Metabolic adjustments of Dentex dentex to prolonged starvation and refeeding.
The particular metabolic strategies of the common dentex (Dentex dentex) to face a period of prolonged starvation and subsequent refeeding were assessed. Plasma metabolites, endogenous reserves, and the activity of key enzymes of intermediary metabolism in liver, white muscle, and heart were evaluated. Plasma glucose, total lipid, triglycerides, total-, HDL- and LDL-cholesterol, and protein levels, liver, and white muscle glycogen, and perivisceral, and muscle fat were significantly reduced by starvation, whereas liver lipid content was surprisingly increased. Those enzymes involved in phosphorylation and oxidation of glucose and lipid synthesis, as well as alanine aminotransferase activity, were significantly depressed in liver of starved fish. The increase in β-hydroxyacyl-CoA dehydrogenase (HOAD) indicated an enhanced fatty acid oxidation during starvation. Part of the acetyl-CoA generated by β-oxidation was oxidized in the hepatic Krebs cycle, as reflected the increased citrate synthase (CS) activity. The oxaloacetate required for the reaction catalized by CS activity would be supplied by aspartate aminotransferase (ASAT) activity whose activity was also enhanced. Glutamate dehydrogenase also increased to deaminate the glutamate produced by transaminases, especially by the increased ASAT activity. Liver gluconeogenesis of starved fish was maintained at the same rate that in controls, with glycerol playing an important role as glucogenic substrate. The increased hepatic β-hydroxybutyrate dehydrogenase (β-OHBDH) activity indicates that part of the acetyl-CoA arriving from β-oxidation was being diverted for ketone bodies production with dentex liver playing an important role in providing ketone bodies as fuels for other tissues under such circumstances. Most enzyme activities in white muscle of starved dentex were significantly depressed. In heart, starvation induced an important inhibition of those enzymes involved in glucose and protein metabolism, whereas CS, HOAD, and β-OHBDH activities were maintained at control levels. Although several biomarkers assayed returned to control values after refeeding, many others did not, which indicate that after 3 weeks of refeeding, pre-starved dentex is still experiencing a transient period of metabolic adjustments directed toward the restoration of body mass.
Departamento de Zoología, Facultad de Ciencias, Universidad de Granada, Campus Universitario Fuentenueva s/n, 18071, Granada, Spain.|CIMAR/CIIMAR-Centro Interdisciplinar de Investigação Marinha e Ambiental, Universidade do Porto, Rua dos Bragas 289, 4050-123, Porto, Portugal.
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Pérez-Jiménez
Departamento de Zoología, Facultad de Ciencias, Universidad de Granada, Campus Universitario Fuentenueva s/n, 18071, Granada, Spain.
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Cardenete
Departamento de Zoología, Facultad de Ciencias, Universidad de Granada, Campus Universitario Fuentenueva s/n, 18071, Granada, Spain.
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Hidalgo
Instituto Español de Oceanografía, Centro Oceanográfico de Murcia, 30860, Puerto de Mazarrón, Murcia, Spain.
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García-Alcázar
Instituto Español de Oceanografía, Centro Oceanográfico de Murcia, 30860, Puerto de Mazarrón, Murcia, Spain.
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Abellán
Departamento de Zoología, Facultad de Ciencias, Universidad de Granada, Campus Universitario Fuentenueva s/n, 18071, Granada, Spain. amaenca@ugr.es.
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Morales
D000818:Animals; D050152:Intra-Abdominal Fat / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D010473:Perciformes / Q000097:blood* / Q000378:metabolism; D013217:Starvation / Q000097:blood* / Q000378:metabolism