Interactions of bovine oocytes with follicular elements with respect to lipid metabolism.

Among many factors, lipid metabolism within the follicular environment emerges as an important indicator of oocyte quality. In the literature a crucial significance is described concerning follicular fluid (FF) composition as well as messenger RNA (mRNA) expression in follicular cells. The aim of this study was to describe the relationship between oocyte, FF and follicular cells with regard to lipid metabolism. The set of data originating from individual follicles comprised: lipid droplets (LD) number in oocytes (BODIPY staining), mRNA expression of seven genes in cumulus and granulosa cells (SCD, FADS2, ELOVL2, ELOVL5, GLUT1, GLUT3, GLUT8; real time polymerase chain reaction) and fatty acid (FA) composition in FF (gas chromatography). Obtained results demonstrate significant correlation between oocyte lipid droplets number and FA composition in FF. However, gene expression studies show significant correlation between LD number and GLUT1 gene only. Moreover, the present experiment revealed correlations between FA content in FF and expression of several genes (SCD, FADS2, ELOVL5, GLUT8) in granulosa cells, whereas only the SCD gene in cumulus cells. We suggest that the results of our experiment indicate the importance of glucose : lipid metabolism balance, which contributes to better understanding of energy metabolism conversion between oocytes and the maternal environment.