Lipid concentrations and couple fecundity: the LIFE study

Lipid Disorders and Pregnancy

Practicing endocrinologists are likely to confront 2 major issues that occur with dyslipidemias during pregnancy. The most dramatic is the development of severe hypertriglyceridemia leading to acute pancreatitis. The second is the approach to treatment of familial hypercholesterolemia, a common genetic disorder. This article reviews the normal physiology and the pathophysiology of lipoproteins that occurs with pregnancy and then discusses the approaches to prevention and/or treatment of dyslipidemia in pregnancy with a focus on lifestyle and acceptable drug therapies.

Proteomic Analysis Identifies Distinct Protein Patterns for High Ovulation in FecB Mutant Small Tail Han Sheep Granulosa Cells

The Booroola fecundity (FecB) mutation in the bone morphogenetic protein receptor type 1B (BMPR1B) gene increases ovulation in sheep. However, its effect on follicular maturation is not fully understood. Therefore, we collected granulosa cells (GCs) at a critical stage of follicle maturation from nine wild-type (WW), nine heterozygous FecB mutant (WB), and nine homozygous FecB mutant (BB) Small Tail Han sheep. The GCs of three ewes were selected at random from each genotype and consolidated into a single group, yielding a total of nine groups (three groups per genotype) for proteomic analysis. The tandem mass tag technique was utilized to ascertain the specific proteins linked to multiple ovulation in the various FecB genotypes. Using a general linear model, we identified 199 proteins significantly affected by the FecB mutation with the LIMMA package (p < 0.05). The differential abundance of proteins was enriched in pathways related to cholesterol metabolism, carbohydrate metabolism, amino acid biosynthesis, and glutathione metabolism. These pathways are involved in important processes for GC-regulated 'conservation' of oocyte maturation. Further, the sparse partial least-squares discriminant analysis and the Fuzzy-C-mean clustering method were combined to estimate weights and cluster differential abundance proteins according to ovulation to screen important ovulation-related proteins. Among them, ZP2 and ZP3 were found to be enriched in the cellular component catalog term "egg coat", as well as some apolipoproteins, such as APOA1, APOA2, and APOA4, enriched in several Gene Ontology terms related to cholesterol metabolism and lipoprotein transport. A higher abundance of these essential proteins for oocyte maturation was observed in BB and WB genotypes compared with WW ewes. These proteins had a high weight in the model for discriminating sheep with different FecB genotypes. These findings provide new insight that the FecB mutant in GCs improves nutrient metabolism, leading to better oocyte maturation by altering the abundance of important proteins (ZP2, ZP3, and APOA1) in favor of increased ovulation or better oocyte quality.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Sex differences in lipids: A life course approach

Differences between men and women in lipids and lipoproteins are observed in distribution and trajectory from infancy to adulthood in the general population. However, these differences are more pronounced in hereditary lipid disorders such as familial hypercholesterolemia (FH) when absolute cholesterol levels are higher from birth onwards. In the early life course, girls compared to boys have higher low-density lipoprotein cholesterol (LDL-C) levels and total cholesterol, while high-density lipoprotein cholesterol (HDL-C) levels are similar. In early adulthood to middle-age, women have lower LDL-C and higher HDL-C levels, as LDL-C levels increase and HDLC levels decrease in men. In the elderly, all lipids - total cholesterol, LDL-C, HDL-C and triglyceride levels decrease but are more pronounced in men. Lipid levels are also affected by specific transitions in girls/women such as the menstrual cycle, pregnancy, breastfeeding and menopause. Lipid levels fluctuate during the menstrual cycle. During pregnancy a physiological increase of LDL-C and even a larger increase in triglyceride levels are observed. Pregnancy has a double impact on LDL-C accumulation in women with FH as they have to stop statins, and the absolute increase in LDL-C is higher than in women without FH. In the menopausal transition, women develop a more adverse lipid profile. Therefore, it is important to take into account both sex and the life course when assessing a lipid profile.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.

Lipid Metabolic Genes and Maternal Supraphysiological Hypercholesterolemia: An Analysis of Maternal-fetal Interaction

CONTEXT

The joint associations of maternal and fetal single nucleotide polymorphisms (SNPs) of lipid metabolic genes with the risk of maternal supraphysiological hypercholesterolemia (MSPH) are unclear.

OBJECTIVE

This study aims to investigate the associations of maternal/fetal SNPs of APOE, LPL, LDLR, PCSK9, and SCARB1 with the risk of MSPH and explore whether the maternal-fetal pairing pattern of the risk alleles can affect MSPH risk.

METHODS

A nested case-control study was conducted that included 182 pregnant women with MSPH and 182 with maternal physiological hypercholesterolemia. Maternal venous and umbilical venous blood were collected to detect the SNPs of genes. The primary outcome was MSPH. Logistic regression model was used to determine the associations of SNPs with risk of MSPH.

RESULTS

The C-allele in maternal APOE rs429358 T > C (adjusted odds ratio [OR] = 1.72, P = 0.033), G-allele in fetal APOE rs440446 C > G (adjusted OR = 1.62, P = 0.012) and T-allele in fetal LPL rs263 C > T (adjusted OR = 1.53, P = 0.011) increased the risk of MSPH. The A-allele in maternal LDLR rs7258950 G > A decreased the risk of MSPH (adjusted OR = 0.67, P = 0.028). For maternal-fetal pairing analysis, the variant concordance of PCSK9 rs2149041, rs7523141, rs7523242, rs7525649, and LDLR rs7258950 were associated with the decreased risk of MSPH under the dominant model. The variant concordance of other SNPs of PCSK9, APOE, LDLR, LPL, and SCARB1 were associated with the increased risk of MSPH.

CONCLUSION

This study supports the hypothesis that maternal and fetal genetic polymorphisms of lipid metabolic genes are associated with the risk of MSPH. The maternal-fetal variant concordance is also associated with this risk.

The current situation and future directions for the study on time-to-pregnancy: a scoping review

Introduction

As problems associated with infertility and population aging increase, there is a growing interest in the factors that cause a decline in human fertility. Time-to-pregnancy (TTP) is a good indicator with which to reflect human fecundability. Here, we present a comprehensive overview of this topic.

Methods

Relevant qualitative and quantitative studies were identified by searching the Web of science and PubMed electronic databases. We included all literature, written in English, from inception to the 10th April 2021 providing the focus was on TTP. We conducted a narrative synthesis using thematic analysis.

Results

Traditional TTP-related study protocols include prospective and retrospective cohorts that provide a wealth of data to reveal potential influences on TTP. Thus far, a variety of factors have been shown to be associated with TTP in couples preparing for pregnancy, including basic demographic characteristics, menstrual status, chronic disease status, environmental endocrine disruptor exposure, and lifestyles. However, there are inevitable epidemiological bias in the existing studies, including recall bias, selection bias and measurement bias. Some methodological advances have brought new opportunities to TTP research, which make it possible to develop precision interventions for population fertility. Future TTP studies should take advantage of artificial intelligence, machine learning, and high-throughput sequencing technologies, and apply medical big data to fully consider and avoid possible bias in the design.

Conclusion

There are many opportunities and future challenges for TTP related studies which would provide a scientific basis for the “precise health management” of the population preparing for pregnancy.

As the problems of infertility and population aging increase, there is a growing interest in the factors that cause a decline in human fertility. Time-to-pregnancy (TTP) is a good indicator with which to reflect human fecundability, and a longer TTP is known to reflect a reduction in fertility. Many original studies, with different designs, have used TTP to explore the factors that might influence fertility, including basic demographic characteristics, chronic disease status, environmental endocrine disruptor exposure, and lifestyles. However, much of the existing evidence is inconsistent and limited by various types of bias. This review provides a synopsis of recent TTP studies, and highlights new opportunities and future challenges.

Metabolic health status and fecundability in a Singapore preconception cohort study

BACKGROUND

Obesity compromises metabolic health and female fertility, yet not all obese women are similar in metabolic status. The extent to which fecundability is influenced by the metabolic health status of women who are overweight or obese before conception is unknown.

OBJECTIVE

This study aimed to: (1) determine the metabolic health status, and (2) examine the association between metabolic health status and fecundability of overweight and obese women trying to conceive in the Singapore PREconception Study of long-Term maternal and child Outcomes cohort study.

