Oleic Acid Counters Impaired Blastocyst Development Induced by Palmitic Acid During Mouse Preimplantation Development: Understanding Obesity-Related Declines in Fertility

Abstract

Obesity is associated with altered fatty acid profiles, reduced fertility, and assisted reproductive technology (ART) success. The effects of palmitic acid (PA), oleic acid (OA), and their combination on mouse preimplantation development, endoplasmic reticulum (ER) stress pathway gene expression, lipid droplet formation, and mitochondrial reactive oxygen species (ROS) were characterized. Two-cell stage mouse embryos collected from superovulated and mated CD1 females were placed into culture with KSOMaa medium, or PA alone or in combination with OA for 46 h. PA significantly reduced blastocyst development in a concentration-dependent manner, which was prevented by co-treatment with OA. PA and OA levels in mouse reproductive tracts were assessed by liquid chromatography coupled to mass spectrometry (LC-MS). LC-MS indicated higher concentrations of PA in the mouse oviduct than the uterus. Transcript analysis revealed that PA alone groups had increased ER stress pathway (ATF3, CHOP, and XBP1 splicing) mRNAs, which was alleviated by OA co-treatment. OA co-treatment significantly increased lipid droplet accumulation and significantly decreased mitochondrial ROS from PA treatment alone. PA treatment for only 24 h significantly reduced its impact on blastocyst development from the 2-cell stage. Thus, PA affects ER stress pathway gene expression, lipid droplet accumulation, and mitochondrial ROS in treated preimplantation embryos. These mechanisms may serve to offset free fatty acid exposure effects on preimplantation development, but their protective ability may be overwhelmed by elevated PA.

Effects of palmitic acid on localization of embryo cell fate and blastocyst formation gene products

“…A statistically significant decrease ( P < 0.001) in the number of blastocysts was observed in the PA-treated group compared to all other groups ( Fig. 1C ), which is consistent with our previous study ( Yousif et al 2020 ). There were no significant differences in blastocyst developmental frequency between the control, OA alone and PA and OA combination (PA/OA) treatment groups ( Fig.…”

“…PA and OA treatment concentrations were derived from concentration responsive experiments conducted and reported in our recent study ( Yousif et al 2020 ); 100 µM PA had a negative effect on blastocyst development and 100 µM OA was able to overcome these deficits. PA is in the low physiological range, as 300–400 µM PA was measured in the regular chow-fed mouse oviduct ( Yousif et al 2020 ).…”

“…PA and OA treatment concentrations were derived from concentration responsive experiments conducted and reported in our recent study ( Yousif et al 2020 ); 100 µM PA had a negative effect on blastocyst development and 100 µM OA was able to overcome these deficits. PA is in the low physiological range, as 300–400 µM PA was measured in the regular chow-fed mouse oviduct ( Yousif et al 2020 ). Third trimester women with normal glucose tolerance had serum levels of 122 µM PA and 83 µM OA ( Chen et al 2010 ) which increased in obese women with gestational diabetes to 151 and 104 µM, respectively.…”

“…OA decreases PA-induced apoptosis and ROS ( Yuzefovych et al 2010 ), decreases PA-induced inflammation and relieves ER stress ( Palomer et al 2018 ). We have recently reported that PA treatment reduces mouse blastocyst development in a concentration-dependent manner and alters ER stress pathway transcript levels, while co-treatment of OA with PA reversed these negative effects ( Yousif et al 2020 ). Interestingly, we observed a small percentage of PA (100 µM) treated two-cell stage embryos that still cavitate, but for this study, we were especially interested in those that were unable to cavitate and become blastocysts.…”

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

“…PA (16:0) is the most abundant non-esterified fatty acid in the Western diet, and in the blood (26)(27)(28), and OA (18:1) is the most abundant monounsaturated non-esterified fatty acid in human serum (27,28). Cell loading with FFAs has been commonly used to construct in vitro models of obesity.…”