Obesity and oocyte quality: Significant implications for ART and Emerging mechanistic insights

Effect of body mass index on pregnancy outcomes in young women with low-prognosis POSEIDON criteria after in vitro fertilization/intracytoplasmic sperm injection

BACKGROUND

The aim of this study was to investeigate the pregnancy outcomes of young women with low prognosis according to the POSEIDON criteria after IVF/ICSI cycles and to explore the effect of body mass index (BMI) on pregnancy outcomes.

METHODS

This was a retrospective cohort study conducted in women who underwent their first IVF/ICSI cycle treatment between January 2018 and December 2020, Among them, these patients who met criteria for POSEIDON group1and 3 were further categorized into four groups according to the China body mass index(BMI) classification, we analyzed the effect of BMI on pregnancy outcomes.

RESULTS

A total of 29,354 patients were conducted first IVF/ICSI cycle between January 2018 and December 2020 in our reproductive center, 5981 women who met the criteria for POSEIDON 1 and POSEIDON 3 were further categorized into four groups according to the China body mass index(BMI) classification. There were not significant differences in the implantation rate and clinical pregnancy rate, regardless of fresh embryo transfer or frozen embryo transfer among the four groups (P > 0.05). The miscarriage rate of fresh embryo transfer was significantly higher in obese patients (P < 0.05), while the live birth rate of fresh embryo transfer and the cumulative live birth rate are significantly lower in obese patients(P < 0.05). BMI was a significant and independent predictor of the miscarriage rate of fresh embryo transfer (adjusted OR 1.111; 95% CI 1.042-1.184; p = 0.001) and the cumulative live-birth rate (adjusted OR 0.937; 95% CI 0.900-0.975; p = 0.001).

CONCLUSIONS

Our study indicated that obesity negatively impacts the IVF/ICSI outcomes of young women with low prognosis, including higher miscarriage rate and lower live birth-rate and cumulative live-birth rate. In our study, we found that BMI was the best independent predictor of the miscarriage rate of fresh embryo transfer and cumulative live-birth rate of low-prognosis patients under 35 years old. Thus the best way to reduce these complications for young patients with a poor prognosis was to keep their BMI between 18.5 kg/m2 and 24 kg/m2.

Impact of maternal body mass index on pregnancy outcomes following frozen embryo transfer: A systematic review and meta-analysis

OBJECTIVE

There is still a significant gap in understanding how maternal body mass index (BMI) impacts outcomes of pregnancy after frozen embryo transfer (FET). This review aims to evaluate the effects of various BMI categories on clinical pregnancy and live birth rates in women undergoing FET.

METHODS

PubMed, Scopus, Embase, and Web of Science databases were searched for studies, published up to March, 2024, using the keywords "obesity", "overweight", "obese", "maternal body mass index," "pregnancy outcomes," "frozen embryo transfer,". Eligible studies were selected based on predefined inclusion criteria, statistical analysis was performed using a random-effects model, and ther results were presented as odds ratios (OR) with 95% confidence intervals (CI).

RESULTS

A total of 17 studies were included in the meta-analysis. Pooled findings indicate significantly reduced live birth rate in underweight (OR 0.93; 95% CI: 0.89, 0.98) and obese (OR 0.85; 95% CI: 0.77, 0.93) women but not in those who were overweight (OR 0.96; 95% CI: 0.92, 1.00), compared to those with normal BMI. Further, only those women who were underweight (OR 0.91; 95% CI: 0.85, 0.97) had reduced odds of clinical pregnancy rate but not those who were overweight (OR 0.99; 95% CI: 0.94, 1.05) or obese (OR 0.92; 95% CI: 0.82, 1.03).

CONCLUSION

Maternal BMI impacts pregnancy outcomes after frozen embryo transfer, with underweight and obese women having lower live birth rates and only underweight women showing reduced clinical pregnancy rates compared to those with normal BMI. These findings underscore the importance of addressing BMI in women undergoing FET to improve pregnancy outcomes.

Diet-Induced Obesity Alters Granulosa Cell Transcriptome and Ovarian Immune Environment in Mice

Obesity affects female reproductive performance by impairing the ovarian and uterine environments. Using a diet-induced obesity mouse model, we examined whether a high-fat diet (HFD) regimen affects the gene expression profile in ovarian granulosa cells (GCs) and whether short-term HFD has similar effects on gene expression as long-term HFD. C57BL/6J mice were fed a HFD or normal diet (ND) for 16-18 weeks (long-term group) or 4 weeks (short-term group). GCs were collected from each group of mice for RNA-sequencing. RT-PCR and immunofluorescence staining were performed to validate the results. RNA-sequencing analyses of the GCs revealed that several immediate early genes, including early growth response 1 (Egr1), an important mediator of ovulation, were significantly downregulated in HFD GCs. Protein tyrosine phosphatase receptor type C (Ptprc) and hematopoietic type prostaglandin D synthase (Hpgds), both of which are associated with increased inflammation, were significantly upregulated in HFD GCs. Downregulation of Egr1 was also confirmed in the GCs of short-term HFD mice, suggesting that it constitutes an early change in response to a HFD. Increased expression of several transcription factors in HFD GCs suggests that a HFD may affect the overall transcriptional landscape. The results may indicate possible modulation of the immune environment in HFD ovaries. These results provide novel insights into the molecular changes in GCs in obese environments.

