Metabolism of fatty acids in follicular cells, oocytes, and blastocysts

Abstract

Fatty acids (FA) are one of the substrates that can be oxidized for energy production. The blood concentration of all types of FA varies according to different nutrition conditions, and follicular fluid levels are generally in line with serum levels. Elevated levels of FA, especially non-esterified fatty acids (NEFA), are commonly found in females with metabolic issues, which are often related to subfertility in many species including humans, pigs, cattle, and mice. Long-time exposure to an excessive quantity of fatty acids impairs the cell structure and functions causing injuries in tissues and organs, resulting in lipotoxicity and eventually hampering health and fertility. High levels of saturated NEFA can have detrimental effects on granulosa cells, oocyte quality, and embryo development. Although the harmful effects of FA are established in reproductive tissues, how granulosa cells and cumulus cells respond and cooperate with oocytes when exposed to NEFA requires further understanding. This review provides a summary of the adverse impacts of exposure to NEFA during in vitro maturation on oocytes, follicular cells, and embryos. A comprehensive understanding of the effects of NEFA on oocytes in vitro would improve our understanding of the impacts of natural exposure in vivo.