Vitamin C Deficiency Activates the Purine Nucleotide Cycle in Zebrafish

ArticleinJournal of Biological Chemistry 287(6):3833-41 · December 2011with23 Reads
DOI: 10.1074/jbc.M111.316018 · Source: PubMed
Vitamin C (ascorbic acid, AA) is a cofactor for many important enzymatic reactions and a powerful antioxidant. AA provides protection against oxidative stress by acting as a scavenger of reactive oxygen species, either directly or indirectly by recycling of the lipid-soluble antioxidant, α-tocopherol (vitamin E). Only a few species, including humans, guinea pigs, and zebrafish, cannot synthesize AA. Using an untargeted metabolomics approach, we examined the effects of α-tocopherol and AA deficiency on the metabolic profiles of adult zebrafish. We found that AA deficiency, compared with subsequent AA repletion, led to oxidative stress (using malondialdehyde production as an index) and to major increases in the metabolites of the purine nucleotide cycle (PNC): IMP, adenylosuccinate, and AMP. The PNC acts as a temporary purine nucleotide reservoir to keep AMP levels low during times of high ATP utilization or impaired oxidative phosphorylation. The PNC promotes ATP regeneration by converting excess AMP into IMP, thereby driving forward the myokinase reaction (2ADP → AMP + ATP). On the basis of this finding, we investigated the activity of AMP deaminase, the enzyme that irreversibly deaminates AMP to form IMP. We found a 47% increase in AMP deaminase activity in the AA-deficient zebrafish, complementary to the 44-fold increase in IMP concentration. These results suggest that vitamin C is crucial for the maintenance of cellular energy metabolism.
    • "Again, information of this nature has been established for murine models and for many commercial aquaculture species, and is a critical and necessary component of standardization. A collection of nutritional studies published over the past decade have provided the basic framework for determining zebrafish dietary requirements for protein (Hedrera et al., 2013; Smith et al., 2013), polyunsaturated fatty acids (Jaya-Ram, Kuah, Lim, Kolkovski, & Shu-Chien, 2008; Kaushik, Georga, & Koumoundouros, 2011; Powell et al., 2015), vitamins (Alsop, Matsumoto, Brown, & Van Der Kraak, 2008; Kirkwood et al., 2012; Lebold et al., 2013; Miller et al., 2012) , , minerals (Craig et al., 2009; Siccardi et al., 2010), and carbohydrates (Robison et al., 2008). However, the field has yet to conduct the kind of systematic studies required to determine the daily nutritional requirements of the fish that will promote health and reproduction. "
    [Show abstract] [Hide abstract] ABSTRACT: The zebrafish (Danio rerio) is a preeminent model organism with a wide and expanding utility for numerous scientific disciplines. The same features that once endeared this small freshwater minnow to developmental biologists combined with its relatively high genetic similarity to mammals and the advent of new, more efficient methods for genome editing are now helping to spur expanded growth in its usage in various fields, including toxicology, drug discovery, transplant biology, disease modeling, and even aquaculture. Continued maturation and adoption of the zebrafish model system in these and other fields of science will require that methods and approaches for husbandry and management of these fish in controlled settings be refined and improved to the extent that, ultimately, zebrafish research becomes more reproducible, defined, cost-effective, and accessible to the masses. Knowledge and technology transfer from laboratory animal science and commercial aquaculture will be a necessary part of this development.
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    • "Measured α-tocopherol concentrations in the EÀ and Eþ diets were 0.4570.01 and 36972 mg/kg (n¼3 replicate samples measured for each diet), respectively ; vitamin C was 143716 mg ascorbic acid/kg. This level of dietary vitamin C has been found to be adequate for the zebrafish [25,26]. Measured α-tocopherol concentrations in the EÀ and Eþ embryos at 24 hpf were 3.470.1 and 10573 pmol/embryo, respectively , similar to previous reports [3,21]. "
    [Show abstract] [Hide abstract] ABSTRACT: We hypothesized that vitamin E (α-tocopherol) is required by the developing embryonic brain to prevent depletion of highly polyunsaturated fatty acids, especially docosahexaenoic acid (DHA, 22:6), the loss of which we predicted would underlie abnormal morphological and behavioral outcomes. Therefore, we fed adult 5D zebrafish (Danio rerio) defined diets without (E-) or with added α-tocopherol (E+, 500mg RRR-α-tocopheryl acetate/kg diet) for a minimum of 80 days, and then spawned them to obtain E- and E+ embryos. The E- compared with E+ embryos were 82% less responsive (p<0.01) to a light/dark stimulus at 96hours post-fertilization (hpf), demonstrating impaired locomotor behavior, even in the absence of gross morphological defects. Evaluation of phospholipid (PL) and lysophospholipid (lyso-PL) composition using untargeted lipidomics in E- compared with E+ embryos at 24, 48, 72, and 120 hpf showed that four PLs and three lyso-PLs containing docosahexaenoic acid (DHA), including lysophosphatidylcholine (LPC 22:6, required for transport of DHA into the brain, p<0.001), were at lower concentrations in E- at all time-points. Additionally, H218O labeling experiments revealed enhanced turnover of LPC 22:6 (p<0.001) and three other DHA-containing PLs in the E- compared with the E+ embryos, suggesting that increased membrane remodeling is a result of PL depletion. Together, these data indicate that α-tocopherol deficiency in the zebrafish embryo causes the specific depletion and increased turnover of DHA-containing PL and lyso-PLs, which may compromise DHA delivery to the brain and thereby contribute to the functional impairments observed in E- embryos.
    Full-text · Article · Jan 2016
    • "In addition , zebrafish embryos develop rapidly and remain transparent throughout much of organogenesis, enabling researchers to perform large-scale and high-throughput screenings at a reduced cost (Hung et al., 2012; Santoro, 2014). Recent studies suggest that zebrafish may be an ideal reference model system for performing metabolomic-related studies (Kirkwood et al., 2012; Seth et al., 2013; Santoro, 2014). Furthermore, the metabolic changes in zebrafish are conserved in human samples (Nath et al., 2013). "
    [Show abstract] [Hide abstract] ABSTRACT: Polycyclic aromatic hydrocarbons (PAHs) and their oxygenated derivatives are ubiquitously present in diesel exhaust, atmospheric particulate matter and soils sampled in urban areas. Therefore, inhalation or non-dietary ingestion of both PAHs and oxy-PAHs are major routes of exposure for people; especially young children living in these localities. While there has been extensive research on the parent PAHs, limited studies exist on the biological effects of oxy-PAHs which have been shown to be more soluble and more mobile in the environment. Additionally, investigations comparing the metabolic responses resulting from parent PAHs and oxy-PAHs exposures have not been reported. To address these current gaps, an untargeted metabolomics approach was conducted to examine the in vivo metabolomic profiles of developing zebrafish (Danio rerio) exposed to 4µM of benz[a]anthracene (BAA) or benz[a]anthracene-7,12-dione (BAQ). By integrating multivariate, univariate and pathway analyses, a total of 63 metabolites were significantly altered after 5 days of exposure. The marked perturbations revealed that both BAA and BAQ affect protein biosynthesis, mitochondrial function, neural development, vascular development and cardiac function. Our previous transcriptomic and genomic data were incorporated in this metabolomics study to provide a more comprehensive view of the relationship between PAH and oxy-PAH exposures on vertebrate development. Copyright © 2015 Elsevier Inc. All rights reserved.
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