Imbalance hepatic metabolism homeostasis in the F1 generation of endometrial DNMT3B conditional knockout female mice.

Numerous studies have suggested the possibility of explaining the etiology of metabolic syndrome through DNA methylation. DNA methyltransferase 3B (DNMT3B) plays an important role in de novo DNA methylation. There was an alteration in maternal (F0) endometrial function, which might lead to growth and developmental disorder in offspring (F1). In this study, we investigated the effect of maternal endometrial DNMT3B deficiency on the metabolism in offspring. We constructed endometrial DNMT3B conditional knockout female mice (cKO) which were mated with normal C57BL/6 male mice to obtain the F1 generation. Further, to study the development of these offspring, we observed them at three different life stages which included the 6-week-old juvenile, 9-week-old sub-adult and 12-week-old adult. Follow the detection of a range of metabolism-related indicators, we found that in the cKO F1 generation, liver triglyceride level was significantly elevated in 9-week-old female mice, lipid droplet deposition was significantly increased in 9-week-old and 12-week-old mice, and the expression of lipid metabolism key factors in the liver was markedly decreased except of 6-week-old male mice. These results indicate that maternal endometrial DNMT3B conditional knockout leads to imbalance in hepatic metabolism in F1 generation, the mechanism of which requires further discussion.

Carnitine palmitoyltransferase 1A is essential for decidualization in mice.

Decidualization accompanies with extensive stromal cell proliferation and differentiation, is a crucial step in early pregnancy. Aberrant decidualization is linked to infertility and miscarriage but the mechanisms remain unclear. Carnitine palmitoyltransferase 1A (CPT1A) is an enzyme catalyzing key steps in the fatty acid beta-oxidation pathway. The objective of this study was to investigate the role of CPT1A in decidualization during early pregnancy. An increased expression of CPT1A was found both in Days 6 and 7 as compared with in Days 1, 4 and 5. Further examination showed that on days 5-7 of pregnancy, the protein level of CPT1A was strongly up-regulated at implantation sites compared with inter-implantation sites, the location of CPT1A protein was distributed in the decidual zone. Upon further exploration, CPT1A expression was significantly increased in response to artificially induced decidualization both in vivo and in vitro. After down-regulating CPT1A expression by CPT1A-small interfering RNA (siCPT1A) in primary mouse endometrial stromal cells, expressions of decidualization markers and cell proliferation markers were decreased. After siCPT1A was transfected into the mouse uterus, decidualization impaired and then led to the loss of the implanted embryos. Thus, CPT1A is important for decidualization in mice and it may regulate the stromal cell proliferation progress. It is worth noting that the expression of CPT1A protein of human decidua was significantly decreased in spontaneous abortion groups compared to normal pregnancy groups. Collectively, CPT1A is essential for endometrium of early pregnant mice and humans.

Exposure to ethylparaben and propylparaben interfere with embryo implantation by compromising endometrial decidualization in early pregnant mice.

Ethylparaben (EtP) and propylparaben (PrP) are common preservatives and well-known endocrine-disrupting chemicals. Studies have demonstrated that they can reduce female fertility, but the underlying mechanism, especially that on embryo implantation, is still poorly understood. Endometrial decidualization is a critical event for embryo implantation. In this study, we aimed to explore the effects of EtP/PrP on endometrial decidualization. Pregnant mice were dosed daily by oral gavage with EtP at 0, 400, 800 and 1600 mg/kg or with PrP at 0, 625, 1250 and 2500 mg/kg from Day 1 of pregnancy until sacrifice. The results showed that the rate of pregnant mice with impaired embryo implantation, whose number of implantation sites was less than 7, was significantly increased after exposure to 1600 mg/kg EtP or 2500 mg/kg PrP. Further study found that the expression of endometrial decidualization markers HOXA10, MMP9 and PR was significantly downregulated in 1600 mg/kg EtP group and 2500 mg/kg PrP group. Notably, serum oestrogen and progesterone levels were significantly increased, whereas the expression of uterine oestrogen receptor and progesterone receptor was decreased following 1600 mg/kg EtP or 2500 mg/kg PrP exposure. In the breeding test, fewer offspring were found after females were exposed to 1600 mg/kg EtP or 2500 mg/kg PrP in early pregnancy. This demonstrated that exposure to EtP/PrP interfered with embryo implantation by compromising endometrial decidualization in early-stage pregnant mice. Disorders of reproductive hormones and hormone receptor signals could be responsible for impaired decidualization. This study broadened the understanding on the biological safety of EtP and PrP.

