on many different factors, not the least of which is the proper provision of energy substrates to fuel the process. Interaction of the oocyte and somatic compartment of the follicle is critical and involves numerous signals exchanged between the two cell types in both directions. One of the prominent functions of the cumulus cells is the channelling of metabolites and nutrients to the oocyte to help stimulate germinal vesicle breakdown and direct development to MII. This entails the careful integration and coordination of numerous metabolic pathways, as well as oocyte paracrine signals that direct certain aspects of cumulus cell metabolism. These forces collaborate to produce a mature oocyte that, along with accompanying physiological changes called cytoplasmic maturation, which impart subsequent developmental competence to the oocyte, can be fertilised and develop to term. This review focuses on nuclear maturation and the metabolic interplay that regulates it, with special emphasis on data generated in the mouse.

Oocyte metabolic function, lipid composition, and developmental potential are altered by diet in older mares

“…Oocyte AMPK activity was not assayed in this study, but we speculate that diet supplementation with grains could have a negative impact, as seen with high-fat diets in multiple other tissues ( Lindholm et al 2013 ). In addition, ingredients in the RSS could have had a positive impact on AMPK function in oocytes, as seen after stimulation of lipid metabolism or addition of l -carnitine to oocyte in vitro maturation ( Downs et al 2009 , Downs 2015 ). Higher oocyte basal mitochondrial metabolism and reduced lipid abundance observed after diet supplementation with the RSS are consistent with this postulation.…”

Paraquat Reduces the Female Fertility by Impairing the Oocyte Maturation in Mice

“…Before meiotic maturation, oocytes are arrested at the prophase of meiosis I with a distinct germinal vesicle (GV). In puberty, fully grown oocytes reinitiate meiosis and complete the first meiotic division with the first polar body (PB1) extrusion and then arrest at the metaphase of meiosis II (MII) waiting for fertilization (Downs, 2015). The meiotic maturation of oocyte is a long and complex process, which is divided into nuclear and cytoplasmic maturation for simplicity (Marteil et al, 2009).…”

Immature oocyte incidence: Contributing factors and effects on mature sibling oocytes in intracytoplasmic sperm injection cycles

“…Of the millions of the primordial oocytes present at birth, only approximately 400 mature during a woman's lifetime (Monniaux et al, 2014). Oocyte maturation is defined as the restart and completion of the first meiotic division from prophase I, through metaphase I (MI stage), to metaphase II (MII stage), with accompanying cytoplasmic maturation, which includes the storage of cytoplasmic enzymes, mRNAs, organelles, and metabolic substrates that are crucial for fertilization and early embryonic development (Coticchio et al, 2015;Downs, 2015).…”