Association of maternal lipid profile and gestational diabetes mellitus: A systematic review and meta-analysis of 292 studies and 97,880 women.

BACKGROUND: Gestational Diabetes Mellitus (GDM) is the most prevalent metabolic disorder during pregnancy, however, the association between dyslipidaemia and GDM remains unclear. METHODS: We searched Medline, Scopus, Web of Science, Cochrane, Maternity and Infant Care database (MIDIRS) and ClinicalTrials.gov up to February 2021 for relevant studies which reported on the circulating lipid profile during pregnancy, in women with and without GDM. Publications describing original data with at least one raw lipid [triglyceride (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), or very low-density lipoprotein cholesterol (VLDL-C)] measurement were retained. Data extraction was performed using a piloted data extraction form. The protocol was registered with PROSPERO (CRD42019139696). FINDINGS: A total of 292 studies, comprising of 97,880 pregnant women (28232 GDM and 69,648 controls) were included. Using random-effects meta-analysis models to pool study estimates, women with GDM had significantly higher (by 20%) TG levels, with a pooled weighted mean difference between GDM and non-GDM pregnancies of 0.388 mM (0.336, 0.439, p < 0.001). Further analyses revealed elevated TG levels occur in the first trimester and persist afterwards. Meta-regression analyses showed that differences in TG levels between women with GDM and healthy controls were significantly associated with age, BMI, study continent, OGTT procedure, and GDM diagnosis criteria. INTERPRETATION: Elevated lipids, particularly, TG, are associated with GDM.

Nitric oxide positively affects endometrial receptivity via FAAH and NAPE-PLD in vitro.

OBJECTIVE: To determine if models of human 'receptive' and 'non-receptive endometrium' differ in their responses to nitric oxide (NO) supplementation by measuring the levels of the enzymes of the endocannabinoid system (ECS) (fatty acid amide hydrolase (FAAH) and N-acylphosphatidylethanolamine-specific phospholipase D (NAPE-PLD)), which control the 'anandamide tone' essential for successful pregnancy. DESIGN: A study of FAAH and NAPE-PLD expression (using human endometrium) through the menstrual cycle and an in vitro using a model of 'receptive' (Ishikawa) and 'non-receptive' (HEC-1A) human endometrial cell lines treated with the NO-donating compound S-nitroso-N-acetylpenicillamine (SNAP). RESULTS: Immunoreactivity measured by optimised H-score for both FAAH and NAPE-PLD was reduced in secretory (receptive) endometrium compared to proliferative (non-receptive) endometrium (P = 0.0009 and <0.0001, respectively). FAAH and NAPE transcript levels were significantly higher in untreated Ishikawa cells than in HEC-1A cells (P = 0.0228 and 0.0001, respectively). Treatment of cultures with SNAP resulted in an increase in the amount of FAAH mRNA produced by Ishikawa cells and a decrease in NAPE-PLD mRNA. No effect of SNAP was observed in HEC-1A cells. Similarly, FAAH protein was significantly decreased in endometria representative of the receptive endometrium. CONCLUSION: These data suggest that NO most likely affects the expression of ECS enzymes in the implantation site of a receptive endometrium; a phenomenon not seen in a non-receptive endometrium. These effects are most marked with FAAH expression, suggesting that FAAH may play the more critical role in ensuring the correct 'anandamide tone' for successful embryo implantation than NAPE-PLD. LAY SUMMARY: Embryo implantation into the wall of the uterus is only successful when the inner wall of the uterus (the endometrium) is 'receptive', because if it is 'non-receptive', implantation will fail. Previous work showed that enzymes of the 'endocannabinoid system' are critical for implantation by maintaining the correct level of a fat called anandamide. This is by balancing its synthesis (by N-acylphosphatidylethanolamine specific phospholipase D, NAPE-PLD) and degradation (by fatty acid amide hydrolase, FAAH). Using immortalised cell lines as models of 'receptive' and 'non-receptive' human endometrium, we demonstrate a key stimulator of implantation, nitric oxide, has a positive effect on implantation by both increasing the mRNA levels of the degrading enzyme (FAAH) and decreasing the expression of the synthesising enzyme (NAPE-PLD). These effects are most marked with the degrading enzyme, suggesting that FAAH plays a more critical role than NAPE-PLD in ensuring the correct 'anandamide tone' for successful embryo implantation.

Of mice and (wo)men: factors influencing successful implantation including endocannabinoids.

BACKGROUND One in six couples suffer from infertility problems requiring in vitro fertilization therapy; however, the average birth rates in the past decade per IVF-embryo transfer cycle have remained static at around 25%. Although implantation failure is considered a major cause of infertility in otherwise healthy women, inadequate uterine receptivity is considered to be responsible for only two-thirds of implantation failures and problems with the embryo itself are responsible for the other third, such that only 30% of oocytes that are contacted by sperm result in successful human term pregnancies. Due to technical and ethical considerations, most research into the factors affecting the success of embryo implantation has been performed in mice, but this may be less than ideal. METHODS Selected relevant literature detailing the similarities and differences between rodent and human reproductive physiology surrounding implantation were nominated for inclusion. Primary papers and review articles (and primary sources within these), published between 1975 and 2012, with a clear indication for a particular ligand or cell being involved in the implantation process or placentation in the mouse or woman, were thoroughly examined and used to construct the review. RESULTS Mice have been identified as suitable models for investigating the processes of early pregnancy in women, for many reasons including their predictable, relatively short gestation and the ability to deliberately breed mice with the absence of a desired gene. There is, however, increasing evidence to suggest that the reproductive systems of humans and mice differ considerably when considering early pregnancy events. CONCLUSIONS In this review, we examine what is already known about the normal implantation process and the intrinsic factors that affect implantation, and then compare the differences between mice models and women in the context of early pregnancy. We highlight numerous differences between the mice and women and conclude it is becoming clear that all of the data from mouse studies cannot be confidently extrapolated to human reproduction.