Mature oocytes have among the highest intracellular concentrations of the potent antioxidant glutathione (GSH). Female mice lacking the modifier subunit of glutamate cysteine ligase (GCLM), the rate-limiting enzyme in GSH synthesis, have low GSH concentrations in oocytes, poor oocyte quality that manifests as increased embryonic mortality prior to the blastocyst stage, chronic ovarian oxidative stress, and accelerated post-pubertal, age-related decline in the primordial follicle pool, which constitutes the irreplaceable ovarian reserve. Therefore, compared to many genetically modified mouse models, which have complete ovarian follicle depletion prior to puberty, these mice more closely model pathological conditions with diminished ovarian reserve in humans. Female Gclm null mice are also resistant to diet- and age-associated gains in body weight and adipose tissue, have decreased hepatic expression of lipogenesis genes, and have increased hepatic mitochondrial oxygen consumption; however, the effects of Gclm deletion on oocyte lipid metabolism and mitochondrial function have not been studied. Gclm null mice thus constitute an excellent model in which to investigate the hypothesis that GSH deficiency causes oocyte mitochondrial dysfunction via increased reactive oxygen species that directly damage mitochondrial macromolecules and/or via decreased lipogenesis resulting in decreased oocyte mitochondrial fatty acid beta oxidation. This hypothesis will be tested via two specific aims: 1) Determine whether oocyte GSH deficiency due to Gclm deletion results in increased oocyte mitochondrial ROS generation, mitochondrial oxidative lipid and DNA damage, and decreased mitochondrial function. 2) Assess the effects of Gclm deficiency on the serum and oocyte lipidomes and on lipogenesis and fatty acid beta oxidation in the oocyte. The proposed studies will address the knowledge gap in understanding the association between decreased ovarian reserve and poor oocyte quality by examining whether oxidative damage to oocyte mitochondria and disruption of oocyte lipid homeostasis are mechanistically involved in decreased oocyte quality in Gclm-/- mice.

Public Health Relevance

This project will delineate mechanisms by which GSH deficiency due to Gclm deletion causes mitochondrial dysfunction in oocytes, focusing on oxidative stress and abnormal lipogenesis. Human polymorphisms in GCLM and the catalytic subunit of GCL, GCLC, are known to affect GSH synthesis, and these studies will point to possible mechanisms by which these polymorphisms may affect oocyte quality. In so doing, they will also identify targets for interventions to improve oocyte quality.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21HD097541-02
Application #
10004697
Study Section
Integrative and Clinical Endocrinology and Reproduction Study Section (ICER)
Program Officer
Ravindranath, Neelakanta
Project Start
2019-09-01
Project End
2021-08-31
Budget Start
2020-09-01
Budget End
2021-08-31
Support Year
2
Fiscal Year
2020
Total Cost
Indirect Cost
Name
University of California Irvine
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
046705849
City
Irvine
State
CA
Country
United States
Zip Code
92617