Oral follicle-stimulating hormone receptor agonist affects granulosa cells differently than recombinant human FSH.

OBJECTIVE: To determine whether TOP5300, a novel oral follicle-stimulating hormone (FSH) receptor (FSHR) allosteric agonist, elicits a different cellular response than recombinant human FSH (rh-FSH) in human granulosa cells from patients undergoing in vitro fertilization. DESIGN: Basic science research with a preclinical allosteric FSHR agonist. SETTING: University hospital. PATIENT(S): Patients with infertility at a single academic fertility clinic were recruited under an Institutional Review Board-approved protocol. Primary granulosa cell cultures were established for 41 patients, of whom 8 had normal ovarian reserve (NOR), 17 were of advanced reproductive age (ARA), 12 had a diagnosis of polycystic ovary syndrome (PCOS), and 4 had a combination of diagnoses, such as ARA and PCOS. INTERVENTION(S): Primary granulosa-lutein (GL) cell cultures were treated with rh-FSH, TOP5300, or vehicle. MAIN OUTCOME MEASURE(S): Estradiol (E2) production using enzyme-linked immunosorbent assay, steroid pathway gene expression of StAR and aromatase using quantitative polymerase chain reaction, and FSHR membrane localization using immunofluorescence were measured in human GL cells. RESULT(S): TOP5300 consistently stimulated E2 production among patients with NOR, ARA, and PCOS. Recombinant FSH was the more potent ligand in GL cells from patients with NOR but was ineffective in cells from patients with ARA or PCOS. The lowest level of FSHR plasma membrane localization was seen in patients with ARA, although FSHR localization was more abundant in cells from patients with PCOS; the highest levels were present in cells from patients with NOR. The localization of FSHR was not affected by TOP5300 relative to rh-FSH in any patient group. TOP5300 stimulated greater expression of StAR and CYP19A1 across cells from all patients with NOR, ARA, and PCOS combined, although rh-FSH was unable to stimulate StAR and aromatase (CYP19A1) expression in cells from patients with PCOS. TOP5300-induced expression of StAR and CYP19A1 mRNA among patients with ARA and NOR was consistently lower than that observed in cells from patients with PCOS. CONCLUSION(S): TOP5300 appears to stimulate E2 production and steroidogenic gene expression from GL cells more than rh-FSH in PCOS, relative to patients with ARA and NOR. It does not appear that localization of FSHR at cell membranes is a limiting step for TOP5300 or rh-FSH stimulation of steroidogenic gene expression and E2 production.

Decidualization of human endometrial stromal cells requires steroid receptor coactivator-3.

Steroid receptor coactivator-3 (SRC-3; also known as NCOA3 or AIB1) is a member of the multifunctional p160/SRC family of coactivators, which also includes SRC-1 and SRC-2. Clinical and cell-based studies as well as investigations on mice have demonstrated pivotal roles for each SRC in numerous physiological and pathophysiological contexts, underscoring their functional pleiotropy. We previously demonstrated the critical involvement of SRC-2 in murine embryo implantation as well as in human endometrial stromal cell (HESC) decidualization, a cellular transformation process required for trophoblast invasion and ultimately placentation. We show here that, like SRC-2, SRC-3 is expressed in the epithelial and stromal cellular compartments of the human endometrium during the proliferative and secretory phase of the menstrual cycle as well as in cultured HESCs. We also found that SRC-3 depletion in cultured HESCs results in a significant attenuation in the induction of a wide-range of established biomarkers of decidualization, despite exposure of these cells to a deciduogenic stimulus and normal progesterone receptor expression. These molecular findings are supported at the cellular level by the inability of HESCs to morphologically transform from a stromal fibroblastoid cell to an epithelioid decidual cell when endogenous SRC-3 levels are markedly reduced. To identify genes, signaling pathways and networks that are controlled by SRC-3 and potentially important for hormone-dependent decidualization, we performed RNA-sequencing on HESCs in which SRC-3 levels were significantly reduced at the time of administering the deciduogenic stimulus. Comparing HESC controls with HESCs deficient in SRC-3, gene enrichment analysis of the differentially expressed gene set revealed an overrepresentation of genes involved in chromatin remodeling, cell proliferation/motility, and programmed cell death. These predictive bioanalytic results were confirmed by the demonstration that SRC-3 is required for the expansion, migratory and invasive activities of the HESC population, cellular properties that are required in vivo in the formation or functioning of the decidua. Collectively, our results support SRC-3 as an important coregulator in HESC decidualization. Since perturbation of normal homeostatic levels of SRC-3 is linked with common gynecological disorders diagnosed in reproductive age women, this endometrial coregulator-along with its new molecular targets described here-may open novel clinical avenues in the diagnosis and/or treatment of a non-receptive endometrium, particularly in patients presenting non-aneuploid early pregnancy loss.

