Lipids are a potential reservoir of energy for initial embryonic development before activation of the embryonic genome and are involved in plasma membrane biosynthesis. Excessive lipid droplet formation is detrimental to cryotolerance and is related to alterations in mitochondrial function, which likely affects lipid metabolism. Increased lipid accumulation in in vitro produced embryos is a consequence of the stress during in vitro embryonic development process. There are several open questions concerning embryo lipid metabolism and developmental potential. Oocyte maturation and embryo development in vivo and in vitro may vary if the donors are subjected to any type of stress before follicle puncture because crucial changes in oocyte/embryonic metabolism occur in response to stress. However, little is known about lipid metabolism under additional stress (such as heat stress). Therefore, in this review, we aimed to update the information regarding the energy metabolism of oocytes and early bovine embryos exhibiting developmental competence, focusing on lipid metabolic pathways observed under in vivo, in vitro, and stress conditions.

Background: Interferon-gamma (IFNγ) is a multifunctional cytokine with antifibrotic and antiproliferative efficiency. We previously found that pancreatic stellate cells (PSC), the main effector cells in cancer-associated fibrosis, are targets of IFNγ action in the pancreas. Applying a combined experimental and computational approach, we have demonstrated a pivotal role of STAT1 in IFNγ signaling in PSC. Using in vivo and in vitro models of pancreatic cancer, we have now studied IFNγ effects on the tumor cells themselves. We hypothesize that IFNγ inhibits tumor progression through two mechanisms, reduction of fibrogenesis and antiproliferative effects on the tumor cells. To elucidate the molecular action of IFNγ, we have established a mathematical model of STAT1 activation and combined experimental studies with computer simulations. Results: In BALB/c-nu/nu mice, flank tumors composed of DSL-6A/C1 pancreatic cancer cells and PSC grew faster than pure DSL-6A/C1 cell tumors. IFNγ inhibited the growth of both types of tumors to a similar degree. Since the stroma reaction typically reduces the efficiency of therapeutic agents, these data suggested that IFNγ may retain its antitumor efficiency in PSC-containing tumors by targeting the stellate cells. Studies with cocultures of DSL-6A/C1 cells and PSC revealed a modest antiproliferative effect of IFNγ under serum-free conditions. Immunoblot analysis of STAT1 phosphorylation and confocal microscopy studies on the nuclear translocation of STAT1 in DSL-6A/C1 cells suggested that IFNγ-induced activation of the transcription factor was weaker than in PSC. The mathematical model not only reproduced the experimental data, but also underscored the conclusions drawn from the experiments by indicating that a maximum of 1/500 of total STAT1 is located as phosphorylated STAT1 in the nucleus upon IFNγ treatment of the tumor cells. Conclusions: IFNγ is equally effective in DSL-6A/C1 tumors with and without stellate cells. While its action in the presence of PSC may be explained by inhibition of fibrogenesis, its efficiency in PSC-free tumors is unlikely to be caused by direct effects on the tumor cells alone but may involve inhibitory effects on local stroma cells as well. To gain further insights, we also plan to apply computer simulations to the analysis of tumor growth in vivo.

The objective of this study was to investigate the influence of long-term temperature stress during the in vitro maturation (IVM) of oocytes on the in vitro embryo production (IVP) and the abundance of HSP70 and HSP90 in zebu cattle. Viable cumulus-oocyte complexes (COCs) were incubated for 24 h at 37 °C, 38.5 °C, or 40 °C for the low-, physiological, and high-temperature stress treatments, respectively. Thereafter, they were subjected to in vitro fertilization and culture. Temperature did not affect the polar body extrusion. However, IVP was adversely affected when IVM took place at 37 °C and 40 °C. The highest abundance of HSP70 was observed in cumulus cells after maturation of COCs at 40 °C. In contrast, HSP70 was more abundant in oocytes at both 37 °C and 40 °C; however, at 40 °C, the difference to the control group (38.5 °C) was not significant. In contrast, the highest abundance of HSP90 was observed in oocytes and cumulus cells at 37 °C. It appears that HSP70 and HSP90 respond to cold and heat stress in different ways. In conclusion, moderately high (40 °C) and low (37 °C) thermal stress for 24 h during IVM is detrimental to the developmental competence of oocyte and is accompanied by changes in the abundances of HSP70 and HSP90, especially in cumulus cells.

Sirtuins are of central importance in many cellular functions and promote cell survival under stress. However, little information is available regarding the relationship between sirtuins and female reproductive biology, especially in response to thermal stress. This study investigated the influence of moderately high (40°C) and low (37°C) thermal stress during in vitro maturation on the development competence of bovine oocytes and embryos. The expression and abundance of sirtuins and other proteins involved in stress response were also studied. The cumulus-oocyte complexes (COCs) of Simmental (Bos taurus) cows underwent in vitro maturation (IVM) at different temperatures (37°C, 38.5°C and 40°C). Before maturation, the oocytes were stained with Brilliant Cresyl Blue (BCB) and categorized as labeled (BCB+) or unlabeled (BCB-). Embryo production was analyzed at the different IVM temperatures. Polar body extrusion was evaluated following IVM, and the mRNA and protein abundance of sirtuins and P53 in oocytes and cumulus cells were analyzed. The differing temperatures during IVM did not significantly alter polar body extrusion and cleavage rates; however, significant differences in blastocyst production were observed. COCs matured at 38.5°C (control, 37.3%) had the highest blastocyst rate, in contrast to those matured at 37°C (33.2%) and 40°C (21.5%). In all groups, the blastocyst rates were higher for BCB+ oocytes than for BCB- oocytes. In BCB+ oocytes, the expression of SIRT1, SIRT2, SIRT3, and SIRT5 genes was higher after maturation than that before maturation and in most of the cases, the expression was higher when IVM was performed at 38.5°C. In the cumulus cells of BCB+ COCs, only SIRT2 remained unaffected by the maturation temperature. In summary, the temperature change of ±1.5°C for 24 h during bovine oocyte maturation impaired in vitro embryo development. This lead to several cellular biochemical alterations in oocytes and granulosa cells from COCs with higher developmental competence (BCB+). Thus, SIRT1 is important for in vitro embryonic development and may protect against cold and heat stress.