Metabolic signature of follicular fluid in infertility-related diseases: a narrative review

Metabolomics offers new methods to identify biomarkers for oocyte and embryo quality, and for a better understanding of the physiopathology of infertility. This review investigated the latest findings regarding metabolome-derived biomarkers in follicular fluid of women with the most common types of infertility, and the potential impact on reproductive medicine outcomes. PubMed was searched for publications on metabolomics and human follicular fluid, and key biomarkers, kinetics and relationships with infertility diseases were identified. A reduced concentration of glucose and increased concentrations of lactate and pyruvate were found in follicular fluid of patients with endometriosis and diminished ovarian reserve, and the opposite was found in patients with polycystic ovary syndrome. These signatures may lead to the hypothesis of changed metabolite concentrations in patients with endometriosis and diminished ovarian reserve, and a metabolic pathway alteration with decreased aerobic glycolysis in patients with polycystic ovary syndrome. However, the pattern found in patients with endometriosis and low responders may also be expected in follicular fluid of fertile women. Larger studies are needed to confirm the results. An international database may help to highlight follicular fluid biomarkers in order to improve the selection of cryopreserved oocytes, and to enrich culture medium to restore normal metabolism and improve reproductive treatment outcomes.

A comprehensive multiplatform metabolomic analysis reveals alterations of 2-hydroxybutyric acid among women with deep endometriosis related to the pesticide trans-nonachlor

BACKGROUND

Exposure to persistent organic pollutants (POPs) has been related to the risk of endometriosis however the mechanisms remain unclear. The objective of the present study was to characterize the metabolic profiles underpinning the associations between POPs and endometriosis risk.

METHODOLOGY

A hospital-based case-control study was conducted in France to recruit women with and without surgically confirmed deep endometriosis. Women's serum was analyzed using gas and liquid chromatography coupled to high-resolution mass spectrometry (HRMS) to measure the levels of polychlorinated biphenyls (PCBs), organochlorinated pesticides (OCPs) and per-/polyfluoroalkyl substances (PFAS). A comprehensive metabolomic profiling was conducted using targeted HRMS and 1H nuclear magnetic resonance (1H NMR) to cover polar and non-polar fractions. A "meet-in-the-middle" statistical framework was applied to identify the metabolites related to endometriosis and POP levels, using multivariate linear and logistic regressions adjusting for confounding variables.

RESULTS

Fourteen PCBs, six OCPs and six PFAS were widely found in almost all serum samples. The pesticide trans-nonachlor was the POP most strongly and positively associated with deep endometriosis risk, with odds ratio (95 % confidence interval) of 2.42 (1.49; 4.12), followed by PCB180 and 167. Women with endometriosis exhibited a distinctive metabolic profile, with elevated serum levels of lactate, ketone bodies and multiple amino acids and lower levels of bile acids, phosphatidylcholines (PCs), cortisol and hippuric acid. The metabolite 2-hydroxybutyrate was simultaneously associated to endometriosis risk and exposure to trans-nonachlor.

CONCLUSIONS

To the best of our knowledge, this is the first comprehensive metabolome-wide association study of endometriosis, integrating ultra-trace profiling of POPs. The results confirmed a metabolic alteration among women with deep endometriosis that could be also associated to the exposure to POPs. Further observational and experimental studies will be required to delineate the causal ordering of those associations and gain insight on the underlying mechanisms.

Effects of dysregulated glucose metabolism on the occurrence and ART outcome of endometriosis

BACKGROUND

Endometriosis is associated with systemic metabolic indicators, including body mass index (BMI), glucose metabolism and lipid metabolism, while the association between metabolic indexes and the occurrence and assisted reproductive technology (ART) outcome of endometriosis is unclear. We aimed to evaluate the characteristics of systemic metabolic indexes of endometriosis patients with infertility and their effects on pregnancy outcome after ART treatment.

METHODS

A retrospective cohort study involve 412 endometriosis patients and 1551 controls was conducted. Primary outcome was metabolic indexes, and secondary measures consisted of the influence of metabolic indexes on the number of retrieved oocytes and ART outcomes.

RESULTS

Endometriosis patients had higher insulin (INS) [6.90(5.10-9.50) vs 6.50(4.80-8.90) μU/mL, P = 0.005]. A prediction model for endometriosis combining the number of previous pregnancies, CA125, fasting blood glucose (Glu) and INS, had a sensitivity of 73.9%, specificity of 67.8% and area under curve (AUC) of 0.77. There were no significant differences in ART outcomes and complications during pregnancy. The serum levels of Glu before pregnancy were associated with GDM both in endometriosis group (aOR 12.95, 95% CI 1.69-99.42, P = 0.014) and in control group (aOR 4.15, 95% CI 1.50-11.53, P = 0.006).

CONCLUSIONS

We found serum Glu is related to the number of retrieved oocytes in control group, serum INS is related to the number of retrieved oocytes in endometriosis group, while serum Glu and INS before pregnancy are related to the occurrence of GDM in two groups. A prediction model based on metabolic indexes was established, representing a promising non-invasive method to predict endometriosis patients with known pregnancy history.

Nontargeted metabolomics analysis of follicular fluid in patients with endometriosis provides a new direction for the study of oocyte quality

Endometriosis is a common, estrogen-dependent chronic gynecological disease that endangers the reproductive system and systemic metabolism of patients. We aimed to investigate the differences in metabolic profiles in the follicular fluid between infertile patients with endometriosis and controls. A total of 25 infertile patients with endometriosis and 25 infertile controls who were similar in age, BMI, fertilization method and ovulation induction treatment were recruited in this study. Metabolomics analysis of follicular fluid was performed by two methods of high-performance liquid chromatography tandem mass spectrometry. There were 36 upregulated and 17 downregulated metabolites in the follicular fluid of patients in the endometriosis group. KEGG pathway analysis revealed that these metabolites were enriched in phenylalanine, tyrosine and tryptophan biosynthesis, aminoacyl-tRNA biosynthesis, phenylalanine metabolism and pyrimidine metabolism pathways. A biomarker panel consisting of 20 metabolites was constructed by random forest, with an accuracy of 0.946 and an AUC of 0.988. This study characterizes differences in follicular fluid metabolites and associated pathway profiles in infertile patients with endometriosis. These findings can provide a better comprehensive understanding of the disease and a new direction for the study of oocyte quality, as well as potential metabolic markers for the prognosis of endometriosis.

