Nicotinamide mononucleotide supplementation improves the quality of porcine oocytes under heat stress

Nicotinamide mononucleotide biosynthesis and the F-actin cytoskeleton regulate spindle assembly and oocyte maturation quality in post-ovulatory aged porcine oocytes

BACKGROUND

Post-ovulatory aging (POA) is associated with reduced fertilization rates and poor embryo quality both in vivo and in vitro. However, the relationship between nicotinamide adenine dinucleotide (NAD+) and the filamentous actin (F-actin) cytoskeleton in POA-induced oocytes remains unknown. Here, we investigated the mechanisms by which the NAD+ salvage pathways function in poor oocyte maturation upon POA through the F-actin cytoskeleton.

METHODS

Porcine oocytes were aged by extending in vitro maturation (IVM) for an additional 24 h to create a POA model. F-actin and adducin 1 (ADD1)-related spindle assembly were analyzed using immunofluorescence, western blotting, and RNA sequencing to identify key gene categories in the POA and IVM groups. To assess NAD+ function in restoring oocyte maturation, nicotinamide mononucleotide (NMN) was added and the maturation efficiency was evaluated. Expression of spindle assembly factors, F-actin cytoskeleton factors, aging markers, and NAD+-related genes was analyzed via quantitative polymerase chain reaction, immunofluorescence, and western blotting.

RESULTS

We revealed unique interactions between the F-actin/ADD1-related cytoskeleton and aging factors (clusterin (CLU) and FAM111 trypsin-like peptidase A (FAM111A)) in poor-quality oocytes. POA oocytes were established with an extension of 24 h based on 44 h of IVM. They exhibited actin collapses and abnormal cortical F-actin, ADD1, and acetyl(Ac)-α-tubulin protein levels, which resulted in defective spindle assembly. RNA sequencing analysis was performed to identify differentially expressed genes involved in the oocyte viability response to aging, the cytoskeleton, and NAD metabolic processes using IVM and/or POA oocytes. This showed that NAD-binding genes were differentially expressed after POA induction, eight of which were downregulated compared with IVM oocytes. Importantly, activation of NAD+ pathways upon addition of NMN to the medium at 24 h after IVM rescued the maturation capability of POA oocytes with perturbations of spindle assembly and cortical F-actin.

CONCLUSION

F-actin polymerization through NAD+ generated from NMN is an essential factor in determining oocyte quality. This effect is mediated by microtubules related to spindle assembly in POA oocytes.

NAD+ Promotes Superovulation of Huaxi Cattle Through Regulation of Cumulus Cell Proliferation and Oocyte Maturation

Superovulation and embryo transfer are key technologies to improve the reproductive ability of female animals and enhance the efficiency of livestock production. However, poor-quality oocytes or abnormal fluctuations of hormone levels caused by superovulation affect the embryonic development environment, which may lead to a significant decline in the number and quality of transferable embryos, thus reducing the efficiency of superovulation. In this study, nicotinamide adenine dinucleotide (NAD+) was injected into Huaxi cows during the superovulation period to observe the proliferation and apoptosis of transplanted embryos. We examined the proliferation, apoptosis, reactive oxygen species (ROS) and mitochondrial membrane potential of cumulus cells and oocytes directly treated with NAD+ and investigated the potential mechanism of NAD+ to improve the superovulation efficiency by serum metabolomics and single-cell RNA sequencing. The results show that the addition of NAD+ significantly increased the quantity and quality of transferable embryos after superovulation. Differential metabolites during estrus synchronization and embryo flushing are enriched in glycerophospholipid metabolic pathways, suggesting that NAD+ can regulate lipid metabolic pathways. We found that NAD+ optimized the secretion levels of the steroid hormone estradiol (E2) and progesterone (P4) during superovulation by regulating the activity of cumulus cells. In oocytes, we found that NAD+ can inhibit apoptosis, scavenge ROS, and enhance mitochondrial function, thereby promoting oocyte maturation and enhancing embryo developmental potential. In conclusion, NAD+ significantly improved the superovulation ability of Huaxi cattle and provides an effective way for animal husbandry to improve the yield of high-quality embryos.

