Excess cholesterol induces mouse egg activation and may cause female infertility

Stromal cell-derived factor-1 alpha improves cardiac function in a novel diet-induced coronary atherosclerosis model, the SR-B1ΔCT/LDLR KO mouse

BACKGROUND AND AIMS

There are a limited number of pharmacologic therapies for coronary artery disease, and few rodent models of occlusive coronary atherosclerosis and consequent myocardial infarction with which one can rapidly test new therapeutic approaches. Here, we characterize a novel, fertile, and easy-to-use HDL receptor (SR-B1)-based model of atherogenic diet-inducible, fatal coronary atherosclerosis, the SR-B1ΔCT/LDLR KO mouse. Additionally, we test intramyocardial injection of Stromal Cell-Derived Factor-1 alpha (SDF-1α), a potent angiogenic cytokine, as a possible therapy to rescue cardiac function in this mouse.

METHODS

SR-B1ΔCT/LDLR KO mice were fed the Paigen diet or standard chow diet, and we determined the effects of the diets on cardiac function, histology, and survival. After two weeks of feeding either the Paigen diet (n = 24) or standard chow diet (n = 20), the mice received an intramyocardial injection of either SDF-1α or phosphate buffered saline (PBS). Cardiac function and angiogenesis were assessed two weeks later.

RESULTS

When six-week-old mice were fed the Paigen diet, they began to die as early as 19 days later and 50% had died by 38 days. None of the mice maintained on the standard chow diet died by day 72. Hearts from mice on the Paigen diet showed evidence of cardiomegaly, myocardial infarction, and occlusive coronary artery disease. For the five mice that survived until day 28 that underwent an intramyocardial injection of PBS on day 15, the average ejection fraction (EF) decreased significantly from day 14 (the day before injection, 52.1 ± 4.3%) to day 28 (13 days after the injection, 30.6 ± 6.8%) (paired t-test, n = 5, p = 0.0008). Of the 11 mice fed the Paigen diet and injected with SDF-1α on day 15, 8 (72.7%) survived to day 28. The average EF for these 8 mice increased significantly from 48.2 ± 7.2% on day 14 to63.6 ± 6.9% on day 28 (Paired t-test, n = 8, p = 0.003).

CONCLUSIONS

This new mouse model and treatment with the promising angiogenic cytokine SDF-1α may lead to new therapeutic approaches for ischemic heart disease.

Effects of Per- and Polyfluoroalkylated Substances on Female Reproduction

Per- and poly-fluoroalkylated substances (PFAS) are a large group of chemicals that persist both in the environment and in the body. Legacy PFAS, e.g., perfluorooctanoic acid and perfluorooctane sulfonic acid, are implicated as endocrine disruptors and reproductive and developmental toxicants in epidemiological and animal model studies. This review describes female reproductive outcomes of reported studies and includes where associative relationships between PFAS exposures and female reproductive outcomes have been observed as well as where those are absent. In animal models, studies in which PFAS are documented to cause toxicity and where effects are lacking are described. Discrepancies exist in both human and animal studies and are likely attributable to human geographical contamination, developmental status, duration of exposure, and PFAS chemical identity. Similarly, in animal investigations, the model used, exposure paradigm, and developmental status of the female are important and vary widely in documented studies. Taken together, support for PFAS as reproductive and developmental toxicants exists, although the disparity in study conditions and human exposures contribute to the variation in effects noted.

Association between depression and infertility risk among American women aged 18-45 years: the mediating effect of the NHHR

BACKGROUND/OBJECTIVE

Depression and infertility are major medical and social problems. The non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio (NHHR) serves as an innovative and reliable lipid marker for cardiovascular disease risk assessment. Previous research has indicated a potential correlation among lipid metabolism, depression, and infertility. Nonetheless, the exact involvement of lipid metabolism in modulating the pathological mechanisms associated with depression-induced infertility remains to be fully elucidated. The aim of this study was to explore the connection between depression and infertility and to assess whether the NHHR mediates this association.

METHODS

A cross-sectional analysis was performed utilizing data from there cycles (2013-2018) of the National Health and Nutrition Examination Survey (NHANES) database. Female infertility was assessed according to the responses to the RHQ074 question in the reproductive health questionnaire module. Depression states were evaluated using the Patient Health Questionnaire-9 and classified into three grades based on the total scores: no depression (0-4 points), minimal-to-mild depression (5-9 points) and moderate-to-severe depression (10 or more points). The NHHR was calculated from laboratory cholesterol test results. Baseline population characteristics were compared, and subgroup analyses were carried out based on the stratification of age and body mass index (BMI). Weighted multivariable logistic regression and linear regression models, with adjustments for various covariables, were employed to examine the associations among depression, infertility and the NHHR. Finally, mediation analysis was utilized to explore the NHHR's potential mediating role in depression states and female infertility.

RESULTS

Within this cross-sectional study, 2,668 women aged 18 to 45 years residing in the United States were recruited, 305 (11.43%) of whom experienced infertility. The study revealed a markedly higher prevalence of depression (P = 0.040) and elevated NHHR (P < 0.001) among infertile women compared to the control cohort. Furthermore, moderate-to-severe depression states independently correlated with increased infertility risk, irrespective of adjustments for various covariables. Subgroup analysis indicated a positive association between depression and infertility risk within certain age categories, although no such relationship was observed within subgroups stratified by BMI. The findings from the weighted logistic regression analysis demonstrated that the elevated NHHR is positively associated with heightened infertility risk. Additionally, the weighted linear regression analysis indicated that moderate-to-severe depression is positively linked to the NHHR levels as well. Finally, the association between depression states and female infertility was partially mediated by the NHHR, with the mediation proportion estimated at 6.57%.

CONCLUSION

In the United States, depression is strongly correlated with an increased likelihood of infertility among women of childbearing age, with evidence suggesting that this relationship is mediated by the NHHR. Subsequent research efforts should further explore the underlying mechanisms connecting depression and infertility.

Associations between exposure to phthalates and liver function among women undergoing assisted reproductive technology

Phthalates can induce hepatotoxicity in animal studies. We aimed to assess the associations of individual and mixture of urinary phthalate metabolites with serum liver function indicators among 764 women undergoing assisted reproductive technology (ART). In linear models, we observed inverse correlations between urinary mono-benzyl phthalate and serum total protein (TP) as well as globulin (β=-0.27 and -0.23, respectively, P<0.05). Additionally, negative associations were identified between mono-isobutyl phthalate and mono-butyl phthalate (MBP) and aspartate aminotransferase-to-alanine transaminase ratio (AST/ALT) (P<0.05). MBP and the sum of all phthalate metabolites (∑all.phth.m) were positively associated with bilirubin, with β ranging from 0.14 to 0.47. Most phthalate metabolites were also positively related to gamma-glutamyl transferase (GGT) (all P<0.05). In Bayesian kernel machine regression models, phthalate mixture was positively associated with bilirubin and GGT, whereas inversely associated with AST/ALT and TP. Our results suggest that phthalate exposure may impair liver function among women undergoing ART.

Maternal exposure to 4-vinylcyclohexene diepoxide during pregnancy leads to disorder of gut microbiota and bile acid metabolism in offspring

Our previous study reveals that maternal exposure to 4-vinylcyclohexene diepoxide (VCD) during pregnancy causes insufficient ovarian follicle reserve and decreased fertility in offspring. The present study aims to further explore the reasons for the significant decline of fecundity in mice caused by VCD, and to clarify the changes of gut microbiota and microbial metabolites in F1 mice. The ovarian metabolomics, gut microbiota and microbial metabolites were analyzed. The results of ovarian metabolomics analysis showed that maternal VCD exposure during pregnancy significantly reduced the concentration of carnitine in the ovaries of F1 mice, while supplementation with carnitine (isovalerylcarnitine and valerylcarnitine) significantly increased the number of ovulation. The results of 16 S rDNA-seq and microbial metabolites analysis showed that maternal VCD exposure during pregnancy caused disordered gut microbiota, increased abundance of Parabacteroides and Flexispira bacteria that are involved in secondary bile acid synthesis. The concentrations of NorDCA, LCA-3S, DCA and other secondary bile acids increased significantly. Our results indicate that maternal exposure to VCD during pregnancy leads to disorder in gut microbiota and bile acid metabolism in F1 mice, accompanying with decreased ovarian function, providing further evidence that maternal exposure to VCD during pregnancy has intergenerational deleterious effects on offspring.