Metabolomics analysis of follicular fluid in ovarian endometriosis women receiving progestin-primed ovary stimulation protocol for in vitro fertilization

This study aimed to investigate the metabolite profile and inflammatory state of follicular fluid (FF) in women with stage III-IV ovarian endometriosis (OE) who underwent in vitro fertilization (IVF). A cohort of 20 consecutive patients with OE were recruited and received progestin-primed ovary stimulation (PPOS) protocol (study group), while another 20 OE patients received one-month ultra-long term protocol (control group) for IVF in this prospective, nonrandomized study. FF samples were obtained from dominant follicles during oocyte retrieval, and liquid chromatography-mass spectrometry (LC-MS) was used to investigate the metabolites profile of FF. Results showed that significant increases in the levels of proline, arginine, threonine, and glycine in patients who received PPOS protocol compared to the control group (P < 0.05). A panel of three metabolites (proline, arginine, and threonine) was identified as specific biomarkers of OE patients using PPOS protocol. Additionally, levels of interleukin-1β, regulated on activation, normal T cell expressed and secreted, and tumor necrosis factor-α markedly decreased in women who received PPOS protocol compared to the control group (P < 0.05). In conclusion, PPOS protocol regulates the metabolism of several amino acids in the FF, which may play critical roles in the oocyte development and blastocyst formation, and their specific mechanism should be further elucidated.

Current Role of Modern Chromatography with Mass Spectrometry and Nuclear Magnetic Resonance Spectroscopy in the Investigation of Biomarkers of Endometriosis

Endometriosis has a wide range of clinical manifestations, and the disease course is unpredictable, making the diagnosis a challenging task. Despite significant advances in the pathophysiology of endometriosis and various proposed theories, the exact etiology is not fully understood and is still unknown. The most commonly used biomarker of endometriosis is CA-125, however, it is nonspecific and is applied for cancers diagnosis. Therefore, the development of reliable noninvasive diagnostic tests for the early diagnosis of endometriosis remains one of the top priorities. Omics technologies are very promising approaches for constructing diagnostic models and biomarker discovery. Their use can greatly facilitate the study of such a complex disease as endometriosis. Nowadays, powerful analytical platforms commonly used in omics, such as gas and liquid chromatography with mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy, have proven to be a promising tools for biomarker discovery. The aim of this review is to summarize the various features of the analytical approaches, practical challenges and features of gas and liquid chromatography with MS and NMR spectroscopy (including sample processing protocols, technological advancements, and methodology) used for profiling of metabolites, lipids, peptides and proteins in physiological fluids and tissues from patients with endometriosis. In addition, this report devotes special attention to the issue of how comprehensive analyses of these profiles can effectively contribute to the study of endometriosis. The search query included reports published between 2012 and 2022 years in PubMed, Web-of-Science, SCOPUS, Science Direct.

Application of long non-coding RNA RBAT1 in improving diagnosis and prognosis of ovarian carcinoma

Tumorigenesis of bladder cancer and retinoblastoma is correlated with long non-coding RNA (lncRNA) RBAT1. However, the role of RBAT1 in ovarian carcinoma (OC) is unclear. Thus, the study explored the role of RBAT1 in OC. This research enrolled patients with OC ( n  = 68), irritable bowel disease (IBD, n  = 68, females), digestive tract inflammation (DTI, n  = 68, females), urinary tract infection (UTI, n  = 68, females), endometriosis (EM, n  = 68, females), and healthy controls (HCs, n  = 68) to collect plasma sampled. OC and paired non-tumor tissues were collected from patients with OC. RBAT1 accumulation in all samples was analyzed using RT-qPCR. The role of plasma RBAT1 in OC diagnosis was examined using the ROC curves with OC patients as the true positive cases and other patients and HCs as the true negative cases. The role of RBAT1 in predicting the survival of OC patients was analyzed using the survival curve study. RBAT1 was overexpressed in both OC plasma and tissues. Plasma RBAT1 levels were correlated with RBAT1 levels in OC tissues but not in non-tumor tissues. Plasma RBAT1 could distinguish OC patients from other patients and HCs. Patients with high plasma RBAT1 levels had a shorter survival. RBAT1 is overexpressed in OC and might be applied to improve the diagnosis and prognosis of OC.

Biomarkers identification in follicular fluid of women with OHSS by using UPLC-MS method

To figure out the differentially changed metabolites and disturbed pathways in follicular fluid (FF) of patients with OHSS in comparison to the control group undergoing in vitro fertilization (IVF), we conducted this metabolomic analysis between two groups, the OHSS group included 30 patients treated with oocyte retrieval and developed OHSS in the next 7-14 days, while another 30 patients without OHSS tendency were selected as the control group. The FF samples were obtained during the process of oocyte retrieval. FF samples were analyzed using ultra-high liquid chromatography-tandem mass spectrometry (UPLC-MS). The results identified a total of 59 differentially changed metabolites, including 33 decreased metabolites (P < 0.01) and 26 increased metabolites (P < 0.01) in FF of OHSS compared with the control group. 12 metabolites could be the most valuable biomarkers for OHSS based on ROC results. Our correlation analyses showed that deoxyinosine levels were found positively correlated with serum estradiol (E2) levels in OHSS patients, while L-isoleucine, pyruvic acid, maleamate, and arachidonic acid were found to be positively correlated with the number of retrieved oocytes. Furthermore, 4-hydroxyphenylacetaldehyde, deoxycorticosterone, creatinine, and creatine were found to be negatively associated with serum E2 levels, while 4-hydroxyphenylacetaldehyde, L-carnitine, isovaleric acid and L-2-hydroxyglutaric acid were negatively related with the number of oocytes retrieved in OHSS patients. Taken together, our study provides better identification of OHSS FF metabolic dynamics, suggesting the metabolic compounds can be used as valuable predictors or treatment targets of OHSS.

Volatilomics as an Emerging Strategy to Determine Potential Biomarkers of Female Infertility: A Pilot Study

Due to its high prevalence, infertility has become a prominent public health issue, posing a significant challenge to modern reproductive medicine. Some clinical conditions that lead to female infertility include polycystic ovary syndrome (PCOS), endometriosis, and premature ovarian failure (POF). Follicular fluid (FF) is the biological matrix that has the most contact with the oocyte and can, therefore, be used as a predictor of its quality. Volatilomics has emerged as a non-invasive, straightforward, affordable, and simple method for characterizing various diseases and determining the effectiveness of their current therapies. In order to find potential biomarkers of infertility, this study set out to determine the volatomic pattern of the follicular fluid from patients with PCOS, endometriosis, and POF. The chromatographic data integration was performed through solid-phase microextraction (SPME), followed by gas chromatography–mass spectrometry (GC-MS). The findings pointed to specific metabolite patterns as potential biomarkers for the studied diseases. These open the door for further research into the relevant metabolomic pathways to enhance infertility knowledge and diagnostic tools. An extended investigation may, however, produce a new mechanistic understanding of the pathophysiology of the diseases.

