Primary Culture of Human Cumulus Cells Requires Stearoyl-Coenzyme A Desaturase 1 Activity for Steroidogenesis and Enhancing Oocyte In Vitro Maturation

De novo synthesis of monounsaturated fatty acids modulates exosome-mediated lipid export from human granulosa cells

BACKGROUND

Ovarian somatic cells support the maturation and fertility of oocytes. Metabolic desaturation of fatty acids in these cells has a positive paracrine impact on the maturation of oocytes. We hypothesized that the enzyme stearoyl-CoA desaturase 1 (SCD1) in granulosa cells regulates the lipid cargo of exosomes secreted from these cells by maintaining the balance between saturated and unsaturated lipids. We investigated the effect of SCD1 on exosome lipid content in a cumulus-granulosa cell model under physiologically relevant in vitro conditions.

METHODS

Non-luteinized human COV434 granulosa cells were subjected to treatment with an inhibitor of SCD1 (SCDinhib) alone, in combination with oleic acid, or under control conditions. Subsequently, the exosomes were isolated and characterized via nanoparticle tracking analysis, transmission electron microscopy, and Western blotting. We used liquid chromatography mass spectrometry to investigate the lipidomic profiles. We used quantitative PCR with TaqMan primers to assess the expression of genes involved in lipogenesis and control of cell cycle progression.

RESULTS

A trend toward exosome production was observed with a shift toward smaller exosome sizes in cells treated with SCD1inhib. This trend reached statistical significance when SCDinhib was combined with oleic acid supplementation. SCD1 inhibition led to the accumulation of saturated omega-6 lipids in exosomes. The latter effect was reversed by oleic acid supplementation, which also improved exosome production and suppressed the expression of fatty acid synthase and Cyclin D2.

CONCLUSION

These findings underscore the critical role of de novo fatty acid desaturation in the regulation of the export of specific lipids through exosomes, with potential implications for controlling intercellular communication within the ovary.

In vitro maturation in synthetic oviductal fluid increases gene expression associated with quality and lipid metabolism in bovine oocytes

Traditionally, in vitro oocyte and embryo culture progresses through a series of varying culture medium. To investigate simplifying the in vitro production of bovine cumulus-oocyte complexes (COCs), this study used synthetic oviductal fluid (SOF) supplemented with conjugated linoleic acid (CLA). Special interest was placed on gene expression linked to lipid metabolism and oocyte maturation. COCs were matured in different media: Medium 199 (M199 group), M199 with 100 μM CLA (M199 + CLA group), SOF (SOF group), and SOF with 100 μM CLA (SOF + CLA group). COCs matured with SOF showed a higher relative abundance of mRNA of quality indicators gremlin 1 (GREM1) and prostaglandin-endoperoxide synthase 2 (PTGS2) in oocytes, and GREM1 in cumulus cells compared with in the M199 group. SOF medium COCs had a higher relative abundance of fatty acid desaturase 2 (FADS2) compared with the M199 group, which is essential for lipid metabolism in oocytes. Furthermore, the abundance of stearoyl-coenzyme A desaturase 1 (SCD1) in oocytes matured with SOF was not influenced by the addition of CLA, whereas the relative abundance of SCD1 was reduced in M199 medium with CLA. We concluded that maturation in SOF medium results in a greater abundance of genes linked to quality and lipidic metabolism in oocytes, regardless of the addition of CLA.

Identification of biomarkers and outcomes of endocrine disruption in human ovarian cortex using In Vitro Models

Endocrine disrupting chemicals (EDCs) are raising concerns about adverse effects on fertility in women. However, there is a lack of information regarding mechanisms and effects in humans. Our study aims to identify mechanisms of endocrine disruption using two EDCs, diethylstilbestrol (DES) and ketoconazole (KTZ)¹. Human ovarian cortical tissue obtained from Caesarean section patients was exposed to 10^-9 M - 10^-5 M KTZ and 10^-10 M - 10^-6 M DES in vitro for 6 days. Follicle survival and growth were studied via histology analysis and liquid-chromatography-mass spectrometry-based steroid quantification. RNA-sequencing was performed on COV434, KGN, and primary ovarian cells that were exposed for 24 h. Significantly lower unilaminar follicle densities were observed in DES 10^-10 M group, whereas low KTZ exposure reduced secondary follicle density. KTZ 10^-5 M reduced levels of pregnenolone and progesterone. RNA-sequencing revealed that 445 and 233 differentially expressed genes (false discovery rate < 0.1) altogether in DES and KTZ exposed groups. Gene set variation analysis showed that both chemicals modulated pathways that are important for folliculogenesis and steroidogenesis. We selected stearoyl-CoA desaturase (SCD) and 7-dehydrocholesterol reductase (DHCR7) for further validation. Up-regulation of both genes in response to KTZ was confirmed by qPCR and in situ RNA hybridization. Further validation with immunofluorescence focused on the expression of SCD in growing follicles in exposed ovarian tissue. In conclusion, SCD may serve as a potential novel human-relevant biomarker of EDC exposure and effects on ovaries.