Decoding immune tolerance in infertility: Exploring immune pathways and non-coding RNAs as pioneering biomarkers and therapeutic targets

Infertility, impacting a significant number of couples, is characterized by the failure to conceive after one year of consistent, unprotected sexual intercourse. It is multifactorial, with etiological contributors including ovulatory dysfunction, male reproductive anomalies, and tubal patency issues. Approximately 15% of infertility cases are classified as "unexplained," highlighting the complexity of this condition. Lifestyle determinants such as obesity and smoking further complicate reproductive outcomes, while infertility can also indicate underlying chronic health conditions. A specialized category, immune infertility, arises from a breakdown of immunological tolerance, an essential aspect for conception and the maintenance of pregnancy. The role of various immunological components, including immune cells, cytokines, chemokines, factors like HLA-G, etc., is pivotal in this context. Moreover, non-coding RNAs (ncRNAs) have emerged as critical regulators of immune tolerance within the reproductive axis. This review synthesizes the complex immunological pathways vital for successful implantation and the early stages of pregnancy alongside the regulatory roles of ncRNAs in these processes. Offering an integrated view of molecular and immunological interactions associated with infertility seeks to enhance our understanding of potential strategies to facilitate successful conception and sustain early pregnancy.

Emerging therapeutic strategies to mitigate female and male reproductive aging

People today are choosing to have children later in life, often in their thirties and forties, when their fertility is in decline. We sought to identify and compile effective methods for improving either male or female fertility in this context of advanced reproductive age. We found few clinical studies with strong evidence for therapeutics that mitigate reproductive aging or extend fertility; however, this Perspective summarizes the range of emerging experimental strategies under development. Preclinical studies, in mouse models of aging, have identified pharmaceutical candidates that improve egg and sperm quality. Further, a diverse array of medically assisted reproduction methodologies, including those that stimulate rare ovarian follicles and rejuvenate egg quality using mitochondria, may have future utility for older patients. Finally, we highlight the many knowledge gaps and possible future directions in the field of therapeutics to extend the age of healthy human reproduction.

Body Composition and Dietary Intake of Women Attending an Infertility Clinic-Polish Observational Study

BACKGROUND AND OBJECTIVES

We aimed to assess the body composition and dietary intake of female patients attending one of the Polish infertility clinics. Additionally, we evaluated if there were any relationships between dietary intake and body composition parameters.

METHODS

The study involved 51 women who met the inclusion criteria. For the nutritional assessment, we used 3-day dietary records. Weight, height, waist and hip circumferences, and body composition were assessed. The participants were divided into three groups, with low (I, n = 12), normal (II, n = 27), and high (III, n = 12) fat tissue content, and then compared in terms of dietary intake.

RESULTS

The lowest protein intake per kilogram of body weight was observed in group III (p < 0.001). In group I, we reported the highest consumption of plant protein in general (p = 0.03) and per kg of body weight (p < 0.001). Higher protein intake per kg body mass was associated with lower values of BMI (r = -0.681; p < 0.001), fat mass (r = -0.641; p < 0.001), waist-hip ratio (r = -0.391; p = 0.005), and abdominal fat index (r = -0.653; p < 0.001).

CONCLUSIONS

Our findings suggest that targeted nutritional counseling focused on optimizing protein intake and emphasizing plant-based sources may improve body composition and potentially support fertility outcomes in women undergoing infertility treatment.

Apigenin as a Promising Agent for Enhancing Female Reproductive Function and Treating Associated Disorders

Apigenin is an organic flavonoid abundant in some plants such as parsley, chamomile, or celery. Recently, it has been investigated for several of its pharmacological characteristics, such as its ability to act as an antioxidant, reduce inflammation, and inhibit the growth of cancer cells. The purpose of this review is to provide a summary of the existing knowledge regarding the effects of apigenin on female reproductive systems and its dysfunctions. Apigenin can influence reproductive processes by regulating multiple biological events, including oxidative processes, cell proliferation, apoptosis, cell renewal and viability, ovarian blood supply, and the release of reproductive hormones. It could stimulate ovarian folliculogenesis, as well as ovarian and embryonal cell proliferation and viability, which can lead to an increase in fertility and influence the release of reproductive hormones, which may exert its effects on female reproductive health. Furthermore, apigenin could inhibit the activities of ovarian cancer cells and alleviate the pathological changes in the female reproductive system caused by environmental pollutants, harmful medications, cancer, polycystic ovarian syndrome, ischemia, as well as endometriosis. Therefore, apigenin may have potential as a biostimulator for female reproductive processes and as a therapeutic agent for certain reproductive diseases.

