SIRT1-dependent modulation of methylation and acetylation of histone H3 on lysine 9 (H3K9) in the zygotic pronuclei improves porcine embryo development

Histone proteoform analysis reveals epigenetic changes in adult mouse brown adipose tissue in response to cold stress

BACKGROUND

Regulation of the thermogenic response by brown adipose tissue (BAT) is an important component of energy homeostasis with implications for the treatment of obesity and diabetes. Our preliminary analyses of RNA-Seq data uncovered many nodes representing epigenetic modifiers that are altered in BAT in response to chronic thermogenic activation. Thus, we hypothesized that chronic thermogenic activation broadly alters epigenetic modifications of DNA and histones in BAT.

RESULTS

Motivated to understand how BAT function is regulated epigenetically, we developed a novel method for the first-ever unbiased top-down proteomic quantitation of histone modifications in BAT and validated our results with a multi-omic approach. To test our hypothesis, wildtype male C57BL/6J mice were housed under chronic conditions of thermoneutral temperature (TN, 28°C), mild cold/room temperature (RT, 22°C), or severe cold (SC, 8°C) and BAT was analyzed for DNA methylation and histone modifications. Methylation of promoters and intragenic regions in genomic DNA decrease in response to chronic cold exposure. Integration of DNA methylation and RNA expression datasets suggest a role for epigenetic modification of DNA in regulation of gene expression in response to cold. In response to cold housing, we observe increased bulk acetylation of histones H3.2 and H4, increased histone H3.2 proteoforms with di- and trimethylation of lysine 9 (K9me2 and K9me3), and increased histone H4 proteoforms with acetylation of lysine 16 (K16ac) in BAT.

CONCLUSIONS

Our results reveal global epigenetically-regulated transcriptional "on" and "off" signals in murine BAT in response to varying degrees of chronic cold stimuli and establish a novel methodology to quantitatively study histones in BAT, allowing for direct comparisons to decipher mechanistic changes during the thermogenic response. Additionally, we make histone PTM and proteoform quantitation, RNA splicing, RRBS, and transcriptional footprint datasets available as a resource for future research.

Epigenetic-related transcriptional reprogramming elucidated by identification and validation of a novel reference gene combination for RT-qPCR studies in porcine oocytes of contrasting quality

BACKGROUND

Reliable RT-qPCR results are dependent on appropriate normalisation. Oocyte maturation studies can be challenging in this respect, as the stage of development can distinctively affect reference gene transcript abundance. The aim of this study was to validate the use of reference genes in oocyte in vitro maturation RT-qPCR studies, and thereafter, examine the abundance of transcripts supporting histone modification during oocyte and early embryo development in oocytes of contrasting quality.

METHODS AND RESULTS

Total RNA from oocytes from prepubertal gilts and sows was extracted either directly succeeding follicle aspiration or after 44 h in vitro maturation, followed by RT-qPCR. The stability of YWHAG, HPRT1, ACTB, GAPDH, HMBS and PFKP, was analysed by NormFinder and further cross-validated by assessing results generated following application of different combinations of potential reference genes for normalisation of the RT-qPCR data. Combining ACTB and PFKP generated high stability according to NormFinder and concordant results. Applying this normalisation, gilt derived oocytes displayed significantly higher abundance than oocytes from sows of almost all the epigenetic-related transcripts studied (HDAC2, SIRT1, SALL4, KDM1A, KDM1B, KDM5A), both before and after maturation.

CONCLUSIONS

This study identified the combined use of ACTB and PFKP as the optimal normalisation for porcine oocyte RT-qPCR data. In oocytes collected from prepubertal gilts, transcription did not appear to be silenced at the time of aspiration, and accumulation of transcripts supporting histone modification facilitating proper fertilization and further embryo development seemed delayed. The results imply the epigenetic-related transcripts may have potential as markers of oocyte quality.

Histone proteoform analysis reveals epigenetic changes in adult mouse brown adipose tissue in response to cold stress

Regulation of the thermogenic response by brown adipose tissue (BAT) is an important component of energy homeostasis with implications for the treatment of obesity and diabetes. Our preliminary analyses uncovered many nodes representing epigenetic modifiers that are altered in BAT in response to chronic thermogenic activation. Thus, we hypothesized that chronic thermogenic activation broadly alters epigenetic modifications of DNA and histones in BAT. Motivated to understand how BAT function is regulated epigenetically, we developed a novel method for the first-ever unbiased top-down proteomic quantitation of histone modifications in BAT and validated our results with a multi-omic approach. To test our hypothesis, wildtype male C57BL/6J mice were housed under chronic conditions of thermoneutral temperature (TN, 28.8°C), mild cold/room temperature (RT, 22°C), or severe cold (SC, 8°C) and BAT was analyzed for DNA methylation and histone modifications. Methylation of promoters and intragenic regions in genomic DNA decrease in response to chronic cold exposure. Integration of DNA methylation and RNA expression data suggest a role for epigenetic modification of DNA in gene regulation in response to cold. In response to cold housing, we observe increased bulk acetylation of histones H3.2 and H4, increased histone H3.2 proteoforms with di- and trimethylation of lysine 9 (K9me2 and K9me3), and increased histone H4 proteoforms with acetylation of lysine 16 (K16ac) in BAT. Taken together, our results reveal global epigenetically-regulated transcriptional "on" and "off" signals in murine BAT in response to varying degrees of chronic cold stimuli and establish a novel methodology to quantitatively study histones in BAT, allowing for direct comparisons to decipher mechanistic changes during the thermogenic response. Additionally, we make histone PTM and proteoform quantitation, RNA splicing, RRBS, and transcriptional footprint datasets available as a resource for future research.

