Elevated Non-Esterified Fatty Acid Concentrations during Bovine Oocyte Maturation Compromise Early Embryo Physiology

Elevated concentrations of serum non-esterified fatty acids (NEFA), associated with maternal disorders such as obesity and type II diabetes, alter the ovarian follicular micro-environment and have been associated with subfertility arising from reduced oocyte developmental competence. We have asked whether elevated NEFA concentrations during oocyte maturation affect the development and physiology of zygotes formed from such oocytes, using the cow as a model. The zygotes were grown to blastocysts, which were evaluated for their quality in terms of cell number, apoptosis, expression of key genes, amino acid turnover and oxidative metabolism. Oocyte maturation under elevated NEFA concentrations resulted in blastocysts with significantly lower cell number, increased apoptotic cell ratio and altered mRNA abundance of DNMT3A, IGF2R and SLC2A1. In addition, the blastocysts displayed reduced oxygen, pyruvate and glucose consumption, up-regulated lactate consumption and higher amino acid metabolism. These data indicate that exposure of maturing oocytes to elevated NEFA concentrations has a negative impact on fertility not only through a reduction in oocyte developmental capacity but through compromised early embryo quality, viability and metabolism

Can time to menopause be predicted?

Menopause represents the definite end of a woman’s reproductive life and the onset of a persistent hypoestrogenic state. This postmenopausal period will for most women last several decades. Although mean menopausal age seems to have increased somewhat during the last century, there is a significant individual variation in age at natural menopause. With efficient contraception, women of reproductive age can now, to some extent, choose when they want to have children. As a consequence of this and other sociodemographic changes, age at first birth has increased significantly over the last 50 years. It is well documented that long before a woman enters the menopausal transition and subsequent menopause, fertility declines and finally ceases. Being able to predict when a woman will enter menopause would therefore, from a reproductive perspective, be of major interest. Several sociodemographic, morphometric, and endocrine factors are associated with age at menopause or time to menopause. Unfortunately the sensitivity and specificity of these in predicting time to or age at menopause are low. Therefore, with the exception of anti-Müllerian hormone measurements, either alone or in combination with chronological age close to menopause, there are as of now no reliable ways of predicting when a woman will enter menopause

Female Reproductive Decline Is Determined by Remaining Ovarian Reserve and Age

<div><p>The early decline and loss of female fertility in humans and other species represents an evolutionary paradox. Despite being born with a vast stock of oocytes, females encounter an exhaustion of ovarian reserve and sterility half way through their natural lives. Female reproductive ageing has been proposed to proceed as an ongoing decline in ovarian reserve, determined by remaining ovarian follicle number. However, despite extensive modelling, the respective contributions of intra-, inter-, and extra-ovarian signalling have not been fully characterised. It remains unclear whether reproductive ageing progresses simply as a pre-determined function of remaining ovarian follicles, or as an age-dependent process in humans. Here, we have analysed ovarian response to hormonal stimulation in women who have undergone surgical removal of a single ovary, in order to investigate the relative contributions of intra-, inter, and extra-ovarian signalling on reproductive ageing. Our data show that in unilaterally oophorectomised women, ovarian response to follicle stimulating hormone (FSH) declines beyond levels predicted by a total ovarian follicle pool model of reproductive ageing. Maintenance of ovarian function later in reproductive life, despite the removal of half of the total ovarian reserve, suggests a role for an extra-ovarian age-dependent regulation of reproductive decline. This highlights the need for further work to identify signalling factors that communicate age-related signals between the soma and the germline.</p></div

ALKBH4 Depletion in Mice Leads to Spermatogenic Defects

<div><p>ALKBH4, an AlkB homologue in the 2-oxoglutarate and Fe²⁺ dependent hydroxylase family, has previously been shown to regulate the level of monomethylated lysine-84 in actin and thereby indirectly influences the ability of non-muscular myosin II to bind actin filaments. ALKBH4 modulates fundamental processes including cytokinesis and cell motility, and its depletion is lethal during early preimplantation embryo stage. The aim of this study was to investigate the effect of ALKBH4 deficiency in a physiological context, using inducible <i>Alkbh4</i> knockout mice. Here, we report that ALKBH4 is essential for the development of spermatocytes during the prophase of meiosis, and that ALKBH4 depletion leads to insufficient establishment of the synaptonemal complex. We also show that ALKBH4 is localized in nucleolar structures of Sertoli cells, spermatogonia and primary spermatocytes.</p></div

Anti-Müllerian Hormone concentration after unilateral oophorectomy.

<p>Serum AMH concentrations in women with two ovaries (<b>a</b>) and one ovary (<b>b</b>), according to age. AMH in women with one ovary according to time since unilateral oophorectomy. The ovarian dynamics match the setting of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0108343#pone-0108343-g003" target="_blank">Figure 3</a>.</p

Modelling of decline in ovarian reserve.