Mechanism of Guilu Erxian ointment based on targeted metabolomics in intervening in vitro fertilization and embryo transfer outcome in older patients with poor ovarian response of kidney-qi deficiency type

OBJECTIVE

To study the effect of Guilu Erxian ointment on the outcome of IVF-ET in older patients with poor ovarian response infertility of kidney-qi deficiency type, and to verify and analyze the mechanism of action of traditional Chinese medicine on improving older patients with poor ovarian response infertility of kidney-qi deficiency type from the perspective of metabolomics using targeted metabolomics technology, identify the related metabolic pathways, and provide metabolic biomarker basis and clinical treatment ideas for improving older patients with poor ovarian response infertility.

METHODS

This study was a double-blind, randomized, placebo-controlled trial, and a total of 119 infertile patients who underwent IVF-ET at Shandong Center for Reproduction and Genetics of Integrated Traditional Chinese and Western Medicine were selected. Eighty older patients with infertility undergoing IVF were randomly divided into older treatment group and older placebo group, and another 39 young healthy women who underwent IVF-ET or ICSI due to male factors were selected as the normal control group. Flexible GnRH antagonist protocol was used for ovulation induction in all three groups, and Guilu Erxian ointment and placebo groups started taking Guilu Erxian ointment and placebo from the third day of menstruation until IVF surgery. And ultra-high performance liquid chromatography-triple quadrupole mass spectrometer (UHPLC-QTRAP MS) was used to detect metabolites in the three groups of samples.

RESULTS

Compared with the placebo group, the number of oocytes retrieved, 2PN fertilization, high-quality embryos, total number of available embryos and estrogen on HCG day were increased in the treatment group, and the differences were statistically significant (P > 0.05), but the clinical pregnancy rate of fresh embryos and frozen embryos were not statistically significant (P > 0.05). The results of targeted metabolomics analysis showed that follicular fluid in the treatment group clustered with the normal young group and deviated from the placebo group. A total of 55 significant differential metabolites were found in the follicular fluid of older patients with poor ovarian response of kidney-qi deficiency type and patients in the normal young group, after Guilu Erxian ointment intervention, Metabolites such as L-Aspartic acid, Glycine, L-Serine, Palmitoleic Acid, Palmitelaidic acid, L-Alanine, Gamma-Linolenic acid, Alpha-Linolenic Acid, and N-acetyltryptophan were down-regulated, mainly involving amino acid metabolism and fatty acid metabolism.

CONCLUSION

Guilu Erxian ointment can effectively improve the clinical symptoms and IVF outcomes of older patients with poor ovarian response of kidney-qi deficiency type. There were differences in follicular fluid metabolites between older patients with poor ovarian response of kidney-qi deficiency type and normal women. L-Aspartic acid, L-Alanine, Aminoadipic acid, L-Asparagine, L-Arginine, L-Serine, Gamma- Linolenic acid, Pentadecanoic acid and Alpha-Linolenic Acid are closely related to older patients with poor ovarian response due to deficiency of kidney-qi and may be inferred as biomarkers. The mechanism of Guilu Erxian ointment intervention may be mainly through amino acid metabolism and fatty acid metabolism regulation.

Free Fatty Acids from Type 2 Diabetes Mellitus Serum Remodel Mesenchymal Stem Cell Lipids, Hindering Differentiation into Primordial Germ Cells