Histone acetyltransferases and histone deacetyl transferases play crucial role during oogenesis and early embryo development

Dynamic epigenetic regulation is critical for proper oogenesis and early embryo development. During oogenesis, fully grown germinal vesicle oocytes develop to mature Metaphase II oocytes which are ready for fertilization. Fertilized oocyte proliferates mitotically until blastocyst formation and the process is called early embryo development. Throughout oogenesis and early embryo development, spatio-temporal gene expression takes place, and this dynamic gene expression is controlled with the aid of epigenetics. Epigenetic means that gene expression can be altered without changing DNA itself. Epigenome is regulated through DNA methylation and histone modifications. While DNA methylation generally ends up with repression of gene expression, histone modifications can result in expression or repression depending on type of modification, type of histone protein and its specific residue. One of the modifications is histone acetylation which generally ends up with gene expression. Histone acetylation occurs through the addition of acetyl group onto amino terminal of the core histone proteins by histone acetyltransferases (HATs). Contrarily, histone deacetylation is associated with repression of gene expression, and it is catalyzed by histone deacetylases (HDACs). This review article focuses on what is known about alterations in the expression of HATs and HDACs and emphasizes importance of HATs and HDACs during oogenesis and early embryo development.

SIRTUINS MODULATORS COUNTERACT MITOCHONDRIAL DYSFUNCTION IN CELLULAR MODELS OF HYPOXIA: RELEVANCE TO SCHIZOPHRENIA

Schizophrenia (SZ) is a neurodevelopmental-associated disorder strongly related to environmental factors, such as hypoxia. Because there is no cure for SZ or any pharmacological approach that could revert hypoxia-induced cellular damages, we evaluated whether modulators of sirtuins could abrogate hypoxia-induced mitochondrial deregulation as a neuroprotective strategy. Firstly, astrocytes from control (Wistar) and Spontaneously Hypertensive Rats (SHR), a model of both SZ and neonatal hypoxia, were submitted to chemical hypoxia. Then, cells were exposed to different concentrations of Nicotinamide (NAM), Resveratrol (Resv), and Sirtinol (Sir) for 48hrs. Our data indicate that sirtuins modulation reduces cell death increasing the acetylation of histone 3. This outcome is related to the rescue of loss of mitochondrial membrane potential, changes in mitochondrial calcium buffering capacity, decreased O₂^-• levels and increased expression of metabolic regulators (Nrf-1 and Nfe2l2) and mitochondrial content. Such findings are relevant not only for hypoxia-associated conditions, named pre-eclampsia but also for SZ since prenatal hypoxia is a relevant environmental factor related to this burdensome neuropsychiatric disorder.

Exploring the Genetic Predisposition to Epigenetic Changes in Alzheimer's Disease

Alzheimer's disease (AD) is a prevalent type of dementia in elderly populations with a significant genetic component. The accumulating evidence suggests that AD involves a reconfiguration of the epigenetic landscape, including DNA methylation, post-translational modification of histone proteins, and chromatin remodeling. Along with environmental factors, individual specific genetic features play a considerable role in the formation of epigenetic architecture. In this study, we attempt to identify the non-coding regulatory SNPs (rSNPs) able to affect the epigenetic mechanisms in AD. To this end, the multi-omics approach is used. The GEO (Gene Expression Omnibus) available data (GSE153875) for AD patients and controls are integrated to reveal the rSNPs that display allele-specific features in both ChIP-seq profiles of four histone modifications and RNA-seq. Furthermore, we analyze the presence of rSNPs in the promoters of genes reported to be differentially expressed between AD and the normal brain (AD-related genes) and involved in epigenetic regulation according to the EpiFactors database. We also searched for the rSNPs in the promoters of the genes coding for transcription regulators of the identified AD-related genes. These regulators were selected based on the corresponding ChIP-seq peaks (ENCODE) in the promoter regions of these genes. Finally, we formed a panel of rSNPs localized to the promoters of genes that contribute to the epigenetic landscape in AD and, thus, to the genetic predisposition for this disease.