<p><b>a–c.</b> Calculated trajectories of follicle loss after unilateral oophorectomy at ages 10 years (a), 20 years (b), and 35 years (c), assuming the total ovarian follicle pool (green) or alternative model of decline of ovarian reserve (red). Arrows on figures c,d and e indicate time of unilateral oophorectomy at the respective ages.</p

Maintained DNA synthesis and increased apoptosis in testes of <i>Alkbh4^Δ/Δ</i> mice.

<p>A Left panel, epifluorescence microscopy of BrdU-labelled testicular sections in 6 weeks old mice treated with tamoxifen for 2 weeks, indicating comparable density of S-phase cells in control and <i>Alkbh4^Δ/Δ</i> mice. DNA was visualized by DAPI staining. Scale bars, 50 µm. Right panel, quantification of the increased BrdU positive cells/stage VIII tubulus in sections (n = 10 tubuli/animal, 2 animals/genotype) in testes of <i>Alkbh4^Δ/Δ</i> compared to <i>Alkbh4^L/L</i> mice. All data expressed as means ± SEM. B Left panel, epifluorescence microscopy of TUNEL-stained testicular sections in 6 weeks old mice treated with tamoxifen for 2 weeks. TUNEL identifies increased proportion of apoptotic germ cells in <i>Alkbh4^Δ/Δ</i> mice compared to control (<i>Alkbh4^L/L</i>). DNA was counterstained with DAPI. Scale bars, 50 µm. Right panel, quantification of the increased number of tubuli with TUNEL positive cells/tubulus in sections (n = 50 tubuli/animal, 3 animals/genotype) in testes of <i>Alkbh4^Δ/Δ</i> compared to <i>Alkbh4^L/L</i> mice. All data expressed as means ± SEM.</p

Ovarian response after unilateral oophorectomy.

<p>Two-piece exponential decay model of ovarian response in women with intact ovaries <i>(</i><b><i>a</i></b><i>)</i>, in women who had undergone unilateral oophorectomy according to age <i>(</i><b><i>b</i></b><i>)</i>, and time since oophorectomy <i>(</i><b><i>c</i></b><i>)</i>. Ovarian response is expressed as ratio of number of collected oocytes and 1000 IU total FSH dose during ovarian stimulation for IVF.</p

Longitudinal ovarian response after unilateral oophorectomy.

<p>Individual changes in ovarian response with age in women with two intact ovaries (<b>a</b>) and after unilateral oophorectomy (<b>d</b>). Ovarian response change/year in women with intact ovaries (<b>b, c</b>), and after unilateral oophorectomy (<b>e, f</b>). Ovarian response change/year in unilaterally oophorectomised women according to time after operation (<b>g</b>). Lines indicate ovarian response index in two successive IVF treatments of individual women, with decrease in blue and increase in red.</p

Loss of Alkbh4 reduces the size of testes and the diameter of seminiferious tubuli.

<p>The phenotype of testis of tamoxifen-treated mice with genotypes <i>Alkbh4^L/L</i> (Control), CreEsr (Control) and <i>Alkbh4 ^Δ/Δ</i>. A Left panel, representative testes from control and <i>Alkbh4 ^Δ/Δ</i> mice after tamoxifen treatment for one week or without treatment (0–1 week), and after deletion of <i>Alkbh4</i> with treatment for 2 weeks. Scale bar, 0.5 cm. Right panel, average testis/body weight ratio of 4–5 weeks old mice before and after 1 week of treatment with tamoxifen (0–1 week), and 6 weeks old mice treated with tamoxifen for 2 weeks (0–1 week: <i>Alkbh4^L/L</i>, n = 3; CreEsr, n = 1; <i>Alkbh4^Δ/Δ</i>, n = 3. 2 weeks: <i>Alkbh4^L/L</i>, n = 5; <i>CreEsr</i>, n = 6; <i>Alkbh4 ^Δ/Δ</i>, n = 6). Data are expressed as means ± SEM. B Left panel, histological overview of representative control and <i>Alkbh4 ^Δ/Δ</i> testis after 2 weeks of tamoxifen induction (HE stain, scale bar, 20 µm). Right panel, decreased diameter of seminiferous tubuli in <i>Alkbh4 ^Δ/Δ</i> mice after 2 weeks tamoxifen treatment compared to control mice (n = 100 tubuli/animal, 2 animals/genotype/time point. 0–1 week CreEsr N/A). Data are expressed as means ± SEM. <b>C</b> High magnification view (scale bar, 20 µm) of testis section in B. Statistical analysis was performed using a non-paired, two-tailed Student's test: *p<0.05.</p