title: Dietary cholesterol supplementation to a plant-based diet suppresses the complete pathway of cholesterol synthesis and induces bile acid production in Atlantic salmon (Salmo salar L.).
abstract: Plants now supply more than 50 % of protein in Norwegian salmon aquafeeds. The inclusion of plant protein in aquafeeds may be associated with decreased lipid digestibility and cholesterol and bile salt levels, indicating that the replacement of fishmeal with plant protein could result in inadequate supplies of cholesterol in fish. A reduction in feed efficiency, fish growth and pathogen resistance is often observed in parallel to alterations in sterol metabolism. Previous studies have indicated that the negative effects induced by plant components can be attenuated when diets are supplemented with cholesterol. The present study evaluated the effects of dietary cholesterol supplementation (1·5 %) in Atlantic salmon fed a plant-based diet for 77 d. The weights of body, intestines and liver were recorded and blood, tissues, faeces, chyme and bile were sampled for the evaluation of effects on growth, nutrient utilisation and metabolism, and transcriptome and metabolite levels, with particular emphasis on sterol metabolism and organ structure and function. Cholesterol supplementation did not affect the growth or organ weights of Atlantic salmon, but seemed to promote the induction of cholesterol and plant sterol efflux in the intestine while suppressing sterol uptake. Cholesterol biosynthesis decreased correspondingly and conversion into bile acids increased. The marked effect of cholesterol supplementation on bile acid synthesis suggests that dietary cholesterol can be used to increase bile acid synthesis in fish. The present study clearly demonstrated how Atlantic salmon adjusted their metabolic functions in response to the dietary load of cholesterol. It has also expanded our understanding of sterol metabolism and turnover, adding to the existing, rather sparse, knowledge of these processes in fish.
authors.affiliation: Department of Basic Sciences and Aquatic Medicine, NMBU School of Veterinary Science, Oslo, Norway.
authors.forename: Trond M
authors.initials: TM
authors.lastname: Kortner
authors.affiliation: Division of Clinical Chemistry, Department of Laboratory Medicine, Karolinska University Hospital, Huddinge, Sweden.
authors.forename: Ingemar
authors.initials: I
authors.lastname: Björkhem
authors.affiliation: Nofima AS, Ås, Norway.
authors.forename: Aleksei
authors.initials: A
authors.lastname: Krasnov
authors.affiliation: Nofima AS, Ås, Norway.
authors.forename: Gerrit
authors.initials: G
authors.lastname: Timmerhaus
authors.affiliation: Department of Basic Sciences and Aquatic Medicine,NMBU School of Veterinary Science, Oslo, Norway.
authors.forename: Åshild
authors.initials: Å
authors.lastname: Krogdahl
mesh_terms: D000818:Animals; D017849:Animals, Inbred Strains; D017756:Aquaculture; D001647:Bile Acids and Salts / Q000378:metabolism*; D002784:Cholesterol / Q000096:biosynthesis*; D002791:Cholesterol, Dietary / Q000008:administration & dosage / Q000009:adverse effects / Q000378:metabolism*; D004032:Diet / Q000009:adverse effects / Q000662:veterinary; D004044:Dietary Proteins / Q000009:adverse effects / Q000378:metabolism; D002149:Energy Intake; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D060434:Herbivory; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000254:growth & development / Q000378:metabolism*; D007422:Intestines / Q000254:growth & development; D008099:Liver / Q000254:growth & development / Q000378:metabolism; D009664:Norway; D010840:Phytosterols / Q000378:metabolism; D010940:Plant Proteins / Q000009:adverse effects / Q000378:metabolism; D011897:Random Allocation; D020317:Salmo salar / Q000254:growth & development / Q000378:metabolism*; D015430:Weight Gain
chemical_list: D001647:Bile Acids and Salts; D002791:Cholesterol, Dietary; D004044:Dietary Proteins; D029941:Fish Proteins; D010840:Phytosterols; D010940:Plant Proteins; D002784:Cholesterol