Elevated Circulatory Proline to Glutamine Ratio (PQR) in Endometriosis and Its Potential as a Diagnostic Biomarker

Endometriosis (EM) is a hormone-dependent gynecological disease associated with chronic pelvic pain and altered immuno-inflammatory processes. It shares some cancer-like characteristics such as increased proline biosynthesis and activated glutaminolysis. Both proline and glutamine are interconvertible metabolically, and studies have shown their roles in cancer cell metabolic reprogramming, redox homeostasis, occurrence/development of endometrial carcinoma, and its further progression toward the malignant state. So based on this, we hypothesized that the circulatory proline to glutamine ratio (PQR) would be altered in EM and may serve as an indicative biomarker to improve the clinical diagnosis of EM. In present study, the circulatory-PQR levels were estimated for 39 EM patients and 48 age matched healthy female subjects using 800 MHz NMR spectroscopy. Among 39 EM patients, 15 were in the clinical stages I to II and referred to here as moderate EM (MEM) patients and 24 were in the clinical stages III to IV and referred here as severe EM (SEM) patients. The circulatory-PQR levels were significantly increased in EM patients (0.99 ± 0.13 μM in MEM; 1.39 ± 0.22 μM in SEM) compared to normal control (NC) subjects (0.52 ± 0.05 μM in NC). Further, the circulatory PQR levels exhibit the highest diagnostic potential with area under receiver operating characteristic (AUROC) curve values equal to 0.87 ± 0.04 [95%CI = 0.79-0.96] for MEM and 0.89 ± 0.04 [95% CI = 0.82-0.96] for SEM. These results suggested that circulatory-PQR has significant potential to serve as a noninvasive biomarker for diagnostic/prognostic screening of EM and further underscored the importance of these two nonessential amino acids (proline and glutamine) in cancer metabolism.

Water-Extracted Prunella vulgaris Alleviates Endometriosis by Reducing Aerobic Glycolysis

Endometriosis is a chronic inflammatory disorder caused by abnormal adhesion of endometrial tissue to the outside of the uterus. The combination of surgery, non-steroidal anti-inflammatory drugs, and hormone treatment is well established therapy for endometriosis, however, case reports have showed that high rates of relapse and unpleasant side effect. For these reasons, recently, the studies have been focused on the Warburg-like metabolic shift of endometriosis. Prunella vulgaris is one of traditionally used herbal medicine for inflammatory disease and the anti-estrogenic effects of P. vulgaris is well-established. Therefore, in this work, we evaluated water-extracted P. vulgaris (PV) as a potential treatment for endometriosis. To this, we artificially induced endometriosis in ovarectomized mice by intra-peritoneal inoculation of uterus extracts. PV was orally administered, and PV significantly alleviated endometriosis, particularly the growth of ectopic endometrial lesions in artificially endometriosis-induced mice. For the mechanism study of anti-endometriosis by PV, we designed an in vitro study using human normal endometrial stromal cells (T-HESCs) and human endometrial cell (12Z) obtained from patients with endometriosis. PV strongly induced the apoptosis of 12Z cells rather than T-HESCs by control the activity or expression of aerobic glycolysis enzymes, such as lactate dehydrogenase A (LDHA), pyruvate dehydrogenase A, and pyruvate dehydrogenase kinase 1/3. In addition, lactate production was enhanced, and oxygen consumption rate was suppressed in 12Z cells upon PV treatment. These changes in aerobic glycolysis eventually caused mitochondrial damage following decreased mitochondrial membrane potential and excessive mitochondrial ROS production. Especially, ulsolic acid (UA), one of the compounds in PV considerably led 12Z cell apoptosis with inhibition of LDHA activity. Therefore, UA could be a major active substance of PV in terms of endometriosis inhibitors. In conclusion, this study provides the evidence that the beneficial efficacy of PV for the prevention/treatment of endometriosis.

Dysregulated sphingolipid metabolism and autophagy in granulosa cells of women with endometriosis

We evaluated metabolic profiles between cumulus cells (CCs) and mural granulosa cells (MGCs) derived from women with endometriosis to identify their correlations with oocyte quality. CCs and MGCs were collected from women with and without endometriosis undergoing in vitro fertilization/intracytoplasmic sperm injection treatment. The metabolomics of CCs and MGCs were measured by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) followed by a quantitative polymerase chain reaction to further confirm the genes involved in the metabolic results. LC-MS/MS analysis revealed differences in 24 metabolites of CCs and 71 metabolites of MGCs between groups. Among them, five metabolites were upregulated and 19 metabolites were downregulated in CCs with endometriosis, whereas three metabolites were upregulated and 68 metabolites were downregulated in MGCs with endometriosis. Metabolites related to sphingolipid metabolism, which included palmitic acid (PA) and docosahexaenoic acid, increased significantly only in CCs with endometriosis, whereas sphingosine and PA were significantly downregulated in MGCs with endometriosis compared with CCs and MGCs without endometriosis. Gene expression involved in ceramide synthesis (CERS1, SPTL1, and SMPD1) and autophagy (BECN1, LAMP, and PC3) were significantly higher in CCs with endometriosis according to FASN, BECN1, and LAMP protein expressions. However, gene expression involved in ceramide synthesis (SPHK1, ASAH1, and SGPP1) and autophagy (BECN1, LAMP, and PC3) were significantly lower in MGCs with endometriosis, whereas CERS1 and UGCG expression increased. There are differences in sphingolipid metabolites in CCs and MGCs with endometriosis compared with women without endometriosis. These differences seem to be involved in the regulation of autophagic cell death in preovulatory follicles.

The Mechanism of Traditional Chinese Medicine Based on Semi-Targeted Metabolomics to Improve IVF Outcomes in Senile Patients

Objective

To identify the biological function and metabolic pathway of differential metabolites in follicular fluid of senile patients with kidney qi deficiency undergoing in vitro fertilization-embryo transfer (IVF-ET) and observe the effect of kidney-invigorating herbs on IVF outcomes in senile patients.

Methods

A total of 95 women undergoing IVF treatment were recruited and divided into three groups, including 34 cases in the treatment group (the senile patients with kidney qi deficiency after the intervention of Chinese medicine), 31 cases in the experiment group (the senile patients with kidney qi deficiency of no intervention of Chinese medicine), and 30 cases in the control group (young women with infertility due to male factor). The three groups of women were treated with long protocol ovarian hyperstimulation; the treatment group was given Qi-Zi-Yu-Si decoction on the day of HCG downregulation. Their IVF clinical outcomes were observed. The metabolites changes of kidney qi deficiency syndrome were analyzed in follicular fluid metabolomics using liquid chromatography-mass spectrometry (UPLC-MS/MS).