Mapping the lipidomic secretome of the early equine embryo

The lipidomic secretions of embryos provide a unique opportunity to examine the cellular processes of the early conceptus. In this study we profiled lipids released by the early equine conceptus, using high-resolution mass spectrometry to detect individual lipid species. This study examined the lipidomic profile in embryo-conditioned media from in vivo-produced, 8-9 day-old equine embryos (n = 3) cultured in vitro for 36 h, analyzed over 3 timepoints. A total of 1,077 lipid IDs were recorded across all samples, containing predominantly glycerolipids. Seventy-nine of these were significantly altered in embryo conditioned-media versus media only control (p < 0.05, fold-change >2 or < 0.5). Fifty-five lipids were found to be released into the embryo-conditioned media, of which 54.5% were triacylglycerols and 23.6% were ceramides. The sterol lipid, cholesterol, was also identified and secreted in significant amounts as embryos developed. Further, 24 lipids were found to be depleted from the media during culture, of which 70.8% were diacylglycerols, 16.7% were triacylglycerols and 12.5% were ceramides. As lipid-free media contained consistently detectable lipid peaks, a further profile analysis of the various components of non-embryo-conditioned media consistently showed the presence of 137 lipids. Lipid peaks in non-embryo-conditioned media increased in response to incubation under mineral oil, and contained ceramides, diacylglycerols and triacylglycerols. These results emphasize the importance of a defined embryo culture medium and a need to identify the lipid requirements of the embryo precisely. This study sheds light on early embryo lipid metabolism and the transfer of lipids during in vitro culture.

Effect of body mass index on ovarian reserve and ART outcomes in infertile women: a large retrospective study

BACKGROUND

Obesity poses a significant global health challenge, with profound implications for women's reproductive health. The relationship between ovarian reserve and body mass index (BMI) remains a subject of debate. While obesity is generally associated with poorer outcomes in assisted reproductive technology (ART), the evidence remains inconclusive. This study aimed to investigate the effect of pre-pregnancy BMI on ovarian reserve and ART outcomes in infertile patients.

METHODS

We conducted a retrospective cohort study involving women who underwent in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) procedures at Tongji Hospital between 2016 and 2023. The study included 30,746 initial fresh cycles and 5,721 singleton deliveries. Patients were stratified by age and further categorized into four BMI groups: lean (< 18.5 kg/m²), normal weight (18.5-24.9 kg/m²), overweight (25.0-29.9 kg/m²), and obese (≥ 30.0 kg/m²). The primary endpoints of the study were pregnancy and perinatal outcomes. To explore the association between BMI and these outcomes, we adjusted for relevant confounding factors and utilized multivariate linear regression models, complemented by multifactorial logistic regression analyses.

RESULTS

Anti-Müllerian hormone (AMH) levels were significantly lower in the overweight and obese groups compared to the normal weight group. After adjusting for age, a negative correlation was found between AMH and BMI in the age subgroups of 20-30 and 30-35 years. Among women aged 20-35 years, those in the overweight and obese groups had significantly fewer retrieved oocytes, mature oocytes, and two-pronuclear (2PN) embryos than their normal weight counterparts. Despite these differences, pregnancy outcomes in the overweight and obese groups were comparable to those in the normal weight group across all age categories. Additionally, obesity was linked to an increased risk of gestational diabetes mellitus, hypertensive disorders of pregnancy, and macrosomia.

CONCLUSIONS

An age-related decrease in AMH levels was evident with increasing BMI. Although being overweight or obese is associated with poorer embryo and perinatal outcomes, it does not seem to have a substantial impact on fertility.

Association between visceral adipose tissue area and infertility: a cross-sectional analysis

RESEARCH QUESTION

Is intra-abdominal fat obesity associated with infertility?

DESIGN

This study analysed data from the 2013-2018 National Health and Nutrition Examination Survey, with a total of 3013 women enrolled. The participants were divided into two groups: infertility and non-infertility. Differences between the two groups were analysed using a weighted Student's t-test or Mann-Whitney U-test for continuous variables, or a weighted chi-squared test for categorical data. Visceral adipose tissue area (VATA) was assessed by dual-energy X-ray absorptiometry. The independent association between infertility and log VATA was assessed by weighted multivariate logistic regression models. Subgroup analyses were performed to assess the strength of the results. Interaction tests were used to examine whether covariates interacted with log VATA to influence infertility.

RESULTS

Log VATA was significantly higher in the infertility group compared with the non-infertility group (P < 0.001). After adjustment for potential confounders, the results of multivariate logistic regression analysis revealed that an increase in log VATA was associated with increased prevalence of female infertility (OR = 2.453, 95% CI 1.278-4.792). Subgroup analyses showed this association in individuals aged <35 years (P = 0.002), Mexican-Americans (P = 0.033), non-hypertensive individuals (P = 0.013) and non-diabetic individuals (P = 0.003).

CONCLUSIONS

An enlarged VATA is associated with increased risk of infertility. The direct effect of VATA on female infertility needs to be clarified further to provide a basis for future prevention and treatment of female infertility.

Granulosa cell metabolism at ovulation correlates with oocyte competence and is disrupted by obesity and aging

STUDY QUESTION

Is oocyte developmental competence associated with changes in granulosa cell (GC) metabolism?

SUMMARY ANSWER

GC metabolism is regulated by the LH surge, altered by obesity and reproductive aging, and, in women, specific metabolic profiles are associated with failed fertilization versus increased blastocyst development.