Oleuropein suppresses endometriosis progression and improves the fertility of mice with endometriosis.

BACKGROUND: Endometriosis is an estrogen-dependent inflammatory reproductive disease. Therefore, systematic estrogen depletion and anti-inflammatory drugs are the current treatment for endometriosis. However, current endometriosis treatments have low efficacy and cause adverse effects in endometriosis patients. Consequently, alternative endometriosis treatments targeting endometriosis-specific factors are in demand. In this context, ERß was selected as a druggable target for endometriosis due to its critical role in progression. Therefore, selective targeting of ERß without inhibiting ERα activity would be a new paradigm for endometriosis treatment to overcome the low efficacy and adverse effects of hormonal endometriosis therapy. METHODS: Cell-based ERß and ERα activity assay systems were employed to define a selective ERß-inhibiting chemical product from a library of natural products. A surgically induced endometriosis mouse model was used to determine whether an ERß inhibitory drug suppressed endometriosis progression. Mice with endometriosis were randomly separated and then orally treated with vehicle or 25 mg/kg oleuropein (once a day for 21 days), an ERß inhibitory drug. The volume of endometriotic lesions or luciferase activity of endometriotic lesions was examined to define the growth of ectopic lesions in mice with endometriosis. The metabolite and levels of metabolic enzymes of the liver and kidney were determined in the serum of female mice treated with vehicle and oleuropein (25 mg/kg, once a day for 21 days) to define the toxicity of oleuropein. The in vitro decidualization assay was conducted with normal human endometrial stromal cells and endometriotic stromal cells to determine whether oleuropein overcomes decidualization in endometriosis patients. The pregnancy rate and pup numbers of C57BL/6 J female mice with endometriosis treated with vehicle or oleuropein (n = 10/group) were determined after mating with male mice. The cytokine profile in endometriotic lesions treated with vehicle and oleuropein (25 mg/kg) was determined with a Mouse Cytokine Array Kit. RESULTS: Among natural products, oleuropein selectively inhibited ERß but not ERα activity in vitro. Oleuropein treatment inhibited the nuclear localization of ERß in human endometrial cells upon estradiol treatment. Oleuropein (25 mg/kg) treatment suppressed the growth of mouse (6.6-fold) and human (sixfold) ectopic lesions in mice with endometriosis compared to the vehicle by inhibiting proliferation and activating apoptosis in endometriotic lesions. Oleuropein treatment did not cause reproductive toxicity in female mice. Additionally, mice with endometriosis subjected to oleuropein treatment had a higher pregnancy rate (100%) than vehicle-treated mice (70%). Furthermore, oleuropein treatment partially recovered the decidualization impact of human endometriotic stromal cells from endometriotic lesions compared to the vehicle. Oleuropein-treated mice with endometriosis exhibited significantly lower levels of cytokines directly regulated by ERß in ectopic lesions than vehicle-treated mice, illustrating the improvement in the hyperinflammatory state of mice with endometriosis. CONCLUSIONS: Oleuropein is a promising and novel nutraceutical product for nonhormonal therapy of endometriosis because it selectively inhibits ERß, but not ERα, to suppress endometriosis progression and improve the fertility of mice with endometriosis.