Type 2 diabetes mellitus (T2DM) adversely affects the essential characteristics of adipose tissue-derived mesenchymal stem cells (AdMSCs). Given that T2DM is associated with an altered serum free fatty acid (FFA) profile, we examined whether diabetic serum FFAs influence the viability, differentiation, and fatty acid composition of the major lipid fractions of human AdMSCs in vitro. Serum FFAs were isolated from 7 diabetic and 10 healthy nondiabetic female individuals. AdMSCs were cultured and differentiated into primordial germ cell-like cells (PGCLCs) in the presence of either diabetic or nondiabetic FFAs. Cell viability was assessed using trypan blue staining. Cell differentiation was evaluated by measuring the PGCLC transcriptional markers Blimp1 and Stella. Lipid fractionation and fatty acid quantification were performed using thin-layer chromatography and gas-liquid chromatography, respectively. Both diabetic and nondiabetic FFAs significantly reduced the viability of PGCLCs. The gene expression of both differentiation markers was significantly lower in cells exposed to diabetic FFAs than in those treated with nondiabetic FFAs. Saturated fatty acids were significantly increased and linoleic acid was significantly decreased in the cellular phospholipid fraction after exposure to diabetic FFAs. In contrast, monounsaturated fatty acids were reduced and linoleic acid was elevated in the cellular triglyceride fraction in response to diabetic FFAs. Such an altered serum FFA profile in patients with T2DM reduces the proliferation and differentiation potential of AdMSCs, presumably due to the aberrant distribution of fatty acids into cell phospholipids and triglycerides.

Maternal erythrocyte fatty acid composition as a predictive marker for pregnancy health

Pregnancy is accompanied by a surge in demand for fatty acids (FAs) in order to support maternal health, as well as fetal growth and development. Of particular demand is essential for long-chain polyunsaturated FAs. FAs are primarily obtained from dietary sources and are distributed in the body. In comparison with the use of self-reporting approaches, measuring the FA levels within different blood compartments can present a more accurate image of nutritional, and thus tissue, FA composition. Hence, the FA profile of plasma or serum is commonly used for physiological analyses. Nevertheless, plasma and serum FAs are not yet incorporated into cell membranes, and consequently may not be a suitable reflection of the FA status of body tissues. The evaluation of erythrocyte FA levels offers a superior possibility for the following reasons: the biological fluctuation of erythrocyte FA composition is low, phospholipids account for almost all the lipid content of erythrocytes, and the FA profiles of erythrocytes represent those of tissues. Here, we elaborate on whether the status of maternal erythrocyte FAs can serve as a prognostic biomarker for reproductive health and fetomaternal complications, including embryonic and fetoplacental development, gestational length, and preeclampsia. In addition, factors with the potential of altering the maternal erythrocyte FAs such as maternal diet, lifestyle habits, genetics, and body composition are discussed.

Impact of Dietary Selenium on Modulation of Expression of Several Non-Selenoprotein Genes Related to Key Ovarian Functions, Female Fertility, and Proteostasis: a Transcriptome-Based Analysis of the Aging Mice Ovaries

Female reproductive (ovarian) aging is characterized by a marked decline in quantity and quality of follicles and oocytes, as well as alterations in the surrounding ovarian stroma. In our previous report, we have shown that dietary selenium (Se) insufficiency and supplementation differentially impacted the reproductive efficiency in aging mice; however, the precise understanding of such modulation is still incomplete. In the present study, we sought to determine the impact of low (mildly low level) and moderately high (medium level) Se diets on expression profile of non-selenoprotein genes in the ovaries of aging mice. For this purpose, the aged mice were divided in two groups and fed either a low Se (Se-L; 0.08 mg Se/kg) diet or a moderately high Se (Se-M; 0.33 mg Se/kg) diet. RNA-seq analysis revealed that a total of 168 genes were differentially expressed between the two groups. From these, 72 and 96 differentially expressed genes (DEGs) were found to be upregulated and downregulated, respectively. Gene Ontology (GO) and pathways enrichment (KEGG) analyses revealed that these DEGs were enriched in several key GO terms and biological pathways including PI3K-Akt signaling pathway, steroid hormone biosynthesis, signaling pathways regulating pluripotency of stem cells, Hippo signaling pathway, ovarian steroidogenesis, and Wnt signaling pathway. Further filtering of RNA-seq data revealed that several DEGs such as Star, Hsd3b6, Scd1, Bmp7, Aqp8, Gas1, Fzd1, and Wwc1 were implicated in key ovarian- and fertility-related functions. In addition, some of the DEGs were related to ER homeostasis and/or proteostasis. These results highlight that dietary low and moderately high (medium level) Se diets, in addition to modulation of selenoproteins, can also have an impact on expression of several non-selenoprotein genes in the ovaries of aging mice. To sum up, these findings add more value to our understanding of Se modulation of ovarian functions and female fertility and will pave a way for the focused mechanistic and functional studies in this domain.