Results

The syndrome score of kidney qi deficiency syndrome in the treatment group was significantly improved after treatment (P < 0.01). Compared with the experiment group, the available embryo rate and implantation rate were increased, and the difference was statistically significant (P < 0.05). Progesterone, indoleacrylic acid, 2-propenyl 1-(1-propenylsulfinyl) propyl disulfide, N-acetyltryptophan, decanoylcarnitine, 20a-dihydroprogesterone, testosterone acetate, eicosatrienoic acid, 1H-indole-3-carboxaldehyde, choline, phosphorylcholine, and tryptophan were downregulated in the treatment group. Through pathway analysis, glycerophospholipid metabolism and steroid hormone biosynthesis were regulated in senile patients with kidney qi deficiency after Qi-Zi-Yu-Si decoction intervention.

Conclusion

Qi-Zi-Yu-Si decoction can effectively improve the IVF outcome and clinical symptoms of senile patients. Follicular fluid metabolites were significantly changed in senile infertile women with kidney qi deficiency, and the mechanism by which kidney-invigorating herbs improve IVF treatment outcomes may be related to glycerophospholipid metabolism and steroid hormone biosynthesis. This study was registered in the Chinese Clinical Trials Registry Platform (ChiCTR1800014422).

The Mechanism Exploration of Follicular Fluids on Granulose Cell Apoptosis in Endometriosis-Associated Infertility

Objective

To explore the mechanisms of follicular fluids (FFs) on granulose cell (GC) apoptosis in endometriosis-associated infertility.

Materials and Methods

60 infertile women were enrolled. The FFs from 30 endometriosis-associated infertility (EI) patients were collected and processed by ELISA hormone assay and proteomic profiling. The ovary GCs collected from 30 tubal-associated infertility (TI) patients were cultured in follicular fluids of endometriosis-associated infertility patients (EI-FFs), and the apoptosis mechanisms were explored by flow cytometry assay, real-time PCR, Western blotting, and protein-protein interaction (PPI) network analysis.

Results

Our results showed that the expression of 22 specific proteins was significantly different in the FFs from EI and TI patients, and the level of testosterone and anti-Müllerian hormone was not obviously different between the two groups. EI-FFs could accelerate the apoptosis process of granulose cells of tubal-associated infertility patients (TI-GCs) by regulating the expression of 5 apoptosis-related proteins including BCL2, BAX, CASP3, CASP9, and TP53. The correlation of these 22 specific proteins and 5 apoptosis-related proteins was analyzed by PPI, and 5 protein biomarkers (INS, CXCL10, ICAM1, WIF1, and TNFRSF13C) and 5 signaling pathways (cytokine-cytokine receptor interaction, apoptosis, regulation of actin cytoskeleton, MAPK, and p53 signaling pathway) were predicted.

Conclusion

This research clarified the effect and explored the mechanisms of EI-FFs on the apoptosis of TI-GCs and indicated the protein biomarkers and signaling pathways for further study.

Altered Follicular Fluid Metabolic Pattern Correlates with Female Infertility and Outcome Measures of In Vitro Fertilization

Nearly 40-50% of infertility problems are estimated to be of female origin. Previous studies dedicated to the analysis of metabolites in follicular fluid (FF) produced contrasting results, although some valuable indexes capable to discriminate control groups (CTRL) from infertile females (IF) and correlate with outcome measures of assisted reproduction techniques were in some instances found. In this study, we analyzed in blind FF of 35 control subjects (CTRL = patients in which inability to obtain pregnancy was exclusively due to a male factor) and 145 IF (affected by: endometriosis, n = 19; polycystic ovary syndrome, n = 14; age-related reduced ovarian reserve, n = 58; reduced ovarian reserve, n = 29; unexplained infertility, n = 14; genetic infertility, n = 11) to determine concentrations of 55 water- and fat-soluble low molecular weight compounds (antioxidants, oxidative/nitrosative stress-related compounds, purines, pyrimidines, energy-related metabolites, and amino acids). Results evidenced that 27/55 of them had significantly different values in IF with respect to those measured in CTRL. The metabolic pattern of these potential biomarkers of infertility was cumulated (in both CTRL and IF) into a Biomarker Score index (incorporating the metabolic anomalies of FF), that fully discriminated CTRL (mean Biomarker Score value = 4.00 ± 2.30) from IF (mean Biomarker Score value = 14.88 ± 3.09, p < 0.001). The Biomarker Score values were significantly higher than those of CTRL in each of the six subgroups of IF. Posterior probability curves and ROC curve indicated that values of the Biomarker Score clustered CTRL and IF into two distinct groups, based on the individual FF metabolic profile. Furthermore, Biomarker Score values correlated with outcome measures of ovarian stimulation, in vitro fertilization, number and quality of blastocysts, clinical pregnancy, and healthy offspring. These results strongly suggest that the biochemical quality of FF deeply influences not only the effectiveness of IVF procedures but also the following embryonic development up to healthy newborns. The targeted metabolomic analysis of FF (using empowered Redox Energy Test) and the subsequent calculation of the Biomarker Score evidenced a set of 27 low molecular weight infertility biomarkers potentially useful in the laboratory managing of female infertility and to predict the success of assisted reproduction techniques.

Metabolomics in endometriosis: challenges and perspectives for future studies

Endometriosis is a complex disease characterized by inflammation and the growth of endometrial- like glands and stroma outside the uterine cavity. The pathophysiology of endometriosis is not entirely understood, however, with a prevalence of ~10% of women in their reproductive years, the disease symptoms significantly affect the quality of life of millions of women globally. Metabolomic studies have previously identified specific metabolites that could be a signature of endometriosis. This approach could potentially be used as a non-invasive tool for early diagnosis and provide a better understanding of endometriosis pathophysiology. This review aims to provide insight as to how endometriosis affects the metabolome by reviewing different studies that have used this approach to design follow-up studies. The search query included the term 'endometriosis' in combination with 'metabolomics', 'lipidomics', or 'sphingolipidomics' published between 2012 and 2020. We included studies in humans and animal models. Most studies reported differences in the metabolome of subjects with endometriosis in comparison to healthy controls and used samples taken from serum, endometrial tissue, follicular fluid, urine, peritoneal fluid, or endometrial fluid. Statistically significant metabolites contributed to group separation between patients and healthy controls. Reported metabolites included amino acids, lipids, organic acids, and other organic compounds. Differences in methods, analytical techniques, and the presence of confounding factors can interfere with results and interpretation of data. Metabolomics seems to be a promising tool for identifying significant metabolites in patients with endometriosis. Nonetheless, more investigation is needed in order to understand the significance of the study results.