Development of a dynamic machine learning algorithm to predict clinical pregnancy and live birth rate with embryo morphokinetics.

Objective: To evaluate the feasibility of generating a center-specific embryo morphokinetic algorithm by time-lapse microscopy to predict clinical pregnancy rates. Design: A retrospective cohort analysis. Setting: Academic fertility clinic in a tertiary hospital setting. Patients: Patients who underwent in vitro fertilization with embryos that underwent EmbryoScope time-lapse microscopy and subsequent transfer between 2014 and 2018. Interventions: None. Main Outcome Measures: Clinical pregnancy. Results: A supervised, random forest learning algorithm from 367 embryos successfully predicted clinical pregnancy from a training set with overall 65% sensitivity and 74% positive predictive value, with an area under the curve of 0.7 for the test set. Similar results were achieved for live birth outcomes. For the secondary analysis, embryo growth morphokinetics were grouped into five clusters using unsupervised clustering. The clusters that had the fastest morphokinetics (time to blastocyst = 97 hours) had pregnancy rates of 54%, whereas a cluster that had the slowest morphokinetics (time to blastocyst = 122 hours) had a pregnancy rate of 71%, although the differences were not statistically significant (P=.356). Other clusters had pregnancy rates of 51%-60%. Conclusions: This study shows the feasibility of a clinic-specific, noninvasive embryo morphokinetic simple machine learning model to predict clinical pregnancy rates.

Pathology of hyperandrogenemia in the oocyte of polycystic ovary syndrome.

Polycystic ovary syndrome (PCOS) is the most common ovulatory disorder in the world and is associated with multiple adverse outcomes. The phenotype is widely varied, with several pathologies contributing to the spectrum of the disease including insulin resistance, obesity and hyperandrogenemia. Of these, the role of hyperandrogenemia and the mechanism by which it causes dysfunction remains poorly understood. Early studies have shown that androgens may affect the metabolic pathways of a cell, and this may pose hazards at the level of the mitochondria. As mitochondria are strictly maternally inherited, this would provide an exciting explanation not only to the pathophysiology of PCOS as a disease, but also to the inheritance pattern. This review seeks to summarize what is known about PCOS and associated adverse outcomes with focus on the role of hyperandrogenemia and specific emphasis on the oocyte.

Hyperandrogenemia alters mitochondrial structure and function in the oocytes of obese mouse with polycystic ovary syndrome.

CAPSULE: Hyperandrogenemia in an obese PCOS mouse model results in altered glucose/insulin metabolism and mitochondrial structure and function in the oocytes, in part explaining adverse outcomes and inheritance patterns seen in PCOS. OBJECTIVE: To study the oocyte quality by means of mitochondrial structure and function in a well-established classic PCOS mouse model. DESIGN: Animal study using an obese PCOS mouse model compared with control. SETTING: Animal research facility in a tertiary care university hospital setting. ANIMALS: C57/B6J mice. INTERVENTION: Three week old mice had subdermal implants of DHT controlled release pellet or placebo for 90 days. MAIN OUTCOME MEASURES: The mouse model was validated by performing glucose tolerance test, HbA1c levels, body weight and estrous cycle analyses. Oocytes were subsequently isolated and were used to investigate mitochondrial membrane potential, oxidative stress, lipid peroxidation, ATP production, mtDNA copy number, transcript abundance, histology and electron microscopy. RESULTS: Results showed glucose intolerance and hyperinsulinemia along with dysregulated estrus cycle. Analysis of the oocytes demonstrated impaired inner mitochondrial membrane function, increased ATP production and mtDNA copy number, altered RNA transcript abundance and aberrant ovarian histology. Electron microscopy of the oocytes showed severely impaired mitochondrial ultrastructure. CONCLUSION: The obese PCOS mouse model shows a decreased oocyte quality related to impaired mitochondrial function.

Polycystic Ovary Syndrome and the Forgotten Uterus.