The Sperm Small RNA Transcriptome: Implications beyond Reproductive Disorder

Apart from the paternal half of the genetic material, the male gamete carries assorted epigenetic marks for optimal fertilization and the developmental trajectory for the early embryo. Recent works showed dynamic changes in small noncoding RNA (sncRNA) in spermatozoa as they transit through the testicular environment to the epididymal segments. Studies demonstrated the changes to be mediated by epididymosomes during the transit through the adluminal duct in the epididymis, and the changes in sperm sncRNA content stemmed from environmental insults significantly altering the early embryo development and predisposing the offspring to metabolic disorders. Here, we review the current knowledge on the establishment of the sperm sncRNA transcriptome and their role in male-factor infertility, evidence of altered offspring health in response to the paternal life experiences through sperm sncRNA species and, finally, their implications in assisted reproductive technology in terms of epigenetic inheritance.

SIRT1, a novel transcriptional downstream target of CD44, linking its deacetylase activity to tumor cell invasion/metastasis

Our tetracycline-off-inducible CD44 expression system previously established in mouse model, revealed that activation of CD44 with its major ligand hyaluronan (HA) promoted breast cancer (BC) metastasis to the liver. To identify the mechanisms that underpin CD44-promoted BC cell invasion, microarray gene expression profiling using RNA samples from (Tet)-Off-regulated expression system of CD44s in MCF7 cells, revealed a set of upregulated genes including, nuclear sirtuin-1 (SIRT1 also known as NAD-dependent deacetylase), an enzyme that requires NAD⁺ as a cofactor to deacetylate several histones and transcription factors. It stimulates various oncogenic pathways promoting tumorigenesis. This data suggests that SIRT1 is a potential novel transcriptional target of CD44-downstream signaling that promote BC cell invasion/metastasis. This review will discuss the evidence supporting this hypothesis as well as the mechanisms linking SIRT1 to cell proliferation and invasion.

Effects of putrescine on the quality and epigenetic modification of mouse oocytes during in vitro maturation

CONTEXT

Low ovarian putrescine levels and decreased peak values following luteinising hormone peaks are related to poor oocyte quantity and quality in ageing women.

AIMS

To investigate the effects of putrescine supplementation in in vitro maturation (IVM) medium on oocyte quality and epigenetic modification.

METHODS

Germinal vesicle oocytes retrieved from the ovaries of 8-week-old and 9-month-old mice were divided into four groups (the young, young+difluoromethylornithine (DFMO), ageing and ageing+putrescine groups) and cultured in IVM medium with or without 1mM putrescine or DFMO for 16h. The first polar body extrusion (PBE), cleavage and embryonic development were evaluated. Spindles, chromosomes, mitochondria and reactive oxygen species (ROS) were measured. The expression levels of SIRT1, H3K9ac, H3K9me2, H3K9me3, and 5mC levels were evaluated. Sirt1 and imprinted genes were detected.

RESULTS

The PBE was higher in the ageing+putrescine group than in the ageing group. Putrescine increased the total and inner cell mass cell numbers of blastocysts in ageing oocytes. Putrescine decreased aberrant spindles and chromosome aneuploidy, increased the mitochondrial membrane potential and decreased ROS levels. Putrescine increased SIRT1 expression and attenuated the upregulation of H3K9ac levels in ageing oocytes. Putrescine did not affect 5mC, H3K9me2 or H3K9me3 levels or imprinted gene expression.

CONCLUSIONS

Putrescine supplementation during IVM improved the maturation and quality of ageing oocytes and promoted embryonic development by decreasing ROS generation, maintaining mitochondrial and spindle function and correcting aberrant epigenetic modification.

IMPLICATIONS

Putrescine shows application potential for human-assisted reproduction, especially for IVM of oocytes from ageing women.

Arginine Regulates Zygotic Genome Activation in Porcine Embryos Under Nutrition Restriction

Arginine has a positive effect on pre-implantation development in pigs. However, the exact mechanism by which arginine promotes embryonic development is undefined. Here, single-cell RNA sequencing technology was applied to porcine in vivo pre-implantation embryos from the zygote to morula stage, it was found that that the expression of arginine metabolism-related genes clearly changed from the 2-cell stage to the 4-cell stage, when zygotic genome activation (ZGA) occurs in porcine embryos. Further analysis showed that arginine metabolism-related genes are significantly correlated with key ZGA genes. To determine the function of arginine in porcine embryos during ZGA, the in vitro fertilization embryos were cultured in PZM-3 medium (0.12 mM arginine, Control group), a modified PZM-3 medium (0 mM arginine, Block group) and a modified PZM-3 medium supplemented with arginine (0.12 mM arginine, Block + Arg group). The results showed that the 4-cell arrest rate was significantly increased in the Block group compared to the Control group (P < 0.05). The 4-cell arrest rate in the Block + Arg group was significantly decreased than that in the Block group (P < 0.05). Meanwhile, the expression of ZGA marker genes and SIRT1 protein in 4-cell embryos was significantly decreased in the Block group compared to the Control group, and their expression was significantly increased in the Block + Arg group. In addition, we observed that the glutathione (GSH), ATP levels, and lipid droplet contents were significantly increased, and the reactive oxygen species (ROS) level was decreased in the Block + Arg group compared to the Block group. Compared with Control group, spermine content in culture medium and the mRNA expression of ornithine decarboxylase1 (ODC1) of embryos in the Block group were significantly decreased (P < 0.05), and those in the Block + Arg group were significantly increased compared with the Block group (P < 0.05). Moreover, when difluoromethylornithine (an inhibitor of ODC1) was added to the modified PZM-3 medium supplemented with arginine, the effect of arginine on ZGA was inhibited. In summary, our findings demonstrated that arginine may regulate ZGA under nutrition restriction in porcine embryos by promoting polyamine synthesis.

