Factors affecting fatty acid oxidation in bovine mammary tissue |
| |
Authors: | G P Dimenna R S Emery |
| |
Affiliation: | (1) Department of Dairy Science, Michigan State University, 48824 East Lansing, MI;(2) Department Physiological Sciences, University of California, 95616 Davis |
| |
Abstract: | Oxidation of fatty acids was studied in bovine mammary tissue slices in order to evaluate their potential contribution to
energy metabolism. Rates of fatty acid oxidation decreased with increasing chain length: acetate>octanoate>palmitate or oleate.
Rates of oxidation of long chain, but not short chain, fatty acids increased over time, which could not be explained by carnitine
palmitoyltransferase (CPT) activity. This phenomenon is not an artifact of the incubation system or caused by substrate solubility,
as rates of palmitate oxidation were constant in rat kidney cortex slices. Preincubating mammary tissue with or without unlabeled
palmitate showed that increasing rates of palmitate oxidation is not caused by use of endogenous fatty acids. Palmitate at
0.26 mM, equivalent to arterial fatty acid concentration, gave maximal rates of oxidation. The β-oxidation enzymes may restrict
fatty acid oxidation as oxidation of 1-14C] palmitate exceeded that of U-14C] palmitate. Acetate inhibited palmitate oxidation (75%) but not esterification, suggesting that acetate inhibits palmitate
oxidation by substrate competition at the mitochondrial level or via malonyl-CoA inhibition of CPT. Glucose inhibited palmitate
oxidation (67%) and stimulated esterification. Low palmitoyl-CoA levels would favor glyceride synthesis over oxidation, since
the apparent Km for palmitoyl-CoA, of the glycerol-3-phosphate acyltransferases is lower than that for CPT. Thus, glucose presumably diverts
palmitate from oxidation to glycerolipids. Clofenapate, a glyceride synthesis inhibitor, decreased triacylglycerol formation,
and marginally increased palmitate oxidation. We estimated that long chain fatty acids can potentially account for 6–10% of
the oxidative metabolism of mammary tissue.
Published with approval of the Director of the Agricultural Experiment Station as Journal Article No. 9292. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|