Lipid metabolites, interleukin-6 and oxidative stress markers in follicular fluid and their association with serum concentrations in mares

The application of trans-vaginal ovum pick up (OPU) and intracytoplasmic sperm injection (ICSI) is well established for commercial in vitro embryo production in horses. These assisted reproductive techniques are especially applied during the non-breeding season of the mare. However, little is known about how the health of the oocyte donor may affect the biochemical composition of the follicular fluid (FF) in small and medium-sized follicles routinely aspirated during OPU. This study aimed to investigate associations between systemic and FF concentrations of interleukin-6 (IL-6), total cholesterol, triglycerides, non-esterified fatty acids (NEFA), reactive oxygen metabolites (d-ROMs), biological antioxidant potential (BAP), and oxidative stress index (OSI) during the non-breeding season in mares. At the slaughterhouse, serum and FF of small (5-10 mm in diameter), medium (> 10-20 mm in diameter), and large (> 20-30 mm in diameter) follicles were sampled from 12 healthy mares. There was a strong positive association (P < 0.01) between the concentration of IL-6 in serum and those measured in small (r = 0.846), medium (r = 0.999), and large (r = 0.996) follicles. Serum concentrations of NEFA were positively correlated (P < 0.05) with those measured in small (r = 0.726), medium (r = 0.720), and large (r = 0.974) follicles. Values of total cholesterol and OSI in serum and medium follicles were significantly associated (r = 0.736 and r = 0.696, respectively). The serum concentrations of all lipid metabolites were markedly higher than those measured in FF of small- and medium-sized follicles. Values of IL-6 and OSI did not change significantly between serum and all follicle classes (P ≥ 0.05). To conclude, changes in the blood composition associated with inflammation, oxidative stress, and disturbed lipid metabolism of mares may lead to an inadequate oocyte microenvironment, which could affect oocyte quality and the success rate of OPU/ICSI programs. Further research should indicate whether these changes may ultimately affect in vitro oocyte developmental capacity and subsequent embryo quality.

Maternal hypercholesterolemia would increase the incidence of embryo aneuploidy in couples with recurrent implantation failure

BACKGROUND

The association of dyslipidemia with embryo development and pregnancy outcomes is largely unknown, especially in unexplained recurrent implantation failure (uRIF) patients. Here, this study aimed to explore the impact of abnormal blood lipid levels on embryo genetic status and pregnancy outcomes after preimplantation genetic testing for aneuploidy (PGT-A) from a clinical perspective.

METHODS

This study retrospectively analyzed 502 patients diagnosed as uRIF. They were divided into four groups according to the levels of cholesterol and triglyceride: nonhyperlipidemia group (NonH group), simple hypercholesterolemia group (SHC group), simple hypertriglyceridemia group (SHC group) and mixed hyperlipidemia group (MixH group). At the same time, patients were divided into non-low HDL-C group and low HDL-C group according to their HDL-C level. The outcomes of embryos genetic testing and pregnancy outcomes after PGT-A was analyzed between groups. Binary logistic regression and/or generalized estimating equation (GEE) model were conducted to investigate the association of different types of dyslipidemia with embryonic aneuploidy rate and cumulative live-birth rate.

RESULTS

474 women who met the inclusion criteria were divided into four groups: NonH group (N = 349), SHC group (N = 55), SHT group (N = 52) and MixH group (N = 18). Compared with the NonH group, SHC group had a significantly increased rate of embryo aneuploidy [48.3% vs. 36.7%, P = 0.006; adjusted OR (95% confidence interval) = 1.52(1.04-2.22), P = 0.029], as well as a reduced number of good-quality embryos on day 5 or 6 [3.00 ± 2.29 vs. 3.74 ± 2.77, P = 0.033]. The SHC group showed a tendency of a lower cumulative live birth rate (47.0% vs. 40.0%), a lower incidence of good birth outcome (37.2% vs. 34.5%) and a higher risk of clinical pregnancy loss (11.1% vs. 17.9%), but did not reach statistical significance (P > 0.05). The incidences of obstetric or neonatal complications and other adverse events were similar in the four groups. Whether patients have low HDL-C did not differ in pregnancy outcomes.

CONCLUSIONS

We found that uRIF women with hypercholesterolemia had an increased proportion of aneuploid embryos and a reduced proportion of high-quality embryos, while different types of hyperlipidemia had no correlation with cumulative live birth rate as well as pregnancy and neonatal outcomes.

Essential Role of Granulosa Cell Glucose and Lipid Metabolism on Oocytes and the Potential Metabolic Imbalance in Polycystic Ovary Syndrome

Granulosa cells are crucial for the establishment and maintenance of bidirectional communication among oocytes. Various intercellular material exchange modes, including paracrine and gap junction, are used between them to achieve the efficient delivery of granulosa cell structural components, energy substrates, and signaling molecules to oocytes. Glucose metabolism and lipid metabolism are two basic energy metabolism pathways in granulosa cells; these are involved in the normal development of oocytes. Pyruvate, produced by granulosa cell glycolysis, is an important energy substrate for oocyte development. Granulosa cells regulate changes in intrafollicular hormone levels through the processing of steroid hormones to control the development process of oocytes. This article reviews the material exchange between oocytes and granulosa cells and expounds the significance of granulosa cells in the development of oocytes through both glucose metabolism and lipid metabolism. In addition, we discuss the effects of glucose and lipid metabolism on oocytes under pathological conditions and explore its relationship to polycystic ovary syndrome (PCOS). A series of changes were found in the endogenous molecules and ncRNAs that are related to glucose and lipid metabolism in granulosa cells under PCOS conditions. These findings provide a new therapeutic target for patients with PCOS; additionally, there is potential for improving the fertility of patients with PCOS and the clinical outcomes of assisted reproduction.

Serum opacity factor normalizes erythrocyte morphology in Scarb1-/- mice in an HDL-free cholesterol-dependent way

Compared with WT mice, HDL receptor-deficient (Scarb1-/-) mice have higher plasma levels of free cholesterol (FC)-rich HDL and exhibit multiple pathologies associated with a high mol% FC in ovaries, platelets, and erythrocytes, which are reversed by lowering HDL. Bacterial serum opacity factor (SOF) catalyzes the opacification of plasma by targeting and quantitatively converting HDL to neo HDL (HDL remnant), a cholesterol ester-rich microemulsion, and lipid-free APOA1. SOF delivery with an adeno-associated virus (AAVSOF) constitutively lowers plasma HDL-FC and reverses female infertility in Scarb1-/- mice in an HDL-dependent way. We tested whether AAVSOF delivery to Scarb1-/- mice will normalize erythrocyte morphology in an HDL-FC-dependent way. We determined erythrocyte morphology and FC content (mol%) in three groups-WT, untreated Scarb1-/- (control), and Scarb1-/- mice receiving AAVSOF-and correlated these with their respective HDL-mol% FC. Plasma-, HDL-, and tissue-lipid compositions were also determined. Plasma- and HDL-mol% FC positively correlated across all groups. Among Scarb1-/- mice, AAVSOF treatment normalized reticulocyte number, erythrocyte morphology, and erythrocyte-mol% FC. Erythrocyte-mol% FC positively correlated with HDL-mol% FC and with both the number of reticulocytes and abnormal erythrocytes. AAVSOF treatment also reduced FC of extravascular tissues to a lesser extent. HDL-FC spontaneously transfers from plasma HDL to cell membranes. AAVSOF treatment lowers erythrocyte-FC and normalizes erythrocyte morphology and lipid composition by reducing HDL-mol% FC.