Lay summary

Endometriosis is a chronic disease affecting the quality of life in one out of every ten women during their reproductive years, causing pain and infertility. It is characterized by inflammation and growth of tissue like the endometrium (uterus lining) outside the uterine cavity. Studies have searched for a predictor of endometriosis-associated changes by observing small molecules necessary for metabolism on a large scale (metabolomics). Metabolomics could serve to resolve one of the biggest challenges that patients with endometriosis face: a delay in diagnosis. In this review, the authors summarize identified potential biomarkers from various bodily fluids and tissues that are characteristic of metabolic processes observed in endometriosis. Biomarkers include cell growth, cell survival, high energy demand, oxidative stress, and fatty acid levels. A metabolomics approach offers promise as a non-invasive tool to identify significant metabolite changes in patients with endometriosis, potentially leading to earlier diagnoses and new opportunities for back-translational strategies.

Protective Effects of Curcumin on the Outcome of Cryopreservation in Human Sperm

Cryopreservation causes decreased sperm fertility potential due to reactive oxygen species (ROS) production and physical-chemical damage, resulting in reduced sperm viability and motility. The addition of antioxidants to freezing media could protect sperm from cryo-damage, counteracting the harmful effects of ROS. The aim of this study was to assess the effects of curcumin supplementation in freezing medium on preventing cryo-damage in human semen. Semen samples collected from fertile men were cryopreserved in freezing medium supplemented with different concentrations of curcumin (2.5, 5, 10, and 20 μM). After freezing-thawing, sperm parameters, DNA fragmentation, intracellular ROS, and glutathione peroxidase 4 (GPX4) gene expression were evaluated. Supplementation with 20 μM curcumin in freezing medium caused increases in progressive and nonprogressive motility and significant reductions in intracellular ROS and DNA fragmentation in frozen-thawed sperm cells. Following cryopreservation, GPX4 mRNA expression was significantly upregulated in thawed semen supplemented with 20 μM curcumin compared to the control. The results showed that curcumin supplementation in freezing medium was protective against human sperm parameters and sperm DNA, counteracting oxidative damage induced by the freeze-thaw process.

N-formyl-l-aspartate: A novel sperm chemoattractant identified in ovulatory phase oviductal fluid using a microfluidic chip

BACKGROUND

Chemotaxis, as a mechanism for sperm guidance although known, has been difficult to demonstrate in vitro. Consequently, very few chemoattractants have been identified till date.

OBJECTIVES

To investigate sperm motility behavior in response to ovulatory (OV) and preovulatory (preOV) oviductal fluid (OF) and identify potential chemotactic metabolites.

MATERIALS AND METHODS

Intracellular calcium ([Ca²⁺ ]_I ) influx in capacitating sperm was determined by spectrofluorimetry. The chemotactic response of rat caudal sperm to OF from the preOV- and OV- phases of normally cycling female rats was assessed in a microfluidic device developed by us. Hydrophilic metabolites extracted from the OF of both the phases were resolved and identified by LC-MS/MS, followed by data analysis using XCMS and MetaboAnalyst software, and chemotactic potential of the most promising compound was validated using the microfluidic device.

RESULTS

Spectrofluorimetric analysis depicts a significant increase in sperm [Ca²⁺ ]_I in response to OV-OF. With the microfluidic chemotaxis assay, sperm population shows a significantly increased directionality and velocity to an ascending gradient of 0.06 µg/µl OV-OF compared to preOV-OF. LC-MS/MS of the OFs demonstrates five and four metabolites to be exclusive to the OV-OF and preOV-OF, respectively, and 25 metabolites common to both, of which 14 metabolites, including N-formyl-l-aspartate (NFA), are increased in OV-OF; NFA was tested for its ability to influence sperm movement, and shows chemotaxis potential.

DISCUSSION AND CONCLUSION(S)

This is the first study that has systematically demonstrated sperm chemotaxis with OV phase rat OF, identified NFA present in this fluid as a novel chemoattractant to sperm, and proven the utility of the device to test putative chemoattractants. It remains to be seen whether NFA is present in the follicular fluid (FF) of infertile women, and whether it may likely be a reason for the failure of natural conception in idiopathic infertile women.

Application of serum markers in diagnosis and staging of ovarian endometriosis

AIMS

Laparoscopic surgery is widely used for diagnosing ovarian endometriosis but it has medical risks. This study explored the application of blood indicators in diagnosis and staging of ovarian endometriosis, aiming to develop a noninvasive diagnostic method.

METHODS

A total of 190 ovarian endometriosis patients were included in observation group, among these participants, 77 patients among them were stages I-II, and the rest 113 patients were stages III-IV, and a total of 103 healthy women as control group. Serum biochemical indexes, tumor markers, and cytokines levels in two groups were used for the diagnosis and staging of the disease. Area under the receiver operating characteristic (ROC) curve (AUC) predicted the value of individual and joint tests for indicators.

RESULTS

Biochemical indexes, namely, alkaline phosphatase (ALP), total protein (TP), and glucose (Glu) could distinguish patients from normal women; and that ALP and Glu could indicate disease staging. In tumor markers, alpha fetoprotein (AFP), carcinoembryonic antigen (CA) 125, CA199 and human epididymis protein 4 (HE4) helped to diagnose endometriosis; CA125, HE4, and cytokeratin 19 fragment (CYFRA21-1) could differentiate stages. In cytokines, vascular endothelial growth factor (VEGF), tumor necrosis factor (TNF)-α, interleukin (IL)-6, soluble fms-like tyrosine kinase receptor 1 (sflt-1), monocyte chemoattractant protein (MCP)-1 therefore, have values to diagnose endometriosis; VEGF, TNF-α, IL-6, and sflt-1 helped to differentiate disease staging.

CONCLUSION

Serological indicators in ovarian endometriosis patients were different from healthy women, which were of certain differential values in diagnosis and disease staging. The current study provided a novel strategy for endometriosis diagnosis.

Metabolic Profile of Patients with Severe Endometriosis: a Prospective Experimental Study

Endometriosis is a common disease affecting women in reproductive age. There are several hypotheses on the pathogenesis of this disease. Often, its lesions and symptoms overlap with those of many other medical and surgical conditions, causing a delay in diagnosis. Metabolomics represents a useful diagnostic tool for the study of metabolic changes during a different physiological or pathological status. We used ¹H-NMR to explore metabolic alteration in a cohort of patients with endometriosis in order to contribute to a better understanding of the pathophysiology of the disease and to suggest new useful biomarkers. Thirty-seven patients were recruited for the metabolomic analysis: 22 patients affected by symptomatic endometriosis and 15 not affected by it. Their serum samples were collected and analyzed with ¹H-NMR. Multivariate statistical analysis was conducted, followed by univariate and pathway analyses. Partial Least Square Discriminant Analysis (PLS-DA) was performed to determine the presence of any differences between the non-endometriosis and endometriosis samples (R²X = 0.596, R²Y = 0.713, Q² = 0.635, and p < 0.0001). β-hydroxybutyric acid and glutamine were significantly increased, whereas tryptophan was significantly decreased in the endometriosis patients. ROC curves were built to test the diagnostic power of the metabolites (β-hydroxybutyric acid: AUC = 0.85 CI = 0.71-0.99; glutamine: AUC = 0.83 CI = 0.68-0.98; tryptophan: AUC = 0.75 CI = 0.54-0.95; β-hydroxybutyric acid + glutamine + tryptophan AUC = 0.92 CI = 0.81-1). The metabolomic approach enabled the identification of several metabolic alterations occurring in women with endometriosis. These findings may provide new bases for a better understanding of the pathophysiological mechanisms of the disease and for the discovery of new biomarkers. Trial registration number NCT02337816.

