title: Lipid, ketone body and oxidative metabolism in the African lungfish, Protopterus dolloi following 60 days of fasting and aestivation.
abstract: The potential importance of lipids and ketone bodies as fuels in the African lungfish, Protopterus dolloi, and the role of oxidative metabolism, were examined under control, fasted and aestivated conditions. In aestivating but not fasting lungfish, the activities of citrate synthase (CS) and cytochrome c oxidase (CCO) (enzymes of oxidative metabolism) showed tissue-specific changes. Significant reductions in CS activity occurred in the kidney, heart, gill and muscle, and in CCO in the liver and kidney tissues. Aestivation, but not fasting, also had a tissue-specific effect on mitochondrial state 3 respiration rates (using succinate as a substrate), with a >50% reduction in the liver, yet no change within muscle mitochondria. There is no indication that enzymes involved in lipid catabolism are up-regulated during periods of fasting or aestivation; however, both 3-hydroxyacyl CoA dehydrogenase (HOAD) and carnitine palmitoyl CoA transferase (CPT) activities were sustained in the liver despite the approximately 42% reduction in CCO activity, potentially indicating lipid metabolism is of importance during aestivation. Lungfish are able to utilize both the d- and l-stereoisomers of the ketone body beta-hydroxybutyrate (beta-HB); however, beta-HB does not appear to be an important fuel source during aestivation or fasting as no changes were observed in beta-HB tissue levels. This study demonstrates that an important aspect of metabolic depression during aestivation in lungfish is the tissue-specific down regulation of enzymes of aerobic metabolism while maintaining the activities of enzymes in pathways that supply substrates for aerobic metabolism.
authors.affiliation: Department of Integrative Biology, University of Guelph, Guelph, Ont. N1G2W1, Canada.
authors.forename: Natasha Therese
authors.initials: NT
authors.lastname: Frick
authors.forename: Jason Scott
authors.initials: JS
authors.lastname: Bystriansky
authors.forename: Yuen Kwong
authors.initials: YK
authors.lastname: Ip
authors.forename: Shit Fun
authors.initials: SF
authors.lastname: Chew
authors.forename: James Stuart
authors.initials: JS
authors.lastname: Ballantyne
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000378:metabolism; D000090:Acetoacetates / Q000378:metabolism; D000349:Africa; D000818:Animals; D002334:Carnitine O-Palmitoyltransferase / Q000378:metabolism; D019069:Cell Respiration; D002950:Citrate (si)-Synthase / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D004956:Estivation / Q000502:physiology*; D005215:Fasting / Q000502:physiology*; D005399:Fishes / Q000378:metabolism*; D007657:Ketone Bodies / Q000378:metabolism*; D050356:Lipid Metabolism; D008930:Mitochondria, Liver / Q000378:metabolism; D009928:Organ Specificity; D010084:Oxidation-Reduction; D019802:Succinic Acid / Q000378:metabolism
chemical_list: D000090:Acetoacetates; D007657:Ketone Bodies; D019802:Succinic Acid; D003576:Electron Transport Complex IV; D002334:Carnitine O-Palmitoyltransferase; D002950:Citrate (si)-Synthase; D020155:3-Hydroxybutyric Acid