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ABSTRACT Neurons are almost exclusively cultured in media containing glucose at much higher concentrations than found in the brain. To test whether these “standard” hyperglycemic culture conditions affect neuronal respiration relative to near‐euglycemic conditions, we compared neuronal cultures grown with minimal glial contamination from the hippocampus and cortex of neonatal C57BL/6NCrl mice in standard commercially available media (25 mM Glucose) and in identical media with 5 mM glucose. Neuronal growth in both glucose concentrations proceeded until at least 14 days in vitro, with similar morphology and synaptogenesis. Neurons grown in high glucose were highly dependent on glycolysis as their primary source of ATP, measured using ATP luminescence and cellular respirometry assays. In contrast, neurons grown in 5 mM glucose showed a more balanced dependence on glycolysis and mitochondrial oxidative phosphorylation (OXPHOS), greater reserve mitochondrial respiration capacity, and increased mitochondrial population relative to standard media. Our results show that neurons cultured in artificially high glucose‐containing media preferentially use glycolysis, opposite to what is known for neurons in vivo as the primary pathway for ATP maintenance. Changes in gene and protein expression levels corroborate these changes in function and additionally suggest that high glucose culture media increases neuronal inflammation. We suggest using neuronal culture systems in 5 mM glucose to better represent physiologically relevant neuronal respiration.image
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Epigenetic Modifier Supplementation Improves Mitochondrial Respiration and Growth Rates and Alters DNA Methylation of Bovine Embryonic Fibroblast Cells Cultured in Divergent Energy Supply
Epigenetic modifiers (EM; methionine, choline, folate, and vitamin B 12 ) are important for early embryonic development due to their roles as methyl donors or cofactors in methylation reactions. Additionally, they are essential for the synthesis of nucleotides, polyamines, redox equivalents, and energy metabolites. Despite their importance, investigation into the supplementation of EM in ruminants has been limited to one or two epigenetic modifiers. Like all biochemical pathways, one-carbon metabolism needs to be stoichiometrically balanced. Thus, we investigated the effects of supplementing four EM encompassing the methionine–folate cycle on bovine embryonic fibroblast growth, mitochondrial function, and DNA methylation. We hypothesized that EM supplemented to embryonic fibroblasts cultured in divergent glucose media would increase mitochondrial respiration and cell growth rate and alter DNA methylation as reflected by changes in the gene expression of enzymes involved in methylation reactions, thereby improving the growth parameters beyond Control treated cells. Bovine embryonic fibroblast cells were cultured in Eagle’s minimum essential medium with 1 g/L glucose (Low) or 4.5 g/L glucose (High). The control medium contained no additional OCM, whereas the treated media contained supplemented EM at 2.5, 5, and 10 times (×2.5, ×5, and ×10, respectively) the control media, except for methionine (limited to ×2). Therefore, the experimental design was a 2 (levels of glucose) × 4 (levels of EM) factorial arrangement of treatments. Cells were passaged three times in their respective treatment media before analysis for growth rate, cell proliferation, mitochondrial respiration, transcript abundance of methionine–folate cycle enzymes, and DNA methylation by reduced-representation bisulfite sequencing. Total cell growth was greatest in High ×10 and mitochondrial maximal respiration, and reserve capacity was greatest ( p < 0.01) for High ×2.5 and ×10 compared with all other treatments. In Low cells, the total growth rate, mitochondrial maximal respiration, and reserve capacity increased quadratically to 2.5 and ×5 and decreased to control levels at ×10. The biological processes identified due to differential methylation included the positive regulation of GTPase activity, molecular function, protein modification processes, phosphorylation, and metabolic processes. These data are interpreted to imply that EM increased the growth rate and mitochondrial function beyond Control treated cells in both Low and High cells, which may be due to changes in the methylation of genes involved with growth and energy metabolism.
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- Award ID(s):
- 2019077
- PAR ID:
- 10357570
- Date Published:
- Journal Name:
- Frontiers in Genetics
- Volume:
- 13
- ISSN:
- 1664-8021
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3389/fgene.2022.812764
