Free fatty acid treatment of mouse preimplantation embryos demonstrates contrasting effects of palmitic acid and oleic acid on autophagy

Fatty acid supplementation during warming improves pregnancy outcomes after frozen blastocyst transfers: a propensity score-matched study

This study aimed to examine the viability of human blastocysts after warming with fatty acids (FAs) using an in vitro outgrowth model and to assess pregnancy outcomes after a single vitrified-warmed blastocyst transfer (SVBT). For the experimental study, we used 446 discarded vitrified human blastocysts donated for research purposes by consenting couples. The blastocysts were warmed using FA-supplemented (FA group) or non-FA-supplemented (control group) solutions. The outgrowth area was significantly larger in the FA group (P = 0.0428), despite comparable blastocyst adhesion rates between the groups. Furthermore, the incidence of outgrowth degeneration was significantly lower in the FA group than in the control group (P = 0.0158). For the clinical study, we retrospectively analyzed the treatment records of women who underwent SVBT in natural cycles between January and August 2022. Multiple covariates that affected the outcomes were used for propensity score matching as follows: 1342 patients in the FA group were matched to 2316 patients in the control group. Pregnancy outcomes were compared between the groups. The rates of implantation, clinical pregnancy, and ongoing pregnancy significantly increased in the FA group after SVBTs (P = 0.0091-0.0266). These results indicate that warming solutions supplemented with FAs improve blastocyst outgrowth and pregnancy outcomes after SVBTs.

Low-input lipidomics reveals lipid metabolism remodelling during early mammalian embryo development

Lipids are indispensable for energy storage, membrane structure and cell signalling. However, dynamic changes in various categories of endogenous lipids in mammalian early embryonic development have not been systematically characterized. Here we comprehensively investigated the dynamic lipid landscape during mouse and human early embryo development. Lipid signatures of different developmental stages are distinct, particularly for the phospholipid classes. We highlight that the high degree of phospholipid unsaturation is a conserved feature as embryos develop to the blastocyst stage. Moreover, we show that lipid desaturases such as SCD1 are required for in vitro blastocyst development and blastocyst implantation. One of the mechanisms is through the regulation of unsaturated fatty-acid-mediated fluidity of the plasma membrane and apical proteins and the establishment of apical-basal polarity during development of the eight-cell embryo to the blastocyst. Overall, our study provides an invaluable resource about the remodelling of the endogenous lipidome in mammalian preimplantation embryo development and mechanistic insights into the regulation of embryogenesis and implantation by lipid unsaturation.

Autophagy-related gene and protein expressions during blastocyst development

PURPOSE

This study aims to examine the expression of autophagic genes and proteins during blastocyst development and differentiation.

METHODS

This is a prospective cohort study. Between March 2018 and November 2019, 30 females aged 30.13 ± 4.83 years underwent an intracytoplasmic sperm injection (ICSI) cycle at Madina Fertility Center. ICSI was used to develop and incubate 82 leftover embryos to day 5. Then, the embryos were divided into two groups based on their developmental structure: group D (n = 49) included embryos that developed into blastocysts, whereas group A (n = 33) included arrested embryos. These embryos were used to investigate the autophagic gene and protein expressions. The current study was approved by the Clinical Trial Ethical Committee of the Faculty of Medicine, Alexandria University, following the ethical standards of scientific research (Registration no. 0303721).

RESULTS

Embryos that developed into blastocysts on day 5 (group D) had significantly higher relative expression of the LC3 gene (1.11 ± 0.52) and beclin-1 gene (1.43 ± 0.34) and beclin-1 protein expression (3.8 ± 0.028) than those that did not develop into blastocysts on day 5 (group A) [0.72 ± 0.18 (P = 0.03), 0.35 ± 0.12 (P = 0.0001), and 3.14 ± 0.05, (P = 0.0001), respectively]. In contrast, mTOR and PIK3C3 protein expression was significantly higher in group A (arrested embryos) than those in group D (developed embryos) (P = 0.007 and P = 0.0001, respectively). Furthermore, the expression of the eIF4E gene was significantly lower in group D embryos (0.32 ± 0.07) than that in group A embryos (4.38 ± 1.16) (P = 0.0001).

CONCLUSIONS

This work identifies  autophagy as a well regulated process required to maintain cell allocation and differentiation during late preimplantation embryo developmental stages.

Associations of fertility parameters with fatty acids and DNA methylation in Mexican women undergoing in vitro fertilization

BACKGROUND

Fatty acids (FA) likely affect human fertility at multiple levels, as deviations from physiological FA profiles are obesogenic, and FA can modify DNA methylation (DNAm). Yet, the interplay of follicular fluid (FF) and serum FA with BMI and percentage body fat (PBF) in human fertility is not completely understood. Also, associations of DNAm with fertility are largely unexplored.

METHODS

Reproductive parameters ranging from retrieved oocyte number to infant birth weight, were recorded in Mexican women undergoing in vitro fertilization (n = 88). Multiple regression analysis sought BMI-adjusted and age-adjusted associations. Receiver operating characteristic analysis tested for discrimination between outcomes.

RESULTS

Associations of FF and serum FA were markedly distinct. While various FF FA (C16:1, C18:0, C20:2, C20:3, arachidonic acid) were significantly and inversely associated only with retrieved oocyte number, selected serum FA were associated with a broad range of pre-fertilization and post-fertilization parameters. Associations of BMI and FF FA were complex, as arachidonic acid was inversely associated with both BMI and retrieved oocyte number, while oleic acid (OA) was directly associated with BMI and PBF. Ultrasound-assessed clinical pregnancy outcome (CP) was directly associated with serum OA but inversely with its trans isomer elaidic acid (EA) and with BMI. Compounded BMI, serum EA and OA discriminated CP well (AUC = 0.74). Whole blood DNA methylation was significantly associated with and a moderate predictor (AUC = 0.66) of percent fertilized oocytes.

CONCLUSIONS

Overall FF FA pool composition rather than FA identity may impact oocyte production and cellular memory of FF FA is lost as the oocyte exits the follicular environment. The contrasting associations of BMI, FF OA and arachidonic acid suggest that the control of oocyte homeostasis by FF FA is uncoupled from BMI. Further studies are warranted to assess the potential of compounding BMI with serum EA and OA to predict CP.