STUDY DESIGN

We conducted a prospective preconception cohort study of Asian women (Chinese, Malay, and Indian) aged 18 to 45 years trying to conceive who were treated from 2015 to 2017 in KK Women's and Children's Hospital in Singapore (n=834). We defined women to have metabolically unhealthy status if they: (1) met 3 or more modified Joint Interim Statement metabolic syndrome criteria; or (2) had homeostasis model assessment-insulin resistance index ≥2.5. Body mass index was categorized as normal (18.5-22.9 kg/m2), overweight (23-27.4 kg/m2), or obese (≥27.5 kg/m2) on the basis of cutoff points for Asian populations. Fecundability was measured by time to pregnancy in menstrual cycles within a year of enrolment. Discrete-time proportional hazards models were used to estimate fecundability odds ratios, with adjustment for confounders and accounting for left truncation and right censoring.

RESULTS

Of 232 overweight women, 28 (12.1%) and 25 (10.8%) were metabolically unhealthy by metabolic syndrome ≥3 criteria and homeostasis model assessment-insulin resistance ≥2.5, respectively. Of 175 obese women, 54 (30.9%) and 93 (53.1%) were metabolically unhealthy by metabolic syndrome ≥3 criteria and homeostasis model assessment-insulin resistance ≥2.5, respectively. Compared with metabolically healthy normal-weight women, lower fecundability was observed in metabolically unhealthy overweight women on the basis of metabolic syndrome criteria (fecundability odds ratios, 0.38 [95% confidence interval, 0.15-0.92]) and homeostasis model assessment-insulin resistance (fecundability odds ratios, 0.68 [95% confidence interval, 0.33-1.39]), with metabolic syndrome criteria showing a stronger association. Metabolically unhealthy obese women showed lower fecundability than the healthy normal-weight reference group by both metabolic syndrome (fecundability odds ratios, 0.35; 95% confidence interval, 0.17-0.72) and homeostasis model assessment-insulin resistance criteria (fecundability odds ratios, 0.43; 95% confidence interval, 0.26-0.71). Reduced fecundability was not observed in overweight or obese women who showed healthy metabolic profiles by either definition.

CONCLUSION

Overweight or obesity was not synonymous with having metabolic syndrome or insulin resistance. In our preconception cohort, metabolically unhealthy overweight and obese women showed reduced fecundability, unlike their counterparts who were metabolically healthy. These findings suggest that metabolic health status, rather than simply being overweight and obese per se, plays an important role in fecundability.

Diet and pravastatin administration prior to in vitro fertilization treatment may improve pregnancy outcome in women with dyslipidemia

In this study, we aimed to identify whether using statins may increase the chance of pregnancy in In Vitro Fertilisation / Intra-Cytoplasmic Sperm Injection (IVF/ICSI) patients with hyperlipidaemia. Therefore, in this retrospective cohort study, 70 patients constituted the study population and all patients were managed by lipid lowering diet. Ten mg pravastatin (pravachol DEVA, Istanbul, Turkey) was added to therapy in case of resistant hypercholesterolaemia after 15 days of the diet. Fifty-one patients were treated with diet only and the remaining nineteen patients were offered both diet and pravastatin. Clinical pregnancy rate was significantly better with the patients who used pravastatin (68.4% vs. 39.2%, p = .029). Ongoing pregnancy rates were 63.2% and 33.3% with pravastatin and diet only, respectively, which were statistically significant (p:.024). According to multivariate analysis, pravastatin use was found independently and statistically significant for clinical pregnancy and ongoing pregnancy rate after IVF/ICSI in patients with dyslipidemia (HR 3.79; 95% CI 1.31-10.97; p:.014 and HR 3.18; 95% CI 1.22-8.27; p:.018). When we analysed stratified data according to the AMH levels, we noticed that as AMH levels increased, the pregnancy rates increased; the most benefit from pravastatin was in the group with AMH levels >2 ng/mL.IMPACT STATEMENTWhat is already known on this subject? Dyslipidemia in In IVF/ICSI patients with polycystic ovary syndrome had negative impact on pregnancy ratesWhat the results of this study add? The findings of the study support that pravastatin may help to improve pregnancy outcome, especially in normal and high responders, regardless of whether decreased serum LDL or total cholesterol level.What the implications are of these findings for clinical practice and/or further research? As a result of our data, we speculated that it should be routine to investigate the lipid profile in every IVF/ICSI patient and should be treated accordingly, if necessary.

Stem Cell Therapies for Human Infertility: Advantages and Challenges

Physical and mental health and hormonal imbalance are associated with the problems related to infertility and reproductive disorders. The rate of infertility has increased globally over the years, due to various reasons. Given the psychosocial implications of infertility and its effects on the life of the affected people, there has been an increased focus on its treatment over the last several years. Assisted reproductive technology can only solve about 50% of the cases. Moreover, it contains significant risks and does not solve the fundamental problem of infertility. As pluripotent stem cells have the potential to differentiate into almost any type of cell, they have been widely regarded as a promising option in the development of stem cell-based fertility treatments, which could even correct genetic diseases in offspring. These advancements in reproductive biotechnology present both challenges and possibilities for solving infertility problems caused by various unexplainable factors. This review briefly presents the different types of infertility disorders and the potential applications of stem cells in the treatment of these reproductive diseases.

Associations between dyslipidaemia and pregnancy outcomes in the first complete cycle of IVF/ICSI: a real-world analysis

RESEARCH QUESTION

Are there associations between dyslipidaemia and pregnancy outcomes in the first complete cycle of IVF/intracytoplasmic sperm injection (ICSI)?

DESIGN

This long-term, retrospective real-world analysis involved 5030 infertile women who underwent a first complete IVF/ICSI cycle between January 2015 and October 2020. They were categorized into dyslipidaemia (n = 1903) and control (n = 3127) groups according to serum lipid concentrations before ovarian stimulation. Propensity score matching and multivariable logistic regression were used to control for confounding variables.

RESULTS

In the raw cohort, women with dyslipidaemia had a significantly increased late miscarriage rate (P = 0.039), decreased term birth rate (P = 0.002) and decreased live birth rate (P = 0.005) compared with non-dyslipidaemic women. In the propensity score-matched cohort, the term birth rate (P = 0.038) and live birth rate (P = 0.044) were significantly lower in the dyslipidaemia group (n = 1686) than the controls (n = 1686). Multivariable logistic regression indicated that infertile women with dyslipidaemia (P = 0.026) and elevated serum total cholesterol concentrations (total cholesterol ≥5.20 mmol/l; P = 0.028) were significantly less likely to have a live birth. Rates of late miscarriage (P = 0.027), term birth (P = 0.003) and live birth (P = 0.010) differed significantly among women with normal, borderline increased and increased serum lipid concentrations. Compared with controls, women with increased serum lipid concentrations had a significantly higher late miscarriage rate, lower term birth rate and lower live birth rate. Women with increased serum lipid concentrations were significantly less likely than controls to have a live birth.

CONCLUSIONS

Dyslipidaemia, total cholesterol ≥5.20 mmol/l and degrees of elevated serum lipid concentrations are negatively associated with live birth rate in the first complete IVF/ICSI cycle in infertile women.

Maternal hypercholesterolemia programs dyslipidemia in adult male mouse progeny

As a collection of metabolic abnormalities including inflammation, insulin resistance, hypertension, hormone imbalance, and dyslipidemia, maternal obesity has been well-documented to program disease risk in adult offspring. Although hypercholesterolemia is strongly associated with obesity, less work has examined the programming influence of maternal hypercholesterolemia (MHC) independent of maternal obesity or high-fat feeding. This study was conducted to characterize how MHC per se impacts lipid metabolism in offspring. Female (n = 6/group) C57BL/6J mice were randomly assigned to: (1.) a standard chow diet (Control, CON) or (2.) the CON diet supplemented with exogenous cholesterol (CH) (0.15%, w/w) throughout mating and the gestation and lactation periods. At weaning (postnatal day (PND) 21) and adulthood (PND 84), male offspring were characterized for blood lipid and lipoprotein profile and hepatic lipid endpoints, namely cholesterol and triglyceride (TG) accumulation, fatty acid profile, TG production, and mRNA expression of lipid-regulatory genes. Both newly weaned and adult offspring from CH mothers demonstrated increased very low-density lipoprotein (VLDL) particle number and size and hepatic TG and n-6 polyunsaturated fatty acid accumulation. Further, adult CH offspring exhibited reduced fatty acid synthase (Fasn) and increased diglyceride acyltransferase (Dgat1) mRNA expression. These programming effects appear to be independent of changes in hepatic TG production and postprandial lipid clearance. Study results suggest that MHC, independent of obesity or high-fat feeding, can induce early changes to serum VLDL distribution and hepatic lipid profile that persist into adulthood.

