Aging involves progressive loss of cellular function and integrity, presumably caused by accumulated stochastic damage to cells. Alterations in energy metabolism contribute to aging, but how energy metabolism changes with age, how these changes affect aging, and whether they can be modified to modulate aging remain unclear. In locomotory muscle of post-fertile Caenorhabditis elegans, we identified a progressive decrease in cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C), a longevity-associated metabolic enzyme, and a reciprocal increase in glycolytic pyruvate kinase (PK) that were necessary and sufficient to limit lifespan. Decline in PEPCK-C with age also led to loss of cellular function and integrity including muscle activity, and cellular senescence. Genetic and pharmacologic interventions of PEPCK-C, muscle activity, and AMPK signaling demonstrate that declines in PEPCK-C and muscle function with age interacted to limit reproductive life and lifespan via disrupted energy homeostasis. Quantifications of metabolic flux show that reciprocal changes in PEPCK-C and PK with age shunted energy metabolism toward glycolysis, reducing mitochondrial bioenergetics. Last, calorie restriction countered changes in PEPCK-C and PK with age to elicit antiaging effects via TOR inhibition. Thus, a programmed metabolic event involving PEPCK-C and PK is a determinant of aging that can be modified to modulate aging.Aging is characterized by the progressive decline in cellular function and integrity that leads to disease vulnerability and eventually death of organisms (1). The leading proposed cause of decline in cellular function and integrity with age is the accumulation of stochastic damage of molecules and organelles by reactive molecules, such as reactive oxygen species (ROS). Whether ROS are detrimental to organisms and whether ROS limit lifespan, however, are in debate (2).Energy metabolism supplies ATP for cellular function and maintenance. Alterations in energy metabolism are linked to the aging process and aging-associated diseases (3). In model organisms, environmental and genetic factors that change energy metabolism, such as calorie restriction (CR) (4), inhibition of target of rapamycin (TOR) (5), and 5Ј AMP kinase (AMPK) (6) are determinants of longevity. A large body of aging research has been focusing on the signaling of CR, TOR inhibition, and AMPK in regulating longevity. The exact alterations in energy metabolism that occur with age, how these changes impact aging, and whether they can be modified to modulate aging are understudied and remain poorly understood, largely due to the intrinsic complexity of energy metabolism, and the indirect impact of these longevity paradigms on energy metabolism. This impedes the understanding of aging mechanisms and the development of mechanism-based strategies to modulate aging.A key regulation of energy metabolism at the cellular level is the reciprocal changes of PK and PEPCK-C (7). Whether this regulation of cellular energy metabolism contributes to organismal aging is...
Neuroblastoma is notable for its broad spectrum of clinical behavior ranging from spontaneous regression to rapidly progressive disease. Hypoxia is well known to confer a more aggressive phenotype in neuroblastoma. We analyzed transcriptome data from diagnostic neuroblastoma tumors and hypoxic neuroblastoma cell lines to identify genes whose expression levels correlate with poor patient outcome and are involved in the hypoxia response. By integrating a diverse set of transcriptome datasets, including those from neuroblastoma patients and neuroblastoma derived cell lines, we identified nine genes (SLCO4A1, ENO1, HK2, PGK1, MTFP1, HILPDA, VKORC1, TPI1, and HIST1H1C) that are up-regulated in hypoxia and whose expression levels are correlated with poor patient outcome in three independent neuroblastoma cohorts. Analysis of 5-hydroxymethylcytosine and ENCODE data indicate that at least five of these nine genes have an increase in 5-hydroxymethylcytosine and a more open chromatin structure in hypoxia versus normoxia and are putative targets of hypoxia inducible factor (HIF) as they contain HIF binding sites in their regulatory regions. Four of these genes are key components of the glycolytic pathway and another three are directly involved in cellular metabolism. We experimentally validated our computational findings demonstrating that seven of the nine genes are significantly up-regulated in response to hypoxia in the four neuroblastoma cell lines tested. This compact and robustly validated group of genes, is associated with the hypoxia response in aggressive neuroblastoma and may represent a novel target for biomarker and therapeutic development.