The utility of nuclear magnetic resonance spectroscopy in assisted reproduction

Infertility affects approximately 15-20% of individuals of reproductive age worldwide. Over the last 40 years, assisted reproductive technology (ART) has helped millions of childless couples. However, ART is limited by a low success rate and risk of multiple gestations. Devising methods for selecting the best gamete or embryo that increases the ART success rate and prevention of multiple gestation has become one of the key goals in ART today. Special emphasis has been placed on the development of non-invasive approaches, which do not require perturbing the embryonic cells, as the current morphology-based embryo selection approach has shortcomings in predicting the implantation potential of embryos. An observed association between embryo metabolism and viability has prompted researchers to develop metabolomics-based biomarkers. Nuclear magnetic resonance (NMR) spectroscopy provides a non-invasive approach for the metabolic profiling of tissues, gametes and embryos, with the key advantage of having a minimal sample preparation procedure. Using NMR spectroscopy, biologically important molecules can be identified and quantified in intact cells, extracts or secretomes. This, in turn, helps to map out the active metabolic pathways in a system. The present review covers the contribution of NMR spectroscopy in assisted reproduction at various stages of the process.

The follicular fluid metabolome differs according to the endometriosis phenotype

RESEARCH QUESTION

Is there a follicular fluid-specific metabolic profile in deep infiltrating endometriosis (DIE) depending on the presence of an associated ovarian endometrioma (OMA) that could lead to the identification of biomarkers for diagnosis and prognosis of the disease?

DESIGN

In this prospective cohort study, proton nuclear magnetic resonance (¹H-NMR) experiments were carried out on 50 follicular fluid samples from patients presenting with DIE, associated or not associated with an OMA, and 29 follicular fluid samples from patients with infertility caused by a tubal obstruction.

RESULTS

Concentrations of glucose, citrate, creatine and amino acids such as tyrosine and alanine were lower in women with DIE than control participants, whereas concentrations of lactate, pyruvate, lipids and ketone bodies were higher. Metabolic analysis revealed enhanced concentrations of glycerol and ketone bodies in patients with OMA, indicative of an activation of lipolysis followed by beta-oxidation. Concentrations of lactate and pyruvate were increased in patients without OMA, whereas the concentration of glucose was decreased, highlighting activation of the anaerobic glycolysis pathway. Differences in concentrations of amino acids such as threonine and glutamine were also statistically relevant in discriminating between the presence or absence of OMA.

CONCLUSIONS

Results indicate a mitochondrial dysregulation in endometriosis phenotypes, with a modified balance between anaerobic glycolysis and beta-oxidation in OMA phenotypes that could affect the fertility of women with endometriosis. As the composition of the follicular fluid has been shown to be correlated with oocyte development and outcome of implantation after fertilization, these findings may help explain the high level of infertility in these patients.

Endometriosis Lowers the Cumulative Live Birth Rates in IVF by Decreasing the Number of Embryos but Not Their Quality

Endometriosis and infertility are closely linked, but the underlying mechanisms are still poorly understood. This study aimed to evaluate the impact of endometriosis on in vitro fertilization (IVF) parameters, especially on embryo quality and IVF outcomes. A total of 1124 cycles with intracytoplasmic sperm injection were retrospectively evaluated, including 155 cycles with endometriosis and 969 cycles without endometriosis. Women with endometriosis had significantly lower ovarian reserve markers (AMH and AFC), regardless of previous ovarian surgery. Despite receiving significantly higher doses of exogenous gonadotropins, they had significantly fewer oocytes, mature oocytes, embryos, and top-quality embryos than women in the control group. Multivariate analysis did not reveal any association between endometriosis and the proportion of top-quality embryo (OR = 0.87; 95% CI [0.66-1.12]; p = 0.3). The implantation rate and the live birth rate per cycle were comparable between the two groups (p = 0.05), but the cumulative live births rate was significantly lower in in the endometriosis group (32.1% versus 50.7%, p = 0.001), as a consequence of the lower number of frozen embryos. In conclusion, endometriosis lowers the cumulative live birth rates by decreasing the number of embryos available to transfer, but not their quality.

Metabolomic Biomarkers in Gynecology: A Treasure Path or a False Path?

Omic-technologies (genomics, transcriptomics, proteomics and metabolomics) have become more important in current medical science. Among them, it is metabolomics that most accurately reflects the minor changes in body functioning, as it focuses on metabolome - the group of the metabolism products, both intermediate and end. Therefore, metabolomics is actively engaged in fundamental and clinical studies and search for potential biomarkers. The biomarker could be used in diagnostics, management and stratification of the patients, as well as in prognosing the outcomes. The good example is gynecology, since many gynecological diseases lack effective biomarkers. In the current review, we aimed to summarize the results of the studies, devoted to the search of potential metabolomic biomarkers for the most common gynecological diseases.

Elevated Levels of Monocyte Chemotactic Protein-1 in the Follicular Fluid Reveals Different Populations among Women with Severe Endometriosis

To determine if a modification of the cytokine profile occurs in the follicular fluid (FF) of women with endometriosis undergoing in vitro fertilization (IVF), we performed a prospective observational study from January 2018 to February 2019. In total, 87 women undergoing IVF were included: 43 for severe endometriosis-related infertility and 40 controls with other causes of infertility. The cytokine profile of the FF was determined by multiplex fluorescent-bead-based technology allowing the measurement of 59 cytokines. Monocyte Chemoattractant Protein 1 (MCP-1) was the only variable retained in the multivariate analysis. We identified two subgroups of patients in the endometriosis group: MCP-1-low group (n = 23), which had FF MCP-1 levels comparable to the control group, and MCP-1-high (n = 20), which had significantly higher FF levels. Only patients in the MCP-1-high group had a significantly altered cytokine profile in the FF, and had a significantly higher serum estradiol level (p = 0.002) and a significantly lower number of oocytes recovered (p = 0.01) compared to the MCP-1-low and the control group. Our study has shown an alteration of the oocyte microenvironment in women with endometriosis associated with high follicular fluid levels of MCP-1, allowing the identification of a subgroup of endometriosis patients with a potentially worse prognosis.

