Stearoyl-CoA desaturase activity in bovine cumulus cells protects the oocyte against saturated fatty acid stress

Abstract

Metabolic rich and poor conditions are both characterized by elevated free fatty acid levels and have been associated with impaired female fertility. In particular, saturated free fatty acids have a dose-dependent negative impact on oocyte developmental competence, while monounsaturated free fatty acids appear less harmful. Cumulus cells seem to protect the oocyte against free fatty acids, and the aim of this study was to determine the mechanism behind this protection In particular, the role of the enzyme stearoyl-CoA desaturase (SCD) that converts saturated into monounsaturated fatty acids was investigated. SCD gene and protein were abundantly expressed in cumulus cells, but expression was low in oocytes. The level of SCD protein expression in cumulus cells did not change when COCs were exposed to saturated stearic acid during maturation. SCD inhibition in the presence of stearic acid significantly reduced the developmental competence of oocytes and increased the incidence of apoptosis in cumulus cells. The esterified oleic/stearic acid ratio of the neutral lipid fraction in cumulus cells decreased in the presence of SCD inhibitors when COCs were exposed to saturated free fatty acids during maturation, indicating the SCD-specific conversion of saturated fatty acids under noninhibiting conditions. The observation that cumulus cells can desaturate the potentially toxic stearic acid into oleic acid via SCD activity provides a mechanistic insight into how the cumulus cells protect the oocyte against toxicity by saturated fatty acid.

A Comparative Analysis of Oocyte Development in Mammals

“…Moreover, a dietary supplementation in n-3 PUFA, as mentioned in the previous paragraph, is able to modulate the lipid composition of bovine oocytes [210]. Such modifications of oocyte lipid composition are also reported after in vitro supplementation of n-3 PUFA during maturation in the bovine [215] or of conjugated linoleic acid in the porcine [221].…”

“…The bovine cumulus-oocyte complex is able to direct toward the desaturation of fatty acids through the stearoyl-CoA desaturase (SCD) enzyme [221]. Such changes consequently reduce the amount of saturated fatty acids, and therefore, protect the oocyte against lipotoxicity.…”

Sperm DNA damage causes genomic instability in early embryonic development

“…Fertilization and embryo culture were performed, according to previously described procedures (50). In short, bovine cumulus oocyte complexes were aspirated from 2-to 8-mm antral follicles of slaughterhouse ovaries from 2-to 6-year-old adult cows.…”

Energy metabolism of follicular environment during oocyte growth and maturation

“…This protective effect is visible even during further uninterrupted embryo development. Cumulus cells are able to protect the oocyte and the nascent embryo probably due to the activity of stearoyl-CoA desaturase, which converts saturated into monounsaturated fatty acids [46]. Bovine oocytes that were denuded before maturation had decreased developmental competence and had significantly less lipid content than cumulus enclosed oocytes [47].…”