A Fatty Diet Induces a Jejunal Ketogenesis Which Inhibits Local SGLT1-Based Glucose Transport via an Acetylation Mechanism—Results from a Randomized Cross-Over Study between Iso-Caloric High-Fat versus High-Carbohydrate Diets in Healthy Volunteers

Background and aims: Insights into the nature of gut adaptation after different diets enhance the understanding of how food modifications can be used to treat type 2 diabetes and obesity. The aim was to understand how diets, enriched in fat or carbohydrates, affect glucose absorption in the human healthy jejunum, and what mechanisms are involved. Methods: Fifteen healthy subjects received, in randomised order and a crossover study design, two weeks of iso-caloric high-fat diet (HFD) and high-carbohydrate diet (HCD). Following each dietary period, jejunal mucosa samples were retrieved and assessed for protein expression using immunofluorescence and western blotting. Functional characterisation of epithelial glucose transport was assessed ex vivo using Ussing chambers. Regulation of SGLT1 through histone acetylation was studied in vitro in Caco-2 and human jejunal enteroid monolayer cultures. Results: HFD, compared to HCD, decreased jejunal Ussing chamber epithelial glucose transport and the expression of apical transporters for glucose (SGLT1) and fructose (GLUT5), while expression of the basolateral glucose transporter GLUT2 was increased. HFD also increased protein expression of the ketogenesis rate-limiting enzyme mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (HMGCS2) and decreased the acetylation of histone 3 at lysine 9 (H3K9ac). Studies in Caco-2 and human jejunal enteroid monolayer cultures indicated a ketogenesis-induced activation of sirtuins, in turn decreasing SGLT1 expression. Conclusion: Jejunal glucose absorption is decreased by a fat-enriched diet, via a ketogenesis-induced alteration of histone acetylation responsible for the silencing of SGLT1 transcription. The work relates to a secondary outcome in ClinicalTrials.gov (NCT02088853).

Resveratrol enhanced mitochondrial recovery from cryopreservation-induced damages in oocytes and embryos

BACKGROUND

Mitochondria play a crucial role in nuclear maturation, fertilization, and subsequent embryo development. Cryopreservation is an important assisted reproductive technology that is used worldwide for humans and domestic animals. Although mitochondrial quantity and quality are decisive factors for successful development of oocytes and embryos, cryopreservation induces mitochondrial dysfunction. Upon thawing, the damaged mitochondria are removed, and de novo synthesis occurs to restore the function of mitochondria. Resveratrol, 3,5,4'-trihydroxystilbene, is a polyphenolic antioxidant that has versatile target proteins, among which sirtuin-1 (SIRT1) is a key regulator of in mitochondrial biogenesis and degradation.

METHODS

The present study is a literature review focusing on experiments involving the hypothesis that the activation of mitochondrial biogenesis and degradation following cryopreservation and warming by resveratrol may help mitochondrial recovery and improve oocyte and embryo development.

MAIN FINDINGS AND CONCLUSION

Resveratrol improves oocyte maturation and development and upregulates mitochondrial biogenesis and degradation. When vitrified-warmed embryos are treated with resveratrol, it helps in mitochondrial regulation and recovery of embryos from cryopreservation-induced damage.

CONCLUSION

Resveratrol treatment is a possible countermeasure against cryopreservation-induced mitochondrial damage.

Reactive oxygen and nitrogen species regulate porcine embryo development during pre-implantation period: A mini-review

Significant porcine embryonic loss occurs during conceptus morphological elongation and attachment from d 10 to 20 of pregnancy, which directly decreases the reproductive efficiency of sows. A successful establishment of pregnancy mainly depends on the endometrium receptivity, embryo quality, and utero-placental microenvironment, which requires complex cross-talk between the conceptus and uterus. The understanding of the molecular mechanism regulating the uterine-conceptus communication during porcine conceptus elongation and attachment has developed in the past decades. Reactive oxygen and nitrogen species, which are intracellular reactive metabolites that regulate cell fate decisions and alter their biological functions, have recently reportedly been involved in porcine conceptus elongation and attachment. This mini-review will mainly focus on the recent researches about the role of reactive oxygen and nitrogen species in regulating porcine embryo development during the pre-implantation period.