Oocytes orchestrate protein prenylation for mitochondrial function through selective inactivation of cholesterol biosynthesis in murine species

Emerging research and clinical evidence suggest that the metabolic activity of oocytes may play a pivotal role in reproductive anomalies. However, the intrinsic mechanisms governing oocyte development regulated by metabolic enzymes remain largely unknown. Our investigation demonstrates that geranylgeranyl diphosphate synthase1 (Ggps1), the crucial enzyme in the mevalonate pathway responsible for synthesizing isoprenoid metabolite geranylgeranyl pyrophosphate from farnesyl pyrophosphate, is essential for oocyte maturation in mice. Our findings reveal that the deletion of Ggps1 that prevents protein prenylation in fully grown oocytes leads to subfertility and offspring metabolic defects without affecting follicle development. Oocytes that lack Ggps1 exhibit disrupted mitochondrial homeostasis and the mitochondrial defects arising from oocytes are inherited by the fetal offspring. Mechanistically, the excessive farnesylation of mitochondrial ribosome protein, Dap3, and decreased levels of small G proteins mediate the mitochondrial dysfunction induced by Ggps1 deficiency. Additionally, a significant reduction in Ggps1 levels in oocytes is accompanied by offspring defects when females are exposed to a high-cholesterol diet. Collectively, this study establishes that mevalonate pathway-protein prenylation is vital for mitochondrial function in oocyte maturation and provides evidence that the disrupted protein prenylation resulting from an imbalance between farnesyl pyrophosphate and geranylgeranyl pyrophosphate is the major mechanism underlying impairment of oocyte quality induced by high cholesterol.

Hepatic and ovarian effects of perfluorooctanoic acid exposure differ in lean and obese adult female mice

Obesity and overweight cause poor oocyte quality, miscarriage, infertility, polycystic ovarian syndrome, and offspring birth defects and affects 40% and 20% of US women and girls, respectively. Perfluorooctanoic acid (PFOA), a per- and poly-fluoroalkyl substance (PFAS), is environmentally persistent and has negative female reproductive effects including endocrine disruption, oxidative stress, altered menstrual cyclicity, and decreased fertility in humans and animal models. PFAS exposure is associated with non-alcoholic fatty liver disease which affects ∼24-26% of the US population. This study investigated the hypothesis that PFOA exposure impacts hepatic and ovarian chemical biotransformation and alters the serum metabolome. At 7 weeks of age, female lean, wild type (KK.Cg-a/a) or obese (KK.Cg-Ay/J) mice received saline (C) or PFOA (2.5 mg/Kg) per os for 15 d. Hepatic weight was increased by PFOA exposure in both lean and obese mice (P < 0.05) and obesity also increased liver weight (P < 0.05) compared to lean mice. The serum metabolome was also altered (P < 0.05) by PFOA exposure and differed between lean and obese mice. Exposure to PFOA altered (P < 0.05) the abundance of ovarian proteins with roles in xenobiotic biotransformation (lean - 6; obese - 17), metabolism of fatty acids (lean - 3; obese - 9), cholesterol (lean - 8; obese - 11), amino acids (lean - 18; obese - 19), glucose (lean - 7; obese - 10), apoptosis (lean - 18; obese - 13), and oxidative stress (lean - 3; obese - 2). Use of qRT-PCR determined that exposure to PFOA increased (P < 0.05) hepatic Ces1 and Chst1 in lean but Ephx1 and Gstm3 in obese mice. Also, obesity basally increased (P < 0.05) Nat2, Gpi and Hsd17b2 mRNA levels. These data identify molecular changes resultant from PFOA exposure that may cause liver injury and ovotoxicity in females. In addition, differences in toxicity induced by PFOA exposure occurs in lean and obese mice.

The Association between Circulating Lipids and Female Infertility Risk: A Univariable and Multivariable Mendelian Randomization Analysis

BACKGROUND

Although observational studies have demonstrated that blood lipids are associated with female infertility, the causality of this association remains unclear. We performed a univariable and multivariable Mendelian randomization (MR) analysis to evaluate the causal relationship between blood lipids and female infertility.

METHODS

Single-nucleotide polymorphisms associated with lipid traits in univariate analysis were obtained from the Million Veteran Program (MVP) and Global Lipids Genetics Consortium (GLGC), involving up to 215,551 and 188,577 European individuals, respectively. Blood lipids in multivariate analysis were obtained from the latest genome-wide association study meta-analysis with lipid levels in 73 studies encompassing >300,000 participants. Data on female infertility were obtained from the FinnGen Consortium R6 release, which included 6481 samples and 75,450 controls. Subsequently, MR analysis was performed using inverse variance-weighted (IVW), weighted median, weighted-mode, simple-mode and MR-Egger regression to demonstrate the causal relationship between lipids and female infertility.

RESULTS

After controlling confounding factors including body mass index and age at menarche, two-sample MR demonstrated that genetically predicted LDL-C and TC were causally associated with the risk of female infertility (When the genetic instruments come from the MVP database, LDL-C and female infertility, IVW OR: 1.13, 95% CI: 1.001-1.269, p = 0.047; TC and female infertility, IVW OR: 1.16, 95% CI: 1.018-1.317, p = 0.025, and when the genetic instruments came from the GLGC database, LDL-C and female infertility, IVW OR: 1.10, 95% CI: 1.008-1.210, p = 0.033; TC and female infertility, IVW OR: 1.14, 95% CI: 1.024-1.258, p = 0.015). However, the IVW estimate showed that HDL-C was not significantly associated with the risk of female infertility (when the genetic instruments came from the MVP database, IVW OR: 1.00, 95% CI: 0.887-1.128, p = 0.999; when the genetic instruments came from the GLGC database, IVW OR: 1.00, 95% CI: 0.896-1.111, p = 0.968). The multivariable MR analysis also provided evidence that LDL-C (OR: 1.12, 95% CI: 1.006-1.243, p = 0.042) was significantly associated with the risk of female infertility after considering the correlation of all lipid-related traits.

CONCLUSION

These findings support a causal relationship between increased LDL-cholesterol and increased female infertility risk. Furthermore, the association between lipid-related traits and female infertility risk merits more studies.

Serum opacity factor rescues fertility among female Scarb1-/- mice by reducing HDL-free cholesterol bioavailability

Human female infertility, 20% of which is idiopathic, is a public health problem for which better diagnostics and therapeutics are needed. A novel cause of infertility emerged from studies of female mice deficient in the HDL receptor gene (Scarb1). These mice are infertile and have high plasma HDL cholesterol (C) concentrations, due to elevated HDL-free cholesterol (FC), which transfers from HDL to all tissues. Previous studies have indicated that oral delivery of probucol, an HDL-lowering drug, to female Scarb1-/- mice reduces plasma HDL-C concentrations and rescues fertility. Additionally, serum opacity factor (SOF), a bacterial virulence factor, disrupts HDL structure, and bolus SOF injection into mice reduces plasma HDL-C concentrations. Here, we discovered that delivering SOF to female Scarb1-/- mice with an adeno-associated virus (AAVSOF) induces constitutive SOF expression, reduces HDL-FC concentrations, and rescues fertility while normalizing ovary morphology. Although AAVSOF did not alter ovary-FC content, the ovary-mol% FC correlated with plasma HDL-mol% FC in a fertility-dependent way. Therefore, reversing the abnormal plasma microenvironment of high plasma HDL-mol% FC in female Scarb1-/- mice rescues fertility. These data provide the rationale to search for similar mechanistic links between HDL-mol% FC and infertility and the rescue of fertility in women by reducing plasma HDL-mol% FC.