Fatty acids of follicular fluid phospholipids and triglycerides display distinct association with IVF outcomes

RESEARCH QUESTION

Are triglyceride fatty acids in the follicular fluid associated with either follicular fluid phospholipid fatty acids or IVF outcomes and, if so, how are they associated?

DESIGN

In a prospective cross-sectional study, 70 women undergoing intracytoplasmic sperm injection were recruited. Follicular fluid phospholipids and triglycerides were separated by thin-layer chromatography. Fatty acids were measured using gas-liquid chromatography and flame ionization detection system.

RESULTS

Significant differences in fatty acid composition were observed between follicular fluid phospholipid and triglyceride fractions. Phospholipid stearic acid and n-3 polyunsaturated fatty acids, particularly alpha-linolenic acid, were negatively associated with the number of mature oocytes and cleaved embryos, whereas arachidonic acid was in direct correlation with cleavage rate per IVF cycle (β = 0.325, P = 0.022). In the case of triglyceride fraction, total monounsaturated fatty acids, oleic acid in particular, displayed significantly positive associations with the number of oocytes (β = 0.261, P = 0.043) and embryos (β = 0.310, P = 0.018). Furthermore, cleavage rate correlated inversely with palmitic acid (β = -0.359, P = 0.007) and directly with pentadecanoic acid (β = 0.378, P = 0.005). Most of these associations, however, were not independent of predictive fatty acids belonging to phospholipid fraction, according to multivariate analysis.

CONCLUSIONS

Fatty acid compositions of phospholipid and triglyceride fractions from human follicular fluid differentially correlate with IVF cycle parameters.

Steroid-depleted endometriosis serum improves oocyte maturation in IVM systems

In vitro maturation (IVM) is a novel approach to overcome the adverse effects of human in vitro fertilization (IVF). The aim of the present study is to evaluate the effect of total and steroid-depleted serum obtained from patients with endometriosis on IVM outcome as supplementation for this system. To this purpose, patients with endometriosis were selected according to in/excluding criteria. Germinal vesicles (GVs) and cumulus cells were treated with 10% of each serum. The expression levels of stearoyl CoA desaturase 1 (SCD 1) and cyclooxygenase-2 (COX-2) genes were evaluated by RT-qPCR. Gas-liquid chromatography and flow cytometry were performed to analyze fatty acids composition and apoptosis. The mRNA expression levels of SCD1 (2.47 fold) and COX-2 (6.4 fold), and also the synthesis of oleate, linoleate, and arachidonate were increased (1.19, 1.06, and 2.37 folds, respectively) in cumulus cells treated with steroid-depleted serum (p < .05). The synthesis of palmitate, palmitoleate, and stearate (0.995, 0.67, and 0.7 folds, respectively) and also the rate of apoptosis were significantly decreased in these cells (p < .05). Moreover, GVs cultured in steroid-depleted group showed a significantly higher rate of maturation (p < .001). Overall, our findings imply a new insight into the expansion of IVM system in oocytes development.

Non-esterified fatty acids in the ovary: friends or foes?

A majority of common metabolic diseases can result in excessive lipolysis, leading to elevated levels of non-esterified fatty acids (NEFAs) in the body fluids. In females, increased NEFA levels in the follicular fluid markedly alter the functions of intrafollicular cells such as granulosa cells (GCs) and oocytes. Therefore, elevated levels of NEFAs have been suggested to be a significant player of subfertility in females of both human and economically important animal species such as cattle, buffalo, sheep, pig, chicken, and dog. However, the effects imposed by saturated and unsaturated fatty acids (SFAs and UFAs) on ovarian follicles are controversial. The present review emphasizes that SFAs induce apoptosis in granulosa and cumulus cells of ovarian follicles in different species. They further could adversely affect oocyte maturation and developmental competence. Many types of UFAs affect steroidogenesis and proliferation processes and could be detrimental for follicular cells, especially when at elevated concentrations. Interestingly, monounsaturated fatty acids (MUFAs) appear to contribute to the etiology of the polycystic ovarian syndrome (PCOS) as they were found to induce the transcription and translation of the androgenic transcription factor SOX9 while downregulating its estrogenic counterpart FOXL2 in GCs. Overall, this review presents our revised understanding of the effects of different fatty acids on the female reproductive success, which may allow other researchers and clinicians to investigate the mechanisms for treating metabolic stress-induced female infertility.