Nicotinamide mononucleotide enhances the developmental potential of mouse early embryos exposed to perfluorooctanoic acid

Perfluorooctanoic acid (PFOA) exposure severely affects the health of animals and humans, including early embryonic development, but the effective approaches to improve the quality of embryos exposed to PFOA have not been explored. Here, we report that nicotinamide mononucleotide (NMN) can be used to attenuate the impairment of mouse early embryos caused by PFOA exposure. We find that NMN supplementation maintains the normal spindle assembly and proper chromosome alignment by restoring the acetylation level of microtubule to enhance the mitotic capacity of embryos at zygotic cleavage stage under PFOA exposure. In addition, NMN exerts its beneficial effect by enhancing mitochondrial function and eliminating accumulated reactive oxygen species (ROS), which in turn alleviates DNA damage and apoptosis in PFOA-exposed 2-cell embryos. Moreover, NMN ameliorates the quality of PFOA-exposed blastocysts via recovering the octamer-binding transcription factor 4 (Oct4) expression, the actin dynamics, and the total number of cells. Collectively, our findings demonstrate that supplementation with NMN is a feasible strategy to restore the compromised early embryonic development under PFOA exposure, providing a scientific basis for application of NMN to increase the female fertility.

Effects of Glutamine or Glucose Deprivation on Inflammation and Tight Junction Disruption in Yak Rumen Epithelial Cells

Yak is a special free-ranging cattle breed in the plateau areas of Qinghai and Tibet. Pasture withering in cold-season pastures results in energy deficiency in yaks, which undermines the rumen epithelial barrier. However, the leading factor causing rumen epithelial injury remains unknown. Glutamine (Gln), a conditionally essential amino acid, is insufficient under pathological conditions. Glucose (GLU) is an important energy source. Thus, we explored the effects of Gln or GLU deprivation on the barrier function of yak rumen epithelial cells and investigated the underlying mechanisms, as well as the differences in rumen epithelial barrier function between Gln deprivation (Gln-D) and GLU deprivation (GLU-D). In previous work, we constructed the yak rumen epithelial cells (YRECs) line by transferring the human telomerase reverse transcriptase gene (hTERT) and simian virus 40 large T antigen (SV40T) into primary YRECs. The YRECs were exposed to normal, Gln-D, GLU-D, and serum replacement (SR) media for 6, 12, and 24 h. Our data displayed that cell viability and tight junction protein expression in the SR group were not significantly changed compared to the normal group. Whereas, compared with the SR group, Gln-D treated for more than 12 h reduced cell viability and proliferation, and GLU-D treated for more than 12 h damaged the cell morphology and reduced cell viability and proliferation. The cell proliferation and cell viability were decreased more in GLU-D than in Gln-D. In addition, Gln-D treated for more than 12 h disrupted YREC cellular partially tight junctions by inducing oxidative stress and inflammation, and GLU-D treated for more than 12 h disrupted YREC cellular tight junctions by inducing apoptosis, oxidative stress, and inflammation. Compared with Gln-D, GLU-D more significantly induced cell injury and reduced tight junction protein levels. Our results provided evidence that GLU-D induced damage through the p38 mitogen-activated protein kinase (p38 MAPK)/c-junN-terminal kinase (JNK) signaling pathway, which was more serious than Gln-D treated for more than 12 h.

The effects and mechanisms of heat stress on mammalian oocyte and embryo development

The sum of nonspecific physiological responses exhibited by mammals in response to the disruption of thermal balance caused by high-temperature environments is referred to as heat stress (HS). HS affects the normal development of mammalian oocyte and embryos and leads to significant economic losses. Therefore, it is of great importance to gain a deep understanding of the mechanisms underlying the effects of HS on oocyte and embryonic development and to explore strategies for mitigating or preventing its detrimental impacts in the livestock industry. This article provides an overview of the negative effects of HS on mammalian oocyte growth, granulosa cell maturation and function, and embryonic development. It summarizes the mechanisms by which HS affects embryonic development, including generation of reactive oxygen species (ROS), endocrine disruption, the heat shock system, mitochondrial autophagy, and molecular-level alterations. Furthermore, it discusses various measures to ameliorate the effects of HS, such as antioxidant use, enhancement of mitochondrial function, gene editing, cultivating varieties possessing heat-resistant genes, and optimizing the animals'rearing environment. This article serves as a valuable reference for better understanding the relationship between HS and mammalian embryonic development as well as for improving the development of mammalian embryos and economic benefits under HS conditions in livestock production.

