Serum metabolomics study of women with different annual decline rates of anti-Müllerian hormone: an untargeted gas chromatography-mass spectrometry-based study

Multiomics insights into the female reproductive aging

The human female reproductive lifespan significantly diminishes with age, leading to decreased fertility, reduced fertility quality and endocrine function disorders. While many aspects of aging in general have been extensively documented, the precise mechanisms governing programmed aging in the female reproductive system remain elusive. Recent advancements in omics technologies and computational capabilities have facilitated the emergence of multiomics deep phenotyping. Through the application and refinement of various high-throughput omics methods, a substantial volume of omics data has been generated, deepening our comprehension of the pathogenesis and molecular underpinnings of reproductive aging. This review highlights current and emerging multiomics approaches for investigating female reproductive aging, encompassing genomics, epigenomics, transcriptomics, proteomics, metabolomics, and microbiomics. We elucidate their influence on fundamental cell biology and translational research in the context of reproductive aging, address the limitations and current challenges associated with multiomics studies, and offer a glimpse into future prospects.

Increased serine synthesis in cumulus cells of young infertile women with diminished ovarian reserve

STUDY QUESTION

What are the differences in gene expression of cumulus cells (CCs) between young women with diminished ovarian reserve (DOR) and those of similar age with normal ovarian reserve (NOR)?

SUMMARY ANSWER

Gene expression and metabolome profiling analysis demonstrate that the de novo serine synthesis pathway (SSP) is increased in the CCs of young women with DOR.

WHAT IS KNOWN ALREADY

The incidence of DOR has risen, tending to present at younger ages. Its mechanisms and aetiologies are still poorly understood. Abnormal metabolism is present in luteinized CCs of patients with DOR. Previous studies have revealed that mitochondrial dysfunction and impaired oxidative phosphorylation in CCs are related to DOR in women of advanced age. The pathogenic mechanisms likely differ between young women with DOR and cases associated with advanced maternal age. Several studies have examined amino acid metabolism in the follicle, with a focus on embryo development, but less information is available about CCs. The physiological significance of de novo serine synthesis in follicles and oocytes remains largely unknown.

STUDY DESIGN, SIZE, DURATION

CC samples were obtained from 107 young infertile women (age <38 years) undergoing ICSI, from July 2017 to June 2019, including 54 patients with DOR and 53 patients with NOR.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Oocyte development data were analysed retrospectively. Comprehensive genome-wide transcriptomics of CCs was performed. Differentially expressed genes (DEGs) were identified. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to categorize the functions of the DEGs and identify significantly enriched pathways. The transcript and protein levels of key enzymes involved in serine synthesis were verified in additional samples using quantitative real-time PCR (qRT-PCR) (n = 10) and capillary western blotting (n = 36). Targeted metabolomics of amino acids in CC extracts was performed by ultrahigh-performance liquid MS (UHPLC-MS/MS).

MAIN RESULTS AND THE ROLE OF CHANCE

The number of oocytes (2.4 ± 2.2 versus 12.1 ± 5.3) and metaphase II oocytes (2.1 ± 2.0 versus 9.9 ± 4.9) retrieved was significantly decreased in the DOR versus the NOR group, respectively (P < 0.0001). The rates of fertilization (80.7% versus 78.8%), viable embryos (73.7% versus 72.5%), and high-quality embryos (42.8% versus 49.0%) did not differ between the DOR and NOR groups, respectively (P > 0.05). A total of 95 DEGs were found by transcriptome sequencing. GO and KEGG analyses demonstrated that the DEGs were linked to amino acid metabolism and suggested significantly higher activity of the de novo SSP in the CCs of young women with DOR. Further qRT-PCR and capillary western blotting revealed that key enzymes (PHGDH, PSAT1, PSPH, and SHMT2) involved in de novo serine synthesis were upregulated, and UHPLC-MS/MS analysis showed increases in serine and glycine (a downstream product of serine) levels in the CCs of young patients with DOR. Our data clearly demonstrate that the de novo SSP, which diverts 3-phosphoglycerate from glycolysis to serine synthesis, was upregulated in young DOR CCs.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Regarding the reproductive capacity of young patients DOR, the pregnancy outcomes were not analysed. The sample size was limited, and only women undergoing ICSI were examined since this was a prerequisite for the acquisition of CCs, which may cause selection bias. The exact mechanisms by which the SSP in CCs regulates ovarian reserve still require further study.