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

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

The effect of statins on semen parameters in patients with hypercholesterolemia: A systematic review

BACKGROUND

Statins constitute the mainstay of treatment in patients with hypercholesterolemia. However, their effect on semen parameters is unknown.

OBJECTIVE

This study aimed to systematically review the best available evidence regarding the effect of statins on ejaculate volume and sperm concentration, motility, morphology, or vitality.

MATERIALS/METHODS

A comprehensive search was conducted in PubMed, CENTRAL and Scopus databases up to January 10, 2021. Either randomized-controlled trials or prospective cohorts, conducted in males with hypercholesterolemia, were included.

RESULTS

Four studies, published between 1992 and 2014, were eligible. The number of participants ranged from 8 to 120 (n = 161). Study duration ranged from 14 to 48 weeks. The type and dose of statin used were pravastatin 20-80 mg/day and simvastatin 20-40 mg/day. With regard to ejaculate volume (n = 3) and sperm concentration (n = 4), no effect was shown with either pravastatin or simvastatin. Regarding sperm motility, either an increase (n = 2; pravastatin, simvastatin), decrease (n = 1; pravastatin), or no effect (n = 1; pravastatin, simvastatin) was found. With respect to sperm morphology, either a decrease (n = 2; pravastatin, simvastatin) or no effect (n = 2; pravastatin, simvastatin) was shown. Concerning sperm vitality, a single study showed a decrease with simvastatin. Because of the high heterogeneity of the populations studied and the limited number of studies, a meta-analysis was not performed.

CONCLUSION

This is the first systematic review on the effect of statins on semen parameters. As there is no evidence for such a detrimental effect, no specific approach has to be suggested regarding the preservation of reproductive function in men with hypercholesterolemia.

Adiposity is associated with anovulation independent of serum free testosterone: A prospective cohort study

BACKGROUND

Obesity, a body mass index (BMI) ≥30 kg/m2 , is linked to infertility, potentially through a greater risk of anovulation due to elevated androgens. Yet, previous studies have not directly assessed the impact of adiposity, or body fat, on anovulation in the absence of clinical infertility.

OBJECTIVE

To characterise the associations between adiposity and anovulation among women menstruating on a regular basis.

METHODS

Women from the EAGeR trial (n = 1200), a randomised controlled trial of low-dose aspirin and pregnancy loss among women trying to conceive, were used to estimate associations between adiposity and incident anovulation. Participants completed baseline questionnaires and anthropometry, and provided blood specimens. Women used fertility monitors for up to six consecutive menstrual cycles, with collection of daily first morning voids for hormone analysis in the first two menstrual cycles for prospective assessment of anovulation. Anovulation was assessed by urine pregnanediol glucuronide or luteinising hormone concentration or the fertility monitor. Weighted mixed-effects log-binomial regression was used to estimate associations between measures of adiposity and incident anovulation, adjusted for free (bioavailable) testosterone, anti-Mullerian hormone (AMH), serum lipids, and demographic and life style factors.

RESULTS

343 (28.3%) women experienced at least one anovulatory cycle. Anovulation risk was higher per kg/m2 greater BMI (relative risk [RR] 1.03, 95% confidence interval (CI) 1.01, 1.04), cm waist circumference (RR 1.01, 95% CI 1.00, 1.02), mm subscapular skinfold (RR 1.02, 95% CI 1.01, 1.03), and mm middle upper arm circumference (RR 1.04, 95% CI 1.01, 1.06) adjusted for serum free testosterone, AMH, lipids, and other factors.

CONCLUSIONS

Adiposity may be associated with anovulation through pathways other than testosterone among regularly menstruating women. This may account in part for reported associations between greater adiposity and infertility among women having menstrual cycles regularly. Understanding the association between adiposity and anovulation might lead to targeted interventions for preventing infertility.

Serum Lipid Levels and Treatment Outcomes in Women Undergoing Assisted Reproduction: A Retrospective Cohort Study

OBJECTIVE

To evaluate associations between serum lipid levels and treatment outcomes in women undergoing assisted reproduction.

MATERIALS AND METHODS

The study included 2011 women who underwent in vitro fertilization/intracytoplasmic sperm injection with fresh embryo transfer. Serum lipid evaluation included total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG). Ovarian stimulation outcomes included endometrial thickness and the number of oocytes retrieved, and reproductive outcomes included live birth, clinical pregnancy, and miscarriage.

RESULTS

Higher HDL-C quartiles were associated with more oocytes retrieved. Lower TC (quartile 1 odds ratio [OR] 1.59 [1.21-2.08], quartile 3 OR 1.36 [1.04-1.77]), LDL-C (quartile 1 OR 1.41 [1.07-1.86]), and TG (quartile 2 OR 1.39 [1.06-1.84]) were independently associated with clinical pregnancy after adjusting for potential confounders. Lower LDL-C (quartile 1 OR 2.22 [1.58-3.13], quartile 2 OR 1.78 [1.27-2.50], quartile 3 OR 1.51 [1.07-2.13]), TC (quartile 1 OR 1.39 [1.00-1.93]), TG (quartile 1 OR 1.44 [1.03-2.03], quartile 2 OR 1.46 [1.04-2.04], quartile 3 OR 1.44 [1.04-1.99]), and higher HDL-C (quartile 2 OR 0.71 [0.51-0.99]) were independently associated with live birth. Higher LDL-C (quartile 1 OR 0.44 [0.30-0.66], quartile 2 OR 0.49 [0.33-0.73], quartile 3 OR 0.63 [0.43-0.94]) and lower HDL-C (quartile 1 OR 1.60 [1.07-2.39]) were independently associated with miscarriage.

CONCLUSIONS

Serum lipid levels were associated with treatment outcomes in women undergoing assisted reproduction.

Activation of nuclear factor-kappa B subunits c-Rel, p65 and p50 by plasma lipids and fatty acids across the menstrual cycle

This study focused on a comprehensive analysis of the canonical activation pathway of the redox-sensitive transcription factor nuclear factor-kappa B (NF-κB) in peripheral blood mononuclear cells, addressing c-Rel, p65 and p50 activation in 28 women at early (T1) and late follicular (T2) and mid (T3) and late luteal (T4) phase of the menstrual cycle, and possible relations with fasting plasma lipids and fatty acids. For the first time, strong inverse relations of c-Rel with apolipoprotein B were observed across the cycle, while those with LDL cholesterol, triglycerides as well as saturated (SFA), particularly C14-C22 SFA, monounsaturated (MUFA), and polyunsaturated fatty acids (PUFA) clustered at T2. In contrast, p65 was positively related to LDL cholesterol and total n-6 PUFA, while p50 did not show any relations. C-Rel was not directly associated with estradiol and progesterone, but data suggested an indirect C22:5n-3-mediated effect of progesterone. Strong positive relations between estradiol and individual SFA, MUFA and n-3 PUFA at T1 were confined to C18 fatty acids; C18:3n-3 was differentially associated with estradiol (positively) and progesterone (inversely). Given specific roles of c-Rel activation in immune tolerance, inhibition of c-Rel activation by higher plasma apolipoprotein B and individual fatty acid concentrations could have clinical implications for female fertility.

Vigilin interacts with ER-β to protect against palmitic acid-induced granulosa cells apoptosis via inhibiting calcineurin-mediated Drp1 signaling pathway

BACKGROUND

Hypercholesterolemia is one of the causes of female infertility, and as a common fatty acid in follicular fluid, palmitic acid (PA) level plays a vital role in granule cell which is closely related to the developmental potential of follicle.