Mutant Nmnat1 leads to a retina-specific decrease of NAD+ accompanied by increased poly(ADP-ribose) in a mouse model of NMNAT1-associated retinal degeneration

Nicotinamide mononucleotide adenylyltransferase 1 (NMNAT1) is required for nuclear nicotinamide adenine mononucleotide (NAD+) biosynthesis in all nucleated cells, and despite its functional ubiquity, mutations in this gene lead to an isolated retinal degeneration. The mechanisms underlying how mutant NMNAT1 causes disease are not well understood, nor is the reason why the pathology is confined to the retina. Using a mouse model of NMNAT1-associated retinal degeneration that harbors the p.Val9Met mutation, we tested the hypothesis that decreased function of mutant NMNAT1 has a greater effect on the levels of NAD+ in the retina than elsewhere in the body. Measurements by liquid chromatography with tandem mass spectrometry showed an early and sustained decrease of NAD+ in mutant retinas that was not observed in other tissues. To understand how consumers of nuclear NAD+ are affected by the reduced availability of NAD+ in mutant retinas, poly(ADP-ribose) polymerase (PARP) and nuclear sirtuin activity were evaluated. PARP activity was elevated during disease progression, as evidenced by overproduction of poly(ADP-ribose) (PAR) in photoreceptors, whereas histone deacetylation activity of nuclear sirtuins was not altered. We hypothesized that PARP could be activated because of elevated levels of oxidative stress; however, we did not observe oxidative DNA damage, lipid peroxidation, or a low glutathione to oxidized glutathione ratio. Terminal deoxynucleotidyl transferase dUTP nick end labeling staining revealed that photoreceptors appear to ultimately die by apoptosis, although the low NAD+ levels and overproduction of PAR suggest that cell death may include aspects of the parthanatos cell death pathway.

Sirtuins and the circadian clock interplay in cardioprotection: focus on sirtuin 1

Chronic disruption of circadian rhythms which include intricate molecular transcription-translation feedback loops of evolutionarily conserved clock genes has serious health consequences and negatively affects cardiovascular physiology. Sirtuins (SIRTs) are nuclear, cytoplasmic and mitochondrial histone deacetylases that influence the circadian clock with clock-controlled oscillatory protein, NAMPT, and its metabolite NAD+. Sirtuins are linked to the multi-organ protective role of melatonin, particularly in acute kidney injury and in cardiovascular diseases, where melatonin, via upregulation of SIRT1 expression, inhibits the apoptotic pathway. This review focuses on SIRT1, an NAD+-dependent class III histone deacetylase which counterbalances the intrinsic histone acetyltransferase activity of one of the clock genes, CLOCK. SIRT1 is involved in the development of cardiomyocytes, regulation of voltage-gated cardiac sodium ion channels via deacetylation, prevention of atherosclerotic plaque formation in the cardiovascular system, protection against oxidative damage and anti-thrombotic actions. Overall, SIRT1 has a see-saw effect on cardioprotection, with low levels being cardioprotective and higher levels leading to cardiac hypertrophy.

SIRT1 reduces epigenetic and non-epigenetic changes to maintain the quality of postovulatory aged oocytes in mice

Postovulatory oocyte aging has a major influence on the development potential of embryos. Many antioxidants can delay oocyte aging by regulating the expression of SIRT1. However, there is a lack of knowledge on SIRT1 function in postovulatory oocyte aging. In vitro transcribed RNA of Sirt1 was injected into fresh oocytes to investigate the function of SIRT1 during postovulatory oocyte aging. In the present study, SIRT1 was found to be down-regulated in aged oocytes compared with fresh oocytes. Meanwhile the intensity of acetylation of H3K9 (H3K9ac) and H3K4 methylation increased in postovulatory aged oocytes. After the oocytes were injected with SIRT1 and aged for 12 h, the intensity of H3K9ac and H3K4 methylation markedly decreased compared with controls. Furthermore, SIRT1 overexpression also reduced the aging-induced oocyte morphological changes and reactive oxygen species accumulation, maintained the spindle normal morphology and attenuated the aging-associated abnormalities of mitochondrial function. The role of SIRT1 in protecting oocyte aging was diminished when oocytes with overexpressed SIRT1 were cultured with SIRT1 inhibitor EX-527. Briefly, these present results show that SIRT1 not only reduced the non-epigenetic changes such as abnormal oocyte morphology, ROS accumulation, spindle defects and mitochondrial dysfunctions but also regulated the epigenetic changes in order to maintain the quality of postovulatory aged oocytes.