WHAT IS KNOWN ALREADY

The cellular environment in which an oocyte matures is critical to its future developmental competence. Metabolism is emerging as a potentially important factor; however, relative energy production profiles between GCs and cumulus cells and their use of differential substrates under normal in vivo ovulatory conditions are not well understood.

STUDY DESIGN, SIZE, DURATION

This study identified metabolic and substrate utilization profiles within ovarian cells in response to the LH surge, using mouse models and GCs of women undergoing gonadotropin-induced oocyte aspiration followed by IVF/ICSI.

PARTICIPANTS/MATERIALS, SETTING, METHODS

To comprehensively assess follicular energy metabolism, we used real-time metabolic analysis (Seahorse XFe96) to map energy metabolism dynamics (mitochondrial respiration, glycolysis, and fatty acid oxidation) in mouse GCs and cumulus-oocyte complexes (COCs) across a detailed time course in the lead up to ovulation. In parallel, the metabolic profile of GCs was measured in a cohort of 85 women undergoing IVF/ICSI (n = 21 with normal ovarian function; n = 64 with ovarian infertility) and correlated with clinical parameters and cycle outcomes.

MAIN RESULTS AND THE ROLE OF CHANCE

Our study reveals dynamic changes in GC energy metabolism in response to ovulatory LH, with mitochondrial respiration and glycolysis differentially affected by obesity versus aging, in both mice and women. High respiration in GCs is associated with failed fertilization (P < 0.05) in a subset of women, while glycolytic reserve and mitochondrial ATP production are correlated with on-time development at Day 3 (P < 0.05) and blastocyst formation (P < 0.01) respectively. These data provide new insights into the cellular mechanisms of infertility, by uncovering significant associations between metabolism within the ovarian follicle and oocyte developmental competence.

LIMITATIONS, REASONS FOR CAUTION

A larger prospective study is needed before the metabolic markers that were positively and negatively associated with oocyte quality can be used clinically to predict embryo outcomes.

WIDER IMPLICATIONS OF THE FINDINGS

This study offers new insights into the importance of GC metabolism for subsequent embryonic development and highlights the potential for therapeutic strategies focused on optimizing mitochondrial metabolism to support embryonic development.

STUDY FUNDING/COMPETING INTEREST(S)

National Health and Medical Research Council (Australia). The authors have no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

The impact of obesity on reproductive health and metabolism in reproductive-age females

Obesity is a highly prevalent chronic disease that impacts >40% of reproductive-aged females. The pathophysiology of obesity is complex and can be understood simply as a chronic energy imbalance whereby caloric intake exceeds caloric expenditure with an energy surplus stored in adipose tissue. Obesity may be categorized into degrees of severity as well as different phenotypes on the basis of metabolic health and underlying pathophysiology. Obesity and excess adiposity have a significant impact on fertility and reproductive health, with direct effects on the hypothalamic-pituitary-ovarian axis, the ovary and oocyte, and the endometrium. There are significant adverse pregnancy outcomes related to obesity, and excess weight gain before, during, and after pregnancy that can alter the lifelong risk for metabolically unhealthy obesity. Given the high prevalence and pervasive impact of obesity on reproductive health, there is a need for better and individualized care for reproductive-aged females that considers obesity phenotype, underlying pathophysiology, and effective and sustainable interventions to treat obesity and manage weight gain before, during, and after pregnancy.

Impact of body mass index on assisted reproductive technology outcomes in patients with polycystic ovary syndrome: a meta-analysis

The effect of obesity on pregnancy outcomes of patients with polycystic ovary syndrome (PCOS) undergoing assisted reproductive technology (ART) remains unclear. As such, a meta-analysis of recent studies was conducted to probe the effect of being overweight or obese on ART pregnancy outcomes in patients with PCOS. PubMed, Embase, MEDLINE, Scopus and Web of Science were searched from inception to 22 July 2023 without language restrictions. The main indicators were: live birth rate, clinical pregnancy rate, spontaneous abortion rate and multiple pregnancy rate. Ten studies were analysed, with a combined sample size of 247,845. Among patients with PCOS undergoing ART who were overweight or obese, the live birth rate, clinical pregnancy rate, implantation rate and number of retrieved oocytes were lower than in normal-weight patients with PCOS, and the spontaneous abortion rate was higher than in normal-weight patients with PCOS. Obese patients with PCOS undergoing ART had a lower multiple pregnancy rate and a lower number of mature oocytes compared with normal-weight patients with PCOS. The data showed that, among patients with PCOS, being overweight or obese has a negative effect on ART pregnancy outcomes. This meta-analysis may inform guidelines for pregnancy with ART, and encourage overweight or obese patients with PCOS to lose weight.

Long-chain acyl-CoA synthetase-4 regulates endometrial decidualization through a fatty acid β-oxidation pathway rather than lipid droplet accumulation

OBJECTIVE

Lipid metabolism plays an important role in early pregnancy, but its effects on decidualization are poorly understood. Fatty acids (FAs) must be esterified by fatty acyl-CoA synthetases to form biologically active acyl-CoA in order to enter the anabolic and/or catabolic pathway. Long-chain acyl-CoA synthetase 4 (ACSL4) is associated with female reproduction. However, whether it is involved in decidualization is unknown.

