Response of hepatic mitochondrial and peroxisomal beta-oxidation to increasing palmitate concentrations in piglets.
Responses of total, mitochondrial, and peroxisomal beta-oxidation to increasing [1-14C]-palmitate concentrations (0.02-1.0 mM) were measured in liver homogenates from neonatal pigs. Incubations were conducted in the absence (total beta-oxidation) or presence (peroxisomal beta-oxidation) of antimycin A and rotenone; mitochondrial beta-oxidation was calculated as total minus peroxisomal oxidation. Total and mitochondrial beta-oxidations were maximized at a palmitate concentration of 0.05 mM, whereas peroxisomal beta-oxidation was maximized at 0.50 mM palmitate. Across concentrations, peroxisomal beta-oxidation contributed 40-47% of total beta-oxidation. An increased rate of CO2 production and a greater ratio of CO2 production to total mitochondrial beta-oxidation as palmitate concentration increased suggested that the limited capacity for mitochondrial beta-oxidation was attributable primarily to limited ketogenic capacity. Comparative observations in liver from adult rats showed that peroxisomal beta-oxidation was maximized at 0.1 mM palmitate, but total and mitochondrial beta-oxidation rates were not maximized even at 1 mM palmitate. At 1 mM palmitate, peroxisomal beta-oxidation was 20% of total beta-oxidation in adult rats and 37% in adult pigs. Therefore, the contribution of peroxisomal beta-oxidation to total beta-oxidation is highly dependent on substrate concentration and appears to be greater in adult pigs than in adult rats. The greater proportional contribution of peroxisomal beta-oxidation in piglet liver might act as a compensatory mechanism for piglets to oxidize milk fatty acids.
Yu
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Division of Nutritional Sciences, University of Illinois, Urbana 61801, USA.
Drackley
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JK
Odle
J
J
Lin
X
X
D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008830:Microbodies / Q000187:drug effects / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D009994:Osmolar Concentration; D010084:Oxidation-Reduction; D010168:Palmitates / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013552:Swine
D010168:Palmitates; D002245:Carbon Dioxide