Ovarian endometrioma infiltrating neutrophils orchestrate immunosuppressive microenvironment

Background

Ovarian endometrioma (EM) lesions not only have overwhelmed the amount of infiltrating immune cells but also display immunosuppressive phenotype. The close relationship between neutrophils and the pathogenesis of endometriosis has been demonstrated. The present study aims to elucidate whether or not neutrophils are involved in the regulation of immunosuppressive microenvironment in ovarian endometrioma.

Methods

Immunochemistry (IHC) and flow cytometry analysis (FACS) were conducted to measure CD66b expression in ovarian endometrioma samples from EM patients. The correlation between percentage of CD66b and PD1 + CD8+, TIM3 + CD8+, CTLA4 + CD8+, IFN-γ + CD8+ of CD45+ cells were analyzed. Neutrophil survival and PD-L1 expression were determined under the stimulations of ovarian endometrioma conditional supernatants (OECS). Finally, CD8+ T cell’s proliferation and IFN-γ expression were detected under co-cultured with OECS cultured neutrophils stimulated with the α-CD3/α-CD28 antibody.

Results

IHC and FACS results revealed correlation between the counts of neutrophils and the severity of ovarian endometrioma. The percentage of CD66b + cells was positively correlated with PD1 + CD8+, TIM3 + CD8+ and CTLA4 + CD8+ of CD45+ cells in ovarian endometrioma. OECS promoted neutrophils’ survival and enhanced PD-L1 expression. OECS cultured neutrophils inhibited proliferation and activity of autologous T cells.

Conclusions

Neutrophils play a crucial role in the progression of ovarian endometrioma by orchestrated the immunosuppressive microenvironment under the PD-1/PD-L1 axis.

Metabolomics in Central Sensitivity Syndromes

Central sensitization syndromes are a collection of frequently painful disorders that contribute to decreased quality of life and increased risk of opiate abuse. Although these disorders cause significant morbidity, they frequently lack reliable diagnostic tests. As such, technologies that can identify key moieties in central sensitization disorders may contribute to the identification of novel therapeutic targets and more precise treatment options. The analysis of small molecules in biological samples through metabolomics has improved greatly and may be the technology needed to identify key moieties in difficult to diagnose diseases. In this review, we discuss the current state of metabolomics as it relates to central sensitization disorders. From initial literature review until Feb 2020, PubMed, Embase, and Scopus were searched for applicable studies. We included cohort studies, case series, and interventional studies of both adults and children affected by central sensitivity syndromes. The majority of metabolomic studies addressing a CSS found significantly altered metabolites that allowed for differentiation of CSS patients from healthy controls. Therefore, the published literature overwhelmingly supports the use of metabolomics in CSS. Further research into these altered metabolites and their respective metabolic pathways may provide more reliable and effective therapeutics for these syndromes.

Endometriosis Knowledgebase: a gene-based resource on endometriosis

Endometriosis is a complex, benign, estrogen-dependent gynecological disorder with an incidence of ~10% women in reproductive age. The implantation and growth of endometrial cells outside the uterus leads to the development of endometriosis. Endometriosis is also associated with comorbid conditions like cardiovascular and autoimmune diseases. The absence of non-invasive diagnostic markers, delayed diagnosis, high risk of recurrence of the disease on surgical removal of the tissue and absence of a definitive cure for endometriosis makes it imperative to gain insights into the complex etiology of endometriosis. A plethora of genes identified from blood and endometrial biopsies, involved in different pathways like steroid metabolism, angiogenesis, inflammation, etc. have been associated with endometriosis. However, the exact mechanism and genetic etiology of endometriosis still remain unclear. The polygenic nature of the disease, incongruent phenotypic manifestations in different ethnic populations and information scattered in literature makes it difficult to delineate the sub-network of genes that will aid in disease diagnosis and effective treatment. Endometriosis Knowledgebase is a manually curated database with information on genes associated with endometriosis. It holds information on 831 genes, their associated polymorphisms, gene ontologys, pathways and diseases. Genes in the database are enriched in pathways important for cell signaling, immune regulation and reproduction. A genetic overlap is seen between endometriosis and cancers, endocrine/reproductive, nervous system, immune and metabolic diseases. Network analysis of genes in the Endometriosis Knowledgebase helped predict 13 new candidate genes for endometriosis. These genes were found to be enriched in biological processes associated with endometriosis. The Endometriosis Knowledgebase and incorporated tools for gene and sequence-based analysis will benefit both researchers and clinicians working in the realm of reproductive biology.

Serum metabolites as predictive molecular markers of ovarian response to controlled stimulation: a pilot study

OBJECTIVE

This study aimed to look into the use of serum metabolites as potential biomarkers of response to controlled ovarian stimulation (COS) in patients undergoing intracytoplasmic sperm injection (ICSI) cycles.

METHODS

This case-control study analyzed serum samples from 30 patients aged <36 years undergoing COS for ICSI in a university-affiliated assisted reproduction center from January 2017 to August 2017. The samples were split into three groups based on response to COS as follows: poor responders: <4 retrieved oocytes (PR group, n=10); normal responders: ≥ 8 and ≤ 12 retrieved oocytes (NR group, n=10); and hyper-responders: >25 retrieved oocytes (HR, n=10). The metabolic profiles of the serum samples were compared between the groups through Principal Component Analysis (PCA). Receiver Operating Characteristic (ROC) curves were built to assess the power of the model at predicting response to COS.

RESULTS

PCA clearly distinguished between PR, NR and HR, and 10 ions were chosen as potential biomarkers of response to COS. These ions were more specific for PR than for NR. The ROC curve considering PR and NR had an area under the curve of 99.6% (95% CI: 88.9 - 100%).

CONCLUSION

The preliminary evidence discussed in this study suggests that serum metabolites may be used as predictive molecular markers of ovarian response to controlled stimulation. The integration of clinical and "omics" findings may allow the migration toward an era of personalized treatment in reproductive medicine.

Metabolomic profile as a noninvasive adjunct tool for the diagnosis of Grades III and IV endometriosis-related infertility

The aim of the present case-control study was to develop a noninvasive adjuvant tool for the diagnosis of endometriosis. Serum samples from 100 patients undergoing intracytoplasmic sperm injection were split into two groups according to the cause of infertility: an endometriosis group (n = 50), consisting of samples derived from patients with Grade III and IV endometriosis, and a control group (n = 50), comprising samples derived from patients with isolated male factor infertility. The metabolomic profile of each sample was obtained, through mass spectrometry. Partial least squares discriminant analysis was able to clearly classify the endometriosis and control groups. Ten potential biomarkers were selected based on their importance for model prediction. These ions were used to build the receiver-operating characteristic curve, which presented an area under the curve of 0.904 (95% confidence interval: 0.796-0.985). To validate the model, 30 other samples from infertile women without any evidence of endometriosis were tested. Considering these ions as possible biomarkers, the model was able to correctly classify 84% of the patients. Finally, a similar prediction potential was observed in the model validated set, when samples from the disease-free group were tested. Serum metabolomics may be useful as a noninvasive adjunct tool for the selection of patients who must undergo laparoscopy for definitive endometriosis diagnosis.

