Link between lipid metabolism and voluntary food intake in rainbow trout fed coconut oil rich in medium-chain TAG.
We examined the long-term effect of feeding coconut oil (CO; rich in lauric acid, C12) on voluntary food intake and nutrient utilisation in rainbow trout (Oncorhynchus mykiss), with particular attention to the metabolic use (storage or oxidation) of ingested medium-chain TAG. Trout were fed for 15 weeks one of the four isoproteic diets containing fish oil (FO) or CO as fat source (FS), incorporated at 5% (low fat, LF) or 15% (high fat, HF). Fat level or FS did not modify food intake (g/kg(0·8) per d), despite higher intestinal cholecystokinin-T mRNA in trout fed the HF-FO diet. The HF diets relative to the LF ones induced higher growth and adiposity, whereas the replacements of FO by CO resulted in similar growth and adiposity. This, together with the substantial retention of C12 (57% of intake), suggests the relatively low oxidation of ingested C12. The down-regulation of carnitine palmitoyl-transferase-1 (CPT-1) confirms the minor dependency of medium-chain fatty acids (MCFA) on CPT-1 to enter the mitochondria. However, MCFA did not up-regulate mitochondrial oxidation evaluated using hepatic hydroxyacyl-CoA dehydrogenase as a marker, in line with their high retention in body lipids. At a low lipid level, MCFA increased mRNA levels of fatty acid synthase, elongase and stearoyl-CoA desaturase in liver, showing the hepatic activation of fatty acid synthesis pathways by MCFA, reflected by increased 16 : 0, 18 : 0, 16 : 1, 18 : 1 body levels. The high capacity of trout to incorporate and transform C12, rather than to readily oxidise C12, contrasts with data in mammals and may explain the absence of a satiating effect of CO in rainbow trout.
INRA, UR1067, Nutrition, Metabolism and Aquaculture, Pôle d'Hydrobiologie INRA, F-64310 St. Pée-sur-Nivelle, France.
A Cláudia
AC
Figueiredo-Silva
Sadasivam
S
Kaushik
Frédéric
F
Terrier
Johan W
JW
Schrama
Françoise
F
Médale
Inge
I
Geurden
D050154:Adiposity; D000818:Animals; D017756:Aquaculture; D002334:Carnitine O-Palmitoyltransferase / Q000235:genetics / Q000378:metabolism; D002766:Cholecystokinin / Q000235:genetics / Q000378:metabolism; D000074263:Coconut Oil; D018752:Diet, Fat-Restricted / Q000662:veterinary; D059305:Diet, High-Fat / Q000662:veterinary; D004435:Eating; D064429:Fatty Acid Synthases / Q000235:genetics / Q000378:metabolism; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D007850:Lauric Acids / Q000008:administration & dosage* / Q000009:adverse effects / Q000032:analysis / Q000378:metabolism; D050356:Lipid Metabolism; D008099:Liver / Q000201:enzymology / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000201:enzymology / Q000378:metabolism*; D017686:Oncorhynchus mykiss / Q000254:growth & development / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D010938:Plant Oils / Q000008:administration & dosage* / Q000009:adverse effects / Q000737:chemistry / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D015430:Weight Gain
D029941:Fish Proteins; D007850:Lauric Acids; D010938:Plant Oils; D012333:RNA, Messenger; D002766:Cholecystokinin; D002334:Carnitine O-Palmitoyltransferase; D064429:Fatty Acid Synthases; D000074263:Coconut Oil