Supplementation with NAD+ and its precursors: A rescue of female reproductive diseases

Nicotinamide adenine dinucleotide (NAD+) is an essential coenzyme involved in many pathophysiological processes. Supplementation with NAD+ and its precursors has been demonstrated as an emerging therapeutic strategy for the diseases. NAD+ also plays an important role in the reproductive system. Here, we summarize the function of NAD+ in various reproductive diseases and review the application of NAD+ and its precursors in the preservation of reproductive capacity and the prevention of embryonic malformations. It is shown that NAD+ shows good promise as a therapeutic approach for saving reproductive capacity.

Zinc alleviates thermal stress-induced damage to the integrity and barrier function of cultured chicken embryonic primary jejunal epithelial cells via the MAPK and PI3K/AKT/mTOR signaling pathways

Zinc (Zn) could alleviate the adverse effect of high temperature (HT) on intestinal integrity and barrier function of broilers, but the underlying mechanisms remain unclear. We aimed to investigate the possible protective mechanisms of Zn on primary cultured broiler jejunal epithelial cells exposed to thermal stress (TS). In Exp.1, jejunal epithelial cells were exposed to 40℃ (normal temperature, NT) and 44℃ (HT) for 1, 2, 4, 6, or 8 h. Cells incubated for 8 h had the lowest transepithelial resistance (TEER) and the highest phenol red permeability under HT. In Exp.2, the cells were preincubated with different Zn sources (Zn sulfate as iZn and Zn proteinate with the moderate chelation strength as oZn) and Zn supplemental levels (50 and 100 µmol/L) under NT for 24 h, and then continuously incubated under HT for another 8 h. TS increased phenol red permeability, lactate dehydrogenase (LDH) activity and p-PKC/PKC level, and decreased TEER, cell proliferation, mRNA levels of claudin-1, occludin, zona occludens-1 (ZO-1), PI3K, AKT and mTOR, protein levels of claudin-1, ZO-1 and junctional adhesion molecule-A (JAM-A), and the levels of p-ERK/ERK, p-PI3K/PI3K and p-AKT/AKT. Under HT, oZn was more effective than iZn in increasing TEER, occludin, ZO-1, PI3K, and AKT mRNA levels, ZO-1 protein level, and p-AKT/AKT level; supplementation with 50 μmol Zn/L was more effective than 100 μmol Zn/L in increasing cell proliferation, JAM-A, PI3K, AKT, and PKC mRNA levels, JAM-A protein level, and the levels of p-ERK/ERK and p-PI3K/PI3K; furthermore, supplementation with 50 μmol Zn/L as oZn had the lowest LDH activity, and the highest ERK, JNK-1, and mTOR mRNA levels. Therefore, supplemental Zn, especially 50 μmol Zn/L as oZn, could alleviate the TS-induced integrity and barrier function damage of broiler jejunal epithelial cells possibly by promoting cell proliferation and tight junction protein expression via the MAPK and PI3K/AKT/mTOR signaling pathways.

Nicotinamide Mononucleotide improves oocyte maturation of mice with type 1 diabetes

BACKGROUND

The number of patients with type 1 diabetes rises rapidly around the world in recent years. Maternal diabetes has a detrimental effect on reproductive outcomes due to decreased oocyte quality. However, the strategies to improve the oocyte quality and artificial reproductive technology (ART) efficiency of infertile females suffering from diabetes have not been fully studied. In this study, we aimed to examine the effects of nicotinamide mononucleotide (NMN) on oocyte maturation of mouse with type 1 diabetes mouse and explore the underlying mechanisms of NMN's effect.

METHODS

Streptozotocin (STZ) was used to establish the mouse models with type 1 diabetes. The successful establishment of the models was confirmed by the results of body weight test, fasting blood glucose test and haematoxylin and eosin (H&E) staining. The in vitro maturation (IVM) rate of oocytes from diabetic mice was examined. Immunofluorescence staining (IF) was performed to examine the reactive oxygen species (ROS) level, spindle/chromosome structure, mitochondrial function, actin dynamics, DNA damage and histone modification of oocytes, which are potential factors affecting the oocyte quality. The quantitative reverse transcription PCR (RT-qPCR) was used to detect the mRNA levels of Sod1, Opa1, Mfn2, Drp1, Sirt1 and Sirt3 in oocytes.