METHODS

The expression of ACSL4 in human and mouse endometrium was detected by immunohistochemistry. ACSL4 levels were regulated by the overexpression of ACSL4 plasmid or ACSL4 siRNA, and the effects of ACSL4 on decidualization markers and morphology of endometrial stromal cells (ESCs) were clarified. A pregnant mouse model was established to determine the effect of ACSL4 on the implantation efficiency of mouse embryos. Modulation of ACSL4 detects lipid anabolism and catabolism.

RESULTS

Through examining the expression level of ACSL4 in human endometrial tissues during proliferative and secretory phases, we found that ACSL4 was highly expressed during the secretory phase. Knockdown of ACSL4 suppressed decidualization and inhibited the mesenchymal-to-epithelial transition induced by MPA and db-cAMP in ESCs. Further, the knockdown of ACSL4 reduced the efficiency of embryo implantation in pregnant mice. Downregulation of ACSL4 inhibited FA β-oxidation and lipid droplet accumulation during decidualization. Interestingly, pharmacological and genetic inhibition of lipid droplet synthesis did not affect FA β-oxidation and decidualization, while the pharmacological and genetic inhibition of FA β-oxidation increased lipid droplet accumulation and inhibited decidualization. In addition, inhibition of β-oxidation was found to attenuate the promotion of decidualization by the upregulation of ACSL4. The decidualization damage caused by ACSL4 knockdown could be reversed by activating β-oxidation.

CONCLUSIONS

Our findings suggest that ACSL4 promotes endometrial decidualization by activating the β-oxidation pathway. This study provides interesting insights into our understanding of the mechanisms regulating lipid metabolism during decidualization.

Intermittent fasting improves the oocyte quality of obese mice through the regulation of maternal mRNA storage and translation by LSM14B

Obesity has significant repercussions for female reproductive health, including adverse effects on oocyte quality, fertility, embryo development and offspring health. Here, we showed that intermittent fasting (IF) has several notable effects on follicular development, oocyte development and maturation and offspring health in obese mice. IF treatment prevents obesity-associated germline-soma communication defects, mitochondrial dysfunction, oxidative damage, apoptosis, and spindle/chromosomal disruption. RNA-sequencing analysis of oocytes from normal diet (ND), high-fat diet (HFD), and HFD + IF mice indicated that IF treatment improved mitochondrial oxidative phosphorylation function and mRNA storage and translation, which was potentially mediated by the Smith-like family member 14 B (LSM14B). Knockdown of LSM14B by siRNA injection in oocytes from ND mice recapitulates all the translation, mitochondrial dysfunction and meiotic defect phenotypes of oocytes from HFD mice. Remarkably, the injection of Lsm14b mRNA into oocytes from HFD mice rescued the translation, mitochondrial dysfunction and meiotic defect phenotypes. These results demonstrated that dysfunction in the oocyte translation program is associated with obesity-induced meiotic defects, while IF treatment increased LSM14B expression and maternal mRNA translation and restored oocyte quality. This research has important implications for understanding the effects of obesity on female reproductive health and offers a potential nonpharmacological intervention to improve oocyte quality and fertility in obese individuals.

Follicular metabolic alterations are associated with obesity in mares and can be mitigated by dietary supplementation

Obesity is a growing concern in human and equine populations, predisposing to metabolic pathologies and reproductive disturbances. Cellular lipid accumulation and mitochondrial dysfunction play an important role in the pathologic consequences of obesity, which may be mitigated by dietary interventions targeting these processes. We hypothesized that obesity in the mare promotes follicular lipid accumulation and altered mitochondrial function of oocytes and granulosa cells, potentially contributing to impaired fertility in this population. We also predicted that these effects could be mitigated by dietary supplementation with a combination of targeted nutrients to improve follicular cell metabolism. Twenty mares were grouped as: Normal Weight [NW, n = 6, body condition score (BCS) 5.7 ± 0.3], Obese (OB, n = 7, BCS 7.7 ± 0.2), and Obese Diet Supplemented (OBD, n = 7, BCS 7.7 ± 0.2), and fed specific feed regimens for ≥ 6 weeks before sampling. Granulosa cells, follicular fluid, and cumulus-oocyte complexes were collected from follicles ≥ 35 mm during estrus and after induction of maturation. Obesity promoted several mitochondrial metabolic disturbances in granulosa cells, reduced L-carnitine availability in the follicle, promoted lipid accumulation in cumulus cells and oocytes, and increased basal oocyte metabolism. Diet supplementation of a complex nutrient mixture mitigated most of the metabolic changes in the follicles of obese mares, resulting in parameters similar to NW mares. In conclusion, obesity disturbs the equine ovarian follicle by promoting lipid accumulation and altering mitochondrial function. These effects may be partially mitigated with targeted nutritional intervention, thereby potentially improving fertility outcomes in the obese female.

