Transcriptome and epigenome analysis of porcine embryos from non-esterified fatty acid-exposed oocytes

Abstract

Increasing evidence indicates that maternal malnutrition leads to decreased female fertility and dysregulated metabolic homeostasis in offspring. High levels of non-esterified fatty acids (NEFAs) in follicular fluid were reported to be involved in these maternal nutritional effects, but the mechanisms remain unclear. This study explored the mechanisms of action of abnormal NEFA levels during porcine oocyte in vitro maturation (IVM) on early embryo development (blastocysts) using phenotypic, transcriptomic, and epigenetic analysis. The oocytes were treated during IVM with, in addition to the 1% (v/v) porcine follicular fluid in the control group, a combination of 468 μmol/L palmitic acid, 194 μmol/L stearic acid, and 534 μmol/L oleic acid supplemented to North Carolina State University-23 (NCSU-23) maturation medium to achieve a high level of NEFAs. After IVM, oocytes were in vitro fertilized and then cultured in regular conditions for blastocysts. Expanded blastocysts were collected to complete transcriptomic and epigenetic analysis. Macroscopically, high level of NEFAs impaired embryo development by reducing the blastocyst rate. Analysis of the transcriptome revealed that pathways related to inflammation, apoptosis, metabolism, and oxidative stress were the most affected. Moreover, DNA methylation data demonstrated differentially methylated regions in genes related to cellular metabolism and inflammation processes. Therefore, our conclusion is that high level of NEFAs during IVM might affect porcine early embryo development by diminishing blastocyst rate and altering gene expression, especially at the metabolism and cell status levels, which could further decrease the embryo quality.