Tissue-specific induction of peroxisomal and mitochondrial β-oxidation enzymes by clofibric acid in piglets

To investigate the effects of peroxisome proliferators on peroxisomal and mitochondrial β-oxidation in piglet tissues, newborn pigs (1 to 2 d old) were allowed ad libitum access to milk replacer supplemented with 0.5% clofibric acid (CA) or 1% aspirin (AS) for 14 days. CA increased liver weight (LW) by 7% kidney weight (KW) by 10.4% and heart weight (HW) by 19.3%, which resulted in greater ratios of LW/body weight (BW: P = 0.07). KW/BW (P < 0.05). and HW/BW (P < 0.001). As decreased daily food intake and thereby the final BW but increased the ratio of HW/BW (P < 0.01). In liver, activities of peroxisomal β-oxidation (POX), fatty acyl-CoA oxidase (FAO), total carnitine palmitoyl-transferase (CPT), and catalase were 3.7-fold, 3.2-fold, 2.5-fold, and 33% greater, respectively, for pigs given CA than for control pigs. In heart, these variables were 3.2-fold, 5.1-fold, 2.9-fold, and 2.8-fold greater, respectively, for pigs given CA than for control pigs. CA did not change these variables in either kidney or muscle, except that CPT activity was increased about twofold (P < 0.01) in kidney, AS increased only hepatic FAO and CPT activities. Northern blot analysis revealed a 3.2-fold greater amount of catalase mRNA in heart from pigs given CA. We concluded that: 1) the enlargement of liver, kidney, and heart caused by CA probably involved not only the proliferation of peroxisomes but also the proliferation of mitochondria; 2) the relatively smaller induction of POX in piglets (vs. that documented in young or adult rodents) may be related to either age differences or species difference: 3) AS has much weaker effects on enzyme induction in piglet tissues than CA.