Bioinformatics analysis of the network of histone H3 lysine 9 trimethylation in acute myeloid leukaemia

Changes in histone H3 lysine 9 trimethylation (H3K9me3) may be related to the development of drug-resistant acute myeloid leukaemia (AML); insights into the network of H3K9me3 may improve patient prognosis. Patient data were derived from the Gene Expression Omnibus (GEO) database and data from AML cells treated with chidamide, a novel benzamide chemical class of histone deacetylase inhibitor (HDACi), in vitro were derived from ChIP-seq. Patients and AML cell data were analysed using GEO2R, GOseq, KOBAS, the STRING database and Cytoscape 3.5.1. We identified several genes related to the upregulation or downregulation of H3K9me3 in AML patients; some of these genes were related to apoptosis, autophagy, and the pathway of cell longevity. AML cells treated with chidamide in vitro showed the same gene changes. The protein interactions in the network did not have significantly more interactions than expected, suggesting the need for more research to identify these interactions. One compelling result from the protein interaction study was that sirtuin 1 (SIRT1) may have an indirect interaction with lysine-specific demethylase 4A (KDM4A). These results help explain alterations of H3K9me3 in AML that may direct further studies aimed at improving patient prognosis. These results may also provide a basis for chidamide as a treatment strategy for AML patients in the future.

Maternal Obesity Programs Offspring Development and Resveratrol Potentially Reprograms the Effects of Maternal Obesity

Maternal obesity during pregnancy is a now a public health burden that may be the culprit underlying the ever-increasing rates of adult obesity worldwide. Understanding the association between maternal obesity and adult offspring’s obesity would inform policy and practice regarding offspring health through available resources and interventions. This review first summarizes the programming effects of maternal obesity and discusses the possible underlying mechanisms. We then summarize the current evidence suggesting that maternal consumption of resveratrol is helpful in maternal obesity and alleviates its consequences. In conclusion, maternal obesity can program offspring development in an adverse way. Maternal resveratrol could be considered as a potential regimen in reprogramming adverse outcomes in the context of maternal obesity.

Positive Roles of Resveratrol in Early Development of Testicular Germ Cells against Maternal Restraint Stress in Mice

Our present study was designed to evaluate the effects of resveratrol (RES) in Swiss mice by exposing them to prenatal stress. Twenty-four Swiss mice were divided into four groups: control (C), maternal restraint stress (MRS), maternal restraint stress + resveratrol (MRS + RES) 2 mg, and maternal restraint stress + resveratrol (MRS + RES) 20 mg. Dams were exposed to stress by restraint in plastic tubes for four hours a day from 12-18 days of gestation. The results showed that male pups of MRS were significantly decreased in the testis weight, anogenital distance, area of seminiferous tubules, diameter of seminiferous tubules, area of the lumen, diameter of the lumen, and epithelial height of seminiferous tubules. However, the anomalies of the reproductive tract produced under restraint stress were neutralized by the use of RES 2 mg/kg. A significant difference was observed between terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)- positive germ cells in MRS and MRS + RES 20 mg/kg groups, while it was non-significant between MRS + RES 2 mg/kg and C groups. Apart from these effects, blood glucose levels were increased in MRS and MRS + RES 20 mg/kg groups, while experimental animals of the MRS + RES 2 mg/kg group significantly recovered. These results suggested that a lower dose of RES could cure the adverse effects of prenatal stress in early age male progeny. Thus, our study suggests, for the first time, practical values for a lower dose of RES 2 mg/kg as a safe and effective agent in the first week age of prenatally stressed mice.

Visualization of Sirtuin 4 Distribution between Mitochondria and the Nucleus, Based on Bimolecular Fluorescence Self-Complementation

Mitochondrial sirtuins (Sirts) control important cellular processes related to stress. Despite their regulatory importance, however, the dynamics and subcellular distributions of Sirts remain debatable. Here, we investigate the subcellular localization of sirtuin 4 (Sirt4), a sirtuin variant with a mitochondrial targeting sequence (MTS), by expressing Sirt4 fused to the superfolder green fluorescent protein (Sirt4-sfGFP) in HeLa and pancreatic β-cells. Super resolution fluorescence microscopy revealed the trapping of Sirt4-sfGFP to the outer mitochondrial membrane (OMM), possibly due to slow mitochondrial import kinetics. In many cells, Sirt4-sfGFP was also present within the cytosol and nucleus. Moreover, the expression of Sirt4-sfGFP induced mitochondrial swelling in HeLa cells. In order to bypass these effects, we applied the self-complementing split fluorescent protein (FP) technology and developed mito-STAR (mitochondrial sirtuin 4 tripartite abundance reporter), a tripartite probe for the visualization of Sirt4 distribution between mitochondria and the nucleus in single cells. The application of mito-STAR proved the importation of Sirt4 into the mitochondrial matrix and demonstrated its localization in the nucleus under mitochondrial stress conditions. Moreover, our findings highlight that the self-complementation of split FP is a powerful technique to study protein import efficiency in distinct cellular organelles.

