title: Carotenoid dynamics in Atlantic salmon.
abstract: BACKGROUND
  Carotenoids are pigment molecules produced mainly in plants and heavily exploited by a wide range of organisms higher up in the food-chain. The fundamental processes regulating how carotenoids are absorbed and metabolized in vertebrates are still not fully understood. We try to further this understanding here by presenting a dynamic ODE (ordinary differential equation) model to describe and analyse the uptake, deposition, and utilization of a carotenoid at the whole-organism level. The model focuses on the pigment astaxanthin in Atlantic salmon because of the commercial importance of understanding carotenoid dynamics in this species, and because deposition of carotenoids in the flesh is likely to play an important life history role in anadromous salmonids.
  
  
  RESULTS
  The model is capable of mimicking feed experiments analyzing astaxanthin uptake and retention over short and long time periods (hours, days and years) under various conditions. A sensitivity analysis of the model provides information on where to look for possible genetic determinants underlying the observed phenotypic variation in muscle carotenoid retention. Finally, the model framework is used to predict that a specific regulatory system controlling the release of astaxanthin from the muscle is not likely to exist, and that the release of the pigment into the blood is instead caused by the androgen-initiated autolytic degradation of the muscle in the sexually mature salmon.
  
  
  CONCLUSIONS
  The results show that a dynamic model describing a complex trait can be instrumental in the early stages of a project trying to uncover underlying determinants. The model provides a heuristic basis for an experimental research programme, as well as defining a scaffold for modelling carotenoid dynamics in mammalian systems.
authors.affiliation: Centre for Integrative Genetics (CIGENE) and Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences (UMB), 1430 As, Norway. hannah.rajasingh@cigene.no
authors.forename: Hannah
authors.initials: H
authors.lastname: Rajasingh
authors.forename: Leiv
authors.initials: L
authors.lastname: Øyehaug
authors.forename: Dag Inge
authors.initials: DI
authors.lastname: Våge
authors.forename: Stig W
authors.initials: SW
authors.lastname: Omholt
mesh_terms: D000818:Animals; D002338:Carotenoids / Q000378:metabolism / Q000502:physiology*; D019295:Computational Biology / Q000379:methods*; D005260:Female; D008297:Male; D008954:Models, Biological; D009132:Muscles / Q000378:metabolism; D010641:Phenotype; D020317:Salmo salar; D049490:Systems Biology; D024341:Xanthophylls / Q000378:metabolism
chemical_list: D024341:Xanthophylls; D002338:Carotenoids; C005948:astaxanthine