Oocyte Aging: A Multifactorial Phenomenon in A Unique Cell

The oocyte is considered to be the largest cell in mammalian species. Women hoping to become pregnant face a ticking biological clock. This is becoming increasingly challenging as an increase in life expectancy is accompanied by the tendency to conceive at older ages. With advancing maternal age, the fertilized egg will exhibit lower quality and developmental competence, which contributes to increased chances of miscarriage due to several causes such as aneuploidy, oxidative stress, epigenetics, or metabolic disorders. In particular, heterochromatin in oocytes and with it, the DNA methylation landscape undergoes changes. Further, obesity is a well-known and ever-increasing global problem as it is associated with several metabolic disorders. More importantly, both obesity and aging negatively affect female reproduction. However, among women, there is immense variability in age-related decline of oocytes' quantity, developmental competence, or quality. Herein, the relevance of obesity and DNA-methylation will be discussed as these aspects have a tremendous effect on female fertility, and it is a topic of continuous and widespread interest that has yet to be fully addressed for the mammalian oocyte.

Effect of hyperlipidemia on the outcome of in vitro fertilization in non-obese patients with polycystic ovary syndrome

Introduction

It is little known whether hyperlipidemia alone has adverse effects on the outcome of in vitro fertilization (IVF) in patients with polycystic ovarian syndrome (PCOS).

Methods

The PCOS patients with body mass index (BMI) < 30 kg/m2 were performed IVF or intracytoplasmic sperm injection treatment, including 208 fresh cycles and 127 frozen embryo transfer (FET) cycles. All the patients were divided into hyperlipidemia and control groups, and embryo quality and pregnancy outcomes between the two groups were compared.

Results

In the fresh cycles, total gonadotropin dosage in the control group was significantly lower than that in the hyperlipidemia group, and serum estradiol levels on trigger day were reversed (P < 0.05). The embryo fragment score was positively correlated with serum low-density lipoprotein level (r = 0.06, P < 0.05) and negatively with serum high-density lipoprotein (HDL) and lipoprotein A levels (r = -0.489 and -0.085, P < 0.01). Logistic regression analysis found that HDL was beneficial for clinical pregnancy (OR = 0.355, 95% CI: 0.135-0.938, P < 0.05). In the FET cycles, there were no differences in pulse index, systolic/diastolic ratio and serum estradiol and progesterone levels between the two groups, but resistance index in the hyperlipidemia group was significantly higher than that in the control group (P < 0.05).

Conclusion

Hyperlipidemia may increase the dosage of gonadotropin and have adverse effect on the embryo quality, endometrial receptivity, and clinical outcomes of lean PCOS patients. It is recommended that the non-obese patients with hyperlipidemia and PCOS perform lipid-lowering treatment before undergoing embryo transfer.

The impact of a maternal and offspring obesogenic diet on daughter's oocyte mitochondrial ultrastructure and bioenergetic responses. Insights from an outbred mouse model

Obesity affects oocyte mitochondrial functions and reduces oocyte quality and fertility. Obesity may also increase the risk of metabolic disorders in the offspring. Children are likely to follow their parents lifestyle and diet, which also contributes to the increased prevelance of obesity across generations. We hypothesise that the impact of obesogenic (OB) diet and obesity on oocyte mitochondrial functions is different in offspring born to obese mothers compared to those born to healthy mothers. To test this hypothesis, we fed a control (C, 10% fat, 7% sugar) or an OB diet (60% fat, 20% sugar) to female mice (for 7 weeks (w)) and then to their female offspring (for 7w after weaning) in a 2 × 2 factorial design (C » C, n = 35, C » OB, n = 35, OB » C n = 49 and OB » OB, n = 50). Unlike many other studies, we used an outbred Swiss mouse model to increase the human pathophysiological relevance. Offspring were sacrificed at 10w and their oocytes were collected. Offspring OB diet increased oocyte lipid droplet content, mitochondrial activity and reactive oxygen species (ROS) levels, altered mitochondrial ultrastructure and reduced oocyte pyruvate consumption. Mitochondrial DNA copy numbers and lactate production remained unaffected. Mitochondrial ultrastructure was the only factor where a significant interaction between maternal and offspring diet effect was detected. The maternal OB background resulted in a small but significant increase in offspring's oocyte mitochondrial ultrastructural abnormalities without altering mitochondrial inner membrane potential, active mitochondrial distribution, mitochondrial DNA copy numbers, or ROS production. This was associated with reduced mitochondrial complex III and V expression and reduced pyruvate consumption which may be compensatory mechanisms to control mitochondrial inner membrane potential and ROS levels. Therefore, in this Swiss outbred model, while offspring OB diet had the largest functional impact on oocyte mitochondrial features, the mitochondrial changes due to the maternal background appear to be adaptive and compensatory rather than dysfunctional.