Cholesterol accumulation in ovarian follicles causes ovulation defects in Abca1a -/- Japanese medaka (Oryzias latipes)

ATP-binding cassette A1 (ABCA1) is a membrane protein, which exports excess cellular cholesterol to generate HDL to reduce the risk of the onset of cardiovascular diseases (CVD). In addition, ABCA1 exerts pleiotropic effects on such as inflammation, tissue repair, and cell proliferation and migration. In this study, we explored the novel physiological roles of ABCA1 using Japanese medaka (Oryzias latipes), a small teleost fish. Three Abca1 genes were found in the medaka genome. ABCA1A and ABCA1C exported cholesterol to generate nascent HDL as human ABCA1 when expressed in HEK293 cells. To investigate their physiological roles, each Abca1-deficient fish was generated using the CRISPR-Cas9 system. Abca1a -/- female medaka was found to be infertile, while Abca1b -/- and Abca1c -/- female medaka were fertile. In vitro ovarian follicle culture suggested that Abca1a deficiency causes ovulation defects. In the ovary, ABCA1A was expressed in theca cells, an outermost layer of the ovarian follicle. Total cholesterol content of Abca1a -/- ovary was significantly higher than that of the wild-type, while estrogen and progestin contents were compatible with those of the wild-type. Furthermore, cholesterol loading to the wild-type follicles caused ovulation defects. These results suggest that ABCA1A in theca cells regulates cholesterol content in the ovarian follicles and its deficiency inhibits successful ovulation through cholesterol accumulation in the ovarian follicle.

Bioinformatics and In silico approaches to identify novel biomarkers and key pathways for cancers that are linked to the progression of female infertility: A comprehensive approach for drug discovery

Despite modern treatment, infertility remains one of the most common gynecologic diseases causing severe health effects worldwide. The clinical and epidemiological data have shown that several cancerous risk factors are strongly linked to Female Infertility (FI) development, but the exact causes remain unknown. Understanding how these risk factors affect FI-affected cell pathways might pave the door for the discovery of critical signaling pathways and hub proteins that may be targeted for therapeutic intervention. To deal with this, we have used a bioinformatics pipeline to build a transcriptome study of FI with four carcinogenic risk factors: Endometrial Cancer (EC), Ovarian Cancer (OC), Cervical Cancer (CC), and Thyroid Cancer (TC). We identified FI sharing 97, 211, 87 and 33 differentially expressed genes (DEGs) with EC, OC, CC, and TC, respectively. We have built gene-disease association networks from the identified genes based on the multilayer network and neighbour-based benchmarking. Identified TNF signalling pathways, ovarian infertility genes, cholesterol metabolic process, and cellular response to cytokine stimulus were significant molecular and GO pathways, both of which improved our understanding the fundamental molecular mechanisms of cancers associated with FI progression. For therapeutic intervention, we have targeted the two most significant hub proteins VEGFA and PIK3R1, out of ten proteins based on Maximal Clique Centrality (MCC) value of cytoscape and literature analysis for molecular docking with 27 phytoestrogenic compounds. Among them, sesamin, galangin and coumestrol showed the highest binding affinity for VEGFA and PIK3R1 proteins together with favourable ADMET properties. We recommended that our identified pathway, hub proteins and phytocompounds may be served as new targets and therapeutic interventions for accurate diagnosis and treatment of multiple diseases.

Hippo Signaling in the Ovary: Emerging Roles in Development, Fertility, and Disease

Emerging studies indicate that the Hippo pathway, a highly conserved pathway that regulates organ size control, plays an important role in governing ovarian physiology, fertility, and pathology. Specific to the ovary, the spatiotemporal expression of the major components of the Hippo signaling cascade are observed throughout the reproductive lifespan. Observations from multiple species begin to elucidate the functional diversity and molecular mechanisms of Hippo signaling in the ovary in addition to the identification of interactions with other signaling pathways and responses to various external stimuli. Hippo pathway components play important roles in follicle growth and activation, as well as steroidogenesis, by regulating several key biological processes through mechanisms of cell proliferation, migration, differentiation, and cell fate determination. Given the importance of these processes, dysregulation of the Hippo pathway contributes to loss of follicular homeostasis and reproductive disorders such as polycystic ovary syndrome (PCOS), premature ovarian insufficiency, and ovarian cancers. This review highlights what is currently known about the Hippo pathway core components in ovarian physiology, including ovarian development, follicle development, and oocyte maturation, while identifying areas for future research to better understand Hippo signaling as a multifunctional pathway in reproductive health and biology.

Implications of High-Density Cholesterol Metabolism for Oocyte Biology and Female Fertility

Cholesterol is an essential component of animal cells. Different regulatory mechanisms converge to maintain adequate levels of this lipid because both its deficiency and excess are unfavorable. Low cell cholesterol content promotes its synthesis and uptake from circulating lipoproteins. In contrast, its excess induces the efflux to high-density lipoproteins (HDL) and their transport to the liver for excretion, a process known as reverse cholesterol transport. Different studies suggest that an abnormal HDL metabolism hinders female fertility. HDL are the only lipoproteins detected in substantial amounts in follicular fluid (FF), and their size and composition correlate with embryo quality. Oocytes obtain cholesterol from cumulus cells via gap junctions because they cannot synthesize cholesterol de novo and lack HDL receptors. Recent evidence has supported the possibility that FF HDL play a major role in taking up excess unesterified cholesterol (UC) from the oocyte. Indeed, genetically modified mouse models with disruptions in reverse cholesterol transport, some of which show excessive circulating UC levels, exhibit female infertility. Cholesterol accumulation can affect the egg´s viability, as reported in other cell types, and activate the plasma membrane structure and activity of membrane proteins. Indeed, in mice deficient for the HDL receptor Scavenger Class B Type I (SR-B1), excess circulating HDL cholesterol and UC accumulation in oocytes impairs meiosis arrest and hinders the developmental capacity of the egg. In other cells, the addition of cholesterol activates calcium channels and dysregulates cell death/survival signaling pathways, suggesting that these mechanisms may link altered HDL cholesterol metabolism and infertility. Although cholesterol, and lipids in general, are usually not evaluated in infertile patients, one study reported high circulating UC levels in women showing longer time to pregnancy as an outcome of fertility. Based on the evidence described above, we propose the existence of a well-regulated and largely unexplored system of cholesterol homeostasis controlling traffic between FF HDL and oocytes, with significant implications for female fertility.

Seasonal Variations in the Lipid Profile of the Ovarian Follicle in Italian Mediterranean Buffaloes

Simple Summary

Reproductive seasonality is a major factor affecting buffalo breeding. The rationale of this work derives from the hypothesis that the reduced cleavage and blastocyst rates observed during the non-breeding season could be due to a suboptimal follicular environment. The present study aimed to evaluate the influence of season on the lipid profile of the ovarian follicle in the Italian Mediterranean buffalo. For this purpose, abattoir-derived ovaries were collected during the breeding and non-breeding seasons, and the apolar phase of follicular components was analyzed. To our knowledge, this is the first report of seasonal variations in lipid content of the buffalo ovarian follicle, including follicular fluid, follicular and cumulus cells, and oocytes. The results undoubtedly demonstrated significant seasonal variations in the lipid profile, including triglycerides, cholesterol, and phospholipids, in the different biological matrices analyzed. Interestingly, an increased amount in the total level of non-esterified fatty acids in the follicular fluid was also observed during the non-breeding season. The results allow a better understanding of the physiology of the ovarian follicle in buffalo and unveil some causes of reduced oocyte competence during the non-reproductive season, laying the groundwork for further studies and corrective strategies.

