This study examines the ability of dietary lipids to regulate gene expression of mitochondrial and peroxisomal fatty acid β-oxidation enzymes in the kidney cortex and medulla of 3-wk-old rats and evaluates the role of glucagon or of the α-isoform of peroxisome proliferator-activated receptor (PPARα) in mediating β-oxidation enzyme gene regulation in the immature kidney. The long-chain (LCAD) and medium-chain acyl-CoA dehydrogenases (MCAD) and acyl-CoA oxidase (ACO) mRNA levels were found coordinately upregulated in renal cortex, but not in medulla, of pups weaned on a high-fat diet from day 16 to 21. Further results establish that switching pups from a low- to a high-fat diet for only 1 day was sufficient to induce large increases in cortical LCAD, MCAD, and ACO mRNA levels, and gavage experiments show that this upregulation of β-oxidation gene expression is initiated within 6 h following lipid ingestion. Treatment of pups with clofibrate, a PPARα agonist, demonstrated that PPARα can mediate regulation of cortical β-oxidation enzyme gene expression, whereas glucagon was found ineffective. Thus dietary lipids physiologically regulate gene expression of mitochondrial and peroxisomal β-oxidation enzymes in the renal cortex of suckling pups, and this might involve PPARα-mediated mechanisms.

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