Alteration of the embryonic microenvironment and sex-specific responses of the preimplantation embryo related to a maternal high-fat diet in the rabbit model

The maternal metabolic environment can be detrimental to the health of the offspring. In a previous work, we showed that maternal high-fat (HH) feeding in rabbit induced sex-dependent metabolic adaptation in the fetus and led to metabolic syndrome in adult offspring. As early development representing a critical window of susceptibility, in the present work we aimed to explore the effects of the HH diet on the oocyte, preimplantation embryo and its microenvironment. In oocytes from females on HH diet, transcriptomic analysis revealed a weak modification in the content of transcripts mainly involved in meiosis and translational control. The effect of maternal HH diet on the embryonic microenvironment was investigated by identifying the metabolite composition of uterine and embryonic fluids collected in vivo by biomicroscopy. Metabolomic analysis revealed differences in the HH uterine fluid surrounding the embryo, with increased pyruvate concentration. Within the blastocoelic fluid, metabolomic profiles showed decreased glucose and alanine concentrations. In addition, the blastocyst transcriptome showed under-expression of genes and pathways involved in lipid, glucose and amino acid transport and metabolism, most pronounced in female embryos. This work demonstrates that the maternal HH diet disrupts the in vivo composition of the embryonic microenvironment, where the presence of nutrients is increased. In contrast to this nutrient-rich environment, the embryo presents a decrease in nutrient sensing and metabolism suggesting a potential protective process. In addition, this work identifies a very early sex-specific response to the maternal HH diet, from the blastocyst stage.

Bariatric surgery and reproduction-implications for gynecology and obstetrics

As the rates of obesity continue to rise across the world, there has been an increasing resort to bariatric surgery amongst the options for treatment. Through the reproductive lifespan, between menarche and menopause, women might benefit from this surgical intervention, which may have a bearing on other aspects of their health. The consequences of bariatric surgery have been reported and evaluated from various perspectives in obstetrics and gynecology. Fertility and sexuality are enhanced, but not all gynecological diseases are ameliorated. There are also psychological and behavioral sequelae to be cognizant of. With multi-disciplinary and responsive care, most post-bariatric pregnancies have satisfactory outcomes. The effects of bariatric surgery on the babies conceived thereafter remains a subject of interest, whereas the possible effect on the climacteric is speculative.

How the Oviduct Lipidomic Profile Changes over Time after the Start of an Obesogenic Diet in an Outbred Mouse Model

We investigated whether a high-fat/high-sugar (HF/HS) diet alters the lipidomic profile of the oviductal epithelium (OE) and studied the patterns of these changes over time. Female outbred Swiss mice were fed either a control (10% fat) or HF/HS (60% fat, 20% fructose) diet. Mice (n = 3 per treatment per time point) were sacrificed and oviducts were collected at 3 days and 1, 4, 8, 12 and 16 weeks on the diet. Lipids in the OE were imaged using matrix-assisted laser desorption ionisation mass spectrometry imaging. Discriminative m/z values and differentially regulated lipids were determined in the HF/HS versus control OEs at each time point. Feeding the obesogenic diet resulted in acute changes in the lipid profile in the OE already after 3 days, and thus even before the development of an obese phenotype. The changes in the lipid profile of the OE progressively increased and became more persistent after long-term HF/HS diet feeding. Functional annotation revealed a differential abundance of phospholipids, sphingomyelins and lysophospholipids in particular. These alterations appear to be not only caused by the direct accumulation of the excess circulating dietary fat but also a reduction in the de novo synthesis of several lipid classes, due to oxidative stress and endoplasmic reticulum dysfunction. The described diet-induced lipidomic changes suggest alterations in the OE functions and the oviductal microenvironment which may impact crucial reproductive events that take place in the oviduct, such as fertilization and early embryo development.

Effect of high-fat diet on the lipid profile of ovarian granulosa cells and female reproduction in mice

Currently, comorbidities of obesity are becoming increasingly frequent. For example, obese women are more susceptible to reproductive diseases; however, the underlying mechanism remains poorly understood. The present study aimed to explore the effect of obesity on female reproduction and discuss changes of the lipid profile in ovarian granulosa cells. Fifty female mice were randomly divided into two groups, one group was fed high-fat diet, the other group was fed standard control diet, food and water freely. After 12 weeks of feeding, the average body weight of the high-fat diet mice (19.027g) was significantly higher than that of the standard control diet mice (36.877g) (P < 0.05). The tissue sections were stained with oil red O, and the online software mage Pro plus 6.0 analyzed the staining results, the lipids in the ovaries and endometria were found to be different between the two groups. Liquid chromatography-electrospray ionization with tandem mass spectrometry (LC-ESI-MS/MS) analysis of ovarian granulosa cells (GCs) was performed, with a total of 228 different lipids being identified, the abundant of 147 were increased and 81 were decreased in the high-fat diet group. Among them, PI (18:1/20:1) was the most different lipid, and high-fat feeding was 85 times higher than standard control group. Among these different lipids, 44% in phospholipid metabolism, 30% in glycerolipid metabolism, and 30% in fat digestion and absorption. The results of this study laid a theoretical foundation of the effects of diet-induced obesity on female reproduction.

Perception and Practice of Bariatric Surgery and Reproductive Health in Women: a Cross-sectional Study of Chinese Bariatric Surgeons

BACKGROUND AND PURPOSE

Western studies have explored bariatric surgeons concerning their views on bariatric surgery (BS) and reproductive health, but Asian data were lacking. The aim of this study was to explore the perception and practice of bariatric surgeons on the reproductive health of female patients who underwent BS in China to better guide clinical practice and improve clinical outcomes.

METHOD

An online questionnaire of 31 questions developed by bariatric surgeons was collected by sending to one online communication group (WeChat group) whose members are Chinese bariatric surgeons.

