Salidroside improves porcine oocyte maturation and subsequent embryonic development by promoting lipid metabolism.

An optimal lipid droplet (LD) content is essential for successful mammalian embryonic development. Salidroside (SAL) is a traditional Chinese medicine and one of the important active components of the Rhodiola plant. SAL possesses antioxidative, anti-aging, and cardiovascular properties. Here, we studied the effects of SAL on in vitro maturation (IVM) of porcine oocytes and the subsequent embryonic development after parthenogenetic activation (PA). We found that 100 µM of SAL had no effect on the extrusion rate of the first polar body of porcine oocytes but significantly improved the subsequent blastocyst formation rate and embryo quality. Our study further revealed that SAL treatment altered the morphology, increased the lipid content in oocytes, increased mitochondrial number. Further analysis revealed that SAL upregulated the expression of genes related to lipid metabolism (FASN, FADS1, HSL, and CPT1a) and the mitochondria function-related genes (PGC-1α). These results suggest that SAL supplementation enhances oocyte maturation and subsequent embryonic development by promoting lipid metabolism, providing the necessary energy for the aforementioned processes.

α-Ketoglutarate Improves Meiotic Maturation of Porcine Oocytes and Promotes the Development of PA Embryos, Potentially by Reducing Oxidative Stress through the Nrf2 Pathway.

α-Ketoglutarate (α-KG) is a metabolite in the tricarboxylic acid cycle. It has a strong antioxidant function and can effectively prevent oxidative damage. Previous studies have shown that α-KG exists in porcine follicles, and its content gradually increases as the follicles grow and mature. However, the potential mechanism of supplementation of α-KG on porcine oocytes during in vitro maturation (IVM) has not yet been reported. The purpose of this study was to explore the effect of α-KG on the early embryonic development of pigs and the mechanisms underlying these effects. We found that α-KG can enhance the development of early pig embryos. Adding 20 µM α-KG to the in vitro culture medium significantly increased the rate of blastocyst formation and the total cell number. Compared with to that of the control group, apoptosis in blastocysts of the supplement group was significantly reduced. α-KG reduced the production of reactive oxygen species and glutathione levels in cells. α-KG not only improved the activity of mitochondria but also inhibited the occurrence of apoptosis. After supplementation with α-KG, pig embryo pluripotency-related genes (OCT4, NANOG, and SOX2) and antiapoptotic genes (Bcl2) were upregulated. In terms of mechanism, α-KG activates the Nrf2/ARE signaling pathway to regulate the expression of antioxidant-related targets, thus combating oxidative stress during the in vitro culture of oocytes. Activated Nrf2 promotes the transcription of Bcl2 genes and inhibits cell apoptosis. These results indicate that α-KG supplements have a beneficial effect on IVM by regulating oxidative stress during the IVM of porcine oocytes and can be used as a potential antioxidant for IVM of porcine oocytes.