Abstract

The reduced oocyte competence recorded during the non-breading season (NBS) is one of the key factors affecting the profitability of buffalo farming and limits the IVEP efficiency. The purpose of this experiment was to evaluate whether season influences the lipid content within the ovarian follicle in the Italian Mediterranean buffalo. Abattoir-derived ovaries were collected during the breeding season (BS) and the NBS, and different matrices (follicular fluid, oocytes, cumulus and follicular cells) were recovered. After the extraction of the apolar fraction, all samples were analyzed by H1 nuclear magnetic resonance and FF samples by gas chromatography–mass spectrometry. Seasonal differences in lipid composition were observed in all matrices. In particular, during the NBS, the triglyceride content was higher in the follicular fluid and in the oocytes but reduced in the follicular cells. Both cholesterol and phospholipids were reduced in the follicular fluid and follicular cells during the NBS. Furthermore, the total amount of non-esterified fatty acids was significantly increased in the follicular fluid. The seasonal variation in lipid profile of the follicle may, in part, account for the reduced buffalo oocyte competence during the NBS, due to the critical role played by lipids in regulating ovarian functions.

Metabolic control of oocyte development

Well balanced and timed metabolism is essential for oocyte development. The effects of extrinsic nutrients on oocyte maturation have been widely reported. In contrast, intrinsic control of oogenesis by intracellular metabolites and metabolic enzymes has received little attention. The comprehensive characterization of metabolic patterns could lead to more complete understanding of regulatory mechanisms underlying oocyte development. A cell's metabolic state is integrated with epigenetic regulation. Epigenetic modifications in germ cells are therefore sensitive to parental environmental exposures. Nevertheless, direct genetic evidence for metabolites involvement in epigenetic establishment during oocyte development is still lacking. Moreover, metabolic disorder-induced epigenetic perturbations during oogenesis might mediate the inter/transgenerational effects of environmental insults. The molecular mechanisms responsible for this deserve further investigation. Here, we summarize the findings on metabolic regulation in oocyte maturation, and how it contributes to oocyte epigenetic modification. Finally, we propose a mouse model that metabolic disorder in oocyte serves as a potential factor mediating the maternal environment effects on offspring health.

Lipid Metabolic Process Involved in Oocyte Maturation During Folliculogenesis

Oocyte maturation is a complex and dynamic process regulated by the coordination of ovarian cells and numerous extraovarian signals. From mammal studies, it is learnt that lipid metabolism provides sufficient energy for morphological and cellular events during folliculogenesis, and numerous lipid metabolites, including cholesterol, lipoproteins, and 14-demethyl-14-dehydrolanosterol, act as steroid hormone precursors and meiotic resumption regulators. Endogenous and exogenous signals, such as gonadotropins, insulin, and cortisol, are the upstream regulators in follicular lipid metabolic homeostasis, forming a complex and dynamic network in which the key factor or pathway that plays the central role is still a mystery. Though lipid metabolites are indispensable, long-term exposure to a high-fat environment will induce irreversible damage to follicular cells and oocyte meiosis. This review specifically describes the transcriptional expression patterns of several lipid metabolism–related genes in human oocytes and granulosa cells during folliculogenesis, illustrating the spatiotemporal lipid metabolic changes in follicles and the role of lipid metabolism in female reproductive capacity. This study aims to elaborate the impact of lipid metabolism on folliculogenesis, thus providing guidance for improving the fertility of obese women and the clinical outcome of assisted reproduction.

High Free Cholesterol Bioavailability Drives the Tissue Pathologies in Scarb1-/- Mice

Objective: Overall and atherosclerosis-associated mortality is elevated in humans with very high HDL (high-density lipoprotein) cholesterol concentrations. Mice with a deficiency of the HDL receptor, Scarb1 (scavenger receptor class B type 1), are a robust model of this phenotype and exhibit several additional pathologies. We hypothesized that the previously reported high plasma concentration of free cholesterol (FC)-rich HDL in Scarb1-/- mice produces a state of high HDL-FC bioavailability that increases whole-body FC and dysfunction in multiple tissue sites. Approach and Results: The higher mol% FC in Scarb1-/- versus WT (wild type) HDL (41.1 versus 16.0 mol%) affords greater FC bioavailability for transfer to multiple sites. Plasma clearance of autologous HDL-FC mass was faster in WT versus Scarb1-/- mice. FC influx from Scarb1-/- HDL to LDL (low-density lipoprotein) and J774 macrophages was greater ([almost equal to]4x) than that from WT HDL, whereas FC efflux capacity was similar. The higher mol% FC of ovaries, erythrocytes, heart, and macrophages of Scarb1-/- versus WT mice is associated with previously reported female infertility, impaired cell maturation, cardiac dysfunction, and atherosclerosis. The FC contents of other tissues were similar in the two genotypes, and these tissues were not associated with any overt pathology. In addition to the differences between WT versus Scarb1-/- mice, there were many sex-dependent differences in tissue-lipid composition and plasma FC clearance rates. Conclusions: Higher HDL-FC bioavailability among Scarb1-/- versus WT mice drives increased FC content of multiple cell sites and is a potential biomarker that is mechanistically linked to multiple pathologies.

Ovarian cholesterol efflux: ATP-binding cassette transporters and follicular fluid HDL regulate cholesterol content in mouse oocytes†

High density lipoproteins (HDL) take up cholesterol from peripheral tissues via ABC transporters and deliver it to the liver via scavenger receptor class B type I (SR-B1). HDL are the main lipoproteins present in follicular fluid (FF). They are thought to derive from plasma, but their origin is still controversial. SR-B1 knock-out (KO) mice have provided important evidence linking HDL metabolism and female fertility. These mice have cholesterol-rich circulating HDL and female infertility that can be restored by treating mice with the cholesterol-lowering drug probucol. Ovulated oocytes from SR-B1 KO females are dysfunctional and show excess cholesterol. The mechanisms explaining the contribution of FF HDL to oocyte cholesterol homeostasis are unknown. Here, using quantitation of filipin fluorescence we show that in SR-B1 KO ovaries, cholesterol excess is first observed in immature oocytes in antral follicles. By performing cross-transplant experiments between WT and apolipoprotein A-I deficient (ApoA-I KO) mice, which lack the main protein component of HDL, we provide evidence supporting the plasmatic origin of FF HDL. Also, we demonstrate that probucol treatment in SR-B1 KO females results in lowering of cholesterol content in their oocytes. Incubation of oocytes from SR-B1 KO mice with purified WT HDL reduces their cholesterol content, suggesting that HDL promote efflux of excess cholesterol from oocytes. In agreement with this hypothesis, we identified ABC transporters in oocytes and observed that ABCA1 KO oocytes have excess cholesterol and lower viability than WT oocytes.

Oocyte Spontaneous Activation: An Overlooked Cellular Event That Impairs Female Fertility in Mammals

In mammals, including humans, mature oocytes are ovulated into the oviduct for fertilization. Normally, these oocytes are arrested at metaphase of the second meiosis (MII), and this arrest can be maintained for a certain period, which is essential for fertilization in vivo and oocyte manipulations in vitro, such as assisted reproduction in clinics and nuclear/spindle transfer in laboratories. However, in some species and under certain circumstances, exit from MII occurs spontaneously without any obvious stimulation or morphological signs, which is so-called oocyte spontaneous activation (OSA). This mini-review summarizes two types of OSA. In the first type (e.g., most rat strains), oocytes can maintain MII arrest in vivo, but once removed out, oocytes undergo OSA with sister chromatids separated and eventually scattered in the cytoplasm. Because the stimulation is minimal (oocyte collection itself), this OSA is incomplete and cannot force oocytes into interphase. Notably, once re-activated by sperm or chemicals, those scattered chromatids will form multiple pronuclei (MPN), which may recapitulate certain MPN and aneuploidy cases observed in fertility clinics. The second type of OSA occurs in ovarian oocytes (e.g., certain mouse strains and dromedary camel). Without ovulation or fertilization, these OSA-oocytes can initiate intrafollicular development, but these parthenotes cannot develop to term due to aberrant genomic imprinting. Instead, they either degrade or give rise to ovarian teratomas, which have also been reported in female patients. Last but not the least, genetic models displaying OSA phenotypes and the lessons we can learn from animal OSA for human reproduction are also discussed.