RESULT

A total of 87 bariatric surgeons from mainland China were surveyed. Almost all (97.7%, 85/87) surgeons considered the reproductive health conversation for women who underwent BS to be important or very important. Only 1/4 of surgeons routinely discuss reproductive health-related issues with patients, and only 56% of doctors always ask patients for postoperative contraception. Less than 20% of bariatric surgeons have full knowledge of postoperative contraception, and nearly 40% of them believe that gynecologists should be responsible for providing contraception. More than 35% of bariatric surgeons have never been involved in the co-management of pregnancy in patients with a history of BS.

CONCLUSION

Although most bariatric surgeons are aware of the importance of female reproductive health, there is a large gap in the perception and clinical practice of bariatric surgeons in terms of reproductive health. It is necessary to further strengthen the education of bariatric surgeons and enhance multidisciplinary cooperation with gynecology, obstetrics, and other disciplines to bring better clinical outcomes.

Obesity management in women of reproductive age

With the increasing prevalence of obesity among women of reproductive age, the detrimental effects on maternal and neonatal health are increasing. The objective of this review is to summarise the evidence that comprehensive management of weight control in women of reproductive age has on maternal-fetal outcomes. First, the impact that obesity has on fertility and pregnancy is described and then the specific aspects of continued weight management in each of the stages (preconception, pregnancy and postpartum) during these years are outlined, not only to benefit women affected by obesity before pregnancy, but also to avoid and reverse weight gain during pregnancy that complicates future pregnancies. Finally, the special planning and follow-up needs of women with a history of bariatric surgery are discussed in order to avoid nutritional deficiencies and/or surgical complications that endanger the mother or affect fetal development.

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

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

Obesity and reproduction

PURPOSE OF REVIEW

The objective of this review is to highlight the recent literature on how obesity affects reproductive capacity in men and women.

RECENT FINDINGS

The relationship between fertility and obesity is complex and involves the hypothalamic-pituitary-ovarian axis, neuroendocrine systems and adipose tissue. The exact pathophysiology of how obesity lowers fertility rates is unknown, but is likely multifactorial involving anovulation, insulin resistance and alterations in gonadotropins. In addition, there is controversy on whether oocyte quality or endometrial receptivity plays a larger role in obese infertile women. Data on effects of bariatric surgery and weight loss on obese infertile men and women are mixed.

SUMMARY

Obesity alters the hormonal profile, gonadotropin secretion, embryo development and in-vitro fertilization outcomes in both men and women.

Lipid metabolism and endometrial receptivity

BACKGROUND

Obesity has now been recognized as a high-risk factor for reproductive health. Although remarkable advancements have been made in ART, a considerable number of infertile obese women still suffer from serial implantation failure, despite the high quality of embryos transferred. Although obesity has long been known to exert various deleterious effects on female fertility, the underlying mechanisms, especially the roles of lipid metabolism in endometrial receptivity, remain largely elusive.

OBJECTIVE AND RATIONALE

This review summarizes current evidence on the impacts of several major lipids and lipid-derived mediators on the embryonic implantation process. Emerging methods for evaluating endometrial receptivity, for example transcriptomic and lipidomic analysis, are also discussed.

SEARCH METHODS

The PubMed and Embase databases were searched using the following keywords: (lipid or fatty acid or prostaglandin or phospholipid or sphingolipid or endocannabinoid or lysophosphatidic acid or cholesterol or progesterone or estrogen or transcriptomic or lipidomic or obesity or dyslipidemia or polycystic ovary syndrome) AND (endometrial receptivity or uterine receptivity or embryo implantation or assisted reproductive technology or in vitro fertilization or embryo transfer). A comprehensive literature search was performed on the roles of lipid-related metabolic pathways in embryo implantation published between January 1970 and March 2022. Only studies with original data and reviews published in English were included in this review. Additional information was obtained from references cited in the articles resulting from the literature search.

OUTCOMES

Recent studies have shown that a fatty acids-related pro-inflammatory response in the embryo-endometrium boundary facilitates pregnancy via mediation of prostaglandin signaling. Phospholipid-derived mediators, for example endocannabinoids, lysophosphatidic acid and sphingosine-1-phosphate, are associated with endometrial receptivity, embryo spacing and decidualization based on evidence from both animal and human studies. Progesterone and estrogen are two cholesterol-derived steroid hormones that synergistically mediate the structural and functional alterations in the uterus ready for blastocyst implantation. Variations in serum cholesterol profiles throughout the menstrual cycle imply a demand for steroidogenesis at the time of window of implantation (WOI). Since 2002, endometrial transcriptomic analysis has been serving as a diagnostic tool for WOI dating. Numerous genes that govern lipid homeostasis have been identified and, based on specific alterations of lipidomic signatures differentially expressed in WOI, lipidomic analysis of endometrial fluid provides a possibility for non-invasive diagnosis of lipids alterations during the WOI.

WIDER IMPLICATIONS

Given that lipid metabolic dysregulation potentially plays a role in infertility, a better understanding of lipid metabolism could have significant clinical implications for the diagnosis and treatment of female reproductive disorders.