Epigenetic and non-epigenetic mode of SIRT1 action during oocyte meiosis progression

Background

SIRT1 histone deacetylase acts on many epigenetic and non-epigenetic targets. It is thought that SIRT1 is involved in oocyte maturation; therefore, the importance of the ooplasmic SIRT1 pool for the further fate of mature oocytes has been strongly suggested. We hypothesised that SIRT1 plays the role of a signalling molecule in mature oocytes through selected epigenetic and non-epigenetic regulation.

Results

We observed SIRT1 re-localisation in mature oocytes and its association with spindle microtubules. In mature oocytes, SIRT1 distribution shows a spindle-like pattern, and spindle-specific SIRT1 action decreases α-tubulin acetylation. Based on the observation of the histone code in immature and mature oocytes, we suggest that SIRT1 is mostly predestined for an epigenetic mode of action in the germinal vesicles (GVs) of immature oocytes. Accordingly, BML-278-driven trimethylation of lysine K9 in histone H3 in mature oocytes is considered to be a result of GV epigenetic transformation.

Conclusions

Taken together, our observations point out the dual spatiotemporal SIRT1 action in oocytes, which can be readily switched from the epigenetic to non-epigenetic mode of action depending on the progress of meiosis.

Electronic supplementary material

The online version of this article (10.1186/s40104-019-0372-3) contains supplementary material, which is available to authorized users.

Polydatin and I-CBP112 protects early bovine embryo against nicotinamide-induced mitochondrial dysfunction

The mammalian Sirtuin family of seven enzymes, members of the NAD⁺-dependent histone deacetylase family that modify histones via direct deacetylation, is involved in the regulation of many antioxidant and oxidative stresses. In the present study, we explored the effects of nicotinamide (NAM)-induced oxidative stress on the in vitro development of bovine embryos, on the acetylation of histone H3 lysine 56 (H3K56ac) and on expression of apoptosis-related genes. Treatment with NAM (10, 20 or 40 mM for 24, 48 or 196 h) during IVC resulted in significantly decreased blastocyst formation (24 h: 38.8 vs. 33.1, 27.3 and 10.2%, with P > 0.05, P < 0.05 and P < 0.01, respectively; 48 h: 37.5 vs. 28.2, 13.4 and 0%, with P < 0.05 and P < 0.01, respectively; 196 h: 35.8 vs. 23.4, 0 and 0%, with P < 0.05, respectively). Treatment with NAM (20 and 40 mM for 24 h) resulted in increased intracellular reactive oxygen species (ROS) levels in 2-cell and blastocysts, and apoptotic cell numbers in blastocysts and decreased mitochondrial membrane potential (ΔΨ) in 2-cell embryos (P < 0.05). Polydatin (PD) and I-CBP112 rescued the 20 mM NAM-induced embryo developmental defects and reduced ROS levels and apoptotic cell numbers in blastocysts (P < 0.05). The gene expression of NF-κB, COX2 and p53 was significantly increased in the NAM-treated group. Immunofluorescence analysis confirmed that the protein levels of nuclear factor-kappa B (NF-κB) decreased significantly after PD and I-CBP112 treatment compared with the control (P < 0.05). High level of H3K56ac induced by NAM was decreased after PD and I-CBP112 treatment (P < 0.05). These findings suggest that NAM treatment induces high levels of H3K56 acetylation that may be involved in oxidative stress-induced bovine developmental defects, which can be tolerated by PD and I-CBP112 treatment.

Genome-wide differences in DNA methylation changes in caprine ovaries between oestrous and dioestrous phases

Background

DNA methylation plays a vital role in reproduction. Entire genome DNA methylation changes during the oestrous phase (ES) and dioestrous phase (DS) in the ovaries of Guanzhong dairy goats were investigated using bisulphite sequencing to understand the molecular biological mechanisms of these goats’ oestrous cycle.

Results

We discovered distinct genome-wide DNA methylation patterns in ES and DS ovaries. A total of 26,910 differentially methylated regions were upregulated and 21,453 differentially methylated regions were downregulated in the ES samples compared with the DS samples (P-values ≤0.05 and fold change of methylation ratios ≥2). Differentially methylated region analysis showed hypomethylation in the gene body regions and hypermethylation in the joining region between upstream regions and gene bodies. The methylation ratios of the STAR, FGF2, FGF12, BMP5 and SMAD6 genes in the ES samples were lower than those of the DS samples (P-values ≤0.05 and fold change of methylation ratios ≥2). Conversely, the methylation ratios of the EGFR, TGFBR2, IGF2BP1 and MMD2 genes increased in the ES samples compared with the DS samples. In addition, 223 differentially methylated genes were found in the GnRH signalling pathway (KO04912), ovarian steroidogenesis pathway (KO04913), oestrogen signalling pathway (KO04915), oxytocin signalling pathway (KO04921), insulin secretion pathway (KO04911) and MAPK signalling pathway (KO04010).

Conclusions

This study is the first large-scale comparison of the high-resolution DNA methylation landscapes of oestrous and dioestrous ovaries from dairy goats. Previous studies and our investigations have shown that the NR5A2, STAR, FGF2 and BMP5 genes might have potential application value in regulating caprine oestrus.