CRISPR/Cas9 has become a powerful tool for genome editing in zebrafish that permits the rapid generation of loss of function mutations and the knock-in of specific alleles using DNA templates and homology directed repair (HDR). We examined the efficiency of synthetic, chemically modified gRNAs and demonstrate induction of indels and large genomic deletions in combination with recombinant Cas9 protein. We developed an in vivo genetic assay to measure HDR efficiency and we utilized this assay to test the effect of altering template design on HDR. Utilizing synthetic gRNAs and linear dsDNA templates, we successfully performed knock-in of fluorophores at multiple genomic loci and demonstrate transmission through the germline at high efficiency. We demonstrate that synthetic HDR templates can be used to knock-in bacterial nitroreductase (ntr) to facilitate lineage ablation of specific cell types. Collectively, our data demonstrate the utility of combining synthetic gRNAs and dsDNA templates to perform homology directed repair and genome editing in vivo.
Trace metals are essential for health but toxic when present in excess. The maintenance of trace metals at physiologic levels reflects both import and export by cells and absorption and excretion by organs. The mechanism by which this maintenance is achieved in vertebrate organisms is incompletely understood. To explore this, we chose zebrafish as our model organism, as they are amenable to both pharmacologic and genetic manipulation and comprise an ideal system for genetic screens and toxicological studies. To characterize trace metal content in developing zebrafish, we measured levels of three trace elements, copper, zinc, and manganese, from the oocyte stage to 30 days post-fertilization using inductively coupled plasma mass spectrometry. Our results indicate that metal levels are stable until zebrafish can acquire metals from the environment and imply that the early embryo relies on maternal contribution of metals to the oocyte. We also measured metal levels in bodies and yolks of embryos reared in presence and absence of the copper chelator neocuproine. All three metals exhibited different relative abundances between yolks and bodies of embryos. While neocuproine treatment led to an expected phenotype of copper deficiency, total copper levels were unaffected, indicating that measurement of total metal levels does not equate with measurement of biologically active metal levels. Overall, our data not only can be used in the design and execution of genetic, physiologic, and toxicologic studies but also has implications for the understanding of vertebrate metal homeostasis.
Study question To assess whether there is a relationship between mitochondrial DNA content and implantation result. Summary answer The embryos with a higher mitochondrial DNA ratio increase pregnancy rate and implantation rate in single euploid embryo transfer. What is known already Mitochondria is an important organelle that generates energy during embryonic development. Recent literature points out that mitochondrial content and function may be related to implantation success and embryo viability. Some studies have linked increased ratios of mitochondrial DNA to aneuploidy, advanced maternal age, and euploid blastocyst with implantation failure, while others have failed to demonstrate similar findings. Study design, size, duration This study is a retrospective cohort study from 2016 to 2019, including 1465 single embryo transfer cycles. Participants/materials, setting, methods The involved embryos were biopsied on Day 5 or 6 and the mitochondrial DNA ratio of 1465 embryos was examined undergoing PGS/NGS. The mitochondrial DNA ratios were normalized for technical batch-to-batch variation. The mitochondrial DNA ratio between the implantation group and non-implantation group was statistically analyzed. Data were analyzed by the student’s t-test for continuous variables and Chi-square test for categorical variables. Main results and the role of chance The mitochondrial DNA ratio of embryos was no significant difference between different age spans ( p = 0.772) and ploidy (p = 0.224). D5 biopsied embryos, however, contained a significantly higher mitochondrial DNA ratio than D6 biopsied embryos (p < 0.0001). All of the single embryo transferred embryos were classified into two groups; implanted and non-implanted embryos. Results from 1465 transferred embryos show that the mitochondrial DNA ratio of implanted embryos was statistically significantly higher than non-implanted embryos (p = 0.0053). Besides, the cut-off values were established, dividing the transferred embryos into high and low mitochondrial DNA ratio groups. The pregnancy rate and implantation rate of the high mitochondrial DNA ratio group was higher than the low mitochondrial DNA ratio group: [Pregnancy rate] 74% vs. 63.5% (p = 0.0209); [Implantation rate] 57.3% vs. 50.8% (p = 0.1907). Limitations, reasons for caution The mitochondrial DNA ratios were analyzed by bioinformatics processing in Miseq reporter software (Illumina) files in the BAM and FASTQ format. Not sure if there is reproducibility in different sequencing platforms. Wider implications of the findings There still remains a lack of clarity regarding the relationship between mitochondrial function and transfer outcome. This retrospective study links an association between increased mtDNA content and increased implantation. Trial registration number not applicable
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