Characterization of Metabolic Patterns in Mouse Oocytes during Meiotic Maturation

Well-balanced and timed metabolism is essential for making a high-quality egg. However, the metabolic framework that supports oocyte development remains poorly understood. Here, we obtained the temporal metabolome profiles of mouse oocytes during in vivo maturation by isolating large number of cells at key stages. In parallel, quantitative proteomic analyses were conducted to bolster the metabolomic data, synergistically depicting the global metabolic patterns in oocytes. In particular, we discovered the metabolic features during meiotic maturation, such as the fall in polyunsaturated fatty acids (PUFAs) level and the active serine-glycine-one-carbon (SGOC) pathway. Using functional approaches, we further identified the key targets mediating the action of PUFA arachidonic acid (ARA) on meiotic maturation and demonstrated the control of epigenetic marks in maturing oocytes by SGOC network. Our data serve as a broad resource on the dynamics occurring in metabolome and proteome during oocyte maturation.

Facial appearance and metabolic health biomarkers in women

Facial appearance has been suggested to provide an honest cue of an individual’s biological condition. However, there is little direct evidence that facial attractiveness reflects actual health. Here we tested if facial appearance is related with metabolic health biomarkers. Face photographs of 161 healthy, young women (M_age = 28.59, SD_age = 2.34) were assessed in terms of perceived attractiveness and health. Metabolic health was evaluated based on levels of markers of lipid and glucose metabolism balance, liver functioning, and inflammation. BMI, testosterone (T), and estradiol (E2) levels were controlled. Facial attractiveness, but not health, was negatively related with lipid profile components detrimental to health (total cholesterol, LDL, triglycerides) but not with relatively protective for health HDL. When controlled for BMI, E2, and T, only the relationship between attractiveness and triglycerides remained significant. Facial appearance was unrelated with glucose metabolism, liver functioning, and inflammatory markers. The results suggest, that for healthy women of reproductive age, such measures as BMI and sex hormone levels may be better predictors of attractiveness, compared to measures of metabolic health. Markers of lipid, glucose homeostasis, liver functioning or low-grade inflammation may be rather indicators of future health, of lesser importance in mating context, thus only modestly reflected in facial appearance.

Molecular analysis of lipid uptake- and necroptosis-associated factor expression in vitrified-warmed mouse oocytes

BACKGROUND

We had previously demonstrated that vitrification reduces the levels of certain phospholipid classes, and that oocytes from aged mice show a similar lipidome alteration, even without vitrification. In the current investigation, we examined if vitrification-warming of mouse oocytes from young and aged mice causes any changes in molecular aspects of lipid-associated features.

METHODS

Metaphase II (MII) stage oocytes were harvested from young (10-14-week-old) and aged (45-54-week-old) mice by a superovulation regime with PMSG followed by hCG. We examined the status of the intracellular lipid pool and the integrity of the plasma membrane by staining oocytes with BODIPY 500/510 and CellMask live dyes. Expression of lipid uptake- and necroptosis-associated genes was assessed by quantitative PCR analyses, in oocytes from young and old mice, before and after vitrification. Localization patterns of two crucial necroptosis proteins, phosphorylated MLKL (pMLKL) and phosphorylated RIPK1 (pRIPK1) were examined in mouse oocytes by immunofluorescence staining. Necrostain-1 (Nec1), an inhibitor of RIPK1, was used to examine if RIPK1 activity is required to maintain oocyte quality during vitrification.

RESULTS

We confirmed that vitrified-warmed oocytes from aged mice showed noticeable decrease in both CellMask and BODIPY 500/510 dyes. Among the lipid uptake-associated genes, Cd36 expression was higher in oocytes from aged mice. Necroptosis is a type of programmed cell death that involves damage to the plasma membrane, eventually resulting in cell rupture. The expression of necroptosis-associated genes did not significantly differ among groups. We observed that localization patterns of pMLKL and pRIPK1 were unique in mouse oocytes, showing association with microtubule organizing centers (MTOCs) and spindle poles. pMLKL was also localized on kinetochores of MII chromosomes. Oocytes treated with Nec1 during vitrification showed a decreased survival rate, indicating the importance of RIPK1 activity in oocyte vitrification.

CONCLUSIONS

We report that oocytes from aged mice show differential expression of CD36, which suggests that CD36-mediated lipid uptake may be influenced by age. We also show for the first time that pMLKL and pRIPK1 exhibit unique localization pattern in mouse oocytes and this may suggest role(s) for these factors in non-necroptosis-associated cellular processes.

The extracellular calcium-sensing receptor promotes porcine egg activation via calcium/calmodulin-dependent protein kinase II

Extracellular calcium is required for intracellular Ca²⁺ oscillations needed for egg activation, but the regulatory mechanism is still poorly understood. The present study was designed to demonstrate the function of calcium-sensing receptor (CASR), which could recognize extracellular calcium as first messenger, during porcine egg activation. CASR expression was markedly upregulated following egg activation. Functionally, the addition of CASR agonist NPS R-568 significantly enhanced pronuclear formation rate, while supplementation of CASR antagonist NPS2390 compromised egg activation. There was no change in NPS R-568 group compared with control group when the egg activation was performed without extracellular calcium addition. The addition of NPS2390 precluded the activation-dependent [Ca²⁺ ]_i rise. When egg activation was conducted in intracellular Ca²⁺ chelator BAPTA-AM and NPS R-568 containing medium, CASR function was abolished. Meanwhile, CASR activation increased the level of the [Ca²⁺ ]_i effector p-CAMKII, and the presence of KN-93, an inhibitor of CAMKII, significantly reduced the CASR-mediated increasement of pronuclear formation rate. Furthermore, the increase of CASR expression following activation was reversed by inhibiting CAMKII activity, supporting a positive feedback loop between CAMKII and CASR. Altogether, these findings provide a new pathway of egg activation about CASR, as the extracellular Ca²⁺ effector, promotes egg activation via its downstream effector and upstream regulator CAMKII.

Alterations in oocytes and early zygotes following oral exposure to di(2-ethylhexyl) phthalate in young adult female mice

Because di(2-ethylhexyl) phthalate (DEHP) toxicity on ovarian function is incomplete, effects of DEHP oocyte fertilization and the resulting zygotes were investigated. Further, an analysis characterizing the stage of zygote arrest was performed. Female CD1 mice were dosed orally with DEHP (0, 20, 200 and 2000 μg/kg/day) for 30 days. Following an in vivo mating post-dosing, DEHP-treated females exhibited fewer oocytes/zygotes, fewer oocytes displaying the polar body extrusion, fewer 1-cell zygotes having 2-pronuclei, more unfertilized oocytes, and decreased number of zygotes at every stage of development. DEHP induced blastomere fragmentation in zygotes. DNA replication in zygotes directly assessed by the 5-Ethynyl-2'-deoxyuridine (5-EdU) incorporation assay and indirectly by dosing mice with 5-fluorouracil (5-FU) suggested that DEHP inhibits DNA replication. Our data suggest that DEHP at doses found in 'every-day' (200 μg/Kg/day) or occupational (2000 μg/Kg/day) environments induces zygote fragmentation and arrests its development from the 2-cell stage potentially impairing DNA replication.