METHODS

The ovarian granulosa cell-like human granulosa (KGN) cell line and the immortalized normal ovarian surface epithelial cell line (IOSE80) were used to verify the effect of PA on cell viability and apoptosis by MTT and flow cytometry assay, respectively. Then mitochondria damage was confirmed by mitochondrial membrane potential, mitochondrial ROS detection assay and western blot in KGN cells. Thorough luciferase reporter assay and RIP-qPCR, the relationship between vigilin and ER-β was investigated.

RESULTS

In our study, PA induced mitochondrial damage-mediated cell apoptosis of KGN cells was dose-dependently, while PA shown no effects on in IOSE80 cells. Then the role of calcineurin (CnA)-mediated Drp1 signaling pathway on KGN cells was confirmed by treating with Mdivi-1 or FK506T. In addition, the changed level of vigilin and ER-β was observed in cell apoptosis of KGN cells induced by PA. By transfecting vigilin vector or ER-β vector into KGN cells, respectively, vigilin and ER-β were demonstrated to regulate the apoptosis of KGN cells. And vigilin was a binding protein of ER-β mRNA.

CONCLUSION

Vigilin could interact with ER-β mRNA to promote ER-β expression. And Vigilin/ ER-β relieve the mitochondrial damage and cell apoptosis induced by PA through regulating CnA-mediated Drp1 signaling pathway, which revealed the mechanism and strategy of hypercholesterolemia in female infertility.

Women's age and total motile normal morphology sperm count predict fecundability: a prospective cohort study

OBJECTIVE

This study investigated the role of women's age, serum anti-Müllerian hormone (AMH) level and semen parameters in predicting fecundability.

METHODS

This was a prospective cohort study on couples attending for preconceptional health check. Occurrence of conception at 1 year after ceasing contraception and time to pregnancy were noted by telephone follow-up. The women's age, serum AMH level and total motile normal morphology sperm count (TMNC) were compared between those who conceived and those who did not after 1 year; their independent predictive value on conception at 1 year was analysed by logistic regression. Among those conceiving within 1 year, Spearman's correlations between time to pregnancy and the clinical parameters were studied.

RESULTS

Of the 100 couples analysed, we found younger age of the women (p=0.008), higher serum AMH level (p=0.038) and higher TMNC (p=0.015) in those that conceived within 1 year. Multivariate logistic regression found that women's age (OR 0.867, 95% CI 0.761 to 0.988, p=0.032) and TMNC (OR 1.089, 95% 1.001-1.185, p=0.047), but not serum AMH level, significantly predicted conception within 1 year. Among those that conceived within 1 year, none of the parameters analysed were correlated with time to pregnancy within 1 year.

CONCLUSIONS

Women's age and TNMC are significant independent predictors of conception within 1 year. No parameter was shown to predict the time to pregnancy within 1 year. This finding can aid preconceptional counselling of couples who are planning for pregnancy.

The effect of excess body fat on female and male reproduction

The dramatic increase in the prevalence of obesity coincides with a decline in reproductive health indices in both sexes. Energy excess mediates changes to the regulatory mechanisms of the reproductive system. Obese individuals exhibit increased estrogen concentrations, due to the overexpression of aromatase in the adipose tissue; via a negative feedback loop, men present with symptoms of hypogonadotropic hypogonadism. These hormonal changes, along with increased oxidative stress, lipotoxicity and disturbances in the concentrations of adipokines, directly affect the gonads, peripheral reproductive organs and the embryo. Clinical evidence is somewhat contradicting, with only some studies advocating worse semen parameters, increased incidence of erectile dysfunction, increased doses of ovulation induction medications, and worse live birth rates in assisted reproductive technology (ART) cycles in obese individuals compared with those of normal weight. Similar conclusions are drawn about patients with insulin resistance syndromes, namely polycystic ovary syndrome (PCOS). As far as treatment options are concerned, lifestyle changes, medical therapy and bariatric surgery may improve the reproductive outcome, although the evidence remains inconclusive. In this review, we summarize the evidence on the association of obesity and reproductive health on both the molecular and the clinical level, and the effect of weight-loss interventions on reproductive potential.

Gestational hypercholesterolemia alters fetal hepatic lipid metabolism and microRNA expression in Apo-E-deficient mice

Maternal hypercholesterolemia (MHC) is a pathological condition characterized by an exaggerated rise in maternal serum cholesterol during gestation, which can alter offspring hepatic lipid metabolism. However, the extent that these maladaptations occur during gestation and the molecular mechanisms involved remain unknown. MicoRNAs (miRNA) are small, noncoding RNAs that contribute to the development and progression of nonalcoholic fatty liver disease. Therefore, we sought to determine the degree to which in utero exposure to excessive cholesterol affects fetal hepatic lipid metabolism and miRNA expression. Twelve female apoE^-/- mice were randomly assigned to two different chow-based diets throughout gestation: control (CON) or the CON diet with cholesterol (0.15%). MHC reduced maternal fecundity and reduced litter size and weight. On gestational day 18, fetuses from MHC dams possessed increased placental cholesterol and hepatic triglycerides (TG), which were accompanied by a downregulation in the expression of hepatic lipogenic and TG synthesis and transport genes. Furthermore, fetal livers from MHC mothers showed increased miRNA-27a and reduced miRNA-200c expression. In summary, in utero exposure to MHC alters fetal lipid metabolism and lends mechanistic insight that implicates early changes in miRNA expression that may link to later-life programming of disease risk.

Lipid levels after childbirth and association with number of children: A population-based cohort study

OBJECTIVE

Low parity women are at increased risk of cardiovascular mortality. Unfavourable lipid profiles have been found in one-child mothers years before they conceive. However, it remains unclear whether unfavourable lipid profiles are evident in these women also after their first birth. The aim was to estimate post-pregnancy lipid levels in one-child mothers compared to mothers with two or more children and to assess these lipid's associations with number of children.

METHODS

We used data on 32 618 parous women (4 490 one-child mothers and 28 128 women with ≥2 children) examined after first childbirth as part of Cohort of Norway (1994-2003) with linked data on reproduction and number of children from the Medical Birth Registry of Norway (1967-2008). Odds ratios (ORs) with 95% confidence intervals (CIs) for one lifetime pregnancy (vs. ≥2 pregnancies) by lipid quintiles were obtained by logistic regression and adjusted for age at examination, year of first birth, body mass index, oral contraceptive use, smoking and educational level.

RESULTS

Compared to women with the lowest quintiles, ORs for one lifetime pregnancy for the highest quintiles of LDL and total cholesterol were 1.30 (95%CI: 1.14-1.45) and 1.43 (95%CI: 1.27-1.61), respectively. Sensitivity analysis (women <40 years) showed no appreciable change in our results. In stratified analyses, estimates were slightly stronger in overweight/obese, physically inactive and women with self-perceived bad health.

CONCLUSIONS

Mean lipid levels measured after childbirth in women with one child were significantly higher compared to mothers with two or more children and were associated with higher probability of having only one child. These findings corroborate an association between serum lipid levels and one lifetime pregnancy (as a feature of subfecundity), emphasizing that these particular women may be a specific predetermined risk group for cardiovascular related disease and death.

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

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

Pilot randomized trial of short-term changes in inflammation and lipid levels during and after aspirin and pravastatin therapy

BACKGROUND

Inflammation and elevated blood lipids are associated with infertility. Aspirin and statin therapy may improve infertility treatment outcomes among overweight and obese women with systemic inflammation, but little is known about the short-term effects of statins in this population. We conducted a pilot study of aspirin, pravastatin, or combined treatment among a group of overweight and obese, reproductive-aged women. Our goal was to characterize short-term changes in inflammatory and lipid biomarkers during and after treatment.

METHODS

In this open-label trial, women aged 18-40 years with a body mass index ≥25 kg/m² were randomized to receive either 162 mg aspirin, 40 mg pravastatin, or both. The study medication was taken daily for 2 weeks, and participants were then followed for a two-week washout period. Participants provided blood samples at baseline, after the intervention period, and after the washout period. The outcomes were changes in biomarkers of inflammation and lipids measured in blood components at each timepoint.

