Differential induction of peroxisomal beta-oxidation enzymes by clofibric acid and aspirin in piglet tissues

Peroxisomal beta -oxidation (POX) of fatty acids is important in lipid cata bolism and thermogenesis. To investigate the effects of peroxisome prolifer ators on peroxisomal and mitochondrial beta -oxidation in piglet tissues, n ewborn pigs (1-2 days old) were allowed ad libitum access to milk replacer supplemented with 0.5% clofibric acid (CA) or 1% aspirin for 14 days. CA in creased ratios of liver weight to body weight (P<0.07), kidney weight to bo dy weight (P<0.05), and heart weight to body weight (P<0.001). Aspirin decr eased daily food intake and final body weight but increased the ratio of he art weight to body weight (P<0.01). In liver, activities of POX, fatty acyl -CoA oxidase (FAO), total carnitine palmitoyltransferase (CPT), and catalas e were 2.7-, 2.2-, 1.5- fold, and 33% greater, respectively, for pigs given CA than for control pigs. In heart, these variables were 2.2-, 4.1-, 1.9-, and 1.8-fold greater, respectively, for pigs given CA than for control pig s. CA did not change these variables in either kidney or muscle, except tha t CPT activity was increased similar to 110% (P<0.01) in kidney. Aspirin in creased only hepatic FAO and CPT activities. Northern blot analysis reveale d that CA increased the abundance of catalase mRNA in heart by;2.2- fold. W e conclude that 1) POX and CPT in newborn pigs can be induced by peroxisoma l proliferators with tissue specificity and 2) the relatively smaller induc tion of POX in piglets (compared with that in young or adult rodents) may b e related to either age or species differences.