Arachidonic acid alleviates the detrimental effects of acetylsalicylic acid on human granulosa cells performance in vitro

Here, we investigated the biological effects of arachidonic acid (AA) in human cumulus granulosa cells (CGCs) after exposure to ASA. Cells were isolated from the follicular fluid and incubated with 0.5 mM acetylsalicylic acid (ASA) and 50 µM AA. Cell viability was analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. E₂ and P₄ levels were measured by chemiluminescence assay. Expression of genes including CYP19A1, FACN, and SCD1 was measured by real-time polymerase chain reaction assay. Oxidative status was analyzed by monitoring glutathione peroxidase activity. The fatty acid profile was analyzed by the gas chromatography technique. Enzyme-linked immunosorbent assay was used to measure prostaglandin E₂ (PGE₂ ) in CGCs after exposure to ASA and AA. Protein levels of the estrogen receptor were studied by immunofluorescence staining. Ultrastructural changes were evaluated by transmission electron microscopy imaging. ASA treatment reduced E₂ production, Cyp19a1 expression, glutathione peroxidase (GPx) activity, and estradiol receptor expression in CGCs. The addition of AA prevented the ASA-induced E₂ reduction (p < .05) and expression of Cyp19a1. Moreover, AA increased the antioxidant capacity of CGCs exposed to ASA by promoting GPx activity (p < .05). AA increased monounsaturated fatty acid/saturated fatty acid ratio compared with the ASA group (p < .05). AA supplementation triggered the synthesis and secretion of PGE₂ in ASA-treated CGCS (p < .05). Cytoplasmic vacuolation observed in the ASA group and treatment with AA intensified vacuolation rate. The expression of the estrogen receptor was increased after AA supplementation. Data demonstrated that AA decreased the detrimental effects of ASA on human CGCs after 72 hr.

Steroid-depleted polycystic ovarian syndrome serum promotes in vitro oocyte maturation and embryo development

In vitro maturation (IVM) of immature oocytes obtained from patients with polycystic ovarian syndrome (PCOS) is considered as a novel strategy in order to reduce clinical side effects and cost of in vitro fertilization (IVF) technique. The aim of this study was to evaluate the effects of PCOS whole and steroid-depleted serums on in vitro oocyte maturation indices. Patients with PCOS were selected according to the Rotterdam criteria. Cumulus-oocyte complexes and blood serums were collected and pooled. Cumulus cells and immature oocytes were treated with 10% whole or steroid-depleted serums. Stearoyl-CoA desaturase-1 (SCD1) and cyclooxygenase-2 (COX2) expression levels in cumulus cells were evaluated by quantitative PCR. Fatty acid composition of cumulus cells was analyzed using gas-liquid chromatography. Polar body observation was considered as the oocyte maturation index. Oleate (1.28-fold, p = .006), SCD1 expression (450-fold, p = .001), and COX2 expression (35-fold, p = .02) in cumulus cell, as well as oocyte maturation (p < .001) and in vitro embryo development (p < .05) were significantly higher in treatment with steroid-depleted serum compared to that of whole serum. Steroid depletion of PCOS serum improved its capacity to increase success rate of oocyte maturation, intra-cytoplasmic sperm injection and early embryo development.

Oleic acid in the modulation of oocyte and preimplantation embryo development

Potential reproductive effects are considered as the major aspect of biomolecules functionality in an organism. The recent identification of differential patterns of fatty acids across ovarian follicles and their association with levels of sexual maturity highlights the importance of these biomolecules. It is well known that fatty acids are highly diverse in terms of their functional properties. Oleic acid is chemically classified as an unsaturated omega-9 fatty acid. Besides serving as an important energy source, oleic acid is involved in metabolic and structural roles. Free and esterified oleic acids are compartmentalized into discrete extracellular fluids, cell organelles and found within the cytosol. This review summarizes the current knowledge on the contribution of oleic acid in regulating female fertility, particularly its involvement in female germ cell growth and development. Oleic acid has been identified as a blastomeric and post-cryopreservation survival biomarker in bovine. Several related studies have shown the critical role of oleic acid in counteracting the detrimental effects of saturated fatty acids and in paracrine support of oocyte development. Although available data are not ideally detailed, most data suggest that oleic acid can contribute to normal oocyte and preimplantation embryo development via mechanisms involving metabolic partitioning of fatty acids, change in the membrane structural organization, attenuation of oxidative stress and regulation of intracellular signalling. Thus, oleic acid may play a significant role in oocyte and early embryo development, suggesting that future studies should explore in more detail its potential effects on the physiopathology of female reproduction.