RESULTS

Nine, 8, and 8 women were randomized to the aspirin, pravastatin, and combined arms, respectively. Analyses were conducted among 8, 7, and 7 women in the aspirin, pravastatin, and combined arms for whom biomarker data was available at baseline. High-sensitivity C-reactive protein (hsCRP) levels were lower after treatment in all arms and continued to decrease after washout in the pravastatin and combined arms. Results were consistent between the whole sample and women with baseline hsCRP between 2 and 10 mg/L. Low-density lipoprotein (LDL) cholesterol was lower after treatment in the pravastatin and combined arms and rose slightly after washout.

CONCLUSIONS

Our results provide preliminary evidence that short-term aspirin and pravastatin therapy reduces hsCRP and LDL cholesterol among overweight and obese women of reproductive age, including those with low-grade inflammation. Because of these short-term effects, these drugs may improve infertility treatment outcomes in this population, which we will assess in a future randomized trial.

Preconception serum lipids and lipophilic micronutrient levels are associated with live birth rates after IVF

RESEARCH QUESTION

Is a mixture of preconception serum lipids and lipophilic micronutrients associated with clinical pregnancy and live births?

DESIGN

In this prospective cohort study, blood serum was collected on the day of oocyte retrieval for 180 women undergoing IVF at an academic reproductive health centre. Concentrations of lipids (phospholipids, total cholesterol, high- and low-density lipoproteins, and triglycerides) and lipophilic micronutrients (α-, δ-, and γ-tocopherols, retinol, β- and α-carotenes, β-cryptoxanthin, lutein and lycopene) were determined using diagnostic reagent kits and high-performance liquid chromatography. Poisson regression was used with robust variance estimation to evaluate changes in Z-scores for the mixture of serum lipid and lipophilic micronutrient concentrations as predictors of embryo implantation, clinical pregnancy and live birth, adjusted for age, body mass index (BMI), race, smoking status, infertility diagnosis, ovarian stimulation protocol and other measured lipid and lipophilic micronutrient concentrations.

RESULTS

Each SD higher serum triglyceride concentration was associated with a lower chance of live birth (RR 0.54; 95% CI 0.33 to 0.90) whereas a 1 SD higher serum α-tocopherol concentration, as part of a mixture of serum lipids and lipophilic micronutrients, was associated with a higher likelihood for a live birth (RR 1.61; 95% CI 1.11 to 2.36). Serum β-carotene concentrations were associated with live birth in a non-linear fashion; low β-carotene was associated with a lower chance of live birth and high β-carotene with a higher chance of live birth.

CONCLUSION

Although components of a mixture of lipids and lipophilic micronutrients were associated with live birth outcomes after IVF, a larger investigation is necessary to fully evaluate the potential clinical implications.

Metabolic Syndrome and Male Fertility

Metabolic syndrome (MetS) represents a cluster of conditions that have a negative impact on human health overall. Its prevalence has been rapidly increasing worldwide and has coincided with a global decrease in birth rates and fertility potential. This review aims to address this observation through studying the relationship between MetS and male reproductive health. The effects of obesity, dyslipidemia, hypertension, and insulin resistance on male fertility were examined and supporting evidence explaining the pathophysiology of sperm dysfunction with each MetS component were described. Adopting a healthy lifestyle appears to be the single most important intervention to prevent the unwanted effects of MetS on men's health and fertility. Further studies addressing the components of MetS and their impact on male reproduction are required to enhance our understanding of the underlying pathophysiology and to propose new methods for therapeutic intervention.

Metabolic syndrome and time to pregnancy: a retrospective study of nulliparous women

OBJECTIVE

To determine: (1) the association between metabolic syndrome (MetS), time to pregnancy (TTP), and infertility; (2) associations between individual and an increasing number of MetS components, TTP, and infertility; and (3) whether these relationships differ by body mass index (BMI < 30 kg/m² versus BMI ≥ 30 kg/m² ).

DESIGN

Retrospective cohort study.

SETTING

Multiple centres (in Australia, Ireland, New Zealand, and the UK).

POPULATION

Five thousand five hundred and nineteen low-risk nulliparous pregnant women.

METHODS

Data on retrospectively reported TTP (number of months to conceive) and a blood sample to assess metabolic health were collected between 14 and 16 weeks of gestation. MetS was defined according to the International Diabetes Federation criteria. Accelerated failure time models with log-normal distribution were conducted to estimate time ratios (TRs) and 95% CIs. Differences in MetS on infertility (TTP > 12 months) were compared using a generalised linear model (Poisson distribution) with robust variance estimates (relative risks, RRs; 95% CIs). All analyses (entire cohort and split by BMI) were controlled for a range of maternal and paternal confounding factors.

MAIN OUTCOME MEASURES

Time to pregnancy and infertility.

RESULTS

Of the 5519 women included, 12.4% (n = 684) had MetS. Compared with women without MetS, women with MetS had a longer TTP (adjusted TR 1.30; 95% CI 1.15-1.46), which was similar in women who were obese and in women who were not obese. Marginal estimates for median TTP in women with MetS versus without MetS was 3.1 months (3.0-3.3 months) versus 4.1 months (3.6-4.5 months), respectively. Women with MetS were at a 62% greater risk for infertility and were at a greater risk for infertility whether they were obese (adjusted RR 1.62; 95% CI 1.15-2.29) or not (adjusted RR 1.73; 95% CI 1.33-2.23). Reduced high-density lipoprotein cholesterol (HDL-C) and raised triglycerides (TGs) were the main individual components associated with risk for infertility.

CONCLUSION

Metabolic syndrome is associated with longer TTP and infertility, independent of obesity. Additional studies, before pregnancy, are required to support our findings and to determine the applicability of which combinations of metabolic abnormalities pose the greatest risk to delayed fertility, or whether individual components are amenable to modification.

TWEETABLE ABSTRACT

Metabolic syndrome is associated with longer time to pregnancy and infertility, independent of obesity.

Childhood cardiovascular health and subfertility: the Bogalusa Heart Study

BACKGROUND

Although childhood cardiovascular risk can contribute to adult cardiovascular disease, and fertility and adult cardiovascular health are linked, the association between early-life cardiovascular risk and female infertility has not been studied.

METHODS

A total of 1799 women participated in the Babies substudy of the Bogalusa Heart Study. Systolic blood pressure (SBP), diastolic blood pressure (DBP), low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglycerides, glucose, and insulin were age-standardized and examined as predictors of self-reported fertility difficulties using multivariable logistic regression with adjustment for confounders. Polycystic ovarian syndrome (PCOS) was assessed via a report of diagnosis and symptoms, using a validated questionnaire.

RESULTS

Women with a history of PCOS were more likely to report fertility difficulties. Childhood and adolescent cardiovascular risk factors were generally not associated with fertility indicators, although childhood LDL (aOR 1.38 per one-SD increase, 0.97-1.96) and total cholesterol (aOR 1.49, 1.06-2.11) were raised in those who never became pregnant. Pre-pregnancy risk SBP (overall fertility, aOR 1.49, 1.00-2.23) and glucose levels (ever tried but unable, aOR 2.65, 1.39-5.06) were associated with an increased risk of some infertility indicators. These results were largely unaffected by exclusion of women with PCOS.

CONCLUSION

Some childhood and pre-pregnancy cardiovascular risk factors are associated with adult subfertility.

More Prevalent Prescription of Medicine for Hypertension and Metabolic Syndrome in Males from Couples Undergoing Intracytoplasmic Sperm Injection

Register-based studies have indicated that men with impaired fertility are at higher risk for developing various adult-onset diseases than fertile men. The majority of men undergoing ICSI treatment are sub-fertile and since they are in contact with the health care system, these men are well suited as target for preventive measures. Our study included all men (N = 459 766) who had fathered children in Sweden between 2006 and 2016. Swedish registry data was used for obtaining information regarding conception method and defining three groups of fathers – ICSI -treated, IVF – treated and non IVF/ICSI. By sourcing data from the Swedish Prescribed Drug Register, we specifically searched for information regarding prescription and usage of at least one prescription for diabetes mellitus, hypertension (HT) or dyslipidemia to serve as a proxy for metabolic disease among the study groups. If all three types of medicine were prescribed, the patient was considered as having metabolic syndrome. Our results indicate male partners in couples who became parents using ICSI to be at higher risk for being treated for hypertension (HR = 1.15 95% CI: 1.06–1.24, p = 0.001) and metabolic syndrome (HR = 1.28 95% CI: 1.01–1.58, p = 0.042) when compared to non IVF/ICSI men.