Hypothyroidism affects lipid and glycogen content and peroxisome proliferator-activated receptor δ expression in the ovary of the rabbit

Dyslipidaemia and hyperglycaemia are associated with ovarian failure and both have been related to hypothyroidism. Hypothyroidism promotes anovulation and ovarian cysts in women and reduces the size of follicles and the expression of aromatase in the ovary of rabbits. Considering that ovarian steroidogenesis and ovulation depend on lipid metabolism and signalling, the aim of the present study was to analyse the effect of hypothyroidism on the lipid content and expression of peroxisome proliferator-activated receptor (PPAR) δ in the ovary. Ovaries from female rabbits belonging to the control (n=7) and hypothyroid (n=7) groups were processed to measure total cholesterol (TC), triacylglycerol (TAG) and glycogen content, as well as to determine the presence of granules containing oxidized lipids (oxysterols and lipofuscin) and the relative expression of perilipin A (PLIN-A) and PPARδ. Hypothyroidism increased TC and glycogen content, but reduced TAG content in the ovary. This was accompanied by a reduction in the expression of PLIN-A in total and cytosolic extracts, changes in the presence of granules containing oxidative lipids and low PPARδ expression. The results of the present study suggest that hypothyroidism modifies the content and signalling of lipids in the ovary, possibly affecting follicle maturation. These results could improve our understanding of the association between hypothyroidism and infertility in females.

Anti-oxidative function of follicular fluid HDL and outcomes of modified natural cycle-IVF

High density lipoproteins (HDL) are the main cholesterol carriers in follicular fluid (FF), the natural environment of oocyte development. Additionally, HDL have critical biological functions such as anti-oxidative capacity, which have not been studied in reproduction. Therefore, this study aimed to investigate whether the anti-oxidative function of FF-HDL is associated with fertility outcomes. From 253 women undergoing modified natural cycle (MNC)- IVF at a single academic centre FF and plasma were collected (n = 375 cycles). Anti-oxidative function of FF was mainly attributable to HDL (n = 8; 83%). FF-HDL had a higher anti-oxidative function than plasma HDL (n = 19, P < 0.001) coinciding with increased vitamin E and sphingosine 1 phosphate content (P = 0.028 each). Proteomic analysis indicated no significant differences in major anti-oxidative proteins such as paraoxonase 1, apolipoprotein (apo) A-I or apoA-IV between FF-HDL and matched plasma-HDL (n = 5), while apoC-III, apoE and apoC-II were relatively lower in FF-HDL. Finally, FF-HDL anti-oxidative function was related to a decrease in the odds of the oocyte undergoing normal fertilization, an association that persisted after adjustment for confounders (odds ratio 0.97 (0.93–1), P = 0.041). In conclusion, FF-HDL has considerable anti-oxidative properties that might be relevant for embryo quality.

Insulin increases cholesterol uptake, lipid droplet content, and apolipoprotein B secretion in CaCo-2 cells by upregulating SR-BI via a PI3K, AKT, and mTOR-dependent pathway

The actions of insulin on intestinal cholesterol absorption and lipoprotein secretion are not well understood. Herein, we determined the effects of insulin on the levels of cholesterol transporter scavenger receptor, class B, type I (SR-BI), cellular cholesterol uptake, intracellular lipid accumulation, and lipoprotein secretion in a cellular model of human intestinal epithelium.

METHODS

CaCo-2 cells were cultured to postconfluency in Transwell filters and stimulated with glucose (25 mM) in the presence or absence of insulin (100 nM) at their basolateral surface. SR-BI mRNA and protein levels were quantified by quantitative reverse transcription-PCR and immunoblot, respectively. Polarized localization of SR-BI was determined by cell surface proteins biotinylation and streptavidin precipitation. Activities of PI3K, AKT, mTOR, and SR-BI were pharmacologically antagonized. Cholesterol uptake was assessed by NBD-cholesterol incorporation. Apolipoprotein (apo) B concentration was quantified by ELISA. Subcellular localization of neutral lipids (BODIPY) and SR-BI (immunofluorescence) was determined by confocal microscopy.

RESULTS

In polarized CaCo-2 cells, insulin increased SR-BI at the mRNA and protein levels. SR-BI was exclusively present at apical cell surface, as indicated by biotinylation and confocal microscopy analysis. Glucose did not modify SR-BI abundance or subcellular localization. Effects of insulin on SR-BI levels were abrogated by PI3K, AKT, or mTOR pharmacological antagonism. Cholesterol uptake, neutral lipid abundance, and apo B secretion were increased by insulin in CaCo-2 cells, and these effects were prevented by SR-BI pharmacological antagonism with block lipid transport-1.

CONCLUSIONS

insulin promotes cholesterol uptake, intracellular lipid store, and apo B-containing lipoproteins secretion by SR-BI-dependent mechanisms in a model of human intestinal epithelium.

The function of high-density lipoprotein and low-density lipoprotein in the maintenance of mouse ovarian steroid balance

The membrane proteins, low-density lipoprotein receptor (LDLR) and scavenger receptor class B member 1 (SR-BI, gene name Scarb1), are lipoprotein receptors that play central roles in lipoprotein metabolism. Cholesterol bound in high-density lipoprotein (HDL) and LDL is transported into cells mainly by SR-BI and LDLR. The relative contribution of LDL and HDL to the steroidogenic cholesterol pool varies among species and may vary among tissues within one species. To investigate which of these pathways is more important in the supply of cholesterol in mouse ovary, we utilized immunohistochemistry, western blotting, RNAi, and RT-PCR as well as Ldlr-/- mice to explore the uptake of HDL and LDL in the ovary. Our data demonstrate that both SR-BI and LDLR are present in the interstitial cells, thecal cells, and corpora lutea (CLs), and their expression fluctuates with the development of follicles and CLs. The intracellular cholesterol concentration was significantly decreased when Ldlr or Scarb1 was silenced in luteal cells. Furthermore, Ldlr-/- mice had lower progesterone and estrogen levels compared to wild-type mice, and when Ldlr-/- mice were treated with the inhibitor of de novo cholesterol synthesis, lovastatin, serum progesterone, and estrogen concentrations were further reduced. These results demonstrate that both LDLR and SR-BI play important roles in importing cholesterol and that both HDL and LDL are crucial in steroidogenesis in mouse ovaries.

Liver X Receptors: A Possible Link between Lipid Disorders and Female Infertility

A close relationship exists between cholesterol and female reproductive physiology. Indeed, cholesterol is crucial for steroid synthesis by ovary and placenta, and primordial for cell structure during folliculogenesis. Furthermore, oxysterols, cholesterol-derived ligands, play a potential role in oocyte maturation. Anomalies of cholesterol metabolism are frequently linked to infertility. However, little is known about the molecular mechanisms. In parallel, increasing evidence describing the biological roles of liver X receptors (LXRs) in the regulation of steroid synthesis and inflammation, two processes necessary for follicle maturation and ovulation. Both of the isoforms of LXRs and their bona fide ligands are present in the ovary. LXR-deficient mice develop late sterility due to abnormal oocyte maturation and increased oocyte atresia. These mice also have an ovarian hyper stimulation syndrome in response to gonadotropin stimulation. Hence, further studies are necessary to explore their specific roles in oocyte, granulosa, and theca cells. LXRs also modulate estrogen signaling and this could explain the putative protective role of the LXRs in breast cancer growth. Altogether, clinical studies would be important for determining the physiological relevance of LXRs in reproductive disorders in women.