Polycystic ovary syndrome (PCOS) is a common disorder that affects various facets of fertility. Although the ovarian and metabolic aspects of the disease is well studied, its role in uterine dysfunction is not well understood. Our objective was to review the features of endometrial and uterine aberrations in women with PCOS. A systematic literature search was performed in PubMed, Medline, and the Cochrane Library databases for papers published in English up to March 2020. The following key words were used for the search: polycystic ovary syndrome, poly cystic ovarian disease, polycystic ovaries, PCOS, PCOD, PCO, PCOM, oligoovulation, anovulation, oligomenorrhea, amenorrhea, hyperandrogenism and this was combined with terms; endometrium, infertility, uterus, progesterone resistance, endometrial hyperplasia, pregnancy outcomes, preterm delivery. In this review, we highlight various uterine pathologies that are associated with PCOS and explore its impact on fertility. We also discuss key uterine molecular pathways that are altered in PCOS that may be related to infertility, endometrial hyperplasia and cancer.

Neonatal and maternal outcomes among twin pregnancies stratified by mode of conception in the United States.

OBJECTIVE: To compare neonatal and maternal outcomes among twin pregnancies conceived as a result of different types of fertility treatments with those of spontaneously conceived twin pregnancies. DESIGN: Retrospective Cohort. SETTING: Population-based analysis. PATIENT(S): Population-based analysis of twin pregnancies in the United States based on their mode of conception using the natality data from the National Center for Health Statistics from the Centers for Disease Control and Prevention (from January 2015 through December 2017). INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Adverse neonatal and maternal outcomes. RESULT(S): The overall prevalence of early adverse maternal outcomes and medical complications and obstetric complications including the risk of unplanned hysterectomy, intensive care unit admission, maternal blood transfusion, and perineal laceration were significantly higher in the fertility treatment group (including both ovulation induction/intrauterine insemination and assisted reproductive technology groups) compared with those of the spontaneous conception group, even after adjusting for several potential confounders. The risk of adverse composite neonatal outcomes was slightly lower in the spontaneous conception live twin birth group even after adjustment for several potential confounders. CONCLUSION(S): The rate of maternal and neonatal morbidity in twins conceived via different fertility treatments was slightly increased compared with those of twins conceived spontaneously. Because the absolute risks of maternal and neonatal morbidity were low, overall reassurance regarding these outcomes can be provided to the patients undergoing all types of fertility treatments.

Progesterone receptor isoform B regulates the Oxtr-Plcl2-Trpc3 pathway to suppress uterine contractility.

Uterine contractile dysfunction leads to pregnancy complications such as preterm birth and labor dystocia. In humans, it is hypothesized that progesterone receptor isoform PGR-B promotes a relaxed state of the myometrium, and PGR-A facilitates uterine contraction. This hypothesis was tested in vivo using transgenic mouse models that overexpress PGR-A or PGR-B in smooth muscle cells. Elevated PGR-B abundance results in a marked increase in gestational length compared to control mice (21.1 versus 19.1 d respectively, P < 0.05). In both ex vivo and in vivo experiments, PGR-B overexpression leads to prolonged labor, a significant decrease in uterine contractility, and a high incidence of labor dystocia. Conversely, PGR-A overexpression leads to an increase in uterine contractility without a change in gestational length. Uterine RNA sequencing at midpregnancy identified 1,174 isoform-specific downstream targets and 424 genes that are commonly regulated by both PGR isoforms. Gene signature analyses further reveal PGR-B for muscle relaxation and PGR-A being proinflammatory. Elevated PGR-B abundance reduces Oxtr and Trpc3 and increases Plcl2 expression, which manifests a genetic profile of compromised oxytocin signaling. Functionally, both endogenous PLCL2 and its paralog PLCL1 can attenuate uterine muscle cell contraction in a CRISPRa-based assay system. These findings provide in vivo support that PGR isoform levels determine distinct transcriptomic landscapes and pathways in myometrial function and labor, which may help further the understanding of abnormal uterine function in the clinical setting.