Shorter Time to Pregnancy With Increasing Preconception Carotene Concentrations Among Women With 1-2 Previous Pregnancy Losses

Although maternal nutrition may affect fecundity, associations between preconception micronutrient levels and time to pregnancy (TTP) have not been examined. We assessed the relationship between preconception fat-soluble micronutrient concentrations and TTP among women with 1-2 prior pregnancy losses. This was a prospective cohort study of 1,228 women set within the Effects of Aspirin in Gestation and Reproduction (EAGeR) Trial (United States, 2007-2011), which assessed the association of preconception-initiated daily low-dose aspirin with reproductive outcomes. We measured preconception levels of zeaxanthin, cryptoxanthin, lycopene, α- and β-carotene, and α- and γ-tocopherol in serum. We used discrete Cox regression models, accounting for left-truncation and right-censoring, to calculate fecundability odds ratios and 95% confidence intervals. The models adjusted for age, body mass index, race, smoking, alcohol, physical activity, income, vitamin use, cholesterol, treatment arm, and study site. Serum α-carotene levels (per log unit (μg/dL) increase, fecundability odds ratio (FOR) = 1.17, 95% confidence interval (CI): 1.00, 1.36) and serum α-carotene concentrations at or above the US average (2.92 μg/dL) versus below the average (FOR = 1.21, 95% CI: 1.02, 1.44) were associated with shorter TTP. Compared with levels below the US average (187 μg/dL), γ-tocopherol concentrations at or above the average were associated with longer TTP (FOR = 0.83, 95% CI: 0.69, 1.00). The potential for these nutrients to influence fecundability deserves further exploration.

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

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

Women's prepregnancy lipid levels and number of children: a Norwegian prospective population-based cohort study

OBJECTIVE

To study prepregnancy serum lipid levels and the association with the number of children.

DESIGN

Prospective, population-based cohort.

SETTING

Linked data from the Cohort of Norway and the Medical Birth Registry of Norway.

PARTICIPANTS

2645 women giving birth to their first child during 1994-2003 (488 one-child mothers and 2157 women with ≥2 births) and 1677 nulliparous women.

MAIN OUTCOME MEASURES

ORs for no and one lifetime pregnancy (relative to ≥2 pregnancies) obtained by multinomial logistic regression, adjusted for age at examination, education, body mass index (BMI), smoking, time since last meal and oral contraceptive use.

RESULTS

Assessed in quintiles, higher prepregnant triglyceride (TG) and TG to high-density lipoprotein (TG:HDL-c) ratio levels were associated with increased risk of one lifetime pregnancy compared with having ≥2 children. Compared with the highest quintile, women in the lowest quintile of HDL cholesterol levels had an increased risk of one lifetime pregnancy (OR 1.7, 95% CI 1.2 to 2.4), as were women with the highest low-density lipoprotein (LDL) cholesterol, TG and TG:HDL-c ratio quintiles (compared with the lowest) (OR 1.2, 95% CI 0.8 to 1.7; OR 2.2, 95% CI 1.5 to 3.2; and OR 2.2, 95% CI 1.5 to 3.2, respectively). Similar effects were found in women with BMI≥25 and the highest LDL and total cholesterol levels in risk of lifetime nulliparity.

CONCLUSION

Women with unfavourable prepregnant lipid profile had higher risk of having no or only one child. These findings substantiate an association between prepregnant serum lipid levels and number of children. Previously observed associations between low parity and increased cardiovascular mortality may in part be due to pre-existing cardiovascular disease lipid risk factors.

Long-term consequences of obesity on female fertility and the health of the offspring

PURPOSE OF REVIEW

Obesity has reached near epidemic levels among reproductive age women with a myriad of consequences. Obesity adversely affects the maternal milieu by creating conditions that decrease fertility and increase the risk of gestational diabetes, hypertensive disease in pregnancy, fetal growth abnormalities and congenital anomalies. The effects of obesity are not limited to pregnancy. Indeed, beyond the immediate postpartum period, obese women maintain a higher prevalence of insulin resistance and cardiovascular disease. In this article, we will review the pathophysiology underlying the effects of obesity on fertility, pregnancy outcome and health status of offspring. The purpose of this review is to outline proposed models responsible for the short-term and long-term consequences of obesity on fertility and offspring development, and identify knowledge gaps where additional research is needed.

RECENT FINDINGS

Maternal over or under nutrition adversely affect maternal reproductive capacity and pregnancy success. Separate from effects on maternal reproductive function, maternal over or under nutrition may also 'program' fetal pathophysiology through inheritance mechanisms that suggest epigenetic modification of DNA, differential RNA translation and protein expression, or modification of the fetal hypothalamic-pituitary axis function through programmed adverse effects on the developing hypothalamic circuitry. The concept of maternal health modifying the risk of developing noncommunicable diseases in the offspring is based on Developmental Origins of Health and Disease hypothesis.

SUMMARY

Of importance, the long-term effects of obesity are not limited to maternal health, but also programs pathophysiology in their offspring. Children of obese gravida are at increased risk for the development of cardiometabolic disease in childhood and throughout adulthood. Future studies directly interrogating mechanisms underlying the risks associated with obesity will allow us to develop interventions and therapies to decrease short-term and long-term morbidities associated with maternal obesity.

Couples' body composition and time-to-pregnancy

STUDY QUESTION

Is couples' body compositions associated with reduced fecundity as measured by a longer time-to-pregnancy (TTP)?

SUMMARY ANSWER

Couples whose BMI are within obese class II (≥35 kg/m2) have a longer TTP in comparison to leaner (BMI < 25 kg/m2) couples, observed only when both partner's BMI was jointly modeled.

WHAT IS KNOWN ALREADY

Extremes of BMI have been associated with a longer TTP and with less successful assisted reproductive technology (ART) outcomes. To our knowledge, the association between measured adiposity in both partners of the couple and prospectively measured TTP has not been investigated despite pregnancy being a couple-dependent outcome.

STUDY DESIGN, SIZE, DURATION

Prospective cohort with preconception recruitment of 501 couples trying for pregnancy and recruited from 16 counties in Michigan and Texas between 2005 and 2009. Couples were followed daily for up to a year of trying or until a hCG pregnancy.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In-home standardized anthropometric assessment of couples upon enrollment included measured height and weight using calibrated stadiometers and scales, and measured waist and hip circumferences. Discrete-time Cox regression was used to estimate fecundability odds ratios (FORs) and 95% CIs, controlling for potential confounders including age, number of days of vigorous physical activity, serum cotinine concentration, race, education, free cholesterol levels for each partner in partner-specific models and for both partners in couple-based models as well as average acts of intercourse per menstrual cycle and menstrual cycle regularity.

MAIN RESULTS AND THE ROLE OF CHANCE

Neither male nor female partner's BMI was associated with TTP when modeled individually. However, obese class II (BMIs ≥ 35.0 kg/m2) couples experienced a reduction in fecundability in both unadjusted (FOR = 0.45; 95% CI: 0.23, 0.89) and adjusted analyses (aFOR = 0.41; 95% CI: 0.17, 0.98) resulting in a longer TTP in comparison to couples with normal BMI (<25 kg/m2). Female partners' waist circumference ≥88.6 cm was associated with a significant reduction in fecundability in the unadjusted model (FOR = 0.64; 95% CI: 0.48, 0.86) but not in the adjusted model (aFOR = 0.77; 95% CI: 0.55, 1.08) in comparison to females with a smaller (<80 cm) circumference.

LIMITATIONS, REASONS FOR CAUTION

BMI and waist circumference are proxy measures of body composition and residual confounding cannot be eliminated. Findings may not be generalizable to clinical populations.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first cohort study known to us with preconception enrollment of couples who underwent standardized anthropometric assessment and for whom TTP was prospectively measured. The findings underscore the importance of considering both partners' body composition for fecundity outcomes and preconception guidance.

STUDY FUNDING/COMPETING INTEREST(S)

Supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (Contracts #N01-HD-3-3355, N01-HD-3-3356 and N01-HD-3-3358). The authors have no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Preconception maternal lipoprotein levels in relation to fecundability

STUDY QUESTION

Are maternal preconception lipid levels associated with fecundability?

