title: Prolonged fasting increases glutathione biosynthesis in postweaned northern elephant seals.
abstract: Northern elephant seals experience prolonged periods of absolute food and water deprivation (fasting) while breeding, molting or weaning. The postweaning fast in elephant seals is characterized by increases in the renin-angiotensin system, expression of the oxidant-producing protein Nox4, and NADPH oxidase activity; however, these increases are not correlated with increased oxidative damage or inflammation. Glutathione (GSH) is a potent reductant and a cofactor for glutathione peroxidases (GPx), glutathione-S transferases (GST) and 1-cys peroxiredoxin (PrxVI) and thus contributes to the removal of hydroperoxides, preventing oxidative damage. The effects of prolonged food deprivation on the GSH system are not well described in mammals. To test our hypothesis that GSH biosynthesis increases with fasting in postweaned elephant seals, we measured circulating and muscle GSH content at the early and late phases of the postweaning fast in elephant seals along with the activity/protein content of glutamate-cysteine ligase [GCL; catalytic (GCLc) and modulatory (GCLm) subunits], γ-glutamyl transpeptidase (GGT), glutathione disulphide reductase (GR), glucose-6-phosphate dehydrogenase (G6PDH), GST and PrxVI, as well as plasma changes in γ-glutamyl amino acids, glutamate and glutamine. GSH increased two- to four-fold with fasting along with a 40-50% increase in the content of GCLm and GCLc, a 75% increase in GGT activity, a two- to 2.5-fold increase in GR, G6PDH and GST activities and a 30% increase in PrxVI content. Plasma γ-glutamyl glutamine, γ-glutamyl isoleucine and γ-glutamyl methionine also increased with fasting whereas glutamate and glutamine decreased. Results indicate that GSH biosynthesis increases with fasting and that GSH contributes to counteracting hydroperoxide production, preventing oxidative damage in fasting seals.
authors: School of Natural Sciences, University of California Merced, Merced, CA 95343, USA. jvazquez-medina@ucmerced
authors: José Pablo
authors: JP
authors: Vázquez-Medina
authors: Tania
authors: T
authors: Zenteno-Savín
authors: Henry Jay
authors: HJ
authors: Forman
authors: Daniel E
authors: DE
authors: Crocker
authors: Rudy M
authors: RM
authors: Ortiz
mesh_terms: D000818:Animals; D005215:Fasting / Q000378:metabolism*; D005260:Female; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism; D005721:Glutamate-Cysteine Ligase / Q000378:metabolism; D005978:Glutathione / Q000096:biosynthesis*; D005979:Glutathione Peroxidase / Q000378:metabolism; D005980:Glutathione Reductase / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D008297:Male; D055432:Metabolomics; D018482:Muscle, Skeletal / Q000378:metabolism; D016877:Oxidants / Q000378:metabolism; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D054464:Peroxiredoxins / Q000378:metabolism; D046048:Seals, Earless / Q000378:metabolism*; D014886:Weaning; D005723:gamma-Glutamyltransferase / Q000378:metabolism
chemical_list: D016877:Oxidants; D006861:Hydrogen Peroxide; D005954:Glucosephosphate Dehydrogenase; D054464:Peroxiredoxins; D005979:Glutathione Peroxidase; D005980:Glutathione Reductase; D005723:gamma-Glutamyltransferase; D005982:Glutathione Transferase; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione