Related Experiment Video
Updated: May 1, 2026
Evaluation of Hepatic Glucose Production in a Polycystic Ovary Syndrome Mouse Model
Published on: March 5, 2022
Hyperglycaemic conditions perturb mouse oocyte in vitro developmental competence via beta-O-linked glycosylation of
L A Frank1, M L Sutton-McDowall, H M Brown
1The Robinson Institute, School of Paediatrics and Reproductive Health, The University of Adelaide, Ground Floor, Norwich Centre, 55 King William Road, North Adelaide, SA 5006, Australia.
Study Question:
What is the effect of beta-O-linked glycosylation (O-GlcNAcylation) on specific proteins in the cumulus-oocyte complex (COC) under hyperglycaemic conditions?
Summary Answer:
Heat shock protein 90 (HSP90) was identified and confirmed as being O-GlcNAcylated in mouse COCs under hyperglycaemic conditions (modelled using glucosamine), causing detrimental outcomes for embryo development.
What Is Known Already:
O-GlcNAcylation of proteins occurs as a result of increased activity of the hexosamine biosynthesis pathway, which provides substrates for cumulus matrix production during COC maturation, and also for O-GlcNAcylation. COCs matured under hyperglycaemic conditions have decreased developmental competence, mediated at least in part through the mechanism of increased O-GlcNAcylation.
Study Design, Size, Duration:
This study was designed to examine the effect of hyperglycaemic conditions (using the hyperglycaemic mimetic, glucosamine) on O-GlcNAc levels in the mouse COC, and furthermore to identify potential candidate proteins which are targets of this modification, and their roles in oocyte maturation.
Participants/Materials, Setting, Methods:
COCs from 21-day-old superovulated CBA × C57BL6 F1 hybrid female mice were matured in vitro (IVM). Levels of O-GlcNAcylated proteins, HSP90 and O-GlcNAc transferase (OGT, the enzyme responsible for O-GlcNAcylation) in COCs were measured using western blot, and localization observed using immunocytochemistry. For glycosylated HSP90 levels, and to test OGT-HSP90 interaction, immunoprecipitation was performed prior to western blotting. Embryo development was assessed using in vitro fertilization and embryo culture post-maturation.
Main Results And The Role Of Chance:
Addition of the hyperglycaemic mimetic glucosamine to IVM medium for mouse COCs increased detectable O-GlcNAcylated protein levels (by western blot and immunocytochemistry), and this effect was reversed using an OGT inhibitor (P < 0.05). HSP90 was identified as a target of O-GlcNAcylation in the COC, and inhibition of HSP90 during IVM reversed glucosamine-induced decreases in oocyte developmental competence (P < 0.05). We also demonstrated the novel finding of an association between HSP90 and OGT in COCs, suggesting a possible client-chaperone relationship.
Limitations, Reasons For Caution:
In vitro maturation of COCs was used so that treatment time could be limited to the 17 h of maturation prior to ovulation. Additionally, glucosamine, a hyperglycaemic mimetic, was used because it specifically activates the hexosamine pathway which provides the O-GlcNAc moieties. The results in this study should be confirmed using in vivo models of hyperglycaemia and different HSP90 inhibitors.
Wider Implications Of The Findings:
This study leads to a new understanding of how diabetes influences oocyte competence and provides insight into possible therapeutic interventions based on inhibiting HSP90 to improve oocyte quality.
Study Funding/Competing Interest(S):
This work was supported by a programme grant from the National Health and Medical Research Council, Australia, ID 453556. J.G.T. is a recipient of funding from and a consultant to Cook Medical Pty Ltd. The other authors have no conflicts of interest to declare.