High-fat diet-induced obesity primes fatty acid ß-oxidation impairment and consequent ovarian dysfunction during early pregnancy.

BACKGROUND: Obesity is associated with many adverse effects on female fertility. Obese women have a higher likelihood of developing ovulatory dysfunction due to dysregulation of the hypothalamic-pituitary-ovarian axis. However, the effect of obesity on ovarian function during early pregnancy needs to be further assessed. METHODS: C57BL6/J mice were given a high-fat diet (HFD) for 12 weeks to induce obesity. An in vitro high-fat model was established by treating the human ovarian granulosa cell line KGN with oleic acid and palmitic acid. Ovarian morphology of obese mice in early pregnancy was assessed by hematoxylin and eosin staining and ovarian function was assessed by enzyme-linked immunosorbent assay, western blotting, and immunohistochemistry. Oil Red O staining and transmission electron microscopy were used to detect fatty acid accumulation. Specific markers relating to the ovarian functional mechanism were assessed by real-time PCR, western blotting, lactate detection, adenosine triphosphate (ATP) detection, biochemical analyses, and enzyme-linked immunosorbent assay. RESULTS: The results of this study showed that during early pregnancy, the number of corpus lutea, serum estradiol and progesterone levels, and the expression of the steroid biosynthesis-related protein CYP19A1 (aromatase), CYP11A1 (cholesterol side chain cleavage enzyme), and StAR (steroidogenic acute regulatory protein), were significantly increased in HFD mice. Mice fed an HFD also showed a significant increase in ovarian lipid accumulation on day 7 of pregnancy. Genes involved in fatty acid synthesis (Acsl4 and Elovl5), and fatty acid uptake and transport (Slc27a4), together with the ß-oxidation rate-limiting enzyme Cpt1a, were significantly upregulated in HFD mice. Specifically, there was abnormal elevation of ATP and aberrant expression of tricarboxylic acid cycle (TCA)- and electron transport chain (ETC)-related genes in the ovaries of pregnant HFD mice. KGN cells treated with etomoxir targeting ß-oxidation of fatty acid showed decreased TCA cycle and ETC related gene expression. The elevation of ATP and estradiol and progesterone levels was reversed. CONCLUSIONS: During early pregnancy, HFD-induced obesity increases fatty acid ß-oxidation, which in turn increases TCA cycle and ETC related gene expression, leading to increased ATP production and ovarian dysfunction.

Exposure to ethephon compromises endometrial decidualization in mice during early pregnancy via GPR120.

Exposure to ethephon (ETH), a plant growth regulator commonly used for several purposes, can potentially decrease sperm numbers and viability. Occasional findings regarding ETH effects on female reproduction during early pregnancy have also been reported. During early pregnancy, endometrial decidualization is a critical event for embryo implantation and pregnancy maintenance. Thus, we aimed to explore the effect and mechanism of ETH on endometrial decidualization both in vivo and in vitro. Mice were gavaged with 0 and 285 mg/kg b.w. ETH from gestational days (GD)1 until sacrifice, whereas pseudopregnant mice from pseudopregnant day 1 (PPD-1) until PPD-8. Primary mouse endometrial stromal cells (mESCs) received 640 ug/ml ETH and added E2 and P4 to induce decidualization. Results indicated female albino CD1 mice exposed to high dose of ETH (285 mg/kg b.w.) by oral gavage, the number of embryo implantation sites on GD6 and GD8 were significantly decreased, the levels of serum E2 and P4 on GD8 were significantly decreased. Compared with the control group, the decidualization response artificially induced by corn oil in pseudopregnant mice and by E2 and P4 in primary mouse endometrial stromal cells (mESCs) was weakened in the high dose of ETH treated group. The high dose, 285 mg/kg b.w ETH treated group altered the expression of endometrial decidual markers on GD6 and GD8. The triglyceride and fatty acid metabolism-related genes were significantly increased after female albino CD1 mice exposed to high does, 285 mg/kg b.w ETH on GD6 and GD8. GPR120 was substantially reduced after ETH treatment. When overexpression of GPR120, the compromised decidualization induced by ETH treatment was rescued. Furthermore, molecular docking presented Thr234 and His251 of GPR120 as preferred binding sites for ETH. Mutation of these two sites rescued the compromised decidualization induced by ETH. In conclusion, we demonstrated that ETH exposure could impair decidualization during early pregnancy. GPR120 expression and binding between GPR120 and ETH are crucial for impaired decidualization mediated via ETH.