Electronic supplementary material

The online version of this article (10.1186/s40104-018-0301-x) contains supplementary material, which is available to authorized users.

SIRT1 overexpression attenuates offspring metabolic and liver disorders as a result of maternal high-fat feeding

KEY POINTS

Maternal high-fat diet (MHF) consumption led to metabolic and liver disorders in male offspring, which are associated with reduced sirtuin (SIRT)1 expression and activity in the offspring liver SIRT1 overexpression in MHF offspring reduced their body weight and adiposity and normalized lipid metabolic markers in epididymal and retroperitoneal adipose tissues SIRT1 overexpression in MHF offspring improved glucose tolerance, as well as systemic and hepatic insulin sensitivity SIRT1 overexpression ameliorated MHF-induced lipogenesis, oxidative stress and fibrogenesis in the liver of offspring.

ABSTRACT

Maternal obesity can increase the risk of metabolic disorders in the offspring. However, the underlying mechanism responsible for this is not clearly understood. Previous evidence implied that sirtuin (SIRT)1, a potent regulator of energy metabolism and stress responses, may play an important role. In the present study, we have shown, in C57BL/6 mice, that maternal high-fat diet (HFD) consumption can induce a pre-diabetic and non-alcoholic fatty liver disease phenotype in the offspring, associated with reduced SIRT1 expression in the hypothalamus, white adipose tissues (WAT) and liver. Importantly, the overexpression of SIRT1 in these offspring significantly attenuated the excessive accumulation of epididymal (Epi) white adipose tissue (WAT) and retroperitoneal (Rp)WAT (P < 0.001), glucose intolerance and insulin resistance (both P < 0.05) at weaning age. These changes were associated with the suppression of peroxisome proliferator-activated receptor gamma (PPAR)γ (P < 0.01), PPARγ-coactivator 1-alpha (P < 0.05) and sterol regulatory element-binding protein-1c in EpiWAT (P < 0.01), whereas there was increased expression of PPARγ in RpWAT (P < 0.05). In the liver, PPARγ mRNA expression, as well as Akt protein expression and activity, were increased (P < 0.05), whereas fatty acid synthase and carbohydrate response element binding protein were downregulated (P < 0.05), supporting increased insulin sensitivity and reduced lipogenesis in the liver. In addition, hepatic expression of endogenous anti-oxidants, including glutathione peroxidase 1 and catalase, was increased (P < 0.01 and P < 0.05 respectively), whereas collagen and fibronectin deposition was suppressed (P < 0.01). Collectively, the present study provides direct evidence of the mechanistic significance of SIRT1 in maternal HFD-induced metabolic dysfunction in offspring and suggests that SIRT1 is a promising target for fetal reprogramming.

Maternal resveratrol consumption and its programming effects on metabolic health in offspring mechanisms and potential implications

A growing body of evidence has clearly demonstrated that maternal nutrition can strongly determine the susceptibility to the development of metabolic diseases in offspring. With the increasing prevalence of maternal overweight, obesity, and gestational diabetes mellitus, it yields enormous burden for individual and public health. Interventions during pregnancy have been proven to be challenging, with limited efficacy and low compliance. Resveratrol, as a natural polyphenolic compound, has a wide-range of beneficial properties, including potent antiobesogenic, antiatherosclerotic, and antidiabetic effects. However, the role of maternal resveratrol intake on metabolic health in offspring has not been extensively investigated. Therefore, the aim of this study was to review the effects of maternal resveratrol supplementation on metabolic health in offspring and its potential mechanisms.

Review: Sperm-oocyte interactions and their implications for bull fertility, with emphasis on the ubiquitin-proteasome system

Fertilization is an intricate cascade of events that irreversibly alter the participating male and female gamete and ultimately lead to the union of paternal and maternal genomes in the zygote. Fertilization starts with sperm capacitation within the oviductal sperm reservoir, followed by gamete recognition, sperm-zona pellucida interactions and sperm-oolemma adhesion and fusion, followed by sperm incorporation, oocyte activation, pronuclear development and embryo cleavage. At fertilization, bull spermatozoon loses its acrosome and plasma membrane components and contributes chromosomes, centriole, perinuclear theca proteins and regulatory RNAs to the zygote. While also incorporated in oocyte cytoplasm, structures of the sperm tail, including mitochondrial sheath, axoneme, fibrous sheath and outer dense fibers are degraded and recycled. The ability of some of these sperm contributed components to give rise to functional zygotic structures and properly induce embryonic development may vary between bulls, bearing on their reproductive performance, and on the fitness, health, fertility and production traits of their offspring. Proper functioning, recycling and remodeling of gamete structures at fertilization is aided by the ubiquitin-proteasome system (UPS), the universal substrate-specific protein recycling pathway present in bovine and other mammalian oocytes and spermatozoa. This review is focused on the aspects of UPS relevant to bovine fertilization and bull fertility.