SUMMARY ANSWER

Fecundability was reduced for all abnormal female lipid levels including total cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and total triglyceride levels.

WHAT IS KNOWN ALREADY

Subfecundity affects 7-15% of the population and lipid disorders are hypothesized to play a role since cholesterol acts as a substrate for the synthesis of steroid hormones. Evidence illustrating this relationship at the mechanistic level is mounting but few studies in humans have explored the role of preconception lipids in fecundity.

STUDY DESIGN, SIZE, DURATION

A secondary analysis of the Effects of Aspirin in Gestation and Reproduction (EAGeR) trial (2007-2011), a block-randomized, double-blind, placebo-controlled trial.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 1228 women, with 1-2 prior pregnancy losses and without a diagnosis of infertility, attempting pregnancy for up to six menstrual cycles were recruited from clinical sites in Utah, New York, PA and Colorado. Time to pregnancy was the number of menstrual cycles to pregnancy as determined by positive hCG test or ultrasound. Individual preconception lipoproteins were measured at baseline, prior to treatment randomization and dichotomized based on clinically accepted cut-points as total cholesterol ≥200 mg/dl, LDL-C ≥130 mg/dl, HDL-C <50 mg/dl and triglycerides ≥150 mg/dl.

MAIN RESULTS AND THE ROLE OF CHANCE

There were 148 (12.3%) women with elevated total cholesterol, 94 (7.9%) with elevated LDL-C, 280 (23.2%) with elevated triglycerides and 606 (50.7%) with low HDL-C. The fecundability odds ratio (FOR) was reduced for all abnormal lipids before and after confounder adjustment, indicating reduced fecundability. Total cholesterol ≥200 mg/dl was associated with 24% (FOR: 0.76, 95% CI: 0.59, 0.97) and 29% (FOR: 0.71, 95% CI: 0.55, 0.93) reduced fecundability for hCG-detected and ultrasound-confirmed pregnancy, respectively, compared with total cholesterol <200 mg/dl. There was a 19-36% decrease in the probability of conception per cycle for women with abnormal lipoprotein levels, though additional adjustment for central adiposity and BMI attenuated observed associations.

LIMITATIONS, REASONS FOR CAUTION

Although the FOR is a measure of couple fecundability, we had only measures of female lipid levels and can therefore not confirm the findings from a previous study indicating the independent role of male lipids in fecundity. The attenuated estimates and decreased precision after adjustment for central adiposity and obesity indicate the complexity of potential causal lipid pathways, suggesting other factors related to obesity besides dyslipidemia likely contribute to reduced fecundability.

WIDER IMPLICATIONS OF THE FINDINGS

Our results are consistent with one other study relating preconception lipid concentrations to fecundity and expand these findings by adding critically important information about individual lipoproteins. As lipid levels are modifiable they may offer an inexpensive target to improve female fecundability.

STUDY FUNDING AND COMPETING INTEREST(S)

This study was funded by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development. The authors have declared that no conflicts of interest exist.

TRIAL REGISTRATION NUMBER

#NCT00467363.

Hormone-sensitive lipase deficiency alters gene expression and cholesterol content of mouse testis

Hormone-sensitive lipase-knockout (HSL−/−) mice exhibit azoospermia for unclear reasons. To explore the basis of sterility, we performed the following three experiments. First, HSL protein distribution in the testis was determined. Next, transcriptome analyses were performed on the testes of three experimental groups. Finally, the fatty acid and cholesterol levels in the testes with three different genotypes studied were determined. We found that the HSL protein was present from spermatocyte cells to mature sperm acrosomes in wild-type (HSL+/+) testes. Spermiogenesis ceased at the elongation phase of HSL−/− testes. Transcriptome analysis indicated that genes involved in lipid metabolism, cell membrane, reproduction and inflammation-related processes were disordered in HSL−/− testes. The cholesterol content was significantly higher in HSL−/− than that in HSL+/+ testis. Therefore, gene expression and cholesterol ester content differed in HSL−/− testes compared to other testes, which may explain the sterility of male HSL−/− mice.

Diabetes, medical comorbidities and couple fecundity

STUDY QUESTION

What is the relationship between couple's health and fecundity in a preconception cohort?

SUMMARY ANSWER

Somatic health may impact fecundity in men and women as couples whose male partner had diabetes or whose female partner had two or more medical conditions had a longer time-to-pregnancy (TTP).

WHAT IS ALREADY KNOWN

The impact of somatic health on human fecundity is hypothesized given the reported declines in spermatogenesis and ovulation among individuals with certain medical comorbidities.

STUDY DESIGN, SIZE, DURATION

A population-based prospective cohort study recruiting couples from 16 counties in Michigan and Texas (2005-2009) using sampling frameworks allowing for identification of couples planning pregnancy in the near future. Five hundred and one couples desiring pregnancy and discontinuing contraception were followed-up for 12 months or until a human chorionic gonadotropin pregnancy was detected.

PARTICIPANTS/MATERIALS, SETTINGS, METHODS

In all, 33 (21.4%) female and 41 (26.6%) male partners had medical conditions at baseline.

MAIN RESULTS AND THE ROLE OF CHANCE

Couples' medical comorbidity was associated with pregnancy status. Diabetes in either partner was associated with diminished fecundity, as measured by a longer TTP. Specifically, fecundability odds ratios (FORs) were below 1, indicating a longer TTP, for male partners with diabetes (0.35, 95% confidence interval (CI): 0.14-0.86) even in adjusted models (0.35, 95% CI: 0.13-0.88). Female partners with diabetes had comparable reductions in FORs; however, the analyses did not reach statistical significance (0.26, 95% CI: 0.03-1.98). Female partners with two or more medical conditions had a significantly longer TTP compared with women with no health problems (0.36, 95% CI: 0.14-0.92). Importantly, the presence of medical conditions was not associated with sexual frequency. We cannot rule out residual confounding, Type 2 errors for less prevalent medical conditions, or chance findings in light of the multiple comparisons made in the analysis.

LIMITATIONS, REASONS FOR CAUTION

The findings require cautious interpretation given that medical diagnoses are subject to possible reporting errors, although we are unaware of any potential biases that may have been introduced, as participants were unaware of how long it would take to become pregnant upon enrollment.

WIDER IMPLICATIONS OF THE FINDINGS

The current report suggests a relationship between male and female diabetes and fecundity, and possibly somatic health more globally. Moreover, while the mechanism is uncertain, if corroborated, our data suggest that early evaluation and treatment may be warranted for diabetics prior to attempting to conceive.

STUDY FUNDING/COMPETING INTERESTS

Intramural research of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (Contract nos. #N01-HD-3-3355, N01-HD-3-3356 and N01-HD-3-3358). The authors have no conflicts of interest to declare.

The Role of Avocados in Maternal Diets during the Periconceptional Period, Pregnancy, and Lactation

Maternal nutrition plays a crucial role in influencing fertility, fetal development, birth outcomes, and breast milk composition. During the critical window of time from conception through the initiation of complementary feeding, the nutrition of the mother is the nutrition of the offspring—and a mother’s dietary choices can affect both the early health status and lifelong disease risk of the offspring. Most health expert recommendations and government-sponsored dietary guidelines agree that a healthy diet for children and adults (including those who are pregnant and/or lactating) should include an abundance of nutrient-rich foods such as fruits and vegetables. These foods should contain a variety of essential nutrients as well as other compounds that are associated with lower disease risk such as fiber and bioactives. However, the number and amounts of nutrients varies considerably among fruits and vegetables, and not all fruit and vegetable options are considered “nutrient-rich”. Avocados are unique among fruits and vegetables in that, by weight, they contain much higher amounts of the key nutrients folate and potassium, which are normally under-consumed in maternal diets. Avocados also contain higher amounts of several non-essential compounds, such as fiber, monounsaturated fats, and lipid-soluble antioxidants, which have all been linked to improvements in maternal health, birth outcomes and/or breast milk quality. The objective of this report is to review the evidence that avocados may be a unique nutrition source for pregnant and lactating women and, thus, should be considered for inclusion in future dietary recommendations for expecting and new mothers.