Elevated insulin levels compromise endometrial decidualization in mice with decrease in uterine apoptosis in early-stage pregnancy.

Women with hyperinsulinism and insulin resistance have reduced fertility, but the underlying mechanism is still poorly understood. Aberrant endometrial decidualization in early pregnancy was linked to pregnancy complications. In this study, we aimed to test whether elevated insulin levels compromise decidualization in early-stage pregnancy. C57BL/6J mice in high insulin-exposed group were given a subcutaneous injection of recombinant insulin at a concentration of 0.05 IU daily. During decidualization in early pregnancy, serum levels of insulin, E2, P4, LH, FSH and blood glucose were significantly altered in mice treated with high insulin levels. The number of embryo implantation sites and endometrial decidual markers BMP2, ER, PR was significantly decreased by high insulin levels in vivo. Artificial decidual induction in primary mouse endometrial stromal cells and immortal human endometrial stromal cells line were all compromised after treated with 100 nmol/L insulin levels. All these results on flow cytometry, transmission electron microscopy and western blotting of Bax, Bcl2, cleaved Caspase3, cleaved PARP proteins level showed that decidual cells apoptosis was significantly decreased. Mitochondrial transmembrane potential also significantly increased by the influence of high insulin levels. PI3K and p-Akt were much higher after insulin exposure and the compromised decidualization by high insulin treatment was rescued by PI3K/Akt inhibitor LY294002 both in vitro and in vivo. In conclusion, we demonstrated that elevated insulin levels could compromise mice decidualization in early-stage pregnancy and PI3K/p-Akt-regulated apoptosis was essential for this role. It provides a clue for future investigation on compromised reproduction in women with hyperinsulinemia.

Hyperinsulinemia restrains endometrial angiogenesis during decidualization in early pregnancy.

Previous research on the role of insulin has focused on metabolism. This study investigated the effect of insulin on angiogenesis in endometrial decidualization. High insulin-treated mouse model was constructed by subcutaneous injection of insulin. Venous blood glucose, serum insulin, P4, E2, FSH and LH levels in the pregnant mice were detected by ELISA. Decidual markers, angiogenesis factors and decidual vascular network were detected during decidualization in the pregnant mouse model and an artificially induced decidualization mouse model. Tube formation ability and angiogenesis factors expression were also detected in high insulin-treated HUVECS cells. To confirm whether autophagy participates in hyperinsulinemia-impaired decidual angiogenesis, autophagy was detected in vivo and in vitro. During decidualization, in the condition of high insulin, serum insulin and blood glucose were significantly higher, while ovarian steroid hormones were also disordered (P < 0.05), decidual markers BMP2 and PRL were significantly lower (P < 0.05). Uterine CD34 staining showed that the size of the vascular sinus was significantly smaller than that in control. Endometrial VEGFA was significantly decreased after treatment with high insulin in vivo and in vitro (P < 0.05), whereas ANG-1 and TIE2 expression was significantly increased (P < 0.05). In addition, aberrant expression of autophagy markers revealed that autophagy participates in endometrial angiogenesis during decidualization (P < 0.05). After treatment with the autophagy inhibitor 3-MA in HUVEC, the originally damaged cell tube formation ability and VEGFA expression were repaired. This study suggests that endometrial angiogenesis during decidualization was impaired by hyperinsulinemia in early pregnant mice.

FOXO3a is essential for murine endometrial decidualization through cell apoptosis during early pregnancy.

Embryo implantation is essential for normal pregnancy, and the process of decidualization is critical for embryo implantation. However, the mechanism of decidualization during early pregnancy is still unknown. Forkhead box O3a (FOXO3a) is the most important functional transcription factor of the forkhead box family and is a highly conserved transcription factor of apoptosis-related genes. In the mouse uterus, FOXO3a was found to be expressed regularly from Days 1-7 of early pregnancy. Upon further exploration, it was found that FOXO3a was expressed at significantly higher levels at the implantation site than at the interimplantation site on Days 5-7 of pregnancy. Under artificial decidualization, FOXO3a was highly expressed in the first and second decidual zones. After decidualization, the expression of FOXO3a was significantly increased both in vivo and vitro. In primary stromal cells, apoptosis was reduced by decreased expression of FOXO3a after inducing decidualization. Moreover, when FOXO3a-small interfering RNA was transfected into the uteri of mice, the expression of decidualization- and apoptosis-related factors was impaired. Thus, FOXO3a might play an important role in decidualization during early pregnancy, and cell apoptosis might be one of pathways for FOXO3a-regulated decidualization.