WIDER IMPLICATIONS OF THE FINDINGS

Our research presents new evidence that alterations of the SSP in CCs of young infertile women are associated with DOR. We believe this is a significant contribution to the field, which should be key for understanding the cause and mechanisms of ovarian hypofunction in young women.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by grants from the Ministry of Science and Technology of China (2018YFC1005001) and National Natural Science Foundation of China (31601197). There were no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Plasma metabolomic characterization of premature ovarian insufficiency

BACKGROUND

Premature ovarian insufficiency (POI) patients are predisposed to metabolic disturbances, including in lipid metabolism and glucose metabolism, and metabolic disorders appear to be a prerequisite of the typical long-term complications of POI, such as cardiovascular diseases or osteoporosis. However, the metabolic changes underlying the development of POI and its subsequent complications are incompletely understood, and there are few studies characterizing the disturbed metabolome in POI patients. The aim of this study was to characterize the plasma metabolome in POI by using ultrahigh-performance liquid chromatography-mass spectrometry (UHPLC-MS/MS) metabolomics and to evaluate whether these disturbances identified in the plasma metabolome relate to ovarian reserve and have diagnostic value in POI.

METHODS

This observational study recruited 30 POI patients and 30 age- and body mass index (BMI)-matched controls in the Center for Reproductive Medicine, Department of Gynecology and Obstetrics, Nanfang Hospital, Southern Medical University, from January 2018 to October 2020. Fasting venous blood was collected at 9:00 am on days 2-4 of the menstrual cycle and centrifuged for analysis. An untargeted quantitative metabolomic analysis was performed using UHPLC-MS/MS.

RESULTS

Our study identified 48 upregulated and 21 downregulated positive metabolites, and 13 upregulated and 48 downregulated negative metabolites in the plasma of POI patients. The differentially regulated metabolites were involved in pathways such as caffeine metabolism and ubiquinone and other terpenoid-quinone biosynthesis. Six metabolites with an AUC value > 0.8, including arachidonoyl amide, 3-hydroxy-3-methylbutanoic acid, dihexyl nonanedioate, 18-HETE, cystine, and PG (16:0/18:1), were correlated with ovarian reserve and thus have the potential to be diagnostic biomarkers of POI.

CONCLUSION

This UHPLC-MS/MS untargeted metabolomics study revealed differentially expressed metabolites in the plasma of patients with POI. The differential metabolites may not only be involved in the aetiology of POI but also contribute to its major complications. These findings offer a panoramic view of the plasma metabolite changes caused by POI, which may provide useful diagnostic and therapeutic clues for POI disease.

The Establishment of a Mouse Model of Recurrent Primary Dysmenorrhea

Primary dysmenorrhea is one of the most common reasons for gynecologic visits, but due to the lack of suitable animal models, the pathologic mechanisms and related drug development are limited. Herein, we establish a new mouse model which can mimic the periodic occurrence of primary dysmenorrhea to solve this problem. Non-pregnant female mice were pretreated with estradiol benzoate for 3 consecutive days. After that, mice were injected with oxytocin to simulate menstrual pain on the 4th, 8th, 12th, and 16th days (four estrus cycles). Assessment of the cumulative writhing score, uterine tissue morphology, and uterine artery blood flow and biochemical analysis were performed at each time point. Oxytocin injection induced an equally severe writhing reaction and increased PGF_2α accompanied with upregulated expression of COX-2 on the 4th and 8th days. In addition, decreased uterine artery blood flow but increased resistive index (RI) and pulsatility index (PI) were also observed. Furthermore, the metabolomics analysis results indicated that arachidonic acid metabolism; linoleic acid metabolism; glycerophospholipid metabolism; valine, leucine, and isoleucine biosynthesis; alpha-linolenic acid metabolism; and biosynthesis of unsaturated fatty acids might play important roles in the recurrence of primary dysmenorrhea. This new mouse model is able to mimic the clinical characteristics of primary dysmenorrhea for up to two estrous cycles.

Maternal Exposure to D-galactose Reduces Ovarian Reserve in Female Rat Offspring Later in Life

BACKGROUND

Embryonic life is critical for the formation of ovaries in mammals, and the intrauterine environment may affect ovarian reserve.

OBJECTIVES

The present study aimed to investigate the impact of prenatal D-galactose exposure on ovarian reserve in female rat offspring in their later lives.

METHODS

Ten pregnant Wistar rats were randomly divided into two groups. In one group, rats were fed with 35% D-galactose-enriched food from the third day to the end of pregnancy, and in the other group, rats were fed with a standard diet throughout pregnancy. Female offspring (prenatally galactose-exposed rats and non-exposed control rats) were examined in terms of hormonal levels [anti-Mullerian hormones (AMH), follicle-stimulating hormone (FSH), and estradiol (E2)] and ovarian histology at 45 - 50, 105 - 110, and 180 - 185 days of their age.