NMR metabolic profiling of follicular fluid for investigating the different causes of female infertility: a pilot study

INTRODUCTION

Several metabolomics studies have correlated follicular fluid (FF) metabolite composition with oocyte competence to fertilization, embryo development and pregnancy but there is a scarcity of research examining the metabolic effects of various gynaecological diseases.

OBJECTIVES

In this study we aimed to analyze and correlate the metabolic profile of FF from women who were following in vitro fertilization (IVF) treatments with their different infertility pathologies.

METHODS

We selected 53 women undergoing IVF who were affected by: tubal diseases, unexplained infertility, endometriosis, polycystic ovary syndrome (PCOS). FF of the study participants was collected at the time of oocytes retrieval. Metabolomic analysis of FF was performed by nuclear magnetic resonance (NMR) spectroscopy.

RESULTS

FF presents some significant differences in various infertility pathologies. Although it was not possible to discriminate between FF of control participants and women with tubal diseases and unexplained infertility, comparison of FF metabolic profile from control women with patients with endometriosis and PCOS revealed significant differences in some metabolites that can be correlated to the causes of infertility.

CONCLUSION

NMR-based metabolic profiling may be successfully applied to find diagnostic biomarkers for PCOS and endometriosis and it might be also used to predict oocyte developmental potential and subsequent outcome.

NMR metabolomics study of follicular fluid in women with cancer resorting to fertility preservation

PURPOSE

The purpose of this study was to evaluate the possible application of metabolomics to identify follicular fluid changes in cancer patients undergoing fertility preservation. Although metabolomics have been applied already in cancer studies, this is the first application on follicular fluid of cancer patients.

METHODS

We selected for the study ten patients with breast cancer and lymphoma who resorted to oocyte cryopreservation to preserve fertility and ten healthy women undergoing in vitro fertilization treatments. Follicular fluid was collected at the time of oocytes retrieval. Metabolomic analysis of follicular fluids was performed by 1H-nuclear magnetic resonance (NMR) spectroscopy in combination with multivariate analysis to interpret the spectral data. Univariate statistical analysis was applied to find correlations between patients' features and metabolites identified by NMR.

RESULTS

Partial least squares discriminant analysis allowed to discriminate samples from cancer patients and healthy controls. Univariate statistical analysis found significant correlations between patients' features and metabolites identified by NMR. This finding allowed to identify biomarkers to differentiate both healthy controls from cancer patients and the two different classes of oncological patients.

CONCLUSION

The follicular fluids of cancer patients display significant metabolic alterations in comparison to healthy subjects. NMR-based metabolomics could be a valid prognostic tool for identifying and selecting the best cryopreserved oocytes and improving the outcome prediction in cancer women undergoing in vitro fertilization.

Preanalytical Processing and Biobanking Procedures of Biological Samples for Metabolomics Research: A White Paper, Community Perspective (for "Precision Medicine and Pharmacometabolomics Task Group"-The Metabolomics Society Initiative)

BACKGROUND

The metabolome of any given biological system contains a diverse range of low molecular weight molecules (metabolites), whose abundances can be affected by the timing and method of sample collection, storage, and handling. Thus, it is necessary to consider the requirements for preanalytical processes and biobanking in metabolomics research. Poor practice can create bias and have deleterious effects on the robustness and reproducibility of acquired data.

CONTENT

This review presents both current practice and latest evidence on preanalytical processes and biobanking of samples intended for metabolomics measurement of common biofluids and tissues. It highlights areas requiring more validation and research and provides some evidence-based guidelines on best practices.

SUMMARY

Although many researchers and biobanking personnel are familiar with the necessity of standardizing sample collection procedures at the axiomatic level (e.g., fasting status, time of day, "time to freezer," sample volume), other less obvious factors can also negatively affect the validity of a study, such as vial size, material and batch, centrifuge speeds, storage temperature, time and conditions, and even environmental changes in the collection room. Any biobank or research study should establish and follow a well-defined and validated protocol for the collection of samples for metabolomics research. This protocol should be fully documented in any resulting study and should involve all stakeholders in its design. The use of samples that have been collected using standardized and validated protocols is a prerequisite to enable robust biological interpretation unhindered by unnecessary preanalytical factors that may complicate data analysis and interpretation.

Endometrium metabolomic profiling reveals potential biomarkers for diagnosis of endometriosis at minimal-mild stages

BACKGROUND

The sensitivity and specificity of non-invasive diagnostic methods for endometriosis, especially at early stages, are not optimal. The clinical diagnostic indicator cancer antigen 125 (CA125) performs poorly in the diagnosis of minimal endometriosis, with a sensitivity of 24%. Therefore, it is urgent to explore novel diagnostic biomarkers. We evaluated the metabolomic profile variation of the eutopic endometrium between minimal-mild endometriosis patients and healthy women by ultra-high-performance liquid chromatography coupled with electrospray ionization high-resolution mass spectrometry (UHPLC-ESI-HRMS).

METHODS

Our study comprised 29 patients with laparoscopically confirmed endometriosis at stages I-II and 37 infertile women who underwent diagnostic laparoscopy combined with hysteroscopy from January 2014 to January 2015. Eutopic endometrium samples were collected by pipelle endometrial biopsy. The metabolites were quantified by UHPLC-ESI-HRMS. The best combination of biomarkers was then selected by performing step-wise logistic regression analysis with backward elimination.

RESULTS

Twelve metabolites were identified as endometriosis-associated biomarkers. The eutopic endometrium metabolomic profile of the endometriosis patients was characterized by a significant increase in the concentration of hypoxanthine, L-arginine, L-tyrosine, leucine, lysine, inosine, omega-3 arachidonic acid, guanosine, xanthosine, lysophosphatidylethanolamine and asparagine. In contrast, the concentration of uric acid was decreased. Metabolites were filtered by step-wise logistic regression with backward elimination, and a model containing uric acid, hypoxanthine, and lysophosphatidylethanolamine was constructed. Receiver-operating characteristic (ROC) analysis confirmed the prognostic value of these parameters for the diagnosis of minimal/mild endometriosis with a sensitivity of 66.7% and a specificity of 90.0%.

CONCLUSIONS

Metabolomics analysis of the eutopic endometrium in endometriosis was effectively characterized by UHPLC-ESI-HRMS-based metabolomics. Our study supports the importance of purine and amino acid metabolites in the pathophysiology of endometriosis and provides potential biomarkers for semi-invasive diagnosis of early-stage endometriosis.