title: High fat intake lowers hepatic fatty acid synthesis and raises fatty acid oxidation in aerobic muscle in Shetland ponies.
abstract: The metabolic effects of feeding soyabean oil instead of an isoenergetic amount of maize starch plus glucose were studied in ponies. Twelve adult Shetland ponies were given a control diet (15 g fat/kg DM) or a high-fat diet (118 g fat/kg DM) according to a parallel design. The diets were fed for 45 d. Plasma triacylglycerol (TAG) concentrations decreased by 55 % following fat supplementation. Fat feeding also reduced glycogen concentrations significantly by up to 65 % in masseter, gluteus and semitendinosus muscles (P < 0.05 and P < 0.01 and P < 0.01 respectively). The high-fat diet significantly increased the TAG content of semitendinosus muscle by 80 % (P < 0.05). Hepatic acetyl-CoA carboxylase and fatty acid synthase activities were 53 % (P < 0.01) and 56 % (P < 0.01) lower respectively in the high-fat group, but diacylglycerol acyltransferase activity was unaffected. Although carnitine palmitoyltransferase-I (CPT-I) activity in liver mitochondria was not influenced, fat supplementation did render CPT-I less sensitive to inhibition by malonyl-CoA. There was no significant effect of diet on the activity of phosphofructokinase in the different muscles. The activity of citrate synthase was raised significantly (by 25 %; P < 0.05) in the masseter muscle of fat-fed ponies, as was CPT-I activity (by 46 %; P < 0.01). We conclude that fat feeding enhances both the transport of fatty acids through the mitochondrial inner membrane and the oxidative capacity of highly-aerobic muscles. The higher oxidative ability together with the depressed rate of de novo fatty acid synthesis in liver may contribute to the dietary fat-induced decrease in plasma TAG concentrations in equines.
authors: Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands. suzannegeelen@hotmail.com
authors: S N
authors: SN
authors: Geelen
authors: C
authors: C
authors: Blázquez
authors: M J
authors: MJ
authors: Geelen
authors: M M
authors: MM
authors: Sloet van Oldruitenborgh-Oosterbaan
authors: A C
authors: AC
authors: Beynen
mesh_terms: D000103:Acetyl-CoA Carboxylase / Q000378:metabolism; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002334:Carnitine O-Palmitoyltransferase / Q000378:metabolism; D002950:Citrate (si)-Synthase / Q000378:metabolism; D064429:Fatty Acid Synthases / Q000378:metabolism; D005227:Fatty Acids / Q000096:biosynthesis / Q000378:metabolism*; D006003:Glycogen / Q000032:analysis; D006736:Horses / Q000378:metabolism*; D008099:Liver / Q000201:enzymology; D008297:Male; D008930:Mitochondria, Liver / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000737:chemistry / Q000378:metabolism*; D009206:Myocardium / Q000201:enzymology; D010084:Oxidation-Reduction; D013024:Soybean Oil / Q000008:administration & dosage*; D014280:Triglycerides / Q000032:analysis / Q000097:blood
chemical_list: D005227:Fatty Acids; D014280:Triglycerides; D013024:Soybean Oil; D006003:Glycogen; D002334:Carnitine O-Palmitoyltransferase; D064429:Fatty Acid Synthases; D002950:Citrate (si)-Synthase; D000103:Acetyl-CoA Carboxylase