On-Site Classification of Pansteatitis in Mozambique Tilapia (Oreochromis mossambicus) using a Portable Lipid-Based Analyzer

While no pansteatitis-related large-scale mortality events have occurred since 2008, the current status of pansteatitis (presence and pervasiveness) in the Olifants River system and other regions of South Africa remain largely unknown. In part, this is due to both a lack of known biological markers of pansteatitis and a lack of suitable non-invasive assays capable of rapidly classifying the disease. Here, we propose the application of a point-of-care (POC) device using lipid-based test strips (total cholesterol (TC) and total triglyceride (TG)), for classifying pansteatitis status in the whole blood of pre-spawning Mozambique tilapia (Oreochromis mossambicus). Using the TC strips, the POC device was able to non-lethally classify the tilapia as either healthy or pansteatitis-affected; the sexes were examined independently because sexual dimorphism was observed for TC (males p = 0.0364, females χ2 = 0.0007). No significant difference between diseased and pansteatitis-affected tilapia was observed using the TG strips. This is one of the first described applications of using POC devices for on-site environmental disease state testing. A discussion on the merits of using portable lipid-based analyzers as an in-field disease-state diagnostic tool is provided.

The Deep Correlation between Energy Metabolism and Reproduction: A View on the Effects of Nutrition for Women Fertility

In female mammals, mechanisms have been developed, throughout evolution, to integrate environmental, nutritional and hormonal cues in order to guarantee reproduction in favorable energetic conditions and to inhibit it in case of food scarcity. This metabolic strategy could be an advantage in nutritionally poor environments, but nowadays is affecting women's health. The unlimited availability of nutrients, in association with reduced energy expenditure, leads to alterations in many metabolic pathways and to impairments in the finely tuned inter-relation between energy metabolism and reproduction, thereby affecting female fertility. Many energetic states could influence female reproductive health being under- and over-weight, obesity and strenuous physical activity are all conditions that alter the profiles of specific hormones, such as insulin and adipokines, thus impairing women fertility. Furthermore, specific classes of nutrients might affect female fertility by acting on particular signaling pathways. Dietary fatty acids, carbohydrates, proteins and food-associated components (such as endocrine disruptors) have per se physiological activities and their unbalanced intake, both in quantitative and qualitative terms, might impair metabolic homeostasis and fertility in premenopausal women. Even though we are far from identifying a "fertility diet", lifestyle and dietary interventions might represent a promising and invaluable strategy to manage infertility in premenopausal women.

Urinary Phytoestrogens Are Associated with Subtle Indicators of Semen Quality among Male Partners of Couples Desiring Pregnancy

BACKGROUND

Phytoestrogens have been associated with subtle hormonal changes, although effects on male fecundity are largely unknown.

OBJECTIVE

We evaluated associations between male urinary phytoestrogen (isoflavone and lignan) concentrations and semen quality.

METHODS

This study was a prospective cohort study of 501 male partners of couples desiring pregnancy and discontinuing contraception. Each participant provided up to 2 semen samples that were analyzed for 35 semen quality endpoints the following day. Linear mixed-effects models were used to estimate associations between baseline urinary phytoestrogen concentrations and semen quality parameters, adjusted for age, body mass index (BMI), research site, and serum lipid and cotinine concentrations.

RESULTS

Most associations between urinary phytoestrogens and semen quality parameters were null. However, select individual phytoestrogens were associated with semen quality parameters, with associations dependent on the class of phytoestrogens and modified by BMI. Specifically, genistein and daidzein were associated with a lower percentage of normal sperm and increased abnormalities in semen morphology, with reduced associations observed as BMI increased (P < 0.05) [percentages (95% CIs) of normal morphology by WHO traditional criteria: genistein, main effect: -5.61% (-9.42%, -1.79%); interaction: 0.19% (0.06%, 0.31%) per log unit increase; daidzein, main effect: -5.35% (-9.36%, -1.34%); interaction: 0.18% (0.05%, 0.32%) per log unit increase]. Enterolactone was associated with fewer abnormalities in semen morphometry and morphology and decreased DNA fragmentation, with reduced associations observed as BMI increased (P < 0.05) [percentages (95% CIs) of abnormalities in the neck and midpiece: enterolactone, main effect: -3.35% (-6.51%, -0.19%); interaction: 0.11% (0.01%, 0.21%) per log unit increase].

CONCLUSIONS

These results suggest that male urinary phytoestrogen concentrations characteristic of the US population may be associated with subtle indicators of male fecundity and semen quality but were not associated with couple fecundity.

Simvastatin decreases steroid production in the H295R cell line and decreases steroids and FSH in female rats

Endocrine modulating effects of Simvastatin (SV) and its metabolite, Simvastatin β-hydroxy acid (SVA), were investigated in H295R cells and in female Sprague-Dawley (SPRD) rats. H295R cells were exposed to SV and SVA concentrations from 0 to 10μM for 48h. Four groups of SPRD rats received 0 (CT), 1.3 (L), 5.0 (M), and 20.0 (H)mg SV/kg bw/day for 14 days. 10 Steroids were investigated in H295R growth media, and in tissues and plasma from rats using GC-MS/MS. Plasma LH and FSH were quantified by ELISA. In the H295R assay, SV and SVA particularly decreased progestagens with IC50-values from 0.10-0.13μM for SV and from 0.019-0.055μM for SVA. In rats, SV decreased progestagens in ovaries, brain and plasma, and plasma FSH in the M (72.4% decrease) and H group (76.6% decrease). Because progestagens and gonadotropins are major players in fertility, administration of SV might exert negative effects on female reproduction.

Relationship between physical occupational exposures and health on semen quality: data from the Longitudinal Investigation of Fertility and the Environment (LIFE) Study

OBJECTIVE

To study the relationship among occupation, health, and semen quality in a cohort of men attempting to conceive.

DESIGN

Observational prospective cohort.

SETTING

Not applicable.

PATIENT(S)

A total of 501 couples discontinuing contraception were followed for 1 year while trying to conceive; 473 men (94%) provided one semen sample, and 80% provided a second sample.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Semen data obtained through at-home semen collection with next-day analysis/quantification.

RESULT(S)

In all, complete data were available for 456 men, with a mean age of 31.8 years. Work-related heavy exertion was consistently associated with lower semen concentration and total sperm count. Thirteen percent of men who reported heavy exertion displayed oligospermia, compared with 6% who did not report workplace exertion. Shift work, night work, vibration, noise, heat, and prolonged sitting were not associated with semen quality. Men with high blood pressure had significantly lower strict morphology scores compared with normotensive men (17% vs. 21%). In contrast, hyperlipidemia, diabetes, and composite of total comorbidities were not associated with semen quality. The number of medications a man was taking as a proxy of health status was associated with semen quality. There was a negative association between number of medications and sperm count.

CONCLUSION(S)

A negative relationship among occupational exertion, hypertension, and the number of medications with semen quality was identified. As these are potentially modifiable factors, further research should determine whether treatment or cessation may improve male fecundity.

Excess cholesterol induces mouse egg activation and may cause female infertility

The HDL receptor scavenger receptor, class B type I (SR-BI) controls the structure and fate of plasma HDL. Female SR-BI KO mice are infertile, apparently because of their abnormal cholesterol-enriched HDL particles. We examined the growth and meiotic progression of SR-BI KO oocytes and found that they underwent normal germinal vesicle breakdown; however, SR-BI KO eggs, which had accumulated excess cholesterol in vivo, spontaneously activated, and they escaped metaphase II (MII) arrest and progressed to pronuclear, MIII, and anaphase/telophase III stages. Eggs from fertile WT mice were activated when loaded in vitro with excess cholesterol by a cholesterol/methyl-β-cyclodextrin complex, phenocopying SR-BI KO oocytes. In vitro cholesterol loading of eggs induced reduction in maturation promoting factor and MAPK activities, elevation of intracellular calcium, extrusion of a second polar body, and progression to meiotic stages beyond MII. These results suggest that the infertility of SR-BI KO females is caused, at least in part, by excess cholesterol in eggs inducing premature activation and that cholesterol can activate WT mouse eggs to escape from MII arrest. Analysis of SR-BI KO female infertility raises the possibility that abnormalities in cholesterol metabolism might underlie some cases of human female infertility of unknown etiology.