Cumulus cells protect the oocyte against saturated free fatty acids

Abstract

In the cow a major characteristic of metabolic stress is an elevated level of plasma free fatty acid, due to increased lipid mobilization from adipose tissue. Elevated levels of free fatty acids in blood (complexed to albumin) are associated with increased lipotoxicity in non-adipose tissue. An overview is provided on the negative impact of free fatty acids and the metabolic stress imposed on the oocyte and early embryo and thus on bovine fertility. There is increasing evidence that in vitro as well as in vivo the elevated levels of free fatty acids in blood during metabolic stress can severely hamper oocyte and embryo development. However, fatty acids do also form an essential nutrient source for the oocyte and embryo, which indicates that these good and bad effects of fatty acids should be in subtle balance to optimize the developmental competence of the oocyte and embryo.

MALDI-TOF Mass Spectrometry Revealed Significant Lipid Variations in Follicular Fluid and Somatic Follicular Cells but Not in Enclosed Oocytes between the Large Dominant and Small Subordinate Follicles in Bovine Ovary

“…In addition, analysis of lipids in bovine ovarian follicular cells and fluid using Matrix Assisted Laser Desorption/Ionisation Time-Of-Flight Mass spectrometry (MALDI MS) revealed very specific lipid fingerprints in GC, TH, CC, oocyte and FF [13]. These differences in lipid composition corroborate with specific expression patterns of lipid metabolism-related genes in somatic follicular cells [13,17] and oocyte-cumulus complex [18][19][20][21]. Each follicle therefore possesses molecular machinery to uptake and transform lipids to assure energy requirement, membrane synthesis and signaling to maintain follicular homeostasis and [13] and provide to oocyte the necessary building blocks for the first steps of embryo development [5,22].…”

“…CC express necessary enzymes to metabolize the huge amounts of FAs and cholesterol for primary production of steroids and transform lipids to provide energy or stock lipid reserves [ 20 , 21 , 52 ]. In contrast to enclosed oocytes, about 10% of lipids in CC showed differential abundance between dominant LF and subordinate SF, and 95.3% of differential lipids were more abundant in LF.…”

“…Inhibition of FA oxidation decreased accumulation of lipid droplets in CC and led to their death [ 21 ]. CC play essential role in protection of the enclosed oocyte from lipotoxicity through lipid droplets accumulation within CC cytoplasm [ 70 ], notably by transforming saturated FAs through SCD (stearoyl-CoA desaturase) activity [ 20 , 71 ].…”

The impact of diabetes and obesity on fertility and the potential role of gut hormones as treatment

“…Under optimal conditions, LH stimulates the oocyte to resume meiosis at the end of growth phase while stimulating its cytoplasmic contents to coordinate and produce a high‐quality oocyte. It is proposed that influx of FFAs in oocytes during obesity can alter cytoplasmic factors like mitochondrial permeability, ER stress and ROS production all affecting oocyte maturity and quality 22 . The altered mitochondrial activity and disrupted meiosis leads to abnormal embryo preimplantation.…”

Lipidomic profiling of dairy cattle oocytes by high performance liquid chromatography-high resolution tandem mass spectrometry for developmental competence markers

“…CL participates in the formation of mitochondrial cristae and interacts with electron transport chain (ETC) proteins. Since CL plays a critical role in the maintenance of mitochondrial structure and function, its deficiency results in mitochondrial dysfunction triggering a series of metabolic disorders as well as chronic diseases in the body [26]. Interestingly, the total CL amount in degenerating oocytes (20.6 ± 14.4 pmol) was as low as only 43.5% of the normal (47.4 ± 12.5 pmol, P < 0.001) ( Figure 5C), strongly indicating its energy production insufficiency.…”