In vitro fertilization as an independent risk factor for placenta accreta spectrum.

BACKGROUND: Placenta accreta spectrum is well known for its association with catastrophic maternal outcomes. However, its pathophysiology is not well defined. There have been emerging data that in vitro fertilization may be a risk factor for placenta accreta spectrum. OBJECTIVE: We investigated the hypothesis that in vitro fertilization is an independent risk factor for placenta accreta spectrum. STUDY DESIGN: A retrospective analysis of all deliveries in a prospective, population-based cohort (2012-2019) was performed in a tertiary academic center. Primary outcome variable was placenta accreta spectrum. Univariate analysis was performed on potential risk factors for predicting placenta accreta spectrum, and a multivariate model was designed to best fit the prediction of placenta accreta spectrum adjusted for risk factors such as cesarean delivery, placenta previa, age, and parity. History of previous cesarean delivery was known as a risk factor for both placenta previa and placenta accreta spectrum; hence, the interaction between "placenta previa" and "previous cesarean delivery" was included in the final model. Odds ratios were calculated as exponential of beta coefficients from the multivariate regression analysis. RESULTS: A total of 37,461 deliveries were included in this analysis, 5464 (15%) of which had a history of cesarean delivery, 281 (0.7%) had placenta previa in their index pregnancy, and 571 (1.5%) had in vitro fertilization pregnancy. The frequency of placenta accreta spectrum was 230 (0.6%). Independent risk factors for placenta accreta spectrum were in vitro fertilization pregnancy (adjusted odds ratio, 8.7; 95% confidence interval, 3.8-20.3), history of previous cesarean delivery (adjusted odds ratio, 21.1; 95% confidence interval, 11.4-39.2), and presence of placenta previa (adjusted odds ratio, 94.6; 95% confidence interval, 29.3-305.1). After adjustment for number of previous cesarean deliveries, the correlation persisted for in vitro fertilization (adjusted odds ratio, 6.7; 95% confidence interval, 2.9-15.6). CONCLUSION: Our data suggested that in vitro fertilization is an independent risk factor for placenta accreta spectrum, although its relative clinical importance compared with that of the presence of placenta previa and history of cesarean delivery is small. The pathophysiology behind this relationship remains to be investigated.

Prenatal testing in pregnancies conceived by in vitro fertilization with pre-implantation genetic testing.

OBJECTIVE: Women with pregnancies resulting from in vitro fertilization (IVF) with normal pre-implantation genetic testing for aneuploidy (PGT-A) are advised to undergo prenatal screening and testing during pregnancy. It is not well known how many follow these recommendations. Our objective was to study prenatal testing decisions made by women with pregnancies conceived through IVF with PGT-A. METHODS: We performed a retrospective review of women who received genetic counseling during pregnancies conceived through IVF with normal PGT-A. We excluded those who received genetic counseling preconceptionally prior to IVF. Statistical analysis included descriptive statistics and after testing for normality by the Kolmogorov-Smirnov test, independent t test, Mann-Whitney U test, or Chi-square/Fisher's exact test. RESULTS: Data from 83 women were included. Of these, 53 (63.9%) had at least one of the following prenatal tests: first trimester combined screening (16.9%), non-invasive prenatal screening (NIPS) (45.8%), second trimester serum screening (6%), and invasive diagnostic testing (6%). 10.8% had more than one of the above tests and 36.1% declined all tests. CONCLUSION: Almost two-thirds of women who were pregnant after IVF with normal PGT-A had prenatal aneuploidy screening or testing. Future prospective studies with larger cohorts are needed to further ascertain decision making in this population.

Prenatal androgen induced lean PCOS impairs mitochondria and mRNA profiles in oocytes.