RESULTS

The NMN supplementation increased the oocyte maturation rate of the mice with diabetes. Furthermore, NMN supplementation improved the oocyte quality by rescuing the actin dynamics, reversing meiotic defects, improving the mitochondrial function, reducing ROS level, suppressing DNA damage and restoring changes in histone modifications of oocytes collected from the mice with diabetes.

CONCLUSION

NMN could improve the maturation rate and quality of oocytes in STZ-induced diabetic mice, which provides a significant clue for the treatment of infertility of the patients with diabetes.

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.

Research progress on mitochondrial damage and repairing in oocytes: A review

Oocytes are the female germ cells, which are susceptible to stress stimuli. The development of oocytes in the ovary is affected by many environmental and metabolic factors, food toxins, aging, and pathological factors. Mitochondria are the main target organelles of these factors, and the damage to mitochondrial structure and function can affect the production of ATP, the regulation of redox reactions, and apoptosis in oocytes. Mitochondrial damage is closely related to the decrease in oocyte quality and is the main factor leading to female infertility. Antioxidant foods or drugs have been used to prevent mitochondrial damage from some stressors or to repair damaged mitochondria, thereby improving oocyte development and female reproductive outcomes. In this paper, the damage of mitochondria during oocyte development by the above factors has been reviewed, and the relevant measures to alleviate the damage of mitochondria in oocytes have been discussed. Our findings may provide a theoretical basis and experimental basis for improving female fertility.

Effects of β-Nicotinamide Mononucleotide, Berberine, and Cordycepin on Lipid Droplet Content and Developmental Ability of Vitrified Bovine Oocytes

Oocyte vitrification is crucial for livestock reproduction, germplasm conservation, and human-assisted reproduction, but the overabundance of lipids is highly detrimental to oocyte development. It is necessary to reduce the lipid droplet content of oocytes before cryopreservation. This study analyzed the impact of β-nicotinamide mononucleotide (NMN), berberine (BER), or cordycepin (COR) on various aspects of bovine oocytes, including lipid droplet content and the expression levels of genes related to lipid synthesis in bovine oocytes, development ability, reactive oxygen species (ROS), apoptosis, and the expression levels of genes associated with endoplasmic reticulum (ER) stress, and mitochondrial function in vitrified bovine oocytes. The results of our study indicated that 1 μM NMN, 2.5 μM BER, and 1 μM COR were effective in reducing the lipid droplet content and suppressing the expression levels of genes involved in lipid synthesis in bovine oocytes. Our findings showed that the vitrified bovine oocytes treated with 1 μM of NMN had a significantly higher survival rate and better development ability compared to the other vitrified groups. Additionally, 1 μM NMN, 2.5 μM BER, and 1 μM COR decreased the levels of ROS and apoptosis, decreased the mRNA expression levels of genes involved in ER stress and mitochondrial fission but increased the mRNA expression levels of genes associated with mitochondrial fusion in the vitrified bovine oocytes. Our study results suggested that 1 μM NMN, 2.5 μM BER, and 1 μM COR effectively decreased the lipid droplet content and enhanced the development ability of vitrified bovine oocytes by lowering ROS levels, reducing ER stress, regulating mitochondrial function, and inhibiting apoptosis. Furthermore, the results showed that 1 μM NMN was more effective than 2.5 μM BER and 1 μM COR.

Resveratrol and SIRT1: Antiaging Cornerstones for Oocytes?

It is well-known that there is an enormous variability in the aging-related decline of oocytes' quantity and their developmental competence among mammalian species. The implication of female germline aging is profound from the perspective of evolutionary conservation of the aging mechanism, a topic of continuous and widespread interest that has yet to be fully addressed for the mammalian oocyte. There is a certain need to develop novel antiaging strategies to delay or slow down aging, or even to reverse the aging phenotype in the oocyte. In the past two decades, several antioxidants have been tested for this purpose. Resveratrol is one of these latter-mentioned compounds, which has shown anti-inflammatory and antiaging properties in a dose-dependent manner. Interestingly, resveratrol appears to enhance the activity of so-called Sirtuin 1, too. Therefore, the aim of this review is to summarize and discuss the latest findings related to resveratrol, Sirtuin 1, and their crosstalk and influence on the mammalian oocyte to elucidate the question of whether these factors can delay or slow down reproductive aging.