RESULTS

The number of primordial follicles significantly decreased time-dependently in prenatally galactose-exposed rats compared to controls (P-value = 0.002). In addition, decreases in AMH (3.25 vs. 7.5 ng/mL; P = 0.000) and E2 (7.9 vs. 19.5 pg/mL; P = 0.000) and increases in FSH (6.5 vs. 0.8 mIU/mL; P < 0.007) were observed in galactose-exposed rats compared to controls at 45 - 50 days of age.

CONCLUSIONS

Prenatal exposure to D-galactose negatively affects ovarian reserve in female rats in their later lives. However, further investigation is needed to confirm our findings and explore underlying mechanisms.

Metabolomic markers of biological fluid in women with reproductive failure: a systematic review of current literatures

Understanding metabolic changes in reproductive failure, including early miscarriage (EM), recurrent miscarriage (RM) and repeated implantation failure (RIF), may be beneficial to understand the pathophysiology, thus improving pregnancy outcomes. Nine metabolomic profiling studies in women with reproductive failures (4 for EM, 3 for RM and 2 for RIF) were included for systematic review. In total 78, 75 and 25 significant metabolites were identified and 40, 40 and 34 metabolic pathways were enriched in EM, RM and RIF, respectively. Among them, 7 and 11 metabolites, and 28 and 28 pathways were shared between EM and RM and between RM and RIF, respectively. Notably, histidine metabolism has the highest impact in EM; phenylalanine, tyrosine and tryptophan biosynthesis. Ubiquinone and other terpenoid-quinone biosynthesis metabolism have the highest impact factor in RM; alanine, aspartate and glutamate metabolism have the highest impact factor in RIF. This study not only summarized the common and distinct metabolites and metabolic pathways in different reproductive failures but also summarized limitations of the study designs and methodologies. Hence, further investigations and validations of these metabolites are still urgently needed to understand the underlying metabolic mechanism for the development and treatment of reproductive failures.

Serum metabolomics study of the association between dairy intake and the anti-müllerian hormone annual decline rate

Background

Dairy intake has been implicated in later ovarian aging but mechanism underlying the association is unknown. This study aimed to investigate (1) associations between dairy intake and metabolites previously shown related to anti-müllerian hormone (AMH) decline rate; (2) mediating roles of these metabolites in the prospective association of total dairy consumption with odds of AMH fast decline rate.

Methods

The participants comprised 186 reproductive-aged women randomly selected from the Tehran Lipid and Glucose Study. AMH was measured at baseline (1999–2001) and the 5th follow-up (2014–2017), and dietary data was collected at the second follow-up (2005–2008) using a food frequency questionnaire. Untargeted metabolomics was performed by gas chromatography–mass spectrometry using fasting-serum samples of the second follow-up. We analyzed dairy intake in association with the eight metabolites linked to the higher odds of AMH fast decline rate using linear regression with the Benjamini–Hochberg false discovery correction. Mediatory roles of the metabolites were assessed by bootstrapping.

Results

Mean age and BMI of the participants at metabolomics assessment were 44.7 ± 5.87 years and 28.8 ± 4.88 kg/m², respectively. Phosphate, branched-chain amino acids (BCAAs), and proline decreased significantly from the first to the third tertile of total dairy intake. Total dairy as a continuous variable inversely associated with phosphate (beta = −0.166; p value = 0.018), valine (beta = −0.176; p value = 0.016), leucine (beta = −0.226; p value = 0.002), proline (beta = −0.219; p value = 0.003), and urea (beta = −0.156; p = 0.035) after accounting for all potential covariates and correction for multiplicity (q-value < 0.1). Fermented dairy showed similar results, but milk did not associate with any of the metabolites. Simple mediation showed significant indirect effects for phosphate, proline, and BCAAs but not urea. Entering the sum of phosphate, proline, and BCAAs as a mediator, the metabolites' total indirect effects were significant [β = −0.12 (95% CIs − 0.26, − 0.04)]. In contrast, the direct association of total dairy intake with the fast decline in AMH was non-significant [β = −0.28 (95% CIs − 0.67, 0.10)].

Conclusions

Total dairy was inversely associated with AMH decline rate-related metabolites. Inverse association of dairy intakes with the odds of AMH fast decline rate was indirectly mediated by lower phosphate, proline, and BCAAs.