Polycystic ovary syndrome (PCOS) is the most common ovulatory defect in women. Although most PCOS patients are obese, a subset of PCOS women are lean but show similar risks for adverse fertility outcomes. A lean PCOS mouse model was created using prenatal androgen administration. This developmentally programmed mouse model was used for this study. Our objective was to investigate if mitochondrial structure and functions were compromised in oocytes obtained from lean PCOS mouse. The lean PCOS mouse model was validated by performing glucose tolerance test, HbA1c levels, body weight and estrous cycle analyses. Oocytes were isolated and were used to investigate inner mitochondrial membrane potential, oxidative stress, lipid peroxidation, ATP production, mtDNA copy number, transcript abundance, histology and electron microscopy. Our results demonstrate that lean PCOS mice has similar weight to that of the controls but exhibited glucose intolerance and hyperinsulinemia along with dysregulated estrus cycle. Analysis of their oocytes show impaired inner mitochondrial membrane function, elevated reactive oxygen species (ROS), increased RNA transcript abundance and aberrant ovarian histology. Electron microscopy of the oocytes showed impaired mitochondrial ultrastructure. In conclusion, the lean PCOS mouse model shows a decreased oocyte quality related to impaired mitochondrial ultrastructure and function.

Validation of the picoAMH assay on the Dynex DS2 platform.

OBJECTIVES: Anti-Müllerian hormone (AMH) is increasingly used as a biomarker of ovarian reserve in clinical practice, and is used both for management of fertility treatments and prediction of menopause. We sought to validate the newly FDA-approved Ansh Laboratories MenoCheck picoAMH ELISA on the Dynex-DS2 platform for clinical use in our obstetrics and gynecology center. DESIGN: Validation of the picoAMH ELISA on the Dynex-DS2 was performed according to CLSI guidelines. Intra- and inter-assay CV, assay linearity, and method comparison studies were carried out to verify assay precision and accuracy. The manufacturer's reference range was verified using 26 volunteer samples, and interference for hemolysis, lipemia, icterus, and biotin was evaluated. picoAMH results were additionally correlated with antral follicle count by ultrasound. RESULTS: Intra- and inter-assay CV of the picoAMH assay on the DS2 was ≤4% and the assay was linear between concentrations of 0.0067-16.24 ng/mL (0.048-116.0 pmol/L) AMH. Method comparison was performed with the manufacturer's laboratory and indicated good correlation, with Deming regression yielding slope of 0.928 and intercept of -0.0421. The assay displayed no significant interference from hemolysis (1000 mg/dL), lipemia (2000 mg/dL), conjugated bilirubin (66 mg/dL), or biotin (10,000 ng/mL). Measurement of AMH on the DS2 was also correlated with antral follicle count, with R = 0.7128. CONCLUSIONS: Our results indicate that the picoAMH ELISA on the DS2 has good analytical performance suitable for clinical use.

30 years of data: impact of the United States in vitro fertilization data registry on advancing fertility care.

OBJECTIVE: To summarize and assess the impact of key research generated through the Society of Assisted Reproductive Technology (SART)-initiated United States IVF registry and annual reporting system. DESIGN: Review. SETTING: Eligible studies included those that analyzed data generated by the National IVF data collection program (through SART or Centers for Disease Control and Prevention). PATIENT(S): Not applicable. INTERVENTION(S): Not applicable. MAIN OUTCOME MEASURE(S): Summarize and report outcomes of research using National IVF registry data. RESULT(S): The Society of Assisted Reproductive Technology was founded in 1985 and published the first annual US IVF data report 30 years ago in 1988 in Fertility and Sterility. In 1995, the Centers for Disease Control and Prevention subsequently began collecting data from IVF programs and published their first report in 1997. This annual National IVF data collection and reporting is a significant responsibility and effort for IVF programs. Using these data sources, 199 articles have been published by clinicians and researchers from across the country. This research has guided the development of evidence-based assisted reproductive technology (ART) practice guidelines during the past 30 years, which have ultimately led to improved quality and patient care. CONCLUSION(S): Since the first SART National IVF data report publication 30 years ago, SART has achieved its original goals of creating a national IVF registry that successfully assesses clinical effectiveness, quality of care, and safety.

Early growth response 1 transcriptionally primes the human endometrial stromal cell for decidualization.

