Insufficient pyruvate in culture medium arrests mouse embryos at the first cleavage stage associated with abnormal epigenetic modifications

Specific regulation of epigenome landscape by metabolic enzymes and metabolites

Metabolism includes anabolism and catabolism, which play an essential role in many biological processes. Chromatin modifications are post-translational modifications of histones and nucleic acids that play important roles in regulating chromatin-associated processes such as gene transcription. There is a tight connection between metabolism and chromatin modifications. Many metabolic enzymes and metabolites coordinate cellular activities with alterations in nutrient availability by regulating gene expression through epigenetic mechanisms such as DNA methylation and histone modifications. The dysregulation of gene expression by metabolism and epigenetic modifications may lead to diseases such as diabetes and cancer. Recent studies reveal that metabolic enzymes and metabolites specifically regulate chromatin modifications, including modification types, modification residues and chromatin regions. This specific regulation has been implicated in the development of human diseases, yet the underlying mechanisms are only beginning to be uncovered. In this review, we summarise recent studies of the molecular mechanisms underlying the metabolic regulation of histone and DNA modifications and discuss how they contribute to pathogenesis. We also describe recent developments in technologies used to address the key questions in this field. We hope this will inspire further in-depth investigations of the specific regulatory mechanisms involved, and most importantly will shed lights on the development of more effective disease therapies.

Smart seq2 revealed distinct molecular responses during in vitro porcine oocyte maturation before or after the addition of mogroside V

Oocyte maturation involves both nuclear and cytoplasmic maturation. Mogroside V (MV) has been shown to enhance nuclear maturation, mitochondrial content, and developmental potential of porcine oocyte during in vitro maturation (IVM). However, the impact of MV on cytoplasmic maturation and its underlying mechanisms are not understood. This study aimed to assess the effect of MV on cytoplasmic maturation. Germinal vesicle (GV) oocytes treated with MV exhibited a noticeable increase in cortical granules (CGs) formation. Additionally, MV enhanced the expression of NNAT and improved glucose uptake in mature oocytes. Further insights were gained through Smart-seq2 analysis of RNA isolated from 100 oocytes. A total of 11,274 and 11,185 transcripts were identified in oocytes treated with and without MV, respectively. Among quantified genes, 438 differentially expressed genes (DEGs) were identified for further analysis. Gene Ontology (GO) enrichment analysis indicated that these DEGs were primarily involved in DNA repair regulation, cellular response to DNA damage, intracellular components, and organelles. Furthermore, the DEGs were significantly enriched in three KEGG pathways: fatty acid synthesis, pyruvate metabolism, and WNT signalling. To validate the results, lipid droplets (LD) and triglyceride (TG) were examined. MV led to an increase in the accumulation of LD and TG production in mature oocytes. These findings suggest that MV enhances cytoplasmic maturation by promoting lipid droplet synthesis. Overall, this study provides valuable insights into the mechanisms through which MV improves oocyte quality during IVM. The results have significant implications for research in livestock reproduction and offer guidance for future studies in this field.

Mogroside V alleviates the heat stress-induced disruption of the porcine oocyte in vitro maturation

Heat stress (HS) is a stressor that negatively affect female reproduction. Specially, oocytes are very sensitive to HS. It has been demonstrated that some active compounds can protect oocyte from HS. We previously found that Mogroside V (MV), extracted from Siraitia grosvenorii (Luo Han Guo), can protect oocyte from many kinds of stresses. However, how MV alleviates HS-induced disruption of oocyte maturation remains unknown. In this study, we treated the HS-induced porcine oocytes with MV to examine their maturation and quality. Our findings demonstrate that MV can effectively alleviate HS-induced porcine oocyte abnormal cumulus cell expansion, decrease of first polar body extrusion rate, spindle assembly and chromosome separation abnormalities, indicating MV attenuates oocyte mature defects. We further observed that MV can effectively alleviate HS-induced cortical granule distribution abnormality and decrease of blastocyst formation rate after parthenogenesis activation. In addition, MV treatment reversed mitochondrial dysfunction and lipid droplet content decrease, reduced reactive oxygen species levels, early apoptosis and DNA damage in porcine oocytes after HS. Collectively, this study suggests that MV can effectively protect porcine oocytes from HS.

Effects of pyruvate on early embryonic development and zygotic genome activation in pigs

Pyruvate is an important energy substance during early embryonic development of mammals. However, the underlying mechanisms of pyruvate during early embryonic development in pigs and its role in zygotic genome activation (ZGA) are not fully understood. Here, based on a previous RNA-seq dataset of porcine early embryos, we found that pyruvate metabolism-related genes started to be expressed at the 4-cell stage and that pyruvate metabolism-related genes were correlated with porcine ZGA marker genes. To determine the function of pyruvate in porcine embryos, in vitro fertilization (IVF) embryos were cultured in PZM-3 medium (control group); modified PZM-3 medium that only contains pyruvate and lactate plus salts (+P group); or modified PZM-3 medium lacking pyruvate (-P group). The 4-cell arrest rate at 72 h was significantly increased in the -P group compared to the +P group (P < 0.05). In addition, we observed that the reactive oxygen species (ROS) level was significantly increased and that the adenosine triphosphate (ATP) level was significantly (P < 0.05) decreased in the -P group compared to the +P group. Moreover, the expression of ZGA marker genes and SIRT1 protein in embryos was significantly decreased in the -P group compared to the +P group (P < 0.05). Furthermore, the acetylation level of H3K9 was significantly decreased (P < 0.05) and the methylation level of H3K9 was significantly increased (P < 0.05) in the -P group compared to the +P group. In summary, our findings demonstrate that pyruvate affects early embryonic development in pigs by promoting ZGA and reducing oxidative stress levels.