Scavenger Receptor Type B1 and Lipoprotein Nanoparticle Inhibit Myeloid-Derived Suppressor Cells

Myeloid-derived suppressor cells (MDSC) are innate immune cells that potently inhibit T cells. In cancer, novel therapies aimed to activate T cells can be rendered ineffective due to the activity of MDSCs. Thus, targeted inhibition of MDSCs may greatly enhance T-cell-mediated antitumor immunity, but mechanisms remain obscure. Here we show, for the first time, that scavenger receptor type B-1 (SCARB1), a high-affinity receptor for spherical high-density lipoprotein (HDL), is expressed by MDSCs. Furthermore, we demonstrate that SCARB1 is specifically targeted by synthetic high-density lipoprotein-like nanoparticles (HDL NP), which reduce MDSC activity. Using in vitro T-cell proliferation assays, data show that HDL NPs specifically bind SCARB1 to inhibit MDSC activity. In murine cancer models, HDL NP treatment significantly reduces tumor growth, metastatic tumor burden, and increases survival due to enhanced adaptive immunity. Flow cytometry and IHC demonstrate that HDL NP-mediated suppression of MDSCs increased CD8⁺ T cells and reduced Treg cells in the metastatic tumor microenvironment. Using transgenic mice lacking SCARB1, in vivo data clearly show that the HDL NPs specifically target this receptor for suppressing MDSCs. Ultimately, our data provide a new mechanism and targeted therapy, HDL NPs, to modulate a critical innate immune cell checkpoint to enhance the immune response to cancer. Mol Cancer Ther; 17(3); 686-97. ©2017 AACR.

Liposome-encapsulated diacyl glycerol and inositol triphosphate-induced delayed oocyte activation and poor development of parthenotes

Objective:

To explore the ability of diacyl glycerol (DAG) and inositol triphosphate (IP3), two major secondary messengers in the calcium signaling pathway, in activating oocytes.

Material and Methods:

Oocyte cumulus complex obtained from superovulated Swiss albino mice were incubated in M16 medium with liposome-encapsulated 1,2-Dipalmitoyl-sn-glycerol (LEDAG) and/or IP3 for 3 h. Strontium chloride was used as positive control. The activation potential, ploidy status, and blastocyst rate was calculated.

Results:

Both DAG and IP3, individually, induced activation in ~98% of oocytes, which was significantly higher (p<0.01) than activation induced by strontium chloride (60%). Delayed pronucleus formation and a higher percentage of diploid parthenotes was observed in oocytes activated with LEDAG and/or IP3. However, these embryos failed to progress beyond the 6-8–cell stage. Only when the medium was supplemented with LEDAG (5 μg/mL) and IP3 (10 μg/mL) could activated oocytes progress till the blastocyst stage (5.26%), which was lower than the blastocyst rate in the positive controls (13.91%).

Conclusion:

The results of the present study indicate that DAG and IP3 can induce delayed oocyte activation and poor development of parthenotes in vitro.

Free cholesterol and cholesterol esters in bovine oocytes: Implications in survival and membrane raft organization after cryopreservation

Part of the damage caused by cryopreservation of mammalian oocytes occurs at the plasma membrane. The addition of cholesterol to cell membranes as a strategy to make it more tolerant to cryopreservation has been little addressed in oocytes. In order to increase the survival of bovine oocytes after cryopreservation, we proposed not only to increase cholesterol level of oocyte membranes before vitrification but also to remove the added cholesterol after warming, thus recovering its original level. Results from our study showed that modulation of membrane cholesterol by methyl-β-cyclodextrin (MβCD) did not affect the apoptotic status of oocytes and improved viability after vitrification yielding levels of apoptosis closer to those of fresh oocytes. Fluorometric measurements based on an enzyme-coupled reaction that detects both free cholesterol (membrane) and cholesteryl esters (stored in lipid droplets), revealed that oocytes and cumulus cells present different levels of cholesterol depending on the seasonal period. Variations at membrane cholesterol level of oocytes were enough to account for the differences found in total cholesterol. Differences found in total cholesterol of cumulus cells were explained by the differences found in both the content of membrane cholesterol and of cholesterol esters. Cholesterol was incorporated into the oocyte plasma membrane as evidenced by comparative labeling of a fluorescent cholesterol. Oocytes and cumulus cells increased membrane cholesterol after incubation with MβCD/cholesterol and recovered their original level after cholesterol removal, regardless of the season. Finally, we evaluated the effect of vitrification on the putative raft molecule GM1. Cholesterol modulation also preserved membrane organization by maintaining ganglioside level at the plasma membrane. Results suggest a distinctive cholesterol metabolic status of cumulus-oocyte complexes (COCs) among seasons and a dynamic organizational structure of cholesterol homeostasis within the COC. Modulation of membrane cholesterol by MβCD improved survival of bovine oocytes and preserved integrity of GM1-related rafts after vitrification.

Carboxy-terminal deletion of the HDL receptor reduces receptor levels in liver and steroidogenic tissues, induces hypercholesterolemia, and causes fatal heart disease

The HDL receptor SR-BI mediates the transfer of cholesteryl esters from HDL to cells and controls HDL abundance and structure. Depending on the genetic background, loss of SR-BI causes hypercholesterolemia, anemia, reticulocytosis, splenomegaly, thrombocytopenia, female infertility, and fatal coronary heart disease (CHD). The carboxy terminus of SR-BI (⁵⁰⁵QEAKL⁵⁰⁹) must bind to the cytoplasmic adaptor PDZK1 for normal hepatic-but not steroidogenic cell-expression of SR-BI protein. To determine whether SR-BI's carboxy terminus is also required for normal protein levels in steroidogenic cells, we introduced into SR-BI's gene a ⁵⁰⁷Ala/STOP mutation that produces a truncated receptor (SR-BIΔCT). As expected, the dramatic reduction of hepatic receptor protein in SR-BIΔCT mice was similar to that in PDZK1 knockout (KO) mice. Unlike SR-BI KO females, SR-BIΔCT females were fertile. The severity of SR-BIΔCT mice's hypercholesterolemia was intermediate between those of SR-BI KO and PDZK1 KO mice. Substantially reduced levels of the receptor in adrenal cortical cells, ovarian cells, and testicular Leydig cells in SR-BIΔCT mice suggested that steroidogenic cells have an adaptor(s) functionally analogous to hepatic PDZK1. When SR-BIΔCT mice were crossed with apolipoprotein E KO mice (SR-BIΔCT/apoE KO), pathologies including hypercholesterolemia, macrocytic anemia, hepatic and splenic extramedullary hematopoiesis, massive splenomegaly, reticulocytosis, thrombocytopenia, and rapid-onset and fatal occlusive coronary arterial atherosclerosis and CHD (median age of death: 9 wk) were observed. These results provide new insights into the control of SR-BI in steroidogenic cells and establish SR-BIΔCT/apoE KO mice as a new animal model for the study of CHD.

MAPK3/1 (ERK1/2) and Myosin Light Chain Kinase in Mammalian Eggs Affect Myosin-II Function and Regulate the Metaphase II State in a Calcium- and Zinc-Dependent Manner

Vertebrate eggs are arrested at metaphase of meiosis II, a state classically known as cytostatic factor arrest. Maintenance of this arrest until the time of fertilization and then fertilization-induced exit from metaphase II are crucial for reproductive success. Another key aspect of this meiotic arrest and exit is regulation of the metaphase II spindle, which must be appropriately localized adjacent to the egg cortex during metaphase II and then progress into successful asymmetric cytokinesis to produce the second polar body. This study examined the mitogen-activated protein kinases MAPK3 and MAPK1 (also known as ERK1/2) as regulators of these two related aspects of mammalian egg biology, specifically testing whether this MAPK pathway affected myosin-II function and whether myosin-II perturbation would produce some of the same effects as MAPK pathway perturbation. Inhibition of the MEK1/2-MAPK pathway with U0126 leads to reduced levels of phosphorylated myosin-regulatory light chain (pMRLC) and causes a reduction in cortical tension, effects that are mimicked by treatment with the myosin light chain kinase (MLCK) inhibitor ML-7. These data indicate that one mechanism by which the MAPK pathway acts in eggs is by affecting myosin-II function. We further show that MAPK or MLCK inhibition induces loss of normal cortical spindle localization or parthenogenetic egg activation. This parthenogenesis is dependent on cytosolic and extracellular calcium and can be rescued by hyperloading eggs with zinc, suggesting that these effects of inhibition of MLCK or the MAPK pathway are linked with dysregulation of ion homeostasis.