Mouse studies support a role for endometrial early growth response 1 (EGR1) in uterine receptivity and decidualization, which are processes controlled by estrogen and progesterone. However, the importance of this transcription factor in similar cellular processes in human is unclear. Analysis of clinical samples indicate that endometrial EGR1 levels are decreased in the endometrium of women with recurrent implantation failure, suggesting that tight control of EGR1 levels are necessary for normal endometrial function. Therefore, we used siRNA-mediated knockdown of EGR1 expression in cultured human endometrial stromal cells (hESCs) to assess the functional role of EGR1 in hESC decidualization. Protein expression studies revealed that EGR1 is highly expressed in pre-decidual hESCs. However, EGR1 protein levels rapidly decrease following administration of an established deciduogenic hormone stimulus containing estradiol, medroxyprogesterone acetate, and cyclic adenosine monophosphate. Intriguingly, EGR1 knockdown in pre-decidual hESCs blocks the ability of these cells to decidualize later, indicating that EGR1 is required to transcriptionally program pre-decidual hESCs for decidualization. Support for this proposal comes from the analysis of transcriptome and cistrome datasets, which shows that EGR1 target genes are primarily involved in transcriptional regulation, cell signaling, and proliferation. Collectively, our studies provide translational support for an evolutionary conserved role for human endometrial stromal EGR1 in the early events of pregnancy establishment.

Preovulatory exposure to a protein-restricted diet disrupts amino acid kinetics and alters mitochondrial structure and function in the rat oocyte and is partially rescued by folic acid.

BACKGROUND: Detrimental exposures during pregnancy have been implicated in programming offspring to develop permanent changes in physiology and metabolism, increasing the risk for developing diseases in adulthood such as hypertension, diabetes, heart disease and obesity. This study investigated the effects of protein restriction on the metabolism of amino acids within the oocyte, liver, and whole organism in a rat model as well as effects on mitochondrial ultrastructure and function in the cumulus oocyte complex. METHODS: Wistar outbred female rats 8-11 weeks of age (n = 24) were assigned to three isocaloric dietary groups, including control (C), low protein (LP) and low protein supplemented with folate (LPF). Animals were superovulated and 48 h later underwent central catheterization. Isotopic tracers of 1-13C-5C2H3-methionine, 2H2-cysteine, U-13C3-cysteine and U-13C3-serine were administered by a 4 h prime-constant rate infusion. After sacrifice, oocytes were denuded of cumulus cells and liver specimens were obtained. RESULTS: Oocytes demonstrated reduced serine flux in LP vs. LPF (p < 0.05), reduced cysteine flux in LP and LPF vs. C (p < 0.05), and a trend toward reduced transsulfuration in LP vs. C and LPF. Folic acid supplementation reversed observed effects on serine flux and transsulfuration. Preovulatory protein restriction increased whole-body methionine transmethylation, methionine transsulfuration and the flux of serine in LP and LPF vs. C (p = 0.003, p = 0.002, p = 0.005). The concentration of glutathione was increased in erythrocytes and liver in LP and LPF vs. C (p = 0.003 and p = 0.0003). Oocyte mitochondrial ultrastructure in LP and LPF had increased proportions of abnormal mitochondria vs. C (p < 0.01 and p < 0.05). Cumulus cell mitochondrial ultrastructure in LP and LPF groups had increased proportions of abnormal mitochondria vs. C (p < 0.001 and p < 0.05). Preovulatory protein restriction altered oocyte expression of Drp1, Opa-1, Mfn1/2, Parl and Ndufb6 (p < 0.05) and Hk2 (p < 0.01), which are genes involved in mitochondrial fission (division) and fusion, mitochondrial apoptotic mechanisms, respiratory electron transport and glucose metabolism. CONCLUSIONS: Preovulatory protein restriction resulted in altered amino acid metabolism, abnormal cumulus oocyte complex mitochondrial ultrastructure and differential oocyte expression of genes related to mitochondrial biogenesis.